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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. JGI's Carbon Cycling Studies on Restored Marshes

    ScienceCinema

    Tringe, Susannah; Theroux, Susanna

    2016-07-12

    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.

  3. [Forest carbon cycle model: a review].

    PubMed

    Wang, Ping

    2009-06-01

    Forest carbon cycle is one of the important items in the research of terrestrial carbon cycle, while carbon cycle model is an important means in studying the carbon cycle mechanisms of forest ecosystem and in estimating carbon fluxes. Based on the sum-up of main carbon cycle models, this paper classified the forest carbon cycle models into two categories, i.e., patch scale forest carbon cycle models and regional scale terrestrial carbon cycle models, with their features commented. The future development trend in the research of forest carbon cycle models in China was discussed.

  4. 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.

  5. 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.

  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. 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,…

  8. 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.

  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

    NASA Astrophysics Data System (ADS)

    Wigley, T. M. L.; Schimel, D. S.

    2005-08-01

    Reducing carbon dioxide (CO2) emissions is imperative to stabilizing our future climate. Our ability to reduce these emissions combined with an understanding of how much fossil-fuel-derived CO2 the oceans and plants can absorb is central to mitigating climate change. In The Carbon Cycle, leading scientists examine how atmospheric carbon dioxide concentrations have changed in the past and how this may affect the concentrations in the future. They look at the carbon budget and the "missing sink" for carbon dioxide. They offer approaches to modeling the carbon cycle, providing mathematical tools for predicting future levels of carbon dioxide. This comprehensive text incorporates findings from the recent IPCC reports. New insights, and a convergence of ideas and views across several disciplines make this book an important contribution to the global change literature.

  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. Task Order 20: Supercritical Carbon Dioxide Brayton Cycle Energy Conversion Study

    SciTech Connect

    Murray, Paul; Lindsay, Edward; McDowell, Michael; Huang, Megan

    2015-04-23

    AREVA Inc. developed this study for the US Department of Energy (DOE) office of Nuclear Energy (NE) in accordance with Task Order 20 Statement of Work (SOW) covering research and development activities for the Supercritical Carbon Dioxide (sCO2) Brayton Cycle energy conversion. The study addresses the conversion of sCO2 heat energy to electrical output by use of a Brayton Cycle system and focuses on the potential of a net efficiency increase via cycle recuperation and recompression stages. The study also addresses issues and study needed to advance development and implementation of a 10 MWe sCO2 demonstration project.

  13. Terrestrial Carbon Cycle Variability.

    PubMed

    Baldocchi, Dennis; Ryu, Youngryel; Keenan, Trevor

    2016-01-01

    A growing literature is reporting on how the terrestrial carbon cycle is experiencing year-to-year variability because of climate anomalies and trends caused by global change. As CO 2 concentration records in the atmosphere exceed 50 years and as satellite records reach over 30 years in length, we are becoming better able to address carbon cycle variability and trends. Here we review how variable the carbon cycle is, how large the trends in its gross and net fluxes are, and how well the signal can be separated from noise. We explore mechanisms that explain year-to-year variability and trends by deconstructing the global carbon budget. The CO 2 concentration record is detecting a significant increase in the seasonal amplitude between 1958 and now. Inferential methods provide a variety of explanations for this result, but a conclusive attribution remains elusive. Scientists have reported that this trend is a consequence of the greening of the biosphere, stronger northern latitude photosynthesis, more photosynthesis by semi-arid ecosystems, agriculture and the green revolution, tropical temperature anomalies, or increased winter respiration. At the global scale, variability in the terrestrial carbon cycle can be due to changes in constituent fluxes, gross primary productivity, plant respiration and heterotrophic (microbial) respiration, and losses due to fire, land use change, soil erosion, or harvesting. It remains controversial whether or not there is a significant trend in global primary productivity (due to rising CO 2, temperature, nitrogen deposition, changing land use, and preponderance of wet and dry regions). The degree to which year-to-year variability in temperature and precipitation anomalies affect global primary productivity also remains uncertain. For perspective, interannual variability in global gross primary productivity is relatively small (on the order of 2 Pg-C y (-1)) with respect to a large and uncertain background (123 +/- 4 Pg-C y (-1)), and

  14. Terrestrial Carbon Cycle Variability

    PubMed Central

    Baldocchi, Dennis; Ryu, Youngryel; Keenan, Trevor

    2016-01-01

    A growing literature is reporting on how the terrestrial carbon cycle is experiencing year-to-year variability because of climate anomalies and trends caused by global change. As CO 2 concentration records in the atmosphere exceed 50 years and as satellite records reach over 30 years in length, we are becoming better able to address carbon cycle variability and trends. Here we review how variable the carbon cycle is, how large the trends in its gross and net fluxes are, and how well the signal can be separated from noise. We explore mechanisms that explain year-to-year variability and trends by deconstructing the global carbon budget. The CO 2 concentration record is detecting a significant increase in the seasonal amplitude between 1958 and now. Inferential methods provide a variety of explanations for this result, but a conclusive attribution remains elusive. Scientists have reported that this trend is a consequence of the greening of the biosphere, stronger northern latitude photosynthesis, more photosynthesis by semi-arid ecosystems, agriculture and the green revolution, tropical temperature anomalies, or increased winter respiration. At the global scale, variability in the terrestrial carbon cycle can be due to changes in constituent fluxes, gross primary productivity, plant respiration and heterotrophic (microbial) respiration, and losses due to fire, land use change, soil erosion, or harvesting. It remains controversial whether or not there is a significant trend in global primary productivity (due to rising CO 2, temperature, nitrogen deposition, changing land use, and preponderance of wet and dry regions). The degree to which year-to-year variability in temperature and precipitation anomalies affect global primary productivity also remains uncertain. For perspective, interannual variability in global gross primary productivity is relatively small (on the order of 2 Pg-C y -1) with respect to a large and uncertain background (123 +/- 4 Pg-C y -1), and

  15. 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.

  16. 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.

  17. 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.

  18. A study of power cycles using supercritical carbon dioxide as the working fluid

    NASA Astrophysics Data System (ADS)

    Schroder, Andrew Urban

    A real fluid heat engine power cycle analysis code has been developed for analyzing the zero dimensional performance of a general recuperated, recompression, precompression supercritical carbon dioxide power cycle with reheat and a unique shaft configuration. With the proposed shaft configuration, several smaller compressor-turbine pairs could be placed inside of a pressure vessel in order to avoid high speed, high pressure rotating seals. The small compressor-turbine pairs would share some resemblance with a turbocharger assembly. Variation in fluid properties within the heat exchangers is taken into account by discretizing zero dimensional heat exchangers. The cycle analysis code allows for multiple reheat stages, as well as an option for the main compressor to be powered by a dedicated turbine or an electrical motor. Variation in performance with respect to design heat exchanger pressure drops and minimum temperature differences, precompressor pressure ratio, main compressor pressure ratio, recompression mass fraction, main compressor inlet pressure, and low temperature recuperator mass fraction have been explored throughout a range of each design parameter. Turbomachinery isentropic efficiencies are implemented and the sensitivity of the cycle performance and the optimal design parameters is explored. Sensitivity of the cycle performance and optimal design parameters is studied with respect to the minimum heat rejection temperature and the maximum heat addition temperature. A hybrid stochastic and gradient based optimization technique has been used to optimize critical design parameters for maximum engine thermal efficiency. A parallel design exploration mode was also developed in order to rapidly conduct the parameter sweeps in this design space exploration. A cycle thermal efficiency of 49.6% is predicted with a 320K [47°C] minimum temperature and 923K [650°C] maximum temperature. The real fluid heat engine power cycle analysis code was expanded to study a

  19. 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

  20. A Science Plan for Integrated Studies of Coupled Biosphere-Atmosphere Carbon and Nitrogen Cycles

    NASA Astrophysics Data System (ADS)

    Carroll, M.; Bertman, S. B.; Guenther, A.; Holland, E. A.; Shepson, P. B.; Sparks, J. P.

    2003-12-01

    Human activities, such as the burning of fossil fuels and the use of nitrogen fertilizers, have approximately doubled levels of reactive nitrogen in the biosphere. This perturbation has the potential to alter fundamental processes in terrestrial ecosystems where composition, diversity, and productivity are largely controlled by the availability of nitrogen. A variety of theoretical and experimental studies indicate that nitrogen inputs have a direct impact on fluxes of carbon into ecosystems controlling both CO2 assimilation and the exchange of carbon-based trace gases. In some systems, plant growth and carbon storage appear to be enhanced by nitrogen addition. In contrast, other systems exhibit stagnant or declining plant growth with nitrogen addition as the ecosystem becomes N-saturated and susceptible to stressors such as soil acidification and ozone damage. The magnitudes of the nitrogen and carbon responses appear to depend directly on the pathway and magnitude of nitrogen flux into ecosystems. However, the pathway of nitrogen entry into ecosystems, the chemical species of that nitrogen and its level of incorporation into plant and soil biomass pools are poorly understood in many, if not all, ecosystems. A workshop was held in Boulder, Colorado, in November 2003 to develop a science plan to address the critical need to integrate leaf-level plant physiology, ecosystem, and atmospheric chemistry perspectives to determine the fate of nitrogen and thus carbon in terrestrial systems. Participants brought expertise in plant physiological ecology, biochemistry, soil microbiology, biogeochemistry, atmospheric chemistry, biosphere/atmosphere fluxes, and integrated modeling. On behalf of all participants, we present here the prioritized results of the workshop; including gaps in understanding, technological challenges of integrating biological, ecosystem and atmospheric compartments of carbon and nitrogen cycling, feedbacks in carbon and nitrogen cycle coupling that are

  1. Carbon Capture (Carbon Cycle 2.0)

    ScienceCinema

    Smit, Berend

    2016-07-12

    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/

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

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

    Treesearch

    Y. He; Q. Zhuang; A.D. McGuire; Y. Liu; M. Chen

    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 inmodeling regional carbon dynamics and explore the...

  8. Towards optimized methods to study viral impacts on soil microbial carbon cycling

    NASA Astrophysics Data System (ADS)

    Trubl, G. G.; Roux, S.; Jang, H. B.; Solonenko, N.; Sullivan, M. B.; Rich, V. I.

    2016-12-01

    Permafrost contains 50% of global soil carbon and is rapidly thawing. While the fate of this carbon is currently unknown, it will undoubtedly be shaped by microbes and their associated viruses, which modulate host activities via mortality and metabolic control. However, little is known about soil viruses generally and their impact on terrestrial biogeochemistry; this is partially due to the presence of inhibitory substances (e.g. humic acids) in soils that interfere with sample processing and sequence-based metagenomics surveys. To address this problem, we examined viral populations in three different peat soils along a permafrost thaw gradient. These samples yielded low viral DNA recoveries, and shallow metagenomic sequencing, but still resulted in the recovery of 40 viral genome fragments. Genome- and network-based classification suggested that these new references represented 11 viral clusters, and ecological patterns (based upon non-redundant fragment recruitment) showed that viral populations were distinct in each habitat. Although only 31% of the genes could be functionally classified, pairwise genome comparisons classified 63% of the viruses taxonomically. Additionally, comparison of the 40 viral genome fragments to 53 previously recovered fragments from the same site showed no overlap, suggesting only a small portion of the resident viral community has been sampled. A follow-up experiment was performed to remove more humics during extraction and thereby obtain better viral metagenomes. Three DNA extraction protocols were tested (CTAB, PowerSoil, and Wizard columns) and the DNA was further purified with an AMPure clean-up. The PowerSoil kit maximized DNA yield (3x CTAB and 6x Wizard), and yielded the purest DNA (based on NanoDrop 260:230 ratio). Given the important roles of viruses in biogeochemical cycles in better-studied systems, further research and humic-removal optimization on these thawing permafrost-associated viral communities is needed to clarify

  9. The Geologic History of the Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Sundquist, E. T.; Visser, K.

    2003-12-01

    Geologists, like other scientists, tend to view the global carbon cycle through the lens of their particular training and experience. The study of Earth's history requires a view both humbled by the knowledge of past global transformations and emboldened by the imagination of details not seen in the fragments of the rock record. In studying the past behavior of the carbon cycle, geologists are both amazed by unexpected discoveries and reassured by the extent to which "the present is the key to the past." Understanding the present-day carbon cycle has become a matter of societal urgency because of concerns about the effects of human activities on atmospheric chemistry and global climate. This public limelight has had far-reaching consequences for research on the geologic history of the carbon cycle as well as for studies of its present and future. The burgeoning new "interdiscipline" of biogeochemistry claims among its adherents many geologists as well as biologists, chemists, and other scientists. The pace of discovery demands that studies of the geologic history of the carbon cycle cannot be isolated from the context of present and future events.This chapter describes the behavior of the carbon cycle prior to human influence. It describes events and processes that extend back through geologic time and include the exchange of carbon between the Earth's surface and the long-term reservoirs in the lithosphere. Chapter 8.10 emphasizes carbon exchanges that are important over years to decades, with a focus on relatively recent human influences and prospects for change during the coming century. Chapter 4.03 presents an overview of the biogeochemistry of methane, again with emphasis on relatively recent events. In these chapters as well as in the present chapter, relationships between the carbon cycle and global climate are a central concern. Together, these chapters provide an overview of how our knowledge of the present-day carbon cycle can be applied both to

  10. Climate and the Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Manley, Jim

    2017-04-01

    Climate and the Carbon Cycle EOS3a Science in tomorrow's classroom Students, like too much of the American public, are largely unaware or apathetic to the changes in world climate and the impact that these changes have for life on Earth. A study conducted by Michigan State University and published in 2011 by Science Daily titled 'What carbon cycle? College students lack scientific literacy, study finds'. This study relates how 'most college students in the United States do not grasp the scientific basis of the carbon cycle - an essential skill in understanding the causes and consequences of climate change.' The study authors call for a new approach to teaching about climate. What if teachers better understood vital components of Earth's climate system and were able to impart his understanding to their students? What if students based their responses to the information taught not on emotion, but on a deeper understanding of the forces driving climate change, their analysis of the scientific evidence and in the context of earth system science? As a Middle School science teacher, I have been given the opportunity to use a new curriculum within TERC's EarthLabs collection, Climate and the Carbon Cycle, to awaken those brains and assist my students in making personal lifestyle choices based on what they had learned. In addition, with support from TERC and The University of Texas Institute for Geophysics I joined others to begin training other teachers on how to implement this curriculum in their classrooms to expose their students to our changing climate. Through my poster, I will give you (1) a glimpse into the challenges faced by today's science teachers in communicating the complicated, but ever-deepening understanding of the linkages between natural and human-driven factors on climate; (2) introduce you to a new module in the EarthLabs curriculum designed to expose teachers and students to global scientific climate data and instrumentation; and (3) illustrate how

  11. 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.

  12. 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.

  13. Material Flows and Carbon Cycles

    NASA Astrophysics Data System (ADS)

    Worrell, E.

    2003-12-01

    The industrial sector emits almost 43 percent of the global anthropogenic carbon dioxide emissions to produce materials and products. Furthermore, energy is used to move materials and products and process the waste. Hence, a large amount of energy is consumed and CO2 is emitted to sustain our materials system. Until recently, studies investigating mitigation options focused on changes in the energy system. For industrial processes most studies evaluate how the current materials system can be maintained producing fewer greenhouse gas emissions. Three elements of a strategy to improve the long-term materials productivity are the reduction of dissipative uses of non-biodegradable materials, secondly, the re-design of products to use less material or design for re-use or recycling, and thirdly, develop more efficient technologies for material conversion and recycling. This will reduce or eliminate the need to extract virgin materials from the environment, and reduce CO2 emissions from the energy-intensive production processes. To assess measures to reduce materials consumption, fossil fuels consumption and CO2 emissions, detailed understanding of the material system is needed. The lifecycle of materials has to be investigated including all branches of industry with all the inputs and outputs. We start with a discussion of materials and the carbon cycle focusing on the contribution of materials to anthropogenic carbon flows. We discuss CO2 emissions from energy use in materials extraction and production, fossil (e.g. plastics) and biomass carbon (e.g. lumber, paper) used as feedstock of materials, and mineral sources (e.g. cement). We discuss opportunities to reduce CO2 emissions by improving the efficiency with which society uses materials through product design, material substitution, product reuse and material recycling.

  14. 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.

  15. 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

    2014-06-26

    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.

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

    USGS Publications Warehouse

    Yuan, Wenping; Liu, Shuguang; Dong, Wenjie; Liang, Shunlin; Zhao, Shuqing; Chen, Jingming; Xu, Wenfang; Li, Xianglan; Barr, Alan; Black, T. Andrew; Yan, Wende; Goulden, Michael; 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.

  17. 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...

  18. 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...

  19. 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...

  20. 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...

  1. Permafrost soils and carbon cycling

    DOE PAGES

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; ...

    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

  2. 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).

  3. Uncovering the Neoproterozoic carbon cycle.

    PubMed

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

    2012-02-29

    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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Global Links to Local Carbon Cycling Perturbation

    NASA Astrophysics Data System (ADS)

    Chen, J.; Montanez, I. P.; Wang, X.; Qi, Y.

    2016-12-01

    Carbon cycle perturbations recorded by stable carbon isotope excursions (CIEs) play an important role in understanding climate, oceanography, and the biosphere through time. Recent studies, however, reveal the influence of regional processes on apparent global CIEs. Deconvolving local/regional from global processes imprinted in the carbon isotopic records of sedimentary successions requires integrated sedimentologic, stratigraphic, and geochemical study. Here we present coupled C and Sr isotopic records of diagenetically screened micrite and brachiopods from late Mississippian shallow-marine, carbonate platform and contemporaneous carbonate slope successions from the east Paleotethys Ocean region (South China). These records reveal distinctly different signatures of the depositional response to the onset of Carboniferous glaciation. C and Sr isotopic compositions of the platform carbonates exhibit systematic fluctuations in step with inferred sea-level changes captured by depositional cycles. CIEs in the platform succession can be correlated to the contemporaneous C isotope record from the Antler carbonate ramp (Idaho, USA). In contrast, slope carbonate and conodont isotopic records exhibit minimal variability interpreted to record the open-ocean seawater composition. The isotopic disparity between successions is interpreted to record the influence of local depositional, but not diagenetic, processes operating on the carbonate platform in response to glacioeustasy. Variability in the nature of coupled isotopic and inferred sea level fluctuations is interpreted to record stepwise onset of the late Paleozoic ice age in the late Mississippian. Initial large magnitude shifts in C and Sr isotopic compositions of late Visean to early Serpukhovian carbonates correspond to 1 to 2 myr-scale cycles driven by the buildup of continental glaciers. Subsequent decreased magnitude of isotopic shifts coincident with a shift to shorter duration and smaller magnitude sea

  9. Ocean carbon cycling during the past 130 000 years - a pilot study on inverse palaeoclimate record modelling

    NASA Astrophysics Data System (ADS)

    Heinze, Christoph; Hoogakker, Babette A. A.; Winguth, Arne

    2016-10-01

    What role did changes in marine carbon cycle processes and calcareous organisms play in glacial-interglacial variation in atmospheric pCO2? In order to answer this question, we explore results from an ocean biogeochemical general circulation model. We attempt to systematically reconcile model results with time-dependent sediment core data from the observations. For this purpose, we fit simulated sensitivities of oceanic tracer concentrations to changes in governing carbon cycle parameters to measured sediment core data. We assume that the time variation in the governing carbon cycle parameters follows the general pattern of the glacial-interglacial deuterium anomaly. Our analysis provides an independent estimate of a maximum mean sea surface temperature drawdown of about 5 °C and a maximum outgassing of the land biosphere by about 430 Pg C at the Last Glacial Maximum as compared to pre-industrial times. The overall fit of modelled palaeoclimate tracers to observations, however, remains quite weak, indicating the potential of more detailed modelling studies to fully exploit the information stored in the palaeoclimatic archive. This study confirms the hypothesis that a decline in ocean temperature and a more efficient biological carbon pump in combination with changes in ocean circulation are the key factors for explaining the glacial CO2 drawdown. The analysis suggests that potential changes in the export rain ratio POC : CaCO3 may not have a substantial imprint on the palaeoclimatic archive. The use of the last glacial as an inverted analogue to potential ocean acidification impacts thus may be quite limited. A strong decrease in CaCO3 export production could potentially contribute to the glacial CO2 decline in the atmosphere, but this remains hypothetical.

  10. 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

  11. Changing carbon cycle: a global analysis

    SciTech Connect

    Trabalka, J.R.; Reichle, D.E.

    1986-01-01

    An attempt is made to examine current knowledge about the fluxes, sources, and sinks in the global carbon cycle, as well as our ability to predict changes in atmospheric CO/sub 2/ concentration resulting from anthropogenic influences. The reader will find authoritative discussions of: past and expected releases of CO/sub 2/ from fossil fuels; the historical record and implications of atmospheric CO/sub 2/ increases; isotopic and geological records of past carbon cycle processes; the role of the oceans in the global carbon cycle; the influence of the world biosphere on changes in atmospheric CO/sub 2/ levels; and, evidence linking the components of the global carbon cycle.

  12. Authigenic Carbonate and the History of the Global Carbon Cycle

    NASA Astrophysics Data System (ADS)

    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 O2 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.

  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.

  14. Dynamics of the Neoproterozoic carbon cycle.

    PubMed

    Rothman, Daniel H; Hayes, John M; Summons, Roger E

    2003-07-08

    The existence of unusually large fluctuations in the Neoproterozoic (1,000-543 million years ago) carbon-isotopic record implies strong perturbations to the Earth's carbon cycle. To analyze these fluctuations, we examine records of both the isotopic content of carbonate carbon and the fractionation between carbonate and marine organic carbon. Together, these are inconsistent with conventional, steady-state models of the carbon cycle. The records can be well understood, however, as deriving from the nonsteady dynamics of two reactive pools of carbon. The lack of a steady state is traced to an unusually large oceanic reservoir of organic carbon. We suggest that the most significant of the Neoproterozoic negative carbon-isotopic excursions resulted from increased remineralization of this reservoir. The terminal event, at the Proterozoic-Cambrian boundary, signals the final diminution of the reservoir, a process that was likely initiated by evolutionary innovations that increased export of organic matter to the deep sea.

  15. 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.

  16. Beyond the Calvin cycle: autotrophic carbon fixation in the ocean.

    PubMed

    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.

  17. 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.

  18. Permafrost soils and carbon cycling

    DOE PAGES

    Ping, C. L.; Jastrow, J. D.; Jorgenson, M. T.; ...

    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

  19. 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.

  20. 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.

  1. 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

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

    PubMed

    Brand, Christian; Goodman, Anna; Ogilvie, David

    2014-09-01

    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

  3. Carbon cycle in advanced coal chemical engineering.

    PubMed

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

    2015-08-07

    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.

  4. 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

  5. Global Impacts (Carbon Cycle 2.0)

    ScienceCinema

    Gadgil, Ashok [EETD and UC Berkeley

    2016-07-12

    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/

  6. Constraining the Carbon Cycle through Tree Rings: A Case Study of the Valles Caldera, NM

    NASA Astrophysics Data System (ADS)

    Alexander, M. R.; Babst, F.; Moore, D. J.; Trouet, V.

    2013-12-01

    Terrestrial ecosystems take up approximately 120 Gt of carbon as Gross Primary Productivity (GPP) from the atmosphere annually, but it is challenging to track the allocation of that carbon throughout the biosphere. Here, we combine eddy covariance measurements of net carbon uptake with above ground biomass increments derived from tree-ring data to better understand the interannual variability associated with biomass accumulation. In the summer of 2012, we collected tree cores near two eddy covariance towers in the Jemez Mountains of northern New Mexico. One tower was located in an upper elevation mixed-conifer forest, and the other in a lower elevation Pinus ponderosa forest. Our analysis shows that the annual above ground biomass increment accounted for approximately 40% of the GPP at the lower elevation Pinus ponderosa site and approximately 70% of GPP at the upper elevation mixed-conifer site. We have also used the above ground biomass increment to constrain the Simple Photosynthesis EvapoTranspiration (SiPNET) model to gain a better understanding of allocation within the forest. Tree growth at both elevations was negatively influenced by spring (March-June) temperature and positively by cool season (October-April) precipitation and warm (May-September) and cool season PDSI. We also analyzed the six most extreme temperature and moisture (PDSI) years of the record to determine the response of productivity to climatic forcing. During the driest years, biomass production was reduced by 40% at the upper elevation site and 43% at the lower elevation site. During the hottest years of the record the biomass decreased 28% at the upper site and 45% at the lower site. Our results indicate that tree rings can be used to effectively constrain the above ground biomass component of a forest's carbon budget and to estimate allocation of carbon to woody biomass as a function of climate. However, many variables remain unknown. The combined results of the extreme year analyses

  7. Comparing Natural and Economic Carbon Cycle Feedbacks

    NASA Astrophysics Data System (ADS)

    Woodard, D.; Fu, W.; Davis, S. J.; Randerson, J. T.

    2016-12-01

    Land and ocean carbon-climate feedbacks may accelerate the build-up of atmospheric carbon dioxide, making it difficult to develop a mitigation strategy that stabilizes the climate system. Natural carbon feedbacks, which include carbon-concentration and carbon-climate components, have been extensively evaluated using full and reduced complexity earth system models. However, climate change also influences many socio-economic systems, creating a parallel set of anthropogenic carbon cycle feedbacks. Although some climate-energy interactions are represented in integrated assessment models, the sign and magnitude of the anthropogenic carbon cycle feedback has not been estimated or compared with that of the natural carbon cycle. Here we develop a framework for conceptualizing socio-economic carbon-climate feedbacks, complementing previous work on the natural carbon cycle. Using a relatively simple box model of the Earth system, scenarios from the Global Change Assessment Model (GCAM), and the Kaya identity, which describes drivers of fossil fuel emissions, we provide estimates of the magnitude of different economic feedbacks. In our analysis we focused on the impact of temperature on gross domestic production (GDP), on the carbon intensity of energy, and on the energy intensity of GDP. Results from this simple model reveal that anthropogenic feedbacks may have magnitudes similar to those reported for the natural carbon cycle; however, more data and detailed analysis on the interactions between temperature, economic productivity, and energy systems are needed to better quantify these feedbacks. Our preliminary findings highlight the need for systematically comparing economic-climate feedbacks across integrated assessment models and the need for integrating this information into future scenarios of global change.

  8. 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.

  9. Modeling the carbon cycle in Lake Matano.

    PubMed

    Kuntz, L B; Laakso, T A; Schrag, D P; Crowe, S A

    2015-09-01

    Lake Matano, Indonesia, is a stratified anoxic lake with iron-rich waters that has been used as an analogue for the Archean and early Proterozoic oceans. Past studies of Lake Matano report large amounts of methane production, with as much as 80% of primary production degraded via methanogenesis. Low δ(13)C values of DIC in the lake are difficult to reconcile with this notion, as fractionation during methanogenesis produces isotopically heavy CO2. To help reconcile these observations, we develop a box model of the carbon cycle in ferruginous Lake Matano, Indonesia, that satisfies the constraints of CH4 and DIC isotopic profiles, sediment composition, and alkalinity. We estimate methane fluxes smaller than originally proposed, with about 9% of organic carbon export to the deep waters degraded via methanogenesis. In addition, despite the abundance of Fe within the waters, anoxic ferric iron respiration of organic matter degrades <3% of organic carbon export, leaving methanogenesis as the largest contributor to anaerobic organic matter remineralization, while indicating a relatively minor role for iron as an electron acceptor. As the majority of carbon exported is buried in the sediments, we suggest that the role of methane in the Archean and early Proterozoic oceans is less significant than presumed in other studies.

  10. 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).

  11. 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.

  12. 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.

  13. 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.

  14. An isopycnic ocean carbon cycle model

    NASA Astrophysics Data System (ADS)

    Assmann, K. M.; Bentsen, M.; Segschneider, J.; Heinze, C.

    2010-02-01

    The carbon cycle is a major forcing component in the global climate system. Modelling studies, aiming to explain recent and past climatic changes and to project future ones, increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here, we present first results from a newly-developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents well the interior ocean transport of biogeochemical tracers and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the ocean biogeochemistry model HAMOCC, for use with an isopycnic coordinate, were in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. The sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of nutrient distributions and liniting factors of biological production.

  15. 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.

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

    ScienceCinema

    Alivisatos, Paul

    2016-07-12

    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/

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

    ScienceCinema

    DePaolo, Don [Director, LBNL Earth Sciences Division

    2016-07-12

    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/

  18. Carbon cycle modeling calculations for the IPCC

    SciTech Connect

    Wuebbles, D.J.; Jain, A.K.

    1993-08-12

    We carried out essentially all the carbon cycle modeling calculations that were required by the IPCC Working Group 1. Specifically, IPCC required two types of calculations, namely, ``inverse calculations`` (input was CO{sub 2} concentrations and the output was CO{sub 2} emissions), and the ``forward calculations`` (input was CO{sub 2} emissions and output was CO{sub 2} concentrations). In particular, we have derived carbon dioxide concentrations and/or emissions for several scenarios using our coupled climate-carbon cycle modelling system.

  19. Terrestrial Carbon Cycle Dynamics under Recent and Future Climate Change.

    NASA Astrophysics Data System (ADS)

    Matthews, H. Damon; Weaver, Andrew J.; Meissner, Katrin J.

    2005-05-01

    The behavior of the terrestrial carbon cycle under historical and future climate change is examined using the University of Victoria Earth System Climate Model, now coupled to a dynamic terrestrial vegetation and global carbon cycle model. When forced by historical emissions of CO2 from fossil fuels and land-use change, the coupled climate-carbon cycle model accurately reproduces historical atmospheric CO2 trends, as well as terrestrial and oceanic uptake for the past two decades. Under six twenty-first-century CO2 emissions scenarios, both terrestrial and oceanic carbon sinks continue to increase, though terrestrial uptake slows in the latter half of the century. Climate-carbon cycle feedbacks are isolated by comparing a coupled model run with a run where climate and the carbon cycle are uncoupled. The modeled positive feedback between the carbon cycle and climate is found to be relatively small, resulting in an increase in simulated CO2 of 60 ppmv at the year 2100. Including non-CO2 greenhouse gas forcing and increasing the model's climate sensitivity increase the effect of this feedback to 140 ppmv. The UVic model does not, however, simulate a switch from a terrestrial carbon sink to a source during the twenty-first century, as earlier studies have suggested. This can be explained by a lack of substantial reductions in simulated vegetation productivity due to climate changes.

  20. 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.

  1. 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)

  2. An isopycnic ocean carbon cycle model

    NASA Astrophysics Data System (ADS)

    Assmann, K. M.; Bentsen, M.; Segschneider, J.; Heinze, C.

    2009-07-01

    The carbon cycle is a major forcing component in the global climate system. Modelling studies aiming to explain recent and past climatic changes and to project future ones thus increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here we present first results from a newly developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents interior ocean transport of biogeochemical tracers well and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the biogeochemical code for use with an isopycnic coordinate are in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. Use of a prognostic slab atmosphere allows us to assess the effect of the changes in export production on global ocean carbon uptake and atmospheric CO2 levels. Sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of modelled air-sea fluxes and nutrient distributions.

  3. Biogeochemical cycling of carbon, nitrogen, and sulfur at the Howland Integrated Forest Study site, Howland, Maine

    Treesearch

    James W. McLaughlin; Ivan J. Fernandez; Stewart M. Goltz; Lindsey E. Rustad; Larry Zibilske

    1996-01-01

    The biogeochemistry of C, N, and S was studied for six years at the Howland Integrated Forest Study (HIFS) site by measuring those constituents in major above- and below-ground pools and fluxes. Leaching losses of C from the solum were much less than CO2 efflux, with a mean annual leaching rate of 31.2 kg ha-1 yr

  4. 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.

  5. Carbon cycle in shrimp polyculture mesocosm

    NASA Astrophysics Data System (ADS)

    Liu, Guo-Cai; Li, De-Shang; Dong, Shuang-Lin

    2000-03-01

    The carbon cycle in shrimp polyculture mesocosm ecosystems was studied in the shrimp farm of the Huanghai Fisheries Group Corporation in Shandong Province from May to August, 1997. The results showed that the plankton community respiration rate fluctuated between 0.07 and 2.28 mgC/(L·d), average of 0.82±0.42 mgC/(L·d), which was 49 percent of the rate of phytoplankton gross production; that the average respiration rates (mgC/(L·d)) of micro-, nano- and pico-plankton were 0.07, 0.38 and 0.31, which were 175, 30 and 207 percent of the corresponding sized phytoplankton production rates; that the sediment respiration rate (mgC/(m2·d)) varied from 178.64 to 373.23, average of 262.60±48.68, and increased gradually with the lapse of culture time; and that the organic carbon accumulation and the respiration in the sediment of the shrimp monoculture mesocosm was higher than that in the polyculture mesocosms. The total sediment respiration per 25 m2 mesocosm in the culture period averaged 571.16 gC, which was 10 percent of the total organic carbon input of the mesocosm.

  6. 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.

  7. Carbon cycling and snowball Earth.

    PubMed

    Goddéris, Yves; Donnadieu, Yannick

    2008-12-18

    The possibility that Earth witnessed episodes of global glaciation during the latest Precambrian challenges our understanding of the physical processes controlling the Earth's climate. Peltier et al. suggest that a 'hard snowball Earth' state may have been prevented owing to the release of CO(2) from the oxidation of dissolved organic carbon (DOC) in the ocean as the temperature decreased. Here we show that the model of Peltier et al. is not self-consistent as it implies large fluctuations of the ocean alkalinity content without providing any processes to account for it. Our findings suggest that the hard snowball Earth hypothesis is still valid.

  8. The Disordered Kinetics of Earth's Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Rothman, Daniel

    2008-03-01

    The carbon cycle describes the transformations of carbon as it cycles through living organisms and the physical environment. In its simplest form, the cycle amounts to a loop between photosynthesis and respiration. Photosynthesis produces organic carbon and molecular oxygen from carbon dioxide and water. Respiration reverses the process by oxidation of organic carbon. The duration of the cycle spans a vast range of time scales: from days or less for fast-growing plankton in the oceans, to hundreds of millions of years or more for the small fraction of organic matter that is buried as rock. The rates at which the cycle is closed set atmospheric carbon dioxide levels at short time scales and oxygen levels at geologic time scales. Respiration rates thereby influence not only climate---by the determination of equilibrium carbon dioxide concentrations---but also biological evolution---because the oxygenation of Earth's atmosphere must have preceded the advent of aerobic metabolism. We review recent advances in the understanding of the rates that control the carbon cycle, with emphasis on the respiratory back-reaction. Given considerable biological, chemical, and environmental variation, it comes as no surprise that measurements of rates vary greatly. Observations suggest, however, some surprising simplicity: for example, the rates of microbial consumption of organic matter in sediments and soils slow down systematically like the inverse of the age of the organic matter. This aging effect can be quantitatively understood as the macroscopic observation of microscopically disordered kinetics. The disorder can arise purely physically as the consequence of a reaction-diffusion process in porous media, but any combination of physical, chemical, and biological parameters that yield a wide range of rates suffices. A predicted practical consequence is a slow, logarithmic decay of organic matter in sediments and soils, which compares well with measurements. Further observations

  9. 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.

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

    USDA-ARS?s Scientific Manuscript database

    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,...

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. Studies of the terrestrial O2 and carbon cycles in sand dune gases and in biosphere 2

    SciTech Connect

    Severinghaus, Jeffrey Peck

    1995-01-01

    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 O2 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 CO2.

  16. 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

  17. 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.

  18. Carbon cycle: New pathways in the sand

    NASA Astrophysics Data System (ADS)

    Rao, Alexandra

    2017-01-01

    Organic carbon decomposition in anoxic marine sediments was thought to be dominated by bacteria, but experimental data and microbial culture studies now show that microalgae buried in coastal sands may also play an important role in carbon turnover.

  19. 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

  20. Zooplankton and the Ocean Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Steinberg, Deborah K.; Landry, Michael R.

    2017-01-01

    Marine zooplankton comprise a phylogenetically and functionally diverse assemblage of protistan and metazoan consumers that occupy multiple trophic levels in pelagic food webs. Within this complex network, carbon flows via alternative zooplankton pathways drive temporal and spatial variability in production-grazing coupling, nutrient cycling, export, and transfer efficiency to higher trophic levels. We explore current knowledge of the processing of zooplankton food ingestion by absorption, egestion, respiration, excretion, and growth (production) processes. On a global scale, carbon fluxes are reasonably constrained by the grazing impact of microzooplankton and the respiratory requirements of mesozooplankton but are sensitive to uncertainties in trophic structure. The relative importance, combined magnitude, and efficiency of export mechanisms (mucous feeding webs, fecal pellets, molts, carcasses, and vertical migrations) likewise reflect regional variability in community structure. Climate change is expected to broadly alter carbon cycling by zooplankton and to have direct impacts on key species.

  1. Upscaling diurnal cycles of carbon fluxes

    NASA Astrophysics Data System (ADS)

    Bodesheim, Paul; Jung, Martin; Mahecha, Miguel; Reichstein, Markus

    2017-04-01

    Carbon fluxes like Gross Primary Production (GPP) and Net Ecosystem Exchange (NEE) are important variables for studying interactions between the atmosphere and the biosphere in different ecosystems. They are typically derived from measurements at Eddy covariance towers and the FLUXNET global network consists of hundreds of such sites. In order to diagnose global GPP and NEE patterns from FLUXNET, upscaling approaches have been used in the past to extrapolate the site measurements to continental and global scale. However, respective products have a daily or monthly temporal resolution and do not allow for analyzing patterns related to diurnal variations of GPP and NEE. To raise these upscaling approaches to the next level, we present our first results on upscaling diurnal cycles of GPP and NEE with half-hourly resolution. We use random forest regression models to estimate the relationship between predictor variables and fluxes based on more than four million half-hourly observations from FLUXNET sites. We have developed and tested two approaches that overcome the mismatch in the temporal resolution between predictor variables at daily resolution and fluxes at half-hourly resolution. Based on thorough leave-one-site-out cross-validation we show that the approach works very well. Finally, we used the trained models for computing global products of half-hourly GPP and NEE that cover the years 2001 to 2014 and present global patterns of diurnal carbon flux variations derived from the upscaling approach.

  2. 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.

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

    ScienceCinema

    Collins, Bill

    2016-07-12

    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/

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

    ScienceCinema

    Alivisatos, Paul

    2016-07-12

    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/

  5. 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.

  6. 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.

  7. 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.

  8. Simulation of the carbon cycle in the ocean

    SciTech Connect

    Fasham, M.J.R.

    1991-09-16

    A dual carbon-nitrogen biological model of the upper ocean has been developed, which has successfully allowed predictions of fluxes of carbon between atmosphere and the deep ocean to made. Regarding studying the carbon cycle in the ocean, the modelling has highlighted the need for a good understanding of the interactions between the carbon and nitrogen cycles, and also the importance of zooplankton grazing and levels of overwintering biological stocks. Problems have been encountered with the accuracy of prediction of the partial pressure of carbon dioxide in the surface ocean, and the sensitivity of the model to zooplankton parameters, and those parameters which effect overwintering stocks (e.g. mortality parameters). The model has recently been incorporated into a physical General Circulation Model of the Atlantic Ocean. Future work will involve assessing the performance of the biological model in General Circulation Models, and making necessary refinements in order to improve its predictive ability. 1 ref., 1 fig.

  9. 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.

  10. 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

  11. Modelling the effects of grassland management on the carbon cycle

    NASA Astrophysics Data System (ADS)

    Rolinski, Susanne; Heinke, Jens; Weindl, Isabelle

    2014-05-01

    Management of grassland is assumed to have a substantial impact on the global carbon cycle and large potential for carbon sequestration. There are few global assessments of the respective fluxes. Within the well-established dynamic global vegetation model LPJmL, we implemented four major options for the management and harvest regimes of grasslands. This approach enables to study the feedbacks of biomass removal through harvest and grazing on grassland productivity. We demonstrate sensitivity of carbon fluxes and stocks under different grassland management options. This opens the possibility for the integration of observation-based estimates of carbon sequestration in global models.

  12. 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

  13. 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

    2015-04-28

    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.

  14. 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.

  15. 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

  16. Carbon cycles and climate: a selected bibliography

    SciTech Connect

    Olson, J.S.; Allison, L.J.; Collier, B.N.

    1980-05-01

    This partially annotated bibliography contains the first 1000 references from a computerized file of literature on the global ecological implications of carbon cycles and climatic changes. Many early citations originated from the Biogeochemical Ecological Information Center established at Oak Ridge National Laboratory in 1968 and from profiles of computerized files such as Government Research Abstracts (GRA) and Biological Abstracts (BA). Later citations have been extracted from the open literature through 1978 and early 1979, from government reports and impact statements, and from profiles of GRA, BA, and the Energy Data Base of the Department of Energy Technical Information Center, Oak Ridge, Tennessee. The subject categories covered by this bibliography may be divided into two main topics: carbon cycling and climate system analysis. Volume 3 provides indexes for author, organization (corporate authority), keywords (or free index terms), taxonomic category, subject category, Chemical Abstracts codes, Biological Abstracts codes (crosscode), and COSATI/Weekly Government Abstracts codes concentrated with permuted title words.

  17. Iron Cycling at Corroding Carbon Steel Surfaces

    DTIC Science & Technology

    2013-01-01

    bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure...iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media. Keywords: seawater; iron-oxidizing bacteria ; iron-reducing bacteria ...carbon steel; microbiologically influenced corrosion Introduction Iron oxidizing bacteria (FeOB) were among the first groups of microorganisms

  18. 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

  19. Models for generation of carbonate cycles

    NASA Astrophysics Data System (ADS)

    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, we 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 metres thick result from low-amplitude sea-level oscillation of a few metres 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.

  20. 129Xe nuclear magnetic resonance study of pitch-based activated carbon modified by air oxidation/pyrolysis cycles: a new approach to probe the micropore size.

    PubMed

    Romanenko, Konstantin V; Py, Xavier; d'Espinose de Lacaillerie, Jean-Baptiste; Lapina, Olga B; Fraissard, Jacques

    2006-02-23

    (129)Xe NMR has been used to study a series of homologous activated carbons obtained from a KOH-activated pitch-based carbon molecular sieve modified by air oxidation/pyrolysis cycles. A clear correlation between the pore size of microporous carbons and the (129)Xe NMR of adsorbed xenon is proposed for the first time. The virial coefficient delta(Xe)(-)(Xe) arising from binary xenon collisions varied linearly with the micropore size and appeared to be a better probe of the microporosity than the chemical shift extrapolated to zero pressure. This correlation was explained by the fact that the xenon collision frequency increases with increasing micropore size. The chemical shift has been shown to vary very little with temperature (less than 9 ppm) for xenon trapped inside narrow and wide micropores. This is indicative of a smooth xenon-surface interaction potential.

  1. 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.

    2013-02-01

    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. Since the beginning of the industrial era, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background concentration. 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, therefore requires that both organic and inorganic carbon be afforded a full 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 parameterisations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal hindcast simulation described (1860-2005), to evaluate the biogeochemical performance of the model.

  2. Tropical forests and the global carbon cycle.

    PubMed

    Detwiler, R P; Hall, C A

    1988-01-01

    New data on the three major determinants of the carbon release from tropical forest clearing are used in a computer model that simulates land use change and its effects on the carbon content of vegetation and soil in order to calculate the net flux of carbon dioxide between tropical ecosystems and the atmosphere. The model also permits testing the sensitivity of the calculated flux to uncertainties in these data. The tropics were a net source of at least 0.4 x 10(15) grams but not more than 1.6 x 10(15) grams of carbon in 1980, considerably less than previous estimates. Decreases in soil organic matter were responsible for 0.1 x 10(15) to 0.3 x 10(15) grams of the release, while the burning and decay of cleared vegetation accounted for 0.3 x 10(15) to 1.3 x 10(15) grams. These estimates are lower than many previous ones because lower biomass estimates and slightly lower land clearing rates were used and because ecosystem recovery processes were included. These new estimates of the biotic release allow for the possibility of a balanced global budget given the large remaining uncertainties in the marine, terrestrial, and fossil fuel components of the carbon cycle.

  3. 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

  4. 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.

  5. Measurable Pools of Soil Carbon for Carbon Cycle Modeling

    NASA Astrophysics Data System (ADS)

    Mayes, M. A.; Wang, G.; Abramoff, R. Z.; Xu, X.; Hartman, M. D.; Feng, W.; Davidson, E.; Finzi, A.; Moorhead, D.; Schimel, J.; O'Brien, S. L.; Thornton, P. E.

    2016-12-01

    Carbon in soils can have long residence times, but the exact mechanisms are not well understood, which complicates defining pools and parameters for carbon cycling models. Physical protection involves the formation of hierarchical aggregates of mineral-associated carbon, microbes, and particulate carbon. Aggregation leads to a complex pore structure, which can alter moisture potentials, gas diffusion rates, ionic strength and composition of soil solutions, and nutrient availability for microbes. Diffusion gradients between pore size classes can also sequester organic materials from microbes and their accompanying enzymes. Mineral protection is considered to involve sorption of dissolved organic compounds onto reactive clays and iron and aluminum oxides, but there is controversy as to whether sorption occurs as a monolayer or in complex architectures, as well as the degree of mineral coverage. Further, pore structure can alter the ionic composition of porewaters, thereby influencing the extent and nature of adsorption and desorption. Only mineral protection is thought to yield the long residence times found in soils, but dynamics of these pools are poorly constrained in models due to an absence of long-term measurements and an accompanying lack of process understanding. This talk will review the evidence for and against these different mechanisms of carbon preservation, with particular attention to definitions of soil pools for modeling and the influence of protection mechanisms on carbon pool residence times.

  6. 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…

  7. 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…

  8. 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…

  9. 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…

  10. Observatory enabled modeling of the Global Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Schimel, D.; Fox, A. M.; Moore, D. J.; Sacks, W. J.; Berukoff, S. J.

    2011-12-01

    A central challenge to global modeling of the terrestrial carbon cycle is the scaling of organism-scale characteristics to large regions. Emerging ground- and space-based global observatories will allow coupling observations directly to state and parameter values in a state-of-the-art coupled carbon climate model. Model-data fusion will qualitatively improve understanding and forecasting of interannual to centennial scale responses of terrestrial ecosystems and carbon cycle to global environmental change. This modeling study will use the baseline measures of global terrestrial ecosystem biochemical composition to reduce uncertainty in forecasting E&CC responses to climate and land-use change. The NCAR Community Land Model (Community Land Model - Carbon/Nitrogen or CLM-CN) simulates carbon, water and energy exchange at the land surface and includes detailed parameters governing plant-mediated fluxes and storage NEON and NCAR are developing a data assimilation version of the CLM, designed to work with new observatory data. Data requirements of CLM are quite different from earlier generation land surface models because the nitrogen cycle is explicitly simulated. Nitrogen concentrations regulate plant photosynthesis and decomposition of dead organic matter but their within biome and global distributions are poorly constrained by observations. Developing a Observatory-enabled version of the CLM, and the cyberinfrastructure to support it creates a very different set of requirements for modeling and observatory information systems than traditional approaches. In the talk, we will discuss briefly the science of carbon data assimilation and the observing requirements it generates.

  11. A weekly cycle in atmospheric carbon dioxide

    NASA Astrophysics Data System (ADS)

    Cerveny, Randall S.; Coakley, Kevin J.

    2002-01-01

    We present a new statistic called the ``Mean Symmetrized Residual'' (MSR) for detection and quantification of a weekly cycle in measured daily atmospheric carbon dioxide (CO2). At the Mauna Loa Observatory in Hawaii, we conclude that CO2 concentrations, on average, are significantly lower (0.022 parts per million by volume, ppmv) on weekends (Saturday-Sunday) than during the rest of the week. Over the past twenty-five years, the variation of the mean values of MSR (as a function of day of the week) has been relatively stable. We speculate that the observed weekday/weekend variation in CO2 at Mauna Loa is the result of anthropogenic emissions on Hawaii and nearby sources. We do not detect a weekly cycle in daily CO2 concentration measured at South Pole, Antarctica. This methodology has applicability to a variety of datasets.

  12. 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.

  13. Evaluation of Linkages Between Carbon Cycling and Denitrification in Groundwater in Riparian Zones: a Case Study at the Guelph Lake Wetland

    NASA Astrophysics Data System (ADS)

    Barahona, M.; Aravena, R.; Wassenaar, L.; Elgood, R.

    2004-05-01

    One of the key factors that control denitrification in riparian zones is the availability of electron donors, specifically dissolved organic carbon (DOC). This study evaluates the linkage between carbon cycling and denitrification at a riparian wetland impacted by a high nitrate plume originated in agricultural upland areas. The site was monitored using 12 sets of piezometer nests installed at different depths along two transects. Samples were collected in order to examine the geochemical and isotopic changes of the groundwater along the flow path and evaluate the relationship between the carbon and nitrogen cycles. Nitrate concentration (~10 ppm) in the upstream areas is reduced to almost zero along the flow system in the riparian zone. This pattern is accompanied by a decrease in oxygen concentration and an enrichment in the δ 18O of the dissolved oxygen due to isotopic fractionation caused by oxygen consumption in the riparian zone. The nitrate pattern is also accompanied by an increase in dissolved inorganic carbon (DIC) and DOC concentrations. The DIC in the high nitrate area is characterized by δ 13C values between -10.4 and -12.2 \\permil changing to -12.6 and -15.3 \\permil in the denitrification area. The increase in DIC concentration is attributed to a carbon input coming from DOC that is acting as an electron donor for nitrate reduction. The main sources of DOC in the study area are the soil zone in the agricultural areas and the wetland sediments. The DOC in the upstream areas is characterized by δ 13C values between -17.6 and -22.1 \\permil attributed to a mixture of corn (C4 plants) and alfalfa (C3 plants) carbon. The δ 13C-DOC change to more depleted values as low as -28.4 \\permil in the denitrification areas. These changes are attributed to an input of DOC from the wetlands sediments, which are characterized, by high organic carbon and a δ 13C value around -29 \\permil. These results indicated the wetlands sediments play a major role as a

  14. 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

  15. Monitoring the Carbon Cycle from Space

    NASA Astrophysics Data System (ADS)

    Bréon, François-Marie

    Carbon dioxide is the main driver of climate change while methane is also an important contributor with the potential for large feedbacks. Both of these gases are emitted through anthropogenic activities but their concentration in the atmosphere are also controlled by natural fluxes. Currently, roughly half of anthropogenic CO2 emissions are absorbed by ocean and vegetation but the processes that control these sinks are still poorly understood. There is therefore a need to monitor the sources and sinks of carbon as well as parameters related to processes linked to these processes. Surfaces fluxes of gases, such as Carbon dioxide and methane, generate concentration gradients that can be monitored from space. In return, the measurement of concentration gradients can be used to estimate the surface fluxes, using atmospheric transport inversion methods. The past decade has seen strong improvements in our ability to monitor the atmospheric concentration gradients starting with the SCIAMACHY instrument onboard ENVISAT. The gradients are tiny however, due to the long lifetime or CO2 and methane in the atmosphere, and the measurement accuracy remains a challenge to really bring new knowledge on the Carbon fluxes from space. This may change with the launch of the NASA OCO-2 mission (first one was lost at launch) that is dedicated to the measurement of the atmospheric CO2 column. Although the long term trend of atmospheric Carbon concentration is linked to anthropogenic emissions, the annual cycle is driven by vegetation photosynthesis. Indeed, annual photosynthesis flux is typically ten times larger than the fossil-fuel emissions. The monitoring of vegetation dynamics from space dates back 30 years, but recent advances make it possible to estimate additional parameters such as the total vegetation biomass or tree height. Improved accuracy make it possible to identify the impact of meteorological events on the vegetation functioning.

  16. 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.

  17. 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.

  18. 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).

  19. The changing carbon cycle of the coastal ocean.

    PubMed

    Bauer, James E; Cai, Wei-Jun; Raymond, Peter A; Bianchi, Thomas S; Hopkinson, Charles S; Regnier, Pierre A G

    2013-12-05

    The carbon cycle of the coastal ocean is a dynamic component of the global carbon budget. But the diverse sources and sinks of carbon and their complex interactions in these waters remain poorly understood. Here we discuss the sources, exchanges and fates of carbon in the coastal ocean and how anthropogenic activities have altered the carbon cycle. Recent evidence suggests that the coastal ocean may have become a net sink for atmospheric carbon dioxide during post-industrial times. Continued human pressures in coastal zones will probably have an important impact on the future evolution of the coastal ocean's carbon budget.

  20. 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.

  1. 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

  2. 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.

  3. The biological pump and lower trophic level controls on carbon cycling in Lake Superior: Insights from a multi-pronged study

    NASA Astrophysics Data System (ADS)

    Schreiner, K. M.; Bramburger, A.; Ozersky, T.; Sheik, C.; Steinman, B. A.

    2016-02-01

    Lake Superior is the largest freshwater lake in the world, supporting economically important fisheries and providing drinking water to hundreds of thousands of people. In recent decades, summer surface water temperature and the intensity and duration of water column stratification in the lake has increased steadily. These physical changes have resulted in significant perturbations to lower trophic level ecosystem characteristics. Recent observations of Great Lakes plankton assemblages have revealed multi-decadal patterns of community reorganization, with increased relative abundance of taxa characteristic of warmer waters. These changes, coupled with changing nutrient concentrations and colonization by non-native taxa, threaten to shift trophic structure and carbon dynamics at the bottom of the food web. To this end, this study seeks to quantify the impacts of this ecosystem shift on carbon fixation, the biological pump, and organic carbon cycling in Lake Superior. Utilizing a combined sampling approach, in the summer of 2015 we collected water, sediment, and biological samples across a nearshore-to-offshore gradient in the western arm of Lake Superior. Analyses included the community composition of bacteria, archaea, phytoplankton, and zooplankton; water column carbon and nutrient speciation; algal pigments and pigment degradation products; and net primary productivity. The collection of surface sediments allowed for additional assessment of benthic-pelagic coupling. The novel combination of this wide-ranging set of analyses to a locally and globally important water body like Lake Superior allowed us to fully assess the interactions between lower trophic level biology and carbon and nutrient cycling throughout the water column. Preliminary data indicates that microbial community composition was variable across the western arm of Lake Superior and showed signs of stratification at individual stations (>100 m deep). Sample collection occurred soon after lake

  4. Biofuels Science and Facilities (Carbon Cycle 2.0)

    ScienceCinema

    Keasling, Jay D

    2016-07-12

    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/

  5. Energy Demand in China (Carbon Cycle 2.0)

    ScienceCinema

    Price, Lynn

    2016-07-12

    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/

  6. Carbon Cycle 2.0: Ashok Gadgil: global impact

    ScienceCinema

    Ashok Gadgi

    2016-07-12

    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/

  7. 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/

  8. Towards a quantitative understanding of the late Neoproterozoic carbon cycle.

    PubMed

    Bjerrum, Christian J; Canfield, Donald E

    2011-04-05

    The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today.

  9. Towards a quantitative understanding of the late Neoproterozoic carbon cycle

    PubMed Central

    Bjerrum, Christian J.; Canfield, Donald E.

    2011-01-01

    The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today. PMID:21422280

  10. Microphytobenthos biomass and community composition studied by pigment biomarkers: importance and fate in the carbon cycle of a tidal flat

    NASA Astrophysics Data System (ADS)

    Barranguet, C.; Herman, P. M. J.; Sinke, J. J.

    1997-12-01

    Microphytobenthos biomass and community composition were studied by the use of pigment biomarkers during one year at a tidal flat located in the Westerschelde (SW Netherlands). Benthic microphytes appeared to be an important carbon source in the Westerschelde, especially in the central part of the flat with a mean biomass as high as 65 mg Chl a m -2 in the superficial 1 mm of sediment. Diatoms (fucoxanthin, Chl c) dominated the population during both spring and autumn blooms. In summer microphytobenthic biomass decreased, and diatoms coexisted with Cyanobacteria (zeaxanthin) and Euglenophyceae (Chl b, zeaxanthin and lutein). The shift in the community composition may possibly be linked with the decrease in silicon concentration in the overlying water. The degradation and recycling of microphytobenthic biomass was assessed by the study of degraded chlorophyll pigments, and pigments in deeper sediment layers. The fate of microphytobenthos appears to include rapid bacterial degradation in spring, episodic grazing by benthic animals in surface layers of sediments in the centre of the flat, and export by resuspension in sediments more exposed to currents.

  11. Modeling Studies of Carbon Cycling at the Tapajos National Forest using the NASA-CASA Ecosystem Model

    NASA Astrophysics Data System (ADS)

    Klooster, S.; Potter, C.; Oliveira, R.; Carvalho, C.; Kramer, M.

    2004-12-01

    The NASA-CASA model is being compared to measurements of energy, water, and carbon exchange at Tapajos National Forest (TNF) tower sites. Daily and monthly model estimates of plant water flux and soil water content, ecosystem productivity, biogeochemical processes, trace gas emissions, and net carbon sequestration are evaluated here for prediction errors and seasonal trends. High resolution (less than 1-km) land cover images for 'footprint' areas of LBA tower sites are being used to define ecosystem model estimates and validation of predictions against measured tower fluxes of carbon and water exchange. Initial model results replicate the seasonal patterns in measured NEE fluxes at km 67, and are consistent with the findings that trees in the eastern Amazon are deeply rooted and their carbon fluxes are not highly stressed during relatively dry seasonal periods. Increased woody debris from past disturbance events could increase the CASA model's predicted loss of carbon to the atmosphere (increase NEE flux). Hence, LBA ecosystem models must better account for recent changes in the forest floor and soil carbon pools at tropical forest sites, specifically those related to disturbance.

  12. 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

  13. Marine biodiversity, ecosystem functioning, and carbon cycles.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Legendre, Louis

    2010-06-01

    Although recent studies suggest that climate change may substantially accelerate the rate of species loss in the biosphere, only a few studies have focused on the potential consequences of a spatial reorganization of biodiversity with global warming. Here, we show a pronounced latitudinal increase in phytoplanktonic and zooplanktonic biodiversity in the extratropical North Atlantic Ocean in recent decades. We also show that this rise in biodiversity paralleled a decrease in the mean size of zooplanktonic copepods and that the reorganization of the planktonic ecosystem toward dominance by smaller organisms may influence the networks in which carbon flows, with negative effects on the downward biological carbon pump and demersal Atlantic cod (Gadus morhua). Our study suggests that, contrary to the usual interpretation of increasing biodiversity being a positive emergent property promoting the stability/resilience of ecosystems, the parallel decrease in sizes of planktonic organisms could be viewed in the North Atlantic as reducing some of the services provided by marine ecosystems to humans.

  14. 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.

  15. 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.

  16. A regularization of the carbon cycle data-fusion problem

    NASA Astrophysics Data System (ADS)

    Delahaies, Sylvain; Roulstone, Ian; Nichols, Nancy

    2013-04-01

    Improving our understanding of the carbon cycle is an important component of modelling climate and the Earth system, and a variety of data assimilation techniques have been used to combine process models with different types of observational data. Here, we carry out a careful mathematical analysis on a simple, yet generic, version of the carbon allocation inverse problem. At the heart of a Bayesian approach to data-model fusion is the following problem: given a generalized observation operator H, and observations y, determine the model state x that minimizes |Hx - y| in a given norm. Such a problem is well-posed if a unique solution x = H-1y exists, and if the inverse of H is continuous. However, in discrete models such a problem can be ill-conditioned, and hence ill-posed, when the singular values of H decay to zero. Our analysis is carried out on the evergreen version of the Data Assimilation-Linked Ecosystem model (DALEC EV). DALEC EV depicts a forest ecosystem as a set of five carbon pools: the gross primary production (GPP) is calculated at a daily time step as a function of the foliar carbon and meteorological drivers, following a mass conservation principle the GPP is then entirely allocated to carbon pools and respiration via fluxes. While this model is very simple, it represents the basic processes simulated by more sophisticated models of the carbon cycle and the low dimension of the state variable (five carbon pools and eleven parameters) allows direct solution using otherwise hopeless methods. Using synthetic observations of net ecosystem exchange (NEE), defined as the difference between GPP and respirations, we study the conditioning of the inverse problem. We found that the generalized observation operator is ill-conditioned and we study the impact of various regularization techniques: generalized Tikhonov regularization, total least square etc. Finally we use the formalism of control theory to apply model reduction techniques to the regularization

  17. 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.

  18. 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.

  19. Reconciling carbon-cycle concepts, terminology, and methodology

    Treesearch

    F.S. III Chapin; G.M Woodwell; J.T. Randerson; G.M. Lovett; E.B. Rastetter; D.D. Baldocchi; D.A. Clark; M.E. Harmon; D.S. Schimel; Valentini R.; Wirth C.; Aber J.D.; Cole J.J.; Goulden M.L.; Harden J.W.; Heimann M.; Howarth R.W.; Matson P.A.; McGuire A.D.; Melillo J.M.; H.A. Mooney; J.C. Neff; R.A. Houghton; M.L. Pace; M.G. Ryan; S.W. Running; O.E. Sala; W.H. Schlesinger; E. D. Schulze

    2005-01-01

    Recent projections of climatic change have focused a great deal of scientific and public attention on patterns of carbon (C) cycling as well as its controls, particularly the factors that determine whether an ecosystem is a net source or sink of atmospheric carbon dioxide (CO2). Net ecosystem production (NEP), a central concept in C-cycling research, has been used by...

  20. A New U.S. Carbon Cycle Science Plan

    NASA Astrophysics Data System (ADS)

    Michalak, A. M.; Jackson, R.; Marland, G.; Sabine, C.

    2009-05-01

    The report "A U.S. carbon cycle science plan" (J. L. Sarmiento and S. C. Wofsy, U.S. Global Change Res. Program, Washington, D. C., 1999) outlined research priorities and promoted coordinated carbon cycle research across federal agencies in the United States for nearly a decade. Building on this framework and subsequent reports (http://www.carboncyclescience.gov/docs.php), a working group comprised of 27 scientists was formed in 2008 under the United States Carbon Cycle Science Program to review the 1999 Science Plan, and to develop an updated strategy for carbon cycle research for the period from 2010 to 2020. This comprehensive review is being conducted with wide input from the research and stakeholder communities. The recommendations of the Carbon Cycle Science Working Group (CCSWG) will go to U.S. agency managers who have collective responsibility for setting national carbon cycle science priorities and for sponsoring much of the carbon cycle research in the United States. This presentation will provide an update on the ongoing planning process, will outline the steps that the CCSWG is undertaking in building consensus towards an updated U.S. Carbon Cycle Science Plan, and will seek input on the best ways in which to coordinate efforts with ongoing and upcoming research in Canada and Mexico, as well as with ongoing work globally.

  1. 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.

  2. 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.

  3. 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

  4. 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

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

    PubMed

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

    2009-11-17

    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 approximately 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.

  6. 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

  7. 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.

  8. Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

    Treesearch

    Atul Jain; Xiaojuan Yang; Haroon Kheshgi; A. David McGuire; Wilfred Post; David. Kicklighter

    2009-01-01

    Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen...

  9. 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.

  10. Iron cycling at corroding carbon steel surfaces

    PubMed Central

    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 three 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Trailblazing the Carbon Cycle of Tropical Forests from Puerto Rico

    Treesearch

    Sandra Brown; Ariel Lugo

    2017-01-01

    We review the literature that led to clarifying the role of tropical forests in the global carbon cycle from a time when they were considered sources of atmospheric carbon to the time when they were found to be atmospheric carbon sinks. This literature originates from work conducted by US Forest Service scientists in Puerto Rico and their collaborators. It involves the...

  16. Carbon Cycle 2.0: Jay Keasling: Biofuels

    ScienceCinema

    Jay Keasling

    2016-07-12

    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.

  17. Carbon Cycle 2.0: Robert Cheng and Juan Meza

    ScienceCinema

    Robert Cheng and Juan Meza

    2016-07-12

    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.

  18. 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.

  19. Carbon Cycle 2.0: Nitash Balsara: Energy Storage

    ScienceCinema

    Nitash Balsara

    2016-07-12

    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.

  20. 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

  1. Incorporating Terrestrial Processes in Models of PETM Carbon Cycle Evolution

    NASA Astrophysics Data System (ADS)

    Bowen, G. J.

    2016-12-01

    Evidence for the massive, rapid release of carbon to the ocean/atmosphere/biosphere system at the onset of the PETM is unequivocal, but the sequence of feedbacks that governed the evolution and recovery of the carbon cycle over the subsequent 150,000 years of the event remain unclear. Sedimentological evidence suggests that much of the excess carbon was eventually sequestered as carbonate in marine sediments, but there is also significant and growing evidence for changes in continental carbon cycle processes, most of which have not been incorporated in models of the event. I describe several aspects of the observed or implied continental response to the PETM, including changes in ecosystem organic carbon storage, soil carbonate growth, and export of organic carbon to the marine margins. These processes, along with continental silicate weathering, have been incorporated in a terrestrial module for a simple box model of the PETM carbon cycle, which is being used to evaluate their potential impact on global carbon cycle response and recovery. Although changes in terrestrial organic carbon storage can help explain patterns of global carbon isotope change throughout the event, constraints from ocean pH records suggest that other mechanisms must have contributed to pacing the duration and recovery of the PETM. Model results suggest that enhanced soil carbonate formation and the provenance of organic carbon buried in continental margin sediments are two poorly constrained variables that could alter the interpretation and implications of the continental records. Given the strong potential for, and high uncertainty in, future changes in terrestrial carbon cycle processes, resolving the nature and long-term impacts of such changes during the PETM represents a major opportunity to leverage the geologic record of this hyperthermal to increase understanding of human-induced global change.

  2. Carbon cycle: Ocean dissolved organics matter

    NASA Astrophysics Data System (ADS)

    Amon, Rainer M. W.

    2016-12-01

    Large quantities of organic carbon are stored in the ocean, but its biogeochemical behaviour is elusive. Size-age-composition relations now quantify the production of tiny organic molecules as a major pathway for carbon sequestration.

  3. Marine biodiversity, ecosystem functioning, and carbon cycles

    PubMed Central

    Beaugrand, Grégory; Edwards, Martin; Legendre, Louis

    2010-01-01

    Although recent studies suggest that climate change may substantially accelerate the rate of species loss in the biosphere, only a few studies have focused on the potential consequences of a spatial reorganization of biodiversity with global warming. Here, we show a pronounced latitudinal increase in phytoplanktonic and zooplanktonic biodiversity in the extratropical North Atlantic Ocean in recent decades. We also show that this rise in biodiversity paralleled a decrease in the mean size of zooplanktonic copepods and that the reorganization of the planktonic ecosystem toward dominance by smaller organisms may influence the networks in which carbon flows, with negative effects on the downward biological carbon pump and demersal Atlantic cod (Gadus morhua). Our study suggests that, contrary to the usual interpretation of increasing biodiversity being a positive emergent property promoting the stability/resilience of ecosystems, the parallel decrease in sizes of planktonic organisms could be viewed in the North Atlantic as reducing some of the services provided by marine ecosystems to humans. PMID:20479247

  4. 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.

  5. The role of harvest residue in rotation cycle carbon balance in loblolly pine plantations

    Treesearch

    Asko Noormets; Steve G. Mcnulty; Jean-Christophe Domec; Michael Gavazzi; Ge Sun; John S. King

    2012-01-01

    Timber harvests remove a significant portion of ecosystem carbon. While some of the wood products moved off-site may last past the harvest cycle of the particular forest crop, the effect of the episodic disturbances on long-term on-site carbon sequestration is unclear. The current study presents a 25 year carbon budget estimate for a typical commercial loblolly pine...

  6. A Carbon Cycle Model for the Social-Ecological Process in Coastal Wetland: A Case Study on Gouqi Island, East China.

    PubMed

    Li, Yanxia; Xiong, Lihu; Zhu, Wenjia

    2017-01-01

    Coastal wetlands offer many important ecosystem services both in natural and in social systems. How to simultaneously decrease the destructive effects flowing from human activities and maintaining the sustainability of regional wetland ecosystems are an important issue for coastal wetlands zones. We use carbon credits as the basis for regional sustainable developing policy-making. With the case of Gouqi Island, a typical coastal wetlands zone that locates in the East China Sea, a carbon cycle model was developed to illustrate the complex social-ecological processes. Carbon-related processes in natural ecosystem, primary industry, secondary industry, tertiary industry, and residents on the island were identified in the model. The model showed that 36780 tons of carbon is released to atmosphere with the form of CO2, and 51240 tons of carbon is captured by the ecosystem in 2014 and the three major resources of carbon emission are transportation and tourism development and seawater desalination. Based on the carbon-related processes and carbon balance, we proposed suggestions on the sustainable development strategy of Gouqi Island as coastal wetlands zone.

  7. A Carbon Cycle Model for the Social-Ecological Process in Coastal Wetland: A Case Study on Gouqi Island, East China

    PubMed Central

    Xiong, Lihu; Zhu, Wenjia

    2017-01-01

    Coastal wetlands offer many important ecosystem services both in natural and in social systems. How to simultaneously decrease the destructive effects flowing from human activities and maintaining the sustainability of regional wetland ecosystems are an important issue for coastal wetlands zones. We use carbon credits as the basis for regional sustainable developing policy-making. With the case of Gouqi Island, a typical coastal wetlands zone that locates in the East China Sea, a carbon cycle model was developed to illustrate the complex social-ecological processes. Carbon-related processes in natural ecosystem, primary industry, secondary industry, tertiary industry, and residents on the island were identified in the model. The model showed that 36780 tons of carbon is released to atmosphere with the form of CO2, and 51240 tons of carbon is captured by the ecosystem in 2014 and the three major resources of carbon emission are transportation and tourism development and seawater desalination. Based on the carbon-related processes and carbon balance, we proposed suggestions on the sustainable development strategy of Gouqi Island as coastal wetlands zone. PMID:28286690

  8. 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

  9. 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.

  10. Path independence of climate and carbon cycle response over a broad range of cumulative carbon emissions

    NASA Astrophysics Data System (ADS)

    Herrington, T.; Zickfeld, K.

    2014-11-01

    Recent studies have identified an approximately proportional relationship between global warming and cumulative carbon emissions, yet the robustness of this relationship has not been tested over a broad range of cumulative emissions and emission rates. This study explores the path dependence of the climate and carbon cycle response using an Earth system model of intermediate complexity forced with 24 idealized emissions scenarios across five cumulative emission groups (1275-5275 Gt C) with varying rates of emission. We find the century-scale climate and carbon cycle response after cessation of emissions to be approximately independent of emission pathway for all cumulative emission levels considered. The ratio of global mean temperature change to cumulative emissions - referred to as the transient climate response to cumulative carbon emissions (TCRE) - is found to be constant for cumulative emissions lower than ∼1500 Gt C but to decline with higher cumulative emissions. The TCRE is also found to decrease with increasing emission rate. The response of Arctic sea ice is found to be approximately proportional to cumulative emissions, while the response of the Atlantic Meridional Overturning Circulation does not scale linearly with cumulative emissions, as its peak response is strongly dependent on emission rate. Ocean carbon uptake weakens with increasing cumulative emissions, while land carbon uptake displays non-monotonic behavior, increasing up to a cumulative emission threshold of ∼2000 Gt C and then declining.

  11. Effects of elevated atmospheric carbon dioxide on soil nitrogen cycling

    NASA Astrophysics Data System (ADS)

    Hofmockel, Kirsten S.

    elevated atmospheric CO2 on soil nitrogen cycling at the ecosystem scale, despite an increase in N demand of 0.86 g m-2 y -1 under elevated CO2. My results suggest that elevated CO2 does not alter soil nitrogen cycling at the decadal time scale. Retranslocation within trees and slowly cycling soil organic pools are likely supporting the increased N demand under elevated CO2. Longer-term studies may reveal differences in soil organic matter and carbon sequestration dynamics under ambient and elevated CO2.

  12. 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

  13. 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.

  14. Role of volcanic forcing on future global carbon cycle

    NASA Astrophysics Data System (ADS)

    Tjiputra, J. F.; Otterå, O. H.

    2011-02-01

    Using a fully coupled global climate-carbon cycle model, we assess the potential role of volcanic eruptions on future projection of climate change and its associated carbon cycle feedback. The volcanic-like forcings are applied together with business-as-usual IPCC-A2 carbon emissions scenario. We show that very large volcanic eruptions similar to Tambora lead to short-term substantial global cooling. However, over a long period, smaller but more frequent eruptions, such as Pinatubo, would have a stronger impact on future climate change. In a scenario where the volcanic external forcings are prescribed with a five-year frequency, the induced cooling immediately lower the global temperature by more than one degree before return to the warming trend. Therefore, the climate change is approximately delayed by several decades and by the end of the 21st century, the warming is still below two degrees when compared to the present day period. The cooler climate reduces the terrestrial heterotrophic respiration in the northern high latitude and increases net primary production in the tropics, which contributes to more than 45% increase in accumulated carbon uptake over land. The increased solubility of CO2 gas in seawater associated with cooler SST is offset by reduced CO2 partial pressure gradient between ocean and atmosphere, which results in small changes in net ocean carbon uptake. Similarly, there is nearly no change in the seawater buffer capacity simulated between the different volcanic scenarios. Our study shows that even in the relatively extreme scenario where large volcanic eruptions occur every five-years period, the induced cooling only leads to a reduction of 46 ppmv atmospheric CO2 concentration as compared to the reference projection of 878 ppmv, at the end of the 21st century. With respect to sulphur injection geoengineering method, our study suggest that small scale but frequent mitigation is more efficient than the opposite. Moreover, the longer we delay

  15. (The ocean's role in the global carbon cycle)

    SciTech Connect

    Joos, L.F.

    1990-12-20

    The traveler collaborated with Dr. J. L. Sarmiento of the Program in Atmospheric Sciences, Princeton University, and Dr. U. Siegenthaler of the University of Bern in box-model studies of the potential enhancement of oceanic CO{sub 2} uptake by fertilizing the southern ocean with iron. As a result of this collaboration, a letter describing the results was submitted to the journal Nature. Sensitivity studies were carried out to gain a better understanding of the processes involved for a hypothetical iron fertilization of the ocean. An article that describes this work has been submitted to the journal Global Biogeochemical Cycles. The traveler and U. Siegenthaler are preparing a journal article describing a box model of the global carbon cycle that is an extension of the one-dimensional box-diffusion model. The traveler attended Oceanography 590b at the University of Washington in Friday Harbor. While at Friday Harbor, he started to collaborate with Drs. M. Warner, R. Gammon, and J. Bullister, all from the University of Washington, Seattle, to calibrate the global carbon cycle model with chlorofluorocarbon (CFC)-11 and CFC-12. The traveler started collaboration with Drs. J. C. Orr and J. L. Sarmiento to calculate apparent eddy diffusivities from the Princeton three-dimensional ocean model. The work is conducted by the University of Bern, Switzerland (the traveler is principal investigator), for a US Department of Energy program managed by Oak Ridge National Laboratory.

  16. Carbon Cycle 2.0: Paul Alivisatos: Introduction

    ScienceCinema

    Paul Alivisatos

    2016-07-12

    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/

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

    ScienceCinema

    Ramesh, Ramamoorthy

    2016-07-12

    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/

  18. 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.

  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. 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

  1. The future of the North American carbon cycle - projections and associated climate change

    NASA Astrophysics Data System (ADS)

    Huntzinger, D. N.; Chatterjee, A.; Cooley, S. R.; Dunne, J. P.; Hoffman, F. M.; Luo, Y.; Moore, D. J.; Ohrel, S. B.; Poulter, B.; Ricciuto, D. M.; Tzortziou, M.; Walker, A. P.; Mayes, M. A.

    2016-12-01

    Approximately half of anthropogenic emissions from the burning of fossil fuels is taken up annually by carbon sinks on the land and in the oceans. However, there are key uncertainties in how carbon uptake by terrestrial, ocean, and freshwater systems will respond to, and interact with, climate into the future. Here, we outline the current state of understanding on the future carbon budget of these major reservoirs within North America and the globe. We examine the drivers of future carbon cycle changes, including carbon-climate feedbacks, atmospheric composition, nutrient availability, and human activity and management decisions. Progress has been made at identifying vulnerabilities in carbon pools, including high-latitude permafrost, peatlands, freshwater and coastal wetlands, and ecosystems subject to disturbance events, such as insects, fire and drought. However, many of these processes/pools are not well represented in current models, and model intercomparison studies have shown a range in carbon cycle response to factors such as climate and CO2 fertilization. Furthermore, as model complexity increases, understanding the drivers of model spread becomes increasingly more difficult. As a result, uncertainties in future carbon cycle projections are large. It is also uncertain how management decisions and policies will impact future carbon stocks and flows. In order to guide policy, a better understanding of the risk and magnitude of North American carbon cycle changes is needed. This requires that future carbon cycle projections be conditioned on current observations and be reported with sufficient confidence and fully specified uncertainties.

  2. How positive is the feedback between climate change and the carbon cycle?

    NASA Astrophysics Data System (ADS)

    Friedlingstein, P.; Dufresne, J. Â.€ńL.; Cox, P. M.; Rayner, P.

    2003-04-01

    Future climate change induced by atmospheric emissions of greenhouse gases is believed to have a large impact on the global carbon cycle. Several offline studies focusing either on the marine or on the terrestrial carbon cycle highlighted such potential effects. Two recent online studies, using ocean-atmosphere general circulation models coupled to land and ocean carbon cycle models, investigated in a consistent way the feedback between the climate change and the carbon cycle. These two studies used observed anthropogenic CO2 emissions for the 1860-1995 period and IPCC scenarios for the 1995-2100 period to force the climate - carbon cycle models. The study from the Hadley Centre group showed a very large positive feedback, atmospheric CO2 reaching 980 ppmv by 2100 if future climate impacts on the carbon cycle, but only about 700 ppmv if the carbon cycle is included but assumed to be insensitive to the climate change. The IPSL coupled climate - carbon cycle model simulated a much smaller positive feedback: climate impact on the carbon cycle leads by 2100 to an addition of less than 100 ppmv in the atmosphere. Here we perform a detailed feedback analysis to show that such differences are due to two key processes that are still poorly constrained in these coupled models: first Southern Ocean circulation, which primarily controls the geochemical uptake of CO2, and second vegetation and soil carbon response to global warming. Our analytical analysis reproduces remarkably the results obtained by the fully coupled models. Also it allows us to identify that, amongst the two processes mentioned above, the latter (the land response to global warming) is the one that essentially explains the differences between the IPSL and the Hadley results.

  3. Black carbon formation by savanna fires: Measurements and implications for the global carbon cycle

    NASA Astrophysics Data System (ADS)

    Kuhlbusch, T. A. J.; Andreae, M. O.; Cachier, H.; Goldammer, J. G.; Lacaux, J.-P.; Shea, R.; Crutzen, P. J.

    1996-10-01

    During a field study in southern Africa (Southern African Fire-Atmosphere Research Initiative (SAFARI-92)), black carbon formation was quantified in the residues of savanna fires. The volatilization ratios of C, H, N, and S were determined by measuring their contents in the fuel and residue loads on six experimental sites. The volatilization of sulfur (86 ± 8%) was significantly higher than previously reported. Volatilization of H, N, and S was significantly correlated with that of carbon, enabling us to estimate their volatilization during savanna fires by extrapolation from those of carbon. By partitioning the residues in various fractions (unburned, partially burned, and ash), a strong correlation between the H/C ratio in the residue and the formation of black carbon was obtained. The ratio of carbon contained in ash to carbon contained in the unburned and partially burned fraction is introduced as an indicator of the degree of charring. As nitrogen was enriched in the residue, especially in the ash fraction of >0.63 mm, this indicator may be useful for an assessment of nutrient cycling. We show that the formation of black carbon is dependent on the volatilization of carbon as well as the degree of charring. The ratio of black carbon produced to the carbon exposed to the fire in this field study (0.6-1.5%) was somewhat lower than in experimental fires under laboratory conditions (1.0-1.8%) which may be due to less complete combustion. The average ratio of black carbon in the residue to carbon emitted as CO2 ranged from 0.7 to 2.0%. Using these ratios together with various estimates of carbon exposed or emitted by savanna fires, the worldwide black carbon formation was estimated to be 10-26 Tg C yr-1 with more than 90% of the black carbon remaining on the ground. The formation of this black carbon is a net sink of biospheric carbon and thus of atmospheric CO2 as well as a source of O2.

  4. Engineering scoping study of the production of hydrogen and oxygen from the cerium oxide-sodium phosphate/carbonate thermochemical cycle

    SciTech Connect

    Goeller, H.E.

    1984-04-01

    One potential industrial application of solar energy is for the production of hydrogen (and oxygen) using a cycle of thermochemical reactions. This report provides a preliminary evaluation of the engineering feasibility of such an operation based on the cerium oxide-sodium phosphate/carbonate thermochemical cycle to produce 2 metric tons of hydrogen per day. Material and heat balances were developed, and equipment was sized. The preliminary pilot plant layout was then compared with a plant of the same capacity for producing hydrogen by the electrolysis of water. The use of water electrolysis seems superior and cheaper in all respects. 7 figures, 4 tables.

  5. Simulation of Interannual Variability in the Terrestrial Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Thompson, S. L.; Govindasamy, B.

    2001-12-01

    Recent observational and modeling studies have shown that the net flux of carbon from the global terrestrial ecosystem is subject to substantial interannual variability. We use an integrated atmospheric general circulation and biosphere dynamics model to investigate the nature and source of this variability in the terrestrial carbon cycle. The Community Climate Model 3 (CCM3) coupled to the Integrated Biosphere Simulator (IBIS 2) is used to perform a 16-member ensemble of AMIP-type present day simulations with observed sea surface temperatures (SSTs) for the period 1979-1992. Interannual global variations in terrestrial carbon uptake as simulated are of the proper magnitude and have good positive correlation with inferred uptake from observationally driven inverse modeling for the same time period. While our ensemble simulations do permit the extraction of a SST-driven signal, they also show that nearly 65% of interannual variability is driven by "internal" chaotic climate variability not related to variations in SST. This unforced interannual variability in carbon uptake appears to originate mainly from the unforced variability in Net Primary Productivity which in turn is driven by the chaotic variability in interannual precipitation and surface temperature. B06. Water, Energy, and Carbon Cycles in Terrestrial Systems: Measuring and Modeling From Site to Region Sponsor: Biogeosciences Conveners: Beverly Law Oregon State University 328 Richardson Hall, College of Forestry Corvallis, OR 973315752 USA Phone: +1-541-737-6111 fax: +1-541-737-1393 lawb@fsl.orst.edu Peter Thornton University of Montana NTSG, School of Forestry Missoula, MT 59812 USA Phone: +1-406-243-4326 fax: +1-406-243-4510 peter@ntsg.umt.edu Index terms: 0400 1851

  6. 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.

  7. Soil carbon model alternatives for ECHAM5/JSBACH climate model: Evaluation and impacts on global carbon cycle estimates

    NASA Astrophysics Data System (ADS)

    Thum, T.; RäIsäNen, P.; Sevanto, S.; Tuomi, M.; Reick, C.; Vesala, T.; Raddatz, T.; Aalto, T.; JäRvinen, H.; Altimir, N.; Pilegaard, K.; Nagy, Z.; Rambal, S.; Liski, J.

    2011-06-01

    The response of soil organic carbon to climate change might lead to significant feedbacks affecting global warming. This response can be studied by coupled climate-carbon cycle models but so far the description of soil organic carbon cycle in these models has been quite simple. In this work we used the coupled climate-carbon cycle model ECHAM5/JSBACH (European Center/Hamburg Model 5/Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg) with two different soil carbon modules, namely (1) the original soil carbon model of JSBACH called CBALANCE and (2) a new soil carbon model Yasso07, to study the interaction between climate variability and soil organic carbon. Equivalent ECHAM5/JSBACH simulations were conducted using both soil carbon models, with freely varying atmospheric CO2 for the last 30 years (1977-2006). In this study, anthropogenic CO2 emissions and ocean carbon cycle were excluded. The new model formulation produced soil carbon stock estimates that were much closer to measured values. It also captured better the seasonal cycle of the direct CO2 exchange measurements at the three grassland sites considered (RMS error reduced by 12%), while for the five forest sites also analyzed, the results were ambiguous and the RMS error was 12% larger for Yasso07 than for CBALANCE. As a response to climatic changes, Yasso07 showed greater release of soil carbon to the atmosphere than the original model formulation during the years 1977-2006. This emphasizes the need for better understanding the processes affecting soil carbon stocks and their turnover rates to predict the climatic feedbacks.

  8. Elevated CO2 influences microbial carbon and nitrogen cycling

    PubMed Central

    2013-01-01

    Background Elevated atmospheric CO2 (eCO2) has been shown to have significant effects on terrestrial ecosystems. However, little is known about its influence on the structure, composition, and functional potential of soil microbial communities, especially carbon (C) and nitrogen (N) cycling. A high-throughput functional gene array (GeoChip 3.0) was used to examine the composition, structure, and metabolic potential of soil microbial communities from a grassland field experiment after ten-year field exposure to ambient and elevated CO2 concentrations. Results Distinct microbial communities were established under eCO2. The abundance of three key C fixation genes encoding ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), carbon monoxide dehydrogenase (CODH) and propionyl-CoA/acetyl-CoA carboxylase (PCC/ACC), significantly increased under eCO2, and so did some C degrading genes involved in starch, cellulose, and hemicellulose. Also, nifH and nirS involved in N cycling were significantly stimulated. In addition, based on variation partitioning analysis (VPA), the soil microbial community structure was largely shaped by direct and indirect eCO2-driven factors. Conclusions These findings suggest that the soil microbial community structure and their ecosystem functioning for C and N cycling were altered dramatically at eCO2. This study provides new insights into our understanding of the feedback response of soil microbial communities to elevated CO2 and global change. PMID:23718284

  9. 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.

  10. Carbon Cycling and Storage in Mangrove Forests

    NASA Astrophysics Data System (ADS)

    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.

  11. 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.

  12. Nitrogen and carbon cycling in the North Sea and exchange with the North Atlantic—A model study, Part II: Carbon budget and fluxes

    NASA Astrophysics Data System (ADS)

    Kühn, Wilfried; Pätsch, Johannes; Thomas, Helmuth; Borges, Alberto V.; Schiettecatte, Laure-Sophie; Bozec, Yann; Prowe, A. E. Friederike

    2010-09-01

    The 3-d coupled physical-biogeochemical model ECOHAM (version 3) was applied to the Northwest-European Shelf (47°41'-63°53'N, 15°5'W-13°55'E) for the years 1993-1996. Carbon fluxes were calculated for the years 1995 and 1996 for the inner shelf region, the North Sea (511,725 km 2). This period was chosen because it corresponds to a shift from a very high winter-time North Atlantic Oscillation Index (NAOI) in 1994/1995, to an extremely low one in 1995/1996, with consequences for the North Sea physics and biogeochemistry. During the first half of 1996, the observed mean SST was about 1 °C lower than in 1995; in the southern part of the North Sea the difference was even larger (up to 3 °C). Due to a different wind regime, the normally prevailing anti-clockwise circulation, as found in winter 1995, was replaced by more complicated circulation patterns in winter 1996. Decreased precipitation over the drainage area of the continental rivers led to a reduction in the total (inorganic and organic) riverine carbon load to the North Sea from 476 Gmol C yr -1 in 1995 to 340 Gmol C yr -1 in 1996. In addition, the North Sea took up 503 Gmol C yr -1 of CO 2 from the atmosphere. According to our calculations, the North Sea was a sink for atmospheric CO 2, at a rate of 0.98 mol C m -2 yr -1, for both years. The North Sea is divided into two sub-systems: the shallow southern North Sea (SNS; 190,765 km 2) and the deeper northern North Sea (NNS; 320,960 km 2). According to our findings the SNS is a net-autotrophic system (net ecosystem production NEP>0) but released CO 2 to the atmosphere: 159 Gmol C yr -1 in 1995 and 59 Gmol C yr -1 in 1996. There, the temperature-driven release of CO 2 outcompetes the biological CO 2 drawdown. In the NNS, where respiratory processes prevail (NEP<0), 662 and 562 Gmol C yr -1 were taken up from the atmosphere in 1995 and 1996, respectively. Stratification separates the productive, upper layer from the deeper layers of the water column where

  13. 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.

  14. 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.

  15. [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.

  16. 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.

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

    ScienceCinema

    Cheng, Robert K; Meza, Juan

    2016-07-12

    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/

  18. 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.

  19. Path dependence of climate and carbon cycle response over a broad range of cumulative carbon emissions

    NASA Astrophysics Data System (ADS)

    Herrington, T.; Zickfeld, K.

    2014-06-01

    Recent studies have demonstrated the proportional relationship between global warming and cumulative carbon emissions, yet the robustness of this relationship has not been tested over a broad range of cumulative emissions and emission rates. This study explores the path dependence of the climate and carbon cycle response using an Earth System model of intermediate complexity forced with 24 idealized emissions scenarios across five cumulative emission groups (1275-5275 GtC) with varying rates of emission. We find the century-scale climate and carbon cycle response after cessation of emissions to be approximately independent of emission pathway for all cumulative emission levels considered. The ratio of global mean temperature change to cumulative emissions - referred to as the transient climate response to cumulative emissions (TCRE) - is found to be constant for cumulative emissions lower than ~1500 GtC, but to decline with higher cumulative emissions. The TCRE is also found to decrease with increasing emission rate. The response of Arctic sea ice is found to be approximately proportional to cumulative emissions, while the response of the Atlantic meridional overturning circulation (AMOC) does not scale linearly with cumulative emissions, as its peak response is strongly dependent on emission rate. Ocean carbon uptake weakens with increasing cumulative emissions, while land carbon uptake displays non-monotonic behavior, increasing up to a cumulative emission threshold of ~2000 GtC and then declining.

  20. Mixed-layer carbon cycling at the Kuroshio Extension Observatory

    NASA Astrophysics Data System (ADS)

    Fassbender, Andrea J.; Sabine, Christopher L.; Cronin, Meghan F.; Sutton, Adrienne J.

    2017-02-01

    Seven years of data from the NOAA Kuroshio Extension Observatory (KEO) surface mooring, located in the North Pacific Ocean carbon sink region, were used to evaluate drivers of mixed-layer carbon cycling. A time-dependent mass balance approach relying on two carbon tracers was used to diagnostically evaluate how surface ocean processes influence mixed-layer carbon concentrations over the annual cycle. Results indicate that the annual physical carbon input is predominantly balanced by biological carbon uptake during the intense spring bloom. Net annual gas exchange that adds carbon to the mixed layer and the opposing influence of net precipitation that dilutes carbon concentrations make up smaller contributions to the annual mixed-layer carbon budget. Decomposing the biological term into annual net community production (aNCP) and calcium carbonate production (aCaCO3) yields 7 ± 3 mol C m-2 yr-1 aNCP and 0.5 ± 0.3 mol C m-2 yr-1 aCaCO3, giving an annually integrated particulate inorganic carbon to particulate organic carbon production ratio of 0.07 ± 0.05, as a lower limit. Although we find that vertical physical processes dominate carbon input to the mixed layer at KEO, it remains unclear how horizontal features, such as eddies, influence carbon production and export by altering nutrient supply as well as the depth of winter ventilation. Further research evaluating linkages between Kuroshio Extension jet instabilities, eddy activity, and nutrient supply mechanisms is needed to adequately characterize the drivers and sensitivities of carbon cycling near KEO.

  1. Linking brownification to carbon cycling in headwater streams

    NASA Astrophysics Data System (ADS)

    Fasching, C.; Behounek, B.; Singer, G. A.; Battin, T. J.

    2013-12-01

    Brownification of inland waters is becoming a global phenomenon with major implications for aquatic ecology and drinking water supply. The unprecedented export of humic substances from the terrestrial environment causes this notable change in colour of stream and lake waters. Given the net heterotrophy of most inland waters, altered carbon fluxes may impact microbial metabolism and ultimately carbon dioxide emissions from these inland waters. Yet the implications for carbon cycling remain elusive. Here, we investigate the coupling of microbial metabolism, organic carbon characteristics and streamwater CO2 concntration along a brownification gradient in 20 headwater streams draining catchments covered with coniferous forest and peatland in the Bohemian Massive, Austria. We break down brownification into its components of concentration and quality, and relate each to carbon cycling in headwater streams. Brownification did not only increase streamwater dissolved organic matter (DOM) concentration but also induced changes in DOM quality. Humic-like and aromatic compounds of terrigenous origin -- conferring the brown colour to the water -- were metabolised by microbial heterotrophs in the streamwater yet at the cost of low carbon use efficiency (CUE). Potential CO2 evasion from headwaters was controlled by the quantity of bioavailable carbon as well as by the coupling of carbon qulity and microbial metabolism. This implies brownification to contribute to CO2 evasion from streams as a large fraction of terrigenous organic carbon is respired by microbial heterotrophs along the flow path. Our results illuminate the impact of brownification on carbon cycling which may gain relevance as global change progresses.

  2. 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.

  3. 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

    2016-02-02

    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.

  4. 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

  5. Reservoirs as hotspots of fluvial carbon cycling in peatland catchments.

    PubMed

    Stimson, A G; Allott, T E H; Boult, S; Evans, M G

    2017-02-15

    Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km(2)) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO2(aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by (14)C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. 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.

  7. 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

  8. Recent climate-induced variations in terrestrial carbon cycle over tropics: A model simulation

    NASA Astrophysics Data System (ADS)

    Ichii, K.; Nemani, R. R.; Hashimoto, H.

    2003-12-01

    Tropical forests accounts for about 20 percent of the world terrestrial carbon and one-third of global terrestrial NPP. Atmospheric inversion studies show that additional factors such as CO2 fertilization and climate changes, should work as a carbon sink despite of CO2 emission due to deforestation in tropical regions. However, responses of tropical ecosystems to environmental changes and current carbon sink mechanisms are still unknown. The goal of this study is (1) to characterize the climate influences on tropical carbon cycle such as GPP, NPP and NEP, and (2) to analyze recent interannual variations in terrestrial carbon cycle over tropics. We investigated the relationship between climate factors (temperature, precipitation, radiation, and VPD) and several carbon cycle components, and analyzed recent carbon cycle variations over tropics using Biome BGC with NCEP reanalysis climate data from 1982 to 1999. In tropical ecosystems, interannual variations in GPP are mainly explained by radiation variations, and temperature and precipitation variation are secondary important. NPP and NEP interannual variations are primarily determined by temperature variation, and radiation came as a secondary important factors. Precipitation, which was considered as an important climate factor that control interannual variations in carbon cycle in tropics, has little effects on interannual variation in tropical carbon cycle possibly because of abundant rainfall. Then, recent interannual variations in terrestrial carbon cycle over tropics were analyzed from 1982-1999. Tropics show gradual increases in GPP, NPP, and NEP at a rate of several percent per recent 18 years with large drop in 1998. Both climate change and CO2 fertilization have impact on recent enhancement of terrestrial carbon uptake. Of all climate factors, radiation-induced enhancement shows important role in enhancing CO2 uptake over Amazon. On the other hand, variations in precipitation and vapor pressure did not make

  9. 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

  10. Investigators share improved understanding of the North American carbon cycle

    Treesearch

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

    2007-01-01

    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 American and adjacent oceans, and to chart a course for improved integration across scientifi c disciplines, scales, and Earth system boundaries. The meeting participants also addressed the need for...

  11. Carbon cycle observations: gaps threaten climate mitigation policies

    Treesearch

    Richard Birdsey; Nick Bates; MIke Behrenfeld; Kenneth Davis; Scott C. Doney; Richard Feely; Dennis Hansell; Linda Heath; et al.

    2009-01-01

    Successful management of carbon dioxide (CO2) requires robust and sustained carbon cycle observations. Yet key elements of a national observation network are lacking or at risk. A U.S. National Research Council review of the U.S. Climate Change Science Program earlier this year highlighted the critical need for a U.S. climate observing system to...

  12. 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.

  13. 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.

  14. Sulphur constraints on the carbon cycle

    NASA Astrophysics Data System (ADS)

    Worrall, Fred; Boothroyd, Ian; Moody, Catherine; Clay, Gareth; Burt, Tim

    2017-04-01

    This study considered the stoichiometry and energy content of organic matter reservoirs and fluxes through and from a peatland. The stoichiometry and energy content were used to constrain the carbon budget of the peatland and the stoichiometric constraints showed that the transition to deep peat was limited by the availability of electron acceptors. The stoichiometry suggests there is insufficient energy available in the organic matter to produce CH4. The alternative pathways need either to use sulphate as a terminal electron acceptor or to use the DOM present in the peat pore water as the energy source. To test these explanations this study considered the sulphur budget of this peatand and the composition of the DOM in the peat profile pore water. Samples of each organic matter reservoir and flux were collected and analysed for their elemental content including S. The samples analysed were: aboveground, belowground, heather, mosses and sedges, litter layer, a peat core, and monthly samples of stream particulate and dissolved organic matter. The dissolved organic matter included samples from the streamwater and two depths within the peat profile. The composition of the organic matter was viewed in the context of ongoing measurement of inorganic S within the catchment which included precipitation, pore waters and stream water.

  15. 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?

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. Comparison of Anthropogenic CO2, NOx, and CO Emissions: Exploiting a Synergy Between Air Quality and Carbon Cycle Studies

    NASA Astrophysics Data System (ADS)

    Fischer, M. L.; Gurney, K. R.; Gregg, J. S.; Murtishaw, S.; Knox, S.; Andres, R. J.; Sieb, B.

    2005-05-01

    Studies of biospheric CO2 exchange at the regional to continental scale would be facilitated by spatiotemporally resolved estimates of CO2 emissions from fossil fuel combustion and other human activities. However, current estimates of fossil CO2 emissions do not provide sufficient temporal or spatial resolution for regional-scale investigations. The US-EPA National Emission Inventory (NEI) for criteria pollutants (e.g., NOx and CO) was developed for control of regional air quality and currently provides high resolution emissions estimates that are based, in part on, estimates of fuel consumption. Here we investigate the applicability of estimating CO2 emissions from either 1) NEI estimates of NOx or CO emissions, or 2) underlying information on fuel use contained within NEI. First, we calculate monthly sums of NOx and CO emissions separately for mobile, distributed area, and point sources for the 48 continental United States. We compare the aggregate NOx and CO emissions with monthly sums of each states CO2 emissions computed from sales of petroleum, natural gas, and coal as reported by the US Energy Information Agency (EIA). We then compute linear regressions to estimate CO:CO2 and NOx:CO2 emissions ratios and quantify the fraction of variance in CO2 captured by NOx and CO. Although the categories in the two data sets do not overlap perfectly, we find that in the cases where a close correspondence between fuel type and use is expected (e.g., petroleum and mobile sources), variations in NOx and CO explain approximately 80% of the variation in CO2 emissions. Second, we employ the Consolidated Community Emissions Processing Tool (CONCEPT) framework to extract estimates of fuel use or other proxy variables and estimate CO2 directly from the information contained in the NEI, and compare with the EIA estimates of CO2 emissions, and with NEI estimates of NOx and CO emissions as above. Finally, we discuss these results with consideration of previous atmospheric

  1. Comparison of Anthropogenic CO2, NOx, and CO Emissions: Exploiting a Synergy Between Air Quality and Carbon Cycle Studies

    NASA Astrophysics Data System (ADS)

    Fischer, M. L.; Gurney, K. R.; Gregg, J. S.; Murtishaw, S.; Knox, S.; Andres, R. J.; Sieb, B.

    2006-12-01

    Studies of biospheric CO2 exchange at the regional to continental scale would be facilitated by spatiotemporally resolved estimates of CO2 emissions from fossil fuel combustion and other human activities. However, current estimates of fossil CO2 emissions do not provide sufficient temporal or spatial resolution for regional-scale investigations. The US-EPA National Emission Inventory (NEI) for criteria pollutants (e.g., NOx and CO) was developed for control of regional air quality and currently provides high resolution emissions estimates that are based, in part on, estimates of fuel consumption. Here we investigate the applicability of estimating CO2 emissions from either 1) NEI estimates of NOx or CO emissions, or 2) underlying information on fuel use contained within NEI. First, we calculate monthly sums of NOx and CO emissions separately for mobile, distributed area, and point sources for the 48 continental United States. We compare the aggregate NOx and CO emissions with monthly sums of each states CO2 emissions computed from sales of petroleum, natural gas, and coal as reported by the US Energy Information Agency (EIA). We then compute linear regressions to estimate CO:CO2 and NOx:CO2 emissions ratios and quantify the fraction of variance in CO2 captured by NOx and CO. Although the categories in the two data sets do not overlap perfectly, we find that in the cases where a close correspondence between fuel type and use is expected (e.g., petroleum and mobile sources), variations in NOx and CO explain approximately 80% of the variation in CO2 emissions. Second, we employ the Consolidated Community Emissions Processing Tool (CONCEPT) framework to extract estimates of fuel use or other proxy variables and estimate CO2 directly from the information contained in the NEI, and compare with the EIA estimates of CO2 emissions, and with NEI estimates of NOx and CO emissions as above. Finally, we discuss these results with consideration of previous atmospheric

  2. Carbon corrosion in PEM fuel cells during drive cycle operation

    DOE PAGES

    Borup, Rodney L.; Papadias, D. D.; Mukundan, Rangachary; ...

    2015-09-14

    One of the major contributors to degradation involves the electrocatalyst, including the corrosion of the carbons used as catalyst supports, which leads to changes in the catalyst layer structure. We have measured and quantified carbon corrosion during drive cycle operation and as a variation of the upper and lower potential limits used during drive cycle operation. The amount of carbon corrosion is exacerbated by the voltage cycling inherent in the drive cycle compared with constant potential operation. The potential gap between upper and lower potentials appears to be more important than the absolute operating potentials in the normal operating potentialmore » regime (0.40V to 0.95V) as changes in the measured carbon corrosion are similar when the upper potential was lower compared to raising the lower potential. Catalyst layer thinning was observed during the simulated drive cycle operation which had an associated decrease in catalyst layer porosity. This catalyst layer thinning is not due solely to carbon corrosion, although carbon corrosion likely plays a role; much of this thinning must be from compaction of the material in the catalyst layer. As a result, the decrease in catalyst layer porosity leads to additional performance losses due to mass transport losses.« less

  3. Carbon corrosion in PEM fuel cells during drive cycle operation

    SciTech Connect

    Borup, Rodney L.; Papadias, D. D.; Mukundan, Rangachary; Spernjak, Dusan; Langlois, David Alan; Ahluwalia, Rajesh; More, Karen L.; Grot, Steve

    2015-09-14

    One of the major contributors to degradation involves the electrocatalyst, including the corrosion of the carbons used as catalyst supports, which leads to changes in the catalyst layer structure. We have measured and quantified carbon corrosion during drive cycle operation and as a variation of the upper and lower potential limits used during drive cycle operation. The amount of carbon corrosion is exacerbated by the voltage cycling inherent in the drive cycle compared with constant potential operation. The potential gap between upper and lower potentials appears to be more important than the absolute operating potentials in the normal operating potential regime (0.40V to 0.95V) as changes in the measured carbon corrosion are similar when the upper potential was lower compared to raising the lower potential. Catalyst layer thinning was observed during the simulated drive cycle operation which had an associated decrease in catalyst layer porosity. This catalyst layer thinning is not due solely to carbon corrosion, although carbon corrosion likely plays a role; much of this thinning must be from compaction of the material in the catalyst layer. As a result, the decrease in catalyst layer porosity leads to additional performance losses due to mass transport losses.

  4. The changing global carbon cycle: linking local plant-soil carbon dynamics to global consequences

    Treesearch

    F. Stuart Chapin; Jack McFarland; A. David McGuire; Eugenie S. Euskirchen; Roger W. Ruess; Knut. Kielland

    2009-01-01

    Most current climate-carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR,...

  5. 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.

  6. 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. © 2016 John Wiley & Sons Ltd/CNRS.

  7. Mineralogical Controls on Carbon Cycling in a Floodplain Environment

    NASA Astrophysics Data System (ADS)

    Arora, B.; Dwivedi, D.; Steefel, C. I.; Spycher, N.; Fox, P. M.; Nico, P. S.

    2016-12-01

    With the overarching goal of understanding mineral-organic-microbe interactions on carbon and nutrient cycles, we are developing a reactive transport model that includes carbon (C) pools and transformations, a realistic treatment of protected C pools, multiple decomposition pathways, and radiocarbon (14C) dynamics. The objective of the modeling is to understand the impact of mineralogy on carbon turnover and residence times in a floodplain site in Rifle, CO. Previous studies have identified naturally reduced zones (NRZs) in the saturated zone of the Rifle site to be C hotspots and regions characterized by diffusion-limited transport and high rates of microbially-mediated biogeochemical reactions. Detailed characterization of the soil organic matter in both the NRZ and non-NRZ sediments at the Rifle site including radiocarbon dating, and extraction and chemical characterization of mineral-bound pool of organic matter, is used to inform the modeling. In this study, we describe the development of a coupled unsaturated-saturated flow and biogeochemical reactive transport model of the Rifle site along a two-dimensional cross-section (parallel to groundwater flow). The biogeochemical reaction network includes representations of bacterial and fungal activity, archetypal polymer and monomer carbon substrate groups, kinetic and equilibrium mineral precipitation and dissolution reactions, and aqueous and surface complexation. We use this model to explore fungal and bacterial community emergence at the site and compare organo-mineral interactions across NRZ and non-NRZ regions. Observed 14C profiles suggest that sediment-associated carbon in NRZ locations is much older than both the depositional age of the floodplain sediments and dissolved organic carbon in the groundwater. Model simulations were able to capture the observed soil organic matter (SOM) and ∆14C profiles across the Rifle site. Modeling results show higher lignin content in the NRZ sediments and greater Fe

  8. Interannual variability in the global carbon cycle

    NASA Astrophysics Data System (ADS)

    Houghton, R. A.

    2000-08-01

    The annual growth rate of atmospheric CO2 has varied between 1 and 5 Pg C yr-1 over the last decades. Most of this variation is associated with terrestrial and oceanic exchanges of carbon which seem to vary independently. Three processes contribute to the annual flux of carbon from terrestrial ecosystems: changes in land use, natural disturbances, and metabolic changes caused by variations in climate. Because rates of land-use change are often not available on an annual basis, estimates of the flux of carbon attributable to land use change may underestimate year-to-year variability. Limited data reviewed here suggest that the interannual variability of this flux is generally small for two reasons. First, although rates of land use change may vary substantially from year to year at a local scale, variability is generally less at regional and global scales because high rates of deforestation in one area do not necessarily coincide with high rates in other areas. Second, less than 50% of the carbon lost to the atmosphere as a result of land use change is lost in the year of disturbance; the rest is released in subsequent years. The interannual variability of the flux of carbon from land use change is thus less variable than rates of land use change and probably accounts, globally, for less than 5-10% of the observed variation in the annual growth rate of CO2 in the atmosphere. Natural disturbances are estimated to account for a similar fraction of the variation. The most important contributor appears to be the effect of short-term changes in climate (temperature and precipitation) on terrestrial metabolism. Over the period 1980-1995, year-to-year differences in the flux of carbon from terrestrial metabolism have almost been as large as variations in the growth rate of atmospheric CO2.

  9. The Carboniferous carbon isotope record from sedimentary organic matter: can we disentangle the carbon cycle?

    NASA Astrophysics Data System (ADS)

    Davies, S. J.; Bennett, C. E.; Leng, M. J.; Kearsey, T.; Marshall, J. E.; Millward, D.; Reeves, E. J.; Snelling, A.; Sherwin, J. E.

    2014-12-01

    A comprehensive analysis of the δ13C composition of sedimentary organic matter from Euramerican Carboniferous successions indicates there are significant shifts in δ13C through this key time interval. Our studies have revealed that, at an individual location, the source and delivery mechanism of the sediment contribute to the type of organic matter preserved and, in turn this influences the measured δ13C values from bulk sedimentary organic matter of organic matter. In general, where marine-derived organic matter is dominant in these Carboniferous successions then δ13C values are characteristically lower compared to the higher values encountered where terrestrial plant-derived material is most abundant. The implication of these observations is that an apparent carbon isotope excursion identified from the bulk organic matter may reflect a change in transport processes, or depositional environment, rather than a perturbation in the global carbon cycle. In our most recent studies, however, we compare δ13C values from specific wood fragments and bulk sedimentary organic matter from non-marine, marine basinal, and marine shelfal successions from the earliest Mississippian through to the early Pennsylvanian. These data indicate that early Mississippian δ13C of organic matter is far less negative (around -22%0) than material of Late Mississippian age (around -26%0), however by the early Pennsylvanian, δ13C values return to -22%0. There are some δ13C data from brachiopod carbonate from this time interval and similar shifts are indicated. Our data are beginning to address whether we can identify a primary carbon cycle signal from the Carboniferous record using δ13C from a range of sedimentary environments. If we can, there are still questions around what the record is telling us about the global carbon cycle during a period when plant groups, including lycopods and seed ferns, rapidly diversified.

  10. 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.

  11. 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.

  12. State of the Carbon Cycle of North America: Overarching Findings

    NASA Astrophysics Data System (ADS)

    Mayes, M. A.; Reed, S.; Najjar, R.; Romero-Lankao, P.; Birdsey, R.

    2016-12-01

    This presentation will provide an overarching summary of the second "State of the Carbon Cycle of North America Report" (SOCCR2) from the perspective of the five editorial lead authors. The chapters of SOCCR2 represent a major update and much new material since the original report published a decade ago. The new report includes an overview of the North American carbon budget and future projections, the consequences of changes to the carbon budget, details of the carbon budget in major terrestrial and aquatic ecosystems and anthropogenic drivers, and implications for carbon management. The chapters focus on advances since the 2007 report, but also include new focus areas such as soil carbon, tribal lands, as well as greater emphasis on aquatic systems and the role of societal drivers and decision making on the carbon cycle. In addition, methane and the role of nitrogen will be considered to a greater extent than before. Each chapter also contains a section focusing on national and regional accounting to complement the overarching North American framework. In conclusion, SOCCR2 is expected to provide an updated assessment and a unique perspective on the carbon cycle, which will contribute to the next U.S. National Climate Assessment.

  13. 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.

  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. Carbon Cycling in Wetland Forest Soils

    Treesearch

    Carl C. Trettin; Martin F. Jurgensen

    2003-01-01

    Wetlands comprise a small proportion (i.e., 2 to 3%) of earth's terrestrial surface, yet they contain a significant proportion of the terrestrial carbon (C) pool. Soils comprise the largest terrestrial C pool (ca. 1550 Pg C in upper 100 cm; Eswaran et al., 1993; Batjes, 1996), and wetlands contain the single largest component, with estimates ranging between 18...

  16. Carbon Isotopes in Ocean and Land Carbon Cycle Models: Atmospheric Forcing Data and Applications for CMIP6 and Beyond

    NASA Astrophysics Data System (ADS)

    Graven, H. D.; Allison, C. E.; Etheridge, D. M.; Hammer, S.; Keeling, R. F.; Krummel, P. B.; Langenfelds, R. L.; Levin, I.; Rubino, M.; Trudinger, C. M.; Vaughn, B. H.; White, J. W. C.

    2016-12-01

    The carbon isotopic composition of ocean and land carbon reservoirs is influenced by fossil fuel burning, carbon residence time, and fractionation associated with biological and physical processes. Additionally, 14C produced during nuclear weapons testing in the 1950s and 60s has enriched 14C/C ratios in decadally overturning reservoirs. Comparisons of simulated 14C and 13C dynamics between models and with observations can provide insights to key processes in the global carbon cycle including air-sea gas exchange, ocean mixing, terrestrial drought response, and vegetation and soil carbon turnover rates. However, the inclusion of carbon isotopes in large-scale model intercomparisons has so far been limited. One study, the Ocean Carbon Cycle Model Intercomparison Project 2 (OCMIP2), used simulations of ocean 14C to identify biases in model ocean circulation that affect simulated anthropogenic CO2 uptake and marine biogeochemistry. Within the context of CMIP6, we are working to advance the use of carbon isotopes for carbon cycle science, model evaluation and model intercomparison. The variables requested for DECK, OMIP and C4MIP simulations in CMIP6 include stocks and fluxes of 14C and 13C (for models that simulate 14C and 13C). We will present the historical and future atmospheric forcing datasets for Δ14C and δ13C in CO2 that we are making available to modeling groups as part of CMIP6. The historical data uses atmospheric measurements and ice core and tree ring records. For future atmospheric forcing, we use a simple carbon cycle model with CO2 emissions and atmospheric CO2 concentration for different scenarios from ScenarioMIP. We will also describe potential applications for carbon isotope simulations from CMIP6 or other modeling activities. In particular, we will present an evaluation of terrestrial carbon turnover with simulations of bomb-derived 14C inventories in simplified off-line models based on carbon stocks and fluxes in CMIP5 terrestrial models.

  17. The Carbon Cycle: Implications for Climate Change and Congress

    DTIC Science & Technology

    2008-03-13

    GtC per year) CRS-4 10 An exception to this is the concept of carbon capture and sequestration, whereby the geologic time scale cycle of carbon storage...7139 (April 26, 2007): pp. 1070-1074. 49 For more information about injection of CO2 into the deep oceans, see CRS Report RL33801, Carbon Capture and...before it is released to the atmosphere and injecting it back into geological reservoirs — carbon capture and sequestration — is one possible strategy to

  18. The seasonal cycle of carbonate system processes in Ryder Bay, West Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Legge, Oliver J.; Bakker, Dorothee C. E.; Meredith, Michael P.; Venables, Hugh J.; Brown, Peter J.; Jones, Elizabeth M.; Johnson, Martin T.

    2017-05-01

    The carbon cycle in seasonally sea-ice covered waters remains poorly understood due to both a lack of observational data and the complexity of the system. Here we present three consecutive seasonal cycles of upper ocean dissolved inorganic carbon (DIC) and total alkalinity measurements from Ryder Bay on the West Antarctic Peninsula. We attribute the observed changes in DIC to four processes: mixing of water masses, air-sea CO2 flux, calcium carbonate precipitation/dissolution and photosynthesis/respiration. This approach enables us to resolve the main drivers of the seasonal DIC cycle and also investigate the mechanisms behind interannual variability in the carbonate system. We observe a strong, asymmetric seasonal cycle in the carbonate system, driven by physical processes and primary production. In summer, melting glacial ice and sea ice and a reduction in mixing with deeper water reduce the concentration of DIC in surface waters. The dominant process affecting the carbonate system is net photosynthesis which reduces DIC and the fugacity of CO2, making the ocean a net sink of atmospheric CO2. In winter, mixing with deeper, carbon-rich water and net heterotrophy increase surface DIC concentrations, resulting in pH as low as 7.95 and aragonite saturation states close to 1. We observe no clear seasonal cycle of calcium carbonate precipitation/dissolution but some short-lived features of the carbonate time series strongly suggest that significant precipitation of calcium carbonate does occur in the Bay. The variability observed in this study demonstrates that changes in mixing and sea-ice cover significantly affect carbon cycling in this dynamic environment. Maintaining this unique time series will allow the carbonate system in seasonally sea-ice covered waters to be better understood.

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

    USDA-ARS?s Scientific Manuscript database

    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...

  20. Equilibration of the terrestrial water, nitrogen, and carbon cycles.

    PubMed

    Schimel, D S; Braswell, B H; Parton, W J

    1997-08-05

    Recent advances in biologically based ecosystem models of the coupled terrestrial, hydrological, carbon, and nutrient cycles have provided new perspectives on the terrestrial biosphere's behavior globally, over a range of time scales. We used the terrestrial ecosystem model Century to examine relationships between carbon, nitrogen, and water dynamics. The model, run to a quasi-steady-state, shows strong correlations between carbon, water, and nitrogen fluxes that lead to equilibration of water/energy and nitrogen limitation of net primary productivity. This occurs because as the water flux increases, the potentials for carbon uptake (photosynthesis), and inputs and losses of nitrogen, all increase. As the flux of carbon increases, the amount of nitrogen that can be captured into organic matter and then recycled also increases. Because most plant-available nitrogen is derived from internal recycling, this latter process is critical to sustaining high productivity in environments where water and energy are plentiful. At steady-state, water/energy and nitrogen limitation "equilibrate," but because the water, carbon, and nitrogen cycles have different response times, inclusion of nitrogen cycling into ecosystem models adds behavior at longer time scales than in purely biophysical models. The tight correlations among nitrogen fluxes with evapotranspiration implies that either climate change or changes to nitrogen inputs (from fertilization or air pollution) will have large and long-lived effects on both productivity and nitrogen losses through hydrological and trace gas pathways. Comprehensive analyses of the role of ecosystems in the carbon cycle must consider mechanisms that arise from the interaction of the hydrological, carbon, and nutrient cycles in ecosystems.

  1. 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.

  2. 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.

  3. 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.

  4. Effect of Vinylene Carbonate on Graphite Anode Cycling Efficiency

    SciTech Connect

    Ridgway, Paul; Zheng, Honghe; Liu, Gao; Song, Xiangun; Ross, Philip; Battaglia, Vincent

    2009-05-05

    Vinylene Carbonate (VC) was added to the electrolyte in graphite-lithium half-cells. We report its effect on the coulombic efficiency (as capacity shift) of graphite electrodes under various formation cycling conditions. Cyclic voltammetry on glassy carbon showed that VC passivates the electrode against electrolyte reduction. The dQ/dV plots of the first lithiation of the graphite suggest that VC alters the SEI layer, and that by varying the cell formation rate, the initial ratio of ethylene carbonate to VC in the SEI layer can be controlled. VC was found to decrease first cycle efficiency and reversible capacity (in ongoing cycling) when used to excess. However, experiments with VC additive used with various formation rates did not show any decrease in capacity shift.

  5. 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; Frankenberg, Christian; Hibbard, Kathy; 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.

  6. 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

  7. Effects of biotic disturbances on forest carbon cycling in the United States and Canada

    Treesearch

    Jeffrey A. Hicke; Craig D. Allen; Ankur R. Desai; Michael C. Dietze; Ronald J. Hall; Edward H. Hogg; Daniel M. Kashian; David Moore; Kenneth F. Raffa; Rona N. Sturrock; James. Vogelmann

    2011-01-01

    Forest insects and pathogens are major disturbance agents that have affected millions of hectares in North America in recent decades, implying significant impacts to the carbon (C) cycle. Here, we review and synthesize published studies of the effects of biotic disturbances on forest C cycling in the United States and Canada. Primary productivity in stands was reduced...

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

    USDA-ARS?s Scientific Manuscript database

    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...

  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. Orbital forcing of the Paleocene and Eocene carbon cycle

    NASA Astrophysics Data System (ADS)

    Zeebe, Richard E.; Westerhold, Thomas; Littler, Kate; Zachos, James C.

    2017-05-01

    Multimillion-year proxy records across the Paleocene and Eocene show prominent variations on orbital time scales. The cycles, which have been identified at various sites across the globe, preferentially concentrate spectral power at eccentricity and precessional frequencies. It is evident that these cycles are an expression of changes in global climate and carbon cycling paced by astronomical forcing. However, little is currently known about the link between orbital forcing and the carbon cycle-climate system and the amplitude of associated atmospheric CO2 variations. Here we use simple and complex carbon cycle models to explore the basic effect of different orbital forcing schemes and noise on the carbon cycle. Our primary modeling target is the high-resolution, ˜7.7 Myr long, benthic isotope record at Ocean Drilling Program Site 1262 in the South Atlantic. For direct insolation forcing (as opposed to artificial eccentricity-tilt-precession), one major challenge is understanding how the system transfers spectral power from high to low frequencies. We discuss feasible solutions, including insolation transformations analogous to electronic AC-DC conversion (DC'ing). Regarding mechanisms, we focus on tropical insolation and a long-term carbon imbalance in terrestrial organic burial/oxidation but do not rule out other scenarios. Our analysis shows that high-latitude mechanisms are unlikely drivers of orbitally paced changes in the late Paleocene-early Eocene (LPEE) Earth system. Furthermore, we provide constraints on the origin and isotopic composition of a possible LPEE cyclic carbon imbalance/source responding to astronomical forcing. Our simulations also reveal a mechanism for the large δ13C-eccentricity lag at the 400 kyr period observed in Paleocene, Oligocene, and Miocene sections. We present the first estimates of orbital-scale variations in atmospheric CO2 during the late Paleocene and early Eocene.

  11. A new stepwise carbon cycle data assimilation system using multiple data streams to constrain the simulated land surface carbon cycle

    DOE PAGES

    Peylin, Philippe; Bacour, Cédric; MacBean, Natasha; ...

    2016-09-20

    Here, large uncertainties in land surface models (LSMs) simulations still arise from inaccurate forcing, poor description of land surface heterogeneity (soil and vegetation properties), incorrect model parameter values and incomplete representation of biogeochemical processes. The recent increase in the number and type of carbon cycle-related observations, including both in situ and remote sensing measurements, has opened a new road to optimize model parameters via robust statistical model–data integration techniques, in order to reduce the uncertainties of simulated carbon fluxes and stocks. In this study we present a carbon cycle data assimilation system that assimilates three major data streams, namely themore » Moderate Resolution Imaging Spectroradiometer (MODIS)-Normalized Difference Vegetation Index (NDVI) observations of vegetation activity, net ecosystem exchange (NEE) and latent heat (LE) flux measurements at more than 70 sites (FLUXNET), as well as atmospheric CO2 concentrations at 53 surface stations, in order to optimize the main parameters (around 180 parameters in total) of the Organizing Carbon and Hydrology in Dynamics Ecosystems (ORCHIDEE) LSM (version 1.9.5 used for the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations). The system relies on a stepwise approach that assimilates each data stream in turn, propagating the information gained on the parameters from one step to the next. Overall, the ORCHIDEE model is able to achieve a consistent fit to all three data streams, which suggests that current LSMs have reached the level of development to assimilate these observations. The assimilation of MODIS-NDVI (step 1) reduced the growing season length in ORCHIDEE for temperate and boreal ecosystems, thus decreasing the global mean annual gross primary production (GPP). Using FLUXNET data (step 2) led to large improvements in the seasonal cycle of the NEE and LE fluxes for all ecosystems (i.e., increased amplitude for

  12. A new stepwise carbon cycle data assimilation system using multiple data streams to constrain the simulated land surface carbon cycle

    SciTech Connect

    Peylin, Philippe; Bacour, Cédric; MacBean, Natasha; Leonard, Sébastien; Rayner, Peter; Kuppel, Sylvain; Kane, Abdou; Maignan, Fabienne; Chevallier, Frédéric; Ciais, Philippe; Prunet, Pascal

    2016-09-20

    Here, large uncertainties in land surface models (LSMs) simulations still arise from inaccurate forcing, poor description of land surface heterogeneity (soil and vegetation properties), incorrect model parameter values and incomplete representation of biogeochemical processes. The recent increase in the number and type of carbon cycle-related observations, including both in situ and remote sensing measurements, has opened a new road to optimize model parameters via robust statistical model–data integration techniques, in order to reduce the uncertainties of simulated carbon fluxes and stocks. In this study we present a carbon cycle data assimilation system that assimilates three major data streams, namely the Moderate Resolution Imaging Spectroradiometer (MODIS)-Normalized Difference Vegetation Index (NDVI) observations of vegetation activity, net ecosystem exchange (NEE) and latent heat (LE) flux measurements at more than 70 sites (FLUXNET), as well as atmospheric CO2 concentrations at 53 surface stations, in order to optimize the main parameters (around 180 parameters in total) of the Organizing Carbon and Hydrology in Dynamics Ecosystems (ORCHIDEE) LSM (version 1.9.5 used for the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations). The system relies on a stepwise approach that assimilates each data stream in turn, propagating the information gained on the parameters from one step to the next.

    Overall, the ORCHIDEE model is able to achieve a consistent fit to all three data streams, which suggests that current LSMs have reached the level of development to assimilate these observations. The assimilation of MODIS-NDVI (step 1) reduced the growing season length in ORCHIDEE for temperate and boreal ecosystems, thus decreasing the global mean annual gross primary production (GPP). Using FLUXNET data (step 2) led to large improvements in the seasonal cycle of the NEE and LE fluxes for all ecosystems (i.e., increased

  13. A new stepwise carbon cycle data assimilation system using multiple data streams to constrain the simulated land surface carbon cycle

    NASA Astrophysics Data System (ADS)

    Peylin, Philippe; Bacour, Cédric; MacBean, Natasha; Leonard, Sébastien; Rayner, Peter; Kuppel, Sylvain; Koffi, Ernest; Kane, Abdou; Maignan, Fabienne; Chevallier, Frédéric; Ciais, Philippe; Prunet, Pascal

    2016-09-01

    Large uncertainties in land surface models (LSMs) simulations still arise from inaccurate forcing, poor description of land surface heterogeneity (soil and vegetation properties), incorrect model parameter values and incomplete representation of biogeochemical processes. The recent increase in the number and type of carbon cycle-related observations, including both in situ and remote sensing measurements, has opened a new road to optimize model parameters via robust statistical model-data integration techniques, in order to reduce the uncertainties of simulated carbon fluxes and stocks. In this study we present a carbon cycle data assimilation system that assimilates three major data streams, namely the Moderate Resolution Imaging Spectroradiometer (MODIS)-Normalized Difference Vegetation Index (NDVI) observations of vegetation activity, net ecosystem exchange (NEE) and latent heat (LE) flux measurements at more than 70 sites (FLUXNET), as well as atmospheric CO2 concentrations at 53 surface stations, in order to optimize the main parameters (around 180 parameters in total) of the Organizing Carbon and Hydrology in Dynamics Ecosystems (ORCHIDEE) LSM (version 1.9.5 used for the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations). The system relies on a stepwise approach that assimilates each data stream in turn, propagating the information gained on the parameters from one step to the next. Overall, the ORCHIDEE model is able to achieve a consistent fit to all three data streams, which suggests that current LSMs have reached the level of development to assimilate these observations. The assimilation of MODIS-NDVI (step 1) reduced the growing season length in ORCHIDEE for temperate and boreal ecosystems, thus decreasing the global mean annual gross primary production (GPP). Using FLUXNET data (step 2) led to large improvements in the seasonal cycle of the NEE and LE fluxes for all ecosystems (i.e., increased amplitude for temperate ecosystems). The

  14. Role of the seasonal cycle in coupling climate and carbon cycling in the subantarctic zone

    NASA Astrophysics Data System (ADS)

    Monteiro, Pedro M. S.; Boyd, Philip; Bellerby, Richard

    2011-07-01

    Workshop on the Seasonal Cycle of the Carbon-Climate System in the Southern Ocean; Cape Town, South Africa, 23-25 August 2010; There is increasing evidence in the Southern Ocean that mesoscales and seasonal scales play an important role in the coupling of ocean carbon cycling and climate. The seasonal cycle is one of the strongest modes of variability in different components of the carbon cycle in the Southern Ocean. It is also the mode that couples climate forcing to ecosystem responses such as productivity and ultimately biogeochemical signals including carbon export. However, not only are these scales of coupling poorly understood, but also there appear to be important regional differences in the way they couple climate to carbon. With this as an overarching theme, a workshop in South Africa brought together scientists working in the Southern Ocean, the waters south of Australia, New Zealand, and South Africa. The importance of the Subantarctic Zone (SAZ) as a carbon sink made it an ideal system on which to focus the workshop.

  15. 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

  16. Interannual variability of carbon cycle implied by a 2-d atmospheric transport model.

    PubMed

    Can, Li; Xu, Li; Shao, Min; Zhang, Ren-Jian

    2004-01-01

    A 2-dimensional atmospheric transport model is deployed in a simplified CO2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible, important role of Asian terrestrial ecosystems in carbon cycle.

  17. 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.

  18. 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.

  19. 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

  20. Benchmark analysis of parameterization for terrestrial carbon cycle model (Invited)

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Zhou, X.; Verburg, P.; Arnone, J.

    2010-12-01

    Parameterization of terrestrial ecosystem models plays an important role in accurately predicting carbon-climate feedback. More and more studies have shown that a fixed set of parameters cannot adequately represent spatial and temporal variations of ecosystem functions over broad geographical locations and/or over long time. In this study, we conducted benchmark analysis of a terrestrial ecosystem (TECO) model against a highly accurate data set from mesocosm study in Ecologically Controlled Enclosed Lysimeter Laboratories (EcoCELLs) at Desert Research Institute, Reno, Nevada. The mesocosm study involved shoot and whole plant harvests in fall, fallow during winter, and fertilization treatments in year 2. We used a Markov chain Monte Carlo (MCMC) technique to estimate parameters of the TECO model and measure the model performance with estimated parameters. Our analysis showed that the model performance with one set of estimated parameters was poor over a two-year experimental duration. The model performance was slightly improved with root exudation as an additional mechanism of carbon transfer from plants to rhizosphere. The performance was significantly improved when five sets of parameters were estimated for five respective periods, which spanned from seeding to shoot harvest in year 1, from shoot to whole plant harvest in year 1, fallow, from seeding to plant harvest with fertilization in year 2, and from plant harvest to the end of the project in year 2. The five sets of parameter values are significantly different, indicating that experimental treatments caused discontinuous (or discrete) changes in ecosystem processes. The discontinuous changes in ecosystem processes pose significant challenges for carbon cycle model parameterization and generate uncertainties for model prediction.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Grate, Jay W.; Zhang, Changyong; Wilkins, Michael; Warner, Marvin G.; Anheier, Norm C.; Suter, Jonathan; Kelly, Ryan; Oostrom, Mart

    2013-06-01

    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 that serve as representations of normally-opaque porous media. These structures enable, for example, visualization of water displacement from pore spaces by hydrophobic fluids, including carbon dioxide, in studies related to carbon sequestration. In situ fluorescent oxygen sensing methods and fluorescent cellulosic materials are being used to investigate processes related to terrestrial carbon cycling involving cellulolytic respiring microorganisms.

  3. The Effects of Insect Outbreak Disturbances on the North American Carbon Cycle: A Review

    NASA Astrophysics Data System (ADS)

    Hicke, J. A.; Hall, R. J.; Raffa, K.; Desai, A. R.; Kashian, D.

    2009-12-01

    Disturbances are important ecosystem processes that greatly affect carbon cycling. In forests, disturbances contribute to modifications to carbon stocks and fluxes by increasing the amount of decomposing dead organic matter and decreasing the amount of carbon taken up by the ecosystem through photosynthesis. The net effect immediately following a disturbance is that forest ecosystems are carbon sources to the atmosphere. Within several decades, the carbon source becomes a carbon sink as the dead wood decays and the forest regrows. In North America, insect outbreaks are major forest disturbances, killing millions of trees in bark beetle and defoliator outbreaks that range over millions of ha. This presentation will review the role that insect infestations have in the North American carbon budget. We summarize estimates of the extent, frequency, and severity of outbreaks and the uncertainty associated with how these estimates are derived. We describe drivers of insect epidemics, which include climate, stand-structure, and predator-prey interactions. Finally, we describe studies that have documented impacts to the carbon cycle by insect infestations and discuss ongoing efforts. Although the role of insect disturbances is not well documented, these forest disturbances appear to be major factors that need inclusion for robust estimates of contemporary carbon budgets and for prediction of future carbon cycling given feedbacks with climate change.

  4. A tree-ring perspective on the terrestrial carbon cycle.

    PubMed

    Babst, Flurin; Alexander, M Ross; Szejner, Paul; Bouriaud, Olivier; Klesse, Stefan; Roden, John; Ciais, Philippe; Poulter, Benjamin; Frank, David; Moore, David J P; Trouet, Valerie

    2014-10-01

    Tree-ring records can provide valuable information to advance our understanding of contemporary terrestrial carbon cycling and to reconstruct key metrics in the decades preceding monitoring data. The growing use of tree rings in carbon-cycle research is being facilitated by increasing recognition of reciprocal benefits among research communities. Yet, basic questions persist regarding what tree rings represent at the ecosystem level, how to optimally integrate them with other data streams, and what related challenges need to be overcome. It is also apparent that considerable unexplored potential exists for tree rings to refine assessments of terrestrial carbon cycling across a range of temporal and spatial domains. Here, we summarize recent advances and highlight promising paths of investigation with respect to (1) growth phenology, (2) forest productivity trends and variability, (3) CO2 fertilization and water-use efficiency, (4) forest disturbances, and (5) comparisons between observational and computational forest productivity estimates. We encourage the integration of tree-ring data: with eddy-covariance measurements to investigate carbon allocation patterns and water-use efficiency; with remotely sensed observations to distinguish the timing of cambial growth and leaf phenology; and with forest inventories to develop continuous, annually-resolved and long-term carbon budgets. In addition, we note the potential of tree-ring records and derivatives thereof to help evaluate the performance of earth system models regarding the simulated magnitude and dynamics of forest carbon uptake, and inform these models about growth responses to (non-)climatic drivers. Such efforts are expected to improve our understanding of forest carbon cycling and place current developments into a long-term perspective.

  5. 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].

  6. 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

  7. 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

  8. Global carbon isotope records and carbon cycle feedbacks following the PETM perturbation (Invited)

    NASA Astrophysics Data System (ADS)

    Bowen, G. J.

    2009-12-01

    Global warming during the Paleocene-Eocene Thermal Maximum is associated with a transient, multi-phase negative carbon isotope excursion documented throughout the global exogenic carbon cycle. The precipitous drop in carbon isotope ratios at the onset of the event is widely accepted to reflect a massive addition of 13C-depleted carbon to the ocean/atmosphere system and resultant increases in atmospheric pCO2 and ocean water acidity. But what, if anything, does the pattern of continued carbon isotope change tell us about the patterns and mechanisms of carbon cycle change during the subsequent 170 kyr? Carbon isotope ratios remain relatively stable and low for some 60 kyr following the initiation of the event, suggesting either continued perturbation of the system away from its pre-PETM state or a change in the rate or net isotopic composition of the carbon burial flux during this interval. The interval of δ13C stability ended abruptly ca. 80 kyr after the beginning of the PETM, when carbon isotope ratios rapidly increased by at least 2‰ over no more than 30 kyr. The rebound rate of δ13C values was an order of magnitude faster than expected based on the residence time of carbon in the exogenic system, and implies either a dramatic decrease in residence time or a substantial change in the isotopic composition of carbon fluxes between this system and the lithosphere. The isotopic record of the PETM carbon cycle oscillates between stability and instability, suggesting discrete changes in global carbon fluxes at points throughout the event. Understanding whether these changes were driven by variation in bulk carbon fluxes or ‘isofluxes’ will be necessary to accurately interpret the carbon isotope record to better understand lithospheric carbon burial feedbacks, CO2 drawdown, and the termination of the PETM hyperthermal climate.

  9. Paleoproductivity And Carbon Cycling During The Middle Miocene Monterey Excursion

    NASA Astrophysics Data System (ADS)

    Billups, K.; Diester-Haass, L.; Emeis, K.; François, L.; Jacquemin, I.; Lefebvre, V.

    2010-05-01

    A prominent middle Miocene (17.5 to 13.5 Ma) carbon-isotope excursion (the so-called Monterey event) is punctuated by six distinct carbon isotope maxima (CM). Orbital tuning of carbon isotope records links each CM event with the long term component of eccentricity (400 kyr) highlighting the importance of insolation control on the global carbon cycle (Holbourn et al., 2008). Here we use proxy reconstructions (benthic foraminiferal accumulation rates) from six sites in the Atlantic and Pacific Oceans combined with geochemical modelling to investigate whether there is a link between long term insolation forcing and the marine carbon isotope record via marine productivity and thus atmospheric CO2 levels. Our results show that none of the CM events are associated with distinctly large changes in paleoproductivity. This observation is consistent with our previous finding that the overall mid Miocene carbon isotope maximum is not associated with a change in marine productivity (Diester-Haass et al., 2009). There are, albeit minor, fluctuations in productivity that can be related to the 400 kyr variability in the carbon isotope records with several productivity maxima between CM events, whereas CM events often show minima in productivity. Only the last of the CM events (CM 6), which occurs in close association with the major step in mid Miocene Antarctic ice growth, is accompanied by an ocean-wide increase in paleoproductivity. To tentatively explain the observed 400 kyr variability of the deep ocean carbon isotope record an improved version of the geochemical box model used Diester-Haass et al. (2009) has been forced by sealevel fluctuations reconstructed for the middle Miocene (Holbourn pers. comm., 2009). Calculations indicate that the induced changes in weathering rates and carbon cycle can explain the temporal variability of the carbon isotope record, but not the observed amplitude.

  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. 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.

  12. Herbivores modify the carbon cycle in a warming arctic

    NASA Astrophysics Data System (ADS)

    Cahoon, S. M.; Sullivan, P.; Welker, J. M.; Post, E.

    2009-12-01

    Typically, our studies of arctic terrestrial ecosystem responses to changes in climate focus on abiotic drivers (i.e. warming or added rain or added snow) and subsequent biogeochemical cycles and plant physiological performance. However, many arctic systems, such as those in western Greenland, are home ranges for large herbivores such as muskoxen and caribou. In order to fully understand how tundra landscapes in Greenland will respond to change, experiments are needed that allow us to quantify whether abiotic (climate warming) and or biotic (presence or absence of herbivores) drivers or their combinations regulate ecosystem function and structure. Here we present the results of two consecutive field seasons in western Greenland in which we quantified the interactive effects of local herbivore foraging and simulated climate warming on ecosystem C and N cycling and leaf level physiology. Large exclosure fences were erected in 2002, and ITEX passive warming chambers were established in 2003 within and adjacent to the fences. We performed weekly CO2 flux measurements during the 2008 and 2009 growing seasons which we normalized to a common irradiance by generating light-response curves at all plots (n=9). Although we observed interannual variability in soil moisture and average daily air temperature, browsing by herbivores was a key factor in the seasonal carbon dynamics. By physically removing leaves and upper stems, caribou and muskoxen altered the community composition, reduced leaf area and in turn decreased gross ecosystem photosynthesis (GEP), regardless of the warming treatment. Neither herbivory nor warming significantly affected ecosystem respiration rates. Thus the reduction in net ecosystem exchange (NEE) was primarily driven by reductions in GEP associated with leaf area removal by grazers. Our results indicate that the biotic influence from large herbivores can significantly influence carbon-derived climatic feedbacks and can no longer be overlooked in

  13. Citric acid cycle biomimic on a carbon electrode.

    PubMed

    Sokic-Lazic, Daria; Minteer, Shelley D

    2008-12-01

    The citric acid cycle is one of the main metabolic pathways living cells utilize to completely oxidize biofuels to carbon dioxide and water. The overall goal of this research is to mimic the citric acid cycle at the carbon surface of an electrode in order to achieve complete oxidation of ethanol at a bioanode to increase biofuel cell energy density. In order to mimic this process, dehydrogenase enzymes (known to be the electron or energy producing enzymes of the citric acid cycle) are immobilized in cascades at an electrode surface along with non-energy producing enzymes necessary for the cycle to progress. Six enzymatic schemes were investigated each containing an additional dehydrogenase enzyme involved in the complete oxidation of ethanol. An increase in current density is observed along with an increase in power density with each additional dehydrogenase immobilized on an electrode, reflecting increased electron production at the bioanode with deeper oxidation of the ethanol biofuel. By mimicking the complete citric acid cycle on a carbon electrode, power density was increased 8.71-fold compared to a single enzyme (alcohol dehydrogenase)-based ethanol/air biofuel cell.

  14. 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%.

  15. 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.

  16. Immiscible hydrocarbon fluids in the deep carbon cycle

    PubMed Central

    Huang, Fang; Daniel, Isabelle; Cardon, Hervé; Montagnac, Gilles; Sverjensky, Dimitri A.

    2017-01-01

    The cycling of carbon between Earth's surface and interior governs the long-term habitability of the planet. But how carbon migrates in the deep Earth is not well understood. In particular, the potential role of hydrocarbon fluids in the deep carbon cycle has long been controversial. Here we show that immiscible isobutane forms in situ from partial transformation of aqueous sodium acetate at 300 °C and 2.4–3.5 GPa and that over a broader range of pressures and temperatures theoretical predictions indicate that high pressure strongly opposes decomposition of isobutane, which may possibly coexist in equilibrium with silicate mineral assemblages. These results complement recent experimental evidence for immiscible methane-rich fluids at 600–700 °C and 1.5–2.5 GPa and the discovery of methane-rich fluid inclusions in metasomatized ophicarbonates at peak metamorphic conditions. Consequently, a variety of immiscible hydrocarbon fluids might facilitate carbon transfer in the deep carbon cycle. PMID:28604740

  17. Immiscible hydrocarbon fluids in the deep carbon cycle

    NASA Astrophysics Data System (ADS)

    Huang, Fang; Daniel, Isabelle; Cardon, Hervé; Montagnac, Gilles; Sverjensky, Dimitri A.

    2017-06-01

    The cycling of carbon between Earth's surface and interior governs the long-term habitability of the planet. But how carbon migrates in the deep Earth is not well understood. In particular, the potential role of hydrocarbon fluids in the deep carbon cycle has long been controversial. Here we show that immiscible isobutane forms in situ from partial transformation of aqueous sodium acetate at 300 °C and 2.4-3.5 GPa and that over a broader range of pressures and temperatures theoretical predictions indicate that high pressure strongly opposes decomposition of isobutane, which may possibly coexist in equilibrium with silicate mineral assemblages. These results complement recent experimental evidence for immiscible methane-rich fluids at 600-700 °C and 1.5-2.5 GPa and the discovery of methane-rich fluid inclusions in metasomatized ophicarbonates at peak metamorphic conditions. Consequently, a variety of immiscible hydrocarbon fluids might facilitate carbon transfer in the deep carbon cycle.

  18. 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.

  19. 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.

  20. [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.

  1. Sensitivity of the marine carbonate cycle to atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Gangstø, R.; Joos, F.; Gehlen, M.

    2010-09-01

    Ocean acidification might reduce the ability of calcifying plankton to produce and maintain their shells of calcite, or of aragonite, the more soluble form of CaCO3. In addition to possibly large biological impacts, reduced CaCO3 production corresponds to a negative feedback on atmospheric CO2. In order to explore the sensitivity of the ocean carbon cycle to increasing concentrations of atmospheric CO2, we use the new biogeochemical Bern3D/PISCES model. The model reproduces the large scale distributions of biogeochemical tracers. With a range of sensitivity studies, we explore the effect of (i) using different parameterizations of CaCO3 production fitted to available laboratory and field experiments, of (ii) letting calcite and aragonite be produced by auto- and heterotrophic plankton groups, and of (iii) using carbon emissions from the range of the most recent IPCC Representative Concentration Pathways (RCP). Under a high-emission scenario, the CaCO3 production of all the model versions decreases from ~1 Pg C yr-1 to between 0.36 and 0.82 Pg C yr-1 by the year 2100. By the year 2500, the ratio of open water CaCO3 dissolution to production stabilizes at a value that is 30-50% higher than at pre-industrial times when carbon emissions are set to zero after 2100. Despite the wide range of parameterizations, model versions and scenarios included in our study, the changes in CaCO3 production and dissolution resulting from ocean acidification provide only a small feedback on atmospheric CO2 of 1-11 ppm by the year 2100.

  2. 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.

  3. Effects of Landscape Position on Carbon Cycling in Siberian Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Curasi, S. R.; Weber, L. R.; Loranty, M. M.

    2014-12-01

    High latitude carbon cycling is important because shifts in climatic conditions are thawing permafrost and altering carbon uptake in ways that will impact global climate. Within arctic ecosystems variation in slope and topography lead to flows of water beneath the soil surface that increase ecosystem moisture and nutrient availability. Consequently, such differences in landscape position often alter ecosystem structure, increase vegetation productivity, and more generally alter carbon cycling, relative to adjacent upland areas. Such differences will likely result in altered ecosystem responses to continued climate change. Understanding this variability in ecosystem function will be necessary in order to accurately understand the future of the arctic carbon cycle. The objective of this study is to characterize differences in biological and environmental conditions associated with landscape position in Siberian arctic tundra, and to understand how these differences impact ecosystem carbon cycling. To quantify the impact of landscape position on tundra ecosystem carbon cycling, we selected pairs of plots in upland and low lying landscape positions with high and low shrub density. We measured CO2 flux, permafrost thaw depth, soil moisture, soil temperature, and meteorological conditions. These variables were compared relative to shrub density and landscape position in order to determine differences in gross primary productivity and ecosystem respiration associated with vegetation type and landscape position. Low-lying wet areas were more productive than adjacent upland areas, irrespective of vegetation type. We also observed shallower permafrost thaw depth, lower soil temperature, greater soil moisture, and higher ecosystem respiration in the low lying plots. The observation of higher ecosystem respiration despite lower permafrost thaw depths and soil temperatures in the low-lying areas highlights the challenges associated with understanding the arctic carbon cycle

  4. Reconciling Top Down and Bottom Up Approaches to Understand Land Carbon Cycle Variability

    NASA Astrophysics Data System (ADS)

    Collatz, G. J.; Gurney, K. R.; Denning, A. S.; Randerson, J. T.; van der Werf, G. R.

    2004-12-01

    Cycle Variability Two fundamentally different approaches for estimating global carbon sources and sinks have been used over the past 15 years. The so-called "Top-down" approach involves analysis of atmospheric composition and often includes inversions of atmospheric transport. Bottom-up approaches, on the other hand, involve using carbon cycle process models driven by various observational data. Reconciling the results of these two approaches can provide powerful constraints on each but is challenging because of the large uncertainties in atmospheric measurements and transport and in our understanding of the processes controlling biogeochemical cycling of carbon. Recently, the Atmospheric Carbon Inversion Intercomparison (TransCom 3) completed mean seasonal cycle and interannual variability inversions using 12 transport models. Their results include predictions of biogeochemically driven net carbon fluxes with associated uncertainties for the globe divided into 22 regions, half of which are land regions. The cyclo-stationary inversions predicted the mean seasonal cycle as well as the mean sink/source of each region. The interannual inversions predicted the interannual variability in the sources and sinks for each region between 1980 and 2000. This study describes an analysis of the processes controlling biogeochemically driven net carbon fluxes over the seasonal cycle for each of the Transcom land regions. The processes considered are those included in the CASA biogeochemical model. The seasonally variable model inputs include NDVI, temperature, precipitation and solar radiation and burned area. The contributions of NPP, heterotrophic respiration and fire season to the seasonal cycle are evaluated for each of the 11 TransCom 3 land regions. We prescribed plausible scenarios in the biogeochemical model to evaluate the mechanisms responsible for the size and seasonality of the mean annual carbon sinks reported by TransCom 3. Initial results will also be presented for

  5. 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.

  6. Modelling feedback mechanisms in the carbon cycle: balancing the carbon budget

    NASA Astrophysics Data System (ADS)

    Rotmans, J.; den Elzen, M. G. J.

    1993-09-01

    Within the carbon cycle feedback, mechanisms that amplify or dampen the exchange of carbon dioxide between the different reservoirs to enhance concentrations of carbon dioxide and increase temperature from anthropogenic perturbations, play a crucial rôle. Quite a lot of these feedbacks are known, but most of them only potentially. This article evaluates the role of a number of these feedback processes within the carbon cycle. In order to assess their impact, some terrestrial feedbacks have been built into a coupled carbon cycle and climate model, as part of the integrated climate assessment model IMAGE. A number of simulation experiments have been performed with this coupled carbon cycle/climate model to compare historical atmospheric concentration values of carbon dioxide with simulated values. Also global biospheric and oceanic carbon fluxes were validated against other modelling estimates. Based on the assumptions of the IPCC's 1990 Business-as-Usual (BaU-1990) scenario, future projections of the carbon dioxide concentration have been made. A key principle in this is that we have used the modelled feedbacks in order to balance the past and present carbon budget. For atmospheric carbon dioxide, this results in substantially lower projections than the IPCC-estimates: the difference in 2100 is approximately 16% from the 1990 level. Furthermore, the IPCC's 'best guess' or 'central estimate' value of the CO2 concentration in 2100 falls outside the uncertainty range estimated with our balanced modelling approach. Sensitivity experiments with the model have been performed to quantify to what extent the terrestrial feedback processes and oceanic fluxes influence the global carbon balance in the model. It is shown that a historical and present carbon balance can be obtained in many different ways, resulting in different biospheric fluxes and thus in considerably different atmospheric CO2 projections.

  7. Upward-shoaling cycles in Smackover carbonates of southwest Alabama

    SciTech Connect

    Kopaska-Merkel, D.C.; Mann, S.D. )

    1993-09-01

    Upper Smackover strata in Alabama commonly consist of one or more upward-shoaling cycles about 15 to 50 ft (3 to 16 m) in thickness. Multiple forcing functions (eustasy, regional tilting, salt halokinesis, and autogenic migration of facies) and varying water depths at the start and end of each upward-shoaling cycle generated an array of sedimentary responses. The Brittain No. 1 well, Permit No. 2478, Healing Springs field, Washington County, Alabama, illustrates nucleation of an offshore bar. Bar deposits are capped by anhydritic sabkha deposits, gradationally overlain by subtidal lagoonal strata. Varying rates (and directions ) of halokinesis controlled this succession. Locally varying rates of salt movement created as many as five sabkha-capped cycles in this area. The International Paper company 20-5 Mo. 1 well, Permit No. 5242, Blacksher field, Baldwin County, Alabama, contains three upward-shoaling cycles capped by evaporites. Limited aggradational potential of supratidal evaporitic settings permitted subsidence-caused immersion, which eventually permitted reactivation of the carbonate factory and formation of the next cycle. The Chatom Unit 20-14 No. 1-04 well, Permit No. 7044, Chatom field, Washington County, contains three different cycles. The lower cycle consists of subtidal lime mudstone, capped by a 5-ft (1.5-m) thick soil zone that contains multiple exposure surfaces, tepee structures, and anhydrite pseudomorphs after lenticular gypsum crystals. The soil zone underlies an intraclastic storm deposit followed by a deepening-upward lagoonal succession. A thin ooid grainstone containing exposure surfaces caps the middle cycle. In the upper cycle, peritidal carbonate strata underlie sabkha deposits.

  8. 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

  9. On the role of headwater catchments in terrestrial carbon cycling

    NASA Astrophysics Data System (ADS)

    Evans, Martin

    2017-04-01

    Headwater systems have been described as 'aqua incognita' in reference to the poorly understood nature of these systems yet they typically represent up to 80% of the stream length in a catchment. In terms of carbon cycling, biological theory characterises headwater streams as systems dominated by coarse organic matter which is exported downstream. This material is largely derived from catchment biomass and soils and is delivered to the stream system during high magnitude sediment transport events such as landsliding or storm events. Geomorphological understanding of lateral carbon fluxes in headwater systems has advanced rapidly in the last decade but the integration of this geomorphological understanding with knowledge of the biological processes determining the fate of organic matter in headwater river systems is poorly developed. This paper considers evidence from forested, peatland and glaciated headwater systems to develop a conceptual 'carbon land-system model' of headwater systems. This model suggests that a more nuanced view of the role of headwaters in carbon cycling is required. Headwater catchments are sources of OM for downstream systems but can also in some circumstances be sites of carbon storage or of dynamic carbon turnover.

  10. Inland Waters and the North American Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Butman, D. E.; Striegl, R. G.; Stackpoole, S. M.; del Giorgio, P.; Prairie, Y.; Pilcher, D.; Raymond, P. A.; Alcocer, J.; Paz, F.

    2016-12-01

    Inland aquatic ecosystems process, store, and release carbon to the atmosphere and coastal margins. The form of this carbon is a function of terrestrial and aquatic primary and secondary production, the weathering of materials in soils and subsurface environments, the hydrologic controls on the movement of carbon from land to inland waters, and the connectivity between streams, rivers, lakes, reservoirs and groundwater. The 2007 1st State of the Carbon Cycle reported fluxes for the continental United States (CONUS) only. Streams and rivers exported 30-40 Tg C yr-1 to coastal environments, and 17-25 Tg C yr-1 were buried in lake and reservoir sediments. Remarkably, the 2007 report did not quantify gas emissions, which represent over half of the total carbon fluxes through inland water in the US. Current research has shown that 71-149 Tg C yr-1 exits freshwater systems either through atmospheric emissions of carbon dioxide or as inorganic and organic carbon fluxes to the coast from the CONUS. These estimates did not include the Laurentian Great Lakes. Variation in the magnitude of these fluxes across regions of the CONUS has been linked to differences in precipitation and terrestrial net ecosystem production. Similar comprehensive assessments have not been done for Canada or Mexico. Here we provide, as part of the 2nd State of the Carbon Cycle report, estimates for the river coastal export and vertical emissions of carbon from inland waters of North America, and report major data gaps, and weaknesses in methodologies. These findings stress that strong international partnerships are needed to improve assessment, monitoring, and modeling of human impacts on the magnitude and timing of aquatic fluxes in the future.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Terrestrial nitrogen–carbon cycle interactions at the global scale

    PubMed Central

    Zaehle, S.

    2013-01-01

    Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen–carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001–2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr−1 (1.9 Pg C yr−1), of which 10 Tg N yr−1 (0.2 Pg C yr−1) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen–carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr−1 per 1°C degree climate warming) will add an important long-term climate forcing. PMID:23713123

  16. Terrestrial nitrogen-carbon cycle interactions at the global scale.

    PubMed

    Zaehle, S

    2013-07-05

    Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen-carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001-2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr(-1) (1.9 Pg C yr(-1)), of which 10 Tg N yr(-1) (0.2 Pg C yr(-1)) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen-carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr(-1) per 1°C degree climate warming) will add an important long-term climate forcing.

  17. The State of the Carbon Cycle: Ten Years On

    NASA Astrophysics Data System (ADS)

    King, A. W.; Dilling, L.; Fairman, D. M.; Houghton, R. A.; Marland, G.; Rose, A.; Wilbanks, T. J.; Zimmerman, G.

    2015-12-01

    It has been nearly ten years since the First State of the Carbon Cycle Report (SOCCR-1) was published in 2007. Much has changed in the intervening years, but much has remained the same. In anticipation of a Second State of the Carbon Cycle Report (SOCCR-2), we, the members of the SOCCR-1 Coordinating Team, felt that a perspective from the first SOCCR and reflection on changes in the state of carbon cycle science and policy in the intervening years would be appropriate. The purpose of SOCCR-1 was to provide "…a synthesis and integration of the current knowledge of the North American carbon budget and its context within the global carbon cycle [i]n a format useful to decision makers." Being "useful to decision makers" was a guiding theme with three stakeholder workshops an integral part of the process. Drafting and revision of SOCCR-1 took place between 2005 and early 2007; the report's carbon budget was for circa 2003. In 2003, North America's fossil-fuel CO2 emissions were approximately 27% of global emissions. Nearly 85% of North American emissions were from the US, still at that time the world's largest emitter of fossil-fuel CO2. China's annual CO2 emissions exceeded those of the US for the first time while SOCCR-1 was being written. Today global CO2 emissions are dominated by emissions from China (28% in 2013), with US emissions only 14% of global emissions. Emissions from the US and North America have actually declined by approximately 10% since 2003 while emissions from China have doubled. Based on inventories of terrestrial carbon stocks, SOCCR-1 estimated that circa 2003 North American vegetation removed and stored a net 500 Mt C y-1 (±50%) from the atmosphere. A more recent synthesis incorporating additional estimates from atmospheric inversions and terrestrial biosphere modeling estimated the North American land sink for the decade of 2000-2009 at 350-470 Mt C y-1, with a slightly greater uncertainty due to the wider range of estimates from the

  18. 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

  19. 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

  20. Capture and release of carbon dioxide by carbon nanotubes via temperature cycling

    NASA Astrophysics Data System (ADS)

    Rende{2}, Deniz; Baysal, Nihat; Ozisik, Rahmi

    2011-03-01

    Carbon nanotubes (CNTs) received remarkable attention since they were shown to possess many unique properties as well as being effective and stable adsorbent materials that make them potentially useful for gas storage and separation of various gas mixtures. In this study, the effect of temperature variations on carbon dioxide (CO2) capture via single walled carbon nanotubes (SWNTs) and multi walled carbon nanotubes (MWNTs) were investigated with molecular dynamics simulations. SWNTs of type (10,10), (15,15), and (20,20) and MWNTs formed from the combination of these were simulated. The temperature was varied between 300 and 360 K. The results suggest that absorption of CO2 into the CNTs were directly related to the internal volume of the nanotube, but the cross-sectional area of the tube entrance had a significant effect on the number of CO2 molecules retained. The number of CO2 molecules collected in CNTs gradually decreases with increasing temperature. Separate simulations were performed to understand the potential use of CNTs as thermal pumps to collect/discharge CO2 molecules via temperature cycling. Supported by the NSF (CMMI-0500324 and DMR-0117792).

  1. 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.

  2. The long-term carbon cycle, fossil fuels and atmospheric composition.

    PubMed

    Berner, Robert A

    2003-11-20

    The long-term carbon cycle operates over millions of years and involves the exchange of carbon between rocks and the Earth's surface. There are many complex feedback pathways between carbon burial, nutrient cycling, atmospheric carbon dioxide and oxygen, and climate. New calculations of carbon fluxes during the Phanerozoic eon (the past 550 million years) illustrate how the long-term carbon cycle has affected the burial of organic matter and fossil-fuel formation, as well as the evolution of atmospheric composition.

  3. 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

  4. Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks.

    PubMed

    Torres, Mark A; Moosdorf, Nils; Hartmann, Jens; Adkins, Jess F; West, A Joshua

    2017-08-15

    Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean-atmosphere CO2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O2 Future work on glaciation-weathering-carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.

  5. Hydrological and biogeochemical constraints on terrestrial carbon cycle feedbacks

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    The feedbacks between climate, atmospheric CO2 concentration and the terrestrial carbon cycle are a major source of uncertainty in future climate projections with Earth systems models. Here, we use observation-based estimates of the interannual variations in evapotranspiration (ET), net biome productivity (NBP), as well as the present-day sensitivity of NBP to climate variations, to constrain globally the terrestrial carbon cycle feedbacks as simulated by models that participated in the fifth phase of the coupled model intercomparison project (CMIP5). The constraints result in a ca. 40% lower response of NBP to climate change and a ca. 30% reduction in the strength of the CO2 fertilization effect relative to the unconstrained multi-model mean. While the unconstrained CMIP5 models suggest an increase in the cumulative terrestrial carbon storage (477 PgC) in response to an idealized scenario of 1%/year atmospheric CO2 increase, the constraints imply a ca. 19% smaller change. Overall, the applied emerging constraint approach offers a possibility to reduce uncertainties in the projections of the terrestrial carbon cycle, which is a key determinant of the future trajectory of atmospheric CO2 concentration and resulting climate change.

  6. 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).

  7. Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks

    NASA Astrophysics Data System (ADS)

    Torres, Mark A.; Moosdorf, Nils; Hartmann, Jens; Adkins, Jess F.; West, A. Joshua

    2017-08-01

    Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean–atmosphere CO2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O2. Future work on glaciation–weathering–carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.

  8. 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.

  9. Modeling carbon cycle process of soil profile in Loess Plateau of China

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Finke, P.; Guo, Z.; Wu, H.

    2011-12-01

    SoilGen2 is a process-based model, which could reconstruct soil formation under various climate conditions, parent materials, vegetation types, slopes, expositions and time scales. Both organic and inorganic carbon cycle processes could be simulated, while the later process is important in carbon cycle of arid and semi-arid regions but seldom being studied. After calibrating parameters of dust deposition rate and segments depth affecting elements transportation and deposition in the profile, modeling results after 10000 years were confronted with measurements of two soil profiles in loess plateau of China, The simulated trends of organic carbon and CaCO3 in the profile are similar to measured values. Relative sensitivity analysis for carbon cycle process have been done and the results show that the change of organic carbon in long time scale is more sensitive to precipitation, temperature, plant carbon input and decomposition parameters (decomposition rate of humus, ratio of CO2/(BIO+HUM), etc.) in the model. As for the inorganic carbon cycle, precipitation and potential evaporation are important for simulation quality, while the leaching and deposition of CaCO3 are not sensitive to pCO2 and temperature of atmosphere.

  10. The impact of a large boreal wildfire on boundary-layer conditions and carbon cycling in adjacent unburned areas: case study of the 2011 Utikuma Complex fire, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Petrone, R. M.; Thompson, D. K.; Chasmer, L.; Kljun, N.; Flannigan, M.; Devito, K. J.; Waddington, J. M.

    2016-12-01

    Boreal wildfire conflagrations have increased in frequency in the western boreal forest of Canada, with notable events in 2011, 2015, and 2016. Significant advances have been made in recent years in understanding fire-atmosphere interactions, with similar gains in the knowledge of carbon emissions and post-fire carbon cycling in forests. However, the focus of such studies is routinely on the burned stands themselves, with little attention to the adjacent forest whose boundary layer meteorology and carbon cycling may be impacted by smoke plume. We capitalize here on opportunistic eddy covariance observations of boundary-layer conditions and carbon cycling taken over a long-term monitoring site adjacent to an active wildfire in Alberta, Canada in 2011. Over a one-week period while the wildfire was burning near the footprint of the tower the turbulent structure of the boundary layer near the tower was altered with significant changes in friction velocity, air temperature, and vapour pressure deficit. Moreover, growing season net ecosystem productivity (NEP) decreased to almost zero largely due to reduced photosynthesis likely due to smoke-related reductions in photosynthetically active radiation (PAR). While the `smoke event' caused a reduction in forest CO2 sequestration by 7 g CO2 m-2 given that the smoked affected area was 120 times greater than the area burned this carbon reduction was equivalent to 30% of gross fire emissions from the fire. Consequently, we argue that smoke related inhibition of photosynthesis via reduced light should be considered when investigating the net radiative forcing of boreal forest wildfires.

  11. 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.

  12. Carbon Cycle Science in Support of Decision-Making

    NASA Astrophysics Data System (ADS)

    Brown, M. E.; West, T. O.; McGlynn, E.; Gurwick, N. P.; Duren, R. M.; Ocko, I.; Paustian, K.

    2016-12-01

    There has been an extensive amount of basic and applied research conducted on biogeochemical cycles, land cover change, watershed to earth system modeling, climate change, and energy efficiency. Concurrently, there continues to be interest in how to best reduce net carbon emissions, including maintaining or augmenting global carbon stocks and decreasing fossil fuel emissions. Decisions surrounding reductions in net emissions should be grounded in, and informed by, existing scientific knowledge and analyses in order to be most effective. The translation of scientific research to decision-making is rarely direct, and often requires coordination of objectives or intermediate research steps. For example, complex model output may need to be simplified to provide mean estimates for given activities; biogeochemical models used for climate change prediction may need to be altered to estimate net carbon flux associated with particular activities; or scientific analyses may need to aggregate and analyze data in a different manner to address specific questions. In the aforementioned cases, expertise and capabilities of researchers and decision-makers are both needed, and early coordination and communication is most effective. Initial analysis of existing science and current decision-making needs indicate that (a) knowledge that is co-produced by scientists and decision-makers has a higher probability of being usable for decision making, (b) scientific work in the past decade to integrate activity data into models has resulted in more usable information for decision makers, (c) attribution and accounting of carbon cycle fluxes is key to using carbon cycle science for decision-making, and (d) stronger, long-term links among research on climate and management of carbon-related sectors (e.g., energy, land use, industry, and buildings) are needed to adequately address current issues.

  13. Uncertainty in the carbon cycle and its contributions to overall uncertainty in future climate projections.

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrei

    2010-05-01

    The contribution of carbon cycle uncertainty to the uncertainty in future climate projections is studied by means of numerical simulations with the MIT Integrated Global System Model (IGSM). Three ensembles of 21st century climate simulations were carried out using input probability distributions for climate sensitivity, rate of heat uptake by the ocean and strength of aerosol forcing consistent with the changes in climate over 20th century. Uncertainties in the rate of oceanic carbon uptake and strength of CO2 fertilization were also included. Each ensemble consists of 400 simulations. In first ensemble all sub-components of the IGSM were fully coupled. To evaluate uncertainty in the feedback between climate and carbon cycle, an additional ensemble of radiatively uncoupled simulations was carried out. Because the terrestrial ecosystem model used in the IGSM takes into account nitrogen limitation on carbon uptake by vegetation, feedbacks associated with terrestrial and oceanic carbon cycle have different signs. As a result, total feedback between climate and carbon cycle is rather weak and can be either positive or negative. This explains why the probability distribution for surface warming obtained from simulations with the IGSM is more symmetric than ones presented in the IPCC AR4. Reference greenhouse gases and aerosol emissions for business as usual scenario were used in first two ensembles. In all simulations of the third ensemble the IGSM was forced by the GHGs concentrations from the simulation with the median values of all climate parameter, thus eliminating uncertainty in the carbon cycle. Contribution of carbon cycle uncertainty to the uncertainties in projected climate changes turned out to be surprisingly small, at least for business as usual emission scenario.

  14. Eocene bipolar glaciation associated with global carbon cycle changes.

    PubMed

    Tripati, Aradhna; Backman, Jan; Elderfield, Henry; Ferretti, Patrizia

    2005-07-21

    The transition from the extreme global warmth of the early Eocene 'greenhouse' climate approximately 55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on Antarctica approximately 34 million years ago, coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world's oceans, and that glaciation in the Northern Hemisphere began much later, between 10 and 6 million years ago. Here we present records of sediment and foraminiferal geochemistry covering the greenhouse-icehouse climate transition. We report evidence for synchronous deepening and subsequent oscillations in the calcite compensation depth in the tropical Pacific and South Atlantic oceans from approximately 42 million years ago, with a permanent deepening 34 million years ago. The most prominent variations in the calcite compensation depth coincide with changes in seawater oxygen isotope ratios of up to 1.5 per mil, suggesting a lowering of global sea level through significant storage of ice in both hemispheres by at least 100 to 125 metres. Variations in benthic carbon isotope ratios of up to approximately 1.4 per mil occurred at the same time, indicating large changes in carbon cycling. We suggest that the greenhouse-icehouse transition was closely coupled to the evolution of atmospheric carbon dioxide, and that negative carbon cycle feedbacks may have prevented the permanent establishment of large ice sheets earlier than 34 million years ago.

  15. Slow growth rates of Amazonian trees: consequences for carbon cycling.

    PubMed

    Vieira, Simone; Trumbore, Susan; Camargo, Plinio B; Selhorst, Diogo; Chambers, Jeffrey Q; Higuchi, Niro; Martinelli, Luiz Antonio

    2005-12-20

    Quantifying age structure and tree growth rate of Amazonian forests is essential for understanding their role in the carbon cycle. Here, we use radiocarbon dating and direct measurement of diameter increment to document unexpectedly slow growth rates for trees from three locations spanning the Brazilian Amazon basin. Central Amazon trees, averaging only approximately 1 mm/year diameter increment, grow half as fast as those from areas with more seasonal rainfall to the east and west. Slow growth rates mean that trees can attain great ages; across our sites we estimate 17-50% of trees with diameter >10 cm have ages exceeding 300 years. Whereas a few emergent trees that make up a large portion of the biomass grow faster, small trees that are more abundant grow slowly and attain ages of hundreds of years. The mean age of carbon in living trees (60-110 years) is within the range of or slightly longer than the mean residence time calculated from C inventory divided by annual C allocation to wood growth (40-100 years). Faster C turnover is observed in stands with overall higher rates of diameter increment and a larger fraction of the biomass in large, fast-growing trees. As a consequence, forests can recover biomass relatively quickly after disturbance, whereas recovering species composition may take many centuries. Carbon cycle models that apply a single turnover time for carbon in forest biomass do not account for variations in life strategy and therefore may overestimate the carbon sequestration potential of Amazon forests.

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

    PubMed

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

    2014-11-25

    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 δ(13)C and age via Δ(14)C. 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.

  17. 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

  18. Response of land carbon cycle to stratospheric aerosol geoengineering

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Ji, D.

    2016-12-01

    Stabilizing the climate through geoengineering aims to mitigate the climate change induced by increasing atmospheric CO2 and other green house gases. These impacts in climate affect terrestrial ecosystem considerably because terrestrial carbon fluxes are sensitivity to climate change. Here we analyzed the responses of land carbon cycle to GeoMIP G4 experiment from six Earth System Models (ESMs), in which negative radiative forcing is produced by an injection of SO2 into the stratosphere to compensate the global warming in RCP4.5. From the year 2020 to 2090, there was an increase in land carbon uptake with significant discrepancy among models (20 PgC to 260 PgC) for both G4 and RCP4.5 scenario, due to the CO2 fertilization effect. For comparison with RCP4.5, all of the models showed higher land carbon uptakes in G4 scenario (30 Pg C on average), with both increases in vegetation and soil carbon stores. These land carbon increases relative to RCP4.5 are mainly resulted from reduced heterotrophic respiration under cooler temperature, whilst changes in vegetation productivity only account a negligible part of land carbon changes. The models also varied in their sensitivities of carbon fluxes to changes in air temperature and precipitation. Partial correlation analysis shows that interannual sensitivities of NBP to temperature and precipitation increased by 2 folds in the G4 experiment, due to higher sensitivities of NPP and Rh, yet with large differences among ESMs and spatial heterogeneity. This work suggests that stratospheric aerosol engineering would have small and positive impact on land carbon uptake but could increase climate sensitivities of terrestrial carbon fluxes significantly.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. Microbial extracellular enzymes and the marine carbon cycle.

    PubMed

    Arnosti, Carol

    2011-01-01

    Extracellular enzymes initiate microbial remineralization of organic matter by hydrolyzing substrates to sizes sufficiently small to be transported across cell membranes. As much of marine primary productivity is processed by heterotrophic microbes, the substrate specificities of extracellular enzymes, the rates at which they function in seawater and sediments, and factors controlling their production, distribution, and active lifetimes, are central to carbon cycling in marine systems. In this review, these topics are considered from biochemical, microbial/molecular biological, and geochemical perspectives. Our understanding of the capabilities and limitations of heterotrophic microbial communities has been greatly advanced in recent years, in part through genetic and genomic approaches. New methods to measure enzyme activities in the field are needed to keep pace with these advances and to pursue intriguing evidence that patterns of enzyme activities in different environments are linked to differences in microbial community composition that may profoundly affect the marine carbon cycle.

  4. Climate and carbon-cycle variability over the last millennium

    NASA Astrophysics Data System (ADS)

    Jungclaus, J. H.; Lorenz, S. J.; Timmreck, C.; Reick, C. H.; Brovkin, V.; Six, K.; Segschneider, J.; Giorgetta, M. A.; Crowley, T. J.; Pongratz, J.; Krivova, N. A.; Vieira, L. E.; Solanki, S. K.; Klocke, D.; Botzet, M.; Esch, M.; Gayler, V.; Haak, H.; Raddatz, T. J.; Roeckner, E.; Schnur, R.; Widmann, H.; Claussen, M.; Stevens, B.; Marotzke, J.

    2010-05-01

    A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that stand out against the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed γ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. The magnitude of γ agrees with a recent statistical assessment based on reconstruction data. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing an explanation for the systematic difference in the observational estimates for different segments of the last millennium.

  5. Climate and carbon-cycle variability over the last millennium

    NASA Astrophysics Data System (ADS)

    Jungclaus, J. H.; Lorenz, S. J.; Timmreck, C.; Reick, C. H.; Brovkin, V.; Six, K.; Segschneider, J.; Giorgetta, M. A.; Crowley, T. J.; Pongratz, J.; Krivova, N. A.; Vieira, L. E.; Solanki, S. K.; Klocke, D.; Botzet, M.; Esch, M.; Gayler, V.; Haak, H.; Raddatz, T. J.; Roeckner, E.; Schnur, R.; Widmann, H.; Claussen, M.; Stevens, B.; Marotzke, J.

    2010-10-01

    A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that differ significantly from the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed γ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing a possible explanation for the systematic difference in the observational estimates for different segments of the last millennium.

  6. The methylaspartate cycle in haloarchaea and its possible role in carbon metabolism.

    PubMed

    Borjian, Farshad; Han, Jing; Hou, Jing; Xiang, Hua; Berg, Ivan A

    2016-03-01

    Haloarchaea (class Halobacteria) live in extremely halophilic conditions and evolved many unique metabolic features, which help them to adapt to their environment. The methylaspartate cycle, an anaplerotic acetate assimilation pathway recently proposed for Haloarcula marismortui, is one of these special adaptations. In this cycle, acetyl-CoA is oxidized to glyoxylate via methylaspartate as a characteristic intermediate. The following glyoxylate condensation with another molecule of acetyl-CoA yields malate, a starting substrate for anabolism. The proposal of the functioning of the cycle was based mainly on in vitro data, leaving several open questions concerning the enzymology involved and the occurrence of the cycle in halophilic archaea. Using gene deletion mutants of H. hispanica, enzyme assays and metabolite analysis, we now close these gaps by unambiguous identification of the genes encoding all characteristic enzymes of the cycle. Based on these results, we were able to perform a solid study of the distribution of the methylaspartate cycle and the alternative acetate assimilation strategy, the glyoxylate cycle, among haloarchaea. We found that both of these cycles are evenly distributed in haloarchaea. Interestingly, 83% of the species using the methylaspartate cycle possess also the genes for polyhydroxyalkanoate biosynthesis, whereas only 34% of the species with the glyoxylate cycle are capable to synthesize this storage compound. This finding suggests that the methylaspartate cycle is shaped for polyhydroxyalkanoate utilization during carbon starvation, whereas the glyoxylate cycle is probably adapted for growth on substrates metabolized via acetyl-CoA.

  7. Carbon Cycle Data from the Carbon Dioxide Information Analysis Center (CDIAC)

    DOE Data Explorer

    CDIAC products are indexed and searchable through a customized interface powered by ORNL's Mercury search engine. Products include numeric data packages, publications, trend data, atlases, models, etc. and can be searched for by subject area, keywords, authors, product numbers, time periods, collection sites, spatial references, etc. Some of the collections may also be included in the CDIAC publication Trends Online: A Compendium of Global Change Data. Most data sets, many with numerous data files, are free to download from CDIAC's ftp area. Information related to carbon cycle includes: • Terrestrial Carbon Sequestration Data Sets • Area and Carbon Content of Sphagnum Since Last Glacial Maximum (2002) (Trends Online) • Carbon Dioxide Emissions from Fossil-Fuel Consumption and Cement Manufacture, (2002) (Trends Online) • Estimates of Monthly CO2 Emissions and Associated 13C/12C Values from Fossil-Fuel Consumption in the U.S.A., (2004) (Trends Online) • Estimates of Annual Fossil-Fuel CO2 Emitted for Each State in the U.S.A. and the District of Columbia for Each Year from 1960 through 2001 (Trends Online) • Global, Regional, and National Annual CO2 Emissions from Fossil-Fuel Burning, Cement Production, and Gas Flaring: 1751-1999 (updated 2002) • Geographic Patterns of Carbon Dioxide Emissions from Fossil-Fuel Burning, Hydraulic Cement Production, and Gas Flaring on a One Degree by One Degree Grid Cell Basis: 1950 to 1990 (1997) • Carbon Dioxide Emission Estimates from Fossil-Fuel Burning, Hydraulic Cement Production, and Gas Flaring for 1995 on a One Degree Grid Cell Basis (1998) • AmeriFlux - Terrestrial Carbon Dioxide, Water Vapor, and Energy Balance Measurements Intergovernmental Panel on Climate Change (IPCC), Working Group 1, 1994: Modelling Results Relating Future Atmospheric CO2 Concentrations to Industrial Emissions (1995) • Interannual Variability in Global Soil Respiration on a 0.5 Degree Grid Cell Basis (1980-1994) (2003) • Global

  8. 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

  9. Multi-century Changes to Global Climate and Carbon Cycle: Results from a Coupled Climate and Carbon Cycle Model

    SciTech Connect

    Bala, G; Caldeira, K; Mirin, A; Wickett, M; Delire, C

    2005-02-17

    In this paper, we use a coupled climate and carbon cycle model to investigate the global climate and carbon cycle changes out to year 2300 that would occur if CO{sub 2} emissions from all the currently estimated fossil fuel resources were released to the atmosphere. By year 2300, the global climate warms by about 8 K and atmospheric CO{sub 2} reaches 1423 ppmv. The warming is higher than anticipated because the sensitivity to radiative forcing increases as the simulation progresses. In our simulation, the rate of emissions peak at over 30 PgC yr{sup -1} early in the 22nd century. Even at year 2300, nearly 50% of cumulative emissions remain in the atmosphere. In our simulations both soils and living biomass are net carbon sinks throughout the simulation. Despite having relatively low climate sensitivity and strong carbon uptake by the land biosphere, our model projections suggest severe long-term consequences for global climate if all the fossil-fuel carbon is ultimately released to the atmosphere.

  10. Chemistry of organic carbon in soil with relationship to the global carbon cycle

    SciTech Connect

    Post, W.M. III )

    1988-09-01

    Soil organic carbon in active exchange with the atmosphere constitutes approximately two-thirds of the carbon in terrestrial ecosystems. The large size and long residence time of this pool make it an important component of the global carbon cycle. The amount of carbon stored in soils and the rate of exchange of soil carbon with the atmosphere depends on many factors related to the chemistry of soil organic matter. The amount of carbon stored in soil is determined by the balance of two biotic processes associated with productivity of terrestrial vegetation and decomposition of organic matter. Each of these processes have strong physical controls that can be related to the climate variables temperature and precipitation at a regional or global scale. Soil carbon density generally increases with increasing precipitation, and there is an increase in soil carbon with decreasing temperature for any particular level of precipitation. Various ecosystem disturbances alter the balances between production and decomposition and therefore change the amount of carbon in soil. The most severe perturbation is conversion of natural vegetation to cultivation. The amount of soil carbon and nitrogen change resulting from cultivation depends on the initial amounts of each. Average changes in nitrogen are about one half to one forth the corresponding average carbon changes. Analysis of carbon and nitrogen linkages in soil shed some light on soil carbon dynamics after conversion to agriculture. The amount of initial carbon lost is associated with the amount of carbon in excess of C/N ratio of about 12 to 14. Soils with a high C/N ratio lose a larger fraction of the initial carbon then those with low C/N ratios. Soils with high C/N ratios have a larger percentage of organic matter in slowly decomposing forms. Cultivation results in a lowered input of slowly decomposing material which causes a reduction in overall carbon levels.

  11. Carbon Dioxide Cycling and the Climate of Ancient Earth

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Sleep, Norman H.

    2001-01-01

    The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the strong temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle links with the mantle via subduction and the midocean ridges. Feedback is provided by the dependence of carbonatization on dissolved carbonates in seawater. Unlike the continental cycle, the oceanic cycle has no thermostat. Currently the continental cycle is more important, but earlier in Earth's history, especially if heat flow were higher than it is now, more vigorous plate tectonics would have made the oceanic cycle dominant. We find that CO2 greenhouses thick enough to defeat the faint early Sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of the Proterozoic and the Archean. We echo current fashion and favor biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in the Hadean. Despite its name, the Hadean would have been the coldest era in the history of the Earth.

  12. Carbon Dioxide Cycling And The Climate of Ancient Earth

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Sleep, Norman H.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    The continental cycle of silicate weathering and metamorphism dynamically buffers atmospheric CO2 and climate. Feedback is provided by the strong temperature dependence of silicate weathering. Here we argue that hydrothermal alteration of oceanic basalts also dynamically buffers CO2. The oceanic cycle links with the mantle via subduction and the midocean ridges. Feedback is provided by the dependence of carbonatization on dissolved carbonates in seawater. Unlike the continental cycle, the oceanic cycle has no thermostat. Currently the continental cycle is more important, but earlier in Earth's history, especially if heat flow were higher than it is now, more vigorous plate tectonics would have made the oceanic cycle dominant. We find that CO2 greenhouses thick enough to defeat the faint early sun are implausible and that, if no other greenhouse gases are invoked, very cold climates are expected for much of the Proterozoic and the Archean. We echo current fashion and favor biogenic methane as the chief supplement to CO2. Fast weathering and probable subduction of abundant impact ejecta would have reduced CO2 levels still further in the Hadean. Despite its name, the Hadean would have been the coldest era in the history of the Earth.

  13. 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.

  14. Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

    NASA Astrophysics Data System (ADS)

    Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

    2015-12-01

    Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

  15. Climatically induced sedimentary cycles in Pliocene deep-water carbonates

    SciTech Connect

    Gardulski, A.F. )

    1991-03-01

    Two DSDP sites (86 and 94) on the Campeche ramp in the southern Gulf of Mexico penetrated more than 100 m of Pliocene pelagic ooze. The ooze is primarily carbonate, with a much smaller volcanic ash component than occurs in some Pleistocene sediments at these sites. Cores recovered from these holes display variations in carbonate mineralogy as well as total carbonate and sand abundances that are correlated with the oxygen isotope stratigraphy. Diagenetic loss of Mg-calcite is complete by the base of the Pleistocene, but aragonite, especially high-Sr aragonite forming algal needles that were transported off the shelf to the slope, persists through upper Pliocene cores. Variations in oxygen isotope ratios in planktonic foraminifera occur throughout the Pliocene, although the amplitude of those cycles is smaller than for the Pleistocene, with its more dramatic glacial-interglacial contrasts. As in overlying Pleistocene slope sediments, cooler intervals correspond with greater abundances of aragonite in the upper Pliocene section, reflecting a shift of the shallow, productive shelf seaward across the ramp surface during times of relatively low sea level. However, the aragonite abundances in the Pliocene are reduced on average compared to the Pleistocene. This difference is due in part to diagenetic loss, but also it likely reflects the overall higher sea level that apparently characterized Pliocene oceans, trapping more algal aragonite landward. Although sea level and climatic fluctuations were indeed less extreme in the Pliocene, they were still sufficient to generate sedimentary cycles in deep-water carbonates.

  16. Calibration and testing or models of the global carbon cycle

    SciTech Connect

    Emanuel, W.R.; Killough, G.G.; Shugart, H.H. Jr.

    1980-01-01

    A ten-compartment model of the global biogeochemical cycle of carbon is presented. The two less-abundant isotopes of carbon, /sup 13/C and /sup 14/C, as well as total carbon, are considered. The cycling of carbon in the ocean is represented by two well-mixed compartments and in the world's terrestrial ecosystems by seven compartments, five which are dynamic and two with instantaneous transfer. An internally consistent procedure for calibrating this model against an assumed initial steady state is discussed. In particular, the constraint that the average /sup 13/C//sup 12/C ratio in the total flux from the terrestrial component of the model to the atmosphere be equal to that of the steady-state atmosphere is investigated. With this additional constraint, the model provides a more accurate representation of the influence of the terrestrial system on the /sup 13/C//sup 12/C ratio of the atmosphere and provides an improved basis for interpreting records, such as tree rings, reflecting historical changes in this ratio.

  17. Propagation of uncertainty in carbon emission scenarios through the global carbon cycle

    SciTech Connect

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

    1994-09-01

    The authors used the GLOCO model, which is a carbon cycling model that considers seven terrestrial biomes, two oceans and one atmosphere, to evaluate the rise in atmospheric CO[sub 2] concentration, (pCO[sub 2]) and the partitioning of carbon to the global compartments (ocean, atmosphere and terrestrial) as a function of time for a number of possible anthropogenic carbon emission scenarios, based on different energy policies as developed by the Energy Modeling Forum (EMF-12). The authors then evaluated the possible uncertainty in carbon emission scenarios and the propagation of this uncertainty in carbon emission scenarios and the propagation of this uncertainty throughout the model to obtain an envelope for the rise in pCO[sub 2]. Large fluctuations in the input signal are smoothed by the carbon cycle, resulting in more than a four-fold reduction in uncertainty in the output signal (pCO[sub 2]). In addition, they looked at the effect that other model variables have on the pCO[sub 2] envelope, specifically the ratio of carbon to nitrogen in the emissions. The carbon to nitrogen ratio (C:N) will vary throughout the next century depending on the mix on energy sources chosen. More nitrogen in the emissions can produce a cofertilization effect in the terrestrial biomes, which would lead to sequestration of additional carbon. The uncertainty in C:N will enlarge the pCO[sub 2] uncertainty envelope by up to 20 ppm.

  18. Warming alters coupled carbon and nutrient cycles in experimental streams.

    PubMed

    Williamson, Tanner J; Cross, Wyatt F; Benstead, Jonathan P; Gíslason, Gísli M; Hood, James M; Huryn, Alexander D; Johnson, Philip W; Welter, Jill R

    2016-06-01

    Although much effort has been devoted to quantifying how warming alters carbon cycling across diverse ecosystems, less is known about how these changes are linked to the cycling of bioavailable nitrogen and phosphorus. In freshwater ecosystems, benthic biofilms (i.e. thin films of algae, bacteria, fungi, and detrital matter) act as biogeochemical hotspots by controlling important fluxes of energy and material. Understanding how biofilms respond to warming is thus critical for predicting responses of coupled elemental cycles in freshwater systems. We developed biofilm communities in experimental streamside channels along a gradient of mean water temperatures (7.5-23.6 °C), while closely maintaining natural diel and seasonal temperature variation with a common water and propagule source. Both structural (i.e. biomass, stoichiometry, assemblage structure) and functional (i.e. metabolism, N2 -fixation, nutrient uptake) attributes of biofilms were measured on multiple dates to link changes in carbon flow explicitly to the dynamics of nitrogen and phosphorus. Temperature had strong positive effects on biofilm biomass (2.8- to 24-fold variation) and net ecosystem productivity (44- to 317-fold variation), despite extremely low concentrations of limiting dissolved nitrogen. Temperature had surprisingly minimal effects on biofilm stoichiometry: carbon:nitrogen (C:N) ratios were temperature-invariant, while carbon:phosphorus (C:P) ratios declined slightly with increasing temperature. Biofilm communities were dominated by cyanobacteria at all temperatures (>91% of total biovolume) and N2 -fixation rates increased up to 120-fold between the coldest and warmest treatments. Although ammonium-N uptake increased with temperature (2.8- to 6.8-fold variation), the much higher N2 -fixation rates supplied the majority of N to the ecosystem at higher temperatures. Our results demonstrate that temperature can alter how carbon is cycled and coupled to nitrogen and phosphorus. The

  19. Long-term climate change and the geochemical cycle of carbon

    NASA Technical Reports Server (NTRS)

    Marshall, Hal G.; Walker, James C. G.; Kuhn, William R.

    1988-01-01

    The response of the coupled climate-geochemical system to changes in paleography is examined in terms of the biogeochemical carbon cycle. The simple, zonally averaged energy balance climate model combined with a geochemical carbon cycle model, which was developed to study climate changes, is described. The effects of latitudinal distributions of the continents on the carbon cycle are investigated, and the global silicate weathering rate as a function of latitude is measured. It is observed that a concentration of land area at high altitudes results in a high CO2 partial pressure and a high global average temperature, and for land at low latitudes a cold globe and ice are detected. It is noted that the CO2 greenhouse feedback effect is potentially strong and has a stabilizing effect on the climate system.

  20. Long-term climate change and the geochemical cycle of carbon

    NASA Technical Reports Server (NTRS)

    Marshall, Hal G.; Walker, James C. G.; Kuhn, William R.

    1988-01-01

    The response of the coupled climate-geochemical system to changes in paleography is examined in terms of the biogeochemical carbon cycle. The simple, zonally averaged energy balance climate model combined with a geochemical carbon cycle model, which was developed to study climate changes, is described. The effects of latitudinal distributions of the continents on the carbon cycle are investigated, and the global silicate weathering rate as a function of latitude is measured. It is observed that a concentration of land area at high altitudes results in a high CO2 partial pressure and a high global average temperature, and for land at low latitudes a cold globe and ice are detected. It is noted that the CO2 greenhouse feedback effect is potentially strong and has a stabilizing effect on the climate system.

  1. Changes in the carbon cycle of northern Eurasia simulated by process models

    NASA Astrophysics Data System (ADS)

    Rawlins, M. A.

    2013-12-01

    Pronounced warming across the northern high latitudes is impacting water and carbon cycles and raising concern over possible feedbacks to global climate. Recent model studied point toward a weakening of the terrestrial land carbon sink across the northern high latitudes, one notable manifestation of a warming Arctic. We explore links between regional climate and the carbon cycle using data from models participating in the Vulnerability of Permafrost Carbon Research Coordination Network (RCN). The domain of interest is the drainage basin within the Northern Eurasia Earth Science Partnership Initiative (NEESPI) region. Model outputs examined include gross primary production (GPP), heterotrophic respiration (RH), net ecosystem exchange (NEE), and total soil carbon storage. Mean flux budgets and their changes over the period 1960-2009 are calculated from the model estimates for the entire NEESPI region and for each major land cover category within the region. Use of an independent model, which captures well the spatial pattern in soil freeze/thaw dynamics, indicates that the reduction in permafrost extent over the NEESPI basin was 4-6% over recent decades. Modeled influences of permafrost thaw on the region's water and carbon cycles are evaluated in the context of recent measurements. Estimates of the flux of CO2 due to fire are also examined in order to better understand how these disturbances are altering regional carbon sink/source dynamics.

  2. Comparing American and Chinese Students' Learning Progression on Carbon Cycling in Socio-Ecological Systems

    ERIC Educational Resources Information Center

    Chen, J.; Anderson, C. W.

    2015-01-01

    Previous studies identified a learning progression on the concept of carbon cycling that was typically followed by American students when they progress from elementary to high school. This study examines the validity of this previously identified learning progression for a different group of learners--Chinese students. The results indicate that…

  3. Continental-pelagic carbonate partitioning and the global carbonate-silicate cycle

    NASA Technical Reports Server (NTRS)

    Caldeira, K.; Rampino, M. R. (Principal Investigator)

    1991-01-01

    A carbonate-silicate geochemical cycle model is developed and used to explore dynamic and climatic consequences of constraints on shallow-water carbonate burial and possible carbon loss to the mantle associated with sea-floor subduction. The model partitions carbonate deposition between shallow-water and deep-water environments and includes carbon fluxes between the mantle and lithosphere. When total lithospheric carbonate mass is constant, there are two stable steady states, one in which the carbonate burial flux is mostly continental and another in which it is mostly pelagic. The continental steady state is characterized by a low metamorphic CO2 flux to the atmosphere and predominantly shallow-water carbonate burial. The pelagic steady state is characterized by a high metamorphic CO2 flux and predominantly deep-water carbonate burial. For reasonable parameter values, when total lithospheric carbonate mass is allowed to vary, the model oscillates between predominantly continental and predominantly pelagic modes. Model results suggest that carbonate deposition patterns established during the Cenozoic may be pushing the Earth system from the continental to the pelagic mode on a time scale of 10(8) yr, with a possible consequent order-of-magnitude increase in the metamorphic CO2 flux to the atmosphere.

  4. Deglacial climate, carbon cycle and ocean chemistry changes in response to a terrestrial carbon release

    NASA Astrophysics Data System (ADS)

    Simmons, C. T.; Matthews, H. D.; Mysak, L. A.

    2016-02-01

    Researchers have proposed that a significant portion of the post-glacial rise in atmospheric CO2 could be due to the respiration of permafrost carbon stocks that formed over the course of glaciation. In this paper, we used the University of Victoria Earth System Climate Model v. 2.9 to simulate the deglacial and interglacial carbon cycle from the last glacial maximum to the present. The model's sensitivity to mid and high latitude terrestrial carbon storage is evaluated by including a 600 Pg C carbon pool parameterized to respire in concert with decreases in ice sheet surface area. The respiration of this stored carbon during the early stages of deglaciation had a large effect on the carbon cycle in these simulations, allowing atmospheric CO2 to increase by 40 ppmv in the model, with an additional 20 ppmv increase occurring in the case of a more realistic, prescribed CO2 radiative warming. These increases occurred prior to large-scale carbon uptake due to the reestablishment of boreal forests and peatlands in the proxy record (beginning in the early Holocene). Surprisingly, the large external carbon input to the atmosphere and oceans did not increase sediment dissolution and mean ocean alkalinity relative to a control simulation without the high latitude carbon reservoir. In addition, our simulations suggest that an early deglacial terrestrial carbon release may come closer to explaining some observed deglacial changes in deep-ocean carbonate concentrations than simulations without such a release. We conclude that the respiration of glacial soil carbon stores may have been an important contributor to the deglacial CO2 rise, particularly in the early stages of deglaciation.

  5. Spatial and Temporal Alterations on Carbon and Water Cycles Due to Grazing

    NASA Astrophysics Data System (ADS)

    Maksimowicz, M. M.; Brunsell, N. A.; Ham, J. M.

    2009-05-01

    Grasslands are vital in the carbon cycle, as large amounts of carbon are stored in the soils of the prairie. As climate change affects the carbon cycle, it is essential for the agricultural communities to understand the impacts of these changes on farming practices such as grazing and meat production. The objective of this study is to determine the effect of grazing on the carbon cycle by characterizing the surface boundary layer of both a grazed field and an ungrazed field. Data were collected from open path eddy covariance systems over Rannells Flint Hills Prairie Preserve in north-central Kansas, one over an ungrazed field and one over a grazed field. Cospectra of fluxes of CO2, heat, water, and momentum for July 2007 were compared to assess the size of eddies contributing energy to each field. For CO2, the cospectra for both the ungrazed and the ungrazed field were similar. For all of the other fluxes, lower frequency eddies contributed more energy in the grazed field than the ungrazed field. By using a footprint model, the contributing source areas were determined for fluxes from May through October of 2007. The grazed field had a larger distance of contribution in both stable and unstable atmospheric conditions. Implications of this study include the alterations on fields and impacts on the carbon and water cycles as a result of grazing.

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

    PubMed Central

    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

    2015-01-01

    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

  7. Effect of increasing CO2 on the terrestrial carbon cycle

    PubMed Central

    Schimel, David; Fisher, Joshua B.

    2015-01-01

    Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Our results, however, show significant tropical uptake and, combining tropical and extratropical fluxes, suggest that up to 60% of the present-day terrestrial sink is caused by increasing atmospheric CO2. This conclusion is consistent with a validated subset of atmospheric analyses, but uncertainty remains. Improved model diagnostics and new space-based observations can reduce the uncertainty of tropical and temperate zone carbon flux estimates. This analysis supports a significant feedback to future atmospheric CO2 concentrations from carbon uptake in terrestrial ecosystems caused by rising atmospheric CO2 concentrations. This feedback will have substantial tropical contributions, but the magnitude of future carbon uptake by tropical forests also depends on how they respond to climate change and requires their protection from deforestation. PMID:25548156

  8. Effect of increasing CO2 on the terrestrial carbon cycle.

    PubMed

    Schimel, David; Stephens, Britton B; Fisher, Joshua B

    2015-01-13

    Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Our results, however, show significant tropical uptake and, combining tropical and extratropical fluxes, suggest that up to 60% of the present-day terrestrial sink is caused by increasing atmospheric CO2. This conclusion is consistent with a validated subset of atmospheric analyses, but uncertainty remains. Improved model diagnostics and new space-based observations can reduce the uncertainty of tropical and temperate zone carbon flux estimates. This analysis supports a significant feedback to future atmospheric CO2 concentrations from carbon uptake in terrestrial ecosystems caused by rising atmospheric CO2 concentrations. This feedback will have substantial tropical contributions, but the magnitude of future carbon uptake by tropical forests also depends on how they respond to climate change and requires their protection from deforestation.

  9. Using Radiocarbon to Test Models of Ecosystem Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Trumbore, S.; Lin, H.; Randerson, J.

    2007-05-01

    The radiocarbon content of carbon stored in and respired by ecosystems provides a direct measure of ecosystem carbon dynamics that can be directly compared to model predictions. Because carbon cycles through ecosystems on a variety of timescales, the mean age of C in standing biomass and soil organic matter pools is older than the mean age of microbially respired carbon. In turn, each pathway for C transit through ecosystems my respond differently to edaphic conditions; for example, soil organic matter mean age is controlled by factors affecting stabilization of C on very long timescales, such as mineralogy, while a factor like litter quality that effects decomposition rates reflects vegetation and climate characteristics. We compare the radiocarbon signature of heterotrophically respired CO2 across a number of ecosystems with models predicted using the CASA ecosystem model. The major controls of microbially respired CO2 from ecosystems include the residence time of C in living plant pools (i.e. the age of C in litter inputs to soil) and factors that control decomposition rates (litter quality and climate). Major differences between model and measured values at low latitudes are related to how woody debris pools are treated differently in models and measurements. The time lag between photosynthesis and respiration is a key ecosystem property that defines its potential to store or release carbon given variations in annual net primary production. Radiocarbon provides a rare case where models can be directly compared with measurements to provide a test of this parameter.

  10. Forest defoliator pests alter carbon and nitrogen cycles

    PubMed Central

    Grüning, Maren; Simon, Judy; Reinhardt, Annett-Barbara; Lamersdorf, Norbert; Thies, Carsten

    2016-01-01

    Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores winter moth (Operophtera brumata L.) and mottled umber (Erannis defoliaria L.). In infested forests, total net canopy-to-soil fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared with uninfested oak forests, with 4333 kg C ha−1 and 319 kg N ha−1, respectively, during a pest outbreak over 3 years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared with the non-infested forests. In a microcosm incubation experiment, soil treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide and 10-fold higher fluxes of dissolved organic carbon compared with soil treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity (i.e. heterotrophic respiration), and therefore, may represent an important mechanism by which climate change can initiate a carbon cycle feedback. PMID:27853551

  11. Forest defoliator pests alter carbon and nitrogen cycles.

    PubMed

    L-M-Arnold, Anne; Grüning, Maren; Simon, Judy; Reinhardt, Annett-Barbara; Lamersdorf, Norbert; Thies, Carsten

    2016-10-01

    Climate change may foster pest epidemics in forests, and thereby the fluxes of elements that are indicators of ecosystem functioning. We examined compounds of carbon (C) and nitrogen (N) in insect faeces, leaf litter, throughfall and analysed the soils of deciduous oak forests (Quercus petraea L.) that were heavily infested by the leaf herbivores winter moth (Operophtera brumata L.) and mottled umber (Erannis defoliaria L.). In infested forests, total net canopy-to-soil fluxes of C and N deriving from insect faeces, leaf litter and throughfall were 30- and 18-fold higher compared with uninfested oak forests, with 4333 kg C ha(-1) and 319 kg N ha(-1), respectively, during a pest outbreak over 3 years. In infested forests, C and N levels in soil solutions were enhanced and C/N ratios in humus layers were reduced indicating an extended canopy-to-soil element pathway compared with the non-infested forests. In a microcosm incubation experiment, soil treatments with insect faeces showed 16-fold higher fluxes of carbon dioxide and 10-fold higher fluxes of dissolved organic carbon compared with soil treatments without added insect faeces (control). Thus, the deposition of high rates of nitrogen and rapidly decomposable carbon compounds in the course of forest pest epidemics appears to stimulate soil microbial activity (i.e. heterotrophic respiration), and therefore, may represent an important mechanism by which climate change can initiate a carbon cycle feedback.

  12. Observing terrestrial ecosystems and the carbon cycle from space.

    PubMed

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

    2015-05-01

    Terrestrial ecosystem and carbon cycle feedbacks will significantly impact future climate, but their responses are highly uncertain. Models and tipping point analyses suggest the tropics and arctic/boreal zone carbon-climate feedbacks could be disproportionately large. In situ observations in those regions are sparse, resulting in high uncertainties in carbon fluxes and fluxes. Key parameters controlling ecosystem carbon responses, such as plant traits, are also sparsely observed in the tropics, with the most diverse biome on the planet treated as a single type in models. We analyzed the spatial distribution of in situ data for carbon fluxes, stocks and plant traits globally and also evaluated the potential of remote sensing to observe these quantities. New satellite data products go beyond indices of greenness and can address spatial sampling gaps for specific ecosystem properties and parameters. Because environmental conditions and access limit in situ observations in tropical and arctic/boreal environments, use of space-based techniques can reduce sampling bias and uncertainty about tipping point feedbacks to climate. To reliably detect change and develop the understanding of ecosystems needed for prediction, significantly, more data are required in critical regions. This need can best be met with a strategic combination of remote and in situ data, with satellite observations providing the dense sampling in space and time required to characterize the heterogeneity of ecosystem structure and function. © 2014 John Wiley & Sons Ltd.

  13. Identifying Chemical and Biological Factors Affecting Soil Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Farrant, D. N.; Naughton, H.; Fendorf, S. E.

    2016-12-01

    Soil organic matter (SOM) constitutes a majority of the terrestrial carbon stock, but current models of carbon compound cycling lack grounding in biological and chemical mechanisms. We investigated microbial aerobic and anaerobic respiration rates with respect to depth and the distribution of electron acceptors as possible climate-sensitive drivers of SOM cycling. Soil reactors were designed to simulate the sediment column such that oxygenated water flows horizontally over a column of soil. A native soil that was rich in iron oxides was treated with nitrate, sulfate, neither, and a combination of nitrate and sulfate to mimic potential gradients of available electron acceptors observed in natural environments. Assuming a typical high-to-low oxygen gradient along a soil profile, microbial respiration is expected to decrease at greater depths as available electron acceptors become less energetically favorable. High-energy SOM is expected to be increasingly depleted with depth to counteract low-energy available electron acceptors. Dissolved inorganic carbon (DIC) concentrations in the reactor effluent were calculated with Henry's Law using the effluent pH and headspace CO2 content. Anaerobic respiration was quantified along the soil profile via incubations and both porewater and solid-state sampling of Mn(II), Fe(II), nitrate, sulfate, and H2S. SOM chemistry was analyzed via carbon near-edge X-ray absorption fine structure spectroscopy. Initial results exhibit highest DIC concentrations in the nitrate treatment, corresponding to nitrate's high reduction potential. This research can improve existing models of carbon storage under different redox conditions through examination of the biological and chemical factors determining SOM respiration and storage.

  14. Slow growth rates of Amazonian trees: Consequences for carbon cycling

    PubMed Central

    Vieira, Simone; Trumbore, Susan; Camargo, Plinio B.; Selhorst, Diogo; Chambers, Jeffrey Q.; Higuchi, Niro; Martinelli, Luiz Antonio

    2005-01-01

    Quantifying age structure and tree growth rate of Amazonian forests is essential for understanding their role in the carbon cycle. Here, we use radiocarbon dating and direct measurement of diameter increment to document unexpectedly slow growth rates for trees from three locations spanning the Brazilian Amazon basin. Central Amazon trees, averaging only ≈1mm/year diameter increment, grow half as fast as those from areas with more seasonal rainfall to the east and west. Slow growth rates mean that trees can attain great ages; across our sites we estimate 17-50% of trees with diameter >10 cm have ages exceeding 300 years. Whereas a few emergent trees that make up a large portion of the biomass grow faster, small trees that are more abundant grow slowly and attain ages of hundreds of years. The mean age of carbon in living trees (60-110 years) is within the range of or slightly longer than the mean residence time calculated from C inventory divided by annual C allocation to wood growth (40-100 years). Faster C turnover is observed in stands with overall higher rates of diameter increment and a larger fraction of the biomass in large, fast-growing trees. As a consequence, forests can recover biomass relatively quickly after disturbance, whereas recovering species composition may take many centuries. Carbon cycle models that apply a single turnover time for carbon in forest biomass do not account for variations in life strategy and therefore may overestimate the carbon sequestration potential of Amazon forests. PMID:16339903

  15. A carbon cycle science update since IPCC AR-4.

    PubMed

    Dolman, A J; van der Werf, G R; van der Molen, M K; Ganssen, G; Erisman, J-W; Strengers, B

    2010-01-01

    We review important advances in our understanding of the global carbon cycle since the publication of the IPCC AR4. We conclude that: the anthropogenic emissions of CO2 due to fossil fuel burning have increased up through 2008 at a rate near to the high end of the IPCC emission scenarios; there are contradictory analyses whether an increase in atmospheric fraction, that might indicate a declining sink strength of ocean and/or land, exists; methane emissions are increasing, possibly through enhanced natural emission from northern wetland, methane emissions from dry plants are negligible; old-growth forest take up more carbon than expected from ecological equilibrium reasoning; tropical forest also take up more carbon than previously thought, however, for the global budget to balance, this would imply a smaller uptake in the northern forest; the exchange fluxes between the atmosphere and ocean are increasingly better understood and bottom up and observation-based top down estimates are getting closer to each other; the North Atlantic and Southern ocean take up less CO2, but it is unclear whether this is part of the 'natural' decadal scale variability; large-scale fires and droughts, for instance in Amazonia, but also at Northern latitudes, have lead to significant decreases in carbon uptake on annual timescales; the extra uptake of CO2 stimulated by increased N-deposition is, from a greenhouse gas forcing perspective, counterbalanced by the related additional N2O emissions; the amount of carbon stored in permafrost areas appears much (two times) larger than previously thought; preservation of existing marine ecosystems could require a CO2 stabilization as low as 450 ppm; Dynamic Vegetation Models show a wide divergence for future carbon trajectories, uncertainty in the process description, lack of understanding of the CO2 fertilization effect and nitrogen-carbon interaction are major uncertainties.

  16. Transparent exopolymer particles: Effects on carbon cycling in the ocean

    NASA Astrophysics Data System (ADS)

    Mari, Xavier; Passow, Uta; Migon, Christophe; Burd, Adrian B.; Legendre, Louis

    2017-02-01

    Transparent Exopolymer Particles (TEP) have received considerable attention since they were first described in the ocean more than 20 years ago. This is because of their carbon-rich composition, their high concentrations in ocean's surface waters, and especially because of their ability to promote aggregation due to their high stickiness (i.e. biological glue). As large aggregates contribute significantly to vertical carbon flux, TEP are commonly seen as a key factor that drives the downward flux of particulate organic carbon (POC). However, the density of TEP is lower than that of seawater, which causes them to remain in surface waters and even move upwards if not ballasted by other particles, which often leads to their accumulation in the sea surface microlayer. Hence we question here the generally accepted view that TEP always increase the downward flux of POC via gravitational settling. In the present reassessment of the role of TEP, we examine how the presence of a pool of non-sinking carbon-rich particulate organic matter in surface waters influences the cycling of organic carbon in the upper ocean at daily to decadal time scales. In particular, we focus on the role of TEP in the retention of organic carbon in surface waters versus downward export, and discuss the potential consequences of climate change on this process and on the efficiency of the biological carbon pump. We show that TEP sink only when ballasted with enough high-density particles to compensate their low density, and hence that their role in vertical POC export is not solely linked to their ability to promote aggregation, but also to their contribution to the buoyancy of POC. It follows that the TEP fraction of POC determines the degree of retention and remineralization of POC in surface waters versus its downward export. A high TEP concentration may temporally decouple primary production and downward export. We identify two main parameters that affect the contribution of TEP to POC cycling

  17. Carbon cycling by cellulose-fermenting nitrogen-fixing bacteria

    NASA Astrophysics Data System (ADS)

    Leschine, S. B.; Canale-Parola, E.

    The most abundant organic materials on Earth are plant polysaccharides such as cellulose and hemicelluloses. Inasmuch as vast quantities of these polymers are present in anaerobic environments (e.g., in soils and sediments), anaerobic microorganisms that ferment plant polysaccharides play a central role in carbon cycling on the planet as a source of CO2 and, indirectly, of CH4. Cellulose-fermenting bacteria from soil and pond sediment were isolated in a medium (incubated in N2) which lacked a source of combined nitrogen. The isolates had the ability to utilize atmospheric N2 as the nitrogen source for cell growth. Nitrogenase (the enzyme which catalyzes the reduction of N2 to ammonia) was demonstrated by means of the acetylene reduction test in these isolates and in several previously described anaerobic cellulolytic bacteria isolated from various natural environments. Thus, cellulose-fermenting bacteria that fix N2 may be widespread and may play a role in nitrogen cycling as well as in carbon cycling on a global scale. Knowledge of the physiology and ecology of these organisms is crucial to detailing the mechanisms producing local sources and sinks of atmospheric gases, interpreting data obtained using space-based sensors, and understanding the effects of atmospheric warming on fermentations as major sources of CO2 and CH4.

  18. Microbial diversity and carbon cycling in San Francisco Bay wetlands

    SciTech Connect

    Theroux, Susanna; Hartman, Wyatt; He, Shaomei; Tringe, Susannah

    2014-03-21

    Wetland restoration efforts in San Francisco Bay aim to rebuild habitat for endangered species and provide an effective carbon storage solution, reversing land subsidence caused by a century of industrial and agricultural development. However, the benefits of carbon sequestration may be negated by increased methane production in newly constructed wetlands, making these wetlands net greenhouse gas (GHG) sources to the atmosphere. We investigated the effects of wetland restoration on below-ground microbial communities responsible for GHG cycling in a suite of historic and restored wetlands in SF Bay. Using DNA and RNA sequencing, coupled with real-time GHG monitoring, we profiled the diversity and metabolic potential of wetland soil microbial communities. The wetland soils harbor diverse communities of bacteria and archaea whose membership varies with sampling location, proximity to plant roots and sampling depth. Our results also highlight the dramatic differences in GHG production between historic and restored wetlands and allow us to link microbial community composition and GHG cycling with key environmental variables including salinity, soil carbon and plant species.

  19. Cycling of beryllium and carbon through hillslope soils in Iowa

    USGS Publications Warehouse

    Harden, J.W.; Fries, T.L.; Pavich, M.J.

    2002-01-01

    Isotopes of Be and C were used to reconstruct loess accumulation, hillslope evolution, and agricultural modification in soils of western Iowa. While both elements are derived from additions by the atmosphere (via plants in the case of carbon), the differences in element cycling allow erosional and depositional processes to be separated from biochemical processing. Based on 10Be, loess accumulation likely occurred simultaneously with hillslope degradation. Rates of loess accumulation declined five-fold between early stages (late Pleistocene and early Holocene) and later stages (late Holocene) of accumulation, but the absolute timing of accumulation requires independent dating methods. Based on 14C measurements, plant inputs and decomposition are significant near the surface, but below 1-1.5 m carbon inputs are minimal and decomposition is nearly arrested. The amount of carbon below 1.5 m is constant (0.1%) and is composed of soil organic matter that was buried by loess. Agricultural modification results in a dramatic redistribution of 10Be through soil erosion and deposition. By contrast, the redistribution of soil organic matter is masked by the rapid cycling of C through the topsoil as it continually decomposes and is replaced by plant inputs.

  20. Landslide disturbance: implications for chemical weathering, vegetation and carbon cycling

    NASA Astrophysics Data System (ADS)

    Milledge, D.; Hilton, R. G.

    2011-12-01

    Landslides disturb physical and ecological systems by periodically stripping away soil and vegetation. This turnover influences the makeup and productivity of vegetation as well as the chemical weathering rate for the soil. Recent research has highlighted these links focusing on landslide magnitude and frequency and calculating turnover on a catchment wide basis. However, landslide probability and therefore turnover is not uniform in space. We investigate the influence of this spatial variability on the frequency distribution of landslide turnover and its implications for: vegetation disturbance, carbon cycling and chemical weathering. We use first synthetic landslide risk distributions then real distributions from the Western Southern Alps and Oregon Coast Range. We use these to generate turnover distributions then compare these with the turnover rate predicted assuming spatially uniform landslide probability. We use published relations to work through the implications for: vegetation disturbance, carbon cycling and chemical weathering. We find that: 1) landslide turnover rates are too slow even in the most active parts of the landscape to chronically disturb the vegetation; 2) the changes to productivity are generally subtle leading to only minor changes in the carbon flux; and 3) landslide related chemical weathering rates are reduced in areas with strongly non-uniform landslide risk distributions.

  1. Linking disturbance intensity and carbon cycle in forest ecosystems

    NASA Astrophysics Data System (ADS)

    Gielen, B.; Hudiburg, T.; Law, B. E.; Luyssaert, S.

    2011-12-01

    There is increasing awareness that natural and anthropogenic disturbance in forests forest affects exchange of CO2, H2O and energy between the ecosystem and the atmosphere. Furthermore, severe disturbance may result in substantial emissions of greenhouse gasses to the atmosphere. Consequently quantification of land use and disturbance intensity (LUDI) is one of the next steps needed to improve our understanding of the carbon cycle, its interactions with the atmosphere and its main drivers at local as well as at global level. The conventional NPP-based approaches to quantify the intensity of land management are limited because they lack a sound ecological basis. Here we apply a new way of characterising the degree of management and disturbance in forest. The index called LUDI: land use and disturbance intensity makes use of the self thinning theory and observations of diameter at breast height and stand density. The application of LUDI was demonstrated by using a very extensive dataset from the Pacific Northwest region (PNW) in North America containing more than 5000 inventory plots. Results show significant relationships between LUDI and forest productivity (NPP) and Carbon uptake (NEP) for seven different forest types in the PNW. In addition the relationships suggest a maximal productivity at mild disturbance. These results further confirm the link between forest disturbance and carbon cycling in forest ecosystems.

  2. Applications of dendrochronology for informing terrestrial carbon cycle modeling

    NASA Astrophysics Data System (ADS)

    Poulter, B.; Babst, F.; Ciais, P.; Frank, D. C.; Hessl, A. E.; Liu, H.; Pederson, N.

    2014-12-01

    Dendrochronology provides unique ecological information on forest dynamics that can be used to develop and benchmark terrestrial carbon cycle models. In recent years, integration between dendrochronology and process-based ecosystem models has been yielded insight into climate sensitivity of tree growth, annual carbon uptake, water-use efficiency, and phenology. Here we review some of these advances as well as some of the scaling challenges associated with representing forest stand-level dynamics from individual tree growth measurements. In particular, increment cores from trees provide annual temporal resolution of biomass gain that is recorded from decade to centennial time scales. Efforts to use such measurements to reconstruct stand level biomass gain, or net primary production, have to address issues related to sampling design as well as account for mortality-driven changes in stem density that take place during stand development, what is referred to as the 'fading record' problem. One solution to the fading record problem is to reconstruct stem density over time by applying self-thinning theory within a calibrated forest dynamics model. With this approach, recorded tree growth and modeled stand density dynamics can be used to estimate stand-level net primary production that more accurately relates to productivity estimates from carbon cycle models. An improved understanding of trends in forest productivity over the past century is critical for a range of forest management and forest science issues, where traditional growth and yield tables exclude effects of climate and atmospheric changes in CO2 on forest growth.

  3. Study of multiple cycles valves

    NASA Technical Reports Server (NTRS)

    Wichmann, H.

    1973-01-01

    A discussion is presented regarding valves which can be cycled repeatedly and are available from industry for application in the inlet system for the Pioneer Venus Probe mass spectrometer. Both solenoid type and latching type valves are considered. The study is divided into two principal areas: (1) preparation of a valve specification reflecting the requirements of the inlet system cyclic valves for the Pioneer Venus Probe mass spectrometer and the submittal of this specification to potential valve suppliers for their response and proposal; (2) preparation of a design layout of an optimum cyclic valve meeting all of the valve specification requirements.

  4. What Have We Learned About Arctic Carbon Since The First State of the Carbon Cycle Report?

    NASA Astrophysics Data System (ADS)

    Schuur, E.

    2015-12-01

    Large pools of organic carbon were reported in The First State of the Carbon Cycle Report, but measurements from high latitude ecosystems, in particular for deeper soils >1m depth, remained scarce. A newly enlarged soil carbon database with an order of magnitude more numerous deep sampling sites has verified the widespread pattern of large quantities of carbon accumulated deep in permafrost (perennially frozen) soils. The known pool of permafrost carbon across the northern circumpolar permafrost zone is now estimated to be 1330-1580 Pg C, with the potential for an additional ~400 Pg C in deep permafrost sediments. In addition, an uncertainty estimate of plus/minus 15% has now been calculated for the soil carbon pool in the surface 0-3m. Laboratory incubations of these permafrost soils reveal that a significant fraction can be mineralized by microbes upon thaw and converted to carbon dioxide and methane on time scales of years to decades, with decade-long average losses from aerobic incubations ranging from 6-34% of initial carbon. Carbon emissions from the same soils incubated in an anaerobic environment are, on average, 78-85% lower than aerobic soils. But, the more potent greenhouse gas methane released under anaerobic conditions in part increases the climate impact of these emissions. While mean quantities of methane are only 3% to 7% that of carbon dioxide emitted from anaerobic incubations (by weight of C), these mean methane values represent 25% to 45% of the overall potential impact on climate when accounting for the higher global warming potential of methane. Taken together though, in spite of the more potent greenhouse gas methane, a unit of newly thawed permafrost carbon could have a greater impact on climate over a century if it thaws and decomposes within a drier, aerobic soil as compared to an equivalent amount of carbon within a waterlogged soil or sediment. Model projections tend to estimate losses of carbon in line with empirical measurements, but

  5. Carbon cycle and climate effects of forcing from fire-emitted aerosols

    NASA Astrophysics Data System (ADS)

    Landry, Jean-Sébastien; Partanen, Antti-Ilari; Damon Matthews, H.

    2017-02-01

    Aerosols emitted by landscape fires affect many climatic processes. Here, we combined an aerosol–climate model and a coupled climate–carbon model to study the carbon cycle and climate effects caused by fire-emitted aerosols (FEA) forcing at the top of the atmosphere and at the surface. This forcing (‘best guess’ present-day values of ‑0.10 and ‑1.3 W m‑2 at the top of the atmosphere and surface, respectively) had a predominant cooling influence that altered regional land carbon stocks on decadal timescales by modifying vegetation productivity and soil–litter decomposition. Changes in regional land and ocean carbon stocks became much stronger for FEA forcing acting on multi-century timescales; this occurred because carbon stocks responded to the forcing itself on such timescales and also due to gradual effects on the climate (e.g. through increased sea ice cover) that further affected the carbon cycle. Carbon increases and decreases in different regions partly offset each other, so that absolute changes in global land, atmosphere, and ocean stocks were all <2 Pg C after 30 years of FEA forcing and <6 Pg C after more than 1000 years of FEA forcing. FEA-caused changes in land carbon storage did not substantially modify the magnitude of FEA emissions, suggesting there is no consequential regional-scale positive feedback loop between these two elements. However, we found indications that the FEA-caused cooling from frequently-burning regions in Africa and Australia increased land carbon stocks in eastern South America and equatorial Asia, respectively. This suggests the potential for remote carbon cycle effects from regions emitting large amounts of fire aerosols.

  6. Land use change effects on forest carbon cycling throughout the southern United States.

    PubMed

    Woodbury, Peter B; Heath, Linda S; Smith, James E

    2006-01-01

    We modeled the effects of afforestation and deforestation on carbon cycling in forest floor and soil from 1900 to 2050 throughout 13 states in the southern United States. The model uses historical data on gross (two-way) transitions between forest, pasture, plowed agriculture, and urban lands along with equations describing changes in carbon over many decades for each type of land use change. Use of gross rather than net land use transition data is important because afforestation causes a gradual gain in carbon stocks for many decades, while deforestation causes a much more rapid loss in carbon stocks. In the South-Central region (Texas to Kentucky) land use changes caused a net emission of carbon before the 1980s, followed by a net sequestration of carbon subsequently. In the Southeast region (Florida to Virginia), there was net emission of carbon until the 1940s, again followed by net sequestration of carbon. These results could improve greenhouse gas inventories produced to meet reporting requirements under the United Nations Framework Convention on Climate Change. Specifically, from 1990 to 2004 for the entire 13-state study area, afforestation caused sequestration of 88 Tg C, and deforestation caused emission of 49 Tg C. However, the net effect of land use change on carbon stocks in soil and forest floor from 1990 to 2004 was about sixfold smaller than the net change in carbon stocks in trees on all forestland. Thus land use change effects and forest carbon cycling during this period are dominated by changes in tree carbon stocks.

  7. Investigating the Early Carbon Cycle Using Carbonaceous Inclusions and Dissolved Carbon in Detrital Zircon

    NASA Astrophysics Data System (ADS)

    Bell, E. A.; Boehnke, P.; Harrison, M.; Mao, W. L.

    2015-12-01

    Because the terrestrial rock record extends only to ~4 Ga and older materials thus far identified are limited to detrital zircons, information about volatile abundances and cycles on early Earth is limited. Carbon, for instance, plays an important role not only in the modern biosphere but also in deep recycling of materials between the crust and mantle. We are investigating the record of carbon abundance and origin in Hadean zircons from Jack Hills (W. Australia) using two main approaches. First, carbon may partition into the zircon structure at trace levels during crystallization from a magma, and better understanding of this partitioning behavior will allow for zircon's use as a monitor of magmatic carbon contents. We have measured carbon abundances in zircon from a variety of igneous rocks (gabbro; I-, A-, and S-type granitoids) via SIMS and found that although abundances are typically low (average raw 12C/30Si ~ 1x10-6), S-type granite zircons can reach a factor of 1000 over this background. Around 10% of Hadean zircons investigated show similar enrichments, consistent with other evidence for the derivation of many Jack Hills zircons from S-type granitoids and with the establishment of modern-level carbon abundances in the crust by ca. 4.2 Ga. Diamond and graphite inclusions reported in the Jack Hills zircons by previous studies proved to be contamination by polishing debris, leaving the true abundance of these materials in the population uncertain. On a second front, we have identified and investigated primary carbonaceous inclusions in these zircons. From a population of over 10,000 Jack Hills zircons, we identified one concordant 4.10±0.01 Ga zircon that contains primary graphite inclusions (so interpreted due to their enclosure in a crack-free zircon host as shown by transmission X-ray microscopy and their crystal habit). Their δ13CPDB of -24±5‰ is consistent with a biogenic origin and, in the absence of a likely inorganic mechanism to produce such a

  8. Belowground carbon cycle of Napier and Guinea grasses

    NASA Astrophysics Data System (ADS)

    Sumiyoshi, Y.; Crow, S. E.; Litton, C. M.; Deenik, J. L.

    2011-12-01

    Soil carbon (C) sequestration may partially offset rising atmospheric CO2 concentration. Napier grass (Pennisetum purpureum) and Guinea grass (Panicum maximum), in particular, are perennial C4 grasses with high capacity to produce large amounts of both aboveground and belowground biomass. Thus, they have a potential to sequester soil C while simultaneously provide aboveground biomass for energy production. In this study, both grasses were ratooned (no-till) to leave belowground biomass intact and facilitate C accumulation through improvement of soil aggregation. The primary objective of the study was to determine if and how these grasses sequester soil C. For 8 selected grass varieties, we: (1) determined the quantity and quality of belowground C input, (2) quantified changes in soil organic C (SOC) during two harvesting cycles (May 2010 to July 2011), and (3) fractionated soil C pools to determine where changes in SOC occurred. Soil-surface CO2 efflux and root biomass were used as measures of the quantity of belowground C input. Root lignin/N ratios and decay constants from litterbag studies were used as measures of the belowground C input quality. We hypothesized that grass varieties with higher quantity and lower quality of belowground C input would sequester more soil C. Root biomass collected on May 2010 ranged from 13 to 302 g m-2 at 15 cm depth, where Local (Napier) and OG05 (Guinea) varieties were significantly greater than the K06 variety (Guinea). However, cumulative soil-surface CO2 efflux showed no significant differences between the three varieties. Root Lignin/N ranged from 16 to 55 and Guinea varieties were significantly higher on average than Napier varieties. Root decay constants were variable among varieties, with OG05 and K06 showing higher resistance to decay compared to Local. Soil C sequestration potentials and factors affecting the process are imperative to determine suitable variety for bioenergy production.

  9. Late Mississippian (Chesterian) carbonate to carbonate-clastic cycles in the eastern Illinois Basin

    SciTech Connect

    Smith, L.B.; Read, J.F. )

    1994-03-01

    Late Mississippian (Chesterian) rocks of the eastern Illinois Basin in Kentucky and Indiana show depositional cycles (3--20 meters thick) composed of a range of facies deposited during the transition from carbonate-dominated deposition of the Middle Mississippian to the predominantly siliciclastic regime of the Pennsylvanian. Within the basal Ste. Genevieve Formation (30--70 meters thick) there are five predominantly carbonate cycles. Cycle bases vary from thin calcareous sandstone near the northern clastic source to ooid-quartz dolomitic pelletal grainstone and mudstone further south. Massive cross-bedded and channeled ooid-skeletal grainstones represent the cycle tops and are commonly capped by caliche and subaerial breccia, particularly where there was no subsequent siliciclastic deposition. The cycles are interpreted to be driven by fourth-order (400 k.y.) glacio-eustatic sea-level fluctuations based on coincidence of the calculated cycle period with the long-term eccentricity signal, the Late Mississippian onset of Gondwana glaciation and cycle correlation over more than 100 kilometers. The breccia and caliche formed during lowstands, the siliciclastics, eolianites and dolomitic pelletal grainstones are transgressive facies and the ooid-skeletal grainstones represent sea-level highstands.

  10. Developing a Multi-Year Learning Progression for Carbon Cycling in Socio-Ecological Systems

    ERIC Educational Resources Information Center

    Mohan, Lindsey; Chen, Jing; Anderson, Charles W.

    2009-01-01

    This study reports on our steps toward achieving a conceptually coherent and empirically validated learning progression for carbon cycling in socio-ecological systems. It describes an iterative process of designing and analyzing assessment and interview data from students in upper elementary through high school. The product of our development…

  11. Developing a Multi-Year Learning Progression for Carbon Cycling in Socio-Ecological Systems

    ERIC Educational Resources Information Center

    Mohan, Lindsey; Chen, Jing; Anderson, Charles W.

    2009-01-01

    This study reports on our steps toward achieving a conceptually coherent and empirically validated learning progression for carbon cycling in socio-ecological systems. It describes an iterative process of designing and analyzing assessment and interview data from students in upper elementary through high school. The product of our development…

  12. Urbanization and the carbon cycle: Current capabilities and research outlook from the natural sciences perspective

    NASA Astrophysics Data System (ADS)

    Hutyra, Lucy R.; Duren, Riley; Gurney, Kevin R.; Grimm, Nancy; Kort, Eric A.; Larson, Elisabeth; Shrestha, Gyami

    2014-10-01

    This paper explores the urban carbon cycle from the natural sciences perspective, identifying key knowledge gaps and priority areas for future research. The combination of large, concentrated carbon fluxes and rapid change makes cities key elements of the carbon cycle and offers the potential for them to serve as "first responders" for climate action. Estimates of urban-scale carbon fluxes are significantly more uncertain than at larger spatial scales, in part because past studies have mostly avoided local/urban scales where the mix of anthropogenic and natural fluxes is complex and difficult to observationally isolate. To develop effective emission reduction policies, we need to understand emission sources and how they may be changing. Such improved quantification and understanding of underlying processes at the urban scale will not only provide policy-relevant information and improve the understanding of urban dynamics and future scenarios, but will also translate into better global-scale anthropogenic flux estimates, and advance our understanding of carbon cycle and climate feedbacks across multiple scales. Understanding the relationship between urbanization and urban carbon flows requires intellectual integration with research communities beyond the natural sciences. Cities can serve as interdisciplinary process laboratories that are sufficiently constrained in both spatial and governance scale to support truly integrated research by the natural sciences, social sciences, and engineering. A thoughtfully crafted science research agenda that is grounded in sustained, dense observations relevant to estimating urban carbon fluxes and their controlling processes and is focused on a statistically significant sample of cities will advance our understanding of the carbon cycle.

  13. Transporting carbon dioxide recovered from fossil-energy cycles

    SciTech Connect

    Doctor, R. D.; Molburg, J. C.; Brockmeier, J. F.

    2000-07-24

    Transportation of carbon dioxide (CO{sub 2}) for enhanced oil recovery is a mature technology, with operating experience dating from the mid-1980s. Because of this maturity, recent sequestration studies for the US Department of Energy's National Energy Technology Laboratory have been able to incorporate transportation into overall energy-cycle economics with reasonable certainty. For these studies, two different coal-fueled plants are considered; the first collects CO{sub 2} from a 456-MW integrated coal gasification combined-cycle plant, while the second employs a 353-MW pulverized-coal boiler plant retrofitted for flue-gas recycling (Doctor et al. 1999; MacDonald and Palkes 1999). The pulverized-coal plant fires a mixture of coal in a 33% O{sub 2} atmosphere, the bulk of the inert gas being made up to CO{sub 2} to the greatest extent practical. If one power plant with one pipe feeds one sequestration reservoir, projected costs for a 500-km delivery pipeline are problematic, because when supplying one reservoir both plant availability issues and useful pipeline life heavily influence capital recovery costs. The transportation system proposed here refines the sequestration scheme into a network of three distinctive pipelines: (1) 80-km collection pipelines for a 330-MW pulverized-coal power plant with 100% CO{sub 2} recovery; (2) a main CO{sub 2} transportation trunk of 320 km that aggregates the CO{sub 2} from four such plants; and (3) an 80-km distribution network. A 25-year life is assumed for the first two segments, but only half that for the distribution to the reservoir. Projected costs for a 500-km delivery pipeline, assuming an infrastructure, are $7.82/tonne ($17.22/10{sup 3} Nm{sub 3} CO{sub 2} or $0.49/10{sup 3} scf CO{sub 2}), a savings of nearly 60% with respect to base-case estimates with no infrastructure. These costs are consistent only with conditioned CO{sub 2} having low oxygen and sulfur content; they do not include CO{sub 2} recovery, drying

  14. Carbon cycling in primary production bottle incubations: inferences from grazing experiments and photosynthetic studies using 14C and 18O in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Laws, Edward A.; Landry, Michael R.; Barber, Richard T.; Campbell, Lisa; Dickson, Mary-Lynn; Marra, John

    Estimates of photosynthesis based on the incorporation of 14C-labeled inorganic carbon into particulate carbon were compared to estimates of gross photosynthesis based on net O 2 production and the production of 18O2 from H218O during the US Joint Global Ocean Flux Study (US JGOFS) Arabian Sea process cruises. For samples incubated below the surface and at optical depths<3, the 14C uptake : gross photosynthesis ratio averaged 0.45±0.1. This result is in accord with theoretical considerations of the combined effects of the Mehler reaction, photorespiration, dark respiration, excretion, and grazing effects on the two estimates of photosynthesis. The 14C uptake : gross photosynthesis ratio was distinctly higher (0.62) for samples incubated at the surface. This result is likely due to UV light effects, since the O 2 and 14C incubations were done in quartz and polysulfone bottles, respectively. The 14C uptake : gross photosynthesis ratio was lower (0.31) for bottles incubated at optical depths>3. This result probably reflects an increase in the ratio of dark respiration to net photosynthesis in the vicinity of the compensation light level.

  15. Black carbon, a 'hidden' player in the global C cycle

    NASA Astrophysics Data System (ADS)

    Santín, C.; Doerr, S. H.

    2012-04-01

    During the 2011 alone more than 600 scientific papers about black carbon (BC) were published, half of them dealing with soils (ISI Web of Knowledge, accessed 15/01/2012). If the search is extended to the other terms by which BC is commonly named (i.e. biochar, charcoal, pyrogenic C or soot), the number of 2011 publications increases to >2400, 20% of them also related to soils. These figures confirm BC as a well-known feature in the scientific literature and, thus, in our research community. In fact, there is a wide variety of research topics where BC is currently studied: from its potential as long-term C reservoir in soils (man-made biochar), to its effects on the Earth's radiation balance (soot-BC), including its value as indicator in paleoenvironmental studies (charcoal) or, even surprisingly, its use in suicide attempts. BC is thus relevant to many aspects of our environment, making it a very far-reaching, but also very complex topic. When focusing 'only' on the role of BC in the global C cycle, numerous questions arise. For example: (i) how much BC is produced by different sources (i.e. vegetation fires, fossil fuel and biofuel combustion); (ii) what are the main BC forms and their respective proportions generated (i.e. proportion of atmospheric BC [BC-soot] and the solid residues [char-BC]); (iii) where does this BC go (i.e. main mobilization pathways and sinks); (iv) how long does BC stay in the different systems (i.e. residence times in soils, sediments, water and atmosphere); (v) which are the BC stocks and its main transformations within and between the different systems (i.e. BC preservation, alteration and mineralization); (vi) what is the interaction of BC with other elements and how does this influence BC half-life (i.e. physical protection, interaction with pollutants, priming effects in other organic materials)? These questions, and some suggestions about how to tackle these, will be discussed in this contribution. It will focus in particular on the

  16. Exploring Viral Mediated Carbon Cycling in Thawing Permafrost Microbial Communities

    NASA Astrophysics Data System (ADS)

    Trubl, G. G.; Solonenko, N.; Moreno, M.; Sullivan, M. B.; Rich, V. I.

    2014-12-01

    Viruses are the most abundant biological entities on Earth and their impact on carbon cycling in permafrost habitats is poorly understood. Arctic C cycling is particularly important to interpret due to the rapid climate change occurring and the large amount of C stockpiled there (~1/3 of global soil C is stored in permafrost). Viruses of microbes (i.e. phages) play central roles in C cycling in the oceans, through cellular lysis (phage drive the largest ocean C flux about 150 Gt yr-1, dwarfing all others by >5-fold), production of associated DOC, as well as transport and expression during infection (1029 transduction events day-1). C cycling in thawing permafrost systems is critical in understanding the climate trajectory and phages may be as important for C cycling here as they are in the ocean. The thawed C may become a food source for microbes, producing CO2 and potentially CH4, both potent greenhouse gases. To address the potential role of phage in C cycling in these dynamic systems, we are examining phage from an arctic permafrost thaw gradient in northern Sweden. We have developed a protocol for successfully extracting phage from peat soils and are quantifying phage in 15 peat and 2 lake sediment cores, with the goal of sequencing viromes. Preliminary data suggest that phage are present at 109 g-1 across the permafrost thaw gradient (compared to the typical marine count ~105 ml-1), implying a potentially robust phage-host interaction web in these changing environments. We are examining phage from 11 depth intervals (covering the active and permafrost layer) in the cores to assess phage-host community dynamics. Phage morphology and abundance for each layer and environment are being determined using qTEM and EFM. Understanding the phage that infect bacteria and archaea in these rapidly changing habitats will provide insight into the controls on current and future CH4 and CO2 emissions in permafrost habitats.

  17. Variations in carbonate shelf cycles in response to Appalachian tectonism

    SciTech Connect

    Algeo, T.J.

    1986-05-01

    Shelf facies strata of the Upper Mississippian Bangor Limestone in northwest Georgia and southeast Tennessee comprise asymmetric regressive cycles that are similar to shallowing-upward cycles described in many ancient and modern shallow marine carbonate sequences. Typical Bangor cycles consist of a lower 0.6-m transgressive hemicycle of poorly sorted intraclast-oolite grainstones, and an upper 15-m regressive hemicycle that grades vertically from open-marine fossil wackestone and packstone through barrier-bar oolite grainstone, to burrowed lagoonal wackestone and laminated fenestral tidal-flat mudstone and dolostone. Lateral variations in the number, thickness, and facies composition of cycles were controlled by the position of each Bangor section relative to the Mississippian shoreline and shelf margin, and by localized shelf downwarping in response to Appalachian foreland basin evolution. To the northeast, at Monteagle, Tennessee, evaporitic tidal flats flanked the low-lying Nashville dome. There, laminated fenestral mudstone and dolostone dominate a thin (58-m) Bangor section, with only one major marine transgression reaching this area. At Raccoon Mountain, Tennessee, in the midshelf area, syndepositional downwarping of the Raccoon Mountain trough controlled sedimentation and deposited a thick (120-m) Bangor section containing seven cycles of highly variable thickness and facies composition. To the southeast, at Pigeon Mountain, Georgia, the outer shelf was increasingly influenced by foreland basin sedimentation during the late Bangor. There, the lower part of a thin (52-m) Bangor section contains two normal regressive cycles, but abundant thin shale laminae and frequent facies shifts in the upper 15 m document increasing clastic influx and tectonic instability in source areas to the southeast.

  18. Methane hydrate in the global organic carbon cycle

    USGS Publications Warehouse

    Kvenvolden, K.A.

    2002-01-01

    The global occurrence of methane hydrate in outer continental margins and in polar regions, and the magnitude of the amount of methane sequestered in methane hydrate suggest that methane hydrate is an important component in the global organic carbon cycle. Various versions of this cycle have emphasized the importance of methane hydrate, and in the latest version the role of methane hydrate is considered to be analogous to the workings of an electrical circuit. In this circuit the methane hydrate is a condenser and the consequences of methane hydrate dissociation are depicted as a resistor and inductor, reflecting temperature change and changes in earth surface history. These consequences may have implications for global change including global climate change.

  19. Methanogenic burst in the end-Permian carbon cycle

    PubMed Central

    Rothman, Daniel H.; Fournier, Gregory P.; French, Katherine L.; Alm, Eric J.; Boyle, Edward A.; Cao, Changqun; Summons, Roger E.

    2014-01-01

    The end-Permian extinction is associated with a mysterious disruption to Earth’s carbon cycle. Here we identify causal mechanisms via three observations. First, we show that geochemical signals indicate superexponential growth of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the expansion of a new microbial metabolic pathway. Second, we show that the efficient acetoclastic pathway in Methanosarcina emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth’s greatest mass extinction by a specific microbial innovation. PMID:24706773

  20. How life affects the geochemical cycle of carbon

    NASA Technical Reports Server (NTRS)

    Walker, James C. G.

    1992-01-01

    Developing a quantitative understanding of the biogeochemical cycles of carbon as they have worked throughout Earth history on various time scales, how they have been affected by biological evolution, and how changes in the carbon content of ocean and atmosphere may have affected climate and the evolution of life are the goals of the research. Theoretical simulations were developed that can be tuned to reproduce such data as exist and, once tuned, can be used to predict properties that have not yet been observed. This is an ongoing process, in which models and results are refined as new data and interpretations become available and as understanding of the global system improves. Results of the research are described in several papers which were published or submitted for publication. These papers are summarized. Future research plans are presented.

  1. Methanogenic burst in the end-Permian carbon cycle

    NASA Astrophysics Data System (ADS)

    Rothman, Daniel H.; Fournier, Gregory P.; French, Katherine L.; Alm, Eric J.; Boyle, Edward A.; Cao, Changqun; Summons, Roger E.

    2014-04-01

    The end-Permian extinction is associated with a mysterious disruption to Earth's carbon cycle. Here we identify causal mechanisms via three observations. First, we show that geochemical signals indicate superexponential growth of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the expansion of a new microbial metabolic pathway. Second, we show that the efficient acetoclastic pathway in Methanosarcina emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth's greatest mass extinction by a specific microbial innovation.

  2. Methanogenic burst in the end-Permian carbon cycle.

    PubMed

    Rothman, Daniel H; Fournier, Gregory P; French, Katherine L; Alm, Eric J; Boyle, Edward A; Cao, Changqun; Summons, Roger E

    2014-04-15

    The end-Permian extinction is associated with a mysterious disruption to Earth's carbon cycle. Here we identify causal mechanisms via three observations. First, we show that geochemical signals indicate superexponential growth of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the expansion of a new microbial metabolic pathway. Second, we show that the efficient acetoclastic pathway in Methanosarcina emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth's greatest mass extinction by a specific microbial innovation.

  3. [Mathematical model of the global carbon cycle in the biosphere].

    PubMed

    Tarko, A M

    2010-01-01

    Changes in the atmospheric carbon dioxide concentration, temperatures of the atmosphere, and parameters of land biota as a result of anthropogenic carbon dioxide emissions, forest clearance, and soil erosion are calculated in a spatial mathematical model of the global carbon cycle in the biosphere. Restrictions on the CO2 emissions to the atmosphere are deduced from the requirements of Kyoto Protocol to The UN Framework Convention on Climate Change and other scenarios. An ability is revealed for the atmospheric CO2 concentration to grow fast, which arises from a number of emerging and developing countries with large population and high CO2 emission rates and which surpasses greatly the effect of growth retardation due to Kyoto Protocol. Those countries' role will become mostly apparent to the year of 2060 and later. Russia has shown to be in an exclusive position relative to other countries: ecosystems of its territory absorb more of the atmospheric carbon dioxide than does any other country, and the inductrial emissions from its territory are practically equal to the absorption by ecosystems.

  4. Carbon and Nitrogen Cycling in a Shallow Coastal Tidal Basin

    NASA Astrophysics Data System (ADS)

    Hohn, S.; Voelker, C. D.; van Beusekom, J.; Schartau, M.

    2008-12-01

    The biogeochemical fluxes of carbon and nitrogen are tightly coupled via the production of biomass. The degree of this coupling is known to vary under different environmental conditions. Nitrogen limitation of phytoplankton organisms leads to increased C:N biomass ratios whereas light limitation at nutrient replete conditions causes a decrease in intracellular C:N ratios. The biogeochemical fluxes of carbon and nitrogen within and between a shallow coastal tidal basin in the danish-german Wadden Sea, the List tidal basin, and the adjacent North Sea are calculated with an ecosystem model that allows for variable C:N ratios in phytoplankton biomass. Differences in plankton C:N biomass ratios between both water boxes affect the net transport budgets of carbon and nitrogen between the North Sea and the List tidal basin and may also change the sign of the C:N ratio of biomass exchange, i.e. leading to net nitrogen export and net import of carbon into the tidal basin over an annual cycle. Benthic filterfeeding organisms consume phytoplankton biomass and release fresh nutrients to the water column. In the List tidal basin, the promoting effect on primary production due to nutrient release by benthic filterfeeders is found to outweigh the limiting effect due to grazing pressure on phytoplankton biomass.

  5. Cryptic carbon and sulfur cycling between surface ocean plankton

    PubMed Central

    Durham, Bryndan P.; Sharma, Shalabh; Luo, Haiwei; Smith, Christa B.; Amin, Shady A.; Bender, Sara J.; Dearth, Stephen P.; Van Mooy, Benjamin A. S.; Campagna, Shawn R.; Kujawinski, Elizabeth B.; Armbrust, E. Virginia; Moran, Mary Ann

    2015-01-01

    About half the carbon fixed by phytoplankton in the ocean is taken up and metabolized by marine bacteria, a transfer that is mediated through the seawater dissolved organic carbon (DOC) pool. The chemical complexity of marine DOC, along with a poor understanding of which compounds form the basis of trophic interactions between bacteria and phytoplankton, have impeded efforts to identify key currencies of this carbon cycle link. Here, we used transcriptional patterns in a bacterial-diatom model system based on vitamin B12 auxotrophy as a sensitive assay for metabolite exchange between marine plankton. The most highly up-regulated genes (up to 374-fold) by a marine Roseobacter clade bacterium when cocultured with the diatom Thalassiosira pseudonana were those encoding the transport and catabolism of 2,3-dihydroxypropane-1-sulfonate (DHPS). This compound has no currently recognized role in the marine microbial food web. As the genes for DHPS catabolism have limited distribution among bacterial taxa, T. pseudonana may use this sulfonate for targeted feeding of beneficial associates. Indeed, DHPS was both a major component of the T. pseudonana cytosol and an abundant microbial metabolite in a diatom bloom in the eastern North Pacific Ocean. Moreover, transcript analysis of the North Pacific samples provided evidence of DHPS catabolism by Roseobacter populations. Other such biogeochemically important metabolites may be common in the ocean but difficult to discriminate against the complex chemical background of seawater. Bacterial transformation of this diatom-derived sulfonate represents a previously unidentified and likely sizeable link in both the marine carbon and sulfur cycles. PMID:25548163

  6. Cryptic carbon and sulfur cycling between surface ocean plankton.

    PubMed

    Durham, Bryndan P; Sharma, Shalabh; Luo, Haiwei; Smith, Christa B; Amin, Shady A; Bender, Sara J; Dearth, Stephen P; Van Mooy, Benjamin A S; Campagna, Shawn R; Kujawinski, Elizabeth B; Armbrust, E Virginia; Moran, Mary Ann

    2015-01-13

    About half the carbon fixed by phytoplankton in the ocean is taken up and metabolized by marine bacteria, a transfer that is mediated through the seawater dissolved organic carbon (DOC) pool. The chemical complexity of marine DOC, along with a poor understanding of which compounds form the basis of trophic interactions between bacteria and phytoplankton, have impeded efforts to identify key currencies of this carbon cycle link. Here, we used transcriptional patterns in a bacterial-diatom model system based on vitamin B12 auxotrophy as a sensitive assay for metabolite exchange between marine plankton. The most highly up-regulated genes (up to 374-fold) by a marine Roseobacter clade bacterium when cocultured with the diatom Thalassiosira pseudonana were those encoding the transport and catabolism of 2,3-dihydroxypropane-1-sulfonate (DHPS). This compound has no currently recognized role in the marine microbial food web. As the genes for DHPS catabolism have limited distribution among bacterial taxa, T. pseudonana may use this sulfonate for targeted feeding of beneficial associates. Indeed, DHPS was both a major component of the T. pseudonana cytosol and an abundant microbial metabolite in a diatom bloom in the eastern North Pacific Ocean. Moreover, transcript analysis of the North Pacific samples provided evidence of DHPS catabolism by Roseobacter populations. Other such biogeochemically important metabolites may be common in the ocean but difficult to discriminate against the complex chemical background of seawater. Bacterial transformation of this diatom-derived sulfonate represents a previously unidentified and likely sizeable link in both the marine carbon and sulfur cycles.

  7. The GLOBE Carbon Project: Integrating the Science of Carbon Cycling and Climate Change into K-12 Classrooms.

    NASA Astrophysics Data System (ADS)

    Ollinger, S. V.; Silverberg, S.; Albrechtova, J.; Freuder, R.; Gengarelly, L.; Martin, M.; Randolph, G.; Schloss, A.

    2007-12-01

    The global carbon cycle is a key regulator of the Earth's climate and is central to the normal function of ecological systems. Because rising atmospheric CO2 is the principal cause of climate change, understanding how ecosystems cycle and store carbon has become an extremely important issue. In recent years, the growing importance of the carbon cycle has brought it to the forefront of both science and environmental policy. The need for better scientific understanding has led to establishment of numerous research programs, such as the North American Carbon Program (NACP), which seeks to understand controls on carbon cycling under present and future conditions. Parallel efforts are greatly needed to integrate state-of-the-art science on the carbon cycle and its importance to climate with education and outreach efforts that help prepare society to make sound decisions on energy use, carbon management and climate change adaptation. Here, we present a new effort that joins carbon cycle scientists with the International GLOBE Education program to develop carbon cycle activities for K-12 classrooms. The GLOBE Carbon Cycle project is focused on bringing cutting edge research and research techniques in the field of terrestrial ecosystem carbon cycling into the classroom. Students will collect data about their school field site through existing protocols of phenology, land cover and soils as well as new protocols focused on leaf traits, and ecosystem growth and change. They will also participate in classroom activities to understand carbon cycling in terrestrial ecosystems, these will include plant- a-plant experiments, hands-on demonstrations of various concepts, and analysis of collected data. In addition to the traditional GLOBE experience, students will have the opportunity to integrate their data with emerging and expanding technologies including global and local carbon cycle models and remote sensing toolkits. This program design will allow students to explore research

  8. Response of annual grassland carbon cycling to experimental rainfall additions

    NASA Astrophysics Data System (ADS)

    Chou, W. W.; Silver, W. L.; Allen-Diaz, B.; Thompson, A.; Jackson, R.

    2006-12-01

    Annual grassland ecosystems are likely to be sensitive to changes in the timing and amount of rainfall, with important implications for climate feedback effects. Many climate models have forecasted rainfall increases for northern California over the next century. We hypothesized that increased rainfall in annual grasslands would increase soil respiration and decrease soil carbon (C) storage. Using microsprinklers, we augmented wet- season (typically November to April) rain events by 50 %, and each year, we added an early-season and a late-season rainfall event to extend wet-season length. Control plots received ambient rainfall only. We measured soil respiration and net primary production over three water years (defined as September to August) to estimate the net change in the soil C pool. The added early- and late-season rain events significantly increased soil respiration for three to four weeks after wetting, but did not significantly increase C respired per year. Soil respiration was not significantly increased by 50 % augmentation of wet-season rainfall over the study. An ANOVA of annual respiration from control plots showed significantly more respired carbon (F = 8.157, p = 0.02) in water year 2004 (WY 04; 1452 ± 152 g m-2 y-1), compared to WY 03 or WY 05 (998 ± 40 and 925 ± 71 g m-2 y-1, respectively). Greater soil respiration in WY 04 resulted not from higher annual rainfall totals, but from unusually late natural storms which occurred under warm summer conditions. Relative to controls, grass in treatment plots allocated more C to roots in the first (drier) year, and slightly more C to shoots in the second (wetter) year. Combined above- and below-ground net primary production was greater in WY04 (913 ± 171 g m-2 y-1 and 668 ± 93 g m-2 y-1 for treatment and control plots, respectively) than in WY03 (588 ± 85 g m-2 y-1 and 483 ± 46 g m-2 y-1 for treatment and controls, respectively), partly offsetting increased C losses from respiration. Our results

  9. Deep Carbon Cycling in the Deep Hydrosphere: Abiotic Organic Synthesis and Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Sherwood Lollar, B.; Sutcliffe, C. N.; Ballentine, C. J.; Warr, O.; Li, L.; Ono, S.; Wang, D. T.

    2014-12-01

    Research into the deep carbon cycle has expanded our understanding of the depth and extent of abiotic organic synthesis in the deep Earth beyond the hydrothermal vents of the deep ocean floor, and of the role of reduced gases in supporting deep subsurface microbial communities. Most recently, this research has expanded our understanding not only of the deep biosphere but the deep hydrosphere - identifying for the first time the extreme antiquity (millions to billions of years residence time) of deep saline fracture waters in the world's oldest rocks. Energy-rich saline fracture waters in the Precambrian crust that makes up more than 70% of the Earth's continental lithosphereprovide important constraints on our understanding of the extent of the crust that is habitable, on the time scales of hydrogeologic isolation (and conversely mixing) of fluids relevant to the deep carbon cycle, and on the geochemistry of substrates that sustain both abiotic organic synthesis and biogeochemical cycles driven by microbial communities. Ultimately the chemistry and hydrogeology of the deep hydrosphere will help define the limits for life in the subsurface and the boundary between the biotic-abiotic fringe. Using a variety of novel techniques including noble gas analysis, clumped isotopologues of methane, and compound specific isotope analysis of CHNOS, this research is addressing questions about the distribution of deep saline fluids in Precambrian rocks worldwide, the degree of interconnectedness of these potential biomes, the habitability of these fluids, and the biogeographic diversity of this new realm of the deep hydrosphere.

  10. Revisiting the subduction zone carbon cycle: What goes down, mostly comes up

    NASA Astrophysics Data System (ADS)

    Kelemen, Peter; Manning, Craig

    2016-04-01

    As we reported (PNAS 2015), carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find it is likely that relatively little carbon is recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5-10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. This is consistent with inferences from noble gas data and crustal carbon inventories (review in Hayes & Waldbauer PTRSL 2006). Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory. Increasing NaCl and decreasing pH and fO2 in aqueous fluids all increase carbon solubility at HP to UHP conditions, strengthening the prediction of wt% solubility (Manning & Kelemen, Fall AGU 2015), while hydrous carbonatite formed on high T subduction geotherms (Poli, Nat Geosci 2015) has still higher concentrations. Fractures heal rapidly at UHP conditions, so fluid transport is mainly via porous flow, with increasing downstream solubility and porosity due to heating in the subducting plate and base of the mantle wedge. Depending on flow and reaction rates vs diffusivity (Damkohler number), this could yield diffuse or channelized flow. High, increasing solubilities and reaction rates, with slow diffusion, can produce diffuse, pervasive porous flow (e.g., Hoefner & Fogler, AIChEJ 1988; Spiegelman et al, JGR 2001) and efficient recycling of carbon.

  11. Carbon cycle dynamics in the geologic record: Speleothems as a source for new biogeochemical and paleoclimate information

    NASA Astrophysics Data System (ADS)

    Frappier, A.; Sahagian, D.

    2003-12-01

    Many of the key outstanding questions in paleoclimate and biogeochemical cycles involve terrestrial ecosystems. Caves provide an important depositional environment for sedimentary archives of past and present terrestrial environmental changes. Until recently, the tools available to the research community have been appropriate for coarse resolution studies, but have been inadequate to address other important questions such as: 1. How have climate changes affect ecosystem carbon cycling in the past? 2. What is the role of tropical ecosystems in climate change and the global carbon cycle? 3. How does disturbance affect below ground carbon processing and export to groundwater? Recent developments in the use of speleothems as a tool for carbon cycle and paleoclimate studies have opened the door for a fresh look at these perennial questions. Our recent carbon isotopic study of a speleothem from Belize indicates that terrestrial carbon cycling may be more sensitive to interannual climatic variability such as El Nino-Southern Oscillation (ENSO) than previously thought. In this case, the geologic record has revealed carbon cycle sensitivity to climate forcing that has not been instrumentally observable over the same period. A number of other studies have revealed intriguing correlations between the speleothem carbon isotopic record and various Earth system processes such as millennial scale climate variations and land use history. These results suggest that our understanding of speleothems as a biogeochemical tool remains largely unexplored. In order to better understand the utility of the speleothem carbon isotopic record, we are conducting a modern process study at the Belize cave site. This will enable us to calibrate the record preserved in speleothems for exploration of past carbon cycle behavior. Our initial analysis suggests that speleothems faithfully record variations in terrestrial ecosystem biogeochemical processes that are measurable in real time, and are thus a

  12. Microbial community profiles and microbial carbon cycling in Orca Basin

    NASA Astrophysics Data System (ADS)

    Hyde, A.; Teske, A.; Joye, S. B.; Montoya, J. P.; Nigro, L.

    2016-12-01

    Orca Basin is the largest seafloor brine pools in the world, covering over 400 km2 and reaching brine layer depths of 200 m. The brine pool contains water 8 times denser than the overlying seawater and is separated from the overlying water column by a sharp pycnocline that prevents vertical mixing. The transition from ambient seawater to brine occurs over 100 m [2150 to 2250 m] and is characterized by distinct changes in temperature, salinity, chemical conditions, oxygen, and organic matter concentration. The sharp brine-seawater interface results in a sharp pycnocline, which serves as a particle trap for sinking marine organic matter. Previous studies have used lipids to show that this organic-rich interface is host to an active microbial community which is potentially involved in deep-sea carbon remineralization and metal-cycling. Additionally, previous work on methane, ethane, and propane concentrations and 13C-isotopic signatures has also implicated the brine pool, as well as the interface, as sources for biogenic low-molecular weight hydrocarbons, resulting from the high concentration of suspended organic matter above and within the brine pool. Here we investigate the profiles of microbial community composition and metabolic potential in Orca Basin, ranging from seawater through the Orca Basin chemocline and into the deep Orca Basin brine. To characterize the microbial community and stratification, we used high-throughput bacterial and archaeal 16S rRNA gene sequencing of filtered water above, within, and below the Orca Basin chemocline. Our sequence data shows that three distinct and unique communities exist in the Orca Basin water column. We also use thermodynamic modeling of hydrocarbon degradation to investigate the favorability of C1-C3 hydrocarbon oxidation at the brine-seawater interface and the potential for Orca Basin to serve as a deep-sea hydrocarbon sink.

  13. Implications of Deep Decarbonization for Carbon Cycle Science

    NASA Astrophysics Data System (ADS)

    Jones, A. D.; Williams, J.; Torn, M. S.

    2016-12-01

    The energy-system transformations required to achieve deep decarbonization in the United States, defined as a reduction of greenhouse gas emissions of 80% or more below 1990 levels by 2050, have profound implications for carbon cycle science, particularly with respect to 4 key objectives: understanding and enhancing the terrestrial carbon sink, using bioenergy sustainably, controlling non-CO2 GHGs, and emissions monitoring and verification. (1) As a source of mitigation, the terrestrial carbon sink is pivotal but uncertain, and changes in the expected sink may significantly affect the overall cost of mitigation. Yet the dynamics of the sink under changing climatic conditions, and the potential to protect and enhance the sink through land management, are poorly understood. Policy urgently requires an integrative research program that links basic science knowledge to land management practices. (2) Biomass resources can fill critical energy needs in a deeply decarbonized system, but current understanding of sustainability and lifecycle carbon aspects is limited. Mitigation policy needs better understanding of the sustainable amount, types, and cost of bioenergy feedstocks, their interactions with other land uses, and more efficient and reliable monitoring of embedded carbon. (3) As CO2 emissions from energy decrease under deep decarbonization, the relative share of non-CO2 GHGs grows larger and their mitigation more important. Because the sources tend to be distributed, variable, and uncertain, they have been under-researched. Policy needs a better understanding of mitigation priorities and costs, informed by deeper research in key areas such as fugitive CH4, fertilizer-derived N2O, and industrial F-gases. (4) The M&V challenge under deep decarbonization changes with a steep decrease in the combustion CO2 sources due to widespread electrification, while a greater share of CO2 releases is net-carbon-neutral. Similarly, gas pipelines may carry an increasing share of

  14. Modelling the carbon cycle though Neoproterozoic Earth system changes

    NASA Astrophysics Data System (ADS)

    Bjerrum, C. J.; Canfield, D. E.

    2011-12-01

    The Neoproterozoic-Cambrian records major changes in geochemical proxies as a result of a profound reorganization of the Earth system. Extensive glaciations and the first oxygenation of the deep ocean with a shift from sulfidic/ferruginous conditions to more oxic conditions was accompanied by the radiation of the first animals. The reorganization was also recorded in enigmatic large-amplitude fluctuations in the isotopic composition of marine carbonate carbon (δ13CIC ), were only some are associated with major known glaciations. The carbon isotope events seem to grow in amplitude through the Neoproterozoic culminating in the Shuram anomaly - the largest in Earth history. The δ13CIC events are also accompanied by changes in the isotope composition of marine organic carbon (δ13COC), where the co-variation of δ13CIC and δ13COC seems to evolve from markedly positive relationship over a subdued δ13COC variation and an almost inverse pattern. There is limited understanding as to why or how the structure of these isotope events evolved over time and how these events may tie to the reorganization of the Earth system. We use our published quantitative model of the Shuram anomaly to explore carbon cycle dynamics during the Neoproterozoic. By changing in pre-event atmosphere-ocean chemistry we explore which factors contribute to the observed patterns of the large Neoproterozoic carbon isotope events. In particular, decreasing atmospheric CO2 and a slight increase of oxygen together with an increasing CO source from rising DOC concentrations results in progressively larger event amplitudes with changing co-variation between δ13CIC and δ13COC , culminating with the structure observed for the Shurum-Wonaka anomaly in the Ediacaran. In our model, the carbon isotope excursions were driven by methane from sediment-hosted clathrate hydrate deposits. Being a powerful greenhouse gas, methane increased temperature and melted icecaps. These combined to produce a negative 18O

  15. Magmatic carbon in Martian meteorites: attempts to constrain the carbon cycle on Mars

    NASA Astrophysics Data System (ADS)

    Grady, M. M.; Verchovsky, A. B.; Wright, I. P.

    2004-04-01

    One of the current goals of Martian exploration is to find evidence for extinct (or even extant) life. Carbon (an essential ingredient of life on Earth) is known to occur on Mars as CO2 in the atmosphere and frozen in the polar caps; it is inferred to be present as carbonates in the Martian crust and soils. We are attempting to define and quantify the different carbon reservoirs on Mars, so that we can follow Mars' carbon cycle. This paper discusses a primordial magmatic component that could be the starting point of such a cycle. The nature, distribution and isotopic composition of carbon was measured in a suite of Martian meteorites, comprising Chassigny and 11 shergottites. Other Martian meteorites were not included, as they sample rocks that have been altered by fluids at Mars' surface. Our results, obtained by high-resolution stepped combustion and mass spectrometry, show that the magmatic component has a very variable abundance of 1 100 ppm, with [delta]13C~[minus sign]20±4‰. This value is close to magmatic carbon determined for Moon and for Vesta (the parent body of the HED basaltic meteorites), but very different from that of Earth.

  16. Numerical study of thermomagnetic cycle

    NASA Astrophysics Data System (ADS)

    Almanza, Morgan; Pasko, Alexandre; Mazaleyrat, Frédéric; LoBue, Martino

    2017-03-01

    We estimate the efficiency and power of a thermal energy harvesting thermodynamic cycle using a magnetocaloric material as active substance. The thermodynamic cycle is computed using an equation of state, either extrapolated from experimental data or deduced using a phenomenological Landau model. The magnetic work is then compared to the maximum work. Afterwards power is estimated using a simple thermal exchange model. Simulations of different cycles for different working points illustrate the tradeoff between power and efficiency.

  17. Interannual Variations of MLS Carbon Monoxide Induced by Solar Cycle

    NASA Technical Reports Server (NTRS)

    Lee, Jae N.; Wu, Dong L.; Ruzmaikin, Alexander

    2013-01-01

    More than eight years (2004-2012) of carbon monoxide (CO) measurements from the Aura Microwave Limb Sounder (MLS) are analyzed. The mesospheric CO, largely produced by the carbon dioxide (CO2) photolysis in the lower thermosphere, is sensitive to the solar irradiance variability. The long-term variation of observed mesospheric MLS CO concentrations at high latitudes is likely driven by the solar-cycle modulated UV forcing. Despite of different CO abundances in the southern and northern hemispheric winter, the solar-cycle dependence appears to be similar. This solar signal is further carried down to the lower altitudes by the dynamical descent in the winter polar vortex. Aura MLS CO is compared with the Solar Radiation and Climate Experiment (SORCE) total solar irradiance (TSI) and also with the spectral irradiance in the far ultraviolet (FUV) region from the SORCE Solar-Stellar Irradiance Comparison Experiment (SOLSTICE). Significant positive correlation (up to 0.6) is found between CO and FUVTSI in a large part of the upper atmosphere. The distribution of this positive correlation in the mesosphere is consistent with the expectation of CO changes induced by the solar irradiance variations.

  18. Influence of sulfur compounds on the terrestrial carbon cycle

    NASA Astrophysics Data System (ADS)

    Eliseev, A. V.

    2015-11-01

    Using the climate model developed at the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM), numerical experiments have been conducted in line with the Coupled Model Intercomparison Project Phase 5 (CMIP5), but scaling the anthropogenic emissions of sulfur compounds into the troposphere by ±25%. Two types of impacts of sulfur compounds on climate and the global carbon cycle are considered: climate impact (CI, associated with the influence of tropospheric sulfates on climate and, as a consequence, on the carbon cycle characteristics) and ecological impact (EI, associated with the influence of SO2 on the rate of photosynthesis of terrestrial plants). The climate impact was found to be generally more important than the ecological one. However, in a number of regions, the EI is comparable to CI, including in the southeast parts of North America and, especially, of Asia. The contribution of EI to the change in global characteristics of terrestrial ecosystems in the 20th century is likewise considerable. The CI is generally more sensitive to the uncertainty in anthropogenic emissions of sulfur compounds into the troposphere than the EI.

  19. Carbon-Climate Feedbacks Through The Global Mathane Cycle

    NASA Astrophysics Data System (ADS)

    Schimel, D.

    2015-12-01

    Methane, a critical greenhouse gas, is increasing rapidly but neither the causes of this increase, nor the recent large variations in the rate are understood. The tropics are the largest natural source for methane, and a likely focus of much recent variation. We will propose two hypotheses to explain why tropical fluxes may be changing, one linked to recent trends in the carbon cycke, and the other suggesting a connection to trends in the wate cycle. We carried out an observing system experiment using model-data-fusion approach and simulated fluxes arising from both of these hyotheses using a diagnostic model, forced with satellite observations, and then translated them into concentration patterns using an attmspheric transport model. We then sampled these simulated concentrations, taking into account cloud cover and estimated the resulting sampling pattern and radiances, using a full-physics radiation model. This allowed us to simulate the performance of alternative approaches for observing XCH4 from space. We then estimated fluxes usng an inverse model to determine the required characteristics of a satellite mission able to distinguish between our two hypotheses. Geostationary observations, obtained at least 3x/day with an uncertainty of 1% are required to determine regional patterns of tropical methane flux with sufficiently high confidence to distinguish between alternative hypotheses. The key instrument characteristics are determined by the need to obtain adequate data in the presene of clouds. Reducing carbon cycle uncertainty in the tropics requires more sampling than low earth orbit missions are likely to provide.

  20. Maintenance Carbon Cycle in Crassulacean Acid Metabolism Plant Leaves 1

    PubMed Central

    Kenyon, William H.; Severson, Ray F.; Black, Clanton C.

    1985-01-01

    The reciprocal relationship between diurnal changes in organic acid and storage carbohydrate was examined in the leaves of three Crassulacean acid metabolism plants. It was found that depletion of leaf hexoses at night was sufficient to account quantitatively for increase in malate in Ananas comosus but not in Sedum telephium or Kalanchoë daigremontiana. Fructose and to a lesser extent glucose underwent the largest changes. Glucose levels in S. telephium leaves oscillated diurnally but were not reciprocally related to malate fluctuations. Analysis of isolated protoplasts and vacuoles from leaves of A. comosus and S. telephium revealed that vacuoles contain a large percentage (>50%) of the protoplast glucose, fructose and malate, citrate, isocitrate, ascorbate and succinate. Sucrose, a major constituent of intact leaves, was not detectable or was at extremely low levels in protoplasts and vacuoles from both plants. In isolated vacuoles from both A. comosus and S. telephium, hexose levels decreased at night at the same time malate increased. Only in A. comosus, however, could hexose metabolism account for a significant amount of the nocturnal increase in malate. We conclude that, in A. comosus, soluble sugars are part of the daily maintenance carbon cycle and that the vacuole plays a dynamic role in the diurnal carbon assimilation cycle of this Crassulacean acid metabolism plant. PMID:16664005

  1. The changing carbon cycle at Mauna Loa Observatory.

    PubMed

    Buermann, Wolfgang; Lintner, Benjamin R; Koven, Charles D; Angert, Alon; Pinzon, Jorge E; Tucker, Compton J; Fung, Inez Y

    2007-03-13

    The amplitude of the CO(2) seasonal cycle at the Mauna Loa Observatory (MLO) increased from the early 1970s to the early 1990s but decreased thereafter despite continued warming over northern continents. Because of its location relative to the large-scale atmospheric circulation, the MLO receives mainly Eurasian air masses in the northern hemisphere (NH) winter but relatively more North American air masses in NH summer. Consistent with this seasonal footprint, our findings indicate that the MLO amplitude registers North American net carbon uptake during the warm season and Eurasian net carbon release as well as anomalies in atmospheric circulation during the cold season. From the early 1970s to the early 1990s, our analysis was consistent with that of Keeling et al. [Keeling CD, Chin JFS, Whorf TP (1996) Nature 382:146-149], suggesting that the increase in the MLO CO(2) amplitude is dominated by enhanced photosynthetic drawdown in North America and enhanced respiration in Eurasia. In contrast, the recent decline in the CO(2) amplitude is attributed to reductions in carbon sequestration over North America associated with severe droughts from 1998 to 2003 and changes in atmospheric circulation leading to decreased influence of Eurasian air masses. With the return of rains to the U.S. in 2004, both the normalized difference vegetation index and the MLO amplitude sharply increased, suggesting a return of the North American carbon sink to more normal levels. These findings indicate that atmospheric CO(2) measurements at remote sites can continue to play an important role in documenting changes in land carbon flux, including those related to widespread drought, which may continue to worsen as a result of global warming.

  2. The changing carbon cycle at Mauna Loa Observatory

    PubMed Central

    Buermann, Wolfgang; Lintner, Benjamin R.; Koven, Charles D.; Angert, Alon; Pinzon, Jorge E.; Tucker, Compton J.; Fung, Inez Y.

    2007-01-01

    The amplitude of the CO2 seasonal cycle at the Mauna Loa Observatory (MLO) increased from the early 1970s to the early 1990s but decreased thereafter despite continued warming over northern continents. Because of its location relative to the large-scale atmospheric circulation, the MLO receives mainly Eurasian air masses in the northern hemisphere (NH) winter but relatively more North American air masses in NH summer. Consistent with this seasonal footprint, our findings indicate that the MLO amplitude registers North American net carbon uptake during the warm season and Eurasian net carbon release as well as anomalies in atmospheric circulation during the cold season. From the early 1970s to the early 1990s, our analysis was consistent with that of Keeling et al. [Keeling CD, Chin JFS, Whorf TP (1996) Nature 382:146–149], suggesting that the increase in the MLO CO2 amplitude is dominated by enhanced photosynthetic drawdown in North America and enhanced respiration in Eurasia. In contrast, the recent decline in the CO2 amplitude is attributed to reductions in carbon sequestration over North America associated with severe droughts from 1998 to 2003 and changes in atmospheric circulation leading to decreased influence of Eurasian air masses. With the return of rains to the U.S. in 2004, both the normalized difference vegetation index and the MLO amplitude sharply increased, suggesting a return of the North American carbon sink to more normal levels. These findings indicate that atmospheric CO2 measurements at remote sites can continue to play an important role in documenting changes in land carbon flux, including those related to widespread drought, which may continue to worsen as a result of global warming. PMID:17360510

  3. U.S. Eastern Continental Shelf Carbon Cycling (USECoS): Modeling, Data Assimilation, and Analysis

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio

    2008-01-01

    Although the oceans play a major role in the uptake of fossil fuel CO2 from the atmosphere, there is much debate about the contribution from continental shelves, since many key shelf fluxes are not yet well quantified: the exchange of carbon across the land-ocean and shelf-slope interfaces, air-sea exchange of CO2, burial, and biological processes including productivity. Our goal is to quantify these carbon fluxes along the eastern U.S. coast using models quantitatively verified by comparison to observations, and to establish a framework for predicting how these fluxes may be modified as a result of climate and land use change. Our research questions build on those addressed with previous NASA funding for the USECoS (U.S. Eastern Continental Shelf Carbon Cycling) project. We have developed a coupled biogeochemical ocean circulation model configured for this study region and have extensively evaluated this model with both in situ and remotely-sensed data. Results indicate that to further reduce uncertainties in the shelf component of the global carbon cycle, future efforts must be directed towards 1) increasing the resolution of the physical model via nesting and 2) making refinements to the biogeochemical model and quantitatively evaluating these via the assimilation of biogeochemical data (in situ and remotely-sensed). These model improvements are essential for better understanding and reducing estimates of uncertainties in current and future carbon transformations and cycling in continental shelf systems. Our approach and science questions are particularly germane to the carbon cycle science goals of the NASA Earth Science Research Program as well as the U.S. Climate Change Research Program and the North American Carbon Program. Our interdisciplinary research team consists of scientists who have expertise in the physics and biogeochemistry of the U.S. eastern continental shelf, remote-sensing data analysis and data assimilative numerical models.

  4. U.S. Eastern Continental Shelf Carbon Cycling (USECoS): Modeling, Data Assimilation, and Analysis

    NASA Technical Reports Server (NTRS)

    Mannino, Antonio

    2008-01-01

    Although the oceans play a major role in the uptake of fossil fuel CO2 from the atmosphere, there is much debate about the contribution from continental shelves, since many key shelf fluxes are not yet well quantified: the exchange of carbon across the land-ocean and shelf-slope interfaces, air-sea exchange of CO2, burial, and biological processes including productivity. Our goal is to quantify these carbon fluxes along the eastern U.S. coast using models quantitatively verified by comparison to observations, and to establish a framework for predicting how these fluxes may be modified as a result of climate and land use change. Our research questions build on those addressed with previous NASA funding for the USECoS (U.S. Eastern Continental Shelf Carbon Cycling) project. We have developed a coupled biogeochemical ocean circulation model configured for this study region and have extensively evaluated this model with both in situ and remotely-sensed data. Results indicate that to further reduce uncertainties in the shelf component of the global carbon cycle, future efforts must be directed towards 1) increasing the resolution of the physical model via nesting and 2) making refinements to the biogeochemical model and quantitatively evaluating these via the assimilation of biogeochemical data (in situ and remotely-sensed). These model improvements are essential for better understanding and reducing estimates of uncertainties in current and future carbon transformations and cycling in continental shelf systems. Our approach and science questions are particularly germane to the carbon cycle science goals of the NASA Earth Science Research Program as well as the U.S. Climate Change Research Program and the North American Carbon Program. Our interdisciplinary research team consists of scientists who have expertise in the physics and biogeochemistry of the U.S. eastern continental shelf, remote-sensing data analysis and data assimilative numerical models.

  5. Sensitivity of the carbon cycle in the Arctic to climate change

    USGS Publications Warehouse

    McGuire, A. David; Anderson, Leif G.; Christensen, Torben R.; Dallimore, Scott; Guo, Laodong; Hayes, Daniel J.; Heimann, Martin; Lorenson, T.D.; Macdonald, Robie W.; Roulet, Nigel

    2009-01-01

    The recent warming in the Arctic is affecting a broad spectrum of physical, ecological, and human/cultural systems that may be irreversible on century time scales and have the potential to cause rapid changes in the earth system. The response of the carbon cycle of the Arctic to changes in climate is a major issue of global concern, yet there has not been a comprehensive review of the status of the contemporary carbon cycle of the Arctic and its response to climate change. This review is designed to clarify key uncertainties and vulnerabilities in the response of the carbon cycle of the Arctic to ongoing climatic change. While it is clear that there are substantial stocks of carbon in the Arctic, there are also significant uncertainties associated with the magnitude of organic matter stocks contained in permafrost and the storage of methane hydrates beneath both subterranean and submerged permafrost of the Arctic. In the context of the global carbon cycle, this review demonstrates that the Arctic plays an important role in the global dynamics of both CO2 and CH4. Studies suggest that the Arctic has been a sink for atmospheric CO2 of between 0 and 0.8 Pg C/yr in recent decades, which is between 0% and 25% of the global net land/ocean flux during the 1990s. The Arctic is a substantial source of CH4 to the atmosphere (between 32 and 112 Tg CH4/yr), primarily because of the large area of wetlands throughout the region. Analyses to date indicate that the sensitivity of the carbon cycle of the Arctic during the remainder of the 21st century is highly uncertain. To improve the capability to assess the sensitivity of the carbon cycle of the Arctic to projected climate change, we recommend that (1) integrated regional studies be conducted to link observations of carbon dynamics to the processes that are likely to influence those dynamics, and (2) the understanding gained from these integrated studies be incorporated into both uncoupled and fully coupled carbon

  6. On the linkages between the global carbon-nitrogen-phosphorus cycles

    NASA Astrophysics Data System (ADS)

    Tanaka, Katsumasa; Mackenzie, Fred; Bouchez, Julien; Knutti, Reto

    2013-04-01

    State-of-the-art earth system models used for long-term climate projections are becoming ever more complex in terms of not only spatial resolution but also the number of processes. Biogeochemical processes are beginning to be incorporated into these models. The motivation of this study is to quantify how climate projections are influenced by biogeochemical feedbacks. In the climate modeling community, it is virtually accepted that climate-Carbon (C) cycle feedbacks accelerate the future warming (Cox et al. 2000; Friedlingstein et al. 2006). It has been demonstrated that the Nitrogen (N) cycle suppresses climate-C cycle feedbacks (Thornton et al. 2009). On the contrary, biogeochemical studies show that the coupled C-N-Phosphorus (P) cycles are intimately interlinked via biosphere and the N-P cycles amplify C cycle feedbacks (Ver et al. 1999). The question as to whether the N-P cycles enhance or attenuate C cycle feedbacks is debated and has a significant implication for projections of future climate. We delve into this problem by using the Terrestrial-Ocean-aTmosphere Ecosystem Model 3 (TOTEM3), a globally-aggregated C-N-P cycle box model. TOTEM3 is a process-based model that describes the biogeochemical reactions and physical transports involving these elements in the four domains of the Earth system: land, atmosphere, coastal ocean, and open ocean. TOTEM3 is a successor of earlier TOTEM models (Ver et al. 1999; Mackenzie et al. 2011). In our presentation, we provide an overview of fundamental features and behaviors of TOTEM3 such as the mass balance at the steady state and the relaxation time scales to various types of perturbation. We also show preliminary results to investigate how the N-P cycles influence the behavior of the C cycle. References Cox PM, Betts RA, Jones CD, Spall SA, Totterdell IJ (2000) Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature, 408, 184-187. Friedlingstein P, Cox P, Betts R, Bopp L, von Bloh

  7. In-operando hard X-ray photoelectron spectroscopy study on the impact of current compliance and switching cycles on oxygen and carbon defects in resistive switching Ti/HfO2/TiN cells

    NASA Astrophysics Data System (ADS)

    Sowinska, Malgorzata; Bertaud, Thomas; Walczyk, Damian; Thiess, Sebastian; Calka, Pauline; Alff, Lambert; Walczyk, Christian; Schroeder, Thomas

    2014-05-01

    In this study, direct experimental materials science evidence of the important theoretical prediction for resistive random access memory (RRAM) technologies that a critical amount of oxygen vacancies is needed to establish stable resistive switching in metal-oxide-metal samples is presented. In detail, a novel in-operando hard X-ray photoelectron spectroscopy technique is applied to non-destructively investigates the influence of the current compliance and direct current voltage sweep cycles on the Ti/HfO2 interface chemistry and physics of resistive switching Ti/HfO2/TiN cells. These studies indeed confirm that current compliance is a critical parameter to control the amount of oxygen vacancies in the conducting filaments in the oxide layer during the RRAM cell operation to achieve stable switching. Furthermore, clear carbon segregation towards the Ti/HfO2 interface under electrical stress is visible. Since carbon impurities impact the oxygen vacancy defect population under resistive switching, this dynamic carbon segregation to the Ti/HfO2 interface is suspected to negatively influence RRAM device endurance. Therefore, these results indicate that the RRAM materials engineering needs to include all impurities in the dielectric layer in order to achieve reliable device performance.

  8. In-operando hard X-ray photoelectron spectroscopy study on the impact of current compliance and switching cycles on oxygen and carbon defects in resistive switching Ti/HfO{sub 2}/TiN cells

    SciTech Connect

    Sowinska, Malgorzata Bertaud, Thomas; Walczyk, Damian; Calka, Pauline; Walczyk, Christian; Thiess, Sebastian; Alff, Lambert; Schroeder, Thomas

    2014-05-28

    In this study, direct experimental materials science evidence of the important theoretical prediction for resistive random access memory (RRAM) technologies that a critical amount of oxygen vacancies is needed to establish stable resistive switching in metal-oxide-metal samples is presented. In detail, a novel in-operando hard X-ray photoelectron spectroscopy technique is applied to non-destructively investigates the influence of the current compliance and direct current voltage sweep cycles on the Ti/HfO{sub 2} interface chemistry and physics of resistive switching Ti/HfO{sub 2}/TiN cells. These studies indeed confirm that current compliance is a critical parameter to control the amount of oxygen vacancies in the conducting filaments in the oxide layer during the RRAM cell operation to achieve stable switching. Furthermore, clear carbon segregation towards the Ti/HfO{sub 2} interface under electrical stress is visible. Since carbon impurities impact the oxygen vacancy defect population under resistive switching, this dynamic carbon segregation to the Ti/HfO{sub 2} interface is suspected to negatively influence RRAM device endurance. Therefore, these results indicate that the RRAM materials engineering needs to include all impurities in the dielectric layer in order to achieve reliable device performance.

  9. Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

    USGS Publications Warehouse

    Jain, A.A.; Yang, Xiaojuan; Kheshgi, H.; McGuire, Anthony; Post, W.; Kicklighter, David W.

    2009-01-01

    Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen availability influences terrestrial carbon sinks and sources in response to changes over the 20th century in global environmental factors including atmospheric CO2 concentration, nitrogen inputs, temperature, precipitation and land use. The two versions of ISAM vary in their treatment of nitrogen availability: ISAM-NC has a terrestrial carbon cycle model coupled to a fully dynamic nitrogen cycle while ISAM-C has an identical carbon cycle model but nitrogen availability is always in sufficient supply. Overall, the two versions of the model estimate approximately the same amount of global mean carbon uptake over the 20th century. However, comparisons of results of ISAM-NC relative to ISAM-C reveal that nitrogen dynamics: (1) reduced the 1990s carbon sink associated with increasing atmospheric CO2 by 0.53 PgC yr−1 (1 Pg = 1015g), (2) reduced the 1990s carbon source associated with changes in temperature and precipitation of 0.34 PgC yr−1 in the 1990s, (3) an enhanced sink associated with nitrogen inputs by 0.26 PgC yr−1, and (4) enhanced the 1990s carbon source associated with changes in land use by 0.08 PgC yr−1 in the 1990s. These effects of nitrogen limitation influenced the spatial distribution of the estimated exchange of CO2 with greater sink activity in high latitudes associated with climate effects and a smaller sink of CO2 in the southeastern United States caused by N limitation associated with both CO2 fertilization and forest regrowth. These results indicate that the dynamics of nitrogen availability are important to consider in assessing the spatial distribution and temporal dynamics of terrestrial carbon

  10. Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

    SciTech Connect

    Jain, Atul; Yang, Xiaojuan; Kheshgi, Haroon; Mcguire, David; Post, Wilfred M

    2009-01-01

    Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen availability influences terrestrial carbon sinks and sources in response to changes over the 20th century in global environmental factors including atmospheric CO2 concentration, nitrogen inputs, temperature, precipitation and land use. The two versions of ISAM vary in their treatment of nitrogen availability: ISAM-NC has a terrestrial carbon cycle model coupled to a fully dynamic nitrogen cycle while ISAM-C has an identical carbon cycle model but nitrogen availability is always in sufficient supply. Overall, the two versions of the model estimate approximately the same amount of global mean carbon uptake over the 20th century. However, comparisons of results of ISAM-NC relative to ISAM-C reveal that nitrogen dynamics: (1) reduced the 1990s carbon sink associated with increasing atmospheric CO2 by 0.53 PgC yr1 (1 Pg = 1015g), (2) reduced the 1990s carbon source associated with changes in temperature and precipitation of 0.34 PgC yr1 in the 1990s, (3) an enhanced sink associated with nitrogen inputs by 0.26 PgC yr1, and (4) enhanced the 1990s carbon source associated with changes in land use by 0.08 PgC yr1 in the 1990s. These effects of nitrogen limitation influenced the spatial distribution of the estimated exchange of CO2 with greater sink activity in high latitudes associated with climate effects and a smaller sink of CO2 in the southeastern United States caused by N limitation associated with both CO2 fertilization and forest regrowth. These results indicate that the dynamics of nitrogen availability are important to consider in assessing the spatial distribution and temporal dynamics of terrestrial carbon sources and

  11. Carbon cycle and climate commitments from early human interference

    NASA Astrophysics Data System (ADS)

    Zickfeld, K.; Solomon, S.

    2015-12-01

    According to the early anthropogenic hypothesis proposed by Ruddiman (2003), human influence on Earth's climate began several thousand years before the beginning of the industrial era. Agriculture and deforestation starting around 8000 years before present (BP) and slowly increasing over the Holocene, would have led to an increase in atmospheric methane (CH4) and carbon dioxide (CO2) concentration, preventing a natural cooling of Earth's climate. Here, the emphasis is not on testing Ruddiman's hypothesis, but rather on exploring the carbon cycle and climate commitment from potential early CH4 and CO2 emissions. In contrast to modern greenhouse gas emissions, early emissions occurred over millennia, allowing the climate system to come to near-equilibrium with the applied forcing. We perform two transient Holocene simulations with an Earth system model of intermediate complexity - the University of Victoria Earth System Climate Model (UVic ESCM). The first simulation is a standard transient Holocene simulation, forced with reconstructed changes in CO2 and CH4 concentrations and orbital and volcanic forcing. The second simulation is forced with CO2 and CH4 concentrations corrected for the net anthropogenic contribution postulated by Ruddiman (2007), with other forcings evolving as in the standard simulation. The difference in diagnosed emissions between the two simulations allows us to determine the anthropogenic emissions. After year 1850, anthropogenic CO2 and CH4 emissions are set to zero and the simulations continued for several hundred years. In this paper, we analyze the carbon cycle and climate response to the applied forcings, and quantify the resulting (post 1850) commitment from early anthropogenic interference.

  12. Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model

    SciTech Connect

    Thornton, Peter E; Doney, Scott C.; Lindsay, Keith; Moore, Jefferson Keith; Mahowald, Natalie; Randerson, James T; Fung, Inez; Lamarque, Jean-Francois H; Feddema, Johan J.

    2009-01-01

    Inclusion of fundamental ecological interactions between carbon and nitrogen cycles in the land component of an atmosphere-ocean general circulation model (AOGCM) leads to decreased carbon uptake associated with CO{sub 2} fertilization, and increased carbon uptake associated with warming of the climate system. The balance of these two opposing effects is to reduce the fraction of anthropogenic CO{sub 2} predicted to be sequestered in land ecosystems. The primary mechanism responsible for increased land carbon storage under radiatively forced climate change is shown to be fertilization of plant growth by increased mineralization of nitrogen directly associated with increased decomposition of soil organic matter under a warming climate, which in this particular model results in a negative gain for the climate-carbon feedback. Estimates for the land and ocean sink fractions of recent anthropogenic emissions are individually within the range of observational estimates, but the combined land plus ocean sink fractions produce an airborne fraction which is too high compared to observations. This bias is likely due in part to an underestimation of the ocean sink fraction. Our results show a significant growth in the airborne fraction of anthropogenic CO{sub 2} emissions over the coming century, attributable in part to a steady decline in the ocean sink fraction. Comparison to experimental studies on the fate of radio-labeled nitrogen tracers in temperate forests indicates that the model representation of competition between plants and microbes for new mineral nitrogen resources is reasonable. Our results suggest a weaker dependence of net land carbon flux on soil moisture changes in tropical regions, and a stronger positive growth response to warming in those regions, than predicted by a similar AOGCM implemented without land carbon-nitrogen interactions. We expect that the between-model uncertainty in predictions of future atmospheric CO{sub 2} concentration and

  13. Microbial potential for carbon and nutrient cycling in a geogenic supercritical carbon dioxide reservoir.

    PubMed

    Freedman, Adam J E; Tan, BoonFei; Thompson, Janelle R

    2017-06-01

    Microorganisms catalyze carbon cycling and biogeochemical reactions in the deep subsurface and thus may be expected to influence the fate of injected supercritical (sc) CO2 following geological carbon sequestration (GCS). We hypothesized that natural subsurface scCO2 reservoirs, which serve as analogs for the long-term fate of sequestered scCO2 , harbor a 'deep carbonated biosphere' with carbon cycling potential. We sampled subsurface fluids from scCO2 -water separators at a natural scCO2 reservoir at McElmo Dome, Colorado for analysis of 16S rRNA gene diversity and metagenome content. Sequence annotations indicated dominance of Sulfurospirillum, Rhizobium, Desulfovibrio and four members of the Clostridiales family. Genomes extracted from metagenomes using homology and compositional approaches revealed diverse mechanisms for growth and nutrient cycling, including pathways for CO2 and N2 fixation, anaerobic respiration, sulfur oxidation, fermentation and potential for metabolic syntrophy. Differences in biogeochemical potential between two production well communities were consistent with differences in fluid chemical profiles, suggesting a potential link between microbial activity and geochemistry. The existence of a microbial ecosystem associated with the McElmo Dome scCO2 reservoir indicates that potential impacts of the deep biosphere on CO2 fate and transport should be taken into consideration as a component of GCS planning and modelling. © 2017 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

  14. Microbial potential for carbon and nutrient cycling in a geogenic supercritical carbon dioxide reservoir

    PubMed Central

    Freedman, Adam J.E.; Tan, BoonFei

    2017-01-01

    Summary Microorganisms catalyze carbon cycling and biogeochemical reactions in the deep subsurface and thus may be expected to influence the fate of injected supercritical (sc) CO2 following geological carbon sequestration (GCS). We hypothesized that natural subsurface scCO2 reservoirs, which serve as analogs for the long‐term fate of sequestered scCO2, harbor a ‘deep carbonated biosphere’ with carbon cycling potential. We sampled subsurface fluids from scCO2‐water separators at a natural scCO2 reservoir at McElmo Dome, Colorado for analysis of 16S rRNA gene diversity and metagenome content. Sequence annotations indicated dominance of Sulfurospirillum, Rhizobium, Desulfovibrio and four members of the Clostridiales family. Genomes extracted from metagenomes using homology and compositional approaches revealed diverse mechanisms for growth and nutrient cycling, including pathways for CO2 and N2 fixation, anaerobic respiration, sulfur oxidation, fermentation and potential for metabolic syntrophy. Differences in biogeochemical potential between two production well communities were consistent with differences in fluid chemical profiles, suggesting a potential link between microbial activity and geochemistry. The existence of a microbial ecosystem associated with the McElmo Dome scCO2 reservoir indicates that potential impacts of the deep biosphere on CO2 fate and transport should be taken into consideration as a component of GCS planning and modelling. PMID:28229521

  15. Organic carbon cycling in landfills: Model for a continuum approach

    SciTech Connect

    Bogner, J.; Lagerkvist, A.

    1997-09-01

    Organic carbon cycling in landfills can be addressed through a continuum model where the end-points are conventional anaerobic digestion of organic waste (short-term analogue) and geologic burial of organic material (long-term analogue). Major variables influencing status include moisture state, temperature, organic carbon loading, nutrient status, and isolation from the surrounding environment. Bioreactor landfills which are engineered for rapid decomposition approach (but cannot fully attain) the anaerobic digester end-point and incur higher unit costs because of their high degree of environmental isolation and control. At the other extreme, uncontrolled land disposal of organic waste materials is similar to geologic burial where organic carbon may be aerobically recycled to atmospheric CO{sub 2}, anaerobically converted to CH{sub 4} and CO{sub 2} during early diagenesis, or maintained as intermediate or recalcitrant forms into geologic time (> 1,000 years) for transformations via kerogen pathways. A family of improved landfill models are needed at several scales (molecular to landscape) which realistically address landfill processes and can be validated with field data.

  16. Shifts in bacterial community composition associated with increased carbon cycling in a mosaic of phytoplankton blooms.

    PubMed

    Landa, Marine; Blain, Stéphane; Christaki, Urania; Monchy, Sébastien; Obernosterer, Ingrid

    2016-01-01

    Marine microbes have a pivotal role in the marine biogeochemical cycle of carbon, because they regulate the turnover of dissolved organic matter (DOM), one of the largest carbon reservoirs on Earth. Microbial communities and DOM are both highly diverse components of the ocean system, yet the role of microbial diversity for carbon processing remains thus far poorly understood. We report here results from an exploration of a mosaic of phytoplankton blooms induced by large-scale natural iron fertilization in the Southern Ocean. We show that in this unique ecosystem where concentrations of DOM are lowest in the global ocean, a patchwork of blooms is associated with diverse and distinct bacterial communities. By using on-board continuous cultures, we identify preferences in the degradation of DOM of different reactivity for taxa associated with contrasting blooms. We used the spatial and temporal variability provided by this natural laboratory to demonstrate that the magnitude of bacterial production is linked to the extent of compositional changes. Our results suggest that partitioning of the DOM resource could be a mechanism that structures bacterial communities with a positive feedback on carbon cycling. Our study, focused on bacterial carbon processing, highlights the potential role of diversity as a driving force for the cycling of biogeochemical elements.

  17. Process analysis of CO{sub 2} capture from flue gas using carbonation/calcination cycles

    SciTech Connect

    Li, Z.S.; Cai, N.S.; Croiset, E.

    2008-07-15

    Process analysis of CO{sub 2} capture from flue gas using Ca-based carbonation/calcination cycles is presented here. A carbonation/calcination system is composed essentially of two reactors (an absorber and a regenerator) with Ca-based sorbent circulating between the two reactors (assumed here as fluidized beds). CO{sub 2} is, therefore, transferred from the absorber to the regenerator. Because of the endothermicity of the calcination reaction, a certain amount of coal is burned with pure oxygen in the regenerator. Detailed mass balance, heat balance and cost of electricity and CO{sub 2} mitigation for the carbonation/calcination cycles with three Ca-based sorbents in dual fluidized beds were calculated and analyzed to study the effect of the Ca-based sorbent activity decay on CO{sub 2} capture from flue gas. The three sorbents considered were: limestone, dolomite and CaO/Ca{sub 12}Al{sub 14}O{sub 33} (75/25 wt %) sorbent. All results, including the amount of coal and oxygen required, are presented with respect to the difference in calcium oxide conversion between the absorber and the regenerator, which is an important design parameter. Finally, costs of electricity and CO{sub 2} mitigation costs using carbonation/calcination cycles for the three sorbents were estimated. The results indicate that the economics of the carbonation/calcination process compare favorably with competing technologies for capturing CO{sub 2}.

  18. Estimating soil carbon change and biofuel life-cycle greenhouse gas emissions with economic, ecosystem and life-cycle models

    NASA Astrophysics Data System (ADS)

    Qin, Z.; Dunn, J.; Kwon, H. Y.; Mueller, S.; Wander, M.

    2015-12-01

    Land-use change (LUC) resulting from biofuel feedstock production can alter soil organic carbon (SOC) stocks of lands producing those crops and the crops they displace, possibly resulting in greenhouse gas (GHG) emissions. LUC GHG emissions included in biofuel life cycle analysis (LCA) have at times been estimated to be so great that biofuels did not offer a greenhouse gas reduction compared to conventional fossil fuels. To improve the accuracy of emissions estimates, SOC changes must be considered at a finer spatial resolution and take into account climate, soil, land use and management factors. This study reports on the incorporation of global LUC as predicted by a computable general equilibrium model (i.e., GTAP) and spatially-explicit modeled SOC estimates (using surrogate CENTURY) for various biofuel feedstock scenarios into a widely-used LCA model (i.e., GREET). Resulting estimates suggest: SOC changes associated with domestic corn production might contribute 2-6% or offset as much as 5% of total corn ethanol life-cycle GHG emissions. On the other hand, domestic LUC GHG emissions for switchgrass ethanol have the potential offset up to 60% of GHG emissions in the fuel's life cycle. Further, large SOC sequestration is predicted for Miscanthus feedstock production, enabling Miscanthus-based ethanol systems to offset all life-cycle GHG emissions and create a net carbon sink. LUC GHG emissions for ethanol derived from corn stover are small compared to other sources. Total life-cycle GHG emissions (g CO2eq MJ-1, 100cm soil) were estimated to be 59-66 for corn ethanol, 14 for stover ethanol, 18-26 for switchgrass ethanol, and -7 - -0.6 for Miscanthus ethanol.

  19. Building carbon-carbon bonds using a biocatalytic methanol condensation cycle.

    PubMed

    Bogorad, Igor W; Chen, Chang-Ting; Theisen, Matthew K; Wu, Tung-Yun; Schlenz, Alicia R; Lam, Albert T; Liao, James C

    2014-11-11

    Methanol is an important intermediate in the utilization of natural gas for synthesizing other feedstock chemicals. Typically, chemical approaches for building C-C bonds from methanol require high temperature and pressure. Biological conversion of methanol to longer carbon chain compounds is feasible; however, the natural biological pathways for methanol utilization involve carbon dioxide loss or ATP expenditure. Here we demonstrated a biocatalytic pathway, termed the methanol condensation cycle (MCC), by combining the nonoxidative glycolysis with the ribulose monophosphate pathway to convert methanol to higher-chain alcohols or other acetyl-CoA derivatives using enzymatic reactions in a carbon-conserved and ATP-independent system. We investigated the robustness of MCC and identified operational regions. We confirmed that the pathway forms a catalytic cycle through (13)C-carbon labeling. With a cell-free system, we demonstrated the conversion of methanol to ethanol or n-butanol. The high carbon efficiency and low operating temperature are attractive for transforming natural gas-derived methanol to longer-chain liquid fuels and other chemical derivatives.

  20. Plumbing the global carbon cycle: Integrating inland waters into the terrestrial carbon budget

    USGS Publications Warehouse

    Cole, J.J.; Prairie, Y.T.; Caraco, N.F.; McDowell, W.H.; Tranvik, L.J.; Striegl, R.G.; Duarte, C.M.; Kortelainen, Pirkko; Downing, J.A.; Middelburg, J.J.; Melack, J.

    2007-01-01

    Because freshwater covers such a small fraction of the Earth's surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y-1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y-1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described. ?? 2007 Springer Science+Business Media, LLC.

  1. Is Titan's shape explained by its meteorology and carbon cycle?

    NASA Astrophysics Data System (ADS)

    Choukroun, M.; Sotin, C.

    2012-04-01

    Titan, Saturn's largest satellite, is unique in the Solar System: it is the only satellite bearing a dense atmosphere and it is the only place besides Earth with stable liquid bodies at its surface. In addition complex organics are produced in its atmosphere by the photolysis of methane, the second most abundant atmospheric molecule that irreversibly produces ethane and other more complex carbon bearing molecules. The Cassini/Huygens mission has revealed that the difference between its equatorial and polar radii is several hundred meters larger than that expected from its spin rate, and that it is in hydrostatic equilibrium. Global circulation models predict a large meridional circulation with upwelling at the summer hemisphere and downwelling at the winter pole where ethane can condense and fall at the surface. Lakes and Mare have been observed at the poles only (Stofan et al., Nature, 2007). Ethane has been spectroscopically identified in one of the lakes (Brown et al., Nature, 2008). The present study investigates the subsidence associated with ethane rain at the poles. As suggested by laboratory experiments, ethane flows very easily in a porous crust made of either pure water ice or methane clathrates. Loading of the lithosphere by liquid hydrocarbons induces a tendency of the polar terrains to subside relative to the lower latitudes terrains. In addition, laboratory experiments suggest that ethane substitutes to methane in a methane clathrate crust. The present study estimates the kinetics of this transformation. It suggests that such a transformation would occur on timescales much smaller than geological timescales. To explain a value of 270 m of the subsidence as determined by the radar instrument onboard the Cassini spacecraft (Zebker et al., Science, 2009), our study predicts that the percolation of ethane liquid in the polar crust should have operated during the last 300 - 1,200 Myr. This number is in agreement with the isotopic age of the atmospheric

  2. Chemistry of organic carbon in soil with relationship to the global carbon cycle

    SciTech Connect

    Post, W.M. III

    1988-01-01

    Various ecosystem disturbances alter the balances between production of organic matter and its decomposition and therefore change the amount of carbon in soil. The most severe perturbation is conversion of natural vegetation to cultivated crops. Conversion of natural vegetation to cultivated crops results in a lowered input of slowly decomposing material which causes a reduction in overall carbon levels. Disruption of soil matrix structure by cultivation leads to lowered physical protection of organic matter resulting in an increased net mineralization rate of soil carbon. Climate change is another perturbation that affects the amount and composition of plant production, litter inputs, and decomposition regimes but does not affect soil structure directly. Nevertheless, large changes in soil carbon storage are probable with anticipated CO2 induced climate change, particularly in northern latitudes where anticipated climate change will be greatest (MacCracken and Luther 1985) and large amounts of soil organic matter are found. It is impossible, given the current state of knowledge of soil organic matter processes and transformations to develop detailed process models of soil carbon dynamics. Largely phenomenological models appear to be developing into predictive tools for understanding the role of soil organic matter in the global carbon cycle. In particular, these models will be useful in quantifying soil carbon changes due to human land-use and to anticipated global climate and vegetation changes. 47 refs., 7 figs., 2 tabs.

  3. Dynamics of decadally cycling carbon in subsurface soils

    NASA Astrophysics Data System (ADS)

    Koarashi, Jun; Hockaday, William C.; Masiello, Caroline A.; Trumbore, Susan E.

    2012-09-01

    Subsurface horizons contain more than half of the global soil carbon (C), yet the dynamics of this C remains poorly understood. We estimated the amount of decadally cycling subsurface C (˜20 to 60 cm depth) from the incorporation of `bomb' radiocarbon (14C) using samples taken over 50 years from grassland and forest soils in the Sierra Nevada Mountains, California. The radiocarbon content of all organic matter fractions (roots, low-density (LF), high-density (HF), and non-oxidizable HF) increased from the pre- to post-bomb samples, indicating ˜1-6 kgC m-2, or about half of the subsoil C, consists of C fixed since 1963. Low-density (LF-C) represented <24% (grassland) to 40-55% (forest) of the subsurface C and represented a mixture of post-bomb C and varying amounts of pre-1950 charcoal, identified using13C-NMR spectroscopy. The14C content of HF-C increased rapidly from 1992 to 2009, indicating a significant time lag (>20 years) for the arrival of `bomb'14C to this fraction. A two-pool (fast-cycling and passive) model including >20 year time lag showed that 28-73% of the subsoil mineral-associated C had turnover times of 10-95 years. Microbially respired C was enriched in bomb14C compared to both LF and HF fractions in 2009. Overall, we estimate that C fluxes through decadally cycling pools in the subsurface are equivalent to 1-9% (grassland) to 10-54% (forest) of the surface litterfall at these sites. Our results demonstrate the importance of decadally cycling C for ecosystem C balance, and that a lagged response of the large subsurface C stores to changes in environmental conditions is possible.

  4. Carbon isotope records reveal synchronicity between carbon cycle perturbation and the "Carnian Pluvial Event" in the Tethys realm (Late Triassic)

    NASA Astrophysics Data System (ADS)

    Dal Corso, Jacopo; Gianolla, Piero; Newton, Robert J.; Franceschi, Marco; Roghi, Guido; Caggiati, Marcello; Raucsik, Béla; Budai, Tamás; Haas, János; Preto, Nereo

    2015-04-01

    In the early Late Triassic a period of increased rainfall, named the Carnian Pluvial Event (CPE), is evidenced by major lithological changes in continental and marine successions worldwide. The environmental change seems to be closely associated with a negative carbon isotope excursion that was identified in a stratigraphic succession of the Dolomites (Italy) but the temporal relationship between these phenomena is still not well defined. Here we present organic-carbon isotope data from Carnian deep-water stratigraphic sections in Austria and Hungary, and carbonate petrography of samples from a marginal marine section in Italy. A negative 2-4‰ δ13C shift is recorded by bulk organic matter in the studied sections and is coincident with a similar feature highlighted in higher plant and marine algal biomarker carbon-isotope records from the Dolomites (Italy), thus testifying to a global change in the isotopic composition of the reservoirs of the exchangeable carbon. Our new observations verify that sedimentological changes related to the CPE coincide with the carbon cycle perturbation and therefore occurred synchronously within the western Tethys. Consistent with modern observations, our results show that the injection of 13C-depleted CO2 into the Carnian atmosphere-ocean system may have been directly responsible for the increase in rainfall by intensifying the Pangaean mega-monsoon activity. The consequent increased continental weathering and erosion led to the transfer of large amounts of siliciclastics into the basins that were rapidly filled up, while the increased nutrient flux triggered the local development of anoxia. The new carbonate petrography data show that these changes also coincided with the demise of platform microbial carbonate factories and their replacement with metazoan driven carbonate deposition. This had the effect of considerably decreasing carbonate deposition in shallow water environments.

  5. PALADYN, a comprehensive land surface-vegetation-carbon cycle model of intermediate complexity

    NASA Astrophysics Data System (ADS)

    Willeit, Matteo; Ganopolski, Andrey

    2016-04-01

    PALADYN is presented, a new comprehensive and computationally efficient land surface-vegetation-carbon cycle model designed to be used in Earth system models of intermediate complexity for long-term simulations and paleoclimate studies. The model treats in a consistent manner the interaction between atmosphere, terrestrial vegetation and soil through the fluxes of energy, water and carbon. Energy, water and carbon are conserved. The model explicitly treats permafrost, both in physical processes and as important carbon pool. The model distinguishes 9 surface types of which 5 are different vegetation types, bare soil, land ice, lake and ocean shelf. Including the ocean shelf allows to treat continuous changes in sea level and shelf area associated with glacial cycles. Over each surface type the model solves the surface energy balance and computes the fluxes