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The Gulf Stream

The Gulf StreamAn underwater river that comes all the way from the Caribbean. Find out about the Gulf Stream, and how much colder we’d be without it!

Imagine a powerful warm river of sea water which, instead of flowing on land, flows in the sea. You have imagined the Gulf Stream, one of the strongest ocean currents in the world.

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.

A giant underwater river

Within the Gulf of Mexico, the Gulf Stream is very narrow, only 50 miles wide, and travels very fast at 3 mph, carrying water at about 25°C. The North Atlantic Drift widens considerably to several hundred miles, slows to less than 1 mph and splits into several sub-currents. Off the British Isles it splits into two branches, one going south (the Canary Current) and the other going north along the coast of West and North Europe.

Surface water of the current in the north Atlantic is cooled by winds from the Arctic. It becomes colder, more salty and more dense and sinks to the ocean floor. The cold water then moves towards the equator where it is slowly warmed until it can resurface and flow back north from the Gulf of Mexico north into the Atlantic.

How does it keep us warm?

The relatively warm waters of the North Atlantic Drift are responsible for moderating the climate of western Europe, so that winters are less cold than would otherwise be expected at this latitude. Without the warm North Atlantic Drift, the UK would be as cold as Canada, at the same latitude. For example, without this steady stream of warmth the British Isles winters would be more than 5 °C cooler.

Some 11,000 years ago the water circulation was severely disrupted because of subtle shifts in global climate. This slowed and diverted the course of the Gulf Stream to such an extent that the regional climate of the Northeast Atlantic became considerably cooler. As a result North-western Europe dropped back to ice age conditions within tens of years. It is now suspected that global warming may trigger another disruption of the water circulation and a slowing or diversion of the Gulf Stream, which would ironically lead to colder climates throughout the UK and Northwest Europe.

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