scholarly journals Simulation of climate, ice sheets and CO<sub>2</sub> evolution during the last four glacial cycles with an Earth system model of intermediate complexity

2017 ◽  
Vol 13 (12) ◽  
pp. 1695-1716 ◽  
Author(s):  
Andrey Ganopolski ◽  
Victor Brovkin
Keyword(s):  
Carbon Cycle ◽  
Ice Sheets ◽  
Co2 Concentration ◽  
System Model ◽  
Model Parameters ◽  
Orbital Forcing ◽  
Earth System ◽  
Glacial Cycles ◽  
The Past ◽  
Paleoclimate Reconstructions

Abstract. In spite of significant progress in paleoclimate reconstructions and modelling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial–interglacial cycles are still not fully understood – in particular, in relation to CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of the co-evolution of climate, ice sheets, and carbon cycle over the last 400 000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume, and other climate system characteristics in good agreement with paleoclimate reconstructions. These results provide strong support for the idea that long and strongly asymmetric glacial cycles of the late Quaternary represent a direct but strongly nonlinear response of the Northern Hemisphere ice sheets to orbital forcing. This response is strongly amplified and globalised by the carbon cycle feedbacks. Using simulations performed with the model in different configurations, we also analyse the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during the interglacial or even declines towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during the interglacial, similar to the Holocene. We also discuss the potential contribution of the brine rejection mechanism for the CO2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.

scholarly journals Simulation of climate, ice sheets and CO<sub>2</sub> evolution during the last four glacial cycles with an Earth system model of intermediate complexity

2017 ◽  
Author(s):  
Andrei Ganopolski ◽  
Victor Brovkin
Keyword(s):  
Ice Sheets ◽  
Co2 Concentration ◽  
Earth System Model ◽  
System Model ◽  
Model Parameters ◽  
Earth System ◽  
Glacial Cycles ◽  
The Past ◽  
Intermediate Complexity ◽  
Paleoclimate Reconstructions

Abstract. In spite of significant progress in paleoclimate reconstructions and modeling of different aspects of the past glacial cycles, the mechanisms which transform regional and seasonal variations in solar insolation into long-term and global-scale glacial-interglacial cycles are still not fully understood, in particular, for CO2 variability. Here using the Earth system model of intermediate complexity CLIMBER-2 we performed simulations of co-evolution of climate, ice sheets and carbon cycle over the last 400,000 years using the orbital forcing as the only external forcing. The model simulates temporal dynamics of CO2, global ice volume and other climate system characteristics in good agreement with paleoclimate reconstructions. Using simulations performed with the model in different configurations, we also analyze the role of individual processes and sensitivity to the choice of model parameters. While many features of simulated glacial cycles are rather robust, some details of CO2 evolution, especially during glacial terminations, are rather sensitive to the choice of model parameters. Specifically, we found two major regimes of CO2 changes during terminations: in the first one, when the recovery of the Atlantic meridional overturning circulation (AMOC) occurs only at the end of the termination, a pronounced overshoot in CO2 concentration occurs at the beginning of the interglacial and CO2 remains almost constant during interglacial or even decline towards the end, resembling Eemian CO2 dynamics. However, if the recovery of the AMOC occurs in the middle of the glacial termination, CO2 concentration continues to rise during interglacial, similar to Holocene. We also discuss potential contribution of the brine rejection mechanism for the CO2 and carbon isotopes in the atmosphere and the ocean during the past glacial termination.

scholarly journals Mid-Pleistocene transition in glacial cycles explained by declining CO2and regolith removal

2019 ◽  
Vol 5 (4) ◽  
pp. eaav7337 ◽  
Author(s):  
M. Willeit ◽  
A. Ganopolski ◽  
R. Calov ◽  
V. Brovkin
Keyword(s):  
Climate Variability ◽  
Carbon Cycle ◽  
Northern Hemisphere ◽  
Seasonal Variations ◽  
Ice Sheets ◽  
Glacial Cycles ◽  
Solar Insolation ◽  
The Past ◽  
Transient Simulations

Variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.

Weak Equatorial Superrotation During the Past 250 Million years

2021 ◽  
Author(s):  
Jiawenjing Lan ◽  
Jun Yang ◽  
Yongyun Hu
Keyword(s):  
Climatic Factors ◽  
Co2 Concentration ◽  
System Model ◽  
Latent Heating ◽  
Earth System ◽  
Solar Constant ◽  
Upper Troposphere ◽  
The Past ◽  
Hadley Cells ◽  
The Waves

&lt;p&gt;For modern Earth, the annual-mean equatorial atmosphere is flowing from east to west or called easterly winds. This is mainly due to the deceleration effect of the seasonal cross-equatorial flows of the Hadley cells, against the acceleration effect of equatorial Rossby and Kelvin waves excited from tropical convection and latent heating release. In this work, we examine the evolution of equatorial winds during the past 250 million years (Ma) using the global Earth system model CESM1.2.2. Three climatic factors different from the modern Earth, solar constant, atmospheric CO2 concentration, and land-sea configuration, are considered in the simulations. We find that the equatorial winds in the upper troposphere change the sign to westerly flows or called atmospheric superrotation in certain eras. The strength of the superrotation is comparable to the magnitude of the present easterly winds, several meters per second, not strong. This phenomenon occurs when the waves are relatively stronger and/or the Hadley cells are relatively weaker, which in turn are due to the changes in the three factors.&lt;/p&gt;

scholarly journals A model-based constraint of CO<sub>2</sub> fertilisation

2012 ◽  
Vol 9 (7) ◽  
pp. 9425-9451 ◽  
Author(s):  
P. B. Holden ◽  
N. R. Edwards ◽  
D. Gerten ◽  
S. Schaphoff
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Co2 Concentration ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Model Parameters ◽  
Earth System ◽  
Atmospheric Co2 Concentration ◽  
Post Industrial

Abstract. We derive a constraint on the strength of CO2 fertilisation of the terrestrial biosphere through a "top-down" approach, calibrating Earth System Model parameters constrained only by the post-industrial increase of atmospheric CO2 concentration. We derive a probabilistic prediction for the globally averaged strength of CO2 fertilisation in nature, implicitly net of other limiting factors such as nutrient availability. The approach yields an estimate that is independent of CO2 enrichment experiments and so provides a new constraint that can in principal be combined with data-driven priors. To achieve this, an essential requirement was the incorporation of a Land Use Change (LUC) scheme into the GENIE earth system model, which we describe in full. Using output from a 671-member ensemble of transient GENIE simulations we build an emulator of the change in atmospheric CO2 concentration change over the preindustrial period (1850 to 2000). We use this emulator to sample the 28-dimensional input parameter space. A Bayesian calibration of the emulator output suggests that the increase in Gross Primary Productivity in response of a doubling of CO2 from preindustrial values is likely to lie in the range 11 to 53%, with a most likely value of 28%. The present-day land-atmosphere flux (1990–2000) is estimated at −0.6 GTC yr−1 (likely in the range 0.9 to −2.0 GTC yr−1). The present-day land-ocean flux (1990–2000) is estimated at −2.2 GTC yr−1 (likely in the range −1.6 to −2.8 GTC yr−1). We estimate cumulative net land emissions over the post-industrial period (land use change emissions net of the CO2 fertilisation sink) to be 37 GTC, likely to lie in the range 130 to −20 GTC.

scholarly journals Description of the Earth system model of intermediate complexity LOVECLIM version 1.2

2010 ◽  
Vol 3 (2) ◽  
pp. 603-633 ◽  
Author(s):  
H. Goosse ◽  
V. Brovkin ◽  
T. Fichefet ◽  
R. Haarsma ◽  
P. Huybrechts ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Sea Ice ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Intermediate Complexity ◽  
Low Latitudes

Abstract. The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVECLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation), the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasi-geostrophic model. The ocean component is CLIO3, which consists of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is of 3° by 3°, and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetation model that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as desert. VECODE also simulates the evolution of the carbon cycle over land while the ocean carbon cycle is represented by LOCH, a comprehensive model that takes into account both the solubility and biological pumps. The ice sheet component AGISM is made up 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. For both the Greenland and Antarctic ice sheets, calculations are made on a 10 km by 10 km resolution grid with 31 sigma levels. LOVECLIM1.2 reproduces well the major characteristics of the observed climate both for present-day conditions and for key past periods such as the last millennium, the mid-Holocene and the Last Glacial Maximum. However, despite some improvements compared to earlier versions, some biases are still present in the model. The most serious ones are mainly located at low latitudes with an overestimation of the temperature there, a too symmetric distribution of precipitation between the two hemispheres, and an overestimation of precipitation and vegetation cover in the subtropics. In addition, the atmospheric circulation is too weak. The model also tends to underestimate the surface temperature changes (mainly at low latitudes) and to overestimate the ocean heat uptake observed over the last decades.

scholarly journals Earth system model simulations show different carbon cycle feedback strengths under glacial and interglacial conditions

2017 ◽  
Author(s):  
Markus Adloff ◽  
Christian H. Reick ◽  
Martin Claussen
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
Co2 Concentration ◽  
System Model ◽  
Earth System ◽  
Concentration Increase ◽  
Terrestrial Carbon ◽  
Model Simulations ◽  
Fertilization Effect ◽  
Simulation Time

Abstract. In Earth system model simulations we find different carbon cycle sensitivities for recent and glacial climate. This result is obtained by comparing the transient response of the terrestrial carbon cycle to a fast and strong atmospheric CO2 concentration increase (roughly 1000ppm) in C4MIP type simulations starting from climate conditions of the Last Glacial Maximum (LGM) and from Pre-Industrial times (PI). The sensitivity β to CO2 fertilization is larger in the LGM experiment during most of the simulation time: The fertilization effect leads to a terrestrial carbon gain in the LGM experiment almost twice as large as in the PI experiment. The larger fertilization effect in the LGM experiment is caused by the stronger initial CO2 limitation of photosynthesis, implying a stronger potential for its release upon CO2 concentration increase. In contrast, the sensitivity γ to climate change induced by the radiation effect of rising CO2 is larger in the PI experiment for most of the simulation time. Yet, climate change is less pronounced in the PI experiment, resulting in only slightly higher terrestrial carbon losses than in the LGM experiment. The stronger climate sensitivity in the PI experiment results from the vastly more extratropical soil carbon under those interglacial conditions whose respiration is enhanced under climate change. Comparing the radiation and fertilization effect in a factor analysis, we find that they are almost additive, i.e. their synergy is small in the global sum of carbon changes. From this additivity, we find that the carbon cycle feedback strength is more negative in the LGM than in the PI simulations.

scholarly journals A model-based constraint on CO<sub>2</sub> fertilisation

2013 ◽  
Vol 10 (1) ◽  
pp. 339-355 ◽  
Author(s):  
P. B. Holden ◽  
N. R. Edwards ◽  
D. Gerten ◽  
S. Schaphoff
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Co2 Concentration ◽  
Earth System Model ◽  
Atmospheric Co2 ◽  
System Model ◽  
Model Parameters ◽  
Earth System ◽  
Atmospheric Co2 Concentration ◽  
Post Industrial

Abstract. We derive a constraint on the strength of CO2 fertilisation of the terrestrial biosphere through a "top-down" approach, calibrating Earth system model parameters constrained by the post-industrial increase of atmospheric CO2 concentration. We derive a probabilistic prediction for the globally averaged strength of CO2 fertilisation in nature, for the period 1850 to 2000 AD, implicitly net of other limiting factors such as nutrient availability. The approach yields an estimate that is independent of CO2 enrichment experiments. To achieve this, an essential requirement was the incorporation of a land use change (LUC) scheme into the GENIE Earth system model. Using output from a 671-member ensemble of transient GENIE simulations, we build an emulator of the change in atmospheric CO2 concentration change since the preindustrial period. We use this emulator to sample the 28-dimensional input parameter space. A Bayesian calibration of the emulator output suggests that the increase in gross primary productivity (GPP) in response to a doubling of CO2 from preindustrial values is very likely (90% confidence) to exceed 20%, with a most likely value of 40–60%. It is important to note that we do not represent all of the possible contributing mechanisms to the terrestrial sink. The missing processes are subsumed into our calibration of CO2 fertilisation, which therefore represents the combined effect of CO2 fertilisation and additional missing processes. If the missing processes are a net sink then our estimate represents an upper bound. We derive calibrated estimates of carbon fluxes that are consistent with existing estimates. The present-day land–atmosphere flux (1990–2000) is estimated at −0.7 GTC yr−1 (likely, 66% confidence, in the range 0.4 to −1.7 GTC yr−1). The present-day ocean–atmosphere flux (1990–2000) is estimated to be −2.3 GTC yr−1 (likely in the range −1.8 to −2.7 GTC yr−1). We estimate cumulative net land emissions over the post-industrial period (land use change emissions net of the CO2 fertilisation and climate sinks) to be 66 GTC, likely to lie in the range 0 to 128 GTC.

scholarly journals Description of the Earth system model of intermediate complexity LOVECLIM version 1.2

2010 ◽  
Vol 3 (1) ◽  
pp. 309-390 ◽  
Author(s):  
H. Goosse ◽  
V. Brovkin ◽  
T. Fichefet ◽  
R. Haarsma ◽  
P. Huybrechts ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Sea Ice ◽  
Three Dimensional ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Intermediate Complexity ◽  
Low Latitudes

Abstract. The main characteristics of the new version 1.2 of the three-dimensional Earth system model of intermediate complexity LOVECLIM are briefly described. LOVECLIM 1.2 includes representations of the atmosphere, the ocean and sea ice, the land surface (including vegetation), the ice sheets, the icebergs and the carbon cycle. The atmospheric component is ECBilt2, a T21, 3-level quasi-geostrophic model. The oceanic component is CLIO3, which is made up of an ocean general circulation model coupled to a comprehensive thermodynamic-dynamic sea-ice model. Its horizontal resolution is 3° by 3°, and there are 20 levels in the ocean. ECBilt-CLIO is coupled to VECODE, a vegetation model that simulates the dynamics of two main terrestrial plant functional types, trees and grasses, as well as desert. VECODE also simulates the evolution of the carbon cycle over land while the oceanic carbon cycle is represented in LOCH, a comprehensive model that takes into account both the solubility and biological pumps. The ice sheet component AGISM is made up 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. For both the Greenland and Antarctic ice sheets, calculations are made on a 10 km by 10 km resolution grid with 31 sigma levels. LOVECLIM 1.2 reproduces well the major characteristics of the observed climate both for present-day conditions and for key past periods such as the last millennium, the mid-Holocene and the Last Glacial Maximum. However, despite some improvements compared to earlier versions, some biases are still present in the model. The most serious ones are mainly located at low latitudes with an overestimation of the temperature there, a too symmetric distribution of precipitation between the two hemispheres, an overestimation of precipitation and vegetation cover in the subtropics. In addition, the atmospheric circulation is too weak. The model also tends to underestimate the surface temperature changes (mainly at low latitudes) and to overestimate the ocean heat uptake observed over the last decades.

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