High frequency variability of current in the western channel of the Tsushima/Korea Straits

Abstract

The temporal characteristics and spatial structures of high frequency variability of the current in the western channel of the Tsushima/Korea Straits (TKS) are studied using ADCP data from 10 years along the cruise line of a regular ferry, “Camilla”, between Busan and Hakata. The eddy kinetic energy analysis shows that the high frequency variability has strong seasonal and spatial dependencies. From December to April, the variability is prominent in the entire western channel of the TKS. From July to October, it is enhanced only in the Korean coastal zone. The EOF analysis for the component of the high frequency currents normal to the ferry route illuminates three types of dominant modes, a transport mode and a vortex mode in the western channel during December–April, and a baroclinic coastal-trapped mode in the Korean coastal zone during July–October. The transport mode with a uniform current direction throughout the channel shows good correlation with the high frequency variability of the volume transport through the western channel with dominant time scales of 3.5 and 7 days. The vortex mode with alternating current directions across the channel explains well the variability of the eddy vorticity in the western channel with dominant time scales of 5–8 days. The baroclinic coastal-trapped mode in the Korean coastal zone has characteristics of both baroclinic Kelvin wave and topographic Rossby wave in the vertical current structure with dominant time scales of 14 and 32 days.