East Antarctic ice sheet vulerable to melting
April 21st, 2010Evidence from an Antarctic geological research drilling program known as ANDRILL suggests that the vast East Antarctic Ice Sheet, which holds at least four-fifths of the continent’s ice, is more susceptible to melting than previously thought and that an abrupt shrinkage of its ice sheets at some greenhouse gas threshold is possible, perhaps beginning within in this century.
The southern McMurdo Sound core yielded clear evidence of some 74 cycles of ice sheet buildup and retreat during a 6-million-year stretch starting in the Miocene Epoch some 20 million years ago. According to geologist Robert DeConto of the University of Massachusetts, Amherst, the policy implications are grim, as many population centers worldwide are within a few meters of sea level.
Our models may be dramatically underestimating how much worse it’s going to get. We’re seeing ice retreat faster and more dramatically than any model predicts.
The answer to the puzzling disparity between model predictions and the core data could lie in an erroneous assumption about Antarctica itself. Some parts of the land underlying the East ice sheet might be much lower than currently believed. As warming oceans strip away the surrounding ice shelves, significant chunks of the ice sheet could slide into the ocean.
A prior core, extracted from the McMurdo Ice Shelf between October 2006 and January 2007, indicated that the West Antarctic Ice Sheet has frequently advanced and retreated.