The Sea of Japan is a marginal sea of the Pacific Ocean and is limited by the shores of Japan, Russia and Korea. The Sea of Japan communicates through the Korea Strait in the south with the East China and Yellow Seas, through the Tsugaru (Sangara) Strait in the East with the Pacific Ocean, and through the La Perouse and Tatar Straits in the north with the Sea of Okhotsk. The area of the Sea of Japan is 980,000 km2, the average depth is 1361 m. The northern boundary of the Sea of Japan runs along 51 ° 45 "N (from Cape Tyk on Sakhalin to Cape South on the mainland). The southern boundary runs from Kyushu Island to the Goto Islands and from there to Korea [Cape Kolcholkap (Izgunov)]
The Sea of Japan has an almost elliptical shape with a major axis in the southwest to northeast direction. Along the coast there are a number of islands or island groups - these are the islands of Iki and Tsushima in the middle part of the Korean Strait. (between Korea and the island of Kyushu), Ulleungdo and Takashima off the east coast of Korea, Oki and Sado off the west coast of the island of Honshu (Hondo) and Tobi Island off the northwestern coast of Honshu (Hondo).
Bottom relief
The straits connecting the Sea of Japan with the marginal seas of the Pacific Ocean are characterized by shallow depths; only the Korea Strait has depths of more than 100 m. Bathymetrically, the Sea of Japan can be divided by 40°N. sh. into two parts: north and south.
The northern part has a relatively flat bottom relief and is characterized by a general smooth slope. The maximum depth (4224 m) is observed in the region of 43°00" N, 137°39" E. d.
The bottom relief of the southern part of the Sea of Japan is quite complex. In addition to the shallow waters around the islands of Iki, Tsushima, Oki, Takashima and Ulleungdo, there are two large isolated
banks separated by deep grooves. This is the Yamato Bank, opened in 1924, in the region of 39°N, 135°E. and the Shunpu Bank (also called the Yamato North Bank), discovered in 1930 and located at about 40 ° N. sh., 134 ° in. e. The smallest depths of the first and second banks are 285 and 435 m, respectively. A depression more than 3000 m deep was found between the Yamato Bank and the island of Honshu.
Hydrological regime
Water masses, temperature and salinity. The Sea of Japan can be divided into two sectors: warm (from Japan) and cold (from Korea and Russia (Primorsky Territory). The boundary between the sectors is the polar front, which runs approximately along the parallel 38-40 ° N, i.e., almost along the same latitudes along which the polar front passes in the Pacific Ocean east of Japan.water masses
Sea of Japan can be divided into surface, intermediate and deep. The surface water mass occupies a layer up to approximately 25 m and is separated from the underlying waters in summer by a clearly defined thermocline layer. The surface water mass in the warm sector of the Sea of Japan is formed by the mixing of surface waters of high temperature and low salinity coming from the East China Sea and the coastal waters of the Japan Islands region, in the cold sector - by the mixing of waters formed during the melting of ice from early summer to autumn , and waters of Siberian rivers.
For the surface water mass, the largest fluctuations in temperature and salinity are observed depending on the season of the year and the region. Thus, in the Korea Strait, the salinity of surface waters in April and May exceeds 35.0 ppm. which is higher than the salinity in the deeper layers, but in August and September the salinity of surface waters drops to 32.5 ppm. At the same time, in the area of the island of Hokkaido, salinity varies only from 33.7 to 34.1 ppm. Summer surface water temperature 25°C, but in winter it varies from 15°C in the Korea Strait to 5°C near the sea. Hokkaido. In coastal areas near Korea and Primorye, salinity changes are small (33.7-34 ppm). The intermediate water mass below the surface water in the warm sector of the Sea of Japan has a high temperature and salinity. It is formed in the intermediate layers of Kuroshio west of Kyushu and flows from there into the Sea of Japan from early winter to early summer.
However, according to the distribution of dissolved oxygen, intermediate water can also be observed in the cold sector. In the warm sector, the core of the intermediate water mass is located approximately in the 50 m layer; salinity is about 34.5 ppm. The intermediate water mass is characterized by a rather strong decrease in temperature along the vertical - from 17 ° C at a depth of 25 m to 2 ° C at a depth of 200 m. The thickness of the layer of intermediate water decreases from the warm sector to the cold; in this case, the vertical temperature gradient for the latter becomes much more pronounced. The salinity of intermediate waters is 34.5–34.8 ppm. in the warm sector and about 34.1 prom. in the cold. The highest salinity values are noted here at all depths - from the surface to the bottom.
The deep water mass, commonly referred to as the water of the Sea of Japan itself, has extremely uniform temperature (about 0-0.5 ° C) and salinity (34.0-34.1 ppm). More detailed studies by K. Nishida, however, showed that the temperature of deep waters below 1500 m rises slightly due to adiabatic heating. At the same horizon, a decrease in the oxygen content to a minimum is observed, in connection with which it is more logical to consider waters above 1500 m as deep, and below 1500 m as near-bottom. Compared with the waters of other seas, the oxygen content in the Sea of Japan at the same depths is exceptionally high (5.8–6.0 cm3/l), which indicates an active renewal of water in the deep layers of the Sea of Japan. The deep waters of the Sea of Japan are formed mainly in February and March as a result of the subsidence of surface waters in the northern part of the Sea of Japan due to horizontal diffusion, cooling in winter and subsequent convection, after which their salinity rises to approximately 34.0 ppm.
Sometimes surface waters of low salinity in the cold sector (1-4°C, 33.9 p.m.) wedged into the polar front and deepened to the south, leaving under the intermediate waters of the warm sector. This phenomenon is analogous to the intrusion of subarctic intermediate water below the warm Kuroshio layer in the Pacific Ocean in the area north of Japan.
In spring and summer, the salinity of warm waters from the East China Sea and cold waters east of Korea decreases due to precipitation and ice melt. These less saline waters mix with the surrounding waters and the overall salinity of the surface waters of the Sea of Japan decreases. In addition, these surface waters gradually warm up during the warmer months. As a result, the density of surface waters decreases, which leads to the formation of a well-defined upper thermocline layer separating surface waters from underlying intermediate waters. The layer of the upper thermocline is located in the summer season at a depth of 25 m. In autumn, heat is transferred from the sea surface to the atmosphere. As a result of mixing with the underlying water masses, the temperature of surface waters decreases, and their salinity increases. The emerging intense convection leads to the deepening of the upper thermocline layer to 25–50 m in September and 50–100 m in November. In autumn, the intermediate waters of the warm sector are characterized by a decrease in salinity due to the inflow of waters from the Tsushima Current with lower salinity. At the same time, convection in the surface water layer intensifies during this period. As a result, the thickness of the intermediate water layer decreases. In November, the layer of the upper thermocline disappears completely due to the mixing of the overlying and underlying waters. Therefore, in autumn and spring, only the upper homogeneous layer of water and the underlying cold layer are observed, separated by a layer of the lower thermocline. The latter for most of the warm sector is located at a depth of 200–250, but to the north it rises and near the coast of Hokkaido is located at a depth of about 100 m. In the warm sector of the surface layer, temperatures reach a maximum in mid-August, although in the northern part of the Sea of Japan they spread to the depths. The minimum temperature is observed in February-March. On the other hand, the maximum temperature of the surface layer near the coast of Korea is observed in August. However, due to the strong development of the upper thermocline layer, only a very thin surface layer is heated. Thus, temperature changes in the 50–100 m layer are almost entirely due to advection. Due to the low temperatures characteristic of most of the Sea of Japan at fairly great depths, the waters of the Tsushima Current cool down significantly as they move north.
The waters of the Sea of Japan are characterized by exceptionally high levels of dissolved oxygen, partly due to abundant phytoplankton. The oxygen content at almost all horizons is about 6 cm3/l and more. Particularly high oxygen content is noted in surface and intermediate waters, with a maximum value at the 200 m horizon (8 cm3/l). These values are much higher than at the same and lower levels in the Pacific Ocean and the Sea of Okhotsk (1-2 cm3/l).
Surface and intermediate waters are most saturated with oxygen. The percentage of saturation in the warm sector is 100% or slightly lower, and the waters near Primorsky Krai and Korea are oversaturated with oxygen due to low temperatures. Off the northern coast of Korea, it is 110% or even higher. In deep waters, there is a very high oxygen content to the very bottom.
Color and transparency
The color of the water of the Sea of Japan (according to the color scale) in the warm sector is more blue than in the cold one, corresponding to the region of 36-38 ° N. latitude, 133–136° E e. index III and even II. In the cold sector, this is mainly the color of indices IV-VI, and in the Vladivostok region it is above III. In the northern part of the Sea of Japan, a greenish color of sea water is noted. Transparency (according to the white disk) in the region of the Tsushima current is more than 25 m. In the cold sector, it sometimes drops to 10 m.
Currents of the Sea of Japan
The main current of the Sea of Japan is the Tsushima Current, which originates in the East China Sea. It is intensified mainly by the branch of the Kuroshio current, going to the SOUTH-WEST from about. Kyushu, as well as partly by coastal runoff from China. The Tsushima Current contains surface and intermediate water masses. The current enters the Sea of Japan through the Korea Strait and flows along the northwestern coast of Japan. In the same place, a branch of the warm current, called the East Korean Current, separates from it, which goes in the north, to the coast of Korea, to the Korean Bay and Ulleungdo Island, then turns to the SE and connects with the main stream.The Tsushima Current, about 200 km wide, washes the coast of Japan and moves further to the NE at a speed of 0.5 to 1.0 knots. Then it is divided into two branches - the warm Sangara current and the warm La Perouse current, which exit respectively into the Pacific Ocean through the Tsugaru (Sangarsky) Strait and into the Sea of Okhotsk through the La Perouse Strait. Both of these currents, after passing through the straits, turn to the east and run respectively near the eastern coast of the island of Honshu and the northern coast of the island of Hokkaido.
Three cold currents are observed in the Sea of Japan: the Liman current, which moves at low speed to the southwest in the area north of Primorsky Krai, the North Korean current, which goes south in the Vladivostok region to eastern Korea, and the Primorskoye, or cold current in the middle part of the Sea of Japan, which originates in the area Tatar Strait and goes to the central part of the Sea of Japan, mainly to the entrance to the Tsugaru (Sangara) Strait. These cold currents form a counterclockwise circulation and in the cold sector of the Sea of Japan contains clearly defined layers of surface and intermediate water masses. Between the warm and cold currents there is a clear boundary of the "polar" front.
Since the Tsushima current contains surface and intermediate water masses, which are about 200 m thick, and is separated from the underlying deep water, the thickness of this current is basically of the same order.
The current velocity to a depth of 25 m is almost constant, and then decreases with depth to 1/6 of the surface value at a depth of 75 m. The flow rate of the Tsushima Current is less than 1/20 of the Kuroshio Current flow rate.
The speed of cold currents is about 0.3 knots for the Liman Current and less than 0.3 knots for the Primorsky Current. The cold North Korea Current, which is the strongest, has a speed of 0.5 knots. This current is 100 km wide and 50 m thick. In general, cold currents in the Sea of Japan are much weaker than warm ones. The average speed of the Tsushima Current passing through the Korean Strait is less in winter, and increases to 1.5 knots in summer (in August). For the Tsushima current, interannual changes are also noted, with a clear period of 7 years being distinguished. The inflow of water into the Sea of Japan mainly occurs through the Korea Strait, since the inflow through the Tatar Strait is very insignificant. The flow of water from the Sea of Japan occurs through the Tsugaru (Sangara) Strait and La Perouse.
Tides and tidal currents
For the Sea of Japan, the tides are small. While off the coast of the Pacific Ocean the tide is 1–2 m, in the Sea of Japan it reaches only 0.2 m. In the straits, the tide increases, reaching in some places more than 2 m.Tidal waves propagate at right angles to these cotidal lines. To the west of Sakhalin and in the area of the Korean Strait. two points of amphidromy are observed. A similar cotidal map can be constructed for the lunisolar diurnal tide. In this case, the amphidromic point is located in the Korea Strait. Since the total cross-sectional area of the La Perouse and Tsugaru straits is only 1/8 of the cross-sectional area of the Korea Strait, and the cross-section of the Tatar Strait is generally insignificant, the tidal wave comes here from the East China Sea mainly through the East passage (Tsushima Strait). The magnitude of forced fluctuations in the mass of water in the entire Sea of Japan is practically negligible. The resulting component of tidal currents and the Tsushima Current going to the east sometimes reaches 2.8 knots. In the Tsugaru (Soigaru) Strait, a diurnal tidal current prevails, but the magnitude of the semidiurnal tide is greater here.
In tidal currents, diurnal inequality is clearly expressed. The tidal current in the La Perouse Strait is less pronounced due to the difference in levels between the Sea of Okhotsk and the Sea of Japan. There is also a daily disparity here. In the La Perouse Strait, the current is directed mainly to the east; its speed sometimes exceeds 3.5 knots.
Ice Conditions
The freezing of the Sea of Japan begins in mid-November in the region of the Tatar Strait and in early December in the upper reaches of Peter the Great Bay. In mid-December, areas near the northern part of Primorsky Krai and Peter the Great Bay freeze over. In mid-December, ice appears in the coastal regions of Primorsky Krai. In January, the area of ice cover increases further from the coast towards the open sea. With the formation of ice, navigation in these areas naturally becomes difficult or stops. Freezing of the northern part of the Sea of Japan is somewhat late: it begins in early to mid-February.The melting of ice begins in the areas most distant from the coast. In the second half of March, the Sea of Japan, with the exception of areas close to the coast, is already free of ice. In the northern part of the Sea of Japan, ice off the coast usually melts in mid-April, at which time navigation resumes in Vladivostok. The last ice in the Tatar Strait is observed in early-mid May. The period of ice cover along the coast of Primorsky Krai is 120 days, and at the De-Kastri harbor in the Tatar Strait - 201 days. Along the northern coast of the DPRK, a large amount of ice is not observed. Near the western coast of Sakhalin, only the city of Kholmsk is free of ice, since a branch of the Tsushima Current enters this area. The remaining areas of this coast freeze for almost 3 months, during which navigation stops.
Geology
The continental slopes of the Japanese Sea basin are characterized by many submarine canyons. From the side of the mainland, these canyons stretch to depths of more than 2000 m, and from the side of the Japanese islands only up to 800 m. The Sea of Japan is composed of bedrock consisting of Precambrian granites and other Paleozoic rocks and overlying igneous and sedimentary rocks of the Neogene. According to paleogeographic studies, the southern part of the modern Sea of Japan, probably in the Paleozoic and Mesozoic and during most of the Paleogene, was dry land. From this it follows that the Sea of Japan was formed during the Neogene and early Quaternary period. The absence of a granite layer in the earth's crust in the northern part of the Sea of Japan indicates the transformation of the granite layer into a basalt layer due to basification, accompanied by the subsidence of the earth's crust. The presence of a "new" oceanic crust here can be explained by the stretching of the continents that accompanies the general expansion of the Earth (Agayed's theory).
Thus, we can conclude that the northern part of the Sea of Japan was once dry land. The present presence of such a large amount of continental material at the bottom of the Sea of Japan at depths of more than 3000 m should indicate that the land was lowered to a depth of 2000–3000 m in the Pleistocene.
The Sea of Japan is currently connected to the Pacific Ocean and the marginal seas surrounding it through the Korean, Tsugaru (Saigarsky), La Perouse and Tatar Straits. However, the formation of these four straits took place in very recent geological periods. The oldest strait is the Tsugaru (Sangara) strait; it already existed during the Wisconsin glaciation, although after that it may have been repeatedly clogged with ice and used in the migration of land animals. The Korea Strait was also dry land at the end of the Tertiary period, and through it the migration of elephants of the southern breed to the Japanese islands was carried out. This strait opened only at the beginning of the Wisconsin glaciation. The La Perouse Strait is the youngest. Fossilized remains of mammoths found on the island of Hokkaido indicate the existence of an isthmus. land on the site of this strait until the end of the Wisconsin glaciation
Bottom relief. Soils. By the nature of the underwater relief, the Sea of Japan is a deep depression. This basin begins from the parallel of the La Perouse Strait and ends at the southern limits of the sea. In the northern part of the basin, the bottom is relatively flat with prevailing depths of 3300-3600 m. In the south, the basin is divided by an underwater ridge into two parts: western and eastern. This range is oriented along the meridian of the Oka Islands and extends into the sea to its middle. At the northern end of the ridge there are two underwater heights: Shunpu with a minimum depth of 417 m and Yamato - 287 m. These two heights are separated by an underwater saddle. By their nature, the Shunpu and Yamato uplands are of volcanic origin; pumice and volcanic (melted) glass can be found on their slopes.
The shores of Primorye, North Korea and the southern part of Hokkaido are steep. Depths of 2000 m are located 60 miles from the coast of Primorye, in some places 15, and sometimes 4-7 miles. So, in North Korea, between the capes of Kazakov and Boltin, the two thousandth isobath is 7-10 miles from the coast, and at the southwestern tip of Hokkaido, at Cape Motsuta (Kutuzov), even 4 miles.
Unlike other seas surrounding the Soviet Union, no large rivers flow into the Sea of Japan. Of the few rivers, predominantly mountainous, the largest river. Tumynjiang (Tumyn-Ula).
On the western coast of Sakhalin there are only streams, often with waterfalls. The rivers flowing from the central mountain ranges of Hokkaido and Honshu and flowing into the Sea of Japan are very short. Even the most important rivers, the Ishikari, the Teshiogawa in Hokkaido, the Shinanogawa and Magamigawa in Honshu, are no more than 350 km long and are accessible only to small boats.
The basin of the rivers of the Sea of Japan is several times smaller than the area of the sea itself. For other seas, for the most part, the opposite relationship is observed: for example, the basin of rivers flowing into the Caspian Sea is more than 8 times larger than the area of the sea itself.
This circumstance affects the nature of the soils that make up the bottom of the Sea of Japan. They form under conditions of limited input of solid particles from the mainland.
Sea bottom soils are extremely diverse. This is due to the peculiarities of the geological processes that took place in the sea, the complexity of the bottom relief, the richness and heterogeneity of the organic world. The solid remains of living beings, falling continuously as rain on the seabed, are one of the main sources of sedimentation in the Sea of Japan. The most common are silty deposits. They are found at depths of more than 3000 m.
With a decrease in depth in the silt, the admixture of sand increases. Sandy silt (silt with a small admixture of sand) occupies vast areas in the central part of the sea at depths of 2000-3000 m. It is also characteristic of the continental slope (a relatively narrow area where the bottom abruptly changes from the coastal continental shoal to great depths of the sea). Above, silty sand is distributed, confined mainly to the continental shelf. It is found on banks and in the bays of Peter the Great, Olga, Vladimir. In the coastal parts of the continental shoal, sand predominates, which borders the shores of a large part of the sea with a strip of 5-10 miles.
There are pebbles and gravel along the coast. However, often pebble-gravel soils are also found far from the coast. The “seaside pebble belt”, first described by N.I. Tarasov, is characteristic. This belt stretches in a relatively narrow strip 10-15 miles from the coast of Primorye and is one of the ancient submerged coastlines of the Sea of Japan.
In some places in the Sea of Japan, outcrops of rocky soil are observed. Most often they are found near rocky shores, on the banks of the Yamato Seamount and on the Musashi Bank, northwest of about. Hokkaido. Sometimes these bedrock outcrops can be traced at great depths (about 1000 m). In such cases, they are confined to the steepest parts of the continental slope with a bottom inclination of up to 7–10° or more, for example, near the southwestern tip of Hokkaido and south of Peter the Great Bay.
flow system. In the Sea of Japan, as in the vast majority of the seas of the northern hemisphere, there is a counterclockwise circulation of water.
A branch of the warm current Kuro-Sivo-Tsushima current enters the Sea of Japan through the Korea Strait (Kuro-Sivo is a continuation of the northern trade wind current, which originates under the influence of the northeast trade wind of the Pacific Ocean, blowing throughout the year. The trade wind current crosses the ocean from east to west between 10 and 20 ° N. Reaching the Philippine Islands, it is divided into several branches, the main of which is directed north, comes to the island of Taiwan and from here follows further north under the name Kuro-Sivo (in translation - blue current, so it is named for its exceptionally pure blue color.) When approaching the southern shores of Kyushu, the current divides into several branches, one of which, the Tsushima Current, penetrates into the Sea of Japan.). To meet him, adhering to the mainland coast, the cold Primorskoye is moving from north to south. These currents play a huge role in the life of the sea.
The Tsushima Current enters the Sea of Japan through both passages of the Korea Strait. The bulk of the water flows in through the Krusenstern pass, a smaller part - through the Broughton pass.
Leaving the Korea Strait behind, the Tsushima Current approaches the Japanese shores. A much smaller part of its waters rushes to the north as a separate branch, towards about. Ulleungdo, from which it goes further under the name of the East Korean Current, gradually deviating to the east, crosses the sea and flows into the Sangar Strait from the western side, connecting with the main branch of the Tsushima Current.
The main flow of the Tsushima Current, directed along the Japanese Islands, has a low speed. On the site of Tsushima - Noto Peninsula, the speed is only 1/2-1/3 knots (Knot is a unit of speed equal to 1.85 km / h). Encountering on its way numerous obstacles in the form of banks, capes protruding far into the sea, the current forms many local eddies.
About three quarters of the waters of the Tsushima Current enters the Pacific Ocean through the Sangar Strait, where the current is always directed from the Sea of Japan to the Pacific Ocean. At high tide, its highest speed is more than
7 knots, and at low tide it drops sharply. Near the northern shores of the strait, with fresh easterly winds, as well as at a strong ebb, there is even a current from the Pacific Ocean to the Sea of Japan.
The rest of the Tsushima Current follows northward along the western shores of Hokkaido and, having reached the La Perouse Strait, exits mainly into the Sea of Okhotsk. Off the southwestern coast of Sakhalin, the current is greatly weakened. Nevertheless, the slow movement of waters along the western shores of Sakhalin can be traced to the northern borders of the sea (On the approaches to the Sangar Strait, the speed of the Tsushima Current is 1-1.5 knots. In the Tatar Strait, the current velocities are very small and do not exceed 1/4-1/2 knots ).
As we move from south to north, the waters of the Tsushima current cool down, giving up their heat to the air, and they arrive north to a large extent modified.
This is what happens in the summer. In winter, the picture changes dramatically.
In the Korea Strait, the bulk of the Tsushima waters are directed through the Broughton Passage, in the Krusenstern Passage the current is insignificant, and in the dead of winter it stops altogether. Off the western shores of Kyushu and off the southwestern shores of Honshu, there is even a reverse current from the Sea of Japan to the East China. The East Korean current also weakens due to the winter monsoon and does not penetrate far to the north. This is explained by the strong northern and northwestern winds of the winter monsoon, which have a decelerating effect on the Tsushima current. Only when the north wind gives way to the south (this happens when cyclones pass through the Sea of Japan), the Tsushima current resumes again, but it is possible that in the deep layers there is always a constant, albeit weak, flow of water to the north.
Regarding the Primorsky current, it was believed that it begins in the Sea of Okhotsk, in the Amur estuary, therefore it was called "estuary". Later, Russian researchers proved that water from the Sea of Okhotsk does not flow through the Nevelskoy Strait. In summer, they cannot penetrate into the Sea of Japan, since its level is higher than in the Sea of Okhotsk. The southern winds of the summer monsoon constantly prop up the waters in the Tatar Strait, thereby preventing the penetration of the waters of the Sea of Okhotsk and the fresh water of the Amur. Only in winter, when northwestern winds drive water into the Sakhalin Bay of the Sea of Okhotsk, conditions are created for the inflow of a certain amount of sea water and fresh Amur water into the Sea of Japan. However, in winter, the flow of water through the Nevelskoy Strait is so small that it cannot create any significant current.
The Primorsky current, so named by the prominent researcher of domestic seas K. M. Deryugin, originates in the area between Sovetskaya Gavan and De-Kastri Bay. Further, it is directed from north to south along the coast of the Soviet Primorye and North Korea. Even in the old sailing directions, it was noted that during the accident of one ship south of De-Kastri Bay, discarded barrels of kerosene were found two months later south of Peter the Great Bay. The Primorsky current brought them here. Along the southeastern coast of Korea, this current is not clearly visible in the surface layers, but it is possible that here it passes at some depth.
The speed of the Primorsky current ranges from 1/4 to 1/2 knots, but can be more at times. In summer, the current approaches the coast, forming local turbulences in its bends. In winter, the nature of the current changes: numerous branches depart from it into the open sea.
The content of salts and gases. Transparency and color of water. Sea water differs from the water of rivers, lakes and other land bodies of water in a number of ways. The bitter-salty taste makes it unsuitable for drinking; it does not dissolve ordinary soap and cannot be used in steam boilers, as it forms a lot of scale. This is because sea water is a weak solution of various salts.
The amount of dissolved salts, expressed in grams per kilogram of sea water, is called its salinity. Usually in the open ocean, far from the mouths of large rivers, the water contains 35 grams of salts per 1 kg of water, or 35 thousandths of a kilogram. Thousandths of a whole are usually called ppm and denoted by "° / oo". Therefore, the average salinity of the World Ocean is 35% o.
Some salts are found in sea water in large quantities, such as sodium chloride (NaCl) and magnesium chloride (MgCl); together they make up 89% of all dissolved salts by weight, while others - in negligible amounts, measured in thousandths of a gram per ton of water. Thus, the content of silver in sea water is only 0.0002 g per ton of water, and gold is only 0.000005. However, the total amount of gold and other rare metals in the oceans is estimated at several billion tons.
The salinity of the seas is both less and more than the ocean. In the seas, surrounded on all sides by countries with a hot climate and having a small flow of rivers, the salinity is greater than that of the ocean. For example, in the Red Sea, surrounded by deserts, salinity reaches 41%o. In most of the world's seas, due to the flow of rivers, the salinity is less than that of the ocean.
In the Sea of Japan, although the flow of the rivers flowing into it is extremely small, the salinity is also less than that of the ocean. This is due to the fact that salinity is determined not only by the flow of rivers, but also by the ratio between precipitation and evaporation, and precipitation in this sea exceeds evaporation, which is why its salinity is less than oceanic, although not by much. On average, the salinity of the waters of the Sea of Japan is 34°/oo, slightly lower under the mainland coast, and higher near the eastern coast. In the Sea of Japan there are no areas with strongly freshened water, in this it differs sharply from all other seas washing the Soviet Union.
The salinity of the sea during the year varies slightly. Its largest seasonal fluctuations are in the north of the sea in the Tatar Strait, where it varies from 34% in autumn and winter to 32% in spring. The decrease in salinity in spring is associated with the desalination effect of ice melting. In the depths of the sea, below 300-500 m, there are no seasonal fluctuations.
In addition to salts, various gases are dissolved in sea water: oxygen, nitrogen, carbon dioxide, and sometimes hydrogen sulfide. They enter the sea from the atmosphere and as a result of the vital activity of animals, plant organisms, as well as complex chemical processes occurring at the bottom or in the water column. Oxygen is of the greatest importance for the development of life in the sea. It enters the water either from the air or is released during the respiration of marine plants. Oxygen is consumed for the respiration of animal organisms and for the oxidation of various substances, and sometimes it is released into the atmosphere with an excess of it in the surface layers.
The amount of gases dissolved in sea water is very small and variable. The most saturated with oxygen are the surface layers of the sea, in which the smallest plant organisms - phytoplankton - intensively develop, and higher plants - sea grasses - off the coast. A large amount of oxygen is absorbed by the surface layers of the sea, it gets to the depths as a result of the mixing of sea water by waves, as well as during the immersion of waters chilled or saline on the surface.
The waters of the Sea of Japan from the surface to the deepest depths are highly saturated with free oxygen. This indicates an intensive exchange between surface and deep waters, which occurs mainly in winter, when surface waters cool down and sink to a depth already heavier, deep water comes out in their place.
The processes of vertical mixing and enrichment of deep waters with free oxygen occur most intensively in the northern part of the Sea of Japan, where, in addition to cooling, the increase in the density of the surface water layer is also affected by ice formation, during which salts precipitate into the water, and sea ice becomes almost fresh. That is why in the Sea of Japan, not only surface, but also deep waters are highly enriched with free oxygen.
The transparency and color of sea water are determined by the substances dissolved and suspended in it. It has been established that the less impurities in the water, the bluer its color. There are few solid substances in the water of the Sea of Japan, so the color of its waters depends mainly on the content of plankton - microscopic organisms suspended in the water. The abundant development of plankton explains the change in the color of sea water from blue to green and even yellow and brown. In spring, with the rapid development of plankton, the color of the sea acquires yellowish-green and even brownish-green hues. This happens mainly near the seaside and Korean coasts.
In most areas, the waters of the Sea of Japan are blue-green. In the southeast, in the zone of the Tsushima current, the color of the water is intense blue, and in the north, in the Tatar Strait, greenish. The blue color of sea water corresponds to high transparency, and green, yellowish and brown - low. The transparency of sea water is usually determined by the depth at which a submerged white disk with a diameter of 60 cm begins to disappear from the eyes.
In the zone of the Tsushima current, water transparency is high and reaches 30 m, in the central part of the sea it is 15-20 m, and near the western coast in spring, with intensive development of plankton, it drops to 10 m.
Water temperature. In terms of water temperature and its change with depth, the Sea of Japan is unlike any of the other seas washing the shores of the Soviet Union. Judging by the surface temperatures in the summer, this is a warm sea. At the depths, the water is cold, only one or two tenths of a degree above zero. First of all, the amazing uniformity of the temperature of the deep layers is striking. Starting from 400-500 m in the eastern part of the sea and from 200 m in the western part, the water temperature is 0.1-0.2°.
The absence of negative water temperatures near the bottom at great depths of the sea is characteristic (the freezing point of sea water at a salinity of 34-35 ° / oo is minus 1.7-1.8 °). Meanwhile, it would seem that the water masses, having cooled down to -1.7° in winter in the northern regions of the sea, should slide to the depths of the central basin of the sea. Of course, at the same time they mix with the surrounding waters and their temperature rises somewhat, but since cold waters enter the depth every winter for a long time, a gradual cooling of the deep waters should be observed. However, this does not happen: no cooling trend has been noticed. Obviously, deep waters reach their thermal equilibrium, that is, the cooling caused by the inflow of waters with negative temperatures from the northern part of the sea is compensated to a certain extent by the influx of the internal heat of the earth, as well as by the inflow of heat from the surface layers of the southern warm part of the sea.
Let us consider in more detail the distribution of water temperature over the area of the sea and how it changes with depth, as well as from season to season.
In the figures showing the distribution of temperatures on the sea surface in February and August, attention is drawn to the location of isotherms oriented from the southwest to the northeast. The large temperature contrast between the western and eastern parts of the sea is clearly visible. This contrast is especially pronounced in winter, and in the south it is little pronounced, and in the north it is very sharp. So in February, on the 42° parallel in the east of the sea, the temperature reaches 5-6°, and in the west, south of Peter the Great Bay, it drops to zero and below.
In summer, the difference between the western and eastern parts of the sea is somewhat smoothed out, but only in the surface layers; with depth, the temperature contrast increases: near the mainland coast, the water temperature at a depth of 50 m is 2-3 °, and in the east of about. Honshu 12-16°. At depths of 300-500 m, this contrast somewhat decreases, and at 1000-1500 m it disappears completely.
To characterize the variability of water temperature from season to season, we will use the graphs of the annual temperature variation, built on the basis of long-term average data for different parts of the sea. On fig. (p. 47) shows the annual temperature variation in the Korea Strait at a point 20 miles northwest of Cape Kawajiri. Here, for many years, the temperature of the water was observed at various depths. This graph is typical for the Tsushima current passing in the Korea Strait through the Krusenstern passage. The minimum temperature at all depths is observed in March, the maximum on the sea surface - in August, at a depth of 25 m - in September, 50 m - in October, and 75 m - in November, that is, it lags from horizon to horizon.
A different character of the annual temperature variation is observed in the same strait near the Korean coast. Up to 25 m, it is almost the same as at a point northwest of Cape Kawajiri. But for greater depths, significant differences emerge. Already by 50 m in June-July, a decrease in water temperature is observed, and by 75, 100 and 120 m, a sharp decrease in temperature is observed throughout the warm half of the year. This is due to the influx of cold waters from the north. Some increase in temperature from the surface to the bottom occurs as a result of wind mixing of waters.
Of great interest are temperature fluctuations in a particular area of the sea from year to year. In a number of places these fluctuations are especially great. They greatly affect the life and behavior of the inhabitants of the sea. With sharp and unusual changes in temperature, some of them are forced to migrate to other places, and many organisms die.
In the Korea Strait, especially in the Krusenstern passage, where the main branch of the Tsushima current flows, temperature fluctuations are small from year to year. The average monthly water temperature in a severe year differs from the temperature of the same month in a warm year by only 2-4°.
A different picture is observed in the open sea. For example, to the west of Wakasa Bay, the temperature can fluctuate from year to year by 6-8° and even more. This is due to a change in the location of the axis of the Tsushima Current. Indeed, if the main stream of the warm current shifts to the left or right of its usual position, then where it has shifted, the water temperature will rise. In this place, a focus of large positive temperature anomalies (deviations from the long-term average) is formed. In the region of the usual position of the current axis, the water will become colder, and a zone of negative anomalies will appear there.
Large fluctuations in temperature from year to year are observed in the zone of the Primorsky Current, especially off the coast of North Korea. But this is connected not so much with a change in the axis of the Primorsky current, but with fluctuations in the "heat reserve" in the current itself. Fluctuations in the heat reserve of the Primorsky current are associated with the severity of winters in the Tatar Strait, where it originates. The heat reserve of the Primorsky current in spring and summer depends to a large extent on the severity or mildness of the preceding winter in the region of the current's sources. This dependence makes it possible to predict temperature fluctuations off the coast of North Korea and in the area of Peter the Great Bay.
Ice. In the Sea of Japan, only the northern part is covered with ice. The border of floating ice stretched from the Korean port of Chongjin (Seishin) northward along the coasts of Korea and Soviet Primorye to Cape Belkin (46°N). First, it goes at a distance of 5-10 miles from the coast, and then 15-25 miles. At Cape Belkin, the border turns to the east, then approaches the northwestern coast of Hokkaido in the area of Cape Kamui.
The bays of northeast Korea in winter are usually covered with only a thin crust of ice, which is easily broken up by wind and waves and carried out to sea. Such ice presents no serious obstacles to navigation. Only in severe winters with severe frosts and low winds does the ice cover in the bays of Tedinman (Gashkevich), Nadzhinman (Kornilov) and others reach a considerable thickness. So on January 12, 1933, at an air temperature of about minus 20 °, the Kornilov Bay was so heavily ice-bound that the local steamship service between the ports of Chongjin and Ungi (Yuki) was stopped. The ice lasted about 10 days, and five days later, from January 27, Kornilov Bay was covered with ice again until February 10. At this time, cargo from the ships was unloaded directly onto the ice.
In very severe winters, ice can appear in the open part of the Gulf of Korea and in the bays of the southeast coast of Korea. The western part of the Peter the Great Bay, in the tops of the Amur and Ussuriysky bays, is usually bound by strong ice, which seriously impedes navigation, and the help of port icebreakers is required.
In the bays of the Soviet Primorye with a wide entrance and the general direction of the longitudinal axis coinciding with the prevailing winter winds (northern or northwestern), the ice is easily broken by them and carried into the sea.
Along the mainland coast from Cape Povorotnoy to Cape Belkin, only primary forms of ice are found: lard, sludge, snezhura, and finely broken ice. To the north of Cape Belkin, they become heavier. In the middle part of the Tatar Strait, coarse and finely broken ice and fragments of ice fields are usually widespread, which are in continuous movement under the influence of winds. For short periods of time, when calm, ice floes can freeze and form large fields that break up at the first fresh wind. The northwest winds of the winter monsoon squeeze the ice from the mainland and drive it to the Sakhalin coast.
The ice of the Tatar Strait is a serious hindrance to navigation. To maintain it in winter, the help of linear icebreakers is required, especially on the approaches to Aleksandrovsk, where the ice reaches considerable thickness and is strongly ruffled. Ice in the northern part of the sea appears in November, first in freshened rivers and closed bays, and then usually in early December in the open sea. In April, the ice quickly breaks down and disappears.
In the narrowness of the Strait of La Perouse, between Cape Crillon and Cape Soya, ice is not observed every year. In the spring, in the second half of March - April, these are mainly the ice of the Sea of \u200b\u200bOkhotsk; they head south along the eastern shores of Sakhalin and end up in Aniva Bay. There they circulate, penetrating into the Sea of Japan only with the tide. However, conditions may arise in which ice blown by easterly winds from Aniva Bay drifts far north along the western shores of Sakhalin, posing a serious threat to the fixed nets. This happens when easterly winds give way to strong southerly winds that carry the ice north to the region of Nevelsk and even Kholmsk. This situation is created when cyclones do not follow their usual path from southwest to northeast, but along the mainland coast from south to north.
The removal of ice can be foreseen in advance if meteorologists servicing the spring season near southwestern Sakhalin, in addition to storm warnings, have data from aerial reconnaissance of ice in the La Perouse Strait and reports from coastal posts about the movement of ice to the north. With timely information about the ice threat, it was possible to sink expensive fixed nets and avoid cutting them off with ice.
Wind waves. Tsunami. The importance of wind waves in the life of the sea is enormous. Sea waves are an important factor in mixing the surface layers of water and enriching them with dissolved oxygen. Waves change the contours of the shores: in some cases they wash them away, in others they contribute to building up, creating beaches and spits. Excitement reduces the speed of ships, lowers their controllability. During severe storms, even large ships can be severely damaged and sink.
Knowledge of the wave elements - height, length, period (Wave period - the time interval between passing through the same point of adjacent crests (or bottoms) of the wave) is necessary for the shipbuilder to calculate the ship's hull strength, buoyancy and stability. It is absolutely necessary to take into account the waves in the design, construction and operation of seaports. The construction of port protective structures should be carried out with strict consideration of the prevailing direction of strong waves and the size of the waves.
The size and shape of the waves in any sea depend not only on the strength and duration of the wind that caused them, but also on the depth of the sea, its size, or, as they say, on the length of the wave acceleration. The seas, the depth of which is commensurate with the lengths of the wind waves acting on its surface, are called "shallow" in oceanography. These include the Aral, Azov, northern part of the Caspian. In the "shallow" seas, the waves are short, high, and very steep.
Seas that are deeper than the wavelength are called "deep"; in them, the depth no longer affects the nature of the excitement. The latter includes the Sea of Japan. Its waves are not particularly large, since in summer the winds are mostly weak, and in winter, although the winds of the winter monsoon are strong, they blow mainly across the sea and there is not enough acceleration to develop large waves.
However, sometimes gigantic waves arise in the Sea of Japan, but they are not caused by winds, but by underwater earthquakes or eruptions of underwater, and sometimes surface coastal volcanoes. Such waves are called tsunamis in Japanese. Over the past two and a half thousand years, 355 tsunamis have been recorded all over the world, of which 17 occurred on the coast of the Sea of Japan.
Level fluctuations. Tides. Fluctuations in the level of the Sea of Japan are mainly of two types: tidal and surge caused by winds (Level fluctuations associated with sharp changes in atmospheric pressure (seiches), although they are observed in the Sea of Japan quite often, they are not significant - they are off the coast are only a few centimeters and very rarely tens of centimeters).
In winter, the northwest monsoon raises the sea level near the western coast of the Japanese Islands by 20 - 25 cm, and near the mainland coast, the level is also lower than the annual average. In summer, it is the other way around: off the coast of North Korea and Primorye, the level rises by 20-25 cm, and off the coast of Japan, it drops by the same amount. But since the shores of the Sea of Japan are shallow, fluctuations in the level of the surge character are of little practical importance.
Tidal level fluctuations are of great practical importance in the Sea of Japan. They are not the same in different parts of the sea: the greatest level fluctuations are observed in the extreme south and extreme north of the sea. At the southern entrance to the Korea Strait, the tide reaches 3 m. As you move north, it quickly decreases and already at Busan does not exceed 1.5 m.
In the middle part of the sea, the tides are small. Along the eastern shores of Korea and the Soviet Primorye, up to the entrance to the Tatar Strait, they are no more than 0.5 m. The tides are of the same magnitude near the western shores of Honshu, Hokkaido and southwestern Sakhalin. In the Tatar Strait near Aleksandrovsk, tides reach 2.3 m, at Cape Tyk - 2.8 m. and smaller sections.
All the main types of tides are observed in the Sea of Japan: semidiurnal, diurnal and mixed per day, then once). In the Korean Strait and in the northern part of the Tatar Strait, the tides are semidiurnal, on the coast of Honshu and Hokkaido they are diurnal and only occasionally mixed. On the coasts of the eastern part of Korea and Primorye, mainly diurnal, only in the bays of Korea and Peter the Great mixed.
Vegetation. Plant organisms live in the sea only at depths where sufficient sunlight penetrates for life. Therefore, there are usually no plants deeper than 100 m in the seas.
Vegetation is rich in the Sea of Japan. Its surface layers are inhabited by a huge amount of phytoplankton - microscopic lower plants. These are unicellular organisms, devoid of special organs of movement, but having bristles, processes and other adaptations that help them stay in the water. Some of them, such as peridinea (flagellates), prefer warm waters, others, such as diatoms, prefer cold ones. Therefore, in summer, peridineans predominate, and in winter - diatoms. Numerous species of flagella and diatoms make up the bulk of phytoplankton.
In winter, there is little phytoplankton, it is concentrated in the very surface layer of water (0-15 m), while in summer there is a lot of it and is located in a layer of 5-20 m. During the day, phytoplankton makes passive vertical movements: at night, under the influence of gravity, it settles to a depth, and during the day, releasing oxygen bubbles, it rises as if on floats.
Phytoplankton plays a huge role in the life of the sea: it serves as food for various crustaceans, small fish and other marine animals. In spring and summer, during the period of abundant development of phytoplankton, even the color of the sea changes. The blue color turns into green, sometimes the waters take on yellowish hues.
Near the coast, various types of multicellular algae grow on the seabed. They differ from terrestrial plants in that their rhizomes serve for attachment, but not for nutrition. That is why algae "do not like" to settle on muddy soil, but prefer a solid base: stones, sand, shells.
In shallow water off the coast, green algae predominate, which need a lot of sunlight, at a depth of up to 30 m - brown algae, which are less demanding on light, and red algae (purples) settle even deeper, they need even less sunlight.
The coastal waters of Korea, Soviet Primorye, Sakhalin and Hokkaido are known for the abundance of kelp (seaweed) - one of the genera of brown algae. In China, Korea and Japan, it is eaten. Seaweed is fed to livestock. Previously, it was used for the production of iodine (Currently, iodine is obtained in a more economical way - from inorganic substances). Along the western coast of Sakhalin, in addition to kelp, other representatives of brown algae are often found: alaria and fucus. On thickets of these algae, herring lays eggs during spawning. Red algae are also widespread off the coast of Primorye. Among them, ahnfeltia and phyllophora are of practical importance, from which agar-agar is extracted, which is used in the food and textile industries, medicine and photography.
In the Sea of Japan, at a depth of 4-6 m, Sargassum algae is found, sprawling bushes of which reach 3 m in height. In a vertical position, it is supported by special floats. Most of these algae develop in August and September; sometimes, under the action of floats, they break away from the ground and float to the surface of the sea.
In the Sea of Japan, there are representatives of higher flowering plants that live in shallow water off the coast. They have roots, stem, leaves, flowers and seeds. These include sea grass - zostera, which forms vast and dense forests and phyllospadix (sea flax). Thickets of these plants border the rocky shores of Primorye. They are widely used in the furniture industry as stuffing material for mattresses and upholstered seats.
Animal world. The fauna of the Sea of Japan is abundant and diverse: in terms of the number of species, it significantly exceeds the world of plants. Unlike plants that live only in the surface layer, animals inhabit the sea from the surface to the very bottom.
Marine animals that live in the water column are usually divided into zooplankton and nekton. Zooplankton includes unicellular and small multicellular organisms - ciliates and crustaceans, eggs and larvae of various animals, and many others. All of them lack strong organs of movement. Their specific gravity differs little from the specific gravity of sea water, so they seem to “soar” in the water and are carried along with it. Nekton include large organisms that can move independently sometimes over long distances, such as fish.
Of the zooplankton in the Sea of Japan, copepods are the most widespread. There are especially many small calanus crustaceans 1-2 mm in size, which serve as the main food of the most important commercial fish: herring, sardines, mackerels. Larvae of bottom animals are also abundant: sea shells (mollusks), crustaceans, worms and echinoderms (sea urchins and stars).
The main mass of zooplankton is concentrated in the upper layer of the sea (up to 50 m), its quantity decreases with depth. During the day in different seasons of the year, planktonic organisms sometimes make significant vertical movements. At night and in winter they usually rise from the depths to the surface, during the day and in summer they go down. For example, the deep-water cold-loving crustacean Calanus-cristatus, which lives in summer at a depth of 500-1000 m, moves to the uppermost horizons in winter.
The totality of various benthic organisms is united under the name benthos. The benthos of the Sea of Japan is dominated by molluscs, which are characteristic mainly of the shallow water zone, deeper echinoderms predominate, and even deeper, worms and crustaceans. Bivalve mollusks are plentiful: sea, or Japanese, scallops and oysters; from echinoderms - trepangs, sea urchins, stars and sea cucumbers - sea cucumbers. Starfish are predators: they eat oysters, scallops, and even fish that have “grown up” in fishing nets.
Crustaceans (shrimps, lobsters, lobsters, crabs) and cephalopods: octopuses, cuttlefish and squids are very common in the Sea of Japan. Some of these mollusks live at the bottom of the sea (octopuses), others are active swimmers who have lost all connection with the bottom of the sea. Squids are terrible predators that eat everything living in the sea that they can handle: molluscs, crustaceans and even fish. Sometimes they reach huge sizes and attack such large animals as a sperm whale.
In the Sea of Japan, you can meet a fur seal that comes here for wintering from more northern regions, representatives of earless seals - a seal, a dolphin and even a whale.
Fish. The richness of the species composition of fish in the Sea of Japan can be judged from the following data:
This diversity is determined primarily by the abundance of food and the thermal contrast of the northern and southern, eastern and western parts of the sea. In the north and northwest of the sea there are species of fish of northern latitudes (gobies, liparids, sea chanterelles, cod, navaga), and in the south there are such representatives of the tropics as flying fish, tuna and moon fish.
Most fish species live in the southern part of the sea, in the Korea Strait and off the coast of about. Honshu. The northern cold part of the sea is poor in species, but due to the rich food (plankton), some of them are numerous and have long been an object of large-scale fishing.
As we move north from the Korea Strait along the western and eastern coasts of the sea, tropical and subtropical fish species disappear. At the same time, the number of inhabitants of cold waters is increasing. There are only 210 species of fish in the Peter the Great Bay, of which cold-water fish predominate, especially in the autumn-winter period and in spring. Southern fish penetrate this area along with jets of warm currents, some of them come regularly (mackerel, saury), others not every year (tuna), some are found as rare finds (moon fish, hammer fish).
The same can be observed in the eastern half of the sea, near the Japanese islands. Only here the southern fish go a little further north compared to the western part of the sea. This applies to fish living in the surface layers of the open sea, they are carried to the north by the Tsushima current.
In the extreme north of the sea, in the Tatar Strait, the number of species decreases. By nature, the fauna becomes more cold-water. Newcomers from the south are not numerous (mackerel, saury), they come here seasonally and irregularly.
The Sea of Japan is characterized by the absence of true deep-sea fish. The fish that still live at great depths of the sea are completely different from the fish of the Pacific Ocean that live at the same depths on the eastern side of the Japanese islands. Fish of great depths are the former inhabitants of the shallow coastal zone, which have descended and adapted to new living conditions. These are northern gobies and liparids. The latter were found at a depth of more than 3500 m. It is interesting that in the depths of the Sea of Japan a fish with such a transparent skull was found that the brain is visible through it.
The absence in the Sea of Japan of true deep-water fish, common in the Pacific Ocean, confirms that this sea is not a section of the Pacific Ocean, laced from it due to the uplift of the Japanese Islands and Sakhalin, but was formed by failure of a section of the earth's crust. Otherwise, representatives of the deep-sea Pacific fauna would have remained in the Sea of Japan.
For demersal and bottom fish, such as cod and flounder, the Sea of Japan is not entirely favorable, primarily due to the poor development of the continental shelf and the lack of shoals and banks - the favorite habitats of these commercial fish.
The Sea of Japan, characterized by temperature contrasts, is convenient for the life of gregarious commercial fish that stay in the upper layer of the open sea and feed on plankton. Life is especially rich in areas where warm and cold waters meet. Fish such as mackerel, herring are collected in numerous shoals. Heat-loving commercial fish include mackerel and sardine.
The story of the catastrophe in the Far Eastern sardine fishery is instructive. Until 1941, it was the main commercial fish in the Sea of Japan. Millions of centners of fish were caught along the eastern coasts of Korea, Japan and the Soviet Primorye. In 1941, the catch was greatly reduced everywhere, and in 1942 it stopped completely in most areas of the Sea of Japan, with the exception of its southernmost limits.
What is this fish, what is the history of its fishing and what are the reasons for its disappearance?
The sardine reaches a length of 30 cm. It does not differ in taste from its sister - the Atlantic sardine, very fatty and tasty, it sometimes contains up to 40% fat.
Unlike many other heat-loving forms, it reacts most sensitively and painfully even to minor changes in temperature. The Soviet scientist P. Yu. Schmidt cites cases of mass mortality of sardines off the coast of Sakhalin in the summer with a sudden and sharp drop in temperature.
Sardine - an alien from the subtropics. It spawns in the south, mainly off the southwestern shores of the Japanese island. Kyushu. Previously, there were spawning sites along the western and northeastern shores of about. Honshu within the Tsushima current. Spawning occurs in the south in January - February, in the northern regions in March - April at a temperature of 12-15 °.
After spawning, the sardine rushes to fattening in the northern regions of the Sea of Japan, where it finds an abundance of plankton. The rapid development of plankton is confined to the junction of warm and cold waters. Many commercial fish are concentrated here. These places represent the centers of world fishing. The junction of the Gulf Stream and the cold Labrador Current in the area of the Great Newfoundland Bank, the frontal zone of the meeting of the Kuro-Sivo and the cold Kuril Current in the northwestern part of the Pacific Ocean are the richest and longest-known areas of the world fishery.
Sardine migrations to the north took place in two ways - along the eastern coast of Korea and the western coasts of Honshu and Hokkaido. Numerous flocks, clearly visible from the ship and especially from the aircraft, the sardine approached the shores of the Soviet Primorye, where they were caught with smooth nets, purse seines in the open sea and, most importantly, with fixed seines near the shore.
The sardine usually reached our shores in the area of Peter the Great Bay in June, and in July-August it penetrated the Tatar Strait, reached De-Kastri Bay, and in October it migrated back, rolling back to the southern limits of the sea.
Iwashi fishing off the coast of Japan began in the middle of the last century, and off the coast of Soviet Primorye only in 1925, when 4400 centners of this fish were first caught. P. Yu. Schmidt wrote: “When I first came to the shores of the Pacific Ocean in 1900, I met Iwashi in Nagasaki, but in Vladivostok, when collecting information about the fishing industry, no one told me anything about this valuable fish. It was not even in the fish market, where at that time it was possible to get a wide variety of representatives of the ichthyofauna.”
In the thirties, the sardine was the main object of the Soviet fishery in the Sea of Japan. In 1937, its catch reached a record figure - 1,400,000 centners. In the thirties, more than 10 million centners were caught off the coast of Korea, and 12-15 million centners off the coast of Japan.
In 1941, a disaster occurred in the sardine fishery in the Sea of Japan.
What happened to the sardine? There is no complete unanimity on this issue among scientists. The Japanese scientist Yasugawa considers the main reason for the disappearance of the sardine to be extremely unfavorable spawning conditions in 1936-1939, as a result of which there was a sharp decrease in the number of sardines.
The Soviet scientist A. G. Kaganovsky explains the disappearance of the sardine not only by a change in temperature conditions, but also by qualitative changes in the number of sardines - its grinding. A small sardine is even more sensitive to a decrease in temperature than a large one.
Beginning in 1941, summer temperature conditions in the Sea of Japan were extremely unfavorable for sardines. In the northern and central parts of the sea, surface waters turned out to be 3-4 ° colder than in ordinary years, and a cold layer of water formed from the Korean port of Wonsan to the Japanese port of Niigata (besides, the sardine is poor in food - plankton), preventing the sardine from penetrating into our water.
P. Yu. Schmidt also considers the cooling of the waters of the Sea of Japan to be the main reason for the disappearance of the Far Eastern sardine. In support of his view, P. Yu. Schmidt in his book “Pisces of the Pacific Ocean” cites maps of water temperatures in the Sea of Japan compiled by A. M. Batalin. These maps clearly show the significant difference in the physical conditions of the sardine in 1941 and 1942. compared to a normal year, such as 1932.
It was found that off the southwestern coast of Kyushu, in the main sardine spawning grounds, the water was 2-3° colder than normal only in the winter of 1936, and in subsequent winters (1937-1940) it turned out to be normal. Therefore, the unfavorable spawning conditions of 1936 could only affect the generation of that year. Thus, the theories of P. Yu. Schmidt and A. G. Kaganovsky are more correct than Yasugawa.
Now let's talk about the reasons for the cooling of the Sea of Japan in 1941-1944. A. M. Batalii believes that it is partly due to a decrease in the amount of heat delivered to the Sea of Japan by the Tsushima current. He saw the main reason in the shift of warm currents to the southeast under the influence of the intensified in 1941-1942. winter monsoon.
However, it seems to us that the cooling is associated with very cold winters of the period 1940-1943. In these winters, powerful ice formed in the Tatar Strait, which persisted in the spring longer than usual, and therefore the Primorsky current intensified in these years. The cold waters of the Primorsky current created the barrier that prevented the sardine from breaking through to the shores of the Soviet Primorye.
The fact that the sardine came to our shores in the twenties, during the period of warming of the Sea of Japan, and disappeared in the forties, during the cooling period, allows us to assume that over time the sardine will again enter the northern part of the sea. The temperature regime of the Sea of Japan had already reached its usual state several years ago, but it will probably take several more years for the sardine, now held in the southernmost reaches of the sea, to gradually spread northward with increasing numbers. It is possible that this process has already begun, as evidenced by the first centners of sardines caught in the north of the sea, off the coast of Sakhalin, in the summer of 1954-1955.
Another heat-loving fish - mackerel - after the disappearance of the sardine became one of the main objects of the Soviet fishery in the Sea of Japan. Adult mackerel in commercial quantities is found at water temperatures from 6 to 22 °. Its temperature optimum is 12-16°. Mackerel in January - March lives in the southern part of the sea, adjacent to the Korea Strait, and keeps mainly at the bottom. Here it is caught at depths of 100-150 m with bottom fixed seines and trawls.
In March, the water temperature in this area is 13-14° and is almost the same from the surface to the bottom. In spring, with the beginning of warming, mackerel migrates north for spawning, which lasts from April to July. Mackerel spawns in the coastal strip, in bays and bays or between islands, mainly along the northeastern coast of Korea and in Peter the Great Bay.
The start of mackerel spawning depends on the maturation of its reproductive products, which in turn depends on the water temperature in the area of its wintering. If the temperature there is above normal, then the gametes will ripen earlier, and mackerel will spawn in the nearby bays of the eastern coast of Korea; very few unspawned fish will reach Peter the Great Bay. When the water temperature is low in the wintering area, the maturation of reproductive products is delayed, a significant part of the mackerel, without spawning, reaches Peter the Great Bay, where the main spawning takes place.
After spawning, mackerel moves further north in search of food until it reaches the northern limits of its habitat: Sovetskaya Gavan - Wide Pad. In September - October, she leaves the northern regions and migrates south to the wintering grounds.
Cold-loving fish of the Sea of Japan include cod, flounder, and herring. However, extremely low temperatures are “contraindicated” for them, just as very high temperatures are “contraindicated” for heat-loving fish. Especially badly they tolerate negative temperatures. In winter, when cold waters appear off the coast of Primorye, cod move to depths and come to the coast in summer when it gets warmer. Off the coast of Hokkaido in summer, when the temperature in the coastal strip rises, cod, on the contrary, migrates from the coast to deeper and colder horizons, and stays off the coast in winter, since the water temperature here is favorable for it.
Unlike the Atlantic cod, which has free-floating eggs, the Pacific cod, like the goby and the stingray, has bottom-dwelling eggs. This biological fitness has developed in the Far Eastern cod due to the fact that it spawns in areas with strong currents and where ice appears in winter. If she did not have bottom caviar, then she would freeze into the ice or be carried by currents and die.
The herring, which lives in the Sea of Japan, like cod, avoids excessively chilled waters, but even more does not tolerate high temperatures. Herring is suitable for spawning on the southwestern shores of Sakhalin in April at a water temperature of 0-4°C. The behavior of fattening (fatting) herring in the Tatar Strait is also highly dependent on temperature. In late May - early June, the development of plankton in the southern part of the Tatar Strait reaches its maximum. It is during this period that shoals of herring rush here for fattening.
The choice of places of abundant fishing, as well as the most efficient fishing gear, to a large extent depends on thermal conditions. In relatively cold years, such as 1946 and 1947, shoals of herring stayed close to the coast all summer and were caught with drift nets (Drift (smooth) nets are usually “swept out” at night, they are kept “afloat” and slowly drift along with the current ) and fixed nets, first in the surface, and then in the bottom layers. In relatively warm years (1948 and 1949), the periods of stay of herring near the coast are greatly reduced, and the fish quickly move to the open sea. Drift net fishing near the coast in such years stops by mid-July, and with fixed nets even earlier. Secondarily, herring comes to the shores in autumn, in September - October, when the waters become colder.
As V. G. Bogaevsky showed, the period of stay of herring in the coastal zone also depends on the thickness of the surface layer of water heated above 10 °. The herring avoids this heated layer and stays lower in the lower temperature waters underlying it. Most of all, it accumulates near the coast during strong northeast winds, when heated water is driven away from the coast, and cold deep waters rise to the surface.
With changes in temperature conditions in the Sea of Japan, rare fish that are not an object of fishing may disappear and appear. According to A.I. Rumyantsev, in the summer of 1949, after a 7-8-year break caused by a sharp cooling in 1941-1944, cases of subtropical and tropical fish were again caught in the area of Peter the Great Bay. So, on September 30, 1949, a conger eel was caught in the Ussuri Bay, which lives off the coast of the southern Japanese islands. On the same day, in the Zarubino area, the so-called caragoid fish, common in the tropical latitudes of the Indian and Pacific oceans, was caught. In August of the same year, three specimens of eastern tuna weighing 245, 261 and 336 kg were caught in Peter the Great Bay, and triggerfish, a representative of the subtropics, were caught near Cape Peschany in the Amur Bay. In the same year, a huge inhabitant of tropical waters, the moon-fish, was found in the waters of Primorye. Her weight reached 300 kg.
These finds testify to the general warming of the waters of the Sea of Japan. The same is said by the first centners of sardines caught in our waters in 1954-1955.
Fish industry. Three countries fish in the Sea of Japan: the Soviet Union, Japan and Korea.
The extraction of fish, sea animals and other products of the sea in the Far East has always been extremely important for our country. The share of fishing in the Far Eastern seas in the postwar years ranged from 20 to 36% of the total production of the Soviet Union.
The raw material resources of the Far Eastern seas make it possible to increase production. This primarily applies to saury, pollock, cod and other fish.
Among the Far Eastern seas, the Sea of Japan until 1941 occupied the first place in terms of the number of fish caught due to the high catches of sardines. After the war, the Sea of Japan gave way to the Sea of Okhotsk and the Kamchatka waters of the Pacific Ocean, where salmon, herring and flounder are caught mainly.
Before the war, a small number of fish species were used in the fishery in the Sea of Japan. These included sardine, salmon (chum salmon, pink salmon, sima), herring, cod, flounder and saffron cod (vakhnya). In the post-war years, fishing for mackerel, pollock, greenlings, smelt, etc. was organized.
Mass fishing of mackerel in the waters of Primorye arose only in 1947, and by 1953 its catch reached 183 thousand centners.
Fishing for flounders in Primorye has existed for a long time. Of the 25 species found in the Far Eastern waters, 19 are caught in Peter the Great Bay (according to P. A. Moiseev). The catches are dominated by yellowfin, sharp-headed and small-mouthed flounders.
This fishery is based on their catch during spring migration from wintering areas to the coast and return migration in autumn. Flounders overwinter at significant depths - from 170 to 250 m and even deeper, avoiding coastal freezing temperatures. Most of all, it accumulates on a bank located southeast of about. Askold.
Flounders are distinguished by relatively low mobility. To determine its migrations, in some places, individual fish were tagged and released back into the sea. Further than 17 miles from the release site, none of the tagged flounders was recaptured.
The fishery mastered the accumulations of flounders in the northern part of the Tatar Strait, the catches of which began to increase after the Second World War and reached 100 thousand centners.
In the Sea of Japan, such an important commercial demersal fish as cod and pollock, another representative of the cod family, is underused.
Until 1941, cod was caught in negligible numbers in the Sea of Japan. After the war, its catch increased due to fishing off the southwestern coast of Sakhalin. Like cod fishing, pollock fishing began in the post-war years. Pollock, living in the bottom and intermediate horizons at depths of up to 150-200 m, is distributed throughout the Sea of Japan, but especially large concentrations of it are formed off the eastern coast of Korea, in the Gulf of Korea. There in 1946-1948. fishing vessels were sent for expedition fishing. Catches reached 5,000 centners per vessel. The total catch of pollock in 1948 amounted to 180 thousand centners. Its reserves in the Sea of Japan are very large and allow a significant increase in production.
Herring lives mainly in the northern part of the Sea of Japan and is caught off the coast of Primorye, Hokkaido and South Sakhalin.
Until very recently, mainly spring spawning herring with a low fat content (up to 5-6%) was caught. Until 1945, spawning herring was caught by the Japanese in huge quantities off southwestern Sakhalin. In 1931, the catch reached 5.5 million centners, then it decreased to 1.5-3 million centners per year. Herring spawning near Sakhalin takes place in April. It approaches the shore quickly and in great numbers. Sakhalin herring catches were: in 1946 - 506 thousand centners, in 1947 - 609; in 1948 - 667, in 1949 - 1135 thousand centners, and since 1950 they began to decline sharply connection with the depletion of the Sakhalin-Hokkaido herring stock. In addition to spawning, there is a fishery for feeding herring, excellent in quality, with a fat content of up to 20%. Salmonids (chum salmon, pink salmon, sim) are caught in the rivers of Primorye and the western coast of Sakhalin during their spawning run.
Saury should be attributed to undeveloped, but very promising objects of fishing. Until 1934, it appeared irregularly in the Sea of Japan, and in subsequent years it began to come up for spawning more regularly and abundantly even to our shores. Saury reacts sensitively to electric light, gathers in the lighting zone, where it is successfully caught with lifting nets.
In the Sea of Japan, the fishery of crabs, mollusks (mainly scallops), marine plants (kelp, seaweed, ahnfeltia, zoster) is developed. Medicines are prepared from kelp, and agar is extracted from anfeltia (red algae). Most marine invertebrates and algae are underexploited by fisheries, and their production can be significantly expanded.
The Sea of Japan is considered one of the largest and deepest seas in the world. It is a marginal sea of the Pacific Ocean.
Origin
The first information about this sea was obtained from Chinese sources in the 2nd century BC. Historically, it is believed that this reservoir was formed as a result of the melting of the glacier and the rise in the water level in the oceans.
Historical events
In the 14th-16th centuries, pirates seized power at sea. All maritime trade was under their control. From 1603 to 1867, the Sea of Japan was one of the busiest transport links and the main entry route for Dutch and Korean embassies.
Sea of Japan on the map photo
The Sea of Japan witnessed the Russo-Japanese War (1901-1902). Today, the Sea of Japan is an important domestic and international transport artery.
Characteristic
The main characteristics of the Sea of Japan:
- Area 1062,000 square km
- Average sea depth: 1536 m.
- Maximum depth: 3742 m.
- Salinity: 34-35‰.
- Length: from north to south 2,255 km, from west to east about 1,070 km.
- In winter, part of the Sea of Japan freezes - the Russian coastal side, but the ice can break periodically;
- Average annual temperature: in the north 0-12C, in the south 17-26C.
shore of the Sea of Japan photo
currents
The main course of the Sea of Japan is the Tsushima, which is approximately 200 km wide. This current contains surface and intermediate water masses. In addition, the following cold currents are observed in the Sea of Japan:
- Limanskoye, moving at low speed to the southwest;
- North Korean, going south;
- Seaside, or cold current, going to the central part.
Japanese Sea. Primorsky Krai photo
These cold currents form a cycle counterclockwise. The warm Kuroshio current prevails in the southern part of the sea.
What rivers flow
Few rivers flow into the Sea of Japan, although they are all mountainous. Let's take a look at the biggest ones:
- Partisan;
- Tumnin;
- Samarga;
- Rudnaya.
Where does the Sea of Japan flow into?
Through the straits, the waters of the sea enter:
- through the Nevelsky Strait to the Sea of Okhotsk;
- through the Sangar Strait to the Pacific Ocean;
- through the Korea Strait to the East China Sea.
Japanese Sea. storm photo
Climate
The climate of the sea is monsoonal, temperate. The western and northern parts of the sea are much colder than the southern and eastern parts. The temperature difference reaches +27 C. Hurricanes and typhoons often pass over the sea surface.
Despite the fact that the sea is separated from the ocean by the Japanese Islands and Sakhalin, storms and hurricanes often rage in the northern part of the sea, especially in autumn. Such a polo can last up to three days, and the waves reach 12 meters in height. The Siberian anticyclone brings such weather. For this reason, the Sea of Japan is not very calm for navigation.
Japanese Sea. port of Vladivostok photo
In November, the northern part of the sea is covered with ice; in March-April, the ice breaks up. In summer, the weather is cloudy, weak monsoon winds from the southeast prevail.
Relief
The bottom relief of the Sea of Japan is divided into:
- the northern part (a wide trough that narrows and rises to the north);
- the central part (deep closed basin, elongated in a northeasterly direction);
- the southern part (the relief is complex, shallow water alternates with gutters).
The shores of this sea are mostly mountainous. Low-lying coasts are extremely rare. The coastline is fairly flat on Sakhalin. The shores of Primorye are more indented.
underwater world of the Sea of Japan photo
Cities and ports
We note the more significant Russian port cities located in the Sea of Japan:
- Vladivostok;
- Nakhodka;
- Oriental;
- Sovetskaya Gavan;
- Vanino;
- Shakhtersk.
Flora and fauna
Brown algae and kelp grow abundantly along the seashores. The Sea of Japan is very rich in fish fauna due to the abundance of oxygen and food. Approximately 610 species of fish live here. The main types of fish fauna are:
- In the southern part of the sea - anchovy, sardine, horse mackerel, mackerel.
- In the northern regions - flounder, herring, salmon, greenling, mussels, saury, hammerhead fish, tuna.
Fishing in the Sea of Japan lasts all year round. This region is inhabited by 6 species of seals, 12 species of sharks that are not dangerous to humans, squids and octopuses.
Few people know the following interesting facts about the Sea of Japan:
- North Koreans call this sea the East Sea of Korea;
- Residents of South Korea - East Sea.
- Here you can meet representatives of 31 orders of fish from 34 orders that exist in the world;
- The Sea of Japan leads in the diversity of fish among all the seas of the Russian Federation;
- A small jellyfish lives in the algae of the sea, capable of infecting the central nervous system, and upon repeated contact, its poison can be fatal. There are no famous resorts here, but the Sea of Japan is very important for the trade and economy of several countries, including Russia.
And North Korea. In the south, a branch of the warm current Kuroshio enters.
| Japanese Sea | |
|---|---|
| Japanese 日本海 box 동해 |
|
| Characteristics | |
| Square | 1,062,000 km² |
| Volume | 1,630,000 km³ |
| Greatest depth | 3742 m |
| Average depth | 1753 m |
| Location | |
| 39°34′55″ N sh. 134°34′11″ E d. HGIOL | |
| Media files at Wikimedia Commons | |
The Sea of Japan is currently bounded by the Russian mainland and Sakhalin Island to the north, the Korean Peninsula to the west, and the Japanese islands of Hokkaido, Honshu and Kyushu to the east and south. It is connected to other seas by five straits: the Tatar Strait between the mainland of Asia and Sakhalin; the La Perouse Strait between Sakhalin and Hokkaido; the Tsugaru Strait between Hokkaido and Honshu; the Kanmon Strait between Honshu and Kyushu; and the Korea Strait between the Korean Peninsula and Kyushu.
The Korea Strait consists of the Western Channel and the Tsushima Strait on either side of Tsushima Island. The straits were formed in recent geological periods. The oldest of them are Tsugaru and Tsushima. The latest is the Strait of La Perouse, which formed about 60,000-11,000 years ago. All the straits are quite shallow with a maximum depth of about 100 meters or less. This prevents water exchange with the ocean, thereby isolating the Sea of Japan from neighboring seas and oceans.
The sea is divided into three parts: the Yamato Basin in the southeast, the Japan Basin in the north, and the Tsushima Basin (Ullung Basin) in the southwest. The Japanese Basin is of oceanic origin and is the deepest part of the sea, while the Tsushima Basin is the shallowest, with depths below 2300 m. On the eastern shores, the continental shelves of the sea are wide, but on the western shores, especially along the Korean coast, they are narrow, on average about 30 km.
In the northern part there are three separate continental shelves (above 44°N). They form steps slightly inclined to the south and submerged to depths of 900-1400, 1700-2000 and 2300-2600 m, respectively. The last step drops sharply to a depth of about 3500 m towards the central (deepest) part of the sea. The bottom of this part is relatively flat, but has several plateaus. In addition, underwater ridges rise up to 3500 m and run from north to south through the middle of the central part.
The Japanese coastal sea area consists of the Okujiri Range, the Sado Range, the Hakusan Banks, the Wakasa Range, and the Oki Range. The Yamato Range is of continental origin and is composed of granite, rhyolite, andesite, and basalt. Its uneven bottom is covered with boulders of volcanic rock. Most of the other areas of the sea are of oceanic origin. The seabed up to 300 m is continental and covered with a mixture of mud, sand, gravel and rock fragments. Depths between 300 and 800 m are covered with hemipelagic (ie, semi-oceanic) deposits; these deposits are composed of blue mud rich in organic matter. Pelagic red mud deposits dominate the deeper areas.
There are no large islands in the sea. Most of the smaller ones are located near the east coast, except for Ulleungdo (South Korea). The most significant islands: Moneron, Rebun, Rishiri, Okushiri, Oshima, Sado, Okinoshima, Askold, Russian, Putyatin. The coastlines are relatively straight and devoid of large bays or capes, coastal forms are simple near Sakhalin and more sinuous in the Japanese islands.
Climate
ice conditions
According to ice conditions, the Sea of Japan can be divided into three areas: the Tatar Strait, the area along the coast of Primorye from Cape Povorotny to Cape Belkin, and Peter the Great Bay. In winter, ice is constantly observed only in the Tatar Strait and Peter the Great Bay, in the rest of the water area, with the exception of closed bays and bays in the northwestern part of the sea, it is not always formed. The coldest region is the Tatar Strait, where more than 90% of all ice observed in the sea is formed and localized in the winter season. According to long-term data, the duration of the period with ice in Peter the Great Bay is 120 days, and in the Tatar Strait - from 40-80 days in the southern part of the strait, to 140-170 days in its northern part.
The first appearance of ice occurs at the tops of bays and gulfs, closed from the wind, waves and having a desalinated surface layer. In moderate winters in the Peter the Great Bay, the first ice forms in the second decade of November, and in the Tatar Strait, in the tops of the Sovetskaya Gavan, Chikhachev and Nevelskoy Straits, primary ice forms are observed already in early November. Early ice formation in Peter the Great Bay (Amur Bay) occurs in early November, in the Tatar Strait - in the second half of October. Later - at the end of November. In early December, the development of ice cover along the coast of Sakhalin Island is faster than near the mainland coast. Accordingly, in the eastern part of the Tatar Strait at this time there is more ice than in the western part. By the end of December, the amount of ice in the eastern and western parts levels out, and after reaching the parallel of Cape Surkum, the direction of the edge changes: its displacement along the Sakhalin coast slows down, and along the mainland it becomes more active.
In the Sea of Japan, the ice cover reaches its maximum development in mid-February. On average, 52% of the area of the Tatar Strait and 56% of the Peter the Great Bay are covered with ice.
The melting of ice begins in the first half of March. In mid-March, the open waters of Peter the Great Bay and the entire seaside coast to Cape Zolotoy are cleared of ice. The boundary of the ice cover in the Tatar Strait recedes to the northwest, and in the eastern part of the strait, ice is clearing at this time. Early clearing of the sea from ice occurs in the second decade of April, later - at the end of May - beginning of June.
Flora and fauna
The underwater world of the northern and southern regions of the Sea of Japan is very different. In the cold northern and northwestern regions, the flora and fauna of temperate latitudes have formed, and in the southern part of the sea, south of Vladivostok, a warm-water faunal complex predominates. Off the coast of the Far East, a mixture of warm-water and temperate fauna occurs. Here you can meet octopuses and squids - typical representatives of warm seas. At the same time, vertical walls covered with sea anemones, gardens of brown algae - kelp - all this resembles the landscapes of the White and Barents Seas. In the Sea of Japan, there is a huge abundance of starfish and sea urchins, of various colors and different sizes, there are brittle stars, shrimps, small crabs (King crabs are found here only in May, and then they go further into the sea). Bright red sea squirts live on rocks and stones. Of the mollusks, scallops are the most common. Of the fish, blennies and sea ruffs are often found.
Sea transport
Fisheries and sea culture
Recreation and tourism
The Japanese side, in turn, shows that the name "Sea of Japan" is found on most maps and is generally accepted, and insists on using the name "Sea of Japan" exclusively.
Notes
- The Sea of Japan // Great Soviet Encyclopedia: [in 30 volumes] / ch. ed. A. M. Prokhorov. - 3rd ed. - M.: Soviet Encyclopedia, 1969-1978.
- Sea of Japan (indefinite) . www.britannica.com, Encyclopædia Britannica online
- A. D. Dobrovolskyi and B. S. Zalogin Seas of USSR. Sea of Japan (Russian). tapemark.narod.ru. Retrieved 10 October 2019., Moscow University (1982) (in Russian)
- Park, S.-C; Yoo, D.-G; Lee, C.-W; Lee, E.-I. Last glacial sea-level changes and paleogeography of the Korea (Tsushima) Strait (English) // Geo-Marine Letters: journal. - 2000. - Vol. 20, no. 2. - P. 64-71. - DOI:10.1007/s003670000039 .
- Atlas of Oceanography of the Bering, Okhotsk and Japan Seas (indefinite) (unavailable link). Far Eastern Branch of the Russian Academy of Sciences. Retrieved March 11, 2009.
It is located between the Asian mainland, the Japanese archipelago and Sakhalin Island. Its shores belong to such countries as Japan, South Korea, North Korea and Russia.
The reservoir is significantly isolated from the Pacific waters. Such isolation is reflected both in the fauna and in the salinity of the water. The latter is below the oceanic. The water balance is regulated by inflows and outflows through the straits that connect the sea with neighboring seas and the ocean. The discharge of fresh water makes an insignificant contribution to water exchange and does not exceed 1%.
Geography
The area of the reservoir is 979 thousand square meters. km. The maximum depth is 3742 meters. The average depth corresponds to 1752 meters. The volume of water is 1630 thousand cubic meters. km. The length of the coastline is 7600 km. Of these, 3240 km belong to Russia. From north to south, the length of the sea is 2255 km. The maximum width corresponds to 1070 km.
Islands
There are no major islands. Most of the small islands are located off the east coast. The most significant islands are: Moneron (30 sq. km), Okushiri (142 sq. km), Oshima (9.73 sq. km), Sado (855 sq. km), Ulleungdo (73.15 sq. km) , Russian (97.6 sq. km).
gulfs
The coastline is relatively straight. One of the largest is Peter the Great Bay with a total area of about 9 thousand square meters. km. The length from north to south is 80 km, from west to east it is 200 km. The length of the coastline is 1230 km. The cities of Vladivostok and Nakhodka are located in the bay. North Korea has East Korea Bay, and Hokkaido Island has Ishikari Bay. In addition, there are many small bays.
Straits
The Sea of Japan is connected with the East China Sea, the Sea of Okhotsk and the Pacific Ocean by straits. This is the Tatar Strait between Asia and Sakhalin Island with a length of 900 km. La Perouse Strait between Sakhalin Island and Hokkaido Island with a length of 40 km. Sangar Strait between the islands of Honshu and Hokkaido. Its length is 96 km.
The Shimonoseki Strait separates the islands of Honshu and Kyushu. Railway, automobile and pedestrian tunnels are laid under it. The Korean Strait with a length of 324 km connects the reservoir we are considering with the East China Sea. It is divided by the Tsushima Islands into 2 parts: the Western Passage and the Eastern Passage (Tsushima Strait). Through this strait, the warm Pacific Kuroshio current enters the reservoir.
Sea of Japan on the map
Climate
The maritime climate is characterized by warm water and monsoons. It is colder in the northern and western regions than in the southern and eastern regions. During the winter months, the average air temperature in the north is minus 20 degrees Celsius, and in the south it is plus 5 degrees Celsius. In summer, humid and warm air blows from the northern regions of the Pacific Ocean. August is considered the warmest month. At this time, the average temperature in the north is 15 degrees Celsius, and in the south it is 25 degrees Celsius.
Annual precipitation is minimal in the northwest and maximal in the southeast. Autumn is characterized by typhoons. The height of the waves during this period reaches 8-12 meters. In winter, the Tatar Strait (90% of all ice) and Peter the Great Bay are covered with ice. The ice crust stays on the water for about 4 months.
Ebb and flow
The reservoir is characterized by complex tides. They have a semi-diurnal cycle in the Korea Strait and in the north of the Tatar Strait. On the east coast of Korea, the Far East coast of Russia, on the coast of the Japanese islands of Hokkaido and Honshu, they are diurnal. Mixed tides are typical for Peter the Great Bay.
The amplitude of the tides is relatively low. It varies from 0.5 to 3 meters. In the Tatar Strait, the amplitude ranges from 2.3 to 2.8 meters due to its funnel-shaped shape. The water level also experiences seasonal fluctuations. The highest is observed in summer, and the lowest in winter. The level is also affected by the wind. He is able to change it by 20-25 cm in relation to the Korean coast to the Japanese one.
Water transparency
Sea water has a color from blue to green-blue. Transparency is about 10 meters. The water of the Sea of Japan is rich in dissolved oxygen. This is especially true for the western and northern regions. They are colder and contain more phytoplankton compared to the eastern and southern regions. The oxygen concentration is 95% near the surface and decreases to 70% at a depth of 3,000 meters.
Fishing in the Sea of Japan
Fishing
The main economic activity is fishing. It is carried out near the continental shelf, and priority is given to such fish as herring, tuna, sardines. Squid are caught mainly in the central sea areas, and salmon off the southwestern and northern coasts. Along with fishing, the production of algae is well developed. The Russian whaling fleet is based in Vladivostok, although it fishes in the northern seas.
