Currents and Tides

Circulation of surface waters is generally clockwise in the North Atlantic and counterclockwise in the South Atlantic. There are, however, many exceptions to the general circulation, particularly along the coasts.

In the North Atlantic, the strongest current is the warm Gulf Stream, which forms in the Gulf of Mexico. It flows northeastward off the United States coast, encounters the cold Labrador Current from the north, and continues across the Atlantic as the North Atlantic Current, or Drift. It continues northward as the Irminger and Norwegian currents.

West of Spain, part of the North Atlantic Current turns southward, flows along the "bulge" of Africa as the Canaries Current, then turns westward as the North Equatorial Current. This current crosses the ocean; part of its water reaches the Gulf of Mexico. South of the North Equatorial Current, running in the opposite direction, is the Equatorial Countercurrent. In the western North Atlantic, around Bermuda, is the Sargasso Sea, a calm area named for its masses of floating sargassum weed.

In the South Atlantic, the cold Benguela Current flows northward up to the coast of Africa, turns west near the Equator, and flows westward as the warm South Equatorial Current. Near the South American coast, part of the current swings southward to become the Brazil Current, which runs down the coast of South America to about 40° South latitude. Here, it meets the cold Falkland Current. Flowing eastward across the South Atlantic in a broad belt around 50° S. is the West Wind Drift.

Most areas bordering the Atlantic have relatively high tides. Occurring with the tides in some narrow river mouths, particularly those with shallow estuaries, are tidal bores—advancing walls of water. The highest tides in the world are in the Bay of Fundy, Canada. Here, the range between high tide and low tide is as much as 60 feet (18 m).