The Physical Oceanography of the Amazon Outflow

Abstract

The North Brazil Current sweeps the waters over the outer shelf and slope northwestward at speeds reaching 1-2 m s -j (Flagg et al.. 1986; Previous current measurements on the shelf indicate across-shelf tidal velocities of 1-2 m s-~ The persistent trade winds impose a cross-shelf wind stress as large as 1 dyn cm -2 The Amazon River discharge, the North Brazil Current transport, and the trade winds all exhibit strong seasonal cycles (see Figure These energetic and highly variable forcing functions result in considerable variability in the hydrographic structure and currents on the Amazon shelf, which in turn lead to marked variations in the transport and fate of sediments and waterborne material. The tremendous flux of suspended sediment is regulated by the structure and energetics of the flow; hence the distribution and deposition of sediments as well as particle-reactive chemicals are intrinsically coupled to the physical oceanographic regime.