Meridional circulation in the tropical North Atlantic

Abstract

A transatlantic CTD/ADCP section nominally located at 11°N was carried out in March 1989. In this paper relative geostrophic velocities are computed from these data via the thermal wind balance, with reference level choices based primarly on water mass distributions. A brief overview of the meridional circulation of the upper waters resulting from these analysis techniques is presented. Schematic circulation patterns of the NADW and AAW are also presented. In both the western and eastern basins these waters are characterized by cyclonic recirculation gyres. A paricularly notable result of the deep western basin analysis is the negligible net flow of middle NADW. Although the horizontal circulation patterns described in this study agree well with results from many previous studies, the meridional overturning cell and net heat flux are considerably lower, while the net freshwater flux is slightly higher than previous estimates. These discrepancies may be attbuted to: (1) differences in methodologies, (2) the increased resolution of this section, and (3) temporal (including decadal, synoptic, and most importantly, seasonal) variability.