During the melting season I'm writing (bi-)weekly updates on the current situation with regards to Arctic sea ice (ASI). Central to these updates are the daily IJIS sea ice extent (SIE) and Cryosphere Today sea ice area (SIA) numbers, which I compare to data from the 2005-2011 period (NSIDC has a good explanation of sea ice extent and area in their FAQ). I also look at other things like regional sea ice area, compactness, temperature and weather forecasts, anything that can be of particular interest.
Check out the Arctic Sea Ice Graphs website for
daily updated graphs, maps and live webcam images.
July 1st 2012
The ASI update from two weeks ago ended with a couple of questions:
Will the conditions that were so conducive to melting have an inertia-like effect on the SIE and SIA numbers? And what is that big low going to do? Will it tear up the ice pack so we get to see the holes we did in the 2010 melting season? And how about those highs over the Siberian coast during Summer Solstice?
As expected the speedy decrease slowed down considerably, but enough was going on all around the Arctic for the 2012 SIE and SIA trend lines to stay close to the bottom years. That big low-pressure system definitely left a mark all over the Arctic, see for instance the holes in the ice pack on this satellite image for June 26th. It is very reminiscent of 2010, but earlier this time around. And those highs over the Siberian coast? I think they had something to do with SST anomaly charts needing extra colours.
On the day the last ASI update came out, LiveScience had an article about this year's potential new record, with a couple of quotes from the NSIDC's Dr Walt Meier (also known as Saint Walt because of his missionary work in certain corners of the blogosphere):
The tilt of the Earth's axis means the sun does not set above the Arctic Circle on the summer solstice, with summer days growing longer even farther north. As a result, the more dark water exposed to sunlight around this time, the more heat it can soak up.
"In a way it is almost like building up a bank account of heat," Meier said.
Everything is pointing towards a lot of savings in this respect, and interest will probably be high too. But 2012 also has a little piggy bank of melting potential that the other years with low SIE and SIA did not have. While melting very rapidly on the Atlantic side of the Arctic, 2012 decrease is still relatively slow in easy ice places like Hudson Bay and the Greenland Sea. If the weather allows 2012 to break that little piggy bank we will witness another radical nosedive.
All of this and more in ASI update 6.
Sea Ice Extent (SIE)
The fast decline in the first two weeks of the month leveled off somewhat, but 2012 has nevertheless just dipped below 2011, and is now in second place behind 2010.
The current difference between 2012 and other years (without the unrealistic last data point that gets revised upwards) is as follows:
- 2005: -496K (-57,531)
- 2006: -169K (-59,609)
- 2007: -288K (-63,328)
- 2008: -578K (-58,500)
- 2009: -667K (-55,938)
- 2010: +282K (-74,120)
- 2011: -3K (-66,010)
Between brackets is the average daily SIE decrease for the month of June. 2012's average daily SIE decrease for June turned out -76,771 km2 per day, which is the highest average daily decrease for June in the 2005-2012 period.
Sea Ice Area (SIA)
After the recent spectacular decline on the Cryosphere Today SIA graph, the 2012 trend line stayed relatively low, but was joined by big melter 2010:
As 2012 keeps producing century breaks it has dipped below 2010 again. One interesting thing to keep an eye on is the CT SIA anomaly graph because we're getting awfully close to the minus 2 million square km anomaly mark, which would be really early for the time of the year:The current difference between 2012 and the other years is as follows:
- 2005: -1,025K (-93,233)
- 2006: -730K (-88,414)
- 2007: -540K (-101,301)
- 2008: -822K (-86,647)
- 2009: -1,340K (-86,332)
- 2010: -43K (-105,310)
- 2011: -373K (-101,230)
Between brackets is the average daily area decrease for the month of June. With one more day to go, 2012's average daily area decrease for June is currently -110,729 square km per day. I think it's safe to say that this will be the highest daily average decrease for June. Can you imagine how high it would've been if the weather wouldn't have switched?
Cryosphere Today area per IJIS extent (CAPIE)
Our CAPIE or compactness ratio went up a bit again, but with CT SIA going down again faster than IJIS SIE in the past couple of days, the ratio is hovering in the record zone again:
Where the main reason for the relatively low CAPIE we saw in the last ASI update was melt ponding, this time around I think a role is also played by those holes that were blown into the ice pack by cyclonic winds. But the Sun is still beating down on the ice and ocean big time, let there be no doubt about it. So lots of melt ponds, but lots of absorbed solar energy in those melt ponds as well.
Regional SIE and SIA
Regional graph of the week:
Baffin Bay SIA is low for this time of the year. Not only because the ice is disappearing fast, but also because there is no ice transport from the straits and channels in the Canadian Archipelago. The Northwest Passage has started to break up at the western entrance, but in Lancaster Sound, the eastern entrance, an ice arch is still holding up (see blog post). The ice arch in at the southern end of Nares Strait has just started to disintegrate, and it will take a week or two for ice transport to get going from the Arctic Basin towards Baffin Bay (see blog post). However, it increasingly looks like the bay will be a death trap for that ice as waters seem to have warmed up significantly in the last three weeks, due to insolation and high air temperatures. I discussed the effects of that for the adjacent southwest coast of Greenland in a blog post that was posted earlier today: The dark side of Greenland. With no sea ice as a buffer temperatures might shoot up even more.
This corner of the Arctic looks particularly bad this year. In a couple of days I will write a blog post comparing the region in 2012 with other years. If you can't wait, you can compare concentration maps yourself on the ASI Graphs page.
Sea Level Pressure
As usual I start with an animation of SLP images from the Danish Meteorological Institute to see what has happened in the past two weeks:
So what the ECMWF model forecasted, came about: a low moved over the Beaufort Sea, increasing cloudiness and bringing the Beaufort Gyre to a grinding halt. This was the main reason that SIE and SIA decrease slowed down. But as we can see, the blue cyclone has disappeared and some yellow has started to reappear. This is already getting reflected in the numbers, with decrease on the increase again, which just goes to show how poised the Arctic still is for rapid decline.
But what does the ECMWF weather forecast have in store for the coming 6 days? Here's the panel:
There's no two ways about it: a big high is taking over. This will almost certainly lead to a rapid decline, as high pressure systems bring clear skies and thus a lot of solar energy will reach the ice and water. 2012 would be taking an even more vertical nosedive on graphs than it did in the first two weeks of this month, if it weren't for that high being so big and spread out. The lack of isobars and strong lows over the Laptev Sea, signals to me that the Beaufort Gyre won't be turning very fast, and so I'm suspecting we won't be seeing an above average transport of ice out of Fram Strait. In other words, no strong Arctic Dipole Anomaly.
Air temperatures are relatively high in important places like the Siberian Seas and the Canadian Archipelago...
...but all in all air temps aren't anything out of the ordinary, with no orange or yellow at northern latitudes. The DMI mean temperature above 80N graph agrees:
On the other hand, I can't remember ever seeing a DMI SST anomaly map like this one:
The colours can jump from one day to the next, but it has been progressing towards this more and more. And it only makes sense, as we knew those highs over the Barentsz and Kara Seas would let a lot of sunshine through to be absorbed by the dark waters below. In the past there used to be ice here to reflect that solar energy back into space. Not any longer.
The only positive thing I see on this SST anomaly map is the purple, blue and green colours in the Bering Sea and Strait. This just might be the one thing (after weather patterns of course) that can keep this year from smashing all the records. But more on that in a separate blog post later this week.
Arctic sea ice decrease had a small hiccup that lasted about 10 days, but 2012 remained close to the other big melt years 2010 and 2011, and now it looks like the weather will give it another turbo boost. Right around the start of July, one of the most important months in the melting season (especially for extent). Clear skies will do destruction, but the winds will determine whether this second nosedive of the melting season will be just a nosedive, or the mother of all nosedives.
There's still enough easy ice potential in Hudson Bay, Baffin Bay, the Greenland and East Siberian Seas for 2012 to take a very big headstart and start nibbling at thicker ice at the edges of the Central Arctic much earlier than other years. Of course, there's no use in looking too far ahead, as weather patterns can completely switch in just a few days. But not the coming week. Look for 2012 to go low again in the 7-10 days to come.
PS the first oil tankers have left port to take advantage of an early opening of the Northern Sea Route.