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Natural Science Forum / Earth Science / Oceanography / March 2008Thermohaline Ocean Circulation
I've been studying the subject circulation and can't quite agree with the explanation in the text. While I see change in density of seawater (temperature and salinity) as driving vertical movement, I don't see this as driving lateral movement. For example, deep water moving south out of the North Atlantic. Isn't it the accumulation of warm water from the south (wind driven) causing a sea level rise and the resulting greater pressure forcing out deeper water? And again in the Indian and Pacific Oceans, warm surface water moving south westerly (wind driven) causes a lower sea level and lower pressure for deeper water to move into the region and replace the surface water. My physics background has me demoting the thermohaline process to a second order effect rather than a prime mover. Can anyone provide discussion/clarification on this point? Phil H friend it seems that you dont have any doubt that thermohaline effect would cause a vertical motion. colder (saltier) water is denser than warmer (fresh) water. the denser water would sink. inorder to conserve continuity of mass/volume , water has to come laterally and replace the vertically displaced water parcel. this drives a thermohaline circulation. anyhow, oceanic circulations could not be explained on the basis of simple wind driving or thermohaline drivings. they do not take the form of a sheet like continous motion, as many schematic diagrams depicts. these diagrams only give a spatially and temporally averaged picture. oceanic currents are discontinuous, at times breaks into eddies and dissipate its energy. the forces that drive these currents can be wind, thermohaline. currents can also be forced remotely by baroclinic waves viz Kelvin and Rossby waves. They get modified by small scale processes such as tides, river runoff etc.. regards viji > I've been studying the subject circulation and can't quite agree with > the explanation in the text. While I see change in density of seawater [quoted text clipped - 15 lines] > > Phil H > friend > it seems that you dont have any doubt that thermohaline effect would [quoted text clipped - 13 lines] > regards > viji Viji, thanks for your response. I guess the whole thing is a lot more complicated than the simplistic account I've been reading (Garrison's Oceanography and Tarbuck and Lutgens' Earth Science). The fact the surface water moves several orders of magnitude faster than deep water allows for the intervention of all kinds of other effects. If the polar icecaps continue to melt, it will be interesting to see how that effects the haline part of the process. Phil H > <vijithvn...@gmail.com> wrote in message > ews:7a78dad7-cf0a-47fc-aeb0-bbe40a6aaee6@p43g2000hsc.googlegroups.com... [quoted text clipped - 3 lines] > > cause a vertical motion. colder (saltier) water is denser than warmer > > (fresh) water. the denser water would sink. Warmer saltier water at the tropics as the North Atlantic supplies denser water to the lower layers aught to force the Arctic cold back home rather than unite to invade the Waddel sea. > I guess the whole thing is a lot more > complicated than the simplistic account I've been reading (Garrison's > Oceanography and Tarbuck and Lutgens' Earth Science). The fact the > surface water moves several orders of magnitude faster than deep water > allows for the intervention of all kinds of other effects. The air impact on surface currents drops off immediately as the force needed increases by orders of magnitude meets inertia and complex reactions to keep the status quo. > If the polar icecaps continue to melt, it will be interesting to see how > that effects the haline part of the process. What exactly is the physics background you have? |
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