References of "Grégoire, Marilaure"
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See detailModeling the nitrogen fluxes in the Black Sea using a 3D coupled hydrodynamical-biogeochemical model: transport versus biogeochemical processes, exchanges across the shelf break and comparison of the shelf and deep sea ecodynamics
Grégoire, Marilaure ULg; Beckers, Jean-Marie ULg

in Biogeosciences (2004), 1(1), 33-61

A 6-compartment biogeochemical model of nitrogen cycling and plankton productivity has been coupled with a 3D general circulation model in an enclosed environment (the Black Sea) so as to quantify and ... [more ▼]

A 6-compartment biogeochemical model of nitrogen cycling and plankton productivity has been coupled with a 3D general circulation model in an enclosed environment (the Black Sea) so as to quantify and compare, on a seasonal and annual scale, the typical internal biogeochemical functioning of the shelf and of the deep sea as well as to estimate the nitrogen and water exchanges at the shelf break. Model results indicate that the annual nitrogen net export to the deep sea roughly corresponds to the annual load of nitrogen discharged by the rivers on the shelf. The model estimated vertically integrated gross annual primary production is 130 g C m(-2) yr(-1) for the whole basin, 220 g C m(-2) yr(-1) for the shelf and 40 g C m(-2) yr(-1) for the central basin. In agreement with sediment trap observations, model results indicate a rapid and efficient recycling of particulate organic matter in the sub-oxic portion of the water column (60-80 m) of the open sea. More than 95% of the PON produced in the euphotic layer is recycled in the upper 100 m of the water column, 87% in the upper 80 m and 67% in the euphotic layer. The model estimates the annual export of POC towards the anoxic layer to 4 10(10) mol yr(-1). This POC is definitely lost for the system and represents 2% of the annual primary production of the open sea. [less ▲]

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See detailNitrogen budget of the northwestern Black Sea shelf inferred from modeling studies and in situ benthic measurements
Grégoire, Marilaure ULg; Friedrich, Jana

in Marine Ecology. Progress Series (2004), 270

A 3D eddy-resolving coupled biogeochemical-hydrodynamical model and in situ observations are used to investigate benthic processes on the Black Sea's NW shelf. Measurements of benthic fluxes (oxygen ... [more ▼]

A 3D eddy-resolving coupled biogeochemical-hydrodynamical model and in situ observations are used to investigate benthic processes on the Black Sea's NW shelf. Measurements of benthic fluxes (oxygen, nutrients, redox compounds) with in situ flux chambers are analyzed in regard to sediment dynamics on the shelf. The seasonal/interannual and spatial variability of benthic processes is explained in terms of 3D ecohydrodynamics. The space/time distribution of benthic fluxes depended on the position of the river plume and the associated primary production, intensity of vertical mixing and water depth. Model results and in situ observations reveal the presence of a region of intense benthic recycling and high benthic nutrient fluxes nearshore and in the northern part of the shelf. The model estimates that this region covers about 15 % of the shelf area and is connected to the high productivity and high sedimentation caused by river input of organic matter. On the offshore shelf, covering about 85 % of the shelf area, benthic nutrient regeneration is low due to low productivity. Benthic mineralization pathways (aerobic respiration, denitrification, sulfate reduction, methanogenesis) are quantified. In the high flux region, more than 55 % and in the offshore low flux region more than 80 % of the organic matter is decomposed by aerobic respiration. In the high flux region, sulfate reduction is the main anaerobic pathway, whereas denitrification is more important on the low flux offshore shelf. At the shelf edge, under the influence of anoxic waters, more than 60 % of organic matter is remineralized by sulfate reduction. Little organic matter is decomposed by methanogenesis. A mass balance of particulate organic carbon (POC) and particulate organic nitrogen (PON), integrated over the whole shelf and year, shows that 3.7 to 4.2 x 10(6) t of POC reach the sediments, while model results give a value of 1.4 x 10(6) t C. The annual ammonium benthic outflux is estimated at 85 x 10(3) and 174 x 10(3) t N by in situ data and the model, respectively. The amount of nitrogen lost by burial and denitrification estimated from in situ observations is 57 x 10(3) and 324 x 10(3) t N, respectively. Therefore, NW shelf Black Sea sediments are an efficient sink for riverine nitrogen, trapping about 50 % of the annual river discharge in total inorganic N. [less ▲]

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See detailExchange processes and nitrogen cycling on the shelf and continental slope of the Black Sea basin
Grégoire, Marilaure ULg; Lacroix, Geneviève

in Global Biogeochemical Cycles (2003), 17(2),

A 3D coupled biogeochemical-hydrodynamical model has been applied to the Black Sea to simulate nitrogen cycling and to estimate the exchange of biogeochemical components at the shelf break and between the ... [more ▼]

A 3D coupled biogeochemical-hydrodynamical model has been applied to the Black Sea to simulate nitrogen cycling and to estimate the exchange of biogeochemical components at the shelf break and between the continental slope and the deep sea. It was found that biological processes on the northwestern shelf are in approximate balance. Primary production is fueled by river discharge, nitrate input from the open sea at the shelf break, and in situ remineralization. The input of nitrate from the open sea is roughly equivalent to the river nitrate discharge but is half the nitrate export from the shelf toward the open sea. Also, the Black Sea shelf acts throughout the year as a nitrate source for the open sea. The amount of shelf production not remineralized in the euphotic layer is 22.2% and is exported to lower layers (20%) or offshore (2.2%). We estimate that the export of carbon from the shelf to the interior of the basin represents 2.5% of the new production of the open sea. The upper slope adjoining the northwestern shelf is the site of downwelling events responsible for the downward transport to the intermediate layer of the continental slope of biogeochemical components exported from the shelf in the upper layer. The shelf has been found to be an efficient trap for the refractory material discharged by the Danube. [less ▲]

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See detailThe Aral Sea: Selected Bibliography
Nihoul, Jacques ULg; Kosarev, A.; Kostianoy, A. et al

Conference (2003, May 05)

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See detailGlobal water and salt budget of the Aral Sea from 1960 to 1991.
Sirjacobs, Damien ULg; Grégoire, Marilaure ULg; Delhez, Eric ULg et al

Conference (2003, May)

Focusing on the global water and salt budget of the Aral sea from 1960 till 1991, a compilation of data available in the litterature is analysed with simple models and compared to the measured evolution ... [more ▼]

Focusing on the global water and salt budget of the Aral sea from 1960 till 1991, a compilation of data available in the litterature is analysed with simple models and compared to the measured evolution of the sea. [less ▲]

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See detailSalt budget and salt composition for the Aral Sea
Konovalov, S.; Belokopitov, V.; Ivanov, L. et al

Poster (2003, May)

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See detailInfluence of the Aral Sea negative water balance on its seasonal circulation and ventilation patterns : use of a 3D hydrodynamic model
Sirjacobs, Damien ULg; Grégoire, Marilaure ULg; Delhez, Eric ULg et al

in Geophysical Research Abstracts (2003, April), 5(09052), 2003509052

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic ... [more ▼]

Within the context of the EU INCO-COPERNICUS program "Desertification in the Aral Sea Region: A study of the Natural and Anthropogenic Impacts" (Contract IAC2-CT-2000-10023), a large-scale 3D hydrodynamic model was adapted to address specifically the macroscale processes affecting the Aral Sea water circulation and ventilation. The particular goal of this research is to simulate the effect of lasting negative water balance on the 3D seasonal circulation, temperature, salinity and water-mixing fields of the Aral Sea. The original Aral Sea seasonal hydrodynamism is simulated with the average seasonal forcings corresponding to the period from 1956 to 1960. This first investigation concerns a period of relative stability of the water balance, before the beginning of the drying process. The consequences of the drying process on the hydrodynamic of the Sea will be studied by comparing this first results with the simulation representing the average situation for the years 1981 to 1985, a very low river flow period. For both simulation periods, the forcing considered are the seasonal fluctuations of wind fields, precipitation, evaporation, river discharge and salinity, cloud cover, air temperature and humidity. The meteorological forcings were adapted to the common optimum one-month temporal resolution of the available data sets. Monthly mean kinetic energy flux and surface tensions were calculated from daily ECMWF wind data. Monthly in situ precipitation, surface air temperature and humidity fields were interpolated from data obtained from the Russian Hydrological and Meteorological Institute. Monthly water discharge and average salinity of the river water were considered for both Amu Darya and Syr Darya river over each simulation periods. The water mass conservation routines allowed the simulation of a changing coastline by taking into account local drying and flooding events of particular grid points. Preliminary barotropic runs were realised (for the 1951-1960 situation, before drying up began) in order to get a first experience of the behaviour of the hydrodynamic model. These first runs provide results about the evolution of the following state variables: elevation of the sea surface, 3D fields of vertical and horizontal flows, 2D fields of average horizontal flows and finally the 3D fields of turbulent kinetic energy. The mean seasonal salinity and temperature fields (in-situ data gathered by the Russian Hydrological and Meteorological Institute) are available for the two simulated periods and will allow a first validation of the hydrodynamic model. Various satellites products were identified, collected and processed in the frame of this research project and will be used for the validation of the model outputs. Seasonal level changes measurements derived from water table change will serve for water balance validation and sea surface temperature for hydrodynamics validation. [less ▲]

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See detailExchange processes and nitrogen cycling on the shelf and slopes area of the Black Sea basin.
Grégoire, Marilaure ULg; Beckers, Jean-Marie ULg; Kostianoy, A. et al

Conference (2003, January)

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See detailThe use of data assimilation in coupled hydrodynamic, ecological and biogeochemical models of the ocean
Grégoire, Marilaure ULg; Brasseur, Pierre; Lermusiaux, Pierre

in Journal of Marine Systems (2003), 40-41(1-3), 405

The International Lie`ge Colloquium on Ocean Dynamics is organized annually. The topic differs from year to year in an attempt to address, as much as possible, recent problems and incentive new subjects ... [more ▼]

The International Lie`ge Colloquium on Ocean Dynamics is organized annually. The topic differs from year to year in an attempt to address, as much as possible, recent problems and incentive new subjects in oceanography. Assembling a group of active and eminent scientists from various countries and often different disciplines, the Colloquia provide a forum for discussion and foster a mutually beneficial exchange of information opening on to a survey of recent discoveries, essential mechanisms, impelling question marks and valuable recommendations for future research. The objective of the 2001 Colloquium was to evaluate the progress of data assimilation methods in marine science and, in particular, in coupled hydrodynamic, ecological and bio-geo-chemical models of the ocean. [less ▲]

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See detailModelling the Danube-influenced North-western continental shelf of the Black Sea. I: Hydrodynamical processes simulated by 3-D and box models
Beckers, Jean-Marie ULg; Grégoire, Marilaure ULg; Nihoul, Jacques ULg et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 453-472

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of ... [more ▼]

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of general circulation in the Black Sea are highlighted. Compared with a coarse resolution model, forced with the same climatic monthly averaged atmospheric data, the high resolution model exhibits stronger variability, including frontal structures and coastal upwellings induced by baroclinic instabilities, in particular along the Turkish coast. A comparison of the shelf-open sea exchanges, with particular focus on the cold intermediate waters, shows that both models lead to a replenishment of the CIL in the basin interior by cold waters formed on the shelf. Due to the better representation of frontal structures, the high resolution model is an appropriate candidate for coupling with a biological model. Problems of calibration, interpretation and data availability typically arise from this kind of coupled 3-D model. In order to overcome such difficulties, the results of the 3-D hydrodynamical model are used to guide the development of an integrated 0-D box model capable of achieving the objectives of projects like EROS21, where the effect of changes in the Danube inflows on the shelf ecosystem is investigated. The 0-D model is thus designed to cover this region and is obtained through integration over an appropriate variable volume. The integration procedure shows where the weaknesses of an 0-D approach might lie. Diagnoses in the 3-D model of the integral quantities show the range of uncertainty one can expect in the exchange laws of the 0-D model. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailCoastal-open ocean exchange in the Black Sea: Observations and modelling
Stanev, Emil; Beckers, Jean-Marie ULg; Lancelot, Christiane et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 601-620

The interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems. The complexity of processes in these areas requires detailed studies ... [more ▼]

The interaction between physical and biological processes in the areas of continental margins governs the variability of ecosystems. The complexity of processes in these areas requires detailed studies combining modelling and surveying efforts. One promising step in this direction was undertaken in the framework of the EROS 21 project, focusing on the shelf part of the north-western Black Sea. In the present paper, we focus on the results of physical studies aiming to improve the understanding of the fundamental exchange processes in the ocean margins, as well as to quantify some of them in the Black Sea. We illustrate the capabilities of circulation models to reproduce physical processes with different time- and space-scales: coastal waves, internal waves, baroclinic Rossby and topographic waves. Another class of important phenomena in the coastal zone is associated with convection. Sources at the sea surface and in the outflow areas give rise to plume dynamics that play a crucial role in the vertical mixing and provide the mechanism for water-mass formation. Most of the results are illustrated for the shelf part of the Black Sea. The verification of simulations is performed by comparison with survey data, altimeter data from the Topex/Poseidon mission and radiotracer observations. The latter, in combination with simulations from circulation models, are used to trace the penetration of tracers into the intermediate and deep layers. We show that although most Sr-90 is introduced by river runoff, large amounts of this signal penetrate the halocline in the Bosphorus Straits area and along the southern coast. Another important fraction of the river water penetrates the intermediate layers at the shelf edge in the north-western Black Sea. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailSpatial and temporal variability of benthic fluxes and diagenetic pathways of organic matter in the north-western Black Sea
Friedrich, J.; Friedl, G.; Bondar, C. et al

in Proceedings of the Second International conference. Oceanography of the eastern Mediterranean and Black Sea. Similarities and differences of two interconnected basins, Zappeion international conference Centre (2002)

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See detailThe north-eastern Black Sea redox zone hydrochemical structure: observed concentrations and estimated fluxes
Yakushev, E.V.; Chasovnikov, V.K.; Debolskaya, E.I. et al

in Proceedings of the Second International conference. Oceanography of the eastern Mediterranean and Black Sea. Similarities and differences of two interconnected basins, Zappeion international conference Centre (2002)

The fine structure of the hydrophysical and hydrochemical parameters observed in the northeastern Black Sea during the 1999-2002 RV ”Akvanavt” cruises is discussed. The observed increase of organic ... [more ▼]

The fine structure of the hydrophysical and hydrochemical parameters observed in the northeastern Black Sea during the 1999-2002 RV ”Akvanavt” cruises is discussed. The observed increase of organic phosphorus and urea at the boundary of oxic and anoxic waters testify that the hydrochmical structure is significantly influenced by chemosynthesis. The calculated nitrogen compound fluxes support the idea that organic nitrogen can be the significant part of total nitrogen in the oxic/anoxic interface. [less ▲]

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See detailOxygen Fluxes, Redox Processes and the Suboxic Zone in the Black Sea
Konovalov, S.; Murray, J.; Luther, G. et al

in International conference. Oceanography of the eastern Mediterranean and Black Sea. Similarities and differences of two interconnected basins, Zappeion international conference Centre (2002)

We use the results of numerical modeling, calibrated and verified againsthistorical data from 1960 to 1995 and the most recent data from the 2001 Knorr cruise,to investigate the redox budget of the Black ... [more ▼]

We use the results of numerical modeling, calibrated and verified againsthistorical data from 1960 to 1995 and the most recent data from the 2001 Knorr cruise,to investigate the redox budget of the Black Sea water column and the main processesgoverning this budget. The results can be summarized as follows: (1) Injection of Mediterranean water, through the Bosporus, into the Black Sea results in intrusions of oxygen in the suboxic and anoxic layers; (2) The intensity of ventilation of the CIL andthe export production of organic matter are the primary control on interannualvariations in the thickness of the suboxic zone; (3) The lateral influx of oxygen resultsin oxidation of sulfide inside the anoxic zone. Almost 70% of the total vertical flux of sulfide is oxidized by this oxygen, mainly through redox Mn(II) – Mn(III,IV) cycling;(4) Nitrate seams to be responsible for oxidation of dissolved Mn(II) in the suboxiczone and Mn(III,IV) hydroxides, the end-products of this oxidation, sink and oxidizeabout 25% of the total flux of sulfide; (5) The vertical flux of oxygen at the onset of sulfide may account for consumption of a small fraction (less than 1%) of the total fluxof sulfide; (6) The lateral flux of oxygen also appears to be the main reason for the presence of the suboxic layer. [less ▲]

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See detailNitrogen budget on the shelf and slope area of the Back Sabasin as inferred from modeling experiments
Grégoire, Marilaure ULg; Beckers, Jean-Marie ULg; Friederich, J. et al

in Second International Conference on "Oceanography of the Eastern Mediterranean and Black Sea: Similarities and Differences of Two Interconnected Basins" (2002)

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See detailCoastal and Estuarine Fine Sediment Processes (book review)
Grégoire, Marilaure ULg

in Journal of Marine Systems (2002), 37

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See detailEcosystem model (MODECOGeL) of the Ligurian Sea revisited. Seasonal and interannual variability due to atmospheric forcing
Lacroix, Geneviève; Grégoire, Marilaure ULg

in Journal of Marine Systems (2002), 37(4), 229-258

A one-dimensional coupled hydrodynamical–biological model, MODe`le d’ECOsyste`me du G.H.E.R. et du L.O.V. (MODECOGeL), of the water column is developed and applied to the Ligurian Sea (North Western ... [more ▼]

A one-dimensional coupled hydrodynamical–biological model, MODe`le d’ECOsyste`me du G.H.E.R. et du L.O.V. (MODECOGeL), of the water column is developed and applied to the Ligurian Sea (North Western Mediterranean). It is an extended and improved version of the model presented by Lacroix and Nival [J. Mar. Syst. 16 (1998) 23]. The hydrodynamic model is a 1D version of the 3D turbulent closure G.H.E.R. model, which takes into account momentum and heat surface fluxes computed from a real meteorological data set. The ecosystem model is defined by a nitrogen cycle described by 12 biological state variables including several plankton size classes and an explicit description of the bacterial loop. One data set coming from the FRONTAL missions is used to initialise and validate the model. To assess the impact of the interannual variability of the meteorological conditions on the ecosystem dynamics, the coupled model is run with 4-year real meteorological conditions (October 1984–September 1988). The model estimated percentages of the interannual variability of the annual mean biomass of phytoplankton, zooplankton and bacteria respectively of 31.0%, 16.2% and 16.3%. The ontribution of the zooplankton related to the total plankton biomass (phytoplankton, zooplankton and bacteria) has been found to be the most sensitive to the meteorological conditions variations (21%), followed by the phytoplankton (12%) and finally, by the bacteria (5%). The model estimated percentages of interannual variability of the annual gross primary production, the annual mean f-ratio and the annual bacterial production respectively of 27.9%, 18.5% and 13.4% although the interannual variability of the real winds conditions is only of 11.3%. Due to the more windy and less sunny conditions prevailing during the years ‘‘1985–1986’’ and ‘‘1986–1987’’, the annual primary production was found higher than during the years ‘‘1984–1985’’ and ‘‘1987–1988’’. The bacterial production is always greater than the primary production, showing the importance of the bacteria in such an oligotrophic environment. On a seasonal scale, the highest interannual variability of the primary production and the f-ratio is found in spring like for the wind intensity. [less ▲]

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