Using Sound To Take The Oceans' Temperature

Scientists still can't say whether the greenhouse effect will substantially warm the Earth. Why? Because so little is known about how interactions between oceans and the atmosphere affect climate, says John L. Spiesberger, a meteorologist at Pennsylvania State University. But that will change soon.

A team led by Spiesberger has just won a $10.4 million grant from the Pentagon's Advanced Research Projects Agency to take the temperature of the seas. Sound pulses will be sent racing thousands of miles under water while hundreds of floating monitors detect the passing pulses. Since sound travels at different speeds depending on the water's temperature, measuring the travel time from place to place provides an accurate thermometer. Experiments dating to 1983 have already proved that the concept works. When the first listening devices are set adrift next year, says Spiesberger, the effect "will be like putting satellites in space and looking at the earth for the first time."

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