Greenland is covered by the biggest ice sheet in the northern hemisphere: almost 772,000 square miles of ice which is up to 1.9 miles thick, the base of which is below sea level. Greenland's icy mountains and the island's entire ice cap could disappear in the next 1,000 years because of global warming, European scientists warn today. If that occurs sea levels will rise by seven metres, drowning low-level coastlines around the world.
But Jonathan Gregory, of the Hadley Centre for climate prediction at the University of Reading, and colleagues from Brussels and Bremerhaven, report in the journal Nature that an average annual warming in the region of 2.7C (37F) would mean that the rate of melting would outpace the annual snowfall.
The greater the warming, the faster the snow melts. The worst-case predictions for Greenland, made by an intergovernmental panel of scientists, involve an average warming of 8C (46F). At those temperatures oceans that have risen by 2.5mm (less than one-tenth of an inch) a year will start to rise by a steady 7mm a year.
There are already signs of consistent melting in Greenland. Researchers reported in 1999 that the ice sheet was thinning by about a metre a year, report guardian.co.uk
For the ice sheet to begin melting, ambient temperatures around Greenland would need to rise more than 3 degrees Celsius, Jonathan Gregory, a climate scientist with the Met Office Hadley Centre and the University of Reading, said. The concentrations of man-made greenhouse gases would probably reach levels that would trigger the melting by about the middle of the century.
"As well as raising sea levels significantly, loss of the Greenland ice sheet would greatly alter the climate of Greenland," Dr Gregory said. "Unlike the ice on the Arctic Ocean, much of which melts and re-forms each year, the Greenland ice sheet might not re-grow even if the global climate were returned to pre-industrial conditions," – inform independent.co.uk
According to newscientist.com The Greenland ice sheet is all but doomed to melt away to nothing, according to a new modelling study. If it does melt, global sea levels will rise by seven metres, flooding most of the world's coastal regions.
Jonathan Gregory, a climatologist at the University of Reading, UK, says global warming could start runaway melting on Greenland within 50 years, and it will "probably be irreversible this side of a new ice age". The only good news is that it a total meltdown is likely to take at least 1000 years.
At present, snowfall onto the ice cap is balanced by meltwater and icebergs draining away into the Atlantic Ocean. But Gregory and co-author Philippe Huybrechts, a glaciologist at the Free University in Brussels, Belgium, calculate that if the island warms by an annual average of 3 degrees Celsius, melting will exceed snowfall and the ice sheet will begin to disappear.
Once under way, the melting will be almost impossible to stop, argues Gregory. As the ice melts, the cap's surface will sink to lower altitudes, warming the surface further, reducing snowfall and accelerating melting.