• Blumberg, A. F., , and G. L. Mellor, 1987: A description of a three-dimensional coastal ocean circulation model. Three-Dimensional Coastal Ocean Model, N. Heapes, Ed., Vol. 4, Coastal and Estuarine Sciences, Amer. Geophys. Union, 1–16.

    • Search Google Scholar
    • Export Citation
  • Blumsack, S., , and P. J. Gierasch, 1972: Mars: The effects of topography on baroclinic stability. J. Atmos. Sci, 29 , 10811089.

  • Boss, E., , and L. Thompson, 1999: Mean flow evolution of a baroclinically unstable potential vorticity front. J. Phys. Oceanogr, 29 , 273287.

    • Search Google Scholar
    • Export Citation
  • Boss, E., , N. Paldor, , and L. Thompson, 1996: Stability of a potential vorticity front: From quasi-geostrophy to shallow water. J. Fluid Mech, 315 , 6584.

    • Search Google Scholar
    • Export Citation
  • Bush, A. B. G., , J. C. McWilliams, , and W. R. Peltier, 1995: The formation of oceanic eddies in symmetric and asymmetric jets. Part I: Early time evolution and bulk eddy transports. J. Phys. Oceanogr, 25 , 19591979.

    • Search Google Scholar
    • Export Citation
  • Bush, A. B. G., , J. C. McWilliams, , and W. R. Peltier, 1996: The formation of oceanic eddies in symmetric and asymmetric jets. Part II: Late time evolution and coherent vortex formation. J. Phys. Oceanogr, 26 , 18251848.

    • Search Google Scholar
    • Export Citation
  • Cornillon, P., , D. Evans, , and W. Large, 1986: Warm outbreaks of the Gulf Stream into the Sargasso Sea. J. Geophys. Res, 91 , 65836596.

  • de Szoeke, R. A., 1975: Some effects of bottom topography on baroclinic instability. J. Mar. Res, 33 , 93122.

  • Eady, E. T., 1949: Long waves and cyclone waves. Tellus, 1 , 3352.

  • Farrell, B. F., 1982: Pulse asymptotics of the Charney baroclinic instability problem. J. Atmos. Sci, 39 , 507517.

  • Flierl, G. R., 1999: Thin jet and contour dynamics models of Gulf Stream meandering. Dyn. Atmos. Oceans, 29 , 189215.

  • Fofonoff, N. P., 1981: The Gulf Stream system. Evolution of Physical Oceanography, B. A. Warren and C. Wunsch, Eds., The MIT Press, 112–139.

    • Search Google Scholar
    • Export Citation
  • Halkin, D., , and H. T. Rossby, 1985: The structure and transport of the Gulf Stream at 73°W. J. Phys. Oceanogr, 15 , 14391452.

  • Hall, M. M., , and N. P. Fofonoff, 1993: Downstream development of the Gulf Stream from 68° to 55°W. J. Phys. Oceanogr, 23 , 225249.

  • Holland, W. R., , and D. B. Haidvogel, 1980: A parameter study of the mixed instability of idealized ocean currents. Dyn. Atmos. Oceans, 4 , 185215.

    • Search Google Scholar
    • Export Citation
  • Huerre, P., , and P. A. Monkewitz, 1990: Local and global instabilities in spatially developing flows. Annu. Rev. Fluid Mech, 22 , 473537.

    • Search Google Scholar
    • Export Citation
  • Ikeda, M., 1981: Meanders and detached eddies of a strong eastward-flowing jet using a two-layer quasigeostrophic model. J. Phys. Oceanogr, 11 , 526540.

    • Search Google Scholar
    • Export Citation
  • Ikeda, M., , and J. R. Apel, 1981: Mesoscale eddies detached from spatially growing meanders in an eastward-flowing oceanic jet using a two-layer quasi-geostrophic model. J. Phys. Oceanogr, 11 , 16381661.

    • Search Google Scholar
    • Export Citation
  • Johns, W. E., , T. J. Shay, , J. M. Bane, , and D. R. Watts, 1995: Gulf Stream structure, transport, and recirculation near 68°W. J. Geophys. Res, 100 , 817838.

    • Search Google Scholar
    • Export Citation
  • Killworth, P. D., 1980: Barotropic and baroclinic instability in rotating stratified fluids. Dyn. Atmos.–Oceans, 4 , 143184.

  • Kontoyannis, H., 1997: Quasi-geostrophic modeling of mixed instabilities in the Gulf Stream neat 73°W. Dyn. Atmos.–Oceans, 26 , 133158.

    • Search Google Scholar
    • Export Citation
  • Lea, T., , and P. Cornillon, 1996: Propagation of Gulf Stream meanders between 75° and 45°W. J. Phys. Oceanogr, 26 , 225241.

  • Leaman, K. D., , E. Johns, , and T. Rossby, 1989: The average distribution of volume transport and potential vorticity with temperature at three sections across the Gulf Stream. J. Phys. Oceanogr, 19 , 3651.

    • Search Google Scholar
    • Export Citation
  • Logoutov, O. G., , G. G. Sutyrin, , and D. R. Watts, 2001: Potential vorticity structure across the Gulf Stream: Observations and a PV-gradient model. J. Phys. Oceanogr, 31 , 637644.

    • Search Google Scholar
    • Export Citation
  • Luther, M. E., , and J. M. Bane, 1985: Mixed instabilities in the Gulf Stream over the continental slope. J. Phys. Oceanogr, 15 , 323.

  • Meacham, S. P., 1991: Meander evolution on quasigeostrophic jets. J. Phys. Oceanogr, 21 , 11391170.

  • Mechoso, C. R., 1980: Baroclinic instability of flows along sloping boundaries. J. Atmos. Sci, 37 , 13931399.

  • Mechoso, C. R., , and D. M. Sinton, 1981: Instability of baroclinic flows with horizontal shear along topography. J. Phys. Oceanogr, 11 , 813821.

    • Search Google Scholar
    • Export Citation
  • Mellor, G. L., 1998: User's guide for a three-dimensional, primitive equation, numerical ocean model. Atmospheric and Oceanic Sciences Program, Princeton University, 39 pp.

    • Search Google Scholar
    • Export Citation
  • Mellor, G. L., , and T. Yamada, 1982: Development of a turbulent closure model for geophysical fluid problem. Rev. Geophys. Space Phys, 20 , 851875.

    • Search Google Scholar
    • Export Citation
  • Mysak, L. A., , E. R. Johnson, , and W. W. Hsieh, 1981: Barotropic and baroclinic instabilities of coastal currents. J. Phys. Oceanogr, 11 , 209230.

    • Search Google Scholar
    • Export Citation
  • Nakamura, N., 1993: Momentum flux, flow symmetry, and the nonlinear barotropic governor. J. Atmos. Sci, 50 , 21592179.

  • Orlansky, I., 1969: The influence of bottom topography on the stability of jets in a baroclinic fluid. J. Atmos. Sci, 26 , 12161232.

  • Pedlosky, J., 1970: Finite-amplitude baroclinic waves. J. Atmos. Sci, 27 , 1530.

  • Phillips, N. A., 1954: Energy transformations and meridional circulations associated with simple baroclinic waves in a two-level, quasigeostrophic model. Tellus, 6 , 273286.

    • Search Google Scholar
    • Export Citation
  • Pierrehaumbert, R. T., , and K. L. Swanson, 1995: Baroclinic instability. Annu. Rev. Fluid Mech, 27 , 419467.

  • Polovarapu, S. M., , and W. R. Peltier, 1990: The structure and nonlinear evolution of synoptic scale cyclones: Life cycle simulations with a cloud-scale model. J. Atmos. Sci, 47 , 26452672.

    • Search Google Scholar
    • Export Citation
  • Pratt, L. J., , and M. E. Stern, 1986: Dynamics of potential vorticity fronts and eddy detachment. J. Phys. Oceanogr, 16 , 11011120.

  • Rhines, P. B., 1977: The dynamics of unsteady currents. The Sea. Vol. 6: Marine Modeling, E. D. Goldberg, Ed., John Wiley and Sons, 189–318.

    • Search Google Scholar
    • Export Citation
  • Robinson, A. R., , J. R. Luyten, , and F. C. Fuglister, 1974: Transient Gulf Stream meandering. Part I: An observational experiment. J. Phys. Oceanogr, 4 , 237255.

    • Search Google Scholar
    • Export Citation
  • Robinson, A. R., , M. A. Spall, , and N. Pinardi, 1988: Gulf Stream simulations and the dynamics of ring and meander process. J. Phys. Oceanogr, 18 , 18111853.

    • Search Google Scholar
    • Export Citation
  • Shepherd, T. G., 1983: Mean motions induced by baroclinic instability in a jet. Geophys. Astrophys. Fluid Dyn, 27 , 3572.

  • Simmons, A. J., , and B. J. Hoskins, 1980: Barotropic influences on the growth and decay of nonlinear baroclinic waves. J. Atmos. Sci, 37 , 16791684.

    • Search Google Scholar
    • Export Citation
  • Smagorinsky, J., 1963: General circulation experiments with primitive equations: I. The basic experiments. Mon. Wea. Rev, 91 , 291304.

    • Search Google Scholar
    • Export Citation
  • Spall, M. A., , and A. R. Robinson, 1990: Regional primitive equation studies of the Gulf Stream meander and ring formation region. J. Phys. Oceanogr, 20 , 9851016.

    • Search Google Scholar
    • Export Citation
  • Stommel, H., 1965: The Gulf Stream: A Physical and Dynamical Description. 2d ed. University of California Press, 248 pp.

  • Straneo, F., , and N. Pinardi, 1994: Deep thermocline eddies in the proximity of the Gulf Stream. A numerical study. Course on Geophysical Fluid Dynamics, International Centre for Theoretical Physics, 1–38.

    • Search Google Scholar
    • Export Citation
  • Sutyrin, G. G., , and I. G. Yushina, 1989: Numerical modelling of the formation, evolution, interaction, and decay of isolated vortices. Mesoscale/Synoptic Coherent Structures in Geophysical Turbulence, J. C. J. Nihoul and B. M. Jamart, Eds., Elsevier Oceanogr. Series, Vol. 50, Elsevier, 721–736.

    • Search Google Scholar
    • Export Citation
  • Swanson, K., , and R. T. Pierrehumbert, 1994: Nonlinear wave packet evolution on a baroclinically unstable jet. J. Atmos. Sci, 51 , 384396.

    • Search Google Scholar
    • Export Citation
  • Tang, C. M., 1976: The influence of meridionally slopping topography on baroclinic instability and its implications for macroclimate. J. Atmos. Sci, 33 , 15151525.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C. D., , B. J. Hoskins, , and M. E. McIntyre, 1993: Two paradigms of baroclinic-wave life-cycle behavior. Quart. J. Roy. Meteor. Soc, 119 , 1755.

    • Search Google Scholar
    • Export Citation
  • Wang, J., , and M. Ikeda, 1997: Diagnosing ocean unstable baroclinic waves and meanders using the quasigeostrophic equations and Q-vector method. J. Phys. Oceanogr, 27 , 11581172.

    • Search Google Scholar
    • Export Citation
  • Watts, D. R., , K. L. Tracey, , J. M. Bane, , and T. J. Shay, 1995: Gulf Stream path and thermocline structure near 74°W and 68°W. J. Geophys. Res, 100 , 18 29118 312.

    • Search Google Scholar
    • Export Citation
  • Wood, R. A., 1988: Unstable waves on oceanic fronts: Large amplitude behavior and mean flow generation. J. Phys. Oceanogr, 18 , 775787.

    • Search Google Scholar
    • Export Citation
  • Wright, D. G., 1980a: On the stability of a fluid with specialized density stratification. Part I: Baroclinic instability and constant bottom slope. J. Phys. Oceanogr, 10 , 639666.

    • Search Google Scholar
    • Export Citation
  • Wright, D. G., 1980b: On the stability of a fluid with a specialized density stratification. Part II: Mixed baroclinic–barotropic instability with application to the northeast Pacific. J. Phys. Oceanogr, 10 , 13071322.

    • Search Google Scholar
    • Export Citation
  • Xue, H., , and G. Mellor, 1993: Instability of the Gulf Stream front in the South Atlantic Bight. J. Phys. Oceanogr, 23 , 23262350.

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Equilibration of Baroclinic Meanders and Deep Eddies in a Gulf Stream–type Jet over a Sloping Bottom

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  • 1 Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island
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Abstract

Spatiotemporal evolution of a small localized meander on a Gulf Stream–type baroclinically unstable jet over a topographic slope is investigated numerically using a three-dimensional, primitive equation model. An unperturbed jet is prescribed by a potential vorticity front in the upper thermocline overlaying intermediate layers with weak isentropic potential vorticity gradients and a quiscent bottom layer over a positive (same sense as isopycnal tilt) cross-stream continental slope. A series of numerical experiments with the same initial conditions over a slope and flat bottom on the β plane and on the f plane has been carried out.

An initially localized meander evolves into a wave packet and generates deep eddies that provide a positive feedback for the meander growth. Meanders found growing over a flat bottom are able to pinch off resembling warm and cold core rings, while in the presence of a weak bottom slope such as 0.002, the maximum amplitudes of meanders and associated deep eddies saturate with no eddy shedding. In the flat bottom case, the growth rate is only 10% larger than in the weak slope case. Nevertheless, the bottom slope efficiently controls nonlinear saturation of meander growth via constraining the development of deep eddies. The topographic slope modifies the evolution of deep eddies and causes the phase displacement of deep eddies in the direction of the upper layer troughs/crests, thus limiting growth of the meanders. Behind the wave packet peak deep eddies form a nearly zonal circulation that stabilizes the jet in an equilibrated state. The main equilibration mechanism is a homogenization of the lower-layer potential vorticity by deep eddies. The width of the homogenized zone is narrower for a larger slope and/or on the β plane.

These results have the following implications to the Gulf Stream dynamics: 1) maximum of the meander amplitudes increase as the topographic slope relaxes in qualitative agreement with observed behavior of the Gulf Stream, 2) the phase locking of the meanders with deep eddies underneath at the nonlinear stage agrees qualitatively with the observed structure of large amplitude cyclonic troughs at the central array, and 3) the increase of the barotropic transport on the warm side of the jet and the generation of the recirculation on the cold side of the jet is consistent with observations in the Gulf Stream system downstream of Cape Hatteras.

Corresponding author address: Dr. Isaac Ginis, Graduate School of Oceanography, University of Rhode Island, Narragansett Bay Campus, Narragansett, RI 02882. Email: iginis@gso.uri.edu

Abstract

Spatiotemporal evolution of a small localized meander on a Gulf Stream–type baroclinically unstable jet over a topographic slope is investigated numerically using a three-dimensional, primitive equation model. An unperturbed jet is prescribed by a potential vorticity front in the upper thermocline overlaying intermediate layers with weak isentropic potential vorticity gradients and a quiscent bottom layer over a positive (same sense as isopycnal tilt) cross-stream continental slope. A series of numerical experiments with the same initial conditions over a slope and flat bottom on the β plane and on the f plane has been carried out.

An initially localized meander evolves into a wave packet and generates deep eddies that provide a positive feedback for the meander growth. Meanders found growing over a flat bottom are able to pinch off resembling warm and cold core rings, while in the presence of a weak bottom slope such as 0.002, the maximum amplitudes of meanders and associated deep eddies saturate with no eddy shedding. In the flat bottom case, the growth rate is only 10% larger than in the weak slope case. Nevertheless, the bottom slope efficiently controls nonlinear saturation of meander growth via constraining the development of deep eddies. The topographic slope modifies the evolution of deep eddies and causes the phase displacement of deep eddies in the direction of the upper layer troughs/crests, thus limiting growth of the meanders. Behind the wave packet peak deep eddies form a nearly zonal circulation that stabilizes the jet in an equilibrated state. The main equilibration mechanism is a homogenization of the lower-layer potential vorticity by deep eddies. The width of the homogenized zone is narrower for a larger slope and/or on the β plane.

These results have the following implications to the Gulf Stream dynamics: 1) maximum of the meander amplitudes increase as the topographic slope relaxes in qualitative agreement with observed behavior of the Gulf Stream, 2) the phase locking of the meanders with deep eddies underneath at the nonlinear stage agrees qualitatively with the observed structure of large amplitude cyclonic troughs at the central array, and 3) the increase of the barotropic transport on the warm side of the jet and the generation of the recirculation on the cold side of the jet is consistent with observations in the Gulf Stream system downstream of Cape Hatteras.

Corresponding author address: Dr. Isaac Ginis, Graduate School of Oceanography, University of Rhode Island, Narragansett Bay Campus, Narragansett, RI 02882. Email: iginis@gso.uri.edu

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