Tuesday 24 April 2018

Trillion-tonne iceberg 'bigger than Mayo' breaks from Antarctic shelf

An aerial view of the Larsen C ice rift in Antarctica, in an image from Nasa via Swansea University. Photo: AFP/John Sonntag.
An aerial view of the Larsen C ice rift in Antarctica, in an image from Nasa via Swansea University. Photo: AFP/John Sonntag.
Paul Melia

Paul Melia

A Trillion-tonne iceberg, one of the biggest on record and larger than Mayo, has broken free from an ice shelf in Antarctica.

Scientists said some 5,800sq km of ice broke away from the Larsen C ice shelf between Monday and yesterday after "hanging by a thread" for the past number of months.

A team from Swansea University's MIDAS project, which has been monitoring the shelf, said the break was confirmed by a US satellite passing overhead. The iceberg, which is likely to be named A68, has a volume twice that of Lake Erie, one of the Great Lakes in the US.

Professor Adrian Luckman, of Swansea University, lead investigator of the MIDAS project, said some of the ice might remain in the area for decades, while parts might also drift to warmer waters. It will have to be monitored to ensure if currents and winds push it northwards, it does not pose a hazard to shipping.

"We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice," he said.

"We will continue to monitor both the impact of this calving event on the Larsen C ice shelf, and the fate of this huge iceberg.

An image obtained from Nasa showing the Antarctic Peninsula’s rift in the Larsen C ice shelf. Photo: AFP/Getty Images
An image obtained from Nasa showing the Antarctic Peninsula’s rift in the Larsen C ice shelf. Photo: AFP/Getty Images

"The iceberg is one of the largest recorded and its future progress is difficult to predict. It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters."

The Larsen C ice shelf, which has a thickness of up to 600 metres, floats on the ocean at the edge of the Antarctic Peninsula, holding back the flow of glaciers that feed into it. MIDAS researchers have monitored the rift for years, following the collapse of the Larsen A ice shelf in 1995 and the sudden break-up of the Larsen B shelf seven years later.

Rapid advances were noted in January, May and June, which increased the length of the rift to more than 200km and left the iceberg hanging on by a thread of ice just 4.5km wide. Scientists stressed it was a natural event, but it put the ice shelf in a "vulnerable position".

While this new iceberg will not immediately raise sea levels, if the shelf loses much more of its area, it could result in glaciers speeding up their passage towards the ocean, which could have an eventual impact, raising sea levels by up to 10cm.

Nasa has raised concerns that climate change is resulting in ancient ice sheets covering Greenland and Antarctica becoming destabilised due to a warming planet. This will result in sea level rise, it said.

Separately, the Sustainable Energy Authority of Ireland has warned that more action is needed to combat growing emissions which are exacerbating climate change. The agency said there has been a "general decrease" in society's acceptance of renewable energy projects despite the need to reduce emissions from electricity generation, and there was a need for a "rational, open debate".

The agency plans to conduct education campaigns to help people reduce energy use, target deep retrofits of buildings and increase take-up of electric vehicles under its five-year strategy to 2021.

Irish Independent

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