Description: Euro-Argo strategy in the context of the OneArgo new international design

Description: This document describes the deployment of instrumentation in the Eastern tropical Atlantic area and shows the preliminary data acquired.

Description: This deliverable presents the Final Assessment of the observation and thematic networks as those represented in work package 3 of EuroSea, taking as a reference the information on Deliverable 3.2 Observing Network Initial Assessment. Following the same approach with D3.2 the original questionnaire was modified accordingly in order to depict the progress made on the same Network Attributes, Commitments and Benefits following the GOOS, OCG guidelines. The unforeseen COVID-19 pandemic had significant effects upon WP3 activities since the main mechanism foreseen to advance progress within the different networks was the organization of in person workshops. Moreover, adequate funds were allocated towards this in order to promote inclusivity and participation. Adapting to the new situation the first series of workshops had to be changed into online only events which despite the inherent difficulty, proved to have significant advantages as well. In particular they gave the opportunity for a significant number of people to join from all around the globe and participate in the events (for example the Sea Level WS). Another challenge proved to be the variability within some networks with sub-components or sub-groups having significantly different characteristics. In particular Eulerian platforms comprise a wide range of platforms - fixed moorings, surface buoys, cable bottom platforms - with some of them being part of mature and well-developed networks (OceanSITES, EMSO etc) while other are loose partners of on-going programs and projects (JERICO RI, coastal buoys). EuroSea activities had a significant positive impact on all the observing and thematic networks, actively promoting synergies and collaboration, with most of them successfully reaching Framework Processes Readiness Criteria Level 7 and above. Although progress at many different aspects must continue beyond EuroSea, it is important that the framework has been set. It is thus suggested that an annual evaluation/assessment process for each network/task team is adopted within EuroGOOS. By going through this exercise annually, each EuroGOOS Task Team (observing network) will be able to describe its current state, assess progress and most importantly to define next targets and priorities.

Description: This report presents the results of task 7.3 on “Quantification of improvements in carbon flux data for the tropical Atlantic based on the multi-platform and neural network approach”. To better constrain changes in the ocean’s capture and sequestration of CO2 emitted by human activities, in situ measurements are needed. Tropical regions are considered to be mostly sources of CO2 to the atmosphere due to specific circulation features, with large interannual variability mainly controlled by physical drivers (Padin et al., 2010). The tropical Atlantic is the second largest source, after the tropical Pacific, of CO2 to the atmosphere (Landschützer et al., 2014). However, it is not a homogeneous zone, as it is affected by many physical and biogeochemical processes that vary on many time scales and affect surrounding areas (Foltz et al., 2019). The Tropical Atlantic Observing System (TAOS) has progressed substantially over the past two decades. Still, many challenges and uncertainties remain to require further studies into the area’s role in terms of carbon fluxes (Foltz et al., 2019). Monitoring and sustained observations of surface oceanic CO2 are critical for understanding the fate of CO2 as it penetrates the ocean and during its sequestration at depth. This deliverable relies on different observing platforms deployed specifically as part of the EuroSea project (a Saildrone, and 5 pH-equipped BGC-Argo floats) as well as on the platforms as part of the TAOS (CO2-equipped moorings, cruises, models, and data products). It also builds on the work done in D7.1 and D7.2 on the deployment and quality control of pH-equipped BGC-Argo floats and Saildrone data. Indeed, high-quality homogeneously calibrated carbonate variable measurements are mandatory to be able to compute air-sea CO2 fluxes at a basin scale from multiple observing platforms.

Description: This report presents the results of Task 7.3 on “Development of BGC-Argo data quality validation based on an integrative multiplatform approach”. Observing changes in ocean conditions on the spatiotemporal scales necessary to constrain carbon uptake is a challenge. Defined as an Essential Ocean Variable (EOV) by the Global Ocean Observing System (GOOS, e.g., Tanhua et al., 2019), pH is relevant to assess numerous crucial questions regarding the oceanic evolution in response to the current global changes. However, the large spatiotemporal variability of this carbonate system parameter requires sustained observations to decipher trends and punctual events. Within this scope, numerous pH sensors suitable for deployments both on autonomous observing tools and fixed stations have been developed. Nevertheless, as interpreting changes relies on accurate data, and because offsets or drifts in pH data might appear in response to changes in the sensor k0 constant, a consistent and rigorous correction procedure to quality-control and process the data has been implemented. This report presents the application of this method to pH data acquired by BGC-Argo floats launched in the Tropical Atlantic area.

Description: Phytoplankton photosynthetic pigment concentrations from various expeditions, analysed by HPLC by the Laboratoire d'Oceanographie de Villefranche (LOV).

Description: The present data set includes 268,127 vertical in situ fluorescence profiles obtained from several available online databases and from published and unpublished individual sources. Metadata about each profiles are given in the file provided here in further details. The majority of profiles comes from the National Oceanographic Data Center (NODC) and the fluorescence profiles acquired by Bio-Argo floats available on the Oceanographic Autonomous Observations (OAO) platform (63.7% and 12.5% respectively). Different modes of acquisition were used to collect the data presented in this study: (1) CTD profiles are acquired using a fluorometer mounted on a CTD-rosette; (2) OSD (Ocean Station Data) profiles are derived from water samples and are defined as low resolution profiles; (3) the UOR (Undulating Oceanographic Recorder) profiles are acquired by a 〈fish〉 equipped with a fluorometer and towed by a research vessel; (4) PA profiles are acquired by autonomous platforms (here profiling floats or elephant seals equipped with a fluorometer). Data acquired from gliders are not included in the compilation.

Description: In vivo chlorophyll a fluorescence, a proxy of chlorophyll a concentration, is one of the most frequently measured biogeochemical property in the ocean. Thousands of profiles are available from historical databases and the integration of fluorescence sensors to autonomous platforms led to a significant increase of chlorophyll fluorescence profiles acquisition. To date, benefits of such numerous data available have not yet been included in global analysis. A total of 268,184 raw chlorophyll fluorescence profiles were collected and subjected to a 10-steps quality control procedure (see supplementary literature publication). The present data product was generated from the remaining 48,600 chlorophyll fluorescence profiles. These were inter-calibrated, converted to total chlorophyll a concentration and phytoplankton community composition (i.e. microphytoplankton, nanophytoplankton and picophytoplankton) using the FLAVOR method (see further details). The data span a time period of 1958-2015, with observations from all oceanic basins and all seasons, and with depths ranging from the surface to a median sampling maximum depth of around 700m. The present data product was obtained by modelling phytoplankton biomass and composition from in situ fluorescence profiles and therefore, individual profiles should NOT BE USED as discrete observations. The correct use of the present data product is to investigate regional or temporal trends, for example to improve the open ocean climatologies of chlorophyll a concentration. This data product is intended as a living data set, with the expectation to retrieve and model additional in situ chlorophyll fluorescence profiles, especially from autonomous acquisition platforms.

Description: Spectral absorption coefficients of total particulate matter ap (lambda) were determined using the in vitro filter technique. The present analysis deals with a set of 1166 spectra, determined in various oceanic (case 1) waters, with field chl a concentrations ([chl]) spanning 3 orders of magnitude (0.02-25 mg/m**3). As previously shown [Bricaud et al., 1995, doi:10.1029/95JC00463] for the absorption coefficients of living phytoplankton a phi (lamda), the ap (labda) coefficients also increase nonlinearly with [chl]. The relationships (power laws) that link ap (lambda) and a phi (lambda) to [chl] show striking similarities. Despite large fluctuations, the relative contribution of nonalgal particles to total absorption oscillates around an average value of 25-30% throughout the [chl] range. The spectral dependence of absorption by these nonalgal particles follows an exponential increase toward short wavelengths, with a weakly variable slope (0.011 ± 0.0025/nm). The empirical relationships linking ap (lambda) to ([chl]) can be used in bio-optical models. This parameterization based on in vitro measurements leads to a good agreement with a former modeling of the diffuse attenuation coefficient based on in situ measurements. This agreement is worth noting as independent methods and data sets are compared. It is stressed that for a given ([chl]), the ap (lambda) coefficients show large residual variability around the regression lines (for instance, by a factor of 3 at 440 nm). The consequences of such a variability, when predicting or interpreting the diffuse reflectance of the ocean, are examined, according to whether or not these variations in ap are associated with concomitant variations in particle scattering. In most situations the deviations in ap actually are not compensated by those in particle scattering, so that the amplitude of reflectance is affected by these variations.