ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-165-2011 An Arctic CCN-limited cloud-aerosol regime Mauritsen T. 1 Sedlar J. 2 3 Tjernström M. 2 3 Leck C. 2 3 Martin M. 4 Shupe M. 5 Sjogren S. 6 Sierau B. 4 Persson P. O. G. 5 Brooks I. M. 7 Swietlicki E. 6 Max Planck Institute for Meteorology, Hamburg, Germany Bert Bolin Center for Climate Research, Stockholm, Sweden Stockholm University, Stockholm, Sweden Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland University of Colorado and NOAA-ESRL, Boulder, Colorado, USA Lund University, Lund, Sweden University of Leeds, Leeds, UK 10 01 2011 11 1 165 173 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/165/2011/acp-11-165-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/165/2011/acp-11-165-2011.pdf

On average, airborne aerosol particles cool the Earth's surface directly by absorbing and scattering sunlight and indirectly by influencing cloud reflectivity, life time, thickness or extent. Here we show that over the central Arctic Ocean, where there is frequently a lack of aerosol particles upon which clouds may form, a small increase in aerosol loading may enhance cloudiness thereby likely causing a climatologically significant warming at the ice-covered Arctic surface. Under these low concentration conditions cloud droplets grow to drizzle sizes and fall, even in the absence of collisions and coalescence, thereby diminishing cloud water. Evidence from a case study suggests that interactions between aerosol, clouds and precipitation could be responsible for attaining the observed low aerosol concentrations.

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