Numerical Experiment on the Wintertime Water exchange between the Yellow Sea and the East China Sea

Abstract

The Yellow Sea is a shallow basin semi-enclosed by the western coast of Korean and the Eastern coast of China. A tongue-shaped frontal structure, occasionally and clearly detected in satellite image (Fig. 1), in the southern Yellow Sea is the distinct feature of the Yellow Sea in winter. The structure is considered as an evidence of northwestward intrusion of the warm and saline Cheju Warm Current water. This warm water intrusion is mainly related to the up-wind flow induced by northerly monsoon and tide induced residual flow. Using a numerical model with idealized bathymetry we investigate the role of tide on the warm water intrusion. We use the POM in a simplified bathymetry and geometry. The Yellow Sea is considered as a rectangular box with central trough deflected eastward. The opening to south is connected with the East China Sea in a trapezium. The Kuroshio and tide is forced by sea surface elevation along the open boundary and the wind stress is assumed as uniform in whole domain. The circulation pattern by each forcing and interaction of the Kuroshio, tide and northerly wind is calculated and compared to understand the dynamics. Using the same numerical model Lie et al. (2009) presented that the steady northerly wind can generate up-wind flow along the Yellow Sea Central Trough and down-wind flow along both coastal sides, however the wind driven flows is drastically attenuated when the tide is added. Numerical model results in this study show that wind driven circulation is dependent on tidal condition (Fig. 2). The northerly wind is the main driving force of the northward intrusion. However the tide plays role in depressing the wind-driven circulation. Therefore the unsteady pulse wind and spring-neap cycle of tide can be possible reasons of intermittent intrusion of warm water in the study area.