Cities and towns along the west coast of the US could be suffering from a serious water shortage by 2050, thanks to global warming. As Arctic sea ice melts, annual rainfall may drop by as much as 30 per cent from Seattle to Los Angeles, and inland as far as the Rocky Mountains.
As temperatures rise over the next 50 years, the area of Arctic sea ice is predicted to shrink by as much as 50 per cent in some areas during the summer. To find out what this would mean for climate, Jacob Sewall and Lisa Cirbus Sloan from the University of California at Santa Cruz first used a climate model to work out how sea ice cover was likely to change through the rest of the year.
Then they took these values for sea ice cover and the resulting sea surface temperatures, and plugged those into a global climate model to see which areas of the world would be most affected. While Europe got off quite lightly, they found that the sea ice changes are likely to mean significantly fewer storms will pass over the west coast of the US.
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Towers of warm air form above areas where sea ice has been lost, and that disturbs the flow of air in the atmosphere around them, "like the supports under a bridge alter the flow of water in a river." In their model Sewall and Cirbus Sloan found that such towers formed between Norway and Greenland, deflecting winter storms that would otherwise have passed over the west coast of the US towards northern British Columbia and southern Alaska. These areas received six per cent more rain, while southern British Columbia down to southern California suffered a 30 per cent drop. The researchers will publish their results in a future issue of Geophysical Research Letters. "Given that water resources in this region are currently stretched close to their limit, a 30 per cent drop would have a serious impact," says Sewall."
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http://www.newscientist.com/news/news.jsp?id=ns99994856