AER Leads Study to Reveal Extreme Winter Weather Is Related to Arctic Change
September 03 2021 - 9:00AM
A new study shows that the frequency of polar vortex disruptions
that is most favorable for extreme winter weather in the United
States is increasing, and that Arctic change is likely contributing
to the increasing trend. Led by Atmospheric and Environmental
Research (AER), University Massachusetts Lowell and the Hebrew
University of Jerusalem, the study is published in the September 3
issue of Science. AER is a Verisk (Nasdaq:VRSK) business.
The analysis demonstrates that a relatively obscure weak or
disrupted state of the stratospheric polar vortex, where it takes
on a stretched appearance rather than the more typical circular
appearance, has been increasing over the satellite era (post 1979).
Extreme winter weather in the US is more common when the polar
vortex is stretched. Both observational analysis and numerical
modeling experiments demonstrate that changes in the Arctic,
including accelerated warming, melting sea ice and increasing
Siberian snowfall, are favorable for stretching the polar vortex
followed by extreme winter weather in North America east of the
Rockies. Such a chain of events occurred in February 2021, when a
stretched polar vortex preceded the destructive and deadly Texas
cold wave.
During the past three decades, the Arctic has experienced the
greatest climate change of anywhere on Earth, including rapidly
rising temperatures, melting sea ice, diminishing spring snow
cover, and increasing autumn snow cover. Rapid Arctic warming
relative to the rest of the globe is referred to as Arctic
amplification. The extent to which these rapid changes in the
Arctic are influencing midlatitude weather has become a topic of
vigorous debate by climate scientists and popular in the press.
“The publication of the paper is especially timely given the
extreme winter of 2020/21: record warm Arctic, low Arctic sea ice,
deep Siberian snows, a protracted and complex polar vortex
disruption, record-breaking cold in the US, Europe and Asia,
disruptive snowfalls in Europe and the US and most notably the
record breaking and possibly unprecedented combination of cold and
snow in Texas,” said Dr. Judah Cohen, director of seasonal
forecasting at AER and lead author of the study.
Cohen adds, “Last winter the severe cold wave across Texas
heated up the debate as to whether climate change can contribute to
more severe winter weather with those arguing for and against.
However, studies supporting or refuting the physical connection
between climate change and the Texas cold wave and other recent US
severe winter weather events don’t exist, until now. The study also
provides cautionary evidence that a warming planet will not
necessarily protect us from the devastating impacts of severe
winter weather.”
The paper presents a physical mechanism of how climate change in
general and Arctic change in particular are contributing to more
severe winter weather despite an overall warming climate that has
not been previously considered. Most theories on the connection
between Arctic amplification and mid-latitude winter weather argue
that the pathway is either through a wavier Jet Stream or sudden
stratospheric warmings, which are the largest and most often
studied disruptions to the polar vortex. This study provides
compelling evidence that the strongest connection between the
Arctic and mid-latitude weather, at least in the US, may be through
this lesser known and weaker “stretched” disruption of the polar
vortex.
These extreme winter weather events begin when a wave of high
pressure between Northern Europe and the Urals and low pressure
over East Asia undergoes amplification. Such an amplification can
be forced by observed Arctic change during the fall season, and
specifically by melting sea ice in the Barents-Kara Seas and
heavier snowfall across Siberia. The excess energy from the
Eurasian wave bounces or reflects off the polar vortex and is
absorbed in a similar North American wave with high pressure over
Alaska and the North Pacific and low pressure over eastern North
America, causing rapid wave amplification. When atmospheric waves
amplify, extreme weather is more likely.
UMass Lowell Environmental, Earth and Atmospheric Sciences Prof.
Mathew Barlow, a co-author on the study, added, “The synthesis of
both observational analysis and computer model experiments is a
particular strength of this study and greatly increases our
confidence in the results. The dynamical pathway explored here –
from surface climate change in the Arctic up to the polar
stratosphere and then back down to the surface in the US –
highlights one example of the wide range of impacts that climate
change can have.”
Israeli collaborator Prof. Chaim Garfinkel, the Hebrew
University of Jerusalem, concludes “There has been a long-standing
contradiction between an apparent increase in cold extremes in
winter in midlatitudes even as temperatures globally are warming.
This study helps resolve this contradiction and highlights that an
apparent increase in such midlatitude cold extremes in winter
should not be used as an excuse to delay taking urgently needed
action to reduce greenhouse gas emissions.”
AER President Dr. Guy Seeley said: “We are very pleased to see
this publication which reflects AER’s long term commitment to
innovative scientific research on topics of vital interest to our
customers and society at large.”
The research is funded by the US National Science Foundation
Office of Polar Programs and the European Research Council.
The study can be viewed here:
https://science.sciencemag.org/lookup/doi/10.1126/science.abi9167
About Atmospheric and Environmental Research
(AER) Atmospheric and Environmental Research (AER)
provides science-based solutions to global environmental
challenges. AER’s internationally renowned scientists and software
engineers collaborate to transform state-of-the-art predictive
science and analytical tools into practical systems that address
both civilian government and defense needs for geophysical
understanding, computer simulation, and forecasting. AER customers
include government agencies and national laboratories, aerospace
and defense contractors, and academia. Areas of expertise comprise
atmospheric and environmental science, air quality, remote sensing,
meteorology, oceanography, space science, climate change, and
software engineering. A Verisk (Nasdaq:VRSK) business, AER was
established in 1977 and is headquartered in Lexington,
Massachusetts. Visit www.aer.com.
Contact:
Ali Krueger Herbert
Verisk
201-469-3998
ali.krueger@verisk.com
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