by Richard Van Noorden, Nature blog, The Great Beyond, September 24, 2009

The edges of ice sheets in Greenland and the Antarctic are thinning faster than we’d thought, thanks to a surprisingly extensive network of fast-flowing and accelerating glaciers, new satellite measurements show (Nature, doi:10.1038/nature08471).

"We were surprised to see such a strong pattern of thinning glaciers across such large areas of coastline – it's widespread and in some cases thinning extends hundreds of kilometres inland. We think that warm ocean currents reaching the coast and melting the glacier front is the most likely cause of faster glacier flow. This kind of ice loss is so poorly understood that it remains the most unpredictable part of future sea level rise," said Hamish Pritchard, of the British Antarctic Survey [press release].

"This report provides a much more ominous picture than we have had, and a depressing prospect of the potential for sea level rise," Inez Fung, an atmospheric scientist at UC Berkeley, told the San Francisco Chronicle. "It's very much a cause for worry."

Pritchard and other researchers analysed some 50 million laser readings from Nasa’s ICESat (Ice, Cloud and land Elevation Satellite) between 2003 and 2007. 81 of 111 Greenland glaciers surveyed are thinning at an accelerating, self-feeding pace, AP highlights. While in parts of Antarctica, ice sheets have been losing 30 feet a year in thickness since 2003 (though there’s plenty of ice to get through – some of these areas are a mile thick). “To some extent, it’s a runaway effect. The question is, how far will it run?” Pritchard tells them.
That’s what everyone wants to know, and the scientists were careful to point out that it was “too early to determine whether the thinning was a sign that sea level rise would accelerate” (Reuters).

Image credit: British Antarctic Survey