You can't exclude the Black Swan

The last month of melting sea ice starts today and the blogosphere continues to look at numbers and charts, but fails to recognize the true nature of the current ice pack. The majority of bloggers and commenters sees 2011 somewhere between 2008 and 2007 at the end of the melting season and take it as a matter of probability.

That might be a correct point of view given the preconditions are same now as in these years. But they are not, we have PIOMAS pointing to less thickness, the average concentration is lower than in 2007 and the years after, the shape of the extent is different and believe it or not there are far more gigatons of CO2 in the atmosphere.

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New Sea Ice Drift Vector and SST Overlay

Now close to the end of the season wind has most impact on sea ice extent. Depending on the average concentration of a region moving ice floes may compact again and overcome the 15% percent threshold of common extent algorithms to appear back on the radar - the opposite effect also happens.

The binary nature of this threshold explains most of the daily fluctuation of the extent, especially because sea ice concentration is lower compared to recent years.

Apart from that, the southward drift through Fram Strait is another cause of sea ice loss. Every year about 10% of the Arctic Basin’s area is exported into the Greenland Sea. Mainly MYI is transported that way southwards into warmer North Atlantic water.

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