David Marshall

Abstract:

Fofonoff solutions to the inviscid barotropic potential vorticity equation are found for the steady, free flow in a basin rotated at an arbitrary angle to a latitude circle. These solutions are used to study the inertial recirculation of the subtropical gyre, which is forced by anomalously low values of potential vorticity within the separated Gulf Stream. -from Author

Abstract:

It is shown that subtle changes in the velocity profile across the seaward extension of midlatitude jets, such as the Gulf Stream, can lead to dramatic changes in the zonal-penetration scale. In particular, if α-dq/dψ >0, where q is the absolute vorticity and ψ is a streamfunction for the geostrophic flow, then the jet tends to penetrate across to the eastern boundary; conversely if α <0, the jet turns back on itself creating a tight recirculation on the scale of order [α]-1/2. This behavior is demonstrated in a quasigeostrophic ocean model. The implications of this study for numerical simulations of ocean gyres are discussed. In particular, it is demonstrated that poor resolution of the horizontal jet structure may lead to a dramatic reduction in penetration. -from Authors