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Ocean Surface Topography from Space
La Niña barely has a pulse
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June 29, 1999

Lingering just a month ago in the eastern Pacific Ocean, the La Niña phenomenon, with its large volume of chilly water, barely has a pulse this month, according to new satellite data from the U.S.-French TOPEX/Poseidon mission.

The data, taken during a 10-day cycle of data collection ending June 18, show that the equatorial Pacific Ocean is warming up and returning to normal (green) as La Niña all but vanishes. The warming trend is most apparent in the equatorial Pacific Ocean, where only a few patches of cooler, low sea levels (seen in blue and purple) remain. The blue areas are between 5 and 13 centimeters (2 and 5 inches) below normal, whereas the purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. Like its counterpart, El Niño, a La Niña condition will influence global climate and weather until it has completely subsided.

As summer begins in the northern hemisphere, lower-than-normal sea surface levels and cool ocean temperatures persist in the northeastern Gulf of Alaska and along the western coast of North America. In contrast, the trend is the opposite over most of the Pacific, where above-normal sea surface heights and warmer ocean temperatures (indicated by the red and white areas) appear
to be increasing and dominating the overall Pacific Ocean. Red areas are about 10 centimeters (4 inches) above normal; white areas show the sea surface height is between 14 and 32 centimeters (6 and 13 inches) above normal.

Scientists are not ready to administer last rites to La Niña, though. In the last 12 months, the pool of unusually cold water in the Pacific has shrunk (warmed) several times before cooling (expanding) again. This summer's altimeter data will help them determine whether La Niña has truly dissipated or whether they will see another resurgence of cool water in the Pacific.

For more information, please visit the TOPEX/Poseidon project web page at

Source: Jet Propulsion Laboratory

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