Gulf Stream, warm ocean current of the N Atlantic Ocean, off E North America. It was first described (1513) by Spanish explorer Ponce de León. The Gulf Stream originates in the Gulf of Mexico and, as the Florida Current, passes through the Straits of Florida and along the coast of SE United States with a breadth of c.50 mi (80 km). North of Cape Hatteras, it is separated from the coast by a narrow southern extension of the cold Labrador Current and flows NE into the Atlantic Ocean. Where the warm surface waters of the Gulf Stream meet the cold winds accompanying the Labrador Current, one of the densest concentrations of fog in the world occurs. Parts of the Gulf Stream current are diverted SE, forming the Canary Currents, which carry cooler waters to the Iberian peninsula and NW Africa. An ensuing current, known as the North Atlantic Drift, flows NW and provides temperate, relatively warm waters to W Europe. The Gulf Stream has an average speed of 4 mi (6.4 km) per hr but slows down as it widens to the north. At the beginning of the Gulf Stream the water temperature is 80°F; (27°C;); the temperature decreases as the current moves north.

Warm ocean current, part of a general clockwise-rotating system of currents in the North Atlantic. A major contribution of the Gulf Stream is its warming effect on the climates of adjacent land areas. In winter, the air over the ocean west of Norway is more than 40°F (22°C) warmer than the average for that latitude, one of the greatest temperature anomalies in the world. Winters in southwestern England are extraordinarily mild for this northern latitude because of the Gulf Stream. Regions of the Gulf Stream, such as the Grand Banks, have been among the most productive commercial fishing grounds in the world.

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