Deep Currents in the Bay of Campeche

Abstract

ata from five moorings deployed in the Bay of Campeche during November 2007?July 2008 are used to analyze subinertial motions of waters below 1000-m depth. To the authors? knowledge, this is the first time such a comprehensive observational program of direct deep-current measurements has been carried out in the region. The mean currents are in agreement with a cyclonic circulation at 1000-m depth; however, this cyclonic pattern is not so clearly defined at deeper levels. Only at the deepest mooring, located at 3500-m depth, are the mean currents uniform all the way to the bottom. Over the Bay of Campeche?s smooth western slope, currents show features compatible with topographic Rossby waves having vertical trapping scales thicker than 700 m, periods between 5 and 60 days, and horizontal wavelengths of 90?140 km. In contrast, the eastern slopes are characterized by rough topography, and motions with periods longer than 28 days decrease toward the bottom, suggesting a substantial reduction in the low-frequency topographic Rossby wave signal. Velocities from one of the two neighboring moorings located over the eastern rough slope have a strong 3-day period signal, which increases toward the bottom and has a vertical trapping scale of about 350 m. These higher frequency motions are interpreted in terms of edge waves.