Post by dogwalker on Feb 16, 2006 23:13:59 GMT -8
Greenland Glaciers Dumping More Ice
ST. LOUIS - Warmer temperatures over the past decade have sped up the march of Greenland's southern glaciers to the Atlantic Ocean, where the ice and water they spill contribute more to the global rise in sea levels than previously thought.
Those faster-moving glaciers now dump in a year twice as much ice into the Atlantic as they did in 1996, researchers said Thursday. The resulting icebergs, along with increased melting of Greenland's ice sheet, could account for nearly 17 percent of the estimated one-tenth of an inch annual rise in global sea levels, or twice what was previously believed, said Eric Rignot of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"It's likely that Greenland is going to contribute more and faster to rising sea levels than previously estimated," Rignot told reporters at the annual meeting of the American Association for the Advancement of Science. A report by Rignot and Pannir Kanagaratnam of the University of Kansas appears Friday in the journal Science.
An increase in surface air temperatures appears to be causing the glaciers to flow faster, albeit at the still-glacial pace of eight miles to nine miles a year at their fastest clip, and discharge increased amounts of ice into the Atlantic.
That stepped-up flow accounted for about two-thirds of the net 54 cubic miles of ice Greenland lost in 2005. That compares with 22 cubic miles in 1996. The most recent volume is more than 200 times the amount of fresh water used by Los Angeles in a year, Rignot said.
Rignot and Kanagaratnam said their report is the first to include measurements of recent changes in glacier velocity in the estimates of how much ice most of Greenland is losing.
"What we found is this is probably the dominant response of the ice sheets," Rignot said.
Gino Casassa, who studies glaciers at Chile's Centro de Estudios Cientificos, called the study a "major finding," since it may provide a missing link to the understanding of shrinking glaciers in Antarctica, Patagonia, Alaska and elsewhere around the globe. Previous studies have only hinted that increased flow rates played such a prominent role, Casassa said.
"This is the first time, with hard data, to conclude this," he said.
Rignot and Kanagaratnam believe warmer temperatures boost the amount of melt water that reaches where the glaciers flow over rock. That extra water lubricates the rivers of ice and eases their downhill movement toward the Atlantic. They tracked the speeds of the glaciers from space, using satellite data collected between 1996 and 2005.
If warmer temperatures spread to northern Greenland, the glaciers there too should pick up their pace, according to the study.
The only way to stem the loss of ice would be for Greenland to receive increased amounts of snowfall, according to Julian Dowdeswell of the University of Cambridge, who wrote an accompanying article.
___
On the Net:
Science: www.scienceonline.org/
ST. LOUIS - Warmer temperatures over the past decade have sped up the march of Greenland's southern glaciers to the Atlantic Ocean, where the ice and water they spill contribute more to the global rise in sea levels than previously thought.
Those faster-moving glaciers now dump in a year twice as much ice into the Atlantic as they did in 1996, researchers said Thursday. The resulting icebergs, along with increased melting of Greenland's ice sheet, could account for nearly 17 percent of the estimated one-tenth of an inch annual rise in global sea levels, or twice what was previously believed, said Eric Rignot of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"It's likely that Greenland is going to contribute more and faster to rising sea levels than previously estimated," Rignot told reporters at the annual meeting of the American Association for the Advancement of Science. A report by Rignot and Pannir Kanagaratnam of the University of Kansas appears Friday in the journal Science.
An increase in surface air temperatures appears to be causing the glaciers to flow faster, albeit at the still-glacial pace of eight miles to nine miles a year at their fastest clip, and discharge increased amounts of ice into the Atlantic.
That stepped-up flow accounted for about two-thirds of the net 54 cubic miles of ice Greenland lost in 2005. That compares with 22 cubic miles in 1996. The most recent volume is more than 200 times the amount of fresh water used by Los Angeles in a year, Rignot said.
Rignot and Kanagaratnam said their report is the first to include measurements of recent changes in glacier velocity in the estimates of how much ice most of Greenland is losing.
"What we found is this is probably the dominant response of the ice sheets," Rignot said.
Gino Casassa, who studies glaciers at Chile's Centro de Estudios Cientificos, called the study a "major finding," since it may provide a missing link to the understanding of shrinking glaciers in Antarctica, Patagonia, Alaska and elsewhere around the globe. Previous studies have only hinted that increased flow rates played such a prominent role, Casassa said.
"This is the first time, with hard data, to conclude this," he said.
Rignot and Kanagaratnam believe warmer temperatures boost the amount of melt water that reaches where the glaciers flow over rock. That extra water lubricates the rivers of ice and eases their downhill movement toward the Atlantic. They tracked the speeds of the glaciers from space, using satellite data collected between 1996 and 2005.
If warmer temperatures spread to northern Greenland, the glaciers there too should pick up their pace, according to the study.
The only way to stem the loss of ice would be for Greenland to receive increased amounts of snowfall, according to Julian Dowdeswell of the University of Cambridge, who wrote an accompanying article.
___
On the Net:
Science: www.scienceonline.org/