Analysis of Lagrangian potential vorticity balance and lateral displacement of water parcels in Gulf Stream meanders

Abstract

The balance of potential vorticity components following fluid parcel motion in Gulf Stream meanders was studied. By introducing curvature dependent variations to the velocity and density fields, the authors relaxed the rigid field assumption used in earlier studies and examined closely the upper layers (13°-16°C) of the main thermocline. Both spatial and temporal changes in curvature affect the regions of divergence in a meandering stream. The growing amplitude meanders are found to be associated with divergence (convergence) upstream, and convergence (divergence) downstream of crests on the anticyclonic (cyclonic) side. This pattern is reversed for decaying meanders. A parcel's cross-stream motion is found to be consistent with the pattern established earlier: upwelling/onshore from trough to crest and downwelling/offshore from crest to trough. Cross-frontal fluid exchange is enhanced by changes in meander amplitude.