Atmospheric Scientist here at Weather Underground, with serious nerd love for tropical cyclones and climate change. Twitter: @WunderAngela
By: Angela Fritz , 17:35 GMT le 02 décembre 2011
By Andrew Freeman
Since 2006, the Arctic has been less Arctic — warmer, and with less snow and ice than the region used to have — according to the latest comprehensive analysis of the Arctic environment released today by the National Oceanic and Atmospheric Administration (NOAA).
This doesn't come as a huge surprise. Scientists have long expected that greenhouse gases would warm the Far North up faster than other parts of the globe since various feedback cycles unique to the Arctic can magnify relatively small temperature changes (melting ice and snow, for example, let exposed land and water absorb more of the Sun's heat, which melts more ice and snow, and so on). This "Arctic amplification" is one reason why the polar bear, which relies on sea ice for survival, has been the enduring symbol of global warming activism.
This past year (October 2010-September 2011), surface temperatures in the Arctic were 1.5 degrees Celsius warmer than average. The image above shows where average air temperatures were up to 3 degrees Celsius above (red) or below (blue) the long-term average (1981-2010). Credit: NOAA
Cute as they are, though, polar bears don't have much to do with the lives of most Americans, so using them as a global-warming mascot sends the message that it's happening far, far away.
But as the new NOAA report makes clear, it isn't. More and more, what happens in the Arctic isn't staying in the Arctic. One of the more intriguing findings of the 2011 Arctic Report Card concerns what some scientists are referring to as the "warm Arctic/cold continents" climate pattern, featuring winds that drive warmer air into the Arctic, while displacing frigid Arctic air masses to the south, into the US and Europe.
When this pattern occurred during December 2010, it contributed to freak snowstorms in the eastern US and western Europe. In western Greenland, meanwhile, and in other parts of the Arctic, temperatures were above average. At Climate Central we like to refer to this pattern as the "Arctic Paradox." We even made a nifty graphic to describe it.This climate pattern may be triggered in part by the loss of summer sea ice in the Arctic, since this alters the exchange of heat and moisture between the Arctic Ocean and the atmosphere.
According to the Report Card, the five deepest summer meltbacks in sea ice in the satellite record, which extends back to 1979, all occurred during the past five years. In 2011, sea ice extent at the end of the melt season was the second-lowest on record, while sea ice volume (that is the ice's extent times its average thickness) set a new record low.
Jim Overland, an oceanographer at NOAA's Pacific Marine Environmental Laboratory, notes that during the 2011 melt season, 35 percent of the Arctic sea ice area was lost, and this is only expected to get worse in coming decades as the climate continues to warm. "We're starting to see modifications of weather patterns... it's a major research question over the next few years of how the climate will change overall [in response to sea ice loss]."
According to the report, the warm Arctic-cold continent climate pattern existed in late fall 2010 and part of last winter. During both periods, the report says, "an increased linkage between Arctic climate and mid-latitude severe weather occurred."
The report warns that it's very tough for the Arctic climate system to reverse course from the accelerated warming and melting path that it is on right now. "Once multi-year sea ice and glacial mass is gone," it says, "it is difficult to return to previous conditions."
The peer-reviewed report, which is the result of an international collaboration among 121 researchers from 14 countries, contains many other findings that point to the rapid pace of climate change in the region. Here are just a few of them:
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