

Contact: Rosemary Sullivant or Nancy Lovato (818) 354-0474



       The Pacific Ocean, the largest and deepest of the world's oceans, suffers periodic mood swings that have a dramatic impact on our weather. These mood swings include a climate phenomenon known as Pacific Decadal Oscillation, or PDO. It's an El Nino- like shift in the ocean's temperature that scientists once thought cycled every 15 to 20 years.

       However, there's new NASA research that now shows there may be a second, much longer, PDO cycle that lasts about 70 years.

       Dr. Yi Chao, an oceanographer at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleagues Drs. Michael Ghil and James McWilliams of the University of California, Los Angeles, have found evidence of the PDO's two-part structure in a study of the past 92-year record of sea-surface temperatures in the North and South Pacific. The results of their study appears in the August 1, 2000, issue of Geophysical Research Letters.







       "Looking into the future," Chao continued, "we are now analyzing the temperature below the sea surface. The goal is to get a three-dimensional picture of the PDO that might help us reach the ultimate goal, a realistic computer model linking the ocean and the atmosphere that will help us predict Earth's climate."

       This research is supported by NASA's Earth Science Enterprise, Washington, D.C., which is dedicated to studying how human-induced and natural changes affect our global environment.

       More information about the Pacific Decadal Oscillation is available on the Internet at: and


8/1/00 RS