Antarctic ice shelf set to collapse

ABC News Online, Posted 14 minutes ago

http://www.abc.net.au/news/stories/2009/01/20/2469687.htm

A huge Antarctic ice shelf is on the brink of collapse with just a sliver of ice holding it in place, the latest victim of global warming that is altering maps of the frozen continent.

"We've come to the Wilkins Ice Shelf to see its final death throes," David Vaughan, a glaciologist at the British Antarctic Survey (BAS), said after the first - and probably last - plane landed near the narrowest part of the ice.

The flat-topped shelf has an area of thousands of square kilometres, jutting 20 metres out of the sea off the Antarctic Peninsula.

But it is held together only by an ever-thinning 40-kilometre strip of ice that has eroded to an hour-glass shape just 500 metres wide at its narrowest.

In 1950, the strip was almost 100 kilometres wide.

"It really could go at any minute," Dr Vaughan said on slushy snow in bright sunshine beside a red Twin Otter plane that landed on skis. He added that the ice bridge could linger weeks or months.

The Wilkins once covered 16,000 square kilometres. It has lost a third of its area but is still about the size of Jamaica. Once the strip breaks up, the sea is likely to sweep away much of the remaining ice.

Icebergs the shape and size of shopping malls already dot the sea around the shelf as it disintegrates. Seals bask in the southern hemisphere summer sunshine on icebergs by expanses of open water.

A year ago, BAS said the Wilkins was "hanging by a thread" after an aerial survey. "Miraculously we've come back a summer later and it's still here. If it was hanging by a thread last year, it's hanging by a filament this year," Dr Vaughan said.

Nine other shelves have receded or collapsed around the Antarctic peninsula in the past 50 years, often abruptly like the Larsen A in 1995 or the Larsen B in 2002. The trend is widely blamed on climate change caused by heat-trapping gases from burning fossil fuels.

"This ice shelf and the nine other shelves that we have seen with a similar trajectory are a consequence of warming," Dr Vaughan said.

In total, about 25,000 square kilometres of ice shelves have been lost, changing maps of Antarctica. Ocean sediments indicate that some shelves had been in place for at least 10,000 years.

- Reuters