What are Ocean Currents?
Ocean Currents are large masses of surface water that circulate in a regular pattern around the oceans.
Warm Currents
Those that flow from equatorial regions polewards have a higher surface temperature and are warm currents.
Cold Currents
Those that flow from polar regions equatorwards have a lower surface temperature and are called cold currents.
In every ocean, there is the circulation of ocean water from the Equator to the poles and from the poles to the equator. The warm currents from the equator flow over the surface of the ocean towards the pole and sink to the bottom of the ocean floor in the higher latitudes due to high density and flow towards the equator to complete the circulation. This large-scale circulation is known as a gyre.
The gyre circulates clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.
Causes of Ocean Currents
Some of the underlying factors for the movements of Ocean currents are Planetary winds, Temperature, Salinity, Earth Rotation and Land Mass.
Ocean currents of the Pacific Ocean
1.1. North Equatorial Current
The north equatorial current originates from Revilla Gigedo Island west of Mexico and flows toward the Philippines Island, covering a distance of about 12,000 km from east to west. It is a warm current. It derives from its water from the Californian current and the Southeast Monsoon drift, which flows north along the Mexican coast.
The volume of water increases from east to west as many small currents join it from the right. It gets divided into two, and the northern branch joins the Kuroshio Current, and the southern branch abruptly turns and forms the Pacific countercurrent.
1.2 South Equatorial Current
The South Equatorial Current originated due to the action of the trade winds from east to west. It is a warm current. It extends for about 13,600km from east to west. It is stronger than the North Equatorial Current. It is further divided into many branches due to the presence of many islands and uneven surface topography.
1.3 Kuroshio Current (Black Tide)
It is a warm ocean current flowing in a north-easterly direction up to 30° N latitude, and it carries warm
water off the Formosa coast. It flows towards the north and meets the Oyashio cold current off the Kuril Islands. It is also called Japan current.
1.4 Oyashio Current (Parental Tide)
It originates from the Bering Strait and flows towards the south, carrying cold water. It is a cold current. It meets with the Kuroshio’s warm current and the Aleutian current.
1.5 Californian Current
The Californian current is flowing towards the south along the west coast of the U.S.A. between 48° N and 23° N latitudes. It is a cold current that exhibits a great amount of upwelled water. When it enters the region of Trade winds, it is deflected to the right and joins the equatorial current.
1.6 Peru Current
Peru Current is perhaps the best-studied ocean current in the Pacific Ocean. Alexander Von Humboldt, in 1802, noted the details of the Peru Current. Hence, it is also known as the Humboldt Current. It is a cold current. It is flowing north along the west coast of South America, carrying cold water from the northerly deflection of the Sub-Antarctic water moving at 40° S.
Humboldt (Peru) Current
A circuit of ocean currents exists in the South Pacific. As there is no land to obstruct the cold streams from the Antarctic Ocean, warm currents are forced nearer to the equator in the South Pacific than in the north. It was a current from the Antarctic that had to be contended against, and it entered the left branch of the current that flows along the coast of Chile and Peru. This current is called Humboldt’s Current. This immense body of icy-cold water has a great effect on the climate of Patagonia and Chile.
The effect of this current on the climate is felt as far as the Galapagos, which is on the equator. The temperature of the current round these islands is more than ten degrees lower than that of the ocean. This hinders the growth of coral on the shores of this Archipelago.
The average rate of this current is twelve miles a day, but in some parts it runs far more rapidly, as of the coast of Valparaiso, where it flows twenty-six miles a day.
Humboldt’s Current is lost near the Galapagos, some of it returns as an inshore current, southward along the coast, and a part flows west into the South Equatorial. The current that crosses warmer water flowing in the same direction as Humboldt’s, which is called Mentor’s Drift.
1.7 El Niño or Countercurrent
It is a warm counter ocean current of the Pacific equatorial waters flowing southward at a depth of 400 m to a distance of about 180 km.
Off the Peruvian coastline, the cold Humboldt current meets a warm ocean current that flows south from the equator. This current is called El Niño. This El Niño, every two to seven years, gets stronger and lasts longer than usual. El Niño causes changes in the winds and precipitation across the tropical Pacific region.
This warm water causes fish to die and creates tropical storms, that brings heavy rain, floods and landslides. This El Niño reaches reach in December.
The El Niño rains disrupt the fishing industry.
1.8 West Wind Drift
It is an easterly moving drift in the Pacific Ocean extending from Tasmania to the South American coast. It is a cold current. The speed of the drift is greater under the influence of the Roaring Forties. It splits into two branches, and one moves south around the Cape Horn into the Atlantic Ocean, and the Other one moves northward along the Peruvian coast due to deflection and joins the Peru Current.
2. Currents of the Atlantic Ocean
2.1 North Equatorial current
The North Equatorial Current flows from east to west. It is a warm current. It is situated between 5° and 20°
N latitudes. After leaving the west coast of Africa, it attains its main characteristics. When it reaches the
east coast of South America, it splits into two branches. One branch, called Antilles Current, moves
along the coast of the West Indies, and the other branch is diverted into the Caribbean Sea.
2.2 South Equatorial Current
It is flowing south of the equator within 0° – 12° S latitude in between the coast of Africa and South America. It
is a warm current. It is a northern continuation of the Benguela current. It is stronger than the North equatorial
ocean current. It is caused by the action of Trade winds.
2.3 Gulf Stream
The Gulf Stream starts from the Gulf of Mexico and carries warm waters into the colder latitudes. It is a warm current. It bends with the coastline up to the 40th parallel, after which the direction is almost to the east, due to the force and the direction of the westerlies and the deflective force of the earth. It joins the Labrador Cold Current near Newfoundland, Canada, after passing through the Strait of Florida. The Gulf Stream was discovered by Ponce de Leon in 1513.
2.4 Canaries Current
The ocean current flowing along the Western coast of North Africa between Madeira and Cape Verde is known as the Canary Current. It is a cold current. It is flowing towards the south and merging with the North equatorial current.
2.5 Labrador Current
In the North Atlantic, a cold current flows from the Baffin Bay and Davis Strait towards the south. It brings cold waters from the polar zone and moves along the coast of green land.
2.6 Benguela Current
It is a cold current flowing northward along the western coast of Africa known as the Benguela current. It carries cold waters from sub-Antarctica surface water and mixes with the south equatorial current.
3. Currents of the Indian Ocean
The South Indian gyre is formed by the South Equatorial Current, the Madagascar current west wind drift, and the West Australian Current. To the north of the equator, the currents in the Arabian Sea and Bay of Bengal flow in the clockwise direction as southwest monsoon drift and in the anti-clockwise direction as northeast monsoon drift due to the influence of monsoon winds.
The Antarctic circumpolar current flows between 40 and 60° S latitude. It flows from west to east influenced by the westerly winds, and circles around the entire Antarctica. There is a counter-westward current within this circumpolar current.
4. Currents of the Southern Ocean
The southern ocean surrounds the continent of Antarctica. The large oceans, the Pacific, the Atlantic, and the
The Indian Ocean merges into this circumglobal zone of water to the south. The movement of water in the southern ocean is, in one sense, a relatively simple, generally west-east circumpolar drift caused under the influence of northwesterly winds.
This general flow sends offshoots to the three major oceans to its north. The Peru or Humboldt Current in the Pacific Ocean, the Falkland Current and the Benguela Current in the Atlantic Ocean, and the West Australian Current in the Indian Ocean receive a part of their cold waters from the Southern Ocean.
Besides the surface currents, there is also a very complex system of sub-surface currents between the southern ocean and the oceans to its north.
Generally, the water moves from this ocean towards the equator on the surface and at great depths, but at intermediate depth, there is a movement of water from the equatorial areas towards the southern ocean.