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Sample records for air-sea co2 fluxes

  1. Annual and seasonal fCO2 and air-sea CO2 fluxes in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Lauvset, S. K.; Chierici, M.; Counillon, F.; Omar, A.; Nondal, G.; Johannessen, T.; Olsen, A.

    2013-03-01

    The Barents Sea is the strongest CO2 sink in the Arctic region, yet estimates of the air-sea CO2 flux in this area show a large span reflecting uncertainty as well as significant variability both seasonally and regionally. Here we use a previously unpublished data set of seawater CO2 fugacity (fCO2), and map these data over the western Barents Sea through multivariable linear regressions with SeaWiFS/MODIS remote sensing and TOPAZ model data fields. We find that two algorithms are necessary in order to cover the full seasonal cycle, mainly because not all proxy variables are available for the entire year, and because variability in fCO2 is driven by different mechanisms in summer and winter. A comprehensive skill assessment indicates that there is a good overall correspondence between observations and predictions. The algorithms are also validated using two independent data sets, with good results. The gridded fCO2 fields reveal tight links between water mass distribution and fCO2 in all months, and particularly in winter. The seasonal cycle show peaks in the total air-sea CO2 influx in May and September, caused by respectively biological drawdown of CO2 and low sea ice concentration leaving a large open water area. For 2007 the annual average air-sea CO2 flux is - 48 ± 5 gC m- 2, which is comparable to previous estimates.

  2. Large Temporal Variations in Air-Sea CO2 Flux off the Coast of Georgia

    NASA Astrophysics Data System (ADS)

    Caves, J. K.; Sabine, C.; Cai, W.; Alin, S.

    2008-12-01

    Though the inner shelf is a small portion of global ocean area, its air-sea CO2 flux is disproportionately high. Due to its tight links with both terrestrial and oceanic systems, the inner shelf is likely to experience significant spatial and temporal variability. We measured the fugacity of CO2 (fCO2) continuously from July 2006 to June 2008 on a moored platform in Gray's Reef National Marine Sanctuary on Georgia's inner shelf. The long-term, high temporal resolution data has allowed us to begin to measure interannual variations in CO2 flux along the inner Georgia shelf. From July 2006-June 2007, the inner Georgia shelf was a CO2 sink (-3.26mmol/m2/day), while during following year, the shelf switched to being a source (2.26mmol/m2/day). Choice of wind data (satellite or buoy-derived) significantly alters these estimates of annual fluxes. QuikSCAT satellite wind data indicate a much larger sink (- 6.13mmol/m2/day) during 2006-2007, and a non-existent source (0.02mmol/m2/day) during 2007- 2008. An earlier, high-resolution spatial study from January 2005-May 2006 found that the inner shelf within the South Atlantic Bight may have been a source of 0.65 to 1.20mmol/m2/day, suggesting that the inner shelf may experience dramatic swings in CO2 flux. Though sea-surface temperature (SST) is the largest influence on surface water fCO2, average monthly SST varied little between both years; instead, possible explanations for the large variation in interannual CO2 flux include decreased biological production and increased river flow (and, hence carbon export) during 2007-2008. This is the first evidence of large-scale, annual switches in air-sea CO2 flux within an inner shelf, and it holds significant implications for global estimates of air-sea CO2 flux.

  3. Influence of precipitation on the CO2 air-sea flux, an eddy covariance field study

    NASA Astrophysics Data System (ADS)

    Zavarsky, Alexander; Steinhoff, Tobias; Marandino, Christa

    2016-04-01

    During the SPACES-OASIS cruise (July-August 2015) from Durban, SA to Male, MV direct fluxes of CO2 and dimethyl sulfide (DMS) were measured using the eddy covariance (EC) technique. The cruise covered areas of sources and sinks for atmospheric CO2, where the bulk concentration gradient measurements resembled the Takahashi (2009) climatology. Most of the time, bulk CO2 fluxes (F=k* [cwater-cair]), calculated with the parametrization (k) by Nightingale et al. 2000, were in general agreement with direct EC measurements. However, during heavy rain events, the directly measured CO2 fluxes were 4 times higher than predicted. It has been previously described that rain influences the k parametrization of air-sea gas exchange, but this alone cannot explain the measured discrepancy. There is evidence that freshwater input and a change in the carbonate chemistry causes the water side concentration of ?c=cwater-cair to decrease. Unfortunately this cannot be detected by most bulk measurement systems. Using the flux measurements of an additional gas like DMS, this rain influence can be evaluated as DMS does not react to changes in the carbonate system and has a different solubility. A pending question is if the enhanced flux of CO2 in the ocean is sequestered into the ocean mixed layer and below. This question will be tackled using the GOTM model to understand the implications for the global carbon cycle.

  4. Spatio-temporal visualization of air-sea CO2 flux and carbon budget using volume rendering

    NASA Astrophysics Data System (ADS)

    Du, Zhenhong; Fang, Lei; Bai, Yan; Zhang, Feng; Liu, Renyi

    2015-04-01

    This paper presents a novel visualization method to show the spatio-temporal dynamics of carbon sinks and sources, and carbon fluxes in the ocean carbon cycle. The air-sea carbon budget and its process of accumulation are demonstrated in the spatial dimension, while the distribution pattern and variation of CO2 flux are expressed by color changes. In this way, we unite spatial and temporal characteristics of satellite data through visualization. A GPU-based direct volume rendering technique using half-angle slicing is adopted to dynamically visualize the released or absorbed CO2 gas with shadow effects. A data model is designed to generate four-dimensional (4D) data from satellite-derived air-sea CO2 flux products, and an out-of-core scheduling strategy is also proposed for on-the-fly rendering of time series of satellite data. The presented 4D visualization method is implemented on graphics cards with vertex, geometry and fragment shaders. It provides a visually realistic simulation and user interaction for real-time rendering. This approach has been integrated into the Information System of Ocean Satellite Monitoring for Air-sea CO2 Flux (IssCO2) for the research and assessment of air-sea CO2 flux in the China Seas.

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

    NASA Astrophysics Data System (ADS)

    LéVy, M.; Lengaigne, M.; Bopp, L.; Vincent, E. M.; Madec, G.; Ethé, C.; Kumar, D.; Sarma, V. V. S. S.

    2012-06-01

    Previous case studies have illustrated the strong local influence of tropical cyclones (TCs) on CO2 air-sea flux ? suggesting that they can significantly contribute to the global ? In this study, we use a state-of-the art global ocean biochemical model driven by TCs wind forcing derived from a historical TCs database, allowing to sample the ? response under 1663 TCs. Our results evidence a very weak contribution of TCs to global ? one or two order of magnitude smaller than previous estimates extrapolated from case studies. This result arises from several competing effects involved in the ? response to TCs, not accounted for in previous studies. While previous estimates have hypothesized the ocean to be systematically oversaturated in CO2 under TCs, our results reveal that a similar proportion of TCs occur over oversaturated regions (i.e. the North Atlantic, Northeast Pacific and the Arabian Sea) and undersaturated regions (i.e. Westernmost North Pacific, South Indian and Pacific Ocean). Consequently, by increasing the gas exchange coefficient, TCs can generate either instantaneous CO2 flux directed from the ocean to the atmosphere (efflux) or the opposite (influx), depending on the CO2 conditions at the time of the TC passage. A large portion of TCs also occurs over regions where the ocean and the atmosphere are in near equilibrium, resulting in very weak instantaneous fluxes. Previous estimates also did not account for any asynchronous effect of TCs on ? during several weeks after the storm, oceanic pCO2 is reduced in response to vertical mixing, which systematically causes an influx anomaly. This implies that, contrary to previous estimates, TCs weakly affect the CO2 efflux when they blow over supersaturated areas because the instantaneous storm wind effect and post-storm mixing effect oppose with each other. In contrast, TCs increase the CO2 influx in undersaturated conditions because the two effects add up. These compensating effects result in a very weak

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Reconstruction of super-resolution fields of ocean pCO2 and air-sea fluxes of CO2 from satellite imagery in the Southeastern Atlantic

    NASA Astrophysics Data System (ADS)

    Hernández-Carrasco, I.; Sudre, J.; Garçon, V.; Yahia, H.; Garbe, C.; Paulmier, A.; Dewitte, B.; Illig, S.; Dadou, I.

    2015-01-01

    The knowledge of Green House Gases GHGs fluxes at the air-sea interface at high resolution is crucial to accurately quantify the role of the ocean in the absorption and emission of GHGs. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO2, pCO2, and air-sea CO2 fluxes at super resolution (4 km) using Sea Surface Temperature (SST) and Ocean Colour (OC) data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). Inference of super-resolution of pCO2, and air-sea CO2 fluxes is performed using novel nonlinear signal processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the Microcanonical Multifractal Formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multiresolution analysis performed on the signal of the so-called singularity exponents allows the correct and near optimal cross-scale inference of GHGs fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred representation of oceanic partial pressure of CO2 improves and enhances the description provided by CarbonTracker, capturing the small scale variability. We examine different combinations of Ocean Colour and Sea Surface Temperature products in order to increase the number of valid points and the quality of the inferred pCO2 field. The methodology is validated using in-situ measurements by means of statistical errors. We obtain that mean absolute and relative errors in the inferred values of pCO2 with respect to in-situ measurements are smaller than for CarbonTracker.

  8. Air-sea CO2 fluxes measured by eddy covariance in a coastal station in Baja California, México

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Loza, L.; Ocampo-Torres, F. J.

    2016-05-01

    The influence of wave-associated parameters controlling turbulent CO2 fluxes through the air-sea water interface is evaluated in a coastal region. The study area, located within the Todos Santos Bay, Baja California, México, was found to be a weak sink of CO2 with a mean flux of -1.32 µmol m-2s-1. The low correlation found between flux and wind speed (r = 0.09), suggests that the influence of other forcing mechanisms, besides wind, is important for gas transfer modulation through the sea surface, at least for the conditions found in this study. In addition, the results suggest that for short periods where an intensification of the wave conditions occurs, a CO2 flux response increases the transport of gas to the ocean.

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

    NASA Astrophysics Data System (ADS)

    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

  10. Inference of super-resolution ocean pCO2 and air-sea CO2 fluxes from non-linear and multiscale processing methods

    NASA Astrophysics Data System (ADS)

    Hernández-Carrasco, Ismael; Sudre, Joel; Garçon, Veronique; Yahia, Hussein; Dewitte, Boris; Garbe, Christoph; Illig, Séréna; Montes, Ivonne; Dadou, Isabelle; Paulmier, Aurélien; Butz, André

    2014-05-01

    In recent years the role of submesoscale activity is emerging as being more and more important to understand global ocean properties, for instance, for accurately estimating the sources and sinks of Greenhouse Gases (GHGs) at the air-sea interface. The scarcity of oceanographic cruises and the lack of available satellite products for GHG concentrations at high resolution prevent from obtaining a global assessment of their spatial variability at small scales. In this work we develop a novel method to reconstruct maps of CO2 fluxes at super resolution (4km) using SST and ocean colour data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). The responsible process for propagating the information between scales is related to cascading properties and multiscale organization, typical of fully developed turbulence. The methodology, based on the Microcanonical Multifractal Formalism, makes use, from the knowledge of singularity exponents, of the optimal wavelet for the determination of the energy injection mechanism between scales. We perform a validation analysis of the results of our algorithm using pCO2 ocean data from in-situ measurements in the upwelling region off Namibia.

  11. Regulation of CO2 Air Sea Fluxes by Sediments in the North Sea

    NASA Astrophysics Data System (ADS)

    Burt, William; Thomas, Helmuth; Hagens, Mathilde; Brenner, Heiko; Pätsch, Johannes; Clargo, Nicola; Salt, Lesley

    2016-04-01

    A multi-tracer approach is applied to assess the impact of boundary fluxes (e.g. benthic input from sediments or lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry, of the North Sea. Analyses of both basin-wide observations in the North Sea and transects through tidal basins at the North-Frisian coastline, reveal that surface distributions of the δ13C signature of dissolved inorganic carbon (DIC) are predominantly controlled by a balance between biological production and respiration. In particular, variability in metabolic DIC throughout stations in the well-mixed southern North Sea indicates the presence of an external carbon source, which is traced to the European continental coastline using naturally-occurring radium isotopes (224Ra and 228Ra). 228Ra is also shown to be a highly effective tracer of North Sea total alkalinity (AT) compared to the more conventional use of salinity. Coastal inputs of metabolic DIC and AT are calculated on a basin-wide scale, and ratios of these inputs suggest denitrification as a primary metabolic pathway for their formation. The AT input paralleling the metabolic DIC release prevents a significant decline in pH as compared to aerobic (i.e. unbuffered) release of metabolic DIC. Finally, long-term pH trends mimic those of riverine nitrate loading, highlighting the importance of coastal AT production via denitrification in regulating pH in the southern North Sea.

  12. Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

    NASA Astrophysics Data System (ADS)

    Yang, Mingxi; Bell, Thomas G.; Hopkins, Frances E.; Kitidis, Vassilis; Cazenave, Pierre W.; Nightingale, Philip D.; Yelland, Margaret J.; Pascal, Robin W.; Prytherch, John; Brooks, Ian M.; Smyth, Timothy J.

    2016-05-01

    We present air-sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l.), each from a different period during 2014-2015. At sampling heights ≥ 18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable ( ≤ ±20 % in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air-sea exchange measurements in shelf regions. Covariance air-sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m-2 d-1 at 15, 18, 27 m a.m.s.l.) than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air-sea CH4 flux by eddy covariance to be 20 µmole m-2 d-1 over hourly timescales (4 µmole m-2 d-1 over 24 h).

  13. Natural Air-Sea Flux of CO2 in Simulations of the NASA-GISS Climate Model: Sensitivity to the Physical Ocean Model Formulation

    NASA Technical Reports Server (NTRS)

    Romanou, A.; Gregg, Watson W.; Romanski, J.; Kelley, M.; Bleck, R.; Healy, R.; Nazarenko, L.; Russell, G.; Schmidt, G. A.; Sun, S.; Tausnev, N.

    2013-01-01

    Results from twin control simulations of the preindustrial CO2 gas exchange (natural flux of CO2) between the ocean and the atmosphere are presented here using the NASA-GISS climate model, in which the same atmospheric component (modelE2) is coupled to two different ocean models, the Russell ocean model and HYCOM. Both incarnations of the GISS climate model are also coupled to the same ocean biogeochemistry module (NOBM) which estimates prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2. Model intercomparison is carried out at equilibrium conditions and model differences are contrasted with biases from present day climatologies. Although the models agree on the spatial patterns of the air-sea flux of CO2, they disagree on the strength of the North Atlantic and Southern Ocean sinks mainly because of kinematic (winds) and chemistry (pCO2) differences rather than thermodynamic (SST) ones. Biology/chemistry dissimilarities in the models stem from the different parameterizations of advective and diffusive processes, such as overturning, mixing and horizontal tracer advection and to a lesser degree from parameterizations of biogeochemical processes such as gravitational settling and sinking. The global meridional overturning circulation illustrates much of the different behavior of the biological pump in the two models, together with differences in mixed layer depth which are responsible for different SST, DIC and nutrient distributions in the two models and consequently different atmospheric feedbacks (in the wind, net heat and freshwater fluxes into the ocean).

  14. Spatio-temporal dynamics of biogeochemical processes and air-sea CO2 fluxes in the Western English Channel based on two years of FerryBox deployment

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Latimier, M.; Macé, E.; Morin, P.; Vernet, M.; Bozec, Y.

    2014-12-01

    From January 2011 to January 2013, a FerryBox system was installed on a Voluntary Observing Ship (VOS), which crossed the Western English Channel (WEC) between Roscoff (France) and Plymouth (UK) up to 3 times a day. The FerryBox continuously measured sea surface temperature (SST), sea surface salinity (SSS), dissolved oxygen (DO), fluorescence and partial pressure of CO2 (from April 2012) along the ferry track. Sensors were calibrated based on 714 bimonthly surface samplings with precisions of 0.016 for SSS, 3.3 μM for DO, 0.40 μg L- 1 for Chlorophyll-a (Chl-a) (based on fluorescence measurements) and 5.2 μatm for pCO2. Over the 2 years of deployment (900 crossings), we reported 9% of data lost due to technical issues and quality checked data was obtained to allow investigation of the dynamics of biogeochemical processes related to air-sea CO2 fluxes in the WEC. Based on this unprecedented high-frequency dataset, the physical structure of the WEC was assessed using SST anomalies and the presence of a thermal front was observed around the latitude 49.5°N, which divided the WEC in two main provinces: the seasonally stratified northern WEC (nWEC) and the all-year well-mixed southern WEC (sWEC). These hydrographical properties strongly influenced the spatial and inter-annual distributions of phytoplankton blooms, which were mainly limited by nutrients and light availability in the nWEC and the sWEC, respectively. Air-sea CO2 fluxes were also highly related to hydrographical properties of the WEC between late April and early September 2012, with the sWEC a weak source of CO2 to the atmosphere of 0.9 mmol m- 2 d- 1, whereas the nWEC acted as a sink for atmospheric CO2 of 6.9 mmol m- 2 d- 1. The study of short time-scale dynamics of air-sea CO2 fluxes revealed that an intense and short (less than 10 days) summer bloom in the nWEC contributed to 29% of the CO2 sink during the productive period, highlighting the necessity for high frequency observations in coastal

  15. Intraseasonal variability linked to sampling alias in air-sea CO2 fluxes in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Monteiro, Pedro M. S.; Gregor, Luke; Lévy, Marina; Maenner, Stacy; Sabine, Christopher L.; Swart, Sebastiaan

    2015-10-01

    The Southern Ocean (SO) contributes most of the uncertainty in contemporary estimates of the mean annual flux of carbon dioxide CO2 between the ocean and the atmosphere. Attempts to reduce this uncertainty have aimed at resolving the seasonal cycle of the fugacity of CO2 (fCO2). We use hourly CO2 flux and driver observations collected by the combined deployment of ocean gliders to show that resolving the seasonal cycle is not sufficient to reduce the uncertainty of the flux of CO2 to below the threshold required to reveal climatic trends in CO2 fluxes. This was done by iteratively subsampling the hourly CO2 data set at various time intervals. We show that because of storm-linked intraseasonal variability in the spring-late summer, sampling intervals longer than 2 days alias the seasonal mean flux estimate above the required threshold. Moreover, the regional nature and long-term trends in storm characteristics may be an important influence in the future role of the SO in the carbon-climate system.

  16. Dynamics of air-sea CO2 fluxes in the northwestern European shelf based on voluntary observing ship and satellite observations

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Macé, E.; Morin, P.; Salt, L. A.; Vernet, M.; Taylor, B.; Paxman, K.; Bozec, Y.

    2015-09-01

    From January 2011 to December 2013, we constructed a comprehensive pCO2 data set based on voluntary observing ship (VOS) measurements in the western English Channel (WEC). We subsequently estimated surface pCO2 and air-sea CO2 fluxes in northwestern European continental shelf waters using multiple linear regressions (MLRs) from remotely sensed sea surface temperature (SST), chlorophyll a concentration (Chl a), wind speed (WND), photosynthetically active radiation (PAR) and modeled mixed layer depth (MLD). We developed specific MLRs for the seasonally stratified northern WEC (nWEC) and the permanently well-mixed southern WEC (sWEC) and calculated surface pCO2 with uncertainties of 17 and 16 μatm, respectively. We extrapolated the relationships obtained for the WEC based on the 2011-2013 data set (1) temporally over a decade and (2) spatially in the adjacent Celtic and Irish seas (CS and IS), two regions which exhibit hydrographical and biogeochemical characteristics similar to those of WEC waters. We validated these extrapolations with pCO2 data from the SOCAT and LDEO databases and obtained good agreement between modeled and observed data. On an annual scale, seasonally stratified systems acted as a sink of CO2 from the atmosphere of -0.6 ± 0.3, -0.9 ± 0.3 and -0.5 ± 0.3 mol C m-2 yr-1 in the northern Celtic Sea, southern Celtic sea and nWEC, respectively, whereas permanently well-mixed systems acted as source of CO2 to the atmosphere of 0.2 ± 0.2 and 0.3 ± 0.2 mol C m-2 yr-1 in the sWEC and IS, respectively. Air-sea CO2 fluxes showed important inter-annual variability resulting in significant differences in the intensity and/or direction of annual fluxes. We scaled the mean annual fluxes over these provinces for the last decade and obtained the first annual average uptake of -1.11 ± 0.32 Tg C yr-1 for this part of the northwestern European continental shelf. Our study showed that combining VOS data with satellite observations can be a powerful tool to

  17. Dynamics of air-sea CO2 fluxes in the North-West European Shelf based on Voluntary Observing Ship (VOS) and satellite observations

    NASA Astrophysics Data System (ADS)

    Marrec, P.; Cariou, T.; Macé, E.; Morin, P.; Salt, L. A.; Vernet, M.; Taylor, B.; Paxman, K.; Bozec, Y.

    2015-04-01

    From January 2011 to December 2013, we constructed a comprehensive pCO2 dataset based on voluntary observing ship (VOS) measurements in the Western English Channel (WEC). We subsequently estimated surface pCO2 and air-sea CO2 fluxes in north-west European continental shelf waters using multiple linear regressions (MLRs) from remotely sensed sea surface temperature (SST), chlorophyll a concentration (Chl a), the gas transfer velocity coefficient (K), photosynthetically active radiation (PAR) and modeled mixed layer depth (MLD). We developed specific MLRs for the seasonally stratified northern WEC (nWEC) and the permanently well-mixed southern WEC (sWEC) and calculated surface pCO2 with relative uncertainties of 17 and 16 μatm, respectively. We extrapolated the relationships obtained for the WEC based on the 2011-2013 dataset (1) temporally over a decade and (2) spatially in the adjacent Celtic and Irish Seas (CS and IS), two regions which exhibit hydrographical and biogeochemical characteristics similar to those of WEC waters. We validated these extrapolations with pCO2 data from the SOCAT database and obtained relatively robust results with an average precision of 4 ± 22 μatm in the seasonally stratified nWEC and the southern and northern CS (sCS and nCS), but less promising results in the permanently well-mixed sWEC, IS and Cap Lizard (CL) waters. On an annual scale, seasonally stratified systems acted as a sink of CO2 from the atmosphere of -0.4, -0.9 and -0.4 mol C m-2 year-1 in the nCS, sCS and nWEC, respectively, whereas, permanently well-mixed systems acted as source of CO2 to the atmosphere of 0.2, 0.4 and 0.4 mol C m-2 year-1 in the sWEC, CL and IS, respectively. Air-sea CO2 fluxes showed important inter-annual variability resulting in significant differences in the intensity and/or direction of annual fluxes. We scaled the mean annual fluxes over six provinces for the last decade and obtained the first annual average uptake of -0.95 Tg C year-1 for this

  18. An Approach to Minimizing Artifacts Caused by Cross-Sensitivity in the Determination of Air-Sea CO2 Flux Using the Eddy-Covariance Technique

    NASA Astrophysics Data System (ADS)

    Duan, Ziqiang; Gao, Huiwang; Gao, Zengxiang; Wang, Renlei; Xue, Yuhuan; Yao, Xiaohong

    2013-07-01

    The air-sea CO2 flux was measured from a research vessel in the North Yellow Sea in October 2007 using an open-path eddy-covariance technique. In 11 out of 64 samples, the normalized spectra of scalars (C}2, water vapour, and temperature) showed similarities. However, in the remaining samples, the normalized CO2 spectra were observed to be greater than those of water vapour and temperature at low frequencies. In this paper, the noise due to cross-sensitivity was identified through a combination of intercomparisons among the normalized spectra of three scalars and additional analyses. Upon examination, the cross-sensitivity noise appeared to be mainly present at frequencies {<}0.8 Hz. Our analysis also suggested that the high-frequency fluctuations of CO2 concentration (frequency {>}0.8 Hz) was probably less affected by the cross-sensitivity. To circumvent the cross-sensitivity issue, the cospectrum in the high-frequency range 0.8-1.5 Hz, instead of the whole range, was used to estimate the CO2 flux by taking the contribution of the high frequency to the CO2 flux to be the same as the contribution to the water vapour flux. The estimated air-sea CO2 flux in the North Yellow Sea was -0.039 ± 0.048 mg m^{-2} s^{-1}, a value comparable to the estimates using the inertial dissipation method and Edson's method (Edson et al., J Geophys Res 116:C00F10, 2011).

  19. Quantifying the air-sea CO2 flux at a time-series in the Eastern Tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Lefevre, Nathalie; Veleda, Doris; Araujo, Moacyr; Caniaux, Guy

    2016-04-01

    Hourly fCO2 is recorded at a time-series at the PIRATA buoy located at 6oS 10oW in the eastern tropical Atlantic since June 2006. This site is located south and west of the seasonal Atlantic cold tongue and is affected by its propagation from June to September. Using an alkalinity-salinity relationship determined for the eastern tropical Atlantic and the observed fCO2, pH and the inorganic carbon concentration are calculated. The time-series of fCO2 exhibits strong intraseasonal, seasonal and interannual variability. On seasonal timescales, the variations of fCO2 and pH are mostly controlled by sea surface salinity. At interannual timescales, some important differences appear in 2011-2012: lower fCO2 and fluxes are observed from September to December 2011 and are explained by higher advection of salty waters at the mooring. In early 2012, the anomaly is still present and is associated with lower sea surface temperatures. No significant long-term trend is detected over the period 2006-2013 on CO2 and any other physical parameter. However, as atmospheric fCO2 is increasing over time, the outgassing of CO2 is reduced over the period 2006-2013 as the flux is mainly controlled by the difference of fCO2 between the ocean and the atmosphere. A longer time-series is required to determine if any significant trend exists in this region.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. In situ evaluation of air-sea CO2 gas transfer velocity in an inner estuary using eddy covariance - with a special focus on the importance of using reliable CO2-fluxes

    NASA Astrophysics Data System (ADS)

    Jørgensen, E. T.; Sørensen, L. L.; Jensen, B.; Sejr, M. K.

    2012-04-01

    The air-sea exchange of CO2 or CO2 flux is driven by the difference in the partial pressure of CO2 in the water and the atmosphere (ΔpCO2), the solubility of CO2 (K0) and the gas transfer velocity (k) (Wanninkhof et al., 2009;Weiss, 1974) . ΔpCO2 and K0 are determined with relatively high precision and it is estimated that the biggest uncertainty when modelling the air-sea flux is the parameterization of k. As an example; the estimated global air-sea flux increases by 70 % when using the parameterization by Wanninkhof and McGillis (1999) instead of Wanninkhof (1992) (Rutgersson et al., 2008). In coastal areas the uncertainty is even higher and only few studies have focused on determining transfer velocity for the coastal waters and even fewer on estuaries (Borges et al., 2004;Rutgersson et al., 2008). The transfer velocity (k600) of CO2 in the inner estuary of Roskilde Fjord, Denmark was investigated using eddy covariance CO2 fluxes (ECM) and directly measured ΔpCO2 during May and June 2010. The data was strictly sorted to heighten the certainty of the results and the outcome was; DS1; using only ECM, and DS2; including the inertial dissipation method (IDM). The inner part of Roskilde Fjord showed to be a very biological active CO2 sink and preliminary results showed that the average k600 was more than 10 times higher than transfer velocities from similar studies of other coastal areas. The much higher transfer velocities were estimated to be caused by the greater fetch and shallower water in Roskilde Fjord, which indicated that turbulence in both air and water influence k600. The wind speed parameterization of k600 using DS1 showed some scatter but when including IDM the r2 of DS2 reached 0.93 with an exponential parameterization, where U10 was based on the Businger-Dyer relationships using friction velocity and atmospheric stability. This indicates that some of the uncertainties coupled with CO2 fluxes calculated by the ECM are removed when including the IDM.

  2. Variability of 14C reservoir age and air-sea flux of CO2 in the Peru-Chile upwelling region during the past 12,000 years

    NASA Astrophysics Data System (ADS)

    Carré, Matthieu; Jackson, Donald; Maldonado, Antonio; Chase, Brian M.; Sachs, Julian P.

    2016-01-01

    The variability of radiocarbon marine reservoir age through time and space limits the accuracy of chronologies in marine paleo-environmental archives. We report here new radiocarbon reservoir ages (ΔR) from the central coast of Chile (~ 32°S) for the Holocene period and compare these values to existing reservoir age reconstructions from southern Peru and northern Chile. Late Holocene ΔR values show little variability from central Chile to Peru. Prior to 6000 cal yr BP, however, ΔR values were markedly increased in southern Peru and northern Chile, while similar or slightly lower-than-modern ΔR values were observed in central Chile. This extended dataset suggests that the early Holocene was characterized by a substantial increase in the latitudinal gradient of marine reservoir age between central and northern Chile. This change in the marine reservoir ages indicates that the early Holocene air-sea flux of CO2 could have been up to five times more intense than in the late Holocene in the Peruvian upwelling, while slightly reduced in central Chile. Our results show that oceanic circulation changes in the Humboldt system during the Holocene have substantially modified the air-sea carbon flux in this region.

  3. Synoptic evaluation of carbon cycling in Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air-sea CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Forest, A.; Coupel, P.; Else, B.; Nahavandian, S.; Lansard, B.; Raimbault, P.; Papakyriakou, T.; Gratton, Y.; Fortier, L.; Tremblay, J.-É.; Babin, M.

    2013-10-01

    The accelerated decline in Arctic sea ice combined with an ongoing trend toward a more dynamic atmosphere is modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air-sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air-sea CO2 exchange, with the aim of identifying indices of ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air-sea CO2 fluxes. The mean atmospheric forcing was a mild upwelling-favorable wind (~5 km h-1) blowing from the N-E and a decaying ice cover (<80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2 with a mean uptake rate of -2.0 ± 3.3 mmol C m-2d-1. We attribute this discrepancy to: (1) elevated PP rates (>600 mg C m-2d-1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (>10mmol C m-2d-1). Although generally <100 mg C m-2d-1, daily PP rates cumulated to a total PP of ~437.6 × 103 t C, which was roughly twice higher than the organic carbon delivery by river inputs (~241.2 × 103 t C). Subsurface PP represented 37.4% of total PP for the

  4. Effect of gas-transfer velocity parameterization choice on air-sea CO2 fluxes in the North Atlantic Ocean and the European Arctic

    NASA Astrophysics Data System (ADS)

    Wrobel, Iwona; Piskozub, Jacek

    2016-09-01

    The oceanic sink of carbon dioxide (CO2) is an important part of the global carbon budget. Understanding uncertainties in the calculation of this net flux into the ocean is crucial for climate research. One of the sources of the uncertainty within this calculation is the parameterization chosen for the CO2 gas-transfer velocity. We used a recently developed software toolbox, called the FluxEngine (Shutler et al., 2016), to estimate the monthly air-sea CO2 fluxes for the extratropical North Atlantic Ocean, including the European Arctic, and for the global ocean using several published quadratic and cubic wind speed parameterizations of the gas-transfer velocity. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic Ocean. This region is a large oceanic sink of CO2, and it is also a region characterized by strong winds, especially in winter but with good in situ data coverage. We show that the uncertainty in the parameterization is smaller in the North Atlantic Ocean and the Arctic than in the global ocean. It is as little as 5 % in the North Atlantic and 4 % in the European Arctic, in comparison to 9 % for the global ocean when restricted to parameterizations with quadratic wind dependence. This uncertainty becomes 46, 44, and 65 %, respectively, when all parameterizations are considered. We suggest that this smaller uncertainty (5 and 4 %) is caused by a combination of higher than global average wind speeds in the North Atlantic (> 7 ms-1) and lack of any seasonal changes in the direction of the flux direction within most of the region. We also compare the impact of using two different in situ pCO2 data sets (Takahashi et al. (2009) and Surface Ocean CO2 Atlas (SOCAT) v1.5 and v2.0, for the flux calculation. The annual fluxes using the two data sets differ by 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal fluxes in the Arctic computed from the two data sets disagree with each

  5. Air-Sea CO2 fluxes and NEP changes in a Baja California Coastal Lagoon during the anomalous North Pacific warm condition in 2014

    NASA Astrophysics Data System (ADS)

    Ávila López, M. D. C.; Martin Hernandez-Ayon, J. M.; Camacho-Ibar, V.; Sandoval Gil, J.; Mejía-Trejo, A.; Félix-Bermudez, A.; Pacheco-Ruiz, I.

    2015-12-01

    The present study examines the temporal variability of seawater carbonate chemistry and air-sea CO2 fluxes (FCO2) in a Baja California Mediterranean-climate coastal lagoon. This study was carried out from Nov-2013 to Nov-2014, a period in which anomalous warm conditions were present in the North Pacific Ocean influenced the local oceanography in the adjacent coastal waters off Baja California. These ocean conditions resulted on a negative anomaly of upwelling index, which led to summer-like season (weak upwelling condition) that could be observed in the response of carbon dynamics and metabolic status in San Quintín Bay. Minor changes in dissolved inorganic carbon (DIC) concentration during spring months (~100 µmol kg-1) where observed and were associated to biological processes within the lagoon. High DIC (~2200 µmol kg-1), pCO2 (~800 μatm), and minimum pH (~7.8) values were observed in summer, reflecting the predominance of respiration processes apparently mostly linked to the remineralization of sedimentary organic matter supplied from macroalgal blooms. San Quintín Bay acted as a weak source of CO2 to the atmosphere during the study period, with maximum value observed in July (~10 mmol C m-2 d-1). Temporal biomass production of macroalgae contributed to about 50% of total FCO2 estimated in spring-summer seasons, that was a potencial internal source of organic matter to fuel respiration processes in San Quintín Bay. Eelgrass metabolism contributes in a lower degree in total FCO2. During the anomalous ocean conditions in 2014, the lagoon switched seasonally between net heterotrophy and net autotrophy during the study period, where photosynthesis and respiration processes in the lagoon were closer to a balance. Whole-system metabolism and FCO2 clearly indicated the strong dependence of San Quintín Bay on upwelling conditions and benthic metabolism activity, which was mainly controlled by dominant primary producer communities.

  6. Synoptic evaluation of carbon cycling in the Beaufort Sea during summer: contrasting river inputs, ecosystem metabolism and air-sea CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Forest, A.; Coupel, P.; Else, B.; Nahavandian, S.; Lansard, B.; Raimbault, P.; Papakyriakou, T.; Gratton, Y.; Fortier, L.; Tremblay, J.-É.; Babin, M.

    2014-05-01

    The accelerated decline in Arctic sea ice and an ongoing trend toward more energetic atmospheric and oceanic forcings are modifying carbon cycling in the Arctic Ocean. A critical issue is to understand how net community production (NCP; the balance between gross primary production and community respiration) responds to changes and modulates air-sea CO2 fluxes. Using data collected as part of the ArcticNet-Malina 2009 expedition in the southeastern Beaufort Sea (Arctic Ocean), we synthesize information on sea ice, wind, river, water column properties, metabolism of the planktonic food web, organic carbon fluxes and pools, as well as air-sea CO2 exchange, with the aim of documenting the ecosystem response to environmental changes. Data were analyzed to develop a non-steady-state carbon budget and an assessment of NCP against air-sea CO2 fluxes. During the field campaign, the mean wind field was a mild upwelling-favorable wind (~ 5 km h-1) from the NE. A decaying ice cover (< 80% concentration) was observed beyond the shelf, the latter being fully exposed to the atmosphere. We detected some areas where the surface mixed layer was net autotrophic owing to high rates of primary production (PP), but the ecosystem was overall net heterotrophic. The region acted nonetheless as a sink for atmospheric CO2, with an uptake rate of -2.0 ± 3.3 mmol C m-2 d-1 (mean ± standard deviation associated with spatial variability). We attribute this discrepancy to (1) elevated PP rates (> 600 mg C m-2 d-1) over the shelf prior to our survey, (2) freshwater dilution by river runoff and ice melt, and (3) the presence of cold surface waters offshore. Only the Mackenzie River delta and localized shelf areas directly affected by upwelling were identified as substantial sources of CO2 to the atmosphere (> 10 mmol C m-2 d-1). Daily PP rates were generally < 100 mg C m-2 d-1 and cumulated to a total PP of ~ 437.6 × 103 t C for the region over a 35-day period. This amount was about twice the

  7. Model estimating the effect of marginal ice zone processes on the phytoplankton primary production and air-sea flux of CO2 in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Dvornikov, Anton; Sein, Dmitry; Ryabchenko, Vladimir; Gorchakov, Victor; Martjyanov, Stanislav

    2016-04-01

    This study is aimed to assess the impact of sea ice on the primary production of phytoplankton (PPP) and air-sea CO2 flux in the Barents Sea. To get the estimations, we apply a three-dimensional eco-hydrodynamic model based on the Princeton Ocean Model which includes: 1) a module of sea ice with 7 categories, and 2) the 11-component module of marine pelagic ecosystem developed in the St. Petersburg Branch, Institute of Oceanology. The model is driven by atmospheric forcing, prescribed from the reanalysis NCEP / NCAR, and conditions on the open sea boundary, prescribed from the regional model of the atmosphere-ocean-sea ice-ocean biogeochemistry, developed at Max Planck Institute for Meteorology, Hamburg. Comparison of the model results for the period 1998-2007 with satellite data showed that the model reproduces the main features of the evolution of the sea surface temperature, seasonal changes in the ice extent, surface chlorophyll "a" concentration and PPP in the Barents Sea. Model estimates of the annual PPP for whole sea, APPmod, appeared in 1.5-2.3 times more than similar estimates, APPdata, from satellite data. The main reasons for this discrepancy are: 1) APPdata refers to the open water, while APPmod, to the whole sea area (under the pack ice and marginal ice zone (MIZ) was produced 16 - 38% of PPP); and 2) values of APPdata are underestimated because of the subsurface chlorophyll maximum. During the period 1998-2007, the modelled maximal (in the seasonal cycle) sea ice area has decreased by 15%. This reduction was accompanied by an increase in annual PPP of the sea at 54 and 63%, based, respectively, on satellite data and the model for the open water. According to model calculations for the whole sea area, the increase is only 19%. Using a simple 7-component model of oceanic carbon cycle incorporated into the above hydrodynamic model, the CO2 exchange between the atmosphere and sea has been estimated in different conditions. In the absence of biological

  8. Temporal variability of air-sea CO2 exchange in a low-emission estuary

    NASA Astrophysics Data System (ADS)

    Mørk, Eva Thorborg; Sejr, Mikael Kristian; Stæhr, Peter Anton; Sørensen, Lise Lotte

    2016-07-01

    There is the need for further study of whether global estimates of air-sea CO2 exchange in estuarine systems capture the relevant temporal variability and, as such, the temporal variability of bulk parameterized and directly measured CO2 fluxes was investigated in the Danish estuary, Roskilde Fjord. The air-sea CO2 fluxes showed large temporal variability across seasons and between days and that more than 30% of the net CO2 emission in 2013 was a result of two large fall and winter storms. The diurnal variability of ΔpCO2 was up to 400 during summer changing the estuary from a source to a sink of CO2 within the day. Across seasons the system was suggested to change from a sink of atmospheric CO2 during spring to near neutral during summer and later to a source of atmospheric CO2 during fall. Results indicated that Roskilde Fjord was an annual low-emission estuary, with an estimated bulk parameterized release of 3.9 ± 8.7 mol CO2 m-2 y-1 during 2012-2013. It was suggested that the production-respiration balance leading to the low annual emission in Roskilde Fjord, was caused by the shallow depth, long residence time and high water quality in the estuary. In the data analysis the eddy covariance CO2 flux samples were filtered according to the H2Osbnd CO2 cross-sensitivity assessment suggested by Landwehr et al. (2014). This filtering reduced episodes of contradicting directions between measured and bulk parameterized air-sea CO2 exchanges and changed the net air-sea CO2 exchange from an uptake to a release. The CO2 gas transfer velocity was calculated from directly measured CO2 fluxes and ΔpCO2 and agreed to previous observations and parameterizations.

  9. Sensitivity analysis of an Ocean Carbon Cycle Model in the North Atlantic: an investigation of parameters affecting the air-sea CO2 flux, primary production and export of detritus

    NASA Astrophysics Data System (ADS)

    Scott, V.; Kettle, H.; Merchant, C. J.

    2010-12-01

    The sensitivity of the biological parameters in a nutrient-phytoplankton-zooplankton-detritus (NPZD) model in the calculation of the air-sea CO2 flux, primary production and detrital export is analysed. The NPZD model is the Hadley Centre Ocean Carbon Cycle model (HadOCC) from the UK Met Office, used in the Hadley Centre Coupled Model 3 (HadCM3) and FAst Met Office and Universities Simulator (FAMOUS) GCMs. Here, HadOCC is coupled to the 1-D General Ocean Turbulence Model (GOTM) and forced with European Centre for Medium-Range Weather Forecasting meteorology to undertake a sensitivity analysis of its twenty biological parameters. Analyses are performed at three sites in the EuroSITES European Ocean Observatory Network: the Central Irminger Sea (60° N 40° W), the Porcupine Abyssal Plain (49° N 16° W) and the European Station for Time series in the Ocean Canary Islands (29° N 15° W) to assess variability in parameter sensitivities at different locations in the North Atlantic Ocean. Reasonable changes to the values of key parameters are shown to have a large effect on the calculation of the air-sea CO2 flux, primary production, and export of biological detritus to the deep ocean. Changes in the values of key parameters have a greater effect in more productive regions than in less productive areas. We perform the analysis using one-at-a-time perturbations and using a statistical emulator, and compare results. The most sensitive parameters are generic to many NPZD ocean ecosystem models. The air-sea CO2 flux is most influenced by variation in the parameters that control phytoplankton growth, detrital sinking and carbonate production by phytoplankton (the rain ratio). Primary production is most sensitive to the parameters that define the shape of the photosythesis-irradiance curve. Export production is most sensitive to the parameters that control the rate of detrital sinking and the remineralisation of detritus.

  10. Carbonate chemistry and air-sea CO2 flux at a fixed point in a NW Mediterranean Bay, Villefranche-sur-Mer, France

    NASA Astrophysics Data System (ADS)

    De Carlo, E. H.; Mousseau, L.; Passafiume, O.; Drupp, P. S.; Gattuso, J.

    2011-12-01

    The purpose of the Service d'Observation de la Rade de Villefranche-sur-Mer (SO-RADE) is to study the temporal variability of hydrological conditions as well as the abundance and composition of holo- and meroplankton at a fixed station in the bay of Villefranche-sur-Mer, North West Mediterranean. The weekly data collected at this site, designated as "Point B (43° 41.10'N - 7° 18.94'E), since 1957 are recognized as a long-term time series describing the evolution of the hydrological conditions in a coastal environment. Since 2007, historical measurements of hydrological and biological conditions have been complemented by measurements of the CO2-carbonate system parameters. In this contribution we present CO2-carbonate system parameters and ancillary data for the period 2007-2010. The data are evaluated in the context of the physical and biogeochemical processes that contribute to the fluxes of CO2 between the ocean and atmosphere. Seasonal cycles of seawater pCO2 are controlled principally by variations in temperature, showing maxima in the summer and minima during the winters. Normalization of pCO2 to the mean seawater temperature (18oC) results in an apparent reversal of the seasonal cycle with maxima observed in the winters and minima in the summers, consistent with a control of pCO2 by primary productivity. Calculations of "instantaneous fluxes" of CO2 between the ocean and atmosphere show this area to be primarily a weak source of CO2 to the atmosphere during the summer and a weak sink during the winter and near neutral overall (range: -0.3 to +0.3 mmol CO2 m-2 h-1, average: 0.02 mmol CO2 m-2 h-1). We will also provide projections of errors incurred from the estimation of annualized fluxes of CO2 based on weekly measurements relative to daily and high-frequency (3 h) data such as those obtained at the Hawaii Kilo Nalu coastal time series station, which shows similar behavior to the Point B location despite significant differences in climate and hydrological

  11. Air-Sea Exchange Of CO2: A Multi-Technology Approach

    NASA Astrophysics Data System (ADS)

    Tengberg, A.; Almroth, E.; Anderson, L.; Hall, P.; Hjalmarsson, S.; Lefevre, D.; Omstedt, A.; Rutgersson, A.; Sahlee, E.; Smedman, A.; Wesslander, K.

    2006-12-01

    We report on experiences and results from a multidisciplinary project in which we try to elucidate the complex processes involved in air-sea exchange of CO2. This study was performed in the Baltic Sea (off the Swedish island Gotland) and combined the following technologies: - Meteorological measurements of wind, turbulence, temperature, humidity, humidity flux, CO2 and CO2 flux at several levels from a fixed observation tower - Hourly PCO2 measurements with a moored automatic instrument - Collection of dissolved oxygen, temperature, salinity and turbidity data at different levels in the water column at 1-minute intervals - Daily light (PAR) and primary production measurements obtained with a moored automatic incubator - Daily primary production measurements using manual methods - Use of an acoustic current profiler to collect water column information on currents, turbulence, water level and waves - Repetitive water column profiles, from a ship, of dissolved inorganic carbon, oxygen, nutrients, alkalinity, pH, PAR, Chlorophyll A, salinity and temperature

  12. Phytoplankton carbon fixation gene (RuBisCO) transcripts and air-sea CO2 flux in the Mississippi River plume

    SciTech Connect

    John, David E.; Wang, Zhaohui A.; Liu, Xuewu; Byrne, Robert H.; Corredor, Jorge E.; López, José M.; Cabrera, Alvaro; Bronk, Deborah A.; Tabita, F. Robert; Paul, John H.

    2007-08-30

    River plumes deliver large quantities of nutrients to oligotrophic oceans, often resulting in significant CO2 drawdown. To determine the relationship between expression of the major gene in carbon fixation (large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBisCO) and CO2 dynamics, we evaluated rbcL mRNA abundance using novel quantitative PCR assays, phytoplankton cell analyses, photophysiological parameters, and pCO2 in and around the Mississippi River plume (MRP) in the Gulf of Mexico. Lower salinity (30–32) stations were dominated by rbcL mRNA concentrations from heterokonts, such as diatoms and pelagophytes, which were at least an order of magnitude greater than haptophytes, alpha-Synechococcus or high-light Prochlorococcus. However, rbcL transcript abundances were similar among these groups at oligotrophic stations (salinity 34–36). Diatom cell counts and heterokont rbcL RNA showed a strong negative correlation to seawater pCO2. While Prochlorococcus cells did not exhibit a large difference between low and high pCO2 water, Prochlorococcus rbcL RNA concentrations had a strong positive correlation to pCO2, suggesting a very low level of RuBisCO RNA transcription among Prochlorococcus in the plume waters, possibly due to their relatively poor carbon concentrating mechanisms (CCMs). These results provide molecular evidence that diatom/pelagophyte productivity is largely responsible for the large CO2 drawdown occurring in the MRP, based on the co-occurrence of elevated RuBisCO gene transcript concentrations from this group and reduced seawater pCO2 levels. This may partly be due to efficient CCMs that enable heterokont eukaryotes such as diatoms to continue fixing CO2 in the face of strong CO2 drawdown. Finally, our work represents the first attempt to relate in situ microbial gene expression to contemporaneous CO2 flux

  13. Comparison of CO2 Dynamics and Air-Sea Exchange in Contrasting Tropical Reef Environments

    NASA Astrophysics Data System (ADS)

    Drupp, P. S.; De Carlo, E. H.; Mackenzie, F. T.; Shamberger, K. E.; Musielewicz, S. B.; Maenner-Jones, S.; Sabine, C. L.; Feely, R. A.

    2011-12-01

    Multiyear high temporal resolution CO2 records in three differing coral reef settings were obtained using buoys deployed in coastal waters of Oahu since June 2008. The buoys are located on the barrier reef of Kaneohe Bay and offshore of Honolulu, on the south shore of Oahu. Annualized CO2 air-sea fluxes at the three buoys ranged from +0.05 mol C/m2/yr offshore Honolulu on a fringing reef well mixed with the open ocean to -1.12 mol C/m2/yr on a barrier reef flat in Kaneohe Bay (positive values represent CO2 sinks from the atmosphere and negative values represent sources). These fluxes compare well to those estimated from previous studies in Kaneohe Bay as well as in other tropical reef environments. pCO2 measurements, made every 3 hours, at each location show strong temporal cycles on multiple time scales ranging from diel to seasonal at each buoy and an anticorrelation with pO2. These records, when combined with those of a prior buoy deployment in southern Kaneohe Bay and several synoptic studies, allow us to examine how the principal biological cycles of productivity/respiration and calcification/carbonate dissolution are influenced by changing water column properties, physical processes (e.g. residence time) and atmospheric conditions and how these processes ultimately impact the exchange of CO2 between the ocean and atmosphere on hourly to interannual cycles. The data clearly demonstrate the need for high frequency pCO2 data to characterize completely and accurately short-term local changes in the CO2-carbonic acid system parameters and how these changes overprint the longer scale process of ocean acidification as a result of invasion of CO2 into the ocean due to emissions of anthropogenic CO2 to the atmosphere. Since many coral reef ecosystems are still sources of CO2 to the atmosphere because of positive net ecosystem calcification, and in some instances net heterotrophy, such data are even more critical in terms of assessing future changes in the direction

  14. On the Global Oxygen Anomaly and Air-Sea Flux

    NASA Technical Reports Server (NTRS)

    Garcia, Hernan E.; Keeling, Ralph F.

    2001-01-01

    A new climatology of monthly air-sea oxygen fluxes throughout the ice-free surface global ocean is presented. The climatology is based on weighted linear least squares regressions using heat flux monthly anomalies for spatial and temporal interpolation of historical O2 data. The seasonal oceanic variations show that the tropical belt (20 S - 20 N) is characterized by relatively small air-sea fluxes when compared to the middle to high latitudes (40 deg - 70 deg). The largest and lowest seasonal fluxes occur during summer and winter in both hemispheres. By means of an atmospheric transport model we show that our climatology is in better agreement with the observed amplitude and phasing of the variations in atmospheric O2/N2 ratios because of seasonal air-sea exchanges at baseline stations in the Pacific Ocean than with previous air-sea O2 climatologies. Our study indicates that the component of the air-sea O2 flux that correlates with heat flux dominates the large-scale air-sea O2 exchange on seasonal timescales. The contribution of each major oceanic basin to the atmospheric observations is described. The seasonal net thermal (SNO(sub T)) and biological (SNO(sub B)) outgassing components of the flux are examined in relation to latitudinal bands, basin-wide, and hemispheric contributions. The Southern Hemisphere's SNO(sub B) (approximately 0.26 Pmol) and SNO(sub T) (approximately 0.29 Pmol) values are larger than the Northern Hemisphere's SNO(sub B) (approximately 0.15 Pmol) and SNO(sub T) (approximately 0.16 Pmol) values (1 Pmol = 10(exp 15) mol). We estimate a global extratropical carbon new production during the outgassing season of 3.7 Pg C (1 Pg = 10(exp 15) g), lower than previous estimates with air-sea O2 climatologies.

  15. Direct measurements of air-sea CO2 exchange over a coral reef

    NASA Astrophysics Data System (ADS)

    McGowan, Hamish A.; MacKellar, Mellissa C.; Gray, Michael A.

    2016-05-01

    Quantification of CO2 exchange with the atmosphere over coral reefs has relied on microscale measurements of pCO2 gradients across the air-sea interfacial boundary; shipboard measurements of air-sea CO2 exchange over adjacent ocean inferred to represent over reef processes or ecosystem productivity modeling. Here we present by way of case study the first direct measurements of air-sea CO2 exchange over a coral reef made using the eddy covariance method. Research was conducted during the summer monsoon over a lagoonal platform reef in the southern Great Barrier Reef, Australia. Results show the reef flat to be a net source of CO2 to the atmosphere of similar magnitude as coastal lakes, while adjacent shallow and deep lagoons were net sinks as was the surrounding ocean. This heterogeneity in CO2 exchange with the atmosphere confirms need for spatially representative direct measurements of CO2 over coral reefs to accurately quantify their role in atmospheric carbon budgets.

  16. Spatial and temporal variability of air-sea CO2 exchange of alongshore waters in summer near Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Ikawa, Hiroki; Oechel, Walter C.

    2014-03-01

    Alongshore water off Barrow, Alaska is a useful area for studying the carbon cycle of the Arctic coastal sea, because the different coastal characteristics extant in the area likely represent much larger regions of the coastal water of the western Arctic Ocean. Especially noteworthy is the inflow shelf water transferred northward by the Arctic Coastal Current into the Chukchi Sea from the North Pacific and turbid water in the Elson Lagoon where a significant amount of coastal erosion has been reported along the extensive coastal line and where a part of the water from the lagoon drains into the Beaufort Sea adjacent to the Chukchi Sea. To investigate spatial and temporal variations of air-sea CO2 flux (CO2 flux) of the alongshore water, partial pressure of CO2 of surface seawater (pCO2sw) was measured in summer, 2007 and 2008, and CO2 flux was directly measured by eddy covariance at a fixed point for the Beaufort Sea in summer 2008. Measured pCO2sw in the Chukchi Sea side was the lowest in the beginning of the measurement season and increased later in the season both in 2007 and 2008. The average CO2 flux estimated based on pCO2sw in the Chukchi Sea side was -0.10 μmol m-2 s-1 (±0.1 s.d.) using the sign convention of positive fluxes into the atmosphere from the ocean. pCO2sw in the Beaufort Sea and the Elson Lagoon was relatively higher in early summer and decreased in the middle of the summer. The overall average CO2 flux was -0.07 μmol m-2 s-1 (±0.1 s.d.) for the Beaufort Sea side and -0.03 μmol m-2 s-1 (±0.07 s.d.) for the Elson Lagoon respectively, indicating a sink of CO2 despite high carbon inflows from the terrestrial margin into the Elson Lagoon. A strong sink of CO2 was often observed from the Beaufort Sea by eddy covariance in the middle of the summer. This sink activity in the middle summer in the Beaufort Sea and Elson Lagoon was likely due to biological carbon uptake as inferred by low apparent oxygen utilization and high chlorophyll

  17. Distribution and air-sea fluxes of carbon dioxide on the Chukchi Sea shelf

    NASA Astrophysics Data System (ADS)

    Pipko, I. I.; Pugach, S. P.; Repina, I. A.; Dudarev, O. V.; Charkin, A. N.; Semiletov, I. P.

    2015-12-01

    This article presents the results of long-term studies of the dynamics of carbonate parameters and air-sea carbon dioxide fluxes on the Chukchi Sea shelf during the summer. As a result of the interaction of physical and biological factors, the surface waters on the west of Chukchi Sea were undersaturated with carbon dioxide when compared with atmospheric air; the partial pressure of CO2 varied in the range from 134 to 359 μatm. The average value of CO2 flux in the Chukchi Sea per unit area varied in the range from-2.4 to-22.0 mmol /(m2 day), which is significantly higher than the average value of CO2 flux in the World Ocean. It has been estimated that the minimal mass of C absorbed by the surface of Chukchi Sea from the atmosphere during ice-free season is 13 × 1012 g; a great part of this carbon is transported to the deeper layers of sea and isolated from the atmosphere for a long period of time. The studies of the carbonate system of the Chukchi Sea, especially of its western part, will provide some new data on the fluxes of carbon dioxide in the Arctic Ocean and their changes. Our analysis can be used for an interpretation of the satellite assessment of CO2 fluxes and dissolved CO2 distribution in the upper layers of the ocean.

  18. Quantifying the drivers of ocean-atmosphere CO2 fluxes

    NASA Astrophysics Data System (ADS)

    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.

  19. Air-sea gas transfer for two gases of different solubility (CO2 and O2)

    NASA Astrophysics Data System (ADS)

    Rutgersson, A.; Andersson, A.; Sahlée, E.

    2016-05-01

    At the land-based marine measuring site Östergarnsholm in the Baltic Sea, the eddy covariance technique was used to measure air-sea fluxes of carbon dioxide and oxygen. High- frequency measurements of oxygen were taken with a Microx TX3 optode using the luminescence lifetime technique. The system gives reasonable oxygen fluxes after the limited frequency response of the sensor was corrected for. For fluxes of carbon dioxide the LICOR-7500 instrument was used. Using flux data to estimate transfer velocities indicates higher transfer velocity for oxygen compared to carbon dioxide for winds above 5 m/s. There are too few data for any extensive conclusions, but a least-square fit of the data gives a cubic wind speed dependence of oxygen corresponding to k 660 = 0.074U 3 10. The more effective transfer for oxygen compared to carbon dioxide above 5 m/s is most likely due to enhanced efficiency of oxygen exchange across the surface. Oxygen has lower solubility compared with carbon dioxide and might be more influenced by near surface processes such as microscale wave breaking or sea spray.

  20. Advances in Air-Sea Flux Measurement by Eddy Correlation

    NASA Astrophysics Data System (ADS)

    Blomquist, Byron W.; Huebert, Barry J.; Fairall, Christopher W.; Bariteau, Ludovic; Edson, James B.; Hare, Jeffrey E.; McGillis, Wade R.

    2014-09-01

    Eddy-correlation measurements of the oceanic flux are useful for the development and validation of air-sea gas exchange models and for analysis of the marine carbon cycle. Results from more than a decade of published work and from two recent field programs illustrate the principal interferences from water vapour and motion, demonstrating experimental approaches for improving measurement precision and accuracy. Water vapour cross-sensitivity is the greatest source of error for flux measurements using infrared gas analyzers, often leading to a ten-fold bias in the measured flux. Much of this error is not related to optical contamination, as previously supposed. While various correction schemes have been demonstrated, the use of an air dryer and closed-path analyzer is the most effective way to eliminate this interference. This approach also obviates density corrections described by Webb et al. (Q J R Meteorol 106:85-100, 1980). Signal lag and frequency response are a concern with closed-path systems, but periodic gas pulses at the inlet tip provide for precise determination of lag time and frequency attenuation. Flux attenuation corrections are shown to be 5 % for a cavity ring-down analyzer (CRDS) and dryer with a 60-m inlet line. The estimated flux detection limit for the CRDS analyzer and dryer is a factor of ten better than for IRGAs sampling moist air. While ship-motion interference is apparent with all analyzers tested in this study, decorrelation or regression methods are effective in removing most of this bias from IRGA measurements and may also be applicable to the CRDS.

  1. Biofilm-like properties of the sea surface and predicted effects on air-sea CO2 exchange

    NASA Astrophysics Data System (ADS)

    Wurl, Oliver; Stolle, Christian; Van Thuoc, Chu; The Thu, Pham; Mari, Xavier

    2016-05-01

    Because the sea surface controls various interactions between the ocean and the atmosphere, it has a profound function for marine biogeochemistry and climate regulation. The sea surface is the gateway for the exchange of climate-relevant gases, heat and particles. Thus, in order to determine how the ocean and the atmosphere interact and respond to environmental changes on a global scale, the characterization and understanding of the sea surface are essential. The uppermost part of the water column is defined as the sea-surface microlayer and experiences strong spatial and temporal dynamics, mainly due to meteorological forcing. Wave-damped areas at the sea surface are caused by the accumulation of surface-active organic material and are defined as slicks. Natural slicks are observed frequently but their biogeochemical properties are poorly understood. In the present study, we found up to 40 times more transparent exopolymer particles (TEP), the foundation of any biofilm, in slicks compared to the underlying bulk water at multiple stations in the North Pacific, South China Sea, and Baltic Sea. We found a significant lower enrichment of TEP (up to 6) in non-slick sea surfaces compared to its underlying bulk water. Moreover, slicks were characterized by a large microbial biomass, another shared feature with conventional biofilms on solid surfaces. Compared to non-slick samples (avg. pairwise similarity of 70%), the community composition of bacteria in slicks was increasingly (avg. pairwise similarity of 45%) different from bulk water communities, indicating that the TEP-matrix creates specific environments for its inhabitants. We, therefore, conclude that slicks can feature biofilm-like properties with the excessive accumulation of particles and microbes. We also assessed the potential distribution and frequency of slick-formation in coastal and oceanic regions, and their effect on air-sea CO2 exchange based on literature data. We estimate that slicks can reduce CO2

  2. Sea surface carbon dioxide at the Georgia time series site (2006-2007): Air-sea flux and controlling processes

    NASA Astrophysics Data System (ADS)

    Xue, Liang; Cai, Wei-Jun; Hu, Xinping; Sabine, Christopher; Jones, Stacy; Sutton, Adrienne J.; Jiang, Li-Qing; Reimer, Janet J.

    2016-01-01

    Carbon dioxide partial pressure (pCO2) in surface seawater was continuously recorded every three hours from 18 July 2006 through 31 October 2007 using a moored autonomous pCO2 (MAPCO2) system deployed on the Gray's Reef buoy off the coast of Georgia, USA. Surface water pCO2 (average 373 ± 52 μatm) showed a clear seasonal pattern, undersaturated with respect to the atmosphere in cold months and generally oversaturated in warm months. High temporal resolution observations revealed important events not captured in previous ship-based observations, such as sporadically occurring biological CO2 uptake during April-June 2007. In addition to a qualitative analysis of the primary drivers of pCO2 variability based on property regressions, we quantified contributions of temperature, air-sea exchange, mixing, and biological processes to monthly pCO2 variations using a 1-D mass budget model. Although temperature played a dominant role in the annual cycle of pCO2, river inputs especially in the wet season, biological respiration in peak summer, and biological production during April-June 2007 also substantially influenced seawater pCO2. Furthermore, sea surface pCO2 was higher in September-October 2007 than in September-October 2006, associated with increased river inputs in fall 2007. On an annual basis this site was a moderate atmospheric CO2 sink, and was autotrophic as revealed by monthly mean net community production (NCP) in the mixed layer. If the sporadic short productive events during April-May 2007 were missed by the sampling schedule, one would conclude erroneously that the site is heterotrophic. While previous ship-based pCO2 data collected around this buoy site agreed with the buoy CO2 data on seasonal scales, high resolution buoy observations revealed that the cruise-based surveys undersampled temporal variability in coastal waters, which could greatly bias the estimates of air-sea CO2 fluxes or annual NCP, and even produce contradictory results.

  3. Decadal trends in air-sea CO2 exchange in the Ross Sea (Antarctica)

    NASA Astrophysics Data System (ADS)

    Tagliabue, Alessandro; Arrigo, Kevin R.

    2016-05-01

    Highly productive Antarctic shelf systems, like the Ross Sea, play important roles in regional carbon budgets, but the drivers of local variations are poorly quantified. We assess the variability in the Ross Sea carbon cycle using a regional physical-biogeochemical model. Regionally, total partial pressure of CO2 (pCO2) increases are largely controlled by the biological pump and broadly similar to those in the offshore Southern Ocean. However, this masks substantial local variability within the Ross Sea, where interannual fluctuations in total pCO2 are driven by the biological pump and alkalinity, whereas those for anthropogenic pCO2 are related to physical processes. Overall, the high degree of spatial variability in the Ross Sea carbon cycle causes extremes in aragonite saturation that can be as large as long-term trends. Therefore, Antarctic shelf polynya systems like the Ross Sea will be strongly affected by local processes in addition to larger-scale phenomena.

  4. Vertical CO2-Flux Gradients in the Marine Boundary Layer?

    NASA Astrophysics Data System (ADS)

    Krupski, Michael; Peters, Gerhard; Münster, Hans; Ament, Felix

    2010-05-01

    A classical method to estimate CO2-fluxes through the air/sea-interface consist of measuring the vertical turbulent flux close to the surface by Eddy-Covariance assuming constant flux between the measuring height and the surface. To re-evaluate this assumption, a two level flux measurement was installed on the research platform FINO2 in order to search for vertical flux gradients. The research platform is located at 55° 00' north and 13°09' east in the Baltic Sea between the coasts of Sweden, Denmark and Germany. At FINO2 the water is about 25 meters deep. A 9 meter long boom carrying the flux sensors is mounted at the south-east corner of the platform pointing south. Raw data with 10 Hz sampling rate are stored locally since June 2008 and can be downloaded remotely via satellite-based internet link. CO2-fluxes were calculated with 30 min time resolution applying a standard eddy covariance processing scheme including tilt- and Webb-corrections. In addition, power and cross spectra were calculated for selected (high wind) periods - mainly in order to verify that there are no artifacts due to wind- and wave-induced vibrations of the platform. Our first results over a period of two months in summer 2008 show significant flux gradients over extended periods (1-2 days). Recent runs of mesoscale circulation models, which consider the time dependent sources and sinks of vegetation-covered land, predict patterns of CO2 concentration with horizontal gradients of considerable magnitude. Moreover these model results show that the gradients fade out over open oceans only very gradually on trajectories several hundred kilometers off the coast. We estimate that these horizontal gradients of atmospheric CO2 concentration in combination with vertical gradients of wind speed could be a potential reason for vertical flux gradients. In coastal waters the gradients can result in flux differences between the height of the flux sensor and the sea surface which can amount the same

  5. Simulation-based study of air-sea momentum fluxes nearshore

    NASA Astrophysics Data System (ADS)

    Hao, Xuanting; Shen, Lian

    2015-11-01

    Momentum fluxes at sea surface are crucial to air-sea interactions. In nearshore regions, the bathymetry variation has a significant impact on the surface wave field and complicates the momentum fluxes at water surface. In this study, we extend a high order spectral method to address wave-bottom interactions and wave modeling. From the wave simulation data, we use the Hilbert-Huang transform to quantify the properties of the wave spectrum, based on which the wave field is reconstructed for the detailed mechanistic study of wind-wave interactions using large-eddy simulation for the wind field. The roughness of the water surface is quantified using a dynamic model for the effects of subgrid-scale waves. The results show that the waves are sensitive to the water depth variation. Associated with the changes in the wave field, the momentum fluxes at the air-sea interface increase in shallow regions.

  6. Climatic Impacts of a Stochastic Parameterization of Air-Sea Fluxes

    NASA Astrophysics Data System (ADS)

    Williams, P. D.

    2014-12-01

    The atmosphere and ocean are coupled by the exchange of fluxes across the ocean surface. Air-sea fluxes vary partly on scales that are too small and fast to be resolved explicitly in numerical models of weather and climate, making them a candidate for stochastic parameterization. This presentation proposes a nonlinear physical mechanism by which stochastic fluctuations in the air-sea buoyancy flux may modify the mean climate, even though the mean fluctuation is zero. The mechanism relies on a fundamental asymmetry in the physics of the ocean mixed layer: positive surface buoyancy fluctuations cannot undo the vertical mixing caused by negative fluctuations. The mechanism has much in common with Stommel's mixed-layer demon. The presentation demonstrates the mechanism in climate simulations with a comprehensive coupled atmosphere-ocean general circulation model (SINTEX-G). In the SINTEX-G simulations with stochastic air-sea buoyancy fluxes, significant changes are detected in the time-mean oceanic mixed-layer depth, sea-surface temperature, atmospheric Hadley circulation, and net upward water flux at the sea surface. Also, El Niño Southern Oscillation (ENSO) variability is significantly increased. The findings demonstrate that noise-induced drift and noise-enhanced variability, which are familiar concepts from simple climate models, continue to apply in comprehensive climate models with millions of degrees of freedom. The findings also suggest that the lack of representation of sub-grid variability in air-sea fluxes may contribute to some of the biases exhibited by contemporary climate models.

  7. Ocean Winds and Turbulent Air-Sea Fluxes Inferred From Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bourassa, Mark A.; Gille, Sarah T.; Jackson, Daren L.; Roberts, J. Brent; Wick, Gary A.

    2010-01-01

    Air-sea turbulent fluxes determine the exchange of momentum, heat, freshwater, and gas between the atmosphere and ocean. These exchange processes are critical to a broad range of research questions spanning length scales from meters to thousands of kilometers and time scales from hours to decades. Examples are discussed (section 2). The estimation of surface turbulent fluxes from satellite is challenging and fraught with considerable errors (section 3); however, recent developments in retrievals (section 3) will greatly reduce these errors. Goals for the future observing system are summarized in section 4. Surface fluxes are defined as the rate per unit area at which something (e.g., momentum, energy, moisture, or CO Z ) is transferred across the air/sea interface. Wind- and buoyancy-driven surface fluxes are called surface turbulent fluxes because the mixing and transport are due to turbulence. Examples of nonturbulent processes are radiative fluxes (e.g., solar radiation) and precipitation (Schmitt et al., 2010). Turbulent fluxes are strongly dependent on wind speed; therefore, observations of wind speed are critical for the calculation of all turbulent surface fluxes. Wind stress, the vertical transport of horizontal momentum, also depends on wind direction. Stress is very important for many ocean processes, including upper ocean currents (Dohan and Maximenko, 2010) and deep ocean currents (Lee et al., 2010). On short time scales, this horizontal transport is usually small compared to surface fluxes. For long-term processes, transport can be very important but again is usually small compared to surface fluxes.

  8. Air-ice CO2 fluxes and pCO2 dynamics in the Arctic coastal area (Amundsen Gulf, Canada)

    NASA Astrophysics Data System (ADS)

    Geilfus, Nicolas-Xavier; Tison, Jean Louis; Carnat, Gauthier; Else, Brent; Borges, Alberto V.; Thomas, Helmuth; Shadwick, Elizabeth; Delille, Bruno

    2010-05-01

    Sea ice covers about 7% of the Earth surface at its maximum seasonal extent. For decades sea ice was assumed to be an impermeable and inert barrier for air - sea exchange of CO2 so that global climate models do not include CO2 exchange between the oceans and the atmosphere in the polar regions. However, uptake of atmospheric CO2 by sea ice cover was recently reported raising the need to further investigate pCO2 dynamics in the marine cryosphere realm and related air-ice CO2 fluxes. In addition, budget of CO2 fluxes are poorly constrained in high latitudes continental shelves [Borges et al., 2006]. We report measurements of air-ice CO2 fluxes above the Canadian continental shelf and compare them to previous measurements carried out in Antarctica. We carried out measurements of pCO2 within brines and bulk ice, and related air-ice CO2 fluxes (chamber method) in Antarctic first year pack ice ("Sea Ice Mass Balance in Antarctica -SIMBA" drifting station experiment September - October 2007) and in Arctic first year land fast ice ("Circumpolar Flaw Lead" - CFL, April - June 2008). These 2 experiments were carried out in contrasted sites. SIMBA was carried out on sea ice in early spring while CFL was carried out in from the middle of the winter to the late spring while sea ice was melting. Both in Arctic and Antarctic, no air-ice CO2 fluxes were detected when sea ice interface was below -10°C. Slightly above -10°C, fluxes toward the atmosphere were observed. In contrast, at -7°C fluxes from the atmosphere to the ice were significant. The pCO2 of the brine exhibits a same trend in both hemispheres with a strong decrease of the pCO2 anti-correlated with the increase of sea ice temperature. The pCO2 shifted from a large over-saturation at low temperature to a marked under-saturation at high temperature. These air-ice CO2 fluxes are partly controlled by the permeability of the air-ice interface, which depends of the temperature of this one. Moreover, air-ice CO2 fluxes are

  9. Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

    SciTech Connect

    Fischer, M

    2005-01-01

    The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

  10. Air-sea fluxes and surface layer turbulence around a sea surface temperature front

    NASA Technical Reports Server (NTRS)

    Friehe, C. A.; Shaw, W. J.; Davidson, K. L.; Rogers, D. P.; Large, W. G.; Stage, S. A.; Crescenti, G. H.; Khalsa, S. J. S.; Greenhut, G. K.; Li, F.

    1991-01-01

    The observed effects of sharp changes in sea surface temperature (SST) on the air-sea fluxes, surface roughness, and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed. In situ flux and turbulence observations were carried out from three aircraft and two ships within the FASINEX framework. Three other aircraft used remote sensors to measure waves, microwave backscatter, and lidar signatures of cloud tops. Descriptions of the techniques, intercomparison of aircraft and ship flux data, and use of different methods for analyzing the fluxes from the aircraft data are described. Changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, wind over both cold-to-warm and warm-to-cold surface temperatures occurred. Model results consistent with the observations suggest that an internal boundary layer forms at the SST.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Couldrey, Matthew; Oliver, Kevin; Yool, Andrew; Halloran, Paul; Achterberg, Eric

    2016-04-01

    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 CO2concentration 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, ΔpCO2and 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, ΔpCO2and α on a range of timescales. On interannual and shorter timescales, both ΔpCO2and 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 non-seasonal 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.

  13. Air-sea interaction and surface flux in non-equilibrium sea-states

    SciTech Connect

    Levy, G.; Ek, M.; Mahrt, L.

    1994-12-31

    The wind forcing over the ocean determines the air-sea exchanges of heat, moisture and momentum which affect and drive the surface wave dynamics and the mixed layer circulation. In turn, it has been shown that wave dynamics and wave age affect ocean surface roughness and air-sea exchange processes so that the wind flow is not always in equilibrium with the ocean surface waves. This effect of wave spectrum on surface roughness has been discussed by many authors; yet it is rarely, if ever, accounted for in flux parameterization in models of the marine atmospheric boundary layer (MABL). Proper representation of these effects in both remote sensors` signal to geophysical-parameter models and in physical models of the ocean and the atmosphere on all scales is essential given the increased reliance of ocean monitoring systems on remote sea-surface sensors and the fundamental sensitivity of physical models to surface fluxes. In this paper the authors present a methodology for modeling these effects from data along with some results from data analyses of observations taken in two field experiments.

  14. Air-Sea Spray Airborne Radar Profiler Characterizes Energy Fluxes in Hurricanes

    NASA Technical Reports Server (NTRS)

    Durden, Stephen L.; Esteban-Fermandez, D.

    2010-01-01

    A report discusses ASAP (Air-sea Spray Airborne Profiler), a dual-wavelength radar profiler that provides measurement information about the droplet size distribution (DSD) of sea-spray, which can be used to estimate heat and moisture fluxes for hurricane research. Researchers have recently determined that sea spray can have a large effect on the magnitude and distribution of the air-sea energy flux at hurricane -force wind speeds. To obtain information about the DSD, two parameters of the DSD are required; for example, overall DSD amplitude and DSD mean diameter. This requires two measurements. Two frequencies are used, with a large enough separation that the differential frequency provides size information. One frequency is 94 GHz; the other is 220 GHz. These correspond to the Rayleigh and Mie regions. Above a surface wind speed of 10 m/ s, production of sea spray grows exponentially. Both the number of large droplets and the altitude they reach are a function of the surface wind speed.

  15. Application of the Hilbert-Huang Transform to the Estimation of Air-Sea Turbulent Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Juanjuan; Song, Jinbao; Huang, Yansong; Fan, Conghui

    2013-06-01

    The Hilbert-Huang transform (HHT) is applied to analyzing the turbulent time series obtained within the atmospheric boundary layer over the ocean. A method based on the HHT is introduced to reduce the influence of non-turbulent motions on the eddy-covariance based flux by removing non-turbulent modes from the time series. The scale dependence of the flux is examined and a gap mode is identified to distinguish between turbulent modes and non-turbulent modes. To examine the effectiveness of this method it is compared with three conventional methods (block average, moving-window average, and multi-resolution decomposition). The data used are from three sonic anemometers installed on a moored buoy at about 6, 4 and 2.7 m height above the sea surface. For each method, along-wind and cross-wind momentum fluxes and sensible heat fluxes at the three heights are calculated. According to the assumption of a constant-flux layer, there should be no significant difference between the fluxes at the three heights. The results show that the fluxes calculated using HHT exhibit a smaller difference and higher correlation than the other methods. These results support the successful application of HHT to the estimation of air-sea turbulent fluxes.

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

    NASA Astrophysics Data System (ADS)

    Landwehr, S.; Miller, S. D.; Smith, M. J.; Saltzman, E. S.; Ward, B.

    2014-04-01

    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 dry air CO2 mixing ratio). Another bias related to water vapour fluctuations has recently been observed with open-path sensors, 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 entered a closed-path gas analyser. Prytherch et al. (2010a) 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 parameterisations. 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. Applying the PKT correction to the flux data from the un-dried analysers did not remove the bias when compared to the data from the dried gas analyser. The results of this study demonstrate the validity of measuring CO2 fluxes using a pre-dried air stream and show that

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Mechanisms controlling the SST air-sea heat flux feedback and its dependence on spatial scale

    NASA Astrophysics Data System (ADS)

    Hausmann, Ute; Czaja, Arnaud; Marshall, John

    2016-05-01

    The turbulent air-sea heat flux feedback (α , in {W m}^{-2}{ K}^{-1} ) is a major contributor to setting the damping timescale of sea surface temperature (SST) anomalies. In this study we compare the spatial distribution and magnitude of α in the North Atlantic and the Southern Ocean, as estimated from the ERA-Interim reanalysis dataset. The comparison is rationalized in terms of an upper bound on the heat flux feedback, associated with "fast" atmospheric export of temperature and moisture anomalies away from the marine boundary layer, and a lower bound associated with "slow" export. It is found that regions of cold surface waters (≤ 10° C) are best described as approaching the slow export limit. This conclusion is not only valid at the synoptic scale resolved by the reanalysis data, but also on basin scales. In particular, it applies to the heat flux feedback acting as circumpolar SST anomaly scales are approached in the Southern Ocean, with feedbacks of ≤ 10 {W m}^{-2}{ K}^{-1} . In contrast, the magnitude of the heat flux feedback is close to that expected from the fast export limit over the Gulf Stream and its recirculation with values on the order of ≈40 {W m}^{-2}{ K}^{-1} . Further analysis suggests that this high value reflects a compensation between a moderate thermodynamic adjustment of the boundary layer, which tends to weaken the heat flux feedback, and an enhancement of the surface winds over warm SST anomalies, which tend to enhance the feedback.

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

    NASA Astrophysics Data System (ADS)

    Landwehr, S.; Miller, S. D.; Smith, M. J.; Saltzman, E. S.; Ward, B.

    2013-10-01

    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 algorithm reveals

  20. OAFlux Satellite-Based High-Resolution Analysis of Air-Sea Turbulent Heat, Moisture, and Momentum Fluxes

    NASA Astrophysics Data System (ADS)

    Yu, Lisan

    2016-04-01

    The Objectively Analyzed air-sea Fluxes (OAFlux) project at the Woods Hole Oceanographic Institution has recently developed a new suite of products: the satellite-based high-resolution (HR) air-sea turbulent heat, moisture, and momentum fluxes over the global ocean from 1987 to the present. The OAFlux-HR fluxes are computed from the COARE bulk algorithm using air-sea variables (vector wind, near-surface humidity and temperature, and ocean surface temperature) derived from multiple satellite sensors and multiple missions. The vector wind time series are merged from 14 satellite sensors, including 4 scatterometers and 10 passive microwave radiometers. The near-surface humidity and temperature time series are retrieved from 11 satellite sensors, including 7 microwave imagers and 4 microwave sounders. The endeavor has greatly improved the depiction of the air-sea turbulent exchange on the frontal and meso-scales. The OAFlux-HR turbulent flux products are valuable datasets for a broad range of studies, including the study of the long-term change and variability in the oean-surface forcing functions, quantification of the large-scale budgets of mass, heat, and freshwater, and assessing the role of the ocean in the change and variability of the Earth's climate.

  1. Air-Sea Methane Flux after the Deepwater Horizon Oil Leak

    NASA Astrophysics Data System (ADS)

    McAdoo, J.; Sweeney, C.; Kiene, R. P.; McGillis, W. R.

    2012-12-01

    One of the key questions associated with the Deepwater Horizon's (DWH) oil leak involves understanding how much of its methane is still entrained in deep waters. Analysis of air-sea fluxes reveals a slight decrease in average aqueous CH4 from 3.3 nM in June to 3.1 and 2.8 nM in August and September, respectively. The flux estimate showed higher methane flux to the atmosphere after the blowout was capped (3.8 μmol m-2 d-1 in August) compared to 0.024 μmol m-2 d-1 during the leak. Almost all observations were within the range of historical levels. The exception was one large peak to the southwest of the wellhead, but its contribution to atmospheric methane is found to be insignificant compared to the total amount of methane released by the leak. This result supports findings that DWH methane remained entrained in the deep waters and consequently is available for biological degradation and threatens to deplete oxygen, adding further stress to an area that already suffers from anoxic-induced dead zones.

  2. Air-sea exchange fluxes of synthetic polycyclic musks in the North Sea and the Arctic.

    PubMed

    Xie, Zhiyong; Ebinghaus, Ralf; Temme, Christian; Heemken, Olaf; Ruck, Wolfgang

    2007-08-15

    Synthetic polycyclic musk fragrances Galaxolide (HHCB) and Tonalide (AHTN) were measured simultaneously in air and seawater in the Arctic and the North Sea and in the rural air of northern Germany. Median concentrations of gas-phase HHCB and AHTN were 4 and 18 pg m(-3) in the Arctic, 28 and 18 pg m(-3) in the North Sea, and 71 and 21 pg m(-3) in northern Germany, respectively. Various ratios of HHCB/AHTN implied that HHCB is quickly removed by atmospheric degradation, while AHTN is relatively persistent in the atmosphere. Dissolved concentrations ranged from 12 to 2030 pg L(-1) for HHCB and from below the method detection limit (3 pg L(-1)) to 965 pg L(-1) for AHTN with median values of 59 and 23 pg L(-1), respectively. The medians of volatilization fluxes for HHCB and AHTN were 27.2 and 14.2 ng m(-2) day(-1) and the depositional fluxes were 5.9 and 3.3 ng m(-2) day(-1), respectively, indicating water-to-air volatilization is a significant process to eliminate HHCB and AHTN from the North Sea. In the Arctic, deposition fluxes dominated the air-sea gas exchange of HHCB and AHTN, suggesting atmospheric input controls the levels of HHCB and AHTN in the polar region.

  3. Extreme air-sea surface turbulent fluxes in mid latitudes - estimation, origins and mechanisms

    NASA Astrophysics Data System (ADS)

    Gulev, Sergey; Natalia, Tilinina

    2014-05-01

    provide locally high winds and air-sea temperature gradients. For this purpose we linked characteristics of cyclone activity over the midlatitudinal oceans with the extreme surface turbulent heat fluxes. Cyclone tracks and parameters of cyclone life cycle (deepening rates, propagation velocities, life time and clustering) were derived from the same reanalyses using state of the art numerical tracking algorithm. The main questions addressed in this study are (i) through which mechanisms extreme surface fluxes are associated with cyclone activity? and (ii) which types of cyclones are responsible for forming extreme turbulent fluxes? Our analysis shows that extreme surface fluxes are typically associated not with cyclones themselves but rather with cyclone-anticyclone interaction zones. This implies that North Atlantic and North Pacific series of intense cyclones do not result in the anomalous surface fluxes. Alternatively, extreme fluxes are most frequently associated with blocking situations, particularly with the intensification of the Siberian and North American Anticyclones providing cold-air outbreaks over WBC regions.

  4. Oceanic distributions and air-sea fluxes of biogenic halocarbons in the open ocean

    NASA Astrophysics Data System (ADS)

    Chuck, Adele L.; Turner, Suzanne M.; Liss, Peter S.

    2005-10-01

    Surface seawater and atmospheric concentrations of methyl iodide, chloroiodomethane, bromoform, dichlorobromomethane, and chlorodibromethane were measured during three open ocean cruises in the Atlantic and Southern oceans. The measurements spanned a longitudinal range of 115°, between 50°N and 65°S. The saturation anomalies and the instantaneous air-sea fluxes of the gases during one of these cruises (ANT XVIII/1) are presented and discussed. Methyl iodide and chloroiodomethane were highly supersaturated (>1000%) throughout the temperate and tropical regions, with calculated mean fluxes of 15 and 5.5 nmol m-2 d-1, respectively. The oceanic emissions of the brominated compounds were less substantial, and a significant area of the temperate Atlantic Ocean was found to be a sink for bromoform. Correlation analyses have been used to investigate possible controls on the concentrations of these gases. In particular, the relationship of CH3I with sea surface temperature and light is discussed, with the tentative conclusion that this compound may be formed abiotically.

  5. Global CO2 simulation using GOSAT-based surface CO2 flux estimates

    NASA Astrophysics Data System (ADS)

    Takagi, H.; Oda, T.; Saito, M.; Valsala, V.; Belikov, D.; Saeki, T.; Saito, R.; Morino, I.; Uchino, O.; Yoshida, Y.; Yokota, Y.; Bril, A.; Oshchepkov, S.; Andres, R. J.; Maksyutov, S.

    2012-04-01

    Investigating the distribution and temporal variability of surface CO2 fluxes is an active research topic in the field of contemporary carbon cycle dynamics. The technique central to this effort is atmospheric inverse modeling with which surface CO2 fluxes are estimated by making corrections to a priori flux estimates such that mismatches between model-predicted and observed CO2 concentrations are minimized. Past investigations were carried out by utilizing CO2 measurements collected in global networks of surface-based monitoring sites. Now, datasets of column-averaged CO2 dry air mole fraction (XCO2) retrieved from spectral soundings collected by GOSAT are available for complementing the surface-based CO2 observations. These space-based XCO2 data are expected to enhance the spatiotemporal coverage of the existing surface observation network and thus reduce uncertainty associated with the surface flux estimates. We estimated monthly CO2 fluxes in 64 sub-continental regions from a subset of the surface-based GLOBALVIEW CO2 data and the GOSAT FTS SWIR Level 2 XCO2 retrievals. We further simulated CO2 concentrations in 3-D model space using the surface flux estimates obtained. In this presentation, we report the result of a comparison between the simulated CO2 concentrations and independent surface observations. As part of an effort in inter-comparing GOSAT-based surface CO2 flux estimates, we also look at results yielded with XCO2 data retrieved with the PPDF-DOAS algorithm and those made available by the NASA Atmospheric CO2 Observations from Space team. For this study, we used version 08.1 of the National Institute for Environmental Studies atmospheric transport model, which was driven by the Japan Meteorological Agency's JCDAS wind analysis data. The CO2 forward simulations were performed on 2.5° × 2.5° horizontal grids at 32 vertical levels between the surface and the top of the atmosphere. The a priori flux dataset used was comprised of the sum of four

  6. Remote sensing model for CO2 flux in wheat fields

    NASA Astrophysics Data System (ADS)

    Zhang, Renhua; Sun, Xiaomin; Zhu, Zhilin; Su, Hongbo; Chen, Gang

    1998-08-01

    In this paper we presented a model for calculating CO2 flux in the wheat field based on field simulate test. We adopted crop transpiration as 'information picker' of CO2 flux instead of the potential evaporation and crop water stress index. Another crucial factor is leaf index and air vapor saturation deficit. Experimental coefficient is equal to 1/58. Calculating values have a good agreement with real measurements. The model is useful to estimate regional distribution of CO2 flux.

  7. pCO2 distribution and CO2 flux on the inner continental shelf of the East China Sea during summer 2011

    NASA Astrophysics Data System (ADS)

    Qu, Baoxiao; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Ma, Qingxia

    2013-09-01

    Measurements of pH, total alkalinity (TA), partial pressure of CO2 ( pCO2) and air-sea CO2 flux ( FCO2) were conducted for the inner continental shelf of the East China Sea (ECS) during August 2011. Variations in pCO2 distribution and FCO2 magnitude during the construction of the Three Gorges Dam (TGD) (2003-2009), and the potential effects of the TGD on the air-sea CO2 exchange were examined. Results showed that the ECS acts as an overall CO2 sink during summer, with pCO2 ranging from 107 to 585 μatm and an average FCO2 of -6.39 mmol/(m2 ·d). Low pCO2 (<350 μatm) levels were observed at the central shelf (28°-32°N, 123°-125.5°E) where most CO2-absorption occurred. High pCO2 (>420 μatm) levels were found in the Changjiang estuary and Hangzhou Bay which acted as the main CO2 source. A negative relationship between pCO2 and salinity ( R 2=0.722 0) in the estuary zone indicated the predominant effect of the Changjiang Diluted Water (CDW) on the seawater CO2 system, whereas a positive relationship ( R 2=0.744 8) in the offshore zone revealed the influence of the Taiwan Current Warm Water (TCWW). Together with the historical data, our results indicated that the CO2 sink has shown a shift southwest while FCO2 exhibited dramatic fluctuation during the construction of the TGD, which is located in the middle reaches of the Changjiang. These variations probably reflect fluctuation in the Changjiang runoff, nutrient import, phytoplankton productivity, and sediment input, which are likely to have been caused by the operations of the TGD. Nevertheless, the potential influence of the TGD on the CO2 flux in the ECS is worthy of further study.

  8. CO2 flux estimation accuracy evaluation of Global and Regional atmospheric CO2 mission concepts

    NASA Astrophysics Data System (ADS)

    Lee, M.; Miller, C.; Weidner, R. J.; Duren, R. M.; Sander, S.; Eldering, A.

    2012-12-01

    We developed an observing system simulation experiment (OSSE) framework to evaluate mission-science-return quantitatively as a function of instrument payload, observation frequency, orbit, and sampling strategy for space-based remote sensing. The OSSE framework integrates GEOSChem and its adjoint system to perform forward/inverse modeling of the simulated measurements. During 2011-2012, we extended the OSSE framework to evaluate CO2 mission concepts in collaboration with the NASA's carbon monitoring system (CMS) flux pilot project team. In this paper, we employ the OSSE framework to analyze the science impact of multiple, simultaneous space-based column CO2 observations from simulated combinations of GOSAT, OCO-2, OCO-3, and a geo-stationary mission concept (GEOFTS). The OSSE process involved generating a CO2 concentration forecast, sampling the CO2 field at the appropriate time and location for each satellite sensor, incorporating realistic cloud climatologies to generate accurate clear-sky viewing statistics, retrieving CO2 profile simulaton in the presence of measurement noise, and finally assimilating the simulated column CO2 retrievals to estimate CO2 fluxes and flux uncertainty reductions. The OSSE process was applied over one-year-long mission period (2009/Jan - 2009/Dec) and the CO2 flux estimation error was analyzed to compute the probability density function (PDF) of CO2 flux estimation-error-reduction. The global OSSEs were performed in 2deg x 2.5 deg spatial resolution with the monthly-average CO2 flux estimation-error-reduction as the science-impact metric. Regional OSSEs were performed in 0.5 deg by 0.666 deg over N. America and the weekly average of the CO2 flux estimation-error-reduction was employed as the science-impact metric. We discuss the results and the projected performance of planned and potential space-based CO2 observing systems.

  9. Soil surface CO2 fluxes on the Konza Prairie

    NASA Technical Reports Server (NTRS)

    Norman, J. M.; Garcia, R.; Verma, Shoshi B.

    1990-01-01

    The utilization of a soil chamber to measure fluxes of soil-surface CO2 fluxes is described in terms of equipment, analytical methods, and estimate quality. A soil chamber attached to a gas-exchange system measures the fluxes every 5-15 min, and the data are compared to measurements of the CO2 fluxes from the canopy and from the soil + canopy. The soil chamber yields good measurements when operated in a closed system that is ported to the free atmosphere, and the CO2 flux is found to have a diurnal component.

  10. Dynamics of CO2 fluxes and concentrations during a shallow subsurface CO2 release

    SciTech Connect

    Lewicki, J.L.; Hilley, G.E.; Dobeck, L.; Spangler, L.

    2009-09-01

    A field facility located in Bozeman, Montana provides the opportunity to test methods to detect, locate, and quantify potential CO2 leakage from geologic storage sites. From 9 July to 7 August 2008, 0.3 t CO2 d{sup -1} were injected from a 100-m long, {approx}2.5 m deep horizontal well. Repeated measurements of soil CO2 fluxes on a grid characterized the spatio-temporal evolution of the surface leakage signal and quantified the surface leakage rate. Infrared CO2 concentration sensors installed in the soil at 30 cm depth at 0 to 10 m from the well and at 4 cm above the ground at 0 and 5 m from the well recorded surface breakthrough of CO2 leakage and migration of CO2 leakage through the soil. Temporal variations in CO2 concentrations were correlated with atmospheric and soil temperature, wind speed, atmospheric pressure, rainfall, and CO2 injection rate.

  11. Assessment of CO2 flux measurements in different soil types

    NASA Astrophysics Data System (ADS)

    Xia, L.; Szlavecz, K.; Musaloiu, R.; Cupchup, J.; Pitz, S.

    2008-12-01

    Accurate measurements of soil CO2 efflux are extraordinarily challenging due to the very properties of CO2 transport in a porous medium of soil. The most commonly used method today is the chamber method, which provides direct measurements of CO2 efflux at the soil surface, but it can not measure the soil CO2 flux continuously. In order to develop new measurement methods in soil CO2 efflux, small solid-state CO2 sensors have been used to continuously to monitor soil CO2 profiles by burying these sensors at different soil depths. Using this method we compared soil CO2 efflux of four different soil types: forests soil, grassland soil (collected in Maryland) commercial potting soil and pure sand as control. CO2 concentration varied between 500 ppm in sand and 8000 ppm in forest soil at depth 12 cm. CO2 flux had the following order: Forest (0.3~0.4 mg CO2 m-2 s-1), potting soil (0.1~0.14 mg CO2 m-2 s-1 ), grassland (0.03~0.05 mg CO2 m-2 s-1), sand ( 0 mg CO2 m-2 s-1 ). Exponential relationship between temperature and CO2 flux was established for forest soil and potting soil only. Leaf litter, often thick layer in many terrestrial ecosystems and a significant source of CO2 production, is not part of the of the diffusivity models. We are currently conducting experiments which include the effect of leaf litter and soil invertebrates into soil respiration.

  12. Response of air-sea carbon fluxes and climate to orbital forcing changes in the Community Climate System Model

    NASA Astrophysics Data System (ADS)

    Jochum, M.; Peacock, S.; Moore, K.; Lindsay, K.

    2010-07-01

    A global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115,000 years ago features significantly cooler northern high latitudes but only moderately cooler southern high latitudes. This asymmetry is explained by a 30% reduction of the strength of the Atlantic Meridional Overturning Circulation that is caused by an increased Arctic sea ice export and a resulting freshening of the North Atlantic. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10%-20%. These climate shifts lead to regional differences in air-sea carbon fluxes of the same order. However, the differences in global net air-sea carbon fluxes are small, which is due to several effects, two of which stand out: first, colder sea surface temperature leads to a more effective solubility pump but also to increased sea ice concentration which blocks air-sea exchange, and second, the weakening of Southern Ocean winds that is predicted by some idealized studies occurs only in part of the basin, and is compensated by stronger winds in other parts.

  13. High resolution measurements of methane and carbon dioxide in surface waters over a natural seep reveal dynamics of dissolved phase air-sea flux.

    PubMed

    Du, Mengran; Yvon-Lewis, Shari; Garcia-Tigreros, Fenix; Valentine, David L; Mendes, Stephanie D; Kessler, John D

    2014-09-01

    Marine hydrocarbon seeps are sources of methane and carbon dioxide to the ocean, and potentially to the atmosphere, though the magnitude of the fluxes and dynamics of these systems are poorly defined. To better constrain these variables in natural environments, we conducted the first high-resolution measurements of sea surface methane and carbon dioxide concentrations in the massive natural seep field near Coal Oil Point (COP), California. The corresponding high resolution fluxes were calculated, and the total dissolved phase air-sea fluxes over the surveyed plume area (∼363 km(2)) were 6.66 × 10(4) to 6.71 × 10(4) mol day(-1) with respect to CH4 and -6.01 × 10(5) to -5.99 × 10(5) mol day(-1) with respect to CO2. The mean and standard deviation of the dissolved phase air-sea fluxes of methane and carbon dioxide from the contour gridding analysis were estimated to be 0.18 ± 0.19 and -1.65 ± 1.23 mmol m(-2) day(-1), respectively. This methane flux is consistent with previous, lower-resolution estimates and was used, in part, to conservatively estimate the total area of the dissolved methane plume at 8400 km(2). The influx of carbon dioxide to the surface water refutes the hypothesis that COP seep methane appreciably influences carbon dioxide dynamics. Seeing that the COP seep field is one of the biggest natural seeps, a logical conclusion could be drawn that microbial oxidation of methane from natural seeps is of insufficient magnitude to change the resulting plume area from a sink of atmospheric carbon dioxide to a source.

  14. Can subterranean cave systems affect soil CO2 fluxes?

    NASA Astrophysics Data System (ADS)

    Krajnc, Bor; Ferlan, Mitja; Ogrinc, Nives

    2015-04-01

    Main factors affecting soil CO2 fluxes in most ecosystems are soil temperature and soil moisture. Nevertheless occasionally high soil CO2 fluxes were observed at carst areas, which could result from ventilation of subterranean cavities (Ferlan et al., 2011). The aim of this work was to determine the influence of cave ventilation to soil CO2 fluxes. Research was done in a dead-end passage of Postojna cave (Pisani rov) and on the surface area above the passage (Velika Jeršanova dolina) in south-western Slovenia. Inside the cave we measured CO2 concentrations, its carbon (13C) stable isotope composition, 222Rn activity concentrations, temperatures and air pressure. At the surface we had chosen two sampling plots; test plot above the cave and control. At both plots we measured soil CO2 fluxes with automatic chambers, CO2 concentrations, temperatures and carbon stable isotope composition of soil air at three different depths (0.2 m, 0.5 m and 0.8 m) and different meteorological parameters such as: air temperature, air pressure, wind speed an precipitation. To detect the cave influence, we compared two surface CO2 flux measurements with air temperatures and changes of CO2 concentrations in the cave atmosphere. Our results on CO2 concentrations in the gallery of the cave indicated that the ventilation of this particular gallery also depends on outside air temperatures. Outside temperature increased and corresponded to higher CO2 concentrations, whereas at lower temperatures (T < 9 oC) cave started to ventilate and exhaled CO2 reach air through unknown fissures and cracks. At the control plot the soil CO2 fluxes were in a good correlation with soil temperatures (r = 0.789, p =0.01), where greater soil temperatures correspond to greater soil CO2 fluxes. Soil CO2 fluxes at the plot above the cave did not show statistically significant correlations with soil temperatures or soil moisture indicating that other factors possibly cave ventilation could influence it. References

  15. Pseudo-data Inversions of California CO2 Fluxes Combining Tower Measurements of CO2 and 14CO2 with OCO2 Column CO2 Retrievals

    NASA Astrophysics Data System (ADS)

    Fischer, M. L.; Jeong, S.; Bagley, J.; Frankenberg, C.; Parazoo, N.; Keeling, R. F.; Graven, H. D.

    2014-12-01

    The majority (~ 80 %) of California's greenhouse gas (GHG) emissions are likely CO2 produced by fossil fuel combustion (ffCO2). While bottom-up estimates of State-annual total ffCO2 emissions are expected to be accurate to ~ 5-10% (68% confidence), net CO2 exchange at smaller spatial and temporal scales (and emissions of other GHGs) are likely less certain. Here, we report initial results of a Carbon Monitoring System (CMS) pseudo-data inversion study combining simulated total and radiocarbon CO2 sampling from a 10-site ground-based tower network with OCO2 satellite column CO2 retrievals. Fossil and biosphere CO2 signals are computed for tower and OCO2 observations across urban and rural areas of California including the South Coast Air Basin (SoCAB), Central Valley, and San Francisco Bay Area using the WRF-STILT transport model simulations coupled with prior fluxes from VULCAN (ffCO2) and CASA (bioCO2) fluxes respectively. Nominal uncertainties are assigned to the prior ffCO2 fluxes and estimated for the model-measurement differences including WRF and STILT model uncertainties and background subtraction. Reductions in posterior uncertainties for regional ffCO2 emissions are estimated for the tower pseudo-data using Bayesian inversions for monthly periods in multiple seasons. Ongoing work will include incorporation of OCO2 pseudo-data to estimate additional uncertainty reductions obtained for ffCO2 and bioCO2 exchange signals across California's urban and rural regions.

  16. Field Comparison of Methods for Measuring Soil CO2 Flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variety of techniques are available for measurement of soil carbon dioxide (CO2) flux in the field, and each method has inherent advantages and disadvantages. On five dates in October, 2005 we measured soil CO2 emissions in a central Iowa soybean field using: i)eddy covariance, ii)a commercially a...

  17. Spatiotemporal variations in CO2 flux in a fringing reef simulated using a novel carbonate system dynamics model

    NASA Astrophysics Data System (ADS)

    Watanabe, A.; Yamamoto, T.; Nadaoka, K.; Maeda, Y.; Miyajima, T.; Tanaka, Y.; Blanco, A. C.

    2013-03-01

    A carbonate system dynamics (CSD) model was developed in a fringing reef on the east coast of Ishigaki Island, southwest Japan, by incorporating organic and inorganic carbon fluxes (photosynthesis and calcification), air-sea gas exchanges, and benthic cover of coral and seagrass into a three-dimensional hydrodynamic model. The CSD model could reproduce temporal variations in dissolved inorganic carbon (DIC) and total alkalinity in coral zones, but not in seagrass meadows. The poor reproduction in seagrass meadows can be attributed to significant contributions of submarine groundwater discharge as well as misclassification of remotely sensed megabenthos in this area. In comparison with offshore areas, the reef acted as a CO2 sink during the observation period when it was averaged over 24 h. The CSD model also indicated large spatiotemporal differences in the carbon dioxide (CO2) sink/source, possibly related to hydrodynamic features such as effective offshore seawater exchange and neap/spring tidal variation. This suggests that the data obtained from a single point observation may lead to misinterpretation of the overall trend and thus should be carefully considered. The model analysis also showed that the advective flux of DIC from neighboring grids is several times greater than local biological flux of DIC and is three orders of magnitude greater than the air-sea gas flux at the coral zone. Sensitivity tests in which coral or seagrass covers were altered revealed that the CO2 sink potential was much more sensitive to changes in coral cover than seagrass cover.

  18. Direct measurements of CO2 flux in the Greenland Sea

    NASA Astrophysics Data System (ADS)

    Lauvset, Siv K.; McGillis, Wade R.; Bariteau, Ludovic; Fairall, C. W.; Johannessen, Truls; Olsen, Are; Zappa, Christopher J.

    2011-06-01

    During summer 2006 eddy correlation CO2 fluxes were measured in the Greenland Sea using a novel system set-up with two shrouded LICOR-7500 detectors. One detector was used exclusively to determine, and allow the removal of, the bias on CO2 fluxes due to sensor motion. A recently published correction method for the CO2-H2O cross-correlation was applied to the data set. We show that even with shrouded sensors the data require significant correction due to this cross-correlation. This correction adjusts the average CO2 flux by an order of magnitude from -6.7 × 10-2 mol m-2 day-1 to -0.61 × 10-2 mol m-2 day-1, making the corrected fluxes comparable to those calculated using established parameterizations for transfer velocity.

  19. CO2 fluxes near a forest edge: a numerical study.

    PubMed

    Sogachev, Andrey; Leclerc, Monique Y; Zhang, Gengsheng; Rannik, Ullar; Vesala, Timo

    2008-09-01

    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 the concentration and flux fields against those of a uniform forested surface. We use an atmospheric boundary layer two-equation closure model that accounts for the flow dynamics and vertical divergence of CO2 sources/sinks within a plant canopy. This paper characterizes the spatial variation of CO2 fluxes 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 in the upper part of the canopy. These results can be useful both for interpretation of existing measurements of net ecosystem exchange of CO2 (NEE) from flux towers in limited fetch conditions and in planning future CO2 transport experiments.

  20. CO2 fluxes near a forest edge: a numerical study.

    PubMed

    Sogachev, Andrey; Leclerc, Monique Y; Zhang, Gengsheng; Rannik, Ullar; Vesala, Timo

    2008-09-01

    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 the concentration and flux fields against those of a uniform forested surface. We use an atmospheric boundary layer two-equation closure model that accounts for the flow dynamics and vertical divergence of CO2 sources/sinks within a plant canopy. This paper characterizes the spatial variation of CO2 fluxes 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 in the upper part of the canopy. These results can be useful both for interpretation of existing measurements of net ecosystem exchange of CO2 (NEE) from flux towers in limited fetch conditions and in planning future CO2 transport experiments. PMID:18767622

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

    NASA Astrophysics Data System (ADS)

    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.

  2. CLIVAR-GSOP/GODAE Ocean Synthesis Inter-Comparison of Global Air-Sea Fluxes From Ocean and Coupled Reanalyses

    NASA Astrophysics Data System (ADS)

    Valdivieso, Maria

    2014-05-01

    The GODAE OceanView and CLIVAR-GSOP ocean synthesis program has been assessing the degree of consistency between global air-sea flux data sets obtained from ocean or coupled reanalyses (Valdivieso et al., 2014). So far, fifteen global air-sea heat flux products obtained from ocean or coupled reanalyses have been examined: seven are from low-resolution ocean reanalyses (BOM PEODAS, ECMWF ORAS4, JMA/MRI MOVEG2, JMA/MRI MOVECORE, Hamburg Univ. GECCO2, JPL ECCOv4, and NCEP GODAS), five are from eddy-permitting ocean reanalyses developed as part of the EU GMES MyOcean program (Mercator GLORYS2v1, Reading Univ. UR025.3, UR025.4, UKMO GloSea5, and CMCC C-GLORS), and the remaining three are couple reanalyses based on coupled climate models (JMA/MRI MOVE-C, GFDL ECDA and NCEP CFSR). The global heat closure in the products over the period 1993-2009 spanned by all data sets is presented in comparison with observational and atmospheric reanalysis estimates. Then, global maps of ensemble spread in the seasonal cycle, and of the Signal to Noise Ratio of interannual flux variability over the 17-yr common period are shown to illustrate the consistency between the products. We have also studied regional variability in the products, particularly at the OceanSITES project locations (such as, for instance, the TAO/TRITON and PIRATA arrays in the Tropical Pacific and Atlantic, respectively). Comparisons are being made with other products such as OAFlux latent and sensible heat fluxes (Yu et al., 2008) combined with ISCCP satellite-based radiation (Zhang et al., 2004), the ship-based NOC2.0 product (Berry and Kent, 2009), the Large and Yeager (2009) hybrid flux dataset CORE.2, and two atmospheric reanalysis products, the ECMWF ERA-Interim reanalysis (referred to as ERAi, Dee et al., 2011) and the NCEP/DOE reanalysis R2 (referred to as NCEP-R2, Kanamitsu et al., 2002). Preliminary comparisons with the observational flux products from OceanSITES are also underway. References Berry, D

  3. Assessing the potential for dimethylsulfide enrichment at the sea surface and its influence on air-sea flux

    NASA Astrophysics Data System (ADS)

    Walker, Carolyn F.; Harvey, Mike J.; Smith, Murray J.; Bell, Thomas G.; Saltzman, Eric S.; Marriner, Andrew S.; McGregor, John A.; Law, Cliff S.

    2016-09-01

    The flux of dimethylsulfide (DMS) to the atmosphere is generally inferred using water sampled at or below 2 m depth, thereby excluding any concentration anomalies at the air-sea interface. Two independent techniques were used to assess the potential for near-surface DMS enrichment to influence DMS emissions and also identify the factors influencing enrichment. DMS measurements in productive frontal waters over the Chatham Rise, east of New Zealand, did not identify any significant gradients between 0.01 and 6 m in sub-surface seawater, whereas DMS enrichment in the sea-surface microlayer was variable, with a mean enrichment factor (EF; the concentration ratio between DMS in the sea-surface microlayer and in sub-surface water) of 1.7. Physical and biological factors influenced sea-surface microlayer DMS concentration, with high enrichment (EF > 1.3) only recorded in a dinoflagellate-dominated bloom, and associated with low to medium wind speeds and near-surface temperature gradients. On occasion, high DMS enrichment preceded periods when the air-sea DMS flux, measured by eddy covariance, exceeded the flux calculated using National Oceanic and Atmospheric Administration (NOAA) Coupled-Ocean Atmospheric Response Experiment (COARE) parameterized gas transfer velocities and measured sub-surface seawater DMS concentrations. The results of these two independent approaches suggest that air-sea emissions may be influenced by near-surface DMS production under certain conditions, and highlight the need for further study to constrain the magnitude and mechanisms of DMS production in the sea-surface microlayer.

  4. High temporal resolution dynamics of wintertime soil CO2 flux

    NASA Astrophysics Data System (ADS)

    Risk, D. A.; McArthur, G. S.; Nickerson, N. R.; Beltrami, H.

    2009-12-01

    Few studies have undertaken soil CO2 flux measurements during winter, despite the fact that even in temperate zones, winter-like conditions may persist for one-third of the year or more. When growing season monitoring equipment is stowed for the winter, we potentially miss a large portion of the carbon budget, and may also fail to develop an adequate appreciation of winter c production dynamics. These are critical gaps, especially with respect to soil carbon stability and CO2 emissions in northern and permafrost areas, which are expected to accelerate as a consequence of climate change and which may create a positive feedback on atmospheric CO2 concentrations. This study undertakes a thorough examination of overwinter soil CO2 dynamics at two contrasting sites; one with deeply frozen soils where snow cover is absent as a result of sustained high winds; and another site with heavy snow load (>150 cm typical) where soils underneath remain frost-free because of snowpack insulation. Our overwinter soil-surface CO2 flux measurements were facilitated by use of a new instrumental technique called Continuous Timeseries - Forced Diffusion (CT-FD) to record soil CO2 fluxes continuously at a temporal resolution of 60 seconds. The high frequency monitoring allows us to look not only at magnitudes of change and carbon budgets, but also in detail at the temporal characteristics of response to environmental forcings. Here, we concentrate our analysis on rates of change near critical thresholds such as freeze-thaw. At the deep snowpack site where soil frost was absent, we observed pronounced diurnal cyclicity in CO2 flux even under a >150 cm snowpack, marked moisture response after midwinter rain events, and a springtime respiratory burst that began slightly before full snowpack melt. The CO2 emission dynamics from the frozen soils of the snow-free site were dominated by respiratory bursts at freeze-thaw thresholds when solar heating and warm air temperatures created a thin active

  5. Open ocean gas transfer velocity derived from long-term direct measurements of the CO2 flux

    NASA Astrophysics Data System (ADS)

    Prytherch, John; Yelland, Margaret J.; Pascal, Robin W.; Moat, Bengamin I.; Skjelvan, Ingunn; Srokosz, Meric A.

    2010-12-01

    Air-sea open ocean CO2 flux measurements have been made using the Eddy Covariance (EC) technique onboard the weathership Polarfront in the North Atlantic between September 2006 and December 2009. Flux measurements were made using an autonomous system ‘AutoFlux’. CO2 mass density was measured with an open-path infrared gas analyzer. Following quality control procedures, 3938 20-minute flux measurements were made at mean wind speeds up to 19.6 m/s, significantly higher wind speeds than previously published results. The uncertainty in the determination of gas transfer velocities is large, but the mean relationship to wind speed allows a new parameterisation of the gas transfer velocity to be determined. A cubic dependence of gas transfer on wind speed is found, suggesting a significant influence of bubble-mediated exchange on gas transfer.

  6. A Preliminary Study of CO2 Flux Measurements by Lidar

    NASA Technical Reports Server (NTRS)

    Gibert, Fabien; Koch, Grady J.; Beyon, Jeffrey Y.; Hilton, T.; Davis, Kenneth J.; Andrews, Arlyn; Ismail, Syed; Singh, Upendra N.

    2008-01-01

    A mechanistic understanding of the global carbon cycle requires quantification of terrestrial ecosystem CO2 fluxes at regional scales. In this paper, we analyze the potential of a Doppler DIAL system to make flux measurements of atmospheric CO2 using the eddy-covariance and boundary layer budget methods and present results from a ground based experiment. The goal of this study is to put CO2 flux point measurements in a mesoscale context. In June 2007, a field experiment combining a 2-m Doppler Heterodyne Differential Absorption Lidar (HDIAL) and in-situ sensors of a 447-m tall tower (WLEF) took place in Wisconsin. The HDIAL measures simultaneously: 1) CO2 mixing ratio, 2) atmosphere structure via aerosol backscatter and 3) radial velocity. We demonstrate how to synthesize these data into regional flux estimates. Lidar-inferred fluxes are compared with eddy-covariance fluxes obtained in-situ at 396m AGL from the tower. In cases where the lidar was not yet able to measure the fluxes with acceptable precision, we discuss possible modifications to improve system performance.

  7. CO2 Flux Estimation Errors Associated with Moist Atmospheric Processes

    NASA Technical Reports Server (NTRS)

    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.

  8. Reconstruction Of Air-Sea Fluxes And Meridional Transport Rates Of Anthropogenic Carbon With An Ensemble Kalman Filter Data Assimilation

    NASA Astrophysics Data System (ADS)

    Gerber, M.; Joos, F.; Vazquez Rodriguez, M.

    2007-12-01

    Regional air-sea fluxes and meridional transport of anthropogenic carbon are inferred by assimilating anthropogenic carbon concentrations within the ocean from different data-based reconstructions. An inverse, Ensemble Kalman Filter method with the Bern3D ocean model is applied. The Bern3D model (Müller et al., 2006) is a computationally-efficient, 3-dimensional coarse resolution ocean model. The Ensemble Kalman Filter (Evenson, 2003) is suited for the assimilation of spatially and temporally varying data into a range of models, for model tuning or for model initialization. Regional fluxes through the air-sea interface and meridional transport rates in the ocean are determined by minimizing deviations between the distributions of anthropogenic carbon from the GLODAP database (Key et al., 2004) and from the Bern3D ocean model in the Ensemble Kalman Filtering optimzation. The resulting anthropogenic carbon fluxes are in agreement with those from another ocean inversion study using the same GLODAP data (Mikaloff Fletcher et al., 2006). Transport uncertainties are addressed by utilizing different configuration of the Bern3D model. The inferred transport uncertainties are comparable in magnitude to the uncertainties obtained by Mikaloff Fletcher et al. The fields of anthropogenic carbon reconstructed with six different reconstruction methods: CFC-shortcut (Thomas et al., 2001), C-star (Gruber et al. 1996), IPSL (Lo Monaco et al., 2005), PHI-CT (Vazquez Rodriguez et al, submitted), TrOCA (Touratier et al., 2004), and TTD (Waugh et al., 2006) from four sections in the Atlantic are assimilated individually to investigate the influence of data uncertainties on the inferred fluxes. Deviations in the inferred fluxes from the different reconstruction methods are comparable or even larger than uncertainties arising from model transport uncertainties. For example, anthropogenic carbon uptake is more than twice as large for the IPSL reconstruction than for the PHI

  9. Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean.

    PubMed

    Mayol, Eva; Jiménez, María A; Herndl, Gerhard J; Duarte, Carlos M; Arrieta, Jesús M

    2014-01-01

    Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 10(4) and 1.6 × 10(7) microbes per m(2) of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m(2) every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes.

  10. Resolving the abundance and air-sea fluxes of airborne microorganisms in the North Atlantic Ocean

    PubMed Central

    Mayol, Eva; Jiménez, María A.; Herndl, Gerhard J.; Duarte, Carlos M.; Arrieta, Jesús M.

    2014-01-01

    Airborne transport of microbes may play a central role in microbial dispersal, the maintenance of diversity in aquatic systems and in meteorological processes such as cloud formation. Yet, there is almost no information about the abundance and fate of microbes over the oceans, which cover >70% of the Earth's surface and are the likely source and final destination of a large fraction of airborne microbes. We measured the abundance of microbes in the lower atmosphere over a transect covering 17° of latitude in the North Atlantic Ocean and derived estimates of air-sea exchange of microorganisms from meteorological data. The estimated load of microorganisms in the atmospheric boundary layer ranged between 6 × 104 and 1.6 × 107 microbes per m2 of ocean, indicating a very dynamic air-sea exchange with millions of microbes leaving and entering the ocean per m2 every day. Our results show that about 10% of the microbes detected in the boundary layer were still airborne 4 days later and that they could travel up to 11,000 km before they entered the ocean again. The size of the microbial pool hovering over the North Atlantic indicates that it could play a central role in the maintenance of microbial diversity in the surface ocean and contribute significantly to atmospheric processes. PMID:25400625

  11. Estimating correlations of CO and CO2 surface fluxes

    NASA Astrophysics Data System (ADS)

    Weir, B.; Pawson, S.; Ott, L. E.; Wargan, K.; Nielsen, J.; Todling, R.

    2014-12-01

    Increased understanding of the processes controlling biospheric CO2 flux isnecessary for improved climate projections. While satellite CO2 observationsare expected to better constrain surface sources and sinks, separatingbiospheric and anthropogenic fluxes is particularly challenging. Correlationsbetween CO and CO2 can help to differentiate between different types offluxes, but a more thorough understanding of these correlations is stillneeded. This presentation discusses the estimation of, and the correspondinguncertainty about, correlations between CO and CO2 surface fluxes in givenregions during given periods of time. The estimates follow from statisticaldiagnostics, including those popularized by Desrozies et al. (2005), appliedto the results of model simulations and assimilations of constituentmeasurements, notably data from satellites, in situ sites, and the TotalCarbon Column Observing Network (TCCON). Nevertheless, the usefulness ofthese estimates is limited by their uncertainty, a property that depends onthe spatial and temporal resolution of the surface fluxes. This workconsiders a variety of different divisions of space (e.g., Global, land andsea, and Transcom regions) and time (e.g., total, seasonal, and monthly) andexamines the conclusions that can be drawn from the correlation estimates.For example, the correlation coefficient can give some indication of thecombustion efficiency of emissions from different regions, or it may suggestthat the surface fluxes of the two constituents are from two differentprocesses. This investigation is used to improve the diagnosis of biosphericflux processes in the GEOS-5 modeling system.

  12. Dissolved methane concentration profiles and air-sea fluxes from 41°S to 27°N

    NASA Astrophysics Data System (ADS)

    Kelley, Cheryl A.; Jeffrey, Wade H.

    2002-07-01

    Water column samples from a transect cruise from southern Chile through the Panama Canal to the Gulf of Mexico were used to determine dissolved methane depth profiles and air-sea methane fluxes. In the Gulf of Mexico, surface concentrations were approximately 40% supersaturated with respect to the atmosphere, whereas near the equator and in the Peru upwelling region, 10-20% supersaturation generally occurred. These saturation ratios translate into an average flux of methane from the sea surface to the atmosphere of 0.38 μmol m-2 d-1. In addition, water column profiles of dissolved methane indicate that subsurface maxima in dissolved methane concentrations are a consistent feature of the open ocean, except near the equator. At the equator, the subsurface peak at the base of the mixed layer may be bowed down by the Equatorial Undercurrent. The highest methane concentration (12 nM) was observed in the Peru upwelling region.

  13. Detecting regional patterns of changing CO2 flux in Alaska

    NASA Astrophysics Data System (ADS)

    Parazoo, Nicholas C.; Commane, Roisin; Wofsy, Steven C.; Koven, Charles D.; Sweeney, Colm; Lawrence, David M.; Lindaas, Jakob; Chang, Rachel Y.-W.; Miller, Charles E.

    2016-07-01

    With rapid changes in climate and the seasonal amplitude of carbon dioxide (CO2) in the Arctic, it is critical that we detect and quantify the underlying processes controlling the changing amplitude of CO2 to better predict carbon cycle feedbacks in the Arctic climate system. We use satellite and airborne observations of atmospheric CO2 with climatically forced CO2 flux simulations to assess the detectability of Alaskan carbon cycle signals as future warming evolves. We find that current satellite remote sensing technologies can detect changing uptake accurately during the growing season but lack sufficient cold season coverage and near-surface sensitivity to constrain annual carbon balance changes at regional scale. Airborne strategies that target regular vertical profile measurements within continental interiors are more sensitive to regional flux deeper into the cold season but currently lack sufficient spatial coverage throughout the entire cold season. Thus, the current CO2 observing network is unlikely to detect potentially large CO2 sources associated with deep permafrost thaw and cold season respiration expected over the next 50 y. Although continuity of current observations is vital, strategies and technologies focused on cold season measurements (active remote sensing, aircraft, and tall towers) and systematic sampling of vertical profiles across continental interiors over the full annual cycle are required to detect the onset of carbon release from thawing permafrost.

  14. Detecting regional patterns of changing CO2 flux in Alaska.

    PubMed

    Parazoo, Nicholas C; Commane, Roisin; Wofsy, Steven C; Koven, Charles D; Sweeney, Colm; Lawrence, David M; Lindaas, Jakob; Chang, Rachel Y-W; Miller, Charles E

    2016-07-12

    With rapid changes in climate and the seasonal amplitude of carbon dioxide (CO2) in the Arctic, it is critical that we detect and quantify the underlying processes controlling the changing amplitude of CO2 to better predict carbon cycle feedbacks in the Arctic climate system. We use satellite and airborne observations of atmospheric CO2 with climatically forced CO2 flux simulations to assess the detectability of Alaskan carbon cycle signals as future warming evolves. We find that current satellite remote sensing technologies can detect changing uptake accurately during the growing season but lack sufficient cold season coverage and near-surface sensitivity to constrain annual carbon balance changes at regional scale. Airborne strategies that target regular vertical profile measurements within continental interiors are more sensitive to regional flux deeper into the cold season but currently lack sufficient spatial coverage throughout the entire cold season. Thus, the current CO2 observing network is unlikely to detect potentially large CO2 sources associated with deep permafrost thaw and cold season respiration expected over the next 50 y. Although continuity of current observations is vital, strategies and technologies focused on cold season measurements (active remote sensing, aircraft, and tall towers) and systematic sampling of vertical profiles across continental interiors over the full annual cycle are required to detect the onset of carbon release from thawing permafrost. PMID:27354511

  15. Air-sea fluxes in a climate model using hourly coupling between the atmospheric and the oceanic components

    NASA Astrophysics Data System (ADS)

    Tian, Fangxing; von Storch, Jin-Song; Hertwig, Eileen

    2016-06-01

    We analyse the changes in the air-sea fluxes of momentum, heat and fresh water flux caused by increasing the ocean-atmosphere coupling frequency from once per day to once per hour in the Max Planck Institute Earth System Model. We diagnose the relative influences of daily averaging and high-frequency feedbacks on the basic statistics of the air-sea fluxes at grid point level and quantify feedback modes responsible for large scale changes in fluxes over the Southern Ocean and the Equatorial Pacific. Coupling once per hour instead of once per day reduces the mean of the momentum-flux magnitude by up to 7 % in the tropics and increases it by up to 10 % in the Southern Ocean. These changes result solely from feedbacks between atmosphere and ocean occurring on time scales shorter than 1 day . The variance and extremes of all the fluxes are increased in most parts of the oceans. Exceptions are found for the momentum and fresh water fluxes in the tropics. The increases result mainly from the daily averaging, while the decreases in the tropics are caused by the high-frequency feedbacks. The variance increases are substantial, reaching up to 50 % for the momentum flux, 100 % for the fresh water flux, and a factor of 15 for the net heat flux. These diurnal and intra-diurnal variations account for up to 50-90 % of the total variances and exhibit distinct seasonality. The high-frequency coupling can influence the large-scale feedback modes that lead to large-scale changes in the magnitude of wind stress over the Southern Ocean and Equatorial Pacific. In the Southern Ocean, the dependence of the SST-wind-stress feedback on the mean state of SST, which is colder in the experiment with hourly coupling than in the experiment with daily coupling, leads to an increase of westerlies. In the Equatorial Pacific, Bjerknes feedback in the hourly coupled experiment reveals a diurnal cycle during the El Niño events, with the feedback being stronger in the nighttime than in the daytime and

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

    NASA Astrophysics Data System (ADS)

    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).

  17. (13) CO2 /(12) CO2 exchange fluxes in a clamp-on leaf cuvette: disentangling artefacts and flux components.

    PubMed

    Gong, Xiao Ying; Schäufele, Rudi; Feneis, Wolfgang; Schnyder, Hans

    2015-11-01

    Leaks and isotopic disequilibria represent potential errors and artefacts during combined measurements of gas exchange and carbon isotope discrimination (Δ). This paper presents new protocols to quantify, minimize, and correct such phenomena. We performed experiments with gradients of CO2 concentration (up to ±250 μmol mol(-1) ) and δ(13) CCO2 (34‰), between a clamp-on leaf cuvette (LI-6400) and surrounding air, to assess (1) leak coefficients for CO2 , (12) CO2 , and (13) CO2 with the empty cuvette and with intact leaves of Holcus lanatus (C3 ) or Sorghum bicolor (C4 ) in the cuvette; and (2) isotopic disequilibria between net photosynthesis and dark respiration in light. Leak coefficients were virtually identical for (12) CO2 and (13) CO2 , but ∼8 times higher with leaves in the cuvette. Leaks generated errors on Δ up to 6‰ for H. lanatus and 2‰ for S. bicolor in full light; isotopic disequilibria produced similar variation of Δ. Leak errors in Δ in darkness were much larger due to small biological : leak flux ratios. Leak artefacts were fully corrected with leak coefficients determined on the same leaves as Δ measurements. Analysis of isotopic disequilibria enabled partitioning of net photosynthesis and dark respiration, and indicated inhibitions of dark respiration in full light (H. lanatus: 14%, S. bicolor: 58%).

  18. Direct Measurement of CO2 Fluxes in Marine Whitings

    SciTech Connect

    Lisa L. Robbins; Kimberly K. Yates

    2001-07-05

    Clean, affordable energy is a requisite for the United States in the 21st Century Scientists continue to debate over whether increases in CO{sub 2} emissions to the atmosphere from anthropogenic sources, including electricity generation, transportation and building systems may be altering the Earth's climate. While global climate change continues to be debated, it is likely that significant cuts in net CO{sub 2} emissions will be mandated over the next 50-100 years. To this end, a number of viable means of CO{sub 2} sequestration need to be identified and implemented. One potential mechanism for CO{sub 2} sequestration is the use of naturally-occurring biological processes. Biosequestration of CO{sub 2} remains one of the most poorly understood processes, yet environmentally safe means for trapping and storing CO{sub 2}. Our investigation focused on the biogeochemical cycling of carbon in microbial precipitations of CaCO{sub 3}. Specifically, we investigated modern whitings (microbially-induced precipitates of the stable mineral calcium carbonate) as a potential, natural mechanism for CO{sub 2} abatement. This process is driven by photosynthetic metabolism of cyanobacteria and microalgae. We analyzed net air: sea CO{sub 2} fluxes, net calcification and photosynthetic rates in whitings. Both field and laboratory investigations have demonstrated that atmospheric CO{sub 2}decreases during the process of microbial calcification.

  19. CO2-fluxing collapses metal mobility in magmatic vapour

    DOE PAGES

    van Hinsberg, V. J.; Berlo, K.; Migdisov, A. A.; Williams-Jones, A. E.

    2016-05-18

    Magmatic systems host many types of ore deposits, including world-class deposits of copper and gold. Magmas are commonly an important source of metals and ore-forming fluids in these systems. In many magmatic-hydrothermal systems, low-density aqueous fluids, or vapours, are significant metal carriers. Such vapours are water-dominated shallowly, but fluxing of CO2-rich vapour exsolved from deeper magma is now recognised as ubiquitous during open-system magma degassing. Furthermore, we show that such CO2-fluxing leads to a sharp drop in element solubility, up to a factor of 10,000 for Cu, and thereby provides a highly efficient, but as yet unrecognised mechanism for metalmore » deposition.« less

  20. Quantifying CO2 fluxes of boreal forests in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Li, C.; Xiao, X.

    2004-12-01

    A number of global carbon balance studies suggested that there is very likely a large carbon sink in the northern Hemisphere, but its spatial patterns and temporal dynamics remain uncertain. International research communities have recently made great efforts establishing a network of CO2 eddy flux towers across boreal forests in Northern Eurasia. The eddy flux tower network has produced and will continue to produce rich data sets of net ecosystem exchange of CO2 (NEE) at the sites. The arisen challenge is how to interpret the rapidly accumulated data sets, and how to upscale the observations into regional scale to explain the global C imbalance. In this presentation, we will introduce a new NASA-funded project that integrates the eddy tower observation, remote sensing analysis, and biogeochemical modeling for quantifying CO2 fluxes of boreal forests in Russia. We will also present some preliminary results from the satellite-based Vegetation Photosynthesis Model (VPM) model and the process-based DNDC model for boreal forests in Europe and North America.

  1. Comparisons of Ship-based Observations of Air-Sea Energy Budgets with Gridded Flux Products

    NASA Astrophysics Data System (ADS)

    Fairall, C. W.; Blomquist, B.

    2015-12-01

    Air-surface interactions are characterized directly by the fluxes of momentum, heat, moisture, trace gases, and particles near the interface. In the last 20 years advances in observation technologies have greatly expanded the database of high-quality direct (covariance) turbulent flux and irradiance observations from research vessels. In this paper, we will summarize observations from the NOAA sea-going flux system from participation in various field programs executed since 1999 and discuss comparisons with several gridded flux products. We will focus on comparisons of turbulent heat fluxes and solar and IR radiative fluxes. The comparisons are done for observing programs in the equatorial Pacific and Indian Oceans and SE subtropical Pacific.

  2. Climatological mean and decadal change in surface ocean pCO 2, and net sea-air CO 2 flux over the global oceans

    NASA Astrophysics Data System (ADS)

    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.; de Baar, Hein J. W.

    2009-04-01

    A climatological mean distribution for the surface water pCO 2 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 pCO 2 obtained from 1970 to 2007. The database used for this study is about 3 times larger than the 0.94 million used for our earlier paper [Takahashi et al., 2002. Global sea-air CO 2 flux based on climatological surface ocean pCO 2, and seasonal biological and temperature effects. Deep-Sea Res. II, 49, 1601-1622]. A time-trend analysis using deseasonalized surface water pCO 2 data in portions of the North Atlantic, North and South Pacific and Southern Oceans (which cover about 27% of the global ocean areas) indicates that the surface water pCO 2 over these oceanic areas has increased on average at a mean rate of 1.5 μatm y -1 with basin-specific rates varying between 1.2±0.5 and 2.1±0.4 μatm y -1. A global ocean database for a single reference year 2000 is assembled using this mean rate for correcting observations made in different years to the reference year. The observations made during El Niño periods in the equatorial Pacific and those made in coastal zones are excluded from the database. Seasonal changes in the surface water pCO 2 and the sea-air pCO 2 difference over four climatic zones in the Atlantic, Pacific, Indian and Southern Oceans are presented. Over the Southern Ocean seasonal ice zone, the seasonality is complex. Although it cannot be thoroughly documented due to the limited extent of observations, seasonal changes in pCO 2 are approximated by using the data for under-ice waters during austral winter and those for the marginal ice and ice-free zones. The net air-sea CO 2 flux is estimated using the sea-air pCO 2 difference and the air-sea gas transfer rate that is parameterized as a function of (wind speed) 2 with a scaling factor of 0.26. This is estimated by inverting

  3. Variability in surface meteorology and air-sea fluxes due to cumulus convective systems observed during CINDY/DYNAMO

    NASA Astrophysics Data System (ADS)

    Yokoi, Satoru; Katsumata, Masaki; Yoneyama, Kunio

    2014-03-01

    This study examines the variability in surface meteorological parameters and air-sea heat fluxes due to cold pools emanating from cumulus convective systems observed over the tropical Indian Ocean in November 2011. In particular, this study focuses on convective systems that are spatially smaller than mesoscale convective systems in a southeasterly trade wind environment. Composite analyses of convectively active periods show an increase in the sensible heat flux by 15-20 W m-2 that is primarily attributed to an increase in the difference between the surface air temperature and sea surface temperature and an increase in the latent heat flux by 30-70 W m-2 due to enhanced surface wind speeds. A succession of convectively active periods leads to a greater influence than those occurring independently. The direction of the surface wind velocity anomaly due to cold pools tends to be close to that of the environmental wind velocity, resulting in an efficient enhancement of wind speed. This study also demonstrates the close relation between cold pool intensities and convective activity. In particular, two measures of cold pool intensity, a minimum surface air temperature and a maximum amount of surface wind speed enhancement, are correlated with each other and with the convective activity around the observation point measured by radar-estimated rainfall and radar echo coverage.

  4. SST, Winds, and Air-Sea Fluxes in the Gulf Stream Region in the First Winter of CLIMODE

    NASA Astrophysics Data System (ADS)

    Kelly, K. A.; Dickinson, S.; Jones, H. R.

    2006-12-01

    The NSF sponsored CLIvar MOde Water Dynamic Experiment (CLIMODE) focuses on the wintertime processes responsible for the formation and dispersal of Eighteen Degree Water (EDW), the subtropical mode water of the North Atlantic. This region has the largest wintertime loss of heat from the ocean to the atmosphere, made possible by the influx of heat from the Gulf Stream (GS). These fluxes fuel the formation and intensification of storms, as cool, dry continental air encounters the warm boundary current waters. The actual impact of the large transfers of heat on the ocean and on the atmosphere are likely underestimated in weather and climate models, owing to poor observational input and inaccurate boundary layer physics. Several new sources of data are available with which to examine the relationship between the Gulf Stream, air-sea heat fluxes, winds, and storms: wind vector and SST measurements from satellites, as well as in situ measurements, including data from CLIMODE. Improved satellite data includes the ocean vector winds from QuikSCAT, re-processed at a spatial resolution of 12.5km, and microwave SST from AMSR-E. Although the microwave resolution is coarser than for infrared SST, the ability of microwave sensors to see through clouds gives better effective resolution of SST, particularly during storms. Two CLIMODE cruises were conducted in the winter of 2005-2006. During the first cruise in November 2005, SST dropped by about 1.5-2C, leaving SST in the recirculation region at about 22C. By the start of the second cruise in January 2006, SST had fallen to 20C near the GS core, and 19C in the mode water region. By the end of the second cruise 2 weeks later, the region of 20C water had dropped to 19C, suggesting that EDW formation was imminent. SST in the mode water region reached 18C the following week. Maximum wind speeds were distinctly centered on the GS warm core for much of January 2006. Recent studies suggest that the Gulf Stream could affect the storm

  5. Using an ensemble data set of turbulent air-sea fluxes to evaluate the IPSL climate model in tropical regions

    NASA Astrophysics Data System (ADS)

    Gainusa-Bogdan, Alina; Servonnat, Jerome; Braconnot, Pascale

    2014-05-01

    Low-latitude turbulent ocean-atmosphere fluxes play a major role in the ocean and atmosphere dynamics, heat distribution and availability for meridional transport to higher latitudes, as well as for the global freshwater cycle. Their representation in coupled ocean-atmosphere models is thus of chief importance in climate simulations. Despite numerous reports of important observational uncertainties in large-scale turbulent flux products, only few model flux evaluation studies attempt to quantify and directly consider these uncertainties. To address this problem for large-scale, climatological flux evaluation, we assemble a comprehensive database of 14 climatological surface flux products, including in situ-based, satellite, hybrid and reanalysis data sets. We develop an associated analysis protocol and use it together with this database to offer an observational ensemble approach to model flux evaluation. We use this approach to perform an evaluation of the representation of the intertropical turbulent air-sea fluxes in a suite of CMIP5 historical simulations run with different recent versions of the IPSL model. To enhance model understanding, we consider both coupled and forced atmospheric model configurations. For the same purpose, we not only analyze the surface fluxes, but also their associated meteorological state variables and inter-variable relationships. We identify an important, systematic underestimation of the near-surface wind speed and a significant exaggeration of the sea-air temperature contrast in all the IPSL model versions considered. Furthermore, the coupled model simulations develop important sea surface temperature and associated air humidity bias patterns. Counterintuitively, these biases do not systematically transfer to significant biases in the surface fluxes. This is due to a combination of compensation of effects and the large flux observational spread. Our analyses reveal several inconsistencies in inter-variable relationships between

  6. Climate simulations with a new air-sea turbulent flux parameterization in the National Center for Atmospheric Research Community Atmosphere Model (CAM3)

    NASA Astrophysics Data System (ADS)

    Ban, Junmei; Gao, Zhiqiu; Lenschow, Donald H.

    2010-01-01

    This study examines climate simulations with the National Center for Atmospheric Research Community Atmosphere Model version 3 (NCAR CAM3) using a new air-sea turbulent flux parameterization scheme. The current air-sea turbulent flux scheme in CAM3 consists of three basic bulk flux equations that are solved simultaneously by an iterative computational technique. We recently developed a new turbulent flux parameterization scheme where the Obukhov stability length is parameterized directly by using a bulk Richardson number, an aerodynamic roughness length, and a heat roughness length. Its advantages are that it (1) avoids the iterative process and thus increases the computational efficiency, (2) takes account of the difference between z0m and z0h and allows large z0m/z0h, and (3) preserves the accuracy of iteration. An offline test using Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) data shows that the original scheme overestimates the surface fluxes under very weak winds but the new scheme gives better results. Under identical initial and boundary conditions, the original CAM3 and CAM3 coupled with the new turbulent flux scheme are used to simulate the global distribution of air-sea surface turbulent fluxes, and precipitation. Comparisons of model outputs against the European Remote Sensing Satellites (ERS), the Objectively Analyzed air-sea Fluxes (OAFlux), and Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) show that: (1) the new scheme produces more realistic surface wind stress in the North Pacific and North Atlantic trade wind belts and wintertime extratropical storm track regions; (2) the latent heat flux in the Northern Hemisphere trade wind zones shows modest improvement in the new scheme, and the latent heat flux bias in the western boundary current region of the Gulf Stream is reduced; and (3) the simulated precipitation in the new scheme is closer to observation in the Asian monsoon

  7. Carbon budgets for three autotrophic Australian estuaries: Implications for global estimates of the coastal air-water CO2 flux

    NASA Astrophysics Data System (ADS)

    Maher, D. T.; Eyre, B. D.

    2012-03-01

    Estuaries are `hot spots' in the global carbon cycle, yet data on carbon dynamics, in particular air-sea CO2 fluxes, from autotrophic systems are rare. Estuarine carbon budgets were constructed for three geomorphically distinct warm temperate Australian estuaries over an annual cycle. All three estuaries were net autotrophic, with annual net ecosystem metabolism (NEM) ranging from 8 ± 13.4 molC m-2 yr-1 to 10 ± 14 molC m-2 yr-1. There was a net flux of CO2 from the atmosphere to the estuaries of between 0.4 ± 0.6 molC m-2 yr-1 and 2 ± 0.9 molC m-2 yr-1. Loading of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) to the estuaries varied markedly within and between the estuaries, and was directly related to freshwater inflow. While NEM was similar in all three estuaries, the ratio of benthic versus pelagic contributions to NEM differed, with NEM dominated by pelagic production in the river dominated system, benthic production dominating in the intermediate estuary, and equal contributions of benthic and pelagic production in the marine dominated lagoon. All three estuaries exported more organic carbon than was imported, fueled by additional organic carbon supplied by NEM. The estuaries essentially acted as bioreactors, transforming DIC to organic carbon. Burial of organic carbon ranged from 1.2 ± 0.3 molC m-2 yr-1 to 4.4 ± 1.2 molC m-2 yr-1 and represented up to half of NEM. The annual net uptake of atmospheric CO2 in these systems, along with previous estimates of the global estuarine CO2flux being based predominantly on heterotrophic, large river dominated estuarine systems, indicates that the global estimate of the estuarine air-water CO2flux may be over-estimated due to the lack of studies from autotrophic marine dominated estuaries.

  8. Parameterization of Sea-Spray Impact on Air-Sea Momentum and Heat Fluxes in Hurricane Prediction Models

    NASA Astrophysics Data System (ADS)

    Bao, Jian-Wen; Fairall, Chris; Michelson, Sara; Bianco, Laura

    2010-05-01

    Although it is widely recognized that sea spray under hurricane-strength winds is omnipresent in the marine surface boundary layer (MSBL), how to parameterize the effects of sea spray on the air-sea momentum and heat fluxes at hurricane-strength winds in numerical weather prediction (NWP) models still remains a subject of research. This paper focuses on how the effects of sea spray on the momentum and heat fluxes are parameterized in NWP models using the Monin-Obukhov similarity theory. In this scheme, the effects of sea spray can be considered as an additional modification to the stratification of the near surface profiles of wind, temperature and moisture in the MSBL. The overall impact of sea-spray droplets on the mean profiles of wind, temperature and moisture depends on the wind speed at the level of sea-spray generation (or wave state if available). As the wind speed increases, the droplet size increases, rendering an increase in the spray-mediated total enthalpy flux from the sea to the air and leveling off of the surface drag. When the wind is below 35 ms-1, the droplets are small in size and tend to evaporate substantially and thus cool the spray-filled layer. When the wind is above 50 ms-1, the size of droplets is so big that they do not have enough time to evaporate that much before falling back into the sea. Furthermore, the scheme includes the physics of the suspended sea-spray droplets reducing the buoyancy of the MSBL air, therefore making the surface layer more stable. Results from testing the scheme in a numerical weather prediction model are presented along with a dynamical interpretation of the impact of sea spray on the intensification of tropical cyclones.

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

    PubMed

    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.

  10. Improving Constraints on Carbon Fluxes using Measurements of Atmospheric CO2 and Ocean pCO2

    NASA Astrophysics Data System (ADS)

    Suntharalingam, P.; Watson, A. J.; Schuster, U.

    2014-12-01

    Spatial and temporal variations in the large-scale distribution of tropospheric CO2 provide valuable constraints on regional to hemispheric-scale carbon exchange between the atmosphere and land and ocean reservoirs. These constraints have been widely exploited in top-down inverse analyses that combine atmospheric measurements of CO2, prior information on component CO2 fluxes, and representations of atmospheric transport. The inversion procedure typically estimates surface carbon fluxes by minimizing the differences between measured and modeled atmospheric CO2 concentrations. Here we report on regional to hemispheric-scale inter-annual CO2 flux estimates for the period 1990-2012, derived from a hierarchy of top-down methods, ranging in complexity from a simple two-box hemispheric analysis, with mixing rates constrained by SF6 data, to Bayesian synthesis inversions developed using the GEOS-Chem atmospheric transport model. A primary aim of this inter-comparison is to investigate the impact on CO2 flux estimates, of recently derived prior ocean fluxes developed using pCO2 measurements from the SOCAT database (http://www.socat.info/). Sensitivity of flux estimates to assumptions on atmospheric transport, and in particular, inter-hemispheric mixing, will also be discussed.

  11. Measurement of Urban fluxes of CO2 and water

    NASA Astrophysics Data System (ADS)

    Grimmond, S.; Crawford, B.; Offerle, B.; Hom, J.

    2006-05-01

    Measurements of surface-atmosphere fluxes of carbon dioxide (FCO2) and latent heat in urban environments are rare even though cities are a major source of atmospheric CO2 and users of water. In this paper, an overview of urban FCO2 measurements will be presented to illustrate how and where such measurements are being conducted and emerging results to date. Most of these studies have been conducted over short periods of time; few studies have considered annual sources/sinks. More investigations have been conducted, and are planned, in European cities than elsewhere, most commonly in areas of medium density urban development. The most dense urban sites are significant net sources of carbon. However, in areas where there is large amounts of vegetation present, there is a net sink of carbon during the summertime. In the second part of the presentation, more detailed attention will be directed to an ongoing measurement program in Baltimore, MD (part of the Baltimore Ecosystem Study). Eddy covariance instrumentation mounted on a tall-tower at 41.2 m has continuously measured local-scale fluxes of carbon dioxide from a suburban environment since 2001. Several features make this particular study unique: 1) for an urban area, the study site is extensively vegetated, 2) the period of record (2001-2005) is among the longest available for urban FCO2 measurements, 3) both closed-path and open-path infrared gas analyzers are used for observations, and 4) several unique data quality control and gap-filling methods have been developed for use in an urban environment. Additionally, detailed surface datasets and GIS software are used to perform flux source area analysis. Results from Baltimore indicate that FCO2 is very dependent on source area land-cover characteristics, particularly the proportion of vegetated and built surfaces. Over the course of a year, the urban surface is a strong net source of CO2, though there is considerable inter-annual variability depending on

  12. Soil respiration vs. soil CO2 efflux: the role of CO2 storage flux in soil respiration models

    NASA Astrophysics Data System (ADS)

    Maier, Martin; Helmer, Schack-Kirchner; Ernst, Hildebrand

    2010-05-01

    Most studies implicitly consider soil surface efflux of CO2 to be the instantaneous soil respiration, thereby neglecting possible changes in the amount of CO2 stored in the soil pore-space. For the widely used chamber-based and micro-meteorological measurements, filling or depletion of this CO2 pool can result in either an under- or overestimation of the soil respiration. Soil temperature and moisture are the major abiotic factors controlling soil respiration, and are used as explanatory variables by most models. However, these two factors also influence soil gas transport, and thus, the amount of stored CO2. This effect can add undesired noise to soil respiration models or even interfere with the model parameters. To examine the effect of CO2 storage flux, we monitored both the soil CO2 efflux and the CO2 storage in the soil pore-space of a deep and well-aerated riparian soil. Measurements were carried out from March 2009 to March 2010 using an automated chamber system and CO2 concentration measurements at various depths (0.05 to 2.1 m) in the soil profile. First results show that the integration of the storage flux can lead to a significant divergence of soil respiration and soil CO2 efflux, potentially affecting respiration models. It will be discussed whether the integration of the storage flux either changes the overall parameter estimation or is only relevant to improve the understanding of particular meteorological situations.

  13. Air-sea fluxes and satellite-based estimation of water masses formation

    NASA Astrophysics Data System (ADS)

    Sabia, Roberto; Klockmann, Marlene; Fernandez-Prieto, Diego; Donlon, Craig

    2015-04-01

    Recent work linking satellite-based measurements of sea surface salinity (SSS) and sea surface temperature (SST) with traditional physical oceanography has demonstrated the capability of generating routinely satellite-derived surface T-S diagrams [1] and analyze the distribution/dynamics of SSS and its relative surface density with respect to in-situ measurements. Even more recently [2,3], this framework has been extended by exploiting these T-S diagrams as a diagnostic tool to derive water masses formation rates and areas. A water mass describes a water body with physical properties distinct from the surrounding water, formed at the ocean surface under specific conditions which determine its temperature and salinity. The SST and SSS (and thus also density) at the ocean surface are largely determined by fluxes of heat and freshwater. The surface density flux is a function of the latter two and describes the change of the density of seawater at the surface. To obtain observations of water mass formation is of great interest, since they serve as indirect observations of the thermo-haline circulation. The SSS data which has become available through the SMOS [4] and Aquarius [5] satellite missions will provide the possibility of studying also the effect of temporally-varying SSS fields on water mass formation. In the present study, the formation of water masses as a function of SST and SSS is derived from the surface density flux by integrating the latter over a specific area and time period in bins of SST and SSS and then taking the derivative of the total density flux with respect to density. This study presents a test case using SMOS SSS, OSTIA SST, as well as Argo ISAS SST and SSS for comparison, heat fluxes from the NOCS Surface Flux Data Set v2.0, OAFlux evaporation and CMORPH precipitation. The study area, initially referred to the North Atlantic, is extended over two additional ocean basins and the study period covers the 2011-2012 timeframe. Yearly, seasonal

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

    NASA Astrophysics Data System (ADS)

    Maksyutov, S.; Takagi, H.; Valsala, V. K.; Saito, M.; Oda, T.; Saeki, T.; Belikov, D. A.; Saito, R.; Ito, A.; Yoshida, Y.; Morino, I.; Uchino, O.; Andres, R. J.; Yokota, T.

    2013-09-01

    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.

  15. A Synthesized Model-Observation Approach to Constraining Gross Urban CO2 Fluxes Using 14CO2 and carbonyl sulfide

    NASA Astrophysics Data System (ADS)

    LaFranchi, B. W.; Campbell, J. E.; Cameron-Smith, P. J.; Bambha, R.; Michelsen, H. A.

    2013-12-01

    Urbanized regions are responsible for a disproportionately large percentage (30-40%) of global anthropogenic greenhouse gas (GHG) emissions, despite covering only 2% of the Earth's surface area [Satterthwaite, 2008]. As a result, policies enacted at the local level in these urban areas can, in aggregate, have a large global impact, both positive and negative. In order to address the scientific questions that are required to drive these policy decisions, methods are needed that resolve gross CO2 flux components from the net flux. Recent work suggests that the critical knowledge gaps in CO2 surface fluxes could be addressed through the combined analysis of atmospheric carbonyl sulfide (COS) and radiocarbon in atmospheric CO2 (14CO2) [e.g. Campbell et al., 2008; Graven et al., 2009]. The 14CO2 approach relies on mass balance assumptions about atmospheric CO2 and the large differences in 14CO2 abundance between fossil and natural sources of CO2 [Levin et al., 2003]. COS, meanwhile, is a potentially transformative tracer of photosynthesis because its variability in the atmosphere has been found to be influenced primarily by vegetative uptake, scaling linearly will gross primary production (GPP) [Kettle et al., 20027]. Taken together, these two observations provide constraints on two of the three main components of the CO2 budget at the urban scale: photosynthesis and fossil fuel emissions. The third component, respiration, can then be determined by difference if the net flux is known. Here we present a general overview of our synthesized model-observation approach for improving surface flux estimates of CO2 for the upwind fetch of a ~30m tower located in Livermore, CA, USA, a suburb (pop. ~80,000) at the eastern edge of the San Francisco Bay Area. Additionally, we will present initial results from a one week observational intensive, which includes continuous CO2, CH4, CO, SO2, NOx, and O3 observations in addition to measurements of 14CO2 and COS from air samples

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

    PubMed Central

    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

  17. [Partial pressure of CO2 and CO2 degassing fluxes of Huayuankou and Xiaolangdi Station affected by Xiaolangdi Reservoir].

    PubMed

    Zhang, Yong-ling; Yang, Xiao-lin; Zhang, Dong

    2015-01-01

    According to periodic sampling analysis per month in Xiaolangdi station and Huayuankou station from November 2011 to October 2012, combined with continuous sampling analysis of Xiaolangdi Reservoir during runoff and sediment control period in 2012, partial pressure of CO2 (pCO2) in surface water were calculated based on Henry's Law, pCO2 features and air-water CO2 degassing fluxes of Huayuankou station and Xiaolangdi station affected by Xiaolangdi Reservoir were studied. The results were listed as follows, when Xiaolangdi Reservoir operated normally, pCO2 in surface water of Xiaolangdi station and Huayuankou station varied from 82 to 195 Pa and from 99 to 228 Pa, moreover, pCO2 in surface water from July to September were distinctly higher than those in other months; meanwhile, pCO, in surface water from Huayuankou station were higher than that from Xiaolangdi station. During runoff and sediment control period of Xiaolangdi Reservoir, two hydrological stations commonly indicated that pCO2 in surface water during water draining were obviously lower than those during sediment releasing. Whether in the period of normal operation or runoff and sediment control, pCO2 in surface water had positive relations to DIC content in two hydrological stations. Since the EpCO,/AOU value was higher than the theoretical value of 0. 62, the biological aerobic respiration effect had distinct contribution to pCO2. Throughout the whole year, air-water CO2 degassing fluxes from Xiaolangdi station and Huayuankou station were 0.486 p.mol (m2 s) -l and 0.588 pmol (m2 x s)(-1) respectively; When Xiaolangdi Reservoir operated normally, air-water CO, degassing fluxes in Huayuankou station were higher than that in Xiaolangdi station; during runoff and sediment control from Xiaolangdi Reservoir, two hydrological stations had one observation result in common, namely, air-water CO2 degassing fluxes in the period of water draining were obviously lower than that in the period of sediment releasing

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  20. Using CO2:CO Correlations to Improve Inverse Analyses of Carbon Fluxes

    NASA Technical Reports Server (NTRS)

    Palmer, Paul I.; Suntharalingam, Parvadha; Jones, Dylan B. A.; Jacob, Daniel J.; Streets, David G.; Fu, Qingyan; Vay, Stephanie A.; Sachse, Glen W.

    2006-01-01

    Observed correlations between atmospheric concentrations of CO2 and CO represent potentially powerful information for improving CO2 surface flux estimates through coupled CO2-CO inverse analyses. We explore the value of these correlations in improving estimates of regional CO2 fluxes in east Asia by using aircraft observations of CO2 and CO from the TRACE-P campaign over the NW Pacific in March 2001. Our inverse model uses regional CO2 and CO surface fluxes as the state vector, separating biospheric and combustion contributions to CO2. CO2-CO error correlation coefficients are included in the inversion as off-diagonal entries in the a priori and observation error covariance matrices. We derive error correlations in a priori combustion source estimates of CO2 and CO by propagating error estimates of fuel consumption rates and emission factors. However, we find that these correlations are weak because CO source uncertainties are mostly determined by emission factors. Observed correlations between atmospheric CO2 and CO concentrations imply corresponding error correlations in the chemical transport model used as the forward model for the inversion. These error correlations in excess of 0.7, as derived from the TRACE-P data, enable a coupled CO2-CO inversion to achieve significant improvement over a CO2-only inversion for quantifying regional fluxes of CO2.

  1. Constraining terrestrial ecosystem CO2 fluxes by integrating models of biogeochemistry and atmospheric transport and data of surface carbon fluxes and atmospheric CO2 concentrations

    NASA Astrophysics Data System (ADS)

    Zhu, Q.; Zhuang, Q.; Henze, D.; Bowman, K.; Chen, M.; Liu, Y.; He, Y.; Matsueda, H.; Machida, T.; Sawa, Y.; Oechel, W.

    2014-09-01

    Regional net carbon fluxes of terrestrial ecosystems could be estimated with either biogeochemistry models by assimilating surface carbon flux measurements or atmospheric CO2 inversions by assimilating observations of atmospheric CO2 concentrations. Here we combine the ecosystem biogeochemistry modeling and atmospheric CO2 inverse modeling to investigate the magnitude and spatial distribution of the terrestrial ecosystem CO2 sources and sinks. First, we constrain a terrestrial ecosystem model (TEM) at site level by assimilating the observed net ecosystem production (NEP) for various plant functional types. We find that the uncertainties of model parameters are reduced up to 90% and model predictability is greatly improved for all the plant functional types (coefficients of determination are enhanced up to 0.73). We then extrapolate the model to a global scale at a 0.5° × 0.5° resolution to estimate the large-scale terrestrial ecosystem CO2 fluxes, which serve as prior for atmospheric CO2 inversion. Second, we constrain the large-scale terrestrial CO2 fluxes by assimilating the GLOBALVIEW-CO2 and mid-tropospheric CO2 retrievals from the Atmospheric Infrared Sounder (AIRS) into an atmospheric transport model (GEOS-Chem). The transport inversion estimates that: (1) the annual terrestrial ecosystem carbon sink in 2003 is -2.47 Pg C yr-1, which agrees reasonably well with the most recent inter-comparison studies of CO2 inversions (-2.82 Pg C yr-1); (2) North America temperate, Europe and Eurasia temperate regions act as major terrestrial carbon sinks; and (3) The posterior transport model is able to reasonably reproduce the atmospheric CO2 concentrations, which are validated against Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) CO2 concentration data. This study indicates that biogeochemistry modeling or atmospheric transport and inverse modeling alone might not be able to well quantify regional terrestrial carbon fluxes. However, combining

  2. Assessing the impact of urban land cover composition on CO2 flux

    NASA Astrophysics Data System (ADS)

    Becker, K.; Hinkle, C.

    2013-12-01

    Urbanization is an ever increasing trend in global land use change, and has been identified as a key driver of CO2 emissions. Therefore, understanding how urbanization affects CO2 flux across a range of climatic zones and development patterns is critical to projecting the impact of future land use on CO2 flux dynamics. A growing number of studies are applying the eddy covariance method to urban areas to quantify the CO2 flux dynamics of these systems. However, interpretation of eddy covariance data in these urban systems presents a challenge, particularly in areas with high heterogeneity due to a mixing of built and green space. Here we present a study aimed at establishing a relationship between land cover composition and CO2 flux for a heterogeneous urban area of Orlando, FL. CO2 flux has been measured at this site for > 4 years using an open path eddy covariance system. Land cover at this site was classified into built and green space, and relative weight of both land covers were calculated for each 30 min CO2 flux measurement using the Schuepp model and a source area based on +/- one standard deviation of wind direction. The results of this analysis established a relationship between built land cover and CO2 flux within the measured footprint of this urban area. These results, in combination with future projected land use data, will be a valuable resource for providing insight into the impact of future urbanization on CO2 flux dynamics in this region.

  3. Accounting for observational uncertainties in the evaluation of low latitude turbulent air-sea fluxes simulated in a suite of IPSL model versions

    NASA Astrophysics Data System (ADS)

    Servonnat, Jerome; Braconnot, Pascale; Gainusa-Bogdan, Alina

    2015-04-01

    Turbulent momentum and heat (sensible and latent) fluxes at the air-sea interface are key components of the whole energetic of the Earth's climate and their good representation in climate models is of prime importance. In this work, we use the methodology developed by Braconnot & Frankignoul (1993) to perform a Hotelling T2 test on spatio-temporal fields (annual cycles). This statistic provides a quantitative measure accounting for an estimate of the observational uncertainty for the evaluation of low-latitude turbulent air-sea fluxes in a suite of IPSL model versions. The spread within the observational ensemble of turbulent flux data products assembled by Gainusa-Bogdan et al (submitted) is used as an estimate of the observational uncertainty for the different turbulent fluxes. The methodology holds on a selection of a small number of dominating variability patterns (EOFs) that are common to both the model and the observations for the comparison. Consequently it focuses on the large-scale variability patterns and avoids the possibly noisy smaller scales. The results show that different versions of the IPSL couple model share common large scale model biases, but also that there the skill on sea surface temperature is not necessarily directly related to the skill in the representation of the different turbulent fluxes. Despite the large error bars on the observations the test clearly distinguish the different merits of the different model version. The analyses of the common EOF patterns and related time series provide guidance on the major differences with the observations. This work is a first attempt to use such statistic on the evaluation of the spatio-temporal variability of the turbulent fluxes, accounting for an observational uncertainty, and represents an efficient tool for systematic evaluation of simulated air-seafluxes, considering both the fluxes and the related atmospheric variables. References Braconnot, P., and C. Frankignoul (1993), Testing Model

  4. Sea-ice melt CO2-carbonate chemistry in the western Arctic Ocean: meltwater contributions to air-sea CO2 gas exchange, mixed-layer properties and rates of net community production under sea ice

    NASA Astrophysics Data System (ADS)

    Bates, N. R.; Garley, R.; Frey, K. E.; Shake, K. L.; Mathis, J. T.

    2014-12-01

    The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and co-located, contemporaneous seawater has rarely been studied in sea-ice-covered oceans. Here, we describe the CO2-carbonate chemistry of sea-ice melt (both above sea-ice as "melt ponds" and below sea-ice as "interface waters") and mixed-layer properties in the western Arctic Ocean in the early summer of 2010 and 2011. At 19 stations, the salinity (∼0.5 to <6.5), dissolved inorganic carbon (DIC; ∼20 to <550 μmol kg-1) and total alkalinity (TA; ∼30 to <500 μmol kg-1) of above-ice melt pond water was low compared to the co-located underlying mixed layer. The partial pressure of CO2 (pCO2) in these melt ponds was highly variable (∼<10 to >1500 μatm) with the majority of melt ponds acting as potentially strong sources of CO2 to the atmosphere. The pH of melt pond waters was also highly variable ranging from mildly acidic (6.1 to 7) to slightly more alkaline than underlying seawater (>8.2 to 10.8). All of the observed melt ponds had very low (<0.1) saturation states (Ω) for calcium carbonate (CaCO3) minerals such as aragonite (Ωaragonite). Our data suggest that sea-ice generated alkaline or acidic type melt pond water. This melt water chemistry dictates whether the ponds are sources of CO2 to the atmosphere or CO2 sinks. Below-ice interface water CO2-carbonate chemistry data also indicated substantial generation of alkalinity, presumably owing to dissolution of CaCO3 in sea-ice. The interface waters generally had lower pCO2 and higher pH/Ωaragonite than the co-located mixed layer beneath. Sea-ice melt thus contributed to the suppression of mixed-layer pCO2, thereby enhancing the surface ocean's capacity to uptake CO2 from the atmosphere. Our observations contribute to growing evidence that sea-ice CO2-carbonate chemistry is highly variable and its contribution to the complex factors that influence the balance of CO2 sinks and sources (and thereby ocean acidification) is difficult to

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

    NASA Astrophysics Data System (ADS)

    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).

  6. Assessing the Effects of Elevated Atmospheric CO2 and LAI Perturbations on Southeastern Grassland Water Vapor and Co2 Fluxes

    NASA Astrophysics Data System (ADS)

    Novick, K. A.; Katul, G.; Ellsworth, D.

    2002-05-01

    Projected increases in atmospheric carbon dioxide concentration increased international interest in predicting CO2 fluxes over various ecosystems. Temperate grassland ecosystems are an important component of this global carbon cycle; however, investigations into the response of grassland ecosystems to human-and climate induced perturbations have been limited. This study reports on the relative importance of Leaf Area Index (LAI) and elevated atmospheric CO2 on Net Ecosystem Exchange (NEE) of CO2 over a Southeastern U.S. grassland for a typical growing season. Towards this end, a combination of model results and field experiments was used. A model for stomatal conductance to water vapor was developed from a boundary layer analysis of latent heat fluxes and vapor pressure deficit (VPD) measured from May-August, 2001. The conductance model was combined with LAI, incident Photosynthetic Active Radiation (PAR), and temperature measurements collected during the same period to model net carbon assimilation prior to and after an LAI perturbation. The predicted assimilation patterns were compared with CO2 fluxes measured by the Eddy Correlation technique, with good agreement even when influenced by rapid transients in LAI. We perturbed the model by increasing the ambient CO2 concentration to 560 ppm, and found the background temperature increment required to maintain present NEE rates varied highly with LAI. Southeastern grasslands with high LAI will require a global "background" temperature increment similar to the increase projected by climate models; hence, the extra C gain in photosynthesis associated with elevated CO2 will be compensated for by the concurrent increase in temperature. Grasslands with low LAI will be unable to support current growing season NEE rates in future climate scenarios; therefore, grazed and mowed grasslands will primarily function as carbon sources during the growing season in future climates.

  7. Potential of satellite CO2 data to infer CO2 fluxes, using atmospheric inversion: influence of data uncertainty correlations

    NASA Astrophysics Data System (ADS)

    Montandon, V.; Peylin, P.; Bousquet, P.; Ciais, P.; Breon, F.-M.

    2003-04-01

    Knowledge of present surface sources and sinks of atmospheric CO2 is crucial to quantify the future man-induced green-house effect. Measurements of radiation from space potentially offer denser samplings of CO2 column amount, both in time and space than in situ measurements. This could allow in turn to decrease the uncertainties of CO2 flux estimates, depending on the achievable precision of CO2 retrievals from space, and on the removal of any spatially coherent bias. In the framework of the COCO project, shaped to take advantage of the sooncoming or present satellite missions, we enriched some investigations about the satellite observations potential to improve the atmospheric CO2 sinks and sources knowledge. Our particular study dealt with the introduction of spatial correlations between the individual measurement errors of CO2 column amount, to inverstigate possible coherent biases between satellite data. One year of pseudo-data was generated according to the CARBOSAT project instrumental and orbital characteristics. These individual data were then grouped month by month onto the grid of the LMDZ transport model. The classical independance assumption made in all priors study about the measurement errors lead to a large decrease of the final satellite data uncertainty. However, spatially coherent bias would bring correlated data uncertainties, a feature that would largely affect the results. We quantified here the influence of these correlations on the retrieved CO2 flux uncertainties. Several transport model grids (regular / non regular) were used to aggregate the individual measurements, and their influence is also discussed. Such results could also be applied to other reactive chemical species like CH4, CO, ...

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

    PubMed

    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

  9. Air-sea transfer of gas phase controlled compounds

    NASA Astrophysics Data System (ADS)

    Yang, M.; Bell, T. G.; Blomquist, B. W.; Fairall, C. W.; Brooks, I. M.; Nightingale, P. D.

    2016-05-01

    Gases in the atmosphere/ocean have solubility that spans several orders of magnitude. Resistance in the molecular sublayer on the waterside limits the air-sea exchange of sparingly soluble gases such as SF6 and CO2. In contrast, both aerodynamic and molecular diffusive resistances on the airside limit the exchange of highly soluble gases (as well as heat). Here we present direct measurements of air-sea methanol and acetone transfer from two open cruises: the Atlantic Meridional Transect in 2012 and the High Wind Gas Exchange Study in 2013. The transfer of the highly soluble methanol is essentially completely airside controlled, while the less soluble acetone is subject to both airside and waterside resistances. Both compounds were measured concurrently using a proton-transfer-reaction mass spectrometer, with their fluxes quantified by the eddy covariance method. Up to a wind speed of 15 m s-1, observed air-sea transfer velocities of these two gases are largely consistent with the expected near linear wind speed dependence. Measured acetone transfer velocity is ∼30% lower than that of methanol, which is primarily due to the lower solubility of acetone. From this difference we estimate the “zero bubble” waterside transfer velocity, which agrees fairly well with interfacial gas transfer velocities predicted by the COARE model. At wind speeds above 15 m s-1, the transfer velocities of both compounds are lower than expected in the mean. Air-sea transfer of sensible heat (also airside controlled) also appears to be reduced at wind speeds over 20 m s-1. During these conditions, large waves and abundant whitecaps generate large amounts of sea spray, which is predicted to alter heat transfer and could also affect the air-sea exchange of soluble trace gases. We make an order of magnitude estimate for the impacts of sea spray on air-sea methanol transfer.

  10. [Effects of straw mulching on CO2 flux in wintry fallow paddy field].

    PubMed

    Yin, Chun-mei; Xie, Xiao-li; Wang, Kai-rong

    2008-01-01

    This paper studied the effects of straw mulching on the CO2 flux in a wintry fallow paddy field at Taoyuan Agro-ecological Station, Chinese Academy of Sciences. The results showed that the effects of straw mulching mainly exerted in two ways. First, it positively affected soil temperature, making the CO2 flux increased obviously. Straw mulching gave a net emission of 2.68 g CO2 x m(-2) x d(-1), while no mulching gave a net fixation of 1.99 g CO2 x m(-2) x d(-1), the difference between them being very significant (P < 0.01). Second, straw mulching decreased the biomass of weeds and the photosynthetically active radiation they absorbed, which in turn resulted in an increase of CO2 flux. Under straw mulching, the water content in surface soil layer (0-15 cm) increased by 9% or more, but no significant change was observed in CO2 flux.

  11. Can CO2 Turbulent Flux Be Measured by Lidar? A Preliminary Study

    NASA Technical Reports Server (NTRS)

    Gilbert, Fabien; Koch, Grady; Beyon, Jeffrey Y.; Hilton, Timothy W.; Davis, Kenneth J.; Andrews, Arlyn; Flamant, Pierre H.; Singh, Upendra N.

    2011-01-01

    The vertical profiling ofCO2 turbulent fluxes in the atmospheric boundary layer (ABL) is investigated using a coherent differential absorption lidar (CDIAL) operated nearby a tall tower in Wisconsin during June 2007. A CDIAL can perform simultaneous range-resolved CO2 DIAL and velocity measurements. The lidar eddy covariance technique is presented. The aims of the study are (i) an assessment of performance and current limitation of available CDIAL for CO2 turbulent fluxes and (ii) the derivation of instrument specifications to build a future CDIAL to perform accurate range-resolved CO2 fluxes. Experimental lidar CO2 mixing ratio and vertical velocity profiles are successfully compared with in situ sensors measurements. Time and space integral scales of turbulence in the ABL are addressed that result in limitation for time averaging and range accumulation. A first attempt to infer CO2 fluxes using an eddy covariance technique with currently available 2-mm CDIAL dataset is reported.

  12. Comparing carbon dioxide (CO2) flux between no-till and conventional tillage agriculture in Lesotho

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil management practices can either sequester or emit carbon (C). Feeding seven billion people mandates that soils be used intensively for food production, but how these soils are managed greatly impacts soil fluxes of carbon dioxide (CO2). However, the lack of CO2 flux measurements on African subs...

  13. Diurnal variation in respiratory CO2 flux in an arid ecosystem

    NASA Astrophysics Data System (ADS)

    van Asperen, Hella; Warneke, Thorsten; Sabbatini, Simone; Höpker, Martin; Chiti, Tommaso; Nicolini, Giacomo; Papale, Dario; Böhm, Michael; Notholt, Justus

    2016-04-01

    The application of stable isotopes to study ecosystem processes is increasingly used. However, continuous in-situ observation of CO2 concentrations, CO2 fluxes, and their isotopic components are still sparse. In this study, we present results from an arid grassland in Italy, in which continuous measurements of δ13CO2 and CO2 were performed by means of an in-situ Fourier Transform Infrared Spectrometer connected to a concentration-tower set up and to soil flux chambers. By use of Keeling plots, daily nighttime Keeling plot-intercepts and hourly flux chamber Keeling plot-intercepts could be derived. The flux chambers solely showed CO2 emission, with respiration peaks during the day. Keeling plot intercepts from the tower, overlooking the arid grassland, showed more enriched δ13CO2 values than Keeling plot intercepts derived from chamber measurements, indicating different dominating respiratory sources in their footprint. Flux chamber respiratory δ13CO2 values showed a daily pattern with on average 3.5‰ more depleted δ13CO2 fluxes during the night. It is hypothesized that the observed diurnal variation in respiratory δ13CO2 is a consequence of the physical process of diffusive fractionation taking place during the nocturnal boundary layer build up.

  14. Iron in the Ross Sea: 1. Impact on CO2 fluxes via variation in phytoplankton functional group and non-Redfield stoichiometry

    NASA Astrophysics Data System (ADS)

    Tagliabue, Alessandro; Arrigo, Kevin R.

    2005-03-01

    We present new model results examining nutrient and carbon biogeochemistry within the Ross Sea, focusing on the sensitivity of ecosystem dynamics to taxon-specific nutrient utilization parameters and the impact of alleviating Fe limitation of phytoplankton growth. The coupled ice-atmosphere-ocean ecosystem (CIAO) model of the Ross Sea was modified to include air-sea CO2 exchange and non-Redfield C/N/P uptake ratios of the dominant phytoplankton taxa. Model results show that the Ross Sea was a substantial sink for atmospheric CO2, driven by the high primary productivity prior to the onset of Fe limitation. Taxon-specific C/N/P uptake ratios controlled the relative rate of removal of each macronutrient, while Fe availability constrained the absolute magnitude of utilization. When Redfield C/N/P stoichiometry was applied to both phytoplankton taxa, net primary production (NPP) was overestimated in areas normally dominated by diatoms and underestimated in regions of Phaeocystis antarctica dominance, and macronutrient dynamics were misrepresented. Simulated shifts in phytoplankton taxonomic composition significantly altered uptake of atmospheric CO2 when the phytoplankton were dominated by diatoms (-70%) or P. antarctica (+35%). The ability to bloom later in the season afforded P. antarctica a relatively greater role than diatoms in controlling the air-sea flux of CO2 in the Ross Sea. In response to alleviation of Fe limitation, both total Ross Sea NPP and CO2 uptake increased by 30%. The response of the carbon cycle to Fe fertilization was predicted to be complex, and its magnitude and nature were dictated by patterns of macronutrient utilization.

  15. [Effects of CO2 storage flux on carbon budget of forest ecosystem].

    PubMed

    Zhang, Mi; Wen, Xue-fa; Yu, Gui-rui; Zhang, Lei-ming; Fu, Yu-ling; Sun, Xiao-min; Han, Shi-jie

    2010-05-01

    Carbon dioxide (CO2) storage flux in the air space below measurement height of eddy covariance is very important to correctly evaluate net ecosystem exchange of CO2 (NEE) between forest ecosystem and atmosphere. This study analyzed the dynamic variation of CO2 storage flux and its effects on the carbon budget of a temperate broad-leaved Korean pine mixed forest at Changbai Mountains, based on the eddy covariance flux data and the vertical profile of CO2 concentration data. The CO2 storage flux in this forest ecosystem had typical diurnal variation, with the maximum variation appeared during the transition from stable atmospheric layer to unstable atmospheric layer. The CO2 storage flux calculated by the change in CO2 concentration throughout a vertical profile was not significantly different from that calculated by the change in CO2 concentration at the measurement height of eddy covariance. The NEE of this forest ecosystem was underestimated by 25% and 19% at night and at daytime, respectively, without calculating the CO2 storage flux at half-hour scale, and was underestimated by 10% and 25% at daily scale and annual scale, respectively. Without calculating the CO2 storage flux in this forest ecosystem, the parameters of Michaelis-Menten equation and Lloyd-Taylor equation were underestimated, and the ecosystem apparent quantum yield (alpha) and the ecosystem respiration rate (Rref) at the reference temperature were mostly affected. The gross primary productivity (GPP) and ecosystem respiration (Re) of this forest ecosystem were underestimated about 20% without calculating the CO2 storage flux at half-hour, daily scale, and annual scale.

  16. Development of a laser remote sensing instrument to measure sub-aerial volcanic CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Queisser, Manuel; Burton, Mike

    2016-04-01

    A thorough quantification of volcanic CO2 fluxes would lead to an enhanced understanding of the role of volcanoes in the geological carbon cycle. This would enable a more subtle understanding of human impact on that cycle. Furthermore, variations in volcanic CO2 emissions are a key to understanding volcanic processes such as eruption phenomenology. However, measuring fluxes of volcanic CO2 is challenging as volcanic CO2 concentrations are modest compared with the ambient CO2 concentration (~400 ppm) . Volcanic CO2 quickly dilutes with the background air. For Mt. Etna (Italy), for instance, 1000 m downwind from the crater, dispersion modelling yields a signal of ~4 ppm only. It is for this reason that many magmatic CO2 concentration measurements focus on in situ techniques, such as direct sampling Giggenbach bottles, chemical sensors, IR absorption spectrometers or mass spectrometers. However, emission rates are highly variable in time and space. Point measurements fail to account for this variability. Inferring 1-D or 2-D gas concentration profiles, necessary to estimate gas fluxes, from point measurements may thus lead to erroneous flux estimations. Moreover, in situ probing is time consuming and, since many volcanoes emit toxic gases and are dangerous as mountains, may raise safety concerns. In addition, degassing is often diffuse and spatially extended, which makes a measurement approach with spatial coverage desirable. There are techniques that allow to indirectly retrieve CO2 fluxes from correlated SO2 concentrations and fluxes. However, they still rely on point measurements of CO2 and are prone to errors of SO2 fluxes due to light dilution and depend on blue sky conditions. Here, we present a new remote sensing instrument, developed with the ERC project CO2Volc, which measures 1-D column amounts of CO2 in the atmosphere with sufficient sensitivity to reveal the contribution of magmatic CO2. Based on differential absorption LIDAR (DIAL) the instrument measures

  17. BOREAS TF-4 CO2 and CH4 Chamber Flux Data from the SSA

    NASA Technical Reports Server (NTRS)

    Anderson, Dean; Striegl, Robert; Wickland, Kimberly; Hall, Forrest G. (Editor); Conrad, Sara (Editor)

    2000-01-01

    The BOREAS TF-4 team measured fluxes of CO2 and CH4 across the soil-air interface in four ages of jack pine forest at the BOREAS SSA during August 1993 to March 1995. Gross and net flux of CO2 and flux of CH4 between soil and air are presented for 24 chamber sites in mature jack pine forest, 20-year-old, 4-year-old, and clear cut areas. The data are stored in tabular ASCII files.

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

    PubMed

    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.

  19. Soil surface CO2 fluxes and the carbon budget of a grassland

    NASA Technical Reports Server (NTRS)

    Norman, J. M.; Garcia, R.; Verma, S. B.

    1992-01-01

    Measurements of soil surface CO2 fluxes are reported for three sites within the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) area, and simple empirical equations are fit to the data to provide predictions of soil fluxes from environmental observations. A prototype soil chamber, used to make the flux measurements, is described and tested by comparing CO2 flux measurements to a 40-L chamber, a 1-m/cu chamber, and eddy correlation. Results suggest that flux measurements with the prototype chamber are consistent with measurements by other methods to within about 20 percent. A simple empirical equation based on 10-cm soil temperature, 0- to 10-cm soil volumetric water content, and leaf area index predicts the soil surface CO2 flux with a rms error of 1.2 micro-mol sq m/s for all three sites. Further evidence supports using this equation to evaluate soil surface CO2 during the 1987 FIFE experiment. The soil surface CO2 fluxes when averaged over 24 hours are comparable to daily gross canopy photosynthetic rates. For 6 days of data the net daily accumulation of carbon is about 0.6 g CO2 sq m/d; this is only a few percent of the daily gross accumulation of carbon by photosynthesis. As the soil became drier in 1989, the net accumulation of carbon by the prairie increased, suggesting that the soil flux is more sensitive to temperature and drought than the photosynthetic fluxes.

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

    PubMed

    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.

  1. BOREAS TF-3 Automated Chamber CO2 Flux Data from the NSA-OBS

    NASA Technical Reports Server (NTRS)

    Goulden, Michael L.; Crill, Patrick M.; Hall, Forrest G. (Editor); Conrad, Sara (Editor)

    2000-01-01

    The BOReal Ecosystem Atmosphere Study Tower Flux (BOREAS TF-3) and Trace Gas Biogeochemistry (TGB-1) teams collected automated CO2 chamber flux data in their efforts to fully describe the CO2 flux at the Northern Study Area-Old Black Spruce (NSA-OBS) site. This data set contains fluxes of CO2 at the NSA-OBS site measured using automated chambers. In addition to reporting the CO2 flux, it reports chamber air temperature, moss temperature, and light levels during each measurement. The data set covers the period from 23-Sep-1995 through 26-Oct-1995 and from 28-May-1996 through 21-Oct-1996. The data are stored in tabular ASCII files.

  2. Atmospheric observations inform CO2 flux responses to enviroclimatic drivers

    NASA Astrophysics Data System (ADS)

    Fang, Yuanyuan; Michalak, Anna M.

    2015-05-01

    Understanding the response of the terrestrial biospheric carbon cycle to variability in enviroclimatic drivers is critical for predicting climate-carbon interactions. Here we apply an atmospheric-inversion-based framework to assess the relationships between the spatiotemporal patterns of net ecosystem CO2 exchange (NEE) and those of enviroclimatic drivers. We show that those relationships can be directly observed at 1° × 1° 3-hourly resolution from atmospheric CO2 measurements for four of seven large biomes in North America, namely, (i) boreal forests and taiga; (ii) temperate coniferous forests; (iii) temperate grasslands, savannas, and shrublands; and (iv) temperate broadleaf and mixed forests. We find that shortwave radiation plays a dominant role during the growing season over all four biomes. Specific humidity and precipitation also play key roles and are associated with decreased CO2 uptake (or increased release). The explanatory power of specific humidity is especially strong during transition seasons, while that of precipitation appears during both the growing and dormant seasons. We further find that the ability of four prototypical terrestrial biospheric models (TBMs) to represent the spatiotemporal variability of NEE improves as the influence of radiation becomes more dominant, implying that TBMs have a better skill in representing the impact of radiation relative to other drivers. Even so, we show that TBMs underestimate the strength of the relationship to radiation and do not fully capture its seasonality. Furthermore, the TBMs appear to misrepresent the relationship to precipitation and specific humidity at the examined scales, with relationships that are not consistent in terms of sign, seasonality, or significance relative to observations. More broadly, we demonstrate the feasibility of directly probing relationships between NEE and enviroclimatic drivers at scales with no direct measurements of NEE, opening the door to the study of emergent

  3. [Periodic characteristics of soil CO2 flux in mangrove wetland of Quanzhou Bay, China].

    PubMed

    Wang, Zong-Lin; Wu, Yan-You; Xing, De-Ke; Liu, Rong-Cheng; Zhou Gui-Yao; Zhao, Kuan

    2014-09-01

    Mangrove wetland ecosystem in Quanzhou Bay in Fujian Province is newly restored with a regular semidiurnal tide. Soil CO2 concentration in the mangrove soil was determined by Li-840 portable gas analyzer, and periodic characteristics of soil CO2 emission was investigated. The soil CO2 flux in the wetland soil was relatively small because the mangrove was young. The change trends of soil CO2 concentration and flux with time were consistent in Kandelia obovate and Aegiceras corniculatum communities in the intertidal periods. The CO2 concentration and flux in the wetland soil were 557.08-2211.50 μmol · mol(-1) and -0.21-0.40 μmol · m(-2) · s(-1), respectively. The average CO2 flux in the wetland soil was 0.26 μmol · mol(-1) · s(-1) in the intertidal of morning and evening tides (early intertidal) and -0.01 μmol · m(-2) · s(-1) in the intertidal of evening and morning tides (late intertidal), respectively. At the same time after the tide, the concentration and flux of CO2 in the mangrove soil in early intertidal was higher than that in late intertidal. In early intertidal, the relationship between the flux and instantaneous concentration of CO2 in the wetland soil was expressed as a bell-shaped curve, and CO2 flux increased first and then decreased with the increasing CO2 concentration, which was in conformity with Gaussian distribution. PMID:25757306

  4. Improved quantification of Chinese carbon fluxes using CO2/CO correlations in Asian outflow

    NASA Astrophysics Data System (ADS)

    Suntharalingam, Parvadha; Jacob, Daniel J.; Palmer, Paul I.; Logan, Jennifer A.; Yantosca, Robert M.; Xiao, Yaping; Evans, Mathew J.; Streets, David G.; Vay, Stephanie L.; Sachse, Glen W.

    2004-09-01

    We use observed CO2:CO correlations in Asian outflow from the TRACE-P aircraft campaign (February-April 2001), together with a three-dimensional global chemical transport model (GEOS-CHEM), to constrain specific components of the east Asian CO2 budget including, in particular, Chinese emissions. The CO2/CO emission ratio varies with the source of CO2 (different combustion types versus the terrestrial biosphere) and provides a characteristic signature of source regions and source type. Observed CO2/CO correlation slopes in east Asian boundary layer outflow display distinct regional signatures ranging from 10-20 mol/mol (outflow from northeast China) to 80 mol/mol (over Japan). Model simulations using best a priori estimates of regional CO2 and CO sources from [2003] (anthropogenic), the CASA model (biospheric), and [2003] (biomass burning) overestimate CO2 concentrations and CO2/CO slopes in the boundary layer outflow. Constraints from the CO2/CO slopes indicate that this must arise from an overestimate of the modeled regional net biospheric CO2 flux. Our corrected best estimate of the net biospheric source of CO2 from China for March-April 2001 is 3200 Gg C/d, which represents a 45% reduction of the net flux from the CASA model. Previous analyses of the TRACE-P data had found that anthropogenic Chinese CO emissions must be ˜50% higher than in 's [2003] inventory. We find that such an adjustment improves the simulation of the CO2/CO slopes and that it likely represents both an underreporting of sector activity (domestic and industrial combustion) and an underestimate of CO emission factors. Increases in sector activity would imply increases in Chinese anthropogenic CO2 emissions and would also imply a further reduction of the Chinese biospheric CO2 source to reconcile simulated and observed CO2 concentrations.

  5. Air-sea flux of methane from selected marine hydrate/seep sites in the northern Gulf of Mexico during HYFLUX

    NASA Astrophysics Data System (ADS)

    Hu, L.; Yvon-Lewis, S. A.; Kessler, J. D.; MacDonald, I.

    2009-12-01

    Methane is one of the most important greenhouse gases, playing a significant role in global climate change and atmospheric chemistry. In spite of tremendous efforts made to constrain the strength of its sources and sinks, large uncertainties remain for some individual sources. Based on the previous observations and modeling studies, the flux of CH4 from marine hydrates and seeps to the atmosphere comprises a significant fraction of the entire methane flux from the global ocean. However, most of the estimates are based on the seafloor methane flux or discrete water column concentrations of methane and the averaged atmospheric methane ratios. In this study, we investigated three marine hydrate/seep sites in northern Gulf of Mexico in July of 2009 during the HYFLUX cruise. Continuous saturation-anomaly (deviation from equilibrium) measurements of methane, ethane and propane were made by alternately sampling the air or the headspace of Weiss-type equilibrator and analyzing it in a GC-FID system. Some 13CH4 measurements were also made continuously using a cavity ring-down spectrometer (CRDS). During this cruise, the maximum concentrations observed at the 3 marine hydrate/seep sites MC118, GC600, and GC185 were 14.5, 5.1, and 2.2 nmol/L, respectively. The air-sea fluxes, calculated from saturation anomalies, are used to create extremely high resolution flux maps for the three marine hydrate/seeps sites.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Implications of elevated CO2 on pelagic carbon fluxes in an Arctic mesocosm study - an elemental mass balance approach

    NASA Astrophysics Data System (ADS)

    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

  8. New constraints on the volcanic CO2 flux from an extended MultiGAS dataset

    NASA Astrophysics Data System (ADS)

    Aiuppa, A.

    2012-12-01

    Refining the currently available CO2 degassing budgets for active and dormant volcanoes is critical to a better understanding of global geochemical cycles, and brings promises to contribute substantially to better understanding of how volcanoes work, and ultimately to forecast their behaviour. While remote (e.g., from space) and direct CO2 flux observations from individual volcanoes remain the future of volcanic gas research, ground-based in-situ techniques still remain the major source of information. Since its advent in the middle of the last decade, the MultiGAS technique, independently developed in Italy and Japan, has fuelled improved indirect observations of volcanic CO2 fluxes, by enabling us to capture 0.1-1 Hz time-series of volcanic gas plume CO2/SO2 ratio compositions. Here, I review the last 7 years of MultiGAS observations, with a focus on CO2 flux emissions from open-vent basaltic volcanism. I show that at Stromboli and Etna, for which the most continuous and longest records are available, the MultiGAS has allowed refining previous CO2 flux inventories, and has become a most unique tool to interpret - and often predict - transition from quiescence to eruption. I also review recently acquired MultiGAS observations taken (during surveys on permanent installations) at a number of degassing volcanoes, in the attempt to add new piece of information to the growing puzzle of global volcanic CO2 flux emissions.

  9. Grazing effects on ecosystem CO2 fluxes differ among temperate steppe types in Eurasia.

    PubMed

    Hou, Longyu; Liu, Yan; Du, Jiancai; Wang, Mingya; Wang, Hui; Mao, Peisheng

    2016-07-01

    Grassland ecosystems play a critical role in regulating CO2 fluxes into and out of the Earth's surface. Whereas previous studies have often addressed single fluxes of CO2 separately, few have addressed the relation among and controls of multiple CO2 sub-fluxes simultaneously. In this study, we examined the relation among and controls of individual CO2 fluxes (i.e., GEP, NEP, SR, ER, CR) in three contrasting temperate steppes of north China, as affected by livestock grazing. Our findings show that climatic controls of the seasonal patterns in CO2 fluxes were both individual flux- and steppe type-specific, with significant grazing impacts observed for canopy respiration only. In contrast, climatic controls of the annual patterns were only individual flux-specific, with minor grazing impacts on the individual fluxes. Grazing significantly reduced the mean annual soil respiration rate in the typical and desert steppes, but significantly enhanced both soil and canopy respiration in the meadow steppe. Our study suggests that a reassessment of the role of livestock grazing in regulating GHG exchanges is imperative in future studies.

  10. Grazing effects on ecosystem CO2 fluxes differ among temperate steppe types in Eurasia

    PubMed Central

    Hou, Longyu; Liu, Yan; Du, Jiancai; Wang, Mingya; Wang, Hui; Mao, Peisheng

    2016-01-01

    Grassland ecosystems play a critical role in regulating CO2 fluxes into and out of the Earth’s surface. Whereas previous studies have often addressed single fluxes of CO2 separately, few have addressed the relation among and controls of multiple CO2 sub-fluxes simultaneously. In this study, we examined the relation among and controls of individual CO2 fluxes (i.e., GEP, NEP, SR, ER, CR) in three contrasting temperate steppes of north China, as affected by livestock grazing. Our findings show that climatic controls of the seasonal patterns in CO2 fluxes were both individual flux- and steppe type-specific, with significant grazing impacts observed for canopy respiration only. In contrast, climatic controls of the annual patterns were only individual flux-specific, with minor grazing impacts on the individual fluxes. Grazing significantly reduced the mean annual soil respiration rate in the typical and desert steppes, but significantly enhanced both soil and canopy respiration in the meadow steppe. Our study suggests that a reassessment of the role of livestock grazing in regulating GHG exchanges is imperative in future studies. PMID:27363345

  11. Fluxes of deep CO 2 in the volcanic areas of central-southern Italy

    NASA Astrophysics Data System (ADS)

    Gambardella, Barbara; Cardellini, Carlo; Chiodini, Giovanni; Frondini, Francesco; Marini, Luigi; Ottonello, Giulio; Vetuschi Zuccolini, Marino

    2004-08-01

    Both the shallow (organic-derived) and deep (mantellic-magmatic-metamorphic) fluxes of CO 2 [ ΦCO 2, mass time -1] and specific fluxes of CO 2 [ ϕCO 2 mass time -1 surface -1] dissolving in the shallow groundwaters of the volcanic areas of Amiata, Vulsini-Vico-Sabatini, Albani, Roccamonfina, Vesuvio, Vulture, and Etna were evaluated by partitioning the composed population of total dissolved inorganic carbon in two individual populations and subsequent subtraction of local background population. The flux of deep CO 2 released from the geothermal fields of Piancastagnaio (Amiata), Torre Alfina, Latera, Marta, Bracciano south, Cesano, and Mofete and from the Overall Northern Latium Hydrothermal Reservoir were also evaluated by means of the total surface heat flux and the enthalpy and CO 2 molality of the single liquid phase circulating in each geothermal reservoir. These data suggest that the ϕCO 2 released to the atmosphere varies from 9.5×10 6 to 3.0×10 6 mol year -1 km -2, over the geothermal fields of Bracciano south and Cesano, respectively, and that a total ΦCO 2 of 3.8×10 8 mol year -1 is cumulatively released from the geothermal fields of Torre Alfina, Latera and Cesano extending over an area of only 66 km 2. In addition, a flux of ˜2.2×10 11 to 3.8×10 11 mol year -1 of gaseous CO 2 entering the atmosphere is obtained for the entire anomalous area of central Italy, extending from the Tyrrhenian coastline to the Apennine chain (45,000 km 2). Thus terrestrial CO 2 emission in central-southern Italy appears to be a significant carbon source.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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. Using eddy covariance to estimate air-sea gas transfer velocity for oxygen

    NASA Astrophysics Data System (ADS)

    Andersson, Andreas; Rutgersson, Anna; Sahlée, Erik

    2016-07-01

    Air-sea gas transfer velocity for O2 is calculated using directly measured fluxes with the eddy covariance technique. It is a direct method and is frequently used to determine fluxes of heat, humidity, and CO2, but has not previously been used to estimate transfer velocities for O2, using atmospheric eddy covariance data. The measured O2 fluxes are upward directed, in agreement with the measured air-sea gradient of the O2 concentration, and opposite to the direction of the simultaneously measured CO2 fluxes. The transfer velocities estimated from measurements are compared with prominent wind speed parameterizations of the transfer velocity for CO2 and O2, previously established from various measurement techniques. Our result indicates stronger wind speed dependence for the transfer velocity of O2 compared to CO2 starting at intermediate wind speeds. This stronger wind speed dependence appears to coincide with the onset of whitecap formation in the flux footprint and the strong curvature of a cubic wind-dependent function for the transfer velocity provides the best fit to the data. Additional data using the measured O2 flux and an indirect method (based on the Photosynthetic Quotient) to estimate oxygen concentration in water, support the stronger wind dependence for the transfer velocity of O2 compared to CO2.

  15. Experimental observations of air-sea parameters and fluxes associated with anomalous event in the Indian Ocean during 1997-1998 El Niño period

    NASA Astrophysics Data System (ADS)

    Ramana, M. V.; Krishnan, Praveena; Muraleedharan Nair, S.; Kunhikrishnan, P. K.

    2004-04-01

    This paper describes the variation of air-sea parameters and fluxes during winter months of 1997 (pre-INDOEX) and 1998 (INDOEX-FFP) using ship-based in situ measurements in the latitude range 15°N to 20°S over the Indian Ocean and Arabian Sea. The 1998 cruise period coincided with one of the strongest El Niño events in the decade over the Pacific Ocean. The tropical Indian Ocean underwent a highly anomalous series of events during 1998 with warm sea surface temperature (SST) anomaly over 2 °C during February 1998 and easterly winds associated with the reversed Walker circulation. In situ observations during 1998 cruise period show that the winds in the Indian Ocean region had basically resumed their climatological state as of March 15, 1998 with lesser wind speeds as El Niño waned. However, the sea surface temperatures in Indian Ocean were found to be high even though climatological state had resumed. The present results are the observational evidence to show that the reduced latent heat flux due to low wind speeds could have contributed to the surface warming in the Indian Ocean. The sensible heat and latent heat fluxes are found to be high during anomalous period due to higher sea surface temperature and wind speeds in comparison to the normal period.

  16. CO2-flux measurements above the Baltic Sea at two heights: flux gradients in the surface layer?

    NASA Astrophysics Data System (ADS)

    Lammert, A.; Ament, F.

    2015-11-01

    The estimation of CO2 exchange between the ocean and the atmosphere is essential to understand the global carbon cycle. The eddy-covariance technique offers a very direct approach to observe these fluxes. The turbulent CO2 flux is measured, as well as the sensible and latent heat flux and the momentum flux, a few meters above the ocean in the atmosphere. Assuming a constant-flux layer in the near-surface part of the atmospheric boundary layer, this flux equals the exchange flux between ocean and atmosphere. The purpose of this paper is the comparison of long-term flux measurements at two different heights above the Baltic Sea to investigate this assumption. The results are based on a 1.5-year record of quality-controlled eddy-covariance measurements. Concerning the flux of momentum and of sensible and latent heat, the constant-flux layer theory can be confirmed because flux differences between the two heights are insignificantly small more than 95 % of the time. In contrast, significant differences, which are larger than the measurement error, occur in the CO2 flux about 35 % of the time. Data used for this paper are published at http://doi.pangaea.de/10.1594/PANGAEA.808714.

  17. CO2-flux measurements above the Baltic Sea at two heights: flux gradients in the surface layer

    NASA Astrophysics Data System (ADS)

    Lammert, A.; Ament, F.

    2015-07-01

    The estimation of CO2 exchange between the ocean and the atmosphere is essential to understand the global carbon cycle. The eddy-covariance technique offers a very direct approach to observe these fluxes. The turbulent CO2 flux is measured as well as the sensible and latent heat flux and the momentum flux, a few meters above the ocean in the atmosphere. Assuming a constant-flux layer in the near surface part of the atmospheric boundary, this flux equals the exchange flux between ocean and atmosphere. The goal of this paper is the comparison of long-term flux measurements at two different heights above the Baltic Sea due to this assumption. The results are based on an one-and-a-half year record of quality controlled eddy covariance measurements. Concerning the flux of momentum and of sensible and latent heat, the constant-flux layer theory can be validated because flux gradients between the two heights are more than 95 % of the time insignificantly small. In contrast, significant gradients, which are larger than the measurement error, occur for the CO2 flux in nearly 35 % of the time. Data, used for this paper are published at http://doi.pangaea.de/10.1594/PANGAEA.808714.

  18. CO2 dynamics in the Amargosa Desert: Fluxes and isotopic speciation in a deep unsaturated zone

    USGS Publications Warehouse

    Walvoord, M.A.; Striegl, R.G.; Prudic, D.E.; Stonestrom, D.A.

    2005-01-01

    Natural unsaturated-zone gas profiles at the U.S. Geological Survey's Amargosa Desert Research Site, near Beatty, Nevada, reveal the presence of two physically and isotopically distinct CO2 sources, one shallow and one deep. The shallow source derives from seasonally variable autotrophic and heterotrophic respiration in the root zone. Scanning electron micrograph results indicate that at least part of the deep CO2 source is associated with calcite precipitation at the 110-m-deep water table. We use a geochemical gas-diffusion model to explore processes of CO2 production and behavior in the unsaturated zone. The individual isotopic species 12CO2, 13CO2, and 14CO2 are treated as separate chemical components that diffuse and react independently. Steady state model solutions, constrained by the measured PCO2 ??13C (in CO2), and ??14C (in CO2) profiles, indicate that the shallow CO2 source from root and microbial respiration composes ???97% of the annual average total CO2 production at this arid site. Despite the small contribution from deep CO2 production amounting to ???0.1 mol m-2 yr-1, upward diffusion from depth strongly influences the distribution of CO2 and carbon isotopes in the deep unsaturated zone. In addition to diffusion from deep CO2 production, 14C exchange with a sorbed CO2 phase is indicated by the modeled ??14C profiles, confirming previous work. The new model of carbon-isotopic profiles provides a quantitative approach for evaluating fluxes of carbon under natural conditions in deep unsaturated zones.

  19. Analyzing consistency of interannual variability in air-sea sensible and latent heat fluxes in CMIP5 model simulations

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Gulev, Sergey

    2015-04-01

    Surface turbulent heat fluxes are critically important in climate model experiments, since they represent a language of communication of the ocean and atmosphere. Interannual variability of surface turbulent heat fluxes is believed to be the major contributor to the changes in the ocean surface heat balance, at least in mid latitudes. Being relatively well assessed and validated in reanalyses, surface turbulent heat fluxes always were of a lesser attention in diagnostics of climate model experiments. We analysed interannual variability of sensible and latent heat fluxes in historical climate simulations with several CMIP5 models. Variability in surface turbulent sensible and latent heat fluxes in model simulations has been analysed during several last decades (from 1950s to 2005) with the emphasis on different scales of variability (short-term, interannual, decadal). At all scales has been found a little consistency between the changes in turbulent surface fluxes diagnosed by reanalyses and blended data sets (OA-FLUX) on one hand and model simulations on the other. Furthermore, some models (e.g. ECHAM, IPSL) surprisingly demonstrate large regions with negative correlations between sensible and latent heat fluxes, which is not the case in observational data sets (reanalyses and OAFLUX). Interestingly, variability in air temperature and surface humidity (which could be potentially considered as the reason for autocorrelation between sensible and latent fluxes) demonstrates consistency with each other at most scales. Further we discuss potential reasons for the discovered phenomenon.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Sea-air CO2 fluxes in the Indian Ocean between 1990 and 2009

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    The Indian Ocean (44° S-30° N) plays an important role in the global carbon cycle, yet it remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea-air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, 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 Indian Ocean sea-air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea-air CO2 uptake of -0.37 ± 0.06 PgC yr-1 is consistent with the -0.24 ± 0.12 PgC yr-1 calculated from observations. The fluxes from the southern Indian Ocean (18-44° S; -0.43 ± 0.07 PgC yr-1 are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), overestimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but overestimate the magnitude. The predicted sea-air CO2 fluxes by ocean biogeochemical models (OBGMs) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predicted an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than that found by atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    The Indian Ocean (44° S-30° N) plays an important role in the global carbon cycle, yet remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea-air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, 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 Indian Ocean sea-air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea-air CO2 uptake of -0.37 ± 0.06 Pg C yr-1, is consistent with the -0.24 ± 0.12 Pg C yr-1 calculated from observations. The fluxes from the Southern Indian Ocean (18° S-44° S; -0.43 ± 0.07 Pg C yr-1) are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), over estimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by a lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but over estimate the magnitude. The predicted sea-air CO2 fluxes by Ocean BioGeochemical Models (OBGM) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predict an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric inversions

  3. [Responses of CO2 fluxes to light intensity and temperature in rice paddy field].

    PubMed

    Zhu, Yong-li; Wu, Jin-shui; Tong, Cheng-li; Wang, Ke-lin; Wang, Qin-xue

    2008-04-01

    CO2 fluxes in rice paddy ecosystem in subtropical hilly region were measured continuously using eddy covariance technique. The objectives were to investigate the responses of CO2 fluxes to light intensity and temperature in the paddy ecosystem. Results showed a rectangular hyperbolic light-response function could be used to describe the relationship of CO2 flux and photosynthetic photon flux density (PPFD). The absolute values of CO2 fluxes increased with the increment of PPFD. When PPFD was higher than 1000 micromol/(m2 x s), the maximum was observed. CO2 fluxes responded differently to light between early and late rice. Values of quantum yield of late rice (0.0465-0.0999 micromol/micromol) were general higher than that of early rice (0.0176-0.0541 micromol/micromol). Moreover, the quantum yield and the maximum rate of photosynthesis assimilation in the blooming stage were higher than that in tillering and ripening stages. In nighttime, respiration from soil and plants (ecosystem respiration, Reco) changed exponentially with the increase of soil temperature at the depth of 5 cm (T5), 10 cm (T10), and 20 cm (T20), respectively. Whereas, T5 was more feasible than others to be considered as the temperature parameter for Reco calculation. During early rice growing season, Reco was more sensitive to temperature change than that during late rice growing season. PMID:18637359

  4. Changes in fluxes of heat, H2O, CO2 caused by a large wind farm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Crop Wind Energy Experiment (CWEX) provides a platform to investigate the effect of wind turbines and large wind farms on surface fluxes of momentum, heat, moisture and carbon dioxide (CO2). In 2010 and 2011, eddy covariance flux stations were installed between two lines of turbines at the south...

  5. Relationships Between the Bulk-Skin Sea Surface Temperature Difference, Wind, and Net Air-Sea Heat Flux

    NASA Technical Reports Server (NTRS)

    Emery, William J.; Castro, Sandra L.; Lindstrom, Eric (Technical Monitor)

    2002-01-01

    The primary purpose of this project was to evaluate and improve models for the bulk-skin temperature difference to the point where they could accurately and reliably apply under a wide variety of environmental conditions. To accomplish this goal, work was conducted in three primary areas. These included production of an archive of available data sets containing measurements of the skin and bulk temperatures and associated environmental conditions, evaluation of existing skin layer models using the compiled data archive, and additional theoretical work on the development of an improved model using the data collected under diverse environmental conditions. In this work we set the basis for a new physical model of renewal type, and propose a parameterization for the temperature difference across the cool skin of the ocean in which the effects of thermal buoyancy, wind stress, and microscale breaking are all integrated by means of the appropriate renewal time scales. Ideally, we seek to obtain a model that will accurately apply under a wide variety of environmental conditions. A summary of the work in each of these areas is included in this report. A large amount of work was accomplished under the support of this grant. The grant supported the graduate studies of Sandra Castro and the preparation of her thesis which will be completed later this year. This work led to poster presentations at the 1999 American Geophysical Union Fall Meeting and 2000 IGARSS meeting. Additional work will be presented in a talk at this year's American Meteorological Society Air-Sea Interaction Meeting this May. The grant also supported Sandra Castro during a two week experiment aboard the R/P Flip (led by Dr. Andrew Jessup of the Applied Physics Laboratory) to help obtain additional shared data sets and to provide Sandra with a fundamental understanding of the physical processes needed in the models. In a related area, the funding also partially supported Dr. William Emery and Daniel

  6. CO2 volume fluxes outgassing from champagne glasses: the impact of champagne ageing.

    PubMed

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

    2010-02-15

    It was demonstrated that CO(2) volume fluxes outgassing from a flute poured with a young champagne (elaborated in 2007) are much higher than those outgassing from the same flute poured with an older champagne (elaborated in the early 1990s). The difference in dissolved-CO(2) concentrations between the two types of champagne samples was found to be a crucial parameter responsible for differences in CO(2) volume fluxes outgassing from one champagne to another. Nevertheless, it was shown that, for a given identical dissolved-CO(2) concentration in both champagne types, the CO(2) volume flux outgassing from the flute poured with the old champagne is, in average, significantly lower than that outgassing from the flute poured with the young one. Therefore, CO(2) seems to "escape" more easily from the young champagne than from the older one. The diffusion coefficient of CO(2) in both champagne types was pointed as a key parameter to thoroughly determine in the future, in order to unravel our experimental observation. PMID:20103140

  7. CO2 volume fluxes outgassing from champagne glasses: the impact of champagne ageing.

    PubMed

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

    2010-02-15

    It was demonstrated that CO(2) volume fluxes outgassing from a flute poured with a young champagne (elaborated in 2007) are much higher than those outgassing from the same flute poured with an older champagne (elaborated in the early 1990s). The difference in dissolved-CO(2) concentrations between the two types of champagne samples was found to be a crucial parameter responsible for differences in CO(2) volume fluxes outgassing from one champagne to another. Nevertheless, it was shown that, for a given identical dissolved-CO(2) concentration in both champagne types, the CO(2) volume flux outgassing from the flute poured with the old champagne is, in average, significantly lower than that outgassing from the flute poured with the young one. Therefore, CO(2) seems to "escape" more easily from the young champagne than from the older one. The diffusion coefficient of CO(2) in both champagne types was pointed as a key parameter to thoroughly determine in the future, in order to unravel our experimental observation.

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

    NASA Technical Reports Server (NTRS)

    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 (< 100 km) on monthly time scales. High precision (< 1 part per million, ppm) is essential to resolve the small, near-surface CO2 variations associated with ocean fluxes and to better constrain the CO2 transport over the ocean. The Japanese Greenhouse gases Observing Satellite (GOSAT) and the NASA Orbiting Carbon Observatory (OCO) were first two 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.

  9. Regulation of CO2 and N2O fluxes by coupled carbon and nitrogen availability

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Carbon (C) and nitrogen (N) interactions contribute to uncertainty in current biogeochemical models that aim to estimate greenhouse gas (GHG, including CO2 and N2O) emissions from soil to atmosphere. In this study, we quantified CO2 and N2O flux patterns and their relationship along with increasing C additions only, N additions only, a C gradient combined with excess N, and an N gradient with excess C via laboratory incubations. Conventional trends, where labile C or N addition results in higher CO2 or N2O fluxes, were observed. However, at low levels of C availability, saturating N amendments reduced soil CO2 flux while with high C availability N amendments enhanced it. At saturating C conditions increasing N amendments first reduced and then increased CO2 fluxes. Similarly, N2O fluxes were initially reduced by adding labile C under N limited conditions, but additional C enhanced N2O fluxes by more than two orders of magnitude in the saturating N environment. Changes in C or N use efficiency could explain the altered gas flux patterns and imply a critical level in the interactions between N and C availability that regulate soil trace gas emissions and biogeochemical cycling. Compared to either N or C amendment alone, the interaction of N and C caused ∼60 and ∼5 times the total GHG emission, respectively. Our findings suggested that the response of CO2 and N2O fluxes along stoichiometric gradients in C and N availability should be accounted for interpreting or modeling the biogeochemistry of GHG emissions.

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

    NASA Astrophysics Data System (ADS)

    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

  11. Influence of Fossil Fuel Emissions on CO2 Flux Estimation by Atmospheric Inversions

    NASA Astrophysics Data System (ADS)

    Saeki, T.; Patra, P. K.; van der Laan-Luijkx, I. T.; Peters, W.

    2015-12-01

    Top-down approaches (or atmospheric inversions) using atmospheric transport models with CO2 observations are an effective way to estimate carbon fluxes at global and regional scales. CO2 flux estimation by Bayesian inversions require a priori knowledge of terrestrial biosphere and oceanic fluxes and fossil fuel (FF) CO2 emissions. In most inversion frameworks, FF CO2 is assumed to be a known quantity because FF CO2 based on world statistics are thought to be more reliable than natural CO2 fluxes. However different databases of FF CO2 emissions may have different temporal and spatial variations especially at locations where statistics are not so accurate. In this study, we use 3 datasets of fossil fuel emissions in inversion estimations and evaluate the sensitivity of the optimized CO2 fluxes to FF emissions with two different inverse models, JAMSTEC's ACTM and CarbonTracker Europe (CTE). Interannually varying a priori FF CO2 emissions were based on 1) CDIAC database, 2) EDGARv4.2 database, and 3) IEA database, with some modifications. Biosphere and oceanic fluxes were optimized. Except for FF emissions, other conditions were kept the same in our inverse experiments. The three a priori FF emissions showed ~5% (~0.3GtC/yr) differences in their global total emissions in the early 2000's and the differences reached ~9% (~0.9 GtC/yr) in 2010. This resulted in 0.5-1 GtC/yr (2001-2011) and 0.3-0.6 GtC/yr (2007-2011) differences in the estimated global total emissions for the ACTM and CTE inversions, respectively. Regional differences in the FF emissions were relatively large in East Asia (~0.5 GtC/yr for ACTM and ~0.3 GtC/yr for CTE) and Europe (~0.3 GtC/yr for ACTM). These a priori flux differences caused differences in the estimated biosphere fluxes for ACTM in East Asia and Europe and also their neighboring regions such as West Asia, Boreal Eurasia, and North Africa. The main differences in the biosphere fluxes for CTE were found in Asia and the Americas.

  12. CO2 flux from tundra lichen, moss, and tussock, Council, Alaska: Assessment of spatial representativeness

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Chae, N.

    2012-12-01

    CO2 flux-measurement in dominant tundra vegetation on the Seward Peninsula of Alaska was examined for spatial representativeness, using a manual chamber system. In order to assess the representativeness of CO2 flux, a 40 m × 40 m (5-m interval; 81 total points) plot was used in June, August, and September of 2011. Average CO2 fluxes in lichen, moss, and tussock tundra were 3.4 ± 2.7, 4.5 ± 2.9, and 7.2 ± 5.7 mgCO2/m2/m during growing season, respectively, suggesting that tussock tundra is a significant CO2 source, especially considering the wide distribution of tussock tundra in the circumpolar region. Further, soil temperature, rather than soil moisture, held the key role in regulating CO2 flux at the study site: CO2 flux from tussock increased linearly as soil temperature increased, while the flux from lichen and moss followed soil temperature nearly exponentially, reflecting differences in surface area covered by the chamber system. Regarding sample size, the 81 total sampling points over June, August, and September satisfy an experimental average that falls within ±10% of full sample average, with a 95% confidence level. However, the number of sampling points for each variety of vegetation during each month must provide at least ±20%, with an 80% confidence level. In order to overcome the logistical constraints, we were required to identify the site's characteristics with a manual chamber system over a 40 m × 40 m plot and to subsequently employ an automated chamber for spatiotemporal representativeness.

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    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 exchange of energy, moisture and CO2 showed that the surface fluxes in the domain strongly influenced the atmospheric properties. The majority of the variability in the afternoon CO2 mixing ratio in the middle of the domain was determined by biospheric and fossil fuel CO2 fluxes in the limited area domain (640×640 km). Variation of the surface CO2 fluxes, reflecting the uncertainty of the parameters in the CO2 flux model 5PM, resulted in a range of simulated atmospheric CO2 mixing ratios of on average 11.7 ppm in the well-mixed boundary layer. Additionally, we found that observed surface energy fluxes and observed atmospheric temperature and moisture could not be reconciled with the simulations. Including this as an uncertainty in the simulation of surface energy fluxes changed simulated atmospheric vertical mixing and horizontal advection, leading to differences in simulated CO2 of on average 1.7 ppm. This is an important source of uncertainty and should be accounted for to avoid biased calculations of the CO2 mixing ratio, but it does not overwhelm the signal in the CO2 mixing ratio due to the uncertainty range of the surface CO2 fluxes.

  14. On Using CO2 Concentration Measurements at Mountain top and Valley Locations in Regional Flux Studies.

    NASA Astrophysics Data System (ADS)

    de Wekker, S. F.; Song, G.; Stephens, B. B.

    2007-12-01

    Data from the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON) are used to investigate atmospheric controls on temporal and spatial variability of CO2 in mountainous terrain and the usefulness of mountain top and valley measurement for the estimation of regional CO2 fluxes. Rocky RACCOON consists of four sites installed in fall of 2005 and spring of 2006: Niwot Ridge, near Ward, Colorado; Storm Peak Laboratory near Steamboat Springs, Colorado; Fraser Experimental Forest, near Fraser Colorado; and Hidden Peak, near Snowbird, Utah. The network uses the NCAR-developed Autonomous Inexpensive Robust CO2 Analyzer. These units measure CO2 concentrations at three levels on a tower, producing individual measurements every 2.5 minutes precise to 0.1 ppm CO2 and closely tied to the WMO CO2 scale. Three of the sites are located on a mountain top while one site is located in a valley. Initial analyses show interesting relationships between CO2 concentration and atmospheric parameters, such as wind speed and direction, temperature, and incoming solar radiation. The nature of these relationships is further investigated with an atmospheric mesoscale model. Idealized and realistic simulations are able to capture the observed behavior of spatial and temporal CO2 variability and reveal the responsible physical processes. The implications of the results and the value of the measurements for providing information on local to regional scale respiration and photosynthesis rates in the Rockies are discussed.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  17. Influence and impact of the parametrization of the turbulent air-sea fluxes on atmospheric moisture and convection in the tropics

    NASA Astrophysics Data System (ADS)

    Torres, Olivier; Braconnot, Pascale; Gainusa-Bogdan, Alina; Hourdin, Frédéric; Marti, Olivier; Pelletier, Charles

    2016-04-01

    The turbulent fluxes across the ocean/atmosphere interface represent one of the principal driving forces of the global atmospheric and oceanic circulation and are also responsible for various phenomena like the water supply to the atmospheric column, which itself is extremely important for atmospheric convection. Although the representation of these fluxes has been the subject of major studies, it still remains a very challenging problem. Our aim is to better understand the role of these fluxes in climate change experiments and in the equator-pole redistribution of heat and water by the oceanic and atmospheric circulation. For this, we are developing a methodology starting from idealized 1D experiments and going all the way up to fully coupled ocean-atmosphere simulations of past and future climates. The poster will propose a synthesis of different simulations we have performed with a 1D version of the LMDz atmosphere model towards a first objective of understanding how different parameterizations of the turbulent fluxes affect the moisture content of the atmosphere and the feedback with the atmospheric boundary layer and convection schemes. Air-sea fluxes are not directly resolved by the models because they are subgrid-scale phenomena and are therefore represented by parametrizations. We investigate the differences between several 1D simulations of the TOGA-COARE campaign (1992-1993, Pacific warm pool region), for which 1D boundary conditions and observations are available to test the results of atmospheric models. Each simulation considers a different version of the LMDz model in terms of bulk formula (four) used to compute the turbulent fluxes. We also consider how the representation of gustiness in these parameterizations affects the results. The use of this LMDz test case (very constrained within an idealized framework) allows us to determine how the response of surface fluxes helps to reinforce or damp the atmospheric water vapor content or cloud feedbacks

  18. A global coupled Eulerian-Lagrangian model and 1 1 km CO2 surface flux dataset for high-resolution atmospheric CO2 transport simulations

    SciTech Connect

    Ganshin, A; Oda, T; Saito, M; Maksyutov, S; Valsala, V; Andres, Robert Joseph; Fischer, R; Lowry, D; Lukyanov, A; Matsueda, H; Nisbet, E; Rigby, M; Sawa, Y; Toumi, R; Tsuboi, K; Varlagin, A; Zhuravlev, R

    2012-01-01

    Abstract. We designed a method to simulate atmospheric CO2 concentrations at several continuous observation sites around the globe using surface fluxes at a very high spatial resolution. The simulations presented in this study were performed using the Global Eulerian-Lagrangian Coupled Atmospheric model (GELCA), comprising a Lagrangian particle dispersion model coupled to a global atmospheric tracer transport model with prescribed global surface CO2 flux maps at a 1 1 km resolution. The surface fluxes used in the simulations were prepared by assembling the individual components of terrestrial, oceanic and fossil fuel CO2 fluxes. This experimental setup (i.e. a transport model running at a medium resolution, coupled to a high-resolution Lagrangian particle dispersion model together with global surface fluxes at a very high resolution), which was designed to represent high-frequency variations in atmospheric CO2 concentration, has not been reported at a global scale previously. Two sensitivity experiments were performed: (a) using the global transport model without coupling to the Lagrangian dispersion model, and (b) using the coupled model with a reduced resolution of surface fluxes, in order to evaluate the performance of Eulerian-Lagrangian coupling and the role of high-resolution fluxes in simulating high-frequency variations in atmospheric CO2 concentrations. A correlation analysis between observed and simulated atmospheric CO2 concentrations at selected locations revealed that the inclusion of both Eulerian-Lagrangian coupling and highresolution fluxes improves the high-frequency simulations of the model. The results highlight the potential of a coupled Eulerian-Lagrangian model in simulating high-frequency atmospheric CO2 concentrations at many locations worldwide. The model performs well in representing observations of atmospheric CO2 concentrations at high spatial and temporal resolutions, especially for coastal sites and sites located close to sources of

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

    NASA Technical Reports Server (NTRS)

    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

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

    PubMed

    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.

  1. CO2 volume fluxes outgassing from champagne glasses in tasting conditions: flute versus coupe.

    PubMed

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

    2009-06-10

    Measurements of CO(2) fluxes outgassing from glasses containing a standard Champagne wine initially holding about 11.5 g L(-1) of dissolved CO(2) were presented, in tasting conditions, during the first 10 min following the pouring process. Experiments were performed at room temperature, with a flute and a coupe, respectively. The progressive loss of dissolved CO(2) concentration with time was found to be significantly higher in the coupe than in the flute, which finally constitutes the first analytical proof that the flute prolongs the drink's chill and helps it to retain its effervescence in contrast with the coupe. Moreover, CO(2) volume fluxes outgassing from the coupe were found to be much higher in the coupe than in the flute in the early moments following pouring, whereas this tendency reverses from about 3 min after pouring. Correlations were proposed between CO(2) volume fluxes outgassing from the flute and the coupe and their continuously decreasing dissolved CO(2) concentration. The contribution of effervescence to the global kinetics of CO(2) release was discussed and modeled by use of results developed over recent years. Due to a much shallower liquid level in the coupe, bubbles collapsing at the free surface of the coupe were found to be significantly smaller than those collapsing at the free surface of the flute, and CO(2) volume fluxes released by collapsing bubbles only were found to be approximately 60% smaller in the coupe than in the flute. Finally, the contributions of gas discharge by invisible diffusion through the free surface areas of the flute and coupe were also approached and compared for each type of drinking vessel.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. CO2 Fluxes: The Upwelling Systems of South America & South Africa

    NASA Astrophysics Data System (ADS)

    Karagali, Ioanna; Badger, Merete; Soresen, Lise Lotte

    2010-12-01

    In order to estimate the atmospheric concentration of car- bon dioxide knowledge of the fluxes between the ocean and atmosphere are important. Different ocean regions can act as sinks or sources of CO2 depending on temperature, salinity and biological activity. The flux of CO2 depends on the partial pressures of atmospheric and oceanic CO2 and the exchange velocity which is commonly parametrized by the wind speed. Direct in-situ measurements are expensive, operationally demanding and of low spatial resolution. It has been shown that in- direct estimation of oceanic pCO2 is possible due to its strong dependence on temperature, however primary production also influences the concentration of CO2 in the water. The present study aims at estimating the oceanic pCO2 with the use of satellite measurements for water temperature and chlorophyll-a (chl-A). Envisat MERIS Level 2 Reduced Resolution products were used for the chl-A concentration. Sea Surface Temperature data were taken from a composite optimally interpolated SST product of the Danish Meteorological Institute (DMI). In-situ measurements were retrieved during the Danish Galathea III expedition, from August 2006 until April 2007. Based on [4] and [5], empirical algorithms for the estimation of pCO2,w were created using regression analyses. The final result was an estimate of the pCO2,w along the known upwelling systems of North Chile-Peru and Namibia. Estimates of pCO2,w produced by different combinations of physical parameters are compared with measurements. Correlation coefficients show that there was a dependency of pCO2,w with SST, Salinity and chl-A.

  4. Do Extreme Climatic Events Drive Ecosystem Water Flux Under Elevated CO2 in a Temperate Forest?

    NASA Astrophysics Data System (ADS)

    Warren, J. M.; Norby, R. J.; Wullschleger, S. D.

    2007-12-01

    In 2007, much of the Southeastern US experienced a combination of extreme weather events that visibly damaged plant communities across entire landscapes; including a Liquidambar styraciflua (sweetgum) plantation in eastern Tennessee concurrently exposed to elevated CO2 treatments. At the Oak Ridge National Lab's FACE facility there was a late spring freeze event (-6.5 °C) as leaves were emerging, followed by a record summer drought with forest understory temperatures reaching 38.5 °C. Trees exposed to elevated CO2 often have lower rates of evapotranspiration (ET) which can reduce total site water use, thereby buffering trees against droughty conditions. Sap flux density was monitored in 16 trees using Granier- style sensors to access the potential of a CO2 treatment-mitigated buffering of perceived plant water stress, and thereby productivity. While up to 60% of young expanding foliage was visibly damaged across treatments following the freeze event, it represented a minor component of subsequent canopy leaf area with no distinguishable impact on sap flux. Trees exposed to elevated CO2 initially had lower ET than ambient trees, but differences diminished as soil water potential dropped below -0.5 MPa reflecting the increasing water limitations. Sap flux density declined more readily in ambient CO2 trees during droughty periods, but subsequently recovered following significant rain events. This research suggests that plant response to seasonal dynamics in water availability may be modulated (less responsive) under a projected future CO2 scenario.

  5. Progress Toward Measuring CO2 Isotopologue Fluxes in situ with the LLNL Miniature, Laser-based CO2 Sensor

    NASA Astrophysics Data System (ADS)

    Osuna, J. L.; Bora, M.; Bond, T.

    2015-12-01

    One method to constrain photosynthesis and respiration independently at the ecosystem scale is to measure the fluxes of CO2­ isotopologues. Instrumentation is currently available to makes these measurements but they are generally costly, large, bench-top instruments. Here, we present progress toward developing a laser-based sensor that can be deployed directly to a canopy to passively measure CO2 isotopologue fluxes. In this study, we perform initial proof-of-concept and sensor characterization tests in the laboratory and in the field to demonstrate performance of the Lawrence Livermore National Laboratory (LLNL) tunable diode laser flux sensor. The results shown herein demonstrate measurement of bulk CO2 as a first step toward achieving flux measurements of CO2 isotopologues. The sensor uses a Vertical Cavity Surface Emitting Laser (VCSEL) in the 2012 nm range. The laser is mounted in a multi-pass White Cell. In order to amplify the absorption signal of CO2 in this range we employ wave modulation spectroscopy, introducing an alternating current (AC) bias component where f is the frequency of modulation on the laser drive current in addition to the direct current (DC) emission scanning component. We observed a strong linear relationship (r2 = 0.998 and r2 = 0.978 at all and low CO2 concentrations, respectively) between the 2f signal and the CO2 concentration in the cell across the range of CO2 concentrations relevant for flux measurements. We use this calibration to interpret CO2 concentration of a gas flowing through the White cell in the laboratory and deployed over a grassy field. We will discuss sensor performance in the lab and in situ as well as address steps toward achieving canopy-deployed, passive measurements of CO2 isotopologue fluxes. 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-675788

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

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

    PubMed

    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 (<30%). The ability of this lidar to remotely sense 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.

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

    PubMed

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

    2015-01-01

    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 (<30%). The ability of this lidar to remotely sense 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. PMID:26324399

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

    PubMed Central

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

    2015-01-01

    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 (<30%). The ability of this lidar to remotely sense 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. PMID:26324399

  10. African tropical rainforest net CO2 fluxes in the 20th century

    NASA Astrophysics Data System (ADS)

    Fisher, J. B.; Sikka, M.; Sitch, S.; Ciais, P.; Poulter, B.; Galbraith, D.; Lee, J.; Huntingford, C.; Viovy, N.; Zeng, N.; Ahlström, A.; Lomas, M. R.; Levy, P. E.; Frankenberg, C.; Saatchi, S. S.; Malhi, Y.

    2013-12-01

    The African humid tropical biome constitutes the second largest rainforest region, significantly impacts global carbon cycling and climate, and has undergone major changes in functioning due to climate and land use change over the past century. We assess changes and trends in CO2 fluxes from 1901-2010 using nine land surface models forced with common driving data, and depict the inter-model variability as the uncertainty in fluxes. The biome is estimated to be a natural (no disturbance) net carbon sink (-0.02 kg C m-2y-1 or -0.04 Pg C y-1, p<0.05) with increasing strength 4x-fold in the second half of the century. The models were in close agreement on net CO2 flux at the beginning of the century (σ1901=0.02 kg C m-2y-1), but diverged exponentially throughout the century (σ2010=0.03 kg C m-2y-1). The increasing uncertainty is due to differences in sensitivity to increasing atmospheric CO2, but not increasing water stress, despite a decrease in precipitation and increase in air temperature. However, the largest uncertainties were associated with the most extreme drought events of the century. These results highlight the need to constrain modeled CO2 fluxes with increasing atmospheric CO2 concentrations and extreme climatic events, as the uncertainties will only amplify in the next century.

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

    NASA Astrophysics Data System (ADS)

    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

  12. Assessing the Potential to Derive Air-Sea Freshwater Fluxes from Aquarius-Like Observations of Surface Salinity

    NASA Technical Reports Server (NTRS)

    Zhen, Li; Adamec, David

    2009-01-01

    A state-of-the-art numerical model is used to investigate the possibility of determining freshwater flux fields from temporal changes io sea-surface salinity (SSS), a goal of the satellite salinity-measuring mission, Aquarius/SAC-D. Because the estimated advective temporal scale is usually longer than the Aquarius/SAC-D revisit time, the possibility of producing freshwater flux estimates from temporal salinity changes is first examined by using a correlation analysis. For the mean seasonal cycle, the patterns of the correlations between the freshwater fluxes and surface salinity temporal tendencies are mainly zonally oriented, and are highest where the local precipitation is also relatively high. Nonseasonal (deviations from the monthly mean) correlations are highest along mid-latitude moon tracks and are relatively small in the tropics. The complex correlation patterns presented here suggest that a global retrieval of the difference between evaporation and precipitation (E-P) from salinity changes requires more complex techniques than a simple consideration of local balance with surface forcing.

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

    NASA Astrophysics Data System (ADS)

    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

  14. Estimating CO(2) flux from snowpacks at three sites in the Rocky Mountains.

    PubMed

    McDowell, Nate G.; Marshall, John D.; Hooker, Toby D.; Musselman, Robert

    2000-06-01

    Soil surface CO(2) flux (F(s)) is the dominant respiratory flux in many temperate forest ecosystems. Snowpacks increase this dominance by insulating the soil against the low temperature to which aboveground components are exposed. However, measurement of F(s) in winter may be impeded by snow cover. Likewise, developing annual F(s) models is complicated by seasonal variation in root and microbial metabolism. We compared three methods of measuring sub-snow F(s): (1) dynamic chamber measurements at the upper snowpack surface (F(snow)), (2) dynamic chamber measurements at the soil surface via snowpits (F(soil)), and (3) static estimates based on measured concentrations of carbon dioxide ([CO(2)]) and conductance properties of the snowpack (F(diffusional)). Methods were compared at a mid-elevation forest in northeastern Washington, a mid-elevation forest in northern Idaho, and a high-elevation forest and neighboring meadow in Wyoming. The methods that minimized snowpack disturbance, F(diffusional) and F(snow), yielded similar estimates of F(s). In contrast, F(soil) yielded rates two to three times higher than F(snow) at the forested sites, and seven times higher at the subalpine meadow. The ratio F(soil)/F(snow) increased with increasing snow depth when compared across all sites. Snow removal appears to induce elevated soil flux as a result of lateral CO(2) diffusion into the pit. We chose F(snow) as our preferred method and used it to estimate annual CO(2) fluxes. The snowpack was present for 36% of the year at this site, during which time 132 g C m(-2), or 17% of the annual flux, occurred. We conclude that snowpack CO(2) flux is quantitatively important in annual carbon budgets for these forests and that the static and dynamic methods yield similar and reasonable estimates of the flux, as long as snowpack disturbance is minimized. PMID:12651510

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

    NASA Astrophysics Data System (ADS)

    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 (< 1 per mil) on an annual basis, despite significant seasonal variations in respired δ 13CO2 values (> 3 per mil). Such subtle isotopic disequilibrium however, when associated with enormous one-way gross fluxes, can effectively affect atmospheric 13C budget.

  16. Seasonal variability of soil CO2 flux and its carbon isotope composition in Krakow urban area, Southern Poland.

    PubMed

    Jasek, Alina; Zimnoch, Miroslaw; Gorczyca, Zbigniew; Smula, Ewa; Rozanski, Kazimierz

    2014-06-01

    As urban atmosphere is depleted of (13)CO2, its imprint should be detectable in the local vegetation and therefore in its CO2 respiratory emissions. This work was aimed at characterising strength and isotope signature of CO2 fluxes from soil in urban areas with varying distances from anthropogenic CO2 emissions. The soil CO2 flux and its δ(13)C isotope signature were measured using a chamber method on a monthly basis from July 2009 to May 2012 within the metropolitan area of Krakow, Southern Poland, at two locations representing different levels of anthropogenic influence: a lawn adjacent to a busy street (A) and an urban meadow (B). The small-scale spatial variability of the soil CO2 flux was also investigated at site B. Site B revealed significantly higher summer CO2 fluxes (by approximately 46 %) than site A, but no significant differences were found between their δ(13)CO2 signatures.

  17. Fluxes of NH3 and CO2 over upland moorland in the vicinity of agricultural land

    NASA Astrophysics Data System (ADS)

    Milford, Celia; Hargreaves, Ken J.; Sutton, Mark A.; Loubet, Benjamin; Cellier, Pierre

    2001-10-01

    Intensive field measurements of NH3 and CO2 exchange were made over a wet heathland in the vicinity (<500 m) of sheep pastures in the Cairngorm mountains of Scotland for a two-week period in the summer. Fluxes of NH3 were determined using the aerodynamic gradient method with a 3-height continuous denuder system; fluxes of CO2 were determined using eddy correlation, while sensible and latent heat fluxes were determined by both methods. Few studies have measured NH3 and CO2 fluxes simultaneously, making these measurements relevant to compare exchange dynamics. Both NH3 and CO2 exchanged bidirectionally, in response to a combination of biological (foliar, soil) and physico-chemical controls (solubility). NH3 was deposited rapidly to leaf surfaces, although during warm, dry daytime conditions periods of emission occurred, explained by the existence of a compensation point concentration for NH3. By contrast, CO2 followed a characteristic pattern of absorption during the day associated with net photosynthesis and emission at night. Both gases showed net uptake from the atmosphere, at 30 μmol NH3 m-2 d-1 and 74 mmol CO2 m-2 d-1. In southeast winds, NH3 emissions from the sheep pasture caused a significant advection error to the measured fluxes (>10%). Corrections were applied using a local-scale dispersion-exchange model. The analysis highlights how advection modifies the classical one-dimensional inferential resistance approach. It is concluded that ecosystems in the vicinity of agricultural land receive more dry deposition than would be estimated using NH3 concentration monitoring and standard inferential models. In the present study, this effect represented an overall increase in total NH3 deposition of 32%.

  18. A joint data assimilation system (Tan-Tracker) to simultaneously estimate surface CO2 fluxes and 3-D atmospheric CO2 concentrations from observations

    NASA Astrophysics Data System (ADS)

    Tian, X.; Xie, Z.; Liu, Y.; Cai, Z.; Fu, Y.; Zhang, H.; Feng, L.

    2014-12-01

    We have developed a novel framework ("Tan-Tracker") for assimilating observations of atmospheric CO2 concentrations, based on the POD-based (proper orthogonal decomposition) ensemble four-dimensional variational data assimilation method (PODEn4DVar). The high flexibility and the high computational efficiency of the PODEn4DVar approach allow us to include both the atmospheric CO2 concentrations and the surface CO2 fluxes as part of the large state vector to be simultaneously estimated from assimilation of atmospheric CO2 observations. Compared to most modern top-down flux inversion approaches, where only surface fluxes are considered as control variables, one major advantage of our joint data assimilation system is that, in principle, no assumption on perfect transport models is needed. In addition, the possibility for Tan-Tracker to use a complete dynamic model to consistently describe the time evolution of CO2 surface fluxes (CFs) and the atmospheric CO2 concentrations represents a better use of observation information for recycling the analyses at each assimilation step in order to improve the forecasts for the following assimilations. An experimental Tan-Tracker system has been built based on a complete augmented dynamical model, where (1) the surface atmosphere CO2 exchanges are prescribed by using a persistent forecasting model for the scaling factors of the first-guess net CO2 surface fluxes and (2) the atmospheric CO2 transport is simulated by using the GEOS-Chem three-dimensional global chemistry transport model. Observing system simulation experiments (OSSEs) for assimilating synthetic in situ observations of surface CO2 concentrations are carefully designed to evaluate the effectiveness of the Tan-Tracker system. In particular, detailed comparisons are made with its simplified version (referred to as TT-S) with only CFs taken as the prognostic variables. It is found that our Tan-Tracker system is capable of outperforming TT-S with higher assimilation

  19. Diurnal variations in CO2 flux from peatland floodplains: Implications for models of ecosystem respiration

    NASA Astrophysics Data System (ADS)

    Goulsbra, Claire; Rickards, Nathan; Brown, Sarah; Evans, Martin; Boult, Stephen; Alderson, Danielle

    2016-04-01

    Peatlands are important terrestrial carbon stores, and within these environments, floodplains have been identified as hotspots of carbon processing, potentially releasing substantial amounts of CO2 into the atmosphere. Previous monitoring campaigns have shown that such CO2 release from ecosystem respiration is linked not only to soil temperature and water table depth, but also to CO2 sequestration via primary productivity, thought to be because the root exudates produced during photosynthesis stimulate microbial activity. This suggests that extrapolation models that are parameterised on data collected during day light hours, when vegetation is photosynthesising, may overestimate ecosystem respiration rates at night, which has important implications for estimates of annual CO2 flux and carbon budgeting. To investigate this hypothesis, monitoring data is collected on the CO2 flux from UK peatland floodplains over the full diurnal cycle. This is done via ex-situ manual data collection from mesocosms using an infra-red gas analyser, and the in-situ automated collection of CO2 concentration data from boreholes within the peat using GasClams®. Preliminary data collected during the summer months suggest that night time respiration is suppressed compared to that during the day, and that the significant predictors of respiration are different when examining day and night time data. This highlights the importance of incorporating diurnal variations into models of ecosystem respiration.

  20. Gas exchange and CO2 flux in the tropical Atlantic Ocean determined from Rn-222 and pCO2 measurements

    NASA Technical Reports Server (NTRS)

    Smethie, W. M., Jr.; Takahashi, T.; Chipman, D. W.; Ledwell, J. R.

    1985-01-01

    The piston velocity for the tropical Atlantic Ocean has been determined from 29 radon profiles measured during the TTO Tropical Atlantic Study. By combining these data with the pCO2 data measured in the surface water and air samples, the net flux of CO2 across the sea-air interface has been calculated for the tropical Atlantic. The dependence of the piston velocity on wind speed is discussed, and possible causes for the high sea-to-air CO2 flux observed in the equatorial zone are examined.

  1. [Distribution and air-sea fluxes of methane in the Yellow Sea and the East China Sea in the spring].

    PubMed

    Cao, Xing-Peng; Zhang, Gui-Ling; Ma, Xiao; Zhang, Guo-Ling; Liu, Su-Mei

    2013-07-01

    A survey was carried out in the Yellow Sea and the East China Sea from March 17 to April 06 of 2011. Dissolved CH4 in various depths were measured and sea-to-air fluxes were estimated. Methane concentrations in surface and bottom waters ranged between 2.39-29.67 nmol x L(-1) and 2.63-30.63 nmol x L(-1), respectively. Methane concentrations in bottom waters were slightly higher than those in surface waters, suggesting the existence of methane source in bottom waters or sediments. The horizontal distribution of dissolved CH4 showed a decrease from the river mouth to the open sea, and was influenced by the freshwater discharge and the Kuroshio intrusion. Surface methane saturations ranged from 93%-1 038%. Sea to air CH4 fluxes were (2.85 +/- 5.11) micromol x (m2 x d)(-1) (5.18 +/- 9.99) micromol x (m2 x d)(-1) respectively, calculated using the Liss and Merlivat (LM86), the Wanninkhof (W92) relationships and in situ wind speeds, and estimated emission rates of methane from the East China Sea and the Yellow Sea range from 7.05 x 10(-2) - 12.0 x 10(-2) Tg x a(-1) and 1.17 x 10(-2) - 2.20 x 10(-2) Tg x a(-1), respectively. The Yellow Sea and East China Sea are the net sources of atmospheric methane in the spring.

  2. Sensitivity of modelled sulfate aerosol and its radiative effect on climate to ocean DMS concentration and air-sea flux

    NASA Astrophysics Data System (ADS)

    Tesdal, Jan-Erik; Christian, James R.; Monahan, Adam H.; von Salzen, Knut

    2016-09-01

    Dimethylsulfide (DMS) is a well-known marine trace gas that is emitted from the ocean and subsequently oxidizes to sulfate in the atmosphere. Sulfate aerosols in the atmosphere have direct and indirect effects on the amount of solar radiation reaching the Earth's surface. Thus, as a potential source of sulfate, ocean efflux of DMS needs to be accounted for in climate studies. Seawater concentration of DMS is highly variable in space and time, which in turn leads to high spatial and temporal variability in ocean DMS emissions. Because of sparse sampling (in both space and time), large uncertainties remain regarding ocean DMS concentration. In this study, we use an atmospheric general circulation model with explicit aerosol chemistry (CanAM4.1) and several climatologies of surface ocean DMS concentration to assess uncertainties about the climate impact of ocean DMS efflux. Despite substantial variation in the spatial pattern and seasonal evolution of simulated DMS fluxes, the global-mean radiative effect of sulfate is approximately linearly proportional to the global-mean surface flux of DMS; the spatial and temporal distribution of ocean DMS efflux has only a minor effect on the global radiation budget. The effect of the spatial structure, however, generates statistically significant changes in the global-mean concentrations of some aerosol species. The effect of seasonality on the net radiative effect is larger than that of spatial distribution and is significant at global scale.

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

    NASA Astrophysics Data System (ADS)

    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

  4. Comparison of CO2 fluxes from eddy covariance and soil chambers measurements in a vineyard

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    In order to study the processes involved in the carbon balance of a vineyard, we set up a long-term monitoring station of CO2, water vapour and energyfluxes. The experimental site is located in an extensive flat vineyard in the north-east of Italy. We measure the net ecosystem exchange with the eddy covariance (EC) technique using a Campbell Scientific closed-path IRGA and sonic anemometer, and the soil CO2 flux using a Li-Cor multiplexed system connected with six automatic dynamic chambers. Ancillary meteorological and soil variables are also measured. The vineyard is planted with north-south oriented rows spaced 2.2 m apart. Floor is grass covered, and a strip 0.6 m wide on the rows is chemically treated. To represent the different soil conditions existing in the EC footprint and to study the components of the CO2 soil flux, we placed dark soil chambers both on the vineyard rows and in the inter-row space. A well-known limit of the EC technique is the underestimation of fluxes during calm wind periods, mainly occurring at night. In the autumn/winter vine dormancy period, the EC and soil chambers CO2 fluxes should be similar. We compared the CO2 fluxes measured using the two methods to evaluate the reliability of EC measurements at different atmospheric turbulent mixing conditions and stability. The EC technique underestimates the ecosystem respiration during night time periods with friction velocity lower than 0.1 m/s. The present comparison could enable the assessment of a friction velocity threshold, representing the limit above which the EC fluxes can be considered representative of the vegetation-atmosphere exchanges at our specific site.

  5. BOREAS TF-11 SSA-Fen Soil Surface CO2 Flux Data

    NASA Technical Reports Server (NTRS)

    Arkebauer, Timothy J.; Hall, Forrest G. (Editor); Knapp, David E. (Editor)

    2000-01-01

    The BOREAS TF-11 team gathered a variety of data to complement its tower flux measurements collected at the SSA-Fen site. These data are soil surface CO 2 flux data at the SSA-Fen site from 27- May-1994 to 23-Sep-1994 and from 13-May-1995 to 03-Oct-1995. A portable gas exchange system was used to make these measurements. The data are stored in tabular ASCII files.

  6. Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2.

    PubMed

    Körner, Christian; Asshoff, Roman; Bignucolo, Olivier; Hättenschwiler, Stephan; Keel, Sonja G; Peláez-Riedl, Susanna; Pepin, Steeve; Siegwolf, Rolf T W; Zotz, Gerhard

    2005-08-26

    Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.

  7. Warming alters food web-driven changes in the CO2 flux of experimental pond ecosystems.

    PubMed

    Atwood, T B; Hammill, E; Kratina, P; Greig, H S; Shurin, J B; Richardson, J S

    2015-12-01

    Evidence shows the important role biota play in the carbon cycle, and strategic management of plant and animal populations could enhance CO2 uptake in aquatic ecosystems. However, it is currently unknown how management-driven changes to community structure may interact with climate warming and other anthropogenic perturbations to alter CO2 fluxes. Here we showed that under ambient water temperatures, predators (three-spined stickleback) and nutrient enrichment synergistically increased primary producer biomass, resulting in increased CO2 uptake by mesocosms in early dawn. However, a 3°C increase in water temperatures counteracted positive effects of predators and nutrients, leading to reduced primary producer biomass and a switch from CO2 influx to efflux. This confounding effect of temperature demonstrates that climate scenarios must be accounted for when undertaking ecosystem management actions to increase biosequestration.

  8. Elevated CO2 reduces sap flux in mature deciduous forest trees.

    PubMed

    Cech, Patrick G; Pepin, Steeve; Körner, Christian

    2003-10-01

    We enriched in CO2 the canopy of 14 broad-leaved trees in a species-rich, ca. 30-m-tall forest in NW Switzerland to test whether elevated CO2 reduces water use in mature forest trees. Measurements of sap flux density (JS) were made prior to CO2 enrichment (summer 2000) and throughout the first whole growing season of CO2 exposure (2001) using the constant heat-flow technique. The short-term responses of sap flux to brief (1.5-3 h) interruptions of CO2 enrichment were also examined. There were no significant a priori differences in morphological and physiological traits between trees which were later exposed to elevated CO2 (n=14) and trees later used as controls (n=19). Over the entire growing season, CO2 enrichment resulted in an average 10.7% reduction in mean daily JS across all species compared to control trees. Responses were most pronounced in Carpinus, Acer, Prunus and Tilia, smaller in Quercus and close to zero in Fagus trees. The JS of treated trees significantly increased by 7% upon transient exposure to ambient CO2 concentrations at noon. Hence, responses of the different species were, in the short term, similar in magnitude to those observed over the whole season (though opposite because of the reversed treatment). The reductions in mean JS of CO2-enriched trees were high (22%) under conditions of low evaporative demand (vapour pressure deficit, VPD <5 hPa) and small (2%) when mean daily VPD was greater than 10 hPa. During a relatively dry period, the effect of elevated CO2 on JS even appeared to be reversed. These results suggest that daily water savings by CO2-enriched trees may have accumulated to a significantly improved water status by the time when control trees were short of soil moisture. Our data indicate that the magnitude of CO2 effects on stand transpiration will depend on rainfall regimes and the relative abundance of the different species, being more pronounced under humid conditions and in stands dominated by species such as Carpinus and

  9. Assessing the magnitude of CO2 flux uncertainty in atmospheric CO2 records using products from NASA's Carbon Monitoring Flux Pilot Project

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    Carbon Monitoring System Flux Pilot Project (FPP) was designed to better understand contemporary carbon fluxes by bringing together state-of-the art models with remote sensing data sets. Here we report on simulations using NASA's Goddard Earth Observing System Model, version 5 (GEOS-5) which was used to evaluate the consistency of two different sets of observationally informed land and ocean fluxes with atmospheric CO2 records. Despite the observation inputs, the average difference in annual terrestrial biosphere flux between the two land (NASA Ames Carnegie-Ames-Stanford-Approach (CASA) and CASA-Global Fire Emissions Database version 3 (GFED)) models is 1.7 Pg C for 2009-2010. Ocean models (NASA's Ocean Biogeochemical Model (NOBM) and Estimating the Circulation and Climate of the Ocean Phase II (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 Atmospheric Infrared Sounder observations. Despite large differences between land and ocean flux estimates, resulting differences in atmospheric mixing ratio were small, typically less than 5 ppm at the surface and 3 ppm 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 inherent measurement variability, regardless of the measurement platform.

  10. Estimating CO2 fluxes in the Bay Area from a dense surface network: First estimates from the Berkeley Atmospheric CO2 Observation Network (BeACON)

    NASA Astrophysics Data System (ADS)

    Turner, A. J.; Mcdonald, B. C.; Teige, V. E.; Shusterman, A.; Maness, H.; Harley, R.; Cohen, R. C.

    2014-12-01

    The paradigm in ground-based trace gas measurements has been to employ a sparse network of high-precision instruments that can be used to measure atmospheric concentrations. However, the Berkeley Atmospheric CO2 Observation Network (BeACON) project aims to provide a better understanding of the emissions and physical processes governing CO2 by deploying a high density of moderate-precision instruments. Here we present the first estimate of hourly urban carbon dioxide fluxes at 1 km spatial resolution in California's Bay Area using the BeACON network. The CO2 fluxes are estimated in a mesoscale inverse modeling framework using WRF-STILT and a custom state-of-the-science prior inventory. We also present a series of Observing System Simulation Experiments (OSSEs) with synthetic observations derived from our custom 1 km inventory that resolves fine-scale CO2 fluxes such as individual highways and attempt to retrieve them using the EDGARv4.2 and VULCAN inventories, which are too coarse to resolve individual highways. These OSSEs allow us to determine the extent to which a dense network can quantify fine-scale CO2 fluxes from sources such as traffic and provide an estimate of the information content of a dense network. This will allow us to place rigorous error bounds on the CO2 fluxes from California's Bay Area and inform future greenhouse gas measurement strategies.

  11. CO2 soil fluxes at bog and forest ecosystems in southern taiga of European Russia

    NASA Astrophysics Data System (ADS)

    Ivanov, Dmitrii; Ivanov, Aleksey; Vasenev, Ivan; Kurbatova, Juliya

    2015-04-01

    Bogs and spruce forests are typical natural ecosystems of the southern taiga of European Russia. They play an important role in carbon balance between soil and atmosphere. In the Central Forest Reserve (33°00' E, 56°30' N) for over 15 years conduct research of these processes. One of the research methods of CO2 emissions is the chamber method, which allows to analyze the local variation of the intensity of fluxes and its depending of the type of vegetation, microrelief and meteorological parameters. Period of measurements was 5 months - from June to November 2013-2014. In the bog were investigated 3 areas - pine boggy forest, as well as hummocks and hollows in the middle of bog. As the forest ecosystem was chosen paludified shallow-peat spruce forest. From the data obtained it can be concluded that in all ecosystems were observed 2 periods with a minimum values of CO2 emission: the first - in early July, associated with a high level of ground water and decrease the intensity of decomposition of organic matter, and the second - in November, associated with natural processes and seasonal cooling. The average intensity of CO2 emissions in summer-autumn season between all ecosystems varied greatly: in the boggy pine forest - 500 mgCO2/m2*h), hummocks - 550 mgCO2/m2*h, hollows - 290 mgCO2/m2*h) and paludified shallow-peat spruce forest - 750 mgCO2/m2*h. Based on these researches, it was found that the intensity of CO2 emissions significantly below in the bog than in paludified shallow-peat spruce forest because it is limited by the level of ground water. In the paludified shallow-peat spruce forest, fluxes are more depend on soil temperature and less on the groundwater level.

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

    PubMed

    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.

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

    PubMed Central

    Wang, FuShun; Wang, Yuchun; Zhang, Jing; Xu, Hai; Wei, Xiuguo

    2007-01-01

    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. PMID:17686186

  14. Potentials and challenges associated with automated closed dynamic chamber measurements of soil CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Görres, Carolyn-Monika; Kammann, Claudia; Ceulemans, Reinhart

    2015-04-01

    Soil respiration fluxes are influenced by natural factors such as climate and soil type, but also by anthropogenic activities in managed ecosystems. As a result, soil CO2 fluxes show a large intra- and interannual as well as intra- and intersite variability. Most of the available soil CO2 flux data giving insights into this variability have been measured with manually closed static chambers, but technological advances in the past 15 years have also led to an increased use of automated closed chamber systems. The great advantage of automated chambers in comparison to manually operated chambers is the higher temporal resolution of the flux data. This is especially important if we want to better understand the effects of short-term events, e.g. fertilization or heavy rainfall, on soil CO2 flux variability. However, the chamber method is an invasive measurement method which can potentially alter soil CO2 fluxes and lead to biased measurement results. In the peer-reviewed literature, many papers compare the field performance and results of different closed static chamber designs, or compare manual chambers with automated chamber systems, to identify potential biases in CO2 flux measurements, and thus help to reduce uncertainties in the flux data. However, inter-comparisons of different automated closed dynamic chamber systems are still lacking. Here we are going to present a field comparison of the most-cited automated chamber system, the LI-8100A Automated Soil Flux System, with the also commercially available Greenhouse Gas Monitoring System AGPS. Both measurement systems were installed side by side at a recently harvested poplar bioenergy plantation (POPFULL, http://uahost.uantwerpen.be/popfull/) from April 2014 until August 2014. The plantation provided optimal comparison conditions with a bare field situation after the harvest and a regrowing canopy resulting in a broad variety of microclimates. Furthermore, the plantation was planted in a double-row system with

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

    NASA Technical Reports Server (NTRS)

    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.

  16. Inclusion of CO2 fluxes in a coupled mesoscale land surface and atmospheric model

    NASA Astrophysics Data System (ADS)

    Uebel, M.; Shrestha, P.; Sulis, M.; Bott, A.

    2012-12-01

    An essential part of numerical weather prediction models is the accurate simulation of the interaction of the land surface with the lower atmosphere. Thus, a detailed knowledge of the land surface characteristics is an inevitable precondition for a successful numerical weather forecast. Here, we present a fully coupled atmospheric model system that comprehensively simulates the exchange processes between the soil, the vegetation and the atmosphere in terms of water, carbon dioxide (CO2), heat and momentum fluxes. The model system couples the Community Land Model (CLM) to the non-hydrostatic weather prediction model COSMO of the German Meteorological Service. Field measurements on the regional scale indicate distinct spatio-temporal heterogeneities of atmospheric CO2 concentrations. This variable atmospheric CO2 partial pressure induces a direct response of the stomatal resistance of the plants resulting in a modified plant transpiration. This effect has a noticeable influence on the moisture and heat fluxes at the land surface which in turn may have a strong impact on the time evolution of the atmospheric planetary boundary layer (PBL). Since the evapotranspiration of plants is strongly controlled by the atmospheric humidity and CO2 concentration, for a consistent modeling of latent and sensible heat fluxes at the land surface a detailed treatment of the exchange of CO2 between the canopy and the PBL is of particular importance. To account for these effects, as a first step we implemented CO2 in the COSMO model as a passive tracer so that the spatial and temporal variations of the atmospheric CO2 concentration as caused by advective, turbulent and convective processes can now be simulated with reasonable accuracy. In the offline version of CLM photosynthesis and plant transpiration are calculated by utilizing a constant value of the atmospheric CO2 partial pressure. In contrast to this treatment, the coupled model system COSMO-CLM considers the varying atmospheric

  17. Spatial and seasonal variability of CO2 flux at the air-water interface of the Three Gorges Reservoir.

    PubMed

    Le, Yang; Lu, Fei; Wang, Xiaoke; Duan, Xiaonan; Tong, Lei; Ouyang, Zhiyun; Li, Hepeng

    2013-11-01

    Diffusive carbon dioxide (CO2) emissions from the water surface of the Three Gorges Reservoir, currently the largest hydroelectric reservoir in the world, were measured using floating static chambers over the course of a yearlong survey. The results showed that the average annual CO2 flux was (163.3 +/- 117.4) mg CO2/(m2.hr) at the reservoir surface, which was larger than the CO2 flux in most boreal and temperate reservoirs but lower than that in tropical reservoirs. Significant spatial variations in CO2 flux were observed at four measured sites, with the largest flux measured at Wushan (221.9 mg CO2/(m2.hr)) and the smallest flux measured at Zigui (88.6 mg CO2/(m(2).hr)); these differences were probably related to the average water velocities at different sites. Seasonal variations in CO2 flux were also observed at four sites, starting to increase in January, continuously rising until peaking in the summer (June-August) and gradually decreasing thereafter. Seasonal variations in CO2 flux could reflect seasonal dynamics in pH, water velocity, and temperature. Since the spatial and temporal variations in CO2 flux were significant and dependent on multiple physical, chemical, and hydrological factors, it is suggested that long-term measurements should be made on a large spatial scale to assess the climatic influence of hydropower in China, as well as the rest of the world.

  18. Soil air and soil flux measurements of 222Radon and CO2: A soil flux parametrization at Lutjewad (NL)

    NASA Astrophysics Data System (ADS)

    Neubert, R. E. M.; Kettner, E.; Palstra, S. W. L.; Hoekman, S.; van der Graaf, E. R.

    2009-04-01

    Atmospheric 222Radon concentration measurements are used as a valuable transport tracer verifying the transport part of Carbon Cycle and Greenhouse Gas models. The production rate of the radioactive noble gas 222Radon (T1•2 = 3.8 days) by radioactive decay of 226Radium in the soil is constant, the absolute quantity depending on the local soil Radium concentration. The flux of 222Radon to the atmosphere (the soil exhalation, or effective atmospheric production rate), however, is not constant. It strongly depends on soil texture, soil humidity, precipitation and other parameters, but is nearly constant if these parameters stay unchanged. Recently, an effort has been done to predict this flux rate with widely available γ-dosimetry measurements (Szegvary et al., Predicting terrestrial 222Rn-flux using gamma dose rate as a proxy, ACP 7, 2789-2795, 2007), but real 222Radon-flux measurements are sparse. 222Radon undergoes the same transport processes on the way from soil to atmosphere as any other soil-derived (greenhouse) gas. This makes 222Radon an ideal tracer to separate variations in e.g. soil CO2-production from changes in the soil-atmosphere CO2-transport, both being reflected in the total soil-atmosphere CO2-flux. At the atmospheric measurement site Lutjewad in the north of the Netherlands (53N24'18", 6E21'13", www.rug.nl/ees/onderzoek/cio/projecten/atmosphericgases) we started in 2006 with the measurements of the soil 222Radon and CO2 concentration through soil probes as well as the Radon and CO2 soil fluxes by means of an automatic soil chamber. While there are up to eight soil air measurements per day, the soil chamber is automatically closed twice per day. The station is situated directly on the Waddensea dike at an elevation of 1 m a.s.l. on seaclay soil. The groundwater table shows variations between 0.5 m and 2 m below terrain. From our measurements we find that in the dryer summer season, from April to July, the mean 222Radon-flux can be up to 40

  19. Comparing Amazon Basin CO2 fluxes from an atmospheric inversion with TRENDY biosphere models

    NASA Astrophysics Data System (ADS)

    Diffenbaugh, N. S.; Alden, C. B.; Harper, A. B.; Ahlström, A.; Touma, D. E.; Miller, J. B.; Gatti, L. V.; Gloor, M.

    2015-12-01

    Net exchange of carbon dioxide (CO2) between the atmosphere and the terrestrial biosphere is sensitive to environmental conditions, including extreme heat and drought. Of particular importance for local and global carbon balance and climate are the expansive tracts of tropical rainforest located in the Amazon Basin. Because of the Basin's size and ecological heterogeneity, net biosphere CO2 exchange with the atmosphere remains largely un-constrained. In particular, the response of net CO2 exchange to changes in environmental conditions such as temperature and precipitation are not yet well known. However, proper representation of these relationships in biosphere models is a necessary constraint for accurately modeling future climate and climate-carbon cycle feedbacks. In an effort to compare biosphere response to climate across different biosphere models, the TRENDY model intercomparison project coordinated the simulation of CO2 fluxes between the biosphere and atmosphere, in response to historical climate forcing, by 9 different Dynamic Global Vegetation Models. We examine the TRENDY model results in the Amazon Basin, and compare this "bottom-up" method with fluxes derived from a "top-down" approach to estimating net CO2 fluxes, obtained through atmospheric inverse modeling using CO2 measurements sampled by aircraft above the basin. We compare the "bottom-up" and "top-down" fluxes in 5 sub-regions of the Amazon basin on a monthly basis for 2010-2012. Our results show important periods of agreement between some models in the TRENDY suite and atmospheric inverse model results, notably the simulation of increased biosphere CO2 loss during wet season heat in the Central Amazon. During the dry season, however, model ability to simulate observed response of net CO2 exchange to drought was varied, with few models able to reproduce the "top-down" inversion flux signals. Our results highlight the value of atmospheric trace gas observations for helping to narrow the

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

    SciTech Connect

    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

  1. Riverine GHG emissions: one year of CO2, 13CO2 and CH4 flux measurements on Vistula river in Krakow, southern Poland

    NASA Astrophysics Data System (ADS)

    Jasek, Alina; Wachniew, Przemyslaw; Zimnoch, Miroslaw

    2013-04-01

    Terrestrial surface waters are generally considered to be sources of carbon dioxide and methane, because respiration of organic matter via aerobic and anaerobic pathways causes supersaturation of surface waters with respect to CO2 and CH4, respectively. In rivers, these processes are influenced by such anthropogenic factors as changes of land-use, wastewater and alteration of river channels. The research object is Vistula, the largest Polish river. It has the length of 1047 km and annual runoff of 6.2x1010m3. The urban section of Vistula in Krakow receives large amounts of organic matter from highly urbanized catchment and point discharges of urban waste waters within the city limits. The river was sampled regularly at three points: the entrance to the city, the center and the point where Vistula leaves the agglomeration. A floating chamber coupled with Picarro G2101-i analyzer was applied to quantify CO2, 13CO2 and CH4 fluxes leaving the surface of the river. A floating chamber was equipped with sensors to measure air pressure, temperature and humidity inside the chamber and the temperature of water. The chamber was equipped with a set of floats and an anchor. The measurements started in October 2011, and were repeated with approximately monthly frequency. Physicochemical properties of water (temperature, conductivity, pH, CO2 partial pressure over the water surface and alkalinity) were also measured during each measurement campaign. In addition, at each site short-term variability of the measured fluxes was also investigated. Additionally, short-term variability of the measured fluxes of CO2, 13CO2 and CH4 were performed in all three sites. The results indicate that fluxes of CO2 released from the river are comparable with the soil emissions of this gas measured in Krakow area. The δ13CO2 signature of riverine CO2 flux allowed to identify decomposition of C3 organic matter as the major source of this gas. No distinct seasonal variability of the CO2 emission and

  2. Controls on the fore-arc CO2 flux along the Central America margin

    NASA Astrophysics Data System (ADS)

    Hilton, D. R.; Barry, P. H.; Ramirez, C. J.; Kulongoski, J. T.; Patel, B. S.; Virrueta, C.; Blackmon, K.

    2015-12-01

    The subduction of carbon to the deep mantle via subduction zones is interrupted by outputs via the fore-arc, volcanic front, and back-arc regions. Whereas output fluxes for arc and back-arc locales are well constrained for the Central America Volcanic Arc (CAVA) [1-2], the fore-arc flux via cold seeps and ground waters is poorly known. We present new He and CO2 data (isotopes and relative abundances) for the volcanic front and inner fore-arc of western Panama to complement on-going studies of fore-arc C-fluxes in Costa Rica [3-4] and to determine tectonic controls on the fore-arc C-outgassing fluxes. Helium isotope (3He/4He) values at Baru, La Yeguada, and El Valle volcanoes are high (5-8RA), consistent with results for other Central America volcanoes. However, CO2/3He values are variable (from > 1012 to < 108). Baru has an arc-like δ13C of - 4‰, whereas the other volcanoes have δ13C < -10 ‰. Cold seeps collected in the coastal fore-arc of Panama show a trend of decreasing He-isotopes from west (~6RA) to east (~1RA). This trend is mirrored by δ13C (-5‰ to <-20‰) values. CO2/3He values of the seeps are also variable and fall between 106 and 1012. Using CO2/3He-δ13C mixing plots with conventional endmember values for Limestone, Organic Sediment and Mantle CO2, we show that several Panama samples have been extensively modified by crustal processes. Nevertheless, there are clear west-to east trends (both volcanoes and coastal seeps), whereby L dominates the CO2 inventory in the west, similar to Costa Rica, and S-derived CO2 increases eastward towards central Panama. Previously [4], we limited the Costa Rica subaerial fore-arc flux to ~ 6 × 107 gCkm-1yr-1, or ~ 4% of the total incoming sedimentary C-load. This flux diminishes to zero within ~400 km to the east of Baru volcano. The transition from orthogonal subduction of the Cocos Plate to oblique subduction of the Nazca Plate, relative to the common over-riding Caribbean Plate, is the major impediment to

  3. Short-term effects of rainfall on CO2 fluxes above rangelands dominated by Artemisia, Bromus tectorum, and Agropyron

    NASA Astrophysics Data System (ADS)

    Ivans, S.; Saliendra, N. Z.; Johnson, D. A.

    2003-04-01

    The short-term effects of rainfall on carbon dioxide (CO_2) fluxes have not been well documented in rangelands of the Intermountain Region of the western USA. We used the Bowen ratio-energy balance technique to continuously measure CO_2 fluxes above three rangeland sites in Idaho and Utah dominated by: 1) Artemisia (sagebrush) near Malta, Idaho; 2) Bromus tectorum (cheatgrass) near Malta, Idaho; and 3) Agropyron (crested wheatgrass) in Rush Valley, Utah. We examined CO_2 fluxes immediately before and after rainfall during periods of 10--19 July 2001 (Summer), 8--17 October 2001 (Autumn), and 16--30 May 2002 (Spring). On sunny days before rainfall during Spring, all three sites were sinks for CO_2. After rainfall in Spring, all three sites became sources of CO_2 for about two days and after that became CO_2 sinks again. During Summer and Autumn when water was limiting, sites were small sources of CO_2 and became larger sources for one day after rainfall. In all three seasons, daytime CO_2 fluxes decreased and nighttime CO_2 fluxes increased after rainfall, suggesting that rainfall stimulated belowground respiration at all three sites. Results from this study indicated that CO_2 fluxes above rangeland sites in the Intermountain West changed markedly after rainfall, especially during Spring when fluxes were highest. KEY WORDS: Bowen ratio-energy balance, Intermountain West, rangelands, sagebrush, cheatgrass, crested wheatgrass

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The Central Russia is still one of the less GHG-investigated European areas especially in case of agroecosystem-level carbon dioxide fluxes monitoring by eddy covariance method. The eddy covariance technique is a statistical method to measure and calculate vertical turbulent fluxes within atmospheric boundary layers. The major assumption of the metod is that measurements at a point can represent an entire upwind area. Eddy covariance researches, which could be considered as repeated for the same area, are very rare. The research has been carried out on the Precision Farming Experimental Field of the Russian Timiryazev State Agricultural University (Moscow, Russia) in 2013 under the support of RF Government grant No. 11.G34.31.0079. Arable derno-podzoluvisls have around 1 The results have shown high daily and seasonal dynamic of agroecosystem CO2 emission. Sowing activates soil microbiological activity and the average soil CO2 emission and adsorption are rising at the same time. CO2 streams are intensified after crop emerging from values of 3 to 7 μmol/s-m2 for emission, and from values of 5 to 20 μmol/s-m2 for adsorption. Stabilization of the flow has come at achieving plants height of 10-12 cm. The vegetation period is characterized by high average soil CO2 emission and adsorption at the same time, but the adsorption is significantly higher. The resulted CO2 absorption during the day is approximately 2-5 times higher than emissions at night. For example, in mid-June, the absorption value was about 0.45 mol/m2 during the day-time, and the emission value was about 0.1 mol/m2 at night. After harvesting CO2 emission is becoming essentially higher than adsorption. Autumn and winter data are fluctuate around zero, but for some periods a small predominance of CO2 emissions over the absorption may be observed. The daily dynamics of CO2 emissions depends on the air temperature with the correlation coefficient changes between 0.4 and 0.8. Crop stage, agrotechnological

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

    USGS Publications Warehouse

    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 - <5 millimoles per square meter per day - during both El 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.

  6. Effects of biased CO2 flux measurements by open-path sensors on the interpretation of CO2 flux dynamics at contrasting ecosystems

    NASA Astrophysics Data System (ADS)

    Helbig, Manuel; Humphreys, Elyn; Bogoev, Ivan; Quinton, William L.; Wischnweski, Karoline; Sonnentag, Oliver

    2015-04-01

    Long-term measurements of net ecosystem exchange of CO2 (NEE) are conducted across a global network of flux tower sites. These sites are characterised by varying climatic and vegetation conditions, but also differ in the type of CO2/H2O gas analyser used to obtain NEE. Several studies have observed a systematic bias in measured NEE when comparing open-path (OP) and closed-path (CP) sensors with consistently more negative daytime NEE measurements when using OP sensors, both during the growing and non-growing season. A surface heating correction has been proposed in the literature, but seems not to be universally applicable. Systematic biases in NEE measurements are particularly problematic for synthesis papers and inter-comparison studies between sites where the 'true' NEE is small compared to the potential instrument bias. For example, NEE estimates for boreal forest sites derived from OP sensors show large, ecologically unreasonable winter CO2 uptake. To better understand the causes and the magnitude of this potential bias, we conducted a sensor inter-comparison study at the Mer Bleue peatland near Ottawa, ON, Canada. An eddy covariance system with a CP (LI7000 & GILL R3-50) and an OP sensor (EC150 & CSAT3A) was used. Measurements were made between September 2012 and January 2013 and covered late summer, fall, and winter conditions. Flux calculations were made as consistently as possible to minimise differences due to differing processing procedures (e.g. spectral corrections). The latent (LE, slope of orthogonal linear regression of LEOP on LECP: 1.02 ± 0.01 & intercept: -0.2 ± 0.6 W m-2 and sensible heat fluxes (H, slope of HCSAT3A on HGILL: 0.96 ± 0.01 & intercept: 0.1 ± 0.03 W m-2) did not show any significant bias. However, a significant bias was apparent in the NEE measurements (slope of NEEOP on NEECP: 1.36 ± 0.02 & intercept: -0.1 ± 0.05). The differences between NEEOP and NEECP were linearly related to the magnitude of HCSAT3A with a slope of -0

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

    NASA Astrophysics Data System (ADS)

    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 < 0.01) than those at penguin-lacking tundra sites (64.0-87.1 mg CO2 m-2 h-1). The gross photosynthesis (Pg) showed a consistent trend to ER with the highest mean Pg (219.7 ± 34.5 mg CO2 m-2 h-1) at penguin colony tundra sites. When all the data were combined from different types of tundra ecosystems, summertime tundra NEE showed a weak or strong positive correlation with air temperature, 0-10 cm soil temperature or precipitation. The NEE from marine animal colony and animal-lacking tundra was significantly positively correlated (P < 0.001) with soil organic carbon (SOC), total nitrogen (TN) contents and C:N ratios. The ER showed a significant exponential correlation (P < 0.01) with mean 0-15 cm soil temperature, and much higher Q10 value (9.97) was obtained compared with other terrestrial ecosystems, indicating greater temperature sensitivity of tundra ecosystem respiration. Our results indicate that marine 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.

  8. Global representation of tropical cyclone-induced ocean thermal changes using Argo data - Part 2: Estimating air-sea heat fluxes and ocean heat content changes

    NASA Astrophysics Data System (ADS)

    Cheng, L.; Zhu, J.; Sriver, R. L.

    2014-12-01

    We use Argo temperature data to examine changes in ocean heat content (OHC) and air-sea heat fluxes induced by tropical cyclones (TC)s on a global scale. A footprint technique that analyzes the vertical structure of cross-track thermal responses along all storm tracks during the period 2004-2012 is utilized (see part I). We find that TCs are responsible for 1.87 PW (11.05 W m-2 when averaging over the global ocean basin) of heat transfer annually from the global ocean to the atmosphere during storm passage (0-3 days) on a global scale. Of this total, 1.05 ± 0.20 PW (4.80 ± 0.85 W m-2) is caused by Tropical storms/Tropical depressions (TS/TD) and 0.82 ± 0.21 PW (6.25 ± 1.5 W m-2) is caused by hurricanes. Our findings indicate that ocean heat loss by TCs may be a substantial missing piece of the global ocean heat budget. Net changes in OHC after storm passage is estimated by analyzing the temperature anomalies during wake recovery following storm events (4-20 days after storm passage) relative to pre-storm conditions. Results indicate the global ocean experiences a 0.75 ± 0.25 PW (5.98 ± 2.1W m-2) net heat gain annually for hurricanes. In contrast, under TS/TD conditions, ocean experiences 0.41 ± 0.21 PW (1.90 ± 0.96 W m-2) net ocean heat loss, suggesting the overall oceanic thermal response is particularly sensitive to the intensity of the event. The net ocean heat uptake caused by all storms is 0.34 PW.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  12. Comparing inversion techniques for constraining CO2 fluxes in the Brazilian Amazon Basin with aircraft observations

    NASA Astrophysics Data System (ADS)

    Chow, V. Y.; Gerbig, C.; Longo, M.; Koch, F.; Nehrkorn, T.; Eluszkiewicz, J.; Ceballos, J. C.; Longo, K.; Wofsy, S. C.

    2012-12-01

    The Balanço Atmosférico Regional de Carbono na Amazônia (BARCA) aircraft program spanned the dry to wet and wet to dry transition seasons in November 2008 & May 2009 respectively. It resulted in ~150 vertical profiles covering the Brazilian Amazon Basin (BAB). With the data we attempt to estimate a carbon budget for the BAB, to determine if regional aircraft experiments can provide strong constraints for a budget, and to compare inversion frameworks when optimizing flux estimates. We use a LPDM to integrate satellite-, aircraft-, & surface-data with mesoscale meteorological fields to link bottom-up and top-down models to provide constraints and error bounds for regional fluxes. The Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by meteorological fields from BRAMS, ECMWF, and WRF are coupled to a biosphere model, the Vegetation Photosynthesis Respiration Model (VPRM), to determine regional CO2 fluxes for the BAB. The VPRM is a prognostic biosphere model driven by MODIS 8-day EVI and LSWI indices along with shortwave radiation and temperature from tower measurements and mesoscale meteorological data. VPRM parameters are tuned using eddy flux tower data from the Large-Scale Biosphere Atmosphere experiment. VPRM computes hourly CO2 fluxes by calculating Gross Ecosystem Exchange (GEE) and Respiration (R) for 8 different vegetation types. The VPRM fluxes are scaled up to the BAB by using time-averaged drivers (shortwave radiation & temperature) from high-temporal resolution runs of BRAMS, ECMWF, and WRF and vegetation maps from SYNMAP and IGBP2007. Shortwave radiation from each mesoscale model is validated using surface data and output from GL 1.2, a global radiation model based on GOES 8 visible imagery. The vegetation maps are updated to 2008 and 2009 using landuse scenarios modeled by Sim Amazonia 2 and Sim Brazil. A priori fluxes modeled by STILT-VPRM are optimized using data from BARCA, eddy covariance sites, and flask measurements. The

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

    NASA Astrophysics Data System (ADS)

    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

  14. Evaluation of Diagnostic CO2 Flux and Transport Modeling in NU-WRF and GEOS-5

    NASA Astrophysics Data System (ADS)

    Kawa, S. R.; Collatz, G. J.; Tao, Z.; Wang, J. S.; Ott, L. E.; Liu, Y.; Andrews, A. E.; Sweeney, C.

    2015-12-01

    We report on recent diagnostic (constrained by observations) model simulations of atmospheric CO2 flux and transport using a newly developed facility in the NASA Unified-Weather Research and Forecast (NU-WRF) model. The results are compared to CO2 data (ground-based, airborne, and GOSAT) and to corresponding simulations from a global model that uses meteorology from the NASA GEOS-5 Modern Era Retrospective analysis for Research and Applications (MERRA). The objective of these intercomparisons is to assess the relative strengths and weaknesses of the respective models in pursuit of an overall carbon process improvement at both regional and global scales. Our guiding hypothesis is that the finer resolution and improved land surface representation in NU-WRF will lead to better comparisons with CO2 data than those using global MERRA, which will, in turn, inform process model development in global prognostic models. Initial intercomparison results, however, have generally been mixed: NU-WRF is better at some sites and times but not uniformly. We are examining the model transport processes in detail to diagnose differences in the CO2 behavior. These comparisons are done in the context of a long history of simulations from the Parameterized Chemistry and Transport Model, based on GEOS-5 meteorology and Carnegie Ames-Stanford Approach-Global Fire Emissions Database (CASA-GFED) fluxes, that capture much of the CO2 variation from synoptic to seasonal to global scales. We have run the NU-WRF model using unconstrained, internally generated meteorology within the North American domain, and with meteorological 'nudging' from Global Forecast System and North American Regional Reanalysis (NARR) in an effort to optimize the CO2 simulations. Output results constrained by NARR show the best comparisons to data. Discrepancies, of course, may arise either from flux or transport errors and compensating errors are possible. Resolving their interplay is also important to using the data in

  15. High CO2 emissions through porous media: Transport mechanisms and implications for flux measurement and fractionation

    USGS Publications Warehouse

    Evans, William C.; Sorey, M.L.; Kennedy, B.M.; Stonestrom, D.A.; Rogie, J.D.; Shuster, D.L.

    2001-01-01

    Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one to three orders of magnitude higher than normally encountered in soil respiration studies, a test system was constructed in the laboratory where known fluxes could be maintained through dry sand. Steady-state gas concentration profiles and fractionation effects observed in the 30-cm sand column nearly match those predicted by the Stefan-Maxwell equations, indicating that the test system was functioning successfully as a uniform porous medium. Eight groups of investigators tested their accumulation chamber equipment, all configured with continuous infrared gas analyzers (IRGA), in this system. Over a flux range of ~ 200-12,000 g m-2 day-1, 90% of their 203 flux measurements were 0-25% lower than the imposed flux with a mean difference of - 12.5%. Although this difference would seem to be within the range of acceptability for many geologic investigations, some potential sources for larger errors were discovered. A steady-state pressure gradient of -20 Pa/m was measured in the sand column at a flux of 11,200 g m-2 day-1. The derived permeability (50 darcies) was used in the dusty-gas model (DGM) of transport to quantify various diffusive and viscous flux components. These calculations were used to demonstrate that accumulation chambers, in addition to reducing the underlying diffusive gradient, severely disrupt the steady-state pressure gradient. The resultant diversion of the net gas flow is probably responsible for the systematically low flux measurements. It was also shown that the fractionating effects of a viscous CO2 efflux against a diffusive influx of air will have a major impact on some important geochemical indicators, such as N2/Ar, ??15N-N2, and 4He/22

  16. The relationship between ocean surface turbulence and air-sea gas transfer velocity: An in-situ evaluation

    NASA Astrophysics Data System (ADS)

    Esters, L.; Landwehr, S.; Sutherland, G.; Bell, T. G.; Saltzman, E. S.; Christensen, K. H.; Miller, S. D.; Ward, B.

    2016-05-01

    Although the air-sea gas transfer velocity k is usually parameterized with wind speed, the so-called small-eddy model suggests a relationship between k and ocean surface dissipation of turbulent kinetic energy ɛ. Laboratory and field measurements of k and ɛ have shown that this model holds in various ecosystems. Here, field observations are presented supporting the theoretical model in the open ocean. These observations are based on measurements from the Air-Sea Interaction Profiler and eddy covariance CO2 and DMS air-sea flux data collected during the Knorr11 cruise. We show that the model results can be improved when applying a variable Schmidt number exponent compared to a commonly used constant value of 1/2. Scaling ɛ to the viscous sublayer allows us to investigate the model at different depths and to expand its applicability for more extensive data sets.

  17. CO2 flux monitoring using Continuous Timeseries-Forced Diffusion (CT-FD): Development, Validation

    NASA Astrophysics Data System (ADS)

    McArthur, G. S.; Risk, D. A.; Nickerson, N. R.; Creelman, C. A.; Beltrami, H.

    2009-12-01

    Land-based CO2 flux measurements are a key indicator of the biological, chemical and physical processes occurring in the soil. While highly dense temporal flux measurements can be acquired using Eddy Covariance towers, or flux chambers, the challenge of gathering data that is rich both temporally and spatially persists. Over the past two years we have developed a new technique for measuring soil CO2 fluxes, called continuous timeseries-forced diffusion (CT-FD) attempts to satisfy the need for spatially and temporally rich data. The CT-FD probe consists of a Vaisala CO2 sensor, embodied in a PVC casing, with tear/UV resistant Tyvek membranes at both the inlet and outlet. The probe delivers continuous flux data and can be inexpensively replicated across the landscape.The CT-FD technique works by forcing a known diffusive regime between the soil and the atmosphere, allowing the calculation of fluxes across the soil/atmosphere boundary to be made from; the internal concentration of a CT-FD probe placed at the soil surface; and a common reference probe designed to capture the atmospheric CO2. For every concentration measurement, the difference between the probe and the reference concentration is indicative of a unique flux value. Here we examine properties of the instrument and method, as documented by a long series of developmental studies involving numerical gas transport modeling, laboratory and field experiments. A suite of 1D and 3D modeling experiments were needed to optimize embodiment and geometries of the probe. These show that the probe should have a relatively long collar, with relatively high diffusivity made possible by having large, highly diffusive membranes, both of which help to induce 1D movement of gases into the probe and reduce the lateral diffusion around the probe. Modeling also shows that correction for lateral diffusion is feasible. As for error, sensor error transfers linearly to errors in the flux, and that the sensor can be used in non free

  18. [Variation characteristics of CO2 flux in Phyllostachys edulis forest ecosystem in subtropical region of China].

    PubMed

    Sun, Cheng; Jiang, Hong; Zhou, Guo-Mo; Yang, Shuang; Chen, Yun-Fei

    2013-10-01

    By using eddy covariance technique, this paper studied the CO2 flux in a Phyllostachys edulis forest ecosystem with high-efficiency management in Zhejiang Province of China from December, 2010 to November, 2011, and analyzed the variations of net ecosystem exchange (NEE), ecosystem respiration (RE), and gross ecosystem exchange (GEE). During the study period, the monthly NEE was always negative, with the maximum (-99.33 g C x m(-2)) in July and the minimum (-23.49 g C x m(-2)) in November, and the seasonal change showed a bimodal shape. The average diurnal change of the monthly CO2 flux varied greatly from -0.30 g CO2 x m(-2) x s(-1) (January) to -0.60 g CO2 x m(-2) x s(-1) (September). The NEE at the time point of positive and negative conversion had obvious seasonal characteristics. The yearly RE changed in unimodal shape, with the maximum in summer and the minimum in winter. The RE at nighttime had significant negative correlation with soil temperature. The yearly NEE, RE, and GEE were -668.40, 932.55, and -1600.95 g C x m(-2) x a(-1), respectively, among which, the NEE occupied 41.8% of the GEE. As compared with other ecosystems, P. edulis forest ecosystem had a strong capability in carbon sequestration. PMID:24483062

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

    NASA Astrophysics Data System (ADS)

    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.

  20. In-situ, high spatio-temporal resolution measurements of CO2 flux and isotopic composition on Mammoth Mountain, CA

    NASA Astrophysics Data System (ADS)

    Lewicki, J. L.; Hilley, G. E.; Marino, B.; Bergfeld, D.; Fischer, M. L.; Hancyk, J.; Xu, L.

    2010-12-01

    Measurement of CO2 emissions from volcano flanks and in ground waters has become an integral part of many monitoring programs, as spatial and temporal variations in these emissions may be indicative of volcanic unrest. The source and magnitude of CO2 emissions have been intensely studied at Mammoth Mountain, a dacitic volcano located on the rim of Long Valley caldera, California. These observations, combined with multiple geophysical data sets, suggest that unrest at Mammoth Mountain is driven by periodic release of CO2-rich magmatic fluid derived from basaltic dikes and sills at mid-crustal depths. While measurements of CO2 flux and determination of CO2 sources at volcanoes can place important constraints on gas transport and its relationship to volcanic activity, the spatio-temporal resolution of these measurements has been limited by the time and cost associated with making “point” CO2 flux measurements using the accumulation chamber (AC) method and sample collection and analysis of isotopic (14C-CO2 and 13C-CO2) compositions. We present a novel instrument platform for real-time monitoring of spatio-temporal distribution, emission rate and source of CO2 in volcanic systems. Time and space averaged CO2 fluxes are measured every half hour by the eddy covariance (EC) method. Least-squares inversions of EC data and modeled footprint functions provide estimates of CO2 emission rate and surface flux spatial distribution. AC measurements of soil CO2 flux yield detailed maps of flux spatial distribution and comparative emission rate estimates. A new field-portable isotopic analyzer provides, for the first time, in-situ, high frequency measurements of 14C and 13C compositions of CO2 in the atmosphere, soil gas, and dissolved in ground water. We tested the CO2 flux-monitoring component of this platform at the Horseshoe Lake tree kill area on Mammoth Mountain from 8 September to 24 October 2006. EC CO2 fluxes ranged from 218 to 3500 g m-2d-1. Maps of surface CO2 flux

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Impact of elevated CO2, water table, and temperature changes on CO2 and CH4 fluxes from arctic tundra soils

    NASA Astrophysics Data System (ADS)

    Zona, Donatella; Haynes, Katherine; Deutschman, Douglas; Bryant, Emma; McEwing, Katherine; Davidson, Scott; Oechel, Walter

    2015-04-01

    Large uncertainties still exist on the response of tundra C emissions to future climate due, in part, to the lack of understanding of the interactive effects of potentially controlling variables on C emissions from Arctic ecosystems. In this study we subjected 48 soil cores (without active vegetation) from dominant arctic wetland vegetation types, to a laboratory manipulation of elevated atmospheric CO2, elevated temperature, and altered water table, representing current and future conditions in the Arctic for two growing seasons. To our knowledge this experiment comprised the most extensively replicated manipulation of intact soil cores in the Arctic. The hydrological status of the soil was the most dominant control on both soil CO2 and CH4 emissions. Despite higher soil CO2 emission occurring in the drier plots, substantial CO2 respiration occurred under flooded conditions, suggesting significant anaerobic respirations in these arctic tundra ecosystems. Importantly, a critical control on soil CO2 and CH4 fluxes was the original vascular plant cover. The dissolved organic carbon (DOC) concentration was correlated with cumulative CH4 emissions but not with cumulative CO2 suggesting C quality influenced CH4 production but not soil CO2 emissions. An interactive effect between increased temperature and elevated CO2 on soil CO2 emissions suggested a potential shift of the soils microbial community towards more efficient soil organic matter degraders with warming and elevated CO2. Methane emissions did not decrease over the course of the experiment, even with no input from vegetation. This result indicated that CH4 emissions are not carbon limited in these C rich soils. Overall CH4 emissions represented about 49% of the sum of total C (C-CO2 + C-CH4) emission in the wet treatments, and 15% in the dry treatments, representing a dominant component of the overall C balance from arctic soils.

  3. BOREAS TGB-1 NSA CH4 and CO2 Chamber Flux Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Crill, Patrick; Varner, Ruth K.

    2000-01-01

    The BOREAS TGB-1 team made methane (CH4) and carbon dioxide (CO2) dark chamber flux measurements at the NSA-OJP, NSA-OBS, NSA-BP, and NSA-YJP sites from 16-May-1994 through 13-Sep-1994. Gas samples were extracted approximately every 7 days from dark chambers and analyzed at the NSA lab facility. The data are provided in tabular ASCII files.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Short-term eddy-covariance measurements of CO2 fluxes at Itaipu Lake, Brazil

    NASA Astrophysics Data System (ADS)

    Dias, N. L.; Crivellaro, B. L.; Armani, F. S.; Chor, T. L.; Gobbi, M. F.; Santos, A. L.; Lemma/UFPR Scientific Team

    2013-05-01

    We describe a 5-day campaign of eddy-covariance measurements at Itaipu Lake, in Southern Brazil and estimates of CO2 fluxes over crops in the same region with a SVAT model. Itaipu Lake was formed from the damming of Paraná River at the border between Brazil and Paraguay close to Foz do Iguaçu (BR) and Ciudad del Leste (PY); Itaipu dam is jointly operated by both countries. The measurements were made on the Brazilian side, at a very small island (Lat: -25o 03'25.72" Long -54o 24'33.67" : Altitude: 220 m ASL) located approximately 420 m away from the left (Brazilian) bank. The fetch to the ragged countour of the lake is rather large in the North-South direction: 2891 m to the North, and 1817 m to the South. Eddy covariance instrumentation mounted on a short tower consisted of a Li-Cor LI7500 open-path gas analyzer measuring CO2 and H2O concentrations; 4 Campbell FW3 fine-wire thermocouples and a Campbell CSAT-3 three-dimensional sonic anemometer, and were made at 3.76 m above the tower base, which remained at 2.8 m above the water level during the campaign. Mean concentrations of CO2 with Vaisala GM343 sensors were made at the tower, at 1.77 and 3.66 m above the tower base. The sensors were intercompared before the field experiment. The measurements reported here took place from 00:00 hrs Local Time of Dec 8th 2012 to 00:00 hrs of Dec 13 8th 2012. During most of the time there was fair weather, and the wind came predominantly from the North or North-East, with very favorable fetches. Standard data processing included coordinate rotation, linear detrending, despiking and density corrections. Peak positive and negative CO2 fluxes were -0.016 and +0.013 mmol/m2/s, respectively, with a mean value over the 5-day period of -0.14 mmol/m2/s. This may be compared to CO2 flux estimates using a SVAT model over soy, which yielded peak daytime values of 0.027 mmol/m2/s. These values should be interpreted as local both in time and space (i.e. neither representative of the whole

  7. Artificial drainage and associated carbon fluxes (CO2/CH4) in a tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Merbold, Lutz; Kutsch, Werner Leo; Corradi, Chiara; Kolle, Olaf; Rebmann, Corinna; Stoy, Paul C.; Zimov, Sergej A.; Schulze, Ernst-Detlef

    2010-05-01

    Ecosystem flux measurements using the eddy covariance (EC) technique were undertaken in 4 subsequent years during summer for a total of 562 days in an arctic wet tundra ecosystem, located near Cherskii, Far-Eastern Federal District, Russia. Methane (CH4) emissions were measured using permanent chambers. The experimental field is characterized by late thawing of permafrost soils in June and periodic spring floods. A stagnant water table below the grass canopy is fed by melting of the active layer of permafrost and by flood water. Following 3 years of EC measurements, the site was drained by building a 3m wide drainage channel surrounding the EC tower to examine possible future effects of global change on the tundra tussock ecosystem. Cumulative summertime net carbon fluxes before experimental alteration were estimated to be about +115 gCm-2 (i.e. an ecosystem C loss) and +18 gCm-2 after draining the study site. When taking CH4 as another important greenhouse gas into account and considering the global warming potential (GWP) of CH4 vs. CO2, the ecosystem had a positive GWP during all summers. However CH4 emissions after drainage decreased significantly and therefore the carbon related greenhouse gas flux was much smaller than beforehand (475 ± 253 gC-CO2-em-2 before drainage in 2003 vs. 23 ± 26 g C-CO2-em-2 after drainage in 2005).

  8. How General is the Current Photosynthate Controls on the soil CO2 Flux Paradigm?

    NASA Astrophysics Data System (ADS)

    Mortazavi, B.; O'Brien, J.; Mitchell, R.

    2008-12-01

    A variety of methods including girdling experiments and isotope labeling approaches have provided some evidence for a tight link between current C assimilation and soil CO2 flux. The results of these investigations have lead to the conclusion that autotrophs control soil CO2 flux. If the results from these investigations are general then our understanding of patterns and regulation of below ground C dynamics and the means by which ecosystem controls are studied and modeled must be reconsidered. While evidence for a coupling between current photosynthate and soil carbon dynamics has been conspicuous, data that may challenge this relationship have not been thoroughly considered. Results from foliar scorching treatments in longleaf pine (Pinus palustris) ecosystem that removed 95% of the foliage demonstrate that (i) mycorrhizal fungi production was not significantly reduced as a result of scorching, (ii) root mortality was not significantly affected because of disturbance of the carbon source, and (iii) total root non-structural carbohydrates were not significantly reduced after scorching. These results together with findings from other regions suggest that in some systems soil CO2 fluxes are less tightly linked to variations in C assimilation because stored C acts as a buffer. This stored C is a critical resource for rebuilding damaged foliage in many frequently burned ecosystems. We propose that plant adaptations to disturbance and recovery from disturbance may explain why some systems may be buffered from variation in C source strength and the link between above and belowground carbon dynamics is more diffuse.

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

    USGS Publications Warehouse

    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.

  10. Interannual variability of the regional CO2 and CH4 fluxes estimated with GOSAT observations

    NASA Astrophysics Data System (ADS)

    Maksyutov, Shamil; Takagi, Hiroshi; Kim, Heon-Sook; Saito, Makoto; Mabuchi, Kazuo; Matsunaga, Tsuneo; Ito, Akihiko; Belikov, Dmitry; Oda, Tomohiro; Valsala, Vinu; Morino, Isamu; Yoshida, Yukio; Yokota, Tatsuya

    2014-05-01

    GOSAT Level 4 products - monthly regional surface flux estimates by inverse modeling from CO2 and CH4 GOSAT column-averaged mixing ratios and ground-based observational data using a global atmospheric transport model - have been updated recently to cover the 2-year period starting June 2009. This temporal extension provides look at the interannual flux variability including events of CO2 and CH4 emissions from a large-scale climate anomaly and resultant forest fires in Russia in 2010. Higher emissions of CO2 and CH4 in western Russia in the summer of 2010 are estimated when GOSAT observations are also included in the inverse modeling compared to just using ground-based data. The estimated summer emissions in 2010 are also higher than in the same season of the adjacent years. GOSAT compliments the ground-based networks by observing the concentration response to emissions closer to fire locations, resulting in the inverse models identifying emission regions more accurately. Elsewhere, GOSAT-aided flux estimates point to higher CH4 emissions (compared to ground-based only estimates) in the remote sub-tropical regions of the South America, Africa and South-East Asia. Higher emissions over South America can be attributed to biomass burning and anthropogenic sources, while in South-East Asia those are likely to be caused by agriculture and natural ecosystems.

  11. Seasonal Variations in CO2 Fluxes in Fluvial Systems in Southstern of Amazonia (acre, Brazil)

    NASA Astrophysics Data System (ADS)

    Sousa, E.; Krusche, A. V.; Salimon, C. I.; Victoria, R. L.; Sawakuchi, H.

    2012-12-01

    Our main objective was to measure the CO2 fluxes in 5 (five) rivers and 2 (two) streams in the Purus Basin. These rivers and streams have different size, water chemical characteristics and type soil, despite all are classified as white-water rivers. We toke measures of pH, electrical conductivity, pCO2, DOC and DIC concentrations and CO2 fluxes in two seasonal periods: Wet Season (dez2010-abr2011 and dez2011-abr2012) and Dry Season (jul2011-set2011). Water samples were taken to DOC (filtered with quartz filters and preserved with hydrochloric acid), DIC (filtered with cellulose acetate filters and preserved with thymol) and δ13C of DIC. These water samples were sent to CENA/USP to be analyzed. EC and pH measurements were made with portable meters. Partial pressure of CO2 (pCO2) was measure with an equilibrator and CO2 fluxes with a floating chamber. Precipitation, water stage and discharge data was obtained by UFAC climatological station and ANA (National Water Agency). Statistical analysis were made using R Program. DOC and DIC concentrations presented significant differences between the periods. In the wet season were observed the highest values to DOC concentrations in all rivers and streams. In the rivers, these concentrations varied between 7.09±3.10 (Acre River) and 9.32±2.31 mg.L-1 (Rôla River). In the dry season, the values observed were 3.15±1.11 (Acre River) and 7.96±0.11 (Caeté River). In the streams, these concentrations also higher in the wet season, with 1.68±0.32 mg.L-1 in the Floresta stream and 3.22±1.08 mg.L-1 in the Escondido stream. To DIC concentrations, this pattern was inverted, with higher concentrations observed in the dry season. Iaco River presented the higher concentration (50.8±4.7 mg.L-1) and Acre River the lower concentration (11.30±2.77 mg.L-1). Despite the DIC concentrations were higher in the dry season, the pCO2 and CO2 fluxes values were higher in the wet season. In the rivers, the pCO2 values varied between 4,189±1

  12. Environmental controls of temporal and spatial variability in CO2 and CH4 fluxes in a neotropical peatland.

    PubMed

    Wright, Emma L; Black, Colin R; Turner, Benjamin L; Sjögersten, Sofie

    2013-12-01

    Tropical peatlands play an important role in the global storage and cycling of carbon (C) but information on carbon dioxide (CO2) and methane (CH4) fluxes from these systems is sparse, particularly in the Neotropics. We quantified short and long-term temporal and small scale spatial variation in CO2 and CH4 fluxes from three contrasting vegetation communities in a domed ombrotrophic peatland in Panama. There was significant variation in CO2 fluxes among vegetation communities in the order Campnosperma panamensis > Raphia taedigera > Cyperus. There was no consistent variation among sites and no discernible seasonal pattern of CH4 flux despite the considerable range of values recorded (e.g. -1.0 to 12.6 mg m(-2) h(-1) in 2007). CO2 fluxes varied seasonally in 2007, being greatest in drier periods (300-400 mg m(-2) h(-1)) and lowest during the wet period (60-132 mg m(-2) h(-1)) while very high emissions were found during the 2009 wet period, suggesting that peak CO2 fluxes may occur following both low and high rainfall. In contrast, only weak relationships between CH4 flux and rainfall (positive at the C. panamensis site) and solar radiation (negative at the C. panamensis and Cyperus sites) was found. CO2 fluxes showed a diurnal pattern across sites and at the Cyperus sp. site CO2 and CH4 fluxes were positively correlated. The amount of dissolved carbon and nutrients were strong predictors of small scale within-site variability in gas release but the effect was site-specific. We conclude that (i) temporal variability in CO2 was greater than variation among vegetation communities; (ii) rainfall may be a good predictor of CO2 emissions from tropical peatlands but temporal variation in CH4 does not follow seasonal rainfall patterns; and (iii) diurnal variation in CO2 fluxes across different vegetation communities can be described by a Fourier model. PMID:23873747

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

    NASA Astrophysics Data System (ADS)

    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

  14. Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua

    USGS Publications Warehouse

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

    2005-01-01

    We present a comparative study of soil CO2 flux (FCO2) measured by five groups (Groups 1-5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1-5 measured (FCO2) using the accumulation chamber method at 5-m spacing within a 900 m2 grid during a morning (AM) period. These measurements were repeated by Groups 1-3 during an afternoon (PM) period. Measured (FCO2 ranged from 218 to 14,719 g m-2 day-1. The variability of the five measurements made at each grid point ranged from ??5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO2 emission rate estimates varied between groups by only ??22%. All three groups that made PM measurements reported an 8-19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO2 emission rate of one data set and to map the spatial FCO2 distribution, 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. While the total CO2 emission rates estimated using the different techniques only varied by ??4.4%, the FCO2 maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of FCO2, but a variety of geostatistical methods are appropriate to estimate the total CO2 emission rate from a study area, which is a primary goal in volcano monitoring research. ?? Springer-Verlag 2005.

  15. Sensitivity of Flux Accuracy to Setup of Fossil Fuel and Biogenic CO2 Inverse System in an Urban Environment

    NASA Astrophysics Data System (ADS)

    Wu, K.; Lauvaux, T.; Deng, A.; Lopez-Coto, I.; Gurney, K. R.; Patarasuk, R.; Turnbull, J. C.; Davis, K. J.

    2015-12-01

    The Indianapolis Flux Experiment (INFLUX) aims to utilize a variety of measurements and a high resolution inversion system to estimate the spatial distribution and the temporal variation of anthropogenic greenhouse gas (GHG) emissions from the city of Indianapolis. We separated biogenic and fossil fuel CO2 fluxes and tested the sensitivity of inverse flux estimates to inverse system configurations by performing Observing System Simulation Experiments (OSSEs). The a priori CO2 emissions from Hestia were aggregated to 1 km resolution to represent emissions from the Indianapolis metropolitan area and its surroundings. With the Weather Research and Forecasting (WRF) model coupled to a Lagrangian Particle Dispersion Model (LPDM), the physical relations between concentrations at the tower locations and emissions at the surface were simulated at 1 km spatial resolution, hourly. Within a Bayesian synthesis inversion framework, we tested the effect of multiple parameters on our ability to infer fossil fuel CO2 fluxes: the presence of biogenic CO2 fluxes in the optimization procedure, the use of fossil fuel CO2 concentration measurements, the impact of reduced transport errors, the sensitivity to observation density, and the spatio-temporal properties of prior errors. The results indicate that the presence of biogenic CO2 fluxes obviously weakens the ability to invert for the fossil fuel CO2 emissions in an urban environment, but having relatively accurate fossil fuel CO2 concentration measurements can effectively compensate the interference from the biogenic flux component. Reduced transport error and more intensive measurement networks are two possible approaches to retrieve the spatial pattern of the fluxes and decrease the bias in inferred whole-city fossil fuel CO2 emissions. The accuracy of posterior fluxes is very sensitive to the spatial correlation length in the prior flux errors which, if they exist, can enhance significantly our ability to recover the known fluxes

  16. Application of the flux noise reducing filter for CO2 inverse modelling

    NASA Astrophysics Data System (ADS)

    Maksyutov, Shamil; Yaremchuk, Alexey

    2010-05-01

    Recent atmospheric remote sensing products from AIRS and GOSAT provide large volume of the observations but with larger errors and variance as compared to in-situ measurements, so efficient noise reduction techniques are required for inverse modeling of the surface fluxes. Inverse models of the atmospheric transport optimize regional or grid resolving surface CO2 fluxes to fit transport model simulation optimally to the observations. The optimization problem appears to be ill-posed so it is usually solved by applying regularization techniques. Most widely used regularization methods apply constraints on flux deviation from prior and/or from adjacent regions of same surface type (land-ocean, vegetation type), and from adjacent time periods. Convenient method for solving the problem of limited dimension is based on singular value decomposition (SVD) of the transport matrix, because it can decompose the solution space into a combination of the independent singular vectors. Introducing a simple constraint on fluxes limits amplitude of the corresponding singular vectors with larger reduction for smaller singular values. However this amplitude reduction is not sufficient in practice for inverse modeling of the regional CO2 fluxes, when we have large underconstrained regions in tropics. Alternatively other means of the amplitude reduction are also used, such as truncation, when all amplitudes below threshold singular value are set to zero. We apply a filter which is less abrupt is less abrupt compared to truncation but still suppressing strongly small singular value related vectors. Setting strength of a constraint is often done empirically. To decide a proper value of the cut-off singular value we suggest analyzing a dependence of the singular vector amplitude vs the singular value and set the cut-off value aiming at retaining most of useful information from observation. A graphical tool based on a plot of amplitude spectra is proposed. Advantage of the technique is

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

    SciTech Connect

    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.

  18. Nitrous oxide and methane in Atlantic and Mediterranean waters in the Strait of Gibraltar: Air-sea fluxes and inter-basin exchange

    NASA Astrophysics Data System (ADS)

    de la Paz, M.; Huertas, I. E.; Flecha, S.; Ríos, A. F.; Pérez, F. F.

    2015-11-01

    The global ocean plays an important role in the overall budget of nitrous oxide (N2O) and methane (CH4), as both gases are produced within the ocean and released to the atmosphere. However, for large parts of the open and coastal oceans there is little or no spatial data coverage for N2O and CH4. Hence, a better assessment of marine emissions estimates is necessary. As a contribution to remedying the scarcity of data on marine regions, N2O and CH4 concentrations have been determined in the Strait of Gibraltar at the ocean Fixed Time series (GIFT). During six cruises performed between July 2011 and November 2014 samples were collected at the surface and various depths in the water column, and subsequently measured using gas chromatography. From this we were able to quantify the temporal variability of the gas air-sea exchange in the area and examine the vertical distribution of N2O and CH4 in Atlantic and Mediterranean waters. Results show that surface Atlantic waters are nearly in equilibrium with the atmosphere whereas deeper Mediterranean waters are oversaturated in N2O, and a gradient that gradually increases with depth was detected in the water column. Temperature was found to be the main factor responsible for the seasonal variability of N2O in the surface layer. Furthermore, although CH4 levels did not reveal any feature clearly associated with the circulation of water masses, vertical distributions showed that higher concentrations are generally observed in the Atlantic layer, and that the deeper Mediterranean waters are considerably undersaturated (by up to 50%). Even though surface waters act as a source of atmospheric N2O during certain periods, on an annual basis the net N2O flux in the Strait of Gibraltar is only 0.35 ± 0.27 μmol m-2 d-1, meaning that these waters are almost in a neutral status with respect to the atmosphere. Seasonally, the region behaves as a slight sink for atmospheric CH4 in winter and as a source in spring and fall. Approximating

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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

  1. Post processing of CO2 flux measurements from an urban landscape

    NASA Astrophysics Data System (ADS)

    Menzer, O.; Meiring, W.; Kyriakidis, P. C.; McFadden, J. P.

    2013-12-01

    Tower based measurements of CO2 fluxes by the eddy covariance method are subject to random error, systematic error, and missing data (gaps). In homogeneous ecosystems such as forests and grasslands, the post processing methods to address these problems are relatively well established. In the urban environment, however, the assumptions of most such methods are violated due to spatial heterogeneity in the tower footprint and localized CO2 sources such as traffic emission. For this reason, work is needed to develop and test methods appropriate to the urban setting. Here, we report comparisons of post processing methods for >3 years of flux measurements from the KUOM tall tower in a suburban neighborhood of Minneapolis, Minnesota, USA. Machine learning regression approaches including Artificial Neural Networks and Gaussian Processes were used to integrate observations from remote sensing, traffic and weather stations, and to extract complex underlying functional relationships, in order to improve gap-filling and minimize uncertainties. Specifically, we tested the sensitivity of the measurements to vehicle emissions by incorporating traffic counts from nearby roads and highways. Also, the selection of the friction velocity (u*) threshold was found to be sensitive to the wind direction but consistent between years. We calculated carbon flux sums for both residential and recreational land use types in the tower footprint, and assessed the random and systematic uncertainties caused by gap-filling and u*-filtering. While these post processing methods are essential for interpreting CO2 flux measurements in urban environments, they may also be useful for other inhomogeneous sites such as logged forests or ecosystems under disturbance from fire or pests.

  2. [Effects of biological soil crust at different succession stages in hilly region of Loess Plateau on soil CO2 flux].

    PubMed

    Wang, Ai-Guo; Zhao, Yun-Ge; Xu, Ming-Xiang; Yang, Li-Na; Ming, Jiao

    2013-03-01

    Biological soil crust (biocrust) is a compact complex layer of soil, which has photosynthetic activity and is one of the factors affecting the CO2flux of soil-atmosphere interface. In this paper, the soil CO, flux under the effects of biocrust at different succession stages on the re-vegetated grassland in the hilly region of Loess Plateau was measured by a modified LI-8100 automated CO, flux system. Under light condition, the soil CO2 flux under effects of cyanobacteria crust and moss crust was significantly decreased by 92% and 305%, respectively, as compared with the flux without the effects of the biocrusts. The decrement of the soil CO, flux by the biocrusts was related to the biocrusts components and their biomass. Under the effects of dark colored cyanobacteria crust and moss crust, the soil CO2 flux was decreased by 141% and 484%, respectively, as compared with that in bare land. The diurnal curve of soil CO2 flux under effects of biocrusts presented a trend of 'drop-rise-drop' , with the maximum carbon uptake under effects of cyanobacteria crust and moss crust being 0.13 and -1.02 micromol CO2.m-2.s-1 and occurred at about 8:00 and 9:00 am, respectively, while that in bare land was unimodal. In a day (24 h) , the total CO2 flux under effects of cyanobacteria crust was increased by 7.7% , while that under effects of moss crust was decreased by 29.6%, as compared with the total CO2 flux in bare land. This study suggested that in the hilly region of Loess Plateau, biocrust had significant effects on soil CO2 flux, which should be taken into consideration when assessing the carbon budget of the 'Grain for Green' eco-project.

  3. When CO2 kills: effects of magmatic CO2 flux on belowground biota at Mammoth Mountain, CA

    NASA Astrophysics Data System (ADS)

    McFarland, J.; Waldrop, M. P.; Mangan, M.

    2011-12-01

    The biomass, composition, and activity of the soil microbial community is tightly linked to the composition of the aboveground plant community. Microorganisms in aerobic surface soils, both free-living and plant-associated are largely structured by the availability of growth limiting carbon (C) substrates derived from plant inputs. When C availability declines following a catastrophic event such as the death of large swaths of trees, the number and composition of microorganisms in soil would be expected to decline and/or shift to unique microorganisms that have better survival strategies under starvation conditions. High concentrations of volcanic cold CO2 emanating from Mammoth Mountain near Horseshoe Lake on the southwestern edge of Long Valley Caldera, CA has resulted in a large kill zone of tree species, and associated soil microbial species. In July 2010, we assessed belowground microbial community structure in response to disturbance of the plant community along a gradient of soil CO2 concentrations grading from <0.6% (ambient forest) to >80% (no plant life). We employed a microbial community fingerprinting technique (automated ribosomal intergenic spacer analysis) to determine changes in overall community composition for three broad functional groups: fungi, bacteria, and archaea. To evaluate changes in ectomycorrhizal fungal associates along the CO2 gradient, we harvested root tips from lodgepole pine seedlings collected in unaffected forest as well as at the leading edge of colonization into the kill zone. We also measured soil C fractions (dissolved organic C, microbial biomass C, and non-extractable C) at 10 and 30 cm depth, as well as NH4+. Not surprisingly, our results indicate a precipitous decline in soil C, and microbial C with increasing soil CO2; phospholipid fatty acid analysis in conjunction with community fingerprinting indicate both a loss of fungal diversity as well as a dramatic decrease in biomass as one proceeds further into the kill zone

  4. Tracing CO2 fluxes and plant volatile organic compound emissions by stable isotopes

    NASA Astrophysics Data System (ADS)

    Werner, Christiane; Wegener, Frederik; Jardine, Kolby

    2014-05-01

    Plant metabolic processes exert a large influence on global climate and air quality through the emission of the greenhouse gas CO2 and volatile organic compounds (VOCs). Despite the enormous importance, processes controlling plant carbon allocation into primary and secondary metabolism, such as respiratory CO2 emission and VOC synthesis, remains unclear. The vegetation exerts a large isotopic imprint on the atmosphere through both, photosynthetic carbon isotope discrimination and fractionation during respiratory CO2 release (δ13Cres). While the former is well understood, many processes driving carbon isotope fractionation during respiration are unknown1. There are striking differences in variations of δ13Cres between plant functional groups, which have been proposed to be related to carbon partitioning in the metabolic branching points of the respiratory pathways and secondary metabolism, which are linked via a number of interfaces including the central metabolite pyruvate2. Notably, it is a known substrate in a large array of secondary pathways leading to the biosynthesis of many volatile organic compounds (VOCs), such as volatile isoprenoids, oxygenated VOCs, aromatics, fatty acid oxidation products, which can be emitted by plants. Here we investigate if carbon isotope fractionation in light and dark respired CO2 is associated with VOC emissions in the atmosphere. Specifically, we hypothesize that a high carbon flux through the pyruvate into various VOC synthesis pathways is associated with a pronounced 13C-enrichment of respired CO2 above the putative substrate, as it involves the decarboxylation of the 13C-enriched C-1 from pyruvate. Based on simultaneous real-time measurements of stable carbon isotope composition of branch respired CO2 (CRDS) and VOC fluxes (PTR-MS) we traced carbon flow into these pathways by pyruvate positional labeling. We demonstrated that in a Mediterranean shrub the 13C-enriched C-1 from pyruvate is released in substantial amounts as

  5. Importance of non CO2 fluxes for agricultural ecosystems - understanding the mechanisms and drivers

    NASA Astrophysics Data System (ADS)

    Klumpp, Katja

    2014-05-01

    In agriculture, a large proportion (about 89%) of greenhouse gas (GHG) emission saving potential may be achieved by means of soil C sequestration. Not surprising that exchange of carbon dioxide (CO2) has been a main research objective during last decades. In spite of this, in agricultural ecosytems (i.e. grassland and croplands) a large proportion of total emissions (about 18% in CO2e worldwide) are linked to non CO2 fluxes (about 50% N2O, 40% CH4 in contraste to 10%CO2). Those emissions are however, diffuse, for example N2O, is emitted on almost all cultivated land, and all humid grasslands emit CH4 related to watertable. However, those emissions can vary largely from one site to another or from one farming system to another, while some studies even report a fixation of CH4 and N2O by grass- and croplands, not to mention the impacts of climate change on fluxes. Finally, given the large number of findings, along with their significant diversity, complicates both estimation of these emissions and the mechanism that the public authorities could implement to encourage their reduction. To determine effective mitigation options, a better knowledge on the drivers of CH4/N2O as well as their temporal and spatial variability are of particular interest. At present, more information is needed on i) the impact of agricultural practices and the contribution of CH4 and N2O to the GHG budgets within contrasting systems, ii) differences among climate regions and climate impacts, and iii) impact of managing soil microbial functioning (through plant diverstiy, litter inputs, etc). This presentation will review recent studies to highlight some new findings on the mentioned topics.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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

  8. Regional and Local Carbon Flux Information from a Continuous Atmospheric CO2 Network in the Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Heck, S. L.; Stephens, B.; Watt, A.

    2007-12-01

    We will present preliminary carbon flux estimates from the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON). In order to improve our understanding of regional carbon fluxes in the Rocky Mountain West, we have developed and deployed autonomous, inexpensive, and robust CO2 analyzers (AIRCOA) at five sites throughout Colorado and Utah, and plan additional deployments on the Navajo Reservation, Arizona in September 2007 and atop Mount Kenya, Africa in November 2007. We have used a one- dimensional CO2 budget equation, following Bakwin et al. (2004), to estimate regional monthly-mean fluxes from our continuous CO2 concentrations. These comparisons between our measurements and estimates of free- tropospheric background concentrations reveal regional-scale CO2 flux signals that are generally consistent with one another across the Rocky RACCOON sites. We will compare the timing and magnitude of these estimates with expectations from local-scale eddy-correlation flux measurements and bottom-up ecosystem models. We will also interpret the differences in monthly-mean flux signals between our sites in terms of their varying upwind areas of influence and inferred regional variations in CO2 fluxes. Our measurements will be included in future CarbonTracker assimilation runs and other planned model-data fusion efforts. However, questions still exist concerning the ability of these models to accurately represent the various influences on CO2 concentrations in continental boundary layers, and at mountaintop sites in particular. We will present an analysis of the diurnal cycles in CO2 concentration and CO2 variability at our sites, and compare these to various model estimates. Several of our sites near major population centers reflect the influence of industrial CO2 sources in afternoon upslope flows, with CO2 concentration increasing and variable in the mid to late afternoon. Other more remote sites show more consistent and decreasing CO2

  9. A joint data assimilation system (Tan-Tracker) to simultaneously estimate surface CO2 fluxes and 3-D atmospheric CO2 concentrations from observations

    NASA Astrophysics Data System (ADS)

    Tian, X.; Xie, Z.; Liu, Y.; Cai, Z.; Fu, Y.; Zhang, H.; Feng, L.

    2013-09-01

    To quantitatively estimate CO2 surface fluxes (CFs) from atmospheric observations, a joint data assimilation system ("Tan-Tracker") is developed by incorporating a joint data assimilation framework into the GEOS-Chem atmospheric transport model. In Tan-Tracker, we choose an identity operator as the CF dynamical model to describe the CFs' evolution, which constitutes an augmented dynamical model together with the GEOS-Chem atmospheric transport model. In this case, the large-scale vector made up of CFs and CO2 concentrations is taken as the prognostic variable for the augmented dynamical model. And thus both CO2 concentrations and CFs are jointly assimilated by using the atmospheric observations (e.g., the in-situ observations or satellite measurements). In contrast, in the traditional joint data assimilation frameworks, CFs are usually treated as the model parameters and form a state-parameter augmented vector jointly with CO2 concentrations. The absence of a CF dynamical model will certainly result in a large waste of observed information since any useful information for CFs' improvement achieved by the current data assimilation procedure could not be used in the next assimilation cycle. Observing system simulation experiments (OSSEs) are carefully designed to evaluate the Tan-Tracker system in comparison to its simplified version (referred to as TT-S) with only CFs taken as the prognostic variables. It is found that our Tan-Tracker system is capable of outperforming TT-S with higher assimilation precision for both CO2 concentrations and CO2 fluxes, mainly due to the simultaneous assimilation of CO2 concentrations and CFs in our Tan-Tracker data assimilation system.

  10. Turbulent CO2 Flux Measurements by Lidar: Length Scales, Results and Comparison with In-Situ Sensors

    NASA Technical Reports Server (NTRS)

    Gilbert, Fabien; Koch, Grady J.; Beyon, Jeffrey Y.; Hilton, Timothy W.; Davis, Kenneth J.; Andrews, Arlyn; Ismail, Syed; Singh, Upendra N.

    2009-01-01

    The vertical CO2 flux in the atmospheric boundary layer (ABL) is investigated with a Doppler differential absorption lidar (DIAL). The instrument was operated next to the WLEF instrumented tall tower in Park Falls, Wisconsin during three days and nights in June 2007. Profiles of turbulent CO2 mixing ratio and vertical velocity fluctuations are measured by in-situ sensors and Doppler DIAL. Time and space scales of turbulence are precisely defined in the ABL. The eddy-covariance method is applied to calculate turbulent CO2 flux both by lidar and in-situ sensors. We show preliminary mean lidar CO2 flux measurements in the ABL with a time and space resolution of 6 h and 1500 m respectively. The flux instrumental errors decrease linearly with the standard deviation of the CO2 data, as expected. Although turbulent fluctuations of CO2 are negligible with respect to the mean (0.1 %), we show that the eddy-covariance method can provide 2-h, 150-m range resolved CO2 flux estimates as long as the CO2 mixing ratio instrumental error is no greater than 10 ppm and the vertical velocity error is lower than the natural fluctuations over a time resolution of 10 s.

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

    NASA Astrophysics Data System (ADS)

    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

  12. Effects of increased upward flux of dissolved salts caused by CO2 storage or other factors

    SciTech Connect

    Murdoch, Lawrence C.; Xie, Shuangshuang; Falta, Ronald W.; Ruprecht, Catherine

    2015-08-01

    Injection of CO2 in deep saline aquifers is being considered to reduce greenhouse gases in the atmosphere, and this process is expected to increase the pressure in these deep aquifers. One potential consequence of pressurization is an increase in the upward flux of saline water. Saline groundwater occurs naturally at shallow depths in many sedimentary basins, so an upward flux of solutes could degrade the quality of freshwater aquifers and threaten aquatic ecosystems. One problem could occur where saline water flowed upward along preferential paths, like faults or improperly abandoned wells. Diffuse upward flow through the natural stratigraphy could also occur in response to basin pressurization. This process would be slower, but diffuse upward flow could affect larger areas than flow through preferential paths, and this motivated us to evaluate this process. We analyzed idealized 2D and 3D geometries representing the essential details of a shallow, freshwater aquifer underlain by saline ground water in a sedimentary basin. The analysis was conducted in two stages, one that simulated the development of a freshwater aquifer by flushing out saline water, and another that simulated the effect of a pulse-like increase in the upward flux from the basin. The results showed that increasing the upward flux from a basin increased the salt concentration and mass loading of salt to streams, and decrease the depth to the fresh/salt transition. The magnitude of these effects varied widely, however, from a small, slow process that would be challenging to detect, to a large, rapid response that could be an environmental catastrophe. The magnitude of the increased flux, and the initial depth to the fresh/salt transition in groundwater controlled the severity of the response. We identified risk categories for salt concentration, mass loading, and freshwater aquifer thickness, and we used these categories to characterize the severity of the response. This showed that risks would

  13. Seasonal variability of CO2 and H2O fluxes in tropical pasture and afforestation

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Eugster, W.; Buchmann, N.

    2011-12-01

    Tropical ecosystems play an important role for the global carbon and water cycle. However, eddy covariance flux measurements in the tropics are still scarce and previous studies have been predominantly conducted in tropical forests. With ongoing deforestation, the tropics are increasingly influenced by agroecosystems and pastures but only few observations have covered these land-use types so far. Comparative eddy covariance measurements of carbon dioxide and water vapour fluxes were performed in a tropical pasture and an adjacent afforestation site in Sardinilla, Panama from 2007 to 2009. We observed a larger seasonal variability of ecosystem CO2 and H2O fluxes at the pasture compared to the afforestation site, which was largely related to the rooting depth of grasses versus trees. Radiation and soil moisture were the main environmental controls of these fluxes in both ecosystems. The pasture ecosystem was more sensitive to water limitations by seasonal drought and in addition, periodical overgrazing significantly contributed to persisting carbon losses from the pasture. Substantial carbon sequestration was found at the afforestation site and was in agreement with independent assessments of biomass and soil inventories. In contrast to the largely differing carbon budgets, the afforestation of tropical pasture only marginally increased total annual evapotranspiration in Sardinilla. Our results clearly indicate the potential for carbon sequestration of tropical afforestation but also highlight the risk of carbon losses from pasture ecosystems in a seasonal tropical climate. Predicted increases in precipitation variability will very likely impact the seasonal variability of CO2 and H2O fluxes in Panama, in particular of pasture ecosystems. At the end of this talk, the overall significance of seasonality in tropical ecosystems will be discussed.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    Krevor, S.; Perrin, J.; Esposito, A.; Rella, C.; Benson, S. M.

    2009-12-01

    side of the pipeline with the end of the gas inlet tube approximate 9 cm above the ground at a walking speed of 1-2m/sec. This simulates the type of survey that could be easily performed if the actual or potential site of a leak was known to within an area on the order of 100 square kilometers or less, the scale of expected industrial CO2 sequestration operations. The surveys were performed both during the day and during the evening when CO2 flux due to respiration from the soil is markedly different. Keeling plots were used to characterize the spatially varying 13C composition of ground source CO2 across the site. A map constructed from this data shows that CO2 flux from sources of leakage was characterized by a δ 13C of -40‰ or less whereas locations away from the leakage spots had much higher δ 13C signatures, -25‰ or higher. The distinct isotopic signature allows for a clear discernment between leakage of petrogenic CO2 and that of natural CO2 fluxes from soil respiration. This is particularly valuable in the circumstance where the leak is slow enough that it could not be identified from CO2 concentration or flux changes above the natural background signal alone.

  16. BOREAS TGB-3 CH4 and CO2 Chamber Flux Data over NSA Upland Sites

    NASA Technical Reports Server (NTRS)

    Savage, Kathleen; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Moore, Tim R.

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-3) team collected methane and carbon dioxide (CH4, CO2) chamber flux measurements at the Northern Study Area (NSA) Fen, Old Black Spruce (OBS), Young Jack Pine (YJP), and auxiliary sites along Gillam Road and the 1989 burn site. Gas samples were extracted from chambers and analyzed at the NSA lab facility approximately every 7 days during May to September 1994 and June to October 1996. The data are provided in tabular ASCII files.

  17. Net drainage effects on CO2 fluxes of a permafrost ecosystem through eddy-covariance measurements

    NASA Astrophysics Data System (ADS)

    Kittler, Fanny; Burjack, Ina; Zimov, Nikita; Zimov, Sergey; Heimann, Martin; Göckede, Mathias

    2015-04-01

    Permafrost landscapes in the Northern high latitudes with their massive organic carbon stocks are critically important for the global carbon cycle, yet feedback processes with the atmosphere under future climate conditions are uncertain. To improve the understanding of mechanisms and drivers dominating permafrost carbon cycling, we established a continuous observation program in moist tussock tundra ecosystem near Cherskiy in North-eastern Siberia (68.75°N, 161.33°E). The experiment has been designed to monitor carbon cycle fluxes at different scales with different approaches, including e.g. the eddy-covariance technique, and their environmental drivers. Recent observations started mid July 2013 and are still ongoing, while 'historic' measurements are available for the period 2002-2005. Since 2004 part of the observation area has been disturbed by a drainage ditch ring, altering the soil water conditions in the surrounding area in a way that is expected for degrading ice-rich permafrost under a warming climate. With parallel observations over the disturbed (drained) area and a reference area nearby, respectively, we aim to evaluate the disturbance effect on the carbon cycle budgets and the dominating biogeochemical mechanisms. Here, findings based on over 1.5 years of continuous eddy-covariance CO2 flux measurements (July 2013 - March 2015) for both observation areas are presented. Results show systematic shifts in the tundra ecosystem as a result of 10 years of disturbance in the drained area, with significant effects on biotic and abiotic site conditions as well as on the carbon cycle dynamics. Comparing the net budget fluxes between both observations areas indicates a reduction of the net sink strength for CO2 of the drained ecosystem during the summer season in comparison to natural conditions, mostly caused by reduced CO2 uptake with low water levels in late summer. Regarding the long-term CO2 uptake dynamics of the disturbance regime (2005 vs. 2013/14) the

  18. Regional variability of grassland CO2 fluxes in Tyrol/Austria

    NASA Astrophysics Data System (ADS)

    Irschick, Christoph; Hammerle, Albin; Haslwanter, Alois; Wohlfahrt, Georg

    2010-05-01

    The FLUXNET project [1] aims at quantifying the magnitude and controls on the CO2, H2O and energy exchange of terrestrial ecosystems. Ideally, the various biomes of the Earth would be sampled in proportion to their spatial extent - in reality, however, study site selection is usually based on other (more practical) criteria so that a bias exists towards certain biomes and ecosystem types. This may be problematic because FLUXNET data are used to calibrate/parameterize models at various scales - if certain ecosystems are poorly replicated this may bias model predictions. Here we present data from a project in Tyrol/Austria where we have been investigating the CO2, H2O and energy exchange of five grassland sites during 2005-2007. The five permanent grassland sites were exposed to similar climate, but differed slightly in management. In a FLUXNET style approach, any of these sites might have been selected for making long-term flux measurements - the aim of this project was to examine the representativeness of these sites and, if evident, elucidate the causes for and controls on differences between sites. To this end we conducted continuous eddy covariance flux measurements at one (anchor) site [2, 3], and episodic, month long flux measurements at the four additional sites using a roving eddy covariance tower. These data were complemented by measurements of environmental drivers, the amount of above ground phytomass and basic data on vegetation and soil type, as well as management. Data are subject to a rigorous statistical analysis in order to quantify significant differences in the CO2, H2O and energy exchange between the sites and to identify the factors which are responsible for these differences. In the present contribution we report results on CO2 fluxes. Our major findings are that (i) site-identity of the surveyed grassland ecosystems was a significant factor for the net ecosystem CO2 exchange (NEE), somewhat less for gross primary production (GPP) and not for

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

    NASA Astrophysics Data System (ADS)

    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

  20. BOREAS TGB-5 CO2, CH4 and CO Chamber Flux Data Over the NSA

    NASA Technical Reports Server (NTRS)

    Burke, Roger; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Zepp, Richard

    2000-01-01

    The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-5) team collected a variety of trace gas concentration and flux measurements at several NSA sites. This data set contains carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) chamber flux measurements conducted in 1994 at upland forest sites that experienced stand-replacement fires. These measurements were acquired to understand the impact of fires on soil biogeochemistry and related changes in trace gas exchange in boreal forest soils. Relevant ancillary data, including data concerning the soil temperature, solar irradiance, and information from nearby un-burned control sites, are included to provide a basis for modeling the regional impacts of fire and climate changes on trace gas biogeochemistry. The data are provided in tabular ASCII files.

  1. Responses of Soil CO2 Fluxes to Short-Term Experimental Warming in Alpine Steppe Ecosystem, Northern Tibet

    PubMed Central

    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 (Q10) 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. PMID:23536854

  2. Soil CO2 Fluxes Following Wetting Events: Field Observations and Modeling

    NASA Astrophysics Data System (ADS)

    O'Donnell, F. C.; Caylor, K. K.

    2009-12-01

    Carbon exchange data from eddy flux towers in drylands suggest that the Birch Effect, a pulse of soil CO2 efflux triggered by the first rain following a dry period, may contribute significantly to the annual carbon budget of these ecosystems. Laboratory experiments on dryland soils have shown that microbes adapted to live in arid ecosystems may be able to remain dormant in dry soil for much longer than expected and an osmotic shock response to sudden increases in soil water potential may play a role in the Birch Effect. However, little has been done to understand how a dry soil profile responds to a rainfall event. We measured soil CO2 production during experimental wetting events in treatment plots at a site on the Botswana portion of the Kalahari Transect (KT). We buried small, solid-state sensors that continuously measure CO2 concentration in the soil air space at four depths and the soil surface and applied wetting treatments intended to simulate typical rainfall for the region to the plots, including single 10 mm wettings (the mean storm depth for the KT), single 20 mm wettings, and repeated 10 mm wettings. We solved a finite difference approximation of the governing equation for CO2 in the soil airspace to determine the source rate of CO2 during and after the wetting treatments, using Richard’s equation to approximate the change in air-filled porosity due to infiltrating water. The wetting treatments induced a rapid spike in the source rate of CO2 in the soil, the timing and magnitude of which were consistent with laboratory experiments that observed a microbial osmotic shock response. The source rate averaged over the first three hours after wetting showed that a 20 mm wetting produced a larger response than the 10 mm wettings. It also showed that a second wetting event produced a smaller response than the first and though it was not significant, an upward trend in response was apparent through the two month period. These results suggest that there may be

  3. CO2 and CH4 Fluxes across Polygon Geomorphic Types, Barrow, Alaska, 2006-2010

    SciTech Connect

    Tweedie,Craig; Lara, Mark

    2014-09-17

    Carbon flux data are reported as Net Ecosystem Exchange (NEE), Gross Ecosystem Exchange (GEE), Ecosystem Respiration (ER), and Methane (CH4) flux. Measurements were made at 82 plots across various polygon geomorphic classes at research sites on the Barrow Environmental Observatory (BEO), the Biocomplexity Experiment site on the BEO, and the International Biological Program (IBP) site a little west of the BEO. This product is a compilation of data from 27 plots as presented in Lara et al. (2012), data from six plots presented in Olivas et al. (2010); and from 49 plots described in (Lara et al. 2014). Measurements were made during the peak of the growing seasons during 2006 to 2010. At each of the measurement plots (except Olivas et al., 2010) four different thicknesses of shade cloth were used to generate CO2 light response curves. Light response curves were used to normalize photosynthetically active radiation that is diurnally variable to a peak growing season average ~400 umolm-2sec-1. At the Olivas et al. (2010) plots, diurnal patterns were characterized by repeated sampling. CO2 measurements were made using a closed-chamber photosynthesis system and CH4 measurements were made using a photo-acoustic multi-gas analyzer. In addition, plot-level measurements for thaw depth (TD), water table depth (WTD), leaf area index (LAI), and normalized difference vegetation index (NDVI) are summarized by geomorphic polygon type.

  4. Contributions of Understory and Overstory to Ecosystem CO2 Fluxes in a Temperate Mixed Forest in Switzerland

    NASA Astrophysics Data System (ADS)

    Paul-Limoges, E.; Wolf, S.; Hörtnagl, L. J.; Eugster, W.; Buchmann, N. C.

    2015-12-01

    Forests play an important role in the global carbon cycle by sequestering large amounts of atmospheric CO2. The CO2 sequestered by a forest varies depending on many factors including climate, species composition, growth strategy, stand age and structure. Forests are structurally complex ecosystems, both horizontally and vertically. In many cases, several canopy layers with distinct functional properties and sun exposure contribute differently to the ecosystem CO2exchange. Only a few studies thus far have investigated the contribution of understory to overstory fluxes, and large variations have been found among sites. Our study focused on partitioning the net ecosystem CO2 flux of a mixed deciduous forest in Switzerland into its understory and overstory components using below and above canopy eddy-covariance (EC) measurements over two years. CO2 concentration profile measurements made at eight levels within the canopy complemented those measurements. We quantified the CO2flux contribution from the understory to the overstory, both in terms of photosynthesis and respiration, and assessed the differences between understory and overstory functional responses to environmental drivers. On an annual basis, the understory was a CO2 source, while the overstory was a CO2 sink. The understory was a CO2 sink only in spring with the early emergence of understory plants before overstory canopy leaf-out. Overall, the understory contributed 54% to annual ecosystem respiration but only 7% to annual ecosystem photosynthesis. Moreover, understory and overstory fluxes became decoupled at full canopy closure, thus leading to unaccounted EC fluxes when measured only above the canopy. CO2 concentration profile measurements supported this finding. Our results showed that understory EC measurements are essential in this mixed deciduous forest, and likely in many other forests, to fully understand the carbon dynamics within structurally complex ecosystems.

  5. Using Carbonyl Sulfide Column Measurements and a Chemical Transport Model to Investigate Variability in Biospheric CO2 Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Palm, M.; Deutscher, N. M.; Warneke, T.; Notholt, J.; Baker, I. T.; Berry, J. A.; Suntharalingam, P.; Campbell, J. E.; Wolf, A.

    2014-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Heterogeneity of CH4 and net CO2 Fluxes Using Nested Chamber, Tower, Aircraft, Remote Sensing, and Modeling Approaches in Arctic Alaska for Regional Flux Estimation

    NASA Astrophysics Data System (ADS)

    Oechel, W. C.; Moreaux, V.; Kalhori, A. A. M.; Murphy, P.; Wilkman, E.; Sturtevant, C. S.; Zhuang, Q.; Miller, C. E.; Dinardo, S. J.; Fisher, J. B.; Gioli, B.; Zona, D.

    2014-12-01

    The topographic, environmental, biotic, and metabolic heterogeneity of terrestrial ecosystems and landscapes can be large even despite a seemingly homogeneous landscape. The error of estimating and simulating fluxes due to extant heterogeneity is commonly overlooked in regional and global estimates. Here we evaluate the pattern and controls on spatial heterogeneity on CH4 and CO2 fluxes over varying spatial scales. Data from the north slope of Alaska from chambers, up to a 16 year CO2 flux record from up to 7 permanent towers, over 20 portable tower locations, eddy covariance CH4 fluxes over several years and sites, new year-around CO2 and CH4 flux installations, hundreds of hours of aircraft concentration and fluxes, and terrestrial biosphere and flux inverse modeling, are used to evaluate the spatial variability of fluxes and to better estimate regional fluxes. Significant heterogeneity of fluxes is identified at varying scales from sub-meter scale to >100km. A careful consideration of the effect that heterogeneity causes when estimating ecosystem fluxes is critical to reliable regional and global estimates. The combination of eddy covariance tower flux, aircraft, remote sensing, and modeling can be used to provide reliable, accurate, regional assessments of CH4 and CO2 fluxes from large areas of heterogeneous landscape.

  8. The importance of replication of CO2 flux measurements in forest clearcuts

    NASA Astrophysics Data System (ADS)

    Paul-Limoges, E.; Black, T. A.; Christen, A.; Nesic, Z.; Ketler, R.; Grant, N. J.; Baker, T. D.; Jassal, R. S.; Humphreys, E.

    2013-12-01

    Stand-replacing disturbances, such as harvesting, have a major impact on the exchange of carbon dioxide (CO2) between forested land and the atmosphere. The former forest CO2 sinks become net CO2 sources due to the continued respiratory losses of CO2 and to the significantly reduced photosynthetic uptake of CO2. The duration and magnitude of this carbon loss has now been quantified for many single sites representing ecosystems worldwide through Fluxnet. However, differences in the characteristics of harvested sites can influence vegetation recovery and respiratory fluxes of such stands and replicated observations are required to quantify the possible differences which can arise within an ecosystem following a stand-replacing disturbance. This study uses data from the well-studied Fluxnet-Canada Douglas-fir chronosequence on Vancouver Island, where the most mature site recently reached harvesting age and was commercially harvested. We compare the first two years following harvesting of eddy-covariance (EC) measurements of CO2 exchange at this recently clearcut harvested site (HDF11) with those from a previously clearcut harvested Douglas-fir site (HDF00) in the chronosequence. The weather conditions during the years used in this analysis were similar and within the climate normals for the area. Half-hourly energy-balance closure was greater than 80% in both clearcuts. Our results for the first two years post-harvest show that both clearcuts were large annual carbon sources (i.e., net ecosystem productivity (NEP) < 0) with HDF11 being a much stronger source. NEP at HDF11 recovered from -1000 g C m-2 yr-1 in the first year to -700 g C m-2 yr-1 in the second year while HDF00 recovered from -620 g C m-2 yr-1 to -520 g C m-2 yr-1. Vegetation recovery was slower at HDF11 with a gross primary productivity (GPP) of 130 g C m-2 yr-1 in the first year and 385 g C m-2 yr-1 in the second year, while HDF00 had a GPP of 220 and 530 g C m-2 yr-1 in the respective years. Ecosystem

  9. The effect of experimental ecosystem warming on CO2 fluxes in a montane meadow

    SciTech Connect

    Saleska, Scott R.; Harte, John; Torn, Margaret S.

    1997-07-01

    Climatic change is predicted to alter rates of soil respiration and assimilation of carbon by plants. Net loss of carbon from ecosystems would form a positive feedback enhancing anthropogenic global warming. We tested the effect of increased heat input, one of the most certain impacts of global warming, on net ecosystem carbon exchange in a Rocky Mountain montane meadow. Overhead heaters were used to increase the radiative heat flux into plots spanning a moisture and vegetation gradient. We measured net whole-ecosystem CO2 fluxes using a closed-path chamber system, relatively nondisturbing bases, and a simple model to compensate for both slow chamber leaks and the CO2 concentration-dependence of photosynthetic uptake, in 1993 and 1994. In 1994, we also measured soil respiration separately. The heating treatment altered the timing and magnitude of net carbon fluxes into the dry zone of the plots in 1993 (reducing uptake by 100 g carbon m2), but had an undetectable effect on carbon fluxes into the moist zone. During a strong drought year (1994), heating altered the timing, but did not significantly alter the cumulative magnitude, of net carbon uptake in the dry zone. Soil respiration measurements showed that when differences were detected in dry zone carbon fluxes, they were caused by changes in carbon input from photosynthesis, not by temperature-driven changes in carbon output from soil respiration. When differences were detected in dry-zone carbon fluxes, they were caused by changes in carbon input from photosynthesis, not by a temperature-driven changes in carbon output from soil respiration. Regression analysis suggested that the reduction in carbon inputs from plants was due to a combination of two soil moisture effects: a direct physiological response to decreased soil moisture, and a shift in plant community composition from high-productivity species to low-productivity species that are more drought tolerant. These results partially support predictions that

  10. New observational evidence of CO2 degassing anomalies on the Piton de la Fournaise and the relationship between seismotectonic structures and CO2 flux from the soil

    NASA Astrophysics Data System (ADS)

    Liuzzo, Marco; Giudice, Gaetano; Di Muro, Andrea; Ferrazzini, Valérie; Michon, Laurent

    2014-05-01

    Piton de la Fournaise (PdF) is recognised as one of the world's most active volcanoes in terms of eruptive frequency and the substantial quantity of lava produced, yet this activity seems to be in contrast with an apparent absence of any type of natural fluid emission during periods of quiescence, with the sole exception of a rather modest intracrateric fumarole activity. The most significant gas emissions are evident only during eruptive episodes and disappear at the cessation of these, all of which making PdF a vulcano that is rather hostile to investigations in terms of gas geochemistry, and, therefore, all the more fascinating to explore. Here we report the results of a campaign to measure CO2 soil flux, focusing on the identification of potential degassing areas and their relation with the main seismotectonic features that involve PdF with the aim of developing a broader understanding of the geometry of the degassing system of the volcano. In order to assess the possible existence of anomalous CO2 soil flux emissions, 395 measurements were taken along transepts roughly orthogonal to the known tectonic lineaments linked to PdF, with allowances made for problems presented by the urbanization of the areas involved and in particular some obstacles and difficult morphology. In addition, samples of gas for C isotope analysis were taken at measurement points that showed a relatively high CO2 value (in general CO2 flux more than 80 g m-2d-1). The results of the investigation reveal a distribution of anomalous CO2 degassing which occurs along the main tectonic structures that intersect PdF and which also correspond to areas that have the highest density of pyroclastic cones. Furthermore there is a particularly interesting correspondence between the highest levels of anomalous CO2 degassing and the distribution of earthquakes occurring at depths greater than 15km. The results of the survey suggest that there is a potential connection between the areas of anomalous

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Quantification of fossil fuel CO2 emissions at the urban scale: Results from the Indianapolis Flux Project (INFLUX)

    NASA Astrophysics Data System (ADS)

    Turnbull, J. C.; Cambaliza, M. L.; Sweeney, C.; Karion, A.; Newberger, T.; Tans, P. P.; Lehman, S.; Davis, K. J.; Miles, N. L.; Richardson, S.; Lauvaux, T.; Shepson, P.; Gurney, K. R.; Song, Y.; Razlivanov, I. N.

    2012-12-01

    Emissions of fossil fuel CO2 (CO2ff) from anthropogenic sources are the primary driver of observed increases in the atmospheric CO2 burden, and hence global warming. Quantification of the magnitude of fossil fuel CO2 emissions is vital to improving our understanding of the global and regional carbon cycle, and independent evaluation of reported emissions is essential to the success of any emission reduction efforts. The urban scale is of particular interest, because ~75% CO2ff is emitted from urban regions, and cities are leading the way in attempts to reduce emissions. Measurements of 14CO2 can be used to determine CO2ff, yet existing 14C measurement techniques require laborious laboratory analysis and measurements are often insufficient for inferring an urban emission flux. This presentation will focus on how 14CO2 measurements can be combined with those of more easily measured ancillary tracers to obtain high resolution CO2ff mixing ratio estimates and then infer the emission flux. A pilot study over Sacramento, California showed strong correlations between CO2ff and carbon monoxide (CO) and demonstrated an ability to quantify the urban flux, albeit with large uncertainties. The Indianapolis Flux Project (INFLUX) aims to develop and assess methods to quantify urban greenhouse gas emissions. Indianapolis was chosen as an ideal test case because it has relatively straightforward meteorology; a contained, isolated, urban region; and substantial and well-known fossil fuel CO2 emissions. INFLUX incorporates atmospheric measurements of a suite of gases and isotopes including 14C from light aircraft and from a network of existing tall towers surrounding the Indianapolis urban area. The recently added CO2ff content is calculated from measurements of 14C in CO2, and then convolved with atmospheric transport models and ancillary data to estimate the urban CO2ff emission flux. Significant innovations in sample collection include: collection of hourly averaged samples to

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

    NASA Astrophysics Data System (ADS)

    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

  14. The role of ozone flux and antioxidants in the suppression of ozone injury by elevated CO2 in soybean.

    PubMed

    Booker, Fitzgerald L; Fiscus, Edwin L

    2005-08-01

    The projected rise in atmospheric CO2 concentration is expected to increase growth and yield of many agricultural crops. The magnitude of this stimulus will partly depend on interactions with other components of the atmosphere such as tropospheric O3. Elevated CO2 concentrations often lessen the deleterious effects of O3, but the mechanisms responsible for this response have received little direct examination. Previous studies have indicated that protection against O3 injury by elevated CO2 can be attributed to reduced O3 uptake, while other studies suggest that CO2 effects on anti-oxidant metabolism might also be involved. The aim of this experiment was to test further the roles of O3 flux and antioxidant metabolism in the suppression of O3 injury by elevated CO2. In a two-year experiment, soybean [Glycine max (L.) Merr.] was exposed from emergence to maturity to charcoal-filtered air or charcoal-filtered air plus a range of O3 concentrations in combination with ambient or approximately twice-ambient CO2 concentrations in open-top field chambers. Experimental manipulation of O3 concentrations and estimates of plant O3 uptake indicated that equivalent O3 fluxes that suppressed net photosynthesis, growth, and yield at ambient concentrations of CO2 were generally much less detrimental to plants treated concurrently with elevated CO2. These responses appeared unrelated to treatment effects on superoxide dismutase, glutathione reductase, and peroxidase activities and glutathione concentration. Total ascorbic acid concentration increased by 28-72% in lower canopy leaves in response to elevated CO2 and O3 but not in upper canopy leaves. Increasing concentrations of atmospheric CO2 will likely ameliorate O3 damage to many crops due to reduced O3 uptake, increased carbon assimilation, and possibly as yet undetermined additional factors. The results of this study further suggest that elevated CO2 may increase the threshold O3 flux for biomass and yield loss in soybean.

  15. Assessing the Influence of Fossil Fuel Emissions on CO2 Flux Measurements Above a Suburban Ecosystem Using Continuous Traffic Data

    NASA Astrophysics Data System (ADS)

    Hiller, R. V.; Wu, J.; McFadden, J. P.

    2007-12-01

    Cities are a major source of CO2, the most important anthropogenic greenhouse gas. Land use within cities is highly heterogeneous and a significant area can be occupied by vegetated surfaces where CO2 is taken up by photosynthesis and released by ecosystem respiration. Recent remote sensing and modeling studies have estimated that turfgrass lawns cover a surface area of perhaps 163,800~km2 in the continental United States with significant CO2 exchange (Milesi et al. 2005). However, direct measurements of land-atmosphere fluxes above lawn ecosystems have been difficult due to the typically small dimensions of lawns and the heterogeneity of land uses that surround them in an urbanized landscape. We made 2~years of continuous CO2 exchange measurements using a mobile eddy covariance tower over a <1~ha lawn, which was within the footprint of the KUOM 170-m tall flux tower in a suburban residential neighborhood of Minneapolis-St. Paul, Minnesota. A satellite-derived land-cover map was analyzed to assess the characteristic patch dimensions of lawns in the region in comparison to the selected mobile tower site. An important consequence of urban landscape heterogeneity is that CO2 fluxes measured above vegetated patches may be influenced by fossil fuel CO2 sources nearby. In this poster, we use high time resolution, continuously monitored traffic data from the roads surrounding the flux site to quantify the influence of fossil fuel emissions on the net ecosystem CO2 exchange measurements. Using a flux source area model, we assess the relative influence of fossil fuel emissions in relation to variations of wind field, atmospheric stability, and temporal patterns of traffic volume. The results will be useful for validating emissions models and for scaling up the CO2 flux from vegetation in developed land. This study is a contribution to the Mid-Continent Intensive Field Campaign of the North American Carbon Program (NACP).

  16. Melting Systematics in Mid-ocean Ridge Basalts and Implications for Global CO2 Fluxes

    NASA Astrophysics Data System (ADS)

    Behn, M. D.; Grove, T. L.; Wanless, V. D.; Brown, S. M.

    2015-12-01

    We present a new model for anhydrous melting in the spinel and plagioclase stability fields that provides enhanced predictive capabilities for the major element compositional variability found in mid-ocean ridge basalts (MORBs). The melting model is coupled to geodynamic simulations of mantle flow and mid-ocean ridge temperature structure to investigate global variations in MORB chemistry and crustal thickness as a function of mantle potential temperature, spreading rate, mantle composition, and the pattern(s) of melt migration. To constrain global variations in mantle melting parameters we incorporate evidence from both MORB major element compositions and seismically determined crustal thicknesses. Specifically, we show that to explain the global data set of crustal thickness, Na8, Fe8, Si8, Ca8/Al8, and K8/Ti8 (oxides normalized to 8 wt% MgO) requires a relatively narrow zone over which melts are pooled to the ridge axis. In all cases, our preferred model involves melt transport to the ridge axis over relatively short horizontal length scales (~25 km), implying that although melting occurs over a wide region, up to 20-40% of the total melt volume is not extracted, and will eventually refreeze and refertilize the lithosphere. We further incorporate constraints from melt inclusion datasets to constrain the global mid-ocean ridge CO2 degassing flux. Our estimates indicate that ~3.4 x1014 g/yr of CO2 are released by MORB melting, however, more than half of this CO2 may remain trapped in the lithospheric mantle.

  17. Controls of Evapotranspiration and CO2 Fluxes from Scots Pine by Surface Conductance and Abiotic Factors

    PubMed Central

    Zha, Tianshan; Li, Chunyi; Kellomäki, Seppo; Peltola, Heli; Wang, Kai-Yun; Zhang, Yuqing

    2013-01-01

    Evapotranspiration (E) and CO2 flux (Fc) in the growing season of an unusual dry year were measured continuously over a Scots pine forest in eastern Finland, by eddy covariance techniques. The aims were to gain an understanding of their biological and environmental control processes. As a result, there were obvious diurnal and seasonal changes in E, Fc, surface conductance (gc), and decoupling coefficient (Ω), showing similar trends to those in radiation (PAR) and vapour pressure deficit (δ). The maximum mean daily values (24-h average) for E, Fc, gc, and Ω were 1.78 mmol m−2 s−1, −11.18 µmol m−2 s−1, 6.27 mm s−1, and 0.31, respectively, with seasonal averages of 0.71 mmol m−2 s−1, −4.61 µmol m−2 s−1, 3.3 mm s−1, and 0.16. E and Fc were controlled by combined biological and environmental variables. There was curvilinear dependence of E on gc and Fc on gc. Among the environmental variables, PAR was the most important factor having a positive linear relationship to E and curvilinear relationship to Fc, while vapour pressure deficit was the most important environmental factor affecting gc. Water use efficiency was slightly higher in the dry season, with mean monthly values ranging from 6.67 to 7.48 μmol CO2 (mmol H2O)−1 and a seasonal average of 7.06 μmol CO2 (μmol H2O)−1. Low Ω and its close positive relationship with gc indicate that evapotranspiration was sensitive to surface conductance. Mid summer drought reduced surface conductance and decoupling coefficient, suggesting a more biotic control of evapotranspiration and a physiological acclimation to dry air. Surface conductance remained low and constant under dry condition, supporting that a constant value of surface constant can be used for modelling transpiration under drought condition. PMID:23894401

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

    NASA Astrophysics Data System (ADS)

    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 < 0.0001). After adjusting for large tree presence, a multiple linear regression of soil temperature, bulk density, and liana DBH explained 19% of remaining CO2 flux variability. Soil N2O fluxes adjacent to Caryocar villosum, Lecythis lurida, Schefflera morototoni, and Manilkara huberi were 84%-196% greater than Erisma uncinatum and Vochysia maxima, both Vochysiaceae. Tree species identity was the most important explanatory factor for N2O fluxes, accounting for more than twice the N2O flux variability as all other factors combined. Two observations suggest a mechanism for this finding: (1) sugar addition increased N2O fluxes near C. villosum twice as much (P < 0.05) as near Vochysiaceae and (2) species mean N2O fluxes were strongly negatively correlated with tree 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.

  19. Seasonal variation in measured H2O and CO2 flux of irrigated rice in the Mid-South

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice production in the Lower Mississippi River Basin constitutes over half of US rice production, but little research has been done on water and carbon flux in this region at the field scale. Eddy covariance measurements of water and CO2 flux allow for an integrated field measurement of the interac...

  20. A Global Synthesis Inversion Analysis of Recent Variability in Natural CO2 Fluxes Using Gosat and in Situ Observations

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Kawa, S. R.; Collatz, G. J.

    2014-12-01

    About one-half of the 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, and the location and year-to-year variability of the CO2 sinks are, however, not well understood. We use a batch Bayesian inversion approach to deduce the global spatiotemporal distributions of CO2 fluxes during 2009-2010. For prior constraints, we utilize fluxes 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 fixed fossil CO2 emissions. Here, we present results from our inversions that 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. Relationships between fluxes and atmospheric concentrations are derived using the PCTM atmospheric transport model run at 2° x 2.5° (latitude/longitude) resolution driven by meteorology from the MERRA reanalysis. We evaluate the posterior CO2 concentrations using independent aircraft and other data sets. The optimized fluxes generally resemble those from other inversion systems using different techniques, for example indicating a net terrestrial biospheric CO2 sink, and a shift in the sink from tropics to northern high latitudes when going from an in-situ-only inversion to a GOSAT inversion. We show that in this inversion framework, GOSAT provides better flux estimates in most regions with its greater spatial coverage, but we also discuss impacts of possible remaining biases in the data.

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

    PubMed

    Li, Haifang; Fu, Shenglei; Zhao, Hongting; Xia, Hanping

    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 x hr)) and ACp (139.8 mg/(m2 x hr)) than in Tp (94.0 mg/(m2 x hr)) and THp (102.9 mg/(m2 x 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 x 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Factors regulating soil surface CO2 and NOx flux in response to high temperature, pulse water events, and nutrient fertilization

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Grantz, D. A.; Chatterjee, A.; Eberwein, J. R.; Allsman, L. A.; Jenerette, D.

    2012-12-01

    Trace gas emissions from the soil surface are often underestimated due to poor understanding of the factors regulating fluxes under extreme conditions when moisture can be highly variable. In particular, dynamics of soil surface trace gas emissions from hot agricultural regions can be difficult to predict due to the sporadic use of flood irrigation and nitrogen fertilization. Soil surface CO2 and NOx fluxes are especially difficult to predict due to nonlinear responses to pulse water and fertilization events. Additionally, models such as Lloyd and Taylor (1994) and Yienger and Levy II (1995) are not well parameterized for soil surface CO2 and NOx flux, respectively, under excessively high temperatures. We measured soil surface CO2 and NOx flux in an agricultural field transitioning from fallow to biofuel crop production (Sorghum bicolor). Soil surface CO2 flux was measured using CO2 probes coupled with the flux-gradient method. NOx measurements were made using chambers coupled with a NOx monitor. Our field site is located at the University of California Desert Research and Extension Center in the Imperial Valley of CA. Air temperatures regularly exceed 42°C in the summer. Flood irrigation is used at the site as well as nitrogen fertilizers. Soil respiration ranged from 0-15 μmoles CO2 m-2 s-1, with strong hysteresis observed both with and without plants. Soil CO2 fluxes measured in the fallow field before the biofuel crop was planted were temperature independent and mainly regulated by soil moisture. When plants were introduced, temperature became an important predictor for soil respiration as well as canopy height. NOx fluxes were highest at intermediate soil moisture and varied significantly across an irrigation cycle. NOx emissions were temperature dependent, ranging from 3-113 ng N cm-2 hr-1. Neither CO2 nor NOx emissions showed inhibition at soil temperatures up to 55°C. Models may underestimate fluxes of CO2 and NOx from hot agricultural regions due to

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

    NASA Astrophysics Data System (ADS)

    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. Multi-scale modeling of Arabidopsis thaliana response to different CO2 conditions: From gene expression to metabolic flux.

    PubMed

    Liu, Lin; Shen, Fangzhou; Xin, Changpeng; Wang, Zhuo

    2016-01-01

    Multi-scale investigation from gene transcript level to metabolic activity is important to uncover plant response to environment perturbation. Here we integrated a genome-scale constraint-based metabolic model with transcriptome data to explore Arabidopsis thaliana response to both elevated and low CO2 conditions. The four condition-specific models from low to high CO2 concentrations show differences in active reaction sets, enriched pathways for increased/decreased fluxes, and putative post-transcriptional regulation, which indicates that condition-specific models are necessary to reflect physiological metabolic states. The simulated CO2 fixation flux at different CO2 concentrations is consistent with the measured Assimilation-CO2intercellular curve. Interestingly, we found that reactions in primary metabolism are affected most significantly by CO2 perturbation, whereas secondary metabolic reactions are not influenced a lot. The changes predicted in key pathways are consistent with existing knowledge. Another interesting point is that Arabidopsis is required to make stronger adjustment on metabolism to adapt to the more severe low CO2 stress than elevated CO2 . The challenges of identifying post-transcriptional regulation could also be addressed by the integrative model. In conclusion, this innovative application of multi-scale modeling in plants demonstrates potential to uncover the mechanisms of metabolic response to different conditions.

  6. What, Where, When, Who and How: Accounting for Biogenic CO2 Emissions Fluxes

    NASA Astrophysics Data System (ADS)

    Ohrel, S. B.

    2013-12-01

    production on U.S. land use, supply of non-energy commodities (e.g., timber, food crops), and related GHG emission fluxes. This paper first assesses current methods for accounting for land use sector biogenic CO2 emissions (i.e., IPCC approach). Based on the finding that no current methods exist for linking stationary source emissions with the land producing biogenic feedstocks, a unique method is needed that takes into consideration the biological cycling of carbon when accounting for biogenic emissions from energy use. The paper then describes the key technical and scientific considerations that should be taken in account, such as: the implications of baseline chosen; the important roles of temporal and spatial scales; emissions fluxes during feedstock production as well as transportation, storage and processing; the role of land use management and change, etc. It also discusses how these considerations can vary depending on feedstock type (e.g., long versus short rotation).

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

    NASA Astrophysics Data System (ADS)

    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

  8. Net uptake of atmospheric CO2 by coastal submerged aquatic vegetation

    PubMed Central

    Tokoro, Tatsuki; Hosokawa, Shinya; Miyoshi, Eiichi; Tada, Kazufumi; Watanabe, Kenta; Montani, Shigeru; Kayanne, Hajime; Kuwae, Tomohiro

    2014-01-01

    ‘Blue Carbon’, which is carbon captured by marine living organisms, has recently been highlighted as a new option for climate change mitigation initiatives. In particular, coastal ecosystems have been recognized as significant carbon stocks because of their high burial rates and long-term sequestration of carbon. However, the direct contribution of Blue Carbon to the uptake of atmospheric CO2 through air-sea gas exchange remains unclear. We performed in situ measurements of carbon flows, including air-sea CO2 fluxes, dissolved inorganic carbon changes, net ecosystem production, and carbon burial rates in the boreal (Furen), temperate (Kurihama), and subtropical (Fukido) seagrass meadows of Japan from 2010 to 2013. In particular, the air-sea CO2 flux was measured using three methods: the bulk formula method, the floating chamber method, and the eddy covariance method. Our empirical results show that submerged autotrophic vegetation in shallow coastal waters can be functionally a sink for atmospheric CO2. This finding is contrary to the conventional perception that most near-shore ecosystems are sources of atmospheric CO2. The key factor determining whether or not coastal ecosystems directly decrease the concentration of atmospheric CO2 may be net ecosystem production. This study thus identifies a new ecosystem function of coastal vegetated systems; they are direct sinks of atmospheric CO2. PMID:24623530

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

    PubMed

    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.

  10. Winter fluxes of CO2 and CH4 from subalpine soils in Rocky Mountain National Park, Colorado

    USGS Publications Warehouse

    Alisa, Mast M.; Wickland, K.P.; Striegl, R.T.; Clow, D.W.

    1998-01-01

    Fluxes of CO2 and CH4 through a seasonal snowpack were measured in and adjacent to a subalpine wetland in Rocky Mountain National Park, Colorado. Gas diffusion through the snow was controlled by gas production or consumption in the soil and by physical snowpack properties. The snowpack insulated soils from cold midwinter air temperatures allowing microbial activity to continue through the winter. All soil types studied were net sources of CO2 to the atmosphere through the winter, whereas saturated soils in the wetland center were net emitters of CH4 and soils adjacent to the wetland were net CH4 consumers. Most sites showed similar temporal patterns in winter gas fluxes; the lowest fluxes occurred in early winter, and maximum fluxes occurred at the onset of snowmelt. Temporal changes in fluxes probably were related to changes in soil-moisture conditions and hydrology because soil temperatures were relatively constant under the snowpack. Average winter CO2 fluxes were 42.3, 31.2, and 14.6 mmol m-2 d-1 over dry, moist, and saturated soils, respectively, which accounted for 8 to 23% of the gross annual CO2 emissions from these soils. Average winter CH4 fluxes were -0.016, 0.274, and 2.87 mmol m-2 d-1 over dry, moist, and saturated soils, respectively. Microbial activity under snow cover accounted for 12% of the annual CH4 consumption in dry soils and 58 and 12% of the annual CH4 emitted from moist and saturated soils, respectively. The observed ranges in CO2 and CH4 flux through snow indicated that winter fluxes are an important part of the annual carbon budget in seasonally snow-covered terrains.

  11. Estimating CO2 Fluxes Pre and Post Drought Using Remote Sensing Data in the Sierra Nevada Range

    NASA Astrophysics Data System (ADS)

    Mazzi, J. R.; Grigsby, S.; Goulden, M.; Ustin, S.

    2015-12-01

    The recent California drought presents an opportunity to study CO2 flux changes over time due to insufficient water uptake by plant life using remote sensing data. Three flux towers were used to create linear regressions between AVIRIS derived Net Ecosystem Exchange (NEE = PRI * NDVI * PAR) and tower measured CO2 flux in the San Joaquin Experimental Range. To estimate CO2 from NEE, two linear regressions were used based on time of day and season, with R2 values of 0.85 and 0.87 respectively. Per-pixel CO2 flux was estimated for AVIRIS flights flown in June 2013, 2014, and 2015, as well as September 2011 and October 2014. There was a significant decrease in post drought photosynthetic CO2 uptake over the 6,700 km2 studied, totaling 2,977 grams per minute less (15.9% decrease) from June 2013 to June 2014. Data from the 2015 HyspIRI flights suggest a continuation of this trend for June 2015. Pre-drought conditions over a 33 km2 area show that the photosynthetic CO2 uptake dropped from 74 mg per minute on September 24, 2011, to 35 mg per minute on October 6, 2014 (a 53% decrease). HyspIRI flight lines also include 434 km2 of the Rim Fire, an area that saw a decrease in CO2 uptake of 413 grams per minute (71.7% decrease from June 2013 to June 2014) from the burn alone. It is estimated that the entire Rim Fire (1,041 km2) has caused a total decrease in photosynthetic CO2 uptake totaling 988 grams less per minute from 2013 to 2014, with some recovery evident in 2015.

  12. Estimating nocturnal ecosystem respiration from the vertical turbulent flux and change in storage of CO2

    SciTech Connect

    Gu, Lianhong; Van Gorsel, Eva; Leuning, Ray; Delpierre, Nicolas; Black, Andy; Chen, Baozhang; Munger, J. William; Wofsy, Steve; Aubinet, M.

    2009-11-01

    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 measured using instrumentation on the single towers typically used at micrometeorological sites. A common approach to minimize bias is to use a threshold in friction velocity, u*, to exclude periods when advection is assumed to be important, but this is problematic in situations when in-canopy flows are decoupled from the flow above. Using data from 25 flux stations in a wide variety of forest ecosystems globally, we examine the generality of a novel approach to estimating nocturnal respiration developed by van Gorsel et al. (van Gorsel, E., Leuning, R., Cleugh, H.A., Keith, H., Suni, T., 2007. Nocturnal carbon efflux: reconciliation of eddy covariance and chamber measurements using an alternative to the u*-threshold filtering technique. Tellus 59B, 397 403, Tellus, 59B, 307-403). The approach is based on the assumption that advection is small relative to the vertical turbulent flux (FC) and change in storage (FS) of CO2 in the few hours after sundown. The sum of FC and FS reach a maximum during this period which is used to derive a temperature response function for ecosystem respiration. Measured hourly soil temperatures are then used with this function to estimate respiration RRmax. The new approach yielded excellent agreement with (1) independent measurements using respiration chambers, (2) with estimates using ecosystem light-response curves of Fc + Fs extrapolated to zero light, RLRC, and (3) with a detailed process-based forest ecosystem model, Rcast. At most sites respiration rates estimated using the u*-filter, Rust, were smaller than RRmax and RLRC. Agreement of our approach with independent measurements indicates that RRmax provides an excellent estimate of nighttime

  13. CO2 flux and seasonal variability in the turbidity maximum zone and surrounding area in the Changjiang River estuary

    NASA Astrophysics Data System (ADS)

    Li, Xuegang; Song, Jinming; Yuan, Huamao; Li, Ning; Duan, Liqin; Qu, Baoxiao

    2015-01-01

    The turbidity maximum zone (TMZ) is one of the most important regions in an estuary. However, the high concentration of suspended material makes it difficult to measure the partial pressure of CO2 ( pCO2) in these regions. Therefore, very little data is available on the pCO2 levels in TMZs. To relatively accurately evaluate the CO2 flux in an example estuary, we studied the TMZ and surrounding area in the Changjiang (Yangtze) River estuary. From seasonal cruises during February, August, November 2010, and May 2012, the pCO2 in the TMZ and surrounding area was calculated from pH and total alkalinity (TA) measured in situ, from which the CO2 flux was calculated. Overall, the TMZ and surrounding area acted as a source of atmosphere CO2 in February and November, and as a sink in May and August. The average FCO2 was -9, -16, 5, and 5 mmol/(m2·d) in May, August, November, and February, respectively. The TMZ's role as a source or sink of atmosphere CO2 was quite different to the outer estuary. In the TMZ and surrounding area, suspended matter, phytoplankton, and pH were the main factors controlling the FCO2, but here the influence of temperature, salinity, and total alkalinity on the FCO2 was weak. Organic carbon decomposition in suspended matter was the main reason for the region acting as a CO2 source in winter, and phytoplankton production was the main reason the region was a CO2 sink in summer.

  14. A satellite data driven biophysical modeling approach for estimating northern peatland and tundra CO2 and CH4 fluxes

    NASA Astrophysics Data System (ADS)

    Watts, J. D.; Kimball, J. S.; Parmentier, F. J. W.; Sachs, T.; Rinne, J.; Zona, D.; Oechel, W.; Tagesson, T.; Jackowicz-Korczyński, M.; Aurela, M.

    2014-04-01

    The northern terrestrial net ecosystem carbon balance (NECB) is contingent on inputs from vegetation gross primary productivity (GPP) to offset the ecosystem respiration (Reco) of carbon dioxide (CO2) and methane (CH4) emissions, but an effective framework to monitor the regional Arctic NECB is lacking. We modified a terrestrial carbon flux (TCF) model developed for satellite remote sensing applications to evaluate wetland CO2 and CH4 fluxes over pan-Arctic eddy covariance (EC) flux tower sites. The TCF model estimates GPP, CO2 and CH4 emissions using in situ or remote sensing and reanalysis-based climate data as inputs. The TCF model simulations using in situ data explained > 70% of the r2 variability in the 8 day cumulative EC measured fluxes. Model simulations using coarser satellite (MODIS) and reanalysis (MERRA) records accounted for approximately 69% and 75% of the respective r2 variability in the tower CO2 and CH4 records, with corresponding RMSE uncertainties of ≤ 1.3 g C m-2 d-1 (CO2) and 18.2 mg C m-2 d-1 (CH4). Although the estimated annual CH4 emissions were small (< 18 g C m-2 yr-1) relative to Reco (> 180 g C m-2 yr-1), they reduced the across-site NECB by 23% and contributed to a global warming potential of approximately 165 ± 128 g CO2eq m-2 yr-1 when considered over a 100 year time span. This model evaluation indicates a strong potential for using the TCF model approach to document landscape-scale variability in CO2 and CH4 fluxes, and to estimate the NECB for northern peatland and tundra ecosystems.

  15. 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

    NASA Astrophysics Data System (ADS)

    Mosier, A. R.; Pendall, E.; Morgan, J. A.

    2003-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  17. Surface CO2 and CH4 fluxes simultaneously inferred from proxy GOSAT XCH4:XCO2 retrievals

    NASA Astrophysics Data System (ADS)

    Feng, Liang; Palmer, Paul I.; Parker, Robert; Boesch, Hartmut

    2016-04-01

    The Japanese Greenhouse gases Observing SATellite (GOSAT) has collected atmospheric column measurements of CO2 and CH4 since it was launched in 2009. Observed atmospheric column variations of CO2 and CH4 can in principle be used to infer the responsible surface fluxes. A major advantage of space-based observations over conventional in-situ measurement networks is their better global coverage. However, to improve our current quantitative understanding of CH4 and CO2 fluxes from in-situ data, space-borne column measurements have to exceed strict precision requirements. Uncharacterized systematic errors at regional or sub-regional spatial scales can compromise the ability of these data to infer surface fluxes. Previous work has demonstrated how to infer simultaneously regional CO2 and CH4 flux estimates directly from the XCH4:XCO2 ratio retrieved using the proxy approach. The proxy retrieval method fits CO2 and CH4 gases in nearby spectral windows (at 1.65 μm and 1.61 μm) under the assumption that the ratio between XCH4 and XCO2 reduces the sensitivity to fitting artefacts common to both gases (e.g. aerosol and clouds). The proxy method is also simpler than the full physics approach, and more robust against scattering, resulting in more useful retrievals over regions, such as the Tropical South America, which currently represent the largest uncertainties in our current understanding of the global carbon cycle. We present monthly regional CO2 and CH4 fluxes from 2009 to 2014 inferred from GOSAT XCH4:XCO2 proxy retrievals and NOAA in-situ atmospheric CO2 and CH4 mole fraction measurements. To improve the spatial resolution as well as the numerical efficiency we use an ensemble Kalman Filter to assimilate each single GOSAT and NOAA observation. We show that the CO2 and CH4 fluxes inferred from the proxy retrieval have generally much lower posterior uncertainties than using the full physics GOSAT retrievals of XCO2 and XCH4 or using the NOAA in-situ data. We find

  18. CO2 CH4 and N20 fluxes during land conversion in early bioenergy systems

    NASA Astrophysics Data System (ADS)

    Zenone, T.

    2012-04-01

    CO2 CH4 and N20 fluxes during land conversion in early bioenergy systems Terenzio Zenone1-2, Jiquan Chen1-2, Ilya Gelfand3-4, G. Philip Robertson3-4 1 Department of Environmental Sciences, University of Toledo, Toledo, OH USA 2 Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI USA 3 W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI USA 4Department of Crop and Soil Sciences, Michigan State University, East Lansing, MI USA Environmental sustainability of bioenergy crop cultivation represents an important challenge and is a topic of intensive scientific and political debate worldwide due to increasing societal needs for renewable energy. Despite the increasing knowledge related to potential bioenergy systems, the effect of land use change (LUC) on GHG fluxes during the conversion remains poorly understood but is likely to be substantial. In order to tackle this issue the Great lake Bioenergy Research Center (GLBRC) of the US Department of Energy (DOE) has established a field experiment and deployed a cluster of eddy-covariance towers to quantify the magnitude and changes of ecosystem carbon assimilation, loss, and balance during the conversion and establishment years in a permanent prairie and four types of candidate biofuel systems [Conservation Reserve Program (CRP) grassland, switchgrass, mixed-species restored prairie and corn]. Six sites were converted to soybean in 2009 before establishing the bioenergy systems in 2010 while one site was kept grassland as reference. Soil N2O and CH4 fluxes were measured biweekly with static chambers in four replicate locations in each fields, within the footprint of the eddy covariance tower using static chamber GHG flux protocols of the KBS LTER site. Our field observations, made between January 2009 through December 2010, showed that conversion of CRP to soybean induced net C emissions during the conversion year that ranging from 288 g C m-2, to 173 g C m-2 . while

  19. A satellite data driven biophysical modeling approach for estimating northern peatland and tundra CO2 and CH4 fluxes

    NASA Astrophysics Data System (ADS)

    Watts, J. D.; Kimball, J. S.; Parmentier, F.-J. W.; Sachs, T.; Rinne, J.; Zona, D.; Oechel, W.; Tagesson, T.; Jackowicz-Korczyński, M.; Aurela, M.

    2013-10-01

    The northern terrestrial net ecosystem carbon balance (NECB) is contingent on inputs from vegetation gross primary productivity (GPP) to offset ecosystem respiration (Reco) of carbon dioxide (CO2) and methane (CH4) emissions, but an effective framework to monitor the regional Arctic NECB is lacking. We modified a terrestrial carbon flux (TCF) model developed for satellite remote sensing applications to estimate peatland and tundra CO2 and CH4 fluxes over a pan-Arctic network of eddy covariance (EC) flux tower sites. The TCF model estimates GPP, CO2 and CH4 emissions using either in-situ or remote sensing based climate data as input. TCF simulations driven using in-situ data explained >70% of the r2 variability in 8 day cumulative EC measured fluxes. Model simulations using coarser satellite (MODIS) and reanalysis (MERRA) data as inputs also reproduced the variability in the EC measured fluxes relatively well for GPP (r2 = 0.75), Reco (r2 = 0.71), net ecosystem CO2 exchange (NEE, r2 = 0.62) and CH4 emissions (r2 = 0.75). Although the estimated annual CH4 emissions were small (<18 g C m-2 yr-1) relative to Reco (>180 g C m-2 yr-1), they reduced the across-site NECB by 23% and contributed to a global warming potential of approximately 165 ± 128 g CO2eq m-2 yr-1 when considered over a 100 yr time span. This model evaluation indicates a strong potential for using the TCF model approach to document landscape scale variability in CO2 and CH4 fluxes, and to estimate the NECB for northern peatland and tundra ecosystems.

  20. Flux to the atmosphere of CH4 and CO2 from wetland ponds on the Hudson Bay lowlands (HBLs)

    NASA Technical Reports Server (NTRS)

    Hamilton, J. David; Kelly, Carol A.; Rudd, John W. M.; Hesslein, Raymond H.; Roulet, Nigel T.

    1994-01-01

    Ponds on peatlands of the Hudson Bay lowlands (HBLs) are complex ecosystems in which the fluxes to the atmosphere of CH4 and CO2 were controlled by interacting physical and biological factors. This resulted in strong diel variations of both dissolved gas concentrations and gas fluxes to the atmosphere, necessitating frequent sampling on a 24-hour schedule to enable accurate estimates of daily fluxes. Ponds at three sites on the HBL were constant net sources of CH4 and CO2 to the atmosphere at mean rates of 110-180 mg CH4 m(exp -2)/d and 3700-11,000 mg CO2 m(exp -2)/d. Rates peaked in August and September. For CH4 the pond fluxes were 3-30 times higher than adjacent vegetated surfaces. For CO2 the net pond fluxes were similar in magnitude to the vegetated fluxes but the direction of the flux was opposite, toward atmosphere. Even though ponds cover only 8-12% of the HBL area, they accounted for 30% of its total CH4 flux to the atmosphere. There is some circumstantial evidence that the ponds are being formed by decomposition of the underlying peat and that this decomposition is being stimulated by the activity of N2 fixing cyanobacteria that grow in mats at the peat-water interface. The fact that the gas fluxes from the ponds were so different from the surrounding vegetated surfaces means that any change in the ratio of pond to vegetated area, as may occur in response to climate change, would affect the total HBL fluxes.

  1. A flux-gradient system for simultaneous measurement of the CH4, CO2, and H2O fluxes at a lake-air interface.

    PubMed

    Xiao, Wei; Liu, Shoudong; Li, Hanchao; Xiao, Qitao; Wang, Wei; Hu, Zhenghua; Hu, Cheng; Gao, Yunqiu; Shen, Jing; Zhao, Xiaoyan; Zhang, Mi; Lee, Xuhui

    2014-12-16

    Inland lakes play important roles in water and greenhouse gas cycling in the environment. This study aims to test the performance of a flux-gradient system for simultaneous measurement of the fluxes of water vapor, CO2, and CH4 at a lake-air interface. The concentration gradients over the water surface were measured with an analyzer based on the wavelength-scanned cavity ring-down spectroscopy technology, and the eddy diffusivity was measured with a sonic anemometer. Results of a zero-gradient test indicate a flux measurement precision of 4.8 W m(-2) for water vapor, 0.010 mg m(-2) s(-1) for CO2, and 0.029 μg m(-2) s(-1) for CH4. During the 620 day measurement period, 97%, 69%, and 67% of H2O, CO2, and CH4 hourly fluxes were higher in magnitude than the measurement precision, which confirms that the flux-gradient system had adequate precision for the measurement of the lake-air exchanges. This study illustrates four strengths of the flux-gradient method: (1) the ability to simultaneously measure the flux of H2O, CO2, and CH4; (2) negligibly small density corrections; (3) the ability to resolve small CH4 gradient and flux; and (4) continuous and noninvasive operation. The annual mean CH4 flux (1.8 g CH4 m(-2) year(-1)) at this hypereutrophic lake was close to the median value for inland lakes in the world (1.6 g CH4 m(-2) year(-1)). The system has adequate precision for CH4 flux for broad applications but requires further improvement to resolve small CO2 flux in many lakes.

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

    NASA Astrophysics Data System (ADS)

    Fraser, A.; Palmer, P. I.; Feng, L.; Bösch, H.; Parker, R.; Dlugokencky, E. J.; Krummel, P. B.; Langenfelds, R. L.

    2014-06-01

    We use the GEOS-Chem global 3-D atmospheric chemistry transport model to interpret XCH4:XCO2 column ratios retrieved using a proxy method 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 suffer less from scattering-related regional bias. We show 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 model bias <2.5%. We also show these variations are driven by emissions of CO2 and CH4 that are typically six 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 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

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

    NASA Astrophysics Data System (ADS)

    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

  4. CO2 CH4 flux Air temperature Soil temperature and Soil moisture, Barrow, Alaska 2013 ver. 1

    SciTech Connect

    Margaret Torn

    2015-01-14

    This dataset consists of field measurements of CO2 and CH4 flux, as well as soil properties made during 2013 in Areas A-D of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Included are i) measurements of CO2 and CH4 flux made from June to September (ii) Calculation of corresponding Gross Primary Productivity (GPP) and CH4 exchange (transparent minus opaque) between atmosphere and the ecosystem (ii) Measurements of Los Gatos Research (LGR) chamber air temperature made from June to September (ii) measurements of surface layer depth, type of surface layer, soil temperature and soil moisture from June to September.

  5. Summer fluxes of atmospheric greenhouse gases N2O, CH4 and CO2 from mangrove soil in South China.

    PubMed

    Chen, G C; Tam, N F Y; Ye, Y

    2010-06-01

    The atmospheric fluxes of N(2)O, CH(4) and CO(2) from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 micromol m(-2)h(-1), 11.9 to 5168.6 micromol m(-2)h(-1) and 0.69 to 20.56 mmol m(-2)h(-1) for N(2)O, CH(4) and CO(2), respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N(2)O and CH(4) fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N(2)O and CO(2) fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH(4)(+)-N contents, as well as the soil porosity. However, only soil NH(4)(+)-N concentration had significant effects on CH(4) fluxes.

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

    NASA Technical Reports Server (NTRS)

    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

  7. Contribution of root respiration to soil surface CO2 flux in a boreal black spruce chronosequence.

    PubMed

    Bond-Lamberty, Ben; Wang, Chuankuan; Gower, Stith T

    2004-12-01

    We quantified the contributions of root respiration (RC) and heterotrophic respiration to soil surface CO2 flux (RS) by comparing trenched and untrenched plots in well-drained and poorly drained stands of a black spruce (Picea mariana (Mill.) BSP) fire chronosequence in northern Manitoba, Canada. Our objectives were to: (1) test different equations for modeling RS as a function of soil temperature; and (2) model annual RS and RC for the chronosequence from continuous soil temperature measurements. The choice of equation to model RS strongly affected annual RS and RC, with an Arrhenius-based model giving the best fit to the data, especially at low temperatures. Modeled values of annual RS were positively correlated with soil temperature at 2-cm depth and were affected by year of burn and trenching, but not by soil drainage. During the growing season, measured RC was low in May, peaked in late July and declined to low values by the end of the growing season. Annual RC was < 5% of RS in the recently burned stands, approximately 40% in the 21-year-old stands and 5-15% in the oldest (152-year-old) stands. Evidence suggests that RC may have been underestimated in the oldest stands, with residual root decay from trenching accounting for 5-10% of trenched plot RS at most sites. PMID:15465701

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

    NASA Astrophysics Data System (ADS)

    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

  9. Ectomycorrhizal fungi and past high CO2 atmospheres enhance mineral weathering through increased below-ground carbon-energy fluxes.

    PubMed

    Quirk, Joe; Andrews, Megan Y; Leake, Jonathan R; Banwart, Steve A; Beerling, David J

    2014-07-01

    Field studies indicate an intensification of mineral weathering with advancement from arbuscular mycorrhizal (AM) to later-evolving ectomycorrhizal (EM) fungal partners of gymnosperm and angiosperm trees. We test the hypothesis that this intensification is driven by increasing photosynthate carbon allocation to mycorrhizal mycelial networks using 14CO2-tracer experiments with representative tree–fungus mycorrhizal partnerships. Trees were grown in either a simulated past CO2 atmosphere (1500 ppm)—under which EM fungi evolved—or near-current CO2 (450 ppm). We report a direct linkage between photosynthate-energy fluxes from trees to EM and AM mycorrhizal mycelium and rates of calcium silicate weathering. Calcium dissolution rates halved for both AM and EM trees as CO2 fell from 1500 to 450 ppm, but silicate weathering by AM trees at high CO2 approached rates for EM trees at near-current CO2. Our findings provide mechanistic insights into the involvement of EM-associating forest trees in strengthening biological feedbacks on the geochemical carbon cycle that regulate atmospheric CO2 over millions of years.

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

    NASA Astrophysics Data System (ADS)

    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

  11. Evaluating CO2 and CH4 fluxes in Arctic peatland and tundra using a satellite remote sensing driven biophysical model

    NASA Astrophysics Data System (ADS)

    Watts, J.; Kimball, J. S.; Parmentier, F. W.; Sachs, T.; Rinne, J.; Zona, D.; Oechel, W. C.; Tagesson, T.

    2013-12-01

    The Arctic terrestrial carbon sink is contingent on the balance between vegetation gross primary productivity (GPP) and emissions of carbon dioxide (CO2) and methane (CH4). With climate change, warming temperatures could increase GPP within high latitude systems but may also accelerate soil decomposition and CO2 loss. Regional wetting may also shift carbon emissions towards greater CH4 release, a greenhouse gas at least 25 times more potent than CO2. However, an effective framework for monitoring changes in the Arctic net ecosystem carbon balance (NECB) is lacking. Here we introduce an integrated terrestrial carbon flux (TCF) model approach to estimate CO2 and CH4 fluxes from northern peatland and tundra ecosystems at a daily time step. The TCF model framework uses a light-use efficiency (LUE) algorithm to estimate GPP according to satellite NDVI inputs and estimated moisture and temperature constraints. Ecosystem respiration is derived using a three-pool soil organic carbon decomposition model regulated by surface (< 10 cm depth) soil temperature and volumetric moisture inputs. A TCF-CH4 component simulates gas production according to near-surface temperature, anaerobic soil fractions and labile soil carbon inputs derived during model spin-up. Plant transport, soil diffusion and ebullition pathways are used to regulate CH4 emissions into the atmosphere. The combined TCF CO2 and CH4 model was evaluated against tower eddy covariance (EC) flux datasets from six peatland and tundra sites in North America, Eurasia and Greenland. TCF model simulations driven with site information explained on average > 70% (r^2; p < 0.05) of the respective EC record 8-day cumulative CO2 and CH4 fluxes. The TCF results from model simulations using coarser satellite (MODIS 250-m resolution) and reanalysis (MERRA; 1/2 x 2/3° resolution) inputs were more variable, but captured the overall seasonality and magnitude of ecosystem carbon exchange. Model simulations of annual carbon fluxes

  12. Stable Isotope Fluxes of CO2 and H2O for a Temperate Deciduous Forest in Canada

    NASA Astrophysics Data System (ADS)

    Santos, E. A.; Wagner-Riddle, C.; Warland, J. S.; Brown, S. E.; Lee, X.; Kim, K.; Staebler, R. M.

    2009-12-01

    Stable isotopes of carbon dioxide and water vapor, including 13CO2, C18O16O, HDO and H218O have been used to study the carbon and water cycle. These stable isotopes are particularly useful to separate the contribution of different ecosystem components to the net flux. For example, 13CO2 can be applied as a tracer at sites where soil organic matter and plants present a different isotopic ratio. C18O16O can be used to partitioning soil from foliar respiration, since leaf water is significantly enriched in 18O during the day as a result of leaf transpiration. Continuous measurements of CO2 and H2O exchange and their isotopic values in ecosystems are necessary to better understand the processes related to isotope discrimination. The objective of this study was to investigate the isotopic fluxes of CO2 and H2O continuously in a temperate deciduous forest. The experiment was conducted at the Environment Canada research station, Camp Borden, ON, Canada from June to August 2009. Mixing ratios of C16O2, 13CO2, C18O16O, H216O, HDO and H218O in the sampled air were measured continuously using two tunable diode laser trace gas analyzers (TGA 100A, Campbell Sci., UT, USA). Air was sampled at two heights above the canopy and two heights in the under-storey. The TGA mixing ratio measurements were calibrated by regularly measuring tanks with known concentrations of CO2 isotopic species and water vapor of known isotopic ratios. Atmospheric carbon dioxide (δ13C, and δ18O) and water vapor isotope ratios were calculated, and the isotope signatures of CO2 (δ13N and δ18N) and water vapor flux were obtained based on the flux ratio method. Atmospheric δ13C ranged from -7 (during daytime) to -10 per mil during nighttime, while δ18O values ranged from -1 to -3 per mil. The isotope ratio of the CO2 fluxes in the overstorey ranged from -15 to -22 per mil for δ18N and -22 to -32 per mil for δ13N. These preliminary data will be discussed in light of H2O vapor and flux isotopic ratio

  13. Temporal variability and spatial dynamics of CO2 and CH4 concentrations and fluxes in the Zambezi River system

    NASA Astrophysics Data System (ADS)

    Teodoru, Cristian; Borges, Alberto; Bouillon, Steven; Nyoni, Frank; Nyambe, Imasiku

    2014-05-01

    Spanning over 2900 km in length and with a catchment of approximately 1.4 million km2, the Zambezi River is the fourth largest river in Africa and the largest flowing into the Indian Ocean from the African continent. Yet, there is surprisingly little or no information on carbon (C) cycling in this large river system. As part of a broader study on the riverine biogeochemistry in the Zambezi River basin, we present here mainstream dissolved CO2 and CH4 data collected during 2012 and 2013 over two climatic seasons (dry and wet) to constrain the interannual variability, seasonality and spatial heterogeneity of partial pressure of CO2 (pCO2) and CH4 concentrations and fluxes along the aquatic continuum, in relation to physico-chemical parameters (temperature, conductivity, oxygen, and pH) and various carbon pools (dissolved and particulate, organic and inorganic carbon, total alkalinity, primary production, respiration and net aquatic metabolism). Both pCO2 and CH4 variability was high, ranging from minimal values of 150 ppm and 7 nM, respectively, mainly in the two large reservoirs (the Kariba and the Cabora Bassa characterized by high pH and oxygen and low DOC), up to maximum values of 12,500 ppm and 12,130 nM, CO2 and CH4, respectively, mostly below floodplains/wetlands (low pH and oxygen levels, high DOC and POC concentrations). The interannual variability was relatively large for both CO2 and CH4 (mean pCO2: 2350 ppm in 2013 vs. 3180 ppm in 2013; mean CH4: 600 nM in 2012 vs. 1000 nM in 2013) and significantly higher (up to two fold) during wet season compared to dry season closely linked to distinct seasonal hydrological characteristics. Overall, no clear pattern was observed along the longitudinal gradient as river CO2 and CH4 concentrations are largely influenced by the presence of floodplains/wetlands, anthropogenic reservoirs or natural barriers (waterfalls/ rapids). Following closely the concentration patterns, river CO2 and CH4 mean fluxes of 3440 mg C-CO2 m

  14. A 13C labelling study on carbon fluxes in Arctic plankton communities under elevated CO2 levels

    NASA Astrophysics Data System (ADS)

    de Kluijver, A.; Soetaert, K.; Czerny, J.; Schulz, K. G.; Boxhammer, T.; Riebesell, U.; Middelburg, J. J.

    2013-03-01

    The effect of CO2 on carbon fluxes (production, consumption, and export) in Arctic plankton communities was investigated during the 2010 EPOCA (European project on Ocean Acidification) mesocosm study off Ny Ålesund, Svalbard. 13C labelled bicarbonate was added to nine mesocosms with a range in pCO2 (185 to 1420 μatm) to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton, bacterial and zooplankton consumers, and export. A nutrient-phytoplankton-zooplankton-detritus model amended with 13C dynamics was constructed and fitted to the data to quantify uptake rates and carbon fluxes in the plankton community. The plankton community structure was characteristic for a post-bloom situation and retention food web and showed high bacterial production (∼31% of primary production), high abundance of mixotrophic phytoplankton, low mesozooplankton grazing (∼6% of primary production) and low export (∼7% of primary production). Zooplankton grazing and export of detritus were sensitive to CO2: grazing decreased and export increased with increasing pCO2. Nutrient addition halfway through the experiment increased the export, but not the production rates. Although mixotrophs showed initially higher production rates with increasing CO2, the overall production of POC (particulate organic carbon) after nutrient addition decreased with increasing CO2. Interestingly, and contrary to the low nutrient situation, much more material settled down in the sediment traps at low CO2. The observed CO2 related effects potentially alter future organic carbon flows and export, with possible consequences for the efficiency of the biological pump.

  15. Combining Simultaneous Heat and Water (SHAW) with photosynthesis model to simulate water and CO2 fluxes over wheat canopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Energy, water and CO2 flux at the soil-atmosphere interface is a key interest among ecosystem researchers. The Simultaneous Heat and Water (SHAW) Model describes radiation energy balance, heat transfer and water movement within the Soil-Plant-Atmosphere Continuum, but has no provisions for carbon as...

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Nitrogen fertility rates and landscape positions impacts on CO2 and CH4 fluxes from a landscape seeded to switchgrass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study was conducted in north central US (Bristol, SD) to evaluate the impacts of nitrogen (N) fertility management and landscape positions on carbon dioxide (CO2) and methane (CH4) fluxes from switchgrass (Panicum virgatum L.). The experimental layout was a factorial design of three N levels (l...

  18. CO2 uptake and ecophysiological parameters of the grain crops of midcontinent North America: estimates from flux tower measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We present 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 re...

  19. Impact of episodic vertical fluxes on sea surface pCO2.

    PubMed

    Mahadevan, A; Tagliabue, A; Bopp, L; Lenton, A; Mémery, L; Lévy, M

    2011-05-28

    Episodic events like hurricanes, storms and frontal- and eddy-driven upwelling can alter the partial pressure of CO(2) (pCO(2)) at the sea surface by entraining subsurface waters into the surface mixed layer (ML) of the ocean. Since pCO(2) is a function of total dissolved inorganic carbon (DIC), temperature (T), salinity and alkalinity, it responds to the combined impacts of physical, chemical and biological changes. Here, we present an analytical framework for assessing the relative magnitude and sign in the short-term perturbation of surface pCO(2) arising from vertical mixing events. Using global, monthly, climatological datasets, we assess the individual, as well as integrated, contribution of various properties to surface pCO(2) in response to episodic mixing. The response depends on the relative vertical gradients of properties beneath the ML. Many areas of the ocean exhibit very little sensitivity to mixing owing to the compensatory effects of DIC and T on pCO(2), whereas others, such as the eastern upwelling margins, have the potential to generate large positive/negative anomalies in surface pCO(2). The response varies seasonally and spatially and becomes more intense in subtropical and subpolar regions during summer. Regions showing a greater pCO(2) response to vertical mixing are likely to exhibit higher spatial variability in surface pCO(2) on time scales of days.

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

    NASA Astrophysics Data System (ADS)

    Babenhauserheide, A.; Basu, S.; Houweling, S.; Peters, W.; Butz, A.

    2015-03-01

    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.

  1. Comparing the CarbonTracker and M5-4DVar data assimilation systems for CO2 surface flux inversions

    NASA Astrophysics Data System (ADS)

    Babenhauserheide, A.; Basu, S.; Houweling, S.; Peters, W.; Butz, A.

    2015-09-01

    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.

  2. Year-round record of Dry Valley soil CO2 flux provides insights into Antarctic soil dynamics

    NASA Astrophysics Data System (ADS)

    Risk, D. A.; Lee, C.; Macintyre, C. M.; Cary, C.

    2012-12-01

    The McMurdo Dry Valleys of Antarctica host extreme soil microbial communities that have been extensively studied within the past decade. Activity of microbial communities is routinely measured via soil CO2 flux, and some useful Antarctic measurements have been made during short Austral summers. These studies are mostly spatial in nature, but temporal patterns are also valuable and may provide insights into critical thresholds and the interplay between various mechanisms that drive CO2 flux and its variation. New membrane-based Forced Diffusion (FD) soil efflux techniques offer promise for this application. The purpose of this study was to use a specially designed FD instrument in Hidden Valley of the Antarctic Dry Valleys to evaluate hardware performance in year-round deployments, and to identify features of interest with respect to soil CO2 flux variation. Overall, the deployment was successful. Small but sustained positive fluxes were present only twice during the year. The first such event was small but consistent and of long duration, occurring in the Austral winter. The second was more volatile and likely of microbial origin, and appeared for roughly a month at the end of the calendar year within the Austral summer. The observed patterns suggest that Hidden Valley soil CO2 fluxes are not solely biological in nature, but likely modulated by a combination of biological, geological, and physical processes, which will be discussed in this presentation. In future studies, additional measurement locations, and simultaneous subsurface and lower atmospheric gradient concentration measurements (power-permitting) would be extremely valuable for interpreting measured fluxes, to help identify advective depletion events, the depth source of fluxes, and changes in soil and atmospheric diffusivities.

  3. Temperature drives inter-annual variability of growing season CO2 and CH4 fluxes of Siberian lowland tundra

    NASA Astrophysics Data System (ADS)

    Kutzbach, Lars; Wille, Christian; Runkle, Benjamin; Schreiber, Peter; Sachs, Torsten; Langer, Moritz; Boike, Julia; Pfeiffer, Eva-Maria

    2015-04-01

    Due to the logistic and technical difficulties associated with experimental work in high latitudes, long-term measurements of CO2 and CH4 fluxes from arctic ecosystems are still rare, and published trace gas balances often rely on measurements from one or few growing seasons. The inter-annual variability of environmental conditions such as temperature, precipitation, snow cover, and timing of snow melt can be high in the Arctic, especially for regions which are influenced by both continental and maritime climates, such as the Siberian arctic lowlands. For these ecosystems, we must also expect a great inter-annual variability in the balance of trace gases. Multi-annual data sets are needed to investigate this variability and its drivers. Here we present multi-annual late summer CO2 and CH4 flux data from the Lena River Delta in the Siberian Arctic (72° N, 126° E). The study site Samoylov Island is characterized by polygonal lowland tundra, a vegetation dominated by mosses and sedges, a soil complex of Glacic, Turbic and Histic Cryosols, and an active layer depth of on average 0.5 m. Seasonal flux measurements were carried out with the eddy covariance technique during the 13-year period 2002 - 2014. Within this period, CO2 flux data overlaps during 37 days (20 July - 25 August) for 12 years, and CH4 flux data overlaps during 25 days (28 July - 21 August) for 9 years. Cumulative net ecosystem CO2 exchange (NEE) during the late summer overlap period is fairly consistent for 9 out of 12 years with a CO2 uptake of 1.9 ± 0.1 mol m-2. Three years show a clearly smaller uptake of

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

    NASA Astrophysics Data System (ADS)

    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

  5. Modeling plant-atmosphere carbon and water fluxes along a CO2 gradient

    Technology Transfer Automated Retrieval System (TEKTRAN)

    At short time scales (hourly to daily), plant photosynthesis and transpiration respond nonlinearly to atmospheric CO2 concentration and vapor pressure deficit, depending on plant water status and thus soil moisture. Modeling vegetation and soil responses to different values of CO2 at multiple time s...

  6. Modeling the impacts of temperature and precipitation changes on soil CO2 fluxes from a Switchgrass stand recently converted from cropland.

    PubMed

    Lai, Liming; Kumar, Sandeep; Chintala, Rajesh; Owens, Vance N; Clay, David; Schumacher, Joseph; Nizami, Abdul-Sattar; Lee, Sang Soo; Rafique, Rashad

    2016-05-01

    Switchgrass (Panicum virgatum L.) is a perennial C4 grass native to North America and successfully adapted to diverse environmental conditions. It offers the potential to reduce soil surface carbon dioxide (CO2) fluxes and mitigate climate change. However, information on how these CO2 fluxes respond to changing climate is still lacking. In this study, CO2 fluxes were monitored continuously from 2011 through 2014 using high frequency measurements from Switchgrass land seeded in 2008 on an experimental site that has been previously used for soybean (Glycine max L.) in South Dakota, USA. DAYCENT, a process-based model, was used to simulate CO2 fluxes. An improved methodology CPTE [Combining Parameter estimation (PEST) with "Trial and Error" method] was used to calibrate DAYCENT. The calibrated DAYCENT model was used for simulating future CO2 emissions based on different climate change scenarios. This study showed that: (i) the measured soil CO2 fluxes from Switchgrass land were higher for 2012 which was a drought year, and these fluxes when simulated using DAYCENT for long-term (2015-2070) provided a pattern of polynomial curve; (ii) the simulated CO2 fluxes provided different patterns with temperature and precipitation changes in a long-term, (iii) the future CO2 fluxes from Switchgrass land under different changing climate scenarios were not significantly different, therefore, it can be concluded that Switchgrass grown for longer durations could reduce changes in CO2 fluxes from soil as a result of temperature and precipitation changes to some extent. PMID:27155405

  7. Overview of meteorological conditions and micrometeorological CO2 fluxes over a Scots pine forest at Sodankyl during SIFLEX-200

    NASA Astrophysics Data System (ADS)

    Laurila, T.; Thum, T.; Aurela, M.; Lohila, A.; Lindfors, V.

    In the boreal region, length of the growing season is one of the most important factors explaining annual CO2 net flux between the forest and the atmosphere. The timing of spring recovery is crucial because during that season there is plenty of solar radiation for CO2 assimilation. It is difficult to observe the actual photochemical efficiency of coniferous tree species using traditional reflectance based remote sensing methods, such as NDVI. Solar induced, passive, fluorescence would offer a remote sensing method which gives direct information on the activity of photochemistry. For the development of passive fluorescence measurement methods European Space Agency organised a field campaign SIFLEX-2002 at Sodankyl in northern Finland. The Finnish Meteorological Institute participated in the campaign together with a research group from LURE, Laboratoire pour l~@~Y Utilisation du Rayonnement Electromagnetique, France, Principal Investigator Ismael Moya and research groups from University of Valencia, Spain, Principal Investigator Jose Moreno. Our main tasks were observations of CO2 fluxes between the forest and the atmosphere, meteorological parameters, biomass characterisation and measurements of seasonal cycle of maximum photochemical efficiency of Scots pine needles. In this presentation, we show the seasonal courses of canopy scale CO2 fluxes and maximum efficiency of photosystem II of a boreal pine forest in 2001 and during the SIFLEX- campaign in spring 2002. The aim is to show that during the spring recovery cholorophyll fluorescence data indeed follows the development of CO2 assimilation. From micrometeorological CO2 flux measurements daily average CO2 assimilation, total respiration, and net fluxes were calculated. We observed that in 2002: There was less than average snow in late winter. Warm period in the end of April thawed the snow cover two weeks earlier than average. Scots pine recovered during this warm period to the "spring stage". Net CO2 uptake was

  8. [Error analysis of CO2 storage flux in a temperate deciduous broadleaved forest based on different scalar variables].

    PubMed

    Wang, Jing; Wang, Xing-chang; Wang, Chuan-kuan

    2013-04-01

    Using the measurement data from an 8-level vertical profile of CO2/H2 0 in a temperate deciduous broadleaved forest at the Maoershan Forest Ecosystem Research Station, Northeast China, this paper quantified the errors of CO2 storage flux (Fs ) calculated with three scalar variables, i. e. , CO2 density (rho c), molar fraction (cc), and molar mixing ratio relative to dry air (Xc). The dry air storage in the control volume of flux measurement was not a constant, and thus, the fluctuation of the dry air storage could cause the CO2 molecules transporting out of or into the control volume, i. e. , the variation of the dry air storage adjustment term (Fsd). During nighttime and day-night transition periods, the relative magnitude of Fsd to eddy flux was larger, and ignoring the Fsd could introduce errors in calculating the net CO2 exchange between the forest ecosystem and the atmosphere. Three error sources in the Fs calculation could be introduced from the atmospheric hydrothermal processes, i. e. , 1) air temperature fluctuation, which could cause the largest error, with one order of magnitude larger than that caused by atmospheric pressure (P) , 2) water vapor, its effect being larger than that of P in warm and moist summer but smaller in cold and dry winter, and 3) P, whose effect was generally smaller throughout the year. In estimating the effective CO2 storage (Fs_E) , the Fs value calculated with rho c, cc, and Xc was overestimated averagely by 8. 5%, suggested that in the calculation of Fs, adopting the Xc conservation to atmospheric hydrothermal processes could be more appropriate to minimize the potential errors.

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

    PubMed

    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. PMID:27247397

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

    2016-01-01

    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 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. PMID:27247397

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Automated modeling of ecosystem CO2 fluxes based on closed chamber measurements: A standardized conceptual and practical approach

    NASA Astrophysics Data System (ADS)

    Hoffmann, Mathias; Jurisch, Nicole; Albiac Borraz, Elisa; Hagemann, Ulrike; Sommer, Michael; Augustin, Jürgen

    2015-04-01

    Closed chamber measurements are widely used for determining the CO2 exchange of small-scale or heterogeneous ecosystems. Among the chamber design and operational handling, the data processing procedure is a considerable source of uncertainty of obtained results. We developed a standardized automatic data processing algorithm, based on the language and statistical computing environment R© to (i) calculate measured CO2 flux rates, (ii) parameterize ecosystem respiration (Reco) and gross primary production (GPP) models, (iii) optionally compute an adaptive temperature model, (iv) model Reco, GPP and net ecosystem exchange (NEE), and (v) evaluate model uncertainty (calibration, validation and uncertainty prediction). The algorithm was tested for different manual and automatic chamber measurement systems (such as e.g. automated NEE-chambers and the LI-8100A soil CO2 Flux system) and ecosystems. Our study shows that even minor changes within the modelling approach may result in considerable differences of calculated flux rates, derived photosynthetic active radiation and temperature dependencies and subsequently modeled Reco, GPP and NEE balance of up to 25%. Thus, certain modeling implications will be given, since automated and standardized data processing procedures, based on clearly defined criteria, such as statistical parameters and thresholds are a prerequisite and highly desirable to guarantee the reproducibility, traceability of modelling results and encourage a better comparability between closed chamber based CO2 measurements.

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

    NASA Technical Reports Server (NTRS)

    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

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

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Kawa, S. R.; Baker, D. F.; Collatz, G. J.; Ott, L. E.

    2015-12-01

    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

  17. Phase I Final Report: New Technology Platform to Measure Atmospheric Fluxes and Concentrations of Carbon Isotopes in CO2

    SciTech Connect

    Miles J. Weida, Ph.D. Senior Scientist, Applications Development

    2009-03-24

    There were four goals of the Phase I research carried out to develop the basis for a new technology platform to measure atmospheric fluxes and concentrations of carbon isotopes in CO2. The first was to extend the Daylight Solutions external cavity quantum cascade laser (ECqcL) package to allow continuous, rapid (<10 msec) sweeping of the laser wavelength to acquire spectra. This involved developing a rapid tuning mechanism for our broadly tunable quantum cascade (QC) lasers that meets the requirements of a CO2 isotopologue sensing application. The second goal was to undertake QC device development to procure QC devices capable of lasing in the 4.3 to 4.5 μm spectral region necessary for CO2 isotopologue detection. Final devices procured from this process were to be mounted, coated, and tested to demonstrate their suitability for scanning from 4.3 to 4.5 μm. The third goal was to develop spectral acquisition and analysis algorithms to enable real-time data acquisition and spectral fitting to determine gas temperature and isotopologue concentrations. This involved determining the best spectral analysis algorithm for retrieving CO2 isotopologue temperature and concentration information based on a targeted (i.e. 5% to 10% of center wavelength) scan of CO2 isotopologue absorption features. The culminating goal of Phase I was integration of these three components into a bench-top prototype that can measure CO2 isotopologue ratios in the laboratory.

  18. CO2 and CH4 Surface Flux, Soil Profile Concentrations, and Stable Isotope Composition, Barrow, Alaska, 2012-2013

    DOE Data Explorer

    Curtis, J.B.; Vaughn, L.S.; Torn, M.S.; Conrad, M.S.; Chafe, O.; Bill, M.

    2015-12-31

    In August-October 2012 and June-October 2013, co-located measurements were made of surface CH4 and CO2 flux, soil pore space concentrations and stable isotope compositions of CH4 and CO2, and subsurface temperature and soil moisture. Measurements were made in intensive study site 1 areas A, B, and C, and from the site 0 and AB transects, from high-centered, flat-centered, and low-centered polygons, from the center, edge, and trough of each polygon.

  19. Effects of Warming on CO2 Fluxes in an Alpine Meadow Ecosystem on the Central Qinghai-Tibetan Plateau.

    PubMed

    Ganjurjav, Hasbagan; Gao, Qingzhu; Zhang, Weina; Liang, Yan; Li, Yawei; Cao, Xujuan; Wan, Yunfan; Li, Yue; Danjiu, Luobu

    2015-01-01

    To analyze CO2 fluxes under conditions of climate change in an alpine meadow on the central Qinghai-Tibetan Plateau, we simulated the effect of warming using open top chambers (OTCs) from 2012 to 2014. The OTCs increased soil temperature by 1.62°C (P < 0.05), but decreased soil moisture (1.38%, P < 0.05) during the experiments. The response of ecosystem CO2 fluxes to warming was variable, and dependent on the year. Under conditions of warming, mean gross ecosystem productivity (GEP) during the growing season increased significantly in 2012 and 2014 (P < 0.05); however, ecosystem respiration (ER) increased substantially only in 2012 (P < 0.05). The net ecosystem CO2 exchange (NEE) increased marginally in 2012 (P = 0.056), did not change in 2013(P > 0.05), and increased significantly in 2014 (P = 0.034) under conditions of warming. The GEP was more sensitive to climate variations than was the ER, resulting in a large increase in net carbon uptake under warming in the alpine meadow. Under warming, the 3-year averages of GEP, ER, and NEE increased by 19.6%, 15.1%, and 21.1%, respectively. The seasonal dynamic patterns of GEP and NEE, but not ER, were significantly impacted by warming. Aboveground biomass, particularly the graminoid biomass increased significantly under conditions of warming. Soil moisture, soil temperature, and aboveground biomass were the main factors that affected the variation of the ecosystem CO2 fluxes. The effect of warming on inter- and intra-annual patterns of ecosystem CO2 fluxes and the mechanism of different sensitivities in GEP and ER to warming, require further researched. PMID:26147223

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

    NASA Astrophysics Data System (ADS)

    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

  1. Effects of Warming on CO2 Fluxes in an Alpine Meadow Ecosystem on the Central Qinghai-Tibetan Plateau.

    PubMed

    Ganjurjav, Hasbagan; Gao, Qingzhu; Zhang, Weina; Liang, Yan; Li, Yawei; Cao, Xujuan; Wan, Yunfan; Li, Yue; Danjiu, Luobu

    2015-01-01

    To analyze CO2 fluxes under conditions of climate change in an alpine meadow on the central Qinghai-Tibetan Plateau, we simulated the effect of warming using open top chambers (OTCs) from 2012 to 2014. The OTCs increased soil temperature by 1.62°C (P < 0.05), but decreased soil moisture (1.38%, P < 0.05) during the experiments. The response of ecosystem CO2 fluxes to warming was variable, and dependent on the year. Under conditions of warming, mean gross ecosystem productivity (GEP) during the growing season increased significantly in 2012 and 2014 (P < 0.05); however, ecosystem respiration (ER) increased substantially only in 2012 (P < 0.05). The net ecosystem CO2 exchange (NEE) increased marginally in 2012 (P = 0.056), did not change in 2013(P > 0.05), and increased significantly in 2014 (P = 0.034) under conditions of warming. The GEP was more sensitive to climate variations than was the ER, resulting in a large increase in net carbon uptake under warming in the alpine meadow. Under warming, the 3-year averages of GEP, ER, and NEE increased by 19.6%, 15.1%, and 21.1%, respectively. The seasonal dynamic patterns of GEP and NEE, but not ER, were significantly impacted by warming. Aboveground biomass, particularly the graminoid biomass increased significantly under conditions of warming. Soil moisture, soil temperature, and aboveground biomass were the main factors that affected the variation of the ecosystem CO2 fluxes. The effect of warming on inter- and intra-annual patterns of ecosystem CO2 fluxes and the mechanism of different sensitivities in GEP and ER to warming, require further researched.

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

    USGS Publications Warehouse

    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).

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

    NASA Astrophysics Data System (ADS)

    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 <1% (ash) to 8% (beech) to total GHG emissions. Summing up all GHG emissions, the tree species

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

    NASA Astrophysics Data System (ADS)

    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 <1% (ash) to 8% (beech) to total GHG emissions. Summing up all GHG

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

    NASA Astrophysics Data System (ADS)

    Castaldi, S.; de Grandcourt, A.; Rasile, A.; Skiba, U.; Valentini, R.

    2010-11-01

    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.

  6. Annual Greenhouse Gas (CO2, CH4, and N2O) Fluxes Via Ebullition from a Temperate Emergent Wetland

    NASA Astrophysics Data System (ADS)

    Mcnicol, G.; Sturtevant, C. S.; Knox, S. H.; Baldocchi, D. D.; Silver, W. L.

    2014-12-01

    Quantifying wetland greenhouse gas exchange is necessary to evaluate their potential for mitigating climate change via carbon sequestration. However measuring greenhouse gas fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in wetlands is difficult due to high spatial and temporal variability, and multiple transport pathways of emission. Transport of biogenic soil gas via highly sporadic ebullition (bubbling) events is often ignored or quantified poorly in wetland greenhouse gas budgets, but can rapidly release large volumes of gas to the atmosphere. To quantify a robust annual ebullition flux we measured rates continuously for a year (2013-2014) using custom-built chambers deployed in a restored emergent wetland located in the Sacramento-San Joaquin Delta, CA. We combined ebullition flux rates with observations of gas concentrations to estimate annual ebullition emissions of CO2, CH4, and N2O and compare flux rates to whole-ecosystem exchange of CO2 and CH4 measured simultaneously by eddy covariance.Mean ebullition flux rates were 18.3 ± 5.6 L m-2 yr-1. Ebullition CH4 concentrations were very high and ranged from 23-76 % with a mean of 47 ± 2.9 %; CO2 concentrations were lower and ranged from 0.7-6.6 % with a mean of 2.8 ± 0.3 %; N2O concentrations were below atmospheric concentrations and ranged from 130-389 ppb(v) with a mean of 257 ± 13 ppb(v). We calculated well-constrained annual ebullition fluxes of: 6.2 ± 1.9 g CH4 m-2 yr-1, 1.0 ± 0.3 g CO2 m-2 yr-1 and 9.3 ± 2.8 mg N2O m-2 yr-1. Methane emissions via ebullition were very large, representing 15-25 % of total wetland CH4 emissions measured at this site, whereas ebullition released only relatively small quantities of CO2 and N2O. Our results demonstrate that large releases of CH4 via ebullition from open water surfaces can be a significant component of restored wetland greenhouse gas budgets.

  7. Interannual variability of Net Ecosystem CO2 Exchange and its component fluxes in a subalpine Mediterranean ecosystem (SE Spain)

    NASA Astrophysics Data System (ADS)

    Chamizo, Sonia; Serrano-Ortiz, Penélope; Sánchez-Cañete, Enrique P.; Domingo, Francisco; Arnau-Rosalén, Eva; Oyonarte, Cecilio; Pérez-Priego, Óscar; López-Ballesteros, Ana; Kowalski, Andrew S.

    2015-04-01

    Recent decades under climate change have seen increasing interest in quantifying the carbon (C) balance of different terrestrial ecosystems, and their behavior as sources or sinks of C. Both CO2 exchange between terrestrial ecosystems and the atmosphere and identification of its drivers are key to understanding land-surface feedbacks to climate change. The eddy covariance (EC) technique allows measurements of net ecosystem C exchange (NEE) from short to long time scales. In addition, flux partitioning models can extract the components of net CO2 fluxes, including both biological processes of photosynthesis or gross primary production (GPP) and respiration (Reco), and also abiotic drivers like subsoil CO2 ventilation (VE), which is of particular relevance in semiarid environments. The importance of abiotic processes together with the strong interannual variability of precipitation, which strongly affects CO2 fluxes, complicates the accurate characterization of the C balance in semiarid landscapes. In this study, we examine 10 years of interannual variability of NEE and its components at a subalpine karstic plateau, El Llano de los Juanes, in the Sierra de Gádor (Almería, SE Spain). Results show annual NEE ranging from 55 g C m-2 (net emission) to -54 g C m-2 (net uptake). Among C flux components, GPP was the greatest contributing 42-57% of summed component magnitudes, while contributions by Reco and VE ranged from 27 to 46% and from 3 to 18%, respectively. Annual precipitation during the studied period exhibited high interannual variability, ranging from 210 mm to 1374 mm. Annual precipitation explained 50% of the variance in Reco, 59% of that in GPP, and 56% for VE. While Reco and GPP were positively correlated with annual precipitation (correlation coefficient, R, of 0.71 and 0.77, respectively), VE showed negative correlation with this driver (R = -0.74). During the driest year (2004-2005), annual GPP and Reco reached their lowest values, while contribution of

  8. A Lagrangian view of longwave radiative fluxes for understanding the direct heating response to a CO2 increase

    NASA Astrophysics Data System (ADS)

    Sejas, Sergio A.; Cai, Ming; Liu, Guosheng; Taylor, Patrick C.; Tung, Ka-Kit

    2016-06-01

    This study puts forward a Lagrangian view of downward and upward longwave (LW) fluxes to improve our physical understanding of the influence of key factors on the downward and upward LW fluxes' response to an increase of CO2. To facilitate such a Lagrangian view, we introduce a new saturation-level concept based on the LW radiative transfer theory. The Lagrangian view and the new saturation-level concept enable us to provide, under a single framework, a general radiative transfer explanation of the spatial variation (e.g., stratospheric cooling and lower tropospheric warming) of the direct radiative heating response to an increase of the CO2 concentration. Following the saturation-level concept, the radiatively unsaturated nature of the downward LW flux in the upper stratosphere, due to the lack of a LW source at the top of the atmosphere, is attributed as the root factor that leads to a cooling of the upper stratosphere in direct response to a CO2 increase. The upward LW flux perturbation further enhances the cooling as a result of the negative lapse rate in the stratosphere but is of secondary importance. Furthermore, this study indicates that ozone is not a necessary ingredient for stratospheric cooling to occur, and the stratospheric cooling is therefore a fundamental consequence of a CO2 increase. The unperturbed vertical profile of water vapor is important only in the lower troposphere, where the relatively large concentration of water vapor leads to a downward LW flux perturbation that warms the lower troposphere at the expense of the surface warming.

  9. Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula.

    PubMed

    Lara, Mark J; McGuire, A David; Euskirchen, Eugenie S; Tweedie, Craig E; Hinkel, Kenneth M; Skurikhin, Alexei N; Romanovsky, Vladimir E; Grosse, Guido; Bolton, W Robert; Genet, Helene

    2015-04-01

    The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006-2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 10(6) gC-CO2 day(-1) (uncertainty using 95% CI is between -438.3 and -1366 10(6) gC-CO2 day(-1)) and CH4 flux at 28.9 10(6) gC-CH4 day(-1) (uncertainty using 95% CI is between 12.9 and 44.9 10(6) gC-CH4 day(-1)), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2 uptake (-166.9 10(6) gC-CO2 day(-1)) and CH4 flux (2.8 10(6) gC-CH4 day(-1)) with geomorphic change from low

  10. Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula.

    PubMed

    Lara, Mark J; McGuire, A David; Euskirchen, Eugenie S; Tweedie, Craig E; Hinkel, Kenneth M; Skurikhin, Alexei N; Romanovsky, Vladimir E; Grosse, Guido; Bolton, W Robert; Genet, Helene

    2015-04-01

    The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006-2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 10(6) gC-CO2 day(-1) (uncertainty using 95% CI is between -438.3 and -1366 10(6) gC-CO2 day(-1)) and CH4 flux at 28.9 10(6) gC-CH4 day(-1) (uncertainty using 95% CI is between 12.9 and 44.9 10(6) gC-CH4 day(-1)), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2 uptake (-166.9 10(6) gC-CO2 day(-1)) and CH4 flux (2.8 10(6) gC-CH4 day(-1)) with geomorphic change from low

  11. Regional and Local Carbon Flux Information from a Continuous Atmospheric CO2 Network in the Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Heck, S.; Stephens, B.; Watt, A.; Schimel, D.; Aulenbach, S.

    2006-12-01

    We have established a Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON) to improve our understanding of regional carbon fluxes and to fill key gaps in the North American Carbon Program (NACP). There are strong scientific and societal motivations for determining CO2 exchanges on regional scales. Mountain forests in particular represent a significant potential net CO2 sink in the U.S. and are highly sensitive to land-use practices and climate change. We have developed a new autonomous, inexpensive, and robust CO2 analysis system (AIRCOA) and have deployed these systems at 4 sites: Niwot Ridge (NWR), near Ward, Colorado (August, 2005); Storm Peak Laboratory (SPL) near Steamboat Springs, Colorado (September, 2005); Fraser Experimental Forest (FEF), near Fraser Colorado (August, 2005); and Hidden Peak (HDP), near Snowbird, Utah (April, 2006). We will deploy a fifth site in Northeastern Arizona in September 2006. Measurements of surveillance gas cylinders, and an ongoing intercomparison with flask measurements made by NOAA GMD at Niwot Ridge, show measurement biases of 0.2 ppm or better. Preliminary analysis of CO2 variability at our sites provides valuable information on the usefulness of mountaintop observations in data-assimilation and inverse modeling. Comparisons between our sites and to background sites can give direct regional-scale flux estimates, and analysis of the nocturnal CO2 build-ups at FEF provides unique insights into valley-scale respiration rates. We will present results of these preliminary analyses and plans for future integration with the NACP effort.

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

    NASA Astrophysics Data System (ADS)

    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 < -200 mV. The average (± sd) values of CH4 flux for the 2013/2014 and 2014/2015 seasons were 0.10 ± 0.06 μmol m-2 s-1 and 0.14 ± 0.04 μmol m-2 s-1, respectively. In contrast, CO2 fluxes are strongly negative during the flooded period, indicating net CO2 uptake by the forest, with average (± sd) values of -4.12 ± 3.34 μmol m-2 s-1 for 2013/2014 and -4.14 ± 2.62 μmol m-2 s-1 for 2014/2015. These data indicate that seasonally flooded forests of the 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

  13. Partitioning CO2 Fluxes in Transitional Bioenergy CROPS:EFFECT of Land Use Change

    NASA Astrophysics Data System (ADS)

    Zenone, T.; Chen, J.; Hamilton, S. K.; Robertson, G. P.

    2010-12-01

    The demand for alternatives to petroleum is increasing the production of bioenergy. Undisturbed ecosystems in different part of the globe were converted to bioenergy cultivations. In this study we examined the effect of land conversion on C Pools and fluxes using the Eddy Covariance (EC) technique in seven sites in southwestern Michigan undergoing such conversions. Of the seven sites, four had been managed for the Conservation Reserve Program (CRP) during the last 20 years to maintain them as grasslands. The other three were cultivated in a corn/soybean rotation. The effects of land use change were studied during 2009 when six of the fields (three CRP and three crop fields) were converted to soybean cultivation, with the 7th site remained as a grassland reference. Daytime estimates of ecosystem respiration (Reco) were obtained from the night NEE-temperature relationship. An Arrhenius-type model was used to describe the temperature dependence of Reco. The Gross Primary Productivity (GPP) was then obtained by subtracting Reco from NEE. Soil CO2 fluxes (SRR) were measured in all sites with a portable EGM-4 infrared gas analyzer (PP-Systems, UK). SRR, soil temperature, and soil moisture were analyzed using a two-way ANOVA with repeated measures analyses on one factor. SRR was modeled using a nonlinear regression function to describe SRR as dependant on soil temperature and soil moisture, expressed as soil water content relative to the soil water content at field capacity (RSWC). Standard errors of nonlinear regression parameters were estimated by a bootstrapping algorithm. During winter the agricultural sites were essentially carbon (C) neutral while the grasslands were C sources, with average emissions of 15 g C m-2 month-1. The annual NEP at sites converted from CRP to soybeans had a net emission of 156 (± 25) - 128 (± 27) g C m-2 year-1. The sites previously cultivated as corn/soybean rotation was a net C uptake, with NEP ranging from -91 (± 26) to -57 (± 21) g

  14. Continuous atmospheric monitoring of the injected CO2 behavior over geological storage sites using flux stations: latest technologies and resources

    NASA Astrophysics Data System (ADS)

    Burba, George; Madsen, Rodney; Feese, Kristin

    2014-05-01

    Flux stations have been widely used to monitor emission rates of CO2 from various ecosystems for climate research for over 30 years [1]. The stations provide accurate and continuous measurements of CO2 emissions with high temporal resolution. Time scales range from 20 times per second for gas concentrations, to 15-minute, hourly, daily, and multi-year periods. The emissions are measured from the upwind area ranging from thousands of square meters to multiple square kilometers, depending on the measurement height. The stations can nearly instantaneously detect rapid changes in emissions due to weather events, as well as changes caused by variations in human-triggered events (pressure leaks, control releases, etc.). Stations can also detect any slow changes related to seasonal dynamics and human-triggered low-frequency processes (leakage diffusion, etc.). In the past, station configuration, data collection and processing were highly-customized, site-specific and greatly dependent on "school-of-thought" practiced by a particular research group. In the last 3-5 years, due to significant efforts of global and regional CO2 monitoring networks (e.g., FluxNet, Ameriflux, Carbo-Europe, ICOS, etc.) and technological developments, the flux station methodology became fairly standardized and processing protocols became quite uniform [1]. A majority of current stations compute CO2 emission rates using the eddy covariance method, one of the most direct and defensible micrometeorological techniques [1]. Presently, over 600 such flux stations are in operation in over 120 countries, using permanent and mobile towers or moving platforms (e.g., automobiles, helicopters, and airplanes). Atmospheric monitoring of emission rates using such stations is now recognized as an effective method in regulatory and industrial applications, including carbon storage [2-8]. Emerging projects utilize flux stations to continuously monitor large areas before and after the injections, to locate and

  15. Combining scintillometry and scalar turbulence measurements to obtain minute interval mass fluxes of H2O and CO2

    NASA Astrophysics Data System (ADS)

    Hartogensis, O. K.; van Dinther, D.; de Bruin, H. A. R.; Moene, A. F.; van Kesteren, A. J. H.; Schüttemeyer, D.; Graf, A.

    2009-09-01

    The goal of this study is to test an alternative method to determine turbulent H2O and CO2 fluxes, which has a faster statistical convergence than the classical eddy-covariance method. The reason to develop such a tool is that eddy-covariance is questionable under non-stationary conditions, e.g. in the intermittent stable boundary layer or rapidly changing cloud-cover. The eddy-covariance method requires an integration time of at least 20 minutes under statistically stationary conditions, see e.g. Aubinet et al. (2000). Under non-stationary conditions this record length may not be available. Howell and Sun (1999) showed that strength of intermittency increases with stability, but, surprisingly, intermittency also occurs under weakly stable conditions, see Kondo et al. (1978). Also, by taking extremely short flux averaging intervals of one minute or even less, we would like to investigate the response time of a crop in terms of the H2O and CO2 flux to rapid changing radiation conditions, i.e. rapidly changing cloud cover. In our new method, that we forward as an alternative to eddy covariance, we suggest a hybrid set-up that combines a point-sensor for scalar H2O and CO2 with a dual-beam laser-scintillometer (DBLS). We used a LiCor7500 open path fast response H2O/CO2 sensor. The H2O/CO2 sensor forms the basis for estimating the turbulent exchange scale for H2O and CO2. The DBLS gives the friction velocity and stability. With the DBLS turbulence is averaged both in time and space allowing short averaging flux intervals down to a couple of seconds (Hartogensis et al., 2002). We will discuss a number of path-ways to combine the scintillometer and point-scalar measurements and demonstrate their potential in obtaining short (~minute) interval mass fluxes of H2O and CO2. The first path-way is based on structure parameters of H2O and CO2. The second path-way uses the variance of H2O and CO2 and applies the ideas posed by De Bruin et al. (1999). The third path-way is based

  16. High-resolution mapping of biogenic carbon fluxes to improve urban CO2 monitoring, reporting, and verification

    NASA Astrophysics Data System (ADS)

    Hardiman, B. S.; Hutyra, L.; Gately, C.; Raciti, S. M.

    2014-12-01

    Urban areas are home to 80% of the US population and 70% of energy related fossil fuel emissions originate from urban areas. Efforts to accurately monitor, report, and verify anthropogenic CO2 missions using atmospheric measurements require reliable partitioning of anthropogenic and biogenic sources. Anthropogenic emissions peak during the daytime, coincident with biogenic drawdown of CO2. In contrast, biogenic respiration emissions peak at night when anthropogenic emissions are lower. This temporal aliasing of fluxes requires careful modeling of both biogenic and anthropogenic fluxes for accurate source attribution through inverse modeling. Biogenic fluxes in urban regions can be a significant component of the urban carbon cycle. However, vegetation in urban areas is subject to longer growing seasons, reduced competition, higher rates of nitrogen deposition, and altered patterns of biomass inputs, all interacting to elevate C turnover rates relative to analogous non-urban ecosystems. These conditions suggest that models that ignore urban vegetation or base biogenic flux estimates on non-urban forests are likely to produce inaccurate estimates of anthropogenic CO2 emissions. Biosphere models often omit biogenic fluxes in urban areas despite potentially extensive vegetation coverage. For example, in Massachusetts, models mask out as much as 40% of land area, effectively assuming they have no biological flux. This results in a ~32% underestimate of aboveground biomass (AGB) across the state as compared to higher resolution vegetation maps. Our analysis suggests that some common biomass maps may underestimate forest biomass by ~520 Tg C within the state of