| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4534993 | Deep Sea Research Part I: Oceanographic Research Papers | 2011 | 20 Pages |
Relative dispersion in the Liguro-Provençal basin (a subregion of the Mediterranean Sea) is investigated using clusters of surface drifters deployed during two Marine Rapid Environment Assessment (MREA) experiments covering different months in 2007 and 2008, respectively. The clusters have initial radii of less than 1 km, or an order of magnitude below a typical deformation radius (approximately 10–20 km). The data set consists of 45 original pairs and more than 50 total pairs (including chance ones) in the spatial range between 1 and 200 km. Relative dispersion is estimated using the mean square separation of particle pairs and the Finite Scale Lyapunov Exponents (FSLEs). The two metrics show broadly consistent results, indicating in particular a clear exponential behaviour with an e -folding time scale between 0.5 and 1 days, or Lyapunov exponent λλ in the range of 0.7–1 days−1. The exponential phase extends for 4–7 days in time and between 1 and 10–20 km in separation space. To our knowledge, this is only the third time that an exponential regime is observed in the world ocean from drifter data. This result suggests that relative dispersion in the Liguro-Provençal basin is nonlocal, namely controlled mainly by mesoscale dynamics, and that the effects of the sub-mesoscale motions are negligible in comparison. NCOM model results are used to complement the data and to quantify errors arising from the sparse sampling in the observations.
Research highlights►One of the few studies in which drifters have been released in closely-spaced clusters so that estimation of relative dispersion at the sub-mesoscale range was possible. ►The third observational study indicating an exponential regime at the sub-mesoscale range. ►The implication is that sub-mesoscale transport is controlled by larger, mesoscale features. ►In practice, this result has broad implications on future development of both observational and modeling techniques for the sub-mesoscale transport.
