[6] NOAA Says Oceans Are Cooling Temporarily

The average temperature in the upper oceans has cooled significantly since 2003, but one scientist who has studied the phenomenon says it's just a speed bump on the road to more warming, NOAA announced in late September.

"This cooling is probably natural climate variability," said Josh Willis, a coauthor of the study at NASA's Jet Propulsion Laboratory, in Pasadena, Calif. "The oceans today are still warmer than they were during the 1980s, and most scientists expect the oceans will eventually continue to warm in response to human-induced climate change."

A Northwest scientist who contributed to the study, John Lyman of the NOAA Pacific Marine Environmental Laboratory in Seattle, estimated the heat content of the upper 2,500 feet of Earth's oceans from 1993 to 2005. This area represents about 20 percent of the global ocean's average depth.

The researchers found that the average temperature of the upper ocean rose by 0.16 degrees Fahrenheit from 1993 to 2003, and then fell 0.055 degrees Fahrenheit from 2003 to 2005. The recent decrease is a dip equal to about one-fifth of the heat gained by the ocean between 1955 and 2003.

Lyman said the recent cooling is not unprecedented, but other studies have shown that a similar rapid cooling took place from 1980 to 1983.

The maximum amount of cooling was seen at a depth of about 1,300 feet, but substantial cooling was still observed at 2,500 feet and the cooling appears to extend deeper.

The scientists also said that the recent cooling should have caused sea levels to decrease, but they have steadily risen, which suggests that melting glaciers and ice sheets are behind most of it.

Lyman said the cause of the recent cooling is not yet clear. Research suggests it may be due to a net loss of heat from the Earth. "Further work will be necessary to solve this cooling mystery," he said. -B. R.

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