| Description |
The Sea of Japan/East Sea is a semi-isolated marginal sea with an area of approximately 978,000 km2, a volume of 1,713,000 km3, and a mean depth of 1,350 m, extending to 3,700 m in the northern basin. It is connected to the Sea of Okhotsk, the Northern Pacific, and East China Sea through four shallow straits: Tartarskiy Strait (15 m), Soya Strait (55 m), and Tsugaru and Tsushima Straits (130 m each). (Terazaki, 1999 in press). The only important current flowing into the Sea of Japan today is the Tsushima Current, a small branch of the warm Kuroshio Current, that enters through the Tsushima Strait between Kyushu and Korea and flows out to the Pacific through the Tsugaru and Soya Straits. The warm inflow peaks in September, with warm flow in the Sea peaking from September to October. Meandering results in large scale cyclonic and anticyclonic eddies on either side of the warm current, as indicated by several cold-water and warm-water areas along the main stream of the current in late summer to autumn. The Current alternates between a relatively straight flow, with increased temperatures at 50 m, and a meandering flow approximately every six years. (Japan Sea National Fisheries Research Institute, 1991; Terazaki, 1999 in press.). Approximately 20 percent of the LME is shelf, and approximately 40 percent each are bathyal and abyssal zones. Sedimentary records of the past 85,000 years derived from core samples indicate changes in inflowing currents and the degree of oxygenated or anoxic bottom waters. (Kato 1979; Masuzawa and Kitano 1983; Oba et al. 1991) The deep waters are well aerated in winter due to the sinking of cooled surface waters. The Sea exhibits lower temperature than the adjacent ocean and Okhotsk and Bering Seas, does not exhibit an oxygen deficient middle layer or a cold intermediate layer. The northwestern Sea of Japan is colder than the remainder, with sharp declines in temperature in the winter and ice present in the Tartarskiy Strait from November to April. Seasonal temperature fluctuations are as high as 20 degrees C in the northwestern portion, and 14 degrees C in the southern portion. (Terazaki, 1999 in press) Imai et al. (1990) demonstrated that the total amount of nutrients in the Tsushima Current throughout the year from 1972 through 1988 is less than 0.5 percent of the total amount in the Sea of Japan. Biomass is maintained by mixing with nutrient rich subsurface water in winter and inflow of nutrient-rich water through the Tsushima Strait. Tropical to arctic animal populations occur in the Sea of Japan, with seasonal occurrences of tropical-subtropical species in the surface layer and arctic-subarctic populations in the lower layer (i.e., tropical species appearing during the summer, arctic species in the winter.) Subtropical to warm temperate mid-water populations are confined to the southeastern Sea of Japan, while the other populations (surface and bottom) are widespread. (Nishamura, 1965, 1968, 1969; Terazaki, 1999 in press) (http://www.na.nmfs.gov/lme/text/lme50.htm; formerly Sea of Japan). |
