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A vast iceberg which calved off an ice shelf three years ago is about to reach the open ocean.
The A-68 iceberg calved from the Larsen C ice shelf in 2017, at which point it weighed up to a trillion tonnes, and measured 2,300 square miles, a quarter of the size of Wales.
Since then it has drifted from Antarctica, edging towards the limit of the continent’s sea ice.
Experts say that it has lost very little of its record-breaking bulk since breaking away.
But A-68 may be no more once it reaches rougher seas, experts told the BBC.
Prof Adrian Luckman from Swansea University, UK said: "With a thickness to length ratio akin to five sheets of A4, I am astonished that the ocean waves haven't already made ice cubes out of A68.”
"If it survives for long as one piece when it moves beyond the edge of the sea-ice, I will be very surprised.”
The huge crack had been spreading across the Antarctic Larsen C ice shelf for many years, but it began accelerating in 2016.
The ice shelf is about 1,100ft thick and floats on the edge of West Antarctica.
“The calving occurred sometime between Monday, July 10 and Wednesday, July 12, when a 5,800-square kilometre (2,200-square mile) section of Larsen C (ice shelf) finally broke away,” Swansea University said in a statement.
The calving of the huge iceberg reduced the size of the ice shelf by 12%.
Scientists from the European Space Agency wrote in 2018: “Sea ice to the east and shallow waters to the north kept this giant berg, named A68, hemmed in.
“So for more than a year it wafted to and fro, but never left its parent ice shelf’s side. Strong winds blowing from Larsen C have finally given it the push it was waiting for.
“In early September 2018, these winds pushed the southern end of the berg out into the Weddell Gyre.
“This clockwise drift of ocean waters and sea ice flowing north past the Larsen shelf, which can be seen in the animation as a flow from right to left, has rotated A68 out into the Weddell Sea.
“Here it is freer to float away and be carried further north into warmer waters.“