Study: Antarctic glaciers slipping swiftly seaward
GENEVA ” Antarctic glaciers are melting faster across a much wider area than previously thought, scientists said Wednesday ” a development that could lead to an unprecedented rise in sea levels.
A report by thousands of scientists for the 2007-2008 International Polar Year concluded that the western part of the continent is warming up, not just the Antarctic Peninsula.
Previously most of the warming was thought to occur on the narrow stretch pointing toward South America, said Colin Summerhayes, executive director of the Britain-based Scientific Committee on Antarctic Research and a member of International Polar Year’s steering committee.
But satellite data and automated weather stations indicate otherwise.
“The warming we see in the peninsula also extends all the way down to what is called west Antarctica,” Summerhayes told The Associated Press. “That’s unusual and unexpected.”
For the International Polar Year, scientists from more than 60 countries have been conducting intense Arctic and Antarctic research over the past two southern summer seasons ” on the ice, at sea, and via icebreaker, submarine and surveillance satellite.
The biggest west Antarctic glacier, the Pine Island Glacier, is moving 40 percent faster than it was in the 1970s, discharging water and ice more rapidly into the ocean, Summerhayes said.
The Smith Glacier, also in west Antarctica, is moving 83 percent faster than it did in 1992, he said.
All the glaciers in the area together are losing a total of around 103 billion tons (114 billion U.S. tons) per year because the discharge is much greater than the new snowfall, he said.
“That’s equivalent to the current mass loss from the whole of the Greenland ice sheet,” Summerhayes said, adding that the glaciers’ discharge was making a significant contribution to the rise in sea levels. “We didn’t realize it was moving that fast.”
The glaciers are slipping into the sea faster because the floating ice shelf that would normally stop them ” usually 650 to 980 feet (200 to 300 meters) thick ” is melting.
The warming of western Antarctica is a real concern.
“There’s some people who fear that this is the first signs of an incipient collapse of the west Antarctic ice sheet,” Summerhayes said.
Antarctica’s average annual temperature has increased by about 1 degree Fahrenheit (0.56 degrees Celsius) since 1957, but is still 50 degrees Fahrenheit (45.6 degrees Celsius) below zero, according to a recent study by Eric Steig of the University of Washington.
Summerhayes said sea levels will rise faster than predicted by the Intergovernmental Panel on Climate Change, a group set up by the United Nations.
A 2007 IPCC report predicted a sea level rise of 7 to 23 inches (18 to 58 centimeters) by the end of the century, which could flood low-lying areas and force millions to flee. The group said an additional 3.9 to 7.8 inches (10 to 20 centimeters) rise was possible if the recent, surprising melting of polar ice sheets continues.
Summerhayes said the rise could be much higher.
“If the west Antarctica sheet collapses, then we’re looking at a sea level rise of between 1 meter and 1.5 meters (3 feet, 4 inches to nearly 5 feet),” Summerhayes said.
Ian Allison, co-chair of the International Polar Year’s steering committee, said many scientists now say the upper limit for sea level rise should be higher than predicted by IPCC.
“That has a very large impact,” Allison said, adding that extremely large storms which might previously have occurred once in a year would start to occur on a weekly basis.
The IPY researchers found the southern ocean around Antarctica has warmed about 0.2 degrees Celsius (0.36 degrees Fahrenheit) in the past decade, double the average warming of the rest of the Earth’s oceans over the past 30 years.