Currents of the Black Sea. A mysterious phenomenon at sea that claims the lives of many people

The main current observed in the Black Sea is called the "main Black Sea current". It spreads along all shores along the perimeter of the sea, directed counterclock-wise and folds into two vortex flows called rings. These rings, reminiscent of giant glasses and the name of the hydrologist who first noticed and described them, gave the name to this phenomenon - “Knipovich glasses”.

The basis for the direction of movement of the Black Sea current is the acceleration obtained sea ​​water due to the rotation of the planet. Physicists call this effect the “Coriolis force.” In addition to cosmic forces, on movement surface waters on the map of the Black Sea, the strength of the wind also influences. This explains the variability of the main Black Sea current: sometimes it is barely noticeable against the background of other, smaller currents, and sometimes its speed reaches one meter per second.

IN coastal areas Black Sea anticyclonic gyres are observed - vortex flows directed opposite to the main flow. They are most noticeable off the coast of the Caucasus and Anatolia. In these areas of the Black Sea, the direction of alongshore currents is usually determined by the direction of the prevailing wind and can change several times a day.

Vacationers on the Black Sea should know about the existence of such a type of local Black Sea currents as “ draft" Most often, this current forms during a storm near sandy, gently sloping shores. Water flowing onto the shore does not return evenly, but in streams along channels spontaneously formed in the sandy bottom. Getting caught in a current is dangerous: even an experienced swimmer, despite all his efforts, can be carried into the open sea far from the shore. To get out of the tug, you need to swim to the shore not directly perpendicular, but at an angle in order to reduce the counter resistance of the receding water.

A type of draft “in action” can be seen in the Black Sea ports. From time to time, ships moored to the pier begin movement along the shore, as if controlled by a huge natural force. Sometimes this movement is so powerful that the metal mooring ends cannot withstand the pressure, and the ships have no choice but to stop loading operations and lie down in a roadstead away from the shore.

The nature of the occurrence of “port” draft differs from the draft that occurs during a storm. It is caused by special waves, invisible to the naked eye, approaching the port gates. They are called long-period - the period of oscillations created by them is much longer than the periods of oscillation of ordinary waves.

Scientists in our country and abroad are studying the nature of this phenomenon. The result of their work is scientific and practical recommendations on the correct mooring of ships during “thrusts” and advice on designing safe ports capable of extinguishing the “evil” energy of long-period waves.

There are many applied, reporting and entertaining texts written on the Internet on the topic “what a tourist needs to know before going to the sea,” but this particular article makes sense to read with the utmost attention and seriousness.

If you are going to the sea, no matter what it is or where, you should know this information. 95% of drowned people in the world died precisely because they did not know about RIP-currents or rip currents. Do you know what the abbreviation RIP stands for? "Rest in peace" in English means "rest in peace."

This is a flow of water perpendicular to the shore. If you don’t go into the scientific description of the occurrence of countercurrents, then the explanation looks like this.

The waves, the surf, which constantly bubbles along the edge of the shore, washes a smooth ridge of sand under the water. Mound, ridge, wall, spit - call it what you want. This ridge is not visible from the shore, it stretches under water along the entire line of the beach or only partially, is present there constantly or is washed up only at certain times of the year (and it happens that in different time day) - but he is there. You probably remember that there is a bottom that becomes deeper literally from the second step, and after a couple of steps it suddenly becomes shallow, and you begin to climb a small slope under water. It is he.

Rip current occurs when in its own weak point the sandy ridge cannot withstand the pressure of the rolling water and is washed away. Do you understand, right? A hole appears in the underwater wall, and all the water to the right and left of the hole, held back by this wall, rushes into it, creating an instant, incredibly strong and very narrow stream of water that knocks you off your feet. mountain river and carries a person away from the shore into the open sea.

Well, in the case of an underwater spit, which does not stretch along the entire coast - at the very edge of the spit, with each outgoing wave an underwater jet appears due to the difference in the volume of water outflow. Where nothing interferes with the water, the sea simply moves back. The spit, preventing the outflow of the lower layers of water, forces them to accelerate.

What are rip currents?

According to some reports, the width of the rip can vary from 2-3 to 50 meters, and the current speed can reach from 4 to 16 km/h. And if with minimal indicators you get off with a slight fright, then if you get into a large rip that can drag you half a kilometer into the sea, it is very important not to panic and remember everything that you are reading now.

Rip current, also known as counter current, also known as rip current, rip current, rip current, is found on most ocean beaches in the world. Where a rescue service is organized and the beach is more or less under the supervision of the state or an adjacent hotel, in areas where rip currents are present, identification signs are always installed and there are information boards with short instructions “what to do if...”.

And there are spontaneous rip currents that arise each time in a new place and with different characteristics. These are the most terrible ones, dangerous for their unpredictability. A mother and a child are standing waist-deep in water, playing in one place for four hours and everything is wonderful. Then there is noise, foam, and before mother and child even have time to shout, they find themselves a hundred meters from the shore. It's very scary.

What is the danger of such currents?

It’s an incredible, paralyzing horror when you don’t understand what’s happening and you see that the shore is getting further and further away, and no one on the shore understands how to help or what needs to be done. What’s sad is that even a husband or a passerby who jumps after him and doesn’t know about the rip current and how to fight it has every chance of dying. Did I manage to scare you? Do you understand how serious this is? So here it is.

It’s not the sea, not the rip current, or even poor swimming skills that kills people—it’s panic. Panic prevents you from assessing the situation and making a decision; panic interferes with everything and pushes the majority of morally unprepared people to the most obvious, but most disastrous act - to row back to the shore.

I’m not even able to row against the current at a speed of 15 km/h Olympic champion. I’m not having a nightmare now - master swimmers, strong, trained athletes drowned in rips. After all, you have to row not just quickly, but faster than the flow, in order to get to the shore. Panic causes people to wave their arms until they are completely exhausted, which leads to their death.

How to escape in a rip current

A rip is just a stream a few steps wide, and to get out of it you just need to row not towards the shore, but to the side. You are in the river, which means that now the calm sea is the shore and salvation for you, swim to it. Don’t resist the flow, swim, gradually rowing to the side; your primary task is to get out of the flow. And if you find so much courage in yourself, then lie down on your back and wait - after a minute or two the flow itself will let you go. After this, swim to the side and begin to return to the shore.

It is very important to save strength and breath, and not allow panic to paralyze the will. A rip current is not a whirlpool; it does not pull you to the bottom. By the time you swim out, those on the shore will already have figured out how to help you, and God bless you, if you were sane and swam on the beach with lifeguards, and not somewhere in the wilderness. And I won’t say anything about the case if you still don’t know how to swim. Although no, I have one piece of advice for you - buy a PPE swimming board, tie it to your wrist and go into the sea only where there are no prohibitory flags and where there is a person on duty on the tower with a life preserver.

How to understand where there are rips

The main sign of the danger of a rip is red flags and a lifeguard running along the beach, waving his arms and swearing at you in all the languages ​​of the world. But rip currents also have others external signs that will help you spot danger even without flags in the sand:

• Rip is a river in the sea. If in the general pattern of the waves you see seething water or a clear stripe perpendicular to the shore, this is it.
• Difference in the color of sea water. The entire beach is blue, and in one place the water turns white - this is a rip.
• Marine debris, algae, foam that moves from the shore into the sea in an unusually organized manner is a rip.

P.S. Don't get caught in the rip. And if you get caught, don’t panic.

As a rule, we are very surprised at the seemingly completely absurd death in the water of people who know how to swim and feel confident in the depths. Often, the cause of such inexplicable accidents is considered to be alcohol intoxication, but in fact, lives are taken away by a phenomenon that, alas, only a few know about - a rip current.

We will tell you what it is and how to escape if you are unlucky enough to find yourself in such an unfortunate place.

So, rip current is a very, very dangerous thing that can kill even professional swimmers.

Attempts to escape the flow lead to nothing, and the person is simply seized by a state of panic.

The most dangerous are considered to be rip currents in shallow seas with flat shores, since sand spits do not allow water to return to the sea during low tide. The water pressure in the strait connecting the estuary and the sea increases, which forms a rapid, and in the middle of the sea a kind of river appears with a flow speed of up to 2.5-3.0 m/sec.




This is what it looks like when the current flows back towards the sea, perpendicular to the shore.

This often happens near the beach during high tides, after which the waves at different speeds return, forming reverse current.

This might look like this:



The seething water is not visible here, but the current itself and, alas, the people caught in it are noticeable:





As a rule, the rip current corridor is narrow: 2-3 meters with a current speed of 4-5 km/h. This kind of rip is not dangerous. But if its width reaches 50 m, and its length is 200-400 meters with a current speed of 15 km/h, this phenomenon becomes deadly!




Signs of a rip current are:

• area of ​​rushing water perpendicular to the shore
• area near the shore with discolored water
• foam, algae and bubbles that move steadily from the shore into the open sea
• discontinuities in continuous wave bands

But it should be remembered that 80% of dangerous rip currents are usually invisible!

As a rule, rips occur near the shore and can carry a person standing in waist-deep water out to sea, so you should not go into the water alone, especially if you are not a strong swimmer.

Rules of conduct in rip currents

• Do not panic! Calm down and use your common sense. Remember that if you know these rules, 100 times out of 100 you will be able to get out of the current!
• Save energy! Don't resist the current and don't swim to the shore - it's useless. Start swimming calmly to the side, parallel to the shore. If the rip is narrow, you will come out of it very quickly.
• If the rip is wide (from 20 meters or more)... If it becomes clear that the rip is wide enough, you should relax on the water and not panic. Remember that the reverse current cannot be long, which means that after 5 minutes it will stop, after which you can swim 50-100 meters in the direction and head to the shore. Do not swim to the shore as soon as you feel that the current has stopped, it may start again!

Remember the following!

• Bump leakLife never sinks to the bottom. This is not a whirlpool. It moves from the shore along the surface, and not into the depths.
• The rip current corridors are not wide. Often their width does not exceed 50 meters, and even more often - 10-20 m. That is, you can get out of the rip by swimming 20-30 meters along the shore.
• The length of the rip current is limited. It quickly weakens and ends where the waves peak and break. Surfers call this a “line up” and this is where they usually try to catch a wave. It is located no further than 100 meters from the shore.

This information can save the lives of your family and friends. Share this post with them!

Reverse Current or Rip

Many Russian tourists and vacationers do not know what awaits them when swimming in the sea with waves. Everyone likes to enjoy bobbing on the waves, jumping or diving on an oncoming wave. Yes, this often gives pleasure and does not foreshadow anything bad, the bottom is nearby, and the shore is not far away. At the same time, if you vacation through a travel agency, they usually never warn you what you can expect when swimming and what dangers may arise at this vacation spot. And this is deadly reverse current or whatever they call it R.I.P.. It will be deadly if you don’t know how to get out of it.

Imagine ocean waves rolling onto the shore, bringing more and more water. And all this water mass does not remain on land, but returns back to the ocean. This reverse movement of water occurs through channels that arise as a result of the action of waves breaking on the shore.

The waves break on the shore shallows, and then, accumulating in one place, go back, forming a reverse current, as if a river flows in the ocean. And this place is the most dangerous on the entire beach. In this channel, the current speed can reach 2-3 meters per second, and if you suddenly fall into it, you will be abruptly carried away from the shore. At this moment, most people begin to panic, they frantically fight against the current and persistently row back towards the shore. But the waves continue to cover, and, having lost strength, a person seriously risks drowning.

Story real person been in this situation:

“That’s exactly what happened to us. We have been vacationing in different places our country and abroad, but they knew nothing about it, no one ever warned about it, that it was dangerous and even deadly. And so, ohWe were on holiday in Thailand on Coron Beach, there were not big waves (there are almost always waves there), we decided to jump on the waves with my wife, but we didn’t go deep, only waist-deep. But with each separation from the bottom, we were carried further and further. At first they didn’t notice this, they swam calmly enjoying the waves, but when their legs no longer reached the bottom and the speed of the current increased, panic began. We immediately decided to swim to the shore, but noticed that we were not approaching it, but were only moving away. At the same time, having swam towards the shore for about 10 minutes, our strength was already running out, panic had reached its maximum, and after assessing the situation, we realized that it was no longer possible to swim to the shore.

In this situation, you can already say goodbye to life. They screamed and called for help, but it was too far to the shore, no one heard. And we were carried further and further. I pushed my wife towards the shore with all my strength, but we were still being carried further and further into the sea. They realized that it was useless to do this, they were only losing strength. Imagine how a person feels in this situation. We had already said goodbye to life and it was a shame that we came to rest, but here it was. There were no lifeguards on the shore, only Thais renting scooters, and there were very few people. By chance, someone noticed that we were waving our arms and realized that people were drowning.

A crowd of onlookers gathered and everyone just looked in our direction; no one dared to enter the sea. Of all the vacationers, only one person risked swimming to us, as we later learned from Bulgaria, who risked helping us from certain death. At the same time, he helped and pointed in which direction to swim. When we were already swimming to the shore, the Thai with a piece of foam plastic also swam in our direction. Slowly, with our last breath and exhausted, we reached the shore. Our savior’s wife, standing on the shore, was in tears, apparently also very worried about her husband, who swam to us. It’s a pity that they didn’t find out his name, they just thanked him for saving him, he had no strength at all, and for this you should be grateful for the rest of your life. If they knew about reverse currents and how to get out of the nick, this would not have happened. After such an incident, we don’t go into the sea when there are waves at all, even at Russian resorts. By the way, now the reverse current has begun to be noticed at the Black Sea resort and in the Crimea, even with no big waves».

You can watch the video on rescuing people on the beach. https://youtu.be/W8-EmKkq1Is

There are several simple rules Behaviors that must be remembered and always observed if you are carried out to sea:

1. Don't panic! Everyone knows that panic is the main enemy in extreme situation. However, not everyone continues to remember this when something happens. When a person panics, instead of soberly assessing the situation and accepting correct solution, he relies on his instincts and most often does absolutely the wrong thing.

2. Save energy! There is no need to fight the current and swim back to the shore - it is useless. Most likely, you will not have enough strength to overcome the current. Relax and calmly swim not straight to the shore, but to the side, that is, parallel to the coast.

3. Do not swim in the ocean or sea alone in the presence of waves and in places indicated by red flags! Try to swim on busy beaches, preferably where there is a lifeguard service and there are still people present.

A reverse flow is formed on the surface, without the formation of funnels and whirlpools. The water in the canal will carry you away from the shore along the surface, but will not drag you into the depths. As a rule, its width does not exceed 50 meters, most often it is 10-20 meters. That is, after swimming along the shore quite a bit, you should feel like you have swam out of the canal. The current weakens quite quickly, the channel ends its action where the waves reach their peak and begin to break. The reverse current is even different in color from the rest of the ocean water. This color comes from sand lifted by waves from the shore shallows and carried into the ocean. That sand is visible from above is proven by the fact that rip currents only form on the surface.

If you see something like the one in the photo, you're in luck, just don't swim in the area. However, 80% of dangerous channels that arise spontaneously do not manifest themselves visually. Professional rescuers can sometimes identify these places, but tourists are unlikely to. On beaches, in most cases, flags are placed, which can change their position throughout the day. The color of flags is accepted all over the world and is easy to remember, but as a rule little attention is paid to them:

A red and yellow flag means that there are lifeguards on the beach and it is safe to swim between these flags.

A red flag means that swimming in this area is strictly prohibited.

If you have any doubts, throw a bunch of seaweed or a piece of driftwood from the beach onto the surface. If there is a rip current, it will quickly carry your projectile out to sea.

In Thailand, for example, every year there are 1-2 cases of drowning from rip currents. It is better to choose a safe holiday destination in Thailand based on reviews from tourists and choose beaches where there is no rip current or is rare, especially when vacationing with children. You can learn more about and its beaches on the pages of this site and your vacation will be safe.

At Russian resorts during a storm or significant sea conditions, a reverse current is also found: on the Black Sea coast in all resorts Krasnodar region, in Crimea, Abkhazia. But they are much smaller and weaker relative to the ocean coast. Even where there are breakwaters, it doesn’t matter when there are big waves, you shouldn’t even go into the water. There are many cases when the reverse current on the Black Sea coast carried people out to the open sea during a storm or large waves. There is no point in indicating in which cities and resorts there were reverse currents; they occur almost everywhere, but we do not always see them.

According to the stories of numerous vacationers, they personally saw reverse currents during a minor storm in the cities: Crimea - Evpatoria, Feodosia, on the Black Sea coast - Lazarevskoye, Lermontovo, Divnomorskoye, and this does not mean that there are reverse currents there, they can be everywhere . On Russian equipped beaches (at hotels, boarding houses, sanatoriums) during a storm and large waves, the administration always closes them and you can see signs with the words “Beach closed, storm.” This can often be seen in Crimea.

There is almost never a reverse current on the beaches and other islands of Greece, as well as in Cyprus and resorts in Turkey, due to the almost always calm sea.

Reverse currents are most common at resorts, but mainly during a storm or large waves.

On the beaches, rip currents also occur in storms and with large waves, but the structure of the coastal bottom of the beaches does not allow swimming in waves, which may be why Vietnam is not famous for rip currents. But still be careful, rip currents can occur anywhere in the presence of waves.

Drawing a conclusion, we can say that the most dangerous beaches with a reverse current in the presence of waves are: in Thailand - Karon beach, in India - the beaches of Goa. Some people can refute this, saying that we often vacationed there and never saw anything like this. Yes, it’s great that I didn’t have the chance to fall into this dangerous direction. And don’t go there, don’t, but be careful and watch for the red flags on the shore.

If you know what it is reverse current and how to get out of it, then you will protect yourself and your friends going on beach holiday. Warn them about this danger before the trip and everyone will return safe and sound. ​

Looking for where to spend your vacation and which hotel to choose, then you can go to other pages of this site:

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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 Sea of ​​Azov, the border between which is the line Takil metro - Panagia metro.

The area of ​​the Black Sea is 422 thousand km 2, the volume is 555 thousand km 3, the average depth is 1315 m, greatest depth- 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. The northwestern and partially northern shores up to the mountainous southern coast of Crimea are 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 the northwestern part of the sea, where the waters carry the most large rivers: Danube (200 km 3 /year), Dnieper (50 km 3 /year), Dniester (10 km 3 /year). On the Black Sea coast of the Caucasus, the Inguri, Rioni, Chorokh and many small rivers flow into the 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, roast, dry summer), and in protected high mountains southeastern part - 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 influence of the Azores High spreads to the sea, clear, dry and hot weather sets in, and thermal conditions become uniform throughout the entire water area. During this season, weak northwest winds (2-5 m/s) prevail, only in rare cases in coastal strip In the northeastern part of the sea, northeastern winds of storm force arise.

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 they 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 Caucasus Ranges block the path of western and southwestern humid Mediterranean winds, 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 of Black Sea water flows annually through the Bosphorus, 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 heights waves reach 7 m, and at very strong storms may 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 caused by surge level fluctuations associated with the influence of stable 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, the fast ice along the western coast extends to Constanta, and the floating ice is 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). Duration ice age 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 winds from the western directions determine the anticyclonic nature. 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 northwestern part to 7-8° in central regions and 9-10° in the southeastern 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 water area open sea it is equal to 17.5-18.3‰.

IN cold season a vertical circulation develops in the sea, by the end of winter covering a layer with a thickness of 30-50 m in the central to 100-150 m in the 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, a slight increase in 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:

upper homogeneous layer and seasonal (summer) thermocline, associated mainly with the process of wind mixing and annual cycle 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) water masses;

deep layer - from 200 m to the bottom, where there are no seasonal changes in 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 by the upper 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 the upper current. 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 question needs 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, occurring in different areas seas are not the same. 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. The third group of 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 Mramornye 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, mackerel, red mullet, mackerel, flounder, stingrays, etc. Of the 20 commercial species of Black Sea fish, only anchovy, small mackerel and sprat, as well as the katran shark, are important.

Currently, the state of the Black Sea ecosystem is unfavorable. Depletion occurs species composition plants and animals, reduction in stocks of 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 number of biogenic and organic matter, 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 toxic effect For some algae, during a mass “bloom”, the fauna is observed to die. In addition, with intensive development of plankton, sediment settles to the bottom. a large number of dead organisms, 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 ecological situation caused the death of a once vast field of phyllophora, an algae used to make agar-agar.

The deterioration of water quality and oxygen conditions is one of the main reasons for the decline in the number of commercial fish in the northwestern part of the Black Sea.