Sensitivity of Loop Current metrics and eddy detachments to different model configurations: The impact of topography and Caribbean perturbations

Maximo Garcia-Jove Navarro, Julio Sheinbaum, Julien Jouanno

Abstract

The dynamics of the Loop Current (LC) and the release of its anticyclonic eddy (Loop Current eddy, LCE) are some of the most important features of the circulation in the Gulf of Mexico (GoM) and key aspects to gauge the validity of numerical simulations. Using a numerical model, we investigate the sensitivity of the LC and LCE detachments to three different mechanisms deemed to be relevant to their behavior: a) suppression of Caribbean vorticity perturbations entering the GoM; b) smoothness of the topography, and c) suppression of a deep canyon on the eastern Campeche Bank.

The main results of these experiments in comparison to a reference run considered to be the more realistic one are:

a. Suppression of Caribbean eddies reduces the number of LCE separations, but they are not the principal mechanism that triggers the separations. Locally generated instabilities over the northeastern Campeche Bank and the LC northward extension, appear to be the controlling factors.

b. Smoothing the topography generates a wider and less intense LC and reduces the energy exchange terms related to flow instabilities. Nevertheless, the number of LCE separations is similar to the reference experiment. Extension of the LC controls the shedding that, in this case, tends to occur in the summer-fall season, when the LC is more extended, and the Yucatan transport abruptly weakens after its seasonal maximum.

c. Removing the deep canyon in the eastern Campeche Bank, makes the LC extension more stable and reduces the number of LCE separations. The canyon appears to play an important role in spinning up cyclones generated over the LC eastern front that finally leads to an LCE release.

The seasonal distribution of LCE separations in the experiments does not appear to be controlled by the strength of the barotropic and baroclinic instability source terms. Instead, a necessary but not sufficient condition for LCE separations is that the LC extends beyond 24º N. Our results indicate that caution should be exercised when interpreting LC statistics from a single numerical configuration.

Keywords

Gulf of Mexico; eddies; energy cycle; barotropic and baroclinic instabilities; numerical modeling

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