scholarly journals A joint global carbon inversion system using both CO<sub>2</sub> and <sup>13</sup>CO<sub>2</sub> atmospheric concentration data

2017 ◽  
Vol 10 (3) ◽  
pp. 1131-1156 ◽  
Author(s):  
Jing M. Chen ◽  
Gang Mo ◽  
Feng Deng
Keyword(s):  
Spatial Distribution ◽  
Diffusion Processes ◽  
Carbon Sink ◽  
Joint Inversion ◽  
Co2 Flux ◽  
Historical Change ◽  
Co2 Fluxes ◽  
Concentration Data ◽  
Terrestrial Ecosystem Model ◽  
Discrimination Rate

Abstract. Observations of 13CO2 at 73 sites compiled in the GLOBALVIEW database are used for an additional constraint in a global atmospheric inversion of the surface CO2 flux using CO2 observations at 210 sites (62 collocated with 13CO2 sites) for the 2002–2004 period for 39 land regions and 11 ocean regions. This constraint is implemented using prior CO2 fluxes estimated with a terrestrial ecosystem model and an ocean model. These models simulate 13CO2 discrimination rates of terrestrial photosynthesis and ocean–atmosphere diffusion processes. In both models, the 13CO2 disequilibrium between fluxes to and from the atmosphere is considered due to the historical change in atmospheric 13CO2 concentration. This joint inversion system using both13CO2 and CO2 observations is effectively a double deconvolution system with consideration of the spatial variations of isotopic discrimination and disequilibrium. Compared to the CO2-only inversion, this 13CO2 constraint on the inversion considerably reduces the total land carbon sink from 3.40 ± 0.84 to 2.53 ± 0.93 Pg C year−1 but increases the total oceanic carbon sink from 1.48 ± 0.40 to 2.36 ± 0.49 Pg C year−1. This constraint also changes the spatial distribution of the carbon sink. The largest sink increase occurs in the Amazon, while the largest source increases are in southern Africa, and Asia, where CO2 data are sparse. Through a case study, in which the spatial distribution of the annual 13CO2 discrimination rate over land is ignored by treating it as a constant at the global average of −14. 1 ‰, the spatial distribution of the inverted CO2 flux over land was found to be significantly modified (up to 15 % for some regions). The uncertainties in our disequilibrium flux estimation are 8.0 and 12.7 Pg C year−1 ‰ for land and ocean, respectively. These uncertainties induced the unpredictability of 0.47 and 0.54 Pg C year−1 in the inverted CO2 fluxes for land and ocean, respectively. Our joint inversion system is therefore useful for improving the partitioning between ocean and land sinks and the spatial distribution of the inverted carbon flux.

scholarly journals A Joint Global Carbon Inversion System Using Both CO<sub>2</sub> and CO<sub>2</sub> Atmospheric Concentration Data

2016 ◽  
Author(s):  
Jing M. Chen ◽  
Gang Mo ◽  
Feng Deng
Keyword(s):  
Spatial Distribution ◽  
Diffusion Processes ◽  
Carbon Sink ◽  
Joint Inversion ◽  
Co2 Flux ◽  
Historical Change ◽  
Co2 Fluxes ◽  
Concentration Data ◽  
Terrestrial Ecosystem Model ◽  
Discrimination Rate

Abstract. Observations of 13CO2 at 73 sites compiled in the GLOBALVIEW database are used for an additional constraint in a global atmospheric inversion of the surface CO2 flux using CO2 observations at 210 sites (62 collocated with 13CO2 sites) for the 2002–2004 period for 39 land regions and 11 ocean regions. This constraint is implemented using prior CO2 fluxes estimated with a terrestrial ecosystem model and an ocean model. These models simulate 13CO2 discrimination rates of terrestrial photosynthesis and ocean-atmosphere diffusion processes. In both models, the 13CO2 disequilibrium between fluxes to and from the atmosphere is considered due to the historical change in atmospheric 13CO2 concentration. This joint inversion system using both 13CO2 and CO2 observations is effectively a double deconvolution system with consideration of the spatial variations of isotopic discrimination and disequilibrium. This 13CO2 constraint on the inversion considerably reduces the total land carbon sink from 3.40 ± 0.84 to 2.78 ± 0.76 Pg C y−1 but increases the total oceanic carbon sink from 1.48 ± 0.40 to 2.26 ± 0.35 Pg C y−1. This constraint also changes the spatial distribution of the carbon sink. The largest sink increase occurs in Amazon, while the largest source increases are in southern Africa, and Asia, where CO2 data are sparse. Through a case study, in which the spatial distribution of the annual 13CO2 discrimination rate over land is ignored by treating it as a constant at the global average of −14.1 ‰, the spatial distribution of the inverted CO2 flux over land was found to be significantly modified (up to 15 % for some regions). The uncertainties in our disequilibrium flux estimation are 11.2 PgC y−1 ‰ and 16.3 Pg C y−1 ‰ for land and ocean, respectively. These uncertainties induced uncertainties of 0.47 Pg C y−1 and 0.54 Pg C y−1 in the inverted CO2 fluxes for land and ocean, respectively. Our joint inversion system is therefore useful for improving the partitioning between ocean and land sinks and the spatial distribution of the inverted carbon flux.

scholarly journals Atmospheric inversion of the surface CO<sub>2</sub> flux with <sup>13</sup>CO<sub>2</sub> constraint

2013 ◽  
Vol 13 (10) ◽  
pp. 26529-26578
Author(s):  
J. M. Chen ◽  
G. Mo ◽  
F. Deng
Keyword(s):  
Diffusion Processes ◽  
Carbon Sink ◽  
Flux Ratio ◽  
Co2 Flux ◽  
Ocean Model ◽  
Historical Change ◽  
Amazon Forest ◽  
Terrestrial Ecosystem Model ◽  
Discrimination Rate ◽  
Atmospheric Inversion

Abstract. Observations of 13CO2 at 73 sites compiled in the GLOBALVIEW database are used for an additional constraint in a global atmospheric inversion of the surface CO2 flux using CO2 observations at 210 sites for the 2002–2004 period for 39 land regions and 11 ocean regions. This constraint is implemented using the 13CO2/CO2 flux ratio modeled with a terrestrial ecosystem model and an ocean model. These models simulate 13CO2 discrimination rates of terrestrial photosynthesis and respiration and ocean-atmosphere diffusion processes. In both models, the 13CO2 disequilibrium between fluxes to and from the atmosphere is considered due to the historical change in atmospheric 13CO2 concentration. For the 2002–2004 period, the 13CO2 constraint on the inversion increases the total land carbon sink from 3.40 to 3.70 Pg C yr−1 and decreases the total oceanic carbon sink from 1.48 to 1.12 Pg C yr−1. The largest changes occur in tropical areas: a considerable decrease in the carbon source in the Amazon forest, and this decrease is mostly compensated by increases in the ocean region immediately west of the Amazon and the southeast Asian land region. Our further investigation through different treatments of the 13CO2/CO2 flux ratio used in the inversion suggests that variable spatial distributions of the 13CO2 isotopic discrimination rate simulated by the models over land and ocean have considerable impacts on the spatial distribution of the inverted CO2 flux over land and the inversion results are not sensitive to errors in the estimated disequilibria over land and ocean.

scholarly journals CO2 fluxes from drained tropical peatland used for oil palm plantation in relation to peat characteristics and crop age after planting

2019 ◽  
Vol 20 (6) ◽  
Author(s):  
EVI GUSMAYANTI ◽  
GUSTI Z ANSHARI ◽  
MUHAMMAD PRAMULYA ◽  
AGUS RULIYANSYAH
Keyword(s):  
Organic Matter ◽  
Groundwater Level ◽  
Oil Palm ◽  
Particle Density ◽  
Carbon Sink ◽  
Co2 Flux ◽  
Co2 Fluxes ◽  
Oil Palm Plantation ◽  
Large Expansion ◽  
Peat Surface

Large expansion of oil palm plantation on peatland has changed its important role for carbon sink into a carbon source.  Conversion of peat swamp forest with high carbon density into a monoculture of oil palm has released the significant amount of carbon into atmosphere either carbon previously stored in forest biomass or carbon stored in peat organic matter.  Drainage canal to artificially lower groundwater level as a prerequisite of oil palm cultivation provides the favorable condition for soil microbes activities in decomposing peat organic matter resulted in CO2 flux increase.  The fluctuation of groundwater level and variation of environmental factors near the peat surface may regulate the rate of CO2 released from the soil.  We aimed to measure CO2 fluxes from two sites of oil palm plantation with different peat characteristics and analyzed the correlation with groundwater level, soil temperature, air temperature,  gravimetric water content, peat pH, oxidative reductive potential, and crop age.  The measurement has been conducted from September 2016 to April 2017 in West Kalimantan, Indonesia by using portable infrared gas analyzer EGM 4.  In addition to soil sampling at the same time as the gas measurement, we collected soil samples for some peat characteristics analysis consist of bulk density, particle density, porosity, soil organic matter, ash content, carbon, and nitrogen content prior to CO2 flux measurement.  Our result shows that the difference of peat chemical characteristics between two sites has resulted in different CO2 flux.  Oil palm ages seemed to affect CO2 flux by regulating microclimatic condition around crop canopy.  Another finding is the insignificant relationship between CO2 fluxes and groundwater level unless the groundwater level reached more than 50 cm from the peat surface.  It implies that maintaining groundwater level-up to 50 cm resulting in similar CO2 flux.

scholarly journals Air–sea carbon flux from high-temporal-resolution data of in situ CO<sub>2</sub> measurements in the southern North Sea

2020 ◽  
Author(s):  
Steven Pint ◽  
Gert Everaert ◽  
Hannelore Theetaert ◽  
Michiel B. Vandegehuchte ◽  
Thanos Gkritzalis
Keyword(s):  
North Sea ◽  
Carbon Flux ◽  
Carbon Sink ◽  
Co2 Flux ◽  
Spatiotemporal Variability ◽  
High Temporal Resolution ◽  
Co2 Fluxes ◽  
Southern North Sea ◽  
Basin Scale ◽  
Carbon Dioxide Co2

Abstract. An important element to keep track of global change is the atmosphere–water exchange of carbon dioxide (CO2) in the ocean as it provides insight in how much CO2 is incorporated in the ocean (i.e. the ocean as a sink for CO2) or emitted to the atmosphere (i.e. the ocean as a source). To date, only few high-resolution observation sets are available to quantify the spatiotemporal variability of air–sea CO2 fluxes. In this study, we used observations of pCO2 collected daily at the ICOS station Thornton Buoy in the southern North Sea from February until December 2018 to calculate air–sea CO2 fluxes. Our results show a seasonal variability of the air–sea carbon flux, with the sea being a carbon sink from February until June switching to a carbon source in July and August, before switching back to a sink until December. We calculated that the sink was largest in April (−0.95 ± 0.90 mmol C m−2 d−1), while in August, the source was at its maximum (0.08 ± 0.13 mmol C m−2 d−1). On an annual basis, we found a sink for atmospheric CO2 of 130.19 ± 149.93 mmol C m−2 y−1. Apart from region- and basin-scale estimates of the air–sea CO2 flux, also local measurements are important to grasp local dynamics of the flux and its interactions with biogeochemical processes.

scholarly journals CO<sub>2</sub> flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

2007 ◽  
Vol 4 (6) ◽  
pp. 1005-1025 ◽  
Author(s):  
L. Kutzbach ◽  
J. Schneider ◽  
T. Sachs ◽  
M. Giebels ◽  
H. Nykänen ◽  
...  
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Co2 Flux ◽  
Exponential Model ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Closed Chamber ◽  
Exponential Regression ◽  
Closure Time ◽  
Over Time

Abstract. Closed (non-steady state) chambers are widely used for quantifying carbon dioxide (CO2) fluxes between soils or low-stature canopies and the atmosphere. It is well recognised that covering a soil or vegetation by a closed chamber inherently disturbs the natural CO2 fluxes by altering the concentration gradients between the soil, the vegetation and the overlying air. Thus, the driving factors of CO2 fluxes are not constant during the closed chamber experiment, and no linear increase or decrease of CO2 concentration over time within the chamber headspace can be expected. Nevertheless, linear regression has been applied for calculating CO2 fluxes in many recent, partly influential, studies. This approach has been justified by keeping the closure time short and assuming the concentration change over time to be in the linear range. Here, we test if the application of linear regression is really appropriate for estimating CO2 fluxes using closed chambers over short closure times and if the application of nonlinear regression is necessary. We developed a nonlinear exponential regression model from diffusion and photosynthesis theory. This exponential model was tested with four different datasets of CO2 flux measurements (total number: 1764) conducted at three peatlands sites in Finland and a tundra site in Siberia. Thorough analyses of residuals demonstrated that linear regression was frequently not appropriate for the determination of CO2 fluxes by closed-chamber methods, even if closure times were kept short. The developed exponential model was well suited for nonlinear regression of the concentration over time c(t) evolution in the chamber headspace and estimation of the initial CO2 fluxes at closure time for the majority of experiments. However, a rather large percentage of the exponential regression functions showed curvatures not consistent with the theoretical model which is considered to be caused by violations of the underlying model assumptions. Especially the effects of turbulence and pressure disturbances by the chamber deployment are suspected to have caused unexplainable curvatures. CO2 flux estimates by linear regression can be as low as 40% of the flux estimates of exponential regression for closure times of only two minutes. The degree of underestimation increased with increasing CO2 flux strength and was dependent on soil and vegetation conditions which can disturb not only the quantitative but also the qualitative evaluation of CO2 flux dynamics. The underestimation effect by linear regression was observed to be different for CO2 uptake and release situations which can lead to stronger bias in the daily, seasonal and annual CO2 balances than in the individual fluxes. To avoid serious bias of CO2 flux estimates based on closed chamber experiments, we suggest further tests using published datasets and recommend the use of nonlinear regression models for future closed chamber studies.

scholarly journals Daily and seasonal patterns of CO2 fluxes and evapotranspiration in maize-grass intercropping

2016 ◽  
Vol 20 (9) ◽  
pp. 777-782 ◽  
Author(s):  
Cássia B. Machado ◽  
José R. de S. Lima ◽  
Antonio C. D. Antonino ◽  
Eduardo S. de Souza ◽  
Rodolfo M. S. Souza ◽  
...  
Keyword(s):  
Soil Water ◽  
Climate Changes ◽  
Carbon Sink ◽  
Soil Water Storage ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Area Index ◽  
Available Energy ◽  
Atmospheric Carbon ◽  
Main Consumer

ABSTRACT Studies that investigate the relationships between CO2 fluxes and evapotranspiration (ET) are important for predicting how agricultural ecosystems will respond to climate changes. However, none was made on the maize-grass intercropping system in Brazil. The aim of this study was to determine the ET and CO2 fluxes in a signal grass pasture intercropped with maize, in São João, Pernambuco, Brazil, in a drought year. Furthermore, the soil water storage (SWS) and leaf area index (LAI) were determined. The latent heat flux was the main consumer of the available energy and the daily and seasonal ET and CO2 variations were mainly controlled by rainfall, through the changes in soil water content and consequently in SWS. The agroecosystem acted as an atmospheric carbon source, during drier periods and lower LAI, and as an atmospheric carbon sink, during wetter periods and higher LAI values. In a dry year, the intercropping sequestered 2.9 t C ha-1, which was equivalent to 8.0 kg C ha-1 d-1. This study showed strong seasonal fluctuations in maize-grass intercropping CO2 fluxes, due to seasonality of rainfall, and that this agroecosystem is vulnerable to low SWS, with significant reduction in CO2 uptake during these periods.

scholarly journals Prediction of photosynthesis in Scots pine ecosystems across Europe by a needle-level theory

2018 ◽  
Vol 18 (18) ◽  
pp. 13321-13328
Author(s):  
Pertti Hari ◽  
Steffen Noe ◽  
Sigrid Dengel ◽  
Jan Elbers ◽  
Bert Gielen ◽  
...  
Keyword(s):  
Scots Pine ◽  
Boreal Forests ◽  
Co2 Flux ◽  
Field Studies ◽  
Co2 Assimilation ◽  
Co2 Fluxes ◽  
New Era ◽  
Evergreen Forests ◽  
Transition Times

Abstract. Photosynthesis provides carbon for the synthesis of macromolecules to construct cells during growth. This is the basis for the key role of photosynthesis in the carbon dynamics of ecosystems and in the biogenic CO2 assimilation. The development of eddy-covariance (EC) measurements for ecosystem CO2 fluxes started a new era in the field studies of photosynthesis. However, the interpretation of the very variable CO2 fluxes in evergreen forests has been problematic especially in transition times such as the spring and autumn. We apply two theoretical needle-level equations that connect the variation in the light intensity, stomatal action and the annual metabolic cycle of photosynthesis. We then use these equations to predict the photosynthetic CO2 flux in five Scots pine stands located from the northern timberline to Central Europe. Our result has strong implications for our conceptual understanding of the effects of the global change on the processes in boreal forests, especially of the changes in the metabolic annual cycle of photosynthesis.

scholarly journals New techniques for gap-filling and partitioning of H<sub>2</sub>O and CO<sub>2</sub> eddy fluxes measured over forests in complex mountainous terrain

2017 ◽  
Author(s):  
Minseok Kang ◽  
Joon Kim ◽  
Bindu Malla Thakuri ◽  
Junghwa Chun ◽  
Chunho Cho
Keyword(s):  
Environmental Changes ◽  
Water Cycle ◽  
Co2 Flux ◽  
Test Method ◽  
Co2 Fluxes ◽  
Gap Filling ◽  
New Techniques ◽  
Diameter Increment ◽  
Filling Method ◽  
Rain Events

Abstract. The continuous measurement of H2O and CO2 fluxes using the eddy covariance (EC) technique is still challenging for forests in complex terrain because of large amounts of wet canopy evaporation (EWC), which occur during and following rain events when the EC systems rarely work correctly, and the horizontal advection of CO2 generated at night. We propose new techniques for gap-filling and partitioning of the H2O and CO2 fluxes: (1) a model-stats hybrid method (MSH) and (2) a modified moving point test method (MPTm). The former enables the recovery of the missing EWC in the traditional gap-filling method and the partitioning of the evapotranspiration (ET) into transpiration and (wet canopy) evaporation. The latter determines the friction velocity (u*) threshold based on an iterative approach using moving windows for both time and u*, thereby allowing not only the nighttime CO2 flux correction and partitioning but also the assessment of the significance of the CO2 drainage. We tested and validated these new methods using the datasets from two flux towers, which are located at forests in hilly and complex terrains. The MSH reasonably recovered the missing EWC of 16 ~ 41 mm year−1 and separated it from the ET (14 ~ 23 % of the annual ET). The MPTm produced consistent carbon budgets using those from the previous research and diameter increment, while it has improved applicability. Additionally, we illustrated certain advantages of the proposed techniques, which enables us to understand better how ET responses to environmental changes and how the water cycle is connected to the carbon cycle in a forest ecosystem.

scholarly journals Impacto do uso do filtro “velocidade de fricção” em estimativas anuais de carbono sobre ecossistemas de pastagem natural

2020 ◽  
Vol 42 ◽  
pp. e7
Author(s):  
Ricardo Acosta ◽  
Gustavo Pujol Veeck ◽  
Tiago Bremm ◽  
Débora Regina Roberti ◽  
Osvaldo Luiz Leal de Moraes
Keyword(s):  
Friction Velocity ◽  
Carbon Sink ◽  
Co2 Flux ◽  
Address Climate Change ◽  
Natural Pasture ◽  
Pampa Biome ◽  
Annual Carbon ◽  
Santa Maria ◽  
Annual Balance ◽  
Change Mitigation

Annual carbon estimation of the most diverse ecosystems is a recurring theme in meetings that address climate change mitigation, as it is essential to have a realistic inventory of carbon stock in the biosphere and the ability to assimilate atmospheric carbon. Measurements of CO2 flux over ecosystems after being taken undergo rigorous post-processing to remove spurious and unrealistic data. In addition, a correction for low turbulence situations, where the eddy-covariance technique may be underestimated, is to take the friction velocity (u*) as a threshold to establish valid measurements, especially at night. This method, although widely used by the scientific community, is not unanimous. Especially since u* is itself a flow and consequently its value correlates with the time scale used for the analysis. This paper presents the annual carbon estimate of a natural pasture ecosystem, Pampa biome, in an experimental site established in Santa Maria - RS. We evaluated three distinct situations in the annual carbon estimate (NEP): i) without a u* filter; ii) with a fixed filter u* for all evaluated years and; iii) with the filter u* varying seasonally. The methodology used to estimate u* is the same as that used by Papale et al. (2006). The results show a total annual carbon sequestration variability of up to 10% depending on the methodology employed. The ecosystem in question, regardless of the method used, proved to be a carbon sink. However, the use of one methodology or another in ecosystem situations that are close to carbon assimaltion neutral should be closely scrutinized for an accurate annual balance.

scholarly journals Joint inverse estimation of fossil fuel and biogenic CO2 fluxes in an urban environment: An observing system simulation experiment to assess the impact of multiple uncertainties

Elem Sci Anth ◽  
2018 ◽  
Vol 6 ◽  
Author(s):  
Kai Wu ◽  
Thomas Lauvaux ◽  
Kenneth J. Davis ◽  
Aijun Deng ◽  
Israel Lopez Coto ◽  
...  
Keyword(s):  
High Resolution ◽  
Urban Environment ◽  
Co2 Emissions ◽  
Fossil Fuel ◽  
Atmospheric Transport ◽  
System Simulation ◽  
Co2 Flux ◽  
Point Sources ◽  
Co2 Fluxes ◽  
The Impact

The Indianapolis Flux Experiment aims to utilize a variety of atmospheric measurements and a high-resolution inversion system to estimate the temporal and spatial variation of anthropogenic greenhouse gas emissions from an urban environment. We present a Bayesian inversion system solving for fossil fuel and biogenic CO2 fluxes over the city of Indianapolis, IN. Both components were described at 1 km resolution to represent point sources and fine-scale structures such as highways in the a priori fluxes. With a series of Observing System Simulation Experiments, we evaluate the sensitivity of inverse flux estimates to various measurement deployment strategies and errors. We also test the impacts of flux error structures, biogenic CO2 fluxes and atmospheric transport errors on estimating fossil fuel CO2 emissions and their uncertainties. The results indicate that high-accuracy and high-precision measurements produce significant improvement in fossil fuel CO2 flux estimates. Systematic measurement errors of 1 ppm produce significantly biased inverse solutions, degrading the accuracy of retrieved emissions by about 1 µmol m–2 s–1 compared to the spatially averaged anthropogenic CO2 emissions of 5 µmol m–2 s–1. The presence of biogenic CO2 fluxes (similar magnitude to the anthropogenic fluxes) limits our ability to correct for random and systematic emission errors. However, assimilating continuous fossil fuel CO2 measurements with 1 ppm random error in addition to total CO2 measurements can partially compensate for the interference from biogenic CO2 fluxes. Moreover, systematic and random flux errors can be further reduced by reducing model-data mismatch errors caused by atmospheric transport uncertainty. Finally, the precision of the inverse flux estimate is highly sensitive to the correlation length scale in the prior emission errors. This work suggests that improved fossil fuel CO2 measurement technology, and better understanding of both prior flux and atmospheric transport errors are essential to improve the accuracy and precision of high-resolution urban CO2 flux estimates.

Sign in / Sign up

Export Citation Format

Share Document