The Paradox of Cold Continents, Warm Arctic

April 4, 2013


According to NASA scientists, a pronounced shift in air pressure conditions above the Arctic triggered unusual ground temperatures across much of North America and Europe during the March. In this map, which shows surface temperature anomalies from March 14 to 20 compared with the same dates from 2005 to 2012, areas that experienced above-average temperatures are shown in red and orange, while areas with below-average temperatures are shown in shades of blue. Click image for larger.

Yale 360:

A pronounced shift in Arctic air pressure systems has triggered unusually cold temperatures across North America, Europe, and northern Asia, while allowing a flood of warmer air into Greenland and northeastern Canada, according to NASA.

In recent weeks, the so-called Arctic Oscillation (AO) index — which tracks the relative pressure differential between the Arctic and mid-latitudes — dropped to the fifth-lowest reading ever recorded, NASA scientists said. When the AO reaches this “negative” phase, scientists say, the pressure gradient between the Arctic and mid-latiutudes weakens, allowing Arctic air to stream south. The NASA graphic above shows unusual land surface temperatures across the Northern Hemisphere, with Europe, Russia, and the U.S. experiencing temperatures as high as 5 to 15 degrees C below normal, while temperatures in Greenland were as high as 15 degrees C above normal. The United Kingdom recorded its fourth-coldest March since 1962, Germany experienced its coldest March since 1883, and Moscow had its coldest March since the 1950s.


Jeff Masters at WeatherUnderground  discussed one of the early papers on this phenomenon back in 2010, in a report from the American Geophysical Union meeting of that year.

 The talk was given by Dr. Jim Overland of NOAA’s Pacific Marine Environmental Laboratory, one of the world’s experts on Arctic weather and climate (I spent many long months flying in the Arctic with him during the three Arctic field programs I participated in during the late 1980s.) Dr. Overland discussed the remarkable winter of 2009 – 2010, which brought record snowstorms to Europe and the U.S. East Coast, along with the coldest temperatures in 25 years, but also brought the warmest winter on record to Canada and much of the Arctic.

He demonstrated that the Arctic is normally dominated by low pressure in winter, and a “Polar Vortex” of counter-clockwise circulating winds develops surrounding the North Pole. However, during the winter of 2009-2010, high pressure replaced low pressure over the Arctic, and the Polar Vortex weakened and even reversed at times, with a clockwise flow of air replacing the usual counter-clockwise flow of air around the pole. This unusual flow pattern allowed cold air to spill southwards and be replaced by warm air moving poleward. This pattern is kind of like leaving the refrigerator door ajar–the refrigerator warms up, but all of the cold air spills out into the house.

Meteo people weigh in. My understanding is that “arctic oscillation” and “north atlantic oscillation” describe much the same phenomena – I’m assuming that “polar vortex” is yet another term for this.


Masters again:

This is all part of a natural climate pattern known as the North Atlantic Oscillation (NAO), which took on its most extreme configuration in 145 years of record keeping during the winter of 2009 – 2010. The NAO is a climate pattern in the North Atlantic Ocean of fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores High. It is one of oldest known climate oscillations–seafaring Scandinavians described the pattern several centuries ago.

Through east-west oscillation motions of the Icelandic Low and the Azores High, the NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward.

In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. Negative NAO winters tend to bring cold winters to Europe and the U.S. East Coast, but leads to very warm conditions in the Arctic, since all the cold air spilling out of the Arctic gets replaced by warm air flowing poleward.

The winter of 2009 – 2010 had the most extreme negative NAO since record keeping began in 1865. This “Hot Arctic-Cold Continents pattern”, resulting in a reversal of Polar Vortex and high pressure replacing low pressure over the Arctic, had occurred previously in only four winters during the past 160 years—1969, 1963, 1936, and 1881.

Dr. Overland called the winter of 2009 – 2010 at least as surprising at the record 2007 loss of Arctic sea ice. He suspected that Arctic sea ice loss was a likely culprit for the event, since Francis et al. (2009) found that during 1979 – 2006, years that had unusually low summertime Arctic sea ice had a 10 – 20% reduction in the temperature difference between the Equator and North Pole. This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative North Atlantic Oscillation, allowing cold air to spill out of the Arctic and into Europe and the Eastern U.S. Dr.

Overland also stressed that natural chaos in the weather/climate system also played a role, as well as the El Niño/La Niña cycle and natural oscillations in stratospheric winds. Not every year that we see extremely high levels of Arctic sea ice loss will have a strongly negative NAO winter. For example, the record Arctic sea ice loss year of 2007 saw only a modest perturbation to the Arctic Vortex and the NAO during the winter of 2007 – 2008.

Below, Dr. Jason Box of Byrd Polar Center describes the effects of this continued pattern on Greenland, especially since the pronounced drop in arctic ice extent that got underway in 2007.

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14 Responses to “The Paradox of Cold Continents, Warm Arctic”

  1. stephengn1 Says:

    From wikipedia:

    “In physics, resonance is the tendency of a system to oscillate with greater amplitude at some frequencies than at others. … At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.”

    The energy collective recently had an interesting article about a study that relates to this.

  2. It never amazes me the limitless ability of the denier mindset to seize upon the “what I want to hear” parts (hey, it’s snowing in late March, what global warming?) while ignoring the inconvenient stuff (what ice mass loss?).

  3. [...] Yale 360: A pronounced shift in Arctic air pressure systems has triggered unusually cold temperatures across North America, Europe, and northern Asia, while allowing a flood of warmer air into Gree…  [...]

  4. stephengn1 Says:

    It seems clear that Dr Box is saying that we passed a tipping point in 2007

  5. „… what global warming?”
    “… what ice mass loss?”

    For both of these questions is probably one answer given for example by: Richard Seager, Yochanan Kushnir, Jennifer Nakamura, Mingfang Ting and Naomi Naik, all of the Lamont Doherty Earth Observatory, Earth Institute, Columbia University (2010, :
    „ … is just another example of the kind of seasonal climate anomaly that can arise from purely natural variability of the atmosphere-ocean system. There seems no evidence that it had anything to do with climate change and should not be exploited to make arguments, one way or another, about the reality of that (which we do not doubt) or how to tackle it.”

    “… ice mass loss …” probably in this way:

    Polish polar research professor Marsz (2009, : “Changes in the concentration of CO2 in the atmosphere could only explain 9% of variations in the SAT in the Arctic.”

    • MorinMoss Says:

      Looking at the Marsz paper, I note that 2005 and 2007 are marked as “outlier years” for SAT anomalies (Fig. 4).

      If the good professor were to update his paper to include all available data, how many more “outlier years” would there be?

    • So I guess the surplus heat is ignored and a purely natural variability is caused by a Wattsprechaun!

      Wattsprechaun. – Any natural variability or natural forcing that is explained by an invisible force or forces in order to Trick Climate Scientist out of the overwhelming scientific consensus and halting the physics of greenhouse gasses. It first appeared in the graph of the original (MBH98) hockey stick during the medieval warm period. Son of Loki this trickster can be called by uttering the magic words “Mann, Mann, Mann hockey smick”. It will then appear screaming “watts up with that”. It is the patron of all fake climate skeptics’ Everywhere

  6. toby52 Says:

    For the record, Ireland (or at least the Republic of Ireland) – situated on most of that island to the west of Britain – had it’s coldest March ever recorded, according to our Met Office.

    We hate being lumped in with the UK.

    • greenman3610 Says:

      right. I just spoke this morning with Jason Box in Copenhagen, where he says it has been remarkably cold this march. Possibly a record.

  7. Tom Andersen Says:

    Or we could quote another expert on the matter, this time from the CRU, in 2000.

    “Children just aren’t going to know what snow is,”

    Dr. David Viner of the CRU.

    So if the models then were too crude (or just plain wrong) to predict this event, why should we believe this time?

    The point is that weather is surprising in general. Yes the earth is warming, and yes it likely got something to do with CO2, but to think that the carbon sensitivity is known is a croc.

    • greenman3610 Says:

      there are certain known constraints on the sensitivity numbers, for instance, interglacial periods result from changes in orbit and axial tilt which can be calculated. The difference between changes due to the orbital forcing, the feedbacks from that, and the remaining extent of change – give some boundaries to what the climate sensitivity is. It’s hard to get the full glacial interglacial changes without a climate sensitivity somewhere in the ballpark of 3° C +/- 1.5, the most often cited figure. It could be somewhat smaller, but at some point you have to invoke fairies or bigfoot to get the known paleoclimate changes without co2 forcing.

      • MorinMoss Says:

        Clearly work has to be done to trim those error bars. Fifty percent makes for huge uncertainty.
        However, in a chaotic system with varying inputs, some of which have self-opposing effects, that’s not a back-of-the-envelope problem.

  8. [...] 2013/04/04: PSinclair: The Paradox of Cold Continents, Warm Arctic [...]

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