[pccgrads] ESS Colloquium by Eric Steig, Director of Future of Ice Initiative, and Professor in Earth and Space Sciences

UW PCC uwpcc at uw.edu
Wed Oct 14 19:53:57 PDT 2015


ESS Colloquium by Eric Steig, Director of Future of Ice Initiative, and Professor in Earth and Space Sciences

3:30 - 4:30 in Johnson 075, Thursday Oct 15.

It goes both ways: on the influence of ice sheet collapse on climate

The potential for climate change to cause the collapse of the West Antarctic Ice Sheet (WAIS) is well known. Collapse – or significant lowering – of the ice sheet, if it occurred, would also affect regional climate and might even have global impacts. The possible influence of meltwater has been examined in previous work, but only recently has it been appreciated that changes in the atmosphere – as a result of the topography and its influence on atmospheric wave dynamics – would also be important. In collaboration with faculty and student colleagues in Atmospheric Sciences, I used climate-model simulations to quantify the impact of topographic changes on the surface climate of Antarctica. As a general rule, lowered topography produces anomalous cyclonic circulation owing to fundamental atmospheric dynamical constraints. In the case of WAIS collapse, this causes increased flow of warm, maritime air toward the South Pole and cold-air advection from the East Antarctic plateau toward the Ross Sea and Marie Byrd Land, West Antarctica. The result is cooling in some areas and warming in others, a pattern that is similar to that observed from ice core paleotemperature data for the last interglacial period, providing indirect supporting evidence WAIS collapse occurred at that time. The magnitude of the response is roughly linear with the magnitude of the imposed elevation change. The regional response over West Antarctica is large enough that it must be taken into account in modeling future changes to the ice sheet. Of particular interest is that lowering of the WAIS topography results in anomalous westerlies along the Amundsen Sea coastline. Anomalous westerlies in this region today are in large part responsible for the intrusion of circumpolar deepwater onto the continental shelf, and the observed rapid thinning of West Antarctic ice shelves. A positive feedback may thus exist in which lowering of the WAIS surface from climate forcing may enhance that forcing, leading to further elevation lowering and ice sheet mass loss.

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