Journal of Geophysical Research: Oceans

The connectivity of eddy variability in the Caribbean Sea, the Gulf of Mexico, and the Atlantic Ocean

Authors

  • Sylvia J. Murphy,

  • Harley E. Hurlburt,

  • James J. O'Brien


Abstract

A set of numerical simulations is used to investigate the connectivity of mesoscale variability in the Atlantic Ocean, the Caribbean, and the Gulf of Mexico. The primitive equation models used for these simulations have a free surface and realistic coastline geometry including a detailed representation of the Lesser Antilles island arc. Two simulations have 1/4° resolution and include a 5.5-layer reduced gravity and a 6-layer model with realistic bottom topography. Both are wind forced and include the global thermohaline circulation. The third simulation is from a 1/2° linear wind-driven model. In the two nonlinear numerical simulations, potential vorticity from decaying rings shed by the North Brazil Current retroflection can be advected through the Lesser Antilles. This potential vorticity acts as a finite amplitude perturbation for mixed barotropic and internal mode baroclinic instabilities, which amplify mesoscale features in the Caribbean. The eddies associated with the Caribbean Current are primarily anticyclonic and transit a narrow corridor across the Caribbean basin along an axis at 14° to 15°N with an average speed of 0.15 m/s. It takes them an average of 10 months to transit from the Lesser Antilles to the Yucatan Channel. Along the way, many of the eddies intensify greatly. The amount of intensification depends substantially on the strength of the Caribbean Current and is greatest during a multiyear period when the current is anomalously strong owing to interannual variation in the wind forcing. Some Caribbean eddies squeeze through the Yucatan Channel into the Gulf of Mexico, where they can influence the timing of Loop Current eddy-shedding events. There is a significant correlation of 0.45 between the Loop Current eddy shedding and the eddies near the Lesser Antilles with a time lag of 11 months. However, Caribbean eddies show no statistically significant net influence on the mean eddy-shedding period nor on the size and strength of shed eddies in the Gulf of Mexico. Additionally, no significant correlation is found between eddy shedding in the Gulf of Mexico and transport variations in the Florida Straits, although transport fluctuations in the Florida Straits at 27°N and the Yucatan Channel and showed a correlation of about 0.7 with a lag of 15 days. The linear solution exhibited a multiyear anomaly in the strength of the Caribbean circulation that was concentrated in the central and eastern Caribbean due to a multiyear anomaly in the wind field over the basin. In the nonlinear simulation this anomaly extended into the western Caribbean and across the entire Gulf of Mexico. This westward extension resulted from the nonlinearity and instability of the Caribbean Current, the westward propagation of the eddies, and the passage of Caribbean eddies through the Yucatan Channel into the Gulf of Mexico.

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