Kinematic models predict that a coherent structure, such as a jet or an edd
y, in an unsteady flow can exchange fluid with its surroundings. The author
s consider the significance of this effect for a fully nonlinear, dynamical
ly consistent, barotropic model of a meandering jet. The calculated volume
transport associated with this fluid exchange is comparable to that of flui
d crossing the Gulf Stream through the detachment of rings. Although the mo
del is barotropic and idealized in other ways, the transport calculations s
uggest that this exchange mechanism may be important in lateral transport o
r potential vorticity budget analyses for the Gulf Stream and other oceanic
jets. The numerically simulated meandering jet is obtained by allowing a s
mall-amplitude unstable meander to grow until a saturated state occurs. The
resulting flow is characterized by finite-amplitude meanders propagating w
ith nearly constant speed, and the results clearly illustrate the stretchin
g and stirring of fluid particles along the edges of the recirculation regi
ons south of the meander crests and north of the troughs. The fluid exchang
e and resulting transport across boundaries separating regions of predomina
ntly prograde, retrograde, and recirculating motion is quantified using a d
ynamical systems analysis. The geometrical structures that result from the
analysis are shown to be closely correlated with regions of the how that ar
e susceptible to high potential vorticity dissipation. Moreover, in a relat
ed study this analysis has been used to effectively predict the entrainment
and detrainment of particles to and from the jet.