Taiwan Current (Kuroshio) and Impinging Eddies

Considerable westward or nothwestward propagating eddies were found east of Taiwan that cross-explains the anomalies in the repeated hydrography, trajectory of drifting buoys and altimetric analyses. The sea level differences (SLD) across the Taiwan Current (Kuroshio) in the East Taiwan Channel (ETC) are utilized in order to examine the possible implication of eddies in the Taiwan Current transport. It is concluded that Taiwan is impinged by both cyclonic and anticyclonic mesoscale eddies at an interval of about 100 days. An approaching anticyclonic eddy will result in a higher SLD across the ETC and a larger mass transport of Taiwan Current, and, vice versa, a reduction of both SLD and the mass transport in the ETC as a cyclonic eddy arrives. The SLD-inferred northward transport in the ETC is highly coherent at the 100-day band with westward propagating eddies that originated in the interior ocean. The generation mechanism of these eddies are, however, still unclear. Leakage of the Kuroshio water to the east of the Ryukyu Islands is suggested due to the presence of cyclonic eddies. This 100-day rate of eddy-impingement invalidates any observation of 4 months or less, whether with direct or indirect measurements, because any conclusions depend on the presence or absence of eddies. To minimize the contamination from eddies, either long-term observations or eddy-removal procedures are required.