Dipole-wind interactions under gap wind jet conditions in the Gulf of Tehuantepec, Mexico: A surface drifter and satellite database analysis.

Mauro W Santiago-García,Armando Trasviña,Alejandro F Parés-Sierra

doi:10.1371/journal.pone.0226366

Mauro W Santiago-García, Armando Trasviña + Show 1 more

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https://doi.org/10.1371/journal.pone.0226366

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Abstract

Gap wind jets (Tehuano winds) trigger supersquirts of colder water and mesoscale asymmetric dipoles in the Gulf of Tehuantepec (GT). However, the effects of successive gap wind jets on dipoles and their effects inside eddies have not yet been studied. Based on the wind fields, geostrophic currents, and surface drifter dispersion, this research documented three dipoles triggered and modified by Tehuano winds. Once a dipole develops, successive gap wind jets strengthen the vortices, and the anticyclonic eddy migrates southwestward while the cyclonic eddy is maintained on the east side of the GT. During the wind relaxation stage, the cyclonic eddy may propagate westward, but due to the subsequent re-intensification of the Tehuano winds, the vortex could break down, as was suggested by surface drifter dispersion pattern and geostrophic field data. The effect of the Tehuano winds was evaluating via eddy-Ekman pumping. Under Tehuano wind conditions, Ekman downwelling (upwelling) inside the anticyclonic (cyclonic) eddies may reach ~ -2.0 (0.5) m d-1 and decrease as the wind weakens. In the absence of Tehuano winds, Ekman downwelling inside the anticyclonic eddy was ~ 0.1 (-0.1) m d-1. The asymmetry of downwelling and upwelling inside eddies during Tehuano wind events may be associated with Tehuano wind forcing.

Highlights

The Gulf of Tehuantepec (GT) is one of the few regions in the world with intense and intermittent gap wind jets that trigger ocean surface cooling [1,2] and asymmetric mesoscale circulation [3,4]
Tehuano wind frequency and intensity are greatest during autumn and winter due to the passage of cold fronts coming from the midlatitudes and to a high-pressure system that forms in North America and moves southeastward over the Gulf of Mexico (GoM)
These synoptic scale atmospheric conditions result in a pressure gradient between the GoM and the GT, generating airflow that is blocked by the mountains of the Sierra Madre but channeled through a mountain gap in the Isthmus of Tehuantepec [5,6] and the wind blowing

Summary

Introduction

The Gulf of Tehuantepec (GT) is one of the few regions in the world with intense and intermittent gap wind jets that trigger ocean surface cooling [1,2] and asymmetric mesoscale circulation [3,4]. Tehuano wind frequency and intensity are greatest during autumn and winter due to the passage of cold fronts coming from the midlatitudes and to a high-pressure system that forms in North America and moves southeastward over the Gulf of Mexico (GoM). These synoptic scale atmospheric conditions result in a pressure gradient between the GoM and the GT, generating airflow that is blocked by the mountains of the Sierra Madre but channeled through a mountain gap in the Isthmus of Tehuantepec [5,6] and the wind blowing. Tehuano winds are associated with the westward elongation and intensification of the Azores-Bermuda high-pressure center [7]

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