SIPRE Report 28 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA by Valter Schytt The research work reported here was performedunder the supervision of Dr. Schytt, then of the Department of Geography, Northwestern University, under contract DA-11-190-ENG-12 with North weswrn University. SNOW ICE AND PERMAFROST RESEARCH ESTABLISHMENT Corps of Engineers, U. S. Army Wilmette, Illinois GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA by Valter Schytt ABSTRACT Durin g the 1954 field season, from 19 ] une to 29 August, accumul a tion and abl a tion measurements were made on the Ramp and farther inland to Mile 20 (from Thule Take-off). Meteorological measurements were obtained fo r correlation with the glaciological work. Accumulation on the Ramp averaged 55 em of snow and varied considerabl y, showing high values on concave slopes and low values on convex slopes. Farther inland, the order of magnitude of winter snow depths was 100 em from Mile 4 to Mile 7 ; 150 em from Mile 8 to Mile 14; and 100 em from Mile 15 to Mile 20. Except for a narrow belt of winter accumulation just inside the edge of the glacier, the Ramp below 700 m belonged to the area with net ablation. Studies were made on formatio n of superimposed ice; debris features in the moraine area ; and ice movement and structure in the vicinity of Thule T a ke-off. Some observations on trafficability of the route are included. CONTENTS Page I. Introduction..... .. ........ ....... .................... ... .... ... .... .... ... ... ....... ... ........ .. .. ... ... ....... ........ .. .. .. .... .... ...... .......... .. 1 II. Meteorology.. .... .. .. .. .................. .... .. ...... ....... ............... ....... .. .... .... ...... ...... ..... ..... ... .. ...... .. .. .. .. .. ........ .. ...... .. 2 Camp Tuto Station ...... ........ .. ... ........ ...... .................. ...... .. ................ .. .. .. ............. .. ...... .. .. ........ .. .. .. 2 Ramp Station ............ .... .................... ........ ...... ......... ............ -~.. .. ................... . ........... .... .. .. . .. ......... .. ... 6 Hardtop Station ... ... ............. .. .. .... .... .. ..... ... ..... ...................................... .. .. .. ........................ .... ...... .... 12 Temperature gradients. ... ... ..................... .. .. .. .. .. ........ ....... .... ...... .. .. .. ...... ... .. ... .... ... .. .. ...... ... .. ..... .... 15 Ill. Glaciology .... ........... ..... .............. ............ ....... .... ............. ..... .... ....... .. .. ...... ..... .... ...... ................ ...... ... ... .... . 16 Accumulation ... .... .. .. .... .............. ..... ................... ........ .. ......... .. ... ... ......... ..... .... ... ..... .. ........ .. .. ...... ...... . 16 Ablation ..... ... ....... ..... ... ... .. ...... ...... .... ........ .... ...... .. ........... ................ ....... .. ............ ... ..... ...... ..... .... .. .. ... 30 Relation between ablation and meteorological factors.. .. ....... .... .. .... .. ...... .. .. ... .. .. ...... .. .. .. ........ 42 Material balance on the Thule Ramp .............. .......... ................ .... .. ........ .. .. .. .. ...... ...... ............ .. .... 46 Thermal regime, Tuto-Alpha .. ...... ...... ........... ...... .. .. ..... .... ..... ... .................. ....... .. ........ .. .... ..... .. ... 4 7 Formation of superimposed ice ............ ....................... ... .... ............ .. .. .. .. ..... ... ... ..... .. .. ,........ ..... ..... 52 Moraine features .... ................... ... .. ................. .. ...... ...... ... ..... ... ... .. ........ ...... ............ .. .... .. ........ .... ...... 57 IV. Debris Features in the Moraine Area, by Barry C. Bishop....... ..... .... .. .. ....... ........... ...... .... .... .... ... 57 General statements.... .. ...... ... .............. ..... .... .. ...... ... .. .. ... ......... ... ............. ...... .... ......... .. .......... .... ... ... . 57 Debris features related to ice structure.......... .... .... .. .. .... .. .. .............. ...... ... .... .... .. .. .. ........ .... .. ..... 58 Conclusions ................. .......... .. .. ..... ........... ...... .............. ... ...... .... ... ... ... .. ....... ..... ....... .. ... .. ...... ... ...... ... 59 Possible explanations for the formation of the irregular shear moraine in the area .............. .... .. .. .......... .. ......... .. ........ ........ ...... .... .. ........ .... ........ .... ....... 60 V. Recommendations for Field Work ....... ...... .......... ... ........... ... .. ...... .... .... .... ...... ......... .... .. ...... ......... ..... ... 60 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA CONTENTS (Continued) Page VI. Trafficability, Tuto to Mile 20, by Richard L. Cameron and Valter Schytt. . ...... .... .. .. ..... 61 Tuto to Mile 20. .... ......... . ............ ... .. .... ..... ........ ....... . ..... .... .. .. ... ... .. ..... .... ..... 62 Thule Ramp.. ..... ... .... .... .... ..... ... .... .... .. . .. ..... ... ....... . ...... .. .. ... ... .. .... ...... ... ... .... 62 VII. Ice Movement and Structure in the Vicinity of Thule Take-off, by Andrew Griscom. .............. ....... .... ...... .... .... ..... ... .. ... .. ... .. ..... .....,.. .. ....... . 64 Introduction... ....... ...... .... ..... ... ................................ . ...... .. ...... .... ...... .. ...... .... 64 Topography. ............. ...... ... ..... ... ....... ........................ ... ... ....... ... .. .......... .... .... 65 Ice movement .... ... ..... ... .............. ...... .... ... .... .... ........... ..... ............... .. .... .... .... 66 Ice structure........ ..... . .......... ..... ... .... ............ .. ....... ... ...... ...... .... .. ......... ... .... .. 68 Appendix A: Movement Stake Data for Thule Take-off and Blue Ice ..... .. ... .... .... , . ... .... .. .. .. . 77 Appendix B: Base-line Data, Thule Take-off ...... ...... .. ..... ......... .. ... ...... .. .....•..... .. ........ 81 Appendix C: Blue Ice .. .... .......... .. .. ...... .. .... .. ...................... ................ ... .............. .... 83 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA I. INTRODUCTION 1. During the spring of 1954 a contract was signed by Northwestern University, Evanston, Illinois, whereby the university agreed to carry out glaciological investigations in Northern Greenland for the Snow Ice and Permafrost Research Establishment, Corps of Engineers, U. S. Army. The work to be done was divided in two parts. One part was placed under the supervision of Laurence H. Nobles of the Geology Department, and the other under the supervision of Valter Schytt of the Geography Department. This report deals with the results obtained by Dr. Schytt's party. In agreement with the wording of the contract and discussions with representatives of the contracting officer, the work done was mainly of a basic research nature, but problems were chosen that sooner or later could be expected to have some military implication. The work was administered from the Geography Department, and much invaluable help was received from Dr. Edward B. Espenshade, without whose knowledge of proper administrative channels, the party would never have reached the field in time. The party, which was in the field from the arrival at Thule on 19 June until the departure on 29 August, was led by Valter Schytt and party members were: Thomas M. Griffiths, University of Denver Barry C. Bishop, Northwestern University Richard L. Cameron, University of New Hampshire (until 2 Aug.) Andrew Griscom, Harvard University John Molholm, Tufts College John Reid, Tufts College Nathaniel Rutter, Tufts College (until 2 Aug.) Robert Schuster, SIPRE (12 J uly-22 Aug.) Thomas Smyth, Tufts College As party leader, the author wants to express his gratitude to all the members for a cooperation, willingness, and friendship that could never have been better. He also would like to thank SIPRE for all valuable assistance rendered by many members of its staff while in the United States and in Greenland. During the field work, it was a great pleasure to work with the 1st Engineer Arctic Task Force. When a need of any sort developed, t he party could depend upon the 1st EATF for help. Even if parts of the scientific equipment were destroyed or missing, the 1st EATF could always find a substitute-if the equipment was not available in Thule, they took care of the manufacturing. The author's special thanks go to Lt. Col. Arthur Lahlum and Lt. Col. George Hesselbacher for their personal interest in the project and for accepting the author as a friend and companion. While living at Camp Tuto (Thule Take-off), all practical problems concerning camp life were taken care of in an excellent manner by Captain John Napier. It should be noted that civilian scientific personnel operating from a mil itary unit could easily have caused friction. For instance, very often the party was not able to be on time for meals, but Captain Napier and all his men understood the situation and never minded our interruption of their off-duty time. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The author thinks that the military-civilian Camp Tuto was an entirely successful arrangement. II. METEOROLOGY 2. The meteorological observations made during the summer were primarily intended for correlation with the glaciological work. Their secondary importance was to add to the information about meteorological conditions within the margin a l zone of the inland ice, which was considered important for future use. According to the plans, three meteorological stations were established as soon as possible after our arrival in the field. One was situated at Camp Tuto, just outside the glacier, one on the middle of the Ramp and one at Camp Hardtop, 5.5 mi to the southeast. Camp Tuto Station. 3. This station was situated at 76°25' N and 68°20' W, 10 mi southeast of Thule and 480 m (1,575 ft) above sea level. The terrain around the instrument shelter was rather flat and the shortest distance to the edge of the ice was slightly over 300 m (Fig. 12). The station was equipped with a standard Weather Bureau instrument shelter containing: hygrothermograph (SIPRE No. 594), standard mercury thermometer, maximum and minimum thermometers. Wind speeds were obtained from an anemometer fixed at 4.8 m(16 ft) above the ground. The station was in operation from 28 June until 8 September, with observations taken twice a day. Since the glaciological work had full priority, the meteorological observations had to be done when time permitted, which at Camp Tuto meant every morning and evening. Regular hours could not be kept. Table I lists the daily mean temperatures, the maximum and minimum temperatures, the daily average humidity, and the wind speed. The daily mean temperatures and the humidity have been computed from the hygrothermograph charts. Frequent time checks were made on these charts with simultaneous readings with a sling psychrometer. The wind speed here is split up into day and night values, but it must be realized that one period may be 9 hr and another 12-14 hr. Table I. Meteorological Table: Camp Tuto Station 480 m (1,575 ft) Above Sea Level Temperature, °C Wind, mph Humidity, Date Mean Maximum Minimum Day Night % June 28 +1.1 42.4 29 +2.8 34.6 12.8 30 +5.8 16.1 31.3 July 1 +1.4 21.3 11.0 2 +5.3 4.2 4.4 3 +6.9 14.8 24.5 4 +1.3 21.2 6.2 (Continued) GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table I (Continued) Temperature, °C Wind, mph Humidity, Date Mean Maximum Minimum Day Night % July 5 6 7 8 9 +2.9 +3.3 +4.5 +2.9 +4.2 8.9 4.4 12.1 /_/8.6 15.6 85 64 81 66 10 +4.3 16.9 15.8 61 11 +6.6 16.6 16.4 47 12 +7.5 +8.6 19.8 16.0 so 13 +8.1 +11.0 +4.7 12.5 3.6 67 14 +6.9 +9.5 +4.6 6.9 5.9 76 15 +6.7 +9.7 +3.0 6.5 14.8 70 16 +6.1 +8.8 +2.6 9.4 8.5 54 17 +3.1 +8.7 +2.9 15.4 11.0 82 18 +1.5 +6.5 -0.3 18.1 27.3 85 19 +0.7 +3.1 -2.0 22.0 7.1 83 20 +2.3 +4.7 -0.2 6.0 32.7 88 21 -1.0 +0.7 -2.5 45.0 17.8 91 22 +1.1 +2.6 -1.4 6.7 4.2 87 23 +3.1 +5.4 -1.9 5.5 6.4 72 24 +4.2 +7.8 +1.2 8.0 4.7 59 25 +4.2 +7.2 +1.2 5.7 4.6 56 26 +4.7 +7.3 +1.4 4.6 8.1 53 27 +3.4 +6.8 +2.3 11.2 9.6 52 28 +2.6 +5.3 -0.6 5.811.4~ 85 29 +4.9 +6.7 +2.1 ~ 10.4 66 30 +5.0 +8.2 +3.7 21.0 27.3 71 31 +2.7 +9.1 +3.1 26.0 16.7 82 Average, July +3.9 71 August 1 +4.0 +7.3 +1.2 4.1 2.0 83 2 +5.0 +7.4 +2.6 3.7 7.8 86 3 +3.9 +7.9 +2.8 8.3 ~ 3.6 96 4 +4.5 +7.2 +1.7 ~ 4.4 85 5 +5.6 +7.8 +2.6 7.1 4.4 69 6 +4.3 +6.4 +2.9 6.7 18.3 75 7 +2.7 +4.9 +1.8 24.1 18.1 91 8 +2.9 +4.3 +1.6 13.8 4.5 91 9 +4.4 +7.2 +1.5 10.4 6.0 72 10 +3.5 +5.8 +0.5 7.7 2.5 71 11 +4,6 +7.2 +0.7 8.5 4.1 73 12 +7.7 +11. 7 +2.1 5.6 3.4 61 13 +8.3 +12.8 +3.8 5.7 5.0 62 14 +7.2 +12.2 +4.1 3.6 7.8 66 15 +5.6 +8.9 +2.9 17.1 15.9 63 16 +3.4 +5.2 +1.2 21.6 10.1 76 17 +2.8 +4.0 +1.5 12.6 8.9 85 (Continued) GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table I (Continued) Temperature, °C Wind, mph Humidity, Date Mean Maximim Minimum Day Night % August 18 +4.1 +7.1 -0.5 11.0 9.6 78 19 +2.6 -0.7 12.3 13.3 80 20 +2.2 +6.1 -1.3 15.5 6.8 76 21 +3.1 +5.6 -0.8 4.7 2.0 79 22 +4.1 +7.1 -0.5 2.2 6.4 68 23 5.0 +10.1 -0.1 8.3 3.6 57 24 3.2 +6.1 -0.6 1.8 1.5 71 25 3.8 +7.8 -0.6 4.1 3.9 64 26 3.1 +5.4 -0.1 4.0 1.0 85 27 4.1 +7.4 +1.2 7.2 17.0 73 28 4.2 +8.1 +1.0 1.6 1.6 57 29 +2.0 +0.7 61 30 ±0.0 72 31 -0.3 61 Average, August +3.9 74 September 1 +1.5 73 2 +0.7 71 3 +2.5 72 4 +3.8 75 5 +2.9 6 +1.4 7 +0.8 8 -0.8 No cloud observations are given in the table above, since much more frequent and regular observations were made at Thule. Appreciable difference between the cloud cover at Thule and that at Tuto could of course occur, but it was then mainly because of fog at Thule. Thule recorded fog on 8 different days during July and on 9 days between 1 August and 28 August. Notes on fog are very sparse from Camp Tuto, mainly because of much less fog fre quency, but also because of insufficient observations. Since we cannot produce statistics of comparable accuracy to those from Thule, we will only touch on this problem here and more from a qualitative than from a quantitative point of view. Frequently Camp Tuto had a clear blue sky while Thule could be seen covered with fog or a dense cover of low stratus. This fog sometimes rose high enough to cover even Camp Tuto, but it never lasted more than a few hours and normally much less. Advection fog seldom hampered the work on the glacier, since clear sky could be counted upon at the top of the Ramp under such circumstances. Low southerly winds could, however, bring cold and moist air in from the Dedodes Fjord, and on such occasions the whole route inland was covered for at least the first 20-30 mi. The fog then formed a very shallow cover (the order of magnitude of the thickness was 100 ft), but it made the visibility extremely poor. This occurred, however, only a very few times during the course of the summer. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 5 In order to give an easily read, over-all picture of the temperature conditions for the whole summer, 5-day running means have been plotted in Figure I. To save space and facilitate comparisons, the recordings from all our three stations have been DAILY MEAN TEMPERATURES AT : CAMP TUTO ---plotted on the same graph. THULE RAMP-HARD TOP Two periods with very oc high temperatures stand out 80 clearly. The daily mean tem1\ peratures at Camp Tuto were I I /\ 0 above +6 C (42.8 F) during 6 6 ' I I I I consecutive days inJuly (11-I I I 16) and during a 3-day period I I r (\'\ 40 0 \ " I in August (12-14). The I v .... -..,) t ,\\ ,/~\ v' I . I II I I highest average in July was I J I I I V) \ I ! \ I 1111/' I +8.1 C ( 46.6 F) on the 13th, and I 2. I \1\ \ t'\1\/. / ~ ' -36 the highest in August was +8.3 C V"' I! v I 1'.\j iv I \ (4 7.1 F) also on the 13th. The ~ I )\ I \ I i \, '\/ .,.J' / corresponding lowest averages \./ r...i ~~rt ' \ were -1.0 C (21 July) and -0.3 rt .r' 32 1\)I C (31 Aug.) respectively. \ i. ) Oddly enough, the 2" 28 5 10 15 20 2 5 JO 1 5 10 15 20 25 30 1 5 10monthly mean temperature for July August Sept. July worked out to exactly the same value as for August, Figure 1. Daily mean temperatures at Camp Tuto, Thule Ramp, and Hardtop; 5-day running means, 28 June-S September 1954. +3.9 C (39.1 F). The variations of the daily averages from the monthly mean were small. Of the 31 days in July, 17 were within ±1.5 C (2.7 F) of the monthly mean of +3.9 C. The corresponding figure for August was 22. The mean diurnal variations were 6-~c----~------~----~------,------.-----. also small, as can be seen from Figure 2. Au gus,......----.._ In July the mean temperature for the 4·~----~--~/~/~~~warmest time of the day (at about 1400) ~Ju~l~ v +------r~~~~----~ was only 2 C higher than the mean for the?? coldest part of the night. This varied of r......-_-/_7_.,;..+- course with the weather. Windy and cloudy 2"·~----~------~-----+------~----~----~ days gave low variations, while the variations on calm and clear days were appreciably higher. do~o-----,L-----~s----~,2---~----~ ,62-o----~2, hour The winds during the summer were rather light and on only two occasions did Figure 2. Mean diurnal variation of air temperature at Camp Tuto. the averages (over one day or one night) go above 40 mph. This happened on 28-29 June and on 21 July. By and large, July was much windier than August. The following table may show this better than Table I. Average wind speeds, mph: 30 June-10 July 10-20 July 20-31 July 31 J uly-10 Aug. 10-20 Aug. 20-29 Aug. 5.2 13.3 13.3 12.1 10.1 9.3 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Most of the storms in this general area (NW Greenland) come from the SW*. These strong winds, however, pass high above the Thule region. The storms here are caused by local depressions coming up along the coast of Baffin Bay. Thus the winds get an easterly component to which the katabatic effect is added-and the result is easterly or southeasterly storms depending upon the local topography. Easterly winds were also completely dominant. Of all wind observations 81% fell between NE and SE (boundaries inclusive) and 33 % fell on SE only. Seven per cent of the observations fell from S through Wto N, and the wind speeds at such occasions were very low. The mean relative humidity was 71% in July and 74% in August. The main variation in relative humidity was of course closely connected with the variation in temperature, but it could also be seen that low winds from the glacier brought low-humidity values. This foehn-effect was also visible-a long and rather narrow strip of blue sky often stayed just outside the ice and parallel to its edge. Ramp Station. 4. This station had the same equipment as the station at Camp Tuto, except that the wind was recorded at 4 different levels, a Robitzsch actinograph was added to the roof of the instrument shelter to record the radiation from sun and sky, and a standard rain gage was put up to measure the precipitation. The hygrothermograph used was SIPRE No. 595. The slope of the glacier at the station was 3.5° (6.2%) and the distance to the ice margin was 1,500 m (0.93 mi). The temperatures were measured 1.5 m (5 ft) above the snow or ice surface. Table II: Meteorological Table: Thule Ramp Station 569 m (1,870 ft) above Sea Level Wind, mph Temperature,°C at 5-m Precipitation, Humidity, Radiation Date Mean Maximum Minimum Level in. % in langley s** June 22 23 73 24 89 25 82 26 82 27 5.0 78 28 -2.4 92 29 -1.5 -1.8 0.36 95 30 2.4 6.5 0.30 77 July 1 -1.2 4.9 -2.0 88 408 2 2.6 -1.9 68 782 3 3.2 7.9 -1.5 65 784 4 -0.6 82 780 5 1.9 1.38 85 347 6 2.1 3.9 -0.6 85 807 7 2.2 5.2 1.2 72 775 • Lauge Koch, "Contributions to the glaciology of North Greenland," Meddelelser om Gronland, vol 65 (1928), p 359. •• I langley (ly) = 1 g-cal/ cm2. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table II (Continued) Wind, mph Temperature, °C at 5-m Precipitation, Humidity, Radiation Date Mean Maximum Minimum Level in. % in langleys** July 8 1.8 7.0 -2.2 79 740 9 1.1 5.3 -1.3 75 752 10 1.5 2.5 1.3 72 408 11 3.5 2.4 63 500 12 4.5 9.0 65 234 13 4.6 8.5 3.3 0.02 78 355 14 3.7 5.6 2.8 87 435 15 2.8 4.7 1.9 81 571 16 2.4 4.8 1.2 70 676 17 0.4 2.7 1.4 15.5 90 418 18 -1.1 -0.3 25.5 90 450 19 -0.7 -0.7 19.0 90 274 20 0.8 6.4 1.8 24~0 91 425 21 -2.4 -2.2 l 323 22 -0.2 2.4 5.8 0.08 459 23 1.0 5.6 9.0 75 572 25 1.3 5.0 -0.8 10.0 68 605 26 2.4 3.6 -1.1 12.2 66 648 27 1.2 0.8 11.4 70 470 28 1.3 5.4 -1.1 11.8 0.17 88 370 29 2.6 4.1 -1.1 18.5 79 590 30 2.6 5.0 1.2 24.9 83 603 31 1.3 0.3 0.07 87 209 Avera ge, July 1.6 78 August 1 2.4 5.0 0.0 13.5 86 455 2 3.3 5.7 1.7 4.6 87 326 3 4 5 2.5 3 .0 3.7 t 6.2 t 0.9 1.7 8.7 7.1 8.5 0 . 05 0.01 94 84 78 192 399 544 6 2.6 8.8 1.8 15.2 82 216 7 1.5 2.7 1.3 19.5 92 138 8 1.7 3.7 0.6 9.0 0.30 91 161 9 2.4 7.1 0.8 10.0 0.02 78 444 10 1.4 3.5 -1.1 8.5 81 464 11 3.0 6.0 -1.3 8.6 75 445 12 5.6 9.1 2.8 11.0 70 476 13 6.2 11.2 0.8 10.6 69 457 14 5.5 9.6 3.2 8.3 71 493 15 3.0 9.9 13.8 73 439 16 17 1.9 1.3 -1.4 15~0 82 87 433 331 18 2.6 5.4 l 83 498 19 1.6 -1.1 14.7 81 386 (Continued) •• 1 lang ley (ly} = 1 g-c ~l / cm2. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table II (Continued) Wind, mph Temperature, °C at 5-m Precipitation, Humidity, Radiation Date Mean Maximum Minimum Level in. % in langleys** August 20 1.3 1.6 13.8 76 457 21 1.6 3.2 1.0 7.5 85 422 22 2.3 5.5 -0.5 10.2 74 420 23 2.8 1.6 10.0 68 361 24 1.9 5.3 75 395 25 2.1 10.5 72 362 26 2.1 79 206 27 2.8 9T7 78 348 28 2.0 l Average, August 2.4 80 ~ ** 1 langley (ly) = 1 g-cal/cm . The wind measurements will be treated separately below. The general temperature conditions were very much like those at Camp Tuto, but naturally somewhat lower (see Fig. 1). The two "heat waves" in the middle of July and the middle of August were also pronounced on the glacier. In ] uly the temperature went above +4.5 C (40.1 F) on 2 days and above +3.5 C (38.3 F) on another 2 days. In August, 3 days had mean temperatures above +5.5 C (41.9 F) and another 2 above +3.0 C (37.4 F . The highest average in July was +4.6 C (40.3 F) on the 13th, and the highest in August was +6.2 C (43.1 F) also on the 13th. The corresponding lowest averages were -2.4 C (21 ] uly) and 1.3 C (17 and 20 Aug.) respectively. t The monthly mean values were: for july +1.6 C (34.9 F) and for Aug st +2.4 C (36.3 F).:j: The variations of the daily averages from the monthly mean were even smaller than at Camp Tuto, naturally because of the stabilizing influence of the melting snow or ice surface with its constant temperature. Of the 31 days in July, 20 were within ±1.5 C (2.7 F) of the monthly mean; for August the corresponding figure was 26 days. Even the mean diurnal variations were smaller than at Camp Tuto. T e noon temperature in]uly was on an average +2.3 C (36.1 F) and the midnight temperature (or more correctly at 03 a.m.) was +0.8 C (33.5 F), a variation of only 1.5 C (2.6 F). The whole diurnal variation for August was 1.6 C (2.8 F). The total precipitation recorded with the rain gage was 70.1 mm (2.76 in.), but the figure is not considered too reliable. The four high readings, 29 and 30 June, 5 July and 18 August, were all taken after periods with high winds, low temperatures, and some snowfall. The snowdrift certainly deposited more snow in the gage than can be considered representative of the surrounding area. The amount of rain that fell on the glacier. was definitely a small fraction of the precipitation recorded by the gage. t The temperature recordings were discontinued on 28 August and most certainly the minimum for the month came on the 31st. The minimum values given cannot therefore be compared with the corresponding value s fro m Camp Tuto , which between 1 and 28 August had a minimum average of+2.2 C on the 2 0 th. :J: The daily averages for the last 3 days of the month have been compu ted from the values at Camp Tuto. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The radiation was recorded with a Robitzsch actinograph placed on top of the instrument . shelter, and great care was taken to keep it as level as possible. The calibration of the instrument was checked before it left the United States, but unfortunately this calibration was lost. Gosta Liljequist (meteorologist of the Norwegian-British-Swedish Antarctic Expedition, 1949-1952) has suggested that the radiation during a few clear days be computed theoretically using a turbidity* of 0.030 (slightly higher than his 0.025 at sea level in Queen Maud Land); using Fowle's equation for computing the absorption from water vapor by means of vapor pressure data from ground level; and using Liljequist's, as yet unpublished, data from Antarctica for computing the diffuse clear-sky radiation. This method has to give a good current calibration, si nee the average turbidity cannot vary appreciably from 0.030 and since it gives a check on any greater changes in calibration during the course of the summer. The results obtained were as follows: Radiation, Noon Value (ly/ min) Date Measured with Actinograph Computed Correction 3 July 0.99 0.96 -3% 9 0.93 0.96 +3% 16 0.86 0.93 +8% 24 0.89 0.89 ±0% 25 0.90 0.89 -1% 30 0.81 0.86 +6% 12 August 0.72 0.76 +6% 20 0. 70 0.70 ±0% 24 0.65 0.65 ±0% 28 0.61 0.61 ±0% The difference between the computed and the measured values is constantly very smal , and the instrument can be said to record the radiation without any correction factor. The radiation (see Table II and Fig. 3) m'~turally reached its highest values (750-800 langleys) durin g clear days in th e beginning of July. Durin g the middle pa rt of Au gust, the 0 indicates days with clear, or very nearly clear, sky 800--e. shows the maximum rod iation to be expected in clear weather 700 600 --- ..,__ 50lT - -~-r- t--t-1--re--t~Z -e 40(} r 30() 200 100 T 1 5 10 15 20 25 30 1 5 10 15 20 25 July August 2 Figure 3. Incoming radiation, Thule Ramp, cal/ c m -24 hr, 1 july-27 August 1954. According to An 12: st;Om-Ho etoer. --------------------------------------------------------------------~ 10 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA radiation on clear days had dropped to around 450 langleys. On overcast days the radiation amounted to around 300 to 400 ly in July. In August, values around 200 ly, and some even lower, were recorded. The sum of the incoming radiation was 16,500 cal for July and about 11,500 cal for August for the first 27 days. Wind measurements: Because of certain practical difficulties, the anemometer mast was not erected until 17 July. Anemometers were fastened to the mast at four different levels (63 em, 198 em, 355 em, and 612 em) and were read whenever the station was visited. It was not possible to keep the anemometers at constant levels, owing to the lowering of the glacier surface by ablation, so the wind-distribution curve has been plotted for each period and the wind speed at the 5-m level (same as Camp Tuto) interpolated. For comparison with conditions outside the glacier, the average wind needs for certain 10day periods have been computed (in mph): 20-31 July 31 July-10 August 10-20 August 20-28 August 15.0 11.2 12.5 9.7 The average wind speeds were thus a few miles higher at the Ramp Station than they were at corresponding periods at Camp Tuto (2.9, 1.1, 3.2 and 4.5 mph, respectively). The wind s peed showed a rapid increase in the lower levels. The wind distribution curve plotted in a logarith mic diagram will generally be a straight line, and can be written as: u z + z 0 u = ___a_ In --, z z In~ 0 z 0 where u = wind speed at the level z ua = the measured wind speed at the level z a z = roughness parameter. 0 For four 10-day periods, the following average wind speeds were obtained (height in m, wind speed in mph): 20-31 July 31 July-10 August 10-20 August 20-28 August Anemometer Wind Wind Wind Wind No. Height Speed Height Speed Height Speed Height Speed 1 0.64 11.9 0.90 8.8 1.01 10.0 1.13 8.2 2 1.99 13.4 2.25 9.9 2.36 11.4 2.48 8.8 3 2.56 14.4 3.82 10.7 3.93 12.1 4.05 9.5 4 6.13 14.9 6.39 10.9 6.50 12.9 6.62 10.0 These data are plotted in Figure 4 and the roughness parameter assumes the following values: 20-31 July, z = 0.2 mm; 31 July-10 August, z = 1.0 mm; 0 0 10-20 August, z = 1.9 mm; and 20-28 August, z = 0.4 mm. 0 0 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA It should be observed Height above ice surface 10.0 mr---=----,----,---,----.,----"-'---'T'TL-'-"-'in-""-"'-_,~'-'l:..l=n that these z-val ues represent the maximum values, since the average vertical temperature distribution was stable. 5.0 In normal meteorological literature and research, the concept "wind speed" refers to the conditions in the 10-m level. For glaciological research it can often be very 2.0 f------l---+---+---+-+--11-----~'---1-->---onoo , I I I I Figure 6. Air temperature profiles, I Thule Ramp, 1954. I t 1.0 r / Hardtop Station. I I ~ I 5. This station was located at Camp Hardtop, 5.5 mi southeast of Camp 0 2 6 a 10 Tuto , and 736 m (2,410 ft) above sea level, m. p. h. on a relatively level snow surface (sloping about 1: 100 to the SW). It was equipped Figure 5. Wind profile s showing katabatic winds, with an anemometer and with a standard inThule Ramp, 1954. str ment shelter containing: one hygrother mograph (SIPRE No. 598), one standard thermometer, one max. and one min. thermometer. The temperature measurements refer to a level varying between 1.5 and 1. 75 m. The reference level for the wind measurements is given in Table III. In general the temperature conditions followed those at Camp Tuto and the Ramp Station rather closely. In] uly the daily average temperature went up to between +3 C and +3.5 C (37.4 38.3 F) on only 3 days. The "heat wave" in August was slightly warmer and brought the mercury up to +4.9 C (40.8 F) on 2 days and to +5.4 C (41.7 F) the day in between-all the rest of the month stayed below +3 C. The coldest day in July (the 21st) gave an average of -2.4 C (27. 7 F). On 20 August, the mean temperature was -0.9 C (30.4 F) but the lowest value of the month probably came after our measurements had been discontinued on 28 August• . The monthly mean values were: for July +0.6 C (33.0 F) and for August +1.4 C (34.6 F). The variations of the daily averages from the monthly mean were small. On 21 days in July the temperature was within ±1.5 C (2. 7 F) of the monthly :nean, and the corresponding figure for August was 24 (the last 3 days were probably cold enough to fall outside these limits). The mean diurnal variations were slightly higher han at the Ramp Station. The highest hourly value in July was on an average +1.5 C (34. 7 F) and the lowest at night -0.4 C (31.4 F)a variation of 1.9 C (3.4 F). The whole diurnal variation for August was 1.8 C (3.2 F). Since the Hardtop Station was so far away from the camp, it could not be visited very frequently. Thus, regular wind observations were not taken until 22 July, when Pfc. Weston Blake, then stationed at Hardtop, took over the responsibility for the routine observations. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table III. Meteorological Table: Station Hardtop, 736 m (2,410 ft) above Sea Level Date Mean Temperature, °C Maximum Minimum Wind, m~h Hei!;;lht, m Day Night Humidity, % June 22 23 24 25 26 27 85 82 84 July 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 -0.7 2.4 -0.7 1.2 2.6 -0.6 0.8 1.5 0.7 0.3 0.4 0.7 2.7 3.2 1:1 3.3 2.3 1.1 -1.3 -2.6 -1.6 t5.1 t 6.6 4.6 t 7.4 j t 9.2 t -2.2 t -4.4 j 211 217 220 247 247 23.4 ---, 17.2 '9.4 ---, 13.2 L__ ---, 12.2 L__ 14.7 I 9.2 Jl 11.0 L Anemometer out of order 98 72 70 90 94 84 82 85 75 75 67 69 78 90 76 69 20 0.7 6.9 21 22 23 24 25 26 27 28 29 30 31 August 1 2 3 4 5 6 -2.4 -0.5 0.8 1.0 -0.2 0.1 -0.9 -0.2 1.0 1.1 -0.1 1.6 2.8 1.7 2.5 2.7 2.3 4.9 6.4 3.4 3.2 1.5 1.3 2.1 2.4 1.6 4.0 5.6 3.1 4.5 4.3 3.8 -4.7 -5.1 -2.2 -4.2 -4.4 -3.4 -2.2 -0.5 -1.3 -1.2 1.8 0.6 0.7 -0.2 0.9 247 248 249 249 249 249 249 251 253 256 256 202 205 206 208 210 6.8 7.9 4.8 9.7 7.5 8.0 6.6 11.0 7.6 11.7 12.8 14.1 10.5 11.9 11.8 15.1 15.0 16.9 /9.3 6.1 4.8 3.9 8.1 6.9 .....-6.5-.6.2 5.9 5.2 10.7 78 72 72 81 77 99 84 90 94 91 89 97 84 79 85 (Continued) GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table III (Continued) Temperature, °C Wind, mph Humidity, Date Mean Maximum Minimum Height, m Day Night % August 7 0.5 1.6 -0.6 213 14.9 11.9 100 8 0.9 1.1 -0.6 215 9.9 9.3 9 1.9 3.1 0.1 215 10.4 5.9 79 10 1.2 3.7 -2.4 216 6.1 7.8 80 11 2.9 6.8 -2.4 217 8.3 8.7 72 12 4.9 6.0 1.7 219 11.5 9.1 76 13 5.4 11.4 3.6 225 9.5 8.0 71 14 4.9 5.4 3.1 230 8· 0 16.2~ 76 15 2.0 5.6 225 ~ 16.6 74 16 0.3 1.8 -1.6 225 24.0 12.9 92 17 0.4 1.8 -2.3 224 7.4 14.1 92 18 1.3 4.2 -1.6 224 11.2 10.7 93 19 0.2 2.5 -2.8 223 .........14.7-- 80 20 -0.9 1.0 -2.5 223 14.3 16.9 88 21 0.1 1.2 -1.9 223 13.3 7.4 94 22 1.7 5.6 -1.1 223 5.3 8.2 71 23 0.4 4.2 -3.8 222 ~8.6 73 24 0.4 -4.6 222 6.7 25 26 1.1 0.5 7.2 2.1 -2.1 -2.9 222 222 5.0 ---__.-7.0 4.7 80 27 2.1 7.3 0.0 222 9.5 20.1 78 28 1.9 -1.3 222 6.2 The wind speeds during the three 10-day periods in August were as follows: 31 july-10 August 10-20 August 20-28 August 8.3 mph 11.8 mph 9.3 mph These winds were measured at about 2.0 m. Assuming the same wind distribution at Hardtop as at the Ramp Station, the values for the 5-m level should read approximately: 31 July-10 August 10-20 August 20-28 August 9.5 mph 13.3 mph 10.5 mph For the last two periods, Hardtop shows higher winds than the other two stations; although it shows slightly lower values during the first period. It is not easy to get a comparison between the three stations since the anemometer readings were not taken simultaneously, but a not too thorough analysis of the records indicates that, in clear weather with light winds (10 mph at Camp Tuto), the wind speeds at the Ramp Station exceed those at Hardtop, while the opposite is true with higher winds. On overcast days, the wind speeds at Hardtop were generally higher than at the Ramp Station. This is another example of the importance of the katabatic wind influencing the conditions more on the steeper ramp than on the flat area around Hardtop. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Temperature gradients. 6. In a later section we will try to correlate the ablation of snow and ice with certain meteorological factors. Temperature is measured at only one place on the actual Ramp, and ablation is measured at 20 places; therefore we want to find out what the temperature is at any given height. For this we can use the records from the other meteorological stations and study how the temperature, on an average, varies with height above sea level (the temperature gradient). The available temperature data come from Thule, Camp Tuto, the Ramp Station, and Hardtop (Fig. 7). The average monthly temperatures were: Thule, 57 m Camp Tuto, 480 m Ramp Station, 569 m Hardtop, 736 m July +4.9 C (40.9 F ) 3.9 C (39.1 F) +1.6 C (34.9 F) +0.6 C (33.0 F) August +5.4 C (41. 7 F ) 3.9 C (39.1 F) +2.4 C (36.3 F) +1.4 C (34.6 F) • The normal temperature decrease with height is 6 C close to 0.6 C per 100 m and th e gradients obtained dur ~hule ing the summer were: 5• '-_, Thule- Camp Tuto- Ramp ~ '-.tug. Camp Tuto Ramp Station Hardtop 04 J ~ ~. Tut o July August 0.24 c 0.35 c 2.6 c 1.7C 0.6 c 0.6 c . ~;m 3 \Ramp Of the four stations, only two are situated fairly simitat ion larly. The Ramp Station and Hardtop are both glacier \~ stations and the main differences between them are 2 '\. elevation and slope. We also find that the temperature ~ ' \. gradient agrees very well with the " normal value." N~rd ·on The gradient between Thule and Camp Tuto is '\ only half of its normal value. This depends probably upon the very local conditions around Thule and upon . 0 200 400 600 800 the inversion that is frequently developed over the meters above sea level valley. The temperature gradient between Thule and Camp Tuto was inverted (negative) 14 times durin g July Figure 7. Average air temperature gradient from Thule to Hardtop, 1954. and August. The records s how that, of those 14 days, Thule reported fog on 10 and rain or trace of rain on another two. It is probable that the average summer temperatures at Thule are not representative for the area for they are at least 1 C too low. If we look at the difference between Camp Tuto and the Ramp Station, we will see the influence of the snow or ice surface on the temperature conditions. The area around the Camp Tuto instrument shelter was snow-free all July, and the ground absorbed a great deal of the very strong incoming radiation. At the Ramp s helter, at least 50% of this radiation was reflected by the snow and ice. During August, the radiation dropped to 70% of its July value and the absorption around the Ramp Station increased an unkno wn amount because of the intense melting of glacier ice. This accounts for the lower August gradient. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The "cooling effect" of the glacier was 2.1 C in July and 1.2 C in August*. It is obvious that the measured temperature gradient between the Ramp Station and Hardtop should be used for computing temperatures at different places on the glacier, even though some of them may be situated lower than the Ramp Station. III. GLACIOLOGY Accumul:.ltion. 7. On the Ramp. The first accumulation measurements were started immediately after our arrival in the field. The air temperature in Thule had been above freezing raost of the time since 21 May, but it is not believed that any appreciable net ablation had yet taken place on the glacier. In the first pit, dug 22 June a few hundred meters up on the glacier (close to the SOO-m contour), the following temperatures were measured: Depth, em: 10 20 30 40 so 60 70 80 90 100 110 120 Temperature, °C: -1.0 -0.8 -O.S -0.4 -0.1 0.0 0.0 0.0 0.0 -0.1 -0.2 -1.3 The total depth of the last winter's snow was 90 em. These temperatures, as well as ice layers even close to the bottom, show that there has been melting, and the whole pack has been soaked by melt water either at the middle of June or perhaps during the last part of May. After this melt period, the temperature must have stayed below freezing for several days, since the upper SO em were frozen. The negative temperatures below 100 em were measured in the dense firn left over from the accumulation season 19S2-S3. Another indication of insignificant melting in the area comes from a pit about S mi inland and about 740 m above sea level. The pit was dug on 28 June, and, though the last days had been very warm, the snow temperature was 0 C down to only 40 em. At SO em it was still -1.7 C. Much runoff cannot possibly have taken place on the Ramp with so little simultaneous temperature increase in the snow only about 200 m higher up on the ice. Because of these observations we can assume that, for this summer, the ablation measurements started at the end of June still give the whole net ablation. The first pit (22 June) gave a mean density of 0.493, and a second pit dug at the same place on 1 July gave O.S04 as a mean. Since all dep h measurements were taken on the Ramp between these two days, we will use O.SO as the density values when computing the water equivalent of the accumulation of the whole Ramp. It is naturally an approximation to say that the density at one place can be used for a considerable area, but earlier experience from systematic pit-digging on glaciers in Kebnekajse, Sweden, has shown surprisingly small variations** over much larger areas than the actual Thule Ramp, and with greater variation in both snow depth and altitude. Depth measurements were taken by probing with a metal rod along two separate profiles with It may be worth mentioning that a similar study, which the author undertook in 1947 on the Star Glacier in the Kebnekajse massif (latitude 67°9" N), Swedish Lappland, gave almost exactly the same results. The "cooling effect" that time was 2 .2 C for July and 1.1 C for August. ** One example: 13 pits were dug on 25-27 May 1946. The snow depth varied from SO to 330 em and the altitude from 1,340 to 1,575 m above sea level. The mean value of the mean densities was 0.46 with a standard deviation in the mean value of only 0.0 1. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA about 25-30 m between each probing. Three measurements, a couple of meters apart, were taken at each place in order to avoid errors from measurements in deep stream channels or on high ridges. The situation of the profiles is shown in Figure 8. The main profile runs the 1. 7 mi from Stake 1 (505 m above sea level) to Stake 5 at 681 m. The mean accumulation along the profile was -----700- Stak~ 7 5 ~700 ----675~ / 675 snow ----650 / 650 625 / ------600--- -- 600 -575 -----575 ~550 ~525 A soo 52 5 ....__.,...-- ----------475---- F i gure 8 . Accumulation profiles, Thule Ramp. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 55 em of snow (28 em of water) and the variations were considerable, as is shown in Figure 9. This variation is directly correlated to the slope, and the accumulation shows high values on concave slopes and low values where the 100 slope is convex. From Stake 1 up to about the 525 contour, the depth e averaged 75-80 em, but dropped rapidly just above. From there up 60 to the weather station (Stake 14) the average depth was only 25 em. 4o The slope was now getting slightly steeper and the accumulation increased to another maximum around 80 ern at the 595-m contour. Stake Stake 1 stake 2 14 3 A new minimum of 35 em was 2~ 00~----~------~----~~------------~------~ reached at 630 m, and the last Miles from Tuto maximum at 665 m had the same accumulation in ems of snow value as the previous one, 80 em. --d e v i a t i on t r o m m ea n s l ope (rising curve shows concave slope falling curve shows co vex slope) Getting closer to the region where the Ramp gradually evened out to the fairly flat, slightly rolling Figure 9. Accumulation along profile 1, Thule Ramp. plateau towards Hardtop, the snow depth started to drop again. The other longitudinal profile, about 250 m south of the one previously described, showed approximately the same conditions, although the variations were a bit greater. On the lower part of the Ramp, the snow reached values around 100 em only to drop down to around 10 em in the hummocky area at 540 m above sea level. Above the 550-m contour, the accumulation was very similar along both profiles. It is clearly seen that the distribution of the accumulation on the Ramp is governed by prevailing easterly winds. The snow is blown off from all humps and convex slopes and accumu lates in the more sheltered areas. This accounts for the heavy accumulation just inside the edge of the ice and therefore for the whole existence of the Ramp. With even accumulation over the Ramp, the "toe" would ablate much faster, and in a short period the slope would increase appreciably. Inland. The accumulation measurement s on the Ramp were easily made by sounding the depth with a metal rod. In the higher areas, where the last year's accumulation rests on more or less loose firn, other methods have to be used. The easiest and most convenient method is to plant stakes at the end of one ablation season and remeasure them at the beginning of the next one. The difference between the height of the stake above the snow surface in the autumn and in the early summer will then be equal to the winter's accumulation. (If extremely accurate measure ments are needed, a correction must be applied for the amount of settling in the snow layer into which the stake was placed.) If no preparations were made during the previous year-as in our case-studies of density and hardness variations, the occurrence of ice layers, and/or differences in crystal structure of the snow can be used. Pit at Mile 5 (depth of pit, 323 em; cores drilled down to 661 em). The first pit in the accumulation area was dug on 28 and 30 June 5.0 mi from Camp Tuto (0. 9 mi from Hardtop in direction 55° magnetic). The snow temperature was negative from 25-30 em down and ice layers of appreciable thickness were found at 20.0-20.5 e m and at 34.0-34.5 em. From 34.5 to 77 em there GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 19 was "tightly packed snow; small crystals; intermittent ice lenses," and in the next 77-117-cm layer "medium crystals with few thin ice lenses." These two layers had never been soaked by melt water, and the few thin ice lenses had been formed either by melting or by supercooled rain during the accumulation season, or they had de veloped during the month of June from melt water penetrating the snow pack along very isolated melt-water pipes or columns (compare Pit, Mi le 8). From 117-117.5 em, there was a continuous ice layer overlying "coarse-grained dry snow, loosely packed" and this was followed by more coarse-grained, old firn, and several continuous ice layers. It was thus very clear that the ice layer at 117-117.5 em formed the boundary between the old firn and the snow from the last accumulation season. The density distri bution in the upper 2.5 m was: 58 82 100 130 155 172 189 205 240Depth (em) 25 45 3 0.495 0.550 Density (g/cm ) 0.435 0.395 0.480 0.380 0.445 0.375 0.445 0.490 0.520 This gives a water equivalent of 48.5 em and a mean density of 0.415 for the last winter's accumulation. Pit, Mile 7 (depth of pit, 393 em; cores drilled down to 916 em). The next pit was dug on 4 July at Mile 7, where also a set of ten thermocouples were drilled down in the firn. The temperature was at 0 C only in the upper 10-15 em, -0.4 C at 20 em, -1.0 C at 30 em, and as low as -4 C at 75 em. There had been some melting previously, because there were ice layers at 19-22 em (series of thin ice layers), at 24-25 em and at 35-35.5 em. Below 35.5 em, however, there was a break in ice-layer occurrence down to 155-156 em ("three thin ice layers, each 1 mm thick"). There were great variations in the snow stratification. From the record: 0 -19 em: Very white fine-grained snow, grain size 0.5 mm. Hardly any ice layers. Represents accumulation during June. 19-22 em: Series of thin ice layers. 22-24 em: Coarser snow, 0.2-1.5-mm grain size. 24-25 em: Ice layer. 24-35 em: Snow, 0.2-1.5-mm grain size. 35-35.5 em: 5-to 10-mm-thick, continuous ice layer. 35.5 -116 em: Very homogeneous, unsoaked winter snow, mostly 0.3-0.5-mm grain size. In one part of the wall, some water has seeped down forming small localized ice layers down to 60 em. 115 -150 em: Fairly homogeneous firn with individual grains around 2 mm. Clusters of grains up to S-6 mm. In this coarse-grained layer, there are exceptionally coarse layers at 128 em, 132 em, and 144 em (1 em thick). 150-1517'2 em: Extremely coarse-grained, big crystals up to 5 and 6 mm. 1517'2 -155 em: Coarse firn, grains 1/ 2 to 2 mm. 155 -156 em: Three thin ice layers, each 1 mm thick. 156-157% em: Extremely coarse-grained layers with lots of vertical colums of crystals. 1577'2 -1591h em: Harder layer, coarse-grained with thin ice layers. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 1597)-164 em: Coarse-grained summer snow. Some cup-shaped, some leaflike crystals, many crystals up to around 4 mm. 164-1657) em: New layer with vertical crysta columns. 1657) -225 em: Fairly homogeneous firn, 1-2-mm grain size; 1 em of coarse-grained (2 to 4 mm) snow at 176 em; thin ice layers at 179 and 181 em (1 to 2 mm thick). Ice lens at 195 em. The above stratification has been interpreted in the following manner: 0-19 em-snow from the storms in June 1954; 19-116 em-snow which fell between the end of the 1953 ablation season and June of 1954; 116-150 em-accumulation during a later part of the summer 1953; 150-165 emaccumulation during an earlier part of the same summer; 165-225 em-firn from the accumulation season, 1952-53. The density distribution in the upper 2 m is: Depth (em) 30 45 60 75 90 105 120 135 150 170 185 205 Density (g/cm3 ) 0.390 0.450 0.440 0.475 0.485 0.345 0.352 0.398 0.460 0.525 0.500 0.495 The accumulation since last summer will thus be 48.8 em of water (116 em of snow) and the mean density of this layer is 0.421. Pit, Mile 20 (depth of pit, 400 em; cores drilled down to 675 em). A series of pits were dug on 7 July, but for certain reasons it is here desirable to report first on the pit at Mile 20, which was dug on 8 July. Temperatures were negative from 30 em (-1.0°) down, but even as far inland as here, surface melting had taken place before our arrival. Ice layers were found at 23-25 em, 38-40 em, 77-79 em (discontinuous), and 94-96 em. The record of the stratification in the upper 1.5 m reads as follows: 0-23 em: Small to medium-grained snow (7) mm). 23-25 em: Ice layer. 25-38 em: Small to medium-grained snow (7) mm). 38-40 em: Ice layer (continuous). 40-77 em: Small to medium-grained snow. 77-79 em: Ice layer (discontinuous). 79-94 em: Small to medium-grained snow. 94-96 em: Continuous ice layer. 96-113 em: Unconsolidated firn. 113-145 em: Medium-grained snow (firn) (7) -17) mm). 145 -156 em: Discontinuous ice lenses, possibly wind crust. The unconsolidated firn from 96 to 113 em is interpreted as the top layer from the end of the summer of 1953, and it is believed that the whole ice layer from 94 to 96 em belongs to last winter's accumulation. The fine-grained, densely packed winter or fall snow has a higher ability to hold water by capillary action than has the coarse-grained, loose summer firn . Therefore, the melt water seeping down through the snow pack will tend to stop at the bottom of the winter accumulation and refreeze in an ice layer. The densities in the above described layers were: Depth (em) 15 30 45 60 75 90 105 120 135 150 Density 0.465 0.400 0.450 0.475 0.505 0.415 0.360 0.320 0.305 0.470 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 21 The water equivalent of the last winter's accumulation* is computed as 44.6 ern and the mean density as 0.464. On 7 July a number of pits were dug along the Tuto-Alpha Trail. The intention was to get simultaneous readings of winter snow depth and temperature conditions along as extended a profile as possible. The party worked in two groups; pits were dug at every mile from Mile 6 out to Mile 16. In order to s peed up the wo rk, densities were not taken. The general snow conditions did not vary considerably from place to place. When choosing a density value, in order to compute water equivalents, we first took the mean of the three values already obtained (Mile 5-0.415, Mile 7-0.421, and Mile 20-0.464), which is 0.433, and then picked 0.44 as a likely value to be used for all the new pits. It is realized that the two lower values (Miles 5 and 7) both belong to the more marginal zone and that more weight should perhaps have been given to the higher value from Mile 20. However, attention is also paid to the fact that the pit at Mile 20 was dug in a pass (about 850 rn above sea level), where the snow originally must have been more wind blown a nd ha rder packed than along the rest of the trail. The value chosen, 0.44, may ha ve an error of ±0.02 for a single observation but hardly more than ±0.01 if the mean for 3-4 pits, representing the conditions over 3-4 rni, is considered. Under all the circumstances, the errors obtained in the actual water equivalents will be smaller than the real difference in accumulation between two pits 100 rn apart. P i t, ,ltil e 6 (depth of pit, 140 ern), 7 July. Temperature readings: Depth(cm) oc Depth(crn) oc Depth(cm) oc 10 0.0 50 0.0 90 -3.2 20 0.0 60 0.0 100 --4.2 30 0.0 70 0.0 110 -5.0 40 0.0 80 -1.3 120 -5.4 Stratigraphic profile: 0-6 em: New snow , melting, quite coarse. 6-7 em: Ice laye r (continuous). 7-12 e m: Medium-grained s now. 12 -13 e m: Ice layer (continuous). 13-22 ern : Medium-grained s now with intermittent ice lenses. 22 -23 ern: Ice layer. 23 -69 em: Fine-grained, hard-packe d snow with some ice lenses . 69-71 em: Ice layer (continuous but not at same le ve l). 71 -84 em: L oos e , large grains. 84 -89 ern: Very large, loose grains. 89-104 em: Loose, large grains. 104 -107 ern: Ve ry large grains-hard. 107-108 ern: Ice layer {continuous). • In this chapter, " l ast winter' s accumulation" is u s ed to mean the accumulation betwe e n the end of the summer 1953 and the day when the pit was dug. Unless otherwise noted, it includes the accumulatio n during the early part of the 1954 summe r . GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 108-122 em: Large grains, hard-packed 122 -140 em: Firn. Probable winter accumulation amounts to 71 em of snow corresponding to 31 em of water. Mile 8 (depth of pit, 200 em), 7 July. Temperature readings: oc oc Depth (em) Depth (em) Depth (em) oc Depth (em) oc 10 0.0 60 0.0 110 -4.7 175 -6.1 20 0.0 70 -1.8 120 -4.1 185 -8.0 30 0.0 80 -2.2 135 -1.3 40 0.0 90 -3.0 155 -1.9 so -0.5 100 -3.9 165 -4.3 Stratigraphic profile: 0-10 em: Granular-June snow, melting. 10-30 em: Fine-grained, white, uni form snow. 30-32'h em: Multiple ice lenses and snow layers. 32'h-40 em: Loose, medium-grained, water-soaked snow just above ice lens. 40 -41¥2 em: Ice lens (thins out to no hing to east). 41'h-45 em: Large-grained, hard-packed. 45-78 em: Mediurn-grained-many t hin ice lenses with water in transit. 78-145 em: Hard-packed fine snow-some thin ice lenses. 145 -147 em: Ice layers-ice pipe from 110 to 145. Many pipes occur at this level. 147-155 em: Medium-grained snow. 155 -157 em: Intermittent ice lenses. 157 -200 em: Coarse-grained loose sn w. This is an interesting pit where the temperature data can help with the interpretation. The profile reads: "78 -145 em: Hard-packed fine snow-Some thin ice lenses." This nearly 70-cmthick homogeneous layer certainly looks like last winter's snow and the temperatures also indicate that this layer has not been soaked by melt water. But where, then, has the ice from 110 em down to the ice layer at 145-147 em come from? Most certainly these ice pipes and this ice layer are just now being formed by the melt water that has penetrated the cold snow and is now refreezing at 145-147 em. The temperature diagram shows an appreciably higher temperature at 135 and 155 em and the heating effect of the refreezing water can be seen even at 120 em and 165 em. This is a beautiful example of the irregular drainage pattern in the snow and it explains certain discrepancies that sometimes occur in temperature diagrams from early 'summer snows, whether these discrepancies show an irregular temperature distribution in vertical or in horizontal direction. Since the ice between 110 and 147 em can be satisfactorily explained, the snow surface of the end of the summer 1953 is most likely put at 147 em, and the layer 147-157 em probably represents the accumulation during the summer of 1953. The water equivalent of the winter ace mulation is then 64.5 em. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 23 Mile 9 (depth of pit, 180 em). Temperature readings: oc Depth (em) °C Depth (em) OC Depth (em) oc Depth (em) 10 0.0 so 0.0 90 -2.0 130 -4.2 20 0.0 60 0.0 100 -3.0 140 -3.9 30 0.0 70 0.0 110 -3.7 1SO -4.0 40 0.0 80 -1.0 120 -4.1 163 -3.7 Stratigraphic profile: 0-34 em: Last new snow (this summer). 34-36 em: Thick ice layer. 36-44 em: Snow. 44-4S em: Ice layer. 4S-48 em: Snow. 48-49 em: Ice layer. 49-160 em: Well-packed, fine-grained snow with 1-cm-thick ice layers at ro em and 70 em and a thin ice layer at 93 em. From 93 em down, no ice layers. 160 em is bottom of last winter's snow. The summer surface was very distinct. Very coarse-grained snow, almost depth hoar. Here, there was no doubt whatever about the position of the summer surface. The slight temperature variations from 130 em down may indicate that melt water has penetrated the cold snow close to where the pit was dug. However, the accuracy of the dial thermometers available to the party was such that half-degree errors are likely to occur sometimes. The last winter's accumulation was thus 160 em of snow or 70.S em of water. Mile 10 (depth of pit, 16S em), 7 July. Temperature readings: Depth (em) oc Depth (em) oc Depth (em) oc Depth (em) oc 10 0.0 so -1.4 90 -3.8 130 -O.S 20 0.0 60 -l.S 100 -4.6 140 -1.8 30 0.0 70 -2.2 110 -S.O 40 -0.9 80 -2.9 120 -4.3 Stratigraphic profile: 0 -14 em: Recent snowfall at 14 em: 0.2S-cm-thick, discontinuous ice layer. 14 -29 em: Winter snow at 29 em: O.S-cm-thick, continuous ice layer. 29 -8S em: Winter snow at 8S em: O.S-cm-thick, continuous ice layer. 8S -14S em: Homogeneous winter snow at 14S em: Distinct summer surface. 14S em down: Firn. This pit is very similar to the previous one (Mile 9). The summer surfaces are very distinct. Melt water has not yet heated the whole winter s now layer, but it must have penetrated 24 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA along isolated ice pipes and reached all the way down to the previous summer surface, though this is indicated only by the high temperatures at 130 and 140 em. Even the ice layers show a good correspondence. The ratio between the accumulation values at Mile 9 and Mile 10 was 160:145 = 1.1. Assuming an even distribution of the accumulation through the winter, the ice layer at 85 em in the Mile 10 pit should have a corresponding layer at 94 em at Mile 9-we find it at 93 em. Similarly we could expect one at 29 x 1.1 = 32 em-we find it at 34-36 em. The main difference between the two pits is that melting has gone farther at Mile 9; the snow is at 0 C to a greater depth, and a greater number of ice layers have therefore developed. The winter accumulation at Mile 10 was 145 em of snow, which equals 64 em of water. tllile 11 (depth of pit, 174 em), 7 July. Temperature readings: Depth (em) oc Depth (em) oc Depth (em) °C 10 0.0 60 -3.6 110 -6.0 20 0.0 70 -4.4 120 -6.4 30 -0.2 80 -4.9 150 -7.2 40 -1.2 90 -5.2 so -2.3 100 -5.4 Stratigraphic profile: 0 -10\/2 em: This summer's snow, coarse-grained, melting. 107'2-25 em: This summer's snow, fine-grained, white. 25-267'2 em: Continuous ice layer. 26V2 -32 em: Medium-grained snow. 32-125 em: Fine, white, tightly packed snow with one noticeable intermittent ice layer and several layers of coarser snow -less than 2 em thick. 125 -174 em: Coarse-grained, loosely packed snow (firn). 174 em: Top of ice layer. The probable position of a summer surface is not noted but the "fine, white, tightly packed snow" from 32 to 125 em followed by "coarse-grained, loosely packed" below 125 em makes it very probable that 125 em forms the summer surface. The ram profile, from close to the pit, also indicated a late summer surface at about 125-135 em depth. The melting had not progressed as far as in the previous pits. Only one thick ice layer had been formed, and there was no indication of water percolation at lower depths. The winter's accumulation was 125 em of snow or 55 em of water. 1 Mile 12 (depth of pit, 170 em), 7 July. Temperature readings: oc Depth (em) oc Depth (em) oc Depth (em) oc Depth (em) 10 0.0 60 -0.9 110 -4.1 160 -6.4 20 0.0 70 -1.4 120 -4.8 170 -7.1 30 0.0 80 -2.1 130 -5.2 40 0.0 90 -3.0 140 -5.9 so 0.0 100 -3.4 150 -7.0 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Stratigraphic profile: 0-24 em: Recent snowfall. 24-26 em: Ice layer. 26-37 em: Winter snow. 37-38 em: Ice layer (2-15 mm thick). 38 -51 em: Winter snow. 51 -52 em: Ice layer (0-12 mm thick). 52-78 em: Winter snow. 78-79 em: Ice layer (0-15 mm), discontinuous, but in all walls. 79 -105 em: Winter snow. 105 -106 em: Ice layer (0-20 mm thick), almost continuous in two walls, not in the others. 106-154 em: Bottom of last winter's snow at 154 em. The melting has been more intense at this pit, which is situated 50 m lower than Mile 11. The summer surface at 154 em was very distinct, and the water equivalent of the accumulation is 67.5 em. Mile 13 (depth of pit, 200 em), 7 July. Temperature readings: Depth (em) oc Depth (em) oc Depth (em) oc 10 0.0 60 0.0 110 -5.3 20 0.0 70 0.0 120 -4.1 30 0.0 80 -1.6 130 -5.1 40 0.0 90 -3.0 140 -5.7 so 0.0 100 -3.0 150 -6.7 Stratigraphic profile: 0-6 em: Medium-grained snow (melting). 6-13 em: White, fine-grained snow. 13 -20 em: Medium to coarse-grained, lightly packed, partly water-soaked. 20-20.5 em: Ice layer, continuous. 20.5-30.Scm: Medium-grained snow. 30.5-33.5 em : Water-soaked layer, incipient ice layer (probably wrong). 33.5-37.5 em: Medium to coarse-grained snow. 37.5-40 em: Ice layer, continuous. 40-50 em: Medium-grained, water-soaked at bottom. so-so~ em: Ice layer, continuous. so~ -127 em: Fine-grained snow, well packed. Water-soaked layers at 55 and 60 em and intermittent lenses to bottom of layer. 127-200 em: Very large-grained, loosely packed snow (firn). Last summer surface at 127 em. This pit is one of the lowest along the profile (about 795-800 m above sea level and about 80 m below Mile 11) and the melt water has penetrated quite deep. The summer surface, at 127 em, was distinct and the water equivalent is computed as 56 em. The Rammsonde indicated a late summer surface at 130-135 e m, which agrees very well with the interpretation of the stratification. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Mile 14, 7 July. Here temperatures are at 0 C down to 60 em and close to 0 C for another 2S em. The depth of the "recent snowfall"-was 21 em, and ice layers were reported from 29 em (0-4 mm), 40-4S em (0-20 mm), 64 em (0-8 mm) and 68 e m (0-2S mm). Then there is a note reading: "next ice layer on top of the summer snow," but nothing is said about the depth of this summer surface. The last temperature reading is from 143 em, and there is of course a chance that this temperature is taken in the loose snow just below the summer s urface. That would mean accumulation of about 140 em of snow or 62 em of water. The value must be considered unreliable, but it cannot be too far off. The true accumulation was most certainly not greater than 143 em. Mile 15 (depth of pit, 160 em), 7 July. Temperature readings: Depth (em) oc Depth (em) oc Depth (em) oc 10 0.0 so -2.1 90 -2.8 20 0.0 60 -2.9 100 -2.7 30 -0.7 70 -2.8 110 -3.0 40 -1.3 80 -2.7 120 -4.1 Stratigraphic profile: 0-7 em: Medium to coarse new snow, melting. 7-14.S em: Medium-grained, water-soaked snow. 14.S -14.7S em: Ice layer. 14.7S -23 em: Fine-grained snow with one intermittent ice lens, water-soaked near bottom. 23-2S em: Ice layer, continuous. 2S-29.S em: Medium-grained snow with intermittent, poorly developed ice lenses (water-soaked). 29.5 -105.5 em: Well-packed, fine-grained, with interm ittent ice lenses as much as 3 em thick, some ice pipes. 10S.S -110 em: Well-developed ice layer. 110-160 em: Coarse-grained, loosely packed snow. The snow pack is conspicuously isothermic from 60 to 110 em, which shows that the main source of heat is not the conduction from above but the percolating water. This percolation has reached all the way down to the bottom of the winter s now and formed the ice layer at 10S.S110 em. Last winter's accumulation was 110 em of snow or SO.S em of water. Mile 16 (depth of pit, 120 em), 7 July. Temperature readings: oc Depth (em) oc Depth (em) oc Depth (em) Depth (em) °C 10 0.0 40 0.0 73 -1.0 108 -2.8 20 -0.2 so 0.0 80 -2.0 30 -0.3 60 -0.3 90 -1.8 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Ice layers were found at: 15.5-16 em (continuous), 23-26.5 em (series of discontinuous ice lenses 0-4 mm thick), 35 em (25 mm), 40 em (discontinuous, 25 mm), 50-50.5 em (discontinuous), 69-70 em (continuous), and 101-105 em (continuous). Last summer surface at 105 em. Considerable melting had taken place and it would not have taken many days before all the winter snow had been brought up to 0 C. This also means that hardly any new ice layers would form in this part of the snow pack. The winter's accumulation was 105 em of snow or 48 em of water. Another pit that should be included in this discussion of the amount of the winter's accumulation was dug close to Camp Hardtop on 23 July. The total depth of the pit was 365 em. The temperature at 10 em was -0.8, but, below that, the first negative temperature was read at 270 em (-0.3 C). Between 270 em and 340 em the temperatures varied between -0.1° and -0. 7°, and below 340 em (-1.1~ read -1.0° at 350 em and -1.6° at 360 em. The stratigraphic profile for the upper layers reads: 0-11 em: Fresh, fine-grained, wind-packed new snow. 11-11.5 em: Surface before recent storm, icy, hard. 11.5-14 em: 0.5-mm granular, medium hard. 14-15 em: Ice layer. 15-18 em: Granular, 1-mm grain size. 18 -31 em: Granular, 2 mm, very.damp at bottom. 31 -32.5 em: Ice layer, discontinuous. 32.5-40 em: Granular, 2 mm. 40-4lcm: Ice layer, discontinuous. 41-44 em: Granular, 2 mm. 44 -46 em: Ice layer, discontinuous. 46 -80 em: Grain size, 1 mm. 80 -84 em: Ice layer, continuous. 84 -118 em: Granular, 2 mm. 118 -119 em: Ice layer. 119 em: Top of surface from summer 1953. 119-120 em: Granular, 3 mm. 120-121 em: Ice layer, continuous. 121 -127 em: Granular, 2-5 mm. Density measurements: Depth (em) Density (g/cm3) Depth (em) Density (g/cm3) Depth (em) Density (g/cm3) Depth (em) Density (g/cm3 ) 6.5 0.36 51 0.54 96 0.50 139 0.52 17.5 0.43 60.5 0.56 106 0.52 179 0.53 28.5 0.53 70 0.59 119 0.48 192.5 0.52 42 0.52 85 0.51 129 0.49 205.5 0.45 It is very likely that the surface at 119 em has been misinterpreted. There was a very distinct change both in whiteness and in crystal structure, but after studying the stratification record with its continuous ice layer at 80-84 em and the rather coarse (2 mm) granular snow underneath, one is tempted to believe that 84 em is the real summer surface. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The Rammsonde data from the upper 145 em read: Depth Ram Hardness Depth Ram Hardness Depth Ram Hardness (em) Number (em) Number (em) Number 1-5 22 25-49 5 73-80 21 5-10 14 49-57 8 80-103 5 10-15 42 57-62 10 103-134 6 15-20 102 62-66 12 134-140 30 20-25 58 66-73 13 140-145 113 Apparently the Rammsonde hit a place where the ice layer from 80 to 84 em thinned out, since it is not registered in the hardness values. It is quite clear that the very low hardness values indicating another summer layer start at about 80 em and continue down to about 135. There is thus every reason to believe that 84 em forms the surface from the late part of the 1953 summer, and that the next 35 em might correspond to the upper hard 25 em in this pit. If we assume that the last winter's accumulation is represented by the upper 84 em, we get a water equivalent of 44 em. There is one more complication to take into account. The pit was dug on 23 July after considerable melting had taken place. Our temperature data show that the snow was at the melting point all the way down to 270 em and had a temperature below -1 C down to 340 em. Some net ablation must therefore have taken place and the total winter accumulation must have had, a water equivalent higher than 44 em. We will now attempt to compute this net ablation in the last-winter's snow previous to 23 July. As soon as the upper layers reach the melting point, all heat conduction from the surface down is automatically stopped by this isothermic layer. After this isothermic layer has become half a meter thick or more, no appreciable heating by direct radiation can take place. Thus the temperature increase after the pits at Mile 5 and Mile 7 were dug must be due mainly to the refreezing of the melt water produced in the layer concerned. On 23 July, temperatures from -1° to 1.6° were measured around 3.5 m, corresponding very accurately to the temperature at the same depth at Mile 7 on 22 July. With the complete temperature records of 4 July and 22 July from Mile 7, the amount of refrozen water required for the temperature increase can be computed from the following expression: BOx= 700 • 0.55 • 0.50 · 5 where x = em of water to refreeze, 80 = latent heat of fusion of water, 700 = depth, em, to which temperature had changed appreciably, 0.55 = mean density in the upper 700 em, 0.50 = specific heat of ice, 5 = temperature increase, degrees in the upper 700 em. We find from the equation that x = 10 em, and since the general ice surface in the area is very flat, so that very little melt water can run off or come in from the surrounding area, we can consider 10 em as an approximate value of the net ablation before 23 July. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA No measurements of the free water content were made, and the ablation value (10 em) obtained must therefore be considered a minimum value. Not only the temperature increase in the firn below is due to the melt water seeping down from the surface layers, but also the free water content in this firn. This should therefore be added to the ablation value, although it is believed that the computed value of 10 em gives the right order of magnitude. The whole winter accumulation would thus be 54 em of water. Obviously, this value must The two be considered less accurate than those obtained from pits dug earlier in the season. main reasons for computing it were: (1) to show that the accumulation around Hardtop (Mi 5.5) fits in very well with the curve (Fig. 10) showing the variation in accumulation from Camp Tuto to Mile 20; (2) to show how the ablation during the early part of em water the summer can be computed at 0 . a place where the topography is --~, r flat and sub-zero temperatures 60 / ~ ~, . ·, are still left at depths below the v 0 ~ ____. ' previous summer surface. v 0/ ~ ~ ~ / I ~0 v Summary of accumulation \__tv /~ measurements inland. Figure 10 I shows the variation in accumu 20 lation between Camp Tuto and /Mile 20. Except for the value / at Mile 6, the variations are t/ 0 2 ~ 6 8 10 12 14 16 18 very small and less than 10 em 2 0 Miles from Camp Tuto of water. The individual varia 0---0 accumulation-winter 1953-195~ -as measured on or before 7 July 195G. Jf---" accumulation-the whole year 1953-195~-os tions depend upon "micro topography," i.e., whether the measured on 20 and 2~ August from the top pit is dug on top of one of the down to the 1953 summer surface. low ridges or in a depression. Figure 10. Accumulation during 1953-1954, I. The curve shows a dis-The decrease from there inland could be due to the increased tinct maximum at about Mile 10. distance from the coast, while the decrease from there towards TUTO could depend on both dif ferences in elevation and the influence of slope and wind. Not yet published data from the Norwegian-British-Swedish Antarctic expedition to Queen Maud Land show that, with prevailing easterly winds, the snow acoumulates heavily on easterly (gentle) slopes and very little, or not at all, on westerly slopes. The reason is, of course, that the wind cannot carry as much drift snow uphill as over a flat surface, therefore accumulation on the east slopes will result. On the westerly slopes, however, the wind will gain speed and be able to pick up drift snow*. If this rule is applied to our profile, we would expect very low accumulation values on the Ramp, where the southeasterly storms are blowing downhill and where the storm winds and the katabatic winds blow in the same direction. Higher up, on the flatter areas around Miles 5-7, the accumulation should be heavier and give a more representative value for the whole region. Farther inland, from Mile 8 to Mile 12, the southeasterly winds meet an obstacle in the form of a high dome, and the accumulation reaches its maximum. From Mile 13 on, the route runs north of a system of ridges and the accumulation drops accordingly. • This is true if both slopes are gentle. If the windward slope is gentle and the leeward one is steep, eddy effects will cause abundant accumulation on the leeward side. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The very low accumulation value at Mile 6 probably depends upon local topographical conditions. It could also be due to a misinterpretation of the stratigraphic profile. However, several layers of "very loose, large grains" make it very improbable that the summer surface is at, for instance, 122 em, which is apparently a border surface and which would give an accumulation value very close to the curve. For practical purposes, a winter snow accumulation of about 100 em ( snow depth) can be expected in the area Mile 4-Mile 7, 150 em from Mile 8 to Mile 13 or 14, and 100 em again from Mile 15 to Mile 20. There are naturally no sharp boundaries between these accumulation regions, but these figures indicate the order of magnitude of the winter snow depths. Since these results are supported by measurements from only one season, yearly variations of at least 50% should be taken into account for any surface construction work. Ablation. 8. On the actual Ramp, "continuous" ablation measurements were made during the whole time the party was in the field. If some care is taken, the ordinary method with stakes drilled down in the ice can be used in the Ramp area, but in the firn region this method was not expected to prove successful. Instead, several pits were dug in thi s area at the beginning of the season (as described under "Accumulation") and again around 20 August, after which date extremely little ablation {if any) could have taken place in the upper regions. By comparing the results from these pits, values of summer ablation can be obtained. Inland. On 20 August and 24 August another series of pits were dug along the same route as on 7 ] uly and as close as possible to the same place. The idea was to remeasure the water equivalent down to the previous summer surface, and let the difference between this value and the corresponding value from 7 July represent the ablation in the meantime. Mile 6, 20 August. Density measurements: Depth Density Depth Density Depth Density (em) (g/cm3 ) (em) (g/cm3 ) (em) (g/cm3 ) 12 0.535 45 0.475 75 0.505 25 0.550 60 0.520 95 0.520 Stratigraphic profile: 0 -12 em: Frozen crust; hard; dry; grain size 0.5 to 2 mm. Some larger grains up to 5-6 mm on surface. 12 -70 em: Snow, grain size 0.5-2 mm; moist discontinuous ice lens at 20 em. Con tinuous ice layer at 38-40 em (2-5 em thick). Discontinuous ice layers at 45 em and at 64-65 em. 70 -72 em: Continuous ice layer at top of last summer's surface. 72 -120 em: Grain size 2 mm; hard, dry. Some small pipes. Discontinuous ice lens at 100 em, 1-3 em thick. Top 20 em (72-92), soft. All temperatures at 0.0 C. Net accumulation above 1953 summer surface: 38 em of water, 72 em of snow. Net summer ablation of the same layer: 7 em of water. Depth (em) 10 20 30 Depth (em) 10 20 30 40 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Mile 7, 20 August. Density measurements: Density (g/cm3) 0.525 0.570 0.570 Stratigraphic profile: Depth Density Depth Density (em) (g/cm3) (em) (g/cm3) 40 0.560 80 0.480 so 0.560 90 0.500 60 0.550 110 0.445 0 -7 em: Frozen surface snow. 7 -72 em: Medium-grained snow. 72 em: Late summer surface. 72 -102 em: Slightly coarser (summer snow). 102-145 em: Very coarse-grained. Ice layers recorded at: 27-36 em, a few thin ice layers; 72 em, varies from 1 to 6 em in thickness; 102-145 em, a few thin lenses. The surface at 72 em corresponds to the one at 116 em in the pit of 5 ] uly*. Net accumulation above 1953 summer surface: 40 em of water, 72 em of snow. Net summer ablation of the same layer: 9 em of water. Mile 8, 24 August. Density measurements: Density (g/cm3 ) 0.580 0.600 0.575 0.585 Stratigraphic profile: Depth Density Depth Density (em) (g/cm3) (em) (g/cm3) so 0.590 90 0.515 60 0.530 100 0.510 70 0.475 110 0.485 80 0.505 120 0.515 0-20 em: 20-66 em: 66-106 em: 106-107.5 em: 107.5 -160 em: Frozen snow, 2-3-mm grain size, very hard; 18-19-cm discontinuous ice layer. Uniform snow, grain size 1-1.5 mm, soft to medium hard, moist. Dis continuous ice layers at 26, 30, 33, 41, 46, 54-SS, and 64-65 em. Grain size 1.0 mm, soft, moist. Discontinuous ice layers at 75, 78, 90, 94, and 103 em. Continuous ice layer, which is top of last year's snow. Grain size 3 mm, hard to very hard, dry to moist. All temperatures 0.0 C. Net accumulation above 1953 summer surface: 59 em of water, 107.5 em of snow. Net summer ablation of the same layer: 5.5 em of water. • When the thermocouples at Mile 7 were inspected on 27 August the 1-m thermocouple was found at a depth of 59 em, indicating a drop of the surface of 41 C t ·1. Thi s agrees very well with the difference (44 em) between 116 and 72 em. 32 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Depth (em) 10 30 Depth (em) 10 20 30 40 so Mile 9, 24 August. Density measurements: Density (g/cm3) 0.540 0.560 Stratigraphic profile: Depth Density Depth Density (em) (g/cm3 ) (em) (g/cm3 ) so 0.590 90 0.510 70 0.580 110 0.600 0-13 em: 13 -15 em: 15 -51 em: 51-51Y2 em : 51Y2 -102 em : 102 -104 e m: 104 -160 em: Frozen layer of granular snow, grain size 1-1/2 mm, hard. Discontinuous ice layer. Loosely packed, granular wet snow, grain size 1-1/2 mm. Discontinuous ice layer. Fine granular snow; medium hard, wet. Discontinuous ice layer (old snow surface?). Firn with prominent ice pipes and layers-grain size at 104 em was 2 mm. Net accumulation above 1953 summer surface: 58 em of water, 104 em of snow. Net summer ablation of the same layer: 12 em of water. Mile 10, 24 August. Density measurements: Density (g/cm3) 0.535 0.535 0.535 0.555 0.570 Stratigraphic profile: Depth Density Depth Density (em) (g/cm3 ) (em) (g/cm3) 60 0.570 110 0.465 70 0.535 120 0.525 80 0.570 130 0.500 90 0.530 140 0.475 100 0.495 0-17 em: Snow with grain size 2.5 mm, hard to very hard, dry to moist. 17-38 em: Snow with grain size 1.5 mm, soft, moist. 38-75 em: Snow with grain size 1-1.5 mm, medium hard to hard, moist. 75-87 em: Snow with grain size 2.5 mm, hard, dry to moist. Continuous ice layer at 84-86 em. 87-140 em: Snow with grain size 1-1.5 mm, soft to medium hard, dry to moist. 140 -141 em: Continuous ice layer. 141-170 em: Firn with grain size up to 3.5 mm, very hard, dry. The same surface that was found at 145 em on 7 ] uly was found at 141 em on 24 August, and the ice layer at 85 em in the old pit was found at 84-86 em. Net accumulation above 1953 summer surface: 75 em of water, 141 em of ice. Net summer ablation of the same layer: 11 em of water. Depth (em) 10 30 Depth (em) 8 22 37 Depth (em) 8 17 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 33 Mile 12, 24 August. Density measurements: Density (g/cm3) 0.510 0.570 Strati graphic profile: Depth Density Depth Density (em) (g/cm3 ) (em) (g/cm3 ) so 0.600 90 0.490 70 0.440 110 0.510 0-20 em: Granular snow, grain size 2 mm, hard. 20-57 em: Snow, grain size 1-1.5 mm; soft, moist. 57-61 em: Ice layer, continuous, 1/2 to 4 em thick. 61-105 em: Very wet snow, grain size< 1 mm; soft, discontinuous ice pipes and lenses. 105 -106 em: Continuous, granular ice layer. 106-109 em: Coarse firn > 2 mm, uniform, dry, soft. Hit hard layer at 109 em. Probable (but not very certain) summer surface at 106 em. Net accumulation above 1953 summer surface: 55 em of water, 106 em of snow. Net summer ablation of the same layer: 12.5 em of water. Mile 13, 20 August. Density measurements: Density (g/cm3) 0.490 0.585 0.430 Stratigraphic profile: Depth Density Depth Density (em) (g/cm3 ) (em) (g/cm3 ) so 0.570 107 0.435 73 0.485 124 0.465 92 0.450 1 -7 em: 7-115 em: 115-125 em: Grain size about 3 mm at surface diminishing to 2 mm at depth. This horizon is crust on last winter's snow, frozen (hard). Uniform snow, grain size 1 mm, soft, moist. Ice layers at 15-16, 25-26, 29, and 51-52 em. Very hard; grain size 2.5 mm; dry firn (last summer's snow). Net accumulation above 1953 summer surface: 57 em of water, 115 em of snow. Net summer ablation of the same layer: 1 em of water. Mile 14, 20 August. Density measurements: Density (g/cm3) 0.505 0.550 Depth (em) -28 36 Density (g/cm3) 0.580 0.575 Depth (em)-45 55 Density (g/cm3 ) 0.575 0.605 Depth (em)-67 89 Density (g/cm3) 0.575 0.460 Depth (em)-112 115 Density (g/cm3) 0.440 0.575 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Depth (em) 12 22 32 Stratigraphic profile: 0-17 em: Snow, grain size 2.5 mm, very hard, dry. 17-42cm: Snow, grain size 2.5-3 mm, soft, moist. 42-43 em: Continuous ice layer, 1-2 em thick. 43-78 em: Snow, grain size 0.5 mm, hard, moist. Discontinuous ice lenses at 56, 67, 69, and 71 em (each about 0.5 em thick). 78-87 em: Snow, grain size 0.5-1 mm, very hard. 87-140 em: Uniform snow, grain size 0.5 mm, soft, moist. 140-142 em: Ice layer (summer surface below?). 142 -167 em: Firn, grain size 2 mm, very hard, dry. Probable summer surface at 142 em. Both hardness values above and the Rammsonde profile seem to indicate a summer surface at 87 em. It is not probable, however, that the uniform, fine-grained (0.5 mm) snow between 87 and 140 em has ever been a surface layer. Net accumulation above 1953 summer surface: 74 em of water, 142 em of snow. Mile 15, 20 August. Density measurements: Density Depth Density Depth Density (g/em3) (em) (g/em3) (em) (g/em3 ) 0.475 45 0.520 98 0.530 0.535 60 0.470 0.555 77 0.500 Stratigraphic profile: 0-17 em: Grain size 1-4 mm, hard. 17-97 em: Grain size 1-3 mm, medium hard , dry to moist. Discontinuous ice lens at 44 em. Continuous ice layer at 50-53 em. Varies in thickness from 0.5 to 10 em. 97-113 em: Grain size 1-3 mm, hard to very hard, moist; Discontinuous ice layers at 98-99 and 103-104 em. 113 -127 em: Continuous light-colored ice lens. 127-135 em: Firn, grain size 1-4 mm, very hard, dry. 135 -155 em: Continuous ice layer. 155 -158 em: Slush. Probable summer surface at 127 em. The ice layer at 113-127 em is most probably the same as at 105.5-110 em in the pit dug on 7 July. Assuming that the ice layer at 50-53 em corresponds to the one at 23-25 em (7 July), we find 42.5 em of water equivalent between 53 and 127 em on 20 August, and 39 em of water between 25 and 110 em on 7 July. That seems to be good evidence for a correct interpretation. Net accumulation above 1953 summer surface: 70 em of water, 127 em of snow. Net summer ablation of the same layer: 19.5 em of water. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Depth (em) 10 20 30 40 Depth (em) 10 30 Mile 16, 24 August. Density measurements: Density (g/cm3) 0.510 0.515 0.540 0.575 Depth (em) 55 68 75 85 Density (g/cm3) 0.560 0.455 0.450 0.490 Depth (em) 95 115 Density (g/cm3 ) 0.505 0.470 Stratigraphic profile: Grains 2-3 mm, hard. 0-9 em: 9-9.5 em: 9.5 -24 em: 24-63 em: 63-65 em: 65 -104 em: 104 -106 em: 106-bottom: Thin continuous ice layer. Grains about 1.5 mm, hard. Grains 0.5-1 mm, medium-hard. Continuous ice layer, from 1 to 6 em thick. Grains about 1 mm, soft; a few discontinuous ice layers. (Early fall accumulation?) Continuous ice layer, 1-5 em thick. This probably marks the top of last summer's snow. Grain size 1-2 mm. Hard to very hard near contact, very hard below. Net accumulation above 1953 summer surface: 55 em of water, 106 em of snow. Net summer ablation of the same layer: 7 em of water. Mile 17, 24 August. Density measurements: Density (g/cm3) 0.51 0.55 Depth (em) so 70 Density (g/cm3) 0.57 0.49 Depth (em) 90 120 Density (g/cm3 ) 0.52 0.54 Stratigraphic profile: Grains 1.5 mm, soft, wet. Discontinuous ice layer. 0-14 em: 14 -21 em: 21-29cm: 29-31 em: 31 -65 em: 65 -94 em: 94 -145 em: Firm, dry, grain size 1.5-2 mm. Hard frozen layer. Grains 1.5-2 mm. Hard-packed snow, grains 1 mm, wet. Hard-packed snow, densely packed at bottom, grains 2 mm. Last year's snow is soft at top and then frozen and hard-packed. Grains 3 mm. All temperatures 0.0 C. Net accumulation above 1953 summer surface: 50 em of water, 94 em of snow. No pit dug at this place on 7 July. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Mile 20, 20 August. Density measurements: Depth (em) Density (g/cm3) Depth (em) Density (g/cm3) Depth (em) Density (g/cm3) 10 0.525 so 0.550 90 0.560 20 0.558 60 0.550 100 0.530 30 0.545 70 0.530 110 0.580 40 0.530 80 4 em ice 120 1-2 em ice Stratigraphic profile: 0-7 em: Fine-grained snow, grains 1 mm. 7 -34 em: Coarse-grained, 1.5-2 mm. 34 -93 em: Grain size gradually getting smaller, 1-1.5 mm at bottom. 93 -160 em: Coarse-grained firn from previous year. Ice layers at the following depths: 17 em (0.5-1 em thick), 18 em (0.5-1 em), 34 em (0.5-1 em), 37 em (0.5-1 em), 43 em (0-3 em), 54 em (0-3 em), 77-81 em, 124 em (0.5-1 em), 130 em (0.5-1 em), 139 em (0.5-1 em), and 144-146 em. Summer surface at 93 em and possibly one at 132 em (this could be from early summer 1953). Net accumulation above 1953 summer surface: 50.5 em of water, 93 em of snow. Net summer ablation of the same layer: 6 em of water. S ummary of ablation meas urements inland. In Figure 10 we have plotted the accumulation values obtained in early July and in the latter part of August. The water equivalent above the "1953 summer surface" has apparently decreased in the outer part of the ice cap, as far as about Mile 9; from th_ere on, accumulation has been dominant. Inland from 1V1ile 10 the summer accumulation has been able to keep the snow depth constant, and the figures for the depth of the winter snow accumulation can be used also for the total annual accumulation in this area. The total annual accumulation was 70 em at Mile 6 and Mile 7 and at Mile 8 and Mile 9 just over 100 em. What has been called "the water equivalent above the 1953 summer surface," is not the net accumulation in its strictest meaning. Therefore, it could not be used for regime computations. When the pits were dug on 7 July, there was still a cold wave left in upper snow layers, or it is perhaps better to say that there was a deficit of heat down to a considerable depth. This deficit could not be filled by anything but the latent heat of fusion of the refreezing melt water trickling down from the surface layers (compare page 28). We must therefore find not only the water equivalent of the snow "above the 1953 summer surface" but also the amount of water refrozen at depth. To this should be added the amount of free water·held in the isothermic layer. However, no measurements of free water content were made, so the correction we apply must be considered as a minimum value. As described later in this report, temperature measurements at different levels down to 10 m were made repeatedly during the summer at Mile 7 and Mile 20. The results that we are interested in here are: Mile 7. The mean temperature of the snow between the summer surface at 1.16 m and the thermometer at 10m was -6.6 Con 5 July and ±0.0 C on 27 July (the thermometer at 7.1 m GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 37 registered -0.5 C on 27 July indicating that the zero surface was perhaps not too far down). Mile 20. The average increase in temperature between the summer surface at 0. 96 m and the thermometer at 10 m was 5.8°, and freezing temperatures were still recorded below 4 m. 3 in the snow layer between the 1953 summer surface Assuming a mea n density of 0.6 g/ cm and the 10-m level, we find that 22 em of water had refrozen at Mile 7 and 20 em at Mile 20. This water has all come from the 1953-1954 accumulation, and evidently it should be added to the values of the water equivalent of the remaining winter (and summer) snow, whenever the regime or the ma terial balance of the inland ice is discussed. Figure 11 shows the winter accumulation (same as in Fig. 10) along the route and the total annual accumulation. The 90 em of water "interior accumulation" is here / -------, ' taken into account but, a s 80 / / ' ' , _ pointed out before, not the re/ / ---- freezing of any free wate r re-I ........__ I ,_.A· maining in the snow at the end 60 ~ of the ablation season. l4;/ - V L ; j _ ---------- Another result of re-'0 freezing melt water should per v haps be mentioned at this time. I/ If density measurements are 20 made along a profile in snow on I a high-polar ice cap, i.e., snow I that has never been soaked by 0 2 6 8 10 12 16 18 20 1' mi es from Camp Tuto water, a fairly steady increase accumulation-winter 1953-195'-as measured on or in density can be seen. In an before 7 Ju ly 195'· area like ours, however, such a net accumulation-the whole year 1953-1954-as measured on 20 and 2' August with melt water steady increase should probably refrozen in deeper layers token into account. not be expected. The ice-pipe and ice-layer formation will Figure 11. Accumulation during 1953-1954, II. take place most readily in snow layers only a few meters below the surface, since the heat deficit will be greatest there and conduction from these layers will be partly responsible for heating the snow at greater depths. All this ice will act as a sort of reinforcement in the snow and obstruct the natural settling. This most likely explains the occurrence of very loose firn layers deep as 9 to 10 m. On the Ramp. It is always easier to make ablation measurements in an ablation area than The stakes can be planted in solid ice, and the melt water must either refreeze in the firn region. in the upper layers or else drain off. As soon as the ablation has reached down to ice, there are no longer any problems about what density to use for computing the water equivalent. However, due attention has to be paid to the refreezing of the melt water, and the stakes must be drilled far enough into the ice to be frozen in properly. The ablation measurements were started before any net ablation occurred. Stakes 1-7 and Stake 14 (see Fig. 12) were drilled down on 26 June along a split longitudinal profile on the Ramp. They covered the height interval from 505 to 690 m. The number of ablation (and movement) stakes was increased, first on 13 July when Stake 9 and the profile 10-16 were planted and later on 14 July GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA ~700 /75 /650 625 / _600 _575 --550 ---/,525 / \5oo Figure 12. --------lOo- '19 -----~75 '------------~50--- -----soo--...__ 50- __----425- Ablation stakes, Thule Ramp. when the transverse profile 17-21 was laid out. Stakes 18 and 20 were not planted until 2 days later. Aluminum tubes (diam 1 in., length 3.5-4 m) were used for the measurements and proved to be very satisfactory. They are more durable than bamboo poles, and they do not require such a GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA wide hole as the bamboo poles often do. They were drilled down with a 1-1/2-in. ice auger of V. Schytt's construction. A small, red, numbered pennant was attached to each stake, making it readily identifiable and fairly easy to detect from a distance. The stakes were visited regularly, apd the height of the stake above the snow or ice surface was measured to half a centimeter whenever the surface level was reasonably well defined. Table IV includes most of the ablation measurements from all Ramp stakes except number 14, at the weather station, which will be treated separately. The table gives only the water equivalents of the ablation since the last measurement reported here and the total ablation since the beginning of the season. It is not worth while to describe the computation of water equivalents for each case, but a few examples and some clarifications are necessary. When there is still snow on the ice, the sinking of the snow surface will naturally not tell everything about the melting. Settling within the snow cover and refreezing both within the snow and on top of the ice will always occur. These errors can be eliminated if the density changes are measured, and if the growth of the superimposed ice is followed. This, however, requires a great amount of time-consuming work, and some short cuts can be used without harming the accuracy of the end result. Example 1: On 26 June a snow depth of 89 em was measured at Stake 1 and a few days before (22 June) the mean density close to the stake was 0.492. On 4 August the total ablation amounted to 91 em. That means that the 89 em of snow plus 2 em of ice have melted away. The water equivalent of this will be 89 · 0.492 + 2 • 0.9 = 45.6 em. Thus we know that, whatever settling andrefreezing has occurred, the net ablation on 4 August was 45.6 em. Working backwards from this value using a density of 0.5, we reached a value of 3.1 em for 5 July. We can therefore assume that the 15 em of apparent ablation before 5 July resulted in a net loss of only 3.1 em, while all the rest of the water has refrozen. By using the low density value of 0.5 for these computations, we have also accounted for a certain amount of refreezing during the whole month of July. Example 2: On 26 June the snow depth was measured to 47.5 em at Stake 4. On 12 July, 8 em of snow remained but the surface had been lowered by only 28 em. Therefore, 11.5 em of superimposed ice must have been formed in the meantime. On 26 June the water equivalent of the snow cover was 23.2 em and for 12 July we get 0.9 . 11.5 + 0.5 · 8 = 14.3 em starting from the same ice level. The net ablation was therefore 23.2-14.3 = 8.9 em up to 12 July. Example 3: The snow depth at Stake 7 was measured to 87.5 em on 26 June, and all this had melted off by 21 August. Using the same density (0.492) as before, we obtain a net ablation of 43.1 em for this period, and we have one "fixed point" in our computations. We also know from our observations that 6.5 em of superimposed ice formed between 26 June and 16 July. Together with the apparent ablation of 48 em of snow, this will give us a net ablation of 20.7 em-the next "fixed point." By the same method, we still get a total net ablation of 20.7 em for 31 July. The apparent ablation (lowering of the surface) was 7 em of snow between 16 July and 31 July, but the melt water has added another 9 em to the previous layer of superimposed ice. The accumulation during these 15 days has exactly balanced the runoff. At the two cross-profiles, measurements were not started until the middle of July. After comparison with the ablation values from Stake 14, the total ablation before 13 July has been put GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA at 30.0 em for all Stakes 10 through 16. The variations a ong the profile were considerable during the course of the summer, but comparison shows that the rate of melting was more similar in the early part of the season (with snow or superimposed ice on the surface). At Stake 9, the ablation before 13 July has bet;n given a value of 25 em, a value supported by the measurements from Stakes 2 and 14. For Stakes 17 through 21, ablation values before 14 or 16 July have been computed by comparison with the values from Stakes 4 through 7. Figure 13 shows the ablation at all the stakes on the Ramp 010 from the beginning of the ablation 01l 120 season until 28 August, when the 016 0 15 party left for Thule. Thanks to?,~ helpful assistance from 1st EATF, 100 I~ six more sets of measurements ~ \ were made during the first half of •3 v September, and the results are 80 ~ recorded in the table. The abla tion after 28 August amounted ~· to only a few centimeters, and 4 21 60 ""17 would not change the look of the @18 ~ ablation curve appreciably. 5 7 -....:.. The most conspicuous feature of the ablation curve is the maximum of 110 em at 20 around 550 to 570 m above sea level. A quick glance at the accumulation curve (Fig. 9) will 500 550 600 650 700 give the explanation for this. meters above sea level Very little snow had collected Figure 13. Ablation of the Thule Ramp. End of here, and after a few days of June-28 August 1954. ablation the ice surface was exposed to the intense radiation. Much more heat could thus be absorbed, and the rate of melting could exceed that at lower levels in spite of slightly lower temperatures. The next thing to explain is the considerable spread along the profile 10-16, with Stake 3 included in the discussion. Here also the cause is differences in the albedo from one place to the other. Stake 3 was surrounded by superimposed ice through the first week of August, and even after that the surface was remarkably free from dirt. This results in high albedo and low ablation. An analysis of the measurements along the profile itself shows that variations very much depend upon when they were made during the summer. Stakes 15 and 16 for instance showed lower ablation values than Stake 14 during July, but appreciably higher during August. At No. 10, ablation during the middle of July compared very well to ablation at No. 14, but later it was up to 58% higher. If all these stakes are plotted to exact location on an air photograph from 9 August, it will be found that the stakes with high ablation values are all located in the darkest areas, while the others fall on lighter surfaces. Moving up to the higher stakes, we can see from the table that ablation of ice took place at Stakes 19 and 21 from the very start of the measurements. Consequently they show the highest Table IV. Ablatioa Measurements on the Thule Ramp a ,. abla tion, em or water, since last (reported) observations A ,.. total ablatio n since beginning of the season Stake !July 5July 10 july 13 july* 16 July* 22 july 25 July 28 july 31 july 2 Aug. 4 Aug. 7 Aug. 10 Aug. 14 Aug. 16 Aug. 19 Aug. 21 Aug. 25 Aug. 28 Aug. A . A . A A . A . A .A . A . A . A . A . A . A . A . A . A . A . A . A I 0 3.1 3. 1 8.0 II. I 16.0 27.1 2.2 29.3 1. 8 3 1.1 1.8 32.9 6.8 39.7 u 4 1.5 4. 1 45 . 6 7.7 53.3 5.9 59.2 No. 15.7 74.9 4.0 78.9 3.6 82.5 0.9 83.4 2.3 85.7 4.5 90.2 103.3 2 2.5 1.0 3.5 5.0 8.5 21.2 29.7 1.2 30.9 0.2 31.1 1.1 32.2 !.U 47.3 5.8 53 . 1 2.7 55.8 5.0 60.8 9.9 70.7 14.4 85.1 0.0 85.1 1.7 96.8 -0.8 96.0 2.0 98.0 5.3 79.6 2.3 81. 9 4 .5 86.4 3 1.6 3.2 4.8 6.3 11.1 13.0 24.1 3.0 27.1 0.5 27.6 1.5 29.1 !.hQ 40.1 6.3 46 .4 3.6 so.o 6.3 56.3 4.0 60.3 10.4 70.7 3. 1 73.8 s.s 79.3 0 .3 4 0.0 0.8 0.8 7.6 8.4 5.4 13.8 3.3 17.1 0.6 17.7 1.5 19.2 5.4 24.6 ~29.1 4.5 33 .6 7.6 41.2 2.3 43.5 9.9 53.4 4.1 57.5 1.4 58. 9 0.5 59.4 2.2 61.6 3.2 64.8 5 0 . 0 0.0 2. 0 2.0 10.5 12.5 2.7 15.2 0.0 15.2 0.0 15.2 2.8 18.0 ·0.4 17.6 7.7 25 .3 2.2 27.5 ----·-· 10.8 38.3 ---·-·· 2. 7 41.0 0.0 41.0 1.3 42.3 4.5 46.8 6 0.0 -1. 2 -1.2 7.3 6.1 11.5 17.6 0.5 18.1 -0 . 2 17.9 1.3 19.2 §,] 25.9 10. 8 36 .7 3.2 39.9 4.9 44.8 3.6 48.4 9.9 58.3 4.0 62.3 1.2 63.5 1.1 64.6 5.4 70.0 2.0 72.0 0.9 43.1 1.7 44.8 1.1 45.9 7 0 .0 1.5 1.5 2.5 4.0 15.5 20.7 -2.2 18.5 -0 .7 17.8 -0.7 17.1 3.6 20.7 2.1 22 .8 2.6 25.4 2.9 28 .3 ---•··· M 36.7 ---·---s.s 42.2 .--8.1 102 .0 1.8 103.8 2. 7 106.5 2.6 109.1 10 N..Q 3.6 33.6 ... --·· 6 .3 39.9 8.5 48.4 15 .8 64.2 6.3 70.5 5 .9 76.4 9.0 85.4 6.7 92.1 15.3 107.4 2.7 110.1 6.3 116.4 -------10.3 126 . 7 3 .2 129.9 11 N..Q 9.9 39.9 3. 7 43.6 0.2 43 .8 0.6 44.4 10.4 54.8 4.9 59 .7 3 .6 63.3 8. 1 71.4 7.2 78.6 10.8 89.4 3.6 93.0 4.5 97.5 ------9 25.0 7.7 32.7 7.6 40 .3 2.3 42 .6 4.5 47.1 12.6 59 . 7 2.2 61.9 8.6 70.5 7. 7 78.2 8.5 86.7 7.2 93.9 ·-· 2.7 100.2 5 .3 105.5 12 30.0 8. 1 38.1 3. 1 41.2 0.5 41.7 7.2 48.9 12.2 61. 1 4.0 65. 1 0.0 65.1 7.2 72.3 9.0 81.3 11.7 93.0 2.7 95.7 5.4 101.1 ... ·-·· 3.3 104.4 1.9 106.3 13 N..Q 9.0 39.0 4.5 43.5 2.3 45.8 7.2 53.0 13.9 66.9 5.8 72.7 4 .5 77.2 9.0 86.2 5.0 91.2 12.6 103.8 1.4 105.2 9 .4 114.6 ... ----3.6 118.2 4.0 122.2 ... IS 30.0 7.2 37.2 1.8 39.0 0 . 0 39.0 1.8 40.8 I S. 7 56.5 4.5 61.0 1.8 62 .8 9 .0 71.8 7. 2 79.0 11.7 90.7 5.0 95.7 7.6 103.3 ----5. 0 108. 3 7.2 115.5 ... 16 30.0 0.0 30. 0 7.2 37.2 2 . 7 39.9 4.5 44.4 14.0 58.4 5.8 64.2 5.0 69 .2 0.4 69.6 14.4 84.0 14.4 98.4 5.0 103.4 6.7 110.1 ----3.2 113.3 3.5 116.8 17 16.3 -2 .7 13.6 ... · ··-0.6 14.2 2.6 16.8 4.0 20.8 5.0 25.8 3.6 29.4 4.0 33. 4 14.0 47.4 3.2 50.6 ---5.4 56.0 .... 0.9 56.9 2.4 59.3 18 16.9 -3 .6 13 .3 ---.... 0.8 14.1 2.8 16.9 -2.0 14.9 -1.4 13.5 7.3 20.8 6.3 27.1 12.6 39.7 1.8 41. 5 4.6 46.1 -0.4 45.7 3.5 49.2 2.7 51.9 19 16.2 -0. 4 15.8 ... ·· ·-3.1 18.9 6.8 25 .7 3. 1 28.8 7.2 36.0 5.0 41.0 2.2 43 .2 13.5 56.7 -1.0 55.7 8 .6 64.3 0.5 64.8 2.3 67.1 3.6 70.7 20 13.9 -5.0 8.9 ... --·-1.4 10.3 2.6 12.9 0.4 13 .3 3 .8 17.1 4 .0 21.1 3.2 24 .3 9 .6 33.9 1.0 34.9 7.8 42.7 0.9 43.6 4.1 47.7 3 .6 51.3 2 1 17.2 0.0 17.2 ... ·-·--1. 0 16.2 3.3 19.5 3.6 23. 1 8.1 31.2 5.0 36.2 3 .6 39. 8 13.9 53.7 4.0 57.7 1.4 59. 1 -1.0 58. 1 3. 7 61.8 0.0 61. 8 IO Seol. . A 0.4 96.5 -0.4 107.3 0.3 92.6 0.6 71.7 0.0 47.4 4. 9 76.6 0.0 48.6 0.4 114.5 -0. 2 132.9 1.0 113.8 1.8 113.7 -0.1 123.3 -{) . 6 118.9 0. 8 119.1 -0.3 64.8 +0.3 51. 3 0.9 72.7 0.0 51.7 0.0 63.9 15 Seot. . A 0.4 96.9 0.0 107.3 0.0 92.6 0.0 71.7 -0.8 46.6 0.0 76.6 -3.0 45.6 -0 .2 114.3 -{), I 132.8 -1.8 11 2.0 2.5 116.2 0. 7 124 .0 -{),1 118.8 -0.5 118.6 0.5 65.3 -0.5 50.8 0.2 72.9 -1.2 50.5 0.1 64.0 C) r > () 0 r 0 C) c; > r z < ~ en s ~ > ~ 0 z en z ~ :I: c:: r ~ ::0 > :: '"0 ~ > ~ 1 Sept. A . 0.0 90.2 0.2 103.5 0.5 0.8 -0.1 0.0 1.5 0.1 1.6 -0. 7 0.9 1.4 0.6 86.9 65 . 6 46 . 7 72 .0 -0.3 47.4 1.0 110.1 1.1 131.0 2.6 108 . 1 3 .3 109.6 1.2 123.4 0.6 116.1 116.9 60.9 6 Sept. . A 5.9 96.1 4.2 107.7 5.4 5 .5 0.7 1.2 4.0 114.1 2. 1 133.1 4.7 112 .8 2.3 111.9 0. 0 123.4 3.4 1.4 4 .2 51.2 -0.2 71.6 0.2 52.7 -1.0 62.4 1.5 92.3 71.1 47.4 71.7 48.6 119.5 118.3 65. 1 5 1.0 71.8 51.7 63.9 • See page 40 for interpolation o r fi rst val ues at Stakes 9 to 16 and 17 to 21. Note: An unde rlined fi gure indicates the fir st observ at io n with ice surface. ~ ...... 42 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA ablation values. Of all these stakes, the snow stayed longest at No. 18 (see the table), and the ablation was lowest here. With all deviations explained qualitatively, even if not quantitatively, we can state that the curve in Figure 13 gives a representative picture of the ablation on the Thule Ramp during the summer 1954. Other winters may give different accumulation, and weather conditions during other summers may cause more or less ablation, but as long as there is a hump just below the 550 curve, and as long as katabatic winds blow from the ice cap, the general shape of the ablation curve will persist. Detailed investigations at Stake 14, the weather station. Stake 14 was located near the Ramp weather station, and was therefore measured every time the station was visited. Table V shows the results. Relation between Ablation and elev. meters number of days stake no above sea level with ice surface Meteorological Factors. 1 505 28 14 569 so 63 3 28 9. The meteorological ob ' 5 681 23 servations made on the Ramp are 100 > ./ 1 not sufficient to work out a com/ plete relationship between abla / / tion and meteorological factors,eo I ----as has been done by Sverdrup on Isachsen's Plateau* or by Wallen ~ / / ~ on the Karsa Glacier**· The ob 60 ,--servations do allow us, however, 1/ / v to separate the influence of the / / two main factors, radiation and '0 / convection, assuming that evap / / _...-' 1---/ ..........--r---oration and/ or condensati on / ~ are negligible, an assumption / v I .21) --- '--1-1--../ that is rather safe to make inrlv this case. /--: ~v 26 29 1 5 1 0 15 2 0 2 5 30 1 5 1 0 15 20 25 30 Let us first look at the July August total amount of heat that has been used"by the glacier during Figure 14. Ablation, in em of water, at selected stakes on the summer, either for increasing Thule Ramp during summer 1954. the ice temperature or for melting the surface layer. Our temperature measurements show that on 6 July the average temperature in the upper 10m was -10.7 C, and that on 28 August, the average down to the same level (now only 887 em below the surface) was -8.4 C. That means that the heat deficit of the ice has decreased by 10.7 x 1000 x 0. 9 x 0.49 8.4 x 887 x 0.9 x 0.49 = 1433 ly . Meanwhile 113 em of ice have melted, which means a heat consumption of 8136 ly. Furthermore, 7.5 em of new snowfall was recorded during summer blizzards and 10 em seems a very reasonable estimate for the new snow that melted before it was recorded. Melting of these 17.5 em required about 500 ly. H. V . Sverdrup, "Scientific results of the Norwegian-Swedish Spitsbergen expedition in 1934," Geogr. Annaler, Part IV, vol 17 (Stockholm, 19 35), p 3-4 . •• C. C . Wallen, "Glacial-meteo rol o gi c al investiga tion on the Karsa Glacier i n S w e di sh Lapp l and, " Ceogr. Annale r ( 1948-49). GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The total heat transferred to the glacier will thus be 1433 + 8136 +500 cal/cm2 , which, with attention paid to possible errors, sums up to 10,000 cal/em 2• To simplify the calculations, we will now make the approximation that the ratio between heating and melting is constant during the whole summer, so that 14% of the consumed heat f,Oes to increasing the ice temperature and 86% goes to ablation*. The incoming radiation from sun and sky was recorded at the Ramp Station (Table II; Fig. 3). In our treatment of the ablation we will confine ourselves to the time from 6 ] uly to 28 August, during which Stake 14 recorded melting of ice and not of snow (except for some new snow fallen during the summer). Since the surface around Stake 14 was fairly free from dirt and either frozen or sprinkled with a light cover of newly fallen snow during part of the summer, we will use 0.50 as a probable mean value of the albedo of the ice. According to as yet unpublished radiation measurements from Antarctica, the outgoing radiation from our ice surface should be very close to 0.130 l y I min (equivalent to 187 ly / 24 hr) for perfectly clear sky. For days with cloud cover, the outgoing radiation is lower, and the ratio of measured actual radiation to maximum, clear sky radiation has been used as a reduction factor. Table VI shows the radiation balance The "maximum radiation" has been obtained from Figure 3. for] uly and August. During these two months, about 5000 l y were gained by the ice and used for heating and melting. The balance is positive until the end of August; after that time the outgoing radiation will be in excess on clear days. Table V. Ablation at Stake 14 a = ablation since last observation (em of water equivalent) A = total ablation since 26 June (em of water equivalent) Month -- Date - a -- A -- Month --- Date - a -- A -- Month --- Date - a -- A -- June 26 started ] uly 23 0.2 40.1 August 12 2.2 78.2 29 0.4 0.4 24 0.0 40.1 13 5.4 83.6 july 1 3 2.4 0.2 2.8 3.0 25 26 0.0 0.3 40.1 40.4 14 16 3.6 1.8 87.2 89.0 5 -0.2 2.8 27 4.6 45.0 18 5.9 94.9 10 10.2 13.0 28 0.9 45.9 19 1.3 96.2 12 9.9 22.9 29 3.1 49.0 20 -0.4 95.8 13 5.0 27.9 31 10.4 59.4 21 -0.5 95.3 14 4.5 32.4 August 2 4.5 63.9 22 2.7 98.0 15 2.2 34.6 4 0.9 64.8 24 1.9 99.9 16 0.9 35.5 5 2.7 67.5 25 -1.2 98.7 18 3.1 38.6 7 4.5 72.0 27 2.5 101.2 19 0.9 39.5 8 5.4 77.4 28 0.9 102.1 20 1.4 40.9 10 -0.9 76.5 22 -1.0 39.9 11 -0.5 76.0 s inc e th e temperature gra dient • In reality the percentag e u sed fo r heating i s slightl y hi gher in the earl y part o f the seAson, below the surface is greate r at th a t ti me . GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Table VI. Radiation Balance on the Thule Ramp (ly) Maximum Total Date Radiation Incoming Absorbed Outgoing Net Gain* Net Gain July 800 408 204 95 109 109 2 790 782 391 185 206 315 3 790 784 392 185 207 522 4 780 780 390 187 203 725 5 780 347 174 83 91 816 6 770 807 404 187 217 1,033 7 770 775 388 187 201 1,234 8 760 740 370 182 188 1,422 9 750 752 376 187 189 1,611 10 740 408 204 103 101 1,712 11 730 500 250 128 122 1,834 12 720 234 117 61 56 1,890 13 720 355 178 92 86 1,976 14 710 435 218 115 103 2,079 15 700 671 336 179 157 2,236 16 690 676 338 183 155 2,391 17 680 418 209 ll5 94 2,485 18 680 450 225 124 101 2,586 19 670 274 137 76 61 2,647 20 660 425 213 120 83 2,730 21 650 323 162 93 69 2,799 22 650 459 230 132 98 2,897 23 640 572 286 167 119 3,016 24 630 695 348 187 161 3,177 25 630 605 302 179 123 3,300 26 620 648 324 187 137 3,437 27 610 470 235 144 91 3,528 28 610 370 185 113 72 3,600 29 600 590 295 184 111 3, 711 30 600 603 302 187 115 3,826 31 590 209 105 66 39 3,865 August 1 580 455 228 147 81 3,946 2 570 326 163 107 56 4,002 3 560 192 96 64 32 4,034 4 550 399 200 136 64 4,098 5 540 544 272 187 85 4,183 6 540 216 108 75 33 4,216 7 530 138 69 49 20 4,236 8 520 161 81 58 23 4,259 9 520 444 222 160 62 4,321 10 510 464 232 170 62 4,383 11 510 445 223 163 60 4,443 12 500 476 238 178 60 4,503 13 490 457 229 174 55 4,558 14 480 439 220 171 49 4,607 15 480 493 247 187 60 4,667 16 470 433 217 172 45 4,712 17 460 331 166 135 31 4,743 18 450 498 249 187 62 4,805 19 440 386 193 164 29 4,834 20 430 457 229 187 42 4,876 21 420 422 211 187 24 4,900 22 410 420 210 187 23 4,923 23 400 361 181 169 12 4,935 24 390 395 198 187 11 4,946 25 380 362 181 178 3 4,949 26 370 206 103 104 -1 4,948 27 360 348 174 181 -7 4,941 28 350 342 171 183 -12 4,933 * Net gain= absorbed radiation minus outgoing radiation. Note: Maximum outgoing radiation 0.130 ly/min = 187ly/24 hr. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 45 We have analyzed the ablation during certain selected periods and listed the different ele ments in Table VII. Table VII. Ablation during Certain Selected Periods From To Period lOOa . 100ac -a-' -a- Date Hour Date Hour (hr) A a t I i i a a. ac ' July 5 1430 ] uly 10 1430 120 10.2 2.0 1.6 896 179 154 1.9 0.1 93 7 14 0940 16 1045 49 3.1 1.5 3.0 263 129 111 1.4 0.1 92 8 19 0800 20 1340 29.7 1.4 1.1 0.2 126 102 88 1.1 0.0 100 0 26 0835 27 1710 32.6 4.6 3.4 2.0 247 182 156 1.9 1.5 56 44 28 1305 29 1700 28 3.1 2.7 2.2 155 133 114 1.4 1.3 52 48 August 4 0955 August 5 0830 22 . 6 2.7 2.9 3.2 47 so 43 0.5 2.4 17 83 5 0830 7 1030 so 4.5 2.2 2.7 133 64 55 0.7 1.5 32 68 11 0805 12 0830 24.4 2.2 2.2 3.9 60 59 51 0.6 1.6 15 85 12 0830 13 0940 25 .2 5.4 5.1 6.6 49 47 40 0.5 4.6 10 90 13 0940 14 0833 23 3.6 3.8 5.6 39 41 35 0.4 3.4 11 89 14 0833 16 0835 48 1.8 0.9 3.7 107 53 46 0.6 0.3 67 33 21 1040 22 1650 30.2 2.7 2.1 2.2 84 67 58 0.7 1.4 33 67 22 1650 24 1900 50.2 1.9 0.9 2.3 30 14 12 0.2 0.7 22 78 27 0908 28 1600 31 0.9 0.7 2.7 59 46 40 0.5 0.2 71 29 A = ablation (em of water) during the whole period, a = ablation per 24 hr, t = mean temperature during the period (°C), I = absorbed incoming radiation minus outgoing (= net gain), = net gain of radiation per 24 hr, t a = radiation used for melting (= 86% of i), ai = ablation caused by radiation (em), ac = ablation from factors other than radiation (em). The values (a) of ablation caused by convection are plotted in Figure 15. Since the convectional influence has been plotted as a function of air temperature only (as measured in the weather shelter), a great spread should be expected. The pe-5 em water riods were selected so that, as far as is known, no accumula / ·0 tion took place in the meantime, 4 but the low ablation (0.3 em) at 3.'f> for instance, can possibly be a result of accumulation that 3 was never recorded. That value, and a few others, are ' 3.0 also bound to be of low ac 2 curacy due to difficulties in 6.0 ?·O v / .5 /. reading the height of the stake ,.3.0 above the "not very" flat sur' 40. ./ face. To give the reader an y impression of the reliability 1.0 • 2.( of the different observations, -- od of July 20 to August 2S. Stakes 1, 18, and 19 w .J w 0 13 showed a rise of only 0.1 m and at the same time 0.3 • 9 • 12 ~ 14• • 16 were the stakes showing the least amount of hori• 2 w tal movement. A plot of horizontal vs vertical "' z • 3 movement made for each stake except 21 (Fig. 26) .. u 0.2 • 17 • 5 ::z::: 07 shows a slight correlation between horizontal and • 4 vertical movement. o 6 18• • I 0 . 1 01 9 The vertical movement amounted to about 0 20 2S% of the total summer lowering of the ice sur face by melting and runoff (ablation). OL-~o--~-o.2. 4~-~~~ The pos~~-~-o~-o. 6~-~-o. a~~ sibility should be considered that the yearly CHAN GE IN Y COORDINATE ( METERS) vertical motion may exceed the yearly ablation so that the net effect is one of advance during Figure 26. Relation between horizontal and vertical movement for the ice movement stakes at Thule the year. Resurveying the stakes in 19SS may Take-off from July 20 to August 25. demonstrate whether this is so. It may be pos sible to contour the vertical motion and discover which portions of the area are rising most rapidly. The line of stakes numbered 10 to 16 and Stakes 2, 3, and 9 have risen the greatest amount (Fig. 26), and these stakes are immediately back of the very prominent shear zone (Fig. 28) which marks the presumed contact between the active and the stagnant zone. The ice close to the stagnant zone is sheared upward the farthest because it is under pressure from the rear and can move for ward horizontally against the stagnant zone only with difficulty. Results of relative ice movement studies. A small moraine, 100 m long by 3-6 m wide and parallel to the ice margin, lies approximately halfway between Stakes 7 and 20. A row of six stakes was set into the ice, crossing the moraine at right angles and extending out SO m on either side. During the summer no significant relative horizontal displacement was noted, nor was there any significant vertical displacement, except for a doubtful 3-mm upward movement of the three stakes on the east side of the moraine. A similar row of 22 stakes was set in the ice in the vicinity of Stake 9, where an extremely Again no signifi pronounced shear pattern suggested that active movement might be taking place. cant horizontal or vertical movement was noted between the stakes. 68 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA If such measurements are to be made in the future, the lines of stakes should be several hundred meters long and should extend between Stakes 1 and 2 or across one of the moraines at the contact of the active and the stagnant zone. It may then be possible to measure relative movement and discover the distribution of such movement at the contact. Results of Blue-Ice movement survey. A survey of four movement stakes was made in the Blue Ice area south of the Moltke Glacier on July 16 and August 17 from a base line on a nunatak. These stakes were set across a tributary glacier which flows west between the base-line nunatak and a snow dome. This tributary joins the main tributary glacier which drains the Blue Ice basin and flows north to join the Moltke Glacier. Stake 22 was on a nearly stagnant shelf of ice adjoining the Meters Scale for Stoke Movement nunatak on the south side, while Stake 24a was out in the center of -----------24o the glacier. As was expected, the 4000 movement was most rapid in the center and amounted to 5 m in one month (Fig. 27). The data are tabulated in Appendix A and pre ~24 dicted angles for 1955 are given in Appendix B. 3000 Vl a: w I w ::1! Ice structure. w I- 25. Active zone. The ac z ~23 <( tive zone is defined in this report 0 a: 2000 as that portion of the area that is 0 u 0 moving actively. This zone in > cludes the entire slope with the exception of a narrow stagnant 22 t ' zone 400 to 500 m wide at the very margin of the ice. The charac 1000 teristic feature of the outer margin of the active zone shows up very clearly on the aerial photographs as a pronounced banding in the ice (Figs. 28-31). These bands are the surface expression of a N Bose Line 1 W layering in the ice that dips very ~---------b~----------~,0~0~0----~'-----~20~0~0----~ steeply at angles greater than X COORDINATE {METERS) 75° away from the edge of the ice. Figure 27. Generalized map showing positions (numbered The layers vary in thickness from dots) and movement of stakes in the Blue Ice area from a millimeter to more than a meter july 17 to August 17. Amount of horizontal movement is exaggerated 200 times. and are composed of different kinds of ice. Some layers are of clear ice, others of bubbly ice. They can be dirty or clean, coarse-grained or fine-grained. This layering is a result of the moving ice being forced to shear up over the stagnant ice ahead. The maximum amount of shear should take place near the contact with the stagnant zone. Evidently, the shears along this contact usually extend down to the bottom of the glacier, so that morainal material is dragged up to accumulate at the surface as the ice melts downward. In the areas where no moraines have formed at the contact between the two zones, the shearing is still very pronounced, A tentative reason for the lack of such moraines in the Thule Take-off area is suggested by the gravity meter measurements of ice thickness made by Mr. David F. Barnes of the United States GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA These measurements indicate that, near Thule Take-off, the ice in the areas Geological Survey. lacking moraine is especially thick because of valleys in the bedrock under the ice. Hence, the shears at the contact between the stagnant and the active zones are less likely to extend to the bottom of the glacier. The actual answer to the problem is undoubtedly more complicated and may relate to availability of morainal material or rates of advance of the ice. Figure 32, taken at a point 4 m north of Thule Take-off, shows the contact of the active and the stagnant zones. The shears actually dip far more steeply than the photograph indicates because the cliff on which they are exposed is nearly parallel to the shears. The shears were ne ver definitely seen on the ground at distances greater than 500 m from the 17 0 1$ 3 0 0 I"' 0 13 0 /2. 0 II 0 /0 0 Center of area studied showing large moraine and position of movement stakes. TheFigure 28. white patch is the remainder of the snow and ice accumulated during the previous winter. The margin of the ice is immediately below the edge of the photograph. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Figure 29. Margin of the ice at Thule Take-off. contact between the two zones or from a patch of moraine on the ice. There is a strong indication that much of the banding inland from the contact may be the result of nearly horizontal annual layering of the accumulated snow and ice from each winter. Figure 28 shows a large white patch of snow and ice between Stakes 3 and 6, which is all that remains of the deposition from the previous winter. The fact that the banding appears to be somewhat concentric to this snow patch is GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Figure 30. Area immediately south of and adjoining Figure 28. The dark line is the heavily sheared contact between the active ice and the stagnant ice, which appears as a narrow strip at the bottom of the photograph. rather suggestive of annual layering. In addition, these bands are so diffuse that they are virtually impossible to identify from the ground. Immediately north (toward the moraine) of Stake 9 (Fig. 28), the rapid variation in thickness of the bandsand the fact that they are widest when curving most rapidly is also very suggestive of folded annual layering. Further study in the field is necessary GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Figure 31. Area overlaps Figure 30. Banding below the moraine is caused by gently folded annual layering in the ice. The ice margin is immediatel y below the bottom of the photograph. to settle this question. Some of the more prominent bands are shown as dashed lines on the map. The various shear bands melt at different rates so that alternating ridges and valleys are formed. The maximum relief in the area studied was about 1.5 m in the vicinity of Stake 9. The melt-water GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 73 Figure 32. Two views of the sheared contact between the active and stagnant ice, 4 mi north of Thule Take-off. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA streams on the surface of the ice flow across these ridges as they form and erode them into a series of hummocks (Fig. 33). Figure 33. Ice hummocks caused by differential melting and stream erosion of shears in the vicinity of Stake 9. Several cores of ice were collected with an ice auger from the well-sheared zone of Stake 9. Various thin sections with a thickness of 1 mm or less were sawed from these cores and studied between two crossed pieces of Polaroid. The grain size in individual bands was fairly constant but there was a considerable variation between different bands. Average grain sizes varied from 2 to 10 mm. Grain outlines were rather angular and the texture as a whole was interlocking. In a few of the shears, especially those of small average grain size, the grains were distinctively tabular in shape, the long dimensions averaging perhaps three times the thickness. The tabular grains were invariably parallel to the shear planes. More than half of the bands did not show any obvious preferred crystallographic orientation within the shears. In a few bands, however, over SO% of the grains would turn black simultaneously when the section was rotated between the crossed Polaraids. This always occurred when the lines of intersection of the shears with the thin section were parallel to the plane of polarization in one of the Polaroid sheets. In addition sections cut parallel to these shears had more than 50% of the grains in complete extinction during a full 360-deg rotation of the section. The only satisfactory explanation of the above facts is that these particular shears must have the c-or main axes of most of the grains oriented perpendicular to the layering. The orientation and shape of the grains suggest a similarity with foliated metamorphic rocks such as gneisses and schists. Elongated bubbles occur in many of the shears. These bubbles are often 1 em long and about 0.03 em wide. They plunge down the dip of the shears and so are nearly vertical. They often GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 75 branch and bend somewhat because these bubbles only occur at grain boundaries. The bubbles were probably once equidimensional and have attained their present shape because of the shearing action of the ice. Most of the bands consist of very clean ice. Rarely is a band light tan in color because of silt and clay suspended in the ice. In a few bands small 1-2-mm clots of silt were included between the grains. The only crevasses observed were at the crest of the slope near Stake 21 and also south of Stake 5. During the summer these crevasses reached a maximum width of 15 em and had a minimum length of at least 100 m. Cracks were common throughout the active zone. They were undeformed and frozen together, and thus were recently formed by minor movements of the ice. The cracks varied in dip but generally had a strike at right angles to the margin of the ice. A point or contour diagram such as those used by structural geologists for joints would give a better indication of any systematic pattern to these cracks. Frost cracks were found throughout much of the active zone. These may form when contraction of the ice during cold weather causes open cracks in the ice. The cracks then fill with melt water which freezes. Layering is common in the ice filling these cracks because repeated cracking, filling, and freezing apparently take place once the original crack forms. The largest crack seen was 20 em wide. Many cracks can be traced for at least SO m. In the vicinity of sheared zones, the cracks tend to strike at right angles to the shears. This is presumably because any tensional stresses from sudden ice contraction in a direction normal to the shears can be relieved by small movements in each shear so that no parallel cracks will form. Also the movement of the ice at right angles to the shears will effectively prevent any tensional stress from ac cumulating in this direction. Stagnant zone. Nearly horizontal layers of snow and ice are characteristic of the stagnant zone. These are sometimes contorted (Fig. 34) and occasionally faulted slightly (Fig. 35). The layering is apparently the result of annual deposition of snow, the dirty bands being formed by the accumulation of wind-blown material during the summer melting season. At the left end of the cliff in Figure 35, the upper 3 m is composed of firn snow which has evidently been deposited under conditions similar to the present because there is a layer of fine gravel at the bottom of this firn which must have been washed down from the moraine above. Three more sandy bands 1-2 em wide are found in the next 4.5 m, but below that such material is found only occasionally. It is thus not clear whether the ice lower down formed from the accumulation of snow under present condi tions or whether it formed under very different conditions before the moraines existed here. Fur ther field work is necessary to answer this question. Thin sections of ice from the cliff had no shear banding or elongated bubbles. Interlocking texture was very poorly developed and sometimes absent. No evident crystallographic orientation was noted. Grains varied from 2 to 8 mm in size. The faultlike features on the far side of Lake Tuto (Fig. 35) dip 45° toward the ice cap. Offsets of as much as 20 em were noted but in all cases the lower side has moved up relative to the upper side of the "fault." Thus, this is not the same sort of movement as the overthrusting suggested for the active zone. In detail these features often branch and undulate somewhat, in a manner that is very similar to a vein in bedrock. They seem to be associated with anticlinal or upward-arching folds in the ice. Two other characteristics of these bands are the deep blue color, since there are virtually no included air bubbles, and the very large grain size, which is commonly from 2 to 10 em. The origin of the "faults" is not satisfactorily explained. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Figure 34. Cliff in the stagnant zone 10 mi northwest of Thule Take-off. The contorted bandin g is clearly seen. Figure 35. Cliff in the stagnant ice seen across Lake Tuto from Thule Take-off. Note the contorted strata and the faultlike features which show as dark lines dipping diagonally down to the right at a 45° angle. The banding in the ice of the stagnant zone sometimes can be seen very clearly. The lower half of Figure 31 shows a pattern of curved bands caused by gentle folding of the originally flat-lying layers. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 77 APPENDIX A MOVEMENT STAKE DATA FOR THULE TAKE-OFF AND BLUE ICE Coordinates of Movement Stakes-Thule Take-off Bench mark N is origin, N-S is positive direction of abscissa (all measurements in m). August 2-4 August 23-26 Stake July 2-6 July 20 605.41 605.42 1 X 605.41 605.41 792.27 y 792.29 792.29 792.28 854.14 854.13 2 X 854.20 854.16 1,312.53 y 1,313.07 1,312.83 1,312.69 1,120.93 1,120.83 3 X 1,121.03 1,121.07 1,871.07 1,870.86 y 1,871.61 1,871.36 1,469.32 4 X 1,469.63 1,469.34 1,469.35 2,598.58 2,598.20 y 2,599.61 2,598.65 1,803.42 5 X 1,803.68 1,803.55 1,803.47 3,297.35 y 3,298.89 3,298.02 3,297.76 1,248.70 1,248.63 6 X 1,248.90 1,248. 75 2,534.40 y 2,535. 71 2,535.04 2,534.75 1,474.71 7 X 1,474.87 1,474.67 1,474.60 3,485.75 3,485.49 y 3,487.06 3,486.00 1,197.16 1,197.25 1,197.21 9 X 1,066.72 1,066.99 1,066.87y 2,016.27 2,016.08 2,015.95 10 X 1,542.55 1,543.17 1,542.87 y 1,791.16 1,791.73 1,791.46 11 X 1,589.08 1,589.93 1,589.46 y 1,588.61 1,588.95 1,588.61 12 X 1,631.40 1,632.20 1,631.71y 1,349.26 1,348.96 1,349.02 13 X 1,681.36 1,682.03 1,681.44 y 1,064.56 14 X 1,064.68 1,064.65 1,064.58 1,740.79 1,740.52 y 1,741.28 1,741.08 868.39 868.30 868.33 15 X 1,781.18 1,781.67 1,781.30 y 735.26 735.30 735.29 16 X 1,809.39 1,809.07 1,808.80 y 1,646.22 1,646.34 1,646.23 17 X 2,541.44 2,541.17 2,541.02 18 y X 1,217.46 1,217.39 1,217.40 2,730.10 2,730.09 2,730.11y 757.90 757.89 757.93 19 X 2,933.14 2,933.27 2,933.04 y 32.01 31.82 31.88 20 X 3,252.71 3,252.67 3,252.29 y -336.71 -336.82 21 X 3,415.54 3,415.83 y GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Horizontal Movement of Stakes-Thule Take-off (all measurements in m) Stake July 4-20 July 20-August 3 August 3-25 July 25-August 25 July 4-August 25 1 X 0.00 0.00 +0.01 +0.01 +0.01 y 0.00 -0.01 -0.01 -0.02 -0.02 2 X -0.04 -0.02 -0.01 -0.03 --0.07 y --0.24 --0.14 -0.16 -0.30 -0.54 3 X +0.04 -0.14 -0.10 -0.24 -0.20 y -0.25 -0.29 -0.21 -0.50 -0.75 4 X -0.29 +0.01 -0.03 -0.02 -0.31 y -0.96 -0.07 -0.38 -0.45 -1.41 5 X -0.13 --0.08 --0.05 -0.13 -0.26 y --0.87 --0.26 -0.41 -0.67 -1.54 6 X -0.15 -0.05 --0.07 -0.12 --0.27 y --0.67 -0.29 --0.35 -0.64 -1.31 7 X --0.20 -0.07 +0.11 +0.04 -0.16 y -1.06 --0.25 -0.26 -0.51 -1.57 9 X -0.04 --0.05 --0.09 y -0.12 --0.15 -0.27 10 X -0.19 -0.13 -0.32 y -0.30 --0.32 -0.62 11 X -0.27 --0.30 -0.57 y -0.47 -0.38 -0.85 12 X -0.34 0.00 --0.34 y -0.49 -0.31 --0.80 13 X -0.30 +0.06 -0.24 y -0.59 -0.08 -0.67 . 14 X --0.03 --0.07 -0.02 --0.11 --0.14 y -0.20 -0.29 -0.27 -0.56 -0.76 15 X -0.09 +0.03 -0.06 y --0.37 -0.12 -0.49 16 X -0.01 --0.03 -0.04 y --0.32 --0.27 -0.59 17 X --0.11 --0.01 -0.12 y -0.27 -0.15 --0.42 18 X -0.07 +0.01 --0.06 y +0.02 -0.01 +0.01 19 X -0.01 +0.04 +0.03 y -0.23 +0.14 -0.09 20 X +0.06 +0.13 +0.19 y -0.04 -0.38 --0.42 21 X --0.11 --0.11 y +0.29 +0.29 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Elevations of Movement Stakes-Thule Take-off (all measurements in m) Elevation Change Ablation Stake July 2-6 July 20 August 23-26 July 20-August 25 July 20-August 25 1 25.10 25.02 25.13 0.11 0.70 2 61.92 61.88 62.14 0.26 0.76 3 96.69 96.66 96.91 0.25 0.63 4 152.30 152.31 152.44 0.15 0.46 5 201.35 (?) 200.85 201.05 0.20 0.35 6 145.22 145.04 145.16 0.12 0.60 7 210.12 210.10 210.27 0.17 0.43 9 59.17 59.47 0.30 0.74 10 100.19 100.65 0.46 0.98 11 96.13 96.51 0.38 0.65 12 93.32 93.62 0.30 0.71 13 90.85 91.16 0.31 0.84 14 89.25 89.12 89.40 0.28 0.65 15 87.70 88.47 0.77 0.77 16 91.48 91.68 0.28 0.85 17 151.63 151.82 0.19 0.44 18 156.32 156.44 0.12 0.47 19 164.63 164.71 0.08 0.57 20 197.72 197.77 0.05 0.50 21 220.77 220.91 0.14 0.52 Coordinates of Movement Stakes-Blue Ice Bench mark N is origin; N-W is positive direction of abscissa. (all measurements in m) Stake July 16 August 17 Horizontal Movement 22 X 333.24 333.21 -0.03 y 1,461.22 1,461.27 +0.05 23 X 446.71 444.96 -1.75 y 2,266.66 2,266.95 +0.29 24 X 522.75 520.20 -2.55 y 3,239.81 3,239.55 -0.26 24a x 662.86 657.84 -5.02 y 4,234.34 4,233.80 -0.54 Elevations of Movement Stakes Relative to Base Point N-Blue Ice (all measurements in m) Stake July 16 August 17 Elevation Change 22 -97.58 -97.68 -0.10 23 -100.99 -101.10 -0.11 24 -97.74 -97.69 +0.05 24a -77.72 -78.45 -0.73 GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA APPENDIX B BASE-LINE DATA, THULE TAKE-OFF 1. The map of the Thule Take-off area accompanying this report (Fig. 37) shows three corners of the quadrilateral used to measure the base lineN-S. These points are N, W, and S. Point E was unfortunately destroyed because of a misunderstanding. Stations N and S were occupied for all movement stake surveys and the angles turned on point Wwhich is visible from both of the surveying stations. Oil drums and signs clearly mark the bench marks. These consist of a steel bolt which is securely set into the largest available boulder in the vicinity. The dimensions of the still existing sections of the quadrilateral are as follows: Angle Value NSW 6°45'04.5" SWN 161'28'31" SNW 5°46'24.5" Distance Value NS (base line) 787.082 m sw 365.103 m WN 426.676 m The measured short diagonal (E-W) of the quadrilateral was 216.293 m. Point Elevation N 0 w +4.69 m s +0.65 m In order to facilitate l oc ating the movement stakes, a table of predicted angles from each survey station turned on Wis included in this appendix. Predicted Angles from Station N Turned on W Stake Angle Elevation Stake Angle Elevation 1 58°23'16" 1°22'30" 12 51°31'10" 2°20'40" 2 62°42'30" 2°14'40" 13 57°01'00" 2°24'30" 3 64°50'40" 2°31'50" 14 64°18'20" 2°29'40" 4 66°16'00" 2°55'00" 15 69°46'20" 2°33'30" 5 61'05'30" 3°02'30" 16 73°38'10" 2°40'20" 6 69°32'10" 2°55'00" 17 62°49'30" 2°51'50" 7 72°50'10" 3°09'40" 18 71°44'20" 2°58'30" 9 41'27'30" 2°05'00" 19 81°17'00" 3°05'20" 10 43°10'40" 2°15 '50" 20 95°11'50" 3°27'00" 11 47°20'10" 2°18'50" 21 101°24'10" 3°39'10" GLACIOLOGICAL INVESTIGATI'JNS IN THE THULE RAMP AREA Predicted Angles From Station S Turned on W Stake Angle Elevation Stake Angle Elevation 1 83°50•12" 1°39'00" 12 122°54'20" 2°54'40" 2 99°40'30" 2°39'00" 13 115°14'10" 2°54'20" 3 106°51'50" 2°53'00" 14 105°48'45" 2°52'00" 4 111°28'10" 3°13'50" 15 99°22'00" 2°49'20" 5 113°53'20" 3°18'40" 16 95°06'20" 2°52'00" 6 107>04'20" 3°11'30" 17 115°26'10" 3°13'40" 7 107°54'50" 3°22'00" 18 105°42'40" 3°12'30" 9 117°46'30" 2°54'40" 19 96°10'40" 3°11'00" 10 135°18'20" 2°53'00" 20 83°40'40" 3°21'30" 11 129°03'10" 2°5S'OO" 21 78°32'10" 3°29'00" GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA APPENDIX C BLUE ICE 1. The bench marks for the Blue Ice movement stake survey are located on a nunatak at the west side of the junction of the Moltke Glacier and the glacier flowing north from Blue Ice. Bench mark N is on the south side of the prominent saddle on the nunatak and bench mark Wis on the highest point of the nunatak. Each point consists of a cross carved on a large boulder which is marked by a rock cairn and an orange and white surveying stake. As the cross for bench mark W is difficult to find, Figure 36 is included in this report in order that the cross may be located easily. The length of base line N-W is Boulder 1,503.69 m. Point W is 160.18 m above bench mark N, Angles from N and W are tabulated here in order to be able to locate the stakes rapidly. Movement is so rapid for the more distant stakes that the predicted angles should be considered as only very approximate. Precise location of Blue Ice bench mark w. Dashed lines ore crocks in the boulder. Predicted Angles from N Stake Angle Elevation 22 7'fl09'50" -3°47'40" 23 79°09'00" -2°33'15" 24 81°08'00" -1°44'50" 24a 81°34'00" -05'20" 35cm Predicted Angles from W Stake Angle Elevation 22 51°18'20" -7°53'20" Detail of crock intersection in boulder showing 23 64°52'00" -6°00'00" position of bench mark . 24 72°51'00" -4°23'30" 24a 78°18'00" -3°12'00" Figure 36. Locatio n of Blue Ice bench mark W. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Ramp Weather Station, showing meteorological mast, ablation and movement stake No. 14, and the instrument shelter with the Robitzsch actinograph. Photograph was taken on 4 August, a day with unusuallyheavy runoff. The meteorological mast was mounted on three beams drilled deep into the ice. If the bottom plate had been put right on the ice, considerable difficulties would have been caused by the ablation. Weather Station at Camp Hardtop, 7 July, equippedwith anemometer and instrument shelter containing one hygrothermograph and three thermometers (standard, maximum, and minimum). Temperature measurements in the ice were taken Cryoconite holes on the Thule Ramp, 10 August. with thermocouples. The can contains the selector The "scale" is an exposure meter case. Picture switch; the reference junction is put down in a vacshows normal distribution of holes. uum bottle; and the thermocurrent is measured with a small microammeter. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA Slumping in the sides of the test road, 13 August. Since the fill will act as an insulation and prevent further ablation underneath, and s i nce the flushedout finer material will increase the rate of melting just outside the road, a considerable slumping will take place. The only way to delay the destruction of such a road is to cover the ice on both sides with fill thick enough to slow down the ablation considerably. The wider those extra shoulders are made, the longer it will take before the road wi ll look like a sharp-edge d ridge . Tracks of slush streams, "slushers," 14 August. Where such tracks can be seen, good trafficability can be expected. The worst conditions occur before the drainage has started, and while there is still a lot of slush under an apparently dry surface. The difference in ice content of the upper snow strata gave the snow a varying bearing capacity. It was found that the ice layers grew thicker when the originating surface was concave upwards, and this reinforcement of the surface snow meant very little sinking of the vehicles. Because of different bearing capacities of the snow, a weasel ride could often be rather bumpy. The track in the left foreground has penetrated about 20 em, while a few meters farther away it has not more than broken the surface. 23 July. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA A section of superimposed ice from 1-m depth (atabout Mile 3.5 towards Hardtop). The Polaroid plate is 4 in. wide. Average crystal size here was between 1 and 2 mm. A few patches of superimposed ice left on top of old dirty ice. The white superimposed ice has a much higher albedo than its surroundings and will melt at a slower rate. The little ridge close to the center of th e picture is capped by a small patch of white ice, which certainly is the main cause for the formation of the ridge. Superimposed ice from about Mile 3. 5 on the TUTOOccasionally dirt layers can be found inside a core Hardtop trail. Stratification of milky and clear ice of superimposed ice. It then represents a summerindicates situations with higher or lower water satu-surface and separates two distinct annual layers. ration of the refrozen slush. The dirt layer here, found at about 30 em on the ruler, shows the position of the summer surface from 1953. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA 87 The "shear plane moraines" in the Thule area reach considerable sizes; compare with the man on top of the high ridge and with the weasel to the right. However, the thickness of the morainal cover was normally not more than 10-20-30 em. In the ice cliffs at the bead of the Piktufik Valley At an altitude of 585 m the large superficial moraine some beautiful sections can be studied. These dirt dominating the TUTO area disappears into the ice. bands can be followed to the north and seen as outThe ice from the left seems to push up over the ice cropping shear planes high up on the glacier. They to the right, so perhaps the moraine is a result of appear as a very black line on air photographs of the the shear plane at the border between two merging glacier. ice lobes. GLACIOLOGICAL INVESTIGATIONS IN THE THULE RAMP AREA The only place where the "Great Land Glacier" ends in a steep cliff is at the head of the Piktufik Valley, due east of Thule. It may be significant that this is the only place where the glacier ends on a downhill slope. The author's own observations of ice cliffs (on land) have all been confined to glacier termini on what have appeared to be downhill slopes. Peculiar appearance of crevasses north of Mile 8. Instead of the normal sagging bridges, these crevassesshowed up as low ridges. The reason was that the surrounding snow settled faster than the icy and highlymetamorphosed bridges, which had been reinforced by sublimation of water vapor transferred from the open crevasse below. The phenomenon does not seem to be very common. It can be comparedwith the "haycocks" of the Ross Shelf Ice. J ~ 1:: -70CW § ~ ~ ~ Kl ., _/ __ -----;'/ ,-·· ~· ~~ ...._, ') CJ::t j ~ ~ ---s, ~ nl(\~··J \o 1:Jl \ LL '\I\ c\ 00 k~ (. \ ..~,....... __.:.. ...... :)'- \ \ ,.." \, } '\ -~/ ~~ .&/11-.! . /r r '7// /I I I I \ \ ~ .500 <:> " \ \ I I I I 1000 I / / II I I I -..,. ''\. 0 18 '-, ' l /I e ~I ~I I ;,1@I '5) I I I I Of 4/I I I I I I 1500 I I \ ) ,---" I I I I Sf1 I \ I I ) I I I I I \. ) // 'I 2000 " \ \ " ~ Iii \\ I I I I I \ \ " ",. ..,_ \ _J \ \ \ \ \ \ I > ~I ~I ! ~ o§1'r I l~o.?--' \ \ I \ \ \ \ ~ I I' \ I I I I I I \ \ \ \ I ?500 ·· \ \ \ \ ' "'',, ',I ' I' 1\ I ',~,....../)/ ...................' ~/ ,i ..... '/ / ! j 1\/I I . I I I I I I , I 11 ,I I I I I I' f I I I --r--I \ ) ///A \ ) ~~ I I ;\ \ \ Figure 37. Map of Thule Take-off Area. Shows position of movement Stakes 1-4, 6,9-18. Stakes 5, 7, 19-21 in area not covered by map. / ~ ~I 1:: ~ ~ 1\: i(J 300dl <::> ~ ~ ~ ~ ~ ~ --1 1/ :_i I /l' )_.~ ,. ~...,.,_\ I ,.,.~ ,.."' -~ ~ /}/ '\. ·. \ j I -500 \ ' + " -+· I 1 '\ _../Ice \ __ / ,. \ ( 7 \. .·· -::._ ./f ..... ---"':..._ ----.::::::. .. · ,? ;, ~·.·..:::::--·.,_ \ ~ .. '\_ ·~.:..:::;-' (;!::! \.....~-..,.->-.·· ~ / . 1 ) !! ~s._ ~ Ill(, '" ~l ;)') 00 \ fl +0 -+-482 '\I 1 + _--<>' \ c\ k.~ ( \ 0 + + II II II II II II II {!; S-482.7 1000 + +! \ + <~?s "473'=:::: ~-~~-:~-···--. ... ~... ? _t ~ /--}-J ···4 ... 1 ~ I !!J/f!// LJi ;;~r~~ ;::...-- ~-+~ L1--fr--t-r~: 1 /i~~J~ !//// /l!/:r:/ /~ (1 /i! ~~~ !/. ///! / ,/ A . I ... .. . / ! // // // / ... /I'm_/ // 1500 + + {9 0 ~~)~ \ \ \ \ \11\ l {/? flJ/l~:rt/l ,/J ~ I ' ' I ;,I I ~ I -/ / I I I I I / )..0 I I I 2000 + + if(~\ \-tt\~~\+\\t1A \ \ \\ !~ f\ [~\ ~{/· I I I~\ \\ \ ~~ 'I \' \ l ! '-\0 \\ \ 1\ \ \ '\ \ I ,, ' ''\'''<' l ' GLACIOLOGICAL SURVEY ~ ~ f 'r ( \ t 1 t t 1 r r r J 1i \ r ' \ l \j ~ \ 1 '\ -l \ ~ GREENLAND \ zsoo SCALE I : 10,000 CON"tOUR INTERVAL 5 METERS + -~~ f f ~ w~ t ur 1 1 1 tm 1 1_\f\f·'?'J~.\\. \ I PREPARED FROM AERIAL PHOTOGRAPHS TAKEN 9 AUGUST 1954 FOR J I r t f t f I I r-rliii·H·i f Lll !!~It Vil \\ ' \ \I', NORTHWESTERN UNIVERSITY EVANSTON, ILLINOIS 8Y ALSTER a ASSOCIATES WASHINGTON, D.C. ~ ' r r g[ :-o ~I ~I ~ 1-·