AN ANTARCTIC ice shelf larger than the Western Isles has astonished scientists by collapsing in just a month.
The 1,250 square mile Larsen B disintegrated into icebergs and fragments amid temperatures that rose on the Antarctic peninsula faster than anywhere on Earth.
The 650ft-thick ice sheet is one of five on the continent that have been steadily shrinking because of global warming.
However, the collapse - the biggest of its kind for three decades - will not immediately raise sea levels because the ice shelf was already floating on the edge of the Antarctic land mass.
Dr David Vaughan, a glaciologist with the British Antarctic Survey, said: "In 1998, we predicted the demise of more ice shelves around the Antarctic peninsula. Since then, warming on the peninsula has continued and we watched as, piece-by-piece, Larsen B has retreated.
"We knew what was left would collapse eventually, but the speed of it is staggering. Hard to believe 500 billion tonnes of ice sheet has disintegrated in less than a month."
Ice experts from the University of Colorado first noted the collapse on satellite images this month, before an aircraft was mobilised to take aerial photographs.
The James Clerk Ross, a BAS research ship, navigated her way through the armada of icebergs to obtain photographs and samples.
The break-up, which has been monitored by scientists across the world, is thought to have been triggered by warm spring temperatures and a 20 per cent increase in the ice shelf’s flow rate. Scientists hope the information will enable them to identify which ice shelves will be threatened in the future.
Sea levels could eventually be affected if ice from a glacier behind the Larsen B, on the eastern side of the Antarctic peninsula, begins to flow into the sea more rapidly.
The ice shelf, named after a Norwegian whaler who sailed along its front in 1893, is now a plume of thousands of icebergs adrift in the Weddell Sea. It is thought to have existed for at least 400 years.
Temperatures on the peninsula have increased by 2.5C since the 1940s - more rapidly than the rest of the continent.
Dr Ted Scambos, a glaciologist at the National Snow and Ice Data Centre at the University of Colorado, said other ice shelves were more vulnerable than previously feared. He said: "They are closer to the limit than we thought. The next shelf to the south, the Larsen C, is very near its stability limit - and regions of the giant Ross ice shelf are just a few degrees Celsius away from being overtaken by the same process. Loss of ice shelves surrounding the Antarctic continent could have a major effect on the rate of ice flow off the continent."
Michael Meacher, the environment minister, said: " I think it is a wake-up call to the world [and] shows the effect we are having on the planet."