• Barton, E. D., 1998: Eastern boundary of the North Atlantic: Northwest Africa and Iberia. The Sea—Ideas and Observations on Progress in the Study of the Seas, A. R. Robinson and K. H. Brink, Eds., The Composition of Sea-Water and Comparative and Descriptive Oceanography, Vol. 2, Wiley and Sons, 633–657.

  • Cessi, P., and C. L. Wolfe, 2009a: Eddy-driven buoyancy gradients on eastern boundaries and their role in the thermocline. J. Phys. Oceanogr., 39, 15951614.

    • Search Google Scholar
    • Export Citation
  • Cessi, P., and C. L. Wolfe, 2009b: Eddy-driven buoyancy gradients on eastern boundaries and their role in the thermocline. J. Phys. Oceanogr., 39, 15951614.

    • Search Google Scholar
    • Export Citation
  • Cessi, P., C. L. Wolfe, and B. Ludka, 2010: Eastern-boundary contribution to the residual and meridional overturning circulations. J. Phys. Oceanogr., 40, 20752090.

    • Search Google Scholar
    • Export Citation
  • Chapman, D. C., and S. J. Lentz, 2005: Acceleration of a stratified current over a sloping bottom, driven by an alongshelf pressure gradient. J. Phys. Oceanogr., 25, 13051317.

    • Search Google Scholar
    • Export Citation
  • Chelton, D., R. DeSzoeke, M. Schlax, K. El Naggar, and N. Siwertz, 1998: Geographical variability of the first baroclinic Rossby radius of deformation. J. Phys. Oceanogr., 28, 433460.

    • Search Google Scholar
    • Export Citation
  • Colas, F., X. Capet, J. C. McWilliams, and Z. Li, 2013: Mesoscale eddy buoyancy flux and eddy-induced circulation in Eastern Boundary Currents. J. Phys. Oceanogr., in press.

    • Search Google Scholar
    • Export Citation
  • Colin de Verdière, A., 1989: On the interaction of wind and buoyancy driven gyres. J. Mar. Res., 47, 595633.

  • Daru, V., and C. Tenaud, 2003: High order one-step monotonicity-preserving schemes for unsteady compressible flow calculations. J. Comput. Phys., 193, 563594.

    • Search Google Scholar
    • Export Citation
  • De Szoeke, R., and A. Bennett, 1993: Microstructure fluxes across density surfaces. J. Phys. Oceanogr., 23, 22542264.

  • Feng, M., S. Wijffels, S. Godfrey, and G. Meyers, 2005: Do eddies play a role in the momentum balance of the Leeuwin Current? J. Phys. Oceanogr., 25, 964975.

    • Search Google Scholar
    • Export Citation
  • Gill, A. E., 1985: An explicit solution of the linear thermocline equations. Tellus, 37A, 276285.

  • Godfrey, J. S., and K. Ridgway, 1985: The large-scale environment of the poleward-flowing Leeuwin Current, western Australia: Alongshore steric height gradients, wind stresses, and geostrophic flow. J. Phys. Oceanogr., 15, 481495.

    • Search Google Scholar
    • Export Citation
  • Godfrey, J. S., and A. Weaver, 1991: Buoyancy driven planetary flows. Prog. Oceanogr., 27, 225272.

  • Luyten, J., J. Pedlosky, and H. Stommel, 1983: The ventilated thermocline. J. Phys. Oceanogr., 13, 292309.

  • Marchesiello, P., J. McWilliams, and A. Skchepetkin, 2003: Equilibrium structure and dynamics of the California Current system. J. Phys. Oceanogr., 33, 753783.

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

    • Search Google Scholar
    • Export Citation
  • McCreary, J. P., 1981: A linear stratified ocean model of the coastal undercurrent. Philos. Trans. Roy. Soc. London, A302, 385413.

  • McDougall, T., and P. McIntosh, 1996: The temporal-residual-mean velocity. Part I: Derivation and the scalar conservation equations. J. Phys. Oceanogr., 26, 26532665.

    • Search Google Scholar
    • Export Citation
  • McDougall, T., and P. McIntosh, 2001: The temporal-residual-mean velocity. Part II: Isopycnal interpretation and the tracer and momentum equations. J. Phys. Oceanogr., 31, 12221246.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., and W. R. Young, 1983: Ventilation, potential vorticity homogenization and the structure of the ocean circulation. J. Phys. Oceanogr., 13, 20202037.

    • Search Google Scholar
    • Export Citation
  • Pedlosky, J., and M. A. Spall, 2005: Boundary intensification of vertical velocity in a β–plane basin. J. Phys. Oceanogr., 35, 24872500.

    • Search Google Scholar
    • Export Citation
  • Penven, P., V. Echevin, J. Pasapera, F. Colas, and J. Tam, 2005: Average circulation, seasonal cycle, and mesoscale dynamics of the Peru Current System: A modeling approach. J. Geophys. Res., 110, C10021, doi:10.1029/2005JC002945.

    • Search Google Scholar
    • Export Citation
  • Pierce, S. D., R. L. Smith, P. M. Kosro, and J. A. B. C. D. Wilson, 2000: Continuity of the poleward undercurrent along the eastern boundary of the mid-latitude North Pacific. Deep-Sea Res. II, 47, 811829.

    • Search Google Scholar
    • Export Citation
  • Rhines, P. B., and W. R. Young, 1982: A theory of the wind-driven circulation. I: Mid-ocean gyres. J. Mar. Res., 40 (Suppl.), 559596.

    • Search Google Scholar
    • Export Citation
  • Rienecker, M. M., and L. L. Ehret, 1988: Wind stress curl variability over the North Pacific from the Comprehensive Ocean–Atmosphere Data Set. J. Geophys. Res., 93 (C5), 50695077.

    • Search Google Scholar
    • Export Citation
  • Schloesser, F., R. Furue, J. McCreary, and A. Timmermann, 2012: Dynamics of the Atlantic meridional overturning circulation. Part 1: Buoyancy-forced response. Prog. Oceanogr., 101, 3362.

    • Search Google Scholar
    • Export Citation
  • Smith, R. L., A. Huyer, J. S. Godfrey, and J. A. Church, 1991: The Leeuwin Current off Western Australia, 1986/87. J. Phys. Oceanogr., 21, 323345.

    • Search Google Scholar
    • Export Citation
  • Spall, M., 2010: Dynamics of downwelling in an eddy-resolving convective basin. J. Phys. Oceanogr., 40, 23412347.

  • Spall, M., and R. Pickart, 2001: Where does dense water sink? A subpolar gyre example. J. Phys. Oceanogr., 31, 810826.

  • Sumata, H., and A. Kubokawa, 2001: Numerical study of eastern boundary ventilation and its effects on the thermocline structure. J. Phys. Oceanogr., 31, 30023019.

    • Search Google Scholar
    • Export Citation
  • Todd, R., D. Rudnick, M. Mazloff, R. Davis, and B. Cornuelle, 2011: Poleward flows in the southern california current system: Glider observations and numerical simulation. J. Geophys. Res., 116, C02026, doi:10.1029/2010JC006536.

    • Search Google Scholar
    • Export Citation
  • Todd, R., D. Rudnick, M. Mazloff, B. Cornuelle, and R. Davis, 2012: Thermohaline structure in the California Current System: Observations and modeling of spice variance. J. Geophys. Res., 117, C02008, doi:10.1029/2011JC007589.

    • Search Google Scholar
    • Export Citation
  • Young, W. R., 2012: An exact thickness-weighted average formulation of the Boussinesq equations. J. Phys. Oceanogr., 42, 692707.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 147 76 2
PDF Downloads 100 41 0

Adiabatic Eastern Boundary Currents

View More View Less
  • 1 Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California
Restricted access

Abstract

The dynamics of the eastern boundary current of a high-resolution, idealized model of oceanic circulation are analyzed and interpreted in terms of residual mean theory. In this framework, it is clear that the eastern boundary current is adiabatic and inviscid. Nevertheless, the time-averaged potential vorticity is not conserved along averaged streamlines because of the divergence of Eliassen–Palm fluxes, associated with buoyancy and momentum eddy fluxes. In particular, eddy fluxes of buoyancy completely cancel the mean downwelling or upwelling, so that there is no net diapycnal residual transport. The eddy momentum flux acts like a drag on the mean velocity, opposing the acceleration from the eddy buoyancy flux: in the potential vorticity budget this results in a balance between the divergences of eddy relative vorticity and buoyancy fluxes, which leads to a baroclinic eastern boundary current whose horizontal scale is the Rossby deformation radius and whose vertical extent depends on the eddy buoyancy transport, the Coriolis parameter, and the mean surface buoyancy distribution.

Corresponding author address: Paola Cessi, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., Mail Code 0213, La Jolla, CA 92093-0213. E-mail: pcessi@ucsd.edu

Abstract

The dynamics of the eastern boundary current of a high-resolution, idealized model of oceanic circulation are analyzed and interpreted in terms of residual mean theory. In this framework, it is clear that the eastern boundary current is adiabatic and inviscid. Nevertheless, the time-averaged potential vorticity is not conserved along averaged streamlines because of the divergence of Eliassen–Palm fluxes, associated with buoyancy and momentum eddy fluxes. In particular, eddy fluxes of buoyancy completely cancel the mean downwelling or upwelling, so that there is no net diapycnal residual transport. The eddy momentum flux acts like a drag on the mean velocity, opposing the acceleration from the eddy buoyancy flux: in the potential vorticity budget this results in a balance between the divergences of eddy relative vorticity and buoyancy fluxes, which leads to a baroclinic eastern boundary current whose horizontal scale is the Rossby deformation radius and whose vertical extent depends on the eddy buoyancy transport, the Coriolis parameter, and the mean surface buoyancy distribution.

Corresponding author address: Paola Cessi, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., Mail Code 0213, La Jolla, CA 92093-0213. E-mail: pcessi@ucsd.edu
Save