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| Titel |
A new mechanism of upwelling generated filaments based on potential vorticity balance |
| VerfasserIn |
C. Troupin, E. Mason, J.-M. Beckers, P. Sangrà |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020754
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| Zusammenfassung |
| Upwelling filaments are typical features in Eastern Boundary Upwelling Systems and were
the object of numerous in situ or numerical studies. However physical processes that
generates filaments are not perfectly understood. Recent works suggest that tehy arise from a
combination of three phenomena:
baroclinic instability of the coastal upwelling jet;
interaction of the flow with coastline and topography shape;
coastal convergence due to wind stress.
In order to explain the generation process with a simple theory, we assume that filament
arise from an injection of positive vorticity; as the flow gains positive vorticity, it becomes
unable to continue southward and detaches from the coast.
The filament-rich region of Cape Ghir (NW Africa) acts as a suitable zone for testing our
hypothesis. Several numerical experiments with ROMS model were carried out to assess the
role of various process (wind curl, bottom friction, variable topography etc) which may be
responsible for positive vorticity injection.
The model reference configuration allows us to reproduce the filament with spacial and
time scales compatible with in situ observations. Results of the experiments highlight the role
of wind stress, since it is at the origin of the upwelling itself. Decreased coastal winds
caused multiple filaments around Cape Ghir. Smoothed topography has significant
effects on the solution, meaning that the model is sensitive to this parameter. With
flattened bathymetry, filaments tend to be much weaker and have lower extension. |
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