The sensitivity of the Mediterranean circulation to the variability of the horizontal mixing is investigated using a Bryan-Cox-type general circulation model (OGCM). Attention is focused on a parameterisation of mixing previously developed in the context of two-dimensional turbulence, that is for the first time implemented in a OGCM. This parameterisation is suitable for velocity fields characterised by the presence of geostrophic coherent structures, and it is a direct application of the well-known Taylor's dispersion relation. Theoretical and experimental justifications of the parameterisation are discussed and results from four numerical experiments, with different tracer mixing schemes, are presented. In particular, it is shown that the proposed diffusivity parameterisation improves the tracers transport due to large eddy dynamics and, ensuring a more correct salt budget in the north western part of the basin, contributes to maintain a realistic vertical stratification and winter deep convection in long climatic integrations.

cited By 5