Breaking down the overturning circulation to local mixing

I will present an analytical relation that directly shows how mixing locally drives the overturning circulation. The theory is based on the application of the well-known Water Mass Transformation framework to each local water column. The budgets for volume and tracer content mapped to tracer space are supplemented by a budget for the squared tracer. Mixing is defined by the destruction term of squared tracer, which is equivalent to the decay of tracer variance. I will present maps of the simulated diahaline mixing and the associated diahaline exchange velocity in the Baltic Sea. In addition, our numerical model offers to separately diagnose the mixing due to turbulence parameterizations and the spurious mixing due to discrete transport schemes. This enables us to also quantify the amount of spuriously induced overturning circulation. The planned application to diapycnal exchange and the global overturing circulation will be outlined.