Tidal and subtidal oscillations in a shallow water system in southern Brazil

Abstract

Andrade et al.: Sea level oscillations in shallow waters 245 Tidal and subtidal oscillations in a shallow water system in southern Brazil Sea level oscillations in time scales between hours and days have a great vertical amplitude regarding the low lying coastal gradient of the beaches in the Rio Grande do Sul coast. However, the mechanism of oscillations is poorly understood since the scarcity of observational data makes it impossible to determine the forces that control sea level oscillations. Therefore, hourly sea level and wind time series with a time period of 650 days were examined. It has been found that the mean tidal and subtidal amplitudes were very similar to each other and that a considerable portion of the energy from sea level oscillations was due to astronomical forces. A new perspective was introduced when high and low frequencies were compared, leading to the comprehension that astronomical tides should be considered in coastal studies in southern Brazil. The sea level time series analyzed in this study showed that the maximum amplitude of the high spring tide was 0.53m, and that the subtidal rise caused by the wind reached up to 0.66m. In general, when large tidal and subtidal amplitudes are added, it can generate extreme events of sea level rise on the coast, which constitute a direct threat to coastal communities and habitats.

Tide level in time and frequency domains at Dili port: Characteristic feature of a Lorentz oscillator

“…In addition to gravitational motion of the sun, the moon, and the earth, meteorology effects such as atmospheric pressure and wind power also contribute to the tide level (Andrade et al 2018;Truccolo et al 2006). Other contributing factors include the shape of the beach, coastline, and coastline depth (Kleinhans et al 2017;Marone et al 2013).…”

“…It should be mentioned that the studies on the tidal changes from the area near the equator are few. Here, we will only focus on gravitational effects, while the meteorological effects, in general, cannot be ignored (Andrade et al 2018;Pugh 1996;Truccolo et al 2006). It is shown that the tide levels are dominated Tide level in time and frequency domains... by four major gravitational constituents from the sun and the moon (M2, S2, K1, O1) and tide level dynamics is replicated well by the Lorentz-type resonance (Wooten 1972).…”

“…An analogy between the electronic polarization in microscopic media and the macroscopic tidal changes is of interest in complex systems in physics (Draper et al 2014;Garrett, Cummins 2005). It is suggested, through this equivalency, that the 1/f-like nature originates only from the gravitational effect, while its origin is commonly attributed to a change in meteorology (Andrade et al 2018).…”

Free and Open-Source Software for Geographic Information System on Coastal Management: A Study Case of Sea-Level Rise in Southern Brazil

“…The tide is semidiurnal, with an average range of about 0.5 m. Storm surges are frequent and can raise the water level by more than 1 m [45]. Based on a 30-year (1979 and 2008) deep-water wave modeling with the NOAA WAVEWATCH III®, the average wave directions are from south quadrant (~51%, the sum of annual occurrence), followed in order of importance by east quadrant (~43%, the sum of annual occurrence).…”

Padrões De Empilhamento Estratigráfico E Seus Reflexos Na Morfologia Da Barreira Costeira Holocênica No Litoral Médio Do Rio Grande Do Sul, Brasil

“…As marés ao longo da costa oceânica do Rio Grande do Sul são semidiurnas com amplitude de micro--maré (<50 cm). Forçantes meteorológicas e oscilações em frequência submareal podem sobrelevar o nível d'água em mais de 66 cm (ANDRADE et al, 2018). Com base em dados de campo e em modelagem numérica, as direções de onda predominantes na plataforma ROSA et al, 2017).…”