The wind-driven circulation of the mid-latitude ocean basins has been described by a hierarchy of models — quasi-geostrophic, shallow-water and primitive equations, with an increasing horizontal resolution and number of vertical levels. We study the low-frequency variability (LFV) of this wind-driven, double-gyre circulation in mid-latitude ocean basins, subject to time-constant, purely periodic and more realistic forms of time-dependent wind stress.

Both analytical and numerical methods of dynamical systems theory are applied to the models of interest. Recent work has focused on the application of non-autonomous and random forcing to double-gyre models. We discuss the associated pullback and random attractors and the non-uniqueness of the invariant measures that are obtained. The effects of the oceanic LFV on the atmosphere above are explored and compared to observations. Finally, connections are made with the highly topical issues of climate change and climate sensitivity.

This talk reflects collaborative work with a large and still increasing number of people. Please visit https://dept.atmos.ucla.edu/tcd for their names, affiliations, and respective contributions.

References

• H. A. Dijkstra and M. Ghil, 2005: Low-frequency variability of the large-scale ocean circulation: A dynamical systems approach, Rev. Geophys., 43, RG3002, doi:10.1029/2002RG000122.
• M. Ghil, 2016. The wind-driven ocean circulation: Applying dynamical systems theory to a climate problem, Discr. Cont. Dyn. Syst. – A, 37(1), 189–228, doi:10.3934/dcds.2017008.