Periodically recurring ocean current. World ocean currents

Sea currents have a significant impact on the climate not only of those coasts along which they flow, but also on changes in weather on a global scale. In addition, sea currents are of great importance for navigation. This is especially true for yachting, as they affect the speed and direction of movement of both sailboats and motorized vessels.

To choose the optimal route in one direction or another, it is important to know and take into account the nature of their occurrence, the direction and speed of the current. This factor should be taken into account when mapping vessel movements both off the coast and on the high seas.

Classification of sea currents

All sea currents, depending on their characteristics, are divided into several types. Classification of sea currents as follows:

By origin.
By sustainability.
By depth.
By the type of movement.
By physical properties (temperature).

Reasons for the formation of sea currents

Formation of sea currents depends on a number of factors that have a complex effect on each other. All reasons are conventionally divided into external and internal. The first include:

The tidal gravitational effect of the Sun and Moon on our planet. As a result of these forces, not only daily ebbs and flows occur on the coast, but also steady movements of water volumes in the open ocean. The gravitational effect in one way or another affects the speed and direction of movement of all ocean currents.
The action of winds on the sea surface. Blowing long time in one direction of the wind (for example, trade winds) inevitably transfer part of the energy of the moved air masses and surface waters, dragging them along. This factor can cause the appearance of both temporary surface currents and steady movements of huge masses of water - the Tradewinds (Equatorial), Pacific and Indian oceans.
Difference atmospheric pressure in different parts of the ocean, bending the water surface in a vertical direction. As a result, a difference in water level arises, and, as a result, sea currents are formed. This factor leads to temporary and unstable surface flows.
Waste currents occur when sea level changes. A classic example is the Florida Current flowing out of the Gulf of Mexico. The water level in the Gulf of Mexico is significantly higher than in the adjacent Sargasso Sea from the northeast due to the surge of water into the Gulf by the Caribbean Current. This creates a stream that rushes through the Florida Strait, and gives rise to the famous Gulf Stream.
Runoffs from continental coasts can also generate steady currents. As an example, we can cite powerful streams that arise at the mouths of large rivers - the Amazon, La Plata, Yenisei, Ob, Lena, and penetrate into the open ocean for hundreds of kilometers in the form of desalinated streams.

Internal factors include the uneven density of water volumes. For example, increased evaporation of moisture in the tropical and equatorial regions leads to a higher concentration of salts, while in regions with abundant precipitation, the salinity, on the contrary, is lower. The density of water also depends on the level of salinity. The temperature also has an effect on the density; at higher latitudes or in deeper layers, the water is colder, and, therefore, denser.

Types of sea currents by stability

The next feature that allows you to produce classification of sea currents, is their stability. On this basis, the following types of sea currents are distinguished:

Permanent.
Fickle.
Periodic.

Constants, in turn, depending on speed and power, are divided into:

Powerful - Gulf Stream, Kuroshio, Caribbean.
Middle - Tradewind Atlantic and Pacific.
Weak - California, Canary, North Atlantic, Labrador, etc.
Local - have low speeds, short length and width. They are often so weakly expressed that it is practically impossible to determine them without special equipment.

Periodic currents include currents that change their direction and speed from time to time. At the same time, a certain cyclicality is manifested in their nature, depending on external factors - for example, on the seasonal change in the direction of the winds (wind), the gravitational action of the Moon and the Sun (tidal), and so on.

If the change in direction, force and speed of the flow is not subject to any recurring laws, they are called non-periodic. These include the arising movements of water masses under the influence of the difference in atmospheric pressure, hurricane winds, accompanied by a surge of water.

Types of sea currents by depth

The movement of water masses occurs not only in the surface layers of the sea, but also in its depths. On this basis, the types of sea currents are:

Surface - they pass in the upper layers of the ocean, up to 15 m deep. Wind is the main factor in their occurrence. It also affects the direction and speed of their movement.
Deepwater - occur in the water column, below the surface, but above the bottom. Their flow rate is lower than that of surface ones.
Bottom currents, as the name suggests, flow in close proximity to the seabed. Due to the constant soil friction force acting on them, their speed is usually low.

Types of sea currents by the nature of movement

Sea currents differ among themselves and in the nature of their movement. On this basis, they are divided into three types:

Meandering. They have a winding, horizontal character. The bends formed in this case are called "meanders", by their similarity to the Greek ornament of the same name. In some cases, meanders can form eddies at the edges of the main stream, up to hundreds of kilometers long.
Straightforward. They are characterized by a relatively straight-line movement.
Circular. They are closed circulation circles. In the Northern Hemisphere, they can go clockwise ("anticyclonic") or against it ("cyclonic"). For the southern hemisphere, respectively, the order will be reversed -.

Classification of sea currents by their temperature

The main classification factor is temperature of sea currents... On this basis, they are divided into warm and cold. At the same time, the concepts of “warm” and “cold” are rather arbitrary. For example, the North Cape, which is a continuation of the Gulf Stream, is considered warm, having an average temperature of 5-7 ° C, but the Canary Island is classified as cold, despite the fact that its temperature is 20-25 ° C.

The reason is that the temperature of the surrounding ocean is taken as the point of determination. Thus, the 7-degree North Cape Current invades the Barents Sea, which has a temperature of 2-3 degrees. And the temperature of the waters surrounding the Canary Current, in turn, is several degrees higher than in the current itself. However, there are also such currents, the temperature of which practically does not differ from the temperature of the surrounding waters. These include the North and South trade winds and the current of the Westerly winds enveloping the Antarctic.

Excitement Is the oscillatory motion of water. It is perceived by the observer as the movement of waves along the surface of the water. In fact, the water surface oscillates up and down from the average level of the equilibrium position. The wave shape during excitement is constantly changing due to the movement of particles in closed, almost circular orbits.

Each wave is a smooth connection of elevations and depressions. The main parts of the wave are: crest - the highest part; sole - lowest part; slope - profile between the crest and base of the wave. The line along the crest of the wave is called wave front (fig. 1).

Figure: 1. The main parts of the wave

The main characteristics of waves are height - the difference in the levels of the crest and the bottom of the wave; length - the shortest distance between adjacent crests or troughs of waves; steepness - the angle between the slope of the wave and the horizontal plane (Fig. 1).

Figure: 1. The main characteristics of the wave

Waves have very high kinetic energy. The higher the wave, the more kinetic energy is contained in it (proportional to the square of the height increase).

Under the influence of the Coriolis force, a water wall appears on the right downstream far from the mainland, and a depression is created near the land.

By origin waves are subdivided as follows:

friction waves;
baric waves;
seismic waves or tsunamis;
seiches;
tidal waves.

Friction waves

Friction waves, in turn, can be wind(fig. 2) or deep. Wind waves are caused by wind waves of friction at the boundary of air and water. The height of wind waves does not exceed 4 m, but with strong and prolonged storms, it increases to 10-15 m and more. The highest waves - up to 25 m - are observed in the westerly winds of the Southern Hemisphere.

Figure: 2. Wind waves and surf waves

Pyramidal, high and steep wind waves are called the crowd. These waves are inherent in the central areas of cyclones. When the wind dies down, excitement takes on character swell, i.e., excitement by inertia.

The primary form of wind waves is ripples. It occurs when the wind speed is 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, was 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 flow levels, near river mouths, at the edge of melting ice. These waves stir the sea water and are very dangerous for sailors.

Baric wave

Baric waves arise due to the rapid change in atmospheric pressure in the places of origin of cyclones, especially tropical ones. Usually these waves are solitary and do not cause much harm. The exception is when they coincide with high tide. The Antilles, the Florida Peninsula, the coasts of China, India, and Japan are most often subjected to such disasters.

Tsunami

Seismic waves occur under the influence of tremors and coastal earthquakes. These are very long and low waves in the open ocean, but the force of their propagation is quite large. They move at a very high speed. At the coasts, their length decreases, and their height increases sharply (on average, from 10 to 50 m). Their appearance entails human casualties. First, the morse retreats several kilometers from the coast, gaining strength for the push, and then waves splash onto the coast at a tremendous speed with an interval of 15-20 minutes (Fig. 3).

Figure: 3. Tsunami transformation

The Japanese named seismic waves tsunamiand this term is used all over the world.

The seismic belt of the Pacific Ocean is the main area of \u200b\u200btsunami formation.

Seiches

Seiches Are standing waves that occur in bays and inland seas. They occur by inertia after the cessation of the action of external forces - wind, seismic shocks, abrupt changes, intense precipitation, etc. At the same time, in one place the water rises, and in another - falls.

Tidal wave

Tidal waves - these are movements performed under the influence of the tidal forces of the Moon and the Sun. The reverse reaction of sea water to tide - low tide. The strip drained at low tide is called drying.

There is a close relationship with the height of the ebb and flow with the phases of the moon. New and full moons have the highest ebb tides and the lowest ebb tides. They're called syzygy. At this time, the lunar and solar tides, coming at the same time, are superimposed on each other. In the intervals between them, on the first and last Thursdays of the moon phase, the lowest are observed, quadrature hot flashes.

As already mentioned in the second section, in the open ocean, the tide height is not high - 1.0-2.0 m, while at the rugged coast it sharply increases. The tide reaches its maximum value on the Atlantic coast North America, in the Bay of Fundy (up to 18 m). In Russia, the maximum tide value - 12.9 m - was recorded in Shelikhov Bay (Sea of \u200b\u200bOkhotsk). In the inland seas, tides are hardly noticeable, for example, in the Baltic Sea near St. Petersburg, the tide is 4.8 cm, but along some rivers the tide can be traced for hundreds and even thousands of kilometers from the mouth, for example, in the Amazon - up to 1400 cm.

The steep tidal wave rising up the river is called boron. On the Amazon, the forest reaches a height of 5 m and is felt at a distance of 1400 km from the river mouth.

Even with a calm surface, waves occur in the ocean water column. 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 action on a vertically heterogeneous mass of water. In addition, since the temperature, salinity and density of the ocean water change with depth not gradually, but in leaps and bounds 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, 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 \u200b\u200bcurrents are subdivided as follows:

permanentthat pass in the same areas of the ocean have one general direction, more or less constant speed and stable physicochemical properties of the transported water masses (North and South trade winds, Gulf Stream, etc.);
periodic, in which the direction, speed, temperature are subject to periodic laws. They occur at regular intervals in a certain sequence (summer and winter monsoon currents in the northern part of the Indian Ocean, tidal currents);
temporarymost often caused by winds.

By temperature indicator sea \u200b\u200bcurrents are:

warmwhich have a temperature higher than the surrounding water (for example, the Murmansk current with a temperature of 2-3 ° C among the waters O ° C); they have a direction from the equator to the poles;
coldthe 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;
neutralwhich have a temperature close to environment (for example, equatorial currents).

By the depth of location in the water column, currents are distinguished:

superficial (up to 200 m depth);
subsurfacehaving a direction opposite to the surface;
deepwhose movement is very slow - on the order of a few centimeters or the first tens of centimeters per second;
bottomregulating the exchange of waters between polar - subpolar and equatorial-tropical latitudes.

By origin the following trends are distinguished:

frictional, which can be drift or wind. Drift ones arise under the influence of constant winds, and wind ones are created by seasonal winds;
gradient-gravity, among which there are stockresulting from the tilt of the surface caused by excess water from the ocean and heavy rainfall, and compensatory, which arise due to the outflow of water, scarce precipitation;
inertthat 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, continuously extending from the North Pole to the South Pole, and superimpose on it a generalized diagram of atmospheric winds, then, taking into account the deflecting Coriolis force, we get six closed rings -
gyres of sea currents: North and South equatorial, North and South subtropical, Subarctic and Subantarctic (Fig. 4).

Figure: 4. Cycles of sea currents

Departures from the ideal scheme are caused by the presence of continents and the peculiarities of their distribution over earth surface Earth. However, as in the ideal diagram, in reality, there is observed on the ocean surface zonal change large - several thousand kilometers long - not completely enclosed 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 - counterclockwise. Directed from west to east equatorial countercurrents.

In the temperate subpolar latitudes of the Northern Hemisphere, there are small current rings around baric minima. The movement of waters in them is directed counterclockwise, and in the Southern Hemisphere - from west to east around Antarctica.

The currents in zonal circulation systems are quite well traced to a depth of 200 m. With depth they change direction, weaken and turn into weak eddies. Instead, meridional currents intensify at depth.

The deepest and most powerful surface currents play a critical role in the global circulation of the oceans. The most stable surface currents are the North and South trade winds of the Pacific and Atlantic oceans and the South trade winds of the Indian Ocean. They have a direction from east to west. Tropical latitudes are characterized by warm runoff 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 Westerly winds in the South. The latter forms a ring in three oceans around Antarctica. The great gyres in the Northern Hemisphere are closed by cold compensatory currents: along the western shores in tropical latitudes - California, Canary, and in the South - Peruvian, Bengal, Western Australian.

The most famous currents are also the warm Norwegian current in the Arctic, the cold Labrador current in the Atlantic, the warm Alaskan and cold Kuril-Kamchatka currents - in Pacific.

The monsoon circulation in the northern part of the 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 runoff of the rivers of Siberia, rotational cyclonic movement (counterclockwise) over the Barents and Kara Seas.

In addition to circulating 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 eddies. 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 rotate at an even higher speed than in the open ocean, their ring system is better expressed, therefore 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, violating its zonal distribution. So, the non-freezing port of Murmansk is located beyond the Arctic Circle, and on the east coast of North America, the Bay of St. Lawrence (48 ° N). Warm currents contribute to precipitation, cold currents, on the contrary, reduce the possibility of precipitation. Therefore, the territories washed by warm currents have a humid climate, and cold ones - dry. With the help of sea currents, plants and animals migrate, nutrients and gas exchange. Currents are also taken into account when sailing.

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

Water streams have significant dimensions: they can be tens, or even hundreds of kilometers wide, and have a great depth (hundreds of meters). The speed of oceanic and sea currents is different - on average, it is 1-3 thousand m / h. But, there are also so-called high-speed ones. Their speed can reach 9,000 m / h.

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 streams (sea and oceanic) collide, precipitation, evaporation. But mainly 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.

Wind-Driven Currents

Trade winds are an example of constantly blowing winds. They begin their lives from the 30's latitudes. The currents created by these air masses are called trade winds. There are South Passat and North Passat 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 cycles of the water flow: cyclonic and anticyclonic. Their formation is influenced by the inertial force of the Earth.

Varieties 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, it is its warm variety. Neutral currents do not differ from the temperature of the surrounding waters. And mixed ones can change along the entire length. It should be noted that there is no constant temperature indicator of currents. This figure is very relative. It is determined by comparing the surrounding water masses.

In tropical latitudes, warm currents circulate along the eastern outskirts of the continents. Cold ones - along the western ones. In temperate latitudes, warm currents pass along the western shores, and cold currents along the east. You can also determine the variety by another factor. So, there is an easier rule: cold currents go to the equator, and warm ones go from it.

Value

It is worth talking about in more detail. Cold and warm currents play an important role on planet Earth. The significance of the circulating water masses is that due to their movement, the solar heat is redistributed on the planet. Warm currents increase the air temperature in 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 cold ones, on the contrary, dry. Also, ocean currents contribute to the migration of ocean ichthyofauna. Under their influence, plankton moves, and fish migrate behind it.

Examples of warm and cold currents can be cited. Let's start with the first variety. The largest are the following water streams: Gulf Stream, Norwegian, North Atlantic, North and South Passat, Brazilian, Kuroshio, Madagascar and others. The coldest ocean currents: Somali, Labrador, California.

Major currents

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

Of the zonal, cold streams, the current is of the greatest importance. In the southern hemisphere, not far from the shores of Antarctica, there are no island or continental accumulations. A large area of \u200b\u200bthe planet is completely filled with water. Here Indian, Quiet converge into one stream and unite into a separate huge reservoir. Some scientists acknowledge its existence and call it Southern. It is here that the largest flow of water is formed - the current of the West Winds. Every second it carries a stream of water that is three times the size of the Gulf Stream.

Canary or cold?

Currents can change their temperature. For example, the flow begins with cold masses. Then it warms up and becomes warm. One of the variants of such a circulating water mass is the Canary Current. It originates in the northeast of the Atlantic Ocean. Sent by a cold stream along Europe. Passing along the west coast of Africa, it gets warm. This current has long been used by seafarers to travel.

The importance of sea currents for the climate is very great: they transport nutrients and heat across the oceans of the planet.

At the beginning of the XIX century. in the south of the English county of Cornwall, Australian ferns were planted. This county is located in the same latitudes as the cities of Calgary (in Canada) and Irkutsk (in Siberia), known for their harsh winters. It would seem that tropical ferns should have died here from the cold. But they felt great. Today in Cornwall, you can visit the Heligan Botanical Garden, where these ferns grow safely in the open air, along with many other tropical and subtropical plants.

In winter, when freezing temperatures crackle in Calgary, the southwest of England is rarely cold. This is partly due to the fact that England is located on an island, and Calgary is located in the interior of the mainland, but much more importantly, the coast of Cornwall is washed by a warm sea current - the Gulf Stream. Thanks to him, the climate in western Europe is much milder than at the same latitudes in central Canada.

Cause of currents

The cause of sea currents is the heterogeneity of the waters. When a substance dissolved in water has a greater concentration in one place than in another, the water begins to move, seeking to equalize the concentrations. This law of diffusion can be observed if two vessels with solutions of different degrees of salinity are connected by a tube. In the oceans, these movements are called currents.

The main sea currents on our planet arise due to differences in temperature and salinity of water masses, as well as due to winds. Currents allow warmth from the tropics to reach high latitudes, while polar cold can refresh equatorial regions. Without sea currents, the flow of nutrients from the depths to the surface of the oceans and oxygen from the surface to the depths would be difficult.

Currents carry out water exchange both within the oceans and seas, and between them. Transferring thermal energy, they heat or cool air masses and largely determine the climate of those land areas, near which they pass, as well as the climate of the planet as a whole.

Ocean conveyor

Thermohaline circulation is a cycle caused by horizontal differences in temperature and salinity between water masses. Such circulations play a huge role in the life of our planet, forming the so-called global ocean conveyor. It transports deep waters from the North Atlantic to the North Pacific Ocean and surface waters in the opposite direction in about 800 years.

Let's choose a starting point, for example, in the middle of the Atlantic - along the Gulf Stream. The water near the surface is heated by the sun and gradually moves northward along the east coast of North America. On its long journey, it gradually cools down, transferring heat to the atmosphere by various mechanisms, including by evaporation. In this case, evaporation leads to an increase in the salt concentration and, consequently, the density of the water.

In the Newfoundland region, the Gulf Stream splits into a northeast-going North Atlantic Current and a branch heading south-east back to the mid-Atlantic. Having reached the Labrador Sea, part of the Gulf Stream cools down and goes down, where it forms a cold deep current that spreads south across the Atlantic to the Antarctic. Along the way, deep waters mix with waters coming through the Strait of Gibraltar from the Mediterranean Sea, which, due to their high salinity, are heavier than surface waters. atlantic waters and therefore spread in the deepest layers.

The Antarctic current moves eastward and, almost at the border of the Indian and Pacific Oceans, splits into two branches. One of them goes north, and the other continues to the Pacific Ocean, where water masses move counterclockwise, again and again returning to the Antarctic cycle. In the Indian Ocean, Antarctic waters mix with warmer tropical waters. At the same time, they gradually become less dense and rise to the surface. Moving from east to west, they make the long journey back to the Atlantic Ocean.

The wind comes into play

Another type of water circulation is associated with the action of wind and is common in the surface layers of the oceans. The winds blowing from the shore drive the surface water away. There is a slope in the level, which is compensated for by water coming from the underlying layers.

The rotation of the Earth leads to the fact that the directions of currents driven by the wind change under the influence of the Coriolis force, deviating to the right from the direction of the wind in the Northern Hemisphere and to the left in the South. The angle of this deflection is about 25 ° off the coast and about 45 ° on the high seas.

Each current corresponds to a countercurrent of opposite temperature. It replaces waters whose movement is deflected to the right or left due to the Coriolis force. For example, in the Atlantic Ocean, the warm Gulf Stream is compensated by the cold Labrador current, which runs along the coast of Canada.

In the Pacific Ocean, the warm Kuroshio Current (flowing north from the Philippines) is complemented by the cold Oyashio flowing out of the Bering Sea. As a result, currents form oceanic gyres on each side of the equator.

Surface water journey

Surface trade winds are associated with trade winds that blow from the northeast in the Northern Hemisphere and from the southeast in the South. Between the northern and southern tropics, these winds drive the water masses to the west. Moving waters gradually heat up. Having reached the western shores of their ocean, they are forced to turn and move along the coast, left or right, depending on the hemisphere. In the Northern Hemisphere, they turn clockwise (to the left), and in the Southern Hemisphere - counterclockwise (to the right).

When these waters reach high latitudes, westerly winds drive them eastward to opposite shores. Having reached the eastern shores of each ocean, they turn south (in the Northern Hemisphere) or north (in the Southern) and so complete their cycles.

Friction and stirring

Deep-water currents interact with the unevenness of the seabed, the uplifts and depressions of which contribute to the formation of huge deep gyres. Friction against the bottom stimulates the mixing of water masses of different temperatures and salinity. Surface currents by means of friction contact the underlying layers, drawing them into motion and mixing with them. The bottom relief can also affect currents in the form of so-called topographic Rossby waves - slow wave disturbances that propagate in the structure of currents and determine the global nature of the circulation of water masses.

Masses of water that move continuously across 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 along the surface of the seas were known. They are called superficial. They flow at a depth of up to 300 meters. We now know that deep currents arise in deeper areas.

How do surface currents arise?

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 east coast of continents (directed toward 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 north-east, in the South - from the south-east. Due to the rotation of the Earth, they always deflect 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. Sailboats use these winds to get to their destination faster.

What are equatorial currents?

Trade winds blow constantly and so strong that they separate ocean waters on both sides of the equator into two powerful western currents, which are called equatorial. 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 currents, are caused not by winds, but by other forces. They depend on the density of the water: cold and salty water denser than warm, and less salty, and therefore sinks lower to the seabed. Deep currents are caused by the fact that the cooled salt water in northern latitudes sinks and continues to move above the seabed. A new, warm surface current begins to move from the south. A cold deep current carries water towards the equator, where it warms up again and rises upward. Thus, a circulation is formed. Deep currents move slowly, so it sometimes takes years until 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 - North and South. 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 in seawater increases when the water evaporates or freezes. There is a lot of ice in the North Atlantic Ocean, so the water there is saltier and colder than at the equator, especially in winter. However, the salinity of warm water increases with evaporation, since 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. The rise in cold water affects the coastal climate: rain falls directly on the cold water. The air comes to 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 originated.

What is the difference between cold and warm currents?

Depending on the temperature, sea currents are divided into warm and cold. The first appear near the equator. They carry warm waters through cold waters near the poles and heat the air. Countercurrents 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?

Boras are called tidal waves that can be observed in those places where rivers flow into the sea - that is, at their estuaries. They arise when so many waves running to the shore accumulate in a shallow and wide funnel-shaped mouth that all of them suddenly pour into the river. In the Amazon, one of the South American rivers, the surf raged so much that a five-meter wall of water moved inland for more than a hundred kilometers. Boras 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 in Latin America... In 1812, he discovered that a cold deep current moved from the polar regions to the equator and cooled the air there. In his honor, the current that carries waters along the coast of Chile and Peru was named the Humboldt Current.

Where are the largest warm sea currents on the planet?

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

Where are the coldest sea currents?

The largest cold sea currents are 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 the climate?

Warm sea currents primarily affect the surrounding air masses and, depending on geographic location continent, warm the air. So, thanks to the Gulf Stream in the Atlantic Ocean, the temperature in Europe is 5 degrees higher than it could be. Cold currents that are directed from the polar regions to the equator, on the contrary, lead to a decrease in air temperature.

What are the effects of changes in the sea current?

Sea currents can be affected by sudden events such as volcanic eruptions or El Niño-related changes. El Niño is a warm water current that can displace cold currents off the coast of Peru and Ecuador in the Pacific Ocean. Although the influence of El Niño is limited to certain areas, its effects affect the climate of remote regions. It causes heavy rainfall on the coasts of South America and eastern Africa, resulting in devastating floods, storms and landslides. In wet rainforest in the vicinity of the Amazon, on the contrary, a dry climate reigns, which reaches Australia, Indonesia and South Africa, contributing to the occurrence of droughts and the spread of forest fires. Near the Peruvian coast, El Niño leads to the mass extinction of fish and corals, since plankton, which lives mainly in cold water, suffers when it is heated.

How far can sea currents carry objects into the sea?

Sea currents can carry objects that have fallen into the water over great distances. For example, in the sea you can find wine bottles that 30 years ago were thrown from ships in the ocean between South America and Antarctica and carried away thousands of kilometers. Currents ferried them across the Pacific and Indian Oceans!

What is worth knowing about the Gulf Stream?

The Gulf Stream is one of the most powerful and well-known sea currents that originates in the Gulf of Mexico and carries warm waters to the Svalbard archipelago. Thanks to the warm waters of the Gulf Stream, Northern Europe enjoys a mild climate, although it should be much colder, as this area is located as far north as Alaska, where freezing cold reigns.