WorldWideScience

Sample records for influence co2 flux

  1. Influence of Land Cover and Climate on CO2 and CH4 fluxes from Urban Soils

    Science.gov (United States)

    Smith, R. M.; Groffman, P. M.; Kaushal, S.; Gold, A.; Cole, J. N.

    2015-12-01

    Soils are important sinks for greenhouse gases globally. Urbanization influences biogeochemical processes and gas fluxes through increased nitrogen deposition, heat island effects, and vegetation management. Previous work at the Baltimore Ecosystem Study LTER site has reported elevated CO2 fluxes and reduced CH4 consumption in urban soils. Differences among soils (urban forest, rural forest, lawns) have been linked to nitrogen cycling and may also be driven by temperature differences between land cover types. A combination of site-specific changes (land cover, nitrogen availability) and climatological (temperature, soil moisture) factors are likely to influence long-term patterns in gas fluxes and therefore carbon storage in growing urban regions. We utilized 15 years of measured gas fluxes and continuous temperature and soil moisture data to model CO2 emissions and CH4 consumption under different vegetation classes. We scaled these fluxes to the metropolitan region using high-resolution spatial, and found that regional CH4 consumption and CO2 fluxes are sensitive to changes in temperature and land cover. For instance, in 2007 land cover in Baltimore City had 21% lawn and 22% forest cover. If all of the lawn area in the city were converted to urban forest, CH4 consumption by urban soils would increase by 70% and CO2 emissions would decrease by 20%. In suburban Baltimore County, lawns and urban forests comprised 35 and 50% of land cover respectively. If all lawns in the county were converted to urban forest, soil CH4 consumption would increase by 55% and soil CO2 flux would decrease by 20%. Soil CO2 fluxes also increase by approximately 0.1g C m-2 d-1 for every 1° C increase across all land cover classes. CH4 consumption increases with temperature in urban and rural forest soils. Our results highlight the interacting effects of land cover change and climate on carbon fluxes from urban soils.

  2. Do plant species influence soil CO2 and N2O fluxes in a diverse tropical forest?

    Science.gov (United States)

    van Haren, Joost L. M.; de Oliveira, R. Cosme; Restrepo-Coupe, Natalia; Hutyra, Lucy; de Camargo, Plinio B.; Keller, Michael; Saleska, Scott R.

    2010-09-01

    To test whether plant species influence greenhouse gas production in diverse ecosystems, we measured wet season soil CO2 and N2O fluxes close to ˜300 large (>35 cm in diameter at breast height (DBH)) trees of 15 species at three clay-rich forest sites in central Amazonia. We found that soil CO2 fluxes were 38% higher near large trees than at control sites >10 m away from any tree (P growth rate (P = 0.002). These observations imply that through enhanced belowground carbon allocation liana and tree species can stimulate soil CO2 and N2O fluxes (by enhancing denitrification when carbon limits microbial metabolism). Alternatively, low N2O fluxes potentially result from strong competition of tree species with microbes for nutrients. Species-specific patterns in CO2 and N2O fluxes demonstrate that plant species can influence soil biogeochemical processes in a diverse tropical forest.

  3. Tree species influence soil-atmosphere fluxes of the greenhouse gases CO2, CH4 and N2O

    Science.gov (United States)

    Steffens, Christina; Vesterdal, Lars; Pfeiffer, Eva-Maria

    2016-04-01

    In the temperate zone, forests are the greatest terrestrial sink for atmospheric CO2, and tree species affect soil C stocks and soil CO2 emissions. When considering the total greenhouse gas (GHG) balance of the forest soil, the relevant GHGs CH4 and N2O should also be considered as they have a higher global warming potential than CO2. The presented data are first results from a field study in a common garden site in Denmark where tree species with ectomycorrhizal colonization (beech - Fagus sylvatica, oak - Quercus robur) and with arbuscular mycorrhizal colonization (maple - Acer pseudoplatanus, ash - Fraxinus excelsior) have been planted in monocultures in adjacent blocks of about 0.25 ha in the year 1973 on former arable land. The soil-atmosphere fluxes of all three gases were measured every second week since August 2015. The hypothesis is that the total GHG efflux from forest soil would differ between species, and that these differences could be related to the type of mycorrhizal association and leaf litter quality. Preliminary results (August to December 2015) indicate that tree species influence the fluxes (converted to CO2-eq) of the three GHGs. Total soil CO2 efflux was in the low end of the range reported for temperate broadleaved forests but similar to the measurements at the same site approximately ten years ago. It was highest under oak (9.6±2.4 g CO2 m-2 d-1) and lowest under maple (5.2±1.6 g CO2 m-2 d-1). In contrast, soil under oak was a small but significant sink for CH4(-0.005±0.003 g CO2-eq m-2 d-1), while there were almost no detectable CH4 fluxes in maple. Emissions of N2O were highest under beech (0.6±0.6 g CO2-eq m-2 d-1) and oak (0.2±0.09 g CO2-eq m-2 d-1) and lowest under ash (0.03±0.04 g CO2-eq m-2 d-1). In the total GHG balance, soil CH4 uptake was negligible (≤0.1% of total emissions). Emissions of N2O (converted to CO2-eq) contributed arbuscular mycorrhiza and produce leaf litter with a lower lignin:N ratio.

  4. CO2 fluxes near a forest edge

    DEFF Research Database (Denmark)

    Sogachev, Andrey; Leclerc, Monique Y.; Zhang, Gensheng

    2008-01-01

    In contrast with recent advances on the dynamics of the flow at a forest edge, few studies have considered its role on scalar transport and, in particular, on CO2 transfer. The present study addresses the influence of the abrupt roughness change on forest atmosphere CO2 exchange and contrasts...... as a function of both sources/sinks distribution and the vertical structure of the canopy. Results suggest that the ground source plays a major role in the formation of wave-like vertical CO2 flux behavior downwind of a forest edge, despite the fact that the contribution of foliage sources/sinks changes...... monotonously. Such a variation is caused by scalar advection in the trunk space and reveals itself as a decrease or increase in vertical fluxes over the forest relative to carbon dioxide exchange of the underlying forest. The effect was more pronounced in model forests where the leaf area is concentrated...

  5. Air-sea CO2 fluxes in the near-shore and intertidal zones influenced by the California Current

    Science.gov (United States)

    Reimer, Janet J.; Vargas, Rodrigo; Smith, Stephen V.; Lara-Lara, Ruben; Gaxiola-Castro, Gilberto; Martín Hernández-Ayón, J.; Castro, Angel; Escoto-Rodriguez, Martin; Martínez-Osuna, Juan

    2013-10-01

    The study of air-sea CO2 fluxes (FCO2) in the coastal region is needed to better understand the processes that influence the direction and magnitude of FCO2 and to constrain the global carbon budget. We implemented a 1 year (January through December 2009) paired study to measure FCO2 in the intertidal zone (the coastline to 1.6 km offshore) and the near-shore (˜3 km offshore) off the north-western coast of Baja California (Mexico); a region influenced by year-round upwelling. FCO2 was determined in the intertidal zone via eddy covariance; while in the near-shore using mooring buoy sensors then calculated with the bulk method. The near-shore region was a weak annual net source of CO2 to the atmosphere (0.043 mol CO2 m-2 y-1); where 91% of the outgassed FCO2 was contributed during the upwelling season. Sea surface temperature (SST) and ΔpCO2 (from upwelling) showed the strongest relationship with FCO2 in the near-shore, suggesting the importance of meso-scale processes (upwelling). FCO2 in the intertidal zone were up to four orders of magnitude higher than FCO2 in the near-shore. Wind speed showed the strongest relationship with FCO2 in the intertidal zone, suggesting the relevance of micro-scale processes. Results show that there are substantial spatial and temporal differences in FCO2 between the near-shore and intertidal zone; likely a result of heterogeneity. We suggest that detailed spatial and temporal measurements are needed across the coastal oceans and continental margins to better understand the mechanisms which control FCO2, as well as reduce uncertainties and constrain regional and global ocean carbon balances.

  6. CO2 flux geothermometer for geothermal exploration

    Science.gov (United States)

    Harvey, M. C.; Rowland, J. V.; Chiodini, G.; Rissmann, C. F.; Bloomberg, S.; Fridriksson, T.; Oladottir, A. A.

    2017-09-01

    A new geothermometer (TCO2 Flux) is proposed based on soil diffuse CO2 flux and shallow temperature measurements made on areas of steam heated, thermally altered ground above active geothermal systems. This CO2 flux geothermometer is based on a previously reported CO2 geothermometer that was designed for use with fumarole analysis. The new geothermometer provides a valuable additional exploration tool for estimating subsurface temperatures in high-temperature geothermal systems. Mean TCO2 Flux estimates fall within the range of deep drill hole temperatures at Wairakei (New Zealand), Tauhara (New Zealand), Rotokawa (New Zealand), Ohaaki (New Zealand), Reykjanes (Iceland) and Copahue (Argentina). The spatial distribution of geothermometry estimates is consistent with the location of major upflow zones previously reported at the Wairakei and Rotokawa geothermal systems. TCO2 Flux was also evaluated at White Island (New Zealand) and Reporoa (New Zealand), where limited sub-surface data exists. Mode TCO2 Flux at White Island is high (320 °C), the highest of the systems considered in this study. However, the geothermometer relies on mineral-water equilibrium in neutral pH reservoir fluids, and would not be reliable in such an active and acidic environment. Mean TCO2 Flux at Reporoa (310 °C) is high, which indicates Reporoa has a separate upflow from the nearby Waiotapu geothermal system; an outflow from Waiotapu would not be expected to have such high temperature.

  7. Quantifying the "chamber effect" in CO2 flux measurements

    Science.gov (United States)

    Vihermaa, Leena; Childs, Amy; Long, Hazel; Waldron, Susan

    2014-05-01

    The significance of aquatic CO2 emissions has received attention in recent years. For example annual aquatic emissions in the Amazon basin have been estimated as 500 Mt of carbon1. Methods for determining the flux rates include eddy covariance flux tower measurements, flux estimates calculated from partial pressure of CO2 (pCO2) in water and the use floating flux chambers connected to an infra-red gas analyser. The flux chamber method is often used because it is portable, cheaper and allows smaller scale measurements. It is also a direct method and hence avoids problems related to the estimation of the gas transfer coefficient that is required when fluxes are calculated from pCO2. However, the use of a floating chamber may influence the flux measurements obtained. The chamber shields the water underneath from effects of wind which could lead to lower flux estimates. Wind increases the flux rate by i) causing waves which increase the surface area for efflux, and ii) removing CO2 build up above the water surface, hence maintaining a higher concentration gradient. Many floating chambers have an underwater extension of the chamber below the float to ensure better seal to water surface and to prevent any ingress of atmospheric air when waves rock the chamber. This extension may cause additional turbulence in flowing water and hence lead to overestimation of flux rates. Some groups have also used a small fan in the chamber headspace to ensure thorough mixing of air in the chamber. This may create turbulence inside the chamber which could increase the flux rate. Here we present results on the effects of different chamber designs on the detected flux rates. 1Richey et al. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416: 617-620.

  8. Quantifying the drivers of ocean-atmosphere CO2 fluxes

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    Lauderdale, Jonathan M.; Dutkiewicz, Stephanie; Williams, Richard G.; Follows, Michael J.

    2016-07-01

    A mechanistic framework for quantitatively mapping the regional drivers of air-sea CO2 fluxes at a global scale is developed. The framework evaluates the interplay between (1) surface heat and freshwater fluxes that influence the potential saturated carbon concentration, which depends on changes in sea surface temperature, salinity and alkalinity, (2) a residual, disequilibrium flux influenced by upwelling and entrainment of remineralized carbon- and nutrient-rich waters from the ocean interior, as well as rapid subduction of surface waters, (3) carbon uptake and export by biological activity as both soft tissue and carbonate, and (4) the effect on surface carbon concentrations due to freshwater precipitation or evaporation. In a steady state simulation of a coarse-resolution ocean circulation and biogeochemistry model, the sum of the individually determined components is close to the known total flux of the simulation. The leading order balance, identified in different dynamical regimes, is between the CO2 fluxes driven by surface heat fluxes and a combination of biologically driven carbon uptake and disequilibrium-driven carbon outgassing. The framework is still able to reconstruct simulated fluxes when evaluated using monthly averaged data and takes a form that can be applied consistently in models of different complexity and observations of the ocean. In this way, the framework may reveal differences in the balance of drivers acting across an ensemble of climate model simulations or be applied to an analysis and interpretation of the observed, real-world air-sea flux of CO2.

  9. Air-sea flux of CO2 in arctic coastal waters influenced by glacial melt water and sea ice

    DEFF Research Database (Denmark)

    Sejr, Mikael Kristian; Krause-Jensen, Dorte; Rysgaard, Søren

    2011-01-01

    and thereby efficiently blocked air–sea CO2 exchange. During sea ice melt, dissolution of CaCO3 combined with primary production and strong stratification of the water column acted to lower surface-water pCO2 levels in the fjord. Also, a large input of glacial melt water containing geochemically reactive......Annual air–sea exchange ofCO2 inYoung Sound,NEGreenlandwas estimated using pCO2 surface-water measurements during summer (2006–2009) and during an ice-covered winter 2008. All surface pCO2 values were below atmospheric levels indicating an uptake of atmospheric CO2. During sea ice formation......, dissolved inorganic carbon (DIC) content is reduced causing sea ice to be under saturated in CO2. Approximately 1% of the DIC forced out of growing sea ice was released into the atmosphere while the remaining 99% was exported to the underlying water column. Sea ice covered the fjord 9 months a year...

  10. Spatial variation in landscape-level CO2 and CH4 fluxes from arctic coastal tundra: influence from vegetation, wetness, and the thaw lake cycle.

    Science.gov (United States)

    Sturtevant, Cove S; Oechel, Walter C

    2013-09-01

    Regional quantification of arctic CO2 and CH4 fluxes remains difficult due to high landscape heterogeneity coupled with a sparse measurement network. Most of the arctic coastal tundra near Barrow, Alaska is part of the thaw lake cycle, which includes current thaw lakes and a 5500-year chronosequence of vegetated thaw lake basins. However, spatial variability in carbon fluxes from these features remains grossly understudied. Here, we present an analysis of whole-ecosystem CO2 and CH4 fluxes from 20 thaw lake cycle features during the 2011 growing season. We found that the thaw lake cycle was largely responsible for spatial variation in CO2 flux, mostly due to its control on gross primary productivity (GPP). Current lakes were significant CO2 sources that varied little. Vegetated basins showed declining GPP and CO2 sink with age (R(2) = 67% and 57%, respectively). CH4 fluxes measured from a subset of 12 vegetated basins showed no relationship with age or CO2 flux components. Instead, higher CH4 fluxes were related to greater landscape wetness (R(2) = 57%) and thaw depth (additional R(2) = 28%). Spatial variation in CO2 and CH4 fluxes had good satellite remote sensing indicators, and we estimated the region to be a small CO2 sink of -4.9 ± 2.4 (SE) g C m(-2) between 11 June and 25 August, which was countered by a CH4 source of 2.1 ± 0.2 (SE) g C m(-2) . Results from our scaling exercise showed that developing or validating regional estimates based on single tower sites can result in significant bias, on average by a factor 4 for CO2 flux and 30% for CH4 flux. Although our results are specific to the Arctic Coastal Plain of Alaska, the degree of landscape-scale variability, large-scale controls on carbon exchange, and implications for regional estimation seen here likely have wide relevance to other arctic landscapes.

  11. On using radon-222 and CO2 to calculate regional-scale CO2 fluxes

    Directory of Open Access Journals (Sweden)

    A. I. Hirsch

    2006-11-01

    Full Text Available Because of its ubiquitous release on land and well-characterized atmospheric loss, radon-222 has been very useful for deducing fluxes of greenhouse gases such as CO2, CH4, and N2O. It is shown here that the radon-tracer method, used in previous studies to calculate regional-scale greenhouse gas fluxes, returns a weighted-average flux (the flux field F weighted by the sensitivity of the measurements to that flux field, f rather than an evenly-weighted spatial average flux. A synthetic data study using a Lagrangian particle dispersion model and modeled CO2 fluxes suggests that the discrepancy between the sensitivity-weighted average flux and evenly-weighted spatial average flux can be significant in the case of CO2, due to covariance between F and f for biospheric CO2 fluxes during the growing season and also for anthropogenic CO2 fluxes in general. A technique is presented to correct the radon-tracer derived fluxes to yield an estimate of evenly-weighted spatial average CO2 fluxes. A new method is also introduced for correcting the CO2 flux estimates for the effects of radon-222 radioactive decay in the radon-tracer method.

  12. On using radon-222 and CO2 to calculate regional-scale CO2 fluxes

    Directory of Open Access Journals (Sweden)

    A. I. Hirsch

    2007-07-01

    Full Text Available Because of its ubiquitous release on land and well-characterized atmospheric loss, radon-222 has been very useful for deducing fluxes of greenhouse gases such as CO2, CH4, and N2O. It is shown here that the radon-tracer method, used in previous studies to calculate regional-scale greenhouse gas fluxes, returns a weighted-average flux (the flux field F weighted by the sensitivity of the measurements to that flux field, f rather than an evenly-weighted spatial average flux. A synthetic data study using a Lagrangian particle dispersion model and modeled CO2 fluxes suggests that the discrepancy between the sensitivity-weighted average flux and evenly-weighted spatial average flux can be significant in the case of CO2, due to covariance between F and f for biospheric CO2 fluxes during the growing season and also for anthropogenic CO2 fluxes in general. A technique is presented to correct the radon-tracer derived fluxes to yield an estimate of evenly-weighted spatial average CO2 fluxes. A new method is also introduced for correcting the CO2 flux estimates for the effects of radon-222 radioactive decay in the radon-tracer method.

  13. Influence of biomass harvesting on fluxes of CO2 CH4 and N2O for a sedge fen in south-west Belarus

    Science.gov (United States)

    Burlo, A.; Minke, M.; Chuvashova, H.; Yarmashuk, T.; Augustin, J.; Thiele, A.; Tichonov, V.; Liashchynskaya, N.; Narkevitch, I.

    2012-04-01

    Until now, it is usual to drain a peatland to be able to use it economically. The consequences are a progressive peat loss and a negative climate impact caused by a strong emission of the greenhouse gases CO2 and N2O (Droesler et al., 2008). To avoid these negative effects of the peatland use, the concept of the so-called Paludiculture was developed. This is the harvest of plant biomass on wet and rewetted peatlands (Wichtmann & Joosten 2007). However, there is only few and contradictory information about the actual effect of the Paludiculture on the greenhouse gas fluxes, the peat carbon budget, and the climate balance so far. Therefore, we investigated the influence of late mowing on a sedge fen in the Paliessie region in SW Belarus. The site is characterized by Carex nigra, Carex rostrata, Calamagrostis canescens, Potentilla palustris, Drepanocladus aduncus and Rhizomnium punctatum and a mean water level close to the surface. The investigation covers two variants: Without use (control), and the removal of the aboveground biomass in late autumn. For every variant, we installed three soil collars distributed randomly as a base for the gas flux measurements. Since August 2010 the CO2, CH4 and N2O exchange rates are measured by the closed chamber approach of Droesler (2005). The first harvest of plant biomass was on 17th of November 2010. It turned out, that the single gas fluxes are influenced very differently by the biomass removal. In case of the CH4 a noticeable impact of mowing became evident directly after melting of the ice layer in spring 2011, when the emissions at the harvested plots for nearly doubled those from the control on two measurement campaigns. The N2O fluxes were very week but these are according to tendency lower on the harvest variant all the time. However, the ecosystem respiration did not show any clear reaction on the mowing at all. Furthermore, we will report about the effects of the biomass removal on the current net CO2 exchange, the

  14. Global CO2 fluxes estimated from GOSAT retrievals of total column CO2

    Directory of Open Access Journals (Sweden)

    S. Basu

    2013-09-01

    Full Text Available We present one of the first estimates of the global distribution of CO2 surface fluxes using total column CO2 measurements retrieved by the SRON-KIT RemoTeC algorithm from the Greenhouse gases Observing SATellite (GOSAT. We derive optimized fluxes from June 2009 to December 2010. We estimate fluxes from surface CO2 measurements to use as baselines for comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we can reproduce the observed CO2 time series at surface and TCCON sites in the tropics and the northern extra-tropics. In contrast, in the southern extra-tropics GOSAT XCO2 leads to enhanced seasonal cycle amplitudes compared to independent measurements, and we identify it as the result of a land–sea bias in our GOSAT XCO2 retrievals. A bias correction in the form of a global offset between GOSAT land and sea pixels in a joint inversion of satellite and surface measurements of CO2 yields plausible global flux estimates which are more tightly constrained than in an inversion using surface CO2 data alone. We show that assimilating the bias-corrected GOSAT data on top of surface CO2 data (a reduces the estimated global land sink of CO2, and (b shifts the terrestrial net uptake of carbon from the tropics to the extra-tropics. It is concluded that while GOSAT total column CO2 provide useful constraints for source–sink inversions, small spatiotemporal biases – beyond what can be detected using current validation techniques – have serious consequences for optimized fluxes, even aggregated over continental scales.

  15. Global CO2 fluxes estimated from GOSAT retrievals of total column CO2

    Directory of Open Access Journals (Sweden)

    M. Torn

    2013-02-01

    Full Text Available We present one of the first estimates of the global distribution of CO2 surface fluxes using total column CO2 measurements retrieved from the Greenhouse gases Observing SATellite (GOSAT. We derive optimized fluxes from June 2009 to December 2010. We estimate fluxes from surface CO2 measurements to use as baselines for comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we can reproduce the observed CO2 time series at surface and TCCON sites in the tropics and the northern extra-tropics. In contrast, in the southern extra-tropics GOSAT XCO2 leads to enhanced seasonal cycle amplitudes compared to independent measurements, and we identify it as the result of a land-sea bias in our GOSAT XCO2 retrievals. A bias correction in the form of a global offset between GOSAT land and sea pixels in a joint inversion of satellite and surface measurements of CO2 yields plausible global flux estimates which are more tightly constrained than in an inversion using surface CO2 data alone. We show that assimilating the bias-corrected GOSAT data on top of surface CO2 data (a reduces the estimated global land sink of CO2, and (b shifts the terrestrial net uptake of carbon from the tropics to the extra-tropics. It is concluded that while GOSAT total column CO2 provide useful constraints for source-sink inversions, small spatiotemporal biases – beyond what can be detected using current validation techniques – have serious consequences for optimized fluxes, even aggregated over continental scales.

  16. Comparison of regional and ecosystem CO2 fluxes

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Søgaard, Henrik; Batchvarova, Ekaterina

    2009-01-01

    A budget method to derive the regional surface flux of CO2 from the evolution of the boundary layer is presented and applied. The necessary input for the method can be deduced from a combination of vertical profile measurements of CO2 concentrations by i.e. an airplane, successive radio-soundings...

  17. Interactive effects of elevated CO2 and drought on nocturnal water fluxes in Eucalyptus saligna.

    Science.gov (United States)

    Zeppel, Melanie J B; Lewis, James D; Medlyn, Belinda; Barton, Craig V M; Duursma, Remko A; Eamus, Derek; Adams, Mark A; Phillips, Nathan; Ellsworth, David S; Forster, Michael A; Tissue, David T

    2011-09-01

    Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO(2) (elevated [CO(2)]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO(2)] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J(s)) and leaf area (E(t)) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J(s) and E(t) were observed during the severe drought period in the dry treatment under elevated [CO(2)], but not during moderate- and post-drought periods. Elevated [CO(2)] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J(s,r)), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J(s,c)). Elevated [CO(2)] wet (EW) trees exhibited higher J(s,r) than ambient [CO(2)] wet trees (AW) indicating greater water flux in elevated [CO(2)] under well-watered conditions. However, under drought conditions, elevated [CO(2)] dry (ED) trees exhibited significantly lower J(s,r) than ambient [CO(2)] dry trees (AD), indicating less water flux during stem recharge under elevated [CO(2)]. J(s,c) did not differ between ambient and elevated [CO(2)]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J(s,r) and had its greatest impact on J(s,r) at high D in ambient [CO(2)]. Our results suggest that elevated [CO(2)] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO(2)] affected J(s,r), it did not affect day-time water

  18. CO2 Fluxes and Concentrations in a Residential Area in the Southern Hemisphere

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    Weissert, L. F.; Salmond, J. A.; Turnbull, J. C.; Schwendenmann, L.

    2014-12-01

    While cities are generally major sources of anthropogenic carbon dioxide (CO2) emissions, recent research has shown that parts of urban areas may also act as CO2 sinks due to CO2 uptake by vegetation. However, currently available results are related to a large degree of uncertainty due to the limitations of the applied methods and the limited number of studies available from urban areas, particularly from the southern hemisphere. In this study, we explore the potential of eddy covariance and tracer measurements (13C and 14C isotopes of CO2) to quantify and partition CO2 fluxes and concentrations in a residential urban area in Auckland, New Zealand. Based on preliminary results from autumn and winter (March to July 2014) the residential area is a small source of CO2 (0.11 mol CO2 m-2 day-1). CO2 fluxes and concentrations follow a distinct diurnal cycle with a morning peak between 7:00 and 9:00 (max: 0.25 mol CO2 m-2 day-1/412 ppm) and midday low with negative CO2 fluxes (min: -0.17 mol CO2 m-2 day-1/392 ppm) between 10:00 and 15:00 local time, likely due to photosynthetic CO2 uptake by local vegetation. Soil CO2 efflux may explain that CO2 concentrations increase and remain high (401 ppm) throughout the night. Mean diurnal winter δ13C values are in anti-phase with CO2 concentrations and vary between -9.0 - -9.7‰. The depletion of δ13C compared to clean atmospheric air (-8.2‰) is likely a result of local CO2 sources dominated by gasoline combustion (appr. 60%) during daytime. A sector analysis (based on prevailing wind) of CO2 fluxes and concentrations indicates lower CO2 fluxes and concentrations from the vegetation-dominated sector, further demonstrating the influence of vegetation on local CO2 concentrations. These results provide an insight into the temporal and spatial variability CO2 fluxes/concentrations and potential CO2 sinks and sources from a city in the southern hemisphere and add valuable information to the global database of urban CO2 fluxes.

  19. Critical Considerations for Accurate Soil CO2 Flux Measurement

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    Xu, L.; Furtaw, M.; Madsen, R.; Welles, J.; Demetriades-Shah, T.; Anderson, D.; Garcia, R.; McDermitt, D.

    2005-12-01

    Soil respiration is a significant component of the carbon balance for an ecosystem, but the environmental (soil moisture, rain event, temperature etc.) and biological (photosynthesis, LAI etc.) factors that contribute to soil respiration remain poorly understood. This limits our ability to understand the carbon budget at the ecosystem level making it difficult to predict the impacts of climate change. Two important reasons for this poor understanding have been the difficulty in making accurate soil respiration measurements and the lack of continuous and long-term soil respiration data at sufficiently fine temporal and spatial scales. To meet these needs, we have developed a new automated multiplexing system, the LI-8100M, for obtaining reliable soil CO2 flux data at high spatial and temporal resolution. The system has the capability to continuously measure the soil CO2 flux at up to 16 locations. Soil CO2 flux is driven primarily by the CO2 diffusion gradient across the soil surface. Ideally, the flux measurement should be made without affecting the diffusion gradient and without having any chamber-induced pressure perturbation. In a closed-chamber system the slope of dCO2/dt is required to compute the flux. To obtain the slope of dCO2/dt, the chamber CO2 concentration must be allowed to rise. Consequently, soil CO2 flux will be affected because of the decreased CO2 diffusion gradient. To minimize the impact of decreased CO2 diffusion gradient on CO2 flux measurement in LI-8100M, the chamber CO2 concentration versus time is fitted with an exponential function. Soil CO2 flux is then estimated by calculating the initial slope from the exponential function at time zero when the chamber touches the soil, and that is when the chamber CO2 concentration is equal to the ambient. Our results show that the flux estimated from a linear function, the widely used method, could underestimate CO2 flux by more than 10% as compared with that from the exponential function. An

  20. Atmosphere–Surface Fluxes of CO2 using Spectral Techniques

    DEFF Research Database (Denmark)

    Sørensen, Lise Lotte; Larsen, Søren Ejling

    2010-01-01

    Different flux estimation techniques are compared here in order to evaluate air–sea exchange measurement methods used on moving platforms. Techniques using power spectra and cospectra to estimate fluxes are presented and applied to measurements of wind speed and sensible heat, latent heat and CO2...

  1. Progress in Modeling Global Atmospheric CO2 Fluxes and Transport: Results from Simulations with Diurnal Fluxes

    Science.gov (United States)

    Collatz, G. James; Kawa, R.

    2007-01-01

    Progress in better determining CO2 sources and sinks will almost certainly rely on utilization of more extensive and intensive CO2 and related observations including those from satellite remote sensing. Use of advanced data requires improved modeling and analysis capability. Under NASA Carbon Cycle Science support we seek to develop and integrate improved formulations for 1) atmospheric transport, 2) terrestrial uptake and release, 3) biomass and 4) fossil fuel burning, and 5) observational data analysis including inverse calculations. The transport modeling is based on meteorological data assimilation analysis from the Goddard Modeling and Assimilation Office. Use of assimilated met data enables model comparison to CO2 and other observations across a wide range of scales of variability. In this presentation we focus on the short end of the temporal variability spectrum: hourly to synoptic to seasonal. Using CO2 fluxes at varying temporal resolution from the SIB 2 and CASA biosphere models, we examine the model's ability to simulate CO2 variability in comparison to observations at different times, locations, and altitudes. We find that the model can resolve much of the variability in the observations, although there are limits imposed by vertical resolution of boundary layer processes. The influence of key process representations is inferred. The high degree of fidelity in these simulations leads us to anticipate incorporation of realtime, highly resolved observations into a multiscale carbon cycle analysis system that will begin to bridge the gap between top-down and bottom-up flux estimation, which is a primary focus of NACP.

  2. CO2 Flux Estimation Errors Associated with Moist Atmospheric Processes

    Science.gov (United States)

    Parazoo, N. C.; Denning, A. S.; Kawa, S. R.; Pawson, S.; Lokupitiya, R.

    2012-01-01

    Vertical transport by moist sub-grid scale processes such as deep convection is a well-known source of uncertainty in CO2 source/sink inversion. However, a dynamical link between vertical transport, satellite based retrievals of column mole fractions of CO2, and source/sink inversion has not yet been established. By using the same offline transport model with meteorological fields from slightly different data assimilation systems, we examine sensitivity of frontal CO2 transport and retrieved fluxes to different parameterizations of sub-grid vertical transport. We find that frontal transport feeds off background vertical CO2 gradients, which are modulated by sub-grid vertical transport. The implication for source/sink estimation is two-fold. First, CO2 variations contained in moist poleward moving air masses are systematically different from variations in dry equatorward moving air. Moist poleward transport is hidden from orbital sensors on satellites, causing a sampling bias, which leads directly to small but systematic flux retrieval errors in northern mid-latitudes. Second, differences in the representation of moist sub-grid vertical transport in GEOS-4 and GEOS-5 meteorological fields cause differences in vertical gradients of CO2, which leads to systematic differences in moist poleward and dry equatorward CO2 transport and therefore the fraction of CO2 variations hidden in moist air from satellites. As a result, sampling biases are amplified and regional scale flux errors enhanced, most notably in Europe (0.43+/-0.35 PgC /yr). These results, cast from the perspective of moist frontal transport processes, support previous arguments that the vertical gradient of CO2 is a major source of uncertainty in source/sink inversion.

  3. Kinetics of CO(2) fluxes outgassing from champagne glasses in tasting conditions: the role of temperature.

    Science.gov (United States)

    Liger-Belair, Gérard; Villaume, Sandra; Cilindre, Clara; Jeandet, Philippe

    2009-03-11

    Measurements of CO(2) fluxes outgassing from a flute poured with a standard Champagne wine initially holding about 11 g L(-1) of dissolved CO(2) were presented, in tasting conditions, all along the first 10 min following the pouring process. Experiments were performed at three sets of temperature, namely, 4 degrees C, 12 degrees C, and 20 degrees C, respectively. It was demonstrated that the lower the champagne temperature, the lower CO(2) volume fluxes outgassing from the flute. Therefore, the lower the champagne temperature, the lower its progressive loss of dissolved CO(2) concentration with time, which constitutes the first analytical proof that low champagne temperatures prolong the drink's chill and helps retains its effervescence. A correlation was also proposed between CO(2) volume fluxes outgassing from the flute poured with champagne and its continuously decreasing dissolved CO(2) concentration. Finally, the contribution of effervescence to the global kinetics of CO(2) release was discussed and modeled by the use of results developed over recent years. The temperature dependence of the champagne viscosity was found to play a major role in the kinetics of CO(2) outgassing from a flute. On the basis of this bubbling model, the theoretical influence of champagne temperature on CO(2) volume fluxes outgassing from a flute was discussed and found to be in quite good accordance with our experimental results.

  4. Quantification of the advected CO2 concentration due to upstream surface fluxes in aircraft vertical profiles

    Science.gov (United States)

    Font, A.; Morguí, J.-A.; Curcoll, R.; Rodó, X.

    2009-04-01

    A model framework which couples the Lagrangian Particle Dispersion Model FLEXPART (LPDM) with the new global surface flux inversion CarbonTracker from NOAA-ESRL (2007B release) is used to quantify the advected CO2 concentration from outbound surface fluxes to measured vertical profiles carried out during different seasons in 2006 at La Muela site in Spain (LMU; 41.60°N, 1.1°W). The Lagrangian Particle Dispersion Model FLEXPART (LPDM) calculates the influence of surface CO2 fluxes upwind of the study area, allowing us to identify those sources or sink areas that strongly modify the CO2 content of air masses that arrives at different altitudes of measured profiles. CarbonTracker is a new assimilation system that informs of global carbon fluxes at 1°x1° at 3 hours resolution. Coupling LPDM results with surface fluxes allows assessing the net CO2 contribution of identified areas to measured concentrations along the profiles above a reference or background concentration. Furthermore, it allows the quantification of the percentage of each component flux (biospheric, anthropogenic and oceanic) to each vertical layer. At LMU, biospheric fluxes account ~70% of total CO2 advection; fossil fuel ~25%; and ~5% is attributed to the oceanic ones. By far, late spring and summer profiles are largely influence by the biospheric component (~90%). Finally, the CO2 concentration above the background value of profiles measured on 22nd February, 13th October and 30th November 2006 are well explained by the advection of upstream surface fluxes. In other profiles examined, the variation of CO2 along the profile is partially explained by the advection of CO2 outbound fluxes.

  5. Recent global CO2 flux inferred from atmospheric CO2 observations and its regional analyses

    Directory of Open Access Journals (Sweden)

    J. M. Chen

    2011-11-01

    Full Text Available The net surface exchange of CO2 for the years 2002–2007 is inferred from 12 181 atmospheric CO2 concentration data with a time-dependent Bayesian synthesis inversion scheme. Monthly CO2 fluxes are optimized for 30 regions of the North America and 20 regions for the rest of the globe. Although there have been many previous multiyear inversion studies, the reliability of atmospheric inversion techniques has not yet been systematically evaluated for quantifying regional interannual variability in the carbon cycle. In this study, the global interannual variability of the CO2 flux is found to be dominated by terrestrial ecosystems, particularly by tropical land, and the variations of regional terrestrial carbon fluxes are closely related to climate variations. These interannual variations are mostly caused by abnormal meteorological conditions in a few months in the year or part of a growing season and cannot be well represented using annual means, suggesting that we should pay attention to finer temporal climate variations in ecosystem modeling. We find that, excluding fossil fuel and biomass burning emissions, terrestrial ecosystems and oceans absorb an average of 3.63 ± 0.49 and 1.94 ± 0.41 Pg C yr−1, respectively. The terrestrial uptake is mainly in northern land while the tropical and southern lands contribute 0.62 ± 0.47, and 0.67 ± 0.34 Pg C yr−1 to the sink, respectively. In North America, terrestrial ecosystems absorb 0.89 ± 0.18 Pg C yr−1 on average with a strong flux density found in the south-east of the continent.

  6. Recent global CO2 flux inferred from atmospheric CO2 observations and its regional analyses

    Directory of Open Access Journals (Sweden)

    J. M. Chen

    2011-04-01

    Full Text Available The net surface exchange of CO2 for the years 2002–2007 is inferred from 12 181 atmospheric CO2 concentration data with a time-dependent Bayesian synthesis inversion scheme. Monthly CO2 fluxes are optimized for 30 regions of the North America and 20 regions for the rest of the globe. Although there have been many previous multiyear inversion studies, the reliability of atmospheric inversion techniques is not yet been systematically evaluated for quantifying regional interannual variability in the carbon cycle. In this study, the global interannual variability of the CO2 flux is found to be dominated by terrestrial ecosystems and is mostly caused by tropical land, and the variations of regional terrestrial carbon fluxes are closely related to climate variations. These interannual variations are mostly caused by abnormal meteorological conditions in a few months in the year or part of a growing season and cannot be well represented using annual means, suggesting that we should pay attention to monthly or submonthly climate variations in ecosystem modeling. We find that, excluding fossil fuel and biomass burning emissions, terrestrial ecosystems and oceans absorb an average of 3.63±0.49 and 1.94±0.41 Pg C/yr, respectively. The terrestrial uptake is mainly in northern land while the tropical and southern lands contribute 0.62±0.47, and 0.67±0.34 Pg C/yr to the sink, respectively. In North America, terrestrial ecosystems absorb 0.89±0.18 Pg C/yr on average with a strong flux density found in the south-east of the continent.

  7. CO2 fluxes from a tropical neighborhood: sources and sinks

    Science.gov (United States)

    Velasco, E.; Roth, M.; Tan, S.; Quak, M.; Britter, R.; Norford, L.

    2011-12-01

    Cities are the main contributors to the CO2 rise in the atmosphere. The CO2 released from the various emission sources is typically quantified by a bottom-up aggregation process that accounts for emission factors and fossil fuel consumption data. This approach does not consider the heterogeneity and variability of the urban emission sources, and error propagation can result in large uncertainties. In this context, direct measurements of CO2 fluxes that include all major and minor anthropogenic and natural sources and sinks from a specific district can be used to evaluate emission inventories. This study reports and compares CO2 fluxes measured directly using the eddy covariance method with emissions estimated by emissions factors and activity data for a residential neighborhood of Singapore, a highly populated and urbanized tropical city. The flux measurements were conducted during one year. No seasonal variability was found as a consequence of the constant climate conditions of tropical places; but a clear diurnal pattern with morning and late afternoon peaks in phase with the rush-hour traffic was observed. The magnitude of the fluxes throughout daylight hours is modulated by the urban vegetation, which is abundant in terms of biomass but not of land-cover (15%). Even though the carbon uptake by vegetation is significant, it does not exceed the anthropogenic emissions and the monitored district is a net CO2 source of 20.3 ton km-2 day-1 on average. The carbon uptake by vegetation is investigated as the difference between the estimated emissions and the measured fluxes during daytime.

  8. Increasing CO2 flux at Pisciarelli, Campi Flegrei, Italy

    Directory of Open Access Journals (Sweden)

    M. Queißer

    2017-09-01

    Full Text Available The Campi Flegrei caldera is located in the metropolitan area of Naples (Italy and has been undergoing different stages of unrest since 1950, evidenced by episodes of significant ground uplift followed by minor subsidence, increasing and fluctuating emission strengths of water vapor and CO2 from fumaroles, and periodic seismic crises. We deployed a scanning laser remote-sensing spectrometer (LARSS that measured path-integrated CO2 concentrations in the Pisciarelli area in May 2017. The resulting mean CO2 flux is 578 ± 246 t d−1. Our data suggest a significant increase in CO2 flux at this site since 2015. Together with recent geophysical observations, this suggests a greater contribution of the magmatic source to the degassing and/or an increase in permeability at shallow levels. Thanks to the integrated path soundings, LARSS may help to give representative measurements from large regions containing different CO2 sources, including fumaroles, low-temperature vents, and degassing soils, helping to constrain the contribution of deep gases and their migration mechanisms towards the surface.

  9. Surface CO2 fluxes implied by a full year of OCO-2 column CO2 measurements

    Science.gov (United States)

    Baker, D. F.

    2015-12-01

    Over one year of full-column CO2 concentration data is now available from the Orbiting Carbon Observatory (OCO-2) satellite, with retrieval biases corrected using upward-looking solar spectrometer data from the TCCON network as well with internal consistency checks. We use this OCO-2 data to estimate weekly surface CO2 flux corrections at 6.7ºx6.7º resolution with a variational data assimilation technique built around the off-line PCTM atmospheric transport model driven with MERRA 1ºx1.25° winds and mixing parameters. Since such flux estimates can depend strongly on the prior fluxes assumed (which may remain unchanged in regions of sparse sampling), the initial 3-D concentrations assumed (especially in the upper part of the atmosphere), vertical transport/mixing errors in the model, and un-corrected biases in the satellite data, we invert the OCO-2 data in multiple inversions in which different prior fluxes are used (e.g. SiB4 vs. CASA land bio, Takahashi vs. Doney ocean, FFDAS vs. CDIAC fossil fuel), in which ACOS GOSAT data and NOAA surface in situ and aircraft profile data are used (or not) to correct the prior fluxes and concentration fields, and in which the vertical mixing in the transport model is artificially increased/decreased by a factor of 3, to assess the sensitivity of the OCO-2 flux corrections. These inversions are done in the context of a longer span (2009-2015) to allow the impact of the fluxes and other data sources to fully impact the upper layers of the model. The bias between the OCO-2 data and the prior forward CO2 fields is also calculated before doing the inversions, and compared to similar retrieval biases solved for the ACOS GOSAT data (B3.5). The impact of these bias corrections, as well as the standard ones provided by the OCO-2 team, is assessed by comparing the fit of the a posteriori CO2 fields to independent data (including surface in situ and NOAA aircraft).

  10. CO2 fluxes at wetland ecosystems in European Russia

    Science.gov (United States)

    Kurbatova, J.; Astafeva, E.; Ivanov, D.; Avilov, V.; Valentini, R.

    2012-12-01

    Peatlands are one of the main element of natural landscapes of Russia (about 10% of territory). Chamber measurements of CO2 fluxes from soil with vegetation were conducted during green seasons 2011, 2012 years in European part of Russia (Central Forest Reserve, Tver region). Two main subjects were selected for field researches: ombrotrophic bog and wet spruce forest. Our previous eddy covariance investigations in the ecosystems have allowed to determine that in common wet forest is source of CO2 for atmosphere but ombrotrophic bog is sink for CO2. Chamber measurements have evaluated net ecosystems exchange, soil respiration, photosynthesis of grass cover and their depending on environmental factors. Photosynthesis of vegetation cover on the bog is significantly more than at the forest. Variation in water level dynamics alone could significantly affect the C balance as at the bog as at the wet forest mainly through altering the decomposition rate of the organic matter accumulated in the soil profile.

  11. CO2 fluxes in wetlands of European Russia

    Science.gov (United States)

    Kurbatova, J.; Tatarinov, F.; Avilov, V.; Varlagin, A.; Olchev, A.

    2012-04-01

    The question on an arrangement, scales and the factors determining ground sink of CO2 in a forest zone of Russia is opened and discussed. Peatlands located in forest zone and wetland forest are main elements of natural landscapes of Russia. During the last years through fires in forest zone and modern climate changes, connected with growth of extreme weather events, such as drought, wetlands are in the focus of scientific investigations. Two subjects for long investigations of CO2 fluxes have selected in southern taiga in European Russia (Central Forest reserve, Tver region): ombrotrophic bog and wet spruce forest. To estimate of seasonal and interannual variations of CO2 fluxes different methods such as eddy covariance, chamber methods and modeling calculations were used. Our researches have allowed to evaluate net ecosystems exchange, soil respiration, photosynthesis of grass cover and their depending on environmental factors. The results of researches have confirmed strong dependence of CO2 fluxes from changes in precipitations and/or temperatures and level of ground water. Bog and wetland forests can be as sink as source of CO2 for atmosphere. Variation in water level dynamics alone could significantly affect the C balance in wetland ecosystems mainly through altering the decomposition rate of the organic matter accumulated in the soil profile. The modeled results supported the hypothesis that the soil processes, especially the decomposition process, in wetlands could play an important role in altering the C dynamics in the ecosystems. The studies were supported by grand RFBR No. 11-05-00854 and RF Government No. 11.G34.31.0079.

  12. Sampling Soil CO2 for Isotopic Flux Partitioning: Non Steady State Effects and Methodological Biases

    Science.gov (United States)

    Snell, H. S. K.; Robinson, D.; Midwood, A. J.

    2014-12-01

    Measurements of δ13C of soil CO2 are used to partition the surface flux into autotrophic and heterotrophic components. Models predict that the δ13CO2 of the soil efflux is perturbed by non-steady state (NSS) diffusive conditions. These could be large enough to render δ13CO2 unsuitable for accurate flux partitioning. Field studies sometimes find correlations between efflux δ13CO2 and flux or temperature, or that efflux δ13CO2 is not correlated as expected with biological drivers. We tested whether NSS effects in semi-natural soil were comparable with those predicted. We compared chamber designs and their sensitivity to changes in efflux δ13CO2. In a natural soil mesocosm, we controlled temperature to generate NSS conditions of CO2 production. We measured the δ13C of soil CO2 using in situ probes to sample the subsurface, and dynamic and forced-diffusion chambers to sample the surface efflux. Over eight hours we raised soil temperature by 4.5 OC to increase microbial respiration. Subsurface CO2 concentration doubled, surface efflux became 13C-depleted by 1 ‰ and subsurface CO2 became 13C-enriched by around 2 ‰. Opposite changes occurred when temperature was lowered and CO2 production was decreasing. Different chamber designs had inherent biases but all detected similar changes in efflux δ13CO2, which were comparable to those predicted. Measurements using dynamic chambers were more 13C-enriched than expected, probably due to advection of CO2 into the chamber. In the mesocosm soil, δ13CO2 of both efflux and subsurface was determined by physical processes of CO2 production and diffusion. Steady state conditions are unlikely to prevail in the field, so spot measurements of δ13CO2 and assumptions based on the theoretical 4.4 ‰ diffusive fractionation will not be accurate for estimating source δ13CO2. Continuous measurements could be integrated over a period suitable to reduce the influence of transient NSS conditions. It will be difficult to disentangle

  13. Uncertainty analysis of CO2 flux components in subtropical evergreen coniferous plantation

    Institute of Scientific and Technical Information of China (English)

    LIU Min; HE HongLin; YU GuiRui; LUO YiQi; SUN XiaoMin; WANG HuiMin

    2009-01-01

    We present an uncertainty analysis of ecological process parameters and CO2 flux components (Reco, NEE and gross ecosystem exchange (GEE)) derived from 3 years continuous eddy covariance meas-urements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters and CO2 flux components. The results show that: (1) Random flux error more closely follows a dou-ble-exponential (Laplace), rather than a normal (Gaussian) distribution. (2) Different optimization meth-ods result in different estimates of model parameters. Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary least square method (OLS). (3) The differences between simulated Rrco, NEE and GEE derived from MLE and those derived for a given parameter optimization method, e temperature-dependent model (T_model) and the models methods are more important than the ecological models in influencing uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO2 flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the timescale, the smaller the uncertainty. The relative uncertainties of Reco, NEE and GEE are 4%-8%, 7%-22% and 2%-4% respectively at annual timescale.

  14. How can mountaintop CO2 observations be used to constrain regional carbon fluxes?

    Science.gov (United States)

    Lin, John C.; Mallia, Derek V.; Wu, Dien; Stephens, Britton B.

    2017-05-01

    Despite the need for researchers to understand terrestrial biospheric carbon fluxes to account for carbon cycle feedbacks and predict future CO2 concentrations, knowledge of these fluxes at the regional scale remains poor. This is particularly true in mountainous areas, where complex meteorology and lack of observations lead to large uncertainties in carbon fluxes. Yet mountainous regions are often where significant forest cover and biomass are found - i.e., areas that have the potential to serve as carbon sinks. As CO2 observations are carried out in mountainous areas, it is imperative that they are properly interpreted to yield information about carbon fluxes. In this paper, we present CO2 observations at three sites in the mountains of the western US, along with atmospheric simulations that attempt to extract information about biospheric carbon fluxes from the CO2 observations, with emphasis on the observed and simulated diurnal cycles of CO2. We show that atmospheric models can systematically simulate the wrong diurnal cycle and significantly misinterpret the CO2 observations, due to erroneous atmospheric flows as a result of terrain that is misrepresented in the model. This problem depends on the selected vertical level in the model and is exacerbated as the spatial resolution is degraded, and our results indicate that a fine grid spacing of ˜ 4 km or less may be needed to simulate a realistic diurnal cycle of CO2 for sites on top of the steep mountains examined here in the American Rockies. In the absence of higher resolution models, we recommend coarse-scale models to focus on assimilating afternoon CO2 observations on mountaintop sites over the continent to avoid misrepresentations of nocturnal transport and influence.

  15. Historical patterns of acidification and increasing CO2 flux associated with Florida springs

    Science.gov (United States)

    Barrera, Kira E.; Robbins, Lisa L.

    2017-01-01

    Florida has one of the highest concentrations of springs in the world, with many discharging into rivers and predominantly into eastern Gulf of Mexico coast, and they likely influence the hydrochemistry of these adjacent waters; however, temporal and spatial trends have not been well studied. We present over 20 yr of hydrochemical, seasonally sampled data to identify temporal and spatial trends of pH, alkalinity, partial pressure of carbon dioxide (pCO2), and CO2flux from five first-order-magnitude (springs that discharge greater than 2.83 m3 s−1) coastal spring groups fed by the Floridan Aquifer System that ultimately discharge into the Gulf of Mexico. All spring groups had pCO2 levels (averages 3174.3–6773.2 μatm) that were much higher than atmospheric levels of CO2 and demonstrated statistically significant temporal decreases in pH and increases in CO2 flux, pCO2, and alkalinity. Total carbon flux emissions increased from each of the spring groups by between 3.48 × 107 and 2.856 × 108 kg C yr−1 over the time period. By 2013 the Springs Groups in total emitted more than 1.1739 × 109 kg C yr−1. Increases in alkalinity and pCO2 varied from 90.9 to 347.6 μmol kg−1 and 1262.3 to 2666.7 μatm, respectively. Coastal data show higher CO2 evasion than the open Gulf of Mexico, which suggests spring water influences nearshore waters. The results of this study have important implications for spring water quality, dissolution of the Florida carbonate platform, and identification of the effect and partitioning of carbon fluxes to and within coastal and marine ecosystems.

  16. Soil CO2, N2O and Nox Flux Responses to Biofuel Crop Plantation

    Science.gov (United States)

    Liang, L.; Eberwein, J.; Allsman, L.; Grantz, D. A.; Jenerette, D.

    2014-12-01

    Biofuel crops in high temperature environments, e.g, sorghum in southern California, USA, have a high capacity to assimilate atmospheric CO2. Photosynthates from the canopy may provide extra labile carbon source to feed soil microorganisms and influence trace gas fluxes, including CO2, N2O and NOx. Understanding how soil microorganisms balance the carbon (energy) and nitrogen (nutrients) allocation between growing microbial biomass and respiration is critical for evaluating the GHG emissions and emissions of regional air quality pollutants. We conducted experiments in a high temperature agroecosystem both in fallow and sorghum production fields with an experimental nitrogen gradient (0,50 and 100 kg/ha, marked as control, low and high with triplicate repeat) to investigate the CO2, N2O and NOx flux responses. All gas fluxes were measured simultaneously from three replicate locations for each treatment in the field biweekly. Measurements were performed 2-5 days after irrigation. We found that planting sorghum has significant effects on soil CO2 (p<0.0001), N2O (p<0.0001) and NOx (p=0.04) fluxes, but nitrogen amendments only have marginally significant effects on CO2 flux (p=0.07). Surprisingly, no significant response of N2O (p=0.27) and NOx (p=0.61) were observed in responses to N amendments. Compared to the fallow field, the CO2 flux in sorghum field increased 77%, 134% and 202% in control, low and high N level amendments, respectively. N2O flux from the sorghum field are consistently higher than from fallow field, with 207%, 174% and 1064% increase in control, low and high N level amendments, respectively. For the NOx flux, no significant difference was found between fallow and sorghum field. Although nitrogen amendments did not show significant effects on CO2, N2O and NOx flux, the high N treatment in sorghum field continuously gains the highest flux rates. Our results suggested additional C inputs may be an important factor regulating CO2, N2O and NOx fluxes in

  17. Estimation of sensible heat, water vapor, and CO2 fluxes using the flux-variance method.

    Science.gov (United States)

    Hsieh, Cheng-I; Lai, Mei-Chun; Hsia, Yue-Joe; Chang, Tsang-Jung

    2008-07-01

    This study investigated the flux-variance relationships of temperature, humidity, and CO(2), and examined the performance of using this method for predicting sensible heat (H), water vapor (LE), and CO(2) fluxes (F(CO2)) with eddy-covariance measured flux data at three different ecosystems: grassland, paddy rice field, and forest. The H and LE estimations were found to be in good agreement with the measurements over the three fields. The prediction accuracy of LE could be improved by around 15% if the predictions were obtained by the flux-variance method in conjunction with measured sensible heat fluxes. Moreover, the paddy rice field was found to be a special case where water vapor follows flux-variance relation better than heat does. However, the CO(2) flux predictions were found to vary from poor to fair among the three sites. This is attributed to the complicated CO(2) sources and sinks distribution. Our results also showed that heat and water vapor were transported with the same efficiency above the grassland and rice paddy. For the forest, heat was transported 20% more efficiently than evapotranspiration.

  18. Comparing Global Atmospheric CO2 Flux and Transport Models with Remote Sensing (and Other) Observations

    Science.gov (United States)

    Kawa, S. R.; Collatz, G. J.; Pawson, S.; Wennberg, P. O.; Wofsy, S. C.; Andrews, A. E.

    2010-01-01

    We report recent progress derived from comparison of global CO2 flux and transport models with new remote sensing and other sources of CO2 data including those from satellite. The overall objective of this activity is to improve the process models that represent our understanding of the workings of the atmospheric carbon cycle. Model estimates of CO2 surface flux and atmospheric transport processes are required for initial constraints on inverse analyses, to connect atmospheric observations to the location of surface sources and sinks, to provide the basic framework for carbon data assimilation, and ultimately for future projections of carbon-climate interactions. Models can also be used to test consistency within and between CO2 data sets under varying geophysical states. Here we focus on simulated CO2 fluxes from terrestrial vegetation and atmospheric transport mutually constrained by analyzed meteorological fields from the Goddard Modeling and Assimilation Office for the period 2000 through 2009. Use of assimilated meteorological data enables direct model comparison to observations across a wide range of scales of variability. The biospheric fluxes are produced by the CASA model at 1x1 degrees on a monthly mean basis, modulated hourly with analyzed temperature and sunlight. Both physiological and biomass burning fluxes are derived using satellite observations of vegetation, burned area (as in GFED-3), and analyzed meteorology. For the purposes of comparison to CO2 data, fossil fuel and ocean fluxes are also included in the transport simulations. In this presentation we evaluate the model's ability to simulate CO2 flux and mixing ratio variability in comparison to remote sensing observations from TCCON, GOSAT, and AIRS as well as relevant in situ observations. Examples of the influence of key process representations are shown from both forward and inverse model comparisons. We find that the model can resolve much of the synoptic, seasonal, and interannual

  19. Land use and rainfall effect on soil CO2 fluxes in a Mediterranean agroforestry system

    Science.gov (United States)

    Quijano, Laura; Álvaro-Fuentes, Jorge; Lizaga, Iván; Navas, Ana

    2017-04-01

    Soils are the largest C reservoir of terrestrial ecosystems and play an important role in regulating the concentration of CO2 in the atmosphere. The exchange of CO2 between the atmosphere and soil controls the balance of C in soils. The CO2 fluxes may be influenced by climate conditions and land use and cover change especially in the upper soil organic layer. Understanding C dynamics is important for maintaining C stocks to sustain and improve soil quality and to enhance sink C capacity of soils. This study focuses on the response of the CO2 emitted to rainfall events from different land uses (i.e. forest, abandoned cultivated soils and winter cereal cultivated soils) in a representative Mediterranean agroforestry ecosystem in the central part of the Ebro basin, NE Spain (30T 4698723N 646424E). A total of 30 measurement points with the same soil type (classified as Calcisols) were selected. Soil CO2 flux was measured in situ using a portable EGM-4 CO2 analyzer PPSystems connected to a dynamic chamber system (model CFX-1, PPSystems) weekly during autumn 2016. Eleven different rainfall events were measured at least 24 hours before (n=7) and after the rainfall event (n=4). Soil water content and temperature were measured at each sampling point within the first 5 cm. Soil samples were taken at the beginning of the experiment to determine soil organic carbon (SOC) content using a LECO RC-612. The mean SOC for forest, abandoned and cultivated soils were 2.5, 2.7 and 0.6 %, respectively. The results indicated differences in soil CO2 fluxes between land uses. The field measurements of CO2 flux show that before cereal sowing the highest values were recorded in the abandoned soils varying from 56.1 to 171.9 mg CO2-C m-2 h-1 whereas after cereal sowing the highest values were recorded in cultivated soils ranged between 37.8 and 116.2 mg CO2-C m-2 h-1 indicating the agricultural impact on CO2 fluxes. In cultivated soils, lower mean CO2 fluxes were measured after direct seeding

  20. Regional CO2 flux estimates for 2009–2010 based on GOSAT and ground-based CO2 observations

    Directory of Open Access Journals (Sweden)

    S. Maksyutov

    2013-09-01

    Full Text Available We present the application of a global carbon cycle modeling system to the estimation of monthly regional CO2 fluxes from the column-averaged mole fractions of CO2 (XCO2 retrieved from spectral observations made by the Greenhouse gases Observing SATellite (GOSAT. The regional flux estimates are to be publicly disseminated as the GOSAT Level 4 data product. The forward modeling components of the system include an atmospheric tracer transport model, an anthropogenic emissions inventory, a terrestrial biosphere exchange model, and an oceanic flux model. The atmospheric tracer transport was simulated using isentropic coordinates in the stratosphere and was tuned to reproduce the age of air. We used a fossil fuel emission inventory based on large point source data and observations of nighttime lights. The terrestrial biospheric model was optimized by fitting model parameters to observed atmospheric CO2 seasonal cycle, net primary production data, and a biomass distribution map. The oceanic surface pCO2 distribution was estimated with a 4-D variational data assimilation system based on reanalyzed ocean currents. Monthly CO2 fluxes of 64 sub-continental regions, between June 2009 and May 2010, were estimated from GOSAT FTS SWIR Level 2 XCO2 retrievals (ver. 02.00 gridded to 5° × 5° cells and averaged on a monthly basis and monthly-mean GLOBALVIEW-CO2 data. Our result indicated that adding the GOSAT XCO2 retrievals to the GLOBALVIEW data in the flux estimation brings changes to fluxes of tropics and other remote regions where the surface-based data are sparse. The uncertainties of these remote fluxes were reduced by as much as 60% through such addition. Optimized fluxes estimated for many of these regions, were brought closer to the prior fluxes by the addition of the GOSAT retrievals. In most of the regions and seasons considered here, the estimated fluxes fell within the range of natural flux variabilities estimated with the component models.

  1. Diffuse degassing at Longonot volcano, Kenya: Implications for CO2 flux in continental rifts

    Science.gov (United States)

    Robertson, Elspeth; Biggs, Juliet; Edmonds, Marie; Clor, Laura; Fischer, Tobias P.; Vye-Brown, Charlotte; Kianji, Gladys; Koros, Wesley; Kandie, Risper

    2016-11-01

    Magma movement, fault structures and hydrothermal systems influence volatile emissions at rift volcanoes. Longonot is a Quaternary caldera volcano located in the southern Kenyan Rift, where regional extension controls recent shallow magma ascent. Here we report the results of a soil carbon dioxide (CO2) survey in the vicinity of Longonot volcano, as well as fumarolic gas compositions and carbon isotope data. The total non-biogenic CO2 degassing is estimated at < 300 kg d- 1, and is largely controlled by crater faults and fractures close to the summit. Thus, recent volcanic structures, rather than regional tectonics, control fluid pathways and degassing. Fumarolic gases are characterised by a narrow range in carbon isotope ratios (δ13C), from - 4.7‰ to - 6.4‰ (vs. PDB) suggesting a magmatic origin with minor contributions from biogenic CO2. Comparison with other degassing measurements in the East African Rift shows that records of historical eruptions or unrest do not correspond directly to the magnitude of CO2 flux from volcanic centres, which may instead reflect the current size and characteristics of the subsurface magma reservoir. Interestingly, the integrated CO2 flux from faulted rift basins is reported to be an order of magnitude higher than that from any of the volcanic centres for which CO2 surveys have so far been reported.

  2. Uncertainty analysis of CO2 flux components in subtropical evergreen coniferous plantation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    We present an uncertainty analysis of ecological process parameters and CO2 flux components (Reco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance meas-urements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters and CO2 flux components. The results show that: (1) Random flux error more closely follows a dou-ble-exponential (Laplace), rather than a normal (Gaussian) distribution. (2) Different optimization meth-ods result in different estimates of model parameters. Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary least square method (OLS). (3) The differences between simulated Reco, NEE and GEE derived from MLE and those derived from OLS are 12.18% (176 g C·m-2·a-1), 34.33% (79 g C·m-2·a-1) and 5.4% (92 g C·m-2·a-1). However, for a given parameter optimization method, a temperature-dependent model (T_model) and the models derived from a temperature and water-dependent model (TW_model) are 1.31% (17.8 g C·m-2·a-1), 2.1% (5.7 g C·m-2·a-1), and 0.26% (4.3 g C·m-2·a-1), respectively, which suggested that the optimization methods are more important than the ecological models in influencing uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO2 flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the timescale, the smaller the uncertainty. The relative uncertainties of Reco, NEE and GEE are 4%-8%, 7%-22% and 2%-4% respectively at annual timescale.

  3. Study on the processing method of nighttime CO2 eddy covariance flux data in ChinaFLUX

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>At present, using Eddy Covariance (EC) method to estimate the "true value" of carbon sequestration in terrestrial ecosystem arrests more attention. However, one issue is how to solve the uncertainty of observations (especially the nighttime CO2 flux data) appearing in post-processing CO2 flux data. The ratio of effective and reliable nighttime EC CO2 flux data to all nighttime data is relatively low (commonly, less than 50%) for all the long-term and continuous observation stations in the world. Thus, the processing method of nighttime CO2 flux data and its effect analysis on estimating CO2 flux annual sums are very important. In this paper, the authors analyze and discuss the reasons for underestimating nighttime CO2 flux using EC method, and introduce the general theory and method for processing nighttime CO2 flux data. By analyzing the relationship between nighttime CO2 flux and air fraction velocity u., we present an alternate method, Average Values Test (AVT), to determine the thresholds of fraction velocity (u.c) for screening the effective nighttime CO2 flux data. Meanwhile, taking the data observed in Yucheng and Changbai Mountains stations for an example, we analyze and discuss the effects of different methods or parameters on nighttime CO2 flux estimations. Finally, based on the data of part ChinaFLUX stations and related literatures, empirical models of nighttime respiration at different sites in ChinaFLUX are summarized.

  4. Comparison of CO2 fluxes estimated using atmospheric and oceanic inversions, and role of fluxes and their interannual variability in simulating atmospheric CO2 concentrations

    Science.gov (United States)

    Patra, P. K.; Mikaloff Fletcher, S. E.; Ishijima, K.; Maksyutov, S.; Nakazawa, T.

    2006-07-01

    We use a time-dependent inverse (TDI) model to estimate regional sources and sinks of atmospheric CO2 from 64 and then 22 regions based on atmospheric CO2 observations at 87 stations. The air-sea fluxes from the 64-region atmospheric-CO2 inversion are compared with fluxes from an analogous ocean inversion that uses ocean interior observations of dissolved inorganic carbon (DIC) and other tracers and an ocean general circulation model (OGCM). We find that, unlike previous atmospheric inversions, our flux estimates in the southern hemisphere are generally in good agreement with the results from the ocean inversion, which gives us added confidence in our flux estimates. In addition, a forward tracer transport model (TTM) is used to simulate the observed CO2 concentrations using (1) estimates of fossil fuel emissions and a priori estimates of the terrestrial and oceanic fluxes of CO2, and (2) two sets of TDI model corrected fluxes. The TTM simulations of TDI model corrected fluxes show improvements in fitting the observed interannual variability in growth rates and seasonal cycles in atmospheric CO2. Our analysis suggests that the use of interannually varying (IAV) meteorology and a larger observational network have helped to capture the regional representation and interannual variabilities in CO2 fluxes realistically.

  5. Air-sea CO2 fluxes in the Atlantic as measured during the FICARAM cruises

    Directory of Open Access Journals (Sweden)

    A. F. Ríos

    2009-06-01

    Full Text Available A total of fourteen hydrographic cruises spanning from 2000 to 2008 were conducted during the spring and autumn seasons between Spain and the Southern Ocean, under the framework of the Spanish research project FICARAM. The performed underway measurements are processed and analysed to describe the meridional air-sea CO2 fluxes (FCO2 along the Atlantic Ocean. The data was organised into different biogeochemical oceanographic provinces, according mainly to the thermohaline characteristics. The obtained spatial and temporal distributions of FCO2 follow the generally expected patterns and annual trends. The Subtropical regions in both hemispheres alternated the CO2 source and sink nature from autumn to spring, respectively. On the other hand, Tropical waters and the Patagonian Sea clearly behaved as sinks of atmospheric CO2 like the waters of the Drake Passage during autumn. The obtained results during the cruises also revealed significant long-term trends, such as the warming of equatorial waters (0.11±0.03°C yr−1 and the decrease of surface salinity (−0.16±0.01 yr−1 in tropical waters caused by the influence of the Amazon River plume. This reduction in surface salinity appears to have a direct influence over the CO2 storage rates, fostering the uptake capacity of atmospheric CO2 (−0.09±0.03 mol m−2 yr−1. An analysis of the biogeochemical forcing on the CO2 fugacity (fCO2 variability performed from an empirical algorithm highlighted the major role of the Amazon River input in the tropical North Atlantic fluxes. In addition, it has provided a quantitative measure of the importance of the thermodynamic control of FCO2 at temperate latitudes.

  6. CO2-Water-Rock Wettability: Variability, Influencing Factors, and Implications for CO2 Geostorage.

    Science.gov (United States)

    Iglauer, Stefan

    2017-05-16

    Carbon geosequestration (CGS) has been identified as a key technology to reduce anthropogenic greenhouse gas emissions and thus significantly mitigate climate change. In CGS, CO2 is captured from large point-source emitters (e.g., coal fired power stations), purified, and injected deep underground into geological formations for disposal. However, the CO2 has a lower density than the resident formation brine and thus migrates upward due to buoyancy forces. To prevent the CO2 from leaking back to the surface, four trapping mechanisms are used: (1) structural trapping (where a tight caprock acts as a seal barrier through which the CO2 cannot percolate), (2) residual trapping (where the CO2 plume is split into many micrometer-sized bubbles, which are immobilized by capillary forces in the pore network of the rock), (3) dissolution trapping (where CO2 dissolves in the formation brine and sinks deep into the reservoir due to a slight increase in brine density), and (4) mineral trapping (where the CO2 introduced into the subsurface chemically reacts with the formation brine or reservoir rock or both to form solid precipitates). The efficiency of these trapping mechanisms and the movement of CO2 through the rock are strongly influenced by the CO2-brine-rock wettability (mainly due to the small capillary-like pores in the rock which form a complex network), and it is thus of key importance to rigorously understand CO2-wettability. In this context, a substantial number of experiments have been conducted from which several conclusions can be drawn: of prime importance is the rock surface chemistry, and hydrophilic surfaces are water-wet while hydrophobic surfaces are CO2-wet. Note that CO2-wet surfaces dramatically reduce CO2 storage capacities. Furthermore, increasing pressure, salinity, or dissolved ion valency increases CO2-wettability, while the effect of temperature is not well understood. Indeed theoretical understanding of CO2-wettability and the ability to

  7. High-frequency analysis of the complex linkage between soil CO(2) fluxes, photosynthesis and environmental variables.

    Science.gov (United States)

    Martin, Jonathan G; Phillips, Claire L; Schmidt, Andres; Irvine, James; Law, Beverly E

    2012-01-01

    High-frequency soil CO(2) flux data are valuable for providing new insights into the processes of soil CO(2) production. A record of hourly soil CO(2) fluxes from a semi-arid ponderosa pine stand was spatially and temporally deconstructed in attempts to determine if variation could be explained by logical drivers using (i) CO(2) production depths, (ii) relationships and lags between fluxes and soil temperatures, or (iii) the role of canopy assimilation in soil CO(2) flux variation. Relationships between temperature and soil fluxes were difficult to establish at the hourly scale because diel cycles of soil fluxes varied seasonally, with the peak of flux rates occurring later in the day as soil water content decreased. Using a simple heat transport/gas diffusion model to estimate the time and depth of CO(2) flux production, we determined that the variation in diel soil CO(2) flux patterns could not be explained by changes in diffusion rates or production from deeper soil profiles. We tested for the effect of gross ecosystem productivity (GEP) by minimizing soil flux covariance with temperature and moisture using only data from discrete bins of environmental conditions (±1 °C soil temperature at multiple depths, precipitation-free periods and stable soil moisture). Gross ecosystem productivity was identified as a possible driver of variability at the hourly scale during the growing season, with multiple lags between ~5, 15 and 23 days. Additionally, the chamber-specific lags between GEP and soil CO(2) fluxes appeared to relate to combined path length for carbon flow (top of tree to chamber center). In this sparse and heterogeneous forested system, the potential link between CO(2) assimilation and soil CO(2) flux may be quite variable both temporally and spatially. For model applications, it is important to note that soil CO(2) fluxes are influenced by many biophysical factors, which may confound or obscure relationships with logical environmental drivers and act at

  8. A new frontier in CO2 flux measurements using a highly portable DIAL laser system

    Science.gov (United States)

    Queiβer, Manuel; Granieri, Domenico; Burton, Mike

    2016-01-01

    Volcanic CO2 emissions play a key role in the geological carbon cycle, and monitoring of volcanic CO2 fluxes helps to forecast eruptions. The quantification of CO2 fluxes is challenging due to rapid dilution of magmatic CO2 in CO2-rich ambient air and the diffuse nature of many emissions, leading to large uncertainties in the global magmatic CO2 flux inventory. Here, we report measurements using a new DIAL laser remote sensing system for volcanic CO2 (CO2DIAL). Two sites in the volcanic zone of Campi Flegrei (Italy) were scanned, yielding CO2 path-amount profiles used to compute fluxes. Our results reveal a relatively high CO2 flux from Campi Flegrei, consistent with an increasing trend. Unlike previous methods, the CO2DIAL is able to measure integrated CO2 path-amounts at distances up to 2000 m using virtually any solid surface as a reflector, whilst also being highly portable. This opens a new frontier in quantification of geological and anthropogenic CO2 fluxes. PMID:27652775

  9. 湿地土壤CO2通量研究进展%A Review on Wetland Soil CO2 Flux

    Institute of Scientific and Technical Information of China (English)

    李兆富; 吕宪国; 杨青

    2002-01-01

    Wetland is considered as a special ecosystem which has some functions in the earth. Wetland's carbon cycle is very important for global climate changes. The research on wetland soil CO2 flux is a key of wetland carbon cycle. This paper analysed observation methods and influential factors of wetland soil CO2 flux, introduced wetland soil CO2 flux model, and discussed research emphases and direction on wetland soil CO2 flux.

  10. Aircraft observations of the urban CO2 dome in London and calculated daytime CO2 fluxes at the urban-regional scale

    Science.gov (United States)

    Font, Anna; Morgui, Josep Anton; Grimmond, Sue; Barratt, Benjamin

    2013-04-01

    dispersed downwind, with peak concentrations displaced from the urban centre along the main wind direction. The urban-regional surface CO2 flux was calculated for four days in October 2011 by either the Integrative Mass Boundary Layer (IMBL) or the Column Integration method (CIM), dependent on meteorological conditions. The diurnal CO2 flux in London obtained from the aircraft observations ranged from 36 to 71 μmol CO2 m-2 s-1 during the day time. This compared well with continuous measurements of CO2 exchange by an eddy-covariance system located in central London. The day-to-day variability observed in the calculated CO2 fluxes responded to the spatial variability of the influence area and emissions that observations were sensitive to. This study provides an example how aircraft surveys in urban areas can be used to estimate CO2 surface fluxes at the urban-regional scale. It also presents an important cross-validation of two independent measurement-based methods to infer the contribution of urban areas to climate change in terms of CO2 emissions that complement bottom-up emissions inventories. References Committee on Methods for Estimating Greenhouse Gas Emissions (2010), The National Academia Press. DECC (2012), http://www.decc.gov.uk/en/content/cms/statistics/indicators/ni186/ni186.aspx

  11. CO2 Fluxes Monitoring at the Level of Field Agroecosystem in Moscow Region of Russia

    Science.gov (United States)

    Meshalkina, Joulia; Mazirov, Ilya; Samardzic, Miljan; Yaroslavtsev, Alexis; Valentini, Riccardo; Vasenev, Ivan

    2014-05-01

    operation and soil moisture has stronger influence on the seasonal dynamics of soil and agroecosystem CO2 emissions. Obtained unique for Russian agriculture data are very useful for land-use practices environmental assessment, for soil organic carbon dynamics analysis and agroecological evaluation, and for food C-footprint calculation. Their system analysis together with the nearest forest eddy covariance stations helps us to understand better the land-use change impact on the GHG fluxes dynamics and ecosystem services.

  12. Separation of biospheric and fossil fuel fluxes of CO2 by atmospheric inversion of CO2 and 14CO2 measurements: Observation System Simulations

    Science.gov (United States)

    Basu, Sourish; Bharat Miller, John; Lehman, Scott

    2016-05-01

    National annual total CO2 emissions from combustion of fossil fuels are likely known to within 5-10 % for most developed countries. However, uncertainties are inevitably larger (by unknown amounts) for emission estimates at regional and monthly scales, or for developing countries. Given recent international efforts to establish emission reduction targets, independent determination and verification of regional and national scale fossil fuel CO2 emissions are likely to become increasingly important. Here, we take advantage of the fact that precise measurements of 14C in CO2 provide a largely unbiased tracer for recently added fossil-fuel-derived CO2 in the atmosphere and present an atmospheric inversion technique to jointly assimilate observations of CO2 and 14CO2 in order to simultaneously estimate fossil fuel emissions and biospheric exchange fluxes of CO2. Using this method in a set of Observation System Simulation Experiments (OSSEs), we show that given the coverage of 14CO2 measurements available in 2010 (969 over North America, 1063 globally), we can recover the US national total fossil fuel emission to better than 1 % for the year and to within 5 % for most months. Increasing the number of 14CO2 observations to ˜ 5000 per year over North America, as recently recommended by the National Academy of Science (NAS) (Pacala et al., 2010), we recover monthly emissions to within 5 % for all months for the US as a whole and also for smaller, highly emissive regions over which the specified data coverage is relatively dense, such as for the New England states or the NY-NJ-PA tri-state area. This result suggests that, given continued improvement in state-of-the art transport models, a measurement program similar in scale to that recommended by the NAS can provide for independent verification of bottom-up inventories of fossil fuel CO2 at the regional and national scale. In addition, we show that the dual tracer inversion framework can detect and minimize biases in

  13. CO2 flux estimation errors associated with moist atmospheric processes

    Directory of Open Access Journals (Sweden)

    S. Pawson

    2012-04-01

    Full Text Available Vertical transport by moist sub-grid scale processes such as deep convection is a well-known source of uncertainty in CO2 source/sink inversion. However, a dynamical link between moist transport, satellite CO2 retrievals, and source/sink inversion has not yet been established. Here we examine the effect of moist processes on (1 synoptic CO2 transport by Version-4 and Version-5 NASA Goddard Earth Observing System Data Assimilation System (NASA-DAS meteorological analyses, and (2 source/sink inversion. We find that synoptic transport processes, such as fronts and dry/moist conveyors, feed off background vertical CO2 gradients, which are modulated by sub-grid vertical transport. The implication for source/sink estimation is two-fold. First, CO2 variations contained in moist poleward moving air masses are systematically different from variations in dry equatorward moving air. Moist poleward transport is hidden from orbital sensors on satellites, causing a sampling bias, which leads directly to continental scale source/sink estimation errors of up to 0.25 PgC yr−1 in northern mid-latitudes. Second, moist processes are represented differently in GEOS-4 and GEOS-5, leading to differences in vertical CO2 gradients, moist poleward and dry equatorward CO2 transport, and therefore the fraction of CO2 variations hidden in moist air from satellites. As a result, sampling biases are amplified, causing source/sink estimation errors of up to 0.55 PgC yr−1 in northern mid-latitudes. These results, cast from the perspective of moist frontal transport processes, support previous arguments that the vertical gradient of CO2 is a major source of uncertainty in source/sink inversion.

  14. Lateral carbon fluxes and CO2 outgassing from a tropical peat-draining river

    Directory of Open Access Journals (Sweden)

    D. Müller

    2015-07-01

    Full Text Available Tropical peatlands play an important role in the global carbon cycle due to their immense carbon storage capacity. However, pristine peat swamp forests are vanishing due to deforestation and peatland degradation, especially in Southeast Asia. CO2 emissions associated with this land use change might not only come from the peat soil directly, but also from peat-draining rivers. So far, though, this has been mere speculation, since there was no data from undisturbed reference sites. We present the first combined assessment of lateral organic carbon fluxes and CO2 outgassing from an undisturbed tropical peat-draining river. Two sampling campaigns were undertaken on the Maludam river in Sarawak, Malaysia. The river catchment is covered by protected peat swamp forest, offering a unique opportunity to study a peat-draining river in its natural state, without any influence from tributaries with different characteristics. The two campaigns yielded consistent results. Dissolved organic carbon (DOC concentrations ranged between 3222 and 6218 μmol L−1 and accounted for more than 99 % of the total organic carbon (TOC. Radiocarbon dating revealed that the riverine DOC was of recent origin, suggesting that it derives from the top soil layers and surface runoff. We observed strong oxygen depletion, implying high rates of organic matter decomposition and consequently CO2 production. The measured median pCO2 was 7795 and 8400 μatm during the two campaigns, respectively. Overall, we found that only 26 ± 15 % of the carbon was exported by CO2 evasion, while the rest was exported by discharge. CO2 outgassing seemed to be moderated by the short water residence time. Since most Southeast Asian peatlands are located at the coast, this is probably an important limiting factor for CO2 outgassing from most of its peat-draining rivers.

  15. Lateral carbon fluxes and CO2 outgassing from a tropical peat-draining river

    Science.gov (United States)

    Müller, D.; Warneke, T.; Rixen, T.; Müller, M.; Jamahari, S.; Denis, N.; Mujahid, A.; Notholt, J.

    2015-10-01

    Tropical peatlands play an important role in the global carbon cycle due to their immense carbon storage capacity. However, pristine peat swamp forests are vanishing due to deforestation and peatland degradation, especially in Southeast Asia. CO2 emissions associated with this land use change might not only come from the peat soil directly but also from peat-draining rivers. So far, though, this has been mere speculation, since there has been no data from undisturbed reference sites. We present the first combined assessment of lateral organic carbon fluxes and CO2 outgassing from an undisturbed tropical peat-draining river. Two sampling campaigns were undertaken on the Maludam River in Sarawak, Malaysia. The river catchment is covered by protected peat swamp forest, offering a unique opportunity to study a peat-draining river in its natural state, without any influence from tributaries with different characteristics. The two campaigns yielded consistent results. Dissolved organic carbon (DOC) concentrations ranged between 3222 and 6218 μmol L-1 and accounted for more than 99 % of the total organic carbon (TOC). Radiocarbon dating revealed that the riverine DOC was of recent origin, suggesting that it derives from the top soil layers and surface runoff. We observed strong oxygen depletion, implying high rates of organic matter decomposition and consequently CO2 production. The measured median pCO2 was 7795 and 8400 μatm during the first and second campaign, respectively. Overall, we found that only 32 ± 19 % of the carbon was exported by CO2 evasion, while the rest was exported by discharge. CO2 outgassing seemed to be moderated by the short water residence time. Since most Southeast Asian peatlands are located at the coast, this is probably an important limiting factor for CO2 outgassing from most of its peat-draining rivers.

  16. Lateral carbon fluxes and CO2 outgassing from a tropical peat-draining river

    Directory of Open Access Journals (Sweden)

    D. Müller

    2015-10-01

    Full Text Available Tropical peatlands play an important role in the global carbon cycle due to their immense carbon storage capacity. However, pristine peat swamp forests are vanishing due to deforestation and peatland degradation, especially in Southeast Asia. CO2 emissions associated with this land use change might not only come from the peat soil directly but also from peat-draining rivers. So far, though, this has been mere speculation, since there has been no data from undisturbed reference sites. We present the first combined assessment of lateral organic carbon fluxes and CO2 outgassing from an undisturbed tropical peat-draining river. Two sampling campaigns were undertaken on the Maludam River in Sarawak, Malaysia. The river catchment is covered by protected peat swamp forest, offering a unique opportunity to study a peat-draining river in its natural state, without any influence from tributaries with different characteristics. The two campaigns yielded consistent results. Dissolved organic carbon (DOC concentrations ranged between 3222 and 6218 μmol L−1 and accounted for more than 99 % of the total organic carbon (TOC. Radiocarbon dating revealed that the riverine DOC was of recent origin, suggesting that it derives from the top soil layers and surface runoff. We observed strong oxygen depletion, implying high rates of organic matter decomposition and consequently CO2 production. The measured median pCO2 was 7795 and 8400 μatm during the first and second campaign, respectively. Overall, we found that only 32 ± 19 % of the carbon was exported by CO2 evasion, while the rest was exported by discharge. CO2 outgassing seemed to be moderated by the short water residence time. Since most Southeast Asian peatlands are located at the coast, this is probably an important limiting factor for CO2 outgassing from most of its peat-draining rivers.

  17. Numerical modeling of cold magmatic CO2 flux measurements for the exploration of hidden geothermal systems

    Science.gov (United States)

    Peiffer, Loïc.; Wanner, Christoph; Pan, Lehua

    2015-10-01

    The most accepted conceptual model to explain surface degassing of cold magmatic CO2 in volcanic-geothermal systems involves the presence of a gas reservoir. In this study, numerical simulations using the TOUGH2-ECO2N V2.0 package are performed to get quantitative insights into how cold CO2 soil flux measurements are related to reservoir and fluid properties. Although the modeling is based on flux data measured at a specific geothermal site, the Acoculco caldera (Mexico), some general insights have been gained. Both the CO2 fluxes at the surface and the depth at which CO2 exsolves are highly sensitive to the dissolved CO2 content of the deep fluid. If CO2 mainly exsolves above the reservoir within a fracture zone, the surface CO2 fluxes are not sensitive to the reservoir size but depend on the CO2 dissolved content and the rock permeability. For gas exsolution below the top of the reservoir, surface CO2 fluxes also depend on the gas saturation of the deep fluid as well as the reservoir size. The absence of thermal anomalies at the surface is mainly a consequence of the low enthalpy of CO2. The heat carried by CO2 is efficiently cooled down by heat conduction and to a certain extent by isoenthalpic volume expansion depending on the temperature gradient. Thermal anomalies occur at higher CO2 fluxes (>37,000 g m-2 d-1) when the heat flux of the rising CO2 is not balanced anymore. Finally, specific results are obtained for the Acoculco area (reservoir depth, CO2 dissolved content, and gas saturation state).

  18. Feedbacks Between Microenvironment and Plant Functional Type and Implications for CO2 Flux in Arctic Ecosystems

    Science.gov (United States)

    Squires, E.; Rodenheizer, H.; Natali, S.; Mann, P.

    2013-12-01

    Future climate models predict a warmer, drier Arctic, with resultant shifts in vegetative composition and implications for ecosystem carbon budgets. The impact of vegetation change, however, may depend on which plant functional groups are favored in a warming Arctic. Physiological and functional differences between plant groups influence both the local microenvironment and, on a broader scale, whole-ecosystem CO2 flux. We examined the interactions between plants and their microenvironment, and analyzed the effect of these interactions on both soil microbial communities and CO2 flux across different functional groups. Physical and biological aspects of the microenvironment differed between plant functional groups. Lichen patches were characterized by deeper thaw depths, lower soil moisture, greater thermal conductivity, and a thinner organic layer than mosses. To better understand the development of these plant-environment interactions, we conducted a reciprocal transplant experiment, switching multiple lichen and moss patches. Temporal changes in environmental parameters at these sites will demonstrate how different plants modify their environment and will help identify associated implications for soil microbial communities and CO2 flux. We measured CO2 flux and used Biolog assays to examine soil microbial communities in undisturbed patches of mosses, lichens, and shrubs. Patches of birch shrubs had more negative net ecosystem exchange, signifying a carbon sink. Soils from alder shrubs and mosses hosted more active microbial communities than soils under birch shrubs and lichens. These results suggest a strong link between environment, plant functional type, and C cycling. Understanding how this relationship differs among plant functional types is an important part of predicting ecosystem carbon budgets as Arctic vegetation composition shifts in response to climate change.

  19. Simulating CO2 flux of three different ecosystems in ChinaFLUX based on artificial neural networks

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>The nonlinearity of the relationship between CO2 flux and other micrometeorological variables flux parameters limits the applicability of carbon flux models to accurately estimate the flux dynamics. However, the need for carbon dioxide (CO2) estimations covering larger areas and the limitations of the point eddy covariance technique to address this requirement necessitates the modeling of CO2 flux from other micrometeorological variables. Artificial neural networks (ANN) are used because of their power to fit highly nonlinear relations between input and output variables without explaining the nature of the phenomena. This paper applied a multilayer perception ANN technique with error back propagation algorithm to simulate CO2 flux on three different ecosystems (forest, grassland and cropland) in ChinaFLUX. Energy flux (net radiation, latent heat, sensible heat and soil heat flux) and temperature (air and soil) and soil moisture were used to train the ANN and predict the CO2 flux. Diurnal half-hourly fluxes data of observations from June to August in 2003 were divided into training, validating and testing. Results of the CO2 flux simulation show that the technique can successfully predict the observed values with R2 value between 0.75 and 0.866. It is also found that the soil moisture could not improve the simulative accuracy without water stress. The analysis of the contribution of input variables in ANN shows that the ANN is not a black box model, it can tell us about the controlling parameters of NEE in different ecosystems and micrometeorological environment. The results indicate the ANN is not only a reliable, efficient technique to estimate regional or global CO2 flux from point measurements and understand the spatiotemporal budget of the CO2 fluxes, but also can identify the relations between the CO2 flux and micrometeorological variables.

  20. Climate impacts on the structures of the North Pacific air-sea CO2 flux variability

    Directory of Open Access Journals (Sweden)

    Y. Nojiri

    2011-05-01

    Full Text Available Some dominant spatial and temporal structures of the North Pacific air-sea CO2 fluxes in response to the Pacific Decadal Oscillation (PDO are identified in four data products from four independent sources: an assimilated CO2 flux product, two forward model solutions, and a gridded pCO2 dataset constructed with a neural network approach. The interannual variability of CO2 flux is found to be an order of magnitude weaker compared to the seasonal cycle of CO2 flux in the North Pacific. A statistical approach is employed to quantify the signal-to-noise ratio in the reconstructed dataset to delineate the representativity errors. The dominant variability with a signal-to-noise ratio above one is identified and its correlations with PDO are examined. A tentative four-box structure in the North Pacific air-sea CO2 flux variability linked to PDO emerges in which two positively correlated boxes are oriented in the northwest and southeast directions and contrarily, the negatively correlated boxes are oriented in the northeast and southwest directions. This pattern is verified with the CO2 and pCO2 from four products and its relations to the interannual El Niño-Southern Oscillation (ENSO and lower-frequency PDO are separately identified. A combined EOF analysis between air-sea CO2 flux and key variables representing ocean-atmosphere interactions is carried out to elicit robust oscillations in the North Pacific CO2 flux in response to the PDO. The proposed spatial and temporal structures of the North Pacific CO2 fluxes are insightful since they separate the secular trends of the surface ocean carbon from the interannual variability. The regional characterization of the North Pacific in terms of PDO and CO2 flux variability is also instructive for determining the homogeneous oceanic domains for the Regional Carbon Cycle and Assessment Processes (RECCAP.

  1. On the use of satellite-derived CH4 : CO2 columns in a joint inversion of CH4 and CO2 fluxes

    NARCIS (Netherlands)

    Pandey, S.

    2015-01-01

    We present a method for assimilating total column CH4 : CO2 ratio measurements from satellites for inverse modeling of CH4 and CO2 fluxes using the variational approach. Unlike conventional approaches, in which retrieved CH4 : CO2 are multiplied by model-derived total column CO2 and only the resulti

  2. On the use of satellite-derived CH4 : CO2 columns in a joint inversion of CH4 and CO2 fluxes

    NARCIS (Netherlands)

    Pandey, S.

    2015-01-01

    We present a method for assimilating total column CH4 : CO2 ratio measurements from satellites for inverse modeling of CH4 and CO2 fluxes using the variational approach. Unlike conventional approaches, in which retrieved CH4 : CO2 are multiplied by model-derived total column CO2 and only the resulti

  3. Simulating global soil-CO2 flux and its response to climate change

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It has been argued that increased soil respiration would become a major atmospheric source of CO2 in the event of global warming. The simple statistical models were developed based on a georeferenced database with 0.5°× 0.5° longitude/latitude resolution to simulate global soil-CO2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil-CO2 fluxes to various climate change scenarios. The statistical models yield a value of 69 PgC/a of global soil CO2 fluxes for current condition. Sensitivity experiments confirm that the fluxes are responsive to changes in temperature,precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil-CO2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO2, it can be found that the largest increases in soil-CO2 fluxes were associated with the boreal and tundra regions. The globally averaged soil-CO2 fluxes were estimated to increase by about 35 % above current values, providing a positive feedback to the greenhouse effect.

  4. Simulating global soil-CO2 flux and its response to climate change

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    It has been argued that increased soil respiration would become a major atmospheric source of CO2 in the event of global warming. The simple statistical models were developed based on a georeferenced database with 0.5° × 0.5° longitude/latitude resolution to simulate global soil-CO2 fluxes, to investigate climatic effects on these fluxes using sensitivity experiments, and to assess possible responses of soil-CO2 fluxes to various climate change scenarios. The statistical models yield a value of 69 PgC/a of global soil CO2 fluxes for current condition. Sensitivity experiments confirm that the fluxes are responsive to changes in temperature,precipitation and actual evapotranspiration, but increases in temperature and actual evapotranspiration affect soil-CO2 fluxes more than increases in precipitation. Using climatic change projections from four global circulation models, each corresponding to an equilibrium doubling of CO2, it can be found that the largest increases in soil-CO2 fluxes were associated with the boreal and tundra regions. The globally averaged soil-CO2 fluxes were estimated to increase by about 35 % above current values, providing a positive feedback to the greenhouse effect.

  5. Soil methane and CO2 fluxes in rainforest and rubber plantations

    Science.gov (United States)

    Lang, Rong; Blagodatsky, Sergey; Goldberg, Stefanie; Xu, Jianchu

    2017-04-01

    Expansion of rubber plantations in South-East Asia has been a land use transformation trend leading to losses of natural forest cover in the region. Besides impact on ecosystem carbon stocks, this conversion influences the dynamics of greenhouse gas fluxes from soil driven by microbial activity, which has been insufficiently studied. Aimed to understand how land use change affects the soil CO2 and CH4 fluxes, we measured surface gas fluxes, gas concentration gradient, and 13C signature in CH4 and soil organic matter in profiles in a transect in Xishuangbanna, including a rainforest site and three rubber plantation sites with age gradient. Gas fluxes were measured by static chamber method and open chamber respiration system. Soil gases were sampled from installed gas samplers at 5, 10, 30, and 75cm depth at representative time in dry and rainy season. The soil CO2 flux was comparable in rainforest and old rubber plantations, while young rubber plantation had the lowest rate. Total carbon content in the surface soil well explained the difference of soil CO2 flux between sites. All sites were CH4 sinks in dry season and uptake decreased in the order of rainforest, old rubber plantations and young rubber plantation. From dry season to rainy season, CH4 consumption decreased with increasing CH4 concentration in the soil profile at all depths. The enrichment of methane by 13CH4 shifted towards to lowerδ13C, being the evidence of enhanced CH4 production process while net surface methane flux reflected the consumption in wet condition. Increment of CH4 concentration in the profile from dry to rainy season was higher in old rubber plantation compared to rainforest, while the shifting of δ13CH4 was larger in rainforest than rubber sites. Turnover rates of soil CO2 and CH4 suggested that the 0-5 cm surface soil was the most active layer for gaseous carbon exchange. δ13C in soil organic matter and soil moisture increased from rainforest, young rubber plantation to old

  6. Microbial imprint on soil-atmosphere H2, COS, and CO2 fluxes

    Science.gov (United States)

    Meredith, L. K.; Commane, R.; Munger, J. W.; Wofsy, S. C.; Prinn, R. G.

    2013-12-01

    Microorganisms drive large trace gas fluxes between soil and atmosphere, but the signal can be difficult to detect and quantify in the presence of stronger exchange processes in an ecosystem. Partitioning methods are often needed to estimate trace gas budgets and to develop process-based models to explore the sensitivity of microbe-mediated fluxes. In this study, we test the performance of trace gases with predominantly microbe-mediated soil fluxes as a metric of the soil microbial uptake activity of other trace gases. Using simultaneous, collocated measurements at Harvard Forest, we consider three trace gases with microbe-mediated soil fluxes of various importance relative to their other (mainly plant-mediated) ecosystem fluxes: molecular hydrogen (H2), carbonyl sulfide (COS), and carbon dioxide (CO2). These gases probe different aspects of the soil trace-gas microbiology. Soil H2 uptake is a redox reaction driving the energy metabolism of a portion of the microbial community, while soil CO2 respiration is a partial proxy for the overall soil microbial metabolism. In comparison, very little is understood about the microbiological and environmental drivers of soil COS uptake and emissions. In this study, we find that H2, COS, and CO2 soil uptake rates are often correlated, but the relative soil uptake between gases is not constant, and is influenced by seasonality and local environmental conditions. We also consider how differences in the microbial communities and pathways involved in the soil fluxes may explain differences in the observations. Our results are important for informing previous studies using tracer approaches. For example, H2 has been used to estimate COS soil uptake, which must be accounted for to use COS as a carbon cycle tracer. Furthermore, the global distribution of H2 deposition velocity has been inferred from net primary productivity (CO2). Given that insufficient measurement frequency and spatial distribution exists to partition global net

  7. Annual patterns and budget of CO2 flux in an Alaskan arctic tussock tundra ecosystem at Atqasuk, Alaska

    Science.gov (United States)

    Oechel, W. C.; Kalhori, A. A.; Burba, G. G.; Gioli, B.

    2013-12-01

    Arctic ecosystem functioning is not only critically affected by climate change, but also has the potential for major positive feedbacks on climate. There is however relatively little information available on the role, patterns, and vulnerabilities of CO2 fluxes during the non-summer seasons. Presented here is a year-around study of CO2 fluxes in an Alaskan Arctic tussock tundra ecosystem. Also presented are key environmental controls on CO2 fluxes as well as possible impacts of likely changes in season timing. This is aided by a new empirical quantification of seasons in the Arctic based on net radiation, which can help describe seasonal responses to greenhouse gas fluxes under climate change. The fluxes were computed using standard FluxNet methodology and corrected using standard WPL density terms, adjusted for influences of instrument surface heating. The results showed that the non-summer season comprises a significant source of carbon to the atmosphere. The summer period was a net sink of 10.83 g C m-2 yr-1, while the non-summer seasons released more than four times the CO2 uptake observed in the summer, resulting in a net annual source of 37.6 g C m-2 yr-1 to the atmosphere. This shows a change in this region of the Arctic from a long-term annual sink of CO2 from the atmosphere to an annual source of CO2 from the terrestrial ecosystem and soils to the atmosphere. The results presented here demonstrate that nearly continuous observations may be required in order to accurately calculate the annual NEE of Arctic ecosystems, and to build predictive understanding that can be used to estimate, with confidence, Arctic fluxes under future conditions. Daily CO2 fluxes over the year, average daily net radiation, average daily PAR, average daily air temperature and average daily soil respiration (at -5 cm).

  8. Characteristics Analysis of CO2 and Heat Flux in Winter Wheat Fields%麦田CO2通量、热通量特征分析

    Institute of Scientific and Technical Information of China (English)

    彭记永; 胡继超; 刘荣花; 马青荣; 杨光仙

    2012-01-01

    为了评价麦田生态系统CO2通量和热通量变化特征以及CO2的收支状况,利用郑州农业气象试验站2009年10月 2010年6月冬小麦生育期内涡度观测数据,分析了麦田CO2通量、热通量变化特征.结果表明:净辐射、潜热通量、显热通量和土壤热通量日变化表现为明显的单峰特征,最大值一般出现在正午前后.其中,净辐射通量、显热通量和土壤热通量的季节变化特征较为一致,均为苗期<中期<后期;潜热通量受到叶面积指数(LAI)的影响,季节变化特征为苗期<后期<中期;CO2的季节变化特征受到LAI、热通量和下垫面特征的共同影响,形成1个CO2吸收高峰的U型曲线,季节变化特征为前期<后期<中期.冬小麦农田CO2、热通量具有明显的日变化和季节变化特征,麦田生态系统总体表现为CO2的汇.%By using the eddy covariance system data of the winter wheat growth stage from Octo-ber 2009 to June 2010 at agro-meteorological experimental station of Zhengzhou,the variations of heat and CO2 flux in winter wheat fields were analyzed. The results indicated that diurnal varia-tions of net radiation, latent heat, sensible heat and soil heat flux showed a uni-peak model, and the maximum values appeared around noon in general. The seasonal variation characteristics of net radiation, sensible heat and soil heat flux were comparatively consistent, minimum in seedling stage,next at metaphase and maximum at anaphase. Latent heat flux was affected obviously by leaf area index (LAI) , which in seeding stage was minimum,next at anaphase but maximum at meta-phase. CO2 flux was influenced by LAI, heat flux and the underlying surface, and its characteristics showed a U-shaped curve with an absorption peak. CO2 flux was minimum at prophase,next at anaphase but maximum at metaphase. The CO2 and heat flux in winter wheat fields had significant diurnal and sea-sonal variations, and overall, the ecosystem was a

  9. Inorganic carbon distribution and CO2 fluxes in a large European estuary (Tagus, Portugal).

    Science.gov (United States)

    Oliveira, A P; Cabeçadas, G; Mateus, M D

    2017-08-07

    Ten field cruises were carried out in Tagus estuary from 1999 to 2007 to study the dynamics of the inorganic carbon system. Dissolved inorganic carbon (DIC) and total alkalinity (TA) increased with salinity. DIC and TA were generally conservative in the estuarine mixing zone (salinity > 10), while a complex distribution pattern was observed at the upper estuary. DIC values peaked 1786.9 ± 155.8 µmol kg(-1) at that segment. Estimated annual mean fluxes of DIC were 0.27 Tg C yr(-1) from the river to the estuary, and 0.37 Tg C yr(-1) from here to the coastal area. The Tagus estuary was always CO2 supersaturated, with partial pressure of CO2 (pCO2) reaching 9160 µatm in the upper estuary. An average emission of 0.11 Tg C yr(-1) was estimated from the estuary to the atmosphere, corresponding to 23% of exported DIC. Only 8% of the riverine DIC was ventilated. The non-conservative behaviour of CO2 parameters in the estuary segment under freshwater influence was attributed to alternations in the relevance of riverine/terrestrial runoff, photosynthesis, aerobic respiration, organic matter mineralization and CaCO3 precipitation/dissolution.

  10. Does Terrestrial Drought Explain Global CO2 Flux Anomalies Induced by El Nino?

    Science.gov (United States)

    Schwalm. C. R.; Williams, C. A.; Schaefer, K.; Baker, I.; Collatz, G. J.; Roedenbeck, C.

    2011-01-01

    The El Nino Southern Oscillation is the dominant year-to-year mode of global climate variability. El Nino effects on terrestrial carbon cycling are mediated by associated climate anomalies, primarily drought, influencing fire emissions and biotic net ecosystem exchange (NEE). Here we evaluate whether El Nino produces a consistent response from the global carbon cycle. We apply a novel bottom-up approach to estimating global NEE anomalies based on FLUXNET data using land cover maps and weather reanalysis. We analyze 13 years (1997-2009) of globally gridded observational NEE anomalies derived from eddy covariance flux data, remotely-sensed fire emissions at the monthly time step, and NEE estimated from an atmospheric transport inversion. We evaluate the overall consistency of biospheric response to El Nino and, more generally, the link between global CO2 flux anomalies and El Nino-induced drought. Our findings, which are robust relative to uncertainty in both methods and time-lags in response, indicate that each event has a different spatial signature with only limited spatial coherence in Amazonia, Australia and southern Africa. For most regions, the sign of response changed across El Nino events. Biotic NEE anomalies, across 5 El Nino events, ranged from -1.34 to +0.98 Pg Cyr(exp -1, whereas fire emissions anomalies were generally smaller in magnitude (ranging from -0.49 to +0.53 Pg C yr(exp -1). Overall drought does not appear to impose consistent terrestrial CO2 flux anomalies during El Ninos, finding large variation in globally integrated responses from 11.15 to +0.49 Pg Cyr(exp -1). Despite the significant correlation between the CO2 flux and El Nino indices, we find that El Nino events have, when globally integrated, both enhanced and weakened terrestrial sink strength, with no consistent response across events

  11. [Rapid measurements of CO2 flux density and water use efficiency of crop community].

    Science.gov (United States)

    Zhu, Zhilin; Sun, Xiaomin; Zhang, Renhua; Su, Hongbo; Tang, Xinzai

    2004-09-01

    In this paper, Eddy Correlation (EC) method was employed to measure the latent heat and CO2 flux density and to calculate Water Use Efficiency (WUE) of winter wheat community in Yucheng district, Shandong Province in 1997. The results showed that the CO2 flux density had an obvious diurnal change, with a maximum about 1.5 mg x s(-1) x m(-2), which appeared at about 9:00-10:00 am in general. The WUE of wheat community presented a fall trend from morning to afternoon, and the CO2 flux density and WUE also had an obvious seasonal change, being lower in the early and late growth stages, and higher in the middle growth stage. The ranges of daily mean CO2 flux density and WUE were 0.2-0.9 mg x s(-1) x m(-2) and 5-20 gCO2 x kg(-1) H2O, respectively.

  12. THE INFLUENCE OF CO2 ON WELL CEMENT

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2010-12-01

    Full Text Available Carbon capture and storage is one way to reduce emissions of greenhouse gases in the atmosphere. Underground gas storage operations and CO2 sequestration in aquifers relay on both the proper wellbore construction and sealing properties of the cap rock. CO2 injection candidates may be new wells or old wells. In both cases, the long-term wellbore integrity (up to 1 000 years is one of the key performance criteria in the geological storage of CO2. The potential leakage paths are the migration CO2 along the wellbore due to poor cementation and flow through the cap rock. The permeability and integrity of the set cement will determine how effective it is in preventing the leakage. The integrity of the cap rock is assured by an adequate fracture gradient and by sufficient set cement around the casing across the cap rock and without a micro-annulus. CO2 storage in underground formations has revived the researc of long term influence of the injected CO2 on Portland cements and methods for improving the long term efficiency of the wellbore sealant. Some researchers predicted that set cement will fail when exposed to CO2 leading to potential leakage to the atmosphere or into underground formations that may contain potable water. Other researchers show set cement samples from 30 to 50 year-old wells (CO2 EOR projects that have maintained sealing integrity and prevented CO2 leakage, in spite of some degree of carbonation. One of reasons for the discrepancy between certain research lab tests and actual field performance measurements is the absence of standard protocol for CO2 resistance-testing devices, conditions, or procedures. This paper presents potential flow paths along the wellbore, CO2 behaviour under reservoir conditions, and geochemical alteration of hydrated Portland cement due to supercritical CO2 injection.

  13. Central Russia agroecosystem monitoring with CO2 fluxes analysis by eddy covariance method

    Directory of Open Access Journals (Sweden)

    Joulia Meshalkina

    2015-07-01

    Full Text Available The eddy covariance (EC technique as a powerful statistics-based method of measurement and calculation the vertical turbulent fluxes of greenhouses gases within atmospheric boundary layers provides the continuous, long-term flux information integrated at the ecosystem scale. An attractive way to compare the agricultural practices influences on GHG fluxes is to divide a crop area into subplots managed in different ways. The research has been carried out in the Precision Farming Experimental Field of the Russian Timiryazev State Agricultural University (RTSAU, Moscow in 2013 under the support of RF Government grant # 11.G34.31.0079, EU grant # 603542 LUС4С (7FP and RF Ministry of education and science grant # 14-120-14-4266-ScSh. Arable Umbric Albeluvisols have around 1% of SOC, 5.4 pH (KCl and NPK medium-enhanced contents in sandy loam topsoil. The CO2 flux seasonal monitoring has been done by two eddy covariance stations located at the distance of 108 m. The LI-COR instrumental equipment was the same for the both stations. The stations differ only by current crop version: barley or vetch and oats. At both sites, diurnal patterns of NEE among different months were very similar in shape but varied slightly in amplitude. NEE values were about zero during spring time. CO2 fluxes have been intensified after crop emerging from values of 3 to 7 µmol/s∙m2 for emission, and from 5 to 20 µmol/s∙m2 for sink. Stabilization of the fluxes has come at achieving plants height of 10-12 cm. Average NEE was negative only in June and July. Maximum uptake was observed in June with average values about 8 µmol CO2 m−2 s−1. Although different kind of crops were planted on the fields A and B, GPP dynamics was quite similar for both sites: after reaching the peak values at the mid of June, GPP decreased from 4 to 0.5 g C CO2 m-2 d-1 at the end of July. The difference in crops harvesting time that was equal two weeks did not significantly influence the daily

  14. Surface energy, CO2 fluxes and sea ice

    CSIR Research Space (South Africa)

    Gulev, SK

    2009-09-01

    Full Text Available , there are serious concerns about the recent decline in the number of VOS observations. Closure of global and regional energy balances still cannot be achieved without adjustments to the flux fields and/or the underlying surface meteorological variables. The impact...

  15. A Re-examination of Density Effects in Eddy Covariance Measurements of CO2 Fluxes

    Institute of Scientific and Technical Information of China (English)

    Heping LIU

    2009-01-01

    Corrections of density effects resulting from air-parcel expansion/compression are important in interpreting eddy covariance fluxes of water vapor and CO2 when open-path systems are used. To account for these effects, mean vertical velocity and perturbation of the density of dry air are two critical parameters in treating those physical processes responsible for density variations. Based on various underlying assumptions, different studies have obtained different formulas for the mean vertical velocity and perturbation of the density of dry air, leading to a number of approaches to correct density effects. In this study, we re-examine physical processes related to different assumptions that are made to formulate the density effects. Specifically, we re-examine the assumptions of a zero dry air flux and a zero moist air flux in the surface layer, used for treating density variations, and their implications for correcting density effects. It is found that physical processes in relation to the assumption of a zero dry air flux account for the influence of dry air expansion/compression on density variations. Meanwhile, physical processes in relation to the assumption of a zero moist air flux account for the influence of moist air expansion/compression on density variations. In this study, we also re-examine mixing ratio issues. Our results indicate that the assumption of a zero dry air flux favors the use of the mixing ratio relative to dry air, while the assumption of a zero moist air flux favors the use of the mixing ratio relative to the total moist air. Additionally, we compare different formula for the mean vertical velocity, generated by air-parcel expansion/compression, and for density effect corrections using eddy covariance data measured over three boreal ecosystems.

  16. Quantifying CO2 Fluxes Across a Gradient of Permafrost in Boreal Alaska

    Science.gov (United States)

    Euskirchen, E. S.; Edgar, C.; Turetsky, M. R.; Harden, J. W.; McGuire, A. D.

    2011-12-01

    Changes in vegetation and soil properties following permafrost degradation and thermokarst development may cause changes in net carbon uptake, either by stimulating primary productivity due to changes in vegetation composition or by stimulating soil microbial decomposition. In order to better understand these dynamics, we established three sites in interior Alaska across a gradient of permafrost in which permafrost varies in presence and stability. These sites include a black spruce ecosystem with cold soils and stable permafrost, a permafrost collapse scar with thermokarst formation, and a moderately rich fen lacking near surface permafrost. Measurements at the sites include year-round eddy covariance estimates of CO2, water, and energy fluxes as well as the associated micrometeorological variables. During winter, the ecosystems each released approximately 15 - 25 g C m-2 mo-1. However, the black spruce ecosystem began to take up CO2 as soon as air temperatures increased in the spring, with an estimated accumulation of ~23 g C m-2 from late March to early May. During this same period, we observed unusually high rates of ecosystem respiration some days at the thermokarst site, potentially due to the release of trapped CO2 from frozen soil gas pockets. While the black spruce ecosystem continued to act as a net sink of CO2 in the summer, taking up ~2.5± 1 g C m-2 d-1, the thermokarst and fen ecosystems remained CO2 sources, respectively releasing ~2.4 ± 0.8 g C m-2 d-1 and ~1.9 ± 1.1 g C m-2 d-1. While ecosystem respiration was similar across all three ecosystems during the summer (~4.8 ± 1.0 g C m-2 d-1), gross primary productivity was much higher in the spruce ecosystem (~7.3 ± 1.4 g C m-2 d-1) compared to the thermokarst (~ 2.5 ± 0.9 g C m-2 d-1) and fen ecosystems (~ 3.0 ± 1.1 g C m-2 d-1). These results suggest that in these boreal peatland ecosystems, permafrost thaw and thermokarst development will increase CO2 emissions to the atmosphere due to

  17. CO2 fluxes in converting a tropical savanna to a managed ecosystem

    Science.gov (United States)

    Bristow, Mila; Hutley, Lindsay; Beringer, Jason; Livesley, Stephen; Arndt, Stefan

    2013-04-01

    Clearing and burning of tropical savanna is a globally significant emission of greenhouse gas although there is large uncertainty relating to the magnitude of this flux. Australia's tropical savannas occupy over 25% of the continental land mass and they significantly influence the national greenhouse gas budget. The tropical savanna region is also earmarked as one potential area of agricultural expansion in Australia given predicted rainfall declines across southern agricultural regions. It is currently unknown what impact a conversion of savanna woodlands to agricultural cropping will have on carbon and water budgets. We measured continuous CO2 exchange using eddy covariance flux towers before, during and after a land use change event in a savanna woodland in the Northern Territory of Australia. Our experimental design included flux measurement in an uncleared savanna and at a second savanna site prior to, during clearing and conversion to agricultural land. In addition, we measured the biomass of the savanna vegetation to quantify loss of standing carbon during conversion. The uncleared savanna was a weak net sink annually (~0.5 t C ha-1yr-1). In the 5 months prior to clearing, the late dry season to the early wet season (Oct 2011 to Mar 2012), the analogue savanna site was also a weak sink (mean daily sink ~0.05 t C ha-1 d-1). Clearing shifted the site to a net source of CO2. It remained a permanent CO2 source regardless of subsequent weather events, with pulses of increased respiration associated with rainfall events. The cleared debris (63 t biomass ha-1) was burnt in the late dry season a process that took 10 days (burning, stock piling, re-burning). Using savanna specific fuel emission factors we calculated the emissions from this fire event assuming all above ground, and 90% below-ground biomass was incinerated. The burning released a further 25.1 t C ha-1 from cleared debris, plus 6.3 t C ha-1 as a net emission as measured by the tower, generating huge CO2

  18. Ecosystem gross CO2 fluxes in a tropical rainforest estimated from carbonyl sulfide (COS)

    Science.gov (United States)

    Seibt, U. H.; Maseyk, K. S.; Lett, C.; Juarez, S.; Sun, W.

    2014-12-01

    Carbonyl sulfide (COS) is a promising new tracer to constrain the gross CO2 fluxes of land ecosystems, particularly in tropical forests where CO2 flux partitioning is often problematic due to the absence of turbulent flow at night. Since vegetation COS and CO2 uptake during photosynthesis is closely coupled, the gross fluxes of photosynthesis and respiration can be quantified through the concurrent measurements of COS and CO2. We measured ecosystem COS and CO2 exchange over four months in a tropical rainforest at La Selva, Costa Rica. We observed a strong ecosystem uptake of COS with a diel signal that was similar but not identical to net CO2 fluxes. Soils at the site mostly acted as COS sinks, correlated with soil moisture. The COS and CO2 data were used to calculate canopy photosynthesis (approx. GPP) from net ecosystem CO2 exchange (NEE) based on the empirical relationship of leaf relative uptake of COS and CO2. Mid-day COS-based GPP estimates ranged from -10 to -15 μmol m-2 s-1, compared to NEE of -5 to -10 μmol m-2 s-1. Ecosystem respiration, calculated as the difference of NEE and GPP, ranged from 5 to 10 μmol m-2 s-1, similar to previous estimates of 5 to 9 μmol m-2 s-1 from CO2 flux partitioning and respiration component measurements at the site. Our results support the application of COS as a new tool in ecosystem flux partitioning that may be particularly useful in tropical forests.

  19. CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes

    NARCIS (Netherlands)

    Hoins, M.; Eberlein, T.; Van de Waal, D.B.; Sluijs, A.|info:eu-repo/dai/nl/311474748; Reichart, G.-J.|info:eu-repo/dai/nl/165599081; Rost, B.

    2016-01-01

    Carbon isotope fractionation (εp) between the inorganic carbon source and organic matter has been proposed to be a function of pCO2. To understand the CO2-dependency of εp and species-specific differences therein, inorganic carbon fluxes in the four dinoflagellate species Alexandrium fundyense, Scri

  20. Innovative CO2 Analyzer Technology for the Eddy Covariance Flux Monitor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build and evaluate NDIR Analyzers that can observe eddy covariance flux of CO2 from unmanned airborne platforms. For both phases, a total of four...

  1. Innovative CO2 Analyzer Technology for the Eddy Covariance Flux Monitor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build and evaluate NDIR Analyzers that can be used to observe Eddy Covariance Flux and Absolute Dry Mole Fraction of CO2 from stationary and airborne...

  2. CO2 air-sea fluxes across the Portuguese estuaries Tagus and Sado

    Science.gov (United States)

    Oliveira, A. P.; Cabeçadas, G.; Nogueira, M.

    2009-04-01

    Generally, estuaries and proximal shelves under the direct influence of river runoff and large inputs of organic matter are mostly heterotrophic and, therefore, act as a carbon source. In this context the CO2 dynamics in Tagus and Sado estuaries (SW Portugal) was studied under two different climate and hydrological situations. These moderately productive mesotidal coastal-plain lagoon-type estuaries, localised in the center of Portugal and distant 30-40 km apart, present quite different freshwater inflows, surface areas and water residence times. A study performed in 2001 revealed that the magnitude of CO2 fluxes in the two estuarine systems varied seasonally. CO2 emissions during the huge rainfall winter were similar in both estuaries, reaching a mean value of ~50 mmol m-2 d-1, while in spring emissions from Sado were ~6 times higher then Tagus ones, attaining a mean value of 62 mmol m-2 d-1. Nevertheless, in both sampling periods, Sado estuary showed, within the upper estuary (salinity

  3. Impact of Siberian observations on the optimization of surface CO2 flux

    Science.gov (United States)

    Kim, Jinwoong; Kim, Hyun Mee; Cho, Chun-Ho; Boo, Kyung-On; Jacobson, Andrew R.; Sasakawa, Motoki; Machida, Toshinobu; Arshinov, Mikhail; Fedoseev, Nikolay

    2017-02-01

    To investigate the effect of additional CO2 observations in the Siberia region on the Asian and global surface CO2 flux analyses, two experiments using different observation data sets were performed for 2000-2009. One experiment was conducted using a data set that includes additional observations of Siberian tower measurements (Japan-Russia Siberian Tall Tower Inland Observation Network: JR-STATION), and the other experiment was conducted using a data set without the above additional observations. The results show that the global balance of the sources and sinks of surface CO2 fluxes was maintained for both experiments with and without the additional observations. While the magnitude of the optimized surface CO2 flux uptake and flux uncertainty in Siberia decreased from -1.17 ± 0.93 to -0.77 ± 0.70 Pg C yr-1, the magnitude of the optimized surface CO2 flux uptake in the other regions (e.g., Europe) of the Northern Hemisphere (NH) land increased for the experiment with the additional observations, which affect the longitudinal distribution of the total NH sinks. This change was mostly caused by changes in the magnitudes of surface CO2 flux in June and July. The observation impact measured by uncertainty reduction and self-sensitivity tests shows that additional observations provide useful information on the estimated surface CO2 flux. The average uncertainty reduction of the conifer forest of Eurasian boreal (EB) is 29.1 % and the average self-sensitivities at the JR-STATION sites are approximately 60 % larger than those at the towers in North America. It is expected that the Siberian observations play an important role in estimating surface CO2 flux in the NH land (e.g., Siberia and Europe) in the future.

  4. The seasonal variation of the CO2 flux over Tropical Asia estimated from GOSAT, CONTRAIL, and IASI

    NARCIS (Netherlands)

    Basu, S.; Krol, M.; Butz, A.; Clerbaux, C.; Sawa, Y.; Machida, T.; Matsueda, H.; Frankenberg, C.; Hasekamp, O. P.; Aben, I.

    2014-01-01

    We estimate the CO2 flux over Tropical Asia in 2009, 2010, and 2011 using Greenhouse Gases Observing Satellite (GOSAT) total column CO2(XCO2) and in situ measurements of CO2. Compared to flux estimates from assimilating surface measurements of CO2, GOSAT XCO2 estimates a more dynamic seasonal cycle

  5. The role of Phragmites in the CH4 and CO2 fluxes in a minerotrophic peatland in southwest Germany

    Science.gov (United States)

    van den Berg, Merit; Ingwersen, Joachim; Lamers, Marc; Streck, Thilo

    2016-11-01

    Peatlands are interesting as a carbon storage option, but are also natural emitters of the greenhouse gas methane (CH4). Phragmites peatlands are particularly interesting due to the global abundance of this wetland plant (Phragmites australis) and the highly efficient internal gas transport mechanism, which is called humidity-induced convection (HIC). The research aims were to (1) clarify how this plant-mediated gas transport influences the CH4 fluxes, (2) which other environmental variables influence the CO2 and CH4 fluxes, and (3) whether Phragmites peatlands are a net source or sink of greenhouse gases. CO2 and CH4 fluxes were measured with the eddy covariance technique within a Phragmites-dominated fen in southwest Germany. One year of flux data (March 2013-February 2014) shows very clear diurnal and seasonal patterns for both CO2 and CH4. The diurnal pattern of CH4 fluxes was only visible when living, green reed was present. In August the diurnal cycle of CH4 was the most distinct, with 11 times higher midday fluxes (15.7 mg CH4 m-2 h-1) than night fluxes (1.41 mg CH4 m-2 h-1). This diurnal cycle has the highest correlation with global radiation, which suggests a high influence of the plants on the CH4 flux. But if the cause were the HIC, it would be expected that relative humidity would correlate stronger with CH4 flux. Therefore, we conclude that in addition to HIC, at least one additional mechanism must be involved in the creation of the convective flow within the Phragmites plants. Overall, the fen was a sink for carbon and greenhouse gases in the measured year, with a total carbon uptake of 221 g C m-2 yr-1 (26 % of the total assimilated carbon). The net uptake of greenhouse gases was 52 g CO2 eq. m-2 yr-1, which is obtained from an uptake of CO2 of 894 g CO2 eq. m-2 yr-1 and a release of CH4 of 842 g CO2 eq. m-2 yr-1.

  6. Net ecosystem production, calcification and CO2 fluxes on a reef flat in Northeastern Brazil

    Science.gov (United States)

    Longhini, Cybelle M.; Souza, Marcelo F. L.; Silva, Ananda M.

    2015-12-01

    The carbon cycle in coral reefs is usually dominated by the organic carbon metabolism and precipitation-dissolution of CaCO3, processes that control the CO2 partial pressure (pCO2) in seawater and the CO2 fluxes through the air-sea interface. In order to characterize these processes and the carbonate system, four sampling surveys were conducted at the reef flat of Coroa Vermelha during low tide (exposed flat). Net ecosystem production (NEP), net precipitation-dissolution of CaCO3 (G) and CO2 fluxes across the air-water interface were calculated. The reef presented net autotrophy and calcification at daytime low tide. The NEP ranged from -8.7 to 31.6 mmol C m-2 h-1 and calcification from -13.1 to 26.0 mmol C m-2 h-1. The highest calcification rates occurred in August 2007, coinciding with the greater NEP rates. The daytime CO2 fluxes varied from -9.7 to 22.6 μmol CO2 m-2 h-1, but reached up to 13,900 μmol CO2 m-2 h-1 during nighttime. Carbon dioxide influx to seawater was predominant in the reef flat during low tide. The regions adjacent to the reef showed a supersaturation of CO2, acting as a source of CO2 to the atmosphere (from -22.8 to -2.6 mol CO2 m-2 h-1) in the reef flat during ebbing tide. Nighttime gas release to the atmosphere indicates a net CO2 release from the Coroa Vermelha reef flat within 24 h, and that these fluxes can be important to carbon budget in coral reefs.

  7. 密度修正对冬小麦/夏玉米轮作田潜热、CO2通量及其能量闭合度的影响%Influence of density correction on latent heat, CO2 flux and energy balance closure in winter wheat/summer maize rotation fields

    Institute of Scientific and Technical Information of China (English)

    王娟; 曹元元; 张志广; 姜永超; 王建林

    2016-01-01

    本文利用涡度相关技术对青岛农业大学现代农业科技示范园试验站2013—2014年冬小麦/夏玉米轮作田与大气之间CO2、水汽和能量交换进行测量,分别对潜热和CO2通量进行两种密度修正(WPL修正和Liu修正)并进行对比,计算了两种密度修正前后冬小麦/夏玉米轮作田的能量闭合度。结果表明: WPL修正与Liu修正可以提高潜热通量, WPL修正后夏玉米田潜热通量约提高6%,冬小麦田约提高2%; Liu修正后夏玉米田提高不足1%,冬小麦田提高约2%。因此WPL修正对于夏玉米田潜热的修正效果明显优于Liu修正,而对冬小麦田潜热修正两种方法效果相同。两种修正方法对于CO2通量具有降低的修正效果, WPL修正后夏玉米田和冬小麦田CO2通量分别降低3%和4%; Liu修正后夏玉米田和冬小麦田CO2分别降低2%和3%。可以看出, WPL 修正和 Liu 修正对 CO2通量修正前后差别非常小(差距均为1%)。通过对青岛地区冬小麦/夏玉米轮作田能量闭合度的分析,发现密度修正可以提高能量闭合度,但不同下垫面有不同的修正效果。裸地情况下, WPL修正可以提高能量闭合度约2.53%~9.76%,夏玉米田为4.05%,冬小麦田为1.35%;而 Liu 修正对裸地能量闭合度的提高小于2.53%,对夏玉米田和冬小麦田提高约为1.35%。显然 WPL修正对于能量闭合度的修正幅度大于Liu修正。能量闭合度大小关系为裸地Ⅰ(夏玉米出苗前)>裸地Ⅱ(冬小麦出苗前)>夏玉米田>冬小麦田。%In the past two decades, the eddy covariance technique has been used as a normalized measure method of exchange of CO2, water vapor and heat between vegetation and the atmosphere. To understand the variation characteristics of CO2, water vapor and heat fluxes of winter wheat/summer maize rotation system, an experiment was conducted in the period from June 2013 to June 2014 at Qingdao Modern Agricultural

  8. Global climate impacts of bioenergy from forests: implications from biogenic CO2 fluxes and surface albedo

    Science.gov (United States)

    Cherubini, Francesco; Bright, Ryan; Strømman, Anders

    2013-04-01

    Production of biomass for bioenergy can alter biogeochemical and biogeophysical mechanisms, thus affecting local and global climate. Recent scientific developments mainly embraced impacts from land use changes resulting from area-expanded biomass production, with several extensive insights available. Comparably less attention, however, is given to the assessment of direct land surface-atmosphere climate impacts of bioenergy systems under rotation such as in plantations and forested ecosystems, whereby land use disturbances are only temporary. In this work, we assess bioenergy systems representative of various biomass species (spruce, pine, aspen, etc.) and climatic regions (US, Canada, Norway, etc.), for both stationary and vehicle applications. In addition to conventional greenhouse gas (GHG) emissions through life cycle activities (harvest, transport, processing, etc.), we evaluate the contributions to global warming of temporary effects resulting from the perturbation in atmospheric carbon dioxide (CO2) concentration caused by the timing of biogenic CO2 fluxes and in surface reflectivity (albedo). Biogenic CO2 fluxes on site after harvest are directly measured through Net Ecosystem Productivity (NEP) chronosequences from flux towers established at the interface between the forest canopy and the atmosphere and are inclusive of all CO2 exchanges occurring in the forest (e.g., sequestration of CO2 in growing trees, emissions from soil respiration and decomposition of dead organic materials). These primary data based on empirical measurements provide an accurate representation of the forest carbon sink behavior over time, and they are used in the elaboration of high-resolution IRFs for biogenic CO2 emissions. Chronosequence of albedo values from clear-cut to pre-harvest levels are gathered from satellite data (MODIS black-sky shortwave broadband, Collection 5, MCD43A). Following the cause-effect chain from emissions to damages, through radiative forcing and changes

  9. The role of vegetation in the CO2 flux from a tropical urban neighbourhood

    Science.gov (United States)

    Velasco, E.; Roth, M.; Tan, S. H.; Quak, M.; Nabarro, S. D. A.; Norford, L.

    2013-10-01

    Urban surfaces are usually net sources of CO2. Vegetation can potentially have an important role in reducing the CO2 emitted by anthropogenic activities in cities, particularly when vegetation is extensive and/or evergreen. A direct and accurate estimation of carbon uptake by urban vegetation is difficult due to the particular characteristics of the urban ecosystem and high variability in tree distribution and species. Here, we investigate the role of urban vegetation in the CO2 flux from a residential neighbourhood in Singapore using two different approaches. CO2 fluxes measured directly by eddy covariance are compared with emissions estimated from emissions factors and activity data. The latter includes contributions from vehicular traffic, household combustion, soil respiration and human breathing. The difference between estimated emissions and measured fluxes should approximate the flux associated with the aboveground vegetation. In addition, a tree survey was conducted to estimate the annual CO2 sequestration using allometric equations and an alternative model of the metabolic theory of ecology for tropical forests. Palm trees, banana plants and turfgrass were also included in the survey with their annual CO2 uptake obtained from published growth rates. Both approaches agree within 2% and suggest that vegetation sequesters 8% of the total emitted CO2 in the residential neighbourhood studied. An uptake of 1.4 ton km-2 day-1 (510 ton km-2 yr-1) was estimated as the difference between assimilation by photosynthesis minus the aboveground biomass respiration during daytime (4.0 ton km-2 day-1) and release by plant respiration at night (2.6 ton km-2 day-1). However, when soil respiration is added to the daily aboveground flux, the biogenic component becomes a net source amounting to 4% of the total CO2 flux and represents the total contribution of urban vegetation to the carbon flux to the atmosphere.

  10. The abiotic contribution to total CO2 flux for soils in arid zone

    Directory of Open Access Journals (Sweden)

    J. Ma

    2015-07-01

    Full Text Available As an important component of ecosystem carbon budgets, soil carbon dioxide (CO2 flux is determined by a combination of a series of biotic and abiotic processes. Although there is evidence that the abiotic component can be important in total soil CO2 flux, its relative importance has never been systematically assessed. In this study, the total soil CO2 flux (Rtotal was partitioned into biotic (Rbiotic and abiotic (Rabiotic components over eight typical landscapes in a desert–oasis ecotone, including cotton field, hops field, halophyte garden, reservoir edge, native saline desert, alkaline soil, dune crest and interdune lowland in the Gurbantunggut Desert, and the relative importance of these two components was analyzed. Results showed that Rabiotic always contributed to Rtotal for the eight landscapes, but the degree of contribution varied greatly. In the cotton and hops fields, the ratio of Rabiotic to Rtotal was extremely low (Rabiotic was dominant in the alkaline soil and dune crest. Statistically, Rabiotic/Rtotal decreased logarithmically with rising Rbiotic, suggesting that Rabiotic strongly affected Rtotal when Rbiotic was low. This pattern confirms that soil CO2 flux is predominantly biological in most ecosystems, but Rabiotic can dominate when biological processes are weak. On a diurnal basis, Rabiotic resulted in no net gain or loss of carbon but its effect on instantaneous CO2 flux was significant. Temperature dependence of Rtotal varied among the eight landscapes, determined by the predominant components of CO2 flux: with Rbiotic driven by soil temperature and Rabiotic regulated by the rate of change in temperature. Namely, declining temperature resulted in negative Rabiotic (CO2 went into soil, while rising temperature resulted in a positive Rabiotic (CO2 released from soil. Furthermore, without recognition of Rabiotic, Rbiotic would have been either overestimated (for daytime or underestimated (for nighttime. Thus, recognition that

  11. Environmental factors regulating winter CO2 flux in snow-covered boreal forest soil, interior Alaska

    Science.gov (United States)

    Kim, Y.; Kodama, Y.

    2012-01-01

    Winter CO2 flux is an important element to assess when estimating the annual carbon budget on regional and global scales. However, winter observation frequency is limited due to the extreme cold weather in sub-Arctic and Arctic ecosystems. In this study, the continuous monitoring of winter CO2 flux in black spruce forest soil of interior Alaska was performed using NDIR CO2 sensors at 10, 20, and 30 cm above the soil surface during the snow-covered period (DOY 357 to 466) of 2006/2007. The atmospheric pressure was divided into four phases: >1000 hPa (HP: high pressure); 985emission represents 20 % of the annual CO2 emissions in this boreal black spruce forest soil. Atmospheric temperature, pressure, and soil temperature correlate at levels of 56, 25, and 31 % to winter CO2 flux, respectively, during the snow-covered period of 2006/2007, when snow depth experienced one of its lowest totals of the past 80 years. Atmospheric temperature and soil temperature at 5 cm depth, modulated by atmospheric pressure, were found to be significant factors in determining winter CO2 emission and fluctuation in snowpack. Regional/global process-based carbon cycle models should be reassessed to account for the effect of winter CO2 emissions, regulated by temperature and soil latent-heat flux, in the snow-covered soils of Arctic and sub-Arctic terrestrial ecosystems of the Northern Hemisphere.

  12. CO2 Flux from a Subtropical Mangrove Ecosystem in Magdalena Bay BCS, Mexico Josediego Uribe, Walter C. Oechel

    Science.gov (United States)

    Uribe, J.; Oechel, W. C.

    2012-12-01

    Mangrove forests are among the most productive ecosystems within the tropical and subtropical coastlines of the world. There is currently limited research on mangrove carbon sequestration potentials but with ongoing climate change and rising atmospheric carbon dioxide (CO2) levels, an understanding of carbon exchange in mangroves forests and the environmental controls influencing fluxes is extremely important for understanding their role in the global carbon cycle and their potential as stores of CO2. In this study, CO2 flux was evaluated for a subtropical mangrove ecosystem in the arid region of Magdalena Bay BCS, Mexico. Measurements were taken using an eddy covariance system above the canopy during January 8 to the 30, and currently from June 21 to August 28, in 2012. The mangrove forest is located (N25° 15'75", W112° 04'79") near the town of Puerto Lopez Mateos, Mexico. During this time period environmental variables such as Net Radiation, photosynthetically active radiation (PAR), air temperature, humidity, ground heat flux, soil temperature and tidal height were measured together with the CO2 flux in order to determine the environmental influence on the fluxes. Preliminary results showed a clear diurnal pattern in CO2 flux that showed high sinks when light availability was high. During January, the winter dry season environmental conditions remained relatively cool with an average air temperature of 17 oC and consistently cloudless days. During this period CO2 flux was -1.3 μmol C m-2s-1, which means that for the month of January, there was a net uptake of carbon by the mangrove ecosystem. For the summer period the development of the data collection for a longer term as well as further correlation analysis with environmental data is currently underway, however expectations are that seasonal variations of CO2 flux can be seen due to longer and more intense periods of solar irradiance as well as the effect of high temperature (+30° C) days. Indirect effects

  13. The role of vegetation in the CO2 flux from a tropical urban neighbourhood

    Science.gov (United States)

    Velasco, E.; Roth, M.; Tan, S. H.; Quak, M.; Nabarro, S. D. A.; Norford, L.

    2013-03-01

    Urban surfaces are usually net sources of CO2. Vegetation can potentially have an important role in reducing the CO2 emitted by anthropogenic activities in cities, particularly when vegetation is extensive and/or evergreen. Negative daytime CO2 fluxes, for example have been observed during the growing season at suburban sites characterized by abundant vegetation and low population density. A direct and accurate estimation of carbon uptake by urban vegetation is difficult due to the particular characteristics of the urban ecosystem and high variability in tree distribution and species. Here, we investigate the role of urban vegetation in the CO2 flux from a residential neighbourhood in Singapore using two different approaches. CO2 fluxes measured directly by eddy covariance are compared with emissions estimated from emissions factors and activity data. The latter includes contributions from vehicular traffic, household combustion, soil respiration and human breathing. The difference between estimated emissions and measured fluxes should approximate the biogenic flux. In addition, a tree survey was conducted to estimate the annual CO2 sequestration using allometric equations and an alternative model of the metabolic theory of ecology for tropical forests. Palm trees, banana plants and turfgrass were also included in the survey with their annual CO2 uptake obtained from published growth rates. Both approaches agree within 2% and suggest that vegetation captures 8% of the total emitted CO2 in the residential neighbourhood studied. A net uptake of 1.4 ton km-2 day-1 (510 ton km-2 yr-1 ) was estimated from the difference between the daily CO2 uptake by photosynthesis (3.95 ton km-2 ) and release by respiration (2.55 ton km-2). The study shows the importance of urban vegetation at the local scale for climate change mitigation in the tropics.

  14. The Influence of CO2 Solubility in Brine on Simulation of CO2 Injection into Water Flooded Reservoir and CO2 WAG

    DEFF Research Database (Denmark)

    Yan, Wei; Stenby, Erling Halfdan

    2010-01-01

    Injection of CO2 into depleted oil reservoirs is not only a traditional way to enhance oil recovery but also a relatively cheaper way to sequester CO2 underground since the increased oil production can offset some sequestration cost. CO2 injection process is often applied to water flooded...... reservoirs and in many situations alternating injection of water and CO2 is required to stabilize the injection front. Both scenarios involve a large amount of water, making CO2 solubility in brine, which is around ten times higher than methane solubility, a non-negligible factor in the relevant reservoir...... simulations. In our previous study, a 1-D slimtube simulator, which rigorously accounts for both CO2 solubility in brine and water content in hydrocarbon phases using the Peng-Robinson EoS modified by Soreide and Whitson, has been used to investigate the influence of CO2 solubility on the simulation...

  15. A biogenic CO2 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts

    Science.gov (United States)

    Agustí-Panareda, Anna; Massart, Sébastien; Chevallier, Frédéric; Balsamo, Gianpaolo; Boussetta, Souhail; Dutra, Emanuel; Beljaars, Anton

    2016-08-01

    Forecasting atmospheric CO2 daily at the global scale with a good accuracy like it is done for the weather is a challenging task. However, it is also one of the key areas of development to bridge the gaps between weather, air quality and climate models. The challenge stems from the fact that atmospheric CO2 is largely controlled by the CO2 fluxes at the surface, which are difficult to constrain with observations. In particular, the biogenic fluxes simulated by land surface models show skill in detecting synoptic and regional-scale disturbances up to sub-seasonal time-scales, but they are subject to large seasonal and annual budget errors at global scale, usually requiring a posteriori adjustment. This paper presents a scheme to diagnose and mitigate model errors associated with biogenic fluxes within an atmospheric CO2 forecasting system. The scheme is an adaptive scaling procedure referred to as a biogenic flux adjustment scheme (BFAS), and it can be applied automatically in real time throughout the forecast. The BFAS method generally improves the continental budget of CO2 fluxes in the model by combining information from three sources: (1) retrospective fluxes estimated by a global flux inversion system, (2) land-use information, (3) simulated fluxes from the model. The method is shown to produce enhanced skill in the daily CO2 10-day forecasts without requiring continuous manual intervention. Therefore, it is particularly suitable for near-real-time CO2 analysis and forecasting systems.

  16. Effect of Sampling Depth on Air-Sea CO2 Flux Estimates in River-Stratified Arctic Coastal Waters

    Science.gov (United States)

    Miller, L. A.; Papakyriakou, T. N.

    2015-12-01

    In summer-time Arctic coastal waters that are strongly influenced by river run-off, extreme stratification severely limits wind mixing, making it difficult to effectively sample the surface 'mixed layer', which can be as shallow as 1 m, from a ship. During two expeditions in southwestern Hudson Bay, off the Nelson, Hayes, and Churchill River estuaries, we confirmed that sampling depth has a strong impact on estimates of 'surface' pCO2 and calculated air-sea CO2 fluxes. We determined pCO2 in samples collected from 5 m, using a typical underway system on the ship's seawater supply; from the 'surface' rosette bottle, which was generally between 1 and 3 m; and using a niskin bottle deployed at 1 m and just below the surface from a small boat away from the ship. Our samples confirmed that the error in pCO2 derived from typical ship-board versus small-boat sampling at a single station could be nearly 90 μatm, leading to errors in the calculated air-sea CO2 flux of more than 0.1 mmol/(m2s). Attempting to extrapolate such fluxes over the 6,000,000 km2 area of the Arctic shelves would generate an error approaching a gigamol CO2/s. Averaging the station data over a cruise still resulted in an error of nearly 50% in the total flux estimate. Our results have implications not only for the design and execution of expedition-based sampling, but also for placement of in-situ sensors. Particularly in polar waters, sensors are usually deployed on moorings, well below the surface, to avoid damage and destruction from drifting ice. However, to obtain accurate information on air-sea fluxes in these areas, it is necessary to deploy sensors on ice-capable buoys that can position the sensors in true 'surface' waters.

  17. Quantifying the magnitude, spatiotemporal variation and age of aquatic CO2 fluxes in western Greenland

    Science.gov (United States)

    Long, H. E.; Waldron, S.; Hoey, T.; Garnett, M.; Newton, J.

    2014-12-01

    High latitude regions are experiencing accelerated atmospheric warming, and understanding the terrestrial response to this is of crucial importance as: a) there is a large store of carbon (C) in permafrost soils which may be released and feedback to climate change; and, b) ice sheet melt in this region is accelerating, and whilst this will cause albedo and heat flux changes, the role of this in atmospheric gas release is poorly known. To understand how sensitive arctic environments may respond to future warming, we need measurements that document current C flux rates and help to understand C cycling pathways. Although it has been widely hypothesised that arctic regions may become increasingly significant C sources, the contribution of aquatic C fluxes which integrate catchment-wide sources has been little studied. Using a floating chamber method we directly measured CO2 fluxes from spatially distributed freshwaters (ice sheet melt, permafrost melt, and lakes/ponds) in the Kangerlussuaq region of western Greenland during the early part of the summer 2014 melt season. Fluxes from freshwaters with permafrost sources were in the range -3.15 to +1.28 μmol CO2 m-2 s-1. Fluxes from a river draining the ice sheet and the Russell Glacier were between -2.19 and +4.31 μmol CO2 m-2 s-1. These ranges show the systems can be both sources (efflux) and sinks (influx) of CO2. Most freshwater data worldwide shows CO2 efflux and so recording aquatic systems being a CO2­ ­sink is unusual. Our data show spatial and temporal variations that are related to hydraulic as well as biogeochemical processes. Additionally, where we recorded CO2 efflux we collected effluxed CO2 for radiocarbon analysis. The measured age of the released gas will help to identify the sources and dominant transport processes of CO­2 (e.g. entrained modern atmospheric CO2, or old CO2 trapped during ice formation released through ice melt, or CO2 derived from respiration of soil and sediment organic matter

  18. Volcanic CO2 flux measurement at Campi Flegrei by tunable diode laser absorption spectroscopy

    Science.gov (United States)

    Pedone, M.; Aiuppa, A.; Giudice, G.; Grassa, F.; Cardellini, C.; Chiodini, G.; Valenza, M.

    2014-04-01

    Near-infrared room temperature tunable diode lasers (TDL) have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in volcanology are still limited to a few examples. Here, we explored the potential of a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) for measurement of volcanic CO2 mixing ratios, and ultimately for estimating the volcanic CO2 flux. Our field tests were conducted at Campi Flegrei near Pozzuoli, Southern Italy, where the GasFinder was used during three campaigns in October 2012, January 2013 and May 2013 to repeatedly measure the path-integrated mixing ratios of CO2 along cross sections of the atmospheric plumes of two major fumarolic fields (Solfatara and Pisciarelli). By using a tomographic post-processing routine, we resolved, for each of the two fields, the contour maps of CO2 mixing ratios in the atmosphere, from the integration of which (and after multiplication by the plumes' transport speeds) the CO2 fluxes were finally obtained. We evaluate a total CO2 output from the Campi Flegrei fumaroles of ˜490 Mg/day, in line with independent estimates based on in situ (Multi-GAS) observations. We conclude that TDL technique may enable CO2 flux quantification at other volcanoes worldwide.

  19. Monitoring Ocean CO2 Fluxes from Space: GOSAT and OCO-2

    Science.gov (United States)

    Crisp, David

    2012-01-01

    The ocean is a major component of the global carbon cycle, emitting over 330 billion tons of carbon dioxide (CO2) into the atmosphere each year, or about 10 times that emitted fossil fuel combustion and all other human activities [1, 2]. The ocean reabsorbs a comparable amount of CO2 each year, along with 25% of the CO2 emitted by these human activities. The nature and geographic distribution of the processes controlling these ocean CO2 fluxes are still poorly constrained by observations. A better understanding of these processes is essential to predict how this important CO2 sink may evolve as the climate changes.While in situ measurements of ocean CO2 fluxes can be very precise, the sampling density is far too sparse to quantify ocean CO2 sources and sinks over much of the globe. One way to improve the spatial resolution, coverage, and sampling frequency is to make observations of the column averaged CO2 dry air mole fraction, XCO2, from space [4, 5, 6]. Such measurements could provide global coverage at high resolution (space based sensors designed specifically for this task. GOSAT was successfully launched on January 23, 2009, and has been returning measurements of XCO2 since April 2009. The OCO mission was lost in February 2009, when its launch vehicle malfunctioned and failed to reach orbit. In early 2010, NASA authorized a re-flight of OCO, called OCO-2, which is currently under development.

  20. Summertime CO2 fluxes and ecosystem respiration from marine animal colony tundra in maritime Antarctica

    Science.gov (United States)

    Zhu, Renbin; Bao, Tao; Wang, Qing; Xu, Hua; Liu, Yashu

    2014-12-01

    Net ecosystem CO2 exchange (NEE) and ecosystem respiration (ER) were investigated at penguin, seal and skua colony tundra and the adjacent animal-lacking tundra sites in maritime Antarctica. Net CO2 fluxes showed a large difference between marine animal colonies and animal-lacking tundra sites. The mean NEE from penguin, seal and skua colony tundra sites ranged from -37.2 to 5.2 mg CO2 m-2 h-1, whereas animal-lacking tundra sites experienced a larger net gain of CO2 with the mean flux range from -85.6 to -23.9 mg CO2 m-2 h-1. Ecosystem respiration rates at penguin colony tundra sites (mean 201.3 ± 31.4 mg CO2 m-2 h-1) were significantly higher (P animal colony and animal-lacking tundra was significantly positively correlated (P exponential correlation (P animals and the deposition of their excreta might have an important effect on tundra CO2 exchanges and ecosystem respiration, and current climate warming will further decrease tundra CO2 sink in maritime Antarctica.

  1. Imposing strong constraints on tropical terrestrial CO2 fluxes using passenger aircraft based measurements

    Science.gov (United States)

    Niwa, Y.; Machida, T.; Sawa, Y.; Matsueda, H.; Schuck, T. J.; Brenninkmeijer, C. A.; Imasu, R.; Satoh, M.

    2011-12-01

    Better understanding of the global and regional carbon budget is needed to perform a reliable prediction of future climate with an earth system model. However, the reliability of CO2 source/sink estimation by inverse modeling, which is one of the promising methods to estimate regional carbon budget, is limited because of sparse observational data coverage. Very few observational data are available in tropics. Therefore, especially the reconstruction of tropical terrestrial fluxes has considerable uncertainties. In this study, regional CO2 fluxes for 2006-2008 are estimated by inverse modeling using the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) in addition to the surface measurement dataset of GLOBALVIEW-CO2. CONTRAIL is a recently established CO2 measurement network using in-situ measurement instruments on board commercial aircraft. Five CONTRAIL aircraft travel back and forth between Japan and many areas: Europe, North America, Southeast Asia, South Asia, and Australia. The Bayesian synthesis approach is used to estimate monthly fluxes for 42 regions using NICAM-TM simulations with existing CO2 flux datasets and monthly mean observational data. It is demonstrated that the aircraft data have great impact on estimated tropical terrestrial fluxes. By adding the aircraft data to the surface data, the analyzed uncertainty of tropical fluxes has been reduced by 15 % and more than 30 % uncertainty reduction rate is found in Southeast and South Asia. Specifically, for annual net CO2 fluxes, nearly neutral fluxes of Indonesia, which is estimated using the surface dataset alone, turn to positive fluxes, i.e. carbon sources. In Indonesia, a remarkable carbon release during the severe drought period of October-December in 2006 is estimated, which suggests that biosphere respiration or biomass burning was larger than the prior fluxes. Comparison of the optimized atmospheric CO2 with independent aircraft measurements of CARIBIC tends to validate

  2. Influence of acoustic waves on TEA CO2 laser performance

    CSIR Research Space (South Africa)

    Von Bergmann, H

    2007-01-01

    Full Text Available In this paper the author’s present results on the influence of acoustic waves on the output laser beam from high repetition rate TEA CO2 lasers. The authors show that acoustic waves generated inside the cavity lead to deterioration in beam quality...

  3. Evaluating the Capacity of Global CO2 Flux and Atmospheric Transport Models to Incorporate New Satellite Observations

    Science.gov (United States)

    Kawa, S. R.; Collatz, G. J.; Erickson, D. J.; Denning, A. S.; Wofsy, S. C.; Andrews, A. E.

    2007-01-01

    As we enter the new era of satellite remote sensing for CO2 and other carbon cyclerelated quantities, advanced modeling and analysis capabilities are required to fully capitalize on the new observations. Model estimates of CO2 surface flux and atmospheric transport are required for initial constraints on inverse analyses, to connect atmospheric observations to the location of surface sources and sinks, and ultimately for future projections of carbon-climate interactions. For application to current, planned, and future remotely sensed CO2 data, it is desirable that these models are accurate and unbiased at time scales from less than daily to multi-annual and at spatial scales from several kilometers or finer to global. Here we focus on simulated CO2 fluxes from terrestrial vegetation and atmospheric transport mutually constrained by analyzed meteorological fields from the Goddard Modeling and Assimilation Office for the period 1998 through 2006. Use of assimilated meteorological data enables direct model comparison to observations across a wide range of scales of variability. The biospheric fluxes are produced by the CASA model at lxi degrees on a monthly mean basis, modulated hourly with analyzed temperature and sunlight. Both physiological and biomass burning fluxes are derived using satellite observations of vegetation, burned area (as in GFED-2), and analyzed meteorology. For the purposes of comparison to CO2 data, fossil fuel and ocean fluxes are also included in the transport simulations. In this presentation we evaluate the model's ability to simulate CO2 flux and mixing ratio variability in comparison to in situ observations at sites in Northern mid latitudes and the continental tropics. The influence of key process representations is inferred. We find that the model can resolve much of the hourly to synoptic variability in the observations, although there are limits imposed by vertical resolution of boundary layer processes. The seasonal cycle and its

  4. Conditional CO2 flux analysis of a managed grassland with the aid of stable isotopes

    Directory of Open Access Journals (Sweden)

    N. Buchmann

    2009-04-01

    Full Text Available Short statured managed ecosystems, such as agricultural grasslands, exhibit high temporal changes in carbon dioxide assimilation and respiration fluxes for which measurements of the net CO2 flux, e.g. by using the eddy covariance (EC method, give only limited insight. We have therefore adopted a recently proposed concept for conditional EC flux analysis of forest to grasslands, in order to identify and quantify daytime sub-canopy respiration fluxes. To validate the concept, high frequency (≈5 Hz stable carbon isotope analyis of CO2 was used. We made eddy covariance measurements of CO2 and its isotopologues during four days in August 2007, using a novel quantum cascade laser absorption spectrometer, capable of high time resolution stable isotope analysis. The effects of a grass cut during the measurement period could be detected and resulted in a sub-canopy source conditional flux classification, for which the isotope composition of the CO2 could be confirmed to be of a respiration source. However, the conditional flux method did not work for an undisturbed grassland canopy. We attribute this to the flux measurement height that was chosen well above the roughness sublayer, where the natural isotopic tracer (δ13C of respiration was too well mixed with background air.

  5. Air-sea CO2 fluxes on the Bering Sea shelf

    Directory of Open Access Journals (Sweden)

    M. A. Jeffries

    2011-05-01

    Full Text Available There have been few previous studies of surface seawater CO2 partial pressure (pCO2 variability and air-sea CO2 gas exchange rates for the Bering Sea shelf. In 2008, spring and summertime observations were collected in the Bering Sea shelf as part of the Bering Sea Ecological Study (BEST. Our results indicate that the Bering Sea shelf was close to neutral in terms of CO2 sink-source status in springtime due to relatively small air-sea CO2 gradients (i.e., ΔpCO2 and sea-ice cover. However, by summertime, very low seawater pCO2 values were observed and much of the Bering Sea shelf became strongly undersaturated with respect to atmospheric CO2 concentrations. Thus the Bering Sea shelf transitions seasonally from mostly neutral conditions to a strong oceanic sink for atmospheric CO2 particularly in the "green belt" region of the Bering Sea where there are high rates of phytoplankton primary production (PPand net community production (NCP. Ocean biological processes dominate the seasonal drawdown of seawater pCO2 for large areas of the Bering Sea shelf, with the effect partly countered by seasonal warming. In small areas of the Bering Sea shelf south of the Pribilof Islands and in the SE Bering Sea, seasonal warming is the dominant influence on seawater pCO2, shifting localized areas of the shelf from minor/neutral CO2 sink status to neutral/minor CO2 source status, in contrast to much of the Bering Sea shelf. Overall, we compute that the Bering Sea shelf CO2 sink in 2008 was 157 ± 35 Tg C yr−1 (Tg = 1012 g C and thus a strong sink for CO2.

  6. Quantifying the Observability of CO2 Flux Uncertainty in Atmospheric CO2 Records Using Products from Nasa's Carbon Monitoring Flux Pilot Project

    Science.gov (United States)

    Ott, Lesley; Pawson, Steven; Collatz, Jim; Watson, Gregg; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile; Bowman, Kevin; Bowman, Kevin; Liu, Junjie; Eldering, Annmarie; Gunson, Michael; Kawa, Stephan R.

    2014-01-01

    NASAs Carbon Monitoring System (CMS) Flux Pilot Project (FPP) was designed to better understand contemporary carbon fluxes by bringing together state-of-the art models with remote sensing datasets. Here we report on simulations using NASAs Goddard Earth Observing System Model, version 5 (GEOS-5) which was used to evaluate the consistency of two different sets of observationally constrained land and ocean fluxes with atmospheric CO2 records. Despite the strong data constraint, the average difference in annual terrestrial biosphere flux between the two land (NASA Ames CASA and CASA-GFED) models is 1.7 Pg C for 2009-2010. Ocean models (NOBM and ECCO2-Darwin) differ by 35 in their global estimates of carbon flux with particularly strong disagreement in high latitudes. Based upon combinations of terrestrial and ocean fluxes, GEOS-5 reasonably simulated the seasonal cycle observed at northern hemisphere surface sites and by the Greenhouse gases Observing SATellite (GOSAT) while the model struggled to simulate the seasonal cycle at southern hemisphere surface locations. Though GEOS-5 was able to reasonably reproduce the patterns of XCO2 observed by GOSAT, it struggled to reproduce these aspects of AIRS observations. Despite large differences between land and ocean flux estimates, resulting differences in atmospheric mixing ratio were small, typically less than 5 ppmv at the surface and 3 ppmv in the XCO2 column. A statistical analysis based on the variability of observations shows that flux differences of these magnitudes are difficult to distinguish from natural variability, regardless of measurement platform.

  7. CO2 flux spatial variability in a tropical reservoir in the Central Amazonia

    Science.gov (United States)

    Santana, R. A. S. D.; do Vale, R. S.; Tota, J.; Miller, S. D.; Ferreira, R. B., Jr.; Alves, E. G.; Batalha, S. S. A.; Souza, R. A. F. D.

    2014-12-01

    The carbon budget over water surfaces in the Amazon has an important role in the total budget of this greenhouse gas a regional and global scale. However, more accurate estimates of the spatial and temporal distribution of the CO2 flux over those water surfaces are still required. In this context, this study aims to understand the spatial distribution of CO2 flux in the Balbina hydroelectric reservoir, located at Presidente Figueiredo city, Amazonas, Brazil. The floating chamber method was used to measure and calculate the CO2 flux. This method coup a chamber of known volume with an infrared gas analyzer (LiCor, LI-840A). Measurements were performed at 1 Hz during 20-30 minutes at 5 different points of the reservoir, four upstream (two near the edge and two in the middle) and one downstream of the dam. At all locations the surface water was supersaturated in pCO2 and fluxes were from the water to the atmosphere. The maximum CO2 flux observed was 1.2 μmol m-2 s-1 at the center point of the reservoir upstream the dam. The minimum CO2 flux was 0.05 μmol m-2 s-1, observed near the edge on the upstream side of the dam. On average, CO2 fluxes were larger downstream of the dam, 0.7 μmol m-2 s-1, compared to upstream, 0.45 μmol m-2 s-1. This pattern is consistent with that found in previous studies at this site using other flux estimation methods, and is consistent with turbulent mixing promoted by the water turbine. However, the mean CO2 flux for all measured points using the chambers, 0.47 μmol m-2 s-1, was much lower than those previously found using other methods. The reason for the difference between methods is unclear. In situ deployment of multiple flux estimation methods would be valuable, as would longer periods of measurements.

  8. Distributions and air-sea fluxes of CO2 in the summer Bering Sea

    Institute of Scientific and Technical Information of China (English)

    CHEN Liqi; GAO Zhongyong; SUN Heng; CHEN Baoshan; CAI Wei-jun

    2014-01-01

    The 3rd Chinese National Arctic Research Expedition (CHINARE-Arctic III) was carried out from July to Sep-tember in 2008. The partial pressure of CO2 (pCO2) in the atmosphere and in surface seawater were deter-mined in the Bering Sea during July 11-27, 2008, and a large number of seawater samples were taken for total alkalinity (TA) and total dissolved inorganic carbon (DIC) analysis. The distributions of CO2 parameters in the Bering Sea and their controlling factors were discussed. The pCO2 values in surface seawater presented a drastic variation from 148 to 563μatm (1μatm=1.013 25×10-1 Pa ). The lowest pCO2 values were observed near the Bering Sea shelf break while the highest pCO2 existed at the western Bering Strait. The Bering Sea generally acts as a net sink for atmospheric CO2 in summer. The air-sea CO2 fluxes in the Bering Sea shelf, slope, and basin were estimated at-9.4,-16.3, and-5.1 mmol/(m2·d), respectively. The annual uptake of CO2 was about 34 Tg C in the Bering Sea.

  9. Estimation of the CO2 flux from Furnas volcanic Lake (São Miguel, Azores)

    Science.gov (United States)

    Andrade, César; Viveiros, Fátima; Cruz, J. Virgílio; Coutinho, Rui; Silva, Catarina

    2016-04-01

    A study on diffuse CO2 degassing was undertaken at Furnas lake (São Miguel island, Azores) in order to estimate the total diffuse CO2 output and identify anomalous degassing areas over the lake. Furnas lake is located in Furnas Volcano, the easternmost of the three active central volcanoes of the São Miguel island. The lake has an area of 1.87 km2 and a maximum length and width equal to 2025 and 1600 m, respectively. The maximum depth of the water column is 15 m and the estimated water storage is 14 × 106 m3. Lake water temperature is cold, with temperature values between 13 °C and 15 °C in the winter period and 18.9 °C to 19.3 °C in early autumn, and the variation along the water column suggests a monomictic character. The major-ion relative composition is in decreasing order Na+ > K+ > Ca2+ > Mg2 + for cations and HCO3- > Cl- > SO42- for anions, and conductivity and pH measurements, respectively in the range of 152 to 165 μS cm- 1 and 5.3 to 8.7, suggests that Furnas has neutral-diluted waters and can be classified as a non-active lake. Diffuse CO2 flux measurements were made using the accumulation chamber method with a total of 1537 and 2577 measurements performed in two different sampling campaigns. The total amount of diffuse CO2 emitted to the atmosphere was estimated between 28 and 321 t km- 2 d- 1, respectively, in the second and first sampling campaigns, corresponding to ~ 52 and ~ 600 t d- 1. The main anomalous degassing area identified over the Furnas lake during both surveys is probably associated to a WNW-ESE trending tectonic structure. Other secondary areas are also suggested to be tectonically influenced. Identified anomalous areas showed similarities to the ones observed during previous soil CO2 degassing studies.

  10. On which timescales do gas transfer velocities control North Atlantic CO2 flux variability?

    Science.gov (United States)

    Couldrey, Matthew P.; Oliver, Kevin I. C.; Yool, Andrew; Halloran, Paul R.; Achterberg, Eric P.

    2016-05-01

    The North Atlantic is an important basin for the global ocean's uptake of anthropogenic and natural carbon dioxide (CO2), but the mechanisms controlling this carbon flux are not fully understood. The air-sea flux of CO2, F, is the product of a gas transfer velocity, k, the air-sea CO2 concentration gradient, ΔpCO2, and the temperature- and salinity-dependent solubility coefficient, α. k is difficult to constrain, representing the dominant uncertainty in F on short (instantaneous to interannual) timescales. Previous work shows that in the North Atlantic, ΔpCO2 and k both contribute significantly to interannual F variability but that k is unimportant for multidecadal variability. On some timescale between interannual and multidecadal, gas transfer velocity variability and its associated uncertainty become negligible. Here we quantify this critical timescale for the first time. Using an ocean model, we determine the importance of k, ΔpCO2, and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2 and k are important controls on F. In contrast, pentadal to multidecadal North Atlantic flux variability is driven almost entirely by ΔpCO2; k contributes less than 25%. Finally, we explore how accurately one can estimate North Atlantic F without a knowledge of nonseasonal k variability, finding it possible for interannual and longer timescales. These findings suggest that continued efforts to better constrain gas transfer velocities are necessary to quantify interannual variability in the North Atlantic carbon sink. However, uncertainty in k variability is unlikely to limit the accuracy of estimates of longer-term flux variability.

  11. Secondary production, calcification and CO2 fluxes in the cirripedes Chthamalus montagui and Elminius modestus.

    Science.gov (United States)

    Golléty, Claire; Gentil, Franck; Davoult, Dominique

    2008-02-01

    Calcification, a process common to numerous marine taxa, has traditionally been considered to be a significant source of CO(2) in tropical waters only. A number of relatively recent studies, however, have shown that significant amounts of CO(2) are also produced in temperate waters, although none of these studies was carried out on rocky shores, which are considered to be very productive systems. We compared the CO(2) fluxes due to respiration and calcification in two temperate species, the cirripedes Chthamalus montagui and Elminius modestus. The population dynamics of both species were estimated at two sites during a 1-year experimental period in order to establish mean organic (ash-free dry weight) and CaCO(3) (dry shell weight) production. Based on these parameters, we estimated the CO(2) fluxes due to respiration and calcification. CaCO(3) production was estimated to be 481.0 and 1,803.9 g(CaCO3) m(-2) year(-1) at each site, representing 3.4 and 12.7 mol(CO2) m(-2) year(-1) respectively, of released CO(2). These fluxes represent each 47% of the CO(2) released as a result of respiration and calcification. The production of CaCO(3) at the high-density site was: (1) among the highest values obtained for temperate organisms, and (2) comparable to the estimated CO(2) fluxes for coral reefs. As calcifying organisms are well represented in temperate ecosystems in terms of both density and biomass, our results provide clear evidence that calcification of temperate organisms should not be underestimated. Additional studies on other rocky shore taxa are needed before the relative importance of calcification in rocky intertidal carbon budgets can be generalized.

  12. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    Science.gov (United States)

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.

  13. Non-linear CO2 flux response to seven years of experimentally induced permafrost thaw.

    Science.gov (United States)

    Mauritz, Marguerite; Bracho, Rosvel; Celis, Gerardo; Hutchings, Jack; Natali, Susan M; Pegoraro, Elaine; Salmon, Verity G; Schädel, Christina; Webb, Elizabeth E; Schuur, Edward A G

    2017-02-16

    Rapid Arctic warming is expected to increase global greenhouse gas concentrations as permafrost thaw exposes immense stores of frozen carbon (C) to microbial decomposition. Permafrost thaw also stimulates plant growth, which could offset C loss. Using data from seven years of experimental Air and Soil warming in moist acidic tundra, we show that Soil warming had a much stronger effect on CO2 flux than Air warming. Soil warming caused rapid permafrost thaw and increased ecosystem respiration (Reco), gross primary productivity (GPP), and net summer CO2 storage (NEE). Over seven years Reco, GPP, and NEE also increased in Control (i.e., ambient plots), but this change could be explained by slow thaw in Control areas. In the initial stages of thaw, Reco , GPP, and NEE increased linearly with thaw across all treatments, despite different rates of thaw. As thaw in Soil warming continued to increase linearly, ground surface subsidence created saturated micro-sites, and suppressed Reco , GPP, and NEE. However Reco and GPP remained high in areas with large Eriophorum vaginatum biomass. In general NEE increased with thaw, but was more strongly correlated with plant biomass than thaw, indicating that higher Reco in deeply thawed areas during summer months was balanced by GPP. Summer CO2 flux across treatments fit a single quadratic relationship that captured the functional response of CO2 flux to thaw, water table depth, and plant biomass. These results demonstrate the importance of indirect thaw effects on CO2 flux: plant growth and water table dynamics. Non-summer Reco models estimated that the area was an annual CO2 source during all years of observation. Non-summer CO2 loss in warmer, more deeply thawed soils exceeded the increases in summer GPP, and thawed tundra was a net annual CO2 source. This article is protected by copyright. All rights reserved.

  14. CO2-dependent carbon isotope fractionation in dinoflagellates relates to their inorganic carbon fluxes.

    Science.gov (United States)

    Hoins, Mirja; Eberlein, Tim; Van de Waal, Dedmer B; Sluijs, Appy; Reichart, Gert-Jan; Rost, Björn

    2016-08-01

    Carbon isotope fractionation (εp) between the inorganic carbon source and organic matter has been proposed to be a function of pCO2. To understand the CO2-dependency of εp and species-specific differences therein, inorganic carbon fluxes in the four dinoflagellate species Alexandrium fundyense, Scrippsiella trochoidea, Gonyaulax spinifera and Protoceratium reticulatum have been measured by means of membrane-inlet mass spectrometry. In-vivo assays were carried out at different CO2 concentrations, representing a range of pCO2 from 180 to 1200 μatm. The relative bicarbonate contribution (i.e. the ratio of bicarbonate uptake to total inorganic carbon uptake) and leakage (i.e. the ratio of CO2 efflux to total inorganic carbon uptake) varied from 0.2 to 0.5 and 0.4 to 0.7, respectively, and differed significantly between species. These ratios were fed into a single-compartment model, and εp values were calculated and compared to carbon isotope fractionation measured under the same conditions. For all investigated species, modeled and measured εp values were comparable (A. fundyense, S. trochoidea, P. reticulatum) and/or showed similar trends with pCO2 (A. fundyense, G. spinifera, P. reticulatum). Offsets are attributed to biases in inorganic flux measurements, an overestimated fractionation factor for the CO2-fixing enzyme RubisCO, or the fact that intracellular inorganic carbon fluxes were not taken into account in the model. This study demonstrates that CO2-dependency in εp can largely be explained by the inorganic carbon fluxes of the individual dinoflagellates.

  15. Soil CO2 flux in hydrothermal areas of the Tatun Volcano Group, Northern Taiwan

    Science.gov (United States)

    Wen, Hsin-Yi; Yang, Tsanyao F.; Lan, Tefang F.; Lee, Hsiao-Fen; Lin, Cheng-Horng; Sano, Yuji; Chen, Cheng-Hong

    2016-07-01

    We measured soil CO2 flux in the representative hydrothermal areas of the Tatun Volcano Group (TVG), to better understand the volcano's dynamic nature, and to estimate its soil CO2 degassing output. Results show that the average soil CO2 fluxes obtained at Da-You-Keng (DYK), Geng-Tze-Ping (GTP), She-Haung-Ping (SHP), and Tatun Natural Park (TNP) were 128 g m- 2 d- 1, 518 g m- 2 d- 1, 420 g m- 2 d- 1, and 25 g m- 2 d- 1, respectively. The range is comparable to other active volcanic/hydrothermal areas in the world. Along with Liu-Huang-Ku (LHK), where the soil CO2 flux is known, the total soil CO2 output from measured areas is evaluated at 82 t d- 1. Furthermore, a first total soil CO2 output from the whole hydrothermal areas of the TVG is roughly estimated at 113 t d- 1, which includes 15 t d- 1 mantle contribution. Considering the mantle-derived CO2 flux and H2O/CO2 ratio of fumarolic gas, thermal energy associated with the diffuse degassing at the TVG hydrothermal area is estimated at 8.2 MW. Carbon (δ13C) and helium (3He/4He) isotopic ratios of soil samples of the studied areas ranged from - 4.4 to - 6.7‰, and 2.45 to 6.98 RA, respectively. The extent of air involvement in the soil-degassing system, as constrained by the helium and carbon isotopic compositions, provides essential information for depicting regional degassing features of the hydrothermal areas.

  16. Air-sea CO2 flux pattern along the southern Bay of Bengal waters

    Science.gov (United States)

    Shanthi, R.; Poornima, D.; Naveen, M.; Thangaradjou, T.; Choudhury, S. B.; Rao, K. H.; Dadhwal, V. K.

    2016-12-01

    Physico-chemical observations made from January 2013 to March 2015 in coastal waters of the southwest Bay of Bengal show pronounced seasonal variation in physico-chemical parameters including total alkalinity (TA: 1927.390-4088.642 μmol kg-1), chlorophyll (0.13-19.41 μg l-1) and also calculated dissolved inorganic carbon (DIC: 1574.219-3790.954 μmol kg-1), partial pressure of carbon dioxide (pCO2: 155.520-1488.607 μatm) and air-sea CO2 flux (FCO2: -4.808 to 11.255 mmol Cm-2 d-1). Most of the physical parameters are at their maximum during summer due to the increased solar radiation at cloud free conditions, less or no riverine inputs, and lack of vertical mixing of water column which leads to the lowest nutrients concentration, dissolved oxygen (DO), biological production, pCO2 and negative flux of CO2 to the atmosphere. Chlorophyll and DO concentrations enhanced due to increased nutrients during premonsoon and monsoon season due to the vertical mixing of water column driven by the strong winds and external inputs at respective seasons. The constant positive loading of nutrients, TA, DIC, chlorophyll, pCO2 and FCO2 against atmospheric temperature (AT), lux, sea surface temperature (SST), pH and salinity observed in principal component analysis (PCA) suggested that physical and biological parameters play vital role in the seasonal distribution of pCO2 along the southwest Bay of Bengal. The annual variability of CO2 flux clearly depicted that the southwest Bay of Bengal switch from sink (2013) to source status in the recent years (2014 and 2015) and it act as significant source of CO2 to the atmosphere with a mean flux of 0.204 ± 1.449 mmol Cm-2 d-1.

  17. Changes in annual CO2 fluxes estimated from inventory data in South Korea

    Institute of Scientific and Technical Information of China (English)

    Lee; Dowon; Yook; Keun; Hyung; Lee; Dongseon; Kang; Sinkyu; Kang; Hojeong; Lim; Jong; Hwan; Lee; Kyeong; Hak

    2002-01-01

    Using a slightly modified IPCC method, we examined changes in annual fluxes of CO2 and contributions of energy consumption, limestone use, waste combustion, land-use change, and forest growth to the fluxes in South Korea from 1990to 1997. Our method required less data and resulted in a larger estimate of CO2released by industrial processes, comparing with the original IPCC guideline. However, net CO2 emission is not substantially different from the estimates of IPCC and modified methods. Net CO2 emission is intimately related to GDP as Koreaneconomy has heavily relied on energy consumption and industrial activities, which are major sources of CO2. Total efflux of CO2 was estimated to be 63.6 Tg C/ain 1990 and amounted to 112.9 Tg C/a in 1997. Land-use change contributed to annual budget of CO2 in a relatively small portion. Carbon dioxide was sequesteredby forest biomass at the rate of 6.5 Tg C/a in 1990 and 8.5 Tg C/a in 1997. Although CO2 storage in the forests increased, the sink effect was overwhelmed by extensive energy consumption, suggesting that energy-saving strategies will be more effective in reducing CO2 emission in Korea than any other practices. It is presumed that plant uptake of CO2 is underestimated as carbon contained in plant detritus and belowground living biomass were not fully considered. Furthermore, the soil organic carbon stored in forest decomposes in various ways in rugged mountains depending on their conditions, such as slope, aspect and elevation, which could have an effect on decomposition rate and carbon stores in soils. Thus, carbon sequestration of forests deserves further attention.

  18. METEOPOLE-FLUX: an observatory of terrestrial water, energy, and CO2 fluxes in Toulouse

    Science.gov (United States)

    Calvet, Jean-Christophe; Roujean, Jean-Louis; Zhang, Sibo; Maurel, William; Piguet, Bruno; Barrié, Joël; Bouhours, Gilles; Couzinier, Jacques; Garrouste, Olivier; Girres, Sandrine; Suquia, David; Tzanos, Diane

    2016-04-01

    The METEOPOLE-FLUX project (http://www.cnrm.meteo.fr/spip.php?article874&lang=en) aims at monitoring a large suburban set-aside field in the city of Toulouse (43.572898 N, 1.374384 E). Since June 2012, these data contribute to the international effort to monitor terrestrial ecosystems (grasslands in particular), to the validation of land surface models, and to the near real time quality monitoring of operational weather forecast models. Various variables are monitored at a subhourly rate: wind speed, air temperature, air humidity, atmospheric pressure, precipitation, turbulent fluxes (H, LE, CO2), downwelling and upwelling solar and infrared radiation, downwelling and upwelling PAR, fraction of diffuse incoming PAR, presence of water intercepted by vegetation (rain, dew), soil moisture profile, soil temperature profile, surface albedo, transmissivity of PAR in vegetation canopy. Moreover, local observations are performed using remote sensing techniques: infrared radiometry, GNSS reflectometry, and multi-band surface reflectometry using an aerosol photometer from the AERONET network. Destructive measurements of LAI, green/brown above-ground biomass, and necromass are performed twice a year. This site is characterized by a large fraction of gravels and stones in the soil, ranging from 17% to 35% in the top soil layer (down to 0.6 m), and peaking at 81% at 0.7 m. The impact of gravels and stones on thermal and moisture fluxes in the soil has not been much addressed in the past and is not represented in most land surface models. Their impact on the available water content for plant transpiration and plant growth is not much documented so far. The long term monitoring of this site will therefore improve the knowledge on land processes. The data will be used together with urban meteorological data to characterize the urban heat island. Finally, this site will be used for the CAL/VAL of various satellite products in conjunction with the SMOSMANIA soil moisture network

  19. Influence of soil erosion on CO2 exchange within the CarboZALF manipulation experiment

    Science.gov (United States)

    Hoffmann, Mathias; Augustin, Jürgen; Sommer, Michael

    2014-05-01

    Agriculture in the hummocky ground moraine landscape of NE-Germany is characterized by an increase in energy crop cultivation, like maize or sorghum. Both enhance lateral C fluxes by erosion and induce feedbacks on C dynamics of agroecosystems as a result of the time limited land cover and the vigorous crop growth. However, the actual impact of these phenomena on the CO2-sink/-source function of agricultural landscapes, is still not clear. Therefore we established the interdisciplinary project 'CarboZALF' in 2009. In our field experiment CarboZALF-D we are monitoring CO2 fluxes for soil-plant systems, which cover all landscape relevant soil states in respect to erosion and deposition, like Albic Cutanic Luvisol, Calcic Cutanic Luvisol, Calcaric Regosol and Endogleyic Colluvic Regosol. Furthermore, we induced erosion / deposition in a manipulation experiment. Automated chamber systems (2.5 m, basal area 1 m2, transparent) are placed at the manipulated sites as well as at one site neither influenced by erosion, nor by deposition. CO2 flux modelling of high temporal resolution includes ecosystem respiration (Reco), gross primary productivity (GPP) and net ecosystem exchange (NEE) based on parallel and continuous measurements of the CO2 exchange, soil and air temperatures as well as photosynthetic active radiation (PAR). Modelling includes gap filling which is needed in case of chamber malfunctions and abrupt disturbances by farming practice. In our presentation we would like to show results of the CO2 exchange measurements for one year. Differences are most pronounced between the non-eroded and the colluvial soil: The Endogleyic Colluvic Regosol showed higher flux rates for Reco and NEE compared to the Albic Cutanic Luvisol. The eroded soil (Calcic Cutanic Luvisol) demonstrated CO2fluxes intermediate between the non-affected and depositional site. Site-specific consequences for the soil C stocks will be also discussed in the presentation.

  20. Diagnosing CO2 fluxes in the upwelling system off the Oregon coast

    Directory of Open Access Journals (Sweden)

    Z. Cao

    2014-05-01

    Full Text Available It is generally known that the interplay between the carbon and nutrients supplied from subsurface waters via biological metabolism would determine the CO2 fluxes in upwelling systems. However, quantificational assessment of such interplay is difficult because of the dynamic nature of both upwelling circulation and the associated biogeochemistry. In this study, the diagnosis approach based upon the carbon/nutrient mass balance in the Ocean-dominated Margin (OceMar framework was applied to resolve the CO2 fluxes in the well-known upwelling system in the US west coast off Oregon, using the data collected along two cross-shelf transects from the inner shelf to the open basin in spring/early summer 2007. Through examining the biological consumption on top of the water mass mixing built upon the total alkalinity–salinity relationship, we successfully predicted and semi-analytically resolved the CO2 fluxes showing strong uptakes from the atmosphere beyond the nearshore regions, primarily resulting from the higher utilization of nutrients relative to dissolved inorganic carbon (DIC based on their concurrent inputs from the depth. On the other hand, we showed significant CO2 outgassing in the nearshore regions associated with intensified upwelling and minor biological consumption, where CO2 fluxes could be simplified without considering DIC/nutrient consumption. We reasoned that our approach in conceptualizing OceMar would be in a steady state with balanced DIC and nutrients via both physical transport and biological alterations in comparable timescales.

  1. New ground-based lidar enables volcanic CO2 flux measurements.

    Science.gov (United States)

    Aiuppa, Alessandro; Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Nuvoli, Marcello; Chiodini, Giovanni; Minopoli, Carmine; Tamburello, Giancarlo

    2015-09-01

    There have been substantial advances in the ability to monitor the activity of hazardous volcanoes in recent decades. However, obtaining early warning of eruptions remains challenging, because the patterns and consequences of volcanic unrests are both complex and nonlinear. Measuring volcanic gases has long been a key aspect of volcano monitoring since these mobile fluids should reach the surface long before the magma. There has been considerable progress in methods for remote and in-situ gas sensing, but measuring the flux of volcanic CO2-the most reliable gas precursor to an eruption-has remained a challenge. Here we report on the first direct quantitative measurements of the volcanic CO2 flux using a newly designed differential absorption lidar (DIAL), which were performed at the restless Campi Flegrei volcano. We show that DIAL makes it possible to remotely obtain volcanic CO2 flux time series with a high temporal resolution (tens of minutes) and accuracy (volcanic CO2 represents a major step forward in volcano monitoring, and will contribute improved volcanic CO2 flux inventories. Our results also demonstrate the unusually strong degassing behavior of Campi Flegrei fumaroles in the current ongoing state of unrest.

  2. Modeling atmospheric CO2 concentration profiles and fluxes above sloping terrain at a boreal site

    Directory of Open Access Journals (Sweden)

    T. Aalto

    2006-01-01

    Full Text Available CO2 fluxes and concentrations were simulated in the planetary boundary layer above subarctic hilly terrain using a three dimensional model. The model solves the transport equations in the local scale and includes a vegetation sub-model. A WMO/GAW background concentration measurement site and an ecosystem flux measurement site are located inside the modeled region at a hilltop and above a mixed boreal forest, respectively. According to model results, the concentration measurement at the hill site was representative for continental background. However, this was not the case for the whole model domain. Concentration at few meters above active vegetation represented mainly local variation. Local variation became inseparable from the regional signal at about 60-100 m above ground. Flow over hills changed profiles of environmental variables and height of inversion layer, however CO2 profiles were more affected by upwind land use than topography. The hill site was above boundary layer during night and inside boundary layer during daytime. The CO2 input from model lateral boundaries dominated in both cases. Daily variation in the CO2 assimilation rate was clearly seen in the CO2 profiles. Concentration difference between the hill site and the forest site was about 5ppm during afternoon according to both model and measurements. The average modeled flux to the whole model region was about 40% of measured and modeled local flux at the forest site.

  3. CO2 and heat fluxes in a recently clear-cut spruce forest in European Russia: experimental and modeling studies

    Science.gov (United States)

    Mamkin, Vadim; Kurbatova, Julia; Avilov, Vitaly; Mukhartova, Yulia; Krupenko, Alexander; Ivanov, Dmitry; Levashova, Natalia; Olchev, Alexander

    2017-04-01

    Ecosystem carbon dioxide, energy, and water fluxes were measured using eddy covariance and portable chambers in a fresh clear-cut surrounded by a mixed spruce-birch-aspen forest in the boreal zone of European Russia. Measurements were initiated in spring 2016 following timber harvest and continued for seven months until the end of October. The influence of surrounding forest on air flow and turbulent fluxes within the clear-cut were examined using a process-based two-dimensional (2D) hydrodynamic turbulent exchange model. Clear-cut was a permanent source of CO2 to the atmosphere. During the period the mean daily latent (LE) and sensible (H) heat fluxes were very similar and the Bowen ratio (β=H/LE) averaged about 1.0. During the late spring and summer months the net ecosystem exchange of CO2 (NEE) remained slightly positive following onset of vegetation growth, while β was changing in the range from 0.6 to 4.0. There was strong diurnal variability in NEE, LE and H over the measurement period that was governed by solar radiation and temperature as well as the leaf area index (LAI) of regrown vegetation. Modeled vertical CO2 and H2O fluxes along a transect that crossed the clear-cut and coincided with the dominate wind direction showed that the clear-cut strongly influenced turbulent fluxes within the atmospheric surface layer. Furthermore, modeled atmospheric dynamics suggested that the clear-cut had a large influence on turbulent fluxes in the downwind forest, but little impact on the upwind side. An aggregated approach including field measurements and process-based models can be used to estimate energy, water and carbon dioxide fluxes in non-uniform forest landscapes. This study was supported by a grant from the Russian Science Foundation (14-14-00956).

  4. Comparing CO2 flux data from eddy covariance methods with bowen ratio energy balance methods from contrasting soil management

    Science.gov (United States)

    Measuring CO2 fluxes from contrasting soil management practices is important for understanding the role of agriculture in source-sink relationship with CO2 flux. There are several micrometeorological methods for measuring CO2 emissions, however all are expensive and thus do not easily lend themselve...

  5. 环境因子对兴安落叶松林生态系统CO2通量的影响%Impact of climate factors on CO2 flux characteristics in a Larix ;gmelinii forest ecosystem

    Institute of Scientific and Technical Information of China (English)

    李小梅; 张秋良

    2015-01-01

    . The assimilation reaches its peak between 12:30 and 13:30. The CO2 flux ranges from -1. 09 to 0. 11 mg/( m2·s) during the day. In the non-growing season, the ecosystem shows a carbon source with the CO2 flux ranging from 0 to 0. 3 mg/(m2·s). 2) In the growing season, there is a logarithmic relationship between the CO2 flux and photosynthetic active radiation ( R2 =0. 486 1 ) , and the carbon sequestration capacity increases with the enhancement of PAR; therefore, PAR is a factor affecting CO2 flux directly. In the non-growing season, such relationship is not significant. 3 ) The CO2 flux is well correlated with air temperature ( ta ) in growing seasons ( R2 = 0. 627 2 ) , and CO2 flux is reduced with the rising ta , suggesting that ta is a main limiting factor in the ecosystem. In the non-growing season from December to February, the change of air temperature has no significant effects on CO2 flux. 4) The influence of soil temperature (ts) and soil moisture content (RH) on CO2 flux is mainly reflected in ecosystem respiration (Re). The soil moisture content ranges between 62% -87% in the ecosystem, with an average of 84%in the growing season and 67% in the non-growing season. Soil moisture content is not the main factor limiting CO2 flux in the ecosystem. On condition that water is not the limiting factor, soil temperature plays the major role on regulating CO2 flux in the ecosystem. Our research shows that there exists an exponential relationship between CO2 flux and soil temperature ( R2 =0. 282 6 in growing season and 0. 222 3 in non-growing season) . Within a certain range, the rise of soil temperature will accelerate the metabolism of plants and microorganisms, and thus enhance the respiration of forest ecosystem and promote the emission of CO2 .

  6. (Uncertain) Carbonyl Sulfide Plant Fluxes Spatially Constrain (Even More Uncertain) CO2 GPP

    Science.gov (United States)

    Hilton, T. W.; Whelan, M.; Kulkarni, S.; Zumkehr, A. L.; Berry, J. A.; Campbell, J. E.

    2015-12-01

    With predictions of future terrestrial carbon dioxide (CO2)gross primary productivity (GPP) remaining stubbornly uncertain,ecosystem carbonyl sulfide (COS) fluxes provide an independent source ofinformation that may be able to reduce that uncertainty. Several openquestions must be addressed before COS may be applied widely as a GPPtracer. Here we employ an atmospheric chemistry and transport model(STEM) and airborne atmospheric COS concentration observations todemonstrate that COS plant uptake spatially constrains CO2 GPP even whenaccounting for soil COS flux uncertainty and COS leaf-scale relativeuptake variability and uncertainty.

  7. Regional-scale geostatistical inverse modeling of North American CO2 fluxes: a synthetic data study

    Directory of Open Access Journals (Sweden)

    A. M. Michalak

    2010-07-01

    Full Text Available A series of synthetic data experiments is performed to investigate the ability of a regional atmospheric inversion to estimate grid-scale CO2 fluxes during the growing season over North America. The inversions are performed within a geostatistical framework without the use of any prior flux estimates or auxiliary variables, in order to focus on the atmospheric constraint provided by the nine towers collecting continuous, calibrated CO2 measurements in 2004. Using synthetic measurements and their associated concentration footprints, flux and model-data mismatch covariance parameters are first optimized, and then fluxes and their uncertainties are estimated at three different temporal resolutions. These temporal resolutions, which include a four-day average, a four-day-average diurnal cycle with 3-hourly increments, and 3-hourly fluxes, are chosen to help assess the impact of temporal aggregation errors on the estimated fluxes and covariance parameters. Estimating fluxes at a temporal resolution that can adjust the diurnal variability is found to be critical both for recovering covariance parameters directly from the atmospheric data, and for inferring accurate ecoregion-scale fluxes. Accounting for both spatial and temporal a priori covariance in the flux distribution is also found to be necessary for recovering accurate a posteriori uncertainty bounds on the estimated fluxes. Overall, the results suggest that even a fairly sparse network of 9 towers collecting continuous CO2 measurements across the continent, used with no auxiliary information or prior estimates of the flux distribution in time or space, can be used to infer relatively accurate monthly ecoregion scale CO2 surface fluxes over North America within estimated uncertainty bounds. Simulated random transport error is shown to decrease the quality of flux estimates in under-constrained areas at the ecoregion scale, although the uncertainty bounds remain realistic. While these synthetic

  8. Biological soil crusts as key drivers for CO2 fluxes in semiarid ecosystems

    Science.gov (United States)

    Chamizo, Sonia; Miralles, Isabel; Rodríguez-Caballero, Emilio; Ortega, Raúl; Ladrón de Guevara, Mónica; Luna, Lourdes; Cantón, Yolanda

    2014-05-01

    The quantification of carbon (C) fluxes for the different ecosystems and the knowledge of whether they act as sources or sinks of C has acquired especial importance during the last years. This is particularly demanding for arid and semiarid ecosystems, for which the available information is very scarce. In these ecosystems, the interplant spaces are commonly covered by a thin layer of organisms including cyanobacteria, green algae, lichens and mosses, which are known as biological soil crusts (BSCs) and, though practically negligible, play a fundamental role in regulating gas exchange into and from soil. BSCs represent the main organisms capable of respiration and photosynthesis in the interplant spaces and are considered the main source of organic carbon in many arid and semiarid areas. Although several studies have pointed to the predominant role of BSCs as sources of CO2, on the contrary, other studies have emphasized their important role as sinks of CO2, being required to establish their precise effect regulating CO2 fluxes. The main purpose of this study was to enlighten the role of BSCs on CO2 fluxes. With this aim, CO2 fluxes were measured on different BSC types (cyanobacteria-, lichen- and moss-dominated BSCs) after several rainfalls and periods of soil drying in two semiarid ecosystems of SE Spain. CO2 exchange was measured using infrared gas analyzers (IRGA): net flux was measured with a transparent custom chamber attached to a Licor Li-6400, and respiration with a respirometer EGM-4 (PPsystems). Photosynthesis was determined as the difference between both measurements. Our results showed that moisture was the major factor controlling CO2 fluxes in BSCs. During the summer season, when soil was dry, all BSCs showed CO2 fluxes close to 0. However, once it rains and BSCs become active, a significant increase in photosynthesis and respiration rates was found. Whereas respiration was the main CO2 flux in bare soils, in BSCs regardless respiration was higher

  9. VARIABILITY OF ATMOSPHERIC CO2 OVER INDIA AND SURROUNDING OCEANS AND CONTROL BY SURFACE FLUXES

    Directory of Open Access Journals (Sweden)

    R. K. Nayak

    2012-08-01

    Full Text Available In the present study, seasonal and inter-annual variability of atmospheric CO2 concentration over India and surrounding oceans during 2002–2010 derived from Atmospheric InfrarRed Sounder observation and their relation with the natural flux exchanges over terrestrial Indian and surrounding oceans were analyzed. The natural fluxes over the terrestrial Indian in the form of net primary productivity (NPP were simulated based on a terrestrial biosphere model governed by time varying climate parameters (solar radiation, air temperature, precipitation etc and satellite greenness index together with the land use land cover and soil attribute maps. The flux exchanges over the oceans around India (Tropical Indian Ocean: TIO were calculated based on a empirical model of CO2 gas dissolution in the oceanic water governed by time varying upper ocean parameters such as gradient of partial pressure of CO2 between ocean and atmosphere, winds, sea surface temperature and salinity. Comparison between the variability of atmospheric CO2 anomaly with the anomaly of surface fluxes over India and surrounding oceans suggests that biosphere uptake over India and oceanic uptake over the south Indian Ocean could play positive role on the control of seasonal variability of atmospheric carbon dioxide growth rate. On inter-annual scale, flux exchanges over the tropical north Indian Ocean could play positive role on the control of atmospheric carbon dioxide growth rate.

  10. Analysis of the PKT correction for direct CO2 flux measurements over the ocean

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    S. Landwehr

    2013-10-01

    Full Text Available Eddy covariance measurements of air–sea CO2 fluxes can be affected by cross-sensitivities of the CO2 measurement to water vapour, resulting in order-of-magnitude biases. Well established causes for these biases are (i cross-sensitivity of the broadband non-dispersive infrared sensors due to band-broadening and spectral overlap (commercial sensors typically correct for this and (ii the effect of air density fluctuations (removed by determining the CO2 mixing ratio respective to dry air. However, another bias related to water vapour fluctuations has recently been observed with open-path sensors, and was attributed to sea salt build-up and water films on sensor optics. Two very different approaches have been used to deal with these water vapour-related biases. Miller et al. (2010 employed a membrane drier to physically eliminate 97% of the water vapour fluctuations in the sample air before it enters the gas analyser. Prytherch et al. (2010a on the other hand, employed the empirical (Peter K. Taylor, PKT post-processing correction to correct open-path sensor data. In this paper, we test these methods side by side using data from the Surface Ocean Aerosol Production (SOAP experiment in the Southern Ocean. The air–sea CO2 flux was directly measured with four closed-path analysers, two of which were positioned down-stream of a membrane dryer. The CO2 fluxes from the two dried gas analysers matched each other and were in general agreement with common parametrisations. The flux estimates from the un-dried sensors agreed with the dried sensors only during periods with low latent heat flux (≤ 7 W m−2. When latent heat flux was higher, CO2 flux estimates from the un-dried sensors exhibited large scatter and an order-of magnitude bias. We applied the PKT correction to the flux data from the un-dried analysers and found that it did not remove the bias when compared to the data from the dried gas analyser. Our detailed analysis of the correction

  11. Meteorological control on CO2 flux above broad-leaved Korean pine mixed forest in Changbai Mountains

    Institute of Scientific and Technical Information of China (English)

    GUAN; Dexin; WU; Jiabing; YU; Guirui; SUN; Xiaomin; ZHAO; X

    2005-01-01

    The impacts of temperature, photosynthetic active radiation (PAR) and vapor pressure deficit (VPD) on CO2 flux above broad-leaved Korean pine mixed forest in the Changbai Mountains were studied based on eddy covariance and meteorological factors measurements.The results showed that, daytime CO2 flux was mainly controlled by PAR and they fit Michaelis-Menten equation. Meanwhile VPD also had an influence on the daytime flux. Drier air reduced the CO2 assimilation of the ecosystem, the drier the air, the more the reduction of the assimilation. And the forest was more sensitive to VPD in June than that in July and August. The respiration of the ecosystem was mainly controlled by soil temperature and they fit exponential equation. It was found that this relationship was also correlated with seasons; respiration from April to July was higher than that from August to November under the same temperature. Daily net carbon exchange of the ecosystem and the daily mean air temperature fit exponential equation. It was also found that seasonal trend of net carbon exchange was the result of comprehensive impacts of temperature and PAR and so on. These resulted in the biggest CO2 uptake in June and those in July and August were next. Annual carbon uptake of the forest ecosystem in 2003 was -184 gC. m-2.

  12. Concurrent CO2 and COS fluxes across major biomes in Europe

    Science.gov (United States)

    Spielmann, Felix M.; Kitz, Florian; Hammerle, Albin; Gerdel, Katharina; Ibrom, Andreas; Kolle, Olaf; Migliavacca, Mirco; Moreno, Gerardo; Noe, Steffen M.; Wohlfahrt, Georg

    2017-04-01

    The trace gas carbonyl sulfide (COS) has been proposed as a tracer for canopy gross primary production (GPP), canopy transpiration and stomatal conductance of plant canopies in the last few years. COS enters the plant leaf through the stomata and diffuses through the intercellular space, the cell wall, the plasma membrane and the cytosol like carbon dioxide (CO2). It is then catalyzed by the enzyme carbonic anhydrase in a one-way reaction to hydrogen sulfide and CO2. This one-way flux into the leaf makes COS a promising tracer for the GPP. However, this approach assumes that the ratio of the deposition velocities between COS and CO2 is constant, which must be determined in field experiments covering a wide variety of ecosystems. The overarching objective of this study was to quantify the relationship between the ecosystem-scale exchange of COS and CO2 and thus, to test for the potential of COS to be used as a universal tracer for the plant canopy CO2 exchange. Between spring 2015 and summer 2016 we set up our quantum cascade laser at different field sites across Europe. These sites included a managed temperate mountain grassland (AUT), a savanna (ESP), a temperate beech forest (DEN) and a hemiboreal forest (EST). On each of these sites, we conducted ecosystem scale eddy covariance and soil chamber measurements. Since the soil COS flux contribution, especially in grass dominated ecosystems, could not be neglected, we had to derive the actual canopy COS fluxes for all the measurement sites. Using these fluxes we compared the ecosystem relative uptake (ERU) of the sites and searched for factors affecting its variability. We then used the influential factors to scale the ERU to be comparable under different field sites and conditions. Furthermore we also calculated the GPP using conventional CO2 flux partitioning and compared the results with the approach of using the leaf relative uptake.

  13. The carbon dioxide system on the Mississippi River-dominated continental shelf in the northern Gulf of Mexico: 1. Distribution and air-sea CO2 flux.

    Science.gov (United States)

    Huang, Wei-Jen; Cai, Wei-Jun; Wang, Yongchen; Lohrenz, Steven E; Murrell, Michael C

    2015-03-01

    River-dominated continental shelf environments are active sites of air-sea CO2 exchange. We conducted 13 cruises in the northern Gulf of Mexico, a region strongly influenced by fresh water and nutrients delivered from the Mississippi and Atchafalaya River system. The sea surface partial pressure of carbon dioxide (pCO2) was measured, and the air-sea CO2 flux was calculated. Results show that CO2 exchange exhibited a distinct seasonality: the study area was a net sink of atmospheric CO2 during spring and early summer, and it was neutral or a weak source of CO2 to the atmosphere during midsummer, fall, and winter. Along the salinity gradient, across the shelf, the sea surface shifted from a source of CO2 in low-salinity zones (0≤S<17) to a strong CO2 sink in the middle-to-high-salinity zones (17≤S<33), and finally was a near-neutral state in the high-salinity areas (33≤S<35) and in the open gulf (S≥35). High pCO2 values were only observed in narrow regions near freshwater sources, and the distribution of undersaturated pCO2 generally reflected the influence of freshwater inputs along the shelf. Systematic analyses of pCO2 variation demonstrated the importance of riverine nitrogen export; that is, riverine nitrogen-enhanced biological removal, along with mixing processes, dominated pCO2 variation along the salinity gradient. In addition, extreme or unusual weather events were observed to alter the alongshore pCO2 distribution and to affect regional air-sea CO2 flux estimates. Overall, the study region acted as a net CO2 sink of 0.96 ± 3.7 mol m(-2) yr(-1) (1.15 ± 4.4 Tg C yr(-1)).

  14. Winter greenhouse gas fluxes (CO2, CH4 and N2O from a subalpine grassland

    Directory of Open Access Journals (Sweden)

    L. Merbold

    2013-05-01

    Full Text Available Although greenhouse gas emissions during winter contribute significantly to annual balances, their quantification is still highly uncertain in snow-covered ecosystems. Here, carbon dioxide (CO2, methane (CH4 and nitrous oxide (N2O fluxes were measured at a subalpine managed grassland in Switzerland using concentration gradients within the snowpack (CO2, CH4, N2O and the eddy covariance method (CO2 during the winter 2010/2011. Our objectives were (1 to identify the temporal and spatial variation of greenhouse gases (GHGs and their drivers, and (2 to estimate the GHG budget of the site during this specific season (1 December–31 March, 121 days. Mean winter fluxes (December–March based on the gradient method were 0.77 ± 0.54 μmol m−2 s−1 for CO2 (1.19 ± 1.05 μmol m−2 s−1 measured by eddy covariance, −0.14 ± 0.09 nmol m−2 s−1 for CH4 and 0.23 ± 0.23 nmol m−2 s−1 for N2O, respectively. In comparison with the CO2 fluxes measured by eddy covariance, the gradient technique underestimated the effluxes by 50%. While CO2 and CH4 fluxes decreased with the progressing winter season, N2O fluxes did not follow a seasonal pattern. The major variables correlating with the fluxes of CO2 and CH4 were soil temperature and snow water equivalent, which is based on snow height and snow density. N2O fluxes were only explained poorly by any of the measured environmental variables. Spatial variability across the valley floor was smallest for CO2 and largest for N2O. During the winter season 2010/2011, greenhouse gas fluxes ranged between 550 ± 540 g CO2 m−2 estimated by the eddy covariance approach and 543 ± 247 g CO2 m−2, −0.4 ± 0.01 g CH4 m−2 and 0.11 ± 0.1 g N2O m−2 derived by the gradient technique. Total seasonal greenhouse gas emissions from the grassland were between 574 ± 276 and 581 ± 569 g CO2 eq. m−2, with N2O contributing 5% to the overall budget and CH4 reducing the budget by 0.1%. Cumulative budgets of CO2 were

  15. Air-sea CO2 fluxes for the Brazilian northeast continental shelf in a climatic transition region

    Science.gov (United States)

    Carvalho, A. C. O.; Marins, R. V.; Dias, F. J. S.; Rezende, C. E.; Lefèvre, N.; Cavalcante, M. S.; Eschrique, S. A.

    2017-09-01

    Oceanographic cruises were carried out in October 2012 (3°S-5°S and 38,5°W-35,5°W) and in September 2014 (1°S-4°S and 43°W-37°W), measuring atmospheric and sea surface CO2 fugacity (fCO2) underway in the northeast coast of Brazil. Sea surface water samples were also collected for chlorophyll a, nutrients and DOC analysis. During the second cruise, the sampling area covered a transition between semi-arid to more humid areas of the coast, with different hydrologic and rainfall regimes. The seawater fCO2sw, in October 2012, was in average 400.9 ± 7.3μatm and 391.1 ± 6.3 μatm in September 2014. For the atmosphere, the fCO2air in October 2012 was 375.8 ± 2.0 μatm and in September 2014, 368.9 ± 2.2 μatm. The super-saturation of the seawater in relation to the atmosphere indicates a source of CO2 to the atmosphere. The entire study area presents oligotrophic conditions. Despite the low concentrations, Chl a and nutrients presented significant influence on fCO2sw, particularly in the westernmost and more humid part of the northeast coast, where river fluxes are three orders of magnitude larger than eastern rivers and rainfall events are more intense and constant. fCO2sw spatial distribution presented homogeneity along the same transect and longitudinal heterogeneity, between east and west, reinforcing the hypothesis of transition between two regions of different behaviour. The fCO2sw at the eastern portion was controlled by parameters such as temperature and salinity. At the western portion, fCO2sw was influenced by nutrient and Chl a. Calculated instantaneous CO2 flux ranged from + 1.66 to + 7.24 mmol m- 2 d- 1 in the first cruise and + 0.89 to + 14.62 mmol m- 2 d- 1 in the second cruise.

  16. Seasonal changes in soil water repellency and their effect on soil CO2 fluxes

    Science.gov (United States)

    Urbanek, Emilia; Qassem, Khalid

    2016-04-01

    Soil water repellency (SWR) is a seasonally variable phenomenon controlled by moisture content and at the same time a regulator of the distribution and conductivity of water in the soil. The distribution and availability of water in soil is also an important factor for microbial activity, decomposition of soil organic matter and exchange of gases like CO2 and CH4 between the soil and the atmosphere. It has been therefore hypothesised that SWR by restricting water availability in soil can affect the production and the transport of CO2 in the soil and between the soil and the atmosphere. This study investigates the effect of seasonal changes in soil moisture and water repellency on CO2 fluxes from soil. The study was conducted for 3 year at four grassland and pine forest sites in the UK with contrasting precipitation. The results show the temporal changes in soil moisture content and SWR are affected by rainfall intensity and the length of dry periods between the storms. Soils exposed to very high annual rainfall (>1200mm) can still exhibit high levels of SWR for relatively long periods of time. The spatial variation in soil moisture resulting from SWR affects soil CO2 fluxes, but the most profound effect is visible during and immediately after the rainfall events. Keywords: soil water repellency, CO2 flux, hydrophobicity, preferential flow, gas exchange, rainfall

  17. Air-sea CO2 flux in the Pacific Ocean for the period 1990–2009

    Directory of Open Access Journals (Sweden)

    M. Ishii

    2013-07-01

    Full Text Available Air-sea CO2 fluxes over the Pacific Ocean are known to be characterized by coherent large-scale structures that reflect not only ocean subduction and upwelling patterns, but also the combined effects of wind-driven gas exchange and biology. On the largest scales, a large net CO2 influx into the extra-tropics is associated with a robust seasonal cycle, and a large net CO2 efflux from the tropics is associated with substantial inter-annual variability. In this work, we have synthesized estimates of the net air-sea CO2 flux from a variety of products drawing upon a variety of approaches in three sub-basins of the Pacific Ocean, i.e., the North Pacific extra-tropics (18° N–66° N, the tropical Pacific (18° S–18° N, and the South Pacific extra-tropics (44.5° S–18° S. These approaches include those based on the measurements of CO2 partial pressure in surface seawater (pCO2sw, inversions of ocean interior CO2 data, forward ocean biogeochemistry models embedded in the ocean general circulation models (OBGCMs, a model with assimilation of pCO2sw data, and inversions of atmospheric CO2 measurements. Long-term means, inter-annual variations and mean seasonal variations of the regionally-integrated fluxes were compared in each of the sub-basins over the last two decades, spanning the period from 1990 through 2009. A simple average of the long-term mean fluxes obtained with surface water pCO2 diagnostics and those obtained with ocean interior CO2 inversions are –0.47 ± 0.13 Pg C yr–1 in the North Pacific extra-tropics, +0.44 ± 0.14 Pg C yr–1 in the tropical Pacific, and –0.37 ± 0.08 Pg C yr–1 in the South Pacific extra-tropics, where positive fluxes are into the atmosphere. This suggests that approximately half of the CO2 taken up over the North and South Pacific extra-tropics is released back to the atmosphere from the tropical Pacific. These estimates of the regional fluxes are also supported by the estimates from OBGCMs after

  18. Estimating Annual CO2 Flux for Lutjewad Station Using Three Different Gap-Filling Techniques

    NARCIS (Netherlands)

    Dragomir, Carmelia M.; Klaassen, Wim; Voiculescu, Mirela; Georgescu, Lucian P.; van der Laan, Sander; Calfapietra, C.; Staebler, R.M.

    2012-01-01

    Long-term measurements of CO2 flux can be obtained using the eddy covariance technique, but these datasets are affected by gaps which hinder the estimation of robust long-term means and annual ecosystem exchanges. We compare results obtained using three gap-fill techniques: multiple regression (MR),

  19. Estimating Annual CO2 Flux for Lutjewad Station Using Three Different Gap-Filling Techniques

    NARCIS (Netherlands)

    Dragomir, Carmelia M.; Klaassen, Wim; Voiculescu, Mirela; Georgescu, Lucian P.; van der Laan, Sander; Calfapietra, C.; Staebler, R.M.

    2012-01-01

    Long-term measurements of CO2 flux can be obtained using the eddy covariance technique, but these datasets are affected by gaps which hinder the estimation of robust long-term means and annual ecosystem exchanges. We compare results obtained using three gap-fill techniques: multiple regression (MR),

  20. CO2 acquisition in Chlamydomonas acidophila is influenced mainly by CO2, not phosphorus, availability.

    Science.gov (United States)

    Spijkerman, Elly; Stojkovic, Slobodanka; Beardall, John

    2014-09-01

    The extremophilic green microalga Chlamydomonas acidophila grows in very acidic waters (pH 2.3-3.4), where CO2 is the sole inorganic carbon source. Previous work has revealed that the species can accumulate inorganic carbon (Ci) and exhibits high affinity CO2 utilization under low-CO2 (air-equilibrium) conditions, similar to organisms with an active CO2 concentrating mechanism (CCM), whereas both processes are down-regulated under high CO2 (4.5 % CO2) conditions. Responses of this species to phosphorus (Pi)-limited conditions suggested a contrasting regulation of the CCM characteristics. Therefore, we measured external carbonic anhydrase (CAext) activities and protein expression (CAH1), the internal pH, Ci accumulation, and CO2-utilization in cells adapted to high or low CO2 under Pi-replete and Pi-limited conditions. Results reveal that C. acidophila expressed CAext activity and expressed a protein cross-reacting with CAH1 (the CAext from Chlamydomonas reinhardtii). Although the function of this CA remains unclear, CAext activity and high affinity CO2 utilization were the highest under low CO2 conditions. C. acidophila accumulated Ci and expressed the CAH1 protein under all conditions tested, and C. reinhardtii also contained substantial amounts of CAH1 protein under Pi-limitation. In conclusion, Ci utilization is optimized in C. acidophila under ecologically relevant conditions, which may enable optimal survival in its extreme Ci- and Pi-limited habitat. The exact physiological and biochemical acclimation remains to be further studied.

  1. Variability and budget of CO2 in Europe: analysis of the CAATER airborne campaigns – Part 2: Comparison of CO2 vertical variability and fluxes between observations and a modeling framework

    Directory of Open Access Journals (Sweden)

    P. Ciais

    2011-06-01

    Full Text Available Our ability to predict future climate change relies on our understanding of current and future CO2 fluxes, particularly on a regional scale (100–1000 km. CO2 regional sources and sinks are still poorly understood. Inverse transport modeling, a method often used to quantify these fluxes, relies on atmospheric CO2 measurements. One of the main challenges for the transport models used in the inversions is to properly reproduce CO2 vertical gradients between the boundary layer and the free troposphere, as these gradients impact on the partitioning of the calculated fluxes between the different model regions. Vertical CO2 profiles are very well suited to assess the performances of the models. In this paper, we conduct a comparison between observed and modeled CO2 profiles recorded during two CAATER campaigns that occurred in May 2001 and October 2002 over Western Europe, as described in a companion paper. We test different combinations between a global transport model (LMDZt, a mesoscale transport model (CHIMERE, and different sets of biospheric fluxes, all chosen with a diurnal cycle (CASA, SiB2 and ORCHIDEE. The vertical profile comparison shows that: 1 in most cases the influence of the biospheric flux is small but sometimes not negligible, ORCHIDEE giving the best results in the present study; 2 LMDZt is most of the time too diffuse, as it simulates a too high boundary layer height; 3 CHIMERE better reproduces the observed gradients between the boundary layer and the free troposphere, but is sometimes too variable and gives rise to incoherent structures. We conclude there is a need for more vertical profiles to conduct further studies to improve the parameterization of vertical transport in the models used for CO2 flux inversions. Furthermore, we use a modeling method to quantify CO2 fluxes at the regional scale from a chosen observing point, coupling influence functions from the transport model LMDZt (that works quite well at the synoptic

  2. Variability and budget of CO2 in Europe: analysis of the CAATER airborne campaigns – Part 2: Comparison of CO2 vertical variability and fluxes from observations and a modeling framework

    Directory of Open Access Journals (Sweden)

    P. Ciais

    2010-02-01

    Full Text Available Our ability to predict future climate change relies on our understanding of current and future CO2 fluxes, particularly at the scale of regions (100–1000 km. Nowadays, CO2 regional sources and sinks are still poorly known. Inverse transport modeling, a method often used to quantify these fluxes, relies on atmospheric CO2 measurements. One of the main challenge for the transport models used in the inversions is to reproduce properly CO2 vertical gradients between the boundary layer and the free troposphere, as these gradients impact on the partitioning ot the calculated fluxes between the different model regions. Vertical CO2 profiles are very well suited to assess the performances of the models. In this paper, we conduct a comparison between observed and modeled CO2 profiles recorded during two CAATER campaigns that occurred in May 2001 and October 2002 over western Europe, and that we have described in a companion paper. We test different combinations between a global transport model (LMDZt, a mesoscale transport model (CHIMERE, and different sets of biospheric fluxes, those latter all chosen to have a diurnal cycle (CASA, SiB2 and ORCHIDEE. The vertical profile comparison shows that: (1 in most cases the influence of the biospheric flux is small but sometimes not negligeable, ORCHIDEE giving the best results in the present study; (2 LMDZt is most of the time too diffusive, as it simulates a too high boundary layer height; (3 CHIMERE reproduces better the observed gradients between the boundary layer and the free troposphere, but is sometimes too variable and gives rise to incoherent structures. We conclude there is a need for more vertical profiles to conduct further studies that will help to improve the parameterization of vertical transport in the models used for CO2 flux inversions. Furthermore, we use a modeling method to quantify CO2 fluxes at the regional scale from any observing point, coupling influence functions from the transport

  3. [Effects of fertilization on soil CO2 flux in Castanea mollissima stand].

    Science.gov (United States)

    Zhang, Jiao-Jiao; Li, Yong-Fu; Jiang, Pei-Kun; Zhou, Guo-Mo; Shen, Zhen-Ming; Liu, Juan; Wang, Zhan-Lei

    2013-09-01

    In June 2011-June 2012, a fertilization experiment was conducted in a typical Castanea mollissima stand in Lin' an of Zhejiang Province, East China to study the effects of inorganic and organic fertilization on the soil CO2 flux and the relationships between the soil CO2 flux and environmental factors. Four treatments were installed, i. e., no fertilization (CK), inorganic fertilization (IF), organic fertilization (OF), half organic plus half inorganic fertilization (OIF). The soil CO2 emission rate was determined by the method of static closed chamber/GC technique, and the soil temperature, soil moisture content, and soil water-soluble organic carbon (WSOC) concentration were determined by routine methods. The soil CO2 emission exhibited a strong seasonal pattern, with the highest rate in July or August and the lowest rate in February. The annual accumulative soil CO2 emission in CK was 27.7 t CO2 x hm(-2) x a(-1), and that in treatments IF, OF, and OIF was 29.5%, 47.0%, and 50.7% higher than the CK, respectively. The soil WSOC concentration in treatment IF (105.1 mg kg(-1)) was significantly higher than that in CK (76.6 mg x kg(-1)), but was obviously lower than that in treatments OF (133.0 mg x kg(-1)) and OIF (121.2 mg x kg(-1)). The temperature sensitivity of respiration (Q10) in treatments CK, IF, OF, and OIF was 1.47, 1.75, 1.49, and 1.57, respectively. The soil CO2 emission rate had significant positive correlations with the soil temperature at the depth of 5 cm and the soil WSOC concentration, but no significant correlation with soil moisture content. The increase of the soil WSOC concentration caused by fertilization was probably one of the reasons for the increase of soil CO2 emission from the C. mollissima stand.

  4. Human impact on the historical change of CO2 degassing flux in River Changjiang

    Directory of Open Access Journals (Sweden)

    Zhang Jing

    2007-08-01

    Full Text Available Abstract The impact of water quality changes in River Changjiang (formally known as the Yangtze River on dissolved CO2 and silicate concentrations and seasonal carbon flux in the past several decades (1960s–2000 was evaluated, based on monitoring data from hydrographic gauge. It was found that dissolved CO2 and silicate in Changjiang decreased dramatically during this decades, as opposed to a marked increase in nutrient (e.g. NO3- concentrations. Our analyses revealed that dissolved CO2 in Changjiang was over-saturated with the atmosphere CO2, and its concentration had showed a declining trend since the 1960s, despite that fluvial DIC flux had maintained stable. Analysis results also suggested that the decrease in dissolved CO2 concentration was attributed to changes on the riverine trophic level and river damming activities in the Changjiang drainage basin. Due to the economic innovation (e.g. agriculture and industry development across the Changjiang watershed, fertilizers application and river regulations have significantly altered the original state of the river. Its ecosystem and hydrological condition have been evolving toward the "lacustrine/reservoir" autotrophic type prevailing with plankton. Accordingly, average CO2 diffusing flux to the atmosphere from the river had been reduced by three-fourth from the 1960s to 1990s, with the flux value being down to 14.2 mol.m-2.yr-1 in the 1990s. For a rough estimate, approximately 15.3 Mt of carbon was degassed annually into the atmosphere from the entire Changjiang drainage basin in the 1990s.

  5. Biogenic CO2 fluxes, changes in surface albedo and biodiversity impacts from establishment of a miscanthus plantation

    DEFF Research Database (Denmark)

    Jørgensen, Susanne Vedel; Cherubini, Francesco; Michelsen, Ottar

    2014-01-01

    Depletion in oil resources and environmental concern related to the use of fossil fuels has increased the interest in using second generation biomass as alternative feedstock for fuels and materials. However, the land use and land use change for producing second generation (2G) biomass impacts...... the environment in various ways, of which not all are usually considered in life cycle assessment.This study assesses the biogenic CO2 fluxes, surface albedo changes and biodiversity impacts for 100 years after changing land use from forest or fallow land to miscanthus plantation in Wisconsin, US. Climate change...... human influenced state to another.Concerning the impacts from biogenic CO2 fluxes, in the case of conversion from a forest to a miscanthus plantation (case A) there is a contribution to global warming, whereas when a fallow land is converted (case B), there is a climate cooling. When the effects from...

  6. Evaluation of various observing systems for the global monitoring of CO2 surface fluxes

    Directory of Open Access Journals (Sweden)

    A. Klonecki

    2010-08-01

    Full Text Available In the context of raising greenhouse gas concentrations, and the potential feedbacks between climate and the carbon cycle, there is an urgent need to monitor the exchanges of carbon between the atmosphere and both the ocean and the land surfaces. In the so-called top-down approach, the surface fluxes of CO2 are inverted from the observed spatial and temporal concentration gradients. The concentrations of CO2 are measured in-situ at a number of surface stations unevenly distributed over the Earth while several satellite missions may be used to provide a dense and better-distributed set of observations to complement this network. In this paper, we compare the ability of different CO2 concentration observing systems to constrain surface fluxes. The various systems are based on realistic scenarios of sampling and precision for satellite and in-situ measurements. It is shown that satellite measurements based on the differential absorption technique (such as those of SCIAMACHY, GOSAT or OCO provide more information than the thermal infrared observations (such as those of AIRS or IASI. The OCO observations will provide significantly better information than those of GOSAT. A CO2 monitoring mission based on an active (lidar technique could potentially provide an even better constraint. This constraint can also be realized with the very dense surface network that could be built with the same funding as that of the active satellite mission. Despite the large uncertainty reductions on the surface fluxes that may be expected from these various observing systems, these reductions are still insufficient to reach the highly demanding requirements for the monitoring of anthropogenic emissions of CO2 or the oceanic fluxes at a spatial scale smaller than that of oceanic basins. The scientific objective of these observing system should therefore focus on the fluxes linked to vegetation and land ecosystem dynamics.

  7. Surface Ocean pCO2 Seasonality and Sea-Air CO2 Flux Estimates for the North American East Coast

    Science.gov (United States)

    Signorini, Sergio; Mannino, Antonio; Najjar, Raymond G., Jr.; Friedrichs, Marjorie A. M.; Cai, Wei-Jun; Salisbury, Joe; Wang, Zhaohui Aleck; Thomas, Helmuth; Shadwick, Elizabeth

    2013-01-01

    Underway and in situ observations of surface ocean pCO2, combined with satellite data, were used to develop pCO2 regional algorithms to analyze the seasonal and interannual variability of surface ocean pCO2 and sea-air CO2 flux for five physically and biologically distinct regions of the eastern North American continental shelf: the South Atlantic Bight (SAB), the Mid-Atlantic Bight (MAB), the Gulf of Maine (GoM), Nantucket Shoals and Georges Bank (NS+GB), and the Scotian Shelf (SS). Temperature and dissolved inorganic carbon variability are the most influential factors driving the seasonality of pCO2. Estimates of the sea-air CO2 flux were derived from the available pCO2 data, as well as from the pCO2 reconstructed by the algorithm. Two different gas exchange parameterizations were used. The SS, GB+NS, MAB, and SAB regions are net sinks of atmospheric CO2 while the GoM is a weak source. The estimates vary depending on the use of surface ocean pCO2 from the data or algorithm, as well as with the use of the two different gas exchange parameterizations. Most of the regional estimates are in general agreement with previous studies when the range of uncertainty and interannual variability are taken into account. According to the algorithm, the average annual uptake of atmospheric CO2 by eastern North American continental shelf waters is found to be between 3.4 and 5.4 Tg C/yr (areal average of 0.7 to 1.0 mol CO2 /sq m/yr) over the period 2003-2010.

  8. Substrate quality and nutrient availability influence CO2 production from tropical peat decomposition

    Science.gov (United States)

    Swails, E.; Jaye, D.; Verchot, L. V.; Hergoualc'h, K.; Wahyuni, N. S.; Borchard, N.; Lawrence, D.

    2015-12-01

    In Indonesia, peatlands are a major and growing source of greenhouse gas emissions due to increasing pressure from oil palm and pulp wood plantations. We are using a combination of field measures, laboratory experiments, and remote sensing to investigate relationships among land use, climatic factors and biogeochemical controls, and their influence on trace gas fluxes from tropical peat soils. Analysis of soils collected from peat sites on two major islands indicated substantial variation in peat substrate quality and nutrient content among land uses and geographic location. We conducted laboratory incubations to test the influence of substrate quality and nutrient availability on CO2 production from peat decomposition. Differences in peat characteristics attributable to land use change were tested by comparison of forest and oil palm peat samples collected from the same peat dome in Kalimantan. Regional differences in peat characteristics were tested by comparison of samples from Sumatra with samples from Kalimantan. We conducted additional experiments to test the influence of N and P availability and labile carbon on CO2 production. Under moisture conditions typical of oil palm plantations, CO2 production was higher from peat forest samples than from oil palm samples. CO2 production from Sumatra and Kalimantan oil palm samples was not different, despite apparent differences in nutrient content of these soils. N and P treatments representative of fertilizer application rates raised CO2 production from forest samples but not oil palm samples. Labile carbon treatments raised CO2 production in all samples. Our results suggest that decomposition of peat forest soils is nutrient limited, while substrate quality controls decomposition of oil palm soils post-conversion. Though fertilizer application could accelerate peat decomposition initially, fertilizer application may not influence long-term CO2 emissions from oil palm on peat.

  9. Measurement of advective soil gas flux: Results of field and laboratory experiments with CO2

    Energy Technology Data Exchange (ETDEWEB)

    Amonette, James E.; Barr, Jonathan L.; Erikson, Rebecca L.; Dobeck, Laura M.; Barr, Jamie L.; Shaw, Joseph A.

    2013-10-01

    We modified our multi-channel, steady-state flow-through (SSFT), soil-CO2 flux monitoring system to include an array of inexpensive pyroelectric non-dispersive infrared detectors for full-range (0-100%) coverage of CO2 concentrations without dilution, and a larger-diameter vent tube. We then conducted field testing of this system from late July through mid-September 2010 at the Zero Emissions Research and Technology (ZERT) project site located in Bozeman, MT, and subsequently, laboratory testing at the Pacific Northwest National Laboratory (PNNL) in Richland, WA using a flux bucket filled with dry sand. In the field, an array of twenty-five SSFT and three non-steady-state (NSS) flux chambers was installed in a 10x4 m area, the long boundary of which was directly above a shallow (2-m depth) horizontal injection well located 0.5 m below the water table. Two additional chambers (one SSFT and one NSS) were installed 10 m from the well for background measurements. Volumetric soil moisture sensors were installed at each SSFT chamber to measure mean levels in the top 0.15 m of soil. A total flux of 52 kg CO2 d-1 was injected into the well for 27 d and the efflux from the soil was monitored by the chambers before, during, and for 27 d after the injection. Overall, the results were consistent with those from previous years, showing a radial efflux pattern centered on a known “hot spot”, rapid responses to changes in injection rate and wind power, evidence for movement of the CO2 plume during the injection, and nominal flux levels from the SSFT chambers that were up to 6-fold higher than those measured by adjacent NSS chambers. Soil moisture levels varied during the experiment from moderate to near saturation with the highest levels occurring consistently at the hot spot. The effects of wind on measured flux were complex and decreased as soil moisture content increased. In the laboratory, flux bucket testing with the SSFT chamber showed large measured-flux enhancement

  10. Estimating surface CO2 fluxes from space-borne CO2 dry air mole fraction observations using an ensemble Kalman Filter

    Directory of Open Access Journals (Sweden)

    S. Dance

    2009-04-01

    Full Text Available We have developed an ensemble Kalman Filter (EnKF to estimate 8-day regional surface fluxes of CO2 from space-borne CO2 dry-air mole fraction observations (XCO2 and evaluate the approach using a series of synthetic experiments, in preparation for data from the NASA Orbiting Carbon Observatory (OCO. The 32-day duty cycle of OCO alternates every 16 days between nadir and glint measurements of backscattered solar radiation at short-wave infrared wavelengths. The EnKF uses an ensemble of states to represent the error covariances to estimate 8-day CO2 surface fluxes over 144 geographical regions. We use a 12×8-day lag window, recognising that XCO2 measurements include surface flux information from prior time windows. The observation operator that relates surface CO2 fluxes to atmospheric distributions of XCO2 includes: a the GEOS-Chem transport model that relates surface fluxes to global 3-D distributions of CO2 concentrations, which are sampled at the time and location of OCO measurements that are cloud-free and have aerosol optical depths 2 profiles to XCO2, accounting for differences between nadir and glint measurements, and the associated scene-dependent observation errors. We show that OCO XCO2 measurements significantly reduce the uncertainties of surface CO2 flux estimates. Glint measurements are generally better at constraining ocean CO2 flux estimates. Nadir XCO2 measurements over the terrestrial tropics are sparse throughout the year because of either clouds or smoke. Glint measurements provide the most effective constraint for estimating tropical terrestrial CO2 fluxes by accurately sampling fresh continental outflow over neighbouring oceans. We also present results from sensitivity experiments that investigate how flux estimates change with 1 bias and unbiased errors, 2 alternative duty cycles, 3 measurement density and correlations, 4 the spatial resolution of estimated flux estimates, and 5 reducing the length of the lag window and the

  11. Spatiotemporal variability and drivers of pCO2 and air–sea CO2 fluxes in the California Current System: an eddy-resolving modeling study

    Directory of Open Access Journals (Sweden)

    G. Turi

    2013-08-01

    Full Text Available We quantify the CO2 source/sink nature of the California Current System (CalCS and determine the drivers and processes behind the mean and spatiotemporal variability of the partial pressure of CO2 (pCO2 in the surface ocean. To this end, we analyze eddy-resolving, climatological simulations of a coupled physical-ecosystem-biogeochemical ocean model on the basis of the Regional Oceanic Modeling System (ROMS. The model-simulated pCO2 agrees very well with in situ observations over the entire domain with virtually no bias, but the model overestimates pCO2 in the nearshore 100 km, and underestimates the observed temporal variability. In the annual mean, the entire CalCS within 800 km of the coast and from ~ 33° N to 46° N is essentially neutral with regard to atmospheric CO2. The model simulates an integrated uptake flux of −0.9 Tg C yr–1, corresponding to a very small average flux density of −0.05 mol C m–2 yr–1, with an uncertainty of the order of ±0.20 mol C m–2 yr–1. This near zero flux is a consequence of an almost complete regional compensation between the strong outgassing in the nearshore region (first 100 km, with flux densities of more than 3 mol C m–2 yr–1 and a weaker, but more widespread uptake flux in the offshore region with an average flux density of −0.17 mol C m–2 yr–1. This pattern is primarily a result of the interaction between upwelling in the nearshore that brings waters with high concentrations of dissolved inorganic carbon (DIC to the surface, and an intense biological drawdown of this DIC, driven by the nutrients that are upwelled together with the DIC. The biological drawdown occurs too slowly to prevent the escape of a substantial amount of CO2 into the atmosphere, but this is compensated by the biological generation of undersaturated conditions offshore of 100 km, permitting the CalCS to take up most of the escaped CO2. Thus, the biological pump over the entire CalCS is essentially 100

  12. Controls over N2O, NOx and CO2 fluxes in a calcareous mountain forest soil

    Directory of Open Access Journals (Sweden)

    B. Kitzler

    2006-01-01

    Full Text Available We measured nitrogen oxides (N2O and NOx, dinitrogen (N2 and carbon dioxide (CO2 emissions from a spruce-fir-beech forest soil in the North Tyrolean limestone Alps in Austria. The site received 10.6–11.9 kg N ha−1 y−1 nitrogen as bulk deposition. Fluxes of nitric oxide (NO were measured by an automatic dynamic chamber system on an hourly basis over a two year period. Daily N2O emissions were obtained by a semi-automatic gas measuring system. In order to cover spatial variability biweekly manual measurements of N2O and CO2 emissions were carried out in addition. For acquiring information on the effects of soil and meteorological conditions and of N-deposition on N-emissions we chose the auto-regression procedure (time-series analysis as our means of investigation. Hence, we could exclude the data's autocorrelation in the course of the time. We found that soil temperature, soil moisture and bulk N-deposition followed by air temperature and precipitation were the most powerful influencing parameters effecting N-emissions. With these variables, up to 89% of observed temporal variations of N-emissions could be explained. During the two-year investigation period between 2.5 and 3.5% of deposited N was reemitted in form of N2O whereas only 0.2% were emitted as NO. At our mountain forest site the main end-product of microbial activity processes was N2 and trace gases (N2O and NO were only of minor importance.

  13. Global Monthly CO2 Flux Inversion Based on Results of Terrestrial Ecosystem Modeling

    Science.gov (United States)

    Deng, F.; Chen, J.; Peters, W.; Krol, M.

    2008-12-01

    Most of our understanding of the sources and sinks of atmospheric CO2 has come from inverse studies of atmospheric CO2 concentration measurements. However, the number of currently available observation stations and our ability to simulate the diurnal planetary boundary layer evolution over continental regions essentially limit the number of regions that can be reliably inverted globally, especially over continental areas. In order to overcome these restrictions, a nested inverse modeling system was developed based on the Bayesian principle for estimating carbon fluxes of 30 regions in North America and 20 regions for the rest of the globe. Inverse modeling was conducted in monthly steps using CO2 concentration measurements of 5 years (2000 - 2005) with the following two models: (a) An atmospheric transport model (TM5) is used to generate the transport matrix where the diurnal variation n of atmospheric CO2 concentration is considered to enhance the use of the afternoon-hour average CO2 concentration measurements over the continental sites. (b) A process-based terrestrial ecosystem model (BEPS) is used to produce hourly step carbon fluxes, which could minimize the limitation due to our inability to solve the inverse problem in a high resolution, as the background of our inversion. We will present our recent results achieved through a combination of the bottom-up modeling with BEPS and the top-down modeling based on TM5 driven by offline meteorological fields generated by the European Centre for Medium Range Weather Forecast (ECMFW).

  14. Spatial variability of soil N2O and CO2 fluxes in different topographic positions in a tropical montane forest in Kenya

    Science.gov (United States)

    Arias-Navarro, C.; Díaz-Pinés, E.; Klatt, S.; Brandt, P.; Rufino, M. C.; Butterbach-Bahl, K.; Verchot, L. V.

    2017-03-01

    Quantifying and understanding the small-scale variability of nitrous oxide (N2O) and carbon dioxide (CO2) emission are essential for reporting accurate ecosystem greenhouse gas budgets. The objective of this study was to evaluate the spatial pattern of soil CO2 and N2O emissions and their relation to topography in a tropical montane forest. We measured fluxes of N2O and CO2 from 810 sampling locations across valley bottom, midslope, and ridgetop positions under controlled laboratory conditions. We further calculated the minimum number of samples necessary to provide best estimates of soil N2O and CO2 fluxes at the plot level. Topography exhibited a major influence on N2O emissions, with soils at midslope position emitting significantly less than at ridgetops and valley bottoms, but no consistent effect of topography on soil CO2 emissions was found. The high spatial variation of N2O and CO2 fluxes was further increased by changes in vegetation and soil properties resulting from human disturbance associated with charcoal production. Soil N2O and CO2 fluxes showed no spatial pattern at the plot level, with "hot spots" strongly contributing to the total emissions (10% of the soil cores represented 73 and 50% of the total N2O and CO2 emissions, respectively). Thus, a large number of samples are needed to obtain robust estimates of N2O and CO2 fluxes. Our results highlight the complex biogeochemical cycling in tropical montane forests, and the need to carefully address it in research experiments to robustly estimate soil CO2 and N2O fluxes at the ecosystem scale.

  15. Regional inversion of CO2 ecosystem fluxes from atmospheric measurements. Reliability of the uncertainty estimates

    Energy Technology Data Exchange (ETDEWEB)

    Broquet, G.; Chevallier, F.; Breon, F.M.; Yver, C.; Ciais, P.; Ramonet, M.; Schmidt, M. [Laboratoire des Sciences du Climat et de l' Environnement, CEA-CNRS-UVSQ, UMR8212, IPSL, Gif-sur-Yvette (France); Alemanno, M. [Servizio Meteorologico dell' Aeronautica Militare Italiana, Centro Aeronautica Militare di Montagna, Monte Cimone/Sestola (Italy); Apadula, F. [Research on Energy Systems, RSE, Environment and Sustainable Development Department, Milano (Italy); Hammer, S. [Universitaet Heidelberg, Institut fuer Umweltphysik, Heidelberg (Germany); Haszpra, L. [Hungarian Meteorological Service, Budapest (Hungary); Meinhardt, F. [Federal Environmental Agency, Kirchzarten (Germany); Necki, J. [AGH University of Science and Technology, Krakow (Poland); Piacentino, S. [ENEA, Laboratory for Earth Observations and Analyses, Palermo (Italy); Thompson, R.L. [Max Planck Institute for Biogeochemistry, Jena (Germany); Vermeulen, A.T. [Energy research Centre of the Netherlands ECN, EEE-EA, Petten (Netherlands)

    2013-07-01

    The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5{sup 0} resolution are applied for the western European domain where {approx}50 eddy covariance sites are operated. These inversions are conducted for the period 2002-2007. They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. Averaged over monthly periods and over the whole domain, the misfits are in good agreement with the theoretical uncertainties for prior and inverted NEE, and pass the chi-square test for the variance at the 30% and 5% significance levels respectively, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion decreases the standard deviation of the misfits by 38 %. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modelling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that this study does not engender confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than

  16. Disequilibrium of 13CO2 fluxes between photosynthesis and respiration in North American temperate forest biomes

    Science.gov (United States)

    Lai, C.; Ehleringer, J.; Schauer, A.; Tans, P.; Hollinger, D.; Paw U, K.; Wofsy, S.

    2003-12-01

    We report the first weekly dataset of seasonal and interannual variability in δ 13C of CO2 fluxes from dominant forest ecosystems in the US. We observed large variations in the δ 13C of respired biosphere-atmosphere fluxes (δ 13CR) across 3 temperate coniferous and deciduous forest ecosystems (-24.9 +/- 0.4 to -31.3 +/- 0.6 per mil). Values of δ 13CR were significantly correlated with growing-season soil water availability. By analyzing daytime flask measurements collected at the top of canopies, we estimated an annual mean, flux-weighted δ 13C of net ecosystem CO2 exchange fluxes (δ 13Cnet). Combining δ 13CR and δ 13Cnet, along with eddy-covariance measured fluxes, we estimated regional discrimination against 13C during photosynthesis (Δ A) for these 3 forest ecosystems. Our approach allows for examination of the interannual correlations between gross primary production fluxes and Δ A that could potentially modulate atmospheric 13C budget. The results showed that C3 forests in temperate regions in the U.S. exhibited a slight isotopic disequilibrium ( 3 per mil). Such subtle isotopic disequilibrium however, when associated with enormous one-way gross fluxes, can effectively affect atmospheric 13C budget.

  17. Soil CO2 Flux in the Amargosa Desert, Nevada, during El Nino 1998 and La Nina 1999

    Science.gov (United States)

    Riggs, Alan C.; Stannard, David I.; Maestas, Florentino B.; Karlinger, Michael R.; Striegl, Robert G.

    2009-01-01

    Mean annual soil CO2 fluxes from normally bare mineral soil in the Amargosa Desert in southern Nevada, United States, measured with clear and opaque soil CO2-flux chambers (autochambers) were small - Nino 1998 and La Nina 1999. The 1998 opaque-chamber flux exceeded 1999 opaque-chamber flux by an order of magnitude, whereas the 1998 clear-chamber flux exceeded 1999 clear-chamber flux by less than a factor of two. These data suggest that above-normal soil moisture stimulated increased metabolic activity, but that much of the extra CO2 produced was recaptured by plants. Fluxes from warm moist soil were the largest sustained fluxes measured, and their hourly pattern is consistent with enhanced soil metabolic activity at some depth in the soil and photosynthetic uptake of a substantial portion of the CO2 released. Flux from cool moist soil was smaller than flux from warm moist soil. Flux from hot dry soil was intermediate between warm-moist and cool-moist fluxes, and clear-chamber flux was more than double the opaque-chamber flux, apparently due to a chamber artifact stemming from a thermally controlled CO2 reservoir near the soil surface. There was no demonstrable metabolic contribution to the very small flux from cool dry soil, which was dominated by diffusive up-flux of CO2 from the water table and temperature-controlled CO2-reservoir up- and down-fluxes. These flux patterns suggest that transfer of CO2 across the land surface is a complex process that is difficult to accurately measure.

  18. Regional CO2 flux estimates from estuarine environments: a reactive-transport modeling approach

    Science.gov (United States)

    Goossens, Nicolas; Laruelle, Goulven G.; Arndt, Sandra; Regnier, Pierre

    2013-04-01

    Estuaries are key components of the land-ocean continuum and play an important role in the global carbon cycle. Large amounts of terrestrial carbon are channelled through estuaries before reaching the ocean. During estuarine transit, numerous biogeochemical processes transform the carbon flux, resulting in a significant CO2 evasion flux to the atmosphere. The global estuarine CO2 outgassing is evaluated at 0.25±0.25 PgC yr-1. Yet, these estimates rely on the extrapolation of local measurements and the scarcity of such measurements conducts to large uncertainties. Furthermore, the global quantification is biased towards anthropogenically impacted estuarine systems located in industrialized countries. Here we provide a first assessment of the estuarine carbon budget and, in particular, CO2 evasion fluxes using a generic and effective reactive-transport model (RTM) approach that is applicable at the regional scale. The new approach is based on the mutual dependency between estuarine geometry and hydrodynamics and uses idealized estuarine geometries. Global river databases (GLORICH) and watershed model outputs (GlobalNEWS) are used to quantify input fluxes for the generic estuarine model. The new modeling approach provides not only a quantification of the estuarine carbon budget, but also allows disentangling the relative contributions of biogeochemical and physical processes to estuarine CO2 emissions. Preliminary results are presented for the North Eastern coast of the US. Model results are consistent with observations and indicate that the net heterotrophy of these systems is the major contributor to estuarine CO2 fluxes (>50%), followed by outgassing of supersaturated riverine waters and nitrification. Results also highlight the strong seasonality in the biogeochemical dynamics. In addition, significant heterogeneity is observed across different estuaries due to spatial heterogeneities in climate forcing, estuarine geometry or riverine input fluxes. The proposed

  19. Eddy covariance measurements of CO2 and energy fluxes in the city of Beijing

    Directory of Open Access Journals (Sweden)

    T. Vesala

    2012-03-01

    Full Text Available Long-term measurement of carbon dioxide flux (Fc was performed using the eddy covariance (EC method in the Beijing megacity over a 4-yr period in 2006–2009. The EC setup was installed at a height of 47 m on the Beijing 325-m meteorological tower in the northwest part of the city. Latent heat flux dominated the energy exchange between the urban surface and the atmosphere in summer, while sensible heat flux was the main component in the spring. The source area of the measurements of CO2 is highly heterogeneous, which consists of buildings, parks, and highways. It is valuable for global carbon budget research to study the temporal and spatial variability of Fc in this urban environment of a developing country. Both on a diurnal and monthly scale, the urban surface acted as a net source for CO2 and downward fluxes were only occasionally observed. The diurnal pattern of Fc showed dependence on automobile traffic and the typical two peak traffic pattern appeared in Fc diurnal cycle. Also, the Fc was higher on weekdays than on weekends due to the higher traffic volumes on weekdays. On seasonal scale, Fc was generally higher in winter than during other seasons, likely due to domestic heating during colder months. Total annual average CO2 emissions were estimated to be 4.90 kg C m−2 y−1 over the 4-yr period.

  20. Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

    Science.gov (United States)

    Boyd, Thomas J.; Montgomery, Michael T.; Cuenca, Richard H.; Hagimoto, Yutaka

    2016-01-01

    A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate the environment. This radiocarbon signal — or rather the absence of signal — is evenly distributed throughout a contaminant source pool (unlike an added tracer) and is not impacted by biological, chemical or physical processes (e.g., the 14C radioactive decay rate is immutable). If the fossil-derived contaminant is fully degraded to CO2, a harmless end-product, that CO2 will contain no radiocarbon. CO2 derived from natural organic matter (NOM) degradation will reflect the NOM radiocarbon content (usually <30,000 years old). Given a known radiocarbon content for NOM (a site background), a two end-member mixing model can be used to determine the CO2 derived from a fossil source in a given soil gas or groundwater sample. Coupling the percent CO2 derived from the contaminant with the CO2 respiration rate provides an estimate for the total amount of contaminant degraded per unit time. Finally, determining a zone of influence (ZOI) representing the volume from which site CO2 is collected allows determining the contaminant degradation per unit time and volume. Along with estimates for total contaminant mass, this can ultimately be used to calculate time-to-remediate or otherwise used by site managers for decision-making. PMID:27805601

  1. Partitioning CO2 fluxes with isotopologue measurements and modeling to understand mechanisms of forest carbon sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Saleska, Scott [Univ. of Arizona, Tucson, AZ (United States); Davidson, Eric [Univ. of Arizona, Tucson, AZ (United States); Finzi, Adrien [Boston Univ., MA (United States); Wehr, Richdard [Harvard Univ., Cambridge, MA (United States); Moorcroft, Paul [Harvard Univ., Cambridge, MA (United States)

    2016-01-28

    1. Objectives This project combines automated in situ observations of the isotopologues of CO2 with root observations, novel experimental manipulations of belowground processes, and isotope-enabled ecosystem modeling to investigate mechanisms of below- vs. aboveground carbon sequestration at the Harvard Forest Environmental Measurements Site (EMS). The proposed objectives, which have now been largely accomplished, include: A. Partitioning of net ecosystem CO2 exchange (NEE) into photosynthesis and respiration using long-term continuous observations of the isotopic composition of NEE, and analysis of their dynamics ; B. Investigation of the influence of vegetation phenology on the timing and magnitude of carbon allocated belowground using measurements of root growth and indices of belowground autotrophic vs. heterotrophic respiration (via trenched plots and isotope measurements); C. Testing whether plant allocation of carbon belowground stimulates the microbial decomposition of soil organic matter, using in situ rhizosphere simulation experiments wherein realistic quantities of artificial isotopically-labeled exudates are released into the soil; and D. Synthesis and interpretation of the above data using the Ecosystem Demography Model 2 (ED2). 2. Highlights Accomplishments: • Our isotopic eddy flux record has completed its 5th full year and has been used to independently estimate ecosystem-scale respiration and photosynthesis. • Soil surface chamber isotopic flux measurements were carried out during three growing seasons, in conjunction with a trenching manipulation. Key findings to date (listed by objective): A. Partitioning of Net Ecosystem Exchange: 1. Ecosystem respiration is lower during the day than at night—the first robust evidence of the inhibition of leaf respiration by light (the “Kok effect”) at the ecosystem scale. 2. Because it neglects the Kok effect, the standard NEE partitioning approach overestimates ecosystem photosynthesis (by ~25%) and

  2. Modelling regional scale surface fluxes, meteorology and CO2 mixing ratios for the Cabauw tower in the Netherlands

    NARCIS (Netherlands)

    Tolk, L. F.; Peters, W.; Meesters, A. G. C. A.; Groenendijk, M.; Vermeulen, A. T.; Steeneveld, G. J.; Dolman, A. J.

    2009-01-01

    We simulated meteorology and atmospheric CO2 transport over the Netherlands with the mesoscale model RAMS-Leaf3 coupled to the biospheric CO2 flux model 5PM. The results were compared with meteorological and CO2 observations, with emphasis on the tall tower of Cabauw. An analysis of the coupled exch

  3. The Martian hydrologic cycle - Effects of CO2 mass flux on global water distribution

    Science.gov (United States)

    James, P. B.

    1985-01-01

    The Martian CO2 cycle, which includes the seasonal condensation and subsequent sublimation of up to 30 percent of the planet's atmosphere, produces meridional winds due to the consequent mass flux of CO2. These winds currently display strong seasonal and hemispheric asymmetries due to the large asymmetries in the distribution of insolation on Mars. It is proposed that asymmetric meridional advection of water vapor on the planet due to these CO2 condensation winds is capable of explaining the observed dessication of Mars' south polar region at the current time. A simple model for water vapor transport is used to verify this hypothesis and to speculate on the effects of changes in orbital parameters on the seasonal water cycle.

  4. Joint CO2 state and flux estimation with the 4D-Var system EURAD-IM

    Science.gov (United States)

    Klimpt, Johannes; Elbern, Hendrik

    2016-04-01

    Atmospheric CO2 inversion studies seek to improve CO2 surface-atmosphere fluxes with the usage of adjoint transport models and CO2 concentration measurements. Terrestrial CO2 fluxes -anthropogenic emissions, photosynthesis, and respiration- bear large spatial and temporal variability and are highly uncertain. Additionally to the high uncertainty of the three CO2 fluxes itself, regional inversion studies suffer from uncertainty of the boundary layer height and atmospheric transport especially during night, leading to uncertainty of atmospheric CO2 mixing ratios during sunrise. This study assesses the potential of the 4-dimensional variational (4D-Var) method to estimate CO2 fluxes and atmospheric CO2 concentrations jointly at each grid cell on a regional scale. Identical twin experiments are executed with the nested EURopean Air pollution Dispersion-Inverse Model (EURAD-IM) with 5 km resolution in Central Europe with synthetic half hourly measurements from eleven concentration towers. The assimilation window is chosen to start from sunrise for 12 hours. We find that joint estimation of CO2 fluxes and initial states requires a more careful balance of the background error covariance matrices but enables a more detailed analysis of atmospheric CO2 and the surface-atmosphere fluxes.

  5. Volcanic CO2 mapping and flux measurements at Campi Flegrei by Tunable Diode Laser absorption Spectroscopy

    Science.gov (United States)

    Pedone, Maria; Aiuppa, Alessandro; Giudice, Gaetano; Grassa, Fausto; Chiodini, Giovanni; Valenza, Mariano

    2014-05-01

    Near-infrared room-temperature Tunable Diode Lasers (TDL) have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in Volcanology are still limited to a few examples. Here, we explored the potentiality of a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) to measurement of volcanic CO2 flux emissions. Our field tests were conducted at Campi Flegrei (near Pozzuoli, Southern Italy), where the GasFinder was used (during three campaigns in October 2012, January 2013 and May 2013) to repeatedly measure the path-integrated concentrations of CO2 along cross-sections of the atmospheric plumes of the two main fumarolic fields in the area (Solfatara and Pisciarelli). By using ad-hoc designed field-set-up and a tomographic post-processing routine, we resolved, for each of the 2 manifestations, the contour maps of CO2 concentrations in their atmospheric plumes, from the integration of which (and after multiplication by the plumes' transport speeds) the CO2 fluxes were finally obtained [1]. The so-calculated fluxes average of 490 tons/day, which agrees well with independent evaluations of Aiuppa et al. (2013) [2] (460 tons/day on average), and support a significant contribution of fumaroles to the total CO2 budget. The cumulative (fumarole [this study] +soil [2]) CO2 output from Campi Flegrei is finally evaluated at 1600 tons/day. The application of lasers to volcanic gas studies is still an emerging (though intriguing) research field, and requires more testing and validation experiments. We conclude that TDL technique may valuably assist CO2 flux quantification at a number of volcanic targets worldwide. [1] Pedone M. et al. (2013) Gold2013:abs:5563, Goldschmidt Conference, session 11a. [2] Aiuppa A. et al. (2013) Geochemistry Geophysics Geosystems. doi: 10.1002/ggge.20261. [3] Chiodini G. et al. (2010) Journal of Geophysical Research, Volume 115, B03205. doi:10.1029/2008JB006258.

  6. Quantifying and reducing uncertainties in estimated soil CO2 fluxes with hierarchical data-model integration

    Science.gov (United States)

    Ogle, Kiona; Ryan, Edmund; Dijkstra, Feike A.; Pendall, Elise

    2016-12-01

    Nonsteady state chambers are often employed to measure soil CO2 fluxes. CO2 concentrations (C) in the headspace are sampled at different times (t), and fluxes (f) are calculated from regressions of C versus t based on a limited number of observations. Variability in the data can lead to poor fits and unreliable f estimates; groups with too few observations or poor fits are often discarded, resulting in "missing" f values. We solve these problems by fitting linear (steady state) and nonlinear (nonsteady state, diffusion based) models of C versus t, within a hierarchical Bayesian framework. Data are from the Prairie Heating and CO2 Enrichment study that manipulated atmospheric CO2, temperature, soil moisture, and vegetation. CO2 was collected from static chambers biweekly during five growing seasons, resulting in >12,000 samples and >3100 groups and associated fluxes. We compare f estimates based on nonhierarchical and hierarchical Bayesian (B versus HB) versions of the linear and diffusion-based (L versus D) models, resulting in four different models (BL, BD, HBL, and HBD). Three models fit the data exceptionally well (R2 ≥ 0.98), but the BD model was inferior (R2 = 0.87). The nonhierarchical models (BL and BD) produced highly uncertain f estimates (wide 95% credible intervals), whereas the hierarchical models (HBL and HBD) produced very precise estimates. Of the hierarchical versions, the linear model (HBL) underestimated f by 33% relative to the nonsteady state model (HBD). The hierarchical models offer improvements upon traditional nonhierarchical approaches to estimating f, and we provide example code for the models.

  7. Net sea-air CO2 fluxes and modelled pCO2 in the southwestern subtropical Atlantic continental shelf during spring 2010 and summer 2011

    Science.gov (United States)

    Ito, Rosane Gonçalves; Garcia, Carlos Alberto Eiras; Tavano, Virginia Maria

    2016-05-01

    Sea-air CO2 fluxes over continental shelves vary substantially in time on both seasonal and sub-seasonal scales, driven primarily by variations in surface pCO2 due to several oceanic mechanisms. Furthermore, coastal zones have not been appropriately considered in global estimates of sea-air CO2 fluxes, despite their importance to ecology and to productivity. In this work, we aimed to improve our understanding of the role played by shelf waters in controlling sea-air CO2 fluxes by investigating the southwestern Atlantic Ocean (21-35°S) region, where physical, chemical and biological measurements were made on board the Brazilian R. V. Cruzeiro do Sul during late spring 2010 and early summer 2011. Features such as discharge from the La Plata River, intrusions of tropical waters on the outer shelf due to meandering and flow instabilities of the Brazil Current, and coastal upwelling in the Santa Marta Grande Cape and São Tomé Cape were detected by both in situ measurements and ocean colour and thermal satellite imagery. Overall, shelf waters in the study area were a source of CO2 to the atmosphere, with an average of 1.2 mmol CO2 m-2 day-1 for the late spring and 11.2 mmol CO2 m-2 day-1 for the early summer cruises. The spatial variability in ocean pCO2 was associated with surface ocean properties (temperature, salinity and chlorophyll-a concentration) in both the slope and shelf waters. Empirical algorithms for predicting temperature-normalized surface ocean pCO2 as a function of surface ocean properties were shown to perform well in both shelf and slope waters, except (a) within cyclonic eddies produced by baroclinic instability of the Brazil Current as detected by satellite SST imagery and (b) in coastal upwelling regions. In these regions, surface ocean pCO2 values were higher as a result of upwelled CO2-enriched subsurface waters. Finally, a pCO2 algorithm based on both sea surface temperature and surface chlorophyll-a was developed that enabled the spatial

  8. Sea–air CO2 fluxes in the Southern Ocean for the period 1990–2009

    Directory of Open Access Journals (Sweden)

    A. Lenton

    2013-06-01

    Full Text Available The Southern Ocean (44–75° S plays a critical role in the global carbon cycle, yet remains one of the most poorly sampled ocean regions. Different approaches have been used to estimate sea–air CO2 fluxes in this region: synthesis of surface ocean observations, ocean biogeochemical models, and atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes project, we combine these different approaches to quantify and assess the magnitude and variability in Southern Ocean sea–air CO2 fluxes between 1990–2009. Using all models and inversions (26, the integrated median annual sea–air CO2 flux of −0.42 ± 0.07 Pg C yr−1 for the 44–75° S region, is consistent with the −0.27 ± 0.13 Pg C yr−1 calculated using surface observations. The circumpolar region south of 58° S has a small net annual flux (model and inversion median: −0.04 ± 0.07 Pg C yr−1 and observations: +0.04 ± 0.02 Pg C yr−1, with most of the net annual flux located in the 44 to 58° S circumpolar band (model and inversion median: −0.36 ± 0.09 Pg C yr−1 and observations: −0.35 ± 0.09 Pg C yr−1. Seasonally, in the 44–58° S region, the median of 5 ocean biogeochemical models captures the observed sea–air CO2 flux seasonal cycle, while the median of 11 atmospheric inversions shows little seasonal change in the net flux. South of 58° S, neither atmospheric inversions nor ocean biogeochemical models reproduce the phase and amplitude of the observed seasonal sea–air CO2 flux, particularly in the Austral Winter. Importantly, no individual atmospheric inversion or ocean biogeochemical model is capable of reproducing both the observed annual mean uptake and the observed seasonal cycle. This raises concerns about projecting future changes in Southern Ocean CO2 fluxes. The median interannual variability from atmospheric inversions and ocean biogeochemical models is substantial in the Southern Ocean; up to 25% of

  9. Bayesian belief network for CO2 leak detection by near-surface flux rates for CO2 and perfluorocarbon (PFC) tracer

    Science.gov (United States)

    Yang, Y.; Small, M. J.; Ogretim, E.; Gray, D. D.; Bromhal, G. S.; Strazisar, B. R.; Wells, A. W.

    2010-12-01

    To incorporate the use of multiple geologic sequestration monitoring techniques, a Bayesian Belief Network (BBN) for leak detection inference is applied to integrate the information provided by different techniques deployed at a site. In this study, two monitoring methods, near-surface soil CO2 flux and perfluorocarbon (PFC) tracer concentration, are included in the BBN. First, possible near-surface flux rates for CO2 and PFC tracer as a function of distance from a leakage point are simulated by TOUGH2, given different leakage rates and permeabilities. Then, the natural near-surface CO2 flux and background PFC tracer concentration measured at the Zero Emission Research and Technology (ZERT) site are used to determine critical values for leak inference and to calculate the probabilities of leak detection given a monitoring network. A BBN of leak detection is established by combing the TOUGH2 simulations and the background characterization of near-surface CO2 flux and PFC tracer at the sequestration site. The results show a positive correlation between the detection abilities of PFC tracer and soil CO2 flux, but the PFC tracer is more sensitive for detecting a leak in most cases. The BBN of leak detection including both soil CO2 flux and PFC tracer concentration gives an integrated probability estimation of leak detection for different permeability and leakage rates for a given monitoring network. A BBN developed using the proposed methodology can be used to help site engineers and decision makers to evaluate leakage signals and the risk of undetected leakage, given a suite of monitoring techniques and site conditions.

  10. Estimate of Global Sea-Air CO2 Flux with Sea-State-Dependent Parameterization

    Institute of Scientific and Technical Information of China (English)

    HU Wei; GUAN Changlong

    2008-01-01

    Although the annual global sea-air CO2 flux has been estimated extensively with various wind-dependent-k parameteri- zations, uncertainty still exists in the estimates. The sea-state-dependent-k parameterization is expected to improve the uncertainty existing in these estimates. In the present study, the annual global sea-air CO2 flux is estimated with the sea-state-dependent-k parameterization proposed by Woolf (2005), using NOAA/NCEP reanalysis wind speed and hindcast wave data from 1998 to 2006, and a new estimate, -2.18 Gt C year-1, is obtained, which is comparable with previous estimates with biochemical methods. It is in- teresting to note that the averaged value of previous estimates with various wind-dependent-k parameterizations is almost identical to that of previous estimates with biochemical methods by various authors, and that the new estimate is quite consistent with these av- eraged estimates.

  11. Temporal variability in the sources and fluxes of CO2 in a residential area in an evergreen subtropical city

    Science.gov (United States)

    Weissert, L. F.; Salmond, J. A.; Turnbull, J. C.; Schwendenmann, L.

    2016-10-01

    Measurements of CO2 fluxes in temperate climates have shown that urban areas are a net source of CO2 and that photosynthetic CO2 uptake is generally not sufficient to offset local CO2 emissions. However, little is known about the role of vegetation in cities where biogenic CO2 uptake is not limited to a 2-8 months growing season. This study used the eddy covariance technique to quantify the atmospheric CO2 fluxes over a period of 12 months in a residential area in subtropical Auckland, New Zealand, where the vegetation cover (surface cover fraction: 47%) is dominated by evergreen vegetation. Radiocarbon isotope measurements of CO2 were conducted at three different times of the day (06:00-09:00, 12:00-15:00, 01:00-04:00) for four consecutive weekdays in summer and winter to differentiate anthropogenic sources of CO2 (fossil fuel combustion) from biogenic sources (ecosystem respiration, combustion of biofuel/biomass). The results reveal previously unreported patterns for CO2 fluxes, with no seasonal variability and negative (net uptake) CO2 midday fluxes throughout the year, demonstrating photosynthetic uptake by the evergreen vegetation all year-round. The winter radiocarbon measurements showed that 85% of the CO2 during the morning rush hour was attributed to fossil fuel emissions, when wind was from residential areas. However, for all other time periods radiocarbon measurements showed that fossil fuel combustion was not a large source of CO2, suggesting that biogenic processes likely dominate CO2 fluxes at this residential site. Overall, our findings highlight the importance of vegetation in residential areas to mitigate local CO2 emissions, particularly in cities with a climate that allows evergreen vegetation to maintain high photosynthetic rates over winter. As urban areas grow, urban planners need to consider the role of urban greenspace to mitigate urban CO2 emissions.

  12. Standardized Automated CO2/H2O Flux Systems for Individual Research Groups and Flux Networks

    Science.gov (United States)

    Burba, George; Begashaw, Israel; Fratini, Gerardo; Griessbaum, Frank; Kathilankal, James; Xu, Liukang; Franz, Daniela; Joseph, Everette; Larmanou, Eric; Miller, Scott; Papale, Dario; Sabbatini, Simone; Sachs, Torsten; Sakai, Ricardo; McDermitt, Dayle

    2017-04-01

    In recent years, spatial and temporal flux data coverage improved significantly, and on multiple scales, from a single station to continental networks, due to standardization, automation, and management of data collection, and better handling of the extensive amounts of generated data. With more stations and networks, larger data flows from each station, and smaller operating budgets, modern tools are required to effectively and efficiently handle the entire process. Such tools are needed to maximize time dedicated to authoring publications and answering research questions, and to minimize time and expenses spent on data acquisition, processing, and quality control. Thus, these tools should produce standardized verifiable datasets and provide a way to cross-share the standardized data with external collaborators to leverage available funding, promote data analyses and publications. LI-COR gas analyzers are widely used in past and present flux networks such as AmeriFlux, ICOS, AsiaFlux, OzFlux, NEON, CarboEurope, and FluxNet-Canada, etc. These analyzers have gone through several major improvements over the past 30 years. However, in 2016, a three-prong development was completed to create an automated flux system which can accept multiple sonic anemometer and datalogger models, compute final and complete fluxes on-site, merge final fluxes with supporting weather soil and radiation data, monitor station outputs and send automated alerts to researchers, and allow secure sharing and cross-sharing of the station and data access. Two types of these research systems were developed: open-path (LI-7500RS) and enclosed-path (LI-7200RS). Key developments included: • Improvement of gas analyzer performance • Standardization and automation of final flux calculations onsite, and in real-time • Seamless integration with latest site management and data sharing tools In terms of the gas analyzer performance, the RS analyzers are based on established LI-7500/A and LI-7200

  13. Air-water gas exchange and CO2 flux in a mangrove-dominated estuary

    Science.gov (United States)

    Ho, David T.; Ferrón, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

    2014-01-01

    Mangrove forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600) = 8.3 ± 0.4 and 8.1 ± 0.6 cm h−1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11 ± 23.69 and 171.13 ± 20.28 mmol C m−2 d−1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

  14. Estimating Annual CO2 Flux for Lutjewad Station Using Three Different Gap-Filling Techniques

    Directory of Open Access Journals (Sweden)

    Carmelia M. Dragomir

    2012-01-01

    Full Text Available Long-term measurements of CO2 flux can be obtained using the eddy covariance technique, but these datasets are affected by gaps which hinder the estimation of robust long-term means and annual ecosystem exchanges. We compare results obtained using three gap-fill techniques: multiple regression (MR, multiple imputation (MI, and artificial neural networks (ANNs, applied to a one-year dataset of hourly CO2 flux measurements collected in Lutjewad, over a flat agriculture area near the Wadden Sea dike in the north of the Netherlands. The dataset was separated in two subsets: a learning and a validation set. The performances of gap-filling techniques were analysed by calculating statistical criteria: coefficient of determination (R2, root mean square error (RMSE, mean absolute error (MAE, maximum absolute error (MaxAE, and mean square bias (MSB. The gap-fill accuracy is seasonally dependent, with better results in cold seasons. The highest accuracy is obtained using ANN technique which is also less sensitive to environmental/seasonal conditions. We argue that filling gaps directly on measured CO2 fluxes is more advantageous than the common method of filling gaps on calculated net ecosystem change, because ANN is an empirical method and smaller scatter is expected when gap filling is applied directly to measurements.

  15. Effects of a holiday week on urban soil CO2 flux: an intensive study in Xiamen, southeastern China

    Science.gov (United States)

    Ye, H.; Wang, K.; Chen, F.

    2012-12-01

    To study the effects of a holiday period on urban soil CO2 flux, CO2 efflux from grassland soil in a traditional park in the city of Xiamen was measured hourly from 28th Sep to 11th Oct, a period that included China's National Day holiday week in 2009. The results of this study revealed that: a) The urban soil CO2 emissions were higher before and after the holiday week and lower during the National Day holiday reflecting changes in the traffic cycles; b) A diurnal cycle where the soil CO2 flux decreased from early morning to noon was associated with CO2 uptake by vegetation which strongly offset vehicle CO2 emissions. The soil CO2 flux increased from night to early morning, associated with reduced CO2 uptake by vegetation; c) During the National Day holiday week in 2009, lower rates of soil respiration were measured after Mid-Autumn Day than earlier in the week, and this was related to a reduced level of human activities and vehicle traffic, reducing the CO2 concentration in the air. Urban holidays have a clear effect on soil CO2 flux through the interactions between vehicle, visitor and vegetation CO2 emissions which indirectly control the use of carbon by plant roots, the rhizosphere and soil microorganisms. Consequently, appropriate traffic controls and tourism travel plans can have positive effects on the soil carbon store and may improve local air quality.

  16. Deriving a sea surface climatology of CO2 fugacity in support of air–sea gas flux studies

    Directory of Open Access Journals (Sweden)

    L. M. Goddijn-Murphy

    2014-07-01

    Full Text Available Climatologies, or long-term averages, of essential climate variables are useful for evaluating models and providing a baseline for studying anomalies. The Surface Ocean Carbon Dioxide (CO2 Atlas (SOCAT has made millions of global underway sea surface measurements of CO2 publicly available, all in a uniform format and presented as fugacity, fCO2. fCO2 is highly sensitive to temperature and the measurements are only valid for the instantaneous sea surface temperature (SST that is measured concurrent with the in-water CO2 measurement. To create a climatology of fCO2 data suitable for calculating air–sea CO2 fluxes it is therefore desirable to calculate fCO2 valid for climate quality SST. This paper presents a method for creating such a climatology. We recomputed SOCAT's fCO2 values for their respective measurement month and year using climate quality SST data from satellite Earth observation and then extrapolated the resulting fCO2 values to reference year 2010. The data were then spatially interpolated onto a 1° × 1° grid of the global oceans to produce 12 monthly fCO2 distributions for 2010. The partial pressure of CO2 (pCO2 is also provided for those who prefer to use pCO2. The CO2 concentration difference between ocean and atmosphere is the thermodynamic driving force of the air–sea CO2 flux, and hence the presented fCO2 distributions can be used in air–sea gas flux calculations together with climatologies of other climate variables.

  17. Autotrophic and heterotrophic soil respiration determined with trenching, soil CO2 fluxes and 13CO2/12CO2 concentration gradients in a boreal forest ecosystem

    Science.gov (United States)

    Pumpanen, Jukka; Shurpali, Narasinha; Kulmala, Liisa; Kolari, Pasi; Heinonsalo, Jussi

    2017-04-01

    Soil CO2 efflux forms a substantial part of the ecosystem carbon balance, and it can contribute more than half of the annual ecosystem respiration. Recently assimilated carbon which has been fixed in photosynthesis during the previous days plays an important role in soil CO2 efflux, and its contribution is seasonally variable. Moreover, the recently assimilated C has been shown to stimulate the decomposition of recalcitrant C in soil and increase the mineralization of nitrogen, the most important macronutrient limiting gross primary productivity (GPP) in boreal ecosystems. Podzolic soils, typical in boreal zone, have distinctive layers with different biological and chemical properties. The biological activity in different soil layers has large seasonal variation due to vertical gradient in temperature, soil organic matter and root biomass. Thus, the source of CO2 and its components have a vertical gradient which is seasonally variable. The contribution of recently assimilated C and its seasonal as well as spatial variation in soil are difficult to assess without disturbing the system. The most common method of partitioning soil respiration into its components is trenching which entails the roots being cut or girdling where the flow of carbohydrates from the canopy to roots has been isolated by cutting of the phloem. Other methods for determining the contribution of autotrophic (Ra) and heterotrophic (Rh) respiration components in soil CO2 efflux are pulse labelling with 13CO2 or 14CO2 or the natural abundance of 13C and/or 14C isotopes. Also differences in seasonal and short-term temperature response of soil respiration have been used to separate Ra and Rh. We compared the seasonal variation in Ra and Rh using the trenching method and differences between seasonal and short-term temperature responses of soil respiration. I addition, we estimated the vertical variation in soil biological activity using soil CO2 concentration and the natural abundance of 13C and 12C

  18. CO2 and energy fluxes from an oil palm plantation in Sumatra, Indonesia

    Science.gov (United States)

    Meijide, Ana; Herbst, Mathias; Knohl, Alexander

    2014-05-01

    Oil palm plantations are expanding in Indonesia due to global increased demand of palm oil. Such plantations are usually set in previously forested land and in Sumatra, massive transformation of lowland forest into oil palm plantations is taking place. These land transformations have been identified as a potential driver of climate change, as they might result in changes of greenhouse gas (GHG) fluxes. However, very limited information is available on GHG fluxes from oil palm plantations and their sink or source strength at ecosystem scale is yet unknown. An eddy covariance tower was therefore installed in a 2 year old oil palm plantation in the province of Jambi, Sumatra (1° 50' 7'S, 103° 17' 44'E), with the aim of studying carbon dioxide, water and energy fluxes during the non-productive phase of oil palm cultivation. The canopy was not yet closed and trees were around 2m high. The eddy covariance system consists of a Licor 7500A and an ultrasonic Metek Anemometer, operating at 10 Hz and installed on a 7m tower. In addition to the eddy covariance measurements, the site is equipped with a weather station, measuring short and long wave radiation, PAR, rainfall, profiles of air temperature, air humidity and wind speed, soil temperature and moisture and soil heat fluxes. Measurements started in July 2013 until January 2014, in order to capture possible differences which may happen during the dry (July-October) and wet (November-February) seasons. A large CO2 uptake would have been expected at this young oil palm plantation, as palm trees during this period of their cultivation are growing fast. However, our preliminary results show that during the first 5 months of measurements, the ecosystem was a small carbon source (below 10 g CO2 m-2). Latent heat flux was higher than sensible heat flux during the period of study, indicative of the high evaporation taking place. Our results show that both for CO2 and energy fluxes, large differences were observed between the

  19. Non-linear response of soil carbon gas (CO2, CH4) flux to oxygen availability

    Science.gov (United States)

    Mcnicol, G.; Silver, W. L.

    2013-12-01

    Soil oxygen (O2) concentration can impact soil carbon (C) fluxes of carbon dioxide (CO2) and methane (CH4), and is an important chemical gradient across the terrestrial-aquatic interface that drives large differences in ecosystem C storage. Few studies have established quantitative relationships between gas-phase O2 concentration and soil C fluxes in controlled settings. Though standard Michaelis-Menten enzyme kinetics would predict a highly non-linear relationship between O2 concentration and microbial consumption, existing studies have imposed coarse changes in O2 concentration that necessarily prevent detection of non-linearity. We report on the results of laboratory incubations designed to explore the short-term sensitivity of soil C emissions to a wide range of gas-phase O2 concentrations. Organic-rich soil was collected from a drained peatland and subjected to seven O2 concentration treatments ranging from 0.03 % - 20 % O2. We compared the fit of the observed C flux response to O2 concentration to linear, log-linear, and Michaelis-Menten functions using MSE and residual fits as performance metrics. We found that both CO2 and CH4 emissions were highly sensitive to O2 concentration, with emission rates increasing and decreasing, respectively, at higher O2. Net CH4 emission rates were attenuated at higher O2 concentrations most likely due to stimulation of gross CH4 consumption. A log-linear or Michaelis-Menten model better fit data than a linear model by both performance metrics, demonstrating, empirically, a non-linear relationship between O2 concentration and soil CO2 and CH4 fluxes. Our results suggest high O2 sensitivity of C-rich soils at the terrestrial-aquatic interface and show that the microbial response to soil redox chemistry must be measured over a biophysically meaningful range of conditions to derive relationships that accurately predict soil C fluxes.

  20. A downward CO2 flux seems to have nowhere to go

    Directory of Open Access Journals (Sweden)

    J. Ma

    2014-07-01

    Full Text Available Recent studies have suggested that deserts, which are a long-neglected region in global carbon budgeting, have strong downward CO2 fluxes and might be a significant carbon sink. This finding, however, has been strongly challenged because neither the reliability of the flux measurements nor the exact location of the fixed carbon has been determined. This paper shows, with a full chain of evidence, that there is indeed strong carbon flux into saline/alkaline land in arid regions. Based on continuous measurement of CO2 exchange from 2002 to 2012 (except for 2003, the saline desert in western China was a carbon sink for 9 out of the 10 years, and average yearly net ecosystem exchange of carbon (NEE for the 10 years was −25.00 ± 12.70 g C m−2yr−1. Supporting evidence for the validity of these NEE estimates comes from the close agreement of NEE values obtained from the chamber and eddy-covariance methods. After ruling out the possibility of changes in C stored in plant biomass or soils, the C uptake was found to be leached downwards into the groundwater body in the process of groundwater fluctuation: rising groundwater absorbs soil dissolved inorganic carbon (DIC, and falling groundwater transports the DIC downward. Horizontal groundwater flow may send this DIC farther away and prevent it from being observed locally. This process has been called "passive leaching" of DIC, in comparison with the active DIC leaching that occurs during groundwater recharge. This passive leaching significantly expands the area where DIC leaching occurs and creates a literally "hidden" carbon sink process under the desert. This study tells us that when a downward CO2 flux is observed, but seems to have nowhere to go, it should not be concluded that the flux measurement is unreliable. By looking deeper and farther away, a place and a process may be found that are "hidden" underground.

  1. Comparative soil CO2 flux measurements and geostatisticalestimation methods on masaya volcano, nicaragua

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J.L.; Bergfeld, D.; Cardellini, C.; Chiodini, G.; Granieri, D.; Varley, N.; Werner, C.

    2004-04-27

    We present a comparative study of soil CO{sub 2} flux (F{sub CO2}) measured by five groups (Groups 1-5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1-5 measured F{sub CO2} using the accumulation chamber method at 5-m spacing within a 900 m{sup 2} grid during a morning (AM) period. These measurements were repeated by Groups 1-3 during an afternoon (PM) period. All measured F{sub CO2} ranged from 218 to 14,719 g m{sup -2}d{sup -1}. Arithmetic means and associated CO{sub 2} emission rate estimates for the AM data sets varied between groups by {+-}22%. The variability of the five measurements made at each grid point ranged from {+-}5 to 167% and increased with the arithmetic mean. Based on a comparison of measurements made by Groups 1-3 during AM and PM times, this variability is likely due in large part to natural temporal variability of gas flow, rather than to measurement error. We compared six geostatistical methods (arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods) to estimate the mean and associated CO{sub 2} emission rate of one data set and to map the spatial F{sub CO2} distribution. While the CO{sub 2} emission rates estimated using the different techniques only varied by {+-}1.1%, the F{sub CO2} maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of F{sub CO2} and is most appropriate for volcano monitoring applications.

  2. Temporal and spatial patterns of internal and external stem CO2 fluxes in a sub-Mediterranean oak.

    Science.gov (United States)

    Salomón, Roberto L; Valbuena-Carabaña, María; Gil, Luis; McGuire, Mary Anne; Teskey, Robert O; Aubrey, Doug P; González-Doncel, Inés; Rodríguez-Calcerrada, Jesús

    2016-11-01

    To accurately estimate stem respiration (RS), measurements of both carbon dioxide (CO2) efflux to the atmosphere (EA) and internal CO2 flux through xylem (FT) are needed because xylem sap transports respired CO2 upward. However, reports of seasonal dynamics of FT and EA are scarce and no studies exist in Mediterranean species under drought stress conditions. Internal and external CO2 fluxes at three stem heights, together with radial stem growth, temperature, sap flow and shoot water potential, were measured in Quercus pyrenaica Willd. in four measurement campaigns during one growing season. Substantial daytime depressions in temperature-normalized EA were observed throughout the experiment, including prior to budburst, indicating that diel hysteresis between stem temperature and EA cannot be uniquely ascribed to diversion of CO2 in the transpiration stream. Low internal [CO2] (90%). Internal [CO2] was found to vary vertically along the stems. Seasonality in resistance to radial CO2 diffusion was related to shoot water potential. The low internal [CO2] and FT observed in our study may result from the downregulation of xylem respiration in response to a legacy of coppicing as well as high radial diffusion of CO2 through cambium, phloem and bark tissues, which was related to low water content of stems. Long-term studies analyzing temporal and spatial variation in internal and external CO2 fluxes and their interactions are needed to mechanistically understand and model respiration of woody tissues.

  3. Multiple quality tests for analysing CO2 fluxes in a beech temperate forest

    Directory of Open Access Journals (Sweden)

    A. Granier

    2007-11-01

    Full Text Available The eddy covariance (EC measurements are widely used to estimate the amount of carbon sequestrated by terrestrial biomes. The data quality and the selection of the correct EC records become an important step in the CO2 flux determination procedure. In this paper an innovative combination of existing assessment tests is used to give a relatively complete evaluation of the net ecosystem exchange measurements. For the 2005 full-leaf season at the Hesse site, the percentage of bad quality data is relatively high (59.6% especially during night-time (68.9%. This result strengthens the importance of the data gap filling method. The filtering used does not lead to a real improvement of the accuracy of the relationship between the CO2 fluxes and the climatic factors. The soil respiration spatial heterogeneity (on a site with relatively homogenous vegetation pattern seems to be too important to allow this improvement. However, the data rejected present some common characteristics. Their removal lead to a 10% increase in the total amount of CO2 respired and photosynthesised during the 2005 full-leaf season. Consequently the application of our combination of multiple quality tests is able improve the inter-annual analysis. The question of a systematic application on the large database like the CarboEurope and FLUXNET is legitimate.

  4. Detectability of CO2 Flux Signals by a Space-Based Lidar Mission

    Science.gov (United States)

    Hammerling, Dorit M.; Kawa, S. Randolph; Schaefer, Kevin; Doney, Scott; Michalak, Anna M.

    2015-01-01

    Satellite observations of carbon dioxide (CO2) offer novel and distinctive opportunities for improving our quantitative understanding of the carbon cycle. Prospective observations include those from space-based lidar such as the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. Here we explore the ability of such a mission to detect regional changes in CO2 fluxes. We investigate these using three prototypical case studies, namely the thawing of permafrost in the Northern High Latitudes, the shifting of fossil fuel emissions from Europe to China, and changes in the source-sink characteristics of the Southern Ocean. These three scenarios were used to design signal detection studies to investigate the ability to detect the unfolding of these scenarios compared to a baseline scenario. Results indicate that the ASCENDS mission could detect the types of signals investigated in this study, with the caveat that the study is based on some simplifying assumptions. The permafrost thawing flux perturbation is readily detectable at a high level of significance. The fossil fuel emission detectability is directly related to the strength of the signal and the level of measurement noise. For a nominal (lower) fossil fuel emission signal, only the idealized noise-free instrument test case produces a clearly detectable signal, while experiments with more realistic noise levels capture the signal only in the higher (exaggerated) signal case. For the Southern Ocean scenario, differences due to the natural variability in the ENSO climatic mode are primarily detectable as a zonal increase.

  5. An empirical model simulating long-term diurnal CO2 flux for diverse vegetation types

    Directory of Open Access Journals (Sweden)

    A. D. Richardson

    2008-10-01

    Full Text Available We present an empirical model for the estimation of diurnal variability in net ecosystem CO2 exchange (NEE. The model is based on the use of a nonrectangular hyperbola for photosynthetic response of canopy and was constructed by using a dataset obtained from the AmeriFlux network and containing continuous eddy covariance CO2 flux from 26 ecosystems over seven biomes. The model uses simplified empirical expression of seasonal variability in biome-specific physiological parameters with air temperature, vapor pressure deficit, and precipitation. The physiological parameters of maximum CO2 uptake rate by the canopy and ecosystem respiration had biome-specific responses to environmental variables. The estimated physiological parameters had reasonable magnitudes and seasonal variation and gave reasonable timing of the beginning and end of the growing season over various biomes, but they were less satisfactory for disturbed grassland and savanna than for forests. Comparison with observational data revealed that the diurnal cycle of NEE was generally well predicted all year round by the model. The model gave satisfactory results even for tundra, which had very small amplitudes of NEE variability. These results suggest that this model with biome-specific parameters will be applicable to numerous terrestrial biomes, particularly forest ones.

  6. Modeling the contribution of abiotic exchange to CO2 flux in alkaline soils of arid areas

    Institute of Scientific and Technical Information of China (English)

    WenFeng WANG; Xi CHEN; GePing LUO; LongHui LI

    2014-01-01

    Recent studies on alkaline soils of arid areas suggest a possible contribution of abiotic exchange to soil CO2 flux (Fc). However, both the overall contribution of abiotic CO2 exchange and its drivers remain unknown. Here we analyzed the environmental variables suggested as possible drivers by previous studies and constructed a function of these variables to model the contribution of abiotic exchange to Fc in alkaline soils of arid areas. An automated flux system was employed to measure Fc in the Manas River Basin of Xinjiang Uygur autonomous region, China. Soil pH, soil temperature at 0-5 cm (Ts), soil volumetric water content at 0-5 cm (θs) and air temperature at 10 cm above the soil surface (Tas) were simultaneously analyzed. Results highlight reduced sensitivity of Fc to Ts and good prediction of Fc by the model Fc=R10Q10(Tas-10)/10+r7q7(pH-7)+λTas+µθs+e which represents Fc as a sum of biotic and abiotic components. This presents an approximate method to quantify the contribution of soil abiotic CO2 exchange to Fc in alkaline soils of arid areas.

  7. The potential for regional-scale bias in top-down CO2 flux estimates due to atmospheric transport errors

    Science.gov (United States)

    Miller, S. M.; Fung, I.; Liu, J.; Hayek, M. N.; Andrews, A. E.

    2014-09-01

    Estimates of CO2 fluxes that are based on atmospheric data rely upon a meteorological model to simulate atmospheric CO2 transport. These models provide a quantitative link between surface fluxes of CO2 and atmospheric measurements taken downwind. Therefore, any errors in the meteorological model can propagate into atmospheric CO2 transport and ultimately bias the estimated CO2 fluxes. These errors, however, have traditionally been difficult to characterize. To examine the effects of CO2 transport errors on estimated CO2 fluxes, we use a global meteorological model-data assimilation system known as "CAM-LETKF" to quantify two aspects of the transport errors: error variances (standard deviations) and temporal error correlations. Furthermore, we develop two case studies. In the first case study, we examine the extent to which CO2 transport uncertainties can bias CO2 flux estimates. In particular, we use a common flux estimate known as CarbonTracker to discover the minimum hypothetical bias that can be detected above the CO2 transport uncertainties. In the second case study, we then investigate which meteorological conditions may contribute to month-long biases in modeled atmospheric transport. We estimate 6 hourly CO2 transport uncertainties in the model surface layer that range from 0.15 to 9.6 ppm (standard deviation), depending on location, and we estimate an average error decorrelation time of ∼2.3 days at existing CO2 observation sites. As a consequence of these uncertainties, we find that CarbonTracker CO2 fluxes would need to be biased by at least 29%, on average, before that bias were detectable at existing non-marine atmospheric CO2 observation sites. Furthermore, we find that persistent, bias-type errors in atmospheric transport are associated with consistent low net radiation, low energy boundary layer conditions. The meteorological model is not necessarily more uncertain in these conditions. Rather, the extent to which meteorological uncertainties

  8. The potential for regional-scale bias in top-down CO2 flux estimates due to atmospheric transport errors

    Directory of Open Access Journals (Sweden)

    S. M. Miller

    2014-09-01

    Full Text Available Estimates of CO2 fluxes that are based on atmospheric data rely upon a meteorological model to simulate atmospheric CO2 transport. These models provide a quantitative link between surface fluxes of CO2 and atmospheric measurements taken downwind. Therefore, any errors in the meteorological model can propagate into atmospheric CO2 transport and ultimately bias the estimated CO2 fluxes. These errors, however, have traditionally been difficult to characterize. To examine the effects of CO2 transport errors on estimated CO2 fluxes, we use a global meteorological model-data assimilation system known as "CAM–LETKF" to quantify two aspects of the transport errors: error variances (standard deviations and temporal error correlations. Furthermore, we develop two case studies. In the first case study, we examine the extent to which CO2 transport uncertainties can bias CO2 flux estimates. In particular, we use a common flux estimate known as CarbonTracker to discover the minimum hypothetical bias that can be detected above the CO2 transport uncertainties. In the second case study, we then investigate which meteorological conditions may contribute to month-long biases in modeled atmospheric transport. We estimate 6 hourly CO2 transport uncertainties in the model surface layer that range from 0.15 to 9.6 ppm (standard deviation, depending on location, and we estimate an average error decorrelation time of ∼2.3 days at existing CO2 observation sites. As a consequence of these uncertainties, we find that CarbonTracker CO2 fluxes would need to be biased by at least 29%, on average, before that bias were detectable at existing non-marine atmospheric CO2 observation sites. Furthermore, we find that persistent, bias-type errors in atmospheric transport are associated with consistent low net radiation, low energy boundary layer conditions. The meteorological model is not necessarily more uncertain in these conditions. Rather, the extent to which meteorological

  9. Continuous measurement of CO2 flux through the snowpack in a dwarf bamboo ecosystem on Rishiri Island, Hokkaido, Japan

    Science.gov (United States)

    Zhu, Chunmao; Nakayama, Momoko; Yoshikawa Inoue, Hisayuki

    2014-09-01

    To investigate the dynamics and environmental drivers of CO2 flux through the winter snowpack in a dwarf bamboo ecosystem (Hokkaido, northeast Japan), we constructed an automated sampling system to measured CO2 concentrations at five different levels in the snowpack, from the base to the upper snow surface. Using a gas diffusion approach, we estimated an average apparent soil CO2 flux of 0.26 μmol m-2 s-1 during the snow season (December-April); temporally, the CO2 flux increased until mid-snow season, but showed no clear trend thereafter; late-season snow-melting events resulted in rapid decreases in apparent CO2 flux values. Air temperature and subnivean CO2 flux exhibited a positive linear relationship. After eliminating the effects of wind pumping, we estimated the actual soil CO2 flux (0.41 μmol m-2 s-1) to be 54% larger than the apparent flux. This study provides new constraints on snow-season carbon emissions in a dwarf bamboo ecosystem in northeast Asia.

  10. Seasonal characteristics of CO2 fluxes in a rain-fed wheat field ecosystem at the Loess Plateau

    Directory of Open Access Journals (Sweden)

    Q. Guo

    2013-11-01

    Full Text Available This study investigated the dynamics of CO2 flux in a rain-fed wheat field ecosystem using an eddy covariance technique during the 2011 to 2012 wheat-growing season at the Loess Plateau, China. Results showed that the daily CO2 flux was closely related to photosynthetically active radiation (PAR, growth stage, soil temperature and rainfall. The average CO2 flux at different growth stages followed the order jointing and booting > erecting > reviving > heading > wintering > seeding and tillering > grain filling > ripening. The first four stages were carbon sinks, whereas the last four stages were carbon sources. The relationship between nighttime CO2 flux and air temperature was significant and fitted the index model (y=aebt. The relationship between daytime CO2 flux and PAR was also significant and fitted the quadratic model (y=ax2+bx+c. Moreover, daytime CO2 flux was significantly correlated with air temperature and PAR at the erecting, jointing and booting, and heading stages. Nighttime CO2 flux was also significantly correlated with soil temperature at 5 cm depth at the heading as well as jointing and booting stages. The carbon budget in the rain-fed wheat ecosystem was -401 g C m-2 yr-1, which was higher than those in other wheat ecosystems. This study implies that the ability of carbon-sequestration in different wheat field ecosystems may respond differently to climate and environment change.

  11. Regional modelling of water and CO2-fluxes with a one-dimensional SVAT model

    Science.gov (United States)

    Kuhnert, M.; Köstner, B.

    2009-04-01

    Climate change affects site conditions for vegetation and may affect changes in the distribution of plant species. Investigations of these effects are difficult, because other influences on plant performance like land use and management also need to be considered. Carbon gain can be used as a sensitive indicator for changes in the vitality of the considered vegetation types that are affected by different climate and weather patterns. The objective of the presented study is the quantification of net photosynthesis rate, respiration and transpiration of different vegetation types on the regional scale. The study regions are the Weißeritz catchment in the Ore Mountains and the region Torgau-Oschatz in the Elbe basin both located in Saxony (East Germany) but significantly differing in elevation and site conditions. The carbon and water fluxes are simulated by an ecophysiological based Soil-Vegetation-Atmosphere-Transfer model for three periods (1996-2006, 2015-2025 and 2035-2045). The considered vegetation types are forest and grassland. The used model SVAT-CN is a multi-layer model, which enables the calculation of hourly carbon gain by coupling micrometerological data with ecophysiological processes. The calculations are based on the equations of Farquhar and Ball for net photosynthesis rate and stomata conductivity, respectively. It is a one-dimensional model which also considers soil water processes. The soil is coupled with the vegetation by one factor that depends on the matric potential and steers the calculation of the stomata conductivity. The equations of the soil water processes are based on a combination of bucket model and Richard's equation. Simulations are based on measured weather data (Dept. of Meteorology at Technische Universität Dresden and LfL Sachsen) with varying levels of atmospheric CO2 concentrations up to 580 ppm. Further, climate projections (ECHAM5-OM, IPCC emission scenario A1B), with downscaling to a 18x18km grid by the regional climate

  12. Acidification and Increasing CO2 Flux Associated with Five, Springs Coast, Florida Springs (1991-2014)

    Science.gov (United States)

    Barrera, Kira E.; Robbins, Lisa L.

    2017-01-01

    Scientists from the South West Florida Management District (SWFWMD) acquired and analyzed over 20 years of seasonally-sampled hydrochemical data from five first-order-magnitude (springs that discharge 2.83 m3 s-1 or more) coastal springs located in west-central Florida. These data were subsequently obtained by the U.S. Geological Survey (USGS) for further analyses and interpretation. The spring study sites (Chassahowitzka, Homosassa, Kings Bay, Rainbow, and Weeki Wachee), which are fed by the Floridan Aquifer system and discharge into the Gulf of Mexico were investigated to identify temporal and spatial trends of pH, alkalinity, partial pressure of carbon dioxide (pCO2) and CO2 flux.

  13. Soil organic carbon storage and soil CO2 flux in the alpine meadow ecosystem

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    High-resolution sampling,measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau,and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic car-bon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12×104 kg C hm-2 to 30.75×104 kg C hm-2 in the alpine meadow eco-systems,with an average of 26.86×104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1,with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%―81.23% of total CO2 emitted from or-ganic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming,the storage,volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed,which needs further research.

  14. Soil organic carbon storage and soil CO2 flux in the alpine meadow ecosystem

    Institute of Scientific and Technical Information of China (English)

    TAO Zhen; SHEN ChengDe; GAO QuanZhou; SUN YanMin; YI WeiXi; LI YingNian

    2007-01-01

    High-resolution sampling, measurements of organic carbon contents and 14C signatures of selected four soil profiles in the Haibei Station situated on the northeast Tibetan Plateau, and application of 14C tracing technology were conducted in an attempt to investigate the turnover times of soil organic carbon and the soil-CO2 flux in the alpine meadow ecosystem. The results show that the organic carbon stored in the soils varies from 22.12(104 kg C hm-2 to 30.75(104 kg C hm-2 in the alpine meadow ecosystems, with an average of 26.86(104 kg C hm-2. Turnover times of organic carbon pools increase with depth from 45 a to 73 a in the surface soil horizon to hundreds of years or millennia or even longer at the deep soil horizons in the alpine meadow ecosystems. The soil-CO2 flux ranges from 103.24 g C m-2 a-1 to 254.93 gC m-2 a-1, with an average of 191.23 g C m-2 a-1. The CO2 efflux produced from microbial decomposition of organic matter varies from 73.3 g C m-2 a-1 to 181 g C m-2 a-1. More than 30% of total soil organic carbon resides in the active carbon pool and 72.8%-81.23% of total CO2 emitted from organic matter decomposition results from the topsoil horizon (from 0 cm to 10 cm) for the Kobresia meadow. Responding to global warming, the storage, volume of flow and fate of the soil organic carbon in the alpine meadow ecosystem of the Tibetan Plateau will be changed, which needs further research.

  15. Estimates of evapotranspiration and CO2 fluxes in a biofiltration system

    Science.gov (United States)

    Daly, E.; Niculescu, A.; Beringer, J.; Deletic, A.

    2009-12-01

    Biofiltration systems (or biofilters, bioretention systems or rain gardens) have been adopted to improve the quality of urban aquatic ecosystems and to reduce volumes and peaks of stormwater runoff. Given their good performances, it is likely that the implementation of such systems in urban areas will greatly increase in the future. As an example, the city of Melbourne (Australia) is planning to install 10,000 biofiltration systems within its area by 2013. Because biofiltration systems are commonly installed in urban areas, along roads and highways, their vegetation is often under atmospheric CO2 concentrations higher than average ambient conditions (i.e., above 380 ppm). Additionally, since these systems are designed to receive runoff from large catchment areas (typically around 50-100 times the area of the biofilter), their vegetation rarely experiences water and nitrogen limitations. These surrounding environmental conditions suggest that biofilters might experience high evapotranspiration (ET) rates and CO2 assimilation via photosynthesis, which could potentially provide benefits to the local microclimate in terms of temperature reduction (cooling due to enhanced ET) and CO2 uptake from the atmosphere, in addition to the benefit related to stormwater treatment. These hypotheses have been strengthen by preliminary tests based on laboratory experiments with soil columns vegetated with C.appressa, in which ET has been estimated to be as high as 0.7-0.8 cm per day. To further study these processes, several measurements are being performed in a biofiltration system installed at Monash University, Clayton Campus (Melbourne, VIC). This biofilter receives runoff diverted from a 100% impervious car park and discharges the treated stormwater to an adjacent pond. A chamber that encloses part of the vegetation in the biofilter has been constructed to monitor water and greenhouse gas fluxes. Preliminary results on daily patterns of water and CO2 fluxes within the system in

  16. Comparative CO2 flux measurements by eddy covariance technique using open- and closed-path gas analysers over the equatorial Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Fumiyoshi Kondo

    2012-04-01

    Full Text Available Direct comparison of air–sea CO2 fluxes by open-path eddy covariance (OPEC and closed-path eddy covariance (CPEC techniques was carried out over the equatorial Pacific Ocean. Previous studies over oceans have shown that the CO2 flux by OPEC was larger than the bulk CO2 flux using the gas transfer velocity estimated by the mass balance technique, while the CO2 flux by CPEC agreed with the bulk CO2 flux. We investigated a traditional conflict between the CO2 flux by the eddy covariance technique and the bulk CO2 flux, and whether the CO2 fluctuation attenuated using the closed-path analyser can be measured with sufficient time responses to resolve small CO2 flux over oceans. Our results showed that the closed-path analyser using a short sampling tube and a high volume air pump can be used to measure the small CO2 fluctuation over the ocean. Further, the underestimated CO2 flux by CPEC due to the attenuated fluctuation can be corrected by the bandpass covariance method; its contribution was almost identical to that of H2O flux. The CO2 flux by CPEC agreed with the total CO2 flux by OPEC with density correction; however, both of them are one order of magnitude larger than the bulk CO2 flux.

  17. Water-air CO2 fluxes in the Tagus estuary plume (Portugal) during two distinct winter episodes.

    Science.gov (United States)

    Oliveira, Ana P; Mateus, Marcos D; Cabeçadas, Graça; Neves, Ramiro

    2015-12-01

    Estuarine plumes are frequently under strong influence of land-derived inputs of organic matter. These plumes have characteristic physical and chemical conditions, and their morphology and extent in the coastal area depends strongly on physical conditions such as river discharge, tides and wind action. In this work we investigate the physical dynamics of the Tagus estuary plume and the CO2 system response during two contrasting hydrological winter periods. A hydrodynamic model was used to simulate the circulation regime of the study area, thus providing relevant information on hydrodynamic processes controlling the plume. Model simulations show that for the studied periods, the major cause of the plume variability (size and shape) was the interaction between Tagus River discharge and wind. The freshwater intrusion on Tagus shelf exerted considerable influence on biochemical dynamics, allowing identification of two regions: a high nutrient region enriched in CO2 inside the estuarine plume and another warmer region rich in phytoplankton in the outer plume. The Tagus estuarine plume behaved as a weak source of CO2 to the atmosphere, with estimated fluxes of 3.5 ± 3.7 and 27.0 ± 3.8 mmol C m(-2) d(-1) for February 2004 and March 2001, respectively.

  18. Effect of Wildfire on Sequoiadendron giganteum Growth and CO2 Flux

    Science.gov (United States)

    Barwegen, S.

    2016-12-01

    Due to global warming, parts of the United States are becoming drier than ever before. In 2015, we surpassed 9 million acres burned by wildfires nationally (Rice 2015). Wildfires are most common in the Western United States due to drought, and the fact that the summer months are drier than other areas such as the East Coast, so there is a higher risk for wildland fires (Donegan 2016). These high-growth forests that are more frequently burned by wildfires each year are located near mountain ranges on the west side of the United States. They are important to tourism, contain many endangered species, and need to maintain the natural cycle of fire and regrowth for the continued success of the native plant life. This project investigated the effect of burnt soil on Sequoiadendron giganteum trees. Three were grown in burnt potting soil that had been roasted over a grill for 45 minutes (which is the average destructive fire time), and the other three were the control group in unburned potting soil. We assessed growth by measuring height, color, photosynthetically active radiation (PAR), and CO2 flux to evaluate the health of the trees in the two soil conditions. We noted that after two weeks the trunks of the trees growing in burnt soil began to brown in color, and they lost leaves. Over the course of the experiment, the trees growing in burnt soil had reduced levels of photosynthesis as compared to the unburned soil (as measured by the net change in CO2 concentration in a sealed chamber over the course of fifteen minutes intervals). On average, the trees growing in burnt soil had flux rates that were 19.59 ppm CO2 /min. more than those growing in unburned soil. In the dark reactions, the burnt soil flux was 54.5 ppm CO2/min., while the unburned soil averaged 40.5 ppm CO2/min. Our results help quantify the impact of fire on delicate ecosystems that are experiencing an increase in fire activity caused by global warming.

  19. Fluxes of H2, COS, and CO2 across a temperate forest snowpack driven by below snow soil microbial processes

    Science.gov (United States)

    Meredith, L. K.; McLaren, J.; Commane, R.; Munger, J. W.; Prinn, R. G.; Wofsy, S. C.; Richardson, A. D.

    2011-12-01

    Snowpack overlying temperate soils insulates soil microbial communities from wintertime subzero air temperatures that would otherwise halt most biogeochemical processes. Moreover, a porous snow matrix permits soil-atmosphere trace gas exchange to continue despite the snowpack cover. Consequently, below snow (subniveal) soil biogeochemical processes proceed throughout the winter season and continue to impact atmospheric trace gas composition. In this study, three atmospheric trace gases (H2, COS, CO2) that exhibit strong soil-atmosphere exchange are investigated to understand the following: 1) how snowpack properties affect the exchange of trace gases and 2) how different biogeochemical cycles behave throughout the low temperature subniveal winter. The selected trace gases represent largely decoupled and distinct biogeochemical cycles. Soil microorganisms act as a net sink for atmospheric hydrogen (H2) and carbonyl sulfide (COS) by oxidation (hydrogenase) and hydrolysis (carbonic anhydrase) reactions, respectively. In contrast, soil microbial respiration is a strong source of atmospheric carbon dioxide (CO2). We present continuous, high frequency atmospheric flux measurements of H2, COS, and CO2 over the winter season in a temperate deciduous forest. Significant soil-atmosphere trace gas exchange was measured above the four-month snowpack, which reached 70 cm at peak accumulation. Additionally, we use a novel camera-based method to monitor snow depth, density, and fractional extent to understand how physical snowpack properties affect the exchange of these trace gases. The episodic nature of snow fall, snow melt, and snowpack ventilation events are also considered. By comparative analysis of the H2, COS, and CO2 fluxes, we investigate differences in subniveal biogeochemical processes at different soil temperature and moisture levels throughout the winter season. Projections for global change anticipate changes in the temperate snowpack; therefore, understanding the

  20. Multiple quality tests for analysing CO2 fluxes in a beech temperate forest

    Directory of Open Access Journals (Sweden)

    A. Granier

    2008-05-01

    Full Text Available Eddy covariance (EC measurements are widely used to estimate the amount of carbon sequestrated by terrestrial biomes. The decision to exclude an EC flux from a database (bad quality records, turbulence regime not adequate, footprint problem,... becomes an important step in the CO2 flux determination procedure. In this paper an innovative combination of existing assessment tests is used to give a relatively complete evaluation of the net ecosystem exchange measurements. For the 2005 full-leaf season at the Hesse site, the percentage of rejected half-hours is relatively high (59.7% especially during night-time (68.9%. This result strengthens the importance of the data gap filling method. The data rejection does not lead to a real improvement of the accuracy of the relationship between the CO2 fluxes and the climatic factors especially during the nights. The spatial heterogeneity of the soil respiration (on a site with relatively homogenous vegetation pattern seems large enough to mask an increase of the goodness of the fit of the ecosystem respiration measurements with a dependence on soil temperature and water content when the tests are used to reject EC data. However, the data rejected present some common characteristics. Their removal lead to an increase in the total amount of CO2 respired (24% and photosynthesised (16% during the 2005 full-leaf season. Consequently the application of our combination of multiple quality tests is able improve the inter-annual analysis. The systematic application on the large database like the CarboEurope and FLUXNET appears to be necessary.

  1. Rapid detection and characterization of surface CO2 leakage through the real-time measurement of δ13C signatures in CO2 flux from the ground

    Science.gov (United States)

    Krevor, Samuel; Benson, Sally; Rella, Chris; Perrin, Jean-Christophe; Esposito, Ariel; Crosson, Eric

    2010-05-01

    The surface monitoring of CO2 over geologic sequestration sites will be an essential tool in the monitoring and verification of sequestration projects. Surface monitoring is the only tool that currently provides the opportunity to detect and quantify leakages on the order of 1000 tons/year CO2. Near-surface detection and quantification can be made complicated, however, due to large temporal and spatial variations in natural background CO2 fluxes from biological processes. In addition, current surface monitoring technologies, such as the use of IR spectroscopy in eddy covariance towers and aerial surveys, radioactive or noble gas isotopic tracers, and flux chamber gas measurements can generally accomplish one or two of the necessary tasks of leak detection, identification, and quantification, at both large spatial scales and high spatial resolution. It would be useful, however, to combine the utility of these technologies so that a much simplified surface monitoring program can be deployed. Carbon isotopes of CO2 provide an opportunity to distinguish between natural biogenic CO2 fluxes from the ground and CO2 leaking from a sequestration reservoir that has ultimate origins in a process giving it a distinct isotopic signature such as natural gas processing. Until recently, measuring isotopic compositions of gases was a time-consuming and expensive process utilizing mass-spectrometry, not practical for deployment in a high-resolution survey of a potential leakage site at the surface. Recent developments in commercially available instruments utilizing wavelength scanned cavity ringdown spectroscopy (WS-CRDS) and Fourier transform infrared spectroscopy (FT-IR) have made it possible to rapidly measure the isotopic composition of gases including the 13C and 12C isotopic composition of CO2 in a field setting. A portable stable carbon isotope ratio analyzer for carbon dioxide, based on wavelength scanned cavity ringdown spectroscopy, has been used to rapidly detect and

  2. Sea–air CO2 fluxes in the Indian Ocean between 1990 and 2009

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V; Lenton, A.; Law, R.M.; Metzl, N.; Patra, P.K.; Doney, S.C.; Lima, I.D.; Dlugokencky, E.; Ramonet, M.; Valsala, V

    ), Global Monitoring Division, Boulder, CO, USA 8Laboratoire des Sciences du Climat et de l’Environnement (LSCE), CEA/CNRS/UVSQ, Gif sur Yvette, France 9Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune, India Correspondence to: V..., 10, 7035–7052, 2013 www.biogeosciences.net/10/7035/2013/ doi:10.5194/bg-10-7035-2013 © Author(s) 2013. CC Attribution 3.0 License. Biogeosciences O pen A ccess Sea–air CO2 fluxes in the Indian Ocean between 1990 and 2009 V. V. S. S. Sarma1, A. Lenton2...

  3. Influence of travel behavior on global CO2 emissions

    NARCIS (Netherlands)

    Girod, B.; Vuuren, D.P. van; Vries, B. de

    2013-01-01

    Travel demand is rising steeply and its contribution to global CO2 emissions is increasing. Different studies have shown possible mitigation through technological options, but so far few studies have evaluated the implications of changing travel behavior on global travel demand, energy use and CO2 e

  4. Summer drought leads to reduced net CO2 uptake and CH4 fluxes in a New Zealand peatland

    Science.gov (United States)

    Goodrich, J. P.; Campbell, D.; Schipper, L. A.; Clearwater, M.

    2013-12-01

    Global climate change is likely to influence the frequency and severity of drought events in many regions. This has implications for changing carbon (C) storage in peatland ecosystems, which provide an important global sink for atmospheric C. However, the relative impacts on ecosystem respiration (ER), gross primary productivity (GPP), and CH4 efflux are not well understood and may alter the C balance differently depending on peatland type, vegetation, and timing of drought. We measured CO2 and CH4 fluxes using eddy covariance in a New Zealand peatland during two contrasting years capturing the impact of an historically extreme drought on these two major components of the net ecosystem C balance. Kopuatai bog is a 96 km2 ombrotrophic raised bog dominated by the endemic peat-forming rush species, Empodisma robustum. The drought impacted the growing season period from January to May, 2013. Net ecosystem exchange of CO2 (NEE) during the drought was approximately half that of the previous relatively wet summer. From January 1 to May 1, cumulative NEE was -133.3 gC m-2 in 2012 and -66.7 gC m-2 in 2013. Increases in ER during the drought were responsible for up to 88% of the difference in NEE, while differences in GPP were comparatively small. For April, mean daily CH4 fluxes during the drought (25 mgCH4 m-2 day-1) reduced to approximately one third of the mean flux measured in April 2012 (80 mgCH4 m-2 day-1). CH4 fluxes remained low for several months following water table recharge, suggesting a substantial lag in the recovery of the methanogenic population. Despite the magnitude of respiration enhancement, the relatively consistent GPP and reduced CH4 flux led to net storage of C during drought, albeit significantly smaller than the previous wet year.

  5. Expanding Spatial and Temporal Coverage of Arctic CH4 and CO2 Fluxes

    Science.gov (United States)

    Murphy, P.; Oechel, W. C.; Moreaux, V.; Losacco, S.; Zona, D.

    2013-12-01

    Carbon storage and exchange in Arctic ecosystems is the subject of intensive study focused on determining rates, controls, and mechanisms of CH4 and CO2 fluxes. The Arctic contains more than 1 Gt of Carbon in the upper meter of soil, both in the active layer and permafrost (Schuur et al., 2008; Tarnocai et al., 2009). However, the annual pattern and controls on the release of CH4 is inadequately understood in Arctic tundra ecosystems. Annual methane budgets are poorly understood, and very few studies measure fluxes through the freeze-up cycle during autumn months (Mastepanov et al., 2008; Mastepanov et al., 2010; Sturtevant et al., 2012). There is no known, relatively continuous, CH4 flux record for the Arctic. Clearly, the datasets that currently exist for budget calculations and model parameterization and verification are inadequate. This is likely due to the difficult nature of flux measurements in the Arctic. In September 2012, we initiated a research project towards continuous methane flux measurements along a latitudinal transect in Northern Alaska. The eddy-covariance (EC) technique is challenging in such extreme weather conditions due to the effects of ice formation and precipitation on instrumentation, including gas analyzers and sonic anemometers. The challenge is greater in remote areas of the Arctic, when low power availability and limited communication can lead to delays in data retrieval or data loss. For these reasons, a combination of open- and closed-path gas analyzers, and several sonic anemometers (including one with heating), have been installed on EC towers to allow for cross-comparison and cross-referencing of calculated fluxes. Newer instruments for fast CH4 flux determination include: the Los Gatos Research Fast Greenhouse Gas Analyzer and the Li-Cor LI-7700. We also included the self-heated Metek Class-A uSonic-3 Anemometer as a new instrument. Previously existing instruments used for comparison include the Li-Cor LI-7500; Li-Cor LI-7200

  6. Biogenic CO2 fluxes, changes in surface albedo and biodiversity impacts from establishment of a miscanthus plantation.

    Science.gov (United States)

    Jørgensen, Susanne V; Cherubini, Francesco; Michelsen, Ottar

    2014-12-15

    Depletion in oil resources and environmental concern related to the use of fossil fuels has increased the interest in using second generation biomass as alternative feedstock for fuels and materials. However, the land use and land use change for producing second generation (2G) biomass impacts the environment in various ways, of which not all are usually considered in life cycle assessment. This study assesses the biogenic CO2 fluxes, surface albedo changes and biodiversity impacts for 100 years after changing land use from forest or fallow land to miscanthus plantation in Wisconsin, US. Climate change impacts are addressed in terms of effective forcing, a mid-point indicator which can be used to compare impacts from biogenic CO2 fluxes and albedo changes. Biodiversity impacts are assessed through elaboration on two different existing approaches, to express the change in biodiversity impact from one human influenced state to another. Concerning the impacts from biogenic CO2 fluxes, in the case of conversion from a forest to a miscanthus plantation (case A) there is a contribution to global warming, whereas when a fallow land is converted (case B), there is a climate cooling. When the effects from albedo changes are included, both scenarios show a net cooling impact, which is more pronounced in case B. Both cases reduce biodiversity in the area where the miscanthus plantation is established, though most in case A. The results illustrate the relevance of these issues when considering environmental impacts of land use and land use change. The apparent trade-offs in terms of environmental impacts further highlight the importance of including these aspects in LCA of land use and land use changes, in order to enable informed decision making.

  7. Environmental influences on soil CO 2 degassing at Furnas and Fogo volcanoes (São Miguel Island, Azores archipelago)

    Science.gov (United States)

    Viveiros, F.; Ferreira, T.; Cabral Vieira, J.; Silva, C.; Gaspar, J. L.

    2008-11-01

    Since October 2001, four soil CO 2 flux stations were installed in the island of São Miguel (Azores archipelago), at Fogo and Furnas quiescent central volcanoes. These stations perform measurements by the accumulation chamber method and, as the gas flux may be influenced by external variables, the stations are equipped with several meteorological sensors. Multivariate regression analysis applied to the large datasets obtained allowed observing that the meteorological variables may influence the soil CO 2 flux oscillations from 18% to 50.5% at the different monitoring sites. Additionally, it was observed that meteorological variables (mainly soil water content, barometric pressure, wind speed and rainfall) play a different role in the control of the gas flux, depending on the selected monitoring site and may cause significant short-term (spike-like) fluctuations. These divergences may be potentially explained by the porosity and hydraulic conductivity of the soils, topographic effects, drainage area and different exposure of the monitoring sites to the weather conditions. Seasonal effects are responsible for long-term oscillations on the gas flux. Before a reliable application of soil CO 2 flux to seismic and/or volcanic monitoring, it is important to recognize those environmental influences on the gas flux. In addition, understanding the external meteorological influences on the gas flux may be important for the public health risk assessment, since meteorological parameters may cause also significant indoor CO 2 increases. In a house at Furnas Village (in Furnas volcano caldera), the values detected reached percentages as high as 20.8% due to significant decreases in the barometric pressure.

  8. Modelling the CO2 atmosphere-ocean flux in the upwelling zones using radiative transfer tools

    Science.gov (United States)

    Krapivin, Vladimir F.; Varotsos, Costas A.

    2016-12-01

    An advanced mathematical model of the radiation forcing on the ocean surface is proposed for the assessment of the CO2 fluxes between atmosphere and ocean boundary in the upwelling zones. Two types of the upwelling are considered: coastal and local in the open ocean that are closely associated with changes in solar irradiance. The proposed model takes into account the maximal number of the carbon fluxes in the upwelling ecosystem considering that in the latter the only original source of energy and matter for all forms of life is the energy of the solar radiation. The vertical structure of the upwelling zone is represented by four levels: the upper mixed layer above the thermocline, the intermediate photic layer below the thermocline, the deep ocean and the near-bottom layer. Peruvian upwelling and typical local upwelling of tropical pelagic region are considered as examples for the model calculations.

  9. Responses of soil CO2 fluxes to short-term experimental warming in alpine steppe ecosystem, Northern Tibet.

    Science.gov (United States)

    Lu, Xuyang; Fan, Jihui; Yan, Yan; Wang, Xiaodan

    2013-01-01

    Soil carbon dioxide (CO2) emission is one of the largest fluxes in the global carbon cycle. Therefore small changes in the size of this flux can have a large effect on atmospheric CO2 concentrations and potentially constitute a powerful positive feedback to the climate system. Soil CO2 fluxes in the alpine steppe ecosystem of Northern Tibet and their responses to short-term experimental warming were investigated during the growing season in 2011. The results showed that the total soil CO2 emission fluxes during the entire growing season were 55.82 and 104.31 g C m(-2) for the control and warming plots, respectively. Thus, the soil CO2 emission fluxes increased 86.86% with the air temperature increasing 3.74°C. Moreover, the temperature sensitivity coefficient (Q 10) of the control and warming plots were 2.10 and 1.41, respectively. The soil temperature and soil moisture could partially explain the temporal variations of soil CO2 fluxes. The relationship between the temporal variation of soil CO2 fluxes and the soil temperature can be described by exponential equation. These results suggest that warming significantly promoted soil CO2 emission in the alpine steppe ecosystem of Northern Tibet and indicate that this alpine ecosystem is very vulnerable to climate change. In addition, soil temperature and soil moisture are the key factors that controls soil organic matter decomposition and soil CO2 emission, but temperature sensitivity significantly decreases due to the rise in temperature.

  10. Transpiration and CO2 fluxes of a pine forest: modelling the undergrowth effect

    Directory of Open Access Journals (Sweden)

    A. Granier

    2005-02-01

    Full Text Available A modelling study is performed in order to quantify the relative effect of allowing for the physiological properties of an undergrowth grass sward on total canopy water and carbon fluxes of the Le-Bray forest (Les-Landes, South-western France. The Le-Bray forest consists of maritime pine and an herbaceous undergrowth (purple moor-grass, which is characterised by a low stomatal control of transpiration, in contrast to maritime pine. A CO2-responsive land surface model is used that includes responses of woody and herbaceous species to water stress. An attempt is made to represent the properties of the undergrowth vegetation in the land surface model Interactions between Soil, Biosphere, and Atmosphere, CO2-responsive, ISBA-A-gs. The new adjustment allows for a fairly different environmental response between the forest canopy and the understory in a simple manner. The model's simulations are compared with long term (1997 and 1998 micro-meteorological measurements over the Le-Bray site. The fluxes of energy, water and CO2, are simulated with and without the improved representation of the undergrowth vegetation, and the two simulations are compared with the observations. Accounting for the undergrowth permits one to improve the model's scores. A simple sensitivity experiment shows the behaviour of the model in response to climate change conditions, and the understory effect on the water balance and carbon storage of the forest. Accounting for the distinct characteristics of the undergrowth has a substantial and positive effect on the model accuracy and leads to a different response to climate change scenarios.

  11. Detectability of CO2 flux signals by a space-based lidar mission

    Science.gov (United States)

    Hammerling, Dorit M.; Kawa, S. Randolph; Schaefer, Kevin; Doney, Scott; Michalak, Anna M.

    2015-03-01

    Satellite observations of carbon dioxide (CO2) offer novel and distinctive opportunities for improving our quantitative understanding of the carbon cycle. Prospective observations include those from space-based lidar such as the active sensing of CO2 emissions over nights, days, and seasons (ASCENDS) mission. Here we explore the ability of such a mission to detect regional changes in CO2 fluxes. We investigate these using three prototypical case studies, namely, the thawing of permafrost in the northern high latitudes, the shifting of fossil fuel emissions from Europe to China, and changes in the source/sink characteristics of the Southern Ocean. These three scenarios were used to design signal detection studies to investigate the ability to detect the unfolding of these scenarios compared to a baseline scenario. Results indicate that the ASCENDS mission could detect the types of signals investigated in this study, with the caveat that the study is based on some simplifying assumptions. The permafrost thawing flux perturbation is readily detectable at a high level of significance. The fossil fuel emission detectability is directly related to the strength of the signal and the level of measurement noise. For a nominal (lower) fossil fuel emission signal, only the idealized noise-free instrument test case produces a clearly detectable signal, while experiments with more realistic noise levels capture the signal only in the higher (exaggerated) signal case. For the Southern Ocean scenario, differences due to the natural variability in the El Niño-Southern Oscillation climatic mode are primarily detectable as a zonal increase.

  12. Using Carbonyl Sulfide column measurements and a Chemical Transport Model to investigate variability in biospheric CO2 fluxes

    Science.gov (United States)

    Wang, Yuting; Petri, Christof; Palm, Mathias; Warneke, Thorsten; Baker, Ian; Berry, Joe; Suntharalingam, Parvadha; Campbell, Elliott; Wolf, Adam; Deutscher, Nick; Notholt, Justus

    2015-04-01

    Understanding the CO2 processes on land is of great importance, because the terrestrial exchange drives the seasonal and interannual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake) and respiration (production). Carbonyl sulfide (OCS) could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential means to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR) spectrometry allows for the retrieval of the atmospheric concentrations of both CO2 and OCS. Here, we investigate co-located and nearly simultaneous measurements of OCS and CO2 measured at 3 sites via FTIR spectrometers. These northern-hemispheric sites span a wide range of latitudes and all have multiple year time-series. The sites include Ny-Alesund (79°N), Bremen (53°N) and Paramaribo (6°N). We compare these measurements to simulations of OCS and CO2 using the GEOS-Chem model. The simulations are driven by different land biospheric fluxes of OCS and CO2 to match the seasonality of the measurements. The simple biosphere model (SiB-COS) are used in the study because it simultaneously calculates the biospheric fluxes of both OCS and CO2. The CO2 simulation with SiB fluxes agrees with the measurements better than a simulation using CASA. Comparison of the OCS simulations with different fluxes indicates that the latitudinal distribution of the OCS fluxes within SiB needs to be adjusted.

  13. Atlantic Ocean Carbon Experiment (acex): Implementation of Eddy Covariance Implementation of Eddy Covariance CO2 Flux Measurements on the SW Atlantic Ocean and Results from the Second Cruise

    Science.gov (United States)

    Schultz, C.; Pezzi, L. P.; Miller, S. D.; Martins, L. G.; Araujo, R. G.; Acevedo, O. C.; Moller, O.; Souza, R.; Tavano, V. M.; Farias, P.; Casagrande, F.

    2013-05-01

    The project observational and numerical study of heat, momentum and CO2 fluxes at the ocean-atmosphere interface in the South Atlantic Ocean - Atlantic Ocean Carbon Experiment (ACEx) combines observational and modeling approaches to characterize heat, momentum and CO2 fluxes at the ocean-atmosphere interface in the South Atlantic Ocean. This project is part of an innovative initiative aimed at providing a better understanding of the chemical, physical and dynamic processes of ocean-atmosphere interaction in micro and meso-scales at the South Atlantic Ocean, as well as fluxes across this interface. The ACEx project has performed three cruises so far, collecting measurements with CTDs and XBTs, launching radiosondes, and deploying a micro-meteorological tower to make in situ measurements of heat, momentum and CO2 fluxes. Our successful deployment of this tower represents the first use of a CO2 flux measurement system using eddy covariance technique in the Southwestern Atlantic Ocean. In this work, we present results from the second ACEx cruise, in which the crew onboard the Hydro-oceanographic Vessel Cruzeiro do Sul took measurements at 31 stations between Paranaguá (PR) and Chuí (RS). In addition to physical data, this cruise collected phytoplankton and nutrient data, allowing carbonic gas fluxes to be analyzed and compared with both physical and biological forcings. The highest chlorophyll concentrations were found in water derived from the La Plata River, which showed low salinity waters close to the surface. The influence of these waters was observed mainly at the southernmost stations of the cruise, coincident with increases on the CO2 fluxes that had remained slightly negative until then. This suggests that the biological forcings might have a significant impact on the gas fluxes in this area, through both respiration and the consumption of organic matter. We are currently working to apply circulation and biogeochemical models to evaluate the importance of

  14. The influence of the stratosphere on the tropospheric zonal wind response to CO2 doubling

    Directory of Open Access Journals (Sweden)

    C. J. Bell

    2011-05-01

    Full Text Available The influence of a CO2 doubling on the stratospheric potential vorticity (PV is examined in two climate models. Subsequently, the influence of changes in the stratosphere on the tropospheric zonal wind response is investigated, by inverting the stratospheric PV. Radiative effects seem to dominate the stratospheric response to CO2 doubling in the Southern Hemisphere. These lead to a stratospheric PV increase at the edge of the polar vortex, resulting in an increased westerly influence of the stratosphere on the troposphere, increasing the midlatitude tropospheric westerlies in late winter. In the Northern Hemisphere, dynamical effects are also important. Both models show a reduced polar PV and an enhanced midlatitude PV in the Northern Hemisphere winter stratosphere. These PV changes are likely related to an enhanced wave forcing of the winter stratosphere, as measured by an increase in the 100 hPa eddy heat flux, and result in a reduced westerly influence of the stratosphere on the high latitude tropospheric winds. In one model, the high latitude PV decreases are, however, restricted to higher altitudes, and the tropospheric response due to the stratospheric changes is dominated by an increased westerly influence in the midlatitudes, related to the increase in midlatitude PV in the lower stratosphere. The tropospheric response in zonal wind due to the stratospheric PV changes is of the order of 0.5 to 1 m s−1. The total tropospheric response has a somewhat different spatial structure, but is of similar magnitude. This indicates that the stratospheric influence is of importance in modifying the tropospheric zonal wind response to CO2 doubling.

  15. The influence of the stratosphere on the tropospheric zonal wind response to CO2 doubling

    Directory of Open Access Journals (Sweden)

    P. C. Siegmund

    2010-10-01

    Full Text Available The influence of a CO2 doubling on the stratospheric potential vorticity (PV is examined in two climate models. Subsequently, the influence of changes in the stratosphere on the tropospheric zonal wind response is investigated, by inverting the stratospheric PV. Radiative effects dominate the stratospheric response to CO2 doubling in the Southern Hemisphere. These lead to a stratospheric PV increase at the edge of the polar vortex, resulting in an increased westerly influence of the stratosphere on the tropospheric midlatitude winds in late winter. In the Northern Hemisphere, dynamical effects are also important. Both models show a reduced polar PV and an enhanced midlatitude PV in the Northern Hemisphere winter stratosphere. These PV changes are related to an enhanced wave forcing of the winter stratosphere, as measured by an increase in the 100 hPa eddy heat flux, and result in a reduced westerly influence of the stratosphere on the high latitude tropospheric winds. In one model, the high latitude PV decreases are, however, restricted to higher altitudes, and the tropospheric response due to the stratospheric changes is dominated by an increased westerly influence in the midlatitudes, related to the increase in midlatitude PV in the lower stratosphere. The tropospheric response in zonal wind due to the stratospheric PV changes is of the order of 0.5 to 1 m s−1. The total tropospheric response has a somewhat different spatial structure, but is of similar magnitude. This indicates that the stratospheric influence is of importance in modifying the tropospheric zonal wind response to CO2 doubling.

  16. Ocean-Atmosphere CO2 Fluxes in the North Atlantic Subtropical Gyre: Association with Biochemical and Physical Factors during Spring

    Directory of Open Access Journals (Sweden)

    Macarena Burgos

    2015-08-01

    Full Text Available Sea surface partial pressure of CO2 (pCO2 was measured continuously in a transect of the North Atlantic subtropical gyre between Santo Domingo, Dominican Republic (18.1° N, 68.5° W and Vigo, Spain (41.9° N, 11.8° W during spring 2011. Additional biogeochemical and physical variables measured to identify factors controlling the surface pCO2 were analyzed in discrete samples collected at 16 sites along the transect at the surface and to a depth of 200 m. Sea surface pCO2 varied between 309 and 662 μatm, and showed differences between the western and eastern subtropical gyre. The subtropical gyre acted as a net CO2 sink, with a mean flux of −5.5 ± 2.2 mmol m−2 day−1. The eastern part of the transect, close to the North Atlantic Iberian upwelling off the Galician coast, was a CO2 source with an average flux of 33.5 ± 9.0 mmol m−2 day−1. Our results highlight the importance of making more surface pCO2 observations in the area located east of the Azores Islands since air-sea CO2 fluxes there are poorly studied.

  17. Seasonal and diurnal variations in moisture, heat and CO2 fluxes over a typical steppe prairie in Inner Mongolia, China

    Directory of Open Access Journals (Sweden)

    L. Wang

    2009-03-01

    Full Text Available In order to examine energy partitioning and CO2 exchange over a steppe prairie in Inner Mongolia, China, fluxes of moisture, heat and CO2 in the surface layer from June 2007 through June 2008 were calculated using the eddy covariance method. The study site was homogenous and approximately 1500 m×1500 m in size. Seasonal and diurnal variations in radiation components, energy components and CO2 fluxes are examined. Results show that all four radiation components changed seasonally, resulting in a seasonal variation in net radiation. The radiation components also changed diurnally. Winter surface albedo was higher than summer surface albedo because during winter the snow-covered surface increased the surface albedo. The seasonal variations in both sensible heat and CO2 fluxes were stronger than those of latent heat and soil heat fluxes. This implies that both sensible heat and CO2 fluxes may be more significant climate signals than latent heat and soil fluxes. Sensible heat flux was the main consumer of available energy for the entire experimental period. The energy imbalance problem was encountered and the causes are analyzed.

  18. CO2 flux determination by closed-chamber methods can be seriously biased by inappropriate application of linear regression

    Directory of Open Access Journals (Sweden)

    J. Alm

    2007-11-01

    Full Text Available 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

  19. CO2, CH4, and DOC Flux During Long Term Thaw of High Arctic Tundra

    Science.gov (United States)

    Stackhouse, B. T.; Vishnivetskaya, T. A.; Layton, A.; Bennett, P.; Mykytczuk, N.; Lau, C. M.; Whyte, L.; Onstott, T. C.

    2013-12-01

    Arctic regions are expected to experience temperature increases of >4° C by the end of this century. This warming is projected to cause a drastic reduction in the extent of permafrost at high northern latitudes, affecting an estimated 1000 Pg of SOC in the top 3 m. Determining the effects of this temperature change on CO2 and CH4 emissions is critical for defining source constraints to global climate models. To investigate this problem, 18 cores of 1 m length were collected in late spring 2011 before the thawing of the seasonal active layer from an ice-wedge polygon near the McGill Arctic Research Station (MARS) on Axel Heiberg Island, Nunavut, Canada (N79°24, W90°45). Cores were collected from acidic soil (pH 5.5) with low SOC (~1%), summertime active layer depth between 40-70 cm (2010-2013), and sparse vegetation consisting primarily of small shrubs and sedges. Cores were progressively thawed from the surface over the course of 14 weeks to a final temperature of 4.5° C and held at that temperature for 15 months under the following conditions: in situ water saturation conditions versus fully water saturated conditions using artificial rain fall, surface light versus no surface light, cores from the polygon edge, and control cores with a permafrost table maintained at 70 cm depth. Core headspaces were measured weekly for CO2, CH4, H2, CO, and O2 flux during the 18 month thaw experiment. After ~20 weeks of thawing maximum, CO2 flux for the polygon edge and dark treatment cores were 3.0×0.7 and 1.7×0.4 mmol CO2 m-2 hr-1, respectively. The CO2 flux for the control, saturated, and in situ saturation cores reached maximums of 0.6×0.2, 0.9×0.5, and 0.9×0.1 mmol CO2 m-2 hr-1, respectively. Field measurements of CO2 flux from an adjacent polygon during the mid-summer of 2011 to 2013 ranged from 0.3 to 3.7 mmol CO2 m-2 hr-1. Cores from all treatments except water saturated were found to consistently oxidize CH4 at ~atmospheric concentrations (2 ppmv) with a maximum

  20. Effects of elevated CO2 and nitrogen deposition on ecosystem carbon fluxes on the Sanjiang plain wetland in Northeast China.

    Directory of Open Access Journals (Sweden)

    Jianbo Wang

    Full Text Available BACKGROUND: Increasing atmospheric CO2 and nitrogen (N deposition across the globe may affect ecosystem CO2 exchanges and ecosystem carbon cycles. Additionally, it remains unknown how increased N deposition and N addition will alter the effects of elevated CO2 on wetland ecosystem carbon fluxes. METHODOLOGY/PRINCIPAL FINDINGS: Beginning in 2010, a paired, nested manipulative experimental design was used in a temperate wetland of northeastern China. The primary factor was elevated CO2, accomplished using Open Top Chambers, and N supplied as NH4NO3 was the secondary factor. Gross primary productivity (GPP was higher than ecosystem respiration (ER, leading to net carbon uptake (measured by net ecosystem CO2 exchange, or NEE in all four treatments over the growing season. However, their magnitude had interannual variations, which coincided with air temperature in the early growing season, with the soil temperature and with the vegetation cover. Elevated CO2 significantly enhanced GPP and ER but overall reduced NEE because the stimulation caused by the elevated CO2 had a greater impact on ER than on GPP. The addition of N stimulated ecosystem C fluxes in both years and ameliorated the negative impact of elevated CO2 on NEE. CONCLUSION/SIGNIFICANCE: In this ecosystem, future elevated CO2 may favor carbon sequestration when coupled with increasing nitrogen deposition.

  1. Coastal upwelling fluxes of O2, N2O, and CO2 assessed from continuous atmospheric observations at Trinidad, California

    Directory of Open Access Journals (Sweden)

    T. J. Lueker

    2004-01-01

    Full Text Available Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed. Regional air-sea fluxes of O2/N2, N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.

  2. Forest soil CO2 fluxes as a function of understory removal and N-fixing species addition

    Institute of Scientific and Technical Information of China (English)

    Haifang Li; Shenglei Fu; Hongting Zhao; Hanping Xia

    2011-01-01

    We report on the effects of forest management practices of understory removal and N-fixing species (Cassia alata) addition on soil CO2 fluxes in an Eucalyptus urophylla plantation (EUp), Acacia crassicarpa plantation (ACp), 10-species-mixed plantation (Tp), and 30-species-mixed plantation (THp) using the static chamber method in southern China. Four forest management treatments, including (1) understory removal (UR); (2) C. alata addition (CA); (3) understory removal and replacement with C. alata (UR+CA); and (4)control without any disturbances (CK), were applied in the above four forest plantations with three replications for each treatment.The results showed that soil CO2 fluxes rates remained at a high level during the rainy season (from April to September), followed by a rapid decrease after October reaching a minimum in February. Soil CO2 fluxes were significantly higher (P < 0.01) in EUp (132.6 mg/(m2·hr)) and ACp (139.8 mg/(m2·hr)) than in Tp (94.0 mg/(m2·hr)) and THp (102.9 mg/(m2·hr)). Soil CO2 fluxes in UR and CA were significantly higher (P < 0.01) among the four treatments, with values of 105.7, 120.4, 133.6 and 112.2 mg/(m2·hr) for UR+CA,UR, CA and CK, respectively. Soil CO2 fluxes were positively correlated with soil temperature (P < 0.01), soil moisture (P < 0.01),NO3--N (P < 0.05), and litterfall (P < 0.01), indicating that all these factors might be important controlling variables for soil CO2 fluxes. This study sheds some light on our understanding of soil CO2 flux dynamics in forest plantations under various management practices.

  3. Gas composition and soil CO2 flux at Changbaishan intra-plate volcano, NE China

    Science.gov (United States)

    wen, H.; Yang, T. F.; Guo, Z.; Fu, C.; Zhang, M.

    2011-12-01

    Changbaishan, located on the border of China and North Korea, is one of the most active volcanoes in China. This volcano violently erupted 1000 years ago and produced massive magma and widespread volcanic ash, resulting in one of the largest explosive eruptions during the last 2000 years. Recent gas emissions and seismic events in the Tianchi area suggested potential increasing volcanic activities. If that is so, then 1 million residents living on the crater flank shall be endangered by enormous volcanic hazards, including the threat of 2 billion tons of water in the crater lake . In order to better understand current status of Changbaishan, we investigated gas geochemistry in samples from the Tianchi crater lake and surrounding areas. Bubbling gas from hot springs were collected and analyzed. The results show that CO2 is the major component gas for most samples. The maximum value of helium isotopic ratio 5.8 RA (where RA = 3He/4He in air) implies more than 60% of helium is contributed by mantle component, while carbon isotope values fall in the range of -5.8 to -2.0% (vs. PDB), indicating magmatic source signatures as well. Nitrogen dominated samples, 18Dawgo, have helium isotopic ratio 0.7 RA and carbon isotope value -11.4% implying the gas source might be associated with regional crustal components in 18Dawgo. The first-time systematic soil CO2 flux measurements indicate the flux is 22.8 g m-2 day-1 at the western flank of Changbaishan, which is at the same level as the background value in the Tatun Volcano Group (24.6 g m-2 day-1), implying that it may not be as active as TVG.

  4. CO2 and CH4 fluxes of an Alpine peatland during extraordinary summer drought

    Science.gov (United States)

    Drollinger, Simon; Glatzel, Stephan

    2016-04-01

    In peatland ecosystems, plant production exceeds decomposition due to their typical characteristic of waterlogged soils leading to peatland growth and an accumulation of thick organic soil layers. As a result, peatlands constitute a major global storage of carbon (C) by storing about 612 PgC in their peat, thus representing the most space-effective C stocks of all terrestrial ecosystems, similar in magnitude as the increasing atmospheric C pool (~ 850 PgC). However, little is known about the effects of climate change on peatlands and the contribution of Alpine peatlands as a source of greenhouse gases in the course of a changing climate. It is debatable how land-use changes and ongoing degradation of Alpine peatlands affect the peatland-atmosphere C exchange. On the one hand, more C may sequester due to increased plant growth in a warmer climate, on the other hand large amounts of respired C may release as a consequence of higher temperatures and lowered peatland water table depths due to increasing evaporation rates and extending drought periods. To examine the potential effects of climate change on the peatland carbon exchange with the atmosphere, we calculated CO2 and CH4 fluxes using the eddy covariance method. The investigated ombrotrophic peatland is located on the bottom of the Styrian Enns valley at an altitude of 632 m above sea level. It is a slightly degraded pine peat bog (62 ha) with a closed peat moss cover featuring the three plant associations Pino mugo-Sphagnetum magellanici, Sphagnetum magellanici, and Caricetum limosae, according to the prevailing hydrological site conditions. During summer drought in 2015, the water level decreased from an annual average water level of -10.44 cm to -28.50 cm below surface at the centre of the peat bog. Here, we present diurnal pattern of CO2 and CH4 fluxes during an extraordinary dry summer and compare them to calculated fluxes during periods characterised by precipitation and higher peat water levels of the

  5. Experimental warming in a dryland community reduced plant photosynthesis and soil CO2 efflux although the relationship between the fluxes remained unchanged

    Science.gov (United States)

    Wertin, Timothy M.; Belnap, Jayne; Reed, Sasha C.

    2016-01-01

    1.Drylands represent our planet's largest terrestrial biome and, due to their extensive area, maintain large stocks of carbon (C). Accordingly, understanding how dryland C cycling will respond to climate change is imperative for accurately forecasting global C cycling and future climate. However, it remains difficult to predict how increased temperature will affect dryland C cycling, as substantial uncertainties surround the potential responses of the two main C fluxes: plant photosynthesis and soil CO2 efflux. In addition to a need for an improved understanding of climate effects on individual dryland C fluxes, there is also notable uncertainty regarding how climate change may influence the relationship between these fluxes.

  6. Effects of biomass burning aerosols on CO2 fluxes on Amazon Region

    Science.gov (United States)

    Soares Moreira, Demerval; Freitas, Saulo; Longo, Karla; Rosario, Nilton

    2015-04-01

    During the dry season in Central Brazil and Southern Amazon, there is an usually high concentration of aerosol particles associated with intense human activities, with extensive biomass burning. It has been observed through remote sensing that the smoke clouds in these areas often cover an area of about 4 to 5 million km2. Thus, the average aerosol optical depth of these regions at 500 ηm, is usually below 0.1 during the rainy season and can exceed 0.9 in the fire season. Aerosol particles act as condensation nuclei and also increase scattering and absorption of the incident radiation. Therefore, the layer of the aerosol alters the precipitation rate; reduces the amount of solar energy that reaches the surface, producing a cooling; and causes an increase of diffuse radiation. These factors directly and indirectly affect the CO2 fluxes at the surface. In this work, the chemical-atmospheric model CCATT-BRAMS (Coupled Chemistry-Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System) coupled to the surface model JULES (Joint UK Land Environment Simulator) was used to simulate the effects of biomass burning aerosols in CO2 fluxes in the Amazon region. Both the total effect of the aerosols and the contribution related only to the increase of the diffuse fraction caused by the their presence were analyzed. The results show that the effect of the scattered fraction is dominant over all other effects. It was also noted that the presence of aerosols from fires can substantially change biophysiological processes of the carbon cycle. In some situations, it can lead to a sign change in the net ecosystem exchange (NEE), turning it from a source of CO2 to the atmosphere, when the aerosol is not considered in the simulations, to a sink, when it is considered. Thus, this work demonstrates the importance of considering the presence of aerosols in numerical simulations of weather and climate, since carbon dioxide is a major

  7. Effects of Biomass Burning Aerosols on CO2 Fluxes in the Amazon Region

    Science.gov (United States)

    Moreira, D. S.; Freitas, S. R.

    2014-12-01

    During the dry season in Central Brazil and Southern Amazon, there is an usually high concentration of aerosol particles associated with intense human activities, with extensive biomass burning. It has been observed through remote sensing that the smoke clouds in these areas often cover an area of about 4 to 5 million km2. Thus, the average aerosol optical depth of these regions at 500 ηm, is usually below 0.1 during the rainy season and can exceed 0.9 in the fire season. Aerosol particles act as condensation nuclei and also increase scattering and absorption of the incident radiation. Therefore, the layer of the aerosol alters the precipitation rate; reduces the amount of solar energy that reaches the surface, producing a cooling; and causes an increase of diffuse radiation. These factors directly and indirectly affect the CO2 fluxes at the surface. In this work, the chemical-atmospheric model CCATT-BRAMS (Coupled Chemistry-Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System) coupled to the surface model JULES (Joint UK Land Environment Simulator) was used to simulate the effects of biomass burning aerosols in CO2 fluxes in the Amazon region. Both the total effect of the aerosols and the contribution related only to the increase of the diffuse fraction caused by the their presence were analyzed. The results show that the effect of the scattered fraction is dominant over all other effects. It was also noted that the presence of aerosols from fires can substantially change biophysiological processes of the carbon cycle. In some situations, it can lead to a sign change in the net ecosystem exchange (NEE), turning it from a source of CO2 to the atmosphere, when the aerosol is not considered in the simulations, to a sink, when it is considered. Thus, this work demonstrates the importance of considering the presence of aerosols in numerical simulations of weather and climate, since carbon dioxide is a major

  8. Distribution of sea-air CO2 fluxes in the Patagonian Sea: Seasonal, biological and thermal effects

    Science.gov (United States)

    Kahl, Lucía C.; Bianchi, Alejandro A.; Osiroff, Ana Paula; Pino, Diana Ruiz; Piola, Alberto R.

    2017-07-01

    Sea-air CO2 fluxes (FCO2) in the Patagonian Sea (PS) were studied using observations collected in 2000-2006. Based on the PS frontal structures and the thermal and biological contributions to FCO2 we present a regional subdivision between distinct regimes that provide new insights on the processes that control these fluxes. The coastal regime (CR) is a net source of atmospheric CO2 (4.9 × 10-3 mol m-2 d-1) while the open shelf regime (SHR) is a net CO2 sink (-6.0 × 10-3 mol m-2 d-1). The interface between these two regions closely follows the location of along-shore fronts. In addition, based on the nature of the processes that drive the FCO2, the PS is subdivided between northern (NR) and southern (SR) regions. Both, NR and SR are CO2 sinks, but the CO2 uptake is significantly higher in NR (-6.4 × 10-3 mol m-2 d-1) than in SR (-0.5 × 10-3 mol m-2 d-1). The data reveal a strong seasonality in FCO2. The mean CO2 capture throughout the PS in austral spring is -5.8 × 10-3 mol m-2 d-1, reaching values lower than -50 × 10-3 mol m-2 d-1 in NR, while in winter FCO2 is close to equilibrium in SR. The analysis of the biological and thermal effects (BE and TE, respectively) on seasonal pCO2 variability indicates that regions of CO2 emission are dominated by the TE while regions of CO2 uptake are dominated by the BE. Our results indicate that the biological pump is the dominant process determining the sea-air CO2 flux in the PS.

  9. Estimating regional fluxes of CO2 and CH4 using space-borne observations of XCH4 : XCO2

    Directory of Open Access Journals (Sweden)

    A. Fraser

    2014-06-01

    ratio to changes in either gas. To simultaneously estimate fluxes of CO2 and CH4 we use a formal Bayesian inverse model infrastructure. We use two approaches to independently resolve flux estimates of these two gases using GOSAT observations of XCH4:XCO2: (1 the a priori error covariance between CO2 and CH4 describing common source from biomass burning; and (2 also fitting independent surface atmospheric measurements of CH4 and CO2 mole fraction that provide additional constraints, improving the effectiveness of the observed GOSAT ratio to constrain fluxes. We demonstrate the impact of these two approaches using Observing System Simulation Experiments. A posteriori flux estimates inferred using only the GOSAT ratios and taking advantage of the error covariance due to biomass burning are not consistent with the true fluxes in our experiments, as the inversion system cannot judge which species' fluxes to adjust. This can result in a posteriori fluxes that are further from the truth than the a priori fluxes. We find that adding the surface data to the inversion dramatically improves the ability of the GOSAT ratios to infer both CH4 and CO2 fluxes. We show that using real GOSAT XCH4:XCO2 ratios together with the surface data during 2010 outcompetes inversions using the individual XCH4 or the full-physics XCO2 data products. Regional fluxes that show the greatest improvements have model minus observation differences with a large seasonal cycle such as Tropical South America for which we report a small but significant annual source of CO2 compared to a small annual sink inferred from the XCO2 data. Based on our analysis we argue that using the ratios we may be reaching the limitations on the precision of these data.

  10. Ecosystem and soil fluxes of carbonyl sulfide (COS) and CO2 to constrain rates of gross photosynthesis (Invited)

    Science.gov (United States)

    Seibt, U. H.; Maseyk, K. S.; Lett, C.; Sun, W.; Berry, J. A.; Billesbach, D. P.; Campbell, J.; Torn, M. S.

    2013-12-01

    A promising new approach to constrain biosphere-atmosphere carbon and water exchange is the use of carbonyl sulfide (COS). COS is taken up by leaves via the same pathway as CO2, leading to a close coupling of vegetation COS and CO2 fluxes during photosynthesis. It has been proposed that the gross fluxes of photosynthesis and respiration can be quantified through the concurrent measurements of COS and CO2. Using newly available instrumentation, we conducted field campaigns to quantify COS and CO2 exchange in the Southern Great Plains, OK, and in the Santa Monica mountains, CA. We found that soils can act as sinks or sources of COS, correlated with soil temperature and moisture. At the ecosystem scale, we observed a strong uptake of COS by the canopy with a diel signal that mirrored net CO2 fluxes. Combining soil and ecosystem data of COS and CO2, we demonstrate how soil COS fluxes can be taken into account when partitioning net ecosystem exchange into photosynthesis and respiration.

  11. Characterizing CO2 fluxes for growing and non-growing seasons in a shrub ecosystem on the Qinghai-Tibet Plateau

    Institute of Scientific and Technical Information of China (English)

    XU; Shixiao; ZHAO; Xinquan; FU; Yuling; ZHAO; Liang; LI; Yi

    2005-01-01

    To assess carbon budget for shrub ecosystems on the Qinghai-Tibet Plateau, CO2flux was measured with an open-path eddy covariance system for an alpine shrub ecosystem during growing and non-growing seasons. CO2 flux dynamics was distinct between the two seasons. During the growing season from May to September, the ecosystem exhibited net CO2uptake from 08:00 to 19:00 (Beijing Standard Time), but net CO2 emission from 19:00 to 08:00.Maximum CO2 uptake appeared around 12:00 with values of 0.71, 1.19, 1.46 and 0.67 g CO2m-2 h-1 for June, July, August and September, respectively. Diurnal fluctuation of CO2 flux showed higher correlation with photosynthetic photon flux density than temperature. The maximum net CO2 influx occurred in August with a value of 247 g CO2 m-2. The total CO2 uptake by the ecosystem was up to 583 g CO2 m-2 for the growing season. During the non-growing season from January to April and from October to December, CO2 flux showed small fluctuation with the largest net CO2 efflux of 0.30 g CO2 m-2 h-1 in April. The diurnal CO2 flux was close to zero during most time of the day, but showed a small net CO2 efflux from 11:00 to 18:00. Diurnal CO2 flux, is significantly correlated to diurnal temperature in the non-growing season. The maximum monthly net CO2 efflux appeared in April, with a value of 105 g CO2 m-2. The total net CO2 efflux for the whole non-growing season was 356 g CO2 m-2.

  12. Integrated observations of CO2 fluxes in vineyards to support the management of soil organic matter

    Science.gov (United States)

    Vendrame, Nadia; Tezza, Luca; Meggio, Franco; Pitacco, Andrea

    2017-04-01

    Vineyard soils are subjected to a substantial depletion of the organic fraction due to the transition to intensive farming systems, the reduction of row spacing and the fast evolution of vineyard mechanization. The use of cover crops, grassed inter-rows and organic fertilization can all contribute to the increase, stabilization and protection of soil organic matter. However, a clear picture of carbon fluxes in the soil-plant-atmosphere system is still lacking, especially in vineyards. A detailed knowledge of these processes is also of primary importance to correctly predict the impact of future climate scenarios on viticulture and understand whether these ecosystems can act as source or sink of greenhouse gases. Even if it is commonly believed that agricultural crops cannot be net carbon sinks, woody perennials can behave differently. In fact, they grow a permanent structure, stand undisturbed in the same field for decades, originate abundant pruning debris, and are often grass-covered. Within the framework of the LIFE project VITISOM (VITiculture Innovative Soil Organic Matter management: variable-rate distribution system and monitoring of impacts, LIFE15 ENV/IT/000392) two integrated observatories of ecosystem CO2 fluxes have been established in Northern Italy, to disentangle the vineyard carbon budget in the mid-term. This knowledge can be of great value to better manage organic fertilization and soil fertility in vineyards.

  13. Arctic microbial community dynamics influenced by elevated CO2 levels

    Directory of Open Access Journals (Sweden)

    K. Schulz

    2012-09-01

    Full Text Available The Arctic Ocean ecosystem is particular vulnerable for ocean acidification (OA related alterations due to the relatively high CO2 solubility and low carbonate saturation states of its cold surface waters. Thus far, however, there is only little known about the consequences of OA on the base of the food web. In a mesocosm CO2-enrichment experiment (overall CO2 levels ranged from ∼180 to 1100 μatm in the Kongsfjord off Svalbard, we studied the consequences of OA on a natural pelagic microbial community. The most prominent finding of our study is the profound effect of OA on the composition and growth of the Arctic phytoplankton community, i.e. the picoeukaryotic photoautotrophs and to a lesser extent the nanophytoplankton prospered. A shift towards the smallest phytoplankton as a result of OA will have direct consequences for the structure and functioning of the pelagic food web and thus for the biogeochemical cycles. Furthermore, the dominant pico- and nanophytoplankton groups were found prone to viral lysis, thereby shunting the carbon accumulation in living organisms into the dissolved pools of organic carbon and subsequently affecting the efficiency of the biological pump in these Arctic waters.

  14. CO2 splitting by DBD: understanding the influence of electrical parameters and regimes

    CERN Document Server

    Ozkan, Alp; Silva, Tiago; Britun, Nikolay; Snyders, Rony; Bogaerts, Annemie; Reniers, François

    2016-01-01

    Plasma processes are an innovative approach for the decomposition of CO2 in O radicals and CO as a valuable carbon source. In this experimental work, a tubular dielectric barrier discharge operating at atmospheric pressure has been used to split CO2 and study its conversion considering the influence of frequency and power, as well as the influence of various electrical regimes (AC, AC pulsed regimes). The CO2 conversion has been measured by mass spectrometry and gas chromatography while gas and walls temperatures have been determined and correlated to evaluate their influence of the CO2 splitting.

  15. Influence of natural and anthropogenic factors on the dynamics of CO2 emissions from chernozems soil

    Science.gov (United States)

    Syabruk, Olesia

    2017-04-01

    5 to 15 % of the average level. The influence of the crop on the allocation dynamics of CO2 was also investigates during the research. Due to root respiration, total CO2 flux from soil increases by an average of 12-32 % when growing grain crops. The mathematical models of dependency between the CO2 emissions intensity and hydrothermal conditions were developed. These models will allow to predict the volume of CO2 emissions from automorphic chernozems under different scenarios of weather conditions during warm period, based on generalizing models with the corrections depending on the method of cultivation, fertilization system and agricultural culture. As a result of the research, it was proved that there is a necessity to conduct periodic direct measurements of CO2 emission losses from the soil surface and to summarize the results in an annual cycle, which allows estimating the probable emission losses of carbon already in the first years of the introduction of new agricultural technologies.

  16. Polyvinylidene fluoride/siloxane nanofibrous membranes for long-term continuous CO2 -capture with large absorption-flux enhancement.

    Science.gov (United States)

    Lin, Yi-Feng; Wang, Chi-Sen; Ko, Chia-Chieh; Chen, Chien-Hua; Chang, Kai-Shiun; Tung, Kuo-Lun; Lee, Kueir-Rarn

    2014-02-01

    In a CO2 membrane contactor system, CO2 passes through a hydrophobic porous membrane in the gas phase to contact the amine absorbent in the liquid phase. Consequently, additional CO2 gas is absorbed by amine absorbents. This study examines highly porous polyvinylidene fluoride (PVDF)/siloxane nanofibrous layers that are modified with hydrophobic fluoroalkylsilane (FAS) functional groups and successfully coated onto a macroporous Al2 O3 membrane. The performance of these materials in a membrane contactor system for CO2 absorption is also investigated. Compared with pristine PVDF nanofibrous membranes, the PVDF/siloxane nanofibrous membranes exhibit greater solvent resistance and mechanical strength, making them more suitable for use in CO2 capture by the membrane contactor. The PVDF/siloxane nanofibrous layer in highly porous FAS-modified membranes can prevent the wetting of the membrane by the amine absorbent; this extends the periods of continuous CO2 absorption and results in a high CO2 absorption flux with a minimum of 500 % enhancement over that of the uncoated membranes. This study suggests the potential use of an FAS-modified PVDF/siloxane nanofibrous membrane in a membrane contactor system for CO2 absorption. The resulting hydrophobic membrane contactor also demonstrates the potential for large-scale CO2 absorption during post-combustion processes in power plants.

  17. Comparison of air-sea fluxes of CO2 in the Southern Ocean and the western Arctic Ocean

    Institute of Scientific and Technical Information of China (English)

    CHEN Liqi; GAO Zhongyong; YANG Xulin; WANG Weiqiang

    2004-01-01

    The data were collected during Chinese Arctic and Antarctic Expeditions in the western Arctic Ocean and the marginal sea ice zone (MSIZ) of the Southern Ocean, respectively in the boreal summer from July to September of 1999 and in the austral summer from December of 1999 to January of 2000. The concentrations of CO2 in surface water of the survey regions would mostly present lower than those in the atmosphere. A significant biological driving force could also been observed in summer waters in both of the above oceans. Air to sea CO2 fluxes were also calculated to compare oceanic uptake capacity of CO2 in both oceans with the world oceans using Liss, Wanninkhof,and Jacobs' s methods. The averaged CO2 fluxes of air to sea in the western Arctic Ocean or in the MSIZ of the Southern Ocean doubled that in the world oceans.

  18. Seasonal and annual variation of CO2 flux above a broad-leaved Korean pine mixed forest

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>Long-term measurement of carbon metabolism of old-growth forests is critical to predict their behaviors and to reduce the uncertainties of carbon accounting under changing climate. Eddy covariance technology was applied to investigate the long-term carbon exchange over a 200 year-old Chinese broad-leaved Korean pine mixed forest in the Changbai Mountains (128°28’E and 42°24’N, Jilin Province, P. R. China) since August 2002. On the data obtained with open-path eddy covariance system and CO2 profile measurement system from Jan. 2003 to Dec. 2004, this paper reports (i) annual and seasonal variation of FNEE, FGPP and Re; (ii) regulation of environmental factors on phase and amplitude of ecosystem CO2 uptake and release Corrections due to storage and friction velocity were applied to the eddy carbon flux. Lal and soil temperature determined the seasonal and annual dynamics of FGPP and RE separately. VPD and air temperature regulated ecosystem photosynthesis at finer scales in growing seasons. Water condition at the root zone exerted a significant influence on ecosystem maintenance carbon metabolism of this forest in winter. The forest was a net sink of atmospheric CO2 and sequestered -449 g C·m-2 during the study period; -278 and -171 gC·m-2 for 2003 and 2004 respectively. FGPP and FRE over 2003 and 2004 were -1332, -1294 g C·m-2. and 1054, 1124 g C·m-2 respectively. This study shows that old-growth forest can be a strong net carbon sink of atmospheric CO2. There was significant seasonal and annual variation in carbon metabolism. In winter, there was weak photosynthesis while the ecosystem emitted CO2. Carbon exchanges were active in spring and fall but contributed little to carbon sequestration on an annual scale. The summer is the most significant season as far as ecosystem carbon balance is concerned. The 90 days of summer contributed 66.9, 68.9% of FGPp, and 60.4, 62.1% of RE of the entire year.

  19. Application of Relaxed Eddy Accumulation (REA) method to estimate CO2 and CH4 surface fluxes in the city of Krakow, southern Poland.

    Science.gov (United States)

    Zimnoch, Miroslaw; Gorczyca, Zbigniew; Pieniazek, Katarzyna; Jasek, Alina; Chmura, Lukasz; Rozanski, Kazimierz

    2013-04-01

    There is a growing interest in the recent years in studies aimed at quantifying carbon cycling in urban centres. Worldwide migration of human population from rural to urban areas and corresponding growth of extensive urban agglomerations and megacities leads to intensification of anthropogenic emissions of carbon and strong disruption of natural carbon cycle on these areas. Therefore, a deeper understanding of the carbon "metabolism" of such regions is required. Apart of better quantification of surface carbon fluxes, also a thorough understanding of the functioning of biosphere under strong anthropogenic influence is needed. Nowadays, covariance methods are widely applied for studying gas exchange between the atmosphere and the Earth's surface. Relaxed Eddy Accumulation method (REA), combined with the CO2 and CH4 CRDS analyser allows simultaneous measurements of surface fluxes of carbon dioxide and methane within the chosen footprint of the detection system, thus making possible thorough characterisation of the overall exchange of those gases between the atmosphere and the urban surface across diverse spatial and temporal scales. Here we present preliminary results of the study aimed at quantifying surface fluxes of CO2 and CH4 in Krakow, southern Poland. The REA system for CO2 and CH4 flux measurements has been installed on top of a 20m high tower mounted on the roof of the faculty building, close to the city centre of Krakow. The sensors were installed ca 42 m above the local ground. Gill Windmaster-Pro sonic anemometer was coupled with self-made system, designed by the Poznan University of Life Sciences, Poland, for collecting air samples in two pairs of 10-liter Tedlar bags, and with Picarro G2101-i CRDS analyser. The air was collected in 30-min intervals. The CO2 and CH4 mixing ratios in these cumulative downdraft and updraft air samples were determined by the CRDS analyser after each sampling interval. Based on the measured mixing ratios difference and the

  20. Changes in ecosystem carbon pool and soil CO2 flux following post-mine reclamation in dry tropical environment, India.

    Science.gov (United States)

    Ahirwal, Jitendra; Maiti, Subodh Kumar; Singh, Ashok Kumar

    2017-04-01

    Open strip mining of coal results in loss of natural carbon (C) sink and increased emission of CO2 into the atmosphere. A field study was carried out at five revegetated coal mine lands (7, 8, 9, 10 and 11years) to assess the impact of the reclamation on soil properties, accretion of soil organic C (SOC) and nitrogen (N) stock, changes in ecosystem C pool and soil CO2 flux. We estimated the presence of C in the tree biomass, soils, litter and microbial biomass to determine the total C sequestration potential of the post mining reclaimed land. To determine the C sequestration of the reclaimed ecosystem, soil CO2 flux was measured along with the CO2 sequestration. Reclaimed mine soil (RMS) fertility increased along the age of reclamation and decreases with the soil depths that may be attributed to the change in mine soils characteristics and plant growth. After 7 to 11years of reclamation, SOC and N stocks increased two times. SOC sequestration (1.71MgCha(-1)year(-1)) and total ecosystem C pool (3.72MgCha(-1)year(-1)) increased with the age of reclamation (CO2 equivalent: 13.63MgCO2ha(-1)year(-1)). After 11years of reclamation, soil CO2 flux (2.36±0.95μmolm(-2)s(-1)) was found four times higher than the natural forest soils (Shorea robusta Gaertn. F). The study shows that reclaimed mine land can act as a source/sink of CO2 in the terrestrial ecosystem and plays an important role to offset increased emission of CO2 in the atmosphere.

  1. Hybrid inversions of CO2 fluxes at regional scale applied to network design

    Science.gov (United States)

    Kountouris, Panagiotis; Gerbig, Christoph; -Thomas Koch, Frank

    2013-04-01

    Long term observations of atmospheric greenhouse gas measuring stations, located at representative regions over the continent, improve our understanding of greenhouse gas sources and sinks. These mixing ratio measurements can be linked to surface fluxes by atmospheric transport inversions. Within the upcoming years new stations are to be deployed, which requires decision making tools with respect to the location and the density of the network. We are developing a method to assess potential greenhouse gas observing networks in terms of their ability to recover specific target quantities. As target quantities we use CO2 fluxes aggregated to specific spatial and temporal scales. We introduce a high resolution inverse modeling framework, which attempts to combine advantages from pixel based inversions with those of a carbon cycle data assimilation system (CCDAS). The hybrid inversion system consists of the Lagrangian transport model STILT, the diagnostic biosphere model VPRM and a Bayesian inversion scheme. We aim to retrieve the spatiotemporal distribution of net ecosystem exchange (NEE) at a high spatial resolution (10 km x 10 km) by inverting for spatially and temporally varying scaling factors for gross ecosystem exchange (GEE) and respiration (R) rather than solving for the fluxes themselves. Thus the state space includes parameters for controlling photosynthesis and respiration, but unlike in a CCDAS it allows for spatial and temporal variations, which can be expressed as NEE(x,y,t) = λG(x,y,t) GEE(x,y,t) + λR(x,y,t) R(x,y,t) . We apply spatially and temporally correlated uncertainties by using error covariance matrices with non-zero off-diagonal elements. Synthetic experiments will test our system and select the optimal a priori error covariance by using different spatial and temporal correlation lengths on the error statistics of the a priori covariance and comparing the optimized fluxes against the 'known truth'. As 'known truth' we use independent fluxes

  2. Air–sea CO2 fluxes in the East China Sea based on multiple-year underway observations

    Directory of Open Access Journals (Sweden)

    X.-H. Guo

    2015-04-01

    Full Text Available This study reports thus far a most comprehensive dataset of surface seawater pCO2 (partial pressure of CO2 and the associated air–sea CO2 fluxes in a major ocean margin, the East China Sea (ECS based on 24 surveys conducted in 2006 to 2011. We showed highly dynamic spatial variability of sea surface pCO2 in the ECS except in winter when it ranged in a narrow band of 330 to 360 μatm. In this context, we categorized the ECS into five different domains featured with different physics and biogeochemistry to better characterize the seasonality of the pCO2 dynamics and to better constrain the CO2 flux. The five domains are (I the outer Changjiang estuary and Changjiang plume, (II the Zhejiang–Fujian coast, (III the northern ECS shelf, (IV the middle ECS shelf, and (V the southern ECS shelf. In spring and summer, pCO2 off the Changjiang estuary was as low as 400 μatm in fall. pCO2 along the Zhejiang–Fujian coast was low in spring, summer and winter (300 to 350 μatm but was relatively high in fall (> 350 μatm. In the northern ECS shelf, pCO2 in summer and fall was > 340 μatm in most areas, higher than in winter and spring. In the middle and southern ECS shelf, pCO2 in summer ranged from 380 to 400 μatm, which was higher than in other seasons (2 flux in the entire ECS shelf was −10.0 ± 2.0 mmol m−2 d−1 in winter, −11.7 ± 3.6 mmol m−2 d−1 in spring, −3.5 ± 4.6 mmol m−2 d−1 in summer and −2.3 ± 3.1 mmol m−2 d−1 in fall. It is important to note that the standard deviations in these flux ranges mostly reflect the spatial variation of pCO2, which differ from the spatial variance nor the bulk uncertainty. Nevertheless, on an annual basis, the average CO2 influx into the entire ECS shelf was −6.9 ± 4.0 mmol m−2 d−1, about twice the global average in ocean margins.

  3. A new disjunct eddy-covariance system for BVOC flux measurements – validation on CO2 and H2O fluxes

    Directory of Open Access Journals (Sweden)

    N. Striebig

    2012-12-01

    Full Text Available The disjunct eddy covariance (DEC method is an interesting alternative to the conventional eddy covariance (EC method because it allows the estimation of turbulent fluxes of species for which fast sensors are not available. We have developed and validated a new disjunct sampling system (called MEDEE. This system is built with chemically inert materials. Air samples are taken quickly and alternately in two cylindrical reservoirs, the internal pressures of which are regulated by a moving piston. The MEDEE system was designed to be operated either on the ground or aboard an aircraft. It is also compatible with most analysers since it transfers the air samples at a regulated pressure. To validate the system, DEC and EC measurements of CO2 and latent heat fluxes were performed concurrently during a field campaign. EC fluxes were first compared to simulated DEC (SDEC fluxes and then to actual DEC fluxes. Both the simulated and actual DEC fluxes showed a good agreement with EC fluxes in terms of correlation. The determination coefficients (R2 were 0.93 and 0.91 for DEC and SDEC latent heat fluxes, respectively. For DEC and SDEC CO2 fluxes R2 was 0.69 in both cases. The conditions of low fluxes experienced during the campaign impaired the comparison of the different techniques especially for CO2 flux measurements. Linear regression analysis showed an 14% underestimation of DEC fluxes for both CO2 and latent heat compared to EC fluxes. A first field campaign, focusing on biogenic volatile organic compound (BVOC emissions, was carried out to measure isoprene fluxes above a downy oak (Quercus Pubescens forest in the south-east of France. The measured standard emission rate was in the lower range of reported values in earlier studies. Further analysis will be conducted through ground-based and airborne campaigns in the coming years.

  4. Uptake of CO2 in the Pelagic Ocean by the Biological Pump; the Global Flux and the Regional Variability

    Science.gov (United States)

    Honjo, S.; Francois, R. H.; Manganini, S. J.; Eglinton, T. I.

    2010-12-01

    POC (particulate organic carbon) is vertically transported to the oceanic interior by ballasted aggregates, CaCO3 and biogenic opal, with a minor role for lithogenic aerosols through the mesopelagic zone. The diel-migrating zooplankton community is intimately involved with the vertical transport and re-mineralization of POC. Below 1.5-km, the zooplankton ecosystem is minimal, thus the aggregates travel mainly by gravity with little zooplankton influence. We examined the mole fluxes of POC, CaCO3, and biogenic opal Si fluxes retrieved from time-series, bottom tethered sediment traps (TS-trap) at 134 globally distributed pelagic stations at 2 km (m/b) as Fm/bCorg, Fm/bCinorg, and Fm/bSibio. The POC fluxes were normalized to the value at 2 km (m/b). We investigated (1) the geographic contrasts of POC export at m/b and (2) the supply rate of ∑CO2 to the world mesopelagic water column. Fm/bCorg varies from 25 (Pacific Warm Pool) to 605 (divergent Arabian Sea) mmolC m -2 yr-1; Fm/bCinorg varies from >8 (high latitude Polar Oceans) or 15 (Pacific Warm Pool) to 459 (divergent Arabian Sea) mmolC m-2yr-1; and Fm/bSibio, the most spatially/temporally variable flux, ranges from 6 (North Atlantic Drift) to 1118 (Pacific Subarctic Gyre) mmolSi m-2yr-1. The oceanic region exhibiting the highest POC flux over a significantly large region is the area of the North Pacific Boreal Gyres where the average Fm/bCorg = 213, Fm/bCinorg = 126, and Fm/bSibio = 578 mmol m-2yr-1. Fm/bCorg and Fm/bCinorg are particularly high in large upwelling margins, including the divergent Arabian Sea and off Cape Verde. The data set shows the lowest flux over a significant region/basin is Fm/bCorg = 39, whereas the Fm/bCinorg = 69, and Fm/bSibio-2yr-1 in the North Pacific subtropical/tropical gyres; Pan-Atlantic average fluxes are similar except Fm/bSibio fluxes are even lower. Where Corg/Cinorg and Sibio/Cinorg are Ocean,” and where these ratios are ≥1 defines the “Silica Ocean.” The Carbonate

  5. Quantifying the magnitude and spatiotemporal variation of aquatic CO2 fluxes in a sub-tropical karst catchment, Southwest China

    Science.gov (United States)

    Ding, Hu; Waldron, Susan; Newton, Jason; Garnett, Mark H.

    2017-04-01

    The role played by rivers in regional and global C budgets is receiving increasing attention. A large portion of the carbon transported via inland waters is returned to the atmosphere by carbon dioxide evasion from rivers and lakes. Karst landscapes represent an important C store on land, and are also considered to play an important role in climate regulation by consuming atmospheric CO2 during chemical weathering. However, we cannot be certain how effective this sink is if we do not know how efficiently the rivers draining karst landscapes remobilise weathered C to the atmosphere as CO2. pCO2 in karst waters is generally greater than atmospheric equilibrium, indicating that there can be a net CO2 efflux to the atmosphere. However, measurement confirming this and quantifying flux rates has been rarely conducted. Using a floating chamber method, in 2016 we directly measured CO2 fluxes from spatially distributed freshwaters (springs, sinkholes, streams and reservoirs/ponds) in the Houzhai Catchment, a karst region in SW China. Fluxes ranged from -0.5 to +267.4 μmol CO2 m-2s-1, and most sites showed seasonal variations with higher CO2 efflux rates in the wet (April - September) than dry season (October - March). There was a significant positive relationship between CO2 efflux and flow velocity, indicating that hydraulic controls on CO2 efflux from flowing water are important, while for water with little movement (sinkholes and reservoirs/ponds), pCO2 appears a more important control on efflux rates. Conditions similar to this study area may exist in many sub-tropical rivers that drain karst landscapes in South China. These waters are rich in DIC which can be an order of magnitude greater than some non-karst catchments. The large DIC pool has the potential to be a considerable source of free CO2 to the atmosphere. Considering that carbonate lithology covers a significant part of the Earth's surface, CO2 evasion in fluvial water from these regions is expected to

  6. Effect of water addition and nitrogen fertilization on the fluxes of CH4, CO2, NOx, and N2O following five years of elevated CO2 in the Colorado Shortgrass Steppe

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    A. R. Mosier

    2003-01-01

    Full Text Available An open-top-chamber (OTC CO2 enrichment (~720 mmol mol-1 study was conducted in the Colorado shortgrass steppe from April 1997 through October 2001. Aboveground plant biomass increased under elevated CO2 and soil moisture content was typically higher than under ambient CO2 conditions. Fluxes of CH4, CO2, NOx and N2O, measured weekly year round were not significantly altered by CO2 enrichment over the 55 month period of observation. During early summer of 2002, following the removal of the open-top-chambers from the CO2 enrichment sites in October 2001, we conducted a short term study to determine if soil microbial processes were altered in soils that had been exposed to double ambient CO2 concentrations during the growing season for the past five years. Microplots were established within each experimental site and 10 mm of water or 10 mm of water containing the equivalent of 10 g m-2 of ammonium nitrate-N was applied to the soil surface. Fluxes of CO2, CH4, NOx and N2O fluxes within control (unchambered, ambient CO2 and elevated CO2 OTC soils were measured at one to three day intervals for the next month. With water addition alone, CO2 and NO emission did not differ between ambient and elevated CO2 soils, while CH4 uptake rates were higher and N2O fluxes lower in elevated CO2 soils. Adding water and mineral N resulted in increased CO2 emissions, increased CH4 uptake and decreased NO emissions in elevated CO2 soils. The N addition study confirmed previous observations that soil respiration is enhanced under elevated CO2 and N immobilization is increased, thereby decreasing NO emission.

  7. Can we distinguish autotrophic respiration from heterotrophic respiration in a field site using high temporal resolution CO2 flux measurements?

    Science.gov (United States)

    Biro, Beatrice; Berger, Sina; Praetzel, Leandra; Blodau, Christian

    2016-04-01

    The processes behind C-cycling in peatlands are important to understand for assessing the vulnerability of peatlands as carbon sinks under changing climate conditions. Especially boreal peatlands are likely to underlie strong alterations in the future. It is expected that C-pools that are directly influenced by vegetation and water table fluctuations can be easily destabilized. The CO2 efflux through respiration underlies autotrophic and heterotrophic processes that show different feedbacks on changing environmental conditions. In order to understand the respiration fluxes better for more accurate modelling and prognoses, the determination of the relative importance of different respiration sources is necessary. Earlier studies used e.g. exfoliation experiments, incubation experiments or modelling approaches to estimate the different respiration sources for the total ecosystem respiration (Reco). To further the understanding in this topic, I want to distinguish autotrophic and heterotrophic respiration using high temporal resolution measurements. The study site was selected along a hydrological gradient in a peatland in southern Ontario (Canada) and measurements were conducted from May to September 2015 once per month. Environmental controls (water table, soil temperature and soil moisture) that effect the respiration sources were recorded. In my study I used a Li-COR 6400XT and a Los Gatos greenhouse gas analyzer (GGA). Reco was determined by chamber flux measurements with the GGA, while simultaneously CO2 respiration measurements on different vegetation compartments like roots, leaves and mosses were conducted using the Li-COR 6400XT. The difference between Reco and autotrophic respiration equals heterotrophic respiration. After the measurements, the vegetation plots were harvested and separated for all compartments (leaves, roots, mosses, soil organic matter), dried and weighed. The weighted respiration rates from all vegetation compartments sum up to

  8. Environment and phenology: CO2 net ecosystem exchange and CO2 flux partitioning at an acid and oligotrophic mire system in northern Sweden

    Science.gov (United States)

    Gažovič, Michal; Peichl, Matthias; Vermeij, Ilse; Limpens, Juul; Nilsson, Mats. B.

    2015-04-01

    Static chamber and environmental measurements in combination with vegetation indices (i.e. vascular green area (VGA) and the greenness chromatic color index (gcc) derived from digital camera images) were used to investigate effects of environment and phenology on the CO2 net ecosystem exchange (NEE) and CO2 flux partitioning at the Degerö Stormyr site in northern Sweden (64°11' 23.565" N, 19°33' 55.291 E) during two environmentally different years. Our measurement design included a control plot, a moss plot (where vascular plants were removed by clipping) and four heterotrophic respiration (RH) collars (where all green moss and vascular plant biomass were removed) to partition between soil heterotrophic and plant autotrophic (moss and vascular plants) respiration (RA), as well as between moss and vascular plant gross primary production (GPP). Environmental conditions, especially the shallow snow cover, peat soil frost and cold spring in 2014 caused delayed onset of spring green up, reduced soil respiration flux and reduced GPP of vascular plants. Soil temperature measured in 26 cm depth started to rise from spring temperatures of ~ 0.6 °C in 2013 and 0.15 °C in 2014 about 20 days earlier in 2013 compared to 2014. With earlier onset of the growing season and higher soil temperatures in 2013, heterotrophic soil respiration was higher in year 2013 than in year 2014. In 2013, RH dominated the total ecosystem respiration in all months but June and August. On contrary, autotrophic respiration dominated ecosystem respiration in all months of 2014. In both years, vascular plants and mosses were more or less equally contributing to autotrophic respiration. We measured higher GPP in year 2013 compared to year 2014. Also VGA and gcc were higher in spring and throughout the rest of 2013 compared to 2014. The onset of VGA was delayed by ~ 10 days in 2014. In general, total GPP was dominated by GPP of vascular plants in both years, although moss GPP had substantial

  9. Responses of CH(4), CO(2) and N(2)O fluxes to increasing nitrogen deposition in alpine grassland of the Tianshan Mountains.

    Science.gov (United States)

    Li, Kaihui; Gong, Yanming; Song, Wei; He, Guixiang; Hu, Yukun; Tian, Changyan; Liu, Xuejun

    2012-06-01

    To assess the effects of nitrogen (N) deposition on greenhouse gas (GHG) fluxes in alpine grassland of the Tianshan Mountains in central Asia, CH(4), CO(2) and N(2)O fluxes were measured from June 2010 to May 2011. Nitrogen deposition tended to significantly increase CH(4) uptake, CO(2) and N(2)O emissions at sites receiving N addition compared with those at site without N addition during the growing season, but no significant differences were found for all sites outside the growing season. Air temperature, soil temperature and water content were the important factors that influence CO(2) and N(2)O emissions at year-round scale, indicating that increased temperature and precipitation in the future will exert greater impacts on CO(2) and N(2)O emissions in the alpine grassland. In addition, plant coverage in July was also positively correlated with CO(2) and N(2)O emissions under elevated N deposition rates. The present study will deepen our understanding of N deposition impacts on GHG balance in the alpine grassland ecosystem, and help us assess the global N effects, parameterize Earth System models and inform decision makers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Contrasting ecosystem CO2 fluxes of inland and coastal wetlands: a meta-analysis of eddy covariance data.

    Science.gov (United States)

    Lu, Weizhi; Xiao, Jingfeng; Liu, Fang; Zhang, Yue; Liu, Chang'an; Lin, Guanghui

    2017-03-01

    Wetlands play an important role in regulating the atmospheric carbon dioxide (CO2 ) concentrations and thus affecting the climate. However, there is still lack of quantitative evaluation of such a role across different wetland types, especially at the global scale. Here, we conducted a meta-analysis to compare ecosystem CO2 fluxes among various types of wetlands using a global database compiled from the literature. This database consists of 143 site-years of eddy covariance data from 22 inland wetland and 21 coastal wetland sites across the globe. Coastal wetlands had higher annual gross primary productivity (GPP), ecosystem respiration (Re ), and net ecosystem productivity (NEP) than inland wetlands. On a per unit area basis, coastal wetlands provided large CO2 sinks, while inland wetlands provided small CO2 sinks or were nearly CO2 neutral. The annual CO2 sink strength was 93.15 and 208.37 g C m(-2) for inland and coastal wetlands, respectively. Annual CO2 fluxes were mainly regulated by mean annual temperature (MAT) and mean annual precipitation (MAP). For coastal and inland wetlands combined, MAT and MAP explained 71%, 54%, and 57% of the variations in GPP, Re , and NEP, respectively. The CO2 fluxes of wetlands were also related to leaf area index (LAI). The CO2 fluxes also varied with water table depth (WTD), although the effects of WTD were not statistically significant. NEP was jointly determined by GPP and Re for both inland and coastal wetlands. However, the NEP/Re and NEP/GPP ratios exhibited little variability for inland wetlands and decreased for coastal wetlands with increasing latitude. The contrasting of CO2 fluxes between inland and coastal wetlands globally can improve our understanding of the roles of wetlands in the global C cycle. Our results also have implications for informing wetland management and climate change policymaking, for example, the efforts being made by international organizations and enterprises to restore coastal wetlands for

  11. Spatial variability of CO2 uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

    Science.gov (United States)

    Pirk, Norbert; Sievers, Jakob; Mertes, Jordan; Parmentier, Frans-Jan W.; Mastepanov, Mikhail; Christensen, Torben R.

    2017-06-01

    The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of -46 gC m-2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (-82 gC m-2). Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

  12. On the calculation of air-sea fluxes of CO2 in the presence of temperature and salinity gradients

    Science.gov (United States)

    Woolf, D. K.; Land, P. E.; Shutler, J. D.; Goddijn-Murphy, L. M.; Donlon, C. J.

    2016-02-01

    The presence of vertical temperature and salinity gradients in the upper ocean and the occurrence of variations in temperature and salinity on time scales from hours to many years complicate the calculation of the flux of carbon dioxide (CO2) across the sea surface. Temperature and salinity affect the interfacial concentration of aqueous CO2 primarily through their effect on solubility with lesser effects related to saturated vapor pressure and the relationship between fugacity and partial pressure. The effects of temperature and salinity profiles in the water column and changes in the aqueous concentration act primarily through the partitioning of the carbonate system. Climatological calculations of flux require attention to variability in the upper ocean and to the limited validity of assuming "constant chemistry" in transforming measurements to climatological values. Contrary to some recent analysis, it is shown that the effect on CO2 fluxes of a cool skin on the sea surface is large and ubiquitous. An opposing effect on calculated fluxes is related to the occurrence of warm layers near the surface; this effect can be locally large but will usually coincide with periods of low exchange. A salty skin and salinity anomalies in the upper ocean also affect CO2 flux calculations, though these haline effects are generally weaker than the thermal effects.

  13. Seasonal and diurnal variations in moisture, heat and CO2 fluxes over a typical steppe prairie in Inner Mongolia, China

    Directory of Open Access Journals (Sweden)

    M. Zhou

    2009-07-01

    Full Text Available In order to examine energy partitioning and CO2 exchange over a steppe prairie in Inner Mongolia, China, fluxes of moisture, heat and CO2 in the surface layer from June 2007 through June 2008 were calculated using the eddy covariance method. The study site was homogenous and approximately 1500 m×1500 m in size. Seasonal and diurnal variations in radiation components, energy components and CO2 fluxes are examined. Results show that all four radiation components changed seasonally, resulting in a seasonal variation in net radiation. The radiation components also changed diurnally. Winter surface albedo was higher than summer surface albedo because during winter the snow-covered surface increased the surface albedo. The seasonal variations in both sensible heat and CO2 fluxes were stronger than those of latent heat and soil heat fluxes. Sensible heat flux was the main consumer of available energy for the entire experimental period. The energy imbalance problem was encountered and the causes are analyzed.

  14. Eddy flux corrections for CO2 exchange in broad-leaved Korean pine mixed forest of Changbai Mountains

    Institute of Scientific and Technical Information of China (English)

    WU; Jiabing; GUAN; Dexin; SUN; Xiaomin; YU; Guirui; ZHAO; X

    2005-01-01

    Based on analysis of mechanisms causing energy no-closure and nocturnal low fluxes issues for CO2 exchange studies by eddy covariance method, corrections were done with the raw data sets obtained from Changbai Mountains forest flux site, to evaluate the impacts of sonic anemometer tilt, frequency response limitations and advection on estimation of CO2 exchange, respectively. The results show that the planar fit coordinate transforming method is superior to the streamline coordinate transforming method in tilt correction. The latter could cause a systematical underestimation of eddy fluxes relating with the angle of sensor and terrain tilt. The underestimation of CO2 and energy fluxes for frequency response limitations average 3.0% and 2.0% during daytime, respectively, which increase by 9.0% and 5.5% during nighttime, respectively. The corrections of frequency response limitations are closely related to atmospheric stability. The advection loss of CO2 fluxes is dominated by nocturnal vertical advection, which is at least 18% when the horizontal advection is neglected. It is suggested that more work be done to understand the characteristics of horizontal advection and turbulent eddies under a complexcircumstance.

  15. Influence of Co2+ in CaCO3 polymorphism.

    Science.gov (United States)

    González-López, Jorge; Fernández-González, Angeles; Jiménez, Amalia

    2014-05-01

    Cobalt is a trace element in the Earth crust but also a toxic metal. Furthermore, Co2+can accumulate in some specific areas due to both natural and anthropogenic factors and hence soils and groundwater can be contaminated. Numerous studies have demonstrated that toxic elements can be removed from aqueous solution by its incorporation in mineral structures. In particular, the uptake of divalent metallic cations in the crystal structure of calcium carbonates has been postulated as a valuable solution to resolve and / or reduce some environmental problems. Here, we have investigated the cobalt uptake during calcium carbonate precipitation at ambient conditions. It is well known that certain anions such as sulphate, chromate and selenite favour the precipitation of vaterite while other cations as Sr2+ or Mg2+, avoid the calcite crystallization favouring the aragonite precipitation. Similar scenery can be depicted for Co2+ behaviour since the precipitation of both aragonite and a low crystallinity phase from aqueous solution have been described. However, the evolution of the polymorphic transformations after the precipitation of the phases remains unknown. In the present work we have precipitated calcium carbonate at room temperature in the presence of a certain amount of Co2+. Then, the precipitated solid has been aged in the remaining aqueous solution for two months. The experiment was carried out by mixing two different aqueous solutions: a) 50 mL of CoCl2 (0.02M) and CaCl2(0.05M) and b) 50 mL of Na2CO3 (0.05M). The aging process was monitored after 5 minutes, 1, 5, 24, and 48 hours and 4, 7, 30 and 60 days by analysing both the aqueous solution and the aged solids. The evolution of the different crystalline phases in the solid was followed by X-ray Powder Diffraction, their morphology was observed by Scanning Electron Microscopy and their chemical composition was analysed by Energy-dispersive X-ray Spectroscopy. Furthermore, the aqueous solution has also been

  16. Application of Space Borne CO2 and Fluorescence Measurements to Detect Urban CO2 Emissions and Anthropogenic Influence on Vegetation

    Science.gov (United States)

    Paetzold, Johannes C.; Chen, Jia; Ruisinger, Veronika

    2017-04-01

    The Orbiting Carbon Observatory 2 (OCO-2) is a NASA satellite mission dedicated to make global, space-based observations of atmospheric, column-averaged carbon dioxide (XCO2). In addition, the OCO-2 also measures Solar Induced Chlorophyll Fluorescence (SIF). In our research we have studied the combination of OCO-2's XCO2 and SIF measurements for numerous urban areas on the different continents. Applying GIS and KML visualization techniques as well as statistical approaches we are able to reliably detect anthropogenic CO2 emissions in CO2 column concentration enhancements over urban areas. Moreover, we detect SIF decreases over urban areas compared to their rural vicinities. We are able to obtain those findings for urban areas on different continents, of diverse sizes, dissimilar topographies and urban constructions. Our statistical analysis finds robust XCO2 enhancements of up to 3 ppm for urban areas in Europe, Asia and North America. Furthermore, the analysis of SIF indicates that urban construction, population density and seasonality influence urban vegetation, which can be observed from space. Additionally, we find that OCO-2's SIF measurements have the potential to identify and approximate green areas within cities. For Berlin's Grunewald Forest as well as Mumbai's Sanjay Gandhi and Tungareshwar National Parks we observe enhancements in SIF measurements at sub-city scales.

  17. Towards a more harmonized processing of eddy covariance CO2 fluxes: algorithms and uncertainty estimation

    Directory of Open Access Journals (Sweden)

    T. Vesala

    2006-07-01

    Full Text Available Eddy covariance technique to measure CO2, water and energy fluxes between biosphere and atmosphere is widely spread and used in various regional networks. Currently more that 250 eddy covariance sites are active around the world measuring carbon exchange at high temporal resolution for different biomes and climatic conditions. These data are usually acquired using the same method but they need a set of corrections that are often differently applied to each site and in a subjective way. In this paper a new standardized set of corrections are proposed and the uncertainties introduced by these corrections are assessed for 8 different forest sites in Europe with a total of 12 yearly datasets. The uncertainties introduced on the two components GPP (Gross Primary Production and TER (Terrestrial Ecosystem Respiration are also discussed and a quantitative analysis presented . The results show that a standardized data processing is needed for an effective comparison across biomes and for underpinning inter-annual variability. The methodology presented in this paper has also been integrated in the European database of the eddy covariance measurements.

  18. Controlling mechanisms of surface partial pressure of CO2 in Jiaozhou Bay during summer and the influence of heavy rain

    Science.gov (United States)

    Li, Yunxiao; Yang, Xufeng; Han, Ping; Xue, Liang; Zhang, Longjun

    2017-09-01

    Due to the combined effects of natural processes and human activities, carbon source/sink processes and mechanisms in the coastal ocean are becoming more and more important in current ocean carbon cycle research. Based on differences in the ratio of total alkalinity (TA) to dissolved inorganic carbon (DIC) associated with terrestrial input, biological process (production and respiration), calcium carbonate (CaCO3) process (precipitation and dissolution) and CO2 evasion/invasion, we discuss the mechanisms controlling the surface partial pressure of CO2 (pCO2) in Jiaozhou Bay (JZB) during summer and the influence of heavy rain, via three cruises performed in mid-June, early July and late July of 2014. In mid-June and in early July, without heavy rain or obvious river input, sea surface pCO2 ranged from 521 to 1080 μatm and from 547 to 998 μatm, respectively. The direct input of DIC from sewage and the intense respiration produced large DIC additions and the highest pCO2 values in the northeast of the bay near the downtown of Qingdao. However, in the west of the bay, significant CaCO3 precipitation led to DIC removal but no obvious increase in pCO2, which was just close to that in the central area. Due to the shallow depth and longer water residence time in this region, this pattern may be related to the sustained release of CO2 into the atmosphere. In late July, heavy rain promoted river input in the western and eastern portions of JZB. Strong primary production led to a significant decrease in pCO2 in the western area, with the lowest pCO2 value of 252 μatm. However, in the northeastern area, the intense respiration remained, and the highest pCO2 value was 1149 μatm. The average air-sea CO2 flux in mid-June and early July was 20.23 mmol m- 2 d- 1 and 23.56 mmol m- 2 d- 1, respectively. In contrast, in late July, sources became sinks for atmospheric CO2 in the western and central areas of the bay, halving the average air-sea CO2 flux to a value of 10.58 mmol m- 2

  19. Soil management practice in Croatian vineyard affect CO2 fluxes and soil degradation in trafficking zones. First results

    Science.gov (United States)

    Bogunovic, Igor; Bilandzija, Darija; Andabaka, Zeljko; Stupic, Domagoj; Cacic, Marija; Brezinscak, Luka; Maletic, Edi; Pereira, Paulo; Kisic, Ivica

    2017-04-01

    Vineyards represent one of the most degradation prone types of intensively managed land on Earth. Steep slopes encourage grape producers to adopt environmental friendly soil management like mulching or continuous no-tillage. In this context, producers have concerns about efficient fertilisation practices and water competitions between vine and grasses in continuous no-tillage inter rows. Vineyards in semi-humid areas like Continental Croatia mostly not suffer from water deficit during growth. Nevertheless, lack of research of different soil management practices open dilemma about soil compaction concerns in intensively trafficked soils in vineyard of semi-humid areas. Soil compaction, determined by bulk density (BD), soil water content (SWC) and CO2 fluxes from trafficked inter row positions were recorded in 2016 in an experiment in which four different soil management systems were compared in a vineyard raised on a silty clay loam soil, near Zagreb, Croatia: No-tillage (NT) system, continuous tillage (CT) and yearly inversed grass covered (INV-GC) and tillage managed (INV-T) inter rows are subjected to intensive traffic. Grape yield and must quality of grape variety Chardonnay was also monitored. Tractor traffic increased the soil BD at 0-10 and 10-20 cm, but especially at the 0-10 cm depth. CT treatment record lowest compaction at 0-10 cm because of tillage. Soil water content showed better conservation possibilities of INV-GC in drier period. In wet period SWC possibilities are similar between treatments. The results of soil compaction under different management indicate that vineyard soil differently response to traffic intensity and impact on microfauna activity and CO2 emissions. INV-GC and NT managed soils record lower CO2 fluxes from vineyard soil compared to CT and INV-T treatments. Management treatments did not statistically influenced on grape yields. Several years of investigation is needed to confirm the overall impact of different management

  20. A new disjunct eddy-covariance system for BVOC flux measurements – validation on CO2 and H2O fluxes

    Directory of Open Access Journals (Sweden)

    N. Striebig

    2012-06-01

    Full Text Available The disjunct eddy covariance (DEC method is an interesting alternative to the conventional eddy covariance (EC method, because it allows the estimation of turbulent fluxes of species for which fast sensors are not available. A new disjunct sampling system (called MEDEE was developed and validated. This system was built with chemically inert materials. Air samples are grabbed quickly and alternately in two cylindrical reservoirs, whose internal pressures are regulated by a moving piston. It was designed to be operated either on ground or aboard an airplane (the French ATR-42 research aircraft. It is also compatible with most analysers since it transfers the air samples at a regulated pressure. For validating the system, DEC and EC measurements of CO2 and latent heat fluxes were performed concurrently during a field campaign. EC fluxes were first compared to simulated DEC (SDEC fluxes and then to actual DEC fluxes. The EC fluxes were in agreement with both the simulated and actual DEC fluxes. The EC fluxes compare well to SDEC fluxes (R2 = 0.92 and 0.68 for latent heat and CO2 fluxes, respectively and to actual DEC fluxes (R2 = 0.91 and 0.67 for latent heat and CO2 fluxes, respectively, in spite of low fluxes experienced during the campaign. This good agreement between the two techniques demonstrates that MEDEE is suitable for DEC measurements and highlights the DEC method as a reliable alternative to EC for slower sensors. A first field campaign focused on biogenic volatile organic compound (BVOC emissions was done to measure isoprene fluxes above a downy oak (Quercus Pubescens forest in the southeast of France. The measured emission rates were in good agreement with the values reported in earlier studies. Further analysis will be conducted from ground-based and airborne campaigns in the forthcoming years.

  1. An empirical model simulating diurnal and seasonal CO2 flux for diverse vegetation types and climate conditions

    Directory of Open Access Journals (Sweden)

    A. D. Richardson

    2009-04-01

    Full Text Available We present an empirical model for the estimation of diurnal variability in net ecosystem CO2 exchange (NEE in various biomes. The model is based on the use of a simple saturated function for photosynthetic response of the canopy, and was constructed using the AmeriFlux network dataset that contains continuous eddy covariance CO2 flux data obtained at 24 ecosystems sites from seven biomes. The physiological parameters of maximum CO2 uptake rate by the canopy and ecosystem respiration have biome-specific responses to environmental variables. The model uses simplified empirical expression of seasonal variability in biome-specific physiological parameters based on air temperature, vapor pressure deficit, and annual precipitation. The model was validated using measurements of NEE derived from 10 AmeriFlux and four AsiaFlux ecosystem sites. The predicted NEE had reasonable magnitude and seasonal variation and gave adequate timing for the beginning and end of the growing season; the model explained 83–95% and 76–89% of the observed diurnal variations in NEE for the AmeriFlux and AsiaFlux ecosystem sites used for validation, respectively. The model however worked less satisfactorily in two deciduous broadleaf forests, a grassland, a savanna, and a tundra ecosystem sites where leaf area index changed rapidly. These results suggest that including additional plant physiological parameters may improve the model simulation performance in various areas of biomes.

  2. Rapid measurements of CO2 flux density and water use efficiency of crop community%作物群体CO2通量和水分利用效率的快速测定

    Institute of Scientific and Technical Information of China (English)

    朱治林; 孙晓敏; 张仁华; 苏红波; 唐新斋

    2004-01-01

    In this paper, Eddy Correlation (EC) method was employed to measure the latent heat and CO2 flux density and to calculate Water Use Efficiency (WISE) of winter wheat community in Yucheng district, Shandong Province in 1997. The results showed that the CO2 flux density had an obvious diurnal change, with a maximum aboutl. 5 mg·s-1·m-2, which appeared at about 9 : 00-10 : 00 am in general. The WUE of wheat community presented a fall trend from morning to afternoon, and the CO2 flux density and WUE also had an obvious seasonal change, being lower in the early and late growth stages, and higher in the middle growth stage. The ranges of daily mean CO2 flux density and WUE were 0.2 - 0.9 mg·s-1·m-2 and 5 - 20 gCO2·kg-1 1H2O, respectively.

  3. Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions

    Directory of Open Access Journals (Sweden)

    A. Babenhauserheide

    2015-03-01

    Full Text Available Data assimilation systems allow for estimating surface fluxes of greenhouse gases from atmospheric concentration measurements. Good knowledge about fluxes is essential to understand how climate change affects ecosystems and to characterize feedback mechanisms. Based on assimilation of more than one year of atmospheric in-situ concentration measurements, we compare the performance of two established data assimilation models, CarbonTracker and TM5-4DVar, for CO2 flux estimation. CarbonTracker uses an Ensemble Kalman Filter method to optimize fluxes on ecoregions. TM5-4DVar employs a 4-D variational method and optimizes fluxes on a 6° × 4° longitude/latitude grid. Harmonizing the input data allows analyzing the strengths and weaknesses of the two approaches by direct comparison of the modelled concentrations and the estimated fluxes. We further assess the sensitivity of the two approaches to the density of observations and operational parameters such as temporal and spatial correlation lengths. Our results show that both models provide optimized CO2 concentration fields of similar quality. In Antarctica CarbonTracker underestimates the wintertime CO2 concentrations, since its 5-week assimilation window does not allow for adjusting the far-away surface fluxes in response to the detected concentration mismatch. Flux estimates by CarbonTracker and TM5-4DVar are consistent and robust for regions with good observation coverage, regions with low observation coverage reveal significant differences. In South America, the fluxes estimated by TM5-4DVar suffer from limited representativeness of the few observations. For the North American continent, mimicking the historical increase of measurement network density shows improving agreement between CarbonTracker and TM5-4DVar flux estimates for increasing observation density.

  4. Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions

    Directory of Open Access Journals (Sweden)

    A. Babenhauserheide

    2015-09-01

    Full Text Available Data assimilation systems allow for estimating surface fluxes of greenhouse gases from atmospheric concentration measurements. Good knowledge about fluxes is essential to understand how climate change affects ecosystems and to characterize feedback mechanisms. Based on the assimilation of more than 1 year of atmospheric in situ concentration measurements, we compare the performance of two established data assimilation models, CarbonTracker and TM5-4DVar (Transport Model 5 – Four-Dimensional Variational model, for CO2 flux estimation. CarbonTracker uses an ensemble Kalman filter method to optimize fluxes on ecoregions. TM5-4DVar employs a 4-D variational method and optimizes fluxes on a 6° × 4° longitude–latitude grid. Harmonizing the input data allows for analyzing the strengths and weaknesses of the two approaches by direct comparison of the modeled concentrations and the estimated fluxes. We further assess the sensitivity of the two approaches to the density of observations and operational parameters such as the length of the assimilation time window. Our results show that both models provide optimized CO2 concentration fields of similar quality. In Antarctica CarbonTracker underestimates the wintertime CO2 concentrations, since its 5-week assimilation window does not allow for adjusting the distant surface fluxes in response to the detected concentration mismatch. Flux estimates by CarbonTracker and TM5-4DVar are consistent and robust for regions with good observation coverage, regions with low observation coverage reveal significant differences. In South America, the fluxes estimated by TM5-4DVar suffer from limited representativeness of the few observations. For the North American continent, mimicking the historical increase of the measurement network density shows improving agreement between CarbonTracker and TM5-4DVar flux estimates for increasing observation density.

  5. Satellite observations reveal high variability and a decreasing trend in CO2 fluxes on the Scotian Shelf

    Directory of Open Access Journals (Sweden)

    J. E. Salisbury

    2010-07-01

    Full Text Available We develop an algorithm to compute pCO2 in the Scotian Shelf region (NW Atlantic from satellite-based estimates of chlorophyll-a concentration, sea-surface temperature, and observed wind speed. This algorithm is based on a high-resolution time-series of pCO2 observations from an autonomous mooring. At the mooring location (44.3° N and 63.3° W, the surface waters act as a source of CO2 to the atmosphere over the annual scale, with an outgassing of −1.1 mol C m−2 yr−1 in 2007/2008. A hindcast of air-sea CO2 fluxes from 1999 to 2008 reveals significant variability both spatially and from year to year. Over the decade, the shelf-wide annual air-sea fluxes range from an outgassing of −1.7 mol C m−2 yr−1 in 2002, to −0.02 mol C m−2 yr−1 in 2006. There is a gradient in the air-sea CO2 flux between the northeastern Cabot Strait region which acts as a net sink of CO2 with an annual uptake of 0.5 to 1.0 mol C m−2 yr−1, and the southwestern Gulf of Maine region which acts as a source ranging from −0.8 to −2.5 mol C m−2 yr−1. There is a decline, or a negative trend, in the air-sea pCO2 gradient of 23 μatm over the decade, which can be explained by a cooling of 1.3 °C over the same period. Regional conditions govern spatial, seasonal, and interannual variability on the Scotian Shelf, while multi-annual trends appear linked to the North Atlantic Oscillation.

  6. Spatial and seasonal variabilities of the stable carbon isotope composition of soil CO2 concentration and flux in complex terrain

    Science.gov (United States)

    Liang, Liyin L.; Riveros-Iregui, Diego A.; Risk, David A.

    2016-09-01

    Biogeochemical processes driving the spatial variability of soil CO2 production and flux are well studied, but little is known about the variability in the spatial distribution of the stable carbon isotopes that make up soil CO2, particularly in complex terrain. Spatial differences in stable isotopes of soil CO2 could indicate fundamental differences in isotopic fractionation at the landscape level and may be useful to inform modeling of carbon cycling over large areas. We measured the spatial and seasonal variabilities of the δ13C of soil CO2 (δS) and the δ13C of soil CO2 flux (δP) in a subalpine forest ecosystem located in the Rocky Mountains of Montana. We found consistently more isotopically depleted values of δS and δP in low and wet areas of the landscape relative to steep and dry areas. Our results suggest that the spatial patterns of δS and δP are strongly mediated by soil water and soil respiration rate. More interestingly, our analysis revealed different temporal trends in δP across the landscape; in high landscape positions δP became more positive, whereas in low landscape positions δP became more negative with time. These trends might be the result of differential dynamics in the seasonality of soil moisture and its effects on soil CO2 production and flux. Our results suggest concomitant yet independent effects of water on physical (soil gas diffusivity) and biological (photosynthetic discrimination) processes that mediate δS and δP and are important when evaluating the δ13C of CO2 exchanged between soils and the atmosphere in complex terrain.

  7. Mesoporous fluorocarbon-modified silica aerogel membranes enabling long-term continuous CO2 capture with large absorption flux enhancements.

    Science.gov (United States)

    Lin, Yi-Feng; Chen, Chien-Hua; Tung, Kuo-Lun; Wei, Te-Yu; Lu, Shih-Yuan; Chang, Kai-Shiun

    2013-03-01

    The use of a membrane contactor combined with a hydrophobic porous membrane and an amine absorbent has attracted considerable attention for the capture of CO2 because of its extensive use, low operational costs, and low energy consumption. The hydrophobic porous membrane interface prevents the passage of the amine absorbent but allows the penetration of CO2 molecules that are captured by the amine absorbent. Herein, highly porous SiO2 aerogels modified with hydrophobic fluorocarbon functional groups (CF3 ) were successfully coated onto a macroporous Al2 O3 membrane; their performance in a membrane contactor for CO2 absorption is discussed. The SiO2 aerogel membrane modified with CF3 functional groups exhibits the highest CO2 absorption flux and can be continuously operated for CO2 absorption for extended periods of time. This study suggests that a SiO2 aerogel membrane modified with CF3 functional groups could potentially be used in a membrane contactor for CO2 absorption. Also, the resulting hydrophobic SiO2 aerogel membrane contactor is a promising technology for large-scale CO2 absorption during the post-combustion process in power plants.

  8. Measurement and modelling of CO2 flux from a drained fen peatland cultivated with reed canary grass and spring barley

    DEFF Research Database (Denmark)

    Kandel, Tanka Prasad; Elsgaard, Lars; Lærke, Poul Erik

    2013-01-01

    Cultivation of bioenergy crops has been suggested as a promising option for reduction of greenhouse gas (GHG) emissions from arable organic soils (Histosols). Here, we report the annual net ecosystem exchange (NEE) fluxes of CO2 as measured with a dynamic closed chamber method at a drained fen pe...

  9. Changes In CO2 Gas Flux And Soil Temperatures Induced By A Vibratory Seismic Source At Solfatara (Phlegrean Fields, Italy).

    Science.gov (United States)

    Vandemeulebrouck, J.; Gresse, M.; Chiodini, G.; Byrdina, S.; Woith, H.; Bruno, P. P.

    2014-12-01

    Solfatara, the most active crater of Phlegrean Fields (Italy) is characterized by a fumarolic activity and an intense diffuse degassing, with 1500 tons of CO2 and > 3000 tons of water vapor released per day. A major part of the emitted water vapor is condensed at the near surface producing a thermal power flux around 100 MW, and contributing substantially to the total water input into the hydrothermal system. On May 2014, during a seismic experiment (RICEN) in the frame of the MED-SUV European project, a Minivib vibratory seismic source was used to generate a frequency modulated seismic signal at different points of Solfatara. We performed CO2 flux measurements at a few meters from the seismic source during the vibrations. In certain points, the vibrations induced a remarkable increase in the CO2 diffuse degassing, with a flux that doubled during the low-frequency seismic vibrations and returned to previous values afterwards. The observed CO2 flux increase could be due to permeability enhancement in the sub-surface soil layers during the seismic vibrations. Close to Fangaia mud pool, we also monitored the soil temperature at different levels above the condensation depth and observed transient temperature changes during the vibrations but also outside the vibration periods. Seismic vibrations likely favor the triggering of thermal instabilities of gravitational or convective origin in the liquid-saturated condensate layer.

  10. Investigations on distributions and fluxes of sea-air CO2 of the expedition areas in the Arctic Ocean

    Institute of Scientific and Technical Information of China (English)

    王伟强; 陈立奇; 杨绪林; 黄宣宝

    2003-01-01

    The distributions and fluxes of sea-air carbon dioxide were investigated the first time based on the firsthand data collected during the First Chinese National Arctic Research Expedition. The results revealed that values of atmospheric CO2 partial pressure (Pa) measured in the summer during the expedition fell between 352 and 370 ((10-6CO2·Air-1, same unit below) with an average value of 358. Particularly, Pa appeared high in the northern sea areas of Poitlay. However, the values of CO2 partial pressure at the surface layer of seawater (Pw) ranged from 98 to 580 with the difference between the low and high being 472. The average value of Pw was 242, which is 116 lower than that of the corresponding Pa. In addition, the distribution of Pw was roughly low in the west and north, but high in the east and south. These phenomena were closely related to plankton, ice, water temperature and circulation of the region. The estimation in carbon fluxes showed that the patterns in distribution were similar through different calculating methods with an exception in eastern sea areas of the region where a weak source of atmospheric CO2 was indicated. Most sea areas of the region were sinks or strong sinks of atmospheric CO2. However, the magnitudes in the fluxes were different. The average values varied from 6.57 (Liss method) to 26.32 mg(CO2·m-2·h-1 (14C method) with a difference of about 4 times between the low and high, which is 2 to 10 times as high as the global average. Compared with the fluxes in the same region obtained using model of Takahashi, Feely et al., the values determined based on Wanninkhof coefficient calculation were 2.38 times as great as those obtained by them.

  11. Termites as a factor of spatial differentiation of CO2 fluxes from the soils of monsoon tropical forests in Southern Vietnam

    Science.gov (United States)

    Lopes de Gerenyu, Valentin; Anichkin, Alexander

    2016-04-01

    wet season, the CO2 emission rate was considerably higher and reached 266±40 and 520 ± 39 mg C/m2/h in SurAr and TerPl, respectively. The highest rates of CO2 fluxes (730-880 mg C/m2/h) were observed in the wet season in some of the chambers installed on TerPl. In the tropical forest, termites are the factor of the significant spatial variability in the CO2 fluxes from the soils. On the plots populated by termites, the coefficient of variation of CO2 emission rates reached 79%, while it rarely exceeded 45% on the surrounding area. The termite mounds occupy about 4% of the area of tropical forest ecosystems. However, the overall effect of termites on the carbon budget was more significant and, according to our estimates, it reached up to 10% of the total annual CO2 flux from the soils. Thus, underestimation of the influence of termites may lead to significant errors in the assessment of the organic carbon budget in the semi-deciduous tropical forests.

  12. Methane and CO2 fluxes of moving point sources - Beyond or within the limits of eddy covariance measurements

    Science.gov (United States)

    Felber, Raphael; Neftel, Albrecht; Münger, Andreas; Ammann, Christof

    2014-05-01

    The eddy covariance (EC) technique has been extensively used for CO2 and energy exchange measurements over different ecosystems. For some years, it has been also becoming widely used to investigate CH4 and N2O exchange over ecosystems including grazing systems. EC measurements represent a spatially integrated flux over an upwind area (footprint). Whereas for extended homogenous areas EC measurements work well, the animals in a grazing system are a challenge as they represent moving point sources that create inhomogeneous conditions in space and time. The main issues which have to be taken into account when applying EC flux measurements over a grazed system are: i) In the presence of animals the high time resolution concentration measurements show large spikes in the signal. These spikes may be filtered/reduced by standard quality control software in order to avoid wrong measurements. ii) Data on the position of the animals relative to the flux footprint is needed to quantify the contribution of the grazing animals to the measured flux. For one grazing season we investigated the ability of EC flux measurements to reliably quantify the contribution of the grazing animals to the CH4 and CO2 exchange over pasture systems. For this purpose, a field experiment with a herd of twenty dairy cows in a full-day rotational grazing system was carried out on the Swiss central plateau. Net CH4 and CO2 exchange of the pasture system was measured continuously by the eddy covariance technique (Sonic Anemometer HS-50, Gill Instruments Ltd; FGGA, Los Gatos Research Inc.). To quantify the contribution of the animals to the net flux, the position of the individual cows was recorded using GPS (5 s time resolution) on each animal. An existing footprint calculation tool (ART footprint tool) was adapted and CH4 emissions of the cows were calculated. CH4 emissions from cows could be used as a tracer to investigate the quality of the evaluation of the EC data, since the background exchange of

  13. Global Monthly CO2 Flux Inversion Based on Results of Terrestrial Ecosystem Modeling

    NARCIS (Netherlands)

    Deng, F.; Chen, J.; Peters, W.; Krol, M.

    2008-01-01

    Most of our understanding of the sources and sinks of atmospheric CO2 has come from inverse studies of atmospheric CO2 concentration measurements. However, the number of currently available observation stations and our ability to simulate the diurnal planetary boundary layer evolution over continent

  14. Global Monthly CO2 Flux Inversion Based on Results of Terrestrial Ecosystem Modeling

    NARCIS (Netherlands)

    Deng, F.; Chen, J.; Peters, W.; Krol, M.

    2008-01-01

    Most of our understanding of the sources and sinks of atmospheric CO2 has come from inverse studies of atmospheric CO2 concentration measurements. However, the number of currently available observation stations and our ability to simulate the diurnal planetary boundary layer evolution over

  15. Ecosystem-scale CH4 and CO2 fluxes in a seasonally flooded scrub forest of the Brazilian Pantanal

    Science.gov (United States)

    Vourlitis, G. L.; Dalmagro, H. J.; Arruda, P. H. Z. D.; Lathuilliere, M. J.; Pinto-Jr, O. B.; Lobo, F. D. A.; Couto, E. G.; Nogueira, J. D. S.; Johnson, M. S.

    2015-12-01

    The Pantanal is the largest floodplain in South America, comprised of a mixture of savannah vegetation with patches of semi-deciduous and seasonally flooded forests. In this study we investigated ecosystem-scale methane (CH4) and carbon dioxide (CO2) fluxes and the possible factors that control these fluxes, such as the water level soil temperature and the soil redox potential. Trace gas fluxes were measured using an eddy covariance system installed on a 28 m tall tower. The study area was chosen because it is densely vegetated and experiences a seasonal flood pulse of about 6 months, which is typical for the Northern Pantanal. The measurements were performed over two flood cycles, from December to June 2013/2014 and 2014/2015. Methane fluxes showed a seasonal progression, with higher emission rates during the flooding period and near zero fluxes prior to inundation and again after recession. Major peaks of CH4 (0.30 μmol m-2 s-1) were observed after the soil became completely flooded and soil redox values were Pantanal are potentially large sinks for CO2 but strong sources for CH4, especially during the flood pulse when anaerobic soil conditions concomitantly enhance CH4 production and limit CO2 production

  16. Very high CO2 exchange fluxes at the peak of the rainy season in a West African grazed semi-arid savanna ecosystem

    DEFF Research Database (Denmark)

    Tagesson, Håkan Torbern; Ardoe, Jonas; Guiro, Idrissa;

    2016-01-01

    Africa is a sink of carbon, but there are large gaps in our knowledge regarding the CO2 exchange fluxes for many African ecosystems. Here, we analyse multi-annual eddy covariance data of CO2 exchange fluxes for a grazed Sahelian semi-arid savanna ecosystem in Senegal, West Africa. The aim of the ...... response to climate change.......Africa is a sink of carbon, but there are large gaps in our knowledge regarding the CO2 exchange fluxes for many African ecosystems. Here, we analyse multi-annual eddy covariance data of CO2 exchange fluxes for a grazed Sahelian semi-arid savanna ecosystem in Senegal, West Africa. The aim...

  17. Estimation of CO2 storage flux between forest and atmosphere in a tropical forest.%热带森林植被冠层CO2储存项的估算方法研究

    Institute of Scientific and Technical Information of China (English)

    姚玉刚; 张一平; 于贵瑞; 宋清海; 谭正洪; 赵俊斌

    2011-01-01

    评价植被冠层CO2储存项有助于提高森林-大气层面净生态系统CO2交换量(FNEE)的估算精度.基于西双版纳热带季节雨林2年完整的涡度相关系统和CO2廓线的同步观测资料,详细分析涡度相关法(Fs-EC)和廓线法(Fs-PM)CO2储存项估算结果和变化趋势.结果表明:1)廓线法CO2储存项年平均日变化曲线相比涡度相关法能更真实地反映冠层内外CO2浓度时空变化特征.2)廓线法估算的CO2储存项年总量值为-0.04 t/(hm2·a),涡度相关法为-0.17 t/(hm2·a).3)由于复杂地形条件下的西双版纳热带季节雨林存在较大CO2浓度梯度,采用廓线法进行CO2储存项估算比涡度相关法更为合适.%Evaluating CO2 storage flux may help us to improve the calculation accuracy of net ecosystem CO2 exchange (FNEE). Based on data of two consecutive years from an eddy covariance system and a vertical CO2 profile system in a tropical seasonal rainforest in Xishuangbanna, southwest China, CO2 storage flux was calculated by two methods, eddy covariance ( F.-EC ) and profile ( F.-PM ) methods. Results show that:1 ) Comparing with eddy covariance method, diurnal variation of CO2 storage flux calculated by profile method could directly reflect the spatial-temporal variation of CO2; 2) Total amount value of CO2 storage flux calculated by profile method was -0. 04 t/( hm2· year), and the value calculated by eddy covariance method was -0. 17 t/(hm2 ·year); 3) Under complex terrain and tall forest conditions, with a large concentration gradient of CO2, profile method for calculation of CO2 storage flux had an advantage over eddy covariance method.

  18. An Inversion Analysis of Recent Variability in Natural CO2 Fluxes Using GOSAT and In Situ Observations

    Science.gov (United States)

    Wang, James S.; Kawa, S. Randolph; Collatz, G. James; Baker, David F.; Ott, Lesley

    2015-01-01

    About one-half of the global CO2 emissions from fossil fuel combustion and deforestation accumulates in the atmosphere, where it contributes to global warming. The rest is taken up by vegetation and the ocean. The precise contribution of the two sinks, and their location and year-to-year variability are, however, not well understood. We use two different approaches, batch Bayesian synthesis inversion and variational data assimilation, to deduce the global spatiotemporal distributions of CO2 fluxes during 2009-2010. One of our objectives is to assess different sources of uncertainties in inferred fluxes, including uncertainties in prior flux estimates and observations, and differences in inversion techniques. For prior constraints, we utilize fluxes and uncertainties from the CASA-GFED model of the terrestrial biosphere and biomass burning driven by satellite observations and interannually varying meteorology. We also use measurement-based ocean flux estimates and two sets of fixed fossil CO2 emissions. Here, our inversions incorporate column CO2 measurements from the GOSAT satellite (ACOS retrieval, filtered and bias-corrected) and in situ observations (individual flask and afternoon-average continuous observations) to estimate fluxes in 108 regions over 8-day intervals for the batch inversion and at 3 x 3.75 weekly for the variational system. Relationships between fluxes and atmospheric concentrations are derived consistently for the two inversion systems using the PCTM atmospheric transport model driven by meteorology from the MERRA reanalysis. We compare the posterior fluxes and uncertainties derived using different data sets and the two inversion approaches, and evaluate the posterior atmospheric concentrations against independent data including aircraft measurements. The optimized fluxes generally resemble those from other studies. For example, the results indicate that the terrestrial biosphere is a net CO2 sink, and a GOSAT-only inversion suggests a shift in

  19. Systematic errors in global air-sea CO2 flux caused by temporal averaging of sea-level pressure

    Directory of Open Access Journals (Sweden)

    H. Kettle

    2005-01-01

    Full Text Available Long-term temporal averaging of meteorological data, such as wind speed and air pressure, can cause large errors in air-sea carbon flux estimates. Other researchers have already shown that time averaging of wind speed data creates large errors in flux due to the non-linear dependence of the gas transfer velocity on wind speed (Bates and Merlivat, 2001. However, in general, wind speed is negatively correlated with air pressure, and a given fractional change in the pressure of dry air produces an equivalent fractional change in the atmospheric partial pressure of carbon dioxide (pCO2air. Thus low pressure systems cause a drop in pCO2air, which together with the associated high winds, promotes outgassing/reduces uptake of CO2 from the ocean. Here we quantify the errors in global carbon flux estimates caused by using monthly or climatological pressure data to calculate pCO2air (and thus ignoring the covariance of wind and pressure over the period 1990-1999, using two common parameterisations for gas transfer velocity. Results show that on average, compared with estimates made using 6 hourly pressure data, the global oceanic sink is systematically overestimated by 7% (W92 and 10% (WM99 when monthly mean pressure is used, and 9% (W92 and 12% (WM99 when climatological pressure is used.

  20. Systematic errors in global air-sea CO2 flux caused by temporal averaging of sea-level pressure

    Directory of Open Access Journals (Sweden)

    C. J. Merchant

    2005-01-01

    Full Text Available Long-term temporal averaging of meteorological data, such as wind speed and air pressure, can cause large errors in air-sea carbon flux estimates. Other researchers have already shown that time averaging of wind speed data creates large errors in flux due to the non-linear dependence of the gas transfer velocity on wind speed (Bates and Merlivat, 2001. However, in general, wind speed is negatively correlated with air pressure, and a given fractional change in the pressure of dry air produces an equivalent fractional change in the atmospheric partial pressure of carbon dioxide (pCO2air. Thus low pressure systems cause a drop in pCO2air, which together with the associated high winds, promotes outgassing/reduces uptake of CO2 from the ocean. Here we quantify the errors in global carbon flux estimates caused by using monthly or climatological pressure data to calculate pCO2air (and thus ignoring the covariance of wind and pressure over the period 1990–1999, using two common parameterisations for gas transfer velocity (Wanninkhof, 1992 (W92 and Wanninkhof and McGillis, 1999 (WM99. Results show that on average, compared with estimates made using 6 hourly pressure data, the global oceanic sink is systematically overestimated by 7% (W92 and 10% (WM99 when monthly mean pressure is used, and 9% (W92 and 12% (WM99 when climatological pressure is used.

  1. Estimating carbon fluxes for North America from a joint inversion for CO2 and COS using STILT

    Science.gov (United States)

    Chen, H.; Petron, G.; Trudeau, M. E.; Karion, A.; Koch, F. T.; Kretschmer, R.; Gerbig, C.; Campbell, J. E.; Berry, J. A.; Baker, I. T.; Nehrkorn, T.; Eluszkiewicz, J.; Miller, B. R.; Montzka, S. A.; Jacobson, A. R.; Sweeney, C.; Andrews, A. E.; Tans, P. P.

    2011-12-01

    Understanding biospheric CO2 fluxes is paramount if climate studies are to be able to analyze the response of terrestrial ecosystems to climate change and monitor fossil fuel emissions reductions. Carbonyl sulfide (COS) may be a useful tracer to provide a constraint on photosynthesis [gross primary production (GPP)]. Here we simulate both COS and CO2 using the Stochastic Time-Inverted Lagrangian Transport (STILT) model coupled with various biospheric fluxes, such as fluxes estimated from the Vegetation Photosynthesis and Respiration Model (VPRM), CarbonTracker, and from the Carnegie-Ames-Stanford Approach (CASA) model. The STILT model is driven by Weather Research and Forecast (WRF) meteorological fields. The WRF-STILT system is compared with the STILT driven by the ECMWF (European Center for Medium range Weather Forecasting) meteorology for the North American domain. This study uses measurements of COS and CO2 in 2008 from the NOAA/ESRL tall tower and aircraft air sampling networks, with ~ 6,000 observations in total. Biospheric COS fluxes will be estimated from a GPP-based model coupled with the GPP estimates from above mentioned biosphere models. Soil uptakes of COS are derived from a biosphere model (SiB) that assimilates the soil moisture and temperature. Estimation of other COS fluxes, such as anthropogenic, biomass burning are based on existing analyses of temporal and spatial variations. Empirical boundary curtains are built based on observations at the NOAA/ESRL marine boundary layer stations and from aircraft vertical profiles, and are utilized as the lateral boundary conditions for COS and CO2 for North America. Comparison of the simulations for both COS and CO2 using different biospheric fluxes provides an opportunity to assess the performance of both the biospheric models and the representation of atmospheric transport. In addition, we will estimate the carbon fluxes for North America from a joint inversion for COS and CO2 in a Bayesian synthesis

  2. Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China.

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G L; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-06-14

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y(-1) of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y(-1), equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the "hotspots," largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m(-2)⋅y(-1)), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

  3. Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G. L.; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-06-01

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt Cṡy-1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt Cṡy-1, equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely distributed in mountainous regions in the most intensive sink areas (>40 g Cṡm-2ṡy-1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

  4. Temporal and spatial variations of soil CO2, CH4 and N2O fluxes at three differently managed grasslands

    Directory of Open Access Journals (Sweden)

    D. Imer

    2013-09-01

    Full Text Available A profound understanding of temporal and spatial variabilities of soil carbon dioxide (CO2, methane (CH4 and nitrous oxide (N2O fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three soil greenhouse gas (GHG fluxes occur due to changes in environmental drivers as well as fertilizer applications, harvests and grazing. To assess how such changes affect soil GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed to 1000 m a.s.l. (moderately intensive managed to 2000 m a.s.l. (extensively managed. The alpine grassland was included to study both effects of extensive management on CH4 and N2O fluxes and the different climate regime occurring at this altitude. Temporal and spatial variabilities of soil GHG fluxes and environmental drivers on various timescales were determined along transects of 16 static soil chambers at each site. All three grasslands were N2O sources, with mean annual soil fluxes ranging from 0.15 to 1.28 nmol m−2 s−1. Contrastingly, all sites were weak CH4 sinks, with soil uptake rates ranging from −0.56 to −0.15 nmol m−2 s−1. Mean annual soil and plant respiration losses of CO2, measured with opaque chambers, ranged from 5.2 to 6.5 μmol m−2 s−1. While the environmental drivers and their respective explanatory power for soil N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42, CH4 and CO2 soil fluxes were much better constrained (adjusted r2 ranging from 0.46 to 0.80 by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for soil N2O and CH4 fluxes. We found permanent hot spots for soil N2O emissions as well as

  5. Analysis of CO2 Fluxes: Inclusion of Wall Conductance (Gw on the Estimation of Rubisco Activity, Vcmax of Soybean Leaves

    Directory of Open Access Journals (Sweden)

    TANIA JUNE

    2011-03-01

    Full Text Available In global change research, where modelling of CO2 fluxes from plants is an important component in determining vegetation capacity to protect the climate, mechanistic-based modelling is needed when projection of future CO2 absorption dynamics need to be estimated more accurately. Rubisco is the world’s most abundant protein in plants and has the job of uniquely preparing CO2 for chemical reduction. Rubisco activity in the leaf, described by Vcmax, can be estimated from gas exchange measurements of the initial slope of the response of CO2 assimilation rate, A, to intercellular [CO2]. This technique of estimation is favourable because it can avoid the uncertainties and difficulties when Vcmax is obtained directly by extraction and biochemical assay in artificial media. Rate of assimilation of soybean plants grown at different temperature (20/15, 25/20, and 32/27 oC day/night temperature and [CO2] (350 and 700 mol mol-1, were measured using gas exchange. The effect of wall conductance (gw on the parameterization of assimilations rate was observed. The temperature dependence of Vcmax depends strongly on wall conductance, where the shape of the curve would change significantly if finite wall conductance were included in the analysis. The implication is that it changes the values and interpretation of the temperature response of assimilation rate.

  6. Effect of microtopography and species composition on small-scale variability of CO2 fluxes in a subalpine grassland

    Science.gov (United States)

    Galvagno, Marta; Filippa, Gianluca; Cremonese, Edoardo; Morra di Cella, Umberto; Isabellon, Michel

    2015-04-01

    Grassland ecosystems cover around 30% of the Earth's land surface and consequently play an important role in the terrestrial carbon balance. Climate and land use changes have a significant effect on the sink/source strength of grasslands, especially in mountain regions. For these reasons the carbon cycle of high-altitude grasslands has recently received higher attention, however little is know on the within-ecosystem variability in CO2 fluxes. In fact, alpine and subalpine grasslands are often characterized by complex topography which generates differences in snowmelt dynamics at site level and related different microhabitats. The deriving patchy distribution of vegetation leads to the coexistence of different plant functional traits and developmental strategies within the same ecosystem. In this study we evaluated the effect of microtopography and associated vegetation types on the CO2 flux components of an unamanaged subalpine grassland located at 2160 m asl, by means of automated clear and opaque chambers. In order to disentangle the contribution of different growth forms to the whole ecosystem carbon sequestration we compare chambers with eddy covariance CO2 flux data. Results show that: i) different growth forms are associated with concave o convex shapes of the terrain and, in detail, grass species dominate in convex areas while forbs are especially found in concave ones ii) two distinct CO2 flux trajectories associated to these shapes can be distinguished in this ecosystem: graminoids show a later beginning of the carbon uptake period but higher CO2 net uptake (NEE), while forbs develop just after snowmelt but show lower NEE. The observed small-scale patterns of carbon sequestration may reflect the distinct vegetation type responses to snowmelt and different adaptations to resource use efficiency (light, temperature, nutrients) specific of their own microhabitat. Further investigations will be carried on to better evaluate the role of microhabitat

  7. Influence of methane in CO2 transport and storage for CCS technology.

    Science.gov (United States)

    Blanco, Sofía T; Rivas, Clara; Fernández, Javier; Artal, Manuela; Velasco, Inmaculada

    2012-12-04

    CO(2) Capture and Storage (CCS) is a good strategy to mitigate levels of atmospheric greenhouse gases. The type and quantity of impurities influence the properties and behavior of the anthropogenic CO(2), and so must be considered in the design and operation of CCS technology facilities. Their study is necessary for CO(2) transport and storage, and to develop theoretical models for specific engineering applications to CCS technology. In this work we determined the influence of CH(4), an important impurity of anthropogenic CO(2), within different steps of CCS technology: transport, injection, and geological storage. For this, we obtained new pressure-density-temperature (PρT) and vapor-liquid equilibrium (VLE) experimental data for six CO(2) + CH(4) mixtures at compositions which represent emissions from the main sources in the European Union and United States. The P and T ranges studied are within those estimated for CO(2) pipelines and geological storage sites. From these data we evaluated the minimal pressures for transport, regarding the density and pipeline's capacity requirements, and values for the solubility parameter of the mixtures, a factor which governs the solubility of substances present in the reservoir before injection. We concluded that the presence of CH(4) reduces the storage capacity and increases the buoyancy of the CO(2) plume, which diminishes the efficiency of solubility and residual trapping of CO(2), and reduces the injectivity into geological formations.

  8. Probe Into the Influence of Crosslinking on CO2 Permeation of Membranes

    Science.gov (United States)

    Li, Jinghui; Chen, Zhuo; Umar, Ahmad; Liu, Yang; Shang, Ying; Zhang, Xiaokai; Wang, Yao

    2017-01-01

    Crosslinking is an effective way to fabricate high-selective CO2 separation membranes because of its unique crosslinking framework. Thus, it is essentially significant to study the influence of crosslinking degree on the permeation selectivities of CO2. Herein, we report a successful and facile synthesis of a series of polyethylene oxide (PEO)-based diblock copolymers (BCP) incorporated with an unique UV-crosslinkable chalcone unit using Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) process. The membranes of as-prepared BCPs show superior carbon dioxide (CO2) separation properties as compared to nitrogen (N2) after UV-crosslinking. Importantly, the influence of different proportions of crosslinked chalcone on CO2 selectivities was systematically investigated, which revealed that CO2 selectivities increased obviously with the enhancement of chalcone fractions within a certain limit. Further, the CO2 selectivities of block copolymer with the best block proportion was studied by varying the crosslinking time which confirmed that the high crosslinking degree exhibited a better CO2/N2 (αCO2/N2) selectivities. A possible mechanism model revealing that the crosslinking degree played a key role in the gas separation process was also proposed. PMID:28051190

  9. Gross primary productivity of the true steppe in central Asia in relation to NDVI: scaling up CO2 fluxes

    Science.gov (United States)

    Gilmanov, Tagir G.; Johnson, Douglas A.; Saliendra, Nicanor Z.; Akshalov, Kanat; Wylie, Bruce K.

    2004-01-01

    Compared to other characteristics of CO2 exchange, gross primary productivity (P g ) is most directly related to photosynthetic activity. Until recently, it was considered difficult to obtain measurement-based P g . The objective of our study was to evaluate if P g can be estimated from continuous CO2 flux measurements using nonlinear identification of the nonrectangular hyperbolic model of ecosystem-scale, light-response curves. Estimates of P g and ecosystem respiration (R e ) were obtained using Bowen ratio– energy-balance measurements of CO2 exchange in a true-steppe ecosystem in northern Kazakhstan during four growing seasons (1998–2001). The maximum mean weekly apparent quantum yield (αmax) was 0.0388 mol CO2 mol photons and the maximum mean weekly P g was 28 g CO2/m2/day in July 2000. The highest mean weekly R e max (20 g CO2m2/day) was observed in July of both 1999 and 2000. Nighttime respiration calculated from daily respiration corrected for length of the dark period and temperature (using Q 10 = 2) was closely associated with measured nighttime respiration (R 2 = 0.67 to 0.93). The 4-year average annual gross primary production (GPP) was 1617 g CO2/m2/ year (range = 1308–1957). Ten-day normalized difference vegetation index corrected for the start of the season (NDVIsos) was closely associated with 10-day average P g (R 2 = 0.66 to 0.83), which was higher than R 2 values for regressions of mean 10-day net daytime fluxes on NDVIsos (0.55–0.72). This demonstrates the advantage of usingP g in scaling up flux-tower measurements compared to other characteristics (net daytime flux or net 24-h flux).

  10. CO2, CH4 and N2O fluxes from soil of a burned grassland in Central Africa

    Directory of Open Access Journals (Sweden)

    R. Valentini

    2010-11-01

    Full Text Available The impact of fire on soil fluxes of CO2, CH4 and N2O was investigated in a tropical grassland in Congo Brazzaville during two field campaigns in 2007–2008. The first campaign was conducted in the middle of the dry season and the second at the end of the growing season, respectively one and eight months after burning. Gas fluxes and several soil parameters were measured in each campaign from burned plots and from a close-by control area preserved from fire. Rain events were simulated at each campaign to evaluate the magnitude and duration of the generated gas flux pulses. In laboratory experiments, soil samples from field plots were analysed for microbial biomass, net N mineralization, net nitrification, N2O, NO and CO2 emissions under different water and temperature soil regimes. One month after burning, field CO2 emissions were significantly lower in burned plots than in the control plots, the average daily CH4 flux shifted from net emission in the unburned area to net consumption in burned plots, no significant effect of fire was observed on soil N2O fluxes. Eight months after burning, the average daily fluxes of CO2, CH4 and N2O measured in control and burned plots were not significantly different. In laboratory, N2O fluxes from soil of burned plots were significantly higher than fluxes from soil of unburned plots only above 70% of maximum soil water holding capacity; this was never attained in the field even after rain simulation. Higher NO emissions were measured in the lab in soil from burned plots at both 10% and 50% of maximum soil water holding capacity. Increasing the incubation temperature from 25 °C to 37 °C negatively affected microbial growth, mineralization and nitrification activities but enhanced N2O and CO2 production. Results indicate that fire did not increase post-burning soil GHG emissions in this tropical grasslands characterized by acidic, well drained and nutrient-poor soil.

  11. High-resolution estimates of net community production and air-sea CO2 flux in the northeast Pacific

    Science.gov (United States)

    Lockwood, Deirdre; Quay, Paul D.; Kavanaugh, Maria T.; Juranek, Lauren W.; Feely, Richard A.

    2012-12-01

    Rates of net community production (NCP) and air-sea CO2 flux in the Northeast Pacific subarctic, transition zone and subtropical regions (22°N-50°N, 145°W-152°W) were determined on a cruise in August-September 2008 by continuous measurement of surface values of the ratio of dissolved oxygen to argon (O2/Ar) and the partial pressure of CO2 (pCO2). These estimates were compared with simultaneous measurements of sea surface temperature (SST), chlorophyll-a (chl-a), flow cytometry, and discrete surface nutrient concentrations. NCP and CO2 influx were greatest in the subarctic (45°N-50°N, 25.8 ± 4.6 and 4.1 ± 0.9 mmol C m-2 d-1) and northern transition zone (40°N-45°N, 17.1 ± 4.4 and 2.1 ± 0.5 mmol C m-2 d-1), with mean NCP ˜6-8× greater than mean CO2 invasion (error estimates reflect 1 σ confidence intervals). Contrastingly, the southern transition zone (32°N-40°N) and subtropics (22°N-32°N) had lower mean NCP (5.4 ± 1.8 and 8.1 ± 2.1 mmol C m-2 d-1, respectively) and mean CO2 efflux (3.0 ± 0.5 and 0.1 ± 0.0 mmol C m-2 d-1, respectively). In the subarctic and transition zone, NCP was highly correlated with surface chl-a and CO2 influx, indicating strong coupling between the biological pump and CO2 uptake. Meridional trends in our NCP estimates in the transition zone and subtropics were similar to those for integrated summertime NCP along the cruise track determined using an upper ocean climatological carbon budget.

  12. Contribution of tropical cyclones to the air-sea CO2 flux: A global view

    Digital Repository Service at National Institute of Oceanography (India)

    Levy, M.; Lengaigne, M.; Bopp, L.; Vincent, E.M.; Madec, G.; Ethe, C.; DileepKumar, M.; Sarma, V.V.S.S.

    of magnitude smaller than previous estimates extrapolated from case studies. This result arises from several competing effects involved in the F sub(CO2) response to TCs, not accounted for in previous studies. While previous estimates have hypothesized...

  13. 海洋微表层对海气CO2通量影响的研究进展%ADVANCES IN THE IMPACT OF SEA SURFACE MICROLAYER ON THE AIR-SEA CO2 FLUX

    Institute of Scientific and Technical Information of China (English)

    管玉平; 邢元明; 杨磊

    2012-01-01

    CO2的海气通量对于研究全球气候变化具有重要的意义.海洋微表层作为CO2在海洋和大气之间传输的重要通道,对于准确估算全球海气CO2通量的大小非常重要.本文主要从微表层中表面活性物质的富集,温度的偏低和与CO2的化学反应3个方面,综述了近年来与微表层相关的CO2通量研究进展,并对未来的相关研究进行了展望.%The research on air-sea CO2 flux is of great significance in researching the global climate change. As an vital channel of the transfer of CO2 between ocean and atmosphere, sea surface microlayer plays an important role in accurately estimating the air-sea CO2 flux. This paper mainly reviewed the progress of air-sea CO2 flux related with microlayer from three aspects i the enrichment of surfactant,the cool skin and chemical enhancement, and then took a preview of further research.

  14. Soil CO 2 Flux in Hövsgöl National Park, Northern Mongolia

    Directory of Open Access Journals (Sweden)

    Avirmed Otgonsuren

    2008-06-01

    Full Text Available We investigated soil CO 2 fl ux and bare soil respiration in grasslands that are located at the southern edge of the Siberian boreal forest in Northern Mongolia. The study area has warmed by almost 1.8 o C over the last 40 years, and the soil and vegetation covers have been changed due to intense nomadic grazing pressure. Bare soil respiration is decreased with increasing grazing pressure, but there was no consistent pattern of total soil CO 2 fl ux under three distinct grazing levels. Bare soil respiration and soil CO 2 fl ux were higher on north-facing slopes than on south-facing slopes, due to high organic matter accumulation and the presence of permafrost. Both bare soil respiration and soil CO 2 fl ux were signi fi cantly higher in riparian areas compared with the lower and upper portions of the south-facing slope. Topography has a stronger effect on variability of soil CO 2 fl ux and bare soil respiration than variability induced by grazing. Inter-annual variability in soil CO 2 fl ux and bare soil respiration was very high, because of high variability in climate conditions.

  15. Synthesis of observed air–sea CO2 exchange fluxes in the river-dominated East China Sea and improved estimates of annual and seasonal net mean fluxes

    Directory of Open Access Journals (Sweden)

    C.-M. Tseng

    2013-08-01

    Full Text Available Limited observations exist for reliable assessment of annual CO2 uptake that takes into consideration the strong seasonal variation in the river-dominated East China Sea (ECS. Here we explore seasonally representative CO2 uptakes by the whole East China Sea derived from observations over a 14 yr period. We firstly identified the biological sequestration of CO2 taking place in the highly productive, nutrient-enriched Changjiang river plume, dictated by the Changjiang river discharge in warm seasons. We have therefore established an empirical algorithm as a function of sea surface temperature (SST and Changjiang river discharge (CRD for predicting sea surface pCO2. Synthesis based on both observation and model show that the annually averaged CO2 uptake from atmosphere during 1998–2011 was constrained to about 1.9 mol C m–2 yr–1. This assessment of annual CO2 uptake is more reliable and representative, compared to previous estimates, in terms of temporal and spatial coverage. Additionally, the CO2 time-series, exhibiting distinct seasonal pattern, gives mean fluxes of −3.0, −1.0, −0.9 and −2.5 mol C m–2 yr–1 in spring, summer, fall and winter, respectively, and also reveals apparent inter-annual variations. The flux seasonality shows a strong sink in spring and a weak source in late summer-early fall. The weak sink status during warm periods in summer-fall is fairly sensitive to changes of pCO2 and may easily shift from a sink to a source altered by environmental changes under climate change and anthropogenic forcing.

  16. Effects of climate warming and declining species richness in grassland model ecosystems: acclimation of CO2 fluxes

    Directory of Open Access Journals (Sweden)

    A. S. Kowalski

    2006-09-01

    Full Text Available To study the effects of warming and declining species richness on the carbon balance of grassland communities, model ecosystems containing one, three or nine species were exposed to ambient and elevated (ambient +3°C air temperature. In this paper, we analyze measured ecosystem CO2 fluxes to test whether ecosystem photosynthesis and respiration had acclimated to warming after 28 months of continuous heating, and whether the degree of acclimation depended on species richness. At first sight, we found no signs of acclimation in photosynthesis or respiration. However, because plant cover was significantly higher in the heated treatment, normalization for plant cover revealed down-regulation of both photosynthesis and respiration. Although CO2 fluxes were larger in communities with higher species richness, species richness did not affect the degree of acclimation to warming. These results imply that models need to take into account thermal acclimation to simulate photosynthesis and respiration in a warmer world.

  17. Relative Linkages of Canopy-Level CO2 Fluxes with the Climatic and Environmental Variables for US Deciduous Forests

    Science.gov (United States)

    Ishtiaq, Khandker S.; Abdul-Aziz, Omar I.

    2015-04-01

    We used a simple, systematic data-analytics approach to determine the relative linkages of different climate and environmental variables with the canopy-level, half-hourly CO2 fluxes of US deciduous forests. Multivariate pattern recognition techniques of principal component and factor analyses were utilized to classify and group climatic, environmental, and ecological variables based on their similarity as drivers, examining their interrelation patterns at different sites. Explanatory partial least squares regression models were developed to estimate the relative linkages of CO2 fluxes with the climatic and environmental variables. Three biophysical process components adequately described the system-data variances. The `radiation-energy' component had the strongest linkage with CO2 fluxes, whereas the `aerodynamic' and `temperature-hydrology' components were low to moderately linked with the carbon fluxes. On average, the `radiation-energy' component showed 5 and 8 times stronger carbon flux linkages than that of the `temperature-hydrology' and `aerodynamic' components, respectively. The similarity of observed patterns among different study sites (representing gradients in climate, canopy heights and soil-formations) indicates that the findings are potentially transferable to other deciduous forests. The similarities also highlight the scope of developing parsimonious data-driven models to predict the potential sequestration of ecosystem carbon under a changing climate and environment. The presented data-analytics provides an objective, empirical foundation to obtain crucial mechanistic insights; complementing process-based model building with a warranted complexity. Model efficiency and accuracy ( R 2 = 0.55-0.81; ratio of root-mean-square error to the observed standard deviations, RSR = 0.44-0.67) reiterate the usefulness of multivariate analytics models for gap-filling of instantaneous flux data.

  18. Multi-Channel Auto-Dilution System for Remote Continuous Monitoring of High Soil-CO2 Fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Amonette, James E.; Barr, Jonathan L.

    2009-04-23

    Geological sequestration has the potential capacity and longevity to significantly decrease the amount of anthropogenic CO2 introduced into the atmosphere by combustion of fossil fuels such as coal. Effective sequestration, however, requires the ability to verify the integrity of the reservoir and ensure that potential leakage rates are kept to a minimum. Moreover, understanding the pathways by which CO2 migrates to the surface is critical to assessing the risks and developing remediation approaches. Field experiments, such as those conducted at the Zero Emissions Research and Technology (ZERT) project test site in Bozeman, Montana, require a flexible CO2 monitoring system that can accurately and continuously measure soil-surface CO2 fluxes for multiple sampling points at concentrations ranging from background levels to several tens of percent. To meet this need, PNNL is developing a multi-port battery-operated system capable of both spatial and temporal monitoring of CO2 at concentrations from ambient to at least 150,000 ppmv. This report describes the system components (sampling chambers, measurement and control system, and power supply) and the results of a field test at the ZERT site during the late summer and fall of 2008. While the system performed well overall during the field test, several improvements to the system are suggested for implementation in FY2009.

  19. Eddy covariance CO2 flux above a Gmelin larch forest on continuous permafrost in Central Siberia during a growing season

    Science.gov (United States)

    Nakai, Y.; Matsuura, Y.; Kajimoto, T.; Abaimov, A. P.; Yamamoto, S.; Zyryanova, O. A.

    2008-08-01

    Gmelin larch ( Larix gmelinii) forests are representative vegetation in the continuous permafrost region of Central Siberia. Information on the carbon budget is still limited for this Siberian larch taiga in comparison to boreal forests in other regions, while the larch forests are expected to play a key role in the global carbon balance due to their wide distribution over North-East Eurasia. The authors reported results of eddy covariance CO2 flux measurements at a mature Gmelin larch stand in Central Siberia, Russia (64°16'N, 100°12'E, 250 m a.s.l.). The measurements were conducted during one growing season (June-early September in 2004). CO2 uptake was initiated in early June and increased sharply until late June, which was closely related to the phenology of the larch trees (i.e., bud-break and needle flush). Maximum half-hourly net CO2 uptake was ˜6 µmol m-2 s-1. Maximum daily net uptake of ˜2 g C m-2 day-1 occurred at the end of June and in mid-July. Cumulative net uptake was 76-78 g C m-2, indicating that the mature larch forest acted as a net sink for CO2 during the growing season (91 days). In comparison with other boreal forests, however, the magnitude of net CO2 uptake and night-time release of the forest, and cumulative net CO2 uptake were lower. We suggest that lower net ecosystem CO2 uptake of the study stand was primarily associated with low leaf area index.

  20. Day and Night Variability of CO2 Fluxes and Priming Effects under zea Mays Measured in High Resolution

    Science.gov (United States)

    Splettstoesser, Thomas; Pausch, Johanna

    2017-04-01

    Plant induced increase of soil organic matter turnover rates contribute to carbon emissions in agricultural land use systems. In order to better understand these rhizosphere priming effects, we conducted an experiment which enabled us to monitor CO2 fluxes under Zea mays plants in high resolution. The experiment was conducted in a climate chamber where the plants were grown in tightly sealed boxes for 40 days and CO2 efflux from soil was measured twice a day. Continuous 13C-CO2 label was used to allow differentiation between plant- and soil-derived CO2.This enabled us to monitor root respiration and soil organic matter turnover in the early stages of plant growth and to highlight changes in soil CO2 emissions and priming effects between day and night. The measurements were conducted with a PICARRO G2131-I C high-precision isotopic CO2 Analyzer (PICARRO INC.) utilizing an automated valve system governed by a CR1000 data logger (Campbell Scientific). After harvest roots and shoots were analyzed for 13C content. Microbial biomass, root length density and enzymatic activities in soil were measured and linked to soil organic matter turnover rates. Results show an increased soil CO2 efflux at day time periods and an overall increase with increasing plant biomass. No difference in chloroform fumigation extractable microbial biomass has been found but a strong negative priming effect was measured in the short experimental period, suggesting that the microbes shifted to the utilization of plant exudates without actual microbial growth triggered by the new labile C input. This is coherent with the observed shift in enzyme kinetics. With this experimental setup we show that measurement of priming effects in high resolution can be achieved.

  1. A preliminary evaluation of an O2/CO2 based eddy covariance theory at Missouri AmeriFlux site

    Science.gov (United States)

    Yan, B.; Gu, L.

    2013-12-01

    The eddy covariance (EC) technique has been widely used at flux sites on every continent, across most ecosystem types and climates to monitor exchanges of momentum, mass and energy between land surface and atmosphere. In an attempt to develop a self-consistent theory for the EC technique, Gu et al. (2012) reformulated the fundamental equations for EC by introducing the concept of constraining gas that has no net ecosystem sink/source. Gu (2013) expanded the theory of Gu et al. (2012) to include paired gases whose ecosystem exchange ratios are stable over an averaging period (e.g. 30 min) and therefore can be used to constrain EC flux measurements of any gases. He proposed that O2 and CO2 are an ideal pair of gases as their biological processes are coupled and their ecosystem exchange ratio (also known as oxidative ratio) is close to 1. Advantages of this new O2/CO2 based EC theory include: 1) avoidance of covariance loss in calculating dry air density induced by spatial separation of measuring instruments and use of multiple indirectly derived variables, 2) the minimum number of assumptions adopted for the derivation of the equation, and 3) avoidance of errors related to linearization of ideal gas law. In this study, we conducted a preliminary evaluation for the basic principle of Gu (2013) EC theory. We crosschecked net ecosystem exchange (NEE) estimations from different, independent methods by using CO2 and H2O as paired constraining gases. Using CO2 and H2O instead of CO2 and O2 as paired constraining gases is not ideal in the framework of Gu (2013); however, no fast response O2 analyzer is currently available. CO2 and H2O are both transported between the inside of plants and canopy air through stomata on leaves in the processes of photosynthesis and transpiration which are known to be closely coupled. However, this close coupling is contaminated by other ecosystem sinks/sources, e.g. respiration of plants and soil for CO2 and evaporation of intercepted and soil

  2. CO2 and CH4 fluxes from oil palm plantations in Sumatra, Indonesia: effects of palm age and environmental conditions

    Science.gov (United States)

    Meijide, A.; Hassler, E.; Corre, M. D.; June, T.; Sabajo, C.; Veldkamp, E.; Knohl, A.

    2015-12-01

    Global increasing demand of palm oil is leading to the expansion of oil palm plantations, particularly in SE Asia, which in Sumatran lowlands has resulted in a 21% forest area loss. Large photosynthesis rates are expected for oil palms, due to their high growth and yield production. However, there is very limited information on their effect on carbon dioxide (CO2) fluxes and their sink or source strength at ecosystem scale. For methane (CH4) fluxes, research has mainly focused in oil palm plantations located on peatlands, but no information is available at ecosystem level from plantations on mineral soils. With the aim of studying CO2 fluxes during the non-productive and productive phases of oil palm cultivation, an eddy covariance (EC) tower was installed in a 2 year old oil palm plantation, where it was measuring for 8 months, and was subsequently moved to a 12 year old plantation, both in the province of Jambi, Sumatra. The EC system consisted of a Licor 7500A and an ultrasonic Metek anemometer, operating at 10 Hz, installed on a 7m and 22m tower respectively. In the 12 year old plantation, the tower was also equipped with a Los Gatos FGGA-24EP, to assess CH4 fluxes. Chamber measurements were also carried out to obtain information on respiration and CH4 fluxes from the soil. Radiation was the major driver controlling net carbon uptake, while soil moisture did not play a significant role. Average net ecosystem exchange in the hours of the day with higher radiation for the whole measurement period was 10 μmol m-2 s-1 for the 2 year old plantation and -22 μmol m-2 s-1 in the 12 year old. The analysis of the cumulative fluxes show that the non-productive plantation was a carbon source of around 636 g CO2 m-2 during the 8 months of measurements, while in the productive period, it acted as a strong carbon sink (-794 g CO2 m-2 yr-1). Methane uptake was observed in the soil in both plantations and also for the whole ecosystem in the 12 year old one, but its

  3. CO 2 flux and photosynthesis of a Sahelian savanna during HAPEX-Sahel

    Science.gov (United States)

    Hanan, N. P.; Elbers, J. A.; Kabat, P.; Dolman, A. J.; de Bruin, H. A. R.

    1996-05-01

    Eddy-covariance measurements of CO 2 exchange above a Sahelian savanna consisting of small shrubs over a continuous herb layer were made during the HAPEX-Sahel experiment in Niger, West Africa. The measurements were made near-continuously during an 8 week period, covering the main part of the rainy season and three weeks at the beginning of the dry season. In this paper the measurements are corrected for in-canopy storage of CO 2 and the nightime measurements used to derive respiration functions for the soil, roots and aerial plant material. Photosynthetic CO 2 uptake was calculated and the measurements compared to simulations using a biochemical photosynthesis model in a simple (“big-leaf”) implementation, with average stomatal conductance given as an independent input. This model was able to reproduce the measurements (RMS error 1.95 μmol m -2 s -1) with only minor parameter adjustment.

  4. UU* filtering of nighttime net ecosystem CO2 exchange flux over forest canopy under strong wind in wintertime

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junhui; HAN Shijie; SUN Xiaomin; TANG Fengde

    2005-01-01

    The mechanism of the negative nighttime net CO2 flux in wintertime and reasonable treatment with it is of great importance in evaluating the carbon metabolism of boreal forest.Results, based on the data obtained with open-path eddy covariance system and CO2 profile measurement system from Nov. 2002 to Apr. 2003 and that obtained with five sonic anemometers in Nov. 1999, show that (1) the negative net ecosystem CO2 exchange flux (NEE) always appeared under conditions of strong wind; (2) the pressure fluctuation and horizontal advection flow are dominantly responsible for the negative NEE. Operable upper bound u* filtering method (UU* filtering) was introduced since the difficulties in real-time measuring of pressure fluctuation and horizontal advection fluxes under conditions of strong wind. Nighttime upper u* threshold for the broad-leaved Korean pine mixed forest of the Changbai Mountains is 0.4 ms-1 and can be applied to the daytime filtering; and (3) the UU* filtering corrected the nighttime ‘problem’ of negative NEE under strong wind and made the estimates more ecologically reasonable.

  5. High resolution fossil fuel combustion CO2 emission fluxes for the United States.

    Science.gov (United States)

    Gurney, Kevin R; Mendoza, Daniel L; Zhou, Yuyu; Fischer, Marc L; Miller, Chris C; Geethakumar, Sarath; de la Rue du Can, Stephane

    2009-07-15

    Quantification of fossil fuel CO2 emissions at fine space and time resolution is emerging as a critical need in carbon cycle and climate change research. As atmospheric CO2 measurements expand with the advent of a dedicated remote sensing platform and denser in situ measurements, the ability to close the carbon budget at spatial scales of approximately 100 km2 and daily time scales requires fossil fuel CO2 inventories at commensurate resolution. Additionally, the growing interest in U.S. climate change policy measures are best served by emissions that are tied to the driving processes in space and time. Here we introduce a high resolution data product (the "Vulcan" inventory: www.purdue.edu/eas/carbon/vulcan/) that has quantified fossil fuel CO2 emissions for the contiguous U.S. at spatial scales less than 100 km2 and temporal scales as small as hours. This data product completed for the year 2002, includes detail on combustion technology and 48 fuel types through all sectors of the U.S. economy. The Vulcan inventory is built from the decades of local/regional air pollution monitoring and complements these data with census, traffic, and digital road data sets. The Vulcan inventory shows excellent agreement with national-level Department of Energy inventories, despite the different approach taken by the DOE to quantify U.S. fossil fuel CO2 emissions. Comparison to the global 1degree x 1 degree fossil fuel CO2 inventory, used widely by the carbon cycle and climate change community prior to the construction of the Vulcan inventory, highlights the space/time biases inherent in the population-based approach.

  6. Influence of CO2 Concentration on Adsorption Behavior of 99Tc in Clay Under Hypoxic Conditions

    Institute of Scientific and Technical Information of China (English)

    SONG; Zhi-xin; BAO; Liang-jin; JIANG; Tao; CHEN; Xi

    2013-01-01

    Under hypoxic conditions,using the Beishan groundwater the influence of the CO2 concentration on the adsorption behavior of 99Tc in the Longdong clay was studied by batch method.Meanwhile,the buffering effect of clay rocks on the pH value of aqueous solution at different CO2 concentrations was discussed.The adsorption behavior of 99Tc on clay at different initial pH values was also researched.

  7. Estimation of air-sea CO2 flux in the coastal waters of Visakhapatnam

    Digital Repository Service at National Institute of Oceanography (India)

    Latha, T.P.; Rao, K.H.; Sarma, V.V.S.S.; Seetaram, P.; Choudhury, S.B.; Nagamani, P.V.; Dutt, B.S.; Dhadwal, V.K.; Manna, S.

    and higher pCO2 levels in the south western region than to the atmospheric levels (Sarma et al., 2012). Previous study reports (George et al., 1994; Kumar et al., 1996) suggest that the coastal Bay of Bengal acts as a net source for CO2 to the atmosphere... throughout the year except for a brief north east monsoon period and acts as a source or sink depending on coastal surface circulation led majorly by riverine influx. In order to examine this, the time-series observations were conducted at a single station...

  8. Energy and CO2 exchanges and influencing factors in spring wheat ecosystem along the Heihe River, northwestern China

    Science.gov (United States)

    Sun, Shuchen; Shao, Ming'an; Gao, Hongbei

    2016-12-01

    Spring wheat ( Triticum aestivum Linn.) is an important crop for food security in the desert-oasis farmland in the middle reaches of the Heihe River in northwestern China. We measured fluxes using eddy covariance and meteorological parameters to explore the energy fluxes and the relationship between CO2 flux and climate change in this region during the wheat growing seasons in 2013 and 2014. The energy balance closures were 70.5% and 72.7% in the 2013 and 2014 growing season, respectively. The wheat ecosystem had distinct seasonal and diurnal dynamics of CO2 fluxes with U-shaped curves. The accumulated net ecosystemic CO2 exchanges (NEE) were -111.6 and -142.2 g C/m2 in 2013 and 2014 growing season, respectively. The ecosystem generally acted as a CO2 sink during the growing season but became a CO2 source after the wheat harvest. A correlation analysis indicated that night-time CO2 fluxes were exponentially dependent on air temperature and soil temperature at a depth of 5 cm but were not correlated with soil-water content, water-vapour pressure, or vapour-pressure deficit. CO2 flux was not correlated with the meteorological parameters during daytime. However, irrigation and precipitation, may complicate the response of CO2 fluxes to other meteorological parameters.

  9. Modelling land surface fluxes of CO2 in response to climate change and nitrogen deposition

    DEFF Research Database (Denmark)

    Hansen, Kristina; Ambelas Skjøth, Carsten; Geels, Camilla

    Climate change, land use variations, and impacts of atmospheric nitrogen (N) deposition represent uncertainties for the prediction of future greenhouse gas exchange between land surfaces and the atmosphere as the mechanisms describing nutritional effects are not well developed in climate...... climate feedback mechanisms of CO2 between changes in management, land use practise, and climate change....

  10. Mapping modern CO2 fluxes and mantle carbon content all along the mid-ocean ridge system

    Science.gov (United States)

    Chavrit, Deborah; Humler, Eric; Grasset, Olivier; Morizet, Yann; Laporte, Didier

    2014-05-01

    Quality criteria have been used to select ~ 400 vesicularity measurements on zero-age mid-ocean ridge glasses from ~ 600 data available in the literature published over the past ~ 30 years. At face value, observations show that for a given depth of sampling, enriched basalts from slow spreading ridge segments are more vesicular than those from depleted and intermediate or fast spreading ridges. A shallower depth of eruption enhances these effects because lower hydrostatic pressure favours bubble expansion. In order to get an insight into these complex and intermingled processes, we used empirical and semi-quantitative approaches based on a limited number of inputs (segment depth, spreading rate and K2O/TiO2 ratios). Both models give equivalent results and predict vesicularities within ± 50%. From these calculations, we compute the equivalent CO2 concentration at the depth of eruption all along the oceanic ridge system. The total calculated CO2 fluxes are low ranging from 6.5±1.8 to 8.7±2.8 ×1011 mol/yr between the models and the CO2 mantle content displays large variabilities from 66-19+27 to 78-40+82 ppm, with values higher near hot spots. In order to test these results, the mantle 3He fluxes have been evaluated using the calculated CO2 fluxes and a CO2/3He ratio of 2.2 × 109. These fluxes range from 295±82 to 395±127 mol/yr and are close to the values reported by Jean-Baptiste (1992) (267-534 mol/yr) and the most recent estimate (Bianchi et al., 2010, ~527±102 mol/yr) using box-model of the three main ocean basins constrained by measurements of 3He and radiocarbon data. As these independent methods give similar helium fluxes at regional and global scales, it provides strong support to a low and heterogeneous mantle carbon concentration and distribution.

  11. Estimating regional fluxes of CO2 and CH4 using space-borne observations of XCH4: XCO2

    Directory of Open Access Journals (Sweden)

    A. Fraser

    2014-12-01

    Full Text Available We use the GEOS-Chem global 3-D atmospheric chemistry transport model to interpret XCH4:XCO2 column ratios retrieved from the Japanese Greenhouse Gases Observing Satellite (GOSAT. The advantage of these data over CO2 and CH4 columns retrieved independently using a full physics optimal estimation algorithm is that they are less prone to scattering-related regional biases. We show that the model is able to reproduce observed global and regional spatial (mean bias =0.7% and temporal variations (global r2=0.92 of this ratio with a model bias 2 and CH4 that are typically 6 months out of phase, which may reduce the sensitivity of the ratio to changes in either gas. To simultaneously estimate fluxes of CO2 and CH4 we use a maximum likelihood estimation approach. We use two approaches to resolve independent flux estimates of these two gases using GOSAT observations of XCH4:XCO2: (1 the a priori error covariance between CO2 and CH4 describing common source from biomass burning; and (2 also fitting independent surface atmospheric measurements of CH4 and CO2 mole fraction that provide additional constraints, improving the effectiveness of the observed GOSAT ratio to constrain flux estimates. We demonstrate the impact of these two approaches using numerical experiments. A posteriori flux estimates inferred using only the GOSAT ratios and taking advantage of the error covariance due to biomass burning are not consistent with the true fluxes in our experiments, as the inversion system cannot judge which species' fluxes to adjust. This reflects the weak dependence of XCH4:XCO2 on biomass burning. We find that adding the surface data effectively provides an "anchor" to the inversion that dramatically improves the ability of the GOSAT ratios to infer both CH4 and CO2 fluxes. We show that the regional flux estimates inferred from GOSAT XCH4:XCO2 ratios together with the surface mole fraction data during 2010 are typically consistent with or better than the

  12. Effects of an Urban Park and Residential Area on the Atmospheric CO2 Concentration and Flux in Seoul, Korea

    Institute of Scientific and Technical Information of China (English)

    Moon-Soo PARK; Seung Jin JOO; Chang Seok LEE

    2013-01-01

    The CO2 concentrations and fluxes over an urban forest site (Namsan) and an urban residential region (Boramae) in Seoul,Korea,during the non-growing season (2-4 March 2011),the growing season (10-12 June 2011),and the late-growing season (22-24 September 2011) were analyzed.The CO2 concentrations of two sites showed nearly the same diurnal variation,with a maximum value occurring during the night and a minimum value occurring during daytime,as well as the same seasonal variation,with a maximum value during the non-growing season (early spring) and a minimum value during the growing season (summer).The CO2 flux over the urban forest did not show any typical diurnal variation during the non-growing season,but did show diurnal variation with a small positive value during the night and a large negative value during daytime in the growing and late-growing seasons due to photosynthesis in the urban forest.The CO2 flux over the urban residential region showed a positive daily mean value for all periods,with large values during the non-growing season and small values during the growing season,and it also showed diurnal variation with two maxima at 0600-1000 LST and 1800-2400 LST,and two minima at 0300-0600 LST and 1100-1500 LST,and was strongly correlated with the use of liquefied natural gas for cooking and heating by surrounding houses.

  13. Fluxes of CO2, CH4 and N2O from soil of burned grassland savannah of central Africa

    Directory of Open Access Journals (Sweden)

    R. Valentini

    2010-06-01

    Full Text Available Grassland savannah ecosystems subject to frequent fires are considered to have an almost neutral carbon balance, as the C released during burning mostly balance the C fixed by the photosynthetic process. However, burning might modify the net soil-atmosphere exchange of GHGs in the post burning phase so that the radiative balance of the site might shift from neutrality. In the present study the impact of fire on soil fluxes of CO2, CH4 and N2O was investigated in a grassland savannah (Congo Brazzaville where high frequency burning is the typical management form of the region. An area was preserved for one season from annual burning and was used as "unburned" treatment. Two field campaigns were carried on at different time length from the fire event, 1 month, in the middle of the dry season, and 8 months after, at the end of the growing season. CO2, CH4 and N2O fluxes, as well as several soil parameters, were measured in each campaign from burned and unburned plots. Rain events were simulated at each campaign to evaluate magnitude and length of the generated GHG flux pulses. In laboratory experiments, on soil samples from the two treatments, microbial biomass, net N mineralization, net nitrification, N2O, NO and CO2 emissions were analyzed in function of soil water and/or temperature variations. Results showed that fire had a significant effect on GHG fluxes but the effect was transient, as after 8 months differences between treatments were no longer significant. One month after burning CO2 soil emissions were significantly lower in the burned plots, CH4 fluxes were dominated by net emissions rather than net consumption in the unburned area and fire shifted the CH4 flux distribution towards more negative values. No significant effect of fire was observed in the field on N2O fluxes. It was assumed that the low water content was the main limiting factor as in fact laboratory data showed that only above 75% of water saturation, N2O emissions

  14. Modeling concentrations and fluxes of atmospheric CO2 in the North East Atlantic region

    DEFF Research Database (Denmark)

    Geels, C.; Christensen, J.H.; Hansen, A.W.

    2001-01-01

    As part of the Danish NEAREX project a three-dimensional Eulerian hemispheric air pollution model is used to study the transport and concentrations of atmospheric CO2 in the North East Atlantic region. The model domain covers the major part of the Northern Hemisphere and currently the model...... source types. Here the model setup and the used parameterizations will be described. The model is validated by comparing the results with atmospheric measurements from four monitoring stations in or close to the northern part of the North Atlantic. Some preliminary model results will be shown and shortly...... includes simple parameterizations of the main sinks and sources for atmospheric CO2. One of the objectives of the project is to study and maybe quantify the relative importance of the various sinks and source types and areas for this region. In order to do so the model has been run with differentiated...

  15. The influence of vegetation and relief heterogeneity on turbulent exchange of CO2 between land surface and the atmosphere

    Science.gov (United States)

    Mukhartova, Juliya; Levashova, Natalia; Volkova, Elena; Olchev, Alexander

    2016-04-01

    The possible effect of spatial heterogeneity of vegetation cover and relief on horizontal and vertical turbulent exchange of CO2 was described using a process-based two-dimensional (2D) turbulent exchange models (Mukhartova et al. 2015). As a key area for this modeling study the hilly territory situated at the boundary between broadleaf forest and steppe zones in European part of Russia (Tula region) was selected. The vegetation cover in the study region is represented by complex mosaic of crop areas, grasslands, pastures, mires and groves. The very heterogeneous vegetation cover and complex dissected relief make very difficult an adequate determining the local and regional CO2 fluxes using experimental methods only. The two-dimensional model based on solution of the Navier-Stokes and continuity equations using well-known one-and-a-half order (TKE) closure scheme is applied. For description of the plant canopy photosynthesis and respiration rates the model uses an aggregated approach based on the model of Ball et al (1987) in Leuning modification (1990, 1995), the Beer-Lambert equation for the description of solar radiation penetration within a plant canopy (Monsi, Saeki 1953), and also an algorithm describing the response of stomatal conductance of the leaves to incoming photosynthetically active radiation. All necessary input parameters describing the photosynthesis and respiration properties of different plants and soil types in the study region were measured in the field or taken from the literature. The system of differential equations in the model is numerically solved by the finite-difference method. It is assumed that the influence of ground surface heterogeneities at the upper boundary of computing domain is very low and the pressure excess can be therefore considered as zero. The concentration of CO2 at the upper boundary of computing domain is assumed to be equal to some background value. It is also assumed that all boundaries between different

  16. Four-year (2006–2009 eddy covariance measurements of CO2 flux over an urban area in Beijing

    Directory of Open Access Journals (Sweden)

    T. Vesala

    2012-09-01

    Full Text Available Long-term measurements of carbon dioxide flux (Fc and the latent and sensible heat fluxes were performed using the eddy covariance (EC method in Beijing, China over a 4-yr period in 2006–2009. The EC setup was installed at a height of 47 m on the Beijing 325-m meteorological tower in the northwest part of the city. Latent heat flux dominated the energy exchange between the urban surface and the atmosphere in summer, while sensible heat flux was the main component in the spring. Winter and autumn were two transition periods of the turbulent fluxes. The source area of Fc was highly heterogeneous, which consisted of buildings, parks, and highways. It was of interest to study of the temporal and spatial variability of Fc in this urban environment of a developing country. Both on diurnal and monthly scale, the urban surface acted as a net source for CO2 and downward fluxes were only occasionally observed. The diurnal pattern of Fc showed dependence on traffic and the typical two peak traffic patterns appeared in the diurnal cycle. Also Fc was higher on weekdays than on weekends due to the higher traffic volumes on weekdays. On seasonal scale, Fc was generally higher in winter than during other seasons likely due to domestic heating during colder months. Total annual average CO2 emissions from the neighborhood of the tower were estimated to be 4.90 kg C m−2 yr−1 over the 4-yr period. Total vehicle population was the most important factor controlling the inter-annual variability of Fc in this urban area.

  17. CO2 flux history 1982–2001 inferred from atmospheric data using a global inversion of atmospheric transport

    Directory of Open Access Journals (Sweden)

    M. Heimann

    2003-05-01

    Full Text Available Based on about 20 years of NOAA/CMDL's atmospheric CO2 concentration data and a global atmospheric tracer transport model, we estimate interannual variations and spatial patterns of surface CO2 fluxes in the period 01/1982–12/2000, by using a time-dependent Bayesian inversion technique. To increase the reliability of the estimated temporal features, particular care is exerted towards the selection of data records that are homogeneous in time. Fluxes are estimated on a grid-scale resolution (~8° latitude×10° longitude, constrained by a-priori spatial correlations, and then integrated over different sets of regions. The transport model is driven by interannually varying re-analysed meteorological fields. We make consistent use of unsmoothed measurements. In agreement with previous studies, land fluxes are estimated to be the main driver of interannual variations in the global CO2 fluxes, with the pace predominantly being set by the El Niño/La Niña contrast. An exception is a 2–3 year period of increased sink of atmospheric carbon after Mt. Pinatubo's volcanic eruption in 1991. The largest differences in fluxes between El Niño and La Niña are found in the tropical land regions, the main share being due to the Amazon basin. The flux variations for the Post-Pinatubo period, the 1997/1998 El Niño, and the 1999 La Niña events are exploited to investigate relations between CO2 fluxes and climate forcing. A rough comparison points to anomalies in precipitation as a prominent climate factor for short-term variability of tropical land fluxes, both through their role on NPP and through promoting fire in case of droughts. Some large flux anomalies seem to be directly related to large biomass burning events recorded by satellite observation. Global ocean carbon uptake shows a trend similar to the one expected if ocean uptake scales proportional to the anthropogenic atmospheric perturbation. In contrast to temporal variations, the longterm spatial

  18. Estimating noctural ecosystem respiration from the vertical turbulent flux and change in storange of CO2

    NARCIS (Netherlands)

    Gorsel, van E.; Delpierre, N.; Leuning, R.; Black, A.; Munger, J.W.; Wofsy, S.; Aubinet, M.; Feigenwinter, C.; Beringer, J.; Bonal, D.; Chen, B.; Chen, J.; Clement, R.; Davis, K.J.; Desai, A.R.; Dragoni, D.; Etzold, S.; Grünwald, T.; Gu, L.; Heinesch, B.; Hutyra, L.R.; Jans, W.W.P.; Kutsch, W.; Law, B.E.; Leclerc, Y.; Mammarella, I.; Montagnani, L.; Noormets, A.; Rebmann, C.; Wharton, S.

    2009-01-01

    Micrometeorological measurements of nighttime ecosystem respiration can be systematically biased when stable atmospheric conditions lead to drainage flows associated with decoupling of air flow above and within plant canopies. The associated horizontal and vertical advective fluxes cannot be measure

  19. Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans

    NARCIS (Netherlands)

    Takahashi, Taro; Sutherland, Stewart C.; Wanninkhof, Rik; Sweeney, Colm; Feely, Richard A.; Chipman, David W.; Hales, Burke; Friederich, Gernot; Chavez, Francisco; Sabine, Christopher; Watson, Andrew; Bakker, Dorothee C.E.; Schuster, Ute; Metzl, Nicolas; Yoshikawa-Inoue, Hisayuki; Ishii, Masao; Midorikawa, Takashi; Nojiri, Yukihiro; Körtzinger, Arne; Steinhoff, Tobias; Hoppema, Mario; Olafsson, Jon; Arnarson, Thorarinn S.; Tilbrook, Bronte; Johannessen, Truls; Olsen, Are; Bellerby, Richard; Wong, C.S.; Delille, Bruno; Bates, N.R.; Baar, Hein J.W. de

    2009-01-01

    A climatological mean distribution for the surface water pCO2 over the global oceans in non-El Niño conditions has been constructed with spatial resolution of 4° (latitude) ×5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO2 obtained from 1970 to 2

  20. Influence of Thinning on Soil CO2 Efflux in Chinese Fir Plantations

    Institute of Scientific and Technical Information of China (English)

    TIAN Da-Lun; YAN Wen-De; FANG Xi; KANG Wen-Xing; DENG Xiang-Wen; WANG Guang-Jun

    2009-01-01

    Forest management is expected to influence soil CO2 efflux (FCO2) as a result of changes in microenvironmental conditions,soil microclimate,and root dynamics.Soil FCO2 rate was measured during the growing season of 2006 in both thinning and non-thinning locations within stands ranging from 0 to 8 years after the most recent thinning in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in Huitong Ecosystem Research Station,Hunan,China.Soil temperature and moisture were also measured to examine relationships between FCO2 and soil properties.Forest thinning resulted in huge changes in FCO2 that varied with time since cutting.Immediately following harvest (year 0) FCO2 in thinning area increased by about 30%,declined to 20%-27% below pre-cutting levels during years 4-6,and recovered to pro-cutting levels at 8 years post-cutting.A similar temporal pattern,but with smaller changes,was found in non-thinning locations.The initial increase in FCO2 could be attributed to a combination of root decay,soil disturbance,and increased soil temperature in gaps,while the subsequent decrease and recovery to the death and gradual regrowth of active roots.Strong effects of soil temperature and soil water content on FCO2 were found.Forest thinning mainly influenced FCO2 through changes in tree root respiration,and the net result was a decrease in integrated FCO2 flux through the entire felling cycle.

  1. Carbon fluxes acclimate more strongly to elevated growth temperatures than to elevated CO2 concentrations in a northern conifer.

    Science.gov (United States)

    Kroner, Yulia; Way, Danielle A

    2016-08-01

    Increasing temperatures and atmospheric CO2 concentrations will affect tree carbon fluxes, generating potential feedbacks between forests and the global climate system. We studied how elevated temperatures and CO2 impacted leaf carbon dynamics in Norway spruce (Picea abies), a dominant northern forest species, to improve predictions of future photosynthetic and respiratory fluxes from high-latitude conifers. Seedlings were grown under ambient (AC, c. 435 μmol mol(-1) ) or elevated (EC, 750 μmol mol(-1) ) CO2 concentrations at ambient, +4 °C, or +8 °C growing temperatures. Photosynthetic rates (Asat ) were high in +4 °C/EC seedlings and lowest in +8 °C spruce, implying that moderate, but not extreme, climate change may stimulate carbon uptake. Asat , dark respiration (Rdark ), and light respiration (Rlight ) rates acclimated to temperature, but not CO2 : the thermal optimum of Asat increased, and Rdark and Rlight were suppressed under warming. In all treatments, the Q10 of Rlight (the relative increase in respiration for a 10 °C increase in leaf temperature) was 35% higher than the Q10 of Rdark , so the ratio of Rlight to Rdark increased with rising leaf temperature. However, across all treatments and a range of 10-40 °C leaf temperatures, a consistent relationship between Rlight and Rdark was found, which could be used to model Rlight in future climates. Acclimation reduced daily modeled respiratory losses from warm-grown seedlings by 22-56%. When Rlight was modeled as a constant fraction of Rdark , modeled daily respiratory losses were 11-65% greater than when using measured values of Rlight . Our findings highlight the impact of acclimation to future climates on predictions of carbon uptake and losses in northern trees, in particular the need to model daytime respiratory losses from direct measurements of Rlight or appropriate relationships with Rdark .

  2. Air–sea CO2 fluxes and the controls on ocean surface pCO2 variability in coastal and open-ocean southwestern Atlantic Ocean: a modeling study

    Directory of Open Access Journals (Sweden)

    R. Arruda

    2015-05-01

    Full Text Available We use an eddy-resolving, regional ocean biogeochemical model to investigate the main variables and processes responsible for the climatological spatio-temporal variability of pCO2 and the air–sea CO2 fluxes in the southwestern Atlantic Ocean. Overall, the region acts as sink of atmospheric CO2 south of 30° S, and is close to equilibrium with the atmospheric CO2 to the north. On the shelves, the ocean acts as a weak source of CO2, except for the mid/outer shelves of Patagonia, which act as sinks. In contrast, the inner shelves and the low latitude open ocean of the southwestern Atlantic represent source regions. Observed nearshore-to-offshore and meridional pCO2 gradients are well represented by our simulation. A sensitivity analysis shows the importance of the counteracting effects of temperature and dissolved inorganic carbon (DIC in controlling the seasonal variability of pCO2. Biological production and solubility are the main processes regulating pCO2, with biological production being particularly important on the shelf regions. The role of mixing/stratification in modulating DIC, and therefore surface pCO2 is shown in a vertical profile at the location of the Ocean Observatories Initiative (OOI site in the Argentine Basin (42° S, 42° W.

  3. Influence of pCO2 on carbon allocation in nodulated Medicago sativa L.

    Science.gov (United States)

    Pereyra, Gabriela; Hartmann, Henrik; Ziegler, Waldemar; Michalzik, Beate; Gonzalez-Meler, Miquel; Trumbore, Susan

    2016-04-01

    Atmospheric CO2 concentrations (pCO_2) have been related to changes in plant carbon (C) availability and photosynthetic capacity, yet there is no clear consensus as to the effect of pCO2 on the plant C balance and on nitrogen fixation in symbiotic systems. We investigated how different pCO2 (Pleistocene: 170 ppm, ambient: 400 ppm and projected future: 700 ppm) influence C allocation in nodulated Medicago sativa L. We labeled 17 week old plants with depleted 13C (-34.7±1.2‰) and traced the label over a 9-day period, to assess the redistribution of newly assimilated C across different sinks, including nodules. We analyzed N concentrations in plant tissues and found no significant differences in leaves and roots across treatments. However, growth and C fixation rates increased with pCO_2, and differences were greatest between 170 ppm and 700 ppm. Across pCO2 treatments we observed a 13C-enrichment in roots compared to leaves. We further observed the highest 13C depletion of non-structural carbohydrates (NSCs) and respired CO2 in tissues of plants grown at 700 ppm, especially in leaves and nodules. Our preliminary results suggest that sink organs like roots and nodules are fed with newly-assimilated NSCs from leaves to support respiration, and especially in 170 ppm plants represented a major respiratory loss of newly assimilated C (≈ 35{%} of the total plant respiration). Our results suggest that although plant metabolic processes like photosynthesis and respiration are affected by changes in pCO_2, nitrogen acquisition in such a symbiotic system is not.

  4. The Influence of Various Operation Modes on Diesel Passenger Cars CO2 Emissions

    Directory of Open Access Journals (Sweden)

    Arina Negoițescu

    2015-07-01

    Full Text Available The amount of emissions released into the atmosphere by polluting sources was significantly reduced due to the limitations introduced by the EU. Since one of the main sources affecting air quality is the car, researches regarding the influence of various factors on exhaust emissions are carried out. As CO2 is the main pollutant responsible for the greenhouse effect, the article treats the influence of vehicle load and traffic levels, running modes, the electric consumer’s utilization, and driving style on CO2 emissions for cars equipped with diesel engine. The results from the conducted study can contribute to adopt solutions in order to decrease the concentration of CO2 emissions from cars equipped with diesel engines.

  5. Calibration of remotely sensed, coarse resolution NDVI to CO2 fluxes in a sagebrush-steppe ecosystem

    Science.gov (United States)

    Wylie, B.K.; Johnson, D.A.; Laca, Emilio; Saliendra, Nicanor Z.; Gilmanov, T.G.; Reed, B.C.; Tieszen, L.L.; Worstell, B.B.

    2003-01-01

    The net ecosystem exchange (NEE) of carbon flux can be partitioned into gross primary productivity (GPP) and respiration (R). The contribution of remote sensing and modeling holds the potential to predict these components and map them spatially and temporally. This has obvious utility to quantify carbon sink and source relationships and to identify improved land management strategies for optimizing carbon sequestration. The objective of our study was to evaluate prediction of 14-day average daytime CO2 fluxes (Fday) and nighttime CO2 fluxes (Rn) using remote sensing and other data. Fday and Rn were measured with a Bowen ratio-energy balance (BREB) technique in a sagebrush (Artemisia spp.)-steppe ecosystem in northeast Idaho, USA, during 1996-1999. Micrometeorological variables aggregated across 14-day periods and time-integrated Advanced Very High Resolution Radiometer (AVHRR) Normalized Difference Vegetation Index (iNDVI) were determined during four growing seasons (1996-1999) and used to predict Fday and Rn. We found that iNDVI was a strong predictor of Fday (R2 = 0.79, n = 66, P Elsevier Science Inc. All rights reserved.

  6. Impact of solar EUV flux on CO Cameron band and CO2+ UV doublet emissions in the dayglow of Mars

    CERN Document Server

    Jain, Sonal Kumar

    2011-01-01

    This study is aimed at making a calculation about the impact of the two most commonly used solar EUV flux models -- SOLAR2000 (S2K) of \\cite{Tobiska04} and EUVAC model of \\cite{Richards94} -- on photoelectron fluxes, volume emission rates, ion densities and CO Cameron and CO$_2^+$ UV doublet band dayglow emissions on Mars in three solar activity conditions: minimum, moderate, and maximum. Calculated limb intensities profiles are compared with SPICAM/Mars Express and Mariner observations. Analytical yield spectrum (AYS) approach has been used to calculate photoelectron fluxes in Martian upper atmosphere. Densities of prominent ions and CO molecule in excited triplet a$^3\\Pi$ state are calculated using major ion-neutral reactions. Volume emission rates of CO Cameron and CO$_2^+$ UV doublet bands have been calculated for dif{}ferent observations (Viking condition, Mariner and Mars Express SPICAM observations) on Mars. For the low solar activity condition, dayglow intensities calculated using the S2K model are $\\...

  7. Effects of climate warming and declining species richness in grassland model ecosystems: acclimation of CO2 fluxes

    Directory of Open Access Journals (Sweden)

    S. Vicca

    2007-01-01

    Full Text Available To study the effects of warming and declining species richness on the carbon balance of grassland communities, model ecosystems containing one, three or nine species were exposed to ambient and elevated (ambient +3°C air temperature. In this paper, we analyze measured ecosystem CO2 fluxes to test whether ecosystem photosynthesis and respiration had acclimated to warming after 28 months of continuous heating, and whether the degree of acclimation depended on species richness. In order to test whether acclimation occurred, short term temperature response curves were established for all communities in both treatments. At similar temperatures, lower flux rates in the heated communities as compared to the unheated communities would indicate thermal acclimation. Because plant cover was significantly higher in the heated treatment, we normalized the data for plant cover. Subsequently, down-regulation of both photosynthesis and respiration was observed. Although CO2 fluxes were larger in communities with higher species richness, species richness did not affect the degree of acclimation to warming. These results imply that models need to take thermal acclimation into account to simulate photosynthesis and respiration in a warmer world.

  8. Sensitivity of heat fluxes in hypersonic CO2 flows to the state-to-state kinetic schemes

    Science.gov (United States)

    Armenise, I.; Kustova, E.

    2016-11-01

    Kinetics and heat transfer in a CO2/CO/O2/O/C mixture in a hypersonic boundary layer is studied using a state-to-state vibrational-chemical kinetic model. The CO2 molecule is detailed in its symmetric stretching, bending and asymmetric stretching modes, which are strongly coupled through inter-mode vibrational energy transfers. Two sets of rate coefficients for the vibrational energy transitions are used. Different kinetic schemes including various physical and chemical processes are assessed. The heat flux is calculated, in the framework of the modified Chapman-Enskog theory, accounting for the vibrational states of involved molecules. Comparisons with results obtained using a simplified model, including mainly vibrational levels of the asymmetric stretching mode, are carried out. It is shown that VT transitions in the symmetric and asymmetric modes do not alter the flow and can be neglected. The heat flux is not sensitive to the rates of vibrational energy transitions but depends noticeably on the processes implemented to the kinetic scheme. Using the simplified model yields under-predicted surface heat fluxes; nevertheless we can recommend it for fast estimates of the fluid dynamic variables and heat transfer in hypersonic flows since its implementation essentially reduces computational costs.

  9. Soil wettability, moisture status and CO2 flux in a long term drought and warming simulation experiment

    Science.gov (United States)

    Urbanek, Emilia; Bösken, Janina; Titema, Albert; Nunez Pastrana, David; Emmett, Bridget

    2014-05-01

    Current climatic predictions include altered rainfall patterns and increased temperatures which in consequence can enhance the development of soil water repellency (SWR; i.e. hydrophobicity). Soils may become more severely water-repellent or SWR may spread into the environments where it has not been observed before. As the soil moisture dynamics, including restricted infiltration and uneven distribution of water is severely altered in water-repellent soils, so might be the decomposition of organic matter and overall exchange of gases like CO2 between the soil and the atmosphere. Long-term climatic simulation study has been conducted for over a decade at upland heathland sites in Oldebroek (Netherlands) and in Clocaenog (UK) [1]. At each site nine 20 m2-large plots were selected and each three were subjected to: a drought effect created by a rainfall exclusion using an automatic self retracting waterproof curtains; a warming effect using a self retracting curtains reflecting infrared radiation overnight, and control plots. The soil at the sites was a peaty podzol and sandy podzol both highly prone to soil water repellency development. The sites were constantly monitored since the start of the experiment and the range of meteorological and environmental measurements included for example: soil moisture, temperature, vegetation and root zone changes, soil CO2 flux. The observations of soil moisture content have shown that the soil moisture did not recover to the original values in the drought system even after the rainfall exclusion has been stopped for winter time, suggesting the development of soil water repellency [2]. The severe changes in moisture dynamics have also significantly affected the soil CO2 flux. The aim of the study was to investigate whether the long-term drought and warming treatments have any effect on the severity and persistence of SWR and how far the moisture changes and the SWR altered the CO2 flux from these soils. The measurements of the SWR

  10. FORECASTED CO2 MODIFIES THE INFLUENCE OF LIGHT IN SHAPING SUBTIDAL HABITAT(1).

    Science.gov (United States)

    Russell, Bayden D; Passarelli, Claire A; Connell, Sean D

    2011-08-01

    Some abiotic conditions are well known to play disproportionately large roles in shaping contemporary assemblages, yet their roles may not continue to have similar magnitudes of effect into the future. We tested whether forecasted levels of CO2 could alter the strength of influence of an abiotic factor (i.e., light intensity) well known for its strength of influence on the subtidal ecology of photosynthetic organisms. We investigated these dynamics in two subtidal algal species that form contrasting associations with kelp forests, one negatively associated with kelp canopies (turf-forming brown algae, Feldmannia spp.) and the other positively associated with kelp as understory (calcifying red crustose algae, Lithophyllum sp.). Using an experimental approach, we assessed the independent and combined effects of [CO2 ] (control and elevated) and light (shade, low ultraviolet B [UVB], full light) on growth, recruitment, and relative electron transport rate (rETR). Under control [CO2 ], the effects of light corresponded to the relative light environments of the two groups of algae. The influence of light on the percentage cover and biomass of understory crusts was substantially reduced under elevated [CO2 ], which caused crusts to grow less. While elevated [CO2 ] had the opposite effect of positively influencing turf cover and biomass, it had the same effect of reducing the structuring effects of light and UVB. Hence, if we are to predict the ecological consequences of future CO2 conditions, the role of contemporary processes cannot be assumed to produce similar effects relative to other processes, which will change with a changing climate. © 2011 Phycological Society of America.

  11. Mapping of the air-sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

    Science.gov (United States)

    Yasunaka, Sayaka; Murata, Akihiko; Watanabe, Eiji; Chierici, Melissa; Fransson, Agneta; van Heuven, Steven; Hoppema, Mario; Ishii, Masao; Johannessen, Truls; Kosugi, Naohiro; Lauvset, Siv K.; Mathis, Jeremy T.; Nishino, Shigeto; Omar, Abdirahman M.; Olsen, Are; Sasano, Daisuke; Takahashi, Taro; Wanninkhof, Rik

    2016-09-01

    We produced 204 monthly maps of the air-sea CO2 flux in the Arctic north of 60°N, including the Arctic Ocean and its adjacent seas, from January 1997 to December 2013 by using a self-organizing map technique. The partial pressure of CO2 (pCO2) in surface water data were obtained by shipboard underway measurements or calculated from alkalinity and total inorganic carbon of surface water samples. Subsequently, we investigated the basin-wide distribution and seasonal to interannual variability of the CO2 fluxes. The 17-year annual mean CO2 flux shows that all areas of the Arctic Ocean and its adjacent seas were net CO2 sinks. The estimated annual CO2 uptake by the Arctic Ocean was 180 TgC yr-1. The CO2 influx was strongest in winter in the Greenland/Norwegian Seas (>15 mmol m-2 day-1) and the Barents Sea (>12 mmol m-2 day-1) because of strong winds, and strongest in summer in the Chukchi Sea (∼10 mmol m-2 day-1) because of the sea-ice retreat. In recent years, the CO2 uptake has increased in the Greenland/Norwegian Sea and decreased in the southern Barents Sea, owing to increased and decreased air-sea pCO2 differences, respectively.

  12. On the ability of a global atmospheric inversion to constrain variations of CO2 fluxes over Amazonia

    Directory of Open Access Journals (Sweden)

    L. Molina

    2015-01-01

    Full Text Available The exchanges of carbon, water, and energy between the atmosphere and the Amazon Basin have global implications for current and future climate. Here, the global atmospheric inversion system of the Monitoring of Atmospheric Composition and Climate service (MACC was used to further study the seasonal and interannual variations of biogenic CO2 fluxes in Amazonia. The system assimilated surface measurements of atmospheric CO2 mole fractions made over more than 100 sites over the globe into an atmospheric transport model. This study added four surface stations located in tropical South America, a region poorly covered by CO2 observations. The estimates of net ecosystem exchange (NEE optimized by the inversion were compared to independent estimates of NEE upscaled from eddy-covariance flux measurements in Amazonia, and against reports on the seasonal and interannual variations of the land sink in South America from the scientific literature. We focused on the impact of the interannual variation of the strong droughts in 2005 and 2010 (due to severe and longer-than-usual dry seasons, and of the extreme rainfall conditions registered in 2009. The spatial variations of the seasonal and interannual variability of optimized NEE were also investigated. While the inversion supported the assumption of strong spatial heterogeneity of these variations, the results revealed critical limitations that prevent global inversion frameworks from capturing the data-driven seasonal patterns of fluxes across Amazonia. In particular, it highlighted issues due to the configuration of the observation network in South America and the lack of continuity of the measurements. However, some robust patterns from the inversion seemed consistent with the abnormal moisture conditions in 2009.

  13. On the ability of a global atmospheric inversion to constrain variations of CO2 fluxes over Amazonia

    Directory of Open Access Journals (Sweden)

    L. Molina

    2015-07-01

    Full Text Available The exchanges of carbon, water and energy between the atmosphere and the Amazon basin have global implications for the current and future climate. Here, the global atmospheric inversion system of the Monitoring of Atmospheric Composition and Climate (MACC service is used to study the seasonal and interannual variations of biogenic CO2 fluxes in Amazonia during the period 2002–2010. The system assimilated surface measurements of atmospheric CO2 mole fractions made at more than 100 sites over the globe into an atmospheric transport model. The present study adds measurements from four surface stations located in tropical South America, a region poorly covered by CO2 observations. The estimates of net ecosystem exchange (NEE optimized by the inversion are compared to an independent estimate of NEE upscaled from eddy-covariance flux measurements in Amazonia. They are also qualitatively evaluated against reports on the seasonal and interannual variations of the land sink in South America from the scientific literature. We attempt at assessing the impact on NEE of the strong droughts in 2005 and 2010 (due to severe and longer-than-usual dry seasons and the extreme rainfall conditions registered in 2009. The spatial variations of the seasonal and interannual variability of optimized NEE are also investigated. While the inversion supports the assumption of strong spatial heterogeneity of these variations, the results reveal critical limitations of the coarse-resolution transport model, the surface observation network in South America during the recent years and the present knowledge of modelling uncertainties in South America that prevent our inversion from capturing the seasonal patterns of fluxes across Amazonia. However, some patterns from the inversion seem consistent with the anomaly of moisture conditions in 2009.

  14. High Resolution Measurement of Rhizosphere Priming Effects and Temporal Variability of CO2 Fluxes under Zea Mays

    Science.gov (United States)

    Splettstößer, T.; Pausch, J.

    2016-12-01

    Plant induced increase of soil organic matter turnover rates contribute to carbon emissions in agricultural land use systems. In order to better understand these rhizosphere priming effects, we conducted an experiment, which enabled us to monitor CO2 fluxes under zea mays plants with high resolution. The experiment was conducted in a climate chamber where the plants were grown in thin, tightly sealed boxes for 40 days and CO2 efflux from soil was measured twice a day. 13C-CO2 was introduced to allow differentiation between plant and soil derived CO2.This enabled us to monitor root respiration and soil organic matter turnover in the early stages of plant growth and to highlight changes in soil CO2 emissions and priming effects between day and night. The measurements were conducted with a PICARRO G2131-I δ13C high-precision isotopic CO2 Analyzer (PICARRO INC.) utilizing an automated valve system governed by a CR1000 data logger (Campbell Scientific). After harvest roots and shoots were analyzed for 13C content. Microbial biomass, root length density and enzymatic activities in soil were measured and linked to soil organic matter turnover rates. In order to visualize the spatial distribution of carbon allocation to the root system a few plants were additionally labeled with 14C and 14C distribution was monitored by 14C imaging of the root systems over 4 days. Based on the 14C distribution a grid was chosen and the soil was sampled from each square of the grid to investigate the impact of carbon allocation hotspots on enzymatic activities and microbial biomass. First initial results show an increase of soil CO2 efflux in the night periods, whereby the contribution of priming is not fully analyzed yet. Additionally, root tips were identified as hotspots of short term carbon allocation via 14C imaging and an in increase in microbial biomass could be measured in this regions. The full results will be shown at AGU 2016.

  15. Predicting of regional transpiration at elevated atmospheric CO2: influence of the PBL vegetation interaction.

    NARCIS (Netherlands)

    Jacobs, C.M.J.; Bruin, de H.A.R.

    1997-01-01

    A coupled planetary boundary layer (PBL)-vegetation model is used to study the influence of the PBL-vegetation interaction and the ambient CO2 concentration on surface resistance rs and regional transpiration E. Vegetation is described using the big-leaf model in which rs is modeled by means of a

  16. Predicting of regional transpiration at elevated atmospheric CO2: influence of the PBL vegetation interaction.

    NARCIS (Netherlands)

    Jacobs, C.M.J.; Bruin, de H.A.R.

    1997-01-01

    A coupled planetary boundary layer (PBL)-vegetation model is used to study the influence of the PBL-vegetation interaction and the ambient CO2 concentration on surface resistance rs and regional transpiration E. Vegetation is described using the big-leaf model in which rs is modeled by means of a co

  17. CO2 and CH4 fluxes of contrasting pristine bogs in southern Patagonia (Tierra del Fuego, Argentina)

    Science.gov (United States)

    Münchberger, Wiebke; Blodau, Christian; Kleinebecker, Till; Pancotto, Veronica

    2015-04-01

    South Patagonian peatlands cover a wide range of the southern terrestrial area and thus are an important component of the terrestrial global carbon cycle. These extremely southern ecosystems have been accumulating organic material since the last glaciation up to now and are - in contrast to northern hemisphere bogs - virtually unaffected by human activities. So far, little attention has been given to these pristine ecosystems and great carbon reservoirs which will potentially be affected by climate change. We aim to fill the knowledge gap in the quantity of carbon released from these bogs and in what controls their fluxes. We study the temporal and spatial variability of carbon fluxes in two contrasting bog ecosystems in southern Patagonia, Tierra del Fuego. Sphagnum-dominated bog ecosystems in Tierra del Fuego are similar to the ones on the northern hemisphere, while cushion plant-dominated bogs can almost exclusively be found in southern Patagonia. These unique cushion plant-dominated bogs are found close to the coast and their occurrence changes gradually to Sphagnum-dominated bogs with increasing distance from the coast. We conduct closed chamber measurements and record relevant environmental variables for CO2 and CH4 fluxes during two austral vegetation periods from December to April. Chamber measurements are performed on microforms representing the main vegetation units of the studied bogs. Gas concentrations are measured with a fast analyzer (Los Gatos Ultraportable Greenhouse Gas Analyzer) allowing to accurately record CH4 fluxes in the ppm range. We present preliminary results of the carbon flux variability from south Patagonian peat bogs and give insights into their environmental controls. Carbon fluxes of these two bog types appear to be highly different. In contrast to Sphagnum-dominated bogs, cushion plant-dominated bogs release almost no CH4 while their CO2 flux in both, photosynthesis and respiration, can be twice as high as for Sphagnum

  18. Soil CO2 flux in relation to dissolved organic carbon, soil temperature and moisture in a subtropical arable soil of China

    Institute of Scientific and Technical Information of China (English)

    LOU Yun-sheng; LI Zhong-pei; ZHANG Tao-lin

    2003-01-01

    Soil CO2 emission from an arable soil was measured by closed chamber method to quantify year-round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil moisture content. Soil CO2 flux, soil temperature, DOC and soil moisture content were determined on selected days during the experiment from August 1999 to July 2000, at the Ecological Station of Red Soil, the Chinese Academy of Sciences, in a subtropical region of China. Soil CO2 fluxes were generally higher in summer and autumn than in winter and spring, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The estimation was 2.23 kgCO2/(m2·a) for average annual soil CO2 flux. Regressed separately, the reasons for soil flux variability were 86.6% from soil temperature, 58.8% from DOC, and 26.3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained approximately 85.2% of the flux variance, however by stepwise regression, soil temperature was the dominant affecting soil flux. Based on the exponential equation developed from soil temperature, the predicted annual flux was 2.49 kgCO2/(m2·a), and essentially equal to the measured one. It is suggested the exponential relationship between soil flux and soil temperature could be used for accurately predicting soil CO2 flux from arable soil in subtropical regions of China.

  19. BOREAS TE-1 CO2 and CH4 Flux Data Over the SSA-OBS Site

    Science.gov (United States)

    Anderson, Darwin; Papagno, Andrea; Hall, Forrest G. (Editor); Newcomer, Jeffrey A. (Editor)

    2000-01-01

    The BOREAS TE-1 team collected various data to characterize the soil-plant systems in the BOREAS SSA. Particular emphasis was placed on nutrient biochemistry, the stores and transfers of organic carbon, and how the characteristics were related to measured methane fluxes. The overall transect in the Prince Albert National Park (Saskatchewan, Canada) included the major plant communities and related soils that occurred in that section of the boreal forest. Soil physical, chemical, and biological measurements along the transect were used to characterize the static environment, which allowed them to be related to methane fluxes. Chamber techniques were used to provide a measure of methane production/uptake. Chamber measurements coupled with flask sampling were used to determine the seasonality of methane fluxes. This particular data set contains carbon dioxide and methane flux values from the SSA-OBS site. The data were collected from 09-Jun to 04-Sep-1994. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  20. CO2 flux through a Wyoming seasonal snowpack: Diffusional and pressure pumping effects

    Science.gov (United States)

    William Massman; Richard Sommerfeld; Karl Zeller; Ted Hehn; Laura Hudnell; Shannon Rochelle

    1995-01-01

    The movement of trace gases through porous media results from a combination of molecular diffusion and natural convection forced by turbulent atmospheric pressure pumping. This study presents observational and modeling results of an experiment to estimate the C02 flux through a seasonal snowpack in the Rocky Mountains of southern Wyoming, USA. Profiles of C02 mole...

  1. Self-potential, soil co2 flux, and temperature on masaya volcano, nicaragua

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J.L.; Connor, C.; St-Amand, K.; Stix, J.; Spinner, W.

    2003-07-01

    We investigate the spatial relationship between self-potential (SP), soil CO{sub 2} flux, and temperature and the mechanisms that produce SP anomalies on the flanks of Masaya volcano, Nicaragua. We measured SP, soil CO{sub 2} fluxes (<1 to 5.0 x 10{sup 4} g m{sup -2} d{sup -1}), and temperatures (26 to 80 C) within an area surrounding a normal fault, adjacent to Comalito cinder cone (2002-2003). These variables are well spatially correlated. Wavelengths of SP anomalies are {le}100 m, and high horizontal SP gradients flank the region of elevated flux and temperature. Carbon isotopic compositions of soil CO{sub 2} ({delta}{sup 13}C = -3.3 to -1.1{per_thousand}) indicate a deep gas origin. Given the presence of a deep water table (100 to 150 m), high gas flow rates, and subsurface temperatures above liquid boiling points, we suggest that rapid fluid disruption is primarily responsible for positive SP anomalies here. Concurrent measurement of SP, soil CO{sub 2} flux, and temperature may be a useful tool to monitor intrusive activity.

  2. Tropical Controls on the CO2 Atmospheric Growth Rate 2010-2011 from the NASA Carbon Monitoring System Flux (CMS-Flux) Project

    Science.gov (United States)

    Bowman, K. W.; Liu, J.; Parazoo, N.; Lee, M.; Menemenlis, D.; Gierach, M. M.; Brix, H.; Gurney, K. R.; Collatz, G. J.; Bousserez, N.; Henze, D. K.

    2014-12-01

    Interannual variations in the atmospheric growth rate of CO2 have been attributed to the tropical regions and the controls are correlated with temperature anomalies. We investigate the spatial drivers of the atmospheric growth rate and the processes controlling them over the exceptional period of 2010-2011. This period was marked by a marked shift from an El Nino to La Nina period resulting in historically high sea surface temperature anomalies in the tropical Atlantic leading to serious droughts in the Amazon. However, in 2011, unusual precipitation in Australia was linked to gross primary productivity anomalies in semi-arid regions. We use satellite observations of CO2, CO, and solar induced fluorescence assimilated into the NASA Carbon Monitoring System Project (CMS-Flux) to attribute the atmospheric growth rate to global, spatially resolved fluxes. This system is based upon observationally-constrained "bottom-up" estimates from the Fossil Fuel Data Assimilation System (FFDAS), the ECCO2­-Darwin physical and biogeochemical adjoint ocean state estimation system, and CASA-GFED3 land-surface biogeochemical model. The system is used to compute regional tropical and extra-tropical fluxes and quantify the role of biomass burning and gross primary productivity in controlling those fluxes.

  3. Impact of drought on the CO2 atmospheric growth rate 2010-2012 from the NASA Carbon Monitoring System Flux (CMS-Flux) Project

    Science.gov (United States)

    Bowman, K. W.; Liu, J.; Parazoo, N.; Jiang, Z.; Bloom, A. A.; Lee, M.; Menemenlis, D.; Gierach, M.; Collatz, G. J.; Gurney, K. R.

    2015-12-01

    The La Nina between 2011-2012 led to significant droughts in the US and Northeastern Brazil while the historic drought in Amazon in 2010 was caused in part by the historic central Pacific El Nino. In order to investigate the role of drought on the atmospheric CO2 growth rate, we use satellite observations of CO2 and CO to infer spatially resolved carbon fluxes and attribute those fluxes to combustion sources correlated with drought conditions. Solar induced fluorescence in turn is used to estimate the impact of drought on productivity and its relationship to total flux. Preliminary results indicate that carbon losses in Mexico are comparable to the total fossil fuel production for that region. These in turn played an important role in the acceleration of the atmospheric growth rate from 2011-2012. These results were enabled using the NASA Carbon Monitoring System Project (CMS-Flux), which is based upon a 4D-variational assimilation system that incorporates observationally-constrained "bottom-up" estimates from the Fossil Fuel Data Assimilation System (FFDAS), the ECCO2-­Darwin physical and biogeochemical adjoint ocean state estimation system, and CASA-GFED3 land-surface biogeochemical model.

  4. The influence of photosynthetic acclimation to rising CO2 and warmer temperatures on leaf and canopy photosynthesis models

    Science.gov (United States)

    There is an increasing necessity to understand how climate change factors, particularly increasing atmospheric concentrations of CO2 ([CO2]) and rising temperature, will influence photosynthetic carbon assimilation (A). Based on theory, an increased [CO2] concomitant with a rise in temperature will ...

  5. [Effects of brackish water irrigation on soil enzyme activity, soil CO2 flux and organic matter decomposition].

    Science.gov (United States)

    Zhang, Qian-qian; Wang, Fei; Liu, Tao; Chu, Gui-xin

    2015-09-01

    Brackish water irrigation utilization is an important way to alleviate water resource shortage in arid region. A field-plot experiment was set up to study the impact of the salinity level (0.31, 3.0 or 5.0 g · L(-1) NaCl) of irrigated water on activities of soil catalase, invertase, β-glucosidase, cellulase and polyphenoloxidase in drip irrigation condition, and the responses of soil CO2 flux and organic matter decomposition were also determined by soil carbon dioxide flux instrument (LI-8100) and nylon net bag method. The results showed that in contrast with fresh water irrigation treatment (CK), the activities of invertase, β-glucosidase and cellulase in the brackish water (3.0 g · L(-1)) irrigation treatment declined by 31.7%-32.4%, 29.7%-31.6%, 20.8%-24.3%, respectively, while soil polyphenoloxidase activity was obviously enhanced with increasing the salinity level of irrigated water. Compared to CK, polyphenoloxidase activity increased by 2.4% and 20.5%, respectively, in the brackish water and saline water irrigation treatments. Both soil microbial biomass carbon and microbial quotient decreased with increasing the salinity level, whereas, microbial metabolic quotient showed an increasing tendency with increasing the salinity level. Soil CO2 fluxes in the different treatments were in the order of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) ≥ saline water irrigation (5.0 g · L(-1)). Moreover, CO2 flux from plastic film mulched soil was always much higher than that from no plastic film mulched soil, regardless the salinity of irrigated water. Compared with CK, soil CO2 fluxes in the saline water and brackish water treatments decreased by 29.8% and 28.2% respectively in the boll opening period. The decomposition of either cotton straw or alfalfa straw in the different treatments was in the sequence of CK (0.31 g · L(-1)) > brackish water irrigation (3.0 g · L(-1)) > saline water treatment (5.0 g · L(-1)). The organic matter

  6. CO2 fluxes and ecosystem dynamics at five European treeless peatlands – merging data and process oriented modelling

    Directory of Open Access Journals (Sweden)

    C. Metzger

    2014-06-01

    Full Text Available The carbon dioxide (CO2 exchange of five different peatland systems across Europe with a wide gradient in landuse intensity, water table depth, soil fertility and climate was simulated with the process oriented CoupModel. The aim of the study was to find out to what extent CO2 fluxes measured at different sites, can be explained by common processes and parameters implemented in the model. The CoupModel was calibrated to fit measured CO2 fluxes, soil temperature, snow depth and leaf area index (LAI and resulting differences in model parameters were analysed. Finding site independent model parameters would mean that differences in the measured fluxes could be explained solely by model input data: water table, meteorological data, management and soil inventory data. The model, utilizing a site independent configuration for most of the parameters, captured seasonal variability in the major fluxes well. Parameters that differed between sites included the rate of soil organic decomposition, photosynthetic efficiency, and regulation of the mobile carbon (C pool from senescence to shooting in the next year. The largest difference between sites was the rate coefficient for heterotrophic respiration. Setting it to a common value would lead to underestimation of mean total respiration by a factor of 2.8 up to an overestimation by a factor of 4. Despite testing a wide range of different responses to soil water and temperature, heterotrophic respiration rates were consistently lowest on formerly drained sites and highest on the managed sites. Substrate decomposability, pH and vegetation characteristics are possible explanations for the differences in decomposition rates. Applying common parameter values for the timing of plant shooting and senescence, and a minimum temperature for photosynthesis, had only a minor effect on model performance, even though the gradient in site latitude ranged from 48° N (South-Germany to 68° N (northern Finland. This was also

  7. CO2 uptake and ecophysiological parameters of the grain crops of midcontinent North America: estimates from flux tower measurements

    Science.gov (United States)

    Gilmanov, Tagir; Wylie, Bruce; Tieszen, Larry; Meyers, Tilden P.; Baron, Vern S.; Bernacchi, Carl J.; Billesbach, David P.; Burba, George G.; Fischer, Marc L.; Glenn, Aaron J.; Hanan, Niall P.; Hatfield, Jerry L.; Heuer, Mark W.; Hollinger, Steven E.; Howard, Daniel M.; Matamala, Roser; Prueger, John H.; Tenuta, Mario; Young, David G.

    2013-01-01

    We analyzed net CO2 exchange data from 13 flux tower sites with 27 site-years of measurements over maize and wheat fields across midcontinent North America. A numerically robust “light-soil temperature-VPD”-based method was used to partition the data into photosynthetic assimilation and ecosystem respiration components. Year-round ecosystem-scale ecophysiological parameters of apparent quantum yield, photosynthetic capacity, convexity of the light response, respiration rate parameters, ecological light-use efficiency, and the curvature of the VPD-response of photosynthesis for maize and wheat crops were numerically identified and interpolated/extrapolated. This allowed us to gap-fill CO2 exchange components and calculate annual totals and budgets. VPD-limitation of photosynthesis was systematically observed in grain crops of the region (occurring from 20 to 120 days during the growing season, depending on site and year), determined by the VPD regime and the numerical value of the curvature parameter of the photosynthesis-VPD-response, σVPD. In 78% of the 27 site-years of observations, annual gross photosynthesis in these crops significantly exceeded ecosystem respiration, resulting in a net ecosystem production of up to 2100 g CO2 m−2 year−1. The measurement-based photosynthesis, respiration, and net ecosystem production data, as well as the estimates of the ecophysiological parameters, provide an empirical basis for parameterization and validation of mechanistic models of grain crop production in this economically and ecologically important region of North America.

  8. Influence of dissolved CO2 on crystallization of epsomite - variation of temperature

    Science.gov (United States)

    Huang, J.; Yin, Q.; Ulrich, J.

    2017-07-01

    Despite the minor amounts of gases dissolved in solutions, they can bring effects on many crystallization systems, which should be regarded as one type of ;invisible; impurity. The evidence of the effect of different dissolved gases on crystallization was provided in previous work. The variation of temperature was taken into consideration in this study. CO2 saturated solutions were prepared and air saturated solutions were used as a comparison. The results indicate that the influence of dissolved CO2 on crystallization of epsomite is altered with the variation of temperature. At low temperature, dissolved CO2 tends to suppress the thermodynamics and kinetic aspects of the solutions. With the increase of temperature the trend is reversed, i.e. at high temperature (>30 °C), dissolved CO2 enhances the relating properties of the solutions. At low temperature, the decrease of the pH value could be the dominating factor. Whereas at high temperature when the dissolved CO2 is in a supersaturated state, it starts to nucleate and grow, and partially changes into nano- or microbubbles, which can attach on crystal surfaces and disturb the crystallization process just as impurities do.

  9. Organic and inorganic fertilizer effect on soil CO2 flux, microbial biomass, and growth of Nigella sativa L.

    Science.gov (United States)

    Salehi, Aliyeh; Fallah, Seyfollah; Sourki, Ali Abasi

    2017-01-01

    Cattle manure has a high carbon/nitrogen ratio and may not decompose; therefore, full-dose application of urea fertilizer might improve biological properties by increasing manure decomposition. This study aimed to investigate the effect of combining cattle manure and urea fertilizer on soil CO2 flux, microbial biomass carbon, and dry matter accumulation during Nigella sativa L. (black cumin) growth under field conditions. The treatments were control, cattle manure, urea, different levels of split and full-dose integrated fertilizer. The results showed that integrated application of cattle manure and chemical fertilizer significantly increased microbial biomass carbon by 10%, soil organic carbon by 2.45%, total N by 3.27%, mineral N at the flowering stage by 7.57%, and CO2 flux by 9% over solitary urea application. Integrated application increased microbial biomass carbon by 10% over the solitary application and the full-dose application by 5% over the split application. The soil properties and growth parameters of N. sativa L. benefited more from the full-dose application than the split application of urea. Cattle manure combined with chemical fertilizer and the full-dose application of urea increased fertilizer efficiency and improved biological soil parameters and plant growth. This method decreased the cost of top dressing urea fertilizer and proved beneficial for the environment and medicinal plant health.

  10. Effects of experimental water table and temperature manipulations on ecosystem CO2 fluxes in an Alaskan rich fen

    Science.gov (United States)

    Chivers, M.R.; Turetsky, M.R.; Waddington, J.M.; Harden, J.W.; McGuire, A.D.

    2009-01-01

    Peatlands store 30% of the world's terrestrial soil carbon (C) and those located at northern latitudes are expected to experience rapid climate warming. We monitored growing season carbon dioxide (CO2) fluxes across a factorial design of in situ water table (control, drought, and flooded plots) and soil warming (control vs. warming via open top chambers) treatments for 2 years in a rich fen located just outside the Bonanza Creek Experimental Forest in interior Alaska. The drought (lowered water table position) treatment was a weak sink or small source of atmospheric CO2 compared to the moderate atmospheric CO2 sink at our control. This change in net ecosystem exchange was due to lower gross primary production and light-saturated photosynthesis rather than increased ecosystem respiration. The flooded (raised water table position) treatment was a greater CO2 sink in 2006 due largely to increased early season gross primary production and higher light-saturated photosynthesis. Although flooding did not have substantial effects on rates of ecosystem respiration, this water table treatment had lower maximum respiration rates and a higher temperature sensitivity of ecosystem respiration than the control plot. Surface soil warming increased both ecosystem respiration and gross primary production by approximately 16% compared to control (ambient temperature) plots, with no net effect on net ecosystem exchange. Results from this rich fen manipulation suggest that fast responses to drought will include reduced ecosystem C storage driven by plant stress, whereas inundation will increase ecosystem C storage by stimulating plant growth. ?? 2009 Springer Science+Business Media, LLC.

  11. Monitoring and simulation of water, heat,and CO2 fluxes in terrestrial ecosystems based on the APEIS-FLUX system

    Institute of Scientific and Technical Information of China (English)

    WATANABEMasataka; WANGQinxue; HAYASHISeiji; MURAKAMIShogo; LIUJiyuan; OUYANGZhu; LIYan; LIYingnian; WANGKelin

    2005-01-01

    The Integrated Environmental Monitoring (IEM) project, part of the Asia-Pacific Environmental Innovation Strategy (APEIS) project, developed an integrated environmental monitoring system that can be used to detect, monitor, and assess environmental disasters, degradation, and their impacts in the Asia-Pacific region. The system primarily employs data from the moderate resolution imaging spectrometer (MODIS) sensor on the Earth Observation System- (EOS-) Terra/Aqua satellite,as well as those from ground observations at five sites in different ecological systems in China. From the preliminary data analysis on both annual and daily variations of water, heat and COz fluxes, we can confirm that this system basically has been working well. The results show that both latent flux and CO2 flux are much greater in the crop field than those in the grassland and the saline desert, whereas the sensible heat flux shows the opposite trend. Different data products from MODIS have very different correspondence, e.g. MODIS-derived land surface temperature has a close correlation with measured ones, but LAI and NPP are quite different from ground measurements, which suggests that the algorithms used to process MODIS data need to be revised by using the local dataset. We are now using the APEIS-FLUX data to develop an integrated model, which can simulate the regional water,heat, and carbon fluxes. Finally, we are expected to use this model to develop more precise high-order MODIS products in Asia-Pacific region.

  12. High CO2 fluxes from grassland on histic Gleysol along soil carbon and drainage gradients

    Science.gov (United States)

    Leiber-Sauheitl, K.; Fuß, R.; Voigt, C.; Freibauer, A.

    2014-02-01

    Drained organic soils are anthropogenic emission hotspots of greenhouse gases (GHGs). Most studies have focused on deep peat soils and on peats with high organic carbon content. In contrast, histic Gleysols are characterized by shallow peat layers, which are left over from peat cutting activities or by peat mixed with mineral soil. It is unknown whether they emit less GHGs than deep Histosols when drained. We present the annual carbon and GHG balance of grasslands for six sites on nutrient-poor histic Gleysols with a shallow (30 cm) histic horizon or mixed with mineral soil in Northern Germany (soil organic carbon concentration (Corg) from 9 to 52%). The net GHG balance, corrected for carbon export by harvest, was around 4 t CO2-C-eq ha-1 yr-1 on soils with peat layer and little drainage (mean annual water table GHG inventories which are likely not to include histic Gleysols. The land area with GHG emission hotspots due to drainage is likely to be much higher than anticipated. Deeply drained histic Gleysols are GHG hotspots that have so far been neglected or underestimated. Peat mixing with sand does not mitigate GHG emissions. Our study implies that rewetting organic soils, including histic Gleysols, has a much higher relevance for GHG mitigation strategies than currently recognized.

  13. The relative influence of H2O and CO2 on the primitive surface conditions and evolution of rocky planets

    Science.gov (United States)

    Salvador, A.; Massol, H.; Davaille, A.; Marcq, E.; Sarda, P.; Chassefière, E.

    2017-07-01

    How the volatile content influences the primordial surface conditions of terrestrial planets and, thus, their future geodynamic evolution is an important question to answer. We simulate the secular convective cooling of a 1-D magma ocean (MO) in interaction with its outgassed atmosphere. The heat transfer in the atmosphere is computed either using the grey approximation or using a k-correlated method. We vary the initial CO2 and H2O contents (respectively from 0.1 × 10-2 to 14 × 10-2 wt % and from 0.03 to 1.4 times the Earth Ocean current mass) and the solar distance—from 0.63 to 1.30 AU. A first rapid cooling stage, where efficient MO cooling and degassing take place, producing the atmosphere, is followed by a second quasi steady state where the heat flux balance is dominated by the solar flux. The end of the rapid cooling stage (ERCS) is reached when the mantle heat flux becomes negligible compared to the absorbed solar flux. The resulting surface conditions at ERCS, including water ocean's formation, strongly depend both on the initial volatile content and solar distance D. For D > DC, the "critical distance," the volatile content controls water condensation and a new scaling law is derived for the water condensation limit. Although today's Venus is located beyond DC due to its high albedo, its high CO2/H2O ratio prevents any water ocean formation. Depending on the formation time of its cloud cover and resulting albedo, only 0.3 Earth ocean mass might be sufficient to form a water ocean on early Venus.

  14. Long-term CO2 flux dynamics and soil C stock changes of a drained fen mire under different grassland management practices in Northeast Germany

    Science.gov (United States)

    Augustin, Juergen; Giebels, Michael; Albiac Borraz, Elisa; Hoffmann, Mathias; Sommer, Michael

    2014-05-01

    Fen mires, widely distributed in Germany and Northern Europe, contain extreme high amounts of carbon (up to 5000 t C per hectare). For this reason, they play an important role in the global cycle of the greenhouse gases carbon dioxide (CO2) and methane (CH4). Currently more than 95% of all fen mires in central Europe are drained. Therefore, they are assumed to represent extremely strong sources for CO2,accompanied by a fast reduction of the peat carbon stocks. For a number of reasons it is not possible to overcome this problem by restoration measures like flooding at the most drained fen sites. Moreover, there are till now just few and contradictory information about the contribution of alternative land use forms like grassland extensification on the reduction of the CO2 source function of these organic soils. As a contribution to clearing this deficit, we have ongoingly measured the CO2 and CH4 exchange as well as the changes in C stock on a deeply drained fen mire near the village of Paulinenaue from 2007 till 2012. The measurement sites is located within the so-called Rhin-Havelluch, an 80000 ha shallow paludification mire complex in the northwest of Berlin. The investigation included extensively and intensively used meadows (one cut vs. three cuts) on two soil types with different C stocks (Hemic Rheic Histosol vs. Mollic Gleysol). We used transparent chambers for measuring the CO2 flux net ecosystem exchange (difference between gross primary production and ecosystem respiration) and non-transparent chambers for measuring the CO2 flux ecosystem respiration and the CH4 exchange. Determined soil stock changes based on a C budget approach, including cumulated annual net ecosystem exchange, cumulated CH4 exchange, C export by harvest, and C import by fertilization. All current C fluxes were influenced in a complex way by ground-water level, plant development, land use intensity (cut frequency) and current weather conditions. Averaged over the whole investigation

  15. Early results from the development of a miniature tunable diode laser gas cell for measuring CO2 isotopologue fluxes in situ

    Science.gov (United States)

    Osuna, J. L.; Bora, M.; Bond, T.; Wharton, S.

    2014-12-01

    In order to accurately predict how ecosystems will respond to climate change, it is necessary to separate the response of respiration and photosynthetic uptake individually to environmental conditions. Currently, the net ecosystem exchange of CO2 is measured continuously at various ecosystems around the world. Net CO­2 flux can be partitioned into the primary components using either models or measurements of 13C/12C in the CO2 flux. We introduce recent technological developments toward in situ, rapid, continuous measurements of fluxes of 13CO2 and 12CO2. We describe a unique approach to achieving 10Hz measurements of CO2 using tunable diode laser gas absorption spectroscopy in a multi-pass White cell capable of being deployed directly to a canopy. We will first discuss proof-of-concept characterization of the technique using wave modulation spectroscopy with a laser tuned to detect 12CO2 fluxes. We show the sensitivity of the 2w component of a wave-modulated signal to CO2 concentration, the precision, and the accuracy of the sensor as well as the stability of the sensor under normal ranges of ambient temperature and humidity in an environmental chamber. We then show preliminary results of sensor performance with a laser tuned to measure 13CO2 and 12CO2 fluxes. We discuss our approach to reliably measuring multiple peaks of gas absorption while maintaining the rapid sampling rates necessary for flux calculations. We will also discuss considerations for extending the sensor from the lab to being directly deployed into a canopy for in situ measurements. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS- 658355

  16. Simulation of CO2 and latent heat fluxes in the North China Plain

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Yongqiang; YU; Qiang; LIU; Changming; WANG; Jing

    2005-01-01

    We constructed a coupled model for simulating plant photosynthesis and evapotranspiration (CPCEM). In the model, non-rectangular hyperbola is used to simulate leaf photosynthesis rate that is scaled up to estimate canopy gross photosynthesis rate by an integral method. Whole canopy in the model is separated into multi-layers, each of which is divided into sunlit leaves and shade leaves. Canopy net photosynthesis rate is expressed as a function of canopy conductance which is coupled with evapotranspiration. Included the coupled function,evapotranspiration is estimated with a two-layer submodel. The main features of CPCEM are: (1)easy suitability, (2) good physiological base, and (3) simple calculation procedure. Simulated results of CPCEM were compared with those by an eddy covariance system that was installed in a winter wheat farmland of the North China Plain. CPCEM gave a quite well diurnal and seasonal dynamics of net ecosystem exchange, compared with the measurements. The root mean square error between simulation and measurements was only about 2.94 μ mol m-2 s-1. Diurnal and seasonal patterns of latent heat flux with the CPCEM were similar to those of measurements.Whereas, simulated latent heat flux was evidently higher than the measured.

  17. Implications of elevated CO2 on pelagic carbon fluxes in an Arctic mesocosm study - an elemental mass balance approach

    Science.gov (United States)

    Czerny, J.; Schulz, K. G.; Boxhammer, T.; Bellerby, R. G. J.; Büdenbender, J.; Engel, A.; Krug, S. A.; Ludwig, A.; Nachtigall, K.; Nondal, G.; Niehoff, B.; Silyakova, A.; Riebesell, U.

    2013-05-01

    Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air-sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification applying KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation), all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down the mentioned uncertainties. Water-column concentrations of particulate and dissolved organic and inorganic matter were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution as well as estimates of wall growth were developed to close the gaps in element budgets. However, losses elements from the budgets into a sum of insufficiently determined pools were detected, and are principally unavoidable in mesocosm investigation. The comparison of variability patterns of all single measured datasets revealed analytic precision to be the main issue in determination of budgets. Uncertainties in dissolved organic carbon (DOC), nitrogen (DON) and particulate organic phosphorus (POP) were much higher than the summed error in determination of the same elements in all other pools. With estimates provided for all other major elemental pools, mass balance calculations could be used to infer the temporal development of DOC, DON and POP pools. Future elevated pCO2 was found to enhance net autotrophic community carbon uptake in two of

  18. Implications of elevated CO2 on pelagic carbon fluxes in an Arctic mesocosm study – an elemental mass balance approach

    Directory of Open Access Journals (Sweden)

    J. Czerny

    2013-05-01

    Full Text Available Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air–sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification applying KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation, all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down the mentioned uncertainties. Water-column concentrations of particulate and dissolved organic and inorganic matter were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution as well as estimates of wall growth were developed to close the gaps in element budgets. However, losses elements from the budgets into a sum of insufficiently determined pools were detected, and are principally unavoidable in mesocosm investigation. The comparison of variability patterns of all single measured datasets revealed analytic precision to be the main issue in determination of budgets. Uncertainties in dissolved organic carbon (DOC, nitrogen (DON and particulate organic phosphorus (POP were much higher than the summed error in determination of the same elements in all other pools. With estimates provided for all other major elemental pools, mass balance calculations could be used to infer the temporal development of DOC, DON and POP pools. Future elevated pCO2 was found to enhance net autotrophic community carbon

  19. CO2 fluxes and respiration of branch segments of sycamore (Platanus occidentalis L.) examined at different sap velocities, branch diameters, and temperatures.

    Science.gov (United States)

    McGuire, M A; Cerasoli, S; Teskey, R O

    2007-01-01

    Respiration of stems and branches of trees (R(S)) has typically been estimated by measuring radial CO(2) efflux from woody tissue (E(A)) and rates of efflux are often scaled temporally using a temperature relationship (Q(10)). High concentrations of CO(2) in xylem sap ([CO(2)*]) have been shown to affect E(A), and the transport of CO(2) in the xylem stream has been suggested as a mechanism to explain field observations of temperature-independent fluctuations in E(A). Sap velocity and temperature were manipulated in detached branch segments of sycamore (Platanus occidentalis L.) under controlled conditions to quantify these effects. Within individual branches of similar size, E(A) and [CO(2)*] were greater at low sap velocity, while the amount of respired CO(2) transported in sap (transport flux, F(T)) was greater at high sap velocity. E(A) was linearly correlated with [CO(2)*]. In branches of three diameter classes (1, 2, and 3 cm), volume-based E(A), F(T), and R(S) did not differ, but surface-area based CO(2) fluxes increased with diameter class. Regardless of diameter, E(A) accounted for only 30% of respired CO(2) at high sap velocity, while at low sap velocity, E(A) accounted for 71% of respired CO(2). E(A), F(T), and R(S) measured at 5, 20, and 35 degrees C at the same sap velocity showed a typical exponential response to temperature. However, at the lowest temperature, E(A) accounted for only 18% of the CO(2) released from respiring cells compared with 44% at the highest temperature, perhaps due to the effect of temperature on the solubility of CO(2) in water. These results directly demonstrate the transport of respired CO(2) in the xylem stream and may help to explain inconsistencies in stem and branch respiration measurements made in situ.

  20. Impact of Ocean Acidification on Fluxes of non-CO2 Climate-Active Species: Report from the GESAMP WG38 workshop

    Science.gov (United States)

    Suntharalingam, Parvadha; Gehlen, Marion; Hopkins, Frances; Duce, Robert; Jickells, Tim; Gesamp WG38 Workshop, Participants

    2017-04-01

    Most investigations of the impact of ocean acidification (OA) have focused on changes in oceanic uptake of anthropogenic CO2, the resulting shifts in carbonate chemical equilibria, and the consequences for marine calcifying organisms. Little attention has been paid to the direct impacts of OA on the ocean sources of a range of other gaseous and aerosol species that are influential in regulating radiative forcing, atmospheric oxidising capacity and atmospheric chemistry. The oceanic processes governing emissions of these species are frequently sensitive to the changes in pH and ocean pCO2 accompanying ocean acidification. Such processes include, for example, metabolic rates of microbial activity, levels of surface primary production, ecosystem composition, and photo-chemical and microbially mediated production/loss pathways for individual species. The direct and indirect influences of these factors on oceanic fluxes of non-CO2 trace-gases and aerosols, and the subsequent feedbacks to climate remain highly uncertain. To address these issues UN/GESAMP Working Group 38, The Atmospheric Input of Chemicals to the Ocean, convened a workshop on this topic at the University of East Anglia in February, 2017. The goals of this workshop are to review and synthesize the current science on the direct impacts of ocean acidification on marine emissions to the atmosphere of key species important for climate, and atmospheric chemistry; and to identify the primary needs for new research to improve process understanding and to quantify the impact of ocean acidification on these marine fluxes (i.e., provide recommendations on the specific laboratory process studies, field measurements and model analyses needed to support targeted research activities on this topic). The results, conclusions, and recommendations of this workshop will be presented.

  1. High temporal resolution ecosystem CH4, CO2 and H2O flux data measured with a novel chamber technique

    Science.gov (United States)

    Steenberg Larsen, Klaus; Riis Christiansen, Jesper

    2016-04-01

    switching automatically between transparent and darkened mode enabling for separation of light-sensitive and light-indifferent processes in chambers. In a pilot study we measured hourly fluxes of CO2, H2O and CH4 continuously for two weeks in Danish Calluna vulgaris (common heather) heathland (Larsen et al. 2011). We will present an analysis of the novel, high-frequency data of CH4 fluxes under light and dark conditions, assess the advantages and limitations of the experimental setup and recommend future improvements of the technology involved. References: Carter, M.S., Larsen, K.S., et al. 2012. Synthesizing greenhouse gas fluxes across nine European peatlands and shrublands: responses to climatic and environmental changes. Biogeosciences 3739-3755. Christiansen, J.R., Korhonen, J.F.J., et al. 2011. Assessing the effects of chamber placement, manual sampling and headspace mixing on CH4 fluxes in a laboratory experiment. Plant and Soil 343, 171-185. Christiansen, J.R., Outhwaite, J., et al. 2015. Comparison of CO2, CH4 and N2O soil-atmosphere exchange measured in static chambers with cavity ring-down spectroscopy and gas chromatography. Agricultural and Forest Meteorology 211-212, 48-57. Creelman, C., Nickerson, N., Risk, D., 2013. Quantifying Lateral Diffusion Error in Soil Carbon Dioxide Respiration Estimates using Numerical Modeling. Soil Science Society of America Journal 77, 699-708. Larsen, K.S., Andresen, L.C., et al. 2011. Reduced N cycling in response to elevated CO2, warming, and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments. Global Change Biology 17, 1884-1899. Pihlatie, M.K., Christiansen, J.R., et al. 2013. Comparison of static chambers to measure CH4 emissions from soils. Agricultural and Forest Meteorology 171-172, 124-136.

  2. Daily variation characteristics of CO2 emission fluxes and contributions of environmental factors in semiarid grassland of Inner Mongolia, China

    Institute of Scientific and Technical Information of China (English)

    QI; Yuchun; DONG; Yunshe; LIU; Jiyuan; GENG; Yuanbo; LI; Mi

    2005-01-01

    Fixed field experimental studies are carried out on daily variations of the undisturbed community and soil respiration fluxes in different phenological phases of 2001-2002 in semiarid Aneurolepidium chinense steppe of Inner Mongolia, China using static black chamber method. Corresponding statistical analysis of the contributions of the water-heat factors (air temperature, ground temperature, surface soil water content) and ecological factors (aboveground biomass, underground biomass, litter biomass) to daily variation law of the undisturbed community and soil respiration fluxes as well as differences in daily respiration are also conducted. The results indicate that undisturbed community and soil respiration have apparent daily variation laws, daily variation patterns of respiration fluxes during different phenological phases are basically the same, and the variations of environmental factors only exert effect on CO2 emission intensities, while the effect on daily variation pattern of grassland CO2 emission fluxes is relatively small. The daily total respiration of the undisturbed community in different phenological phases ranges from 1.34-10.13 g·m-2; soil daily total respiration ranges from 0.98-5.17 g·m-2; both daily variations of undisturbed community and soil respiration fluxes are significantly correlated (p < 0.05) or extremely significantly correlated (p < 0.01) with air temperatures and ground surface temperatures, but the correlativity with the soil temperature at 5 and 10 cm depths is relatively weak; multiple regression analysis indicates that about 80% of the difference in daily respiration of the undisturbed community among different phenological phases is induced by the variation of the aboveground biomass, while the variations of the remaining factors can jointly explain around 20% of the daily respiration variations of the whole grassland ecosystem; about 83% of the soil daily respiration variation of the different phenological phases is caused

  3. A Modern Automatic Chamber Technique as a Powerful Tool for CH4 and CO2 Flux Monitoring

    Science.gov (United States)

    Mastepanov, M.; Christensen, T. R.; Lund, M.; Pirk, N.

    2014-12-01

    A number of similar systems were used for monitoring of CH4 and CO2 exchange by the automatic chamber method in a range of different ecosystems. The measurements were carried out in northern Sweden (mountain birch forest near Abisko, 68°N, 2004-2010), southern Sweden (forest bog near Hässleholm, 56°N, 2007-2014), northeastern Greenland (arctic fen in Zackenberg valley, 74°N, 2005-2014), southwestern Greenland (fen near Nuuk, 64°N, 2007-2014), central Svalbard (arctic fen near Longyearbyen, 78°N, 2011-2014). Those in total 37 seasons of measurements delivered not only a large amount of valuable flux data, including a few novel findings (Mastepanov et al., Nature, 2008; Mastepanov et al., Biogeosciences, 2013), but also valuable experience with implementation of the automatic chamber technique using modern analytical instruments and computer technologies. A range of high resolution CH4 analysers (DLT-100, FMA, FGGA - Los Gatos Research), CO2 analyzers (EGM-4, SBA-4 - PP Systems; Li-820 - Li-Cor Biosciences), as well as Methane Carbon Isotope Analyzer (Los Gatos Research) has shown to be suitable for precise measurements of fluxes, from as low as 0.1 mg CH4 m-1 d-1 (wintertime measurements at Zackenberg, unpublished) to as high as 2.4 g CH4 m-1 d-1 (autumn burst 2007 at Zackenberg, Mastepanov et al., Nature, 2008). Some of these instruments had to be customized to accommodate 24/7 operation in harsh arctic conditions. In this presentation we will explain some of these customizations. High frequency of concentration measurements (1 Hz in most cases) provides a unique opportunity for quality control of flux calculations; on the other hand, this enormous amount of data can be analyzed only using highly automated algorithms. A specialized software package was developed and improved through the years of measurements and data processing. This software automates the data flow from raw concentration data of different instruments and sensors and various status records

  4. A synthesis of air-sea fluxes of CO2 along the west coast of the Americas

    Science.gov (United States)

    Chavez, F.; Friederich, G.; Bushinsky, S.; Gaxiola, G.; Lara Lara, R.; Ledesma, J.

    2008-12-01

    This contribution summarizes coastal measurements of the air-sea flux of CO2 made from the United States to Chile over the last several years using ships and moorings. The general patterns of neutral to into the ocean fluxes at high latitudes and out of the ocean at low latitudes are clearly evident in the data. In some cases the gradient is rather sharp. The paper analyzes the high frequency spatial and temporal scales variability over the region and the long term changes off central California where a 15 year time series is now available. The scale analysis provides recommended sampling frequencies to resolve the mean and year to year changes. Analysis of onshore-offshore transects provides insight into the processes controlling the air- sea fluxes on a regional scale. Similar insight can be gleaned from the high frequency measurements from moorings. To conclude we suggest an observing strategy for documenting the impacts of climate change and highlight areas that need require further study

  5. 湖南会同杉木人工林生态系统CO2通量特征%Characteristics of CO2 Flux in a Chinese Fir Plantation Ecosystem in Huitong County, Hunan Province

    Institute of Scientific and Technical Information of China (English)

    赵仲辉; 张利平; 康文星; 田大伦; 项文化; 闫文德; 彭长辉

    2011-01-01

    利用开路式涡动相关系统与自动气象梯度观测系统2008年12个月的观测数据,研究会同13年生杉木人工林CO2通量特征.结果表明:13年生杉木人工林生态系统CO2通量日变化存在明显的季节差异,晴天平均碳汇持续时间表现为夏>春>秋>冬,平均日较差表现为夏>秋>春>冬,最大碳汇出现时间由早到晚依次为夏、秋、春和冬;1年中,月累积碳通量除1和2月为碳源外,其他各月均表现为碳汇,碳汇最大值出现在6月(-53.0 g C·m-2);13年生杉木林的年碳汇总量为-255.3 g C·m-2.白天CO2通量与光合有效辐射的关系可用Michaelis-Menten模型模拟(P<0.05),但模型参数随温度而异;夜间CO2通量与5 cm土壤温度呈指数关系(P<0.05).%Characteristics of CO2 flux were investigated by using the data collected from an open path eddy covariance system and an automatic weather gradient system in a 13-year-old Chinese fir plantation ecosystem in Huitong County, Hunan Province, in 2008. The results showed that there were pronounced diurnal and annual variations in CO2 flux in the Chinese fir plantation. In clear days, mean duration of negative CO2 fluxes decreased from summer, spring, autumn to winter, and the biggest mean daily carbon dioxide flux range and the earliest time of the average minimum carbon dioxide appeared in summer, followed by autumn, spring and winter. The Chinese fir plantation ecosystem had a negative monthly CO2 flux that acted as a carbon sink except for January and February. The minimum accumulated monthly net carbon ecosystem exchange (maximum carbon sink) was -53.0 g C ? M-2 occurred in June. The annual net carbon ecosystem exchange amounted to - 255. 3 g C ? M-2 . The CO2 flux was closely related to several meteorological factors including photosynthetic active radiation, air temperature and soil temperature. The Michaelis-Menten model could be used to express the relationship between CO2 flux and

  6. Influence of CO2 corrosion on rock structure and its mechanical characteristics

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Influence of CO2 corrosion on reservoir mineralogical composition,pore structure and their mechanical characteristics was studied using XRD,SEM,rock tri-axial machine and core flow experimental equipment.It was found that the corrosion effect was mainly attributed to rock texture and structure,fluid composition and external dynamical conditions in the experimental conditions.For cores with bedding structures,their bedding surfaces were the preferential corrosion regions,because micro-cracks would evolve at these surfaces in the pressure-releasing process.However,for cores with massive structures controlled by stable water environment,the CO2 corrosion would result in pore enlargement and secondary pore formation.The gas velocity from outlet showed sharp increase in the injection process of CO2-H2O solution.This could be explained by two changes caused by corrosion.One was the opening and closure of micro-cracks.The other was particle migration.As the corrosion time increased,both tensile strength and compressive strength decreased,which confirmed decrease of cementation strength.It should also be noted that permeability increase and micro-cracks generation would pose damage to the capacity of CO2 geological storage.

  7. Influences of Hole Shape on Film Cooling Characteristics with CO2 Injection

    Institute of Scientific and Technical Information of China (English)

    Li Guangchao; Zhu Huiren; Fan Huiming

    2008-01-01

    This article presents the data about heat transfer coefficient ratios, film cooling effectiveness and heat loads for the injection through cylindrical holes, 3-in-1 holes and fanned holes in order to characterize the film cooling performance downstream of a row of holes with 45° inclination and 3 hole spacing apart. The trip wire is placed upstream at a distance of 10 times diameter of the cooling hole from the hole center to keep mainstream fully turbulent. Both inlet and outlet of 3-in-1 holes have a 15° lateral expansion. The outlet of faaned holes has a lateral expansion. CO2 is applied for secondary injection to obtain a density ratio of 1.5. Momentum flux ratio varies from 1 to 4. The results indicate that the increased momentum flux ratio significantly inoreases heat transfer coefficient and slightly improve film cooling effectiveness for the injection through cylindrical holes. A weak dependence of heat transfer coefficient and film cooling effectiveness, respectively, on momentum flux ratio has been identified for the injection through 3-in-1 holes. The increase of the momentum flux ratio decreases heat transfer coefficient and significantly increases film cooling effectiveness for the injection through fanned holes. In terms of the film cooling performance, the fanned holes are the best while the cylindrical holes are the worst among the three hole shapes under study.

  8. Intermediate-scale community-level flux of CO2 and CH4 in a Minnesota peatland: putting the SPRUCE project in a global context

    Science.gov (United States)

    P. J. Hanson; A. L. Gill; X. Xu; J. R. Phillips; D. J. Weston; Randy Kolka; J. S. Riggs; L. A. Hook

    2016-01-01

    Peatland measurements of CO2 and CH4 flux were obtained at scales appropriate to the in situ biological community below the tree layer to demonstrate representativeness of the spruce and peatland responses under climatic and environmental change (SPRUCE) experiment. Surface flux measurements were made using dual open-path...

  9. Response of CO2 and H2O fluxes in a mountainous tropical rainforest in equatorial Indonesia to El Niño events

    DEFF Research Database (Denmark)

    Olchev, A.; Ibrom, Andreas; Panferov, O.

    2015-01-01

    The possible impact of El Niño–Southern Oscillation (ENSO) events on the main components of CO2 and H2O fluxes in a pristine mountainous tropical rainforest growing in Central Sulawesi in Indonesia is described. The fluxes were continuously measured using the eddy covariance method for the period...

  10. Coastal upwelling fluxes of O2, N2O, and CO2 assessed from continuous atmospheric observations at Trinidad,California

    Directory of Open Access Journals (Sweden)

    T. J. Lueker

    2004-08-01

    Full Text Available Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed. Regional air-sea fluxes of O2/N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.

  11. Estimation of sea-air CO2 flux in seaweed aquaculture area, Lidao Bay%大型藻类规模化养殖水域海-气界面CO2交换通量估算

    Institute of Scientific and Technical Information of China (English)

    蒋增杰; 方建光; 韩婷婷; 李加琦; 毛玉泽; 王巍

    2013-01-01

    选择山东俚岛湾大型藻类养殖水域作为研究区域,根据2011年4、8、10月和2012年1月4个航次的大面调查获得的pH、总碱度(TA)、叶绿素a等基础数据,分析了该区域表层海水溶解无机碳(DIC)体系各分量的浓度、组成比例及时空变化特征,估算了海-气界面CO2的交换通量.结果表明,该区域表层海水DIC、HCO3-、CO32-及CO2的年平均浓度分别为2 024.8±147.0、1 842.4±132.1、170.0±42.8和12.4±2.5μmol/L.养殖区与非养殖区之间DIC、HCO3-浓度差异不显著(P>0.05),而CO2浓度差异极显著(P<0.01).表层海水pCO2和海-气界面CO2的交换通量的年平均值分别为287.8±37.9 μatm和-32.7±17.2 mmol/m2·d,养殖区与非养殖区之间、不同季节之间均差异极显著(P<0.01).大型藻类的养殖活动有利于海洋对大气CO2的吸收.%In order to assess the effect of seaweed aquaculture on sea-air CO2 flux, a large-scale seaweed aquaculture area which is located in Lidao Bay, was selected as the investigation area. Based on the investigation data of pH, total alkalinity (TA), Chl-a, etc. During four cruises from April 2011 to January 2012, the spatial and seasonal variations of dissolved inorganic carbon (DIC) system parameters and aqueous pCO2 were investigated. Results showed that the mean annual concentrations of DIC, HCO3-,CO32- and CO2 were 2 024. 8 ± 147.0μmol/ L, 1 842. 4 ± 132. 1 μmol/L, 170. 0 ± 42. 8μmol/L and 12. 4 ± 2. 5 μmol/L, respectively. There were no significant differences between areas in concentrations of DIC and HCO3- (P> 0. 05) , while the differences for the concentration of CO2 were highly significant(P< 0. 01). The mean annual values of aqueous pCO2 and sea-air CO2 flux were 287. 8 ± 37. 9 juatm and —32. 7 ± 17. 2 μmol/m2 · d, respectively. There were highly significant differences (P<0. 01) for aqueous pCO2 and sea-air CO2 flux not only between different areas, but also between different seasons. Seaweed

  12. Chambers versus Relaxed Eddy Accumulation: an intercomparison study of two methods for short-term measurements of biogenic CO2 fluxes

    Science.gov (United States)

    Jasek, Alina; Zimnoch, Miroslaw; Gorczyca, Zbigniew; Chmura, Lukasz; Necki, Jaroslaw

    2014-05-01

    The presented work is a part of comprehensive study aimed at thorough characterization of carbon cycle in the urban environment of Krakow, southern Poland. In the framework of this study two independent methods were employed to quantify biogenic CO2 flux in the city: (i) closed chambers, and (ii) Relaxed Eddy Accumulation (REA). The results of a three-day intensive intercomparison campaign performed in July 2013 and utilizing both measurement methods are reported here. The chamber method is a widely used approach for measurements of gas exchange between the soil and the atmosphere. The system implemented in this study consisted of a single chamber operating in a closed-dynamic mode, combined with Vaisala CarboCAP infrared CO2 sensor in a mobile setup. An alternative flux measurement method, covering larger area is represented by REA, which is a modification of the eddy covariance method. It consists of a 3D anemometer (Gill Windmaster Pro) and the system collecting updraft and downdraft samples to 5-litre Tedlar bags. The CO2 mixing ratios in the collected samples are measured by Picarro G2101i analyzer. The setup consists of two sets of bags so that the sampling can be performed continuously with 15-min temporal resolution. A 48-hectares open meadow located close the city center was chosen as a test site for comparison of the two methods of CO2 flux measurements outlined above. In the middle of the meadow a 3-metre high tripod was installed with the anemometer and REA inlet system. For a period of 46 hours the system was measuring net CO2 flux from the surrounding area. A meteorological conditions and intensity of photosynthetically active radiation (PAR) were also recorded. In the same time, CO2 flux from several points around the REA inlet was measured with the chamber system, resulting in 93 values for both respiration and net CO2 flux. Chamber results show rather homogenous distribution of the soil CO2 flux (the mean value equal to 40.9 ± 2.2 mmol/m2h), with

  13. Towards understanding the variability in biospheric CO2 fluxes: using FTIR spectrometry and a chemical transport model to investigate the sources and sinks of carbonyl sulfide and its link to CO2

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    Y. Wang

    2015-09-01

    Full Text Available Understanding carbon dioxide (CO2 biospheric processes is of great importance because the terrestrial exchange drives the seasonal and inter-annual variability of CO2 in the atmosphere. Atmospheric inversions based on CO2 concentration measurements alone can only determine net biosphere fluxes, but not differentiate between photosynthesis (uptake and respiration (production. Carbonyl sulfide (OCS could provide an important additional constraint: it is also taken up by plants during photosynthesis but not emitted during respiration, and therefore is a potential mean to differentiate between these processes. Solar absorption Fourier Transform InfraRed (FTIR spectrometry allows for the retrievals of the atmospheric concentrations of both CO2 and OCS from measured solar absorption spectra. Here, we investigate co-located and quasi-simultaneous FTIR measurements of OCS and CO2 performed at three selected sites located in the Northern Hemisphere. These measurements are compared to simulations of OCS and CO2 using a chemical transport model (GEOS-Chem. The OCS simulations are driven by different land biospheric fluxes to reproduce the seasonality of the measurements. Increasing the plant uptake of Kettle et al. (2002a by a factor of three resulted in the best comparison with FTIR measurements. However, there are still discrepancies in the latitudinal distribution when comparing with HIPPO (HIAPER Pole-to-Pole Observations data spanning both hemispheres. The coupled biospheric fluxes of OCS and CO2 from the simple biosphere model (SiB are used in the study and compared to measurements. The CO2 simulation with SiB fluxes agrees with the measurements well, while the OCS simulation reproduced a weaker drawdown than FTIR measurements at selected sites, and a smaller latitudinal gradient in the Northern Hemisphere during growing season. An offset in the timing of the seasonal cycle minimum between SiB simulation and measurements is also seen. Using OCS as a

  14. Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes.

    Science.gov (United States)

    Musa-Aziz, Raif; Occhipinti, Rossana; Boron, Walter F

    2014-11-01

    Human carbonic anhydrase IV (CA IV) is GPI-anchored to the outer membrane surface, catalyzing CO2/HCO3 (-) hydration-dehydration. We examined effects of heterologously expressed CA IV on intracellular-pH (pHi) and surface-pH (pHS) transients caused by exposing oocytes to CO2/HCO3 (-)/pH 7.50. CO2 influx causes a sustained pHi fall and a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA IV increases magnitudes of maximal rate of pHi change (dpHi/dt)max, and maximal pHS change (ΔpHS) and decreases time constants for pHi changes (τpHi ) and pHS relaxations (τpHS ). Decreases in time constants indicate that CA IV enhances CO2 fluxes. Extracellular acetazolamide blocks all CA IV effects, but not those of injected CA II. Injected acetazolamide partially reduces CA IV effects. Thus, extracellular CA is required for, and the equivalent of cytosol-accessible CA augments, the effects of CA IV. Increasing the concentration of the extracellular non-CO2/HCO3 (-) buffer (i.e., HEPES), in the presence of extracellular CA or at high [CO2], accelerates CO2 influx. Simultaneous measurements with two pHS electrodes, one on the oocyte meridian perpendicular to the axis of flow and one downstream from the direction of extracellular-solution flow, reveal that the downstream electrode has a larger (i.e., slower) τpHS , indicating [CO2] asymmetry over the oocyte surface. A reaction-diffusion mathematical model (third paper in series) accounts for the above general features, and supports the conclusion that extracellular CA, which replenishes entering CO2 or consumes exiting CO2 at the extracellular surface, enhances the gradient driving CO2 influx across the cell membrane.

  15. Preliminary results on yield and CO2 fluxes when using alternate wetting and drying on different varieties of European rice

    Science.gov (United States)

    Oliver, Viktoria; Monaco, Stefano; Volante, Andrea; Cochrane, Nicole; Gennaro, Massimo; Orasen, Gabriele; Valè, Giampiero; Price, Adam; Arn Teh, Yit

    2016-04-01

    In Europe, rice is grown (467 000 ha) under permanently flooded conditions (PF) using irrigation waters of major rivers. Climate change, which has led to a greater fluctuation in river flows, is a major challenge to rice production systems, which depend on large and consistent water supplies. This challenge will become more acute in the future, with more frequent extreme weather (e.g. drought) predicted under climate change and increased demands for rice. Alternate wetting and drying (AWD) is a system in where irrigation is applied to obtain 2-5 cm of field water depth, after which the soil is allowed to drain naturally to typically 15 cm below the surface before re-wetting once more. Preliminary studies suggest that AWD can reduce water use by up 30 %, with no net loss in yield but significantly reducing CH4 emissions. However, uncertainties still remain as to the impacts of AWD on CO2 exchange, N2O fluxes, and plant acclimation responses to a fluctuating water regime. For example, CO2 emissions could potentially increase in AWD due to higher rates of soil organic matter decomposition when the fields are drained. The work presented here evaluated the impacts of AWD on the productivity and yield of twelve varieties of European rice, whilst simultaneously measuring CO2 exchange, N2O fluxes, and plant biomass allocation patterns under different treatment regimes. Field experiments were conducted in the Piedmont region (northern Italy Po river plain) in a loamy soil during the growing season of 2015 in a 2-factor paired plot design, with water treatment (AWD, PF) and variety (12 European varieties) as factors (n=4 per variety per treatment). The varieties chosen were commercially important cultivars from across the rice growing regions of Europe (6 Italian, 3 French, 3 Spanish). Light and dark CO2 fluxes were measured six times over the growing season, using an infra-red gas analyzer. Environmental variables (soil moisture, temperature, water table depth, water

  16. Inferences from CO2 and CH4 concentration profiles at the Zotino Tall Tower Observatory (ZOTTO on local summer-time ecosystem fluxes

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    J. Winderlich

    2013-09-01

    Full Text Available The Siberian region is still sparsely covered by ecosystem observatories, which motivates to exploit existing datasets to gain spatially and temporally better-resolved carbon fluxes. The Zotino Tall Tower Observatory (ZOTTO, 60°48' N, 89°21' E observations of CO2 and CH4 mole fractions as well as meteorological parameters from six different heights up to 301 m allow for an additional estimate of surface-atmosphere fluxes of CO2 and CH4 for the Middle-Siberian region since 2009. The total carbon flux is calculated from the storage and the turbulent flux component. The gradients between the different tower levels determine the storage flux component, which dominates the local fluxes, especially during night. As a correction term, the turbulent flux component was estimated by the modified Bowen ratio method based on the sensible heat flux measurements at the top of the tower. The gained average night time fluxes (23:00 to 04:00 local time are 2.7 ± 1.1 μmol (m2 s−1 for CO2 and 5.6 ± 4.5 nmol (m2 s−1 for CH4 during the summer months June-September in 2009 and 2011. During day, the method is limited due to numeric instabilities from vanishing vertical gradients; however, the derived CO2 fluxes exhibit reasonable diurnal shape and magnitude compared to the eddy covariance technique, which become available at the site in 2012. Therefore, the tall tower data facilitates the extension of the new eddy covariance flux dataset back in time. The diurnal signal of the CH4 flux is predominantly characterized by a strong morning transition, which is explained by local topographic effects.

  17. On the ratio of intercellular to ambient CO2 (c i/c a) derived from ecosystem flux

    Science.gov (United States)

    Tan, Zheng-Hong; Wu, Zhi-Xiang; Hughes, Alice C.; Schaefer, Douglas; Zeng, Jiye; Lan, Guo-Yu; Yang, Chuang; Tao, Zhong-Liang; Chen, Bang-Qian; Tian, Yao-Hua; Song, Liang; Jatoi, Muhammad Tahir; Zhao, Jun-Fu; Yang, Lian-Yan

    2017-07-01

    The ratio of intercellular to ambient CO2 concentrations (c i/c a) plays a key role in ecophysiology, micrometeorology, and global climatic change. However, systematic investigation on c i/c a variation and its determinants are rare. Here, the c i/c a was derived from measuring ecosystem fluxes in an even-aged monoculture of rubber trees (Hevea brasiliensis). We tested whether c i/c a is constant across environmental gradients and if not, which dominant factors control c i/c a variations. Evidence indicates that c i/c a is not a constant. The c i/c a exhibits a clear "V"-shaped diurnal pattern and varies across the environmental gradient. Water vapor pressure deficit (D) is the dominant factor controls over the c i/c a variations. c i/c a consistently decreases with increasing D. c i/c a decreases with square root of D as predicted by the optimal stomatal model. The D-driving single-variable model could simulate c i/c a as well as that of sophisticated model. Many variables function on longer timescales than a daily cycle, such as soil water content, could improve c i/c a model prediction ability. Ecosystem flux can be effectively used to calculate c i/c a and use it to better understand various natural cycles.

  18. Whole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds (Palma Bay, NW Mediterranean

    Directory of Open Access Journals (Sweden)

    A. V. Borges

    2004-10-01

    Full Text Available The relationship between whole-system metabolism estimates based on planktonic and benthic incubations (bare sediments and seagrass, Posidonia oceanica meadows, and CO2 fluxes across the air-sea interface were examined in the Bay of Palma (Mallorca, Spain during two cruises in March and June 2002. Moreover, planktonic and benthic incubations were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the bay. From the annual study, results showed a contrast between the planktonic compartment, which was heterotrophic during most of the year, except for occasional bloom episodes, and the benthic compartment, which was slightly autotrophic. Whereas the seagrass community was autotrophic, the excess organic carbon production therein could only balance the excess respiration of the planktonic compartment in shallow waters (2 fields and fluxes across the bay observed during the two extensive cruises in 2002. Finally, dissolved inorganic carbon and oxygen budgets provided NEP estimates in fair agreement with those derived from direct metabolic estimates based on incubated samples over the Posidonia oceanica meadow.

  19. Mesure des flux de CO2 et bilan carboné de grandes cultures : état de la question et méthodologie

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    Bodson B.

    2008-01-01

    Full Text Available CO2 flux measurement and carbon balance of agricultural crops. The increase of carbon dioxide (CO2 atmospheric concentration, which is a greenhouse gas, put in stress the need of a better understanding of the carbon cycle and its dynamic. In particular, the exchanges between ecosystems and atmosphere are characterized by large uncertainties. Regional networks were set up to study these CO2