Thursday, March 28, 2013

Arctic Sea Ice Maximum - Winter 2013

Some mixed news from the National Snow and Ice Data Center (NSIDC) provides us with a preliminary update on the Arctic sea ice conditions for the winter of 2013 and a foreshadowing of what the summer might bring to the Arctic.

Scientists at NSIDC estimate that the Arctic sea ice reached its maximum extent on March 15, 2013, the date that marks the beginning of the 2013 ice melting season.  The maximum areal extent reached 5.84 million square miles or 15.13 million square kilometres, 283,000 square miles or 733,000 square kilometres below the 1979 to 2000 average areal extent.  This is the sixth lowest maximum sea ice extent since the satellite record began.  It also continues a streak of the 10 lowest maximums all of which have occurred in the last 10 years.

Here is a map and a graph showing the Arctic ice extent this winter and the areal extent over the past five winter seasons and the average for the period from 1979 to 2000:

This past winter, Arctic sea ice extent grew by a record 4.53 million square miles or 11.72 million square kilometres.  Before we pat ourselves on the back, here's what happened last summer:

On September 16, 2012, Arctic sea ice reached its minimum extent of 1.32 million square miles or 3.41 million square kilometres, the lowest seasonal minimum sea ice extent in the satellite record which goes back to 1979.  This was 1.32 million square miles or 3.43 million square kilometres below the average between 1979 and 2000.  The larger than normal areal extent of open water forms a feedback into the environment; more open water means that there are larger transfers of heat from the open water areas to the atmosphere which keeps the entire Arctic ecosystem warmer than usual.  

Here is a similar graphic to the one shown above, showing the Arctic ice extent over the past five summer seasons and the average for the period between 1979 and 2000:

As I noted above, during the freezing season of 2012 - 2013, the areal extent of sea ice grew by a record amount, surpassing the old record by 5.5 percent.  Unfortunately, all of this ice is classified as "first-year ice".  Multi-year ice which has been through several freeze-thaw cycles contains much less brine and more air pockets than first year ice.  It is stiffer and is much more resistant to melting than first-year ice.  If first-year ice does not grow thick enough over the winter period, it will completely melt during the following summer.

Here is a video from NASA showing how the areal extent of multi-year Arctic sea ice has declined over the past three decades:

It will be interesting to see how next summer's Arctic ice situation measures up when compared to other years.  With a record low areal ice extent this winter and formation of vast areas of fragile first-year ice, the globe could once again find itself breaking last year's minimum Arctic ice extent record.

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