Deep Lagrangian Trajectories Under the Loop Current in the Eastern Gulf of Mexico

Between July 2011 and October 2013, ~ 180 isobaric RAFOS floats were deployed in the Gulf of Mexico at nominal depths of 1500 and 2500 m. Resulting mission lengths ranged from 3 to 21 months. The Loop Current (LC) dominates the eastern Gulf of Mexico basin with dynamics that include the extension to the north or northwest, the shedding of large anticyclones or LC eddies, and the development of frontal eddies and meanders with wavelengths of ~ 100 to 400 km and time scales of ~ 10 to 100 days. Below the LC, flows are largely depth independent, and deep eddies are spun up over a few months prior to, or during a LC eddy detachment by baroclinic instabilities. Lagrangian floats provide a unique perspective on these deep circulation processes, including coupling to large-scale meanders (derived from altimeter sea-surface height maps) on the north and east sides of an extended LC, mean flows, and the radiation of deep energy towards the northwest and west in the form of eddies and topographic Rossby waves. It was noteworthy that relatively few of the floats deployed in the eastern basin transferred to the western Gulf. Also, none of the 1500-m floats were exported to the Caribbean through the Yucatan Channel (2000 m sill depth) during the course of the experiment.