Thermohaline circulation, ocean

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Thermohaline circulation Deep-water circulaUon caused by density differences created in the surface waters of polar regions. Cooling increases the density of the surface waters, which sink and then advect horizontally throughout the deep ocean. The water is returned to the sea surface by eddy diffusion. 

The concentration of RDOM is simply equal to the measured concentration of DOM in deep waters (>1000 m), where its apparent radiocarbon age of 4000-6000 years is substantially greater than the timescale of thermohaline circulation in the earth s oceans (Druffel et al., 1992). Bioassay experiments have been used to verify the refractory nature of DOM in the deep sea (Barber, 1968). 

The thermohaline circulation dominated by the Arctic Ocean and Nordic Seas is responsible for a considerable part of the Earth s poleward heat transport and may also serve as a sink for CO2. Alterations of this circulation, as have been observed during climatic changes of the past, can affect global climate and in particular the climate of Europe and North America. ... 

Calculations of anthropogenic (greenhouse) climate change show that thermohaline circulation (THC) in NH oceans may weaken in the future. However, even the models that show this weakening still demonstrate that greenhouse warming in Europe will persist. So far, no one knows whether irreversible collapse of THC is a possibility or which threshold conditions correspond to such a collapse. No existing model predicts total cessation of THC for the next 60 years. 

The density of the water controls the deepwater circulation. If the density of a water body increases, it has a tendency to sink. Subsequently, it will spread out over a horizon of uniform circulatory system is also known as thermohaline circulation. As shown in Figure 5 of the ocean conveyor belt, the densest oceanic waters are formed in Polar Regions due to the relatively low temperatures and the salinity increase that results from ice formation. Antarctic Bottom Water (ABW) is generated in the Weddell Sea and flows northward into the South Atlantic. North Atlantic Deep Water (NADW)... 

Figure 5 A schematic diagram of the thermohaline circulation of the world ocean, also know as the great ocean conveyor belt, highlighting polar regions of deepwater formation, deepwater circulation eastward from the poles and the returning westward surface water flow (Adapted from IPCC, 2001. )...

Ruhlemann C., Mulitza S., Muller P. J., Wefer G., and Zahn R. (1999) Warming of the tropical Atlantic Ocean and slowdown of thermohaline circulation during the last deglaciation. Nature 402, 511-514. 

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