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Real Winters To Return, New NASA Data Suggest
By Andrew Bridges
Chief Pasadena Correspondent
posted: 03:19 pm ET
19 January 2000
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topex_weather_000119PASADENA, Calif. Data collected by a joint U.S.-French satellite suggest the western Pacific Ocean may be swinging into a protracted warm phase that could bring decades of colder, wetter weather to the northern United States and warmer, drier weather to the south. The change could be associated with what scientists call the Pacific Decadal Oscillation, where a large, horseshoe-shaped region alternates every 20 to 30 years between abnormally warm and cool water temperatures in the western portion of the Pacific Ocean. If the Pacific is indeed entering a warm phase, that could mean a long-term repeat of weather like that seen during the La Nina-influenced winter of 1998-99, including record-breaking snowfall in the Northwest and below-average rainfall across the Southwest. A NASA scientist studying data collected by the TOPEX/Poseidon satellite said the large-scale changes to water temperature across the entire Pacific could wreak havoc with weather patterns. "It steers the jet stream farther north, so the northern tier of the United States gets stormier and wetter, much like last year, and the southern tier is dry," said Bill Patzert, a research oceanographer at NASAs Jet Propulsion Laboratory. The JPL-managed TOPEX/Poseidon satellite measures sea surface height with 4-inch (10-centimeter) accuracy, which in turn gives an approximation of ocean temperature. Data gathered during the satellites seven-plus years in orbit indicate the Pacific may be beginning to flip-flop, with a giant horseshoe of warmer water massing in the north, west and south portions of the ocean, edging out cooler water that had lurked there since the late 1970s.  NASA data show a giant horseshoe of warmer water massing in the north, west and south portions of the Pacific Ocean. Patzert said TOPEX/Poseidon could be spying the onset of a large, long-lasting climate pattern and not just the lingering effects of last years La Nina. During a La Nina, essentially the opposite of El Nino, cooler-than-usual water masses in the eastern and equatorial Pacific Ocean. The last cool period associated with the Pacific Decadal Oscillation lasted from 1947 to 1976, affecting not only weather patterns but marine life as well. During that time, salmon runs were abundant in Washington and Oregon but languished in Alaska the exact opposite of the situation during a warm period that lasted from 1925 to 1946. Kevin Trenberth, head of the climate analysis section of the National Center for Atmospheric Research in Boulder, Colo., said it was early to determine whether the observed changes would last only a few years or a few decades. "You really can only split these things out after the fact," Trenberth said. "Its like looking at the stock market index, Are we in a long-term boom and should I invest or is it just a bubble?"
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