September 17, 2009

Greenland Icesheet Could Melt Faster Than Scientists Thought

A new study released on Wednesday showed the Greenland icesheet responded to global warming over the past 10,000 years more quickly than thought, AFP reported.

The report suggests that as a result, a medium-sized temperature increase this century could cause the continent-sized ice block to start melting at an alarming rate.

The study warns that it is entirely possible that a future temperature increase of a few degrees Celsius in Greenland will result in a icesheet mass loss and contribution to sea level rise larger than previously projected.

There is enough ice in Greenland to raise sea levels by about 23 feet, should it melt. But experts say that even a far more modest increase would put major coastal cities under water and force hundreds of millions of people to flee.

Many experts were confident that the planet's two icesheets in Greenland and Antarctica would remain largely stable over the coming centuries despite global warming, but more recent studies have cast doubt on this.

New statistics show the pace at which glaciers are sliding off from both icesheets into the oceans has picked up over recent decades.

A new technique was used for measuring changes in the icesheet over the last 10,000 years that resolves a paradox, according to the study published in the British journal Nature.

Previous measurements appeared to show that parts of Greenland had somehow defied a trend of general warming in the northern hemisphere throughout a 3,000-year period that started around 9,000 years ago.

Bo Vinther of the University of Copenhagen in Denmark led the new research that demonstrates that the problem lay with how the raw data had been interpreted.

Core samples were taken from four locations on the icesheet, which reaches depths of more than two miles. But the results were inconsistent, as with earlier studies.

However, using two new samples taken from two areas just beyond the icesheet, the researchers were able to determine that the variations were due to changes in height, not because of inconsistent warming.

Vinther said the elevation itself causes different temperatures and as a consequence, during this period the icesheet responded more uniformly -- and more vigorously -- to rising temperatures.


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