FORMATION AND STABILITY OF SHELF BREAK FRONTS

An analytical, inviscid two dimensional model is used to examine the formation of surface-to-bottom density fronts over shelf slope topography. Previous studies have examined the geostrophic adjustment of a vertical front near the shelf break. However, our approach makes no such assumption about the initial density field, requiring only that all upper-layer fluid originate over the shelf. The main limitation of the study is that the lower-layer velocities are assumed to be negligible. The simple model demonstrates that geostrophy and potential vorticity conservation are sufficient conditions to ensure that a front will intersect the bottom close to the shelf break. Aspects of the theory have been compared with results from simple laboratory experiments. The experiments also reveal the influence of frontal processes such as instability and wave formation that are not included in the theoretical model. In particular, they provide clear confirmation of the stabilizing influence of steep topography below fronts.