• Berloff, N., and L. Howard, 1997: Solitary waves and periodic pulse trains as exact solutions for nonlinear nonintegrable systems. Studies Appl. Math.,99, 1–24.

  • Berloff, P. and S. Meacham, 1998a: The dynamics of a simple baroclinic model of the wind-driven circulation. J. Phys. Oceanogr.,28, 361–388.

  • ——, and ——, 1998b: On the stability of the wind-driven circulation. J. Mar. Res.,56, 937–993.

  • ——, and J. McWilliams, 1999: Large-scale, low-frequency variability in wind-driven ocean gyres. J. Phys. Oceanogr.,29, 2607–2634.

  • Blandford, R., 1971: Boundary conditions in homogeneous ocean models. Deep-Sea Res.,18, 739–751.

  • Bryan, K., 1963: A numerical investigation of a nonlinear model of a wind-driven ocean. J. Atmos. Sci.,20, 594–606.

  • Cessi, P., and G. Ierley, 1993: Nonlinear disturbances of western boundary currents. J. Phys. Oceanogr.,23, 1727–1735.

  • Cox, M., 1979: A numerical study of Somali Current eddies. J. Phys. Oceanogr.,9, 311–326.

  • Feron, R., 1995: The Southern Ocean western boundary currents: Comparison of fine resolution Antarctic model results with Geosat altimeter data. J. Geophys. Res.,100, 4959–4975.

  • Haidvogel, D., and W. Holland, 1978: The stability of ocean currents in eddy-resolving general circulation models. J. Phys. Oceanogr.,8, 393–413.

  • ——, J. McWilliams, and P. Gent, 1992: Boundary current separation in a quasigeostrophic, eddy-resolving ocean circulation model. J. Phys. Oceanogr.,22, 882–902.

  • Holland, W., 1978: The role of mesoscale eddies in the general circulation of the ocean—Numerical experiments using a wind-driven quasigeostrophic model. J. Phys. Oceanogr.,8, 363–392.

  • Ierley, G., 1990: Boundary layers in the general ocean circulation. Annu. Rev. Fluid Mech.,22, 111–142.

  • ——, and W. Young, 1991: Viscous instabilities in the western boundary layer. J. Phys. Oceanogr.,21, 1323–1332.

  • Ikeda, M., 1983: Linear instability of a current flowing along a bottom slope using a three-layer model. J. Phys. Oceanogr.,13, 208–223.

  • Munk, W., 1950: On the wind-driven ocean circulation. J. Meteor.,7, 79–93.

  • Pedlosky, J., 1987: Geophysical Fluid Dynamics. 2d ed. Springer-Verlag, 710 pp.

  • Sheremet, V., G. Ierley, and V. Kamenkovich, 1997: Eigenanalysis of the two-dimensional wind-driven ocean circulation problem. J. Mar. Res.,55, 57–92.

  • Veronis, G., 1966: Wind-driven ocean circulation. Part 2. Deep-Sea Res.,13, 31–55.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 116 116 1
PDF Downloads 22 22 2

Quasigeostrophic Dynamics of the Western Boundary Current

View More View Less
  • 1 Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, California
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

A local model is used to investigate the dynamics of the western boundary current in a midlatitude, wind-driven gyre. This current is important for the gyre as a whole, and its local instability is correlated with structural changes of the separated eastward jet and the interior gyres. In particular, the eastward jet can be disrupted and broadened in the regime with a strong, local instability in the western boundary current. Such a regime occurs with a no-slip lateral boundary condition. Alternatively, in the absence of local instability, the eastward jet is narrow and penetrates farther in the basin interior. This behavior is typical with free-slip boundary condition.

Both the linear stability and nonlinear time-dependent behavior of the western boundary current are analyzed for a wide range of parameters. The current loses stability at moderate Reynolds numbers, and the stability threshold strongly depends upon the vertical stratification profile. The nonlinear time-dependent flow contains well-defined mesoscale eddies with adjacent meanders. The finite amplitude dynamics is fundamentally different in the no-slip and free-slip situations, because the free-slip boundary substantially stabilizes the flow. It is shown that fluctuations in nonlinear regime are rather different from the linearly unstable modes. Multiple stable equilibria are also found.

Corresponding author address: Dr. Pavel S. Berloff, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA 90095-1567.

Email: pavel@atmos.ucla.edu

Abstract

A local model is used to investigate the dynamics of the western boundary current in a midlatitude, wind-driven gyre. This current is important for the gyre as a whole, and its local instability is correlated with structural changes of the separated eastward jet and the interior gyres. In particular, the eastward jet can be disrupted and broadened in the regime with a strong, local instability in the western boundary current. Such a regime occurs with a no-slip lateral boundary condition. Alternatively, in the absence of local instability, the eastward jet is narrow and penetrates farther in the basin interior. This behavior is typical with free-slip boundary condition.

Both the linear stability and nonlinear time-dependent behavior of the western boundary current are analyzed for a wide range of parameters. The current loses stability at moderate Reynolds numbers, and the stability threshold strongly depends upon the vertical stratification profile. The nonlinear time-dependent flow contains well-defined mesoscale eddies with adjacent meanders. The finite amplitude dynamics is fundamentally different in the no-slip and free-slip situations, because the free-slip boundary substantially stabilizes the flow. It is shown that fluctuations in nonlinear regime are rather different from the linearly unstable modes. Multiple stable equilibria are also found.

Corresponding author address: Dr. Pavel S. Berloff, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, Los Angeles, CA 90095-1567.

Email: pavel@atmos.ucla.edu

Save