Castro Belmiro Mendes
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PreprintNumerical study of circulation on the inner Amazon Shelf( 2008-06-02) Fontes, Roberto Fioravanti Carelli ; Castro, Belmiro Mendes ; Beardsley, Robert C.We studied the circulation on the coastal domain of the Amazon Shelf by applying the hydrodynamic module of the Estuarine and Coastal Ocean Model and Sediment Transport - ECOMSED. The first barotropic experiment aimed to explain the major bathymetric effects on tides and those generated by anisotropy in sediment distribution. We analyzed the continental shelf response of barotropic tides under realistic bottom stress parametrization (Cd), considering sediment granulometry obtained from a faciologic map, where river mud deposits and reworked sediments areas are well distinguished, among others classes of sediments. Very low Cd values were set in the fluid mud regions off the Amapa coast (1.0 10-4 ), in contrast to values around 3:5 10-3 for coarser sediment regions off the Para coast. Three-dimensional experiments represented the Amazon River discharge and trade winds, combined to barotropic tide influences and induced vertical mixing. The quasi-resonant response of the Amazon Shelf to the M2 tide act on the local hydrodynamics by increasing tidal admittance, along with tidal forcing at the shelf break and extensive fluid mud regions. Harmonic analysis of modeled currents agreed well with analysis of the AMASSEDS observational data set. Tidal-induced vertical shear provided strong homogenization of threshold waters, which are subject to a kind of hydraulic control due to the topographic steepness. Ahead of the hydraulic jump, the low-salinity plume is disconnected from the bottom and acquires negative vorticity, turning southeastward. Tides act as a generator mechanism and topography, via hydraulic control, as a maintainer mechanism for the low-salinity frontal zone positioning. Tidally induced southeastward plume fate is overwhelmed by northwestward trade winds so that, along with background circulation, probably play the most important role on the plume fate and variability over the Amazon Shelf.
Technical ReportA multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) : physical oceanography moored array component(Woods Hole Oceanographic Institution, 1992-09) Alessi, Carol A. ; Lentz, Steven J. ; Beardsley, Robert C. ; Castro, Belmiro Mendes ; Geyer, W. RockwellA Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) is a cooperative research program by geological, chemical, physical, and biological oceanographers from Brazil and the United States to study sedimentary processes occurring over the continental shelf near the mouth of the Amazon River. The physical oceanography component of AmasSeds included a moored array deployed on the continental shelf approximately 300km northwest of the Amazon River mouth near 3.5°N. The moored array consisted of a cross-shelf transect of three mooring sites located on the 18-m, 65-m, and 103-m isobaths. The moored array was deployed for approximately 4 months, from early February, 1990 to mid-June, 1990, obtaining time series measurements of current, temperature, conductivity, and wind. This report describes the physical oceanography moored array component and provides a statistical and graphical summary of the moored observations.