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La Niña barely has a pulse
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
http://topex-www.jpl.nasa.gov/
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