Is Sandy Just the Beginning? Are We Setting up for (another) Winter of Extremes?

November 4, 2012

Negative Arctic Oscillation conditions are associated with higher pressure in the Arctic and a weakened polar vortex (yellow arrows). A weakened jet stream (black arrows) is characterized by larger-amplitude meanders in its trajectory and a reduction in the wave speed of those meanders.

This morning, people in the northeast US, while still recovering from Superstorm Sandy, an unusual, late season hurricane – are being pounded by an unusual, early season Nor’Easter snow storm.

This is a further discussion related to the sea ice/jet stream issues discussed by Dr. Jeff Masters in a nearby posting.

Cornell University News:

The dramatic melt-off of Arctic sea ice due to climate change is hitting closer to home than millions of Americans might think. That’s because melting Arctic sea ice can trigger a domino effect leading to increased odds of severe winter weather outbreaks in the Northern Hemisphere’s middle latitudes — think the “Snowmageddon” storm that hamstrung Washington, D.C., during February 2010.

Cornell’s Charles H. Greene, professor of earth and atmospheric sciences, and Bruce C. Monger, senior research associate in the same department, detail this phenomenon in a paper published in the June issue of the journal Oceanography.

“Everyone thinks of Arctic climate change as this remote phenomenon that has little effect on our everyday lives,” Greene said. “But what goes on in the Arctic remotely forces our weather patterns here.”

A warmer Earth increases the melting of sea ice during summer, exposing more dark ocean water to incoming sunlight. This causes increased absorption of solar radiation and excess summertime heating of the ocean — further accelerating the ice melt. The excess heat is released to the atmosphere, especially during the autumn, decreasing the temperature and atmospheric pressure gradients between the Arctic and middle latitudes.

A diminished latitudinal pressure gradient is linked to a weakening of the winds associated with the polar vortex and jet stream. Since the polar vortex normally retains the cold Arctic air masses up above the Arctic Circle, its weakening allows the cold air to invade lower latitudes.

The recent observations present a new twist to the Arctic Oscillation (AO) — a natural pattern of climate variability in the Northern Hemisphere. Before humans began warming the planet, the Arctic’s climate system naturally oscillated between conditions favorable and those unfavorable for invasions of cold Arctic air.

Greene says, “What’s happening now is that we are changing the climate system, especially in the Arctic, and that’s increasing the odds for the negative AO conditions that favor cold air invasions and severe winter weather outbreaks.

“It’s something to think about given our recent history,” Greene continued. This past winter, an extended cold snap descended on central and eastern Europe in mid-January, with temperatures approaching -22 Fahrenheit and snowdrifts reaching rooftops. And, of course, there were the record snowstorms fresh in the memories of residents from several eastern U.S. cities, such as Washington, New York and Philadelphia, as well as many other parts of the Eastern Seaboard during the previous two years.

But wait — Greene and Monger’s paper is being published just after one of the warmest winters in the eastern U.S. on record. How does that relate?

“It’s a great demonstration of the complexities of our climate system and how they influence our regional weather patterns,” Greene said. In any particular region, many factors can have an influence, including the El Nino/La Nina cycle. This winter, La Nina in the Pacific shifted undulations in the jet stream so that while many parts of the Northern Hemisphere were hit by the severe winter weather patterns expected during a bout of negative AO conditions, much of the eastern United States basked in the warm tropical air that swung north with the jet stream.

“It turns out that while the eastern U.S. missed out on the cold and snow this winter, and experienced record-breaking warmth during March, many other parts of the Northern Hemisphere were not so fortunate,” Greene said. Europe and Alaska experienced record-breaking winter storms, and the global average temperature during March 2012 was cooler than any other March since 1999.

“A lot of times people say, ‘Wait a second, which is it going to be — more snow or more warming?’ Well, it depends on a lot of factors, and I guess this was a really good winter demonstrating that,” Greene said. “What we can expect, however, is the Arctic wildcard stacking the deck in favor of more severe winter outbreaks in the future.”

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One Response to “Is Sandy Just the Beginning? Are We Setting up for (another) Winter of Extremes?”


  1. “Greene and Monger’s paper …”

    It was already several similar works showing the possible impact of climate change (in different ways) in Arctic atmospheric circulation and NH. Eg:

    http://www.agu.org/pubs/crossref/2010/2009JD013568.shtml

    http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1379.html

    http://www.deas.harvard.edu/climate/seminars/pdfs/FrancisVavrus2012.pdf

    “A diminished latitudinal pressure gradient is linked to a weakening of the winds associated with the polar vortex and jet stream.”

    But it is worth to draw attention to the possible “additional” reasons weakening and meandering jet stream.

    http://www.bbc.co.uk/blogs/paulhudson/2012/05/weakest-solar-cycle-in-100yrs.shtml:

    “… weak solar activity will continue, leading to the weakest solar cycle in around 100 years …”
    “Research over the last few years has pointed to a link between low solar activity, and incidences of ‘blocking’ weather patterns.”
    “ In three out of the last four winters, the jet stream has been much weaker than normal, leaving us more exposed to colder air from the north and the east, as ‘blocking’ areas of high pressure become established.”
    “And it’s certainly a headache for computer models that predict our future climate based on increasing levels of man-made greenhouse gases.”
    “They are unable to model the impact of weak solar activity, simply because the precise mechanism of how this affects climate patterns is unknown [...].”

    http://www.bbc.co.uk/blogs/paulhudson/2012/10/a-step-forward-in-forecasting.shtml:

    “SSW [Sudden stratospheric warming ] is linked to sudden large increases in temperature over a few days in the stratosphere over the Arctic.
    This temperature change cause winds to reverse their normal direction.
    For some time, forecasters have noted that a sudden weakening in high altitude winds in the stratosphere was often followed in winter by blocking surface weather systems.
    These blocking weather systems tend to bring much colder conditions across Europe and the UK from the east, stopping milder air pushing in from the Atlantic.”
    “There are several competing influences each winter, such as Atlantic sea surface temperatures, volcanic eruptions, snow cover and solar forcing.”
    “But separating their effects, and establishing which has the largest impact, remains a big headache for forecasters.”

    Climate change and solar variability: What’s new under the Sun?, Barfd and Frank, 2006. (http://www.citeulike.org/group/1174/article/969558):
    “Overall, the role of solar activity in climate changes — such as the Quaternary glaciations or the present global warming – remains unproven and most probably represents a second-order effect.”
    http://www.ncdc.noaa.gov/oa/climate/globalwarming.html: “Our understanding of the indirect effects of changes in solar output and feedbacks in the climate system is minimal.”

    I propose reflections about “understanding”, by T. Knutson (2011): (http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0566-103.pdf/$file/EE-0566-103.pdf).
    “First, it is possible that 21st century changes in tropical cyclones will be less potentially damaging than the scenarios outlined in the projections section.”
    “Alternatively, it is also possible that the reverse could be true in these cases, i.e., that transient climate sensitivity, future greenhouse gas concentrations, sea level rise, and so forth could be higher than expected, or even that storm tracks could shift systematically more toward major landfalling regions, in contrast to a number of current projections.”

    To all who say YES too easily (but NOT) also I recommend this post: Twenty Times More Likely (Not): The Science, by John Nielsen-Gammon

    http://blog.chron.com/climateabyss/2012/07/twenty-times-more-likely-not-the-science/.

    Title post (but also contents) is beautiful “call” a rationality … is not it?


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