5.000 km² iceberg broke free from Antarctic ice shelf

An iceberg from the Antarctic Peninsula that is more than four times the size of London broke off and it is adrift.

12 Jul 2017 – The Guardian

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.

“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.

5.000 km² iceberg broke free from Antarctic ice shelf

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