A preliminary study of glacial geomorphology in area between Breid Bay and the Sør Rondane Mountains in Queen Maud Land, East Antarctica

During the period from 12 to 17 February 1983,a preliminary study of glacial geomorphology was carried out in the area between Breid Bay and the Sør Rondane Mountains by the 23rd and 24th Japanese Antarctic Research Expedition to implement earth science programs in the Sør Rondane Mountains. The obstruction by the Sør Rondane Mountains to the ice flow is the cause of the elevated ice surface in the south of the mountains, and also the cause of the extremely low level in the north of the mountains, probably aided by the shelter effect of the mountains. Outlines of the ice shelf front and the respective positions have indeed remained unchanged over twenty-three years, but the reentrant, a widely and deeply fractured zone, is formed in the ice shelf between the Base Roi Baudouin and the ice front. It was found that the reentrant was formed between 1967 and 1973,and further fracturing of the platform of this ice shelf may occur with the development of crevasses, and therefore the ice shelf may break off in not so far future. A rough estimate of the mass budget of the ice sheet in the area between Breid Bay and the Sør Rondane Mountains suggests that the ice sheet may keep the present shape owing to the high accumulation rate over the ice sheet surface at present. If the present accumulation rate decreases, the lowering of the ice sheet surface may occur and, therefore, the thinning of the ice sheet may cause the retreat of grounding line, since most of the base of the ice sheet lies well below see level. The detailed radio-echo sounding is essential for clarifying whether the ice sheet in this area is of a marine type or not. At least, it is grounding in the front of the ice shelf at present.