References of "Munhoven, Guy"
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See detailAn inversion method for cometary atmospheres
Hubert, Benoît ULg; Opitom, Cyrielle ULg; Hutsemekers, Damien ULg et al

in Icarus (2016)

Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight. This integration is the so-called Abel transform of the local emission rate ... [more ▼]

Remote observation of cometary atmospheres produces a measurement of the cometary emissions integrated along the line of sight. This integration is the so-called Abel transform of the local emission rate. The observation is generally interpreted under the hypothesis of spherical symmetry of the coma. Under that hypothesis, the Abel transform can be inverted. We derive a numerical inversion method adapted to cometary atmospheres using both analytical results and least squares fitting techniques. This method, derived under the usual hypothesis of spherical symmetry, allows us to retrieve the radial distribution of the emission rate of any unabsorbed emission, which is the fundamental, physically meaningful quantity governing the observation. A Tikhonov regularization technique is also applied to reduce the possibly deleterious effects of the noise present in the observation and to warrant that the problem remains well posed. Standard error propagation techniques are included in order to estimate the uncertainties affecting the retrieved emission rate. Several theoretical tests of the inversion techniques are carried out to show its validity and robustness. In particular, we show that the Abel inversion of real data is only weakly sensitive to an offset applied to the input flux, which implies that the method, applied to the study of a cometary atmosphere, is only weakly dependent on uncertainties on the sky background which has to be subtracted from the raw observations of the coma. We apply the method to observations of three different comets observed using the TRAPPIST telescope: 103P/ Hartley 2, F6/ Lemmon and A1/ Siding Spring. We show that the method retrieves realistic emission rates, and that characteristic lengths and production rates can be derived from the emission rate for both CN and C2 molecules. We show that the retrieved characteristic lengths can differ from those obtained from a direct least squares fitting over the observed flux of radiation, and that discrepancies can be reconciled for by correcting this flux by an offset (to which the inverse Abel transform is nearly not sensitive). The A1/Siding Spring observations were obtained very shortly after the comet produced an outburst, and we show that the emission rate derived from the observed flux of CN emission at 387 nm and from the C2 emission at 514.1 nm both present an easily-identifiable shoulder that corresponds to the separation between pre- and post-outburst gas. As a general result, we show that diagnosing properties and features of the coma using the emission rate is easier than directly using the observed flux, because the Abel transform produces a smoothing that blurs the signatures left by features present in the coma. We also determine the parameters of a Haser model fitting the inverted data and fitting the line-of-sight integrated observation, for which we provide the exact analytical expression of the line-of-sight integration of the Haser model. [less ▲]

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See detailAssessing the Risk of Ecosystem Disruption in Europe using a Dynamic Vegetation Model driven by CMIP5 Regional Climatic Projections from EURO-CORDEX
Dury, Marie ULg; Hambuckers, Alain ULg; Henrot, Alexandra-Jane ULg et al

Conference (2015, December 18)

While the combination of warmer and drier mean climatic conditions can have severe impacts on ecosystems, extreme events like droughts or heat waves that break the gradual climate change can have more ... [more ▼]

While the combination of warmer and drier mean climatic conditions can have severe impacts on ecosystems, extreme events like droughts or heat waves that break the gradual climate change can have more long-term consequences on ecosystem composition, functioning and carbon storage. Hence, it is essential to assess the changes in climatic variability and the changes in frequency of extreme events projected for the future. Ecosystems could not be in a condition to adapt to these new conditions and might be disrupted. Here, the process-based dynamic vegetation model CARAIB DVM was used to evaluate and analyze how future climate and extreme events will affect European ecosystems. To quantify the uncertainties in the climatic projections and in their potential impacts on ecosystems, the vegetation model was driven with the outputs of different regional climatic models (RCMs), nested in CMIP5 GCM projections for the EURO-CORDEX project. We used the ALADIN version 5.3 (Météo-France/CNRM) and other EURO-CORDEX RCMs. These climatic projections are at a high spatial resolution (0.11-degree, ~12 km). CARAIB simulations were performed across Europe over the historical period 1951-2005 and the future period 2006-2100 under RCP4.5 and RCP8.5 emission scenarios. We simulated a set of 99 individual species (47 herbs, 12 shrubs and 40 trees) representing the major European ecosystem flora. First, we analyzed the climatic variability simulated by the climatic models over the historical period and compared it with the observed climatic variability. None of these climatic models can reproduce accurately the present natural climatic variability. Then, to assess the risk of ecosystem disruption in the future and to identify the vulnerable areas in Europe, we created an index combining several CARAIB outputs: runoff, mean NPP, soil turnover, burned area, appearance and disappearance of species. We evaluated the severity of change projected for these variables (period 2071-2100) relative to their current variability (period 1961-1990). Mean changes were considered severe if they exceed observed variability. The highest values of the index were found in southern Europe, indicating that the amplitude of the expected ecosystem changes largely exceeds current interannual variability in this area. [less ▲]

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See detailAnalysing the response of European ecosystems to droughts and heat waves within ISI-MIP2 simulations
Henrot, Alexandra-Jane ULg; Dury, Marie ULg; François, Louis ULg et al

Conference (2015, December 14)

With unprecedented speed and extent, the future climate change can be expected to severely impact terrestrial ecosystems due to more frequent extreme events, such as droughts or heat waves. What will be ... [more ▼]

With unprecedented speed and extent, the future climate change can be expected to severely impact terrestrial ecosystems due to more frequent extreme events, such as droughts or heat waves. What will be the impacts of these extreme events on ecosystem functioning and structure? How far will net primary production be reduced by such events? What will be the impact on plant mortality? Could such events trigger changes in the abundance of plant species, thus leading to biome shifts? In this contribution, we propose to use ISI-MIP2 model historical simulations from the biome sector to analyse the response of ecosystems to droughts or heat waves, trying to understand the differences between several vegetation models (e.g. CARAIB, HYBRID, LPJ). The analysis will focus on Europe. It will compare and assess the model responses for a series of well-marked drought or heat wave events in the simulated historical period, such as those that occurred in 1976, 2003 or 2010. This analysis will be performed in terms of several important environmental variables, like soil water and hydric stress, runoff, PFT abundance, net primary productivity and biomass, fire frequency, turnover of soil organic matter, etc. Whenever possible, the response of the model will be compared to available data for the most recent well-marked events. Examples of data to be used are eddy covariance, satellite data (including leaf area and fire occurrence) or tree rings. [less ▲]

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See detailThe last four glacial cycles simulated with the CLIMBER-2 model
Ganopolski, Andrey; Brovkin, Victor; Calov, Reinhard et al

Conference (2015, March 19)

We present results from our simulation experiments for the last four glacial cycles with the Earth System Model of Intermediate Complexity (EMIC) CLIMBER-2, with fully coupled ice-sheet and carbon cycle ... [more ▼]

We present results from our simulation experiments for the last four glacial cycles with the Earth System Model of Intermediate Complexity (EMIC) CLIMBER-2, with fully coupled ice-sheet and carbon cycle components. [less ▲]

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See detailCarbon cycle dynamics during recent interglacials
Kleinen, T.; Brovkin, V.; Munhoven, Guy ULg

in Climate of the Past Discussions (2015), 11(3), 1945-1983

Trends in the atmospheric concentration of CO2 during three recent interglacials, the Holocene, the Eemian and Marine Isotope Stage (MIS) 11, are investigated using an Earth system Model of Intermediate ... [more ▼]

Trends in the atmospheric concentration of CO2 during three recent interglacials, the Holocene, the Eemian and Marine Isotope Stage (MIS) 11, are investigated using an Earth system Model of Intermediate Complexity, which we extended with modules to dynamically determine two slow carbon cycle processes – peat accumulation and shallow-water CaCO3 sedimentation (coral reef formation). For all three interglacials, model simulations considering peat accumulation and shallow water CaCO3 sedimentation substantially improve the agreement between model results and ice core CO2 reconstructions in comparison to a carbon cycle setup neglecting these processes. This enables us to model the trends in atmospheric CO2, with modelled trends similar to the ice core data, forcing the model only with orbital and sea level changes. During the Holocene, anthropogenic CO2 emissions are required to match the observed rise in atmospheric CO2 after 3 ka BP, but are not relevant before this time. Therefore our model experiments show for the first time how the CO2 evolution during the Holocene and two recent interglacials can be explained consistently using an identical model setup. [less ▲]

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See detailInteractive comment on “Improved routines to model the ocean carbonate system: mocsy 1.0” by J. C. Orr and J.-M Epitalon
Munhoven, Guy ULg

in Geoscientific Model Development Discussions [=GMDD] (2014), 7

The manuscript "Improved routines to model the ocean carbonate system: mocsy 1.0" by J. C. Orr and J.-M Epitalon is reviewed and related issues and ideas are discussed.

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See detailCarbon and Other Biogeochemical Cycles
Ciais, Philippe; Sabine, Christopher; Bala, Govindasamy et al

in Stocker, T. F.; Qin, D.; Plattner, G.-K. (Eds.) et al Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (2014)

The present perturbations of the biogeochemical cycles of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as their past variations (coupled to climate variations) and their projected ... [more ▼]

The present perturbations of the biogeochemical cycles of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as their past variations (coupled to climate variations) and their projected future evolutions over the 21st century are reviewed. [less ▲]

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See detailSensitivity of the CaCO3 content of marine sediments to the kinetic expression of CaCO3 dissolution
Schneider, Birgit; Munhoven, Guy ULg; Regenberg, Anke

Poster (2013, September 05)

The preservation of calcite in marine sediments depends on the CaCO3 saturation state of the ambient pore waters and - to a lesser degree - of overlying seawater. A simple sensitivity analysis shows that ... [more ▼]

The preservation of calcite in marine sediments depends on the CaCO3 saturation state of the ambient pore waters and - to a lesser degree - of overlying seawater. A simple sensitivity analysis shows that the two common expressions to quantify the saturation of seawater with respect to CaCO3 (ΔCO3 =[CO3 ]-[CO3 ]sat , Ω = [CO3 ]/[CO3 ]sat ), when used for the calculation of the time dependent rate of CaCO3 dissolution either in the water column or in the sediments, yield very different rates of CaCO3 dissolution. With the help of an ocean biogeochemical model it was found that different kinetic expressions for pelagic CaCO3 dissolution in an ocean acidification scenario result in a wide range of surface to mid-depth calcite fluxes in the open ocean, which has strong implications for particle ballasting, the flux of calcite to the sediments and finally the global carbon cycle. In the present study we employ a marine sediment model that is fed by calcite and other biogeochemical fluxes from the ocean biogeochemical model using different realizations of calcite dissolution kinetics under (1) preindustrial and (2) last glacial maximum background climate conditions to assess the model-data agreement of the calcite content of deep sea sediments. A better understanding of the mechanisms driving calcite dissolution in the ocean is important to assess the time scale of calcite compensation, for example during glacial-interglacial cycles, but also in future greenhouse scenarios. [less ▲]

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See detailEmulation of the MBM-MEDUSA model: exploring the sea level and the basin-to-shelf transfer influence on the system dynamics
Ermakov, Ilya; Munhoven, Guy ULg; Crucifix, Michel

Poster (2013, April 12)

Complex climate models require high computational burden. However, computational limitations may be avoided by using emulators. In this work we present several approaches for dynamical emulation (also ... [more ▼]

Complex climate models require high computational burden. However, computational limitations may be avoided by using emulators. In this work we present several approaches for dynamical emulation (also called metamodelling) of the Multi-Box Model (MBM) coupled to the Model of Early Diagenesis in the Upper Sediment A (MEDUSA) that simulates the carbon cycle of the ocean and atmosphere [1]. We consider two experiments performed on the MBM-MEDUSA that explore the Basin-to-Shelf Transfer (BST) dynamics. In both experiments the sea level is varied according to a paleo sea level reconstruction. Such experiments are interesting because the BST is an important cause of the CO2 variation and the dynamics is potentially nonlinear. The output that we are interested in is the variation of the carbon dioxide partial pressure in the atmosphere over the Pleistocene. The first experiment considers that the BST is fixed constant during the simulation. In the second experiment the BST is interactively adjusted according to the sea level, since the sea level is the primary control of the growth and decay of coral reefs and other shelf carbon reservoirs. The main aim of the present contribution is to create a metamodel of the MBM-MEDUSA using the Dynamic Emulation Modelling methodology [2] and compare the results obtained using linear and non-linear methods. The first step in the emulation methodology used in this work is to identify the structure of the metamodel. In order to select an optimal approach for emulation we compare the results of identification obtained by the simple linear and more complex nonlinear models. In order to identify the metamodel in the first experiment the simple linear regression and the least-squares method is sufficient to obtain a 99,9% fit between the temporal outputs of the model and the metamodel. For the second experiment the MBM’s output is highly nonlinear. In this case we apply nonlinear models, such as, NARX, Hammerstein model, and an ’ad-hoc’ switching model. After the identification we perform the parameter mapping using spline interpolation and validate the emulator on a new set of parameters. [less ▲]

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See detailAssessing the potential of calcium-based artificial ocean alkalinization to mitigate rising atmospheric CO2 and ocean acidification
Ilyina, Tatiana; Wolf-Gladrow, Dieter; Munhoven, Guy ULg et al

in Geophysical Research Letters (2013), 40(22), 5909-5914

Enhancement of ocean alkalinity using calcium compounds, e.g., lime has been proposed to mitigate further increase of atmospheric CO2 and ocean acidification due to anthropogenic CO2 emissions. Using a ... [more ▼]

Enhancement of ocean alkalinity using calcium compounds, e.g., lime has been proposed to mitigate further increase of atmospheric CO2 and ocean acidification due to anthropogenic CO2 emissions. Using a global model, we show that such alkalinization has the potential to preserve pH and the saturation state of carbonate minerals at close to today's values. Effects of alkalinization persist after termination: Atmospheric CO2 and pH do not return to unmitigated levels. Only scenarios in which large amounts of alkalinity (i.e., in a ratio of 2:1 with respect to emitted CO2) are added over large ocean areas can boost oceanic CO2 uptake sufficiently to avoid further ocean acidification on the global scale, thereby elevating some key biogeochemical parameters, e.g., pH significantly above preindustrial levels. Smaller-scale alkalinization could counteract ocean acidification on a subregional or even local scale, e.g., in upwelling systems. The decrease of atmospheric CO2 would then be a small side effect. [less ▲]

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See detailMathematics of the total alkalinity–pH equation – pathway to robust and universal solution algorithms: the SolveSAPHE package v1.0.1
Munhoven, Guy ULg

in Geoscientific Model Development [=GMD] (2013), 6

The total alkalinity–pH equation, which relates total alkalinity and pH for a given set of total concentrations of the acid–base systems that contribute to total alkalinity in a given water sample, is ... [more ▼]

The total alkalinity–pH equation, which relates total alkalinity and pH for a given set of total concentrations of the acid–base systems that contribute to total alkalinity in a given water sample, is reviewed and its mathematical properties established. We prove that the equation function is strictly monotone and always has exactly one positive root. Different commonly used approximations are discussed and compared. An original method to derive appropriate initial values for the iterative solution of the cubic polynomial equation based upon carbonate-borate-alkalinity is presented. We then review different methods that have been used to solve the total alkalinity–pH equation, with a main focus on biogeochemical models. The shortcomings and limitations of these methods are made out and discussed. We then present two variants of a new, robust and universally convergent algorithm to solve the total alkalinity–pH equation. This algorithm does not require any a priori knowledge of the solution. SolveSAPHE (Solver Suite for Alkalinity-PH Equations) provides reference implementations of several variants of the new algorithm in Fortran 90, together with new implementations of other, previously published solvers. The new iterative procedure is shown to converge from any starting value to the physical solution. The extra computational cost for the convergence security is only 10–15% compared to the fastest algorithm in our test series. [less ▲]

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See detailAnthropogenic perturbation of the carbon fluxes from land to ocean
Regnier; Friedlingstein, P.; Ciais, P. et al

in Nature Geoscience (2013)

A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to ... [more ▼]

A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to the ocean. So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times. A synthesis of published work reveals the magnitude of present-day lateral carbon fluxes from land to ocean, and the extent to which human activities have altered these fluxes. We show that anthropogenic perturbation may have increased the flux of carbon to inland waters by as much as 1.0 Pg C yr-1 since pre-industrial times, mainly owing to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (~0.4 Pg C yr-1) or sequestered in sediments (~0.5 Pg C yr-1) along the continuum of freshwater bodies, estuaries and coastal waters, leaving only a perturbation carbon input of ~0.1 Pg C yr-1 to the open ocean. According to our analysis, terrestrial ecosystems store ~0.9 Pg C yr-1 at present, which is in agreement with results from forest inventories but significantly differs from the figure of 1.5 Pg C yr-1 previously estimated when ignoring changes in lateral carbon fluxes. We suggest that carbon fluxes along the land–ocean aquatic continuum need to be included in global carbon dioxide budgets. [less ▲]

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See detailModelling of the Marine Carbon Cycle
Munhoven, Guy ULg

Scientific conference (2012, October 17)

The lecture is subdivided into two parts. The first one deals with the essence of modelling, with the main principles and stages of development. The procedure of model development will be exemplified on ... [more ▼]

The lecture is subdivided into two parts. The first one deals with the essence of modelling, with the main principles and stages of development. The procedure of model development will be exemplified on the basis of a practical question. During this first part, a number of concepts and parameters that are important for the particular case of ocean carbon cycle modelling are already introduced. In the second part, we further deepen these. We explore the main physical and biogeochemical processes that are important to understand how the carbon cycle operates in the world ocean and provide insight into the way they are represented in different types of models currently used. [less ▲]

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See detailThe Rain Ratio Hypothesis Revisited
Munhoven, Guy ULg

Poster (2012, September 21)

The Rain Ratio Hypothesis (Archer and Maier-Reimer, 1994, Nature 367, 260–263) ascribes an important part of the observed glacial-interglacial variations of CO2 in the atmosphere to reduced sea-floor rain ... [more ▼]

The Rain Ratio Hypothesis (Archer and Maier-Reimer, 1994, Nature 367, 260–263) ascribes an important part of the observed glacial-interglacial variations of CO2 in the atmosphere to reduced sea-floor rain ratio (i.e., carbonate-C/organic-C in the biogenic particle flux at the sea-floor) during glacial times. With a lower sea-floor rain ratio the influence of organic carbon respiration on carbonate dissolution is stronger. The deep-sea carbonate ion concentration required for global ocean carbonate compensation will then be higher, which in turn contributes to lower atmospheric pCO2. Munhoven (2007, Deep-Sea Research II, 722–746) showed that the suggested rain ratio reductions lead to unrealistic sedimentary records for %CaCO3: the transition zone changes in the model sedimentary record were too large and opposite in phase to available observational data. The rain ratio reduction applied by Munhoven (2007) was uniform over the ocean and the author hypothesised that a non-uniform reduction could change the complete picture. If the rain ratio variations had primarily taken place in open ocean areas of great depth—essentially in regions where the sea floor was deeper than the saturation horizon or the CCD—then the transition zone boundaries could possibly have moved less. Here, we test this hypothesis and analyse the effect of depth dependent variations. We find that concentrating rain ratio changes over areas of great water depth completely alters the sedimentary imprint: the phase relationship of the signal reverts (compared to the uniform case) and the amplitude of the change decreases, bringing it into better agreement with available observations. However, the global average rain ratio reduction of 40% that yielded a 40 ppm reduction of atmospheric pCO2 in the uniform case only leads to 25 ppm in this non-uniform case. [less ▲]

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See detailMitigation Potential of Artificial Ocean Alkalinization For Ocean Acidification and Atmospheric CO2
Ilyina, Tatiana; Wolf-Gladrow, Dieter; Munhoven, Guy ULg et al

Poster (2012, September)

Fossil fuel CO2 emissions result in climate change and ocean acidification. Enhanced weathering or artificial ocean alkalinization (AOA) has been proposed as a geoengineering method to mitigate further ... [more ▼]

Fossil fuel CO2 emissions result in climate change and ocean acidification. Enhanced weathering or artificial ocean alkalinization (AOA) has been proposed as a geoengineering method to mitigate further increase of atmospheric CO2 and decrease of ocean pH. A variant of AOA involves reacting carbonates and adding the dissolved materials into the upper ocean. The net effect of this approach is to increase ocean alkalinity, thereby increasing the oceanic capacity to store fossil fuel CO2. Another effect of adding alkalinity would be to drive seawater to higher pH values and thus counteract the ongoing ocean acidification. We test implications of AOA for marine carbon cycle using the global ocean biogeochemical model HAMOCC. In our model scenarios we add alkalinity in the amounts proportional to fossil fuel emissions. We show that large-scale AOA scenarios in which large amounts of alkalinity are added would be necessary to avoid a significant increase in atmospheric CO2 and to hold the global seawater pH close to today’s value. Even a short-term AOA would have long-lasting effects on seawater chemistry. When AOA stops, atmospheric CO2 (and pH) reverts back to rising (decreasing) at the rate determined by the fossil fuel CO2 emissions growth, but the effect of AOA is permanent. Hence, in contrast to SRM, effects of AOA on seawater chemistry and atmospheric CO2 retain after stopping alkalinity addition; AOA would not involve a long-term commitment. [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 detailLong-term biogeochemical impacts of liming the ocean
Ilyina, Tatiana; Wolf-Gladrow, Dieter; Munhoven, Guy ULg et al

Conference (2011, December 08)

Fossil fuel CO2 emissions result in large-scale long-term perturbations in seawater chemistry. Oceans take up atmospheric CO2, and several geo-engineering approaches have been suggested to mitigate ... [more ▼]

Fossil fuel CO2 emissions result in large-scale long-term perturbations in seawater chemistry. Oceans take up atmospheric CO2, and several geo-engineering approaches have been suggested to mitigate impacts of CO2 emissions and resulting ocean acidification that are based on this property. One of them is to enhance weathering processes to remove atmospheric CO2. This method involves dissolving rocks (i.e. limestone) or adding strong bases (i.e. calcium hydroxide) in the upper ocean and is termed as liming the oceans. The net effect of this approach is to increase ocean alkalinity, thereby increasing the oceanic capacity to store anthropogenic CO2. Another effect of adding alkalinity would be to drive seawater to higher pH values and thus counteract the ongoing ocean acidification. However, whereas adding bases only alter alkalinity of seawater, dissolution of carbonates perturb both, alkalinity and dissolved inorganic carbon budgets. Thus, on longer time scales, these two methods will likely have different biogeochemical effects in the ocean. Here we test enduring implications of the two approaches for marine carbon cycle using the global ocean biogeochemical model HAMOCC. In our model scenarios we add alkalinity in the amounts proportional to fossil fuel emissions. We compare the longterm effectiveness of the two geo-engineering approaches to decrease atmospheric CO2. [less ▲]

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See detailInteractive comment on “LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model” by R. E. Zeebe
Munhoven, Guy ULg

in Geoscientific Model Development Discussions [=GMDD] (2011), 4

The paper "LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model” by R. E. Zeebe is reviewed.

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See detailClimate-carbon cycle feedback during glacial cycles
Ganopolski, A; Brovkin, V; Calov, R et al

Conference (2011, August 15)

Paleoclimate records reveal a close link between global ice volume and atmospheric CO2 concentration, at least, through the last 800,000 years. Despite many efforts over the last two decades, mechanisms ... [more ▼]

Paleoclimate records reveal a close link between global ice volume and atmospheric CO2 concentration, at least, through the last 800,000 years. Despite many efforts over the last two decades, mechanisms of glacial-interglacial CO2 variability and its role for the glacial cycles remain elusive. Here using the Earth system model of intermediate complexity CLIMBER-2 which includes all major components of the Earth system – atmosphere, ocean, land surface, ice sheets, terrestrial biota, eolian dust and marine biogeochemistry – we performed simulations of the last glacial cycles employing variations in the Earth’s orbital parameters as the only prescribed climatic forcing. In the experiments with constant CO2 concentration, temporal dynamics of the simulated glacial cycles strongly depend on the CO2 level. For CO2 concentrations about and above preindustrial one, the model simulates only short glacial cycles with precessional and obliquity frequencies. However, for lower CO2 concentrations the model simulates long glacial cycles with dominant 100 kyr periodicity. Simulated glacial cycles agreed favorably with paleoclimate reconstructions, but their amplitude is underestimated compared to those of the simulations with time-dependent CO2 concentration. These results confirm that the positive climate-carbon cycle feedback plays an important role in amplification of long glacial cycles. Experiments with fully interactive CO2 shed some light on the mechanism of climate-carbon cycle feedback during glacial cycles. Forced by orbital variations only, the model is able to reproduce the main features of CO2 changes: the 40 ppmv CO2 drop during glacial inception, the minimum concentration at the last glacial maximum being 80 ppmv lower than the Holocene value, and the relatively abrupt CO2 rise during the deglaciation. 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 glacial inception and deglaciation, while changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycles, respectively. [less ▲]

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