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Warm ocean currents cause melting of Antarctica ice

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Ice Shelf in Antarctica (Image courtesy - BAS)

Researchers have established, warm ocean currents cause melting of ice shelves in the Antarctica region.  An international team of scientists led by British Antarctic Survey used new techniques to differentiate, for the first time, between the two known causes of melting of ice shelves – warm ocean currents attacking the underside and warm air melting from above. The finding brings scientists a step closer to providing reliable projections of future sea-level rise.

Using a laser instrument mounted on NASA’s ICESat satellite to map the changing thickness of almost all the floating ice shelves around Antarctica, researchers revealed the pattern of ice-shelf melt across the continent and found 20 of the 54 mapped ice shelves melted by global warming, mostly in the western part of Antarctica.

Antarctic Ice Shelf (Image courtesy: BAS)

“In most places in Antarctica, we can’t explain the ice-shelf thinning through melting of snow at the surface, so it has to be driven by warm ocean currents melting them from below,” said Dr Hamish Pritchard from British Antarctic Survey.

“We’ve looked all around the Antarctic coast and we see a clear pattern: in all the cases where ice shelves are being melted by the ocean, the inland glaciers are speeding up. It’s this glacier acceleration that’s responsible for most of the increase in ice loss from the continent and this is contributing to sea-level rise.”

Studies have shown that Antarctic winds have changed because of changes in climate, and that this has affected the strength and direction of ocean currents. As a result warm water is funneled beneath the floating ice. These studies therefore suggest Antarctica’s glaciers are responding rapidly to a changing climate, said Dr Pritchard.

NASA’s ICESat satellite (Image courtesy: BAS)

A different picture is seen on the eastern Antarctic Peninsula (the long stretch of land pointing towards South America), where warm summer winds directly melt the snow on the ice-shelf surfaces. Both patterns, of widespread ocean-driven melting and summer melting on the Antarctic Peninsula are attributed to Antarctica’s changing wind patterns.

The research is part of international efforts to improve understanding of the interactions between ice and climate in order to improve the reliability of sea-level rise projections.

“This study shows very clearly why the Antarctic ice sheet is currently losing ice, which is a major advance.  But the real significance is that it also shows the key to predicting how the ice sheet will change in the future is in understanding the oceans. Perhaps we should not only be looking to the skies above Antarctica, but also into the surrounding oceans,” said Professor David Vaughan, leader of ice2sea – a major EU-funded FP7 programme

The study was carried out by an international team from British Antarctic Survey, Utrecht University, Scripps Institution of Oceanography and Earth & Space Research in Corvallis, Oregon. NASA’s ICESat – Ice, Cloud and Land Elevation Satellite – measurements were collected during the period 2003 – 2008 to detect changes in ice-shelf thickness through time.

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