title: Persistent transport barrier on the West Florida Shelf.
abstract: Analysis of drifter trajectories in the Gulf of Mexico has revealed the existence of a region on the southern portion of the West Florida Shelf (WFS) that is not visited by drifters that are released outside of the region. This so-called "forbidden zone" (FZ) suggests the existence of a persistent cross-shelf transport barrier on the southern portion of the WFS. In this letter a year-long record of surface currents produced by a Hybrid-Coordinate Ocean Model simulation of the WFS is used to compute Lagrangian coherent structures (LCSs), which reveal the presence of a persistent cross-shelf transport barrier in approximately the same location as the boundary of the FZ. The location of the cross-shelf transport barrier undergoes a seasonal oscillation, being closer to the coast in the summer than in the winter. A month-long record of surface currents inferred from high-frequency (HF) radar measurements in a roughly 60 km × 80 km region on the WFS off Tampa Bay is also used to compute LCSs, and these also reveal the presence of transient transport barriers. While the HF-radar-derived transport barriers cannot be unambiguously linked to the boundary of the FZ, this analysis does demonstrate the feasibility of monitoring transport barriers on the WFS using a HF-radar-based measurement system. The implications of a persistent cross-shelf transport barrier on the WFS for the development of harmful algal blooms on the shoreward side of the barrier are considered.
authors.affiliation: Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Olascoaga
authors.forename: I I
authors.initials: II
authors.lastname: Rypina
authors.forename: M G
authors.initials: MG
authors.lastname: Brown
authors.forename: F J
authors.initials: FJ
authors.lastname: Beron-Vera
authors.forename: H
authors.initials: H
authors.lastname: Koçak
authors.forename: L E
authors.initials: LE
authors.lastname: Brand
authors.forename: G R
authors.initials: GR
authors.lastname: Halliwell
authors.forename: L K
authors.initials: LK
authors.lastname: Shay