The planktonic foraminiferal species Globorotalia truncatulinoides is widely used as a biostratigraphic proxy for the Quaternary in the Mediterranean region. High-resolution quantitative studies performed on sediment cores collected in the central and western Mediterranean Sea evidence a significant abundance of G. truncatulinoides during the Middle Holocene. The robust chronological frame allows us to date this bio-event to 4.8-4.4 ka Before Present (BP), very close to the base of the Meghalayan stage (4.2 ka BP). As a consequence, we propose that G. truncatulinoides can be considered a potential marker for the Middle-Late Holocene chronological subdivision. G. truncatulinoides is a deep-dwelling planktonic foraminifer and their distributional pattern in the central and western Mediterranean Sea provides a tool to monitor the onset of the regional deep vertical mixing of the water column. During the Holocene, the significant increase in the abundance of this species is in phase with the end of African Humid Period, which marks the transition from a more humid climate to the present-day semi-arid climate.

The neodymium isotopic composition (epsilon(Nd)) of seawater is one of the most important geochemical tracers to investigate water mass provenance, which can also serve as a proxy to reconstruct past variations in ocean circulation. Nd isotopes have recently also been used to reconstruct past circulation changes in the Mediterranean Sea on different time scales. However, the modern seawater epsilon(Nd) dataset for the Mediterranean Sea, which these reconstructions are based on, is limited and up to now only 160 isotopic measurements are available for the entire basin. The lack of present-day data also limits our understanding of the processes controlling the Nd cycle and Nd isotopic distribution in this semi-enclosed basin. Here we present new epsilon(Nd) data from 24 depth profiles covering all Mediterranean sub-basins, which significantly increases the available dataset in the Mediterranean Sea. The main goal of our study is to better characterize the relationship between the dissolved Nd isotope distributions and major water masses in the Mediterranean Sea and to investigate the impact and relative importance of local non-conservative modifications, which include input of riverine particles and waters, aeolian-derived material and exchange with the sediments at continental margins. This comprehensive epsilon(Nd) dataset reveals a clear epsilon(Nd) - salinity correlation and a zonal and depth gradient with epsilon(Nd) systematically increasing from the western to the eastern Mediterranean basin (average epsilon(Nd) = -8.8 +/- 0.8 and -6.7 +/- 1 for the entire water column, respectively), reflecting the large-scale basin circulation. We have evaluated the conservative epsilon(Nd) behaviour in the Mediterranean Sea and quantified the non-conservative components of the epsilon(Nd) signatures by applying an Optimum Multiparameter (OMP) analysis and results from the Parametric Optimum Multiparameter (POMP) analysis of Jullion et al. (2017). The results of the present study combined with previously published Nd isotope values indicate that dissolved epsilon(Nd) behaves overall conservatively in the open Mediterranean Sea and show that its water masses are clearly distinguishable by their Nd isotope signature. However, misfits between measured and OMP- and POMP-derived epsilon(Nd) values exist in almost all sub-basins, especially in the eastern Levantine Basin and Alboran Sea at intermediate-deep depths, which can be explained by the influence of detrital lithogenic epsilon(Nd) signatures through interaction with highly radiogenic Nile sourced volcanic fractions and unradiogenic sediments, respectively. The radiogenic signature acquired in the eastern Levantine Basin is carried by the Levantine Intermediate Water and transferred conservatively to the entire Mediterranean at intermediate depths. Our measured epsilon(Nd) values and OMP- and POMP-derived results indicate that non-conservative contributions originating from sediment sources are then propagated by water mass circulation (with distinct preformed epsilon(Nd)) along the Mediterranean Sea through advection and conservative mixing. Mediterranean epsilon(Nd) effectively traces the mixing between the different water masses in this semi-enclosed basin and is a suitable water mass tracer. (C) 2022 Elsevier Ltd. All rights reserved.

Coccolithophores were collected at 21 stations during summer 2016, from coastal and offshore areas of the Central Mediterranean Sea, to describe the ecology of the coccolithophore community integrating information on their abundance, environmental parameters (salinity, temperature, dissolved oxygen, and fluorescence) and oceanographic data. Emiliania huxleyi dominated the assemblage from surface to intermediate layers, while Florisphaera profunda was more abundant in the deep photic zone. Principal Component Analysis revealed that the distribution of coccolithophore taxa was influenced by environmental parameters: K-strategist taxa were related to warm surface waters, whereas lower photic zone taxa were influenced by the development of a Deep Chlorophyll Maximum and high salinity values, well below the thermocline. These results confirmed that a vertical species zonation, as a typical feature of low-middle latitude, characterizes the Central Mediterranean during summer. The distribution of F. profunda once again confirmed its use as a proxy of Deep Chlorophyll Maximum development and paleoproductivity estimates. Gephyrocapsa spp. (= total Gephyrocapsa), and in particular G. oceanica, were more abundant along the Atlantic Water pathway. Finally, the high concentration value of Helicosphaera carteri, recorded in the Ligurian Sea at an offshore station, suggested an expansion of the opportunist nature of this taxon from coastal environments to the offshore areas characterized by high turbidity and high productivity.

Globorotalia truncatulinoides oscillations have been recorded from different marine sediment cores collected in the central and western Mediterranean Sea. The abundances of this species over the last 500 yrs. demonstrates its potential value as bio-indicator of particular oceanographic condition during the Maunder Minimum (MM) event of the Little Ice Age (LIA). The comparison between the G. truncatulinoides abundance patterns of the Balearic Basin, central and south Tyrrhenian Sea and central and eastern Sicily Channel allows to highlight a similar response of this species during the MM event in the central-western Mediterranean Sea. The ecological meanings of this species and its peculiar high abundance percentages in the total assemblages suggest the development of enhanced vertical mixing conditions during MM winter season with a strong advection of nutrients from the nutrient-rich deeper layers and enhances the productivity levels in the mixed layer. The intensified vertical mixing could be linked to persistence of an atmospheric blocking event recorded by several authors during the MM.

In Summer 2015 (4-31 August), CNR-ISMAR carried out an oceanographic field-study in the Western Mediterranean Sea, on board of R/V MINERVA UNO. Sampling stations consisted in 7 transects, that spanned from Sicily Channel to Ligurian sea, Catalan sea, and Balearic Basin, dividing the area in sub-basins. 92 stations were visited totally. The dataset includes 550 discrete data of carbonate chemistry (pH-total scale and Total Alkalinity), concentrations of dissolved oxygen, and basic hydrological data (temperature, salinity and density). Methods: At each station, pressure (dbar), temperature (°C), and conductivity(mS/cm) were measured with a CTD SBE 911 plus General Oceanics Rosette System, equipped with 24 12-litres Niskin Bottles. Salinity (S, psu) and depth (m) were calculated by Sea-Bird Scientific routines. Seawater samples (n = 550) for the determination of biogeochemical parameters were collected from the Niskin bottles. Samples for dissolved oxygen (DO) were drawn in 60-mL BOD bottles and treated with Winkler reagents immediately after collection. For the determination of pH on the total hydrogen ion scale at 25 °C (pHT25), the samples were drawn after DO samples into 10 cm long cylindrical glass cells and analyzed spectrophotometrically. For the determination of total alkalinity (TA; ?mol kg-1), the samples were collected in 300 ml borosilicate bottles, poisoned with mercuric chloride, tightly closed and stored in the dark at a temperature similar to the in situ one (4-25 °C). DO samples were analyzed by the Winkler method (Grasshoff et al., 1999) using an automated Metrohm 798 MPT Titrino potentiometric titration system (CV = 0.17 % at 210 µmol L-1). pHT25 was measured on board, within 24 h after the sampling, using the spectrophotometric method with m-cresol purple as indicator (Clayton and Byrne, 1993). The precision was ±0.002 units (n = 3), accuracy and stability of the method were checked daily with reference seawater certified for TA and TCO2 (n = 34, CRM batch 146 provided by Prof A. G. Dickson, Scripps, 210 California). TA was determined by potentiometric titration in an open cell with a difference derivative readout (Hernandez-Ayon et al., 1999). The average precision was ±2.0 ?mol kg-1 (n = 86 duplicate samples) and the accuracy was checked daily by the titration of certified reference seawater (n = 59, CRM batch 146)

A basin-scale oceanographic cruise (OCEANCERTAIN2015) was carried out in the Western Mediterranean (WMED) in summer 2015 to study the evolution of hydrological and biogeochemical properties of the most ubiquitous water mass of the Mediterranean Sea, the Intermediate Water (IW). IW is a relatively warm water mass, formed in the Eastern Mediterranean (EMED) and identified by a salinity maximum all over the basin. While it flows westward, toward and across the WMED, it gradually loses its characteristics. This study describes the along-path changes of thermohaline and biogeochemical properties of the IW in the WMED, trying to discriminate changes induced by mixing and changes induced by interior biogeochemical processes. In the first part of the path (from the Sicily Channel to the Tyrrhenian Sea), respiration in the IW interior was found to have a dominant role in determining its biogeochemical evolution. Afterward, when IW crosses regions of enhanced vertical dynamics (Ligurian Sea, Gulf of Lion and Catalan Sea), mixing with surrounding water masses becomes the primary process. In the final part of the investigated IW path (the Menorca-Mallorca region), the role of respiration is further masked by the effects of a complex circulation of IW, indicating that short-term sub-regional hydrological processes are important to define IW characteristics in the westernmost part of the investigated area. A pronounced along-path acidification was detected in IW, mainly due to remineralization of organic matter. This induced a shift of the carbonate equilibrium toward more acidic species and makes this water mass increasingly less adequate for an optimal growth of calcifying organisms. The carbonate buffering capacity also decreases as IW flows through the WMED, making it more exposed to the adverse effects of a decreasing pH. The present analysis indicates that IW evolution in the sub-basins of the WMED is currently driven by complex hydrological and biogeochemical processes, which could be differently impacted by coming climate changes, in particular considering expected increases of extreme meteorological events, mainly due to the warming of the Mediterranean basin.

Long-term time-series are a fundamental prerequisite to understand and detect climate shifts and trends. Understanding the complex interplay of changing ocean variables and the biological implication for marine ecosystems requires extensive data collection for monitoring and hypothesis testing and validation of modelling products. In marginal seas, such as Mediterranean Sea, there are still monitoring gaps, both in time and in space. To contribute filling these gaps, an extensive dataset of dissolved inorganic nutrients profiles (nitrate, NO3; phosphate, PO43-; and silicate, SiO2) have been collected between 2004 and 2017 in the Western Mediterranean Sea and subjected to quality control techniques to provide to the scientific community a publicly available, long-term, quality controlled, internally consistent biogeochemical data product. The database includes 870 stations of dissolved inorganic nutrients sampled during 24 cruises, including temperature and salinity. Details of the quality control (primary and secondary quality control) applied are reported. The data are available in PANGAEA (https://doi.org/10.1594/PANGAEA.904172, Belgacem et al. 2019).

It is well known that in the Mediterranean major oceanic processes may occur, of which the most important example is deep water formation (DWF) that sustains the basin-wide thermohaline circulation cell. This is also the main oceanic mechanism that sustains the physical carbon pump: once carbon dioxide is dissolved in surface water, it can enter into the ocean carbon cycle and be sequestered and transported to different depths and parts of the ocean thanks to the processes of DWF and thermohaline circulation. The deep waters that are formed via DWF have long residence times, thus trapping great parts of the anthropogenic carbon released to the atmosphere. The most ubiquitous water mass of the Mediterranean Sea is the IntermediateWater (IW). It forms via salinification and densification of the surface waters in the Levantine Basin and in the Cretan Sea. After sinking to its equilibrium depth, the IW spreads throughout the whole Mediterranean Sea. The core of this water mass can be easily identified by its absolute maximum in salinity (and relative maximum in temperature), when looking at vertical profiles of these properties. While flowing back towards the Western Mediterranean (WMED), it tends to gradually lose its characteristics, due to dilution with adjacent water masses, becoming thus less salty and less warm. Not only salinity and temperature change along the IW path across the WMED, but also its biogeochemical and carbonate system properties: these non-conservative properties change also as a consequence of bio-chemical processes. The aim of this investigation is to understand the evolution of physical (temperature, salinity), biogeochemical (AOU, nutrients and DOM) and carbonate system properties (TA, pH) of the IW along its pathway through the WMED, assessing the role of changes induced by physical mixing of the IW with adjacent water masses and those induced by biological and biochemical processes. To discriminate between the acting processes and assess their relative roles, a mixing analysis has been performed. Along IW path the increase of AOU with age of the water mass indicates the preponderance of respiration over the production. The most important increase of AOU occurs while the IW enters and circulates within the Tyrrhenian Sea. In all other areas persistent strong hypoxic conditions are maintained with scarce changes. The decrease in TA is consistent with the change in salinity, as expected given the strong linear relationship between these two parameters, while the decrease of pH and the increases of the concentrations of the main inorganic nutrients (+77%, +34 and +26 %, for phosphates, nitrates and silicates, respectively) indicated an active remineralization of organic matter in this water mass. The process of acidification of IW also causes a shift of the carbonate equilibrium, toward more acidic species, and a decrease of the saturation state of calcite and aragonite, indicating a reduction of the oversaturation of these calcium carbonate minerals along IW path. The concomitant increase of the Revelle buffer factor suggest that this water is potentially less efficient to take up atmospheric CO2 with aging.

The database includes 870 stations sampled during 24 cruises between 2004 and 2017 in the Western Mediterranean Sea mainly on board R/Vs of the Italian National Research Council. It includes bottle data combined with CTD data. In all stations, measurements were carried out with a CTD-rosette system consisting of a CTD SBE 911 plus and a General Oceanics rosette with 24 12-l Niskin Bottles at the observed depth of the bottle sample. Temperature measurements were performed with an SBE-3/F thermometer and conductivity measurements were performed with an SBE-4 sensor. The probes were calibrated before and after the cruise. Samples of nitrate, phosphate and silicate were frozen to -20°C and stored before being analysed in laboratories onshore using standard colorimetric methods. Measurements were subjected to a rigorous quality control and this dataset includes both the original dataset after primary quality control (see "Original version") and the product after secondary quality control (crossover analysis)

The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in real-time and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintian and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.

The dissipation flux coefficient, a measure of the mixing efficiency of a turbulent flow, was computed from microstructure measurements collected with a vertical microstructure profiler in the Sicily Channel. This hotspot for turbulence is characterised by strong shear in the transitional waters between the south-eastward surface flow and the north-westward deep flow. Observations from the two deep passages in the channel showed a contrast in turbulent kinetic energy dissipation rates, with higher dissipation rates at the location with the strongest deep currents. This study investigated the dissipation flux coefficient variability in the context of mechanically driven turbulence with a large range of turbulence intensities. The dissipation flux coefficient was shown to decrease on average with increasing turbulence intensity Re-b, with median values of 0.74 for low Re-b (<8.5), 0.48 for moderate Re-b (8.5 Re-b <400) and 0.30 for high Re-b (400). The dissipation flux coefficient inferred from the measurements was systematically higher on average than the parameterisation as a function of turbulence intensity suggested by Bouffard and Boegman (Dyn Atmos Oceans 61:14-34, 2013). A plateau at moderate turbulence intensities was observed, followed by a decrease in the dissipation flux coefficient with increasing turbulence intensity as predicted by the parameterisation, but at higher turbulence intensity. The dissipation flux coefficient showed a strong variability with the water column stability regime for the different water masses. In particular, high dissipation flux coefficient (median 0.40) was found at Re-b between 400 and 10(4) for the transitional waters at the northeastern passage, where dissipation rates were high, stratification and shear were strong but the Richardson number Ri was sub-critical. Vertical diapycnal diffusive fluxes were computed, and upward salinity sustained density fluxes of the order of 9 x 10(-6) and 4 x 10(-6) kg m(-2) s(-1) were found to be characteristic of the transitional (28 < sigma <29 kg m(-3)) and intermediate (sigma >29 kg m(-3)) waters, respectively. Turbulent mixing led to a lightening of the transitional and intermediate waters, which was consistent with previous estimates (Sparnocchia et al. J Mar Syst 20:301-317, 1999), but an order of magnitude lower when inferred from the (Bouffard and Boegman Dyn Atmos Oceans 61:14-34, 2013) parameterisation.

not available

Diel vertical migration (DVM) is a survival strategy adopted by zooplankton that we investigated in the Corsica Channel using acoustic Doppler current profiler (ADCP) data from April 2014 to November 2016. The principal aim of the study is to characterize migration patterns and biomass temporal evolution of zooplankton along the water column. The ADCP measured vertical velocity and echo intensity in the water column range between about 70 and 390m (the bottom depth is 443m). During the investigated period, zooplanktonic biomass had a well-defined daily and seasonal cycle, with peaks occurring in late winter to spring (2015 and 2016) when the stratification of the water column is weaker. Zooplanktonic biomass temporal distribution in the whole water column is well correlated with biomass of primary producers, estimated with satellite data. Zooplanktonic blooming and non-blooming periods have been identified and studied separately. During the non-blooming period zooplanktonic biomass was most abundant in the upper and the deep layers, while during the blooming period the upper-layer maximum in zooplanktonic biomass disappeared and the deep layer with high zooplanktonic biomass became thicker. These two layers are likely to correspond to two different zooplanktonic communities. The evolution of zooplanktonic biomass is well correlated with chlorophyll, with phytoplankton biomass peaks preceding the upper-layer secondary production by a lag of about 3.5 weeks. Nocturnal DVM appears to be the main pattern during both periods, but reverse and twilight migration are also detected. Nocturnal DVM was more evident at mid-water than in the deep and the upper layers. DVM occurred with different intensities during blooming and non-blooming periods. One of the main outcomes is that the principal drivers for DVM are light intensity and stratification, but other factors, like the moon cycle and primary production, are also taken in consideration.

The Mediterranean community represented in this paper is the result of more than 30 years of EU and nationally funded coordination, which has led to key contributions in science concepts and operational initiatives. Together with the establishment of operational services, the community has coordinated with universities, research centers, research infrastructures and private companies to implement advanced multi-platform and integrated observing and forecasting systems that facilitate the advancement of operational services, scientific achievements and mission-oriented innovation. Thus, the community can respond to societal challenges and stakeholders needs, developing a variety of fit-for-purpose services such as the Copernicus Marine Service. The combination of state-of-the-art observations and forecasting provides new opportunities for downstream services in response to the needs of the heavily populated Mediterranean coastal areas and to climate change. The challenge over the next decade is to sustain ocean observations within the research community, to monitor the variability at small scales, e.g., the mesoscale/submesoscale, to resolve the sub-basin/seasonal and inter-annual variability in the circulation, and thus establish the decadal variability, understand and correct the model-associated biases and to enhance model-data integration and ensemble forecasting for uncertainty estimation. Better knowledge and understanding of the level of Mediterranean variability will enable a subsequent evaluation of the impacts and mitigation of the effect of human activities and climate change on the biodiversity and the ecosystem, which will support environmental assessments and decisions. Further challenges include extending the science-based added-value products into societal relevant downstream services and engaging with communities to build initiatives that will contribute to the 2030 Agenda and more specifically to SDG14 and the UN's Decade of Ocean Science for sustainable development, by this contributing to bridge the science-policy gap. The Mediterranean observing and forecasting capacity was built on the basis of community best practices in monitoring and modeling, and can serve as a basis for the development of an integrated global ocean observing system.

time series has been collected by the Italian Consiglio Nazionale delle Ricerche (CNR) in a station located at about 3500 m depth in the central Tyrrhenian Sea (39° 46.85 N, 011° 53.00 E) over the period 2003-2016. The dataset contains 21 hydrological profiles (Pressure (dbar), Temperature (ITS-90, °C) and Salinity) performed on average every six months, with a lack of data in the period 2007-2010.

The longest historical time series (14 years, from 2003 to 2016) of temperature and salinity of thermohaline staircases with highly homogeneous and reliable data ever observed is here presented and studied. The thermohaline staircase system of the central Tyrrhenian Sea is due to double diffusion in salt finger regime, and our study reveals its conservative behavior, oscillating among slightly different shapes, passing through merging processes, with a systematic upward drift of the interfaces. Data also show enhanced salt finger processes after 2010, near the bottom, promoted by the ingression from the Western Mediterranean of a new denser water mass due to the Western Mediterranean Transition. Our results are relevant for studying the mixing in the intermediate and deep region and open the way for modeling and theoretical follow-up studies aimed to reproduce and explain these observations.

IFON integrates 17 fixed monitoring systems and an oceanographic transect (Senigallia-Susak), providing multidisciplinary monitoring of coastal and deep marine environments, with high temporal resolution, for a number of marine and atmospheric variables.

The Mediterranean Sea has been identified as a hot spot for climatic change, i.e. a region most impacted by ongoing warming trend. It is also a potential model for global patterns that will be experienced in the next decades worldwide not only regarding ocean circulation, but for the marine biota as well (Lejeusne et al., 2010). Evidence of warming trend in the region has been already documented by the scientific community (e.g., Rixen et al, 2005). In addition to long-term trends, Schroeder et al. (Sci. Rep., 2016) reported an abrupt shift in terms of temperature, salinity and density in the deep Western Mediterranean Sea. This shift, originally called "Western Mediterranean Transition", is actually moving the basic physical properties of the Western Mediterranean from an old equilibrium to a new different one. The warming and salinification, with faster increase than in the past, is also detected in the intermediate waters, with signals coming from the eastern Mediterranean that are now propagating into the western Mediterranean (Schroeder et al., Sci. Rep. 2017). Since 2017 the new glider line Sardinia - MAllorca Repeated Transect (SMART) has been made operational. It integrates the existing distributed multiplatform observing system in the Western Mediterranean Sea. The SMART missions are scheduled twice a year (in spring and in fall) along a meridional track (latitude 39.8 oN), within a framework of collaboration between CNR and SOCIB. A deep Teledyne Slocum G2 glider (depth range 0-900 m) is measuring temperature, salinity and dissolved oxygen with high vertical and horizontal resolution. The glider is equipped also with a Rockland Scientific MicroRider for measuring the microstructure. The main goal is to set-up and maintain a long-term repeated transect to monitor medium-to-long-term variability of surface and intermediate water masses. It also supports mesoscale studies, operational forecasts and climate monitoring. The glider reaches the transitional layer between intermediate and deep water, which is undergoing the Western Mediterranean Transition, where thermohaline staircases likely develop. Data coming from the first mission are under preliminary scientific analysis. The data show evidence of significant warming taking place in the area from 900 m depth horizon up to the lower interface of the surface waters (200m), consistent with a general warming trend of the Western Mediterranean Sea. In particular, it is observed a warming with respect to a mission run in 2013 (Olita et al., 2014) of 0.3o (0.065 oC /year), comparable with estimates provided by Schroeder et al., 2017 in the Sicily Channel. The mission shows a clear zonal distribution of salinity at the surface, with relatively new Atlantic water (lower salinity) to the east and older Atlantic water to the west.

Small scale turbulence in the two main deep passages of the Sicily Channel was characterised for the first time with microstructure measurements collected during four cruises spanning a two year period. Large turbulent kinetic energy dissipation rates (epsilon) were observed, with averaged values below the mixed layer reaching 10(-7) W kg(-1), confirming that the Sicily Channel is a hotspot for turbulence. Contrasted depth-averaged epsilon were observed between the two passages below the mixed layer: enhanced epsilon in the northeastern passage ranging from 1.3 x 10(-8) - 2.7 x 10(-7) W kg(-1) over the different cruises, and much weaker epsilon in the southwestern passage ranging from 3.5 x 10(-9) to 7.7 x 10(-9) W kg(-1). This contrast in epsilon occurs due to a stronger deep flow at the northeastern passage, resulting in larger shear and stronger turbulence. Internal tides act as another important source of turbulence in both passages, modulating the subinertial flow and inducing shear instabilities. Enhanced turbulence was also revealed by additional measurements made downstream (with respect to the deep flow) in the northeastern passage towards the deeper Tyrrhenian Sea, as dense waters overflow above steep topography. A wave-wave parameterisation was tested for epsilon, which showed a reasonable consistency for the less turbulent southwestern passage, but not for the more turbulent northeastern passage, suggesting a difference in the mechanism of turbulence.

During winter 2012-2013, open-ocean deep convection which is a major driver for the thermohaline circulation and ventilation of the ocean, occurred in the Gulf of Lions (Northwestern Mediterranean Sea) and has been thoroughly documented thanks in particular to the deployment of several gliders, Argo profiling floats, several dedicated ship cruises, and a mooring array during a period of about a year. Thanks to these intense observational efforts, we show that deep convection reached the bottom in winter early in February 2013 in a area of maximum 28±3 109m2. We present new quantitative results with estimates of heat and salt content at the subbasin scale at different time scales (on the seasonal scale to a 10 days basis) through optimal interpolation techniques, and robust estimates of the deep water formation rate of 2.0 ±0.2Sv. We provide an overview of the spatiotemporal coverage that has been reached throughout the seasons this year and we highlight some results based on data analysis and numerical modeling that are presented in this special issue. They concern key circulation features for the deep convection and the subsequent bloom such as Submesoscale Coherent Vortices (SCVs), the plumes, and symmetric instability at the edge of the deep convection area.