Meeting Abstracts
Submesoscale dispersion in a coastal frontal zone: results from a targeted Lagrangian experiment
A. Griffa, K. Schroeder, J. Chiggiato, A. C. Haza, T. M. Ozgokmen, P. Zanasca, A. Molcard, M. Borghini, P. M. Poulain, R. Gerin, E. Zambianchi, P. Falco, C. Trees
CNR-ISMAR, RSMAS-UM, NURC-NATO, LSEET, OGS, Universita' Parthenope
(Abstract received 05/12/2012 for session A)
ABSTRACT
A persistent coastal front driven by river outflows in the North-Western Mediterranean Sea has been targeted by two observational cruises conducted in the summer of 2010. The frontal zone is sampled using drifters launched with a multi-scale strategy consisting of modules of triplets, released on either side of the front by small boats. The submesoscale range of 100 m to 1000 m is directly targeted, and the results are expected to provide guidance for practical applications, such as prediction of the initial spreading of pollutants and biogeochemical tracers. The influence of submesoscale motions on relative dispersion is quantified using both particle mean square separation as a function of time, and scale-dependent finite-size Lyapunov exponents (FSLEs). The main finding is the identification of a local dispersion regime with FSLes maximum values
reaching as high as ≈ 20 days−1 at drifter pair separation distances
of < 100 m. These values are more than an order of magnitude greater
than those obtained by drifters in the offshore Ligurian current and they
are significantly underestimated by a fully realistic Regional Ocean Modeling
System (ROMS) with 1/60◦ horizontal resolution indicating the need for particle dispersion parameterizations for the
unresolved processes.