Basin and Channel Contributions to a Model Antarctic Circumpolar Current

Louis-Philippe Nadeau Department of Atmospheric and Oceanic Sciences, McGill University, Montréal, Quebec, Canada

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David N. Straub Department of Atmospheric and Oceanic Sciences, McGill University, Montréal, Quebec, Canada

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Abstract

The idea that basinlike dynamics may play a major role in determining the Antarctic Circumpolar Current (ACC) transport is revisited. A simple analytic model is developed to describe the relationship between the wind stress and transport. At very low-wind stress, a nonzero minimum is predicted. This is followed by two distinct dynamical regimes for stronger forcing: 1) a Stommel regime in which transport increases linearly with forcing strength; and 2) a saturation regime in which the transport levels off. The baroclinic structure of the Sverdrup flux into the Drake Passage latitude band is central to the analytic model, and the geometry of characteristics, or geostrophic contours, is key to predicting the transition between the two regimes. A robustness analysis is performed using an eddy-permitting quasigeostrophic model in idealized geometries. Many simulations were carried out in large domains across a range of forcing strengths. The simulations agree qualitatively with the analytic model, with two main discrepancies being related to zonal jet structures and to a western boundary inertial recirculation. Eddy fluxes associated with zonal jets modify the baroclinic structure and lower the saturation transport value. Inertial effects increase the transport, although this effect is mainly limited to smaller domains.

Corresponding author address: Louis-Philippe Nadeau, Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montréal QC H2W 1S9, Canada. Email: louis-philippe.nadeau@mail.mcgill.ca

Abstract

The idea that basinlike dynamics may play a major role in determining the Antarctic Circumpolar Current (ACC) transport is revisited. A simple analytic model is developed to describe the relationship between the wind stress and transport. At very low-wind stress, a nonzero minimum is predicted. This is followed by two distinct dynamical regimes for stronger forcing: 1) a Stommel regime in which transport increases linearly with forcing strength; and 2) a saturation regime in which the transport levels off. The baroclinic structure of the Sverdrup flux into the Drake Passage latitude band is central to the analytic model, and the geometry of characteristics, or geostrophic contours, is key to predicting the transition between the two regimes. A robustness analysis is performed using an eddy-permitting quasigeostrophic model in idealized geometries. Many simulations were carried out in large domains across a range of forcing strengths. The simulations agree qualitatively with the analytic model, with two main discrepancies being related to zonal jet structures and to a western boundary inertial recirculation. Eddy fluxes associated with zonal jets modify the baroclinic structure and lower the saturation transport value. Inertial effects increase the transport, although this effect is mainly limited to smaller domains.

Corresponding author address: Louis-Philippe Nadeau, Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montréal QC H2W 1S9, Canada. Email: louis-philippe.nadeau@mail.mcgill.ca

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  • Arakawa, A., 1966: Computational design for long-term numerical integrations of the equations of atmospheric motion. J. Comput. Phys., 1 , 119143.

    • Search Google Scholar
    • Export Citation
  • Baker, D. J., 1982: A note on Sverdrup balance in the Southern Ocean. J. Mar. Res., 40 , 2126.

  • Becker, J. M., and R. Salmon, 1997: Eddy formation over a continental slope. J. Mar. Res., 55 , 181200.

  • Briggs, W. L., V. E. Henson, and S. F. McCormick, 2000: A Multigrid Tutorial. 2nd ed. SIAM, 193 pp.

  • Dewar, W. K., 1998: Topography and barotropic transport control by bottom friction. J. Mar. Res., 56 , 295328.

  • Gent, P. R., W. G. Large, and F. O. Bryan, 2001: What sets the mean transport through Drake Passage? J. Geophys. Res., 106 , 26932712.

    • Search Google Scholar
    • Export Citation
  • Gnanadesikan, A., and R. W. Hallberg, 2000: On the relationship of the Circumpolar Current to Southern Hemisphere winds in coarse-resolution ocean models. J. Phys. Oceanogr., 30 , 20132034.

    • Search Google Scholar
    • Export Citation
  • Hughes, C. W., 2002: Sverdrup-like theories of the Antarctic Circumpolar Current. J. Mar. Res., 60 , 117.

  • Johnson, G. C., and H. Bryden, 1989: On the strength of the circumpolar current. Deep-Sea Res., 36 , 3953.

  • Karsten, R., H. Jones, and J. Marshal, 2002: The role of eddy transfer in setting the stratification and transport of a circumpolar current. J. Phys. Oceanogr., 32 , 3954.

    • Search Google Scholar
    • Export Citation
  • Krupitsky, A., and M. A. Cane, 1997: A two-layer wind-driven ocean model in a multiply connected domain with bottom topography. J. Phys. Oceanogr., 27 , 23952404.

    • Search Google Scholar
    • Export Citation
  • MacCready, P., and P. B. Rhines, 2001: Meridional transport across a zonal channel: Topographic localization. J. Phys. Oceanogr., 31 , 14271439.

    • 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
  • Marshall, J., D. O. Olbers, H. Ross, and D. Wolf-Gladrow, 1993: Potential vorticity constraints on the dynamics and hydrography of the Southern Ocean. J. Phys. Oceanogr., 23 , 465487.

    • Search Google Scholar
    • Export Citation
  • Maximenko, N. A., B. Bang, and H. Sasaki, 2005: Observational evidence of alternating zonal jets in the world ocean. Geophys. Res. Lett., 32 , L12607. doi:10.1029/2005GL022728.

    • Search Google Scholar
    • Export Citation
  • McWilliams, J., 1977: A note on a consistent quasigeostrophic model in a multiply connected domain. Dyn. Atmos. Oceans, 1 , 427441.

  • Munk, W., and E. Palmén, 1951: Note on the dynamics of the Antarctic Circumpolar Current. Tellus, 3 , 5355.

  • Nadiga, B., 2006: On zonal jets in oceans. Geophys. Res. Lett., 33 , L10601. doi:10.1029/2006GL025865.

  • Nakano, H., and H. Hasumi, 2005: A series of zonal jets embedded in the broad zonal flows in the Pacific obtained in eddy-permitting ocean general circulation models. J. Phys. Oceanogr., 35 , 474488.

    • Search Google Scholar
    • Export Citation
  • Olbers, D., D. Borowski, C. Völker, and J-O. Wölff, 2004: The dynamical balance, transport, and circulation of the Antarctic Circumpolar Current. Antarct. Sci., 16 , 439470.

    • Search Google Scholar
    • Export Citation
  • Panetta, R. L., 1993: Zonal jets in wide baroclinically unstable regions: Persistence and scale selection. J. Atmos. Sci., 50 , 20732106.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., 1996: Ocean Circulation Theory. Springer, 453 pp.

  • Press, W. H., S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery, 1996: Numerical Recipes in Fortran 90. Vol. 2. Cambridge University Press, 552 pp.

    • Search Google Scholar
    • Export Citation
  • Rhines, P. B., 1975: Waves and turbulence on a beta-plane. J. Fluid Mech., 69 , 417443.

  • Rhines, P. B., and W. R. Young, 1982: A theory of wind driven circulation. I. Mid-ocean gyres. J. Mar. Res., 40 , 559596.

  • Rhines, P. B., and R. Schopp, 1991: The wind-driven circulation: Quasi-geostrophic simulations and theory for nonsymmetric winds. J. Phys. Oceanogr., 21 , 14381469.

    • Search Google Scholar
    • Export Citation
  • Rintoul, S., C. Hughes, and D. Olbers, 2001: The Antarctic Circumpolar Current system. Ocean Circulation and Climate, G. Siedler et al., Eds., International Geophysical Series, Vol. 77, Academic Press, 271–302.

    • Search Google Scholar
    • Export Citation
  • Stommel, H., 1957: A survey of ocean current theory. Deep-Sea Res., 6 , 149184.

  • Straub, D. N., 1993: On the transport and angular momentum balance of channel models of the Antarctic Circumpolar Current. J. Phys. Oceanogr., 23 , 776782.

    • Search Google Scholar
    • Export Citation
  • Tansley, C. E., and D. P. Marshall, 2001: On the dynamics of wind-driven circumpolar currents. J. Phys. Oceanogr., 31 , 32583273.

  • Treguier, A. M., and J. C. McWilliams, 1990: Topographic influences on wind-driven, stratified flow in a β-plane channel: An idealized model for the Antarctic Circumpolar Current. J. Phys. Oceanogr., 20 , 321343.

    • Search Google Scholar
    • Export Citation
  • Warren, B. A., J. H. LaCase, and P. E. Robbins, 1996: On the obscurantist physics of “form drag” in theorizing about the circumpolar current. J. Phys. Oceanogr., 26 , 22972301.

    • Search Google Scholar
    • Export Citation
  • Webb, D., 1993: A simple model of the effect of the Kerguelen Plateau on the strength of the Antarctic Circumpolar Current. Geophys. Astrophys. Fluid Dyn., 70 , 5784.

    • Search Google Scholar
    • Export Citation
  • Wolff, J-O., E. Maier-Reimer, and D. J. Olbers, 1991: Wind-driven flow over topography in a zonal β-plane channel: A quasi-geostrophic model of the Antarctic Circumpolar Current. J. Phys. Oceanogr., 21 , 236264.

    • Search Google Scholar
    • Export Citation
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