A numerical study on the influences of the variations of transport through the Korea Strait upon the upper layer circulation of the East Sea

Abstract

Numerical experiments were performed in order to investigate the effects of transport variation through the Korea Strait (KS) on the upper layer circulation in the East/Japan Sea (ES) based on transport observation for ten months from May 1999 to March 2000 by NRL and KORDI. The spatial distributions of the transport of the inflow boundary condition followed that of the mean transport perpendicular to the north mooring line. All external forcings to the model were annual mean fields except the transport variation through the Korea Strait. The experiments were carried out in cases of volume and temporal variation of the transport. Results show that the volume transport through the KS influences the separation latitude of the East Korean Warm Current (EKWC) from the Korean coast. As the volume transport increases, the separation latitude of the EKWC moves southward because the density gradient parallel to the KS increases in the Japanese coast and then the northward transport along the Japanese coast results in strengthening the northern cyclonic gyre. In experiments where transport varies continuously in sinusoid with several periods, the highest sea surface height (SSH) variability is detected in the region covering from the KS to the Japanese coast (near 135oE) : the prominent periods (5, 10, 30, and 40-day) in transport observation and longer periods (50, 60, 120, 180, and 360-day). The SSH variability along the Korean coast is relatively high for the longer 90-day period of the transport variation. In two experiments forced by realistic transport and seasonal one, the difference in rms of SSH is highest at the Japanese coast and relatively high at the EKWC separation region (128∼130oE, 39∼41oN). The difference in the eddy kinetic energy (EKE) at 100m deep is similar to that of SSH. On the other hand, the mean fields of SSH and MKE are similar in both regions. The temporal variation of the transport excites variability of the East Sea, but has little effects on