Interdecadal Variation in the East/Japan Sea
Kuh Kim
Research Institute of Oceanography, Seoul National University
Potential temperature in the East Sea has risen since 1940's for its whole water column except for the surface layer in the Yamato Basin. The slope of the warming trend is 0.0005 deg C/yr at 3000m and increase graudally upwards to 0.0054 deg C at 500m. This warming could have been forced by the overlying atmosphere. Cooling of the surface layer in the Yamato Basin seems to be related to the cooling of the inflow through the Korea/Tsushima Strait, which is mainly controlled by the interdecadal variation in the Pacific Ocean.
Salinity has undergone a two-mode change at the same time. It has increased above 1200m, but decreased below it since 1965. Dissolved oxygen shows three modes; a decrease at 20-500m, an increase at 500-1200m and another decrease below 1200m.
These long-term trends indicate a possibility of major change in the thermohaline circulation in the East Sea: formation of deep and bottom waters may have stopped or have been reduced significantly in the East Sea. Mean while a new water mass has formed, sunk and spread at intermediate depths.