Variability of upper circulation in the southwestern East/Japan Sea

Abstract

The Ulleung Basin located in the southwestern East Sea is one of three deep basins that are contained in the East Sea. Upper circulation features in the Ulleung Basin are investigated using highly-resolved continuous temperature fields at 100 m depth for two years and supporting CTD data. Mesoscale variability of upper circulation is predominant with little seasonal variation. Five flow patterns have been identified with each pattern persisting 3~5 months and transitions between successive patterns occurring in a few days or a couple of months. The variability mainly results from the path variability and meandering of the East Korean Warm Current, the evolution of the Ulleung Warm Eddy, and the fluctuation of the subpolar front. The amplification and shrinking of the UWE appear to be related with an increase and decrease of the volume transport through the Korea Strait. The upper circulation, however, exhibits high variability even when the transport shows little temporal variation. Freshening and wide spreading of the East Sea Intermediate Water occurred when the East Korean Warm Current disappeared. This period also coincided with the low transport through the Korea Strait and high velocity of inflowing deep water into the UB through the UIG.