Topographic controls on the Loop Current System variability

The Loop Current (LC) system, which consists of the LC and its associated eddies, is strongly affected by the complex topography of the Gulf of Mexico (GoM). The GoM exhibits strong topographic gradients in the Northeastern GoM and along the West Florida Shelf (WFS) that the LC and cyclonic frontal eddies interact with along their path. We investigate the extent to which the topography of the WFS affects the behavior of the LC system and the exchange of properties between shelf and deep waters along the continental margin. We approach the problem numerically, by employing the Hybrid Coordinate Ocean Model (HYCOM), at 1/25° horizontal resolution and 26 hybrid vertical layers, applied on the GoM (GoM-HYCOM) for a 5-year period (2007-2011). Realistic topography simulations are analyzed in comparison to simulations with targeted (WFS shelf and slope) modifications to quantify topographic controls on the variability of the predominant Gulf Stream boundary current system in the GoM (LC and associated anticyclonic and cyclonic frontal eddies). Based on an energetics perspective, we examine the main hypothesis that the modified WFS topography promotes the LC to extend farther into the northern GoM with an enhanced westward tilt that favors the Loop Current Eddy (LCE) shedding in the basin interior, a major factor in LC variability and cross-basin connectivity. The energetic analyses include the response of the eddy field on topographic controls, as cyclonic frontal eddies are associated with LCE shedding and LC extension. Results will be shown along the WFS slope, focusing on topography influence on cyclonic eddy intensification. A particular example is the southern WFS slope, where topography influences cross-marginal exchanges through the release of anticyclonic eddies from the LC that travel along the WFS slope, in addition to the LCE that travels in the deep interior.