SCIENTIFIC RESULTS 71 



between Cape Farewell and the opposite northern extremity. A top- 

 ographic map of the ice sheet, moreover, shows a fairly good agree- 

 ment with the coast ])roiiles. establishing beyond reasonable doubt 

 that Greenland, as well as its ice cap. is crossed from Disko Bay to 

 near Angmagssalik by a great transverse depression. This conti- 

 nental crease is believed to be of great importance in converging the 

 ice and in concentrating the maximum discharge of icebergs near 

 the seventieth parallel of latitude on both coasts. 



Knowledge of the topography of the ice sheet is not yet complete. 

 Apparently there are two main domes of glaciation, one in the north- 

 central part and the other in the south-central part with altitudes of 

 9.750 and 8,775 feet, respectively. A third center of doubtful alti- 

 tude and position is believed to lie in the region north of Angmags- 

 salik, but in any case it does not interfere with the major depres- 

 sional feature which appears to be well established. An accurate 

 east to west profile of the ice cap made by de Quervain shows a con- 

 vexity from the thickest portions which lie slightly to the eastward 

 of the continental median line. The ice is fed mostly in the high 

 mountains of the east, which are themselves submerged by inland ice 

 even to their tops. The west side of Greenland, on the other hand, 

 is the region of dissipation, both because of the topography and 

 of the warm climate, the mean annual temperature of the west coast 

 of Greenland being much higher than is that of the east. In general 

 contour, the cap is noticeably flattened in the interior, but near the 

 edges the slope is steeper, the eastern descent being short while the 

 western slope is longer. Thus the main mass of ice moves toward 

 Baffin Bay and Davis Strait. Preliminary seismic soundings made 

 on the inland ice of west Greenland (see Wegener, 1930) indicate 

 that although the ice rises toward the interior, the continental bed- 

 rock is depressed there. The fjord systems of Disko Bay and 

 Northeast Bay, between parallels 69 and 72, extend inland under the 

 cap for a known distance of at least 100 miles and perhaps farther, 

 the formative effect of this topography being clearly traceable in the 

 configuration of the ice surface. The movement of the ice upon 

 reaching these drainage basins is noticeably increased through the 

 various vallej' systems, as many active glaciers feeding into the sea. 

 The volume of the annual discharge from the west coast fjord system 

 is estimated to be equivalent to that of the river system before 

 glaciation prevailed.^* 



Brooks (1923. p. 445) using de Quervain's and other data con- 

 cludes that the Greenland ice cap is not a relic of the ice age, but 

 is fully maintaining itself at present. He shows that the snow line, 

 situated about 50 miles in from the western edge, divides the cap 

 into a central interior called the accumulator, and a marginal dissi- 

 pator. The accumulator is estimated to receive annually through 

 Drecipitation an increment of ice 36 centimeters in mean thickness. 

 The reduction of thickness in the dissipator ranges from a maximum 

 of 2 meters around the edge of the cap to zero at the snow line, or an 

 average of 95 centimeters over the whole width of the 50-mile margin. 

 The wastage takes place in two ways — 75 per cent is ablation by in- 

 solation and wind and 25 per cent is attributed to calvings of the tide- 



■*' Mecking (1928, p. 2511 gives an excellent description of the actual app(>araiice of the 

 surface features of the inland ice. 



120860—31 



