• Clark, P., N. Pisias, T. Stocker, and A. Weaver, 2001: The role of the thermohaline circulation in abrupt climate change. Nature, 415 , 863869.

    • Search Google Scholar
    • Export Citation
  • Döös, K., 1994: Semi-analytical simulation of the meridional cells in the Southern Ocean. J. Phys. Oceanogr, 24 , 12811293.

  • Gill, A., and F. Bryan, 1971: Effects of geometry on the circulation of a three-dimensional Southern Hemisphere ocean model. Deep-Sea Res, 18 , 685721.

    • Search Google Scholar
    • Export Citation
  • Luyten, J., J. Pedlosky, and H. Stommel, 1983: The ventilated thermocline. J. Phys. Oceanogr, 13 , 292309.

  • Marotzke, J., 1997: Boundary mixing and the dynamics of three-dimensional thermohaline circulations. J. Phys. Oceanogr, 27 , 17131728.

    • Search Google Scholar
    • Export Citation
  • Marshall, J., and T. Radko, 2003: Residual-mean solutions for the Antarctic Circumpolar Current and its associated overturning circulation. J. Phys. Oceanogr, 33 , 23412354.

    • Search Google Scholar
    • Export Citation
  • Munk, W., 1966: Abyssal recipes. Deep-Sea Res, 13 , 707730.

  • Munk, W., and C. Wunsch, 1998: Abyssal recipes II: Energetics of tidal and wind mixing. Deep-Sea Res, 45A , 19772010.

  • Nof, D., 2003: The Southern Ocean's grip on the northward meridional flow. Progress in Oceanography, Vol. 56, Pergamon, 223– 247.

  • Pedlosky, J., and R. Samelson, 1989: Wind forcing and the zonal structure of the Equatorial Undercurrent. J. Phys. Oceanogr, 19 , 12441254.

    • Search Google Scholar
    • Export Citation
  • Polzin, K., J. Toole, J. Ledwell, and R. Schmitt, 1997: Spatial variability of turbulent mixing in the abyssal ocean. Science, 276 , 9396.

    • Search Google Scholar
    • Export Citation
  • Samelson, R. M., 1998: Large-scale circulation with locally enhanced vertical mixing. J. Phys. Oceanogr, 28 , 712726.

  • Samelson, R. M., 1999: Geostrophic circulation in a rectangular basin with a circumpolar connection. J. Phys. Oceanogr, 29 , 31753184.

    • Search Google Scholar
    • Export Citation
  • Samelson, R. M., 2003: Meridional overturning as a “pump and valve” system. Near-Boundary Processes and Their Parameterization: Proc. 'Aha Huliko'a Hawaiian Winter Workshop, Honolulu, HI, University of Hawaii at Manoa, 205–209.

    • Search Google Scholar
    • Export Citation
  • Samelson, R. M., and G. K. Vallis, 1997: Large-scale circulation with small diapycnal diffusion: The two-thermocline limit. J. Mar. Res, 55 , 223275.

    • Search Google Scholar
    • Export Citation
  • Schmitz Jr., W. J., 1996a: On the World Ocean circulation: Volume I. Woods Hole Oceanographic Institution Tech. Rep. WHOI-96-03, 141 pp.

    • Search Google Scholar
    • Export Citation
  • Schmitz Jr., W. J., 1996b: On the World Ocean circulation: Volume II. Woods Hole Oceanographic Institution Tech. Rep. WHOI-96-08, 237 pp.

    • Search Google Scholar
    • Export Citation
  • Sloyan, B., and S. Rintoul, 2000: Estimates of area-averaged diapycnal fluxes from basin-scale budgets. J. Phys. Oceanogr, 30 , 23202341.

    • Search Google Scholar
    • Export Citation
  • Sloyan, B., and S. Rintoul, 2001a: The Southern Ocean limb of the global deep overturning circulation. J. Phys. Oceanogr, 31 , 143173.

    • Search Google Scholar
    • Export Citation
  • Sloyan, B., and S. Rintoul, 2001b: Circulation, renewal, and modification of Antarctic Mode and Intermediate Water. J. Phys. Oceanogr, 31 , 10051030.

    • Search Google Scholar
    • Export Citation
  • Spall, M., 2000: Buoyancy-forced circulations around islands and ridges. J. Mar. Res, 58 , 957982.

  • Speer, K., S. R. Rintoul, and B. Sloyan, 2000: The diabatic Deacon cell. J. Phys. Oceanogr, 30 , 32123222.

  • Stocker, T., and D. Wright, 1991: Rapid transition of the ocean's deep circulation induced by changes in surface water fluxes. Nature, 351 , 729732.

    • Search Google Scholar
    • Export Citation
  • Stommel, H., 1958: The abyssal circulation. Deep-Sea Res, 5 , 8082.

  • Talley, L., 2003: Shallow, intermediate, and deep overturning components of the global heat budget. J. Phys. Oceanogr, 33 , 530560.

  • Toggweiler, J. R., and B. Samuels, 1995: Effect of Drake Passage on the global thermohaline circulation. Deep-Sea Res, 42 , 477500.

  • Veronis, G., 1973: Model of World Ocean circulation. Part I. J. Mar. Res, 31 , 228288.

  • Webb, D. J., and N. Suginohara, 2001: Vertical mixing in the ocean. Nature, 409 , 37.

  • Welander, P., 1959: An advective model of the ocean thermocline. Tellus, 11 , 309318.

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Simple Mechanistic Models of Middepth Meridional Overturning

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  • 1 College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
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Abstract

Two idealized, three-dimensional, analytical models of middepth meridional overturning in a basin with a Southern Hemisphere circumpolar connection are described. In the first, the overturning circulation can be understood as a “pump and valve” system, in which the wind forcing at the latitudes of the circumpolar connection is the pump and surface thermodynamic exchange at high northern latitudes is the valve. When the valve is on, the overturning circulation extends to the extreme northern latitudes of the basin, and the middepth thermocline is cold. When the valve is off, the overturning circulation is short-circuited and confined near the circumpolar connection, and the middepth thermocline is warm. The meridional overturning cell in this first model is not driven by turbulent mixing, and the subsurface circulation is adiabatic. In contrast, the pump that primarily drives the overturning cell in the second model is turbulent mixing, at low and midlatitudes, in the ocean interior. In both models, however, the depth of the midlatitude deep layer is controlled by the sill depth of the circumpolar gap. The thermocline structures in these two models are nearly indistinguishable. These models suggest that Northern Hemisphere wind and surface buoyancy forcing may influence the strength and structure of the circumpolar current in the Southern Hemisphere.

Corresponding author address: R. M. Samelson, 104 COAS Admin. Bldg., Oregon State University, Corvallis, OR 97331-5503. Email: rsamelson@coas.oregonstate.edu

Abstract

Two idealized, three-dimensional, analytical models of middepth meridional overturning in a basin with a Southern Hemisphere circumpolar connection are described. In the first, the overturning circulation can be understood as a “pump and valve” system, in which the wind forcing at the latitudes of the circumpolar connection is the pump and surface thermodynamic exchange at high northern latitudes is the valve. When the valve is on, the overturning circulation extends to the extreme northern latitudes of the basin, and the middepth thermocline is cold. When the valve is off, the overturning circulation is short-circuited and confined near the circumpolar connection, and the middepth thermocline is warm. The meridional overturning cell in this first model is not driven by turbulent mixing, and the subsurface circulation is adiabatic. In contrast, the pump that primarily drives the overturning cell in the second model is turbulent mixing, at low and midlatitudes, in the ocean interior. In both models, however, the depth of the midlatitude deep layer is controlled by the sill depth of the circumpolar gap. The thermocline structures in these two models are nearly indistinguishable. These models suggest that Northern Hemisphere wind and surface buoyancy forcing may influence the strength and structure of the circumpolar current in the Southern Hemisphere.

Corresponding author address: R. M. Samelson, 104 COAS Admin. Bldg., Oregon State University, Corvallis, OR 97331-5503. Email: rsamelson@coas.oregonstate.edu

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