This research was sponsored by the Dutch National Research Program on Global Change (NOP II), Grant 013001237.10, and the Mixing of Agulhas Rings Experiment (MARE), and by the Stichting Nationale Computerfaciliteiten [National Computer Facilities Foundation (NCF)] for the use of supercomputer facilities, with financial support from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Netherlands Organization for Scientific Research (NWO)]. The author thanks his colleagues from the “Agulhas group” for the valuable discussions on this topic and two anonymous reviewers who helped to clarify matters and pointed to literature about which the author was unaware.
Adem, J., 1956: A series solution for the barotropic vorticity equation and its application in the study of atmospheric vortices. Tellus, 8 , 364–372.
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.
De Steur, L., , P. J. van Leeuwen, , and S. S. Drijfhout, 2004: Tracer leakage from modeled Agulhas rings. J. Phys. Oceanogr., 34 , 1387–1399.
Flierl, G., , V. D. Larichev, , J. C. McWilliams, , and G. M. Reznick, 1980: The dynamics of baroclinic and barotropic solitary eddies. Dyn. Atmos. Oceans, 5 , 1–41.
Flierl, G. R., , M. E. Stern, , and J. A. Whitehead Jr., 1983: The physical significance of modons: Laboratory experiments and general integral constraints. Dyn. Atmos. Oceans, 7 , 233–263.
Killworth, P. D., , D. B. Chelton, , and R. A. de Szoeke, 1997: The speed of observed and theoretical long extratropical planetary waves. J. Phys. Oceanogr., 27 , 1946–1966.
McDonald, N. R., 1998: The time-dependent behaviour of a spinning disc on a rotating planet: A model for geostrophical vortex motion. Geophys. Astrophys. Fluid Dyn., 87 , 253–272.
Nycander, J., 1996: Analogy between the drift of planetary vortices and the precession of a spinning body. Plasma Phys. Rep., 22 , 771–774.
Reznik, G. M., , and W. K. Dewar, 1994: An analytical theory of distributed axisymmetric barotropic vortices on the β plane. J. Fluid Mech., 269 , 301–321.
Reznik, G. M., , and R. Grimshaw, 2001: Ageostrophic dynamics of an intense localized vortex on a beta plane. J. Fluid Mech., 443 , 351–376.
Sutyrin, G. G., , J. S. Hesthaven, , J. P. Lynov, , and J. J. Rasmussen, 1994: Dynamical properties of vortical structures on the beta plane. J. Fluid Mech., 268 , 103–131.
Van der Toorn, R., 1997: Geometry, angular momentum and the intrinsic drift of ocean monopolar vortices. Ph.D. thesis, Utrecht University, Utrecht, Netherlands, 271 pp.