Origin of the Tsushima Warm Current in a high resolution ocean circulation model

Abstract

Using the results from a high-resolution global ocean circulation model, the present study describes the circulation over the East China Sea and the origin of the Tsushima Warm Current. We focus on the interaction between the Taiwan Warm Current, the Tsushima Warm Current, and the Kuroshio intrusion north of Taiwan and east of Kyushu by comparing mass fluxes. Although the modeled transport of the Tsushima Warm Current is weaker than observed values by about 30 %, that of the Taiwan Warm Current is within the known range. The transport of the latter is large enough to supply the former. Thus, in this model, the net intrusion of the Kuroshio towards the shelf between Taiwan and Kyushu would not make a significant contribution to the Tsushima Warm Current. Conversely, the flows northeast of Taiwan and west of Kyushu show a strong presence of branch currents toward the inner shelf from the Kuroshio. To resolve this apparent contradiction, we estimated mass budgets for the areas around Taiwan and west of Kyushu. The Taiwan Tsushima Current System and the Kuroshio are located very closely to each other along the shelf break, and if they are not differentiated properly using high-resolution data, one could overestimate the strength of the branch currents or the onshore intrusion of the Kuroshio. Considering the similarity between the apparent branch currents from this model and the previously reported results, the branch currents, especially west of Kyushu, may not be as strong as previously suggested.