• Abernathey, R., , J. Marshall, , and D. Ferreira, 2011: The dependence of Southern Ocean meridional overturning on wind stress. J. Phys. Oceanogr., 41, 22612278, doi:10.1175/JPO-D-11-023.1.

    • Search Google Scholar
    • Export Citation
  • Bengtsson, L., , K. I. Hodges, , and E. Roeckner, 2006: Storm tracks and climate change. J. Climate, 19, 35183543, doi:10.1175/JCLI3815.1.

    • Search Google Scholar
    • Export Citation
  • Boland, E. J. D., , A. F. Thompson, , E. Shuckburgh, , and P. H. Haynes, 2012: The formation of nonzonal jets over sloped topography. J. Phys. Oceanogr., 42, 16351651, doi:10.1175/JPO-D-11-0152.1.

    • Search Google Scholar
    • Export Citation
  • Böning, C. W., , A. Dispert, , M. Visbeck, , S. R. Rintoul, , and F. U. Schwarzkopf, 2008: The response of the Antarctic Circumpolar Current to recent climate change. Nat. Geosci., 1, 864869, doi:10.1038/ngeo362.

    • Search Google Scholar
    • Export Citation
  • Chang, E. K. M., , S. Lee, , and K. L. Swanson, 2002: Storm track dynamics. J. Climate, 15, 21632183, doi:10.1175/1520-0442(2002)015<02163:STD>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chapman, C. C., , and A. M. Hogg, 2013: Jet jumping: Low-frequency variability in the Southern Ocean. J. Phys. Oceanogr., 43, 9901003, doi:10.1175/JPO-D-12-0123.1.

    • Search Google Scholar
    • Export Citation
  • Chereskin, T. K., , L. D. Talley, , and B. M. Sloyan, 2010: Nonlinear vorticity balance of the Subantarctic Front in the southeast Pacific. J. Geophys. Res.,115, C06026, doi:10.1029/2009JC005611.

  • Dencausse, G., , M. Arhan, , and S. Speich, 2011: Is there a continuous Subtropical Front south of Africa? J. Geophys. Res.,116, C02027, doi:10.1029/2010JC006587.

  • Dufour, C. O., , J. Le Sommer, , J. D. Zika, , M. Gehlen, , J. C. Orr, , P. Mathiot, , and B. Barnier, 2012: Standing and transient eddies in the response of the Southern Ocean meridional overturning to the southern annular mode. J. Climate, 25, 69586974, doi:10.1175/JCLI-D-11-00309.1.

    • Search Google Scholar
    • Export Citation
  • Ferrari, R., , and M. Nikurashin, 2010: Suppression of eddy diffusivity across jets in the Southern Ocean. J. Phys. Oceanogr., 40, 15011519, doi:10.1175/2010JPO4278.1.

    • Search Google Scholar
    • Export Citation
  • Firing, Y. L., , T. K. Chereskin, , and M. R. Mazloff, 2011: Vertical structure and transport of the Antarctic Circumpolar Current in Drake Passage from direct velocity observations. J. Geophys. Res.,116, C08015, doi:10.1029/2011JC006999.

  • Fu, L.-L., 2009: Pattern and velocity of propagation of the global ocean eddy variability. J. Geophys. Res.,114, C11017, doi:10.1029/2009JC005349.

  • Fu, L.-L., , D. B. Chelton, , P.-Y. Le Traon, , and R. Morrow, 2010: Eddy dynamics from satellite altimetry. Oceanography, 23, 1425, doi:10.5670/oceanog.2010.02.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., , and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20, 150155, doi:10.1175/1520-0485(1990)020<0150:IMIOCM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Gill, A. E., 1982: Atmosphere–Ocean Dynamics.Academic Press, 662 pp.

  • Gille, S. T., , and K. A. Kelly, 1996: Scales of spatial and temporal variability in the Southern Ocean. J. Geophys. Res., 101, 87598773, doi:10.1029/96JC00203.

    • Search Google Scholar
    • Export Citation
  • Hallberg, R., , and A. Gnanadesikan, 2006: The role of eddies in determining the structure and response of the wind-driven Southern Hemisphere overturning: Results from the Modeling Eddies in the Southern Ocean (MESO) project. J. Phys. Oceanogr., 36, 22322252, doi:10.1175/JPO2980.1.

    • Search Google Scholar
    • Export Citation
  • Hogg, A. M., , M. P. Meredith, , J. R. Blundell, , and C. Wilson, 2008: Eddy heat flux in the Southern Ocean: Response to variable wind forcing. J. Climate, 21, 608620, doi:10.1175/2007JCLI1925.1.

    • Search Google Scholar
    • Export Citation
  • Hughes, C. W., 2005: Nonlinear vorticity balance of the Antarctic Circumpolar Current. J. Geophys. Res.,110, C11008, doi:10.1029/2004JC002753.

  • Hughes, C. W., , and E. R. Ash, 2001: Eddy forcing of the mean flow in the Southern Ocean. J. Geophys. Res., 106, 27132722, doi:10.1029/2000JC900332.

    • Search Google Scholar
    • Export Citation
  • Hughes, C. W., , and B. A. de Cuevas, 2001: Why western boundary currents in realistic oceans are inviscid: A link between form stress and bottom pressure torques. J. Phys. Oceanogr., 31, 28712885, doi:10.1175/1520-0485(2001)031<2871:WWBCIR>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hughes, C. W., , M. S. Jones, , and S. Carnochan, 1998: Use of transient features to identify eastward currents in the Southern Ocean. J. Geophys. Res., 103, 29292943, doi:10.1029/97JC02442.

    • Search Google Scholar
    • Export Citation
  • Johnson, G. C., , and H. L. Bryden, 1989: On the size of the Antarctic Circumpolar Current. Deep-Sea Res., 36, 3953, doi:10.1016/0198-0149(89)90017-4.

    • Search Google Scholar
    • Export Citation
  • Kaspi, Y., , and T. Schneider, 2011: Downstream self-destruction of storm tracks. J. Atmos. Sci., 68, 24592464, doi:10.1175/JAS-D-10-05002.1.

    • Search Google Scholar
    • Export Citation
  • Large, W. G., , and S. G. Yeager, 2009: The global climatology of an interannually varying air–sea flux data set. Climate Dyn., 33, 341364, doi:10.1007/s00382-008-0441-3.

    • Search Google Scholar
    • Export Citation
  • Lu, J., , and K. Speer, 2010: Topography, jets and eddy mixing in the Southern Ocean. J. Mar. Res., 68, 479502, doi:10.1357/002224010794657227.

    • Search Google Scholar
    • Export Citation
  • Lynch-Stieglitz, J., and Coauthors, 2007: Atlantic meridional overturning circulation during the Last Glacial Maximum. Science, 316, 6669, doi:10.1126/science.1137127.

    • Search Google Scholar
    • Export Citation
  • Marshall, J., , and K. Speer, 2012: Closure of the meridional overturning circulation through Southern Ocean upwelling. Nat. Geosci., 5, 171180, doi:10.1038/ngeo1391.

    • Search Google Scholar
    • Export Citation
  • Marshall, J., , E. Shuckburgh, , H. Jones, , and C. Hill, 2006: Estimates and implications of surface eddy diffusivity in the Southern Ocean derived from tracer transport. J. Phys. Oceanogr., 36, 18061821, doi:10.1175/JPO2949.1.

    • Search Google Scholar
    • Export Citation
  • Masumoto, Y., and Coauthors, 2004: A fifty-year eddy-resolving simulation of the World Ocean—Preliminary outcomes of OFES (OGCM for the Earth Simulator). J. Earth Simul., 1, 3556.

    • Search Google Scholar
    • Export Citation
  • Mazloff, M. R., , P. Heimbach, , and C. Wunsch, 2010: An eddy-permitting Southern Ocean state estimate. J. Phys. Oceanogr., 40, 880899, doi:10.1175/2009JPO4236.1.

    • Search Google Scholar
    • Export Citation
  • Mazloff, M. R., , R. Ferrari, , and T. Schneider, 2013: The force balance of the Southern Ocean meridional overturning circulation. J. Phys. Oceanogr., 43, 11931208, doi:10.1175/JPO-D-12-069.1.

    • Search Google Scholar
    • Export Citation
  • Meredith, M. P., , and A. M. Hogg, 2006: Circumpolar response of Southern Ocean eddy activity to a change in the southern annular mode. Geophys. Res. Lett.,33, L16608, doi:10.1029/2006GL026499.

  • Meredith, M. P., and Coauthors, 2011: Sustained monitoring of the Southern Ocean at Drake Passage: Past achievements and future priorities. Rev. Geophys., 49, RG4005, doi:10.1029/2010RG000348.

    • Search Google Scholar
    • Export Citation
  • Morrow, R., , M. L. Ward, , A. M. Hogg, , and S. Pasquet, 2010: Eddy response to Southern Ocean climate modes. J. Geophys. Res.,115, C10030, doi:10.1029/2009JC005894.

  • Munday, D. R., , H. L. Johnson, , and D. P. Marshall, 2013: Eddy saturation of equilibrated circumpolar currents. J. Phys. Oceanogr., 43, 507532, doi:10.1175/JPO-D-12-095.1.

    • Search Google Scholar
    • Export Citation
  • Munk, W. H., , and E. Palmèn, 1951: Note on the dynamics of the Antarctic Circumpolar Current. Tellus, 3, 5355, doi:10.1111/j.2153-3490.1951.tb00776.x.

    • Search Google Scholar
    • Export Citation
  • Naveira Garabato, A. C., , R. Ferrari, , and K. L. Polzin, 2011: Eddy stirring in the Southern Ocean. J. Geophys. Res.,116, C09019, doi:10.1029/2010JC006818.

  • Nikurashin, M., , and R. Ferrari, 2011: Global energy conversion rate from geostrophic flows into internal lee waves in the deep ocean. Geophys. Res. Lett.,38, L08610, doi:10.1029/2011GL046576.

  • Ochoa, J., , and P. P. Niiler, 2007: Vertical vorticity balance in meanders downstream the Agulhas retroflection. J. Phys. Oceanogr., 37, 17401744, doi:10.1175/JPO3064.1.

    • 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, doi:10.1017/S0954102004002251.

    • Search Google Scholar
    • Export Citation
  • Pierrehumbert, R. T., 1984: Local and global baroclinic instability of zonally varying flow. J. Atmos. Sci., 41, 21412162, doi:10.1175/1520-0469(1984)041<2141:LAGBIO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Plumb, R. A., 1986: Three-dimensional propagation of transient quasi-geostrophic eddies and its relationship with the eddy forcing of the time-mean flow. J. Atmos. Sci., 43, 16571678, doi:10.1175/1520-0469(1986)043<1657:TDPOTQ>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., , K. Speer, , and S. R. Rintoul, 2011: Mean-flow and topography control on surface eddy-mixing in the Southern Ocean. J. Mar. Res., 69, 753777, doi:10.1357/002224011799849408.

    • Search Google Scholar
    • Export Citation
  • Scott, R. B., , J. A. Goff, , A. C. Naveira Garabato, , and A. J. G. Nurser, 2011: Global rate and spectral characteristics of internal gravity wave generation by geostrophic flow over topography. J. Geophys. Res.,116, C09029, doi:10.1029/2011JC007005.

  • Smith, I. J., , D. P. Stevens, , K. J. Heywood, , and M. P. Meredith, 2010: The flow of the Antarctic Circumpolar Current over the North Scotia Ridge. Deep-Sea Res. I, 57, 1428, doi:10.1016/j.dsr.2009.10.010.

    • Search Google Scholar
    • Export Citation
  • Smith, K. S., 2007: Eddy amplitudes in baroclinic turbulence driven by nonzonal mean flow: Shear dispersion of potential vorticity. J. Phys. Oceanogr., 37, 10371050, doi:10.1175/JPO3030.1.

    • Search Google Scholar
    • Export Citation
  • Sokolov, S., , and S. R. Rintoul, 2009: Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 1. Mean circumpolar paths. J. Geophys. Res.,114, C11018, doi:10.1029/2008JC005108.

  • Spall, M. A., 1997: Baroclinic jets in confluent flow. J. Phys. Oceanogr., 27, 10541071, doi:10.1175/1520-0485(1997)027<1054:BJICF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Stevens, D. P., , and V. O. Ivchenko, 1997: The zonal momentum balance in an eddy-resolving general-circulation model of the Southern Ocean. Quart. J. Roy. Meteor. Soc., 123, 929951, doi:10.1002/qj.49712354008.

    • Search Google Scholar
    • Export Citation
  • Stewart, A. L., , and A. F. Thompson, 2013: Connecting Antarctic cross-slope exchange with Southern Ocean overturning. J. Phys. Oceanogr., 43, 14531471, doi:10.1175/JPO-D-12-0205.1.

    • Search Google Scholar
    • Export Citation
  • Stewart, A. L., , R. Ferrari, , and A. F. Thompson, 2014: On the importance of surface forcing in conceptual models of the deep ocean. J. Phys. Oceanogr.,44, 891–899, doi:10.1175/JPO-D-13-0206.1.

  • Thompson, A. F., 2010: Jet formation and evolution in baroclinic turbulence with simple topography. J. Phys. Oceanogr., 40, 257278, doi:10.1175/2009JPO4218.1.

    • Search Google Scholar
    • Export Citation
  • Thompson, A. F., , and J.-B. Sallée, 2012: Jets and topography: Jet transitions and the impact on transport in the Antarctic Circumpolar Current. J. Phys. Oceanogr., 42, 956972, doi:10.1175/JPO-D-11-0135.1.

    • Search Google Scholar
    • Export Citation
  • Thompson, A. F., , P. H. Haynes, , C. Wilson, , and K. J. Richards, 2010: Rapid Southern Ocean front transitions in an eddy-resolving ocean GCM. Geophys. Res. Lett.,37, L23602, doi:10.1029/2010GL045386.

  • Venaille, A., , G. K. Vallis, , and K. S. Smith, 2011: Baroclinic turbulence in the ocean: Analysis with primitive equation and quasigeostrophic simulations. J. Phys. Oceanogr., 41, 16051623, doi:10.1175/JPO-D-10-05021.1.

    • Search Google Scholar
    • Export Citation
  • Viebahn, J., , and C. Eden, 2012: Standing eddies in the meridional overturning circulation. J. Phys. Oceanogr., 42, 14861508, doi:10.1175/JPO-D-11-087.1.

    • Search Google Scholar
    • Export Citation
  • Ward, M. L., , and A. M. Hogg, 2011: Establishment of momentum balance by form stress in a wind-driven channel. Ocean Modell., 40, 133146, doi:10.1016/j.ocemod.2011.08.004.

    • Search Google Scholar
    • Export Citation
  • Waterman, S. N., , A. C. N. Garabato, , and K. L. Polzin, 2013: Internal waves and turbulence in the Antarctic Circumpolar Current. J. Phys. Oceanogr., 43, 259282, doi:10.1175/JPO-D-11-0194.1.

    • Search Google Scholar
    • Export Citation
  • Williams, R. G., , C. Wilson, , and C. W. Hughes, 2007: Ocean and atmosphere storm tracks: The role of eddy vorticity forcing. J. Phys. Oceanogr., 37, 22672289, doi:10.1175/JPO3120.1.

    • Search Google Scholar
    • Export Citation
  • Zika, J. D., and Coauthors, 2013a: Vertical eddy fluxes in the Southern Ocean. J. Phys. Oceanogr., 43, 941955, doi:10.1175/JPO-D-12-0178.1.

    • Search Google Scholar
    • Export Citation
  • Zika, J. D., , J. L. Sommer, , C. Dufour, , and A. C. Naveira Garabato, 2013b: Acceleration of the Antarctic Circumpolar Current by wind stress along the coast of Antarctica. J. Phys. Oceanogr., 43, 2772–2784, doi:10.1175/JPO-D-13-091.1.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 84 84 28
PDF Downloads 85 85 28

Equilibration of the Antarctic Circumpolar Current by Standing Meanders

View More View Less
  • 1 California Institute of Technology, Pasadena, California
  • 2 National Oceanography Centre, University of Southampton, Southampton, United Kingdom
© Get Permissions
Restricted access

Abstract

The insensitivity of the Antarctic Circumpolar Current (ACC)’s prominent isopycnal slope to changes in wind stress is thought to stem from the action of mesoscale eddies that counterbalance the wind-driven Ekman overturning—a framework verified in zonally symmetric circumpolar flows. Substantial zonal variations in eddy characteristics suggest that local dynamics may modify this balance along the path of the ACC. Analysis of an eddy-resolving ocean GCM shows that the ACC can be broken into broad regions of weak eddy activity, where surface winds steepen isopycnals, and a small number of standing meanders, across which the isopycnals relax. Meanders are coincident with sites of (i) strong eddy-induced modification of the mean flow and its vertical structure as measured by the divergence of the Eliassen–Palm flux and (ii) enhancement of deep eddy kinetic energy by up to two orders of magnitude over surrounding regions. Within meanders, the vorticity budget shows a balance between the advection of relative vorticity and horizontal divergence, providing a mechanism for the generation of strong vertical velocities and rapid changes in stratification. Temporal fluctuations in these diagnostics are correlated with variability in both the Eliassen–Palm flux and bottom speed, implying a link to dissipative processes at the ocean floor. At larger scales, bottom pressure torque is spatially correlated with the barotropic advection of planetary vorticity, which links to variations in meander structure. From these results, it is proposed that the “flexing” of standing meanders provides an alternative mechanism for reducing the sensitivity of the ACC’s baroclinicity to changes in forcing, separate from an ACC-wide change in transient eddy characteristics.

Corresponding author address: Andrew F. Thompson, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125. E-mail: andrewt@caltech.edu

Abstract

The insensitivity of the Antarctic Circumpolar Current (ACC)’s prominent isopycnal slope to changes in wind stress is thought to stem from the action of mesoscale eddies that counterbalance the wind-driven Ekman overturning—a framework verified in zonally symmetric circumpolar flows. Substantial zonal variations in eddy characteristics suggest that local dynamics may modify this balance along the path of the ACC. Analysis of an eddy-resolving ocean GCM shows that the ACC can be broken into broad regions of weak eddy activity, where surface winds steepen isopycnals, and a small number of standing meanders, across which the isopycnals relax. Meanders are coincident with sites of (i) strong eddy-induced modification of the mean flow and its vertical structure as measured by the divergence of the Eliassen–Palm flux and (ii) enhancement of deep eddy kinetic energy by up to two orders of magnitude over surrounding regions. Within meanders, the vorticity budget shows a balance between the advection of relative vorticity and horizontal divergence, providing a mechanism for the generation of strong vertical velocities and rapid changes in stratification. Temporal fluctuations in these diagnostics are correlated with variability in both the Eliassen–Palm flux and bottom speed, implying a link to dissipative processes at the ocean floor. At larger scales, bottom pressure torque is spatially correlated with the barotropic advection of planetary vorticity, which links to variations in meander structure. From these results, it is proposed that the “flexing” of standing meanders provides an alternative mechanism for reducing the sensitivity of the ACC’s baroclinicity to changes in forcing, separate from an ACC-wide change in transient eddy characteristics.

Corresponding author address: Andrew F. Thompson, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125. E-mail: andrewt@caltech.edu
Save