The Washington Post
SCIENCE
Notebook

Monday, February 11, 2002; Page A12

Pacific Circulation and El Nino

A giant water circulation pattern in the Pacific Ocean has apparently slowed since the 1970's, which could help explain why the disruptive El Nino weather phenomenon has been occurring more frequently and more severely.

Michael J. McPhaden of the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory and Dongxiao Zhang of the University of Washington in Seattle studied data collected between 1950 and 1999. Water circulating in an area on both sides of the equator in the Pacific Ocean slowed during that period, they found. That caused a 25 percent decrease in the amount of relatively cool water that has been rising to the surface, which could explain why the sea surface has warmed, they reported in the Feb. 7 Nature.

Although the implications remain unclear, the change could have wide-ranging effects, including influencing El Nino, which appears to be making another appearance this year, and reducing the amount of carbon dioxide the ocean is releaseing into the atmosphere, the researchers said.

--Compiled from reports by Rob Stein

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