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Q&A: Trapped under ice

autosub1.jpgThe team behind a new Antarctic ice-mapping submarine is breathing a sigh of relief at its safe return, Daniel Cressey reports over on Nature News. The Autosub 3 robot submarine was sent out early this year on a 110-kilometre journey under Pine Island Glacier, which juts out into the Admunsen Sea. But, Cressey writes, there was no guarantee that the sub would ever come back:

Its sister craft, Autosub 2, had been lost on a similar mission in 2005. Autosub 3 was being sent on a much more ambitious mapping expedition, in an environment in which escaping to the surface is not an option.

In a Q&A, the mission’s technical and scientific leaders tell Cressey what might have happened to the lost sub, and why they risked sending out another. Adrian Jenkins of the British Antarctic Survey explains :

Pine Island Glacier is both thinning and accelerating. It’s one of the fastest changing regions in Antarctica at the moment. What we’re trying to do is understand what is driving those changes.

This thinning has been measured by radar altimetry. It’s strongest on the floating parts of the glacier. The favoured hypothesis is that it is a change that has been driven by the oceans — there is some change in the supply of ocean heat and the floating parts of the glaciers, the ice shelves themselves, are now thinning. Because of the thinning, the glaciers feeding the ice shelves flow faster.

Autosub 3’s map of the ice-sheet base and the sea floor topography will help illuminate how the changing ocean interacts with the thinning ice, says Jenkins.

We had some idea of the large scale structure of the ice, but we will certainly come away with a much better picture of how the warm water gets to the crucial regions.

Also weighing in on the sub’s success is Steve McPhail of the UK National Oceanography Centre. Read the full Q&A here.

Anna Barnett

Image: The intrepid autosub / BAS


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