Monday, December 12, 2011

Tropical Sea Temperatures Influence Melting in Antarctica

A photo from the window of a NASA aircraft shows the rift across the Pine Island Glacier ice shelf running off toward the horizon. The plane flew across the crevasse on Oct. 26, 2011 as part of Operation IceBridge, taking detailed measurements of depth, width and shape. The ice shelf has not calved a major iceberg since 2001. (Credit: Michael Studinger/NASA)

Accelerated melting of two fast-moving outlet glaciers that drain Antarctic ice into the Amundsen Sea Embayment is likely the result, in part, of an increase in sea-surface temperatures in the tropical Pacific Ocean, according to new University of Washington research.

Higher-than-normal sea-level pressure north of the Amundsen Sea sets up westerly winds that push surface water away from the glaciers and allow warmer deep water to rise to the surface under the edges of the glaciers, said Eric Steig, a UW professor of Earth and space sciences.

"This part of Antarctica is affected by what's happening on the rest of the planet, in particular the tropical Pacific," he said.

The research involves the Pine Island and Thwaites glaciers on the West Antarctic Ice Sheet, two of the five largest glaciers in Antarctica. Those two glaciers are important because they drain a large portion of the ice sheet. As they melt from below, they also gain speed, draining the ice sheet faster and contributing to sea level rise. Eventually that could lead to global sea level rise of as much as 6 feet, though that would take hundreds to thousands of years, Steig said.

NASA scientists recently documented that a section of the Pine Island Glacier the size of New York City had begun breaking off into a huge iceberg. Steig noted that such an event is normal and scientists were fortunate to be on hand to capture a video recording. Neither that event nor the new UW findings clearly link thinning Antarctic ice to human causes.

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