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:
- 2005: -529K (-83,709)
- 2006: -604K (-70,025)
- 2007: +167K (-98,608)
- 2008: -729K (-81,068)
- 2009: -10K (-92,127)
- 2010: -414K (-62,601)
Between brackets is the average daily extent decrease for the month of July. 2011's average daily extent decrease for July is currently -85,099 square kilometers, which is a far cry from the more than 100K average daily extent decrease we saw during the first half of the month.
Sea ice area (SIA)
Whereas SIE stalled quite radically in the past week, SIA bounced back downwards, with 2011 even increasing its lead over 2007. But after a slowdown of two consecutive days of reported sea ice area increases, both years are now virtually tied. This means of course that the trend line on the Cryosphere Today SIA anomaly graph is still pretty low:
Sea ice area in the East Siberian Sea had a small hiccup, but is still dropping very, very fast. With weather patterns switching again and ice transport through Fram Strait stalling (see animation), the SIA in the Greenland Sea has resumed its decline. In the Arctic Basin SIA decrease has slowed down a bit, as it has in the Canadian Archipelago.
Cryosphere Today area per IJIS extent (CAPIE)
This year's trend line on our CAPIE graph lost almost 10% in ten days, followed by a bump upwards of 2% in two days, and going down again 2% in two days. The influence of melt ponds is minimal now, so the ice pack must have been diverging a lot:
Sea Level Pressure
As mentioned in this SIE update's intro high-pressure areas have been forming north of Scandinavia, mirrored by a big low-pressure area over the Beaufort Sea, as this animation of SLP images from the DMI Centre for Ocean and Ice of the past week clearly show:
Needless to say, the PIPS ice displacement forecast maps have shown small arrows pointing every which way. There is no need even to show how those arrows look, if only for the fact that they haven't been updated since the 27th. I'll just skip straight away to the forecast for the coming week.
According to the NOAA Ensemble Mean AO forecasts the Arctic Oscillation will become more negative in the short term:
This, of course, means more high-pressure areas. But where will they be? Let's have a look at the ECMWF forecast for the coming 5 days:
It looks like the model expects the high to extend itself towards Greenland. With a low forming between the Laptev and Kara Seas, the ice transport towards Fram Strait might get some more traction again. But all of it is looking very fickle, like it has been for the past two weeks.
The big question is how long 2011 will remain in this state ressembling 2010 which started two weeks later than last year. Around this time 2010 was also moving towards a negative Arctic Oscillation, but it was only towards mid-August that extent decrease numbers were reflectiung this effect.
The past week more or less matched my expectations, until the last two days where IJIS reported abysmal extent decreases of just over 20K. Daily extent decrease probably won't stay this low for long, but I don't expect things to change very radically this coming week.
Lots of clouds and shifting winds will make 2011 fall behind 2007 even more. Again, if by August 10th the difference is over 200K, we can effectively rule out a new minimum extent record.
TIPS - Other blog posts and news articles concerning the Arctic and its ice:
Patrick Lockerby has released his Arctic Ice August 2011 update.
Chris R has written another thought provoking post called Arctic sea ice free this decade?
Mauri Pelto has another interesting article on one of Greenland's lesser known glaciers: Umiamako Glacier acceleration and retreat