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Thursday, October 25, 2012

"Recent shift in early summer Arctic atmospheric circulation," by James E. Overland, Jennifer A. Francis, Edward Hanna & Muyin Wang, GRL 39 (2012); doi: 10.1029/2012GL053268

Geophysical Research Letters, 39 (2012) L19804; doi: 10.1029/2012GL053268
The recent shift in early summer Arctic atmospheric circulation
Key Points
  • There is an apparent sustained shift in early summer Arctic winds since 2007
  • Such Arctic changes are linked to increased North American atmospheric blocking
  • Highlights potential connectivity of Arctic climate and mid-latitude weather
James E. Overland (Pacific Marine Environmental Laboratory, NOAA, Seattle, WA, U.S.A.), Jennifer A. Francis (Institute of Marine and Coastal Sciences, Rutgers, State University of New Jersey, New Brunswick, NJ, U.S.A.), Edward Hanna (Department of Geography, University of Sheffield, Sheffield, U.K.) and Muyin Wang (Joint Institute for the Study of the Atmosphere and Oceans, University of Washington, Seattle, WA, U.S.A.)


The last six years (2007–2012) show a persistent change in early summer Arctic wind patterns relative to previous decades. The persistent pattern, which has been previously recognized as the Arctic Dipole (AD), is characterized by relatively low sea-level pressure over the Siberian Arctic with high pressure over the Beaufort Sea, extending across northern North America and over Greenland. Pressure differences peak in June. In a search for a proximate cause for the newly persistent AD pattern, we note that the composite 700-hPa geopotential height field during June 2007–2012 exhibits a positive anomaly only on the North American side of the Arctic, thus creating the enhanced mean meridional flow across the Arctic. Coupled impacts of the new persistent pattern are increased sea ice loss in summer, long-lived positive temperature anomalies, and ice sheet loss in west Greenland, and a possible increase in Arcticsubarctic weather linkages through higher-amplitude upper-level flow. The North American location of increased 700-hPa positive anomalies suggests that a regional atmospheric blocking mechanism is responsible for the presence of the AD pattern, consistent with observations of unprecedented high-pressure anomalies over Greenland since 2007.
Received 24 July 2012; accepted 31 August 2012; published 10 October 2012.
Overland, J. E., J. A. Francis, E. Hanna, and M. Wang. (2012). The recent shift in early summer Arctic atmospheric circulationGeophys. Res. Lett.39, L19804, doi:10.1029/2012GL053268.

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