What Lagrangian Trajectories Reveal about Deep Circulation in the Western Gulf of Mexico

A major Lagrangian program is underway to map the deep (1500-2500) circulation of the entire Gulf of Mexico. From 2011 through 2015, ~180 two-year acoustically-tracked RAFOS floats were released across the Gulf, many in pairs and triplets. In the western Gulf, the float trajectories reveal a slow persistent deep boundary current along the Gulf boundary, from the Mississippi Fan to the eastern Campeche Bank. Trajectories show that this boundary current is interrupted, or split, mid-traverse of the Campeche Bank slope, as an accelerating jet separates and turns northward, into the interior Gulf. The trajectories show the first-ever observations of deep energetic anticyclonic eddies (possibly lenses) forming at and separating from this northeastward-flowing current. This eddy formation region appears to be a major exchange site between the deep boundary current along the Mexican continental slope and the interior Gulf. The pathways of the deep trajectories also challenge the idea of deep closed-streamline cyclonic circulation under the Campeche Gyre.