Abstract
Using an eddy-resolving two layer primitive-equation model forced by symmetric wind stress, we investigate the asymmetry of the recirculation of a double gyre (subpolar gyre and subtropical gyre). In the case where the layer thickness change is large, cyclonic recirculation becomes unstable and splits into meso-scale vortices more easily than anti-cyclonic recirculation in their developing stage. The subpolar gyre is, therefore, filled with more vortices than the subtropical gyre. Moreover, the effect of the upper layer potential vorticity on the lower layer potential vorticity in the subpolar gyre is stronger than that in the subtropical gyre. The characteristic of turbulence in the subpolar gyre is different from that found in the subtropical gyre and, therefore, the asymmetry of the recirculation of the double gyre is maintained by this difference. The asymmetry can not be produced in a quasi-geostrophic model because it ignores the nonlinearity associated with layer thickness change. Moreover, we investigate the effects of layer thickness and lateral viscosity on the asymmetry of the recirculation of the double gyre. In the case of realistic physical parameters, the asymmetry of the recirculation of the double gyre is noticeable from the view of the activities of the eddies. In the case with the shallowest upper layer, the position of separation of the western boundary current moves further southward.
Similar content being viewed by others
References
Arai, M. (1994): Asymmetric evolution of eddies in rotating shallow water. Ph.D. Thesis, Kyusyu Univ., 101 pp.
Cessi, P. (1988): A stratified model of the inertial recirculation. J. Phys. Oceanogr., 18, 662–682.
Cessi, P., G. Ierley and W. R. Young (1987): A model of the inertial recirculation driven by potential vorticity anomalies. J. Phys. Oceanogr., 17, 1640–1652.
Chassignet, E. P. (1992): Rings in numerical models of ocean general circulation: A statistical study. J. Geophys. Res., 97, 9479–9492.
Chassignet, E. P. and R. Bleck (1993): The influence of layer outcropping on the separation of boundary currents. Part 1: The wind-driven experiments. J. Phys. Oceanogr., 23, 1485–1507.
Chassignet, E. P. and B. Cushman-Roisin (1991): On the influence of a lower layer on the propagation of nonlinear oceanic eddies. J. Phys. Oceanogr., 21, 939–957.
Chassignet, E. P. and P. R. Gent (1991): The influence of boundary conditions on midlatitude jet separation in ocean numerical models. J. Phys. Oceanogr., 21, 1290–1299.
Cushman-Roisin, B., G. G. Sutyrin and B. Tang (1992): Two-layer geostrophic dynamics. Part I: Governing equations. J. Phys. Oceanogr., 22, 117–127.
Hockney, R. W. (1971): The potential calculation and some applications. Meth. Comput. Phys., 9, 135–211.
Holland, W. R. (1978): The role of mesoscale eddies in the general circulation of the ocean—numerical experiments using a wind-driven quasi-geostrophic model. J. Phys. Oceanogr., 8, 363–392.
Holland, W. R. and L. B. Lin (1975): On the generation of mesoscale eddies and their contribution to the oceanic general circulation. I A preliminary numerical experiment. J. Phys. Oceanogr., 5, 642–657.
Holland, W. R. and P. B. Rhines (1980): An example of Eddy-induced ocean circulation. J. Phys. Oceanogr., 10, 1010–1031.
Holland, W. R., T. Keffer and P. B. Rhines (1984): Dynamics of the oceanic general circulation: the potential vorticity field. Nature, 308, 698–705.
Huang, R. X. (1986): Numerical simulation of wind-driven circulation in a subtropical/subpolar basin. J. Phys. Oceanogr., 16, 1636–1650.
Ierley, G. R. and W. R. Young (1988): Inertial recirculation in a β-plane corner. J. Phys. Oceanogr., 18, 683–689.
Keffer, T. (1985): The ventilation of the world's oceans: Maps of the potential vorticity field. J. Phys. Oceanogr., 15, 509–523.
Marshall, J. and G. Nurser (1986): Steady, free circulation in a stratified quasi-geostrophic ocean. J. Phys. Oceanogr., 16, 1799–1813.
Matsuura, T. (1995): The evolution of frontal-geostrophic vortices in a two-layer ocean. J. Phys. Oceanogr., 25, 2298–2318.
Nagata, Y., K. Ohtani and M. Kashiwai (1992): North Pacific subpolar gyre. Umi no Kenkyu, 1, 75–104 (in Japanese with English abstract and figure captions).
Nezlin, M. V. and E. N. Snezhkin (1993): Rossby Vortices, Spiral Structures, Solutions. Springer-Verlag, 225 pp.
Qui, B. (1995): Why is the spreading of the North Pacific intermediate water confined on density surfaces around σ ϑ = 26.8? J. Phys. Oceanogr., 25, 168–180.
Rhines, P. B. (1986): Vorticity dynamics of the oceanic general circulation. Ann. Rev. Fluid Mech., 18, 433–497.
Rhines, P. B. and W. R. Holland (1979): A theoretical discussion of eddy-driven mean flows. Dyn. Atmos. Oceans, 3, 289–325.
Tang, B. and B. Cushman-Roisin (1992): Two-layer geostrophic dynamics, Part II: Geostrophic turbulence. J. Phys. Oceanogr., 22, 128–138.
Thompson, J. D. and W. J. Schmitz (1989): A limited-area model of the Gulf stream: Design, initial experiments and model-data intercomparison. J. Phys. Oceanogr, 19, 791–814.
Williams, G. P. and T. Yamagata (1984): Geostrophic Regimes, intermediate solitary vortices and Jovian eddies. J. Atmos. Sci., 15, 453–478.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Shimokawa, S., Matsuura, T. The Asymmetry of Recirculation of a Double Gyre in a Two Layer Ocean. Journal of Oceanography 55, 449–462 (1999). https://doi.org/10.1023/A:1007818802779
Issue Date:
DOI: https://doi.org/10.1023/A:1007818802779