A numerical study on the formation of upwelling off northeast Taiwan

We examined the spatial and temporal variations of upwelling off northeast Taiwan, using a fine-resolution numerical model with realistic bathymetry. The zonally running shelf break in the area deflects the Kuroshio seaward and produces upwelling on its onshelf edge. The upwelling, in turn, manifests a cold dome or a cyclonic eddy. In depths below 150 m or so, the upwelling and hence the cyclonic eddy exist year-round. Above this depth, the eddy waxes and wanes as the upper portion of the Kuroshio migrates seaward and shoreward, respectively. The eddy event fluctuates in a wide range of timescales. Seasonally, the occurrence heavily favors summer rather than winter, because the mean Kuroshio axis migrates seaward in summer. Intraseasonally, the fluctuation contains two dominant periods centered at 70 days and 30 days. Local wind forcing and channeling by two local canyons do not affect the eddy statistics significantly.