References of "Brovkin, Victor"
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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 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 detailThe interglacial carbon cycle
Kleinen, Thomas; Brovkin, Victor; Munhoven, Guy ULiege et al

Poster (2011, April 07)

Explaining the difference in carbon cycle dynamics (and hence atmospheric CO2) between various interglacials is an elusive issue. Several biogeochemical mechanisms of different origin are involved in ... [more ▼]

Explaining the difference in carbon cycle dynamics (and hence atmospheric CO2) between various interglacials is an elusive issue. Several biogeochemical mechanisms of different origin are involved in interglacial CO2 dynamics, leading to a CO2 release from the ocean (carbonate compensation, coral growth) compensated by a land carbon uptake (biomass and soil carbon buildup, peat accumulation). The balance between these fluxes of CO2 is delicate and time-dependent, and it is not possible to provide firm constraints on these fluxes from proxy data. The best framework for quantification of all these mechanisms is an Earth System model that includes all necessary physical and biogeochemical components of the atmosphere, ocean, and land. To perform multi-millennial model integrations through the Holocene, Eemian, and MIS11, we use an earth system model of intermediate complexity, CLIMBER-2, coupled to the dynamic global vegetation model LPJ with a recently implemented module for boreal peatland dynamics. During glacial-interglacial cycles, the carbon cycle never is in complete equilibrium due to a number of small but persistent fluxes such as terrestrial weathering. This complicates setting up interglacial experiments as the usual approach to start model integrations from an equilibrium state is not valid any more. In order to circumvent the problem of non-equilibrium initial conditions, the model is initialised with the oceanic biogeochemistry state taken from a transient simulation through the last glacial cycle with CLIMBER-2 only. In this simulation, the CLIMBER-2 model was run through the last glacial cycle with carbon cycle in “offline mode” as interactive components of the physical climate system (atmosphere, ocean, ice sheets) were driven by concentration of greenhouse gases reconstructed from ice cores. Using these initial conditions, we performed coupled climate carbon cycle experiments for the Holocene, the Eemian and MIS11, driven by orbital forcing. Contrary to the results we published previously (Kleinen et al. 2010), peat accumulation was not prescribed, but rather determined dynamically, making this model setup applicable to previous interglacials as well. For the Holocene, our results resemble the carbon cycle dynamics as reconstructed from ice cores quite closely, both for atmospheric CO2 and delta13CO2. These experiments will be presented, analysing the role of different forcing mechanisms. The land surface appears to be an overall sink for CO2, due to carbon accumulation in the soil, as well as peat accumulation, and oceanic contributions due to temperature and circulation changes are quite small. Finally, results for MIS11 and the Eemian will be shown. [less ▲]

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See detailGlacial CO2 cycle as a succession of key physical and biogeochemical processes
Brovkin, Victor; Ganopolski, Andrey; Munhoven, Guy ULiege 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 detailSimulation of glacial-interglacial atmospheric CO2 variations using a comprehensive Earth system model of intermediate complexity
Brovkin, Victor; Ganopolski, Andrei; Calov, Reinhard et al

Conference (2010, May 04)

The mechanisms of strong glacial-interglacial variations in the atmospheric CO2 concentration and the role of CO2 in driving glacial cycles still remain debatable. Here using the model of intermediate ... [more ▼]

The mechanisms of strong glacial-interglacial variations in the atmospheric CO2 concentration and the role of CO2 in driving glacial cycles still remain debatable. Here using the model of intermediate complexity CLIMBER-2 which includes all major components of the Earth system – atmosphere, ocean, land surface, ice sheets, terrestrial biota and weathering, aeolian dust and marine biogeochemistry – we performed simulation of the last glacial cycle using variations in the Earth’s orbital parameters as the only prescribed climatic forcing. The model simulates rather realistically temporal and spatial dynamics of the Northern Hemisphere glaciation and temporal dynamics of the atmospheric CO2 concentration. During the glacial inception, the model is able to simulate a decrease in the atmospheric CO2, despite of release of terrestrial biosphere carbon. The drop in CO2 concentration during the first part of the glacial cycle is between 20 and 40 ppmv. It is related primarily to the physical mechanisms – increase of the ocean solubility and relative volume and the age of the Antarctic bottom water masses. The latter is related to increased sea ice formation in the Southern Ocean and lowering of the surface salinity in the northern North Atlantic. During the second part of the glacial cycle, the atmospheric CO2 concentration decreases towards the level of 200 ppmv. A part of this drop is due an increase of biological productivity in the Southern Ocean which is directly related in the CLIMBER-2 model to increase of aeolian dust supply into the Southern Hemisphere via the iron fertilization mechanism. Significant part of the decreasing CO2 trend is also explained by increased weathering on land, especially on the exposed tropical shelves. A decrease in shallow water carbonate sedimentation and shift of CaCO3 sedimentation towards the deep ocean also plays important role in CO2 decrease. With the onset of the glacial termination, initial rise in the atmospheric CO2 concentration is explained by a weakening of the Atlantic thermohaline circulation due to increased freshwater input into the northern North Atlantic. The model is able to simulate the return of CO2 concentration to its interglacial value after termination of the glacial cycle but simulated CO2 concentration still lags considerably behind the ice core reconstructions. [less ▲]

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See detailHolocene carbon cycle dynamics
Kleinen, Thomas; Brovkin, Victor; von Bloh, Werner et al

in Geophysical Research Letters (2010), 37

We are investigating the late Holocene rise in CO2 by performing four experiments with the climate-carbon-cycle model CLIMBER2-LPJ. Apart from the deep sea sediments, important carbon cycle processes ... [more ▼]

We are investigating the late Holocene rise in CO2 by performing four experiments with the climate-carbon-cycle model CLIMBER2-LPJ. Apart from the deep sea sediments, important carbon cycle processes considered are carbon uptake or release by the vegetation, carbon uptake by peatlands, and CO2 release due to shallow water sedimentation of CaCO3. Ice core data of atmospheric CO2 between 8 ka BP and preindustrial climate can only be reproduced if CO2 outgassing due to shallow water sedimentation of CaCO3 is considered. In this case the model displays an increase of nearly 20 ppmv CO2 between 8 ka BP and present day. Model configurations that do not contain this forcing show a slight decrease in atmospheric CO2. We can therefore explain the late Holocene rise in CO2 by invoking natural forcing factors only, and anthropogenic forcing is not required to understand preindustrial CO2 dynamics. [less ▲]

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See detailAtmospheric Lifetime of Fossil Fuel Carbon Dioxide
Archer, David; Eby, Michael; Brovkin, Victor et al

in Annual Review of Earth and Planetary Sciences (2009), 37

CO2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a ... [more ▼]

CO2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO3. Common measures of the atmospheric lifetime of CO2, including the e-folding time scale, disregard the long tail. Its neglect in the calculation of global warming potentials leads many to underestimate the longevity of anthropogenic global warming. Here, we review the past literature on the atmospheric lifetime of fossil fuel CO2 and its impact on climate, and we present initial results from a model intercomparison project on this topic. The models agree that 20–35% of the CO2 remains in the atmosphere after equilibration with the ocean (2–20 centuries). Neutralization by CaCO3 draws the airborne fraction down further on timescales of 3 to 7 kyr. [less ▲]

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See detailModeling the influence of the Greenland ice sheet melting on the Atlantic meridional overturning circulation during the next millennia
Fichefet, Thierry; Driesschaert, Emmanuelle; Goosse, Hugues et al

Conference (2007, April 19)

A three-dimensional Earth system model of intermediate complexity including a dynamic ice sheet component has been used to investigate the long-term evolution of the Greenland ice sheet and its effects on ... [more ▼]

A three-dimensional Earth system model of intermediate complexity including a dynamic ice sheet component has been used to investigate the long-term evolution of the Greenland ice sheet and its effects on the Atlantic meridional overturning circulation (AMOC) in response to a range of stabilized anthropogenic forcings. Our results suggest that the Greenland ice sheet volume should experience a significant decrease in the future. For a radiative forcing exceeding 7.5 W m-2, the modeled ice sheet melts away within 3000 years. A number of feedbacks operate during this deglaciation, implying a strong non-linear relationship between the radiative forcing and the melting rate. In the most extreme scenario considered, the freshwater flux from Greenland into the surrounding oceans is higher than 0.1 Sv during a few centuries. This is however insufficient to induce a shutdown of the AMOC in the model. [less ▲]

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See detailImpact of future Greenland deglaciation on global weathering fluxes and atmospheric CO2
Munhoven, Guy ULiege; Brovkin, Victor; Ganopolski, A. et al

Conference (2007)

About 1.76×10^6 km2 of Greenland are currently covered by ice. It is expected that this large ice mass will melt away over the next 3000 years if anthropogenic CO2 emissions continue to rise (Alley et al ... [more ▼]

About 1.76×10^6 km2 of Greenland are currently covered by ice. It is expected that this large ice mass will melt away over the next 3000 years if anthropogenic CO2 emissions continue to rise (Alley et al., 2006). As a result, the bedrock currently covered by ice will lie free and become subject to chemical weathering. The resulting weathering fluxes will contribute to increase both the consumption rate of atmospheric CO2 and the production rate of riverine bicarbonate. Increasing these two fluxes will tend to decrease the atmospheric CO2 partial pressure, as a result of the modified ocean-atmosphere carbon cycle. Chemical weathering may thus possibly act as a negative feedback in the Greenhouse World. Other changes (e.g., vegetation cover and additional climate change) concomitant with the melting of the Greenland ice-sheet may either amplify or dampen, if not reverse the weathering effect. Here we use the intermediate complexity Earth System model CLIMBER-2 to quantify and analyse the weathering flux changes that result from the projected melting of the Greenland ice sheet and the implications for atmospheric CO2. The biogeochemical module of CLIMBER-2 has been extended to account for the consumption of atmospheric CO2 and the production of riverine bicarbonate by continental weathering processes, as a function of geographically distributed runoff (interactively provided by the CLIMBER-2 climate module) and lithology (derived from Amiotte Suchet et al., 2003). We find that the increased weathering processes alone would lead to a sustained 0.2 ppm/kyr decrease in atmospheric pCO2. The climate change resulting from the deglaciation of Greenland reduces the magnitude of this trend to 0.1 ppm/kyr. Only in the case where the effect of freshly comminuted bedrock is taken into account (Clark et al., 2006) does the weathering feedback help to reduce atmospheric pCO2 by about 10 ppm in 5000 years. Alley R.B. et al. (2005) Science 310, 456–460. Amiotte Suchet P. et al. (2003) Global Biogeochemical Cycles 17, 1139, doi:10.1029/2002GB001891. Clark P.U. et al. (2006) Quaternary Science Reviews 25, 3150–3184. [less ▲]

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See detailImpact of a Greenland deglaciation on climate during the next millennia
Driesschaert, Emmanuelle; Brovkin, Victor; Fichefet, Thierry et al

Conference (2006, April 04)

A new Earth system model of intermediate complexity, LOVECLIM, has been developed in order to study long-term future climate changes. It includes an interactive Greenland and Antarctic ice sheet model ... [more ▼]

A new Earth system model of intermediate complexity, LOVECLIM, has been developed in order to study long-term future climate changes. It includes an interactive Greenland and Antarctic ice sheet model (AGISM) as well as an oceanic carbon cycle model (LOCH). Those climatic components can have a great impact on future climate. The few studies in recent literature assessing the impact of polar ice sheets on future climate draw very different conclusions, which shows the need for developing such a model. A set of numerical experiments have been performed in order to study the possible perturbations of climate induced by human activities over the next millennia. A particular attention is given to the Greenland ice sheet. In most of the projections, the Greenland ice sheet undergoes a continuous reduction in volume, leading to an almost total disappearance in the most pessimistic scenarios. The impact of the Greenland deglaciation on climate has therefore been assessed through a sensitivity experiment using the scenario SRES A2. The removal of the Greenland ice sheet is responsible for a regional amplification of the global warming inducing a total melt of Arctic sea ice in summer. The freshwater flux from Greenland generates large salinity anomalies in the North Atlantic Ocean that reduce the rate of North Atlantic Deep Water formation, slowing down slightly the oceanic thermohaline circulation. [less ▲]

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