Evidence shows glaciers' thinning is speeding up

Long-term sea levels could be affected globally

The Nation

September 24, 2004|By Earl Lane | Earl Lane,NEWSDAY

WASHINGTON - Scientists are finding new evidence some glaciers in Antarctica may be slip-sliding away, a process with potentially serious consequences over the long term for global sea levels.

In a study published online today by the journal Science, a team of researchers reports that several glaciers in West Antarctica are thinning more rapidly than a decade ago. While most of the thinning is close to the coast, one of the largest ice masses, the Pine Island Glacier, is thinning at an accelerated rate as far as 186 miles inland.

Two other studies, published Wednesday in Geophysical Research Letters, report that elsewhere several glaciers on the Antarctic Peninsula have been thinning and flowing more rapidly into the Weddell Sea since the quick breakup in 2002 of an ice shelf called Larsen B.

Ice shelves, some as large as Texas, form in the bays of the Antarctic when land-based glaciers creep seaward, become detached from the underlying bedrock and float. Scientists have debated whether they slow the glaciers that feed them.

The Larsen B shelf broke apart in a matter of weeks. The new studies found that between 2002 and 2003, three glaciers behind it then began moving eight times as fast.

The Larsen shelf may have broken up as warming air temperatures in the peninsula caused water to pool on the shelf surface, opening deep cracks in the ice, experts said.

"If anyone was waiting to find out whether Antarctica would respond quickly to climate warming, I think the answer is yes," Ted Scambos, a University of Colorado glaciologist and lead author of one of the papers, said in a statement. "We've seen 150 miles of coastline change drastically in just 15 years."

In an interview, Scambos said he suspects that the Antarctic warming may reflect more general global warming due to release of heat-trapping gases by human activity.

While the Larsen-area glaciers are too small to significantly affect global sea levels, specialists said, their fate could offer clues to what may happen if the larger ice shelves and glaciers of West Antarctica are similarly affected. For the West Antarctic glaciers studied, the amount of ice entering the ocean and melting is sufficient to raise sea levels globally by about 0.24 millimeters a year, the authors say. If the glacier thinning were to continue accelerating, experts said, the sea-level rise could become more troubling over the next century or more.

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