Temporal and Spatial Variations of Kuroshio East of Taiwan

Chau-Ron Wu
National Taiwan Normal University, Taipei, Taiwan

A fine grid resolution model with realistic bathymetry was constructed to study the spatial and temporal variations of Kuroshio east of Taiwan where observations are limited. The model covers an expanded domain that includes the entire East China Sea and South China Sea, as well as the region occupied by the Kuroshio. The fine-resolution model derives its open boundary conditions from a larger scale Northern Pacific Ocean model. Two numerical weather products from European Center for Medium-Range Weather Forecasts and National Centers for Environmental Prediction, and one satellite observation-based wind set (QSCAT) are used to force the ocean model. All model experiments are collaborated by both bottom-mounted Acoustic Doppler Current Profiler (ADCP) and shipboard ADCP observations. Further, model experiments suggested that the best simulation is achieved when the model is driven by the QSCAT wind forcing. Several important features are reproduced in the model simulation. An eddy-Kuroshio interaction is evident in the model simulation. Most eddies are concentrated in a zonal band near 22˚N, and there is an interannual variation in the number of eddies. Eddies propagate westward along over 22 ~ 24˚N to reach the Kuroshio east of Taiwan, where eddies were dissipated and in turn affected the Kuroshio in many ways. The simulation results also indicate that the seasonal variation of Kuroshio east of Taiwan is generally weak except for the shallow water regimes. The Kuroshio has double velocity cores southeast of Taiwan, but gradually combines into one as the Kuroshio flowed north. The Kuroshio is deflected by the I-Lan Ridge east of Taiwan and turns eastward northeast of Taiwan afterwards. At the shelf break, the Kuroshio splits, with one branch intruding onto the shelf. Further, a branch of the Kuroshio intrudes steadily into the South China Sea through the central Luzon Strait. The Kuroshio intrusion waters flow out of the South China Sea through the northern Luzon Strait and hugs the main stream Kuroshio finally.