A Two-Layer Model of Shelfbreak Jets with Application to the Labrador Current

Abstract

The role played by bottom friction, bottom slope, ? effect, and density mixing in exchange between the shelf and a frontal jet is examined in the light of a two-layer model. The model uses linear dynamics and bottom and interfacial friction to parameterize vertical momentum mixing, and Newtonian cooling to parameterize density mixing. It is assumed that the dynamics approximately obey Csanady?s diffusion equations in both shelf and frontal regions. Assuming a velocity profile appropriate to a shelfbreak jet, the authors examine how the various dynamical factors can affect cross-shelf exchange in the frontal region and derive some front solutions by assuming a simple torque balance. It is shown that the ? effect and density mixing both produce onshore geostrophic fluxes and counteract the offshore flux due to the frictional torque. Consideration of the conditions at the intersection point of the front with the bottom shows an important role of the JEBAR effect in changing the cross-shelf circulations obtained from barotropic numerical models. It is also found that only bottom slope can provide the alongshelf structure of the front, whereas other factors such as ? and density mixing determine only the cross-shelf structure.