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March 27, 2008
A VAST iceberg seven times the size of Manhattan has broken away from the Antarctic coast, threatening the collapse of a bigger ice shelf that is now "hanging by a thread".
The Wilkins Shelf on March 6. Picture: AFP Satellite images have revealed that about 415sqkm of the Wilkins Shelf has been lost since the end of last month, suggesting that climate change could be causing it to disintegrate more quickly than scientists had predicted.
"The ice shelf is hanging by a thread," said David Vaughan, of the British Antarctic Survey. "We'll know in the next few days or weeks what its fate will be."
Professor Vaughan was a member of a 1993 BAS team that said the Wilkins Shelf could collapse within 30 years, if the pace of global warming continued.
"Wilkins is the largest ice shelf on the Antarctic Peninsula yet to be threatened," he said. "I didn't expect to see things happen this quickly. We predicted it would happen, but it's happened twice as fast as we predicted."
The retreat of the shelf was first spotted from satellite data by Ted Scambos, a glaciologist at the University of Colorado, who alerted Professor Vaughan and his BAS colleagues. BAS sent a Twin Otter aircraft on a reconnaissance mission.
Jim Elliott, who was on the plane to video the break-up, said: "I've never seen anything like this before - it was awesome. We flew along the main crack and observed the sheer scale of movement from the breakage. Big chunks of ice, the size of small houses, look as though they've been thrown around like rubble - it's like an explosion."
The Wilkins Shelf is protected by only a thin thread of ice between two islands. It covers an area of 14,500sqkm. The Antarctic Peninsula, which stretches north from the frozen continent towards South America, has had unprecedented warming over the past 50 years, leading to the retreat and collapse of several ice shelves. Six have been lost entirely: the Prince Gustav Channel, Larsen Inlet, Larsen B, Wordie, Muller and Jones shelves.
The Wilkins Shelf is farther south than other ice that has retreated, and should thus be protected by colder temperatures. But Professor Vaughan said: "Climate warming in the Antarctic Peninsula has pushed the limit of viability for ice shelves further south, setting some of them that used to be stable on a course of retreat and eventual loss.
"The importance of it is that it's farther south than any ice shelf we've seen retreating before, it's bigger than any ice shelf we've seen retreating before and in the long term it could be a taste of other things to come.
"It is another indication of the impact that climate change is having on the region."
As the shelf is already afloat, it will not affect sea level, but Antarctica's ice shelves act as buffers for land ice that could lead to big changes in sea level if it melts.
The Times
