This work includes explanations of the concepts of “water circulation”, “currents”, the general circulation diagram of the oceans, covers the issues of classification of currents, modern ideas about the horizontal and vertical structure of current flows; Based on some research results on the problem of "Ocean-Atmosphere Interaction", he examines the influence of ocean currents on climate. The work provides a list of the main surface currents of the World Ocean.

Currents are a horizontally directed flow of water that has a certain speed and direction.

Currents are divided according to various characteristics: the forces causing their formation, the direction of movement, stability, and physical properties.

1 Division of currents according to the forces causing them

Depending on the forces exciting the flows, they are combined into the following groups: 1) frictional, 2) gravitational-gradient,

3) tidal, 4) inertial.

1) Friction currents are divided into drift and wind, which are formed with the participation of friction forces.

Wind currents are caused by temporary and short-lived winds; in this case, the level does not tilt.

Drift currents are created by constant or long-lasting winds and lead to a tilt of the level surface (North and South Equatorial or Trade Wind Currents of the Atlantic and Pacific Oceans, South Equatorial Current of the Indian Ocean). The monsoon currents of the northern Indian Ocean, the Antarctic Circular Current, and the Arctic Drift are also drift currents.

The basis of the theory of drift currents was developed by the Swedish scientist Ekman in 1903-1905, the geographical conclusions of which are:

Surface currents deviate from the wind direction in the northern hemisphere by 45° to the right, and in the southern hemisphere by 45° to the left. The deviation of drift currents from the wind direction is caused by the Coriolis force, which occurs when the Earth rotates around its axis.

As the depth increases, the speed and direction of the current change. With depth, the velocity vector deviates more and more to the right of the wind direction in the northern hemisphere and more and more to the left in the southern hemisphere. At some depth, the deep vector is opposite to the surface vector.

The depth at which the flow has a direction opposite to the surface one is called the friction depth. The current speed at this horizon is about 4% of the surface speed.

In practice, purely drift currents stop at a depth of 100-200 m at low latitudes and at 50 m at a latitude of 50°.

2) Gravity-gradient currents, depending on the reasons creating the tilt of the sea surface, are divided into:

a) surge-driven, caused by the surge and displacement of water under the influence of

b) barogradient, associated with changes in atmospheric pressure. An increase (decrease) in atmospheric pressure by 1 mb leads to a decrease (increase) in sea level by 1.33 cm. Barogradient currents are directed from an area of ​​higher level (low pressure) to an area with a low level (high atmospheric pressure);

c) runoff currents are formed as a result of the inclination of the sea surface caused by the influx of river waters from the land (Ob-Yenisei and Lena currents in the Kara Sea and the Laptev Sea, a current in the Caspian Sea associated with the runoff of the Volga), precipitation, evaporation, and influx of water from other areas or their outflow. A type of drainage currents are drainage currents caused by the influx of water from another area (the Florida Current, which gives rise to the Gulf Stream). The Caribbean Drift Current pushes a large mass of water into the Gulf of Mexico, where the level rises. Excess water flows through the Straits of Florida into the Atlantic Ocean;

d) gradient currents caused by the horizontal gradient of water density are called density currents. The density of ocean water generally increases from the equator to the poles. Examples of local gradient (density) currents are bottom currents in the straits of the seas of the Atlantic Ocean basin - the Bosphorus and Gibraltar. The difference in water salinity (and density) between the Black (average S = 22 0 / 0 o) and Marmara (38-38.5 0 / 0 o) seas creates a density current in the Bosphorus from the Marmara Sea to the Black Sea. In the bottom layers of Gibraltar, the density current is directed from the Mediterranean Sea (S=38-38.5 0/00) to the Atlantic Ocean (S=36-37.5 0/00);

e) compensatory currents that replenish the loss of water due to outflow. As a result of the outflow of water from the eastern regions of the oceans, the action of trade winds creates a mass deficit, which is replenished by a compensatory equatorial countercurrent. Compensatory currents also include the Canary, Benguela, California, and partly Peruvian, surface currents in the Bosphorus and Gibraltar straits, directed respectively to the Marmara and Mediterranean seas.

3) Tidal currents arising under the influence of the tidal forces of the Moon and the Sun. They differ in that they cover the entire thickness of the water. The change in speed from the surface to the bottom is insignificant. They are typical in narrow areas (bays, straits) - the speed reaches up to 5-10 m/s.

4) Inertial flows are residual flows observed after the cessation of the forces that caused the movement.

Zonal ones have a direction close to the latitude and move to the east or west (North and South Equatorial Currents of the Atlantic and Pacific Oceans, South Equatorial Current of the Indian Ocean, Arctic Drift in the Arctic Ocean, North Atlantic and North Pacific Currents). The most striking example of zonal currents is the Antarctic Circular.

Meridional currents connecting zonal ones into a single system. They are divided into western border (Gulf Stream, Brazilian, Agulhasovo, Kuroshio, East Australian) - narrow and fast, and eastern border (Canary, Benguela, California, Peruvian, Western Australian) - wide and slow currents.

3 Based on their location, countercurrents are distinguished in the horizontal and vertical planes.

In the horizontal plane - Inter-trade wind, Antilo-Guiana, Trade wind currents.

In the vertical plane, they are called subsurface (Peru-Chile, California, Cromwell in the Pacific Ocean, Lomonosov in the Atlantic Ocean, Toreyev in the Indian Ocean, which is less stable due to monsoon currents) or deep countercurrents (for example, under the Gulf Stream). In addition to them, bottom currents are also distinguished.

4 Based on the duration of action (stability), currents can be divided into permanent, periodic and temporary (random).

Constant currents are displayed on the map - these are the majority of surface currents; they retain their basic parameters (direction, speed, flow).

Periodic or variable flows are associated with changes in the forces that form them. Monsoon currents in the northern part of the Indian Ocean have a westerly direction during the winter season of the northeast monsoon and an easterly direction in the summer season during the action of the southwest monsoon. The Somali Current, associated with the monsoon circulation, is also periodic, which during the winter monsoon is directed to the south; under the influence of the summer monsoon, it changes direction and flows to the north, thereby lowering its temperature. Variables also include tidal currents, which have a predominant diurnal or semidiurnal period.

Temporary or random currents reflect the variability of the causes that cause them: short-term changes in wind, level, density, etc.

5 Based on the nature of movement, currents are divided into straight, curvilinear, cyclonic and anticyclonic.

6 Based on their physicochemical properties, currents are classified into cold, warm, desalinated, salted and neutral.

Meridional currents directed from the equator to the poles are always warm, from the subtropics - always salty and vice versa. The nature of zonal currents is determined by the ratio of the temperature or salinity of the current waters and the surrounding waters. If the temperature of the current is higher than the temperature of the surrounding waters, the current is called warm; if lower, it is called cold. Salty and desalinated currents are defined similarly. Neutral currents (for example, trade winds in the central parts of the oceans) carry waters that do not differ from those around them in temperature and salinity.

The influence of currents on climate. The direct influence of currents on climate is clearly manifested and well studied. Warm currents have a softening effect, slightly increasing the duration of the warm season and the annual amount of precipitation. The beneficial influence of the Gulf Stream and its continuation of the North Atlantic Current on the climate of northwestern Europe is widely known. The average January temperature in Oslo is 25-30° higher than at the same latitude in Magadan. The frost-free period in Canada is 60 days, in Europe - 150-200 days. The warm Kuro-Sio current has a significant influence on the climatic conditions of the Pacific coast, although it is weaker than the influence of the Gulf Stream and the North Atlantic, since it penetrates to the north almost 40° to the south. In addition, the heat content of Kuro Sio is significantly less than the indicated Atlantic warm currents.

Cold currents affect the climate in the direction of cooling, increasing the duration of the cold season and significantly reducing the annual amount of precipitation. On the Canadian coast, washed by the Labrador Current between 55° and 70°N. There is an annual isotherm of 0. -10°, at the same latitude in Northern Europe there is an isotherm of 0. +10°. These properties of cold currents have a decisive influence on the formation of desert areas

Lands (Canary and deserts of northwestern Africa, Peruvian and Atacama desert, etc.). The cold currents of Kamchatka and Oya-Sio have a great influence on the climate of the Kuril ridge and Hokkaido. Their heat content depends on the severity of winters in the Bering and Okhotsk Seas. The colder these currents are, the cooler and cloudier the summer, and, accordingly, the lower the rice yield in Japan.

The indirect impact of currents on climate manifests itself through atmospheric circulation and has not been sufficiently studied. First of all, it manifests itself in the fact that troughs of low atmospheric pressure form above warm currents, and spurs of high pressure form above cold currents. Thus, off the coast of North America above the Gulf Stream, such a trough of low pressure is especially pronounced in winter, so the prevailing westerly winds here intensify even more, bringing cooled air masses from the mainland and creating climatic conditions more severe than in northwestern Europe, warmed by the same the very current. Spurs of high pressure above cold currents (Peruvian, Californian) determine a decrease in the amount of atmospheric precipitation. The heat content of currents and the location of the main jets affect the development of atmospheric processes. Cyclones, passing over water areas with increased heat transfer to the atmosphere, receive additional energy and the possibility of further development and movement. Cyclones passing over very cold water areas quickly waste their heat reserves and cease to exist.

Studies of the influence of currents on climate through interaction with the atmosphere made it possible to establish the following patterns. If the heat content of the Gulf Stream is greater in its southern part, then the weather and climate conditions of Europe do not change. If the heat reserve of the Gulf Stream increases in its middle part, then winter in Europe will be colder than usual as a result of sharpening pressure gradients over the trough and an increase in the frequency of cold westerly, northwestern and northern winds. Warming Gulf Stream waters cause cooling of the US coast as a result of increased monsoon circulation. With an increase in the heat reserve of the Gulf Stream in its northern part, winters in Europe will be warmer than usual, and in Greenland - colder, and the colder the warmer the Gulf Stream is.

The most striking example of the interaction of processes occurring in the ocean and atmosphere is the region of the cold Peruvian Current and the periodically occurring warm El Niño current, discovered in the 60s. This powerful flow occurs once every 7-14 years, when the normal southeast trade wind for this area of ​​the Pacific Ocean weakens or even disappears. In this case, a huge mass of warm water from the western part of the ocean moves to the west coast of America and, coming into collision with the northward Peruvian Current, deflects it into the open sea. This flow, as it continues the inter-trade wind current, forms the warm El Niño current, the appearance of which leads to serious disruptions to the meteorological situation, living conditions of fish, birds, and wildlife in vast areas of the equatorial region of the Pacific Ocean, islands and coasts. This situation arose in the winter of 1982, when the intensity of El Niño exceeded all known cases so far. Under the influence of El Niño, the temperature of the waters surrounding the Galapagos Islands reached +30°C, i.e. 5° above normal, the sea lion herd moved into colder waters, and high mortality was noted. On the Galapagos Islands in January 1983, the amount of precipitation that fell in 2 weeks exceeded the amount over the previous 6 years. The arid lands during the period of the cold Peruvian Current are now covered with lush vegetation, an extraordinary revival is observed among birds, reptiles, especially giant turtles, butterflies, horseflies, and mosquitoes are breeding. Heavy rains in northern Peru and on the coast led to the death of millions of birds inhabiting the "guan islands", etc. Serious consequences of this phenomenon also manifested themselves in the Peruvian economy - anchovy catches fell sharply. El Niño's influence was not limited to the islands and west coast of South America. As the trade winds weakened, the atmospheric pressure increased over Australia and Indonesia, where drought led to crop failures and famine. At the same time, over the eastern part of the Pacific Ocean in the area of ​​California and Hawaii, the deepening of the low pressure area was reflected in increased storm activity, and unprecedented high tides were noted.

Thus, the variability of heat carried by ocean currents determines large-scale anomalies in the atmosphere, and these, in turn, have an inverse effect on the ocean. Quantitative study of these processes, their spatial and temporal variability, are the most important factors in predicting long-term weather anomalies and climate change.

Main tasks of the work

Laboratory work is performed on a contour map of the World of any cartographic projection. Ocean current maps for winter and summer are used to plot the main currents.

1 The practical part is to map the main surface currents of the World Ocean (warm currents in red, cold currents in blue), indicated below.

Main surface currents of the World Ocean

South ocean

1. Antarctic circular (Western winds current)35.

2. Coastal Antarctic (Eastern Wind Current)

Atlantic Ocean

3. Northern trade wind

4. Azores

5. Florida

6. Portuguese

7. Angolan

8. Levontiiskoe

9. North African

10. Antilles

11. Gulf Stream

12. North Atlantic

13. Portuguese

14. Canary

15. Irminger

16. West Greenland

17. Baffinova

18. Labrador

19. South trade wind

20. Guiana

21. Caribbean

22. Interpass countercurrent

23. Guinean

24. Brazilian

25. Falklands

26. Bengal

Pacific Ocean

27. Northern trade wind

28. New Zealand Western

29. New Zealand Eastern

30. Formosan

31. Mindanao

32. Primorskoe

33. Tsushima

34. Kuroshio

35. North Pacific

36. Californian

37. Kamchatsky

38. Oyashio

39. Alaskan

40. Aleutian

41. Interpass countercurrent

42. El Niño current (periodic)

43. South trade wind

44. East Australian

45. Western New Zealand

46. ​​East New Zealand

47. Peruvian

Indian Ocean

48. South trade wind

49. Madagascar

50. Mozambican

51. Needle

52. Interpass countercurrent

53. Western monsoon (winter)

54. Eastern monsoon (summer)

55. Somali (changeable according to seasons)

56. Western Australian

Arctic Ocean

57. Norwegian

58. North Cape

59. Spitsbergen

60. East Greenland

61. Western Arctic (Arctic drift)

Is the Gulf Stream, El Niño, Kuroshio. What other currents exist? Why are they called warm? Read about it further.

Where do currents come from?

Currents are directional flows of water masses. They can have different widths and depths - from several meters to hundreds of kilometers. Their speed can reach up to 9 km/h. The direction of water flows is determined by the rotational force of our planet. Thanks to it, currents in the Southern Hemisphere deviate to the right, and in the Northern Hemisphere - to the left.

The formation and character of currents is influenced by many conditions. The reason for their appearance may be the wind, the tidal forces of the Moon and the Sun, different densities and temperatures, and the water level of the World Ocean. Most often, several factors contribute to the formation of currents.

There is a neutral, in the ocean. They are defined as such not because of the temperature of their own water masses, but because of the difference with the temperature of the surrounding waters. This means that the current can be warm, even if its waters are considered cold by many indicators. For example, the Gulf Stream is warm, although its temperature ranges from 4 to 6 degrees, and the cold temperature is up to 20 degrees.

A warm current is one that forms near the equator. They form in warm waters and move to colder ones. In turn, they move towards the equator. Neutral currents are those that do not differ in temperature from the surrounding waters.

Warm currents

Currents influence the climate of coastal areas. Warm water currents warm the ocean waters. They contribute to a mild climate, high air humidity and large amounts of precipitation. Forests form on the banks next to which warm waters flow. There are such warm currents of the World Ocean:

Pacific Ocean Basin

• East Australian.
• Alaskan.
• Kuroshio.
• El Niño.

Indian Ocean Basin

• Agulhasskoe.

Atlantic Ocean Basin

• Irminger.
• Brazilian.
• Guiana.
• Gulf Stream.
• North Atlantic.

Arctic Ocean Basin

• West Spitsbergen.
• Norwegian.
• West Greenland.

Gulf Stream

The warm Atlantic current, one of the largest in the Northern Hemisphere, is the Gulf Stream. It begins in the waters of the Atlantic Ocean and moves in a northeast direction.

The current carries a lot of floating algae and various fish. Its width reaches up to 90 kilometers, and the temperature is 4-6 degrees Celsius. The waters of the Gulf Stream have a bluish tint, contrasting with the surrounding greenish ocean water. It is not homogeneous, and consists of several streams that can separate from the general flow.

The Gulf Stream is a warm current. Meeting with the cold Labrador Current in the Newfoundland area, it contributes to the frequent formation of fogs along the coast. In the very center of the North Atlantic, the Gulf Stream divides, forming the Canary and North Atlantic currents.

El Niño

El Niño is also a warm current - the most powerful current. It is not constant and occurs once every few years. Its appearance is accompanied by a sharp increase in water temperature in the surface layers of the ocean. But this is not the only sign of El Niño.

Other warm currents of the World Ocean can hardly compare with the power of influence of this “baby” (as the name of the current is translated). Together with warm waters, the current brings with it strong winds and hurricanes, fires, droughts, and prolonged rains. Residents of coastal areas are suffering from the damage caused by El Niño. Vast areas are flooded, leading to the destruction of crops and livestock.

The current is formed in the Pacific Ocean, in its equatorial part. It stretches along the coast of Peru and Chile, replacing the cold Humboldt Current. When El Niño occurs, fishermen also suffer. Its warm waters trap cold waters (which are rich in plankton) and prevent them from rising to the surface. In this case, the fish do not come to these territories to feed, leaving fishermen without a catch.

Kuroshio

In the Pacific Ocean, another warm current is the Kuroshio. It flows near the eastern and southern coasts of Japan. The current is often defined as a continuation of the Northern Trade Wind. The main reason for its formation is the difference in levels between the ocean and the East China Sea.

Flowing between the straits of Ryukkyu Island, the Kuroshio becomes the North Pacific Current, which turns into the Alaskan Current off the coast of America.

It has similar features to the Gulf Stream. It forms a whole system of warm currents in the Pacific Ocean, just like the Gulf Stream in the Atlantic. Thanks to this, Kuroshio is an important climate-forming factor, softening the climate of coastal areas. The current also has a strong influence on the water area, being an important hydrobiological factor.

The waters of the Japanese current are characterized by a dark blue color, hence its name “Kuroshio”, which translates as “black current” or “dark water”. The current reaches a width of 170 kilometers, and its depth is about 700 meters. Kuroshio's speed ranges from 1 to 6 km/h. The water temperature of the current is 25 -28 degrees in the south and about 15 degrees in the north.

Conclusion

The formation of currents is influenced by many factors, and sometimes a combination of them. A current whose temperature exceeds the temperature of the surrounding waters is called warm. At the same time, the water in the current can be quite cold. The most famous warm currents are the Gulf Stream, which flows in the Atlantic Ocean, as well as the Pacific Kuroshio and El Niño currents. The latter occurs periodically, bringing with it a chain of environmental disasters.

Mariners learned about the presence of ocean currents almost as soon as they began to plow the waters of the World Ocean. True, the public paid attention to them only when, thanks to the movement of ocean waters, many great geographical discoveries were made, for example, Christopher Columbus sailed to America thanks to the North Equatorial Current. After this, not only sailors, but also scientists began to pay close attention to ocean currents and strive to study them as best and deeply as possible.

Already in the second half of the 18th century. the sailors studied the Gulf Stream quite well and successfully applied the acquired knowledge in practice: from America to Great Britain they walked with the current, and in the opposite direction they kept a certain distance. This allowed them to stay two weeks ahead of ships whose captains were not familiar with the area.

Ocean or sea currents are large-scale movements of water masses in the World Ocean at speeds from 1 to 9 km/h. These streams do not move chaotically, but in a certain channel and direction, which is the main reason why they are sometimes called rivers of the oceans: the width of the largest currents can be several hundred kilometers, and the length can reach several thousand.

It has been established that water flows do not move straight, but deviate slightly to the side and are subject to the Coriolis force. In the Northern Hemisphere they almost always move clockwise, in the Southern Hemisphere it’s the other way around.. At the same time, currents located in tropical latitudes (they are called equatorial or trade winds) move mainly from east to west. The strongest currents were recorded along the eastern coasts of the continents.

Water flows do not circulate on their own, but are set in motion by a sufficient number of factors - the wind, the rotation of the planet around its axis, the gravitational fields of the Earth and the Moon, the bottom topography, the outlines of continents and islands, the difference in temperature indicators of water, its density, depth in different places in the ocean and even its physical and chemical composition.

Of all types of water flows, the most pronounced are the surface currents of the World Ocean, the depth of which is often several hundred meters. Their occurrence was influenced by trade winds constantly moving in tropical latitudes in a west-east direction. These trade winds form the huge flows of the North and South Equatorial Currents near the equator. A smaller part of these flows returns to the east, forming a countercurrent (when the movement of water occurs in the opposite direction from the movement of air masses). Most of them, when colliding with continents and islands, turn to the north or south.

Warm and cold water currents

It must be taken into account that the concepts of “cold” or “warm” currents are conditional definitions. So, despite the fact that the temperature of the water flows of the Benguela Current, which flows along the Cape of Good Hope, is 20°C, it is considered cold. But the North Cape Current, which is one of the branches of the Gulf Stream, with temperatures from 4 to 6 ° C, is warm.

This happens because cold, warm and neutral currents got their names based on a comparison of the temperature of their water with the temperature of the surrounding ocean:

• If the temperature indicators of the water flow coincide with the temperature of the surrounding waters, such a flow is called neutral;
• If the temperature of the currents is lower than the surrounding water, they are called cold. They usually flow from high latitudes to low latitudes (for example, the Labrador Current), or from areas where, due to high river flows, ocean water has a reduced salinity of surface waters;
• If the temperature of the currents is warmer than the surrounding water, then they are called warm. They move from tropical to subpolar latitudes, for example, the Gulf Stream.

Main water flows

At the moment, scientists have recorded about fifteen major oceanic water flows in the Pacific, fourteen in the Atlantic, seven in the Indian and four in the Arctic Ocean.

It is interesting that all currents of the Arctic Ocean move at the same speed - 50 cm/sec, three of them, namely the West Greenland, West Spitsbergen and Norwegian, are warm, and only the East Greenland is a cold current.

But almost all oceanic currents of the Indian Ocean are warm or neutral, with the Monsoon, Somali, Western Australian and Cape Agulhas current (cold) moving at a speed of 70 cm/sec, the speed of the rest varies from 25 to 75 cm/sec. The water flows of this ocean are interesting because, together with the seasonal monsoon winds, which change their direction twice a year, the oceanic rivers also change their course: in winter they mainly flow to the west, in summer - to the east (a phenomenon characteristic only of the Indian Ocean ).

Since the Atlantic Ocean stretches from north to south, its currents also have a meridional direction. Water flows located in the north move clockwise, in the south - counterclockwise.

A striking example of the flow of the Atlantic Ocean is the Gulf Stream, which, starting in the Caribbean Sea, carries warm waters to the north, breaking up into several side streams along the way. When the waters of the Gulf Stream find themselves in the Barents Sea, they enter the Arctic Ocean, where they cool and turn south in the form of the cold Greenland Current, after which at some stage they deviate to the west and again join the Gulf Stream, forming a vicious circle.

The currents of the Pacific Ocean are mainly latitudinal and form two huge circles: northern and southern. Since the Pacific Ocean is extremely large, it is not surprising that its water flows have a significant impact on much of our planet.

For example, trade wind water currents transport warm waters from the western tropical coasts to the eastern ones, which is why in the tropical zone the western part of the Pacific Ocean is much warmer than the opposite side. But in the temperate latitudes of the Pacific Ocean, on the contrary, the temperature is higher in the east.

Deep Currents

For quite a long time, scientists believed that deep ocean waters were almost motionless. But soon special underwater vehicles discovered both slow and fast-flowing water streams at great depths.

For example, under the Equatorial Current of the Pacific Ocean at a depth of about one hundred meters, scientists have identified the underwater Cromwell Current, moving eastward at a speed of 112 km/day.

Soviet scientists found a similar movement of water flows, but in the Atlantic Ocean: the width of the Lomonosov Current is about 322 km, and the maximum speed of 90 km/day was recorded at a depth of about one hundred meters. After this, another underwater flow was discovered in the Indian Ocean, although its speed turned out to be much lower - about 45 km/day.

The discovery of these currents in the ocean gave rise to new theories and mysteries, the main one of which is the question of why they appeared, how they were formed, and whether the entire area of ​​the ocean is covered by currents or there is a point where the water is still.

The influence of the ocean on the life of the planet

The role of ocean currents in the life of our planet can hardly be overestimated, since the movement of water flows directly affects the planet’s climate, weather, and marine organisms. Many compare the ocean to a huge heat engine driven by solar energy. This machine creates a constant exchange of water between the surface and deep layers of the ocean, providing it with oxygen dissolved in the water and influencing the life of marine inhabitants.

This process can be traced, for example, by considering the Peruvian Current, which is located in the Pacific Ocean. Thanks to the rise of deep waters, which lift phosphorus and nitrogen upward, animal and plant plankton successfully develop on the ocean surface, resulting in the organization of a food chain. Plankton is eaten by small fish, which, in turn, become prey to larger fish, birds, and marine mammals, which, given such food abundance, settle here, making the region one of the most highly productive areas of the World Ocean.

It also happens that a cold current becomes warm: the average ambient temperature rises by several degrees, causing warm tropical showers to fall on the ground, which, once in the ocean, kill fish accustomed to cold temperatures. The result is disastrous - a huge amount of dead small fish ends up in the ocean, large fish leave, fishing stops, birds leave their nesting places. As a result, the local population is deprived of fish, crops destroyed by heavy rains, and profits from the sale of guano (bird droppings) as fertilizer. It can often take several years to restore the previous ecosystem.

As a rule, their movement occurs in a strictly defined direction and can have a large extent. The current map below displays them in full.

Water flows are of considerable size: they can reach tens, or even hundreds of kilometers in width, and have great depth (hundreds of meters). The speed of ocean and sea currents varies - on average, it is 1-3 thousand m/hour. But there are also so-called high-speed ones. Their speed can reach 9,000 m/hour.

Where do currents come from?

The causes of water currents can be a sharp change in water temperature due to heating, or, conversely, cooling. They are also affected by different densities, for example, in a place where several currents (sea and ocean) collide, precipitation, evaporation. But basically, cold and warm currents arise due to the action of winds. Therefore, the direction of the largest oceanic water flows depends mainly on the air currents of the planet.

Currents formed by winds

An example of constantly blowing winds is the trade winds. They begin their life from 30 latitudes. The currents created by these air masses are called trade winds. There are the Southern Trade Wind and Northern Trade Wind Currents. In the temperate zone, such water flows are formed under the influence of westerly winds. They form one of the largest currents on the planet. In the northern and southern hemispheres there are two water flow cycles: cyclonic and anticyclonic. Their formation is influenced by the inertial force of the Earth.

Types of currents

Mixed, neutral, cold and warm currents are types of circulating masses on the planet. When the temperature of the stream water is lower than the temperature of the surrounding water, this is If, on the contrary, this is its warm variety. Neutral currents do not differ from the temperature of surrounding waters. And mixed ones can change throughout their entire length. It is worth noting that there is no constant temperature indicator for currents. This figure is very relative. It is determined by comparing the surrounding water masses.

In tropical latitudes, warm currents circulate along the eastern edges of the continents. Cold ones - along the western ones. In temperate latitudes, warm currents pass along the western shores, and cold currents along the eastern shores. The variety can be determined by another factor. So, there is an easier rule: cold currents go towards the equator, and warm currents - from it.

Meaning

It’s worth talking about it in more detail. Cold and warm currents play an important role on planet Earth. The significance of circulating water masses is that due to their movement, solar heat is redistributed on the planet. Warm currents increase the air temperature of nearby areas, while cold currents lower it. Formed on water, water flows have a serious impact on the mainland. In areas where warm currents constantly pass, the climate is humid, where there are cold currents, on the contrary, it is dry. Ocean currents also contribute to the migration of oceanic ichthyofauna. Under their influence, plankton moves, and fish migrate after them.

We can give examples of warm and cold currents. Let's start with the first variety. The largest water flows are: Gulf Stream, Norwegian, North Atlantic, Northern and Southern Trade Winds, Brazilian, Kuroshio, Madagascar and others. The coldest ocean currents: Somali, Labrador, California.

Major currents

The largest warm current on the planet is the Gulf Stream. This is a meridional circulating flow that carries 75 million tons of water every second. The width of the Gulf Stream is from 70 to 90 km. Thanks to him, Europe receives a comfortable mild climate. It follows from this that cold and warm currents largely affect the life of all living organisms on the planet.

Of the zonal, cold watercourses, the current is of greatest importance. In the southern hemisphere, near the shores of Antarctica, there are no island or continental accumulations. A large area of ​​the planet is completely filled with water. The Indian and Quiet streams converge here into one stream and unite into a separate huge body of water. Some scientists recognize its existence and call it Southern. It is here that the largest flow of water is formed - the current of the Western Winds. Every second it carries a flow of water that is three times larger than the Gulf Stream.

Canary or cold?

Currents can change their temperature. For example, the flow starts from cold masses. Then it warms up and becomes warm. One of the options for such a circulating water mass is the Canary Current. It originates in the northeast Atlantic Ocean. It is directed by a cold stream along Europe. Passing along the western coast of Africa, it becomes warm. This current has long been used by sailors to travel.

Masses of water that continuously move through the oceans are called currents. They are so strong that no continental river can compare with them.

What types of currents are there?

Until a few years ago, only currents moving on the surface of the seas were known. They are called superficial. They flow at depths of up to 300 meters. We now know that deep currents occur in deeper areas.

How do surface currents occur?

Surface currents are caused by constantly blowing winds - trade winds - and reach speeds of 30 to 60 kilometers per day. These include equatorial currents (directed to the west), off the eastern coasts of continents (directed towards the poles) and others.

What are trade winds?

Trade winds are air currents (winds) that are stable throughout the year in the tropical latitudes of the oceans. In the Northern Hemisphere, these winds are directed from the northeast, in the Southern Hemisphere - from the southeast. Due to the rotation of the Earth, they always deviate to the west. The winds that blow in the Northern Hemisphere are called northeast trade winds, and in the Southern Hemisphere they are called southeast trade winds. Sailing ships use these winds to arrive at their destination faster.

What are equatorial currents?

Trade winds blow constantly and so strongly that they divide the ocean waters on both sides of the equator into two powerful westerly currents, which are called equatorial currents. On their way they find themselves on the eastern coasts of parts of the world, so these currents change direction to the north and south. Then they fall into other wind systems and break up into small currents.

How do deep currents arise?

Deep currents, unlike surface ones, are caused not by winds, but by other forces. They depend on the density of the water: cold and salty water is denser than warm and less salty, and therefore sinks lower to the seabed. Deep currents occur because cooled, salty water in northern latitudes sinks and continues to move above the seabed. A new, warm surface current begins its movement from the south. The cold deep current carries water towards the equator, where it warms up again and rises. Thus, a cycle is formed. Deep currents move slowly, so sometimes years pass before they rise to the surface.

What is worth knowing about the equator?

The equator is an imaginary line that passes through the center of the Earth perpendicular to the axis of its rotation, that is, it is equally distant from both poles and divides our planet into two hemispheres - the Northern and Southern. The length of this line is about 40,075 kilometers. The equator is located at zero degree latitude.

Why does the salt content of seawater change?

The salt content of seawater increases when the water evaporates or freezes. The North Atlantic Ocean has a lot of ice, so the water there is saltier and colder than at the equator, especially in winter. However, the salinity of warm water increases with evaporation, as salt remains in it. Salt content decreases when, for example, ice melts in the North Atlantic and fresh water flows into the sea.

What are the effects of deep currents?

Deep currents carry cold water from polar regions to warm tropical countries, where water masses mix. Rising cold water affects the coastal climate: rain falls directly on the cold water. The air arrives on the warm continent almost dry, so the rains stop and deserts appear on the coastal shores. This is how the Namib Desert on the South African coast came into being.

What is the difference between cold and warm currents?

Depending on the temperature, sea currents are divided into warm and cold. The first ones appear near the equator. They carry warm waters through cold waters located near the poles and heat the air. Counter sea currents flowing from the polar regions towards the equator transport cold waters through the surrounding warm ones, and as a result the air cools. Sea currents are like a huge air conditioner that distributes cold and warm air around the globe.

What are burs?

Bores are tidal waves that can be observed in those places where rivers flow into the seas - that is, at the mouths. They arise when so many waves running towards the shore accumulate in a shallow and wide funnel-shaped mouth that they all suddenly flow into the river. In the Amazon, one of the South American rivers, the surf became so raging that a five-meter wall of water advanced more than a hundred kilometers inland. Bors also appear in the Seine (France), the Ganges delta (India) and on the coast of China.

Alexander von Humboldt (1769-1859)

German naturalist and scientist Alexander von Humboldt traveled extensively throughout Latin America. In 1812, he discovered that a cold deep current moves from the polar regions to the equator and cools the air there. In his honor, the current that carries water along the coast of Chile and Peru was named the Humboldt Current.

Where on the planet are the largest warm sea currents?

The largest warm sea currents include the Gulf Stream (Atlantic Ocean), Brazil (Atlantic Ocean), Kuroshio (Pacific Ocean), Caribbean (Atlantic Ocean), North and South Equatorial Currents (Atlantic, Pacific and Indian Oceans), and the Antilles (Atlantic Ocean). ocean).

Where are the largest cold sea currents?

The largest cold sea currents are the Humboldt (Pacific Ocean), Canary (Atlantic Ocean), Oyashio or Kuril (Pacific Ocean), East Greenland (Atlantic Ocean), Labrador (Atlantic Ocean) and California (Pacific Ocean).

How do sea currents affect climate?

Warm sea currents, first of all, affect the air masses surrounding them and, depending on the geographical location of the continent, warm the air. Thus, thanks to the Gulf Stream in the Atlantic Ocean, the temperature in Europe is 5 degrees higher than it could be. Cold currents that move from the polar regions to the equator, on the contrary, lead to a decrease in air temperature.

What are the effects of changes in sea currents?

Ocean currents can be affected by sudden events such as volcanic eruptions or changes associated with El Niño. El Niño is a warm water current that can displace cold currents near the coasts of Peru and Ecuador in the Pacific Ocean. Although El Niño's influence is limited to certain areas, its effects affect the climate of remote regions. It causes heavy rainfall along the coasts of South America and eastern Africa, resulting in devastating floods, storms and landslides. In contrast, the tropical rainforests around the Amazon experience a dry climate that reaches Australia, Indonesia and South Africa, contributing to droughts and the spread of forest fires. Near the Peruvian coast, El Niño leads to mass die-offs of fish and corals as plankton, which live primarily in cold water, suffer as it warms.

How far can sea currents carry objects out to sea?

Sea currents can carry objects that fall into the water over vast distances. For example, wine bottles can be found in the sea, which 30 years ago were thrown from ships in the ocean between South America and Antarctica and carried thousands of kilometers away. Currents carried them across the Pacific and Indian oceans!

What is worth knowing about the Gulf Stream?

The Gulf Stream Current is one of the most powerful and famous sea currents that arises in the Gulf of Mexico and carries warm waters to the Spitsbergen archipelago. Thanks to the warm waters of the Gulf Stream, Northern Europe enjoys a mild climate, although it should be much colder here since it is located as far north as Alaska, where it is freezing cold.

What are sea currents - video