West Antarctica's biggest glacier is melting 50pc faster than in 1994, adding to a global increase in sea levels, US and UK scientists have found.
The Pine Island glacier is losing about 78 cubic km (30 cubic miles) of ice per year, the researchers at Columbia University in New York and the British Antarctic Survey in Cambridge, England, said yesterday. That's up from 53 cubic km in 1994.
The study in the journal 'Nature Geoscience' is based on data from a 2009 expedition.
Scientists are grappling to understand how much Antarctica's ice could contribute to higher sea levels after the United Nations in 2007 predicted they will rise by 18 to 59cm this century.
"The glaciers from the Amundsen Sea region are contributing more to sea-level rise than any other part of Antarctica, so it's imperative we understand the processes involved," Adrian Jenkins, at the British Antarctic Survey, said.
The Pine Island glacier and smaller glaciers that flow into it contain enough ice to boost sea levels by 24cm, according to Columbia. The regional increase in ocean temperatures of 0.2C (0.4F) isn't enough to cause the increase in melt at Pine Island, the researchers said.
They sent a robot submarine beneath the floating portion of the glacier and determined that the ice mass had previously been grounded on a ridge. The ice melted free from the ridge, opening room for warmer waters to circulate, they said.
"More warm water is entering the cavity beneath the ice shelf, and it is warmest where the ice is thickest," Stan Jacobs, an oceanographer at Columbia's Lamont-Doherty Earth Observatory said.