February 16, 2006

Greenland Glaciers Disappearing More Quickly: Study

By Maggie Fox, Health and Science Correspondent

ST. LOUIS (Reuters) - Greenland's glaciers are dumping more than twice as much ice into the Atlantic Ocean now as 10 years ago because glaciers are sliding off the land more quickly, researchers said on Thursday.

This could mean oceans will rise even faster than forecast, and rising surface air temperatures appear to be to blame, the researchers report in Friday's issue of the journal Science.

Glaciers around the world are disappearing quickly, several researchers told a meeting of the American Association for the Advancement of Science, which publishes Science.

"Greenland is probably going to contribute more and faster to sea level rise than predicted," Eric Rignot of NASA's Jet Propulsion Laboratory at the California Institute of Technology told a news conference.

Between 1996 and 2006, the amount of water lost from Greenland's ice sheet has more than doubled from 90 cubic kilometers to 220 cubic kilometers a year, Rignot said.

"One cubic kilometer is the amount of water Los Angeles uses in a year. Two-hundred cubic kilometers of water is a lot of fresh water," Rignot said.

Other experts agreed this could mean scientists have underestimated how much the sea level will rise in the future as the planet warms.

"At 1.7 million square km (656,000 square miles), up to 3 km (nearly two miles) thick and a little smaller than Mexico, the Greenland Ice Sheet would raise global sea level by about 7 meters (22 feet) if it melted completely," Julian Dowdeswell of the Scott Polar Research Institute at Britain's Cambridge University wrote in a commentary in Science.

The study did not explore what is causing the rising air temperatures in Greenland, but most scientists agree that human activity, notably the burning of fossil fuels, is playing an important role in global warming.


Rignot and Pannir Kanagaratnam of the University of Kansas used satellite data to track the movement of Greenland's glaciers, which slide slowly down to the sea and deposit ice.

They calculated that Greenland contributes about 0.02 inch (half a millimeter) to the annual 0.1 inch (3 mm) rise in global sea levels.

Since 1996, southeast Greenland's outlet glaciers have been flowing more quickly and since 2000 glaciers farther north have also sped up.

One glacier that once was stable is now disappearing at the rate of 14 km (8.7 miles) a year, Rignot said.

"It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes," Rignot said.

Rising air temperatures are clearly a factor, the researchers told the meeting. "This is clearly a result of warming around the periphery of Greenland," Rignot said.

Over the last 20 years, the air temperature in southeast Greenland has risen by 5.4 degrees F (3 degrees C).

Warmer air lubricates the bottoms of glaciers, helping them slide faster.

"Climate warming can work in different ways, but generally speaking, if you warm up the ice sheet, the glacier will flow faster," said Rignot.

And it may melt even more quickly in years to come, he added.

"The southern half of Greenland is reacting to what we think is climate warming. The northern half is waiting, but I don't think it's going to take long," Rignot said.

Rignot and other researchers noted that in some parts of Greenland, increased snowfall is making parts of some glaciers thicker.

"A few years back, we thought ice sheets might grow because of increased precipitation," Rignot said. "Now we see that rates of glacier flow are changing. We think the process that is winning overall is the rate of glacier flow."