On co-existing diffusive and anti-diffusive tracer transport by oceanic mesoscale eddies

A common approach for parameterising eddy transport of passive tracers by mesoscale eddies in the ocean is invoking a tensor. The symmetric part this tensor, diffusion quantifies diffusive tracer transport. Recent studies have diagnosed opposite-signed eigenvalues (diffusivities) tensor from eddy-resolving simulations, while all current parameterisations implement only positive diffusivities. For associated flux not necessarily down-gradient and therefore may mix transferring variance to small scales. In study we explore such fluxes using an simulation with relaxation (source/sink) forcing. After confirming that tensors different pairs eigenvalues, show corresponding drives net transfer variance, as would be guaranteed when are both positive. Locally up-gradient common, their frequency strongly dependent on profile. effects weakening/strengthening each tracer. However, considered amplitude weakens strengthens, consequence homogeneous dissipating less variance. Our results indicate oceanic sources/sinks parameterised should globally down-gradient.