Processes of the Long-Term Carbon Cycle: Chemical Weathering of Silicates

2004 ◽  
Author(s):  
Robert A. Berner
Keyword(s):  
Carbon Cycle ◽  
Time Scales ◽  
Chemical Weathering ◽  
Continental Drift ◽  
Atmospheric Co2 ◽  
Silicate Weathering ◽  
Geological Time ◽  
Orogenic Uplift ◽  
Steep Slopes ◽  
Primary Minerals

Carbon dioxide is removed from the atmosphere during the weathering of both silicates and carbonates, but, over multimillion year time scales, as pointed out in chapter 1, only Ca and Mg silicate weathering has a direct effect on CO2. Carbon is transferred from CO2 to dissolved HCO3– and then to Ca and Mg carbonate minerals that are buried in sediments (reaction 1.4). In this chapter the factors that affect the rate of silicate weathering and how they could have changed over Phanerozoic time are discussed. Following classical studies (e.g., Jenny, 1941), the factors discussed include relief, climate (rainfall and temperature), vegetation, and lithology. However, over geological time scales, additional factors come into consideration that are necessarily ignored in studying modern weathering. These include the evolution of the sun and continental drift. The aim of this book is to consider all factors, whether occurring at present or manifested only over very long times, that affect weathering as it relates to the Phanerozoic carbon cycle. Within the past decade much attention has been paid to the effect of mountain uplift on chemical weathering and its effect on the uptake of atmospheric CO2, an idea originally espoused by T.C. Chamberlin (1899). The uplift of the Himalaya Mountains and resulting increased weathering has been cited as a principal cause of late Cenozoic cooling due to a drop in CO2 (Raymo, 1991). Orogenic uplift generally results in the development of high relief. High relief results in steep slopes and enhanced erosion, and enhanced erosion results in the constant uncovering of primary minerals and their exposure to the atmosphere. In the absence of steep slopes, a thick mantle of clay weathering product can accumulate and serve to protect the underlying primary minerals against further weathering. An excellent example of this situation is the thick clay-rich soils of the Amazon lowlands where little silicate weathering occurs (Stallard and Edmond, 1983). In addition, the development of mountain chains often leads to increased orographic rainfall and, at higher elevations, increased erosion by glaciers. All these factors should lead to more rapid silicate weathering and faster uptake of atmospheric CO2.

Time-scale dependence of climate-carbon cycle feedbacks for weak perturbations in CMIP5 models

2021 ◽  
Author(s):  
Guilherme Torres Mendonça ◽  
Julia Pongratz ◽  
Christian Reick
Keyword(s):  
Climate Change ◽  
Carbon Cycle ◽  
Time Scales ◽  
Radiative Forcing ◽  
Global Carbon Cycle ◽  
Atmospheric Co2 ◽  
Ice Age ◽  
Cmip5 Models ◽  
Global Carbon ◽  
Different Time Scales

<p>The increase in atmospheric CO2 driven by anthropogenic emissions is the main radiative forcing causing climate change. But this increase is not only a result from emissions, but also from changes in the global carbon cycle. These changes arise from feedbacks between climate and the carbon cycle that drive CO2 into or out of the atmosphere in addition to the emissions, thereby either accelerating or buffering climate change. Therefore, understanding the contribution of these feedbacks to the global response of the carbon cycle is crucial in advancing climate research. Currently, this contribution is quantified by the α-β-γ framework (Friedlingstein et al., 2003). But this quantification is only valid for a particular perturbation scenario and time period. In contrast, a recently proposed generalization (Rubino et al., 2016) of this framework for weak perturbations quantifies this contribution for all scenarios and at different time scales. </p><p>Thereby, this generalization provides a systematic framework to investigate the response of the global carbon cycle in terms of the climate-carbon cycle feedbacks. In the present work we employ this framework to study these feedbacks and the airborne fraction in different CMIP5 models. We demonstrate (1) that this generalization of the α-β-γ framework consistently describes the linear dynamics of the carbon cycle in the MPI-ESM; and (2) how by this framework the climate-carbon cycle feedbacks and airborne fraction are quantified at different time scales in CMIP5 models. Our analysis shows that, independently of the perturbation scenario, (1) the net climate-carbon cycle feedback is negative at all time scales; (2) the airborne fraction generally decreases for increasing time scales; and (3) the land biogeochemical feedback dominates the model spread in the airborne fraction at all time scales. This last result therefore emphasizes the need to improve our understanding of this particular feedback.</p><p><strong>References:</strong></p><p>P. Friedlingstein, J.-L. Dufresne, P. Cox, and P. Rayner. How positive is the feedback between climate change and the carbon cycle? Tellus B, 55(2):692–700, 2003.</p><p>M. Rubino, D. Etheridge, C. Trudinger, C. Allison, P. Rayner, I. Enting, R. Mulvaney, L. Steele, R. Langenfelds, W. Sturges, et al. Low atmospheric CO2 levels during the Little Ice Age due to cooling-induced terrestrial uptake. Nature Geoscience, 9(9):691–694, 2016.</p>

scholarly journals Sensitivity of atmospheric CO<sub>2</sub> and climate to explosive volcanic eruptions

2011 ◽  
Vol 8 (8) ◽  
pp. 2317-2339 ◽  
Author(s):  
T. L. Frölicher ◽  
F. Joos ◽  
C. C. Raible
Keyword(s):  
Global Warming ◽  
Carbon Cycle ◽  
Surface Temperature ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Time Scales ◽  
Volcanic Eruptions ◽  
Stratospheric Aerosol ◽  
Atmospheric Co2 ◽  
Explosive Volcanic Eruptions

Abstract. Impacts of low-latitude, explosive volcanic eruptions on climate and the carbon cycle are quantified by forcing a comprehensive, fully coupled carbon cycle-climate model with pulse-like stratospheric aerosol optical depth changes. The model represents the radiative and dynamical response of the climate system to volcanic eruptions and simulates a decrease of global and regional atmospheric surface temperature, regionally distinct changes in precipitation, a positive phase of the North Atlantic Oscillation, and a decrease in atmospheric CO2 after volcanic eruptions. The volcanic-induced cooling reduces overturning rates in tropical soils, which dominates over reduced litter input due to soil moisture decrease, resulting in higher land carbon inventories for several decades. The perturbation in the ocean carbon inventory changes sign from an initial weak carbon sink to a carbon source. Positive carbon and negative temperature anomalies in subsurface waters last up to several decades. The multi-decadal decrease in atmospheric CO2 yields a small additional radiative forcing that amplifies the cooling and perturbs the Earth System on longer time scales than the atmospheric residence time of volcanic aerosols. In addition, century-scale global warming simulations with and without volcanic eruptions over the historical period show that the ocean integrates volcanic radiative cooling and responds for different physical and biogeochemical parameters such as steric sea level or dissolved oxygen. Results from a suite of sensitivity simulations with different magnitudes of stratospheric aerosol optical depth changes and from global warming simulations show that the carbon cycle-climate sensitivity γ, expressed as change in atmospheric CO2 per unit change in global mean surface temperature, depends on the magnitude and temporal evolution of the perturbation, and time scale of interest. On decadal time scales, modeled γ is several times larger for a Pinatubo-like eruption than for the industrial period and for a high emission, 21st century scenario.

scholarly journals Sensitivity of atmospheric CO<sub>2</sub> and climate to explosive volcanic eruptions

2011 ◽  
Vol 8 (2) ◽  
pp. 2957-3007 ◽  
Author(s):  
T. L. Frölicher ◽  
F. Joos ◽  
C. C. Raible
Keyword(s):  
Global Warming ◽  
Carbon Cycle ◽  
Surface Temperature ◽  
Time Scales ◽  
Radiative Forcing ◽  
Volcanic Eruptions ◽  
Atmospheric Co2 ◽  
Dynamical Response ◽  
Steric Sea Level ◽  
Explosive Volcanic Eruptions

Abstract. Impacts of low-latitude, explosive volcanic eruptions on climate and the carbon cycle are quantified by forcing a comprehensive, fully coupled carbon cycle-climate model with pulse-like stratospheric sulfur release. The model represents the radiative and dynamical response of the climate system to volcanic eruptions and simulates a decrease of global and regional atmospheric surface temperature, regionally distinct changes in precipitation, a positive phase of the North Atlantic Oscillation, and a decrease in atmospheric CO2 after volcanic eruptions. The volcanic-induced cooling reduces overturning rates in tropical soils, which dominates over reduced litter input due to soil moisture decrease, resulting in higher land carbon inventories for several decades. The perturbation in the ocean carbon inventory changes sign from an initially weak carbon sink to a carbon source. Positive carbon and negative temperature anomalies in subsurface waters last up to several decades. The multi-decadal decrease in atmospheric CO2 yields an additional radiative forcing that amplifies the cooling and perturbs the Earth System on much longer time scales than the atmospheric residence time of volcanic aerosols. In addition, century-scale global warming simulations with and without volcanic eruptions over the historical period show that the ocean integrates volcanic radiative cooling and responds for different physical and biogeochemical parameters such as steric sea level or dissolved oxygen. Results from a suite of sensitivity simulations with different amounts of sulfur released and from global warming simulations show that the carbon cycle-climate sensitivity γ, expressed as change in atmospheric CO2 per unit change in global mean surface temperature, depends on the perturbation. On decadal time scales, modeled γ is several times larger for a Pinatubo-like eruption than for the industrial period and for a high emission, 21st century scenario.

scholarly journals Preindustrial-Control and Twentieth-Century Carbon Cycle Experiments with the Earth System Model CESM1(BGC)

2014 ◽  
Vol 27 (24) ◽  
pp. 8981-9005 ◽  
Author(s):  
Keith Lindsay ◽  
Gordon B. Bonan ◽  
Scott C. Doney ◽  
Forrest M. Hoffman ◽  
David M. Lawrence ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Carbon Cycle ◽  
Time Scales ◽  
Seasonal Cycle ◽  
Earth System Model ◽  
Surface Fluxes ◽  
Atmospheric Co2 ◽  
System Model ◽  
Biogeochemical Model ◽  
Earth System

Abstract Version 1 of the Community Earth System Model, in the configuration where its full carbon cycle is enabled, is introduced and documented. In this configuration, the terrestrial biogeochemical model, which includes carbon–nitrogen dynamics and is present in earlier model versions, is coupled to an ocean biogeochemical model and atmospheric CO2 tracers. The authors provide a description of the model, detail how preindustrial-control and twentieth-century experiments were initialized and forced, and examine the behavior of the carbon cycle in those experiments. They examine how sea- and land-to-air CO2 fluxes contribute to the increase of atmospheric CO2 in the twentieth century, analyze how atmospheric CO2 and its surface fluxes vary on interannual time scales, including how they respond to ENSO, and describe the seasonal cycle of atmospheric CO2 and its surface fluxes. While the model broadly reproduces observed aspects of the carbon cycle, there are several notable biases, including having too large of an increase in atmospheric CO2 over the twentieth century and too small of a seasonal cycle of atmospheric CO2 in the Northern Hemisphere. The biases are related to a weak response of the carbon cycle to climatic variations on interannual and seasonal time scales and to twentieth-century anthropogenic forcings, including rising CO2, land-use change, and atmospheric deposition of nitrogen.

scholarly journals Millennial-scale atmospheric CO<sub>2</sub> variations during the Marine Isotope Stage 6 period (190–135 kyr BP)

2019 ◽  
Author(s):  
Jinhwa Shin ◽  
Christoph Nehrbass-Ahles ◽  
Roberto Grilli ◽  
Jai Chowdhry Beeman ◽  
Frédéric Parrenin ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Time Scales ◽  
Ice Core ◽  
Major Change ◽  
Meridional Overturning Circulation ◽  
Marine Isotope Stage ◽  
Atmospheric Co2 ◽  
Climate Variations ◽  
The North ◽  
Glacial Periods

Abstract. Understanding natural carbon cycle/climate feedbacks on various time scales is highly relevant to reliably predict future climate changes. During the last two glacial periods, climate variations on millennial time scales were observed but the background conditions and duration of climate variations are different. Here we make use of contrasting climatic boundary conditions during the last two glacial periods to gain insight into the co-occurring carbon cycle changes. We reconstruct a new high-resolution record of atmospheric CO2 from the EPICA Dome C (EDC) ice core during Marine Isotope Stage (MIS) 6 (190 to 135 kyr BP). During long stadials in the North Atlantic (NA) region, atmospheric CO2 appears to be associated with the coeval Antarctic temperature changes at millennial time scale connected to the bipolar seesaw process. However, during one short stadial in the NA, atmospheric CO2 variation is negligible and the relationship between temperature variation in EDC and atmospheric CO2 is unclear. We suggest that the amplitude of CO2 variation may be affected by the duration of perturbations of the Atlantic Meridional Overturning Circulation (AMOC). In addition, similar to the last glacial period, in the earliest MIS 6 (MIS 6e and 6d, corresponding to 189 to 169 kyr BP), Carbon Dioxide Maxima (CDM) show different lags with respect to the corresponding abrupt CH4 jumps, the latter reflecting rapid warming in the Northern Hemisphere (NH). During MIS 6e at around 181.5 ± 0.3 kyr BP, CDM 6e.2 lags abrupt warming in the NH by only 200 ± 360 yrs. During MIS 6d which corresponds to CDM 6d.1 (171.1 ±0.2 kyr BP) and CDM 6d.2 (175.4 ± 0.4 kyr BP), the lag is much longer, i.e., 1,400 ± 375 yrs on average. The timing of CO2 variations with respect to abrupt warming in the NH may be affected by a major change in the organization of the AMOC from MIS 6e to MIS 6d.

Mechanisms controlling the chemical weathering flux and CO2 consumption rate of Cauvery river, South India: Role of secondary soil minerals (in weathered profiles) versus primary minerals and anthropogenic sources

2020 ◽  
Author(s):  
Badimela Upendra ◽  
Ciba Manohar ◽  
Aiswarya Aji ◽  
Vinu Dev Vasudevan ◽  
Anoop Krishnan Krishnan
Keyword(s):  
Chemical Weathering ◽  
Anthropogenic Activities ◽  
Anthropogenic Sources ◽  
Silicate Weathering ◽  
Soil Minerals ◽  
Atmospheric Input ◽  
Cauvery River ◽  
Co2 Consumption ◽  
Consumption Rates ◽  
Primary Minerals

&lt;p&gt;Abstract&lt;br&gt;Hydrochemical assessment have been carried out for a tropical, east flowing Western Ghats river Cauvery, southern India, to understand the dissolved load sources, acquisition processes and their controlling factors. Silicate weathering rates (SWR) and associated CO2 consumption rates (CCR) are estimated along with quantification of source wise solute load contribution towards total solute load of the Cauvery River Basin (CRB). Atmospheric input, anthropogenic activities and water-mineral interaction processes are identified as the major solute sources. Using the chemical mass balance forward model, source wise solute load contributions are estimated to be 13%, 32%, 47% and 8% from atmospheric input, anthropogenic activities, silicates and carbonates weathering respectively. It&amp;#8217;s found that, chemical weathering followed by anthropogenic activities are the controlling factors for the solute load of CRB with minor influence of atmospheric input. Weathering index calculated for CRB (Re &gt; 3), suggest incomplete weathering of drainage rocks resulting in formation of secondary soil minerals along the river course. Further, detailed analysis of chemical weathering mechanisms is accomplished via end-member mixing analysis approach (EMMA) by using Ca/Na and Mg/Na ratios of different end-members including primary minerals form country rocks and secondary soil (weathered profile) minerals. End-member mixing diagram referred as modified Na-normalized Ca versus Mg, reveal that chemical weathering of secondary soil minerals is as significant as primary minerals and source wise solute load contribution to the river is almost equal from both sources primary and secondary. At outlet of the basin (Musiri), SWR and associated CCR values are estimated to be 12.9 t.km-2.y-1 and 3.3 &amp;#215; 105 mole.km-2.y-1 respectively. Results indicate that average SWR values estimated for the east flowing Cauvery river are several times (~ 4) lower than the average SWR values of west flowing Western Ghats rivers, even though the associated CO2 consummation rates are comparable for both river systems.&lt;br&gt;Keywords: Cauvery river, solute acquisition mechanisms, chemical weathering, anthropogenic sources, primary minerals, secondary soil minerals, silicate weathering, CO2 consumption rates.&lt;/p&gt;

Carbonation possibilities of Steel slags -- a review

2021 ◽  
Author(s):  
Raghavendra Ragipani ◽  
Sankar Bhattacharya ◽  
Akkihebbal K. Suresh
Keyword(s):  
Carbon Dioxide ◽  
Time Scales ◽  
Carbon Dioxide Sequestration ◽  
Mineral Carbonation ◽  
Geological Time ◽  
The Stability ◽  
Significant Attention

Research pertaining to carbon dioxide sequestration via mineral carbonation has gained significant attention, primarily due to the stability of sequestered \ce{CO2} over geological time scales. Use of industry-derived alkaline wastes...

Revising key parameters for long-term carbon cycle models

2021 ◽  
Author(s):  
Chloé M. Marcilly ◽  
Trond H. Torsvik ◽  
Mathew Domeier ◽  
Dana L. Royer
Keyword(s):  
Sea Level ◽  
Age Distribution ◽  
Silicate Weathering ◽  
Geological Time ◽  
Sea Levels ◽  
Climate Fluctuations ◽  
Climate Gradients ◽  
Sea Level Fluctuations ◽  
Temperature And Precipitation

&lt;p&gt;CO&lt;sub&gt;2&lt;/sub&gt; is the most important greenhouse gas in the Earth&amp;#8217;s atmosphere and has fluctuated considerably over geological time. However, proxies for past CO&lt;sub&gt;2 &lt;/sub&gt;concentrations have large uncertainties and are mostly limited to Devonian and younger times. Consequently, CO&lt;sub&gt;2&lt;/sub&gt; modelling plays a key role in reconstructing past climate fluctuations. Facing the limitations with the current CO&lt;sub&gt;2&lt;/sub&gt; models, we aim to refine two important forcings for CO&lt;sub&gt;2&lt;/sub&gt; levels over the Phanerozoic, namely carbon degassing and silicate weathering.&lt;/p&gt;&lt;p&gt;Silicate weathering and carbonate deposition is widely recognized as a primary sink of carbon on geological timescales and is largely influenced by changes in climate, which in turn is linked to changes in paleogeography. The role of paleogeography on silicate weathering fluxes has been the focus of several studies in recent years. Their aims were mostly to constrain climatic parameters such as temperature and precipitation affecting weathering rates through time. However, constraining the availability of exposed land is crucial in assessing the theoretical amount of weathering on geological time scales. Associated with changes in climatic zones, the fluctuation of sea-level is critical for defining the amount of land exposed to weathering. The current reconstructions used in&lt;sub&gt;&lt;/sub&gt;models tend to overestimate the amount of exposed land to weathering at periods with high sea levels. Through the construction of continental flooding maps, we constrain the effective land area undergoing silicate weathering for the past 520 million years. Our maps not only reflect sea-level fluctuations but also contain climate-sensitive indicators such as coal (since the Early Devonian) and evaporites to evaluate climate gradients and potential weatherablity through time. This is particularly important after the Pangea supercontinent formed but also for some time after its break-up.&lt;/p&gt;&lt;p&gt;Whilst silicate weathering is an important CO&lt;sub&gt;2&lt;/sub&gt; sink, volcanic carbon degassing is a major source but one of the least constrained climate forcing parameters. There is no clear consensus on the history of degassing through geological time as there are no direct proxies for reconstructing carbon degassing, but various proxy methods have been postulated. We propose new estimates of plate tectonic degassing for the Phanerozoic using both subduction flux from full-plate models and zircon age distribution from arcs (arc-activity) as proxies.&lt;/p&gt;&lt;p&gt;The effect of revised modelling parameters for weathering and degassing was tested in the well-known long-term models GEOCARBSULF and COPSE. They revealed the high influence of degassing on CO&lt;sub&gt;2&lt;/sub&gt; levels using those models, highlighting the need for enhanced research in this direction. The use of arc-activity as a proxy for carbon degassing leads to interesting responses in the Mesozoic and brings model estimates closer to CO&lt;sub&gt;2 &lt;/sub&gt;&amp;#160;proxy values. However, from simulations using simultaneously the revised input parameters (i.e weathering and degassing) large model-proxy discrepancies remain and notably for the Triassic and Jurassic.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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