RISES in sea levels are unlikely to be as high as worst-case scenarios have forecast, according to research that shows Greenland's glaciers are slipping into the sea more slowly than previously thought. But the scientists warned that ice loss had still increased by 30 per cent over the past decade and was driving rises in sea levels that endanger low-lying coasts.
Along with Antarctica, the loss of ice from the huge Greenland ice cap is the biggest direct contributor to rising sea levels, pouring 250 billion tonnes of water into the oceans each year. But the predictions of future losses as global warming continues have been wide ranging and controversial. The new research, published in the journal Science, used satellite data for the first time to track the progress of more than 200 Greenland glaciers between 2000 and 2010.
''Previous studies only had a couple of observations from big glaciers,'' said Twila Moon, at the University of Washington in Seattle, who led the research. ''We found we are certainly not on the worst-case scenario, but the glaciers are speeding up and we see no sign of that stopping.''
Half of the ice lost from Greenland is due to simple melting, while the other half is due to the increased flow of glaciers, which leads to more icebergs calving into the sea.
Other recent studies have shown the world's greatest peaks in the Himalayas have lost no ice in the last decade, while the Karakoram glaciers have grown. However, Greenland and Antarctica remain the biggest contributors to sea level rise.
Earlier analyses of Greenland's glaciers found that their speed had doubled in 10 years and was accelerating. Extrapolation of that doubling implied that glacier loss in Greenland would drive up sea level by nine centimetres by 2100, leading to an overall rise of 80 centimetres. Another extrapolation imagined a tenfold rise in glacier speed, leading to 47 centimetres of sea level rise from Greenland and two metres overall. The new research shows glacier acceleration remains ''well below'' even the lower scenario.
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