During the melting season I'm regularly writing updates on the current sea ice extent (SIE) as reported by IJIS (a joint effort of the International Arctic Research Center and the Japan Aerospace Exploration Agency) and compare it to the sea ice extents in the period 2005-2010. NSIDC has a good explanation of what sea ice extent is in their FAQ. I also look at other things like sea ice area, concentration, volume, temperature and weather forecasts, anything that can be of particular interest. Check out the Arctic sea ice graph webpage for daily updated graphs, maps and live webcam images.
July 31st 2011
In the last SIE update I mentioned some of the differences between this year's melting season and last year's. These differences, however, do not seem to make much of a difference when it comes to extent decrease.
The rate of extent decrease has been stalling big time ever since weather patterns started shifting two weeks ago, offseting the influence of insolation that has warmed up the water considerably through June and the first half of July.
Area decrease was quite significant for a while though, making this year's trend line on the CAPIE graph plunge precipitously, a sign that the ice pack has been spreading out quite a bit. Not to the level of last year when we saw 'holes' showing up in large areas of the interior of the ice pack, but we might start seeing those in the coming two weeks.
The big difference with last year is in my view that last year had been dealing with a very positive Arctic Oscillation around this time, whereas this year the AO was slightly positive for a while, but is now increasingly turning negative. Here's a blink comparison of the two years:
But the AO index only tells us one thing: whether hig-pressure areas or low-pressure areas are dominating the Arctic. It doesn't tell us anything about the distribution of those areas, which is of major importance for ice transport to lower latitudes.
High-pressure areas on the North American side of the Arctic - if they are stable and stay put for a while - will invariably lead to a higher extent decrease, especially if they combine with strong low-pressure areas on the Siberian side of the Arctic.
Whereas we have high-pressure areas moving into the Arctic for a couple of days now, they are on the wrong side, ie north of Novaya Zemlya and Scandinavia, and mirrored by a low-pressure area over the Beaufort Sea, which is reversing the circular direction of the Beaufort Gyre.
2010's slowdown came to an end mid-August, leading to a final sprint that secured a top 3 position. Whether this year the same will happen, remains to be seen. I personally believe 2011 still has a lot of untapped potential, but it will have to assert itself in the coming weeks, as the window for extent decrease is slowly, but inexorably starting to close.
Sea ice extent (SIE)
Here's the current IJIS SIE graph:
2007 has clearly taken over the lead, despite some slow days which were matched by even slower days this year (just 23K yesterday and today), and opens the first 9 days of August very strongly with 4 century breaks. If 2011 doesn't manage to keep up with that and the difference between the two years grows to over 200K, I think the chances of this year breaking the minimum extent record are minimal and we'll have to start focusing on the question whether 2011 can hold on to second place. It still has a comfortable lead over other years, but 2008 is about to go turbo.
The current difference between 2011 and the other years is as follows: