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Link: http://www.guardian.co.uk/climatechange/story/0,12374,1466032,00.html

Antarctic glaciers retreat under climate onslaught

Biggest changes have occurred in last five years, say scientists

Ian Sample, science correspondent
Friday April 22, 2005
The Guardian

Glaciers on the Antarctic Peninsula are shrinking rapidly as a result of climate change, scientists have found.

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In the most comprehensive study of its kind, researchers measured 244 glaciers on the peninsula, each typically stretching tens of miles from the Antarctic mountains to the surrounding seas. They found 87% had retreated significantly in the past 50 years.

The peninsula is the most northern part of Antarctica, and the only part of the continent that extends outside the Antarctic Circle. It lies in the western hemisphere, facing South America.

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Alison Cook, a scientist with the British Antarctic Survey, built up a picture of the glaciers' history by taking measurements from more than 2,000 aerial photographs taken since the 1940s, along with more than 100 modern satellite images.

She found that the vast majority of glaciers had begun to shrink, with the most dramatic retreats being seen since the turn of the millennium.

"Fifty years ago, most of the glaciers we looked at were slowly growing in length, but since then this pattern has changed. In the last five years, the majority were actually shrinking rapidly," she said.

Temperatures in the region have warmed considerably, with a rise of more than 2C in the past 50 years.

Scientists are unsure whether the increase - up to five times greater than would be expected from typical global warming - can be attributed solely to man-made climate change or is exacerbated by natural climate variation.

"Either way, continuing retreat of the glaciers in this area is important because it could allow more ice to drain from further inland and contribute to sea level rise," said David Vaughan, another British Antarctic Survey scientist involved in the study.

The retreat of the glaciers could have minor benefits for local wildlife, as previously covered ground becomes exposed, though the long term effects of such an ecological change are hard to predict.

Although the steady loss of the glaciers is unlikely to lead to local ecological disaster, the speed with which they are disappearing was an alarming indication of the effects of climate change, said Dr Vaughan.

According to the study, which was carried out with researchers at the US Geological Survey and appears today in the journal Science, the Sjogren glacier at the northern end of the peninsula has retreated the most, eight miles, since 1993, while the Widdowson glacier on the peninsula's west coast has shrunk the fastest, at a rate of 1,100 metres a year for the past five years.

On average, glaciers were found to have retreated at a rate of 50 metres a year in the past five years, faster than at any time in the past five decades.

"This is another piece of the jigsaw that tells us how climate change is changing the planet," said Dr Vaughan.

Dotted between the 212 glaciers that were shrinking, the scientists found 32 that had grown longer by an average of 300 metres in the past 50 years. This could be down to specific geological conditions beneath the glaciers which meant they could grow even when temperatures were rising, said Dr Vaughan.

Last year, scientists reported that several glaciers in western Antarctica were thinning and melting even faster into the sea, most probably because of warmer air and sea temperatures.

They estimated the glaciers were losing 250 cubic kilometres of ice to the seas each year, about 60% more than they gained through snowfall.