Iceberg twice size of Luxembourg breaks off Antarctic ice shelf: VIDEO
Iceberg twice size of Luxembourg breaks off Antarctic ice shelf
Satellite data confirms ‘calving’ of trillion-tonne, 5,800 sq km iceberg from the Larsen C ice shelf, dramatically altering the landscape
A rift across the Larsen C Ice Shelf as seen from a NASA research aircraft in November. Credit John Sonntag/NASA
source nyt
Wednesday 12 July 2017 10.53 BST First published on Wednesday 12 July 2017 10.16 BST
A giant iceberg twice the size of Luxembourg has broken off an ice shelf on the Antarctic peninsula and is now adrift in the Weddell Sea.
Reported to be “hanging by a thread” last month, the trillion-tonne iceberg was found to have split off from the Larsen C segment of the Larsen ice shelf on Wednesday morning after scientists examined the latest satellite data from the area.
The Larsen C ice shelf is more than 12% smaller in area than before the iceberg broke off – or “calved” – an event that researchers say has changed the landscape of the Antarctic peninsula and left the Larsen C ice shelf at its lowest extent ever recorded.
The Larsen C ice shelf has released an enormous iceberg
“It is a really major event in terms of the size of the ice tablet that we’ve got now drifting away,” said Anna Hogg, an expert in satellite observations of glaciers from the University of Leeds.
At 5,800 sq km the new iceberg, expected to be dubbed A68, is half as big as the record-holding iceberg B-15 which split off from the Ross ice shelf in the year 2000, but it is nonetheless believed to be among the 10 largest icebergs ever recorded.
The huge crack that spawned the new iceberg grew over a period of years, but between 25 May and 31 May alone, the rift grew by 17km – the largest increase since January. Between the 24 June and 27 June the movement of the ice sped up, reaching a rate of more than 10 metres per day for the already-severed section.
But in the end it wasn’t a simple break – data collected just days before the iceberg calved revealed that the rift had branched multiple times. “We see one large [iceberg] for now. It is likely that this will break into smaller pieces as time goes by,” said Adrian Luckman, professor of glaciology at Swansea University and leader of the UK’s Midas project which is focused on the state of the ice shelf.
Unlike thin layers of sea ice, ice shelves are floating masses of ice, hundreds of metres thick, which are attached to huge, grounded ice sheets. These ice shelves act like buttresses, holding back and slowing down the movement into the sea of the glaciers that feed them.
“There is enough ice in Antarctica that if it all melted, or even just flowed into the ocean, sea levels [would] rise by 60 metres,” said Martin Siegert, professor of geosciences at Imperial College London and co-director of the Grantham Institute for Climate Change & Environment.
But while the birth of the huge iceberg might look dramatic, experts say it will not itself result in sea level rises. “It’s like your ice cube in your gin and tonic – it is already floating and if it melts it doesn’t change the volume of water in the glass by very much at all,” said Hogg.
Following the collapse of the more northerly Larsen A ice shelf in 1995 and Larsen B in 2002, all eyes have turned to Larsen C.
But Siegert is quick to point out that the calving of the new iceberg is not a sign that the ice shelf is about to disintegrate, stressing that ice shelves naturally break up as they extend further out into the ocean. “I am not unduly concerned about it – it is not the first mega iceberg ever to have formed,” he said.
Andrew Shepherd, professor of Earth Observation at the University of Leeds, agreed. “Everyone loves a good iceberg, and this one is a corker,” he said. “But despite keeping us waiting for so long, I’m pretty sure that Antarctica won’t be shedding a tear when it’s gone because the continent loses plenty of its ice this way each year, and so it’s really just business as usual!”
Luckman said that while the Larsen C ice shelf might continue to shed icebergs, it might regrow. Nevertheless previous research by the team has suggested that the remaining ice shelf is likely less stable now that the iceberg has calved, although it is unlikely the event would have any short-term effects. “We will have to wait years or decades to know what will happen to the remainder of Larsen C,” he said, pointing out that it took seven years after the release of a large iceberg from Larsen B before the ice shelf became unstable and disintegrated.
