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See detailGlaciaçoes neodevonianas E Eocarboniferas na America do sul.
Caputo, M.V.; Streel, Maurice ULg; Melo, H.G. et al

in Simposio da Amazonias (2006)

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See detailThe Glacial Carbon Cycle:Changing continental weathering and glacial-interglacial atmospheric CO2 variations.
Munhoven, Guy ULg

Conference (2002, December 12)

The role of continental weathering in the global carbon cycle is detailed and a quantitative analysis presented.

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See detailGlacial CO2 cycle as a succession of key physical and biogeochemical processes
Brovkin, Victor; Ganopolski, Andrey; Munhoven, Guy ULg et al

Conference (2011, April 05)

Ice core records of atmospheric CO2 concentration through the last 800,000 years show the carbon cycle amplifying the climate forcing from variations in Earth’s orbit. This positive climate-carbon cycle ... [more ▼]

Ice core records of atmospheric CO2 concentration through the last 800,000 years show the carbon cycle amplifying the climate forcing from variations in Earth’s orbit. This positive climate-carbon cycle feedback could weaken or even possibly reverse present-day fossil fuel CO2 uptake by the natural carbon cycle. Despite much effort over the last two decades, a mechanistic, process-based explanation of the carbon cycle feedbacks responsible for the glacial / interglacial CO2 cycles remains elusive.We will present first transient simulations of the last glacial cycle using an Earth System model of intermediate complexity to predict atmospheric CO2 , driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean d13 C also resembles the reconstructions from the real ocean. The main drivers of atmospheric CO2 evolve with time: changes in sea surface temperature and volume of bottom water of southern origin exert CO2 control during the glacial inception and deglaciation, while changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. Changes in terrestrial carbon storage counteract oceanic mechanisms during glacial inception and deglaciation, unless the potential for permafrost development is included in the soil carbon model. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation. [less ▲]

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See detailGlacial CO2 cycle as a succession of key physical and biogeochemical processes
Brovkin, V.; Ganopolski, A.; Archer, D. et al

in Climate of the Past (2012), 8(1), 251--264

During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that have led to the low glacial CO2 level could be done in equilibrium ... [more ▼]

During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that have led to the low glacial CO2 level could be done in equilibrium model experiments, an ultimate goal is to explain CO2 changes in transient simulations through the complete glacial-interglacial cycle. The computationally efficient Earth System model of intermediate complexity CLIMBER-2 is used to simulate global biogeochemistry over the last glacial cycle (126 kyr). The physical core of the model (atmosphere, ocean, land and ice sheets) is driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The carbon cycle model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean δ13C also resembles reconstructions from deep-sea cores. The main drivers of atmospheric CO2 evolve in time: changes in sea surface temperatures and in the volume of bottom water of southern origin control atmospheric CO2 during the glacial inception and deglaciation; changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation. [less ▲]

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See detailGlacial-interglacial atmospheric CO2 variations
Munhoven, Guy ULg

in Explaining Glacial/Interglacial CO2 changes (2000)

A review of the observed glacial-interglacial variations of CO2 in the atmosphere is made. The different hypotheses proposed to date are presented. An extensive list with key references and reading ... [more ▼]

A review of the observed glacial-interglacial variations of CO2 in the atmosphere is made. The different hypotheses proposed to date are presented. An extensive list with key references and reading material is provided. [less ▲]

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See detailGlacial-interglacial changes in continental weathering: possible implications for atmospheric CO2
Munhoven, Guy ULg; François, Louis ULg

in Zahn, Rainer; Pedersen, Thomas F.; Kaminski, Michael A. (Eds.) et al Carbon Cycling in the Glacial Ocean: Constraints on the Ocean's Role in Global Change (1994)

An eleven-box model of the ocean-atmosphere subsystem of the global carbon cycle is developed to study the potential contribution of continental rock weathering and oceanic sedimentation to the variations ... [more ▼]

An eleven-box model of the ocean-atmosphere subsystem of the global carbon cycle is developed to study the potential contribution of continental rock weathering and oceanic sedimentation to the variations of the atmospheric CO2 pressure over glacial-interglacial timescales. The model is capable of reproducing the distribution of total dissolved inorganic carbon, total alkalinity, phosphate, delta C-13, and Delta C-14 between the various ocean basins today, as well as the partial pressure of atmospheric CO2. A simple sedimentation scheme at 20 different depth levels drives carbonate deposition and dissolution as a function of the depths of carbonate and aragonite lysoclines in each ocean basins considered (Atlantic, Antarctic and Indo-Pacific). The coral-reef erosion-deposition cycle is also taken into account. Furthermore, a simple cycle of oceanic strontium isotopes has been added to this model to take advantage of the Sr-87/Sr-86 data recently published by Dia et al. [1992] for the last 300,000 years. These data emphasize the importance of weathering of continental silicate rocks at glacial-interglacial timescales. They are used to construct several scenarios of changes of continental weathering over the last glacial cycles. They suggest that the flux of alkalinity delivered to the ocean from continental silicate weathering may have been substantially larger during glacial times than today. We show that such variations of continental weathering may explain at least in part the observed changes of the partial pressure of atmospheric CO2 between glacial and interglacial periods. [less ▲]

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See detailGlacial-interglacial changes of continental weathering: estimates of the related CO2 and HCO3- flux variations and their uncertainties
Munhoven, Guy ULg

in Global and Planetary Change (2002), 33(1-2), 155-176

A range of estimates for the glacial-interglacial variations in CO, consumption and HCO3- production rates by continental weathering processes were calculated with two models of continental weathering ... [more ▼]

A range of estimates for the glacial-interglacial variations in CO, consumption and HCO3- production rates by continental weathering processes were calculated with two models of continental weathering: the Gibbs and Kump Weathering Model (GKWM) [Paleoceanography 9(4) (1994) 529] and an adapted version of Amiotte Suchet and Probst's Global Erosion Model for CO2 Consumption (GEM-CO2) [C. R, Acad. Sci. Paris, Ser. 11317 (1993) 615; Tellus 47B (1995) 273]. Both models link CO2 consumption and HCO3- production rates to the global distributions of lithology and runoff. A spectrum of 16 estimates for the runoff distribution at the Last Glacial Maximum (LGM) was constructed on the basis of two different data sets for present-day runoff and climate results from eight GCM climate simulation experiments carried out in the framework of the Paleo Modelling Intercomparison Project (PMIP). With these forcings, GKWM produced 3.55-9.0 Tmol/year higher and GEM-CO2 4.7-13.25 Tmol/year higher global HCO3- (1 Tmol=10(12) mol) production rates at the LGM, Mean variations (plus/minus one standard error of the mean with 7 df) were 6.2+/-0.6 and 9.4+/-1.0 Tmol/year, respectively. The global CO2 consumption rates obtained with GKWM were 1.05-4.5 Tmol/year (mean: 2.8+/-0.4 Tmol/year) higher at the LGM than at present. With GEM-CO2 this increase was 1.95-7.15 Tmol/year (mean: 4.8+/-0.6 Tmol/year). The large variability in the changes obtained with each weathering model was primarily due to the variability in the GCM results. The increase in the CO2 consumption rate due to continental shelf exposure at the LGM was always more than 60% larger than its reduction due to ice cover. For HCOT production rates, the increase related to shelf exposure was always more than twice as large as the decrease due to ice cover. Flux variations in the areas exposed both now and at the LGM were, in absolute value, always more than 3.5 times lower than those in the shelf environment. The calculated CO2 consumption rates by carbonate weathering were consistently higher at the LGM, by 2.45-4.5 Tmol/year (mean: 3.4+/-0.2 Tmol/year) according to GKWM and by 2.75-6.25 Tmol/year (mean: 4.6+/-0.4 Tmol/year) according to GEM-CO, For silicate weathering, GKWM produced variations ranging between a 1.9 Tmol/year decrease and a 0.4 Tmol/year increase for the LGM (mean variation: -0.7+/-0.2 Tmol/year); GEM-CO, produced variations ranging between a 0.8 Tmol/year decrease and a 1.05 Tmol/year increase (mean variation: +0.2+/-0.2 Tmol/year). In the mean, the calculated variations of CO2 and HCO3- fluxes would contribute to reduce atmospheric p(CO2) by 5.7+/-1.3 ppmv (GKWM) or 3 12.1+/-1.7 ppmv (GEM-CO2), which might thus represent a non-negligible part of the observed glacial interglacial variation of similar to 75 ppmv. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailGlacial-interglacial pCO2 Variations and the Rain Ratio Hypothesis: Implications for Sedimentary Carbonate Preservation/Dissolution Processes
Munhoven, Guy ULg

Conference (2008, May 27)

A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times has been for years one of the favourite hypotheses to explain the glacial-interglacial atmospheric CO2 ... [more ▼]

A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times has been for years one of the favourite hypotheses to explain the glacial-interglacial atmospheric CO2 variations. This hypothesis have been tested and implications for the dynamics of sedimentary carbonate preservation and dissolution explored with MBM, a multi-box model of the ocean carbon cycle, fully coupled to the transient early diagenesis model MEDUSA. With this coupled model, a peak reduction of the rain ratio by 40% at the Last Glacial Maximum (LGM) was found to produce a net atmospheric pCO2 reduction of about 40 ppm. Changing shelf carbonate accumulation rates and continental weathering inputs produced a 55-60 ppm reduction. The combination of the two mechanisms generates a 90-95 ppm pCO2 change, which compares well with the observations. However, the resulting model sedimentary record is at odds with actual sedimentary records. Changing carbonate accumulation rates on the continental shelf and variable weathering fluxes depress the calcite saturation horizon (CSH) by about 1 km at the LGM; rain ratio variations depress it by another km. In addition to this large amplitude for the CSH, the changing rain ratio also leads to transition zone changes in the model sedimentary record that are opposite in phase with data-based reconstructions. [less ▲]

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See detailGlacial-interglacial rain ratio variations: effect on atmospheric CO2 levels and sedimentary carbonate preservation/dissolution processes
Munhoven, Guy ULg

Conference (2006, February 10)

A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times is commonly advanced to explain an important part of the observed glacial-interglacial atmospheric CO2 ... [more ▼]

A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times is commonly advanced to explain an important part of the observed glacial-interglacial atmospheric CO2 variation. This hypothesis was tested and side-effects on the evolution of carbonate preservation/dissolution in the surface sediment explored with a multi-box model (MBM) of the ocean carbon cycle, fully coupled to a new transient advection-diffusion-reaction model (called MEDUSA) representing early diagenesis processes of carbonate minerals in the surface sediment. MEDUSA explicitly considers the role of organic matter remineralisation in the sediment column to enhance calcite (and aragonite) dissolution. It is fully bi-directional and takes chemical erosion into account in times when carbonate dissolution makes the sediment mixed-layer collapse faster than the sediment supply to the surface is able to counterbalance. Coupled model experiments were run for 240,000 years, forced by variable sea-level, temperature and salinity histories, and variable continental weathering inputs. Various scenarios for the evolution of the rain ratio over glacial to interglacial periods were adopted. A peak reduction of the rain ratio by 40% at the Last Glacial Maximum (LGM) was found to produce a net atmospheric pCO2 reduction of about 30ppm, on top of a 60ppm reduction produced by changing continental shelf carbonate accumulation and changing continental weathering inputs. The overall 90ppm oscillation compares well with the observed data. However, the effect on the model sedimentary record is clearly at odds with actual sediment records. The changes related to continental shelf processes and variable weathering flux depress the calcite saturation horizon by about 1km at the LGM; if rain ratio variations are also considered, that depression increases by another km. An assessment of the respective contributions from various model parameters will be presented. [less ▲]

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See detailGlacial-interglacial variability of atmospheric CO2 due to changing continental silicate rock weathering: A model study
Munhoven, Guy ULg; Francois, Louis ULg

in Journal of Geophysical Research (1996), 101(D16), 21423-21437

An 11-box model of the oceanic carbon cycle including sedimentary processes is used to explore the role chemical weathering of continental silicate rocks might play in driving atmospheric CO2 levels on ... [more ▼]

An 11-box model of the oceanic carbon cycle including sedimentary processes is used to explore the role chemical weathering of continental silicate rocks might play in driving atmospheric CO2 levels on glacial-interglacial timescales. Histories for the consumption of CO2 by silicate rock weathering processes are derived from the marine Ge/Si record. Taking the major uncertainties in the knowledge of the Ge and Si cycles into account, several histories for the evolution of the riverine dissolved silica fluxes are calculated from this record. The investigation of the systematics between riverine dissolved silica and bicarbonate fluxes under different weathering regimes leads us to the tentative conclusion that although there is no correlation between dissolved silica and total bicarbonate concentrations in the major rivers, there may exist a negative correlation between weathering intensity and the ratio of dissolved silica to bicarbonate derived from silicate weathering alone. With this correlation as a working hypothesis, it is possible to interpret the dissolved silica fluxes in terms of equivalent CO2 consumption rates. The calculated histories indicate that glacial rates of CO2 consumption by chemical silicate rock weathering could have been twice, and possibly up to 3.5 times, as high as they are today. When used to force the carbon cycle model, they are responsible for glacial-interglacial pCO2 variations in the atmosphere of typically 50–60 ppm and up to 95–110 ppm. These variations are superimposed to a basic oscillation of 60 ppm generated by the model, mainly in response to coral reef buildup and erosion processes. The total pCO2 signal has an amplitude of about 80–90 ppm and up to 125–135 ppm. Although these large amplitudes indicate that silicate weathering processes should be taken into account when studying glacial-interglacial changes of CO2 in the atmosphere, it also raises new problems, such as too high CO2 levels during the period from 110–70 kyr B.P., requiring further study. [less ▲]

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See detailGlacial/interglacial instabilities of the Western Boundary Under Current during the last 365 kyr from Sm/Nd ratios of the sedimentary clay-size fractions at ODP site 646 (Labrador Sea)
Fagel, Nathalie ULg; Hillaire-Marcel, Claude ULg

in Marine Geology (2006), 232(1-2), 87-99

We present 40 Sm-Nd isotope measurements of the clay-size (< 2 mu m) fractions of sediments from the Southern Greenland rise (ODP-646) that span the last 365 kyr. These data track changes in the relative ... [more ▼]

We present 40 Sm-Nd isotope measurements of the clay-size (< 2 mu m) fractions of sediments from the Southern Greenland rise (ODP-646) that span the last 365 kyr. These data track changes in the relative supply of fine particles carried into the deep Labrador Sea by the Western Boundary Under Current (WBUC) back to the fourth glacial-interglacial cycles. Earlier studies revealed three general sources of particles to the core site: (i) Precambrian crustal material from Canada, Greenland, and/or Scandinavia (North American Shield-NAS), (ii) Palaeozoic or younger crustal material from East Greenland, NW Europe, and/or western Scandinavia (Young Crust-YQ and (iii) volcanic material from Iceland and the Mid-Atlantic Ridge (MAR). Clay-size fractions from glacial sediments have the lowest Nd isotopic ratios. Supplies of young crustal particles were similar during glacial oxygen isotope stages (OIS) 2, 6, and 10. In contrast the mean volcanic contributions decreased relative to old craton material from OIS 10 to OIS 6 and then from OIS 6 to OIS 2. The glacial OIS 8 interval displays a mean Sm/Nd ratio similar to those of interglacials OIS 1, 5, and 9. Compared with other interglacials, OIS 7 was marked by a higher YC contribution but a similar similar to 30% MAR supply. The overall NAS contribution dropped by a factor of 2 during each glacial/interglacial transition, with the MAR contribution broadly replacing it during interglacials. To decipher between higher supplies and/or dilution, particle fluxes from each end member were estimated. Glacial NAS fluxes were systematically higher than interglacial fluxes. During the time interval examined, fine particle supplies to the Labrador Sea were strongly controlled by proximal ice-margin erosion and thus echoed the glacial stage intensity. In contrast, the WBUC-carried MAR supplies from the eastern basins did not change significantly throughout the last 365 kyr, except for a marked increase in surface-sediments that suggests unique modem conditions. Distal WBUC-controlled inputs from the Northern and NE North Atlantic seem to have been less variable than proximal supplies linked with glacial erosion rate. (c) 2006 Elsevier B.V All rights reserved. [less ▲]

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See detailGlacial–interglacial rain ratio changes: Implications for atmospheric CO2 and ocean–sediment interaction
Munhoven, Guy ULg

in Deep-Sea Research Part II, Topical Studies in Oceanography (2007), 54(5-7), 722-746

A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times has been advanced to explain the glacial–interglacial atmospheric CO2 variations. This hypothesis is tested and ... [more ▼]

A reduction of the carbonate-carbon to organic-carbon export rain ratio during glacial times has been advanced to explain the glacial–interglacial atmospheric CO2 variations. This hypothesis is tested and implications for the dynamics of sedimentary carbonate preservation and dissolution are explored with a multi-box model (MBM) of the ocean carbon cycle, fully coupled to a new transient early diagenesis model (called MEDUSA). A peak reduction of the rain ratio by 40% at the Last Glacial Maximum (LGM) was found to produce a net atmospheric pCO2 reduction of about 40 ppm. Changing shelf carbonate accumulation rates and continental weathering inputs produced a 55–60 ppm reduction. The combination of the two mechanisms generates a pCO2 change of 90–95 ppm, which compares well with the observed data. However, the resulting model sedimentary record does not conform to actual sedimentary records. The changes related to continental shelf processes and variable weathering flux depress the calcite saturation horizon (CSH) by about 1 km at the LGM; if rain ratio variations are also considered, that depression increases by another km. In addition to this large amplitude for the CSH, possibly due to the adopted box-model approach, the changing rain ratio also leads to transition zone changes in the model sedimentary record that are opposite in phase with data-based reconstructions. Realistic changes in the aragonite fraction of the carbonate rain were found to have only a minimal impact on atmospheric pCO2. Finally, chemical erosion of deep-sea sediment was shown to reduce the amplitude of variation of the sedimentary CCD by about 10–20%. It may provide a mechanism to improve the model-data agreement. [less ▲]

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See detailGlageon: une coupe du Givetien en Avesnois (France). Sédimentologie, Coraux, géologie régionale, diagenèse
Boulvain, Frédéric ULg; Coen-Aubert, M.; Mansy, J. L. et al

in Bulletin de la Société Belge de Géologie (1995), 103(1-2), 171-203

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See detailGlance on preliminary nutritional data ORISCAV-LUX Survey
Alkerwi; Guillaume, Michèle ULg

Conference (2009)

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See detailGlances at the EC Nitrate Directive implementation in the Walloon Region of Belgium
Marcoen, Jean Marie ULg

Scientific conference (2006, July 04)

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See detailGlass eel swimming behaviour during their estuarine migration: new insights from video tracking analysis
Delcourt, Johann ULg; bolliet, Valérie; Ylieff, Marc ULg et al

Conference (2010, July)

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See detailGlass production in late antiquity
Van Wersch, Line ULg; Mathis, François ULg; Dupuis, Thomas ULg et al

Poster (2009)

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See detailGlass production in Merovingian time
Van Wersch, Line ULg; Mathis, François ULg; Othmane, G. et al

Poster (2010, May)

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See detailGlass transition phenomena applied to powdered amorphous food carbohydrates
Ronkart, Sebastien N; Blecker, Christophe ULg; Deroanne, Claude et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2009), 13(1), 177-186

Glass transition phenomena applied to powdered amorphous food carbohydrates. During these last fifteen years, some food technologists and scientists have become aware of the importance of the glass ... [more ▼]

Glass transition phenomena applied to powdered amorphous food carbohydrates. During these last fifteen years, some food technologists and scientists have become aware of the importance of the glass transition, a thermal property of glassy or amorphous material, in food preparation processes. Recent studies have successfully correlated this fundamental notion to technofunctional changes within the powder. The aim of this paper is to present in a non exhaustive manner the relationship between glass transition characteristics and applications in food technology (caking, alterations, etc.). [less ▲]

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