This study deals with the interannual variation of summer upwelling in the Taiwan Strait (TS), based on the empirical orthogonal function analysis. NOAA AVHRR sea surface temperature dataset from 1985-2005 and hydrographic records at two coastal stations from 1970-2001 are used. The results indicate that the first mode (85.3%) of the spatial variance shows a persistent front, which is generally aligned northeast-southwestward in the western TS. The eigenvector time series show that the variability of this front with time is closely correlated with the change in the wind stress anomaly of alongshore wind component derived from 17 years of ERS and QuickSCAT wind dataset from 1992-2005. The records of the water temperature and salinity anomaly at Pingtan Is. located in the northwestern TS, and Dongshan Is. located in the southwestern TS show that a negative temperature anomaly appears along with a positive salinity anomaly in some years. This suggests a dominant influence of cold and saline upwelling water at the surface. The years for notable cooling events derived from the station measurements are generally consistent with the time series of EOF Mode 1. These results indicate that for the entire west TS, the summer coastal upwelling was strong in 1987, 1993, and 1998 during the period from 1985 to 2005. A delayed ENSO effect is suggested as a major mechanism for the interannual variability of TS coastal upwelling.
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