Two researchers, who have reviewed old maps of Greenland, have discovered that the area is experiencing the effects of global warming again after nearly 90 years.
According to Jason Box, an Associate Professor of Geography at Ohio State University and a researcher with the Byrd Polar Research Centre, the evidence reinforces the view that glaciers and other bodies of ice are sensitive to climate change and that rising temperatures will eventually speed up the demise of theisland's ice fields, hastening sea level rise.
AdvertisementRuling out the possibility of this being a one off instance, Box and undergraduate student Adam Herrington concentrated their study on three large glaciers flowing out from the central ice sheet towards the ocean - the Jakobshavn Isbrae, the Kangerdlugssuaq and the Helheim.
Herrington, who co-authored the paper, spent weeks in the university's libraries and archives, scouring the faded, dusty books that contained the logs of early scientific expeditions, looking primarily for photos and maps of several of Greenland 's key glaciers.
"These three glaciers are huge and collectively, they drain as much as 40 percent of the southern half of the ice sheet. All three have recently increased their speed as the temperature rose," Box said.
"I must have paged through more than a hundred such volumes to get the data we needed for this study," Herrington said.
Box said that the Kangerdlugssuaq, at 3.1 miles (5 kilometres) wide is as wide as New York's Manhattan Island.
Digging through the old data, Herrington found a map from 1932 and an aerial photo from 1933 that documented how, during a warm period, the Kangerdlugssuaq Glacier lost a piece of floating ice that was nearly the size of New York 's Manhattan Island.
"In 2002 to 2003, that same glacier retreated another 3.1 miles (5 kilometres), and that it tripled its speed between 2000 and 2005."
The fact that recent changes to Greenland's ice sheet mirrors its behavior nearly 70 years ago is increasing researchers' confidence and alarm as to what the future holds.
Recent warming around the frozen island actually lags behind the global average warming pattern by about 1-2 degrees C but if it fell into synch with global temperatures in a few years, the massive ice sheet might pass its "threshold of viability" - a tipping point where the loss of ice couldn't be stopped.
"Once you pass that threshold," Box said, "the current science suggests that it would become an irreversible process. And we simply don't know how fast that might happen, how fast the ice might disappear."
Greenland 's ice sheet contains at least 10 percent of the world's freshwater and it has been losing more than 24 cubic miles (100 cubic kilometres) of ice annually for the last five years and 2007 was a record year for glacial melting there.
The report was reported at this week's annual meeting of the American Geophysical Union in San Francisco.
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