On Frontal Dynamics in Two Model Oceans

Abstract

Vertically homogeneous variable-temperature layer models are often used to describe upper-ocean variability, the dynamics of jets and fronts included. Frontogenesis is known to have a preference for strong cyclonic shears. When a frontal wave winds up ageostrophically, one would expect intense cyclones and more diffuse anticyclones to be the result. This is characteristic of both atmospheric weather and the oceanic equivalent. The frontal dynamics of the variable-temperature layer model is here compared with that of the three-dimensional primitive equations, the origin of the layer model. Whereas the primitive equation numerical experiments produce dynamics according to the above, the cyclonic and anticyclonic shears and eddies are equally amplified in the corresponding variable-temperature layer experiments. It is suggested that thermal wind is basal to the desired frontal characteristics and that the layer description fails because of the way it has been defined to have none.