Arctic sea ice shrinkage a little less in 2009

Arctic sea ice extent for September 2009 was 5.36 million square km, the third-lowest in the satellite record. The magenta line shows the median ice extent for September from 1979 to 2000. (COURTESY NATIONAL SNOW AND ICE DATA CENTRE)

This September a bit more of the Arctic Ocean remained covered by ice than last year.

The minimum sea ice extent in 2009 was the third lowest since satellite record-keeping began in 1979, the University of Colorado’s National Snow and Ice Data Center said in an Oct. 6 news release.

But Arctic sea ice cover was still “significantly below previous years.”

If trends continue, Arctic summers will be ice-free within decades, the NSIDC says.

The centre’s scientists measure the sea ice in September when it reaches its minimum, and for the past five years they have seen the five lowest Arctic sea ice extents ever recorded.

“It’s nice to see a little recovery over the past couple of years, but there’s no reason to think that we’re headed back to conditions seen in the 1970s,” said NSIDC director Mark Serreze. “We still expect to see ice-free summers sometime in the next few decades.”

The 2009 ice cover also remained thin, with about half of the ice cover made of younger, thinner ice.

Second- year ice made up 32 per cent of the ice cover, compared to 21 per cent in 2007 and 9 per cent in 2008.

“We’ve preserved a fair amount of first-year ice and second-year ice after this summer compared to the past couple of years,” said NSIDC scientist Walt Meier.

“If this ice remains in the Arctic thorough the winter, it will thicken, which gives some hope of stabilizing the ice cover over the next few years. However, the ice is still much younger and thinner than it was in the 1980s, leaving it vulnerable to melt during the summer.”

Arctic sea ice in September is now declining at a rate of 11.2 per cent every 10 years, and in the winter months it’s declining, too, by about three per cent every 10 years, says the NSIDC.