A Europe–South America network for climate change assessment and impact studies

The goal of the CLARIS project was to build an integrated European–South American network dedicated to promote common research strategies to observe and predict climate changes and their consequent socio-economic impacts taking into account the climate and societal peculiarities of South America. Reaching that goal placed the present network as a privileged advisor to contribute to the design of adaptation strategies in a region strongly affected by and dependent on climate variability (e.g. agriculture, health, hydro-electricity). Building the CLARIS network required fulfilling the following three objectives: (1) The first objective of CLARIS was to set up and favour the technical transfer and expertise in earth system and regional climate modelling between Europe and South America together with the providing of a list of climate data (observed and simulated) required for model validations; (2) The second objective of CLARIS was to facilitate the exchange of observed and simulated climate data between the climate research groups and to create a South American high-quality climate database for studies in extreme events and long-term climate trends; (3) Finally, the third objective of CLARIS was to strengthen the communication between climate researchers and stakeholders, and to demonstrate the feasibility of using climate information in the decision-making process.     

The astrophysical consequences of the bimodal hydrodynamic solution of the super star cluster winds

The mass reinserted by young stars in an emerging massive compact cluster shows a bimodal hydrodynamic behaviour. In the inner parts of the cluster, it is thermally unstable, while in its outer parts it forms an outflowing wind. The chemical homogeneity/inhomogeneity of low/high-mass clusters demonstrates the relevance of this solution to the presence of single/multiple stellar populations. We show the consequences which the thermal instability of the reinserted mass has on galactic superwinds and discuss the open issues raised by the bimodal solution of stellar winds of massive clusters.     

Upscaling of Navier–Stokes equations in porous media: Theoretical, numerical and experimental approach

The accurate estimation of hydraulic conductivity is important for many geotechnical engineering applications, as the presence of fluids affects all aspects of soil behaviour, including its strength. Darcy’s law is the key experimental (or phenomenological) equation employed to model ground water flow. Yet, this phenomenological equation can be linked to a more fundamental microscale model of flow through the pore spaces of the porous material. This paper provides an experimental verification of the relationships between Darcy’s law (macroscale) and the Navier–Stokes equations (microscale) for actual complex pore geometries of a granular material. The pore geometries are experimentally obtained through state-of-the-art X-ray computer assisted micro-tomography. From the numerical modelling of the microscale flow based on actual pore geometries, it is possible to quantify and visualize the development of pore-scale fluid preferential flow-paths through the porous material, and to assess the importance of pore connectivity in soil transport properties.     

Sorption and desorption of mercury(II) in saline and alkaline soils of Bahía Blanca, Argentina

The objective of this work was to study sorption–desorption and/or precipitation–dissolution processes of Hg(II) compounds considering an eventual contact of soils with Hg-bearing wastes. In addition, this study contributes new data about Hg(II) chemistry in alkaline systems. Saline and alkaline soils with low organic matter (<1 %) and high clay content (60–70 %) were obtained near a chlor-alkali plant. Batch techniques were used to perform the experiments using 0.1 M NaNO₃ solutions. Total Hg(II) concentrations ranged from 6.2 × 10^?8 to 6.3 × 10^?3 M. Sorption of Hg(II) was evaluated at two concentration ranges: (a) 6.2 × 10^?8 to 1.1 × 10^?4 M, and (b) 6.4 × 10^?4 to 6.3 × 10^?3 M. At low Hg(II) concentrations, adsorption occurred with a maximum sorption capacity ranging from 4 to 5 mmol/kg. At high Hg(II) concentrations, sorption–precipitation reactions occurred and maximum sorption capacity ranged from 17 to 31 mmol/kg. The distribution of Hg(II) hydrolysis products showed that Hg(OH)₂ was the predominant species under soil conditions. According to sorption experiments, X-ray diffraction and chemical speciation modelling, the presence of Hg(OH)₂ in the interlayer of the interstratified clay minerals can be proposed. Hg(OH)₂ was partially desorbed by repeated equilibrations in 0.1 M NaNO₃ solution. Desorption ranged from 0.1 to 0.9 mmol/kg for soils treated with 5.8 × 10^?5 M Hg(II), whereas 2.1–3.8 mmol/kg was desorbed from soils treated with 6.3 × 10^?3 M Hg(II). Formation of soluble Hg(II) complexes was limited by low organic matter content, whereas neutral Hg(OH)₂ was retained by adsorption on clay mineral surfaces.     

Aeolization on the Atlantic coast of Galicia (NW Spain) from the end of the last glacial period to the present day: Chronology,origin and evolution of coastal dunes linked to sea-level oscillations

The Atlantic coast of Galicia (NW Spain) is a high-energy environment where shingle beaches are currently developing. These coarser sediments alternate with sandy deposits which are also considered as beaches typical of a low-energy environment. The physical association of both types of sediment with contrasted sedimentary significance raises problems of interpretation. The study of four outcrops of fossil aeolianites on this coast has allowed us to reconstruct their evolution from the end of the Upper Pleistocene to the present day. Their chronology, estimated by optically stimulated luminescence between 35 and 14 ky at the end of the last glaciation (MIS2), coincides with a local sea level 120 m below the present one. This implies a coastline shifted several kilometres from its current location and the subaerial exposure of a wide strip of the continental shelf covered by sands. The wind blew sand to form dunes towards the continent, covering the coastal areas, which then emerged with no other limitation than the active river channels. Sea-level rise during the Holocene transgression has progressively swamped these aeolian deposits, leaving only flooded dunes, relict coastal dunes and climbing dunes on cliffs up to 180 m high. The aeolian process continued as long as there was a sandy source area to erode, although accretion finished when the sea reached its current level (Late Holocene). Since then, the wind turned from accretion to erosion of the dunes and sand beaches. This erosion exposes the older shingle beaches (probably of Eemian age) buried under the aeolian sands, as well as old, submerged forest remains and megalithic monuments. The destruction of sand beaches and dunes currently observed along the Galician coast is linked, according to most researchers, to anthropogenic global warming. However, their management should consider these evolutive issues.     

Do Spartina maritima Plantations Enhance the Macroinvertebrate Community in European Salt Marshes?

Ecological restoration of salt marshes using plantations may enhance the macroinvertebrate community, but little is known about the development of benthic macroinvertebrates after ecological engineering projects in European salt marshes. This study analyzed the environment and the macroinvertebrate community in European salt marshes 3 years after restoration using Spartina maritima plantations in comparison with non-restored and preserved marshes in Odiel Marshes (Southwest Iberian Peninsula). We hypothesized that planting Spartina maritima on intertidal mudflats would increase species richness and diversity (Shannon–Weaver index) of the benthic macroinvertebrate community by increasing environmental heterogeneity, providing feeding resources and improving sediments characteristics. Benthic macrofauna samples (composed mainly of annelids, crustaceans, and mollusks) were sampled in plots of 20 cm?×?25 cm to 5 cm depth between +1.8 and +3.0 m above Spanish Hydrographic Zero. Sediment organic matter content, bulk density, pH, and redox potential were the variables that best explained macroinvertebrate distribution. Restored marshes achieved similar diversity and even higher specific richness than preserved marshes, although with differences in species composition. Non-restored marshes showed the lowest diversity. Restored and preserved marshes did not differ in total abundance or biomass of macroinvertebrates, both being higher than in non-restored marshes. The macroinvertebrate communities in preserved and non-restored marshes showed the largest difference in taxa composition, with restored marshes occupying an intermediate position. Salt marsh restoration using S. maritima increased the complexity (ecological diversity and species richness) and abundance of the benthic macroinvertebrate community. Our study offers new information about the role of salt marsh plants in mediating faunal communities via ecological engineering projects.     

The Uncertain Value of Perfect ENSO Phase Forecasts: Stochastic Agricultural Prices and Intra-Phase Climatic Variations

Climate and crop yield variability associated with El Niño—Southern Oscillation (ENSO) are now predictable within limits. This predictability suggests a potential to tailor agricultural management to mitigate impacts of adverse conditions and to take advantage of favorable conditions. However, improved climate predictions may benefit society only with parallel advances in our ability to use this knowledge. We show that the value that will accrue to any given actor from an ENSO phase forecast should be viewed not as a known number but instead as a random draw from a distribution, even when the forecast is always correct. Forecast value depends on the highly variable contexts in which forecasts are used. Randomness in forecast value has significant implications for choices made by forecasters, forecast users and policy makers. To show randomness, we estimate potential economic values of ENSO forecasts for agricultural producers based on two realistic assumptions: the crop prices farmers receive are uncertain; and within an ENSO phase, the actual climate is variable in ways that affect profits. The use of synthetic weather and crop price series, with crop simulation models, helps show the range and likelihood of climate forecast value.     

Megafan formation driven by explosive volcanism and active tectonic processes in a humid tropical environment

Quaternary volcanism in the Central Cordillera of Costa Rica has created an orographic barrier that concentrates rainfall on its northern side. This humid climate produces weathered bedrock prone to landsliding. Ash fall from explosive eruptions kills the vegetation cover and intensifies erosion processes. These eruptions, hydrothermal activity and associated earthquakes destabilize the slopes of river valleys, and even the volcanic edifices, producing landslides and large debris avalanches. All these processes mobilize an extra sediment input that is deposited in the piedmont lowlands forming the Santa Clara megafan. The megafans described in the literature mainly grow according to climatic fluctuations; however, sedimentation in the Santa Clara megafan is also controlled by endogenic processes with longer recurrence periods. Analysis of this megafan provides new insight into the origin and evolution of these landforms. In volcanic regions, active volcanism should be considered when investigating the formation of some megafans.