14 

 The Sea of Japan 



I. PHYSICAL GEOGRAPHY 



The area of the Sea of Japan is about 978,000 km 2 ; its volume is 1,713,000 

 km 3 ; its average depth is 1,752 m and its greatest depth 4,036 m. 



Owing to the shallowness of the straits connecting it with the Ocean, the 

 Sea of Japan occupies a special position among the Far Eastern Seas which 

 wash the shores of the u.s.s.r. In spite of this shallowness the isolation of its 

 deep waters is only relative, since in winter, as a result of the sinking of 

 cooled surface waters along its slopes, the deep waters are well aerated ; they 

 differ from the adjacent parts of the Ocean and from the Okhotsk and Bering 

 Seas by their lower temperature and by the absence of oxygen deficiency in 

 the middle layers. The cold intermediate layer is also absent from the Sea of 

 Japan. The salinity of the Sea of Japan is practically the same as that of the 

 Ocean {Table 304). 



Table 304. Vertical distribution of temperature, salinity and oxygen in the central parts of the 



Seas of Japan and Okhotsk and of the Bering Sea 



Water exchange in the Sea of Japan is also different from that of the Sea 

 of Okhotsk and the Bering Sea. All the deep waters of the Sea of Japan are 

 isolated from the trenches of the Pacific Ocean and adjacent seas ; only the 

 surface waters flow into the Sea of Japan from the neighbouring basins. 

 Warmer deep oceanic waters penetrate freely into the Sea of Okhotsk and the 

 Bering Sea through the deep straits and fill their trenches (Fig. 368). 



The Sea of Japan has a varied bottom topography (Fig. 369) (N. Zenkevitch, 

 1959). Its greatest depth is situated in the northern, deep-water part. The sea- 

 floor is mostly below 3,000 m. Its shelf zone is very narrow except for the Bay 

 of Peter the Great, the northern part of Tartary Bay and the northern coast of 

 Hokkaido Island. Its bathyal zone is comparatively large. The shelf zone 

 forms only about 20 per cent of the total area of the Sea, and the bathyal 

 zone some 40 per cent ; the area of the deep-sea floor is also about 40 percent. 



750 



