Thoughts on the ocean, the environment, the universe and everything from nearly a mile high.

Panorama of The Grand Tetons From the top of Table Mountain, Wyoming © Alan Holyoak, 2011

Thursday, September 13, 2012

Record sea ice melt season reduces sea ice extent to only about 50% of its historical average

It's nearly the middle of September, the traditional end of the sea ice melt season in the Arctic Ocean.  The rate of sea ice melt has slowed over the past few days, perhaps signaling the beginning of the end of the Arctic Ocean sea ice melt season for 2012, but it's not completely done yet, and it's been a crazy summer in the Arctic!

Do you see what I see?  The extent of sea ice cover in the Arctic Ocean is WAY smaller now than the 1979-2000 average (orange lines) with only ~51% of the 1979-2000 average sea ice cover remaining today.

Consider this...

The average sea ice cover (extent) in the Arctic from 1979-2000 was about 6.7 million square kilometers.  Right now there is only about 3.45 million square kilometers of sea ice in the Arctic (as shown above).  The area of ice that is MISSING is shown on the map below.  Sea ice extent has NEVER been this low.

How does this compare to the previous sea ice melt record?  The previous sea ice melt record was in 2007.  The dark gray line on the graph below shows the 1979-2000 average sea ice cover.  The dashed green line shows the sea ice cover during 2007, and the blue line shows sea ice cover during 2012.  The 2012 ice melt smashed the 2007 record, with over 750,000 km2 more sea ice melting than in 2007.

Interestingly, the high amount of sea ice melt in 2007 was largely the result of an unusual Arctic weather year.  It had huge high pressure regions over large areas of the polar north, and lots and lots of sunshine, which meant lots of sea ice melting.  In 2012 however weather conditions did not appear to be set up to produce lots of sea ice melt.  There was a major cyclonic low pressure system that produced lots of cloud cover.  And that combined with associated winds normally slows sea ice melt.  But not this year.  It has just apparently gotten too warm overall in the Arctic for that kind of weather system to slow sea ice melt as much as it used to.

Maybe the sea ice melt in 2007 and 2012 were just statistical outliers.  I would have considered that as a possibility...until I saw the data for sea ice in the Arctic for the years between 2007 and 2012.

The graph below shows the sea ice cover data for the years 2007-2012 plus the 1979-2000 average.  An outlier is an observation that falls well outside of the observed long term trend.  What we see when we look at the data is that every year since 2007, and others not shown here, all fall well outside the 1979-2000 average.  But because there are getting to be so many years outside that average they collectively no longer can really be considered outliers.  Instead, they are possibly representing a new trend.
I just read an extremely interesting paper on what is and has been going on in the Arctic with respect to sea ice.  I recommend it highly if you are seriously interested in this topic.

  • Stroeve, J. C., et al. 2012. The Arctic's rapidly shrinking sea ice cover: a research synthesis. Climate Change 110:1005-1027 DOI 10:1007/s10585-011-0101-1

Here is a link to a PDF file containing that paper: 

One of the things I found most compelling in Stroeve's article was the analysis of sea ice extent over the last 30+ years.  The conclusion is that the rate of sea ice loss is no longer linear.  Annual sea ice extents are dropping faster over the past decade than during previous decades.  The upper graph shows the rate of sea ice loss 1979-1998 in blue, and the rate of sea ice loss 1999-2010 in red.  The significant difference in these rates of sea ice loss is worth noting.  Stroeve's paper refers to models that suggest that the Arctic could become ice free in the summer as soon as 30 years from now.    

On the heels of this year's record sea ice melt, however, some climatologists are starting to suggest the possibility of a summer free of ice in the Arctic as soon as 10 years from now.  Yow!

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