The latest gauging of West Antarctic glaciers confirms that when the ocean eats at one end of a glacier, it can draw far distant ice toward the sea, with potentially dangerous consequences.
As the world warms up, glaciologists' big worry is the impact on polar ice, especially the ice sheet of West Antarctica, which juts from the huge mound of ice in East Antarctica. Although the ice sheet should hold out against warm air for millennia, researchers have long wondered whether warming could somehow get at the sheet indirectly, destabilize it, and send its ice into the sea to melt, raising sea level as much as a disastrous 5 meters in a few centuries. The latest survey of glaciers flowing into West Antarctica's Amundsen Sea, published online today by Science, lends support to this scenario.
By analyzing recent satellite and aircraft data, glaciologist Robert Thomas of NASA contractor EG&G at the Wallops Island facility in Virginia and colleagues confirm that the half-dozen glaciers flowing into the Amundsen Sea have thinned over the past 15 years, and that one of them--the Pine Island Glacier--has been flowing ever faster for more than 100 kilometers inland.
These latest results from West Antarctica confirm an unsettling view of glacier behavior. For 30 years, glaciologists have debated whether one part of a glacier can "feel" what's happening in a distant part of the same glacier. At the coastal, floating end of the Pine Island Glacier, for example, warmer water seems to be melting the ice from below, causing more of it to lift off the sea floor and reducing the ice's resistance to the glacier's flow. This could be why the glacier is accelerating upstream. "I'm convinced the glacier feels what is happening a long way away," says Thomas.
"It's a very impressive piece of work," says glaciologist Richard Alley of Pennsylvania State University, University Park. "Too many different lines of evidence are agreeing now" for them to be wrong about the thinning or the speedup of the past 10 to 15 years. However, Alley and others point out, no one can say whether the recent glacial acceleration will continue, whether it could reach more distant ice if it does continue, or whether other, more voluminous parts of the West Antarctic Ice Shelf could suffer a similar fate.
The West Antarctic Ice Sheet Initiative