FRONTOGENESIS IN GRAVITY-DRIVEN FLOWS WITH NONUNIFORM DENSITY GRADIENTS

A horizontal density gradient may be steepened to form a front if the horizontal flow which it drives is convergent. This convergence may be caused by an initial nonlinearity in the density gradient (as described by Simpson & Linden 1989). A quadratic density profile is analysed to illustrate the mechanism, and it is shown how the flow and the density profile interact to intensify and concentrate the front near a horizontal boundary. Linear and curved density profiles in a container of finite length are also studied: the most favourable location for frontogenesis is found to be where the flow emerges into a region of significant curvature after passing through a maximum of the density gradient.