The Gulf Stream is perhaps the best known example of a warm, surface ocean current. It originates in the western Caribbean Sea and flows through the Gulf of Mexico and the Straits of Florida. It moves north along the east coast of the United States to Cape Hatteras in North Carolina, where it turns northeast towards Europe. The current is driven by prevailing trade winds.

The Gulf Stream influences the climate of the UK and northwest Europe by bringing with it humid mild air. Without the warm Gulf Stream, the UK and other places in Europe would be as cold as Canada, at the same latitude. In winter, the air over the ocean to the west of Norway is more than 22 degrees centigrade, warmer than the average for that latitude.

Within the Gulf of Mexico, the Gulf Stream is very narrow, only 50 miles wide, and travels very quickly, carrying water which has a temperature of about 25 degrees centigrade (38 degrees Fahrenheit). The North Atlantic Drift widens considerably to several hundred miles, slows to less than 1.5km/h and splits into several sub-currents.

At its strongest, the Gulf Stream is one of the fastest currents in the world, travelling at 6.5kph. It moves about 135 billion litres (30 billion gallons) of water every second. It was used to advantage by merchant ships crossing the Atlantic for trade in the 17th, 18th and 19th centuries.

Warm currents are vital for marine life. They transport specially adapted tropical and sub tropical species such as tuna to rich food supplies in temperate areas. Where the warm currents meet cold waters another feeding opportunity is created where upwelling occurs. Warm currents also shed small pockets of warm water that provide localised feeding zones for surface-layer hunters.

The Gulf Stream is one of many major currents that join together to form gyres.