Eddies and their Potential Role in the General Circulation

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0002295This project is an attempt to provide a better understanding of (a) processes determining the structure, distribution and scale content of the oceanic mesoscale field and (b) the role of mesoscale eddies in determining the large-scale structure of the ocean, looking in turn at the structure of the thermocline, abyssal flows, and structure of the mid-depth flows below the base of the thermocline. The physical effects that will be considered are broad-ranging and include, wind-forcing, mesoscale instabilities of large scale flows, the response of the ocean to stochastic forcing, adiabatic advection (ventilated thermocline dynamics), and eddy-topography interactions. The approach will be a combination of theory and numerical simulations. Much of the numerical simulation will be with stratified quasi-geostrophic models although some will use a primitive equation model (MOM4). The project will begin by looking at the life-cycles of baroclinic eddies in a broad, baroclinically unstable, wind-driven flow, studying their equilibration and the scaling of the vertical structure of the equilibrated eddies. The effects of inhomogeneity will be studied by stochastically forcing a quasigeostrophic model linearized about a time-mean wind-driven gyre. The project will go on to look at the role of the planetary and topographic vorticity gradients in introducing anisotropies in the nonlinear cascade of eddy energy in wavenumber space, leading to coherent and energetic deep flows. Lastly the role of mesoscale eddies in establishing the vertical structure of the thermocline will be examined using a primitive equation model.