• Berloff, P. S., , and S. P. Meacham, 1998: On the stability of the wind-driven circulation. J. Mar. Res, 56 , 937993.

  • Berloff, P. S., , and J. C. McWilliams, 1999: Large-scale, low-frequency variability in wind-driven ocean gyres. J. Phys. Oceanogr, 29 , 19251949.

    • Search Google Scholar
    • Export Citation
  • Bower, A. S., , and H. D. Hunt, 2000a: Lagrangian observations of the deep western boundary current in the North Atlantic Ocean. Part I: Large-scale pathways and spreading rates. J. Phys. Oceanogr, 30 , 764783.

    • Search Google Scholar
    • Export Citation
  • Bower, A. S., , and H. D. Hunt, 2000b: Lagrangian observations of the deep western boundary current in the North Atlantic Ocean. Part II: The Gulf Stream–deep western boundary current crossover. J. Phys. Oceanogr, 30 , 784804.

    • Search Google Scholar
    • Export Citation
  • Dijkstra, H. A., , and C. A. Katsman, 1997: Temporal variability of the wind-driven quasi-geostrophic double gyre ocean circulation: Basic bifurcation diagrams. Geophys. Astrophys. Fluid Dyn, 85 , 195232.

    • Search Google Scholar
    • Export Citation
  • Dijkstra, H. A., , and M. J. Molemaker, 1999: Imperfections of the North-Atlantic wind-driven ocean circulation: Continental geometry and windstress. J. Mar. Res, 57 , 128.

    • Search Google Scholar
    • Export Citation
  • Dijkstra, H. A., , M. J. Molemaker, , A. van der Ploeg, , and E. F. F. Botta, 1995: An efficient code to compute nonparallel flows and their linear stability. Comput. Fluids, 24 , 415434.

    • Search Google Scholar
    • Export Citation
  • Dijkstra, H. A., , M. J. Schmeits, , and C. A. Katsman, 1999: Variability of the North Atlantic wind-driven ocean circulation. Surv. Geophys, 20 , 463503.

    • Search Google Scholar
    • Export Citation
  • Hogg, N. G., 1983: A note on the deep circulation of the western North Atlantic: Its nature and its causes. Deep-Sea Res, 30 , 945961.

    • Search Google Scholar
    • Export Citation
  • Jiang, S., , F. F. Jin, , and M. Ghil, 1995: Multiple equilibria and aperiodic solutions in a wind-driven double-gyre, shallow-water model. J. Phys. Oceanogr, 25 , 764786.

    • Search Google Scholar
    • Export Citation
  • Katsman, C. A., , H. A. Dijkstra, , and S. S. Drijfhout, 1998: The rectification of wind-driven flow due to its instabilities. J. Mar. Res, 56 , 559587.

    • Search Google Scholar
    • Export Citation
  • McCalpin, J. D., , and D. B. Haidvogel, 1996: Phenomenology of the low-frequency variability in a reduced-gravity, quasigeostrophic double-gyre model. J. Phys. Oceanogr, 26 , 739752.

    • Search Google Scholar
    • Export Citation
  • Meacham, S. P., 2000: Low-frequency variability in the wind-driven circulation. J. Phys. Oceanogr, 30 , 269293.

  • Nayfeh, A. H., , and B. Balachandran, 1995: Applied Nonlinear Dynamics. John Wiley and Sons, 685 pp.

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

  • Pedlosky, J., 1996: Ocean Circulation Theory. Springer Verlag, 453 pp.

  • Pickart, R. S., 1994: Interaction of the Gulf Stream and Deep Western Boundary Current where they cross. J. Geophys. Res, 99 , (C12),. 25 15525 164.

    • Search Google Scholar
    • Export Citation
  • Pickart, R. S., , and W. M. Smethie Jr., 1993: How does the deep western boundary current cross the Gulf Stream? J. Phys. Oceanogr, 23 , 26022616.

    • Search Google Scholar
    • Export Citation
  • Pickart, R. S., , and W. M. Smethie Jr., 1998: Temporal evolution of the Deep Western Boundary Current where it enters the sub-tropical domain. Deep-Sea Res. I, 45 , 10531083.

    • Search Google Scholar
    • Export Citation
  • Plaut, G., , and R. Vautard, 1994: Spells of low-frequency oscillations and weather regimes in the Northern Hemisphere. J. Atmos. Sci, 51 , 210236.

    • Search Google Scholar
    • Export Citation
  • Qiu, B., 2000: Interannual variability of the Kuroshio Extension system and its impact on the wintertime SST field. J. Phys. Oceanogr, 30 , 14861502.

    • Search Google Scholar
    • Export Citation
  • Richardson, P. L., 1977: On the crossover between the Gulf Stream and the western boundary undercurrent. Deep-Sea Res, 24 , 139159.

  • Schmeits, M. J., , and H. A. Dijkstra, 2000: Physics of the 9-month variability in the Gulf Stream region: Combining data and dynamical systems analyses. J. Phys. Oceanogr, 30 , 19671987.

    • Search Google Scholar
    • Export Citation
  • Spall, M. A., 1996a: Dynamics of the Gulf Stream/deep western boundary current crossover. Part I: Entrainment and recirculation. J. Phys. Oceanogr, 26 , 21522168.

    • Search Google Scholar
    • Export Citation
  • Spall, M. A., 1996b: Dynamics of the Gulf Stream/deep western boundary current crossover. Part II: Low-frequency internal oscillations. J. Phys. Oceanogr, 26 , 21692182.

    • Search Google Scholar
    • Export Citation
  • Speich, S., , H. A. Dijkstra, , and M. Ghil, 1995: Successive bifurcations of a shallow water model, applied to the wind-driven circulation. Nonlinear Proc. Geophys, 2 , 241268.

    • Search Google Scholar
    • Export Citation
  • Tansley, C. E., , and D. P. Marshall, 2000: On the influence of bottom topography and the Deep Western Boundary Current on Gulf Stream separation. J. Mar. Res, 58 , 297325.

    • Search Google Scholar
    • Export Citation
  • Thompson, J. D., , and W. J. Schmitz Jr., 1989: A limited-area model of the Gulf Stream: Design, initial experiments and model–data comparison. J. Phys. Oceanogr, 19 , 791814.

    • Search Google Scholar
    • Export Citation
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The Interaction of a Deep Western Boundary Current and the Wind-Driven Gyres as a Cause for Low-Frequency Variability

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  • 1 Royal Netherlands Meteorological Institute, Oceanographic Research, De Bilt, Netherlands, and Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands
  • | 2 Royal Netherlands Meteorological Institute, Oceanographic Research, De Bilt, Netherlands
  • | 3 Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands
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Abstract

Recent modeling and observational studies have indicated that the interaction of the Gulf Stream and the deep western boundary current (DWBC) in the North Atlantic may induce low-frequency (decadal timescale) variability. To understand the origin of this low-frequency variability, a line of studies is continued here addressing the stability and variability of the wind-driven circulation using techniques of dynamical systems theory. In an idealized quasigeostrophic 2-layer model setup, stationary solutions of the coupled wind-driven gyres/DWBC system are computed, using the lateral friction as control parameter. Simultaneously, their stability is assessed. When a DWBC is absent, only oscillatory instabilities with intermonthly timescales are found. However, when the strength of the DWBC is increased, the coupled 2-layer flow becomes susceptible to instabilities with interannual timescales. By computing transient flows at relatively low friction, it is found that the existence of these interannual modes induces low-frequency variability in the coupled Gulf Stream/DWBC system with a preferred interannual timescale.

Corresponding author address: Caroline A. Katsman, Royal Netherlands Meteorological Institute, Oceanographic Research, P.O. Box 201, 3730 AE De Bilt, Netherlands. Email: katsman@phys.uu.nl

Abstract

Recent modeling and observational studies have indicated that the interaction of the Gulf Stream and the deep western boundary current (DWBC) in the North Atlantic may induce low-frequency (decadal timescale) variability. To understand the origin of this low-frequency variability, a line of studies is continued here addressing the stability and variability of the wind-driven circulation using techniques of dynamical systems theory. In an idealized quasigeostrophic 2-layer model setup, stationary solutions of the coupled wind-driven gyres/DWBC system are computed, using the lateral friction as control parameter. Simultaneously, their stability is assessed. When a DWBC is absent, only oscillatory instabilities with intermonthly timescales are found. However, when the strength of the DWBC is increased, the coupled 2-layer flow becomes susceptible to instabilities with interannual timescales. By computing transient flows at relatively low friction, it is found that the existence of these interannual modes induces low-frequency variability in the coupled Gulf Stream/DWBC system with a preferred interannual timescale.

Corresponding author address: Caroline A. Katsman, Royal Netherlands Meteorological Institute, Oceanographic Research, P.O. Box 201, 3730 AE De Bilt, Netherlands. Email: katsman@phys.uu.nl

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