May 15, 2009

Scientists Review Projected Impact of Ice Sheet Melt

Scientists have reevaluated the repercussions that the Earth would suffer if the West Antarctic Ice Sheet were to completely melt.

In the journal Science, researchers said a complete melt of the WAIS would cause a 3.3 meter (10 ft) increase in sea level, compared to previous studies that predicted a rise of five to six meters.

They added that even a rise of lesser levels would still have an impact on coastal cities, including New York.

"Sea level rise is considered to be the one of the most serious consequences of climate change," said lead author Jonathan Bamber of the University of Bristol's Glaciology Centre.

"A sea level rise of just 1.5m would displace 17 million people in Bangladesh alone," he added.

"So it is of the utmost importance to understand the potential threats to coastlines and people living in coastal areas."

The Earth has three ice sheets: Greenland, East Antarctica and West Antarctica. The West Antarctic Ice Sheet is largely considered to be the most dangerous due to impacts from global warming.

"It has been hypothesized for more than 30 years now that the WAIS is inherently unstable," said Professor Bamber.

"This instability means that the ice sheet could potentially rapidly collapse or rapidly put a lot of ice into the oceans."

When scientists first began considering the possibility of a melting WAIS in the 1970s, scientists estimated a global sea level rise of about five meters. Bamber said no one had really challenged that assessment since then, despite the new amounts of data collected.

"Ice thickness data gives you information about the depth of the bedrock underneath the ice sheet," he said.

"Over the past 30 years, we have acquired much more ice thickness data over the whole of Antarctica, particularly over West Antarctica."
"We also have much better surface topography. Those two data sets are critical in determining two things."

"Our reassessment of West Antarctica's contribution to sea level rise if the ice sheet was to collapse is about 3.3 meters," he said.
"That is about half of the value that has been quoted up until now."

In a separate study, Professor Peter Wadhams reported on Wednesday that he believes that the once-permanent ice found in the Arctic may now be so thin that it could be eliminated during the summer seasons in about a decade.

"By 2013 we will see a much smaller area in summertime than now, and certainly by about 2020, I can imagine that only one area will remain in summer," Wadhams told BBC News.

Scientists have previously projected that sea ice would be a mainstay even during the summers until near the end of the century.

"The change is happening so fast. It's the result of this steady thinning over four decades that has brought it to a state where its summer melt is causing it to disappear," Wadhams added.

"It's like the Arctic is covered with an egg shell and the egg shell has been thinning to the point where it is now just cracking completely."


Image Credit: NASA


On The Net:

Bristol Glaciology Centre

British Antarctic Survey