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Atlantic Trade Winds and Currents

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Trade winds is the name given to certain winds that regularly blow within or near the tropics, either all the year round or at certain times of the year.

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Trade winds continually drive the waters of the intertropical region of the Atlantic from the shores of Africa to America, producing what is known as the equatorial current.

The area over which the trade winds blow shifts, altering the northern and southern boundaries of the equatorial current, as a result of the northward and southward declination of the sun. Consequently, the current flows generally westward in latitudes north of the Tropic of Cancer during summer in the northern hemisphere. South of the Tropic of Capricorn, the current flows generally west through summer in the southern hemisphere. In the northern and southern winters the boundaries of the equatorial current contract to within the tropic of each hemisphere.

Because the thermal equator lies two to three degrees north of the geographical equator, the Atlantic trade winds, and the equatorial current they propel, extend further north than south.

The equatorial current passes directly across the Atlantic towards the Antilles and the coast of South America. The greater part of the current strikes the coast of South America north of Cabo São Roque (Cape St Roque), and is deflected northward. That part which hits the coast between Sã Roque and the mouth of the Orinoco River moves northward at an accelerated rate, forming the Guiana Current that flows through the Carribean.

The Guiana Current is in turn reunited with the portion of the equatorial current flowing westward between the Lesser Antilles. This causes the reunited stream of water to be deflected further northwards by the coastline of Central America into the Gulf of Mexico. The current then sweeps across the gulf until it again hits the equatorial current north west of Cuba and is pushed northwards again through the Florida channel, where it becomes the Gulf Stream running northwards along the North American coast.

Eventually the Gulf Stream thins out after passing the Banks of Newfoundland, and becomes a mild current flowing easterly across the Northern Atlantic.

The smaller portion of the Equatorial Current that strikes the coast of South America to the south of Cabo São Roque forms the Brazil Current, which flows south along the coast of that country as far as the estuary of the La Plata River.

Before reaching the La Plata estuary, however, much of this current is deflected eastwards across the Southern Atlantic to the Cape of Good Hope.

This easterly flowing current is called the Southern Connecting Current.

Once the Southern Connecting Current meets the South African coast, it turns northwards and runs towards the Bight of Biafra, forming the South African Current.

For eighteenth century navigators, the Atlantic trades winds, and the currents they generated, provided a reliable means of crossing from the Canary Archipelago and then heading north with the equatorial current through the islands of the Lesser Antilles into the Caribbean.

It also gave voyagers a way of reaching the Cape of Good Hope without having to sail against the northerly South African Current. They could cross the Atlantic, head southwards of Cabo São Roque with the Brazil Current and then sail back across the Atlantic to the Cape of Good Hope with the Southern Connecting Current.

 

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Prepared by: Turnbull, P
Created: 4 October 2001
Modified: 10 December 2003

Published by South Seas, 1 February 2004
Comments, questions, corrections and additions: Paul.Turnbull@jcu.edu.au
Prepared by: Paul Turnbull
Updated: 28 June 2004
To cite this page use: http://nla.gov.au/nla.cs-ss-biogs-P000048

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