Yahoo News 28 Apr 09;
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 square kilometres (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 degrees Celsius (4.5 degrees Fahrenheit), 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 (http://www.esa.int/esaEO/SEMWZS5DHNF_index_0.html).
New York City-Sized Ice Collapses Off Antarctica
Alister Doyle PlanetArk 29 Apr 09;
TROMSOE - An area of an Antarctic ice shelf almost the size of New York City has broken into icebergs this month after the collapse of an ice bridge widely blamed on global warming, a scientist said Tuesday.
"The northern ice front of the Wilkins Ice Shelf has become unstable and the first icebergs have been released," Angelika Humbert, glaciologist at the University of Muenster in Germany, said of European Space Agency satellite images of the shelf.
Humbert told Reuters about 700 sq km (270.3 sq mile) of ice -- bigger than Singapore or Bahrain and almost the size of New York City -- has broken off the Wilkins this month and shattered into a mass of icebergs.
She said 370 sq kms of ice had cracked up in recent days from the Shelf, the latest of about 10 shelves on the Antarctic Peninsula to retreat in a trend linked by the U.N. Climate Panel to global warming.
The new icebergs added to 330 sq kms of ice that broke up earlier this month with the shattering of an ice bridge apparently pinning the Wilkins in place between Charcot island and the Antarctic Peninsula.
Nine other shelves -- ice floating on the sea and linked to the coast -- have receded or collapsed around the Antarctic peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002.
The trend is widely blamed on climate change caused by heat-trapping gases from burning fossil fuels, according to David Vaughan, a British Antarctic Survey scientist who landed by plane on the Wilkins ice bridge with two Reuters reporters in January.
Humbert said by telephone her estimates were that the Wilkins could lose a total of 800 to 3,000 sq kms of area after the ice bridge shattered.
The Wilkins shelf has already shrunk by about a third from its original 16,000 sq kms when first spotted decades ago, its ice so thick would take at least hundreds of years to form.
Temperatures on the Antarctic Peninsula have warmed by up to 3 Celsius (5.4 Fahrenheit) this century, Vaughan said, a trend climate scientists blame on global warming from burning fossil fuels in cars, factories and power plants.
The loss of ice shelves does not raise sea levels significantly because the ice is floating and already mostly submerged by the ocean.
But the big worry is that their loss will allow ice sheets on land to move faster, adding extra water to the seas.
Wilkins has almost no pent-up glaciers behind it, but ice shelves further south hold back vast volumes of ice.
The Arctic Council, grouping nations with territory in the Arctic, is due to meet in Tromsoe, north Norway, Wednesday to debate the impact of melting ice in the north.
(Editing by Sophie Hares)
