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Climate Hustle

Declining Arctic sea-ice and record U.S. and European snowfalls: are they linked?

Posted on 14 March 2012 by John Mason

It is often said of the Arctic that, when it comes to climate change, this region of Earth is the proverbial 'Canary in the Coalmine' - that is, if anywhere is going to alert us that something's up, it's up there in the far north. So we have seen sea-ice coverage diminishing dramatically and sea-ice volume falling off a cliff. Land-ice too is on the retreat: a mineral exploration company that has returned to the Black Angel mine in western Greenland, last worked from 1973-1990, have found a new orebody exposed at surface, where "the existence of mineralisation at this location was known, but previously it was covered by 60m of ice." Just recently Skeptical Science reviewed the science and ran an interview with one of the lead scientists in a team investigating extensive outgassing of methane from the sea-bed of the East Siberian Arctic Shelf, possibly linked to the degradation of undersea permafrost. There's a lot going on up there, to which we can add the accumulating evidence that, paradoxically, reductions in sea-ice cover may be driving changes in atmospheric circulation patterns that have been behind the severely cold plunges and record-breaking snowfalls seen over the continents at more temperate latitudes in recent winters.

Living where I do, not far from the west coast of Wales, in that part of NW Europe that sticks furthest out into the Atlantic Ocean, cold winters are in general uncommon. The months of December, January and February are often dominated by zonal conditions in which Atlantic depressions are bowled at us one after another by a strong westerly jetstream. On occasion, high pressure builds on a N-S axis in the mid-Atlantic, allowing a northerly flow bringing snow-showers, but typically such events are over within a few days. In both 2009-10 and 2010-11, things were radically different. I well recall Christmas morning in 2010: it was symbolic of the whole affair in a month that had seen almost continuous snow and ice, and just when I thought it couldn't get any worse, I came downstairs to be greeted by a centimetre of solid ice on the tiled bathroom floor. I had left the taps a-dripping overnight, but what I hadn't accounted for was that ice built up outside, sealing the outflow-pipe so that back-pressure had forced an 'o'-ring joint apart where the pipe went through the wall, allowing the water to make its way across the floor until it got so cold that it, too, froze. The taps by that point had both stopped dripping as well. Not the most auspicious start to a day.

Ice-floes on the Dyfi Estuary, December 2010

above: ice-floes along the Dyfi Estuary, Mid-Wales, December 2010. Photo: Author

I've included that tale of woe for the simple reason that it was an unprecedented event in my time in this part of the world (1981-present day) and locals reckoned that nothing like it had been seen since the Great Winter of 1962-63. Temperatures were plummeting to -15C or colder at night and deep snow stayed put for very many days. Not only that, it was the second winter in a row that had seen severe cold. Moreover, the tabloids gleefully ran headlines with various phrases, all sarcastic and including the words 'Global' and 'Warming'. It is intriguing, then, that there is a building body of evidence that changes up in the Arctic as a consequence of warming may well be driving this severe winter weather.

Regional-scale fluctuations in weather are influenced by a number of factors: thus we have El Nino and La Nina in the Tropical Pacific, with their sometimes major impacts on rainfall – or lack of it. In the North Atlantic, strong controls are exerted by the steepness of the pressure-gradient between the quasi-permanent Azores High and the Icelandic Low and by their positions relative to one another. If the gradient between them is strong – as would be the case with intense high pressure over the Azores and deep low pressure over Iceland, a strong west-to-east airflow results, bringing mild, wet and often windy conditions to NW Europe. This weather-pattern represents the North Atlantic Oscillation (NAO) in its positive phase. Conversely, the weaker the pressure-gradient between the Azores High and the Icelandic Low, the more negative the NAO becomes. This results in strongly reduced zonality, to the point that instead a meridional pattern develops – where the jetstream is relatively weak and weather-systems meander longitudinally past slow-moving anticyclones, known as blocking highs, for days or even weeks at a time. These blocks can bring much colder weather down to temperate latitudes in areas situated downstream.

The North Atlantic Oscillation in its positive phase

above: typical pressure-pattern when the North Atlantic Oscillation is in its positive phase, with westerlies flowing in a circumpolar manner

In the later part of the last decade, it was increasingly being recognised that changes were afoot in Arctic circulation patterns: specifically, the NAO and the related Arctic Oscillation (AO), both of which featured air flowing in an overall circumpolar pattern, either zonally or meridionally, had begun to alternate with a new pattern. This, variously termed the Arctic Rapid change Pattern or the Arctic Dipole pattern (Wu & Walsh, 2006), features anomalous high pressure situated on the North American side of the Arctic and anomalous low pressure situated on the Eurasian side. As a consequence, a new connectivity was at times established between polar and temperate regions, with two effects: firstly, heat was being transported into the Arctic from the south via the Bering Strait - the Dipole pattern occurred throughout the summer of 2007's record-breaking sea-ice melt season, but secondly, much colder air was also able to periodically escape from the Arctic southwards, a factor that could have major relevance during the winter months (Honda et al, 2008).

The Arctic Dipole pressure-pattern

above: the Arctic Dipole pressure-pattern in August 2010. Note high pressure (red) over N Canada and low pressure (purple) over N Russia.


In terms of sea-ice melt, this pressure-pattern is a positive feedback: as ice extent dwindles, more open water is available to incident UV radiation and therefore warms: in turn this impedes the autumnal refreeze. In addition, the open water causes warming and increased water-vapour loading of the air above, which has increased average September - November tropospheric temperatures in the Arctic to 1°C or more above normal; surface temperatures have increased by around 3C. In turn, the warmer airmass has brought changes to the circulation-patterns that have brought more heat into the Arctic, exascerbating ice-melt. Perhaps this is an important factor in explaining why Arctic sea-ice melt has in recent seasons exceeded the model projections cited in the IPCC AR4. Models can just as much underestimate an effect if an hitherto unknown factor crops up!

The winters of 2009-2010 and 2010-11 showed how the connectivity between the Arctic and temperate regions could plunge the latter into chaos. February 2010 saw Nor-easters dragging in moisture from the warm seas of the west Atlantic and colliding it head-on with Arctic air coming down via Canada - the result being some exceptional dumpings of snow across the NE United States. November 28th 2010 saw a Welsh record-breaking (for the month) overnight low minimum of -18C not far from where I live in Wales. On the very same morning, the temperature on the warm side of the block, at Kangerlussuaq in Arctic western Greenland, was +9C, or 27C warmer. That's extreme meridionality for you!

This change in wind directions to phases of extreme meridionality that permits teleconnection between the Arctic and the temperate latitudes has been christened the Warm Arctic-Cold Continents climate pattern. It commenced some time ago: as Overland and Wang (2010) note, "a persistent positive Arctic Oscillation pattern in late autumn (OND) during 1988–1994 and in winter (JFM) during 1989–1997 shifted to more interannual variability in the following years. An anomalous meridional wind pattern with high SLP on the North American side of the Arctic [the Arctic Dipole pattern], shifted from primarily small interannual variability to a persistent phase during spring (AMJ) beginning in 1997 (except for 2006) and extending to summer (JAS) beginning in 2005."

Extreme meridionality: December 2010

above: late December 2010 saw extreme meridionality with Polar air surging deep into NW Europe - compare with the positive NAO illustration above!

This brings us to the recent paper by Liu et al that has been in the news. In a nutshell their work involved examining observational data for winter (DJF) in the extratropical Northern Hemisphere and comparing it using numerical methods with the variations in Autumn sea-ice extent. They found changes in winter atmospheric circulation that resembled the negative phase of the AO - except that the meridional meanders that occurred took a different form and a different year-to-year variability than shown by the classic AO, with more frequent blocking patterns and greater snowfall, a factor with respect to the latter being an enhanced air-moisture content. Thus, they suggested, the ongoing reduction in sea-ice is playing a critical role in recent cold and snowy winters. They found that the most pronounced increase in blocking-related cold Arctic surges was over the eastern and midwestern USA and from NW Europe east and southeast to central China, with, as mentioned above, a rather persistent warm anomaly over NE Canada and Western Greenland, affected by warm air advection up from the Atlantic.

To quote Liu et al, "while natural chaotic variability remains a component of midlatitude atmospheric variability, recent loss of Arctic sea ice, with its signature on midlatitude atmospheric circulation, may load the dice in favour of snowier conditions in large parts of northern midlatitudes". This does not, of course, mean that just one factor will from now on control our winters: ENSO, the AO and the NAO will all continue to play their roles and at the time of writing conditions here are mild and the NAO has been running in positive mode for some time, keeping NW Europe mild with double-figure daytime maxima widespread.

So, to conclude: the Arctic has become an area of substantial positive temperature anomalies: this has been directly observed. The sea-ice anomalies and lower atmosphere heating over open Arctic water in Autumn have been directly observed. The relatively new Arctic pressure and atmospheric circulation patterns have been directly observed. Papers have been published citing lines of evidence for these features to a) be connected and b) have a potential effect on the climate further afield, including an increased severity of temperate-latitude winters. Although climate trends are multidecadal affairs and the research discussed above is relatively recent,  the influence of open sea water in the Arctic, where at one time there was extensive sea-ice, is clearly one to watch in the coming years. This may not be the black-or-white conclusion that policymakers seem to expect these days, but that's how the world works: they might like to stop and reflect that the decisions that led to the Allies' victory in World War 2 were not made in the light of absolute certainty of outcomes.

Wu, B., J. Wang, and J. E. Walsh, 2006: Dipole anomaly in the winter Arctic atmosphere and its association with sea ice motion. Journal of Climate, 19, 210–225. [abstract]

Honda, M., J. Inoue, and S. Yamane, 2009. Influence of low Arctic sea-ice minima on anomalously cold Eurasian winters, Geophysical Research Letters, 36, L08707, doi:10.1029/2008GL037079. [abstract]

Overland, J.E., and M. Wang (2010): Large-scale atmospheric circulation changes associated with the recent loss of Arctic sea ice. Tellus, 62A, 1–9. [abstract]

Liu, J., Curry, J.A., Wang, H., Song, M. and Horton, R.M (2012): Impact of declining Arctic sea-ice on winter snowfall. PNAS 2012 ; published ahead of print February 27, 2012, doi:10.1073/pnas.1118734109 [abstract]


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Comments 1 to 17:

  1. It may have been relatively balmy in Wales this year but Italy certainly got plenty of snow (in Rome for instance) and ice (in the Venetian Lagoon for instance).

    It will be interesting (in the Chinese sense of the word I suspect) to see what happens when we have an ice free arctic.
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  2. what happens when we have an ice free arctic
    All the energy currently consumed by melting ice will have to go somewhere. The atmosphere has a limited capacity to absorb energy, so will it go to heating the ocean? Will a warmer Arctic basin lead to the ocean releasing more CO2 than it absorbs? Will the spectre of the clathrate bomb come back to haunt us?

    These and more thrilling questions will be answered in our next episode of "Earth: The Human Waste Dump".
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  3. Central, E and Southern Europe certainly had a severe blast this winter, but it was more like the classic pattern of cold air draining SW around the Siberian/Scandanavian High, AKA "Siberian Blast" (all UK tabloids) or "the Beast from the East" (snow-rampers on UK weather forums).
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  4. John,

    One of the favourite discussion topics of BBC Look North's weatherman Paul Hudson (who is a physicist) is the influence of solar activity on climate. There does seem to be a link between low solar activity and cold winters in Europe (eg. the very cold winters during the LIA) and Paul's view appears to be that this may have been responsible for some of our recent cold winters.

    I don't think the solar mechanism could have explained the very cold winter across much of Europe this year. It's also pretty obvious even to me as a biologist that removing most of the ice from the Arctic is bound to have knock-on effects on climate.

    I'd be interested to know your thoughts on the possible "solar" influence and how it might interact with the effect you've described here.

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  5. Paul,

    I think the important thing to consider for a start is the difference in incoming solar radiation between solar max and solar min. It really isn't that great, and as you note the conditions in some parts of Europe were bitter this winter, yet the sun has been quite active. Also, it is important to record that the period 1980-82 was a solar max, yet the 1981-82 winter featured some very severe weather either side of Christmas, with temperatures down to double-figure minima and some historic snowfalls such as the Great Blizzard of January 9, 1982.
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  6. Regarding the cold winter/low solar activity link: deniers liked to explain the cold 09/10 and 10/11 winters by pointing to the low solar activity. Then we had an extremely mild autumn in Europe, and that was explained by the more active sun. The severe January/February cold blast put the solar activity/cold winter theory in a sea of trouble. Of course, that does not prevent deniers from using the more active sun as the sole explanation for the extremely mild spring conditions, with March temperatures being more like May and smashing temperature records every day.
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  7. The "low solar" explanation has substance considering that the stratospheric influences are largely seasonal. Low solar, particularly low solar ultraviolet, has a strong influence on the stratosphere by inducing uneven cooling. In winter the decreased contrast in troposphere to stratosphere allows greater wave penetration so stratospheric waves can impact tropospheric waves and vice versa so that uneven stratospheric temperatures are more likely to result in negative AO.

    Over the next century however, the main influence of greenhouse gases will be to warm the troposphere, cool the stratosphere and reduce the influences of uneven stratospheric warming on tropospheric weather. The AO has been predicted to become more positive and winters like our past winter here in North America (very warm due to largely positive AO) will become more common.

    There are somewhat alternative explanations to the OP and the papers referenced in it. One is here: (The NAO, the AO, and Global Warming: How Closely Related? by Judah Cohen and Mathew Barlow) where they say:

    For example, they suggest that greenhouse gases cool the stratospheric polar regions relative to midlatitudes and the Tropics, refracting propagating tropospheric planetary waves equatorward, resulting in a positive AO. However, it is possible that greenhouse gases might cool the midlatitudes and Tropics relative to the polar regions, therefore refracting planetary waves poleward and favoring a negative AO.
    I also like their explanation of the negative AO, a bit of a twist on the OP above, that the open waters caused more early winter Siberian snowfall which then caused negative AO which occasionally results in lower latitude snowstorms but those are mostly weather flukes.
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  8. Related thread: Global-Warming-Cold-Winters.html. Don't miss the great cartoon in post 50.
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  9. True that there is some merit to it (Lockwood, etc), but this winter, the AO went very negative for a while, despite the much higher solar activity than the two previous winters. Interestingly, the NAO stayed positive when the AO went negative. They are normally closely linked.
    The deniers long tem forecast for the coming years is strong cooling due to the proposed weak solar cycle, but when we break the global temp record in either 2013 or 2014, they will explain that by pointing to high solar activity. They can do this because the press rarely points out their failed predictions. When 2010 broke the record, hardly anyone asked for an explanation for the failed denier predictions from 2008 of rapid cooling from that year.
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  10. My opinion on solar cycles has changed a bit over time- I always thought that low solar would affect weather more than climate, but there are many influences in different directions even for weather, never mind climate. Anyways, it is OT for this thread.

    The sea ice influence is quite weak IMO and won't do much to influence weather patterns compared to other factors. The more obvious connection is that the weather patterns dictate where the sea ice gets melted and where it gets compacted (usually the same areas). This year that was the Barents sea. Although the warm anomaly could essentially have created a high to pull cold air down into Eastern Europe, it is more likely that other effects caused the pattern of the high which warmed the Barents sea and pulled cold air into eastern Europe.
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  11. Is greater snow cover in the Northern hemisphere during winter likely to have any effect on the albido of the Eurasian landmass?
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  12. garethman, yes it will strongly increase albedo - but on a very short-term basis.
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  13. Before the thread dies out completely, what about Judah Cohen, who has proposed very similar ideas (2009 or so - with predictions), but doesn't appear to have predated the first Wang paper?
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  14. @Jsquared

    If you check on other topics I think you'll find that threads on SkS never die out!
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  15. John, thanks for another great article. I've linked to it in a short overview I wrote concerning the WACC phenomenon.
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  16. Thanks for that, Neven.
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  17. Spring is clearly progressing in Finland, Photo 2.4.2012, people are out in terraces:
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