Particle Exchange in an Unstable Jet

Abstract

A one-dimensional model of baroclinic instability is used to reconcile two differing interpretations on why neutrally buoyant floats cross the Gulf Stream more readily at subthermocline depths. The study compares the location of the steering level, where the particle speed matches the speed of a propagating meander, to the location of the minimum in the meridional potential vorticity gradient The former locale is the expected site of a maxima in particle exchange, based on kinematic arguments, while the latter is the expected site based on potential vorticity dynamics. Model results show that the two levels are not coincident; in general, the steering level is deeper in the water column than the minimum in the potential vorticity gradient. Additionally, it is the steering level where the largest cross-stream particle exchange is expected to occur.