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FROM VOLUME 9, NUMBER 5, MAY 1996

PROFESSIONAL PUBLICATIONS...
EARTH SYSTEM SCIENCE: ICE SHEET STABILITY

Item #d96may26

Two related items in Science 271(5052), Feb. 9, 1996:

"Rapid Collapse of Northern Larsen Ice Shelf, Antarctica," H. Rott (Inst. Meteor., Univ. Innsbruck, Innrain 52, A-6020 Innsbruck, Austria), P. Skvarca, T. Nagler, 788-792. Documents the January 1995 breakup of 4200 square kilometers of the ice shelf, based on radar images from the ERS-1 satellite and field observations. The nearly complete disintegration of the ice occurred within a few days, following a period of steady retreat that coincided with a regional trend of atmospheric warming. The observations imply that after an ice shelf retreats beyond a certain limit, it may collapse as a result of altered mass balance.

"An Ice Shelf Breakup," M. Fahnestock (Ctr. for Earth System Sci., Univ. Maryland, College Pk. MD 20742), 775-776. Discusses the difficulties of interpreting the results of the previous paper in the context of climatic trends. The breakup of the Larson ice shelf did not directly influence sea level because it was already floating, but it may be a signal of changing conditions on the Antarctic peninsula.

Item #d96may27

"Recent Atmospheric Warming and Retreat of Ice Shelves on the Antarctic Peninsula," D.G. Vaughan (British Antarctic Survey, Natural Environ. Res. Council, Madingley Rd., Cambridge CB3 0ET, UK), C.S.M. Doake, Nature, 379(6563), 328-331, Jan. 25, 1996.

Compares the 50-year trend of the areal extent of nine ice shelves to meteorological records. The five northerly ones have retreated dramatically in the past 50 years, consistent with the existence of an abrupt thermal limit on ice-shelf viability, the location of which has drifted southward. Ice shelves therefore appear to be sensitive indicators of climate change. The authors cannot determine whether this Antarctic Peninsula warming is related to a global warming, or is a natural oscillation.

Item #d96may28

"Pliocene-Pleistocene Diatoms in Paleozoic and Mesozoic Sedimentary and Igneous Rocks from Antarctica: A Sirius Problem Solved," L.H. Burckle (Lamont-Doherty Earth Observ., Rte. 9W, Palisades NY 10964), N. Potter Jr., Geology, 24(3), 235-238, Mar. 1996.

The 1984 discovery of fossilized oceanic plants (diatoms) in the Sirius Group sedimentary rocks of the Transantarctic Mountains sparked a debate on the stability of the East Antarctic ice sheet, suggesting that the sheet may have melted in the past, and could do so in the future. However, geological evidence presented in this paper is consistent with an alternative theory—that the diatoms were blown there by wind.

Item #d96may29

"Behavior of the East Antarctic Ice Sheet as Deduced from a Coupled GCM/Ice Sheet Model," M. Verbitsky (Dept. Geol., Yale Univ., New Haven CT 06520), B. Saltzman, Geophys. Res. Lett., 22(21), 2913-2916, Nov. 1, 1995.

The possible instability of the West Antarctic ice sheet has been widely recognized for some time as a potential source of sea-level rise in an enhanced greenhouse warming, but only recently has the East Antarctic ice sheet been the subject of such a conjecture. Model results given here show little chance of collapse from changes in normal glacial creep and topographic instabilities. But the mechanics of basal sliding, non-isothermal effects, and ice shelves are as yet too poorly understood to make quantitative estimates of possible instabilities related to these processes.