Huge ice fracture could create one of Antarctica's biggest icebergs ever in coming months, scientists warn

By Victoria Craw

The crack in the Larsen C ice shelf as pictured by NASA. Photo / NASA/John Sonntag
The crack in the Larsen C ice shelf as pictured by NASA. Photo / NASA/John Sonntag

A massive rift in an Antarctic ice shelf is rapidly extending and could create one of the largest icebergs ever within months, scientists have warned.

The UK based Project Midas which is monitoring the Larsen C ice shelf in West Antarctica has warned that a rift on the shelf extended by 18km in the second half of December 2016 and is "poised to calve".

"The Larsen C Ice shelf in Antarctica is primed to shed an area of more than 5000 square km following further substantial rift growth," the team, which is led by Professor Adrian Luckman, wrote on their website.

"Only a final 20km of ice now connects an iceberg one quarter the size of Wales to its parent ice shelf."

"When it calves, the Larsen C Ice Shelf will lose more than 10 per cent of its area to leave the ice front at its most retreated position ever recorded; this event will fundamentally change the landscape of the Antarctic Peninsula."

If it does break away, scientists fear the Larsen C shelf could follow the fate of its predecessors Larsen A and Larsen B which broke up in 1995 and 2002 respectively.

The 2002 event, which was recorded by NASA in a dramatic time-lapse took just over one month for a huge area of ice to break up.

"They had never witnessed such a large area - 3250 square kilometres, or 1250 square miles - disintegrate so rapidly," NASA said at the time.

The Larsen C fracture more than is 350 metres thick, 90 metres wide and 112 kilometres long, according to NASA. It grew more than 20 kilometres between March and August last year, and has expanded rapidly again since then.

Professor Adrian Luckman, who is leading the project, told the BBC he would be "amazed" if the iceberg did not break away in the "next few months".

"There hasn't been enough cloud-free Landsat images but we've managed to combine a pair of Esa Sentinel-1 radar images to notice this extension, and it's so close to calving that I think it's inevitable," he said.

The fracture has rapidly expanded in the last few years, as the picture above shows.  Photo  / Project Midas
The fracture has rapidly expanded in the last few years, as the picture above shows. Photo / Project Midas

Scientists believe the potential break up is a geographic event rather than a climate one as the rift has been present for decades. However it could have been accelerated and may leave the area prone to more "calving" events in future.

"We would expect in the ensuing months to years further calving events, and maybe an eventual collapse - but it's a very hard thing to predict, and our models say it will be less stable; not that it will immediately collapse or anything like that," the professor said.

NASA's Operation IceBridge recently flew 24 flights over Antarctica in a six-week period as part of a project to monitor the rift.

The organisation said the creation of an iceberg will not raise sea levels itself, however the collapse of an ice shelf could accelerate the rate at which the glaciers behind it move towards the ocean, which can lead to sea level rise.

It's estimated if the entire Larsen C shelf collapses, global waters could rise by 10 centimetres due to the enhanced rate at which grounded ice would flow into the ocean.

IceBridge deputy project scientist and glaciologist Joe MacGregor said the team are "curious" about the iceberg that could be created the same size as the state of Delaware.

"It's a large rift on an ice shelf whose future we are curious about. Inevitably, when you see it in satellite imagery or from a plane, you wonder what is going to happen when it breaks off," he said.

"However, large icebergs calve from ice shelves regularly and they normally do not lead to ice-shelf collapse. The growth of this rift likely indicates that the portion of the ice shelf downstream of the rift is no longer holding back any grounded ice."

Follow the rift's progress at Project Midas.

- news.com.au

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