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 15th 2011
It happens some times. Just when things get exciting one graph or other stops updating. For many weeks we had to go without the PIPS ice displacement map, which in my view is quite indispensable for short-term forecasts of extent decrease. But when IJIS stops reporting new data, things get really awkward. I mean, this whole SIE update business revolves around the IJIS extent data, right?
So I was fumbling through the dark when the IJIS data file froze up on us on the 11th. Was the extremely high rate of extent decrease continuing? Or was there a slump due to atmospheric patterns switching again? To be fair, I thought the latter was going on. That big high over the Arctic Basin was slowly moving towards the Alaskan coast, PIPS ice displacement arrows becamse a bit smaller, and Cryosphere Today sea ice area decrease was slowing down considerably, diminishing chances of a new global sea ice area anomaly record I alluded to in the previous SIE update.
So you can imagine my surprise when I just woke up this afternoon after a long night of work to see that 2011 has actually fended off 2007's attack in the form of a 4 day consecutive series of century breaks. In fact, 2011 responded by noting 4 century breaks in a row itself. Of the last 14 days 10 had century breaks reported.
We have to invent a new word, as amazing, awesome, fantastic, gigantic, enormous and grandiose no longer cut it. Okay, I'm doing a bit of the hyperbole stuff here, but how long can this keep up?
Sea ice extent (SIE)
Here's the current IJIS SIE graph:
So 2011 is still tracking 2007 and actually keeping a slim stroke of white between them. The difference with other years and earlier contenders such as 2006 and 2010 is increasing very fast at the moment. Except for 2009 most years are going to start slowing down, although 2007 is maintaining a formidable rate of extent decrease all throughout the month.
The current difference between 2011 and the other years is as follows:
- 2005: -1022K (-83,709)
- 2006: -615K (-70,025)
- 2007: -260K (-98,608)
- 2008: -1173K (-81,068)
- 2009: -953K (-92,127)
- 2010: -567K (-62,601)
Between brackets is the average daily extent rate for the month of July. 2011's average daily extent rate for July is currently -115,926 square kilometers, which is virtually the same as last week. Crandles rightly remarked that it'd be good to compare the current average with the average other years had after the first 14 days of July, so here it is:
- 2005: -78,125
- 2006: -83,839
- 2007: -117,656
- 2008: -77,500
- 2009: -95,212
- 2010: -55,067
- 2011: -115,926
2007 and 2011 really stand out, don't they? July's rate of extent decrease is double that of 2010!
Sea ice area (SIA)
Extent is still dropping faster than area. CT sea ice area had a few very slow days (which, as I said, led me to believe the party was over for IJIS extent too), resulting in the trend on the Cryosphere Today SIA anomaly graph shooting up a bit again to -1.39 million square km. But after two days of decent area decrease the anomaly is settling back around the -1.5 million square km mark:
I'd like to mention that as an experiment I have made a special page on the Daily Graphs page for the CT regional SIA graphs. These are combined with some excellent extent graphs provided by the NSIDC/NIC MASIE product that also show extent for previous years (these images are slow to load because they come from the NSIDC FTP server). Mind you, I believe CT and MASIE define the regions differently. Still very nice to compare though.
The ice continues to disappear fast along the Siberian coast. To my surprise, as I was expecting the Beaufort Gyre to push ice into these regions. Of course air and sea surface temperatures have been very high over there, so maybe it isn't so surprising. A few regions are so close to melting out completely (like Hudson Bay) that I wont be mentioning them any longer. From now on I'll be concentrating on the Arctic Basin, the Canadian Archipelago and the East Siberian Sea, as that's where the remaining ice is.
Had area gone down as fast as extent, I think there would have been a good chance the global sea ice area anomaly would have reached a new bottom. This is mainly due to an anomalously slow freeze-up of sea ice around the Antarctic. The combined anomaly reached -2.31 million square km, very close to the 2007 record of -2.44 million square km. It has gone up again as the Antarctic anomaly has gone up (currently -2.19 million square km), so I don't think a new record is in the books. It's too early in the season anyway.
Cryosphere Today area per IJIS extent (CAPIE)
With SIA slowing down a bit this past week, but SIE continuing to go down hard, our CAPIE percentage has shot upwards. Apparently compaction is overriding the effect of melt ponding.
I can't repeat this often enough: If we want to know what is going to happen in the short term, we have to focus on sea level pressure. What kind of pressure systems are dominating and how are they distributed over the Arctic? The past week was very educative, and so I'll start with this animation of SLP images from the DMI Centre for Ocean and Ice that shows what happened:
As can clearly be seen, that huge high-pressure system weakened considerably and moved from the Central Arctic to the Beaufort Sea. We see a couple of low-pressure systems moving in and positioning themselves off the Siberian coast.
This was also reflected in the AO index graph that has gone slightly positive in the past couple of days (indicating that low-pressure systems are dominating the Arctic, albeit not so much). What was the effect on ice displacement, you ask? Well, have a look:
You can really see the influence of that high-pressure system becoming weaker, with arrows becoming smaller and less pronounced. Towards the end of the animation we see some bigger arrows showing up pointing from the Siberian coast towards Fram Strait, under the influence of those low-pressure areas moving in.
Which brings us to the short-term forecast. The Ensemble Mean AO forecasts are showing the Arctic Oscillation to remain fairly neutral the coming 7-14 days. So some highs and some lows, just like life. But how will they be distributed? Here's the ECMWF forecast for the coming 7 days:
That high-pressure system that has been with us for quite a while now is going to move again, from the Beaufort Sea to the Canadian Archipelago, complemented by low-pressure systems on the other side of the Arctic. This means we will witness a shift from a regime that is dominated by the Beaufort Gyre to a regime that is known as the Dipole Anomaly (two poles, one over the CA/Greenland, the other between the Kara and Laptev Seas), which is more of a combination of the Beaufort Gyre and the Transpolar Drift Stream, pushing ice out towards Fram Strait.
More low-pressure systems means more clouds and less insolation. But it also means more wind and - with the forecasted distribution - more ice transport towards Fram Strait and Nares Strait. Those clouds are also keeping the air temperatures higher than under clear skies.
It remains to be seen if this can compensate for that big high-pressure system relinquishing its throne, but I think it will. Perhaps extent decrease will slow down a bit because of some divergence of the ice pack and conditions shifting, but I'm not expecting anything radical. July 2011 could match or even beat July 2007.
Somebody call the UN. We are witnessing cryocide. ;-)
TIPS - Other blog posts and news articles concerning the Arctic and its ice:
David Appell has written a marvelous piece on the boxing match between 2007 and 2011: Does 2011 have what it takes?