A new study led by the Georgia Institute of Technology provides further evidence of a relationship between melting ice in the Arctic regions and widespread cold outbreaks in the Northern Hemisphere….
Since the level of Arctic sea ice set a new record low in 2007, significantly above-normal winter snow cover has been seen in large parts of the northern United States, northwestern and central Europe, and northern and central China. During the winters of 2009-2010 and 2010-2011, the Northern Hemisphere measured its second and third largest snow cover levels on record.
?Our study demonstrates that the decrease in Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation,? said Judith Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech. ?The circulation changes result in more frequent episodes of atmospheric blocking patterns, which lead to increased cold surges and snow over large parts of the northern continents.?
That’s from the news release of an NASA- and NSF-funded study in the journal Proceedings of the National Academy of Sciences, “Impact of declining Arctic sea ice on winter snowfall.”
I think Curry’s use of the phrase “cold surges” is important. Although there have definitely been some major cold blasts, our winters aren’t actually getting colder — see the 10/11 Climate Progress post, “Last Two Winters? Warm Extremes More Severe Than Their Cold Snaps, Study Finds.” And that’s without counting this winter. Of course, winters are just going to keep getting warmer globally — so I think some of the reporting on this study has been a tad misleading.
The point is that it now appears over the next couple of decades, the gradual rate of warming will not be able to overcome the occasional incredible winter cold surges fueled by the loss of Arctic ic. This is particularly true if, as I and others have argued, we’re going to see continued rapid ice loss in the next decade (see “The New Arctic Abnormal: Record Low Sea Ice Volume, Area and Extent*” and “The death spiral continues“).
Arctic sea ice in September 2007 reached its lowest extent on record, approximately 40% lower than when satellite records began in 1979. Sea ice loss in 2011 was virtually tied with the ice loss in 2007, despite weather conditions that were not as unusual in the Arctic.
The new PNAS report is about the third study to come to the same conclusion:
The disinformers have repeatedly suggested that big snowstorms disprove (!) climate science. They can’t stand the fact that actual science says that the Snowpocalypses we’ve been seeing can be directly linked to global warming, which, of course, wasn’t news to anyone who actually reads the scientific literature or talks to real climatologists (see “An amazing, though clearly little-known, scientific fact: We get more snow storms in warm years!“).
This study is probably particularly annoying to the disinformers since it was co-authored by Curry, who has transformed herself from climate science advocate into a promoter of many long-debunked disinformers (see ?The curious incident of Curry with the fringe?).
The lead author, Jiping Liu, a senior research scientist at Georgia Tech, explained that the study looked at more than just changes in atmospheric circulation. It also looked at changes in atmospheric water vapor content, which into scientists have long said would increase because of global warming and drive more extreme precipitation events, which in fact is what has happened (see “Two seminal Nature papers join growing body of evidence that human emissions fuel extreme weather, flooding that harm humans and the environment“).
As ABC News reports, “more water is evaporating into the air as Arctic ice at the ocean?s surface melts away”:
?This greatly enhances the transfer of moisture from the ocean to the atmosphere,? Liu said. That humidity, he says, essentially acts as fuel to help supercharge ?Snowmageddon?-type storms like the ones that paralyzed parts of the northeastern U.S. in 2010. A more recent, deadly deep freeze in Eastern Europe left 650 people dead.
?The record decline in Arctic sea ice is at least a critical contributor to recent snowy winters in northern continents,? Liu said.
Liu says the new research may also help connect the dots between human-caused global warming, vanishing ice and our changing weather.
As Climate Central notes, “The Arctic has been warming at about twice the rate of the rest of the globe, a trend studies show is largely due to manmade climate change. Fall sea ice cover declined by 27 percent between 1979-2010, and the five lowest sea ice extent years have all occurred during the past five years.”
They spoke to another leading expert on the subject:
Jennifer Francis, an atmospheric scientist at Rutgers University who was not involved in this study, said the findings largely fit with other investigations into the ways in which Arctic climate change is reshaping weather patterns.
?… Enhanced Arctic warming, caused by climate change, is increasing the tendency for weather patterns of all sorts to become more ?stuck,? she said via email. ?The cold [and] snowy winters of late have received a lot of attention, but it should be noted that at the same time other places had abnormally dry and warm conditions.?
Francis said a warming Arctic will increase the chances of extreme winters, both cold and warm. ?Which areas will experience which conditions is a tough call.?
Here’s more background on the study from the release:
In this study, scientists from Georgia Tech, the Chinese Academy of Sciences and Columbia University expanded on previous research by combining observational data and model simulations to explore the link between unusually large snowfall amounts in the Northern Hemisphere in recent winters and diminishing Arctic sea ice.
The researchers analyzed observational data collected between 1979 and 2010 and found that a decrease in autumn Arctic sea ice of 1 million square kilometers — the size of the surface area of Egypt — corresponded to significantly above-normal winter snow cover in large parts of the northern United States, northwestern and central Europe, and northern and central China.
The analysis revealed two major factors that could be contributing to the unusually large snowfall in recent winters — changes in atmospheric circulation and changes in atmospheric water vapor content — which are both linked to diminishing Arctic sea ice. Strong warming in the Arctic through the late summer and autumn appears to be enhancing the melting of sea ice.
?We think the recent snowy winters could be caused by the retreating Arctic ice altering atmospheric circulation patterns by weakening westerly winds, increasing the amplitude of the jet stream and increasing the amount of moisture in the atmosphere,? explained Jiping Liu, a senior research scientist in the School of Earth and Atmospheric Sciences at Georgia Tech. ?These pattern changes enhance blocking patterns that favor more frequent movement of cold air masses to middle and lower latitudes, leading to increased heavy snowfall in Europe and the Northeast and Midwest regions of the United States.?
Diminishing Arctic sea ice can cause changes in atmospheric circulation that lead to a circulation pattern that is different than the ?negative phase? of the Arctic Oscillation.
In addition to analyzing observational data, the researchers also assessed the impact of the diminishing Arctic sea ice on atmospheric circulation by comparing the results of model simulations run with different sea ice distribution. They ran one experiment that assumed seasonally varying Arctic sea ice and utilized sea ice concentration data collected between 1979 and 2010. Another simulation incorporated prescribed sea ice loss in autumn and winter based on satellite-derived Arctic sea ice concentrations.
The simulations showed that diminishing Arctic sea ice induced a significant surface warming in the Arctic Ocean and Greenland/northeastern Canada, and cooling over northern North America, Europe, Siberia and eastern Asia. The models also showed above-normal winter snowfall in large parts of the northern United States, central Europe, and northern and central China.
The bottom line is that for the foreseeable future, we can expect to see whipsawing winters and more Snowmaggedons, thanks in large part to human emissions of greenhouse gases.