What kind of current does the Black Sea have? Bottom currents in the Black Sea: why they are deadly

Located in the depths of the continent, the Black Sea (together with the Sea of Azov) is the most isolated part of the World Ocean. In the southwest it communicates with the Sea of Marmara through the Bosphorus Strait, the border between the seas runs along the line Rumeli Cape - Anadolu Cape. The Kerch Strait connects the Black and Azov Seas, the border between which is the line Cape Takil - Cape Panagia.

The area of the Black Sea is 422 thousand km 2, the volume is 555 thousand km 3, the average depth is 1315 m, the greatest depth is 2210 m.

The coastline, with the exception of the north and northwest, is slightly indented. The eastern and southern shores are steep and mountainous, the western and northwestern shores are low and flat, steep in places. The only large peninsula is Crimean. In the east, spurs of the Greater and Lesser Caucasus ranges, separated by the Colchis Lowland, come close to the sea. The Pontic Mountains stretch along the southern coast. In the Bosphorus area, the shores are low but steep; in the southwest the Balkan Mountains approach the sea; further to the north is the Dobrudzha Upland, gradually turning into the lowlands of the vast Danube Delta. Northwestern and partially northern shores up to the mountainous South Bank The Crimea is low, dissected by ravines, extensive estuaries at the mouths of rivers (Dniester, Dnieper-Bug), fenced off from the sea by spits.

Beach near Pitsunda

In the northwestern part of the sea there are the largest bays - Odessa, Karkinitsky, Kalamitsky. In addition to them, on the southern coast of the sea there are Samsun and Sinop bays, and on the western coast - Burgas. The small islands of Zmeiny and Berezan are located in the northwestern part of the sea, Kefken - east of the Bosphorus.

The main part of the river flow (up to 80%) flows into northwestern part seas where the waters carry the most large rivers: Danube (200 km 3 /year), Dnieper (50 km 3 /year), Dniester (10 km 3 /year). On Black Sea coast The Inguri, Rioni, Chorokh and many small rivers flow into the Caucasus Sea. On the rest of the coast, the flow is negligible.

Climate

Remote from the ocean and surrounded by land, the Black Sea has a continental climate, which is manifested in large seasonal changes in air temperature. On climatic features individual parts of the sea are significantly influenced by orography - the nature of the relief of the coastal strip. Thus, in the northwestern part of the sea, open to influence air masses from the north, the climate of the steppes appears ( Cold winter, hot, dry summer), and in the south-eastern part protected by high mountains - the climate of humid subtropics (abundance of precipitation, warm winter, wet summer).

In winter, the sea is affected by the spur of the Siberian anticyclone, which causes intrusions of cold continental air. They are accompanied by northeastern winds (at a speed of 7 - 8 m/s), often reaching storm force, sharp drops in air temperature, and precipitation. Particularly strong northeastern winds are typical for the Novorossiysk (Bora) region. Here, masses of cold air accumulate behind the high coastal mountains and, having passed over the peaks, fall with great force down to the sea. The wind speed during bora reaches 30-40 m/s, the frequency of bora is up to 20 or more times a year. When the spur of the Siberian anticyclone weakens in winter, Mediterranean cyclones enter the Black Sea. They cause unstable weather with warm, sometimes very strong southwesterly winds and temperature fluctuations.

In summer, the sea is influenced by the Azores High, clear, dry and hot weather, thermal conditions become uniform for the entire water area. During this season, weak northwestern winds (2-5 m/s) predominate; only in rare cases do northeastern winds of storm force occur in the coastal strip of the northeastern part of the sea.

The most low temperature in January - February it is observed in the northwestern part of the sea (–1-5°), on the southern coast of Crimea it rises to 4°, and in the east and south - to 6-9°. Minimum temperatures in the northern part of the sea reach -25 - 30°, in the southern part -5 - 10°. In summer, the air temperature is 23 - 25°, maximum values at different points reach 35-37°.

Atmospheric precipitation falls very unevenly on the coast. In the southeastern part of the sea, where the Caucasus ridges block the path of the western and southwestern humid Mediterranean winds, it falls greatest number precipitation (in Batumi - up to 2500 mm/year, in Poti - 1600 mm/year); on the flat northwestern coast it is only 300 mm/year, off the southern and western coasts and on the southern coast of Crimea - 600-700 mm/year. 340-360 km 3 black flows through the Bosphorus annually sea water, and about 170 km 3 of Mediterranean water enters the Black Sea. Water exchange through the Bosphorus experiences seasonal changes, determined by the difference in levels of the Black and Marmara Seas and the nature of the winds in the area of the strait. The Upper Bosphorus current from the Black Sea (occupying a layer of about 40 m at the entrance to the strait) reaches its maximum in summer, and its minimum is observed in autumn. The intensity of the Lower Bosphorus current into the Black Sea is greatest in autumn and spring, least in early summer. In accordance with the nature of wind activity over the sea, strong waves most often develop in autumn and winter in the northwestern, northeastern and central parts of the sea. Depending on the wind speed and wave acceleration length, waves with a height of 1-3 m predominate in the sea. In open areas, maximum wave heights reach 7 m, and in very strong storms they can be higher. The southwestern and southeastern parts of the sea are the calmest; strong waves are rarely observed here, and there are almost no waves over 3 m high.

Crimean coast

Seasonal changes in sea level are created mainly due to intra-annual differences in river flow input. Therefore, in the warm season the level is higher, in the cold season it is lower. The magnitude of these fluctuations is not the same and is most significant in areas influenced by continental runoff, where it reaches 30-40 cm.

The greatest magnitude in the Black Sea is the surge level fluctuations associated with the impact steady winds. They are especially often observed in autumn-winter in the western and northwestern parts of the sea, where they can exceed 1 m. In the west, strong surges are caused by easterly and northeasterly winds, and in the northwest - southeasterly ones. Strong surges in these parts of the sea occur during northwestern winds. Along the Crimean and Caucasian coasts, surges and surges rarely exceed 30-40 cm. Usually their duration is 3-5 days, but sometimes it can be longer.

In the Black Sea, seiche level fluctuations up to 10 cm in height are often observed. Seiches with periods of 2-6 hours are excited by wind, and 12-hour seiches are associated with tides. The Black Sea is characterized by irregular semidiurnal tides.

Ice cover

Ice is formed annually only in a narrow coastal strip in the northwestern part of the sea. Even in harsh winters it covers less than 5%, and in moderate winters - 0.5-1.5% of the sea area. In very severe winters, fast ice along the western coast extends to Constanta, and floating ice carried to the Bosphorus. Over the past 150 years, ice floes in the strait have been observed 5 times. In mild winters, only estuaries and individual bays are covered with ice.

Ice formation usually begins in mid-December, with maximum ice expansion observed in February. The boundary of stationary ice in moderate winters in the northwestern part of the sea runs from the Dniester estuary to the Tendrovskaya spit at a distance of 5-10 km from the coast. Further, the ice edge crosses the Karkinitsky Bay and reaches the middle part of the Tarkhankut Peninsula. Clearing of the sea from ice occurs in March (early - in early March, later - in early April). The duration of the ice period varies greatly: from 130 days in very severe winters to 40 days in mild ones. The ice thickness on average does not exceed 15 cm, in severe winters it reaches 50 cm.

Bottom relief

Underwater canyon in the Black Sea

In the topography of the seabed, three main structures are clearly distinguished: the shelf, the continental slope and the deep-sea basin. The shelf occupies up to 25% of the total bottom area and is on average limited to depths of 100-120 m. It reaches its greatest width (more than 200 km) in the northwestern part of the sea, which is all located within the shelf zone. Almost along the entire length of the mountainous eastern and southern coasts of the sea, the shelf is very narrow (only a few kilometers), and in the southwestern part of the sea it is wider (tens of kilometers).

The continental slope, occupying up to 40% of the bottom area, descends to approximately 2000 m depth. It is steep and indented by underwater valleys and canyons. The bottom of the basin (35%) is a flat accumulative plain, the depth of which gradually increases towards the center.

Water circulation and currents

Water circulation throughout the year is cyclonic in nature with cyclonic gyres in the western and eastern parts of the sea and the main Black Sea alongshore current that goes around them. Seasonal changes in circulation are reflected in the speeds and details of this current system. The main Black Sea current and cyclonic gyres are most clearly expressed in winter and summer. In spring and autumn, water circulation becomes weaker and more complex in structure. In the southeastern part of the sea, a small anticyclonic gyre is formed in the summer.

In the water circulation system, three characteristic areas can be distinguished, the structure of currents in which is distinguished by its originality: the coastal part, the zone of the main Black Sea current and the open parts of the sea.

The boundaries of the coastal part of the sea are determined by the width of the shelf. The current regime here depends on local factors and is significantly variable in space and time.

The zone of the main Black Sea current, 40-80 km wide, is located above the continental slope. The currents in it are very stable and have a cyclonic orientation. Current speeds on the surface are 40-50 cm/s, sometimes exceeding 100 and even 150 cm/s (in the flow core). In the upper hundred-meter layer of the main current, velocities decrease slightly with depth; the maximum vertical gradients occur in the 100-200 m layer, below which the velocities slowly attenuate.

In open parts of the sea, currents are weak. Average velocities here do not exceed 5-15 cm/s on the surface, slightly decreasing with depth to 5 cm/s at horizons of 500-1000 m. The boundaries between these structural regions are quite arbitrary.

In the shallow northwestern part of the sea, circulation is mainly driven by the wind. Northern and northeastern winds determine the cyclonic nature of the currents, and the winds western directions- anticyclonic. In accordance with the nature of the winds, the establishment of anticyclonic circulation is possible in the summer season.

The general circulation of sea waters is unidirectional to a depth of about 1000 m. In deeper layers it is very weak, and it is difficult to talk about its general nature.

An important feature of the main Black Sea current is its meandering, which can lead to the formation of isolated eddies that differ in temperature and salinity from the surrounding waters. The size of the eddies reaches 40-90 km; the phenomenon of eddy formation is essential for water exchange not only in the upper, but also in the deep layers of the sea.

Inertial currents with a period of 17-18 hours are widespread in the open sea. These currents influence mixing in the water column, since their speeds even in a layer of 500-1000 m can be 20-30 cm/s.

Water temperature and salinity

The water temperature on the sea surface in winter rises from –0.5-0° in the coastal areas of the north-western part to 7-8° in the central regions and 9-10° in the south-eastern part of the sea. In summer, the surface layer of water warms up to 23-26°. Only during surges can short-term significant drops in temperature occur (for example, off the southern coast of Crimea). During the period of sea warming, a temperature jump layer is formed at the lower boundary of wind mixing, limiting the spread of heat to the upper homogeneous layer.

Salinity on the surface is minimal all year round in the northwestern part of the sea, where the bulk of river water flows. In the estuary areas, salinity increases from 0-2 to 5-10‰, and in most of the open sea it is 17.5-18.3‰.

During the cold season, a vertical circulation develops in the sea, which by the end of winter covers a layer with a thickness of 30-50 m in central to 100-150 m in coastal areas. The waters cool most strongly in the northwestern part of the sea, from where they are distributed by currents at intermediate horizons throughout the sea and can reach areas farthest from the centers of cold. As a consequence of winter convection, with subsequent summer heating, a cold intermediate layer is formed in the sea. It persists throughout the year at horizons of 60-100 m and is distinguished by its temperature at the boundaries of 8°, and in the core - 6.5-7.5°.

Convective mixing in the Black Sea cannot extend deeper than 100-150 m due to an increase in salinity (and therefore density) in deeper layers as a result of the influx of salty Marmara Sea waters there. In the upper mixed layer, salinity increases slowly, and then at 100-150 m it sharply increases from 18.5 to 21‰. This is a permanent salinity jump layer (halocline).

Starting from horizons of 150-200 m, salinity and temperature slowly increase towards the bottom due to the influence of saltier and warmer Marble Sea waters entering the deeper layers. At the exit from the Bosphorus they have a salinity of 28-34‰ and a temperature of 13-15°, but quickly change their characteristics when mixed with Black Sea water. In the bottom layer slight increase temperature also occurs due to geothermal heat influx from the seabed. Deep waters, located in a layer from 1000 m to the bottom and occupying more than 40% of the sea volume in the Black Sea in winter (II) and summer (VIII), are characterized by great constancy of temperature (8.5-9.2 °) and salinity (22- 22.4‰.

Vertical distribution of water temperature (1) and salinity (2)

Thus, the main components are distinguished in the vertical hydrological structure of the Black Sea waters:

an upper homogeneous layer and a seasonal (summer) thermocline, associated mainly with the process of wind mixing and the annual cycle of heat flow through the sea surface;

a cold intermediate layer with a minimum temperature in depth, which in the northwest and northeast of the sea arises as a result of autumn-winter convection, and in other areas is formed mainly by the transfer of cold waters by currents;

constant halocline - a layer of maximum increase in salinity with depth, located in the contact zone of the upper (Black Sea) and deep (Marmara Sea) water masses;

deep layer - from 200 m to the bottom, where there is no seasonal changes hydrological characteristics, and their spatial distribution is very uniform.

The processes occurring in these layers, their seasonal and interannual variability, determine the hydrological conditions of the Black Sea.

The Black Sea has a two-layer hydrochemical structure. Unlike other seas, only the upper well-mixed layer (0-50 m) is saturated with oxygen (7-8 ml/l). Deeper, the oxygen content begins to decrease rapidly, and already at horizons of 100-150 m it is equal to zero. Hydrogen sulfide appears at the same horizons, the amount of which increases with depth to 8-10 mg/l at a horizon of 1500 m, and then stabilizes towards the bottom. In the centers of the main cyclonic gyres, where water rises, the upper boundary of the hydrogen sulfide zone is located closer to the surface (70-100 m) than in coastal areas (100-150 m).

At the border between the oxygen and hydrogen sulfide zones there is an intermediate layer of the existence of oxygen and hydrogen sulfide, which represents the lower “limit of life” in the sea.

Vertical distribution of oxygen and hydrogen sulfide in the Black Sea. 1 - average oxygen content, 2 - average hydrogen sulfide content, 3 - deviation from the average

The spread of oxygen into the deep layers of the sea is hampered by large vertical density gradients in the contact zone of the Black Sea and Marmara Sea water masses, limiting convective mixing top layer.

At the same time, the exchange of water in the Black Sea occurs between all layers, although slowly. Deep salty waters, constantly replenished by the lower Bosphorus current, gradually rise and mix with the upper layers, which flow into the Bosphorus with upstream. This circulation maintains a relatively constant salinity ratio in the sea water column.

In the Black Sea, the following main processes are distinguished (Vodyanitsky V.A. et al.), causing vertical exchange in the water column: the rise of water in the centers of cyclonic gyres and the descent at their periphery; turbulent mixing and diffusion in the sea water column; autumn-winter convection in the upper layer; bottom convection due to heat flow from the bottom; mixing in synoptic eddies; surge phenomena in the coastal zone.

Estimates of the time of vertical water exchange in the sea are very approximate. This important issue requires further research.

As the main mechanism for the formation of hydrogen sulfide in the Black Sea, most authors accept the reduction of sulfuric acid compounds (sulfates) during the decomposition of organic residues (dead organisms) under the influence of sulfate-reducing microspira bacteria. This process is possible in any reservoir, but the hydrogen sulfide formed in them quickly oxidizes. It does not disappear in the Black Sea due to the slow exchange of waters and the lack of possibility of its rapid oxidation in the deep layers. When deep water rises into the upper oxygen layer of the sea, hydrogen sulfide is oxidized into sulfates. Thus, in the sea there is a steady equilibrium cycle of sulfur compounds, determined by the rate of water exchange and other hydrodynamic processes.

Currently, there is an opinion that in recent decades there has been a constant unidirectional rise (trend) of the upper boundary of the hydrogen sulfide zone to the sea surface, reaching tens of meters. This is associated with anthropogenic withdrawals of river flow and changes in the density structure of the sea. However, the available data so far only indicate natural interannual fluctuations in the position of the boundary of the hydrogen sulfide zone, which occur differently in different areas of the sea. Isolating an anthropogenic trend against the background of these fluctuations is difficult due to the lack of systematic observations of the topography of the boundary of the hydrogen sulfide layer and the imperfection of the methodology for its determination.

Fauna and environmental issues

Diverse plant and animal world The Black Sea is almost entirely concentrated in the upper layer 150-200 m thick, constituting 10-15% of the sea's volume. The deep water column, devoid of oxygen and containing hydrogen sulfide, is almost lifeless and inhabited only by anaerobic bacteria.

The ichthyofauna of the Black Sea was formed from representatives of different origins and has about 160 species of fish. One of the groups is fish of freshwater origin: bream, crucian carp, perch, rudd, pike perch, ram and others, found mainly in the northwestern part of the sea. In desalinated areas and brackish-water estuaries there are representatives of ancient fauna that have been preserved since the existence of the ancient Ponto-Caspian basin. The most valuable of them are sturgeon, as well as several types of herring. Third group Black Sea fish consists of immigrants from the North Atlantic - these are cold-loving sprat, whiting, spiny dogfish shark, etc. The fourth, largest group of fish - Mediterranean invaders - has over a hundred species. Many of them enter the Black Sea only in summer, and winter in the Marmara and Mediterranean Seas. These include bonito, mackerel, tuna, Atlantic horse mackerel etc. Only 60 species of fish of Mediterranean origin that permanently live in the Black Sea can be considered Black Sea. These include anchovy, garfish, mullet, horse mackerel, red mullet, mackerel, flounder, stingrays, etc. Of 20 commercial species Among the Black Sea fish, only anchovy, small horse mackerel and sprat, as well as the katran shark are of importance.

Currently, the state of the Black Sea ecosystem is unfavorable. There is a depletion of the species composition of plants and animals, a reduction in reserves useful species. This is primarily observed in shelf areas experiencing significant anthropogenic pressure. The greatest changes are observed in the northwestern part of the sea. A large amount of biogenic and organic substances coming here with continental runoff causes the massive development of planktonic algae (“blooming”). In the area influenced by the Danube runoff, the biomass of phytoplankton increased 10-20 times, cases "red tides". Due to the toxic effect of some algae, the death of fauna is observed during mass blooms. In addition, with the intensive development of plankton, a large number of dead organisms settle to the bottom, the decomposition of which consumes dissolved oxygen. With a well-defined stratification of waters, which prevents the flow of oxygen from the surface layer to the bottom layer, oxygen deficiency develops in it (hypoxia), which can lead to the death of organisms (deaths). Since 1970, death tolls of varying intensity have been repeated almost every year. Unfavorable environmental conditions have caused the death of a once vast field of phyllophora - an algae used to make agar-agar.

Deterioration of water quality and oxygen regime is one of the main reasons for the decline in numbers commercial fish in the northwestern part of the Black Sea.

Surface currents of the Black Sea originate in estuaries big rivers and in the Kerch Strait. River waters entering the sea are deflected to the right by the Coriolis force. Subsequently, the direction of the currents is influenced by the wind and the configuration of the banks. In spring, when river flow is at its maximum, it is the main cause of surface circulation in the sea. In autumn, when surface currents depend only on the wind, currents in the underlying layers may have a different direction.

The main amount of river water flows into the northwestern part of the sea. A coastal current arises here. Having collected the waters of the Dnieper, Southern Bug and Dniester, it reaches its true scale when it receives the Danube waters. Near the Romanian and Bulgarian coasts, this current is directed to the south. East of Varna, where the Crimean Current flows into it, a current is formed, directed southward, towards the Bosphorus. A few miles from the coast, where the axis of the current passes, it becomes most powerful, and the salinity here is the lowest. From the axis of the current to the shore, the salinity increases slightly, the speed of the current weakens, and conditions appear for the occurrence of a countercurrent (directed to the north). Directly off the coast, depending on its configuration, there are local currents. Under the influence of local river flow, the salinity here decreases. Currents adjacent to the shore are weak and are more strongly influenced by winds. In general, however, the southerly current dominates. Due to seasonal change winds and the influx of river water, the southern current is most intense in winter and spring. In summer, when it weakens, the northern countercurrent is more pronounced. The latter also intensifies in the fall, sometimes even more significantly.

From the Bosphorus, the main part of the coastal current continues to move near Anatolia. Prevailing winds favor the easterly direction of the current. From Cape Kerempe, one stream of current deviates north to Crimea, the other continues to move east, capturing the flow of Turkish rivers along the way.

The surface current usually forms a vortex in the southwestern part of the sea, which arises mainly under the influence of southeastern and northern winds.

Near the coast of the Caucasus, the current prevails in a northwestern direction. In the area of the Kerch Strait it merges with the Azov Current. Near the southeastern coast of Crimea, the current divides. One branch, descending to the south, diverges from the current coming from Cape Kerempe, and in the Sinop region flows into the Anatolian Current. Thus, the circle of the Eastern Black Sea cyclonic gyre closes. Another branch of the Azov Current from Crimea heads west and is divided into currents in the northwestern direction (towards Odessa) and southwestern directions (towards Varna). The latter is called the Crimean Current and, when it merges with the “river current” created by the waters of the Dnieper, Southern Bug, Dniester and Danube, it closes the circle of the Western Black Sea cyclonic gyre.

Under cyclonic surface currents at a depth of 150-200 m, compensatory anticyclonic currents often form. Such currents also exist near the mouths of large rivers. Toward the central regions of the sea, the current speed decreases.

In the central regions there are practically no definitely directed currents; there is only drift movement of water masses that occurs under the influence of the wind.

During strong winds from land, there is sometimes an outflow of surface water from the shore and a rise in the waters of the underlying layers.

With strong winds from the sea, in addition to causing waves, the surface coastal current also increases, but only slightly in all seasons except winter. In winter, the surge effect, combined with strong cooling of coastal water, creates conditions for the formation of vertical circulation and the lowering of water along the shelf slope to great depths.

Excitement. The intensity of waves, wave height and speed depend on the wind speed, its duration and wave acceleration.

The maximum waves off the Bulgarian coast should obviously be at east winds, and in the Caucasian - with the Western ones. With a wind force of 7-8, lasting two days, waves 7 m high and about 90 m long should form off the Bulgarian coast. In fact, even with very strong storms, the maximum waves are smaller - due to the influence of coastal shallow water.

Near the Caucasian coast, where there are significant depths, the waves are higher; Thus, in the Poti region, waves with a height of about 5 m were recorded, and in the Sochi region, during a strong storm on January 28-29, 1968, a wave with a height of 7 m was recorded with a period of 9-10 s.

Off the Bulgarian coast, waves of approximately this height were observed only on January 17-18, 1977 and October 18, 1979.

In the open sea with a force 5-7 wind, the Black Sea wave has the following average values: period 6-7 s, speed 2.4-5 m/s, length 10-30 m and height 1.5-2.5 m. In rare cases during strong storms, the wave height reaches 5-6 m and the length is 70-80 m.

The impact force of the waves is very high. According to the recording of a dynamograph installed on the breakwater in Tuapse, with a west wind of 4-5 points and a wave with a period of 11 s, the impact force was 5.7 tons per 1 m2.

The intensity of waves varies with the seasons - it is maximum in autumn and winter, and minimum in May? and June.

In the wave mode, daily changes are also observed. In most cases, the wave height in the afternoon hours is greater than in the morning. This is most clearly expressed in summer, when breeze circulation develops - in the afternoon the wave becomes 10 cm higher than in the morning. In winter, such differences are insignificant - on average 1 cm, and even at night the waves are higher than in the afternoon.

After the wind has stopped, the excitement does not subside immediately; the swell remains - gentle, smoothly moving waves. If a strong wind causes a surge of water in one part of the sea and a rush in another, level fluctuations occur, similar to fluctuations in the scales. These vibrations are called seiches. They can also be caused by a sharp change in atmospheric pressure. The disturbance that begins on the surface of the sea penetrates into the deep layers and gradually, with depth, fades. At the boundaries of layers that differ in density, internal waves of large amplitude and length are formed. They cause rapid changes in temperature, salinity and other hydrological and hydrochemical parameters of water, most often at depths of 150-200 m.

Vertical exchange

Analyzing data on the seasonal distribution of layer stability, it can be noted that in winter, when conditions are favorable for maximum vertical mixing, even during strong storms it is limited to the upper 100-meter layer; only occasionally, weakening, mixing can penetrate to a depth of 150-200 m. Despite strong winter cooling, the waters of the upper 200-meter layer turn out to be less dense than the waters of the underlying more saline layers. As a result, winter vertical mixing in the Black Sea develops only to a depth of 200 m. Below this horizon, vertical water exchange is difficult.

Main role V vertical water exchange Between the 200-meter upper layer and the deep waters of the Black Sea there is an influx of Marble Sea water. Many authors are of the opinion that its role is not so significant, since in a year approximately 1/2000 of the volume of deep Black Sea waters passes through the Bosphorus from the Sea of Marmara, i.e. the Marmara Sea influx completely replaces deep waters in about 2000 years. However, such conclusions were made for the case when the salinity of the Marmara Sea stream is about 35 °/oo. In fact, according to Bulgarian scientists, the salinity of the Lower Bosphorus stream in most cases is about 24-25 °/oo, since in the Bosphorus and in the Bosphorus region there is a - the sea waters intensively mix with the Black Sea waters, the salinity of which is about 18°/oo. Consequently, less saline waters enter the deep layers of the Black Sea, but in a larger volume - not 229 km3 per year, but about 1000 km3. Thus, complete renewal of deep water should occur in approximately 480 years. In reality, it will occur faster due to compensatory withdrawal of water, vertical mixing, under the influence of internal waves, turbulence, exothermic processes, rise and fall of water in systems of cyclonic and anticyclonic currents and a number of other reasons.

From 35 million years ago to the present time, a basin was formed. The Black Sea is an internal sea of the Atlantic Ocean. The Bosphorus Strait connects with the Sea of Marmara, then, through the Dardanelles, with the Aegean and Mediterranean Seas. The Kerch Strait connects with Sea of Azov. From the north it cuts deep into the sea Crimean peninsula. The water border between Europe and Asia Minor runs along the surface of the Black Sea.

Length 1150 km

Width 580 km

Area 422,000 km²

Volume 547,000 km³

Coastline length 3400 km³

Maximum depth 2210 m

Average depth 1240 m

The catchment area is more than 2 million km²

Black Sea Map

Black Sea salinity map

The salty taste of sea water is given by sodium chloride, and the bitter taste is given by magnesium chloride and magnesium sulfate. Water contains 60 different elements. But it is assumed that it contains all the elements found on Earth. Sea water has a number of healing properties. Water salinity is about 18%.

Rivers flowing into the Black Sea

Due to the excess inflow of fresh water from the rivers Agoy, Ashe, Bzugu, Bzyp, Veleka, Vulan, Gumista, Dnieper, Dniester, Danube, Yeshilyrmak, Inguri, Kamchia, Kodor, Kyzylyrmak,

Kyalasur, Psou, Reprua, Rioni, Sakarya, Sochi, Khobi, Chorokhi, Southern Bug.

(more than 300 rivers) above evaporation it has less salinity than the Mediterranean Sea.

Rivers contribute 346 cubic meters to the sea. km of fresh water and 340 cubic meters. km of salt water flows from the Black Sea through the Bosphorus.

Current of the Black Sea

International experts claim that the natural cyclonic circulation of water in the Black Sea - the so-called “Knipovich glasses” - cleans the sea naturally.

Of particular interest is the issue of Black Sea currents. In the Black Sea there is a main closed ring of current from 20 to 50 miles wide, running 2-5 miles from the coast counterclockwise, and several connecting jets between its individual parts. average speed current in this ring is 0.5-1.2 knots, but with strong and stormy winds it can reach 2-3 knots. In spring and early summer, when rivers bring large amounts of water to the sea, the current intensifies and becomes more stable.

Underwater river in the Black Sea

An underwater river in the Black Sea is a bottom flow of highly salty water from the Sea of Marmara through the Bosphorus and along the seabed of the Black Sea. The trench through which the river flows is about 35 m deep, 1 km wide and about 60 km long. The water flow speed reaches 6.5 km/h, that is, 22 thousand m³ of water passes through the canal every second. If this river flowed on the surface, it would be sixth in the list of rivers in terms of fullness. The underwater river has elements characteristic of surface rivers, such as banks, floodplains, rapids and waterfalls. Interestingly, the whirlpools in this underwater river swirl not counterclockwise (as in ordinary rivers of the Northern Hemisphere due to the Coriolis force), but along it.

The channels at the bottom of the Black Sea were presumably formed 6 thousand years ago, when the sea level was approaching its current position. The waters of the Mediterranean Sea broke into the Black Sea and formed a network of trenches that are still active today.

The water in the river has a higher salinity and concentration of sediments than the surrounding water, so it flows under gravity and possibly supplies nutrients to abyssal plains that would otherwise be lifeless.

The river was discovered by scientists from the University of Leeds on August 1, 2010, and is the first such river to be discovered. Based on sonar sounding, it was previously known about the existence of channels on the ocean floor, and one of the largest such channels stretches from the mouth of the Amazon to Atlantic Ocean. The assumption that these channels may be rivers was confirmed only with the discovery of an underwater river in. The strength and unpredictability of such flows makes it impossible to study them directly, so scientists used autonomous underwater vehicles.

Sea water transparency

The transparency of sea water, that is, the ability to transmit light rays, depends on the size and quantity of suspended particles of various origins in the water, which significantly change the depth of penetration of light rays. There is a distinction between absolute and relative transparency of sea water.

Relative transparency refers to the depth (measured in meters) at which a white disk with a diameter of 30 cm disappears. Absolute transparency refers to the depth (measured in meters) to which any ray of light from the solar spectrum can penetrate. It is believed that in clear sea waters this depth is approximately 1000 to 1700 m.

Table of relative transparency of the waters of the World Ocean

Atlantic Ocean, Sargasso Sea to 66

Atlantic Ocean, equatorial zone 40 - 50

Indian Ocean, trade wind zone 40 - 50

Pacific Ocean, trade wind zone up to 45

Barents Sea, southwestern part to 45

Mediterranean Sea, off the African coast 40 - 45

Aegean Sea up to 50

Adriatic Sea about 30 - 40

Black Sea about 30

Baltic Sea, near the island of Bornholm 11 - 13

North Sea, English Channel 6.5 - 11

Caspian Sea, South part 11-13

Results of expeditions on the research vessel “Professor Vodyanitsky” (2002-2006)

If the methane outlet is deep enough underwater, the gas becomes bound in the composition " warm ice" But sometimes the thickness of gas hydrates is broken through by free, very powerful gas emissions.

Sometimes such a “methane fountain” flows for days, months... or even begins to “work” periodically, then dying down, then breaking through to the surface of the sea again. Such phenomena are called mud volcanoes, because gas, rushing upward from the bottom, takes with it masses of bottom soil, stones, water...

In many places, much more modest streams of methane rise from the bottom, spreading into clouds. We call them vultures. Some of them emit gas in an even, constant stream, others pulsate, reminiscent of a smoker's puffing pipe... There are quite a lot of seeps in the Kerch-Taman region, and off the coast of the Caucasus, and off the coasts of Georgia, Bulgaria...

Methane gas plume on the Black Sea shelf emerging on the water surface

there is a so-called main Black Sea Current(VERT). It spreads throughout the Black Sea perimeter. This flow is directed counterclockwise and forms two vortex flows, the so-called rings.

This phenomenon is scientific name"Knipovich glasses". Nikolai Mikhailovich Knipovich was the first hydrologist who noticed and described this phenomenon in detail.

The acceleration imparted to seawater by the rotation of the planet is the basis for the characteristic direction of this movement. In physics, this effect is called “Coriolis force”. But, due to the fact that the Black Sea has a relatively small water area, a significant impact on the main The strength of the wind also has an effect. Due to this factor, the main flow The Black Sea is very changeable. Sometimes it happens that it becomes faintly noticeable against the background of other sea currents of a smaller scale. And it happens that the speed of the main Black Sea current exceeds one hundred centimeters per second.

In the coastal Black Sea waters, eddy currents are formed with the opposite direction to the main one. Black Sea current direction - the so-called anticyclonic gyres. Such eddies are especially pronounced near the Anatolian and Caucasian coasts. In these regions, longshore currents in the surface layer of the Black Sea are usually determined by the wind. The direction of such currents can change during the day.

Exists special kind local Black Sea current called the draft. Tyagun is formed during a storm (strong sea waves) near gently sloping sandy shores. The principle of this currents lies in the fact that the sea water flowing onto the shore does not retreat equally evenly over the entire area of the tide, but along channels formed in the sandy bottom. Getting caught in the current of such a jet is very dangerous, since, despite all the efforts of the swimmer, he can be carried far from the shore directly into the open sea.

To get out of such a current, you need to swim not straight to the shore, but diagonally, this way it is easier to overcome the force of the receding water.

The current of “dragons” is one of the little-studied phenomena that is associated with waves.

The flow of the "tyagun" is the most dangerous looking coastal currents, it is formed due to the outflow of sea water, which was brought to the coast by waves. There is a well-established opinion that the “dragon” is pulled under the water; this is not true; the waves carry it away from the shore.

The power of the tug is high; it can pull even very experienced and strong swimmers with it from the shore. A person caught in a “thrust” should not fight it and try to swim straight to the shore by any means; the best option for salvation would be to move diagonally. This way you will be able to gradually leave the range of action of the thruster, this will allow you to save energy and stay afloat, as well as wait for help. It is also possible for the victim himself to gradually reach the shore on his own, trying not to return to the area of influence of this dangerous phenomenon.

This phenomenon can be observed; in many Black Sea ports, ships moored to the pier suddenly begin to move from time to time and move along the piers, seemingly under the influence of some force. It happens that such a movement is so powerful that the steel mooring ends cannot withstand the pressure, because of this, cargo ships are forced to stop loading and unloading operations and go to roadstead. Tyagun can form not only during a storm, but also in completely calm seas.

There are several hypotheses about the formation of the draft, but they all define the draft as a consequence of the approach of a special type of sea waves to the port gates, which are difficult to notice with the naked eye. These waves are called long-period, they create an oscillation period much longer than ordinary ones visible to people waves. By periodically creating strong fluctuations in the mass of water located in the port waters, these waves cause the movements of ships moored at the pier.

The formation of this phenomenon, which poses a danger to fleet vessels, is being studied both in our country and abroad. Conducted research papers give scientific and practical recommendations on the rules for mooring ships during the “thrust”, as well as advice on the construction of safe ports that will dampen the energy of this wave.

which sea currents by the Black Sea? please help and got the best answer

Answer from Alexey Khoroshev[guru]

Map of Black Sea currents.

The current in question originates at the mouths of large rivers and in the Kerch Strait. River waters, flowing into the sea, go to the right. Then the direction is formed under the influence of wind, shore configuration, bottom topography and other factors. From the Kerch Strait the current runs along the Crimean shores. At the southern tip of Crimea, division is taking place. The main current goes north to the mouth of the Dnieper-Bug estuary, and part of it goes to the Danube shores. Having received the Dnieper and then the Dniester waters, the main current goes to the Danube and then to the Bosphorus. Strengthened by the Danube waters and the Crimean branch, it gains its greatest strength here. From the Bosphorus, the main branch of the current, having given part of the water to the Sea of Marmara, turns to Anatolia (the main part of Turkey, located on the Asia Minor peninsula). Prevailing winds here favor an easterly direction. At Cape Kerempe, one branch of the current deviates north to the Crimea, and the other goes further to the east, absorbing the flow of the rivers of Asia Minor. At the Caucasian coast the current turns to the northwest. Near the Kerch Strait it merges with the Azov Current. And off the southeastern coast of Crimea, division is occurring again. One branch descends to the south, diverges from the current coming from Cape Kerempe, and in the Sinop area connects with the Anatolian current, closing the Eastern Black Sea circle. And the other branch of the current from the southeastern coast of Crimea goes to its southern tip. Here the Anatolian current flows into it from Cape Kerempe, which closes the Western Black Sea circle.
An underwater river in the Black Sea is a bottom flow of highly salty water from the Sea of Marmara through the Bosphorus and along the seabed of the Black Sea. The trench through which the river flows is about 35 m deep, 1 km wide and about 60 km long. The water flow speed reaches 6.5 km/h, that is, 22 thousand m³ of water passes through the canal every second. If this river flowed on the surface, it would be sixth in the list of rivers in terms of full flow. The underwater river has elements characteristic of surface rivers, such as banks, floodplains, rapids and waterfalls. It is interesting that the whirlpools in this underwater river swirl not counterclockwise (as in ordinary rivers of the Northern Hemisphere due to the Coriolis force), but along it.
The channels at the bottom of the Black Sea were presumably formed 6 thousand years ago, when the sea level was approaching its current position. The waters of the Mediterranean Sea broke into the Black Sea and formed a network of trenches that are still active today.
The river's water has greater salinity and sediment concentrations than the surrounding water, so it flows under gravity and perhaps supplies nutrients to otherwise lifeless abyssal plains.
The river was discovered by scientists from the University of Leeds on August 1, 2010, and is the first such river to be discovered.
Source: Geography

Answer from Vova Dorokhov[active]

Answer from Anna Emelyanova[active]
Of particular interest is the issue of Black Sea currents. In the Black Sea there is a main closed ring of current from 20 to 50 miles wide, running 2-5 miles from the coast counterclockwise, and several connecting jets between its individual parts. The average current speed in this ring is 0.5-1.2 knots, but in strong and stormy winds it can reach 2-3 knots. In spring and early summer, when rivers bring large amounts of water to the sea, the current intensifies and becomes more stable.
The current in question originates at the mouths of large rivers and in the Kerch Strait. River waters, flowing into the sea, go to the right. Then the direction is formed under the influence of wind, shore configuration, bottom topography and other factors. From the Kerch Strait the current runs along the Crimean shores. At the southern tip of Crimea, division is taking place. The main current goes north to the mouth of the Dnieper-Bug estuary, and part of it goes to the Danube shores. Having received the Dnieper and then the Dniester waters, the main current goes to the Danube and then to the Bosphorus. Strengthened by the Danube waters and the Crimean branch, it gains its greatest strength here. From the Bosphorus, the main branch of the current, having given part of the water to the Sea of Marmara, turns towards Anatolia. Prevailing winds here favor an easterly direction. At Cape Kerempe, one branch of the current deviates north to the Crimea, and the other goes further to the east, absorbing the flow of the rivers of Asia Minor. At the Caucasian coast the current turns to the northwest. Near the Kerch Strait it merges with the Azov Current. And off the southeastern coast of Crimea, division is occurring again. One branch descends to the south, diverges from the current coming from Cape Kerempe, and in the Sinop area connects with the Anatolian current, closing the Eastern Black Sea circle. And the other branch of the current from the southeastern coast of Crimea goes to its southern tip. Here the Anatolian current flows into it from Cape Kerempe, which closes the Western Black Sea circle.

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