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Posted at 11:00 AM ET, 12/05/2011

Unusual winter weather may be connected to rapid Arctic climate change, report warns


(NOAA)

It’s often said that the Arctic is the proverbial “canary in the coal mine” of global warming, an overused expression that applies in this instance, since the profound changes occurring there as a result of the warming climate are a warning sign for the rest of the world. What is not said enough, however, is that the rapid Arctic climate change, with its associated loss of sea ice and other impacts, may already be influencing weather and climate patterns in the Northern Hemisphere.

A comprehensive international report on the state of the Arctic climate system, released last week, makes clear that Arctic climate change has not only tipped the entire polar region into a fundamentally different state, but that the changes there may be having spillover effects elsewhere - including the mid-Atlantic region.

The 2011 Arctic Report Card, which was produced by an international scientific team and published under NOAA’s auspices, concludes that the Arctic has taken on very different characteristics during just the past five years.

“The 2011 Report Card shows that record-setting changes are occurring throughout the Arctic environmental system,” the report states.

Another section of the report contains this strong language on how marine ecosystems have changed in response to warming of both the air and sea. “Observations of the Arctic marine ecosystems provide a glimpse of what can only be described as profound and continuing changes.”

The Report Card, which was subjected to peer review, contains a fascinating update on unusual weather patterns observed in the Arctic as well as lower latitudes during the past few years.

As the report details, the Arctic has been warming about twice as fast as the rest of the planet, which is a consequence of local feedback mechanisms and global heat transport, via the atmosphere and the oceans, from the equator to the poles.

As I’ve previously written, the steep decline in Arctic sea ice extent and thickness during recent years alters the flow of heat between the Arctic Ocean and the air. The past five years have seen the five lowest sea ice extent recordings during the satellite era. Since the dark ocean surface absorbs more incoming solar radiation than sea ice does, increasing areas of open water during fall can have a dramatic influence on Arctic air temperatures, and this in turn can alter atmospheric circulation.

Specifically, the report notes that warmer air leads to higher atmospheric pressure surfaces over the Arctic Ocean, and this can weaken the high-altitude winds that circle the North Pole from west to east, known as the “polar vortex.”

A weaker polar vortex can provide greater opportunities for Arctic air to flow southward, into areas like the U.S. and parts of Europe, while the Arctic experiences warmer-than-average conditions. The polar vortex also influences the phase of the Arctic Oscillation, which has a major influence on winter weather in the Washington area, as I detailed in a story last week.

The report card refers to this as the “Warm Arctic - Cold Continents” pattern, and notes that this pattern occurred in December 2009 and February 2010. Both of those months brought major snowstorms to the East Coast.


Warm Arctic (red) - Cold Continents (purple) pattern in December 2010. Shown are departures from the average near-surface air temperature values observed from 1968-1996 (NOAA/ESRL)
“Meteorological attribution to these sub-Arctic events is difficult,” the report states.

The last five years have been the warmest recorded period in the Arctic and climate conditions over the Arctic cannot be ruled out as influencing weather in some sub-Arctic regions, making it relative colder for part of the winter.
More combined observational and modeling studies to understand causes and latitudinal extent of this recent Warm Arctic - Cold Continent pattern are a high priority in Arctic research. In summary, the most we can now say is that loss of sea ice pushes in the right direction to weaken the Polar Vortex and increase the chance for sub-Arctic impacts.

Or as I put it in a recent story for Climate Central: “More and more, what happens in the Arctic isn’t staying in the Arctic.”

Scientists are just beginning to understand some of the ramifications of a rapidly changing Arctic. Given computer model projections showing a seasonally ice-free Arctic Ocean by 2035, it’s possible there will be more instances of this weather pattern, and other unexpected connections emerging between Arctic climate change and areas well outside the Far North.

By  |  11:00 AM ET, 12/05/2011

Categories:  Climate Change, Freedman, Latest

 
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