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See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Poster (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [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 detailModelling the Danube-influenced north-western continental shelf of the Black Sea. II: Ecosystem response to changes in nutrient delivery by the Danube River after its damming in 1972
Lancelot, Christiane; Staneva, J.; Van Eeckhout, D. et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 473-499

The ecological model BIOGEN, describing the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, has ... [more ▼]

The ecological model BIOGEN, describing the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, has been implemented in the north-western Black Sea to assess the response of this coastal ecosystem to eutrophication by the Danube River. The trophic resolution of BIOGEN was chosen to simulate the major ecological changes reported in this coastal area since the 1960s. Particular attention was paid to establishing the link between quantitative and qualitative changes in nutrients, phytoplankton composition and food-web structures. The BIOGEN numerical code structure includes 34 state variables assembled in five interactive modules describing the dynamics of (1) phytoplankton composed of three distinct groups, each with a different trophic fate (diatoms, nanophytoflagellates, non-silicified opportunistic species); (2) meso- and microzooplankton; (3) trophic dead-end gelatinous organisms composed of three distinct groups (the omnivorous Noctiluca and the carnivores Aurelia and the alien Mnemiopsis), and organic matter degradation and associated nutrient regeneration processes by (4) planktonic and (5) benthic bacteria. The capability of the BIOGEN model to simulate the recent ecosystem changes reported for the Black Sea was demonstrated by running the model for the period 1985-1995. The BIOGEN code was implemented in an aggregated and simplified representation of the north-western Black Sea hydrodynamics. The numerical frame consisted of coupling a 0-D BIOGEN box model subjected to the Danube with a 1-D BIOGEN representing the open-sea boundary conditions. Model results clearly showed that the eutrophication-related problems of the north-western Black Sea were not only driven by the quantity of nutrients discharged by the Danube, but that the balance between them was also important. BIOGEN simulations clearly demonstrated that phosphate, rather than silicate, was the limiting nutrient driving the structure of the phytoplankton community and the planktonic food-web. In particular, it showed that a well-balanced N:P:Si nutrient enrichment, such as that observed in 1991, had a positive effect on the linear, diatom-copepod food-chain, while the regenerated-based microbial food-chain remained at its background level. When present, the gelatinous carnivores also benefited from this enrichment throughout their feeding on copepods. A synergetic effect of fishing pressure and cultural eutrophication was further indirectly suggested by modifying the mortality coefficient of copepods. However, BIOGEN scenarios with unbalanced nutrient inputs, such as nitrogen or phosphate deficiency recorded in 1985 and 1995, predicted the dominance of an active microbial food-web in which bacteria and microzooplankton played a key role; the former as nutrient regenerator, the latter as a trophic path to the copepods and hence to the carnivorous. In such conditions, however, a significant biomass reduction of all gelatinous organisms was simulated, in perfect agreement with recent observations. From these model scenarios it is suggested that the observed positive signs of Black Sea ecosystem recovery might well be related to the reduction of nutrient loads in particular phosphate, by the Danube. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModelling the disturbed argillite - Strain localization
Pardoen, Benoît ULg; Collin, Frédéric ULg; Charlier, Robert ULg

Scientific conference (2012, February 09)

The excavation process creates a damaged zone around the galleries composing underground structures. The prediction of the extension but especially of the fracturing structure in this zone remains an ... [more ▼]

The excavation process creates a damaged zone around the galleries composing underground structures. The prediction of the extension but especially of the fracturing structure in this zone remains an unresolved issue in the context of underground storage. Disturbed argillite and damage (fracturing) can be numerically modeled by the development of strain localization bands. Within the framework of classical finite elements, the strain localization depends on the mesh while the second gradient method overcomes this difficulty. This method is implemented in the finite element code Lagamine and is used to model biaxial compression tests performed in laboratory. [less ▲]

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See detailModelling The Dynamic Distribution Of Spray Deposits
Lebeau, Frédéric ULg

in Biosystems Engineering (2004), 89(3),

A mathematical model to estimate the spray distribution of phytopharmaceutical deposits under a spray boom is proposed. It focuses on the need to take account of the dynamic effects of the forward ... [more ▼]

A mathematical model to estimate the spray distribution of phytopharmaceutical deposits under a spray boom is proposed. It focuses on the need to take account of the dynamic effects of the forward movement of the boom. These are related both to the horizontal and vertical boom movement and to the influence of aerodynamic factors on the nozzle spray distribution. The distribution of the spray deposits is computed by multiplying the nozzle spray pattern by the time needed to move from one position to the next. Mathematically, this is expressed by a convolution of the trajectory function with the nozzle spray pattern function. The model is validated through a dynamic test bench to reproduce the boom movements observed in the field. The chosen method to measure the distribution of the spray deposits is a chemical dosage of the sprayed potassium chloride (KCl) solution collected in Petri dishes. A pulse-width modulation (PWM) nozzle body fitted on the test bench is used to generate a dynamic distribution of spray deposits from which the dynamic two-dimensional nozzle spray pattern is reconstructed. This dynamic nozzle spray pattern introduced in the model allows a far better estimation of the spray deposit distribution to be made than the one obtained using the static nozzle spray pattern which was computed using filtered back-projection. [less ▲]

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See detailModelling the early phases of bone regeneration around an endosseous oral implant
Amor, N.; Geris, Liesbet ULg; Vander Sloten, J. et al

in Computer Methods in Biomechanics & Biomedical Engineering (2009), 12(4), 459-468

The objective of this study was to see whether a mathematical model of fracture healing was able to mimic bone formation around an unloaded screw-shaped titanium implant as it is well-believed that both ... [more ▼]

The objective of this study was to see whether a mathematical model of fracture healing was able to mimic bone formation around an unloaded screw-shaped titanium implant as it is well-believed that both processes exhibit many biological similarities. This model describes the spatio-temporal evolution of cellular activities, ranging from mesenchymal stem cell migration, proliferation, differentiation to bone formation, which are initiated and regulated by the growth factors present at the peri-implant site. For the simulations, a finite volume code was used and adequate initial and boundary conditions were applied. Two sets of analyses have been performed, in which either initial and boundary condition or model parameter values were changed with respect to the fracture healing model parameter values. For a number of combinations, the spatio-temporal evolution of bone density was well-predicted. However reducing cell proliferation rate and increasing osteoblast differentiation and osteogenic growth factor synthesis rates, the simulation results were in agreement with the experimental data. [less ▲]

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See detailModelling The Effect Of Temperature, Water Activity And Solute On The In Vitro Growth Of The Biocontrol Yeast Pichia Anomala Strain K
Lahlali, R.; Bajji, M.; Serrhini, Mn. et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008), 12(4),

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See detailModelling the effects of the current policy measures in agriculture: an unique model from field to regional scale in Walloon region of Belgium
Sohier, Catherine ULg; Degre, Aurore ULg

in Environmental Science & Policy (2010), 13(2010), 754-765

Diffuse nutrient loss from agriculture into the soil, groundwater and surface water affects their quality. Different policies are in force throughout the European Union aiming for their limitation. They ... [more ▼]

Diffuse nutrient loss from agriculture into the soil, groundwater and surface water affects their quality. Different policies are in force throughout the European Union aiming for their limitation. They were implemented through action plans on a regional scale. Hydrological modelling can be a powerful method for efficiently evaluating their effectiveness. In order to be useful whatever the action and for every reporting unit (whole Region, water bodies, nitrate vulnerable zones, fields...) the model must be physically based, it must simulate water and nutrient fluxes in the root zone and the vadose zone as well as being geographically flexible. This paper presents such a model and its application in the context of Wallonia (Southern part of Belgium). It also presents a calculation of what water and nutrient flows could be under a given climatic scenario until 2015. In Belgium, water quality depends upon Regions. Wallonia implemented the European Nitrate Directive through two action plans the first in 2002 and the second in 2007. These actions plans were modelled and compared to a scenario without any modification in the farmers’ practices. The modelling showed the need for two indicators: nitrate concentration under the root zone as fast indicator of the actions’ efficiency and transfer time from surface to groundwater table. The first action plan hardly modified farmers’ field practices and consequently it did not impact water quality. The second action plan had more impact (reduction up to 10 mg/l NO3 under the root zone). It was mainly due to catch crop introduction in the nitrate vulnerable zone, if they are followed by a reduction of the mineral fertilisation (not mandatory). Our results show that new actions are necessary. We show where and to what extent they have to be implemented. Nevertheless, the greatest variation in nitrate leaching from the root zone seems to be dependent on the weather, more than the action plans. Particularly the rainy period between 1998 and 2002 had a huge impact on nitrogen flows. Our hydrological modelling is showed to be a powerful tool of nitrogen management in a still uncertain climatic evolution context. Finally, we showed that patience and perseverance will be necessary to reach the targets of the WFD in the Walloon context. The map of transfer time shows that 8% of the groundwater bodies need over 15 years to be impacted by mitigation measures. [less ▲]

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See detailModelling the evolution of climate and sea level over the third millennium (MILMO)
Fichefet, Thierry; Driesschaert, Emmanuelle; Goosse, Hugues et al

Report (2007)

A new three-dimensional Earth system model of intermediate complexity was developed. This model, named LOVECLIM, consists of five major components representing the atmosphere (ECBilt), the ocean and sea ... [more ▼]

A new three-dimensional Earth system model of intermediate complexity was developed. This model, named LOVECLIM, consists of five major components representing the atmosphere (ECBilt), the ocean and sea ice (CLIO), the terrestrial biosphere (VECODE), the oceanic carbon cycle (LOCH) and the Greenland and Antarctic ice sheets (AGISM). It also includes a global glacier-melt algorithm which is run in off-line mode. It is worth mentioning that there are very few models of this type worldwide. ECBilt is a quasi-geostrophic atmospheric model with 3 levels and a T21 horizontal resolution. It includes simple parameterisations of the diabatic heating processes and an explicit representation of the hydrological cycle. Cloud cover is prescribed according to present-day climatology. CLIO is a primitive-equation, free-surface ocean general circulation model coupled to a thermodynamic–dynamic sea-ice model. Its horizontal resolution is 3° × 3°, and there are 20 levels in the ocean. VECODE is a reduced-form model of vegetation dynamics and of the terrestrial carbon cycle. It simulates the dynamics of two main terrestrial plant functional types (trees and grassland) at the same resolution as that of ECBilt. LOCH is a comprehensive model of the oceanic carbon cycle that takes into account both the solubility and biological pumps. The version utilised here has the same resolution as the one of CLIO, which greatly facilitates the coupling between both models. Finally, AGISM is composed of a three-dimensional thermomechanical model of the ice sheet flow, a visco-elastic bedrock model and a model of the mass balance at the ice–atmosphere and ice–ocean interfaces. The Antarctic ice-sheet module also contains a model of the ice-shelf dynamics to enable interactions with the ocean and migration of the grounding line. For both ice sheets, calculations are made on a 10 km × 10 km resolution grid with 31 sigma levels. The performance of LOVECLIM was assessed by conducting ensemble simulations over the last few centuries. Starting from different initial conditions, the model was integrated from year 1500 AD up to year 2000 AD with solar irradiance, volcanic activity, tropospheric ozone amount, greenhouse-gas (including CO2) concentrations and sulphate-aerosol load evolving with time according to reconstructions. Over the last 140 years, the model simulates a global surface warming ranging from 0.33°C to 0.43°C, with a mean value of 0.38°C. This value is about 0.15°C lower than the observed one. A detailed analysis of the results has revealed the model behaves reasonably well at mid- and high latitudes. By contrast, at low latitudes, the agreement between the model results and observational estimates is less good, especially in the Southern Hemisphere. In those regions, LOVECLIM significantly underestimates the warming and the climate variability observed during the last few decades. The coarse resolution of the model and the simplified representation of the atmospheric dynamical and physical processes seem to be the two major candidates responsible for this deficiency. Regarding the Greenland ice sheet, we found a slightly increasing ice volume during the period 1700–2000 AD. This trend is largely explained as a residual response to the late Holocene forcing, in particular to the Little Ice Age cooling after year 1500 AD. The effect is not particularly large, however, amounting to only 1.2 cm of global sea-level rise over the entire period. The growing trend stabilizes during the 20th century, with almost no net effect on ice volume. Only during the last decades of the 20th century, the ice volume begins to decrease in response to the imposed warming. We also found the Antarctic ice sheet to be retreating slowly at a rate equivalent to a global sea-level rise of about 1.7 cm during the 20th century. This evolution is mostly due to a long-term background trend of +2.6 cm, mitigated by about 0.9 cm from slightly rising accumulation rates over the same period. The ongoing dominance of past climatic changes on the contemporary ice-sheet evolution is a fine illustration of the inertia encountered when studying the response of large continental ice sheets. In this case, it mainly results from an ongoing grounding-line retreat in West Antarctica following rising sea levels since the Last Glacial Maximum. As far as mountain glaciers and small ice caps are concerned, their area and volume are found to reach a maximum in the late 19th century corresponding to the Little Ice Age, but this maximum and the ensuing 20th century glacier retreat are not very pronounced. Over the last hundred years, the model simulates an ice loss equivalent to only 0.89 cm of sea-level rise. This value is at the lower end compared to other assessments. One reason is the low total ice volume assumed by the global glacier-melt algorithm (about 20 cm of total sea-level rise, a factor 2.5 less than previous estimates). A second reason is the prescribed global ice mass balance for the 1961–1990 reference period, which is also at the lower end of other simulations. For the 20th century, LOVECLIM explains about 7.6 cm of sea-level rise. The bulk of that value, about 4.7 cm, comes from thermal expansion of the World Ocean. The Antarctic and Greenland ice sheets combined lead to a sea-level rise of 2 cm, and glaciers and ice caps are responsible for about 0.9 cm of sea-level rise. These numbers are similar to those that have been derived for the IPCC Third Assessment Report (TAR) for the same components except for the lower glacier contribution as found here. Over the industrial era, the net uptake of carbon by the ocean simulated by LOVECLIM is within the range of current estimates, although at the lower end of this range. It should be noted that a detailed evaluation of the performance of the terrestrial carbon-cycle module was impossible to perform given the very wide range of available data. Experiments with interactive atmospheric CO2 concentration were also carried out with LOVECLIM forced by CO2 emissions from fossil fuel burning and land-use change. Interestingly enough, the atmospheric CO2 level computed by the model in year 2000 AD compares relatively well with the observed one. A series of climate-change projections were then conducted over the 21st century. In these experiments, LOVECLIM was driven by changes in greenhouse-gas (including CO2), tropospheric ozone and sulphate-aerosol concentrations following the IPCC SRES scenarios B1, A1B and A2. In year 2100 AD, the model predicts a globally averaged, annual mean surface warming of 1°C, 1.4°C and 1.8°C for scenarios B1, A1B and A2, respectively, and an associated increase in precipitation of 3.6%, 5.1% and 6.6%, respectively. In agreement with studies performed with climate general circulation models (CGCMs), a weakening of the Atlantic meridional overturning circulation (MOC) is noticed in all runs. At the end of the 21st century, the decrease in the maximum value of the annual mean meridional overturning streamfunction below the surface layer in the Atlantic basin, which is an index of the MOC intensity, reaches 19% for scenario B1, 21% for scenario A1B and 27% for scenario A2. In our model, as in the majority of CGCMs, this decrease is caused more by changes in surface heat flux than by changes in surface freshwater flux. Under the forcing scenario A1B, LOVECLIM simulates a global sea-level rise of 31.3 cm in year 2100 AD. As for the 20th century, the most important contributor is the oceanic thermal expansion (+18.8 cm), followed by the contributions from the Greenland ice sheet (+5.2 cm), glaciers and ice caps (+3.8 cm) and the Antarctic ice sheet (+3.5 cm). The total rise is equivalent to a quadrupling of the sea-level rise simulated for the 20th century. Our sea-level value is somewhat lower than the central estimate for the same four components of about 40 cm in the IPCC TAR predictions. This can be explained by the low climate sensitivity of LOVECLIM, and hence the lower global temperature rise, which mostly affects the largest contribution of thermal expansion of the World Ocean. Another difference with the IPCC TAR predictions is the positive contribution from Antarctica of several cm of sea-level rise. That is in contrast to most other simulations showing a growing ice sheet and a negative contribution to global sea level of typically between -5 and -20 cm. The IPCC TAR also found a generally larger contribution from mountain glaciers and small ice caps. Our glacier-volume loss is smaller because of the lower initial glacier volume assumed by the glacier-melt algorithm. The total projected sea-level rise for the 21st century is only slightly affected by the scenario itself. For the range of SRES scenarios used by LOVECLIM, the total sea-level rise is found to vary between +22 and +35 cm by year 2100 AD. The much larger range of between +9 and +88 cm obtained for the IPCC TAR arose mainly from the inclusion of model uncertainties, and not from the greenhouse-gas-forcing scenarios employed. As expected, climate change impacts the air–sea CO2 exchange in the model by lowering the solubility and hence the net uptake of carbon by the ocean. The effect is however rather modest at the century time-scale given the moderate increase in sea-surface temperature simulated by LOVECLIM. In addition, we do not observe any significant change in the oceanic biology at the global scale during the 21st century. The picture is a bit different regarding the terrestrial biosphere. Both the climate and fertilization effects strongly increase the carbon uptake in VECODE. A number of experiments with interactive atmospheric CO2 concentration were also carried out over the 21st century. Contrary to other modelling studies, LOVECLIM predicts lower atmospheric CO2 levels at the end of the 21st century when the effect of climate change on the carbon cycle is accounted for in the model. The warming enhances the net uptake of carbon by the terrestrial biosphere which more than offsets the reduction in oceanic uptake resulting from the solubility decrease. Finally, we have thoroughly analysed the model response to a range of stabilized anthropogenic forcings over the next millennia. For the variety of forcing scenarios considered, LOVECLIM simulates a globally averaged, annual mean surface warming ranging between 0.55°C and 3.75°C and an associated decrease in Arctic and Antarctic sea-ice extent. However, no simulation predicts an entirely ice-free Arctic Ocean during summertime at the millennium time-scale. In the most pessimistic case, a small ice pack of about 0.5×106 km2 persists. Our results also suggest that it is very likely that the volume of the Greenland ice sheet will largely decrease in the future. After 1000 years of model integration, the ice volume is reduced by more than 20% when the radiative forcing is higher than 6.5 W m-2. Moreover, for a radiative forcing greater than 7.5 W m-2, the ice sheet melts away in less than 3000 years. Note that the ice-sheet disintegration might be even more rapid if processes responsible for the widespread glacier acceleration currently observed in Greenland were taken into consideration in the model. We also found that the freshwater flux from the melting Greenland ice sheet into the neighbouring oceans, which peaks in the most extreme scenario tested at 0.11 Sv (1 Sv = 10^6 m3 s-1) and remains above 0.1 Sv during three centuries, is not large enough to trigger a shutdown of the Atlantic MOC in our model, in contrast to some other models. Those models are however more responsive to freshwater perturbations than ours. Besides, we showed that climate feedbacks play a crucial role in the ice-sheet evolution and that the Greenland deglaciation considerably enhances the greenhouse-gas-induced warming over Greenland and the central Arctic. This stresses the importance of incorporating the two-way interactions between the Greenland ice sheet and climate in climate- and sea-level-change projections at the millennial time-scale. For the Antarctic ice sheet, the response is much less drastic than for the Greenland ice sheet. For instance, after 3000 years of 4×CO2 forcing (∼7.7 W m-2), the Antarctic grounded ice volume and area are reduced in our model by only 8% and 4%, respectively. For a sustained radiative forcing of 8.5 W m-2 (the highest forcing scenario considered in our study), LOVECLIM predicts a global sea-level rise of 7.15 m by year 3000 AD. Most of it is due to melting of the Greenland ice sheet (+4.25 m), followed by melting of the Antarctic ice sheet (+1.42 m), thermal expansion (+1.29 m) and the contribution from mountain glaciers and small ice caps (+0.19 m). Our results show that it will be very difficult to limit the eventual sea-level rise to less than 1 m after 1000 years, unless the atmospheric CO2 concentration can be stabilized to less than twice its pre-industrial level. Such a goal can only be reached by emission reductions far larger than any policy currently pursued. Concerning the carbon cycle, the experiments carried out with LOVECLIM highlight the opposite responses of the terrestrial and oceanic carbon reservoirs to climate change. We also found that, when anthropogenic CO2 emissions cease, the terrestrial biosphere becomes a weak carbon source, while the ocean continues to be a sink. It should be mentioned that no dramatic change in the global marine productivity is observed in our simulations. This arises from the fact that the modifications of the oceanic properties that affect this productivity (stratification, meridional overturning, …) are rather moderate. The effects of climate change are however not negligible. In particular, the decrease in sea-ice extent predicted by the model results in a longer growing season and a larger nutrient uptake (especially silica) in polar regions. As a result, by the end of the 23rd century, silica concentrations in the upper 100 m of the Southern Ocean drop by as much of 30% for the most extreme forcing scenarios. [less ▲]

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See detailModelling the evolution of domestic wastes landfills.
Thonart, Philippe ULg; Dumont, M.; Destain, Jacqueline ULg et al

Poster (1995, February)

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See detailModelling the Excavated damage zone around an underground gallery- Coupling mechanical, thermal and hydraulical aspects
Charlier, Robert ULg; Chambon, René; Li, Xiang Ling et al

in Management and Disposal of Radioactive Waste Euradwast’08 (2008)

A zone with significant irreversible deformations and significant changes in flow and transport properties is expected to be formed in clay around underground excavations. The stress perturbation around ... [more ▼]

A zone with significant irreversible deformations and significant changes in flow and transport properties is expected to be formed in clay around underground excavations. The stress perturbation around the excavation could lead to a significant increase of the permeability, related to diffuse and/or localized crack propagation in the material. Further the drainage and the heating of disposal will modified the size and the structure of the damage zone. The main objective of the study is to model these processes at small and large scale in order to assess their impacts on the performance of radioactive waste geological repositories. This paper concerns more particularly the thermo-hydro-mechanical modelling of a hollow cylinder experiment performed in Boom Clay and the hydro-mechanical modelling of a long term dilatometer experiment performed in Opalinus Clay at Mont Terri Rock Laboratory in Switzerland. This study shows that simple models already permit to reproduce the behaviours observed experimentally. [less ▲]

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See detailModelling the excavation damaged zone in Callovo-Oxfordian claystone with strain localization
Pardoen, Benoît ULg; Collin, Frédéric ULg; Levasseur, Séverine ULg et al

Conference (2012, October)

Gallery excavation in clayey rocks induces stress perturbations that trigger damage propagation. The excavation process creates then the so-called excavation damaged zone in which properties are modified ... [more ▼]

Gallery excavation in clayey rocks induces stress perturbations that trigger damage propagation. The excavation process creates then the so-called excavation damaged zone in which properties are modified. The prediction of the extension and especially of the fracturing structure in this zone remains a crucial issue in the context of underground storage. Since strain localization in shear band mode is frequently observed in experimental works, the excavation damaged zone can be modeled by considering the development of strain localization bands. A hydro-mechanical modelling of a gallery excavation is performed. The numerical results exhibit an excavation damaged zone extension similar to the in situ measurements and provides information about the rock state within this zone. [less ▲]

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See detailModelling the excavation damaged zone in claystone with strain localisation using coupled second gradient model and the influence of gallery ventilation
Pardoen, Benoît ULg; Levasseur, Séverine ULg; Collin, Frédéric ULg

Conference (2013, July 09)

Drilling of galleries induces stress perturbations that trigger damage propagation in the surrounding medium. The excavation process creates then the so-called excavation damaged zone around the galleries ... [more ▼]

Drilling of galleries induces stress perturbations that trigger damage propagation in the surrounding medium. The excavation process creates then the so-called excavation damaged zone around the galleries. The prediction of the extension and of the fracture structure within this zone remains nowadays a major issue especially in the context of underground storage. Since localised deformation in shear band mode is frequently observed in experimental works, the excavation damaged zone can be modelled by considering the development of shear strain localisation bands. To correctly model this behaviour, an enhanced model with a regularisation method is required. In underground structures, air ventilation inside the galleries induces a rock-atmosphere interaction that may lead to drainage and to rock desaturation close to the gallery wall. Such desaturation may influence the damage zone structure and needs to be studied. A hydro-mechanical modelling of a gallery excavation including air ventilation is thus performed and the numerical results provide information about the damaged zone extension, the strain localisation bands pattern and the influence of rock desaturation. [less ▲]

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See detailModelling the fracture generation in EDZ
Charlier, Robert ULg; Chambon, René; Al-Holo, Sama et al

in Report of the Swiss Geological Survey (2007), 2

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See detailModelling the Fringing of the FORS2 CCD
Walsh, J. R.; Kuntschner, H.; Jehin, Emmanuel ULg et al

in Kaufer, A. (Ed.) The 2007 ESO Instrument Calibration Workshop (2008)

Thinned CCD detectors display fringing which arises from the interference of multiply reflected light in the layers of the CCD. If the layer construction - the thicknesses and refractive indexes of the ... [more ▼]

Thinned CCD detectors display fringing which arises from the interference of multiply reflected light in the layers of the CCD. If the layer construction - the thicknesses and refractive indexes of the layers - is known, then the observed fringing can be accurately modelled and used to correct imaging and spectroscopic data for its effects. In practice the specifications on the actual deposited layer thicknesses may not be known to sufficient accuracy to predict the fringe behaviour. Thus calibration data, in the form of monochromatic flat fields, is required and can be modelled using the technique outlined by Malamuth et al. 2003, which has been applied to ACS CCDs. [less ▲]

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See detailModelling the general circulation of shelf seas by 3Dk-ε models
Nihoul, Jacques ULg; Deleersnijder, Eric; Djenidi, Salim ULg

in Earth-Science Reviews (1989), 26(1-3), 163-189

One examines the modifications which must be made-and the limitations which must be set-to classicalk-ε models to extend their application to the simulation of marine mesoscale, synopticscale and ... [more ▼]

One examines the modifications which must be made-and the limitations which must be set-to classicalk-ε models to extend their application to the simulation of marine mesoscale, synopticscale and macroscale processes which compose the weather-like and general circulations of the sea. The case of the general circulation—for which sub-grid scale fluctuations include such semi-organized motions as tides and storm surges-is discussed in more detail. A 3Dk-ε model appropriate to the study of the general circulation in a shallow stratified sea is presented and illustrated with the results of a simulation of the general summer circulation in the Northern Bering Sea, made in the scope of the NSF ISHTAR (“Inner Shelf Transfer and Recycling”) Program. [less ▲]

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See detailModelling the Gibraltar Strait/Western Alboran Sea ecohydrodynamics
Skliris, Nikolaos; Beckers, Jean-Marie ULg

in Ocean Dynamics (2009), 59(3), 489-508

The ecohydrodynamics of the Gibraltar Strait and the Western Alboran Sea is investigated using a 3-D, two-way nested, coupled hydrodynamic/plankton ecosystem model, exploiting the MEDATLAS climatological ... [more ▼]

The ecohydrodynamics of the Gibraltar Strait and the Western Alboran Sea is investigated using a 3-D, two-way nested, coupled hydrodynamic/plankton ecosystem model, exploiting the MEDATLAS climatological database. A high-resolution model (~1 km) of the Gibraltar/Western Alboran region embedded within a coarse-resolution model of the West Mediterranean (~5 km) is implemented. The model seasonal climatology of the 3-D circulation and the flow characteristics at the Gibraltar Strait and the Alboran Sea are discussed, and their impact on the plankton ecosystem evolution is explored. An important ecohydrodynamic feature produced by the model is a permanent upwelling zone in the northwestern part of the Alboran Sea in agreement with observations. Model results show that both horizontal and vertical current intensity of the Atlantic Jet increases progressively at the strait to obtain maximum values in the northeastern Mediterranean entrance, inducing an upward displacement of the nitracline. The nutrient-rich water transport through the strait along with the generation of cyclonic vorticity in the northwestern Alboran Sea result in the accumulation of nutrients there and thus induce a permanent fertilisation of this area. [less ▲]

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