Tidal propagation over fluid mud layers on the Amazon shelf

Gabioux, Mariela; Vinzón, Susana B.; Paiva, Afonso M.

doi:10.1016/j.csr.2004.09.001

Cited by 57 publications

(47 citation statements)

References 13 publications

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“…Sand is the dominant bottom sediment in the upper part of the estuary up to the mouth, and at the southern part of the Amazon continental shelf. Thick mud deposits have been recorded (AmasSeds 1990) in the front and the north of the mouth, which has been shown, is important for tidal propagation (Gabioux et al 2005).…”

Section: Description Of the Areamentioning

confidence: 99%

Generation of overtides and compound tides in Amazon estuary

2005

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Tidal propagation in estuaries is affected by friction and fresh water discharge, besides changes in the depth and morphology of the channel. Main distortions imply variations in the mean water level and asymmetry. Tidal asymmetry can be important as a mechanism for sediment accumulation and turbidity maximum formation in estuaries, while mean water level changes can affect navigation depths. Data from several gauges stations from the Amazon estuary and the adjacent coast were analyzed and a 2DH hydrodynamic model was configured in a domain covering the continental shelf up to the last section of the river where the tidal signature is observed. Based on data, theoretical and numerical results, the various influences in the generation of estuarine harmonics are presented, including that of fresh water discharge. It is shown that the main overtide, M 4 , derived from the most important astronomic component in the Amazon estuary, M 2 , is responsible for the tidal wave asymmetry. This harmonic has its maximum amplitude at the mouth, where minimum depths are found, and then decreases while tide propagates inside the estuary. Also, the numerical results show that the discharge does not affect water level asymmetry; however, the Amazon river discharge plays an important role in the behavior of the horizontal tide. The main compound tide in Amazon estuary, Msf, generated from the combination of the M 2 and S 2 , can be strong enough to provoke neap low waters lower than spring ones. The results show this component increasing while going upstream in the estuary, reaching a maximum and then slightly decaying.

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Section: Description Of the Areamentioning

confidence: 99%

Generation of overtides and compound tides in Amazon estuary

2005

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“…Os estuários do Amazonas e Pará apresentam um regime de macromaré semidiurna (Dyer 1997), com amplitudes de 4 a 6 m (Gabioux et al 2005;Gallo e Vinzon 2005). A descarga destes rios e as condições hidrodinâmicas permitem uma redução forte da salinidade da água ao longo de todo o estuário e costas adjacentes (Figura 1a; Vinzon et al 2008;Santos et al 2008;Rosário et al 2009).…”

Section: Clima E Parâmetros Estuarinosunclassified

Qualidade das águas superficiais e avaliação do estado trófico do Rio Arari (Ilha de Marajó, norte do Brasil)

et al. 2012

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A deterioração da qualidade da água pode ser causada tanto por resultado da pressão antrópica sobre os ambientes aquáticos em maiores escalas, como por fatores naturais em menores escalas, tal como ocorre em parte da bacia hidrográfica do Rio Arari (Ilha de Marajó, Pará). Este artigo teve como objetivo a avaliação da qualidade das águas superficiais e o estado trófico do Rio Arari, no trecho entre Santana e Cachoeira do Arari, considerando as variações temporais e espaciais de variáveis físicas, químicas e biológicas da água em dois períodos hidrológicos distintos de 2009: descarga máxima (abril e maio) e descarga mínima (setembro e novembro). Os Índices de Qualidade da Água (IQA) e Estado Trófico (IET) foram determinados simultaneamente em amostras de água superficial durante 12 horas consecutivas nas três estações de coleta ao longo do Rio Arari. Os valores do IQA variaram entre "Ruim" e "Regular", e estão provavelmente relacionadas aos elevados níveis de coliformes fecais, baixas concentrações de oxigênio dissolvido e pH ácido do Rio Arari. Conforme o IET, o rio pode ser classificado como supereutrófico e hipereutrófico, reflexo da grande disponibilidade de nutrientes (e.g. fósforo) e elevada biomassa fitoplanctônica em termos de clorofila a. O Rio Arari está sob um processo de eutrofização natural, visto que as fontes de contaminação antrópica ainda são incipientes, mas elas podem contribuir para um processo de longo prazo de eutrofização artificial. PalavRas-Chave: Eutrofização, Índices de qualidade da água, Índice de estado trófico, Hidroquímica. Surface water´s quality and trophic status assessment in the Arari River (Marajo Island, Northern Brazil) abstRaCtThe deterioration of the water quality may be caused either by the result of human pressure on aquatic environments in larger scales, or by natural factors in smaller scales, such as part of the Arari River basin (Marajó Island, Pará state, Brazil) .This work aimed to evaluate the surface water´s quality and the trophic state of the Arari River, between Santana and Cachoeira do Arari localities, taking into account the seasonal and spatial variations of physical, chemical and biological parameters in two different hydrological periods in 2009: the maximum discharge (April to May) and minimum discharge (September to November). The Water Quality Index (WQI) and Trophic State Index (TSI) were determined simultaneously in water surface's samples collected during 12 consecutive hours in three stations along the Arari River. The WQI data ranged from "Poor" and "Regular" and are probably related to the high levels of fecal coliform, low concentrations of dissolved oxygen and acid pH of the Arari River. Regards the TSI, the river may be classified as "supereutrophic" and "hipereutrophic", indicating the wide availability of nutrients (e.g. phosphorus) and high phytoplankton biomass in terms of chlorophyll a content. The Arari River is under a natural eutrophication, since the sources of anthropic contamination are still incipient, although they may contribute...

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“…Here, we demonstrate this using two examples. The first is of the Amazon shelf, with concentrations of more than 100 g/l (Kineke and Sternberg 1995), while the average bed shear stresses are estimated by model studies to be of the order of 1 Pa (Gabioux et al 2005). The second example is the Ems River, where concentrations of over 30 g/l have been observed (Talke et al 2009), while bed shear stresses are up to 2 Pa (Van Maren et al 2015).…”

Section: Necessity Of Hindered Settling To Reproduce High Concentrationsmentioning

confidence: 99%

The hyperturbid state of the water column in estuaries and rivers: the importance of hindered settling

2018

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Over the last few decades, some estuaries have undergone a transition to a hyperturbid state, characterised by suspended sediment concentrations of several grammes per litre averaged over the water column. To improve our understanding of this transition and of naturally hyperturbid estuaries, we systematically identify the processes allowing for high suspended sediment concentrations using a water column (1DV) model. Under a range of realistic forcing conditions, the state of the water column can be characterised by one of two equilibrium states. The first is an erosion-limited state, in which there still is sediment available for erosion at the bed. We find that this state only occurs with relatively low concentrations. The second is a supply-limited state, in which all erodable sediment is in suspension. The concentration in this state depends entirely on the amount of sediment in the system and can potentially be very high. We identify the conditions under which the state of the water column can jump from a low to a high concentration and identify hysteresis in the transition between the two states. The mechanism responsible for this hysteresis is hindered settling. It thus follows that hyperturbidity is only possible in a supply-limited state. From this observation we derive a necessary condition for an estuarine system to make the transition from low turbidity to hyperturbidity in a 1DV context. This is an important step towards understanding why some estuaries are hyperturbid and assessing the risk that particular estuaries may become hyperturbid in the future.

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Tidal propagation over fluid mud layers on the Amazon shelf

Cited by 57 publications

References 13 publications

Generation of overtides and compound tides in Amazon estuary

Generation of overtides and compound tides in Amazon estuary

Qualidade das águas superficiais e avaliação do estado trófico do Rio Arari (Ilha de Marajó, norte do Brasil)

The hyperturbid state of the water column in estuaries and rivers: the importance of hindered settling

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