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Double Paradox: Global Warming Brings More Snowfall To Antarctica, More Ice Loss; 'Major Contributor To Future Sea-Level Rise'

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POTSDAM, Germany -- "Warmer air transports more moisture and hence produces more precipitation - in cold Antarctica this takes the form of snowfall," lead author Katja Frieler from the Potsdam Institute for Climate Impact Research (PIK) explains. "We have now pulled a number of various lines of evidence together and find a very consistent result: Temperature increase means more snowfall on Antarctica," says Frieler. "For every degree of regional warming, snowfall increases by about 5 percent." Published in the journal Nature Climate Change, the scientists' work builds on high-quality ice-core data and fundamental laws of physics captured in global and regional climate model simulations.

To narrow down future snowfall on Antarctica to a robust estimate, the scientists from Potsdam collaborated with colleagues in the US and the Netherlands. "Ice-cores drilled in different parts of Antarctica provide data that can help us understand the future," says Peter U. Clark from the Oregon State University, USA. "Information about the snowfall spanning the large temperature change during the last deglaciation 21,000 to 10,000 years ago tells us what we can expect during the next century." The researchers combined the ice-core data with simulations of the Earth's climate history and comprehensive future projections by different climate models, and were able to pin down temperature and accumulation changes in warming Antarctica.

Double paradox: Warming brings more snowfall, more snowfall enhances ice loss

"Under global warming, the Antarctic ice sheet with its huge volume could become a major contributor to future sea-level rise, thus potentially affecting millions of people living in coastal areas," Frieler says. Hence the interest of quantifying snowfall which would make the ice sheet grow in height and gain mass. Unfortunately, building on a previous PIK study, the scientists found that additional snowfall will also increase the ice flow to the ocean, partly countering the gain.

"Snow piling up on the ice is heavy and presses down - the higher the ice, the more pressure. Because additional snowfall elevates the grounded ice-sheet on the Antarctic continent but less so the floating ice shelves at its shore, the ice flows more rapidly into the ocean and contributes to sea level," co-author Ricarda Winkelmann from PIK explains. Accounting for this effect a 5-percent increase in snowfall on Antarctica would mean a calculative drop in sea-level of about 3 cm after 100 years. Other processes, however, will effect a rise in sea-level in the end. For instance, already rather little warming of the ocean could cause ice at the Antarctic shore to break off more easily, hence more ice mass from the continent would flow out and discharge into the ocean.

Antarctica is a key factor to future sea level rise

"So, if we look at the big picture these new findings don't change the fact that Antarctica will lose more ice than it will gain, and that it will contribute to future sea-level change," says co-author Anders Levermann from PIK, who is also one of the lead authors of the sea-level rise chapter in the latest report of the IPCC. "For decision makers in coastal areas it is vital to know how much sea-level rise can still be avoided by limiting global warming, and how quickly we will have to adapt to the unavoidable - the role of Antarctica is key to those considerations. Our findings provide another piece in the puzzle that we need to quantify future sea-level rise."

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Article: Frieler, K., Clark, P.U., He, F., Buizert, C., Reese, R., Ligtenberg, S.R.M., van den Broeke, M.R., Winkelmann, R., Levermann, A. (2015): Consistent evidence of increasing Antarctic accumulation with warming. Nature Climate Change [doi: 10.1038/nclimate2574]

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