New climate model predicts almost ice-free Arctic Ocean in just 30 years

Ice thickness, estimated by combining six climate models selected for this study, is shown for the Arctic in September now (left) compared with conditions of a nearly ice-free Arctic Ocean in 30 years (right). Image: University of Washington/NOAA

April 9, 2009 According to new research the Arctic Ocean may be ice free in the summer months much faster than previously estimated. Research based on earlier climatic models suggested that this would not occur until the end of the century, but new models suggest that the Arctic might lose most of its ice cover in as little as 30 years - three times more rapid than previous studies have indicated. If this was to occur, the amount of the arctic covered by ice at the end of the summer could be down to around 1 million square kilometers (390 000 square miles) compared with the currently coverage of 4.6 million square kilometers (1.8 million square miles).

The Intergovernmental Panel on Climate Change in 2007 based their assessments of future ice cover in the region on more than a dozen climatic models. Since then two researchers, Muyin Wang, a University of Washington climate scientist with the Joint Institute for the Study of the Atmosphere and Ocean, and James Overland, an oceanographer with the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle, have sought models to reflect what is happening based on dramatic declines in the extent of the ice at the end of the summer periods of 2007 and 2008.

Wang and Overland sought six climatic models for assessing sea ice from the 23 that are now available, based on their ability to match what is happening in recent years. Eliminated were models that showed too little or too much ice based on conditions that have already occurred. According to Wang, models were chosen that have the ability to differentiate between summer and winter ice packs and therefore take into account the changing amounts of solar radiation from summer to winter. Out of the six models that met the research criteria, three are equipped with sophisticated sea ice physics and dynamic capabilities.

All six models showed rapid sea-ice declines when the extent of the ice dropped at the end of summer to 4.6 million square kilometres (390,000 square miles). Actual figures are 4.3 million square kilometres (1.7 million square miles) in 2007, and 4.7 million kilometres (1.8 million square miles) in 2008. When the models are averaged together, the results point to a nearly ice free Arctic ocean within 32 years, with some of the models registering results that place this event as early as 11 years from now.

According to Overland, a combination of factors are contributing to the earlier summer sea-ice losses. "In recent years the combination of unusual warm temperatures from natural causes and the global warming signal have worked together to provide an earlier summer sea-ice loss than was predicted when scientists considered the effects from human-caused carbon dioxide alone," says Overland.

"The uncertainty in future timing for a September sea-ice free Arctic is strongly influenced by the chaotic nature of natural variability," but "the one climate realization that we are living through appears to be a fast track for September sea ice loss."

Scientists don't expect the Arctic to be totally ice free, with ice still expected to be found along northern Canada and Greenland where powerful winds sweep across the Arctic Ocean to form a very thick ice cover.

This depressing scenario opens up many questions. Will it provide a path for extracting more minerals and extra shipping lanes? What of the impact on the ecosystem and what will be the long term effects? Time - and not much time - will tell.

Wang is lead author and Overland is co-author of a paper being published April 3 by the American Geophysical Union’s Geophysical Research Letters.

Anne Hanrahan

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