Climate Science

Antarctica's Adolescence

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Science  13 Aug 2010:
Vol. 329, Issue 5993, pp. 729
DOI: 10.1126/science.329.5993.729-c
CREDIT: DON BLANKENSHIP/UTIG

Antarctica, particularly East Antarctica, harbors much of the world's ice. Thus, accurate knowledge of its sensitivity to melting from global warming is critical for assessing likely sea-level rise in the years ahead. To this end, two recent studies examine the region's dynamics during past glacial cycles and the period when it first grew. Lilly et al. use cosmogenic isotopes, which accumulate in exposed bedrock, to show that the height of the East Antarctic ice sheet fluctuated by only about 100 m through at least the last glacial cycle; the best model fit to the data includes a slow decline in height over longer times. Thus, the East Antarctic ice sheet has had a stable height during past glaciations. In exploring its stability during warmer times, Peters et al. show that an incised coastal valley in Egypt records a sudden and rapid change (within 2 million years) in sea level of about 40 m, at the time when global records imply that major ice sheets first grew in Antarctica, about 35 million years ago. Several smaller fluctuations in sea level (of about 10 m) are also recorded. The rapid changes correlate with estimated fluctuations in atmospheric CO2 levels and occurred when levels dropped below about 750 ppm.

Geology 38, p. 703; 723 (2010).

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