He and his colleagues initially thought the fast-moving ice streams within the West Antarctic Ice Sheet might be the culprit.
"We studied these ice streams for a long time, but they're not providing the signal for a large increase in sea-level rise. One has stopped, and another major one is decelerating," Bindschadler said.
On the other hand, a certain region making up approximately 20 percent of the ice sheet does appear to be retreating and thinning quite rapidly, Bindschadler and his colleagues have found. This region includes the basin that feeds the Pine Island and Thwaites Glaciers.
"That's where the action is," Bindschadler said.
He noted that these glaciers may behave quite differently from the well-studied ice streams, so more research is needed before scientists can say exactly what the West Antarctic ice sheet is doing now and what it will do in the future.
Evidence of recent warming isn't limited to the Antarctic. The northern high latitudes are showing key signs of change, according to Mark Serreze of the University of Colorado at Boulder.
He cited the thinning and breakup of sea ice, the warming of water masses deep in the oceans, the diminishing of snow cover, and the thawing of permafrost in Alaska and Russia. In addition, new research by Serreze suggests that Siberian rivers have begun discharging more freshwater into the sea.
"Together, these data create a coherent picture of high latitude change," Serreze said.
Researchers have yet to determine whether this change is the result of human activity, or whether it simply corresponds to natural atmospheric variations that occur on the order of decades, according to Serreze.
"It isn't resolved yet. To be a responsible scientist you have to be a fence sitter on this issue," he said.
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Contact: Monica Amarelo
mamarelo@aaas.org
617-236-1550
American Association for the Advancement of Science
16-Feb-2002