GM+PV: Testing a new mesoscale eddy parameterization in an Arctic configuration

Mesoscale eddy parameterizations deployed in climate models are typically unable to produce eddy-driven topography-following flows which are known to dominate the flow structure in the Arctic. One theory for the development of topography-following flows is that they arise as a result of the cascades of energy and enstrophy in quasigeostrophic turbulence and the dissipation of enstrophy at small scales. Recent work in the field of eddy parameterizations has seen an emerging focus on developing energetically consistent parameterizations, but the same focus has not been applied as thoroughly to the enstrophy.

In this work, a parameterization of barotropic eddy potential vorticity fluxes is introduced which incorporates an energetic constraint and an additional enstrophetic constraint. The parameterization mixes potential vorticity in a manner that produces a net eddy-to-mean kinetic energy transfer and a net mean-to-eddy potential enstrophy transfer, consistent with the inverse kinetic energy cascade and direct potential enstrophy cascade typical of the barotropic mode of quasigeostrophic turbulence. The barotropic parameterization is integrated with the Gent and McWilliams (1990) parameterization of baroclinic eddies by providing a mechanism through which available potential energy, extracted by the baroclinic parameterization, can be converted to barotropic eddy kinetic energy.

The parameterization is tested in an Arctic configuration. We find that the parameterization is successful in driving a large-scale topography-following flow, broadly resembling the Arctic Circumpolar Boundary Current. We explain the evolution of this large-scale flow through a balance in the energy and potential enstrophy transfers.