Satellite reveals surge in Arctic melt rate

The Arctic ice shelf lost 14% of permannet ice cover last year, NASA satellite images have revealed - much more than total losses since measurements began three decades ago.

Perennial sea ice can be over 3m thick.

Perennial sea ice can be over 3m thick.

A NASA satellite monitoring study found that the surface of the Arctic covered by sea ice that stays all year round shrank by 14% in just 12 months from 2004 to 2005.

NASA Scientists from the Jet Propulsion Laboratory in California found that 720,000 km2 of permanent sea ice was lost over the 2004-5 period - an area the size of Turkey.

Son Nghiem who led the Jet Propulsion Lab study said: "Recent changes in Arctic sea ice are rapid and dramatic.

"If the seasonal ice in the East Arctic Ocean were to be removed by summer melt, a vast ice-free area would open up. Such an ice-free area would have profound impacts on the environment, as well as on marine transportation and commerce."

In some areas of the Arctic losses were much higher than 14% - in the East Arctic Ocean almost half of the entire ice cover was lost.

Separate research from NASA's Goddard Space Flight Centre detected a sudden acceleration in winter melting rates over the last 2 years. In 2005 and 2006, the winter ice cover maximum was about 6% higher than the average over the last quarter century.

This melting experienced over the course of one winter was higher than the rate per decade over the previous thirty years, with a long-term average of 0.15% since satellite observations began in 1979.

Josefino comiso, who led the Goddard Space Flight Centre study, said: "A continued reduction of the Arctic winter ice cover would be a clear indicator of the warming effect of increasing greenhouse gases in the atmosphere. It would at least confirm our current understanding of the physics of the Arctic climate system that has been incorporated in our models."

"It's vital that we continue to closely monitor this region, using both satellite and surface-based data," he said.

The Arctic is warming about twice as fast as the global average. The effects of disappearing sea ice could be disastrous for the survival of species like polar bears, which are dependent for sea ice as a seal-hunting ground, Josefino Comiso said.

"The seasonal ice regions in the Arctic are among the most biologically productive regions in the world," he said. "Some of the richest fisheries are found in the region, in part because of sea ice. Sea ice provides melt-water in spring that floats because of low density.

"This melt-water layer is considered by biologists as the ideal layer for phytoplankton growth because it does not sink, and there is plenty of sunlight reaching it to enable photosynthesis. Plankton are at the bottom of the food web. If their concentration goes down, animals at all tropics level would be deprived of a basic source of food."

The melting of Arctic ice could also accelerate the global warming that is causing it in the first place though a positive 'feedback effect' - as water reflects less sunlight back into space than water, more heat could be absorbed by an earth with less snow and ice cover.

The results of both NASA studies are published in the journal Geophysical Research Letters this month.

For more information on NASA's satellite missions see here.

Goska Romanowicz



Waste & resource management
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