The Water Budget in Antarctica

Nearly the whole Antarctic ice sheet, including the attached ice shelves, shows a net accumulation. Factors other than precipitation influence the budget only to a small degree. In the inner parts of the ice sheet it is frequently difficult to establish the annual accumulation. Determinations by isotope frequency do not always agree with those derived from stratigraphic evidence. A mean accumulation of 15cm water equivalent corresponding to 1900gt/year (1 gt=1 gigaton=1km^3 water) is rather on the low side. The loss by runoff of meltwater or by evaporation in the border regions of prevailing ablation is small, 10gt/year. The open ice sheet moves slowly; the ice loss is 50gt/year. Glaciers move with varying speeds; an estimate of 520gt/year from glaciers and ice streams is rather high. Ice shelves surround one-half of the continent. A high estimate gives 880gt as their productivity. Some melting will occur at the bottom of the floating ice shelves and glaciers. The amount is not well known; it is estimated at 200gt/year but will hardly exceed 300gt/year. With a total loss of 1660gt/year the final balance is slightly positive. In view of the uncertainties, gain and loss might be equal, but the budget will not be markedly negative. With the ice sheets of Antarctica and Greenland in balance, the present rise of sea level can be caused by the mass loss of the mountain glaciers combined with a warming of the ocean

Historical Reference to Ice Islands

Some years ago M. Dunbar gave a detailed account of earlier ice reports which could refer to ice islands, as distinguished by G. Hattersley-Smith from other ice in the polar sea by their great unit area, thickness, structural strength and rolling relief. Among the old descriptions of 'floebergs' and 'palaeocrystic ice' some of Greely's come closest to a description of an ice island. Another early report might be worth mentioning: Franz Boas, the German-born anthropologist and later professor at Columbia University states that in October 1883 a huge iceberg drifted into Cumberland Sound, Baffin Island. It had a height of 15 m to 20 m, a length of 14 km and a width of 5 km. The total thickness of 100 m to 150 m could be seen when the ice broke into pieces. The estimated volume was 13 cu km. Similar ice formations of smaller size had been repeatedly encountered when approaching Cumberland Sound. The upper surface consisted of long low rounded parallel rolls with a wavelength of about 150 m and extending over 1 km to 3 km. The surface and the uppermost 2 m of the ice contained stones; no stratification or crevasses were visible. The description fits that of a typical ice island. That ice islands from the northern coast of Ellesmere Island can reach Baffin Bay and Cumberland Sound is shown by the recent drift of ice island WH55; a segment of at least 14 sq km passed through southern Davis Strait