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June 21st, 2009

Ice sheets can retreat in a geologic instant

Jason Briner (former INSTAAR, now SUNY-Buffalo) and Bob Anderson worked with Aaron Bini, a student of Briner's, to produce an exceptionally detailed record of past ice-sheet retreat through a fjord and, in the process, have provided insight into how present ice sheets in Greenland and Antarctica may thin and retreat with continued global warming.  The authors carefully collected rock, shell, and other samples from Sam Ford Fjord in the eastern Canadian Arctic, with the target of documenting retreat of this portion of the eastern margin of the Laurentide Ice Sheet at the end of the last Ice Age.  Dating of these samples, combined with previous and nearby records, showed that the outlet glacier in the fjord retreated ~40% of the distance between its maximum position and the present ice limit within only a few hundred years, equivalent to ~5% of the total time of deglaciation. Rates of retreat in the deep fjord were about an order of magnitude higher than in the either the shallow waters further offshore or once the glacier margin had reached land. 

This outlet glacier's response appears to be similar to the rapid retreat being documented in some of Greenland’s outlet glaciers, and by Tad Pfeffer’s group (INSTAAR) in Alaska’s Columbia Glacier. Rapid motion by sliding at the bed promotes thinning, which in turn leads to further acceleration. The new findings will help to develop more robust climate and ice sheet models that can better predict how global warming will affect ice sheets and the potential for rising sea levels in the future.

The paper was published in the June 21 issue of Nature Geoscience.

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