Northwestern Mediterranean Basin Research Articles

Identification of archaeological barley grains using geometric morphometrics and experimental charring

Barley is one of the main cereals found in archaeological sites in the north-western Mediterranean basin, over the last 8 millennia. Grains are preserved in archaeological sediments by charring after or before dehusking. Morphological criteria for distinguishing 2-row from 6-row barley, but also hulled barley from naked barley, can be affected by charring and this can complicate identification of barley subgroups. In the last decade, geometric morphometrics applied to uncharred barley grains has shown the possibility of identifying barley subgroups, but its applicability to archaeological remains still needs to be ascertained. We used 3985 raw and charred grains of 113 current varieties to (1) assess charring effects on the shape of barley caryopses, depending on their subgroup and whether they were charred husked or dehusked and (2) select the best dataset for identifying barley subgroups. We also used 700 archaeological grains, from the Neolithic period to the end of the Middle Ages, to (3) compare the morphometric taxonomic assignment of the grains with their carpological identification based on discrete anatomical features in a series of 7 archaeological samples. Our results indicate size and shape differences between barley grains when charred husked or dehusked. Although the charring process results in greater morphometric homogeneity, it allows subgroups of barley to be identified. For the 2-row vs. 6-row identification, more than 71% of the charred modern grains can be correctly identified. For the hulled vs. naked identification, the correct cross-validation percentages range from 70 to 73%. Finally, the good correlation between carpological and morphometric identifications of archaeological grains suggests that it is possible to identify archaeobotanical samples in the future.

Summer distribution of the Mediterranean sperm whale: insights from the acoustic Accobams survey initiative

The Mediterranean sperm whale population, Physeter macrocephalus, is listed as endangered due to population decline caused by human activities. To mitigate the impact of these activities, accurate knowledge of their distribution and abundance is crucial. During their long dives, sperm whales are not available to visual observation, but since they produce sounds when they dive, they are available to acoustic detection. Therefore, we aimed to use towed acoustic data to model their habitat and fill the knowledge gap on Mediterranean sperm whale distribution. Generalised additive models were used to link the number of sperm whales detected acoustically during the ACCOBAMS Survey Initiative in 2018 with different environmental variables integrated over different depth classes, encompassing the depth range used by the species for foraging. Sperm whale distribution was influenced by water temperature at the bottom, eddy kinetic energy between 200 and 600 m, as well as gradients of sea surface temperature and chlorophyll-a concentrations. The abundance of sperm whales was estimated at 2,959 individuals [2,077 - 4,265] in the sampled areas of the Mediterranean Sea. We predicted that sperm whales were mainly distributed in summer along the continental slope of the north-western Mediterranean basin from the Balearic Islands to the Ligurian Sea and off the Algerian coast. They were present throughout the western Mediterranean Sea and in the northern Ionian Sea. In contrast, predicted densities were low in the eastern part of the Mediterranean Sea. The use of acoustic data compensated for the main difficulty in studying sperm whales, the unavailability of animals at the surface during visual observation and the paucity of visual data. We thus encourage more systematic use of passive acoustics to study sperm whale distribution. The model highlighted a higher concentration of sperm whales in the western Mediterranean basin than in the eastern basin in summer, opening up avenues to improve the conservation of this endangered Mediterranean sub-population.

Unexpected Records of Newborn and Young Sharks in Ligurian and North Tyrrhenian Seas (North-Western Mediterranean Basin)

Between 2007 and 2022, 112 specimens of newborn and young pelagic sharks were recorded in the waters of Tuscany Region, in the South Ligurian–North Tyrrhenian Seas (north-western Mediterranean basin). The sharks belonged to the Carcharhinus plumbeus (n = 14), Prionace glauca (n = 66), Isurus oxyrinchus (n = 16), Mobula mobular (n = 5) Alopias vulpinus (n = 7) and Hexanchus griseus (n = 4) species. Each animal was correctly identified thanks to the photographs or videos collected. All specimens were incidentally captured with set nets in inshore shallow waters, except bluntnose six-gill sharks, which were bycatch of deep-water bottom-trawl fishery. Body mass, sex, total length and biometric measurements were recorded in 34 baby sharks following the Mediterranean Large Elasmobranches Monitoring (MEDLEM) protocol. The presence of very evident and often non-healed umbilical scar confirmed that some of the sample specimens were newborn. Further confirmation came from the comparison between the total length observed and the size at birth known for the sampled species as reported in the literature. Some baby sharks were preserved in the Museums of Natural History of Pisa and Florence University collections. The importance of the coastal area studied as a possible shark nursery is discussed.

Deconstructing Ecosystem Service Conflicts through the Prisms of Political Ecology and Game Theory in a North-Western Mediterranean River Basin

Power relationships, access and control, (in)equity, and (in)justice are key modulators of conflicts arising from ecosystem services between multiple stakeholders. A greater knowledge of stakeholder value systems and behaviors is crucial for understanding socioecological dynamics. We propose an analytical framework that combines political ecology and game theory to analyze water ecosystem services. This integrated framework was used to reinterpret concepts such as common goods, (a)symmetric flows, and (un)fair trade-offs in the context of ecosystem services. The purpose was to gain a better understanding of behaviors and (a)symmetries in power relationships between multiple stakeholders. We studied the case of a north-western Mediterranean river basin using data obtained from stakeholder interviews and newspaper articles. Our findings uncovered different types of stakeholder relationships, ranging from mutual support and cooperation to conflict. The proposed analytical framework shows how social mechanisms can affect ecosystem services flows, potentially facilitating or hindering the development of more equitable management models for natural resources.

NeoNet Dataset. Radiocarbon Dates for the Late Mesolithic/Early Neolithic Transition in the North Central-Western Mediterranean Basin

The NeoNet dataset aims to provide a new research tool for the study of the pioneer farming front (i.e. Neolithisation) in the North Central and North Western Mediterranean basin by focusing on the period of transition from a foraging to a farming economy (ca. 7000 to 3500 cal BC). The complete dataset is formed by the elencoc14.tsv file, a dataframe with tab-separated values, and a connex dataframe: thesaurus.tsv. The dataset contains 2,506 radiocarbon dates from 526 archaeological sites and 1,769 different archaeological records (stratigraphic units, structures, negative features, hearths, etc.). To ensure and facilitate the reuse of the radiocarbon dates, NeoNet’s data structure is based on the Euroevol database layout. Among other fields, particular attention has been paid to homogenisation of the laboratory code, the archaeological context, and the references, in order to facilitate further data extractions. Indeed, the dataset is linked to an opensource R Shiny interactive web app (NeoNet app), and a getter function (R package c14bazAAr, R function get_neonet).

Shift in demographic structure and increased reproductive activity of loggerhead turtles in the French Mediterranean Sea revealed by long-term monitoring

Climate-induced environmental changes are profoundly impacting marine ecosystems and altering species distribution worldwide. Migratory organisms, including sea turtles, are expected to be particularly sensitive to these variations. Here, we studied changes in the size structure and reproductive activity of loggerhead turtles in the French Mediterranean over 30 years. Overall, there was a significant increase in the size of observed loggerheads between 1990 and 2020. However, this increase was only significant during the breeding/nesting season (May to September) and was driven by the increased presence of adults. Furthermore, nesting activity along the French coast was detected in 2002 for the first time in more than 50 years, and has become frequent after 2014, with nests discovered every year. The number of eggs laid as well as incubation duration and success varied among sites but fell within the range reported at established Mediterranean nesting sites. These observations, along with recent reports of breeding activity and evidence of significant sea surface warming, suggest that the north-western Mediterranean basin has become increasingly suitable to loggerhead turtles. We postulate that this range expansion is the result of climate change and propose that emerging nesting activity in France should be closely monitored and guarded against human activities.

Aircraft vertical profiles during summertime regional and Saharan dust scenarios over the north-western Mediterranean basin: aerosol optical and physical properties

Abstract. Accurate measurements of the horizontal and vertical distribution of atmospheric aerosol particle optical properties are key for a better understanding of their impact on the climate. Here we present the results of a measurement campaign based on instrumented flights over north-eastern Spain. We measured vertical profiles of size-segregated atmospheric particulate matter (PM) mass concentrations and multi-wavelength scattering and absorption coefficients in the western Mediterranean basin (WMB). The campaign took place during typical summer conditions, characterized by the development of a vertical multi-layer structure, under both summer regional pollution episodes (REGs) and Saharan dust events (SDEs). REG patterns in the region form under high insolation and scarce precipitation in summer, favouring layering of highly aged fine-PM strata in the lower few kma.s.l. The REG scenario prevailed during the entire measurement campaign. Additionally, African dust outbreaks and plumes from northern African wildfires influenced the study area. The vertical profiles of climate-relevant intensive optical parameters such as single-scattering albedo (SSA); the asymmetry parameter (g); scattering, absorption and SSA Ångström exponents (SAE, AAE and SSAAE); and PM mass scattering and absorption cross sections (MSC and MAC) were derived from the measurements. Moreover, we compared the aircraft measurements with those performed at two GAW–ACTRIS (Global Atmosphere Watch–Aerosol, Clouds and Trace Gases) surface measurement stations located in north-eastern Spain, namely Montseny (MSY; regional background) and Montsec d'Ares (MSA; remote site). Airborne in situ measurements and ceilometer ground-based remote measurements identified aerosol air masses at altitudes up to more than 3.5 kma.s.l. The vertical profiles of the optical properties markedly changed according to the prevailing atmospheric scenarios. During SDE the SAE was low along the profiles, reaching values < 1.0 in the dust layers. Correspondingly, SSAAE was negative, and AAE reached values up to 2.0–2.5, as a consequence of the UV absorption increased by the presence of the coarse dust particles. During REG, the SAE increased to > 2.0, and the asymmetry parameter g was rather low (0.5–0.6) due to the prevalence of fine PM, which was characterized by an AAE close to 1.0, suggesting a fossil fuel combustion origin. During REG, some of the layers featured larger AAE (> 1.5), relatively low SSA at 525 nm (< 0.85) and high MSC (> 9 m2 g−1) and were associated with the influence of PM from wildfires. Overall, the SSA and MSC near the ground ranged around 0.85 and 3 m2 g−1, respectively, and increased at higher altitudes, reaching values above 0.95 and up to 9 m2 g−1. The PM, MSC and MAC were on average larger during REG compared to SDE due to the larger scattering and absorption efficiency of fine PM compared with dust. The SSA and MSC had quite similar vertical profiles and often both increased with height indicating the progressive shift toward PM with a larger scattering efficiency with altitude. This study contributes to our understanding of regional-aerosol vertical distribution and optical properties in the WMB, and the results will be useful for improving future climate projections and remote sensing or satellite retrieval algorithms.

Key issues in Northwestern Mediterranean dry grassland restoration

Dry grasslands of the Northwestern Mediterranean Basin are seminatural species‐rich ecosystems, composed of many annual species and some structuring perennial species. As these grasslands have been used as rangelands for centuries, human management (grazing; fire regimes) is one of their main ecological and evolutionary drivers, along with the Mediterranean climate. Despite EU conservation policy, damage to such grasslands still occurs and efficient ecological restoration is needed. This article reviews restoration constraints, effective techniques, and research perspectives for restoring them in the light of their ecological characteristics. Major restoration constraints specifically include (1) a poor contribution of the internal (seed bank) and external (seed rain) species pools, and (2) low establishment of some perennial species. The latter may be the result of the low seed quantity or quality of perennial species, stochastic or extended droughts, high soil nutrient content that may lead to competition (e.g. between weed and target species), inappropriate grazing management or fire regimes leading to shrub encroachment, or the death of target species seedlings in early stages of restoration. Successful restoration techniques include seeding, transplanting, hay transfer, and timely soil transfer, all of which have to be adapted to regional plant phenology and to local Mediterranean climate. They must be combined with appropriate grazing or fire management. Their success may depend on years with particular rainfall amounts or patterns or on particular target plant species. We discuss research perspectives contributing to a better understanding of seed dispersal, seedling recruitment, and soil processes and suggest the benefits of using ecosystem engineer species.

Assessing the Potential of Short Sea Shipping and the Benefits in Terms of External Costs: Application to the Mediterranean Basin

The paper aims to investigate short sea shipping services as a competitive, sustainable freight transport system which is able to respond to economic, social and environmental needs. An assessment methodology is proposed which considers an aggregate discrete choice model, simulating the split between the competitive transport alternatives in the Mediterranean basin. The proposed methodology was used to assess the potential of short sea shipping (SSS) and the net benefits deriving from lower external costs in the north-western Mediterranean basin. Two future scenarios are considered: introduction of new SSS services as envisaged by current EU projects and plans, and the introduction of new SSS routes and an increase in frequencies of existing services. Significant results were obtained in terms of shifting freight traffic from the road network as well as external benefits.

Transfer zones and associated volcanic province in the eastern Valencia Basin: Evidence for a hot rifted margin?

The role of NW-SE transfer zones during the opening of the Northwestern Mediterranean Basin has long been evidenced, mostly from seismic-reflection and magnetic data. Each of these features corresponds to transverse basement steps and/or fractures controlling the progressive deepening from the Valencia Basin toward the center of the Liguro-Provençal Basin. The most important one, the North-Balearic-Fracture-Zone, accounts for the counterclockwise rotation of the Corsica-Sardinia block and separates the Valencia continental basin from the Liguro-Provençal oceanic basin. Another transfer zone, the Central Fracture Zone is the limit of the NE part of the Valencia Basin floored with volcanic basement. Further north, the Catalan Fracture Zone corresponds to a large scale transfer zone that limits between the eastern Pyrenees and the thinned crust of the Gulf of Lion. New observations on deep seismic lines show in detail the extent of a 1–3 km thick volcanic Province around the North-Balearic-Fracture-Zone. It includes the numerous volcanoes of the Valencia Basin mostly superimposed on the transverse fractures zones. The transfer zones are also characterized by narrow syn-rift grabens interpreted as transtensional pull-apart basins along the transfer faults. The transfer zones are associated at depth with domes uplifting the Moho, thinning locally the crust down to 3 km and exhuming deeper material. Deep reflections and thinning at the base of the crust draw extensional shear-zones and crustal boudins that, together with the large amount of syn-rift volcanism in the area, suggests a ductile behavior during early stage of extension. This ductile behavior has then evolved toward more brittle deformation and deposition of syn-rift sediments in asymmetric basins. The volcanic Province disappears in the distal prolongation of the Catalan Fracture Zone that we observe and characterize for the first time. Here a thin crust with flat top consists of westward-dipping reflections in the upper part, rooted in reflective layers. This crust passes laterally to the type II exhumed domain of the Liguro-Provençal Basin and to the oceanic domain to the south. Three crustal domains can thus be distinguished in the transition between the Valencia and Liguro-Provençal Basins illustrating the complex 3D deformation of the area.

Modeling organic aerosol concentrations and properties during winter 2014 in the northwestern Mediterranean region

Abstract. Organic aerosols are measured at a remote site (Ersa) on the cape of Corsica in the northwestern Mediterranean basin during the winter campaign of 2014 of the CHemistry and AeRosols Mediterranean EXperiment (CharMEx), when high organic concentrations from anthropogenic origins are observed. This work aims to represent the observed organic aerosol concentrations and properties (oxidation state) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Because intermediate and semi-volatile organic compounds (I/S-VOCs) are the main precursors of SOAs at Ersa during winter 2014, different parameterizations to represent the emission and aging of I/S-VOCs were implemented in the chemistry-transport model of Polyphemus (different volatility distribution emissions and single-step oxidation vs multi-step oxidation within a volatility basis set – VBS – framework, inclusion of non-traditional volatile organic compounds – NTVOCs). Simulations using the different parameterizations are compared to each other and to the measurements (concentration and oxidation state). The highly observed organic concentrations are well reproduced in all the parameterizations. They are slightly underestimated in most parameterizations. The volatility distribution at emissions influences the concentrations more strongly than the choice of the parameterization that may be used for aging (single-step oxidation vs multi-step oxidation), stressing the importance of an accurate characterization of emissions. Assuming the volatility distribution of sectors other than residential heating to be the same as residential heating may lead to a strong underestimation of organic concentrations. The observed organic oxidation and oxygenation states are strongly underestimated in all simulations, even when multigenerational aging of I/S-VOCs from all sectors is modeled. This suggests that uncertainties in the emissions and aging of I/S-VOC emissions remain to be elucidated, with a potential role of formation of organic nitrate and low-volatility highly oxygenated organic molecules.

Particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern Mediterranean basin

The effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern Mediterranean basin were studied by near-bottom moored instruments recording trapped particle fluxes, suspended particle fluxes, water properties and hydrodynamics from November 2011 to July 2012. During this period, near-bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth, increasing by more than one order of magnitude the ambient suspended sediment concentrations, the trapped particle fluxes and the suspended sediment fluxes. During the preconditioning phase of the open sea convection, from December 2011 to mid-February 2012, currents (1–10 cm s−1), suspended sediment concentrations (<0.1 mg l−1), Chl-a fluorescence values (<0.063 μg l−1), trapped total mass fluxes (10–50 mg m−2 d−1) and trapped organic carbon fluxes (1–4 mg m−2 d−1) were low, and organic matter was mainly undegraded and of marine origin. Open sea convection was observed at the study site in mid-February, at the beginning of the violent mixing phase, increasing current velocities up to 26 cm s−1 and Chl-a fluorescence values up to 0.074 μg l−1, supplying particles with fresh marine organic matter content. During the last fortnight of February, two major dense shelf water cascading pulses generated Chl-a fluorescence increases (up to 0.116 μg l−1) and large suspended sediment concentration peaks (up to19 mg l−1), suspended sediment fluxes (up to 6500 mg m−2 d−1) and trapped total mass flux increases (up to 22,900 mg m−2 d−1), which were associated with benthic storms resuspension. During this phase, trapped organic carbon flux increased almost two orders of magnitude (up to 260 mg m−2 d−1), with pulses of both marine and terrestrial organic matter. The sinking and spreading phase occurred from early March to mid-June. The signal of deep dense shelf water cascading lasted past early April, and the spreading of the newly formed dense water maintained maximum currents of up to 25 cm s−1 and trapped particle fluxes of up to 2000 mg m−2 d−1 until mid-June. At the beginning of this phase, organic matter was terrestrial and several turbidity peaks occurred during current speed increases generated by benthic storms. At the end of this phase, the organic matter became less terrestrial, trapped organic carbon fluxes decreased from about 190 to 10 mg m−2 d−1 and turbidity peaks occurred with low current velocities indicating the arrival of storm tails at the mooring site. The large particle fluxes of fresh or relatively undegraded organic carbon induced by deep dense water formation during winter 2012, contributed to the “fertilization” of the northwestern Mediterranean deep benthic ecosystems.

Coastally trapped disturbances caused by the tramontane wind on the northwestern Mediterranean: numerical study and sensitivity to short‐wave radiation

The Tramontane‐Cierzo wind system is a recurrent feature of the northwestern Mediterranean basin in front of the Catalan coast (northeast Spain). Associated with this feature, northeast wind surges occasionally affect the coast and become a weather hazard for low‐level aircraft operations, affecting for example the Barcelona international airport. This article first reports these surges characterizing them as Coastal‐Trapped Disturbances (CTDs). Climatological features are described, showing that CTDs occur frequently during the warm season and between the afternoon and the evening. We classified CTDs into two synoptic patterns related to the location of a mid‐level tropospheric geopotential trough and the Iberian Peninsula: pattern A, with the trough crossing eastwards along the north of Spain; and pattern B, with the trough over the Mediterranean, after crossing the Iberian Peninsula. To study the CTDs in detail, numerical simulations were conducted using the non‐hydrostatic and convection‐permitting numerical weather prediction model HARMONIE‐AROME. Two cases, one for each synoptic pattern, were studied showing that CTDs generate in the discontinuity between cool outflows and warmer air progressing southward as a density current, trapped by the mountain ranges parallel to the coastline. Cool outflows may have two different sources: in Pattern A the origin of the cold air is the tramontane itself, while in Pattern B convective outflows associated with storm downdraughts play this role. Both cases show similarities with CTDs studied on the California coast, showing an antitriptic and ageostrophic flow behind the CTD. An additional numerical sensitivity experiment was conducted by varying the short‐wave radiation to explore the effects of diabatic warming on CTDs. It is demonstrated that a large warming influences CTDs by enhancing the potential temperature gradient between the density current and the environment, modulating their intensity and speed.

Applying network analysis to assess coastal risk planning

Adequate response to risks affecting coasts requires an integrated and coordinated multi-risk governance system, with ongoing evaluation of statutory planning documents and responsible stakeholders. Traditionally, such analyses have been carried out using mainly qualitative approaches. This paper adopts a more systemic and quantitative perspective on assessing planning systems and stakeholder relationships in connection with coastal risk. We apply network analysis to the Catalan coast (Northwestern Mediterranean Basin), paying special attention to the level of climate change integration in the planning system, as an aggravating factor of current risk dynamics. Our results demonstrate and quantify the complexity of Catalan coastal risk planning, which requires dealings with multi-level legal and administrative frameworks. Also highlighted is dissimilar management traditions according to risk type: the perspective on flooding risk is more unified and multi-risk focused, whereas coastal erosion (a significant issue for the Catalan coast) is managed more sectorially from a centralized administrative level. Climate change, moreover, is weakly accounted for in current statutory planning. We also acknowledge the relevance of using qualitative information as an important complement in interpreting results and making policy recommendations.

Sources and mixing state of summertime background aerosol in the north-western Mediterranean basin

Abstract. An aerosol time-of-flight mass spectrometer (ATOFMS) was employed to provide real-time single particle mixing state and thereby source information for aerosols impacting the western Mediterranean basin during the ChArMEx-ADRIMED and SAF-MED campaigns in summer 2013. The ATOFMS measurements were made at a ground-based remote site on the northern tip of Corsica. Twenty-seven distinct ATOFMS particle classes were identified and subsequently grouped into eight general categories: EC-rich (elemental carbon), K-rich, Na-rich, amines, OC-rich (organic carbon), V-rich, Fe-rich and Ca-rich particles. Mass concentrations were reconstructed for the ATOFMS particle classes and found to be in good agreement with other co-located quantitative measurements (PM1, black carbon (BC), organic carbon, sulfate mass and ammonium mass). Total ATOFMS reconstructed mass (PM2. 5) accounted for 70–90 % of measured PM10 mass and was comprised of regionally transported fossil fuel (EC-rich) and biomass burning (K-rich) particles. The accumulation of these transported particles was favoured by repeated and extended periods of air mass stagnation over the western Mediterranean during the sampling campaigns. The single particle mass spectra proved to be valuable source markers, allowing the identification of fossil fuel and biomass burning combustion sources, and was therefore highly complementary to quantitative measurements made by Particle into Liquid Sampler ion chromatography (PILS-IC) and an aerosol chemical speciation monitor (ACSM), which have demonstrated that PM1 and PM10 were comprised predominantly of sulfate, ammonium and OC. Good temporal agreement was observed between ATOFMS EC-rich and K-rich particle mass concentrations and combined mass concentrations of BC, sulfate, ammonium and low volatility oxygenated organic aerosol (LV-OOA). This combined information suggests that combustion of fossil fuels and biomass produced primary EC- and OC-containing particles, which then accumulated ammonium, sulfate and alkylamines during regional transport. Three other sources were also identified: local biomass burning, marine and shipping. Local combustion particles (emitted in Corsica) contributed little to PM2. 5 particle number and mass concentrations but were easily distinguished from regional combustion particles. Marine emissions comprised fresh and aged sea salt: the former was detected mostly during a 5-day event during which it accounted for 50–80 % of sea salt aerosol mass, while the latter was detected throughout the sampling period. Dust was not efficiently detected by the ATOFMS, and support measurements showed that it was mainly in the PM2. 5–10 fraction. Shipping particles, identified using markers for heavy fuel oil combustion, were associated with regional emissions and represented only a small fraction of PM2. 5 particle number and mass concentration at the site.

Plant Resources from the Bronze Age and the first Iron Age in the northwestern arc of the Mediterranean Basin

This paper updates the question of plant resources during the Bronze Age and First Iron Age in the northwestern Mediterranean Basin. Among the cereals, six-row hulled barley is dominant throughout the territory, whereas naked and hulled wheats take on greater or lesser roles from region to region. Millet cultivation developed during the Bronze Age and became widespread in the First Iron Age. Apart from cereals, pulses, oil species and fruit appear to be secondary. Results from the study of archaeobotanical remains on wetland sites, however, lead us to question this finding, as oil plants and fruits are much better represented in waterlogged conditions. The cultivation of vine began in the First Iron Age. In spite of a number of characteristics common to plants throughout the study area, regional differences, evident in the Bronze Age, seem to dissipate in the First Iron Age.

Impact of aerosol microphysical properties on mass scattering cross sections

We assessed the sensitivity of simulated mass scattering cross sections (αλsca) of three aerosol species to perturbed particle microphysical properties and derived constraints on these microphysical properties, suitable for the north-western Mediterranean basin, from a comparison between code calculations and observations. In detail, we calculated αλsca of mineral dust, organic carbon and sulfate at three wavelengths in the visible range (λ1=0,450μm; λ2=0,525μm; λ3=0,635μm) with a T-matrix optical code, considering ±20% perturbations on size distribution, refractive index and mass density (respect to reference values mainly taken from the OPAC database), and spheroids with two different axial ratios as shape perturbations (reference shape: sphere). Then, we compared the simulation results with a set of observed αλsca of mineral dust, aged organics and ammonium sulfate sources, available at the same three wavelengths of the code calculations. These observations, provided by the Institute of Environmental Assessment and Water Research (IDAEA-CSIC), have been derived through Multilinear Regression (MLR) analysis from measurements of aerosol mass concentrations and optical properties, collected during a 4-year campaign at the Montseny regional background station (Spain) and representative of the north-western Mediterranean basin. We observed quite different impacts of the microphysical perturbations on αλsca values and spectral dependence for different aerosol species, due mainly to the different size of the particles respect to the visible wavelengths. Moreover, by means of a compatibility test on best fit parameters, we constrained the mineral dust log-normal size distribution to a geometric radius and a standard deviation of rg=3,583·10−1μm and σg=1,600, respectively (effective radius: reff=6,221·10−1μm), the organic carbon log-normal size distribution parameters to rg=2,544·10−2μm and σg=1,760 (reff=5,656·10−2μm), the organic carbon real refractive index to nR=(1,576;1,576;1,576) at (λ1;λ2;λ3), the sulfate log-normal size distribution parameters to rg=8,340·10−2μm and σg=1,624 (reff=1,501·10−1μm) and the sulfate real refractive index to nR=(1,547;1,545;1,543) at (λ1;λ2;λ3), in the north-western Mediterranean basin. Regarding the other perturbed microphysical properties, we found the reference prescriptions to be suitable for this geographical region, according to the same analysis procedure.

Temporal and spatial variability of ground level atmospheric methane concentrations in the Ebro River Delta

Deltas provide many worthy ecosystem services. Yet, delta basins are quite vulnerable, especially in the face of climate change, which can affect the outcome of both agriculture and biodiversity. Moreover, rice paddy cultivation is well known to contribute with strong emissions of greenhouse gases (GHGs), such as methane (CH4). Thus, knowing the atmospheric variability of CH4 in relation to the different stages of the rice culture cycle could help to improve GHGs' mitigation strategies in deltas.The Ebro River Delta, in the northwestern Mediterranean basin, forms part of the largest Spanish river basin and is mainly covered by rice fields. In this study, for the first time, ground level (40 cm a.g.l.) atmospheric CH4 concentrations have been monitored in this area, through twenty-seven car mobile transects, over the course of one year. Seasonal, diurnal and spatial variability of CH4 concentrations were studied to identify its relationship with rice cultivation, meteorological conditions and land-use distribution.With regard to seasonal variability, autumn transects showed the highest mean values for atmospheric CH4 (2.466 ppm) when dead rice straw is mixed with the sediment, and weed growth is prevented. Spring and summer measurements gave the highest mean CH4 values at dawn (1.897–3.544 ppm), whereas autumn and winter produced the mean values after sunset (2.148–2.930 ppm). Spatial differences were accounted for by proximity to urban areas, presence of shallow water storage structures, and distance to seawater.

A PV-approach for dense water formation along fronts: Application to the Northwestern Mediterranean

The mechanisms of dense water formation (σ >29.0 kg m−3) at work in the baroclinic cyclonic gyre of the North-Western Mediterranean basin are investigated through a PV-budget (PV: Potential Vorticity). The PV-budget is diagnosed from an eddy-resolving (1/36°) ocean simulation driven in surface by hourly air-sea fluxes provided by a non-hydrostatic atmospheric model at 2.5km-resolution. The PV-budget is controlled by the diabatic, frictional and advective PV-fluxes. Around the gyre the surface diabatic PV-flux dominates the PV-destruction, except along the northern branch of the North Current where the surface frictional PV-flux is strongly negative. In this region, the bathymetry stabilizes the front and maintains the current northerly in the same direction as the dominant northerly wind. This configuration leads to optimal wind-current interactions and explains the preponderance of frictional PV-destruction on diabatic PV-destruction. This mechanical forcing drives a cross-front ageostrophic circulation which subducts surface low-PV waters destroyed by wind on the dense side of the front and obducts high-PV waters from the pycnocline on the light side of the front. The horizontal PV-advections associated with the geostrophic cyclonic gyre and turbulent entrainment at the pycnocline also contribute to the PV-refueling in the frontal region. The surface non-advective PV-flux involves energy exchanges down to −1400 W m−2 in the frontal zone: this flux is 3.5 times stronger than atmospheric buoyancy flux. These energy exchanges quantify the coupling effects between the surface atmospheric forcing with the oceanic frontal structures at submesoscale. This article is protected by copyright. All rights reserved.

Modeling the interaction between presalt seamounts and gravitational failure in salt-bearing passive margins: The Messinian case in the northwestern Mediterranean Basin

The northwest Mediterranean Basin includes a thick Messinian salt sequence composed of three evaporitic units. From these, the intermediate unit, which is dominantly composed of halite, acted as a gravitational detachment favoring the downslope failure of the overlying sediments in a thin-skinned deformation regime. As a result, the structure of the margin is characterized by an upper extensional domain with basinward-dipping listric normal faults and a lower contractional domain that accommodates upslope extension by folding, salt inflation, or diapir squeezing. Lower to middle Miocene volcanic seamounts (presalt reliefs) located at the upper extensional domain locally disrupted the evaporitic units and produced salt flow perturbations. They acted as passive buttresses during the gravitational failure modifying the structural zonation of the margin. Using an experimental approach (sandbox models), we analyze the role played by seamounts during the kinematic evolution of passive margins and how they alter salt flow and suprasalt deformation during gravitational gliding. The experiments found that the seamounts locally interrupt the structural zonation of the margin because they hindered downdip salt flow during early deformation. Seamounts initially compartmentalize the margin architecture, resulting in the development of two gravitational subsystems with two extensional/contractional pairs that are subsequently reconnected when the accumulation of salt analog upslope of the relief is enough to overthrust it. From this point onward, the cover is passively translated downslope as a regional system. The changes in the viscous layer flow velocity related to the dip differences between the flanks and edges of the seamount determine the kinematic evolution of this system. Our experiments also provide geometric constraints to consider during interpretation of these structures, which are commonly poorly imaged in seismic data.