scholarly journals Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up

2015 ◽  
Vol 112 (30) ◽  
pp. E3997-E4006 ◽  
Author(s):  
Peter B. Kelemen ◽  
Craig E. Manning
Keyword(s):  
Carbon Concentration ◽  
Subduction Zones ◽  
Noble Gas ◽  
Carbon Fluxes ◽  
Aqueous Fluid ◽  
Mantle Lithosphere ◽  
Mantle Peridotites ◽  
Ocean Atmosphere ◽  
Global Carbon ◽  
Carbon Inventory

Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5–10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory.

scholarly journals A global CO<sub>2</sub> flux dataset (2015–2019) inferred from OCO-2 retrievals using the Tan-Tracker inversion system

2021 ◽  
Author(s):  
Zhe Jin ◽  
Xiangjun Tian ◽  
Rui Han ◽  
Yu Fu ◽  
Xin Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Carbon Cycle ◽  
Carbon Flux ◽  
Carbon Budget ◽  
Terrestrial Ecosystem ◽  
Carbon Fluxes ◽  
Global Carbon Cycle ◽  
Ocean Carbon ◽  
Global Carbon ◽  
Regional Fluxes

Abstract. Accurate assessment of the various sources and sinks of carbon dioxide (CO2), especially terrestrial ecosystem and ocean fluxes with high uncertainties, is important for understanding of the global carbon cycle, supporting the formulation of climate policies, and projecting future climate change. Satellite retrievals of the column-averaged dry air mole fractions of CO2 (XCO2) are being widely used to improve carbon flux estimation due to their broad spatial coverage. However, there is no consensus on the robust estimates of regional fluxes. In this study, we present a global and regional resolved terrestrial ecosystem carbon flux (NEE) and ocean carbon flux dataset for 2015–2019. The dataset was generated using the Tan-Tracker inversion system by assimilating Observing Carbon Observatory 2 (OCO-2) column CO2 retrievals. The posterior NEE and ocean carbon fluxes were comprehensively validated by comparing posterior simulated CO2 concentrations with OCO-2 independent retrievals and Total Carbon Column Observing Network (TCCON) measurements. The validation showed that posterior carbon fluxes significantly improved the modelling of atmospheric CO2 concentrations, with global mean biases of 0.33 ppm against OCO-2 retrievals and 0.12 ppm against TCCON measurements. We described the characteristics of the dataset at global, regional, and Tibetan Plateau scales in terms of the carbon budget, annual and seasonal variations, and spatial distribution. The posterior 5-year annual mean global atmospheric CO2 growth rate was 5.35 PgC yr−1, which was within the uncertainty of the Global Carbon Budget 2020 estimate (5.49 PgC yr−1). The posterior annual mean NEE and ocean carbon fluxes were −4.07 and −3.33 PgC yr−1, respectively. Regional fluxes were analysed based on TransCom partitioning. All 11 land regions acted as carbon sinks, except for Tropical South America, which was almost neutral. The strongest carbon sinks were located in Boreal Asia, followed by Temperate Asia and North Africa. The entire Tibetan Plateau ecosystem was estimated as a carbon sink, taking up −49.52 TgC yr−1 on average, with the strongest sink occurring in eastern alpine meadows. These results indicate that our dataset captures surface carbon fluxes well and provides insight into the global carbon cycle. The dataset can be accessed at https://doi.org/10.11888/Meteoro.tpdc.271317 (Jin et al., 2021).

scholarly journals A Global Carbon Assimilation System using a modified EnKF assimilation method

2014 ◽  
Vol 7 (5) ◽  
pp. 6519-6547
Author(s):  
S. Zhang ◽  
X. Zheng ◽  
Z. Chen ◽  
B. Dan ◽  
J. M. Chen ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Carbon Assimilation ◽  
Terrestrial Ecosystem ◽  
Carbon Fluxes ◽  
Ecosystem Model ◽  
Atmospheric Co2 ◽  
Forecast Errors ◽  
Global Carbon ◽  
Assimilation System

Abstract. A Global Carbon Assimilation System based on Ensemble Kalman filter (GCAS-EK) is developed for assimilating atmospheric CO2 abundance data into an ecosystem model to simultaneously estimate the surface carbon fluxes and atmospheric CO2 distribution. This assimilation approach is based on the ensemble Kalman filter (EnKF), but with several new developments, including using analysis states to iteratively estimate ensemble forecast errors, and a maximum likelihood estimation of the inflation factors of the forecast and observation errors. The proposed assimilation approach is tested in observing system simulation experiments and then used to estimate the terrestrial ecosystem carbon fluxes and atmospheric CO2 distributions from 2002 to 2008. The results showed that this assimilation approach can effectively reduce the biases and uncertainties of the carbon fluxes simulated by the ecosystem model.

scholarly journals Mathematical Modeling of Carbon Flux Parameters for Low-Pressure Vacuum Carburizing with Medium-High Alloy Steel

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1075
Author(s):  
Haojie Wang ◽  
Jing Liu ◽  
Yong Tian ◽  
Zhaodong Wang ◽  
Xiaoxue An
Keyword(s):  
Carbon Concentration ◽  
Carbon Flux ◽  
Carbon Fluxes ◽  
Low Pressure ◽  
Process Conditions ◽  
Flux Method ◽  
Vacuum Carburizing ◽  
Initial Carbon ◽  
Vacuum Carburization ◽  
And Diffusion

Low-pressure vacuum carburizing adopts a pulse process mode to improve the carburizing efficiency and reduces gas and energy consumption. Carbon flux is the key to accurately control the time of strong infiltration and diffusion in each pulse. In order to obtain the carbon fluxes with various materials under diffident carburizing process conditions, an evenly segmented carbon flux method is proposed. A systematic study with each model using different materials (12Cr2Ni4A, 16Cr3NiWMoVNbE, and 18Cr2Ni4WA represent different initial carbon concentrations and different alloy compositions), carburizing temperatures, and carburizing pressures to determine the effect of these conditions on carbon flux is conducted. Compared with traditional segmented carbon flux method, an evenly segmented carbon flux method can predict the actual carbon flux more precisely and effectively in order to finely control the pulse carburization process. The paper also indicates that carbon fluxes increase with the increase of pressure. The optimal carburization pressure for low-pressure vacuum carburization is 300 Pa. Raising the carburization temperature to 980 °C instead of 920 °C can increase effective carbon flux by more than 30%. Among the material compositions, alloy content has the biggest impact over the carbon, initial carbon concentration the second, and saturated carbon concentration the third biggest impact.

Evaluating the carbon inventory, carbon fluxes and carbon cycles for a long-term sustainable world

2019 ◽  
Vol 21 (15) ◽  
pp. 3994-4013 ◽  
Author(s):  
P. Tomkins ◽  
T. E. Müller
Keyword(s):  
Carbon Fluxes ◽  
Valuable Resource ◽  
Systematic Analysis ◽  
Carbon Cycles ◽  
Anthropogenic Carbon ◽  
Environmental Compartments ◽  
Carbon Inventory

Propositioning carbon to be seen a valuable resource, pathways towards establishing anthropogenic carbon cycles are outlined based on systematic analysis of the carbon inventory and fluxes throughout the different environmental compartments on earth.

scholarly journals Subduction sediment-lherzolite interaction at 2.9 GPa: effects of metasomatism and partial melting

2019 ◽  
Vol 27 (5) ◽  
pp. 503-524
Author(s):  
A. L. Perchuk ◽  
A A. Serdyuk ◽  
N. G. Zinovievа
Keyword(s):  
Subduction Zones ◽  
Central Zone ◽  
Aqueous Fluid ◽  
Piston Cylinder ◽  
Mineral Growth ◽  
Hydrous Melt ◽  
Liquid Flows ◽  
Dissolved Components ◽  
Sedimentary Layer ◽  
Upper Boundary

We present the results of analogue experiments carried out in a piston–cylinder apparatus at 750–900°C and 2.9 GPa aimed to simulate metasomatic transformation of the fertile mantle caused by fluids and melts released from the subducting sediment. A synthetic H2O- and CO2-bearing mixture that corresponds to the average subducting sediment (GLOSS, Plank, Langmuir, 1998) and mineral fractions of natural lherzolite (analogue of a mantle wedge) were used as starting materials. Experiments demonstrate that the mineral growth in capsules is controlled by ascending fluid and hydrous melt (from 850°C) flows. Migration of the liquids and dissolved components develops three horizontal zones in the sedimentary layer with different mineral parageneses that slightly changed from run to run. In the general case, however, the contents of omphacite and garnet increase towards the upper boundary of the layer. Magnesite and omphacite (± garnet ± melt ± kyanite ± phengite) are widespread in the central zone of the sedimentary layer, whereas SiO2 polymorph (± kyanite ± phengite ± biotite ± omphacite ± melt) occurs in the lower zone. Clinopyroxene disappears at the base of lherzolite layer and the initial olivine is partially replaced by orthopyroxene (± magnesite) in all experiments. In addition, talc is formed in this zone at 750°C, whereas melt appears at 850°C. In the remaining volume of the lherzolite layer, metasomatic transformations affect only grain boundaries where orthopyroxene (± melt ± carbonate) is developed. The described transformations are mainly related to a pervasive flow of liquids. Mineral growth in the narrow wall sides of the capsules is probably caused by a focused flow: omphacite grows up in the sedimentary layer, and talc or omphacite with the melt grow up in the lherzolite layer. Experiments show that metasomatism of peridotite related to a subducting sediment, unlike the metasomatism related to metabasites, does not lead to the formation of garnet-bearing paragenesis. In addition, uprising liquid flows (fluid, melt) do not remove significant amounts of carbon from the metasedimentary layer to the peridotite layer. It is assumed that either more powerful fluxes of aqueous fluid or migration of carbonate-bearing rocks in subduction melanges are necessary for more efficient transfer of crustal carbon from metasediments to a mantle in subduction zones.

scholarly journals Regional CO<sub>2</sub> fluxes from 2010 to 2015 inferred from GOSAT XCO<sub>2</sub> retrievals using a new version of the Global Carbon Assimilation System

2021 ◽  
Vol 21 (3) ◽  
pp. 1963-1985
Author(s):  
Fei Jiang ◽  
Hengmao Wang ◽  
Jing M. Chen ◽  
Weimin Ju ◽  
Xiangjun Tian ◽  
...  
Keyword(s):  
Carbon Assimilation ◽  
Carbon Fluxes ◽  
Atmospheric Co2 ◽  
Interannual Variations ◽  
Carbon Sinks ◽  
Area Index ◽  
Spatial Coverage ◽  
The Impact ◽  
Global Carbon ◽  
Assimilation System

Abstract. Satellite retrievals of the column-averaged dry air mole fractions of CO2 (XCO2) could help to improve carbon flux estimation due to their good spatial coverage. In this study, in order to assimilate the GOSAT (Greenhouse Gases Observing Satellite) XCO2 retrievals, the Global Carbon Assimilation System (GCAS) is upgraded with new assimilation algorithms, procedures, a localization scheme, and a higher assimilation parameter resolution. This upgraded system is referred to as GCASv2. Based on this new system, the global terrestrial ecosystem (BIO) and ocean (OCN) carbon fluxes from 1 May 2009 to 31 December 2015 are constrained using the GOSAT ACOS (Atmospheric CO2 Observations from Space) XCO2 retrievals (Version 7.3). The posterior carbon fluxes from 2010 to 2015 are independently evaluated using CO2 observations from 52 surface flask sites. The results show that the posterior carbon fluxes could significantly improve the modeling of atmospheric CO2 concentrations, with global mean bias decreases from a prior value of 1.6 ± 1.8 ppm to −0.5 ± 1.8 ppm. The uncertainty reduction (UR) of the global BIO flux is 17 %, and the highest monthly regional UR could reach 51 %. Globally, the mean annual BIO and OCN carbon sinks and their interannual variations inferred in this study are very close to the estimates of CarbonTracker 2017 (CT2017) during the study period, and the inferred mean atmospheric CO2 growth rate and its interannual changes are also very close to the observations. Regionally, over the northern lands, the strongest carbon sinks are seen in temperate North America, followed by Europe, boreal Asia, and temperate Asia; in the tropics, there are strong sinks in tropical South America and tropical Asia, but a very weak sink in Africa. This pattern is significantly different from the estimates of CT2017, but the estimated carbon sinks for each continent and some key regions like boreal Asia and the Amazon are comparable or within the range of previous bottom-up estimates. The inversion also changes the interannual variations in carbon fluxes in most TransCom land regions, which have a better relationship with the changes in severe drought area (SDA) or leaf area index (LAI), or are more consistent with previous estimates for the impact of drought. These results suggest that the GCASv2 system works well with the GOSAT XCO2 retrievals and shows good performance with respect to estimating the surface carbon fluxes; meanwhile, our results also indicate that the GOSAT XCO2 retrievals could help to better understand the interannual variations in regional carbon fluxes.

scholarly journals Glacial-interglacial atmospheric CO<sub>2</sub> change: a possible "standing volume" effect on deep-ocean carbon sequestration

2009 ◽  
Vol 5 (3) ◽  
pp. 537-550 ◽  
Author(s):  
L. C. Skinner
Keyword(s):  
Carbon Sequestration ◽  
Deep Water ◽  
Deep Ocean ◽  
Volume Effect ◽  
Lower Circumpolar Deep Water ◽  
Mixing Rates ◽  
Ocean Carbon ◽  
Oceanic Carbon ◽  
Global Carbon ◽  
Carbon Inventory

Abstract. So far, the exploration of possible mechanisms for glacial atmospheric CO2 drawdown and marine carbon sequestration has tended to focus on dynamic or kinetic processes (i.e. variable mixing-, equilibration- or export rates). Here an attempt is made to underline instead the possible importance of changes in the standing volumes of intra-oceanic carbon reservoirs (i.e. different water-masses) in influencing the total marine carbon inventory. By way of illustration, a simple mechanism is proposed for enhancing the marine carbon inventory via an increase in the volume of relatively cold and carbon-enriched deep water, analogous to modern Lower Circumpolar Deep Water (LCDW), filling the ocean basins. A set of simple box-model experiments confirm the expectation that a deep sea dominated by an expanded LCDW-like watermass holds more CO2, without any pre-imposed changes in ocean overturning rate, biological export or ocean-atmosphere exchange. The magnitude of this "standing volume effect" (which operates by boosting the solubility- and biological pumps) might be as large as the contributions that have previously been attributed to carbonate compensation, terrestrial biosphere reduction or ocean fertilisation for example. By providing a means of not only enhancing but also driving changes in the efficiency of the biological- and solubility pumps, this standing volume mechanism may help to reduce the amount of glacial-interglacial CO2 change that remains to be explained by other mechanisms that are difficult to assess in the geological archive, such as reduced mass transport or mixing rates in particular. This in turn could help narrow the search for forcing conditions capable of pushing the global carbon cycle between glacial and interglacial modes.

Fluid-mediated carbon release by infiltration of serpentinite dehydration fluids during subduction: insights from thermodynamic models of serpentinite-hosted carbonate rocks

2020 ◽  
Author(s):  
Manuel Menzel ◽  
Carlos J. Garrido ◽  
Vicente López Sánchez Vizcaíno
Keyword(s):  
Open System ◽  
Carbonate Rocks ◽  
Subduction Zones ◽  
Carbon Fluxes ◽  
Oceanic Lithosphere ◽  
Chemical System ◽  
Fluid Composition ◽  
Plate Interface ◽  
Carbon Solubility ◽  
Carbon Release

&lt;p&gt;Serpentinites can significantly modulate the carbon fluxes in subduction zones because they occasionally host substantial concentrations of carbonate formed during the oceanic stage of subducting oceanic lithosphere (ophicalcite; [1]) or during metasomatic reaction with CO&lt;sub&gt;2&lt;/sub&gt;-bearing fluids at the subduction plate interface (e.g. hybrid carbonate&amp;#8211;talc rocks; [2]). At subarc depth, fluid-mediated carbon release from lithologies like serpentinite-hosted carbonates is critical to understand the global carbon balance and magnitude of carbon fluxes from the subducting plate into the deep mantle. However, the solubility of carbon and the open-system metasomatic reactions during fluid-rock interactions in carbonated serpentinites at high P are not fully understood. In line with previous studies of prograde devolatilization [3], newer models show that the carbon release during prograde devolatilization reactions of serpentinite-hosted carbonate rocks is limited even if accounting for the higher carbon solubility of electrolytic fluids compared to molecular fluid models [4]. Therefore, devolatilization reactions driven by infiltration of Atg-serpentinite dehydration fluids into serpentinite-hosted meta-carbonate rocks determines how much carbon in the mantle lithosphere subducts deep into the mantle. Here we present the results of thermodynamic modelling &amp;#8211; using the implementation of the DEW aqueous database in Perple_X [5] &amp;#8211; to explore subduction fluid compositions and metasomatism of serpentinite-hosted carbonate rocks during prograde and infiltration-driven devolatilization reactions. The chemical system of serpentinite + carbonate is ideal to understand the interplay of changes in fluid composition, pH, bulk chemical modification and mineral assemblage during open-system fluid infiltration metamorphism. Our models provide new insights into the interaction of carbon-bearing subduction fluids with the cold hydrated mantle wedge, and the carbon release from serpentinite-hosted carbonates related to infiltration of serpentinite dehydration fluids at subarc depths. Our results further show that even though high fluid fluxes from serpentinite dehydration will transform meta-ophicalcites and talc-carbonate rocks into carbonate-garnet-clinopyroxene-olivine rocks and carbon-bearing orthopyroxenites, these rocks can subduct carbon beyond subarc depths into the deeper mantle where they may be related to the formation of deep diamonds, carbonatites and kimberlites.&lt;/p&gt;&lt;p&gt;REFERENCES&lt;/p&gt;&lt;p&gt;[1] Menzel et al., 2019, JMG 37, 681&amp;#8211; 715.&lt;/p&gt;&lt;p&gt;[2] Spandler et al., 2008, CMP 155, 181-198.&lt;/p&gt;&lt;p&gt;[3] Kerrick &amp; Connolly, 1998, Geology 26, 375-378.&lt;/p&gt;&lt;p&gt;[4] Menzel et al., 2020, EPSL 531.&lt;/p&gt;&lt;p&gt;[5] Connolly &amp; Galvez, 2018, EPSL 501, 90-102.&lt;/p&gt;

scholarly journals A global carbon assimilation system using a modified ensemble Kalman filter

2015 ◽  
Vol 8 (3) ◽  
pp. 805-816 ◽  
Author(s):  
S. Zhang ◽  
X. Zheng ◽  
J. M. Chen ◽  
Z. Chen ◽  
B. Dan ◽  
...  
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Carbon Assimilation ◽  
Terrestrial Ecosystem ◽  
Carbon Fluxes ◽  
Ecosystem Model ◽  
Atmospheric Co2 ◽  
Forecast Errors ◽  
Global Carbon ◽  
Assimilation System

Abstract. A Global Carbon Assimilation System based on the ensemble Kalman filter (GCAS-EK) is developed for assimilating atmospheric CO2 data into an ecosystem model to simultaneously estimate the surface carbon fluxes and atmospheric CO2 distribution. This assimilation approach is similar to CarbonTracker, but with several new developments, including inclusion of atmospheric CO2 concentration in state vectors, using the ensemble Kalman filter (EnKF) with 1-week assimilation windows, using analysis states to iteratively estimate ensemble forecast errors, and a maximum likelihood estimation of the inflation factors of the forecast and observation errors. The proposed assimilation approach is used to estimate the terrestrial ecosystem carbon fluxes and atmospheric CO2 distributions from 2002 to 2008. The results show that this assimilation approach can effectively reduce the biases and uncertainties of the carbon fluxes simulated by the ecosystem model.

Sign in / Sign up

Export Citation Format

Share Document