WACC overview

I've been planning to write about this for ages, but hibernation and life in general always get in the way. Never mind the fact that it's a complex subject, surrounded on all sides by uncertainty. But why burden yourself with a (seemingly) herculean task, when others have already written about it so eloquently, and explained it so well?

WACC stands for Warm Arctic Cold Contintents, and refers to blocking patterns that cause outbursts of cold air to spill out from the Arctic and cause extreme winter conditions further down on the Northern Hemisphere (image on the right found here). The theory is that these blocking patterns are in turn caused by a breakdown in the Polar Vortex, due to a combination of Arctic amplification, autumnal snow cover increase and sea ice retreat (particularly in the Barentsz and Kara Sea).

Here are some research papers on the subject, the most recent of which received quite a bit of media attention in the past few months:

• Budikova, 2008, "Role of Arctic sea ice in global atmospheric circulation: A review." PDF
• Francis et al., 2009, "Winter Northern Hemisphere weather patterns remember summer Arctic sea-ice extent." PDF
• Overland and Wang, 2010, "Large-scale atmospheric circulation changes are associated with the recent loss of Arctic sea ice." PDF
• Petoukhov and Semenov, 2010, "A link between reduced Barents-Kara sea ice and cold winter extremes over northern continents." PDF
• Overland et al., 2011, "Warm Arctic–cold continents: Impacts of the newly open Arctic Sea." PDF
• Cohen et al., 2012, "Arctic warming, increasing snow cover and widespread boreal winter cooling." PDF
• Jaiser et al., 2012, "Impact of sea ice cover changes on the Northern Hemisphere atmospheric winter circulation." PDF

Most or all of these papers will at one point be included in the paper subsection for Atmospheric patterns.

Some excellent articles have recently come out, explaining this seemingly new phenomenon. Chris R has a whole series of posts on the subject on his Dosbat blog. Last week professor Jennifer Francis wrote an excellent article for Yale Environment 360: Linking Weird Winter to a Rapid Warming of the Arctic. And over at Skeptical Science, John Mason had another great post related to the Arctic: Declining Arctic sea-ice and record U.S. and European snowfalls: are they linked?

Nobody really knows what the exact consequences of these interlinked atmospheric phenomena will be, but I think a lot more will be found out in the next 5 years, as it looks like the causes behind WACC will get worse: the Arctic getting warmer, sea ice retreating more in summer and reforming later in fall, snow cover increasing in fall, followed by a rapid reduction in spring.

So, we'll soon find out. For better or for worse. Probably not better...

Comments

[Pete Williamson]

So this is my problem.

You have a plausible hypothesis as outlined in Budikova 2008 and then you have a couple of years that show the conditions that would confirm the hypothesis and then you get papers such as Overland 2011 that starts

"Recent Arctic changes are likely due to coupled Arctic amplification mechanisms with increased linkage between Arctic climate and sub-Arctic weather."

Which in their words was based on "Winter 2009/10 and December 2010". There seems to be some horrible urge to jump to conclusions as quickly as possible.

Can somebody tell me why this won't go the same way as 'arctic death spirals' based on hasty conclusion drawn after the 2007 minimum?

[AmbiValent]

Blame a system that rewards publishing a lot over better research.

As for "arctic death spiral" - that term was used for the dissappearance of arctic sea ice *within a number of decades*... do you want to say there's a chance it will not do so?

[Daniel Bailey]

@ Pete Williamson:

Actually, Arctic researcher Wieslaw Maslowski of the US Navy Postgraduate School made the initial remark in March of 2006 (Slide 6) and further supported it the next year (January 2007) with additional research (Slide 12). The ice has never wavered in adhering to this timetable of prediction (See here and below).

Note that both predictions were made well in advance of the 2007 melt season minimum; not after, as you have wrongly asserted.

Rumors of the Death Spirals demise have been greatly exaggerated...

[Kris]

Daniel wrote:

Rumors of the Death Spirals demise have been greatly exaggerated...

Moreover, ever since 2007 the annual minimum always plunged under 5 millions km². Always. Which alas is pretty much is a confirmation of the "Daeth Spiral" hypothesys.

[Neven]

Can somebody tell me why this won't go the same way as 'arctic death spirals' based on hasty conclusion drawn after the 2007 minimum?

Pete, like Jennifer Francis said: “The question is not whether sea ice loss is affecting the large-scale atmospheric circulation…. It’s how can it not?”

And, like others say, as things currently stand, the Arctic sea ice is most definitely in a death spiral. Whether we see the Arctic in a virtually ice-free state this decade, or the next, or the one after that, is not really relevant. Even 2100 would be extremely fast, on a geological timescale.

But like I say at the end of the post: we will soon find out if the WACC theories hold any merit, because it looks very much like the alleged causes will worsen. If they do hold merit, so much the better for having started researching it as soon as possible. If the theories turn out to be wrong, we will learn why (maybe professor Francis will have her answer as well). That's science. That's how collective human knowledge grows.

[Chris Reynolds]

Pete,

There's a lot of detailed research that's been going into this issue. It's not an issue that will go away. What Francis has said, as quoted by Neven, is true.

With regards 2009/10, the development of the WACC pattern has been explained by Cohen according to a framework developed in papers published before the event.

See the third graphic on this page:
http://dosbat.blogspot.co.uk/2011/10/cold-winters-siberian-snowfall.html
And the paragraph below that explains the process.

Since then there has been a repeat of this activity over the Winter of 2010/11. Last October's snowfall over Siberia was not exceptional. So according to Cohen's framework this winter should not have shown the WACC pattern, it didn't.

Here's the WACC from 2009/10.
http://farm8.staticflickr.com/7090/6851551182_47ed5c6558_o.png
Winter 2010/11 shows the same pattern - a warm Arctic with a cold band around it in the mid lattitudes.

Here's the same period this Winter.
http://farm8.staticflickr.com/7047/6997686923_50e5f3252b_o.png

They aren't the same pattern.

Yet there was a cold breakout this Winter over Europe. So what happened this Winter?

In 2009 Petoukhov & Semenov published a paper that detailed a mechanism by which reduced sea ice in Barents/Kara causes cold European winters. This seems to be being linked to 2009/10, however I view that as incorrect. This winter saw the same scenario as Petoukhov & Semenov's modelling study being played out for real.
http://dosbat.blogspot.co.uk/2012/03/cold-winters-from-theory-into-practice.html

So in three successive Winters we have seen weather patterns that can be viewed as confirmation of two seperate theories about mid latitude impacts of the loss of Arctic sea ice. Next winter we may not see such strong examples, but given the rate of warming in the Arctic (notably in Autumn and Winter), we will see further confiration in the years to come.

[Neven]

Again, Chris has written a series of interesting pieces on this on the Dosbat blog.

[Neven]

Francis has a new paper out: Evidence linking Arctic amplification to extreme weather in mid-latitudes

Arctic amplification (AA) – the observed enhanced warming in high northern latitudes relative to the northern hemisphere – is evident in lower-tropospheric temperatures and in 1000-to-500 hPa thicknesses. Daily fields of 500 hPa heights from the National Centers for Environmental Prediction Reanalysis are analyzed over N. America and the N. Atlantic to assess changes in north-south (Rossby) wave characteristics associated with AA and the relaxation of poleward thickness gradients. Two effects are identified that each contribute to a slower eastward progression of Rossby waves in the upper-level flow: 1) weakened zonal winds, and 2) increased wave amplitude. These effects are particularly evident in autumn and winter consistent with sea-ice loss, but are also apparent in summer, possibly related to earlier snow melt on high-latitude land. Slower progression of upper-level waves would cause associated weather patterns in mid-latitudes to be more persistent, which may lead to an increased probability of extreme weather events that result from prolonged conditions, such as drought, flooding, cold spells, and heat waves.

Hat-tip to Ari Jokimäki on SkS.

[Chris Reynolds]

Neven,

Just sent you a copy of that paper.

I've just been reading Wayne K's blog and its lead me onto something I wasn't aware of:

The 2012 Heatwave: Almost like Science Fiction.
http://www.popsci.com/science/article/2012-03/2012-heat-wave-almost-science-fiction-mind-boggling

Here in the UK we've got very warm March temperatures, hitting up to 18degC today, forecast the same over the weekend. This is all due to the jetstream getting 'stuck', like in Dr Francis' research (although one instance can't be attributed*):
http://squall.sfsu.edu/gif/jetstream_norhem_00.gif
Source page: http://squall.sfsu.edu/crws/jetstream.html
It's been in that configuration - kinking up over the Great Lakes, down south of Greenland, and over the Atlantic up over Iceland to Scandinavia.

Jeff Masters covers it here:
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2059

Here in the UK the high pressure has moved up towards Scandinavia but earlier this week the synoptic looked just like an August heatwave...

I still bet the UK will have a cool wet Summer though.

I'm reminded of an impacts study I once read, its title was - The Age of Consequences.

*Yes I know - repeating that mantra is wearing thin.

[Chris Reynolds]

Oops forgot to say - the UK has had a blocking high for over a week so far, March is usually front after front.

Here's the BBC Weather synoptic plot.
http://www.bbc.co.uk/weather/2635167#pressure-map
The blocking high stays in charge through to at least Tuesday.

[Neven]

Just to collect in one place: SciencePoles interview with Jiping Liu.

[Wayne Kernochan]

@Neven: At a quick glance, I didn't see Liu cover the case where the processes he cites drives colder and snowier weather, but global warming drives big jumps in winter heat in the Arctic. Of course, that's more speculative and long term ... but I'd still like some thoughts about how those countervailing factors play out -- especially since he still seems to be assuming the "not until 2050 Arctic sea ice melt" card, and so he might be underestimating the strength of both factors.