Global bifurcation of Shilnikov type in a double-gyre ocean model

The dynamics of an idealized wind-driven double-gyre circulation in an ocea n basin are studied from a dynamical systems point of view in an effort to better understand its variability. While previous analyses of this circulat ion have mostly dealt with local bifurcations of steady states and limit cy cles, this study demonstrates the importance of considering global bifurcat ions as well. In one case, a coherent picture of the global dynamics spanni ng a range of parameters from where there are only stable steady-state solu tions to where there is chaotic eddy shedding is presented. A simple but no vel use of power spectra along with dynamical projections of the dynamics s uggests that just beyond the regime in which there are only stable steady s tates, the system exhibits a complicated global bifurcation known as the "S hitnikov phenomenon."