24 Jan 2022
24 Jan 2022
Status: this preprint is currently under review for the journal ACP.

Satellite-based evidence of regional and seasonal Arctic cooling by brighter and wetter clouds

Luca Lelli1,2, Marco Vountas1, Narges Khosravi3, and John Philipp Burrows1 Luca Lelli et al.
  • 1Institute of Environmental Physics and Remote Sensing, University of Bremen, Germany
  • 2NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 3Alfred-Wegener-Institut, Bremerhaven, Germany

Abstract. Using two decades of satellite-based measurements of reflectance of solar radiation at the top-of-atmosphere and a complementary record of cloud properties, it is concluded that the loss of Arctic brightness due to sea ice retreat is not compensated by a pan-Arctic increase in cloudiness, but rather by a systematic change in the thermodynamic phase of cloud and a resultant effect on cloud reflectance. Liquid water content of the clouds has increased resulting in positive trends in susceptible cloud properties. Consequently, a cooling trend by clouds is superimposed on top of the pan-Arctic amplified warming, induced by the anthropogenic release of greenhouse gases, the ice albedo feedback and related effects. Except above the permanent and marginal sea ice zone around the Arctic circle, the rate of surface cooling by clouds has increased, both in spring (−32 % in total radiative forcing for the whole Arctic) and in summer (−14 %). The magnitude of this effect depends on both the underlying surface type and changes in the regional Arctic climate.

Luca Lelli et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-28', Anonymous Referee #1, 23 Feb 2022
  • RC2: 'Comment on acp-2022-28', Anonymous Referee #2, 20 Apr 2022

Luca Lelli et al.

Luca Lelli et al.


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Short summary
Arctic Amplification describes the recent period in which temperatures are rising twice as fast as the global average and sea ice and Greenland ice shelf are approaching a tipping point. Hence, the Arctic ability to reflect solar energy decreases and absorption by the surface increases. Using two decades of complementary satellite data, we discovered that clouds unexpectedly increase the pan-Arctic reflectance by increasing their liquid water content, thus cooling the Arctic environment.