The Ocean currents They are massive displacements of both superficial and deep water, caused by winds, the earth's rotation, differences in temperature and salinity. They can be superficial and deep, the superficial ones appearing in the first 200 to 400 m of depth. For their part, deep currents in greater depths.
The superficial marine currents are produced due to the push of the water by the winds and the deep ones due to differences in temperature and salinity.
Both surface and deep currents complement each other forming a large oceanic conveyor belt. Thus, the water masses move in superficial currents that go from the equator to the polar circle and return in deep currents..
In the case of deep currents, they return to the equator and continue to Antarctica, crossing all the oceans. In Antarctica they head east, crossing the Indian Ocean and from there to the Pacific, where warm surface currents move north and return to the Atlantic..
The systems of marine currents form the so-called ocean gyres, through which water circulates in the planet's oceans. There are 5 main gyres, two in the Atlantic Ocean, two in the Pacific and one in the Indian Ocean..
Among the most prominent currents are the Gulf of Mexico, Las Agujas, Eastern Australia, Humboldt and Mediterranean currents. All marine currents fulfill important functions in the planetary system by regulating the climate, distributing nutrients and biodiversity, as well as facilitating navigation..
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In the oceans there is a surface temperature gradient, where the maximum temperature is located in the Red Sea with 36 ºC and the minimum in the Weddell Sea (Antarctica) with -2 ºC. Likewise, there is a vertical temperature gradient, with warm waters in the first 400 m and a very cold area below 1,800 m..
There is also a salinity gradient, with saltier waters in areas with less rainfall such as the Atlantic and less salty where it rains more (Pacific). On the other hand, there is less salinity on the coasts where rivers that provide fresh water flow in relation to the offshore.
In turn, both temperature and salinity affect the density of the water; the higher the temperature the lower the density and the higher the salinity the higher the density. However, when seawater freezes and forms ice, its density is greater than that of liquid water..
The Earth rotates on its axis to the east, causing an apparent deflection in any object that moves across its surface. For example, a projectile launched from the equator toward a site in Alaska (north) will land slightly to the right of the target..
This same phenomenon affects winds and ocean currents and is known as the Coriolis effect..
Due to differential warming of the Earth, there are warm temperatures near the equator and cold at the poles. The hot air masses rise creating a vacuum, that is, a low pressure area.
Thus, the space left by the hot air is filled with air from a cold region (high pressure zone), which moves there due to the action of the winds. In addition, the Earth in its rotational movement causes a centrifugal force at the equator, causing the water to move north and south in this area..
Likewise, the waters near the equator are less salty because there are more rains that provide fresh water and dilute the salts. While towards the poles it rains less and a large percentage of the water is frozen, so the concentration of salts in liquid water is higher.
On the other hand, at the equator the waters are warmer due to the higher incidence of solar radiation. This causes the water in this area to expand and raise its level or height.
When analyzing the effect of these factors in the North Atlantic, it is observed that a large system of closed circulation of marine currents is generated. It begins with the winds that come from the northeast (trade winds) causing superficial sea currents.
These northeast currents, upon reaching the equator, move westward due to rotation, starting from the western coast of Africa. Then when arriving at America, the equatorial current is with continuous terrestrial obstacles until the north.
The presence of the obstacles, plus the centrifugal force of the equator and the difference in temperature between the equatorial and polar waters, direct the current to the northeast. The current increases its speed when it circulates in the narrow channels between the Caribbean islands and the Yucatan channel.
Then, from the Gulf of Mexico, it continues through the Straits of Florida, strengthening as it joins the current of the Antilles. From here it continues its course north along the east coast of North America and later northeast.
On its journey north, the Gulf Stream loses heat and the water evaporates, becomes saltier and denser, sinking to become a deep current. Later on reaching the ground obstacle of northern western Europe it splits and one branch continues north, then turns west, while the other continues south and returns to the equator..
The branch of currents of the North Atlantic Giro that collides with Western Europe heads south and forms the Canary Current. In this process the currents of the Mediterranean Sea in a west direction are incorporated, which contribute a large amount of salts to the Atlantic Ocean.
Similarly, the trade winds push the waters of the African coast to the west, completing the North Atlantic Turn..
The current heading north forms the North Atlantic Subpolar Gyre, going west meets North America. Here the cold and deep Labrador current is formed, which heads south.
This Labrador Ocean Current passes under the Gulf Stream in the opposite direction. The movement of these currents is given by differences in temperature and saline concentration (thermohaline currents).
The set of thermohaline currents form the system of currents that circulates below the surface currents, forming the great oceanic conveyor belt. It is a system of cold and deep currents that goes from the North Atlantic to Antarctica..
In Antarctica the currents go east and when passing Australia it heads towards the North Pacific. In this process, the waters are warming, so they rise when they reach the North Pacific. Then, they return to the Atlantic in the form of a warm surface current, passing through the Indian Ocean and connecting with the oceanic gyres..
There are two basic types of marine currents defined by the factors that give rise to them and the ocean level through which they circulate..
These currents occur in the first 400-600 m depth of the sea and are originated by the winds and the rotation of the Earth. They comprise 10% of the mass of water in the oceans.
Deep currents occur below 600 m depth and displace 90% of the seawater mass. These currents are called thermohaline circulation, since they are caused by differences in water temperature ("thermo") and salt concentration ("haline")..
According to the pattern of the winds and by action of the earth's rotation, the marine currents form circular systems of currents called oceanic gyres. There are 6 main turns:
Each turn is formed by different currents, of which the current of the western limit of each turn is directed towards the corresponding pole. That is, the North Atlantic and North Pacific gyres go to the North Pole and the South Atlantic, South Pacific and Indian gyres go to the South Pole..
The currents of the western limit of each turn are the strongest and thus the Gulf of Mexico current corresponds to the North Atlantic Giro and the Kuroshio current to the North Pacific Giro..
In the South Atlantic Gyre, the strongest current is that of Brazil and in the South Pacific that of Eastern Australia. For its part, in the Giro del Indico is the Las Agujas current, which runs along the eastern coast of Africa from north to south..
Taking the North Atlantic Gyre as an example, we find that the entire system is made up of four currents. In this Giro, in addition to the Gulf Stream in the west, there is that of the North Atlantic that goes northeast.
Then, in the east is the Las Canarias current, which heads southeast, and the circuit closes with the North Equatorial current to the west.
This current is part of the North Atlantic gyre and is so named because it is born in the Gulf of Mexico. Here the surface waters heat up and expand, raising the sea level relative to the colder northern waters..
Therefore, the current is generated from the Gulf to the north, where the water will lose heat sinking and forming the North Atlantic current.
The Gulf Stream contributes greatly to regulating the climate of Western Europe, thanks to the heat it carries from the Gulf of Mexico. This heat released off Greenland is blown towards the continent by westerly winds, moderating continental temperatures..
The Mediterranean Sea is an almost closed basin, except for the 14.24 km wide connection with the Atlantic Ocean through the Strait of Gibraltar. This sea loses about 1 m of water annually through evaporation in its warm summers.
The connection with the Atlantic and the currents that are generated, allow the lost water to be renewed and oxygenated. The currents leaving the Mediterranean contribute to the formation of the Gulf Stream.
Salinity and temperature are the fundamental factors that act to produce the current between the Mediterranean and the Atlantic. By losing water through evaporation in a closed area, the salinity in the Mediterranean is higher than in the Atlantic Ocean beyond the Strait.
Water with a higher salt content is denser and goes to the bottom, forming a deep current towards the Atlantic with a lower concentration of salts. On the other hand, the surface layer of water in the Atlantic is warmer than that of the Mediterranean and generates a surface current from the Atlantic to the Mediterranean..
It is a superficial stream of cold water that travels from Antarctica to the equator along the South American Pacific coast. It comes from the rise or rise of part of the cold waters of the deep current of the South Pacific when colliding with the South American coast.
It is part of the subtropical Giro of the South Pacific and is responsible for providing a large amount of nutrients to the coasts of Chile, Peru and Ecuador.
Marine currents flow from places with warmer and saltier waters to colder regions with less saline concentration. In this process, they contribute to the distribution of environmental heat and the content of salts in the oceans..
By moving masses of hot water to cold areas, currents participate in the regulation of the Earth's climate. An example of this is the moderating effect of the environmental temperature exerted by the current of the Gulf of Mexico in Western Europe.
Thus, if the Gulf Stream stopped flowing, the temperature of Western Europe would drop by an average of 6 ° C..
Sea currents, by transporting heat, provide moisture by evaporation and generate a circular movement in close relationship with the winds, which are the cause of hurricanes..
Sea water maintains a constant gaseous exchange with the atmosphere, including water vapor, oxygen, nitrogen and COtwo. This exchange is made possible due to the movement of water by marine currents that contributes to breaking the surface tension..
The marine currents exert a force of wear and drag (erosion) on the surface of the seabed and the coasts through which they pass. This erosive effect over thousands of years has shaped the seabed, seamounts and coastlines..
On the other hand, the marine currents carry with them the nutrients as well as the plankton that feed on them. This conditions the distribution of marine fauna, since it is concentrated where there is more food available..
Plankton are passively carried away by surface currents, and part of the nutrients precipitate to the bottom, where they are displaced by deep currents. Later, these nutrients return to the surface in the so-called upwellings or marine outcrops of waters..
The deep currents give rise to the so-called upwellings or outcrops of marine waters. It is the rise of deep cold waters to the surface, which carry nutrients deposited in the deep ocean.
In the areas where this occurs, there is a greater development of the populations of phytoplankton and therefore of fish. These areas become important fishing zones, such as the Peruvian Pacific coast..
The oceans suffer serious pollution problems due to human action, which incorporates large amounts of waste, especially plastic. The marine currents carry this debris and due to the circular pattern of the surface, these are concentrated in defined areas.
From here arise the so-called islands of plastic, which are formed by concentrating fragments of plastic in large areas of the center of the oceanic gyres..
In the same way, the combination of the superficial marine currents with the waves and the shape of the coastline, concentrate the waste in certain areas..
Many marine species, such as turtles, cetaceans (whales, dolphins), and fish, use ocean currents for their long-distance ocean migrations. These currents help define the route, reduce travel energy and provide food..
The distribution of nutrients both horizontally and vertically in the oceans depends on marine currents. This in turn affects the phytoplankton populations that are the primary producers and the basis of food webs..
Where there are nutrients there are plankton and fish that feed on it, as well as other species that feed on fish like seabirds.
The distribution of nutrients through marine currents affects the availability of fishing for humans.
Marine currents by mobilizing water contribute to its oxygenation, which is essential for the development of aquatic life.
Coastal and inland ecosystems are influenced by marine currents to the extent that they regulate the continental climate..
Marine currents have allowed the development of navigation by human beings, allowing marine travel to distant destinations. This has made possible the exploration of the Earth, the dispersal of the human species, trade and economic development in general..
The direction that ocean currents take is expressed in a regular pattern in the world's oceans. This pattern of directions is determined by multiple factors whose forces are solar energy and the Earth and Moon's gravity..
Solar radiation influences the direction of ocean currents by being the cause of the winds. These are the main cause of the formation of surface currents that follow the direction of the winds..
Solar radiation also affects the direction of ocean currents by heating the water and causing it to expand. Due to this, the water increases in volume and raises the sea level; areas of the ocean appearing higher (hot) than others (cold).
This forms a difference in level, that is, a slope, moving the water towards the lower part. For example, in the equator the temperatures are high and therefore the water expands, determining a sea level 8 cm higher than in other areas..
Another factor that affects the direction of ocean currents is the difference in salinity between different areas of the ocean. As the water is saltier, its density increases and sinks, and deep currents move as a function of temperature and salinity gradients..
The shape of the continental shelf and the coastline also influence the direction of the marine currents. In the case of surface currents that run along the coasts, geographical features influence their direction.
For their part, deep currents when impacting with the continental shelf can suffer both horizontal and vertical deviations..
The rotation of the Earth affects the direction of the winds by generating a centrifugal force at the equator, pushing currents towards the poles. Furthermore, the Coriolis effect deflects currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere..
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