- Related Topics:
- ocean current
- Equatorial countercurrent
Equatorial current
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What is an equatorial current?
Equatorial currents are ocean currents that flow westward near the equator and are mainly driven by winds. These current systems typically consist of two westward-flowing currents, known as the North and South equatorial currents, which are approximately 600 miles (1,000 km) wide. These are separated by an eastward-flowing countercurrent that is only 300 miles (480 km) wide.
The Coriolis force, caused by Earth's rotation, also affects equatorial currents. In the Northern Hemisphere, this force deflects moving objects to the right, while in the Southern Hemisphere, it deflects them to the left. However, there is no apparent horizontal deflection at the Equator.
These currents typically flow at depths of less than 1,650 feet (500 m) and travel at speeds of 10 to 40 inches per second (25 to 100 cm per second).
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Where are equatorial currents found in the ocean?
Equatorial currents are found in the ocean flowing westward near the equator, predominantly controlled by winds. These current systems consist of two westward-flowing currents, the North and South equatorial currents, separated by an eastward-flowing countercurrent.
The Pacific South Equatorial Current flows between 5° N and 15°–20° S, propelled westward by the Southeast Trade Winds to about longitude 180° E. The Pacific North Equatorial Current is pushed westward by the Northeast Trade Winds between 10°–25° N. The Atlantic South Equatorial Current is pushed westward by the Southeast Trade Winds between 0°–20° S. The Atlantic North Equatorial Current is pushed westward by the Northeast Trade Winds between 10° and 20° N. In the Indian Ocean, the Monsoon Current replaces the North Equatorial Current, but there is an Indian South Equatorial Current flowing west with the trades north of 22° S.
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What causes equatorial currents to form?
Equatorial currents, which flow westward near the Equator, are primarily caused by winds. These currents typically consist of two westward-flowing currents, the North and South equatorial currents, which are separated by an eastward-flowing countercurrent.
The trade winds give a westward push to the Pacific North Equatorial Current and the Atlantic North Equatorial Current. Similarly, the Southeast Trade Winds drive the Pacific and Atlantic South Equatorial Currents westward.
The east-to-west wind across the tropical ocean waters induces Ekman transport divergence at the Equator, which cools the surface water there.
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How do equatorial currents move water along the equator?
Equatorial currents, driven primarily by winds, flow westward near the equator. These systems feature the North and South equatorial currents, which are separated by an eastward-flowing countercurrent.
Wind stress on the sea surface induces ocean circulation. At the Equator, currents mostly move west: the North Equatorial Current in the Northern Hemisphere and the South Equatorial Current in the Southern Hemisphere. The eastward-flowing Equatorial Counter Current occurs near the thermal equator, where the warmest surface water is.
The east-to-west wind across tropical ocean waters causes Ekman transport divergence at the Equator, cooling the surface water. A jetlike current, the Equatorial Undercurrent, flows east below the surface, driven by higher sea level in the western margins of the tropical ocean. The Coriolis force also influences these dynamics.
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What is the difference between the North and South Equatorial Currents?
The North and South Equatorial Currents are wind-driven ocean currents that flow westward near the equator.
The Pacific North Equatorial Current is propelled westward by the Northeast Trade Winds, between 10° and 25° N latitude. Upon reaching the Philippines, it divides, with a smaller portion turning south to form the Pacific Equatorial Countercurrent and the larger portion flowing north as the Kuro Current.
The Pacific South Equatorial Current flows between 5° N and 15°–20° S latitude, pushed westward by the Southeast Trade Winds to about 180° E longitude. Here, it splits, with some of its water turning north to merge with the countercurrent, and the rest veering south to become the East Australian Current.
The sea surface temperature is warmer off the eastern coast than off the western one in latitudes of about 10° to 30° S and 10° to 30° N.
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How do equatorial currents influence weather and marine life near the equator?
Equatorial currents significantly influence weather and marine life near the equator. These currents, driven by winds, consist of westward-flowing North and South Equatorial Currents, separated by an eastward-flowing countercurrent.
These currents have similar climatic effects on continental shores, bringing warmth and higher humidity to the east coasts while causing dry conditions on the west coasts. The westward-moving trade winds displace surface ocean waters, causing colder waters to move to the surface. This upwelling enriches sea life by transporting oxygen and organic nutrients.
Anomalies in equatorial currents, such as El Niño, can cause major climate changes and affect precipitation patterns across the globe.
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Equatorial current, ocean current flowing westward near the equator, predominantly controlled by the winds. Characteristically, equatorial-current systems consist of two westward-flowing currents approximately 600 miles (1,000 km) wide (North and South equatorial currents) separated by an eastward-flowing countercurrent only 300 miles (480 km) wide. Usually flowing at depths of less than 1,650 feet (500 m), equatorial currents travel at rates of 10 to 40 inches per second (25 to 100 cm per second). Equatorial undercurrents, centred on the equator at depths of 160 to 500 feet (49 to 152 m), flow eastward at rates up to 5 feet/s (1.5 m/s) and are approximately 1,000 feet (305 m) deep and 640 miles (1,030 km) wide.
The Pacific South Equatorial Current, flowing approximately between latitude 5° N and 15°–20° S, is propelled westward by the Southeast Trade Winds to about longitude 180° E. There it splits, part turning north to blend with the countercurrent and the rest veering south to become the East Australian Current and a flow passing east of New Zealand. The latter feeds the South Pacific Current and West Wind Drift, which move eastward to the Peru Current. The Peru Current flows north as a source of the Pacific South Equatorial Current.
The Pacific North Equatorial Current is given a westward impetus by the Northeast Trade Winds (latitude 10°–25° N). Upon reaching the Philippines, the current divides, with the lesser part turning south and then east to start the Pacific Equatorial Countercurrent, and the greater part flowing north. This flow, known as the Kuro Current, moves north as far as Japan, then east as the North Pacific Current (West Wind Drift), part of which then turns south as the California Current, which joins the equatorial countercurrent to form the Pacific North Equatorial Current.
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The Atlantic South Equatorial Current is pushed westward by the Southeast Trade Winds (latitude 0°–20° S). Approaching Cape St. Roque, Brazil, it divides. One stream goes north as the Guiana Current, which in turn feeds the Caribbean Current, the equatorial countercurrents, and the Guinea Current. The other, moving south as the Brazil Current, turns east off the Río de la Plata (as the South Atlantic Current) then pushes to the African coast, where it veers north as the Benguela Current. This joins the Guinea Current to re-form the Atlantic South Equatorial Current.
The Atlantic North Equatorial Current is pushed westward by the Northeast Trade Winds between latitude 10° and 20° N. Fed in part by the South Atlantic Equatorial, it turns north as the Antilles, Caribbean, and Florida currents, which eventually become the Gulf Stream. Some of the Gulf Stream’s waters eventually arc southward as the Azores and Canary currents, which swing west to join upwelling water off the west coast of North Africa. This gives birth to the Atlantic North Equatorial, which, as it crosses the Mid-Atlantic Ridge, jogs north only to bend south beyond the ridge.
In the Indian Ocean the place of a north equatorial current is taken by the Monsoon Current. There is, however, an Indian South Equatorial Current. Flowing westerly with the trades north of latitude 22° S, it divides to form the East Africa Coastal Current, moving northward, and a south-flowing stream. The latter passes by Madagascar as the Mozambique (west) and Mascarene currents, which become the Agulhas Current. At the Cape of Good Hope this feeds east into the South Indian Current, which supplies the West Australian Current. The latter is a source of the Indian South Equatorial Current.
The equatorial currents have similar climatic effects upon continental shores they touch, bringing warmth and higher humidity to the east coasts and dry conditions to the west.
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