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- Coastline evolution of the Portuguese south eastern coast: a high-resolution approach in a 65 years’ time-windowPublication . Nave, Silvia; Rebêlo, LuísAbstract. The coast, as the interface between land and sea, is a highly dynamic area, endangered by erosion and flooding, particularly at times of sea-level rise. At the present context of climate change, the use of scientific knowledge to understand coastal dynamics and coastal evolution assessment through time is essential to find a suitable management response for a successful adaptive coastal governance. It is proposed that the obtained high-resolution and long-term coastline change dataset is of crucial impor tance to improve the knowledge on mesoscale evolution of the Portuguese south-eastern coast, from Ancão to Vila Real de Santo António (VRSA), a 55 km long coastal stretch. The evolutionary trend, from 1950 to 2015, points to a general seaward progradation at the western (Barreta island) and eastern (Cacela peninsula – VRSA) sectors, and mostly an erosional trend at the central barrier island system (Culatra, Tavira and Cabanas islands). Moreover, a considerable average landward displacement of approximately 130 m is observed at Cabanas island. Regarding overall coastline movement, seaward displacement prevails, with a prograding coastline occupying approximately 54% of the studied sector even though this is mostly associated with human intervention on the coast. The exception is the Manta Rota - Monte Gordo sector where accumulation is likely related to natural processes. Considering the significant influence man-made interventions have had on the coastline evolution, it is believed that the natural evolutionary pattern would point to an overall erosional trend in the islands sector and a progradational trend from Manta Rota to VRSA beach.
- Long-term coastline evolution of Figueira da Foz - Nazaré sector (Portugal)Publication . Nave, Silvia; Rebêlo, LuísABSTRACT: ome sectors of the west Portuguese coast are particularly endangered by erosion and flooding. Regional to local scale information, on coastline evolutionary trend, is particularly valuable in sectors that includes areas with relevant erosion. A continuous, high-resolution, dataset on coastal evolution, from 1947 and 2015, between Figueira da Foz and Nazaré, was achieved within the Programme “Geological and Coastal Hazard Mapping at a 1:3000 resolution scale” at the National Laboratory of Energy and Geology (LNEG). This work, due to the detailed scale of analysis in a wide geographic context, allows to have both, a general overview of the coastal evolution and, at the same time, when zooming in up to 1:3000 scale, to observe the local behaviour and to quantify the occurred changes. Also, the well time-spaced aerial photograph dataset allows to compare the resultant coastline movement between the oldest and the youngest coastline (NSM index), with the total coastline oscillation (SCE index), bringing new insights on the coastline stability at a local scale. The evolution trend shows an overall erosional behaviour, if considering the entire sector. Erosion occurs predominantly in the north, as the south shows more stability and progradation. Quantification of the land-lost and land-gain due to the coastline shift in a 68-year period shows that 1 164 888 m2 of land were lost along 30 470 m of the coastal fringe, and 462 330 m2 were gained along an extension of 21 010 m.
- LUÍS REBÊLO : missão e dedicação ao litoral e aos sistemas dunaresPublication . Nave, Silvia; Monteiro, José HipólitoRESUMO: Luís Rebêlo foi o principal impulsionador, nas últimas duas décadas, da área de geologia costeira da Instituição onde trabalhou durante 33 anos nos Serviços Geológicos Portugueses. O seu abrupto falecimento veio provocar uma enorme perda e um dano de difícil reparação, dada a falta que faz um especialista consagrado em geologia costeira à Unidade de Geologia, Hidrogeologia e Geologia Costeira. Licenciou-se em Geologia pela Faculdade de Ciências da Universidade Clássica de Lisboa. O início da sua carreira profissional deu-se como Hidrogeólogo da PGIRH/T – Projecto Tejo, num breve período entre 1988 e 1989, data em que ingressou, como geólogo, e sob orientação de Hipólito Monteiro, no Departamento de Geologia Aplicada dos Serviços Geológicos de Portugal (SGP), da então Direcção-Geral de Minas e Serviços Geológicos. Em 1993, com a criação do novo Departamento de Geologia Marinha, transitou para esta unidade onde iniciou o seu percurso de investigação no domínio da Geologia Costeira.
- Atlantic circulation changes across a stadial-interstadial transitionPublication . Waelbroeck, Claire; Tjiputra, Jerry; Guo, Chuncheng; Nisancioglu, Kerim H.; Jansen, Eystein; Riveiros, Natalia Vazquez; Toucanne, Samuel; Eynaud, Frédérique; Rossignol, Linda; Dewilde, Fabien; Marches, Elodie; Lebreiro, Susana; Nave, SilviaABSTRACT: We combine consistently dated benthic carbon isotopic records distributed over the entire Atlantic Ocean with numerical simulations performed by a glacial configuration of the Norwegian Earth System Model with active ocean biogeochemistry in order to interpret the observed Cibicides delta C-13 changes at the stadial-interstadial transition corresponding to the end of Heinrich Stadial 4 (HS4) in terms of ocean circulation and remineralization changes. We show that the marked increase in Cibicides delta C-13 observed at the end of HS4 between similar to 2000 and 4200 m in the Atlantic can be explained by changes in nutrient concentrations as simulated by the model in response to the halting of freshwater input in the high-latitude glacial North Atlantic. Our model results show that this Cibicides delta C-13 signal is associated with changes in the ratio of southern-sourced (SSW) versus northern-sourced (NSW) water masses at the core sites, whereby SSW is replaced by NSW as a consequence of the resumption of deep-water formation in the northern North Atlantic and Nordic Seas after the freshwater input is halted. Our results further suggest that the contribution of ocean circulation changes to this signal increases from similar to 40 % at 2000 m to similar to 80 % at 4000 m. Below similar to 4200 m, the model shows little ocean circulation change but an increase in remineralization across the transition marking the end of HS4. The simulated lower remineralization during stadials compared to during interstadials is particularly pronounced in deep subantarctic sites, in agreement with the decrease in the export production of carbon to the deep Southern Ocean during stadials found in previous studies.
- Patterns of sediment distribution on the Portuguese southeastern coastPublication . Nave, Silvia; Rebêlo, LuísSUMÁRIO: A granulometria dos sedimentos pode fornecer informações importantes sobre a origem e evolução dos ambientes sedimentares da zona costeira. Este trabalho apresenta a distribuição espacial da granulometria dos sedimentos no sotavento algarvio, resultante da análise de 395 amostras recolhidas em 133 perfis posicionados ao longo de uma faixa de 55km, desde a península do Ancão até Vila Real de Santo António. A análise preliminar dos resultados, apresentados em função do valor da média e agrupados nas classes normalizadas da escala de tamanho de grão (classificação de Wentworth), revela a ausência das classes granulométricas de areia muito fina e fina, mesmo na zona dunar, onde a classe de areia média domina no sector leste, e a de areia grosseira, no sector ocidental. O padrão geral de distribuição espacial da granulometria dos sedimentos exibe uma variação distinta ao longo da área de estudo, decorrente da exposição aos principais agentes forçadores (ondas e correntes).