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.
Highlights
Off shore of eastern China, the three-sea (East China Sea, Yellow Sea, and Bohai) system over the continental shelf borders the deep western Pacific Ocean (Fig. 1a)
We focus on the conversion from tidal to subtidal currents primarily in the region from the Changjiang mouth to the southern end of the East China Sea
In light of the importance of tidal currents, in this study we focused on the tidal to subtidal circulation and have examined other parts of the three-sea system
Summary
Off shore of eastern China, the three-sea (East China Sea, Yellow Sea, and Bohai) system over the continental shelf borders the deep western Pacific Ocean (Fig. 1a). The Yellow Sea and Bohai become increasingly landlocked due to the presence of Korean peninsula and Japanese land masses to the east. Both tidal and subtidal circulations are sufficiently strong in the three-sea system. Moving one step further, Moon et al (2010) and Wu et al (2011) included the mean shelf circulation in addition to river and tidal forcing, focusing on how tides induce the offshore detachment of Changjiang plume in summer. The modeled summer intrusion of Changjiang plume into the Yellow Sea is much reduced, bringing the modeled plume dispersal closer to reality (Wu et al 2011). In light of the importance of tidal currents, in this study we focused on the tidal to subtidal circulation and have examined other parts of the three-sea system
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