Atmosphere Ocean Science Colloquium

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Eddy-mean flow interaction in a multiple-scale ocean model

Speaker: Bruno Deremble, LMD, Ecole Normale

Location: Warren Weaver Hall 1302

Date: Wednesday, May 1, 2019, 3:30 p.m.

Synopsis:

In the extratropical oceans, the combination of wind and surface heat fluxes maintain the subtropical and subpolar gyres. These gyres have a large-scale component, also known as the ventilated thermocline which is well described by the formalism. In places where the large-scale flow is baroclinically unstable, small-scale eddies are generated with characteristic length scale the deformation radius, which is O(50km) in mid-latitudes. The baroclinic instability and the eddy dynamics are well described by the quasi-geostrophic formalism. In this talk, I will illustrate the non-linear interaction between the small scale eddies and the large-scale flow at the basin scale. We find that the average feedback of these oceanic eddies rectifies the large-scale flow by flattening isopycnal surfaces and by maintaining a sharp western boundary current. This feedback is the expression of the inverse cascade and we find that this cascade extends at the basin.