Definition of Sea Currents
Sea currents are the movement of the mass of water in the sea either vertically or horizontally so as to form a balanced movement that is very wide across the oceans in the world. There are several causes of the emergence of sea water, including wind blowing or differences in density or movement of ocean waves.
In general, there are two factors that cause the occurrence of ocean currents, namely:
- Internal factors: Factors related to seawater itself, for example, water density, pressure gradients, and seawater friction.
- External factors: Factors that are related to the other components around the ocean, for example, the movement of wind, air pressure, gravitational force, attraction of the sun, moon, etc.
Factors That Influence Sea Currents
1. Topography (Surface) of the Ocean Floor and Island
Oceans that are limited to many land masses will produce a system that tends to open up and make the flow lead in a form like circling the land.
2. Difference in Density
The most easily observed difference in density is in the deep sea in the south pole and north pole which flows into the tropics.
Blowing winds on the surface will make waves in the ocean. It turns out that this wind also causes the formation of seawater movements called currents. The ocean currents that are formed later will follow the strength of the gusts, the distance of the wind, the direction of the wind, and the length of the gusts.
4. Levels of Salt in Seawater
Different types of water will also cause the formation of ocean currents. On the surface, the water of small specific gravity will flow in the direction of water of large specific gravity whereas, in the deep sea, water with a large density will flow into the water of low specific gravity.
5. Temperature and Sunlight
The difference in temperature into the sea cannot be separated from the influence of sunlight. The heat from sunlight can enter the sea to a depth of 50 – 70 m. Now the structure of the sun-exposed layer with the ocean layer that is not affected by sunlight will be different, therefore this condition will affect the ocean currents.
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The Formation Process of the Sea Currents
Seawater is formed because of the process of moving the mass of water in towards balance which involves the horizontal and vertical displacement of the mass of the water. This movement is formed from the resultant of several working forces and several factors (described above) that influence it.
When the wind blows at sea, energy is transferred from the wind to the surface. The faster the wind moves, the greater the friction force acting on the surface so that the larger the ocean currents are formed. Then at the same time, there is a rotation of the earth on its axis so that it will give rise to the Coriolis force, this force will divert the current in the northern part of the earth to the right, and to the south to the left. At the same time, factors such as gravity, salt content, density, temperature, air pressure, sunlight, etc., play a role in the system of ocean currents formation.
Classifications of Sea Current
- Based on the Cause
- Ekman currents are ocean currents that are affected by wind.
- Thermohaline currents are currents that are influenced by density and gravity.
- Tidal currents are currents that are affected by tides.
- Geostrophic currents are ocean currents that are affected by horizontal pressure gradients and Coriolis forces.
- Flow wind-driven current is a current that is influenced by patterns of wind movement and occurs in the sea surface layer.
- Based on the Depth
Surface currents are currents that occur at several hundred meters from the surface, usually moving horizontally influenced by patterns of wind distribution.
Deep currents, occurring far on the ocean floor, the direction of movement is not affected by wind movements, usually carrying a mass of water from the polar region to the equator.
The Spread of Sea Current
- In the Pacific Ocean
North of the Equator
The north equatorial current is a hot current that flows westward (parallel to the equator). It is usually influenced by northeast trade movements.
- Kuroshio current is a continuation of the northern equator. This current is the current that flows from the Philippine archipelago, along eastern Japan and towards the coast of North America. This current is usually influenced by the West Wind.
- The California current is the current that flows along the west coast of North America to the south towards the equator (continued Kuroshio stream).
- Orashio currents are cold currents that are influenced by east wind movements. Flowing from the Strait of Berin to the east of Japan, then met the current of Kuroshio. Area Meeting of Orashio cold currents with hot currents Kuroshio is a place rich in fish.
Next to the Equator Strait
- The South Equatorial current is a hot current whose flow is westward (parallel to the equator) which is affected by southeast trade wind movements.
- The current of eastern Australia is a continuation of the southern equatorial currents that flow along the east Australian coast from north to south.
- West wind current is the current of east Australia flowing eastward (parallel to the equator), this current is influenced by West Wind movements.
- The current of Peru (Humboldt) is a continuation of the current of the west wind that flows west of South America along the North. Peru currents include cold currents.
- On the Atlantic Ocean
In the North of the Equator
- The North Equatorial current is the current whose flow is westward parallel to the strait. This flow is affected by the northeast wind market movements.
- Gulf Gulfstream currents are deviant currents that are reinforced and driven by large winds. Gulfstream Bay current is a hot current.
- The East Green Land current is the current flowing from the North Pole to the south along the Green Land east coast. This current includes cold currents whose movements are affected by the east wind.
- The Labrador current is a current that originates from the north pole and flows south along the east coast of the Labrador. Labrador currents include cold currents whose movements are influenced by the east wind.
- The Canari current is an advanced deviant current, some of the currents have changed direction due to the influence of the Spanish mainland flowing south along the west coast of North Africa and including cold currents.
In the South of the Equator
- The southern equatorial current is the current that flows towards the west, parallel to the equator. The southern equatorial currents include heat flows whose movements are affected by southeast trade winds.
- The current of Brazilia is a current flowing south along the east coast of South America (especially Brazil). This current includes heat and deviant currents.
- West Wind current is a continuation of a part of the flow of Brazil that flows eastward, parallel to the equator. West Wind current is a cold current whose movement is influenced by the west wind.
- The Benguela current is a continuation of some of the west wind currents flowing north along the coast of South Africa. These currents include cold currents which eventually return to the South Equatorial current.
- In the Indian Ocean
In the North of the Equator
The current north of the equator of the Indian Ocean is different from other oceans. The direction of the current is not fixed in a year but changes direction in 6 months or half a year. In accordance with the motion of the monsoon that caused it. Following are the currents that occur:
- Southwest Season current is a current flowing eastward, along the Arabian Sea. These currents include heat currents whose movements are affected by the southwest monsoon.
- The current of the East Season is the ocean currents flowing westward along the Benguela Bay. These currents include heat currents and their movements are influenced by two mutually reinforcing winds, namely the east windstorm and northeast monsoon winds.
In the South of the Equator
- The South Equatorial current is a hot current flowing westward parallel to the equator, is influenced by the southeast trade wind. Later this current will break in two (Mascarene current and Agulhas current).
- The Mascarene current is a continuation of the southern equatorial current that leads to the eastern island of Madagascar.
- Agulhas current is a continuation of the southern equatorial currents leading to the western island of Madagascar.
- West Wind current is a current that flows to the north along the coast on the Australian continent. These currents include deviant currents and cold currents which eventually return to the southern equatorial currents.