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Antarctic iceberg creates shipping hazard

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July 13, 2017

One of the biggest icebergs ever recorded can be seen from a European Space Agency satellite.

The one trillion tonne iceberg that broke away from Antarctica will not change the sea level but could create an enormous hazard for ships if it breaks up into hundreds of smaller pieces, experts say.

One of the biggest icebergs ever recorded, measuring 5800 square km, or more than twice the size of the ACT, finally calved away from the Larsen C Ice Shelf in Antarctica sometime between July 10 and 12.

Marine physicist Dr Natalie Robinson said the event itself will have no impact on sea level as it was already floating.

The potential for an effect on sea level depends on whether the glaciers feeding the ice shelf speed up as a result of this release of pressure, said Dr Robinson, from New Zealand's National Institute of Water and Atmospheric Research.

"What is potentially a much greater immediate impact is the shipping hazard the iceberg presents," she said on Thursday.

She said the iceberg can be observed and tracked from space while it is large and intact.

"However, once it begins to break up it could disintegrate into hundreds (maybe thousands) of smaller icebergs that are too small to be individually tracked, but still represent an enormous hazard from the perspective of a ship navigating these waters."

Researchers from the UK-based Project MIDAS said the iceberg had been hanging on by a thread of ice just 4.5 km wide after rapid advances in the rift in Larsen C earlier this year.

"Although this is a natural event, and we're not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position," team member and Swansea University glaciologist Dr Martin O'Leary said.

It is the furthest back that the ice front has been in recorded history, and the researchers will be watching for signs of the rest of the shelf becoming unstable.

Dr Robinson said there appeared to be no evidence that Larsen C had been subject to the surface melt that led to the rapid collapse of the Larsen B shelf in 2002.

Assistant Professor Duanne White, from the University of Canberra's Institute for Applied Ecology, said the glaciers behind Larsen C hold relatively little ice in the Antarctic context.

"However, should this be the start of the break-up of Larsen C, it adds weight to the question of the stability of the larger, more southerly ice shelves and ice drainage systems, which have the potential to contribute several metres to sea level rise during the next few centuries."

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