Bruno Buongiorno Nardelli, Institute for Coastal Marine Environmnet, CNR i Napoli i Italien holder foredraget "Diagnosing 3D currents at mesoscale from combined satellite and in situ observations: recent advances and possible impact on biogeochemical fluxes" i Kaffeklubben på DTU Aqua. Gæster er velkomne.
Resumé
Mesoscale and sub-mesoscale features are present anywhere in the World Ocean. They modulate the surface and internal dynamics and contain most of the ocean kinetic energy. Mesoscale eddies eventually transport phytoplankton and modify the flux of nutrients from the deep layers into the sunlit zone, affecting the photosynthetic fixation of carbon dioxide in the open ocean surface waters, as well as the distribution and dispersal of larvae or organisms with limited swimming ability along the water column.
Eddies are generally identified in oceanic observations as sea surface height and isopycnal domes that result from baroclinicity and first-order geostrophic balance. The conceptual model invoked to explain the impact of eddies on the marine ecosystem thus links vortex growth and decay to the shoaling or deepening of isopycnal surfaces, and relates primary production variations to corresponding nutricline displacements.
Recent studies demonstrate that this model fails to describe the vertical fluxes estimated through a higher order dynamical approximation from combined satellite-in situ observations. Analysing the evolution of a cyclonic eddy, Brune Nardelli shows that vortex azimuthal oscillations dominate the vertical velocity field. Vortex waves have been widely analysed in theoretical studies, laboratory experiments, and numerical models, but difficult to detect in the oceans. Synthetic Lagrangian trajectories inside the eddy indicate that observed oscillations drive vertical displacements in a range of frequencies for which a biogeochemical response is expected.
Om Kaffeklubben
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