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Sample records for carbon cycling studies

  1. JGI's Carbon Cycling Studies on Restored Marshes

    SciTech Connect

    Tringe, Susannah; Theroux, Susanna

    2015-06-02

    DOE Joint Genome Institute Metagenome Program Head, Susannah Tringe, and postdoc, Susie Theroux, discuss the lessons to be learned from studying the microbial diversity of marshes that have been converted to other uses, and are now being restored, as well as the potential impacts on the global carbon cycle.

  2. Various supercritical carbon dioxide cycle layouts study for molten carbonate fuel cell application

    NASA Astrophysics Data System (ADS)

    Bae, Seong Jun; Ahn, Yoonhan; Lee, Jekyoung; Lee, Jeong Ik

    2014-12-01

    Various supercritical carbon dioxide (S-CO2) cycles for a power conversion system of a Molten Carbonate Fuel Cell (MCFC) hybrid system are studied in this paper. Re-Compressing Brayton (RCB) cycle, Simple Recuperated Brayton (SRB) cycle and Simple Recuperated Transcritical (SRT) cycle layouts were selected as candidates for this study. In addition, a novel concept of S-CO2 cycle which combines Brayton cycle and Rankine cycle is proposed and intensively studied with other S-CO2 layouts. A parametric study is performed to optimize the total system to be compact and to achieve wider operating range. Performances of each S-CO2 cycle are compared in terms of the thermal efficiency, net electricity of the MCFC hybrid system and approximate total volumes of each S-CO2 cycle. As a result, performance and total physical size of S-CO2 cycle can be better understood for MCFC S-CO2 hybrid system and especially, newly suggested S-CO2 cycle shows some success.

  3. Further Studies on Oceanic Biogeochemistry and Carbon Cycling

    NASA Technical Reports Server (NTRS)

    Signorini, S. R.; McClain, C. R.

    2003-01-01

    This TM consists of two chapters. Chapter I describes the development of a coupled, one-dimensional biogeochemical model using turbulence closure mixed layer (TCMLM) dynamics. The model is applied to the Sargasso Sea at the BATS (Bermuda Atlantic Time Series) site and the results are compared with a previous model study in the same region described in NASNTP-2001-209991. The use of the TCMLM contributed to some improvements in the model simulation of chlorophyll, PAR, nitrate, phosphate, and oxygen, but most importantly, the current model achieved good agreement with the data with much more realistic background eddy diffusivity. However, off-line calculations of horizontal transport of biogeochemical properties revealed that one-dimensional dynamics can only provide a limited assessment of the nutrient and carbon balances at BATS. Future studies in the BATS region will require comprehensive three-dimensional field studies, combined with three-dimensional eddy resolving numerical experiments, to adequately quantify the impact of the local and remote forcing on ecosystem dynamics and carbon cycling. Chapter II addresses the sensitivity of global sea-air CO, flux estimates to wind speed, temperature, and salinity. Sensitivity analyses of sea-air CO, flux to wind speed climatologies, gas transfer algorithms, SSS and SST were conducted for the global oceans and regional domains. Large uncertainties in the global sea-air flux are identified, primarily due to the different gas transfer algorithms used. The sensitivity of the sea-air flux to SST and SSS is similar in magnitude to the effect of using different wind climatologies. Globally, the mean ocean uptake of CO, changes by 5 to 16%, depending upon the combination of SST and SSS used.

  4. The Contemporary Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Houghton, R. A.

    2003-12-01

    the past 150 years as a result of human-induced emissions of carbon. The processes responsible for sinks of carbon on land and in the sea are reviewed from the perspective of feedbacks, and the chapter concludes with some prospects for the future.Earlier comprehensive summaries of the global carbon cycle include studies by Bolin et al. (1979, 1986), Woodwell and Pecan (1973), Bolin (1981), NRC (1983), Sundquist and Broecker (1985), and Trabalka (1985). More recently, the Intergovernmental Panel on Climate Change (IPCC) has summarized information on the carbon cycle in the context of climate change ( Watson et al., 1990; Schimel et al., 1996; Prentice et al., 2001). The basic aspects of the global carbon cycle have been understood for decades, but other aspects, such as the partitioning of the carbon sink between land and ocean, are being re-evaluated continuously with new data and analyses. The rate at which new publications revise estimates of these carbon sinks and re-evaluate the mechanisms that control the magnitude of the sinks suggests that portions of this review will be out of date by the time of publication.

  5. Study of Supercritical Carbon Dioxide Power Cycle for Low Grade Heat Conversion

    SciTech Connect

    Vidhi, Rachana; Goswami, Yogi D.; Chen, Huijuan; Stefanakos, Elias; Kuravi, Sarada; Sabau, Adrian S

    2011-01-01

    Research on supercritical carbon dioxide power cycles has been mainly focused on high temperature applications, such as Brayton cycle in a nuclear power plant. This paper conducts a comprehensive study on the feasibility of a CO2-based supercritical power cycle for low-grade heat conversion. Energy and exergy analyses of the cycle were conducted to discuss the obstacles as well as the potentials of using supercritical carbon dioxide as the working fluid for supercritical Rankine cycle, Carbon dioxide has desirable qualities such as low critical temperature, stability, little environmental impact and low cost. However, the low critical temperature might be a disadvantage for the condensation process. Comparison between a carbon dioxide-based supercritical Rankine cycle and an organic fluid-based supercritical Rankine cycle showed that the former needs higher pressure to achieve the same efficiency and a heat recovery system is necessary to desuperheat the turbine exhaust and pre-heat the pressure charged liquid.

  6. The Carbon Cycle and the Earth Systems--Studying the Carbon Cycle in Multidisciplinary Environmental Context.

    ERIC Educational Resources Information Center

    Gudovitch, Yossi; Orion, Nir

    This paper describes a method that attempts to confront the challenges of developing an environmentally-based earth sciences program. The research scheme includes five stages: (1) predevelopment study; (2) curriculum development; (3) implementation; (4) formative evaluation; and (5) curriculum modification. The research results indicate that the…

  7. Export and Cycling of Continental Shelf Carbon: A Modeling Study

    NASA Astrophysics Data System (ADS)

    Siedlecki, S.; Archer, D.; Mahadevan, A.

    2004-12-01

    Continental margins play a significant role in the production and burial of organic carbon in the ocean, but these areas are poorly resolved in global circulation models. In this study, a high-resolution three-dimensional, nonhydrostatic idealized coastal model of the eastern United States after Mahadevan and Archer, 2000, 1998, was modified to simulate organic carbon production and export off the shelf. The model assumes a periodic north and south boundary, solid offshore and bottom boundaries, and a shelf-break density front determined by bathymetry. The model uses a free surface and a sigma grid in the vertical. We are in the process of formulating a carbon and nutrient component for this model. The model is initialized with a vertical nutrient profile taken from the open Atlantic Ocean. Mesoscale wind-driven circulation and vertical diffusion bring nutrients to the euphotic zone. Primary production is based on light availability and nutrient concentration. The particles advect with the flow and sink with a specified velocity. Remineralization is first-order in carbon concentration, and produces ammonia. Ammonia is slowly reoxidized to nitrate in subsurface waters, and used for recycled production in the euphotic zone. We are searching for a model of the production, sinking, and interconversion of multiple types of particles, which predicts the observed trends in f-ratio from coastal to pelagic ecosystems. The model is sensitive to sinking velocity, remineralization rate, vertical diffusivity, the uptake rate of nitrate, the uptake rate of ammonia, and the oxidation rate of ammonia to nitrate. Using the steady state solution of the one-dimensional model to initialize the three-dimensional model, we study the effect of vertical and horizontal advection and three-dimensional oceanographic processes on the distribution and export of carbon from the coastal system. We will compare the sensitivities of a box-budget, a one-dimensional diffusional, and the full 3-D

  8. The global carbon cycle

    SciTech Connect

    Sedjo, R.A. )

    1990-10-01

    The author discusses the global carbon cycle and cites the results of several recently completed research projects, that seem to indicate that the temperate zone forests are a sink for carbon rather than a source, as was previously believed.

  9. Seeing the Carbon Cycle

    ERIC Educational Resources Information Center

    Drouin, Pamela; Welty, David J.; Repeta, Daniel; Engle-Belknap, Cheryl A.; Cramer, Catherine; Frashure, Kim; Chen, Robert

    2006-01-01

    In this article, the authors present a classroom experiment that was developed to introduce middle school learners to the carbon cycle. The experiment deals with transfer of CO[subscript 2] between liquid reservoirs and the effect CO[subscript 2] has on algae growth. It allows students to observe the influence of the carbon cycle on algae growth,…

  10. The carbon cycle revisited

    NASA Technical Reports Server (NTRS)

    Bolin, Bert; Fung, Inez

    1992-01-01

    Discussions during the Global Change Institute indicated a need to present, in some detail and as accurately as possible, our present knowledge about the carbon cycle, the uncertainties in this knowledge, and the reasons for these uncertainties. We discuss basic issues of internal consistency within the carbon cycle, and end by summarizing the key unknowns.

  11. The carbon dioxide cycle

    USGS Publications Warehouse

    James, P.B.; Hansen, G.B.; Titus, T.N.

    2005-01-01

    The seasonal CO2 cycle on Mars refers to the exchange of carbon dioxide between dry ice in the seasonal polar caps and gaseous carbon dioxide in the atmosphere. This review focuses on breakthroughs in understanding the process involving seasonal carbon dioxide phase changes that have occurred as a result of observations by Mars Global Surveyor. ?? 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  12. Integrated Climate and Carbon-cycle Model

    Energy Science and Technology Software Center (ESTSC)

    2006-03-06

    The INCCA model is a numerical climate and carbon cycle modeling tool for use in studying climate change and carbon cycle science. The model includes atmosphere, ocean, land surface, and sea ice components.

  13. The Value of Agricultural Data in Carbon Cycle Studies: A Case Study from Ontario

    NASA Astrophysics Data System (ADS)

    Chan, E. C.; Lin, J. C.

    2009-05-01

    Agricultural activities can play a significant role in the terrestrial carbon cycle by either serving as a source or sink of carbon dioxide (CO2). Specifically, cultivation can act as a sink when carbon is photosynthetically fixed and sequestered into soils during crop growth. Ontario is one of the major field crop producing regions in Canada, accounting for 55.2% of total national production of corn and 60% of winter wheat during 2006. As a result, understanding Ontario's agricultural net primary production (NPP) is of great importance to resource managers and policy makers when managing risks and opportunities arising from climate change. In this study, Ontario's agricultural data were used in order to determine the following: (1) relationships between Ontario's crop NPP and climatic variables such as temperature, precipitation, as well as climate indices; and (2) uncertainties in a carbon flux model - the Vegetation Photosynthesis and Respiration Model (VPRM). VPRM is a data-driven, diagnostic biospheric carbon model designed for data assimilation purposes. To calculate crop NPP, two different published approaches that relied on using known yield information along with a series of crop-specific parameters and coefficients were applied. Then, environmental factors and spatiotemporal changes of crop NPP were examined statistically through exploring historical weather records of the province. With respect to the NPPs' interannual variability, comparison of their times series and that of climate indices such as the multivariate El-Nino-Southern Oscillation (ENSO) index and others during 1987 to 2007 found that NPP values were fairly positively correlated with the East Atlantic (EA) pattern. In fact, this teleconnection pattern showed stronger correlations than ENSO and North Atlantic Oscillation (NAO). Comparisons of the crop data against VPRM estimates revealed biases in VPRM simulations. The model underestimated fractions of cropland areas and overestimated annual

  14. Soil, environmental, and watershed measurements in support of carbon cycling studies in northwestern Mississippi

    USGS Publications Warehouse

    Huntington, T.G.; Harden, J.W.; Dabney, S.M.; Marion, D.A.; Alonso, C.; Sharpe, J.M.; Fries, T.L.

    1998-01-01

    Measurements including soil respiration, soil moisture, soil temperature, and carbon export in suspended sediments from small watersheds were recorded at several field sites in northwestern Mississippi in support of hillslope process studies associated with the U.S. Geological Survey's Mississippi Basin Carbon Project (MBCP). These measurements were made to provide information about carbon cycling in agricultural and forest ecosystems to understand the potential role of erosion and deposition in the sequestration of soil organic carbon in upland soils. The question of whether soil erosion and burial constitutes an important net sink of atmospheric carbon dioxide is one hypothesis that the MBCP is evaluating to better understand carbon cycling and climate change. This report contains discussion of methods used and presents data for the period December 1996 through March 1998. Included in the report are ancillary data provided by the U.S. Department of Agriculture (USDA) ARS National Sedimentation Laboratory and U.S. Forest Service (USFS) Center for Bottomland Hardwoods Research on rainfall, runoff, sediment yield, forest biomass and grain yield. Together with the data collected by the USGS these data permit the construction of carbon budgets and the calibration of models of soil organic matter dynamics and sediment transport and deposition. The U.S. Geological Survey (USGS) has established cooperative agreements with the USDA and USFS to facilitate collaborative research at research sites in northwestern Mississippi.

  15. The Pyrogenic Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Bird, Michael I.; Wynn, Jonathan G.; Saiz, Gustavo; Wurster, Christopher M.; McBeath, Anna

    2015-05-01

    Pyrogenic carbon (PyC; includes soot, char, black carbon, and biochar) is produced by the incomplete combustion of organic matter accompanying biomass burning and fossil fuel consumption. PyC is pervasive in the environment, distributed throughout the atmosphere as well as soils, sediments, and water in both the marine and terrestrial environment. The physicochemical characteristics of PyC are complex and highly variable, dependent on the organic precursor and the conditions of formation. A component of PyC is highly recalcitrant and persists in the environment for millennia. However, it is now clear that a significant proportion of PyC undergoes transformation, translocation, and remineralization by a range of biotic and abiotic processes on comparatively short timescales. Here we synthesize current knowledge of the production, stocks, and fluxes of PyC as well as the physical and chemical processes through which it interacts as a dynamic component of the global carbon cycle.

  16. Simple ocean carbon cycle models

    SciTech Connect

    Caldeira, K.; Hoffert, M.I.; Siegenthaler, U.

    1994-02-01

    Simple ocean carbon cycle models can be used to calculate the rate at which the oceans are likely to absorb CO{sub 2} from the atmosphere. For problems involving steady-state ocean circulation, well calibrated ocean models produce results that are very similar to results obtained using general circulation models. Hence, simple ocean carbon cycle models may be appropriate for use in studies in which the time or expense of running large scale general circulation models would be prohibitive. Simple ocean models have the advantage of being based on a small number of explicit assumptions. The simplicity of these ocean models facilitates the understanding of model results.

  17. An integrated modeling study of ocean circulation, the ocean carbon cycle, marine ecosystems, and climate change

    NASA Astrophysics Data System (ADS)

    Cao, Long

    The unifying theme of this study is to conduct an extensive exploration of various interactions between ocean circulation, the carbon cycle, marine ecosystems, and climate change using an earth system model of intermediate complexity, ISAM-2.5D (Integrated Science Assessment Model). First, through the simulation of radiocarbon (in terms of Delta14C) it is demonstrated that the inclusion of isopycnal diffusion and a parameterization of eddy-induced circulation in the ISAM-2.5D model yields the most realistic representation of ocean mixing and circulation. Secondly, I demonstrate the value of the simulation of multiple tracers, combined with a variety of observational data, in constraining the ISAM-2.5D model that has been constrained by the simulation of Delta14C. Through the simulation of ocean biogeochemical cycles and CFC-11 and the use of the updated observational data of bomb radiocarbon, I improve the Delta14C-constrained ISAM-2.5D model's performance in simulating ocean circulation and air-sea gas exchange, as well as its credibility in predicting oceanic carbon uptake. Third, I use the ISAM-2.5D model to assess the efficiency of direct carbon injection into the deep ocean with the influence of climate change. It is shown that the consideration of climate change enhances the retention time of injected carbon into the Atlantic Ocean as a result of weakened North Atlantic overturning circulation in a warming climate. However, the climatic effect is insignificant on the efficiency of carbon injection into the Pacific and Indian Oceans. Finally, I quantify that increased atmospheric CO2 concentrations would be mainly responsible for future ocean acidification, including lowering in ocean pH and sea water saturation state with respect to carbonate minerals. The consideration of climate change produces a second-order modification to projected ocean acidification. Therefore, in addition to its radiative effects on climate change, increased atmospheric CO2

  18. A Brief Review of the Application of 14C in Terrestrial Carbon Cycle Studies

    SciTech Connect

    Guilderson, T; Mcfarlane, K

    2009-10-22

    An over-arching goal of the DOE TCP program is to understand the mechanistic controls over the fate, transport, and residence time of carbon in the terrestrial biosphere. Many of the modern process and modeling studies focus on seasonal to interannual variability. However, much of the carbon on the landscape and in soils is in separate reservoirs with turnover times that are multi-decadal to millennial. It is the controls on these longer term pools or reservoirs that is a critical unknown in the face of rising GHGs and climate change and uncertainties of the terrestrial biosphere as a future global sink or source of atmospheric CO{sub 2} [eg., Friedlingstein et al., 2006; Govindasamy et al., 2005; Thompson et al., 2004]. Radiocarbon measurements, in combination with other data, can provide insight into, and constraints on, terrestrial carbon cycling. Radiocarbon (t{sub 1/2} 5730yrs) is produced naturally in the stratosphere when secondary neutrons generated by cosmic rays collide with {sup 14}N atoms [Libby 1946; Arnold and Libby, 1949]. Upon formation, {sup 14}C is rapidly oxidized to CO and then to CO{sub 2}, and is incorporated into the carbon cycle. Due to anthropogenic activities, the amount of {sup 14}C in the atmosphere doubled in the mid/late 1950s and early 1960s from its preindustrial value of {sup 14}C/{sup 12}C ratio of 1.18 x 10{sup -12} [eg., Nydal and Lovseth, 1983]. Following the atmospheric weapons test ban in 1963, the {sup 14}C/{sup 12}C ratio, has decreased due to the net isotopic exchange between the ocean and terrestrial biosphere [eg., Levin and Hessheimer, 2000] and a dilution effect due to the burning of {sup 14}C-free fossil fuel carbon, the 'Suess Effect' [Suess, 1955]. In the carbon cycle literature, radiocarbon measurements are generally reported as {Delta}{sup 14}C, which includes a correction for mass dependent fractionation [Stuiver and Polach, 1977]. In the context of carbon cycle studies radiocarbon measurements can be used to

  19. Carbon and Nitrogen Cycling in Urban Landscapes: Global, Regional Dynamics and Case Studies.

    NASA Astrophysics Data System (ADS)

    Svirejeva-Hopkins, A.; Nardoto, G. B.; Schellnhuber, H.

    2008-12-01

    The urban population has been growing rapidly in the last decades and is predicted to continue its exponential trend, especially in the developing countries, which would create additional pressure on the environment by overpopulated unsustainable cities and will continue to substantially change the main Biogeochemical cycles. Such disturbances in the main driving cycle of the Biosphere (global carbon cycle) and the nitrogen cycle, induced by sprawling urban human activities, lead to global, regional and local environmental problems, i.e. global warming, photochemical smog, stratospheric ozone depletion, soil acidification, nitrate pollution of surface and ground water, coastal ecosystem disturbances. Since urban areas are expected to continue their rapid expansion in the 21st century, accompanied by growing energy production, increased food demand, expanding transportation and industrialization it becomes more and more important to be able to describe and forecast the dynamics of biogeochemical functioning of these landscapes (which have altered characteristics compared to the natural ecosystems). Moreover, from the environmental policy perspective, a high density of people makes cities focal points of vulnerability to global environmental change. The model based on the forecasting the dynamics of urban area growth, allows us to forecast the dynamics of Carbon and Nitrogen on the urban territories at different scales. However, nitrogen cycle is very complex and is closely interlinked with the other major biogeochemical cycles, such as oxygen and water. The system of water supply and liquid waste carried by water out of the system 'city' is investigated. In order to better understand the mechanisms of cycling, we consider the case studies, when we investigated the detailed fluxes of Carbon and Nitrogen in Sao Paolo (Brazil) and Paris (France). When we know the yearly amounts of carbon and nitrogen, produced by a city, we should be capable of coming up with what

  20. Carbon Cycling Studies in Forest and Rangeland Ecosystems of Northern and Central Coastal California

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Gross, P.; Hiatt, S.; Genovese, V.

    2008-12-01

    The varied topography and micro-climates of northern and central coastal California result in high biodiversity and many different levels of primary production driving regional carbon cycles. Coastal mountains trap moisture from low clouds and fog in summer to supplement rainfall in winter. This creates a favorable micro-environment for coniferous forests, including the southernmost habitat of the coast redwood (Sequoia sempervirens), which grows mainly on lower north-facing slopes in Big Sur. In rain shadows, forests transition to open oak woodland, and then into the more fire-tolerant chaparral and coast scrub. Field sites for our on-going climate change studies on the California northern and central coasts currently include the University of California Santa Cruz Campus Natural Reserve, the US Forest Service Brazil Ranch, and the University of California Big Creek Reserve. We are conducting research at each of these sites to better understand possible impacts of climate change, including: (1) biological and physical capacity of soils to capture carbon and retain plant-essential nutrients; (2) rates of plant-soil water and carbon cycling and energy flow; and (3) recovery mechanisms for disturbances such as invasive weed species, grazing, and wildfire. The NASA-CASA simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate carbon cycling for much of the central coast as far north as Mendocino County. Net primary production (NPP) of all vegetation cover was mapped at 30-meter resolution for selected years by combining MODIS and Landsat images across the region. Results show annual NPP predictions of between 200-400 grams C per square meter for coastal scrub and 800-1200 grams C per square meter for coastal evergreen forests, Net ecosystem fluxes of carbon will be presented for the region based on NASA-CASA modeling and field measurements of soil respiration fluxes.

  1. CarboNA: International Studies of the North American Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Denning, S.; Cavallaro, N.; Ste-Marie, C.; Muhlia-Melo, A.

    2009-05-01

    A Science Steering Committee has been formed consisting of carbon cycle scientists from Canada, Mexico, and the United States and government agency contacts from each country, to draft a Science Plan for CarboNA. Science questions that we will address include: 1. What's the current carbon budget of NA and adjacent oceans, including spatial structure and seasonal-to- interannual variations? 2. What mechanisms are involved? What processes control the time mean vs the interannual variability? 3. When will sinks saturate? Will they become sources? Are there surprises in store? What roles will be played by melting permafrost, boreal warming, and subtropical desertification, and tropical development? 4. What are the likely responses of terrestrial ecosystems and coastal oceans to climate change and enhanced CO2? 5. What roles will economic development, energy technology, and trade play in mitigating increases in fossil fuel emissions? In addition to the national research programs already underway in the three countries, we anticipate special collaborative projects of international scope. For example: 1. Studies of the response of terrestrial ecosystems to climate change along an ecological gradient from the Arctic to the Tropics; 2. Truly continental budgets for atmospheric greenhouse gases using data from land-based, airborne, marine, and spaceborne platforms; 3. An aggressively interdisciplinary intensive experiment to understand and quantify carbon cycle processes and budgets in the Gulf of Mexico Basin; 4. Investigation of the turrent state and likely future changes in carbon cycling in coastal ocean environments, including river inputs of POC, DOC, DIC, and nutrients; impacts on fisheries and coastal economies; exchange between coastal oceans and deep ocean basins; and air-sea gas exchange; 5. Government-level agreements on data sharing and harmonization, including but not limited to forest inventories, agricultural data, fossil fuel emissions data, land-use data

  2. Application of stable carbon isotopes in long term mesocosm studies for carbon cycle investigation

    NASA Astrophysics Data System (ADS)

    Esposito, Mario

    2016-04-01

    Carbon dioxide (CO2) is an effective greenhouse gas. The Oceans absorb ca. 30% of the anthropogenic CO2 emissions and thereby partly attenuate deleterious climate effects. A consequence of the oceanic CO2 uptake is a decreased seawater pH and planktonic community shifts. The quantification of the anthropogenic perturbation was investigated through stable carbon isotope analysis in three "long term" mesocosm experiments (Sweden 2013, Gran Canaria 2014, Norway 2015) which reproduced near natural ecosystem conditions under both controlled and modified future CO2 level (up to 2000 ppm) scenarios. Parallel measurements of the stable isotope composition of dissolved inorganic carbon (δ13CDIC) dissolved organic carbon (δ13CDOC) and particulate carbon (δ13CTPC) both from the mesocosms water column and sediment traps showed similar trends in all the three experiments. A CO2 response was noticeable in the isotopic dataset, but increased CO2 levels had only a subtle effect on the concentrations of the dissolved and particulate organic carbon pool. Distinctive δ13C signatures of the particulate carbon pool both in the water column and the sediments were detectable for the different CO2 treatments and they were strongly correlated with the δ13CDIC signatures but not with the δ13CDOC pool. The validity of the isotopic data was verified by cross-analyses of multiple substances of known isotopic signatures on a GasBench, Elemental Analyser (EA) and on an in-house TOC-IRMS setup for the analysis of δ13CDIC, δ13CTPC and δ13CDOC, respectively. Results from these mesocosm experiments proved the stable carbon isotope approach to be an effective tool for quantifying the uptake and carbon transfer among the various compartments of the marine carbon system.

  3. Carbon Capture (Carbon Cycle 2.0)

    ScienceCinema

    Smit, Berend

    2011-06-08

    Berend Smit speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 3, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  4. Ocean Carbon Cycle Data from the Joint Global Ocean Flux Study (JGOFS)

    DOE Data Explorer

    The U.S. JGOFS program, a component of the U.S Global Change Research Program, grew out of the recommendations of a National Academy of Sciences workshop in 1984. An ambitious goal was set to understand the controls on the concentrations and fluxes of carbon and associated nutrients in the ocean. A new field of ocean biogeochemistry emerged with an emphasis on quality measurements of carbon system parameters and interdisciplinary field studies of the biological, chemical and physical process which control the ocean carbon cycle. U.S. JGOFS, ended in 2005 with the conclusion of the Synthesis and Modeling Project (SMP). Data are available throughout the U.S. JGOFS web site at http://usjgofs.whoi.edu/ and from the U.S. JGOFS Data System at http://usjgofs.whoi.edu/jg/dir/jgofs/. Major named segments of the project are: Bermuda Atlantic Time Series (BATS) Study, Hawaii Ocean Time-series (HOT) Study, Equatorial Pacific Process Study, North Atlantic Bloom Experiment (1989), Arabian Sea Process Study, and the Southern Ocean Process Study.

  5. TEM Studies of Carbon Coated LiFePO4 after Charge DischargeCycling

    SciTech Connect

    Gabrisch, H.; Wilcox, J.; Doeff, M.

    2006-11-30

    Carbon coating has proven to be a successful approach toimprove the rate capability of LiFePO4 used in rechargeable Li-ionbatteries. Investigations of the microstructure of carbon coated LiFePO4after charge discharge cycling shows that the carbon surface layerremains intact over 100 cycles. We find micro cracks in the cycledmaterial that extend parallel to low indexed lattice planes. Ourobservations differ from observations made by other authors. However thedifferences between the orientations of crack surfaces in both studiescan be reconciled considering the location of weak bonds in the unit celland specimen geometry as well as elastic stress fields ofdislocation.

  6. Carbon Cycling in Northern Peatlands

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2010-11-01

    Northern peatlands span only 3 million square kilometers, about 3% of the terrestrial area of the globe, yet they represent a significant terrestrial sink for carbon dioxide. They are also important emitters of methane, an even more potent greenhouse gas. Despite their substantial role in the global carbon cycle, peatlands are not typically incorporated into global climate models. The AGU Monograph Carbon Cycling in Northern Peatlands, edited by Andrew J. Baird, Lisa R. Belyea, Xavier Comas, A. S. Reeve, and Lee D. Slater, looks at the disproportionate role peatlands play in the global carbon budget. In this interview, Eos talks with Andy Baird, University of Leeds, Leeds, United Kingdom.

  7. Rock weathering and Carbon cycle

    NASA Astrophysics Data System (ADS)

    Strozza, Patrick

    2010-05-01

    In the history of the Earth system, we can find indicators of hot or glacial periods, as well as brutal climatic change… How can we explain those climate variations on a geological timescale ? One of the causative agents is probably the fluctuation of atmospheric CO2 amounts, (gas responsible for the greenhouse effect). A concrete study of some CO2 fluxes between Earth system reservoirs (atmo, hydro and lithosphere) is proposed in this poster. Hydrogencarbonate is the major ion in river surface waters and its amount is so high that it can not be explained by a simple atmospheric Carbon diffusion. From a simple measurement of river HCO3- concentration, we can estimate the consumption of atmospheric CO2 that arises from carbonate and silicate weathering processes. Practical experiments are proposed. These are carried out in the local environment, and are conform to the curriculums of Chemistry and Earth sciences. These tests enable us to outline long-term Carbon cycles and global climatic changes. Key words : Erosion, rock weathering, CO2 cycle, Hydrogencarbonate in waters, climatic changes

  8. Carbon cycle feedbacks and future climate change.

    PubMed

    Friedlingstein, Pierre

    2015-11-13

    Climate and carbon cycle are tightly coupled on many timescales, from interannual to multi-millennial timescales. Observations always evidence a positive feedback, warming leading to release of carbon to the atmosphere; however, the processes at play differ depending on the timescales. State-of-the-art Earth System Models now represent these climate-carbon cycle feedbacks, always simulating a positive feedback over the twentieth and twenty-first centuries, although with substantial uncertainty. Recent studies now help to reduce this uncertainty. First, on short timescales, El Niño years record larger than average atmospheric CO2 growth rate, with tropical land ecosystems being the main drivers. These climate-carbon cycle anomalies can be used as emerging constraint on the tropical land carbon response to future climate change. Second, centennial variability found in last millennium records can be used to constrain the overall global carbon cycle response to climatic excursions. These independent methods point to climate-carbon cycle feedback at the low-end of the Earth System Models range, indicating that these models overestimate the carbon cycle sensitivity to climate change. These new findings also help to attribute the historical land and ocean carbon sinks to increase in atmospheric CO2 and climate change. PMID:26438284

  9. Closing the fuel carbon cycle

    SciTech Connect

    Powicki, C.R.

    2007-04-01

    The global carbon cycle involves constant exchange of carbon atoms between the atmosphere, land, and ocean through biological, chemical and geological processes. This natural cycle of uptake and release of carbon is roughly in balance. However, the global industrialization of the past two centuries has released carbon to the atmosphere, mostly in the form of CO{sub 2} that had been locked up in underground coal, oil, and natural gas deposits for millions of years. It is primarily combustion of these long-stored fossil fuels that threatens to tip the balance of the carbon cycle, leading to a substantial buildup of CO{sub 2} in the upper atmosphere. Scientists believe that one key to stabilizing future atmospheric CO{sub 2} concentrations will be essentially to close the fuel carbon cycle, to capture the carbon from fossil fuels before it is released to the atmosphere and return it to permanent reservoirs in the earth or oceans. The article summarises the various options for carbon capture and storage (CCS) and looks at the state of development of technologies. It also addresses regulatory uncertainties, legal issues risks and perceptions of CCS. 3 figs., 1 tab.

  10. Carbon cycling in Lake Superior

    NASA Astrophysics Data System (ADS)

    Urban, N. R.; Auer, M. T.; Green, S. A.; Lu, X.; Apul, D. S.; Powell, K. D.; Bub, L.

    2005-06-01

    Carbon (C) cycling in Lake Superior was studied within the Keweenaw Interdisciplinary Transport Experiment in Superior (KITES) project to assess (1) whether the lake is net heterotrophic, (2) sources, sinks and residence time for dissolved organic carbon (DOC), (3) importance of terrigenous organic C subsidies, and (4) factors limiting C flow through bacteria. During 3 years of fieldwork, measurements were made of spatial and temporal distributions of C pools and rates of photosynthesis, community respiration, and bacterial production. Measurements were made of the composition of dissolved organic matter (DOM), rates of DOM photolysis, lability of DOM toward microbial consumption, and river inputs of DOM. All measurements suggest the lake is net heterotrophic. The C:N ratios of DOM suggest that it is primarily of terrigenous origin, but other characteristics (size distribution, UV absorption) point to the presence of autochthonous DOM and to alteration of terrigenous material. The lake mass balance indicates that the residence time (˜8 years) of the DOC pool (17 Tg) is short relative to the hydrologic residence time (170 years). The known flux of terrigenous DOC (˜1 Tg/yr) is too low to support annual bacterial carbon demand (6-38 Tg/yr), but microbial respiration is the major sink for terrigenous DOC. A rapidly cycling, autochthonous DOC pool must exist. Microbial activity was correlated with temperature, phosphorus availability, and DOC concentration but not with photosynthesis rates. Measurements of respiration (˜40 Tg/yr), photosynthesis (2-7 Tg/yr), and bacterial production (0.5-2 Tg/yr) are not all mutually compatible and result in a discrepancy in the organic carbon budget.

  11. Effects of model structural uncertainty on carbon cycle projections: biological nitrogen fixation as a case study

    NASA Astrophysics Data System (ADS)

    Wieder, William R.; Cleveland, Cory C.; Lawrence, David M.; Bonan, Gordon B.

    2015-04-01

    Uncertainties in terrestrial carbon (C) cycle projections increase uncertainty of potential climate feedbacks. Efforts to improve model performance often include increased representation of biogeochemical processes, such as coupled carbon-nitrogen (N) cycles. In doing so, models are becoming more complex, generating structural uncertainties in model form that reflect incomplete knowledge of how to represent underlying processes. Here, we explore structural uncertainties associated with biological nitrogen fixation (BNF) and quantify their effects on C cycle projections. We find that alternative plausible structures to represent BNF result in nearly equivalent terrestrial C fluxes and pools through the twentieth century, but the strength of the terrestrial C sink varies by nearly a third (50 Pg C) by the end of the twenty-first century under a business-as-usual climate change scenario representative concentration pathway 8.5. These results indicate that actual uncertainty in future C cycle projections may be larger than previously estimated, and this uncertainty will limit C cycle projections until model structures can be evaluated and refined.

  12. Differentiating moss from higher plants is critical in studying the carbon cycle of the boreal biome.

    PubMed

    Yuan, Wenping; Liu, Shuguang; Dong, Wenjie; Liang, Shunlin; Zhao, Shuqing; Chen, Jingming; Xu, Wenfang; Li, Xianglan; Barr, Alan; Andrew Black, T; Yan, Wende; Goulden, Mike L; Kulmala, Liisa; Lindroth, Anders; Margolis, Hank A; Matsuura, Yojiro; Moors, Eddy; van der Molen, Michiel; Ohta, Takeshi; Pilegaard, Kim; Varlagin, Andrej; Vesala, Timo

    2014-01-01

    The satellite-derived normalized difference vegetation index (NDVI), which is used for estimating gross primary production (GPP), often includes contributions from both mosses and vascular plants in boreal ecosystems. For the same NDVI, moss can generate only about one-third of the GPP that vascular plants can because of its much lower photosynthetic capacity. Here, based on eddy covariance measurements, we show that the difference in photosynthetic capacity between these two plant functional types has never been explicitly included when estimating regional GPP in the boreal region, resulting in a substantial overestimation. The magnitude of this overestimation could have important implications regarding a change from a current carbon sink to a carbon source in the boreal region. Moss abundance, associated with ecosystem disturbances, needs to be mapped and incorporated into GPP estimates in order to adequately assess the role of the boreal region in the global carbon cycle. PMID:24967601

  13. USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

  14. USE OF THE COMPOSITION AND STABLE CARBONIISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

    EPA Science Inventory

    We use measurements of the concentration and stable carbon isotopic ratio (*13C) of individual microbial phospholipid fatty acids (PLFAs) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SOM) cy...

  15. Bioenergy, the Carbon Cycle, and Carbon Policy

    NASA Astrophysics Data System (ADS)

    Kammen, D. M.

    2003-12-01

    The evolving energy and land-use policies across North America and Africa provide critical case studies in the relationship between regional development, the management of natural resources, and the carbon cycle. Over 50 EJ of the roughly 430 EJ total global anthropogenic energy budget is currently utilized in the form of direct biomass combustion. In North America 3 - 4 percent of total energy is derived from biomass, largely in combined heat and power (CHP) combustion applications. By contrast Africa, which is a major consumer of 'traditional' forms of biomass, uses far more total bioenergy products, but largely in smaller batches, with quantities of 0.5 - 2 tons/capita at the household level. Several African nations rely on biomass for well over 90 percent of household energy, and in some nations major portions of the industrial energy supply is also derived from biomass. In much of sub-Saharan Africa the direct combustion of biomass in rural areas is exceeded by the conversion of wood to charcoal for transport to the cities for household use there. There are major health, and environmental repercussions of these energy flows. The African, as well as Latin American and Asian charcoal trade has a noticeable signature on the global greenhouse gas cycles. In North America, and notably Scandinavia and India as well, biomass energy and emerging conversion technologies are being actively researched, and provide tremendous opportunities for the evolution of a sustainable, locally based, energy economy for many nations. This talk will examine aspects of these current energy and carbon flows, and the potential that gassification and new silvicultural practices hold for clean energy systems in the 21st century. North America and Africa will be examined in particular as both sources of innovation in this field, and areas with specific promise for application of these energy technologies and biomass/land use practices to further energy and global climate management.

  16. Development and application of the EPIC model for carbon cycle, greenhouse-gas mitigation, and biofuel studies

    SciTech Connect

    Izaurralde, Roberto C.; Mcgill, William B.; Williams, J.R.

    2012-06-01

    This chapter provides a comprehensive review of the EPIC model in relation to carbon cycle, greenhouse-gas mitigation, and biofuel applications. From its original capabilities and purpose (i.e., quantify the impacts or erosion on soil productivity), the EPIC model has evolved into a comprehensive terrestrial ecosystem model for simulating with more or less process-level detail many ecosystem processes such as weather, hydrology, plant growth and development, carbon cycle (including erosion), nutrient cycling, greenhouse-gas emissions, and the most complete set of manipulations that can be implemented on a parcel of land (e.g. tillage, harvest, fertilization, irrigation, drainage, liming, burning, pesticide application). The chapter also provides details and examples of the latest efforts in model development such as the coupled carbon-nitrogen model, a microbial denitrification model with feedback to the carbon decomposition model, updates on calculation of ecosystem carbon balances, and carbon emissions from fossil fuels. The chapter has included examples of applications of the EPIC model in soil carbon sequestration, net ecosystem carbon balance, and biofuel studies. Finally, the chapter provides the reader with an update on upcoming improvements in EPIC such as the additions of modules for simulating biochar amendments, sorption of soluble C in subsoil horizons, nitrification including the release of N2O, and the formation and consumption of methane in soils. Completion of these model development activities will render an EPIC model with one of the most complete representation of biogeochemical processes and capable of simulating the dynamic feedback of soils to climate and management in terms not only of transient processes (e.g., soil water content, heterotrophic respiration, N2O emissions) but also of fundamental soil properties (e.g. soil depth, soil organic matter, soil bulk density, water limits).

  17. Permafrost soils and carbon cycling

    DOE PAGESBeta

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; Michaelson, G. J.; Shur, Y. L.

    2015-02-05

    Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous organic carbon stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global carbon cycle and the potential vulnerability of the region's soil organic carbon (SOC) stocks to changing climatic conditions. Inmore » this review, we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils, and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of organic carbon stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this organic carbon to permafrost thaw under a warming climate. Overall, frozen conditions and cryopedogenic processes, such as cryoturbation, have slowed decomposition and enhanced the sequestration of organic carbon in permafrost-affected soils over millennial timescales. Due to the low temperatures, the organic matter in permafrost soils is often less humified than in more temperate soils, making some portion of this stored organic carbon relatively vulnerable to mineralization upon thawing of permafrost.« less

  18. Uncovering the Neoproterozoic carbon cycle.

    PubMed

    Johnston, D T; Macdonald, F A; Gill, B C; Hoffman, P F; Schrag, D P

    2012-03-15

    Interpretations of major climatic and biological events in Earth history are, in large part, derived from the stable carbon isotope records of carbonate rocks and sedimentary organic matter. Neoproterozoic carbonate records contain unusual and large negative isotopic anomalies within long periods (10-100 million years) characterized by δ(13)C in carbonate (δ(13)C(carb)) enriched to more than +5 per mil. Classically, δ(13)C(carb) is interpreted as a metric of the relative fraction of carbon buried as organic matter in marine sediments, which can be linked to oxygen accumulation through the stoichiometry of primary production. If a change in the isotopic composition of marine dissolved inorganic carbon is responsible for these excursions, it is expected that records of δ(13)C(carb) and δ(13)C in organic carbon (δ(13)C(org)) will covary, offset by the fractionation imparted by primary production. The documentation of several Neoproterozoic δ(13)C(carb) excursions that are decoupled from δ(13)C(org), however, indicates that other mechanisms may account for these excursions. Here we present δ(13)C data from Mongolia, northwest Canada and Namibia that capture multiple large-amplitude (over 10 per mil) negative carbon isotope anomalies, and use these data in a new quantitative mixing model to examine the behaviour of the Neoproterozoic carbon cycle. We find that carbonate and organic carbon isotope data from Mongolia and Canada are tightly coupled through multiple δ(13)C(carb) excursions, quantitatively ruling out previously suggested alternative explanations, such as diagenesis or the presence and terminal oxidation of a large marine dissolved organic carbon reservoir. Our data from Namibia, which do not record isotopic covariance, can be explained by simple mixing with a detrital flux of organic matter. We thus interpret δ(13)C(carb) anomalies as recording a primary perturbation to the surface carbon cycle. This interpretation requires the revisiting of

  19. Carbon Cycling with Nuclear Power

    NASA Astrophysics Data System (ADS)

    Lackner, Klaus S.

    2011-11-01

    Liquid hydrocarbon fuels like gasoline, diesel or jet fuel are the most efficient ways of delivering energy to the transportation sector, in particular cars, ships and airplanes. Unfortunately, their use nearly unavoidably leads to the emission of carbon dioxide into the atmosphere. Unless an equivalent amount is removed from the air, the carbon dioxide will accumulate and significantly contribute to the man-made greenhouse effect. If fuels are made from biomass, the capture of carbon dioxide is a natural part of the cycle. Here, we discuss technical options for capturing carbon dioxide at much faster rates. We outline the basic concepts, discuss how such capture technologies could be made affordable and show how they could be integrated into a larger system approach. In the short term, the likely source of the hydrocarbon fuels is oil or gas; in the longer term, technologies that can provide energy to remove oxygen from carbon dioxide and water molecules and combine the remaining components into liquid fuels make it possible to recycle carbon between fuels and carbon dioxide in an entirely abiotic process. Here we focus on renewable and nuclear energy options for producing liquid fuels and show how air capture combined with fuel synthesis could be more economic than a transition to electric cars or hydrogen-fueled cars.

  20. Understanding the Carbon Cycle : A Jigsaw Approach

    NASA Astrophysics Data System (ADS)

    Hastings, D. W.

    2006-12-01

    A thorough understanding of the carbon cycle is fundamental to understanding the eventual fate of CO2. To achieve this, students must understand individual processes, such as photosynthesis and respiration, as well as an integrated knowledge of how these processes relate to each other. In this "jigsaw" exercise, each student is assigned one five fundamental geochemical processes in the short- term carbon cycle to research and fully understand. In class, students first meet with others who have studied the same process to strengthen and deepen their understanding of this process. They then form teams of five students and explain to other students their particular process. In exchange, other students explain the other aspects of the carbon cycle. At the end of class all students will know about each of the five processes, and thus develop an integrated understanding of the entire carbon cycle. This approach is an efficient method for students to learn the material. As in a jigsaw puzzle, each student's part is essential for the full understanding of the carbon cycle. Since each student's part is essential, then each student is essential, which is what makes this strategy effective The jigsaw approach encourages listening, engagement, and collaboration by giving each member of the group an essential part to play in the academic activity.

  1. Predictability of the terrestrial carbon cycle.

    PubMed

    Luo, Yiqi; Keenan, Trevor F; Smith, Matthew

    2015-05-01

    Terrestrial ecosystems sequester roughly 30% of anthropogenic carbon emission. However this estimate has not been directly deduced from studies of terrestrial ecosystems themselves, but inferred from atmospheric and oceanic data. This raises a question: to what extent is the terrestrial carbon cycle intrinsically predictable? In this paper, we investigated fundamental properties of the terrestrial carbon cycle, examined its intrinsic predictability, and proposed a suite of future research directions to improve empirical understanding and model predictive ability. Specifically, we isolated endogenous internal processes of the terrestrial carbon cycle from exogenous forcing variables. The internal processes share five fundamental properties (i.e., compartmentalization, carbon input through photosynthesis, partitioning among pools, donor pool-dominant transfers, and the first-order decay) among all types of ecosystems on the Earth. The five properties together result in an emergent constraint on predictability of various carbon cycle components in response to five classes of exogenous forcing. Future observational and experimental research should be focused on those less predictive components while modeling research needs to improve model predictive ability for those highly predictive components. We argue that an understanding of predictability should provide guidance on future observational, experimental and modeling research. PMID:25327167

  2. An introduction to global carbon cycle management

    USGS Publications Warehouse

    Sundquist, Eric T.; Ackerman, Katherine V.; Parker, Lauren; Huntzinger, Deborah N.

    2009-01-01

    Past and current human activities have fundamentally altered the global carbon cycle. Potential future efforts to control atmospheric CO2 will also involve significant changes in the global carbon cycle. Carbon cycle scientists and engineers now face not only the difficulties of recording and understanding past and present changes but also the challenge of providing information and tools for new management strategies that are responsive to societal needs. The challenge is nothing less than managing the global carbon cycle.

  3. A comparative study on life cycle analysis of molten carbon fuel cells and diesel engines for marine application

    NASA Astrophysics Data System (ADS)

    Alkaner, Selim; Zhou, Peilin

    The study performed a life cycle assessment (LCA) of a molten carbonate fuel cell (MCFC) plant for marine applications. The results are compared to a benchmark conventional diesel engine (DE) which operates as an auxiliary power generating unit. The LCA includes manufacturing of MCFC and DE, fuel supply, operation and decommissioning stages of the system's life cycle. As a new technology in its very early stages of commercialisation, some detailed data for the FC systems are not available. In order to overcome this problem, a series of scenario analysis has also been performed to evaluate the effect of various factors on the overall impact, such as change in power load factors and effect of recycling credit at the end of life cycle. Environmental benefits from fuel cell operation are maximised with the use of hydrogen as an input fuel. For the manufacturing stage of the life cycle, input material and process energy required for fuel cell stack assemblies and balance-of-plants (BOP) represent a bigger impact than that of conventional benchmark mainly due to special materials used in the stack and the weights of the BOP components. Additionally, recovering valuable materials through re-use or re-cycle will reduce the overall environmental burden of the system over its life cycle.

  4. Peatland carbon cycling and the implications of permafrost thaw; a chronosequence study.

    NASA Astrophysics Data System (ADS)

    Olefeldt, D.; Pelletier, N.; Talbot, J.; Blodau, C.; Turetsky, M. R.

    2015-12-01

    Peatlands in the Mackenzie River valley initiated ~9000 years ago and have built up vast soil carbon stores since. Peatland development history in this region is characterized by several distinct stages, varying in nutrient status and permafrost conditions. Widespread permafrost thaw has recently occurred in response to warming, thus making large soil C stores available for microbial processes and mineralization. A crucial question to answer is whether these peatland become net sinks or sources of C following thaw. The net response to thaw will either be dominated by new peat C accumulation at the surface or by mineralization of old peat C released from permafrost. In order to address this question we cored peat plateaus and nearby thermokarst bogs near Fort Simpson, Northwest Territories, representing 4 chronosequences. The cores were analyzed for C content, radiocarbon dates, macrofossils, testate amoebas, peat humification degree, elemental analysis, and microbial lability through an incubation experiment. Together, these approaches reveal peatland development histories, both before and following permafrost thaw. It is clear from our findings that C cycling following permafrost thaw will be intrinsically dependent on the developmental history of the peatland.

  5. Soil Carbon and Nitrogen Cycle Modeling

    NASA Astrophysics Data System (ADS)

    Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.

    2012-12-01

    Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased

  6. Evaluating the impacts of new walking and cycling infrastructure on carbon dioxide emissions from motorized travel: a controlled longitudinal study

    PubMed Central

    Brand, Christian; Goodman, Anna; Ogilvie, David

    2015-01-01

    Walking and cycling is widely assumed to substitute for at least some motorized travel and thereby reduce energy use and carbon dioxide (CO2) emissions. While the evidence suggests that a supportive built environment may be needed to promote walking and cycling, it is unclear whether and how interventions in the built environment that attract walkers and cyclists may reduce transport CO2 emissions. Our aim was therefore to evaluate the effects of providing new infrastructure for walking and cycling on CO2 emissions from motorised travel. A cohort of 1849 adults completed questionnaires at baseline (2010) and one-year follow-up (2011), before and after the construction of new high-quality routes provided as part of the Sustrans Connect2 programme in three UK municipalities. A second cohort of 1510 adults completed questionnaires at baseline and two-year follow-up (2012). The participants reported their past-week travel behaviour and car characteristics from which CO2 emissions by mode and purpose were derived using methods described previously. A set of exposure measures of proximity to and use of the new routes were derived. Overall transport CO2 emissions decreased slightly over the study period, consistent with a secular trend in the case study regions. As found previously the new infrastructure was well used at one- and two-year follow-up, and was associated with population-level increases in walking, cycling and physical activity at two-year follow-up. However, these effects did not translate into sizeable CO2 effects as neither living near the infrastructure nor using it predicted changes in CO2 emissions from motorised travel, either overall or disaggregated by journey purpose. This lack of a discernible effect on travel CO2 emissions are consistent with an interpretation that some of those living nearer the infrastructure may simply have changed where they walked or cycled, while others may have walked or cycled more but few, if any, may have substituted

  7. Carbon and Hydrogen Isotope Fractionation in Lipid Biosynthesis of Piezophilic Bacteria - Implications for Studying Microbial Metabolism and Carbon Cycle in Deep Biosphere

    NASA Astrophysics Data System (ADS)

    Fang, J.; Dasgupta, S.; Zhang, L.; Li, J.; Kato, C.; Bartlett, D.

    2012-12-01

    Piezophiles are pressure-loving microorganisms, which reproduce preferentially or exclusively at pressures greater than atmospheric pressure. In this study, we examined stable carbon and hydrogen isotope fractionation in fatty acid biosynthesis of a piezophilic bacterium Moritella japonica DSK1. The bacterium was grown to stationary phase at hydrstatic pressures of 0.1, 10, 20, and 50 MPa (mega-passcal) in media prepared using sterilized natural seawater supplied with glucose as the sole carbon source. Bacterial cell biomass and individual fatty acids exhibited consistent pressure-dependent carbon and hydrogen isotope fractionations relative to substrates. Average carbon isotope fractionation (delta(FA-glucose)) at high pressures was much higher than that for surface bacteria: -15.7, -15.3, and -18.3‰ at 10, 20, and 50 MPa, respectively. For deltaD, fatty acids are more depleted in D relative to glucose than to water. Monounsaturated fatty acids are more depleted in D than corresponding saturated fatty acids by as much as 36‰. Polyunsaturated fatty acids are most depleted in D. For example, DHA (22:6omega3) has the most negative hydrogen isotope ratio (-170.91‰) (delta(FA-glucose) = -199, delta(FA-water) = -176). The observed isotope effects can be ascribed to the kinetics of enzymatic reactions that are affected by hydrostatic pressure and to operating of two independent lipid biosynthetic pathways of the piezophilic bacteria. Given that most of the biosphere lives under high pressures, our results have important important implications for studying microbial metabolism and carbon cycle in the deep biosphere.

  8. Cycling of Black Carbon in the Ocean

    NASA Astrophysics Data System (ADS)

    Coppola, Alysha I.; Druffel, Ellen R. M.

    2016-04-01

    Black Carbon (BC) is a byproduct of biomass burning and fossil fuel combustion and is a slow-cycling component of the carbon cycle. Whether BC accumulates and ages on millennial timescales in the world's oceans has remained unknown. Here, we quantified dissolved BC (DBC) in marine dissolved organic carbon (DOC) isolated by solid phase extraction (SPE) and determined its residence time. The range of DBC structures and 14C ages indicates that DBC is not homogeneous in the ocean. We conclude that there are at least two distinct pools of marine DBC, a younger pool that cycles on centennial timescales and an ancient pool that cycles on >105 year timescales.

  9. Beyond the Calvin Cycle: Autotrophic Carbon Fixation in the Ocean

    NASA Astrophysics Data System (ADS)

    Hügler, Michael; Sievert, Stefan M.

    2011-01-01

    Organisms capable of autotrophic metabolism assimilate inorganic carbon into organic carbon. They form an integral part of ecosystems by making an otherwise unavailable form of carbon available to other organisms, a central component of the global carbon cycle. For many years, the doctrine prevailed that the Calvin-Benson-Bassham (CBB) cycle is the only biochemical autotrophic CO2 fixation pathway of significance in the ocean. However, ecological, biochemical, and genomic studies carried out over the last decade have not only elucidated new pathways but also shown that autotrophic carbon fixation via pathways other than the CBB cycle can be significant. This has ramifications for our understanding of the carbon cycle and energy flow in the ocean. Here, we review the recent discoveries in the field of autotrophic carbon fixation, including the biochemistry and evolution of the different pathways, as well as their ecological relevance in various oceanic ecosystems.

  10. Permafrost soils and carbon cycling

    DOE PAGESBeta

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; Michaelson, G. J.; Shur, Y. L.

    2014-10-30

    Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environment. These efforts significantly increased estimates of the amount of organic carbon (OC) stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enormous OC stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global C cycle and the potential vulnerability of the region's soil OC stocks to changing climatic conditions. In this review,more » we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils and discuss their effects on soil structures and on organic matter distributions within the soil profile. We then examine the quantity of OC stored in permafrost-region soils, as well as the characteristics, intrinsic decomposability, and potential vulnerability of this OC to permafrost thaw under a warming climate.« less

  11. Decadally cycling soil carbon is more sensitive to warming than faster-cycling soil carbon.

    PubMed

    Lin, Junjie; Zhu, Biao; Cheng, Weixin

    2015-12-01

    The response of soil organic carbon (SOC) pools to globally rising surface temperature crucially determines the feedback between climate change and the global carbon cycle. However, there is a lack of studies investigating the temperature sensitivity of decomposition for decadally cycling SOC which is the main component of total soil carbon stock and the most relevant to global change. We tackled this issue using two decadally (13) C-labeled soils and a much improved measuring system in a long-term incubation experiment. Results indicated that the temperature sensitivity of decomposition for decadally cycling SOC (>23 years in one soil and >55 years in the other soil) was significantly greater than that for faster-cycling SOC (<23 or 55 years) or for the entire SOC stock. Moreover, decadally cycling SOC contributed substantially (35-59%) to the total CO2 loss during the 360-day incubation. Overall, these results indicate that the decomposition of decadally cycling SOC is highly sensitive to temperature change, which will likely make this large SOC stock vulnerable to loss by global warming in the 21st century and beyond. PMID:26301625

  12. Alternative ways of using field-based estimates to calibrate ecosystem models and their implications for carbon cycle studies

    USGS Publications Warehouse

    He, Yujie; Zhuang, Qianlai; McGuire, David; Liu, Yaling; Chen, Min

    2013-01-01

    Model-data fusion is a process in which field observations are used to constrain model parameters. How observations are used to constrain parameters has a direct impact on the carbon cycle dynamics simulated by ecosystem models. In this study, we present an evaluation of several options for the use of observations in modeling regional carbon dynamics and explore the implications of those options. We calibrated the Terrestrial Ecosystem Model on a hierarchy of three vegetation classification levels for the Alaskan boreal forest: species level, plant-functional-type level (PFT level), and biome level, and we examined the differences in simulated carbon dynamics. Species-specific field-based estimates were directly used to parameterize the model for species-level simulations, while weighted averages based on species percent cover were used to generate estimates for PFT- and biome-level model parameterization. We found that calibrated key ecosystem process parameters differed substantially among species and overlapped for species that are categorized into different PFTs. Our analysis of parameter sets suggests that the PFT-level parameterizations primarily reflected the dominant species and that functional information of some species were lost from the PFT-level parameterizations. The biome-level parameterization was primarily representative of the needleleaf PFT and lost information on broadleaf species or PFT function. Our results indicate that PFT-level simulations may be potentially representative of the performance of species-level simulations while biome-level simulations may result in biased estimates. Improved theoretical and empirical justifications for grouping species into PFTs or biomes are needed to adequately represent the dynamics of ecosystem functioning and structure.

  13. Study of molten carbonate fuel cell—microturbine hybrid power cycles

    NASA Astrophysics Data System (ADS)

    Jurado, Francisco

    The interaction realized by fuel cell—microturbine hybrids derive primarily from using the rejected thermal energy and combustion of residual fuel from a fuel cell in driving the gas turbine. This leveraging of thermal energy makes the high temperature molten carbonate fuel cells (MCFCs) ideal candidates for hybrid systems. Use of a recuperator contributes to thermal efficiency by transferring heat from the gas turbine exhaust to the fuel and air used in the system. Traditional control design approaches, consider a fixed operating point in the hope that the resulting controller is robust enough to stabilize the system for different operating conditions. On the other hand, adaptive control incorporates the time-varying dynamical properties of the model (a new value of gas composition) and considers the disturbances acting at the plant (load power variation).

  14. Carbon cycle in advanced coal chemical engineering.

    PubMed

    Yi, Qun; Li, Wenying; Feng, Jie; Xie, Kechang

    2015-08-01

    This review summarizes how the carbon cycle occurs and how to reduce CO2 emissions in highly efficient carbon utilization from the most abundant carbon source, coal. Nowadays, more and more attention has been paid to CO2 emissions and its myriad of sources. Much research has been undertaken on fossil energy and renewable energy and current existing problems, challenges and opportunities in controlling and reducing CO2 emission with technologies of CO2 capture, utilization, and storage. The coal chemical industry is a crucial area in the (CO2 value chain) Carbon Cycle. The realization of clean and effective conversion of coal resources, improving the utilization and efficiency of resources, whilst reducing CO2 emissions is a key area for further development and investigation by the coal chemical industry. Under a weak carbon mitigation policy, the value and price of products from coal conversion are suggested in the carbon cycle. PMID:25978270

  15. Tropical Cyclones and the Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Zimmerman, N. L.; Emanuel, K.

    2010-12-01

    then used to estimate the net flux of carbon between the deep ocean and the atmosphere for a large number of tropical cyclones around the world over the period 1999-2007. It is found that while in a few cases there is a large flux of carbon from the atmosphere to the deep ocean due biological sinking, for a large majority of storms the effect is quite small. For storms to cause a large carbon sink, they must be rather strong, and they must pass over a region of ocean with a both shallow nutricline and a relatively low stratification. While Typhoon Chanchu, which passed through the South China Sea in 2006, caused a large and well-studied sink of carbon that gave some initial cause for optimism that tropical cyclones might in general cause a similar effect, it now appears that such events are both too infrequent and cover too small an area to be a critical part of the carbon cycle in the current climate. It is reasoned that this may not necessarily be the case for previous climates with many more and stronger tropical cyclones, e.g. the early Pliocene.

  16. Carbon cycle: Hoard of fjord carbon

    NASA Astrophysics Data System (ADS)

    Keil, Richard

    2015-06-01

    Fjords account for less than 0.1% of the surface of Earth's oceans. A global assessment finds that organic carbon is buried in fjords five times faster than other marine systems, accounting for 11% of global marine organic carbon burial.

  17. Carbon footprint estimation of municipal water cycle

    NASA Astrophysics Data System (ADS)

    Bakhshi, Ali A.

    2009-11-01

    This research investigates the embodied energy associated with water use. A geographic information system (GIS) was tested using data from Loudoun County, Virginia. The objective of this study is to estimate the embodied energy and carbon emission levels associated with water service at a geographical location and to improve for sustainability planning. Factors that affect the carbon footprint were investigated and the use of a GIS based model as a sustainability planning framework was evaluated. The carbon footprint metric is a useful tool for prediction and measurement of a system's sustainable performance over its expected life cycle. Two metrics were calculated: tons of carbon dioxide per year to represent the contribution to global warming and watt-hrs per gallon to show the embodied energy associated with water consumption. The water delivery to the building, removal of wastewater from the building and associated treatment of water and wastewater create a sizable carbon footprint; often the energy attributed to this water service is the greatest end use of electrical energy. The embodied energy in water depends on topographical characteristics of the area's local water supply, the efficiency of the treatment systems, and the efficiency of the pumping stations. The questions answered by this research are: What is the impact of demand side sustainable water practices on the embodied energy as represented by a comprehensive carbon footprint? What are the major energy consuming elements attributed to the system? What is a viable and visually identifiable tool to estimate the carbon footprint attributed to those Greenhouse Gas (GHG) producing elements? What is the embodied energy and emission associated with water use delivered to a building? Benefits to be derived from a standardized GIS applied carbon footprint estimation approach include: (1) Improved environmental and economic information for the developers, water and wastewater processing and municipal

  18. Global Impacts (Carbon Cycle 2.0)

    ScienceCinema

    Gadgil, Ashok [EETD and UC Berkeley

    2011-06-08

    Ashok Gadgil, Faculty Senior Scientist and Acting Director, EETD, also Professor of Environmental Engineering, UC Berkeley, speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  19. Global Impacts (Carbon Cycle 2.0)

    SciTech Connect

    Gadgil, Ashok

    2010-02-02

    Ashok Gadgil, Faculty Senior Scientist and Acting Director, EETD, also Professor of Environmental Engineering, UC Berkeley, speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  20. Studies of the terrestrial O{sub 2} and carbon cycles in sand dune gases and in biosphere 2

    SciTech Connect

    Severinghaus, J.P.

    1995-12-31

    Molecular oxygen in the atmosphere is coupled tightly to the terrestrial carbon cycle by the processes of photosynthesis, respiration, and burning. This dissertation examines different aspects of this coupling in four chapters. Chapter 1 explores the feasibility of using air from sand dunes to reconstruct atmospheric O{sub 2} composition centuries ago. Such a record would reveal changes in the mass of the terrestrial biosphere, after correction for known fossil fuel combustion, and constrain the fate of anthropogenic CO{sub 2}.

  1. Nonautonomous linear system of the terrestrial carbon cycle

    NASA Astrophysics Data System (ADS)

    Luo, Y.

    2012-12-01

    Carbon cycle has been studied by uses of observation through various networks, field and laboratory experiments, and simulation models. Much less has been done on theoretical thinking and analysis to understand fundament properties of carbon cycle and then guide observatory, experimental, and modeling research. This presentation is to explore what would be the theoretical properties of terrestrial carbon cycle and how those properties can be used to make observatory, experimental, and modeling research more effective. Thousands of published data sets from litter decomposition and soil incubation studies almost all indicate that decay processes of litter and soil organic carbon can be well described by first order differential equations with one or more pools. Carbon pool dynamics in plants and soil after disturbances (e.g., wildfire, clear-cut of forests, and plows of soil for cropping) and during natural recovery or ecosystem restoration also exhibit characteristics of first-order linear systems. Thus, numerous lines of empirical evidence indicate that the terrestrial carbon cycle can be adequately described as a nonautonomous linear system. The linearity reflects the nature of the carbon cycle that carbon, once fixed by photosynthesis, is linearly transferred among pools within an ecosystem. The linear carbon transfer, however, is modified by nonlinear functions of external forcing variables. In addition, photosynthetic carbon influx is also nonlinearly influenced by external variables. This nonautonomous linear system can be mathematically expressed by a first-order linear ordinary matrix equation. We have recently used this theoretical property of terrestrial carbon cycle to develop a semi-analytic solution of spinup. The new methods have been applied to five global land models, including NCAR's CLM and CABLE models and can computationally accelerate spinup by two orders of magnitude. We also use this theoretical property to develop an analytic framework to

  2. Discussion of Refrigeration Cycle Using Carbon Dioxide as Refrigerant

    NASA Astrophysics Data System (ADS)

    Ji, Amin; Sun, Miming; Li, Jie; Yin, Gang; Cheng, Keyong; Zhen, Bing; Sun, Ying

    Nowadays, the problem of the environment goes worse, it urges people to research and study new energy-saving and environment-friendly refrigerants, such as carbon dioxide, at present, people do research on carbon dioxide at home and abroad. This paper introduces the property of carbon dioxide as a refrigerant, sums up and analyses carbon dioxide refrigeration cycles, and points out the development and research direction in the future.

  3. Increase of Carbon Cycle Feedback with Climate Sensitivity: Results from a coupled Climate and Carbon Cycle Model

    SciTech Connect

    Govindasamy, B; Thompson, S; Mirin, A; Wickett, M; Caldeira, K; Delire, C

    2004-04-01

    Coupled climate and carbon cycle modeling studies have shown that the feedback between global warming and the carbon cycle, in particular the terrestrial carbon cycle, could accelerate climate change and result in larger warming. In this paper, we investigate the sensitivity of this feedback for year-2100 global warming in the range of 0 K to 8 K. Differing climate sensitivities to increased CO{sub 2} content are imposed on the carbon cycle models for the same emissions. Emissions from the SRES A2 scenario are used. We use a fully-coupled climate and carbon cycle model, the INtegrated Climate and CArbon model (INCCA) the NCAR/DOE Parallel Coupled Model coupled to the IBIS terrestrial biosphere model and a modified-OCMIP ocean biogeochemistry model. In our model, for scenarios with year-2100 global warming increasing from 0 to 8 K, land uptake decreases from 47% to 29% of total CO{sub 2} emissions. Due to competing effects, ocean uptake (16%) shows almost no change at all. Atmospheric CO{sub 2} concentration increases were 48% higher in the run with 8 K global climate warming than in the case with no warming. Our results indicate that carbon cycle amplification of climate warming will be greater if there is higher climate sensitivity to increased atmospheric CO{sub 2} content; the carbon cycle feedback factor increases from 1.13 to 1.48 when global warming increases from 3.2 to 8 K.

  4. Influence of soil moisture-carbon cycle interactions on the terrestrial carbon cycle over Europe

    NASA Astrophysics Data System (ADS)

    Mystakidis, Stefanos; Davin, Edouard L.; Gruber, Nicolas; Seneviratne, Sonia I.

    2016-04-01

    Water availability is a crucial limiting factor for terrestrial ecosystems, but relatively few studies have quantitatively assessed the influence of soil moisture variability on the terrestrial carbon cycle. Here, we investigate the role of soil moisture variability and state in the contemporary terrestrial carbon cycle over Europe. For this we use a Regional Earth System Model (RESM) based on the COSMO-CLM Regional Climate Model, coupled to the Community Land Model version 4.0 (CLM4.0) and its carbon-nitrogen module. The simulation setup consists of a control simulation over the period 1979-2010 in which soil moisture is interactive and three sensitivity simulations in which soil moisture is prescribed to a mean, a very dry or a very wet seasonal cycle without inter-annual variability. The cumulative net biome productivity varies markedly between the different experiments ranging from a strong sink of up to 6PgC in the wet experiment to a source of up to 1.2PgC in the dry experiment. Changes in the land carbon uptake are driven by a combination of two factors: the direct impact of soil moisture on plant's carbon uptake (essentially in southern Europe) and an indirect effect through changes in temperature affecting ecosystem respiration (mainly in central and northern Europe). We find that removing temporal variations in soil moisture dampens interannual variations in terrestrial carbon fluxes (Gross Primary Productivity, respiration, Net Biome Productivity) by more than 50% over most of Europe. Moreover, the analysis reveals that on annual scale about two-thirds of central Europe and about 70% of southern Europe display statistically significant effect of drying and/or wetting on the terrestrial carbon budget and its components. Our findings confirm the crucial role of soil moisture in determining the magnitude and the inter-annual variability in land CO2 uptake which is a key contributor to the year-to-year variations in atmospheric CO2 concentration.

  5. Oceanography: Carbon cycle at depth

    NASA Astrophysics Data System (ADS)

    Edwards, Katrina J.

    2011-01-01

    The existence of a microbial community in the ocean crust has long been hypothesized. Isotopic evidence indicates that a deep biosphere of microbes both scrubs oceanic fluids of organic matter and produces new, yet old, organic carbon in situ.

  6. The Wildland Fire Emissions Information System: Providing information for carbon cycle studies with open source geospatial tools

    NASA Astrophysics Data System (ADS)

    French, N. H.; Erickson, T.; McKenzie, D.

    2008-12-01

    A major goal of the North American Carbon Program is to resolve uncertainties in understanding and managing the carbon cycle of North America. As carbon modeling tools become more comprehensive and spatially oriented, accurate datasets to spatially quantify carbon emissions from fire are needed, and these data resources need to be accessible to users for decision-making. Under a new NASA Carbon Cycle Science project, Drs. Nancy French and Tyler Erickson, of the Michigan Technological University, Michigan Tech Research Institute (MTRI), are teaming with specialists with the USDA Forest Service Fire and Environmental Research Applications (FERA) team to provide information for mapping fire-derived carbon emissions to users. The project focus includes development of a web-based system to provide spatially resolved fire emissions estimates for North America in a user-friendly environment. The web-based Decision Support System will be based on a variety of open source technologies. The Fuel Characteristic Classification System (FCCS) raster map of fuels and MODIS-derived burned area vector maps will be processed using the Geographic Data Abstraction Library (GDAL) and OGR Simple Features Library. Tabular and spatial project data will be stored in a PostgreSQL/PostGIS, a spatially enabled relational database server. The browser-based user interface will be created using the Django web page framework to allow user input for the decision support system. The OpenLayers mapping framework will be used to provide users with interactive maps within the browser. In addition, the data products will be made available in standard open data formats such as KML, to allow for easy integration into other spatial models and data systems.

  7. Recuperative supercritical carbon dioxide cycle

    SciTech Connect

    Sonwane, Chandrashekhar; Sprouse, Kenneth M; Subbaraman, Ganesan; O'Connor, George M; Johnson, Gregory A

    2014-11-18

    A power plant includes a closed loop, supercritical carbon dioxide system (CLS-CO.sub.2 system). The CLS-CO.sub.2 system includes a turbine-generator and a high temperature recuperator (HTR) that is arranged to receive expanded carbon dioxide from the turbine-generator. The HTR includes a plurality of heat exchangers that define respective heat exchange areas. At least two of the heat exchangers have different heat exchange areas.

  8. Solar Fuels and Carbon Cycle 2.0 (Carbon Cycle 2.0)

    ScienceCinema

    Alivisatos, Paul

    2011-06-03

    Paul Alivisatos, LBNL Director speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 4, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  9. Geologic Carbon Sequestration and Biosequestration (Carbon Cycle 2.0)

    ScienceCinema

    DePaolo, Don [Director, LBNL Earth Sciences Division

    2011-06-08

    Don DePaolo, Director of LBNL's Earth Sciences Division, speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 3, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  10. Geologic Carbon Sequestration and Biosequestration (Carbon Cycle 2.0)

    SciTech Connect

    DePaolo, Don

    2010-02-03

    Don DePaolo, Director of LBNL's Earth Sciences Division, speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 3, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  11. Investigators Share Improved Understanding of the North American Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Birdsey, Richard A.; Cook, Robert; Denning, Scott; Griffith, Peter; Law, Beverly; Masek, Jeffrey; Michalak, Anna; Ogle, Stephen; Ojima, Dennis; Pan, Yude; Sabine, Christopher; Sheffner, Edwin; Sundquist, Eric

    2007-06-01

    The U.S. North American Carbon Program (NACP) sponsored an "all-scientist" meeting to review progress in understanding the dynamics of the carbon cycle of North America and adjacent oceans, and to chart a course for improved integration across scientific disciplines, scales, and Earth system boundaries. The meeting participants also addressed the need for better decision support tools for managing the carbon cycle of North America, so that strong science can inform policy as interest in taking action increases across the nation. Herein we report on themes to integrate the diversity of NACP science and fill significant gaps for understanding and managing the North American carbon cycle: integration among disciplines involving land, atmosphere, and ocean research; strengthening data management infrastructure to support modeling and analysis; identification of study regions that are critical for reducing uncertainties in the North American carbon balance; and integrating biophysical science with the human dimensions of carbon management and decision support.

  12. Chemical Oceanography and the Marine Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Emerson, Steven; Hedges, John

    The principles of chemical oceanography provide insight into the processes regulating the marine carbon cycle. The text offers a background in chemical oceanography and a description of how chemical elements in seawater and ocean sediments are used as tracers of physical, biological, chemical and geological processes in the ocean. The first seven chapters present basic topics of thermodynamics, isotope systematics and carbonate chemistry, and explain the influence of life on ocean chemistry and how it has evolved in the recent (glacial-interglacial) past. This is followed by topics essential to understanding the carbon cycle, including organic geochemistry, air-sea gas exchange, diffusion and reaction kinetics, the marine and atmosphere carbon cycle and diagenesis in marine sediments. Figures are available to download from www.cambridge.org/9780521833134. Ideal as a textbook for upper-level undergraduates and graduates in oceanography, environmental chemistry, geochemistry and earth science and a valuable reference for researchers in oceanography.

  13. Authigenic carbonate and the history of the global carbon cycle.

    PubMed

    Schrag, Daniel P; Higgins, John A; Macdonald, Francis A; Johnston, David T

    2013-02-01

    We present a framework for interpreting the carbon isotopic composition of sedimentary rocks, which in turn requires a fundamental reinterpretation of the carbon cycle and redox budgets over Earth's history. We propose that authigenic carbonate, produced in sediment pore fluids during early diagenesis, has played a major role in the carbon cycle in the past. This sink constitutes a minor component of the carbon isotope mass balance under the modern, high levels of atmospheric oxygen but was much larger in times of low atmospheric O(2) or widespread marine anoxia. Waxing and waning of a global authigenic carbonate sink helps to explain extreme carbon isotope variations in the Proterozoic, Paleozoic, and Triassic. PMID:23372007

  14. Atmospheric carbon dioxide and the global carbon cycle

    SciTech Connect

    Trabalka, J R

    1985-12-01

    This state-of-the-art volume presents discussions on the global cycle of carbon, the dynamic balance among global atmospheric CO2 sources and sinks. Separate abstracts have been prepared for the individual papers. (ACR)

  15. A Study of the Abundance and 13C/12C Ratio of Atmospheric Carbon Dioxide to Advance the Scientific Understanding of Terrestrial Processes Regulating the Global Carbon Cycle

    SciTech Connect

    Stephen C. Piper

    2005-10-15

    The primary goal of our research program, consistent with the goals of the U.S. Climate Change Science Program and funded by the terrestrial carbon processes (TCP) program of DOE, has been to improve understanding of changes in the distribution and cycling of carbon among the active land, ocean and atmosphere reservoirs, with particular emphasis on terrestrial ecosystems. Our approach is to systematically measure atmospheric CO2 to produce time series data essential to reveal temporal and spatial patterns. Additional measurements of the 13C/12C isotopic ratio of CO2 provide a basis for distinguishing organic and inorganic processes. To pursue the significance of these patterns further, our research also involved interpretations of the observations by models, measurements of inorganic carbon in sea water, and of CO2 in air near growing land plants.

  16. Carbon sequestration and its role in the global carbon cycle

    USGS Publications Warehouse

    McPherson, Brian J.; Sundquist, Eric T.

    2009-01-01

    For carbon sequestration the issues of monitoring, risk assessment, and verification of carbon content and storage efficacy are perhaps the most uncertain. Yet these issues are also the most critical challenges facing the broader context of carbon sequestration as a means for addressing climate change. In response to these challenges, Carbon Sequestration and Its Role in the Global Carbon Cycle presents current perspectives and research that combine five major areas: • The global carbon cycle and verification and assessment of global carbon sources and sinks • Potential capacity and temporal/spatial scales of terrestrial, oceanic, and geologic carbon storage • Assessing risks and benefits associated with terrestrial, oceanic, and geologic carbon storage • Predicting, monitoring, and verifying effectiveness of different forms of carbon storage • Suggested new CO2 sequestration research and management paradigms for the future. The volume is based on a Chapman Conference and will appeal to the rapidly growing group of scientists and engineers examining methods for deliberate carbon sequestration through storage in plants, soils, the oceans, and geological repositories.

  17. Study of the Role of Terrestrial Processes in the Carbon Cycle Based on Measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    SciTech Connect

    Piper, Stephen C; Keeling, Ralph F

    2012-01-03

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic ratios 13C/12C, 18O/16O, and 14C/12C. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. Using models of varying complexity, the concentration and isotopic measurements were used to study long-term change in the interhemispheric gradients in CO2 and 13C/12C to assess the magnitude and evolution of the northern terrestrial carbon sink, to study the increase in amplitude of the seasonal cycle of CO2, to use isotopic data to refine constraints on large scale changes in isotopic fractionation which may be related to changes in stomatal conductance, and to motivate improvements in terrestrial carbon cycle models. The original proposal called for a continuation of the new time series of 14C measurements but subsequent descoping to meet budgetary constraints required termination of measurements in 2007.

  18. Iron, phytoplankton growth, and the carbon cycle.

    PubMed

    Street, Joseph H; Paytan, Adina

    2005-01-01

    Iron is an essential nutrient for all living organisms. Iron is required for the synthesis of chlorophyll and of several photosynthetic electron transport proteins and for the reduction of CO2, SO4(2-), and NO3(-) during the photosynthetic production of organic compounds. Iron concentrations in vast areas of the ocean are very low (<1 nM) due to the low solubility of iron in oxic seawater. Low iron concentrations have been shown to limit primary production rates, biomass accumulation, and ecosystem structure in a variety of open-ocean environments, including the equatorial Pacific, the subarctic Pacific and the Southern Ocean and even in some coastal areas. Oceanic primary production, the transfer of carbon dioxide into organic carbon by photosynthetic plankton (phytoplankton), is one process by which atmospheric CO2 can be transferred to the deep ocean and sequestered for long periods of time. Accordingly, iron limitation of primary producers likely plays a major role in the global carbon cycle. It has been suggested that variations in oceanic primary productivity, spurred by changes in the deposition of iron in atmospheric dust, control atmospheric CO2 concentrations, and hence global climate, over glacial-interglacial timescales. A contemporary application of this "iron hypothesis" promotes the large-scale iron fertilization of ocean regions as a means of enhancing the ability of the ocean to store anthropogenic CO2 and mitigate 21st century climate change. Recent in situ iron enrichment experiments in the HNLC regions, however, cast doubt on the efficacy and advisability of iron fertilization schemes. The experiments have confirmed the role of iron in regulating primary productivity, but resulted in only small carbon export fluxes to the depths necessary for long-term sequestration. Above all, these experiments and other studies of iron biogeochemistry over the last two decades have begun to illustrate the great complexity of the ocean system. Attempts to

  19. Carbon cycling in terrestrial environments: Chapter 17

    USGS Publications Warehouse

    Wang, Yang; Huntington, Thomas G.; Osher, Laurie J.; Wassenaar, Leonard I; Trumbore, Susan E.; Amundson, Ronald; Harden, Jennifer W.; McKnight, Diane M.; Schiff, Sherry L.; Aiken, George R.; Lyons, W. Berry; Aravena, Ramon O.; Baron, Jill S.

    1998-01-01

    This chapter reviews a number of applications of isotopic techniques for the investigation of carbon cycling processes. Carbon dioxide (C02) is an important greenhouse gas. Its concentration in the atmosphere has increased from an estimated 270 ppm at the beginning of the industrial revolution to ∼ 360 ppm at present. Climatic conditions and atmospheric C02 concentration also influence isotopic discrimination during photosynthesis. Natural and anthropogenically induced variations in the carbon isotopic abundance can be exploited to investigate carbon transformations between pools on various time scales. It also discusses one of the isotopes of carbon, the 14C, that is produced in the atmosphere by interactions of cosmic-ray produced neutrons with stable isotopes of nitrogen (N), oxygen (O), and carbon (C), and has a natural abundance in the atmosphere of ∼1 atom 14 C per 1012 atoms 12C. The most important factor affecting the measured 14C ages of soil organic matter is the rate of organic carbon cycling in soils. Differences in the dynamics of soil carbon among different soils or soil horizons will result in different soil organic 14C signatures. As a result, the deviation of the measured 14C age from the true age could differ significantly among different soils or soil horizons.

  20. A primer on the carbon cycle

    NASA Astrophysics Data System (ADS)

    Fano, Guido

    2010-04-01

    The atmosphere-ocean carbon cycle with particular attention to the residence time of CO2 in the atmosphere is clarified using a set of elementary box models along the lines of Schmitz. The coupling between surface of the ocean and the atmosphere is discussed using linear and nonlinear models. The different behavior of C12O2 and C14O2 is clarified. The diffusion of carbon dioxide in the deep ocean is briefly discussed.

  1. Carbon cycling in polycyclic driftsand sequences

    NASA Astrophysics Data System (ADS)

    Jansen, B.; Van Mourik, J. M.; De Vreng, A.; Kalbitz, K.

    2012-04-01

    Polycyclic driftsand sequences are a common soil type in The Netherlands related to historic plaggen agriculture, where heath sods were seasonally removed from sandy soils to fertilize adjacent fields upon mixing with animal manure. When sods were removed too rigorously, this led to instable periods with sand drifting. These were alternated by stable periods with soil formation (initial podzols). Polycyclic sequences such as these are valuable geoecological records that contain important soil archives used for landscape evolution studies. Proxies commonly used for this purpose are fossil pollen analysis and 14C dating. We recently combined the mentioned proxies with OSL dating and biomarker analysis in a landscape evolution study in a typical polycyclic driftsand deposit in The Netherlands. For biomarker analysis we used the VERHIB model that we recently developed to unravel preserved biomarker patterns (n-alkanes and n-alcohols) in soils or sediments into their plant species-specific origin [1]. We discovered that the combination of proxies not only yielded information about landscape evolution, but also about carbon cycling in the soils in question. OSL dating yielded the age of the initial deposition of the driftsand. Therefore, the observed difference with the 14C derived age of various organic matter fractions at the same depth in a profile provided initial clues about soil organic carbon input and turnover [2]. We found that such information could be expanded through application of the VERHIB model. The leaves and roots of plant species have distinctly different biomarker patterns that are both considered by the model; it uses the root to leaf input ratio as well as rooting depth as explicit parameters [2]. We found that when VERHIB modeling results were related to the fossil pollen based vegetation reconstruction from the same driftsand sequence, information could be obtained about the relative input of root material vs. leaf material. Therefore, a multi

  2. Implications of carbon dust emission for terrestrail carbon cycling and carbon accounting

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion preferentially removes the finest carbon- and nutrient-rich soil fractions, and consequently its role may be significant within terrestrial carbon (C) cycles. However, the impacts of wind erosion on soil organic carbon (SOC) redistribution are not considered in most carbon cycle models,...

  3. Moving Carbon, Changing Earth: Bringing the Carbon Cycle to Life

    NASA Astrophysics Data System (ADS)

    Zabel, I.; Duggan-Haas, D.; Ross, R. M.; Stricker, B.; Mahowald, N. M.

    2014-12-01

    The carbon cycle presents challenges to researchers - in how to understand the complex interactions of fluxes, reservoirs, and systems - and to outreach professionals - in how to get across the complexity of the carbon cycle and still make it accessible to the public. At Cornell University and the Museum of the Earth in Ithaca, NY, researchers and outreach staff tackled these challenges together through a 2013 temporary museum exhibition: Moving Carbon, Changing Earth. Moving Carbon, Changing Earth introduced visitors to the world of carbon and its effect on every part of our lives. The exhibit was the result of the broader impacts portion of an NSF grant awarded to Natalie Mahowald, Professor in the Department of Earth and Atmospheric Sciences at Cornell University, who has been working with a team to improve simulations of regional and decadal variability in the carbon cycle. Within the exhibition, visitors used systems thinking to understand the distribution of carbon in and among Earth's systems, learning how (and how quickly or slowly) carbon moves between and within these systems, the relative scale of different reservoirs, and how carbon's movement changes climate and other environmental dynamics. Five interactive stations represented the oceans, lithosphere, atmosphere, biosphere, and a mystery reservoir. Puzzles, videos, real specimens, and an interview with Mahowald clarified and communicated the complexities of the carbon cycle. In this talk we'll present background information on Mahowald's research as well as photos of the exhibition and discussion of the components and motivations behind them, showing examples of innovative ways to bring a complex topic to life for museum visitors.

  4. Coal weathering and the geochemical carbon cycle

    SciTech Connect

    Chang, S.; Berner, R.A.

    1999-10-01

    The weathering rate of sedimentary organic matter in the continental surficial environment is poorly constrained despite its importance to the geochemical carbon cycle. During this weathering, complete oxidation to carbon dioxide is normally assumed, but there is little proof that this actually occurs. Knowledge of the rate and mechanisms of sedimentary organic matter weathering is important because it is one of the major controls on atmospheric oxygen level through geologic time. The authors have determined the aqueous oxidation rates of pyrite-free bituminous coal at 24 and 50 C by using a dual-cell flow-through method. Coal was used as an example of sedimentary organic matter because of the difficulty in obtaining pyrite-free kerogen for laboratory study. The aqueous oxidation rate obtained in the present study for air-saturated water (270 {micro}M O{sub 2}) was found to be on the order of 2 x 10{sup {minus}12} mol O{sub 2}/m{sup 2}/s at 25 C, which is fast compared to other geologic processes such as tectonic uplift and exposure through erosion. The reaction order with respect to oxygen level is 0.5 on a several thousand hour time scale for both 24 and 50 C experiments. Activation energies, determined under 24 and 50 C conditions, were {approx}40 kJ/mol O{sub 2} indicating that the oxidation reaction is surface reaction controlled. The oxygen consumption rate obtained in this study is two to three orders of magnitude smaller than that for pyrite oxidation in water, but still rapid on a geologic time scale. Aqueous coal oxidation results in the formation of dissolved CO{sub 2}, dissolved organic carbon (DOC), and solid oxidation products, which are all quantitatively significant reaction products.

  5. Long-term pressure and thermal cycling studies on lithium imide-lithium amide complex hydrides and vanadium-carbon hydrides, and electrochemical hydrogen permeation studies

    NASA Astrophysics Data System (ADS)

    Lamb, Joshua H.

    Solid-state hydrogen storage is becoming increasingly important for future development of non-polluting vehicular fuels and nuclear technology. Understanding the nature of classical and complex hydrides is of great importance in developing new high gravimetric or volumetric capacity hydrides. Towards the nuclear technology, we have studied vanadium hydrides with lattice impurities for high volumetric capacities and very low pressures. For the vehicular technology, we have studied complex hydrides with emphasis on gaseous impurity effects upon pressure cycling. Another aspect of this work is to understand fundamental hydrogen permeation in materials, for example permeations in steel. In nuclear applications, vanadium hydride has been generally studied at high pressures, but very little work has been done on low pressure hydriding and the effect of impurities. Thermodynamic pressure composition-isotherms and structural studies were performed on V-0.5 at.%C. The addition of carbon did not change the thermodynamics significantly but it had an impact on the decrepitation effects usually observed in metal hydrides. In vehicular applications, high gravimetric capacities are desirable. This study was focused on modern complex hydrides especially Li based imide-amide and binary amide-alanate systems. In this case, the emphasis was on effect of gaseous impurities upon pressure cycling, and other related. These contamination studies are important as candidate materials must have long-term stability under repeated loading of the hydride beds with fresh hydrogen charges. The starting material was Li3N and during hydriding Li2NH (imide) and subsequently, LiNH 2 (amide) phases were formed with a full capacity of ˜10 wt.% hydrogen. The pressure cycling occurred between the imide and amide phases, yielding ˜5.6 wt.% reversible hydrogen. The gaseous contamination effects on the amide-imide system were studied using 100 ppm levels of impurity gases such as O 2, H2O, CH4, CO and NH3

  6. Africa and the global carbon cycle

    PubMed Central

    Williams, Christopher A; Hanan, Niall P; Neff, Jason C; Scholes, Robert J; Berry, Joseph A; Denning, A Scott; Baker, David F

    2007-01-01

    The African continent has a large and growing role in the global carbon cycle, with potentially important climate change implications. However, the sparse observation network in and around the African continent means that Africa is one of the weakest links in our understanding of the global carbon cycle. Here, we combine data from regional and global inventories as well as forward and inverse model analyses to appraise what is known about Africa's continental-scale carbon dynamics. With low fossil emissions and productivity that largely compensates respiration, land conversion is Africa's primary net carbon release, much of it through burning of forests. Savanna fire emissions, though large, represent a short-term source that is offset by ensuing regrowth. While current data suggest a near zero decadal-scale carbon balance, interannual climate fluctuations (especially drought) induce sizeable variability in net ecosystem productivity and savanna fire emissions such that Africa is a major source of interannual variability in global atmospheric CO2. Considering the continent's sizeable carbon stocks, their seemingly high vulnerability to anticipated climate and land use change, as well as growing populations and industrialization, Africa's carbon emissions and their interannual variability are likely to undergo substantial increases through the 21st century. PMID:17343752

  7. Reconstructing Late Ordovician carbon cycle variations

    NASA Astrophysics Data System (ADS)

    Pancost, Richard D.; Freeman, Katherine H.; Herrmann, Achim D.; Patzkowsky, Mark E.; Ainsaar, Leho; Martma, Tõnu

    2013-03-01

    The role of carbon dioxide in regulating climate during the early Paleozoic, when severe glaciations occurred during a putative greenhouse world, remains unclear. Here, we present the first molecular carbon isotope proxy-based estimates for Late Ordovician (early Katian) pCO2 levels, and explore the limitations of applying this approach to the reconstruction of Paleozoic pCO2. Carbon isotope profiles from three sites in Laurentia (Iowa, Ontario and Pennsylvania) and one site in Baltica (Estonia) exhibit overall low isotope fractionation between organic and inorganic carbon during photosynthesis (ɛp) and these values declined during the early Katian carbonate carbon isotope excursion (or Guttenberg Carbon Isotope Excursion, GICE). Algal ɛp values are sensitive to changes in CO2 concentrations, algae cell morphologies, and cell growth rates. To constrain these factors, we present molecular evidence that a decrease in the relative abundance of cyanobacteria and a change in the eukaryotic algae community co-occurred with the GICE. Regardless of local biotic or oceanographic influences, a decline in ɛp values indicates photosynthesis was sensitive to carbon concentrations, and via analogy with modern taxa, constrains pCO2 to below ˜8× pre-industrial levels (PIL), or about half of previous estimates. In addition, the global, positive carbon isotope excursions expressed in a wide variety of sedimentary materials (carbonate, bulk organic matter, n-alkanes, acyclic and cyclic isoprenoid hydrocarbons), provide compelling evidence for perturbation of the global carbon cycle, and this was likely associated with a decrease in pCO2 approximately 10 million years prior to the Hirnantian glaciations. Isotopic records from deeper water settings suggest a complex interplay of carbon sources and sinks, with pCO2 increasing prior to and during the early stages of the GICE and then decreasing when organic carbon burial outpaced increased volcanic inputs.

  8. Integration of a Physically based Distributed Hydrological Model with a Model of Carbon and Nitrogen Cycling: A Case Study at the Luquillo Critical Zone Observatory, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Bastola, S.; Dialynas, Y. G.; Bras, R. L.; Arnone, E.; Noto, L. V.

    2015-12-01

    The dynamics of carbon and nitrogen cycles, increasingly influenced by human activities, are the key to the functioning of ecosystems. These cycles are influenced by the composition of the substrate, availability of nitrogen, the population of microorganisms, and by environmental factors. Therefore, land management and use, climate change, and nitrogen deposition patterns influence the dynamics of these macronutrients at the landscape scale. In this work a physically based distributed hydrological model, the tRIBS model, is coupled with a process-based multi-compartment model of the biogeochemical cycle to simulate the dynamics of carbon and nitrogen (CN) in the Mameyes River basin, Puerto Rico. The model includes a wide range of processes that influence the movement, production, alteration of nutrients in the landscape and factors that affect the CN cycling. The tRIBS integrates geomorphological and climatic factors that influence the cycling of CN in soil. Implementing the decomposition module into tRIBS makes the model a powerful complement to a biogeochemical observation system and a forecast tool able to analyze the influences of future changes on ecosystem services. The soil hydrologic parameters of the model were obtained using ranges of published parameters and observed streamflow data at the outlet. The parameters of the decomposition module are based on previously published data from studies conducted in the Luquillio CZO (budgets of soil organic matter and CN ratio for each of the dominant vegetation types across the landscape). Hydrological fluxes, wet depositon of nitrogen, litter fall and its corresponding CN ratio drive the decomposition model. The simulation results demonstrate a strong influence of soil moisture dynamics on the spatiotemporal distribution of nutrients at the landscape level. The carbon in the litter pool and the nitrate and ammonia pool respond quickly to soil moisture content. Moreover, the CN ratios of the plant litter have

  9. The Carbon Cycle at the Nile Headwaters

    NASA Astrophysics Data System (ADS)

    Jones, Michael; Saunders, Matthew

    2014-05-01

    The carbon cycle at the Nile headwaters M B Jones, School of Natural Sciences, Trinity College, University of Dublin, Dublin 2, Ireland M Saunders, Environmental and Biochemical Sciences Group, The James Hutton Institute, Aberdeen, Scotland River systems play an integral role in the global carbon cycle by connecting the terrestrial biosphere, the atmosphere and the oceans. Extensive wetland systems, such as those found in the Amazon region, have been shown to export significant amounts of carbon to river waters as dissolved carbon dioxide (CO2) that can be transported and emitted hundreds of km downstream. The assessment of both regional and global carbon budgets could therefore be improved by quantifying these lateral carbon fluxes, especially from highly productive temporarily or permanently flooded areas where substantial CO2 evasion from inland waters can occur. The Nile is the longest river in the world and the headwaters are located in the extensive Papyrus dominated wetlands in central Africa that are associated with Lake Victoria. From its source the White Nile flows northwards through wetlands in Uganda and Sudan before it joins the Blue Nile. Papyrus wetlands have been shown to be some of the most productive global ecosystems, with recorded rates of aerial net primary productivity of up to 3.09 kg C m-2 yr-1. In addition, where anaerobic conditions occur they also accumulate large amounts of carbon in the form of peat, and under these circumstances they represent a significant carbon sink. However, as water moves through these wetlands and is exchanged with surrounding rivers and lakes significant quantities of dissolved organic and inorganic carbon as well as suspended particulate organic matter are exported, which are either released further downstream by degassing, decomposition or deposition. Information on such losses from these wetland ecosystems is extremely sparse but in order to better constrain ecosystem scale carbon dynamics more accurate

  10. THE C2 OXIDATIVE PHOTOSYNTHETIC CARBON CYCLE.

    PubMed

    Tolbert, N. E.

    1997-06-01

    The C2 oxidative photosynthetic carbon cycle plus the C3 reductive photosynthetic carbon cycle coexist. Both are initiated by Rubisco, use about equal amounts of energy, must regenerate RuBP, and result in exchanges of CO2 and O2 to establish rates of net photosynthesis, CO2 and O2 compensation points, and the ratio of CO2 and O2 in the atmosphere. These concepts evolved from research on O2 inhibition, glycolate metabolism, leaf peroxisomes, photorespiration, 18O2/16O2 exchange, CO2 concentrating processes, and a requirement for the oxygenase activity of Rubisco. Nearly 80 years of research on these topics are unified under the one process of photosynthetic carbon metabolism and its self-regulation. PMID:15012254

  11. A Call to Action: Carbon Cycle 2.0 (Carbon Cycle 2.0)

    ScienceCinema

    Alivisatos, Paul

    2011-06-08

    Berkeley Lab Director Paul Alivisatos speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 1, 2010. Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences.Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  12. A Future with (out) Carbon Cycle 2.0 (Carbon Cycle 2.0)

    ScienceCinema

    Collins, Bill

    2011-06-08

    Bill Collins, Head of LBNL's Climate Sciences Department, speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 1, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  13. A Call to Action: Carbon Cycle 2.0 (Carbon Cycle 2.0)

    SciTech Connect

    Alivisatos, Paul

    2010-02-01

    Berkeley Lab Director Paul Alivisatos speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 1, 2010. Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences.Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  14. Understanding Oscillations of the Geological Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Bachan, A.; Payne, J.; Saltzman, M.; Thomas, E.; Kump, L. R.

    2015-12-01

    The geological cycling of carbon ties together the sedimentary reservoirs with Earth's biosphere and climate. Perturbations to this coupled system are recorded in the carbon isotopic composition of marine limestones (δ13Ccarb). In the past decade numerous intervals of large-amplitude oscillations in δ13Ccarbhave been identified, with a variety of explanations proposed for individual events. Yet, when data spanning the past ~1 Ga are viewed as a whole, it is clear that large-scale oscillations are a common feature of the carbon isotopic record. The ubiquity of oscillations suggests that they may share a single origin rather than having many disparate causes. Here we present a simple two-box model of the geological carbon cycle exhibiting such oscillations: the Carbon-Cycle Oscillator. Analogous to a damped mass-spring system, the burial fluxes of carbonate and phosphate in the model act like friction, whereas P supply and Corg burial act like the restoring force of the spring. When the sensitivities of P supply and Corg burial to the sizes of the C and P reservoirs, respectively, increase above a critical threshold, the model exhibits oscillations upon perturbation. We suggest that intervals with large oscillations in bulk ocean-atmosphere δ13C are characterized by a greater sensitivity of the C:P burial-ratio and ALK:P weathering-ratio to the state of the ocean-atmosphere carbon pool. In addition, moderating of the slope of that dependence in general can account for the observed decrease in the amplitude of oscillations over the past billion years. We hypothesize that factors with a unidirectional trajectory during Earth history (e.g. increased oxygenation of the deep ocean, and evolution of pelagic calcifiers) led to a decrease in the Earth System's gain and increase in its resilience over geologic time, even in the face of continuing perturbations from the solid Earth and extraterrestrial realms.

  15. Carbon cycle uncertainty in the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Fisher, J. B.; Sikka, M.; Oechel, W. C.; Huntzinger, D. N.; Melton, J. R.; Koven, C. D.; Ahlström, A.; Arain, M. A.; Baker, I.; Chen, J. M.; Ciais, P.; Davidson, C.; Dietze, M.; El-Masri, B.; Hayes, D.; Huntingford, C.; Jain, A. K.; Levy, P. E.; Lomas, M. R.; Poulter, B.; Price, D.; Sahoo, A. K.; Schaefer, K.; Tian, H.; Tomelleri, E.; Verbeeck, H.; Viovy, N.; Wania, R.; Zeng, N.; Miller, C. E.

    2014-08-01

    Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for the Alaskan Arctic from four recent model intercomparison projects - NACP (North American Carbon Program) site and regional syntheses, TRENDY (Trends in net land atmosphere carbon exchanges), and WETCHIMP (Wetland and Wetland CH4 Inter-comparison of Models Project) - we provide a baseline of terrestrial carbon cycle uncertainty, defined as the multi-model standard deviation (σ) for each quantity that follows. Mean annual absolute uncertainty was largest for soil carbon (14.0 ± 9.2 kg C m-2), then gross primary production (GPP) (0.22 ± 0.50 kg C m-2 yr-1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m-2 yr-1), net primary production (NPP) (0.14 ± 0.33 kg C m-2 yr-1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m-2 yr-1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m-2 yr-1), net ecosystem exchange (NEE) (-0.01 ± 0.19 kg C m-2 yr-1), and CH4 flux (2.52 ± 4.02 g CH4 m-2 yr-1). There were no consistent spatial patterns in the larger Alaskan Arctic and boreal regional carbon stocks and fluxes, with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic and larger boreal region.

  16. Cycling of black carbon in the ocean

    NASA Astrophysics Data System (ADS)

    Coppola, Alysha I.; Druffel, Ellen R. M.

    2016-05-01

    Black carbon (BC) is a by-product of combustion from wildfires and fossil fuels and is a slow-cycling component of the carbon cycle. Whether BC accumulates and ages on millennial time scales in the world oceans has remained unknown. Here we quantified dissolved BC (DBC) in marine dissolved organic carbon isolated by solid phase extraction at several sites in the world ocean. We find that DBC in the Atlantic, Pacific, and Arctic oceans ranges from 1.4 to 2.6 μM in the surface and is 1.2 ± 0.1 μM in the deep Atlantic. The average 14C age of surface DBC is 4800 ± 620 14C years and much older in a deep water sample (23,000 ± 3000 14C years). The range of DBC structures and 14C ages indicates that DBC is not homogeneous in the ocean. We show that there are at least two distinct pools of marine DBC, a younger pool that cycles on centennial time scales and an ancient pool that cycles on >105 year time scales.

  17. Urbanization and the carbon cycle: Contributions from social science

    NASA Astrophysics Data System (ADS)

    Marcotullio, Peter J.; Hughes, Sara; Sarzynski, Andrea; Pincetl, Stephanie; Sanchez Peña, Landy; Romero-Lankao, Patricia; Runfola, Daniel; Seto, Karen C.

    2014-10-01

    This paper outlines the contributions of social science to the study of interactions between urbanization patterns and processes and the carbon cycle, and identifies gaps in knowledge and priority areas for future social scientific research contributions. While previously studied as a unidimensional process, we conceptualize urbanization as a multidimensional, social and biophysical process driven by continuous changes across space and time in various subsystems including biophysical, built environment, and socio-institutional (e.g., economic, political, demographic, behavioral, and sociological). We review research trends and findings focused on the socio-institutional subsystem of the urbanization process, and particularly the dynamics, relationships, and predictions relevant to energy use and greenhouse gas emissions. Our findings suggest that a multidimensional perspective of urbanization facilitates a wider spectrum of research relevant to carbon cycle dynamics, even within the socio-institutional subsystem. However, there is little consensus around the details and mechanisms underlying the relationship between urban socio-institutional subsystems and the carbon cycle. We argue that progress in understanding the relationship between urbanization and the carbon cycle may be achieved if social scientists work collaboratively with each other as well as with scientists from other disciplines. From this review, we identify research priorities where collaborative social scientific efforts are necessary in conjunction with other disciplinary approaches to generate a more complete understanding of urbanization as a process and its relationship to the carbon cycle.

  18. Carbon cycle uncertainty in the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Fisher, J. B.; Sikka, M.; Oechel, W. C.; Huntzinger, D. N.; Melton, J. R.; Koven, C. D.; Ahlström, A.; Arain, A. M.; Baker, I.; Chen, J. M.; Ciais, P.; Davidson, C.; Dietze, M.; El-Masri, B.; Hayes, D.; Huntingford, C.; Jain, A.; Levy, P. E.; Lomas, M. R.; Poulter, B.; Price, D.; Sahoo, A. K.; Schaefer, K.; Tian, H.; Tomelleri, E.; Verbeeck, H.; Viovy, N.; Wania, R.; Zeng, N.; Miller, C. E.

    2014-02-01

    Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for Alaska, we provide a baseline of terrestrial carbon cycle structural and parametric uncertainty, defined as the multi-model standard deviation (σ) against the mean (x\\bar) for each quantity. Mean annual uncertainty (σ/x\\bar) was largest for net ecosystem exchange (NEE) (-0.01± 0.19 kg C m-2 yr-1), then net primary production (NPP) (0.14 ± 0.33 kg C m-2 yr-1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m-2 yr-1), gross primary production (GPP) (0.22 ± 0.50 kg C m-2 yr-1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m-2 yr-1), CH4 flux (2.52 ± 4.02 g CH4 m-2 yr-1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m-2 yr-1), and soil carbon (14.0± 9.2 kg C m-2). The spatial patterns in regional carbon stocks and fluxes varied widely with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Additionally, a feedback (i.e., sensitivity) analysis was conducted of 20th century NEE to CO2 fertilization (β) and climate (γ), which showed that uncertainty in γ was 2x larger than that of β, with neither indicating that the Alaskan Arctic is shifting towards a certain net carbon sink or source. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic.

  19. Hyperdominance in Amazonian forest carbon cycling

    PubMed Central

    Fauset, Sophie; Johnson, Michelle O.; Gloor, Manuel; Baker, Timothy R.; Monteagudo M., Abel; Brienen, Roel J.W.; Feldpausch, Ted R.; Lopez-Gonzalez, Gabriela; Malhi, Yadvinder; ter Steege, Hans; Pitman, Nigel C.A.; Baraloto, Christopher; Engel, Julien; Pétronelli, Pascal; Andrade, Ana; Camargo, José Luís C.; Laurance, Susan G.W.; Laurance, William F.; Chave, Jerôme; Allie, Elodie; Vargas, Percy Núñez; Terborgh, John W.; Ruokolainen, Kalle; Silveira, Marcos; Aymard C., Gerardo A.; Arroyo, Luzmila; Bonal, Damien; Ramirez-Angulo, Hirma; Araujo-Murakami, Alejandro; Neill, David; Hérault, Bruno; Dourdain, Aurélie; Torres-Lezama, Armando; Marimon, Beatriz S.; Salomão, Rafael P.; Comiskey, James A.; Réjou-Méchain, Maxime; Toledo, Marisol; Licona, Juan Carlos; Alarcón, Alfredo; Prieto, Adriana; Rudas, Agustín; van der Meer, Peter J.; Killeen, Timothy J.; Marimon Junior, Ben-Hur; Poorter, Lourens; Boot, Rene G.A.; Stergios, Basil; Torre, Emilio Vilanova; Costa, Flávia R.C.; Levis, Carolina; Schietti, Juliana; Souza, Priscila; Groot, Nikée; Arets, Eric; Moscoso, Victor Chama; Castro, Wendeson; Coronado, Euridice N. Honorio; Peña-Claros, Marielos; Stahl, Clement; Barroso, Jorcely; Talbot, Joey; Vieira, Ima Célia Guimarães; van der Heijden, Geertje; Thomas, Raquel; Vos, Vincent A.; Almeida, Everton C.; Davila, Esteban Álvarez; Aragão, Luiz E.O.C.; Erwin, Terry L.; Morandi, Paulo S.; de Oliveira, Edmar Almeida; Valadão, Marco B.X.; Zagt, Roderick J.; van der Hout, Peter; Loayza, Patricia Alvarez; Pipoly, John J.; Wang, Ophelia; Alexiades, Miguel; Cerón, Carlos E.; Huamantupa-Chuquimaco, Isau; Di Fiore, Anthony; Peacock, Julie; Camacho, Nadir C. Pallqui; Umetsu, Ricardo K.; de Camargo, Plínio Barbosa; Burnham, Robyn J.; Herrera, Rafael; Quesada, Carlos A.; Stropp, Juliana; Vieira, Simone A.; Steininger, Marc; Rodríguez, Carlos Reynel; Restrepo, Zorayda; Muelbert, Adriane Esquivel; Lewis, Simon L.; Pickavance, Georgia C.; Phillips, Oliver L.

    2015-01-01

    While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant' species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region. PMID:25919449

  20. Hyperdominance in Amazonian forest carbon cycling.

    PubMed

    Fauset, Sophie; Johnson, Michelle O; Gloor, Manuel; Baker, Timothy R; Monteagudo M, Abel; Brienen, Roel J W; Feldpausch, Ted R; Lopez-Gonzalez, Gabriela; Malhi, Yadvinder; ter Steege, Hans; Pitman, Nigel C A; Baraloto, Christopher; Engel, Julien; Pétronelli, Pascal; Andrade, Ana; Camargo, José Luís C; Laurance, Susan G W; Laurance, William F; Chave, Jerôme; Allie, Elodie; Vargas, Percy Núñez; Terborgh, John W; Ruokolainen, Kalle; Silveira, Marcos; Aymard C, Gerardo A; Arroyo, Luzmila; Bonal, Damien; Ramirez-Angulo, Hirma; Araujo-Murakami, Alejandro; Neill, David; Hérault, Bruno; Dourdain, Aurélie; Torres-Lezama, Armando; Marimon, Beatriz S; Salomão, Rafael P; Comiskey, James A; Réjou-Méchain, Maxime; Toledo, Marisol; Licona, Juan Carlos; Alarcón, Alfredo; Prieto, Adriana; Rudas, Agustín; van der Meer, Peter J; Killeen, Timothy J; Marimon Junior, Ben-Hur; Poorter, Lourens; Boot, Rene G A; Stergios, Basil; Torre, Emilio Vilanova; Costa, Flávia R C; Levis, Carolina; Schietti, Juliana; Souza, Priscila; Groot, Nikée; Arets, Eric; Moscoso, Victor Chama; Castro, Wendeson; Coronado, Euridice N Honorio; Peña-Claros, Marielos; Stahl, Clement; Barroso, Jorcely; Talbot, Joey; Vieira, Ima Célia Guimarães; van der Heijden, Geertje; Thomas, Raquel; Vos, Vincent A; Almeida, Everton C; Davila, Esteban Álvarez; Aragão, Luiz E O C; Erwin, Terry L; Morandi, Paulo S; de Oliveira, Edmar Almeida; Valadão, Marco B X; Zagt, Roderick J; van der Hout, Peter; Loayza, Patricia Alvarez; Pipoly, John J; Wang, Ophelia; Alexiades, Miguel; Cerón, Carlos E; Huamantupa-Chuquimaco, Isau; Di Fiore, Anthony; Peacock, Julie; Camacho, Nadir C Pallqui; Umetsu, Ricardo K; de Camargo, Plínio Barbosa; Burnham, Robyn J; Herrera, Rafael; Quesada, Carlos A; Stropp, Juliana; Vieira, Simone A; Steininger, Marc; Rodríguez, Carlos Reynel; Restrepo, Zorayda; Muelbert, Adriane Esquivel; Lewis, Simon L; Pickavance, Georgia C; Phillips, Oliver L

    2015-01-01

    While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few 'hyperdominant' species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region. PMID:25919449

  1. Climate extremes and the carbon cycle (Invited)

    NASA Astrophysics Data System (ADS)

    Reichstein, M.; Bahn, M.; Ciais, P.; Mahecha, M. D.; Seneviratne, S. I.; Zscheischler, J.

    2013-12-01

    The terrestrial biosphere is a key component of the global carbon cycle and its carbon balance is strongly influenced by climate. Ongoing environmental changes are thought to increase global terrestrial carbon uptake. But evidence is mounting that rare climate extremes can lead to a decrease in ecosystem carbon stocks and therefore have the potential to negate the expected increase in terrestrial carbon uptake. Here we explore the mechanisms and impacts of climate extremes on the terrestrial carbon cycle, and propose a pathway to improve our understanding of present and future impacts of climate extremes on the terrestrial carbon budget. In addition to direct impact on the carbon fluxes of photosynthesis and respiration via extreme temperature and (or) drought, effects of extreme events may also lead to lagged responses, such as wildfires triggered by heat waves and droughts, or pest and pathogen outbreaks following wind-throw caused by heavy storms, reduced plant health due to drought stress or due to less frequent cold extremes in presently cold regions. One extreme event can potentially override accumulated previous carbon sinks, as shown by the Western European 2003 heat wave.. Extreme events have the potential to affect the terrestrial ecosystem carbon balance through a single factor, or as a combination of factors. Climate extremes can cause carbon losses from accumulated stocks, as well as long-lasting impacts on (e.g. lagged effects) on plant growth and mortality, extending beyond the duration of the extreme event itself. The sensitivity of terrestrial ecosystems and their carbon balance to climate change and extreme events varies according to the type of extreme, the climatic region, the land cover, and the land management. Extreme event impacts are very relevant in forests due to the importance of lagged and memory effects on tree growth and mortality, the longevity of tree species, the large forest carbon stocks and their vulnerability, as well as the

  2. Subsurface Carbon Cycling Below the Root Zone

    NASA Astrophysics Data System (ADS)

    Wan, J.; Dong, W.; Kim, Y.; Tokunaga, T. K.; Bill, M.; Conrad, M. E.; Williams, K. H.; Long, P. E.; Hubbard, S. S.

    2014-12-01

    Carbon in the subsurface below the root zone is an important yet poorly understood link in the terrestrial C cycle, interfacing between overlying soil and downstream aquatic systems. Thus, the nature and behavior of C in the vadose zone and groundwater, particularly the dynamics of mobile dissolved and suspended aqueous species, need to be understood for predicting C cycling and responses to climate change. This study is designed to understand the C balance (influxes, effluxes, and sequestration) and mechanisms controlling subsurface organic and inorganic C transport and transformation. Our initial investigations are being conducted at the Rifle Site floodplain along the Colorado River, in Colorado (USA). Within this floodplain, sediment samples were collected and sampling/monitoring instruments were installed down to 7 m depth at three sites. Pore water and gas samplers at 0.5 m depth intervals within the ~3.5 m deep vadose zone, and multilevel aquifer samplers have yielded depth- and time-resolved profiles of dissolved and suspended organic and inorganic C, and CO2 for over 1.5 years. Analyses conducted to determine seasonally and vertically resolved geochemical profiles show that dissolved organic matter (DOM) characteristics vary among three distinct hydrobiogeochemical zones; the vadose zone, capillary fringe, and saturated zone. The concentrations of dissolved organic matter (DOM) are many times higher in the vadose zone and the capillary fringe than in groundwater, and vary seasonally. The DOM speciation, aqueous geochemistry, solid phase analyses, and d13C isotope data show the importance of both biotic and abiotic C transformations during transport through the vertical gradients of moisture and temperature. In addition to DOM, suspended organic C and bacteria have been collected from samplers within the capillary fringe. Based on the field-based findings, long-term laboratory column experiments are being conducted under simulated field moisture

  3. Models for generation of carbonate cycles

    SciTech Connect

    Read, J.F.; Grotzinger, J.P.; Bova, J.A.; Koerschner, W.F.

    1986-02-01

    Computer modeling provides a quantitative approach to a better understanding of actual carbonate cyclic sequences. To model carbonate cycles, the authors can use water-depth-dependent sedimentation rate for each facies, an initial lag time, linear subsidence, tidal range, and period and amplitude of sea-level oscillation about a horizontal datum. Tidal-flat-capped cycles up to a few meters thick result from low-amplitude sea-level oscillation of a few meters and short lag times. Nonerosive caps reflect sea-level lowering being balanced by subsidence, and basinward migration of the shoreline not exceeding tidal-flat progradation rate. When higher amplitude sea-level oscillations occur, the tidal flats are abandoned on the inner shelf during sea-level fall, because seaward movement of the strandline outpaces progradation rate of flats. Increased amplitude also results in sea-level falling faster than flats can subside, so that disconformities with thick vadose profiles develop. High-amplitude (100 m or more) oscillations result in incipient drowning of platforms and juxtaposition of deep-water facies against shallow-water facies within cycles. Sea level falls before the platform can build to the sea-level highstand, and the shoreline migrates much more rapidly than tidal flats can prograde; thus, cycles are disconformity-bounded and lack tidal-flat caps. 10 references.

  4. High efficiency carbonate fuel cell/turbine hybrid power cycle

    SciTech Connect

    Steinfeld, G.; Maru, H.C.; Sanderson, R.A.

    1996-07-01

    The hybrid power cycle studies were conducted to identify a high efficiency, economically competitive system. A hybrid power cycle which generates power at an LHV efficiency > 70% was identified that includes an atmospheric pressure direct carbonate fuel cell, a gas turbine, and a steam cycle. In this cycle, natural gas fuel is mixed with recycled fuel cell anode exhaust, providing water for reforming fuel. The mixed gas then flows to a direct carbonate fuel cell which generates about 70% of the power. The portion of the anode exhaust which is not recycled is burned and heat transferred through a heat exchanger (HX) to the compressed air from a gas turbine. The heated compressed air is then heated further in the gas turbine burner and expands through the turbine generating 15% of the power. Half the exhaust from the turbine provides air for the anode exhaust burner. All of the turbine exhaust eventually flows through the fuel cell cathodes providing the O2 and CO2 needed in the electrochemical reaction. Exhaust from the cathodes flows to a steam system (heat recovery steam generator, staged steam turbine generating 15% of the cycle power). Simulation of a 200 MW plant with a hybrid power cycle had an LHV efficiency of 72.6%. Power output and efficiency are insensitive to ambient temperature, compared to a gas turbine combined cycle; NOx emissions are 75% lower. Estimated cost of electricity for 200 MW is 46 mills/kWh, which is competitive with combined cycle where fuel cost is > $5.8/MMBTU. Key requirement is HX; in the 200 MW plant studies, a HX operating at 1094 C using high temperature HX technology currently under development by METC for coal gassifiers was assumed. A study of a near term (20 MW) high efficiency direct carbonate fuel cell/turbine hybrid power cycle has also been completed.

  5. Marine carbon cycling following end Cretaceous extinction

    NASA Astrophysics Data System (ADS)

    Ridgwell, Andy; Thomas, Ellen; Alegret, Laia; Schmidt, Daniela

    2010-05-01

    Knowing how the transport of particulate organic carbon and associated nutrients into the ocean interior is controlled, is a prerequisite to reliable predictions of future changes in marine carbon cycling as the circulation and carbonate chemistry of the oceans are perturbed. Multiple mechanisms for particulate organic carbon transport have been proposed, most commonly based on sediment trap observations. Yet these observations primarily provide evidence for correlations between fluxes rather than being able to pin-point any particular mechanism. Despite this, global models tend to adopt one or other mechanism (e.g., ballasting) without independent justification. The geological record may help, as the evolution of pelagic ecosystems through the Phanerozoic has seen the emergence of animals (faecal pellets) and silicification and calcification of planktic organisms (ballasting), with evolutionary innovation fundamentally altering the nature of the oceanic biological pump. Moreover, catastrophic and transitory events, in which pelagic ecosystems were temporary disrupted, altering and biological pumping mechanisms, produced a tell-tale marine geochemical signature than may help elucidate the working of the biological pump. Here we focus on the bolide impact at the Cretaceous-Palaeogene boundary as it induced an enigmatic ‘collapse' in surface-to-deep carbon isotope (d13C) gradients, previously interpreted as representing a complete cessation of biological productivity and/or carbon pumping. Contemporaneous with this was a pronounced extinction of planktic calcifiers, resulting in an order of magnitude reduction in carbonate burial in deep-sea sediments. On face value, no (or little) carbonate ballasting and only a minor possible importance for dust together with ceased organic carbon transport to depth, is consistent with the existence of a dominant (carbonate) mineral ballasting mechanism prior to the event. However, a collapsed surface-to-deep d13C gradient does

  6. The Carbon Cycle: Teaching Youth about Natural Resource Sustainability

    ERIC Educational Resources Information Center

    Warren, William A.

    2015-01-01

    The carbon cycle was used as a conceptual construct for organizing the curriculum for a youth summer camp on natural resource use and sustainability. Several studies have indicated the importance of non-traditional youth education settings for science education and understanding responsible natural resource use. The Sixth Grade Forestry Tour, a…

  7. Using the 5E Learning Cycle Sequence with Carbon Dioxide

    ERIC Educational Resources Information Center

    Schlenker, Richard M.; Blanke, Regina; Mecca, Peter

    2007-01-01

    The authors used the 5E learning cycle (engage, explore, explain, extend, and evaluate) and a pulmonary carbon dioxide mystery to introduce eighth grade students to the study of chemistry. The activity engages students in measurement, data collection, data analysis, media and internet research, research design, and report writing as they search…

  8. Human Domination of Today's Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Tans, P. P.

    2014-12-01

    Observations of isotopic ratios show that the seasonal cycle as well as interannual variations of atmospheric CO2 are caused primarily by the response of terrestrial ecosystems to short-term variations of climate. Multiple lines of evidence demonstrate that the ongoing multi-decadal increase is 100% due to human activitites, and thus we are collectively responsible for the enhanced greenhouse effect, accompanied by acidification of the oceans, that is expected to last hundreds, and likely thousands, of years. Potential carbon cycle climate feedbacks, such as emissions of CH4 and CO2 from Arctic permafrost warming, are still difficult to quantify, so that in the forseeable future the emissions from fossil fuel burning will continue to dominate. CO2 removal from the atmosphere, which is energetically expensive, will cause the rate of transfer into the oceans to slow, and eventually to reverse. Managed carbon storage in the terestrial biosphere has very limited potential compared to current fossil fuel emissions. The primary imperative of climate change mitigation is to remove reduced carbon entirely from our sources of primary energy at the greatest possible pace.

  9. Biogeochemical Cycles of Carbon and Sulfur

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    The elements carbon (C) and sulfur (S) interact with each other across a network of elemental reservoirs that are interconnected by an array of physical, chemical and biological processes. These networks are termed the biogeochemical C and S cycles. The compounds of C are highly important, not only as organic matter, but also as atmospheric greenhouse gases, pH buffers in seawater, oxidation-reduction buffers virtually everywhere, and key magmatic constituents affecting plutonism and volcanism. The element S assumes important roles as an oxidation-reduction partner with C and Fe in biological systems, as a key constituent in magmas and volcanic gases, and as a major influence upon pH in certain environments. This presentation describes the modern biogeochemical C and S cycles. Measurements are described whereby stable isotopes can help to infer the nature and quantitative significance of biological and geological processes involved in the C and S cycles. This lecture also summarizes the geological and climatologic aspects of the ancient C and S cycles, as well as the planetary and extraterrestrial processes that influenced their evolution over millions to billions of years.

  10. Carbon cycles on super-Earth exoplanets

    NASA Astrophysics Data System (ADS)

    Wordsworth, Robin; Pierrehumbert, Raymond; Hébrard, Eric

    2013-04-01

    On Earth, the long-term global carbon cycle primarily consists of a balance between volcanic emissions of CO2 and the formation and burial of carbonate rocks (the carbonate-silicate weathering 'thermostat'), with important modifications due to the biosphere. On gas giant planets, the carbon cycle is driven by photolysis in the upper atmosphere: methane is converted to longer-chain hydrocarbons such as acetylene, ethane and soot particles, which are then dissociated by thermolysis lower in the atmosphere where the temperature and pressure are much higher. Hydrogen escape rates on terrestrial exoplanets are predicted to be a strong function of their orbital distances, ages and masses. In particular, larger exoplanets around stars with lower extreme ultraviolet (XUV) emissions may have significant difficulties in losing their hydrogen to space, and hence may retain H2 envelopes of varying mass. It is therefore interesting to investigate what happens in the transition between the terrestrial and hydrogen-dominated regimes. Here we present a first attempt to investigate the range of scenarios that occur for terrestrial mass (~1-10 ME) planets with varying hydrogen escape rates. We are developing climate evolution simulations for a range of cases that account for surface processes (primarily outgassing and weathering), hydrogen escape to space, and simple atmospheric chemistry. We discuss various feedbacks that may occur as a result of the influences of CO2, CH4 and H2 on atmospheric and surface temperatures. Finally, we discuss the implications of our results for future observations, with a particular emphasis on the search for biosignatures on exoplanets similar to the Earth.

  11. MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

    NASA Astrophysics Data System (ADS)

    Yool, A.; Popova, E. E.; Anderson, T. R.

    2013-10-01

    MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically driven change in the World Ocean (Yool et al., 2011). The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. However, due to anthropogenic activity, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background. As such, simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, requires that both organic and inorganic carbon be afforded a more complete representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter), as well as a simple benthic formulation and extended parameterizations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal spin-up simulation (1860-2005) is performed. The biogeochemical performance of the model is evaluated using a diverse range of observational data, and MEDUSA-2.0 is assessed relative to comparable models using output from the Coupled Model Intercomparison Project (CMIP5).

  12. Future changes in global terrestrial carbon cycle under RCP scenarios

    NASA Astrophysics Data System (ADS)

    Lee, C.; Boo, K. O.; Hong, J.; Seong, H.; Heo, T. K.; Seol, K. H.; La, N.; Shim, S.; Lee, J. H.

    2014-12-01

    Terrestrial ecosystem plays the important role as carbon sink in the global carbon cycle. Understanding of interactions of terrestrial carbon cycle with climate is important for better prediction of future climate change. In this study, terrestrial carbon cycle is investigated by Hadley Centre Global Environmental Model, version 2, Carbon Cycle (HadGEM2-CC) that considers vegetation dynamics and an interactive carbon cycle with climate. The simulation for future projection is based on the three (8.5 / 4.5 / 2.6) representative concentration pathways (RCPs) from 2006 to 2100 and compared with historical land carbon uptake from 1979 to 2005. Projected changes in ecological features such as production, respiration, net ecosystem exchange and climate condition show similar pattern in three RCPs, while the response amplitude in each RCPs are different. For all RCP scenarios, temperature and precipitation increase with rising of the atmospheric CO2. Such climate conditions are favorable for vegetation growth and extension, causing future increase of terrestrial carbon uptakes in all RCPs. At the end of 21st century, the global average of gross and net primary productions and respiration increase in all RCPs and terrestrial ecosystem remains as carbon sink. This enhancement of land CO2uptake is attributed by the vegetated area expansion, increasing LAI (Leaf Area Index), and early onset of growing season. After mid-21st century, temperature rising leads to excessive increase of soil respiration than net primary production and thus the terrestrial carbon uptake begins to fall since that time. Regionally the NEE (Net Ecosystem Exchange) average value of East-Asia (90°E-140°E, 20°N-60°N) area is bigger than that of the same latitude band. In the end-21st the NEE mean values in East-Asia area are -2.09 PgC yr-1, -1.12 PgC yr-1, -0.47 PgC yr-1 and zonal mean NEEs of the same latitude region are -1.12 PgC yr-1, -0.55 PgC yr-1, -0.17 PgC yr-1 for RCP 8.5, 4.5, 2

  13. Carbon dioxide adsorbent study

    NASA Technical Reports Server (NTRS)

    Onischak, M.; Baker, B. S.

    1973-01-01

    A study was initiated on the feasibility of using the alkali metal carbonate - bi-carbonate solid-gas reaction to remove carbon dioxide from the atmosphere of an EVA life support system. The program successfully demonstrates that carbon dioxide concentrations could be maintained below 0.1 mole per cent using this chemistry. Further a practical method for distributing the carbonates in a coherent sheet form capable of repeated regeneration (50 cycles) at modest temperatures (423 K), without loss in activity was also demonstrated. Sufficiently high reaction rates were shown to be possible with the carbonate - bi-carbonate system such that EVA hardware could be readily designed. Experimental and design data were presented on the basis of which two practical units were designed. In addition to conventional thermally regenerative systems very compact units using ambient temperature cyclic vacuum regeneration may also be feasible. For a one man - 8 hour EVA unit regenerated thermally at the base ship a system volume of 14 liters is estimated.

  14. Sulfur and carbon cycling in organic-rich marine sediments

    NASA Technical Reports Server (NTRS)

    Martens, C. S.

    1985-01-01

    Nearshore, continental shelf, and slope sediments are important sites of microbially mediated carbon and sulfur cycling. Marine geochemists investigated the rates and mechanisms of cycling processes in these environments by chemical distribution studies, in situ rate measurements, and steady state kinetic modeling. Pore water chemical distributions, sulfate reduction rates, and sediment water chemical fluxes were used to describe cycling on a ten year time scale in a small, rapidly depositing coastal basin, Cape Lookout Bight, and at general sites on the upper continental slope off North Carolina, U.S.A. In combination with 210 Pb sediment accumulation rates, these data were used to establish quantitative carbon and sulfur budgets as well as the relative importance of sulfate reduction and methanogeneis as the last steps in the degradation of organic matter.

  15. Some aspects of understanding changes in the global carbon cycle

    NASA Technical Reports Server (NTRS)

    Emanuel, W. R.; Moore, B., III; Shugart, H. H.

    1984-01-01

    The collective character of carbon exchanges between the atmosphere and other pools is partially revealed by comparing the record of CO2 concentration beginning in 1958 with estimates of the releases from fossil fuels during this period. In analyzing the secular increase in CO2 concentration induced by fossil fuel use, the atmosphere is generally treated as a single well-mixed reservoir; however, to study finer structure in the CO2 records, the influence of atmospheric circulation must be more carefully considered. The rate of carbon uptake by the oceans, the primary sink for fossil fuel CO2, is assessed more reliably than influences on the atmosphere due to interactions with other pools. Models of the global carbon cycle are being substantially refined while data that reflect the response of the cycle to fossil fuel use and other perturbations are being extended.

  16. Nutrient Cycling Study

    SciTech Connect

    Peter A. Pryfogle

    2005-09-01

    The particular goal of this study is to develop measurement techniques for understanding how consortia of organisms from geothermal facilities utilize sulfur and iron for metabolic activity; and in turn, what role that activity plays in initiating or promoting the development of a biofilm on plant substrates. Sulfur cycling is of interest because sulfur is produced in the resource. Iron is found in some of the steel formulations used in plant components and is also added as chemical treatment for reducing sulfide emissions from the plants. This report describes the set-up and operation of a bioreactor for evaluating the response of colonies of geothermal organisms to changes in nutrient and environmental conditions. Data from initial experiments are presented and plans for future testing is discussed.

  17. Advancing the use of radiocarbon in studies of global and regional carbon cycling with high precision measurements of carbon-14 in carbon dioxide from the Scripps Carbon Dioxide Program

    NASA Astrophysics Data System (ADS)

    Graven, Heather Dawn

    Measurements of 14C in atmospheric CO2 have served as a powerful geochemical tracer since the first observation programs began over 50 years ago. As the nuclear weapons tests of the 1950s and 60s caused an enormous perturbation to natural atmospheric 14C levels, tracking the response of 14C in CO2 provided a measure of exchange rates between different regions of the atmosphere and between the troposphere and the ocean surface and terrestrial biosphere. Early measurements of 14C/12C, or Delta14 C, in tree rings provided clear evidence that rising CO2 concentrations were due to human activities by revealing the dilution of 14C in the atmosphere by the combustion of million year old fossil carbon, a process termed the "Suess Effect". This thesis aimed to continue and expand the use of Delta14 C in atmospheric CO2 for investigating carbon cycle dynamics. Since much of the excess 14C derived from nuclear weapons testing has been redistributed into oceanic and biospheric reservoirs, trends and gradients in Delta14C of CO2 have diminished to levels that are nearly commensurate with measurement precision at most laboratories. Development of improved methods for Delta14C analysis by accelerator mass spectrometry at Lawrence Livermore National Laboratory advanced measurement uncertainty to 1.7‰. Application of the improved analytical procedures to an archive of CO 2 samples from the Scripps CO2 Program produced 2-15 year monthly time series of Delta14C at seven global sampling stations. The high precision observations show variability in the secular trend of Delta14C that could enable new insights to the climatic influences on CO2 exchange. Measurement of a shift in the Delta 14C gradient between the Northern and Southern Hemispheres since the 1980s also places constraints on regional fluxes of carbon, with particular relevance to Southern Ocean dynamics. The measurements presented here contribute significantly to the amount and global coverage of recent Delta14 C

  18. Wilson Cycle studies

    NASA Technical Reports Server (NTRS)

    Burke, Kevin

    1987-01-01

    The main activity relating to the study during this half year was a three week field trip to study Chinese sedimentary basins (June 10 to July 3, 1986) at no cost to the project. This study, while of a reconnaissance character, permitted progress in understanding how the processes of island arc-collision and micro-continental collision operated during the Paleozoic in far western China (especially the Junggar and Tarim basins and in the intervening Tien Shan Mountains). These effects of the continuing collision of India and Asia on the area were also studied. Most specifically, these result in the elevation of the Tien Shan to more than 4 km above sea level and the depression of Turfan to move 150m below sea level. Both thrusting and large-scale strike-slip motion are important in producing these elevation changes. Some effort during the half year was also devoted to the study of greenstone-belts in terms of the Wilson Cycle.

  19. Global Carbon Cycle and Climate Change

    NASA Astrophysics Data System (ADS)

    Wofsy, Steven C.

    2004-11-01

    Kirill Kondratyev and his colleagues present an unusual look at global change issues, with particular emphasis on quantitative models that can capture diverse aspects of the complete Earth system-vegetation, atmosphere, oceans, and human beings. The focus is on the global carbon cycle as a prime indicator of global environmental stresses. It includes some remarkably sharp, and insightful critical analysis of the Kyoto Protocol and IPCC activity, and provides citations to a large sampling of Russian-language papers mostly unknown elsewhere. The critique of current policy trends is, in many respects, the most interesting part of the book. The authors are skeptical of claims about attribution of recent climate trends to human intervention, but devastating in their demolition of the ``skeptics'' views that nothing is seriously wrong in the global environmental system. They convincingly bring to bear the most telling observations and facts to make these arguments compelling and clarifying.

  20. Carbon and Carbon Isotope Cycling in the Western Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Mol, Jacoba; Thomas, Helmuth

    2016-04-01

    Increasing carbon dioxide levels in the atmosphere are having drastic effects on the global oceans. The Arctic Ocean is particularly susceptible to change as warming, sea-ice loss and a weak buffering capacity all influence this complicated semi-enclosed sea. In order to investigate the inorganic carbon system in the Canadian Arctic, water samples were collected in the Beaufort Sea, on the Alaskan shelf, at the Mackenzie river delta, and in Amundsen Gulf during the summer of 2014 and were analyzed for dissolved inorganic carbon (DIC), total alkalinity (TA), DI13C and 18O isotopes. Carbon isotopes are used to investigate the role of biological production on the uptake and transfer of inorganic carbon to depth. A preferential uptake of the lighter 12C relative to the heavier 13C isotope during biological production leads to a fractionation of the 13C/12C isotopes in both the organic matter and the water column. This results in an enrichment of DI13C in the high productivity surface waters and a depletion of DI13C at depth. Physical processes including freshwater input, brine rejection, and water mass mixing are investigated through the measurement of oxygen isotopes. Differences in the carbon system across the study area due to both biological and physical processes are assessed using depth profiles of DI13C and related carbon system parameters.

  1. Energy Demand in China (Carbon Cycle 2.0)

    ScienceCinema

    Price, Lynn

    2011-06-08

    Lynn Price, LBNL scientist, speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  2. Carbon Cycle 2.0: Ashok Gadgil: global impact

    ScienceCinema

    Ashok Gadgi

    2010-09-01

    Ashok Gadgil speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  3. Biofuels Science and Facilities (Carbon Cycle 2.0)

    ScienceCinema

    Keasling, Jay D

    2011-06-03

    Jay D. Keasling speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  4. Carbon Cycle 2.0: Ashok Gadgil: global impact

    SciTech Connect

    Ashok Gadgi

    2010-02-09

    Ashok Gadgil speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  5. Supercritical carbon dioxide cycle control analysis.

    SciTech Connect

    Moisseytsev, A.; Sienicki, J. J.

    2011-04-11

    This report documents work carried out during FY 2008 on further investigation of control strategies for supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle energy converters. The main focus of the present work has been on investigation of the S-CO{sub 2} cycle control and behavior under conditions not covered by previous work. An important scenario which has not been previously calculated involves cycle operation for a Sodium-Cooled Fast Reactor (SFR) following a reactor scram event and the transition to the primary coolant natural circulation and decay heat removal. The Argonne National Laboratory (ANL) Plant Dynamics Code has been applied to investigate the dynamic behavior of the 96 MWe (250 MWt) Advanced Burner Test Reactor (ABTR) S-CO{sub 2} Brayton cycle following scram. The timescale for the primary sodium flowrate to coast down and the transition to natural circulation to occur was calculated with the SAS4A/SASSYS-1 computer code and found to be about 400 seconds. It is assumed that after this time, decay heat is removed by the normal ABTR shutdown heat removal system incorporating a dedicated shutdown heat removal S-CO{sub 2} pump and cooler. The ANL Plant Dynamics Code configured for the Small Secure Transportable Autonomous Reactor (SSTAR) Lead-Cooled Fast Reactor (LFR) was utilized to model the S-CO{sub 2} Brayton cycle with a decaying liquid metal coolant flow to the Pb-to-CO{sub 2} heat exchangers and temperatures reflecting the decaying core power and heat removal by the cycle. The results obtained in this manner are approximate but indicative of the cycle transient performance. The ANL Plant Dynamics Code calculations show that the S-CO{sub 2} cycle can operate for about 400 seconds following the reactor scram driven by the thermal energy stored in the reactor structures and coolant such that heat removal from the reactor exceeds the decay heat generation. Based on the results, requirements for the shutdown heat removal system may be defined

  6. Elevated temperature alters carbon cycling in a model microbial community

    NASA Astrophysics Data System (ADS)

    Mosier, A.; Li, Z.; Thomas, B. C.; Hettich, R. L.; Pan, C.; Banfield, J. F.

    2013-12-01

    Earth's climate is regulated by biogeochemical carbon exchanges between the land, oceans and atmosphere that are chiefly driven by microorganisms. Microbial communities are therefore indispensible to the study of carbon cycling and its impacts on the global climate system. In spite of the critical role of microbial communities in carbon cycling processes, microbial activity is currently minimally represented or altogether absent from most Earth System Models. Method development and hypothesis-driven experimentation on tractable model ecosystems of reduced complexity, as presented here, are essential for building molecularly resolved, benchmarked carbon-climate models. Here, we use chemoautotropic acid mine drainage biofilms as a model community to determine how elevated temperature, a key parameter of global climate change, regulates the flow of carbon through microbial-based ecosystems. This study represents the first community proteomics analysis using tandem mass tags (TMT), which enable accurate, precise, and reproducible quantification of proteins. We compare protein expression levels of biofilms growing over a narrow temperature range expected to occur with predicted climate changes. We show that elevated temperature leads to up-regulation of proteins involved in amino acid metabolism and protein modification, and down-regulation of proteins involved in growth and reproduction. Closely related bacterial genotypes differ in their response to temperature: Elevated temperature represses carbon fixation by two Leptospirillum genotypes, whereas carbon fixation is significantly up-regulated at higher temperature by a third closely related genotypic group. Leptospirillum group III bacteria are more susceptible to viral stress at elevated temperature, which may lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, this proteogenomics approach revealed the effects of climate change on carbon cycling pathways and other

  7. Resource quality affects carbon cycling in deep-sea sediments.

    PubMed

    Mayor, Daniel J; Thornton, Barry; Hay, Steve; Zuur, Alain F; Nicol, Graeme W; McWilliam, Jenna M; Witte, Ursula F M

    2012-09-01

    Deep-sea sediments cover ~70% of Earth's surface and represent the largest interface between the biological and geological cycles of carbon. Diatoms and zooplankton faecal pellets naturally transport organic material from the upper ocean down to the deep seabed, but how these qualitatively different substrates affect the fate of carbon in this permanently cold environment remains unknown. We added equal quantities of (13)C-labelled diatoms and faecal pellets to a cold water (-0.7 °C) sediment community retrieved from 1080 m in the Faroe-Shetland Channel, Northeast Atlantic, and quantified carbon mineralization and uptake by the resident bacteria and macrofauna over a 6-day period. High-quality, diatom-derived carbon was mineralized >300% faster than that from low-quality faecal pellets, demonstrating that qualitative differences in organic matter drive major changes in the residence time of carbon at the deep seabed. Benthic bacteria dominated biological carbon processing in our experiments, yet showed no evidence of resource quality-limited growth; they displayed lower growth efficiencies when respiring diatoms. These effects were consistent in contrasting months. We contend that respiration and growth in the resident sediment microbial communities were substrate and temperature limited, respectively. Our study has important implications for how future changes in the biochemical makeup of exported organic matter will affect the balance between mineralization and sequestration of organic carbon in the largest ecosystem on Earth. PMID:22378534

  8. Oligocene to Miocene carbon isotope cycles and abyssal circulation changes

    NASA Astrophysics Data System (ADS)

    Miller, Kenneth G.; Fairbanks, Richard G.

    Three cycles of δ13C occurred in Oligocene to Miocene benthic and planktonic foraminifera at western North Atlantic Sites 558 and 563. Intervals of high δ13C occurred at about 35-33 Ma (early Oligocene), 25-22 Ma (across the Oligocene/Miocene boundary), and 18-14 Ma (across the early/middle Miocene boundary). Similar carbon isotopic fluctuations have been measured in benthic and planktonic foraminifera from the Atlantic, Pacific, and Indian oceans, suggesting that these cycles represent global changes in the δ13C of mean ocean water. The average duration of the carbon cycles is 50 times greater than the residence time of carbon in the oceans. Therefore, the mechanism controlling these cycles must be tied to changes in the input ratio of organic carbon to carbonate from weathering rocks or to changes in the output ratio of organic carbon to carbonate in marine sediments. Following a strategy used to study modern and Pleistocene oceans, benthic foraminiferal δ13C differences between the Atlantic and Pacific are used to infer Oligocene through Miocene abyssal circulation changes. The Atlantic was most enriched in l3C relative to the Pacific from about 36-33 Ma (early Oligocene) and 26-10 Ma (late Oligocene to late Miocene). We interpret this as indicating supply of nutrient-depleted bottom water in the North Atlantic, perhaps analogous to modern North Atlantic Deep Water. High benthic foraminiferal δ13O values at about 36-35 Ma, 31-28 Ma, 25-24 Ma, and younger than 15 Ma indicate the presence of ice sheets at these times. Covariance between benthic and planktonic foraminiferal δ18O records of 0.3-0.5°/ºº at 36 Ma, 31 Ma, and 25 Ma suggests that three periods of continental glaciation caused eustatic (global sea-level) lowerings of 30-50 m during the Oligocene epoch. The δ13C cycles do not correlate with sea-level changes deduced from oxygen isotopic data, nor do they correlate with other proxy indicators for sea level.

  9. Vegetation and carbon cycle dynamics in Holocene

    NASA Astrophysics Data System (ADS)

    Rachmayani, R.; Prange, M.; Schulz, M.

    2009-04-01

    Holocene climate has been relatively well investigated with global climate models. Ruddiman suggested that the growth of atmospheric carbon dioxide during the Holocene recorded in the Taylor Dome ice core is a result of profound human impact on climate due to slash-and-burn agricultural practice during the Neolithic period. A series of numerical time slice experiments using the comprehensive global climate model CCSM3 (Community Climate System Model, version 3) has been carried out to study orbitally driven climate variability during the Holocene. The importance of biogeophysical feedbacks between vegetation and climate as well as the role of terrestrial carbon storage in atmospheric carbon dioxide dynamics will be analyzed. The results will be compared to other climate models in order to address some aspects of the Ruddiman hypothesis on exceptional long-term atmospheric carbon dioxide increase during the Holocene. To this end, the land model component of CCSM3 has been improved. The improvements lead to a better simulation of global forest cover and net primary production. Key words Climate, CCSM3, Holocene, Vegetation

  10. Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

    NASA Astrophysics Data System (ADS)

    Komar, N.; Zeebe, R. E.

    2016-01-01

    Negative carbon and calcium isotope excursions, as well as climate shifts, took place during the most severe mass extinction event in Earth's history, the end-Permian (˜252 Ma). Investigating the connection between carbon and calcium cycles during transient carbon cycle perturbation events, such as the end-Permian, may help resolve the intricacies between the coupled calcium-carbon cycles, as well as provide a tool for constraining the causes of mass extinction. Here we identify the deficiencies of a simplified calcium model employed in several previous studies, and we demonstrate the importance of a fully coupled carbon cycle model when investigating the dynamics of carbon and calcium cycling. Simulations with a modified version of the Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir model, which includes a fully coupled carbon-calcium cycle, indicate that increased weathering rates and ocean acidification (potentially caused by Siberian Trap volcanism) are not capable of producing trends observed in the record, as previously claimed. Our model results suggest that combined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the cessation of biological carbon export, and variable calcium isotope fractionation (due to a change in the seawater carbonate ion concentration) represents a more plausible scenario. This scenario successfully reconciles δ13C and δ44Ca trends observed in the sediment record, as well as the proposed warming of >6°C.

  11. Microbial Carbon Cycling in Permafrost-Affected Soils

    SciTech Connect

    Vishnivetskaya, T.; Liebner, Susanne; Wilhelm, Ronald; Wagner, Dirk

    2011-01-01

    The Arctic plays a key role in Earth s climate system as global warming is predicted to be most pronounced at high latitudes and because one third of the global carbon pool is stored in ecosystems of the northern latitudes. In order to improve our understanding of the present and future carbon dynamics in climate sensitive permafrost ecosystems, present studies concentrate on investigations of microbial controls of greenhouse gas fluxes, on the activity and structure of the involved microbial communities, and on their response to changing environmental conditions. Permafrost-affected soils can function as both a source and a sink for carbon dioxide and methane. Under anaerobic conditions, caused by flooding of the active layer and the effect of backwater above the permafrost table, the mineralization of organic matter can only be realized stepwise by specialized microorganisms. Important intermediates of the organic matter decomposition are hydrogen, carbon dioxide and acetate, which can be further reduced to methane by methanogenic archaea. Evolution of methane fluxes across the subsurface/atmosphere boundary will thereby strongly depend on the activity of anaerobic methanogenic archaea and obligately aerobic methane oxidizing proteobacteria, which are known to be abundant and to significantly reduce methane emissions in permafrost-affected soils. Therefore current studies on methane-cycling microorganisms are the object of particular attention in permafrost studies, because of their key role in the Arctic methane cycle and consequently of their significance for the global methane budget.

  12. Carbon cycle: Global warming then and now

    NASA Astrophysics Data System (ADS)

    Stassen, Peter

    2016-04-01

    A rapid warming event 55.8 million years ago was caused by extensive carbon emissions. The rate of change of carbon and oxygen isotopes in marine shelf sediments suggests that carbon emission rates were much slower than anthropogenic emissions.

  13. Carbon Dioxide Carbonates in the Earth;s Mantle: Implications to the Deep Carbon Cycle

    SciTech Connect

    Yoo, Choong-Shik; Sengupta, Amartya; Kim, Minseob

    2012-05-22

    An increase in the ionic character in C-O bonds at high pressures and temperatures is shown by the chemical/phase transformation diagram of CO{sub 2}. The presence of carbonate carbon dioxide (i-CO{sub 2}) near the Earth's core-mantle boundary condition provides insights into both the deep carbon cycle and the transport of atmospheric CO{sub 2} to anhydrous silicates in the mantle and iron core.

  14. Impact of carbon storage through restoration of drylands on the global carbon cycle

    SciTech Connect

    Keller, A.A.; Goldstein, R.A.

    1998-09-01

    The authors evaluate the potential for global carbon storage in drylands as one of several policy options to reduce buildup of carbon dioxide in the atmosphere. They use the GLOCO model, a global carbon cycle model with eight terrestrial biomes that are described mechanistically in detail in terms of the biological processes that involve carbon and nitrogen cycling and the effect of temperature on these processes. GLOCO also considers low-latitude and high-latitude oceans, each divided further into a surface layer and several deeper layers, with an explicit description of biogeochemical processes occurring in each layer, and exchanges among ocean reservoirs and the atmosphere. GLOCO is used to study the transient response of actual vegetation, which is more realistic than looking at equilibrium conditions of potential vegetation. Using estimates of land suitable for restoration in woodlands, grasslands, and deserts, as well as estimates of the rate at which restoration can proceed, the authors estimate that carbon storage in these biomes can range up to 0.8 billion tons of carbon per year for a combination of land management strategies. A global strategy for reducing atmospheric carbon dioxide concentration will require the implementation of multiple options. The advantage of carbon storage in restored drylands is that it comes as a side benefit to programs that are also justifiable in terms of land management.

  15. Carbon nanofiber polymer composites: evaluation of life cycle energy use.

    PubMed

    Khanna, Vikas; Bakshi, Bhavik R

    2009-03-15

    Holistic evaluation of emerging nanotechnologies using systems analysis is pivotal for guiding their safe and sustainable development. While toxicity studies of engineered nanomaterials are essential, understanding of the potential large scale impacts of nanotechnology is also critical for developing sustainable nanoproducts. This work evaluates the life cycle energetic impact associated with the production and use of carbon nanofiber (CNF) reinforced polymer nanocomposites (PNC). Specifically, both simple CNF and carbon nanofiber-glass fiber (CNF-GF) hybrid PNCs are evaluated and compared with steel for equal stiffness design. Life cycle inventory is developed based on published literature and best available engineering information. A cradle-to-gate comparison suggests that for equal stiffness design, CNF reinforced PNCs are 1.6-12 times more energy intensive than steel. It is anticipated that the product use phase may strongly influence whether any net savings in life cycle energy consumption can be realized. A case study involving the use of CNF and CNF-GF reinforced PNCs in the body panels of automobiles highlights that the use of PNCs with lower CNF loading ratios has the potential for net life cycle energy savings relative to steel owing to improved fuel economy benefits. Other factors such as cost, toxicity impact of CNF, and end-of-life issues specific to CNFs need to be considered to evaluate the final economic and environmental performance of CNF reinforced PNC materials. PMID:19368217

  16. Historical constraints on the origins of the carbon cycle concept

    NASA Astrophysics Data System (ADS)

    Galvez, Matthieu Emmanuel; Gaillardet, Jérôme

    2012-11-01

    Understanding the geological carbon cycle remains a major scientific challenge, although studies dedicated to this issue, in particular those of J.J. Ebelmen in the mid 19th century, have existed for over 200 years. The exact scientific and social pathways leading to the construction of the contemporaneous carbon cycle requires further investigation, which in turn may provide valuable insights into the modern state of scientific knowledge. The present study contributes to this question by demonstrating that, following the discovery of the compound nature of carbonic acid by A.L. Lavoisier at the end of the 18th century, studies initially investigated the mechanisms of respiration and photosynthesis until they were recognized as exerting an antagonistic effect on the composition of air. In the early 19th century, the consequence of these studies at the global scale had been foreseen, and applied to investigate the stability of the atmospheric composition over time. These early steps were only concerned with the fate of carbonic acid through life processes. However, between 1820 and 1840, the works of A.L. Brongniard and J.B. Boussingault established that geologic processes, such as the burial of carbonaceous material (CM) in sedimentary rocks and the release of CO2 by volcanoes, affect the composition of the atmosphere. By 1845, J.J. Ebelmen had brilliantly contributed to the emerging question of atmospheric composition by proposing that the alteration of silicates on continents and the precipitation of carbonates in the ocean should be considered as a sink of atmospheric CO2. He also used chemical formula of the time to quantify this process, which led him to mention a carbon rotation for the first time. The rotation of this element through geologic processes became, in itself, a matter worthy of investigation as was the composition of the atmosphere. We argue that J.J. Ebelmen's brilliant synthesis was made possible by the parallel development of the atomistic

  17. Climate, carbon cycling, and deep-ocean ecosystems

    PubMed Central

    Smith, K. L.; Ruhl, H. A.; Bett, B. J.; Billett, D. S. M.; Lampitt, R. S.; Kaufmann, R. S.

    2009-01-01

    Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy ≈60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate. PMID:19901326

  18. Carbon and nitrogen cycling in thermally heated sediments

    NASA Astrophysics Data System (ADS)

    Meyer-Dombard, D. R.; Burton, M.; Vennelakanti, S.; Havig, J. R.; Shock, E.

    2009-12-01

    Hydrothermally heated sediment environments, such as are found in abundance throughout Yellowstone National Park, host fully functional microbial ecosystems. As with any ecosystem, both sources and sinks of carbon, nitrogen, and a myriad of other nutrients and energy-driving factors must be supplied. While we know microbial communities in hydrothermal environments can be surprisingly diverse, we know little about basic ecological functions such as carbon and nitrogen cycling. Previous work has shown that carbon cycling in one hot spring in Yellowstone National Park [“Bison Pool”] and its associated runoff channel functions as a complex system. Analysis of carbon and nitrogen isotopes in sediments and biofilms across a temperature and chemical gradient at this location revealed that the four best studied carbon fixation pathways [Calvin, reverse tricarboxylic acid, acetyl-CoA, 3-hydroxypropionate cycles] may all be functioning in this system, and nitrogen fixation varies across the chemosynthetic/photosynthetic ecotone [1]. Microcosm experiments using biofilms from this hot spring as inoculae with 13C labeled carbon substrates indicate heterotrophic growth [2]. In addition, metagenomic analysis of environmental DNA has indicated the presence of genes involved in carbon fixation [both phototrophic and autotrophic], and heterotrophy, as well as nitrogen fixation [3]. Studies from other Yellowstone locations have also found genetic evidence for carbon and nitrogen fixation [4, 5]. Of particular interest is the role of individuals in carbon and nitrogen cycling as environmental conditions suitable for chemosynthetic and photosynthetic growth vary. This study explores the diversity of cbbM/cbbL [Calvin cycle], aclB/oor/porA [rTCA cycle], nifH [nitrogen fixation], nirK [nitrite reduction] and amoA [ammonia oxidation] genes across a variety of Yellowstone environments. The transition of genetic diversity within sediments and biofilms is focused on the chemosynthetic

  19. Thermal Cycling of Thermal Control Paints on Carbon-Carbon and Carbon-Polyimide Composites

    NASA Technical Reports Server (NTRS)

    Jaworske, Donald A.

    2006-01-01

    Carbon-carbon composites and carbon-polyimide composites are being considered for space radiator applications owing to their light weight and high thermal conductivity. For those radiator applications where sunlight will impinge on the surface, it will be necessary to apply a white thermal control paint to minimize solar absorptance and enhance infrared emittance. Several currently available white thermal control paints were applied to candidate carbon-carbon and carbon-polyimide composites and were subjected to vacuum thermal cycling in the range of -100 C to +277 C. The optical properties of solar absorptance and infrared emittance were evaluated before and after thermal cycling. In addition, adhesion of the paints was evaluated utilizing a tape test. The test matrix included three composites: resin-derived carbon-carbon and vapor infiltrated carbon-carbon, both reinforced with pitch-based P-120 graphite fibers, and a polyimide composite reinforced with T-650 carbon fibers, and three commercially available white thermal control paints: AZ-93, Z-93-C55, and YB-71P.

  20. Iron cycling at corroding carbon steel surfaces.

    PubMed

    Lee, Jason S; McBeth, Joyce M; Ray, Richard I; Little, Brenda J; Emerson, David

    2013-01-01

    Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media. PMID:24093730

  1. Advanced Supercritical Carbon Dioxide Brayton Cycle Development

    SciTech Connect

    Anderson, Mark; Sienicki, James; Moisseytsev, Anton; Nellis, Gregory; Klein, Sanford

    2015-10-21

    Fluids operating in the supercritical state have promising characteristics for future high efficiency power cycles. In order to develop power cycles using supercritical fluids, it is necessary to understand the flow characteristics of fluids under both supercritical and two-phase conditions. In this study, a Computational Fluid Dynamic (CFD) methodology was developed for supercritical fluids flowing through complex geometries. A real fluid property module was implemented to provide properties for different supercritical fluids. However, in each simulation case, there is only one species of fluid. As a result, the fluid property module provides properties for either supercritical CO2 (S-CO2) or supercritical water (SCW). The Homogeneous Equilibrium Model (HEM) was employed to model the two-phase flow. HEM assumes two phases have same velocity, pressure, and temperature, making it only applicable for the dilute dispersed two-phase flow situation. Three example geometries, including orifices, labyrinth seals, and valves, were used to validate this methodology with experimental data. For the first geometry, S-CO2 and SCW flowing through orifices were simulated and compared with experimental data. The maximum difference between the mass flow rate predictions and experimental measurements is less than 5%. This is a significant improvement as previous works can only guarantee 10% error. In this research, several efforts were made to help this improvement. First, an accurate real fluid module was used to provide properties. Second, the upstream condition was determined by pressure and density, which determines supercritical states more precise than using pressure and temperature. For the second geometry, the flow through labyrinth seals was studied. After a successful validation, parametric studies were performed to study geometric effects on the leakage rate. Based on these parametric studies, an optimum design strategy for the see

  2. Warm Spring Reduced Impact of Summer Drought on Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Keenan, T. F.; Fisher, J. B.; Baldocchi, D. D.

    2014-12-01

    Drought severely impacts biosphere-atmosphere carbon and water fluxes of terrestrial ecosystems by reducing productivity, carbon uptake and water transport to the atmosphere. The 2012 US drought was among the most intense and widespread drought events in the U.S. since the 'Dust Bowl' period in the 1930s, and had devastating effects on agricultural production. In addition, 2012 was among the warmest years on record. Using eddy covariance measurements of carbon, water and energy exchange from 25 AmeriFlux sites along with remote sensing products, we show that this summer drought substantially reduced ecosystem productivity, net carbon uptake and water transport to the atmosphere. However, the warm spring with higher ecosystem productivity reduced the impact of the summer drought on annual carbon uptake. Shifts in vegetation activity during spring also triggered feedbacks that contributed to the summer heatwave. Although the drought was exceptional, 2012 was an example of what is expected in terms of future climate change - i.e. warmer temperatures all year and an increased frequency and duration of drought in summer. Understanding the response of ecosystem carbon and water cycling to drought will help to mitigate these changes, and our study provides important new insights for that.

  3. Warm Spring Reduced Impact of Summer Drought on Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Wolf, Sebastian; Keenan, Trevor F.; Fisher, Joshua B.; Baldocchi, Dennis

    2015-04-01

    Drought severely impacts biosphere-atmosphere carbon and water fluxes of terrestrial ecosystems by reducing productivity, carbon uptake and water transport to the atmosphere. The 2012 US drought was among the most intense and widespread drought events in the U.S. since the 'Dust Bowl' period in the 1930s, and had devastating effects on agricultural production. In addition, 2012 was among the warmest years on record. Using eddy covariance measurements of carbon, water and energy exchange from AmeriFlux sites along with remote sensing products, we show that this summer drought substantially reduced ecosystem productivity, net carbon uptake and water transport to the atmosphere. However, the warm spring with higher ecosystem productivity reduced the impact of the summer drought on annual carbon uptake. Shifts in vegetation activity during spring also triggered feedbacks that contributed to the summer heatwave. Although the drought was exceptional, 2012 was an example of what is expected in terms of future climate change - i.e. warmer temperatures all year and an increased frequency and duration of drought in summer. Understanding the response of ecosystem carbon and water cycling to drought will help to mitigate these changes, and our study provides important new insights for that.

  4. Carbon Cycle 2.0: Jay Keasling: Biofuels

    ScienceCinema

    Jay Keasling

    2010-09-01

    Feb. 4, 2010: Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future.

  5. Carbon Cycle 2.0: Nitash Balsara: Energy Storage

    SciTech Connect

    Nitash Balsara

    2010-02-16

    Feb. 4, 2010: Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future.

  6. Carbon Cycle 2.0: Jay Keasling: Biofuels

    SciTech Connect

    Jay Keasling

    2010-02-16

    Feb. 4, 2010: Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future.

  7. Carbon Cycle 2.0: Robert Cheng and Juan Meza

    SciTech Connect

    Robert Cheng and Juan Meza

    2010-02-16

    Feb. 4, 2010: Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future.

  8. Carbon Cycle 2.0: Robert Cheng and Juan Meza

    ScienceCinema

    Robert Cheng and Juan Meza

    2010-09-01

    Feb. 4, 2010: Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future.

  9. Carbon Cycle 2.0: Nitash Balsara: Energy Storage

    ScienceCinema

    Nitash Balsara

    2010-09-01

    Feb. 4, 2010: Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future.

  10. Impacts of Human-induced Land Cover Change on China Carbon and Water Cycle - an Extreme Case Study, Potential Vegetation Versus Realistic Land Cover

    NASA Astrophysics Data System (ADS)

    Zhao, M.; Running, S. W.; Mu, Q.

    2006-05-01

    China, especially east China, has been undergoing the conversion from natural vegetation to cropland by increased human activities for thousands of years. On the other hand, during recent years, since the Chinese government has realized the severely environmental consequences induced by the degrading ecosystems and their services, measures such as restoring cropland to forest or grass have been implemented. To evaluate how land use change, either converting natural vegetation to cropland or restoration, will influence carbon and water cycle for China ecosystems, we use a general process-based ecosystem model, BIOME-BGC, to simulate changes in these related variables under an extreme scenario, i.e., potential vegetation versus realistic land cover. The potential vegetation is derived by a process-based biogeography model, MAPSS, and MODIS collection 4 land cover is assumed to be realistic land cover. To minimize the uncertainties in the estimated potential vegetation by MAPSS, if the forest type by MAPSS is different from that by MODIS, MAPSS forest type will be replaced with the MODIS one, by assuming there is no human conversion within different forest types. The simulation by BIOME-BGC shows that potential vegetation significantly enhances carbon storage, leaf area index, and rates of primary production, but reduces regional runoff, implying policies of restoring natural vegetation from crops can greatly contribute to stabilizing anthropogenic CO2. There are two main limitations in this study, however. The first is that the restoring natural vegetation will occur for a relatively small fraction of cropland, and secondly, climate changes induced by feedbacks between regional climate system and land cover change have not been taken into consideration. Despite these limitations, the study highlights the severe consequences of land use change induced by human activities.

  11. Performance improvement options for the supercritical carbon dioxide brayton cycle.

    SciTech Connect

    Moisseytsev, A.; Sienicki, J. J.; Nuclear Engineering Division

    2008-07-17

    The supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle is under development at Argonne National Laboratory as an advanced power conversion technology for Sodium-Cooled Fast Reactors (SFRs) as well as other Generation IV advanced reactors as an alternative to the traditional Rankine steam cycle. For SFRs, the S-CO{sub 2} Brayton cycle eliminates the need to consider sodium-water reactions in the licensing and safety evaluation, reduces the capital cost of the SFR plant, and increases the SFR plant efficiency. Even though the S-CO{sub 2} cycle has been under development for some time and optimal sets of operating parameters have been determined, those earlier development and optimization studies have largely been directed at applications to other systems such as gas-cooled reactors which have higher operating temperatures than SFRs. In addition, little analysis has been carried out to investigate cycle configurations deviating from the selected 'recompression' S-CO{sub 2} cycle configuration. In this work, several possible ways to improve S-CO{sub 2} cycle performance for SFR applications have been identified and analyzed. One set of options incorporates optimization approaches investigated previously, such as variations in the maximum and minimum cycle pressure and minimum cycle temperature, as well as a tradeoff between the component sizes and the cycle performance. In addition, the present investigation also covers options which have received little or no attention in the previous studies. Specific options include a 'multiple-recompression' cycle configuration, intercooling and reheating, as well as liquid-phase CO{sub 2} compression (pumping) either by CO{sub 2} condensation or by a direct transition from the supercritical to the liquid phase. Some of the options considered did not improve the cycle efficiency as could be anticipated beforehand. Those options include: a double recompression cycle, intercooling between the compressor stages, and reheating

  12. Importance of vegetation dynamics for future terrestrial carbon cycling

    NASA Astrophysics Data System (ADS)

    Ahlström, Anders; Xia, Jianyang; Arneth, Almut; Luo, Yiqi; Smith, Benjamin

    2015-05-01

    Terrestrial ecosystems currently sequester about one third of anthropogenic CO2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand

  13. Carbon and sulfur cycling through geologic time

    NASA Technical Reports Server (NTRS)

    Garrels, R. M.

    1985-01-01

    Mathematical models of the coupled global systems of sedimentary reservoirs and fluxes are used to infer variations in reservoir sizes and rates of sedimentation over periods of hundreds of millions of years. Perhaps most interesting is the coupled sulfide/sulfate carbon/carbonate system that controls global oxygen and carbon dioxide production and consumption is discussed.

  14. Progress and Future Directions in North American Carbon Cycle Science

    NASA Astrophysics Data System (ADS)

    Michalak, Anna; Huntzinger, Deborah; Shrestha, Gyami

    2013-05-01

    The North American Carbon Program (NACP) convened its fourth biennial "All Investigators" meeting (AIM4, http://www.nacarbon.org/meeting_2013) to review progress in understanding the dynamics of the carbon cycle of North America and adjacent oceans and to chart a course for a more integrative and holistic approach to future research. The meeting was structured around the six decadal goals outlined in the new "A U.S. Carbon Cycle Science Plan" (Michalak et al., University Corporation for Atmospheric Research, 2011, available at http://www.carboncyclescience.gov) and focused on (1) diagnosis of the atmospheric carbon cycle, (2) drivers of anthropogenic emissions, (3) vulnerability of carbon stocks to change, (4) ecosystem impacts of change, (5) carbon management, and (6) decision support.

  15. Calcium and calcium isotope changes during carbon cycle perturbations at the end-Permian

    NASA Astrophysics Data System (ADS)

    Komar, Nemanja; Zeebe, Richard

    2016-04-01

    Negative carbon and calcium isotope excursions, as well as climate shifts, took place during the most severe mass extinction event in Earth's history, the end-Permian (˜252 Ma). Investigating the connection between carbon and calcium cycles during transient carbon cycle perturbation events, such as the end-Permian, may help resolve the intricacies between the coupled calcium-carbon cycles, as well as provide a tool for constraining the causes of mass extinction. Here, we identify the deficiencies of a simplified calcium model employed in several previous studies and we demonstrate the importance of a fully coupled carbon-cycle model when investigating the dynamics of carbon and calcium cycling. Simulations with a modified version of the LOSCAR model, which includes a fully coupled carbon-calcium cycle, indicate that increased weathering rates and ocean acidification (potentially caused by Siberian Trap volcanism) are not capable of producing trends observed in the record, as previously claimed. Our model results suggest that combined effects of carbon input via Siberian Trap volcanism (12,000 Pg C), the cessation of biological carbon export, and variable calcium isotope fractionation (due to a change in the seawater carbonate ion concentration) represents a more plausible scenario. This scenario successfully reconciles δ13C and δ44Ca trends observed in the sediment record, as well as the proposed warming of >6oC.

  16. Carbon cycling and gas exchange in soils

    SciTech Connect

    Trumbore, S.E.

    1989-01-01

    This thesis summaries three independent projects, each of which describes a method which can be used to study the role of soils in regulating the atmospheric concentrations of CO{sub 2} and other trace gases. The first chapter uses the distribution of natural and bomb produced radiocarbon in fractionated soil organic matter to quantify the turnover of carbon in soils. A comparison of {sup 137}Cs and {sup 14}C in the modern soil profiles indicates that carbon is transported vertically in the soil as dissolved organic material. The remainder of the work reported is concerned with the use of inert trace gases to explore the physical factors which control the seasonal to diel variability in the fluxes of CO{sub 2} and other trace gases from soils. Chapter 2 introduces a method for measuring soil gas exchange rates in situ using sulfur hexafluoride as a purposeful tracer. The measurement method uses standard flux box technology, and includes simultaneous determination of the fluxes and soil atmosphere concentrations of CO{sub 2} and CH{sub 4}. In Chapter 3, the natural tracer {sup 222}Rn is used as an inert analog for exchange both in the soils and forest canopy of the Amazon rain forest.

  17. The Deep Carbon Cycle and CO2 Sequestration

    NASA Astrophysics Data System (ADS)

    Filipovitch, N. B.; Mao, W. L.; Chou, I.; Mu, K.

    2009-12-01

    Increased understanding of the Earth’s carbon cycle may provide insight for future carbon storage. Long term geologic sequestration of CO2 occurs in the earth via exothermic reactions between CO2 and silicate minerals to form carbonate minerals. It has been shown that while there is a large enough supply of ultra mafic igneous rock to sequester the CO2 [1], the kinetics of this natural process are too slow to effectively manage our CO2 output. Most studies have focused on studying reaction kinetics at relatively low temperatures and pressures [2,3], and have found that the reaction kinetics are either too slow or (in the case of serpentine) necessitate an uneconomical heat pretreatment [3,4]. Our experiments expand the pressures and temperatures (up to 500 bars and exceeding 200 °C) at which the CO2 + silicate reaction is studied using fused silica capillary cells and Raman and XRD analysis. By increasing our understanding of the kinetics of this process and providing a valuable input for reactive flow and transport models, these results may guide approaches for practical CO2 sequestration in carbonate minerals as a way to manage atmospheric CO2 levels. High pressure and temperature results on carbonates have implications for understanding the deep carbon cycle. Most of the previous high pressure studies on carbonates have concentrated on magnesite (MgCO3), calcite (CaCO3), or dolomite ((Ca,Mg)CO3) [5,6]. While the Mg and Ca carbonates are the most abundant, iron-rich siderite (FeCO3) may be a significant player at greater depths within the earth. We performed XRD and Raman spectroscopy experiments on siderite to lower mantle pressures (up to 40 GPa) and observed a possible phase change around 13 GPa. References 1. Lackner, Klaus S., Wendt, Christopher H., Butt, Darryl P., Joyce, Edward L., Sharp, David H., 1995, Carbon dioxide disposal in carbonate minerals, Energy, Vol.20, No. 11, pp. 1153-1170 2. Bearat, Hamdallah, McKelvy, Michael J., Chizmeshya, Andrew V

  18. Low Cost Solar Energy Conversion (Carbon Cycle 2.0)

    ScienceCinema

    Ramesh, Ramamoorthy

    2011-06-08

    Ramamoorthy Ramesh from LBNL's Materials Science Division speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  19. Carbon Cycle 2.0: Paul Alivisatos: Introduction

    SciTech Connect

    Paul Alivisatos

    2010-02-09

    Berkeley Lab Director Paul Alivisatos speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 1, 2010. Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences.Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  20. Carbon Cycle 2.0: Paul Alivisatos: Introduction

    ScienceCinema

    Paul Alivisatos

    2010-09-01

    Berkeley Lab Director Paul Alivisatos speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 1, 2010. Humanity emits more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences.Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  1. Low Cost Solar Energy Conversion (Carbon Cycle 2.0)

    SciTech Connect

    Ramesh, Ramamoorthy

    2010-02-04

    Ramamoorthy Ramesh from LBNL's Materials Science Division speaks at the Carbon Cycle 2.0 kick-off symposium Feb. 2, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  2. Investigators Share Improved Understanding of the North American Carbon Cycle

    SciTech Connect

    Birdsey, Richard A.; Cook, Robert B; Denning, Scott; Griffith, Peter; Law, Beverly E.; Masek, Jeffrey; Michalak, Anna; Ogle, Stephen; Ojima, Dennis; Pan, Yude; Sabine, Christopher; Sheffner, Edwin; Sundquist, Eric

    2007-06-01

    U.S. North American Carbon Program Investigators Meeting, Colorado Springs, Colorado, 22-25 January 2007. The U.S. North American Carbon Program (NACP) sponsored an "all-scientist" meeting to review progress in understanding the dynamics of the carbon cycle of North America and adjacent oceans, and to chart a course for improved integration across scientific disciplines, scales, and Earth system boundaries. The meeting participants also addressed the need for better decision support tools for managing the carbon cycle of North America, so that strong science can inform policy as interest in taking action increases across the nation.

  3. High efficiency carbonate fuel cell/turbine hybrid power cycles

    SciTech Connect

    Steinfeld, G.

    1995-10-19

    Carbonate fuel cells developed by Energy Research Corporation, in commercial 2.85 MW size, have an efficiency of 57.9 percent. Studies of higher efficiency hybrid power cycles were conducted in cooperation with METC to identify an economically competitive system with an efficiency in excess of 65 percent. A hybrid power cycle was identified that includes a direct carbonate fuel cell, a gas turbine and a steam cycle, which generates power at a LHV efficiency in excess of 70 percent. This new system is called a Tandem Technology Cycle (TTC). In a TTC operating on natural gas fuel, 95 percent of the fuel is mixed with recycled fuel cell anode exhaust, providing water for the reforming of the fuel, and flows to a direct carbonate fuel cell system which generates 72 percent of the power. The portion of the fuel cell anode exhaust which is not recycled, is burned and heat is transferred to the compressed air from a gas turbine, raising its temperature to 1800{degrees}F. The stream is then heated to 2000{degrees}F in the gas turbine burner and expands through the turbine generating 13 percent of the power. Half the exhaust from the gas turbine flows to the anode exhaust burner, and the remainder flows to the fuel cell cathodes providing the O{sub 2} and CO{sub 2} needed in the electrochemical reaction. Exhaust from the fuel cells flows to a steam system which includes a heat recovery steam generator and stages steam turbine which generates 15 percent of the TTC system power. Studies of the TTC for 200-MW and 20-MW size plants quantified performance, emissions and cost-of-electricity, and compared the characteristics of the TTC to gas turbine combined cycles. A 200-MW TTC plant has an efficiency of 72.6 percent, and is relatively insensitive to ambient temperature, but requires a heat exchanger capable of 2000{degrees}F. The estimated cost of electricity is 45.8 mills/kWhr which is not competitive with a combined cycle in installations where fuel cost is under $5.8/MMBtu.

  4. Decay of cacti and carbon cycling.

    PubMed

    Garvie, Laurence A J

    2006-03-01

    Cacti contain large quantities of Ca-oxalate biominerals, with C derived from atmospheric CO(2). Their death releases these biominerals into the environment, which subsequently transform to calcite via a monohydrocalcite intermediate. Here, the fate of Ca-oxalates released by plants in arid environments is investigated. This novel and widespread form of biomineralization has unexpected consequences on C cycling and calcite accumulation in areas with large numbers of cacti. The magnitude of this mineralization is revealed by studying the large columnar cactus Carnegiea gigantea (Engelm.) Britton and Rose in southwestern Arizona (locally called the saguaro). A large C. gigantea contains on the order of 1 x 10(5) g of the Ca-oxalate weddellite-CaC(2)O(4) x 2H(2)O. In areas with high C. gigantea density, there is an estimated 40 g C(atm) m(-2) sequestered in Ca-oxalates. Following the death of the plant, the weddellite transforms to calcite on the order to 10-20 years. In areas with high saguaro density, there is an estimated release of up to 2.4 g calcite m(-2) year(-1) onto the desert soil. Similar transformation mechanisms occur with the Ca-oxalates that are abundant in the majority of cacti. Thus, the total atmospheric C returned to the soil of areas with a high number density of cacti is large, suggesting that there may be a significant long-term accumulation of atmospheric C in these soils derived from Ca-oxalate biominerals. These findings demonstrate that plant decay in arid environments may have locally significant impacts on the Ca and inorganic C cycles. PMID:16453105

  5. Decay of cacti and carbon cycling

    NASA Astrophysics Data System (ADS)

    Garvie, Laurence A. J.

    2006-03-01

    Cacti contain large quantities of Ca-oxalate biominerals, with C derived from atmospheric CO2. Their death releases these biominerals into the environment, which subsequently transform to calcite via a monohydrocalcite intermediate. Here, the fate of Ca-oxalates released by plants in arid environments is investigated. This novel and widespread form of biomineralization has unexpected consequences on C cycling and calcite accumulation in areas with large numbers of cacti. The magnitude of this mineralization is revealed by studying the large columnar cactus Carnegiea gigantea (Engelm.) Britton and Rose in southwestern Arizona (locally called the saguaro). A large C. gigantea contains on the order of 1×105 g of the Ca-oxalate weddellite—CaC2O4·2H2O. In areas with high C. gigantea density, there is an estimated 40 g Catm m-2 sequestered in Ca-oxalates. Following the death of the plant, the weddellite transforms to calcite on the order to 10-20 years. In areas with high saguaro density, there is an estimated release of up to 2.4 g calcite m-2 year-1 onto the desert soil. Similar transformation mechanisms occur with the Ca-oxalates that are abundant in the majority of cacti. Thus, the total atmospheric C returned to the soil of areas with a high number density of cacti is large, suggesting that there may be a significant long-term accumulation of atmospheric C in these soils derived from Ca-oxalate biominerals. These findings demonstrate that plant decay in arid environments may have locally significant impacts on the Ca and inorganic C cycles.

  6. Carbon cycling and storage in mangrove forests.

    PubMed

    Alongi, Daniel M

    2014-01-01

    Mangroves are ecologically and economically important forests of the tropics. They are highly productive ecosystems with rates of primary production equal to those of tropical humid evergreen forests and coral reefs. Although mangroves occupy only 0.5% of the global coastal area, they contribute 10-15% (24 Tg C y(-1)) to coastal sediment carbon storage and export 10-11% of the particulate terrestrial carbon to the ocean. Their disproportionate contribution to carbon sequestration is now perceived as a means for conservation and restoration and a way to help ameliorate greenhouse gas emissions. Of immediate concern are potential carbon losses to deforestation (90-970 Tg C y(-1)) that are greater than these ecosystems' rates of carbon storage. Large reservoirs of dissolved inorganic carbon in deep soils, pumped via subsurface pathways to adjacent waterways, are a large loss of carbon, at a potential rate up to 40% of annual primary production. Patterns of carbon allocation and rates of carbon flux in mangrove forests are nearly identical to those of other tropical forests. PMID:24405426

  7. Dissolved Organic Carbon Cycling in Forested Watersheds: A Carbon Isotope Approach

    NASA Astrophysics Data System (ADS)

    Schiff, S. L.; Aravena, R.; Trumbore, S. E.; Dillon, P. J.

    1990-12-01

    Dissolved organic carbon (DOC) is important in the acid-base chemistry of acid-sensitive freshwater systems; in the complexation, mobility, persistence, and toxicity of metals and other pollutants; and in lake carbon metabolism. Carbon isotopes (13C and 14C) are used to study the origin, transport, and fate of DOC in a softwater catchment in central Ontario. Precipitation, soil percolates, groundwaters, stream, beaver pond, and lake waters, and lake sediment pore water were characterized chemically and isotopically. In addition to total DOC, isotopic measurements were made on the humic and fulvic DOC fractions. The lake is a net sink for DOC. Δ14C results indicate that the turnover time of most of the DOC in streams, lakes, and wetlands is fast, less than 40 years, and on the same time scale as changes in acidic deposition. DOC in groundwaters is composed of older carbon than surface waters, indicating extensive cycling of DOC in the upper soil zone or aquifer.

  8. [Carbon balance analysis of corn fuel ethanol life cycle].

    PubMed

    Zhang, Zhi-shan; Yuan, Xi-gang

    2006-04-01

    The quantity of greenhouse gas emissions (net carbon emissions) of corn-based fuel ethanol, which is known as an alternative for fossil fuel is an important criteria for evaluating its sustainability. The methodology of carbon balance analysis for fuel ethanol from corn was developed based on principles of life cycle analysis. For the production state of fuel ethanol from summer corn in China, carbon budgets in overall life cycle of the ethanol were evaluated and its main influence factors were identified. It presents that corn-based fuel ethanol has no obvious reduction of carbon emissions than gasoline, and potential improvement in carbon emission of the life cycle of corn ethanol could be achieved by reducing the nitrogen fertilizer and irrigation electricity used in the corn farming and energy consumption in the ethanol conversion process. PMID:16767974

  9. Wilson Cycle studies

    NASA Technical Reports Server (NTRS)

    Burke, Kevin

    1987-01-01

    Regional lineaments in continental evolution were studied. It was concluded that lineaments within continents are attributed to a small number of processes of continent formation and modification, but interactions among these processes may produce complex patterns.

  10. Rapid carbon cycling in the oligotrophic ocean

    NASA Astrophysics Data System (ADS)

    Duarte, C. M.; Agustí, S.

    2011-12-01

    The dynamics of organic carbon production, release and bacterial use was examined across a range of communities spanning from highly oligotrophic ones in the Subtropical Atlantic Ocean, mesotrophic ones in the Mediterranean Sea and productive ones in the Northern African upwelling and the Southern Ocean. A comparative analysis of experiments examining total and particulate organic carbon production across a range of time scales (15 min to 24 h) for 20 communities with contrasting phytoplankton cell status, as assessed by cell lysis rates, and the use of a simple inverse model was used to resolve patterns of carbon flow in the microbial food web. Communities in productive ocean waters accumulated organic carbon over hourly time scales, whereas only a small fraction of net primary production accumulated in communities from oligotrophic waters. These communities supported high phytoplankton cell lysis rates leading to a rapid flux of organic carbon to bacteria, which had high affinity for phytoplankton-derived carbon, much of which was rapidly respired. Conventional assessments of primary production in the oligotrophic ocean severely underestimate net phytoplankton production, as carbon flow in microbial communities from oligotrophic ocean waters occurs within short (minutes) time scales. This explains difficulties to reconcile estimates of primary production with independent estimates of carbon use by bacteria in oligotrophic marine ecosystems.

  11. Soil carbon cycling in pasture systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Carbon accumulation in soil under pastures occurs to various degrees depending upon management and length of time. This presentation describes research results on soil carbon sequestration under pastures from the southeastern USA to help inform the scientific basis for development of a protocol to ...

  12. Phanerozoic cycles of sedimentary carbon and sulfur.

    PubMed

    Garrels, R M; Lerman, A

    1981-08-01

    A reservoir model of a Recent steady-state sedimentary system in which the reduced sulfur and oxidized sulfur reservoirs were coupled with the oxidized carbon and reduced carbon reservoirs was constructed. The time curve of the sulfur isotope ratios of the sedimentary sulfate reservoir was used to drive the model back to the beginning of Cambrian time (600 million years ago), producing the reservoir sizes and isotope values and material fluxes of the carbon-sulfur system. The predicted values of carbon isotope ratios of the carbonate reservoir agree well with observed values, showing that the model is basically sound. Some general conclusions from this success are (i) material flux rates in the carbon-oxygen-sulfur system of the geologic past (averaged over tens of millions of years) lie within about a factor of 2 of Recent rates. (ii) The oxidation-reduction balances of Phanerozoic time were dominated by reciprocal relationships between carbon and sulfur compounds. (iii) The rate of production of atmospheric oxygen by storage in sediments of organic carbon of photosynthetic origin increased from the Cambrian Period to the Permian Period and declined somewhat from the Permian Period to the Present. (iv) The storage of oxygen in oxidized sulfur compounds kept pace (within the limits of the data) with oxygen production. (v) Transfer of oxygen from CO(2) to SO(4) from the Cambrian to the Permian Period was several times the Recent free oxygen content of the atmosphere. PMID:16593066

  13. Climate impacts of bioenergy: Inclusion of carbon cycle and albedo dynamics in life cycle impact assessment

    SciTech Connect

    Bright, Ryan M. Cherubini, Francesco; Stromman, Anders H.

    2012-11-15

    Life cycle assessment (LCA) can be an invaluable tool for the structured environmental impact assessment of bioenergy product systems. However, the methodology's static temporal and spatial scope combined with its restriction to emission-based metrics in life cycle impact assessment (LCIA) inhibits its effectiveness at assessing climate change impacts that stem from dynamic land surface-atmosphere interactions inherent to all biomass-based product systems. In this paper, we focus on two dynamic issues related to anthropogenic land use that can significantly influence the climate impacts of bioenergy systems: i) temporary changes to the terrestrial carbon cycle; and ii) temporary changes in land surface albedo-and illustrate how they can be integrated within the LCA framework. In the context of active land use management for bioenergy, we discuss these dynamics and their relevancy and outline the methodological steps that would be required to derive case-specific biogenic CO{sub 2} and albedo change characterization factors for inclusion in LCIA. We demonstrate our concepts and metrics with application to a case study of transportation biofuel sourced from managed boreal forest biomass in northern Europe. We derive GWP indices for three land management cases of varying site productivities to illustrate the importance and need to consider case- or region-specific characterization factors for bioenergy product systems. Uncertainties and limitations of the proposed metrics are discussed. - Highlights: Black-Right-Pointing-Pointer A method for including temporary surface albedo and carbon cycle changes in Life Cycle Impact Assessment (LCIA) is elaborated. Black-Right-Pointing-Pointer Concepts are applied to a single bioenergy case whereby a range of feedstock productivities are shown to influence results. Black-Right-Pointing-Pointer Results imply that case- and site-specific characterization factors can be essential for a more informed impact assessment. Black

  14. Combustion and Carbon Cycle 2.0 and Computation in CC 2.0 (Carbon Cycle 2.0)

    ScienceCinema

    Cheng, Robert K; Meza, Juan

    2011-06-08

    Robert Cheng and Juan Meza provide two presentations in one session at the Carbon Cycle 2.0 kick-off symposium Feb. 3, 2010. We emit more carbon into the atmosphere than natural processes are able to remove - an imbalance with negative consequences. Carbon Cycle 2.0 is a Berkeley Lab initiative to provide the science needed to restore this balance by integrating the Labs diverse research activities and delivering creative solutions toward a carbon-neutral energy future. http://carboncycle2.lbl.gov/

  15. Ectomycorrhizal fungi slow soil carbon cycling.

    PubMed

    Averill, Colin; Hawkes, Christine V

    2016-08-01

    Respiration of soil organic carbon is one of the largest fluxes of CO2 on earth. Understanding the processes that regulate soil respiration is critical for predicting future climate. Recent work has suggested that soil carbon respiration may be reduced by competition for nitrogen between symbiotic ectomycorrhizal fungi that associate with plant roots and free-living microbial decomposers, which is consistent with increased soil carbon storage in ectomycorrhizal ecosystems globally. However, experimental tests of the mycorrhizal competition hypothesis are lacking. Here we show that ectomycorrhizal roots and hyphae decrease soil carbon respiration rates by up to 67% under field conditions in two separate field exclusion experiments, and this likely occurs via competition for soil nitrogen, an effect larger than 2 °C soil warming. These findings support mycorrhizal competition for nitrogen as an independent driver of soil carbon balance and demonstrate the need to understand microbial community interactions to predict ecosystem feedbacks to global climate. PMID:27335203

  16. The Role of Carbon Cycle Observations and Knowledge in Carbon Management

    SciTech Connect

    Dilling, Lisa; Doney, Scott; Edmonds, James A.; Gurney, Kevin R.; Harriss, Robert; Schimel, David; Stephens, Britton; Stokes, Gerald M.

    2003-08-14

    Agriculture and industrial development have led to inadvertent changes in the natural carbon cycle. As a consequence, concentrations of carbon dioxide and other greenhouse gases have increased in the atmosphere, leading to potential changes in climate. The current challenge facing society is to develop options for future management of the carbon cycle. A variety of approaches has been suggested: direct reduction of emissions, deliberate manipulation of the natural carbon cycle to enhance sequestration, and capture and isolation of carbon from fossil fuel use. Policy development to date has laid out some of the general principles to which carbon management should adhere. These can be summarized as: how much carbon is stored, by what means, and for how long. To successfully manage carbon for climate purposes requires increased understanding of carbon cycle dynamics and improvement to the scientific capabilities available for measurement as well as policy needs. Specific needs for scientific information to underpin carbon cycle management decisions are not yet broadly known. A stronger dialogue between decision makers and scientists must be developed to foster improved application of scientific knowledge to decisions. This paper reviews the current state of knowledge of the carbon cycle and measurement capabilities, with an emphasis on the continental-scale, and its relevance to carbon sequestration goals.

  17. Carbon cycling and burial in New Zealand's fjords

    NASA Astrophysics Data System (ADS)

    Hinojosa, Jessica L.; Moy, Christopher M.; Stirling, Claudine H.; Wilson, Gary S.; Eglinton, Timothy I.

    2014-10-01

    carbon cycling in continental margin settings is critical for constraining the global carbon cycle. Here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six New Zealand fjords. Using carbon and nitrogen concentrations and isotopes, lipid biomarkers, and redox-sensitive element concentrations, we show that the New Zealand fjords have carbon-rich surface sediments in basins that promote long-term storage (i.e., semirestricted basins with sediment accumulation rates of up to 4 mm yr-1). Using δ13C distributions to develop a mixing model, we find that organic carbon in fjord sediments is well-mixed from marine and terrestrial sources in down-fjord gradients. This is driven by high regional precipitation rates of >6 m yr-1, which promote carbon accumulation in fjord basins through terrestrial runoff. In addition, we have identified at least two euxinic subbasins, based on uranium, molybdenum, iron, and cadmium enrichment, that contain >7% organic carbon. Because the strength and position of the Southern Hemisphere westerly winds control precipitation and fjord circulation, carbon delivery and storage in the region are intimately linked to westerly wind variability. We estimate that the fjord region (759 km2) may be exporting up to 1.4 × 107 kgC yr-1, outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude.

  18. The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times.

    PubMed

    Bloom, A Anthony; Exbrayat, Jean-François; van der Velde, Ivar R; Feng, Liang; Williams, Mathew

    2016-02-01

    The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle and its processes is, therefore, necessary to better understand its current state and predict its future state. We combine a diagnostic ecosystem carbon model with satellite observations of leaf area and biomass (where and when available) and soil carbon data to retrieve the first global estimates, to our knowledge, of carbon cycle state and process variables at a 1° × 1° resolution; retrieved variables are independent from the plant functional type and steady-state paradigms. Our results reveal global emergent relationships in the spatial distribution of key carbon cycle states and processes. Live biomass and dead organic carbon residence times exhibit contrasting spatial features (r = 0.3). Allocation to structural carbon is highest in the wet tropics (85-88%) in contrast to higher latitudes (73-82%), where allocation shifts toward photosynthetic carbon. Carbon use efficiency is lowest (0.42-0.44) in the wet tropics. We find an emergent global correlation between retrievals of leaf mass per leaf area and leaf lifespan (r = 0.64-0.80) that matches independent trait studies. We show that conventional land cover types cannot adequately describe the spatial variability of key carbon states and processes (multiple correlation median = 0.41). This mismatch has strong implications for the prediction of terrestrial carbon dynamics, which are currently based on globally applied parameters linked to land cover or plant functional types. PMID:26787856

  19. The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times

    PubMed Central

    Bloom, A. Anthony; Exbrayat, Jean-François; van der Velde, Ivar R.; Feng, Liang; Williams, Mathew

    2016-01-01

    The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle and its processes is, therefore, necessary to better understand its current state and predict its future state. We combine a diagnostic ecosystem carbon model with satellite observations of leaf area and biomass (where and when available) and soil carbon data to retrieve the first global estimates, to our knowledge, of carbon cycle state and process variables at a 1° × 1° resolution; retrieved variables are independent from the plant functional type and steady-state paradigms. Our results reveal global emergent relationships in the spatial distribution of key carbon cycle states and processes. Live biomass and dead organic carbon residence times exhibit contrasting spatial features (r = 0.3). Allocation to structural carbon is highest in the wet tropics (85–88%) in contrast to higher latitudes (73–82%), where allocation shifts toward photosynthetic carbon. Carbon use efficiency is lowest (0.42–0.44) in the wet tropics. We find an emergent global correlation between retrievals of leaf mass per leaf area and leaf lifespan (r = 0.64–0.80) that matches independent trait studies. We show that conventional land cover types cannot adequately describe the spatial variability of key carbon states and processes (multiple correlation median = 0.41). This mismatch has strong implications for the prediction of terrestrial carbon dynamics, which are currently based on globally applied parameters linked to land cover or plant functional types. PMID:26787856

  20. The role of urbanization in the global carbon cycle

    NASA Astrophysics Data System (ADS)

    Churkina, Galina

    2016-04-01

    Increasing urbanization and global environmental change are two of the grand challenges of the Anthropocene. There are many important connections between these two challenges, which are still poorly understood. The role of urbanization in the global carbon cycle is one of them. Until now, the known facts about the its role encompassed only CO2 emissions. Urban areas account for more than 70% of CO2 emissions from burning fossil fuels. Urban expansion in tropics is responsible for 5% of the annual emissions from land use change. Here I show that the effect of urbanization on the global carbon cycle extends beyond these emissions. I quantify the contribution of urbanization to the major carbon fluxes and pools globally and identify gaps crucial for predicting the evolution of the carbon cycle in the future. Urban residents currently control ~22 (12-40)% of the land carbon uptake (112 PgC/yr) and ~24 (15-39)% of the carbon emissions (117 PgC/yr) from land globally. Urbanization resulted in the creation of new carbon pools on land such as buildings (~6.7 PgC) and landfills (~30 PgC). Together these pools store 1.6 (±0.3)% of the total vegetation and soil carbon pools globally. The creation and maintenance of these new pools has been associated with high emissions of CO2, which are currently better understood than the processes associated with the dynamics of these pools and accompanying uptake of carbon. Predictions of the future trajectories of the global carbon cycle will require a much better understanding of how urban development affects the carbon cycle over the long term.

  1. Mission Design for Continental-Scale Carbon Cycle Applications

    NASA Astrophysics Data System (ADS)

    Gervin, J. C.; Esper, J.; McClain, C. R.; Hall, F. G.; Middleton, E. M.; Gregg, W. W.; Mannino, A.; Knox, R. G.; Dabney, P. W.; Huemmrich, K. F.; Wood, H. J.; Roberto, M.

    2003-12-01

    Carbon cycle scientific requirements in both land and ocean studies point toward the need for multiple spectrally detailed observations per day. For terrestrial research, accurate estimates of carbon, water and energy (CWE) exchange between the terrestrial biosphere and atmosphere are needed to identify the geographical locations of carbon sources/sinks and to improve regional climate models and global climate change assessments. It is an enormous challenge to estimate CWE exchange from the infrequent temporal coverage provided by most polar-orbiting satellites, and without benefit of spectral indices that capture vegetation responses to stress conditions that down-regulate photosynthesis. Physiological status can be better assessed with spectral indices based on narrow (<10 nm) bands. Sensors that can measure CWE exchange would also provide accurate biomass observations, although geosynchronous platforms are not required to observe the slowly changing land biomass and biomass change. A hyperspectral instrument (400-1000 nm) would enable improved estimates of seasonal and annual terrestrial productivity, using narrow band and red edge indices not available with current of near-future operational satellites. The overall goal for geosynchronous ocean observations is to predict the variability of carbon uptake in the ocean, and thereby evaluate its role in climate change scenarios. In the plan for developing new observations, we need to: 1)continue to improve estimates of ocean productivity; and 2 expand the emphasis of coastal ocean processes and specific regions of critical importance. Remote sensing of the coastal ocean represents a unique challenge due to the small-scale spatial variability and elevated concentrations of dissolved organic carbon, detritus and chlorophyll, which are difficult to distinguish, because they absorb light intensely in the blue spectrum. Observations in the ultraviolet are essential to improve our capability to distinguish these ocean

  2. Dinoflagellate biogeochemistry: developing new proxies for past carbon cycling (Invited)

    NASA Astrophysics Data System (ADS)

    Sluijs, A.; Hoins, M.; van de Waal, D.; Reichart, G.; Rost, B.

    2013-12-01

    Accurate reconstructions of atmospheric CO2 levels for time intervals that are beyond the reach of the ice cores (> ~850 kyr) remain one of the grand challenges of paleoclimate and paleoenvironmental research. Despite recent progress in analytical techniques and application in several proxies, uncertainties in reconstructed values remain large. Based on culturing experiments combined with gene expression analysis and physiological assays, we quantify and mechanistically underpin the geochemical response of dinoflagellates and their cysts to various CO2 concentrations. The results confirm theoretical inferences that the isotopic composition of both organic and calcite dinoflagellate cysts may serve as a proxy for past ocean carbonate chemistry, notably pCO2. We found a strong effect (~10x as strong as in foraminifera) of pCO2 on the stable oxygen isotopic composition of a calcareous dinoflagellate cyst. Moreover, we found that the stable carbon isotopic composition of four dinoflagellate species, of which two have organic dinocyst fossil records down to the early Cenozoic and Cretaceous, strongly respond to pCO2. Critically, the experiments show that the mechanisms forcing the changes in fractionation factors differ between species, opening a suite of opportunities to study past carbon cycling as well as protist physiology during Earth System perturbations. The dinoflagellate Apectodinium dominated dinoflagellate assemblages during the Paleocene-Eocene Thermal Maximum. Will its carbon isotopic composition reveal CO2 concentrations at that time?

  3. The carbon cycle on early Earth—and on Mars?

    PubMed Central

    Grady, Monica M; Wright, Ian

    2006-01-01

    One of the goals of the present Martian exploration is to search for evidence of extinct (or even extant) life. This could be redefined as a search for carbon. The carbon cycle (or, more properly, cycles) on Earth is a complex interaction among three reservoirs: the atmosphere; the hydrosphere; and the lithosphere. Superimposed on this is the biosphere, and its presence influences the fixing and release of carbon in these reservoirs over different time-scales. The overall carbon balance is kept at equilibrium on the surface by a combination of tectonic processes (which bury carbon), volcanism (which releases it) and biology (which mediates it). In contrast to Earth, Mars presently has no active tectonic system; neither does it possess a significant biosphere. However, these observations might not necessarily have held in the past. By looking at how Earth's carbon cycles have changed with time, as both the Earth's tectonic structure and a more sophisticated biology have evolved, and also by constructing a carbon cycle for Mars based on the carbon chemistry of Martian meteorites, we investigate whether or not there is evidence for a Martian biosphere. PMID:17008211

  4. The carbon cycle on early Earth--and on Mars?

    PubMed

    Grady, Monica M; Wright, Ian

    2006-10-29

    One of the goals of the present Martian exploration is to search for evidence of extinct (or even extant) life. This could be redefined as a search for carbon. The carbon cycle (or, more properly, cycles) on Earth is a complex interaction among three reservoirs: the atmosphere; the hydrosphere; and the lithosphere. Superimposed on this is the biosphere, and its presence influences the fixing and release of carbon in these reservoirs over different time-scales. The overall carbon balance is kept at equilibrium on the surface by a combination of tectonic processes (which bury carbon), volcanism (which releases it) and biology (which mediates it). In contrast to Earth, Mars presently has no active tectonic system; neither does it possess a significant biosphere. However, these observations might not necessarily have held in the past. By looking at how Earth's carbon cycles have changed with time, as both the Earth's tectonic structure and a more sophisticated biology have evolved, and also by constructing a carbon cycle for Mars based on the carbon chemistry of Martian meteorites, we investigate whether or not there is evidence for a Martian biosphere. PMID:17008211

  5. Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial

    USGS Publications Warehouse

    Stallard, R.F.

    1998-01-01

    This paper examines the linkages between the carbon cycle and sedimentary processes on land. Available data suggest that sedimentation on land can bury vast quantities of organic carbon, roughly 1015 g C yr-1. To evaluate the relative roles of various classes of processes in the burial of carbon on land, terrestrial sedimentation was modeled as a series of 864 scenarios. Each scenario represents a unique choice of intensities for seven classes of processes and two different global wetland distributions. Comparison was made with presumed preagricultural conditions. The classes of processes were divided into two major component parts: clastic sedimentation of soil-derived carbon and organic sedimentation of autochthonous carbon. For clastic sedimentation, masses of sediment were considered for burial as reservoir sediment, lake sediment, and combined colluvium, alluvium, and aeolian deposits. When the ensemble of models is examined, the human-induced burial of 0.6-1.5.1015 g yr-1 of carbon on land is entirely plausible. This sink reaches its maximum strength between 30 ?? and 50??N. Paddy lands stand out as a type of land use that warrants future study, but the many faces of rice agriculture limit generalization. In an extreme scenario, paddy lands alone could be made to bury about 1.1015 g C yr-1. Arguing that terrestrial sedimentation processes could be much of the sink for the so called 'missing carbon' is reasonable. Such a hypothesis, however, requires major redesign of how the carbon cycle is modeled. Unlike ecosystem processes that are amenable to satellite monitoring and parallel modeling, many aspects of terrestrial sedimentation are hidden from space.

  6. Carbon cycling in high-latitude ecosystems

    NASA Technical Reports Server (NTRS)

    Townsend, Alan; Frolking, Stephen; Holland, Elizabeth

    1992-01-01

    The carbon-rich soils and peatlands of high-latitude ecosystems could substantially influence atmospheric concentrations of CO2 and CH4 in a changing climate. Currently, cold, often waterlogged conditions retard decomposition, and release of carbon back to the atmosphere may be further slowed by physical protection of organic matter in permafrost. As a result, many northern ecosystems accumulate carbon over time (Billings et al., 1982; Poole and Miller, 1982), and although such rates of accumulation are low, thousands of years of development have left Arctic ecosystems with an extremely high soil carbon content; Schlesinger's (1984) average value of 20.4 kg C/m(sup 2) leads to a global estimate of 163 x 10(exp 15) g C. All GCM simulations of a doubled CO2 climate predict the greatest warming to occur in the polar regions (Dickinson, 1986; Mitchell, 1989). Given the extensive northern carbon pools and the strong sensitivity of decomposition processes to temperature, even a slight warming of the soil could dramatically alter the carbon balance of Arctic ecosystems. If warming accelerates rates of decomposition more than rates of primary production, a sizeable additional accumulation of CO2 in the atmosphere could occur. Furthermore, CH4 produced in anaerobic soils and peatlands of the Arctic already composes a good percentage of the global efflux (Cicerone and Oremlund, 1988); if northern soils become warmer and wetter as a whole, CH4 emissions could dramatically rise. A robust understanding of the primary controls of carbon fluxes in Arctic ecosystems is critical. As a framework for a systematic examination of these controls, we discussed a conceptual model of regional-scale Arctic carbon turnover, including CH4 production, and based upon the Century soil organic matter model.

  7. Bioavailability of dissolved organic carbon linked with the regional carbon cycle in the East China Sea

    NASA Astrophysics Data System (ADS)

    Gan, Shuchai; Wu, Ying; Zhang, Jing

    2016-02-01

    The regional carbon cycle on continental shelves has created great interest recently due to the enigma of whether these areas are a carbon sink or a source. It is vital for a precise carbon cycle model to take the bioavailability of dissolved organic carbon (DOC) into account, as it impacts the sink and source capacity, especially on dynamic shelves such as the East China Sea. Nine bio-decomposition experiments were carried out to assess differences in the bioavailability of DOC. Samples were collected from different water masses in the East China Sea, such as the Coastal Current, the Taiwan Current, and the Kuroshio Current, as well as from the Changjiang (Yangtze River), the main contributor of terrestrial DOC in the East China Sea. This study aimed to quantify and qualify bioavailable DOC (BDOC) in the East China Sea. Both the degradation constant of BDOC and the carbon output from microorganisms have been quantitatively evaluated. Qualitatively, excitation-emission matrix fluorescence spectra (EEMs) were used to evaluate the intrinsic reasons for BDOC variation. By using EEMs in conjunction with parallel factor analysis (PARAFAC), five individual fluorescent components were identified in this study: three humic-like and two protein-like components (P1, P2). The highest P1 and P2 fluorescence intensities were recorded in the coastal water during a phytoplankton algal bloom, while the lowest intensities were recorded in the Changjiang estuary. Quantitatively, BDOC observed during the incubation ranged from 0 to 26.1 μM. The DOC degradation rate constant varied from 0 to 0.027 (d-1), and was lowest in the Changjiang and highest in algal bloom water and warm shelf water (the Taiwan current). The Taiwan Current and mixed shelf water were the major contributors of BDOC flux to the open ocean, and the East China Sea was a net source of BDOC to the ocean. The results verified the importance of BDOC in regional carbon cycle modeling. Combining the data of BDOC and EEMs

  8. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Nuclear Space Power Systems: A Feasibility Assessment

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2004-01-01

    The feasibility of using carbon-carbon recuperators in closed-Brayton-cycle (CBC) nuclear space power conversion systems (PCS) was assessed. Recuperator performance expectations were forecast based on projected thermodynamic cycle state values for a planetary mission. Resulting thermal performance, mass and volume for a plate-fin carbon-carbon recuperator were estimated and quantitatively compared with values for a conventional offset-strip-fin metallic design. Material compatibility issues regarding carbon-carbon surfaces exposed to the working fluid in the CBC PCS were also discussed.

  9. Toward a Mexican eddy covariance network for carbon cycle science

    NASA Astrophysics Data System (ADS)

    Vargas, Rodrigo; Yépez, Enrico A.

    2011-09-01

    First Annual MexFlux Principal Investigators Meeting; Hermosillo, Sonora, Mexico, 4-8 May 2011; The carbon cycle science community has organized a global network, called FLUXNET, to measure the exchange of energy, water, and carbon dioxide (CO2) between the ecosystems and the atmosphere using the eddy covariance technique. This network has provided unprecedented information for carbon cycle science and global climate change but is mostly represented by study sites in the United States and Europe. Thus, there is an important gap in measurements and understanding of ecosystem dynamics in other regions of the world that are seeing a rapid change in land use. Researchers met under the sponsorship of Red Temática de Ecosistemas and Consejo Nacional de Ciencia y Tecnologia (CONACYT) to discuss strategies to establish a Mexican eddy covariance network (MexFlux) by identifying researchers, study sites, and scientific goals. During the meeting, attendees noted that 10 study sites have been established in Mexico with more than 30 combined years of information. Study sites span from new sites installed during 2011 to others with 9 to 6 years of measurements. Sites with the longest span measurements are located in Baja California Sur (established by Walter Oechel in 2002) and Sonora (established by Christopher Watts in 2005); both are semiarid ecosystems. MexFlux sites represent a variety of ecosystem types, including Mediterranean and sarcocaulescent shrublands in Baja California; oak woodland, subtropical shrubland, tropical dry forest, and a grassland in Sonora; tropical dry forests in Jalisco and Yucatan; a managed grassland in San Luis Potosi; and a managed pine forest in Hidalgo. Sites are maintained with an individual researcher's funds from Mexican government agencies (e.g., CONACYT) and international collaborations, but no coordinated funding exists for a long-term program.

  10. Global Biodiversity and the Ancient Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Rothman, D. H.

    2001-05-01

    Paleontological data for the diversity of marine animals and land plants are shown to correlate significantly with a concurrent measure of stable carbon isotope fractionation for approximately the last 400 million years. The correlations can be deduced from the assumption that increasing plant diversity led to increasing chemical weathering of rocks, and therefore an increasing flux of carbon from the atmosphere to rocks, and nutrients from the continents to the oceans. The CO2 concentration dependence of photosynthetic carbon isotope fractionation then indicates that the diversification of land plants led to decreasing CO2 levels, while the diversification of marine animals derived from increasing nutrient availability. Under the explicit assumption that global biodiversity grows with global biomass, the conservation of carbon shows that the long-term fluctuations of CO2 levels were dominated by complementary changes in the biological and fluid reservoirs of carbon while the much larger geological reservoir remained relatively constant in size. As a consequence, the paleontological record of biodiversity provides an indirect estimate of the fluctuations of ancient CO2 levels.

  11. The contribution of bacteria to algal growth by carbon cycling.

    PubMed

    Bai, Xue; Lant, Paul; Pratt, Steven

    2015-04-01

    Algal mass production in open systems is often limited by the availability of inorganic carbon substrate. In this paper, we evaluate how bacterial driven carbon cycling mitigates carbon limitation in open algal culture systems. The contribution of bacteria to carbon cycling was determined by quantifying algae growth with and without supplementation of bacteria. It was found that adding heterotrophic bacteria to an open algal culture dramatically enhanced algae productivity. Increases in algal productivity due to supplementation of bacteria of 4.8 and 3.4 times were observed in two batch tests operating at two different pH values over 7 days. A kinetic model is proposed which describes carbon limited algal growth, and how the limitation could be overcome by bacterial activity to re-mineralize photosynthetic end products. PMID:25312046

  12. Simulated Carbon Cycling in a Model Microbial Mat.

    NASA Astrophysics Data System (ADS)

    Decker, K. L.; Potter, C. S.

    2006-12-01

    We present here the novel addition of detailed organic carbon cycling to our model of a hypersaline microbial mat ecosystem. This ecosystem model, MBGC (Microbial BioGeoChemistry), simulates carbon fixation through oxygenic and anoxygenic photosynthesis, and the release of C and electrons for microbial heterotrophs via cyanobacterial exudates and also via a pool of dead cells. Previously in MBGC, the organic portion of the carbon cycle was simplified into a black-box rate of accumulation of simple and complex organic compounds based on photosynthesis and mortality rates. We will discuss the novel inclusion of fermentation as a source of carbon and electrons for use in methanogenesis and sulfate reduction, and the influence of photorespiration on labile carbon exudation rates in cyanobacteria. We will also discuss the modeling of decomposition of dead cells and the ultimate release of inorganic carbon. The detailed modeling of organic carbon cycling is important to the accurate representation of inorganic carbon flux through the mat, as well as to accurate representation of growth models of the heterotrophs under different environmental conditions. Because the model ecosystem is an analog of ancient microbial mats that had huge impacts on the atmosphere of early earth, this MBGC can be useful as a biological component to either early earth models or models of other planets that potentially harbor life.

  13. [Application of stable carbon isotope technique in the research of carbon cycling in soil-plant system].

    PubMed

    Liu, Wei; Lü, Hao-Hao; Chen, Ying-Xu; Wu, Wei-Xiang

    2008-03-01

    As a main life element, carbon plays important role in the matter cycling in soil-plant system. Stable carbon isotope 13C has been widely used in the study of carbon cycling in soil-plant system, due to its safe, no pollution, and easy to be handled. Through the analysis of both natural and labeled 13C organic matter in soil-plant system, a better understanding of the mechanisms of photosynthesis, the distribution of photosynthates in plant-soil system, the fate of plant litter, and the source of new carbon in soil could be achieved. In this paper, the applications of stable carbon isotope technique in the researches of photosynthesis, reconstruction of paleoclimate, turnover of soil organic matter, and interactions between plants and rhizosphere microorganisms were briefly summarized, and the perspectives of the application of stable carbon isotope technique were also discussed, based on the issues existed in current researches. PMID:18533543

  14. Carbon dioxide, ground air and carbon cycling in Gibraltar karst

    NASA Astrophysics Data System (ADS)

    Mattey, D. P.; Atkinson, T. C.; Barker, J. A.; Fisher, R.; Latin, J.-P.; Durrell, R.; Ainsworth, M.

    2016-07-01

    We put forward a general conceptual model of CO2 behaviour in the vadose zone of karst aquifers, based on physical principles of air flow through porous media and caves, combined with a geochemical interpretation of cave monitoring data. This 'Gibraltar model' links fluxes of water, air and carbon through the soil with the porosity of the vadose zone, the circulation of ground air and the ventilation of caves. Gibraltar hosts many natural caves whose locations span the full length and vertical range of the Rock. We report results of an 8-year monitoring study of carbon in soil organic matter and bedrock carbonate, dissolved inorganic carbon in vadose waters, and gaseous CO2 in soil, cave and ground air. Results show that the regime of cave air CO2 results from the interaction of cave ventilation with a reservoir of CO2-enriched ground air held within the smaller voids of the bedrock. The pCO2 of ground air, and of vadose waters that have been in close contact with it, are determined by multiple factors that include recharge patterns, vegetation productivity and root respiration, and conversion of organic matter to CO2 within the soil, the epikarst and the whole vadose zone. Mathematical modelling and field observations show that ground air is subject to a density-driven circulation that reverses seasonally, as the difference between surface and underground temperatures reverses in sign. The Gibraltar model suggests that cave air pCO2 is not directly related to CO2 generated in the soil or the epikarstic zone, as is often assumed. Ground air CO2 formed by the decay of organic matter (OM) washed down into the deeper unsaturated zone is an important additional source of pCO2. In Gibraltar the addition of OM-derived CO2 is the dominant control on the pCO2 of ground air and the Ca-hardness of waters within the deep vadose zone. The seasonal regime of CO2 in cave air depends on the position of a cave in relation to the density-driven ground air circulation pattern which

  15. Contribution of fish to the marine inorganic carbon cycle.

    PubMed

    Wilson, R W; Millero, F J; Taylor, J R; Walsh, P J; Christensen, V; Jennings, S; Grosell, M

    2009-01-16

    Oceanic production of calcium carbonate is conventionally attributed to marine plankton (coccolithophores and foraminifera). Here we report that marine fish produce precipitated carbonates within their intestines and excrete these at high rates. When combined with estimates of global fish biomass, this suggests that marine fish contribute 3 to 15% of total oceanic carbonate production. Fish carbonates have a higher magnesium content and solubility than traditional sources, yielding faster dissolution with depth. This may explain up to a quarter of the increase in titratable alkalinity within 1000 meters of the ocean surface, a controversial phenomenon that has puzzled oceanographers for decades. We also predict that fish carbonate production may rise in response to future environmental changes in carbon dioxide, and thus become an increasingly important component of the inorganic carbon cycle. PMID:19150840

  16. A Comparison of Supercritical Carbon Dioxide Power Cycle Configurations with an Emphasis on CSP Applications (Presentation)

    SciTech Connect

    Neises, T.; Turchi, C.

    2013-09-01

    Recent research suggests that an emerging power cycle technology using supercritical carbon dioxide (s-CO2) operated in a closed-loop Brayton cycle offers the potential of equivalent or higher cycle efficiency versus supercritical or superheated steam cycles at temperatures relevant for CSP applications. Preliminary design-point modeling suggests that s-CO2 cycle configurations can be devised that have similar overall efficiency but different temperature and/or pressure characteristics. This paper employs a more detailed heat exchanger model than previous work to compare the recompression and partial cooling cycles, two cycles with high design-point efficiencies, and illustrates the potential advantages of the latter. Integration of the cycles into CSP systems is studied, with a focus on sensible heat thermal storage and direct s-CO2 receivers. Results show the partial cooling cycle may offer a larger temperature difference across the primary heat exchanger, thereby potentially reducing heat exchanger cost and improving CSP receiver efficiency.

  17. A carbonate-silicate aqueous geochemical cycle model for Mars

    NASA Astrophysics Data System (ADS)

    Schaefer, M. W.; Leidecker, H.

    1992-12-01

    A model for the carbonate-silicate geochemical cycle of an early, wet Mars is under development. The results of this study will be used to constrain models of the geochemical history of Mars and the likely mineralogy of its present surface. Although Mars today is a cold, dry planet, it may once have been much warmer and wetter. Values of total outgassed CO2 from several to about 10 bars are consistent with present knowledge (Pollack et al. 1987), and this amount of CO2 implies an amount of water outgassed at least equal to an equivalent depth of 500-1000 meters (Carr 1986). Pollack et al. (1987), in addition, estimate that a thick CO2 atmosphere may have existed for an extended period of time, perhaps as long as a billion years. The greenhouse effect of such an atmosphere would permit the presence of liquid water on the surface, most likely in the form of a shallow sea in the lowest regions of the planet, such as the northern plains (Schaefer 1990). The treatment of geochemical cycles as complex kinetic chemical reactions has been undertaken for terrestrial systems in recent years with much success (Lasaga 1980, 1981; Berner et al. 1983; Lasaga et al. 1985). Although the Martian system is vastly less well understood, and hence less well-constrained, it is also a much simpler system, due to the lack of biogenic reactions that make the terrestrial system so complex. It should be possible, therefore, to use the same techniques to model the Martian system as have been used for terrestrial systems, and to produce useful results. A diagram of the carbonate-silicate cycle for Mars (simplified from the terrestrial system) is given.

  18. Research and application of role theory in ocean carbon cycle ontology construction

    NASA Astrophysics Data System (ADS)

    Jia, Haipeng; Xiong, Jing; Xu, Jianliang; Wang, Jipeng

    2014-12-01

    Many researchers have studied the ocean carbon cycle model trying to regulate the level of CO2 in atmosphere from viewpoint of quantification. Unlike other researches, this paper analyzes the conversion process of carbon element in the ocean from the qualitative viewpoint. There are many complex roles in the ocean carbon cycle, and it is hard to represent the case that an entity plays different role in different environment. An ontology technology Hozo role theory developed by Osaka University Mizoguchi Laboratory is proposed as a solution. The basic concepts and representation mode of Hozo role theory is introduced. The conversion process of ocean carbon cycle is abstracted and an ontology model using Hozo role theory is proposed. Instead of comprehensive common ontology construction method, we propose our own ontology development steps. Then an ontology about ocean carbon cycle is built in order to describe and share the basic knowledge of ocean carbon cycle. A knowledge base of material circulation is proposed based on the ontology. Its construction framework is described and some knowledge base query examples are also illustrated. Conclusions show that the role theory can effectively solve the problem of multirole description in ocean carbon cycle, and knowledge reasoning based on ontology is also effective.

  19. An International Research Strategy: Towards a Joint IGBP/IHDP/WCRP Global Carbon Cycle Project

    NASA Astrophysics Data System (ADS)

    Hibbard, K. A.

    2001-05-01

    The International Geosphere Biosphere Programme (IGBP), the International Human Dimensions Programme (IHDP) and the World Climate Research Programme (WCRP) have agreed upon a joint project that integrates the biological, ecological, social, and physical climate communities is crucial towards understanding the Earth's global carbon system. This joint science project will provide a platform to address the needs of the assessment, observing, and other scientific research communities. The aim is to address the necessary science needs while keeping in mind the policy relevance for carbon management strategies. The Joint Carbon Cycle has several fundamental drivers: first, the human-environment system is intimately linked with the biophsysical carbon cycle; second, it is clear that the terrestrial and ocean biosphere respond variably over space and time to fluctuations in atmospheric CO2, however, the patterns and processes that drive these responses in a coupled human-biophysical Earth's systems are largely unknown; and third, to predict and understand a linked human-biophysical carbon cycle, a multiple constraint approach must be utilized that integrates process studies, manipulative experiments, observations and models. Finally, an international Project is necessary to facilitate and coordinate cooperation between national and regional programmes and governments to fit the pieces of the global carbon puzzle in a coherent manner. A central problem in carbon cycle research is the synthesis of a wide variety of different measurements to provide the best possible information about the space-time distribution of carbon fluxes and stores in the human, oceanic and terrestrial biospheres. Three key strategies will be employed to address our uncertainties in global carbon sources and sinks: (1) To constrain global carbon fluxes and stores from multiple sources by integrating process studies, experiments, models, observations and case studies; (2) To incorporate institutions as

  20. A study of the abundance and {sup 13}C/{sup 12}C ratio of atmospheric carbon dioxide and oceanic carbon in relation to the global carbon cycle. Final technical report, February 15, 1990--July 31, 1995

    SciTech Connect

    Keeling, C.D.

    1995-12-31

    Knowledge can be gained about the fluxes and storage of carbon in natural systems and their relation to climate by detecting temporal and spatial patterns in atmospheric CO{sub 2}. When patterns in its {sup 13}C/{sup 12}C isotopic ratio are included in the analysis, there is also a basis for distinguishing organic and inorganic processes. The authors systematically measured the concentration and {sup 13}C/{sup 12}C ratio of atmospheric CO{sub 2} to produce time series data essential to reveal these temporal and spatial patterns. To pursue the significance of these patterns further, the result also involved measurements of inorganic carbon in sea water and of CO{sub 2} in air near growing land plants. The study was coordinated with a study of the same title concurrently funded by the National Science Foundation (NSF). The study called for continued atmospheric measurements at an array of ten stations from the Arctic Basin to the South Pole. Air was collected in flasks brought back to the laboratory for analysis, except at Mauna Loa. Observatory, Hawaii, where continuous measurements were also carried out.

  1. Simulations of the global carbon cycle and anthropogenic CO{sub 2} transient. Annual report

    SciTech Connect

    Sarmiento, J.L.

    1994-07-01

    This research focuses on improving the understanding of the anthropogenic carbon dioxide transient using observations and models of the past and present. In addition, an attempt is made to develop an ability to predict the future of the carbon cycle in response to continued anthropogenic perturbations and climate change. Three aspects of the anthropogenic carbon budget were investigated: (1) the globally integrated budget at the present time; (2) the time history of the carbon budget; and (3) the spatial distribution of carbon fluxes. One of the major activities of this study was the participation in the model comparison study of Enting, et al. [1994] carried out in preparation for the IPCC 1994 report.

  2. Soil organic carbon enrichment of dust emissions: Magnitude, mechanisms and its implications for the carbon cycle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil erosion is an important component of the global carbon cycle. However, little attention has been given to the role of aeolian processes in influencing soil organic carbon (SOC) flux and the release of greenhouse gasses, such as carbon-dioxide (CO2), to the atmosphere. Understanding the magnitu...

  3. Carbon and oxygen cycles: Sensitivity to changes in environmental forcing in a coastal upwelling system

    NASA Astrophysics Data System (ADS)

    Bianucci, L.; Denman, K. L.

    2012-03-01

    Biogeochemical cycles in the coastal ocean are changing and will continue to change in response to a changing climate. Effects on the oxygen and carbon cycles are particularly important, as either episodic or permanent shifts toward lower oxygen and/or higher inorganic carbon conditions can impact coastal ecosystems negatively. Here we study the sensitivity of these cycles to changes that may occur in the coastal ocean, focusing on a summer wind-driven upwelling region off southern Vancouver Island shelf. We use a quasi 2-D configuration of the Regional Ocean Modeling System (ROMS) to perform six sensitivity experiments. Results indicate that carbon and oxygen cycles in this region may be significantly affected by an altered upwelling season, a shallower offshore Oxygen Minimum Zone, and a carbon-enriched environment. Combinations of these scenarios suggest a potentially increasing risk for the development of coastal hypoxia and corrosive conditions in the region.

  4. Development and evaluation of the carbon-nitrogen cycle module for the GPFARM-Range model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rangelands cover approximately 50% of the terrestrial surface of the earth. The soil carbon and nitrogen storage and turnover in rangeland systems are becoming increasingly important for sustainable grazing management and adaptations to climate change. In this study, a carbon-nitrogen (C-N) cycle m...

  5. Biochar and biological carbon cycling in temperate soils

    NASA Astrophysics Data System (ADS)

    McCormack, S. A.; Vanbergen, A. J.; Bardgett, R. D.; Hopkins, D. W.; Ostle, N.

    2012-04-01

    Production of biochar, the recalcitrant residue formed by pyrolysis of plant matter, is suggested as a means of increasing storage of stable carbon (C) in the soil (1). Biochar has also been shown to act as a soil conditioner, increasing the productivity of certain crops by reducing nutrient leaching and improving soil water-holding capacity. However, the response of soil carbon pools to biochar addition is not yet well understood. Studies have shown that biochar has highly variable effects on microbial C cycling and thus on soil C storage (2,3,4). This discrepancy may be partially explained by the response of soil invertebrates, which occupy higher trophic levels and regulate microbial activity. This research aims to understand the role of soil invertebrates (i.e. Collembola and nematode worms) in biochar-mediated changes to soil C dynamics across a range of plant-soil communities. An open-air, pot-based mesocosm experiment was established in May, 2011 at the Centre for Ecology and Hydrology, Edinburgh. Three treatments were included in a fully-factorial design: biochar (presence [2 % w/w] or absence), soil type (arable sandy, arable sandy loam, grassland sandy loam), and vegetation type (Hordeum vulgare, Lolium perenne, unvegetated). Monitored parameters include: invertebrate and microbial species composition, soil C fluxes (CO2 and trace gas evolution, leachate C content, primary productivity and soil C content), and soil conditions (pH, moisture content and water-holding capacity). Preliminary results indicate that biochar-induced changes to soil invertebrate communities and processes are affected by pre-existing soil characteristics, and that soil texture in particular may be an important determinant of soil response to biochar addition. 1. Lehmann, 2007. A handful of carbon. Nature 447, 143-144. 2. Liang et al., 2010. Black carbon affects the cycling of non-black carbon in soil. Organic Geochemistry 41, 206-213. 3. Van Zwieten et al., 2010. Influence of

  6. Important role for organic carbon in subduction-zone fluids in the deep carbon cycle

    NASA Astrophysics Data System (ADS)

    Sverjensky, Dimitri A.; Stagno, Vincenzo; Huang, Fang

    2014-12-01

    Supercritical aqueous fluids link subducting plates and the return of carbon to Earth's surface in the deep carbon cycle. The amount of carbon in the fluids and the identities of the dissolved carbon species are not known, which leaves the deep carbon budget poorly constrained. Traditional models, which assume that carbon exists in deep fluids as dissolved gas molecules, cannot predict the solubility and ionic speciation of carbon in its silicate rock environment. Recent advances enable these limitations to be overcome when evaluating the deep carbon cycle. Here we use the Deep Earth Water theoretical model to calculate carbon speciation and solubility in fluids under upper mantle conditions. We find that fluids in equilibrium with mantle peridotite minerals generally contain carbon in a dissolved gas molecule form. However, fluids in equilibrium with diamonds and eclogitic minerals in the subducting slab contain abundant dissolved organic and inorganic ionic carbon species. The high concentrations of dissolved carbon species provide a mechanism to transport large amounts of carbon out of the subduction zone, where the ionic carbon species may influence the oxidation state of the mantle wedge. Our results also identify novel mechanisms that can lead to diamond formation and the variability of carbon isotopic composition via precipitation of the dissolved organic carbon species in the subduction-zone fluids.

  7. Observing terrestrial ecosystems and the carbon cycle from space

    SciTech Connect

    Schimel, David; Pavlick, Ryan; Fisher, Joshua B.; Asner, Gregory P.; Saatchi, Sassan; Townsend, Philip; Miller, Charles E.; Frankenberg, Christian; Hibbard, Kathleen A.; Cox, Peter

    2015-02-06

    Modeled terrestrial ecosystem and carbon cycle feedbacks contribute substantial uncertainty to projections of future climate. The limitations of current observing networks contribute to this uncertainty. Here we present a current climatology of global model predictions and observations for photosynthesis, biomass, plant diversity and plant functional diversity. Carbon cycle tipping points occur in terrestrial regions where fluxes or stocks are largest, and where biological variability is highest, the tropics and Arctic/Boreal zones. Global observations are predominately in the mid-latitudes and are sparse in high and low latitude ecosystems. Observing and forecasting ecosystem change requires sustained observations of sufficient density in time and space in critical regions. Using data and theory available now, we can develop a strategy to detect and forecast terrestrial carbon cycle-climate interactions, by combining in situ and remote techniques.

  8. The deep carbon cycle and melting in Earth's interior

    NASA Astrophysics Data System (ADS)

    Dasgupta, Rajdeep; Hirschmann, Marc M.

    2010-09-01

    Carbon geochemistry of mantle-derived samples suggests that the fluxes and reservoir sizes associated with deep cycle are in the order of 10 12-13 g C/yr and 10 22-23 g C, respectively. This deep cycle is responsible for the billion year-scale evolution of the terrestrial carbon reservoirs. The petrology of deep storage modulates the long-term evolution and distribution of terrestrial carbon. Unlike water, which in most of the Earth's mantle is held in nominally anhydrous silicates, carbon is stored in accessory phases. The accessory phase of interest, with increasing depth, typically changes from fluids/melts → calcite/dolomite → magnesite → diamond/Fe-rich alloy/Fe-metal carbide, assuming that the mass balance and oxidation state are buffered solely by silicates. If, however, carbon is sufficiently abundant, it may reside as carbonate even in the deep mantle. If Earth's deep mantle is Fe-metal saturated, carbon storage in metal alloy and as metal carbide cannot be avoided for depleted and enriched domains, respectively. Carbon ingassing to the interior is aided by modern subduction of the carbonated oceanic lithosphere, whereas outgassing from the mantle is controlled by decompression melting of carbonated mantle. Carbonated melting at > 300 km depth or redox melting of diamond-bearing or metal-bearing mantle at somewhat shallower depth generates carbonatitic and carbonated silicate melts and are the chief agents for liberating carbon from the solid Earth to the exosphere. Petrology allows net ingassing of carbon into the mantle in the modern Earth, but in the hotter subduction zones that prevailed during the Hadean, Archean, and Paleoproterozoic, carbonate likely was released at shallow depths and may have returned to the exosphere. Inefficient ingassing, along with efficient outgassing, may have kept the ancient mantle carbon-poor. The influence of carbon on deep Earth dynamics is through inducing melting and mobilization of structurally bound mineral

  9. Investigation on Carbon-Deposition Behavior from Heating Cycle Gas in Oxygen Blast Furnace Process

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhou; Wang, Jingsong; She, Xuefeng; Zhang, Shiyang; Xue, Qingguo

    2015-02-01

    Among the different ways to study carbon deposition in the ironmaking process, not much attention was paid to that of heating the gas mixture, especially cycle gas in an oxygen blast furnace. In this work, the carbon-deposition characteristics of heating 100 pct CO, CO-H2 gas mixture, and cycle gas in the oxygen blast furnace process were, respectively, experimentally and theoretically investigated. First, the thermodynamics on carbon-deposition reactions were calculated. Then, the impacts of discharging operation temperature, the proportion of CO/H2 in heating the CO-H2 gas mixture, and the CO2 concentration in heating the cycle gas of an oxygen blast furnace on the carbon deposition were tested and investigated. Furthermore, the carbon-deposition behaviors in heating the CO-H2 gas mixture were compared with the thermodynamic calculation results for discussing the role of H2. In addition, carbon deposition in heating cycle gas includes CO decomposition and a carbon-deposition reaction by hybrid of CO and H2; the possible roles of each were analyzed by comparing thermodynamic calculation and experimental results. The deposited carbon was characterized by scanning electron microscope (SEM) to analyze the deposited carbon microstructure.

  10. Application of δ13c Values Recorded in Neoproterozoic Marine Dolomite As a Marker for Global Correlations: Significance of Major δ13c Variations for the Carbon Cycle Based on Studies of Modern Dolomite Precipitating Environments

    NASA Astrophysics Data System (ADS)

    McKenzie, J. A.; Bontognali, T. R. R.; Bahniuk, A.; Vasconcelos, C.

    2014-12-01

    Since the early Paleozoic, the average bulk δ13C value of marine carbonates has remained relatively positive varying between 0 and +4‰ with distinctive positive excursions that are associated with global changes in the carbon cycle. Unlike the Phanerozoic δ13C data for marine limestones, a major δ13C excursion has been recorded in a globally deposited Neoproterozoic marine dolomite formation, known as the cap dolostone. This excursion with δ13C values ranging systematically between -3 and -5‰ represents a global chronstratigraphic marker used to correlate the end of the major Marinoan glaciation at 636 Ma1. Does this excursion signify a primary seawater value and how might it be interpreted as a primary carbon cycle signal, considering the widespread distribution of the cap dolostone? Studies of modern dolomite precipitating environments, such as supratidal sabkhas of Abu Dhabi, U.A.E. and Qatar and coastal hypersaline lagoons of Rio de Janiero State, Brazil, indicate that microbial activity or the biological products, thereof, influence or mediate mineral formation. The precipitating solutions are sourced from normal seawater, which has experienced variable stages of concentration through evaporative processes. Comparison of δ13C values of sabkha dolomite with that formed in the hypersaline lagoons reveals that the former are always rather positive (approx. +2 to +7 ‰), whereas the latter are always negative (approx. -5‰ to -11‰). During very early diagenesis, the original δ13C value of the initial precipitate is not necessarily retained, indicating that synsedimentary processes can alter the carbon signal prior to burial and later diagenesis. However, the potential for very early lithification of microbial dolomite promotes the preservation of original δ13C values, which, thus, can be useful for evaluation of the ancient carbon cycle. 1Halverson, G.P. et al., 2005. Toward a Neoproterozoic composite carbon-isotope record, GSA Bulletin, v. 117, p

  11. The carbon cycle and associated redox processes through time

    PubMed Central

    Hayes, John M; Waldbauer, Jacob R

    2006-01-01

    Earth's biogeochemical cycle of carbon delivers both limestones and organic materials to the crust. In numerous, biologically catalysed redox reactions, hydrogen, sulphur, iron, and oxygen serve prominently as electron donors and acceptors. The progress of these reactions can be reconstructed from records of variations in the abundance of 13C in sedimentary carbonate minerals and organic materials. Because the crust is always receiving new CO2 from the mantle and a portion of it is being reduced by photoautotrophs, the carbon cycle has continuously released oxidizing power. Most of it is represented by Fe3+ that has accumulated in the crust or been returned to the mantle via subduction. Less than 3% of the estimated, integrated production of oxidizing power since 3.8 Gyr ago is represented by O2 in the atmosphere and dissolved in seawater. The balance is represented by sulphate. The accumulation of oxidizing power can be estimated from budgets summarizing inputs of mantle carbon and rates of organic-carbon burial, but levels of O2 are only weakly and indirectly coupled to those phenomena and thus to carbon-isotopic records. Elevated abundances of 13C in carbonate minerals ca 2.3 Gyr old, in particular, are here interpreted as indicating the importance of methanogenic bacteria in sediments rather than increased burial of organic carbon. PMID:16754608

  12. CO/sub 2/ and the carbon cycle: atmospheric aspects

    SciTech Connect

    Machta, L.

    1981-09-01

    The contents of and fluxes between several reservoirs for carbon exchange are used in a simplified carbon cycle model. Variability in CO/sub 2/ measurements in the atmosphere are discussed in terms of changes observed at the Mauna Loa station. The results indicate that these changes are probably average for the global atmosphere. Analytical reproducibility has caused some problems which may be due to sampling or shipping-induced errors, rather than by errors in measurement. 7 figures.

  13. Redesigning Urban Carbon Cycles: from Waste Stream to Commodity

    NASA Astrophysics Data System (ADS)

    Brabander, D. J.; Fitzstevens, M. G.

    2013-12-01

    While there has been extensive research on the global scale to quantify the fluxes and reservoirs of carbon for predictive climate change models, comparably little attention has been focused on carbon cycles in the built environment. The current management of urban carbon cycles presents a major irony: while cities produce tremendous fluxes of organic carbon waste, their populations are dependent on imported carbon because most urban have limited access to locally sourced carbon. The persistence of outdated management schemes is in part due to the fact that reimagining the handling of urban carbon waste streams requires a transdisciplinary approach. Since the end of the 19th century, U.S. cities have generally relied on the same three options for managing organic carbon waste streams: burn it, bury it, or dilute it. These options still underpin the framework for today's design and management strategies for handling urban carbon waste. We contend that urban carbon management systems for the 21st century need to be scalable, must acknowledge how climate modulates the biogeochemical cycling of urban carbon, and should carefully factor local political and cultural values. Urban waste carbon is a complex matrix ranging from wastewater biosolids to municipal compost. Our first goal in designing targeted and efficient urban carbon management schemes has been examining approaches for categorizing and geochemically fingerprinting these matrices. To date we have used a combination of major and trace element ratio analysis and bulk matrix characteristics, such as pH, density, and loss on ignition, to feed multivariable statistical analysis in order to identify variables that are effective tracers for each waste stream. This approach was initially developed for Boston, MA, US, in the context of identifying components of municipal compost streams that were responsible for increasing the lead inventory in the final product to concentrations that no longer permitted its use in

  14. On the effect of non-carbon nanostructured supports on the stability of Pt nanoparticles during voltage cycling: A study of TiO2 nanofibres

    NASA Astrophysics Data System (ADS)

    Savych, I.; Bernard d'Arbigny, J.; Subianto, S.; Cavaliere, S.; Jones, D. J.; Rozière, J.

    2014-07-01

    Electrospun carbon and Nb-doped TiO2 nanofibres (CNFs, TNFs) have been investigated as electrocatalyst supports for polymer electrolyte membrane fuel cells (PEMFC). The optimal Nb doping amount has been identified for TNFs, and thermal treatment of titanium oxide fibres optimised to balance the surface area and electronic conductivity requirements. The most highly conducting material is characterised by a high concentration of surface Ti3+ and Nb4+ (and oxygen vacancies). Pt nanoparticles of average diameter of 2.3 nm were loaded onto 10%at Nb doped-TiO2, retained as the best candidate for further electrochemical analysis, and on CNFs, using a microwave-assisted polyol method. Significantly higher electrochemically active surface area was retained after voltage cycling to 1.2 V for Pt supported on TNF (73%) than on CNFs, where only 8% of the original ECSA was conserved after 1000 voltammetric cycles. The mass activity was also slightly higher for the titanium oxide based electrodes in the oxygen reduction reaction.

  15. Gasification combined cycle: Carbon dioxide recovery, transport, and disposal

    SciTech Connect

    Doctor, R.D.; Molburg, J.C.; Thimmapuram, P.; Berry, G.F.; Livengood, C.D. ); Johnson, R.A. )

    1993-01-01

    Initiatives to limit carbon dioxide (CO[sub 2]) emissions have drawn considerable interest to integrated gasification combined-cycle (IGCC) power generation. This process can reduce C0[sub 2] production because of its higher efficiency, and it is amenable to C0[sub 2] capture, because C0[sub 2] can be removed before combustion and the associated dilution with atmospheric nitrogen. This paper presents a process-design baseline that encompasses the IGCC system, C0[sub 2] transport by pipeline, and land-based sequestering of C0[sub 2] in geological reservoirs.The intent of this study is to provide the C0[sub 2] budget, or an equivalent C0[sub 2]'' budget, associated with each of the individual energy-cycle steps. Design capital and operating costs for the process are included in the full study but are not reported in the present paper. The value used for the equivalent C0[sub 2]'' budget will be 1 kg C0[sub 2]/kWh[sub e].

  16. Improving the assessment of the State of the Carbon Cycle in North America by integrating inventory- and process- based approaches: A case study for Canada

    NASA Astrophysics Data System (ADS)

    Hayes, D. J.; Smyth, C.; Chen, G.; Kurz, W.; Stinson, G.; McGuire, A. D.

    2015-12-01

    Regional and continental carbon stock and flux estimates differ among assessments depending on the scaling approach used and the budget components considered. This is particularly manifest across the vast circum-boreal region, which has experienced substantial modification of the major driving forces of the carbon cycle in recent decades, including pronounced climate warming and associated increases in the frequency and severity of disturbances. In Canada, inventory-based estimates suggest a small carbon sink for its managed forest, but do not include unmanaged lands nor capture major driving forces such as climate change and atmospheric chemistry. On the other hand, estimates from process-based models vary widely and often do not consider critical disturbance and management impacts. Here, we demonstrate results from an updated approach that integrates inventory-based information on management and disturbances with process-level representation of ecological dynamics using a terrestrial biogeochemistry model. The integrated approach facilitates more comprehensive diagnosis of Canada's land-based carbon budget within a framework that also allows for attribution of the major driving forces and prediction under future scenarios. Using this framework, we diagnose an approximately 30 Tg C yr-1 sink in Canada over the first decade of the 21st Century, which represents a significant reduction in the strength of the CO2 sink estimated for previous decades. This decline in sink strength is attributed primarily to CO2 emissions from the substantial area disturbed by wildfire and insect outbreaks in recent years. Such changes are predicted to create positive feedbacks to the climate system that accelerate global warming. Compared to other assessments, our results suggest that CO2 uptake by the region's ecosystems may not be as strong as estimated by atmospheric inverse approaches, which are highly uncertain over the high latitudes, or by process-based models that do not

  17. Chemical sensing and imaging in microfluidic pore network structures relevant to natural carbon cycling and industrial carbon sequestration

    SciTech Connect

    Grate, Jay W.; Zhang, Changyong; Wilkins, Michael J.; Warner, Marvin G.; Anheier, Norman C.; Suter, Jonathan D.; Kelly, Ryan T.; Oostrom, Martinus

    2013-06-11

    Energy and climate change represent significant factors in global security. Atmospheric carbon dioxide levels, while global in scope, are influenced by pore-scale phenomena in the subsurface. We are developing tools to visualize and investigate processes in pore network microfluidic structures with transparent covers as representations of normally-opaque porous media. In situ fluorescent oxygen sensing methods and fluorescent cellulosic materials are being used to investigate processes related to terrestrial carbon cycling involving cellulytic respiring microorganisms. These structures also enable visualization of water displacement from pore spaces by hydrophobic fluids, including carbon dioxide, in studies related to carbon sequestration.

  18. Anthropogenic chemical carbon cycle for a sustainable future.

    PubMed

    Olah, George A; Prakash, G K Surya; Goeppert, Alain

    2011-08-24

    Nature's photosynthesis uses the sun's energy with chlorophyll in plants as a catalyst to recycle carbon dioxide and water into new plant life. Only given sufficient geological time, millions of years, can new fossil fuels be formed naturally. The burning of our diminishing fossil fuel reserves is accompanied by large anthropogenic CO(2) release, which is outpacing nature's CO(2) recycling capability, causing significant environmental harm. To supplement the natural carbon cycle, we have proposed and developed a feasible anthropogenic chemical recycling of carbon dioxide. Carbon dioxide is captured by absorption technologies from any natural or industrial source, from human activities, or even from the air itself. It can then be converted by feasible chemical transformations into fuels such as methanol, dimethyl ether, and varied products including synthetic hydrocarbons and even proteins for animal feed, thus supplementing our food chain. This concept of broad scope and framework is the basis of what we call the Methanol Economy. The needed renewable starting materials, water and CO(2), are available anywhere on Earth. The required energy for the synthetic carbon cycle can come from any alternative energy source such as solar, wind, geothermal, and even hopefully safe nuclear energy. The anthropogenic carbon dioxide cycle offers a way of assuring a sustainable future for humankind when fossil fuels become scarce. While biosources can play a limited role in supplementing future energy needs, they increasingly interfere with the essentials of the food chain. We have previously reviewed aspects of the chemical recycling of carbon dioxide to methanol and dimethyl ether. In the present Perspective, we extend the discussion of the innovative and feasible anthropogenic carbon cycle, which can be the basis of progressively liberating humankind from its dependence on diminishing fossil fuel reserves while also controlling harmful CO(2) emissions to the atmosphere. We also

  19. Estimates of carbon cycle surface fluxes from the NASA Carbon Monitoring System Flux Pilot Project

    NASA Astrophysics Data System (ADS)

    Bowman, K. W.; Liu, J.; Lee, M.; Gurney, K. R.; Menemenlis, D.; Brix, H.; Hill, C. N.; Denning, S.; Haynes, K.; Baker, I. T.; Henze, D. K.; Bousserez, N.; Marland, G.; Marland, E.; Badurek, C. A.

    2013-12-01

    The goal of NASA Carbon Monitoring Study (CMS) Flux Pilot Project is to incorporate the full suite of NASA observational, modeling, and assimilation capabilities in order to attribute changes in globally distributed CO2 concentrations to spatially resolved surface fluxes across the entire carbon cycle. To that end, CMS has initiated a coordinated effort between land surface, ocean, fossil fuel, and atmospheric scientists to provide global estimates of CO2 constrained by satellite observations and informed by contemporaneous estimates of 'bottom up' fluxes from land surface, ocean, and fossil fuel models. The CMS Flux has evolved to incorporate a spatially explicit fossil fuel data assimilation system (FFDAS), an updated ECCO2 Darwin biogeochemical adjoint ocean state estimation system, and the new Simple Biospheric Model (Sib4) terrestrial ecosystem model. We compare GOSAT xCO2 observations, processed by the JPL ACOS v33, to predicted CMS Flux atmospheric CO2 concentrations for 2010-2011, and attribute the differences to spatially-resolved fluxes. We examine these fluxes in terms of interannual variability, correlative satellite measurements, and uncertainty across the carbon cycle

  20. Landscape controls on carbon and nitrogen cycling in boreal forests

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Climate change in the boreal forest biome is having a large impact on two of the main controllers of carbon (C) and nitrogen (N) cycling within this region: permafrost and fire. Permafrost, and its effects on soil drainage, controls the inputs and losses of C and N via net primary productivity (NP...

  1. Microbial control over carbon cycling in soil

    PubMed Central

    Schimel, Joshua P.; Schaeffer, Sean M.

    2012-01-01

    A major thrust of terrestrial microbial ecology is focused on understanding when and how the composition of the microbial community affects the functioning of biogeochemical processes at the ecosystem scale (meters-to-kilometers and days-to-years). While research has demonstrated these linkages for physiologically and phylogenetically “narrow” processes such as trace gas emissions and nitrification, there is less conclusive evidence that microbial community composition influences the “broad” processes of decomposition and organic matter (OM) turnover in soil. In this paper, we consider how soil microbial community structure influences C cycling. We consider the phylogenetic level at which microbes form meaningful guilds, based on overall life history strategies, and suggest that these are associated with deep evolutionary divergences, while much of the species-level diversity probably reflects functional redundancy. We then consider under what conditions it is possible for differences among microbes to affect process dynamics, and argue that while microbial community structure may be important in the rate of OM breakdown in the rhizosphere and in detritus, it is likely not important in the mineral soil. In mineral soil, physical access to occluded or sorbed substrates is the rate-limiting process. Microbial community influences on OM turnover in mineral soils are based on how organisms allocate the C they take up – not only do the fates of the molecules differ, but they can affect the soil system differently as well. For example, extracellular enzymes and extracellular polysaccharides can be key controls on soil structure and function. How microbes allocate C may also be particularly important for understanding the long-term fate of C in soil – is it sequestered or not? PMID:23055998

  2. Life Cycle Assessment of Carbon Fiber-Reinforced Polymer Composites

    SciTech Connect

    Das, Sujit

    2011-01-01

    Carbon fiber-reinforced polymer matrix composites is gaining momentum with the pressure to lightweight vehicles, however energy-intensity and cost remain some of the major barriers before this material could be used in large-scale automotive applications. A representative automotive part, i.e., a 30.8 kg steel floor pan having a 17% weight reduction potential with stringent cash performance requirements has been considered for the life cycle energy and emissions analysis based on the latest developments occurring in the precursor type (conventional textile-based PAN vs. renewable-based lignin), part manufacturing (conventional SMC vs. P4) and fiber recycling technologies. Carbon fiber production is estimated to be about 14 times more energy-intensive than conventional steel production, however life cycle primary energy use is estimated to be quite similar to the conventional part, i.e., 18,500 MJ/part, especially when considering the uncertainty in LCI data that exists from using numerous sources in the literature. Lignin P4 technology offers the most life cycle energy and CO2 emissions benefits compared to a conventional stamped steel technology. With a 20% reduction in energy use in the lignin conversion to carbon fiber and free availability of lignin as a by-product of ethanol and wood production, a 30% reduction in life cycle energy use could be obtained. A similar level of life cycle energy savings could also be obtained with a higher part weight reduction potential of 43%.

  3. Urbanization and the Carbon Cycle: Synthesis of Ongoing Research

    NASA Astrophysics Data System (ADS)

    Gurney, K. R.; Duren, R. M.; Hutyra, L.; Ehleringer, J. R.; Patarasuk, R.; Song, Y.; Huang, J.; Davis, K.; Kort, E. A.; Shepson, P. B.; Turnbull, J. C.; Lauvaux, T.; Rao, P.; Eldering, A.; Miller, C. E.; Wofsy, S.; McKain, K.; Mendoza, D. L.; Lin, J. C.; Sweeney, C.; Miles, N. L.; Richardson, S.; Cambaliza, M. O. L.

    2015-12-01

    Given the explosive growth in urbanization and its dominant role in current and future global greenhouse gas emissions, urban areas have received increasing research attention from the carbon cycle science community. The emerging focus is driven by the increasingly dense atmospheric observing capabilities - ground and space-based - in addition to the rising profile of cities within international climate change policymaking. Dominated by anthropogenic emissions, urban carbon cycle research requires a cross-disciplinary perspective with contributions from disciplines such as engineering, economics, social theory, and atmospheric science. We review the recent results from a sample of the active urban carbon research efforts including the INFLUX experiment (Indianapolis), the Megacity carbon project (Los Angeles), Salt Lake City, and Boston. Each of these efforts represent unique approaches in pursuit of different scientific and policy questions and assist in setting priorities for future research. From top-down atmospheric measurement systems to bottom-up estimation, these research efforts offer a view of the challenges and opportunities in urban carbon cycle research.

  4. A LEO Hyperspectral Mission Implementation for Global Carbon Cycle Observations

    NASA Technical Reports Server (NTRS)

    Gervin, Janette C.; Esper, Jaime; McClain, Charles R.; Hall, Forrest G.; Middleton, Elizabeth M.; Gregg, Watson W.; Mannino, Antonio; Knox, Robert G.; Huemmrich, K. Fred

    2004-01-01

    For both terrestrial and ocean carbon cycle science objectives, high resolution (less than l0 nm) imaging spectrometers capable of acquiring multiple regional to global scale observations per day should enable the development of new remote sensing measurements for important but as yet unobservable variables, with the overall goal of linking both terrestrial and ocean carbon cycle processes to climate variability. For terrestrial research, accurate estimates of carbon, water and energy (CWE) exchange between the terrestrial biosphere and atmosphere a needed to id- the geographical locations and temporal dynamics of carbon sources/sinks and to improve regional climate models and climate change assessments. It is an enormous challenge to estimate CWE exchange from the infrequent temporal coverage and sparse spectral information provided by most single polar-orbiting, earth-looking satellite. The available satellite observations lack a sufficient number of well-placed narrow bands from which to derive spectral indices that capture vegetation responses to stress conditions associated with down-regulation of photosynthesis. Physiological status can best be assessed with spectral indices based on continuous, narrow bands in the visible/near infrared spectra, as can seasonal and annual terrestrial productivity. For coastal and ocean constituents, narrow-band observations in the ultraviolet and visible are essential to investigate the variability, dynamics and biogeochemical cycles of the world's coastal and open ocean regions, which will in turn help in measuring ocean productivity and predicting the variability of ocean carbon uptake and its role in climate change.

  5. Evolving Human Alteration of the Carbon Cycle: the Watershed Continuum

    NASA Astrophysics Data System (ADS)

    Kaushal, S.; Delaney Newcomb, K.; Newcomer Johnson, T.; Pennino, M. J.; Smith, R. M.; Beaulieu, J. J.; Belt, K.; Grese, M.; Blomquist, J.; Duan, S.; Findlay, S.; Likens, G.; Mayer, P. M.; Murthy, S.; Utz, R.; Yepsen, M.

    2014-12-01

    Watersheds experiencing land development are constantly evolving, and their biogeochemical signatures are expected to evolve across both space and time in drainage waters. We investigate how land development influences spatial and temporal evolution of the carbon cycle from small streams to major rivers in the Eastern U.S. Along the watershed continuum, we show that there is spatial evolution in: (1) the amount, chemical form, and bioavailability of carbon; (2) carbon retention/release at the reach scale; and (3) ecosystem metabolism of carbon from headwaters to coastal waters. Over shorter time scales, the interaction between land use and climate variability alters magnitude and frequency of carbon "pulses" in watersheds. Amounts and forms of carbon pulses in agricultural and urban watersheds respond similarly to climate variability due to headwater alteration and loss of ecosystem services to buffer runoff and temperature changes. Over longer time scales, land use change has altered organic carbon concentrations in tidal waters of Chesapeake Bay, and there have been increased bicarbonate alkalinity concentrations in rivers throughout the Eastern U.S. due to human activities. In summary, our analyses indicates that the form and reactivity of carbon have evolved over space and time along the watershed continuum with major implications for downstream ecosystem metabolism, biological oxygen demand, carbon dioxide production, and river alkalinization.

  6. Autonomous observing strategies for the ocean carbon cycle

    SciTech Connect

    Bishop, James K.; Davis, Russ E.

    2000-07-26

    Understanding the exchanges of carbon between the atmosphere and ocean and the fate of carbon delivered to the deep sea is fundamental to the evaluation of ocean carbon sequestration options. An additional key requirement is that sequestration must be verifiable and that environmental effects be monitored and minimized. These needs can be addressed by carbon system observations made from low-cost autonomous ocean-profiling floats and gliders. We have developed a prototype ocean carbon system profiler based on the Sounding Oceanographic Lagrangian Observer (SOLO; Davis et al., 1999). The SOLO/ carbon profiler will measure the two biomass components of the carbon system and their relationship to physical variables, such as upper ocean stratification and mixing. The autonomous observations within the upper 1500 m will be made on daily time scales for periods of months to seasons and will be carried out in biologically dynamic locations in the world's oceans that are difficult to access with ships (due to weather) or observe using remote sensing satellites (due to cloud cover). Such an observational capability not only will serve an important role in carbon sequestration research but will provide key observations of the global ocean's natural carbon cycle.

  7. Science and Observation Recommendations for Future NASA Carbon Cycle Research

    NASA Technical Reports Server (NTRS)

    McClain, Charles R.; Collatz, G. J.; Kawa, S. R.; Gregg, W. W.; Gervin, J. C.; Abshire, J. B.; Andrews, A. E.; Behrenfeld, M. J.; Demaio, L. D.; Knox, R. G.

    2002-01-01

    Between October 2000 and June 2001, an Agency-wide planning, effort was organized by elements of NASA Goddard Space Flight Center (GSFC) to define future research and technology development activities. This planning effort was conducted at the request of the Associate Administrator of the Office of Earth Science (Code Y), Dr. Ghassem Asrar, at NASA Headquarters (HQ). The primary points of contact were Dr. Mary Cleave, Deputy Associate Administrator for Advanced Planning at NASA HQ (Headquarters) and Dr. Charles McClain of the Office of Global Carbon Studies (Code 970.2) at GSFC. During this period, GSFC hosted three workshops to define the science requirements and objectives, the observational and modeling requirements to meet the science objectives, the technology development requirements, and a cost plan for both the science program and new flight projects that will be needed for new observations beyond the present or currently planned. The plan definition process was very intensive as HQ required the final presentation package by mid-June 2001. This deadline was met and the recommendations were ultimately refined and folded into a broader program plan, which also included climate modeling, aerosol observations, and science computing technology development, for contributing to the President's Climate Change Research Initiative. This technical memorandum outlines the process and recommendations made for cross-cutting carbon cycle research as presented in June. A separate NASA document outlines the budget profiles or cost analyses conducted as part of the planning effort.

  8. How Sensitive Is the Carbon Budget Approach to Potential Carbon Cycle Changes?

    NASA Astrophysics Data System (ADS)

    Matthews, D.

    2014-12-01

    The recent development of global Earth-system models, which include dynamic representations of both physical climate and carbon cycle processes, has led to new insights about how the climate responds to human carbon dioxide emissions. Notably, several model analyses have now shown that global temperature responds linearly to cumulative CO2 emissions across a wide range of emissions scenarios. This implies that the timing of CO2 emissions does not affect the overall climate response, and allows a finite global carbon carbon budget to be defined for a given global temperature target. This linear climate response, however, emerges from the interaction of several non-linear processes and feedbacks involving how carbon sinks respond to changes in atmospheric CO2 and climate. In this presentation, I will give an overview of how carbon sinks and carbon cycle feedbacks contribute to the overall linearity of the climate response to cumulative emissions, and will assess how robust this relationship is to a range of possible changes in the carbon cycle, including (a) potential positive carbon cycle feedbacks that are not well represented in the current generation of Earth-system models and (b) negative emission scenarios resulting from possible technological strategies to remove CO2 from the atmosphere.

  9. Evaluating the travel, physical activity and carbon impacts of a ‘natural experiment’ in the provision of new walking and cycling infrastructure: methods for the core module of the iConnect study

    PubMed Central

    Bull, Fiona; Cooper, Ashley; Rutter, Harry; Adams, Emma; Brand, Christian; Ghali, Karen; Jones, Tim; Mutrie, Nanette; Powell, Jane; Preston, John; Sahlqvist, Shannon; Song, Yena

    2012-01-01

    Introduction Improving infrastructure to support walking and cycling is often regarded as fundamental to encouraging their widespread uptake. However, there is little evidence that specific provision of this kind has led to a significant increase in walking or cycling in practice, let alone wider impacts such as changes in overall physical activity or carbon emissions. Connect2 is a major new project that aims to promote walking and cycling in the UK by improving local pedestrian and cycle routes. It therefore provides a useful opportunity to contribute new evidence in this field by means of a natural experimental study. Methods and analysis iConnect is an independent study that aims to integrate the perspectives of public health and transport research on the measurement and evaluation of the travel, physical activity and carbon impacts of the Connect2 programme. In this paper, the authors report the study design and methods for the iConnect core module. This comprised a cohort study of residents living within 5 km of three case study Connect2 projects in Cardiff, Kenilworth and Southampton, supported by a programme of qualitative interviews with key informants about the projects. Participants were asked to complete postal questionnaires, repeated before and after the opening of the new infrastructure, which collected data on demographic and socioeconomic characteristics, travel, car fuel purchasing and physical activity, and potential psychosocial and environmental correlates and mediators of those behaviours. In the absence of suitable no-intervention control groups, the study design drew on heterogeneity in exposure both within and between case study samples to provide for a counterfactual. Ethics and dissemination The study was approved by the University of Southampton Research Ethics Committee. The findings will be disseminated through academic presentations, peer-reviewed publications and the study website (http://www.iconnect.ac.uk) and by means of a

  10. Anthropogenic perturbation of the global carbon cycle as a result of agricultural carbon erosion and burial

    NASA Astrophysics Data System (ADS)

    Wang, Zhengang; Govers, Gerard; Kaplan, Jed; Hoffmann, Thomas; Doetterl, Sebastian; Six, Johan; Van Oost, Kristof

    2016-04-01

    Changes in terrestrial carbon storage exert a strong control over atmospheric CO2 concentrations but the underlying mechanisms are not fully constrained. Anthropogenic land cover change is considered to represent an important carbon loss mechanism, but current assessments do not consider the associated acceleration of carbon erosion and burial in sediments. We evaluated the role of anthropogenic soil erosion and the resulting carbon fluxes between land and atmosphere from the onset of agriculture to the present day. We show, here, that agricultural erosion induced a significant cumulative net uptake of 198±57 Pg carbon on terrestrial ecosystems. This erosion-induced soil carbon sink is estimated to have offset 74±21% of carbon emissions. Since 1850, erosion fluxes have increased 3-fold. As a result, the erosion and lateral transfer of organic carbon in relation to human activities is an important driver of the global carbon cycle at millennial timescales.

  11. Low/Medium Density Biomass, Coastal and Ocean Carbon: A Carbon Cycle Mission

    NASA Technical Reports Server (NTRS)

    Esper, Jaime; Gervin, Jan; Kirchman, Frank; Middleton, Elizabeth; Knox, Robert; Gregg, Watson; Mannino, Antonio; McClain, Charles; Herman, Jay; Hall, Forrest

    2003-01-01

    As part of the Global Carbon Cycle research effort, an agency-wide planning initiative was organized between October 2000 and June 2001 by the NASA Goddard Space Flight Center (GSFC) at the behest of the Associate Administrator for Earth Science. The goal was to define future research and technology development activities needed for implementing a cohesive scientific observation plan. A timeline for development of missions necessary to acquire the selected new measurements was laid out, and included missions for low - medium density terrestrial biomass / coastal ocean / and ocean carbon. This paper will begin with the scientific justification and measurement requirements for these specific activities, explore the options for having separate or combined missions, and follow-up with an implementation study centered on a hyperspectral imager at geosynchronous altitudes.

  12. [Responses of forest soil carbon pool and carbon cycle to the changes of carbon input].

    PubMed

    Wang, Qing-kui

    2011-04-01

    Litters and plant roots are the main sources of forest soil organic carbon (C). This paper summarized the effects of the changes in C input on the forest soil C pool and C cycle, and analyzed the effects of these changes on the total soil C, microbial biomass C, dissoluble organic C, and soil respiration. Different forests in different regions had inconsistent responses to C input change, and the effects of litter removal or addition and of root exclusion or not differed with tree species and regions. Current researches mainly focused on soil respiration and C pool fractions, and scarce were about the effects of C input change on the changes of soil carbon structure and stability as well as the response mechanisms of soil organisms especially soil fauna, which should be strengthened in the future. PMID:21774335

  13. Decoupling of the Carbon Cycle during Ocean Anoxic Event-2

    NASA Astrophysics Data System (ADS)

    Eldrett, J.; Bergman, S. C.; Minisini, D.

    2013-12-01

    The Cenomanian to Turonian Boundary transition (95-93 Ma) represents one of the most profound global perturbations in the carbon cycle of the last 140 million years. This interval is characterized by widespread deposition of organic-rich fine-grained sediment marked by a globally recognised positive carbon isotope excursion (CIE) reflecting the widespread removal of 12C-enriched organic matter in marine sediments under global anoxic conditions. However, the exact timing and trigger of this inferred global phenomenon, termed Oceanic Anoxic Event-2 is still debated, with recent studies showing diachroneity between the deposition of the organic-rich sediment and the CIE, and conflicting interpretations on detailed redox analyses in several of these inferred anoxic settings. Here we present the first evidence for widespread and persistent oxygenation during OAE-2 based primarily on the distribution of redox-sensitive trace metals preserved in sediments from the Eagle Ford Formation, Western Interior Seaway of North America. We generated a δ13C curve which indicates an earlier initiation of the CIE in Texas compared to the Global Stratotype and Point Section at Pueblo, Colorado. Our data also indicate anoxic-euxinic conditions in the mid-late Cenomanian, but improved bottom-water oxygenation prior to and during the CIE, corroborated by increased bioturbation, abundance of benthic foraminifera and reduced total organic carbon values. Trace metal enrichments support large volumes of mafic volcanism possibly from the High Arctic Large Igneous Province (LIP), which occur during peak bottom-water oxygenation and a plateau in δ13Corg values and does not immediately precede the Cenomanian-Turonian CIE, as previously stated. This suggests that the emplacement of a LIP was not the primary trigger of the OAE-2 event. It is also unlikely that bottom-water oxygenation was promoted by the introduction of volcanogenic Fe inhibiting sulfate reduction, as the depletion in redox

  14. Current systematic carbon cycle observations and needs for implementing a policy-relevant carbon observing system

    NASA Astrophysics Data System (ADS)

    Ciais, P.; Dolman, A. J.; Bombelli, A.; Duren, R.; Peregon, A.; Rayner, P. J.; Miller, C.; Gobron, N.; Kinderman, G.; Marland, G.; Gruber, N.; Chevallier, F.; Andres, R. J.; Balsamo, G.; Bopp, L.; Bréon, F.-M.; Broquet, G.; Dargaville, R.; Battin, T. J.; Borges, A.; Bovensmann, H.; Buchwitz, M.; Butler, J.; Canadell, J. G.; Cook, R. B.; DeFries, R.; Engelen, R.; Gurney, K. R.; Heinze, C.; Heimann, M.; Held, A.; Henry, M.; Law, B.; Luyssaert, S.; Miller, J.; Moriyama, T.; Moulin, C.; Myneni, R. B.; Nussli, C.; Obersteiner, M.; Ojima, D.; Pan, Y.; Paris, J.-D.; Piao, S. L.; Poulter, B.; Plummer, S.; Quegan, S.; Raymond, P.; Reichstein, M.; Rivier, L.; Sabine, C.; Schimel, D.; Tarasova, O.; Valentini, R.; van der Werf, G.; Wickland, D.; Williams, M.; Zehner, C.

    2013-07-01

    A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The goal of this study is to identify the current state of carbon observations and needs for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion (by several orders of magnitude) of the ground-based observation networks required to reach the high spatial resolution for CO2 and CH4 fluxes, and for carbon stocks for addressing policy relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over remote areas such as the southern oceans, tropical forests and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with ground-based data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in-situ and remotely sensed data at much higher resolution and density than currently achieved for natural fluxes, although over a small land area (cities, industrial sites, power plants

  15. Simulations of the carbon cycle in the oceans

    SciTech Connect

    Not Available

    1992-07-01

    This study includes models of oceanic CO{sub 2} uptake. This perturbation simulation of carbon dioxide uptake gives strong support to estimates of oceanic uptake of fossil CO{sub 2} of order 2 GtC/yr. over the last decade. Carbon and carbon-nitrogen models are considered.

  16. Simulations of the carbon cycle in the oceans

    SciTech Connect

    Not Available

    1992-01-01

    This study includes models of oceanic CO{sub 2} uptake. This perturbation simulation of carbon dioxide uptake gives strong support to estimates of oceanic uptake of fossil CO{sub 2} of order 2 GtC/yr. over the last decade. Carbon and carbon-nitrogen models are considered.

  17. Bony fish and their contribution to marine inorganic carbon cycling

    NASA Astrophysics Data System (ADS)

    Salter, Michael; Perry, Chris; Wilson, Rod; Harborne, Alistair

    2016-04-01

    Conventional understanding of the marine inorganic carbon cycle holds that CaCO3 (mostly as low Mg-calcite and aragonite) precipitates in the upper reaches of the ocean and sinks to a point where it either dissolves or is deposited as sediment. Thus, it plays a key role controlling the distribution of DIC in the oceans and in regulating their capacity to absorb atmospheric CO2. However, several aspects of this cycle remain poorly understood and have long perplexed oceanographers, such as the positive alkalinity anomaly observed in the upper water column of many of the world's oceans, above the aragonite and calcite saturation horizons. This anomaly would be explained by extensive dissolution of a carbonate phase more soluble than low Mg-calcite or aragonite, but major sources for such phases remain elusive. Here we highlight marine bony fish as a potentially important primary source of this 'missing' high-solubility CaCO3. Precipitation of CaCO3 takes place within the intestines of all marine bony fish as part of their normal physiological functioning, and global production models suggest it could account for up to 45 % of total new marine CaCO3 production. Moreover, high Mg-calcite containing >25 % mol% MgCO3 - a more soluble phase than aragonite - is a major component of these precipitates. Thus, fish CaCO3 may at least partially explain the alkalinity anomaly in the upper water column. However, the issue is complicated by the fact that carbonate mineralogy actually varies among fish species, with high Mg-calcite (HMC), low Mg-calcite (LMC), aragonite, and amorphous calcium carbonate (ACC) all being common products. Using data from 22 Caribbean fish species, we have generated a novel production model that resolves phase proportions. We evaluate the preservation/dissolution potential of these phases and consider potential implications for marine inorganic carbon cycling. In addition, we consider the dramatic changes in fish biomass structure that have resulted

  18. Cenozoic carbon cycle imbalances and a variable weathering feedback

    NASA Astrophysics Data System (ADS)

    Caves, Jeremy K.; Jost, Adam B.; Lau, Kimberly V.; Maher, Kate

    2016-09-01

    The long-term stability of Earth's climate and the recovery of the ocean-atmosphere system after carbon cycle perturbations are often attributed to a stabilizing negative feedback between silicate weathering and climate. However, evidence for the operation of this feedback over million-year timescales and in response to tectonic and long-term climatic change remains scarce. For example, the past 50 million years of the Cenozoic Era are characterized by long-term cooling and declining atmospheric CO2 (pCO2). During this interval, constant or decreasing carbon fluxes from the solid Earth to the atmosphere suggest that stable or decreasing weathering fluxes are needed to balance the carbon cycle. In contrast, marine isotopic proxies of weathering (i.e., 87Sr/86Sr, δ7 Li , and 187Os/188Os) are interpreted to reflect increasing weathering fluxes. Here, we evaluate the existence of a negative feedback by reconstructing the imbalance in the carbon cycle during the Cenozoic using the surface inventories of carbon and alkalinity. Only a sustained 0.25-0.5% increase in silicate weathering is necessary to explain the long-term decline in pCO2 over the Cenozoic. We propose that the long-term decrease in pCO2 is due to an increase in the strength of the silicate weathering feedback (i.e., the constant of proportionality between the silicate weathering flux and climate), rather than an increase in the weathering flux. This increase in the feedback strength, which mirrors the marine isotope proxies, occurs as transient, <1 million year increases in the weathering flux, which remove CO2. As runoff and temperature decline in response, the integrated weathering flux over >1 million year timescales remains invariant to match the long-term inputs of carbon. Over the Cenozoic, this results in stable long-term weathering fluxes even as pCO2 decreases. We attribute increasing feedback strength to a change in the type and reactivity of rock in the weathering zone, which collectively has

  19. Soil Carbon Cycling - More than Changes in Soil Organic Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Lorenz, K.

    2015-12-01

    Discussions about soil carbon (C) sequestration generally focus on changes in soil organic carbon (SOC) stocks. Global SOC mass in the top 1 m was estimated at about 1325 Pg C, and at about 3000 Pg C when deeper soil layers were included. However, both inorganically and organically bound carbon forms are found in soil but estimates on global soil inorganic carbon (SIC) mass are even more uncertain than those for SOC. Globally, about 947 Pg SIC may be stored in the top 1 m, and especially in arid and semi-arid regions SIC stocks can be many times great than SOC stocks. Both SIC and SOC stocks are vulnerable to management practices, and stocks may be enhanced, for example, by optimizing net primary production (NPP) by fertilization and irrigation (especially optimizing belowground NPP for enhancing SOC stocks), adding organic matter (including black C for enhancing SOC stocks), and reducing soil disturbance. Thus, studies on soil C stocks, fluxes, and vulnerability must look at both SIC and SOC stocks in soil profiles to address large scale soil C cycling.

  20. The global carbon cycle and Quaternary paleoclimates.

    USGS Publications Warehouse

    Sundquist, E.T.

    1987-01-01

    Key evidence of ancient CO2 concentrations has come from studies of ice cores, marine sediments, ocean current patterns, and oceanic biochemistry and biota, but there are conflicting views about the role of the marine biological pump, especially as regards the deglacial increase in CO2.-from Author

  1. A model ensemble for explaining the seasonal cycle of globally averaged atmospheric carbon dioxide concentration

    NASA Astrophysics Data System (ADS)

    Alexandrov, Georgii; Eliseev, Alexey

    2015-04-01

    The seasonal cycle of the globally averaged atmospheric carbon dioxide concentrations results from the seasonal changes in the gas exchange between the atmosphere and other carbon pools. Terrestrial pools are the most important. Boreal and temperate ecosystems provide a sink for carbon dioxide only during the warm period of the year, and, therefore, the summertime reduction in the atmospheric carbon dioxide concentration is usually explained by the seasonal changes in the magnitude of terrestrial carbon sink. Although this explanation seems almost obvious, it is surprisingly difficult to support it by calculations of the seasonal changes in the strength of the sink provided by boreal and temperate ecosystems. The traditional conceptual framework for modelling net ecosystem exchange (NEE) leads to the estimates of the NEE seasonal cycle amplitude which are too low for explaining the amplitude of the seasonal cycle of the atmospheric carbon dioxide concentration. To propose a more suitable conceptual framework we develop a model ensemble that consists of nine structurally different models and covers various approaches to modelling gross primary production and heterotrophic respiration, including the effects of light saturation, limited light use efficiency, limited water use efficiency, substrate limitation and microbiological priming. The use of model ensembles is a well recognized methodology for evaluating structural uncertainty of model-based predictions. In this study we use this methodology for exploratory modelling analysis - that is, to identify the mechanisms that cause the observed amplitude of the seasonal cycle of the atmospheric carbon dioxide concentration and its slow but steady growth.

  2. A Scientific Synthesis and Assessment of the Arctic Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Hayes, Daniel J.; Guo, Laodong; McGuire, A. David

    2007-06-01

    The Arctic Monitoring and Assessment Programme (AMAP), along with the Climate and Cryosphere (CliC) Project and the International Arctic Science Committee (IASC), sponsored the Arctic Carbon Cycle Assessment Workshop, at the Red Lion Hotel in Seattle, Wash., between 27 February and 1 March 2007. The workshop was held in a general effort toward the scientific synthesis and assessment of the Arctic system carbon cycle, as well as to generate feedback on the working draft of an assessment document. The initial assessment was prepared by the Arctic carbon cycle assessment writing team, which is led by A. David McGuire (University of Alaska Fairbanks) and includes Leif Anderson (Goteborg University, Sweden), Torben Christensen (Lund University, Sweden), Scott Dallimore (Natural Resources Canada), Laodong Guo (University of Southern Mississippi), Martin Heimann (Max Planck Institute, Germany), Robie MacDonald (Department of Fisheries and Oceans, Canada), and Nigel Roulet (McGill University, Canada). The workshop brought together leading researchers in the fields of terrestrial, marine, and atmospheric science to report on and discuss the current state of knowledge on contemporary carbon stocks and fluxes in the Artie and their potential responses to a changing climate. The workshop was attended by 35 scientists representing institutions from 10 countries in addition to two representatives of the sponsor agencies (John Calder for AMAP and Diane Verseghy for CliC).

  3. Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.

    PubMed

    Zaehle, Sönke; Medlyn, Belinda E; De Kauwe, Martin G; Walker, Anthony P; Dietze, Michael C; Hickler, Thomas; Luo, Yiqi; Wang, Ying-Ping; El-Masri, Bassil; Thornton, Peter; Jain, Atul; Wang, Shusen; Warlind, David; Weng, Ensheng; Parton, William; Iversen, Colleen M; Gallet-Budynek, Anne; McCarthy, Heather; Finzi, Adrien; Hanson, Paul J; Prentice, I Colin; Oren, Ram; Norby, Richard J

    2014-05-01

    We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2 ] (eCO2 ) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)-nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO2 , given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections. PMID:24467623

  4. Hydrological and biogeochemical constraints on terrestrial carbon cycle projections

    NASA Astrophysics Data System (ADS)

    Mystakidis, Stefanos; Davin, Edouard L.; Gruber, Nicolas; Seneviratne, Sonia I.

    2016-04-01

    The terrestrial biosphere is currently acting as a sink for about a third of the total anthropogenic CO2 emissions. However, the future fate of this sink in the coming decades is very uncertain, as current Earth System Models (ESMs) simulate diverging responses of the terrestrial carbon cycle to upcoming climate change. Here, we use observation-based constraints of water and carbon fluxes to reduce uncertainties in the projected terrestrial carbon cycle response derived from simulations of ESMs conducted as part of the 5th phase of the Coupled Model Intercomparison Project (CMIP5). We find in the ESMs a clear linear relationship between present-day Evapotranspiration (ET) and Gross Primary Productivity (GPP), as well as between these present-day fluxes and projected changes in GPP, thus providing an emergent constraint on projected GPP. Constraining the ESMs based on their ability to simulate present-day ET and GPP leads to a substantial decrease of the projected GPP and to a ca. 50% reduction of the associated model spread in GPP by the end of the century. Given the strong correlation between projected changes in GPP and in NBP in the ESMs, applying the constraints on Net Biome Productivity (NBP) reduces the model spread in the projected land sink by more than 30% by 2100. Also, the projected decline in the land sink is at least doubled in the constrained ensembles and the probability that the terrestrial biosphere is turned into a net carbon source by the end of the century is strongly increased. Moreover, a similar strategy is used to provide constraints on the feedbacks involving the terrestrial carbon cycle and the climate system. The findings indicate that the decline in the future land carbon uptake might be stronger than previously thought, which would have important implications for the rate of increase of the atmospheric CO2 concentration and for future climate change.

  5. Hidden cycle of dissolved organic carbon in the deep ocean

    PubMed Central

    Follett, Christopher L.; Repeta, Daniel J.; Rothman, Daniel H.; Xu, Li; Santinelli, Chiara

    2014-01-01

    Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ13C and age via Δ14C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle. PMID:25385632

  6. Impacts of urbanization on the carbon cycle (Invited)

    NASA Astrophysics Data System (ADS)

    Hutyra, L.; Raciti, S. M.; Dunn, A. L.; Gately, C.; Sue Wing, I.; Woodcock, C.; Olofsson, P.; Friedl, M. A.

    2013-12-01

    Urban areas are expanding rapidly in population and land area. The impact of urban areas on carbon budgets is especially profound. Cities consume nearly 80% of total global energy use and produce approximately 70% of CO2 emissions. Expansion of urban areas in the coming decades is expected to outpace urban population growth, making urban land use change and associated impacts on regional C dynamics a critical element of the global C cycle. Despite the rapid urban expansion, the trajectories of carbon losses and gains following urban development remain poorly quantified, particularly at the urban-rural interface. This is the zone where land use change and C stocks are most dynamic, but least well quantified. While a growing body of research has allowed us to better quantify biomass in forested areas and within the boundaries of major cities, comparatively little work has addressed C stocks and dynamics in the 'middle ground' where the majority of land use change is occurring. Existing spatially-explicit regional and continental scale biomass estimates exclude urban developed areas or presume that they contain little or no biomass. Data on urban C fluxes to and from the atmosphere are likewise very sparse. Our existing network of surface CO2 observation sites intentionally avoids cities. We describe a multidisciplinary study across the greater Boston metropolitan region to characterize the sources and sinks of CO2 across urban-to-rural gradients including the development of new emissions inventories, assessment of land cover change, and process-level studies of variations in ecosystem productivity.

  7. Coordinated carbon cycle research: achievements and opportunities for innovation

    NASA Astrophysics Data System (ADS)

    Shrestha, G.

    2014-12-01

    Providing an overview of milestones achieved by one of the longest running U.S. interagency partnerships in the geosciences, the USGCRP's U.S. Carbon Cycle Science Program, this talk will examine the model employed for its success. The innovative pathways that the Program established in collaboration with the scientific community in order to catalyze scientific advances will be described, along with the governmental mandates and community input that guided their implementation. Within the context of emerging and innovative U.S. global change priorities and instruments, new challenges and opportunities for additional engagement, coordination and collaborations among government and non-government entities involved in funding, conducting, facilitating and using carbon cycle science will be explored.

  8. Comparative carbon cycle dynamics of the present and last interglacial

    NASA Astrophysics Data System (ADS)

    Brovkin, Victor; Brücher, Tim; Kleinen, Thomas; Zaehle, Sönke; Joos, Fortunat; Roth, Raphael; Spahni, Renato; Schmitt, Jochen; Fischer, Hubertus; Leuenberger, Markus; Stone, Emma J.; Ridgwell, Andy; Chappellaz, Jérôme; Kehrwald, Natalie; Barbante, Carlo; Blunier, Thomas; Dahl Jensen, Dorthe

    2016-04-01

    Changes in temperature and carbon dioxide during glacial cycles recorded in Antarctic ice cores are tightly coupled. However, this relationship does not hold for interglacials. While climate cooled towards the end of both the last (Eemian) and present (Holocene) interglacials, CO2 remained stable during the Eemian while rising in the Holocene. We identify and review twelve biogeochemical mechanisms of terrestrial (vegetation dynamics and CO2 fertilization, land use, wildfire, accumulation of peat, changes in permafrost carbon, subaerial volcanic outgassing) and marine origin (changes in sea surface temperature, carbonate compensation to deglaciation and terrestrial biosphere regrowth, shallow-water carbonate sedimentation, changes in the soft tissue pump, and methane hydrates), which potentially may have contributed to the CO2 dynamics during interglacials but which remain not well quantified. We use three Earth System Models (ESMs) of intermediate complexity to compare effects of selected mechanisms on the interglacial CO2 and δ13CO2 changes, focusing on those with substantial potential impacts: namely carbonate sedimentation in shallow waters, peat growth, and (in the case of the Holocene) human land use. A set of specified carbon cycle forcings could qualitatively explain atmospheric CO2 dynamics from 8 ka BP to the pre-industrial. However, when applied to Eemian boundary conditions from 126 to 115 ka BP, the same set of forcings led to disagreement with the observed direction of CO2 changes after 122 ka BP. This failure to simulate late-Eemian CO2 dynamics could be a result of the imposed forcings such as prescribed CaCO3 accumulation and/or an incorrect response of simulated terrestrial carbon to the surface cooling at the end of the interglacial. These experiments also reveal that key natural processes of interglacial CO2 dynamics - shallow water CaCO3 accumulation, peat and permafrost carbon dynamics - are not well represented in the current ESMs. Global

  9. Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts.

    PubMed

    Frank, Dorothea; Reichstein, Markus; Bahn, Michael; Thonicke, Kirsten; Frank, David; Mahecha, Miguel D; Smith, Pete; van der Velde, Marijn; Vicca, Sara; Babst, Flurin; Beer, Christian; Buchmann, Nina; Canadell, Josep G; Ciais, Philippe; Cramer, Wolfgang; Ibrom, Andreas; Miglietta, Franco; Poulter, Ben; Rammig, Anja; Seneviratne, Sonia I; Walz, Ariane; Wattenbach, Martin; Zavala, Miguel A; Zscheischler, Jakob

    2015-08-01

    Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global

  10. Controls on aquatic carbon cycling in a carbonate dominated groundwater catchment using dissolved oxygen dynamics

    NASA Astrophysics Data System (ADS)

    Butler, A. P.; Parker, S. J.

    2015-12-01

    Carbon cycling in aquatic systems is increasingly seen as playing an important role in global carbon budgets and hence on potential impacts and controls on global warming. However, determining the partitioning within and transfer between different carbon stores is a major challenge, particularly where there are multiple sources and controls on carbon utilisation. Dissolved oxygen, DO, provides a proxy for investigating the dynamics of carbon utilisation in aquatic systems. High temporal resolution monitoring of DO at multiple site on the Hampshire Avon, a chalk dominated permeable catchment in southern England, UK, has been investigated using a dynamic DO model in order to investigate the biochemical cycling of carbon. Gross primary production, governed by photosynthetically active radiation, is determined through inverse modelling. Model simplification though parameter reduction is achieved through investigating controls on aeration (the transfer of oxygen across the atmosphere-river interface) and respiration. Seasonal changes in biomass affect long term oxygen dynamics, which are compounded by episodic hydrological events that control the partitioning of surface water and groundwater in the stream channel and consequently the sources of carbon and DO in the river channel. Using variations in surface geology across the catchment the impacts of varying baseflow characteristics on carbon cycling within the catchment is demonstrated.