C 55. 30a '. Er^ S For Review Purposes Only THE ENVIRONMENT OF THE UNITED STATES LIVING MARINE RESOURCES 1974 MARMAP Contribution No. 104 (Marine Resources Monitoring, Assessment, and Prediction Program) Compiled by Julien R. Goulet, Jr. January 1976 U. S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service For Review Purposes Only THE ENVIRONMENT OF THE UNITED STATES LIVING MARINE RESOURCES 1974 MARMAP Contribution No. 104 (Marine Resources Monitoring, Assessment, and Prediction Program) Compiled by Julien R. Goulet, Jr. January 1976 U. S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service TABLE OF CONTENTS Section INTRODUCTION ^ ATLANTIC PACIFIC CONTRIBUTIONS El Nino, anomalous Equatorial Pacific conditions and their prediction. W.H. Quinn Atomospheric climatology and its effect on sea surface temperature. J. Namias and R.R. Dickson 3 Climatic change in the Pacific Ocean J.H. Johnson, D.R. McLain and C.S. Nelson 4 Sea surface temperature conditions in the North Pacific Ocean - 1974. L.E. Eber 5 Changes in the transition zone and heat storage in 1974 between Hawaii and California. J.F.T. Saur ^ Anomalously cold winters in the southeastern Bering Sea, 1971-1975. D.R. McLain and F. Favorite 7 Oceanography and Albacore Tuna, Thunnus Alalunga (Bonnaterre) , in the Northeast Pacific during 1974. R.M. Laurs ^ Sea surface temperatures in the eastern tropical Pacific during 1974 and the tropical fishery. F.R. Miller 9 Temperature and dissolved oxygen define Skipjack Tuna habitat. R.A. Barkley 1° Quinn ^^ Coastal upwelling off western North America, 1974. A. Bakun 12 Review of the physical oceanography of Georges Bank. (accepted for publication as ICNAF Research Bulletin #12, 1976) D. F. Bumpus 13 Wind-driven transport, Atlantic coast and Gulf of Mexico. M.C. Ingham 14 Sea surface temperature anomalies at shore stations in the Gulf of Maine during 1970-74. J.L. Chamber lin and J.J. Kosmark 15 Sea Surface temperature anomalies: Gulf of Maine and Georges Bank-Nantucket Shoals Region during 1970-74. J.L. Chamber lin and J.J. Kosmark 16 Variations in the shelf water front off the Atlantic coast between Cape Hatteras and Georges Bank. M.C. Ingham 17 Bottom temperatures on the continental shelf and slope shouth of New England during 1974. J.L. Chamber lin 18 Tidal station temperatures, U.S. east coast and Long Island Sound. J.R. Goulet, Jr. 19 Monthly maps of sea surface temperature anomaly in the northwest Atlantic Ocean and Gulf of Mexico, 1974. D.R. McLain 20 Environmental conditions in the Gulf of Mexico and western North Atlantic as observed from NMFS/MARAD ships of opportunity for 1974. S.K. Cook and K.A. Hausknecht 21 INTRODUCTION The Marine Resources Monitoring, Assessment, and Prediction (MARMAP) program is an NMFS national program providing information needed for management and allocation of the Nation's marine fishery resources. The program encompasses the collection and analysis of data to provide basic information on the abundance, composition, location, and condition of the commercial and recreational marine fishery resources of the United States. Changes in physical and chemical properties of the ocean (currents, temperature, nutrients, etc.) directly or indirectly affect not only long-term yields and annual abundances of fish stocks, but also their distribution. MARMAP oceanography activities include the analyses of physical, chemical, and biological oceanographic data collected during MARMAP surveys and from oceanographic and meteorological operational and research activities of other agencies. The MARMAP program places emphasis on providing information in a usable manner. Part of this approach involves the preparation of annual summary reports on the status of the United States marine fisheries resource (Status of Stocks - SOS) and on the status of the environment influencing those resources (Status of Environment - SOE). This report, the Environment of the United States Living Marine Resources - 1974, is the first SOE. It presents an overview of the environment of the living marine resources of the United States. This overview contributes to the understanding necessary for optimal development, allocation, management, and control of our living marine resources. The report includes contributions from oceanographers and meteor- ologists both inside and outside of the NMFS. The emphasis of these contributions is toward an understanding of the oceans as a dynamic system rather than a static one, and toward an understand- ing of causal relations between the environment and the resource rather than simple correlations. Attempts have been made in the past to develop correlations between fish catch and properties traditional available to marine biologists such as temperature, salinity, oxygen concentration, and nutrient concentration. In some cases significant correlations have been found but more often correlations have held for a while and then have broken down. The fact is that the simplistic approach to the fishery-environment problem has only limited value, but is frequently a necessary first step. Knowledge of the dynamics of the relation 0-1 of fish populations to their environment is vital. Indices of environmental processes of significance to life in the sea, such as upwelling, can now be made available in addition to the proper- ties that have traditionally been available. Such indices can be derived from oceanographic and meteorological observations and are usually time dependent. Measures of the seasonal and interyear changes of time-dependent parameters that are known to affect the survival of early life stages and recruitment of fishes as well as the distribution and concentration of fishes at all stages of development are now becoming state of the art. Their analysis and interpretation is a goal of the SOE and may go a long way towards improving a number of population dynamics models. 0-2 ATLANTIC by Merton C. Ingham and Julien R. Goulet, Jr. The oceanographic area of the Atlantic Ocean of principal concern to NMFS scientists includes the waters over the U.S. continental shelf and adjacent slope seaward to the Gulf Stream and the waters of the northern Gulf of Mexico. These waters are subject to considerable periodic and aperiodic variation in wind stress, precipitation and run-off, temperature and water mass properties. In this changing environment reside demersal and pelagic organisms with variable biological cycles and vital requirements. Any attempt to understand bio-environmental relationships in this area will begin with the understanding of interactions between specific physical pro- cesses or cycles and a single species or group of species with similar re- quirements. Understanding of ecosystems will eventually be built in this fashion, as a complex of these species-environment interactions. One of the roles of the SOE report is to portray the variation of environmental processes which have recognized or suspected significance to resource species and to describe the interactions between organisms and their environment when- ever they are known. Namias and Dickson's paper (section 3) serves as a starting point for an overview of both the Atlantic and Pacific Oceans. As a whole, 1974 was characterized by extreme strength of the mid-latitude westerlies from the western Pacific to the eastern Atlantic. The sub-polar lows and the sub- tropical highs were equally intense. These conditions were associated with abnormally warm sea surface temperatures in the western North Atlantic. The mean winter sea surface temperatures along the Atlantic coast were 2°F. warmer than normal and reached 5°F. warmer in the Mid-Atlantic Bight. The strength of the Bermuda High in the winter months (January-March) of 1974, which blocked the invasion of the Atlantic coastal area by polar continental air masses, also provided generally southerly and westerly winds off the Carol inas, resulting in little or no onshore transport in the ocean's upper layer. During this time period, onshore transport produced by northerly winds is critical for the success of spawning of Atlantic Menhaden south of Cape Hatteras. Sea surface temperatures, examined by Chamberlin and Kosmark (section 16) were warmer than the long term average by more than S^C. in Feb. -Mar. and Oct. -Dec. in the Gulf of Maine and in Jan. -Mar. over Georges Bank. Ingham (section 17) found that shoreward excursions of the shelf water front brought the front 100 kilometers more shoreward than normal over southern Georges Bank in August, covering about 14% of Georges Bank with slope water. In early September this expanded to about 18% coverage, but decreased to only 4% cover- age by the end of the month, near the average for the year. 1-1 Bottom temperatures on the continental shelf and upper continental slope south of New England, as reported by Chamberlin (section 18) generally ranged from 2° to 3°C. higher throughout 1974 than the monthly mean values for 1940-66. In the warm band on the outer continental shelf, where the slope water contacts the bottom, the maximum temperatures did not fall below 12°C. during 1974, whereas the highest monthly mean values in this band fall below 10°C. from mid-February through April and below 9°C. in March. The cold core at mid-depth of the continental shelf was about 2°C warmer than the average from its forma- tion in May to its dissipation in the autumn as a result of vertical mixing of the water column. In March, 1974, a warm core Gulf Stream eddy, which progressed generally southwestward along the edge of the continental shelf during the winter and spring, raised the bottom temperatures on the outer continental shelf and upper continental slope by as much as 4°C. Because of the unusual behavior of this eddy, its effect on shelf and slope temperatures may have been longer than is fully revealed by the available data. From early March until mid-May it resided in the waters south of New England, moving about irregularly and apparently making repetitive contacts with the bottom. It is possible that the early warming of bottom temperatures south of New England may have advanced the times of inshore spring migrations of hakes and other groundfish that winter on the outer continental shelf and upper slope. Another possibility is that in the fall the generally high bottom temperatures on the shelf may also have delayed the seasonal offshore migration of these species. The autumn spawning of herring on Georges Bank, as reported by Bumpus (section 13) was late in 1974, beginning only in late September-early October. In mid-October there was a westward advection from the spawning area over eastern Georges Bank at a speed of 3 to 8 miles per day. There was a general dispersion from the spawning area in early November, and in late November there was a slight westward drift of 1 to 2 miles per day while the north-south extent of the area occupied by larval herring contracted slightly. Goulet (section 19) reports water temperatures recorded at tidal stations' to have been 5°F. warmer in Jan. -Feb. in 1974 than in 1973 at locations just north of Cape Hatteras in the Mid-Atlantic Bight. McLain's data (section 20) showed offshore water temperatures in the Mid-Atlantic Bight were up to 4°F. warmer in Jan. -Feb. 1974 than the long term mean. Temperature stations along the southeast U.S. coast show that 1974 was slightly warmer than 1973. Cooling in October-December was more intense in 1974 than in 1973, apparently associated with the northeasterly winds that increased shoreward transport in October. Wind-driven transport off the southeast U.S. coast presented by Ingham (section 14) had a weak eastward component in January and a weak westward component in February 1974. The 10-year mean shows a moderate westward transport during these months. The east-west component of wind-driven trans- port in this season is important for the shoreward transport of larval menhaden 1-2 and it is expected that larval survival in 1974 will be poorer than average. During October 1974 an unusually strong transport to the NNW occurred. This condition should have led to the close approach of oceanic waters to the coast and a strong alongshore northward current along the southeast U.S. coast. In the Gulf of Mexico in Januar/ 1974, coastal waters just west of the Mississippi Delta were set eastward, by wind-driven transport, instead of westward as shown in the 10-year average. There was stronger than average wind-driven transport to the NNW in the central and eastern Gulf in October 1974. There was also a deeper than average penetration of the loop current (Cook and Hausknecht, section 21) in the eastern Gulf during October. 1-3 OVERVIEW OF THE PACIFIC OCEAN, 1974 James H. Johnson Pacific Environmental Group National Marine Fisheries Service Monterey, California June 2-4, 1958 a group of scientists met at Rancho Santa Fe, California in an attempt to explain an extraordinary climatic change in the eastern Pacific Ocean. The unusual warming that occurred in 1957 and 1958, and events associated with it, are described in papers in proceedings of this symposium "The Changing Pacific Ocean in 1957 and 1958" edited by John Isaacs of Scripps Institution of Oceanography and the late Elton Sette of the Bureau of Commercial Fisheries. The papers presented at this meeting indicated clearly that no longer could the Pacific Ocean be thought of as invarient insofar as the environment of fishery resources were concerned; nor no longer could the atmospheric scientists ignore the varying nature of the ocean in both weather pre- diction and climatic change. The following papers concerning the Pacific Ocean deal to a large extent with large scale processes. This is in keeping with comments of Isaacs and Sette in the proceedings of the symposium as follows: "It appears to the Editors that one of the most valuable results of the Symposium is to have pointed out clearly and unequivocally, and from a wide range of evidence, that locally observed changes in ocean condi- tions, marine fauna, fisheries success, weather, etc., are often the demonstrable result of processes acting over vast areas. In the case 2-1 of local Pacific conditions, the changes obviously often are only a part of changes involving the entire North Pacific if not the entire Pacific or the entire planet. "It appears that this realization should emancipate many provincial marine investigations and stimulate much thought and inquiry into these vast and critical events that so profoundly influence the local areas of the Pacific. "This is to say, for example, that a basic understanding and sub- sequent basic forecasting of the fluctuations of a coastal fishery, probably can be best achieved by a thoughtfully limited study of the entire ocean, in addition to concentrated concern with the immediate area of the fishery. " At about this same time, Jim McGary of the Bureau of Commercial Fisheries began publishing sea surface temperature charts of the Pacific Ocean derived from merchant and naval vessel weather reports; in fact, these charts were used at the Symposium to show the degree to which warming had occurred. Publication of these charts was assumed by the Tuna Resources Laboratory, San Diego in 1960 and has since remained in that laboratory and its subsequent organization, the Southwest Fisheries Center. The charts are now published in the monthly publication. Fishing Information , as well as charts showing the subsurface temperature structure across the California Current in a proc|ram supported by the National Marine Fisheries Service, International Decade of Ocean Exploration Program of the National Science Foundation, the Navy's Fleet Numerical Weather Central and the Office of Naval Research. Over the years these 2-2 charts have provided "A Status of the Environment" for the Pacific Ocean, as far as sea temperatures are concerned. It is now time to advance this stage of reporting of the Pacific Ocean environment to another level. This first annual issue of The Environment of the United States Marine Fisheries Resource, 1974 not only will contain information on sea temperatures but also various analyses of environmental processes in 1974, i.e., air-sea interaction, upwelling, and how the changing environment affected fisheries. By the wery nature of the interaction of the atmosphere, ocean and living resources therein, over-lapping of information in papers in this report occurs. A natural starting point in describing the state of the Pacific Ocean in 1974 is to look at the large scale air-sea interactions that took place. Namias and Dickson's paper clearly describe the interaction of ocean and atmosphere over the Pacific. The year was characterized by extreme strength of the mid-latitude westerlies, especially in winter and spring. A reflection of the high index circulation over the Pacific was the large pool of cold sea surface temperature that dominated the area generally to the north of 30°N latitude. This may have been a result of open ocean-upwelling. Generally to the south of 30°N latitude and to the east of Hawaii a warmer pool of water prevailed. These con- ditions over the Pacific Ocean were associated in the upper air circula- tion with a trough development over the western United States and ridging in the eastern section of the country. This led to exceptional winter warmth in the eastern United States. 2-3 The general description of conditions over the Pacific Ocean as a whole as described by Namias and Dickson agrees with the paper by Eber who has summarized the monthly sea surface temperature charts published by the Southwest Fisheries Center. His analysis also shows generally cold conditions over the North Pacific except for somewhat warmer than normal water northeast of Hawaii in the latter part of the year. Johnson, McLain and Nelson have provided a brief description of sea temperatures at "index stations" and also have examined time series at these stations over the past 25 years. At 30 index stations examined north of the equator, 21 were colder in 1974 than the 1948-67 mean, although, when examined in a historical context, the anomalies are relatively small. Their analysis of long term trends at these "index stations" suggest that, in general, over the last quarter of a century the surface waters of the Pacific in northern latitudes have undergone a cooling trend as have the waters off the Central American coast. At the El Nino Symposium at the Eastern Pacific Oceanic Conference, Lake Arrowhead, October 1974, Quinn predicted a minor El Nino in early 1975 based on his studies of variations in atmospheric pressure differences between Darwin and Easter Island which are part of variations in the overall atmospheric circulation commonly called the Southern Oscillation. In his paper Quinn describes the procedure used in reaching his forecast of the El Nino. It would seemingly be a highly unusual event for another El Nino to follow so closely on the heels of the one in 1972-73. Nevertheless, the prediction by Quinn seems to have verified; 2-4 sea surface temperature between the Galapagos Islands and the mainland of South America changed from -6°F anomaly in October 1974 to +6°F anomaly in April 1975. Sea temperature did not change, however, in the area of the large anchoveta fishery off Peru which may be a charac- teristic of certain weak El Ninos. Upwelling may be the most important oceanic and coastal process affecting the abundance and distribution of fishery resources. Scientists have known for years that, in a gross sense, high upwelling areas are endowed with abundant fishery resources. It has been difficult indeed, however, to determine annual variations in upwelling and to relate changes in fish populations to these variations. Bakun has now developed an index of upwelling which he describes in his paper presented- herein and in previous work. His chart of percentiles of upwelling index values suggest that 1974 was a wery strong upwelling year at stations at 36°and 39°N latitude off central California. Conversely, downwelling was especially evident in the general region in the Gulf of Alaska. Whereas most papers described above focused on conditions at the sea surface and in the overlying atmosphere, Saur has examined subsurface temperature structure, as well as surface temperature and salinity data. His observations were collected from "ships of opportunity," mainly along a transect from San Francisco to Hawaii. On most of this track the heat content of the upper 100 meters of the ocean was greater in 1974 than in 1973, except that it was much colder near the California Coast during the sunmer of 1974. These facts show that the surface warm pool northeast of Hawaii mentioned by Namias and Dickson and by 2-5 Eber extended well below the surface, and confirms strong summer upwelling around 36°N latitude suggested by Bakun's upwelling index. From the surface salinity maximum Saur also infers that the center of the Eastern North Pacific Central waters shifted to the northeast in 1974 as compared to 1972 and 1973. The shift was accompanied by lower salinity near Hawaii suggesting greater penetration of California Current Extension waters, and by less well defined boundaries and weaker fronts associated with the Transition Zone, which lies between the Eastern North Pacific Central water and the California Current waters. What then can one say about the relation of living resources to the environment in 1974? At the base of the food chain, that is the production of phyto- plankton, one can infer from Bakun's high upwelling index off Central Ccilifornia in work not yet published, that plankton downstream and some time later was probably high also. Furthermore, this work suggests higher abundance of eggs and larvae of certain fish species. Future reports of The Environment of the United States Marine Fisheries Resource will describe this relationship in some detail. The climatic change of rare proportions that affected the South- eastern Bering Sea region in the early 1970 's caused serious perturba- tions in a number of fisheries including two of the most important species, halibut and salmon. This climatic change is described by McLain and Favorite as a result of persistent northerly winds over the area which are a result of shifts in the upper air circulation. The northerly 2-6 winds caused changes in air and sea temperatures, extent of ice cover, and changes in the abundance and growth of salmon and halibut. Con- ditions in the winter of 1973-74 continued cold, became warmer than normal in summer 1974 and again reverted to very cold in the winter, 1974-75. Laurs describes the early distribution and apparent abundance of the albacore tuna in relation to Transition Zone waters and associated oceanic fronts. The Transition Zone is defined as a region of mixing in the mid-latitudes between low salinity subarctic waters to the north and warm, saline subtropic waters to the south. In June of 1974 the frontal structure in the Transition Zone was more diffuse than at the same time the previous two years; consequently, in 1974 the early season albacore catches were more scattered than in 1972 and 1973. Miller has examined the 1974 purse seine fishery in the eastern tropical tuna fisheries in relation to sea surface temperatures. In 1974 nearly 86% of all successful purse seine sets occurred in water with surface temperature between 79°F and 84°F. Less than 10% successful sets were in water temperature less than 79°F and 4% in water temperature greater than 85°F. This agrees well with findings of others who have studied purse seining success in relation to sea surface temperatures. He points out that studies to the present time have not found significant relationships between sea surface temperatures and abundance of yellowfin tuna in selected areas of the eastern tropical Pacific. Although Berkley's paper does not specifically pertain to 1974, it is of such fundamental importance to understanding the distribution of skipjack that it is included here. Experiments carried out at the 2-7 Southwest Fishery Center, Honolulu Laboratory, suggest that skipjack should inhabit water with oxygen content in excess of 3.5 mil/liter and temperatures between about 18°C and an upper limit for their size and activity. Thus the oxygen requirement appears to be limiting the maximum habitat depth in the equatorial Pacific Ocean, whereas, in higher latitudes, low temperature appears to be the limiting feature. He points out that location and extent of areas unfavorable for skip- jack probably vary with season and from year to year depending upon mixing and advection and thus winds and currents. 2-8 Atmospheric climatology and its effect on sea surface temperature . Jerome Namias* and Robert R. Dickson** In 1974, the atmospheric circulation over the Pacific, North American and Atlantic sectors showed certain major abnormalities peculiar to that year, yet retained other characteristics which were in keeping with the established trends of recent climatic change. The mean annual distributions of 700 mb height and its anomaly (Fig. 3.1) show that the year as a whole was charac- terized by extreme strength of the mid-latitude westerlies over a broad belt of the northern hemisphere from the west Pacific to the east Atlantic. In both oceans the subpolar lows were intense (mean annual 700 mb heights 90-110 feet lower than normal) , and these cells were coupled with sub- tropical anticyclones of almost equal intensity (mean annual 700 mb heights 70-100 feet higher than normal) . This parallel increase in the vigour of the North Pacific and North Atlantic oscillations, and the high index circulation which resulted over both oceans, led to predominantly mild conditions over North America and Europe. In eastern North America this mild- ness was partly a direct result of the warm, moist southerly *Scripps Institution of Oceanography, La Jolla, California **M.A.F.F. Fisheries Laboratory, Lowestoft, Suffolk, England, (On leave as Visiting Scientist at Scripps Institution of Oceanography, La Jolla, California) 3-1 airstream circulating around the western flank of the strength- ened Bermuda High, but more generally to the rather "flat" circulation which prevailed over North America precluding deep penetration of the U.S. by cold Canadian air masses. This weakening of the zonal flow shown in the mean annual circulation over North America is at least partly attributable to the effect of the Continental Divide operating on the strong Pacific westerlies . The mean annual distribution of Pacific sea surface temperature (SST) anomaly (Fig. 3.2) was the expected reflection of the high index circulation in that sector. Across the northern North Pacific, in the domain occupied by the strengthened Aleutian Low, a broad belt of abnormally cold water with a core anomaly of <-1.7°F under- lay the area of enhanced westerlies, cyclonicity, cold-frontal activity and Ekman divergence with open-ocean upwelling. To the south a zonal pool of warm water with temperature anomalies in excess of +1.1°F reflected the light winds, clear skies and horizontal oceanic convergence associated with the intensified subtropical high, though norther lies running along the eastern flank of this cell maintained cooler conditions locally along the North American seaboard. While equivalent data are not yet readily accessible for the Atlantic as a whole, the available SST data for the western Atlantic (U.S. Naval Oceanographic Office, 1973-74) show a rather uncomplicated development throughout 1974, readily explicable in the light of the dominant circulation anomaly in that area. Seasonal variations will be discussed more fully below, but the 3-2 seasonal charts of SST anomaly distribution shown in Fig. 3.3a, b, c and d indicate that abnormally warm water conditions pre- vailed throughout the year in the Atlantic west of 55 °W. Again the cause is attributed to the warm southerly anomaly wind prevailing along the western flank of the strengthened Bermuda High, lessening the transfer of sensible and latent heat from the ocean, while the anticyclonic cell itself was positioned to minimize the deep out-breaks of polar continental air from North America to the western Atlantic during the cold season. Needless to say, this interpretation of "mean annual" charts provides a deceptively simple impression of climatic developments in ocean and atmosphere. This approach has a validity in indicating the dominant residual climatic controls at work in a particular year but will conceal the existence of seasonal or monthly variations which may run counter to the overall climatic trend. Equally it ignores the influence of antecedent conditions which may be of great importance in under- standing the development of temperature variations in the ocean. To give one example, the cold surface temperature conditions in the west and northwest Pacific became established as early as the December 1972 and indeed Wagner (1975) pointed out that 1974 was the fourth consecutive year in which the winter atmospheric circulation was stronger than normal over most of the western half of the Northern Hemisphere. These antecedent trends of change are discussed more fully below. As regards seasonal variations within 1974, Fig. 3.4 {from Wagner, op. cit.) shows that while the mid-latitude westerlies 3-3 were generally strong throughout 1974 the strongest zonal index was principally a feature of winter and spring with an absolute maximum in February. In that month they represented "the strongest mean westerlies between 35°N and 55°N over the Western Hemisphere for any February since tabulations began in 1949. It was the second highest monthly mean mid-latitude westerly zonal index (13.3 m/s) of record - only January 1972 had stronger westerlies (13.9 m/s). At their peak near 43°N the westerlies averaged 6 m/s above normal" (Wagner, op. cit. p. 29). As in- dicated in Fig. 3.4, westerlies 5 m/s stronger than normal persisted through April and May, and even in summer and fall mean windspeeds 2 m/s in excess of normal were rather commonly observed. The seasonal mean distributions of 700 mb height anomaly for winter and spring (Fig. 3.3a and b) confirm the extreme strength of westerlies in these seasons, but provide additional information on their geographical distribution and on the timing of peak zonal wind strength. It is clear that the enhanced westerlies were chiefly a feature of the ocean areas, and although, on a "Western Hemisphere" average, they reached maximum intensity in February, they attained (on aggregate) a seasonal maximum in winter over the western Atlantic but in spring over the eastern Pacific. In winter the anomalous north-south height difference in the 700 mb surface at 55°W was in excess of 330 feet (-170 to +160 feet) , while in spring the peak anomaly in the meridional direction exceeded 300 feet (-220 to +80) in the eastern Pacific (at 150°-170°W). The seasonal distributions of 3-4 SST anomaly, also shown in Fig. 3.3a and b, reflect these differ- ences in the timing of maximum zonality over the two oceans. Under the western flank of the intense Bermuda High, surface temperatures reached a peak seasonal mean value of +5.1°F in winter, and temperature anomalies in excess of +2°F were more widespread along the Atlantic Coast than at any other season of 1974. In the eastern Pacific sea surface temperature anomalies became organized into a more extreme zonal distribution as the westerlies strengthened from winter to their maximum in spring . In summer (Fig. 3.3c) events in the western Atlantic were dominated by the partial collapse of the Bermuda anticyclone and by the lowering of positive SST anomalies which resulted. In the eastern Pacific, however, the situation was much more complex and the seasonal distributions of SST and 700 mb height shown in Fig. 3.3c were overwhelmingly a reflection of an extremely abnormal development in the month of July. In that month the sudden intensification of a trough off the coasts of Oregon and British Columbia was accompanied by a major amplification of a ridge centered to the north and east of Hawaii. These cells represented anomalies in the 700 mb sur- face of 1.7 and 3.1 standard deviations respectively. The seasonal distribution of 700 mb height shown in Fig. 3.3c pro- vides only a week reflection of this development, but its effect is perhaps more clearly reflected in the seasonal distribution of SST anomaly. Along the maximum pressure gradient a family of storms was guided in to the Pacific West Coast at a southerly latitude (40-45°N) where storms are rarely observed in mid-summer (see Anon, 1975 Fig. 37) bringing 1-2" 3-5 of rain to areas which are usually practically rainless at that time of year. In his statistical analysis of the principal tracks and mean frequencies of storms in the northern hemisphere, Klein (1957) showed that during 40 Julys, 1899-1938, there was a total of only one to three days when a low pressure center of any type was encountered at these latitudes on the west coast, since the area is normally dominated by the summer expansion of the North Pacific subtropical anticyclone. The effect of this series of storms on Pacific surface temperature was striking, with an anomaly of -4°F developing rapidly along their track (see Eber and Miller, 1974, Fig. 3.5), and this "corridor" of cooling was sufficiently intense to dominate the seasonal distribution of SST anomaly, (Fig. 3.3c). The factors which gave rise to the unusual circulation of July are unexplained but are certainly complex. While the cold sea surface temperatures in the northeastern Pacific in ante- cedent months (Fig. 3.3b) may have been (to some extent) effective in bringing about a hydrostatic deflation of the over- lying air column, and hence may have played some part in deepening the offshore trough in that area, it is likely that remote influences also played a major, perhaps even the dominant, role in causing the intensification of this cell. A rapid amplification of a trough off Asia (along 165°E) was also observed in July and this event may be expected to have had some effect on the development of an augmented ridge to its east and a trough in the eastern Pacific. However that may be, this cir- culation itself had a more than local importance in that a 3-6 falling away of pressure in the eastern Pacific in summer and a relative tendency towards ridging in mid Pacific is charac- teristically associated with a drought-producing circulation over the U.S. This case proved to be no exception, and re- sulted in the "worst heat wave and drought since the 'Dust Bowl' summers of the 1930 's" at many localities in the northern and central Great Plains, (Wagner, op. cit. p. 33). Drought conditions were subsequently relieved in August as the mid-latitude atmospheric circulation of the Western Hemisphere showed an almost complete reversal from that of July. This in itself is a rather unusual event serving to underline the anomalous nature of the July circulation; Namias (1952, p. 281) showed that over North America the month- to-month persistence of climatic anomalies is normally near its peak between July and August. This reversal of the circulation in August resulted in the domination of the north eastern Pacific by a high pressure anomaly cell which maintained its identity into the fall (Fig. 3.3d). As might be expected the southerly airflow, clear skies and light winds associated with this cell encouraged the spread of relatively warm water northwards into the Gulf of Alaska. The complete change in circulation patterns between summer and fall (cf. Figs. 3.3c and d) brought an extensive meridional trough to northeast Canada in place of the pre-exist- ing ridge. Enhanced northerly airflow between this cell and the newly-formed ridge over the west coast brought cooling to the entire North American continent east of the Rockies during fall. Wagner (op. cit. p. 34) showed that September, with 3-7 temperatures as much as 10 °F below normal over Texas, was also the coldest of record at several cities in the southern and central Great Plains and Mississippi Valley. Although in the seasonal average, this enhanced northerly airflow was directed from the Arctic towards the Atlantic coast states, the trough was not of sufficient meridional extent to produce extensive cooling in the already-warm surface waters of the west Atlantic. Instead, with the southern flank of this trough lying along the Canadian Maritime Coast and with a restrengthening Bermuda High offshore, an intensified southerly airflow brought re- newed warming to the Western Atlantic; colder-than-normal sea surface temperatures were limited to a restricted area in New York Bight where the northerly airflow from the Canadian Arctic retained some effectiveness. As mentioned earlier, a full understanding of the evolution of the ocean surface temperature distribution relies partly on a knowledge of antecedent atmospheric and oceanic conditions, and it is the purpose of this final section to set these 1974 observations into the context of longer-term climatic change. In Figure 3.5 the mean SST anomalies in zonal bands of 5° x 5° squares running offshore from the west and east coasts of North America have been plotted for each month of the period January 1969 to November/December 1974, and the resulting "sections" of SST anomaly versus time have been contoured at 2°F intervals. Cooler than normal surface temperatures are shown by cross- hatching, and the core values of anomaly are plotted on each section. 3-8 The SST anomaly section for the Pacific captures the major changeover in SST pattern which occurred between the 1960 's and 1970 's already by Namias (1972). Prior to 1971, SST anomaly patterns (especially in winter) were characterized by anom- alously warm water off the west coast of the United States and cold water in the Central Pacific, but subsequent winters have tended to show the opposite pattern with cold water off the west coast and warm water further offshore. Thus abnormally cold surface temperature conditions were already present in the northeast Pacific prior to 1974 and the cold conditions observed throughout the section in 1974 represent merely a reinforcement of earlier cold conditions by the strongly zonal circulation in that year. This major changeover in the SST patterns of the eastern Pacific was accompanied by, and is thought to have assisted in the development of, a major break in the atmosphere cir- culation over continental North America such that a stronger- than-normal ridge in the long wave over western North America and an intensified trough over the east were replaced by a circulation of the opposite tendency, most noteably in V7inter. (The reverse circulation change had in fact occurred in the winter of 1957-58 so that the changeover in 1971-72 represented merely a revision to the characteristic winter circulation pattern of the period 1948-57) . In the specific area of the Atlantic seaboard the circulation change after 1971 (with a weakening of the pre-existing trough over eastern North America and a strengthening of the Bermuda High) led to conditions of exceptional winter warmth, and indeed the SST anomaly section 3-9 for the Atlantic shown in Figure 3.5 reflects this change in showing a general warming of the ocean surface along the Atlantic coast in winters subsequent to 1971. Thus the warm conditions prevailing offshore throughout 1974 were also based partly on antecedent warm conditions, though the ex- ceptional strength of the Bermuda anticyclone from the fall of 1973 produced an exaggerated development of this general warming trend. 3-10 ACKNOWLEDGMENTS Our thanks go to Ms. Madge Sullivan for computational assistance, to Mrs. Keiko Akutagawa for drafting and Miss Carolyn Heintskill for typing the manuscript. All are employed at Scripps Institution of Oceanography. Part of this research was sponsored by the National Science Foundation Office of the Decade for Ocean Exploration and the Office of Naval Research as part of the North Pacific Experiment under National Science Foundation Contract No. ID074-24592, Office of Naval Research Contract No. N000-14-75-C-0260, and the University of California, San Diego, Scripps Institution of Oceanography through NORPAX . 3-11 REFERENCES Anon, 1975. "Smooth log, North Pacific weather, July and August 1974". Mariners Weather Log 19_ (1): 36-49. Eber, L. and Miller, F., 1974. "Sea surface temperature and environmental conditions". NOAA/NMFS Fishing In- formation (7) : 1+9 Fig. Klein, W. H. , 1957. "Principal tracks and mean frequencies of cyclones and anticyclones in the Northern Hemisphere". U. S. Dept. of Conmierce. Weather Bureau Res. Paper No . 4 0, 60 pp . Namias, J., 1952. "The annual course of month-to-month per- sistence in climatic anomalies". Bull. Amer. Meteor. Soc. 32 (7) : 279-285. , J., 1972. "Experiments in objectively predicting some atmospheric and oceanic variables for the winter of 1971- 72. J. Applied Meteor. IJ^ (8): 1164-1174. U. S. Naval Oceanographic Office, 197 3-74. "Monthly Summaries December 1973 - November 1974". The Gulf Stream, 8_ (12) - 9 (11). Wagner, A. J., 1975. "The circulation and weather of 1974". Weatherwise 28 (1): 26-35. 3-12 1974 MEAN ANNUAL TOOmb HEIGHT AND ITS ANOMALY (FEET- 10) Figure 3.1 Mean annual distribution of 700 mb height and its anomaly, 1974, (Feet i 10) o M-l o CO > S-i 0) ■u c to TJ ?^J*^^^^^^"^^^^*y J>\^ \ 1 ^v^ ^r^y ■*■ ^^^=^'3^ \. ' ' \f'^ ' ^^V^ ^T\ ^^^T^ yv\ I'W fc^^^WV^^/C^^iL^' - ' ' 1 "" -^ ^J&s?''^Tp^^ I ■ ^'^ y< 1-^ f^-^/^S:"'? '^^S i: '\ +rf M ^^ r^W+Fah?^ s^:^K^?l^^ jp^^TR \^^* *^r%'^ , • .rT^.7*w\V\ V ^~~^ x^^^^V^- ■ '^3^ ^^^J^^I^vsX^^A. '^ ^^^^^t^P5^^, AK,/S- 1 ^^^^-^r^/T^C JAcn \ ,^-' ^. \ i— ' A^>S*^? '^^ N#/ , / ^ X -J i—A"" '"W^C>' )<■■■/ / < ■ 1- L Li_ J-i ■o o 01 4-1 x: ^s TJ o -Q >. H 4J S^ 1—1 r— 1 CO CO o Si 5-1 e CO 1 01 o CO 4.) c U CO C CO — ^ CO IH i4 >. O CO o 1—4 C 1—1 CO CO o e c •1^ U-l o o i-> o G m 3 ^ CO ^ to 01 •H I-l H w !-i CO CA) 4-) > C/3 c •r-( j-i 1—1 •1-1 4-1 o CO CO M-l c 4J bO o CO 0) y<-^ to C o CO TD rH OJ OJ M-l CO ^ O I* 3 C O CO JJ CO 4J CO OJ 0» C OJ OJ s o u M-( < ■TJ >. y^N c c 1—1 CO [5 CO CO (U O E c X ♦> o •H CO T3 c I— 1 (U CO o 1—1 T3 CO a, w •r-* I-l a, x: 1—1 CO •1-4 Ml o 4J •1-1 CO •1-1 -d 4J >. o ••.^ C 1—4 o CO CO r^ •H T) •r-l V4 s_x -n 4-1 4J C •1-4 CO -a CO CO •1-1 C o TJ CO o •1-1 a. c V4 14-1 C4-I CO OJ •1-1 O 0) g o S g CO CO 3 p-l CO CO 01 c u CO ^-s M < • u ^ 4J CO m cu oc CO x-v u c (U CO 3 •1-1 cu bO >^ 01 c •1-4 a j= •H P^ CO 4J 1-4 IT) lo o LO o m 00 1^ l\ O ^O IT) H — h- 1 — I 1 h I M CO H — f- m IT) o Lo o Lo 00 f\ F\ ^ vO LO * o in LO o LO o LO CN •HE CO E o n cu Qi O O U ffi CO >^:s C "-I I-" ^H J-l >. CO oj oj XI E iz; CO CO 03 O , c v_^ ^J 1—1 -r-l QJ ^-1 --I > i 00 0) >— 1 OJ J= >-< JH TJ -U > d 01 O <-< 4J TJ 4J ^ M 3 C 0) CO 1— 1 ■U O -U CL •H U CO (U JJ OJ TJ CO -n [3 t— 1 -H 4J ■-I E CO C O 3 cu 1— 1 CO 0^ O O X o >-< < O IS 4J O o :s }-4 C -U 13 01 CO -^N o C oj 00 CO X ao E r>- "^ CO CO S c^ E IS >^r-l w CO ■-I C E x; !-< TJ bO O 4J 01 C -r-l !-l C ^ -H CO Pl< O E ^ E Qj x: CJ U 4J . Uh M-l 0) -H T-l CO o Q x: 5 oj a c C E O CO -H O O V) }-i r-l •t-l M 4J 0) 4J 14-1 CO J3 13 CO O E OJ »— » •r-i /-\ Q) 3 X! ^^ S bO IS CO coiD CO > O C XI (» CO • r-i tU >, >, I E --^ -Q /-\ TJ CO ^-^ O -H 01 4J 4J (U (U -U CJ U M ^ C OJ (U 3 OJ (U Oi C oox: c CO c •H a o Qj o [X4 CO a. v^ u WEST LONGITUDE 155° 150° 145° 140° 135° 130° 125° JAN. 1969 JAN. 1970 JAN 1971 JAN 1972 JAN. - 1973 JAN. - 1974 JAN WEST LONGITUDE 8 0° 75° 70° 65° 60 ° 55° JAN 1969 f- JAN 1970 JAN. 1971 - JAN. 1972 JAN. 1973 - JAN. 1974 -JAN. Figure 3,5 Temperature "sections" for zonal bands of 5° x 5° squares running offshore from the west and east coasts of North America. In each section the mean SST anomalies for each 5° x 5° square have been plotted for each month of the period January 1969 to November/December 1974, and are contoured at inter- vals of 2°F. Areas of negative SST anomaly are shown by cross-hatching and the core values of anomalies are plotted on each section. A location chart is also shown. CLIMATIC CHANGE IN THE PACIFIC OCEAN James H. Johnson, Douglas R. McLain and Craig S. Nelson Pacific Environmental Group, NMFS INTRODUCTION Over the past fifteen years the National Marine Fisheries Service and its predecessor the Bureau of Commercial Fisheries have published sea surface temperature and anomaly charts of the Pacific Ocean. These charts have been used by the fishing industry in development of fishing strategy (Felando 1966), by marine scientists studying changes in distribution of marine resources (Laurs 1975) and by those studying large scale air-sea interactions in relation to long range weather forecasting (Namias 1972; Quinn 1972). It is becoming increasingly clear that some fish populations may respond not only to short term changes in the environment, but also to long term climatic change. As a complement to the ongoing effort of the publication of sea temperature charts, this report and ensuing annual reports of "The Environment of the United States Living Marine Resources" will examine climatic changes for use in fisheries research and other related studies. This study provides time series of sea surface temperature for 33 selected 5° blocks of latitude and longitude in the Pacific Ocean (Figure 4.1) where abundant observations of sea surface temperature are available historically. The blocks are identified in this report LU I — I <: uj Q cc Q 00 in I— I q; H- q: <: LU s LU 2: h— ;2: o LU 1— < ^ 2: I— d; I — 1 » n LU O 00 oo :z I— ^ cC ct q; q; LU o Q ni h- >< I— cC ID ID O Z LU o o !— q: o LU CO CQ •-< 2: 2: o ZD LU I— I 2: CQ I— O O _i LU • O 00 <: LU LU LU :n h- o t- 2: o h-. Ll. C_) O LU »— ' in u- to I— I — I fy 'O LU I— «C i — eg; < 00 " ID LU 00 crtD ^ ^ o a: <=c "-< ID m (— o o <: Li- I— LU 00 LU O IC s X I— LU LU ID s: o LU t— I Lt_ 00 LU o 4-2 by Marsden Square number and quadrant of the Marsden Square and are referred to as "index stations." Since most such observations were made by merchant or naval vessels, the index stations generally lie along shipping routes. Also included is a composite of 5° blocks showing the trend in sea surface temperatures over the entire North Pacific for summers, winters and annually. DATA SOURCES AND PROCESSING The time series of sea surface temperature were derived from weather reports from merchant, naval, and other ships of many nations. Several files of such reports were used to develop the series. A historical file of reports covering the period 1854 to June 1968 was obtained by Fleet Numerical Weather Central from the National Climatic Center. An update to this file was subsequently obtained by the North Pacific Experiment (NORPAX) Project at Scripps Institution of Ocean- ography and included reports to December 1972. These files were merged, sorted by 1° blocks, duplicate reports eliminated, and monthly means of all reports of sea surface temperature in the selected 5° blocks developed. Weather reports received in "real-time" by Fleet Numerical Weather Central by teletype were used to update the series through 1974. Monthly means of these reports were made for the period November 1971 to December 1974. These means were used during 1973 and 1974 4-3 and occasionally during November 1971 to December 1972 whenever more real-time reports were available than were available from the historical files. Various sources of errors associated with the means of sea surface temperature are as follows: 1) Due to the need for ships to avoid areas of bad weather, the original observations are biased towards fair weather conditions. This bias has become more important in recent years as marine weather report- ing, forecasting, and optimum track ship routing have improved. 2) The observations are not randomly distributed over large ocean areas but instead are concentrated along various shipping lanes. Thus observations are much more dense off Japan and California than in in- frequently traveled portions of the South Pacific Ocean. Also the data are biased due to varying distribution of observations in time and space within each 5 degree block. This error may be particularly significant where the sea surface temperature changes rapidly in time or space. 3) Most of the observations of sea surface temperature are "injection temperature," that is, they are made with a thermometer in the ship's main cooling water intake. Thus they are subject to instru- ment calibration error and to warming of the intake water in the engine room. Saur (1963) studied these errors and found that the injection temperatures in the class of ships he studied averaged about 1.2°F higher than surface water temperatures taken by a bucket thermometer. 4-4 All reports of sea surface temperature were edited by a two stage editing technique prior to development of the 5° block means. The first stage of editing rejected all observations that were less than -2.0°C or greater than +40.0°C to eliminate obviously erroneous values. The second stage of editing differed slightly for the historical and real time data. For the historical data, running means of 10 reports were main- tained for each of the 12 months and each report was compared with the appropriate running mean. Values greater than 9°C from the running mean were rejected. Because the data had been sorted in the sequence: 1 degree block, year, and month, the running mean contained only observations for the month in question and at worst observations from several previous years. The running means were restarted for each new 1 degree block using the 10 earliest reports available (starting as early as 1854). Monthly means were computed by 5° blocks from the accepted reports, and from these a 20-year (1948-1967) mean computed for use in editing of real time reports and for use in computation of anomalies. Generally there were 19 or 20 years of data in the 1948-67 mean. The lowest number of years represented at any one index station was 14 at station 195-3. In editing of real time reports, values greater than 10°C from the 1948-67 mean were rejected. The monthly means were stored on a summary data tape from which the time series plots were made. Though data are available at some stations back to 1854, some of the early 4-5 reports may be of questionable accuracy. In addition, the early data were sparse and at most stations insufficient for analysis until about 1948 and 1949. Time series were prepared, therefore, only for the period 1948 or 1949 to 1974. Marine organisms may be most sensitive at the extremes of temperature ranges, that is, to extreme cold and warm temperatures. To detect these extremes of temperatures, we present time series not only as annual means but also as winter (January, February and March) and summer (July, August, and September) means. (See Appendix I for time series plots) . DISCUSSION A. Method used to calculate trends Non-random variations in time series of sea surface temperature take the form of periodic or aperiodic fluctuations, persistence, trend, or a combination of these. Seasonal periodicities are evident in the time series of sea surface temperatures throughout most of the north Pacific. However, these data also indicate significant longer term climatic trends which appear to be coherent over large areas. Alth'ough there is no reason to believe that trends in climato- logical time series are linear (Mitchell et al. 1966), a test for trend against randomness may provide an approximation of the warming or cooling indicated by the data. Results from this analysis specifically apply to the 27-year data record from 1948 to 1974. We have not attempted to resolve shorter 4-6 term fluctuations which may be evident in the data, nor do we imply that these results can be extrapolated in time. It is probable, however, that significant climatic changes, such as the recent pro- nounced cooling trend in the Gulf of Alaska, have important long term effects on the biota. An analysis of trend against randomness was considered for time series of monthly mean sea surface temperature summarized by five degree blocks for the 27 years from 1948 to 1974. Missing data were filled with appropriate 20-year (1948-1967) long term monthly means. Time series containing more than 3 years (36 months) of missing data were not considered in the trend analysis, which was applied to time series of annual means, winter means, and summer means computed from the monthly mean data. Linear trends for the 27 year time series (annual, winter, summer) were computed in the least squares sense as described by Bendat and Ptersol (1971, p. 291). The slope of the regression line was considered to be a first order approximation of the magnitude of the warming or cooling tendency. A Mann-Kendall rank statistic (Mann 1945; Kendall 1948) was computed for each time series. The sign and magnitude of the computed rank statistic indicates the sign and magnitude of the trend. Comparison of the computed statistic with a Gaussian (normal) distribution substantiates the presence of (linear or non-linear) trend in the data, or indicates that the data series is random. 4-7 B. General areas of most highly significant trends The most significant trends over large areas in the north- east Pacific appear particularly in the Gulf of Alaska (Marsden squares 194, 195, 196 and 197) and off the coast of Mexico (Marsden squares 47, 48) (Figure 4.2, 4.3, and 4.4). The cooling trends of approximately 0.02°C/year to 0.03°C/year are significant at the 95% level. This tendency may be partially attributed to significant cooling during the summer quarter (July, August, September). In the Western Pacific (parts of Marsden squares 129, 130, 162, 163, 164), warming trends of approximately 0.02°C/year are significant at the 90% level. This climatic change can be partially attributed to warming during the winter quarter (January, February, March). C. Trends at selected index stations 1 . Northeast Pacific The most significant trends at specific index stations in the northeast Pacific are in the most northern latitudes. At index station 195-3 the annual mean ranged from nearly 10°C at the time of the "warm" 1957-58 years in the eastern Pacific to about 7°C in the early 1970 's. The maximum anomaly of +2.7°C appears in the summer of 1957. In the region of the Aleutian Islands, index stations 197-1 and 198-1 show clearly the yery cold anomalies in the early 1970's. Response of the Alaskan salmon and other fisheries to this climatic shift is explained elsewhere in this volume (McLain and Favorite 1975). 4-8 Q »> ^ P" LU ■=c £>: UJ 1— o o o ^ <_J 1 — 1 1 — 1 ^ Ll_ o 1 — 1 o C_) CJ ■21 oo LU LU • OC O iz 1— ^Z C_) 12 z^ >- Z:^ CQ OO «3: i^ «< C_) ^ ^ o 1 — 1 r>- _i CTi CQ C/1 r— Ci 1 i^ ■pr. CO C_) LiJ '^ <=t q; en _l 1— ■"" CQ (NJ •d- LU or 13 CD 4-9 LU \— O O CD CJ) I— I ►-( _J Ui- o •-^ o C_) o ■< D_ CO LU LU H- ct: o •=3: Q LlJ O) D- i^ 2: O LU O (— —1 cc LU O Q ct LU u- x: q; o rD t— tn -i LU uo ca: z >- 2: >:d- o t— I r^ _j h- oo cc cC ~ LU C/1 CO C/1 O Li_ oc:. o o Q CO LU LU . ci: O i^ H- ^ o — H LU LD ea: :d cQ oo CO :^ CO r— Q I ^:i 2: 00 cj LU 'ci- . ■ \ 1 1966 27.8 .2 68"6 1967 28.2 .5 531 1968 27.8 .2 593 1969 28.2 .6 5-3 1970 28.5 .9 338 .... 1971 28.0 .4 Z-'-J 1972 27.8 .7 1053 1973 28.2 .6 834 1974 27.7 .1 9:'9 ; i : 1 ^ ( 5> ) JflNFEBMnR JUlRUGSEP QTR VALUE RNOMRLY r3S -5 5 10 15 20 25 30 35 [ -4-3-2-1 e I 2 3 4 1 194803 29.0 194903 29.7 195003 29. 1 195103 28.4 195203 29.0 195303 28.7 195403 29.3 195503 28.3_ 195603 28. 1 '95703 28.6 195803 28.7 195903 29.0 196203 29.4 196303 29.2 196403 28.9 iiili— tl- 196703 29.4 196603 29.3 196903 29.7 mm 23.5 .1 28 .7 3b ..1 29..,. -.5 U .1 52 -.3 2:1 .4 135< _ -..6 _2i?> -.8 631 -.3 7:3 -.2 1123 .0 12-1 - _-^l_.._l,3S.4.,_ .5 3l2 .4 Al .3 39 -.1 I0-6 -.3 1.53i,_ . ! 17.>8 .5 'ZZ .4 134 .8 U-.3 .6 1?5 1 i 1 ^ ^r ^ 1 1 1 i 1 i ( <- ^ i I i \ <' 1 ) ; 1 ^ \ 197103 29.5 197203 28.8 197303 29.3 197403 28.9 .6 3b -. 1 335 .4 2:? -.0 235 i : 5^ ) MSQ 83-2 YEAR VALUE flNOMRLY C3S YERR 5" -2 10 -1 15 20 25 2 30 3 35 1946 1949 ._i950__ 1951 1952 1253 1954 25.7 25.5 25.9 25.9 26.0 25.9 -.1 2"1 -.4 937 -..1 . 132/l_ -.0 13^2 ... 1955 24.7 -1.1 1956 26.1 .2 1957 26.3 .5 1958 26.9 1.1 1959 26.7 .9 ...iS60_ 25.6 __-,3._ 1961 26.0 .1 1962 25.9 -.0 1963 26.4 .5 1964 25.1 -.8 19E5 25. 6 -.3 1966 25 8 - 1 1967 25.6 -.3 1968 25.6 -.3 19C9 25.5 -.4 _.J97L. 25.3 . r..5 19/1 25.0 -.8 1972 26.1 .3 1973 25.1 -.8 1974 25.2 -.7 1832 17^0 1833 1955 25^5 2853 333u 3536 3254 3333 2735 3033 2J37 '25^0 2'Zm 27 dH 2/^1 2'=3.: ;h:7 1633 1S12 i':5v .jnNrEBMRR QTR VALUE RNOHRLY C3S 194801 22.6 -.6 .7 194901 23.0 -.1 ?.,'' J19500.L^ 195101 22.7 -.5 29:' 23.2 -.0 •3 ->'J 195201 24.0 .8 3^:-i 195301 23.4 .2 m 19G401 23.6 .4 1 d'Z 13550 1__ 2J.^e -:1.3 . 459 195601 22.5 -.5 5H 195701 23.7 .5 b5j 195801 24.8 1.6 ^^q 195901 24.2 1.0 =11.^ A5600L.. ^i.0. -.1 e-"-; 19G101 23.4 .2 R-'' 196201 22.9 -.3 81/ 196301 23.2 .1 r;.^ 196401 22.8 -.4 If?. 19651L._ _22J„ -.9 Rl'i 196601 23.6 .4 7^^ 196701 22.7 -.5 S^H 196801 23.4 .2 B^f! 198901 23.5 .3 R■^9 15700 L. 23.0 .. -_>_2. _D4iH 197101 22.0 -1.1 197201 22.9 -.3 3-.:i 197301 24.0 .8 :-ti4 1P7401 21.7 -1.5 -(^^v JU:_RIjGSEP 186203 196303 1964B3 |i9fi503_ M96603 196703 196803 196903 19Z0II3 1971B3 197203 1S7303 197403 26. 6 .1 29.4 .8 27.9 -.8 2fl^ -.n 28.1 -.5 28.0 -.7 27.9 -.7 28.0 -.7 28.0 -J 27.7 -KB 28.7 .0 27.1 -1.6 MSQ 87-3 YERR JRNKEPMRR QTP VRLUE RNOCIRLY CIS 194601 INSUF DflTn 194901 19.4 -.7 233 JS5001.. _ 20_..1__ -.0 153 195101 20.2 .1 33'^ 195201 19.8 -.3 23i 195301 19.5 -.6 338 195401 19.9 -.? 3--)? JL95501_. A3...-L. -.4 338 195601 20.0 -.1 334 195701 20.0 -.1 J-1 195801 20.0 -.1 5.'8 1S5901 20.8 .7 4 '3 198001 20.2 .2 .i3b_... 196101 20.2 .1 t6/ 196201 20.1 .0 5:7 196301 20.5 .4 5.S 196401 20.6 • .5 537 196501 _20,.4 ._ ..4__ 630 196601 19.8 -.5 7^7 196701 20.4 .3 I'.o 198801 20.7 .b 03' 196961 20.5 .4 7"! JIS7ML_. _._20^0 _. _-a . 933 197101 20.0 -.1 6CP 197201 19.5 -.5 S.'ti 197301 19.6 ~. 5 5~1;' 197401 20.3 .2 331 JUi.nUGSEP MSQ 89-1 YERR YERR VALUE ANOMflLY C 33 1948 1949 -J95JL 1951 1952 1953 1954 ..1S55 1956 1957 1958 1959 1961 1961 1962 1963 1964 _.iafi5_ 1966 1967 1968 1969 _ja70_. 1971 1972 1973 1974 INSUF DRTfl 24.8 _25.L 25.6 25.0 25.4 25.3 25.3 25.4 25.0 25.6 4_ 25.6 25.4 25.3 25.3 .2&.3_ 25.6 25.8 26.1 25.6 .25,J_ 25.4 25.2 25.0 25.7 -.5 1039 -.? 4il .3 ^ '4-7' -.3 657 .1 75S --1 359 -.B 931 -.0 10:0 .1 1^.4 -.3 1256 .3 1439 .1 _ \Z-i. .3 153& .^ 1730 .0 16-:5 -.0 lbi9 .fi 2137 .? Z/'T^K .5 27215 .8 303h .3 25 J 1 .0 24-2^ . 1 17:5 -.1 16il -.3 1132 .4 1035 JR^JFEBiIRR QTR VALUE RNOriflLY C'JS ,^ 61 5 10 3 -? -: 15 20 25 30 35 1 I 2 3 L \ 194801 23.7 194901 23.3 1S5001 23^5_ 195101 23.7 195201 23.9' 195301 24.1 195401 23.8 1S5501_ .__2a._5_ 195601 24.3 195701 23.9 195801 23.5 195901 23.7 ASM0L„_2a.._8__ 196101 24.5 196201 24.1 196301 24.0 196401 24.2 1 9650 L. 25.8 196601 24.0 196701 24.2 196801 24.1 196901 24.2 19Z001_ 24.0 _ 197101 23.8 197201 23.6 197301 23.4 197401 24.4 -.2 a? -.6 2^8 i „ -.4 \m .,. _ -.1 1:5 -.0 1>1 .2 223 -.0 2i6 1 .4 211^ ; ^ -.0 3.3^ ■ -.K d:2 1 -. 1 235 I _^.-.ja 32i L , .7 4'-<3 ; 1 .2 489 .1 336 .4 4S4 .._-.j_. . 5:"? J . 1 RS-*. .3 751 .2 928 . 4 727 A 833 i -. 1 523 -.3 339 1 -.4 334 .6 357 1 1 , i-- .'; 4:4 K-->. 3:0 2''0 5 -2 10 -1 15 20 1 25 2 30 3 35 4 MSQ 90-1 YERR VRLUE FINOMPLY C3S -3 YERR " 5" -2 10 -1 15 20 1 25 2 30 3 35 4 :.948 IN3UF DflTfl 1949 25.2 1 950 25.6 1951 25.7 1952 25.8 1953 25.9 1954 25.5 .1^5 a5^2_ 1956 25.5 1957 25.7 1958 25.2 1959 25.7 ^1960 2B^0.„ 1961 26.0 1962 26. 1 1963 26.0 1964 25.8 J565 _25.3^ 1966 25.7 1967 26.1 1968 26. 1 1969 25.7 Ja70._.^9_ 1971 25.6 1972 25.5 1973 25.3 1974 26. 1 6:3 239, 3:4 4iS 597 591 553 7^2 823 99ia^ 8"/ 994 1234 .14d2_ 18di^ 16i? 2\U 1537 ^143^ 1331 11315 t:4 \ ■■""'--J — i^^ J-' - I 130 !. i' "-;, ■ ' ! \ i ) 15'i n ?.'. 1 ■)-'■ ' 194 1 \^i^ i ) ~4 ' 4u":i 1 : i. 1 ; ■ . ^ 1 ! 1 1 b^7 1 5.3 5-'-H . _....,..„_ 1 ^'---'^ 1 I \ 3:a 2i"'l- 35PI ■ i yl I JULPUGSEP QTR ■ VRLUE BNOMfll Y C?S -5 ■4 5 -3 • -2 10 15 -1 T 20 25 30 35 1 1 2 3 4 1 194603 27.9 194903 26.6 i950M_ ?7^4 195103 27.4 195203 27.4 195303 27.6 195403 27.3 I95>503_ _..26*9 195603 27. 1 195703 27.5 195803 26.8 195903 27.7 196201 2?: 8 196303 27.4 196403 27.0 196503__i7.l 196603 27.5 196703 27.9 196803 28. 1 196903 27.3 197203 27.2 197303 26.9 197403 27.6 .5 -.6 .0 .0 " .1 .2 -, 1 -' r . -.3 .1 -.6 .3 3 _ .? .4 -.0 -.4 -.3 -;i ■ .5 .7 .3 -..3. _ .1 -.2 -.5 .2 36 2ib 53 "■3 ' 13? 12/ HO . So. Ic'-^ 2.ti n^ 1^7 190 152 191 238 i^r 0'' ' 3it' 2?'-, .2?:? _.J. .. 1 1 1 1 1 L... _ '!_ ^ I " ! 1 i 1 ^' ' _iL_.. 1 "4i 1 ) i i < V i 1 : <*" > 2 - 1'3& 156 1 ( MSQ 91-3 YEAR YERR VALUE HNOMflLY C3S 1948 INSUF DFITP 1949 24.6 .5 359 1950 1951 24.1 24.3 -^_ _Jil3... .2 /1 33 1952 24.9 .7 410 1953 24.5 .4 830 1954 24.4 .2 636 1955^ 1956 _-a4^5.. 23.8 . .^ .3 -.3 524 537 1957 23. C -.3 635 1958 24.3 .1 832 1959 24.1 -.0 753 ..I960 24.1 -.1 Til.. 1961 24.2 .0 C'-3 1962 23.9 -.3 731 1963 23.9 -.2 326 1964 24.2 .0 1? -2 -. 1965... .23.3 -.B 1550 1966 24.0 -.2 2231 1967 24.1 -.1 2233 1968 24.2 .1 2059 1969 24.6 .5 18-9 -.1970 2_4._2. .1 1331 1971 24.6 .4 10d6 1972 23. S -.6 10.0 1973 24.7 .6 £31 1974 24.2 .1 \zm JHNFBP^RR QTR VRLUE flNOMRLr C3S •S 3 5 -4 -3 -i •0 15 20 n 1 25 30 35 1 2 3 4 1 194801 194901 195001 195101 195201 195301 195401 195501 INSUF DRTfl 21.6 .6 _2.K4 .t___ 21.2 .2 21. ?l -.0 21.5 .5 21.5 .6 2U7 _...7.. 39 124 128 " 234 154 PI 157 1'5 256 214 _2"'5. 336 239 239 437 432 . - - - ...i...„ ; ..' Li 1 : 1- 1 1 ^ ' 1 ■■ 1 195601 195701 195801 195901 .156001 196101 196201 196301 196401 196501 20.4 -.5 19.9 -1.1 20.6 -.1 21.2 .2 21.1 .1 21.2 .3 20.3 -.7 20.7 -.3 21.2 .2 19.9 -1.1 1 i i : • 1 196601 196701 196801 196901 197001 20.9 -.1 21.2 .2 20.8 -.2 21.4 .4 21.2 .2 735 790 5"2 5J1 333 3_G 39] 431 , — 1> ] 1 1 ! . 197101 197201 197301 197401 21.3 .3 20.4 -.6 21.3 .3 21.3 .3 '^- i i JU;_RUGSEP QTR VALUE RNOMflLY C3S -5 B ■= 1? 13 20 -4 -3 -2 -1 1 25 30 35 1 2 3 4 1 194803 194903 195003 195103 195203 195303 195403 195503 INSUF DRTfl 26.9 -.5 36 28.2 .8 38 27.6 .2 121 27.5 .1 138 27.6 .2 "3 ■---'" 1 ^ c i ',{ 1 ) i 195603 195703 195803 195903 Tpl03 1B6203 196303 196403 1965.03__ 196603 196703 196803 196903 197203 197303 197403 27.4 .0 31 27.7 .2 154 27.4 -.0 1-2 27.7 .3 131 .. 27.6 .1 12.3 . 27.6 .2 i:6 27.4 -.1 129 27.6 .1 116 27.7 .2 26E 26.8 -.8 ':':; 27V7 " .3 ?-o 26.9 -.5 334 28.! .7 /"/I 27.7 .3 33' 27.2 -.2 :;3 27.8 .4 192 27.? -.1 Z' 27.6 .? 11) 27.3 -.1 ii/1 1 . 1 ^ 1 1 <' ' 1 ' ' , : '^^ 1 ■ \ 1 I 1 < > I ) r MSQ 95-3 YERR YEFIR VALUE flNOMHLY C3S 1948 1949 _1950_ 1951 1952 1953 1954 ' 1956 1957 1958 1959 jae0_ 1961 1962 24.8 1963 24.7 1964 24.4 _i965 23^8 INSUF DRTfl 24.0 _2A.0_ = 24.0 24.6 24.3 24.3 24^1 - 24.2 23.5 23.8 24.1 _Z3^9 :_ 24.5 1966 1967 1968 1969 24.1 24.7 24.3 24.8 _iaZ0 24^6. 1971 24.5 1972 24. 1 1973 24.3 1974 24.3 2 -.1 -.1 .4 .1 .1 -J -.0 -.7 -.4 -.0 'j_3_ .3 .6 .5 .2 -.4 -Vi .5 .1 .6 ^4 ". 3 ' !i .1 JflNF EBMRR QTR VALUE flNOMRLY C^5 194801 194901 JL9£001_. 195101 195201 195301 195401 19550L. 195601 195701 195801 195901 i560Pil_. 196101 196201 1S6301 1964e>l 1S65£I1_ 196601 196701 196801 196901 197101 197201 197301 197401 INSUF DRTfi 21.0 __21^1 20.4 20.9 20.8 21.0 _20^5__ 19.7 19.6 20.3 20.7 _2IL.5_ _ 19.7 20.6 20.3 20.8 _.13^8„ 20.9 20.8 20.6 21.7 _20L7__ 20.6 20.8 21.4 20.4 .5 .6 -:e .4 .4 .5 -.0 -.8 -.9 -.2 .2 .Z -.d .1 -.?. .4 .4 .3 .1 1.2 __.2_ .1 .3 .9 -.1 i:4 2.7 1'^ ^S2 3:3 5i/! KJ ^ 1237 in 1H27 22^ 10-j1 3io 2ZA lbs,' i4;s 17-^ 53,1 4'-' PI 3:3 4^4 4ic; 4i'" 10 lb 20 1 25 2 30 3 35 4 JULRUGSEP MSQ 120-2 YEAR JRNFEBMPP MSQ 121-3 YEPR JRNFEor^qR JU.PUG3EP QTR VRLUE HNOmLY CBS ".^ .? .f If ^^ 2P 25 30 35 | 194803 194903 195003 15.1 .2 2-^8 1 14.5 -.4 5.4 1 14.1 -.8 231 i 1 195103 195203 195303 195403 1S5505_ 14.3 -.6 2-7 14.2 -.7 2::'4 15.5 .6 333 14.5 -.4 32) L3.3 -1.6 3i2 .^^ 195603 195703 195803 195903 4§i9g|- 14.5 -.4 330 15.9 1.0 355 16.7 1.8 635 16.4 1.4 8.2 _15^0 .1 713 "' isrfp- 196103 196203 196303 196403 19550 3__ 1SS503 196703 196303 1 196903 I9700.3_ 1£7103 197203 197303 197403 15.3 .4 636 14.1 -.8 4^0 15.5 .6 4-J8 14.5 -.4 6-4 15.4 .f. t ' "^^ 1 1512 A /'.;', ~""^^^>--. 15.3 ./ >^,< ,'.^^ 14.7 -.? A--' -- -#'" JL3..3 -i.._6 i,--:;y ._,. '. ---^=-:r < 15.1 A Z:, ' " '"^^V--. 15.4 .5 .;■■' 1 _^-^ 14.2 -.e Z9J -^^T 14.4 -.b 3.'S ; "• \ MSQ 122-1 YEAR JRNFEBfinR MSQ 123-3 YERR JflNFEBMRR JULflUGSEP MSQ 124-1 YERR jnNFEBMflR riSQ 125-2 YEAR JRNFEBMflR JULRUGSEP MSQ 127-3 YERR YEAR VALUE flNOMRLY CJS 1948 INSUF DflTR 1949 16.0 19.2 .1 1^ 1952 1953 1954 18.5 18.5 17.7 17.6 18.6 .7 .6 -.1 -.0 .7 1957 1958 1959 1960 18.8 16.6 17.2 17.4 17,6 .9 -1.3 -.6 -.5 17.3 18.1 17.2 JRNFEBMRR JULRUGSEP QTR VALUE flNOMRLY DBS -5 -i 30 3 35 4 194803 194903 115003. 195103 195203 195303 195403 1135503.. 195603 195703 195803 195903 19610? 196203 196303 196403 1S6503 196603" 196703 196803 196903 ia20ei3_ 197103 197203 197303 197403 22.8 22.0 22.1 22.2" 23.2 22.4 22.6 23.6 22.6 21.9 23.2 21.2 .6 19/ .3 248 -.5 191 -.4 390 :il.3 47? -73 533 .6 382 -.1 388 .1 388 _U. 323 .1 1H5 -.6 345 .6 3?? -1.4 300 MSQ 129-1 YEAR JRNFEBMRR JULHUGSEP MSQ 130-3 YERR JRNFEBMflR MSQ 157-4 YERR -S 5 10 15 20 25 30 35 YEAR VALUE ANOMflLY CBS -^ -3 -3 -i n i 2 3 4 1948 11.5 -.2 5.4 1949 11.3 -.4 699 1950 10.9 -.8 539 1 (A 1951 11.3 -.4 9^4 1952 11.2 -.5 677 1953 11.7 .0 6^1 1954 11.7 -.0 699 1955 10.9 -.3 11-5 i is 1956 11.5 -.2 11-6 1957 12.0 .3 13il 1958 12.7 1.0 1230 1959 12.3 .6 lUl 1960 12.3 .6 21:2 1 ^ . J 1961 12.2 .5 1U6 1962 11.8 .1 10.8 1963 INSUF DflTfl 1964 INSUF DATA 1965 INSUF DflTfl ill; ' i 1 1§66 11.3 -.4 1410 "■ 1967 11.9 .2 2358 1968 11.4 -.3 3850 1969 11.6 -.1 1731 1970 11.6 -.1 IS. 3 ^ ]t \ 1971 10.8 -.8 1557 1972 10.5 -1.2 2730 1973 11.1 -.6 13-6 1974 11.2 -.5 18:3 JRNFEBMnR .JULRUGSEF QTR 196203 196303 196403 196603 196703 196803 196903 197103 197203 197303 197403 VflLUE flNOMflLY C3S 1.0 -.0 INSUF DflTfl 14.1 -1.2 INSUF _Qeia_^ 14.5 -.7 15.9 .6 14.8 -.4 15.5 .2 15.0 13.8 14.6 14.5 -.3 -1.4 -.7 -.7 MSQ 159-3 YEAR JR^rEBMRR MSQ 160-2 YERR jnNFEBMflR W 15 20 25 30 35 JULRUGSEP QTR VALUE flNOMRLY INSUF DflTfl 18.6 16.9 19.0 17.4 17.3 7.4 15.5 17.9 15.1 1862B3 196303 196403 1 96 T966a3 196703 196803 196903 16.8 19.5 19.6 17.3 16.5 17.4 19 7003 16.9 _- T97103 17.7 197203 17.5 197303 197403 16.6 16.1 MSQ 160-3 YEAR jnNFEBMflR MSQ 162-1 YEAR JRNFEBMHR C3S 25 2 30 3 35 A JULRUGSEP MSQ 163-3 YEAR JRNFEBMflR JULRL'GSEP QTR VPLUE PNOMflLY C 3S 194803 INSUF 194903 10.3 19 5003 11.5 195103 10.9 195203 10.5 195303 9.7 195403 9.6 1955 03 11. 1 T95603 12.0 195703 10.2 195803 10.6 185903 11.7 II 1962B3 11.8 186303 10.6 196403 9.4 19B503 la.a T9M03 11.4 " 196703 12. 1 196803 10.9 196903 11.7 197003 H.H_ ' 197103 10t8 197203 10.3 197303 9.8 197403 10.1 ORTfi -.5 150 .7 37 .1 ZH° -.3 2U -1.2 3::^ -1.2 335 _^3.. 4' 5 1.2 638 -.6 738 -.2 833 .9 9"'3 . .1 939 -.1 231 1.0 198 -.0 135 -l.< 1133 -.8 937 .6 2:u 1.2 \'Z .1 123 .9 ^^L .2 32 -.0 i2 -.5 356 -1.0 397 -.7 Ml MSQ 165-2 YEAR JRNJFEBMRR QTR 194801 194901 195001 195101 195201 195301 195401 iS5501_ 195601 195701 195801 195901 13200 L_ 198101 196201 196301 196401 _iaB50i_ 196601 196701 196801 196901 i9Z00.L 197101 197201 197301 197401 VRLUE PNOMRLY C dS INSUF DflTH 6.2 6.0 6.7 6.5 7.2 _6^7. 7.8 7.2 6.7 6.1 _6^2_ 5.9 7.1 6.9 5.6 _5^7__ 5.8 6.1 7.5 6.8 5.3 8.5 5.9 6.5 5.9 -.2 37 -.4 IM -.4 i:7 .? rs .1 us .8 159 .2 ?L?. 1.4 ?92 .7 i.:2 .2 438 -.3 63*1 -.3 7?8 -.5 634 .7 159 .4 138 -.9 'iu -.7 10i6 -.s llP!30 -.4 57 1.0 las .3 38 ■1,1 59 2.0 :r -.6 3-1 .1 4C3 -.5 439 JULRUGSEP MSQ 195-3 YEAR YERR VRLUE RNOtinrY C 3S 1948 1949 INSUF INSUF 1S50 msuE 1951 INSUF 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1971 1972 1973 1974 INSUF INSUF 9.2 8.8 9.7 9.9 9.3 8.7 DRTR DRTR Jffilfl DRTR DRTR DRTR .4 ^5_ .0 1.0 1.2 .6 =..0 .4 .5 .7 1964 8.7 -.0 7.7 -1.0 1966 8.0 -.8 1967 8.5 -.2 1968 8.5 -.3 1969 7.8 -1.0 1970 8.1 -.6 7.0 7.1 7.2 7.9 -1.7 -1.7 -1.5 JRNFEBMRR MSQ 197-1 YEAR JRNFFBIinR 194801 194981 195101 195201 195301 195401 LISS50L. QTR VALUE RNOMflLY INSUF DflTn 3.3 ___4^3__ 3.6 3.3 3.7 3.6 4.1 3.6 4.5 4.1 4.1 -i.6__ 3.8 3.9 4.4 195601 195701 195801 195901 U9600L_ 196101 196201 196301 196401 19650 1 195601 196701 196801 196901 197101 3.8 197201 3.4 197301 3.7 197401 3.4 3.5 .6 ^4 -.3 -.1 -.3 -.3 __.J_ -.3 .5 .2 .2 -_.3 '-".1" -.0 .5 _l2 -.0" -.1 -.0 -.4 J -.2 -.5 -.3 -.5 10 15 20 25 30 35 -1 ?! 2 3 4 JULflUGSEP QTR 194803 194903 1 95003 T95103 195203 195303 195403 195503 195603 195703 195803 195903 iSeTaS 196203 196303 196403 UaesaL T96603 196703 196803 196903 JISZM3_ T97103 197203 197303 197403 VALUE RNOMRLY C33 MSQ 198-1 YEAR JRNFEBMRR DTR VALUE RNOMRLY -5 C3S , .^ s le 3 -> -1 15 ^^ 25 3B 35 1 2 t 2 3 4 1 194801 INSUF DRTfl 194901 3.6 -.4 laSBSL 4.4_ . .4_. 195101 3.6 -.4 195201 3.7 -.3 195301 3.8 -.1 195401 3.4 -.5 195501 4.1 .2 195601 4. 1 .1 195701 4.3 .3 195801 4.3 .3 195901 3.7 -.3 19.6001 3.6 -.3 391 _^ V ~4~, u tZ 51 00 J K c 1 i hi. 37 33 1,32 n 1 W 1 ....../J . _j. I 196101 3.8 -.1 196201 4. 1 .1 196301 4.0 .0 196401 4.2 .3 J96501 3,9 -,1 l.J3 "1 1/9 2^0 293 V > 196601 3.9 -.1 196701 4.9 .9 196801 4.5 .5 196901 4.3 .3 137001 _iJ^ ^6 197101 5.2 1.2 197201 3.6 -.3 197301 3.3 -.7 197401 3.8 -.1 la; 33 1 91 . ,31_ ___ ^ i h' 238 2.7 L : »-L„ > C*^ S 1 $ /i Pa A % ^ u^fl 4^ ^^^^^■^^JKK^^xsN^^ A (^^^ ^^^^■■Ah/ ^^\/ V 7---^ / /^ — 4— . 3 ^idM f? •». »^Tx \ ^---''''tB Ifc.^^ "r* %i S ) ^ IT li • b fO «+- S- E JC -M S S- c (U JD c: fO a •r- C <+- -r- 00 fO (T3 D_ CU S- o; 03 Ji: -fj -0 O) c ^ •I- u +J ^-^ (O U_ Ji_ c -^ •1— r~« ^— -cri ^^ >> -— >> (O s_ E E 03 fO s- , Q. S_ E C fO O) '"3 03 i- ^- S- 4- 3 I/) ^ ■ 10 fO O) OJ C\J s- CO 3 OJ +J O) -a 03 CD 3 S- 03 +-> O) s- •■- CL O) 4-J E > 03 (U CC r- 4-> O) CD • r-. b • lOMALY AR-APR 1974 pr+ 1 1 k 1 1 b b e s 1 i 1 b "1 i. ■| i ^ - ^ '^J^^T^wm^ ft- ^ .^ — CO j^^^^^^^^^Blp— r ' Pw .^ — r •09 ^ F r h j^^^l^^^^:^^^ Ss^ — xVS, "^ w 1 \\^ \S\ ^ i — ' ^ >\ > 4 k --^ j[_jy ■• 1- 1 -S 1 — H r ^KiSi y L / ^r — ■Hr^^-X^li^ — - 1^ yM- /^ TO feO- ^^^^^^^K'^^ofv^^ ^"v^VN^VVtx' H- J* #^ A \S- ■^^^^^^^^^^^^^^^^^K^ ^BB^ \\ n \ VtW W T "" - • k lH^^I i 11^ - — .fj •». fc.- "** 'V* \ M Br % Q 14- ^^ -E 03 4-> E S- i. E C E S fO OJ r— a O) -Q 4- (O •r- -r- fD "O Q. E •r™ O) JZ CO -t-> 03 QJ E S- •1- ft3 .— v-o U. J -E a E -l-> •r- fO 'IE >> • r- ^ fO r^ E CT. I— E fO 1— •r~ QJ i- i- Q. 3 < -M (O -o S- E S- rO cu s: u 03 S- 4- S- M- 13 00 -Z. . QJ T3 fO cn U s- fO -M QJ S- -r- Q. QJ +-> E > fO OJ <: .— 4-> s- .— (T3 c E S- c: fti c -r- C CO •r- ro (U -^ i- L^ ro -0 C O) •t- x: ^ u -M >, fO r— 3C n3 E • ^ c r-. fO en r^ OJ i- 3 (T3 --D S- oj -0 Q- C E fO OJ ■M >, ro o) s: a fO s- i+- s- <+- 3 CO S • CO ro OJ CU 00 S- CO Z2 O) +J QJ T3 (t3 05 3 S- fO -M E > ro 0) < r- •4-> OO LO CD i- 3 CD , b ^^ 1 ■^ \ % 9 b b b b in s 1 i • s 1 1 1 °\ ''^ 1 1 si i 1 ^^ 1 / :e ^ h^ AoV^^t^nll—- .1 p /""/■^ ^ / " n i- ^^ ^^Btf •09 ^ '^IbP TO 1 ^^^Bi 1 f — — R^B^^^^tl — — k m F 1 1 ^ ^ :^ h * k ^TO CM 1 jfsx f — ^ ^ H ^> 1 fis. y — — - — 1 / I^^^^HHk~~~^ ^/"^^nSavIoAn L- ^ . . ^f^ , feWi ^^^^fe^x^lVT^^^^^^f^ .< 4ii ..o- ^^^^^^^^^B^^o^'oK. li^^$Vl^c\N^^ovv1 i- — !* ^^^m'^^^^^^^^^^^Ll A \^ w "^^^^^^^^^^^^^^^^^K^ IB^ f ^I^rWW N ~~ ~ • u i jp ^^^^^^N^ ^^Q* ^^i^^\NSs\5v'\H^^J 1 f? ■^ a II a • en V i b i 4-> S- 03 U E ■■- -a c c re -1- c: • •1- r:}- r^ -^cn Ll_ , — S- C OJ •r- J3 ^^ E CU >, u r— O) fO Q E -E e CD fO =3 -t-> fO s_ S- OJ . O) -Q ^ 4-> CL+J t/1 ^ p— n3 (13 O) C\J F (jO s- OJ oi -a c en 13 ro +-> 5 i- -r- OJ -M , — > 03 CU cC .— JD CU s- en SEA SURFACE TEMPERATURE »F. U.S. DEPARTMENT OF COMMERCE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION NATIONAL MARINE FISHERIES SERVICE SOUTHWEST FISHERIES CENTER P. O. BOX 271 UA JOI.LA, CALIFORNIA K0}7 7U-4S3-2a20 PROGRESSION OF THE 60*>F ISOTHERM DURING THE WARMING SEASON OF 1974. I35* Figure 5.6. 130* 125* I20« 115* Locations of the 60°F (15.6°C) surface isotherm in the eastern north Pacific for the first 15 days of May through September 1974, respectively. CHANGES IN THE TRANSITION ZONE AND HEAT STORAGE IN 1974 BETWEEN HAWAII AND CALIFORNIA J.F.T. Saur* INTRODUCTION In 1974 the oceanic conditions in the northeast Pacific Ocean were significantly changed from those in the two previous years, according to data obtained from a National Marine Fisheries Service (NMFS) project for ocean monitoring between Hawaii and the U.S. West Coast. One of several objectives of this monitoring is to detect seasonal and non-seasonal move- ments and changes in character of the Transition Zone which is found be- tween the modified subarctic waters of the California Current and the subtropical or Eastern North Pacific central waters centered northeast of Hawaii, Figure 6.1. Laurs and Lynn (1975) have shown that this zone and its associated oceanic fronts influence the distribution and apparent abundance of albacore tuna during their early season migration toward the U.S. west coast fishery (see Section 8). Throughout most of 1974 the Transition Zone was diffuse and its edges poorly defined as compared to 1973. As the year ended a strong temperature and surface salinity front was forming at its boundary with the California Current, whereas in 1973 the stronger salinity front had been on the subtropical side of the Transition Zone. GENERAL OCEANIC FEATURES Between the California coast and Hawaii we can identify three ocean- ic regions: (1) a California Current region, (2) a Transition Zone, and (3) a subtropic region. Figure 6.1. The waters in the California Current *Scripps Institution of Oceanography, La Jolla, CA. (Affiliated with NMFS Southwest Fisheries Center, La Jolla, through 1974). 6-1 originate as cool and low salinity subarctic waters but undergo contin- uous modification (warming and increasing salinity) in their southward movement along the coast. These generally extend some 500 to 600 nauti- cal miles out from the coast on the Honolulu - San Francisco route. The subtropical waters, or Eastern North Pacific Central (ENP) waters, are warm, high salinity waters. They occupy about one-half of the route, i.e. from Hawaii for 1,000 miles northeastward to the neighborhood of 31° N latitude and 139° W longitude. Between these two principle water masses lies a Transition Zone (Roden, 1971). Its temperatures and salinities are characteristic of a mixture of the two primary water masses (Christensen and Lee, 1965), and the boundaries are often marked by sharp horizontal salinity gradients (Roden, 1971). In early spring the vertical temperature profiles in the Transition Zone often exhibit complex minimum-maximum structures at depths of 50-150 meters below the surface. These features between Hawaii and California are extensions of the Transition Zone and its associated subtropical front and subarctic front which occur between Hawaii and Alaska. Roden (1970) has shown that at longitude 158° W and 178° W the fronts are oriented east-west and the Transition Zone lies between 32° N and 42° N. Between Hawaii and Cali- fornia the features are oriented WNW-ESE or NW-SE due to the currents turning clockwise around the central gyre of the North Pacific Ocean. OBSERVATIONS Observations for the ocean monitoring are made from merchant vessels or "ships of opportunity" (Saur and Stevens, 1972). Underway observations of subsurface temperatures to depths of 500 meters are made by the ship's mates using an XBT (expendable bathythermograph) system. Engineers draw water samples from the sea water intake system for determination of "sur- face" salinity. With observations eyery 4 hours the distance between ob- servations varies from 65 nautical miles (120 km) to 90 nautical miles (165 km) depending upon vessel speed. 6-2 Monitoring is now done regularly on 3 routes in the NE Pacific, Figure 6.1. It began with a pilot project on the San Francisco - Hawaii route in June 1966 at the rate of 15-18 sections per year. During the past two years the monitoring has been expanded and intensified. Obser- vations started on the Los Angeles - Honolulu route in October 1973 and on the Seattle - Honolulu route in April 1974 at the rate of 15-20 sections per year. On the San Francisco route the number of sections was increased to 27 (650 observations) in 1973 and the route intensively sampled in 1974 with 52 sections (1420 observations). Selected sections, along with a narrative interpretation (Saur, 1972-75) are published monthly in Fishing Information , a NOAA/NMFS publication compiled and distributed monthly by the Southwest Fisheries Center, La Jolla, California. Figure 6.2 is an example of the graphical presentation of the data for March, 1974, on the Honolulu - San Francisco route. This paper will focus its attention on oceanic conditions observed along the San Francisco route because of the intensified sampling in recent years. It should be noted that the "monitoring" permits a description of meso-scale features throughout each year to supplement the knowledge gained from highly detailed sections by oceanographic research vessels (Laurs and Lynn, 1975; Roden, 1970 and 1971) at only one time in a given year. OCEANIC CONDITIONS IN 1974 For our purposes the oceanic conditions in 1974 can best be described by noting the shift from those which were found in 1973. (Conditions in 1972 and 1973 were quite similar.) To summarize these I will use the sur- face salinity and temperature observations and the heat content derived from the subsurface temperature data. Figures 6.3 and 6.4 show the distribution of surface salinity and temperature, respectively, along the Honolulu - San Francisco route for 1973 and 1974. Whereas, the temperature patterns exhibit large seasonal cycles, the salinity patterns do not. 6-3 Surface Salinity Surface salinities of greater than 35 °/oo are typical of the ENP central waters. Salinities below 33.5 °/oo are typical of California Current waters and salinities below 33 °/oo persist most of the year in the core of the current. The Transition Zone on the San Francisco route has surface salinities generally between 33.7 °/oo and 34.7 °/oo. Several changes from 1973 may be noted in the 1974 salinity pattern. (1) In 1974 as opposed to 1973 there is a large amount of water with sa- linities below 35 °/oo at the Hawaii end of the section. These appeared at the end of 1973 and persisted throughout 1974. (2) The salinity reached 35.5 "/oo on only one observation in 1973 but values this high were ob- served for several months in the latter half of 1974. The position of the maximum salinity also shifted towards the west coast by 100-200 miles. (3) In the eastern half of the section the 35 °/oo and 34 °/oo isohalines in 1974 shifted somewhat eastward. These changes in salinity patterns suggest that in 1974 the center of the ENP waters moved northward about 2° latitude and protruded east- ward, and lower salinity waters of the California Current Extension (Seckel, 1962) and equatorial regions moved into the Hawaiian Island area. This movement coincided with stronger and more persistent trade winds in 20-25° N and 25-30° N latitude belts east of Hawaii. A change in the strength of the salinity boundary of the Transition Zone occurred with the above described shift in salinity pattern. This could be seen in the horizontal profiles of surface salinity. Figure 6.5 shows salinity for March in each of four years 1972 through 1975. March profiles, as a rule, are typical of the predominant pattern from the pre- vious winter through the following spring and summer. In March 1973 two steep gradients, or fronts, in the salinity pro- files occurred, one near 140° W and another near 133° W. In between these fronts the salinities were near 34 °/oo. The Transition Zone appeared to be a separate distinct region of relatively uniform salinity and bounded 6-4 by two salinity fronts. The front on the subtropical, or Hawaii, side was the stronger of the two. In March 1974 there were no distinct gradients to bound a Transition Zone. Throughout spring, summer and fall the salinities, and also temper- ature, showed the transition from California Current waters to ENP central waters was broad and diffuse. On its early season albacore scouting cruises in June-July 1974, the research vessel, David Starr Jordan , also found only weak fronts and a diffuse Transition Zone as opposed to two sharp boundaries in 1973. About October 1974 a steep salinity gradient began to appear near 130°-132'' W and by March 1975 sharply defined the outer boundary of the low salinity California Current waters, Figure 6.5. Surface Temperature and Heat Storage Changes in temperature and heat storage occurred in conjunction with the shift in salinity patterns just described. A greater range of sur- face temperatures occurred in the annual pattern in 1974 than 1973, Fig- ure 6.4. A temperature minimum of 11.8°C occurred at the San Francisco end of the section in February of 1973. The maximum off Hawaii was 25.9°C in September for a total range of 14°C. In 1974, however, the February minimum was 11° and the September maximum was 27°C for a total range of 16°C. The contrast between temperatures near San Francisco and those near Hawaii, even on a month-by-month basis. Figure 6.4, were 2°C greater in 1974 than in 1973. The temperature changes were not confined to the surface, but also penetrated below the surface. This is shown by the March and September heat content (relative to 0°C) of the upper 100 meters in 1973 and 1974, Figure 6.6. Except near the California coast the heat content in the 0-100 meter layer was generally greater in both seasons in 1974 than in "•personal communication, R. J. Lynn, Scientist-in-charge. 6-5 1973. The excess was about 10 kilogram-calories. This amount raises the average temperature of a 100 meter column of water by 1**C. This indicates that the warm pool (in surface temperature) in the subtropics noted in 1974 by Namias and Dickson (see Section 3) and by Eber (see Section 5) extended well below the surface, at least, in the region northeast of Hawaii. In the western half of the section where the 1974 excess was greatest, the warming from March to September was about the same in each year. The difference between years occurred because the cooling in the winter of 1973-74 did not offset the warming that had taken place in the summer of 1973. The cause of this has not yet been identified. The only significant cooling from 1973 to 1974 occurred in the few hundred miles closest to the California coast. In contrast to when warm- ing occurred in other areas, the coastal cooling occurred mainly because of March to September differences between years. The increase of heat content during these months in 1974 was small compared to that in 1973. This indicates that the California Current became confined to a narrower band closer to the coast by September 1974 in comparison with September 1973. Greater upwelling and a stronger California Current advecting more heat out of the region would account for the smaller summer rise in heat content. This confirms stronger upwelling around 36° N latitude predicted by Bakun's upwelling index (see Section 12). SUMMARY In 1974 the center of the warm high salinity Eastern North Pacific Central water shifted northward by about 2° latitude (from about 28° N to 30° N) and protruded northeastward (near 32° N, 138° W) toward the California coast. This movement was accompanied by a change in the character of the Transition Zone. In 1973 the zone had been well de- fined by sharp boundaries with the California Current waters and with the subtropical Eastern North Pacific central waters. The latter bound- ary had the stronger surface salinity front. In most of 1974 the fronts 6-6 were weak so that the Transition Zone was diffuse and its limits not clearly identified. Near the end of 1974 the boundary between the sub- tropical waters and the Transition Zone remained indistinct. However, a strong temperature and surface salinity front formed at the boundary between the cool low salinity waters of the California Current and the Transition Zone. The contrast in temperature and heat content between the subtropical waters and coastal waters of California increased from 1973 to 1974. The year 1974 ended with a larger pool of heat in the subtropical waters. This contrasted with cooler conditions in a 400-500 nautical mile band along the California coast. The difference in distribution of heat could be of importance to air-sea interaction and feedback of energy from the ocean to the atmos- phere. On the other hand the environmental features which could be of importance to fisheries were the change in character of the Transition Zone and the shift of the stronger frontal boundary to the California side of the zone. ACKNOWLEDGMENTS A monitoring program of this nature involves many people and activi- ties. Cooperation of companies and the mates and engineers of the follow- ing ships is greatly appreciated; SS Monterey and SS Mariposa , Pacific Far East Line; Hawaiian Enterprise , Californian , and Hawaiian Queen , Mat- son Navigation Company; and Chevron Mississippi and Chevron California , Chevron Shipping Company. Robert Melrose, Marine Technician, NMFS Pacific Environmental Group, Tiburon, CA (succeeded by Brian Jarvis in November 1974) performed the difficult tasks of maintaining equipment and servicing ships. Dr. Douglas R. McLain supervised the initial processing of obser- vations at NMFS Pacific Environmental Group, Monterey, using the computer facilities of the Fleet Numerical Weather Central (FNWC), Monterey. FNWC also furnished the XBT probes for the observations - a major cost item of the project. Hilary Hogan, NMFS Southwest Fisheries Center, La Jolla, 6-7 supplied indispensable assistance to me in data handling and analyses. The project was supported by National Science Foundation (Office of IDOE) grant AG-256, Office of Naval Research Gov, Order NAour-9-74 to the National Marine Fisheries Service, and ONR contract N00014-75-C-0260 with Scripps Institution of Oceanography (NORPAX program). 6-8 REFERENCES Christensen, Niels, and Owen S. Lee. 1965. Sound channels in the bound- ary region between Eastern North Pacific Central Water and Transi- tion Water, hi P'^oc66^''"9S' Second U.S. Navy Symposium on Mili- tary Oceanography, Vol. II, pp 203-225. Laurs, R. Michael and Ronald J. Lynn. 1975. The association of ocean boundary features and albacore tuna in the northeast Pacific, hi Proceedings: Third S/T/D Conference and Workshop, February 12-14, 1975. Plessey Environmental Systems, San Diego, CA, pp 23-30. Roden, Gunnar I. 1970. Aspect of the Mid-Pacific Transition Zone. J. Geophys. Res. 7^(6): 1097-1109. Roden, Gunnar I. 1971. Aspects of the Transition Zone in the northeast- ern Pacific. J. Geophys. Res. 76(15): 3462-3475. Saur, J.F.T. and Paul D. Stevens. 1972. Expendable bathythermograph observations from ships of opportunity. Mariners Weather Log 16^ (1): 1-8. Saur, J.F.T. 1972-75. Subsurface temperature structure in the northeast Pacific Ocean. In Fishing Information (monthly series). NOAA/ Nat. Mar. Fish. Serv., SW Fish.Ctr., La Jolla, CA: 1972 (11-12), 1973 (1-12), 1974 (1-12), 1975 (1-3). Seckel, Gunter R. 1962. Atlas of oceanographic climate of the Hawaiian Islands region. U.S. Fish and Wildlife Serv., Fishery Bulletin 193 61: i-iv, 371-427. 6-9 50* 160* 40' icy 20* ISO* - I I I I I I I : ■ I I '— ^ MO* 00* 120* ' ' ' '' ' ■' ■ V 'nSL ' ' ' ' ' ' ' =^ Stroil of Juon de Fucq>;0 \ ^Seattle jCdumbia R. Porllond A<^ >' ^^ C> Kowoiian Islonds Figure 6.1. Location of water masses and Transition Zone in late July and early August 197A. (Adapted from FISHING INFORMATION , August 1974, Wo. 8.) Ocean monitoring by merchant ships was conducted in 1974 along the three routes sho\m by dashed lines. •o* 40* -+ tt-r. o HONOLULU - SAN FRANCISCO MARCH 16-20,1974 SS HAWAIIAN ENTERPRISE. VOYAGE 86 -HoncAjkj- ~ 30 UJ c 3 < o: bJ CL 20 10 500 __J -NAUTICAL MILES - 1.000 , I ' —i I 1,500 -Son Francbco— I 2,000 -I I_ I SURFACE TEMPERATURE SURFACE SALINITY a. UJ o 100 200 300 400 T — I — i — i — \ — 1 — 1 — I — I — I — I — I — r I55*W I50*W 145'W J I I I. ' ' 'I It I I I I I I I I I I I i I I i I I I I40*W I35*W I30*W r-rf 32 36 34 2 ^- < V) 500*? SUB-SURFACE TEMERATURE CO J_«= DEPTH OF OBSERVATION <460m Objervotion No.N 22 21 20 19 18 17 16 15 14 13 12 II 10 9 8 7 6 5 4 3 2 I 100 ZOO 30O 400 I •- UJ boo Figure 6.2. Surface temperature and salinity and subsurface temperature structure, Honolulu - San Francisco ship route, March, 1974. Selected sections for the three routes shown in Figure 6.1 were published in monthly issues of FISHING INFORIIATION , distri- buted by the Southwest Fisheries Center, La Jolla. SURFACE SALINITY 1973 1974 Honolulu Son Francisco Honolulu Son Francisco 2000 NAUTICAL MILES NAUTICAL MILES Figure 6.3. Temporal distribution of surface salinity on the great circle route between Honolulu and San Francisco, 1973 and 1974. Under- lined values indicate maximums and mininums in tlie salinity field. Mininums occur both near Hawaii and in the California Current. 1973 Honolulu SURFACE TEMPERATURE San Francisco Honolulu JAN 1974 Son Froncisco 1000 NAUTICAL MILES 2000 1000 NAUTICAL MILES 2000 Figure 6.4. Temporal distribution of surface temperature on the great circle shipping route between Honolulu and San Francisco in 1973 and 1974. Underlined values indicate rnaximuins and nininuias in temperature field. Q C9 UJ § 3 • iH m 3 r^ O .H C I O CM K (^ o\ C r-l O Q > b! >% u W o •H «H a < q: UJ 1- UJ o 4 / ^'4 /_ - _J I- z llJ g UJ f ^1 f — o < ^^ f o u. vCxT v^ o <^^ X^^ »- to \i^^ < /^ vvv/ '^^ ol . ^^ UJ X 1 vvvf f*- UJ ^ 22 (o 22 Id K ^ 1 f\. r to on 222 ro o> z < X 1- on UJ < 1 r 1 J f 5 22 J 1 P< i i \ y f • 1 1 1 1 1 CO UJ o < - S:2 I- < O O lO 0) x: ij c o £ 0) 4J >-l o «4-l u (U >» • CO <3- iH r^ M <-i O 4-1 73 '""^^^r"^^ ANOMALY OF AIR TEMPERATURE AT KING SALMON (°F) ANOMALY OF AIR TEMPERATURE AT ST^N. iyO°W (°C) 2-1 1 -1 - -2- I'^^V^v ANOMALY OF SEA SURFACE TEMPERATURE AT 5T°N, ITO^W (°C) 19T2 I 197'3 I 197-4 | 1975" 1967" 1968 1969 19TO 19T1 Figure 7.1 - Anomaly of air temperature and sea surface temperature in southeastern Bering Sea during 1967-75. Series 1 is anomaly of air temperature in °F at St. Paul Island, Alaska from 1941-70 mean. Series 2 is anomaly of air temperature in °F at King Salmon, Alaska from 1941-70 mean. Series 3 is anomaly of air temperature in °C at 57°N, 170°W (near St. Paul Island) from April 1962-May 1975 mean. Series 4 is anomaly of sea surface temperature in °C at 57°N, 170°W from January 1968-May 1975 mean. Data for Series 1 and 2 from National Climatic Center and data for Series 3 and 4 from Fleet Numerical Weather Central. 7-2 below normal, and the cold air temperatures persisted into the spring and summer of 1 971 --al though normal conditions prevailed in the fall quarter. During the winter of 1971-72 cold conditions were reestablished; the -7.0°F temperature anomaly reached during the first quarter of 1972 was the lowest first quarter anomaly since published records began in 1934. Negative anomalies persisted into spring and summer but became positive during the fall quarter. Extremely low monthly anomalies of air temperature occurred in March 1971 (-9.1°F) and March 1972 (-13.1°F). Air temperatures during 1973 were more normal than either 1971 or 1972 with quarterly anomalies of only -1.2 to -2.7°F, but the seasonal cycle of anomalies was again similar to 1972 in that positive anomalies also occurred in the fall. Further, the cold anomaly was greatest in the spring quarter, rather than during the winter quarter as in 1971 and 1972. During 1974, anomalies were again below normal but not as extreme as those of 1971 and 1972 and were similar to 1973. Unlike the previous 3 years, however, cold conditions persisted in all quarters and were much colder than normal in the fall quarter. Conditions in 1975 so far have again been yery cold and similar to the cold periods of 1971 and 1972. The greatest monthly negative anomaly of the winter of 1974-75 at St. Paul was in January 1975 (-8.5°F). Other anomalously cold winters have occurred at St. Paul in 1940, 1946, 1947, 1954, and 1956; unusually warm winters have occurred in 1935, 1937, 1950, 1966, and 1967. 7-3 King Salmon, near the head of Bristol Bay and about 10 degrees of longitude east of St. Paul Island, is another weather station in the southeastern Bering Sea where good quality, long-period weather records are available. The station, much more subject to continental air masses than the maritime St. Paul Island, has greater extremes of air temperature. The extremely cold winters since 1971 are evident in the data. The greatest quarterly anomaly (^10-3°F )occurred during the first quarter of 1972, but this was not a record low (as at St. Paul) because a similar negative anomaly had occurred during the winter of 1954. The years 1973 and 1974 were relatively mild at King Salmon compared to 1971 and 1972. Anomalies of air temperature were positive during the winter of 1972-73 except for January 1973 when a -9.7°F anomaly occurred. In the following winter positive anomalies occurred during all months except January and February when anomalies of -3.9°F and -16.2°F were observed. Summers were mild in 1973 and especially so in 1974. The winter of 1974-75 was again cold but unlike the cold winters of 1970-71 and 1971-72, marked cooling began in October rather than in January. Air temperatures in early 1975 have been colder than normal. The years of historically warm and cold winters at King Salmon are slightly different than those at St. Paul due to the different factors affecting its climate. Unusually cold winters occurred in 1954, 1956, as well as 1971 and 1972; warm winters occurred in 1944, 7-4 1955, 1958, 1960, and 1963. Sea Temperatures Observations of sea water temperature are not abundant in the southeastern Bering Sea, particularly during winter and spring. Johnson, McLain, and Nelson (1975) presented sea temperature anomaly data for the area 50 to 55°N, 160 to 165°W (Index Station 197-1) which indicate cold sea surface temperatures south of Alaska Peninsula since 1971. Straty (1974) reported sea temperature data near for the head of Bristol Bay during June and July for 1967, 1969, 1970, and 1971 which clearly reflect a lowering of sea surface tempera- ture between 1967 and 1971; temperatures of 6 to 9°C at 10m. in June and July 1967 decreased to 0.5 to 4°C in June of 1971. Favorite and Ingraham (1973) reported unseasonably cold surface temperatures at the edge of the continental shelf in the eastern Bering Sea in spring 1971. A summary of sea surface temperature and air temperature data fields are available from Fleet Numerical Weather Central (FNWC) for the area on a 12 hourly basis since 1962. These data represent analyses of temperature reports sent in by radio from merchant, naval, and other vessels as well as historical data. In these presentations, the actual origin of reports cannot be ascertained and, thus, one cannot tell if the values represent actual observations obtained in the 12 hour period or merely a long-term mean, or whether it was 7-5 extrapolated from distant observations. In spite of these limitations, the fields provide a time continuity not otherwise obtainable and reflect relative changes of temperature with time. Monthly means of anomaly of air and sea temperature at a location near St. Paul Island (see Fig. 7,1) indicate that sea temperature anomaly lags behind the air temperature anomaly by a month or more. The cold winters are also reflected in bottom temperatures obtained during annual surveys by the International Pacific Halibut Commission. These have been conducted on a fixed station grid in the southeastern Bering Sea in early June since 1966 (Best 1974), where a lowering of water temperatures was observed between 1967 and 1972 (Table 1). Temperatures recorded during June 1973 were 2 to 4°C above those of June 1972 or 1974 but aresuspect as the mechanical bathythermograph did not function properly when tested after use. Fujii et al . (1974) showed that bottom water temperatures of less than 1.0°C did not occur offshore of Bristol Bay in the summer of 1967 but that temperatures of less than -1.0°C occurred in the summer of 1971, 1972, and 1973. Ice Cover Ice cover in the southeastern Bering Sea has been much more extensive during the winter and spring since the winter of 1970-71 than it was in the four previous winters. This is readily apparent in the duration of winter and spring ice cover in the eastern Bering Sea during 1966 to 1975 (Fig. 7. 2). The extent of ice cover is divided into four common situations: 7-6 Table 1. Bottom temperatures in °C on line of trawl stations across Bristol Bay on IPHC Line No. 6 from Cape Seniavin near Port Moller to Cape Newenham. Data collected by International Pacific Halibut Commission from Best (1974) and personal communication. TRAWL STATIONS Date Cape Seniavin Cape Newenh lam June 1967 3.4 3.3 - 2.2 2.9 2.9 3.9 3.7 - 4.1 June 1968 No data June 1969 5.6 4.0 5.2 4.9 3.4 3.1 4.1 4.1 - - June 1970 1.4 2.1 1.7. 0.5 0.9 2.5 1.3 1.6 1.6 1.7 June 1971 0.6 0.0 0.1 0.7 0.9 0.8 1.4 2.1 3.2 1.9 June 1972 1.1 0.3 -1.0 -0.8 -0.8 - - - - - June 1973 3.9 - 2.1 2.4 3.0 3.4 - - - - June 1974 1 .6 0.9 1.1 0.1 0.6 0.5 - - - - June 1975 0.6 0.0 -1.1 -1.1 0.6 0.6 - - - - 7-7 NUNIVAK BERING STR. BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. BB BLOCKED BB CORRIDOR NUNIVAK BERING STR. JAN. 10 20 30 -r— rnr FEB. I MAR. I APR. K) 20 W 10 20 30 10 20 30 -1 — I — I — I — I i| I — I — rt MAY i JUN 10 20 30 10 20 30 T T-r-| z h < z D J J ■ 1^ '? :^___i- "-- .^ . - ^■■■■i ■ ? - , — , ^-, .- 196T 1968 1969 19TO 19T1 19T2 I9T3 19T-^ 19T4 19TS X 4 I I ■ I 1 10 20 30 10 20 28 10 20 30 10 20 30 10 20 30 10 20 30 I JAN. I FEB. I MAR. | APR. | MAY | JUN. | Figure 7.2 - Duration of 4 situations of ice cover (see text) in Eastern Bering Sea during winter and spring periods 1967-75. Data for 1967-74 (upper) from Dr. George Kukla, Lamont-Doherty Geological Observatory, Columbia University and data for 1974-75 (lower) derived from National Environmental Satellite Service information. 7-8 1) ice cover inside the Bering Strait or just north of it 2) ice margin joining the Alaskan coast near Nunivak Island with Bristol Bay free of ice 3) pack ice along northern shore of Bristol Bay with open water in southern Bristol Bay 4) pack ice fully blocking Bristol Bay These conditions were identified from satellite data by Dr. George Kukla of Lamont-Doherty Geophysical Observatory, Columbia University, for the period 1967 to May 1974 using weekly maps of average snow and ice cover of the Northern Hemisphere issued by the National Oceanic and Atmospheric Administration. To update the series, we used 2 to 5 day Experimental Ice Analyses of the Alaskan region issued by the National Environmental Satellite Service (NESS) during 1974 and 1975; these are summarized at the bottom of the figure in a similar manner as the previous data. Differences in interpretation are evident in the two sets of data for 1974. In general, the ice cover was most extensive in early 1972 and 1975, less in 1971 and 1974, and still less in 1973. All 5 years had greater coverage than did the years 1966 to 1970. Kukla and Kukla (1974) describe similar increases in ice and snow cover over other areas of the Northern Hemisphere since 1971. In the Bristol Bay area the annual surveys of the International Pacific Halibut Commission 7-9 during June 1972 and June 1975 have been limited by extensive ice cover. Also, Konishi and Saito (1974) show that drift ice in the Eastern Bering Sea extended farther south in 1971 than in 1967 and that in 1967 the ice disappeared earlier in the spring than normal. Ice cover was also extensive in 1956, when it extended westward from Bristol Bay to and beyond the Pribilof Islands. Relation to Northerly Winds Konishi and Saito (1974) have attributed the cause of the anomalously cold temperatures and ice cover in 1971 in the Eastern Bering Sea to unusually persistent northerly winds from March to May. They contrast this with 1967 when there was a predominance of winds from the south in May. To examine the relation of northerly winds to anomalously cold air and water temperatures, we computed a time series from January 1946 to May 1975 of monthly mean meridional components of the surface wind velocity on an east-west line of points at 5° intervals of longitude along 57°N across the southern Bering Sea and northern Gulf of Alaska (Fig. 7.;^. This series was based on monthly mean fields of surface atmospheric pressure developed by FNWC from two basic sources: from 1946 to 1963 the fields were developed from daily or more frequent pressure charts available from National Climatic Center or from National Center for Atmospheric Research; from 1963 to the present, digital fields of monthly mean pressure are available from means of 6 or 12 hourly analyses made by 7-10 1^ ,.,,• aJ '*«^ > ^ ro iTv O) ii> u^ J- cj t? J- cj .\j -^ O ^^ >v •• OO ^^ ^H fsj :j ^ -^J CNJ ro TO f -« O CO <-> O ^ ^ ,:J- -O OJ "^J rH tH -r-* '■^ ir* -^ :t cu , — *" OJE ^^ P, ^ TO f^ o J- ir^ -o ^- t ir. T> so S -• '-' "^ ^-' '"• '^ ^'' '^^ '>^ 00 1^ ^ . — ' / I - w o) -o H ^ -^ '-U -.3 )-_• -M o^ ^- »-t ■^-'"^ --• • « c E ^^ oj x-t ^u tH T-( -H tM tH ro .,- o '''.',.... i '.'. '. ^ ^ , \\ ^ J-' UJ vJi t-' u. ^u J- OL' C-J i-" H M ^ m t? ^ 5^ , .; E -M M -0 ;-- ro ,H ~r t^ ^ r^ '^ ^- '^-J -, ^ A' i ' cuo ^ ^* viJ >SJ --I -J ^ ^i) (VJ '■■' -T t^ -^ S ■ • i I I I ^ ^-< ^ I I +f^ : J . A ...:..■'.'.. . ^Z ^ _ (P^ :r(i^ ■vo c/ -^ ir-,'; i.-n o -o i^- * '^"' -r- o % ^^ I'' III CIT) • ,)••••••••••• (^ f-j-^ • Cvi lO 'T^ ■ J CT" '^ ■"^ ^ '^ ^-' "^ ■^- O E Oo ,'. I • , ' ' o'fo r^ r^ S. ,0 r^ ^ '^f r- -J^ ^4 ♦ ^t -^ '^ ^ •Jr"""^^ Ti ',\J T-l • I •/ -H '^ -^' ^ '^ fO -r- r* III ' I I I I o ^ O U3 U-N .-\( -H ^ '^' iy M O -0 X t — ' _J;^ III '.vj ro rvi r^ I » • -^ f^ "^ 0-) I c tf> !r • • • ' •''•'•- 7-11 s- • O XJ 14- C O cu o > > — c/i +-> ^^-^ s- +-> to O) •.- O C- c (/I O) s- S- O) nD +-) O) ■a CO E C QJ •>- •r- -r- (J ■? +-> O) •r- -O O) u a o c ra 1 — •.- <+- CD s- :> to O > FNWC; The surface winds were computed by first interpolating the pressure fields to a regular grid with a spacing of 3 degrees latitude by 3 degrees longitude. Geostrophic winds computed on this grid were rotated 15° to the left and reduced in magnitude by 30% to approximate the surface wind. These winds are subject to a variety of errors such as relatively few original pressure observations over the Bering Sea (particularly during winter), to inaccuracies in the FNWC analyses and in the interpolation to the 3 degree grid, to inaccuracies in the computation of geostrophic winds and in their rotation and contraction to approximate the surface wind. This method is useful, however, in that it produces a reasonably consistent time series over many years over long distances. The computed meridional wind velocities were variable by position along the line 57°N, by month of the year and from year to year. A long-term monthly mean of the velocities (for 1946-69) shows strong southerly winds over the eastern Gulf of Alaska that are generated by the low pressure systems, often over the Gulf. These southerlies are strongest in winter and greatly reduced in summer. In the western Pacific, northerly winds occur in winter, but these shift to southerly and reduce in velocity in summer. Meridional winds over the Bering Sea are more variable than over either the Gulf of Alaska or Western Pacific. Northerlies are common in fall and winter and southerlies are common in summer. 7-12 For brevity, the computed time series of meridional winds at the line of stations is not shown; these data show, however, that during 1966 and particularly during 1967, southerly as well as northerly winds were frequent over the Bering Sea but, during 1971 and later, southerly winds of speeds greater than 3.0 m/sec are much less common. In fact, during 1972, 1974, and the first 4 months of 1975 no strong southerly winds are evident over the Bering Sea region, and during the periods when they did occur (fall 1971 and summer and fall 1973), unusually cold air temperatures were not observed at St. Paul Island. To compare the periods when southerly flow was frequent and rare, monthly mean meridional wind velocities for two contrasting 2 year periods, 1966-67 and 1971-72, (Fig. 7.4 were obtained. General southerly winds characterize the former period over much of the southern Bering Sea during November to April, with variable north and south winds during May to October. In contrast, during the latter period, strong northerly winds are obtained from January to April or May, and winds during the remainder of the year are weak and variable. Particularly strong northerly winds are obtained over the southeast Bering Sea during February and March, the months of greatest negative air temperature anomalies at St. Paul Island during these years. Table 2 shows a summary of the monthly mean northerly and southerly winds along 57°N for the two periods. During 7-13 ITO' lTO*»W 150*»W 16Q J F M A M J J A S o N D 160*»W I 19. 19. 2^-27.-33 26. 21. ^.^ -9.-15 6. C^T^^X.'Sd.'i^Z 1 Ifi. 27. 18. 1<4. 16. 22. 22. 9. Ti7^T2r-it^7:at:x,:3:r 10. 16. 12. 2. 10. 19. 2£ 1^ -^^.-t+Z. -2'2 .' 31.-29. -2 3."^=TT7^.5a-^^ 27.-32. -29. -31.- 3d. -f5 I'l. lB7 l€.^|j:>-2. -t 10. 1^. -^fi<^=^lT-37.-37 -V •loT; 3. 6. 15. 19. 39. ^♦9. 19. -3> I kJ. 22. 3. 16. 1. 5. 29. 5**. 2^. 49. w 68. 52. 2^. d: 22. 51. 37. 60. 1966- 1967 J F M A M J J A S o N D Sy-Z, -10.-Z0.-39.-h1.- -22.-i+l,-5G. -^8. -4^4. -37. -It, CZ»>-3.-ll. -l8.-31.-52.-3S. -3.-13.-19. -21.-2 3.- 2j+j;__-^'<' -o.^jl^g.*'— e^'' 3. 9. ^^«"'..U..i-,g.C_^ 21. 15. -^6.-io. -^. ,/^323^ 3 . -la^^-.-'^T'ii'. 11. ^4. 1. 5. k, Zlbj^zl^ 13. 1"^. 97 1-+. 3. 3. 7. 3. -8.-1^ .N 1972 Figure 7.4 - Monthly mean northward comDonent of surface wind velocity by point along 57"N and month for years 1966-67 and 1971-72. Velocities are positive for southerly winds and negative for northerly winds in decimeters per second. 7-14 I— o ^^ . O -EZ o en CO c o s- I— o O U OJ «/) Q. ■o > c: •!- 4-> •1- -M CU CO •!— r- O U n3 Q. O) c -a o >•■- 2 I— u s- o >, (U I— 1— .C CD S- -(-> > CD O -M o CO CO fO I— s- r^ o T ■" CU CU "D > .C C -r- +J ro 4-> o r^ CD C <£> CU I E 4- CO O . ZJ Ln r- O o r — C^J CM CO cr> CU E ti CU CO CO T3 E O CU CTi C\J 00 O I— CM O CM CM O • • CO LO <^ ^ o O 00 CO o • • r^ CO CO CO CO CD O o 00 CO o • • CO t^ O cn cri ^ CT) o CO ^ o • • r^ CM I— 00 CO CO in LU O CO LD o • • CO 1^ LD -a CU t^ CM CU CD t^ Q. I I C/) CO I— CO I^ E cr> cri (T3 I— I— CU +-> S- o CU -E -M o E o CU CO r^ r-^ 00 CM O "v^ I— CM CM en r^ CM CM 00 CO CM CO CM O CO "^ r~- 00 CM 00* oo' 16.6 14.5 en «* CM CO r^ r^ 00 Ch CO CO CO LD CO o CM CM in 00 CM I — -o CU r^ CM CU lO i^ Ol I I C«0 CO I — CD r^ E Cr> CT> fO r— I— CU o o CO CO CD VO r^ CD Lf) CO ^ CD in r^ CO r^ CD CTi 1^ CTi r-. 00 1^ 00 CO -E +-> c o M- r^ CM O CO t^ I I S- CD r- CU UD 1^ Xl ' U3 CO VO LO O CM ro r^ CM oo CO o o CM 1 — O CO 1— CO 00 o r^ CO 00 en CO o -a CU r^ CM CU UJ r^ a. I I C-O CD I — CD r^ E en cri ro I — I — CU CTi .— CM CM CTi CTi CO CD LO CO r~^ CD 00 CO r^ LO CD LO CD CO LO CV^ LO "!d- LO "^ o 4- r^ CM o vo i^ I I S- CO I— CU LO r-^ XI cr> cTi E .— .— 3 O ^ t^ LO CO CO CO CO CO CO CO CO 1^ CM CO r^ ^i- CO ^ o -M E CU E CU u m CO r~s. CM CO r-^ I I vo ■— CO r^ o CO LO CO 00 CM CO 1 CO CO LD CO CM r^ CM LO LO r-~. CO CO CM CO LO CO ^ LO 1 00 CT> CM LO LO LO o 1 ■"" CO ^ CO rv. o 1 ■"J" CO 00 u:) LO CM o r^ r^ LO CM 1 ■"J" 1— CT> 1 1 LO LO 1 r-. CU CD E fO 7-15 the cold period, 1971-72, the mean meridional winds were lower in absolute magnitude than during the earlier warm period, 1966-67, suggesting that the cold conditions were not caused by an increase in meridional wind velocities but were related to increased persistence of northerly winds. The meridional winds from the north were also of lower speeds during 1966-67 over most of the Bering Sea except in the Bristol Bay region where northerly winds were stronger during 1971-72. The number of months that northerly winds occurred was greater during 1971-72 than during 1966-67 over most of the Bering Sea except at 160°W near the head of Bristol Bay where northerlies occurred in 5 months in each period. Meridional winds from the south were much weaker during 1971-72 than during 1966-67 over all of the Bering Sea stations except at the extreme western end over Kamchatka. By summing the speeds, we obtained the net displacement or resultant meridional wind. Here we did not correct for the varying number of days per month but this would be a minor correction. The net movement of air during 1966-67 was from the south over the central Bering Sea with northerly net flow over Bristol Bay and near Kamchatka. During 1971- 72, however, net flow was from the north over the entire line in the Bering Sea and even the western two points in the Gulf of Alaska. The last line in Table 2 shows the change in net displace' ment from 1966-67 to 1971-72 and shows that the reversal of 7-16 wind directions between the two periods was centered in the central Bering Sea near 175°E and 180°. Relation to Upper Air Circulation The variability of meridional winds over the Bering Sea since 1966 is related to variations in the circulation of the upper atmosphere. The position of idges and troughs are a particularly important aspect of the upper air circulation. In the Northern Hemisphere, a ridge in the upper air circulation causes warm, southern air to be advected to the north under its western flank and cold northern air to be advected to the south under its eastern flank. Thus when a ridge is centered to the west of a given point, winds are cold and northerly and when a ridge is east of the point, winds are warm and southerly. Three processes occur which cause cooling of surface air and water temperatures in response to northerly winds. First, although the Coriolis effect causes a deflection of the water to the right of the wind, northerly winds cause flow of the surface water to the south. When meridional gradients of sea surface temperature exist, such southward water movements cause cold anomalies of sea surface temperature. A second factor causing cooling of the sea water is cooling by loss of sensible heat and latent heat of evaporation. These losses can be large when cold, dry air blows from land or ice covered areas over open water areas. Both processes are roughly proportional to the speed of the wind and to the vertical gradients of temperature and humidity, respectively. 7-17 A third process that would cool the sea water under northerly winds in the Bering Sea is that of increased southerly drift of ice. The warm air advected into the Bering Sea region during 1966, particularly during 1967, was related to the occurrence of blocking ridges in the northeast Pacific centered to the east of the Bering Sea. Exceptionally strong southerly winds over the Bering Sea under the western flank of these ridges occurred during spring (March, April, and May) 1967 when a wery strong ridge formed south of western Alaska. This ridge (Fig. 7.^ was the strongest such ridge ever observed during the period of record--33 years (Andrews, 1968). The ridge combined with an unusually deep polar depression north of Alaska to drive the strong intrusion of southern air into the Bering Sea region. The effect of this upper level ridge at the surface was to shift the Aleutian Low westward over Kamchatka where its cyclonic motion contributed to the southerly flow of air over the Bering Sea. White and Clark (1975) describe the development of ridges over the central North Pacific and show that particularly strong ridges formed over the northeast Pacific during March, April, and December 1967 and January 1968. These were months of strongest advection of southerly winds at 57°N, 170°W near St. Paul Island. The ridges are often referred to as blocking ridges because the ridge blocks westerly zonal flow and causes meridional flow. 7-18 700 MB MEAN AND DN SPRING 1967 lj_ Figure 7.5- Mean sea level pressure, height of the 700 mb surface, and departures from normal for Spring 1967> (from National Weather Service). 7-19 The cold winters and springs in the southeastern Bering Sea since 1971 have been caused by the persistent occurrence of ridges or high elevation centers to the west of the Bering Sea over Siberia or the Arctic Ocean. These high pressure systems caused northerly winds over the Bering Sea under their eastern flanks. Associated with this westward shift of ridges since 1971 has been the frequent occurrence of troughs or low elevation centers over the Gulf of Alaska or northern Canada. During the cold winter of 1970-71, a blocking ridge formed over the western Bering Sea and extended to the northwest over the Laptev Sea north of Siberia. Anomalous circulation from the north occurred along the eastern flank of this ridge over the Bering Sea. By spring 1971 the blocking ridge had disappeared but was replaced by a strong low elevation center over western Alaska. Cyclonic circulation around this low again caused northerly winds over the Bering Sea. During the cold winter of 1971-72, a blocking ridge (Fig. 7. 5) again formed over the Bering Sea and northeastern Siberia as it had during the previous winter. Strong northerly anomalous winds occurred over western Alaska and the eastern Being Sea. Unlike the previous spring this situation persisted in spring 1972 and maintained northerly winds. The relatively mild winter of 1972-73 was different from the previous two winters in that weak southerly winds occurred over the Bering Sea under the western flank of a ridge over Alaska and western Canada. A 7-20 Figure 7.6- Mean sea level pressure, height of the 700 mb surface, and departures from normal for Winter 1971-72, (from National Weather Service) . 7-21 strong low elevation center formed over Bristol Bay in the spring of 1973 and caused anomalous northerly winds along its western side over the central and western Bering Sea. The winter of 1973-74 was again cold. Again the pattern reverted to that of the winters of 1970-71 and 1971-72 with a strong high elevation region centered over northeastern Siberia and related anomalous northerly winds over the entire Bering Sea. The high over northeastern Siberia persisted into spring 1974 but the primary feature of the circulation was a low elevation region south of the central Aleutians. This low caused easterly winds over the southern Bering Sea and meridional winds were weak and variable, allowing the relatively mild temperatures and ice cover that spring. The winter of 1974-75 again had persistent strong northerly winds over the southeastern Bering Sea in response to a continued high elevation center over northeastern Siberia and a low elevation center over western Alaska. Relation to Hemispheric Circulation We have seen that the cold winters and springs since 1971 in the southeastern Bering Sea have been caused by a westward shift of ridges or high pressure systems and related occurrence of troughs or low pressure systems to the east. These systems create air flow from the north which cools the region by heat loss and by southward transport of air, water, and ice. 7-22 This westward shift of high pressure systems is associated with other atmospheric fluctuations elsewhere. For example, since 1971 the high pressure systems occurring in northeastern Siberia have been associated with either a strengthening of the polar depression or a shift of its principal lobe to the south over northeastern Canada or Baffin Bay. Concurrent with these changes has been a general strengthening of high pressure systems in the mid-latitudes. Thus winters since 1970-71 have had stronger meridional gradients of height, hence stronger zonal winds. Wagner (1975) mentioned that the winter of 1973-74 was the fourth consecutive winter in which the zonal atmospheric circulation over most of the western half of the Northern Hemisphere has been stronger than normal. This suggests that a teleconnection exists between strong mid-latitude, westerly winds over North America and cold winters in the Bering Sea region. The cold winters over the southeastern Bering Sea since 1971 were also associated with major shifts in the patterns of sea surface temperature in the North Pacific Ocean. In 1972 Namias (1972) pointed out that in the winter of 1971-72 the coastal waters along the entire West Coast from California were anomalously cold, while a pool of warmer than normal water was present in the east central North Pacific. In contrast, during the 14 winters previous to 1971-72 the general sea surface temperature pattern was the opposite: 7-23 warm along the West Coast of North America and cold in the central North Pacific. Namias also suggested that the winter of 1971-72 may have started a new pattern that would persist for several years. This appears to have been a good prediction as it has persisted for 5 winters now. How long the new pattern will persist is, of course, unknown. Effects on Fisheries Sal mon According to preliminary reports of the Alaska Region of the National Marine Fisheries Service (Anon. 1974), the 1974 commercial harvest of Pacific salmon, Oncorhynchus spp. , may have been the lowest since the inception of the Alaska salmon fishery in the late 1800's and followed almost equal low catch in 1973. The low statewide catch was reportedly due to poor catches of pink salmon, 0. gorbuscha , which were attributed to the continued effects of the unusually severe winters of 1970-71 and 1971-72. Pink salmon spawn in many streams of southern and western Alaska. The adults spawn in summer, or fall, the eggs mature in the stream beds over winter, and the juvenile fry migrate to sea the following summer. Salmon eggs are susceptible to cold winter weather by ice-caused erosion of the spawning beds and by reduced flow of water through the spawning gravel and consequent reduction in supply of oxygen to the eggs. 7-24 In contrast to the pink salmon which migrate directly to sea following their emergence from the spawning gravel, sock eye salmon, 0. nerka , typically spend 1 or 2 years as juveniles in a lake before migrating downstream to the ocean. A large population of sockeye salmon spawn in rivers tributary to Bristol Bay that have lakes within their watersheds^ these salmon have constituted a yery important fishery in the Bristol Bay region since the turn of the century. Catches of sockeye salmon in Bristol Bay during 1972 to 1974 were the lowest on record since 1896 due to the fishery being severely restricted to obtain desired escapement levels. This caused adverse effects on the economy of the area. The cold air temperatures observed at King Salmon during the first 6 months of 1971 and 1972 had various apparent effects on the Bristol Bay sockeye salmon. Mature sockeye salmon returning to Bristol Bay streams to spawn were 1 to 2 weeks late in 1971, which caused considerable concern that the run would be much smaller than predicted. Although there is no specific evidence as to the manner by which cold oceanic conditions may have affected the onshore movements in 1971, large catches of mature salmon by research vessels in another year of anomalously cold shelf temperatures, 1956, indicated that onshore migrations may be delayed until near surface waters over the shelf have warmed to 3°C or higher (INPFC, 1958). 7-25 A number of anomalous phenomena were noted in Lake Iliamna in the summer of 1971 following the cold winter of 1970-71 (Mathisen, et al . 1972)-^. The lake ice melted about 3 weeks later than normal, and colder than normal conditions existed throughout the summer. A heat budget study indicated that stored heat in Lake Iliamna in June (Fig. 7. 7) was not only the lowest recorded since 1961 when records began, but also was only half the maximum value recorded during that period. The heat stored in Lake Iliamna in June is inversely correlated with timing of the escapements of sockeye to the Kvichak River which were 8 or 9 days later in 1971 than in 1970. A delay of 5 to 7 days in the peak of spawning was observed on the spawning grounds. The effects of cold temperatures on the abundance of sockeye salmon are probably of greater importance at the egg and juvenile stages than at the adult stages. Mathisen 2/ et al . (1975)— , as a result of numerous studies of sockeye salmon in the Kvichak River and its source Lake Iliamna, state that "temperature strongly affects hatching, emergence, and subsequent growth and survival of juvenile sockeye salmon. The cold winter of 1970-71 caused a reduction in both number of fry produced in the spawning streams and in the growth of the fry in the Kvichak River District. Although there was a 657o increase in the number of spawners (13.9 vs 8.4 million) in 1970 over 1969, the relative fry production as measured in 1971 was only 52% of that of the previous year, in fact, 7-26 30 26- 22 M o 18 _l 3 14 i o 8- t5 UJ I 0- o UJ oc. P -4 -8 TOTAL SUMMER HEAT BUDGET 1964-71 MEAN JUNE HEAT BUDGET I I I I 1 1 1 1 1 1 I 1961 1963 1965 1967 1969 1971 Figure 7.7 - Amounts of stored heat in excess of 4°C in June from 1964 through 1971 and total summer heat budgets (in August / September) from 1961 through 1971 Lake Iliamna, Alaska. Data from Mathi sen, et. al . , 1972. 7-27 the lowest recorded since sampling began in 1961. Also the mean length of fry in September 1971 was the lowest on record since sampling began--about 21% less than the mean length for 1962-70. Factors related to overs tressi ng of the ecosystem by number of spawners are also of importance in fry production and growth, but such factors may be of less importance than the cold weather of the winter of 1970 and 1971. For example, although the number of spawners producing the 1965 brood year (24.3 million) was almost twice that of the 1970 brood year (13.9 million), reduction of the mean length of fry at age was only 1% for the 1965 brood year as opposed to 21% less for the 1970 brood year--accordi ng to 3 / data presented by Mathisen, et al . , (1974)— . They also reported that the cold winter of 1971-72 also resulted in poor growth of sockeye fry in the Kvichak District. The mean length of age fry in the summer 1972 was the second lowest on record since sampling began in 1961. The winter of 1972-73 was not extremely cold and mean lengths of age fry in the Kvichak District were near the average length for 1962-70. The poor return of mature sockeye salmon from the 1969 brood year to the Bristol Bay inshore fishery in 1973 was "attributed to poor marine survival as a result of the severely cold winter of 1970-71 and the subsequent late spring of 1971" (Mathisen, et al . 1974); even poorer initial returns from the 1970 brood year were reported (Mathisen, et 7-28 al . 1975). However, returns from this brood year are not complete even at this time. Fujii et al . (1974) discussed the poor return of sockeye salmon to Bristol Bay in 1973 and attributed the low catches to cold sea water temperatures in the southeastern Bering Sea in 1971. The winters of 1973-74 and 1974-75 were again very cold and should cause similar effects on the Bristol Bay sockeye populations as did the winter of 1970-71. According to / \ 4/ Rogers, et al . (1975)— , conditions in the Wood River Lake system of the Nushagak District of Bristol Bay indicated that the winter of 1973-74 was colder than average for the fourth consecutive year; they also note that cold temperatures in winter generally results in poor survival in the Wood River Lakes where spawning occurs primarily on the beaches It should be pointed out that delayed spring conditions may have more severe effects than cold winters. Temperatures in spring and summer 1974 vero much warmer than normal and ice breakup occurred 10 days earlier than normal in the Wood River area. The mild conditions resulted in rapid growth of the juvenile sockeye which evidently more than compensated for poor growth rates during the previous winter. Rogers, et al. (1975) noted that mean size of sockeye salmon fry in June 1974 was the largest since such observations were started in 1962. Mathisen, et al . (1975) also reported unusually warm air temperatures in spring 1974 in the Lake Iliamna area and one of the earliest 7-29 The relative abundance of 3-year old halibut is considered to be the best indicator of year class strength; in 1974, the rate of capture of the 1971 year class was the lowest for the age group since the surveys began. The 1972 year class was present in below average numbers at both inshore and offshore station. (Reeves, Macintosh and McBride, 1974)^/. King Crab The effect of cold water conditions on the abundance of king crab, Paralithodes camtschacti ca , in the eastern Bering Sea is an enigma. Estimates of male abundance by the Northwest Fisheries Center from a fixed grid of stations over the continental shelf in 1968, 1969, 1970, 1972, and 1973 (Fig. 7. 8) indicate low numbers of small and medium length crabs in 1968, 1970 and 1972 (note no data for 1971) and 2-3 times as many crabs in 1969 and 1973. (Hayes and Reid, 1973)-^. Crab growth from to 5 years is largely linear, from to 100 m; thus, it would appear that 1968 was an exceptional spawning year, but discrepancies in the related abundances of specific year classes in individual years severely challenges the consistency of these data. It is not clear at this time whether this is another case of organisms moving out of the standard sampling area as a result of environmental conditions, reaction of the organism to sampling gear, or inadequate 8/ sampling methods. Beardsley— believes that if there is a temperature/recruitment relationship, cold temperatures 7-30 I5r 1968 1969 — 1970 — 1972 1973 •••• 40- 60- 49 69 80- 100- 89 109 LENGTH 120- 140- 129 149 CLASSES 160- ISO- 200- 169 189 209 (lOmm) Figure 7.8- Estimates of male king crab abundance by 10 mm length classes from the 1968, 1969, 1970, and 1972 spring research cruises of the NMFS Northwest Fisheries Center in the Eastern Bering Sea. 7-31 breakups of ice on Lake Iliamna, as well as exceptionally high water temperatures and low lake level in summer 1974. Hal i but Another species of fish affected by the recent cold winters is the Pacific halibut. Hippoglossus stenolepis . Pacific halibut are a demersal species which spawn in winter over the continental slope and move into the shallow continental shelf waters in spring to feed when water temperatures rise. The halibut fishery is largely restricted to waters in the 3-8°C temperature range. Data from the annual trawl surveys by the International Pacific Halibut Commission in the southeastern Bering Sea on a fixed station grid since 1966 document the lowering of bottom water temperatures from 1967 to 1972. Based on these surveys, the southward extent of the 2°C isotherm in 1972 was considered to inhibit the migration of halibut to the usual summer feeding grounds 5 / (Best, 1974)- . Normally 2-year old halibut are a significant proportion of the catch in the nearshore, shallow water stations along the north shore of the Alaska Peninsula, and 3-year old halibut dominate the catches in Bristol Bay. However, in 1972, the catch rate of the 3-year old halibut (the 1969 year class) in the inshore area was four times the average. It was reported that the distribution of 3-year old halibut had shifted far enough inshore to be partially bypassed by the standardized station grid, thus resulting in an underestimation of their abundance. 7-32 may increase the number of crabs, but there is not much evidence for any specific relationship at this time. Nevertheless, there is evidence that a strong year class of king crab was produced in 1970 or 1971. 7-33 References Cited ANDREWS, J. F. 1968. The Circulation and Weather of 1967. Weatherwise, February 1968,. pp 5-13. ANONYMOUS 1974. Monthly Narrative Report, October 1974, Alaska Region, National Marine Fisheries Service, Juneau, Alaska. 11 pp. BEST, E.A. 1974. Juvenile Halibut in the Eastern Bering Sea: Trawl Surveys, 1970-72. International Pacific Halibut Commission, Technical Report No. 11. 32 pp. FAVORITE, F. and W.J. INGRAHAM, JR. 1973. Oceanography. In. International North Pacific Fisheries Commission, Annual Report 1971: 89-97. FUJII, T., K. MASUDA, T. NISHIYAMA, G. KOBAYASHI , and G. ANMA. 1974. A Consideration on the Relation Between Oceano- graphic Conditions and Distribution of Bristol Bay Sockeye Salmon Oncorhynchus nerka (Walbaum) in the Eastern Bering Sea, with Special Reference to its Poor Return in 1973. Bull. Fac. Fisheries, Hokkaido Univ. 25(3), pp. 215-229. 7-34 INTERNATIONAL NORTH PACIFIC FISHERIES COMMISSION 1958. Annual Report, 1957. 86 p. JOHNSON, J.H., D.R. MCLAIN, and C.S. NELSON. 1975. Climatic Change in the Pacific Ocean. 1974 Status of the Environment Report, National Marine Fisheries Service, Washington, D.C. KONISHI, R. and M. SAITO. 1974. The Relationship Between Ice and Weather Conditions in the Eastern Bering Sea. In_ Oceanography of the Bering Sea, D.W. Hood and E.J. Kelley, editors. Institute of Marine Science, University of Alaska, Occasional Publication 2, pp. 425-450. KUKLA, G.J. and H.J. KUKLA. 1974. Increased Surface Albedo in the Northern Hemisphere, Science 183 (4126), pp 709-714. NAMIAS, J. 1972. Experiments in Objectively Predicting Some Atmospheric and Oceanic Variables for the winter of 1971-72. Journal of Applied Meteorology 11(8), pp. 1164-1174. STRATY, R. R. 1974. Ecology and Behavior of Juvenile Sockeye Salmon ( Oncorhynchus nerka ) in Bristol Bay and the Eastern Bering Sea. In Oceanography of the Bering Sea, D.W. Hood and E.J. Kelley, editors. Institute of Marine Science, University of Alaska, pp. 285-320. 7-35 WAGNER, A.J. 1975. The Circulation and Weather of 1974. Weatherwise, February 1975, pp. 27-50. WHITE, W.B. and N.E. CLARK. 1975. On the Development of Blocking Ridge Activity Over the Central North Pacific. Journal of Atmospheric Sciences 32(3), pp. 489-502. 7-36 FOOTNOTES 1/ Mathisen, O.A., P.H. Poe, L.L. Low, and T.J. Carlson. 1972. Kvichak Sock eye Salmon Studies. XH ^^^^ Research in Fisheries. Annual Report of the College of Fisheries, Fisheries Research Institute, University of Washington, Seattle, WA , pp. 19-22. 2/ Mathisen, O.A., P.H. Poe, P.B. Roger, G.D. Cortner, and N.A. Limberg. 1975. Kvichak Sockeye Salmon Studies, jji 1974 Research in Fisheries. Annual Report of the College of Fisheries, University of Washington, Seattle, WA , pp 17-20 3/ Mathisen, O.A., P.H. Poe, P.B. Roger, and T.J. Carlson. 1974. Kvichak Sockeye Salmon Studies. j_n 1973 Research in Fisheries. Annual Report of the College of Fisheries, Fisheries Research Institute, University of Washington, Seattle, WA, pp 18-21 . ^_| Rogers, D.E., B.J. Leistikow and N. Newcome. 1975. Wood River Sockeye Salmon Studies. Jji 1974 Research in Fisheries Annual Report of the College of Fisheries, Fisheries Research Institute, University of Washington, Seattle, WA, pp 15-17. 5^/ Best, E.A. 1974. Distribution and abundance of juvenile Pacific halibut in the eastern Bering Sea. International Pacific Halibut Commission, 37 p. (Unpublished report). 7-37 6/ Reeves, J.E., R.A. Macintosh, and R.N. McBride. 1974. King and tanner crab research in the eastern Bering Sea, 1974. Northwest Fisheries Center, Seattle, WA , 38 p. (Processed) (INPFC Document No. 1734). l_l Hayes, Murray L. and Gerald Reid. 1973. King and tanner crab research in the eastern Bering Sea 1973 Northwest Fisheries Center, Seattle, WA , 41 p. (Processed) (INPFC Document No 1611) 8/ Beardsley, A.J. Director Kodiak Facility, Northwest Fisheries Center, Seattle, WA ; personal communication. 7-38 OCEANOGRAPHY AND ALBACORE TUNA, THUNNUS ALALUNGA (BONNATERRE) , IN THE NORTHEAST PACIFIC DURING 1974 R. MICHAEL LAURS AND RONALD J. LYNN National Oceanic and Atmospheric Administration National Marine Fisheries Service Southwest Fisheries Center La Jolla, California 92038 JULY 1975 SOUTHWEST FISHERIES CENTER ADMINISTRATIVE REPORT NO. LJ-75-65 Oceanography and Albacore Tuna, Thunnus alalunga (Bonnaterre) , in the Northeast Pacific During 1974* R. Michael Laurs and Ronald J. Lynn The early-season distribution and apparent abundance of the North Pacific albacore tuna, Thunnus alalunga (Bonnaterre), are apparently related to oceanographic conditions of the Transition Zone and associated oceanic frontal structure. Results from fishery-oceanography research cruises conducted cooperatively by the NOAA/NMFS Southwest Fisheries Center and the American Fishermen's Research Foundation show that the relative abundance of albacore is greater within the Transition Zone than outside it during their migration through offshore waters and that year-to-year variations in ocean structure are reflected in variations in albacore distribution (Laurs and Lynn, 1974, 1975). It also appears that the migration patterns of albacore in the offshore waters are impor- tant in determining the subsequent distribution of fish in inshore waters during the usual fishing season. Transition Zone and Associated Frontal Structure The Transition Zone is a region of mixing between cold, low salinity subarctic waters to the north and warm, saline subtropic waters to the south (Sverdrup, Johnson and Fleming, 1942). The Transition Zone waters are found in a zonal band across the North Pacific middle latitudes within *This contribution has been taken from a manuscript in preparation for publication by R. Michael Laurs and Ronald J. Lynn entitled "The offshore distribution and relative abundance of albacore tuna, Thunnus alalunga (Bonnaterre) during early-season and the migration routes followed by albacore into North American water." 8-1 the westward- flowing North Pacific Current (McGary and Stroup, 1956; Roden, 1971). They are bounded at the north by the subarctic front and at the south by the subtropic front (Roden, 1974). Both of these fronts have abrupt gradients in temperature and salinity. The dynamic proces- ses which produce and maintain the gradients also enrich these waters (McGary and Stroup, 1956), which give reason why these regions are biolog- ically important to albacore. To the east of 135° W, the North Pacific Current turns southeast and south as does the Transition Zone, and the boundary gradients begin to lose their continuity. Temperature and salinity data are used to identify the Transition Zone as distinct from the water masses to the north and south. Three oceanographic sections of the vertical distribution of temperature and salinity along 137°30' W taken in June of 1972, 1973, and 1974 are given in Figure 1. In this figure, subarctic waters are depicted by hatching- shading of salinity less than 33.8Xo, subtropic waters by dot-shading of salinity greater than 34.2Xo, and Transition Zone waters by no shading; the temperature field, shown by dashed lines, is simplified to the 62° F (16.7° C) and 58° F (14.4° C) isotherms. In 1972 and 1973, the subarctic waters were found north of 35° N and the subtropic waters south of 31°30' N and 32° N, respectively. The boundaries of the Transition Zone between these water masses were well -developed and readily identifiable. The subarctic front was marked by the sharp shoaling of the 33.8^oisoha- line and 58° F (14.4° C) isotherm and abrupt gradients in salinity extending from the surface to 200 m where a strong halocline was evi- dent. The subtropic front was delineated by the steep shoaling of the 8-2 34.2Xo isohaline and 62° F (16.7° C) isotherm and marked gradients in salinity extending from the surface to 200 m where a well -developed halocline was apparent. Mixing was indicated in the Transition Zone in 1972 with low-salinity water penetrating southward and some high-salinity water northward at intermediate depths. This distribution and those along other meridians, indicate that a large wave-like feature or large eddy existed in the Transition Zone region centered at about 137°30' W. Oceanographic conditions were different in the region of the Transition Zone in 1974 from those which were observed in 1972 and 1973 (also see Saur, Sec. 6). In 1974, subarctic waters were found north of 36°30' N with a lens of Transition Zone water between 37° to 39° N extending from the surface to 100 m, and extending in a tongue southward between 36°30' N and 34°30' N at intermediate depths. Subtropic waters were found south of 33°30' N and in a small, shallow lens at the surface near 35° N. The boundaries of the Transition Zone were poorly developed and broken. The subarctic front was virtually non-existent and the Transition Zone waters graded gradually into the subarctic waters. The subtropic front was weak, but not as weak as the subarctic front. The salinity gradients were more diffuse and the changes in depth of the isotherms more gradual and variable in the regions of the subarctic and subtropic fronts in 1974 than in 1972 and 1973. These year-to-year differences match the findings of J. F. T. Saur using independent data. Albacore Catches in Relation to Oceanic Fronts During June 1972 and 1973, commercially productive centers of fishing developed in Transition Zone waters between 33° to 35° N and west of 8-3 135° W with small or no catches made in the region between the offshore area and inshore waters within 150 miles of the coast where fishing takes place during the traditional albacore fishing season. These fishing centers persisted for 2 and 3 weeks before fishing effort was withdrawn. In these years, the frontal structure was strongly developed and the Transition Zone easily identifiable. During June 1974 when the frontal structure was poorly developed and the boundaries were less distinct, the catches were more scattered and distributed over a large range of latitude, 31° to 36° N, and longi- tude. High catches were made in the area offshore of 135° N, and also in the region between the offshore area of high catches and inshore waters where fishing normally takes place. Catches were substantial in 1974, however, they did not demonstrate persistence in any area for more than a few days, and more search time was required in 1974 than in the previous 2 years, to make catches. There was one area which did have abrupt gradients during June 1974. An eastward protruding tongue of Transition Zone water was found centered at 35°30' N, 132°30' W which had salinity gradients comparable to those found in previous years. Sub- stantial catches of albacore persisted in this region for a week until fishing effort was withdrawn. Summary The influence of extensive lateral mixing between water masses and the diffuse nature of the boundary frontal structure apparently was not effective in concentrating albacore in offshore waters during early- season 1974 as had occurred in the previous 2 years. 8-4 REFERENCES CITED Laurs, R. Michael and Ronald J. Lynn. 1974. Report of joint National Marine Fisheries Service-American Fishermen's Research Foundation during 1973. SWFC Admin. Rep. No. LJ-74-47: 19-62. . 1975. The association of ocean boundary features and albacore tuna in the northeast Pacific. STD Conference and Work- shop Proceedings, February 12-14, 1975, San Diego, CA, pp. 23-30. McGary, James W. and E. D. Stroup. 1956. Mid-Pacific oceanography. Part VIII, middle latitude waters, January-March 1954. U.S. Fish Wildl. Serv., Spec. Sci . Rep. Fish 180, 83 p. Roden, Gunner I. 1971. Aspects of the Transition Zone in the northeastern Pacific. J. Geophys. Res. 76(15): 3462-2475. . 1974. Thermocline structure, fronts, and air-sea energy exchange of the trade wind region east of Hawaii. J. Phys. Oceanog, 4: 168-182. Sverdrup, H. U., Martin W. Johnson and Richard H. Fleming. 1942. The oceans, their physics, chemistry and general biology. Prentiss-Hall, New Jersey, 1087 p. 8-5 (Sa313A) Hid3a U33J) Hid30 (Sa313A) HidBQ (i33J) Hld30 (Sa3i3W) HXd3Q (1333) HidSa 0) T3 }-l E 3 v-' CO 01 !^ (U 4J CO IS [i. O O 00 •H U-| Q. O Q) 00 I « c . O -i-l i O 'D •^ CO o x: -OO CD M CO o , D CO XI ^-' x; 4-1 CO [^ CO . 0) bO cj o c c -u o -1-1 O CO ^^ r-H ■-< XO CO rg 13 >.j3 > CO -r-l 4J > CO CL CO , }J > o •u x: •H CO c ■r-l (1) Vj CO CO O CO CO •H X CO ■u 3 u-i E ^1 C« O }^ > oox • C 4J /— \ -H O !-i TJ CO i-H (U CO -r-l • 15 x: CX3 O CO /-N , I— I fjL, ^ Xi -^ SEA SURPACE TEMPERATURES IN THE EASTERN TROPICAL PACIFIC DURING 1974 AND THE TROPICAL FISHERY by Forrest R. Miller Inter-American Tropical Tuna Cominission The eastern tropical Pacific supports a major part of the international fishery for yellowfin and skipjack tuna and it also supports the world's largest anchoveta fishery which is foiond on the eastern boiandary of the tropical Pacific. According to the Inter-American Tropical Tuna Commission's 1974 Annual Report over 300,000 tons of yellowfin and skipjack were cap- tured during 1974 in the eastern tropical Pacific east of 150°W. The catch of yellowfin was the largest in the history of the fishery; and the skip- jack catch was nearly 17,000 tons above the average of the previous five years . Published literature covers in detail the latitudinal range of several species of tropical tionas in terms of sea surface temperatures. Uda (1961), Schaefer (1961), Broadhead and Barrett (1964), Blackburn (1965), Laevastu and Rosa (1970) and Williams (1970) have all noted that yellowfin and skip- jack tunas, particularly, are found in commercial quantities in tropical areas bo^anded on the north and south (northern hemisphere) by the 58°F (20°C) and 63°F (17°C) isotherms for the two species, respectively. The upper limit of the tuna's temperature range has been described by most of the aforementioned researchers to be between 84°F (28.9°C) and 86°F (30°C) . Throughout the year in the eastern Pacific, the 68°F (20°C) isotherms reach the ocean surface along the southern boundary of the California current off Baja, California and along the cold side of the equatorial ocean front near the equator. Surface temperatures greater than 85°F (29.4°C) are found occasionally off southern Mexico during the spring and summer months. During the past four years tropical tuna fishermen have recorded and transmitted to the Southwest Fisheries Center (SWFC) , National Marine Fish- eries Service, La Jolla, California, surface and subsurface marine obser- Ann. Rep. Inter-Amer. Trop. Tuna Comm. , 1974. The Fishery in 1974; pp. 21-25. (in English and Spanish). 9-1 vations from the fishing grounds in the eastern tropical Pacific. In a joint research project the Inter-American Tropical Tuna Commission (lATTC) and the SWFC have been evaluating statistical relationships between tuna catch and concomitant ocean properties. The three dimensional thermal structure, down through the thermocline, over the tropical fishing grounds is closely related to the success in purse seining for yellowfin and skipjack. Nearly 86% of all successful purse seine sets in 1974 occurred in water with surface temperatures between 79°F and 84°F. Less than 10% of the sets were made where temperatures were less than 79° F; and only 4% of the sets were made in very warm water of 85 °F or greater. Based on over 4,000 tuna boat bathythermograph (XBT) observations the distribution of successful sets on tuna, as a function of sea surface temperature (Figure 1) , was similar in all areas and fishing seasons from 1971 through 1974 in the eastern tropical Pacific. Each year the lATTC publishes in its annual report the distributions of the total yellowfin and skipjack catches by 1° guadrangles. Figure 2 shows the distribution of yellowfin catch captured by the international tuna fleet in 1974. In addition, the composite positions of the 68°F and 79°F isotherms have been superimposed on the yellowfin catch in Figure 2. The position of each isotherm represents the annual, composited position determined from surface temperatures published in Fishing Information (Miller, 1974) and observed by tuna boats and commercial ships. In find- ing the composite location of each isotherm maximtim weight was given to temperatures observed by tuna boats in areas of most active fishing. After March 18, 1974, when yellowfin fishing became regulated east of 120°W, the tuna fleet expanded its fishing westward to 150°W. The positions of the 79° F isotherms west of 120°W for example, were based primarily on data from April through November 1974. Figure 2 shows that the 79°F isotherms enveloped those areas where most of the yellowfin were captured in 1974. The areas from 5°N to 15°N between 115°W and 120°W and to the west of 145°W all had surface temperatures greater than 79°F; but these were areas of limited fishing effort. In other years studied (1971-1973) similar hori- zontal relationships between annual yellowfin catch and the 79°F isotherms were found. However, the distributions of catch and temperature were dif- ferent, especially south of 10 °N. Surface temperatures below 79 °F in the 9-2 Gulf of Panama and westward from the Costa Rica (upwelling) dome (near 8°N, 92°W, in 1974) were associated with vertical ocean mixing and up- welling. Along the southwest coast of Baja, California the 68°F isotherm marked the northern limit of yellowfin catches. Along the coast of southern Ecuador and Peiru temperatures remained below 68°F. During 1974 the anchoveta fishery was recovering from a record low catch of 1.96 million (metric) tons in 1973 following the devastating 1972-73 El Nino. Some yellow- fin tiina were captured in the Gulf of Guayaquil during periods when temper- atures were above 68° F. During all of 1974 surface temperatures were 2°F to 6°F below normal along the equator and in the Peru Current. Figure 3 shows the composited patterns of negative temperature anomalies of 2°F and greater. The annual temperature anomaly patterns in Figure 3 were obtained by graphically com- positing the anomaly charts published monthly in Fishing Information (Miller, 1974) . Other areas where temperatures remained below normal during 1974 were southwest of Baja and along 10°N around 115°W. As indicated in Figure 2, fishing in these areas was not good in 1974. A comparison of Figures 2 and 3 reveals that the most productive fish- ing areas in 1974 had surface temperatures near or slightly above noional. One exception was off Costa Rica where strong northeast trades increased ocean mixing and kept surface temperatures below normal during the most active fishing period. Along the coast of Peru, temperatures were also low, but this condition in 1974 helped to restore the anchoveta fishery. In early 1974 high rates of anchoveta catch were reported during a very re- stricted fishing period. Past studies have not uncovered any significant relationships between sea surface temperatures and abiondance of yellowfin tiina in selected areas of the eastern tropical Pacific. However, sea surface temperatures and their deviations from the long term means (anomalies) are good indicators of large scale ocean changes. Apparently the most active tropical tiina fishery is found where seasonal temperatures remain in the 79°F to 84°F range. The largest year-to-year changes in temperature occur on the peri- phery of the traditional fishing grounds and occasionally inshore along Central America. Therefore, monitoring ocean surface temperatures can pro- vide useful information about tropical ocean conditions, especially just 9-3 before and after the beginning of the fishing season. Conventional sur- face and subsurface (XBT) marine data supplemented by the high resolution (thermal infrared) satellite temperature data (Stevenson and Miller, 1975) now provides an improved data base for monitoring the ocean thermal struc- ture in the mixed layer. 9-4 Literature Cited Blackburn, M. 1965. Oceanography and the Ecology of T\ina. Oceanogr. Mar. Biol. Ann. Rev. 3:'299-322. Broadhead, G.C. and I. Barrett. 1964. Some factors affecting the distribution and apparent abundance of yellowfin and skipjack tima in the Eastern Tropical Pacific Ocean [in English and Spanish]. Ixiter-Amer. Trop. T^Ina Coiran. , Bull., 8(8):417-473. Eber, L. 1974. Fishing Information. U.S. Dept. Commerce, NQAA, Nos. 1-12, 1974. Laevastu, T,, and H. Rosa. 1970. Fisheries Oceanography . pp. 16-22. Fishing News (Books) Ltd., London, F.C.A., England Shaefer, M. B., 1961. Tuna Oceanography Programs in the Tropical Central and Eastern Pacific. Calif. Coop. Fish Invest. Rep., _8, pp. 41-44. Stevenson, M. R. and F. R. Miller. 1975. Application of satellite data in fishery oceanography. Inter-Amer. Trop. Tuna Comm. Final Report for SPOC, NOAA Grant No. 04-4-158-28. 98 p. Williams, F. 1970. Sea Surface Temperature and the Distribution and Apparent abundance of skipjack (Katsumonua Pelamis) in the Eastern Pacific Ocean, 1951-1968 [in English and Spanish]. Inter-Amer. Trop. Tuna Comm. Bull., _15 (2) : 231-281. Uda, M. 1961. Fisheries oceanography in Japan, especially on the 'principles of fish distribution, concentration, dispersal and fluctuation. Rep. Calif. Coop. Oceanic. Fish. Invest., 8:25-31. 9-5 78 79 80 81 82 SEA SURFACE TEMPERATURE (*F) Figure 9.1 Percentage distribution of the total successful purse seine sets on yellowfin and skipjack tuna as a function of sea surface temperature observed by tuna boats in the fishing grounds of the eastern tropical Pacific from 1971 to 1974. 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X ^3^ A / / / A / / V / / / A / / / \ > w J>d^ / A / / ^ / A y / / / 1 ^ )vj^ r A /' / / / / / / / / /■ 1 > 3p ^ A y y / o / / / / / / ,/ / / A r V XL ^ / / ^ / ' 1/ A y / / / / / r Wr '^ A /' / / A ' A / / / > / / / / F > C^ Ay / y ( / / / / A / / / / / ,/ y / / A , %\* \J ^^ A / / 1 / A J A / / / A / / 'S 7 jS( '^ ^ A A ir> / y / / A A ^ A / ^ / / A ,/ ^ , /' i< > c^ Ay ''a cl y / / / ./ / / A / / / J / A ,/ P* > w, A y / . / ' / 4 A / / A A A / / / ^ / A / L X ^?Vj «| ^A / / ,/ / / A y A A 4 A y / ' A /{' A r jJrt / A. ^ ^ 1 / Y / / y / A / / / / / / 'A A < S^c VJ A / A 1 S / / ^ A ^ AL A V^A A / A -^ _i / ^-Y — ^ ^ i> Sl>r 1^ / ^ ' ^- — — 1 1 TEMPERATURE AND DISSOLVED OXYGEN DEFINE SKIPJACK TUNA HABITAT By Richard A. Barkley Southwest Fisheries Center National Marine Fisheries Service, NOAA Honolulu, Hawaii 96812 ABSTRACT Neill, Gooding and others at the National Marine Fisheries Service Honolulu Laboratory have measured a variety of physiological parameters of skipjack tuna. The factors which most obviously tend to limit the distribution of these fish are: (1) the lower lethal temperature, approximately 1A° to 18° C depending upon prior condition- ing; (2) the lower lethal dissolved oxygen concentration, 4 to 5 ppm. or 2.8 to 3.5 ml/liter; and (3) an upper temperature bound which varies with size and metabolic rate of the fish. According to Neill, a normally active skipjack tuna, whose metabolic activity requires some 3 mg oxygen/gram/hour, undergoes thermal stress if the ambient water temperature exceeds 33°C for fish smaller than 1 kg, and lesser temperatures for larger fish, such as 20°C for a 12 kg animal. If the water is too warm, skipjack tuna must either reduce their activity, or risk overheating of muscle tissue, because they conserve body heat with marked efficiency. Skipjack tuna should therefore inhabit waters with oxygen concentration in excess of 3.5 ml/liter, and temperatures between about 18°C and the upper bound appropriate for their size and activity. Throughout the equatorial Pacific Ocean, water in the lower portion of this temperature range is deficient in oxygen, and the maximum habitat depth is set by the oxygen requirement. At higher latitudes, the water at the cold limit has enough oxygen, and low temperature is the limiting factor. Skipjack tuna can exceed their thermal limits for short periods of time, because the time constant (the e-folding response time for a step change in water temperature) for skipjack tuna muscle temperature ranges between 30 minutes and an hour. That is, skipjack tuna can forage for some time in water which is clearly too warm, provided that cool oxygenated water is available immediately below; similarly, they could move into water which is oxygenated but too cold for long-term comfort, as long as there is water overhead in which to warm up afterward. Clearly the normal habitat of all but the smallest skipjack tuna is the upper thermocline, for most of the year, throughout most of their range. In much of the eastern tropical Pacific, however, water 10-1 with at least 3.5 ml/liter of oxygen is warmer than medium and large skipjack tuna can tolerate; some 300 km off Mexico's west coast, the minimum temperature of adequately oxygenated water may exceed 26°C, which would stress fish larger than 4 kg. This warm, low oxygen water is found between 10° and 15 N, 105° to 120°W, approximately. Fish which require water cooler than 24°C (those larger than 6.5 kg) should in addition be excluded from coastal waters between Tehuantepec and Cape Corrientes. The location and extent of these "forbidden" areas probably varies with season, and from year to year, depending upon mixing and advection — and thus upon winds and currents. These variations should be reflected in the geographic distributions of skipjack tuna of various sizes caught off western Mexico. April 15, 1975 10-2 El Nino, Anomalous Equatorial Pacific Conditions and their Prediction by William H. Quinn School of Oceanography Oregon State University Corvallis, Oregon 97331 9 May 1975 11-1 ABSTRACT A technique for monitoring and predicting the El Nino-type activity and its antithesis has been developed over the past year and a half; and for the last nine months a real-time monitoring, prediction, and verifica- tion program has been conducted to test and improve this technique. The technique uses the trends in plots of various length running mean values (e.g., 1-, 3-, 6-, 12-month running means) of Southern Oscillation indices •for monitoring the developmental stages and predicting anomalous equatorial Pacific activity and El Nino. A brief discussion of the technique and its application is included. A chronological account concerning the author's prediction for El Nino- type activity in 1975 and how it led to the El Nino Watch project is pre- sented. Based on information from the first El Nino Watch cruise and the UNESCO oceanographic representative in Guayaquil, Ecuador, it appears that the forecast for a weak El Nino occurrence off the South American west coast has verified. This test result on the forecasting technique is significant in that: (1) it not only predicted the event occurrence but also its inten- sity; (2) it was issued sufficiently in advance to allow preparation for the subsequent El Nino Watch project and its cruises to study the onset of an El Nino in the early stages of its development; (3) it predicted an event to occur three years after the onset of the strong 1972 El Nino, a situation which would have been considered quite unlikely from the general statistics on past occurrences . 11-2 1. Introduction Earlier studies showed there was a relatively close relationship between phases of the Southern Oscillation and the anomalous extremes in rainfall over the central and western equatorial Pacific (Quinn and Burt, 1970, 1972). In the 1972 paper, monthly mean sea level atmospheric pres- sure differences between Easter Island and Darwin, Australia were used to represent circulation fluctuations; and, simplified approaches for deter- mining the occurrence or nonoccurrence of anomalous equatorial Pacific rainfall, based on the graphic trend of the pressure difference, were suggested. Recently, this Southern Oscillation index and additional indices have been treated so as to emphasize the interannual changes and used in an improved method for monitoring and predicting the El Nino-type activity and its antithesis (Quinn, 1974, 1975). This article is devoted to a brief background discussion of the fore- casting method, a chronological account of the recent forecast that led to the El Nino Watch Project, findings through March 1975 off the coasts of southern Ecuador and Peru, and some conclusions concerning the forecasting technique . To clarify the use of certain terms in this discussion, the following definitions are provided: a. The Southern Oscillation, a term introduced by Walker (1923, 1924), is loosely defined as a fluctuation in the intensity of the intertropical general atmospheric and hydrospheric circulation over the Indo-Pacific region (Berlage, 1961). Troup (1955) describes it as an exchange of air between Eastern and Western Hemispheres, principally in tropical and subtropical latitudes. This exchange of air is associated with variations in a mean toroidal circulation driven by temperature differences between the two areas. For simplicity, Troup (1965) considers there is a single drift of most importance in the upper troposphere and that this flow is from the area of the Indonesian equatorial low across the Pacific to its central and eastern regions. It is compensated by a return flow near the surface from the eastern Pacific to the region of the low. There is descent in this circulation over the central and eastern Pacific, ascent in the vicinity of the equatorial low and a toroidal circulation in the vertical- zonal plane is maintained. The pressure changes which result in the index variations discussed in this paper are a consequence of variations in this circulation. Quinn (1971) contains a capsulized discussion of this large- scale feature. b. The term El Nifio-type development , situation , or condition is occasionally used in this proposal for convenience. This broad connotation represents the occurrence of anomalously warm sea surface temperatures in the equatorial Pacific along with abnormally heavy precipitation, and at times a disastrous invasion of anomalously warm surface waters along the coast of Peru (the actual El NiKo occurrence) . This type of development is brought about by relaxation from a prolonged period of strong southeast trades (represented by high Southern Oscillation indices) to a period of unusually weak southeast trades (represented by low Southern Oscillation 11-3 indices) . The intensity of this relaxation and its timing appear to determine whether or not a strong El Nino occurs along the Peruvian coast (Quinn, 1974) . By using this broader term, we avoid getting into hassles over what is and what is not an El NiTio, and can then account for those events that evolve in a similar manner but vary in timing and intensity. c. The El Nino antithesis , or as some call it the anti-El Nino , refers to the contrasting situation when a prolonged strong southeast trade system prevails. In this case, there are strong upwelling, anomalously low sea surface temperatures and abnormally low amounts of rainfall over the equa- torial Pacific (Quinn and Burt, 1972; Quinn, 1975), with strong coastal upwelling, low sea surface temperatures and high primary productivity off the coast of Peru. 2. Prediction of El Nino-type activity The monitoring and prediction technique of Quinn (1974), as briefly discussed here, pertains to the El Ni?io-type development which involves relaxation from a prolonged strong southeast trade system to a weak one. This results in a slackening or cessation of equatorial upwelling, a rise in sea surface temperatures and abnormally large amounts of rainfall over the equatorial Pacific; and, in the strong cases. El Nino invasions. Considering the 12-month running mean plot for the Easter-Darwin index (see Figure 1) , in the case of unusually large developments the buildup time from a prior trough to the pre-El Nino peak is quite variable and generally takes place over a period ranging from 15-30 months. However, the drop from this peak to the subsequent trough in such cases usually takes place over a 15 to 21-month period. Of course, smaller developments may show a shorter time span for peak buildup and also shorter relaxation time in the drop to a subsequent trough. The time involved in relaxation from peak to trough, determines how far in advance of event occurrence a forecast can be issued. Here we consider the larger developments. In forecast applications, when a prolonged steep rise in the 12-month running mean plot is noted (for either the Easter-Darwin or Juan Fernandez- Darwin index) , the possibility of a pre-event peak development must be considered. If this steep rise continues and the plot approaches the 12 mb level, some equatorial Pacific activity can be expected and possibly a weak El Nino. This alerts one to a detailed study of the situation with additional indices (e.g.. Figure 2), shorter period running mean plots (e.g.. Figure 3), and similar plots for index components (e.g.. Figure 4). If the 12-month running mean plot continues +-o rise and reaches or exceeds 13 mb, extensive abnormally heavy equatorial rainfall can be expected and the likelihood of a significant El Nino occurrence becomes apparent. When an index peak in excess of 13 mb is reached, and a downward trend sets in early in a particular year, one can expect the El NiSo invasion between January and March of the following year if the relaxation continues. The heavy central and western equatorial Pacific precipitation usually starts a few months after the El NiHo sets in but this may not always be the case. The 5-month lead time required for a 12-month running mean value allows about a 3-6 month forecast for El Nino using this approach; however, speculative outlooks 11-4 t2 ?i! = Q o> CO f^ 1 I.I 1 1 • • ;j ^ • • 0> 1 Q 01 03 • • • 1 1 • • ro S?^ • • • 0} Anomalo^ equatoria El Nifio • • • • o to • • z /\ •* UJ . • .^ • • « • V Uj • • If) • , • *i — A ; . • h— « ^~ ▼ • • CO • o in « 1^ 4 ^ (D • 91 z • : UJ •^ • • • • t^ • (D • in • CD ^ f O) • 0> z I u • U) • <5 ^ • in • i£> • O) • 91 • • • • • • ,' ^~ • • * in * ^ h- • in • U) • O) ;* cr> • ^ « • • • -• • • • • ?; '•. CO • 0^ y i 91 • • « • • • • • y s, • . • ro • in • in • lO ' • a> > r .* 91 2 • ^ Z UJ < t ^ • UJ • • • CM .* 't • in • f ,• rO z ' f . • * O) •^ 0} UJ • • • ^* o • • CO • in • to • 22 • o> • • 1 • • ""~ • 1* • • • 0) *, • • CD h - J n — 1 ^. d n -1 _k u J — • ^ VJ JJ w d) ^ 1 ■p TJ c U-l § C) ^.^ ^ en (0 (0 X rH 0) +J cn ^ C H >1 fc W rH (U rH CN -p fO iH ^ Q) w • -C c -d ■P •^ •p iw 0) (d 5 ^3 u ■P C •H Q) >H nS tp (I) 13 fl rH CM ty •H Q) C fO nj § cn •H rH g Vh (rt 0) c ^ ■p ^ •H +J cn +J CO 0) C QJ d & n U < g C 'd 1 0) ^ c CN Jh fi Id rH 0) •rl m a rH 0) m fd 4:: •H fd u EH T) a ■p •H Em /l-J rO OJ — O 1 r (D If) 1 \ — r en 03 (D in en CVJ N (D O cn ID en 00 CD cn ID CD cn 1 ^ — r ID c 0) 05 a) j:: c c S +J 0) 0) (d -p m s •O XI ■p C 0) (0 TJ 0) Xi ^ c: r-f tn (ti 'C ^0-^ H •H •i U " e 1 (U a) m H ^ iq n3 v-.* +j 3 en W C +j w C ■H (0 a) a Tl ft & «J 0) ■P P +J o 0) 4J •H X! Ti M § • r-l 0) ^ '* 0^ x ^—^ r- ft Q ^-» 1 IS) en 1 tn H ■P fo -d VD C E h) c CJ> •H ■P (C iH (0 H ft (C en ^ iH •H H 0) t-\ ip tn > (d >^ § 00 J L CD m a-d CD CD /h^ CL' = 01 I I I I I I inro_^2:?^Qooio^!:02:POO 1 r~\ \ I \ \ r I I I 03 CD rO OJ — O CD OO I I I I I I inro — oit^iDfO — -(uD9i/\| A|4tuoi/M) a -3 — • ID ^ CM O 00 ID <3- I— 0-3 dOd lAldl/M £-» I I I I ID 5 OJ O 00 ID 't I— a-3 dOd i/\iaiAi 9-* cr> cn cn cn o cr> ^ I I I I -1. I I L _ — O CT> OO 0-3 aOd l/Md^M Z\ ^D tp c •H C !^ B5 0) rH M en T) (C 'O x; w •H ■p g c c (U a) g QJ 4:: 1 15 ■p CN 4-1 rH (U 4-1 XI (d TJ c — •o "^•i 0) en ^ +J C (0 (U rH (U s^ ft a :3 U) Q) Cri CO ^4 C 0) nj •H Vj -P 3 o C Vl -H •H !^ j::; OJ P^ +J x: C £1, tn 6J • 1 b ■^ v£) 4J r- ft 1 ^ CN U) nH VD C 0) CTi (0 > rH q; q) E rH Cn fd MH C Q) •H tn rO d •r( d -rH rH m ^-v V^ >-i • C IW § •H >i O n-i 13 0) Xi CO c: ^ +3 c (ti +J C (0 t-\ S Si V) MH S g H CO H I /H7 ^ ^ S CD ® = Q § o o o o o o o o 1 1 1 1 1 • 1 1 1 • jr • • N • • 0^ • • • • • • • • • • lO • • h- ^ ^ S 2i 59 ^ ^ o • • 0) M-i O O O O Q O Q o • , • • 1 1 -1 1 1 1 !• 1 to 1 1*1 1 1 1 1 • 1 • • -^ -H o • • OJ W r-i • • ID • x: (0 • * 0> • • • • • • • § 2? ^ ' I , ' I 6 3 • • • m • *• << CN • • • If) • • • ; • • ■ ,* *, Q) -H •^ • • 5 a \ '^ ', • • • fd • m oo • , o tw P • • • m • • • • • • • ^ ^-d • • s • (U c '. .' : .* i-l (0 •a ,' ' ^ ' • • • • •O Tl •^ • N • • • • O iH • • • • 0) u} • • • • • x: H » ' • -p • • u • \ (£> .• * CD -P 0) • • in • • (i? (d -P • • o> • • CD w , • * •. • '0 (tJ / I . • .* rH M-l • • 0^ • '* • • • • cj « • • • iH iH rH • • • • • • • • 52 0) rd V^ E-i CO "W « • • • • • • • • • "^ • • • • ,• \ • ^ • (1) • • • • 1022 1021 1020 1019 1018 = o S •H § o g o 5 9 o 8 2 o § b g \j-n 1 Own k •— NiMdva- -¥ • d3iSV3 ► n — NIMdVQ- -¥ • ddJ-oVd * //-r can at times be issued 12 or more months prior to an event. When monitoring the situation as it sets in, the shorter period running means and monthly mean sea surface temperature analyses for the tropical Pacific (U.S. Depart- ment of Commerce, 1972-75) are particularly useful. After the 12-month rianning mean trough has occurred and a persistent, relatively steep rise in the running mean trend agair prevails , one can expect a return to the meteorological and oceanographic conditions characteristic of a strong southeast trade condition. The index component inputs (see Figure 4) become important considera- tions when an apparent pre-event peak is developing. If the contribution to a high 12-month running mean peak of the index is relatively small from the Darwin component but relatively large from the Easter component (very strong South Pacific subtropical high) stronger activity would be favored in the eastern equatorial Pacific on relaxation. If the input is relatively large from the Darwin component (unusually deep Indonesian equatorial low) but only moderately large from the Easter component, stronger activity in the western equatorial Pacific would be favored on relaxation. The situation leading up to the strong 1972 El Nino was quite unusual. The irregular interannual fluctuation (Southern Oscillation) was large and in this case had a period of about three years. Also, the interannual peak was in phase with the regular annual peak (the regular annual fluctuation in the index shows up clearly in the 6-month riinning mean plot of Figure 3, with its peak near the beginning of each year and its trough near the middle of the year) , giving an exceptionally high 6-month running mean peak at the beginning of 1971. Likewise, in this case (Southern Oscillation of about a three-year period) an exceptionally deep trough occurred in the middle of the following year (1972) when the second annual trough (following the high early 1971 peak) was in phase with the longer period interannual trough (see Figure 3) . Over a period of 18 months on the 6-month running mean plot (for the Easter-Darwin index) there was an excursion of 12 mb (between the early 1971 peak and the mid-1972 trough) ; and, over this same period there was a 14 mb excursion in the 3-month running mean plot (see Figure 3) . This represents an extreme relaxation in the southeast trade system. Since the average annual fluctuation in the Easter-Darwin 6-month running mean is about 4 mb and in the 3-month running mean is about 6 mb, it indicates how large the interannual contribution can be and how important the Southern Oscillation is to the development of anomalous equatorial Pacific activity and El Nino. If the two index fluctuations (the regular annual and the irregular interannual) are out of phase, they tend to coianteract one another and the 6-month running mean plot shows stunted peaks and troughs. In cases where peaks are in phase and troughs are out of phase, developments are weak. It is essential that the troughs of the two fluctuations be in phase to get significant developments [Figure 5 is taken from Quinn (1975) and shows schematically the 6-month running mean trend associated with the 1972 development] . 3. The El Nino antithesis It appeared that this monitoring and prediction technique could be applied more generally in support of fishery environments affected by the 11-9 SNJMMJSNJMMJ SNJMMJSN PIT TT TTT I I I I I I I I I I I I IN PHASE PEAK TT EL NINO 16 -^16 Figure 5 . Schematic representation for the 6-month running mean trend of the Easter-Darwin atmospheric pressure dif- ference (mb) relating to an exceptionally strong equatorial Pacific event and El Nino. n-/o k anomalous equatorial Pacific conditions (Quinn, 1975) . Here reference is made to fishery zones which are significantly affected by variations in primary productivity [as a consequence of strengthening or slackening in upwelling activity (in response to a strengthening or weakening of the southeast trade system) , in the equatorial Pacific and off the coast of Peru] or by the sizable associated variations in surface and near-surface sea temperatures. The high degree of consistency between index features and equatorial meteorological (see Figure 6) and oceanographic activity tends to justify the use of the running mean trends of the indices for this more generalized monitoring and prediction purpose. The possibility of forecasting this opposite extreme, using monthly means of the indices, was first discussed in Quinn and Burt (1972) . It was noted at that time that the persistent high Easter-Darwin pressure differences favored extensive unusually dry equatorial Pacific conditions. Several examples were cited where this opposite extreme prevailed over periods 18 months to three years in length. Here we consider monitoring and predicting physical conditions that favor primary productivity in the affected oceanic zones, by following trends in the running mean plots of the indices. When the 12-month running mean plot rises steeply for many months and reaches and remains at high levels, it indicates a strengthening and strong southeast trade system prevails and that a return to widespread upwelling and anomalously low sea surface temperatures is occurring over the equatorial Pacific and along the Peruvian coast. The height and breadth of the 12-month running mean peaks determine the intensity and time span respectively of developments which favor this widespread upwelling condition. Perhaps persistence-type forecasts would be more appropriate for developments of this nature, since we will often be dealing with peaks of lesser intensity than the pre-El Nino variety and also since such activity may often persist for periods in the 18 month to three-year range. The 12-month running means of the Southern Oscillation indices and the monthly sea surface temperature analyses (U.S. Department of Commerce, 1972-75) should be excellent tools for monitoring such developments and issuing persistence- type forecasts. An approaching deep 12-month running mean trough will signal the end to conditions of this nature. 4. Outlook for weak 1975 El Nino and the El Nino Watch The following is a chronological account concerning the prediction made for El Nino-type activity in 1975 which led to the "El Nino Watch Project," in order to give some idea of the capability of this technique for monitoring and predicting such conditions . The first sign noted was the steep rise toward a pre-El Nino peak which became apparent in the trend of the 12-month running mean plot of the Easter-Darwin index when considering data available through 1973. Based on these data (at this time I was relying on library data sources which are usually about 8 months late) , I gave a speculative outlook for El Nino-type activity in 1975 at the end of my presentation to the ONR-NSF NORPAX review 11-11 in o o m O o o 8 o ^ in Q a> CD ID in 1 \ r o o in O to K> O in O O CM O in o in (Ti oo o — o o *- '^ 2 OJ £) c E m 1 — ^ — \ — \ — \ — \ — \ — \ — \ — \ — r _L 1 J \ \ \ \ L ..:l_ ^ J L OOOOQOQOQO — O(J>00NiDin O O r— OCOi — C\JOVOCMC\J(ri<^^OOOLn I I I — I — I I I I I I cvjooLnr^ini — iX5i — «*cr>r-»s^3-c«5i-i — > (T3 > -M fC •I- CJ! "D E OJ C r^ (/) f— o o O M- 4- O 1/1 -E OJ ^-J O CD to OJ +-> O S- to a. LU C/) ■a c— O E +-> CDO S- COO •I- r- Q- 1 — to I— S- C O) (U 03 S CL S- D- +J c I— o 03 U +-> CU t/) to fO O S- a o) c. >> I — to +J O) E +-> O OJ CU o to O) +J n3 O -a E a: Q_ or 1 — oooooco^j-tocord-oocTii — "v^oo"v^ r — C\JCVJi — 1 — ooocoun^cTiLn CMC\jLnr^^r--.c\iLnor^Lor^Lnoo r — ^^OOr^OOLDi — "^t£3i — IT) r— C\J CVI C\J 1 — I— c\jLnuDo^cx3o^v£)r^CM(^crii — ^r-v«^^ r— I— r — COCX)00i — C\J^^DOJ 1 — CM OU I — Lr)(Tic\j(X)i^ooor^r^oocrooc\jcNi I I rooor^Kocor^ ^^nroncMCMC\jc\iCMi — ■ — ■— i — o oo^^"=:^^— ootncMCTivcoocDr^^i— tovDLDLOtn^^^nconrocMCMCM 12-3 LiJ Q o^oocvjoo«^ocri^oocM»^crvooooocnr^LnCTi«vt-cr>f*^ C) en 1— I— cocjcM 1 — ii c o • 1— 0) •■- +J O > +J 1/1 o •1- (tj (T3 -MOO fO O O i^~ r~~ OJ 4- S- -o O Q- c LU -* (O ^ (/) r^ -M cri .c oi 1— +-> c C OJ ^ O 1 — O E ts M- E rD .C cC CO u o O) ro o •I- O) ■— ^^ 03 S- S- E O 0) _J O <4- Dl rD c ■-^ (T3 CU "O =5 C X r- O OJ ro o ■o > (U E 00 Ty •r- E ID ^ s- 0) KO - 2 1 4-> ^ Q-CO OJ =3 ^ E cri I— 1— o rO r- +-> JD lO S- 3 q; fO >, O Q- O 1 cC O O OJ CVJ s- >, fC f— OJ .^ Jd i/) -M -M +-> CU E •>- ^ CM ill II 1— ooc>JOOoo^ocM^oooo^•:;^^^«x^ I I I ii — cor^rotni — voro^i— I — III CCMVD0O<^V£)00nCM00Cri^<£>«*CO I I I I r^ ro ID 00 00 en CM I— CMVOVOOO«:d-COr^CM<£>OOC3^COO! — 1^ I If— I I 1.1 lOOCMCMCriVOCM^ f^i — "^OOVDi — •— (Ti en , — C3^CO<:d-I^VD I — mil — I — cMi — roincMCM i — II I I I I I I I I LncoLOcrii — cmcoi — ocmloi^i — ^o cricy>oocricoi— coinLOi— «a- lOjCOOO^DLOLOini— I— I— OOr — i— I I I I i cr>uDr^«sj-i— LnLr>ir)Lr)CMcricri<£>ooi^ ^^^roroncMCMCMCMCMi— I— 1— I— o oor^^a-f— ooiDCMO^vorooi^^i— vD«i>unintr)«;S-«;a-«^rorocorocvjcMCM 12-4 distortion. The Cape Mendocino area near 39N latitude is actually the region of maximum upwelling intensity (Bakun, McLain, and Mayo, 1974). The major point to be made to users is that these series are designed to indicate temporal variations at each particular location rather than the spatial distribution at a particular time. The information in Table 12.1 is presented in Figure 12.2 in terms of percentiles of the frequency distribution made up of the 29 values for each month and location within the 29-year (1946-74) series. In this presentation the spatial distortion is removed since no reference is made to absolute value but only to relative value among other yearly samples for the same month and location. Values above the median fall above the fiftieth percentile, etc. The Northern Gulf of Alaska The northern Gulf of Alaska is primarily an area of negative index values (Table 12.1) indicating convergence at the coast and resulting downwelling. Values in the early part of 1974 are below the median (Figure 12,2), i.e. more neaative than normal, indicating more intense downwelling than normal. A possiblti result is that surface water conditions affected an unusually extensive area of the floor of the continental shelf. May, June and July show higher than normal upwelling index values. However, summer is characteristically a season of wery little upwell ing-downwelling activity in this region; the positive anomaly, even in July when it reaches the ninety-first percentile, is not wery large in terms of quantity upwell ed. 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CO I CM 1^ o 1— c o ,— CM CM ^ CM r^ KO VD «=^ 1 ' 'Y • in '^ o ,_ 1^ CM «^ CM 1 CM in CM CO CM 1 in CM J <:J- CO ^ r-^ «d- f— r— CO "^ till CO cn r^ 00 r^ 00 ^ CO CM 1 1 1 CM CM in •;*• in 1 CM cc: cc CO CO in o CM r— cr> CT^ in CO r— ' CM CO CM »r> CM y£> ^ y£> «£) in vo in I— o CO CO o "* ^ CM '=^ 00 00 C\J CO KO «.o 1 1 1 — CM CO C7> CO CO CO in CO CM r— in «£) CTi •^ in CM CO 00 o KD O ' CM KO 1 1 1 1 •a- 1 X »— I o a. a. yo r^ ^ CO o CTi CO I To 1 T CO CSJ 1 CO 1 CO 1 1 CO CO CO r>> r— r- CVJ CT>»^i^«^i — inininincMCTicrivD ro r>. «;J-sa-COCOCOCMCMCMCMCMi — r— i — r-O OCDI^^i — COincMCTitOCOor^^' — vD'X)ininin»d-^^cococococMCMCM 12-16 REVIEW OF THE PHYSICAL OCEANOGRAPHY OF GEORGES BANK* by Dean F. Bumpus Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543 Abstract Previously published information on the bathymetry, rotating tidal currents, temperature-salinity distribution and general circulation of the Gulf of Maine and Georges Bank are discussed. New information on surface temperature fronts in relation to monthly Ekman transport vectors is presented. Data on the distribution of herring larvae during successive periods during the autumns of 1972, 1973, and 1974 are used as evidence of dispersion and advection. Feasible approaches toward development of a circulation model are mentioned. Contribution Number 3 594 from the VJoods Hole Oceano- graphic Institution. Accepted for publication as ICNAF Research Bulletin #12, 1976. 13-1 Introduction Thirty-seven and a half years ago as a young biologist I cut my oceanographic eyeteeth as we commenced a study of the distribution of certain planktonic species on Georges Bank. It became obvious over the next several years of the study that the key to the problem lay in an understand- ing of the circulation of the area. World War II interrupt- ed the study, and in spite of intermittent attempts by numerous people and agencies over the intervening years, we still have only an approximate understanding of the circulation over Georges Bank, and many other continental shelf areas for that matter. We shall have to acquire a much better understanding of the dynamics if we are to evaluate the role of circulation in controlling dispersal of planktonic forms and organic production in general. Hope springs eternal, even in the breast of one soon to retire from this field of endeavor. New techniques for making Eulerian and Lagrangian measurements are now at hand, and bright young minds are available to develop theoretical models to be compared with the real world measurements. It would appear that the chances for suc- cessfully defining the circulation scheme are now good if v/e arc v;illing to make a serious attempt to elucidate it. As background for developing a plan of attack on the problem, I shall briefly review the major knov/n features of 13-2 the physical oceanography of Georges Bank and the Gulf of Maine and then attempt to relate these features to v/hat is known about the movement and dispersion of herring larvae. Finally I shall comment on what seem to be feasible ap- proaches toward development of a circulation model. Bathymetry Uchupi's (1965) chart (Figure 1) handsomely illustrates the bathymetry of the Gulf of Maine, characterized by its rocky laybrinthine coastline and bottom topography on the north, its smoother coastline and bottom topography on the west, its deep basins interrupted by ridges and swells en- closed by the offshore banks. Browns and Georges which are intersected by the deep Northeast Channel and the shallow Great South Channel. The south side of Georges Bank is deeply penetrated by canyons, as the continental margin slopes away to the deep ocean basin. Rotary Tidal Currents One of the distinctive features of Georges Bank is the strong semi-diurnal rotary tidal currents with speeds ranging from a fraction of a knot to greater than 2 knots. Pro- gressive vector diagrams for surface current measurements (the upper 14 feet) as reported in Ilaight (1942) and Anonymous (1973) are shown to scale in Figure 2. Those over 13-3 Georges Bank appear for the most part as elipses, with the long axes oriented NNW-SSE ranging from 4 to 8 miles in length. The short axes are 2 to 4.5 miles. Rotation is clockwise. Those over the northern edge of the bank and over the deeper parts of the south side are somewhat ir- regular. Those to the west of Georges, i.e., in Great South Channel and over Nantucket Shoals, have various orientations, the westernmost over the Nantucket Shoal and another east of Chatham having a NNE-SSW orientation. One directly east of Nantucket has a counterclockwise rotation. The number alongside each tidal elipse represents the sum of the hourly speeds over a 12 hour period, an approxima- tion of the distance traveled by a parcel of water during that time. These range from 10.7 to 19.9 miles over the shallower parts of Georges Bank, as little as 6.5 miles near the southern edge and 5 . 5 miles off the northern edge and 8.8 to 19.4 miles off Nantucket. One thus might think of the tidal oscillation over Georges Bank as being like a semi-solid irrotational eliptical motion with a circumfer- ence of the order of 20 nautical miles over the shallow parts of the bank, grading off to 5-6 nautical miles over the deeper parts. Temperature and Salinity Distribution The profiles of Colton, ct al. (1968) along the 67^30' lacridicin from the northern shore of the Gulf of Maine, acro.ss 13-i^ Georges Bank to the slope water on the south provide a reasonably good characterization of the temperature/salinity depth distribution. Profiles for mid-DecGmber 1964 and 1965 are shown in Figure 3. Note that the deepest parts of the Gulf of Maine are slightly warmer and saltier than the v/aters above, the total range in temperature of the Gulf being 1 to 2° C, the total range in salinity from 2 to 2.5 Voo • The water over the bank is mixed vertically. An oceanographic front occurs well off the bank in December 1964, but lies above the 100 meter contour in December 1965. In Figure 4 we see profiles for March 1965 and 1966. The temperature increases with depth every\'7here throughout the Gulf of Maine. Over the bank the water is isothermal v/ith a front along the southern edge, somewhat diffuse in 1965, very sharp in 1966. The salinity distribution on these occasions is markedly similar with increasing salin- ity V7ith depth in the Gulf, isohaline conditions over the Bank and a salinity gradient between the southern edge of the Bank and the slope water. Figure 5 represents the distributions in May 1965 and 1966, By this time a seasonal thermocline has begun to develop over the Gulf in the upper 50 meters below which the temperature increases with depth. Although warmer than in March the water is isothermal over the shallow (<50 m) parts of the bank v;ith a r,light thermocline beginning to 13-5 develop over the deeper southern part producing an iso- lated cold core of "winter water" next to the bottom, which extends all the way westerly along the outer edge of the continental margin as far as about 38° N latitude, nicely illustrated in Whitcomb (197 0) . A bulge of this cold core extends out over the edge of the bank in the 1965 section. The temperature front between the Shelf and Slope water lies beyond this bulge in 1965, whereas it is close in over the edge of the shelf in 1966. The salinity distribution for May is almost identical with that for March. In Figure 6 we can see the distribution for September 1965 and 19 66. The strong therraocline which has developed over the central Gulf of Maine to a depth of 50 meters has begun to weaken. The coldest water appears at raid-depth with slightly warmer below. A temperature front appears at depth along the northern edge of Georges Bank occasioned by the colder vertically-mixed water over the bank. The cold core of winter water persists over the southern side of the bank and the sharp thermal front in the upper 50 meters lies just off the southern edge. The salinity dis- tribution is little changed from that seen in May. In discussing the general hydrographical conditions pertaining to Georges Bank, Clarke, Pierce, and Bum.pus (19 43) wrote in part: 13-6 "The depth of the major portion of Georges Bank lies between 4 0m and 100 m, although areas of less than 25 m occur in the north central position, and shoals themselves are covered by only 5 to 15 m of water. Along the northern edge of the Bank the bottom drops rapidly from about 40 m to more than 200 m as the deep basin of the Gulf of Maine is approached. Along the southern edge the depth changes somewhat more gradually from 100 m to 200 m. Beyond 200 m it increases rapidly to about 2000 m. "Georges Bank is therefore roughly speaking, a sub- merged, flat-topped plateau and it presents a sufficiently large obstacle to water movement to produce a profound effect on the ocean currents of this region. — "The turbulence produced by the tidal currents and by the wind in the relatively shallow water overlying Georges Bank causes a vertical mixing of the water which results in a nearly uniform distribution of temperature and salinity from top to bottom at- all seasons of the year, particularly in the central part of the bank. The bank water thus con- trasts sharply with the surrounding v/ater masses, which are typically stratified during all except the winter months. Since the temperatures and salinity values on the Bank are generally intermediate between those of the surface and deeper strata on the Gulf of Maine but usually much lower than those of the water lying to the south, we know that tiie bank v.'ater is originally derived, in a large part at 13-T least, from the Gulf. That portion of the Bank over which vertically uniform water was found is termed the Mixed Area , and all stations at V7hich the salinity does not vary by more than 0.2 part per mille from surface to bottom are con- sidered to lie within it. The limits of the Mixed Area are ordinarily rather sharp... ." A review of the profiles presented in Colton, et al. (1958) reveals that the mixed area covers all of Georges Bank shallower than 50 meters in December, deepening to 80 meters in March and returning to an area of less than 50 meters in depth during the remainder of the year. General Circulation of the Gulf of Maine The development of our concepts of the circulation in the Gulf of Maine, including Georges Bank, have been docu- mented in Bumpus (1973) . It is not necessary to repeat that here but we shall review the circulation as described by Bumpus and Lauzier (1965) on the basis of drift bottle data, and Bumpus (1973) on the basis of drift bottle and sea-bed drifter data. There have also been a few experi- ments with "drifting buoys which help to confirm or amplify the inferences made from the drift bottle data. To quote from Bumpus and Lauzier (1965) relative to surface drift: "Gulf of Maine - 13-^ "The indraft from off Cape Sable, from across Brov/ns Bank Exnd the eastern Gulf of Maine into the Bay of Fundy, is the chief characteristic during the winter season. A southerly flow develops along the v/estern side of the Gulf of Maine and continues past Cape Cod through Great South Channel. Between the indraft in the Bay and the southerly flow along the western side of the Gulf several irregular eddies develop by February. An area of divergence north of Georges Bank is well developed by February. "The Gulf of Maine eddy develops rapidly during the Spring months so that one large cyclonic gyre encompasses the whole of the Gulf of Maine by the end of May. There is an indraft on the eastern side of this gyre from the Scotian Shelf and Browns Bank. Abreast of Lurcher Shoals the drift may continue on northward into the Bay of Fundy or it may turn westward toward the coast of southern Maine, continue south and across Massachusetts Bay where it may divert into Cape Cod Bay or turn toward the east, north of Georges Bank. "The Maine eddy, which reached its climax in May, be- gins to slow down in June. By autumn and winter the southern side breaks down into a drift across Georges Bank. "Georges Bank - "The few returned drift bottles from winter releases on Georges Dank suggest a southerly flow across this area during the winter months, with a westerly component across Great South Channel. During the Spring months an anti-cyclonic 13-9 eddy develops over Georges Bank. The northern side of this Georges eddy is common with the southern side of the Maine eddy; an area of divergence continues along the northern edge of Georges Bank. A persistent westerly drift along the southern side of the Bank continues across Great South Channel. "During the summer the eastern side of the Georges eddy veers southerly and off-shore. With the onset of atutumn the west side of the Georges eddy breaks dov>;n into a westerly and southerly drift." Bumpus (1973) points out that the limited drift bottle data for the 1960-1970 period in the Gulf of Maine and over Georges Bank add very little to our previous understanding of the circulations in that area. One may note, however, that the diagrams in Bumpus and Lauzier (1965) indicate the speeds of residual drift range from 1 to 8 nautical miles per day, the greater speeds re- stricted to the approaches of the Bay of Fundy or the western side of the Gulf of Maine, where the circulation is significantly influenced by river runoff. The drifts over Georges Bank are frequently on the order of 2 to 3 nautical miles per day, although greater speeds have occasionally been inferred. The classic diagraiTi of Bigelow (1927), Figure 7, illustrates as well as any the general circula- tion pattern. 13-10 Thus to return to our "serai-solid irrotational eliptical motion" induced by the tide over Georges Bank, we might now add a clockv;ise rotation of 2-3 miles per day. We might liken this surface circulation over Georges Bank to a very slowly clockwise turning record in a record player esti- mated at one rotation per 100 days (3.6 rotations/year) on a spindle v/ith a large (8 mile by 4 mile) eliptical eccentricity. As for the bottom drift, Bumpus (1973) in reporting on the sea-bed drifter results states: "A persistent and continuous bottom drift of 0.5 ± 0.2 nautical mile/day ex- tends toward the southern tip of Nova Scotia and the eastern side of the Bay of Fundy from Browns and LeHave Banks east of the Northeast Channel. This is in agreement with Lauzier's (1967) findings. Along the western side of the Gulf of Maine the drifts next to the coast tend to flovr directly ashore, whereas farther offshore the drift is more nearly parallel with the coast in a v/esterly direction. Fewer than 10% of the drifters are recovered from the deeper parts of the Gulf of Maine and from Georges Bank whereas returns are substantially greater from the periphery of the Gulf of Maine and from the Continental Shelf west of Nan- tucket Shoals. The drifts in the deep parts (>100 w) are less than 0.1 nautical mile/day whereas those from Georges Bi\nk are on the 03:der of 1 nautical mile/day. A line of divergence occurs at Nortlioast Cl;anncl witl"'. northerly drifts 13-11 north and east of the channel and westerly drifts south of it. In general, the drifts over Georges Bank follow a clockwise rotation around the shoals with a net drift to the west and across Great South Channel." Because there are so few returns of drift bottles and sea-bed drifters from Georges Bank, one cannot help but sus- pect that a great number are carried offshore, rather than drifting to the west to strand, in the case of drift bottles, or be recovered by fishermen's trawls, in the case of sea- bed drifters. Certainly when one views the results of some drogued drifting buoy experiments conducted jointly by the U. S. Fish and Wildlife Service and the Woods Hole Oceanographic Institution in 1957, one obtains the feeling that there are ample opportunities for exchanges between Georges Bank water and Slope v/ater. Buoys equipped with on-demand radio signals were located via ship or air-borne radio direction finders. They drifted vvith the top five meters of the water column. One experiment. Figure 8, was conducted between North- east Peak and central Georges during the period 15 April to ]. June, 19 57. Buoys set out at the Northeast Peak ( Mike and India ) moved rapidly, more than 5 miles per day, and southerly into deep water. Buoys launched in the shallower areas exhibi(--Gd a slov/er not inovomont , betv.'een 1 and 4 miles per day, in a clocl-vwiso rotation. Buoy Ilotol , after a slow f^outhwc^r. l.cri\/ riovcnioiit {?>1 nilos j.n 55 days), suddenly 13-12 increased speed and moved 128 miles to the WSW in 12 days. Buoy November ^ which failed to respond after the 21st of April, was reported on 20 June just east of Hudson Canyon on the 1000 fathom contour, possibly having run parallel to the track of Hotel . This buoy, November , was subsequently sighted 500 miles to the eastward (38° 42' N, 60** 30' W) on 31 July, obviously drawn into the Gulf Stream. Another experiment with four drift buoys was conducted during 9-17 October 1957 in the South Channel area. Figure 9. An easterly drift along the northern edge of the bank, between 6 and 13 miles per day was indicated, with a slower, less definite drift in the center of the channel, and a southerly set of about 5 miles per day on the western side of the channel. Five more buoys were set out on December 6, 1 , and 17, 1957, Figure 10. Hotel , launched on the southeastern part of the bank subsequently failed to function and is not shown in the figure. It was recovered about 500 miles to the SE 8 months later. Mike v/as picked up and replaced by a fisher- man, but was apparently damaged as it ceased to respond to radio calls. It had moved 50 miles eastward in 12 days. The remainder were repeatedly located during December. This experiment yields evidence of an easterly set on Georges Bank in December 1957 on the order of >1 to >4 miles per day as indicated by Papa and Mike^. Papa eventually driftc^d off into doop v/ater southeast of the ban}: Vs'here it 13-13 Wcis sighted. India moved at a similar rate but skirted the northern edge of Georges, then turned northerly before reaching Browns Bank, being ultimately recovered by a fisherman 21 miles SE of Matinicus Rock. This buoy was ob- viously in the Gulf eddy. Alpha following the innerpart of the Gulf eddy, moved more slowly, at >5 miles per day. This experiment perhaps explains why so few drift bottles set out on Georges during the autumn and winter have been recovered. The Georges eddy has given way to an east- erly drift. Bigelow (1927, p. 864-5) examined the current measurements made by the U. S. Coast and Geodetic Survey during 1911 and 1912 at Nantucket Lightship. This analysis showed "a dominant drift toward the north and west during the spring, summer, and early autumn, averaging about 3.4 miles per day; but about as strong a southeasterly set (3 miles daily) during the late autumn, winter, and early spring, averaging about S. 50° E (SE x E) in direction." Bigelov^ credited the presence of the strong northwest winds of the season with the reversal in drift. During our Decem- ber experiment the winds were predominantely from the south- west, with strong easterlies on a few occasions. Whatever the reason, the surface drift across Georges Bank during the autumn and v;inter is different and apparently contrary to the drift of other seasons. It is quite probable, at this stage of our information, that the net circulation on Georges Bank is not readily predic Lable . It is reasonable 13-1^ to expect that the water movements on the Bank, especially during those seasons where the v/ater is well mixed, respond to the short-term wind effects as postulated by Chase (1955) for Georges Bank in regard to Haddock larvae and as reported by Howe (1962) in the Middle Atlantic Bight and more re- cently Beardsley and Butman (197 4) . The latter authors with measurements south of New England demonstrated that short intense wind events dominate the circulation over the shelf in winter and account for most of the observed net flow. Their observations show that large westward mass transports along the shelf were produced by strong easterly winds and the sea level rise at the coast (see Miller, 1957), while westerly winds produced little along-shore flow. However, the storm producing the westerly winds was much weaker than the one with the easterly v/inds. It may be that we cannot extrapolate the southern New England Shelf response to Georges Bank because the geography is quite different. However, it is quite possible that when an intense low pressure cell moves south of Georges causing easterly winds over the Bank and an increase in sea level over the shoals, there will be a strong net westerly flow over the south side of the bank. Contraryv;ise , an intense low passing north of Georges could similarly create strong easterly flows along the north side of the bank, with weaker flows south of the shoals. 13-15 Sea Surface Temperature Fronts As V7e have seen from Colton's profiles, the inter- face between the colder, less saline Shelf Water and warmer, more saline Slope Water appears at the sea surface as a thermal front. This front can be observed by satellite- borne infra-red radiometers. The National Environmental Satellite Service prepares charts of the sea surface tempera- ture fronts off the east coast of the U. S. on a weekly- basis. Ingham and co-workers at the NMFS Atlantic Environ- mental Group have used these charts to monitor and analyze the position of the Shelf Water front from June 1973 through December 1974. Figure 11 is an example. Figure 12 is a composite of the frontal positions during September-December 1973 and 1974. The dashed line represents the shelf edge as defined by the 100 fathom contour. In the course of the analysis the temporal variation of the Shelf Water front was established along certain stand- ard lines (Figure 11). The results of the first four, Casco Bay 120°, 140^, 160'', and Nantucket 18 0"* are shown in Figure 13. The location of the front is plotted as the dis- tance from the shelf edge to the front. The mean position of the front during the 18 month per- iod is shov;n in Table 1. The variability of the front's position, as indicated by the standard deviation, is large on cill aziniutlis, being larcjcsL al: the eastern corner of Georges Ban); and Jeact south of Nantucket. 13-16 Table 1 Distance from shelf edge (Km) Sample + = shoreward, Standard Bearing Line Size - = seaward Deviation Casco Bay 120 30 -45.5 70.9 140 31 -35,4 64.0 160 36 - 6.1 39,3 Nantucket 180 37 + 0.6 38.5 13-17 Major offshore excursions occurred on the Casco 120* line in July and October 1973 and during the winter of 1974; on Casco 14 0° line in July 1973 and during the v/inter and early spring of 1974; on Casco 160° line during March of 1974 and on the Nantucket 18 0° line during June and November 1973 and winter of 1974. Intrusions of Slope Water appear greater on the Casco 16 0° and Nantucket 18 0° lines than over the eastern parts of Georges. On Casco 160° the intrusions, occurred during June 1973 and during the summer of 1974 whereas they were fairly extensive on the Nantucket 18 0° line during the summers of 1973 and 1974. Ingham estimates 14% of Georges was invaded by Slope V7ater in late August 1914, increasing to 18% coverage by early Septerober, then decreasing to about 4% by the end of the month. He states: "At no time during the year did the invasion of the Bank by Slope Water exceed 18% and the average coverage for the year was 3.5%, with a standard deviation of 4.8% based on a sample of 30 observations." Wright (1975) has carefully examined the position of the Shelf Water/Slope Water boundary between 69° and 7 2° W longitude, an area v;hich slightly overlaps our area of in- terest. His study shows that this interface, identified by the 10° isotherm, intersects the bottom v/ithin 16 Km of the 100 meter contour about 80% of the time, with a seasonal progression from south in the winter to north in the autumn. The sea surface boundary position is much more variable. 13-18 averaging 4 5 Km seaward of the 100 meter contour in v/inter and 75 Km seaward in late summer. This boundary is much more nearly horizontal than vertical. He also finds de- tached parcels of shelf water in the slope water at all seasons of the year. Estimates of Wind-Driven Ekman Transports The Pacific Environmental Group of the N.M.F.S. pro- vides estimates of monthly wind-driven Ekman transports com- puted from the monthly average atmospheric pressure charts after the method of Fofonoff (1952) as described by Bakun (1973) . Figure 14 shows the estimated monthly Ekman Trans- port at 40^ N 70° W for 1972, 1973, and 1974. It is quite obvious from this figure that the direction and intensity of the transport is extremely variable from month to month and from year to year. One is not at all assured either that the water movements are going to be in the direction of the computed Ekman transports, in the shallow waters of Georges Bank and Nantucket Shoals. They may indeed be more directly downwind, i.e., 90° to the left of these Ekman transport vectors. What these vectors mean to me is that there are periods of intense forcing which may indeed in- duce extrciiie v/ind-stressed flows as well as periods of minimal forcing. 13-19 We have compared the data for 40° N 70° W with data for 39° N 69° W, 39° N 66° W, 42° N 60° W, and 42° N 66° W for 1974 and found the 40° N 70° W representative of the area. However, the position of the fronts relative to the edge of the bank in the last half of 1973 and all of 1974 do not appear to correlate well with the monthly Ekman trans- port vectors. It is very possible that the development of eddies north of the Gulf Stream have a significant impact on the location of the Shelf Water-Slope Water front. Evidence from the Distribution of Herring Larvae We have inspected the information presented by Schnack and Stobo (1973) and Schnack (1974) summarizing the results of the 197 2 and 1973 joint herring larval surveys and the several separate reports on the 1974 cruises. These cruises took place as follows; 1972 1973 1974 22-30 Sep 16-28 Sep 6-24 Sep 2-28 Oct 29 Sep-20 Oct 27 Sep-18 Oct 12-28 Oct 15 Oct-1 Nov 18-30 Oct 31 Oct-12 Nov 28 Oct-8 Nov 16-23 Nov 28 Nov-15 Dec 4-20 Dec 4-19 Dec VJe have delineated the aroas whoro 10 or more herring larvae per 10 m were caught, Figures 13, 16, and 17, and made some 13-20 inferences from the distributions of the various size cate- gories. We have inferred that the area occupied by herring larvae <10 mm in length to be the spawning area and have outlined it and the spawning area for the preceding cruise. We have then outlined the area occupied by the 10-15 mm larvae and the >15 mm larvae and drawn arrows representing the inferred spread of the larval distribution of the larger size categories- from the spawning areas. It is quite ap- parent that advection and dispersion have occurred. The spread from the "spawning- area" between the first and second cruises in 197 2 appears to be on the order of one mile per day and due to dispersion by the tidal oscilla- tion. Between the second and third cruises an advective spread of >10 miles per day southv/estward occurred with a lesser northerly drift north of Georges Shoal and north- easterly drift from Nantucket Shoals. Betv/een the third and fourth cruises mixed movements of 1-2 miles per day occurred over Georges Bank, but a four mile per day spread occurred westward from Nantucket Shoals spavzing area. By the fifth cruise herring larvae are well spread over the whole area, the major drift having been westward from Nantucket Shoals at about two miles per day. It would appear that there had been no drifts away from the shallov; waters except for a small tongue of 10-15 mm larvae over the edge of SE Georges on the second cruise. An anticyclonic eddy was drifting v/estward just south of Georges Ban): during this period (U.S. Naval Oc(Vinograpl^ic Office, 1972). 13-21 During the interval between the first and second cruises of 1973 there was a southwestv/ard advection from the Georges spawning area of about five miles per day and a weak southeasterly drift. Between the second and third cruise the southwestward drift continued coupled with a general expansion from the Nantucket Shoals spawning area and possibly a northeastward drift along the NW side of Georges . The westward drift continued between the third and fourth cruises and a weak southerly drift was apparent between the fourth and fifth cruises. The larval popula- tion was larger in 1973 than in 197 2 and tended to move closer to the southern edge of Georges Bank or even beyond the 100 meter contour during 1973. There were no anti- cyclonic Gulf Stream eddies in the vicinity during this period (U.S. Naval Oceanographic Office, 1973). Spawning was late in 197 4 so that no herring larvae were caught during the first cruise. Between the second and third cruises there appear to be westv/ard advections from the spawning areas at speeds of 3 to 8 miles per day. Between the third and fourth cruises there appeared a gen- eral dispersion from the spawning areas. Betv/een the fourth and fifth cruises the overall tendency was for the area occupied by larval herring to compress slightly lati- tudinally with a slight westward drift of the whole at be- tween 1 and 2 miles per day. As in 1973, the larval herring population tended to extend beyond the limits of the 13-22 10 meter contour. The computed monthly Ekman transports during this period were moderate toward the SW, being somev/hat stronger in October than for the 10-year mean for October, which is usually weak. It is interesting to note that an anticyclonic eddy drifted during November from the vicinity of the Gulf Stream to the southern edge of Georges Bank and continued westward along the edge during December (U.S. Naval Oceanographic Office, 1974) . Table 2 provides us with an idea of how the total population of herring larvae changes from cruise to cruise in relation to the change in area occupied. It is apparent from this information that the herring population tends to increase at a greater rate than the area it occupies through the end of October (the third cruise) but somewhat later in 1974, and then begins to decrease due to the various exigencies which cause a decrease in the population while the area occupied by the population continues to increase through the fourth cruise (prior to the first of December) following vzhich the area decreases slightly. The evidence from the Joint Herring Larvae Surveys appears to suggest that the larvae are retained v/ithin the shelf water. The area they occupy expands with time due to the vigorous tidal stirring and advection. The advection appears to be principally toward the west. There are some indications of a northeasherly drift north of Georges Shoal, i.e., a continuation of a clocla.'iso gyro around the shoal 13-23 Table 2 Change in total number of herring larvae and area occupied from cruise to cruis.e A Total Number of Herring Larvae A Area 1972 1973 1974 1972 1973 1974 From. 1st to 2nd cruise 3.8* 24 - 4.7 5.0 - From 2nd to 3rd cruise 1,5 2.5 1.3 1.2 1.6 1.3 From 3rd to 4 th cruise .42 .64 1.4 1.1 1.3 3.0 From 4 th to 5th cruise .34 .16 .47 .73 .80 .82 Georges Bank only. 13-2J+ part of the bank. We do not have adequate data to evaluate the effect of the passage of storms through the area. It is possible that some larvae may drift off the southeast edge of Georges Bank. This is the location where the thermal fronts, as observed by satellite, appear to have their maximum excursion. It is also possible that the anticyclonic eddies drifting away from the Gulf Stream along the southern edge of the bank may entrain shelf water along their perimeter. The sampling pattern for larval herring may not extend far enough off the bank in this vicinity. It is also fairly obvious that we do not know how far the larvae drift west of Nantucket Shoals in November and December, inasmuch as the sampling is not adequate west of 71^ V? longitude. Summary In summary, we are dealing with an area which has the temperature and salinity characteristics of the Continental Shelf bordering on Slope Water to the south. The front be- tween the Shelf and Slope water ranges from diffuse to very sharp and it frequently wanders large distances (several hundreds of kilometers) at the surface, probably much shorter distances (tens of kilometers) at the bottom. Anticyclonic eddies from the Gulf Stream drift close to the southern edge of the bank, .impinging directly against it as they move westward. The energetic tidal oscillations over the bank are 13-25 predictable v/hereas the net drifts are much less well under- stood. There appears to be a clockwise rotation around the bank during the seasons when the thermocline is developing. At other seasons it would appear that the winds may be the mechanism for providing advective forces of the sea surface. It is high time that a concerted effort be made to understand the advective processes above and around Georges Bank and the physical forces which regulate theml In order to determine how the circulation is condi- tioned by the wind systems,, it would seem that a drogued buoy progreim should be conducted with initial buoy plantings in the spa\'7ning areas. The movements of these buoys should be related to the daily, or better stilly 6 hourly, components of the wind stress. Equipping the drogues with recording thermistors or conductivity meters would provide some clues as to how well the buoys stay within the shelf water. The presence of the winter water, as seen in Figure 6, is engimatic. Does this water move at all? Is there a shear zone above it? Drogues should be placed in it and above it to determine this. The forcing by the wind and an evaluation of the Ekman transport needs also to be determined by judicious em.ploy- ment of current meter arrays at the northern and southern edges of the bank, with at least one array over a shallower part of the bank. Equipping thor.e current meter arrays with conductivity cells would permit an estimate of the flux of salt across the bank and its boundaries. 13-26 Both Lagrangian and Eulerian current measurement studies should be accompanied by concurrent synoptic tem- perature and salinity profiles in order to gain a clear understanding of the characteristics of the water being advected. Sampling for nutrients along these profiles would also make it possible to estimate nutrient fluxes across isobaths so necessary in the evaluation of primary production. As learning proceeds the locations of fixed and drift- ing elements of the experiments should be modified to develop time and space scales of the transport processes. Assistance from oceanographers skilled in the technical and theoretical aspects of this research should be enlisted. Acknowledgements The preparation of this report has been funded through National Marine Fisheries Service Contract No. 03-5-043-327 and the National Sea 'Grant Program Grant No. 04-5-158-8. The author gratefully acknowledges the generous assistance of Marvin D. Grosslein, Merton C. Ingham, and R. Gregory Lough, all of the National Marine Fisheries Service, in providing data and v;ise counsel. 13-27 References Anonymous. 1973. Tidal current tables 1974 Atlantic Coast of North America, U, S. Department of Commerce, N.O.A.A., National Ocean Survey, 200 p. Bakun, A. 1973. Coastal upwelling indices. West Coast of North America 1946-1971, N.O.A.A. Tech. Report NMFS SSRF-671, 103 p. Beardsley, R. C. and B» Butman, 1974. Circulation on the New England Continental Shelf: Response to strong winter storms, Geophys, Res. Letters 1^(4) ; 181-184 . Bigelov7, H. B. 1927. Physical oceanography of the Gulf of Maine. Bull. U. S. Bur. Fish. 40 (2) ;511-1027 . Bumpus, D. F. and Lauzier, L, M. 1965. Surface circulation on the Continental Shelf of eastern North America between Newfoundland and Florida. Am. Geograph. Soc, Serial Atlas of the Marine Environment, Folio 7, 4 p., 8 pi.. Appendix, Bmnpus, D. F. 1973. A descripLion of the circulation on the Continental Shelf of the east coast of the United Slatos, Procn-o^sf> in Ooeanography 6_, Ch. 4: 111-157. AnpcMidix. 13-28 Chase, J. 1955. Winds and temperatures in relation to the brood-strength of Georges Bank haddock. Jour, du Conseil Int. p. I'explor. de la Mer 21^(1) :17-24. Clarke, G. L. , E. L. Pierce, and D. F. Bumpus. 1943. The distribution and reproduction of Sagitta elegans on Georges Bank in relation to hydrographic conditions. Biol. Bull. 85, 201-226, Colton, J. B. , Jr., R. R. Marak, S. E, Nicker son, and R. R. Stoddard. 1968, Physical, chemical, and biological observations on the Continental Shelf, Nova Scotia to Long Island, 1964-1966. U.S.F.W.S. Data Report 23, 190 p. Fofonoff, N. P. 1962, Machine computations of mass trans- port in the North Pacific Ocean, J. Fish. Res. Bd. Can. 19 (6) -.1121-1141. Haight, F, J, 1942. Coastal currents along the Atlantic Coast of the United States. U. S. Coast and Geo- detic Surv. Spec. Pub. No, 230, 73 pp, 35 figs. Hov/e , M. R. 1962. Some direct measurement of the non-tidal drift on the Continental Shelf betv;een Cape Cod and Capo llattora.s. Doop-Sea Kos_^ 9:445-455. 13-29 Ingham, M. C. 1974. Variations in the Shelf Water Front off the Atlantic Coast between Cape Hatteras and Georges Bank, Prepared for the NMFS 1974 Status of the Environment Report, Draft copy of unpublished manuscript. Lauzier, L. M. 1957. Bottom residual drift on the Continen- tial Shelf area of the Canadian Atlantic Coast. J. Fish. Res. Bd. Can. 24 , 1845-1859, Miller, A. R. 1957. The effect of steady winds on sea level at Atlantic City. Meteorological Monographs 2(10) :24-31. Schnack, D. and W. T. Stobo. 1973. ICNAF joint larval herring survey in Georges Bank - Gulf of Maine areas in 1972 - preliminary summary. ICNAF Res. Doc. 73/115:55 p. Manuscript restricted, Schnack, D. 1974. Summary reporii of the 1973 ICNAF joint larval herring survey in Georges Bank - Gulf of Maine areas. ICNAF Res. Doc, 74/105:23 p. Manu- script restricted. 13-30 Whitcomb^ V. L. 197 0, Oceanography of the mid-Atlantic bight in support of ICNAF, September-December 1967. U. S. Coast Guard Oceanographic Report No. 35, 157 p. Uchupi, E. 1965. Map showing relation of land and sub- marine topography, Nova Scotia to Florida. U.S . Geol. Surv. Misc. Geol. Invest,, Map 1-451. U. S. Naval Oceanographic Office. 1972. Monthly summary, the Gulf Stream (116782-6S) , Vol. 7, Nos. 9, 10, 11, and 12. U. S. Naval Oceanographic Office, 1973. Monthly summary, the Gulf Stream C116782-6S) , Vol. 8, Nos. 8, 9, 10, and 11. U. S. Naval Oceanographic Office. 1974. Monthly summary, the Gulf Stream (116782-6S) , Vol. 9, Nos. 10, 11, and 12. Wright, W. R, 1975. The limits of shelf water south of Cape Cod, 1941 to 1972. J. Mar. Res, (submitted for publication) . 13-31 •-\ r- 4 i^ v\ 5 ^r ,^ .<< CJ' ^. > ^ mS. W^- "^ 1^ X V X .4i : V ;■ \- .-, ^v ■■"Si ^ v-^^v- 1 -; - ■" -f •■'^y ''-' j^^ <^>-',>,. %, (> O' / ** K^f / iT' ^- « IMM ^H.I«ir!XU»l O Ll) O i_ Sd313IN in u 0) ja S 0) o 0) Q u o c •H CO IS o o r-l 3 o O CO CO o o ca o on 60 c o .H o CO o CO f-1 o a: <0 lit ** m t- (U -u UJ 2 M 0) 3 O CO C -1 ^ O a) 4J CUiH o a o M Q) CJ H ^ CO o CO o iH SU313IN SM313IN SU313V^ Sd313t^ fO <0 i 1 / . \ 1 ro Njrrr ^ lO ON 'a a 03 \o ON H o ?-< o 0) a •H 03 O 5 09 o u o 03 O m o vo tiO a o H 03 ra 0) H •H O in ft -P 00 •H VX) •H H 03 m ON +3 0) +3 03 ft H a o (D O Eh-— ' _:t- H Sy313W SU313VN Sd313V\l Sd313IN ON CO ^1 o a •H CO o O CD CO o O CO I V — r- ^ I '^) J NX y^ ___^ ^ P/fc lO ^ N IKY (A y<< ~ ~* r • .' • ^ =^:'''"'%^.: •:■;■■ ^ ^ ;/( 1 cvj \ v. to \ v* \ \ / '^^ \.. 1 f " ^ V -^(M U' vL' ^ ': ■ •^xv: vUtv..- - 1^;^ 1 J V) UJ U o o on o a o H CO CQ 0) CM O u ft +3 CO •H VO PI •H CO ON H -P 4J CO 0) -P a o en H SU313Vyi Sti313lf\l O Sd313lf«l S»3i3M vo o o\ ♦ H 13 a CO m a: LfA r^ UJ MD 8 Z. 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X O . ■ < _j > \- < til < UJ ro if) -z. n^ fo o rr (Ti UJ ro CO o -J h- X "" ^ CM < _j h- UJ t _) _J UJ :z ID ro 2 o o Q < 5 S SUITE CH AVE.. d 2 h- z UJ o O cr (0 _j < < in OJ 00 ^ UJ < o h- > O) h- UL 2 c: iD UJ UJ 71 O Ld > o 1 m z. o UJ C.\} U- UJ X C/) z. 2: Id CC 1 ir. 00 O r^ < 1— C) LlI •-C l.d < ?■ ro ^ < 00 Q_ !h 0) w 0) ^J •H H H +^ crt W H . 05 TJ +> 0) a ra Q) t-^ a a •H ^ U •H flj > Pi fl pi N CQ H 'O 05 (D a ^ •H W +3 01 01 (1) S a >5 a) ,Q ?H aj 'd 15 (U 03 ?3 +3 T3 fl ^ ^ +3 4:5 ?^ 01 •H ^ .c; 13 H bO 0! a 4-3 fl H 03 u «H ra (D >5 fl H •H AJ H Q) 0) T3 > ;h 05 , 1 L) J 1 .1 C : c'^ C.^ ». > ( ) (. ) CM 1) / C) •d I i.} V\ I C) I CM i o \ < <^.' v< o CO < G^ O ^ < iL Q o 4:^ CO (U a cd — •H -H z: -P T3 CQ 'H „ ft 0) ^ -P ^ +3 bO ro fl 05 -P ^) H fl 05 0) fH a -r) 00 H 00 1973 1974 MONTHLY EKMAN TRANSPORT AT 40^N 70° I -I WO METRIC TONS PER SEC. 13. lU Monthly Ekman Transport at iiO°N-TO°W for 1972-197^, u-i -cz x: -c COI-l-1- C\J CM a\ H a •H (D ra •H p o CO p o •H !> ^1 ft o -p •H -p CO H (D u 0) 03 !> ^ 03 a •H ft 0) H CO p o •H 03 > O CO a o •H ■P 03 CJ O H m _ u o u _ e c: c o o o o j= o o o •— CU O) (U i^ CO CO CO c en a 5 CO Q, O > e e 0) in Q) ^ o t: -c o ~ Ll_ Ll_ I £ £ 0) o > D - CO .9 8 .-t: CD I I £ £ £ in £ 1 lO o A #), #• a> Q) CO I/) 3 r3 V- u. 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Lockwood Chamberlin Atlantic Environmental Group Page Construction of bottom temperature diagram for 1974 18-1 Construction of long term monthly mean bottom temperature diagram— 1940-66 18-2 Bottom temperatures in 1974 18-2 Incursion of warm core Gulf Stream eddy in March., 18-2 Bottom temperatures above normal throughout the year 18-5 Acknowl edgments 18-5 References 18-7 BOTTOM TEMPERATURES ON THE CONTINENTAL SHELF AND SLOPE SOUTH OF NEW ENGLAND DURING 1974 Preparation of an analysis of bottom temperatures during 1974 for the important fishing grounds of the continental shelf and slope south of New England has been possible because of the large amount of data found available for this region. The data obtained during 20 cruises of 9 different vessels, are mostly from expendable bathythermograph sections made aboard research vessels going to or from Woods Hole. The analysis has entirely depended on the cooperation of several oceanographers, from as many organizations, who generously supplied the data, largely in the form of contoured temperature sections. Their specific contributions are acknowledged at the end of this contribution. Construction of Bottom Temperature Diagram for 1974 (Figure 1) A contoured diagram of bottom temperatures (Figure 1) was prepared in three steps: 1. Tabulation of (1) the values of the isotherms on vertical temperature sections and the depths where these intersect the bottom and (2) the actual or extrapolated bottom temperature values that appear on the temperature sections. 2. Plotting the tabulated values at the depths of bottom and at the times of year when the observations were made. 3. Contouring at 1°C intervals. Information from NOAA Satellite imagery on the passage of a warm core Gulf Stream eddy (or ring) through or near the area of the diagram was used as a guide in some of the contour timing. Bottom temperature data from immediately outside the area provided similar guidance on a few occasions. The process of the contouring, itself, led to minor re-interpretations of some vertical sections, concomitant changes in the depths at which bottom temperature values were plotted, as well as the addition of a few values. Although the diagram is designed to show only the gross pattern of bottom temperature change in the region south of New England, it has, 18-1 because of the manner of its construction, a characteristic that could be misleading, unless explained. The temperature sections used for the diagram all run in a more or less north south direction across the shelf and slope, but are from various positions between 69°47' and 71°18'W longitude (a band about 70 nautical miles wide) (Figures 3-4). In the diagram, however, they are treated essentially as though all were from a single line or narrow band. An adverse result of this treatment is possible ambiguity in the timing of the "temperature events" as dis- played, because the apparent timing, although largely a product of the actual timing of temperature changes, is partly a product of the relative spacial locations of the successive sections. Because the shelf and slope region south of New England extends generally east-west and the main direction of the circulation is westward (Bumpus, 1973), sections from the eastern part of the region tend to give an "early" bias to the timing and sections in the west a "late" bias. As an aid to making judgments regarding these biases, the geographical positions of the sections used are shown in Figures 3 and 4. The flow rates in the area (Bumpus, 1973) indicate that most of the timing errors from this bias will not exceed a week or two. General coherence of the diagram supports the assumption that the temperature regime in the region covered is reasonably homogenous. This assumption is also supported by previous studies of this region, such as those of Bigelow, 1933, Walford and Wicklund, 1968, and Colton and Stoddard, 1973. Construction of long term monthly mean bottom temperature diagram--l 940-66 (Figure 2) To provide a basis for comparison with the diagram of bottom tempera- tures during 1974, a similar one was constructed based on mean monthly bottom temperatures (Figure 2). The data employed were selected from mean monthly values computed by Colton and Stoddard (1973) for prepara- tion of an atlas of bottom temperatures on the continental shelf from Nova Scotia to New Jersey (Colton and Stoddard 1973). These mean values were computed for the period 1940-66, from data extracted from the bathythermograph file in the Woods Hole Oceanographic Institution. The particular mean values used in preparing Figure 2 are those for the quarter degree squares between 70°30' and 71°00'W longitude. Bottom Temperatures in 1974 Incursion of Warm Core Gulf Stream Eddy in March:- By far the most striking feature in the bottom temperature diagram is the sequence of strong and abrupt warming and cooling during March over most of the width of the continental shelf and downward on the continental slope 18-2 to below 360 meters. This temperature anomaly, occurring at the time of year when the bottom temperatures have usually been at their annual minimum (Figure 2), was caused by a warm core Gulf Stream eddy which entered the region from the east and moved unusually close along the continental slope (Applications Research Division, U.S. Naval Oceano- graphic Office, 1974). The pronounced effect of this eddy on bottom temperatures is clearly shown by an expendable bathythermograph section taken on March 28-29 by NMFS scientists of the Northeast Fisheries Center aboard the RV "Albatross" in the course of the annual spring ground- fish survey (Figure 5). Temperature sections from three other vessels that operated in the region during March and early April also show the presence of the eddy, but indicate marked fluctuations in its effect on bottom temperatures. Fortunately, five of these sections (one from the R/V "Albatross IV", one from the USCGC "Dallas", and 3 from the R/V "Verrill") were made along nearly the same track line, particularly at the offshore end (Figure 4). Data from these sections were, therefore selected when preparing the bottom temperature diagram (Figure 1) for the period March 1 - April 5, so as to present the best available evidence on the rates of change of bottom temperatures. To obtain additional information on the progress of the eddy through the southern New England region, its positions at the surface, as revealed by NOAA satellite imagery, were compiled for the months of January to June (Figure 6). This compilation is based on: 1) the Experimental Gulf Stream Analysis, issued weekly by the National Environmental Satellite Service, 2) the Experimental Ocean Frontal Analysis, issued semi-monthly by the U.S. Naval Oceanographic Office, 3) interpretive tracings from the satellite imagery of the positions of eddies and fronts (on file at the U.S. Naval Oceanographic Office), and 4) personal re-interpretation of the satellite imagery for the first half of April The resulting"track line" of the eddy (Figure 6) shows: 1) relatively steady westward movement at an average speed of about 0.2 knots (10 cm/sec) from south of Georges Bank into the southern New England region, during the period from late January until early March 18-3 2) irregular movement in the region south of New England, from early March until mid May, and 3) relatively steady southwestward movement at an average speed of about 0.17 knots (8 cm/sec) from south of New England to the latitude of Virginia, during the period from mid May to the end of June, after which time the eddy was no longer observed in the satellite imagery. Although stagnation of the eddy in the southern New England region from March until mid May is clearly demonstrated in Figure 6, the details of movement as diagrammed should not be regarded as ^/ery accurate, because: 1) Mismatch problems encountered when overlaying the available transparent graticules on the satellite imagery prints indicates a positional recovery error of about 10 to 20 nautical miles, and 2) the apparent center of the eddy at the surface as seen in the satellite imagery, may often be many miles from the core of the eddy below the surface, because of surface over-riding by entrained or wind driven shelf and slope water The stagnation of the eddy south of New England, from early March until mid May (Figure 6), indicates that its effect on bottom tempera- tures in this region may have been more prolonged than appears in Figure 1. Irregular movement of the eddy throughout this period suggests that repetitive contacts with the bottom, such as apparently occurred during March (Figure 1) may also have occurred during April and early May. This possibility is left open to question by the few vertical temperature sections found available for the months of April and May. To the westward of the southern New England region, however, in the vicinity of the Hudson Canyon, temperature sections show that the eddy made strong contact with the continental slope on May 19-20, apparently causing bottom temperature elevations above 14°C to a depth of about 300 meters (Gulf Stream Monthly Summary, June and December, 1974). A special note was published by the Applications Research Division (1974) on the unusual character of this eddy. It remained close to the continental shelf throughout its observed life and had a core temperature at 200 meters of only 14.4°C. They observed that in con- trast "an anticyclonic eddy formed in late August 1970 contained much 18° water when surveyed on 13 December 1970", and suggested that the 18-4 1974 eddy, having fomed in mid winter, lost more heat to the atmosphere than the eddy of 1970. Interpretations of satellite imagery reveal the passage of only one other warm core eddy through the region south of New England during 1974 (personal communication, J.J. Bisagni, Atlantic Environmental Group, NMFS). This eddy, however, was apparently too far to the south during the passage-- in late June and early July--to have had a warming effect on the con- tinental shelf and slope. Although no vertical temperature sections have been found to document the bottom temperature effect of this eddy in the southern New England region during the time of its passage, sections from farther to the west -- in the Hudson Canyon area-- show the eddy to have been far off the continental slope in mid July (Gulf Stream Monthly Summary, December 1974). Bottom Temperatures Above Normal Throughout the Year :- Comparison of Figures 1 and 2 shows that bottom temperatures on the outer continental shelf and upper continental slope were generally a few to several degrees centigrade warmer during 1974 than the monthly mean temperatures for the years 1940-66. In the warm band on the outer shelf, where Slope Water usually is in contact with the bottom, maximum temperatures were not recorded lower than 12°C in 1974. In the mean temperature diagram, however, the maximum values in this warm band are below 11°C from mid- February through April and below 9°C in March (Figure 2). At mid depth on the continental shelf in 1974, the characteristic core of cold bottom water (Bigelow, 1933) was about 2*'C warmer than the monthly mean values, from the time of its formation in February until the autumn when it was dissipated by vertical mixing of the water column. In the Hudson Canyon area, just to the west of southern New England, bottom temperatures on the outer continental shelf during 1974 can be compared with those of the immediately preceding years. Vertical temperature sections obtained by the Naval Oceanographic Office on passenger liners between New York and Bermuda from spring to fall in 1970, -71, -73, and -74 indicate that the bottom temperatures during the months of observations in 1974 (March-October) were similar to those south of New England, but generally ^° to 2°C warmer than in any of the previous years (Gulf Stream Monthly Summary, November 1970, December 1971, July 1974, and December 1974). Acknowledgments Compilation of the data used here was stimulated by the suggestion of John B. Co.lton, Jr., National Marine Fisheries Service, Northeast Fisheries Center, that temperature sections had been collected year around in southern New England waters by scientists at the Woods Hole Oceanographic Institution since 1969. He also provided the data used in preparing the 18-5 diagram of monthly mean bottom temperatures (Figure 2). A majority of the temperature sections used in the present analysis were provided by . W. Redwood Wright, WHOI, who had assembled them in conjunction with his research on the slope water front. He had collected some of them himself, at sea, and obtained the rest through the cooperation of other scientists. The sections from this source are those indicated in Figure 1 from vessels "Knorr", "Chain", "Eastward", and "Westward". Sections from the Coast Guard Cutter "Dallas" and R/V "Verrill" were obtained from a data report (Flagg and Beardsley 1975). Charles N. Flagg, Massachusetts Institute of Technology, kindly supplied additional data relating to these sections. In addition, Charles W. Morgan, U.S. Coast Guard Oceanographic Unit, sent sections he had prepared from 2 cruises of the Cutter "Evergreen". The data for the sections from the"Albatross IV" were provided by Samuel R. Nickerson, Northeast Fisheries Center, National Marine Fisheries Service. Two sections from the passenger liner "Sea Venture" were used as published in the Gulf Stream Monthly Summary, December 1974. Alvan Fisher, Jr. and G.J. Potocsky, Applications Research Division, U.S. Naval Oceanographic Office, supplied copies of the Experimental Ocean Frontal Analysis, made available files of NOAA satellite imagery, and provided valuable advice. In the Atlantic Environmental Group, NMFS, John J. Kosmark carried out much of the data processing for the figures and Reed S. Armstrong gave helpful advice. 18-6 REFERENCES Applications Research Division, 1974. An unusual anticyclonic eddy. Gulf Stream Monthly Summary, U.S. Naval Oceanographic Office, 9^, No. 6, centerfold. Bigelow, H.B. 1933. Studies on waters on the continental shelf, Cape Cod to Chesapeake Bay. Papers Phys. Oceanog. Meteorol . 2^, No. 4, 135 p. Bumpus, D.F. 1973. A description of the circulation of the continental shelf of the east coast of the United States. Progress in Oceano- graphy, 6, pp. 111-157, 2 tables. Colton, J.B. and R.R. Stoddard. 1973. Bottom-water temperatures on the continental shelf. Nova Scotia to New Jersey. NOAA Tech. Report, NMFS CIRC-376, iii + 55 p. Flagg, C.N. and R.C. Beardsley, 1975. 1974 M.I.T. New England Shelf Dynamics Experiment (March, 1974) Data Report: Part I: Hydrography, M.I.T. Meteorology Dept. Report 75-1. Walford, L.A., and R.I. Wicklund. 1968. Monthly sea temperature structure from the Florida Keys to Cape Cod. Ser. Atlas Mar. Environ. Am. Geogr. Soc. (Folio 15), 2 p. , 16 pis., appendix. 18-7 ro d: q: o z CO en O CQ 13: ><>ii: Q CC ^ < (T 5 (T H CO 2 UJ i»i ^ 5^ K — — ro 0: ^ ^ < 5>S < UJ J- -o •r- >> • TD -M •O nj O •«- J= -O • (U U C Ol 3 Ul (U 4-> (U C •1- 4J 3 +J • » 4-> (U t. .i^ •!- J- fO C I— 3 3 nj I— +i S- CQ (U n] -Q 4-> C U. 1- E o o o a* *+- O) s- u CiJ *f- W» JT t- , c en -o * a> nl o s- •«-> » t/» C E J-.r-.r- J_ «J r— nj 3 C +J S c S 3 rO O O «4- o j: O W T3 O «/) E O i- O'f- S «^ Q.t/1 00 o o O o 00 ro 3 o> TIDAL STATION TEMPERATURES U.S. EAST COAST AND LONG ISLAND SOUND J. R. Goulet, Jr. Atlantic Environmental Group Mean monthly temperatures from observations at tidal stations along the U.S. east coast and Long Island Sound were contoured on a distance versus time plot for 1973 and 1974. The change in temperature between months, to indicate warming and cooling, was also contoured. The east coast data (figs. 1 & 2) , from Montauk to Key west, were plotted versus latitude, while the Long Island Sound data (figs. 3 & 4) , from New Rochelle to Buzzards Bay, were plotted versus longitude. In Long Island Sound, the temperatures showed the onset of warming in late January both in 1973 and 1974. The peak of warming occurred in late April in 1973 and reached slightly higher values than in 1974 when it occurred in early April. The onset of cooling occurred in late July in 1973 and early August in 1974. Cooling was not as intense in 1974 but the peak of cooling began one month earlier and persisted longer. Maximum temperatures at Bridgeport reached above 75"? in August 1973, but did not reach as high in 1974. In December 1973 the temperatures the length of Long Island Sound did not fall below 45''F, but did so in 1974. In the Mid-Atlantic Bight, from Montauk to Cape Hatteras, the temperatures at tidal stations showed no noticeable differences between 1973 and 1974, except just north of Cape Hatteras where they were up to S^F warmer in January-February 1974. The warming and cooling cycle also shows very little difference between 1973 and 1974. The peak of warming is a little more intense in 1974, but begins slightly later and ends slightly earlier. The peak in cooling extends from September through December in 1973. In 1974 the cooling peak starts earlier, weakens in November, and peaks again in December. Warming begins in late January both in 1973 and 1974 except just north of Cape Hatteras where it begins in early January in 1974. Along the southeast U.S. coast, temperatures at tidal stations show that 1974 was slightly warmer than 1973. Warming began in early January in 1974, but only in February in 1973. Cooling began in July 1973 and August 1974. Cooling in October -Dec ember was more intense in 1974 than 1973, so that the two years ended with nearly equal temperatures . 19-1 Zh-Z-lQ. 0<<|-< O 2 < $ (U O CD t- -r UJ UJ 2S-- _l -I iOT3a:>- >- I .Z 0<<(_< 5CD(0<0 CO « 0) o h •H CO •U nj CO 4-t 0) m s iH 0) CO 03 > •H 4J CU > 4J •H CO 4J CO CO o t>0 o CU s ■u CO CO • cu fX4 o 4J «* CO CD CO •H CU u iH 3 CO 4-1 CO ^ u QJ 0) 4J cu c 6 •H s u M 3 ^ iH 42 • 4J i-> c CO o (U e s d >. CO (U (U i^ 6 o fl ■u •H ^ • (U 3 T3 OG CO 0) Ci U 73 CO 13 CO £-S XI iH • ON H 0) M 3, Fm o O o O ro o O cvj ♦J c o s 09 a o •H 4-> (» 0) CO nS o o 4-) CO cd - o54 J-l 0) 4-1 CO J3 4-) c o Is cd (U 0) i^ 6 o CJ 4J •H 60 td a 4J td d €^ CM ON H 0) M •H o CVi 1^ o O o O o o (O o o o O o O o o lO o o Ld _l _J LJ X o o liJ Q. O) I- LJ _l _J CD O CL LJ CD Q (T 00 O Q LlI 5 UJ (D I- (T. O UJ CO Q O O Q tr < N N ID CD _ -3 CO C o •H ■U n) ■u CO (U •H 4J T) C 3 O W •^ c rt r-l CO M t»0 C! O hJ 4-J CO CO 0) • U (U 3 iH 4J H CO (U h X! ^ >% iH CO Xi pq u a CO o T3 a M CO d ta Rt N ^ 3 s pq CO CO • iH o iH •u >. >. tH cd J3 PQ 4J C! CO O T) a >-l CO Cl N cfl N (U 3 « C • •H CO c (U o 60 •H c ■p CO cd 43 4J O CO 43 fO • ON rH ^i Q bJ a: ZOO d o o z o _J UJ I- O CL UJ iu2 XQ >0Q CO (U TJ •H 4-1 -o c d o en •T3 d rt rH CO M 60 c o hJ ■u to CO • 0) 0) u iH 3 T-i 4J (U C« ^ M o 0) o CU pij g ^ 4J 0) z CO r^ o C3^ ■u iH >> >^ C(J iH PQ ^ U CO C T3 o U 6 CO N fj N cd d d) M S d CO •H d o 0) •H &o ^ c cd ^ 4J CO u ^ «d- • a\ rH (U M S 00 PL4 Monthly Maps of Sea Surface Temperature Anomaly in the Northwest Atlantic Ocean and Gulf of Mexico, 1974. Douglas R. McLain Pacific Environmental Group, NMFS ABSTRACT Sea surface temperature observations taken by merchant. Naval, and other vessels in the area of the Northwest Atlantic Ocean and Gulf of Mexico bounded by the east coast of North America and longitude 60 °W and latitude 20 °N to 46 °N are summarized by month and 1 degree square during 1974. INTRODUCTION The Pacific Environmental Group has access to unclassified real-time weather reports received by the U.S. Navy Fleet Numerical Weather Central. These weather reports are available globally and have been stored on magnetic tape since before 1968. This report presents monthly maps of sea surface temperature anomaly based on these reports. Since 1965 the U.S. Naval Oceanographic Office has pub- lished maps of sea surface temperature and its anomaly monthly in the publication "Gulf Stream. " The maps presented in this report differ from those of the "Gulf Stream" in several ways. First, these maps include the Gulf of Mexico and a larger area of the Caribbean Sea than those of the "Gulf Stream." The area covered is that portion of the Northwest Atlantic Ocean bounded by the coast of North America, 60** west longitude and 20-1 20° and 46° north latitude. The maps of the "Gulf Stream" cover the region bounded by the coast and longitude 54°V7 and latitude 24 °N to 45°N. Second, the maps are part of a series of such maps that can be generated in a consistent manner 1/ back to 1948. McLain, Mayo, and Oven have developed such maps for the period 1948 to 1967 based on historical data and are now updating the series to 1972. Third, the actual observations used for making these and the "Gulf Stream" maps, although both being made by merchant and naval vessels, are not completely identical sets and thus differences in the number of observations in particular areas and months exist between the two series of maps. Finally, these maps are based on a 20 year reference period, 1948 to 1967, which was chosen as a recent 20-year period in which numerous observations were available. McLain, Mayo and Oven used this same reference period whereas the "Gulf Stream" maps are based on a historical mean of approximately 100 years. DATA PROCESSING The maps were constructed from observations of sea surface temperature received in "real-time" from merchant, naval, and other vessels by Fleet Numerical Weather Central. These reports were edited by a two stage filter similar to that used by 1,/ Manuscript submitted for publication as NOAA Technical Report NI4FS SSRF. 20-2 McLain, Mayo, and Oven for historical data. In the first stage all observations less than -5.0°C or greater than +35.0° were rejected to eliminate obviously erroneous values. Second, repotts greater than 9°C from the 1948-67 monthly mean were rejected. Means of sea surface temperature by 1° square of longitude and latitude and anomalies from the 1948-67 mean were then computed. The anomalies were then plotted on an electrostatic plotter with the 1948-67 mean and the number of reports in each 1° square. Following the convention of the "Gulf Stream" maps, values were plotted only if there were 4 or more observations in each square. The squares were shaded for anomalies of 1.0 °C or greater and for -1.0 °C or less to emphasize the patterns of sea temperature anomaly. SOURCES OF ERROR As mentioned by McLain, Mayo, and Oven, there are a number of potential sources of bias and error associated with the sea surface temperature observations from ships of opportunity. Some of these errors are as follows: 1) Ships tend to avoid areas of bad weather, consequently, the observations are biased towards areas of fair weather conditions. This bias has become more important in recent years as marine weather reporting, forecasting, and optimum track ship routing have improved. 2) The observations are not randomly distributed over large ocean areas but instead are concentrated along shipping lanes. Thus observations are much more dense off New York 20-3 than in the infrequently travelled western portion of the Gulf of Mexico. Also the data may be biased due to varying distri- bution of observations in time and space within each 1 degree square. 3) Most of the observations of sea surface temperature are "injection temperatures," that is, they are made with a thermometer in the ship's main cooling water intake. Thus they are subject to instrument calibration error and to warming of the intake water in the engine room. Using data from 12 selected ships, Saur (1963) studied these errors and found that the injection temperatures averaged about 1.2°F higher than surface water temperatures taken by a bucket thermometer. DISCUSSION Elsewhere in this Status of the Environment Report, Namias and Dickson discuss the large scale atmospheric circulation during 1974 and its effects on sea surface temperature. They show that the sea surface temperature was generally warmer than normal throughout 19 74 along the East Coast of North America. They attributed this to "the v;arm southerly anomaly wind prevailing along the western flank of the strengthened Bermuda High, lessening the transfer of sensible and latent heat from the ocean, while the anticyclonic cell itself is positioned to minimize the deep outbreaks of polar continental air from North America to the western Atlantic during the cold season." The "Gulf Stream" Monthly Summaries published by the Naval Oceano- graphic Office indicate that positive temperature anomalies 20-4 in the Slope Water northeast of Cape Hatteras out to about 70°W were associated with displacements of the Gulf Stream to the north of its normal position during all months of 1974. One could speculate that the northerly displacements of the Gulf Stream might be related to an increased strength or transport of the stream which could have in turn been related to unusually strong wind stress over the North Atlantic. Mamias and Dickson 2/ and Wagner indicate that the Icelandic Low and Bermuda High circulation systems were unusually intense during 1974 which led to abnormally high index circulation over the North Atlantic. Such a high index circulation v/ould cause increased wind stress over the North Atlantic and increase the advection of water around the North Atlantic Gyre. 2/ WAGNER, A.J. 1975. The Circulation and Weather of 1974. Weatherwise, February, 19 75 20-5 1, i:-^ ■*"- 1 05- '" " 1 __■ ■'^' -+^-- -oa r.d"- sd- -?' ,id^- 1 ~4 T,OJ -id- 1 1 + ^\\ \^ :f\ '■■■(a '' 1 ■+■ ■ ■ -o?: : :af^:: + (M "S '"^ + .CD Sd "" '"'?" + -.tn r:d = 0-.O) rid- ^ ) 1 V?" '?" 7>S + Sis '^ + 1 1 .id- ?i^H + cdCSJ ^ "5^^" ^ ^ ^= o-CD T o:.in Sea "= 1 1 iS oS ..-. 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'■■: *-•" " 1 • ea '' + i-:©: :] ^ ^'i -CM s \" I- — ^, \~: /--X^ —"T/ ^ 2 fxV = , ID 1 ^CO "•is + ^(c ■ + crtO 1^ ■'. ■ '■?■'! + 1 ' )' !.iiD -,o> ! 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'^ d "' rid'- rid- t s,IC ad ' jrid'J 1 ^^ '' 1 ''T + Z2- -CD . — 1 — 1 «d= «d- fid- 1 rid = rid' -in rid- 1 rid- \^ ^ r 1 ■ ■ + " ■ +- 1 <• - ^ csj i Q in 1 ". -^ + 1 i 1 1 CO 1 ad ■" rid - rid- ■U / I i,. 2^, 'ttc ;i:ia " " , cn 1 :: in ^^ ' .-, ^ IB C*^ . rid" rid- 2^ - - + ni--. [ 1 t 1 ^ -A,^ ,oOT r, — . .1 ,13. _ cj"-* ' rr-, TI .1 .„« , t^.OD . jOJ \ ^.'^ ^m o05 : 1 + mS Rd- ; " + •=• + "'' t" " "ipj " 1 1 d^ - -id- rid" ri d "■ 1^ ( 3- i f- -^ j s CSJ rilp'SIP' r-.d" jSiJj" Rip- r-tn 3 ) ^ . sISJ 4l i: rlip- rilp- rilp = rid' ^,05 ''?"r?*' ^?" 1^—^ -T®-... ''?" -CD «d' :'^. -'^-.i?-:.! rid = Sd - -CM ^ !5d = - + '■^""r" + 1? > " 1 ■7 '^ ■■ , + 1 :n?:^:] ^ TO-* -?" ■ •+- - + rid- .31 m a. 1 "io..BTi..:. * ■ 'id - od - ,IM ?]d '" =9*" " 1 n'h^ — >^ ~^v^" J\ 3=:-j.id^ "T + ■ ■ + - r. in 1 b-. tsi + + t-IM ^CSI rid- rid'- ^^ i 1 rid-;rid- sr.IO sd- r^ (^ .*ii.: ^A^ ,. CD ^ + rid- U-. H rr, W rid- rid" s D3 ^ : ir. to _ 1 ' 1 a.m.:. + ,/ lis '^ 1 V \ 5"^ fr,fM _ iTllO., . :«ioa:,^ o:.in r.eD rilp- a.in .cOD *-• wCNJ 1 '+ - \ 1\ -x T* >: ,H,: ,<0 ^ ^-t .^; „,(D fi s - ' S IS - 1 „05 riifS- ri^^ 1 •^i ed- t T ? r^ ^^" ,t-. sin ^ ?-]d ~ + ,i.CO 1„ sin ?3d = -m SSd- Rd " U '~'"?'°' '' ' 1 '^ (• rid- rid = rid = sd- ^ ^d^ I ,~^ 1/ 1 ^ i ' 1 1 •^ \ Fi"- 1 1 rid- sd- ^d- '1, t ^'' ^' f'^ 1-^ , £ -.5 -CO '■ 1 id-fs-*^ 1 1 ?3d-[Sd'' Sid- sd- '^ I ;'"- 1 \ 1 1 = (" ,' \ r-CS. ^ ^''-"' 7|-Y / sCn • +- - -?1 ! "^ K" -J ^ ^ \.^ V --^^ \ ,,05 .„. I ,IM ^ Rid - 1 ^d - 1 ?id" 1 i ■) ^d = ^d- '^ 1 Sd" 1 I „in ^d- H^ Sd " cnID ssija - ,„I\I ^^' " IX 0) Sis'- -UJ Sd - j ^t- r^ *- y^ 1 ) ^ i 1 1 1 1 — : j i 1 ; : : i r J ■ ; i i i ? < 1 1 5 ii '■ -< (1 ( C I I 1 I ^ ( ( 3 1 : \ i C : • --;--=.^-- j ..to 1 I 1 -?^ 1 , '"l . c. - iC 1 ■jca "' ■? . 1 — a — + „,_4 1 -J ca '"' 1 "l^ ^d "^ ^d ''^ :''id ' 1 ill p.. CO 1 I 2=5- rJS "^ rr.CO r «■=- + rid- 1 ■stD - s r. to - .^,d " rid- rid"^ 1 f^J S '^' rid- ,/Ln i ■Kl "" --El .CM iVr 1', s > 1 ■itsf : ■ + '■?' -ID 1 >-C2 1 rid' 1 r. CO .d^ pi" '^^. '^ -CD _. "7" + I ,.-.¥1 1 rid' ' _t^ i 1 1 ; .ID 1 ! -•"?'■ .,-,ISj — 8— ^ x_ \f:^^ ri<|5-!ri^'^ |«f' ,,CM '^- ri,^' riip = -CM rid-- fe ) "iF*; ri^' a2^ -M ,[\i riip' 1 ^^^ -^ TOO s=S- o:. ro 1 2ia - ! "'7* rid- rid = rV d ' ,. m ,„ CD u.Ba I..TH S r ~ 1 " - :f:oB:,,: ■'■+'■ ■ win 1 coin fld = ! -BJ |,„cn .ib-.i'l^ 5, CO fid " B 0> ^ 1 r. CD nin -?'' V ISl r * ^\n : : -■+■-■ 4^' „:,cn ^ 1 "is"' + -in 1 4 ji 1 a; CD 1 „: ED L-. CD '■ d " r.. in _ :,- ea ^ «:; en ris=rid-ris» rid- ..,u> ^ ^ ,. CM , ID l.^ \ +- 7 - ^. tVJ rid- ■■■; ^ " , !-j s ~ 1 1- 1*- ,~.aD ^ rid', rid- =1^- =¥' rid"rid' ''■?" ! _, ^ -all?. . ""■?'' ri>p- ri^ = jOD riifS- -, oo U-, in o 19 1 -CD f^05 r -•"^ 1'.-:^, ID _CVJ _, CD ■ a r^ '^"^i'^?' «^', jriifS- ri,p» i^f-. '.f^., ^■"p ' 1 -~ riip-:i^ = -00 rif^ > _^ ■ -+-7- ^^-^^"v win r-: OS " 1 Tg S ■" ' 1 1 -.-1 1 rid - ^.U3 Sd '" ridl .r V ^■*r-i X— — w^ ^ J ^ 1. f^^ 1 - en ^__ U-. CM i U-. j _ t-i 's rid.- I = r ^-. 1 1 .5. to r,-. CO 1 - s V (D <=; 7^-^ ^CO )' ''] ?' V t 'i 1 1 rid 'rid "iS'-i " 1 1 1 ■+ 4ip ' ■2. 7', --J CT>CD rid = rid'' 1 1 2 r J \, L^, win ri^- .,IM ^ ,S - CM . ^_.■' riff ^-, CO [r-j '^ 1 ^ '^^ "\ ') 5^- r ri.^^lrif» rid- ■.to It'" + 1^. 1 ^-^ ,= ). 1 __^ _■■ rid-- . ] ^- y ,/'' ^-., ^. J ..-•'" , w(Sl /--at ^^ 1 u-.(SI 'id- 5.CO 1 + 1 ,- di riip;^ y-i eg '■"' siL/l -^ '> 1 \?. \ - \ |-.~ + \ — '^ "^- ''\ r o-.M rid- + , , CO ^ -• ^ (O (— i -^ "^ ~^_ ^ J %^f- 1^' U-, S ■ , . CD \- ! ) 1 ^f= .00 5?" i '■3 ) sd- "* 1 Sd" rid" ..^O) ^S-^' i a DC CO (J « z g 2 Q- ^' ) sd' rid = rid» ■'■ ly J 1 + rid- Sd "^ rid- — 3 ') ^d = — i { ri^- ri,p= 4^ '-y - - "^B^ '1 Olio i» ^ r^ ^ . -^- ^ "^ IS ) 3 1 I ) i 5 r 1 i i i c : i i 1 1 i 1 1 i I < \ i i i 'i ; - i a i T o c B i ) C '< I =1 ; i i g c < c ;] ^ f\-* ^ ':m"a>: : fnCD cn-«t I'"; OB '^ + ^?' r-05 B>OD nlA R.p- Ris - i b i\ ^ ■ ' + ■ + ij" -co en 10 , 1^ / SS*' ' m ^i^ tots Rp nCJl ^if^ /■f^ ^- -CD ,s,tD ,«■« ^■P' s"* -CD ."is- sCO KioB- Rip- I ^?" _cn S.p = ^ ^< ~-- '■"^'^^■ ^-■T - - ^?' 1 . - : 1 . tPJ '" ■^f* "+ l"^ \ V ,S = tS . ' + ->CSJ cn(M ^■P' (T, CD t4^ ,,in ^ en rjCO R^' -r- Rip' P t^ ) '■^C- ,-?" + ■ -?" 00 r> Sip' 0,00 Rea' ™C0 !-■< R.^" ;;^' slD ftip- s«p- =5 ^ N a. 1/5 ^ ■■-+-- : ^d- ^^« + 1 1 ■nCO Kid' ^2^- :id- Sp - mm Sep- ^ < r, (SI 1 + - ^' t -in Sip- CO CD -00 Rs " 1 -.SO Rip"- -.CB Siip = sin Sp- n^-* ?;p = V -.r-- ^■p" -(SJ 2f^' ^ - Rip- c-jtn ^p- iCT ::■■: ^ 3 -V ;^^ ^^> "7 -=5- oCM :iS? R=S- ?i4:' -en ..p = .-jlVl. a> 1 ;? V, '^\ -CO ,(SI «^ " IS M 1 1 sin RfS- Sip = £r.C~- in CO if- / Sep- I (?^ :sp:E „(D »(NJ (S T -CD .CD Sip- 3 V ^^. lit- 3~2 ■" 1. " 1 .CD oCmV ^cn (9 'IB '7* '^ - > ^"^a .^^ 1 Rip'' ^?^^ 1 1 ; . mC»5 J X X \ / v k sjisi ■" KJia - -^ ^i^ R^« f ,' s b ^ -^.^ '*' — \ V \ ^ -^ J R^^ n ' 1 3 ^ [/ .^ -Q^ t r\ r" Rb5~ i r^ i 3/ V "''''~""~.. b \/ / sD ^r'" ^ 1 ■:■:■ CNJ f. CO \\ :"! ^. ; \ 1 Rip^ i?. k" ^-p'' ^ 1 1 L ^ ^ - y ) Rs3 = '^ b 2 R=5^ kCD j;-! ,10_ Sp- , 1^- ---^ "^-- ^ ^ Roa " «,lft^ ,- CD 1 1 1 = 1^ 5^" ' ■' 9? \^ -^ -_., _^ ^) \ _ir> .V, t^ V 1 ^ 1 ■■ 1 ■^CD R

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'V-~' -X^ ;^^ -^> -'^*„ en ID -CD SJB" r„IM 35; = Sb " 1 -in «B^- a>a3 SB' f\ 5 .-^ »: - ^ I, b 1 -CM ^;r^ " SB- S75- / a.p- cn l^i" u-,tD B S!b "" sip' "^ 1 . p Sip' -* V 1-i, :it - > ^00 I'-ao ^?" -ID S;f' ( i^- r ^?'' ^?^ _f>i r-in G.^ - 1 iy" f^"^ ._:.»„ =E \. J^ r" ^^ «B- -0) SB- ?iB" ^ ^ J > V \: ^ ^ \i^ m ^b' «B- If* a;B ;^?" mD «B' roOD ^ -'iB" 1 ^ RB/ ■. 1 ^^' a, IV. «B = 0.0) ICb- + min «B' ^ 1*^ J ^ ^" r S \ Sip-- c(0 SB" $» c ^/ f f / 3 n :M Cx R ' 1 'S l«B- 1 .;b- S2- Sb = 1 s^ 1 „<0 1: - , :t 7 / 1 3 / \. \ V 1 ,nin % -B _ Ss~ LoGQ Sip-, y h" s^ r — -^, ; S,p = 0./ a, CM (jip- ll P P^ ~d ' r ?■ — r' S,p^ ^i\ r / ----- b \/ y ^^= \\ .0-* M- ""3 ^f. 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H"' ;' V ^ 5j = ^ ; \ 1 ^^ '¥" ^3. : / : ^-v r^ ^ ^ g 1 1 ; i 3 1 j i f : : 1 ( ■'' ! a i t I f > i I CI 5 ■ 1 ( i < 1 ( » ( ! ■ ) ( ; 1 i J C i \ \ ; ; i i : < z Environmental Conditions in the Gulf of Mexico and Western North Atlantic as Observed from NMFS/MARAD Ships of Opportunity for 1974 Steven K. Cook and Keith A. Hausknecht Atlantic Environmental Group National Marine Fisheries Service INTRODUCTION The purpose of the NMFS Ship of Opportunity Program (SOOP) is to monitor the major fluctuations of the Gulf Stream, Shelf Water-Slope Water front and bottom water cold cell in the western North Atlantic and the Loop Current and any associated eddies in the Gulf of Mexico. NMFS scientists believe that the distribution and abundance of resource species are influenced by variations in temperature, salinity, and nutrients. Changes in the environment can manifest themselves in the form of early or late spawning, onshore or offshore migrations of pelagic or benthic species, or concentration or dispersal of various fish populations. Monitoring the perturbations of the various frontal features (i.e. the intrusion of Shelf Water onto southeastern Georges Bank, etc.) can be a useful aid to NMFS scientists in predicting year class strengths. The monitoring of the various eddies (anticyclonic- clockwise and cyclonic-counterclockwise) may provide NMFS scientists with a hint as to the basic productivity of an area. Cyclonic, cold core, eddies provide discrete areas of upwelling. These areas of up- welling bring more nutrient rich subsurface waters into the photic zone where photosynthesis can commence. These eddies also provide an area of divergence at the surface thereby enlarging the area avail- able for photosynthetic activity. Anticyclonic, warm core, eddies provide an area of convergence at the surface thereby concentrating the nutrients, phytoplankton and zoo- plankton. Therefore, anticyclonic eddies act as entrapment areas for the planktonic forms and cyclonic eddies act as areas of surface en- richment. Because these eddies are constantly on the move, the moni- toring of their migrations and extent becomes important. TRANSECT ANALYSIS Gulf of Mexico Loop Current In 1974 the Loop Current was transected on 7 occasions (Table 21.1) ships. There were two crossings in March (fig.21 .l)one in April (fig.21.2) two in May (fig.21 .3)and one each in June (fig.21 .4 ]feind July (fig. 21. 5). Utilizing the criterion of 20°C at 125 m as the left edge of the Loop Current (Maul, personal communication) the position of the front can 21.1 TABLE 21.1 SOOP 1974 LOOP CURRENT CROSSINGS SOOP 1974 Figure 1 1 2 3 3 4 5 Ship DELTA SUD DELTA NORTE DELTA SUD DELTA SUD DELTA SUD DELTA SUD DELTA SUD Station # Date 20-23 March 8-9 11-15 March 21-23 28-31 April 15-17 40-32 May 21 22-24 May 27-29 9-2 June 28-29 17-20 July 7-8 21.2 be monitored from XBT data. Most migrations of the Loop Current edge ranged randomly between 22°N and 24°N latitude. Movements of more than 1" of latitude in less than 2 weeks was not uncommon. One migration of about 90 nm (167 km) occurred within 9 days, between June 28 (fig.21.4and July 7 (fig. 21.5). The Loop Current was crossed by the Delta Sud on March 9 at 23°15'N latitude at station 23 (f ig. 21. 1 ). Again on~March 23 at 22°30'N the Delta Norte crossed the Loop Current (fig. 21.1). In April (fig.21.2)a crossing of the Loop Current by the Delta Sud determined the front to be at 22°N. In May (fig.21 .3)the Loop Current appeared as a broad flowing current. At this time the front's position had intruded up to 24°N latitude. Again in May (fig. 21. 3), the Delta Sud crossed the Loop Current at 23°N. In June (fig. 21. 4), the Loop Current again appeared as a broad flowing current. The main front (20°C and 125 meters) showed up at about 24°N. In July (fig.21 .5), the Loop Current was crossed by the Delta Sud at 22°30'N. Eddies In 1974 the SOOP ships transected eddies on 19 occasions (table 21.2) all of which were anticyclonic. Eddies were transected in March, April, May, June, July, August and November (figs. 21 .1-6). The diameters of these eddies range from about 75 nm to 335 nm and ranged fn depth from 200 to 700 m. Some eddies were transected more than once. One anticyclonic eddy, in particular was easy to track because it had a subsurface signature in the form of a peak in the 26° isotherm that was opposite to the trend of the rest of the isotherms. This peak also happened to occur at the center of the eddy. This eddy was transected on May 21 (fig21.3) July 7 (fig.21. 5)by the Delta Sud and July 21 (fig.21 .5)by the Delta Norte and migrated in position from 26°24'N, 87°52'W (fig21 .TTto 2?'^'N, 88°55'W (fig21.5)to 25°26'N, 89°44'W (fig21.5). On all crossings the eddy structure extended to depths of greater than 600 m. The eddy moved 140 nm in 2 months in a southwesterly direction or about 2.3 nm/day. 21.3 cn to tr> > O O CO >. .Q O U •r" X (U o c o •r— -M O E > a o o u •1 — o >> o >> u o >> u o u u 1 — o >> o o -M -«-> +J -M c c: c c -M -»-> -M C c c: (O «a itJ rtS +J -M ■!-> -M •♦-> c: c C C c O in in in in o o in in r^ r^ CM CM o O 1^ r^ cn cn cn cn ■* •=J- 1 — ■ — ■ — r— CM CM r— 1 — CM CM CM CM «4- O CD CU o o o o o o O O o o o O O o o o o o o o o O o o o O o o o in in in Ln VD UD r>- r^ UD ID CO VO lO ID ■a (U 4-> o O) to c u to u JZ o c: Q o i. n3 T3 S- o o =tfc o -M -M CO CM CO CM I CM JC a &- LO Q. CM CO ,_ tn CM ^ r^ oo in , cn CT. ^ CO CO CM O CO in «=!- CM o in CM CM 00 in ^ o o o o o 1 — CT> o^ p^ CM cr\ cn r^ 1 — O O CD CD 00 CT> CO 00 CO cn 00 CO 00 CT> CTv cn CO 00 CO ^ 2: z: 2: ^ sr ■zz. 2: z: z: 2: Z 2: z: UD 00 CO o CM cn o in , o CD cn CT» i-n o in "^ in o in in o o ^ CO o o o o o o o CO in «* CO r^ in -* CM r^ CO CO CM «* 00 CM C> o u >> 1" o >> o o a a 40 c to c: c c *"* "■^ lO lO s- CSJ CO to in CVJ CM CVJ CM in in lO lO o o O) CSJ CM ID in CO CO lO lO CM CM CO CO CO CO 4-> "—' ■■"^ * — "-^ * — ^-^ " — ' "" — "*-' "•^ ^^ ""^ "^ F CD o o o in in in in o CD tn in in m la CSJ CJ o o r>. r^ CO CO ^ «a- CJ» lO u> T- r— ^— CO CO r— r— CO CO r— ^ ^ ^— r— r— o. o o o o o o o o o o o o C3 o o o o o o o o o o o o o O o o vo u> vo vo in .1" vo vo vo vo r^ r^ vo vo 0) en CM I CNJ > >» c 3 3 3 O •^ •o 00 I 3 o> 3 «3 S- o o o c o •M VO o CM 00 o o CJ> 00 o o in in o vo 00 CO o o CO CM in o 00 CO o CO f— o 00 o CM m o O <7t in o o C7t o 00 00 «3- ** o 00 00 o vo 00 00 CM O CM O VO CM at o vo CM o\ O t— f— -* o o CO in CM CM CO o o 00 CM o CM O CO O CO CM CO o CM o vo CM CM CM Oi r^ 00 CO o vo CM CO ■— o o o CM CM CM F~ CM CM CM o rs. CM O CM CM oo 3 C/) 01 C3 « T3 ■o 4J 3 3 t- CO tn O ns to •M 4J +-> +-> c: c c c CO rtj «o rt3 (O . >, >, >> >> >> >. >. >> >> u u o o o u o u o u la ra E LD LO UD U3 CO CTi en 1 — CM CM o O O o o o Ln LO O o +-> fO CD CT> Q rs ::3 •=C cC CM CO s- S- (U O) J3 J=i E E (U O) > > o o TJ 00 OJ -M TO -a i- o o <_) =te CO en ro CO r~- r~~ CM CO CO CO ^ on en CM CM CM CM CO O CO CM o o o CM IT) CO CO CO ^ r^ CO r^ LO 00 CO oo CO CO 00 CO CO 00 00 2: 2: :z ^: 2: s: ^ 2: 2: 2r •^ «=j' «=t- en cr. r-. (^ CM CO r-- CM ii'> »* 1 — , — on CO •Cf- CO o o o <::.»- IjO CO 1^ 1 — . LO en CO r-- CO C\J CM CM CM CM CM CM CVJ CM CM cr> CM CO CO (J^ n .— CO CM CM cu 4-> CJ Ol c fO +-> 00 -o -a > >. n o JQ O 21.6 On March 8 and 9 the Delta Sud (fig^l .l)crossed two anticyclonic eddies, one at 26°19'N, 91°0TW and the other at 23°52'N, 87°49'W. The hori- zontal extents at the points of crossing were 170 nm and 120 nm respect- ively and both extended in depth to greater than 500 meters. On March 21 and 23 the Delta Norte (fig.21 .1 )possibly crossed the same two anticyclonic eddies. One was located at 27°02'N, 9r45'W and the other at 23''42'N, 88°07'W. The horizontal extent of these two eddies were 200 nm and 175 nm with depth ranges of 600 meters and 700 meters, respectively. Between April 15 and 17 the Delta Sud (fig.21. 2) again crossed 2 eddies. One was located at 26°25'N, 9P03'W and the other at 24°23'N, 88°19'W. The horizontal extent of these 2 eddies were 95 nm and 290 nm respec- tively. They both extended to greater than 600 meters depth. On May 21 the Delta Sud (fig.21 .3 )crossed an anticyclonic eddy centered at approximately 26°24'N, 87^52 'W. The eddy had a horizontal extent of 245 nm and was greater than 600 meters in depth. As previously mentioned, this was the first of three crossings of this particular eddy. Between May 27 and 29 the Delta Sud (fig.21. 3)again crossed 2 anticyclonic eddies. One was centered at 26°44^N and 91°28'W the other was centered at 25°05'N, 89°38'W. The horizontal extent of these 2 eddies were 120 nm and 300 nm respectively. They both extended to greater than 600 meters depth. On June 28 and 29 the Delta Sud (fig.21 .4):rossed an anticyclonic eddy centered at 26°32'N and 87°48T7. The eddy had a horizontal extent of 175 nm and was greater than 500 meters in depth. On July 6 and 8 the Delta Sud (fig.21 .5):rossed an anticyclonic eddy centered at 24°55'N and 88^^' W. The eddy had a horizontal extent of 335 nm and was greater than 600 meters in depth. This was the second crossing of the eddy first mentioned in Figure 21.3. On July 20 and 21 the Delta Norte (fig. 21.3 ):rossed 2 anticyclonic eddies. One was centered at 26°30'N and 9r09'W, the other was centered at 25°26'N and 89°44'W. They ranged in extent and depth from 140 nm to 195 nm and 600 meters to 700 meters in depth, respectively. The eddy centered at 25°26'N and 89°44'W was the eddy crossed previously in May (fig.21. 3)and early July (fig. 21.5). On August 17 and 18 the Mayaquez (fig.21 .6)crossed an anticyclonic eddy centered at 27°35'N and 86°50'W. The eddy had a horizontal extent of 165 nm and was greater than 600 meters in depth. 21.7 On August 25 and 26 the Mayaquez (fig.21.6)crossed an anticyclonic eddy centered at 25°48'N and 84°42'W. The eddy had a horizontal extent of 240 nm and was greater than 700 meters 1n depth. Low Salinity Surface Water River runoff along the Gulf coast in the form of low surface salinities (<34.5%) sometimes extended great distances offshore (well beyond the shelf break). In 1974 9 transects of low salinity water were detected. Crossings in March, April, May, June, July and August (figs. 21 .1-6). showed large variations in the horizontal extent of the low salinity water (table 21.3). In March (fig.21 .1 )the Delta Sud crossed through coastal low salinity water. These stations were located on the continental shelf in water less than 50 m in depth. The offshore extent of the low salinity water was 50 nm. In April (fig21.2)the Delta Sud crossed through coastal water as low as 24.5 °/oo- These stations were, again, on the continental shelf in water less than 50 meters in depth. The offshore extent of the low salinity water was 70 nm. In May (fig.21 .3 )the Delta Sud crossed through coastal water as low as 29.0 °/oo- These stations were located at the shelf break (100 meters depth). The offshore extent of the low salinity water was 70 nm and stopped at the interface (front) of an anticyclonic eddy. In June (fig.21 .4)the Delta Sud crossed through low salinity water less than 32 °/oo- The stations were located in water greater than 500 meters. The offshore extent of the low salinity water was 90 nm and, again, was stopped at the interface of an anticyclonic eddy that was transporting higher salinity oceanic water northward. In July (fig.21 .3)the Delta Sud crossed through coastal water as low as 28,3 °/oo- Stations 1 and 2 were on the continental shelf but station 3 was in deep water. The offshore extent of the low salinity water was 195 nm and stopped, again, at the interface of an anticyclonic eddy. This was the same eddy as described in Figure 21 .3.The westward movement of the eddy had apparently allowed the lower salinity water to extend further out to sea. Again, in July (fig.21 .5)the Delta Norte crossed through coastal low salinity water less than 29 °/oo. These stations extended from the continental shelf to waters greater than 650 meters in depth. The offshore extent of the low salinity water was 230 nm and, again, stopped at the interface of an anticyclonic eddy. 21.8 LOW SALINITY WATER < 34.5 °/oo SOOP 1974 Figure Ship Date Station # Offshore Extent 1 DELTA SUD March 8-9 2-4 50 nm 2 DELTA SUD April 15-17 1-4 70 nm 3 DELTA SUD May 21 49-51 70 nm 3 DELTA SUD May 27-29 1-2 90 nm 4 DELTA SUD June 28-29 16-18 90 nm 5 DELTA SUD July 6-8 1-3 195 nm 5 DELTA NORTE July 20-21 1-11 230 nm 6 MAYAQUEZ August 17-18 1-3 85 nm 6 MAYAQUEZ August 25-26 25-27 210 nm TABLE 21.3 21.9 The offshore extent of the low surface salinity water discussed in Figures 21.3 and 5 apparently was controlled b^/ the migration of 1 par- ticular anticyclonic eddy. The southwestward migration of this eddy (as previously discussed in the eddy section) provided the mechanism for increasing the distance offshore of the lower salinity surface water. In August (fig.21.6)the Mayaquez crossed through coastal water as low as 25 °/oo- These stations were located in deep water and the low salinity water had an offshore extent of 85 nm. Again, in August (fig.21 .6)the Mayaquez crossed through low salinity water less than 33 °/oo- The stations were located in deep water far removed from the shelf break and the low salinity water had an offshore extent of 210 nm. The extent of the low salinity surface waters in the eastern Gulf of Mexico seemed to be controlled by the northward migrations of either eddies or the Loop Current itself. In some instances the low salinity surface waters were entrained into the eddy structure themselves (fig.21. 3, 4, 5 and 6). In most cases where the low surface salinity water was entrained within the eddies the low salinity water appeared on only the northern side of the eddy. Peaks (ups and downs) in the surface plots (not shown) indicate the instances where low salinity water was transected, exited and then transected again. This indicated that the less saline surface waters were being entrained by the leading edges of the northward moving eddies. The more saline oceanic waters were entraining the fresher coastal waters which developed into bands or rings of consecutively less saline- more saline-less saline water. The movements of the various eddies around the Gulf of Mexico would provide one mechansim for the extension tonguing and eventual mixing of the less saline coastal waters with the more saline oceanic waters. 21.10 Western Atlantic Transects Specific features that were monitored in western North Atlantic by the program were the position of the Gulf Stream, variations in temperature and position of the bottom water cold cell on the continen- tal shelf, position of the Shelf Water-Slope Water front, and eddies formed from the Gulf Stream. Where data were available and observations were close enough in time to permit comparison, correlations have been made with the National Environmental Satellite Service (NESS), Experi- mental Gulf Stream Analysis (N-69) charts and The Gulf Stream Monthly Summary which show the positions of the Gulf Stream and associated features. Characteristics of the bottom water cold cell In his discussion of temperature patterns in continental shelf water, Bigelow (1933) described a core of cold bottom water that extended from south of Long Island to the mouth of the Chesapeake and was evident throughout the summer months. According to Bigelow, this core was sur- rounded entirely by warmer water and could receive no replenishment during the summer; thus, he concluded it was formed in wintertime and then per- sisted throughout the year. Further descriptions of this cold cell have been given by Ketchum and Corwin (1966) and Whitcomb (1967). The data which are presented here show the formation, structure, and modification of this cell during 1974. Nine observations of the cold cell were made by SOOP vessels in 1974. The cell characteristics at the time of observation are summarized in Table21 .4. For purposes of discussion, the observations have been grouped into three separate geographic areas, chosen because they represent regularly-scheduled merchant ship cruise tracks. These tracks have been designated as the MORMAC transect (fig.21j), SANTA CRUZ transect (fig. 21 .8) and HOTEL transect (fig. 21 . 9). The MORMAC transect is the cruise track used by Moore-McCormack Line ships and closely follows a line between New York and Bermuda. The SANTA CRUZ transect extends from New York to Cape Hatteras, approximately along 74°W. The HOTEL transect is the cruise track used by Coast Guard cutters operating between Norfolk and OWS HOTEL (38°N, 71 °W). In the following discussion, the seasonal char- acteristics and variations in the cold cell temperature and position along each transect have been summarized. The temperature structure of water on the continental shelf during February (fig.21 .lO^hould be considered, because the cold cell was formed from these waters and the minimum temperature that could be attained in the cell was dependent upon conditions during the winter months. At this time, cold water (7-1 2°C) extended from surface to bottom on the shelf and structure of the cell had not yet been established by stratification. 21.11 +-> c c — - o N -M •r- E S- (U O +J 3: X J 1 E E "e" E E E E CVJ o CM to 00 00 00 CM LO CO o CO ^ zz^ 3 , C- , ^ , CM ,^ , 00 U3 LO o o CO LO o LO CT» CM O lO 1^ Q) J- ^•-%, 3 O +-> V o V o V o V o CM o CM O o CM a. o o t/> >» x> •o (U o O) +J to iA s- E to 0) •r— 0) -M X E E O -^ LO CM O o CM CM CM 1 — ^- CM CO CM JE O) •♦-> o ■»-> Q.-t-> E LO 4-> O sz o o 4-> X -•-> Qj (O o lO o LO CO cn CD CO <* LO r>. LO VO a\ r^ ^-^ E E 3 E E O-EI •1— 4J +J E -M a •f— O (1) S: OQ Q| 00 o CM O LO O o <^ LO CM CM CO «* 'd- ^ J 1 VO LO •~ CO CM +-> CO en >, >> E CT> Ol Ol o ■t-> 4-> « * 3 3 (U CO o o N N "oJ N >> "O r— 3 o 3 CD =3 (U E a> s- CD $- •»- S_ E (O ■•-> o tn ^ to O oo to o ^ E o s: rD o. X O OO CO o o 2: •— < 21.12 Along the MORMAC transect, the first evidence that the cell had formed was obtained on May 6 (fig. 21. 11). The characteristic shape of the cell had formed as shown by the outline of the 11°C isotherm in shelf waters. Within this "bubble-like" structure, temperatures ranged from less than 9° to 11°C. and the cell extended from a minimum bottom depth of 20 m to a maximum of 38 m. The horizontal extent was 65 nm (120 km) and the cell was approximately 20 m thick at the center. When next observed on August 14 (fig. 21 .12) temperatures in the cell ranged from less than 9° to 13°C and the bottom depth range of 40-55 m indicated that the cell was migrating into deeper water. The last observation was made on October 3 (fig. 21 .13). By this time, temperatures had warmed to 14°C in the outer edges of the cell and it had moved over the shelf break and bottom.. The depth range extended from 34-99 m. These changes in temperature and depth are summarized in Figure 21.7. Along the Santa Cruz transect the earliest observation of the cold cell was made on May 6 (fig. 21 .14). Temperatures in the cell ranged from less than 8° to 9''C. The horizontal extent was 68 nm (126 km) and the cell ranged from 28-41 m in bottom depth with a thickness of about 18 m at the center. By June 11-12 (fig.21.15) the outer fringes of the cell had warmed to 13°C and water with temperatures from 10° - 13°C had be- gun to move seaward over the shelf break. The bottom depth range at this time was 32-49 m. Within the cell, two separate parcels of water (less than 9°C) were present between Stations 26-30. On September 3-4 (fig.21.1 6)temperatures in the cell were in the 9*'-14°C range and part of the cell had moved over the shelf break and extended to a depth of 70 m. The tongue-like shape of the 13° and 14°C isotherms showed the initial stages of a process called"calving" by Cresswell (1967) whereby a parcel of water separates from the parent mass and moves seaward. During October 9-10 (fig.21 .17)the "calving" process was detected in an advanced stage. A mass of water with temperatures ranging from 12-14°C had separated from the cell on the shelf and was moving seaward over the shelf break. At this time, the cell extended to a maximum bottom depth of 70 m. These changes in temperature and depth are summa- rized in Figure 21 .8. Only two observations of the cold cell were made along the HOTEL transect, and these were closely spaced in time - September 29-30 (fig. 21.l8and October 1 (fig. 21.19). Figure 21.18 showed temperatures ranging from less than 12 ° to 15°C in the cell over a bottom depth range of 40-55 m. The horizontal extent was only 15 nm (28 km). Slightly further south, the temperatures ranged from less than 12° to 16° over a bottom depth range of 40-63 m. Here the horizontal extent was 29 nm (54 km). The changes in temperature and depth are summarized in Figure 21.9. 21.13 Gulf Stream Considerable attention has been focused on fluctuations in the position of the Gulf Stream. In addition to shipboard observations of temperature and salinity, satellite and aircraft observations of surface temperature are being used to differentiate between water masses. Because the SOOP transects intersect with the Gulf Stream at discrete points with considerable spatial and temporal variations between transects, complete coverage of the Gulf Stream and associated features is impossible. However, when correlated with the satellite observations the transect data provide a source of ground truth for the remote sensors, as well as providing additional information for in- vestigators involved in study of the Gulf Stream system and other water masses. During 1974, SOOP transects crossed the Gulf Stream 12 times. These crossings are summarized in Figures 21.20, 21.21, 21.22, and 21.23 and Table 21.5. Gulf Stream crossings were identified by the strong horizontal gradients shown on vertical temperature sections and positions of the North Wall were determined by using the 15°C isotherm at 200 m (Worthington, 1964). Both The Gulf Stream Monthly Summary and the NESS Experimental Gulf Stream Analysis (N-69) charts provide information about fluctu- ations in the Gulf Stream position. The information provided in these publications gives more complete and synoptic coverage over the entire Gulf Stream system than is possible through SOOP transects. However, since the N-69 charts are derived solely from remote sensing of sea surface temperatures and The Gulf Stream Monthly Summary is at least partially dependent upon these data, the patterns shown by these publi- cations may not be as accurate as those portrayed from subsurface tem- perature data. The information collected by the SOOP affords an ex- cellent source with which these data can be verified. Table 21.6 shows the Gulf Stream positions as determined from each source. In each case, the distance has been measured with dividers along identical bearing lines and this distance converted to nautical miles. Several sources of error were apparent. The inconsistent quality of reproduced N-69 charts and the distortion introduced by photocopying lead to some uncertainty in measurements, though this varied between sources. In addition, some interpolation was necessary to locate positions between stations on vertical sections. Interpolation was also necessary to determine positions during mid-month from The Gulf Stream Monthly Summary because positions were given only at the begin- ning and end of the month. An estimate of these errors accompanies each measurement. 21.14 TABLE 21.5 - Gulf Stream Crossings by NMFS/MARAD Ships of Opportunity in 1974. Figure 31 32 33 34 35 37 39 40 41 42 44 45 Ship Name Date Mormac Argo May 5-6 Santa Cruz May 17-18 Santa Cruz June 11-12 Santa Cruz July 28 Mormac Rigel Aug 14 Santa Cruz Sep 3-4 Export Defender Oct 1 Mormac Rigel Oct 3 Santa Cruz Oct 9-10 Santa Cruz Oct 19 Export Defender Nov 27-28 Santa Cruz Dec 7-8 Position 38°30'N, 7ri2'W 3r48'N, 79°06'W 38°12'N, 73°57'W 34°48'N, 75°24'W 37°42'N, 70°48'W 35°30'N, 75°00'W 36°42*N, 72°18'W 37°30'N, 71°00'W 36°12'N, 74*'12'W 35''00'N, 75*'00'W 36°00'N, 74°00'W 36°00'N, 75°18'W 21.15 CO 4-> C o ra a; s- 4-> C/0 C5 TO s- u U3 CO CO UJ a. o o CO -o O) +J «a o o c: o ^ o o^ OJ CVJ 00 CO o en *:1- ^ O CT> ^— ^— r— CVJ I— ro 1— r~ CVl "d- 1^ ^— +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 LO tn ^ VD C5 m ^ r-- LO 00 LO CO ro ro CX3 LT) O CO «d- vo 1— CT» r— r^ CVJ «* f — r— CVl CVJ CO f— CVJ o o o o • CVJ r>>. ^ o o r>M ^M r^ r— O • 1 1 ro 1 CO to (/) w f—^ w 1 — O >^ «/) 3; (U-C >,zn >> t/1 1^ c o r— <_3 3 4-> O «o «o a» ■^ Z3 ZJ Oi >, Q. s- >, s: r— «^ •-0 (/) t/) -M •f— S- Q «o -C CJ CT> VO OJ LO LO CO VO +1 +1 LO r^ LO 00 f— CVJ •r- o _J O «* CO CTI r^ 1 — s- C cy» 1 «: > s- o o «o •> o o (U 1^ 31 CQ 1 T3 ^s» •=1- >> 3 i e: ii c j«: LO 00 CD cn o cr> c— CVJ 1 ^— ^^ r*" r^ +1 +1 1 +1 +1 +1 +1 o r->. LO r^ CD CVJ CT> LO CVJ ,— CVJ CVJ 1 — CVJ «:d- 1— CVJ "■ — ■ ^ — ' ' ' «* «* o r>^ r^ «* cy> cy> o «d- CVJ 1 — o ■ — I— r^ r— 1^ LO LO O ^ 1— 1— ro o r— O s- 1 ,^ <_> IC i. ro LO C_) -•-> , JH <_) C2. rj <_) C_> ) o TiTi r^ r— 00 vo c_) CO c: o -M o f— CVJ (U ro c_> o £ c ^ lO LD CVJ «=i- +1 +1 O CT> ^ LO r— CVJ «/» o o 00 CVJ r-^ ro •— >» ro CT* CVJ I CO r— CO c CT» 00 «d- CVJ CO >> 13 "-3 lO 00 lO 00 r^ CVJ ,— CVJ +1 +1 +1 +1 CVJ 1 — CVJ LO CVJ t-^ CO ^* CVJ ^ 1— CVJ LO O) .^ "si o ro o -C ^ o o o >>l^ 0)1— T3 CO C3.VO c ^~ ro •— ro C_) OO CT> ^ ^— r~>. A •^ E CO VI CO Q) 3 4-> o> O. 3 i c ^ c^ E ^ c ^ o O CM CM o cr> O CT> ■!-> f" ^" r^ ^^ r** r~* r— CM f"^ ^^ ^^ r*~ CO +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 •r- O 00 o en O CM ID CM o ir> t— ^ Q LO r^ r- 00 CM CM CM CO O 00 CM CM t— CM C\J CO 1— CM f— CM f— r— 1— CM E ^■.■^ ^ta_«^ ^.^^ --I - ^^.^ xm-^ fO a 00 f— O vo CO c o o CM \o "sj- 'r— in h^ ^— fm— r— 1 *t- _J (O ja -c >» +J 4-> > o Q. E E E E E E E E E E E E Qi O c Js<: c ^ E ^ E J-i E .i». O CTi in 00 in 00 CM CM +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 C/) CO in vo o vo in vo O CM f— cr> in o 4-> *•— vn o CO CM CT» r«. CM CM CTi vo CO in $- Q I— CO CM ^J- r— 1— CM rr>* I— CM O 1 E o 1^ «;3- 00 ^— r-* O r- CO ^ •1— "* in CT» O r^ CM vo «^ VO _l 1 r-- ■— rv. CT> ,— •» ^— •>1- I— •* ^— CT» 1 CO 1 — 1 CM 1 CM 1 cr> 1 O) r^ I— (/) •* ^— CO CM CO 1 CO r— CO c CM (U vo 1 n (U 1 (U f— ^ (U JD -o >> XJ J3 E ca. +-> E -!-> Q. ■l-> CL > Q. o ca. CO ^ E .i<: E ^ E ^ E Ji«: E ^ vo , VO , o r>. CD VO , o CO CO ^— ^— CM CO f-^ f-~— r— in cn 4-> +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 to Sj- CM in r^ O CM O CM CM a\ o in •t— r^ CM CM f^ CM CM CM CM O CO O 00 o 1 — CO CM sl- I — CM I — CM r— I — 1 — to a; to >r- £2.00 a. I — x: Q. •I— (ucn T3 CO CO CM (O vo o CO *>■— ^ S- Q. E r— O ^— tj ^— "d- CJ -o CO CO CM r^ CM -o S- s- S- $- S- Qi s- 0) LU Qi * E CQ 3 O O o O ■*-> ■♦-> 4-> > o 1- U u o O o Qi iZ O o o O z: Q 21.17 Within the estimated range measurement errors, the sources agreed closely on the position of the Gulf Stream North Wall. Only in May was there a significant discrepancy in the measurements. The distance of the North Wall measured from The Gulf Stream Monthly Summary was about 40 nm greater than the distance determined from SOOP data on the N-69 charts. This probably was due to the fact that The Gulf Stream Monthly Summary only provided information at the beginning and end of the month and thus the Gulf Stream position determined from this source during mid-May was highly conjectural. Eddies From analysis of the vertical sections contained in this report, four Gulf Stream eddies were detected during 1974 (see Table 21.7 and fig. 21.24) Eddy #1 (fig. 21.25) was crossed by Santa Cruz on May 5-6 and was centered at Station 7 (32°00'N, 75°00'W). The sloping of the isotherms indicated an asymetrical cold core eddy, possibly in the act of becoming entrained in the Gulf Stream. The Gulf Stream Monthly Summary (April) showed an eddy centered at 33°00'N, 74°00'W on 30 March 1974. Since the eddy was not shown in the May issue, it may have become entrained during the interval. This eddy was not shown on the N-69 charts. On May 5-6 (fig. 21.11 ) Mormac Argo crossed a cyclonic, cold core eddy (Eddy #2) that was centered around Station 8 (36°00'N, 68°00'W). The structure of the eddy was evident to a depth of about 600 m and the width at the surface was approximately 145 nm (269 km). The May issue of The Gulf Stream Monthly Summary showed a cyclonic eddy with a width of about 80 nm (148 km) centered at a position of 36''30'N, 68°00'W, which corresponded closely to the position of Eddy #2. No correlation could be made with the NESS N-69 charts of 4-7 May 1974 because there was heavy cloud cover in the study area. However, the 14 May 1974 N-69 charts showed a cold water intrusion in this area. Comparison of the XBT traces with the sample traces shown in The Gulf Stream Monthly Summary revealed reasonable similarity; it was concluded that Eddy #2 was the same eddy depicted in the May summary. Figure 21.11 also showed another unusual feature. An unusually strong thermal gradient (surface temperatures changed from 23''-20°C over a distance of 15 nm or 28 km) was present between Stations 3 and 4. Similar fronts in the Sargasso Sea have been described by Katz (1969), Voorhis (1969), and Voorhis and Hersey (1964). Eddy #3 (fig. 21.2 6) was located by USCGC Ingham on 20 October 1974. This anticyclonic warm core eddy was located around 37°N, 74°W. An intrusion of warm water shown on the 23-28 October and 31 Octo.ber-3 November N-69 charts, could be a result of this warm eddy moving into this region. However, no eddy was shown at this location in the October or November issues of The Gulf Stream Monthly Summary . 21.18 TABLE 21.7 - Gulf Stream Eddies Surveyed by SOOP Vessels in 1974 Maximum Direction Eddy Figure/ Location of Approximate Observed of Number Date Center Surface Diameter Depth Rotation 1 29 32°N, 75°W 165 nm (306 km) 650 m Cyclonic May 5 2 31 36°N, 68°W 145 nm (269 km) 500 m Cyclonic May 5-6 3 43 37°N. 74°W 90 nm (167 km) 450 m Anticyclonic Oct 20 4 45 32°N, 73°30'W 150 nm (278 km) 660 m Cyclonic Dec 7-8 21.19 Eddy #4 (fig. 21.27), a cold core, cyclonic eddy, was crossed by Santa Cruz on 7-8 December 1974. The maximum depth observed by XBT was 660 m, while the eddy center was located around 32°00'N, 73°30'W (station 14). This eddy was apparently the same one that was monitored with neutrally buoyant floats by the U.S. Naval Oceanographic Office and surveyed on 11 December 1974 by P.L Richardson aboard R/V Trident (Gemill, 1974; Anonymous, 1975; Gemill and Cheney, 1975). Surface heating had destroyed any surface signature of the eddy and only subsurface data proved its existence. Shelf Water-Slope Water Front SOOP transects crossed the Shelf Water-Slope Water front five times during 1974. Determinations of frontal crossings were made primarily on the basis of subsurface temperature gradients shown on the vertical sections with additional supporting evidence being drawn from surface temperature and salinity gradients. A summary of these crossings is given in Table 21.8 and in Figures 21.20, 21.21, 21.22, and 21.23. In order to provide a means of verification of the position of the front as determined from SOOP sections, comparisons have been made with NESS N-69 charts. After the position of the front was determined on the SOOP sections, a bearing line was established to a nearby landmark. The distance in nautical miles was measured with a pair of dividers and an estimate of error was made. The position of the front was then measured along the same bearing line on the N-69 charts. These compari- sons are shown in Table 21.9. Within the estimated range of measurement error, the positions determined from the two sources agreed closely, suggesting that the methods currently used are reliable indicators of the frontal position. 21.20 TABLE 21.8- Shelf Water-Slope Water Front Crossings by NMFS/MARAD Ships of Opportunity in 1974 Figure Ship Name Date Frontal Position 33 Santa Cruz June 11-12 38°N, 7r48'W 35 Mormac Rigel August 14 39°42'N, 73°W 37 Santa Cruz September 3-4 38°N, 74°W 38 USCGC Taney September 29-30 37°N, 75°W 41 Santa Cruz October 9-10 38°18'N, 73°54'W 21.21 CO I Qi >»•■- JQ <0 •O t— (u E •o lO CO O 3 Qi ■*-> <0 rO Qi 3 -E 4-> 4- 1— T3 > •I- +■> to f- O E Q. 3 o o o. C Q. o o Q. Q. S- E 'r- « o J= x: o CO o en E E E E c ^ c ^ 0) 00 CO O t/) VD 0> o r^ •I— to 00 O^ U) Q f— CVJ f^ E E E E CVJ CM r— OJ O CT» +1 +1 +1 +1 KO CVJ «£> CVJ CVJ a\ O 00 CT> CO in 0) «/) c 0) •«— ^M —1 j- «o CT -C c o $- Qi «o a. (U to QO o 00 CO r^ Qi 4-> > Qi -O f— 3 .a ■M -r- CO «/l CO E O 1- Q. o o T3 3 O C_> o KO 00 (/) Qi H to .E CJ 01 Q. «o C_J I 1^ CVI i. t— o 00 o o CO in I CO Qi to JE <_) (U ca. to o (U O +-> CJ O Qi O E lO +-> CO iJ E E E .:>!: E E E .^ E e E ^ iJ tn 00 f— CVJ to 00 1— CVJ CVI CVI t— CVJ o cr> o r>^ CVJ CO +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 CVJ in CO ^ r— CVJ CVJ CO 1*^ CO 00 o o o 1— CsJ KO CVI CO CVJ CVI in CO -^a- 1— CVJ a. o o tn to o a- o CO m (/) Qi to Qi a. to o 5- o o -a E to C/) CVI I E 3 CO CO C/) 3 CD in CO o CO in {A 01 'Z. as .E <_) 01 Q. to C_J I CO s- 01 J3 E (U ■M CL A 21.25 o o ro o to CM o o CVJ ^1.26 o 00 o O o to 0> 21.27 o GO o O o ID 0> 21.28 o 00 o O o a> 21.29 o UJ CO < O < o z o -J < I- Q. UJ O (5!- o o o o I o UJ q: UJ Q. Ul Ul o o o o CO o q: Ih OH _i_ o CJ fi •H CO C o CO •H U CO > CM U W) •H o 0) o 00 o o o o o O CVJ >- < O 2 (Sy313W) HldBQ 21.30 O liJ (O z < N O < CO z o -J < I- Q. lil O O z < UJ tr. q: UJ Q. UJ I- UJ o o CO g °S I,. ^^^ o «/> 2| K -I- § I CJt- 00 CM (U 00 •H 21.31 e O o UJ CO z < qe: LU h- o o z o -I < X I- Q. UJ o I 1 , 1 1 1 c Ui to: bJ UJ (0 ID X '*■ \V *.^ <;.° A V- '\\ ••• ej — V v/iU **' •• i^MI^v " ••• U. <9 '^^^v §i^ ^>>\,^ •••. ■; ■ : ■ •'■ ' "^^^ ■^r *"•••• ' **' ■' .*l^^^ li "WA^ ^^P>^ 1 ■•;-'%>/>^ ftf UJ q: I- < tr. UJ Q. UJ -J UJ o o o CO z o a: o I- li. »- s X o o o o o o ? o o 0> 00 N (0 lO rO o o w c CD ■u h4 M H O 60 O P. (U 73 > o z T3 C3 CO (1) M 3 4J CO t- U o ~3 a> • iH CN Z 0) 3 "^ v^ 3 &0 FE4 (Sd313W) HldSQ 21.32 PfiRflMETER RT SURFBCE CO 16 u Ui o m ^ 13 _^ cc ec U' 12 _ ?: 11 20. 40. 60. 80. DISTANCE (N. MILES) _3>4. .35. o o o a. in O .33. 100. - 50 f ^^^ .:=5r / ^ K/^ 7 / i CPUISE TRACK PLOT 100 _200 300 _U00 _500 _600 _700 800 0. MO. 80. MORMfiC RICEL 7410 STATIONS l-ll 10/3/74 - 10/3/711 F1qure21.13. Horizontal distribution of sea surface temoerature ( C.) and sea surface salinity (Voo) and vertical distribution Of temperature (°C.) in the upper 200 and 800 M. 21.36 PRRftMETER fiT SURFACE 3«. en iii iij u 111 a c ui A. x: UJ »- 10 ■40. 60. OlSTRNCE (N. MILES) o o -33. :: cr in O -, 50 _ V* - 100 a. A 150 J 200 (-.:'. '■ ■ 1^ 20. "T" lO. 60. 80. 50 _100 _ 150 .200 100. 120. CRUISE TRRCK PLOT in UJ 200 tu X 300 _ a. UJ ° 1*00 _ 500 _ 600 700 _ 800 _100 ^200 300 _400 -500 -600 700 800 0. 20. UO. 60. 80. 100. 120. SRNTfl CRUZ 7U01 STATIONS 13-18 05/06/7U - 05/06/711 Figure 21.14. Horizontal distribution of sea surface temperature {°C.) and sea surface salinity (*'/oo) and vertical distribution of temperature (°C.) 1n the uoper 200 and 800 M. 21.37 PRRAHCTCR «T SURFACE 120. 160. 200. 2M0. OISTfiNCE fN, MILES) o o - -3<4. - L33. S O .32. 2140. in ^ CO rv» — o UJ s so 100 _so 100 CRUISE TRACK PLOT oo r~(D ina-tofvi— o «2 100 _ to a 200 300 _ •100 _ SOO 30. 60. 90. 120. ISO. TflNEY 7U09 STATIONS 1-18 9/29/7U 1.00 _200 _300 -MOO 500 180. 210. 9/30/711 Figure 21.18. Horizontal distribution of sea surface temperature (°C.) and sea surface salinity (Voo) and vertical distribution of temperature (^'C.) In the upper 200 and 800 M. 21. 41 PARnnETER fiT SURFACE DISTANCE (N. MILES) - 50 _ = 100 _ ISO _ r 200 -50. _ 100 . -ISO .200 f le / CRUISE TRACK PLOT o — cu 9 m (D r^ 00 1 1 T 0. so. 100. ISO. 200. 2S0. 300. 3S0. >(00 EXPORT DEFENDER 7Ulb STATIONS 1-18 10/l/7^ - l0/l/7^ 800 F1nurp21 1 9 Horizontal distribution of sea surface temperature (°C.) Figure2l.i . Honzo^ ^^^^^^^ ^^^_^^ ^,^^^^ ^^^ vertical distnbutio of temperature {K.) in the upper 200 and 800 M. 21. 42 on 80* 75 45* - 40* 35* 30* 25* 80*» Figure 21.20. - 45* TRANSeCT SULF STREAM SHELF WATER - SLOPE WATER FRONT 1 75« TO** 65* Location of Gulf Stream as observed by SOOP Vessels - May 1974, 21.43 80* 75 45* - 40" 35* 30* 25* 80** Figure 21.21 MORMAC RIGEL 14 AUG '74 lOOfm SANTA CRUZ 28JUL'74 TRANSECT GULF STREAM SHELF WATER - SLOPE WATER FRONT 45* 40* 35* 30* - 25* 75** 70*» 65*' Location of Gulf Stream and Shelf Water - Slope Water as observed by SOOP vessels. June-August 1974. 21.44 80* 75* 45* 40* 35* 30* 25* 80** Figure 21.22. 70* lOOfm EXPORT DEFENDER * I OCT '74 EXPORT DEFENDER 27-28 NOV'74 V SANTA CRUZ ' I90CT'74 TRANSECT GULF STREAM SHEL F WATER - SLOPE WATER FRONT 75* 70* 65* - 40* 45* 35* 30* 25* Location of Gulf Stream and Shelf Water - Slope front as observed by SOOP vessels. September- November 1974. 21.45 80« 75' 70« 65* 45* - 40* - 35* - 30* - 25" I 1 1 - . , ■# ^'".'.■-U^^:^ ) * Ws-^l^i^ii^^ j^^' i^J^^*^^^^^ ^ - />y^^ ^^? -x ___ / .'.'^ /j'" '.'f ',j#^ %i/^ / •'^ -" ^ . :vy //>n ■ ' -.'^ ^' " ■" "x "^ ■■?S V > ^ ■ ""^^^ » ' ""^V ^ \ ;.-,;,- .■»!*\-^>?/ ' ;■ :_^^^j^^M^^^^ ■■■■f^^^^^ '~' . ' 1^^''^ ./)-'' i: \^\ ..,.:# X^SANTA CRUZ ^ar ^r''^ >^*^7-8DEC'74 ' ■•■«>' / \ / / / / \ - 1 1 — k I \^ l/ ^v^ '..y '' ^-y^' ^ SHELF WATER 'SLOPE WATER FRONT ^ 3^ 1 1 1 1 - 45* 80* Figure 21.23. - 40' 35* - 30* - 25* 75* 70* 65* Location of Gulf Stream as observed by SOOP vessels -December 1974, 21.46 80*" 75« 70* 65* /. SANTA CRUZ — 5-6 MAY 1974 2. MORMAC ARGO - 5-6 MAY 1974 3. U.S.C.&C INGHAM- 20 OCT 19719 4 SANTA CRUZ— 7-e DEC 1974 80* 75** 70* 65* Figure 21.24. Composite plot of eddies located by SOOP vessels - 1974. 21.47 PftRfiMETER fiT SURFRCE 19 20 _ 5 19 90. 120. 150. IBO. DISTANCE (N. HILES) o o V. o O 36. 240. B 100 ■0 _50 100 -ISO .200 120. 150. 160. 210. 2H0. CRUISE TRACK PLOT 800 _100 _200 _300 -1400 _500 -600 _700 1 1 1 1 1 1 1 0. 30. 60. 90. 120. ISO. 160. 210. 2^0. SRNTfl CRUZ 7II0I1 STATIONS 5-12 0S/0S/7U - OS/OS/714 600 Figure 21.25. Horizontal distribution of sea surface temperature ( C.) and sea surface salinity (Voo) and vertical distribution of temperature (°C.) in the upper 200 and 800 M. 21.48 PRBRMETER AT SURFRCE 90, 120. 150. DISTRNCE (N. MILESl ui 3- (n cvj — 70 _50 100 210. CRUISE TRACK PLOT to (\1 " 100 _ f 200 _ 300 400 _ SOO 100 _200 30. 60. 90. 120. ISO. 180. INCHRM 7m0 STATIONS 1-13 10/20/714 - 10/20/74 _300 _ilOO 500 10. Figure 21.2 6. Horizontal distribution of sea surface temperature rt ; and sea surface salinity (V^J and vertical distribution of temperature (*'C.) in t^^ uDper 200 and COO M. PflRRMETER RT SURFfiCE o o O 150. 200. 250. 300. DISTRNCE tN. MILES) MOO. >150. O -< (M CO 3> Ul U3 _ 100 M 70 _150 200 CRUISE TRACK PLOT Q too Jo uj 200 bJ X 300 ►- o. ° UOO 500 600 700 800 IP JO r- 00 CD o — rvi CO 3* If) to _100 ^200 -300 -MOO 500 l_600 700 ' 1 1 1 1 1 1 i \ 0. 50. 100. 150. 200. 250. 300, 350. 400. U50 SRNTR CRUZ 71112 STATIONS 1-16 12/7/74 - 12/8/7U 800 Figure 21.27. Horizontal distribution of sea surface temperature (^C.) and sea surface salinity (°/oo) af^d vertical distribution of temperature (°C.) in the ucper 200 and 800 M. 21.50 '^USGPO: 1976 - 653-348/56 Region 5-1 PENN STATE UNIVERSITY LIBRARIES A0DDD7EDMM7Efl