Publications of Marilaure Grégoire
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See detailDynamics of the deep chlorophyll maximum in the Black Sea as depicted by BGC-Argo floats
Ricour, Florian ULiege; Capet, Arthur ULiege; D'Ortenzio, Fabrizio et al

in Biogeosciences (2021), 18

This paper addresses the phenology of the deep chlorophyll maximum (DCM) in the Black Sea (BS). We show that the DCM forms in March at a density level set by the winter mixed layer. It maintains this ... [more ▼]

This paper addresses the phenology of the deep chlorophyll maximum (DCM) in the Black Sea (BS). We show that the DCM forms in March at a density level set by the winter mixed layer. It maintains this location until June, suggesting an influence of the DCM on light and nutrient profiles rather than mere adaptation to external factors. In summer, the DCM concentrates ~55 % of the chlorophyll in a 10 m layer at ~35 m depth and should be considered a major feature of the BS phytoplankton dynamics. [less ▲]

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See detailDynamics of the Deep Chlorophyll Maximum in the Black Sea as depicted by BGC-Argo floats
Capet, Arthur ULiege; Ricour, Florian ULiege; d'ortenzio, Fabrizio et al

in Geophysical Research Abstracts (2021)

The deep chlorophyll maximum (DCM) is a well known feature of the global ocean. However, its description and the study of its formation are a challenge, especially in the peculiar environment that is the ... [more ▼]

The deep chlorophyll maximum (DCM) is a well known feature of the global ocean. However, its description and the study of its formation are a challenge, especially in the peculiar environment that is the Black Sea. The retrieval of chlorophyll a (Chla) from fluorescence (Fluo) profiles recorded by biogeochemical-Argo (BGC-Argo) floats is not trivial in the Black Sea, due to the very high content of colored dissolved organic matter (CDOM) which contributes to the fluorescence signal and produces an apparent increase of the Chla concentration with depth. Here, we revised Fluo correction protocols for the Black Sea context using co-located in-situ high-performance liquid chromatography (HPLC) and BGC-Argo measurements. The processed set of Chla data (2014–2019) is then used to provide a systematic description of the seasonal DCM dynamics in the Black Sea and to explore different hypotheses concerning the mechanisms underlying its development. Our results show that the corrections applied to the Chla profiles are consistent with HPLC data. In the Black Sea, the DCM begins to form in March, throughout the basin, at a density level set by the previous winter mixed layer. During a first phase (April-May), the DCM remains attached to this particular layer. The spatial homogeneity of this feature suggests a hysteresis mechanism, i.e., that the DCM structure locally influences environmental conditions rather than adapting instantaneously to external factors. In a second phase (July-September), the DCM migrates upward, where there is higher irradiance, which suggests the interplay of biotic factors. Overall, the DCM concentrates around 45 to 65% of the total chlorophyll content within a 10 m layer centered around a depth of 30 to 40 m, which stresses the importance of considering DCM dynamics when evaluating phytoplankton productivity at basin scale. [less ▲]

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See detailEffects of nutrient Management Scenarios on Marine Eutrophication Indicators: A pan european, Multi-model assessment in support of the Marine Strategy Framework Directive
Friedland, René; Macias, Diego; Cossarini, Gianpiero et al

in Frontiers in Marine Science (2021)

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See detailA new intermittent regime of convective ventilation threatens the Black Sea oxygenation status
Capet, Arthur ULiege; Vandenbulcke, Luc ULiege; Grégoire, Marilaure ULiege

in Biogeosciences (2020), 17

The Black Sea is entirely anoxic, except for a thin (∼ 100 m) ventilated surface layer. Since 1955, the oxygen content of this upper layer has decreased by 44 %. The reasons hypothesized for this decrease ... [more ▼]

The Black Sea is entirely anoxic, except for a thin (∼ 100 m) ventilated surface layer. Since 1955, the oxygen content of this upper layer has decreased by 44 %. The reasons hypothesized for this decrease are, first, a period of eutrophication from the mid-1970s to the early 1990s and, second, a reduction in the ventilation processes, suspected for recent years (post-2005). Here, we show that the Black Sea convective ventilation regime has been drastically altered by atmospheric warming during the last decade. Since 2009, the prevailing regime has been below the range of variability recorded since 1955 and has been characterized by consecutive years during which the usual partial renewal of intermediate water has not occurred. Oxygen records from the last decade are used to detail the relationship between cold-water formation events and oxygenation at different density levels, to highlight the role of convective ventilation in the oxygen budget of the intermediate layers and to emphasize the impact that a persistence in the reduced ventilation regime would bear on the oxygenation structure of the Black Sea and on its biogeochemical balance. [less ▲]

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See detailHydrodynamic variability in the Southern Bight of the North Sea in response to typical atmospheric and tidal regimes. Benefit of using a high resolution model
Ivanov, Evgeny ULiege; Capet, Arthur ULiege; Barth, Alexander ULiege et al

in Ocean Modelling (2020), 154

In this paper, the hydrodynamics of the Southern Bight of the North Sea (SBNS) and in particular, the Belgian Coastal Zone (BCZ) is investigated on daily to seasonal time scales using a high resolution ... [more ▼]

In this paper, the hydrodynamics of the Southern Bight of the North Sea (SBNS) and in particular, the Belgian Coastal Zone (BCZ) is investigated on daily to seasonal time scales using a high resolution hydrodynamical model. The Regional Ocean Modeling System (ROMS) is implemented over the SBNS with 5 km resolution and downscaled at 1 km resolution over the BCZ in a two-way nesting configuration run over a three years period (i.e. 2006–2008). The benefit of using a high resolution model over the BCZ is assessed through an extensive comparison of model results with data from satellite and in-situ fixed platforms as well as reference products available for the region. The validation exercise and the results analysis are conducted with a particular focus on hydrodynamic features that are expected to impact the sediment transport. We find that despite the validation procedure does not allow to clearly demonstrate better performance of the high resolution model compared to the coarse resolution model in terms of overtidal circulation, sea surface temperature (SST) and salinity (SSS), the high resolution model resolves additional details in the variability of residual circulation and Scheldt salinity plume dynamics. The analysis of the response of the simulated hydrodynamics to atmospheric regimes for neap and spring tide highlights the major role played by the wind direction on the averaged currents and plume extension. The strongest currents and minimum plume extension are obtained under southwestern winds and neap tide while when northeastern winds prevail, the plume extension is at its maximum and the circulation is the weakest. We show that while neap tides allow the establishment of streamlined circulation, the spring tides induce more turbulent circulation which can favor the retention of transported elements. This latter property could not be resolved with the 5 km resolution model. [less ▲]

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See detailCopernicus Marine Service Ocean State Report, Issue 4
von Schuckmann, Karina; Le Traon, Pierre-Yves; Smith, Neville et al

Book published by Taylor & Francis (2020)

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See detailMultidisciplinary Observing in the World Ocean’s Oxygen Minimum Zone regions: from climate to fish- the VOICE initiative
Garçon, Véronique; Karstensen, Johannes; Palacz, Artur et al

in Frontiers in Marine Science (2020)

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See detailThe chlorophyll seasonal dynamics in the Black Sea as inferred from Biogeochemical-Argo floats
Ricour, Florian ULiege; Capet, Arthur ULiege; Delille, Bruno ULiege et al

Poster (2019, April)

Biogeochemical-Argo (BGC-Argo) floats offer the opportunity to investigate the spatial and temporal dynamics of chlorophyll a (Chla) profiles. In the Black Sea, the unusual abundance of colored dissolved ... [more ▼]

Biogeochemical-Argo (BGC-Argo) floats offer the opportunity to investigate the spatial and temporal dynamics of chlorophyll a (Chla) profiles. In the Black Sea, the unusual abundance of colored dissolved organic matter (CDOM) and the absence of oxygen below ∼80-100m require a revision of the classic formulation used to link the fluorescence signal and the algal chlorophyll concentration (e.g. Xing et al., 2017). Indeed, the very high content of CDOM in the basin is thought to be responsible for the apparent increase of Chla concentrations at depth, where it should be zero due to the absence of light. Here, the classic formulation to link fluorescence and Chla is revised based on a reference Chla dataset sampled during a scientific cruise onboard RV Akademik and analysed with High Performance Liquid Chromatography (HPLC). Then, using the established equation to remove the contribution of CDOM to the fluorescence signal, we estimated the Chla profiles from 4 BGC-Argo floats during the period 2014-2017. All Chla profiles were thus highly quality controlled by using the Argo documentation (Schmechtig et al., 2015). Especially, we removed bad data (e.g. spikes, outliers) and we corrected the Non-Photochemical Quenching effect, a photoprotective mechanism resulting in a decrease in the fluorescence signal at the surface. The Chla profiles are categorized based on fitting algorithms (e.g. sigmoid, exponential, gaussian) and empirical criteria. They display a large variety of shapes across the seasons (e.g. homogeneity in the mixed layer, subsurface maximum, double peaks below the surface, etc.) with roughly homogeneous profiles dominating between November and February while subsurface maxima are present during the rest of the year, with in summer a clearly-marked deep chlorophyll maximum (DCM). We then investigate the formation mechanism of DCMs based on the hysteresis hypothesis for the temperate ocean proposed by Navarro et al., (2013). For this, we looked at the correlation between the position of DCMs and the potential density anomaly of the mixed layer when it is maximum in winter, usually between February and March. We show that DCMs are highly correlated with the potential density anomaly of the previous winter mixed layer where a winter bloom initiated while the correlation with the 10% and 1% light levels is poor. This is in agreement with the hysteresis hypothesis that assumes that in regions where a bloom forms in late winter/early spring, this bloom remains established at a fixed density (i.e. the density of the mixed layer when it is maximum) until the end of summer acting as a barrier for the diffusion of nutrients from below and preventing the occurrence of deeper blooms due to a shading effect. This bloom is finally progressively eroded in autumn, when the depth of the mixed layer increases again. [less ▲]

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See detailDiagenetic Modelling
Capet, Arthur ULiege; Grégoire, Marilaure ULiege; Soetaert, Karline

Learning material (2019)

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See detailIntroduction to ecological modelling
Capet, Arthur ULiege; Grégoire, Marilaure ULiege; Soetaert, Karline

Learning material (2019)

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See detailWhat is ocean deoxygenation?
Grégoire, Marilaure ULiege; Gilbert, Denis; Oschlies, Andreas et al

in Baxter, John; Lafolley, Daniel (Eds.) Ocean deoxygenation: everyone’s problem. Causes, impacts, consequences and solutions (2019)

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See detailUpscaling macro-benthic activity from local diagenesis to biogeochemical cycles
Capet, Arthur ULiege; Plante, Audrey; Chou, Lei et al

Poster (2019)

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See detailAdvancing marine biogeochemical and ecosystem reanalyses and forecasts as tools for monitoring and managing ecosystem health
Fennel, K.; Gehlen, M.; Brasseur, P. et al

in Frontiers in Marine Science (2019), 6(MAR),

Ocean ecosystems are subject to a multitude of stressors, including changes in ocean physics and biogeochemistry, and direct anthropogenic influences. Implementation of protective and adaptive measures ... [more ▼]

Ocean ecosystems are subject to a multitude of stressors, including changes in ocean physics and biogeochemistry, and direct anthropogenic influences. Implementation of protective and adaptive measures for ocean ecosystems requires a combination of ocean observations with analysis and prediction tools. These can guide assessments of the current state of ocean ecosystems, elucidate ongoing trends and shifts, and anticipate impacts of climate change and management policies. Analysis and prediction tools are defined here as ocean circulation models that are coupled to biogeochemical or ecological models. The range of potential applications for these systems is broad, ranging from reanalyses for the assessment of past and current states, and short-term and seasonal forecasts, to scenario simulations including climate change projections. The objectives of this article are to illustrate current capabilities with regard to the three types of applications, and to discuss the challenges and opportunities. Representative examples of global and regional systems are described with particular emphasis on those in operational or pre-operational use. With regard to the benefits and challenges, similar considerations apply to biogeochemical and ecological prediction systems as do to physical systems. However, at present there are at least two major differences: (1) biogeochemical observation streams are much sparser than physical streams presenting a significant hinderance, and (2) biogeochemical and ecological models are largely unconstrained because of insufficient observations. Expansion of biogeochemical and ecological observation systems will allow for significant advances in the development and application of analysis and prediction tools for ocean biogeochemistry and ecosystems, with multiple societal benefits. © 2019 Fennel, Gehlen, Brasseur, Brown, Ciavatta, Cossarini, Crise, Edwards, Ford, Friedrichs, Gregoire, Jones, Kim, Lamouroux, Murtugudde, Perruche and the GODAE OceanView Marine Ecosystem Analysis and Prediction Task Team. [less ▲]

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See detailBlack Sea observing System
Palazov, Atanas; Ciliberti, S; Peneva, E et al

in Frontiers in Marine Science (2019)

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See detailFrom observation to information and users: The Copernicus Marine Service Perspective
Le Traon, P. Y.; Reppucci, A.; Fanjul, E. A. et al

in Frontiers in Marine Science (2019), 6(May),

The Copernicus Marine Environment Monitoring Service (CMEMS) provides regular and systematic reference information on the physical and biogeochemical ocean and sea-ice state for the global ocean and the ... [more ▼]

The Copernicus Marine Environment Monitoring Service (CMEMS) provides regular and systematic reference information on the physical and biogeochemical ocean and sea-ice state for the global ocean and the European regional seas. CMEMS serves a wide range of users (more than 15,000 users are now registered to the service) and applications. Observations are a fundamental pillar of the CMEMS value-added chain that goes from observation to information and users. Observations are used by CMEMS Thematic Assembly Centres (TACs) to derive high-level data products and by CMEMS Monitoring and Forecasting Centres (MFCs) to validate and constrain their global and regional ocean analysis and forecasting systems. This paper presents an overview of CMEMS, its evolution, and how the value of in situ and satellite observations is increased through the generation of high-level products ready to be used by downstream applications and services. The complementary nature of satellite and in situ observations is highlighted. Long-term perspectives for the development of CMEMS are described and implications for the evolution of the in situ and satellite observing systems are outlined. Results from Observing System Evaluations (OSEs) and Observing System Simulation Experiments (OSSEs) illustrate the high dependencies of CMEMS systems on observations. Finally future CMEMS requirements for both satellite and in situ observations are detailed. © 2019 Le Traon, Reppucci, Alvarez Fanjul, Aouf, Behrens, Belmonte, Bentamy, Bertino, Brando, Kreiner, Benkiran, Carval, Ciliberti, Claustre, Clementi, Coppini, Cossarini, De Alfonso Alonso-Muñoyerro, Delamarche, Dibarboure, Dinessen, Drevillon, Drillet, Faugere, Fernández, Fleming, Garcia-Hermosa, Sotillo, Garric, Gasparin, Giordan, Gehlen, Gregoire, Guinehut, Hamon, Harris, Hernandez, Hinkler, Hoyer, Karvonen, Kay, King, Lavergne, Lemieux-Dudon, Lima, Mao, Martin, Masina, Melet, Buongiorno Nardelli, Nolan, Pascual, Pistoia, Palazov, Piolle, Pujol, Pequignet, Peneva, Pérez Gómez, Petit de la Villeon, Pinardi, Pisano, Pouliquen, Reid, Remy, Santoleri, Siddorn, She, Staneva, Stoffelen, Tonani, Vandenbulcke, von Schuckmann, Volpe, Wettre and Zacharioudaki. [less ▲]

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See detail3.6 Decline of the Black Sea oxygen inventory. In: Copernicus Marine Service Ocean State Report, Issue 2
Capet, Arthur ULiege; Vandenbulcke, Luc ULiege; Veselka, Marinova et al

in Journal of Operational Oceanography (2018), 11(sup1),

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See detailUpscaling the impact of coastal hypoxia from species to ecosystem function. Bioturbation on the Black Sea Shelf.
Capet, Arthur ULiege; Pena, Fatima; Plante, Audrey et al

Conference (2018, October)

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See detailGlobal Ocean Oxygen Network 2018. The ocean is losing its breath: Declining oxygen in the world’s ocean and coastal waters.
Breitburg, Denise; Grégoire, Marilaure ULiege; Isensee, Kirsten et al

in IOC-UNESCO, IOC Technical Series, (2018), 137

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