Lagrangian transport through an ocean front in the North-Western Mediterranean Sea
| by A.M. Mancho, E. Hernandez-Garcia,D. Small, S. Wiggins and V. Fernandez |
| Journal of Physical Oceanography 38, 1222-1237 (2008) |
| Output type: publication |
 URL: http://dx.doi.org/10.1175/2007JPO3677.1 |
We analyze with the tools of lobe dynamics the velocity field from a numerical
simulation of the surface circulation in the Northwestern Mediterranean Sea. We identify
relevant hyperbolic trajectories and their manifolds, and show that the transport
mechanism known as the ‘turnstile’, previously identified in abstract dynamical systems
and simplified model flows, is also at work in this complex and rather realistic
ocean flow. In addition nonlinear dynamics techniques are shown to be powerful
enough to identify the key geometric structures in this part of the Mediterranean. In
particular the North Balearic Front, the westernmost part of the transition zone between
saltier and fresher waters in theWestern Mediterranean is interpreted in terms
of the presence of a semipermanent “Lagrangian barrier” across which little transport
occurs. Our construction also reveals the routes along which this transport happens.
Topological changes in that picture, associated with the crossing by eddies and that
may be interpreted as the breakdown of the front, are also observed during the simulation.
