Dynamics of the surface circulation of La Paz bay, Mexico

The Bay of La Paz (BLP) is the largest and deepest coastal body in the Gulf of California (GC). The factors that can influence the flow of nutrients in this coastal zone are multiple: the local wind, the tide, the bathymetry, the shape of the coast, and the influence of the mesoscale structures of the GC. In particular, the literature reports the presence of an eddy in the northern area of the bay. In this work, we explore the influence of sub-mesoscale phenomena on the dynamics of the bay and the generation of the eddy. We present the balance of forces in the surface layer for the case of two observation periods with drifters in 2004. These drifters describe a trajectory in an anti-clockwise direction with an average radius of 15 km (sub-mesoscale) and an average duration inside the bay of 30 days. Our balance of forces model adequately represents the motion of the drifters. It is forced by a combination of the wind over the bay; the tidal pressure gradient; and advection through the Boca Grande at the mouth of the bay. The observed life of these structures is greater than 30 days. The presence of persistent sub-mesoscale structures poses research questions regarding their influence on the vertical transport of properties inside the bay.