The Sea of Japan is a marginal sea of the western Pacific Ocean, between the Asian mainland, the Japanese archipelago and Sakhalin. It is bordered by Japan, North Korea, Russia and South Korea. Like the Mediterranean Sea, it has almost no tides due to its nearly complete enclosure from the Pacific Ocean. This isolation also reflects in the fauna species and in the water salinity, which is lower than in the ocean.
The sea has no large islands, bays or capes. Its water balance is mostly determined by the inflow and outflow through the straits connecting it to the neighboring seas and Pacific Ocean. Few rivers discharge into the sea and their total contribution to the water exchange is within 1%.
The seawater is characterized by the elevated concentration of dissolved oxygen that results in high biological productivity. Therefore, fishing is the dominant economic activity in the region. The intensity of shipments across the sea has been moderate owing to political issues, but it is steadily increasing as a result of the growth of East Asian economies. A controversy exists about the sea name, with South Korea promoting the appellation East Sea.
Geography and geology :
The Sea of Japan was once a landlocked sea when the land bridge of East Asia existed.
Onset of formation of Japan Arc was in Early Miocene. Early Miocene period also corresponds to incipient opening of the Japan Sea, and the northern and southern parts of the Japanese archipelago that were separated from each other. During the Miocene there was expansion of Sea of Japan. The northern part of the Japanese archipelago was further fragmented at later periods until the orogenesis of the northeastern Japanese archipelago began in the later Late Miocene. The southern part of the Japanese archipelago remained as a relatively large landmass. The land area had expanded northward in the Late Miocene. The orogenesis of high mountain ranges in the northeastern Japan started in Late Miocene and it lasts in Pliocene also.
There are no large islands in the sea. Most of the smaller ones are located near the eastern coast, except for Ulleungdo (South Korea). The most significant islands are Moneron, Rebun, Rishiri, Okushiri, Ōshima, Sado, Okinoshima, Ulleungdo, Askold, Russky and Putyatin. The shorelines are relatively straight and are lacking large bays or capes; the coastal shapes are simplest for Sakhalin and are more winding in the Japanese islands. The largest bays are Peter the Great Gulf, Sovetskaya Gavan, Vladimira, Olga, Posyet in Russia, East Korea Bay in North Korea and Ishikari (Hokkaidō), Toyama and Wakasa (Honshū) in Japan. Prominent capes include Lazareva, Peschanyi (sandy), Povorotny, Gromova, Pogibi, Tyk, Korsakova, Crillon, Sōya, Nosappu, Tappi, Nyuda, Rebun, Rishiri, Okushiri, Daso and Oki.
The sea climate is characterized by warm waters and monsoons. This combination results in strong evaporation, which is especially noticeable between October and March when the strong (12–15 m/s or higher) northwestern monsoon wind brings cold and dry continental air. The evaporation is blown further south causing snowfall in the mountainous western coasts of Japan. This winter monsoon brings typhoons and storms with the waves reaching 8–10 meters which erode the western coasts of Japan. Tsunami waves were also recorded in the sea. In addition, the monsoon enhances the surface water convection, down to the depths of 30 meters.
The coldest months are January and February with the average air temperature of −20 °C in the north and 5 °C in the south. The northern one-quarter of the sea, particularly the Siberian coast and the Strait of Tartary, freezes for about 4–5 months. The timing and extent of freezing vary from year to year, so ice may start forming in the bays as early as in October and its remains may be seen even in June. Ice cover is continuous only in the bays and forms floating patches in the open sea. Ice melting in spring results in cold currents in the northern areas.
In summer the wind weakens to 2–7 m/s and reverses its direction, blowing warm and humid air from the North Pacific onto the Asian mainland. The warmest month is August with the average air temperature of 15 °C in the north and 25 °C in the south. Annual precipitation increases from 310–500 mm in the north-west to 1,500–2,000 mm in the south-east.
Flora and fauna :
The high concentration of dissolved oxygen results in the rich aquatic life of the Sea of Japan - there are more than 800 species of aquatic plants and more than 3,500 animal species, including more than 900 species of crustaceans, about 1000 of fish and 26 of mammals. The coastal areas contain several kg/m square of biomass. Pelagic (oceanic) fishes include saury, mackerel, Jack mackerels, sardines, anchovies, herring, sea bream, squid and various species of salmon and trout.
The demersal (sea-bottom) fishes include cod, pollock and Atka mackerel. Mammals are represented by seals and whales, and the crustaceans by shrimps and crabs. Because of the shallow straits connecting the sea with Pacific Ocean, the sea of Japan has no characteristic oceanic deep-water fauna. Flora and fauna unique to the region near the Sea of Japan are known as "Japan Sea elements".