Global circulation patterns shift, bringing more frequent blocking patterns and polar outbreaks
By Summit Voice
SUMMIT COUNTY — Evidence is growing that the loss of Arctic sea ice is having a profound effect on seasonal weather patterns over North America, Europe and Asia.
In addition to previous research from the Rutgers University Institute of Marine and Coastal Sciences, a new study led by the Georgia Institute of Technology again shows the relationship between melting ice in the Arctic regions and widespread cold outbreaks in the Northern Hemisphere.
The study’s findings could be used to improve seasonal forecasting of snow and temperature anomalies across northern continents.
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.”
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 — 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,” said 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.”
Various computer 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 consistent relationships seen in the model simulations and observational data illustrate that the rapid loss of sea ice in summer and delayed recovery of sea ice in autumn modulates snow cover, winter temperature and the frequency of cold air outbreaks in northern mid-latitudes.
The study was published on Feb. 27, 2012 in the online early edition of the journal Proceedings of the National Academy of Sciences. The research was supported by NASA and the National Science Foundation. Huijun Wang and Mirong Song of the Chinese Academy of Sciences Institute of Atmospheric Physics and Radley Horton from the Columbia University Center for Climate Systems Research also contributed to this work.
Filed under: climate and weather, Environment, global warming, seasons, Snow and weather, Summit County news Tagged: | Arctic sea ice decline, climate, Environment, Georgia Institute of Technology, global warming, weathe