Antarctic coastal ice thinning surprises experts

OSLO (Reuters) - Scientists are surprised at how extensively coastal ice in Antarctica and Greenland is thinning, according to a study Wednesday that could help predict rising sea levels linked to climate change.

A seal swims by icebergs off the British Antarctic Survey's Rothera base January 23, 2009. REUTERS/Alister Doyle

Analysis of millions of NASA satellite laser images showed the biggest loss of ice was caused by glaciers speeding up when they flowed into the sea, according to scientists at the British Antarctic Survey (BAS) and Bristol University.

“We were surprised to see such a strong pattern of thinning glaciers across such large areas of coastline -- it’s widespread and in some cases thinning extends hundreds of kilometers inland,” said Hamish Pritchard of BAS who led the study.

“We think that warm ocean currents reaching the coast and melting the glacier front is the most likely cause of faster glacier flow,” he said in a statement.

“This kind of ice loss is so poorly understood that it remains the most unpredictable part of future sea level rise,” he added. BAS said the study gave the “most comprehensive picture” of the thinning glaciers so far.

Rising seas caused by a thaw of vast stores of ice on Antarctica and Greenland could threaten Pacific islands, coasts from China to the United States and cities from London to Buenos Aires.

U.N. Secretary-General Ban Ki-moon said earlier this month global warming, blamed mainly on burning fossil fuels, could raise sea levels by 50 cm to 2 meters (20 inches to 6 ft 6 in) this century -- higher than most experts have predicted.

Among findings, Wednesday’s study said 81 of 111 fast-moving glaciers in Greenland were thinning at twice the rate of slow-flowing ice at the same altitude.

“Dynamic thinning of Greenland and Antarctic ice-sheet margins is more sensitive, pervasive, enduring and important than previously realized,” they wrote. “Dynamic thinning” means loss of ice due to a faster flow.

They said it was too early to determine whether the thinning was a sign that sea level rise would accelerate from a current rate of about 3 mm (0.12 inches) a year.

“Working that out is the next task,” David Vaughan, a BAS glaciologist among the authors, told Reuters. Thinning in some areas could be caused by changes in snowfall, for instance, not the slide of ice toward the ocean, he said.