Ambitious journey to benefit science

ANNA PEARSON
Last updated 13:00 23/01/2013

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New Zealanders and a scientist from Cambridge University have embarked on an ambitious mission to study the Ross Ice Shelf in Antarctica.

Craig Stewart, Tom Arnold and Poul Christoffersen aim to traverse more than 1000 kilometres on snowmobiles while gathering data on the thickness of the ice shelf.

Their machines and six sleds will be roped together in a 140-metre chain for the duration of their 20-day journey, in case they meet a crevasse along the way.

Mr Stewart was an oceanography technician with the National Institute of Water and Atmospheric Research in Wellington for 4 years before moving to Britain a year ago.

He is gathering measurements for his PhD, after being awarded a one-off Scott Polar Centenary Scholarship funded by the Rutherford Foundation, the Cambridge Commonwealth Trust and Antarctica New Zealand.

Mr Arnold is a field training instructor with Antarctica NZ, and Dr Christoffersen is Mr Stewart's supervisor at the Scott Polar Research Institute at Cambridge.

Mr Stewart is trialling ground-penetrating radar equipment supplied by the British Antarctic Survey, designed specifically for measuring the melt rate of ice shelves.

He measured ice shelves in Antarctica for the British research centre more than a decade ago, but he said the new radar equipment was a lot smaller and lighter, and used less power.

"It can measure thickness with precision much better than a millimetre. It's ridiculously accurate."

He will take measurements at about 60 to 70 sites on the Ross Ice Shelf, and will repeat the exercise next summer to get a melt rate over a year.

He said his research was aimed at understanding how the ocean affected ice shelves in the West Antarctic, to help estimate what might happen to them as a result of climate change.

"We want to cover an area that's big enough to hopefully show a bit of a pattern. If you zoom out, it's like a postage stamp in the corner of the ice shelf."

The radar data would be supplemented by measurements of oceanographic conditions such as temperature, salinity, and the speed and direction of currents, from a mooring under the Ross Ice Shelf about 150km from Scott Base.

Mr Stewart said ice shelves were the "floating extension" of the Antarctic ice sheet, where snow accumulated in the centre and gradually flowed out.

He said there would be no change in sea level if they melted instantly, because they were already displacing water - like ice cubes floating in a glass.

But their absence would eventually contribute to sea level rise, via an indirect effect. Glaciers flowed faster without the buttressing effect of ice shelves, and sea levels increased when glaciers melted or floated away.

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"[Ice shelves] are sort of like corks in a bottle. They push against the glaciers that are feeding them.

"The West Antarctic Ice Sheet, if fully floated, would cause about 3 metres of sea level rise."

He said the logistics required to support his research in Antarctica were "huge", and included setting up a fuel cache about 50km from Scott Base and undergoing crevasse rescue training.

The most dangerous part of the 1000km journey would be crossing the "shear zone", where the McMurdo Ice Shelf met the Ross Ice Shelf.

"The Ross Ice Shelf is rubbing past the McMurdo Ice Shelf. There are a lot of crevasses there because of the motion."

- The Nelson Mail

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