Mechanisms of shelf-break frontogenesis

摘要

The shelf-break front is an omnipresent phenomenon in coastal oceans all over the world, but there is still no definitive explanation for the genesis of such a front. It is possible that different mechanisms are operative at different times and locations, but all of them should have something to do with the sharp change of bottom topography near the shelf-break. A couple of recently proposed mechanisms of shelf-break frontogenesis are dicussed. One of them invokes a flow convergence produced by local air-sea interaction over sloping topography, whereas the other relies on the depth dependence of wind-induced shear dispersion. These novel ideas are based on new observational evidences and previous theoretical studies, and they are demonstrated here using an idealized ocean-atmosphere coupled model and a stand-alone ocean model. The air-sea interaction mechanism seems plausible for the shelf-break front in the East China Sea, and the shear dispersion mechanism is likely to be applicable to the shelf-break front off the northeastern United States.