THE NORTHERN BOUNDARY THE TSUSHIMA CURRENT AND ITS FOUCTUATIONS

하계 동해에 있어서 대마난류의 북상한계와 변동

The northern boundary of the Tsusgima Current and its fluctuations are divcussed in the Japan Sea in summer. This current was characterized with high slinity, and its path was traced by following the salinity maximum on the basis of oceanographical data collected during the period from 1963 to 1979. The salinity maxima (34.45-34.85 ) of the Tsushima Current in the areas between 29 N in the East China Sea and northern part of the Japan Sea were found at depths between 46m and 135m. The representative thermosteric anomaly corresponding to the salinity maximum eas examined in order to analyze the advection of this currint. In the Tsushima Current region in the Japan Sen, the thermosteric anomaly values in the layer of salinity maximum during the period of 1970 to 1979 was beween 220 cl/t and 260 cl/t. In general, as the current moves northward its salinity decreascs, its thermosteric anomaly decreases and the depth of salinity maximum becomes shallower. The northern boundary of this current, which is indicated by 34.4 isohaline on 240 cl/t isanosteric surface during the study period of ten years, was confined to south of 40 N of the Japan Sea. The 34.4 isohaline edvealed two types of flow; one of them flows northward along the eastern coast of South Korea and then meanders eastward, while the oter flows basically northeastward along the coast of Japan. The meanders of northern boundary of this currint idrntified th isohaline in this word were nearly similar to those studied by others on the bases of isotherm analysis.

1970∼1979년 기간중 하계의 동해에 있어서 대마난류의 북상한계와 연변동을 규명하기 위해서 염분최대를 추적하고, 이값에 대한 deltaT(thermosteric anomaly) 에 관하여 검토했다. 29 N 이북의 동지나해로부터 동해북부해역에 이르기 까지 대마난류의 염분최대치 및 그 층의 낮아지는 경향을 보였으며, 그 층도 얕아졌다. 동해의 대마난류역에서 염분최대가 나타나는 층에 대한 deltaT의 값은 220-260 cl/t 이었다. 240cl/t면상의 34.4 등염선을 지표로하여 조사한 대마난류의 북상한계 는 한국 동해안측에서는 4 N 이남해역으로 한정으며, 동염선은 두가지 형태로 나타났다. 즉 동서방향인한국동해안쪽으로 치우쳐 북상하는 경우와 남남서-북북동 방향인 일본연안쪽으로 북상하는 경우였다.