Oscillation is defined as a 2- to 3-year cycle in which there is an alteration 

 of regional pressure anomalies about two nodes, a low-pressure system located 

 over the Indian Ocean and a high-pressure system that is over the southeast 

 Pacific Ocean. Fairbridge and Krebs (1952) concluded that for every 1 mb of 

 pressure increase there is a fall of sea level by 10 mm. Observed El Nino 

 phenomenon in the tropical Pacific Ocean have been explained as a response to 

 changes in the surface wind stress As prevailing winds shift, westerly anom- 

 alies accelerate equatorial counter currents and depress the thermocline in 

 the east, reduce equatorial upwelling, and enhance the eastward transport of 

 warm surface waters from the western Pacific (Cane and Zebiak 1985). The 

 connection between El Nino and anomalous ocean behavior in other parts of the 

 world is documented but unexplained. High winds and long fetch can produce 

 long and high waves that add to these extreme sea levels. During the winter 

 of 1982-1983, the California coast was subjected to high tides, frequent 

 storms, and high sea levels associated with El Nino, causing severe storm 

 damage in excess of $100 million (Flick and Cayan 1984). 



Global Effects 



7. Eustatic changes, or worldwide sea-level fluctuations, have been 

 attributed to: (a) glacio-eustasy, or ocean level changes caused by the melt- 

 ing or formation of glaciers; (b) geodetic changes in ocean basins affected by 

 the Earth's gravity, structure, density, rotation, and astronomical gravity; 

 and (c) tectonic-eustasy that includes the vertical and horizontal movements 

 of the oceanic basins. Background information on the concept of eustasy can 

 be found in Fairbridge (1961), Morner (1973, 1976, 1978, 1981, 1986), and 

 Lisitzin (1974). The global rate of sea-level change varies due to the 

 methodologies used by scientists to measure still-water levels. General 

 consensus, however, is that average global sea-level rates of rise are between 

 1.0 and 1.2 millimeters/year (Gornitz et al. 1987, Barnett 1983. These rates 

 are dependent on the accuracy of tide-gage measurements, correction for long- 

 term movements, signal in the record, and geographic bias. The estimate of 

 eustatic mean sea-level rise remains biased toward the Northern Hemisphere 

 because of the relatively high number of tide gages. 



