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