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  • 1
    Publikationsdatum: 2017-12-18
    Beschreibung: In the North Ionian, water circulation is characterized by a decadal alternation of cyclonic and anticyclonic regime driven by the mechanism called BiOS (Bimodal Oscillating System). The circulation regime affects the vertical dynamics and the nutrient distribution. The North Ionian is then a good study area to investigate how changes in circulation can affect phytoplankton dynamics in oligotrophic regions. From in situ observations, for each circulation regime the averaged distribution of isopycnals is provided, and a depth difference of about 80 m is estimated for the nitracline between cyclonic and anticyclonic regime. Based on phytoplankton phenology metrics extracted from annual time-series of satellite ocean color data for the period 1998–2012, the cyclonic and anticyclonic regimes are compared. Results show that the average chlorophyll in March, the date of bloom initiation and the date of maximum chlorophyll were affected by circulation patterns in the North Ionian. In the center of the gyre, bloom initiation occurred in December and chlorophyll was low in March when circulation was anticyclonic, whereas during the cyclonic circulation regime, a late chlorophyll peak, likely resulting from different phytoplankton dynamics, was commonly observed in March. An additional analysis shows that the winter buoyancy losses, which govern the Mixed Layer Depth (MLD) also contribute to explain the interannual variability in bloom initiation and intensity. Two scenarios involving the relative position of the MLD and nitracline are finally developed, discussed and tested with model data to explain the different phenology patterns observed in the North Ionian.
    Print ISSN: 1810-6277
    Digitale ISSN: 1810-6285
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2017-07-13
    Beschreibung: Since 2012, an array of 105 Biogeochemical (BGC) Argo floats has been deployed across the world’s oceans to fill the observational gap characterizing most of open-ocean environments. Profiles of biogeochemical (chlorophyll and fluorescent dissolved organic matter) and optical (single-wavelength particulate optical backscattering, downward irradiance at three wavelengths and photosynthetically available radiation) variables are collected in the upper 1000 m every 1 to 10 days. The global database of 9837 vertical profiles collected up to January 2016 is presented and its spatial and temporal coverage is discussed. Each variable is quality controlled with specifically-developed procedures and its time-series is quality-assessed to identify issues related to biofouling and/or instrumental drift. A second database of 5748 profile-derived products within the first optical depth (i.e. the layer of interest for satellite remote sensing) is also presented and its spatio-temporal distribution discussed. This database, devoted to field and remote ocean color applications, includes diffuse attenuation coefficients for downward irradiance at three narrow wavebands and one broad waveband (photosynthetically available radiation), calibrated chlorophyll and dissolved organic matter fluorescence, and single-wavelength particulate optical backscattering. To demonstrate the applicability of these global databases, data within the first optical depth are finally compared with previously established bio-optical models and used to validate remotely-derived bio-optical products. The quality-controlled databases are publicly available from SEANOE (SEA scieNtific Open data Edition) publisher at http://doi.org/10.17882/49388 and http://doi.org/10.17882/47142 for vertical profiles and products within the first optical depth, respectively.
    Digitale ISSN: 1866-3591
    Thema: Geologie und Paläontologie
    Publiziert von Copernicus
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2017-11-06
    Beschreibung: We report on data from an oceanographic cruise, covering western, central and eastern parts of the Mediterranean Sea, on the French research vessel Tethys 2 in May 2015. This cruise was fully dedicated to the maintenance and the metrological verification of a biogeochemical observing system based on a fleet of BGC-Argo floats. During the cruise, a comprehensive dataset of parameters sensed by the autonomous network was collected. The measurements include ocean currents, seawater salinity and temperature, concentration of inorganic nutrients, of dissolved oxygen, and chlorophyll pigments. The analytical protocols and data processing methods are detailed, together with a first assessment of the calibration state for all the sensors deployed during the cruise. Data collected at stations are available under http://doi.org/10.17882/51678, data collected along ship track are available under http://doi.org/10.17882/51691.
    Digitale ISSN: 1866-3591
    Thema: Geologie und Paläontologie
    Publiziert von Copernicus
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2018-07-30
    Beschreibung: The present work is based on a dataset comprised of 31 Biogeochemical (BGC) Argo floats that collected 0–1000m vertical profiles of biogeochemical and optical data from 2012 to 2016 in the Mediterranean Sea. The dataset was integrated in 1-dimensional model simulations following the trajectories of each float and considering measured photosynthetically available radiation (PAR) profiles as the reference light parameterization. The simulations were aimed to be consistent with data measured by float sensors, especially in terms of the deep chlorophyll maximum (DCM) depth. Moreover, we tested several light models in order to estimate their impact on modeled biogeochemical properties, including self-shading dynamics based on chlorophyll and colored dissolved organic matter (CDOM) concentrations. The results, evaluated with the corresponding in-situ BGC-Argo chlorophyll data, indicate that the proposed approach allows to properly simulate the chlorophyll dynamics and illustrate how PAR and vertical mixing are essential environmental regulation factors driving primary producers dynamics. The higher skills are reached using in-situ PAR, but some of the alternative bio-optical models here presented show comparable skill in reproducing DCM depth spatial variability. Simulation results show that during the stratification phase the diel cycle has significant impact on the surface chlorophyll regimes. The approach here presented serves as a computationally smooth solution to analyse BGC-Argo floats data and to corroborate hypotheses on their spatio-temporal variability.
    Print ISSN: 1810-6277
    Digitale ISSN: 1810-6285
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2018-09-03
    Beschreibung: As commonly observed in oligotrophic stratified waters, a Subsurface (or Deep) Chlorophyll Maximum (SCM) frequently characterizes the vertical distribution of phytoplankton chlorophyll in the Mediterranean Sea. Occurring far from the surface layer seen by ocean color satellites, SCMs are difficult to observe with adequate spatio-temporal resolution and their biogeochemical impact remains unknown. BioGeochemical-Argo (BGC-Argo) profiling floats represent appropriate tools for studying the dynamics of SCMs. Based on data collected from 36 BGC-Argo floats deployed in the Mediterranean Sea, our study aims to address two main questions: (1) What are the different types of SCMs in Mediterranean Sea? (2) Which environmental factors control their occurrence and dynamics? First, we analyzed the seasonal and regional variations of the chlorophyll concentration (Chla), particulate backscattering coefficient (bbp), a proxy of the Particulate Organic Carbon (POC), and environmental parameters (PAR and nitrates) within the SCM layer over the Mediterranean basin. The vertical profiles of Chla and bbp were then statistically classified, and the seasonal occurrence of each of the different types of SCMs quantified. Finally, a case study was performed on two contrasted regions and the environmental conditions at depth were further investigated to understand which parameter controls the SCMs. In the Eastern Basin, SCMs result, at a first order, from photoacclimation process. Conversely, SCMs in the Western Basin reflect a biomass increase at depth benefiting from both light and nitrate resources. Our results also suggest that a variety of intermediate types of SCMs are encountered between these two end-member situations.
    Print ISSN: 1810-6277
    Digitale ISSN: 1810-6285
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2018-11-08
    Beschreibung: Ocean bioregions are generally defined using remotely-sensed sea surface chlorophyll fields, based on the assumption that surface chlorophyll is representative of euphotic layer phytoplankton biomass. Here we investigate the impact of subsurface phytoplankton dynamics on the characterisation of ocean bioregions. The Mediterranean Sea is known for its contrasting bioregimes despite its limited area, and represents an appropriate case for this study. We modelled this area using a high resolution regional dynamical model, NEMO-MED12, coupled to a biogeochemical model, PISCES, and focused our analysis on the bioregions derived from lower trophic levels. Validated by satellite and Biogeochemical-Argo float observations, our model shows that chlorophyll phenology can be significantly different when estimated from surface concentrations or integrated over the first 300m deep layer. This was found in both low chlorophyll, oligotrophic bioregions as well as in high chlorophyll, bloom bioregions. The underlying reason for this difference is the importance of subsurface phytoplankton dynamics, in particular those associated with the Deep Chlorophyll Maximum (DCM) at the base of the upper mixed layer. Subsurface phytoplankton are found to significantly impact the bloom bioregions, while in oligotrophic regions, surface and subsurface chlorophyll are of similar importance. Consequently, our results show that surface chlorophyll is not representative of total phytoplankton biomass. Analysis of the DCM finds that its dynamics are extremely homogeneous throughout the Mediterranean Sea, and that it follows the annual cycle of solar radiation. In the most oligotrophic bioregion, the total phytoplankton biomass is almost constant along the year, implying that the summertime DCM biomass increase is not due to DCM photoacclimation, nor an increase of DCM production, but instead of the migration – with photoacclimation – of surface phytoplankton into the DCM.
    Print ISSN: 1810-6277
    Digitale ISSN: 1810-6285
    Thema: Biologie , Geologie und Paläontologie
    Publiziert von Copernicus im Namen von European Geosciences Union.
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2019-07-12
    Beschreibung: This report presents the Bouee pour l'acquisition de Series Optiques a Long Terme (BOUSSOLE) project, the primary objectives of which are to provide a long-term time series of optical properties in support of a) calibration and validation activities associated with satellite ocean color missions, and b) bio-optical research in oceanic waters. The following are included in the report: 1) an introduction to the rationale for establishing the project; 2) a definition of vicarious calibration and the specific requirements attached to it; 3) the organization of the project and the characteristics of the measurement site--in the northwestern Mediterranean Sea; 4) a qualitative overview of the collected data; 5) details about the buoy that was specifically designed and built for this project; 6) data collection protocols and data processing techniques; 7) a quantitative summary of the collected data, and a discussion of some sample results, including match-up analyses for the currently operational ocean color sensors, namely MERIS, SeaWiFS, and MODIS; and 8) preliminary results of the vicarious radiometric calibration of MERIS, including a tentative uncertainty budget. The results of this match-up analysis allow performance comparisons of various ocean color sensors to be performed, demonstrating the ability of the BOUSSOLE activity, i.e., combining a dedicated platform and commercial-off-the-shelf instrumentation, to provide data qualified to monitor the quality of ocean color products on the long term.
    Schlagwort(e): Oceanography
    Materialart: NASA/TM-2006-214147 , Rept-2007-00282-0
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    Unbekannt
    AtlantOS
    In:  AtlantOS Deliverable, D7.2 . AtlantOS, 23 pp.
    Publikationsdatum: 2019-03-11
    Beschreibung: The purpose of task 1 in WP7 in AtlantOS project is to harmonize data exchange and data processing procedures for the EOVs that are acquired by multiple networks. In this framework, the present report [D7.2] establishes recommendations for automatic quality control procedures in Near RT (a few hours to several days) for the core of 7 EOVs (measured by more than one of Networks involved in AtlantOS): • Physics : temperature (T), Salinity (T), Current for surface and subsurface and Sea level • Biogeochemistry : Oxygen (O2), Chlorophyll-A, Nitrate (NO3) and Carbon (pCO2) for surface and subsurface The recommendations have been compiled by experts on those EOVs and validated by the Networks acquiring those EOVs in NRT (link with WP2, WP3 and WP4). These recommendations will evolve with time under the EuroGOOS DATAMEQ working group umbrella (http://eurogoos.eu/data-management-exchange-quality-working-group-data-meq/) and benefit from scientific progress made by the observing Networks via the Task teams established within EuroGOOS (http://eurogoos.eu/task-teams/) These recommendations do not address the delayed mode quality control proceeses.
    Materialart: Report , NonPeerReviewed , info:eu-repo/semantics/book
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    facet.materialart.
    Unbekannt
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 42 (13). pp. 5403-5410.
    Publikationsdatum: 2017-04-07
    Beschreibung: An analysis of seasonal variations in climatological surface chlorophyll points to distinct biogeographical zones in the North Atlantic subpolar gyre. In particular, the Labrador Sea appears well delineated into two regions on either side of the 60°N parallel, with very different climatological phytoplankton biomass cycles. Indeed, north of 60°N, an early and short spring bloom occurs in late April, while south of 60°N, the bloom gradually develops 1 month later and significant biomass persists all summer long. Nevertheless, at climatological scale, the first-order mechanism that controls the bloom is identical for both bioregions. The light-mixing regime can explain the bloom onset in both bioregions. In the Labrador Sea, the blooms seem to rely on a mean community compensation irradiance threshold value of 2.5 mol photon m−2 d−1 over the mixed layer.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 2019-02-01
    Beschreibung: Since 2010, an intense effort in the collection of in situ observations has been carried out in the northwestern Mediterranean Sea thanks to gliders, profiling floats, regular cruises, and mooring lines. This integrated observing system enabled a year-to-year monitoring of the deep waters formation that occurred in the Gulf of Lions area during four consecutive winters (2010–2013). Vortical structures remnant of wintertime deep vertical mixing events were regularly sampled by the different observing platforms. These are Submesoscale Coherent Vortices (SCVs) characterized by a small radius (∼5–8 km), strong depth-intensified orbital velocities (∼10–20 cm s−1) with often a weak surface signature, high Rossby (∼0.5) and Burger numbers O(0.5–1). Anticyclones transport convected waters resulting from intermediate (∼300 m) to deep (∼2000 m) vertical mixing. Cyclones are characterized by a 500–1000 m thick layer of weakly stratified deep waters (or bottom waters that cascaded from the shelf of the Gulf of Lions in 2012) extending down to the bottom of the ocean at ∼2500 m. The formation of cyclonic eddies seems to be favored by bottom-reaching convection occurring during the study period or cascading events reaching the abyssal plain. We confirm the prominent role of anticyclonic SCVs and shed light on the important role of cyclonic SCVs in the spreading of a significant amount (∼30%) of the newly formed deep waters away from the winter mixing areas. Since they can survive until the following winter, they can potentially have a great impact on the mixed layer deepening through a local preconditioning effect.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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