Gulf Stream

The Gulf Stream, also known as the North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean current that originates in the Gulf of Mexico, exits through the Strait of Florida, and follows the eastern coastlines of the United States and Newfoundland.The Gulf Stream is especially influential on the climate of the east coast of Florida, especially southeast Florida helping to keep temperatures warmer in the winter and less hot than the rest of the southeastern United States in summer. Its extension toward Europe, called the North Atlantic drift, makes West-European countries considerably warmer than they would be otherwise.

A river of sea water, called the North Equatorial Current, flows westward off the coast of northern Africa. When this current interacts with the northwestern coast of South America, the current forks into two branches. One passes into the Caribbean, while a second flows north and east of the West Indies. These two branches rejoin to pour through the Straits of Florida.

Consequently, the resulting Gulf Stream is one of the strongest ocean currents known, transporting 1.4 petawatts of power. It moves at an incredible rate of 30 million cubic meters per second. After it passes Cape Hatteras, this rate increases to 80 million cubic meters per second. The volume of the Gulf Stream easily dwarfs all rivers that empty into the Atlantic combined, which barely total 0.6 million cubic meters per second.

As it travels north, some of the warm water transported by the Gulf Stream evaporates. This increases the salinity of the water in the stream, and in the North Atlantic Ocean the water is so cold and dense with salt that it begins to sink. It then becomes a part of the North Atlantic Deep Water, a southgoing stream.

The effect of the Gulf Stream is sufficient to cause certain parts of the west of Britain and Ireland to be an average of several degrees warmer than most other parts of those countries. Indeed, in Cornwall, and particularly the Isles of Scilly, its effects are such that plants associated with much warmer climates, such as palm trees, are able to survive the rigours of northern winters. Logan Botanic Garden in Scotland benefits strongly from the Gulf Stream, allowing their specimens of Gunnera manicata to grow to over 3 metres tall.

With the recent phenomenon of global warming, some scientists have expressed concern about the sink mechanism outlined above. Specifically, fresh water resulting from the melting of the Arctic polar cap could dilute the Gulf Stream and make it light enough not to sink. The result would be a huge climate change in northern Europe, with unknown consequences. Some fossil remnants hint at the possibility that a similar event has already happened several times in the past, but fossil evidence is questioned.

Evidence of the Gulf Stream slowing

Recently this theory received a boost when a retrospective analysis of U.S. satellite data seemed to show a slowing of the North Atlantic Gyre, the northern swirl of the Gulf Stream.

In May 2005, Peter Wadhams, professor of ocean physics at Cambridge University, reported to the Times about the results of investigations in a submarine under the Arctic ice sheet measuring the giant chimneys of cold dense water, in which the cold dense water normally sinks down to the sea bed and is replaced by warm water, forming one of the engines of the North Atlantic Drift. He and his team found the chimneys to have virtually disappeared. Normally there are seven to twelve giant columns, but Wadhams found only two giant columns, both extremely weak.

References

• NASA: Slowing of North Atlantic Gyre (http://www.nasa.gov/centers/goddard/news/topstory/2004/0415gyre.html)
• Corona Magazine Issue 124: Science (http://www.corona-magazine.de/archiv/corona124.html#wissenschaft) (German, Transported amount of power)
• Peter Wadhams interview (http://www.timesonline.co.uk/article/0,,2087-1602579,00.html) in the Times - disappearance of sinking chimneys of cold, dense water

Further reading

Hycom Consortium (http://oceancurrents.rsmas.miami.edu/atlantic/north-atlantic-drift.html)

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