In Situ Measurements of Circulation Features Influencing Cross‐Shelf Transport Around Northwest Cuba

Abstract

AbstractWe analyzed circulation processes sampled in the Gulf of Mexico in May 2016 by the National Oceanic and Atmospheric Administration (NOAA) Ship Nancy Foster. This data set is one of the first in situ surveys in Cuban waters available to the international community. Along northwest Cuba, these data suggested coastal upwelling and revealed, for the first time, a ~50 km diameter Cuban ANticyclonic (CubAN) eddy and a ~25 km diameter cyclonic eddy, which together advected upwelled waters offshore. The CubAN eddy was associated with downwelling, and the cyclonic eddy with upwelling. At the western tip of Cuba, local currents were predominantly anticyclonic, presumably due to the proximity of the retracted Loop Current, with limited export of coastal waters. Conversely, additional data from two cruises when the Loop Current was extended showed cyclonic circulation within upwelling filaments extending far offshore. These processes are important, as they can potentially entrain marine organism larvae from local reefs into the Loop Current system and to other reef ecosystems of the region. They might also affect the transport of pollutants, as hydrocarbons in case of a spill in Cuban waters. The 2016 cruise took place after the shedding of a Loop Current Ring, which involved an unusually large (~250 km) cyclonic frontal eddy. The eddy signature was observed down to 1,200 m depth, deeper than the Loop Current. A surface drifter revealed a low relative vorticity (0.19 f) inside the eddy. Along its southern edge, filaments exported from the Campeche Bank were associated with high relative chlorophyll a at 3,060 m depth.