What are the factors that form ocean currents?
After research, it was discovered that the ocean current can be either a shallow and narrow current that only flows along the surface of the ocean, or it can be a deep and broad torrent with millions of tons of seawater flowing toward it. Run ahead.
There are many factors that affect the formation of ocean currents. It is generally believed that it is mainly the tricks played by the wind, followed by the different density of sea water, and the rotation of the earth, the outline of the continent and the distribution of islands, the undulations of the seafloor, Seasonal changes and the amount of water flowing from rivers into the sea also have a considerable impact on the formation and distribution of ocean currents.
Think about it, what happens if the wind always blows in one direction? When the prevailing wind blows on the ocean surface, the friction force of the wind on the sea surface, and the force exerted by the wind on the windward side of the waves Pressure forces seawater to travel long distances in the vast ocean in the direction of the wind. The ocean currents formed in this way are called wind currents. Wind currents, also called drifts, are the largest and most distant ocean currents in the ocean current system. At the same time, affected by the deflection force of the Earth's rotation, the flow direction of surface seawater deviates from the wind direction. The surface ocean currents in the Northern Hemisphere skew to the right of the wind direction, while in the Southern Hemisphere skew to the left. That is, the Northern Hemisphere skews to the right and the Southern Hemisphere skews to the left. .
The flow of surface seawater drives the lower seawater to flow due to friction; due to the top-down layer-by-layer traction, deep seawater can also flow. It’s just that the flow rate is less and less affected by friction. When reaching a certain depth, the flow rate is only about 4.3% of the surface flow rate. This depth is the lower limit of the influence of wind and sea currents on deep waters. It is called the friction depth of wind and sea currents. It is generally 200 to 300 meters deep in the ocean. For example, if the velocity of the surface ocean current is 50 cm/s, the velocity at this depth is only 2 cm/s.
The stronger the wind on the ocean surface, the greater the wind speed, the greater the speed of the surface wind current, and the greater the depth it can affect.
The flow of seawater caused by the uneven distribution of seawater density in the horizontal direction is called density flow.
Some of the world's famous ocean currents, such as the Gulf Stream, Kuroshio Current, and Equatorial Current, are all ocean currents related to the density distribution of ocean water. The exchange of water between the Atlantic Ocean and the Mediterranean Sea, and between the Mediterranean Sea and the Black Sea, through the Strait of Gibraltar and the Turkish Strait respectively, are typical examples of density currents formed due to differences in salinity.
Seawater is continuous and incompressible. When seawater flows out of one sea area, seawater in adjacent sea areas must be replenished. The ocean current formed in this way is called compensating current. The compensating flow is both horizontal and vertical. For example, under the long-term blowing of offshore wind, the surface seawater leaves the coast, and the seawater in the adjacent sea area will flow to this sea area, forming a compensating flow in the horizontal direction; at the same time, the lower seawater also rises to the sea surface to compensate for the rip current. The sea water goes away, forming a vertical upwelling. Upwelling is more obvious on the west coast of the continent, and is found on the coasts of Peru and Chile, the coast of California, and the southwest and northwest coasts of Africa. When ocean currents encounter coasts or islands in the surface flow, they not only diverge in the horizontal direction, but also produce downwelling and bottom currents in the vertical direction. Compensating currents often cooperate with wind currents and density currents to form huge circulations on the ocean surface.
According to the temperature of the ocean current, it can be divided into warm current and cold current with different properties. The water temperature of ocean currents is higher than the water temperature of the sea area flowing through it, which is called warm current. The water temperature of the ocean current is lower than the water temperature of the sea area flowing through it, which is called cold current. Warm currents mostly originate from low-latitude sea areas and flow from lower latitudes to higher latitudes. Generally, the water temperature is higher, the salinity is higher, the oxygen content is lower, the number of plankton is smaller, the seawater is more transparent, and the water color is mostly blue. Cold currents mostly originate from high-latitude sea areas and flow from higher latitudes to lower latitudes. Generally, the water temperature is lower, the salinity is lower, the oxygen content is higher, the number of plankton is larger, the water transparency is lower, and the water color is mostly dark green. Usually in the northern hemisphere, warm currents flow from south to north, and cold currents flow from north to south. In the southern hemisphere, the opposite is true.
In addition, according to the vertical distribution of the ocean, it can also be divided into surface ocean currents and deep ocean currents; according to the change in velocity of the ocean current, it can also be divided into stable currents and unsteady currents. Generally speaking, most of the ocean currents we talk about refer to stable currents.