Greenland's ice-cap has thickened slightly in recent years despite wide predictions of a thaw triggered by global warming, a team of scientists said on Thursday.
OSLO Greenland's ice-cap has thickened slightly in recent years despite wide predictions of a thaw triggered by global warming, a team of scientists said on Thursday.
The 3,000-metre (9,842-feet) thick ice-cap is a key concern in debates about climate change because a total melt would raise world sea levels by about 7 metres. And a runaway thaw might slow the Gulf Stream that keeps the North Atlantic region warm.
But satellite measurements showed that more snowfall was falling and thickening the ice-cap, especially at high altitudes, according to the report in the journal Science.
Glaciers at sea level have been retreating fast because of a warming climate, making many other scientists believe the entire ice-cap was thinning.
"The overall ice thickness changes are ... approximately plus 5 cms (1.9 inches) a year or 54 cms (21.26 inches) over 11 years," according to the experts at Norwegian, Russian and U.S. institutes led by Ola Johannessen at the Mohn Sverdrup centre for Global Ocean Studies and Operational Oceanography in Norway.
However, they said that the thickening seemed consistent with theories of global warming, blamed by most experts on a build-up of heat-trapping gases from burning fossil fuels in power plants, factories and cars.
Warmer air, even if it is still below freezing, can carry more moisture. That extra moisture falls as snow below 0 Celsius (32.00F).
And the scientists said that the thickening of the ice-cap might be offset by a melting of glaciers around the fringes of Greenland. Satellite data was not good enough to measure the melt nearer sea level.
Most models of global warming indicate that the Greenland ice might melt within thousands of years if warming continues.
Oceans would rise by about 70 metres if the far bigger ice-cap on Antarctica melted along with Greenland. Antarctica's vast size acts as a deep freeze likely to slow any melt of the southern continent.
The panel that advises the United Nations has predicted that global sea levels might rise by almost a metre by 2100 because of a warming climate.
Such a rise would swamp low-lying Pacific islands and warming could trigger more hurricanes, droughts, spread deserts and drive thousands of species to extinction.
Still, a separate study in Science on Thursday said sea levels were probably rising slightly because of a melt of ice sheets.
"Ice sheets now appear to be contributing modestly to sea level rise because warming has increased mass loss from coastal areas more than warming has increased mass gain from enhanced snowfall in cold central regions," it said.
"Greenland presently makes the largest contribution to sea level rise," according to the report by scientists led by Richard Alley of Pennsylvania State University in the United States.