Tidal Effects on Circulation in and near the East China Sea

Abstract

We incorporate tidal currents into a previously validated, three-dimensional, subtidal circulation model to assess tidal effects on the circulation in and around the East China Sea. Of particular interest is the tide-enhanced Changjiang plume dispersal and circulation in the southern East China Sea. The modeling results show that without tides, the Changjiang plume in summer presents itself as a stagnant, expansive pool in regions bordering the northern East China Sea and Yellow Sea, too far north and too accumulating relative to observations. The winter plume dispersal pushed by the north-northeast monsoon follows the China coastline southeastward as a coastal current that matches more closely with observations with or without tides. Incorporating the effect of tides brings the model closer to observation, especially in summer. During summer the Taiwan Warm Current shifts to lower latitudes, enhances upwelling off southeast China and induces a southward tidal residual coastal flow off southeast China. Tides also induce the observed seaward detachment of the summer plume. In winter, the prevailing north-northeast monsoon suppresses the Taiwan Warm Current to the minimum. However, if the winter monsoon is weakened for a few weeks, the Taiwan Warm Current reappears and these three mechanisms begin to operate as in summer. CTD surveys and satellite observations south of the Changjiang River estuary contribute to a better understanding of the tidal effects on regional ocean currents.

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