Friday, July 11, 2008

Antarctic ice shelf 'hanging on by a thread'

ABC News Online, 

Posted Fri Jul 11, 2008 2:23pm AEST

It might be the depths of winter in Antarctica but scientists say they're seeing more signs of global warming on the frozen continent.

New satellite photos show the Wilkins Ice Shelf is even closer to breaking from the peninsula. Experts say the effects of warming there now look irreversible.

That may eventually lead to rising sea levels in more populated parts of the world.

Neal Young is a glaciologist with the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart, and is scrutinising pictures from the European Space Agency.

"What we can see is a sequence of images so you can from late May through to early July, showing this ice shelf, Wilkins Ice Shelf, gradually breaking up," he said.

"We can see large icebergs forming.

"We can see fractures forming in the shelf itself such that it is now reducing down to a slender strip of ice connecting to one island called Charcot Island, and back to another island behind it, Alexander Island."


Dr Young says he expects this ice shelf will break free soon.

"This ice shelf is in the region called the Antarctic Peninsula. This one is on the west side of the peninsula," he said.

"Two sections of another ice shelf called Larsen Ice Shelf on the eastern side of the peninsula broke up over the last decade or so - one section back in 1995 and another one, Larsen B in 2002."

He says it's a progression that calls attention to what's happening in Antarctica - and an irreversible one at that.

"There are indicators of change going on and the message that is coming through now is this change is continuing," he said.

"The way things are trending and what we can see right now, it certainly looks [irreversible]."

World is watching

On the other side of the world, developments are also being watched at the United States National Snow and Ice Data Centre in Colorado.

Walt Meier is a research scientist there.

"Summertime is becoming warmer in the Antarctic Peninsula area where the Wilkins is and so we have had more melt than in the past, and that's obviously going to make things more susceptible to breaking up," he said.

"We also have had a strong decrease in sea ice in that area particularly in the summertime and that allows warmer ocean currents and oceans waves to kind of buffet that ice shelf, and that also probably contributes to the break up.

"So it's really a fundamentally, at the most basic level, a response to warmer temperatures."

Dr Meier contributed to last October's report by the Intergovernmental Panel on Climate Change.

He says it's no exaggeration to say the Wilkins Ice Shelf is hanging by the thinnest of threads.

"There is still a fair amount of ice there but one of the things that has been stabilising it is this rather thin kind of narrow slab of ice that is connecting the main part of the ice shelf to an island to the north," he said.

"You can see in the image - the most recent imagery - that that thin kind of connection, that thread so to speak, is getting thinner and thinner.

"And once that breaks away, it is going to destabilise the ice shelf. It is kind of like an arch in a cathedral or something.

"It can be quite a delicate structure but it can be reasonably strong because it is all connected but when you take away that keystone, you suddenly weaken the structure and it could collapse quite quickly."

Adapted from a story by Simon Santow for The World Today, July 11.

No comments: