THE M2 AND M4 TIDES IN THE PARÁ RIVER ESTUARY

The Para River estuary is a complex and special system in amazon continental shelf, with micro and mesoscale physical processes generated by forces of different sources (e.g., astronomical tides and river discharge). In this study, the main semidiurnal (M 2 ) and the overtide (M 4 ) components were analyzed by quantifying distortions degrees and identifying tidal asymmetries in the Para River estuary. Two submersible tidal gauges were moored to measure the water level. One on the right margin (point #RG) and another on the left margin (#LF) recorded measurements 6 months (from September 2014 to March 2015). Furthermore, we used harmonic charts from Marine Studies Foundation (FEMAR, Fundacao de Estudos do Mar). Lateral variations were also identified between #RG and #LF points from the amplitude and phase cotidal charts, with about 10 minutes delay and variation of 2 cm in tidal amplitude. We verified that the tidal wave enters in system by the right margin (#RF). The results show distortion degrees higher than 10% and positive asymmetry of the tidal wave in the Para River, and the tidal attenuation in the estuary may be greater than 400 km upstream along the drainage basin. Keywords: Tidal distortion, Tidal asymmetry, Tidal components, Lateral variations.