Arctic Sea Ice in 2nd Place, However...

Arctic Sea Ice appears to have reached it minimum extent for the year, at 4.53 Mkm² (IJIS data; NSIDC gives 4.33 Mkm²).

That's the second lowest in the records, after 2007's 4.25 Mkm² (IJIS).

However, I think a more relevant metric (after volume, of course) is the extent's yearly average. By that measure, 2011 is the lowest, at 10.65 Mkm² (as of Sept 14th), lower than 2007's 10.70 Mkm² as of the same date that year.

Last year at this time the year-to-date average was 10.91 Mkm². We'll see how the year ends. The 2007-2011 difference peaked at 0.062 Mkm² on August 24th, and lately 2007 has been gaining ground to where the difference is now 0.043 Mkm².

In terms of volume it's not even close: the latest PIOMAS data, which gives modeled ice volume up until 8/31/11, has that date's sea ice volume as 36% below 2007. (4.28 Kkm³ to 6.65 Kkm³.) That's astonishing. Over 1/3rd of the sea ice have melted in just 4 years.