"It's sort of enigmatic, because it means temperatures are warming, but snowfall is increasing," Meier said.
Also important for understanding the consequences of climate change, at least in Antarctica, is the behavior of ice shelves, the steep ice cliffs at the edge of an ice sheet.
Research by Ted Scambos of the University of Colorado at Boulder, suggests that ice shelves in the Antarctic may be more vulnerable to warming-induced break up than previously thought.
He and his colleagues developed a model for how cracks push their way through an ice shelf, and applied it to the so-called "Larson B Ice Shelf" in the Antarctic. In the model, a relatively small amount of melted water on the surface seeps into fractures in the ice, breaking up the ice shelf when it freezes. The shelf then collapses surprisingly quickly, without first having to warm all the way through, as scientists had generally assumed.
"We found that ice shelves thought to be stable are probably susceptible to breakup," Scambos said.
Since the late 1970s, ice shelves in some of the northernmost areas of the Antarctic ice sheet have exhibited the dramatic breakup style that Scambos and his colleagues attribute to this "inside-out" disintegration process. Before that, the shelves shed their ice in a more gradual fashion, he said.
The researchers have observed melt ponds forming in these particular regions, and believe this melting may be triggering the ice-shelf collapse. It would take several more decades of warming, however, before the actively shedding Ross Ice Shelf would be likely to undergo such a change, Scambos noted.
"This area is clearly experiencing a strong regional warming," Scambos said. It's too early, however, to make a connection between this trend and greenhouse warming caused by humans, Scambos cautioned.
Melting ice from somewhere else in the Antarctic ice sheet is contributing to sea-level rise, but the source
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Contact: Monica Amarelo
mamarelo@aaas.org
617-236-1550
American Association for the Advancement of Science
16-Feb-2002