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Figure 7.1: Left: Surface temperatures of the ocean show a sharp temperature gradient, just as in the atmospheresimilar to the polar cell. The difference is that the cold water is less dense than the warmer water surrounding, while the cold air is denser than the warm air surrounding. As a result, the flows travel in opposite directions. Right: Anticyclonic current around Antarctica.
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Figure 7.2: Salinity as a function of depth. Near the surface the water is the cold and fresh water melting , having melted from the ice , then between 100 and on the poles. Between 100-200 meters deep the water becomes much saltier (and more dense), as well as warmer. There is a sharp gradient between the fresh and salt water; the boundary is known as a halocline.