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Arctic sea ice 2005 Arctic sea ice 2012

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Arctic sea ice shatters previous low records

4 October 2012
National Snow and Ice Data Center, Boulder, Colorado

On September 16th, sea ice covering the Arctic Ocean fell to the lowest extent in the satellite record, which began in 1979  The average sea ice extent for the month of September was also the lowest.

The record ice melt occurred without the unusual weather conditions that contributed to the extreme melt of 2007, when winds and weather patterns helped melt large expanses of ice.

The record lowest extent of Arctic summer sea ice for 2012 of 3.61 million, was 51 percent of the 1979 to 2000 average.

“Atmospheric and oceanic conditions were not as conducive to ice loss this year, but the melt still reached a new record low," said NSIDC scientist Walt Meier.  “This probably reflects loss of multi-year ice in the Arctic, as well as other factors that are making the ice more vulnerable.”  Multi-year ice is ice that has survived more than one melt season and is thicker than first-year ice.

Arctic sea ice extent reached its lowest point this year on September 16, when sea ice extent dropped to 3.41 million square kilometers (1.32 million square miles).

Averaged over the month of September, ice extent was 3.61 million square kilometers (1.39 million square miles).  Ice extent was 3.29 million square kilometers (1.27 million square miles) below the 1979 to 2000 average.

The lowest extent of Arctic summer sea ice for 2012 was 51 percent of the 1979 to 2000 average.

Above right: The September 2012 Arctic sea ice extent was 3.41 million (1.32 million sq.miles), the lowest in the satellite record. The orange line shows the median sea ice extent for September from 1979 to 2000. Sea ice in 2012 was 51 percent of the 1979 to 2000 average.

Above left: The September 2005 Arctic sea ice extent was 5.32 million (2.05 million sq.miles).  The sea ice extent in 2012 of 3.41 million was 64 percent of the 2005 extent. The magenta line shows the median sea ice extent for September from 1979 to 2000.  Images: National Snow and Ice Data Center

The Arctic ice cap grows each winter as the sun sets for several months, and shrinks each summer as the sun rises higher in the northern sky. Each year the Arctic sea ice reaches its annual minimum extent in September.

This summer's low ice extent continued the downward trend seen over the last 33 years. Scientists attribute this trend in large part to warming temperatures caused by climate change.

Since 1979, September Arctic sea ice extent has declined by 13 percent per decade. Summer sea ice extent is important because, among other things, it reflects sunlight, keeping the Arctic region cool and moderating global climate.

Above: The graph shows Arctic sea ice extent of 2012 in blue, below the dashed 2007 line. The 1979 to 2000 average line is in dark gray. The gray area around this average line shows the two standard deviation range of the data.  Image: National Snow and Ice Data Center.

Arctic sea ice has become thinner and less resistant to melt .....

In addition to the decline in sea ice extent, a two-dimensional measure of the ice cover, the ice cover has grown thinner and less resistant to summer melt.

Recent data on the age of sea ice, which scientists use to estimate the thickness of the ice cover, shows that the youngest, thinnest ice, which has survived only one or two melt seasons, now makes up the large majority of the ice cover.

NSIDC Director Mark Serreze said, “It looks like the spring ice cover is so thin now that large areas melt out in summer, even without persistent extreme weather patterns.”  A storm that tracked through the Arctic in August helped break up the weakened ice pack.

Climate models have suggested that the Arctic could lose almost all of its summer ice cover by 2100, but in recent years, ice extent has declined faster than the models predicted.

A greater rate of reduction in the area of sea ice can be expected, as ice thichness decreases.

According to Mark Serreze “The big summer ice loss in 2011 sets us up for another big melt year in 2012.  We may be looking at an Arctic Ocean essentially free of summer ice only a few decades from now.”.


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