SEASONAL AND INTERANNUAL VARIABILITY OF SEA-SURFACE TEMPERATURES IN THE TROPICAL PACIFIC, 1969-1991

Water sample data derived from a ship-of-opportunity program are used to describe changes in sea surface temperature (SST) for the tropical Pacific. Time series up to 23 y long (1969-1991) allow investigation o f both seasonal and interannual SST variability along four selected sh ipping tracks crossing the equator near 155 degrees E, and 160, 140 an d 100 degrees W. Poleward of 6-8 degrees Latitude, the seasonal variab ility increases, reflecting the growing impact of surface thermal forc ing. Within 6-8 degrees latitude, the seasonal and interannual variabi lities in the eastern Pacific are of the same order of magnitude, wher eas in the western Pacific the interannual variability is 2-10 times g reater than the seasonal variability. Maximum interannual Variability appears trapped at and along the equator, in relation with the occurre nce of El Nino (1976, 1982-1983, 1987 and 1991) and La Nilia (198-1989 ) events. Complementing various other local investigations, the presen t study enables basin-scale SST changes to be documented in a concise fashion.