Contribuição para o estudo da morfodinâmica da embocadura da Ria de Aveiro

Doutoramento em FisicaOver the years it was observed at the Ria de Aveiro lagoon inlet, near the head of the north breakwater, a depth increase that might threaten the stability of this structure. A trend of accretion in the navigation channel of this lagoon is observed, endangering the navigation in this region. In order to understand the origin of these and other trends observed, the knowledge of the sediment transport in the study area is imperative. The main aim of this work is understanding the dominant physical processes in the sediment transport of sediment at the Ria de Aveiro lagoon inlet and adjacent area, improving knowledge of this region morphodynamics. The methodology followed in this study consisted in the analyzes of the topohydrographic surveys performed by the Administration of the Aveiro Harbor, and in the numerical simulations results performed with the morphodynamic modeling system MORSYS2D. The analysis of the surveys was performed by studying the temporal evolution of the bathymetry. The numerical analysis was based on the implementation of the model at the study area, sensitivity analysis of the formulations used to compute the sediment transport to the variation of input parameters (e.g. depth, sediment size, tidal currents) and analysis of the sediment uxes and bathymetric changes predicted. The simulations considered as sediment transport forcing the tidal currents only and the coupled forcing of tides and waves. Considering the wave e ect as sediment transport forcing, both monochromatic waves and a wave regime were simulated. The results revealed that the observed residual sediment transport patterns are generated due to the channel con guration. Inside the lagoon the uxes are mainly induced by the tidal currents action, restricting the action of waves to the inlet and adjacent coast. In the navigation channel the residual sediment uxes predicted are directed o - shore with values between 7 and 40 m3=day generating accretions of approximately 10 m3=day for the shallower region and 35 m3=day for the region between the tidal gauge and the tri^angulo das mar es. At the inlet, the residual uxes are approximately 30 m3=day inducing trends of erosion of approximately 20 m3=day. At the North side of the nearshore accretion is predicted, while at the South side is predicted erosion, at the rates of 250 and 1500 m3=day, respectively. It was also concluded that the waves with higher contribution to the residual sediment uxes are those with heights between 4 and 5 m. However, the storm waves with heights bigger than 5 m, despite their 10% of frequency of occurrence are responsible for 25% of the observed sediment transport.Ao longo dos anos observou-se junto ao quebramar norte da embocadura da Ria de Aveiro um aumento da profundidade, que poder a colocar em perigo a estabilidade desta mesma estrutura. E igualmente observada uma tendência de acreção no canal de navegação desta laguna, colocando em risco a navegabilidade nesta região. Para compreender a causa destas tendências e de outras observadas, e necess ario um conhecimento do transporte de sedimentos nesta região de estudo. Este trabalho tem assim como objectivo principal a compreensão dos processos físicos dominantes no transporte de sedimentos na embocadura e area adjacente da Ria de Aveiro, aumentando os conhecimentos da morfodinâmica desta região. A metodologia seguida neste estudo consistiu na análise de levantamentos topohidrográficos realizados pela Administração do Porto de Aveiro e de resultados de simulações num ericas efectuadas com o sistema de modelos morfodinâmico MORSYS2D. A análise dos levantamentos foi feita através do estudo de evolução temporal da batimetria. A análise numérica teve como base a implementação do modelo para a area de estudo, análises de sensibilidade das fórmulas de cálculo do transporte de sedimentos a variação de parâmetros de entrada (por exemplo: profundidade, diâmetro médio do sedimento, velocidade da corrente de mar e), e análise dos resultados numéricos de uxos de sedimentos e de variações batimétricas. As simulações efectuadas consideraram apenas o for camento de correntes de mar e e o forçamento conjunto de mar e e ondas no transporte de sedimentos. No caso do forçamento de ondas foram efectuadas simulações com ondas monocromáticas e com um regime de agitação real. Os resultados revelaram que os padrões observados para o transporte residual de sedimentos têm origem na configuração do canal. Verificou-se também que no interior da laguna os uxos são maioritariamente induzidos pela acção do campo de correntes de mar e, restringindo-se a acção do campo de agitação a embocadura e costa adjacente. No canal de navegação são previstos uxos residuais de sedimentos direccionados para o exterior da laguna que oscilam entre 7 e 40 m3=dia e originam acreções na ordem de 10 m3=dia na região menos profunda e de 35 m3=dia para a região entre o mar egrafo e o triângulo das marés. Na região da embocadura os uxos residuais de sedimentos são de aproximadamente 30 m3=dia gerando tendências de erosão de aproximadamente 20 m3=dia. Na area exterior da embocadura e prevista acreção a Norte da embocadura e erosão a Sul as taxas de 250 e 1500 m3=dia, respectivamente. Concluiu-se ainda que as ondas com maior contributo para o uxo residual de sedimentos têm alturas compreendidas entre 4 e 5 m. No entanto, as ondas de tempestade, com alturas superiores a 5 m, apesar de terem apenas 10% de frequência de ocorrência são respons aveis por 25% do transporte de sedimentos observado

The marine heatwave west of Ireland in June 2023

The summer of 2023 had been notable for a number of climate extremes: sea ice in the Antarctic dropped to its lowest for the time of year since satellite records began in the 1970s (NASA Earth Observatory, 2023), terrestrial heatwaves engulfed southern Europe and southern United States/Mexico that would have been ‘virtually impossible’ without climate change (WorldWeatherAttribution, 2023), and sea-surface temperatures (SSTs) in the North Atlantic reached their highest since satellite records began in 1982 (NOAA, 2023). In concert with these terrestrial heatwaves and high Atlantic SSTs, a severe marine heatwave(MHW) developed in the eastern North Atlantic, west of Ireland (Figure 1a). Except for a narrow band close to the coast from Greenland to Canada, SSTs everywhere in the North Atlantic were above the 41-yearaverage (1982–2023), with many regions experiencing temperatures 2 degC higher than average. In the study region westof Ireland (highlighted in Figure 1b), the SST reached an impressive 4 degC above average

Esquemas de elementos finitos para ondas dispersivas

Tese de mestrado. Métodos Computacionais em Ciências e Engenharia. 2005. Faculdade de Engenharia. Universidade do Port

Coastal wave regime influence on Ria de Aveiro inlet dynamics

The adjacent coastal zone of Ria de Aveiro lagoon is exposed to a highly energetic wave climate, with a yearly mean significant wave height of 2-2.5 m and wave periods of 9-11 s, corresponding to WNW to NNW swell. Consequently, it should be expected that the lagoon inlet hydrodynamic be dependent on the coupled forcing of tidal wave and wave regime. Thus, the main goal of this study is to assess the influence of the coastal wave regime at the inlet channel dynamics. The modeling system MORSYS2D, comprising the hydrodynamic model ELCIRC coupled with the wave model SWAN, is used to perform this study. The methodology developed consists in forcing the numerical models with local tidal harmonic constituents and with different constant regular wave scenarios typical of the northern Portuguese coast (high and normal wave activity and absence of waves). Under the normal wave activity scenario results show that the inlet channel hydrodynamics is mainly dominated by the tidal forcing. For the highest wave regime are found higher sea levels induced by the wave set-up. Consequently, it was found that the storm events induce important wave's set-up that change the inlet hydrodynamics, requiring that the coupling between waves and tides should required to accurately represent the physical processes of the lagoon. Although the dominant forcing of the Ria de Aveiro inlet hydrodynamics is the tide, it may be concluded that fluctuations at the wave regime influences the sea level and current velocity at the Ria de Aveiro inlet.This work was been supported by FCT and by European Union (COMPETE, QREN, FEDER) in the framework of the research project PTDC/AAC-AMB/113469/2009 - PAC:MAN - Pollution accidents in coastal areas: a Risk management system. The authors thank Profs. Y. Zhang and A.M. Baptista for the model ELCIRC (www.stccmop.org/CORIE/modeling/elcirc) and to Anabela Oliveira, André Fortunato and Alberto Azevedo from the Portuguese National Laboratory of Civil Engineering (LNEC) for adapting and making available the numerical codes used.publishe

HGPT2: An ERA5-Based Global Model to Estimate Relative Humidity

The neutral atmospheric delay is one of the major error sources in Space Geodesy techniques such as Global Navigation Satellite Systems (GNSS), and its modeling for high accuracy applications can be challenging. Improving the modeling of the atmospheric delays (hydrostatic and non-hydrostatic) also leads to a more accurate and precise precipitable water vapor estimation (PWV), mostly in real-time applications, where models play an important role, since numerical weather prediction models cannot be used for real-time processing or forecasting. This study developed an improved version of the Hourly Global Pressure and Temperature (HGPT) model, the HGPT2. It is based on 20 years of ERA5 reanalysis data at full spatial (0.25° × 0.25°) and temporal resolution (1-h). Apart from surface air temperature, surface pressure, zenith hydrostatic delay, and weighted mean temperature, the updated model also provides information regarding the relative humidity, zenith non-hydrostatic delay, and precipitable water vapor. The HGPT2 is based on the time-segmentation concept and uses the annual, semi-annual, and quarterly periodicities to calculate the relative humidity anywhere on the Earth’s surface. Data from 282 moisture sensors located close to GNSS stations during 1 year (2020) were used to assess the model coefficients. The HGPT2 meteorological parameters were used to process 35 GNSS sites belonging to the International GNSS Service (IGS) using the GAMIT/GLOBK software package. Results show a decreased root-mean-square error (RMSE) and bias values relative to the most used zenith delay models, with a significant impact on the height component. The HGPT2 was developed to be applied in the most diverse areas that can significantly benefit from an ERA5 full-resolution model

Influence of morphological changes in a lagoon flooding extension: case study of Ria de Aveiro (Portugal)

Coastal lagoons are interface zones where land, water and atmosphere interact in a dynamic balance that is constantly being changed by natural and human influence. The hydrodynamics and morphology of these coastal systems continuously adapt to changes in the forcing agents and show a complex interconnection. Worldwide studies show that tidal propagation is strongly dependent on local morphologic features. Attending to these concerns, the present study aims to assess the changes in flooding extension at Ria de Aveiro, as well as in the tidal prism, induced by local morphological modifications. The analysis of the topo-hydrography available for the Ria de Aveiro, comprising two general surveys carried out in 1987/88 and 2011 and two updates of the inlet bathymetry performed in 2001 and 2012, shows the deepening of the lagoon main channels and of the inlet evolving region. A flooding assessment of the lagoon margins and the determination of the tidal prism were performed applying the hydrodynamic model ELCIRC considering the four morphologic configurations described and different tidal conditions. The numerical results show the importance of lagoon morphological changes, which induce an increase of about 16% between 1987/88 and 2012 in the lagoon flooded area for spring tide. The new flooded regions correspond to the margins of S.Jacinto channel head and lagoon central areas. Additionally, the tidal prism results evidence a redistribution of the water volume flowing into the lagoon among their main channels during the period under analysis.The European Commission, under the 7th Framework Programme, also supported this study through the collaborative research project LAGOONS (contract n°283157).publishe

Assessment of the spawning habitat, spatial distribution, and Lagrangian dispersion of the European anchovy (Engraulis encrasicolus) early stages in the Gulf of Cadiz during an apparent anomalous episode in 2016

Modelling the environmental factors influencing the spatial variation of fish early life stages density and their drift history can identify the key biological and physical processes for the recruitment variability. Distance-based linear multivariate techniques were used to characterize the spawning areas of the European anchovy Engraulis encrasicolus in the Gulf of Cadiz (GoC). Chlorophyll is the environmental variable that best characterized its spawning areas with a time-lag of three days. The use of Lagrangian models to simulate the dispersal of small pelagic species more dependent on advection such as the European anchovy early life stages (early larvae and eggs) in the GoC could provide the degree of connectivity between spawning and nursery areas and identify the physical drivers of the recruitment variability. The larval final destination is critical for the survival of a marine species which is coastal-dependent during its early life stages. Simulations with a Lagrangian transport model in the Southwest Iberian Peninsula were performed during the most intense spawning peak of 2016, when a strong and persistent countercurrent event developed. Most of the simulated early life stages were transported to the western Portuguese coast and, to a lesser extent, to the Atlantic oligotrophic waters, suggesting an increase in the connectivity between the subdivision 9a South and West components. Although different environmental processes occurring during ontogenetic stages, as well as overfishing, among others, can explain part of the variability observed in recruitment, events such as the development of coastal countercurrents during the spawning season could partly account for an increase of anchovy on the western Portuguese coast and a decrease in the Gulf of Cadiz one year later.Financial support was given by ECOCADIZ 2016 (Spanish Institute of Oceanography, Spain). The authors thank the crews of the R/V Miguel Oliver for technical assistance on the field. ATM acknowledges project 'SARDINHA2020-Abordagem Ecossistémica para a gestão da pesca da sardinha (MAR-01.04.02-FEAMP-0009)', from the Programa Operacional MAR 2020 (Portugal). Open Access has been partly financed by the University of Cadiz (Spain), the Campus de Excelencia Internacional/Global del Mar (CEI MAR, Spain), and the research group RNM337-Oceanograflía y Teedetección (Spain)