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Greenland Ice Sheet is Melting Faster, Study Says
National Geographic ^ | 08/10/2006 | John Roach

Posted on 08/11/2006 10:49:56 AM PDT by cogitator

The Greenland ice sheet is melting three times faster today than it was five years ago, according to a new study.

The finding adds to evidence of increased global warming in recent years and indicates that melting polar ice sheets are pushing sea levels higher, the authors report.

According to the study, Greenland ice loss now amounts to more than 48 cubic miles (200 cubic kilometers) each year.

"Significant melting has a significant impact on sea level rise," said Jianli Chen, a research scientist at the University of Texas at Austin who led the study.

The finding, reported today by the online edition of the journal Science, closely agrees with another study on the rapid wasting of Greenland's glaciers published in the journal in February.

Both studies suggest the shrinking ice sheet now contributes about 0.02 inch (0.5 millimeter) a year to global sea level rise.

"That's a very big number," Chen said.

Losses and Gains

Global sea levels have risen by about 0.1 inch (2.8 millimeters) a year over the past decade.

If all the ice on Greenland were to melt into the North Atlantic Ocean, global sea levels would rise by about 21.3 feet (6.5 meters).

Thus scientists are keen to understand if the Danish-owned Arctic island (Greenland map) is losing more ice mass through melting and discharge of glaciers than it is gaining from fresh snowfall.

Richard Alley is a glaciologist at Pennsylvania State University in University Park who was not involved with the study.

He says the new study fits well with other recent studies showing a Greenland meltdown.

"It really does appear that the ice sheet is losing mass," he said in an email.

"Looking at the history of these measurements, the ice sheet was probably near balance a couple of decades ago and has begun shrinking recently," he continued.

"This parallels recent warming."

Full of GRACE

The new study is based on an analysis of gravity measurements collected by a pair of twin wedge-shaped satellites that orbit the Earth in tandem.

The satellites are part of the Gravity Recovery and Climate Experiment (GRACE), which was launched in March 2002 and is run by a team of experts in the U.S. and Germany.

GRACE measures landmass based on its gravitational pull. The denser a region is, the stronger its pull and the faster the satellites will move above it.

The satellites are separated by a distance of 137 miles (220 kilometers) when they are in stable orbit. As the front satellite crosses over an area of strong gravity, it speeds up, increasing the distance between the two satellites.

"Any tiny change in the distance can be used to infer the surface mass change," Chen said.

Liquid water is generally denser than ice and so has a stronger gravitational pull.

Chen and his University of Texas colleagues analyzed the gravity measurements over Greenland between April 2002 and November 2005, separating the mass change from other signals.

The team found that Greenland is now losing between 52 and 63 cubic miles (216 and 262 cubic kilometers) of ice mass each year.

The current wasting is about three times the rate gleaned from an earlier study of the first two years of GRACE data.

Jay Zwally is a glaciologist with the NASA Goddard Space Flight Center in Greenbelt, Maryland.

He agrees that Greenland ice loss has accelerated in recent years.

But based on he and his colleagues' unpublished analysis of the latest GRACE data, he believes the current ice loss rate is less than half what Chen's team reports.

Nevertheless, he says, Greenland does appear to be losing more ice mass than it gains.

"I would say Greenland now is beginning to contribute significantly to sea level rise," Zwally said. "There's been a significant change in a relatively short period of time."

As methods for analyzing GRACE data are refined and combined with other techniques, scientists will reach agreement over just how quickly the continent is wasting away, Zwally adds.

Historical Perspective

GRACE has only been orbiting Earth for three and a half years, not long enough to determine if the increase in melting is due to global warming or natural variability, the University of Texas's Chen says.

Longer term trends, and confidence in data interpretation, must wait until several more years of data are collected, he says.

According to Alley, the Pennsylvania State glaciologist, increasing snowfall, increasing melting, and increasing flow of glaciers into the ocean are all expected to result from global warming.

Historical analyses indicate that Greenland shrank when changes in Earth's orbit gave more summer sunshine to the island a few thousand years ago and about 130,000 years ago, he says.

"History and physics and recent observations tie warming to ice shrinkage," he said.

And projections of future climate change indicate continued warming over Greenland if greenhouse gas emissions remain unchecked.

"So shrinkage seems likely," Alley said.


TOPICS: Culture/Society; Foreign Affairs; Government; News/Current Events
KEYWORDS: climate; climatechange; greenland; ice; melting; rise; sealevel; snow; warming
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To: agooga

Ice has a greater volume that liquid water. So the sea level will go down. Boyle's Law.


21 posted on 08/11/2006 11:02:28 AM PDT by massgopguy (massgopguy)
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To: cogitator

surely it will all be gone by the time the 2008 election rolls around.


22 posted on 08/11/2006 11:02:33 AM PDT by the invisib1e hand (in defiance of all hazard.)
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To: pabianice

23 posted on 08/11/2006 11:03:13 AM PDT by pabianice
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To: cogitator

If this keeps up, the Vikings will be able to move back.


24 posted on 08/11/2006 11:03:48 AM PDT by Argus
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To: cogitator

I just have one word...


SOLAR FLARES!


25 posted on 08/11/2006 11:04:43 AM PDT by Clint N. Suhks (If you don't love Jesus, you can go to hell.)
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To: FreePaul
As for when the current loss started, that's not known; the study is for data collected when the GRACE mission started.

Good question about the last meltdown, I don't know the answer.

Greenland ice sheet volume: ~2.6 million cubic km.

26 posted on 08/11/2006 11:05:36 AM PDT by cogitator
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To: Names Ash Housewares

Ay, that's a problem!


27 posted on 08/11/2006 11:05:59 AM PDT by cogitator
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To: massgopguy
Ice has a greater volume that liquid water. So the sea level will go down. Boyle's Law.

The Greenland ice sheet is on land, not immersed in water.

28 posted on 08/11/2006 11:06:34 AM PDT by cogitator
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To: cogitator
This research may have been financed by a solar energy company or an ethanol producers co-op. There is so much conflicting information it is impossible to know who is right, if anyone.
29 posted on 08/11/2006 11:06:55 AM PDT by Brad from Tennessee (Anything a politician gives you he has first stolen from you)
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To: cogitator

Faster than what? Faster than jellyfish are evolving into jelly doughnuts?


30 posted on 08/11/2006 11:07:14 AM PDT by Antoninus (Public schools are the madrassas of the American Left. --Ann Coulter, Godless)
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To: DaveLoneRanger

** PING **


31 posted on 08/11/2006 11:08:03 AM PDT by cogitator
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To: Lil'freeper

I hear some startup brewery is doing just that.


32 posted on 08/11/2006 11:08:52 AM PDT by printhead
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To: Antoninus
Faster than what?

Faster than a couple of years ago.

33 posted on 08/11/2006 11:09:03 AM PDT by cogitator
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To: FreePaul
600,000 cubic miles (from ga.water.usgs.gov/edu/watercycleice.html) so the 60 cubic mile loss is still pretty small.
34 posted on 08/11/2006 11:09:11 AM PDT by palmer (Money problems do not come from a lack of money, but from living an excessive, unrealistic lifestyle)
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To: cogitator

Gotta keep the Dominator busy, y'know.


35 posted on 08/11/2006 11:09:55 AM PDT by cogitator
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If this would have happened centuries ago, hundreds of lives could have been saved.

The Little Ice Age: When global cooling gripped the world

Europe...enjoyed an undeniably balmy climate during the early medieval period. Agriculture flourished farther north and at higher elevations on mountains than is possible even in today's warmish climate, and harvests generally were good.

Farmers raised wine grapes in England 300 miles north of present limits, and in what now are icebound parts of Greenland, Norse settlers grazed sheep and dairy cattle. In his book Climate History and Modern Man, H.H. Lamb noted that the great burst of cathedral-building and population expansion in medieval Europe coincided with the peak of the Medieval Warm Period.

By about 1400, the climate had cooled to temperatures comparable to today. Over the next century or two, the world would cool still further, bringing on the Little Ice Age. ...

The effects of the Little Ice Age were anything but uniform.

...Perhaps hardest hit were the Norse settlements in Iceland and Greenland. The population of famine-ridden Iceland dwindled during the Little Ice Age to half its previous numbers.

Greenlanders fared even worse. Growing sea ice cut off communication with the outside world beginning about 1370, and when German ships landed in Greenland more than a century later, they found a single frozen corpse but no living colonists among the ruins.


36 posted on 08/11/2006 11:10:06 AM PDT by syriacus (A vote 4 Lamont is a vote 4 the right of abusive men to kill women + children, here + abroad.)
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To: agooga
Next problem, please.

You leave Pittsburgh traveling towards NYC. Your train is going 30mph. Ben R. leaves NYC traveling to Pittsburgh on his motorcycle (helmet on) going 88mph. Which traveler will cause more ice to melt in Greenland?
37 posted on 08/11/2006 11:10:44 AM PDT by carumba (The secret of life is honesty and fair dealing. If you can fake that, you've got it made. Groucho)
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To: cogitator
If you aren't already familiar with this website--World Climate Report--they will probably eventually do a critique of this study:

http://www.worldclimatereport.com/index.php/2005/05/27/antarctic-ice-a-global-warming-snow-job/
38 posted on 08/11/2006 11:11:23 AM PDT by Brad from Tennessee (Anything a politician gives you he has first stolen from you)
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To: agooga

Hmmm, I get 1/20 meter after 100 years.


39 posted on 08/11/2006 11:11:56 AM PDT by kallisti
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To: Enchante
"It was "Greenland" before it became completely covered in ice"

Probably, but that was over 100,000 years ago.
40 posted on 08/11/2006 11:12:00 AM PDT by ndt
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