Thursday, May 1, 2008

Climate Change Chokes Oceans

May 01, 2008 - Rising temperatures have caused oxygen-starved swaths of ocean to expand over the last half-century -- a disturbing trend that, if it continues, could wreak havoc on global fisheries.
Led by University of Kiel oceanographer Lothar Stramma, researchers analyzed 50 years of ocean oxygen data. The findings, published today in Science, dovetail with predictions made by earlier climate models. Two mechanisms are responsible for the drop. As water warms, it holds less oxygen. More significantly, Earth's oceans are oxygenated in large part by cold waters that sink at high latitudes, then ride deep-sea currents to the equator. But water becomes buoyant as it warms: it no longer sinks so readily into this cycle.
"The surface warmer getting warmer means it's harder for oxygen to mix down, to the deeper parts, and that's the dominant effect," said study co-author and National Oceanic and Atmospheric Administration researcher Greg Johnson.
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