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: 

https://arcus.org/files/projects/supplemental/674/stroeve_etal_seaice_synthesis_2011.pdf

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!

2012 Arctic sea ice melt sets new record with no signs of slowing down

This is amazing...it's like watching a slow motion train wreck.  You want to look away, but you just can't do it!

The former record Arctic Ocean sea ice melt was set five years ago, in 2007, and though a couple of other years since then looked like they might flirt with setting a new record, none of them really came close.  In October 2007 The National Snow and Ice Data Center reported that the Arctic sea ice had shattered the pre-exisitng record from 2005.  You can read that full report by clicking the link below.

http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html

This graph from the NSIDC October 2007 report shows the difference between the sea ice melt in 2005 and 2007.

The dark gray line shows the 1979-2000 satellite data showing the average sea ice extent during those 20 years.  The dashed green line shows the record set in 2005, and the blue line shows the new record that was set in 2007.

The NSIDC analysts concluded that the 2007 record ice melt was the result of a series of weather and other factors including the following:

• Lower than average sea ice extent at the beginning of the ice melt season
• Thinner ice than average at the beginning of the ice melt season
• A persistent high pressure cell over the central Arctic Ocean through much of the melt season.  That high pressure cell meant clearer skies, and increased amount of solar radiation that struck the ice and ocean surface, accelerating melting.
• Low pressure cells over northern Siberia that produced strong offshore winds that pushed sea ice offshore faster and earlier than normal, plus these winds were warm and promoted further sea ice melt

OK, so what!?

Well, this year, 2012, the Arctic Ocean sea ice melt season still has anywhere from 2 weeks to a month to go, and there is already a new sea ice melt record that from all current indications has the potential to not only exceed, but smash the old record!

This is what the 2012 sea ice melt season looks like so far.

The dark gray line shows the 1979-2000 average, and the dashed green line shows pattern of sea ice melt in 2007, the year of the previous record sea ice melt.  The blue line in this graph shows the sea ice melt pattern for 2012.  If you look at the vertical axis on the left of the graph you can eyeball it and see that the sea ice extent for 29 Aug is probably between 500,000 and 1,000,000 km2 less in 2012 than it was in 2007.  All right, so what were the conditions this year?

The map below shows the maximum sea ice cover of the Arctic Ocean in spring 2012 (18 March 2012). If you look, the sea ice extent is greater than average in the Bering Sea and off Kamchatka.  It reached historical average extents off of the east coast of Greenland and exceeded them off the west coast of Greenland.  At the same time Arctic sea ice cover was below average in the Barents Sea north of Scandinavia and Russia's Kola Peninsula, but not really many other places.

OK, so what conditions existed over the Arctic that led to the current sea ice melt record?

Well, for one thing, there was a strong, cyclonic Arctic low pressure cell that appeared near the end of the first week of August.  Analysts at the NSIDC reported that this type of storm normally spreads sea ice out and slows the rate of sea ice melt, but if you look at the graph of 29 Aug 2009 for the first part of August 2012 the rate of sea ice melt actually increased instead of decreasing!  This is completely counterintuitive when compared to the effects of similar conditions in the past.

This map shows the high and low pressure cells that produced that Arctic storm.  The low pressure cell in the middle of the map should have been a place where cloud cover formed, blocked solar radiation, and produced winds that slowed the compacting of sea ice and sea ice melt...but that didn't happen.

So, to sum up, there was a lot of ice when the melt season began, conditions conducive to rapid sea ice melt were not particularly evident in this year's weather patterns, but a record-setting sea ice melt has already occurred and there are still at least two weeks and perhaps as many as four weeks to go in the ice melt season.

This is what the sea ice cover looked like as of 29 August 2012.  Remember that the orange lines represent the average area of sea ice cover from 1979-2000.  The map speaks for itself.

The only thing we can do now is sit back and see how long the sea ice melt will continue, and by how much the old sea ice melt record will be broken.  Sigh...