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Meander -induced exchange across the Gulf Stream

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  • Physical Oceanography

Abstract

Meander-induced exchange is the most important mechanism of exchange of watermass and properties across a meandering midlatitude jet, such as the Gulf Stream. Two extant hypotheses regarding meander-induced exchange and its increase with depth are considered in this dissertation. In the first, the potential vorticity (PV) front at the northern edge of the stream is considered to inhibit lateral motion of particles across the stream. This was investigated based on observations of Lagrangian particles at the northern edge of the Gulf Stream and how PV fields evolved in the vicinity. A method to track Lagrangian trajectories from Conductivity-Temperature-Depth (CTD) sensor and Acoustic Doppler Current Profiler (ADCP) data was developed for this study. Observational evidence shows that the PV field in the vicinity of a parcel moves laterally and evolves as the parcel moves downstream, suggesting that the PV front is more of a response to lateral motion of parcels than an inhibitor to it. The second hypothesis dealing with meander-induced exchange uses kinematic arguments that are consistent with an exchange increasing with depth. This kinematic argument was supplemented with the inclusion of barotropic fields, whose contribution a significant contribution that increases with the amplitude of the meander had been previously ignored. The dissertation thus furthers the current understanding of the depth-dependent meander-induced exchange by questioning the basis for the PV front hypothesis, with the observed lateral motion of the PV front, and by generalizing the steering-level hypothesis, with the inclusion of what turns out to be a significant barotropic field. ^

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