Circulation and salt intrusion in the Piaçaguera Channel, Santos (SP)

Abstract

Analysis of thermohaline properties and currents sampled at an anchor station in the Piaçaguera Channel (Santos Estuary) in the austral winter was made in terms of tidal (neap and spring tidal cycles) and non-tidal conditions, with the objective to characterize the stratification, circulation and salt transport due to the fortnightly tidal modulation. Classical methods of observational data analysis of hourly and nearly synoptic observations and analytical simulations of nearly steady-state salinity and longitudinal velocity profiles were used. During the neap tidal cycle the flood (v<0) and ebb (v>0) velocities varied in the range of -0.20 m/s to 0.30 m/s associated with a small salinity variation from surface to bottom (26.4 psu to 30.7 psu). In the spring tidal cycle the velocities increased and varied in the range of -0.40 m/s to 0.45 m/s, but the salinity stratification remained almost unaltered. The steady-state salinity and velocity profiles simulated with an analytical model presented good agreement (Skill near 1.0), in comparison with the observational profiles. During the transitional fortnightly tidal modulation period there was no changes in the channel classification (type 2a - partially mixed and weakly stratified), because the potential energy rate was to low to enhance the halocline erosion. These results, associated with the high water column vertical stability (RiL >20) and the low estuarine Richardson number (RiE=1.6), lead to the conclusions: i) the driving mechanism for the estuary circulation and mixing was mainly balanced by the fresh water discharge and the tidal forcing associated with the baroclinic component of the gradient pressure force; ii) there was no changes in the thermohaline and circulation characteristics due to the forthnigtly tidal modulation; and iii) the nearly steady-state of the vertical salinity and velocity profiles were well simulated with a theoretical classical analytical model.<br>A análise de dados termohalinos e correntes medidos em uma estação fixa no Canal de Piaçaguera (Estuário de Santos) no inverno foi feita em termos de condições cíclicas da maré (quadratura e sizígia) e quase-estacionária, com o objetivo de caracterizar a estratificação da massa de água estuarina, sua circulação e transporte de sal forçados pela modulação quinzenal da maré. Foram utilizados métodos clássicos de análise de dados observacionais horários e quase sinóticos e de simulações analíticas de perfis estacionários de salinidade e do componente longitudinal da velocidade. Durante o ciclo de maré de quadratura as velocidades de enchente (v<0) e vazante (v>0) variaram de -0.20 m/s a 0.30 m/s, associadas à pequena variação de salinidade entre a superfície e o fundo (26.4 psu a 30.7 psu). No ciclo de sizígia a velocidade aumentou de -0.40 m/s a 0.45 m/s, mas a estratificação de salinidade permaneceu praticamente a mesma. Os perfis estacionários teóricos de salinidade e de velocidade apresentaram boa concordância (Skill próximo a 1,0) quando comparados aos perfis observacionais. Durante a m...

Circulation and salt balance in the São Francisco river Estuary (NE/Brazil)

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Improvement of an Operational Forecasting System for Extreme Tidal Events in Santos Estuary (Brazil)

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“…Santos harbor is the most important port in Brazil and the largest harbor in Latin America, which traded more than 110 million tons of cargo in the year 2018 [7]. The Santos estuary is a complex system whose geometry and river discharge has been drastically altered during the last century by urban and industrial development, land reclamation, dredging and effluent reception from multiple industries [6]. The estuary receives freshwater inflow from several small rivers that develop on the slopes of Serra do Mar, at heights of 700 meters [8].…”

“…The main forcing agent driving water circulation is the tide, with an average amplitude of 1.43 m (measured at Santos port), being considered a micro-tidal estuary. The estuary is partially mixed to stratified, where the salt transport within the estuary is due to the up-estuary propagation of the salt wedge and eddy diffusion [6], inducing changes in circulation patterns. The estuarine system is characterized by a flat area surrounded by scarps of the plateau of Serra do Mar [1], and bordered by the cities of Santos, S. Vicente, Guarujá, Bertioga and Cubatão, which is one the most industrialized areas of South America [6].…”

Seasonal Hydrodynamics and Salt Exchange of a Shallow Estuary in Northern China

“…Previous studies showed that net salt flux is a balance of advection flux and a number of dispersive fluxes, including tide effect, shear effect and turbulence effect. The tidal effects are component of tidal sloshing, Stokes drift and cross-correlation between tide and salinity ( Kjerfve, 1986;Miranda et al, 2012;Restrepo and Kjerfve, 2002) . In steady-state, there is a balance between seaward advection of fluvial discharge and landward dispersion of saltier ocean water ( Hunkins, 1981;Miranda and Kjerfve, 1998;Siegle et al, 2009;Simpson et al, 1997;Uncles and Lewis, 2001) .…”