This thesis investigated physical oceanographic processes in the Pará River estuary, focusing on saline intrusion and hydrodynamic process. The choice of this topic arose from the motivation to consolidate the understanding of hydrodynamic and hydrographic issues in the Pará River estuary since this region of the Amazon Coastal Zone still a challenge to researchers. The first step was to define the methods and parameter to get better data in time and space difference. In this context, direct observations were conducted in the estuary in two moments, the low and high river discharge, using velocity, salinity profile (longitudinal and vertical), and temperature profile. Furthermore, in an unprecedented way, it was conducted over a year and ten months salinity and water level (tide) monitoring at strategic points of the estuary. The main conclusions of this research obtained from this data set was the identification of salt water intrusion in the estuary of the Pará River, entering about 100 km from the mouth. The sensitivity of salinity intrusion is affected by river discharge (seasonal variability), and tide energy (daily variability). The Stokes drift generated by tidal propagation in the estuary was the responsible for the net salt flux landward. The innermost portion of the estuary (more than 60 km from the mouth) does not show gravitational circulation and the estuary salt transport above is performed entirely by turbulent diffusion; and the outer portion of the resulting stream reverts to the depth and advective and diffusive processes are important to contribute to the salt transport in the estuary.
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