Sapientia
Repositório Científico da UAlg
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Storm impact assessment for Scotland’s wave-dominated sedimentary coasts
Publication . Horsburgh, Nicola; Loureiro, Carlos; Hurst, Martin; Rennie, Alistair; Tyler, Andrew
Along wave-dominated sedimentary coasts, risks posed by chronic coastal erosion and rising sea levels during this century have received much atten-tion. However, extreme wave runup during large storms are still poorly charac-terised at large spatial scales, and can contribute significantly to coastal flooding and erosion. This creates an important challenge for coastal management and adaptation planning. This work presents a national-scale storm impact assessment for Scotland’s wave-dominated sand and gravel coasts. It uses readily available national and European datasets to model extreme total water levels that include storm wave runup, tides, storm surge and changes in mean sea level. Future impacts are assessed by integrating likely climate-driven changes to storm forcing and coastal morphology. Outputs estimate the likely storm impact regime at 50 m alongshore transects in Scotland’s natural sand and gravel coasts for the present day, 2050 and 2100, considering climate change scenarios RCP4.5 and RCP8.5. Results indicate 65%, 11% and 4% of transects currently experience collision, overwash and inundation as the most severe storm impact. Towards 2100, tran-sects in overwash and inundation increase to 20% (22%) for RCP4.5 (RCP8.5), but local increases vary considerably between coastal cells. This study contributes to a strategic, national scale understanding of coastal risk that supports the spatial prioritisation of areas in need of proactive adaptation solutions.
The supply of copper to the settlement of Leceia (Portugal) and the Estremadura region during the third millennium BC
Publication . Valério, Pedro; Cardoso, João Luis; Alves, Luís C.; Soares, António M. Monge
The Chalcolithic settlement of Leceia (Portugal) has one of the largest collections of copper artefacts and metallurgical debris in the Portuguese Estremadura. However, the absence of ores and smelting remains suggests that local metallurgical operations were related to the production of artefacts. In fact, the metal assemblage includes several fragments of flat axes, most of them with traces of sectioning, which may have been used as ingots. In order to validate this hypothesis and to identify the copper sources used, elemental, microstructural and Pb isotope characterisation of five axe-ingots was undertaken. The assemblage turned out to be composed of copper with varying amounts of arsenic (0.08–2.94 wt%) and oxide inclusions (Cu2O and Cu-As-O). Some inclusions containing distinct contents of Bi, Sb and/or Sn were also identified, indicating the exploitation of different sources of copper ores. Pb isotope ratios displayed a cluster of four samples (206Pb/204Pb: 18.2378–18.3444) and one outlier with low radiogenic lead (206Pb/204Pb: 17.6625), signatures that compare well with those previously obtained for local artefacts and prills. Euclidean distances identified ore deposits in the Spanish provinces of Huelva and Cordoba as potential suppliers of copper, particularly the supergene copper ores from the mines of Rio Tinto, Cabezadas del Sandino, Preciosa and Quita Pellejo, all of which are located a considerable distance from the settlement of Leceia. Other probable copper sources are located in the mining districts of Linares-La Carolina and Los Pedroches, situated even further away from the Portuguese Estremadura. Consequently, the copper axe-ingots of Leceia, like the previously analysed local artefacts, provide evidence of long-distance trade relations with south-central Iberian Peninsula, which appear to be shared with coeval settlements in Estremadura, such as Vila Nova de São Pedro and Zambujal.
Do vertebrate-type steroids play a role in bivalve reproduction? a case study across two reproductive cycles of magallana gigas
Publication . Rato, Ana Cláudia Nunes; Joaquim, Sandra; Silva, José Paulo da; Anjos, Catarina; Matias, Domitília; Hubbard, Peter
In bivalves, reproduction is regulated by a complex interaction between endogenous and environmental factors, including temperature and food availability. However, hormonal control of the reproductive cycle in bivalves is poorly understood. There is a general belief that vertebrate-type steroids (testosterone, progesterone and 17βoestradiol) are involved in the reproductive cycle of bivalves, even though the necessary enzymes and receptors for such steroids are apparently lacking in the molluscan genome. To investigate the potential role of vertebratetype steroids in reproduction, the current study characterized two consecutive reproductive cycles of the Pacific oyster (Magallana gigas), integrating biochemical composition, reproductive indices, environmental parameters, and steroid levels. Gonadal index (GI), gonadosomatic index, and condition index exhibited clear seasonal fluctuations. Protein, glycogen, and total lipid displayed distinct seasonal patterns, with protein exhibiting structural functions, whereas glycogen and total lipid acted as energy reserves supporting gametogenesis. Both progesterone (0.69-142.33 ng g− 1 ) and testosterone progesterone (2.55-262 ng g− 1 ) levels fluctuated during sampling; progesterone showed correlations with GI, temperature, and protein content, whereas testosterone was mainly associated with environmental factors. These patterns suggest that progesterone may reflect gonadal tissue development and energetic investment rather than acting as a classical sex steroid. The absence of sexspecific steroid patterns, together with the lack of classical steroid receptors in the molluscan genome, supports the hypothesis of an environmental origin and/or an eco-physiological rather than an endocrine role for vertebrate-type steroids in oysters. These findings demonstrate that hormonal studies in bivalves should integrate biochemical, reproductive, and environmental data to understand reproductive strategies.
Can global datasets be used to predict storm-induced coastal erosion?
Publication . Fanti, Valeria; Ferreira, Óscar; Loureiro, Carlos
The scarcity of high-resolution in situ data hampers effective storm impact assessment and the development of early warning systems for coastal bar riers worldwide. This study introduces a novel methodology utilising a SWAN XBeach modelling chain, leveraging global hydrodynamic (WAVERYS and GTSM) and topo-bathymetric (TanDEM-X and ETOPO2022) datasets to perform first-order, globally applicable storm impact assessments for barrier coasts. The approach is validated with high-resolution data from Duck, North Carolina, using pre- and post-storm topographic LiDAR, recorded wave conditions and water levels. The results indicate that global datasets can reasonably reproduce barrier ero sion patterns, despite underestimation of total water levels and dune morphology due to the coarse resolution and inaccuracies in the GTSM and TanDEM-X data. The simulations effectively capture dune retreat and erosion trends, aligning with measured data, but inconsistencies are observed in morphological changes for the upper beach face. These discrepancies are likely due to differences in intertidal elevation and beach face steepness between the LiDAR data and global models at Duck. Additionally, the approach does not account for short-scale (~100 m) longshore variability, which can contribute to deviations in modelled results. This study demonstrates the potential of global datasets for storm impact mod elling, providing a first-order assessment with relevant information about storm induced erosion, which can be particularly useful in areas lacking high resolution data. However, it also highlights the need for further validation across diverse sites to enhance reliability and address methodological constraints.
Decoding storm response in geologically controlled coastal barriers using XBeach
Publication . Kümmerer, Vincent; Loureiro, Carlos; Ferreira, Óscar
Storm-induced morphological changes in coastal barriers are primar ily driven by hydrodynamic forcing. However, in rock-fronted coasts the pres ence of geological features can modulate storm impacts, but the extent to which these non-dynamic variables influence barrier morphological response to storms is still poorly understood. This study explores the influence of intertidal rock plat forms on storm-driven morphological changes. Using the process-based XBeach model, dune erosion during an energetic winter storm was simulated across dif ferent schematic cross-shore profiles, incorporating variable intertidal rock plat form configurations. The schematic profiles are based on existing barrier pro files in the Outer Hebrides, NW Scotland. Calibration of the model involved adjusting friction coefficients of exposed bedrock surfaces to improve the abil ity to reproduce observed nearshore wave heights and morphological changes in pre- and post-storm profiles. The results show that higher intertidal rock plat forms (above mean sea level) are associated with reduced dune erosion, while lower rock platforms are associated with more extensive dune erosion. This high lights the complex interaction between geological control and storm impacts, with implications for improved understanding of coastal resilience and storm-driven morphosedimentary dynamics in rock-fronted barrier systems.