A Numerical Study of the Tide and Tidal Dynamics Effects in the Amazon River Plume

The North Brazil Continental Shelf (NBCS) shelters the plume of the world’s largest river in terms of freshwater discharge, the Amazon River. The plume extends for hundreds of kilometers offshore and along the northwest coast of Brazil and interacts with the Northern Brazil Current, a western boundary current that flows along the edge of the continental shelf. The exchange of freshwater between the two hemispheres is dependent on this interaction. This poster addresses a numerical study of the NBCS water circulation which was carried out with ROMS. The influence of the tidal currents in the vertical stratification of the Amazon River plume is investigated, as well as the along shore plume water spreading. A grid was developed with a spatial resolution of 1/24° and 10 vertical levels. The grid spans the region limited by the latitudes 2°S and 8°N and longitudes 54°W and 44°W. The experiments were configured with ETOPO bathymetry data, NCODA (Navy coupled ocean Assimilation Data) salinity data as initial condition, TPXO tide data, and river discharge measured by ANEEL (Agency national Electricity). Two experiments were conducted; one with and one without tidal forcing. Both experiments were run for 400 days. Monthly average salinity maps show that the tide has great influence on the vertical structure of the plume. Because tidal mixing changes the water plume vertical stratification, fresh water spreads across the continental shelf reaching the continental slope beyond the shelf limits.

(Nascimento, F. P. S. (UFES, Brazil);
Soares, I. D. (Atlantis, Brazil))