Tritiumconcentrations in oceanswere compiled fromthe literature, online databases and originalmeasurements in order to determine the global distribution of tritium concentrations according to latitude and depth in all oceans. The total inventory of tritiumdecay corrected in 2016 has been estimated using evaluation of the natural and artificial contributions in 23 spatial subdivisions of the total ocean. It is determined equal to 26.8 +/- 14 kg including 3.8 kg of cosmogenic tritium. That is in agreementwith the total atmospheric input of tritiumfromnuclear bomb tests and the natural inventory at steady-state estimated from natural production rates in the literature (27.8-29.3 kg in the Earth). We confirmthe global increase in tritiumaccording to latitude observed in theNorthern hemisphere since 1967 with amaximumin the Arctic Ocean. The minimumtritiumconcentrations observed in the Southern Ocean were close to steady-state with known natural tritium deposition. We focused on the temporal evolution of surface (0 to 500 m) tritium concentrations in a selected area of the North Atlantic Ocean (30 degrees N-60 degrees N) where we found the 2016 concentration to be 0.60 +/- 0.10 TU (1s). Results showed that in that area, between 1988 and 2013, tritiumconcentrations: i) decreased faster than the sole radioactive decay, due to a mixing with lower and lateral less concentrated waters, and ii) decreased towards an apparent steady state concentration. The half-timemixing rate of surfacewaters and the steady state concentration were respectively calculated to be 23 +/- 5 years (1 sigma) and 0.38 +/- 0.07 TU (1 sigma). This apparent steady-state concentration in the North Atlantic Ocean implies a mean tritium deposition of 1870 +/- 345 Bq.m(-2) (1 sigma), five folds higher than the known inputs (natural, nuclear tests fallout and industrial releases, similar to 367 Bq.m(-2)) in this area. (c) 2018 Elsevier B.V. All rights reserved.

High-frequency temperature fluctuations recorded in the English Channel are compared using two long-term autonomous underwater monitoring stations at less than 20-min time resolution. Measurements were taken from 2005 to 2011 from two systems 460 km apart in the western and eastern parts of the English Channel. Spectral analysis reveals similar statistical behaviors, with approximate 5/3 spectra and several forcing frequencies in relation to tidal and daily cycles. A co-spectra study reveals a transition scale of 11 days. The influence of this scale is also visible though Time-Dependent Intrinsic Correlation analysis ( TDIC)-a recently introduced cross-correlation analysis based on Empirical mode decomposition. This helps to spatialize high-frequency temporal records at a fixed location. (C) 2016 The Authors. Published by Elsevier Masson SAS on behalf of Academie des sciences.

The JERICO European research infrastructure (RI) is integrating several platform types i.e. fixed buoys, piles, moorings, drifters, Ferryboxes, gliders, HF radars, coastal cable observatories and the associated technologies dedicated to the observation and monitoring of the European coastal seas. The infrastructure is to serve both the implementation of European marine policies and the elucidation of key scientific questions through dedicated observation and monitoring plans. It includes observations of the physical, chemical and biological compartments and aims at a better integration of marine biology with physical and chemical oceanology, through specific interactions with other relevant ocean observing systems that provide complementary observations. The first phase of the implementation of JERICO encompasses setting up, coordination and harmonization, and were performed between 2011 and 2015 in the framework of FP7-JERICO (www.jerico-fp7.eu), a 4-year long infrastructure project co-funded by the European Commission, with 27 partners from 17 European countries under the coordination of IFREMER. The next 4-year phase is to be carried out through the H2020-JERICO-NEXT European project, starting in 2015 and involving 33 scientific and industrial partners. The main objective of the JERICO consortium is to establish a common approach for a pan-European coastal marine observatory network. This is a dynamic and long-lasting effort necessitating continuous work towards harmonization (i.e. design, operation, and maintenance), evolution and extension of the current systems as well as the delivery of data and products to the users. Success relies on a good coordination and follow-up between FP7-JERICO and JERICO-NEXT, and onwards, at both hardware and software levels. More specifically, the existing network and its possible evolution are continuously assessed taking in account the evolution of the user needs, the harmonization effort to be driven, the existing sensors and technologies, their upgrades for integration on dedicated platforms, also the accompanying of under development sensors and/or systems with involvement of providers and stakeholders when possible. Nevertheless, a major issue relates to the sustainability of the infrastructure, both at economical and governance levels, and the capability in integrating the latest technology while preserving the scientific value of the data. This paper briefly summarizes the work carried out in FP7-JERICO project and drafts strategic aspects of the JERICO-RI sustainability on the long-term. s. We will present the 6 priority scientific areas that are the drivers of JERICO-NEXT scientific strategy and the subsequent technology development to be implemented through dedicated Joint Research Activity Projects. Emphasis is put on how the consortium intends to address long term financial and legal governance structures for the sustainable implementation of JERICO-NEXT infrastructures, as well as access to the infrastructure and associated services and link to stakeholders such as relevant funding agencies and SMEs.

From January 2011 to December 2013, we constructed a comprehensive pCO2 data set based on voluntary observing ship (VOS) measurements in the western English Channel (WEC). We subsequently estimated surface pCO2 and air–sea CO2 fluxes in northwestern European continental shelf waters using multiple linear regressions (MLRs) from remotely sensed sea surface temperature (SST), chlorophyll a concentration (Chl a), wind speed (WND), photosynthetically active radiation (PAR) and modeled mixed layer depth (MLD). We developed specific MLRs for the seasonally stratified northern WEC (nWEC) and the permanently well-mixed southern WEC (sWEC) and calculated surface pCO2 with uncertainties of 17 and 16 μatm, respectively. We extrapolated the relationships obtained for the WEC based on the 2011–2013 data set (1) temporally over a decade and (2) spatially in the adjacent Celtic and Irish seas (CS and IS), two regions which exhibit hydrographical and biogeochemical characteristics similar to those of WEC waters. We validated these extrapolations with pCO2 data from the SOCAT and LDEO databases and obtained good agreement between modeled and observed data. On an annual scale, seasonally stratified systems acted as a sink of CO2 from the atmosphere of −0.6± 0.3, −0.9± 0.3 and −0.5± 0.3 mol C m yr in the northern Celtic Sea, southern Celtic sea and nWEC, respectively, whereas permanently well-mixed systems acted as source of CO2 to the atmosphere of 0.2± 0.2 and 0.3± 0.2 mol C m yr in the sWEC and IS, respectively. Air–sea CO2 fluxes showed important inter-annual variability resulting in significant differences in the intensity and/or direction of annual fluxes. We scaled the mean annual fluxes over these provinces for the last decade and obtained the first annual average uptake of −1.11± 0.32 Tg C yr for this part of the northwestern European continental shelf. Our study showed that combining VOS data with satellite observations can be a powerful tool to estimate and extrapolate air–sea CO2 fluxes in sparsely sampled area.

Introduction Conclusions References Tables Figures

From January 2011 to December 2013, we constructed a comprehensive pCO2 data set based on voluntary observing ship (VOS) measurements in the western English Channel (WEC). We subsequently estimated surface pCO2 and air–sea CO2 fluxes in northwestern European continental shelf waters using multiple linear regressions (MLRs) from remotely sensed sea surface temperature (SST), chlorophyll a concentration (Chl a), wind speed (WND), photosynthetically active radiation (PAR) and modeled mixed layer depth (MLD). We developed specific MLRs for the seasonally stratified northern WEC (nWEC) and the permanently well-mixed southern WEC (sWEC) and calculated surface pCO2 with uncertainties of 17 and 16 μatm, respectively. We extrapolated the relationships obtained for the WEC based on the 2011–2013 data set (1) temporally over a decade and (2) spatially in the adjacent Celtic and Irish seas (CS and IS), two regions which exhibit hydrographical and biogeochemical characteristics similar to those of WEC waters. We validated these extrapolations with pCO2 data from the SOCAT and LDEO databases and obtained good agreement between modeled and observed data. On an annual scale, seasonally stratified systems acted as a sink of CO2 from the atmosphere of −0.6 ± 0.3, −0.9 ± 0.3 and −0.5 ± 0.3 mol C m−2 yr−1 in the northern Celtic Sea, southern Celtic sea and nWEC, respectively, whereas permanently well-mixed systems acted as source of CO2 to the atmosphere of 0.2 ± 0.2 and 0.3 ± 0.2 mol C m−2 yr−1 in the sWEC and IS, respectively. Air–sea CO2 fluxes showed important inter-annual variability resulting in significant differences in the intensity and/or direction of annual fluxes. We scaled the mean annual fluxes over these provinces for the last decade and obtained the first annual average uptake of −1.11 ± 0.32 Tg C yr−1 for this part of the northwestern European continental shelf. Our study showed that combining VOS data with satellite observations can be a powerful tool to estimate and extrapolate air–sea CO2 fluxes in sparsely sampled area.

There is now a strong scientific consensus that coastal marine systems of Western Europe are highly sensitive to the combined effects of natural climate variability and anthropogenic climate change. However, it still remains challenging to assess the spatial and temporal scales at which climate influence operates. While large-scale hydro-climatic indices, such as the North Atlantic Oscillation (NAO) or the East Atlantic Pattern (EAP) and the weather regimes such as the Atlantic Ridge (AR), are known to be relevant predictors of physical processes, changes in coastal waters can also be related to local hydro-meteorological and geochemical forcing. Here, we study the temporal variability of physical and chemical characteristics of coastal waters located at about 48°N over the period 1998–2013 using (1) sea surface temperature, (2) sea surface salinity and (3) nutrient concentration observations for two coastal sites located at the outlet of the Bay of Brest and off Roscoff, (4) river discharges of the major tributaries close to these two sites and (5) regional and local precipitation data over the region of interest. Focusing on the winter months, we characterize the physical and chemical variability of these coastal waters and document changes in both precipitation and river runoffs. Our study reveals that variability in coastal waters is connected to the large-scale North Atlantic atmospheric circulation but is also partly explained by local river influences. Indeed, while the NAO is strongly related to changes in sea surface temperature at the Brest and Roscoff sites, the EAP and the AR have a major influence on precipitations, which in turn modulate river discharges that impact sea surface salinity at the scale of the two coastal stations.

Phytoplankton blooms are usually dominated by chain-forming diatom species that can alter food pathways from primary producers to predators by reducing the interactions between intermediate trophic levels. The food-web modifications are determined by the length of the chains; however, the estimation is biased because traditional sampling strategies damage the chains and, therefore, change the phytoplankton size structure. Sedimentological studies around oceanic fronts have shown high concentrations of giant diatom mats (>1 cm in length), suggesting that the size of diatom chains is underestimated in the pelagic realm. Here, we investigate the variability in size and abundance of phytoplankton chains at the Ushant tidal front (NW France) using the Video Fluorescence Analyzer (VFA), a novel and non-invasive system. CTD and Scanfish profiling characterized a strong temperature and chlorophyll front, separating mixed coastal waters from the oceanic-stratified domain. In order to elucidate spring-neap variations in the front, vertical microstructure profiler was used to estimate the turbulence and vertical nitrate flux. Key findings were: (1) the VFA system recorded large diatom chains up to 10.7 mm in length; (2) chains were mainly distributed in the frontal region, with maximum values above the pycnocline in coincidence with the maximum chlorophyll; (3) the diapycnal fluxes of nitrate enabled the maintenance of the bloom in the frontal area throughout the spring-neap tidal cycle; (4) from spring to neap tide the chains length was significantly reduced; (5) during neap tide, the less intense vertical diffusion of nutrients, as well as the lower turbulence around the chains, intensified nutrient-depleted conditions and, thus, very large chains became disadvantageous. To explain this pattern, we suggest that size plasticity is an important ecological trait driving phytoplankton species competition. Although this plasticity behavior is well known from experiments in the laboratory, it has never been reported from observations in the field.

To design a prototype for an Integrated Ocean Observing System (IOOS), at least three components are mandatory: a modeling platform, an in situ observing system and a structure to collect and to disseminate the information (e.g. database, website). The PREVIMER project followed this approach and in order to sustain model applications, PREVIMER has developed, funded and organized part of in situ observing networks in the Bay of Biscay and the Channel. For a comprehensive system, focus was addressed on fi xed platforms (MAREL MOLIT, MAREL Iroise, Island network and D4 for sediment dynamics), ships of opportunity (RECOPESCA program and FerryBoxes), and coastal profi lers (ARVOR-C/Cm). Each system is briefl y described and examples of scientifi c results obtained with corresponding data are highlighted to show how these systems contribute to solve scientifi c multidisciplinary issues from the coastal ocean dynamics to the biodiversity including pelagic and benthic habitats.

From January 2011 to January 2013, a FerryBox system was installed on a Voluntary Observing Ship (VOS), which crossed the Western English Channel (WEC) between Roscoff (France) and Plymouth (UK) up to 3 times a day. The FerryBox continuously measured sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen (DO), fluorescence and partial pressure of CO2 (from April 2012) along the ferry track. Sensors were calibrated based on 714 bimonthly surface samplings with precisions of 0.016 for SSS, 3.3μM for DO, 0.40μgL−1 for Chlorophyll-a (Chl-a) (based on fluorescence measurements) and 5.2μatm for pCO2. Over the 2years of deployment (900 crossings), we reported 9% of data lost due to technical issues and quality checked data was obtained to allow investigation of the dynamics of biogeochemical processes related to air–sea CO2 fluxes in the WEC. Based on this unprecedented high-frequency dataset, the physical structure of the WEC was assessed using SST anomalies and the presence of a thermal front was observed around the latitude 49.5°N, which divided the WEC in two main provinces: the seasonally stratified northern WEC (nWEC) and the all-year well-mixed southern WEC (sWEC). These hydrographical properties strongly influenced the spatial and inter-annual distributions of phytoplankton blooms, which were mainly limited by nutrients and light availability in the nWEC and the sWEC, respectively. Air–sea CO2 fluxes were also highly related to hydrographical properties of the WEC between late April and early September 2012, with the sWEC a weak source of CO2 to the atmosphere of 0.9mmolm−2d−1, whereas the nWEC acted as a sink for atmospheric CO2 of 6.9mmolm−2d−1. The study of short time-scale dynamics of air–sea CO2 fluxes revealed that an intense and short (less than 10days) summer bloom in the nWEC contributed to 29% of the CO2 sink during the productive period, highlighting the necessity for high frequency observations in coastal ecosystems. During the same period in the sWEC, the tidal cycle was the main driver of air–sea CO2 fluxes with a mean difference in pCO2 values between spring and neap tides of +50μatm. An extraction of day/night data at 49.90°N showed that the mean day–night differences accounted for 16% of the mean CO2 sink during the 5months of the study period implying that the diel biological cycle was also significant for air–sea CO2 flux computations. The 2years of deployment of our FerryBox allowed an excellent survey of the variability of biogeochemical parameters from inter-annual to diurnal time scales and provided new insights into the dynamics of air–sea CO2 fluxes in the contrasted ecosystems of the WEC.

Two profiling floats, equippedwith nitrate concentration sensors were deployed in the northwestern Mediterranean from summer 2012 to summer 2013. Satellite ocean color data were extracted to evaluate surface chlorophyll concentration at float locations. Time series of mixed layer depths and nitrate and chlorophyll concentrations were analyzed to characterize the interplay between the physical-chemical and biological dynamics in the area. Deep convection (mixed layer depth> 1000m) was observed in January–February, although high-nitrate surface concentrations could be already observed in December. Chlorophyll increase is observed since December, although high values were observed only inMarch. The early nitrate availability in subsurface layers, which is likely due to the permanent cyclonic circulation of the area, appears to drive the bloom onset. The additional nitrate supply associated to the deep convection events, although strengthening the overall nitrate uptake, seems decoupled of the December increase of chlorophyll.

An optimum multiparameter (OMP) analysis was applied to samples collected during a cruise in the northeast North Atlantic with the aim of objectively defining water mass realms and calculating water mass mixing‐weighted average (archetypal) concentrations of dissolved organic carbon (DOC) and nitrogen (DON) and fluorescent dissolved organic matter (FDOM). The profile of archetypal DOC, which retains the basin‐scale variability from the formation area of the water masses to the study area, was modeled with a constant initial concentration of 60 ± 1 mmol kg−1 that decreased linearly with increasing apparent oxygen utilization (AOU) at a rate of −0.20 ± 0.03 mol C per mol of AOU. The archetypal C:N ratio of dissolved organic matter was also modeled with a constant initial molar ratio of 11.5 ± 0.4 that increased at a rate of 0.06 ± 0.01 per μmol kg−1 of AOU. The profile of archetypal FDOM was modeled with a constant initial humic‐like fluorescence of 0.54 ± 0.07 quinine sulfate units that increased at a rate of 0.009 ± 0.001 g equivalent of quinine sulphate per mol of AOU. Only the Denmark Strait Overflow Water departed from this behavior because of the marked terrestrial influence of Arctic rivers during the formation of this water mass. The variability not explained by the archetypal concentrations, which retain the local variability, suggesting that N‐poor DOM was mineralized in the study area, and that the efficiency of the local production of humic‐like substances was directly proportional to the ventilation of the corresponding water mass realms.

Kelp ecosystems form widespread underwater forests playing a major role in structuring the biodiversity at a regional scale. Some seaweeds such as Laminaria digitata are also economically important, being exploited for their alginate and iodine content. Although some studies have shown that kelp ecosystems are regressing and that multiple causes are likely to be at the origin of the disappearance of certain populations, the extent to which global climate change may play a role remains speculative. Here we show that many populations of L. digitata along European coasts are on the verge of local extinction due to a climate-caused increase in sea temperature. By modeling the spatial distribution of the seaweed, we evaluate the possible implications of global climate change for the geographical patterns of the species using temperature data from the Coupled Model Intercomparison Project phase 5 (CMIP5). Projections of the future range of L. digitata throughout the 21st century show large shifts in the suitable habitat of the kelp and a northward retreat of the southern limit of its current geographic distribution from France to Danish coasts and the southern regions of the United Kingdom. However, these projections depend on the intensity of warming. A medium to high warming is expected to lead to the extirpation of the species as early as the first half of the 21st century and there is high confidence that regional extinction will spread northwards by the end of this century. These changes are likely to cause the decline of species whose life cycle is closely dependent upon L. digitata and lead to the establishment of new ecosystems with lower ecological and economic values.

We investigated the dynamics of the CO2 system across the Western English Channel (WEC) between Roscoff (France) and Plymouth (UK) using a Voluntary Observing Ship (VOS). From December 2010 to December 2011, 20 return crossings were carried out to collect a comprehensive dataset of CO2 system parameters and ancillary data. The hydrographical structure of the water column across the latitudinal transect was investigated at 3 fixed stations: ASTAN (southern WEC, offshore Roscoff), El and L4 (northern WEC, offshore Plymouth). Based on these profiles, we defined two provinces, the stratified northern WEC (>49.5 degrees N) and the well-mixed southern WEC (<49.5 degrees N), which were periodically separated by a thermal front. These contrasted hydrographical properties strongly influenced the ecosystem dynamics. Biological production/respiration processes were the main driver of pCO(2) variability during the year except for winter cooling in the northern WEC. The seasonally stratified northern WEC showed enhanced biological activities characterized by an extensive autotrophic phase, which maintained the pCO(2) below the atmospheric equilibrium until early fall and acted as a sink for atmospheric CO2 at a rate of 1.1 mol C m(-2) y(-1). The permanently well mixed southern WEC was characterized by a shorter autotrophic phase due to a delayed spring phytoplankton growth and an early start of the fall heterotrophic phase, resulting in an annual air-sea CO2 flux close to equilibrium at a rate of -0.4 mol C m(-2) y(-1). On annual scale, calculation of Net Ecosystem Production (NEP) revealed that surface waters at El and ASTAN were both autotrophic at rates of 1.5 mol C m(-2) y(-1) and 1.0 mol C m(-2) y(-1), respectively. Our latitudinal approach resolved the discrepancy between the directions of the fluxes in the WEC observed in previous studies by differentiating between the hydrological regions. The combined approach of using data from VOS tracks and fixed coastal observatories stations provided new insights into the control of air-sea CO2 fluxes in the different provinces of the WEC. This combined approach could be applied in other continental shelf systems where data on the CO2 system are sparse. (C) 2013 Elsevier B.V. All rights reserved.

Annual report on the hydrological conditions of the North Atlantic in 2012: 1) General conditions deduced from the analyzed fields ISAS based on ARGO floats data; 2) Ships of opportunity along 60°N; 3) South Western Channel time series.

The North Atlantic subpolar gyre is considered to be one of the strongest marine anthropogenic CO2 sinks, a consequence of extensive deep convection occurring during winter. Observations collected in this region since 1981 have shown large changes in Dissolved Inorganic Carbon (DIC) concentrations in intermediate and deep waters, which have been attributed to both anthropogenic CO2 penetration and natural variability in the ocean carbon cycle (Wanninkhof et al., 2010). In this context, we describe new δ13CDIC observations obtained in the Irminger Basin during two OVIDE cruises (2002 and 2006) which we compare to historical data (TTO-NAS 1981) in order to estimate the oceanic 13C Suess Effect over the more than twenty years that separates these surveys. The data reveal a significant decrease in δ13CDIC, of between −0.3‰ and −0.4‰ from 1981 to 2006. The anthropogenic change, extracted by using the extended Multi Linear Regression (eMLR) approach, explains 75% of this signal for oldest water mass and 90% for youngest. The reminding signal is due to the natural processes, such as remineralization and vertical mixing. The eMLR method was also applied to DIC measurements which i) reveal strong relationships between the increase of anthropogenic CO2 and the oceanic 13C Suess Effect over the whole water column during the 25-year period and ii) support the hypothesis of change in the Cant storage rate in the Irminger Basin between 1981 and 2006.

Based on a multidisciplinary survey in the Iberian upwelling during late summer 2007, this paper analysed comparatively the cross-shore variability and offshore transport across the upwelling front and within a mesoscale filament.Along the East–West (EW) sections, transient upwelling pulses bring regularly cold, fresh and nutrient-enriched waters to the surface, triggering intense biological responses. Offshore advection by wind-forced Ekman drift of the successive fronts, interrupted by relaxation periods, drive the variability of the planktonic communities. While the near-shore areas are dominated by relatively small phytoplankton controlled by mesozooplankton grazing, large cells of diatoms appear after a short decay. Although microphytoplankton dominates largely the shelf communities, the species composition varies during the offshore drift with the apparition of dinoflagellates and the gradual development of large zooplankton individuals. The oligotrophic ecosystem characterised by small organisms and low biomass (∼80km offshore) contrasts strongly with the transitional area and the coastal upwelling.The low density waters within the filament and the existence of a pair of opposite rotating eddies at its base and tip promote its generation and rapid seaward extension. The intensified offshore advection of coastal enriched waters considerably increases the area favouring a productive ecosystem (until ∼160km off the coast). Cross-shelf variability of bio-physical variables is observed in the filament as along EW sections, although a subsequent homogenisation within the mesoscale structure erases the sharp fronts. Off the shelf within the filament, the chlorophyll a is distinctly organised as a shallow subsurface maximum dominated by nano-phytoplankton. The relative physical isolation of a dynamical food-web in the filament is also promoting nutrient remineralisation under the structure.Finally, we estimate that mesoscale filaments, although being less extended meridionally than the upwelling front itself (∼40% of the length of the front) are responsible for a greater offshore transport of chlorophyll (∼60% of total cross-shelf exchanges) over the Iberian system. Despite the favourable wind pulses advecting westward the successive upwelling fronts, self-propelled filaments provide permanent offshore transport, even under wind relaxation period, thus playing a major role in cross-shelf exchanges.