Ice collapse speeds up glaciers

The collapse of an Antarctic ice shelf two years ago has accelerated the flow of glaciers into the nearby Weddell Sea

The Larsen B ice shelf probably blocked the glaciers' progress before its collapse in 2002, but now they are able to deposit their loads more freely.

US researchers say the findings, which come from satellite data, provide evidence that climate change is bringing major changes to Antarctica.

Details appear in two reports published in Geophysical Research Letters.

The researchers say this is evidence that climate change is bringing major changes to Antarctica.

US researchers used a variety of data from satellites to track the speed of the glaciers before and after the collapse of Larsen B.

In one study, Ted Scambos of the National Snow and Ice Data Center in Boulder, US, analysed five images taken by the Landsat 7 satellite between January 2000 and February 2003.

The analysis reveals that four glaciers flowing into the now collapsed section of Larsen B increased in speed by between two and six times over the study period.

"If anyone was waiting to find out whether Antarctica would respond quickly to climate warming, I think the answer is yes," said Dr Scambos.

The second report, by Eric Rignot of the US space agency's Jet Propulsion Laboratory in Pasadena, US, showed an eightfold increase in the speed of three glaciers, called Hektoria, Green and Evans, between 2000 and 2003.

Two others, Jorum and Crane, moved twice as quickly at the beginning of 2003 than they did in 2000 and nearly three times as fast by the end of the year.

"These two papers clearly illustrate, for the first time, the relationship between ice shelf collapses caused by climate warming, and accelerated glacier flow," said Dr Rignot.

The extra ice presumably translates into higher sea level. But how much this is raising the level of the oceans isn't known.

The authors of the published papers point out that in other places around the continent, much larger glaciers are also held in check by ice shelves.

So further warming could lead to much larger quantities of ice falling into the sea.

The Antarctic peninsula is one of the three fastest-warming regions on Earth - temperatures have risen 2.5 degrees in 50 years.

But the picture generally in Antarctica is complicated, with temperatures in the interior actually falling over the same period.

There is also some evidence that the retreat of the West Antarctic ice sheet, on the other side of the peninsula to the Larsen B shelf, has halted.

Accelerating glaciers contirbute to raised sea levels

Story from BBC NEWS:

Published: 2004/09/22 13:04:29 GMT

Earth warned on 'tipping points'
26 Aug 04 | Science/Nature

Climate fears for rising waters
14 Jul 04 | UK

Ice mission delights scientists
14 Dec 03 | Science/Nature

Ice-tracking satellite in trouble
04 Jul 03 | Science/Nature

Antarctic ice shelf breaks apart
19 Mar 02 | Science/Nature

Geophysical Research Letters http://www.agu.org/journals/gl/


Informant: Teresa Binstock


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