Study predicts ice-free Arctic summers by 2040


NASA-funded research shows decrease could be far more dramatic than previously thought

The recent retreat of Arctic sea ice is likely to accelerate so rapidly that the Arctic could become nearly devoid of ice during summertime as early as 2040, according to a new study by three researchers, including Bruno Tremblay of McGill University's Department of Atmospheric and Oceanic Sciences. The study, by Tremblay, lead researcher Marika M. Holland of the U.S. National Center for Atmospheric Research (NCAR) and Cecilia M. Bitz of the University of Washington, is being published in the December 12 issue of Geophysical Research Letters.

In the study, which analyzes the impact of greenhouse gas emissions on the Arctic, scenarios run on supercomputers show that sea ice measured each September could undergo such abrupt reductions that, within about 20 years, it may begin retreating four times faster than at any time in the observed record. The computer models indicate that, if greenhouse gases continue to build up at the current rate, the Arctic's future ice cover will go through periods of relative stability followed by abrupt retreat. One simulation projects that by 2040, only a small amount of perennial ice would remain along the north coasts of Greenland and Canada during the summer months. That decrease, say the researchers, could be far more dramatic than anything that has happened so far.

"Open water absorbs more sunlight than does ice," explains Tremblay. "This means that the growing regions of ice-free water will accelerate the warming trend." In addition, global climate change is expected to influence ocean circulations and drive warmer ocean currents into the Arctic.

The scientists also concluded, by examining 15 additional leading climate models, that if emissions of carbon dioxide and other greenhouse gases were to slow, the likelihood of rapid ice loss would decrease and summer sea ice could undergo a much slower retreat.

The study was funded by the National Science Foundation and NASA.

Bruno Tremblay joined McGill University's Department of Oceanic and Atmospheric Sciences in 2006, after ten years as a faculty member and researcher at Columbia University. He is a past winner of the Canadian Meteorological and Oceanographic Society prize for the best doctoral dissertation in atmospheric and oceanic sciences; the Award of Excellence of the Academy of Great Montrealers; the NOAA Fellowship of the U.S. National Oceanic and Atmospheric Administration; and the Storke Doherty Lectureship of Columbia University.

Images of sea ice loss are available at

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Mark Shainblum
McGill University
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