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 Comparison of floating chamber and eddy covariance measurements of lake greenhouse gas fluxes

2013 ◽  
Vol 10 (11) ◽  
pp. 18309-18335 ◽  
Author(s):  
E. Podgrajsek ◽  
E. Sahlée ◽  
D. Bastviken ◽  
J. Holst ◽  
A. Lindroth ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Carbon Sink ◽  
Co2 Flux ◽  
Flux Footprint ◽  
Gas Fluxes ◽  
Partial Pressure Of Co2 ◽  
Flux Measurements ◽  
Eddy Covariance Measurements ◽  
Terrestrial Carbon Sink ◽  
Carbon Dioxide Co2

Abstract. Fluxes of carbon dioxide (CO2) and methane (CH4) from lakes may have a large impact on the magnitude of the terrestrial carbon sink. Traditionally lake fluxes have been measured using the floating chambers (FC) technique, however, several recent studies use the eddy covariance (EC) method. We present simultaneous flux measurements using both methods at the lake Tämnaren in Sweden during field campaigns in 2011 and 2012. Only very few similar studies exist. For CO2 flux, the two methods agree relatively well during some periods, but deviate substantially at other times. The large discrepancies might be caused by heterogeneity of partial pressure of CO2 (pCO2w) in the EC flux footprint. The methods agree better for CH4 fluxes, it is, however, clear that short-term discontinuous FC measurements are likely to miss important high flux events.

scholarly journals Estimated regional CO<sub>2</sub> flux and uncertainty based on an ensemble of atmospheric CO<sub>2</sub> inversions

2021 ◽  
Author(s):  
Naveen Chandra ◽  
Prabir K. Patra ◽  
Yousuke Niwa ◽  
Akihiko Ito ◽  
Yosuke Iida ◽  
...  
Keyword(s):  
Atmospheric Carbon Dioxide ◽  
Transport Model ◽  
Carbon Sink ◽  
A Priori ◽  
Inversion Method ◽  
Co2 Fluxes ◽  
Emission Mitigation ◽  
Regional Sources ◽  
Carbon Dioxide Co2 ◽  
Riverine Export

Abstract. Global and regional sources and sinks of carbon across the earth’s surface have been studied extensively using atmospheric carbon dioxide (CO2) observations and chemistry-transport model (ACTM) simulations (top-down/inversion method). However, the uncertainties in the regional flux (+ve: source to the atmosphere; −ve: sink on land/ocean) distributions remain unconstrained mainly due to the lack of sufficient high-quality measurements covering the globe in all seasons and the uncertainties in model simulations. Here, we use a suite of 16 inversion cases, derived from a single transport model (MIROC4-ACTM) but different sets of a priori (bottom-up) terrestrial biosphere and oceanic fluxes, as well as prior flux and observational data uncertainties (50 sites) to estimate CO2 fluxes for 84 regions over the period 2000–2020. The ensemble inversions provide a mean flux field that is consistent with the global CO2 growth rate, land and ocean sink partitioning of −2.9 ± 0.3 (±1σ uncertainty on mean) and −1.6 ± 0.2 PgC yr−1, respectively, for the period 2011–2020 (without riverine export correction), offsetting about 22–33 % and 16–18 % of global fossil-fuel CO2 emissions. Aggregated fluxes for 15 land regions compare reasonably well with the best estimations for (approx. 2000–2009) given by the REgional Carbon Cycle Assessment and Processes (RECCAP), and all regions appeared as a carbon sink over 2011–2020. Interannual variability and seasonal cycle in CO2 fluxes are more consistently derived for different prior fluxes when a greater degree of freedom is given to the inversion system (greater prior flux uncertainty). We have evaluated the inversion fluxes using independent aircraft and surface measurements not used in the inversions, which raises our confidence in the ensemble mean flux rather than an individual inversion. Differences between 5-year mean fluxes show promises and capability to track flux changes under ongoing and future CO2 emission mitigation policies.

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 Forest stand age information improves an inverse North American carbon flux estimate

2013 ◽  
Vol 10 (3) ◽  
pp. 4781-4817 ◽  
Author(s):  
F. Deng ◽  
J. M. Chen ◽  
Y. Pan ◽  
W. Peters ◽  
R. Birdsey ◽  
...  
Keyword(s):  
Carbon Flux ◽  
Age Factors ◽  
Carbon Sources ◽  
Co2 Flux ◽  
Forest Stand ◽  
Atmospheric Co2 ◽  
Stand Age ◽  
Ecosystem Carbon ◽  
Net Ecosystem Carbon Exchange ◽  
Carbon Dioxide Co2

Abstract. Atmospheric inversions have become an important tool in quantifying carbon dioxide (CO2) sinks and sources at a variety of spatiotemporal scales, but associated large uncertainties restrain the inversion research community from reaching agreements on many important subjects. We enhanced an atmospheric inversion of the CO2 flux for North America by introducing spatially-explicit information on forest stand age for US and Canada as an additional constraint, since forest carbon dynamics are closely related to time since disturbance. To use stand age information in the inversion, we converted stand age into an age factor, and included the covariances between sub-continental regions in the inversion based on the similarity of the age factors. Our inversion results show that, considering age factors, regions with recently-disturbed or old forests are often nudged towards carbon sources, while regions with middle-aged productive forests are shifted towards sinks. This conforms to stand age effects observed in flux networks. At the sub-continental level, our inverted carbon fluxes agree well with continuous estimates of net ecosystem carbon exchange (NEE) upscaled from eddy covariance flux data (EC) based on MODIS data. Inverted fluxes with the age constraint exhibit stronger correlation to these upscaled NEE estimates than those inverted without the age constraint. While the carbon flux at the continental and sub-continental scales is predominantly determined by atmospheric CO2 observations, the age constraint is shown to have potential to improve the inversion of the carbon flux distribution among sub-continental regions, especially for regions lacking atmospheric CO2 observations.

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 The use of forest stand age information in an atmospheric CO<sub>2</sub> inversion applied to North America

2013 ◽  
Vol 10 (8) ◽  
pp. 5335-5348 ◽  
Author(s):  
F. Deng ◽  
J. M. Chen ◽  
Y. Pan ◽  
W. Peters ◽  
R. Birdsey ◽  
...  
Keyword(s):  
North America ◽  
Carbon Flux ◽  
Age Factors ◽  
Carbon Sources ◽  
Co2 Flux ◽  
Forest Stand ◽  
Atmospheric Co2 ◽  
Stand Age ◽  
Net Ecosystem Carbon Exchange ◽  
Carbon Dioxide Co2

Abstract. Atmospheric inversions have become an important tool in quantifying carbon dioxide (CO2) sinks and sources at a variety of spatiotemporal scales, but associated large uncertainties restrain the inversion research community from reaching agreement on many important subjects. We enhanced an atmospheric inversion of the CO2 flux for North America by introducing spatially explicit information on forest stand age for US and Canada as an additional constraint, since forest carbon dynamics are closely related to time since disturbance. To use stand age information in the inversion, we converted stand age into an age factor, and included the covariances between subcontinental regions in the inversion based on the similarity of the age factors. Our inversion results show that, considering age factors, regions with recently disturbed or old forests are often nudged towards carbon sources, while regions with middle-aged productive forests are shifted towards sinks. This conforms to stand age effects observed in flux networks. At the subcontinental level, our inverted carbon fluxes agree well with continuous estimates of net ecosystem carbon exchange (NEE) upscaled from eddy covariance flux data based on MODIS data. Inverted fluxes with the age constraint exhibit stronger correlation to these upscaled NEE estimates than those inverted without the age constraint. While the carbon flux at the continental and subcontinental scales is predominantly determined by atmospheric CO2 observations, the age constraint is shown to have potential to improve the inversion of the carbon flux distribution among subcontinental regions, especially for regions lacking atmospheric CO2 observations.

scholarly journals Spatial and seasonal variability of diffusive carbon flux in contrasting reservoirs: magnitudes and contribution of the aquatic surface and exposed sediment

2021 ◽  
Author(s):  
◽  
José Reinaldo Paranaíba Vilela Alves Teixeira
Keyword(s):  
Seasonal Variability ◽  
Carbon Flux ◽  
Carbon Emission ◽  
Co2 Flux ◽  
Spatial And Temporal Variability ◽  
Emission Rates ◽  
Ch4 Flux ◽  
Tropical Regions ◽  
Spatially Resolved ◽  
Carbon Dioxide Co2

Reservoirs are globally significant sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. The patterns of spatial and temporal variability in CO2 and CH4 emission from reservoirs are still poorly studied, especially in tropical regions where hydropower is growing rapidly. We performed spatially resolved measurements of dissolved CO2 and CH4 surface water concentrations and their gas-exchange coefficients (k) to compute diffusive carbon flux from four contrasting tropical reservoirs across Brazil during different hydrological seasons. Diffusive CO2 emissions were higher during the dry season than during the rainy season, whereas there were no consistent seasonal patterns for diffusive CH4 emissions. Our results reveal that the magnitude and the spatial within-reservoir patterns of diffusive CO2 and CH4 flux varied strongly among hydrological seasons. River inflow areas were often characterized by high seasonality in diffusive flux. Areas close to the dam generally showed low seasonal variability in diffusive CH4 flux but high variability in diffusive CO2 flux. Overall, we found that reservoir areas exhibiting highest emission rates (‘hotspots’) shifted substantially across hydrological seasons. Estimates of total diffusive carbon emission from the reservoir surfaces differed between hydrological seasons by a factor up to 7 in Chapéu D’Úvas reservoir, up to 13 in Curuá-Una reservoir, up to 4 in Furnas reservoir, and up to 1.8 in Funil reservoir, indicating that spatially-resolved measurements of gas concentrations and k need to be performed at different hydrological seasons in order to constrain annual diffusive carbon emission.

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