Flow structures from Lagrangian tracers in a tidal driven flow (Ria de Vigo, Spain)
Florian Huhn, Vicente Perez-Munuzuri, Pedro Montero
Universidad de Santiago de Compostela
(Abstract received 08/11/2009 for session C)
ABSTRACT
We analyze the 2-dimensional surface velocity field from a 3-dimensional flow model for an estuarine (Ria de Vigo, Galicia, Spain). Fields of the Finite-time Lyapunov Exponent (FTLE) are calculated from passive advected tracers in the time-dependent flow to detect Lagrangian Coherent Structures (LCS). These structures seperate the flow and act as transport barriers. They reveal zones of retention and allow for an exact localization of the tidal inflow from the shelf. First comparisons of the LCSs to drifter trajectories show good agreement, as long as the drifters are hardly influenced by the local winds in the estuarine. Measured surface velocity fields from HF radar will be used to verify the results from the model and the drifters. Knowledge about the flow structures in the Ria de Vigo are useful to follow contaminations from the large harbour and intense ship traffic. Furthermore, the region has one of the most productive mussel industries of the world due to the seasonal upwelling of cold nutrient rich water. The transport of nutrients or eggs and larvae of fish and shellfish, but also the presence of harmful algae blooms are directly connected to the present flow structures.
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