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Thermohaline Circulation (THC)

Thermohaline Circulation (THC). By Ross Alter. What is it?. “…that part of the ocean circulation which is driven by fluxes of heat and freshwater across the sea surface and subsequent interior mixing of heat and salt” (Rahmstorf, 2006)

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Thermohaline Circulation (THC)

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  1. Thermohaline Circulation(THC) By Ross Alter

  2. What is it? • “…that partof the ocean circulation which is driven by fluxes of heatandfreshwater across the sea surface and subsequent interior mixing of heat and salt” (Rahmstorf, 2006) • One driving mechanism of large-scale “deep” ocean circulation • Temperature + salinity density • “Thermo-” + “-haline” • Requires turbulent mixing to complete the circulation • Physical concept, not observational

  3. Source: Rahmstorf (2006)

  4. Figure 2: Idealized meridional section representing a zonally averaged picture of the Atlantic Ocean. Straight arrows sketch the MOC. The color shading depicts a zonally averaged density profile derived from observational data [Levitus, 1982]. Source: Kuhlbrodt et al. (2007)

  5. Why is it important? • Maintains ocean stratification • Comparable transport to that of the surface • Global volume transport ~ 30 Sv • Climate modulator • Cold water absorbs CO2 more efficiently • THC modulates heat transport • ~ 1 PW (1015 W) in N. Atlantic

  6. Speculation about the future… • Global warming – warming and freshening • Will the THC break down? • Low probability, high impact • Most likely scenario – weakening of THC • Would take decades tocenturies to change • No “Day After Tomorrow” scenario…

  7. References • Stewart, R. H., 2002. Introduction to Physical Oceanography. • Kuhlbrodt, T., et al., 2007. On the driving processes of the Atlantic meridional overturning circulation, Rev. Geophys., 45, RG2001, doi:10.1029/2004RG000166 • Rahmstorf, S. Thermohaline Ocean Circulation. In: Encyclopedia of Quaternary Sciences, Edited by S. A. Elias. Elsevier, Amsterdam 2006.

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