Meeting Abstracts
A Lagrangian Approach to the Loop Current Eddy Separation.
Fernando Andrade-Canto, Julio Sheinbaum and Luis Zavala-Sanson
Physical Oceanography, CICESE, Ensenada, Baja California, Mexico
(Abstract received 05/11/2012 for session C)
ABSTRACT
Determining when and how a Loop Current Eddy (LCE) in the Gulf of Mexico (GoM) will finally separate is a difficult task, since several detachment re-attachment processes can occur during one of these events. We suggest that computation of Lagrangian Coherent Structures (LCS) associated with the flow can provide such a method of precise LCE detachment identification. The basic idea is very simple: separation should be defined whenever water particles from the cyclonic side of the Loop Current (LC) move swiftly from Yucatan Peninsula to the Florida Straits instead of penetrating into the Gulf of Mexico. Finite Time Lyapunov Exponents (FTLE) computed from a numerical model of the GoM are used to identify LCS involved in detachment events and the results compared to the SSH separation metric of Leben (2005). We define an Eulerian metric based on the slope of the strain direction of the instantaneous hyperbolic point of the LC anticyclone that provides useful information to forecast final LCE detachments. We highlight cases in which the SSH method suggests there is a separated LCE that later re-attaches, whereas the FTLE-LCS and slope methods clearly show the eddy remains dynamically connected to the Loop Current during the process.