Contribution of the wind and Loop Current Eddies to the circulation in the southern Gulf of Mexico

The Bay of Campeche in the southern Gulf of Mexico (GoM) is characterized by a semi-permanent cyclonic circulation commonly referred to as the Campeche Gyre (CG). Several studies, documenting its upper layer structure, have suggested a relationship between its seasonal occurrence and the wind, and have proposed that non-seasonal variability arises mainly from interaction of the gyre with Loop Current Eddies that arrive in the region. Other studies have shown that the topography of the region is such that an equivalent-barotropic flow can develop, confining the CG to the west of the bay. Nevertheless, a partition of the contributions of these forcings to the circulation of the gyre in a statistically consistent manner is still needed. In this study, the wind-and eddy-driven circulation are examined with a set of long-term numerical simulations of the GoM using HYCOM. Our results show that, in the absence of eddies, the wind is able to sustain a seasonal-modulated circulation in the CG, confined within the upper 600 m. When LCEs are taken into consideration, the gyre appears to extend below 1000 m, however this behavior results from the presence of the cyclonic bottom boundary current in the southern GoM. Interaction with eddies impose high fluctuations in the circulation of the gyre at intraseasonal time scales, leading to reversals in the current if the event is strong. Additionally , we provide evidence of a northward flux of cyclonic vorticity out of the bay during eddy-gyre interaction events. Finally, we found that the role of topography manifests similarly among these different dynamic conditions, resulting in closed geostrophic contours to the west of the bay that confine an upper-layer, symmetric, equivalent-barotropic CG.