Ocean current is a flow of water mass that moves with a certain cyclicity and frequency. Differs in a constancy of physical and chemical properties and a specific geographical location. It can be cold or warm, depending on belonging to the hemispheres. Each such flow is characterized by increased density and pressure. The flow of water masses is measured in sverdrupa, in a broader sense - in units of volume.
Varieties of currents
First of all, cyclically directed water flows are characterized by such features as stability, speed of movement, depth and width, chemical properties, influencing forces, etc. Based on the international classification, flows are divided into three categories: 1. Gradient. Occur when hydrostatic pressure is applied to isobaric layers of water. A gradient ocean current is a flow characterized by horizontal movements of the isopotential surfaces of the water area. According to the initial features, they are divided into density, baric, stock, compensation and seiche. The runoff causes precipitation and ice melt.
2. Wind. Are determinedthe slope of the sea level, the strength of the air flow and fluctuations in mass density. A subspecies is the drift ocean current. This is the flow of water caused purely by the action of the wind. Only the surface of the pool is subject to vibrations.
3. Tidal. They appear most strongly in shallow water, in estuaries and near 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
At the moment, the circulation of waters in the world's waters is just beginning to be studied in detail. By and large, specific information is known only about surface and shallow currents. The main snag 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. Space impact. This is the most interesting and at the same time difficult to learn process. In this case, the flow is determined by the rotation of the Earth, the influence of cosmic bodies on the atmosphere and hydrological system of the planet, etc. A striking example is the tides.
2. The impact of the wind. The circulation of water depends on the strength and direction of air masses. In rare cases, one can speak of deepcurrents.
3. Density difference. Streams are formed due to uneven distribution of salinity and temperature of water masses.
Atmospheric influence
In the world's waters, 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 prime 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 accelerated simultaneously by opposite and fair winds. This phenomenon forms a cyclic pressure on the layers of the pool, accelerating the flow. From here, in a certain period of time, there is a significant outflow and inflow of a large amount of water. The lower the pressure of the atmosphere, the higher the tide.
When the water level drops, the slope of the Strait of Florida becomes less. Because of this, the flow rate is significantly reduced. Thus, it can be concluded that increased pressure reduces the strength of the flow.
Wind effect
The connection between the flows of air and water is so strong and simple at the same time that it is hard not to notice even with the naked eye. Since ancient times, navigators have been able to calculate the appropriate ocean current. This became possible thanks to the work of the scientist W. 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 the main outsiders affecting the water masses.strength.
From a mathematical point of view, the theory was substantiated by the physicist Zeppritz 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 wind becomes the main influencing force on the movement. The current velocity in this case decreases in proportion to the depth. The determining condition for the constant circulation of waters is an infinitely long time of action of the wind. The only exceptions are the trade winds of air, which cause the movement of water masses in the equatorial strip of the World Ocean seasonally.
Density difference
The impact of this factor on water circulation is the most important cause of the flow in the oceans. Large-scale studies of the theory were carried out by the international expedition Challenger. Subsequently, the work of scientists was confirmed by Scandinavian physicists.
The heterogeneity of the densities of water masses is the result of several factors at once. They have always existed in nature, representing a continuous hydrological system of the planet. Any deviation in water temperature entails a change in its density. In this case, an inversely proportional relationship is always observed. The higher the temperature, the lower the density.
Also, the difference in physical parameters is affected by the state of aggregation of water. Freezing or evaporation increases density, precipitation decreases it. Affects the strength of the current and salinity of water masses. It depends on the melting of ice, precipitation and the level of evaporation. By indicatorsDensity The World Ocean is quite uneven. This applies to both surface and deep layers of the water area.
Currents of the Pacific Ocean
The general pattern of flows is determined by the circulation of the atmosphere. Thus, the east trade wind contributes to the formation of the North Current. It crosses the waters from the Philippine Islands to the coast of Central America. It has two branches that feed the Indonesian Basin and the Pacific Equatorial Ocean Current.
In the Northern Hemisphere, the Kuroshio, Alaska and California currents are the largest streams in the water area. The first two are warm. The third stream is the cold ocean current of the Pacific Ocean. The basin of the Southern Hemisphere is formed by the Australian and Tradewind currents. A little to the east of the center of the water area, the Equatorial countercurrent is observed. Off the coast of South America, there is a branch of the cold Peruvian current.
In the summer, the El Niño oceanic current operates near the equator. It pushes back the cold water masses of the Peruvian Stream, creating a favorable climate.
Indian Ocean and its currents
The northern part of the basin is characterized by a seasonal change of warm and cold flows. This constant dynamics is caused by the action of the monsoon circulation.
In winter, the Southwest Current dominates, which originates in the Bay of Bengal. A little further south is Western. This oceanic current of the Indian Ocean crosseswater area from the coast of Africa to the Nicobar Islands.
In summer, the east monsoon contributes to a significant change in surface waters. The equatorial countercurrent shifts to a depth and noticeably loses its strength. As a result, powerful warm Somali and Madagascar currents take its place.
Arctic Ocean Circulation
The main reason for the development of the undercurrent in this part of the World Ocean is a powerful influx of water masses from the Atlantic. The fact is that the centuries-old ice cover does not allow the atmosphere and cosmic bodies to influence the internal circulation.
The most important course of the Arctic Ocean is the North Atlantic. It brings in 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 streams include the Yamal, Svalbard, 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 zonality of water circulation is the weakest among other basins.
Here the main ocean current is the Gulf Stream. Thanks to him, the average water temperature is kept at around +17 degrees. This warm oceanic current of the Atlantic Ocean warms both hemispheres.
Also the most important currents of the basin are the Canaries. Brazilian, Benguela and Tradewind currents.
