Collaborative research: Deep eastern ocean boundary currents from local submesoscale potential vorticity dynamics to global climate implications

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Evidence for substantial deep eastern boundary currents emerges repeatedly from observational studies in all southern hemisphere ocean basins. The core of these poleward flows carries a significant component of the meridional overturning circulation. These deep poleward flows occur in some areas well beneath upwelling systems characterized by an equatorward surface current and a poleward undercurrent. These flows affect the Southern Ocean water mass configuration and are an important part of the deep general circulation. Yet their dynamics are not well understood, and they are either poorly represented or not represented at all in climate models. This study will be the first attempt to understand the dynamics of deep eastern boundary currents and their consequences to climate simulation and projections. The project includes training of two graduate students, one postdoctoral researcher, and outreach to the public via the World Wide Web.This project studies deep eastern boundary currents using an analysis of varied observations, a Bayesian inverse model, and a high resolution regional ocean model. The high resolution ocean model can resolve mesoscale and submesoscale eddy processes that may participate in the potential vorticity dynamics of these deep boundary currents. The results of the inverse model and high resolution regional ocean model will be used to develop an idealized theoretical model and understanding of deep eastern boundary currents. The proposed study will also examine the simulation of deep eastern boundary currents in global coupled models, and the consequences of their poor simulation on the climate models? large scale dynamics and future climate projections. While deep eastern boundary currents are completely distinct from upper-ocean undercurrents in upwelling systems, this study will benefit from work done on such undercurrents, helping identify relevant dynamical processes. These include: beta effect, wind curl, bottom slope, submesoscale eddies generating and dissipating Rossby waves, eddy-topography interactions, up-gradient eddy momentum fluxes, potential vorticity inflow conditions, potential vorticity transport and mixing by submesoscale eddies and by vertical mixing processes, submesoscale and quasi-geostrophic mesoscale eddy effects on the deep stratification, and interior topography-related zonal ocean flows feeding deep eastern boundary currents.