Rapid ice movement monitored by UK polar base

By | September 13, 2023

Scientists are looking closely at the fast pace of a vast band of floating Antarctic ice that hosts a British base.

Halley Station is located on the Brunt Ice Shelf, which has seen a sharp acceleration in recent months after giant icebergs calved.

There is no immediate concern that the rest of Brunt will split and condemn the currently unoccupied base.

But British Antarctic Survey officials say more stability is needed before expanded operations can resume.

‘Daily monitoring’

The decision to lay off winter staffing was made seven years ago, with Halley now only staffing during the Southern Hemisphere summer season, which begins in November. Forty people will visit the station, along with a ship carrying supplies.

Professor Dominic Hodgson said he was happy for this work to proceed.

“The shelf has given no indication that it is about to fragment and pose an imminent danger to our infrastructure,” he told BBC News.

“And we will continue to do what we have done for the last few years, which is to monitor the situation on a daily basis to see if any behavior emerges that we didn’t anticipate.”

Brunt ice shelf

Brunt ice shelf

Professor Hodgson, together with BAS colleague Dr Oliver Marsh and remote sensing expert Professor Adrian Luckman, from Swansea University, have just submitted a report on the state of the Brunt Ice Shelf to the online magazine The Cryosphere .

The Brunt is an amalgam of ice, about 150-200 meters thick, which broke away from the Antarctic continent and pushed into the Weddell Sea.

This floating mass has historically had a forward speed of 400-800 meters per year. But there has been a dramatic acceleration, from about 900 million per year in early 2023 to 1,500 million by August.

The data comes from precise GPS measurements around Halley and radar observations from the European Union’s Sentinel-1a satellite.

The acceleration follows the calving of two major icebergs from Brunt’s leading edge: a 1,300-square-kilometer behemoth called A74, in February 2021, and an equally gigantic sheet called A81, in January this year. .

The A74’s impact was minimal, but the A81 appears to have freed the platform from a shallow section of seabed that normally locks it in place and slows its seaward momentum.

Furthermore, these calvings – and there was another smaller one in June – have resulted in new areas of stress on the ice shelf.

Beveled edge

The Brunt is a floating mass of ice measuring a few thousand square kilometers

Professor Luckman said: “The Brunt has lost contact with this anchor point, known as the McDonald Ice Rumples, and as a result, it has accelerated and is thinning. And now you can actually see cracks starting to open up at the base “. line (the area where ice from the continent becomes floating), west and south of Halley.”

“How this will end, no one knows,” Professor Luckman added.

The latest data from Sentinel-1a indicates that the acceleration of the platform on the grounding line has faltered in recent days but continues to move at high speed, so cracks are likely still opening up in the ice.

What seems clear is that the behavior observed by Brunt has nothing to do with climate change. There is no atmospheric or oceanic data to suggest this is a factor.

‘Settle down’

The UK has had a foothold in various forms on the Brunt since the 1950s. Critical research included the discovery of the ozone hole in the 1980s.

Occasionally, Halley’s buildings were demolished or abandoned when they had exceeded their maintenance life or were simply buried in deep snow.

But the current situation, the sixth iteration of the base, is very different and the possibility that it could run aground on a fragmented ice shelf cannot be entirely ignored, Professor Hodgson said.

“The hope must be that a thicker section of the shelf will eventually cling to the seafloor again to re-establish the old stability. And we can see from the geological record that these anchor points are being occupied and re-occupied. So everything might just settle back down “, he added.

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