The latest image of sea-surface height measurements from the U.S./French
Jason-1 oceanography satellite shows the Pacific Ocean remains locked in a
strong, cool phase of the Pacific Decadal Oscillation, a large, long-lived
pattern of climate variability in the Pacific associated with a general
cooling of Pacific waters. The image also confirms that El Niño and La
Niña remain absent from the tropical Pacific.
The image is based on the average of 10 days of data centered on Nov. 15,
2008, compared to the long-term average of observations from 1993 through
2008. In the image, places where the Pacific sea-surface height is higher
(warmer) than normal are yellow and red, and places where the sea surface
is lower (cooler) than normal are blue and purple. Green shows where
conditions are near normal. Sea-surface height is an indicator of the heat
content of the upper ocean.
The Pacific Decadal Oscillation is a long-term fluctuation of the Pacific
Ocean that waxes and wanes between cool and warm phases approximately
every five to 20 years. In the present cool phase, higher-than-normal
sea-surface heights caused by warm water form a horseshoe pattern that
connects the north, west and southern Pacific. This is in contrast to a
cool wedge of lower-than-normal sea-surface heights spreading from the
Americas into the eastern equatorial Pacific. During most of the 1980s and
1990s, the Pacific was locked in the oscillation's warm phase, during
which these warm and cool regions are reversed. For an explanation of the
Pacific Decadal Oscillation and its present state, see:
http://jisao.washington.edu/pdo/ and http://www.esr.org/pdo_index.html.
Sea-surface temperature satellite data from the National Oceanic and
Atmospheric Administration mirror Jason sea-surface height measurements,
clearly showing a cool Pacific Decadal Oscillation pattern, as seen at:
http://www.cdc.noaa.gov/map/images/sst/sst.anom.gif.
"This multi-year Pacific Decadal Oscillation 'cool' trend can cause La
Niña-like impacts around the Pacific basin," said Bill Patzert, an
oceanographer and climatologist at NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "The present cool phase of the Pacific Decadal
Oscillation will have significant implications for shifts in marine
ecosystems, and for land temperature and rainfall patterns around the
Pacific basin."
According to Nathan Mantua of the Climate Impacts Group at the University
of Washington, Seattle, whose research contributed to the early
understanding of the Pacific Decadal Oscillation, "Even with the strong La
Niña event fading in the tropics last spring, the North Pacific's sea
surface temperature anomaly pattern has remained strongly negative since
last fall. This cool phase will likely persist this winter and, perhaps,
beyond. Historically, this situation has been associated with favorable
ocean conditions for the return of U.S. west coast Coho and Chinook
salmon, but it translates to low odds for abundant winter/spring
precipitation in the southwest (including Southern California)."
Jason's follow-on mission, the Ocean Surface Topography Mission/Jason-2,
was successfully launched this past June and will extend to two decades
the continuous data record of sea surface heights begun by Topex/Poseidon
in 1992. The new mission has produced excellent data, which have recently
been certified for operational use. Fully calibrated and validated data
for science use will be released next spring.
JPL manages the U.S. portion of the Jason-1 mission for NASA's Science
Mission Directorate, Washington. JPL is managed for NASA by the California
Institute of Technology in Pasadena.
For more information on NASA's ocean surface topography missions, see
http://sealevel.jpl.nasa.gov/ or to view the latest Jason data see
http://sealevel.jpl.nasa.gov/science/jason1-quick-look/.