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 graphs webpage for daily updated graphs, maps and live webcam images.
September 3rd 2011
We are slowly approaching the end of the melting season. 2011 has secured a second spot on most area and extent graphs. The only question now is whether there's enough momentum left to break the 2007 record(s).
We have seen some signs this melting season that extent and area numbers aren't so dependent on weather conditions any more. In the past week for instance, we saw how a small and short-lived high-pressure area over the Beaufort Sea almost led to a century break and two more days of above average extent decrease.
In absence of a strong Beaufort Gyre and Transpolar Drift Stream we can only conclude this has to do with the weak or slush puppie ice at the Pacific side of the ice pack. It did quite a lot of melting in situ and who knows how well it would have compacted had weather patterns looked anything like 2007. Because, just like last year, they didn't. Around mid-July the weather turned bad for extent decrease, recovered somewhat after 3 weeks, but with hiccups. This kind of weather in the pre-2007 era would have inevitably led to a minimum extent above 5.5 million square km.
Still, there is one thing that can prevent weak, thin ice from completely melting out, and that's freezing temperatures and diverging winds. In other words, the end of the melting season. Last week I ended my introduction to SIE update 18 with the following remark:
Barring some really strong weather patterns that keep the ice in place and freeze the water over at the edges, we are in for a final phase of the melting season where everything is possible.
So what can we expect? More on that further below, but I think the fat lady could be humming a few bars.
Sea ice extent (SIE)
Here's the current IJIS SIE graph:
2011 has halved 2007's lead yet again, but didn't manage to fully profit from 2007's slow extent decrease of the last couple of days. I think it's going to be very difficult to break the IJIS record minimum extent now, because 2007 had three weeks of extreme compaction in the final weeks of the melting season, leading to some very strong extent decrease days (for the time of year), and of course a very late date for the minimum extent. However, 2011 is about to edge past 2008's minimum extent in a day or so.
The current difference between 2011 and the other years is as follows:
- 2005: -950K (+3,370)
- 2006: -1257K (+234)
- 2007: +104K (-469)
- 2008: -237K (+172)
- 2009: -678K (+6,417)
- 2010: -583K (+7,865)
Between brackets is the average daily extent decrease for the month of September. 2011's average daily extent decrease for September is currently -11,485 square kilometers. But this doesn't say anything of course, as we only have 2 days so far, and we get a lot of extent increase after the minimum extent. Do note however that 2007 is the only year with a negative average.
If 2011 loses as much sea ice extent as...
- 2005 did after this date it will bottom out at 4.37 million square km
- 2006 did after this date it will bottom out at 4.52 million square km
- 2007 did after this date it will bottom out at 4.36 million square km
- 2008 did after this date it will bottom out at 4.47 million square km
- 2009 did after this date it will bottom out at 4.57 million square km
- 2010 did after this date it will bottom out at 4.23 million square km
The 2007 IJIS minimum extent was 4.25 million square km. 2008 was 4.71 million square km. We are currently at 4.72 million square km.
Sea ice area (SIA)
The Cryosphere Today sea ice area numbers went up quite a bit, but have come down again and we are only 10K away from going below this year's preliminary minimum SIA of 2.983 million square km. SIA is lower than 2008 and 2007 were around this date, but another 75K is needed to break the 2007 record minimum area.
The Cryosphere Today SIA anomaly graph is of course still showing the largest anomaly ever recorded for this date:
As we can see on the Regional Graphs page, the Arctic Basin and Canadian Archipelago are relatively flatlining at the moment. Everything seems to depend now on the slush puppie ice left in the East Siberian Sea that still has some more room to go down, as has the Greenland Sea graph.
Cryosphere Today area per IJIS extent (CAPIE)
On our CAPIE graph we can see how 2007 started shooting up towards the end of August, due to freezing over of melt ponds and of course compacting winds. We see this year's trend line going up as well, but not as strongly. To really break records, CAPIE will have to go up by a couple of percentage points. And not because freezing melt ponds cause SIA to shoot up, but because compaction makes SIE go down faster than SIA.
As usual, we first have a look at the animation of SLP images from the DMI Centre for Ocean and Ice to see what happened in the past week:
The high that caused IJIS sea ice extent to dip quite fiercely, can barely be made out, if just by the isobars above the Beaufort Sea with a tinge of yellow in the middle. The only other noteworthy thing is a cyclone over Svalbard towards the end of the animation. This didn't seem to have much of an effect, except perhaps for some transport towards Fram Strait (which reminds me, I have to update the animation).
Now we come to the reason I'm thinking I can hear the fat lady humming a few bars. The weather hasn't really been great for extent and area decrease in the past couple of weeks (even though extent and area dropped without cessation). I remember how last year around this time some high-pressure areas managed to elbow their way into the American side of the Arctic - ie Greenland, the Canadian Archipelago and the Beaufort Sea - causing trend lines to drop quite a bit more, all the way to a third position on most graphs. But this year those highs simply aren't there (or just for a very short time) and according to the ECMWF weather forecast maps they're not going to come in the next 7 days either:
As things now stand, I think we're going to see an early end to the melting season. SIE will drop some more, and so might SIA. But with the weather forecast maps showing a lot of SLP areas flipping around (which is never good for extent decrease as it needs stable weather patterns to go down steadily), and on top of that the Arctic being dominated by low-pressure areas, I don't think the combination of thin ice and warm waters is going to be able to put up a fight against diverging winds and freezing temperatures.
Of course, I could be wrong. There still is a huge area - in the East Siberian Sea mainly - with low concentration ice that could melt out in a flash under the right circumstances (a gyring Beaufort Gyre and a streaming Transpolar Drift Stream). And maybe it will even melt out significantly in absence of those right circumstances.
In this sense, the ice pack is going to be confronted with the ultimate challenge. Have we definitely reached the stage where the ice melts out, regardless of weather conditions, even at the end of the melting season? Or will that be for another year?
We are going to find out in the next two weeks.
TIPS - Other blog posts and news articles concerning the Arctic and its ice:
Patrick Lockerby has just released his latest blog post on Arctic Ice: September 2011
Tamino explains convincingly that the Death Spiral Continues