Impact of Caribbean Anticyclones on Loop Current variability

The Loop Current evolves in the Gulf of Mexico as a continuation of the Yucatan Current and its upstream Caribbean Current, entering through the Yucatan Channel from the Northwestern Caribbean Sea. The Loop Current system contains the associated rich eddy field and together with the Florida Current controls the exit of the Gulf Stream toward the Atlantic Ocean and its downstream evolution along the US coasts. We examine the consequences of this natural connectivity, focusing on the dynamical synergy of mesoscale circulation processes downstream (north) of the Yucatan Channel (Gulf interior, dominated by Loop Current variability) and upstream (south) of the Yucatan Channel (Northwestern Caribbean Sea). We focus on Caribbean Anticyclones, their characteristics and evolution as they feed into the Loop Current system. We employ observational (satellite altimetry and drifters) and simulated (ocean numerical model) data for a 9-year period (2010–2018). Several metrics related to the Loop Current (maximum latitude, axis), Yucatan Current (zonal position), and Caribbean Sea mesoscale circulation (vorticity) are used to quantify how the accurate representation of Caribbean eddies can improve the prediction of the Loop Current. The numerical results, the altimetry observational fields, and the respective drifter trajectories show a strong relationship between the Caribbean Anticyclones and the Loop Current variability, both at the base of the Loop Current (position of the Yucatan Current) and within the Gulf interior (northern Loop Current position and orientation). During retracted Loop Current periods, the evolution of anticyclones in the Yucatan Channel plays a role on the eastward tilt of the Loop Current axis and the zonal shift of the Yucatan Current close to the island of Cuba. Lagrangian analyses confirmed that coherent anticyclonic flux across the Yucatan Channel usually evolves closer to Cuba and is associated with retracted Loop Current phases. A lag of 5 to 10 days between the anticyclonic vorticity in the northwestern Caribbean and the Loop Current variability was identified. The evolution of Caribbean Anticyclones crossing the Yucatan Channel is thus an influencing factor on the interior dynamics of the Gulf of Mexico and the connectivity processes with the Caribbean Sea.