The Summer/Fall Variability of the Southern East/Japan Sea in the ENSO Period

Abstract

The summer/fall variability of the upper ocean circulations and properties of the East/Japan Sea occurring during the El Nino-Southern Oscillation (ENSO) period is investigated by use of the high-resolution HYCOM reanalysis data. From August to November of the La Nina period, the inflow through the Korea/Tsushima Strait is intensified, and so are the East Korean Warm Current (EKWC) and the Nearshore Branch of the Tsushima Warm Current (NBTWC) in the southern East/Japan Sea. The intensified EKWC induces an offshore current anomaly near 36°N, weakening the anticyclonic gyre circulation in Ulleung basin, and the intensified NBTWC leads to weakening of the Offshore Branch of the Tsushima Warm Current (OBTWC). The sea surface temperature begins to increase from the northeastern coast of Japan in August, and its positive anomalies expand to the largest area of southern East/Japan Sea in October and last until November. The positive anomalies of sea surface salinity are mainly observed along the south and east coast of Korea. The cyclonic gyre circulation anomaly in Ulleung Basin is accompanied by the negative SSH anomaly and shallowing of the upper ocean isopycnal lines, which leads to substantial cooling of the subsurface water. The reverse is true in the El Nino period.