Ice returns to most of the Arctic Ocean, data center says

Monthly October ice extent for 1979 to 2011 shows a decline of 6.6 per cent every decade. (IMAGE COURTESY OF THE NSIDC)

Arctic sea ice cover increased rapidly through October, as is typical this time of year, the National Snow and Ice Data Center reported this week.

The ice increased at an average rate of 114,900 square kilometres per day, faster than it did on the average from 1979 to 2000 during October.

But last October large areas of open water were still present in the Beaufort and Chukchi seas at the end of the month.

There, the open water contributed to unusually warm conditions and reduced ice along the coast of Siberia and in the Beaufort and Chukchi seas.

Ice extent was near average in the East Greenland Sea, and new ice growth closed both the Northwest Passage and the Northern Sea Route, the NSIDC said in its Nov. 2 update.

On Oct. 30, Arctic sea ice extent was 8.41 million sq. km., 226,000 sq. km. more than the ice extent on Oct. 30, 2007, the lowest extent on that date in the satellite record.

In recent years, low Arctic sea ice extent in the summer has been linked to unusually warm temperatures at the surface of the Arctic Ocean in the fall.

This pattern appeared yet again this year, the NSIDC said.

Air temperatures over most of the Arctic Ocean last month ranged from one to four degrees Celcius above average, at about 1,000 metres above the surface.

However, over the eastern Canadian Arctic and Greenland, temperatures were as much as three degrees Celsius below average.

Declining sea ice in the western Arctic has also led to increasing erosion rates along the coast of the Beaufort Sea over the past 50 years, according to a new study led by Irina Overeem of the University of Colorado Institute for Arctic and Alpine Research cited by the NSIDC.

As the period of open water on the coast of the Beaufort Sea has increased, so has the mean annual erosion rate, the study showed.

From 1979 to 1999, the average erosion rate was 8.5 m per year.

The rate for 2008 to 2009 was 14.4 m per year.

With a longer open water season, ocean water warms more and waves eat away at the coastline.

The sediments comprising the coastal bluffs are locked together by permafrost. As the waves lap at the permafrost, they also help to thaw it, making the ground much more vulnerable to erosion, the NSIDC said.