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Monday, February 4, 2008

West Antarctic Ice Sheet (WAIS): "Peering beneath glacier might explain speedier slide" by Anil Ananthaswamy

It must be one of the most dangerous places on Earth to be doing science. Last month, researchers landed on the Pine Island glacier in Antarctica to prepare to make measurements on the ice in the area. The work is crucial. Without it, evidence suggesting that global warming is having a far greater effect on the region than anyone thought will go unrecognised by official climate models.

This remote and heavily crevassed mass of ice is one of many glaciers at the fringes of the massive West Antarctic ice sheet (WAIS). In 2004, satellite measurements showed that it had started thinning, and that the flow of ice had speeded up by 25 per cent over the past 30 years. This raised fears that the acceleration - along with that of nearby glaciers - is a sign of a wider problem in the region.

The glaciers flow towards the Amundsen Sea, where ice shelves are thought to slow their progress. If this ice-shelf "plug" breaks up, around a third of the ice stored in the WAIS could be released, leading to a global rise in sea level of more than a metre.

Like many glaciologists, Robert Bindschadler of NASA's Goddard Space Flight Center in Greenbelt, Maryland, is concerned that the ice-shelf plug is indeed disintegrating - and that this is happening faster than we thought. He says his latest study of satellite measurements, which has yet to be published, shows that the Pine Island glacier has speeded up again over the past two years, from 3 to 3.6 kilometres per year.

One theory is that a layer of warm water a few hundred metres below the sea surface is flowing into trenches beneath the ice shelves and melting them, but no one can be sure. "We have yet to observe what is really going on right where the action is taking place," Bindschadler says. Because of this uncertainty, models used by the Intergovernmental Panel on Climate Change (IPCC) ignore the possible melting of ice shelves and the speed-up of glaciers, so they are unable to predict any global sea level rise due to warming in Antarctica.

Last month, Bindschadler and colleagues deployed the first weather station and GPS units in the region, to keep an eye on the glacier's progress. Over the next two years, they want to drill through 500 metres of ice on the shelf to measure the water temperature and currents underneath. "If we're right, then it will be a great leap forward," says Bindschadler. "But it will be tough to make these observations."

From issue 2641 of New Scientist magazine, 04 February 2008, page 12

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