Hydrography and estimation of density currents in the southern part of the Bay of Campeche, Mexico

Abstract

This paper reports the temperature, salinity and sigma-t distributions at the surface, 10 and 30 m depth, derived from data obtained in the autumn of 1987 in the southern part of the Bay of Campeche, as well as the density distribution along two cross sections which intersect near the most important river system in the region. Based on density field data, density driven currents and the vertical stratification were estimated, the latter by means of the potential energy anomaly. A strong haline gradient, that dominates the sigma-t distribution and is associated with the discharge of the rivers in the region, was observed. The calculated potential energy anomaly had a maximum value of 70 J m^–3 near the mouth of the Grijalva-Usumacinta system and the San Pedro and San Pablo rivers. The surface current induced by the density gradient was estimated at 11.2 cm s^–1 northeastward. On the other hand, the distribution of isohalines and isopycnals at the surface and 10 m depth showed certain symmetry with respect to a normal axis to the coast. This axis was displaced towards the west of the mouth of the Grijalva-Usumacinta system, suggesting the existence of a littoral current in the east-west direction.