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Linking Weird Weather to Rapid Warming of the Arctic

Posted on 13 April 2012 by Daniel Bailey

NOTE: This post is reprinted from an article originally appearing in Yale Environment 360, by permission of the author, Dr. Jennifer Francis and Yale Environment 360. 

Does it seem as though your weather has become increasingly “stuck” lately? Day after day of cold, rain, heat, or blue skies may not be a figment of your imagination. While various oceanic and atmospheric patterns such as El Niño, La Niña, and the North Atlantic Oscillation have been blamed for the spate of unusual weather recently, there’s now a new culprit in the wind: Arctic amplification. Directly related to sea-ice loss and earlier snowmelt in the Far North, it is affecting the jet stream around the Northern Hemisphere, with potentially far-reaching effects on the weather.

Arctic amplification describes the tendency for high Northern latitudes to experience enhanced warming or cooling relative to the rest of the Northern Hemisphere. This heightened sensitivity is linked to the presence of snow and sea ice, and the feedback loops that they trigger. For example, as sea ice retreats, sunshine that would have been reflected back to space by the bright ice is instead absorbed by the ocean, which heats up, melting even more ice. As the world has warmed since the fossil-fuel revolution after World War II, Arctic temperatures have increased at more than twice the global rate. A dramatic indicator of this warming is the loss of Arctic sea ice in summer, which has declined by 40 percent in just the past three decades. The area of lost ice is about 1.3 million square miles, or roughly 42 percent of the area of the Lower 48 United States.

Extra heat entering the vast expanses of open water that were once covered in ice is released back to the atmosphere in the fall. This has led to an increase in near-surface, autumn air temperatures of 2 to 5 degrees C (3.6 to 9 degrees F) over much of the Arctic Ocean during the past decade.

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Fig 1.  This graphic shows how near-surface air temperatures over much of the Arctic Ocean in autumn have increased by 2 to 5 degrees C (3.6 to 9 degrees F) in the past decade, compared with the previous 30 years. That increased heat, related in part to the loss of sea ice, is changing some weather patterns over the Northern Hemisphere. (Courtesy of National Center for Environmental Prediction and National Center for Atmospheric Research.) 

All that extra heat being deposited into the atmosphere cannot help but affect the weather, both locally and on a large scale. And there are growing indications that some weather phenomena in recent years — such as prolonged cold spells in Europe, heavy snows in the northeastern U.S. and Alaska, and heat waves in Russia — may be related to Arctic amplification.

But if so, how does it work?

The Arctic region is of course colder than the temperate zones, and it is this difference in temperature that propels the west-to-east river of fast-moving air known as the jet stream. This atmospheric feature separates warm air to its south from cold air to the north, and tends to follow a wavy path as it flows around the Northern Hemisphere between about 30 degrees N and 60 degrees N. It usually resides near the altitude where jets fly, hence its name. As high latitudes warm more than mid-latitudes, however, this north-south temperature difference weakens, which has two impacts on the jet stream.


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Fig 2.  This graphic depicts how the drop in high-altitude winds in autumn over the past 30 years has closely tracked the decline in Arctic sea ice (dashed line). The rapid warming of the Arctic has reduced the temperature difference between the Far North and temperate regions, slowing down the jet stream and leading to more persistent, or “stuck,” weather patterns. (Jennifer Francis, based on data from the National Center for Environmental Prediction, National Center for Atmospheric Research, and National Snow and Ice Data Center)

The first effect is to slow the west-to-east speed of the jet stream, a phenomenon that already appears to be occurring. Upper-level winds around the Northern Hemisphere have slowed during autumn, from October to December, which is exactly when sea ice loss exerts its strongest effect on the north-south temperature gradient. Some regions exhibit even larger drops in wind speed, such as over North America and the North Atlantic, where winds have slowed by about 14 percent since 1980.

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Fig 3.  The warming of the Arctic appears to be changing the trajectory of the jet stream in certain seasons, leading to more persistent weather patterns. The solid line represents a typical jet stream trajectory, and the dashed line represents the expected northward elongation of the waves in the jet stream in response to Arctic warming. (Courtesy of Jennifer Francis, Rutgers University)

Theory tells us that a decrease in the west-east flow tends to slow the eastward progression of waves in the jet stream. Because these waves control the formation and movement of storms, slower wave progression means that weather conditions will be more persistent. In other words, they will seem more “stuck.” This effect appears to play an important role mainly in autumn, because as sea ice reforms in winter, the north-south temperature difference gradually returns to more normal values.

The second way that Arctic amplification is expected to influence the jet stream and our weather is by increasing the “waviness” of the jet stream. Because of Arctic amplification, the northern peaks of waves, called ridges, will experience more warming than the southward dips, called troughs. This is expected to cause the ridges to stretch northward, which will increase the size of the waves. Larger swings in the jet stream allow frigid air from the Arctic to plunge farther south, as well as warm, moist tropical air to penetrate northward. These wavy flows often lead to record-breaking temperatures. Meteorologists have also known for a long time that larger jet-stream waves progress eastward more slowly, as will the weather systems associated with them. Consequently this represents another mechanism that will cause weather conditions to linger.

Increased waviness seems to be occurring during summer, as well; but instead of sea ice loss, the culprit appears to be the progressively earlier melt of snow on Arctic and sub-Arctic land in the spring.

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Fig 4.  Spring Northern Hemisphere Snow Extent (courtesy Rutgers University Global Snow Lab)

As snow disappears, bare soil is exposed to the strong spring sunshine earlier, which allows it to dry and warm sooner. This effect is at least partly responsible for the approximately 2 degrees C of warming over high-latitude land areas since the mid-1980s. This heat contributes to Arctic amplification during summer, which is expected once again to stretch ridges northward, increase waviness, and promote sluggish weather.

There have been many examples of “stuck” weather patterns during the past few years. Deep troughs in the jet stream hung over the U.S. east coast and Western Europe during the winters of 2009/2010 and 2010/2011, bringing a seemingly endless string of snow storms and teeth-chattering cold. In the early winter of 2011/2012, in contrast, these same areas were under ridges, or northward bulges of the jet stream, which brought unusually warm and snowless conditions over much of North America. At the same time, however, a deep trough sat over Alaska, dumping record snows. In early February this year, the jet stream plunged unusually far southward over Europe, bringing frigid Arctic air and snow to some areas that hadn’t seen those conditions in over half a century. During summer, persistent weather patterns are responsible for droughts and heat. The record heat waves in Europe and Russia in the past several years have been linked to early snowmelt in Siberia, and a sluggish high-pressure area caused last summer’s sweltering conditions in the south-central U.S.

While it’s difficult to point the finger at Arctic amplification in causing any of these weather events, they are the types of phenomena that are expected to occur more frequently as the world continues to warm and the Arctic continues to lose its ice. Further research may find ways to predict which regions will experience which conditions. But in the meantime, it’s increasingly likely that the weather you have today will stick around awhile.

ABOUT THE AUTHOR: Jennifer Francis is a research professor at the Institute of Marine and Coastal Sciences at Rutgers University, where she studies Arctic climate change and the link between Arctic and global climates. She has authored more than 40 peer-reviewed publications on these topics. She was also the co-founder of the Rutgers Climate and Environmental Change Initiative. 

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Comments 1 to 20:

  1. This change to negative AO was not predicted, but the opposite was. For example, see Alternative explanations include low solar UV causing blocking, I have links for that, but not handy. The best explanation will incorporate the various factors, tropospheric forcing from factors like lack of ice and other factors and concurrent stratospheric solar forcing. The resultant weather patterns result from both feeding from the other. Ice anomalies is not going to be one of the stronger factors IMO.
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  2. Eric @ 1 No mention is made of "negative AO" in the article. In fact, searching it, I find there is not even one example of the letters "AO" or "ao" appearing sequentially. If you think you read an article about the Arctic Oscillation, I think you should take another look. The topic is in fact "Arctic amplification." That two word phrase appears in the article seven times.
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  3. Don9000, it's pretty much the same, the positive AO described in the paper I linked is a measurement corresponding to a stronger polar jet (i.e. 500mb zonal winds in figure 2).
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  4. To followup my first comment, here's a post with an AO description and although the chart there is a little out of date: it looks like the long term trend is still positive. Although variable, this past winter's AO index was mostly positive. See
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  5. Eric: I see what you're saying in terms of the effects on the jetstream being similar, but Arctic amplification looks nothing like the graph you show above. Look at this figure: Arctic amplification describes difference in rate of warming between the Arctic and the rest of the planet. As you can see, there is no significant difference before about 1980, but after 1995 the difference goes through the roof.
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  6. Eric, I still think you are talking about oranges when Bailey is discussing apples. I will wait for him to clarify the issue, but . . . If you click on the Arctic Amplification link in the post, the explanation of the term includes this definition: "“Polar amplification” usually refers to greater climate change near the pole compared to the rest of the hemisphere or globe in response to a change in global climate forcing, such as the concentration of greenhouse gases (GHGs) or solar output (see e.g. Moritz et al 2002). Polar amplification is thought to result primarily from positive feedbacks from the retreat of ice and snow. There are a host of other lesser reasons that are associated with the atmospheric temperature profile at the poles, temperature dependence of global feedbacks, moisture transport, etc. Observations and models indicate that the equilibrium temperature change poleward of 70N or 70S can be a factor of two or more greater than the global average." Thus, as I understand the Arctic Oscillation, which has to do with atmospheric pressure variations and not "greater climate change near the pole", it is not the same as Arctic amplification The AO is defined by the National Snow and Ice Data Center as follows: "An atmospheric circulation pattern in which the atmospheric pressure over the polar regions varies in opposition with that over middle latitudes (about 45 degrees North) on time scales ranging from weeks to decades. The oscillation extends through the depth of the troposphere. During the months of January through March it extends upward into the stratosphere where it modulates in the strength of the westerly vortex that encircles the Arctic polar cap region. The North Atlantic Oscillation and Arctic Oscillation are different ways of describing the same phenomenon."
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  7. "Don9000, it's pretty much the same" Actually, Don9000 has the right of it. The only thing the two terms have in common is the word "Arctic". AO and AA are to each other as weather is to climate or polo is to golf. One describes a meteorological conditional with a short temporal sphere of influence; the other describes in a summary fashion the net effects of forcings and feedbacks in the polar regions. That the South Pole experiences polar amplification differently than does the North Pole is entirely due to the vagaries of geography/geomorphology.
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  8. If Eric wishes to specifically discuss the AO more, better threads than this exist for that purpose. The subject of the OP (itself but a reprint of a well-written exposition by researcher Dr. Jennifer Francis) is "Linking Weird Weather to Rapid Warming of the Arctic".
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  9. OMG Spring Snow Extent has been increasing since 1968!
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  10. Thanks for clarifying Don. The start of the piece is Arctic amplification as shown in figure 1. Then DB says: "As high latitudes warm more than mid-latitudes, however, this north-south temperature difference weakens, which has two impacts on the jet stream [slower and more wavy]". The paper I linked in #1 theorizes that in winter the high latitude oceans retain heat while the land masses cool which increases the horizontal temperature gradient which strengthens the jet. The only difference in explanations is which temperature gradient is more dominant. It seems likely that the dominance is not constant, but varying due to factors other than the temperature gradients themselves. Kevin C, as Don has pointed out, my graph is not Arctic Amplification (or temperature) but AO, an index of Arctic pressures related to the jet stream and its undulations. Sorry for the confusion, but my diagram is related to figure 2 in the OP, not figure 1.
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  11. Sorry Daniel Bailey, I didn't realize it was a reprint. My comment is related to the piece. As Don quotes in his comment, the AO modulates the strength of the vortex (which is shown in figure 2).
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  12. An interesting Paper, outlining mechanics responsible for changes in mid latitude weather – seemingly down to the phenomena known as Arctic amplification. But what exactly are the causes of Arctic amplification and why it so much more pronounced than Antarctic amplification? The Paper suggests Arctic amplification is caused by the slow feedbacks of more rapid losses of sea ice and snow cover. On the other hand once could argue that acceleration of these slow feedbacks is caused by, rather than causative of, Arctic amplification and that the latter is largely the product of methane emissions not evident in the Antarctic. One of the highest areas of temperature increase in the Arctic appears to affect areas in close proximity to Spitsbergen and East Central Siberia. Both of these regions are notable for sub-surface methane deposits which, due to ocean warming, are venting from the seabed and are expected to increase. If this is causative of Arctic amplification, it should be expected that this will result in continuous and accelerating loss of sea ice and land-based snow cover producing further weakening of the jet stream and higher incidence of “extreme” weather in mid latitudes. As Daniel Bailey is wont to say … we live in interesting times.
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  13. "why it so much more pronounced than Antarctic amplification?" Antarctica is essentially a continent-sized monolithic ice block stretching more than 2 miles into the sky. The Arctic is a warm chunk of the ocean (and therefore at sea level) surfaced with a thin skim of ice surrounded by cold continents, fed by warming tendrils of currents from the Pacific and Atlantic. The proximity to the enormous thermal inertia of the world ocean means that the polar amplification is felt sooner, and much more strongly, in the Arctic than in the Antarctic. But polar amplification is already affecting the Antarctic Peninsula and the ice shelves of the WAIS, PIG and Thwaites glaciers. And in time, by the EAIS itself. EAIS = East Antarctic Ice Sheet WAIS = West Antarctic Ice Sheet PIG = Pine Island Glacier
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  14. Daniel Bailey, comment 13: that's a fantastically intuitive description of the difference, thanks.
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  15. #13 continuing RE: Antarctica... Sea ice in Antarctica is much less common in summer too. ~3 million sq km versus the ~8 million sq km that the Arctic started off with (although recently been dipping below 5 million) I think the Antarctic Circumpolar Current has also been implicated in 'insulating' parts of Antarctica (well, not like normal insulation, but as in moving heat away from certain areas), but my Antarctic knowledge is pretty weak.
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  16. Agnostic, Are you suggesting that warming due to methane emissions is localised? Spitsbergen and East Central Siberia clathrates melt and emit methane therefore Spitsbergen and East Central Siberia warm more. I would be surprised if the effect would be so localised. BTW, what's going on with sea-ice extent this year. Seems like a hell of a lot of ice hanging around south of the Bering Straight in the northern Pacific.
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  17. mercpl, keep in mind that extent only requires 15% ice area... and says nothing about volume. If you look at the thickness and concentration of the ice it becomes apparent that the high 'extent' near the Bering straight currently is mostly just thin ice spread out by currents. Extent can fluctuate sharply based on (literally) a change in wind direction.
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  18. Keep in mind, mercpl, that the ice you reference is seasonal, new ice (with some nilas ice mixed in) and historically will melt in its entirety (and rapidly, when it goes). Like the ice in Hudson Bay does. Bering Strait ice history Sea of Okhotsk ice history Hudson Bay ice history
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  19. Another way to gauge Arctic Sea Ice is by looking at other assessments and metrics that are tracked by research organizations. For example, from Mercator Ocean we have: Arctic Sea Ice Thickness Bulletin Arctic Sea Ice Concentration Bulletin Arctic Sea Ice Drift Bulletin [Source] By combining the first two we can see that the Bering Sea, Sea of Okhotsk, Chukchi Sea, Hudson Bay, Baffin Bay, Barents Sea and Kara Sea will all readily melt out by summer insolation max in late June or early July. The East Greenland Sea will also largely melt out by then, except for ice being advected out the Fram (which quickly meets its doom in the relatively hot waters of the North Atlantic).
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  20. This could be only a taste of what is to come.
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