Arctic atmosphere June-July 2012

In this exciting battle between Greenland and the Arctic sea ice (who gets the most media coverage?), it's now time for one of those boring comparisons that give the current melting season some more context. For that I have used the excellent maps on the daily mean composites page from NOAA's Earth Science Research Laboratory.

Let me start off with sea level pressure (SLP) from June 1st to July 15th, divided into three two-week periods. Since 2012 is still so low on SIE and SIA graphs, I figured it's best to compare it with other record years such as 2007, 2010 and 2011 (2008 became competitive towards the end of the melting season).

Quick explanation: The green, yellow and orange stands for high pressure, the blue and purple for low pressure. In high-pressure areas the winds blow in a clockwise fashion along the isobars (dividing lines between different pressures). There are no isobars in these graphs, but the colours make it clear enough. In low-pressure areas it's the other way around: winds blow in an anti-clockwise fashion. The important thing to remember is that the ice follows the wind, with a bit of a lag and not as fast. What makes area/extent decrease fast is when highs dominate the American side and centre of the Arctic (the right half of the maps) and lows dominate the Siberian side of the Arctic (left half of the maps), because together they act like cogwheels - one turning clockwise, the other anti-clockwise -  that push all the ice together and towards the Atlantic where it melts out. With lows on the American side and centre of the Arctic, and highs on the other side, area/extent decrease slows down considerably.

These maps show SLP averaged over two weeks, which makes them a bit crude, but they still tell the story of each respective melting season during June and the first half of July. 2010 was going down very fast on the area/extent graphs during June, with a lot of high pressure in the right spot. But in July this decrease came to a grinding halt, with low-pressure systems taking over (see orange arrow on the IJIS SIE graph on the right). 2011 took over the lead, because it kept going strong all the way to mid-July. However, a switch in weather patterns would cut that lead short as well (purple arrow), with 2007 taking over for the remainder of the melting season with its ideal decrease conditions from start to late finish. High pressure on the American side of the Arctic, low pressure on the Siberian side, all the way.

And now 2012. We can clearly see on the SLP map in the top right what was causing that nosedive in June. The rapid decrease slowed down when that big high-pressure system over the Beaufort Sea was replaced by an equally big and powerful low-pressure system. Interestingly though, we didn't see the trend line on the IJIS SIE graph bend to the right as sharp as the 2010 trend line, when the weather patterns switched back then. Despite relatively unfavourable conditions for area and extent decrease trend lines on all graphs kept plodding downwards steadily. It's only in the past week that we see the trend line veer off slightly to the right (red arrow), and that probably has to do with this:

That's one big low-pressure area right there, and though area/extent decrease has slowed down a bit, we are certainly not witnessing the grinding halt we saw at the beginning of July in 2010 (orange arrow) or mid-July in 2011 (purple arrow). This leaves us with only one possible conclusion - if we exclude the nefarious influence of icebreakers, undersea volcanoes and aliens - and that's that a large part of the ice pack is so thin it doesn't really care what the weather does. I concluded the same at the end of last year's melting season, but this is at least 6 weeks earlier. If weather patterns switch to that ideal mix of high-pressure and low-pressure areas, there's no telling what can happen...

Hold on a minute.

Although I really believe my conclusion is broadly correct, I must admit that I am jumping to it. There are two other factors besides SLP and ice thickness that influence sea ice area and extent decrease, namely air and sea surface temperatures. So here's a comparison for July 8th to July 22nd:

2012 looks slightly warmer than the other years, especially over the Canadian Archipelago and Greenland (no kidding!). The same goes for sea surface temperatures, although the maps don't look nearly as exciting as the winter maps. Except for the Bering Strait, the sea water is warmer everywhere, with Baffin Bay and the Beaufort Sea standing out with a tad of orange and red (4-5 °C warmer than the long-term average). And of course Barentsz and Kara, our WACC-y Weather regions.

So temps play a part as well, but it definitely looks like PIOMAS is on the right track. And the Arctic sea ice isn't. This weekend's ASI update will have more detailed info on what we can expect in the coming 1-2 weeks.

Comments

[Apocalypse4Real]

Thanks Neven for the comparative work.

As I detailed before the buoys suggest warm water and air temps continuing in some areas of the Arctic, especially in the thickest areas north of Greenland and the CA.

The Godiva2 ice thickness maps reveal less than two meter thick ice all the way to the NP on the Atlantic side, north of Svalbard.

[Kevin McKinney]

Thanks, indeed, Neven. More good context.

Perhaps a factor to keep in mind as the season progresses is that the role of lows tends to shift a bit: as the more southerly Arctic areas start to get less sun as the days shorten, the cloudy conditions tending to go with lows can begin to hold in enough heat (especially at night) that they act as a positive forcing.

More on cloud and ice loss in the Arctic:

http://www.cgd.ucar.edu/staff/mholland/papers/vavrus_holland_bailey_2010.pdf

[Paradoxnl.wordpress.com]

Neven, nice overview!

[crandles]

>Neven, nice overview!

+1

>the role of lows tends to shift a bit ... lows can begin to hold in ... heat

Perhaps also worth mentioning more swell, vertical ocean mixing, Ekman pumping as well as atmospheric effects.

[Charles Longway]

Neven, Can you report on the Beaufort and Chukchi regions. It looks like we have some flash melting in Beaufort. The Bremen graph of the Chukchi region looks like there has been 'a disturbance in the Force'.

http://www.iup.uni-bremen.de:8084/ssmis/index.html

[Steve Bloom]

Interesting, Charles. I checked the last five days and they're consistent (i.e. seem to show a steady progression toward the current graphic).

Looking at the adjacent CT and NSIDC concentration graphics on the graphs page here and noting that Bremen shows anything below 10% concentration the same as open water, however, what looks to have happened is that a bunch of ice that was somewhat above 10% concentration has dropped a bit below.

Even so, it's quite striking. Also, I would assume that such low-concentration ice at this time of year at that latitude can't be long for the world.

[Steve Bloom]

Also, it appears that the Bremen graphic is a day ahead of the other two. Neven?

[Steve Bloom]

Also also also, see the NWS Anchorage Ice Desk analysis for 7/27. I'll leave a careful comparison for more experienced hands, but off the top it appears to show a lot more ice than the three aforementioned graphics. Possibly there's a different standard used, as the Ice Desk is concerned about navigation hazards.

[Steve Bloom]

Also^4, looking around the site a little I see that the Ice Desk has lots of sat photos linked. This one seems to show the ice still present throughout much of the Chukchi and Beaufort, but in a pretty rotten state (if all those apparent areas of small holes are indeed that).

[Johannes]

Here is an animation of two previous days of the Bremen map.

http://imghost.me/images/2xKUR.gif

[Bob Wallace]

The three holes, yes. But what's with the appearance of much ice on the southwest tip of Greenland?

[AmbiValent]

Steve: I think UB updates about 12 hours before CT and NIDSC.

Bob: That's almost certainly a data error. It sometimes happens that something shows up on the map one day where there was nothing and is gone the next day or two days later. (I call it "folks playing with liquid nitrogen again" as it even sometimes pops up on the Great Lakes in summer)

[Neven]

It looks like the flash melting game has started. There was an instance of that a couple of days back, albeit not as big as this one. Some of that ice will reappear again, but it's definite sign that there is still an enormous melting potential.

Two things are of note:
- This flash melting is three weeks earlier than last year.
- Last year a very big cyclone was the main culprit. I'm not seeing anything like it on the SLP maps this time around.

I think we can expect more instances of flash melting. 2012 is already so low, so it's only logical to assume that it will keep the lead. Especially if the weather switches. I'm going to have a look at the weather forecast now.

[Neven]

BTW, I also notice on the UB SIC map that the NWP is opening up big time.

[Espen Olsen]

Jøkelbugt North East Greenland:

I reported yesterday that within a week the the last real fast ice in all of Greenland will be broken up, I withdraw that, we are only hours away from the big break up, have a look:
http://rapidfire.sci.gsfc.nasa.gov/cgi-bin/imagery/single.cgi?image=crefl2_143.A2012210055500-2012210060000.250m.jpg

[Rob Dekker]

Guys, in the latest Modis pictures today (still incomplete) the clouds are thin and the 'holes' are clearly showing up :
http://lance-modis.eosdis.nasa.gov/imagery/subsets/?mosaic=Arctic
Concentration just dropped below the threshold it seems.
In fact, the entire area from the Beaufort all the way to the Laptev looks like Swiss cheese. This can't be good...

[Espen Olsen]

I would rather say looks like cottage cheese.

[crandles]

Flash melting and area going up!

What does that mean???

[Neven]

That means that SIA has been reported for the 26th, and the flash melting took place on the 27th. Give it some time, crandles, this has to show up on the graphs in the coming days.

[Neven]

Here's the SLP image for the last week of July. Blue, blue, purple.