From the shore, we are likely to overlook the real dynamics of the Atlantic Ocean. Surface and deep ocean currents stir its waters in a global circulation that each year carries more water than all the rivers of the world combined.
Warm tropical waters move northward in the Gulf Stream, which passes along the eastern coast of the United States. These waters lose heat along the way, especially where the Gulf Stream leaves the coast near Cape Hatteras and heads eastward, out to sea. A portion of the Gulf Stream waters are then diverted northward where they deliver enough heat to the British Isles that they host a temperate climate much further north than one might expect.
When these northward moving surface waters cool in the winter, they overturn and mix with the deep waters of the Atlantic. Afterwards they begin a long journey southward to replace the water that moves northward at the surface.
Oceanographers have pondered whether changes in the strength of the Gulf Stream might accompany climate change. Susan Lozier is an oceanographer at Duke University…
“All modeling data suggest that we should expect changes in the Gulf Stream with climate change. However, to date – either because our observational record is too short or either because other processes are obscuring the signal – we have not yet seen changes in the transport or properties of the Gulf Stream that we would associate with climate change.”
For now, there is no indication that the Gulf Stream has diminished. But oceanographers note that during past geologic epochs, changes in the Gulf Stream have followed and caused major changes in the world’s climate.
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Photo, taken September 11, 2009, courtesy of Matt Chan via Flickr.
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Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.