The cause of ocean current formation

The main driving force of ocean current movement is wind, and it can also be the uneven distribution of seawater density caused by hot salt effect. Do you want to know the formation of ocean currents? The following is my answer to how the ocean current is formed, I hope it will help you!

The formation of ocean currents can be divided into wind currents, density currents and compensation current according to their causes.

Airflow (blowing airflow)

Also known as blowing and drifting: formed under the action of wind. The prevailing wind blows the sea surface, pushing the seawater to drift with the wind, and making the upper seawater drive the lower seawater to flow, forming a large-scale ocean current, which is called wind ocean current. From the origin, most of the ocean systems on the surface of the world's oceans belong to airflow.

Atmospheric movement is the main driving force of seawater movement. Land shape and geostrophic deflection will also have some influence on the direction of ocean currents.

The surface layer with a depth of less than 200-300 meters in the ocean is the wind drift layer. The resultant force of wind stress and horizontal turbulence stress acting on the sea surface by planetary wind system is balanced with geostrophic bias, and then wind drift occurs. The magnitude and direction of wind force in planetary wind system change with latitude, which leads to the convergence and divergence of sea surface water. On the one hand, it redistributes the density of seawater and produces a horizontal pressure gradient force. When it is balanced with the geostrophic bias force, a horizontal geostrophic flow is formed in a fairly thick horizontal layer. On the other hand, at the bottom of the wind drift layer in the equatorial region, seawater flows upward from subsurface water or falls into subsurface water, forming ascending and descending airflow in the equatorial region.

The wind drift on the ocean surface constitutes the wind-driven circulation on the ocean surface. Among them, the northern equatorial current and the southern equatorial current at low latitude and middle latitude are blocked by the coast at the western boundary of the ocean, and their mainstream turns to the north and south respectively. Due to the variation of Coriolis parameters with latitude (? -effect) and horizontal turbulent friction, forming a westward strengthened ocean current with narrow flow radiation and high velocity. Half of the heat transported from the equatorial region to the high latitudes of the earth every year is transported by the westward dense current at the western boundary of the ocean. In the northern hemisphere, the hot salt circulation entering the upper ocean is in the same direction as the westward strengthening current of the ocean, which increases the velocity; In the southern hemisphere, due to the opposite direction and slow flow rate, the ocean circulation is not obviously strengthened westward.

In the mid-latitude and high-latitude areas of the southern hemisphere, due to the lack of continental coast, the wind-driven circulation on the ocean surface forms the Antarctic circumpolar current that flows continuously around the Antarctic continent.

Density flow

Caused by density difference. The difference of seawater temperature and salinity in different sea areas will lead to the difference of seawater density and thus the difference of seawater level. The inclination of the sea surface between two sea areas with different seawater densities will cause the flow of seawater, and the ocean current thus formed is called density current.

Hot salt effects such as freezing, melting ice, precipitation and evaporation in the ocean cause uneven distribution of seawater density in a large area of the sea surface, which can generate high-density seawater on the surface of polar and high-latitude parts of the sea and sink to the deep sea and seabed. Under the action of horizontal pressure gradient force, it flows horizontally, and it can flow upward through the bottom of middle water and then to the surface. This is the hot salt cycle in the ocean.

compensation current

Because seawater is squeezed or dispersed. When the seawater in a certain sea area decreases, the seawater in the adjacent sea area will be replenished, and the ocean current thus formed is called compensation current. The compensation current can flow horizontally or vertically, and the vertical compensation current can be divided into upward flow and downward flow. For example, the Peru cold current belongs to the rising compensation current.

Ocean current is the main regulator of the thermal environment on the earth's surface. Ocean currents can be divided into warm currents and cold currents. If the water temperature of ocean current is higher than the water temperature reaching the sea area, it is called warm current; If the water temperature of the ocean current is lower than the water temperature reaching the sea area, it is called a cold current. Generally, the ocean current from low latitude to high latitude is warm current, and the ocean current from high latitude to low latitude is cold current. Sailing along ocean currents can save fuel and speed up. When cold and warm air currents meet, sea fog often forms, which is not conducive to maritime navigation. In addition, ocean currents carry icebergs south from the Arctic, posing a great threat to maritime shipping.

Ocean current, also known as ocean current, refers to the large-scale and relatively stable flow of surface seawater in a certain direction all the year round.

Ocean current is the main regulator of the thermal environment on the earth's surface, and the huge ocean current system promotes the energy exchange in high and low latitudes of the earth. The environmental characteristics between ocean currents and the areas they pass through are also changed through capacity exchange.

Geographical significance of ocean current: Ocean current affects and restricts many physical, chemical, biological and geological processes in the ocean, as well as the formation and change of climate and weather over the ocean. Therefore, understanding and mastering the laws of ocean currents, large-scale air-sea interaction and long-term climate change is of great significance to fisheries, shipping, sewage discharge and military affairs.

Climate impact

Generally speaking, warm current will increase temperature and humidity, while cold current will decrease temperature and humidity.

Influence on temperature Ocean current transfers heat from low latitude to high latitude, especially the contribution of warm current. The influence of ocean current on the temperature on both sides of the continent at the same latitude: the coastal temperature of the continent where warm current passes is high, and the coastal temperature of the continent where cold current passes is low.

Influence on precipitation and fog: heat and water vapor are transported upward with warm current, which makes stratification unstable, air humidity increases, and precipitation is easy to occur. The cold current produces inversion, stratification is stable, water vapor is not easy to be transported upward, evaporation is weak, and the relative humidity of the lower layer is sometimes very high, but it can only become fog, not rain. The cold front is mostly advection fog, which appears in the following situations: sea and land wind fog: during the day, the land wind flows to the cold front to form advection fog; Sea fog: At the intersection of cold and warm air, the wind blows from the surface of warm current to the surface of cold current, forming advection fog.

Marine biological impact

In the sea area where cold current and warm current meet, the seawater is disturbed, which can bring nutrients from the lower layer to the surface, which is beneficial to the proliferation of fish and provide bait for fish; Can two kinds of ocean currents still form? Water barrier? , hinder fish activities, fish concentration, often forming a larger fishing ground. The causes of the four major fishing grounds in the world and their currents are as follows: Hokkaido Fishing Ground: located near Hokkaido Island, Japan, where the warm current of Japan meets the cold current of Thousand Islands. Beihai Fishing Ground: Located in the North Sea of Europe, the warm current of the North Atlantic meets the cold water of the Arctic Ocean brought by the polar easterly wind. Fishing ground in Peru: The prevailing southeast wind along the coast is offshore wind, which causes the compensation current (also known as ocean current) to rise. Newfoundland Fishing Ground: Near Newfoundland, Canada, the Gulf Warm Current and Labrador Cold Current meet. Penguins in the equatorial region: Penguins are distributed in the Cologne Islands (also known as Galapagos Islands) in the equatorial region of the eastern Pacific Ocean, which is due to the cold current in Peru.

marine pollution

There are advantages and disadvantages: it can not only speed up the dilution and purification of pollutants due to their rapid diffusion, but also expand the pollution scope accordingly.

The importance of ocean currents:

1. Transfer heat energy from different ocean areas to different ocean areas (heat energy balance);

2. Transfer nutrients from different marine areas to different marine areas;

3. Because ocean currents distribute seawater with different oxygen content in different ocean regions to different ocean regions.