|Lagrangian analysis of 3D mesoscale dynamics from altimetry and modelling:
application to jellyfish tracking in Mediterranean |
Conference: Ocean Surface Topography Science Team Meeting 2011 (San-Diego, US, 2011-10-18)
Oceanic mesoscale plays a key role in modulating large-scale circulation, heat flux transfer and primary production enhancement. Such hydrodynamic processes are also crucial for Jellyfish transport and distribution along the Mediterranean coastal areas. Therefore, investigating the relationship between jellyfish distribution and mesoscale hydrodynamic processes provides a rationale to understand the influence of such physical structures on the dynamics of regional ecosystems, at the interface between the open ocean and the continental shelf. Nevertheless, the high spatial/temporal variability and complexity associated with coastal mesoscale processes makes them difficult to study with sparse in-situ observations. Alternative options rely on developing methodologies based on the combination of multi-sensor platforms in conjunction with numerical simulations. In this respect, we use a lagrangian code to simulate particle trajectories from both a circulation regional model and currents derived from satellite altimetric maps specifically adapted to the coastal areas of the North Western Mediterranean Sea (NWM). Satellite geostrophic currents both at surface and depth were reconstructed using a high resolution altimetric current mapping tool and vertical EOFs computed from the model velocity fields. By comparison with several in-situ measurements (drifter, ADCP) and model outputs, it follows that our approach successfully characterizes the main mesoscale features and 3D exchanges between the Gulf of Lion continental shelf and the open Mediterranean. Moreover, the lagrangian analysis allows us to better understand the influence of coastal circulation on jellyfish trajectories and distribution over the NWM coastal domain, and thus represents a key aspect for the long-term purpose of forecasting their trajectories.