The ocean current is a stream of water mass that moves with a certain cyclicality and frequency. It is distinguished by the constancy of physico-chemical properties and specific geographical location. It can be cold or warm depending on hemisphere affiliation. Each such stream is characterized by increased density and pressure. The flow rate of water masses is measured in sverdrups, in a broader sense - in units of volume.
Varieties of currents
First of all, cyclically directed water flows are characterized by such signs as stability, speed, depth and width, chemical properties, acting forces, etc. Based on the international classification, there are three categories of flows:
1. Gradient. Occur under the influence of hydrostatic pressure on isobaric layers of water. Gradient oceanic current is a stream that is characterized by horizontal movements of isopotential surfaces of the water area. According to the initial signs, they are divided into density, pressure, stock, compensation and seiche. As a result of the effluent, precipitation and ice melting are formed.
2. Wind. They are determined by the slope of the sea level, the strength of the air flow and fluctuations in the density of masses. A subspecies is a drift ocean current. This is a stream of water caused by the purely action of the wind. Only the surface of the pool is exposed to vibrations.
3. Tidal. Manifest most strongly in shallow water, in estuaries and off the coast.
A separate type of flow is inertial. It is caused by the action of several forces at once. According to the variability of movement, constant, periodic, monsoon and trade wind flows are distinguished. The last two are determined by direction and speed seasonally.
Causes of ocean currents
Currently, the circulation of water in the global water area is only beginning to be studied in detail. By and large, specific information is known only about surface and shallow currents. The main catch is that the oceanographic system has no clear boundaries and is in constant motion. It is a complex network of flows due to various physical and chemical factors.
Nevertheless, the following causes of ocean currents are known today:
1. Cosmic impact. This is the most interesting and at the same time difficult to study process. In this case, the flow is caused by the rotation of the Earth, the impact on the atmosphere and hydrological system of the planet of cosmic bodies, etc. A vivid example is the tides.
2. The effect of wind. Water circulation depends on the strength and direction of the air masses. In rare cases, one can speak of deep currents.
3. The difference in density. Streams are formed due to the uneven distribution of salinity and temperature of water masses.
Atmospheric exposure
In the world water area, this kind of influence is determined by the pressure of inhomogeneous masses. Together with space anomalies, water flows in the oceans and smaller basins change not only their direction, but also their power. This is especially noticeable in the seas and straits. A vivid example is the Gulf Stream. At the beginning of his journey, he is characterized by increased speed.
In
the Strait of Florida, the Gulf Stream is simultaneously accelerated by nasty and fair winds. This phenomenon creates cyclic pressure on the layers of the pool, accelerating the flow. From here, in a certain period of time, a significant outflow and influx of a large amount of water occurs. The weaker the atmospheric pressure, the higher the tide.
When the water level drops, the slope of the Florida Strait becomes smaller. Because of this, the flow velocity is significantly reduced. Thus, it can be concluded that increased pressure reduces the strength of the flow.
Wind exposure
The connection between air and water flows is so strong and at the same time simple that it is hard not to notice it even with the naked eye. For a long time, sailors were able to calculate a suitable ocean current. This was made possible thanks to the work of the scientist W. Franklin on the Gulf Stream, dating from the 18th century. After several decades, A. Humboldt indicated precisely the wind in the list of the main extraneous forces affecting the water masses.
From a mathematical point of view, the theory was justified by the physicist Zepritz in 1878. He proved that in the oceans there is a constant transfer of the surface layer of water to deeper levels. In this case, the main force acting on the movement becomes the wind. The flow velocity in this case decreases in proportion to the depth. The decisive condition for the constant circulation of water is the infinitely long duration of the wind. Only trade winds are considered an exception, which determine the movement of water masses in the equatorial strip of the World Ocean seasonally.
Density difference
The effect of this factor on water circulation is the most important cause of the current in the oceans. Extensive research of the theory was carried out by the international expedition Challenger. Subsequently, the work of scientists was confirmed by Scandinavian physicists.
The heterogeneity of the density of water masses is the result of several factors. They have always existed in nature, representing a continuous hydrological system of the planet. Any deviation of the temperature of the water entails a change in its density. In this case, an inverse proportion is always observed. The higher the temperature, the lower the density.
The aggregate state of water also affects the difference in physical indicators. Freezing or evaporation increases density; precipitation decreases it. Affects the strength of the current and the salinity of the water masses. It depends on melting ice, precipitation and evaporation. In terms of density, the oceans are quite uneven. This applies to both the surface and deep layers of the water area.
Pacific Ocean Currents
The general flow pattern is determined by atmospheric circulation. Thus, the eastern trade wind contributes to the formation of the Northern current. It crosses the waters from the Philippine Islands to the coast of Central America. It has two arms that feed the Indonesian basin and the Equatorial Oceanic Pacific Ocean.
In the
Northern Hemisphere, the largest flows of the water area are Kuroshio, Alaska and California currents. The first two are warm. The third stream is the cold ocean current of the Pacific Ocean. The southern hemisphere basin is formed by the Australian and Passat currents. A little east of the center of the water area is the Equatorial countercurrent. Off the coast of South America there is a branch of the cold Peruvian stream.
In summer, the El Niño ocean current operates in the equator region. It pushes the cold masses of water of the Peruvian stream, forming a favorable climate.
Indian Ocean and its currents
The northern part of the basin is characterized by a seasonal change in warm and cold flows. Such constant dynamics is caused by the action of monsoon circulation.
In winter, the Southwestern Current dominates, which originates in the Bay of Bengal. A little south is West. This ocean current of the Indian Ocean crosses the waters from the coast of Africa to the Nicobar Islands.
In summer, the eastern monsoon contributes to a significant change in surface water. The equatorial counterflow moves to a depth and noticeably loses its strength. As a result, its place is occupied by powerful warm Somali and Madagascar currents.
Arctic Ocean Circulation
The main reason for the development of the underwater current in this part of the World Ocean is the powerful influx of water from the Atlantic. The fact is that the centuries-old cover of ice does not allow the atmosphere and cosmic bodies to affect the internal circulation.
The most important current of the Arctic Ocean is considered the North Atlantic. It drives huge volumes of warm masses, preventing the water temperature from dropping to critical levels.
The Transarctic current is responsible for the direction of ice drift. Other major flows include the Yamal, Spitsbergen, North Cape and Norwegian currents, as well as a branch of the Gulf Stream.
Currents of the Atlantic Basin
The salinity of the ocean is extremely high. The zoning of water circulation is the weakest among other basins.
Here the main ocean current is the Gulf Stream. Thanks to him, the average temperature indicators of water are kept at around +17 degrees. This warm oceanic
current of the Atlantic Ocean warms both hemispheres.
Also the most important flows of the basin are the Canary, Brazilian, Bengel and Passat currents.