August 5, 2011

Arctic Sea Ice May Be Melting Slower Than Thought

Danish researchers say the rate of melting in the Arctic sea may be slower than previously thought.

A team from the Danish National Research Foundation for Geogenetics at the University of Copenhagen developed a method to measure the variations in the ice several millennia back in time.

The scientists based their results on material gathered along the coast of northern Greenland, which experts believe will be the final place summer ice will survive.

"Our studies show that there have been large fluctuations in the amount of summer sea ice during the last 10,000 years," Svend Funder, team leader of the study, said in a press release.

"During the so-called Holocene Climate Optimum, from approximately 8000 to 5000 years ago, when the temperatures were somewhat warmer than today, there was significantly less sea ice in the Arctic Ocean, probably less than 50% of the summer 2007 coverage, which was absolutely lowest on record."

Funder said their studies show that when the ice disappears in one area, it may accumulate in another.  He said they discovered this by comparing the results with observations from northern Canada.

"While the amount of sea ice decreased in northern Greenland, it increased in Canada," Funder said in a press release. "This is probably due to changes in the prevailing wind systems. This factor has not been sufficiently taken into account when forecasting the imminent disappearance of sea ice in the Arctic Ocean."

He said the key to their finding lies in the driftwood the researchers found along the coast.  He wrote that the amount of driftwood found indicates how much multiyear sea ice there was in the ocean back then. 

The team studied the wood they had collected to determine its type, as well as carbon dated it.  They said it originated near the great rivers of North America and Siberia.

The researchers said the different wood types are evidence of changing travel routes and altered current and wind conditions in the ocean.

They also examined 310 miles of the beach ridges along the coast and found that during the warm period from about 8,000 until 4,000 years ago, there was more open water and less coastal ice than today.

"Our studies show that there are great natural variations in the amount of Arctic sea ice," Funder said in a statement. "The bad news is that there is a clear connection between temperature and the amount of sea ice. And there is no doubt that continued global warming will lead to a reduction in the amount of summer sea ice in the Arctic Ocean.

"The good news is that even with a reduction to less than 50% of the current amount of sea ice the ice will not reach a point of no return: a level where the ice no longer can regenerate itself even if the climate was to return to cooler temperatures."

He concluded by saying that the study shows that the changes are caused by the effect that temperature has on the wind systems.  He said this has not been taken into account when forecasting the imminent disappearance of the ice.

The team's findings will be published in the journal Science.


Image 1: During the last 10.000 years the North Pole ice cover has been even smaller than it is today. Credit: Svend Funder/University of Copenhagen

Image 2: University of Copenhagen researchers surveyed North Greenland beaches to find evidence of fluctuations in the North Pole ice cover over time. Credit: Svend Funder/University of Copenhagen


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