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Tuesday, April 28, 2009

European Space Agency: Wilkins Ice Shelf's northern front now calving and breaking up into ice bergs

Icebergs break away from Antarctic iceshelf

PARIS (AFP) — A huge iceshelf that has wrenched away from the Antarctic peninsula has started to fracture into icebergs, the European Space Agency (ESA) here said on Tuesday.

"Satellite images show that icebergs have begun to calve (break away) from the northern front of the Wilkins Ice Shelf -- indicating that the huge shelf has become unstable," it said in a statement.

The first icebergs started to detach last Friday, in a process that is likely to continue for weeks, ESA said.

"The icebergs are calving as a result of fracture zones that have formed over the last 15 years and which turned Wilkins into a fragile and vulnerable ice shelf," it added.

The Wilkins once covered around 16,000 km² (6,000 square miles) before it began to retreat in the 1990s, and by last May a narrow ice bridge was all that connected it to Charcot and Latady islands.

That last link was smashed on April 5, making the Wilkins the biggest casualty in a two-decade-old series of Antarctic ice-shelf losses and retreats.

"There is little doubt that these changes are the result of atmospheric warming on the Antarctic Peninsula, which has been the most rapid in the Southern Hemisphere," explained David Vaughan from the British Antarctic Survey (BAS).

Pictures have been captured by radar images from ESA's Envisat satellite and the German Aerospace Centre's TerraSAR-X satellite, providing the most detailed evidence yet of an ice shelf's demise.

A long tongue of land that points northwards towards South America, the Antarctic peninsula has been hit by greater warming than almost any other region on Earth.

In the past 50 years, temperatures have risen by 2.5 °C (4.5 °F), around six times the global average.

Ice shelves are ledges that float on the sea and are formed when ice is exuded from the coast by glaciers.

The process of shelf loss is marked by shrinkage and the breakaway of increasingly bigger chunks before the remainder of the shelf snaps away from the coast. It then disintegrates into debris or into icebergs that eventually melt as they drift northwards into warmer water.

ESA has set up a "Webcam from space" with automatic updates from Envisat as it flies over the Wilkins (

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