Abstract: Pressure gradient across the Luzon Strait, or depth-integrated dynamic height difference (DHD) between its northern end at the continental slope southwest of Taiwan and its southern end at the continental slope northwest of Luzon, is commonly regarded as the most direct dynamics of the intrusion of waters from the Pacific into the South China Sea through the Luzon Strait. Such a positive DHD is determined by seasonal occurrence of a meso-scale cyclonic cold eddy off west Luzon (Luzon cold eddy, LCE), and a positive wind stress curl (WSC) over the LCE active area or direct Ekman pumping may play a major role in generating the LCE. Based on the above ideas, prominent interannual (roughly 3 years and 7 years) and decadal (roughly 14 years) variability in the upper-layer Luzon Strait transport (LST) was first revealed using the 62-year (1950-2011) hindcast outputs from an eddy-resolving ocean general circulation model. To seek local factors affecting the interannual and decadal variability of LST, deseasonalized anomaly field of WSC over the LCE active area was analyzed using empirical orthogonal function (EOF). Dominant EOF modes of WSC anomaly were obtained. Spatio-temporal variability of the first EOF mode is of prominent decadal oscillation with a period of roughly 14.2 years and decadal southward shift of positive phase of the WSC anomaly, while the second EOF mode is of interannual oscillation of roughly 3.3 years and interannual northward shift of positive phase of the WSC anomaly. On the other hand, the near 7-year interannual oscillation was noticeable and can be regarded as an imprint of the variability of Kuroshio volume transport at its origin.

Key words: Luzon strait transport, decadal variability, Luzon cold eddy, wind stress curl, EOF mode