Full-size depth map of the Japanese sea. Sea of Japan, map
It is located between the Asian mainland, the Japanese archipelago and Sakhalin Island. Its shores belong to countries such as Japan, South Korea, North Korea and Russia.
The reservoir is significantly isolated from Pacific waters. This isolation affects both the fauna and the salinity of the water. The latter is below the oceanic one. The water balance is regulated by inflows and outflows through the straits connecting the sea with neighboring seas and the ocean. Reset fresh water makes an insignificant contribution to water exchange and amounts to no more than 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 large islands. Most of small islands located off the east coast. The most significant islands include: Moneron (area 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).
Bays
Coastline 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. In North Korea there is East Korea Bay, and on the island of Hokkaido there is Ishikari Bay. In addition, there are many small bays.
Straits
The Sea of Japan is connected to the East China Sea, the Sea of Okhotsk and the Pacific Ocean by straits. This is the Strait of Tartary between Asia and Sakhalin Island with a length of 900 km. The 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. There are railway, road and pedestrian tunnels underneath it. The Korea Strait, with a length of 324 km, connects the body of water we are considering with the East China Sea. It divides 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. The northern and western regions are colder than the southern and eastern regions. In 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 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 maximum in the southeast. Typhoons are typical for autumn. The wave height 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.
Ebbs and flows
The reservoir is characterized by complex tides. They have a semi-diurnal cycle in the Korea Strait and in the north of the Tartary Strait. On the east coast of Korea, the Far East coast of Russia, and on the coast of the Japanese islands of Hokkaido and Honshu, they are daytime. 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 wind. He is able to change it by 20-25 cm in relation to the Korean coast to the Japanese coast.
Water clarity
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 thousand meters.
Fishing on the Sea of Japan
Fishing
Fishing is considered the main economic activity. It is carried out near the continental shelf, and priority is given to fish such as herring, tuna, and sardines. Squid are caught mainly in the central sea areas, and salmon off the southwestern and northern coasts. Along with fishing, algae production is well developed. The Russian whaling fleet is based in Vladivostok, although it fishes in the northern seas.
In size it is inferior to the sea and, its area is up to 1,062 tons km2, and the most deep depression reaches up to 3745 m. It is generally accepted that average depth 1535 m. Great depths and geographical location indicate that the sea belongs to the marginal oceanic seas.
There are medium and small islands in the sea. The most significant of them are Rishiri, Oshima, Sado, Momeron, Russian. Almost all the islands are located along the mainland in the eastern part.
The coastline is slightly indented, the outlines of Sakhalin Island are especially simple. with the Japanese Islands it has a more indented coastline. Main major ports seas are Eastern Port, Wonsan, Kholmsk, Vladivostok, Tsuruga, Chongjin.
Currents of the Sea of Japan
Tides in the Sea of Japan
IN different areas The sea tides are expressed differently, they are especially distinct in the summer and reach up to three meters in the Korea Strait. To the north, the tides decrease and do not exceed 1.5 m. This is explained by the fact that the bottom has a funnel shape. The greatest fluctuations are observed in the northern and southern extreme regions of the sea in the summer.
I suggest you interesting video « A parallel world— Sea of Japan" from the series "Russian underwater expeditions".
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The Sea of Japan is a marginal sea of the Pacific Ocean and is limited by the coasts of Japan, Russia and Korea. The Sea of Japan is connected 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 border of the Sea of Japan runs along 51 ° 45 "N latitude (from Cape Tyk on Sakhalin to Cape Yuzhny on the mainland). The southern border runs from the island of Kyushu to the Goto Islands and from there to Korea [Cape Kolcholkap (Izgunov)]
The Sea of Japan has an almost elliptical shape with the major axis in the direction from southwest to northeast. 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 Kyushu Island), Ulleungdo and Takashima off the east coast of Korea, Oki and Sado off the west coast of Honshu Island (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. w. into two parts: northern and southern.
The northern part has a relatively flat bottom topography and is characterized by an overall smooth slope. The maximum depth (4224 m) is observed in the area of 43°00"N, 137°39"E. d.
The bottom topography 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
jars separated by deep grooves. This is the Yamato Bank, opened in 1924, in the area of 39°N, 135°E. etc., and the Shunpu Bank (also called the Northern Yamato Bank), opened in 1930 and located approximately 40° N. latitude, 134° east. d. The smallest depths of the first and second banks are 285 and 435 m, respectively. A depression with a depth of more than 3000 m was discovered 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, running approximately along the parallel of 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
The Sea of Japan can be divided into surface, intermediate and deep. The surface water mass occupies a layer up to approximately 25 m and in summer is separated from the underlying waters 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 high temperature and low salinity surface waters coming from the East China Sea and the coastal waters of the area Japanese Islands, in the cold sector - by mixing waters formed when ice melts from early summer to autumn, and the waters of Siberian rivers.
The surface water mass exhibits the largest fluctuations in temperature and salinity depending on the season and 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. In summer surface water temperature 25°C, but in winter it varies from 15°C in the Korea Strait to 5°C near the island. Hokkaido. In the coastal areas of Korea and Primorye, changes in salinity are small (33.7-34 ppm). The intermediate water mass, which lies below the surface water in the warm sector of the Sea of Japan, has high temperature and salinity. It is formed in the intermediate layers of Kuroshio west of Kyushu Island and enters the Sea of Japan from there during the period of early winter to early summer.
However, based on 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 vertical temperature - 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 to the cold sector; 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 industrial. in the cold. The highest salinity values are observed here at all depths - from the surface to the bottom.
The deep water mass, usually called 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 increases slightly due to adiabatic heating. At the same horizon, a decrease in oxygen content to a minimum is observed, and therefore it is more logical to consider waters above 1500 m as deep, and below 1500 m as bottom. Compared to 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 the 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 increases to approximately 34.0 ppm.
Sometimes the low-salinity surface waters of the cold sector (1-4° C, 33.9 ppm) wedge into the polar front and deepen in a southerly direction, going under the intermediate waters of the warm sector. This phenomenon is similar to the penetration 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 melting ice. These less saline waters mix with surrounding waters and the overall salinity of the surface waters of the Sea of Japan decreases. Additionally, 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 clearly defined upper thermocline layer that separates the surface waters from the underlying intermediate waters. The upper thermocline layer is located in the summer season at a depth of 25 m. In autumn, heat is transferred from the sea surface to the atmosphere. Due to mixing with underlying water masses, the temperature of surface waters decreases and their salinity increases. The resulting intense convection leads to a deepening of the upper thermocline layer to 25–50 m in September and 50–100 m in November. In autumn, intermediate waters of the warm sector are characterized by a decrease in salinity due to the influx of waters of 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 upper thermocline layer disappears completely due to the mixing of overlying and underlying waters. Therefore, in autumn and spring there is only an upper homogeneous layer of water and an underlying cold layer, separated by a layer of 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 off the coast of the island 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 surface layer temperature off the Korean coast 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 large depths, the waters of the Tsushima Current are greatly cooled as they move north.
The waters of the Sea of Japan are characterized by exceptionally high levels of dissolved oxygen, partly due to the abundance of phytoplankton. The oxygen content at almost all horizons here is about 6 cm3/l or more. Particularly high oxygen content is observed in surface and intermediate waters, with a maximum value at the horizon of 200 m (8 cm3/l). These values are much higher than at the same and lower horizons 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. north coast In Korea it is 110% and even higher. In deep waters there is a very high oxygen content right down to the bottom.
Color and transparency
The color of the water of the Sea of Japan (according to the color scale) in the warm sector is bluer than in the cold sector, corresponding to the region of 36-38° N. latitude, 133-136° east. etc. 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, the sea water has a greenish color. Transparency (by the white disk) in the Tsushima Current region 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 strengthened mainly by the branch of the Kuroshio Current, going to the SOUTHWEST of the island. Kyushu, as well as partially 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 heads along the northwestern coast of Japan. There, 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 Gulf and Ulleungdo Island, then turns to the SE and connects with the main flow.The Tsushima Current, about 200 km wide, washes the shores of Japan and goes further to the NE at a speed of 0.5 to 1.0 knots. Then it divides into two branches - the warm Sangar Current and the warm La Perouse Current, which respectively exit 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 east and go, respectively, near the eastern coast of the island of Honshu and the northern coast of the island of Hokkaido.
There are three cold currents in the Sea of Japan: the Liman current, moving at low speed to the southwest in the area north of the Primorsky Territory, the North Korean current, going south in the Vladivostok area to eastern Korea, and the Primorsky current, or the 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, contain clearly defined layers of surface and intermediate water masses. There is a clear boundary of the “polar” front between the warm and cold currents.
Because the Tsushima Current contains surface and intermediate water masses that 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 speed is almost constant to a depth of 25 m, 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 flow rate of the Kuroshio Current.
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 Korean Current, which is the strongest, has a speed of 0.5 knots. The width of this current is 100 km, thickness - 50 m. 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 lower in winter, and increases to 1.5 knots in summer (in August). For the Tsushima Current, interannual changes are also observed, with a clear period of 7 years being distinguished. The flow of water into the Sea of Japan mainly occurs through the Korea Strait, since the inflow through the Tartary Strait is very insignificant. The flow of water from the Sea of Japan occurs through the Tsugaru (Sangara) and La Perouse Straits.
Tides and tidal currents
Tides are low for the Sea of Japan. 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. Slightly higher values are observed off the coast of the Primorsky Territory - up to 0.4-0.5 m. In the Korean and Tatar Territories In the straits, the tide increases, reaching more than 2 m in some places.Tidal waves propagate at right angles to these cotidal lines. 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 area cross section Since the La Perouse and Tsugaru straits are only 1/8 of the cross-sectional area of the Korea Strait, and the cross-section of the Tartary Strait is generally insignificant, the tidal wave comes here from the East China Sea mainly through the Eastern 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 eastward Tsushima Current sometimes reaches 2.8 knots. In the Tsugaru (Soigarsky) Strait, a tidal current of the diurnal type predominates, but the magnitude of the semidiurnal tide is greater here.
There is a clear diurnal inequality in tidal currents. 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 diurnal inequality here. In the La Perouse Strait, the current is directed mainly to the east; its speed sometimes exceeds 3.5 knots.
Ice Conditions
Freezing of the Sea of Japan begins in mid-November in the area 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. In mid-December, ice appears in the coastal areas of Primorsky Krai. In January, the area of ice cover increases further from the coast to the side open sea. With the formation of ice, navigation in these areas naturally becomes difficult or stops. The freezing of the northern part of the Sea of Japan is somewhat delayed: it begins in early to mid-February.Ice melting begins in areas furthest 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 in Vladivostok resumes. The last ice in the Tartary Strait is observed in early to mid-May. The period of ice cover along the coast of the Primorsky Territory is 120 days, and near the De-Kastri harbor in the Strait of Tartary - 201 days. Along the northern coast of the DPRK large quantity no ice is observed. On 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 Sea of Japan basin are characterized by many submarine canyons. On the mainland side, these canyons stretch to depths of more than 2000 m, and on the side of the Japanese Islands only to 800 m. The mainland shoals of the Sea of Japan are poorly developed, the edge runs at a depth of 140 m on the mainland side and at a depth of more than 200 m. Yamato Bank and other banks The Sea of Japan is composed of bedrock consisting of Precambrian granites and other Paleozoic rocks and overlying Neogene igneous and sedimentary rocks. According to paleogeographic studies, the southern part of the modern Sea of Japan was probably dry land in the Paleozoic and Mesozoic and during most of the Paleogene. It follows from this that the Sea of Japan was formed during the Neogene and early Quaternary periods. The absence of a granite layer in the earth's crust of the northern part of the Sea of Japan indicates the transformation of the granite layer into a basalt layer due to basification, accompanied by subsidence of the earth's crust. The presence of “new” oceanic crust here can be explained by the stretching of continents accompanying the general expansion of the Earth (Egayed’s theory).
Thus, we can conclude that the northern part of the Sea of Japan was once dry land. The current presence of such a large amount of continental material on the bottom of the Sea of Japan at depths of more than 3000 m should indicate that the land subsided to a depth of 2000-3000 m in the Pleistocene.
The Sea of Japan currently has a connection with the Pacific Ocean and the surrounding marginal seas through the Korean, Tsugaru (Saigarsky), La Perouse and Tatar straits. However, the formation of these four straits occurred in very recent times. geological periods. The oldest strait is the Tsugaru (Sangara) Strait; it already existed during the Wisconsinian glaciation, although it may have been filled with ice several times after that 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 southern elephants to the Japanese islands took place; 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
Physiographic characteristics and hydrometeorological conditions
The Sea of Japan is located in the northwestern part of the Pacific Ocean between the mainland coast of Asia, the Japanese Islands and Sakhalin Island in geographical coordinates 34°26"-51°41" N, 127°20"-142°15" E According to its physical and geographical position, it belongs to the marginal oceanic seas and is fenced off from adjacent basins by shallow barriers. In the north and northeast, the Sea of Japan connects with the Sea of Okhotsk straits Nevelsky and La Perouse (Soya), in the east - with the Pacific Ocean, the Sangar (Tsugaru) Strait, in the south - with the East China Sea, the Korean (Tsushima) Strait. The shallowest of them, the Nevelskoy Strait, has a maximum depth of 10 m, and the deepest Sangarsky Strait is about 200 m. The greatest influence on the hydrological regime of the basin is exerted by subtropical waters flowing through the Korea Strait from the East China Sea. The width of this strait is 185 km, and the greatest depth of the threshold is 135 m. The second largest water exchange is the Sangarsky Strait, which has a width of 19 km. The La Perouse Strait, the third largest water exchange, has a width of 44 km and a depth of up to 50 m. The surface area of the sea surface is 1062 thousand km 2, and the total volume of sea waters is 1631 thousand km 3.
The nature bottom relief The Sea of Japan is divided into three parts: northern - north of 44° N, central - between 40° and 44° N. and southern - south of 40° N. The bottom surface of the northern bathymetric step, which is a wide trench, gradually rising to the north, merges at 49°30" N with the surface of the shelf of the Tatar Strait. The basin of the central part with maximum depths for the sea (up to 3700 m) has a flat bottom and is elongated from west to east, northeast. From the south, its border is defined by the Yamato underwater rise. The southern part of the sea has the most complex bottom topography. The main geological landmark here is the Yamato underwater rise, formed by two ridges elongated in the east-northeast direction and located between between the Yamato Rise and the slope of Honshu Island stretches the Honshu Basin with depths of about 3000 m. In the southwestern part of the sea there is a shallower Tsushima Basin. In the area of the Korea Strait, the shallows of the Korean Peninsula and Honshu Island, merging, form shallow waters with depths of 120-140 m.
A feature of the morphology of the bottom of the Sea of Japan is a poorly developed shelf, which stretches along the coast in a strip from 15 to 70 km in most of the water area. The narrowest strip of the shelf, from 15 to 25 km wide, is noted along south coast Primorye. The shelf reaches greater development in the Peter the Great Gulf, in the northern part of the Tatar Strait, the East Korean Gulf and in the area of the Korea Strait.
The total length of the sea coastline is 7531 km. It is slightly indented (with the exception of Peter the Great Bay), sometimes almost straight. A few islands lie mainly near the Japanese Islands and in Peter the Great Gulf.
The Sea of Japan is located in two climatic zones: subtropical and temperate. Within these zones, two sectors with different climatic and hydrological conditions are distinguished: the harsh, cold northern sector (partially covered with ice in winter) and the soft, warm sector adjacent to Japan and the shores of Korea. The main factor shaping the climate of the sea is the monsoon circulation of the atmosphere.
The main pressure formations that determine the atmospheric circulation over the Sea of Japan are the Aleutian depression, the Pacific subtropical maximum and the Asian center of atmospheric action located above the mainland. Changes in their position throughout the year determine the monsoon climate in the Far East. In distribution atmospheric pressure over the Sea of Japan, determined by the main pressure formations, the following features are revealed: a general decrease in pressure from west to east, an increase in pressure from north to south, an increase in the excess of winter pressure values over summer in the direction from northeast to southwest, as well as a pronounced seasonal variability. In the annual course of pressure, most of the sea is characterized by the existence of a pressure maximum in winter and a minimum in summer. In the northeastern part of the sea - near the northern half of the island. Honshu, oh. Hokkaido and off the southern coast of Sakhalin there are two pressure maxima: the first in February and the second in October, with a minimum in summer. The amplitudes of the annual pressure variation, as a rule, decrease from south to north. Along the mainland coast, the amplitude decreases from 15 mb in the south to 6 mb in the north, and along the coast of Japan - from 12 to 6 mb, respectively. The absolute amplitude of pressure fluctuations in Vladivostok is 65 mb, and on the island. Hokkaido - 89 mb. To the southeast, in central and southern parts of Japan, it increases to 100 mb. The main reason for the increase in the amplitudes of pressure fluctuations in the southeast direction is the passage of deep cyclones and typhoons.
The features of atmospheric pressure distribution discussed above determine General characteristics wind regime over the Sea of Japan. Along the mainland coast in the cold season, strong winds northwest direction with speeds of 12-15 m/s. The frequency of these winds in the period from November to February is 60 - 70%. In January and February, the frequency of occurrence of prevailing winds at certain points on the coast reaches 75 - 90%. From north to south, wind speeds gradually decrease from 8 m/s to 2.5 m/s. Along the island's east coast, cold season winds are not as distinct in direction as they are off the mainland coast. Wind speeds are lower here, but also decrease on average from north to south. Every year, at the end of summer and beginning of autumn, tropical cyclones (typhoons) enter the Sea of Japan, accompanied by hurricane winds. During the cold season, the frequency of storm winds caused by deep cyclones increases sharply. During the warm period of the year, southern and southeastern winds prevail over the sea. Their frequency of occurrence is 40 - 60%, and the speeds, as in winter, on average decrease from north to south. In general, wind speeds in the warm season are significantly lower than in winter. During the transition seasons (spring and autumn), wind directions and speeds undergo significant changes.
For open areas of the northwestern regions of the sea in winter, the prevailing winds are northwestern and northern directions. In the direction to the southwest, the winds turn from northwestern to western, and in areas adjacent to southern Sakhalin and Hokkaido, from northwestern to northern and even northeastern. In the warm season, such a regular picture of the general structure of the wind field cannot be established for the entire sea. However, it is found that in the northern regions of the sea the prevailing winds are eastern and northeastern, and in the southern regions - southern directions.
In the Sea of Japan air temperature changes naturally both from north to south and from west to east. In the northern, more severe climatic zone, average annual temperature is 2°, and in the south, in the subtropics - +15°. In the seasonal course of air temperature, the minimum occurs in the winter months (January - February), and the maximum occurs in August. In the north, the average monthly temperature in January is about -19°, and the absolute minimum is -32°. In the south, the average monthly temperature in January is 5°, and the absolute minimum is -10°. In August in the north, the average temperature is 15°, and the absolute maximum is +24°; in the south, respectively, 25° and 39°. Temperature changes from west to east have a smaller amplitude. West Coast throughout the year it is colder than in the east, with temperature differences increasing from south to north. In winter they are greater than in summer and average 2°, but at some latitudes they can reach 4 - 5°. Number of cold days (from average temperature below 0°) decreases sharply from north to south.
In general, the sea has a negative (about 50 W/m) annual radiative heat balance on the surface, which is compensated by the constant influx of heat with waters entering through the Korea Strait. The water balance of the sea is determined mainly by its water exchange with adjacent basins through three straits: the Korean (inflow), Sangarsky and La Perouse (outflow). Compared to the amount of water exchange through the straits, the contribution to the water balance from precipitation, evaporation and continental runoff is negligible. Due to its insignificance, continental runoff exerts its influence only in coastal areas of the sea.
The main factors determining hydrological regime The Sea of Japan is the interaction of its surface waters with the atmosphere against the background of changing climatic conditions and water exchange through the straits with adjacent water basins. The first of these factors is decisive for the northern and northwestern parts of the sea. Here, under the influence of northwestern monsoon winds, bringing cold air masses from continental regions in the winter season, surface waters are significantly cooled as a result of heat exchange with the atmosphere. At the same time, an ice cover is formed in the shallow areas of the mainland coast, Peter the Great Bay and the Tatar Strait, and convection processes develop in the open areas of the sea adjacent to them. Convection covers significant layers of water (up to depths of 400-600 m), and in some abnormally cold years it reaches the bottom layers of the deep-sea basin, ventilating the cold, relatively homogeneous deep water mass, constituting 80% of the total volume of sea waters. Throughout the year, the northern and northwestern parts of the sea remain colder than the southern and southeastern parts.
Water exchange through the straits has a dominant influence on the hydrological regime of the southern and eastern half of the sea. The subtropical waters of the Kuroshio branch flowing through the Korea Strait throughout the year warm the southern regions of the sea and the waters adjacent to the coast of the Japanese islands up to the La Perouse Strait, as a result of which the waters of the eastern part of the sea are always warmer than the western.
This section briefly summarizes basic information about the spatial distribution and variability of seawater temperature and salinity, water masses, currents, tides and ice conditions in the Sea of Japan, based on published works and analysis of graphic material in the Atlas. All values of air and water temperature are given in degrees Celsius (o C), and salinity - in ppm (1 g/kg = 1‰).
On maps of the horizontal distribution of water temperature on the surface, the northern and southern parts of the sea are clearly separated by thermal front, the position of which remains approximately constant throughout all seasons of the year. This front separates the warm and salty waters of the southern sector of the sea from the colder and fresher waters of the northern part of the sea. The horizontal temperature gradient on the surface across the front varies throughout the year from maximum values of 16°/100 km in February to minimum values of 8°/100 km in August. In November-December, north of the main front, parallel to the Russian coast, a secondary front with a gradient of 4°/100 km is formed. The temperature difference within the entire sea area in all seasons remains almost constant and equal to 13-15°. The warmest month is August, when temperatures in the north are 13-14°, and in the south, in the Korea Strait, reach 27°. The lowest temperatures (0...-1.5 0) are typical for February, when ice forms in the northern shallow areas, and in the Korea Strait the temperature drops to 12-14°. The magnitude of seasonal changes in surface water temperature generally increases from southeast to northwest from minimum values (12-14 0) near the Korea Strait to maximum values (18-21 0) in the central part of the sea and near the bay. Peter the Great. Relative to the average annual values, negative temperature anomalies occur from December to May (during the winter monsoon), and positive ones - from June to November (summer monsoon). The strongest cooling (negative anomalies up to -9°) occurs in February in the region of 40-42°N, 135-137°E, and the greatest heating (positive anomalies of more than 11°) is observed in August near the Gulf of Petra Great.
With increasing depth, the range of spatial changes in temperature and its seasonal fluctuations at different horizons narrows significantly. Already at a horizon of 50 m, seasonal temperature fluctuations do not exceed 4-10 0. The maximum amplitudes of temperature fluctuations at this depth are observed in the southwestern part of the sea. At a horizon of 200 meters, average monthly water temperatures in all seasons increase from 0-1 0 in the north of the sea to 4-7° in the south. The position of the main front here does not change in relation to the surface one, but its meandering appears in the area between 131° and 138° E. In the central part of the basin to the north of the main front, the temperature at this horizon is 1-2 0, and to the south it increases abruptly to 4-5°. At a depth of 500 m, the temperature within the entire sea changes slightly. It is 0.3-0.9° and experiences virtually no seasonal variations. The frontal separation zone does not appear at this depth, although in the area adjacent to the coasts of Japan and Korea, there is a slight increase in temperature due to the transfer of heat to the deep layers by vortex formations actively forming in this area of the sea.
Among the regional features of the horizontal temperature distribution, upwelling zones, eddy formations and coastal fronts should be noted.
Upwelling southern shores Primorye is intensively developed in late October - early November, but individual cases of its fleeting manifestation can be identified in September - early October. The diameter of the cold water spot in the upwelling zone is 300 km, and the temperature difference between its center and the surrounding waters can reach 9 0 . The occurrence of upwelling is due not only to the strengthening of deep-sea circulation, but also, mainly, to the monsoon change of winds, which is confined to this particular period of time. Strong northwest winds blowing from the mainland create favorable conditions for the development of upwelling in the area. At the end of November, under the influence of cooling, the stratification in the upwelling zone is destroyed and the temperature distribution on the surface becomes more uniform.
In the coastal zone of the northwestern part of the Sea of Japan (in the region of the Primorsky Current), the frontal section is formed at the beginning of summer against the background of a general increase in the temperature of the surface layer. The main front runs parallel to the coastline. In addition to it, there are secondary fronts oriented perpendicular to the coast. In September-October, the main front is present only in the northern part of the sea, and to the south there are individual spots of cold water limited by the fronts. It is possible that the appearance of cold water cells near the coast is due to rapid cooling of the surface layer in shallow areas. These waters, after the final destruction of the thermocline, spread towards the open part of the sea in the form of continuous intrusions.
The most active vortex formations are formed on both sides of the front and, covering a significant thickness of water, introduce anomalies into the field of the horizontal temperature distribution.
The lack of water exchange between the Sea of Japan and neighboring basins at depths of more than 200 m, as well as active ventilation of deep layers due to autumn-winter convection in the northern and northwestern regions, lead to a clear division of the water column into two layers: near-surface active layer, characterized by seasonal variability, and deep, where both seasonal and spatial variability are almost undetectable. According to existing estimates, the boundary between these layers is located at depths of 300-500 m. Extreme depths (400-500 m) are confined to the southern part of the sea. This is due to the downward movement of water observed here in the center of the extensive anticyclonic meander of the East Korean Current, as well as variations in the position of the frontal zone on its northern and eastern boundaries. Up to a horizon of 400 m, seasonal temperature fluctuations can be traced off the coast of Japan, which is a consequence of the subsidence of water in anticyclonic gyres formed during the interaction of the Tsushima Current with the continental slope. High penetration depths of seasonal temperature fluctuations (up to 400-500 m) are found in the Strait of Tartary. This is mainly due to convective processes and significant seasonal variability in surface water parameters, as well as intra-annual variability in the intensity and spatial position of the water branch of the Tsushima Current. Off the coast of southern Primorye, seasonal variations in water temperature appear only in the upper three hundred-meter layer. Below this limit, seasonal temperature fluctuations are almost invisible. As can be seen in the vertical sections of the temperature field, the characteristics of the active layer undergo significant changes not only in the seasonal course, but also from region to region. The waters of the deep layer, which occupies about 80% of the sea's volume, are weakly stratified and have a temperature of 0.2 to 0.7°.
The thermal structure of the waters of the active layer consists of the following elements (layers): upper quasi-homogeneous layer(VKS), seasonal jump layer temperature and main thermocline. The characteristics of these layers in different seasons in the sea area have regional differences. Off the coast of Primorye in summer time year, the lower boundary of the UML is at a depth of 5-10 m, and in the southern regions of the sea it deepens to 20-25 m. In February, the lower boundary of the UML in the southern sector is at depths of 50-150 m. The seasonal thermocline intensifies from spring to summer. In August, the vertical gradient in it reaches a maximum of 0.36°/m. In October, the seasonal thermocline collapses and merges with the main one, located throughout the year at depths of 90-130 m. In the central regions of the sea, the noted patterns are preserved against the background of a general decrease in contrasts. In the northern and northwestern parts of the sea, the main thermocline is weakened and sometimes completely absent. The seasonal thermocline here begins to form with the beginning of the spring warming of the waters and exists until the winter period, when it is completely destroyed by convection within the entire water column of the active layer.
Horizontal distribution of salinity
Large-scale features of the distribution of salinity on the surface are determined by the water exchange of the sea with neighboring sea basins, the balance of precipitation and evaporation, ice formation and melting, as well as continental runoff in coastal areas.
In the winter season, over most of the sea surface, the water salinity exceeds 34, which is mainly due to the influx of highly saline waters (34.6) from the East China Sea. Less saline waters are concentrated in the coastal areas of the Asian mainland and islands, where their salinity decreases to 33.5-33.8. In the coastal areas of the southern half of the sea, the minimum salinity on the surface is observed in the second half of summer and early autumn, which is associated with rainfall in the second half of summer and the desalination of waters brought in from the East Kamchatka Sea. In the northern part of the sea, in addition to the summer-autumn decrease, a second minimum of salinity is formed in the spring during the period of melting of the ice of the Tatar Strait and Peter the Great Bay. The highest salinity values in the southern half of the sea occur in the spring-summer season, when the influx of salty Pacific waters from the East China Sea increases at this time. Characteristic is a gradual delay in salinity maxima from south to north. If in the Korea Strait the maximum occurs in March-April, then off the northern coast of Honshu Island it is observed in June, and off the La Perouse Strait in August. Along the mainland coast, maximum salinity occurs in August. The most saline waters are located near the Korea Strait. In spring, these features are largely preserved, but the area of lower salinity values in coastal areas due to melting ice and an increase in continental runoff, as well as the amount of precipitation, increases. Further towards summer, following the entry into the sea through the Korea Strait of surface waters of the East China Sea desalinated due to the abundance of precipitation, the general background salinity in the sea area decreases to values less than 34. In August, the range of salinity variability within the entire sea is 32.9-33.9. At this time, in the north of the Tatar Strait, salinity decreases to 31.5, and in certain areas of the coastal zone - to 25-30. In autumn, with the strengthening of northern winds, the waters of the upper layer are driven and mixed and a slight increase in salinity is observed. The minimum seasonal changes in salinity on the surface (0.5-1.0) are observed in the central part of the sea, and the maximum (2-15) in the coastal areas of the northern and northwestern parts and in the Korea Strait. At great depths, along with a general increase in salinity values, there is a sharp decrease in the range of its variability both in space and time. According to average long-term data, already at a depth of 50 m, seasonal changes in salinity in the central part of the sea do not exceed 0.2-0.4, and in the north and south of the water area – 1-3. At a horizon of 100 m, horizontal changes in salinity fall within the range of 0.5, and at a horizon of 200 m (Fig. 3.10) in all seasons of the year they do not exceed 0.1, i.e. values characteristic of deep waters. Somewhat higher values are observed only in the southwestern part of the sea. It should be noted that the horizontal distributions of salinity at depths greater than 150-250 m are very similar: minimum salinities are confined to the northern and northwestern parts of the sea, and maximum salinities are confined to the southern and southeastern parts. At the same time, the haline front, weakly expressed at these depths, completely repeats the outlines of the thermal one.
Vertical distribution of salinity
The vertical structure of the salinity field in different parts of the Sea of Japan is characterized by significant diversity. In the northwestern part of the sea, there is a monotonous increase in salinity with depth in all seasons of the year, with the exception of winter, when it is almost constant throughout the entire water column. In the southern and southeastern parts of the sea during the warm period of the year, below the desalinated surface waters, an intermediate layer of increased salinity is clearly visible, formed by highly saline waters (34.3-34.5) entering through the Korea Strait. Its core is located at depths of 60-100 m in the north and somewhat deeper in the south of the sea. To the north, salinity in the core of this layer decreases and on the periphery reaches values of 34.1. In the winter season this layer is not expressed. At this time of year, vertical changes in salinity in most of the water area do not exceed 0.6-0.7. In a limited area located east of the Korean Peninsula at depths of 100-400 m, an intermediate layer of low salinity is distinguished, which is formed in the winter season due to the subsidence of surface waters in the frontal interface zone. The salinity in the core of this layer is 34.00-34.06. Seasonal changes in the vertical structure of the salinity field are clearly visible only in the upper 100-250 m layer. The maximum depth of penetration of seasonal fluctuations in salinity (200-250 m) is noted in the zone of distribution of waters of the Tsushima Current. This is due to the peculiarities of the intra-annual variation of salinity in subsurface Pacific waters entering the sea through the Korea Strait. At the top of the Tatar Strait, off the coast of Primorye, Korea, as well as in the area to the south and southwest of the hall. Peter the Great, seasonal variations in salinity appear only in the upper 100-150-meter layer. Here, the influence of the waters of the Tsushima Current is weakened, and intra-annual changes in the salinity of the surface water layer, associated with ice formation processes and river runoff, are limited to the water areas of bays and bays. This area with minimal values of the depth of manifestation of seasonal fluctuations in salinity is interspersed with zones with higher values, the origin of which is associated with the penetration of branches of highly saline waters of the Tsushima Current to the northwestern shores of the sea. A general idea of the vertical structure of the salinity field is given by spatial sections of the distribution of this characteristic and the tabular values given in the atlas.
Water masses
In accordance with the considered features of the spatiotemporal variability of temperature and salinity, the water column of the Sea of Japan consists of various water masses, the classification of which is carried out mainly according to the extreme elements of the vertical distribution of salinity.
By verticals The water masses of the open part of the Sea of Japan are divided into surface, intermediate and deep. Superficial The water mass (its varieties: PSA - subarctic, PVF - frontal zones, PST - subtropical) is located within the upper mixed layer and is limited from below by the seasonal thermocline. In the warm southern sector (PST) it is formed as a result of the mixing of waters coming from the East China Sea and the coastal waters of the Japanese Islands, and in the cold northern sector (PSA) - by the mixing of coastal waters desalinated by continental runoff with waters open areas adjacent part of the sea. As shown above, throughout the year the temperature and salinity of surface waters vary over a wide range, and their thickness ranges from 0 to 120 m.
In the below intermediate In the water layer over most of the sea in the warm period of the year, a water mass of high salinity is released (its varieties: PPST - subtropical, PPSTT - transformed), the core of which is located at depths of 60-100 m, and the lower boundary at a depth of 120-200 meters. The salinity in its core is 34.1-34.8. In a local area east of the coast of the Korean Peninsula, at depths of 200-400 m, a water mass of low (34.0-34.06) salinity is sometimes identified.
Deep The water mass, usually called the water of the Sea of Japan proper, covers the entire lower layer (deeper than 400 m) and is characterized by uniform temperatures (0.2-0.7°) and salinity (34.07-34.10). The high content of dissolved oxygen in it indicates the active renewal of deep layers by surface waters.
IN coastal areas In the northwestern part of the sea, due to significant freshening by continental runoff, increased tidal phenomena, wind upwellings and winter convection, a specific coastal water structure is formed, represented by a vertical combination of surface waters (SW) less saline than the waters of adjacent areas of the open sea, and having more significant temperature fluctuations, as well as subsurface waters (SSW) of higher salinity and lower temperature formed during winter convection. In some areas (Tatar Strait, Peter the Great Bay), during intense ice formation in winter, a highly saline (up to 34.7 and very cold (up to -1.9 0)) water mass (WM) is formed. Spreading near the bottom, it can reach the shelf edge and flow along the continental slope, participating in the ventilation of deep layers.
On the part of the shelf, where desalination by continental runoff is small, the stratification of waters is weakened or even destroyed by tidal mixing. As a result, a weakly stratified shelf structure is formed, consisting of a relatively cold desalinated surface shelf water mass (SH) and a relatively warm and desalinated shelf modification of deep waters (GS). At certain directions of prevailing winds, this structure is distorted by the phenomenon of upwelling. In winter, it is destroyed by a more powerful mechanism - convection. The waters formed in the tidal mixing zones are drawn into the circulation existing in the northwestern part of the sea and spread beyond the region of their formation, usually considered as “waters of the Primorsky Current.”
| Characteristics of water structures and water masses in the northwestern part |
||||
| Sea of Japan (numerator - February, denominator - August) |
||||
| Water structure |
Water masses |
Depths, m |
Temperature, |
Salinity, ‰ |
| Subtropical |
0-200 |
> 8 |
33,9-34,0 |
|
| 0-20 |
> 21 |
33,6-33,8 |
||
| absent |
absent |
absent |
||
| 30-200 |
10-15 |
34,1-34,5 |
||
| Deep |
>200 |
0-2 |
33,9-34,1 |
|
| >200 |
34,0-34,1 |
|||
| Polar zones |
0-50 |
3 - 6 |
33,9-34,0 |
|
| 0-30 |
18-20 |
33,5-33,9 |
||
| absent |
absent |
absent |
||
| 30-200 |
33,8-34,1 |
|||
| Deep |
>50 |
0-2 |
33,9-34,1 |
|
| >200 |
33,9-34,1 |
|||
| Subarctic |
0-bottom |
0-3 |
33,6-34,1 |
|
| 0-20 |
16-18 |
33,1-33,7 |
||
| Deep |
0-bottom |
0-3 |
33,6-34,1 |
|
| 33,9-34,1 |
||||
| Coastal |
absent |
absent |
absent |
|
| 0-20 |
16-19 |
>32,9 |
||
| 0-bottom |
-2 - -1 |
>34,0 |
||
| absent |
absent |
|||
| absent |
absent |
absent |
||
| 1 - 5 |
33,2-33,7 |
|||
| Convection zones |
0-bottom |
-1 - 1 |
33,7-34,0 |
|
| on the shelf |
||||
| Offshore |
absent |
absent |
absent |
|
| 0-20 |
33,0-33,5 |
|||
| absent |
absent |
absent |
||
| 33,4-33,8 |
||||
Note: In February, the surface and deep water masses of the subarctic structure do not differ in their thermohaline characteristics.
Water circulation and currents
The main elements of the water circulation diagram given in the atlas are the warm currents of the southern and eastern and cold currents of the northwestern sectors of the sea. Warm currents are initiated by the influx of subtropical waters entering through the Korea Strait and are represented by two streams: the Tsushima Current, consisting of two branches - calm-sea and more turbulent, moving under the very coast of Honshu Island, and the East Korean Current, spreading as a single stream along the coast of the Korean Peninsula. At latitude 38-39° N. The East Korean Current is divided into two branches, one of which, bending around the Yamato Rise from the north, follows in the direction of the Sangar Strait, the other, deviating to the southeast, part of the water closes the anticyclonic circulation off the southern coast of Korea, and the other merges with the seaward branch Tsushima Current. The combination of all branches of the Tsushima and East Korean currents into a single flow occurs at the Sangar Strait, through which the main part (70%) of the incoming warm subtropical waters is carried out. The rest of these waters move further north towards the Strait of Tartary. Upon reaching the La Perouse Strait, the bulk of this flow is carried out of the sea and only a small part of it, spreading within the Tatar Strait, gives rise to a cold current spreading southward along the mainland coast of Primorye. Divergence zone at 45-46° N. this current is divided into two parts: the northern - Limannoye (Schrenk) Current and the southern - Primorsky Current, which south of the Peter the Great Gulf is divided into two branches, one of which gives rise to the cold North Korean Current, and the other turns to the south and, in contact with the northern flow of the East Korean Current, forms a large-scale cyclonic gyre centered at 42°N, 138°E. over the Sea of Japan basin. The cold North Korean Current reaches 37° N, and then merges with the powerful flow of the warm East Korean Current, forming, together with the southern branch of the Primorsky Current, a frontal separation zone. The least pronounced element of the general circulation pattern is the West Sakhalin Current, which flows southward from latitude 48° N. along the southern coast of the island. Sakhalin and carrying part of the water flow of the Tsushima Current, which separated from it in the waters of the Tatar Strait.
Throughout the year, the noted features of water circulation are practically preserved, but the power of the main currents changes. In winter, due to a decrease in water influx, the speed of both branches of the Tsushima Current does not exceed 25 cm/s, with the coastal branch having greater intensity. The total width of the current of about 200 km remains in the summer, but the speeds increase to 45 cm/s. The East Korean Current also intensifies in summer, when its speed reaches 20 cm/s and its width reaches 100 km, and attenuates in winter to 15 cm/s and is reduced in width to 50 km. The speed of cold currents throughout the year does not exceed 10 cm/s, and their width is limited to 50-70 km (with a maximum in summer). In transition seasons (spring, autumn), current characteristics have average values between summer and winter. Current velocities in layer 0-25 are almost constant, and with a further increase in depth they decrease to half the surface value at a depth of 100 meters. The atlas shows water circulation patterns on the surface of the Sea of Japan in different seasons, obtained by calculation methods.
Tidal phenomena
Tidal movements in the Sea of Japan are formed predominantly by the semidiurnal tidal wave M, which is almost purely standing, with two amphidromic systems located near the borders of the Korea and Tartary Straits. Synchronous oscillations of the tidal profile of sea level and tidal currents in the Tatar and Korean straits are carried out according to the law of a two-node seiche, the antinode of which covers the entire central deep-water part of the sea, and the nodal lines are located near the boundaries of these straits.
In turn, the relationship of the sea with adjacent basins through three main straits contributes to the formation of an induced tide in it, the influence of which, based on morphological features (shallow water of the straits compared to the depth of the sea), affects the straits and areas immediately adjacent to them. The sea experiences semi-diurnal, diurnal and mixed tides. The greatest level fluctuations are observed in the extreme southern and northern regions 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 it does not exceed 1.5 m. In the middle part of the sea, the tides are small. Along eastern shores Korea and Russian Primorye before entering the Tatar Strait they are no more than 0.5 m. The tides are of the same magnitude off the western coasts of Honshu, Hokkaido and southwestern Sakhalin. In the Tatar Strait, the magnitude of the tides is 2.3-2.8 m. The increase in the magnitude of the tides in the northern part of the Tatar Strait is determined by its funnel-shaped shape.
In open areas of the sea, semidiurnal symptoms are mainly observed. tidal currents with speeds of 10-25 cm/s. Tidal currents in the straits are more complex, where they have very significant speeds. Thus, in the Sangar Strait, the speed of tidal currents reaches 100-200 cm/s, in the La Perouse Strait - 50-100 cm/s, in the Korean Strait - 40-60 cm/s.
Ice conditions
According to ice conditions, the Sea of Japan can be divided into three areas: the Strait of Tartary, 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 does not always form. The coldest area is the Strait of Tartary, where more than 90% of all ice observed in the sea is formed and localized during the winter season. According to long-term data, the duration of the period with ice in the Peter the Great Gulf 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 bays, closed from wind and waves and having a desalinated surface layer. In moderate winters in Peter the Great Bay, the first ice forms in the second ten days of November, and in the Tatar Strait, at the tops of Sovetskaya Gavan, Chekhacheva Bays and Nevelskoy Strait, primary forms of ice are observed already in early November. Early ice formation in the Peter the Great Gulf (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 occurs faster than near the mainland coast. Accordingly, at this time there is more ice in the eastern part of the Tatar Strait than in the western part. By the end of December, the amount of ice in the eastern and western parts is equalized, and after reaching the parallel of Cape Syurkum, the direction of the edge changes: its displacement along the Sakhalin coast slows down, and along the continental coast it intensifies.
In the Sea of Japan, the ice cover reaches its maximum development in mid-February. On average, ice covers 52% of the area of the Tatar Strait and 56% of the Peter the Great Bay.
Ice melting begins in the first half of March. In mid-March, the open waters of Peter the Great Bay are cleared of ice and all seaside coast to Cape Zolotoy. The ice boundary in the Tatar Strait retreats to the northwest, and in the eastern part of the strait clearing of ice occurs at this time. Early clearing of the sea from ice occurs in the second ten days of April, later - at the end of May - beginning of June.
Hydrological conditions of the hall. Peter the Great and coastal
zones of Primorsky Krai
Peter the Great Bay is the largest in the Sea of Japan. It is located in the northwestern part of the sea between parallels 42 0 17 "and 43 ° 20" N. w. and meridians 130°41" and 133°02" E. d. The waters of Peter the Great Bay are limited from the sea by a line connecting the mouth of the Tumannaya River (Tyumen-Ula) with Cape Povorotny. Along this line, the width of the bay reaches almost 200 km.
The Muravyov-Amursky Peninsula and group of islands, located to the southwest of it, Peter the Great Bay is divided into two large bays: Amursky and Ussuriysky. Amur Bay represents the northwestern part of Peter the Great Bay. From the west it is limited by the coast of the mainland, and from the east by the mountainous Muravyov-Amursky peninsula and the islands of Russky, Popov, Reinike, and Ricord. Southern border The Amur Bay is a line connecting Cape Bruce with the islands of Tsivolko and Zheltukhin. The bay extends in a northwest direction for approximately 70 km, and its width, averaging 15 km, ranges from 13 to 18 km. Ussuri Bay occupies the northeastern part of Peter the Great Bay. From the northwest it is limited by the Muravyov-Amursky Peninsula, Russky Island and those lying southwest of last islands. The southern border of the bay is considered to be the line connecting the southern ends of the Zheltukhin and Askold islands.
The area of Peter the Great Bay is about 9 thousand km 2, and the total length of the coastline, including islands, is about 1500 km. In the vast water area of the bay there are many different areas islands, concentrated mainly in the western part of the bay in the form of two groups. The northern group is located southwest of the Muravyov-Amursky Peninsula and is separated from it by the Eastern Bosphorus Strait. This group consists of four large and many small islands. The largest in this group is Russky Island. The southern group - the Rimsky-Korsakov Islands - includes eight islands and many islets and rocks. The most significant in it is the island of Bolshoi Pelis. There are two more in the eastern part of the bay big islands: Putyatina, located in the middle of Strelok Bay, and Askold, lying southwest of Putyatina Island.
The most significant strait is the Eastern Bosphorus, separating Russky Island from the Muravyov-Amursky Peninsula. The straits between the Rimsky-Korsakov islands are deep and wide; between the islands adjacent directly to the Muravyov-Amursky Peninsula, the straits are narrower.
The coastline of Peter the Great Bay is very winding and forms many secondary bays and bays. The most significant of them are the bays of Posiet, Amursky, Ussuriysky, Strelok, Vostok and Nakhodka (America). The western coast of the southern part of the Amur Bay juts out into the Slavyansky Bay, Tabunaya, Narva and Perevoznaya bays. The coastline of the northeastern part of the Amur and northwestern part of the Ussuri Bay is relatively weakly indented. On the eastern shore of the Ussuri Bay, the bays of Sukhodol, Andreeva, Telyakovsky, Vampausu and Podyapolsky stand out. Capes protruding far into the sea form rocky, mostly steep shores bordered by stones. The largest of peninsulas are: Gamow, Bruce and Muravyov-Amursky.
Bottom relief Peter the Great Bay is characterized by developed shallow waters and a steep continental slope, indented by underwater canyons. The continental slope runs 18 and 26 miles south of the Askold and Rikord islands, almost parallel to the line connecting the mouth of the Tumannaya River and Cape Povorotny. The bottom in Peter the Great Bay is quite flat and rises smoothly from south to north. In the eastern part of the bay, depths reach 100 m or more, and in the western part they do not exceed 100 m. Seaward of the entrance to the bay, the depths increase sharply. On the continental slope, in a strip 3 to 10 miles wide, depths vary from 200 to 2000 m. Secondary bays - Amursky, Ussuriysky, Nakhodka - are shallow. In the Amur Bay, the bottom topography is quite flat. Extensive shallows extend from the shores of the bay's head. From the northwestern coast of Russky Island to the opposite shore of the bay, an underwater threshold with depths of 13-15 m stretches. At the entrance to the Ussuriysky Bay, the depths are 60-70 m, then decrease to 35 m in the middle part of the bay and to 2-10 m at the top . In Nakhodka Bay, depths at the entrance reach 23-42 m, in the middle part 20-70 m, and the top of the bay is occupied by shallow water with depths of less than 10 m.
Meteorological regime Peter the Great Bay, determine the monsoon circulation of the atmosphere, geographical position area, the influence of the cold Primorsky and warm Tsushima (in the south) currents. From October-November to March, due to the action of the formed baric centers of the atmosphere (Asian maximum of atmospheric pressure and Aleutian minimum), cold continental air is transferred from the mainland to the sea (winter monsoon) . As a result, frosty, partly cloudy weather sets in in Peter the Great Bay. big amount precipitation and the predominance of winds from the north and northwest directions. In spring, the wind regime is unstable, the air temperature is relatively low and long periods of dry weather are possible. The summer monsoon operates from May-June to August-September. In this case, a transfer occurs sea air to the mainland and there is warm weather with relatively high amounts of precipitation and fog. Autumn in Peter the Great Bay is best time year - usually warm, dry, with a predominance of clear, sunny weather. Warm weather lasts in some years until the end of November. The generally stable monsoon weather pattern is often disrupted by intense cyclonic activity. The passage of cyclones is accompanied by an increase in cloudiness to continuous, heavy precipitation, deterioration of visibility and significant storm activity. The average annual precipitation in the Vladivostok region reaches 830 mm. Atmospheric precipitation is minimal in January and February (10-13 mm). Summer accounts for 85% of the annual precipitation, with an average of 145 mm falling in August. In some years, precipitation comparable in quantity to monthly norms can be sudden, short-term in nature and lead to natural disasters.
In the annual course of average long-term monthly values atmospheric pressure the minimum (1007-1009 mb) is observed in June-July, and the maximum (1020-1023 mb) in December-January. In the Amur and Ussuri Bays, the range of pressure fluctuations from maximum to minimum values gradually increases with distance from coastal areas to more continental ones. Short-term changes in pressure during the daily cycle reach 30-35 mb and are accompanied by sharp fluctuations in wind speed and direction. In fact, the recorded maximum pressure values in the Vladivostok region are 1050-1055 mb.
Average annual t air temperature is approximately 6°. The coldest month of the year is January, when the average monthly air temperature in the northern part of the Amur and Ussuri bays is -16°...-17°. At the top of the Amur and Ussuri bays, the air temperature can drop to -37°. The warmest month of the year is August, when the average monthly temperature rises to +21°.
During the winter monsoon period, from October-November to March, winds northern and northwestern directions. In the spring, when the winter monsoon changes to summer, the winds are less stable. In summer, southeast winds prevail in the bay. Calm is more often observed in the summer. The average annual wind speed varies from 1 m/s (at the top of the Amur Bay) to 8 m/s (Askold Island). On some days the wind speed can reach 40 m/sec. In summer, the wind speed is lower. At the tops of the Amur and Ussuri bays, the average monthly wind speed is 1 m/s, in bays and bays - 3-5 m/s. Storms are mainly associated with cyclonic activity and are observed mainly during the cold period of the year. The greatest number of days with stormy winds is observed in December-January and amounts to 9-16 per month. At the tops of the Amur and Ussuri bays, storm winds are not observed every year.
They come to Peter the Great Bay typhoons, originating in tropical latitudes, in the area of the Philippine Islands. Approximately 16% of all tropical cyclones emerging there enter the Sea of Japan and the Primorsky Territory mainly in August-September. The paths of their movement are very diverse, but none follows the trajectory of the other exactly. If the typhoon does not enter Peter the Great Bay and is observed only in the southern part of the Sea of Japan, it still affects the weather in this area: heavy rains occur and the wind increases to stormy winds.
Hydrological characteristics
Horizontal temperature distribution
Surface water temperatures experience significant seasonal variability, mainly due to the interaction of the surface layer with the atmosphere. In spring, the water temperature in the surface layer of the bay varies within 4-14°C. At the tops of the Amur and Ussuri bays it reaches 13-14° and 12°, respectively. In general, the Amur Bay is characterized by higher temperatures than the Ussuri Bay. In summer, the waters of the bay warm up well. At this time, at the tops of the Amur and Ussuri bays it reaches 24-26°, in the Gulf of America - 18°, and in the open part of the bay - 17°. In autumn, the temperature drops to 10-14° in the secondary bays and to 8-9° in the open part. In winter, the entire mass of water cools, its temperature ranges from 0 to –1.9°. Freezing temperatures occur throughout the shallow waters, as well as in the secondary bays. The position of the 0° isotherm approximately coincides with the 50-meter isobath. At this time, the waters of the open part of the bay are warmer than the coastal ones and are characterized by positive temperature values. With increasing depth, the range of temperature changes decreases and already at a depth of 50 m does not exceed 3°, and at depths of more than 70 meters, seasonal changes hardly appear.
Vertical temperature distribution
During the warm period of the year (April-November), a monotonous decrease in temperature with depth is observed. At this time, a seasonal thermocline layer is formed on the subsurface horizons - everywhere except in shallow waters, where the entire water column is well heated and mixed. In autumn, with the onset of the winter monsoon and cooling, cold deep waters rise in shallow waters and a second layer of temperature jump is formed at a depth of 40 m. In December, both layers of the temperature jump are destroyed under the influence of convection, and throughout the winter period (from December to March) the temperature remains constant throughout the entire water column of the bay.
Salinity distribution
The orographic conditions of the bay and the influence of continental runoff create a unique regime of salinity distribution and variability. The water in some coastal areas of the bay is desalinated to brackish, and in open areas it is close to the salinity of the adjacent part of the sea. The annual variation of salinity is characterized by a minimum in summer and a maximum in winter. In spring, the minimum salinity values on the surface are confined to the top of the Amur Bay, where they are 28. At the top of the Ussuri Bay, salinity is 32.5, and in the rest of the water area it rises to -33-34. In summer, the surface layer is subject to the greatest desalination. At the top of the Amur Bay, salinity is 20%, and in general in coastal waters and secondary bays it does not exceed 32.5 and increases in open areas to 33.5. In autumn, the horizontal distribution of salinity is similar to that in spring. In winter, throughout the entire water area of the bay, salinity is close to 34. At depths of more than 50 meters, salinity varies within the water area of the bay in the range of 33.5-34.0.
As depth increases, salinity usually increases (spring-autumn) or remains constant (winter). In the bottom layer of the bay, due to the process of salinization during the formation of ice in the winter months, high-density waters with a temperature of less than -1.5° and a salinity of 34.2-34.7 are formed. In extremely ice-covered years, high-density waters, spreading near the bottom, reach the shelf edge, roll down along the slope and ventilate the deep sea layers.
Water masses
In the winter season, in the Peter the Great Gulf, the water characteristics throughout its entire thickness correspond to the deep water mass of the Sea of Japan (temperature less than 1°, salinity - about 34). In the bottom 20-meter layer during this period of time, a water mass of increased density with low (up to –1.9°) temperature and high (up to 34.8) salinity is released, which disappears already in mid-March, mixing with the surrounding waters.
In the summer season, due to an increase in heat influx and continental runoff, stratification of the water column occurs. In coastal areas, especially in areas where fresh water flows from river mouths, there is an estuarine water mass with low (on average 25) salinity, high (on average 20°) temperature in the summer season and a distribution depth of up to 5-7 meters. The water masses of the open areas of the bay are divided by the seasonal thermocline into: surface coastal, which extends extremely from the surface to a depth of 40 m and in summer has the indices: temperature - 17-22°, salinity - 30-33; subsurface - to a depth of 70 m with a temperature of 2-16° and a salinity of 33.5-34.0; and deep shelf - below the horizon 70 m to the bottom with a temperature of 1-2° and a salinity of about 34.
Currents
Water circulation in Peter the Great Bay is formed under the influence of constant currents of the Sea of Japan, tidal, wind and runoff currents. In the open part of the bay, the Primorsky Current is clearly visible, which spreads in a southwestern direction at speeds of 10-15 cm/s. In the southwestern part of the bay, it turns south and gives rise to the North Korean Current, which is most pronounced at subsurface levels. In the Amur and Ussuri Bays, the influence of the Primorsky Current is clearly manifested only in the absence of wind, when an anticyclonic water circulation is formed in the Ussuri Bay, and a cyclonic one in the Amur Bay. Wind, tidal phenomena and the flow of the Razdolnaya River (in the Amur Bay) cause a significant restructuring of the current field. Diagrams of the main components of the total currents of the Amur and Ussuriysk bays, given in the atlas, show that the greatest contribution is made by wind currents, which in the winter season strengthen the anticyclonic circulation in the Ussuriysk gulf, and in the summer change it to cyclonic. When cyclones pass, the speeds of the total currents on the surface can reach 50 cm/s.
Tidal phenomena
The semi-diurnal tidal wave enters Peter the Great Bay from the southwest and spreads to the secondary bays of Posyet, Ussuriysky and America. She runs around the bay in a period of less than one hour. The time of onset of full water of the semidiurnal tide is slowed down in closed bays and secondary bays separated by islands and peninsulas. The maximum possible tide level (during the day) in the bay is 40-50 cm. Tidal level fluctuations are most well developed in the Amur Bay, in its northwestern region, where the maximum level slightly exceeds 50 cm, and least of all in the Ussuri Bay and the strait between about. Putyatin and the mainland (tide level up to 39 cm). Tidal currents in the bay are insignificant and maximum speeds do not exceed 10 cm/s.
Ice conditions
Ice regime the area practically does not interfere with regular navigation throughout the year. In the gulf, ice occurs in the winter season in the form of fast ice and drifting ice. Ice formation begins in mid-November in the bays of the Amur Bay. At the end of December, most of the bays of the Amur and partly Ussuri Bays are completely covered with ice. Drifting ice is observed in the open part of the sea. The ice cover reaches its maximum development in late January - mid-February. Since the end of February, the ice situation has eased, and in the first half of April, the bay’s water area is usually completely cleared of ice. In severe winters, especially in the first ten days of February, the ice reaches a high concentration, which excludes the possibility of ships sailing without the use of an icebreaker.
Hydrochemical characteristics
In this version of the atlas, hydrochemical characteristics are presented in the form of distribution maps at various horizons of average long-term values of dissolved oxygen (ml/l), phosphates (μM), nitrates (μM), silicates (μM) and chlorophyll (μg/l) for winter and spring , summer and autumn without additional description. In the data source used (WOA"98), the time frame of the hydrological seasons is defined as follows: Winter: January-March. Spring: April-June. Summer: July-September. Autumn: October-December.
Hydrological-acoustic characteristics
The main changes in sound speed values, both seasonal and spatial, occur in the 0-500 m layer. The difference in sound speed values in the same season on the sea surface reaches 40-50 m/s, and at a depth of 500 m – 5 m/s With. The maximum values are noted in the southern and southeastern parts of the sea, and the minimum in the northern and northwestern parts. The range of seasonal changes in the speed of sound in both zones is approximately the same and reaches 35-45 m/s. The frontal zone runs from southwest to northeast through the central part of the sea. Here, in the 0-200 m layer, maximum horizontal gradients of sound speed values are observed at any time of the year (from 0.2 s‾¹ in summer to 0.5 s‾¹ in winter). In this case, the maximum changes in horizontal sound speed values are observed in summer at a depth of 100 m.
Based on the vertical distribution of sound speed in the southern and southeastern parts of the sea, we can distinguish:
- the upper homogeneous layer, the thickness of which varies from 50 to 150 m throughout the year, with sound speed values of more than 1490-1500 m/s;
- a layer of jump in sound speed values with large negative gradients (on average 0.2-0.4 s‾¹), extending to a depth of 300 m;
- layer 300-600 m with minimum values (and gradients) of sound speed;
- Below 600 m there is a constant increase in the speed of sound, mainly due to an increase in hydrostatic pressure.
The PZK axis is located at depths of 300–500 m, and off the coast of Japan at 40º N. w. drops to 600 m. The sound channel extends from the surface to the bottom.
In the northern and northwestern parts of the sea, a homogeneous layer, but with minimal values of sound speed (less than 1455 m/s) is formed in winter and is associated with winter convection. The thickness of the layer can reach 600 m, and a surface sound channel is formed. During the rest of the year, changes in sound speed with depth are characterized by negative gradients, increasing from spring to autumn to 0.5-0.8 s‾¹ in a layer of 0-100 m, minimal gradients in a layer up to 500 m thick, and then an increase in sound speed at constant gradient value. The PZK axis with minimum sound speed values of 1455-1460 m/s in this part of the sea comes to the surface in winter, and from spring to autumn gradually drops to a depth of 200-300 m. When moving south in the front area, the PZK axis sharply deepens to 300 m In the central part of the sea, the width of the sound channel in winter does not exceed 1000-1200 m, in spring it increases to 1500 m, and in summer and early autumn it is determined only by the depth of the place.
The Sea of Japan lies between the continent of Asia, the Korean Peninsula, and Sakhalin and the Japanese islands, separating it from the ocean and two neighboring seas. In the north, the border between the Sea of Japan and the Sea of Okhotsk runs along the line between Cape Sushchev and Cape Tyk on Sakhalin. In the La Perouse Strait, the border is the line between Cape Soya and Cape Crillon. In the Sangar Strait, the border runs along the line of Cape Syria - Cape Estan, and in the Korea Strait - along the line of Cape Nomo (Kyushu Island) - Cape Fukae (Goto Island) - Island. Jeju - Korean Peninsula.
The Sea of Japan is one of the largest and deepest seas in the world. Its area is 1062 km 2, volume - 1631 thousand km 3, average depth - 1536 m, greatest depth - 3699 m. This is a marginal oceanic sea.
There are no large islands in the Sea of Japan. Of the small ones, the most significant are the islands of Moneron, Rishiri, Okushiri, Ojima, Sado, Okinoshima, Ullyndo, Askold, Russky, and Putyatina. Tsushima Island is located in the Korea Strait. All islands (except Ulleungdo) are located near the coast. Most of them are located in the eastern part of the sea.
The coastline of the Sea of Japan is relatively slightly indented. The simplest in outline is the coast of Sakhalin; the coasts of Primorye and the Japanese Islands are more winding. The large bays of the mainland coast include De-Kastri, Sovetskaya Gavan, Vladimir, Olga, Peter the Great, Posyet, Koreysky, on the island. Hokkaido - Ishikari, on the island. Honshu - Toyama and Wakasa.
Landscapes of the Sea of Japan
The coastal boundaries are cut through by straits that connect the Sea of Japan with the Pacific Ocean, the Sea of Okhotsk and the East China Sea. The straits vary in length, width and, most importantly, depth, which determines the nature of water exchange in the Sea of Japan. Through the Sangar Strait, the Sea of Japan communicates directly with the Pacific Ocean. The depth of the strait in the western part is about 130 m, in the eastern part, where it is located maximum depths, about 400 m. The Nevelskoy and La Perouse straits connect the Japanese and Sea of Okhotsk. The Korea Strait, divided by the islands of Jeju, Tsushima and Ikizuki into the western (Broughton passage with the greatest depth of about 12.5 m) and eastern (Kruzenshtern passage with the greatest depth of about 110 m) parts, connects the Sea of Japan and the East China Sea. The Shimonoseki Strait, with depths of 2-3 m, connects the Sea of Japan with the Inland Sea of Japan. Due to the shallow depths of the straits and the great depths of the sea itself, conditions are created for isolating its deep waters from the Pacific Ocean and adjacent seas, which is the most important natural feature Sea of Japan.
The coast of the Sea of Japan, varied in structure and external forms in different areas, belongs to different morphometric types of coasts. These are predominantly abrasive, mostly unaltered, shores. To a lesser extent, the Sea of Japan is characterized by accumulative shores. This sea is surrounded by predominantly mountainous shores. In some places, single rocks - kekurs - characteristic formations of the Sea of Japan coast rise from the water. Low-lying shores are found only on certain sections of the coast.
Bottom relief
Bottom topography and currents of the Sea of Japan
According to the nature of the bottom topography, the Sea of Japan is divided into three parts: northern - north of 44° N, central - between 40 and 44° N. and southern - south of 40° N.
The northern part of the sea is like a wide trench, gradually rising and narrowing towards the north. Its bottom in the direction from north to south forms three steps, which are separated from one another by clearly defined ledges. The northern step is located at a depth of 900-1400 m, the middle one is at a depth of 1700-2000 m, and the southern step is at a depth of 2300-2600 m. The surfaces of the steps are slightly inclined to the south.
The coastal sandbank of Primorye in the northern part of the sea is approximately 20 to 50 km long, the edge of the sandbank is located at a depth of about 200 m.
The surfaces of the northern and middle steps of the central trench are more or less level. The relief of the southern step is significantly complicated by numerous individual uplifts up to 500 m high. Here, on the edge of the southern step, at a latitude of 44°, there is a vast hill called “Vityaz” with a minimum depth above it of 1086 m.
The southern step of the northern part of the Sea of Japan breaks off with a steep ledge to the bottom of the central basin. The steepness of the ledge is on average 10-12°, in some places 25-30°, and the height is approximately 800-900 m.
The central part of the sea is a deep closed basin, slightly elongated in the east-northeast direction. From the west, north and east it is limited by the steep slopes of mountain structures sloping into the sea in Primorye, the Korean Peninsula, the islands of Hokkaido and Honshu, and from the south by the slopes of the Yamato underwater hill.
In the central part of the sea, coastal shallows are very poorly developed. A relatively wide sandbank is found only in the area of southern Primorye. The edge of the shallows in the central part of the sea is very clearly expressed throughout its entire length. The bottom of the basin, located at a depth of about 3500 m, in contrast to the complexly dissected surrounding slopes, is leveled. On the surface of this plain there are isolated hills. Approximately in the center of the basin there is an underwater ridge stretching from north to south with a height of up to 2300 m. The southern part of the sea has a very complex topography, since in this area there are the marginal parts of large mountain systems- Kuril-Kamchatka, Japanese and Ryu-Kyu. Here is the vast underwater Yamato Rise, which consists of two ridges elongated in the east-northeast direction with a closed basin located between them. From the south, a wide underwater ridge of approximately meridional strike adjoins the Yamato Rise.
In many areas of the southern part of the sea, the structure of the underwater slope is complicated by the presence of underwater ridges. On the underwater slope of the Korean Peninsula, wide underwater valleys can be traced between the ridges. The continental shelf is no more than 40 km wide throughout almost its entire length. In the area of the Korea Strait, the shallows of the Korean Peninsula and about. The Honshu close together and form shallow waters with depths of no more than 150 m.
Climate
The Sea of Japan lies entirely in the monsoon climate zone of temperate latitudes. In the cold season (from October to March) it is influenced by the Siberian anticyclone and the Aleutian low, which is associated with significant horizontal gradients of atmospheric pressure. In this regard, strong northwest winds with speeds of 12-15 m/s and more dominate over the sea. Local conditions change wind conditions. In some areas, under the influence of coastal topography, there is a high frequency of northern winds, while in others, calms are often observed. On southeast coast The regularity of the monsoon is disrupted; western and northwestern winds predominate here.
During the cold season, continental cyclones enter the Sea of Japan. They cause strong storms, and sometimes severe hurricanes, which last for 2-3 days. At the beginning of autumn (September), tropical cyclones-typhoons sweep over the sea, accompanied by hurricane winds.
The winter monsoon brings dry and cold air to the Sea of Japan, the temperature of which increases from south to north and from west to east. In the coldest months - January and February - the average monthly air temperature in the north is about -20°, and in the south about 5°, although significant deviations from these values are often observed. During the cold seasons, the weather is dry and clear in the northwestern part of the sea, wet and cloudy in the southeast.
In warm seasons, the Sea of Japan is affected by the Hawaiian High and, to a lesser extent, by the depression that forms in the summer over Eastern Siberia. In this regard, southern and southwestern winds prevail over the sea. However, pressure gradients between areas of high and low pressure are relatively small, so wind speeds average 2-7 m/s. A significant increase in wind is associated with the entry of oceanic, and less often continental, cyclones into the sea. In summer and early autumn (July-October), the number of typhoons over the sea increases (with a maximum in September), causing hurricane-force winds. In addition to the summer monsoon, strong and hurricane winds associated with the passage of cyclones and typhoons, local winds are observed in different areas of the sea. They are mainly caused by the peculiarities of coastal orography and are most noticeable in the coastal zone.
In the Far Eastern seas
The summer monsoon brings warm and humid air. Average monthly temperature the warmest month - August - in the northern part of the sea is approximately 15°, and in the southern regions about 25°. In the northwestern part of the sea, significant cooling is observed due to the influx of cold air brought by continental cyclones. In spring and summer, cloudy weather with frequent fogs prevails.
A distinctive feature of the Sea of Japan is the relatively small number of rivers flowing into it. The largest of them is Suchan. Almost all rivers are mountainous. Continental flow into the Sea of Japan is approximately 210 km 3 /year and is fairly evenly distributed throughout the year. Only in July does the river flow increase slightly.
The geographical location, the outlines of the sea basin, separated from the Pacific Ocean and adjacent seas by high thresholds in the straits, pronounced monsoons, water exchange through the straits only in the upper layers are the main factors in the formation of the hydrological conditions of the Sea of Japan.
The Sea of Japan receives a large amount of heat from the sun. However, the total heat consumption for effective radiation and evaporation exceeds the supply of solar heat, therefore, as a result of processes occurring at the water-air interface, the sea loses heat annually. It is replenished by the heat brought by Pacific waters entering the sea through the straits, therefore, on the average long-term value, the sea is in a state of thermal equilibrium. This indicates the important role of water heat exchange, mainly heat influx from outside.
Hydrology
Significant natural factors are the exchange of water through the straits, the flow of precipitation onto the sea surface and evaporation. The main influx of water into the Sea of Japan occurs through the Korea Strait - about 97% of the total annual amount of incoming water. The largest flow of water goes through the Sangar Strait - 64% of the total flow; 34% flows through the La Perouse and Korean straits. The share of fresh components of the water balance (continental runoff, precipitation) remains only about 1%. Thus, main role Water exchange through the straits plays a role in the water balance of the sea.
Scheme of water exchange through straits in the Sea of Japan
Features of the bottom topography, water exchange through the straits, and climatic conditions form the main features of the hydrological structure of the Sea of Japan. It is similar to the subarctic type of structure of the adjacent areas of the Pacific Ocean, but has its own characteristics that have developed under the influence of local conditions.
The entire thickness of its waters is divided into two zones: surface - to a depth of an average of 200 m and deep - from 200 m to the bottom. The waters of the deep zone are relatively uniform in physical properties throughout the year. The characteristics of surface water under the influence of climatic and hydrological factors change in time and space much more intensely.
In the Sea of Japan, three water masses are distinguished: two in the surface zone: the surface Pacific, characteristic of the southeastern part of the sea, and the surface Sea of Japan - for the northwestern part of the sea, and one in the deep part - the deep Sea of Japan water mass.
The surface Pacific water mass is formed by the water of the Tsushima Current; it has the largest volume in the south and southeast of the sea. As you move north, its thickness and area of distribution gradually decrease, and at approximately 48° N latitude. due to a sharp decrease in depth, it wedges out into shallow water. In winter, when the Tsushima Current weakens, the northern boundary of the Pacific waters is located at approximately 46-47° N latitude.
Water temperature and salinity
Surface Pacific water is characterized by high temperatures (about 15-20°) and salinity (34-34.5‰). This water mass contains several layers, the hydrological characteristics of which and their thickness vary throughout the year:
the surface layer, where the temperature throughout the year varies from 10 to 25°, and salinity - from 33.5 to 34.5‰. The thickness of the surface layer varies from 10 to 100 m;
the upper intermediate layer has a thickness varying from 50 to 150 m. It exhibits significant gradients in temperature, salinity and density;
the lower layer has a thickness of 100 to 150 m. The depth of its occurrence and the boundaries of its distribution change throughout the year; temperature varies from 4 to 12°, salinity - from 34 to 34.2‰. The lower intermediate layer has very slight vertical gradients in temperature, salinity and density. It separates the surface Pacific water mass from the deep Sea of Japan.
As you move north, the characteristics of Pacific water gradually change under the influence of climatic factors as a result of its mixing with the underlying deep Sea of Japan water. With the cooling and desalination of Pacific water at latitudes 46-48° N. The surface water mass of the Sea of Japan is formed. It is characterized by relatively low temperature (on average about 5-8°) and salinity (32.5-33.5‰). The entire thickness of this water mass is divided into three layers: surface, intermediate and deep. As in the Pacific Ocean, in the surface water of the Japanese Sea, the greatest changes in hydrological characteristics occur in the surface layer with a thickness of 10 to 150 m or more. The temperature here varies throughout the year from 0 to 21°, salinity - from 32 to 34‰. In the intermediate and deep layers, seasonal changes in hydrological characteristics are insignificant.
Deep Sea of Japan water is formed as a result of the transformation of surface waters that descend to depths due to the process of winter convection. The vertical changes in the characteristics of the deep Sea of Japan water are extremely small. The bulk of these waters have a temperature of 0.1-0.2° in winter, 0.3-0.5° in summer, and a salinity throughout the year of 34.1-34.15‰.
Water temperature on the surface of the seas of Japan, Yellow, East China, South China, Philippines, Sulu, Sulawesi in summer
The structural features of the waters of the Sea of Japan are well illustrated by the distribution of oceanological characteristics in it. Surface water temperatures generally increase from northwest to southeast.
In winter, the water temperature on the surface rises from negative values close to 0° in the north and northwest to 10-14° in the south and southeast. This season is characterized by a well-defined contrast in water temperature between western and eastern parts sea, and in the south it is less pronounced than in the north and central part of the sea. Thus, at the latitude of Peter the Great Bay, the water temperature in the west is close to 0°, and in the east it reaches 5-6°. This is explained, in particular, by the influence of warm waters moving from south to north in the eastern part of the sea.
As a result of spring warming, the surface water temperature throughout the sea rises quite quickly. At this time, temperature differences between the western and eastern parts of the sea begin to smooth out.
In summer, the surface water temperature rises from 18-20° in the north to 25-27° in the south of the sea. Temperature differences across latitude are relatively small.
U western shores the water temperature on the surface is 1-2° lower than in the east, where warm waters spread from south to north.
In winter, in the northern and northwestern regions of the sea, the vertical water temperature changes slightly, and its values are close to 0.2-0.4°. In the central, southern and southeastern parts of the sea, the change in water temperature with depth is more pronounced. In general, the surface temperature, equal to 8-10°, remains up to horizons of 100-150 m, from which it gradually decreases with depth to approximately 2-4° at horizons of 200-250 m, then it decreases very slowly - to 1-1. 5° at horizons of 400-500 m, deeper the temperature drops slightly (to values less than 1°) and remains approximately the same to the bottom.
In summer, in the north and northwest of the sea, high surface temperature (18-20°) is observed in the 0-15 m layer, from here it drops sharply with a depth of up to 4° at a horizon of 50 m, then its decrease occurs very slowly to a horizon of 250 m, where it is approximately 1°, deeper and to the bottom the temperature does not exceed 1°.
In the central and southern parts of the sea, the temperature decreases quite smoothly with depth and at a horizon of 200 m is approximately 6°, from here it decreases somewhat faster and at horizons of 250-260 m it is equal to 1.5-2°, then it decreases very slowly at horizons 750-1500 m (in some areas at horizons of 1000-1500 m) reaches a minimum of 0.04-0.14°, from here the temperature rises towards the bottom to 0.3°. The formation of an intermediate layer of minimum temperature values is presumably associated with the immersion of the waters of the northern part of the sea, cooled during severe winters. This layer is quite stable and is observed all year round.
Salinity on the surface of the seas of Japan, Yellow, East China, South China, Philippines, Sulu, Sulawesi in summer
The average salinity of the Sea of Japan, approximately 34.1‰, is slightly lower than the average salinity of the waters of the World Ocean.
In winter, the highest salinity of the surface layer (about 34.5‰) is observed in the south. The lowest surface salinity (about 33.8‰) is observed along the southeastern and southwestern coasts, where heavy precipitation causes some desalination. In most of the sea, salinity is 34.l‰. In spring, in the north and northwest, desalination of surface water occurs due to melting ice, and in other areas it is associated with an increase in precipitation. Salinity remains relatively high (34.6-34.7‰) in the south, where at this time the influx of saltier waters entering through the Korea Strait increases. In summer, the average salinity on the surface varies from 32.5‰ in the north of the Tatar Strait to 34.5‰ off the coast of the island. Honshu.
In the central and southern regions of the sea, precipitation significantly exceeds evaporation, which leads to desalination of surface waters. By autumn, the amount of precipitation decreases, the sea begins to cool, and therefore the salinity on the surface increases.
The vertical variation of salinity is generally characterized by small changes in its values along the depth.
In winter, most of the sea experiences a uniform salinity from surface to bottom, equal to approximately 34.1‰. Only in coastal waters is there a weakly expressed minimum salinity in the surface horizons, below which the salinity increases slightly and remains almost the same to the bottom. At this time of year, vertical changes in salinity in most of the sea do not exceed 0.6-0.7‰, and in its central part they do not reach
Spring-summer desalination of surface waters forms the main features of the summer vertical distribution of salinity.
In summer, minimal salinity is observed on the surface as a result of noticeable desalination of surface waters. In subsurface layers, salinity increases with depth, creating noticeable vertical salinity gradients. The maximum salinity at this time is observed at horizons of 50-100 m in the northern regions and at horizons of 500-1500 m in the southern regions. Below these layers, salinity decreases slightly and remains almost unchanged to the bottom, remaining within the range of 33.9-34.1‰. In summer, the salinity of deep waters is 0.1‰ less than in winter.
Water circulation and currents
The density of water in the Sea of Japan depends mainly on temperature. The highest density is observed in winter, and the lowest in summer. In the northwestern part of the sea the density is higher than in the southern and southeastern parts.
In winter, the surface density is quite uniform throughout the sea, especially in its northwestern part.
In spring, the uniformity of surface density values is disrupted due to different heating of the upper layer of water.
In summer, horizontal differences in surface density values are greatest. They are especially significant in the area of mixing waters with different characteristics. In winter, the density is approximately the same from surface to bottom in the northwestern part of the sea. In the southeastern regions, the density increases slightly at horizons of 50-100 m; deeper and to the bottom it increases very slightly. The maximum density is observed in March.
In summer in the northwest, the waters are noticeably interlayered in density. It is small on the surface, rises sharply at horizons of 50-100 m and increases more gradually deeper to the bottom. In the southwestern part of the sea, the density increases noticeably in the subsurface (up to 50 m) layers, at horizons of 100-150 m it is quite uniform, below the density increases slightly to the bottom. This transition occurs at horizons of 150-200 m in the northwest and at horizons of 300-400 m in the southeast of the sea.
In autumn, the density begins to level out, which means a transition to a winter type of density distribution with depth. Spring-summer density stratification determines a fairly stable state of the waters of the Sea of Japan, although it is expressed to varying degrees in different areas. In accordance with this, more or less favorable preconditions are created in the sea for the emergence and development of mixing.
Due to the predominance of winds of relatively low strength and their significant intensification during the passage of cyclones under conditions of water stratification in the north and northwest of the sea, wind mixing penetrates here to horizons of about 20 m. In the less stratified waters of the southern and southwestern regions, the wind mixes the upper layers to the horizons 25-30 m. In autumn, stratification decreases and winds increase, but at this time of year the thickness of the upper homogeneous layer increases due to density mixing.
Autumn-winter cooling, and in the north, ice formation, cause intense convection in the Sea of Japan. In its northern and northwestern parts, as a result of rapid autumn cooling of the surface, convective mixing develops, which covers deep layers within a short time. With the onset of ice formation, this process intensifies, and in December convection penetrates to the bottom. At great depths, it extends to horizons of 2000-3000 m. In the southern and southeastern regions of the sea, cooled to a lesser extent in autumn and winter, convection extends mainly to horizons of 200 m. In areas of sharp changes in depth, convection is enhanced by the sliding of water along slopes, as a result of which density mixing penetrates to horizons of 300-400 m. Below mixing is limited by the density structure of water, and ventilation of the bottom layers occurs due to turbulence, vertical movements and other dynamic processes.
On the roadstead of Tokyo port
The nature of the circulation of sea waters is determined not only by the influence of the winds acting directly above the sea, but also by the circulation of the atmosphere over the northern part of the Pacific Ocean, since the strengthening or weakening of the influx of Pacific waters depends on it. In summer, the southeast monsoon increases water circulation due to the influx of large amounts of water. In winter, the persistent northwest monsoon prevents the flow of water into the sea through the Korea Strait, causing weakening water circulation.
Through the Korea Strait, the waters of the western branch of the Kuroshio, which passed through the Yellow Sea, enter the Sea of Japan and spread in a wide stream to the northeast along the Japanese islands. This flow is called the Tsushima Current. In the central part of the sea, the Yamato Rise divides the flow of Pacific waters into two branches, forming a divergence zone, which is especially pronounced in the summer. In this zone, deep waters rise. After going around the hill, both branches connect in an area located in the northwest of the Noto Peninsula.
At a latitude of 38-39°, a small flow separates from the northern branch of the Tsushima Current to the west, towards the Korea Strait, and turns into a countercurrent along the coast of the Korean Peninsula. The bulk of the Pacific waters are carried out from the Sea of Japan through the Sangarsky and La Perouse straits, while some of the waters, having reached the Tatar Strait, give rise to the cold Primorsky Current, moving south. South of Peter the Great Bay, the Primorsky Current turns east and merges with the northern branch of the Tsushima Current. A small part of the water continues to move south to Korea Bay, where it flows into the countercurrent formed by the waters of the Tsushima Current.
Thus, moving along the Japanese Islands from south to north, and along the coast of Primorye - from north to south, the waters of the Sea of Japan form a cyclonic gyre centered in the northwestern part of the sea. In the center of the gyre, rising waters are also possible.
In the Sea of Japan, two frontal zones are distinguished - the main polar front, formed by the warm and salty waters of the Tsushima Current and the cold, less saline waters of the Primorsky Current, and the secondary front, formed by the waters of the Primorsky Current and coastal waters, which in summer have a higher temperature and lower salinity than the waters of the Primorsky Current. In winter, the polar front passes slightly south of the parallel of 40° N, and near the Japanese Islands it runs approximately parallel to them almost to the northern tip of the island. Hokkaido. In summer, the location of the front is approximately the same, it only moves slightly to the south, and off the coast of Japan - to the west. The secondary front passes near the coast of Primorye, approximately parallel to them.
The tides in the Sea of Japan are quite distinct. They are created mainly by the Pacific tidal wave entering the sea through the Korea and Sangar Straits.
The sea experiences semi-diurnal, diurnal and mixed tides. In the Korea Strait and in the north of the Tatar Strait there are semi-diurnal tides, on the eastern coast of Korea, on the coast of Primorye, near the islands of Honshu and Hokkaido - diurnal tides, in Peter the Great and Korean Gulfs - mixed.
The nature of the tide corresponds to tidal currents. In open areas of the sea, semidiurnal tidal currents with speeds of 10-25 cm/s are mainly observed. Tidal currents in the straits are more complex, where they have very significant speeds. Thus, in the Sangar Strait, tidal current speeds reach 100-200 cm/s, in the La Perouse Strait - 50-100, in the Korea Strait - 40-60 cm/s.
The greatest level fluctuations are observed in the extreme southern and northern regions 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 it does not exceed 1.5 m.
In the middle part of the sea the tides are low. Along the eastern coasts of the Korean Peninsula and 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 off the western coasts of Honshu, Hokkaido and Southwestern Sakhalin. In the Tatar Strait, the tide height is 2.3-2.8 m. In the northern part of the Tatar Strait, the tide heights increase, which is determined by its funnel-shaped shape.
In addition to tidal fluctuations, seasonal level fluctuations are well expressed in the Sea of Japan. In summer (August - September) the maximum rise in level is observed on all shores of the sea; in winter and early spring (January - April) the minimum level is observed.
In the Sea of Japan, surge level fluctuations are observed. During the winter monsoon off the western coast of Japan, the level can rise by 20-25 cm, and off the mainland coast it can drop by the same amount. In summer, on the contrary, off the coast of North Korea and Primorye the level rises by 20-25 cm, and near Japanese shores decreases by the same amount.
Strong winds caused by the passage of cyclones and especially typhoons over the sea develop very significant waves, while monsoons cause less strong waves. In the northwestern part of the sea, northwestern waves predominate in autumn and winter, and eastern waves prevail in spring and summer. Most often, disturbances with a force of 1-3 points are observed, the frequency of which varies from 60 to 80% per year. In winter, strong waves prevail - 6 points or more, the frequency of which is about 10%.
In the southeastern part of the sea, thanks to the stable northwest monsoon, waves from the northwest and north develop in winter. In summer, weak, most often southwesterly, waves prevail. The largest waves have a height of 8-10 m, and during typhoons, the maximum waves reach a height of 12 m. Tsunami waves are observed in the Sea of Japan.
The northern and northwestern parts of the sea, adjacent to the mainland coast, are covered with ice annually for 4-5 months, the area of which occupies about 1/4 of the entire sea.
Ice cover
The appearance of ice in the Sea of Japan is possible as early as October, and last ice lingers in the north sometimes until mid-June. Thus, the sea is completely ice-free only during the summer months - July, August and September.
The first ice in the sea forms in closed bays and bays of the mainland coast, for example in Sovetskaya Gavan Bay, De-Kastri and Olga Bays. In October - November, ice cover mainly develops within bays and bays, and from late November - early December, ice begins to form in the open sea.
At the end of December, ice formation in coastal and open sea areas extends to Peter the Great Bay.
Fast ice is not widespread in the Sea of Japan. It forms first in the bays of De-Kastri, Sovetskaya Gavan and Olga; in the bays of Peter the Great Bay and Posyet it appears after about a month.
Every year, only the northern bays of the mainland coast freeze completely. South of Sovetskaya Gavan, the fast ice in the bays is unstable and can break up repeatedly during the winter. In the western part of the sea, floating and stationary ice appears earlier than in the eastern part; it is more stable. This is explained by the fact that the western part of the sea in winter is under the predominant influence of cold and dry air masses, spreading from the mainland. In the east of the sea, the influence of these masses weakens significantly, and at the same time the role of warm and humid marine air masses increases. The ice cover reaches its greatest development around mid-February. From February to May, conditions favorable for ice melting (in situ) are created throughout the sea. In the eastern part of the sea, ice melting “begins earlier and occurs more intensely than at the same latitudes in the west.
Ice cover in the Sea of Japan varies significantly from year to year. There may be cases when the ice cover in one winter is 2 times or more greater than the ice cover in another.
Economic importance
Inhabitants of the Sea of Japan
The fish population of the Sea of Japan includes 615 species. The main commercial species of the southern part of the sea include sardine, anchovy, mackerel, and horse mackerel. In the northern regions, the main fish caught are mussels, flounder, herring, greenling and salmon. in summer northern part tuna, hammerfish, and saury penetrate the sea. The leading place in the species composition of fish catches is occupied by pollock, sardine and anchovy.
