In the equatorial belt of the Atlantic Ocean, the Trade wind drives two streams of surface water westwards. One stream flows north of equator and other south of equator. They are known as the North Equatorial Current and South Equatorial Current respectively.
Between these two equatorial currents is the Equatorial Counter Current, which flows from west to east. This counter current replaces the water removed from the eastern side of the ocean.
The South Equatorial Current bifurcates into two branches near the Cape De Sao Roque in Brazil.
Its northern branch joins the North Equatorial Current. This combined current enters the Caribbean Sea and the Gulf of Mexico, while the remaining current passes along the eastern side of the West Indies as the Antilles Current.
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The part of the current, which enters the Gulf of Mexico, comes out from the Florida Strait and joins the Antilles Current. This combined current moves along the southeastern coast of the United States as Florida Current upto the Cape Hatteras.
Beyond the Cape Hatteras, upto the Grand Banks, off New Foundland, it is called the Gulf Stream.
From the Grand Banks, the Gulf Stream is deflected eastwards under the combined influence of the Westerlies and the rotation of the Earth. It crosses the Atlantic Ocean as North Atlantic Drift.
The North Atlantic Drift bifurcates into two branches on reaching the eastern part of the ocean. The northern branch continues as North Atlantic Drift; reaches the British Isles from where it flows along the coast of Norway as the Norwegian Current and enters the Arctic Ocean.
image source: sealevel.jpl.nasa.gov/files/ostm/saraceno.jpg
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The southern branch flows between Spain and Azores Island as the cold Canaries Current.
Thie Canaries Current finally joins the North Equatorial Current and completes the circuit in the North Atlantic Ocean. Within this circuit lies the Sargasso Sea, which is full of large quantities of seaweeds called sargassum-a brown algae.
Apart from the clockwise circulation of the currents in the North Atlantic Ocean, there are also two cold currents-the East Greenland Current and the Labrador Current which flow from the Arctic Ocean into the Atlantic Ocean.
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The confluence of Labrador Current and the Gulf Stream-one cold and the other hot, produces fog around Newfoundland and makes it the most important fishing ground of the world.
East Greenland current flows between Iceland and Greenland and cools the North Atlantic Drift at the point of confluence.
At about 35° S latitude, the influence of the Westerlies and the rotation of the Earth propel the Brazilian current eastward to merge with the West Wind Drift.
Near the Cape of Good Hope, the South Atlantic Current is diverted northward as the cold Benguela Current. It finally joins the South Equatorial Current, thus completing the circuit.
Another cold current, known as the Falkland current, flows along the southeastern coast of South America from south to north.