Threat to Arctic Ecosystem as Ice Cover Reduced to 'Young, Thin' Floes

on October 13 2011 7:10 AM

Severe seasonal melting has reduced ice floes, floating chunk of ice, in the Arctic Ocean to the thinnest on record, according to researchers.

Scientists from the Alfred Wegener Institute for Polar and Marine Research in Germany said the proportion of old, thick sea ice in the central arctic has declined significantly. The ice cover now largely consists of thin, 1-year-old floes, they said, revealing measurements obtained from the TransArc project that aimed to track changes in water, air and ice across the polar sea.

Researchers said that at sites where the sea ice was mainly composed of old, thicker ice floes in the past decades, there is now primarily one-year-old ice with an average thickness of 90 centimetres. Only in the Canadian Basin and near the Severnaya Zemlya island group in northern Siberia did the sea ice physicists encounter significant amounts of several-year-old ice.

The ice has not recovered. This summer it appears to have melted to exactly the same degree as in 2007. Yes, it is exactly as thin as in the record year, said sea ice physicist Stefan Hendricks.

Changes in sea ice thickness and extent also have direct consequences for the ecosystem of the Arctic Ocean, the researchers said. The reason is that the marginal ice zone is sort of like a Garden of the Arctic Ocean. Due to the melting of sea ice, algae are released from the ice into the sea. In addition, the freshwater in the ice mixes with the seawater. Since the former has a lower density than seawater, a stable stratification of the surface water occurs.

The summer sea ice melt season has ended in the Arctic. Last week, the National Snow and Ice Data Center (NSIDC) said Arctic sea ice extent reached its low for the year, the second lowest in the satellite record, on Sept. 9.

NSIDC data showed that the average ice extent for September 2011 was 1.78 million square miles, 938,000 square miles below the 1979 to 2000 average.

Climate scientists have suggested that the record meltdown of sea ice is being caused by human-induced global warming.

Ice extent was below the 1979 to 2000 average everywhere except in the East Greenland Sea, where conditions were near average, NSIDC had said.

The sea-ice retreat can no more be explained with the natural variability from one year to the next, caused by weather influence, The Guardian quoted a scientist at the Institute of Environmental Physics at Bremen, Germany, as saying.

It seems to be clear that this is a further consequence of the man-made global warming with global consequences. Climate models show that the reduction is related to the man-made global warming, which, due to the albedo effect, is particularly pronounced in the Arctic, he said. The albedo effect is related to a surface's reflecting power - whiter sea ice reflects more of the sun's heat back into space than darker seawater, which absorbs the sun's heat and gets warmer, said Georg Heygster.

Because sea ice reflects most of incoming sunlight and keeps the Arctic cold throughout summer, the sea ice level on long days of summer plays a significant role in blocking solar radiation. When the Arctic is covered by large areas of open water in the beginning of the summer, the solar radiation heats the ocean and melts more sea ice, leading to the ice-albedo feedback, a negative cycle where warming decreases ice cover and greater solar energy is absorbed.

We're getting close, but there is possibility for further loss of ice, according to Walt Meier, a research scientist at the Boulder, Colo.-based National Snow and Ice Data Center.


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