Scambos alerted colleagues at the British Antarctic Survey (BAS) that it looked like the entire ice shelf — about 6,180 square miles (about the size of Northern Ireland)— was at risk of collapsing.

David Vaughan of the BAS had predicted in 1993 that the northern part of the Wilkins Ice Shelf was likely to be lost within 30 years if warming on the Peninsula continued at the same rate.

"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. The ice shelf is hanging by a thread — we'll know in the next few days and weeks what its fate will be."

The area collapsed measures about 415 sq km, almost two thirds the size of singapore, according to the satellite imagery from the University of Colorado's National Snow and Ice Data Centre. The wilkins sheet of permanant floating ice spanning about 3000 sq km of the rapidly warming south-west Antarctica Peninsular, about south of South America.

"Block after block of ice just tumbling into the ocean," said Dr Ted Scambos, lead scientist at the National Snow and Ice Data Centre. "The shelf is not just cracking off and a piece goes drifting away, but totally shattering. These kinds of events we don't see very often." He said a large part of the shelf is now supported by only a thin strip of ice. "The warming that's going on in the penisula is pretty clearly tied to green house gases increases."

Aircraft reconnaissance
The BAS scientists sent an aircraft out on a reconnaissance mission to survey the extent of damage to the ice shelf.

Jim Elliot, who captured video of the breakout 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 hefty chunks of ice, the size of small houses, look as though they've been thrown around like rubble — it's like an explosion."

An initial iceberg calved away from the Wilkins Ice Shelf on Feb. 28. A series of images shows the edge of the ice shelf proceeding to crumble and disintegrate in a pattern characteristic of climate-caused ice shelf retreats throughout the northern Antarctic Peninsula. The disintegration left a sky-blue patch of hundreds of large blocks of exposed old glacier ice floating across the ocean surface.


By March 8, the ice shelf had lost just over 160 square miles of ice, and the disintegrated ice had spread over 540 square miles. As of mid-March only a narrow strip of shelf ice between Charcot and Latady islands was protecting several thousand more kilometers of the ice shelf from potentially breaking up.

The region where the Wilkins Ice Shelf lies has experienced unprecedented warming in the past 50 years, with several ice shelves retreating in the past 30 years. Six of these ice shelves have collapsed completely: Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B , Wordie, Muller and the Jones Ice Shelf.

Antarctic warming
The Wilkins Ice Shelf was stable for most of the last century until it began retreating in the 1990s. A previous major breakout occurred there in 1998 when 390 square miles of ice was lost in just a few months.


"We believe the Wilkins has been in place for at least a few hundred years, but warm air and exposure to ocean waves are causing it to break up," Scambos said.

The Antarctic Peninsula has warmed faster than anywhere else in the Southern Hemisphere; temperature records show that the region has warmed by 4.5 degrees Fahrenheit during the past 50 years — several times the global average and only matched in Alaska.

source: reuters/msnbc