Beron-Vera, F. J., RSMAS, University of Miami, Miami, USA, fberon@rsmas.miami.edu
Olascoaga, M. J., RSMAS, University of Miami, Miami, USA, jolascoaga@rsmas.miami.edu
Goni, G. J., NOAA/AOML, Miami, USA, Gustavo.Goni@noaa.gov

MESOSCALE VORTICES AS REVEALED BY LAGRANGIAN COHERENT STRUCTURES

We use Lagrangian coherent structures (LCSs) to identify and track mesoscale vortices. LCSs are material lines which delineate boundaries of fluid domains with different advection characteristics that do not mix, and thereby provide an objective (i.e., frame independent) vortex identification method. Being of a fundamentally Lagrangian nature, LCSs cannot be revealed visually from velocity snapshots. Rather, they can be identified as maximizing curves or ``ridges'' in direct finite-time Lyapunov exponents (DFTLEs). We compute DFTLE fields, and identify LCSs on these fields, based on altimetry-derived surface geostrophic currents in two regions of the Atlantic. These regions are the North Brazil and Agulhas retroflection regions, where application of nonobjective vortex identification methods, such as the Okubo--Weiss criterion, has shown limited success. Identification and monitoring of rings in particular using this methodology will improve estimates of critical oceanic parameters, such as the interbasin exchange of mass, salt, and heat between the Indian and Atlantic basins and between the South and North Atlantic oceans, which are key in the study of the Meridional Overturning Circulation.

Oral presentation

Presentation is given by student: No
Session #:006
Date: 03-05-2008
Time: 13:45