New Research: East Antarctic at Risk of Unstoppable Melt May 5, 2014

Big Story. The East Antarctic Ice sheet – the world’s icebox, once thought all but impervious to melt on any meaningful time scale, is , on deeper inspection, much more vulnerable than we supposed. The video above, from December, fleshed that idea out.

Now, new research adds to the picture.

Climate News Network:

The East Antarctic ice sheet is thought by most scientists to be stable. But a German team says it has found how part of it could in time melt unstoppably. LONDON, 4 May – Part of the East Antarctic ice sheet may be less stable than anyone had realised, researchers based in Germany have found. Writing in Nature Climate Change, two scientists from the Potsdam Institute for Climate Impact Research (PIK) say the melting of quite a small volume of ice on the East Antarctic shore could ultimately trigger a discharge of ice into the ocean which would result in unstoppable sea-level rise for thousands of years ahead. http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2226.html Their findings, which they say amount to the discovery of a hitherto overlooked source of sea level rise, appear unlikely to happen any time soon. They are based on computer simulations of the Antarctic ice flow using improved data of the ground profile beneath the ice sheet. “East Antarctica’s Wilkes Basin is like a bottle on a slant,” said Matthias Mengel, the lead author of the study. “Once uncorked, it empties out.” The basin is the largest region of marine ice on rocky ground in East Antarctica. At the moment a rim of ice at the coast holds the ice behind it in place, like a cork holding back the contents of a bottle. The air over Antarctica remains cold, but oceanic warming can cause the ice on the coast to melt. This could make the relatively small “cork” disappear. Once it had gone, the result would be a long-term sea level rise of three to four metres. “The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork,” says the study’s co-author, Anders Levermann. “Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk.”

Nature Climate Change:

Changes in ice discharge from Antarctica constitute the largest uncertainty in future sea-level projections, mainly because of the unknown response of its marine basins1. Most of West Antarctica’s marine ice sheet lies on an inland-sloping bed2 and is thereby prone to a marine ice sheet instability3, 4, 5. A similar topographic configuration is found in large parts of East Antarctica, which holds marine ice equivalent to 19 m of global sea-level rise6, that is, more than five times that of West Antarctica. Within East Antarctica, the Wilkes Basin holds the largest volume of marine ice that is fully connected by subglacial troughs. This ice body was significantly reduced during the Pliocene epoch7. Strong melting underneath adjacent ice shelves with similar bathymetry8 indicates the ice sheet’s sensitivity to climatic perturbations. The stability of the Wilkes marine ice sheet has not been the subject of any comprehensive assessment of future sea level. Using recently improved topographic data6 in combination with ice-dynamic simulations, we show here that the removal of a specific coastal ice volume equivalent to less than 80 mm of global sea-level rise at the margin of the Wilkes Basin destabilizes the regional ice flow and leads to a self-sustained discharge of the entire basin and a global sea-level rise of 3–4 m. Our results are robust with respect to variation in ice parameters, forcing details and model resolution as well as increased surface mass balance, indicating that East Antarctica may become a large contributor to future sea-level rise on timescales beyond a century.