Ice crack to put UK Antarctic base in shut-down

Aurora: Halley base has become a centre for the study of space weather

The British Antarctic Survey is to pull all staff out of its space-age Halley base in March for safety reasons.

The highly unusual move is necessary because the Brunt Ice Shelf on which the research station sits has developed a big new crack.

BAS officials say neither staff nor the base are in any immediate danger but believe it would be prudent to withdraw while the situation is assessed.

The plan would be to go back once the Antarctic winter is over, in November.

Halley station comprises a series of hi-tech pods that are mounted on hydraulic legs and skis so that they can be moved periodically further inland, to get away from the shelf edge where icebergs are calved into the ocean.

Unpredictable situation

BAS is in the process of conducting such a move right now. The relocation is all but complete, with the last pod currently in the final stage of being shifted 23km to the new site.

The move was necessitated by a chasm that had opened up in the shelf and which threatened to cut off Halley. But this huge fissure to the west of the station is not the cause of the temporary closure.

Rather, it is another break in the ice some 17km to the north and east of the new base position. It has been dubbed the "Halloween Crack" because it was discovered on 31 October.

"Changes to the ice, particularly the growth of a new crack, presents a complex glaciological picture that means that BAS scientists are unable to predict with certainty what will happen to the ice shelf during the forthcoming Antarctic winter," the research organisation said in a statement.

"As a precautionary measure, BAS will remove its people before the Antarctic winter begins."

Broadly speaking, "north" is towards the top-left of this graphic

The organisation says it does not believe the ice shelf is about to experience a major calving event, but makes the point that if something were to happen it would be very difficult to react in the depths of an Antarctic winter.

"What we've decided is that given the unpredictability, combined with our inability to do anything about it in winter - no aircraft in the continent, it's dark, it's very cold; all those kinds of issues - then actually the prudent thing to do is withdraw our staff, close the station down in a controlled manner and then go back in next summer," BAS director of operations Captain Tim Stockings told BBC News.

Together with the Rothera base on the Antarctic Peninsula, Halley spearheads the UK presence - and scientific activity - on the White Continent.

Halley gathers important weather and climate data, and it played a critical role in the research that identified the ozone "hole" in 1985.

In recent years, Halley has also become a major centre for studying solar activity and the impacts it can have on Earth.

This is most evident in the beautiful auroras that form over the base - the consequence of particles from the Sun crashing into air molecules high in the atmosphere.

Flying the flag

Just under 20 permanent staff reside at Halley. In winter, they would watch over experiments. BAS now has to decide if any of those experiments can be left running autonomously, or whether it is better to just shut everything down.

Scientists have placed sensors on either side of the more than 40km-long Halloween Crack so that they can monitor its status.

"Obviously, we'll seek to get out of those whatever we can; we'll also be using satellite imagery over the winter as well. Then, next season we'll send a team in to re-open the station, verify the measurements from our instruments and take the situation from there," explained Captain Stockings.

"But I should say - we are committed to our presence in that part of the British Antarctic Territory and to the science we do there. Absolutely.

"We've spent a long time finding the new site for Halley VI and of itself this site isn't directly at risk - it's just the unpredictability of the whole area."

The chasm to the west prompted the move but it is not the reason for the winter shut-down

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