UNI101Y1 Chapter 4: Ch4 Variation in the Environment4.pdf
16 Feb 2013
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Document Summary
Tthheerrmmoohhaalliinnee cciirrccuullaattiioonn causes currents by changes in the density of water caused by variations in temperature and salinity. As wind-driven surface currents (i. e. gulf stream) move towards higher latitudes, the water cools, becomes dense, and sinks. In the far north (towards iceland and greenland) ocean surfaces freeze in the winter. Salts are excluded from sea ice, thus the underlying water increases in salinity. This cold water becomes more dense and sinks, forming the north atlantic deep. Then flow through abyssal depths of the ocean basins back into equatorial regions: eventually surfaces as upwelling currents. Distributes heat energy from tropics to higher latitudes. The southward movement of the nadw is crucial to the northward movement of the gulf. The global thermohaline circulation pattern is like the ocean conveyor belt. Shutdown of thermohaline circulation and the younger dryas. Melting greenland ice sheets and arctic ocean sea ice will flood the north atlantic with low-salinity surface waters, preventing the formation of nadw.
