Towards the end of last melting season we had a lot of fun speculating about large patches of ice getting separated from the main pack. Well, at least I did. So much so that I wrote an article about it, called Breaking away from the pack. Much of the ice seemed to be very thin at the time and there was so much divergence that a bit of consistent freak weather ought to have been enough to blow away a patch. It didn't come about in the end, but was educative nonetheless.
I was reminded of this as we witnessed two things in the past few weeks. The first was that the ice south of the narrow Bering Strait seemed to get cut off from the ice in the Chukchi Sea. The other was a huge polynya forming north of Franz Josef Land (a group of islands more or less halfway between Svalbard and Severnaya Zemlya) that seems to extend towards Svalbard, cutting off all the ice south of it. A very important factor in this is the upwelling of warm water from the West Spitsbergen Current.
The large patches of blue water can easily be discerned through the clouds on yesterday's MODIS satellite image:
To prevent my becoming a prisoner of premature spouting of speculations I decided to have a look at previous years, using the University of Bremen's excellent archive of sea ice concentration maps. Let's see how peculiar these dark blue holes really are:
As we can see, the hole north of Franz Josef Land is a pretty normal feature, at least in the past 8 years. 2010 had one more to to the west of Franz Josef Land, 2004 has a few holes, and 2006 looks quite spectacular, with a hole the size of Mick Jagger's mouth. Of course 2006 had lowest extent and area around this date, so it's no surprise to see how far the ice pack had already retreated by this time, with Svalbard and some left-over ice surrounded by open water.
This year's ice looks a bit less concentrated than previous years, with a lot of pink (approximately 90%) and even some yellow (75%) in all of the ice south of the line between Svalbard and Franz Josef Land. In the lower right corner we can also see some of the action in the Kara Sea off the Siberian coast, which seems to be ahead of other years. One minor thing of interest is that according to the PIPS 2.0 sea ice thickness model the ice just north of Svalbard should be close to 5 meters thick, but I see mostly open water there. We'll get back to this one some other time.
Now let's have a look at the current situation in Bering Strait, compared to previous years. By the way, I have covered this area almost two months back (my, how time melts):
2011 is a few steps ahead of the most recent years 2008-2010 and 2006. In 2004 and 2005 the Bering Sea seems to contain less ice, but there are still some substantial patches of ice left in the Gulf of Anadyr. 2007 has some ice left over there as well, but the shape of the rest of the ice resembles the shape of this year's ice, so far.
To top the whole thing off, I have a sneak preview of how other years looked at the end of the month, so we get an inkling of what's ahead:
I'll fill in the last image for 2011 three weeks from now and look at SST in the Bering Strait.