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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L23503, doi:10.1029/2006GL028024, 2006

Future abrupt reductions in the summer Arctic sea ice

Marika M. Holland

National Center for Atmospheric Research, Boulder, Colorado, USA


Cecilia M. Bitz

Atmospheric Sciences, University of Washington, Seattle, Washington, USA


Bruno Tremblay

Lamont Doherty Earth Observatory of Columbia University, Palisades, New York, USA


Abstract

We examine the trajectory of Arctic summer sea ice in seven projections from the Community Climate System Model and find that abrupt reductions are a common feature of these 21st century simulations. These events have decreasing September ice extent trends that are typically 4 times larger than comparable observed trends. One event exhibits a decrease from 6 million km2 to 2 million km2 in a decade, reaching near ice-free September conditions by 2040. In the simulations, ice retreat accelerates as thinning increases the open water formation efficiency for a given melt rate and the ice-albedo feedback increases shortwave absorption. The retreat is abrupt when ocean heat transport to the Arctic is rapidly increasing. Analysis from multiple climate models and three forcing scenarios indicates that abrupt reductions occur in simulations from over 50% of the models and suggests that reductions in future greenhouse gas emissions moderate the likelihood of these events.

Received 30 August 2006; accepted 19 October 2006; published 12 December 2006.

Keywords: Arctic sea ice; climate change.

Index Terms: 0750 Cryosphere: Sea ice (4540); 1605 Global Change: Abrupt/rapid climate change (4901, 8408); 1621 Global Change: Cryospheric change (0776); 1626 Global Change: Global climate models (3337, 4928).

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Citation: Holland, M. M., C. M. Bitz, and B. Tremblay (2006), Future abrupt reductions in the summer Arctic sea ice, Geophys. Res. Lett., 33, L23503, doi:10.1029/2006GL028024.