Shallow-depth slab decarbonation prevents recharge of the deep carbon cycle

2020 ◽  
Author(s):  
Leonie Strobl ◽  
Andreas Beinlich ◽  
Markus Ohl ◽  
Oliver Plümper
Keyword(s):  
Carbon Cycle ◽  
Subduction Zone ◽  
Atmospheric Carbon Dioxide ◽  
Carbon Dioxide Concentration ◽  
Oceanic Lithosphere ◽  
Aqueous Fluid ◽  
Shallow Depth ◽  
Plate Motion ◽  
The Earth

<p>Long-term oscillations of the Earth’s atmospheric carbon dioxide concentration and climate are intrinsically linked to tectonic plate motion controlling CO<sub>2</sub> uptake in rocks, their transport into the Earth’s mantle and recycling back into the atmosphere by volcanic activity. In this long-term deep carbon cycle, the efficiency of mantle ingassing is controlled by the stability of carbon carrier phases at subduction zone pressure-temperature conditions, during deformation and their interaction with subduction zone dehydration fluids. However, the current understanding of carbonate stability under these conditions is controversial. This is reflected by studies predicting carbonate transport deep into the asthenospheric mantle [1, 2] in contrast to more recently postulated shallow-depth carbon release from subducting slabs [e.g. 3]. Some of this controversy is related to the lack of available field sites that allow for the quantification of subduction-related decarbonation and its driving force. Here we present novel observations on the release of carbon during subduction of previously carbonated, ultramafic, oceanic lithosphere. Our observations are based on a recently discovered, exceptionally well-exposed, outcrop in northern Norway [4] containing frozen-in decarbonation reaction textures at the km scale. Our observations and textural analyses indicate breakdown of magnesium carbonate and serpentine to secondary olivine at depths shallower than 20 km. Secondary olivine is present as up to fist-sized nodules pseudomorphically replacing magnesite and as veins delineating escape pathways for the carbon-bearing aqueous fluid. We present first field observations and reaction textures and will discuss implications for the efficiency of carbon transport into the Earth’s mantle by subduction of carbonate-bearing oceanic lithosphere.</p><p>[1] Kerrick, D.M. & Connolly, J.A.D. (1998). Geology <strong>26</strong>, 375-378.</p><p>[2] Dasgupta, R. & Hirschmann, M.M. (2010). EPSL <strong>298, </strong>1-13.</p><p>[3] Kelemen, P.B. & Manning, C.E. (2015). PNAS <strong>112</strong>, E3997-E4006.</p><p>[4] Beinlich, A., Plümper, O., Hövelmann, J., Austrheim, H. & Jamtveit, B. (2012). Terra Nova <strong>24, </strong>446-455.</p>

scholarly journals Including a full carbon cycle into the <i>i</i>LOVECLIM model (v1.0)

2014 ◽  
Vol 7 (3) ◽  
pp. 3937-3984 ◽  
Author(s):  
N. Bouttes ◽  
D. M. Roche ◽  
V. Mariotti-Epelbaum ◽  
L. Bopp
Keyword(s):  
Carbon Cycle ◽  
Atmospheric Carbon Dioxide ◽  
Climate Model ◽  
Carbon Dioxide Concentration ◽  
Deep Ocean ◽  
Carbon Cycle Model ◽  
Radiative Balance ◽  
Natural Variations ◽  
Good Agreement

Abstract. The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a climate model to understand and simulate past and future changes of the carbon cycle. In particular, natural variations of atmospheric CO2 have happened in the past, while anthropogenic carbon emissions are predicted to continue in the future. To study changes of the carbon cycle and climate on timescales of a few hundred to a few thousand years, we have included a simple carbon cycle model into the iLOVECLIM Earth System Model. In this study, we describe the ocean and terrestrial biosphere carbon cycle models and their performance relative to observational data. We focus on the main carbon cycle variables including the carbon isotope ratios δ13C and the Δ14C. We show that the model results are in good agreement with modern observations both at the surface and in the deep ocean for the main variables, in particular phosphates, DIC and the carbon isotopes. The model can thus be used for long-term past and future climate–carbon studies.

Introduction

2004 ◽  
Author(s):  
Robert A. Berner
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Carbon Cycle ◽  
Global Climate ◽  
Geological Time ◽  
Short Term ◽  
Quaternary Period ◽  
Geological Time Scale ◽  
The Earth

The cycle of carbon is essential to the maintenance of life, to climate, and to the composition of the atmosphere and oceans. What is normally thought of as the “carbon cycle” is the transfer of carbon between the atmosphere, the oceans, and life. This is not the subject of interest of this book. To understand this apparently confusing statement, it is necessary to separate the carbon cycle into two cycles: the short-term cycle and the long-term cycle. The “carbon cycle,” as most people understand it, is represented in figure 1.1. Carbon dioxide is taken up via photosynthesis by green plants on the continents or phytoplankton in the ocean. On land carbon is transferred to soils by the dropping of leaves, root growth, and respiration, the death of plants, and the development of soil biota. Land herbivores eat the plants, and carnivores eat the herbivores. In the oceans the phytoplankton are eaten by zooplankton that are in turn eaten by larger and larger organisms. The plants, plankton, and animals respire CO2. Upon death the plants and animals are decomposed by microorganisms with the ultimate production of CO2. Carbon dioxide is exchanged between the oceans and atmosphere, and dissolved organic matter is carried in solution by rivers from soils to the sea. This all constitutes the shortterm carbon cycle. The word “short-term” is used because the characteristic times for transferring carbon between reservoirs range from days to tens of thousands of years. Because the earth is more than four billion years old, this is short on a geological time scale. As the short-term cycle proceeds, concentrations of the two principal atmospheric gases, CO2 and CH4, can change as a result of perturbations of the cycle. Because these two are both greenhouse gases—in other words, they adsorb outgoing infrared radiation from the earth surface—changes in their concentrations can involve global warming and cooling over centuries and many millennia. Such changes have accompanied global climate change over the Quaternary period (past 2 million years), although other factors, such as variations in the receipt of solar radiation due to changes in characteristics of the earth’s orbit, have also contributed to climate change.

scholarly journals Abrupt tectonics and rapid slab detachment with grain damage

2015 ◽  
Vol 112 (5) ◽  
pp. 1287-1291 ◽  
Author(s):  
David Bercovici ◽  
Gerald Schubert ◽  
Yanick Ricard
Keyword(s):  
Grain Size ◽  
Simple Model ◽  
Subduction Zone ◽  
Continental Crust ◽  
Subduction Zones ◽  
Oceanic Lithosphere ◽  
Plate Motion ◽  
Size Evolution ◽  
Grain Damage ◽  
Rapid Changes

A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

scholarly journals Including an ocean carbon cycle model into <i>i</i>LOVECLIM (v1.0)

2015 ◽  
Vol 8 (5) ◽  
pp. 1563-1576 ◽  
Author(s):  
N. Bouttes ◽  
D. M. Roche ◽  
V. Mariotti ◽  
L. Bopp
Keyword(s):  
Carbon Cycle ◽  
Atmospheric Carbon Dioxide ◽  
Climate Model ◽  
Dissolved Inorganic Carbon ◽  
Carbon Dioxide Concentration ◽  
Deep Ocean ◽  
Cycle Model ◽  
Carbon Cycle Model ◽  
Radiative Balance ◽  
Ocean Carbon

Abstract. The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a climate model to understand and simulate past and future changes of the carbon cycle. In particular, natural variations of atmospheric CO2 have happened in the past, while anthropogenic carbon emissions are likely to continue in the future. To study changes of the carbon cycle and climate on timescales of a few hundred to a few thousand years, we have included a simple carbon cycle model into the iLOVECLIM Earth System Model. In this study, we describe the ocean and terrestrial biosphere carbon cycle models and their performance relative to observational data. We focus on the main carbon cycle variables including the carbon isotope ratios δ13C and the Δ14C. We show that the model results are in good agreement with modern observations both at the surface and in the deep ocean for the main variables, in particular phosphates, dissolved inorganic carbon and the carbon isotopes.

scholarly journals The capacity of northern peatlands for long-term carbon sequestration

2020 ◽  
Vol 17 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Georgii A. Alexandrov ◽  
Victor A. Brovkin ◽  
Thomas Kleinen ◽  
Zicheng Yu
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Carbon Sink ◽  
Carbon Dioxide Concentration ◽  
Interglacial Period ◽  
Natural Carbon ◽  
Northern Peatlands ◽  
The Last Glacial Maximum ◽  
Potential Carbon ◽  
The Last Glacial

Abstract. Northern peatlands have been a persistent natural carbon sink since the Last Glacial Maximum. The continued growth and expansion of these carbon-rich ecosystems could offset a large portion of anthropogenic carbon emissions before the end of the present interglacial period. Here we used an impeded drainage model and gridded data on the depth to bedrock and the fraction of histosol-type soils to evaluate the limits to the growth of northern peatland carbon stocks. Our results show that the potential carbon stock in northern peatlands could reach a total of 875±125 Pg C before the end of the present interglacial, which could, as a result, remove 330±200 Pg C of carbon from the atmosphere. We argue that northern peatlands, together with the oceans, will potentially play an important role in reducing the atmospheric carbon dioxide concentration over the next 5000 years.

scholarly journals Do fossil plants signal palaeoatmospheric carbon dioxide concentration in the geological past?

1998 ◽  
Vol 353 (1365) ◽  
pp. 83-96 ◽  
Author(s):  
J. C. McElwain
Keyword(s):  
Carbon Dioxide ◽  
Atmospheric Carbon Dioxide ◽  
Middle Eocene ◽  
Stomatal Density ◽  
Carbon Dioxide Concentration ◽  
Fossil Plants ◽  
Early Devonian ◽  
Carbon Dioxide Concentrations ◽  
Atmospheric Carbon

Fossil, subfossil, and herbarium leaves have been shown to provide a morphological signal of the atmospheric carbon dioxide environment in which they developed by means of their stomatal density and index. An inverse relationship between stomatal density/index and atmospheric carbon dioxide concentration has been documented for all the studies to date concerning fossil and subfossil material. Furthermore, this relationship has been demonstrated experimentally by growing plants under elevated and reducedcarbon dioxide concentrations. To date, the mechanism that controls the stomatal density response to atmospheric carbon dioxide concentration remains unknown. However, stomatal parameters of fossil plants have been successfully used as a proxy indicator of palaeo–carbon dioxide levels. This paper presents new estimates of palaeo–atmospheric carbon dioxide concentrations for the Middle Eocene (Lutetian), based on the stomatal ratios of fossil Lauraceae species from Bournemouth in England. Estimates of atmospheric carbon dioxide concentrations derived from stomatal data from plants of the Early Devonian, Late Carboniferous, Early Permian and Middle Jurassic ages are reviewed in the light of new data. Semi–quantitative palaeo–carbon dioxide estimates based on the stomatal ratio (a ratio of the stomatal index of a fossil plant to that of a selected nearest living equivalent) have in the past relied on the use of a Carboniferous standard. The application of a new standard based on the present–day carbon dioxide level is reported here for comparison. The resultant ranges of palaeo–carbon dioxide estimates made from standardized fossil stomatal ratio data are in good agreement with both carbon isotopic data from terrestrial and marine sources and long–term carbon cycle modelling estimates for all the time periods studied. These data indicate elevated atmospheric carbon dioxide concentrations during the Early Devonian, Middle Jurassic and Middle Eocene, and reduced concentrations during the Late Carboniferous and Early Permian. Such data are important in demonstrating the long–term responses of plants to changing carbon dioxide concentrations and in contributing to the database needed for general circulation model climatic analogues.

scholarly journals Some illustrations of large tectonically driven climate changes in Earth history

2021 ◽  
Author(s):  
Zhongshi Zhang ◽  
Gilles Ramstein
Keyword(s):  
General Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Climate Changes ◽  
Circulation Model ◽  
Ocean Dynamics ◽  
Plate Motion ◽  
Mountain Range ◽  
Earth System ◽  
Western Asia

&lt;p&gt;&lt;span&gt;Nearly A century ago the pioneering book published in 1924 &amp;#8220;&lt;em&gt;Die Klimate der &lt;/em&gt;g&lt;em&gt;eologischen Vorzeit &lt;/em&gt;&amp;#8220; explained by plate motion the evolution of vegetation revealed in sedimentary records. Nevertheless, they did not invoke climate changes. In the second part of the 20th century the intricate relationship between tectonics, long-term carbon cycle and climate was depicted by James G. C. Walker (1981). Since these major steps, climate modeling of the Earth system kept on improving and including more and more components and processes to enable the investigation of deep time periods using general circulation model that can account for atmosphere and ocean dynamics. Here we illustrate long but drastic climate changes clearly related with tectonics, through three different examples: &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;1)&amp;#160; The crucial role of paleogeography (continental distribution) to explain the drawdown of atmospheric carbon dioxide and the huge glaciation associated that occured during the Neoproterozoic period.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;2)&amp;#160; The shrinkage of large epicontinental Paratethys that covered a large part of Eastern Europe and Western Asia and its impact on both monsoonal systems (African and Asian) since 40 Ma.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;3) The large impact of mountain range uplifts since Eocene both in Asia (Tibetan Plateau and Himalaya) and in Africa (buildup of the rift), on atmosphere and ocean dynamics. &lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;These studies not only allow for testing the ability of Earth system models to capture long term changes of Earth climate, but they pinpoint the pivotal role tectonics played in shaping the long-term evolution of atmospheric CO2 and monsoon patterns.&lt;/span&gt;&lt;/p&gt;

Atmospheric Carbon Dioxide over Phanerozoic Time

2004 ◽  
Author(s):  
Robert A. Berner
Keyword(s):  
Organic Matter ◽  
Steady State ◽  
Carbon Cycle ◽  
Atmospheric Carbon Dioxide ◽  
Total Carbon ◽  
Atmospheric Composition ◽  
Burial Flux ◽  
State Models ◽  
Fundamental Equations

In this chapter the methods and results of modeling the long-term carbon cycle are presented in terms of predictions of past levels of atmospheric CO2. The modeling results are then compared with independent determinations of paleo-CO2 by means of a variety of different methods. Results indicate that there is reasonable agreement between methods as to the general trend of CO2 over Phanerozoic time. Values of fluxes in the long-term carbon cycle can be calculated from the fundamental equations for total carbon and 13C mass balance that are stated in the introduction and are repeated here: . . . dMc/dt = Fwc + Fwg + Fmc + Fmg – Fbc – Fbg (1.10) . . . . . . d(δcMc)/dt = δwcFwc + δwgFwg + δmcFmc + δmgFmg – δbcFbc – δbgFbg (1.11) . . . where Mc = mass of carbon in the surficial system consisting of the atmosphere, oceans, biosphere, and soils Fwc = flux from weathering of Ca and Mg carbonates Fwg = flux from weathering of sedimentary organic matter Fmc = degassing flux for carbonates from volcanism, metamorphism, and diagenesis Fmg = degassing flux for organic matter from volcanism, metamorphism, and diagenesis Fbc = burial flux of carbonates in sediments Fbg = burial flux of organic matter in sediments δ = [(13C/12C)/(13C/12C)stnd – 1]1000. Variants of equations (1.10) and (1.11) have been treated in terms of non–steady-state modeling (e.g., Berner et al., 1983; Wallmann, 2001; Hansen and Wallmann, 2003; Mackenzie et al., 2003; Bergman et al., 2003), where the evolution of both oceanic and atmospheric composition, including Ca, Mg, and other elements in seawater, is tracked over time. However, since the purpose of this book is to discuss the carbon cycle with respect to CO2 and O2, and so as not to overburden the reader with too many mathematical expressions, I discuss only those aspects of the non–steady-state models that directly impact carbon. These are combined with results from steady-state strictly carbon-cycle modeling (Garrels and Lerman, 1984; Berner, 1991, 1994; Kump and Arthur, 1997; Francois and Godderis, 1998; Tajika, 1998; Berner and Kothavala, 2001; Kashiwagi and Shikazono, 2002).

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