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This study investigates a long-term assessment of the wave energy resource propagated along the Algerian basin, based on a 39-year wave hindcast. The wave energy hindcast dataset was developed using the Simulating WAve Nearshore (SWAN) model, calibrated and validated [1] against wave measurements performed on the Algerian coast. A detailed spatial and local analysis was performed following the hindcast results. We have determined several parameters including; hourly, monthly, seasonal and annual variations of wave energy resources, the probability of occurrence distribution for different wave power ranges with different directions, the probability of calm sea states, the wave energy development index (WEDI) and the total annual wave energy and their distribution as a function of significant wave height and energy period. All these results enabled a very important benchmark for decision making regarding the future implementation and design of wave energy converters (WECs) and other offshore structures in the Algerian basin. Our findings have shown that the Algerian coasts are characterized by a considerable wave energy potential with a large hotspot area in the eastern coasts. Thus, we have recorded a significant variability in the wave energy characteristics available in each zone along the Algerian coast. The western zone was characterized by an average energy of ∼7.5 kW/m with a low monthly and seasonal variation (<1.2), the central zone was characterized by a significant total annual wave energy of 63 MWh/m/year and a considerable WEDI of 0.019, and the eastern Algerian coast was characterized by one of the highest energy potential in the Mediterranean basin with a total annual energy exceeding 100 MWh/m for less than 15 km from the coast and a calm sea state probability lower than 18%. Thus, it has been concluded that since 1995, wave energy resources have tended to increase further. • A first detailed long-term assessment of wave energies in the Algerian coast. • Largest hotspot area in the W-Med basin is located in the Eastern coast of Algeria. • High resolution SWAN model (∼3 km) calibrated for the Algerian basin was used. • A new accurate 39-year wave energy hindcast dataset has been developed. • Wave energy resources tend to increase further since 1995 in the Algerian coast. [ABSTRACT FROM AUTHOR]

Marine phytoplankton forms the basis of the marine food web. Its diversity (size and pigmentation) has a significant impact on biogeochemical processes such as photosynthetic efficiency, trophic interactions, and global carbon fluxes. To date, little is known about the Algerian Basin regarding phytoplankton quality and quantity. In this study, we analyzed the distribution of phytoplankton communities in the Algerian Basin based on HPLC/Chemotaxonomy analysis for the summer season of 2014. The chemical taxonomy software CHEMTAX v1.95 was used to estimate the contributions of various phytoplankton groups to total Chlorophyll a (TChl a). The results showed that prymnesiophytes were the dominant group (16%) in the nanoplankton and occupied the entire water column, whereas cryptophytes were observed exclusively in the western region of the basin, and contributed about 6% to the TChl a. Diatoms had the highest contributions (18%) to the TChl a , and their emergence was linked to nutrient enrichment. Dinoflagellates had a contribution of about 12% with little variation throughout the basin. Prochlorococcus had a contribution of about 13% and prevailed in the deep layers (60–100 m) following the nitracline, while Synechococcus (11%) occupied the shallower layers (10–60 m) (beneath the MLD) following the nutrient depletion. Moreover, it is noteworthy that phytoplankton communities in the western part of the basin showed greater diversity and abundance, influenced by Atlantic waters and deep nutrient enrichment. In contrast, the eastern part of the basin displayed lower productivity, characterized by reduced diversity and the prevalence of nano- and picoplankton. • Phytoplankton communities in the Algerian basin are characterized by the CHEMTAX approach. • Nano- and micro-phytoplankton prevail in the Algerian basin. • Diatoms, prymnesiophytes, and Prochlorococcus are the major phytoplankton groups in the Algerian basin. • Phytoplankton communities are more abundant and diverse in the west of the Algerian basin than in the east. • Phytoplankton community composition is linked to the Algerian Basin's physical-chemical dynamics. [ABSTRACT FROM AUTHOR]

Highlights • A high resolution hindcast model SWAN was calibrated and validated for the Algerian Basin. • Janssen (1991) formulation with C ds1 = 1 for whitecapping in the W-Med Sea has a better performance. • Komen et al. (1984) formulation for wind growth in the W-Med Sea presents a better accuracy. • The calibrated SWAN performs better using Komen formula compared to the new ST6. Abstract This study aims to present an evaluation and implementation of a high-resolution SWAN wind wave hindcast model forced by the CFSR wind fields in the west Mediterranean basin, taking into account the recent developments in wave modelling as the new source terms package ST6. For this purpose, the SWAN model was calibrated based on one-year wave observations of Azeffoune buoy (Algerian coast) and validated against eleven wave buoys measurements through the West Mediterranean basin. For the calibration process, we focused on the whitecapping dissipation coefficient C ds and on the exponential wind wave growth and whitecapping dissipation source terms. The statistical error analysis of the calibration results led to conclude that the SWAN model calibration corrected the underestimation of the significant wave height hindcasts in the default mode and improved its accuracy in the West Mediterranean basin. The exponential wind wave growth of Komen et al (1984) and the whitecapping dissipation source terms of Janssen (1991) with C ds = 1.0 have been thus recommended for the western Mediterranean basin. The comparison of the simulation results obtained using this calibrated parameters against eleven measurement buoys showed a high performance of the calibrated SWAN model with an average scatter index of 30% for the significant wave heights and 19% for the mean wave period. This calibrated SWAN model will constitute a practical wave hindcast model with high spatial resolution (˜3 km) and high accuracy in the Algerian basin, which will allow us to proceed to a finer mesh size using the SWAN nested grid system in this area. [ABSTRACT FROM AUTHOR]

The Algerian Basin is a key component of the general circulation in the Western Mediterranean Sea. The presence of both fresh Atlantic water and more saline Mediterranean water gives the basin an intense inflow/outflow regime and complex circulation patterns. Energetic mesoscale structures that evolve from meanders of the Algerian Current into isolated cyclonic and anticyclonic eddies dominate the area, with marked repercussions on biological activity. Despite its remarkable importance, this region and its variability are still poorly known and basin-wide knowledge of its meso- and submesoscale features is still incomplete. Studying such complex processes requires a synergistic approach that involves integrated observing systems. In recent years, several studies have demonstrated the advantages of combined use of autonomous underwater vehicles, such as gliders, with a new generation of satellite altimetry. In this context, we present results of an observational program conducted in the Algerian Basin during fall 2014 and 2015 that aimed to advance our knowledge of its main features. The study was carried out through analysis of high resolution glider observations, collected along the Algerian BAsin Circulation Unmanned Survey (ABACUS) chokepoint, in synergy with co-located SARAL/AltiKa altimetric products and CMEMS numerical simulations. Results show that glider-derived dynamic height and SARAL/AltiKa absolute dynamic topography have similar patterns, with RMS of the differences ranging between 1.11 and 2.90 cm. Even though larger discrepancies are observed near the Balearic and Algerian coasts, correlation coefficients between glider and satellite observations seem mostly to be affected by reduced synopticity between the measurements. Glider observations acquired during the four surveys reveal the presence of several water masses of Atlantic and Mediterranean origin (i.e., AW and LIW at different modification levels) with marked seasonal variability. [ABSTRACT FROM AUTHOR]

Despite an extensive bibliography for the circulation of the Mediterranean Sea and its sub-basins, the debate on mesoscale dynamics and their impacts on bio-chemical processes is still open because of their intrinsic time scales and of the difficulties in their sampling. In order to clarify some of these processes, the “Algerian BAsin Circulation Unmanned Survey-ABACUS” project was proposed and realized through access to the JERICO Trans National Access (TNA) infrastructure between September and December 2014. In this framework, a deep glider cruise was carried out in the area between the Balearic Islands and the Algerian coast to establish a repeat line for monitoring of the basin circulation. During the mission a mesoscale eddy, identified on satellite altimetry maps, was sampled at high-spatial horizontal resolution (4 km) along its main axes and from the surface to 1000 m depth. Data were collected by a Slocum glider equipped with a pumped CTD and biochemical sensors that collected about 100 complete casts inside the eddy. In order to describe the structure of the eddy, in situ data were merged with next generation remotely sensed data: daily synoptic sea surface temperature (SST) and chlorophyll concentration (Chl-a) images from the MODIS satellites, as well as sea surface height and geostrophic velocities from AVISO. From its origin along the Algerian coast in the eastern part of the basin, the eddy propagated northwest at a mean speed of about 4 km/day, with a mean diameter of 112–130 km, mean amplitude of 15.7 cm; the eddy was clearly distinguished from the surrounding waters thanks to its higher SST and Chl-a values. Temperature and salinity values over the water column confirm the origin of the eddy from the Algerian Current (AC) showing the presence of recent Atlantic water in the surface layer and Levantine Intermediate Water (LIW) in the deeper layer. The eddy footprint is clearly evident in the multiparametric vertical sections conducted along its main axis. Deepening of temperature, salinity and density isolines at the center of the eddy is associated with variations in Chl-a, oxygen concentration and turbidity patterns. In particular, at 50 m depth along the eddy borders, Chl-a values are higher (1.1–5.2 μg/l) in comparison with the eddy center (0.5–0.7 μg/l) with maximum values found in the southeastern sector of the eddy. Calculation of geostrophic velocities along transects and vertical quasi-geostrophic velocities (QG-w) over a regular 5 km grid from the glider data helped to describe the mechanisms and functioning of the eddy. QG-w presents an asymmetric pattern, with relatively strong downwelling in the western part of the eddy and upwelling in the southeastern part. This asymmetry in the vertical velocity pattern, which brings LIW into the euphotic layer as well as advection from the northeastern sector of the eddy, may explain the observed increases in Chl-a values. [ABSTRACT FROM AUTHOR]

The Yaddene complex, located in Lesser Kabylia (northeastern Algeria), is composed of Tertiary mafic and ultramafic rocks that outcrop within syn-rift sedimentary rocks of the Algerian marginal basin, in the Maghrebide belt of North Africa. Petrographic observations show that the Yaddene complex is composed mainly of two distinct lithologies: (1) a layered quartz-bearing gabbro at the bottom, which consists mainly of plagioclase (An 93), clinopyroxene (altered to actinolite) and rare interstitial quartz; and (2) layered plagioclase-bearing lherzolites composed of olivine (Fo 86-88) orthopyroxene (En 86 – 87), clinopyroxene (diopside and augite), rare plagioclase (anorthite) and amphibole of pargasitic composition. The trace element concentrations in pyroxenes and olivine of the Yadenne complex show a depletion in light rare earth elements (LREE) similar to basalts of the Mid-Ocean Ridge (N-MORB), which reflects the depletion of the mantle source. In addition, high #Cr in spinel reflects a high degree of partial melting of the mantle source. On the other hand, slight enrichment in Large Ion Lithophile Elements (Cs, Rb, Ba), weak but significant negative Nb, Ta, Zr, Hf and Ti anomalies, and positive Pb spikes are observed in both whole-rocks and minerals. These patterns are best explained by interaction between parental mantle and fluids and/or siliceous melts derived from a subducting oceanic slab. The tectonic discrimination diagrams of minerals and whole rocks indicate that the most likely geodynamic setting for emplacement of the Yaddene Complex is a back arc basin environment. In situ U-Pb dating of euhedral zircons and titanite from a quartz-bearing gabbro yields an age of 18.97 ± 0.12 Ma (2σ), which is interpreted as the crystallization age of magmatic zircons and the gabbroic magma. Zircons from a plagioclase-bearing lherzolite gave a consistent age of 19.05 ± 0.39 Ma (2σ), which is attributed to zircon growth during metamorphic/metasomatic processes coeval to gabbroic magma emplacement. The mafic/ultramafic rocks of the Yaddene complex are intercalated within fine-grained sediments of the syn-rift "Oligo-Miocene Kabyle" and the obtained early Burdigalian ages are interpreted as the early stages of an extensional regime that ultimately led to the opening of the oceanic Algerian Basin. • Minerals composition reflects the very high rate of partial melting of the mantle source. • Trace element contents indicate a slightly metasomatized mantel and suggest a back-arc basin environment proximal to the arc. • The thermobarometric calculations show very high temperatures (≈1000 °C) for low pressures (1–3 Kbar). • U-Pb zircon dating yields ages of 19 Ma attributed to emplacement of gabbroic magma from the Yadenne complex. [ABSTRACT FROM AUTHOR]

We present an overview of the crustal architecture of the continental margins of the oceanic Algerian Basin in the westernmost Mediterranean Sea. During the Cenozoic, and with a variable oblique convergence between the African and Eurasian plates, the Western Mediterranean Sea has experienced thinning and extension behind a tight orogenic arc formed by the Betics, Rif, and Tell Cordilleras. This study is focused on the structural style affecting the Messinian salt layer, which is mostly restricted to the deep domains of the Algerian Basin, where it is floored by a thin oceanic crust of probable Miocene age. Using deep-penetrating seismic profiles and wells from offshore western Algeria to southeastern Spain, we have analyzed the crustal structures affecting the domains close to the oceanic-continent transition on the three margins of the western Algerian Basin. Since the Early Miocene, active shortening in the Tell-Atlas domain has accommodated most of the plate convergence in the basin, whereas the Alboran margin in the west and the Iberian margin in the north experienced eastward and southward crustal extension and thinning, respectively, accompanied by volcanism. The Algerian margin in the south shows incipient thrusting of African continental crust over oceanic crust. This shortening occurred since at least the Late Miocene, also promoting decoupling and contraction of the deep, sub-horizontal Messinian salt layer. The salt exhibits diapir squeezing and suprasalt folding, whereas the presalt sequence preserves partially-inverted half-grabens. Salt tectonic processes along the northern and western margins of the Western Mediterranean Basin show contrasting structural styles formed by narrow extensional and transtensional domains with gentle salt anticlines. This region shows therefore a somewhat unusual salt-tectonic style, departing from the gravity-driven model typical of continental margins that contain an initial continuous, gently-dipping salt layer. In the Algerian Basin, salt is mostly restricted to deep water domain floored by oceanic crust, so it does not participate in significant gravity-driven deformation. Instead, Messinian salt and the suprasalt sequences underwent significant shortening along the southern margin, simultaneous with thick-skinned extension involving the Messinian evaporites in the northern and eastern margins. [Display omitted] • Crustal structure of the W Algerian Basin is reviewed by the first time. • Seismic interpretation to unravel the crustal structures of the basin and margins. • How the Messinian salt layer is deformed in the oceanic floor of the basin. • How the deformation occurring in the margins affected the deep–seated salt layer. • Restoration to evaluate timing, magnitude, and rate of post-6 Ma deformations. [ABSTRACT FROM AUTHOR]

We report for the first time the discovery of diamond inclusions (5–30 μm in size), identified by Raman spectroscopy and the characteristic sharp band at 1332 cm − 1 for crystalline diamond, in a garnet megacryst (≥ 5 cm) from the Edough Massif (NE Algeria). The garnet is adjacent to actinolite and ultramafic boudins and slices of marbles that are inserted within a major mylonite–ultramylonite band. This tectonic contact sharply delineates the Kef Lakhal oceanic unit from the granite-gneiss core below. The host garnet is almandine-dominant and is rich in exsolution of acicular rutile needles. Major and trace elements show a gradual but significant zonation from core to rim, and a sharp increase in grossular component in the rim. Trace element analyses of prismatic rutile inclusions up to 300 μm in size indicate that the host metamorphic rock was a mafic protolith of MORB affinity. The Zr-in-rutile thermometry indicates a temperature range of 724–778 °C that we relate to rutile growth, either during prograde metamorphism or under peak UHP metamorphic conditions of ≥ 3.6 GPa that were reached during subduction of the UHP-rock precursors. We suggest that the mafic protolith originates from the subducted retreating Calabrian branch of the Tethyan slab, that broke or tore, and which fragments were dragged upward and thrust onto the North African margin along with the Kef Lakhal unit, shortly followed by formation of the Edough dome and opening of the Algerian basin. [ABSTRACT FROM AUTHOR]

The pelagic decapod crustacean fauna of two different zones (Sóller and Cabrera) with different hydrographic dynamics and oligotrophy levels was studied around Mallorca (western Mediterranean), the latter with a higher degree of oligotrophy than the former. Samples were taken with a Pelagic Trawl and an IKMT in the upper 600 m of the water column, targeting larger and middle-sized nektonic species, respectively. Fourteen species were collected: five dendrobranchiate shrimps, eight caridean shrimps and one scyllarid lobster. Some species were restricted to the shelf-break: Chlorotocus crassicornis and Plesionika heterocarpus . Others were exclusive of the middle slope: Pasiphaea multidentata , and Sergia robusta . Pasiphaea sivado and Gennadas elegans occurred in all pelagic strata. Multivariate analyses showed several distinct assemblages related to bathymetry and sampling depth. No significant differences were found concerning zone or sampled seasons. Bathymetrically, Deep Scattering Layers showed the highest diversity. No decapod crustaceans occurred in epipelagic daytime samples. The pelagic decapod community sampled was structured by both the geomorphology (and associated hydrographic characteristics over the shelf-break) and the influence of light in the water column. Size analysis showed species-specific patterns concerning size/age movements into the water column throughout the day–night cycle. [ABSTRACT FROM AUTHOR]

Abstract: The Maghrebides, Betics and some parts of the Calabrian, NE Sicilian and Tuscan allochtons constitute dismembered fragments of the Alpine belt that resulted from the Cenozoic collision between Africa and Eurasia and the opening of the Western Mediterranean basin. Mineral and whole-rock geochemical analyses have been performed on three distinct outcrops of mantle material from the Edough Massif of NE Algeria, namely the Bou Maiza (BM) gabbros, the La Voile Noire (LVN) amphibolites and the Sidi Mohamed (SM) peridotites. In all samples, Sr isotopes are largely affected by seawater alteration (87Sr/86Sract. >0.70384 and up to 0.70888) and cannot be used to evaluate the nature of the source reservoirs. SM peridotites display variable depleted mantle Nd isotopic signatures (εNdact. from +7.0 to +12.2) and geochemical features suggesting no significant chemical depletion as a result of partial melting and melt extraction (Mg#<90; slightly LREE-depleted patterns with La/YbN =0.33–0.39). These rocks are interpreted as parts of the subcontinental lithospheric mantle incorporated into the crustal units of the Edough Massif during the early stages of opening of the Algerian basin. BM gabbros and LVN amphibolites show geochemical signatures indicating derivation from a common depleted mantle reservoir (εNd >+7.9) and are likely cogenetic, but without filiation with the SM peridotites. Pb isotopes indicate a contribution of sediments in the source reservoir, which is attributed to contamination solely by hydrous fluids released from a sedimentary component. This observation, together with a LILE-enrichment, suggests a back-arc basin environment. These results indicate that BM and LVN units were obducted onto the North African margin and subsequently fragmented, probably during doming and exhumation of the lower continental crust of the Edough massif. Doming resulted in opposite movements of the overlying oceanic units, southward for the BM units and northward for LVN amphibolites. [Copyright &y& Elsevier]

Abstract: Caesium-137 and 239,240PU were analysed in the water column along the Algerian coast. The 137Cs activity concentration in surface water increased from the west to the east from 1.6 to 3.3mBqL−1, documenting a presence of Modified Atlantic Water (MAW) in the region. Higher concentrations observed in deep waters may be due to an intrusion of Levantine Intermediate Water (LIW), which has been carrying higher levels of 137Cs from Chernobyl accident. The 239,240Pu sub-surface concentration peaked at about 250m water depth as a result of biogeochemical processes in the water column. The observed 239,240Pu/137Cs activity ratio at the surface (0.003) was significantly lower than that in global fallout (0.04). This decrease exceeds that expected from radioactive decay of 137Cs, and confirms that Pu due to its adsorption on sinking particles is more effectively removed from surface layers than is 137Cs. An increase of the 239,240Pu/137Cs activity ratio with depth suggests that 239,240Pu, similarly as 137Cs, should be also transported by advection to maintain the observed ratios in deep waters. An intrusion of LIW may enhance therefore both the 137Cs and 239,240Pu concentrations in deep waters. The average 238Pu/239+240Pu activity ratio in seawater was 0.03±0.02, confirming a global fallout origin of Pu in the Algerian Basin. Caesium-137 and 239,240Pu inventories in the water column were estimated to be from 2.7±0.5kBqm−2 to 3.8±0.7kBqm−2, and from 13.8±2.6Bqm−2 to 41±7Bqm−2, respectively. The 137Cs massic activities in surface sediment were almost constant, the average activity was 9.0±0.8Bqkg−1. Sedimentation rates obtained using the 210Pb method were from 0.1 to 0.7cmy−1, and resulting penetration depths of 137Cs in the sediment cores were from 15 to over 40cm. The 137Cs peaks found in the sediment cores were associated with the Chernobyl accident (1986) and global fallout (1964). The 137Cs inventories in the sediment were increasing from the west (180Bqm−2) to the east (350Bqm−2). [Copyright &y& Elsevier]

Abstract: This work represents a first step in understanding the impact of hydrodynamic features on the zooplankton dynamics in the Algerian Basin (southwestern Mediterranean Sea). The mesoscale distribution of mesozooplankton abundance, biomass, specific composition and size structure was investigated during ELISA-1 campaign (1997) in the framework of the program ELISA (Eddies and Leddies Interdisciplinary Study off Algeria, 1997–1998), partly dedicated to study the mesoscale features during 1997. Physical, biogeochemical and biological measurements were made on transects through two hydrodynamic features, one anticyclonic eddy and a small secondary shear cyclonic eddy. The use of combined zooplankton descriptors, i.e. biomass, abundance, size structure (e.g. NB-SS slope) and taxonomic structure, and of cumulative function allowed us to extract spatial trends in the anticyclonic eddy (AE 96-1). It is hypothesized here that the eastern edge of AE 96-1, characterized by thick layer of chlorophyll (between 100 and 150m) due to the downward entrainment of chlorophyll down to 200m, was favorable for small organisms (Paracalanus/Clausocalanus, Calocalanus, and Calanus) while higher abundance of large active swimmer such as chaetognaths was observed in the center. In the cyclonic eddy, the highest abundance of filter-feeders (ostracods, cladocerans, doliolids and salps) was related to enhance trophic conditions, i.e. highest chlorophyll concentration (4–8mgm−3). These results show that cyclonic and anticyclonic eddies strongly influence the mesoscale characteristics of zooplankton in the Algerian basin during summer. Higher chlorophyll concentrations observed in spring suggest that such eddies can have an even more pronounced impact on the structuring of the ecosystem during high productive season. [Copyright &y& Elsevier]

Kinetic energy spectra appeared similar at all observational depths in the 3000m deep Algerian Basin, Western Mediterranean Sea. They were featureless except for a single peak at ∼2% above the local inertial frequency (f), even at depths (z) where stratification was very weak, . At great depths a second peak was observed at ∼0.99f. However, at a single point, we observed rotary spectra varying considerably with stratification and depth. Where that is between 600 and 1200m in a series of homogeneous layers associated with a double diffusion process and below 2200m in a dense homogeneous water formed nearby, all near-inertial horizontal motions were almost rectilinear. The observation of near-rectilinear inertial motions was in contrast with common observations of near-circularly polarized inertial motions, which were found, for example, from the same mooring at depths where , that is in continuously stratified waters encountered near the surface (100m) and at intermediate depths (1800m). Our observations suggested that the near-inertial motions in the Algerian Basin did not always represent internal gravity waves, but also dominant inertio (gyroscopic) waves. These waves could have been generated after excitation of the surface layer by atmospheric disturbances and the surface pressure gradient (barotropic) excitation of a simple 2-layer model via a coastal boundary condition, a process common in shelf seas. [Copyright &y& Elsevier]

The westward evolution of an open-sea anticyclonic eddy along the western Algerian Basin is shown, for the first time, by means of 15 buoy trajectories and remote sensing observations. For ∼3 months, the buoy trajectories described several anticyclonic loops in periods of 4–21 days. The eddy''s movement, translation, and rotation were separated with a kinematic model, resulting in a mean translation speed of ∼2 km/day, which fits the self-propulsion speed predicted on theoretical models for isolated eddies on a beta plane. Fluctuations in translation speed were associated with advection of the mean flow and topographic interactions. Both mechanisms changed the eddy''s horizontal shape from circular to elliptical, inducing fluctuations in its swirl velocity and solid-body rotation. The initial stage of the eddy is an isolated asymmetric dipole, comprised by a small cyclone and a large anticyclone, the latter generated from a frontal instability, which under the Coriolis term acquires anticyclonic relative vorticity. During its first days of life, the anticyclonic eddy was shallow Ro=0.9 and small (diameter less than 50 km). Later on, it reached a diameter of ∼150 km and a vertical structure of 3 km (Ro=0.1). A retrospective analysis with infrared images shows that the eddy''s generation took place at about 3–4°E. Then, the eddy completed a counterclockwise circuit never before reported in other studies and ended up at the entrance of the Algerian Basin, where the interaction with the topography and the coastal instability induced its decay. The eddy''s life span was ∼10 months. Computations of the heating rate following clusters of buoy trajectories show fluctuations throughout the eddy''s journey, induced by advection and a seasonal warming. [Copyright &y& Elsevier]

The Algerian Basin dynamics is dominated by the presence of very energetic mesoscale structures. Deep open sea eddies are key features that influence the regional circulation of water masses at all depths. In May 1998, an open sea eddy was sampled near 38°N 2°E by means of CTD, Acoustic Doppler Current Profiler (ADCP) and surface Lagrangian drifters. For the first time, it has been possible to characterise one of these mesoscale structures in its full depth, down to 2800 m. The density distribution indicated the presence of lighter water in the centre of the eddy from the surface to the bottom. The direct velocity measurements in the surface layer, plus the determination of the baroclinic shear from CTD data, evidenced that the anticyclonic motion was present in the whole water depth. [Copyright &y& Elsevier]

The position of the middle-upper Miocene volcanic arc, encompassing the Maghrebides, the Sardinia Channel and the Sardinia-Corsica block, implies that the Algerian and Tyrrhenian basins developed, respectively, as backarc and forearc extensional zones in the Western-Central Mediterranean. The opening of the Western-Central Mediterranean Neogene extensional basin has been commonly interpreted as a two-step process: the opening of the Provençal-Algerian basin during the early-middle Miocene, followed, in the late Miocene, by the formation of the Tyrrhenian Basin. This article is an attempt to synthesize knowledge about the hinge zone between Algerian and Tyrrhenian basins by combining the analysis of seismic reflection profiles with dredge and borehole data in order to investigate how the transition between the eastern Algerian backarc and Tyrrhenian forearc geodynamic settings took place. We identified three sectors: the western Tyrrhenian characterized by a Tortonian forearc extension; the Sardinia Channel, which preserves the architecture of the lower Miocene Maghrebian thrust belt formed during the collision between Europe and Africa plates; and the easternmost Algerian basin-Sicily Channel where a backarc–thrust belt system developed during the Tortonian stage. During the extensional events, we hypothesize the re-activation of inherited structures during Tortonian rifting, (that is a negative tectonic inversion of pre-existing Eocene and early Miocene thrust faults). The contemporaneity of two different geodynamic environments, the forearc extension in the northern area and backarc–thrust belt system in the southern area, can be directly related with a lateral variation of the lower plate paleogeography of the Africa continental margin. This evidence contributes to the understanding of how the paleogeography of the lower plate can control, to a certain extent, the tectonic evolution of the upper plate in a subduction setting. • We study the area between Algerian backarc and Tyrrhenian forearc geodynamic settings. • We combine the analysis of seismic reflection profiles, dredge and borehole data. • An older thrust belt lies between Tortonian forearc rift and backarc–thrust belt. • We propose a link among upper plate and paleogeography of the lower plate. [ABSTRACT FROM AUTHOR]

Recent studies have provided a better understanding of carbonate system parameters and their spatial and temporal variability in several areas of the Mediterranean Sea. This study uses a new dataset that covered the entire Algerian Basin during the summer of 2014 (SOMBA cruise) to describe the distribution of carbonate system parameters. The findings show that almost the entire basin was a source of CO 2 to the atmosphere during the studied period. Besides the well-known TrOCA (Tracer combining Oxygen, Carbon and total Alkalinity) approach, the study proposes new parametrization for the standard back calculation method to assess the anthropogenic carbon concentration. The results of both approaches yield similar distributions and concentration ranges (81 ± 4.3 and 69 ± 5.2 μmol/kg, respectively). This study assesses the errors for both approaches and emphasizes the importance of mesoscale and submesoscale structures on anthropogenic carbon sequestration and the distribution of carbonate parameters in the Algerian Basin. It shows that these features enhance basin ventilation and acidification. The first inventory of the anthropogenic carbon trapped by the Algerian Basin is estimated at 0.44–0.53 ± 0.06 Pg C, based on the new dataset. • The first high resolution spatial coverage of the Algerian Basin allowed a detailed study of the carbonate parameters. • A refitted back-calculation method is applied to estimate anthropogenic carbon concentrations. • Highlighting the role of the submesoscale processes in the increase of anthropogenic carbon sequestration. • The estimated acidification of the Algerian Basin, from the preindustrial era to 2014, range between −0.19 and −0.1 pH unit. • The first estimate of the anthropogenic carbon inventory trapped by the Algerian Basin is at 0.44–0.53 ± 0.06 Pg C. [ABSTRACT FROM AUTHOR]