The ocean current is what? Causes of ocean currents

The oceanic current is a stream of water mass that moves with a certain cyclicity and frequency. It is distinguished by the constancy of physicochemical properties and specific geographical location. It can be cold or warm, depending on the hemisphere. Each such flow is characterized by increased density and pressure. The flow of water masses in the sverdrups is measured, in a broader sense - in terms of volume.

Varieties of currents

First of all cyclically directed streams of water are characterized by such signs as stability, speed of movement, depth and width, chemical properties, acting forces, etc. Based on the international classification, currents come in three categories:

1. Gradient. Occur under the influence of hydrostatic pressure on the isobaric layers of water. A gradient oceanic current is a stream that is characterized by horizontal displacements of isopotential surfaces of the water area. According to initial signs, they are divided into density, baric, sink, compensatory and seiche. As a result of the sewage current, precipitation and melting of ice form.

2. The wind. Determined by the slope of sea level, the force of the air flow and the fluctuations in the mass density. The subspecies is the drifting ocean current. This is the flow of water caused by the action of the wind. Only the surface of the basin is affected by vibrations.

3. The tidal ones. They show themselves most strongly in the shallow waters, in the mouths of rivers and off the coast. An individual type of flow is inertial. It is caused by the action of several forces at once. According to the variability of motion, constant, periodic, monsoon and trade winds are distinguished. The last two are determined by the direction and speed seasonally.

Causes of ocean currents

At the moment, the circulation of water in the world's water area is just beginning to be studied in detail. By and large, specific information is known only for surface and shallow currents. The main snag is that the oceanographic system has no clear boundaries and is in constant flux. It is a complex network of flows caused by various physical and chemical factors.

Nevertheless, today the following causes of ocean currents are known:

1. Cosmic impact. This is the most interesting and at the same time difficult to study process. In this case, the current is caused by the rotation of the Earth, the impact of the cosmic bodies on the atmosphere and the hydrological system of the planet, etc. A vivid example is the tides.

2. Wind impact. The circulation of water depends on the strength and direction of the air masses. In rare cases, one can speak of deep currents.

3. Difference in densities. Flows are formed due to the uneven distribution of salinity and temperature of water masses.

Atmospheric impact

In the world water area, this kind of influence is caused by the pressure of heterogeneous masses. Coupled with cosmic 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 its journey it is characterized by increased speed. In the Florida Strait, the Gulf Stream is dispersed at the same time by both nasty and tailwinds. This phenomenon forms a cyclic pressure on the layers of the basin, accelerating the flow. Hence, in a certain period of time, a considerable outflow and a large amount of water flow occurs. The weaker the pressure of the atmosphere, the higher the tide.

When the water level falls, the slope of the Florida Strait becomes smaller. Because of this, the velocity of the current decreases significantly. Thus, it can be concluded that increased pressure reduces the flow strength.

Impact of wind

The connection between the streams of air and water is so strong and at the same time simple that it is hard not to notice it even with the naked eye. Long time navigators knew how to calculate the appropriate ocean current. This became possible thanks to the work of the scientist V. Franklin on the Gulf Stream, dating back to the 18th century. A few decades later, A. Humboldt indicated precisely the wind in the list of extraneous forces acting on the water masses. From the mathematical point of view, the theory was substantiated by the physicist Zeppitz in 1878. He proved that in the World Ocean there is a constant transfer of the surface layer of water to deeper levels. In this case, the main force affecting the movement becomes the wind. The flow velocity in this case decreases in proportion to the depth. The determining condition for the constant circulation of water is the infinitely long time of the action of the wind. Exceptions are only trade winds of air, which cause the movement of water masses in the equatorial band of the World Ocean seasonally.

Difference in densities

The influence of this factor on water circulation is the most important cause of the current in the World Ocean. Large-scale studies of the theory were cited by the international expedition Challenger. Subsequently, the work of scientists was confirmed by Scandinavian physicists.

The inhomogeneity of the densities of water masses is the result of several factors at once. They always existed in nature, representing a continuous hydrological system of the planet. Any deviation in the temperature of the water entails a change in its density. In this case, an inverse relationship is always observed. The higher the temperature, the lower the density.

The difference in physical parameters is also affected by the aggregate state of water. Freezing or evaporation increases density, precipitation - it reduces. Affects the force of flow and salinity of water masses. It depends on the melting of ice, precipitation and evaporation. In terms of density, the World Ocean is fairly uneven. This applies to both surface and deep layers of the water area.

The currents of the Pacific

The general scheme of flows is determined by the circulation of the atmosphere. Thus, the eastern trade winds contribute to the formation of the Northern Current. It crosses the water area from the Philippine Islands to the coast of Central America. It has two branches that feed the Indonesian basin and the Equatorial Pacific Ocean. In the Northern Hemisphere, the largest streams of water are Kuroshio, Alaska and California currents. The first two are warm. The third stream is a cold oceanic current of the Pacific Ocean. The Southern Hemisphere basin forms the Australian and Trade winds. Slightly to the 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 the summer, the El Niño oceanic current operates around the equator. It pushes out the cold masses 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 of warm and cold currents. This constant dynamics is caused by the action of monsoon circulation. In the winter period, the South-West Current dominates, which originates in the Bay of Bengal. Slightly to the south is the Western. This oceanic current of the Indian Ocean crosses the water area 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 shifts to a depth and noticeably loses its force. As a result, its place is occupied by powerful warm Somali and Madagascar currents.

Circulation of the Arctic Ocean

The main reason for the development of the underwater current in this part of the World Ocean is a powerful inflow of water masses 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 the North Atlantic. It brings huge amounts of warm masses, not allowing the water temperature to drop to critical levels.

The Transarctic Current responds to the direction of ice drift. Among the other major streams, one can distinguish the Yamal, Spitsbergen, North Stream and Norwegian currents, as well as the offshoot of the Gulf Stream.

The currents of the Atlantic basin

The salinity of the ocean is extremely high. Zoning of water circulation is the weakest among other basins. Here the main oceanic current is the Gulf Stream. Thanks to him, the average temperature of water is 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, Benguela and Trade winds.