Effects of Double Diffusion and Turbulence on Interleaving at Baroclinic Oceanic Fronts

Abstract

Treating the problem of interleaving in ocean fronts, a linear stability analysis is applied to a thermohaline, baroclinic front in which the vertical diffusivity for mass and momentum is determined by both the double diffusion and turbulence. If the mass and momentum diffusivity is controlled by double diffusion solely, interleaving in baroclinic fronts is possible at any value of the geostrophic Richardson number Ri. However, it is shown that turbulent mixing always works to suppress double-diffusive interleaving. Due to turbulent mixing, at some range of the input parameters there is a range of Ri where the maximum growth rate of interleaving, ??max, vanishes. Several asymptotic criteria governing the Ri dependence of ??max are found. These criteria fit well the results of numerical calculations of ??max(Ri). One of the criteria has been applied to describe intrusions observed in the Azores Front of the North Atlantic.