The West Antarctic Ice Sheet, whose melt currently contributes substantially to sea level rise each year, is warming twice as quickly as previously thought, a new study has found.

The temperature record from Byrd Station, a scientific outpost in the centre of the West Antarctic Ice Sheet (WAIS), demonstrates a marked increase of 2.4 degrees Celsius in average annual temperature since 1958 – three times faster than the average temperature rise around the globe.

This temperature increase is nearly double what previous research has suggested, and reveals – for the first time – warming trends during the summer months of the Southern Hemisphere, said David Bromwich, professor of geography at Ohio State University.

“Our record suggests that continued summer warming in West Antarctica could upset the surface mass balance of the ice sheet, so that the region could make an even bigger contribution to sea level rise than it already does,” said Bromwich.

“Even without generating significant mass loss directly, surface melting on the WAIS could contribute to sea level indirectly, by weakening the West Antarctic ice shelves that restrain the region’s natural ice flow into the ocean, he said in a statement.

Andrew Monaghan, study co-author, said that these findings place West Antarctica among the fastest-warming regions on Earth.

“We’ve already seen enhanced surface melting contribute to the breakup of the Antarctic’s Larsen B Ice Shelf, where glaciers at the edge discharged massive sections of ice into the ocean that contributed to sea level rise,” Monaghan said.

“The stakes would be much higher if a similar event occurred to an ice shelf restraining one of the enormous WAIS glaciers,” said Monaghan.

Since the base of the ice sheet rests below sea level, it is vulnerable to direct contact with warm ocean water.

Its melting currently contributes 0.3 mm to sea level rise each year – second to Greenland, whose contribution to sea level rise has been estimated as high as 0.7 mm per year.

The study suggests that if this warming trend continues, melting will become more extensive in the region in the future, Bromwich said.

The study was published in the journal Nature Geoscience.

(This article was published on December 24, 2012)
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