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AGU: Geophysical Research Letters

 

Keywords

  • Arctic sea ice
  • radiation
  • clouds

Index Terms

  • Global Change: Cryospheric change
  • Global Change: Atmosphere
  • Global Change: Remote sensing
  • Atmospheric Processes: Clouds and cloud feedbacks
  • Atmospheric Processes: Polar meteorology

Abstract

The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum

Jennifer E. Kay

Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA

Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado, USA

Tristan L'Ecuyer

Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado, USA

Andrew Gettelman

Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado, USA

Graeme Stephens

Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado, USA

Chris O'Dell

Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado, USA

Reduced cloudiness and enhanced downwelling radiation are associated with the unprecedented 2007 Arctic sea ice loss. Over the Western Arctic Ocean, total summertime cloud cover estimated from spaceborne radar and lidar data decreased by 16% from 2006 to 2007. The clearer skies led to downwelling shortwave (longwave) radiative fluxes increases of +32 Wm−2 (−4 Wm−2) from 2006 to 2007. Over three months, simple calculations show that these radiation differences alone could enhance surface ice melt by 0.3 m, or warm the surface ocean by 2.4 K, which enhances basal ice melt. Increased air temperatures and decreased relative humidity associated with an anti-cyclonic atmospheric circulation pattern explain the reduced cloudiness. Longer-term observations show that the 2007 cloudiness is anomalous in the recent past, but is not unprecedented. Thus, in a warmer world with thinner ice, natural summertime circulation and cloud variability is an increasingly important control on sea ice extent minima.

Received 29 January 2008; accepted 13 March 2008; published 22 April 2008.

Citation: Kay, J. E., T. L'Ecuyer, A. Gettelman, G. Stephens, and C. O'Dell (2008), The contribution of cloud and radiation anomalies to the 2007 Arctic sea ice extent minimum, Geophys. Res. Lett., 35, L08503, doi:10.1029/2008GL033451.

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