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A quick rebound of Antarctic crust promotes ice-sheet stability

June 21, 2018

The unexpectedly rapid rebound of the Amundsen Sea Embayment (ASE) may help stabilize the West Antarctic Ice Sheet against catastrophic collapse, says a new study offering a rare silver-lining in glacier research. The marine portion of the WAIS accounts for a quarter of the world's ice contribution to global sea level rise and is currently vulnerable to catastrophic collapse. As glaciers and ice sheets ebb and flow, they deform the Earth's crust. When loaded with icy weight, the crust is depressed, and as ice retreats, the surface rebounds like a spring, uplifting at a rate largely determined by the viscosity of the upper mantle underlying the region. This slow process is called glacial isostatic adjustment (GIA) and was thought to occur over a 10,000 year-timescale. However, Barletta et al. now show that in fact, the ASE is undergoing one the fastest glacial isostatic uplift rates ever recorded - a 41 millimeters annually. The authors used GPS data that measures the deformation rates of the ASE to model the viscosity of the mantle below the region and found it to be much lower than expected (approximately 4x1018 pascal seconds). The new data suggests that GIA can happen on a timescale measured not in thousands or tens of thousands of years, but rather, on the far faster scale of centuries or decades. Based on their estimates, as the WAIS retreats, the rapid uplift of the ASE has the potential to produce a deformation that is both large and early enough in the deglaciation to prevent the complete collapse of the ice sheet, even under strong climate forcing. The rapid uplift may even be able to delay collapse events outlined in more extreme scenarios, the authors say.
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American Association for the Advancement of Science

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