With a drop of 174,867 square km for July 17th reported by Cryosphere Today (run by the Polar Research Group at the University of Illonois at Urbana-Champaign), the 2012 sea ice area anomaly has dropped below 2 million square kilometres, compared to the 1979-2008 mean:
So what, one may ask. It happened before, right?
It did, as we can see on CT's Tale of the Tape:
It happened four times before, twice in 2007 and twice in 2011. Both record minimum years in the CT SIA data set had a first small dip a couple of weeks before the minimum, and a bigger one during the period of re-freeze:
First dip 2007: Aug. 19th - Aug. 23rd
Big dip 2007: Sep. 25th - Oct.29th (reaching the record anomaly of -2.635 million km2)
First dip 2011:Aug. 24th - Aug. 25th
Big dip 2011: Oct. 13th - Oct. 24th (reaching -2.224 million km2)
This year the negative anomaly has dipped below 2 million km2 on July 17th, more than a month earlier than the previous earliest record.
As we can see on the first image in this post, total CT sea ice area has also dropped below the 5 million km2 mark. This, of course, is also the earliest date for this to happen on record, as shown by this graph made by Jim Pettit (see his other graphs here):
Jim also sent me this info concerning the drop below the 5 million km2 mark:
- This year’s drop below 5 million was the earliest ever, beating 2011 by two days and 2007 by three.
- 2012 has now been in first place for 19 consecutive days, and 35 of the last 40. (2007 is in second, and 2011 is in third).
- 2012 area only spent nine days in the 5 millions, the shortest amount of time ever. By way of comparison, both 1979 and 1985 spent 48 days there.
- 2012 area fell from maximum to below 5 million in just 110 days, by far the quickest time ever. Nine previous years in the 33 year record failed to even fall below 5 million, but for those years which did, it took an average of 159 days. (1989 and 1997 took the longest—191 days—while the previous shortest was 2011, at 135 days.)
- 2012 SIA is now below the minimum reached in 12 of the 33 previous years in the record.