ENSO and
Sea-Level Variability: A Historical Perspective
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Among the many changes in oceanic and atmospheric conditions related to ENSO is a pattern of changes in mean (or average) sea level across the tropical Pacific. PEAC Research Scientist, Dr. Rashed Chowdhury, is studying the connection between the ENSO Cycle and sea level variations. By using a statistical analysis of the past events, Dr. Chowdhury has been able to look at the patterns between sea surface temperature (SST) and sea level variations (monthly or seasonal difference from mean sea level). In locations where the SST and sea level variation correlate well, a seasonal outlook for sea level variation can be made based on predictions of SST.
The following is a summary of the effects of previous ENSO
events on sea level variations in
During strong El Niņo events,
A similar relationship occurs
during La Niņa years. During both
strong and moderate La Niņa events,
With a few exceptions,
For this study,
Sea Level
Outlook
Most of the models predicted SST
anomalies in the Niņo 3.4 region will likely to be positive (at or above +0.5 C)
through the end of 2004; therefore a weak El Niņo situation is likely to
develop. As a result, little or no upwelling is expected in the region of north Pacific Ocean during the next two to three months.
Therefore, the north
On the other hand, in
For the purposes of the study, the years for event ranking were:
Strong El Niņo Years: 1951, 1958, 1972, 1982, and 1997
Moderate El Niņo Years: 1963 1965, 1969, 1974, and 1987
Strong La Niņa Years: 1964, 1973, 1975, 1988, and 1998
Moderate La Niņa Years: 1956, 1970, 1971, 1984, and 1999
The process of ranking the strong/moderate events is subjective and based on Niņo 3.4 SST, average SOI for six months, and season-by-season cold and warm episodes. For more information on the ranking, see the following web sites.
http://iri.columbia.edu/climate/ENSO/background/pastevent
http://www.wrcc.dri.edu/enso/ensodef
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuf
Based upon this research, PEAC plans to develop a more
detailed seasonal sea level outlook for