Movement and structural variation of warm eddy WE92 for three years in the Western East/Japan Sea

Abstract

Approximately three years of longitudinal research (from December 1992 to May 1995) examined movement and structural variation of a specific warm eddy (WE92) in the western East Japan Sea. WE92. found off the south of Ulleung Island in the East/Japan Sea. moved northward west of Ulleung Island and then eastward along the Polar Front. The intrusion of East/Japan Sea intermediate water and lateral mixing between the warm eddy and intermediate water in the summer and fall of 1993 gradually reduced WE92's diameter ( 150 170 km) and maximum depth (about 310m). The East Korean Warm Current (EKWC) and WE92 converged around Ulleung Island, and the EKWC supplied WE92 with high-temperature and high-salinity water. High-salinity water, which flowed into the edge of the warm eddy, gradually expanded into the inner portion of WE92 in summer and fall. before convective mixing occurred in winter. Energy from the EKWC replenished vorticity in the warm eddy, which had been gradually declining. A homogeneous layer (lens) caused by atmospheric cooling in the core of WE92 formed from the surface layer to a maximum depth of similar to 250m throughout the winter, The temperature of the mixed layer at the Surface near Ulleung Island was almost homogeneous, averaging approximately 10 C the first winter and lower than 8 C in the other two winters. If a warm eddy moves north several times throughout the winter and then moves east. it much lower temperature can be expected in the mixed layer at the eddy's center, The maximum velocity of the warm eddy (30-60cm/s) nearly equaled that of the EKWC, but the depth of maximum velocity (50 150m) exceeded that of the EKWC. Based on the effects of the EKWC on WE92. the currents of the warm eddy flowed fastest on the west side of WE92. (c) 2005 Elsevier Ltd. All rights reserved.