Backbarrier shores along the Ria Formosa lagoon

Low energy beaches are located in sheltered and fetch-limited environments. The fetch, also called the fetch length, is the uninterrupted distance over the sea surface for which the wind can blow without a change in direction and affects the growth of wind-waves. Fetch-limited beaches are found in estuaries and bays (e.g. Chesapeake Bay, USA), behind ocean barriers (e.g. Pamlico Sound, USA), adjacent to inlets (e.g. Tapora Bank, New Zealand), deltas (e.g. Menderes River, Turkey), eroding thermokarst (e.g. Yensei Bay, Russia), and glacial outwash fans (e.g. Canal Baker, Chile; Cooper et al., 2007). In the case of barrier island systems, the back of barrier islands facing the lagoon environments i.e., backbarrier shores are fetch-limited environments. A barrier is an elongated ridge that is composed predominantly of unconsolidated sand and/or gravel and protect the adjacent mainland from open-water processes (Figure 2.1). From the sea to the mainland, the barriers are generally composed of the shoreface, dune and backbarrier environments, and they are separated alongshore by tidal inlets (Figure 2.1). Barrier islands are dynamic systems, constantly on the move, migrating under the influence of waves, tides, currents, storms, and changing mean sea levels. The backbarrier is a narrow, elongated, intertidal landform that is located on the lagoon or estuary side of the barrier island and can take the form of sandy beaches, tidal flats or salt marshes (Figure 2.1). Backbarrier beaches tend to be morphodynamically reflective (according to the classification of Wright & Short, 1984), with steep narrow foreshores that have smaller seasonal variations than open ocean beaches. The tidal flat is bound to the foreshore and might end in a salt marsh fringe. Salt marshes are among the most productive ecosystems on earth.info:eu-repo/semantics/publishedVersio

Prediction of overwash in alongshore variable barrier islands [Previsão da ocorrência de galgamentos em ilhas barreira com variabilidade longilitoral]

Overwash prediction is very important for coastal zone management. This work intends to identify alongshore variations in storm impact and evaluate the role of sub-aerial and submerged morphologies in overwash occurrence. For this study, 24 cross-shore topo-bathymetric profiles were set on Barreta Island (Ria Formosa barrier island system, Portugal). Pre- and post-overwash surveys were made between August 2012 and April 2013. During overwash events, tidal levels and wave parameters at breaking were obtained. Overwash occurred under storm and non-storm conditions, the latter coincident with spring high-tide. Beach morphology was spatially variable, and changeable from one overwash episode to the next. Predictions of overwash occurrence were made using the Overwash Potential, defined as the difference between runup and barrier elevation. Several runup equations were tested, and the results compared to the actual observations. The selected predictor provided an accuracy of 88% for the identification of the locations where overwash occurred. This study proves that nearshore and foreshore morphologies have a major impact on the longshore distribution of overwash.info:eu-repo/semantics/publishedVersio

Engaging children in geosciences through storytelling and creative dance

Natural sciences have traditionally been disseminated in outreach activities as formal, one-way presentations. Nevertheless, innovative strategies are being increasingly developed using arts, gaming, and sketching, amongst others. This work aimed at testing an alternative and innovative way to engage non-expert audiences in ocean and coastal geology through a combination of scientific concept explanations and creative dancing. An informal education activity focusing on ocean dynamics was designed for 10-yearold students. It combines coastal science concepts (wind, waves, currents, and sand), storytelling techniques (narrative arc), and creative dance techniques (movement, imaginative play, and sensory engagement). A sequence of six exercises was proposed, starting with the generation of offshore ocean waves and ending with sediment transport on the beach during storm/fair-weather conditions. Scientific concepts were then translated into structured creative movements, within imaginary scenarios, and accompanied by sounds or music. The activity was performed six times with a total of 112 students. It was an inclusive activity given that all students in the class participated, including children with several mild types of cognitive and neurological impairment. The science and art activity aroused emotions of enjoyment and pleasure and allowed for effective communication between scientists and school community. Moreover, the results provide evidence of the activity’s effectiveness in engaging children and developing their willingness to further participate in similar activities.PTDC/MAR-EST/1031/2014/ IF/00354/201/ 57/2016/CP1361/CT0002 and DL 57/2016/CP1432/CT0001info:eu-repo/semantics/publishedVersio

Exploring open-source multispectral satellite remote sensing as a tool to map long-term evolution of salt marsh shorelines

From an ecological and socio-economic perspective, salt marshes are one of the most valuable natural assets on Earth. As external pressures are causing their extensive degradation and loss globally, the ability to monitor salt marshes on a long-term scale and identify drivers of change is essential for their conservation. Remote sensing has been demonstrated to be one of the most adept methods for this purpose and open-source multispectral satellite remote sensing missions have the potential to provide worldwide long-term time-series coverage that is non-cost-prohibitive. This study derives the long-term lateral evolution of four salt marsh patches in the Ria Formosa coastal lagoon (Portugal) using data from the Sentinel-2 and Landsat missions as well as from aerial photography surveys to quantitatively examine the accuracy and associated uncertainty in using open-source multispectral satellite remote sensing for this purpose. The results show that these open-source satellite archives can be a useful tool for tracking long-term salt marsh extent dynamics. During 1976-2020, there was a net loss of salt marsh in the study area, with erosion rates reaching an average of-3.3 m/yr opposite a tidal inlet. The main source of error in the satellite results was the dataset spatial resolution limits, but the specific salt marsh shoreline environment contributed to the relative magnitude of that error. The study notes the influence of eco-geomorphological dynamics on the mapping of sedimentary environments, so far not extensively discussed in scientific literature, highlighting the difference between mapping a morphological process and a sedimentary environment.info:eu-repo/semantics/publishedVersio

Superficial sedimentary stocks and sources of carbon and nitrogen in coastal vegetated assemblages along a flow gradient

Coastal vegetated ecosystems are major organic carbon (OC) and total nitrogen (TN) sinks, but the mechanisms that regulate their spatial variability need to be better understood. Here we assessed how superficial sedimentary OC and TN within intertidal vegetated assemblages (saltmarsh and seagrass) vary along a flow gradient, which is a major driver of sediment grain size, and thus of organic matter (OM) content. A significant relationship between flow current velocity and OC and TN stocks in the seagrass was found, but not in the saltmarsh. OC and TN stocks of the saltmarsh were larger than the seagrass, even though that habitat experiences shorter hydroperiods. Mixing models revealed that OM sources also varied along the flow gradient within the seagrass, but not in the saltmarsh, showing increasing contributions of microphytobenthos (17-32%) and decreasing contributions of POM (45-35%). As well, OM sources varied vertically as microphytobenthos contribution was highest at the higher intertidal saltmarsh (48%), but not POM (39%). Macroalgae, seagrass and saltmarsh showed low contributions. Local trade-offs between flow current velocities, hydroperiod and structural complexity of vegetation must be considered, at both horizontal and vertical (elevation) spatial dimensions, for better estimates of blue carbon and nitrogen in coastal ecosystems.Foundation of Science and Technology of Portugal (FCT) PTDC/MAR-EST/3223/2014 UID/Multi/04326/2013 FCT UID/MAR/00350/2018 SFRH/BPD/119344/2016info:eu-repo/semantics/publishedVersio

Vertical intertidal variation of organic matter stocks and patterns of sediment deposition in a mesotidal coastal wetland

Tidal coastal wetlands, common home to seagrass and salt marshes, are relevant carbon sinks due to their high capacity to accumulate and store organic carbon in their sediments. Recent studies demonstrated that the spatial variability of this organic carbon within the same wetland system can be significant. Some of the environmental drivers of this spatial variability remain understudied and the selection of the most relevant ones can be context dependent. Here we investigated the role of bed elevation, hydrodynamics, and habitat type (salt marsh and seagrass) on the organic matter (OM) net deposition-resuspension rate and superficial sedimentary stocks (top 5 cm) at the tidal wetlands of the Ria Formosa, a mesotidal coastal lagoon in South Portugal. Results showed that two vectors of spatial variation need to be considered to describe the intertidal sedimentary OM stocks: the bed elevation that imposes a decrease of the hydroperiod and thus the change of habitat from the lower seagrass Z. noltei to the upper saltmarsh S. maritimus, and the horizontal spatial variation along the secondary channels of the lagoon that imposes a decrease in the current flow velocity magnitude. The multiple linear regression analyses, using data from 40 sampling points, explained 59% of the variation of the superficial sedimentary stocks of OM in salt marshes and seagrasses of the Ria Formosa lagoon and revealed that stocks generally decrease with elevation, yet with variation among sites and habitats. It was also found that the decrease of the OM net deposition-resuspension rate with bed elevation was exponential. Our study emphasizes the importance of considering multiple environmental drivers and spatial variation for regional estimations of organic matter (and organic carbon) sedimentary stocks in coastal wetlands.info:eu-repo/semantics/publishedVersio

Carbon and nitrogen stocks and burial rates in intertidal vegetated habitats of a Mesotidal coastal lagoon

Coastal vegetated ecosystems such as saltmarshes and seagrasses are important sinks of organic carbon (OC) and total nitrogen (TN), with large global and local variability, driven by the confluence of many physical and ecological factors. Here we show that sedimentary OC and TN stocks of intertidal saltmarsh (Sporobolus maritimus) and seagrass (Zostera noltei) habitats increased between two- and fourfold along a decreasing flow velocity gradient in Ria Formosa lagoon (south Portugal). A similar twofold increase was also observed for OC and TN burial rates of S. maritimus and of almost one order of magnitude for Z. noltei. Stable isotope mixing models identify allochthonous particulate organic matter as the main source to the sedimentary pools in both habitats (39–68%). This is the second estimate of OC stocks and the first of OC burial rates in Z. noltei, a small, fast-growing species that is widely distributed in Europe (41,000 ha) and which area is presently expanding (8600 ha in 2000s). Its wide range of OC stocks (29–99 Mg ha-1 ) and burial rates (15–122 g m2 y-1 ) observed in Ria Formosa highlight the importance of investigating the drivers of such variability to develop global blue carbon models. The TN stocks (7–11 Mg ha-1 ) and burial rates (2–4 g m-2 y-1 ) of Z. noltei were generally higher than seagrasses elsewhere. The OC and TN stocks (29–101 and 3–11 Mg ha-1 , respectively) and burial rates (19–39 and 3–5 g m-2 y-1 ) in S. maritimus saltmarshes are generally lower than those located in estuaries subjected to larger accumulation of terrestrial organic matter.DL57/2016/CP1361/CT0002; MinECo, MDM2015-0552info:eu-repo/semantics/publishedVersio

Field measurements and hydrodynamic modelling to evaluate the importance of factors controlling overwash

Overwash hydrodynamic datasets are mixed in quality and scope, being difficult to obtain due to fieldwork experimental limitations. Nevertheless, these measurements are crucial to develop reliable models to predict overwash. Aiming to overcome such limitations, this work presents accurate fieldwork data on overwash hydrodynamics, further exploring it to model overwash on a low-lying barrier island. Fieldwork was undertaken on Barreta Island (Portugal) in December 2013, during neap tides and under energetic conditions, with significant wave height reaching 2.6 m. During approximately 4 h, more than 120 shallow overwash events were measured with a video-camera, a pressure transducer and a current-meter. This high-frequency fieldwork dataset includes runup, overwash number, depth and velocity. Fieldwork data along with information from literature were used to implement XBeach model in non-hydrostatic mode (wave-resolving). The baseline model was tested for six verification cases; and the model was able to predict overwash in five. Based in performance metrics and the verification cases, it was considered that the Barreta baseline overwash model is a reliable tool for the prediction of overwash hydrodynamics. The baseline model was then forced to simulate overwash under different hydrodynamic conditions (waves and lagoon water level) and morpho-sedimentary settings (nearshore topography and beach grain-size), within the characteristic range of values for the study area. According to the results, the order of importance of factors controlling overwash predictability in the study area are: 1st) wave height (more than wave period) can promote overwash 3–4 times more intense than the one recorded during fieldwork; 2nd) nearshore bathymetry, particularly shallow submerged bars, can promote an average decrease of about 30% in overwash; 3rd) grain-size, finer sediment produced an 11% increase in overwash due to reduced infiltration; and 4th) lagoon water level, only negligible differences were evidenced by changes in the lagoon level. This implies that for model predictions to be reliable, accurate wave forecasts are necessary and topo-bathymetric configuration needs to be monitored frequently

Magnetic Field and Electron Density Data Analysis from Swarm Satellites Searching for Ionospheric Effects by Great Earthquakes: 12 Case Studies from 2014 to 2016

We analyse Swarm satellite magnetic field and electron density data one month before and one month after 12 strong earthquakes that have occurred in the first 2.5 years of Swarm satellite mission lifetime in the Mediterranean region (magnitude M6.1+) or in the rest of the world (M6.7+). The search for anomalies was limited to the area centred at each earthquake epicentre and bounded by a circle that scales with magnitude according to the Dobrovolsky’s radius. We define the magnetic and electron density anomalies statistically in terms of specific thresholds with respect to the same statistical quantity along the whole residual satellite track (|geomagnetic latitude| ≤ 50°, quiet geomagnetic conditions). Once normalized by the analysed satellite tracks, the anomalies associated to all earthquakes resemble a linear dependence with earthquake magnitude, so supporting the statistical correlation with earthquakes and excluding a relationship by chance.PublishedID 3711A. Geomagnetismo e PaleomagnetismoJCR Journa