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Ocean Circulation
Figure 1
shows the major movement of water in the oceans of
the world. Note the location of the Equator and the general direction of
motion in the Northern and Southern Hemisphere. The Southern Hemisphere
has major counterclockwise circulation gyres in the South Pacific and South
Atlantic Oceans. The Indian Ocean directly west of Australia also has a
smaller gyre, with an even smaller circulation pattern in the Arabian Sea
and Bay of Bengal to the north. These circulation patterns all contribute
to create a west-to-east flow around the rather circular Antarctic continent
and a generally east-to-west flow around the equator.
The clockwise circulation patterns in the Northern Hemisphere include a single gyre in the North Atlantic and two cells in the North Pacific Ocean. At latitudes above N, circulation patterns become more complicated due to interactions with continents and the Arctic Ocean, but where smaller circulations exist, clockwise rotation is preserved. Note the position and direction of the Gulf Stream off the east coast of the US and the North Atlantic drift current between Greenland and Scandinavia. A close-up satellite picture of the Gulf Stream, with color enhancement to show temperatures, shows the horizontal extent of the warm current and the eddy structure that develops off the New England coast (Figure 2).
An interesting consequence of these circulations is that, in both hemispheres, the west coasts of continents generally have flow toward the Equator and east coasts have flow away from the Equator. Other factors being equal, this suggests that west coasts of continents will have slightly cooler water offshore compared to east coasts at the same latitude. In the US, the water off northern California is much colder than off New York, at the same latitude.
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