Trillion-tonne iceberg breaks off Antarctic ice shelf
Ocean currents could drag the berg as far as the Falkland Islands, posting a threat for ships
An iceberg four times the size of London and one of the largest on record was set adrift after snapping off a West Antarctic ice shelf that is now at increased risk of collapse, scientists said on Wednesday.
A crack in the Larsen C ice shelf, a drifting extension of the land-based ice sheet, finally broke through after inching its way across the ice formation for years.
The calving of ice shelves occurs naturally, though global warming is believed to have accelerated the process. Warmer ocean water erodes the underbelly of the ice shelves, while rising air temperatures weaken them from above.
The calving created an iceberg about 5,800 square kilometres big, with a volume twice that of Lake Erie, one of the North American Great Lakes. It is about 350 metres thick.
“The iceberg weighs more than a trillion tonnes, but it was already floating before it calved away so has no immediate impact on sea level,” said a team of researchers from the MIDAS Antarctic research project. However, it may end up having a considerable impact as its removal could speed up the flow of glaciers from the land into the sea.
It will likely be named A68.
“The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12 per cent, and the landscape of the Antarctic peninsula changed forever,” the team added.
Separation occurred somewhere between Monday and Wednesday, and was recorded by a Nasa satellite.
Icebergs calving from Antarctica are a regular occurrence. But given its size, this behemoth will be closely watched for any potential risk to shipping traffic.
The fate of the berg is hard to predict. It may stay in one piece, or break up.
“Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters,” said lead investigator Adrian Luckman.
According to the European Space Agency, ocean currents could drag the berg, or pieces of it, as far as the Falkland Islands, posting a threat for ships in the Drake Passage.
Floating ice shelves are fed by slow-flowing glaciers from land. Without them, the glaciers would flow directly into the ocean.
With its new shape and size, Larsen C may be less stable than before, the team warned.
If the glaciers held in check by Larsen C were to spill into the Antarctic Ocean, it would lift the global water mark by about 10 centimetres (four inches), other researchers have said.
In 2000, iceberg B-15 broke away from the Ross Ice Shelf in Antarctica, and was the world’s largest recorded iceberg. It was around 295 km long and 37 km wide.