NOAA: Decline of Arctic Sea Ice is Affecting Fall and Winter in U.S. and Elsewhere
The National Oceanic and Atmospheric Administration (NOAA) said earlier this week (16 March 2010) that the decline in Arctic sea ice is affecting the patterns of atmospheric pressure in the region, particularly in the Fall and early Winter. It says that these pressure changes in turn "impact large scale wind patterns over the Northern Hemisphere, allowing cold air to move southward." Simply stated, changes in Arctic sea ice already are affecting climate and weather outside the region -- and the effects are likely to grow with further declines in sea ice.
NOAA added to its Arctic Web site a series of pages on the Future of Arctic Sea Ice and Global Impacts. Drawing from recent research, and distilling the science into terms we can all understand, the site clearly illustrates the already profound impacts occurring in mid- and high- latitude weather and climate as sea ice declines. The site explains:
"As sea ice cover is diminished during autumn, air temperature near the surface is increased, decreasing the stability of atmospheric pressure surfaces.
When the normal stable stratification of the atmosphere over the Arctic is eroded by the warm temperatures from the surface, the result is a dome of warm air and elevated pressure surfaces over the North Pole
The elevated pressure surfaces above the North Pole persist into early winter and impact large scale wind patterns over the Northern Hemisphere, allowing cold are to move southward." [emphasis added]
NOAA notes in particular reduced winds in some areas, especially north of Alaska and in western Canada. NOAA continues:
The reduction in winds opposes the usual atmospheric circulation patterns, allowing outbreaks of cold Arctic air to move southward.
It must be noted that there is considerable year-to-year variability in pressure fields, and that modifications of mid-latitude weather by wind patterns associated with sea ice reduction can be complex (involving storm track and longwave interactions).
However a consequence of the changes in Arctic atmospheric temperature and pressure, following loss of sea ice, is increased likelihood of cold air moving southward via teleconnections to impact weather at mid-latitudes.
As summer Arctic open water area increases over the next decades, we anticipate an increasing influence of loss of summer sea ice on the atmospheric northern hemisphere general circulation in following seasons with resultant impacts on northern hemisphere weather.[emphasis added]
NOAA adds that there are implications for storm patterns in Europe and East Asia:
"Observational evidence shows that the recent significant cold anomalies over the Far East in early winter and cold temperature anomalies from Europe to Far East in late winter are associated with the decrease of the Arctic sea-ice cover in the preceding summer-to-autumn seasons.[emphasis added]
Results from numerical computer simulations using an atmospheric general circulation model support these notions. "
And for the U.S. -- where climate change denialists have cynically exploited the cold and snowy winter in the U.S. to feed doubts about climate change -- NOAA says:
Preliminary results from numerical computer simulations indicate that the significant cold anomalies over the eastern US in winter are associated with the decrease of the Arctic sea-ice cover in the preceding summer-to-autumn seasons.[emphasis added]
Other Online Resources:
- New NOAA Web Site Emphasizes Broader Impacts of Sea Ice Loss. "More than local problem, Arctic’s future affects weather, climate elsewhere." Pres release (March 16, 2010) from NOAA.