Waves on the water are caused primarily by wind. On a pond, mirror-smooth in calm weather, when the wind blows, ripples appear; on the lake there are waves. There are places in the ocean where the height of wind waves reaches 30-40 m. This is explained by the fact that in a shallow pond the close bottom dampens water vibrations. And only in the vast expanses of the ocean can the wind seriously disturb the surface of the water.
However, even huge waves are not always scary. After all, the water in a wave does not run in the direction of the wind, but only moves up and down. More precisely, it moves in a small circle inside the wave. Only in strong winds do the tops of the waves, picked up by the wind, move ahead of the rest of the wave, causing collapse - then whitecaps appear on the waves. 
It seems to us that a wave is running across the sea. In fact, the water inside the wave moves in a small circle. Near the shore, the lower part of the wave touches the bottom, and the neat circle is destroyed.
A wave can cause serious damage to a tall ship, especially a sailing ship whose mast height is much greater than the height of the sides. Such a ship is like a man being pushed under the knee. The raft is a different matter. It protrudes quite a bit above the water, and tipping it over is like turning over a mattress lying on the floor.
When a sea wave approaches the shore, where the depth gradually decreases, its lower part is slowed down by the bottom. At the same time, the wave rises upward, and collapses appear even on the most modest waves. Its upper part collapses onto the shore and immediately goes back along the bottom, continuing its circular motion. That’s why it’s so difficult to go ashore even with slight waves. 
Waves near the shore can become destructive.
On steep rocky shores, the wave does not gradually slow down on the bottom, but immediately brings down all its power onto the shore. That is probably why the waves near the shore are called surf.
While the surface of the lake may be smooth, the ocean is covered with waves almost constantly. The fact is that in a huge ocean there is always a place where wind waves form. And it is rare to find land that can stop these waves. The highest wind waves on the planet occur in the 40-50 latitudes of the Southern Hemisphere. Constant westerly winds blow there and there is almost no land to slow down the waves. 
Such a storm is caused by wind waves (fragment of I.K. Aivazovsky’s painting “Wave”).
An earthquake or volcanic eruption shakes the surface of the sea not as often as the wind, but much more powerfully. Sometimes this creates powerful waves that travel at speeds of hundreds of meters per second. They can travel around the Pacific Ocean, and sometimes the entire Earth, before they begin to fade. They are called tsunamis. The height of a tsunami in the open ocean is only 1-2 m. But the wavelength (the distance between the crests) is large. Therefore, it turns out that each wave carries a huge mass of water moving at colossal speed. When such a wave approaches the shore, it sometimes grows up to 50 m. There is little that can resist a tsunami on the shore. Humanity has still not come up with anything better than evacuating residents of coastal areas to the interior of the mainland.
The headline sounds like it will be about yet another anti-scientific study that the yellow newspapers love to use. Man from Mars, pyramids built by aliens, rogue waves - it would seem a completely logical series. In fact, this is a truly scientific term that refers to incredibly huge waves wandering across the ocean that can swallow almost any ship.
Unlike a completely predictable tsunami or storm, a wandering wave appears completely suddenly, growing along the way like a giant shaft, ready to absorb all living things in its path.
As you know, fear has big eyes. Therefore, for a long time the existence of rogue waves was considered a sea legend and even a myth. But that was exactly until someone from the crew of the ship, in whose path another wave stood, filmed this monster on video.
Interestingly, the amplitude of the occurrence of waves is almost independent of the size of the reservoir and the weather. We have put together everything we need this moment we know about a phenomenon that all sailors who go out into the open ocean fear.
What it is
A giant single wave, appearing completely unpredictably in the vastness of the ocean, has long been considered an idle invention of the lungs based on the frightening stories of sailors. It was only in the last century that scientists actually received documented evidence of the existence of this phenomenon. A rogue wave can reach up to 30 meters - this, for a minute, is the height of a fourteen-story building.The strangest thing is that they appear almost suddenly - researchers have still not been able to create any, even approximate, algorithm for their appearance. Consequently, almost every ship that goes out to the open sea is in danger of being “attacked” by such a giant monster.
Causes
No one has fully understood the exact causes of this dangerous phenomenon. Or rather, there are so many factors that may well contribute to the formation of a rogue wave that it is simply impossible to bring them to common denominator. For example, ordinary waves can move towards the current that slows them down at one point, unite and turn into one giant wave. Shallow water also contributes to this, where waves interact with each other, the bottom and the current at the same time. Therefore, it becomes impossible to predict the appearance of a rogue wave in a timely manner, which means that protecting against them in advance also does not seem realistic.
Dropner wave
For a very long time, giant rogue waves were considered an idle fiction. And this is completely understandable - just read the title again! In addition, the existing mathematical model of the appearance of sea waves simply did not allow the existence of a suddenly appearing wall of water more than twenty meters high. But on January 1, 1995, mathematicians had to develop the analytical system anew: the wave that appeared at the Dropner oil platform exceeded 25 meters. The myth turned out to be true, and for a long time the sailors did not know whether to rejoice at the confirmed story or begin to fear the very real rogue waves.
Research project
The emergence of the Dropner wave initiated the development of a new research project aimed at studying the phenomenon. MaxWave Project scientists have begun using radar satellites to monitor the entire surface of the world's oceans. In less than a month, researchers discovered a dozen waves exceeding 25 meters. The loss of massive ships such as container ships and supertankers.
Death Catalog
Another big headline, and again - completely justified. The so-called “Rogue Wave Catalog” was compiled by the famous oceanologist Irina Didenkulova. She decided to collect absolutely all available information not only from official sources, but also from navigation sites, media data and even YouTube videos. As a result, a very smooth and competent statistical picture of the occurrence of these terrible waves was obtained. Not all scientists are ready to consider the “death catalog” as serious Scientific research However, the data presented here really allows us to bring the phenomenon to a common denominator.
Killer Sisters
Oceanologists were sure that giant rogue waves could only arise in the World Ocean. Until the information about the death of the warship Edmund Fitzgerald, which occurred on Lake Superior, USA, was confirmed. As it turned out, on this lake local residents For many years they have been observing an amazing phenomenon: several times a year, the surface of the water gives birth to three huge waves running one after another, each about 25 meters high. They were called "Three Sisters".
Major disasters
The untimely recording of the terrible and extremely unusual phenomenon of rogue waves led to the fact that the disappearance and death of many ships remained unsolved. But now that the fundamental existence of such a phenomenon has been scientifically proven, researchers can compile a list of the most terrible disasters that occurred through their fault. IN last decade, there were several dangerous collisions with rogue waves: the Norwegian Dawn liner encountered three 24-meter waves at once, but remained afloat. In 2001, two ships (the liner Bremen and the scientific vessel Star of Caledonia) were less fortunate: several crew members disappeared from both ships.Killer waves or wandering waves, monster waves are giant single waves 20-30 meters high, sometimes appearing larger in the ocean and exhibiting behavior uncharacteristic of sea waves.
Killer waves have a different origin from tsunamis and have long been considered a fiction.
However, as part of the MaxWave project ("Maximum Wave"), which involved monitoring the surface of the world's oceans using the ERS-1 and ERS-2 radar satellites of the European Space Agency (ESA), more than 10 single giant waves were recorded in three weeks around the globe, whose height exceeded 25 meters.
This forced the scientific community to reconsider their views, and despite the impossibility of mathematical modeling of the process of the occurrence of such waves, to recognize the fact of their existence.
1 Robber waves are waves whose height is more than twice the significant wave height.
Significant wave heights are calculated for a given period in a given region. To do this, a third of all recorded waves with the highest height are selected and their average height is found.
2 The first reliable instrumental evidence of the appearance of a rogue wave is considered to be the readings of instruments on the Dropner oil platform located in the North Sea.
On January 1, 1995, at significant height waves of 12 meters (which is a lot, but quite common), suddenly a 26-meter wave appeared and hit the platform. The nature of the equipment damage corresponded to the specified wave height.
3 Rogue waves can appear without known reasons in light winds and relatively small waves, reaching a height of 30 meters.
This is a mortal threat to even the most modern ships: the surface on which a giant wave crashes can experience pressure of up to 100 tons per square meter.
4 The most probable zones of wave formation in this case are called zones of sea currents, since in them the disturbances caused by the inhomogeneity of the current and the unevenness of the bottom are the most constant and intense. Interestingly, such waves can be both crests and troughs, which is confirmed by eyewitnesses. Further research involves the effects of nonlinearity in wind waves, which can lead to the formation of small groups of waves (packets) or individual waves (solitons) that can travel long distances without significantly changing their structure. Similar packages have also been observed many times in practice. Characteristic Features Such groups of waves, confirming this theory, are that they move independently of other waves and have a small width (less than 1 km), and the heights drop off sharply at the edges.
5 In 1974, off the coast South Africa A rogue wave severely damaged the Norwegian tanker Wilstar.
Some scientists suggest that between 1968 and 1994, rogue waves destroyed 22 supertankers (and it is very difficult to destroy a supertanker). Experts, however, disagree on the causes of many shipwrecks: it is unknown whether rogue waves were involved.
6 In 1980, the Russian tanker Taganrog Bay collided with a rogue wave". Description from the book by I. Lavrenov. “Mathematical modeling of wind waves in a spatially inhomogeneous ocean,” op. based on the article by E. Pelinovsky and A. Slyunyaev. The sea state after 12 o'clock also decreased slightly and did not exceed 6 points. The ship's speed was slowed down to the very minimum, it obeyed the rudder and “played out” well on the wave. The tank and deck were not filled with water. Suddenly, at 13:01, the bow of the ship dropped slightly, and suddenly, at the very stem at an angle of 10-15 degrees to the ship's heading, the crest of a single wave was noticed, which rose 4-5 m above the forecastle (the bulwark of the forecastle was 11 m). The ridge instantly collapsed on the tank and covered the sailors working there (one of them died). The sailors said that the ship seemed to smoothly go down, sliding along the wave, and “buried” in the vertical section of its front part. No one felt the impact; the wave smoothly rolled over the tank of the ship, covering it with a layer of water more than 2 m thick. There was no continuation of the wave either to the right or to the left.
7 Analysis of radar data from the Goma oil platform in the North Sea showed, that over 12 years, 466 rogue waves were recorded in the available field of view.
While theoretical calculations showed that in this region the appearance of a rogue wave could occur approximately once every ten thousand years.
8 A rogue wave is usually described as a rapidly approaching wall of water of enormous height.
In front of it moves a depression several meters deep - a “hole in the sea.” Wave height is usually specified precisely as the distance from highest point ridge to the lowest point of the trough. By appearance"Rogue waves" are divided into three main types: "white wall", "three sisters" (a group of three waves), a single wave ("single tower").
9 According to some experts, rogue waves are dangerous even for helicopters flying low over the sea: first of all, rescue ones.
Despite the seeming improbability of such an event, the authors of the hypothesis believe that it cannot be ruled out and that at least two cases of death of rescue helicopters are similar to the result of being hit by a giant wave.
10 In the 2006 film Poseidon, the passenger liner Poseidon fell victim to a rogue wave. sailing in the Atlantic Ocean on New Year's Eve.
The wave turned the ship upside down, and a few hours later it sank.
Based on materials:
Video on the topic “Killer Waves”:
Sea roughness is the oscillation of the water surface up and down from the average level. However, they do not move horizontally during waves. You can verify this by observing the behavior of a float swinging on the waves.
Waves are characterized by the following elements: the lowest part of the wave is called the base, and the highest is called the crest. The steepness of a slope is the angle between its slope and the horizontal plane. The vertical distance between the base and the crest is the height of the wave. It can reach 14-25 meters. The distance between two troughs or two crests is called the wavelength. The longest length is about 250 m; waves up to 500 m are extremely rare. The speed of wave movement is characterized by their speed, i.e. the distance covered by the comb usually in a second.
The main reason for wave formation is. At low speeds, ripples appear - a system of small uniform waves. They appear with every gust of wind and instantly fade away. With a very strong wind turning into a storm, the waves can be deformed, with the leeward slope being steeper than the windward one, and with very strong winds the crests of the wave break off and form white foam - “lambs”. When the storm ends, high waves continue to travel across the sea for a long time, but without sharp crests. Long and gentle waves after the wind stops are called swell. A large swell with low steepness and a wave length of up to 300-400 meters in the complete absence of wind is called a wind swell.
The transformation of waves also occurs as they approach the shore. When approaching a gently sloping shore, the lower part of the oncoming wave is slowed down by the ground; the length decreases and the height increases. Top part the waves move faster than the bottom. The wave overturns, and its crest, falling, crumbles into small, air-saturated, foamy splashes. The waves, breaking up near the shore, form a surf. It is always parallel to the shore. The water splashed onto the shore slowly flows back down the beach.
When the wave approaches the steep shore, it hits the rocks with all its force. In this case, the wave throws up in the form of a beautiful, foamy shaft, reaching a height of 30-60 meters. Depending on the shape of the rocks and the direction of the waves, the shaft is broken into parts. The impact force of the waves reaches 30 tons per 1 m2. But it must be noted that main role It is not the mechanical impacts of masses of water on the rocks that play, but the resulting air bubbles and hydraulic changes, which basically destroy the rocks that make up the rocks (see Abrasion).
Waves actively destroy coastal land, roll over and abrade debris, and then distribute it along the underwater slope. Near the inland coastline, the impact force of the waves is very high. Sometimes at some distance from the shore there is a shoal in the form of an underwater spit. In this case, the breaking of waves occurs on the shallows, and a breaker is formed.
The shape of the wave changes all the time, giving the impression of running. This occurs due to the fact that each water particle, with a uniform movement, describes circles around the equilibrium level. All these particles move in one direction. At every moment the particles are in different points circle; this is the wave system.
The largest wind waves were observed in the Southern Hemisphere, where the ocean is most extensive and where westerly winds are most constant and strong. Here the waves reach 25 meters in height and 400 meters in length. Their movement speed is about 20 m/s. In the seas the waves are smaller - even in the big ones they reach only 5 m.
A 9-point scale is used to assess the degree of sea roughness. It can be used when studying any body of water.
9-point scale for assessing the degree of sea state
| Points | Signs of excitement |
|---|---|
| 0 | Smooth surface |
| 1 | Ripples and small waves |
| 2 | Small wave crests begin to capsize, but there is no white foam yet |
| 3 | In some places “lambs” appear on the crests of the waves |
| 4 | “Lambs” are formed everywhere |
| 5 | High ridges appear, and the wind begins to tear off white foam from them |
| 6 | The crests form the swells of storm waves. The foam begins to stretch completely |
| 7 | Long stripes of foam cover the sides of the waves and in some places reach their base |
| 8 | Foam completely covers the slopes of the waves, the surface becomes white |
| 9 | The entire surface of the wave is covered with a layer of foam, the air is filled with water dust and splashes, visibility is reduced |
To protect port facilities, piers, and coastal areas of the sea from waves, breakwaters are built from stone and concrete blocks to absorb wave energy.
Excitement is the oscillatory movement of water. It is perceived by the observer as the movement of waves on the surface of the water. In fact, the water surface oscillates up and down from the average level of the equilibrium position. The shape of waves during waves is constantly changing due to the movement of particles in closed, almost circular orbits.
Each wave is a smooth combination of elevations and depressions. The main parts of the wave are: crest- the highest part; sole - lowest part; slope - profile between the crest and trough of a wave. The line along the crest of the wave is called wave front(Fig. 1).
Rice. 1. Main parts of the wave
The main characteristics of waves are height - the difference in the levels of the wave crest and wave bottom; length - the shortest distance between adjacent wave crests or troughs; steepness - the angle between the wave slope and the horizontal plane (Fig. 1).
Rice. 1. Main characteristics of the wave
Waves have very high kinetic energy. The higher the wave, the more kinetic energy it contains (proportional to the square of the increase in height).
Under the influence of the Coriolis force, a water swell appears on the right side of the current, away from the mainland, and a depression is created near the land.
By origin waves are divided as follows:
- friction waves;
- pressure waves;
- seismic waves or tsunamis;
- seiches;
- tidal waves.
Friction waves
Friction waves, in turn, can be wind(Fig. 2) or deep. Wind waves arise as a result of wind waves, friction at the boundary of air and water. The height of wind waves does not exceed 4 m, but during strong and prolonged storms it increases to 10-15 m and higher. The highest waves - up to 25 m - are observed in the westerly wind zone of the Southern Hemisphere.
Rice. 2. Wind waves and surf waves
Pyramidal, high and steep wind waves are called crowding. These waves are inherent in the central regions of cyclones. When the wind subsides, the excitement takes on a character swell, i.e., disturbances due to inertia.
The primary form of wind waves is ripple It occurs at a wind speed of less than 1 m/s, and at a speed greater than 1 m/s, first small and then larger waves are formed.
A wave near the coast, mainly in shallow waters, based on forward movements, is called surf(see Fig. 2).
Deep waves arise at the boundary of two layers of water with different properties. They often occur in straits with two levels of current, near river mouths, at the edge of melting ice. These waves mix up the sea water and are very dangerous for sailors.
Pressure wave
Pressure waves arise due to rapid changes in atmospheric pressure in the places of origin of cyclones, especially tropical ones. Usually these waves are single and do not cause much harm. The exception is when they coincide with high tide. The Antilles, the Florida Peninsula, and the coasts of China, India, and Japan are most often exposed to such disasters.
Tsunami
Seismic waves occur under the influence of underwater tremors and coastal earthquakes. These are very long and low waves in the open ocean, but the force of their propagation is quite strong. They move at very high speed. Along the coasts, their length decreases and their height increases sharply (on average from 10 to 50 m). Their appearance entails human casualties. First, the sea water retreats several kilometers from the shore, gaining strength to push, and then the waves splash onto the shore with great speed at intervals of 15-20 minutes (Fig. 3).
Rice. 3. Tsunami transformation
The Japanese named seismic waves tsunami, and this term is used all over the world.
The seismic belt of the Pacific Ocean is the main area for tsunami generation.
Seiches
Seiches are standing waves that arise in bays and inland seas. They occur by inertia after the action ceases external forces- wind, seismic shocks, sudden changes, intense precipitation, etc. At the same time, in one place the water rises, and in another it falls.
Tidal wave
Tidal waves- these are movements made under the influence of the tidal forces of the Moon and the Sun. Backlash sea water at high tide - low tide. The strip that drains during low tide is called drying.
There is a close connection between the height of the tides and the phases of the moon. New and full moons have the highest tides and lowest tides. They're called Syzygy. At this time, the lunar and solar tides, occurring simultaneously, overlap each other. In the intervals between them, on the first and last Thursdays of the Moon phases, the lowest, quadrature tides.
As already mentioned in the second section, in the open ocean the tide height is low - 1.0-2.0 m, but near dissected coasts it increases sharply. The tide reaches its maximum on the Atlantic coast North America, in the Bay of Fundy (up to 18 m). In Russia, the maximum tide - 12.9 m - was recorded in Shelikhov Bay (Sea of Okhotsk). In inland seas, the tides are little noticeable, for example, in the Baltic Sea near St. Petersburg the tide is 4.8 cm, but in some rivers the tide can be traced hundreds and even thousands of kilometers from the mouth, for example, in the Amazon - up to 1400 cm.
A steep tidal wave rising up a river is called boron In the Amazon, boron reaches a height of 5 m and is felt at a distance of 1400 km from the mouth of the river.
Even with a calm surface, disturbances occur in the thickness of the ocean waters. These are the so-called internal waves - slow, but very significant in scope, sometimes reaching hundreds of meters. They arise as a result of external influence on a vertically heterogeneous mass of water. In addition, since the temperature, salinity and density of ocean water do not change gradually with depth, but abruptly from one layer to another, specific internal waves arise at the boundary between these layers.
Sea currents
Sea currents- these are horizontal translational movements of water masses in the oceans and seas, characterized by a certain direction and speed. They reach several thousand kilometers in length, tens to hundreds of kilometers in width, and hundreds of meters in depth. In terms of physical and chemical properties, the waters of sea currents are different from those around them.
By duration of existence (sustainability) sea currents are divided as follows:
- permanent, which pass in the same areas of the ocean, have the same general direction, more or less constant speed and stable physicochemical properties of transported water masses (Northern and Southern trade winds, Gulf Stream, etc.);
- periodic, in which direction, speed, temperature are subject to periodic patterns. They occur at regular intervals in a certain sequence (summer and winter monsoon currents in the northern part of the Indian Ocean, tidal currents);
- temporary, most often caused by winds.
By temperature sign sea currents are:
- warm which have a temperature higher than the surrounding water (for example, the Murmansk Current with a temperature of 2-3 ° C among waters O ° C); they have a direction from the equator to the poles;
- cold, the temperature of which is lower than the surrounding water (for example, the Canary Current with a temperature of 15-16 ° C among waters with a temperature of about 20 ° C); these currents are directed from the poles to the equator;
- neutral, which have a temperature close to environment(for example, equatorial currents).
Based on the depth of their location in the water column, currents are distinguished:
- superficial(up to 200 m depth);
- subsurface, having a direction opposite to the surface;
- deep, the movement of which is very slow - on the order of several centimeters or a few tens of centimeters per second;
- bottom regulating the exchange of water between polar - subpolar and equatorial-tropical latitudes.
By origin The following currents are distinguished:
- friction, which can be drift or wind. Drift ones arise under the influence of constant winds, and wind ones are created by seasonal winds;
- gradient-gravitational, among which are stock, formed as a result of the tilting of the surface caused by excess water due to its influx from the ocean and heavy rainfall, and compensatory, which arise due to the outflow of water, scanty precipitation;
- inert, which are observed after the cessation of the action of the factors that excite them (for example, tidal currents).
The system of ocean currents is determined by the general circulation of the atmosphere.
If we imagine a hypothetical ocean extending continuously from the North Pole to the South Pole, and superimpose on it a generalized scheme of atmospheric winds, then, taking into account the deflecting Coriolis force, we obtain six closed rings -
gyres of sea currents: Northern and Southern equatorial, Northern and Southern subtropical, Subarctic and Subantarctic (Fig. 4).
Rice. 4. Cycles of sea currents
Deviations from the ideal scheme are caused by the presence of continents and the peculiarities of their distribution across earth's surface Earth. However, as in the ideal diagram, in reality there is zonal change large - several thousand kilometers long - not completely closed circulation systems: it is equatorial anticyclonic; tropical cyclonic, northern and southern; subtropical anticyclonic, northern and southern; Antarctic circumpolar; high-latitude cyclonic; Arctic anticyclonic system.
In the Northern Hemisphere they move clockwise, in the Southern Hemisphere they move counterclockwise. Directed from west to east equatorial inter-trade wind countercurrents.
In the temperate subpolar latitudes of the Northern Hemisphere there are small current rings around baric minimums. The movement of water in them is directed counterclockwise, and in the Southern Hemisphere - from west to east around Antarctica.
Currents in zonal circulation systems are quite well traced down to a depth of 200 m. With depth, they change direction, weaken and turn into weak vortices. Instead, meridional currents intensify at depth.
The most powerful and deepest surface currents play a critical role in the global circulation of the World Ocean. The most stable surface currents are the Northern and Southern trade winds of the Pacific and Atlantic Oceans and the Southern Trade Wind Current of the Indian Ocean. They have a direction from east to west. Tropical latitudes are characterized by warm waste currents, for example the Gulf Stream, Kuroshio, Brazilian, etc.
Under the influence of constant westerly winds in temperate latitudes there are warm North Atlantic and North-
The Pacific Current in the Northern Hemisphere and the cold (neutral) current of the Western Winds in the Southern Hemisphere. The latter forms a ring in the three oceans around Antarctica. The large gyres in the Northern Hemisphere are closed by cold compensatory currents: along the western coasts in tropical latitudes there are the Californian and Canary currents, and in the Southern Hemisphere there are the Peruvian, Bengal, and Western Australian currents.
The most famous currents are also the warm Norwegian Current in the Arctic, the cold Labrador Current in the Atlantic, the warm Alaskan Current and the cold Kuril-Kamchatka Current in the Pacific Ocean.
The monsoon circulation in the northern Indian Ocean generates seasonal wind currents: winter - from east to west and summer - from west to east.
In the Arctic Ocean, the direction of movement of water and ice occurs from east to west (Transatlantic Current). Its reasons are the abundant river flow of the rivers of Siberia, the rotational cyclonic movement (counterclockwise) over the Barents and Kara seas.
In addition to circulation macrosystems, there are open ocean eddies. Their size is 100-150 km, and the speed of movement of water masses around the center is 10-20 cm/s. These mesosystems are called synoptic vortices. It is believed that they contain at least 90% of the kinetic energy of the ocean. Eddies are observed not only in the open ocean, but also in sea currents such as the Gulf Stream. Here they are spinning with more higher speed than in the open ocean, their ring system is better expressed, which is why they are called rings.
For the climate and nature of the Earth, especially coastal areas, the importance of sea currents is great. Warm and cold currents maintain the temperature difference between the western and eastern coasts of the continents, disrupting its zonal distribution. Thus, the ice-free port of Murmansk is located above the Arctic Circle, and on the east coast of North America the Gulf of St. Lawrence (48° N). Warm currents promote precipitation, while cold currents, on the contrary, reduce the possibility of precipitation. Therefore, areas washed by warm currents have a humid climate, while areas washed by cold currents have a dry climate. With the help of sea currents, the migration of plants and animals, the transfer nutrients and gas exchange. Currents are also taken into account when sailing.