Interaction of anticyclonic eddies with the topography in the western Gulf of Mexico

The western Gulf of Mexico (GoM) is strongly dominated by the presence of Loop Current eddies (LCEs) (~100-200 km diameter), in particular the region north of 22^oN they impinge on the slope and continental shelf, interact with the topography, and dissipate. These anticyclonic coherent structures are important because they trap and transport westward heat, salt, and tracers across the Gulf. The propagation of coastal trapped waves (or Topographic Rossby Waves, TRWs) in the western Gulf of Mexico which propagate anticlockwise along the topography has been strongly discussed during the last several years, however, the generation mechanism of these subinertial waves is still unknown. It has been proposed that the TRWs could be forced by meridional Loop Current vacillations, LCE shedding, or directly by LCEs. Total velocity measurements have been made in the western and southwestern part of the GoM using 30 moorings highly instrumented with acoustic Doppler current profilers that sampled continuously the water column from the near-surface to the bottom at one hour resolution during more than 5 years (July 2008 – October 2013). Spatial decorrelation scales were estimated from the space-time dataset and then used to interpolate objectively in order to get maps of the regional circulation at constant depth levels. Several features are discussed; in particular it is shown deep coherent structures (dipoles) coupled with upper ocean LCEs and the dissipation of these LCEs by generation of topographic wave energy.