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Sample records for carbon cycle highly

  1. 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.

  2. 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.

  3. Crosslinked Carbon Nanotubes/Polyaniline Composites as a Pseudocapacitive Material with High Cycling Stability

    PubMed Central

    Liu, Dong; Wang, Xue; Deng, Jinxing; Zhou, Chenglong; Guo, Jinshan; Liu, Peng

    2015-01-01

    The poor cycling stability of polyaniline (PANI) limits its practical application as a pseudocapacitive material due to the volume change during the charge-discharge procedure. Herein, crosslinked carbon nanotubes/polyaniline (C-CNTs/PANI) composites had been designed by the in situ chemical oxidative polymerization of aniline in the presence of crosslinked carbon nanotubes (C-CNTs), which were obtained by coupling of the functionalized carbon nanotubes with 1,4-benzoquinone. The composite showed a specific capacitance of 294 F/g at the scan rate of 10 mV/s, and could retain 95% of its initial specific capacitance after 1000 CV cycles. Such high electrochemical cycling stability resulting from the crosslinked skeleton of the C-CNTs makes them potential electrode materials for a supercapacitor.

  4. High resolution analysis of tropical forest fragmentation and its impact on the global carbon cycle

    NASA Astrophysics Data System (ADS)

    Brinck, Katharina; Fischer, Rico; Groeneveld, Jürgen; Lehmann, Sebastian; Dantas de Paula, Mateus; Pütz, Sandro; Sexton, Joseph O.; Song, Danxia; Huth, Andreas

    2017-03-01

    Deforestation in the tropics is not only responsible for direct carbon emissions but also extends the forest edge wherein trees suffer increased mortality. Here we combine high-resolution (30 m) satellite maps of forest cover with estimates of the edge effect and show that 19% of the remaining area of tropical forests lies within 100 m of a forest edge. The tropics house around 50 million forest fragments and the length of the world's tropical forest edges sums to nearly 50 million km. Edge effects in tropical forests have caused an additional 10.3 Gt (2.1-14.4 Gt) of carbon emissions, which translates into 0.34 Gt per year and represents 31% of the currently estimated annual carbon releases due to tropical deforestation. Fragmentation substantially augments carbon emissions from tropical forests and must be taken into account when analysing the role of vegetation in the global carbon cycle.

  5. 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,…

  6. 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.

  7. 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.

  8. 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.

  9. Sulfur Encapsulated in Graphitic Carbon Nanocages for High-Rate and Long-Cycle Lithium-Sulfur Batteries.

    PubMed

    Zhang, Juan; Yang, Chun-Peng; Yin, Ya-Xia; Wan, Li-Jun; Guo, Yu-Guo

    2016-11-01

    Hybrid sp(2) carbon with a graphene backbone and graphitic carbon nanocages (G-GCNs) is demonstrated as an ideal host for sulfur in Li-S batteries, because it serves as highly efficient electrochemical nanoreactors as well as polysulfides reservoirs. The as-obtained S/(G-GCNs) with high S content exhibits superior high-rate capability (765 mA h g(-1) at 5 C) and long-cycle life over 1000 cycles.

  10. High resolution analysis of tropical forest fragmentation and its impact on the global carbon cycle

    PubMed Central

    Brinck, Katharina; Fischer, Rico; Groeneveld, Jürgen; Lehmann, Sebastian; Dantas De Paula, Mateus; Pütz, Sandro; Sexton, Joseph O.; Song, Danxia; Huth, Andreas

    2017-01-01

    Deforestation in the tropics is not only responsible for direct carbon emissions but also extends the forest edge wherein trees suffer increased mortality. Here we combine high-resolution (30 m) satellite maps of forest cover with estimates of the edge effect and show that 19% of the remaining area of tropical forests lies within 100 m of a forest edge. The tropics house around 50 million forest fragments and the length of the world's tropical forest edges sums to nearly 50 million km. Edge effects in tropical forests have caused an additional 10.3 Gt (2.1–14.4 Gt) of carbon emissions, which translates into 0.34 Gt per year and represents 31% of the currently estimated annual carbon releases due to tropical deforestation. Fragmentation substantially augments carbon emissions from tropical forests and must be taken into account when analysing the role of vegetation in the global carbon cycle. PMID:28303883

  11. High resolution analysis of tropical forest fragmentation and its impact on the global carbon cycle.

    PubMed

    Brinck, Katharina; Fischer, Rico; Groeneveld, Jürgen; Lehmann, Sebastian; Dantas De Paula, Mateus; Pütz, Sandro; Sexton, Joseph O; Song, Danxia; Huth, Andreas

    2017-03-17

    Deforestation in the tropics is not only responsible for direct carbon emissions but also extends the forest edge wherein trees suffer increased mortality. Here we combine high-resolution (30 m) satellite maps of forest cover with estimates of the edge effect and show that 19% of the remaining area of tropical forests lies within 100 m of a forest edge. The tropics house around 50 million forest fragments and the length of the world's tropical forest edges sums to nearly 50 million km. Edge effects in tropical forests have caused an additional 10.3 Gt (2.1-14.4 Gt) of carbon emissions, which translates into 0.34 Gt per year and represents 31% of the currently estimated annual carbon releases due to tropical deforestation. Fragmentation substantially augments carbon emissions from tropical forests and must be taken into account when analysing the role of vegetation in the global carbon cycle.

  12. The Contemporary Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Houghton, R. A.

    2003-12-01

    The global carbon cycle refers to the exchanges of carbon within and between four major reservoirs: the atmosphere, the oceans, land, and fossil fuels. Carbon may be transferred from one reservoir to another in seconds (e.g., the fixation of atmospheric CO2 into sugar through photosynthesis) or over millennia (e.g., the accumulation of fossil carbon (coal, oil, gas) through deposition and diagenesis of organic matter). This chapter emphasizes the exchanges that are important over years to decades and includes those occurring over the scale of months to a few centuries. The focus will be on the years 1980-2000 but our considerations will broadly include the years ˜1850-2100. Chapter 8.09, deals with longer-term processes that involve rates of carbon exchange that are small on an annual timescale (weathering, vulcanism, sedimentation, and diagenesis).The carbon cycle is important for at least three reasons. First, carbon forms the structure of all life on the planet, making up ˜50% of the dry weight of living things. Second, the cycling of carbon approximates the flows of energy around the Earth, the metabolism of natural, human, and industrial systems. Plants transform radiant energy into chemical energy in the form of sugars, starches, and other forms of organic matter; this energy, whether in living organisms or dead organic matter, supports food chains in natural ecosystems as well as human ecosystems, not the least of which are industrial societies habituated (addicted?) to fossil forms of energy for heating, transportation, and generation of electricity. The increased use of fossil fuels has led to a third reason for interest in the carbon cycle. Carbon, in the form of carbon dioxide (CO2) and methane (CH4), forms two of the most important greenhouse gases. These gases contribute to a natural greenhouse effect that has kept the planet warm enough to evolve and support life (without the greenhouse effect the Earth's average temperature would be -33

  13. Carbonation of subduction-zone serpentinite (high-pressure ophicarbonate; Ligurian Western Alps) and implications for the deep carbon cycling

    NASA Astrophysics Data System (ADS)

    Scambelluri, Marco; Bebout, Gray E.; Belmonte, Donato; Gilio, Mattia; Campomenosi, Nicola; Collins, Nathan; Crispini, Laura

    2016-05-01

    Much of the long-term carbon cycle in solid earth occurs in subduction zones, where processes of devolatilization, partial melting of carbonated rocks, and dissolution of carbonate minerals lead to the return of CO2 to the atmosphere via volcanic degassing. Release of COH fluids from hydrous and carbonate minerals influences C recycling and magmatism at subduction zones. Contradictory interpretations exist regarding the retention/storage of C in subducting plates and in the forearc to subarc mantle. Several lines of evidence indicate mobility of C, of uncertain magnitude, in forearcs. A poorly constrained fraction of the 40-115 Mt/yr of C initially subducted is released into fluids (by decarbonation and/or carbonate dissolution) and 18-43 Mt/yr is returned at arc volcanoes. Current estimates suggest the amount of C released into subduction fluids is greater than that degassed at arc volcanoes: the imbalance could reflect C subduction into the deeper mantle, beyond subarc regions, or storage of C in forearc/subarc reservoirs. We examine the fate of C in plate-interface ultramafic rocks, and by analogy serpentinized mantle wedge, via study of fluid-rock evolution of marble and variably carbonated serpentinite in the Ligurian Alps. Based on petrography, major and trace element concentrations, and carbonate C and O isotope compositions, we demonstrate that serpentinite dehydration at 2-2.5 GPa, 550 °C released aqueous fluids triggering breakdown of dolomite in nearby marbles, thus releasing C into fluids. Carbonate + olivine veins document flow of COH fluids and that the interaction of these COH fluids with serpentinite led to the formation of high-P carbonated ultramafic-rock domains (high-P ophicarbonates). We estimate that this could result in the retention of ∼0.5-2.0 Mt C/yr in such rocks along subduction interfaces. As another means of C storage, 1 to 3 km-thick layers of serpentinized forearc mantle wedge containing 50 modal % dolomite could sequester 1.62 to

  14. 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

  15. 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

  16. Carbonation by fluid-rock interactions at high-pressure conditions: Implications for carbon cycling in subduction zones

    NASA Astrophysics Data System (ADS)

    Piccoli, Francesca; Vitale Brovarone, Alberto; Beyssac, Olivier; Martinez, Isabelle; Ague, Jay J.; Chaduteau, Carine

    2016-07-01

    Carbonate-bearing lithologies are the main carbon carrier into subduction zones. Their evolution during metamorphism largely controls the fate of carbon, regulating its fluxes between shallow and deep reservoirs. Recent estimates predict that almost all subducted carbon is transferred into the crust and lithospheric mantle during subduction metamorphism via decarbonation and dissolution reactions at high-pressure conditions. Here we report the occurrence of eclogite-facies marbles associated with metasomatic systems in Alpine Corsica (France). The occurrence of these marbles along major fluid-conduits as well as textural, geochemical and isotopic data indicating fluid-mineral reactions are compelling evidence for the precipitation of these carbonate-rich assemblages from carbonic fluids during metamorphism. The discovery of metasomatic marbles brings new insights into the fate of carbonic fluids formed in subducting slabs. We infer that rock carbonation can occur at high-pressure conditions by either vein-injection or chemical replacement mechanisms. This indicates that carbonic fluids produced by decarbonation reactions and carbonate dissolution may not be directly transferred to the mantle wedge, but can interact with slab and mantle-forming rocks. Rock-carbonation by fluid-rock interactions may have an important impact on the residence time of carbon and oxygen in subduction zones and lithospheric mantle reservoirs as well as carbonate isotopic signatures in subduction zones. Furthermore, carbonation may modulate the emission of CO2 at volcanic arcs over geological time scales.

  17. Carbonation by fluid-rock interactions at High-Pressure conditions: implications for Carbon cycling in subduction zones

    NASA Astrophysics Data System (ADS)

    Piccoli, Francesca; Vitale Brovarone, Alberto; Beyssac, Olivier; Martinez, Isabelle; Ague, Jay J.; Chaduteau, Carine

    2016-04-01

    Carbonate-bearing lithologies are the main carbon carrier into subduction zones. Their evolution during metamorphism largely controls the fate of carbon regulating its fluxes between shallow and deep reservoirs. In subduction zones, most works have focused on subtractive processes responsible for carbon release from subducting slabs. As an example, several recent works have stressed on the importance of carbonate dissolution as a mean to mobilize large amounts of carbon in subduction zones. By contrast, little is known on additive processes such as rock carbonation at high-pressure (HP) conditions. At shallow depths (e.g. ocean floor and shallow subduction zones, i.e. <40 km), carbonation of mafic and ultramafic rocks deeply contributes to the regulation of carbon fluxes between the geo-biosphere and the atmosphere. We report the occurrence of eclogite-facies marbles associated with metasomatic systems in HP metamorphic unit in Alpine Corsica (France). We performed a field-based study on metasomatic marbles. We will present the petrology and geochemistry that characterize carbonate metasomatism together with fluid inclusions study and pseudosection modeling. Altogether, we bring strong evidences for the precipitation of these carbonate-rich assemblages from carbonic fluids during HP metamorphism. We propose that rock carbonation can occur at HP conditions by either vein-injection or chemical replacement mechanisms. Rock carbonation indicates that carbonic fluids produced by decarbonation reactions and carbonate dissolution may not be directly transferred to the mantle wedge, but may have a preferential and complex pathway within the slab and along slab/mantle interface. Rock carbonation by fluid-rock interactions has a potentially great impact on the residence time of carbon and oxygen and on carbonates isotopic signature in subduction zones. Lastly, carbonation may modulate the emission of CO2 at volcanic arcs over geological time scales.

  18. The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE): Five Years of Insights into the High Latitude Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Miller, C. E.

    2015-12-01

    CARVE is a NASA Earth Ventures (EV-1) investigation designed to quantify correlations between atmospheric and surface state variables for the Alaskan terrestrial ecosystems through intensive seasonal aircraft campaigns, ground-based observations, and analysis. In 2015 CARVE completed its 5-year mission. CARVE campaigns across the 2012-2015 growing seasons have established a baseline for monthly, regional scale estimates for surface-atmosphere fluxes of carbon dioxide (CO2) and methane (CH4), and begun to elucidate their environmental and biogeochemical controls. We find that large interannual variability in biogenic CH4 and CO2 fluxes, fire, and significant cold season fluxes complicate attempts to estimate accurate annual C budgets or C balance trends for high latitude ecosystems. We discuss our current estimates for seasonal to interannual CH4 and CO2 fluxes as well as lessons learned from CARVE to guide future investigations of carbon cycling and ecosystem vulnerability in the Arctic-Boreal region with particular emphasis on NGEE-Arctic and ABoVE.

  19. Linking Sediment Microbial Communities to Carbon Cycling in High-Latitude Lakes

    NASA Astrophysics Data System (ADS)

    Emerson, J. B.; Varner, R. K.; Johnson, J. E.; Owusu-Dommey, A.; Binder, M.; Woodcroft, B. J.; Wik, M.; Freitas, N. L.; Boyd, J. A.; Crill, P. M.; Saleska, S. R.; Tyson, G. W.; Rich, V. I.

    2015-12-01

    It is well recognized that thawing permafrost peatlands are likely to provide a positive feedback to climate change via CH4 and CO2 emissions. High-latitude lakes in these landscapes have also been identified as sources of CH4 and CO2 loss to the atmosphere. To investigate microbial contributions to carbon loss from high-latitude lakes, we characterized sediment geochemistry and microbiota via cores collected from deep and shallow regions of two lakes (Inre Harrsjön and Mellersta Harrsjön) in Arctic Sweden in July, 2012. These lakes are within the Stordalen Mire long-term ecological area, a focal site for investigating the impacts of climate change-related permafrost thaw, and the lakes in this area are responsible for ~55% of the CH4 loss from this hydrologically interconnected system. Across 40 samples from 4 to 40 cm deep within four sediment cores, Illumina 16S rRNA gene sequencing revealed that the sedimentary microbiota was dominated by candidate phyla OP9 and OP8 (Atribacteria and Aminicenantes, respectively, including putative fermenters and anaerobic respirers), predicted methanotrophic Gammaproteobacteria, and predicted methanogenic archaea from the Thermoplasmata Group E2 clade. We observed some overlap in community structure with nearby peatlands, which tend to be dominated by methanogens and Acidobacteria. Sediment microbial communities differed significantly between lakes, by overlying lake depth (shallow vs. deep), and by depth within a core, with each trend corresponding to parallel differences in biogeochemical measurements. Overall, our results support the potential for significant microbial controls on carbon cycling in high-latitude lakes associated with thawing permafrost, and ongoing metagenomic analyses of focal samples will yield further insight into the functional potential of these microbial communities and their dominant members.

  20. High-resolution carbon isotope records of the Toarcian Oceanic Anoxic Event (Early Jurassic) from North America and implications for the global drivers of the Toarcian carbon cycle

    NASA Astrophysics Data System (ADS)

    Them, T. R.; Gill, B. C.; Caruthers, A. H.; Gröcke, D. R.; Tulsky, E. T.; Martindale, R. C.; Poulton, T. P.; Smith, P. L.

    2017-02-01

    The Mesozoic Era experienced several instances of abrupt environmental change that are associated with instabilities in the climate, reorganizations of the global carbon cycle, and elevated extinction rates. Often during these perturbations, oxygen-deficient conditions developed in the oceans resulting in the widespread deposition of organic-rich sediments - these events are referred to as Oceanic Anoxic Events or OAEs. Such events have been linked to massive injections of greenhouse gases into the ocean-atmosphere system by transient episodes of voluminous volcanism and the destabilization of methane clathrates within marine environments. Nevertheless, uncertainty surrounds the specific environmental drivers and feedbacks that occurred during the OAEs that caused perturbations in the carbon cycle; this is particularly true of the Early Jurassic Toarcian OAE (∼183.1 Ma). Here, we present biostratigraphically constrained carbon isotope data from western North America (Alberta and British Columbia, Canada) to better assess the global extent of the carbon cycle perturbations. We identify the large negative carbon isotope excursion associated with the OAE along with high-frequency oscillations and steps within the onset of this excursion. We propose that these high-frequency carbon isotope excursions reflect changes to the global carbon cycle and also that they are related to the production and release of greenhouse gases from terrestrial environments on astronomical timescales. Furthermore, increased terrestrial methanogenesis should be considered an important climatic feedback during Ocean Anoxic Events and other similar events in Earth history after the proliferation of land plants.

  1. Ecosystem development and carbon cycle on a glacier foreland in the high Arctic, Ny-Alesund, Svalbard.

    PubMed

    Nakatsubo, Takayuki; Bekku, Yukiko Sakata; Uchida, Masaki; Muraoka, Hiroyuki; Kume, Atsushi; Ohtsuka, Toshiyuki; Masuzawa, Takehiro; Kanda, Hiroshi; Koizumi, Hiroshi

    2005-06-01

    The Arctic terrestrial ecosystem is thought to be extremely susceptible to climate change. However, because of the diverse responses of ecosystem components to change, an overall response of the ecosystem carbon cycle to climate change is still hard to predict. In this review, we focus on several recent studies conducted to clarify the pattern of the carbon cycle on the deglaciated area of Ny-Alesund, Svalbard in the high Arctic. Vegetation cover and soil carbon pools tended to increase with the progress of succession. However, even in the latter stages of succession, the size of the soil carbon pool was much smaller than those reported for the low Arctic tundra. Cryptogams contributed the major proportion of phytomass in the later stages. However, because of water limitation, their net primary production was smaller than that of the vascular plants. The compartment model that incorporated major carbon pools and flows suggested that the ecosystem of the later stages is likely to be a net sink of carbon at least for the summer season. Based on the eco-physiological characteristics of the major ecosystem components, we suggest several possible scenarios of future changes in the ecosystem carbon cycle.

  2. 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/

  3. 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.

  4. [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.

  5. Multi-cycle operation of enhanced biological phosphorus removal (EBPR) with different carbon sources under high temperature.

    PubMed

    Shen, Nan; Chen, Yun; Zhou, Yan

    2017-05-01

    Many studies reported that it is challenging to apply enhanced biological phosphorus removal (EBPR) process at high temperature. Glycogen accumulating organisms (GAOs) could easily gain their dominance over poly-phosphate accumulating organisms (PAOs) when the operating temperature was in the range of 25 °C-30 °C. However, a few successful EBPR processes operated at high temperature have been reported recently. This study aimed to have an in-depth understanding on the impact of feeding strategy and carbon source types on EBPR performance in tropical climate. P-removal performance of two EBPR systems was monitored through tracking effluent quality and cyclic studies. The results confirmed that EBPR was successfully obtained and maintained at high temperature with a multi-cycle strategy. More stable performance was observed with acetate as the sole carbon source compared to propionate. Stoichiometric ratios of phosphorus and carbon transformation during both anaerobic and aerobic phases were higher at high temperature than low temperature (20±1 °C) except anaerobic PHA/C ratios within most of the sub-cycles. Furthermore, the fractions of PHA and glycogen in biomass were lower compared with one-cycle pulse feed operation. The microbial community structure was more stable in acetate-fed sequencing batch reactor (C2-SBR) than that in propionate-fed reactor (C3-SBR). Accumulibacter Clade IIC was found to be highly abundant in both reactors.

  6. Perturbation of the carbon cycle during the late Pliensbachian - early Toarcian: New insight from high-resolution carbon isotope records in Morocco

    NASA Astrophysics Data System (ADS)

    Bodin, Stéphane; Krencker, Francois-Nicolas; Kothe, Tim; Hoffmann, René; Mattioli, Emanuela; Heimhofer, Ulrich; Kabiri, Lahcen

    2016-04-01

    Preceding the early Toarcian Oceanic Anoxic Event by ∼1 Myr, the Pliensbachian-Toarcian boundary event is in many aspects as severe and disturbing for the environment as its better-studied successor. Both events are associated with rapid and pronounced global warming, major faunal and floral turnover, increased hydrological cycling and dramatic collapses of carbonate production. To better characterize the Pliensbachian-Toarcian boundary event, a high-resolution, paired carbonate and organic matter carbon isotope survey of three sections from the Central High Atlas Basin of Morocco has been undertaken. A pronounced negative shift in the carbonate carbon-isotope record, not paralleled by a similar excursion in the organic carbon, can be linked to the collapse of the neritic carbonate factory in the earliest Toarcian. These results show that, contrary to the Toarcian Oceanic Anoxic Event, a rapid and massive injection of 13C-depleted carbon into the atmosphere is not responsible for the environmental perturbations observed during the Pliensbachian-Toarcian boundary event. However, input of isotopically non-depleted carbon such as mantle source CO2 into the atmosphere as a potential cause for the Pliensbachian-Toarcian boundary event cannot be excluded. This would most probably be sourced from an early pulse of the Karoo-Ferrar Large Igneous Province.

  7. 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.

  8. Carbon-Coated Porous Aluminum Foil Anode for High-Rate, Long-Term Cycling Stability, and High Energy Density Dual-Ion Batteries.

    PubMed

    Tong, Xuefeng; Zhang, Fan; Ji, Bifa; Sheng, Maohua; Tang, Yongbing

    2016-12-01

    A 3D porous Al foil coated with a uniform carbon layer (pAl/C) is prepared and used as the anode and current collector in a dual-ion battery (DIB). The pAl/C-graphite DIB demonstrates superior cycling stability and high rate performance, achieving a highly reversible capacity of 93 mAh g(-1) after 1000 cycles at 2 C over the voltage range of 3.0-4.95 V. In addition, the DIB could achieve an energy density of ≈204 Wh kg(-1) at a high power density of 3084 W kg(-1) .

  9. 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.

  10. Evergreen shrub traits and peatland carbon cycling under high nutrient load

    NASA Astrophysics Data System (ADS)

    Larmola, Tuula; Bui, Vi; Bubier, Jill L.; Wang, Meng; Murphy, Meaghan; Moore, Tim R.

    2016-04-01

    The reactive nitrogen (N) assimilated by plants is usually invested in chlorophyll to improve light harvesting capacity and in soluble proteins such as Rubisco to enhance carbon (C) assimilation. We studied the effects of simulated atmospheric N deposition on different traits of two evergreen shrubs Chamaedaphne calyculata and Rhododendron groenlandicum in a nutrient-poor Mer Bleue Bog, Canada that has been fertilized with N as NO3 and NH4 (2-8 times ambient annual wet deposition) with or without phosphorus (P) and potassium (K) for 7-12 years. We examined how nutrient addition influences the plant performance at leaf and canopy level and linked the trait responses with ecosystem C cycling. At the leaf level, we measured physiological and biochemical traits: CO2 exchange and chlorophyll fluorescence, an indicator of plant stress in terms of light harvesting capacity; and to study changes in photosynthetic nutrient use efficiency, we also determined the foliar chlorophyll, N, and P contents. At the canopy level, we examined morphological and phenological traits: growth responses and leaf longevity during two growing seasons. Regardless of treatment, the majority of leaves showed no signs of stress in terms of light harvesting capacity. The plants were N saturated: with increasing foliar N content, the higher proportion of N was not used in photosynthesis. Foliar net CO2 assimilation rates did not differ significantly among treatments, but the additions of N, P, and K together resulted in higher respiration rates. The analysis of the leaf and canopy traits showed that the two shrubs had different strategies: C. calyculata was more responsive to nutrient additions, more deciduous-like, whereas R. groenlandicum maintained evergreen features under nutrient load, shedding its leaves even later in the season. In all, simulated atmospheric N deposition did not benefit the photosynthetic apparatus of the dominant shrubs, but resulted in higher foliar respiration

  11. 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

  12. How important is subsidence in evaluating high frequency cycles in the interior of isolated carbonate platforms?

    SciTech Connect

    Lomando, A.J.; Ginsburg, R.

    1995-08-01

    Differential regional subsidence can play a strong role in determining facies composition of adjacent isolated platforms. In the majority of platform oil & gas fields, reservoir architecture is dominated by the composition and stratial geometries in the platform interiors rather than the platform rims. Most work to develop analogues from modern reef-rimmed isolated platforms has focused on the platform margins where reef growths rates are capable of keeping pace with the Holocene sea level rise plus tectonic subsidence. We have focused on platform interiors where accumulation rate and style may be more sensitive to accommodation space generated by regional passive margin subsidence. The Belize platforms are located on a series of parallel ridges which extend progressively eastward, farther from the regional subsidence hingeline near the coast. Greater regional subsidence is reflected in the open, deeper, patch reef and sand rich platform interiors in the outermost platform (Lighthouse and Glovers Platform) in comparison to the mud-dominated interior within the innermost platform (Turneffe), which has filled up due to lesser subsidence rate. The facies response to a portion of a single eustatic cycle produces a {open_quotes}keep-up{close_quotes} transgressive systems tract appearance at Lighthouse and Glovers but a {open_quotes}choked-up{close_quotes} high stand or regressive systems tract appearance within Turneffe. Chinchorro Bank, offshore Yucatan, is a special case where subsidence changes along the length of the platforms. The entire windward margin has a well developed reef system which has uniformly kept pace with the Holocene transgression. The northern platform interior contains a patch reef/sand rich character similar to Lighthouse Platform whereas the southern platform interior is {open_quotes}drowning{close_quotes} due to subsidence along a series of northwest trending faults which downstep southward.

  13. Effects of Water Amount on the Surface Environment of Terrestrial Planets: High Pressure Ice and Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Nakayama, Akifumi; Abe, Yutaka

    2015-12-01

    Terrestrial planets with several wt% of H2O in extrasolar planetary systems are theoretically predicted in the habitable zone [Raymond et al., 2004]. Such planets are expected to be covered by an ocean entirely (called as “ocean planets”). Amount of atmospheric CO2 (PCO2) is important for surface environment because CO2 is a strong greenhouse gas. PCO2 is determined by a race between degassing and sink through weathering on carbon cycle. On an ocean planet, seafloor weathering is important because continental weathering can’t work [Abbot et al., 2012]. In addition, ocean planets with large water amount may have high-pressure (HP) ice on the seafloor [Leger et al., 2004]. Since the ocean floor is covered by ice in such case, it has been thought that any weathering processes will not work and PCO2 will be extremely high. When plate tectonics works, heat flow from oceanic crust decreases with distance from the mid ocean ridge. Therefore, HP ice near the mid ocean ridge will be kept solid-liquid coexistent state at the melting point because of high heat flow. Seafloor weathering works in this region. The seafloor weathering under this condition efficiently works because weathering temperature is kept melting point regardless of surface temperature. Thus, our aim is to clarify the relationship between water amount and surface environment focusing seafloor environment. We develop a carbon cycle model considering the seafloor weathering. Our major assumptions are following; 1) Earth-sized ocean planets with various water amount, 2) Degassing rate is depended on the total amount of carbon and total carbon inventory is proportional to the surface water amount. We investigated thermal state of HP ice and determined effective weathering region where HP ice is coexistent with water, then we investigated the PCO2 in equilibrium state where degassing and regassing are balanced. As a result, forming of HP ice may cause snowball state due to high weathering rate. When solar

  14. 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

  15. 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.

  16. 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.

  17. 1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability.

    PubMed

    Hao, Pin; Tian, Jian; Sang, Yuanhua; Tuan, Chia-Chi; Cui, Guanwei; Shi, Xifeng; Wong, C P; Tang, Bo; Liu, Hong

    2016-09-15

    The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo2S4 nanotube array/carbon aerogel and NiCo2O4 nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo2S4 nanotube array/carbon aerogel and NiCo2O4 nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg(-1) and 47.5 Wh kg(-1) at a power density of 400 W kg(-1), respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

  18. Risk of natural disturbances makes future contribution of Canada's forests to the global carbon cycle highly uncertain

    PubMed Central

    Kurz, Werner A.; Stinson, Graham; Rampley, Gregory J.; Dymond, Caren C.; Neilson, Eric T.

    2008-01-01

    A large carbon sink in northern land surfaces inferred from global carbon cycle inversion models led to concerns during Kyoto Protocol negotiations that countries might be able to avoid efforts to reduce fossil fuel emissions by claiming large sinks in their managed forests. The greenhouse gas balance of Canada's managed forest is strongly affected by naturally occurring fire with high interannual variability in the area burned and by cyclical insect outbreaks. Taking these stochastic future disturbances into account, we used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to project that the managed forests of Canada could be a source of between 30 and 245 Mt CO2e yr−1 during the first Kyoto Protocol commitment period (2008–2012). The recent transition from sink to source is the result of large insect outbreaks. The wide range in the predicted greenhouse gas balance (215 Mt CO2e yr−1) is equivalent to nearly 30% of Canada's emissions in 2005. The increasing impact of natural disturbances, the two major insect outbreaks, and the Kyoto Protocol accounting rules all contributed to Canada's decision not to elect forest management. In Canada, future efforts to influence the carbon balance through forest management could be overwhelmed by natural disturbances. Similar circumstances may arise elsewhere if global change increases natural disturbance rates. Future climate mitigation agreements that do not account for and protect against the impacts of natural disturbances, for example, by accounting for forest management benefits relative to baselines, will fail to encourage changes in forest management aimed at mitigating climate change. PMID:18230736

  19. 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.

  20. Atmospheric Carbon Dioxide and its Relation to Carbon Cycle Perturbations During Ocean Anoxic Event 1d: A High Resolution Record From Dispersed Plant Cuticle

    NASA Astrophysics Data System (ADS)

    Richey, J. D.; Upchurch, G. R.; Joeckel, R.; Smith, J. J.; Ludvigson, G. A.; Lomax, B. H.

    2013-12-01

    Past geological greenhouse intervals are associated with Ocean Anoxic Events (OAEs), which result from an increase in marine primary productivity and/or an increase in the preservation of organic matter. The end point is widespread black shale deposition combined with a long-term atmospheric positive δ13C excursion and an increase in the burial of 12C. Some OAEs show a negative δ13C excursion preceding the positive excursion, indicating a perturbation in the global carbon cycle prior to the initiation of these events. The Rose Creek (RCP) locality, southeastern Nebraska, is the only known terrestrial section that preserves OAE1d (Cretaceous, Albian-Cenomanian Boundary) and has abundant charcoal and plant cuticle. These features allow for a combined carbon isotope and stomatal index (SI) analysis to determine both changes in the cycling between carbon pools (C isotope analysis) and changes in paleo-CO2 via changes in SI. Preliminary (and ongoing) SI data analysis using dispersed cuticle of Pandemophyllum kvacekii (an extinct Laurel) collected at 30 cm intervals indicate changes in SI consistent with changes in CO2. Fitting our samples to a published RCP δ13C profile, pre-excursion CO2 concentrations are high. CO2 decreases to lower concentrations in the basal 1.2 m of the RCP section, where δ13Cbulk shows a negative excursion and δ13Ccharcoal remains at pre-excursion values. CO2 concentrations become higher toward the top of the negative δ13C excursion, where δ13Cbulk and δ13Ccharcoal are at their most negative values, and drop as the negative carbon excursion terminates. Using published transfer functions, we estimate that pre-excursion CO2 concentrations were a maximum of 900 ppm. In the basal 1.2 m of RCP, CO2 drops to a maximum of 480 ppm, and rises to a maximum of 710 ppm near the top of the negative excursion. As δ13C values rise towards pre-excursion values, CO2 declines to a maximum of 400 ppm. The trend in SI is comparable to the trend in δ13

  1. Graphene-winged carbon nanotubes as high-performance lithium-ion batteries anode with super-long cycle life

    NASA Astrophysics Data System (ADS)

    Ye, Minghui; Hu, Chuangang; Lv, Lingxiao; Qu, Liangti

    2016-02-01

    Graphene-winged carbon nanotubes (G-CNTs) have been prepared by the well-controlled outer-wall peeling of the multi-walled carbon nanotubes (MWCNTs). The final hybrid structure features the few layers of graphene nanosheets attaching to the intact inner walls of CNTs. On one hand, the outer branched graphene nanosheets could suppress the aggregation of CNTs and introduce abundant defects and active-edges for easily accessible chemical interaction. On the other hand, the CNTs could bridge the graphene nanosheets for rapid electron transfer and mechanical robustness. As a result, the G-CNTs was used as the electrode materials exhibiting an extremely steady reversible capacity of 603 mAh g-1 over 2200 cycles at a current density of 1 A g-1 (the corresponding area capacity is 0.16 mAh cm-2 at a current density of 0.26 mA cm-2) and owning a high rate capability much superior to those of the pristine MWCNT-based counterparts. The hierarchical G-CNTs architecture provides a new material platform for development of advanced energy-storage devices.

  2. 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.

  3. Carbon cycle dynamics and solar activity embedded in a high-resolution 14C speleothem record from Belize, Central America

    NASA Astrophysics Data System (ADS)

    Lechleitner, Franziska A.; Breitenbach, Sebastian F. M.; McIntyre, Cameron; Asmerom, Yemane; Prufer, Keith M.; Polyak, Victor; Culleton, Brendan J.; Kennett, Douglas J.; Eglinton, Timothy I.; Baldini, James U. L.

    2015-04-01

    of old recalcitrant carbon to the soil water, and resulting in closer coupling between atmosphere and cave environment. The resolution of the record (0.3-0.7 mm/sample) permits identification of the dominant drivers of stalagmite 14C during different intervals. For example, hydrologic control on 14C appears dominant during the 11th century drought, while in the 16th to 18th century a clear solar influence exists. Solar activity is reflected in YOK-I as lower a14Cinit, reflecting the atmospheric a14C. We apply simple hydrological models to investigate the different factors influencing 14C in YOK-I. We estimate the importance of mean SOM age to signal dampening, and quantify the strength of the solar influence and the global carbon cycle on the record. References: Genty, D., Baker, A., Massault, M., Proctor, C., Gilmour, M., Pons-Branchu, E., Hamelin, B. (2001) Dead carbon in stalagmites: carbonate bedrock paleodissolution vs. ageing of soil organic matter. Implications for 13C variations in speleothems, GCA, 65 Griffiths, M.L., Fohlmeister, J., Drysdale, R.N., Hua, Q., Johnson, K.R., Hellstrom, J.C., Gagan, M.K., Zhao, J.-x. (2012) Hydrological control of the dead carbon fraction in a Holocene tropical speleothem, Quat. Geochron. 14 Ridley, H.E., Baldini, J.U.L., Prufer, K.M., Walczak, I.W., Breitenbach, S.F.M. (in press) High resolution monitoring of a tropical cave system reveals dynamic ventilation and hydrologic resilience to seismic activity, Journal of Cave and Karst Studies

  4. Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    ScienceCinema

    Wullschleger, Stan [ORNL

    2016-07-12

    Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

  5. Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    SciTech Connect

    Wullschleger, Stan

    2012-03-22

    Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

  6. Carbon, nutrient and trace metal cycling in sandy sediments: A comparison of high-energy beaches and backbarrier tidal flats

    NASA Astrophysics Data System (ADS)

    Reckhardt, Anja; Beck, Melanie; Seidel, Michael; Riedel, Thomas; Wehrmann, Achim; Bartholomä, Alexander; Schnetger, Bernhard; Dittmar, Thorsten; Brumsack, Hans-Jürgen

    2015-06-01

    In order to evaluate the importance of coastal sandy sediments and their contribution to carbon, nutrient and metal cycling we investigated two beach sites on Spiekeroog Island, southern North Sea, Germany, and a tidal flat margin, located in Spiekeroog's backbarrier area. We also analyzed seawater and fresh groundwater on Spiekeroog Island, to better define endmember concentrations, which influence our study sites. Intertidal sandy flats and beaches are characterized by pore water advection. Seawater enters the sediment during flood and pore water drains out during ebb and at low tide. This pore water circulation leads to continuous supply of fresh organic substrate to the sediments. Remineralization products of microbial degradation processes, i.e. nutrients, and dissolved trace metals from the reduction of particulate metal oxides, are enriched in the pore water compared to open seawater concentrations. The spatial distribution of dissolved organic carbon (DOC), nutrients (PO43-, NO3-, NO2-, NH4+, Si(OH)4 and total alkalinity), trace metals (dissolved Fe and Mn) as well as sulfate suggests that the exposed beach sites are subject to relatively fast pore water advection, which leads to organic matter and oxygen replenishment. Frequent pore water exchange further leads to comparatively low nutrient concentrations. Sulfate reduction does not appear to play a major role during organic matter degradation. High nitrate concentrations indicate that redox conditions are oxic within the duneward freshwater influenced section, while ammonification, denitrification, manganese and iron reduction seem to prevail in the ammonium-dominated seawater circulation zone. In contrast, the sheltered tidal flat margin site exhibits a different sedimentology (coarser beach sands versus finer tidal flat sands) and nutrients, dissolved manganese and DOC accumulate in the pore water. Ammonium is the dominant pore water nitrogen species and intense sulfate reduction leads to the formation

  7. 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

  8. 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.

  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, 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.

  10. 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.

  11. 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.

  12. 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.

  13. High-Resolution Isotope Records of the Late Ordovician and Late Carboniferous: A Comparative Perspective on Glacial Carbon and Sulfur Cycles

    NASA Astrophysics Data System (ADS)

    Gill, B. C.; Lyons, T. W.; Saltzman, M. R.

    2005-12-01

    Carbonate-associated sulfate (CAS) faithfully tracks the sulfur isotope composition of seawater in both modern and ancient environments. Therefore, analyses of carbonate rocks permit the generation of parallel, high-resolution carbon and sulfur isotope data for seawater spanning geologic history. Our previous work in the early and middle Paleozoic has revealed parallel, short-term (1-4 Myrs) carbon and sulfur isotope excursions. The relationship between the two isotope systems seems to change over time, perhaps tracking longer-term evolution of the marine sulfur reservoir and of the primary loci of carbon burial, including increased burial on land. CAS isotope records therefore have the potential to shed essential mechanistic light on the causes (global versus regional) for carbon isotope excursions observed throughout the geological record. Previous work on the Late Carboniferous and Late Ordovician documented the existence of carbon isotope excursions of varying magnitude during these glacial episodes. The Late Carboniferous glaciations classically show evidence for multiple glacial-interglacial cycles with repeated, low magnitude (1 to 3 per mil) carbon isotope excursions. By contrast, the Late Ordovician was characterized by a short-lived glaciation with a corresponding single 4-6 per mil carbon isotope excursion. The modes and rates of carbon cycling reflected in the differing styles of C isotope behavior are the subject of debate, making these time-slices ideal for the CAS isotope approach. Carbon and sulfur isotope data from Pennsylvanian (Missourian Stage) cyclothems exposed in Kansas City, Missouri, show rapid isotope variability. We have preliminarily attributed these rapid changes to local reservoir effects linked to fluctuating sea level and its relationship to black shale deposition within the midcontinent basin and weathering on the basin margin during lowstands. Other work on the cyclic Carboniferous Bird Spring Formation, Nevada, is also

  14. Selenium encapsulated into 3D interconnected hierarchical porous carbon aerogels for lithium-selenium batteries with high rate performance and cycling stability

    NASA Astrophysics Data System (ADS)

    Jiang, Shaofeng; Zhang, Zhian; Lai, Yanqing; Qu, Yaohui; Wang, XiWen; Li, Jie

    2014-12-01

    Selenium encapsulated into 3D interconnected hierarchical porous carbon aerogels (HPCA) as a carbon/selenium composite material is prepared for lithium-selenium batteries. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show the hierarchical porous structures of the carbon aerogels and the homogeneous distribution of selenium in the composite. The performance of the HPCA/Se cathode is evaluated in lithium-selenium batteries using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. It is found that the HPCA/Se cathode shows high rate performance, coulombic efficiency and cycling stability. The HPCA/Se cathode has a highest coulombic efficiency which is kept above 98% after 50th cycle in ionic liquid N-methyl-(n-butyl) pyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) modified electrolyte and retains 309 mAh g-1 after 100 discharge/charge cycles at a high rate of 0.5 C (337.5 mAh g-1) in LiNO3 modified electrolyte, respectively. Even at the current density of 5 C (3375 mAh g-1), it can still maintain at a reversible capacity of 301 mAh g-1. The excellent electrochemical properties benefit from the high electron conductivity and 3D interconnected hierarchical porous structures of the carbon aerogels, which contribute to disperse selenium and absorb polyselenides, and suppress the formation of residual Li2Se layer.

  15. 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.

  16. 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.

  17. 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.

  18. Significantly improved long-cycle stability in high-rate Li-S batteries enabled by coaxial graphene wrapping over sulfur-coated carbon nanofibers.

    PubMed

    Lu, Songtao; Cheng, Yingwen; Wu, Xiaohong; Liu, Jie

    2013-06-12

    Long-term instability of Li-S batteries is one of their major disadvantages compare to other secondary batteries. The reasons for the instability include dissolution of polysulfide intermediates and mechanical instability of the electrode film caused by volume changes during charging/discharging cycles. In this paper, we report a novel graphene-sulfur-carbon nanofibers (G-S-CNFs) multilayer and coaxial nanocomposite for the cathode of Li-S batteries with increased capacity and significantly improved long-cycle stability. Electrodes made with such nanocomposites were able to deliver a reversible capacity of 694 mA h g(-1) at 0.1C and 313 mA h g(-1) at 2C, which are both substantially higher than electrodes assembled without graphene wrapping. More importantly, the long-cycle stability was significantly improved by graphene wrapping. The cathode made with G-S-CNFs with a initial capacity of 745 mA h g(-1) was able to maintain ~273 mA h g(-1) even after 1500 charge-discharge cycles at a high rate of 1C, representing an extremely low decay rate (0.043% per cycle after 1500 cycles). In contrast, the capacity of an electrode assembled without graphene wrapping decayed dramatically with a 10 times high rate (~0.40% per cycle after 200 cycles). These results demonstrate that the coaxial nanocomposites are of great potential as the cathode for high-rate rechargeable Li-S batteries. Such improved rate capability and cycle stability could be attributed to the unique coaxial architecture of the nanocomposite, in which the contributions from graphene and CNFs enable electrodes with improved electrical conductivity, better ability to trap soluble the polysulfides intermediate and accommodate volume expansion/shrinkage of sulfur during repeated charge/discharge cycles.

  19. 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

  20. 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.

  1. Carbon gel assisted low temperature liquid-phase synthesis of C-LiFePO4/graphene layers with high rate and cycle performances

    NASA Astrophysics Data System (ADS)

    Tang, Hongwei; Si, Yanli; Chang, Kun; Fu, Xiaoning; li, Bao; Shangguan, Enbo; Chang, Zhaorong; Yuan, Xiao-Zi; Wang, Haijiang

    2015-11-01

    Nano-scale LiFePO4/graphene oxide (GO) as cathode materials for lithium ion batteries has been successfully synthesized via a one-step carbon gel assisted liquid-phase approach at a low-temperature (108 °C) and normal pressure. C-LiFePO4/graphene layers (G) composites, composed of LiFePO4, amorphous carbon and graphene layers, are then produced after rapid high temperature carbon treatment. Interface tunnel effect, produced by the intimate contact of LiFePO4 particles with amorphous carbon and graphene layers, greatly improves the properties of the composites. Electrochemical tests indicate that the optimal amount of GO addition is 1 wt.% in terms of achieving a high electrochemical performance of the C-LiFePO4/G composites. Discharge capacity of the C-LiFePO4/G composites is 160.0 mAh g-1 at 0.2 C. When the current rate is further increased to 60 C, the discharge capacity of C-LiFePO4/G can reach 68 mAh g-1. At a high current rate of 20 C, the capacity attenuation rate of the C-LiFePO4/G electrode is only 9.6% after 200 cycles, showing excellent high-rate discharge capability and cycle performance. This is achieved under a facile synthesis condition of a simple procedure, low temperature, and normal pressure.

  2. 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.

  3. Precipitation Mediates the Response of Carbon Cycle to Rising Temperature in the Mid-to-High Latitudes of the Northern Hemisphere.

    PubMed

    Lin, Xin; Li, Junsheng; Luo, Jianwu; Wu, Xiaopu; Tian, Yu; Wang, Wei

    2015-01-01

    Over the past decades, rising air temperature has been accompanied by changes in precipitation. Despite relatively robust literature on the temperature sensitivity of carbon cycle at continental to global scales, less is known about the way this sensitivity is affected by precipitation. In this study we investigate how precipitation mediates the response of the carbon cycle to warming over the mid-to-high latitudes in the Northern Hemisphere (north of 30 °N). Based on atmospheric CO2 observations at Point Barrow (BRW) in Alaska, satellite-derived NDVI (a proxy of vegetation productivity), and temperature and precipitation data, we analyzed the responses of carbon cycle to temperature change in wet and dry years (with precipitation above or below the multiyear average). The results suggest that, over the past three decades, the net seasonal atmospheric CO2 changes at BRW were significantly correlated with temperature in spring and autumn, yet only weakly correlated with temperature and precipitation during the growing season. We further found that responses of the net CO2 changes to warming in spring and autumn vary with precipitation levels, with the absolute temperature sensitivity in wet years roughly twice that in dry years. The analyses of NDVI and climate data also identify higher sensitivity of vegetation growth to warming in wet years for the growing season, spring and summer. The different temperature sensitivities in wet versus dry years probably result from differences in soil moisture and/or nutrient availability, which may enhance (inhibit) the responsiveness of carbon assimilation and/or decomposition to warming under high (low) precipitation levels. The precipitation-mediated response of the terrestrial carbon cycle to warming reported here emphasizes the important role of precipitation in assessing the temporal variations of carbon budgets in the past as well as in the future. More efforts are required to reduce uncertainty in future precipitation

  4. Precipitation Mediates the Response of Carbon Cycle to Rising Temperature in the Mid-to-High Latitudes of the Northern Hemisphere

    PubMed Central

    Lin, Xin; Li, Junsheng; Luo, Jianwu; Wu, Xiaopu; Tian, Yu; Wang, Wei

    2015-01-01

    Over the past decades, rising air temperature has been accompanied by changes in precipitation. Despite relatively robust literature on the temperature sensitivity of carbon cycle at continental to global scales, less is known about the way this sensitivity is affected by precipitation. In this study we investigate how precipitation mediates the response of the carbon cycle to warming over the mid-to-high latitudes in the Northern Hemisphere (north of 30°N). Based on atmospheric CO2 observations at Point Barrow (BRW) in Alaska, satellite-derived NDVI (a proxy of vegetation productivity), and temperature and precipitation data, we analyzed the responses of carbon cycle to temperature change in wet and dry years (with precipitation above or below the multiyear average). The results suggest that, over the past three decades, the net seasonal atmospheric CO2 changes at BRW were significantly correlated with temperature in spring and autumn, yet only weakly correlated with temperature and precipitation during the growing season. We further found that responses of the net CO2 changes to warming in spring and autumn vary with precipitation levels, with the absolute temperature sensitivity in wet years roughly twice that in dry years. The analyses of NDVI and climate data also identify higher sensitivity of vegetation growth to warming in wet years for the growing season, spring and summer. The different temperature sensitivities in wet versus dry years probably result from differences in soil moisture and/or nutrient availability, which may enhance (inhibit) the responsiveness of carbon assimilation and/or decomposition to warming under high (low) precipitation levels. The precipitation-mediated response of the terrestrial carbon cycle to warming reported here emphasizes the important role of precipitation in assessing the temporal variations of carbon budgets in the past as well as in the future. More efforts are required to reduce uncertainty in future precipitation

  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. Free-standing and binder-free sodium-ion electrodes with ultralong cycle life and high rate performance based on porous carbon nanofibers.

    PubMed

    Li, Weihan; Zeng, Linchao; Yang, Zhenzhong; Gu, Lin; Wang, Jiaqing; Liu, Xiaowu; Cheng, Jianxiu; Yu, Yan

    2014-01-21

    Free-standing and binder-free porous carbon nanofibers (P-CNFs) electrodes were prepared by pyrolysis of PAN-F127/DMF nanofibers via an electrospinning process as potential anodes for Na-ion batteries (NIB). The P-CNFs delivers a reversible capacity of 266 mA h g(-1) after 100 cycles at 0.2 C, corresponding to ~80% of the initial charge capacity. When cycled at a current density as high as 500 mA g(-1) (2 C), it still delivers a reversible capacity of ~140 mA h g(-1) after 1000 cycles. The improvement of electrochemical performance is attributed to the special design and microstructure of P-CNFs, which conferred a variety of advantages: hierarchical porous channels enabling short transport length for ions and electrons, 3D interconnected structure resulting in low contact resistances, good mechanical properties leading to the excellent morphology stability.

  7. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability.

    PubMed

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M

    2016-06-20

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

  8. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    NASA Astrophysics Data System (ADS)

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.

    2016-06-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.

  9. High Area Capacity Lithium-Sulfur Full-cell Battery with Prelitiathed Silicon Nanowire-Carbon Anodes for Long Cycling Stability

    PubMed Central

    Krause, Andreas; Dörfler, Susanne; Piwko, Markus; Wisser, Florian M.; Jaumann, Tony; Ahrens, Eike; Giebeler, Lars; Althues, Holger; Schädlich, Stefan; Grothe, Julia; Jeffery, Andrea; Grube, Matthias; Brückner, Jan; Martin, Jan; Eckert, Jürgen; Kaskel, Stefan; Mikolajick, Thomas; Weber, Walter M.

    2016-01-01

    We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm2. The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm2, a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging. PMID:27319783

  10. 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.

  11. Fracture morphologies of carbon-black-loaded SBR (styrene-butadiene rubber) subjected to low-cycle, high-stress fatigue. [Styrene-butadiene rubber

    SciTech Connect

    Goldberg, A.; Lesuer, D.R.; Patt, J.

    1988-02-01

    Experimental results, together with an analytical model, related to the loss in tensile strength of styrene-butadiene rubber (SBR) loaded with carbon black (CB) that had been subjected to low-cycle, high-stress fatigue tests were presented in a prior paper. The drop in tensile strength relative to that of a virgin sample was considered to be a measure of damage induced during the fatigue test. The present paper is a continuation of this study dealing with the morphological interpretations of the fractured surfaces, whereby the cyclic-tearing behavior, resulting in the damage, is related to the test and material parameters. It was found that failure is almost always initiated in the bulk of a sample at a material flaw. The size and definition of a flaw increase with an increase in carbon-black loading. Initiation flaw sites are enveloped by fan-shaped or penny-shaped regions which develop during cycling. The size and morphology of a fatigue-tear region appears to be independent of the fatigue load or the extent of the damage (strength loss). By contrast, either an increase in cycling load or an increase in damage at constant load increases the definition of the fatigue-region morphology for all formulations of carbon-black. On the finest scale, the morphology can be described in terms of tearing of individual groups of rubber strands, collapsing to form a cell-like structure. 18 refs., 13 figs.

  12. 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

  13. 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.

  14. Aquatic carbon fluxes in HD: using in-situ sensors to obtain a high definition picture of carbon cycling in streams (Invited)

    NASA Astrophysics Data System (ADS)

    Clow, D. W.; Dornblaser, M.; Saraceno, J.; Pellerin, B. A.; Mast, A.; Shanley, J. B.

    2013-12-01

    In-situ sensors provide a means to collect water-quality data in streams at time resolutions ranging from minutes to days, weeks, or months. Instruments may be deployed individually to investigate specific constituents of interest or in sensor arrays to provide a more complete picture for a suite of related compounds. Data from the instruments can provide direct measurements of some constituents (e.g., nitrate or dissolved CO2), or may be used as surrogates for other parameters (e.g., FDOM as a surrogate for DOC). These data may be used to improve estimates of nutrient or carbon fluxes, and to investigate processes influencing high-frequency variability in constituent concentrations. In this study, we examine high-temporal-resolution data from a suite of sensor arrays installed in mountain streams in Rocky Mountain National Park, Colorado. The sensor arrays include fluorescing dissolved organic matter (FDOM), turbidity, and CO2 sensors, which are being used to characterize variability in dissolved and particulate forms of carbon. We will (1) compare these data to concentrations obtained through manual grab sampling to document the utility of in-situ measurements as surrogates for dissolved organic carbon (DOC) and particulate organic carbon (POC), (2) compare stream-water fluxes of carbon calculated using a conventional sample-based approach to those computed using high-temporal resolution data from in-situ sensors, and (3) use ancillary data from co-located stream gages (e.g. streamflow) and meteorological stations (e.g., solar radiation) to investigate the influences of hydrology and climate on high-frequency variability in carbon fluxes in streams.

  15. 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/

  16. 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.

  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. 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.

  19. High-rate and ultralong cycle-life LiFePO4 nanocrystals coated by boron-doped carbon as positive electrode for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Feng, Jinpeng; Wang, Youlan

    2016-12-01

    An evolutionary modification approach, boron-doped carbon coating, has been used to improve the electrochemical performances of positive electrodes for lithium-ion batteries, and demonstrates apparent and significant modification effects. In this study, the boron-doped carbon coating is firstly adopted and used to decorate the performance of LiFePO4. The obtained composite exhibits a unique core-shell structure with an average diameter of 140 nm and a 4 nm thick boron-doped carbon shell that uniformly encapsulates the core. Owing to the boron element which could induce high amount of defects in the carbon, the electronic conductivity of LiFePO4 is greatly ameliorated. Thus, the boron-doped composite shows superior rate capability and cycle stability than the undoped sample. For instance, the reversible specific capacity of LiFePO4@B0.4-C can reach 164.1 mAh g-1 at 0.1C, which is approximately 96.5% of the theoretical capacity (170 mAh g-1). Even at high rate of 10C, it still shows a high specific capacity of 126.8 mAh g-1 and can be maintained at 124.5 mAh g-1 after 100 cycles with capacity retention ratio of about 98.2%. This outstanding Li-storage property enable the present design strategy to open up the possibility of fabricating the LiFePO4@B-C composite for high-performance lithium-ion batteries.

  20. 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.

  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. 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.

  3. On interlayer stability and high-cycle simulator performance of diamond-like carbon layers for articulating joint replacements.

    PubMed

    Thorwarth, Kerstin; Thorwarth, Götz; Figi, Renato; Weisse, Bernhard; Stiefel, Michael; Hauert, Roland

    2014-06-11

    Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and -3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic.

  4. On Interlayer Stability and High-Cycle Simulator Performance of Diamond-Like Carbon Layers for Articulating Joint Replacements

    PubMed Central

    Thorwarth, Kerstin; Thorwarth, Götz; Figi, Renato; Weisse, Bernhard; Stiefel, Michael; Hauert, Roland

    2014-01-01

    Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and −3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic. PMID

  5. Synthesis of high-density, large-diameter, and aligned single-walled carbon nanotubes by multiple-cycle growth methods.

    PubMed

    Zhou, Weiwei; Ding, Lei; Yang, Sungwoo; Liu, Jie

    2011-05-24

    A dense array of parallel single-walled carbon nanotubes (SWNTs) as the device channel can carry higher current, be more robust, and have smaller device-to-device variation, thus is more desirable for and compatible with applications in future highly integrated circuits when compared with single-tube devices. The density of the parallel SWNT arrays and the diameter of SWNTs both are key factors in the determination of the device performance. In this paper, we present a new multiple-cycle chemical vapor deposition (CVD) method to synthesize horizontally aligned arrays of SWNTs with densities of 20-40 SWNT/μm over large area and a diameter distribution of 2.4 ± 0.5 nm on the quartz surface based on a methanol/ethanol CVD method. The high nucleation efficiency of catalyst particles in multiple-cycle CVD processes has been demonstrated to be the main reason for the improvements in the density of SWNT arrays. More interestingly, we confirmed the existence of an etching effect, which strongly affects the final products in the multiple-cycle growth. This etching effect is likely the reason that only large-diameter SWNTs were obtained in the multiple-cycle CVD growth. Using these high-density and large-diameter nanotube arrays, two-terminal devices with back-gates were fabricated. The performances of these devices have been greatly improved in overall resistance and on-state current, which indicates these SWNT arrays have high potential for applications such as interconnects, high-frequency devices, and high-current transistors in future micro- or nanoelectronics.

  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. 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.

  11. Rapid High Spatial Resolution Chemical Characterization of Soil Structure to Illuminate Nutrient Distribution Mechanisms Related to Carbon Cycling Using Laser Ablation Aerosol Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Hicks, R. K.; Alexander, M. L. L.; Newburn, M. K.

    2015-12-01

    Soils contain approximately half of Earth's terrestrial carbon. As such, it is important to understand the factors that control the cycling of this soil organic carbon between the land and the atmosphere. Models that attribute the persistence of soil organic carbon to the intrinsic properties of the molecules themselves are inconsistent with recent observations— for example, materials that are more thermodynamically stable have been found to have a shorter lifetime in soils than ones that are less stable, and vice versa. A new explanation has therefore been posited that invokes ecosystem properties as a whole, and not just intrinsic molecular properties, as the kinetic factor controlling soil carbon dynamics. Because soil dynamics occur on a small scale, techniques with high spatial resolution are required for their study. Existing techniques such as TOF-SIMS require preparation of the sample and introduction into a high vacuum system, and do not address the need to examine large numbers of sample systems without perturbation of chemical and physical properties. To address this analytical challenge, we have coupled a laser ablation (LA) module to an Aerodyne aerosol mass spectrometer (AMS), thereby enabling sample introduction and subsequent measurement of small amounts of soil organic matter by the laser ablation aerosol mass spectrometer (LA-AMS). Due to the adjustable laser beam width, the LA-AMS can probe spot sizes ranging from 1-150 μm in diameter, liberating from 10-100 ng/pulse. With a detection limit of 1 pM, the AMS allows for chemical characterization of the ablated material in terms of elemental ratios, compound classes, and TOC/TOM ratios. Furthermore, the LA-AMS is capable of rapid, in-situ sampling under ambient conditions, thereby eliminating the need for sample processing or transport before analysis. Here, we will present the first results from systematic studies aimed at validating the LA-AMS method as well as results from initial measurements

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  13. Complex carbon cycle responses to multi-level warming and supplemental summer rain in the high Arctic.

    PubMed

    Sharp, Elizabeth D; Sullivan, Patrick F; Steltzer, Heidi; Csank, Adam Z; Welker, Jeffrey M

    2013-06-01

    The Arctic has experienced rapid warming and, although there are uncertainties, increases in precipitation are projected to accompany future warming. Climate changes are expected to affect magnitudes of gross ecosystem photosynthesis (GEP), ecosystem respiration (ER) and the net ecosystem exchange of CO2 (NEE). Furthermore, ecosystem responses to climate change are likely to be characterized by nonlinearities, thresholds and interactions among system components and the driving variables. These complex interactions increase the difficulty of predicting responses to climate change and necessitate the use of manipulative experiments. In 2003, we established a long-term, multi-level and multi-factor climate change experiment in a polar semidesert in northwest Greenland. Two levels of heating (30 and 60 W m(-2) ) were applied and the higher level was combined with supplemental summer rain. We made plot-level measurements of CO2 exchange, plant community composition, foliar nitrogen concentrations, leaf δ(13) C and NDVI to examine responses to our treatments at ecosystem- and leaf-levels. We confronted simple models of GEP and ER with our data to test hypotheses regarding key drivers of CO2 exchange and to estimate growing season CO2 -C budgets. Low-level warming increased the magnitude of the ecosystem C sink. Meanwhile, high-level warming made the ecosystem a source of C to the atmosphere. When high-level warming was combined with increased summer rain, the ecosystem became a C sink of magnitude similar to that observed under low-level warming. Competition among our ER models revealed the importance of soil moisture as a driving variable, likely through its effects on microbial activity and nutrient cycling. Measurements of community composition and proxies for leaf-level physiology suggest GEP responses largely reflect changes in leaf area of Salix arctica, rather than changes in leaf-level physiology. Our findings indicate that the sign and magnitude of the future

  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. 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.

  16. 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.

  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. 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.

  19. 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/

  20. 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/

  1. 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.

  2. Evolution of Temperature and Carbon Storage Within the Deep Southeast Atlantic Ocean Across the Last Glacial/Interglacial Cycle Inferred from a Highly-Resolved Sedimentary Depth Transect

    NASA Astrophysics Data System (ADS)

    Foreman, A. D.; Charles, C. D.; Rae, J. W. B.; Adkins, J. F.; Slowey, N. C.

    2015-12-01

    Many models show that the relative intensity of stratification is a primary variable governing the sequestration and release of carbon from the ocean over ice ages. The wide-scale observations necessary to test these model-derived hypotheses are not yet sufficient, but sedimentary depth transects represent a promising approach for making progress. Here we present paired stable isotopic (d18O, d13C) and trace metal data (Mg/Ca, B/Ca) from benthic foraminifera collected from a highly vertically-resolved depth transect from the mid-depth and deep SE Atlantic. These observations, which cover Marine Isotope Stages 5e, 5d, 5a, 4, and the Last Glacial Maximum, document the evolution of glacial conditions from the previous interglacial, and provide detailed observations regarding the magnitude and timing of changes in temperature and salinity within the deep ocean at key time points over the last glacial/interglacial cycle. Furthermore, the comparison between purely 'physical' tracers (i.e. Mg/Ca, d18O) and tracers sensitive to the carbon cycle (i.e. d13C and B/Ca) provides critical insight into the relationship between deep/mid-depth stratification and global carbon dynamics. Notably among our observations, the paired stable isotope and trace metal results strongly suggest that much of the ice-age cooling of deep South Atlantic occurred at the MIS 5e/5d transition, while the onset of salinity stratification in the mid-depth South Atlantic occurred at the MIS 5/4 transition.

  3. Coupled ecosystem carbon and nutrient cycling in a High Arctic ecosystem are altered by long-term experimental warming and higher rainfall

    NASA Astrophysics Data System (ADS)

    Schaeffer, S. M.; Schimel, J.; Welker, J. M.

    2013-12-01

    The rapid changes in temperature and precipitation in High Arctic tundra ecosystems are altering the biogeochemical cycles of nitrogen (N) and carbon (C), but in ways that are difficult to anticipate. The challenge grows from the complexity of tundra soil organic matter, the uncertainty of N cycle responses and the extent to which shifts in soil N processes are coupled with the C cycle, including leaf-level photosynthesis, gross ecosystem photosynthesis (GEP-productivity) and net CO2 exchange (NEE-C sequestration). Understanding the processes that are leading to changes in High Arctic biogeochemical processes are especially important today as soil organic C pools in the High Arctic are up to 6 times greater than previously estimated, and are sensitive to being oxidized to the atmosphere through changes in microbial decomposition associated with warmer and wetter conditions. We used a long-term (since 2003) experiment of summer warming and supplemental summer water additions to a High Arctic ecosystem in NW Greenland to determine the impact of interactions between temperature, water availability, and microbial metabolism on the cycling of C and plant-available N in High Arctic tundra soil. We have found that water availability plays a critical role in these cycles in High Arctic tundra, over and above that from temperature increases. On seasonal time scales, we observed greater net N mineralization under both global change scenarios, yet water addition also significantly increased net nitrification rates, loss of NO3--N via leaching from surface soil layers, and lowered rates of labile organic C and N production. We also expected the chronic warming and watering would lead to long-term changes in soil N-cycling that would be reflected in soil δ15N values. However, we found that soil δ15N decreased under the different climate change scenarios. Our findings indicate that warmer, wetter High Arctic tundra will be cycling N and C in ways that may transform these

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. High frequency peritidal cycles of the upper Araras Group: Implications for disappearance of the neoproterozoic carbonate platform in southern Amazon Craton

    NASA Astrophysics Data System (ADS)

    Rudnitzki, Isaac Daniel; Romero, Guilherme Raffaeli; Hidalgo, Renata; Nogueira, Afonso Cesar Rodrigues

    2016-01-01

    The Araras Group is an extensive carbonate platform developed at the southeastern margin of the Amazon Craton during the Neoproterozoic. The Nobres Formation corresponds to the upper unit of the Neoproterozoic Araras Group. It is exposed in road cuts and quarries in the Northern Paraguay Belt, and is characterized by meter-scale shallowing upward cycles. Forty-four fourth-to fifth-order parasequence cycles are enclosed into three third order sequences/megacycles, unconformably overlain by siliciclastic deposits of the Alto Paraguay Group. The cycles are generally of peritidal type, limited by exposure surfaces composed of asymmetrical tidal flat/sabkha lithofacies in the basal Nobres Formation. They consist of fine dolostone, intraclastic dolostones with megaripples, stromatolites biostrome, sandy dolostone with enterolithic structures and silicified evaporite molds. Upsection, the cycles progressively become symmetrical, comprising arid tidal flat deposits with abundant stromatolite biostrome, fine-grained sandstone and rare evaporitic molds. The stacking patterns for hundreds of meters indicate continuous and recurrent generation of accommodation space, probably triggered by subsidence concomitant with relative sea-level changes. Palynomorphs found in the upper part of Nobres Formation comprehend spheroidal forms, such as Leiospharidia, rare filamentous and acanthomorphous acritarchs, mostly Tanarium correlated to the Ediacaran Complex Acantomorph Palynoflora of ˜580-570 Ma. Previous data of carbon isotopes and paleogeographic reconstructions, and also the presence of evaporites and storm-influenced deposits in the Araras Group, suggest a wet to tropical setting for Amazonia during the Mid-Ediacaran, which is incompatible with previous claims for Gaskiers-related glacial sedimentation in the region. During the final stages of evolution of the Araras carbonate platform, a progressive input of terrigenous has occurred in the peritidal setting likely due tectonic

  12. A High-Resolution Multitechniques Approach to Characterize Bio-Organo-Mineral Associations Within Rock Samples: Tracking Biological vs Abiotic Processes? Towards a Better Understanding of the Deep Carbon Cycle.

    NASA Astrophysics Data System (ADS)

    Pisapia, C.

    2015-12-01

    Among all elements, carbon plays one of the major roles for the sustainability of life on Earth. Past considerations of the carbon cycle have mainly focused on surface processes occurring at the atmosphere, oceans and shallow crustal environments. By contrast, little is known about the Deep Carbon cycle whereas both geochemical and biological processes may induce organic carbon production and/or consumption at depth. Indeed, the nowadays-recognized capability of geochemical processes such as serpentinization to generate abiotic organic compounds as well as the existence of a potentially important intraterrestrial life raises questions about the limit of biotic/abiotic carbon on Earth's deep interior and how it impacts global biogeochemical cycles. It is then mandatory to increase our knowledge on the nature and extent of carbon reservoirs along with their sources, sinks and fluxes in the subsurface. This implies to be able to finely characterize organomineral associations within crustal rocks although it might be hampered by the scarceness and heterogeneous micrometric spatial distribution of organic molecules in natural rocks. We then developed an in situ analytical strategy based on the combination of high-resolution techniques to track organic molecules at the pore level in natural rocks and to determine their biological or abiotic origin. We associated classical high-resolution techniques and synchrotron-based imaging techniques in order to characterize their nature and localization (SEM/TEM, coupled CLSM/Raman spectroscopy, Tof-SIMS) along with their 3D-distribution relatively to mineral phases (S-FTIR, S-DeepUV, XANES, Biphoton microscopy). The effectiveness of this approach to shed light on the speciation and nature of carbon in subsurface environments will be illustrated through the study of (i) subsurface ecosystems and abiotic organic carbon within ultramafic rocks of the oceanic lithosphere as putative analogs for the nature and functioning of primitive

  13. 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/

  14. 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/

  15. 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/

  16. 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.

  17. 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.

  18. 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.

  19. Characterization of lead (Ⅱ)-containing activated carbon and its excellent performance of extending lead-acid battery cycle life for high-rate partial-state-of-charge operation

    NASA Astrophysics Data System (ADS)

    Tong, Pengyang; Zhao, Ruirui; Zhang, Rongbo; Yi, Fenyun; Shi, Guang; Li, Aiju; Chen, Hongyu

    2015-07-01

    In this work, lead (Ⅱ)-containing activated carbon (Pb@C) is prepared as the additive of negative active mass (NAM), aiming to enhance the electrochemical characteristics of the lead-acid battery. The characters of the Pb@C materials and their electrochemical properties are characterized by XRD, SEM, back-scattering electron image (BESI) and electrochemical methods. The lead (Ⅱ) ions disperse well in the carbon bulk of the obtained Pb@C materials as observed, and these materials exhibit remarkable higher specific capacitance and higher hydrogen evolution over-potential compared with original carbons. Many 2 V lead-acid batteries are assembled manually in our lab, and then the batteries are disassembled after formation and high-rate-partial-state-of-charge (HRPSoC) cycling. Results manifest that the Pb@C additives exhibit high affinity to lead and act as a porous-skeleton in the formation process as well as under HRPSoC cycling conditions, leading to the small and fine formation of PbSO4 particles and accordingly higher active material utilization rate more than 50%, better cycling performance and charging acceptance. Besides, excellent cycle performances of these batteries have great relationship with the dazzling hydrogen evolution performance of Pb@C materials. A possible working mechanism is also proposed based on the testing data in this paper.

  20. 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

  1. 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.

  2. Damage Assessment of Stress-Thermal Cycled High Temperature

    NASA Technical Reports Server (NTRS)

    Ju, Jach-Yung; Prochazka, Michael; Ronke, Ben; Morgan, Roger; Shin, Eugene

    2003-01-01

    We report on the characterization of bismaleimide and polyimide carbon fiber composite, microcrack development under stress thermal cycling loading. Such cycle range from cryogenic temperatures associated with cryogenic fuel (LN, LOX) containment to high temperatures of 300 degrees associated with future hypervelocity aeropropulsion systems. Microcrack development thresholds as a function of temperature range of the thermal cycle, the number of cycles, and the applied stress level imposed on the composite are reported. We have conducted stress-thermal cycles on thin bismaleimide-woven carbon fiber foils for three temperature range cycles. The principle findings are that the full cycles from -196 degree celsius up to 250 degree celsius cause the most significant microcrack development. These observations indicate that the high temperature portion of the cycle under load causes fiber-matrix interface failure and subsequent exposure to higher stresses at the cryogenic, low temperature region results in composite matrix microcracking as a result of the additional stresses associated with the fiber-matrix thermal expansion mismatch. Our initial studies for 12 ply PMR-II-50 polyimide/M6OJB carbon fabric [0f, 90f, 90f, 0f, 0f, 90f] composites will be presented. The stress-thermal cycle test procedure for these will be described. Moisture absorption characteristics between cycles will be used to monitor interconnected microcrack development. The applied stress level will be 75 percent of the composite cryogenic -196 degree celsius ultimate strength.

  3. 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.

  4. 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

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Galvez, Matthieu Emmanuel; Gaillardet, Jérôme

    2012-11-01

    model of matter in the early 19th century by the influential works of J. Dalton and J.J. Berzelius. Finally, through the 19th century, the development of the theory of sediment subsidence and its application by T.S. Hunt to the rotation of carbon, along with the correlated experimental results obtained on the stability of materials at high pressure and temperature, led progressively to a synthetic model of the carbon cycle by V. Vernadsky in the early 20th century. A final shift to this model occurred with the emergence of the theory of plate tectonics and subduction zones that provides a major physical ground to account for C recycling between surfacial and deep reservoirs of the planet.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Nanospherical solid electrolyte interface layer formation in binder-free carbon nanotube aerogel/Si nanohybrids to provide lithium-ion battery anodes with a long-cycle life and high capacity.

    PubMed

    Shim, Hyung Cheoul; Kim, Ilhwan; Woo, Chang-Su; Lee, Hoo-Jeong; Hyun, Seungmin

    2017-04-06

    Silicon anodes for lithium ion batteries (LiBs) have been attracting considerable attention due to a theoretical capacity up to about 10 times higher than that of conventional graphite. However, huge volume expansion during the cycle causes cracks in the silicon, resulting in the degradation of cycling performance and eventual failure. Moreover, low electrical conductivity and an unstable solid electrolyte interface (SEI) layer resulting from repeated changes in volume still block the next step forward for the commercialization of the silicon material. Herein we demonstrate the carbon nanotube (CNT) aerogel/Si nanohybrid structure for anode materials of LiBs via freeze casting followed by an RF magnetron sputtering process, exhibiting improved capacity retention compared to Si only samples during 1000 electrochemical cycles. The CNT aerogels as 3D porous scaffold structures could provide buffer volume for the expansion/shrinkage of Si lattices upon cycling and increase electrical conductivity. In addition, the nanospherical and relatively thin SEI layers of the CNT aerogel/Si nanohybrid structure show better lithium ion diffusion characteristics during cycling. For this reason, the Si@CNT aerogel anode still yielded a high specific capacity of 1439 mA h g(-1) after 1000 charge/discharge cycles with low capacity fading. Our approach could be applied to other group IV LiB materials that undergo large volume changes, and also has promising potential for high performance energy applications.

  13. 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

  14. A high-resolution benthic stable-isotope record for the South Atlantic: Implications for orbital-scale changes in Late Paleocene-Early Eocene climate and carbon cycling

    NASA Astrophysics Data System (ADS)

    Littler, Kate; Röhl, Ursula; Westerhold, Thomas; Zachos, James C.

    2014-09-01

    The Late Paleocene and Early Eocene were characterized by warm greenhouse climates, punctuated by a series of rapid warming and ocean acidification events known as “hyperthermals”, thought to have been paced or triggered by orbital cycles. While these hyperthermals, such as the Paleocene Eocene Thermal Maximum (PETM), have been studied in great detail, the background low-amplitude cycles seen in carbon and oxygen-isotope records throughout the Paleocene-Eocene have hitherto not been resolved. Here we present a 7.7 million year (myr) long, high-resolution, orbitally-tuned, benthic foraminiferal stable-isotope record spanning the late Paleocene and early Eocene interval (∼52.5-60.5 Ma) from Ocean Drilling Program (ODP) Site 1262, South Atlantic. This high resolution (∼2-4 kyr) record allows the changing character and phasing of orbitally-modulated cycles to be studied in unprecedented detail as it reflects the long-term trend in carbon cycle and climate over this interval. The main pacemaker in the benthic oxygen-isotope (δ18O) and carbon-isotope (δ13C) records from ODP Site 1262, are the long (405 kyr) and short (100 kyr) eccentricity cycles, and precession (21 kyr). Obliquity (41 kyr) is almost absent throughout the section except for a few brief intervals where it has a relatively weak influence. During the course of the Early Paleogene record, and particularly in the latest Paleocene, eccentricity-paced negative carbon-isotope excursions (δ13C, CIEs) and coeval negative oxygen-isotope (δ18O) excursions correspond to low carbonate (CaCO3) and coarse fraction (%CF) values due to increased carbonate dissolution, suggesting shoaling of the lysocline and accompanied changes in the global exogenic carbon cycle. These negative CIEs and δ18O events coincide with maxima in eccentricity, with changes in δ18O leading changes in δ13C by ∼6 (±5) kyr in the 405-kyr band and by ∼3 (±1) kyr in the higher frequency 100-kyr band on average. However, these

  15. 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

  16. 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.

  17. 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.

  18. Effect of mission cycling on the fatigue performance of SiC-coated carbon-carbon composites

    NASA Technical Reports Server (NTRS)

    Mahfuz, H.; Das, P. S.; Jeelani, S.; Baker, D. M.; Johnson, S. A.

    1993-01-01

    The effects of thermal and pressure cycling on the fatigue performance of carbon-carbon composites, and the influence of mission cycling on these effects, were investigated by subjecting both virgin and mission-cycled two-dimensional specimens of SiC-coated carbon-carbon composites to fatigue tests, conducted at room temperature in three-point bending, with a stress ratio of 0.2 and a frequency of 1 Hz. It was found that the fatigue strength of C-C composites is high (about 90 percent of the ultimate flexural strength), but decreased with the mission cycling. The lowering of the fatigue strength with mission cycling is attributed to the increase in interfacial bond strength due to thermal and pressure cycling of the material. The already high sensitivity of C-C composites to stress during cyclic loading increases further with the amount of mission cycling. Results of NDE suggest that the damage growth in virgin C-C, in the high-cycle range, is slow at the initial stage of the cyclic life, but propagates rapidly after certain threshold cycles of the fatigue life.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. The GLOBE Carbon Cycle Project: Using a systems approach to understand carbon and the Earth's climate system

    NASA Astrophysics Data System (ADS)

    Silverberg, S. K.; Ollinger, S. V.; Martin, M. E.; Gengarelly, L. M.; Schloss, A. L.; Bourgeault, J. L.; Randolph, G.; Albrechtova, J.

    2009-12-01

    National Science Content Standards identify systems as an important unifying concept across the K-12 curriculum. While this standard exists, there is a recognized gap in the ability of students to use a systems thinking approach in their learning. In a similar vein, both popular media as well as some educational curricula move quickly through climate topics to carbon footprint analyses without ever addressing the nature of carbon or the carbon cycle. If students do not gain a concrete understanding of carbon’s role in climate and energy they will not be able to successfully tackle global problems and develop innovative solutions. By participating in the GLOBE Carbon Cycle project, students learn to use a systems thinking approach, while at the same time, gaining a foundation in the carbon cycle and it's relation to climate and energy. Here we present the GLOBE Carbon Cycle project and materials, which incorporate a diverse set of activities geared toward upper middle and high school students with a variety of learning styles. A global carbon cycle adventure story and game let students see the carbon cycle as a complete system, while introducing them to systems thinking concepts including reservoirs, fluxes and equilibrium. Classroom photosynthesis experiments and field measurements of schoolyard vegetation brings the global view to the local level. And the use of computer models at varying levels of complexity (effects on photosynthesis, biomass and carbon storage in global biomes, global carbon cycle) not only reinforces systems concepts and carbon content, but also introduces students to an important scientific tool necessary for understanding climate change.

  12. High Thermal Conductivity Carbon/Carbon Composites.

    DTIC Science & Technology

    1995-09-30

    The objective of this project was to develop a lowcost, high thermal conductivity carbon/carbon composite with a mesophase pitch -based matrix. A low...carbonization technique and heat treatment of the mesophase pitch was utilized to enhance composite properties by increasing the composite density...Three different fibers, T300 PAN-based, P55 pitch -based, and an experimental high thermal conductivity mesophase pitch -based, were incorporated as the

  13. 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/

  14. 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/

  15. 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.

  16. [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.

  17. Cheng Cycle reporting high availability

    SciTech Connect

    Not Available

    1986-02-01

    Operating results from the Cheng Cycle cogeneration plants at San Jose State University and at Sunkist Growers in Ontario, California look very good so far, according to officials of International Power Technology (IPT). Both plants contain IPT's Cheng Cycle Series 7-Cogen system, which produces between 3 and 6 MW of electricity and up to 45,000 pounds of steam per hour. The company is developing the patented technology as an improved combined cycle system which can produce steam and electricity under widely varying load demands.

  18. [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.

  19. 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.

  20. 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/

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

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

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2004-01-01

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

  9. High-Melt Carbon-Carbon Coating for Nozzle Extensions

    NASA Technical Reports Server (NTRS)

    Thompson, James

    2015-01-01

    Carbon-Carbon Advanced Technologies, Inc. (C-CAT), has developed a high-melt coating for use in nozzle extensions in next-generation spacecraft. The coating is composed primarily of carbon-carbon, a carbon-fiber and carbon-matrix composite material that has gained a spaceworthy reputation due to its ability to withstand ultrahigh temperatures. C-CAT's high-melt coating embeds hafnium carbide (HfC) and zirconium diboride (ZrB2) within the outer layers of a carbon-carbon structure. The coating demonstrated enhanced high-temperature durability and suffered no erosion during a test in NASA's Arc Jet Complex. (Test parameters: stagnation heat flux=198 BTD/sq ft-sec; pressure=.265 atm; temperature=3,100 F; four cycles totaling 28 minutes) In Phase I of the project, C-CAT successfully demonstrated large-scale manufacturability with a 40-inch cylinder representing the end of a nozzle extension and a 16-inch flanged cylinder representing the attach flange of a nozzle extension. These demonstrators were manufactured without spalling or delaminations. In Phase II, C-CAT worked with engine designers to develop a nozzle extension stub skirt interfaced with an Aerojet Rocketdyne RL10 engine. All objectives for Phase II were successfully met. Additional nonengine applications for the coating include thermal protection systems (TPS) for next-generation spacecraft and hypersonic aircraft.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. Global warming and marine carbon cycle feedbacks on future atmospheric CO2

    PubMed

    Joos; Plattner; Stocker; Marchal; Schmittner

    1999-04-16

    A low-order physical-biogeochemical climate model was used to project atmospheric carbon dioxide and global warming for scenarios developed by the Intergovernmental Panel on Climate Change. The North Atlantic thermohaline circulation weakens in all global warming simulations and collapses at high levels of carbon dioxide. Projected changes in the marine carbon cycle have a modest impact on atmospheric carbon dioxide. Compared with the control, atmospheric carbon dioxide increased by 4 percent at year 2100 and 20 percent at year 2500. The reduction in ocean carbon uptake can be mainly explained by sea surface warming. The projected changes of the marine biological cycle compensate the reduction in downward mixing of anthropogenic carbon, except when the North Atlantic thermohaline circulation collapses.

  15. Damage Assessment of Stress-Thermal Cycled high temperature

    NASA Technical Reports Server (NTRS)

    Ju, Jae-Hyung; Prochazka, Michael; Ronke, Ben; Morgan, Roger; Shin, Eugence

    2004-01-01

    We report on the characterization of bismaleimide and polyimide carbon fiber composite, microcrack development under stress thermal cycling loading. Such cycles range from cryogenic temperatures associated with cryogenic fuel (LN, LOX) containment to high temperatures of 300 degrees Celsius associated with future hypervelocity aeropropulsion systems. Microcrack development thresholds as a function of temperature range of the thermal cycle; the number of cycles; the applied stress level imposed on the composite are reported. We have conducted stress-thermal cycles on thin bismaleimide-woven carbon fiber foils for three temperature range cycles: 1. Ambient temperature - -196 degrees celsius. 2. Ambient temperature - 150 degrees Celsius; 200 degrees Celsius; 250 degrees Celsius. 3. -196 degrees Celsius - 250 degrees Celsius. The Principle findings are that the full cycles from -196 degrees Celsius to to 250 degrees Celsius cause the most significant microcrack of development. These observations indicate that the high temperature portion of the cycle under load causes fiber-matrix interface failure and subsequent exposure to higher stresses at the cryogenic, low temperature region results in composite matrix microcracking as a result of the additional stresses associate with the fiber-matrix thermal expansion mismatch. Our initial studies for 12 ply PMR-II-50 polyimide/M60JB carbon fabric [0f,90f,90f,0f,0f,90f]ls composites will be presented. The stress-thermal cycle test procedure for these will be described. Moisture absorption characteristics between cycles will be used to monitor interconnected microcrack development. The applied stress level will be 75% of the composite cryogenic (-196 degrees Celsius) ultimate strength.

  16. Automotive high color carbon

    SciTech Connect

    Ducote, R.E.; Dees, R.G.; Musick, V.L.

    1988-06-14

    A method of making a low porosity carbon black is described comprising: (1) feeding into a carbon black reactor a carbonaceous feed; (2) contacting the feed in the reactor with combustion gases containing oxygen thereby cracking the feed to produce carbon black; and (3) contacting the produced carbon black in the reactor with vaporizable hydrocarbon oil injected into the reaction at a point where the carbon black forming reaction is substantially complete to at least partially quench the carbon black producing reaction, the vaporizable hydrocarbon oil being cracked and serving to plate the carbon black to reduce the porosity thereof.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Ocean Margins Program: Closure on the global carbon cycle. Program description

    SciTech Connect

    Riches, M.R.

    1994-08-01

    The Department of Energy`s Ocean Margins Program (OMP) is designed to quantitatively assess the importance of coastal ocean systems in the global carbon cycle. Since the beginning of the Industrial Revolution, human energy-related activities have dramatically altered the global carbon cycle, and consequently, this cycle is not presently in a steady-state. To reduce major uncertainties in predicting future global environmental quality, it is imperative to understand the sources and sinks of atmospheric CO{sub 2}, the role of anthropogenic activities in disrupting the natural carbon cycle, and the effects of, and feedbacks between, these activities and the natural carbon cycle. Due to continuously increased loading of nutrients to the margins, which, globally, is related to the rate of human population growth and high population densities in coastal states, biological carbon fixation has been stimulated. Depending on the fate of the fixed carbon, this stimulation has the potential to mitigate the anthropogenically derived Co{sub 2}. Determining the factors that control the magnitude of carbon exchanges between the ocean margins and the atmosphere, and the subsequent fate of this carbon, is crucial to predicting the strength and capacity of the oceans to absorb excess anthropogenic atmospheric CO{sub 2}. The goals of the OMP are to: quantify the ecological and biogeochemical processes and mechanisms that define the cycling, flux, and storage of carbon and other biogenic elements at the land/ocean interface; identify how ocean-margin sources and sinks of carbon change in response to human activities; and determine whether continental shelves are quantitatively significant in removing atmospheric carbon dioxide and isolating it via burial in sediments or export to the interior of the open ocean.

  4. Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle.

    PubMed

    Merlini, Marco; Crichton, Wilson A; Hanfland, Michael; Gemmi, Mauro; Müller, Harald; Kupenko, Ilya; Dubrovinsky, Leonid

    2012-08-21

    Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO(3)-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth's surface.

  5. Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle

    PubMed Central

    Merlini, Marco; Crichton, Wilson A.; Hanfland, Michael; Gemmi, Mauro; Müller, Harald; Kupenko, Ilya; Dubrovinsky, Leonid

    2012-01-01

    Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO3-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth’s surface. PMID:22869705

  6. Phase heterogeneity in carbonate production by marine fish influences their roles in sediment generation and the inorganic carbon cycle.

    PubMed

    Salter, Michael A; Harborne, Alastair R; Perry, Chris T; Wilson, Rod W

    2017-04-10

    Marine teleost fish are important carbonate producers in neritic and oceanic settings. However, the fates of the diverse carbonate phases (i.e., mineral and amorphous forms of CaCO3) they produce, and their roles in sediment production and marine inorganic carbon cycling, remain poorly understood. Here we quantify the carbonate phases produced by 22 Bahamian fish species and integrate these data with regional fish biomass data from The Bahamas to generate a novel platform-scale production model that resolves these phases. Overall carbonate phase proportions, ordered by decreasing phase stability, are: ~20% calcite, ~6% aragonite, ~60% high-Mg calcite, and ~14% amorphous carbonate. We predict that these phases undergo differing fates, with at least ~14% (amorphous carbonate) likely dissolving rapidly. Results further indicate that fisheries exploitation in The Bahamas has potentially reduced fish carbonate production by up to 58% in certain habitats, whilst also driving a deviation from natural phase proportions. These findings have evident implications for understanding sedimentary processes in shallow warm-water carbonate provinces. We further speculate that marked phase heterogeneity may be a hitherto unrecognised feature of fish carbonates across a wide range of neritic and oceanic settings, with potentially major implications for understanding their role in global marine inorganic carbon cycling.

  7. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  9. Growth of Si nanowires in porous carbon with enhanced cycling stability for Li-ion storage

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaoxu; Rui, Xianhong; Zhou, WenWen; Tan, Liping; Yan, Qingyu; Lu, Ziyang; Hng, Huey Hoon

    2014-03-01

    Si nanowires are successfully grown in porous carbon by supercritical fluid-liquid-solid (SFLS) process, which show high specific capacities and charge-discharge cycling stability as anode materials for Li-ion storage. The enhancement capacity and cycling stability of the Si nanowires/porous carbon composite nanostructures is attributed to the porous carbon serving as a highly conductive framework and absorption of volume changes of Si nanowires during the lithiation/delithiation process. At optimized condition, the Si nanowires/porous carbon electrodes maintain reversible capacities of 1678 mAh g-1 for the 100th cycle at a current density of 420 mA g-1, which is much better as compared to that of pure Si nanowires.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Soil Microbial Activity Provides Insight to Carbon Cycling in Shrub Ecotones of Sub-Arctic Sweden

    NASA Astrophysics Data System (ADS)

    Marek, E.; Kashi, N. N.; Chen, J.; Hobbie, E. A.; Schwan, M. R.; Varner, R. K.

    2015-12-01

    Shrubs are expanding in Arctic and sub-Arctic regions due to rising atmospheric temperatures. Microbial activity increases as growing temperatures cause permafrost warming and subsequent thaw, leading to a greater resource of soil nutrients enabling shrub growth. Increased carbon inputs from shrubs is predicted to result in faster carbon turnover by microbial decomposition. Further understanding of microbial activity underneath shrubs could uncover how microbes and soil processes interact to promote shrub expansion and carbon cycling. To address how higher soil carbon input from shrubs influences decomposition, soil samples were taken across a heath, shrub, and forest ecotone gradient at two sites near Abikso, Sweden. Samples were analyzed for soluble carbon and nitrogen, microbial abundance, and microbial activity of chitinase, glucosidase, and phosphatase to reflect organic matter decomposition and availability of nitrogen, carbon, and phosphate respectively. Chitinase activity positively correlated with shrub cover, suggesting microbial demands for nitrogen increase with higher shrub cover. Glucosidase activity negatively correlated with shrub cover and soluble carbon, suggesting decreased microbial demand for carbon as shrub cover and carbon stores increase. Lower glucosidase activity in areas with high carbon input from shrubs implies that microbes are decomposing carbon less readily than carbon is being put into the soil. Increasing soil carbon stores in shrub covered areas can lead to shrubs becoming a net carbon sink and a negative feedback to changing climate.

  3. 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…

  4. 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…

  5. 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.

  6. 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%.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    PubMed

    Wang, Qing-kui

    2011-04-01

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

  13. 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.

  14. 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.

  15. High Cycle-life Shape Memory Polymer at High Temperature

    NASA Astrophysics Data System (ADS)

    Kong, Deyan; Xiao, Xinli

    2016-09-01

    High cycle-life is important for shape memory materials exposed to numerous cycles, and here we report shape memory polyimide that maintained both high shape fixity (Rf) and shape recovery (Rr) during the more than 1000 bending cycles tested. Its critical stress is 2.78 MPa at 250 °C, and the shape recovery process can produce stored energy of 0.218 J g‑1 at the efficiency of 31.3%. Its high Rf is determined by the large difference in storage modulus at rubbery and glassy states, while the high Rr mainly originates from its permanent phase composed of strong π-π interactions and massive chain entanglements. Both difference in storage modulus and overall permanent phase were preserved during the bending deformation cycles, and thus high Rf and Rr were observed in every cycle and the high cycle-life will expand application areas of SMPs enormously.

  16. High Cycle-life Shape Memory Polymer at High Temperature

    PubMed Central

    Kong, Deyan; Xiao, Xinli

    2016-01-01

    High cycle-life is important for shape memory materials exposed to numerous cycles, and here we report shape memory polyimide that maintained both high shape fixity (Rf) and shape recovery (Rr) during the more than 1000 bending cycles tested. Its critical stress is 2.78 MPa at 250 °C, and the shape recovery process can produce stored energy of 0.218 J g−1 at the efficiency of 31.3%. Its high Rf is determined by the large difference in storage modulus at rubbery and glassy states, while the high Rr mainly originates from its permanent phase composed of strong π-π interactions and massive chain entanglements. Both difference in storage modulus and overall permanent phase were preserved during the bending deformation cycles, and thus high Rf and Rr were observed in every cycle and the high cycle-life will expand application areas of SMPs enormously. PMID:27641148

  17. 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.

  18. 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

  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. Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers

    NASA Astrophysics Data System (ADS)

    Wood, Deborah; Crocket, Kirsty; Brand, Tim; Stutter, Marc; Wilson, Clare; Schröder, Christian

    2016-04-01

    Linking carbon and iron cycles by investigating transport, fate and mineralogy of iron-bearing colloids from peat-draining rivers - Scotland as model for high-latitude rivers Wood, D.A¹, Crocket, K², Brand, T², Stutter, M³, Wilson, C¹ & Schröder, C¹ ¹Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA ²Scottish Association for Marine Science, University of the Highlands and Islands, Dunbeg, Oban, PA37 1QA ³James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH The biogeochemical iron cycle exerts significant control on the carbon cycle¹. Iron is a limiting nutrient in large areas of the world's oceans and its bioavailability controls CO2 uptake by marine photosynthesizing microorganisms. While atmospheric iron inputs to the open ocean have been extensively measured, global river inputs have likely been underestimated because most major world rivers exhibit extensive iron removal by flocculation and sedimentation during seawater mixing. Iron minerals and organic matter mutually stabilise each other², which results in a 'rusty carbon sink' in sediments³ on the one hand but may also enhance transport beyond the salinity gradient on the other. Humic-rich, high latitude rivers have a higher iron-carrying capacity⁴-⁶ but are underrepresented in iron flux calculations. The West Coast sea lochs in Scotland are fed by predominantly peatland drainage catchments, and the rivers entering the sea lochs carry a high load of organic matter. The short distance between many of these catchments and the coastal ocean facilitates source-to-sea research investigating transport, fate and mineralogy of iron-bearing colloids providing a good analogue for similar high latitude fjordic systems. We use SeaFAST+ICP-MS and Mössbauer spectroscopy to survey trace metal concentrations, with emphasis on iron concentrations, speciation and mineralogy, across salinity gradients. In combination with ultra-filtration techniques, this allows

  1. Modeling carbon cycle dynamics and response to drought in semi-arid ecosystems

    NASA Astrophysics Data System (ADS)

    Hilton, T. W.; Fox, A. M.; Krofcheck, D. J.; Litvak, M. E.

    2012-12-01

    The southwestern United States is presently experiencing a multi-year drought. Though the carbon uptake per unit area of the semi-arid biomes in this region is smaller than that of more temperate biomes, these biomes cover roughly 40 percent of the world's land surface, and thus make a significant contribution to the global terrestrial biological carbon cycle. Here we test the ability of two land surface model structures to diagnose the carbon cycle dynamics of semi-arid landscapes during the ongoing extreme drought. We use the New Mexico Elevation Gradient (NMEG) as a testbed for these modeling experiments. The NMEG comprises eight eddy covariance towers observing ecosystems ranging from desert grassland ( 1600 m elevation) to alpine mixed coniferous forest ( 3000 m elevation). During the drought the ecosystems observed by these towers saw their annual net carbon uptake decline between 33 and 100 percent (50 to 150 gC m^{-2} year^{-1}), with two of the eight sites becoming net sources of carbon to the atmosphere and one transitioning from a net carbon sink to carbon-neutral. We parametrize a simple light-use efficiency (LUE)-based model (Vegetation Photosynthesis and Respiration Model, VPRM) and a complex model which simulates many land surface processes (Community Land Model, CLM). We explore the capacity of both models to diagnose the terrestrial carbon cycle in semi-arid biomes where water availability is highly episodic.

  2. Atmospheric CO2 Reconstructions from Polar Ice: What Do High-Resolution CO2 Records and δ13CO2 Analyses Tell Us about Past Climate and Global Carbon Cycle Processes?

    NASA Astrophysics Data System (ADS)

    Schmitt, J.; Eggleston, S.; Marcott, S. A.; Brook, E.; Chappellaz, J. A.; Köhler, P.; Joos, F.; Fischer, H.

    2014-12-01

    Today, a monitoring network measures atmospheric CO2 at high temporal and spatial resolution. Atmospheric transport models then calculate regional CO2 source and sink fluxes. Prior to this instrumental period, archived air, firn air, and air trapped in polar ice are the only direct atmospheric archives to reconstruct past CO2 changes. Only ice from Antarctica allows reliable CO2 measurements, either from classical ice cores or outcropping ice, while Greenland records are subject to in situ production. They provide high-resolution and high-precision CO2 reconstructions up to 800,000 years back in time. Ice core records have revealed an intimate connection between CO2 variations and major changes in Earth's climate and have fundamentally shaped the community's view of the global carbon cycle. Knowing the concentration of past atmospheric CO2 and the other greenhouse gases is key to provide the radiative forcing for climate simulations. Ice core reconstructions broadly fulfilled this task. On the contrary, we are far from a coherent understanding of the mechanisms driving these changes. Analyzing phase relations between CO2, other ice-core derived species, and proxies from marine sediment cores allow for the identification of factors likely responsible for the observed CO2 changes. Specifically, the strength of the Atlantic overturning circulation and Southern Ocean upwelling are thought to be key players. However, the observed CO2 changes cannot uniquely be related to a specific process. Here, stable carbon isotope analysis on CO2 extracted from ice provides additional constraints as any process leads to isotope fractionation of the reservoir. Analytical progress during the last decade affords us with a growing data set on this long-awaited parameter. This presentation provides a state-of-the-art overview on ice-based CO2 and its carbon isotopic signature focusing both on the long-term orbital changes as well as rapid changes documented during the last deglaciation.

  3. 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.

  4. 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).

  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. 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.

  7. Quasar Absorption Line Survey - Cycle 4 High

    NASA Astrophysics Data System (ADS)

    Bahcall, John

    1994-01-01

    The Absorption Line Survey of bright quasars provides a homogeneous data base for studying fundamental questions about the origin and evolution of gaseous systems in the universe. The initial results determine at small redshifts the number densities of Ly-ALPHA systems, of metal-lines and extragalactic halos, of Lyman-limit systems, of associated absorption systems, and the shapes and intensities of quasar emission lines and spectral energy distributions. The survey reveals that much of the sky is covered by high or very high velocity metal-line clouds present in the Galactic halo. A larger sample, which includes the requested Cycle 3 observations, is required to answer many important questions. For example, what is the correlation function of Ly-ALPHA systems at small redshifts? What fraction of the metal, the Ly-ALPHA, and the Ly-limit systems are associated with galaxies and what are the characteristic sizes of the outer gaseous regions of different types of galaxies? Do absorbing systems show evidence of the large-scale structure seen with galaxies and clusters of galaxies? The observations requested in Cycle 3 will extend the region of coverage of the Key Project sample from the redshift range of z = 0.0 to 1.0 (Cycles 1& 2) to z = 0.0 to 1.6 (Cycles 1-3). THIS FILE CONTAINS THE HIGH PRIORITY OBSERVATIONS FROM CYCLES 2 and 3 WHICH WERE NOT COMPLETED IN THOSE CYCLES.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Microbial contributions to climate change through carbon cycle feedbacks.

    PubMed

    Bardgett, Richard D; Freeman, Chris; Ostle, Nicholas J

    2008-08-01

    There is considerable interest in understanding the biological mechanisms that regulate carbon exchanges between the land and atmosphere, and how these exchanges respond to climate change. An understanding of soil microbial ecology is central to our ability to assess terrestrial carbon cycle-climate feedbacks, but the complexity of the soil microbial community and the many ways that it can be affected by climate and other global changes hampers our ability to draw firm conclusions on this topic. In this paper, we argue that to understand the potential negative and positive contributions of soil microbes to land-atmosphere carbon exchange and global warming requires explicit consideration of both direct and indirect impacts of climate change on microorganisms. Moreover, we argue that this requires consideration of complex interactions and feedbacks that occur between microbes, plants and their physical environment in the context of climate change, and the influence of other global changes which have the capacity to amplify climate-driven effects on soil microbes. Overall, we emphasize the urgent need for greater understanding of how soil microbial ecology contributes to land-atmosphere carbon exchange in the context of climate change, and identify some challenges for the future. In particular, we highlight the need for a multifactor experimental approach to understand how soil microbes and their activities respond to climate change and consequences for carbon cycle feedbacks.

  14. Carbon and Nitrogen cycling in a permafrost soil profile

    NASA Astrophysics Data System (ADS)

    Salmon, V. G.; Schaedel, C.; Mack, M. C.; Schuur, E.

    2015-12-01

    In high latitude ecosystems, active layer soils thaw during the growing season and are situated on top of perennially frozen soils (permafrost). Permafrost affected soil profiles currently store a globally important pool of carbon (1330-1580 PgC) due to cold temperatures constraining the decomposition of soil organic matter. With global warming, however, seasonal thaw is expected to increase in speed and extend to deeper portions of the soil profile. As permafrost soils become part of the active layer, carbon (C) and nitrogen (N) previously stored in soil organic matter will be released via decomposition. In this experiment, the dynamic relationship between N mineralization, C mineralization, and C quality was investigated in moist acidic tundra soils. Soils from the active layer surface down through the permafrost (80cm) were incubated aerobically at 15°C for 225 days. Carbon dioxide fluxes were fit with a two pool exponential decay model so that the size and turnover of both the quickly decomposing C pool (Cfast) and the slowly decomposing C pool (Cslow) could be assessed. Soil extractions with 2M KCl were performed at six time points throughout the incubation so that dissolve inorganic N (DIN) and dissolved organic C (DOC) could be measured. DIN was readily extractable from deep permafrost soils throughout the incubation (0.05 mgN/g dry soil) but in active layer soils DIN was only produced after Cfast had been depleted. In contrast, active layer soils had high levels of DOC (0.65 mgC/g dry soil) throughout the incubation but in permafrost soils, DOC became depleted as Cfast reduced in size. The strong contrasts between the C and N cycling in active layer soils versus permafrost soils suggest that the deeper thaw will dramatically increase N availability in these soil profiles. Plants and soil microbes in the tundra are currently N limited so our findings imply that deepening thaw will 1) provide N necessary for increased plant growth and 2) stimulate losses of

  15. Direct Carbon Conversion: Review of Production and Electrochemical Conversion of Reactive Carbons, Economics and Potential Impact on the Carbon Cycle

    SciTech Connect

    Cooper, J F; Cherepy, N; Upadhye, R; Pasternak, A; Steinberg, M

    2000-12-12

    Concerns over global warning have motivated the search for more efficient technologies for electric power generation from fossil fuels. Today, 90% of electric power is produced from coal, petroleum or natural gas. Higher efficiency reduces the carbon dioxide emissions per unit of electric energy. Exercising an option of deep geologic or ocean sequestration for the CO{sub 2} byproduct would reduce emissions further and partially forestall global warming. We introduce an innovative concept for conversion of fossil fuels to electricity at efficiencies in the range of 70-85% (based on standard enthalpy of the combustion reaction). These levels exceed the performance of common utility plants by up to a factor of two. These levels are also in excess of the efficiencies of combined cycle plants and of advanced fuel cells now operated on the pilot scale. The core of the concept is direct carbon conversion a process that is similar to that a fuel cell but differs in that synthesized forms of carbon, not hydrogen, are used as fuel. The cell sustains the reaction, C + O{sub 2} = CO{sub 2} (E {approx} 1.0 V, T = 800 C). The fuel is in the form of fine particulates ({approx}100 nm) distributed by entrainment in a flow of CO{sub 2} to the cells to form a slurry of carbon in the melt. The byproduct stream of CO{sub 2} is pure. It affords the option of sequestration without additional separation costs, or can be reused in secondary oil or gas recovery. Our experimental program has discovered carbon materials with orders of magnitude spreads in anode reactivity reflected in cell power density. One class of materials yields energy at about 1 kW/m{sup 2} sufficiently high to make practical the use of the cell in electric utility applications. The carbons used in such cells are highly disordered on the nanometer scale (2-30 nm), relative to graphite. Such disordered or turbostratic carbons can be produced by controlled pyrolysis (thermal decomposition) of hydrocarbons extracted from

  16. 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.

  17. 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

  18. 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

  19. [Design of dynamic simulation system for carbon cycle in forest ecosystem].

    PubMed

    Zhu, Jian-Gang; Yu, Xin-Xiao; Zhang, Zhen-Ming; Wang, Chen; Gan, Jing; Wang, Xiao-Ping; Li, Jin-Hai

    2009-11-01

    Modeling techniques are indispensable for the researches on the carbon cycle of forest ecosystem. In this paper, a new general simulation system FORCASS (FORest CArbon Simulation System) was designed and developed under Simulink environment, with the objectives of modeling the carbon cycle dynamics of forest ecosystems. A comprehensive analysis on the framework, design solution, and development process showed that the FORCASS was feasible. This simulation system had the characteristics of 1) it divided the carbon storage in forest ecosystem into four compartments, i.e., vegetation, litter, soil, and animal, and took into account the carbon flows between the compartments, possessing high mechanism and easily to be comprehended, 2) it was a process-based system, taking the Richards growth function of vegetation component biomass carbon storage as the input to solve difference equations, and was easily to export the outputs such as net primary productivity (NPP) and net ecosystem productivity (NEP) at different stand ages, and 3) it had the explicit expansibility because it was developed based on a general framework for carbon cycle patterns.

  20. 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

  1. 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…

  2. 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…

  3. 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.

  4. 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.

  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. 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.

  7. Quantifying the Indirect Effect of Sulfate Aerosol on Climate Change Through the Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Cadule, P.; Friedlingstein, P.; Bopp, L.; Piao, S.; Ciais, P.

    2008-12-01

    Elevated atmospheric concentrations of greenhouse gases will continue to warm the Earth's climate in the coming century. Coupled climate-carbon models have demonstrated a significant climate-induced reduction of natural carbon sinks, which acts as a positive feedback on the atmospheric CO2 concentration (between +20 and +220 ppm in 2100, for the SRES A2 emission scenario). Sulfate aerosols are known to affect climate through a radiative direct effect and a series of indirect effects involving the atmospheric water cycle. However, the effects of sulfate aerosols and non-CO2 greenhouse gases were neglected in these coupled climate-carbon cycle models. Here we performed new coupled climate-carbon simulations wherein the evolution of sulfate aerosols and non-CO2 greenhouse gases were explicitly represented. We show a hitherto undocumented indirect effect of aerosols on climate, via the carbon cycle. While sulfate aerosols cool the climate by 0.79°C globally, this cooling reduces land carbon sinks, leaving additional CO2 in the atmosphere. At mid-to-high northern latitudes, the aerosol-induced cooling is responsible for a decline in photosynthesis and land carbon uptake (-63 PgC by 2100). On the other hand, a variety of processes yields increased tropical carbon uptake (+28 PgC) in response to aerosol induced cooling, which is insufficient to balance the decline in the northern hemisphere. Overall, including non- CO2 greenhouse gases and sulfate aerosols, in coupled simulations, doubles the additional quantity of CO2 accumulating in the atmosphere due to climate change. Our results demonstrate that any climate mitigation policy that aims to reduce warming via sulfate aerosols must also account for their indirect warming effect, which arises from interactions between climate and the carbon cycle.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. The carbon cycle and atmospheric CO2: Natural variations archean to present; Proceedings of the Chapman Conference on Natural Variations in Carbon Dioxide and the Carbon Cycle, Tarpon Springs, FL, January 9-13, 1984

    NASA Astrophysics Data System (ADS)

    Sundquist, E. T.; Broecker, W. S.

    The present conference on the history of the relationship between atmospheric CO2 and the carbon cycle treats data obtained concerning the most recent deglaciation, the Pleistocene, the Zenozoic, and the Phanerozoic-Precambrian. Specific attention is given to the geophysical implications of the tropospheric methane cycle, transient response of the marine carbon cycle, factors regulating glacial to interglacial CO2 changes, the high latitude ocean as a control of atmospheric CO2, and the relationships among atmospheric CO2, orbital forcing, and climate. Also discussed are the distribution of major vegetation types during the Tertiary, a 'Strangelove' ocean in the earliest Tertiary, high atmospheric CO2 as a plausible mechanism for warm Cretaceous climates, and potential estimation errors in carbonate rock accumulation over geologic time.

  13. 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.

  14. 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

  15. 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.

  16. High strength, high ductility low carbon steel

    DOEpatents

    Koo, Jayoung; Thomas, Gareth

    1978-01-01

    A high strength, high ductility low carbon steel consisting essentially of iron, 0.05-0.15 wt% carbon, and 1-3 wt% silicon. Minor amounts of other constituents may be present. The steel is characterized by a duplex ferrite-martensite microstructure in a fibrous morphology. The microstructure is developed by heat treatment consisting of initial austenitizing treatment followed by annealing in the (.alpha. + .gamma.) range with intermediate quenching.

  17. Large perturbations of the carbon cycle during recovery from the end-permian extinction.

    PubMed

    Payne, Jonathan L; Lehrmann, Daniel J; Wei, Jiayong; Orchard, Michael J; Schrag, Daniel P; Knoll, Andrew H

    2004-07-23

    High-resolution carbon isotope measurements of multiple stratigraphic sections in south China demonstrate that the pronounced carbon isotopic excursion at the Permian-Triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the Early Triassic before ending abruptly early in the Middle Triassic. The unusual behavior of the carbon cycle coincides with the delayed recovery from end-Permian extinction recorded by fossils, suggesting a direct relationship between Earth system function and biological rediversification in the aftermath of Earth's most devastating mass extinction.

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

    NASA Astrophysics Data System (ADS)

    Hofmockel, Kirsten S.

    Human activities including fossil fuel combustion, deforestation, and land conversion to agriculture have caused the concentration of atmospheric CO2 to increase since the Industrial Revolution. One approach to atmospheric CO2 reduction is sequestration in forest ecosystems. Presently little is known about the overall impact of elevated atmospheric CO2 on net ecosystem carbon storage, particularly in terms of nutrient limitations. In this dissertation I tested the hypothesis that elevated atmospheric CO2 will stimulate soil N availability, supporting long-term CO 2 sequestration in southeastern forests, examined asymbiotic N2 fixation, amino acid assimilation and ecosystem scale N cycling to understand changes in soil N cycling induced by elevated atmospheric CO 2. All research was conducted at the Duke Forest free Air CO2 Enrichment (FACE) experiment, where atmospheric CO2 concentrations have been maintained at 200 ul l-1 above ambient levels in the 30-m diameter treatment plots since 1996. This body of research indicates that elevated atmospheric CO2 does not stimulate soil N cycling at the decadal time scale. Field measurements of exogenous N inputs via asymbiotic N2 fixing bacteria reveal no CO2 stimulation. Soil moisture was the most important factor controlling field rates of N2 fixation. Changes in endogenous N cycling were evaluated using stable isotope tracer field experiments. Short-term experiments showed that more amino acid N was assimilated by both fine roots and microbes under ambient compared to elevated CO2. This significant treatment effect indicates that soil C limitation was a stronger driver of amino acid cycling than N limitation. Intact amino acid assimilation was comparable to NH4 assimilation and may make a small, but important contribution to plant N uptake in warm-temperate forest ecosystems. Inorganic N cycling was not affected by elevated atmospheric CO2. After two growing seasons, a 15N field tracer experiment showed no effects of

  19. Building robust architectures of carbon-wrapped transition metal nanoparticles for high catalytic enhancement of the 2LiBH4-MgH2 system for hydrogen storage cycling performance

    NASA Astrophysics Data System (ADS)

    Huang, Xu; Xiao, Xuezhang; Shao, Jie; Zhai, Bing; Fan, Xiulin; Cheng, Changjun; Li, Shouquan; Ge, Hongwei; Wang, Qidong; Chen, Lixin

    2016-08-01

    Nanoscale catalyst doping is regarded as one of the most effective strategies to improve the kinetics performance of hydrogen storage materials, but the agglomeration of nanoparticles is usually unavoidable during the repeated de/rehydrogenation processes. Herein, hierarchically structured catalysts (Fe/C, Co/C and Ni/C) were designed and fabricated to overcome the agglomeration issue of nanocatalysts applied to the 2LiBH4-MgH2 system for the first time. Uniform transition metal (TM) nanoparticles (~10 nm) wrapped by few layers of carbon are synthesized by pyrolysis of the corresponding metal-organic frameworks (MOFs), and introduced into the 2LiBH4-MgH2 reactive hydride composites (RHCs) by ball milling. The particular features of the carbon-wrapped architecture effectively avoid the agglomeration of the TM nanoparticles during hydrogen storage cycling, and high catalysis is maintained during the subsequent de/rehydrogenation processes. After de/rehydrogenation cycling, FeB, CoB and MgNi3B2 can be formed as the catalytically active components with a particle size of 5-15 nm, which show a homogeneous distribution in the hydride matrix. Among the three catalysts, in situ-formed MgNi3B2 shows the best catalytic efficiency. The incubation period of the Fe/C, Co/C and Ni/C-doped 2LiBH4-MgH2 system between the two dehydrogenation steps was reduced to about 8 h, 4 h and 2 h, respectively, which is about 8 h, 12 h and 14 h shorter than that of the undoped 2LiBH4-MgH2 sample. In addition, the two-step dehydrogenation peak temperatures of the Ni/C-doped 2LiBH4-MgH2 system drop to 323.4 °C and 410.6 °C, meanwhile, the apparent activation energies of dehydrogenated MgH2 and LiBH4 decrease by 58 kJ mol-1 and 71 kJ mol-1, respectively. In particular, the cycling hydrogen desorption of the Ni/C-doped 2LiBH4-MgH2 sample exhibits very good stability compared with the undoped sample. The present approach, which ideally addresses the agglomeration of nanoparticles with efficient

  20. Integrating the nitrogen cycle in carbon and GHG observation systems

    NASA Astrophysics Data System (ADS)

    Kutsch, W. L.; Brummer, C.

    2013-12-01

    Nitrogen is an important factor for the regulation of carbon and GHG fluxes within ecosystems and between ecosystems and the atmosphere. Nitrogen fertilization is important for high agricultural yields but also increases N2O emissions. In Germany, e.g., N2O emissions from agriculture comprise about 6 % of the total GHG inventory. Nitrogen deposition may enhance productivity of ecosystems (e.g. forests, natural grasslands or wetlands) but may also change community structure - in particular in ecosystems that are adapted to low nitrogen availability. It also can lead to increased N2O emissions. Global nitrogen fluxes due to the trade of agricultural products may concentrate nitrogen in specific areas (e.g. in areas with high animal stock). In these areas increased N2O emissions are to be expected. The Thünen Institute of Climate-Smart Agriculture drives parts of the German ICOS consortium with a special focus on agricultural sites or indirect effects of agriculture on GHG emissions. We propose a concept to integrate nitrogen into research infrastructures for GHG monitoring. A conceptual frame will identify the most important parameters of the N cycle. Data from the CarboEurope and NitroEurope core site Gebesee (crop) will be presented to show first integrative results.Finally, first experiences with new technologies will be presented, comprising quantum cascade laser measurements of N2O and ammonia used with eddy covariance (EC) and chambers and EC measurements of total reactive nitrogen with the TRANC methodology (Marx et al. 2012).

  1. 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.

  2. Eccentricity pacing of eastern equatorial Pacific carbonate dissolution cycles during the Miocene Climatic Optimum

    NASA Astrophysics Data System (ADS)

    Kochhann, Karlos G. D.; Holbourn, Ann; Kuhnt, Wolfgang; Channell, James E. T.; Lyle, Mitch; Shackford, Julia K.; Wilkens, Roy H.; Andersen, Nils

    2016-09-01

    The Miocene Climatic Optimum (MCO; ~16.9 to 14.7 Ma) provides an outstanding opportunity to investigate climate-carbon cycle dynamics during a geologically recent interval of global warmth. We present benthic stable oxygen (δ18O) and carbon (δ13C) isotope records (5-12 kyr time resolution) spanning the late early to middle Miocene interval (18 to 13 Ma) at Integrated Ocean Drilling Program (IODP) Site U1335 (eastern equatorial Pacific Ocean). The U1335 stable isotope series track the onset and development of the MCO as well as the transitional climatic phase culminating with global cooling and expansion of the East Antarctic Ice Sheet at ~13.8 Ma. We integrate these new data with published stable isotope, geomagnetic polarity, and X-ray fluorescence (XRF) scanner-derived carbonate records from IODP Sites U1335, U1336, U1337, and U1338 on a consistent, astronomically tuned timescale. Benthic isotope and XRF scanner-derived CaCO3 records depict prominent 100 kyr variability with 400 kyr cyclicity additionally imprinted on δ13C and CaCO3 records, pointing to a tight coupling between the marine carbon cycle and climate variations. Our intersite comparison further indicates that the lysocline behaved in highly dynamic manner throughout the MCO, with >75% carbonate loss occurring at paleodepths ranging from ~3.4 to ~4 km in the eastern equatorial Pacific Ocean. Carbonate dissolution maxima coincide with warm phases (δ18O minima) and δ13C decreases, implying that climate-carbon cycle feedbacks fundamentally differed from the late Pleistocene glacial-interglacial pattern, where dissolution maxima correspond to δ13C maxima and δ18O minima. Carbonate dissolution cycles during the MCO were, thus, more similar to Paleogene hyperthermal patterns.

  3. 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.

  4. 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

  5. Effect of increasing CO2 on the terrestrial carbon cycle

    NASA Astrophysics Data System (ADS)

    Schimel, David; Stephens, Britton B.; 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.

  6. (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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Carbon cycling in salt marsh dominated estuaries along the US Atlantic coast

    NASA Astrophysics Data System (ADS)

    Forbrich, Inke; Nahrawi, Hafsah B.; Wang, Shiyu; Leclerc, Monique; Hopkinson, Charles S.; Giblin, Anne E.; Alber, Merryl; Cai, Wei-Jun

    2016-04-01

    Salt marshes are effective carbon sinks, because they rely on vertical accretion of organic and inorganic matter to keep their relative position to sea level. They are also described as 'carbon pumps' that fix atmospheric carbon but deliver organic and inorganic carbon to estuarine and coastal waters. These fluxes are still highly uncertain due to their temporal and spatial variability. Here, we present observations on atmospheric CO2 exchange and lateral DIC exchange measured at two salt marsh dominated estuaries along the US Atlantic coast. Atmospheric exchange was measured with the eddy covariance method supplemented by measurements of DIC concentrations and discharge in tidal creeks during selected tidal cycles. Together with estimates of long-term carbon burial, this allows us to constrain their export potential. Since the Plum Island Ecosystems LTER and Georgia Coastal Ecosystems LTER are located along a temperature gradient, we will use the data to assess the temperature effect on ecosystem productivity and respiration.

  12. Carbon cycling in the upper waters of the Sargasso Sea: I. Numerical simulation of differential carbon and nitrogen fluxes

    NASA Astrophysics Data System (ADS)

    Bissett, W. P.; Walsh, J. J.; Dieterle, D. A.; Carder, K. L.

    1999-02-01

    A complex ecosystem model is developed for the area around Bermuda in the Sargasso Sea. The model is physically driven by seasonal changes in spectral light, temperature, and water column mixing. Autotrophic growth is represented by four functional groups of phytoplankton. The groups have light and nutrient utilization characteristics that reflect those of Prochlorococcus, Synechococcus and Chromophycota species. The model includes differential carbon and nitrogen cycling, nitrification, and nitrogen fixation to effect realistic allochthonous and autochthonous nutrient sources to the euphotic zone. This simulation yields realistic seasonal and vertical (1) succession of phytoplankton functional groups' biomass, productivity, and pigments; (2) profiles of dissolved inorganic carbon, nitrate, and ammonium; and (3) fluxes of carbon dioxide at the air-sea boundary and particulate carbon and nitrogen settling losses, when compared to the JGOFS BATS site. The addition of local nitrification, differential carbon and nitrogen remineralization, and nitrogen fixation removes the need for an unrealistically high upward vertical flux of nitrate to mimic the productivity and chlorophyll a stocks. The explicit numerical description of carbon and nitrogen utilization by heterotrophic bacteria simulated a population that was not nitrogen-limited in these waters. Instead, the heterotrophic bacteria community was limited by energy resources in the form of DOC, and was a nitrogen source for the autotrophic community through the excretion of excess NH 4 from the labile DOM energy source. Numerical descriptions of ecosystems based solely on nitrogen dynamics, or fixed carbon to nitrogen ratios, may yield an inaccurate prediction of carbon and nitrogen fluxes, and fail to properly predict the carbon cycle.

  13. 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.

  14. Sulfur Cycling Mediates Calcium Carbonate Geochemistry in Modern Marine Stromatolites

    NASA Technical Reports Server (NTRS)

    Visscher, P. T.; Hoeft, S. E.; Bebout, B. M.; Reid, R. P.

    2004-01-01

    Modem marine stromatolites forming in Highborne Cay, Exumas (Bahamas), contain microbial mats dominated by Schizothrix. Although saturating concentrations of Ca2+ and CO32- exist, microbes mediate CaCO3 precipitation. Cyanobacterial photosynthesis in these stromatolites aids calcium carbonate precipitation by removal of HS+ through CO2 use. Photorespiration and exopolymer production predominantly by oxygenic phototrophs fuel heterotrophic activity: aerobic respiration (approximately 60 umol/sq cm.h) and sulfate reduction (SR; 1.2 umol SO42-/sq cm.h) are the dominant C- consuming processes. Aerobic microbial respiration and the combination of SR and H2S oxidation both facilitate CaCO3 dissolution through H+ production. Aerobic respiration consumes much more C on an hourly basis, but duel fluctuating O2 and H2 depth profiles indicate that overall, SR consumes only slightly less (0.2-0.5) of the primary production. Moreover, due to low O2 concentrations when SR rates are peaking, reoxidation of the H2S formed is incomplete: both thiosulfate and polythionates are formed. The process of complete H2S oxidation yields H+. However, due to a low O2 concentration late in the day and relatively high O2 concentrations early in the following morning, a two-stage oxidation takes place: first, polythionates are formed from H2S, creating alkalinity which coincides with CaCO3 precipitation; secondly, oxidation of polythionates to sulfate yields acidity, resulting in dissolution, etc. Vertical profiles confirmed that the pH peaked late in the afternoon (greater than 8.8) and had the lowest values (less than 7.4) early in the morning. Thus, the effect of this S-cycling through alkalinity production, followed by acidification during H2S oxidation, results in a six times stronger fluctuation in acidity than photosynthesis plus aerobic respiration accomplish. This implies that anaerobic processes play a pivotal role in stromatolite formation.

  15. 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.

  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. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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

  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. 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.

  6. The Role of Hyporheic Zones in Cycling of Carbon and Nitrogen

    NASA Astrophysics Data System (ADS)

    Dwivedi, D.; Steefel, C. I.; Arora, B.; Bisht, G.; Williams, K. H.

    2015-12-01

    Hyporheic zones impact the biogeochemical cycling of carbon and nitrogen, both organic and inorganic. To investigate and develop a predictive understanding of the coupled carbon and nitrogen cycling in the subsurface, we integrated a genome inspired complex reaction network with a high-resolution, three-dimensional, reactive flow and transport code - PFLOTRAN. Three-dimensional reactive flow and transport simulations were performed, making use of the high performance computing platform provided by PFLOTRAN, to describe the biogeochemical zonation developed because of the organic carbon rich sediments and a gradient of dissolved oxygen and pH within the hyporheic zone. We conducted this study in the lower East River, a high elevation catchment in southwestern Colorado. The lower East River site displays a rolling-to-mountainous topography with multiple river meanders that extend over a distance of 11 km. We carried out simulations within two stream meanders to examine (1) the impact of hyporheic exchanges on the biogeochemical zonation of variables and (2) how carbon and nitrogen fluxes at the meander scale influence coupled carbon and nitrogen cycling at the river scale. Three-dimensional model domain - 330 m (X) by 400 m (Y) by 48 m (Z) - was uniformly discretized with 10 m horizontal (X and Y) and 0.25 m vertical (Z) resolutions using structured grids in PFLOTRAN. Simulation results show that the intra-meander hyporheic flow paths and biogeochemical reactions result in the lateral redox zonation, which considerably impact the carbon and nitrogen fluxes into the stream system. The meander-driven hyporheic flow paths enhance the denitrification because of relatively longer residence times in the organic carbon-rich sediments.

  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. Carbonate cycle stacking patterns and hierarchies of orbitally forced eustatic sealevel change

    SciTech Connect

    Drummond, C.N.; Wilkinson, B.H. )

    1993-05-01

    Ordered stacking of meter-scale upward-shallowing cycles, manifested as repeated thickness hierarchies within cratonic carbonate sequences, has been considered primary evidence for causal relations between orbitally forced climate change and eustatic sealevel variation. Explicit in this argument is the assumption that each individual cycle represents a single sealevel rise. Sensitivity testing of one-dimensional forward models incorporating a depth threshold of carbonate accumulation indicates that multiple upward-shallowing cycles may originate during any single rise in sealevel. Variation in resultant cycle stacking pattern is sensitive to changes in sealevel amplitude, sedimentation rate, and subsidence rate, with highest stacking ratios (ratio of number of cyclic units to number of eustatic periods) produced by low sealevel amplitudes and high sedimentation and subsidence rates. These relations indicate that direct correlation between multiple-frequency eustatic sealevel variations and meter-scale cycle stacking hierarchies is unwarranted. Thus, prevalent interpretations regarding the stacking record of orbital forcing in ancient carbonate rock sequences should be reevaluated.

  9. Stable isotope constraints on Holocene carbon cycle changes from an Antarctic ice core.

    PubMed

    Elsig, Joachim; Schmitt, Jochen; Leuenberger, Daiana; Schneider, Robert; Eyer, Marc; Leuenberger, Markus; Joos, Fortunat; Fischer, Hubertus; Stocker, Thomas F

    2009-09-24

    Reconstructions of atmospheric CO(2) concentrations based on Antarctic ice cores reveal significant changes during the Holocene epoch, but the processes responsible for these changes in CO(2) concentrations have not been unambiguously identified. Distinct characteristics in the carbon isotope signatures of the major carbon reservoirs (ocean, biosphere, sediments and atmosphere) constrain variations in the CO(2) fluxes between those reservoirs. Here we present a highly resolved atmospheric delta(13)C record for the past 11,000 years from measurements on atmospheric CO(2) trapped in an Antarctic ice core. From mass-balance inverse model calculations performed with a simplified carbon cycle model, we show that the decrease in atmospheric CO(2) of about 5 parts per million by volume (p.p.m.v.). The increase in delta(13)C of about 0.25 per thousand during the early Holocene is most probably the result of a combination of carbon uptake of about 290 gigatonnes of carbon by the land biosphere and carbon release from the ocean in response to carbonate compensation of the terrestrial uptake during the termination of the last ice age. The 20 p.p.m.v. increase of atmospheric CO(2) and the small decrease in delta(13)C of about 0.05 per thousand during the later Holocene can mostly be explained by contributions from carbonate compensation of earlier land-biosphere uptake and coral reef formation, with only a minor contribution from a small decrease of the land-biosphere carbon inventory.

  10. 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.

  11. 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

  12. 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

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

    PubMed

    Marshall, H G; Walker, J C; Kuhn, W R

    1988-01-20

    We study the interactions between the geochemical cycles of carbon and long-term changes in climate. Climate change is studied with a simple, zonally averaged energy balance climate model that includes the greenhouse effect of carbon dioxide explicitly. The geochemical model balances the rate of consumption of carbon dioxide in silicate weathering against its release by volcanic and metamorphic processes. The silicate weathering rate is expressed locally as a function of temperature, carbon dioxide partial pressure, and runoff. The global weathering rate is calculated by integrating these quantities over the land area as a function of latitude. Carbon dioxide feedback stabilizes the climate system against a reduction in solar luminosity and may contribute to the preservation of equable climate on the early Earth, when solar luminosity was low. The system responds to reduced land area by increasing carbon dioxide partial pressure and warming the globe. Our model makes it possible to study the response of the system to changing latitudinal distribution of the continents. A concentration of land area at high latitudes leads to high carbon dioxide partial pressures and high global average temperature because weathering of high-latitude continents is slow. Conversely, concentration of the continents at low latitudes yields a cold globe and ice at low latitudes, a situation that appears to be representative of the late Precambrian glacial episode. This model is stable against ice albedo catastrophe even when the ice line occurs at low latitudes. In this it differs from energy balance models that lack the coupling to the geochemical cycle of carbon.

  14. 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

  15. 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

  16. 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

  17. New Adsorption Cycles for Carbon Dioxide Capture and Concentration

    SciTech Connect

    James Ritter; Armin Ebner; Steven Reynolds Hai Du; Amal Mehrotra

    2008-07-31

    The objective of this three-year project was to study new pressure swing adsorption (PSA) cycles for CO{sub 2} capture and concentration at high temperature. The heavy reflux (HR) PSA concept and the use of a hydrotalcite like (HTlc) adsorbent that captures CO{sub 2} reversibly at high temperatures simply by changing the pressure were two key features of these new PSA cycles. Through the completion or initiation of nine tasks, a bench-scale experimental and theoretical program has been carried out to complement and extend the process simulation study that was carried out during Phase I (DE-FG26-03NT41799). This final report covers the entire project from August 1, 2005 to July 31, 2008. This program included the study of PSA cycles for CO{sub 2} capture by both rigorous numerical simulation and equilibrium theory analysis. The insight gained from these studies was invaluable toward the applicability of PSA for CO{sub 2} capture, whether done at ambient or high temperature. The rigorous numerical simulation studies showed that it is indeed possible to capture and concentrate CO{sub 2} by PSA. Over a wide range of conditions it was possible to achieve greater than 90% CO{sub 2} purity and/or greater than 90% CO{sub 2} recovery, depending on the particular heavy reflux (HR) PSA cycle under consideration. Three HR PSA cycles were identified as viable candidates for further study experimentally. The equilibrium theory analysis, which represents the upper thermodynamic limit of the performance of PSA process, further validated the use of certain HR PSA cycles for CO{sub 2} capture and concentration. A new graphical approach for complex PSA cycle scheduling was also developed during the course of this program. This new methodology involves a priori specifying the cycle steps, their sequence, and the number of beds, and then following a systematic procedure that requires filling in a 2-D grid based on a few simple rules, some heuristics and some experience. It has been

  18. A 100 Myr history of the carbon cycle based on the 400 kyr cycle in marine δ13C benthic records

    NASA Astrophysics Data System (ADS)

    Paillard, Didier; Donnadieu, Yannick

    2014-12-01

    Documenting the past coevolution of Earth temperatures and of the carbon cycle is of paramount importance for our understanding of climate dynamics. Atmospheric CO2 is well constrained over the last million years through direct measurements in air bubbles from Antarctic ice cores. For older times, many different and sometimes conflicting proxies have been suggested. Here we provide a new methodology to constrain the carbon cycle in the past, based on marine benthic δ13C records. Marine δ13C data are recording a persistent 400 kyr cycle, with an amplitude primarily linked to the total amount of carbon in the ocean, or dissolved inorganic carbon (DIC). By extracting this amplitude from published records, we obtain a new strong constraint on the 100 Myr history of Earth's carbon cycle. The obtained Cenozoic evolution of DIC is in surprisingly in a good agreement with existing reconstructions of pCO2, suggesting that pCO2 is mostly driven by DIC changes over this period. In contrast, we find no strong decreasing trend in DIC between the Cretaceous and the Cenozoic, suggesting that Cretaceous atmospheric pCO2 levels were limited, and high temperatures at this time should be explained by other mechanisms. Alternatively, high Cretaceous atmospheric pCO2 could occur as a consequence of changes in oceanic chemistry but not carbon content.

  19. High efficiency Brayton cycles using LNG

    DOEpatents

    Morrow, Charles W.

    2006-04-18

    A modified, closed-loop Brayton cycle power conversion system that uses liquefied natural gas as the cold heat sink media. When combined with a helium gas cooled nuclear reactor, achievable efficiency can approach 68 76% (as compared to 35% for conventional steam cycle power cooled by air or water). A superheater heat exchanger can be used to exchange heat from a side-stream of hot helium gas split-off from the primary helium coolant loop to post-heat vaporized natural gas exiting from low and high-pressure coolers. The superheater raises the exit temperature of the natural gas to close to room temperature, which makes the gas more attractive to sell on the open market. An additional benefit is significantly reduced costs of a LNG revaporization plant, since the nuclear reactor provides the heat for vaporization instead of burning a portion of the LNG to provide the heat.

  20. 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.

  1. Impact of volcanic eruptions on the marine carbon cycle

    NASA Astrophysics Data System (ADS)

    Segschneider, Joachim; Ulrike, Niemeier; Martin, Wiesner; Claudia, Timmreck

    2010-05-01

    The impact of volcanic eruptions on the marine carbon cycle is investigated for the example of the Pinatubo eruption with model simulations of the distribution of the ash cloud and deposition on the ocean surface and the impact of the nutrient addition from ash leachates on the oceanic biological production and hence biological carbon pump. Natural variations of aerosols, especially due to large-magnitude volcanic eruptions, are recognized as a significant climate forcing, altering the Earth's radiation balance and thus tending to cause global temperature changes. While the impact of such events on climate and the terrestrial biosphere is relatively well documented, scientific knowledge of their effects on marine ecosystems and consequent feedbacks to the atmosphere is still very limited. In the deep sea, subaerial eruptive events of global significance are commonly recorded as widespread ash layers, which were often found to be associated with increased abundances of planktic organisms. This has led to the hypothesis that the influx of volcanic ash may provide an external nutrient source for primary production (in particular through iron fertilization) in ocean surface waters. Recent laboratory experiments have demonstrated that pristine volcanic ash indeed releases significant amounts of macronutrients and bioactive trace metals (including phosphate, iron and silica) adsorbed to the surface of the ash particles. The release of these components most likely has its largest impact in ocean regions where their availability is crucial for the growth of oceanic biomass, which are the high-nutrient but low-productivity (low-iron) areas in the Pacific and the Southern Ocean. These in turn are neighbored by most of those subaerially active volcanoes that are capable of ejecting huge amounts of aerosols into the high-velocity stratospheric wind fields. The dispersal and fallout of ash thus has a high potential to induce globally significant, transient net CO2 removal from

  2. 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

  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. 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.

  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. Model of carbon cycling in planktonic food webs

    SciTech Connect

    Connolly, J.P.; Coffin, R.B.

    1995-10-01

    A mathematical model of carbon fluxes through the heterotrophic microbial food web is developed from a synthesis of laboratory and field research. The basis of the model is the segregation of organic carbon into lability classes that are defined by bioassay experiments. Bacteria, phytoplankton, three trophic levels of zooplankton, and dissolved organic carbon (DOC) and particulate organic carbon (POC) are modeled. The descriptions of bacterial growth and utilization of the various classes of substrate were treated as universal constants in the application of the model to three distinct ecosystems, ranging from oligotrophic to highly eutrophic. The successful application of the model to these diverse ecosystems supports the basic validity of the description of the microbial food web and the dynamics of carbon flux. The model indicates that the dynamics of bacteria and protozoan zooplankton production govern the rates of oxidation of carbon entering the water column. Explicit consideration of these groups would improve the capability of eutrophication models to predict dissolved oxygen dynamics, particularly when projecting responses to loading changes.

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

    NASA Astrophysics Data System (ADS)

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

    1990-12-01

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

  8. Design of a Multisensory Probe for Measuring Carbon Cycle Processes in Aqueous Subterranean Environments

    SciTech Connect

    McIntyre, Timothy J; Kisner, Roger; Woodworth, Ken; Lenarduzzi, Roberto; Frank, Steven Shane; McKnight, Timothy E

    2015-01-01

    The global carbon cycle describes the exchange of carbon between the atmosphere, terrestrial vegetation, oceans, and soil. Mechanisms involving carbon in sub-terrestrial ecosystems and their impact on climate are not well understood. This lack of understanding limits current climate models and prevents accurate soil-carbon storage predications for future climate conditions. To address the lack of instrumentation for conducting high fidelity measurements of appropriate parameters in the field, a multi-sensory probe using a mix of optical, fiber optic, and electronic technologies to measure CO2, temperature, dissolved oxygen, redox potential, and water level in subsurface environments has been developed. Details of the design, fabrication and laboratory performance verification are presented. Use cases and the anticipated impacts of such measurements on climate models are discussed.

  9. 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

  10. Warm spring reduced carbon cycle impact of the 2012 US summer drought.

    PubMed

    Wolf, Sebastian; Keenan, Trevor F; Fisher, Joshua B; Baldocchi, Dennis D; Desai, Ankur R; Richardson, Andrew D; Scott, Russell L; Law, Beverly E; Litvak, Marcy E; Brunsell, Nathaniel A; Peters, Wouter; van der Laan-Luijkx, Ingrid T

    2016-05-24

    The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphere-atmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The warm spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by warming-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of warm spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.

  11. Warm spring reduced carbon cycle impact of the 2012 US summer drought

    PubMed Central

    Keenan, Trevor F.; Fisher, Joshua B.; Richardson, Andrew D.; Scott, Russell L.; Law, Beverly E.; Litvak, Marcy E.; Brunsell, Nathaniel A.; Peters, Wouter

    2016-01-01

    The global terrestrial carbon sink offsets one-third of the world’s fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphere-atmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The warm spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by warming-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of warm spring enhances water limitations and can increase summer heating through biosphere–atmosphere feedbacks. PMID:27114518

  12. 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.

  13. Building carbon–carbon bonds using a biocatalytic methanol condensation cycle

    PubMed Central

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

    2014-01-01

    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 13C-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. PMID:25355907

  14. Waste Tire Derived Carbon-Polymer Composite Paper as Pseudocapacitive Electrode with Long Cycle Life.

    PubMed

    Boota, M; Paranthaman, M Parans; Naskar, Amit K; Li, Yunchao; Akato, Kokouvi; Gogotsi, Y

    2015-11-01

    Recycling hazardous wastes to produce value-added products is becoming essential for the sustainable progress of our society. Herein, highly porous carbon (1625 m(2)  g(-1)) is synthesized using waste tires as the precursor and used as a supercapacitor electrode material. The narrow pore-size distribution and high surface area led to good charge storage capacity, especially when used as a three-dimensional nanoscaffold to polymerize polyaniline (PANI). The composite paper was highly flexible, conductive, and exhibited a capacitance of 480 F g(-1) at 1 mV s(-1) with excellent capacitance retention of up to 98% after 10,000 charge/discharge cycles. The high capacitance and long cycle life were ascribed to the short diffusional paths, uniform PANI coating, and tight confinement of the PANI in the inner pores of the tire-derived carbon through π-π interactions, which minimized the degradation of the PANI upon cycling. We anticipate that the same strategy can be applied to deposit other pseudocapacitive materials to achieve even higher electrochemical performance and longer cycle life-a key challenge for redox active polymers.

  15. Waste tire derived carbon-polymer composite paper as pseudocapacitive electrode with long cycle life

    SciTech Connect

    Boota, M.; Paranthaman, Mariappan Parans; Naskar, Amit K.; Gogotsi, Yury; Li, Yunchao; Akato, Kokouvi

    2015-09-25

    Recycling hazardous wastes to produce value-added products is becoming essential for the sustainable progress of our society. Herein, highly porous carbon (1625 m2/g–1) is synthesized using waste tires as the precursor and used as supercapacitor electrode. The narrow pore size distribution (PSD) and high surface area led to a good charge storage capacity, especially when used as a three-dimensional nanoscaffold to polymerize polyaniline (PANI/TC). The composite film was highly flexible, conductive and exhibited a capacitance of 480 F/g–1 at 1 mV/s–1 with excellent capacitance retention up to 98% after 10,000 charge/discharge cycles. The high capacitance and long cycle life were ascribed to the short diffusional paths, uniform PANI coating and tight confinement of the PANI in the inner pores of the tire-derived carbon via - interactions, which minimized the degradation of the PANI upon cycling. Here, we anticipate that the same strategy can be applied to deposit other pseudocapacitive materials with low-cost TC to achieve even higher electrochemical performance and longer cycle life, a key challenge for redox active polymers.

  16. Waste tire derived carbon-polymer composite paper as pseudocapacitive electrode with long cycle life

    DOE PAGES

    Boota, M.; Paranthaman, Mariappan Parans; Naskar, Amit K.; ...

    2015-09-25

    Recycling hazardous wastes to produce value-added products is becoming essential for the sustainable progress of our society. Herein, highly porous carbon (1625 m2/g–1) is synthesized using waste tires as the precursor and used as supercapacitor electrode. The narrow pore size distribution (PSD) and high surface area led to a good charge storage capacity, especially when used as a three-dimensional nanoscaffold to polymerize polyaniline (PANI/TC). The composite film was highly flexible, conductive and exhibited a capacitance of 480 F/g–1 at 1 mV/s–1 with excellent capacitance retention up to 98% after 10,000 charge/discharge cycles. The high capacitance and long cycle life weremore » ascribed to the short diffusional paths, uniform PANI coating and tight confinement of the PANI in the inner pores of the tire-derived carbon via - interactions, which minimized the degradation of the PANI upon cycling. Here, we anticipate that the same strategy can be applied to deposit other pseudocapacitive materials with low-cost TC to achieve even higher electrochemical performance and longer cycle life, a key challenge for redox active polymers.« less

  17. Amazonia and the modern carbon cycle: lessons learned.

    PubMed

    Ometto, Jean Pierre H B; Nobre, Antonio D; Rocha, Humberto R; Artaxo, Paulo; Martinelli, Luiz A

    2005-05-01

    In this paper, we review some critical issues regarding carbon cycling in Amazonia, as revealed by several studies conducted in the Large Scale Biosphere Atmosphere Experiment in Amazonia (LBA). We evaluate both the contribution of this magnificent biome for the global net primary productivity/net ecosystem exchange (NPP/NEE) and the feedbacks of climate change on the dynamics of Amazonia. In order to place Amazonia in a global perspective and make the carbon flux obtained through the LBA project comparable with global carbon budgets, we extrapolated NPP/NEE values found by LBA studies to the entire area of the Brazilian Amazon covered by rainforest. The carbon emissions due to land use changes for the tropical regions of the world produced values from 0.96 to 2.4 Pg C year(-1), while atmospheric CO2 inversion models have recently indicated that tropical lands in the Americas could be exchanging a net 0.62+/-1.15 Pg C year(-1) with the atmosphere. The difference calculated from these two methods would imply a local sink of approximately 1.6-1.7 Pg C year(-1), or a source of 0.85 ton C ha(-1) year(-1). Using our crude extrapolation of LBA values for the Amazon forests (5 million km2) we estimate a range for the C flux in the region of -3.0 to 0.75 Pg C year(-1). The exercise here does not account for environmental variability across the region, but it is an important driver for present and future studies linking local process (i.e. nutrient availability, photosynthetic capacity, and so forth) to global and regional dynamic approaches.

  18. 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.

  19. 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.

  20. Carbon Cycling and Biosequestration Integrating Biology and Climate Through Systems Science Report from the March 2008 Workshop

    SciTech Connect

    Graber, J.; Amthor, J.; Dahlman, R.; Drell, D.; Weatherwax, S.

    2008-12-01

    One of the most daunting challenges facing science in the 21st Century is to predict how Earth's ecosystems will respond to global climate change. The global carbon cycle plays a central role in regulating atmospheric carbon dioxide (CO{sub 2}) levels and thus Earth's climate, but our basic understanding of the myriad of tightly interlinked biological processes that drive the global carbon cycle remains limited at best. Whether terrestrial and ocean ecosystems will capture, store, or release carbon is highly dependent on how changing climate conditions affect processes performed by the organisms that form Earth's biosphere. Advancing our knowledge of biological components of the global carbon cycle is thus crucial to predicting potential climate change impacts, assessing the viability of climate change adaptation and mitigation strategies, and informing relevant policy decisions. Global carbon cycling is dominated by the paired biological processes of photosynthesis and respiration. Photosynthetic plants and microbes of Earth's land-masses and oceans use solar energy to transform atmospheric CO{sub 2} into organic carbon. The majority of this organic carbon is rapidly consumed by plants or microbial decomposers for respiration and returned to the atmosphere as CO{sub 2}. Coupling between the two processes results in a near equilibrium between photosynthesis and respiration at the global scale, but some fraction of organic carbon also remains in stabilized forms such as biomass, soil, and deep ocean sediments. This process, known as carbon biosequestration, temporarily removes carbon from active cycling and has thus far absorbed a substantial fraction of anthropogenic carbon emissions.

  1. 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

  2. Climate cycling on early Mars caused by the carbonate-silicate cycle

    NASA Astrophysics Data System (ADS)

    Batalha, Natasha E.; Kopparapu, Ravi Kumar; Haqq-Misra, Jacob; Kasting, James F.

    2016-12-01

    For decades, scientists have tried to explain the evidence for fluvial activity on early Mars, but a consensus has yet to emerge regarding the mechanism for producing it. One hypothesis suggests early Mars was warmed by a thick greenhouse atmosphere. Another suggests that early Mars was generally cold but was warmed occasionally by impacts or by episodes of enhanced volcanism. These latter hypotheses struggle to produce the amounts of rainfall needed to form the martian valleys, but are consistent with inferred low rates of weathering compared to Earth. Here, we provide a geophysical mechanism that could have induced cycles of glaciation and deglaciation on early Mars. Our model produces dramatic climate cycles with extended periods of glaciation punctuated by warm periods lasting up to 10 Myr-much longer than those generated in other episodic warming models. The cycles occur because stellar insolation was low, and because CO2 outgassing is not able to keep pace with CO2 consumption by silicate weathering followed by deposition of carbonates. While CO2 by itself is not able to deglaciate early Mars in our model, we assume that the greenhouse effect is enhanced by substantial amounts of H2 outgassed from Mars' reduced crust and mantle. Our hypothesis can be tested by future Mars exploration that better establishes the time scale for valley formation.

  3. Accounting for agriculture in modelling the global terrestrial carbon cycle

    NASA Astrophysics Data System (ADS)

    Bondeau, A.; Smith, P.; Schaphoff, S.; Zaehle, S.; Smith, B.; Sitch, S.; Gerten, D.; Schröder, B.; Lucht, W.; Cramer, W.

    2003-04-01

    Among the different approaches that investigate the role of the terrestrial biosphere within the global carbon cycle, Dynamic Global Vegetation Models (DGVMs) are an important tool. They represent the major biogeochemical mechanisms (carbon and water fluxes), depending on climate and soil, in order to simulate vegetation type (tree/grass, evergreen/deciduous, etc) as well as ecosystem function. The models should be validated for different features at various scales, in order to be used to assess the future terrestrial productivity in relation to climate change scenarios. The Lund-Potsdam-Jena (LPJ) model (Sitch et al. 2002) is one of the few existing DGVMs, from which some interesting features have been validated like the seasonal atmospheric CO2 concentrations as measured at the global network of monitoring stations, the increase of the growing season length in the northern areas (Lucht et al. 2002), the runoff of large catchment (Gerten et al. Nice 2003, session HS25). In agreement with other models, LPJ estimates that the terrestrial biosphere is currently a carbon sink that will reduce in the middle of the century because of climate change (Cramer et al. 2000). However, regarding the terrestrial productivity, land use and cover change might be even more important than climate change. Until now, none of the global vegetation models were considering agriculture, or in the best case, agricultural areas were represented as a grassland. We describe the first implementation of crop parameterization within LPJ. As compared to natural vegetation, the main features of crops that must be accounted for in a global vegetation model are: i) the specific phenology, related to the sowing date, ii) the farming practices (nutrient inputs, irrigation), iii) the man-made dynamics (harvest, choice of variety, crop rotation). In a first step we consider the 8 crops types for which a global land cover data set is available for the 20th Century (RIVM). A simple phenological model

  4. High Cycle Thermal Fatigue in French PWR

    SciTech Connect

    Blondet, Eric; Faidy, Claude

    2002-07-01

    Different fatigue-related incidents which occurred in the world on the auxiliary lines of the reactor coolant system (SIS, RHR, CVC) have led EDF to search solutions in order to avoid or to limit consequences of thermodynamic phenomenal (Farley-Tihange, free convection loop and stratification, independent thermal cycling). Studies are performed on mock-up and compared with instrumentation on nuclear power stations. At the present time, studies allow EDF to carry out pipe modifications and to prepare specifications and recommendations for next generation of nuclear power plants. In 1998, a new phenomenal appeared on RHR system in Civaux. A crack was discovered in an area where hot and cold fluids (temperature difference of 140 deg. C) were mixed. Metallurgic studies concluded that this crack was caused by high cycle thermal fatigue. Since 1998, EDF is making an inventory of all mixing areas in French PWR on basis of criteria. For all identified areas, a method was developed to improve the first classifying and to keep back only potential damage pipes. Presently, studies are performing on the charging line nozzle connected to the reactor pressure vessel. In order to evaluate the load history, a mock-up has been developed and mechanical calculations are realised on this nozzle. The paper will make an overview of EDF conclusions on these different points: - dead legs and vortex in a no flow connected line; - stratification; - mixing tees with high {delta}T. (authors)

  5. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.; Naples, Andrew G.

    2006-01-01

    The feasibility of using carbon-carbon (C-C) recuperators in conceptual closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance expectations were forecast based on notional thermodynamic cycle state values for potential planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 30 to 60 percent were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25 to 1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, 60 percent savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed.

  6. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

    NASA Technical Reports Server (NTRS)

    Barrett, Michael J.; Johnson, Paul K.

    2006-01-01

    The use of carbon-carbon (C-C) recuperators in closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance was forecast based on notional thermodynamic cycle state values for planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 40-55% were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25-1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, at least 50% savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed.

  7. Nitrogen Alters Fungal Communities in Boreal Forest Soil: Implications for Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Allison, S. D.; Treseder, K. K.

    2005-12-01

    One potential effect of climate change in high latitude ecosystems is to increase soil nutrient availability. In particular, greater nitrogen availability could impact decomposer communities and lead to altered rates of soil carbon cycling. Since fungi are the primary decomposers in many high-latitude ecosystems, we used molecular techniques and field surveys to test whether fungal communities and abundances differed in response to nitrogen fertilization in a boreal forest ecosystem. We predicted that fungi that degrade recalcitrant carbon would decline under nitrogen fertilization, while fungi that degrade labile carbon would increase, leading to no net change in rates of soil carbon mineralization. The molecular data showed that basidiomycete fungi dominate the active fungal community in both fertilized and unfertilized soils. However, we found that fertilization reduced peak mushroom biomass by 79%, although most of the responsive fungi were ectomycorrhizal and therefore their capacity to degrade soil carbon is uncertain. Fertilization increased the activity of the cellulose-degrading enzyme beta-glucosidase by 78%, while protease activity declined by 39% and polyphenol oxidase, a lignin-degrading enzyme, did not respond. Rates of soil respiration did not change in response to fertilization. These results suggest that increased nitrogen availability does alter the composition of the fungal community, and its potential to degrade different carbon compounds. However, these differences do not affect the total flux of CO2 from the soil, even though the contribution to CO2 respiration from different carbon pools may vary with fertilization. We conclude that in the short term, increased nitrogen availability due to climate warming or nitrogen deposition is more likely to alter the turnover of individual carbon pools rather than total carbon fluxes from the soil. Future work should determine if changes in fungal community structure and associated differences in

  8. Microbial food web mapping: linking carbon cycling and community structure in soils through pyrosequencing enabled stable isotope probing

    SciTech Connect

    Buckley, Daniel H.

    2015-03-15

    Soil represents a massive reservoir of active carbon and climate models vary dramatically in predicting how this carbon will respond to climate change over the coming century. A major cause of uncertainty is that we still have a very limited understand the microorganisms that dominate the soil carbon cycle. The vast majority of soil microbes cannot be cultivated in the laboratory and the diversity of organisms and enzymes that participate in the carbon cycle is staggeringly complex. We have developed a new toolbox for exploring the carbon cycle and the metabolic and ecological characteristics of uncultivated microorganisms. The high-resolution nucleic acid stable isotope probing approach that we have developed makes it possible to characterize microbial carbon cycling dynamics in soil. The approach allows us to track multiple 13C-labeled substrates into thousands of microbial taxa over time. Using this approach we have discovered several major lineages of uncultivated microorganisms that participate in cellulose metabolism and are found widely in soils (including Verrucomicrobia and Chloroflexi, which have not previously been implicated as major players in the soil carbon cycle). Furthermore, isotopic labelling of nucleic acids enables community genomics and permits genome fragment binning for a majority of these cellulolytic microorganisms allowing us to explore the metabolic underpinnings of cellulose degradation. This approach has allowed us to describe unexpected dynamics of carbon metabolism with different microbial taxa exhibiting characteristic patterns of carbon substrate incorporation, indicative of distinct ecological strategies. The data we describe allows us to characterize the activity of novel microorganisms as they occur in the environment and these data provide a basis for understanding how the physiological traits of discrete microorganisms sum to govern the complex responses of the soil carbon cycle.

  9. Understanding spatial heterogeneity in soil carbon and nitrogen cycling in regenerating tropical dry forests

    NASA Astrophysics Data System (ADS)

    Waring, B. G.; Powers, J. S.; Branco, S.; Adams, R.; Schilling, E.

    2015-12-01

    Tropical dry forests (TDFs) currently store significant amounts of carbon in their biomass and soils, but these highly seasonal ecosystems may be uniquely sensitive to altered climates. The ability to quantitatively predict C cycling in TDFs under global change is constrained by tremendous spatial heterogeneity in soil parent material, land-use history, and plant community composition. To explore this variation, we examined soil carbon and nitrogen dynamics in 18 permanent plots spanning orthogonal gradients of stand age and soil fertility. Soil C and N pools, microbial biomass, and microbial extracellular enzyme activities were most variable at small (m2) spatial scales. However, the ratio of organic vs. inorganic N cycling was consistently higher in forest stands dominated by slow-growing, evergreen trees that associate with ectomycorrhizal fungi. Similarly, although bulk litter stocks and turnover rates varied greatly among plots, litter decomposition tended to be slower in ectomycorrhizae-dominated stands. Soil N cycling tended to be more conservative in older plots, although the relationship between stand age and element cycling was weak. Our results emphasize that microscale processes, particularly interactions between mycorrhizal fungi and free-living decomposers, are important controls on ecosystem-scale element cycling.

  10. Metal corrosion in a supercritical carbon dioxide - liquid sodium power cycle.

    SciTech Connect

    Moore, Robert Charles; Conboy, Thomas M.

    2012-02-01

    A liquid sodium cooled fast reactor coupled to a supercritical carbon dioxide Brayton power cycle is a promising combination for the next generation nuclear power production process. For optimum efficiency, a microchannel heat exchanger, constructed by diffusion bonding, can be used for heat transfer from the liquid sodium reactor coolant to the supercritical carbon dioxide. In this work, we have reviewed the literature on corrosion of metals in liquid sodium and carbon dioxide. The main conclusions are (1) pure, dry CO{sub 2} is virtually inert but can be highly corrosive in the presence of even ppm concentrations of water, (2) carburization and decarburization are very significant mechanism for corrosion in liquid sodium especially at high temperature and the mechanism is not well understood, and (3) very little information could be located on corrosion of diffusion bonded metals. Significantly more research is needed in all of these areas.

  11. Not all droughts are created equal: The impacts of interannual drought pattern and magnitude on grassland carbon cycling

    USGS Publications Warehouse

    Hoover, David L.; Rogers, Brendan M.

    2016-01-01

    Climate extremes, such as drought, may have immediate and potentially prolonged effects on carbon cycling. Grasslands store approximately one-third of all terrestrial carbon and may become carbon sources during droughts. However, the magnitude and duration of drought-induced disruptions to the carbon cycle, as well as the mechanisms responsible, remain poorly understood. Over the next century, global climate models predict an increase in two types of drought: chronic but subtle ‘press-droughts’, and shorter term but extreme ‘pulse-droughts’. Much of our current understanding of the ecological impacts of drought comes from experimental rainfall manipulations. These studies have been highly valuable, but are often short term and rarely quantify carbon feedbacks. To address this knowledge gap, we used the Community Land Model 4.0 to examine the individual and interactive effects of pulse- and press-droughts on carbon cycling in a mesic grassland of the US Great Plains. A series of modeling experiments were imposed by varying drought magnitude (precipitation amount) and interannual pattern (press- vs. pulse-droughts) to examine the effects on carbon storage and cycling at annual to century timescales. We present three main findings. First, a single-year pulse-drought had immediate and prolonged effects on carbon storage due to differential sensitivities of ecosystem respiration and gross primary production. Second, short-term pulse-droughts caused greater carbon loss than chronic press-droughts when total precipitation reductions over a 20-year period were equivalent. Third, combining pulse- and press-droughts had intermediate effects on carbon loss compared to the independent drought types, except at high drought levels. Overall, these results suggest that interannual drought pattern may be as important for carbon dynamics as drought magnitude and that extreme droughts may have long-lasting carbon feedbacks in grassland ecosystems.

  12. Not all droughts are created equal: the impacts of interannual drought pattern and magnitude on grassland carbon cycling.

    PubMed

    Hoover, David L; Rogers, Brendan M

    2016-05-01

    Climate extremes, such as drought, may have immediate and potentially prolonged effects on carbon cycling. Grasslands store approximately one-third of all terrestrial carbon and may become carbon sources during droughts. However, the magnitude and duration of drought-induced disruptions to the carbon cycle, as well as the mechanisms responsible, remain poorly understood. Over the next century, global climate models predict an increase in two types of drought: chronic but subtle 'press-droughts', and shorter term but extreme 'pulse-droughts'. Much of our current understanding of the ecological impacts of drought comes from experimental rainfall manipulations. These studies have been highly valuable, but are often short term and rarely quantify carbon feedbacks. To address this knowledge gap, we used the Community Land Model 4.0 to examine the individual and interactive effects of pulse- and press-droughts on carbon cycling in a mesic grassland of the US Great Plains. A series of modeling experiments were imposed by varying drought magnitude (precipitation amount) and interannual pattern (press- vs. pulse-droughts) to examine the effects on carbon storage and cycling at annual to century timescales. We present three main findings. First, a single-year pulse-drought had immediate and prolonged effects on carbon storage due to differential sensitivities of ecosystem respiration and gross primary production. Second, short-term pulse-droughts caused greater carbon loss than chronic press-droughts when total precipitation reductions over a 20-year period were equivalent. Third, combining pulse- and press-droughts had intermediate effects on carbon loss compared to the independent drought types, except at high drought levels. Overall, these results suggest that interannual drought pattern may be as important for carbon dynamics as drought magnitude and that extreme droughts may have long-lasting carbon feedbacks in grassland ecosystems.

  13. 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.

  14. Uncertainties and Key Open Questions in the Geological Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Burton, M. R.

    2015-12-01

    The geological carbon cycle determines the long term distribution of CO2 between the mantle, crust and atmosphere, and therefore controls the concentration of CO2 in the Earth's atmosphere. Records of CO2 concentrations and temperature for the last 600,000 years indicate a relative stability in atmospheric CO2 concentrations, reflecting a balance between CO2 input to the atmosphere from volcanism and metamorphism, and output via silicate weathering. The absolute rates of these global fluxes contributes to controlling the lifetime of CO2 in the atmosphere. It is therefore extremely relevant and important to quantify the rate of the geological cycle for CO2, as this will contribute to the timescale of recovery from a change in policy on anthropogenic CO2 emissions. Here we review the state of the art in our knowledge of Earth's geological CO2 output, and highlight causes of large underestimates, largely due to methodological errors in measurement of CO2 flux. We produce a new, corrected estimate and use this to estimate a CO2 lifetime which is significantly shorter than previously thought.

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

    SciTech Connect

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

    1993-01-01

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

  16. Inorganic carbon cycling and biogeochemical processes in an Arctic inland sea (Hudson Bay)

    NASA Astrophysics Data System (ADS)

    Burt, William J.; Thomas, Helmuth; Miller, Lisa A.; Granskog, Mats A.; Papakyriakou, Tim N.; Pengelly, Leah

    2016-08-01

    The distributions of carbonate system parameters in Hudson Bay, which not only receives nearly one-third of Canada's river discharge but is also subject to annual cycles of sea-ice formation and melt, indicate that the timing and magnitude of freshwater inputs play an important role in carbon biogeochemistry and acidification in this unique Arctic ecosystem. This study uses basin-wide measurements of dissolved inorganic carbon (DIC) and total alkalinity (TA), as well as stable isotope tracers (δ18O and δ13CDIC), to provide a detailed assessment of carbon cycling processes within the bay. Surface distributions of carbonate parameters reveal the particular importance of freshwater inputs in the southern portion of the bay. Based on TA, we surmise that the deep waters in the Hudson Bay are largely of Pacific origin. Riverine TA end-members vary significantly both regionally and with small changes in near-surface depths, highlighting the importance of careful surface water sampling in highly stratified waters. In an along-shore transect, large increases in subsurface DIC are accompanied by equivalent decreases in δ13CDIC with no discernable change in TA, indicating a respiratory DIC production on the order of 100 µmol kg-1 DIC during deep water circulation around the bay.

  17. Energy Storage: Breakthrough in Battery Technologies (Carbon Cycle 2.0)

    ScienceCinema

    Balsara, Nitash

    2016-07-12

    Nitash Balsara 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. Carbon Cycle 2.0: Bill Collins: A future without CC2.0

    ScienceCinema

    Bill Collins

    2016-07-12

    Bill Collins 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/

  19. Carbon Cycle 2.0: Mary Ann Piette: Impact of efficient buildings

    ScienceCinema

    Mary Ann Piette

    2016-07-12

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

  20. Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle.

    PubMed

    Swart, Peter K

    2008-09-16

    The carbon isotopic (delta(13)C) composition of bulk carbonate sediments deposited off the margins of four carbonate platforms/ramp systems (Bahamas, Maldives, Queensland Plateau, and Great Australian Bight) show synchronous changes over the past 0 to 10 million years. However, these variations are different from the established global pattern in the delta(13)C measured in the open oceans over the same time period. For example, from 10 Ma to the present, the delta(13)C of open oceanic carbonate has decreased, whereas platform margin sediments analyzed here show an increase. It is suggested that the delta(13)C patterns in the marginal platform deposits are produced through admixing of aragonite-rich sediments, which have relatively positive delta(13)C values, with pelagic materials, which have lower delta(13)C values. As the more isotopically positive shallow-water carbonate sediments are only produced when the platforms are flooded, there is a connection between changes in global sea level and the delta(13)C of sediments in marginal settings. These data indicate that globally synchronous changes in delta(13)C can take place that are completely unrelated to variations in the global carbon cycle. Fluctuations in the delta(13)C of carbonate sediments measured during previous geological periods may also be subject to similar processes, and global synchroniety of delta(13)C can no longer necessarily be considered an indicator that such changes are related to, or caused by, variations in the burial of organic carbon. Inferences regarding the interpretation of changes in the cycling of organic carbon derived from delta(13)C records should be reconsidered in light of the findings presented here.

  1. Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle

    PubMed Central

    Swart, Peter K.

    2008-01-01

    The carbon isotopic (δ13C) composition of bulk carbonate sediments deposited off the margins of four carbonate platforms/ramp systems (Bahamas, Maldives, Queensland Plateau, and Great Australian Bight) show synchronous changes over the past 0 to 10 million years. However, these variations are different from the established global pattern in the δ13C measured in the open oceans over the same time period. For example, from 10 Ma to the present, the δ13C of open oceanic carbonate has decreased, whereas platform margin sediments analyzed here show an increase. It is suggested that the δ13C patterns in the marginal platform deposits are produced through admixing of aragonite-rich sediments, which have relatively positive δ13C values, with pelagic materials, which have lower δ13C values. As the more isotopically positive shallow-water carbonate sediments are only produced when the platforms are flooded, there is a connection between changes in global sea level and the δ13C of sediments in marginal settings. These data indicate that globally synchronous changes in δ13C can take place that are completely unrelated to variations in the global carbon cycle. Fluctuations in the δ13C of carbonate sediments measured during previous geological periods may also be subject to similar processes, and global synchroniety of δ13C can no longer necessarily be considered an indicator that such changes are related to, or caused by, variations in the burial of organic carbon. Inferences regarding the interpretation of changes in the cycling of organic carbon derived from δ13C records should be reconsidered in light of the findings presented here. PMID:18772393

  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. 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.

  4. Microbial Mediation of Ca-Mg-Carbonates and Mg-Phosphates: Linking the Carbon and Phosphorous Cycles

    NASA Astrophysics Data System (ADS)

    Vasconcelos, C.; Roman, M. S.; McKenzie, J. A.

    2003-12-01

    An extensive literature exists on the involvement of microbes in mineral precipitation, including in situ studies performed in natural environments where a specific mineral occurs, as well as laboratory experiments. In order to understand the mechanism of biomineralization, bacteria culture experiments must be conducted to evaluate the involvement of microorganisms, which can act as geochemical agents promoting mineral formation by affecting local geochemical conditions. To date, much research on the biomineralization of carbonate minerals has been performed, but little attention has been given to phosphate mineral formation, in spite of its importance in sustaining life and its intrinsic relation with the carbon cycle. We report the results of 25 bacteria culture experiments that were designed to precipitate carbonate and phosphate minerals, using bacteria strains isolated from saline soils in Spain and a hypersaline lagoon, Brejo do Espinho, near Rio de Janeiro, Brazil. In these environments, there is a predominance of carbonate mineral precipitation, such as calcite, high Mg-calcite and dolomite. Of the 25 strains that produced dolomite and calcite, 14 contained, in addition, struvite, while 6 of these produced large amounts of struvite crystals. For any given microorganism, a slight increase in the amount of crystal formation was observed when less calcium acetate was added to the culture media, and a transformation from struvite to monohydrocalcite and dolomite was observed in these experiments. This study provides information to understand the relationship between the phosphorus and carbon cycle during mineral precipitation. Although struvite is not abundant in the geological record, defining its mechanism of precipitation may provide information to better interpret the contribution of microbes in the recycling of phosphorus, as well as the diagenetic processes involving carbonate and phosphate minerals.

  5. Bacterioplankton carbon cycling along the Subtropical Frontal Zone off New Zealand

    NASA Astrophysics Data System (ADS)

    Baltar, Federico; Stuck, Esther; Morales, Sergio; Currie, Kim

    2015-06-01

    Marine heterotrophic bacterioplankton (Bacteria and Archaea) play a central role in ocean carbon cycling. As such, identifying the factors controlling these microbial populations is crucial to fully understanding carbon fluxes. We studied bacterioplankton activities along a transect crossing three water masses (i.e., Subtropical waters [STW], Sub-Antarctic waters [SAW] and neritic waters [NW]) with contrasting nutrient regimes across the Subtropical Frontal Zone. In contrast to bacterioplankton production and community respiration, bacterioplankton respiration increased in the offshore SAW, causing a seaward increase in the contribution of bacteria to community respiration (from 7% to 100%). Cell-specific bacterioplankton respiration also increased in SAW, but cell-specific production did not, suggesting that prokaryotic cells in SAW were investing more energy towards respiration than growth. This was reflected in a 5-fold decline in bacterioplankton growth efficiency (BGE) towards SAW. One way to explain this decrease in BGE could be due to the observed reduction in phytoplankton biomass (and presumably organic matter concentration) towards SAW. However, this would not explain why bacterioplankton respiration was highest in SAW, where phytoplankton biomass was lowest. Another factor affecting BGE could be the iron limitation characteristic of high-nutrient low-chlorophyll (HNLC) regions like SAW. Our field-study based evidences would agree with previous laboratory experiments in which iron stress provoked a decrease in BGE of marine bacterial isolates. Our results suggest that there is a strong gradient in bacterioplankton carbon cycling rates along the Subtropical Frontal Zone, mainly due to the HNLC conditions of SAW. We suggest that Fe-induced reduction of BGE in HNLC regions like SAW could be relevant in marine carbon cycling, inducing bacterioplankton to act as a link or a sink of organic carbon by impacting on the quantity of organic carbon they incorporate

  6. Hydrologic control of carbon cycling and aged carbon discharge in the Congo River basin

    NASA Astrophysics Data System (ADS)

    Schefuß, Enno; Eglinton, Timothy I.; Spencer-Jones, Charlotte L.; Rullkötter, Jürgen; de Pol-Holz, Ricardo; Talbot, Helen M.; Grootes, Pieter M.; Schneider, Ralph R.

    2016-09-01

    The age of organic material discharged by rivers provides information about its sources and carbon cycling processes within watersheds. Although elevated ages in fluvially transported organic matter are usually explained by erosion of soils and sedimentary deposits, it is commonly assumed that mainly young organic material is discharged from flat tropical watersheds due to their extensive plant cover and rapid carbon turnover. Here we present compound-specific radiocarbon data of terrigenous organic fractions from a sedimentary archive offshore the Congo River, in conjunction with molecular markers for methane-producing land cover reflecting wetland extent. We find that the Congo River has been discharging aged organic matter for several thousand years, with apparently increasing ages from the mid- to the Late Holocene. This suggests that aged organic matter in modern samples is concealed by radiocarbon from atmospheric nuclear weapons testing. By comparison to indicators for past rainfall changes we detect a systematic control of organic matter sequestration and release by continental hydrology, mediating temporary carbon storage in wetlands. As aridification also leads to exposure and rapid remineralization of large amounts of previously stored labile organic matter, we infer that this process may cause a profound direct climate feedback that is at present underestimated in carbon cycle assessments.

  7. Tropical wetlands: A missing link in the global carbon cycle?

    PubMed Central

    Sjögersten, Sofie; Black, Colin R; Evers, Stephanie; Hoyos-Santillan, Jorge; Wright, Emma L; Turner, Benjamin L

    2014-01-01

    Tropical wetlands are not included in Earth system models, despite being an important source of methane (CH4) and contributing a large fraction of carbon dioxide (CO2) emissions from land use, land use change, and forestry in the tropics. This review identifies a remarkable lack of data on the carbon balance and gas fluxes from undisturbed tropical wetlands, which limits the ability of global change models to make accurate predictions about future climate. We show that the available data on in situ carbon gas fluxes in undisturbed forested tropical wetlands indicate marked spatial and temporal variability in CO2 and CH4 emissions, with exceptionally large fluxes in Southeast Asia and the Neotropics. By upscaling short-term measurements, we calculate that approximately 90 ± 77 Tg CH4 year−1 and 4540 ± 1480 Tg CO2 year−1 are released from tropical wetlands globally. CH4 fluxes are greater from mineral than organic soils, whereas CO2 fluxes do not differ between soil types. The high CO2 and CH4 emissions are mirrored by high rates of net primary productivity and litter decay. Net ecosystem productivity was estimated to be greater in peat-forming wetlands than on mineral soils, but the available data are insufficient to construct reliable carbon balances or estimate gas fluxes at regional scales. We conclude that there is an urgent need for systematic data on carbon dynamics in tropical wetlands to provide a robust understanding of how they differ from well-studied northern wetlands and allow incorporation of tropical wetlands into global climate change models. PMID:26074666

  8. Tropical wetlands: A missing link in the global carbon cycle?

    NASA Astrophysics Data System (ADS)

    Sjögersten, Sofie; Black, Colin R.; Evers, Stephanie; Hoyos-Santillan, Jorge; Wright, Emma L.; Turner, Benjamin L.

    2014-12-01

    Tropical wetlands are not included in Earth system models, despite being an important source of methane (CH4) and contributing a large fraction of carbon dioxide (CO2) emissions from land use, land use change, and forestry in the tropics. This review identifies a remarkable lack of data on the carbon balance and gas fluxes from undisturbed tropical wetlands, which limits the ability of global change models to make accurate predictions about future climate. We show that the available data on in situ carbon gas fluxes in undisturbed forested tropical wetlands indicate marked spatial and temporal variability in CO2 and CH4 emissions, with exceptionally large fluxes in Southeast Asia and the Neotropics. By upscaling short-term measurements, we calculate that approximately 90 ± 77 Tg CH4 year-1 and 4540 ± 1480 Tg CO2 year-1 are released from tropical wetlands globally. CH4 fluxes are greater from mineral than organic soils, whereas CO2 fluxes do not differ between soil types. The high CO2 and CH4 emissions are mirrored by high rates of net primary productivity and litter decay. Net ecosystem productivity was estimated to be greater in peat-forming wetlands than on mineral soils, but the available data are insufficient to construct reliable carbon balances or estimate gas fluxes at regional scales. We conclude that there is an urgent need for systematic data on carbon dynamics in tropical wetlands to provide a robust understanding of how they differ from well-studied northern wetlands and allow incorporation of tropical wetlands into global climate change models.

  9. The role of peatlands in interglacial carbon cycle dynamics - a modeling perspective (Invited)

    NASA Astrophysics Data System (ADS)

    Kleinen, T.; Brovkin, V.

    2009-12-01

    Peatlands cover about 3% of the Earth's land surface area only, but they contain substantial amounts of carbon. Estimates of peat accumulated during the Holocene reach up to 450 GtC. On longer timescales the carbon uptake by peatlands therefore becomes a cumulative flux of substantial magnitude, though it is rather small if one considers the short timescales only. Using the coupled climate carbon cycle model CLIMBER2-LPJ we are considering all natural factors influencing the atmospheric CO2 concentration, including carbon uptake by peatlands. CLIMBER2 is a climate model of intermediate complexity, containing a dynamic atmosphere and ocean, as well as sea ice and land surface modules. Its coarse spatial resolution leads to a high computational efficiency, which allows long-term transient integrations of the coupled model. Land carbon dynamics are computed using the dynamic global vegetation model LPJ. LPJ is run at a high spatial resolution of 0.5° and coupled to CLIMBER2 using the climate anomalies approach. Changes in land carbon storage as a response to changes in climate or atmospheric CO2 are therefore taken into account interactively at high spatial resolution. While it is easily possible to consider the influence of peat formation on the carbon cycle during the Holocene by using external scenarios of peat accumulation, this approach is not viable for previous interglacials. Most peat deposits accumulated during previous interglacials were decomposed in the course of glacial cycles, and we therefore have no estimates to base external scenarios on. In order to consider this forcing in models, it is therefore necessary to incorporate peat formation and decay into global models dynamically. Integrating peatland dynamics into dynamic global vegetation models is a challenge due to the coarse representation of the land surface in global models. Since wetland and therefore peatland extent often is substantially smaller than the model grid cells, the dynamic

  10. Carbon Quantum Dots and Their Derivative 3D Porous Carbon Frameworks for Sodium-Ion Batteries with Ultralong Cycle Life.

    PubMed

    Hou, Hongshuai; Banks, Craig E; Jing, Mingjun; Zhang, Yan; Ji, Xiaobo

    2015-12-16

    A new methodology for the synthesis of carbon quantum dots (CQDs) for large production is proposed. The as-obtained CQDs can be transformed into 3D porous carbon frameworks exhibiting superb sodium storage properties with ultralong cycle life and ultrahigh rate capability, comparable to state-of-the-art carbon anode materials for sodium-ion batteries.

  11. Hot carbon corona in Mars' upper thermosphere and exosphere: 2. Solar cycle and seasonal variability

    NASA Astrophysics Data System (ADS)

    Lee, Yuni; Combi, Michael R.; Tenishev, Valeriy; Bougher, Stephen W.

    2014-12-01

    This work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self-consistently the exosphere and the upper thermosphere, a 3-D kinetic particle simulator, the Adaptive Mesh Particle Simulator, and the 3-D Mars Thermosphere General Circulation Model are one-way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s-1 (AL) to 55.1 × 1023 s-1 (PL).

  12. Water and carbon cycling along the Sierra Nevada climate gradient

    NASA Astrophysics Data System (ADS)

    Kelly, A. E.; Goulden, M.; Meadows, M. W.; Bales, R. C.; Winston, G.

    2011-12-01

    Conifer forests dominate the western slope of the southern Sierra Nevada above 1000 m elevation. The climate of this region is Mediterranean, with hot dry summers and cool wet winters. The lower elevations of the conifer belt receive most precipitation as rain, while the upper elevations receive nearly all precipitation as snow. We have found that the differences in temperature and precipitation regime along the gradient affect interactions between water and carbon balance at seasonal and annual scales. Timing, degree of drought stress, and cold limitation along the western slope of the Sierra drive critical differences in biomass, productivity, carbon allocation, carbon turnover rates, seasonality of production, and seasonality and rates of evapotranspiration. We measured eddy covariance, weather, sap flux, biomass, productivity, and soil moisture at four sites along an elevation transect from 400 to 2700 m within the Southern Sierra Critical Zone Observatory (SSCZO). At lower elevations, summer drought and mild winters produce low biomass, high turnover, winter-productive forests. At high elevations, cold snowy winters and short mild summers produce low biomass, low turnover, summer-productive forests. At mid elevations, cool winters and warm summers produce high biomass forests, including giant sequoia groves, with a year-round growing season.

  13. High cycle life secondary lithium battery

    NASA Technical Reports Server (NTRS)

    Yen, Shiao-Ping S. (Inventor); Carter, Boyd J. (Inventor); Shen, David H. (Inventor); Somoano, Robert B. (Inventor)

    1985-01-01

    A secondary battery (10) of high energy density and long cycle is achieved by coating the separator (18) with a film (21) of cationic polymer such as polyvinyl-imidazoline. The binder of the positive electrode (14) such as an ethylene-propylene elastomer binder (26) containing particles (28) of TiS.sub.2 chalcogenide can also be modified to contain sulfone functional groups by incorporating liquid or solid sulfone materials such as 0.1 to 5 percent by weight of sulfolane into the binder. The negative lithium electrode (14), separator (18) and positive electrode (16) are preferably spirally wound and disposed within a sealed casing (17) containing terminals (32, 34). The modified separator and positive electrode are more wettable by the electrolytes in which a salt is dissolved in a polar solvent such as sulfolane.

  14. Land-atmosphere carbon cycle research in the southern Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Bowling, D. R.; Blanken, P.; Brooks, P. D.; Ehleringer, J. R.; Ewers, B. E.; Lehman, S.; Litvak, M. E.; Massman, W. J.; Miller, J. B.; Stephens, B. B.; Vaughn, B. H.

    2013-12-01

    The majority of land-atmosphere carbon exchange in the southern U.S. Rocky Mountains (Wyoming, Utah, Colorado, Arizona, and New Mexico) occurs in mid- to high-elevation forests, and in urban metropolitan areas. Forest-atmosphere carbon exchange is highly variable from year to year due to fluctuations in environmental conditions (particularly water availability) and following disturbances by insects and fire. A wide variety of long-term carbon cycle datasets from many locations are freely available to the scientific community from this region, varying in length from a few years to several decades. These include flask observations from the NOAA Cooperative Air Sampling Network (UTA, NWR, NWF, and BAO sites) which include CO2, CO2 stable and radioisotopes, CH4, and CO, continuous CO2 observations from the Rocky RACCOON mountaintop and Salt Lake Valley urban CO2 monitoring sites, forest flux observations from several AmeriFlux towers (GLEES, Niwot Ridge, and Valles Caldera sites), and continuous CO2 isotope observations (Niwot Ridge). Many of these sites include measurements before and after major ecological disturbances. This presentation will describe the publicly available datasets that exist, examining some of the features of these datasets that highlight the regional carbon cycle in the southern Rocky Mountains. Our goal is to encourage use and synthesis of these data by the observational, modeling, and remote sensing communities.

  15. Soils and Global Change in the Carbon Cycle over Geological Time

    NASA Astrophysics Data System (ADS)

    Retallack, G. J.

    2003-12-01

    sedimentary rocks; organic matter burial is an important long-term control on CO2 levels in the atmosphere (Berner and Kothavala, 2001). The magnitudes of carbon pools and fluxes involved provide a perspective on the importance of soils compared with other carbon reservoirs ( Figure 1). (6K)Figure 1. Pools and fluxes of reduced carbon (bold) and oxidized carbon (regular) in Gt in the pre-industrial carbon cycle (sources Schidlowski and Aharon, 1992; Siegenthaler and Sarmiento, 1993; Stallard, 1998). Before industrialization, there was only 600 Gt (1 Gt=1015g) of carbon in CO2 and methane in the atmosphere, which is about the same amount as in all terrestrial biomass, but less than half of the reservoir of soil organic carbon. The ocean contained only ˜3 Gt of biomass carbon. The deep ocean and sediments comprised the largest reservoir of bicarbonate and organic matter, but that carbon has been kept out of circulation from the atmosphere for geologically significant periods of time (Schidlowski and Aharon, 1992). Humans have tapped underground reservoirs of fossil fuels, and our other perturbations of the carbon cycle have also been significant ( Vitousek et al., 1997b; see Chapter 8.10).Atmospheric increase of carbon in CO2 to 750 Gt C by deforestation and fossil fuel burning has driven ongoing global warming, but is not quite balanced by changes in the other carbon reservoirs leading to search for a "missing sink" of some 1.8±1.3 GtC, probably in terrestrial organisms, soils, and sediments of the northern hemisphere (Keeling et al., 1982; Siegenthaler and Sarmiento, 1993; Stallard, 1998). Soil organic matter is a big, rapidly cycling reservoir, likely to include much of this missing sink.During the geological past, the sizes of, and fluxes between, these reservoirs have varied enormously as the world has alternated between greenhouse times of high carbon content of the atmosphere, and icehouse times of low carbon content of the atmosphere. Oscillations in the atmospheric

  16. Valley Formation on Early Mars Caused by Carbonate-Silicate Cycle-Induced Climate Cycling

    NASA Astrophysics Data System (ADS)

    Batalha, Natasha; Kopparapu, Ravi Kumar; Haqq-Misra, Jacob; Kasting, James

    2016-10-01

    For decades, scientists have tried to explain the evidence for fluvial activity on early Mars, but a consensus has yet to emerge regarding the mechanism for producing it. One hypothesis suggests early Mars was warmed by a thick greenhouse atmosphere. Another suggests early Mars was generally cold but was warmed occasionally by impacts or by episodes of enhanced volcanism. These latter hypotheses struggle to produce the amounts of rainfall needed to form the martian valleys, but are consistent with inferred low rates of weathering compared to Earth. We suggest that both schools of thought are partly correct. Mars experienced dramatic climate cycles with extended periods of glaciation punctuated by warm periods lasting up to 10 Myr. Cycles of repeated glaciation and deglaciation occurred because stellar insolation was low, and because CO2 outgassing could not keep pace with CO2 consumption by silicate weathering followed by deposition of carbonates. In order to deglaciate early Mars , substantial outgassing of molecular hydrogen from Mars' reduced crust and mantle was also required. Our hypothesis can be tested by future Mars exploration that better establishes the time scale for valley formation.

  17. Long-term calcination/carbonation cycling and thermal pretreatment for CO{sub 2} capture by limestone and dolomite

    SciTech Connect

    Zhongxiang Chen; Hoon Sub Song; Miguel Portillo; C. Jim Lim; John R. Grace; E.J. Anthony

    2009-03-15

    Capturing carbon dioxide is vital for the future of climate-friendly combustion, gasification, and steam-re-forming processes. Dry processes utilizing simple sorbents have great potential in this regard. Long-term calcination/carbonation cycling was carried out in an atmospheric-pressure thermogravimetric reactor. Although dolomite gave better capture than limestone for a limited number of cycles, the advantage declined over many cycles. Under some circumstances, decreasing the carbonation temperature increased the rate of reaction because of the interaction between equilibrium and kinetic factors. Limestone and dolomite, after being pretreated thermally at high temperatures (1000 or 1100{sup o}C), showed a substantial increase in calcium utilization over many calcination/carbonation cycles. Lengthening the pretreatment interval resulted in greater improvement. However, attrition was significantly greater for the pretreated sorbents. Greatly extending the duration of carbonation during one cycle was found to be capable of restoring the CO{sub 2} capture ability of sorbents to their original behavior, offering a possible means of countering the long-term degradation of calcium sorbents for dry capture of carbon dioxide. 12 refs., 12 figs., 2 tabs.

  18. Non-Redfield carbon and nitrogen cycling in the Arctic: Effects of ecosystem structure and dynamics

    NASA Astrophysics Data System (ADS)

    Daly, Kendra L.; Wallace, Douglas W. R.; Smith, Walker O.; Skoog, Annelie; Lara, RubéN.; Gosselin, Michel; Falck, Eva; Yager, Patricia L.

    1999-02-01

    The C:N ratio is a critical parameter used in both global ocean carbon models and field studies to understand carbon and nutrient cycling as well as to estimate exported carbon from the euphotic zone. The so-called Redfield ratio (C:N = 6.6 by atoms) [Redfield et al., 1963] is widely used for such calculations. Here we present data from the NE Greenland continental shelf that show that most of the C:N ratios for particulate (autotrophic and heterotrophic) and dissolved pools and rates of transformation among them exceed Redfield proportions from June to August, owing to species composition, size, and biological interactions. The ecosystem components that likely comprised sinking particles and had relatively high C:N ratios (geometric means) included (1) the particulate organic matter (C:N = 8.9) dominated by nutrient-deficient diatoms, resulting from low initial nitrate concentrations (approximately 4 μM) in Arctic surface waters; (2) the dominant zooplankton, herbivorous copepods (C:N = 9.6), having lipid storage typical of Arctic copepods; and (3) copepod fecal pellets (C:N = 33.2). Relatively high dissolved organic carbon concentrations (median 105 μM) were approximately 25 to 45 μM higher than reported for other systems and may be broadly characteristic of Arctic waters. A carbon-rich dissolved organic carbon pool also was generated during summer. Since the magnitude of carbon and nitrogen uncoupling in the surface mixed layer appeared to be greater than in other regions and occurred throughout the productive season, the C:N ratio of particulate organic matter may be a better conversion factor than the Redfield ratio to estimate carbon export for broad application in northern high-latitude systems.

  19. Possible roles of uncultured archaea in carbon cycling in methane-seep sediments

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Marcos Y.; Lazar, Cassandre S.; Elvert, Marcus; Lin, Yu-Shih; Zhu, Chun; Heuer, Verena B.; Teske, Andreas; Hinrichs, Kai-Uwe

    2015-09-01

    Studies on microbial carbon cycling uniformly confirm that anaerobic methane-oxidizing archaea (ANME) and sulfate-reducing bacteria represent the dominant and most active fraction of the sedimentary microbial community in methane-seep sediments. However, little is known about other frequently observed and abundant microbial taxa, their role in carbon cycling and association with the anaerobic oxidation of methane (AOM). Here, we provide a comprehensive characterization of stable carbon isotopes (δ13C) from several intact polar lipid (IPL) classes and metabolite pools in a downcore profile at a cold seep within the oxygen minimum zone off Pakistan. We aimed to evaluate microbial carbon metabolism using IPLs in relation to redox conditions, metabolites and 16S rRNA gene libraries. The 13C-depleted signature of carbon pools and microbial metabolites in pore waters (e.g., dissolved inorganic carbon, lactate and acetate) demonstrated high accumulation of AOM-associated biomass and subsequent turnover thereof. ANMEs accounted for a small fraction of the archaeal 16S rRNA gene survey, whereas sequences of other uncultured benthic archaea dominated the clone libraries, particularly the Marine Benthic Group D. On the basis of lipid diversity and carbon isotope information, we suggest that structurally diverse phospho- and glycolipids, including the recently identified unsaturated tetraethers that are particularly abundant in this setting, are likely derived from archaea other than ANMEs. Through the evaluation of δ13C values of individual IPL, our results indicate heterotrophy as a possible metabolic pathway of archaea in these AOM-dominated sediments.

  20. Carbon and nitrogen cycles in European ecosystems respond differently to global warming.

    PubMed

    Beier, C; Emmett, B A; Peñuelas, J; Schmidt, I K; Tietema, A; Estiarte, M; Gundersen, P; Llorens, L; Riis-Nielsen, T; Sowerby, A; Gorissen, A

    2008-12-15

    The global climate is predicted to become significantly warmer over the next century. This will affect ecosystem processes and the functioning of semi natural and natural ecosystems in many parts of the world. However, as various ecosystem processes may be affected to a different extent, balances between different ecosystem processes as well as between different ecosystems may shift and lead to major unpredicted changes. In this study four European shrubland ecosystems along a north-south temperature gradient were experimentally warmed by a novel nighttime warming technique. Biogeochemical cycling of both carbon and nitrogen was affected at the colder sites with increased carbon uptake for plant growth as well as increased carbon loss through soil respiration. Carbon uptake by plant growth was more sensitive to warming than expected from the temperature response across the sites while carbon loss through soil respiration reacted to warming in agreement with the overall Q10 and response functions to temperature across the sites. Opposite to carbon, the nitrogen mineralization was relatively insensitive to the temperature increase and was mainly affected by changes in soil moisture. The results suggest that C and N cycles respond asymmetrically to warming, which may lead to progressive nitrogen limitation and thereby acclimation in plant production. This further suggests that in many temperate zones nitrogen deposition has to be accounted for, not only with respect to the impact on water quality through increased nitrogen leaching where N deposition is high, but also in predictions of carbon sequestration in terrestrial ecosystems under future climatic conditions. Finally the results indicate that on the short term the above-ground processes are more sensitive to temperature changes than the below ground processes.

  1. Improving the Modelled Global Terrestrial Carbon Cycle by Assimilating CO2 Mole Fractions and FAPAR with the MPI Carbon Cycle Data Assimilation System (MPI-CCDAS)

    NASA Astrophysics Data System (ADS)

    Schürmann, Gregor; Köstler, Christoph; Kaminski, Thomas; Giering, Ralf; Scholze, Marko; Kattge, Jens; Carvalhais, Nuno; Voßbeck, Michael; Rödenbeck, Christian; Reick, Christian; Zaehle, Sönke

    2015-04-01

    Long-term monitoring of ecosystem carbon fluxes and atmospheric CO2 concentrations provides independent observations of the land's carbon balance at different scales. However, the scale-gap between these observations makes a direct quantification of regional carbon balances based on these data impossible. Here, we describe first results of the MPI Carbon Cycle Data Assimilation System (MPI-CCDAS), designed to use multiple data streams at different scales to constrain parameters in the biosphere model JSBACH. We constrain the MPI-CCDAS with two complementary data-streams: CO2 mole fractions observed at a network of atmospheric monitoring stations, and remotely-sensed fraction of absorbed photosynthetically active radiation (TIP-FAPAR). The assimilation procedure greatly improves the representation of the seasonal cycle of atmospheric CO2, and reduces the global gross primary productivity (GPP) from 160 PgC/year to 118 PgC/year. Applying the MPI-CCDAS separately and jointly on both data streams allows to analyse the contribution of each data stream to the improved global carbon cycle model. Evaluation against independent carbon cycle estimates based on upscaled ecosystem flux measurements corroborates the adequacy of the model improvements, and demonstrates the utility of the CCDAS framework in consistently integrating carbon cycle data.

  2. Hierarchical porous carbon by ultrasonic spray pyrolysis yields stable cycling in lithium-sulfur battery.

    PubMed

    Jung, Dae Soo; Hwang, Tae Hoon; Lee, Ji Hoon; Koo, Hye Young; Shakoor, Rana A; Kahraman, Ramazan; Jo, Yong Nam; Park, Min-Sik; Choi, Jang Wook

    2014-08-13

    Utilizing the unparalleled theoretical capacity of sulfur reaching 1675 mAh/g, lithium-sulfur (Li-S) batteries have been counted as promising enablers of future lithium ion battery (LIB) applications requiring high energy densities. Nevertheless, most sulfur electrodes suffer from insufficient cycle lives originating from dissolution of lithium polysulfides. As a fundamental solution to this chronic shortcoming, herein, we introduce a hierarchical porous carbon structure in which meso- and macropores are surrounded by outer micropores. Sulfur was infiltrated mainly into the inner meso- and macropores, while the outer micropores remained empty, thus serving as a "barricade" against outward dissolution of long-chain lithium polysulfides. On the basis of this systematic design, the sulfur electrode delivered 1412 mAh/g sulfur with excellent capacity retention of 77% after 500 cycles. Also, a control study suggests that even when sulfur is loaded into the outer micropores, the robust cycling performance is preserved by engaging small sulfur crystal structures (S2-4). Furthermore, the hierarchical porous carbon was produced in ultrahigh speed by scalable spray pyrolysis. Each porous carbon particle was synthesized through 5 s of carrier gas flow in a reaction tube.

  3. The role of peatlands in interglacial Carbon cycle dynamics - a modelling perspective

    NASA Astrophysics Data System (ADS)

    Kleinen, Thomas; Brovkin, Victor

    2010-05-01

    Arctic and Boreal peatlands cover about 3% of the Earth's land surface area only, but they contain substantial amounts of carbon. Estimates of peat accumulated during the Holocene reach up to 450 GtC. On longer timescales the carbon uptake by peatlands therefore becomes a cumulative flux of substantial magnitude, though it is rather small if one considers the short timescales only. We will present results showing the influence of the carbon uptake by peatlands on Holocene CO2 concentrations. Using the coupled climate carbon cycle model CLIMBER2-LPJ we are considering all natural factors influencing the atmospheric CO2 concentration, including carbon uptake by peatlands. CLIMBER2 is a climate model of intermediate complexity, containing a dynamic atmosphere and ocean, as well as sea ice and land surface modules. Its coarse spatial resolution leads to a high computational efficiency, which allows long-term transient integrations of the coupled model. Land carbon dynamics are computed using the dynamic global vegetation model LPJ. LPJ is run at a high spatial resolution of 0.5° and coupled to CLIMBER2 using the climate anomalies approach. Changes in land carbon storage as a response to changes in climate or atmospheric CO2 are therefore taken into account interactively at high spatial resolution. While it is easily possible to consider the influence of peat formation on the carbon cycle during the Holocene by using external scenarios of peat accumulation, this approach is not viable for previous interglacials. Most peat deposits accumulated during previous interglacials were removed in the course of glaciation, and we therefore have no estimates to base external scenarios on. In order to consider this forcing in models, it is therefore necessary to incorporate peat formation into global models dynamically. Integrating peatland dynamics into dynamic global vegetation models is a non-trivial problem due to the coarse representation of the land surface. Since wetland

  4. Constraining future terrestrial carbon cycle projections using observation-based water and carbon flux estimates.

    PubMed

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

    2016-06-01

    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 in the projected GPP and to a ca. 50% reduction in 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. Moreover, 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. This indicates 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 in the atmospheric CO2 concentration and for future climate change.

  5. Closing the carbon cycle through rational use of carbon-based fuels.

    PubMed

    MacElroy, J M Don

    2016-01-01

    In this paper, a brief overview is presented of natural gas as a fuel resource with subsequent carbon capture and re-use as a means to facilitate reduction and eventual elimination of man-made carbon emissions. A particular focus is shale gas and, to a lesser extent, methane hydrates, with the former believed to provide the most reasonable alternative as a transitional fuel toward a low-carbon future. An emphasis is placed on the gradual elimination of fossil resource usage as a fuel over the coming 35 to 85 years and its eventual replacement with renewable resources and nuclear power. Furthermore, it is proposed that synthesis of chemical feedstocks from recycled carbon dioxide and hydrogen-rich materials should be undertaken for specific applications in the transport sector which require access to high energy density fuels. To achieve the latter, carbon dioxide capture is imperative and possible synthetic routes for chemical feedstock production are briefly reviewed.

  6. The effects of climate sensitivity and carbon cycle interactions on mitigation policy stringency

    EPA Science Inventory

    Climate sensitivity and climate-carbon cycle feedbacks interact to determine how global carbon and energy cycles will change in the future. While the science of these connections is well documented, their economic implications are not well understood. Here we examine the effect o...

  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. 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.

  9. Capturing and sequestering carbon by enhancing the natural carbon cycle: Prelimary identification of basic science needs and opportunities

    SciTech Connect

    Benson, S.M.

    1997-07-01

    This document summarizes proceedings and conclusions of a US DOE workshop. The purpose of the workshop was to identify the underlying research needed to answer the following questions: (1) Can the natural carbon cycle be used to aid in stabilizing or decreasing atmospheric CO{sub 2} and CH{sub 4} by: (a) Increasing carbon capture; (b) Preventing carbon from returning to the atmosphere through intermediate (<100 years) to long-term sequestration (> 100 years)?; and (2) What kind of ecosystem management practices could be used to achieve this? Three working groups were formed to discuss the terrestrial biosphere, oceans, and methane. Basic research needs identified included fundamental understanding of carbon cycling and storage in soils, influence of climate change and anthropogenic emissions on the carbon cycle, and carbon capture and sequestration in oceans. 2 figs., 4 tabs.

  10. 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

  11. Potential for progress in carbon cycle modeling: models as tools and representations of reality (Invited)

    NASA Astrophysics Data System (ADS)

    Caldeira, K.

    2013-12-01

    Some carbon cycle modelers conceive of themselves as developing a representation of reality that will serve as a general purpose tool that can be used to make a wide variety of predictions. However, models are tools used to solve particular problems. If we were to ask, 'what tool is best for fastening two pieces of wood together,' depending on the circumstances that tool could be hammer, a screw driver, or perhaps some sort of glue gun. And the best kind of screw driver might depend on whether we were thinking about Philips or flat headed screws. If there is no unique answer to the question of which type of tool is best for fastening two pieces of wood together, surely there is no unique answer to the question of which type of model is best for making carbon-cycle predictions. We must first understand what problem we are trying to solve. Some modeling studies try to make the most reliable projections, considering as many processes and predicting as many observables as possible, whereas other modeling studies try to show how general trends depend on relatively few (perhaps highly aggregated) processes. This talk will look at CMIP5 carbon-cycle model results and address the issue of the extent to which the overall global-scale trends projected by these detailed models might projected by models with many fewer degrees of freedom. It should be noted that an ocean carbon-cycle model that predicts many observables at local scale is much more easily falsified (and thus in some sense is more ';scientific') than an ocean model that predicts only global scale phenomena. Nevertheless, if all that is needed is a crude estimate of global ocean CO2 uptake (say, to permit as study of the carbon-cycle on land), a simple representation of the ocean carbon cycle may suffice. This talk will take as its jumping off point two quotes: 'All models are wrong, some are useful.' - George E.P. Box 'Models should be as simple as possible but no simpler.' - Albert Einstein (likely an erroneous

  12. Seasonal patterns of photosynthetic capacity: photoperiodic control and its carbon cycling implications

    NASA Astrophysics Data System (ADS)

    Bauerle, W.; Oren, R.; Way, D.; Qian, S.; Stoy, P. C.; Thornton, P. E.; Bowden, J.; Hoffman, F. M.; Reynolds, R.

    2012-12-01

    While temperature is an important driver of seasonal changes in photosynthetic physiology, photoperiod also regulates leaf activity. Climate change will extend growing seasons if temperature cues predominate, but photoperiod-controlled species will show limited responsiveness to warming. We show that photoperiod explains more seasonal variation in photosynthetic activity across 23 tree species than temperature. Although leaves remain green, photosynthetic capacity peaks just after summer solstice and declines with decreasing photoperiod, before air temperatures peak. In support of these findings, saplings grown at constant temperature, but exposed to an extended photoperiod maintained high photosynthetic capacity, while photosynthetic activity declined in saplings experiencing a naturally shortening photoperiod; leaves remained equally green in both treatments. Incorporating a photoperiodic correction of photosynthetic physiology into a global-scale terrestrial carbon cycle model significantly improves predictions of seasonal atmospheric CO2 cycling, demonstrating the benefit of such a function in coupled climate system models. Accounting for photoperiod-induced seasonality in photosynthetic parameters reduces modeled global gross primary production ~4 PgC y-1, resulting in a ~2 PgC y-1 decrease of net primary production. Such a correction is also needed in models estimating current carbon uptake based on remotely-sensed greenness. Photoperiod-associated declines in photosynthetic capacity could limit autumn carbon gain in forests, even if warming delays leaf senescence. Assessments of late season carbon sequestration under a changing climate should focus on potential adverse impacts of warming via increased ecosystem respiration.

  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. Isothermal microcalorimetry provides new insight into terrestrial carbon cycling.

    PubMed

    Herrmann, Anke M; Coucheney, Elsa; Nunan, Naoise

    2014-04-15

    Energy is continuously transformed in environmental systems through the metabolic activities of living organisms, but little is known about the relationship between the two. In this study, we tested the hypothesis that microbial energetics are controlled by microbial community composition in terrestrial ecosystems. We determined the functional diversity profiles of the soil biota (i.e., multiple substrate-induced respiration and microbial energetics) in soils from an arable ecosystem with contrasting long-term management regimes (54 years). These two functional profiling methods were then related to the soils' microbial community composition. Using isothermal microcalorimetry, we show that direct measures of energetics provide a functional link between energy flows and the composition of below-ground microbial communities at a high taxonomic level (Mantel R = 0.4602, P = 0.006). In contrast, this link was not apparent when carbon dioxide (CO2) was used as an aggregate measure of microbial metabolism (Mantel R = 0.2291, P = 0.11). Our work advocates that the microbial energetics approach provides complementary information to soil respiration for investigating the involvement of microbial communities in below-ground carbon dynamics. Empirical data of our proposed microbial energetics approach can feed into carbon-climate based ecosystem feedback modeling with the suggested conceptual ecological model as a base.

  15. Monolith catalysts for closed-cycle carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.

    1994-01-01

    The general subject area of the project involved the development of solid catalysts that have high activity at low temperature for the oxidation of gases such as CO. The original application considered was CO oxidation in closed-cycle CO2 lasers. The scope of the project was subsequently extended to include oxidation of gases in addition to CO and applications such as air purification and exhaust gas emission control. The primary objective of the final phase grant was to develop design criteria for the formulation of new low-temperature oxidation catalysts utilizing Monte Carlo simulations of reaction over NASA-developed catalysts.

  16. Abundance, Distribution and Cycling of Organic Carbon and Nitrogen in University Valley (McMurdo Dry Valleys of Antarctica) Permafrost Soils with Differing Ground Thermal and Moisture Conditions: Analogue to C-N Cycle on Mars

    NASA Astrophysics Data System (ADS)

    Faucher, B. F.; Lacelle, D. L.; Davila, A. D.; Pollard, W. P.; McKay, C. P. M.

    2016-05-01

    High elevation McMurdo Dry Valleys of Antarctica are key Mars analogue sites. Our investigation focuses on the link between ground ice origin, distribution and cycling of organic carbon and nitrogen in University Valley, and its soil habitability.

  17. Integrating Natural Gas Hydrates in the Global Carbon Cycle

    SciTech Connect

    David Archer; Bruce Buffett

    2011-12-31

    We produced a two-dimensional geological time- and basin-scale model of the sedimentary margin in passive and active settings, for the simulation of the deep sedimentary methane cycle including hydrate formation. Simulation of geochemical data required development of parameterizations for bubble transport in the sediment column, and for the impact of the heterogeneity in the sediment pore fluid flow field, which represent new directions in modeling methane hydrates. The model is somewhat less sensitive to changes in ocean temperature than our previous 1-D model, due to the different methane transport mechanisms in the two codes (pore fluid flow vs. bubble migration). The model is very sensitive to reasonable changes in organic carbon deposition through geologic time, and to details of how the bubbles migrate, in particular how efficiently they are trapped as they rise through undersaturated or oxidizing chemical conditions and the hydrate stability zone. The active margin configuration reproduces the elevated hydrate saturations observed in accretionary wedges such as the Cascadia Margin, but predicts a decrease in the methane inventory per meter of coastline relative to a comparable passive margin case, and a decrease in the hydrate inventory with an increase in the plate subduction rate.

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

    PubMed

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

    2016-02-02

    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.

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

    PubMed Central

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

    2016-01-01

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

  20. Examination of hypotheses for the Permo-Triassic boundary extinction by carbon cycle modeling.

    PubMed

    Berner, Robert A

    2002-04-02

    The biological extinction that occurred at the Permian-Triassic boundary represents the most extensive loss of species of any known event of the past 550 million years. There have been a wide variety of explanations offered for this extinction. In the present paper, a number of the more popular recent hypotheses are evaluated in terms of predictions that they make, or that they imply, concerning the global carbon cycle. For this purpose, a mass balance model is used that calculates atmospheric CO2 and oceanic delta13C as a function of time. Hypotheses considered include: (i) the release of massive amounts of CO2 from the ocean to the atmosphere resulting in mass poisoning; (ii) the release of large amounts of CO2 from volcanic degassing; (iii) the release of methane stored in methane hydrates; (iv) the decomposition and oxidation of dead organisms to CO2 after sudden mass mortality; and (v) the long-term reorganization of the global carbon cycle. The modeling indicates that measured short-term changes in delta13C at the boundary are best explained by methane release with mass mortality and volcanic degassing contributing in secondary roles. None of the processes result in excessively high levels of atmospheric CO2 if they occurred on time scales of more than about 1,000 years. The idea of poisoning by high levels of atmospheric CO2 depends on the absence of subthermocline calcium carbonate deposition during the latest Permian. The most far-reaching effect was found to be reorganization of the carbon cycle with major sedimentary burial of organic matter shifting from the land to the sea, resulting in less burial overall, decreased atmospheric O2, and higher atmospheric CO2 for the entire Triassic Period.

  1. 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.

  2. 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).

  3. Impacts of the Central Atlantic Magmatic Province on the Terrestrial Carbon Cycle in Western Pangea

    NASA Astrophysics Data System (ADS)

    Knobbe, T.; Suarez, C. A.

    2014-12-01

    Carbon isotope analysis of bulk organic and inorganic carbon preserved in the lacustrine deposits of the late Triassic to Jurassic Moenave Formation were analyzed to construct a carbon isotope chemostratigraphic profile of western Pangea. Negative carbon isotope excursions (NCIE) are characteristic of the Late Triassic and are attributed to the effects of the Central Atlantic Magmatic Province (CAMP) on climate and the global C-cycle. The aerial extent of the CAMP basalts is the largest in Earth's history spanning four continents with an area of ~ 7 x 106 km2 and a volume of 3 to 11 x 106 km3. Carbon isotope and paleontological evidence has shown that the end Triassic extinction is near synchronous to the CAMP and likely spurred on the extinction event as well as an increase in global temperatures of 2 - 2.5°C. Global correlations of NCIEs between marine and terrestrial strata provide a connection between the CAMP basalts and the end-Triassic extinction. Preliminary data collected at Potter Canyon, Arizona reveal a 5.5 ‰ decrease in δ13Corganic and a 2.75‰ decrease in δ13Ccarbonate in the lower portion of the Whitmore Point Member. These NCIEs indicate the global carbon cycle perturbation caused by the CAMP is recorded in lacustrine sediments of the Whitmore Point Member in southern Utah and northern Arizona. Additional samples collected at high sampling frequencies at other locations in the Whitmore Point Member will corroborate the terrestrial impacts of the CAMP perturbation at these locations across the region. Correlation of NCIES associated with the CAMP and any identified microfossils of the Whitmore Point Member will also illustrate the global effects of increased atmospheric CO2 on the terrestrial environment and biota.

  4. Astronomical constraints on global carbon-cycle perturbation during Oceanic Anoxic Event 2 (OAE2)

    NASA Astrophysics Data System (ADS)

    Li, Yong-Xiang; Montañez, Isabel P.; Liu, Zhonghui; Ma, Lifeng

    2017-03-01

    Oceanic Anoxic Event 2 (OAE2) was a major disturbance in global carbon cycling and transient climate disruption, triggered by a pulse of volcanic CO2. Although this well-studied perturbation to the ocean-atmosphere system offers a unique opportunity to better understand abrupt climate change in response to CO2-forcing, the origin, evolution and duration of the event are still debated due in large part to the temporal resolution of existing OAE2 records and uncertainty over the duration of the overall perturbation and C cycle shifts within it. Here we report coupled magnetic susceptibility (MS) and carbon-isotope time-series of ∼2.5 to 5 ± 0.5kyr resolution from an expanded OAE2 interval from southern Tibet, China. MS cyclicity indicates short eccentricity modulation, permitting the construction of a high-precision orbital timescale which, when integrated with the high resolution δ13Ccarb record, fully constrains the timing and nature of onset through recovery of OAE2, revealing finer-scale structure than previously recognized. Abrupt coupled shifts in δ13Ccarb and MS, and changing phase relationships in-step with transitions between high and low long eccentricity, indicate orbitally linked changes in marine carbon cycling and monsoon dynamics superimposed on repeated wholesale oceanographic changes. In particular, the high-resolution Tibetan record reveals dynamic shifts in the phasing relationship of MS and δ13 C, which suggests that the initiation of ocean anoxia was probably not orbitally forced. This finding is in sharp contrast with the paradigm of orbitally forced ocean anoxia. Conversely, the new record suggests that termination of anoxia was likely orbitally forced and superimposed on a dramatic oceanographic change.

  5. Carbon Cycle 2.0: Don DePaolo: Geo and Bio Sequestration

    ScienceCinema

    Don DePaolo:

    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.

  6. Carbon Cycle 2.0: Ramamoorthy Ramesh: Low-cost Solar

    ScienceCinema

    Ramamoorthy Ramesh:

    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.

  7. The effect of compost on carbon cycling in soil

    NASA Astrophysics Data System (ADS)

    Singer, E.; Woyke, T.

    2013-12-01

    Rangelands cover an estimated 40-70% of global landmass, approximately one-third of the landmass of the United States and half of California. The soils of this vast land area has high carbon (C) storage capacity, which makes it an important target ecosystem for the mitigation of greenhouse gas emission and effects on climate change, in particular under land management techniques that favor increased C sequestration rates. While microbial communities are key players in the processes responsible for C storage and loss in soils, we have barely shed light on these highly complex processes in part due to the tremendous and seemingly intractable diversity of microbes, largely uncultured, that inhabit soil ecosystems. In our study, we compare Mediterranean grassland soil plots that were amended with greenwaste of various C:N ratios and biochar in a single event. Monthly subsampling of control and amended plots over the course of three months was performed in depth increments of 0-12 cm and 12-24 cm. We present data on greenhouse gas emissions and budgets of carbon, nitrogen, phosphorus, and micronutrients in dependence of amendment types and seasonality. Changes in the active members of the soil microbial community were assessed using a novel approach combining flow cytometry and metagenomic sequencing disclosing 'who does what'. This is the first study revealing the nature of actively metabolizing microbial community members linked to the geochemical characteristics of compost-amended soil.

  8. A Natural Light/Dark Cycle Regulation of Carbon-Nitrogen Metabolism and Gene Expression in Rice Shoots.

    PubMed

    Li, Haixing; Liang, Zhijun; Ding, Guangda; Shi, Lei; Xu, Fangsen; Cai, Hongmei

    2016-01-01

    Light and temperature are two particularly important environmental cues for plant survival. Carbon and nitrogen are two essential macronutrients required for plant growth and development, and cellular carbon and nitrogen metabolism must be tightly coordinated. In order to understand how the natural light/dark cycle regulates carbon and nitrogen metabolism in rice plants, we analyzed the photosynthesis, key carbon-nitrogen metabolites, and enzyme activities, and differentially expressed genes and miRNAs involved in the carbon and nitrogen metabolic pathway in rice shoots at the following times: 2:00, 6:00, 10:00, 14:00, 18:00, and 22:00. Our results indicated that more CO2 was fixed into carbohydrates by a high net photosynthetic rate, respiratory rate, and stomatal conductance in the daytime. Although high levels of the nitrate reductase activity, free ammonium and carbohydrates were exhibited in the daytime, the protein synthesis was not significantly facilitated by the light and temperature. In mRNA sequencing, the carbon and nitrogen metabolism-related differentially expressed genes were obtained, which could be divided into eight groups: photosynthesis, TCA cycle, sugar transport, sugar metabolism, nitrogen transport, nitrogen reduction, amino acid metabolism, and nitrogen regulation. Additionally, a total of 78,306 alternative splicing events have been identified, which primarily belong to alternative 5' donor sites, alternative 3' acceptor sites, intron retention, and exon skipping. In sRNA sequencing, four carbon and nitrogen metabolism-related miRNAs (osa-miR1440b, osa-miR2876-5p, osa-miR1877 and osa-miR5799) were determined to be regulated by natural light/dark cycle. The expression level analysis showed that the four carbon and nitrogen metabolism-related miRNAs negatively regulated their target genes. These results may provide a good strategy to study how natural light/dark cycle regulates carbon and nitrogen metabolism to ensure plant growth and

  9. Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

    NASA Astrophysics Data System (ADS)

    Smith, S. V.; Gattuso, J.-P.

    2009-07-01

    Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3- to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3- and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle. While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2 over time, which leads to ocean acidification, alters the relationship between organic and inorganic C reactions and carbon storage in the ocean. Thus, the carbon reactions and ψ can cause large variations in oceanic carbon storage with little exchange with the atmosphere.

  10. High Temperature Carbonized Grass as a High Performance Sodium Ion Battery Anode.

    PubMed

    Zhang, Fang; Yao, Yonggang; Wan, Jiayu; Henderson, Doug; Zhang, Xiaogang; Hu, Liangbing

    2017-01-11

    Hard carbon is currently considered the most promising anode candidate for room temperature sodium ion batteries because of its relatively high capacity, low cost, and good scalability. In this work, switchgrass as a biomass example was carbonized under an ultrahigh temperature, 2050 °C, induced by Joule heating to create hard carbon anodes for sodium ion batteries. Switchgrass derived carbon materials intrinsically inherit its three-dimensional porous hierarchical architecture, with an average interlayer spacing of 0.376 nm. The larger interlayer spacing than that of graphite allows for the significant Na ion storage performance. Compared to the sample carbonized under 1000 °C, switchgrass derived carbon at 2050 °C induced an improved initial Coulombic efficiency. Additionally, excellent rate capability and superior cycling performance are demonstrated for the switchgrass derived carbon due to the unique high temperature treatment.

  11. 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

  12. Deciphering Complex Carbon Cycle Changes Across the K-Pg Boundary Using Compound-Specific Carbon Isotopic Analyses

    NASA Astrophysics Data System (ADS)

    Pancost, R. D.; Taylor, K. W.; Hollis, C. J.; Crouch, E. M.

    2014-12-01

    The consequences of the Cretaceous-Paleogene (K/Pg) boundary event on the Earth system have been the subject of much scrutiny. Postulated climate events include a brief (10 - 2000 yr) period of global cooling induced by sulphate aerosols (the so-called 'impact winter'), an interval of warming caused by impact-induced CO2release, as well as longer-term climatic oscillations during the subsequent 1 to 3Myr. Associated with these were putative changes in the biogeochemical cycle, manifested as carbon isotope excursions on both short- and long-term timescales. In this study we develop new biomarker-based climate and biogeochemical records for the mid-Waipara River and Branch Stream sections, NZ. At Branch Stream, a pronounced negative (ca 6 to 8 permil) carbon isotope excursion occurs at the K/Pg; the excursion is recorded by higher plant biomarkers, consistent with some terrestrial records and suggesting that the immediate aftermath of the K/Pg boundary event was characterised by the massive release of 13C-depleted reduced carbon into the ocean-atmosphere reservoir. Mixing across the K/Pg boundary at the Waipara section precludes a similar high-resolution investigation. Lower-resolution, longer-term records, however, also reveal a negative carbon istope excursion documented by both algal and higher plant biomarkers. This event appears to be distinct from that recorded at Branch Stream, being of lower magnitude and longer duration. It coincided with a transient terrestrial and marine warming and appears to have lasted at least 100 kyr and perhaps longer. We argue that this protracted negative CIE reflects a secondary and longer-term consequence of the K/Pg on the global carbon cycle. There is little evidence for an algal extinction as a range of C27 to C30 sterols continued to be deposited throughout the entire section, but changes in GDGT distributions do suggest a change in carbon export dynamics which could have impacted burial of 13C-depleted marine organic matter

  13. Sulfate-Reducing Microorganisms in Wetlands – Fameless Actors in Carbon Cycling and Climate Change

    PubMed Central

    Pester, Michael; Knorr, Klaus-Holger; Friedrich, Michael W.; Wagner, Michael; Loy, Alexander

    2012-01-01

    Freshwater wetlands are a major source of the greenhouse gas methane but at the same time can function as carbon sink. Their response to global warming and environmental pollution is one of the largest unknowns in the upcoming decades to centuries. In this review, we highlight the role of sulfate-reducing microorganisms (SRM) in the intertwined element cycles of wetlands. Although regarded primarily as methanogenic environments, biogeochemical studies have revealed a previously hidden sulfur cycle in wetlands that can sustain rapid renewal of the small standing pools of sulfate. Thus, dissimilatory sulfate reduction, which frequently occurs at rates comparable to marine surface sediments, can contribute up to 36–50% to anaerobic carbon mineralization in these ecosystems. Since sulfate reduction is thermodynamically favored relative to fermentative processes and methanogenesis, it effectively decreases gross methane production thereby mitigating the flux of methane to the atmosphere. However, very little is known about wetland SRM. Molecular analyses using dsrAB [encoding subunit A and B of the dissimilatory (bi)sulfite reductase] as marker genes demonstrated that members of novel phylogenetic lineages, which are unrelated to recognized SRM, dominate dsrAB richness and, if tested, are also abundant among the dsrAB-containing wetland microbiota. These discoveries point toward the existence of so far unknown SRM that are an important part of the autochthonous wetland microbiota. In addition to these numerically dominant microorganisms, a recent stable isotope probing study of SRM in a German peatland indicated that rare biosphere members might be highly active in situ and have a considerable stake in wetland sulfate reduction. The hidden sulfur cycle in wetlands and the fact that wetland SRM are not well represented by described SRM species explains their so far neglected role as important actors in carbon cycling and climate change. PMID:22403575

  14. Developing a data life cycle for carbon and greenhouse gas measurements: challenges, experiences and visions

    NASA Astrophysics Data System (ADS)

    Kutsch, W. L.

    2015-12-01

    Environmental research infrastructures and big data integration networks require common data policies, standardized workflows and sophisticated e-infrastructure to optimise the data life cycle. This presentation summarizes the experiences in developing the data life cycle for the Integrated Carbon Observation System (ICOS), a European Research Infrastructure. It will also outline challenges that still exist and visions for future development. As many other environmental research infrastructures ICOS RI built on a large number of distributed observational or experimental sites. Data from these sites are transferred to Thematic Centres and quality checked, processed and integrated there. Dissemination will be managed by the ICOS Carbon Portal. This complex data life cycle has been defined in detail by developing protocols and assigning responsibilities. Since data will be shared under an open access policy there is a strong need for common data citation tracking systems that allow data providers to identify downstream usage of their data so as to prove their importance and show the impact to stakeholders and the public. More challenges arise from interoperating with other infrastructures or providing data for global integration projects as done e.g. in the framework of GEOSS or in global integration approaches such as fluxnet or SOCAt. Here, common metadata systems are the key solutions for data detection and harvesting. The metadata characterises data, services, users and ICT resources (including sensors and detectors). Risks may arise when data of high and low quality are mixed during this process or unexperienced data scientists without detailed knowledge on the data aquisition derive scientific theories through statistical analyses. The vision of fully open data availability is expressed in a recent GEO flagship initiative that will address important issues needed to build a connected and interoperable global network for carbon cycle and greenhouse gas

  15. The HIPPO Project Archive: Carbon Cycle and Greenhouse Gas Data

    NASA Astrophysics Data System (ADS)

    Christensen, S. W.; Aquino, J.; Hook, L.; Williams, S. F.

    2012-12-01

    The HIAPER (NSF/NCAR Gulfstream V Aircraft) Pole-to-Pole Observations (HIPPO) project measured a comprehensive suite of atmospheric trace gases and aerosols pertinent to understanding the global carbon cycle from the surface to the tropopause and approximately pole-to-pole over the Pacific Ocean. Flights took place over five missions during different seasons from 2009 to 2011. Data and documentation are available to the public from two archives: (1) NCAR's Earth Observing Laboratory (EOL) provides complete aircraft and flight operational data, and (2) the U.S. DOE's Carbon Dioxide Information Analysis Center (CDIAC) provides integrated measurement data products. The integrated products are more generally useful for secondary analyses. Data processing is nearing completion, although improvements to the data will continue to evolve and analyses will continue many years into the future. Periodic new releases of integrated measurement (merged) products will be generated by EOL when individual measurement data have been updated as directed by the Lead Principal Investigator. The EOL and CDIAC archives will share documentation and supplemental links and will ensure that the latest versions of data products are available to users of both archives. The EOL archive (http://www.eol.ucar.edu/projects/hippo/) provides the underlying investigator-provided data, including supporting data sets (e.g. operational satellite, model output, global observations, etc.), and ancillary flight operational information including field catalogs, data quality reports, software, documentation, publications, photos/imagery, and other detailed information about the HIPPO missions. The CDIAC archive provides integrated measurement data products, user documentation, and metadata through the HIPPO website (http://hippo.ornl.gov). These merged products were derived by consistently combining the aircraft state parameters for position, time, temperature, pressure, and wind speed with meteorological

  16. 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

  17. 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

  18. 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

  19. Linking calcification by exotic snails to stream inorganic carbon cycling.

    PubMed

    Hotchkiss, Erin R; Hall, Robert O

    2010-05-01

    Biotic calcification is rarely considered in freshwater C budgets, despite calculations suggesting that calcifying animals can alter inorganic C cycling. Most studies that have quantified biocalcification in aquatic ecosystems have not directly linked CO(2) fluxes from biocalcification with whole-ecosystem rates of inorganic C cycling. The freshwater snail, Melanoides tuberculata, has achieved a high abundance and 37.4 g biomass m(-2) after invading Kelly Warm Springs in Grand Teton National Park. This high biomass suggests that introduced populations of Melanoides may alter ecosystem processes. We measured Melanoides growth rates and biomass to calculate the production of biomass, shell mass, and CO(2). We compared Melanoides biomass and inorganic C production with ecosystem C pools and fluxes, as well as with published rates of CO(2) production by other calcifying organisms. Melanoides calcification in Kelly Warm Springs produced 12.1 mmol CO(2) m(-2) day(-1) during summer months. We measured high rates of gross primary productivity and respiration in Kelly Warm Springs (-378 and 533 mmol CO(2) m(-2) day(-1), respectively); CO(2) produced from biocalcification increased net CO(2) production in Kelly Warm Springs from 155 to 167 mmol CO(2) m(-2) day(-1). This rate of CO(2) production via biocalcification is within the published range of calcification by animals. But these CO(2) fluxes are small when compared to ecosystem C fluxes from stream metabolism. The influence of animals is relative to ecosystem processes, and should always be compared with ecosystem fluxes to quantify the importance of a specific animal in its environment.

  20. Cycles of soils. Carbon, nitrogen phosphorus, sulfur, micronutrients

    SciTech Connect

    Stevenson, F.J.

    1985-01-01

    This book is a single-volume treatment of the biochemical cycles in soil. It examines all major aspects of nutrient cycling, including fluxes with other ecosystems, biochemical pathways and transformation, gains and losses, chemical fixation reactions, and plant availability. It integrates environmental issues into the classical treatment of cycling processes. Two chapters are devoted exclusively to pollution of the environment.

  1. A Bayesian calibration of a simple carbon cycle model: The role of observations in estimating and reducing uncertainty

    SciTech Connect

    Davis, Kenneth; Keller, Klaus

    2008-01-01

    The strengths of future carbon dioxide (CO2) sinks are highly uncertain. A sound methodology to characterize current and predictive uncertainties in carbon cycle models is crucial for the design of efficient carbon management strategies. We demonstrate such a methodology, Markov Chain Monte Carlo (MCMC), by performing a Bayesian calibration of a simple global-scale carbon cycle model with historical carbon cycle observations to (1) estimate probability density functions (PDFs) of key carbon cycle parameters, (2) derive statistically sound probabilistic predictions of future CO2 sinks, and (3) assess the utility of hypothetical observation systems to reduce prediction uncertainties. We find that the PDFs of model parameter estimates are not normally distributed, and the residuals show statistically significant temporal autocorrelation. The assumption of normally distributed PDFs likely causes biased results, and the neglect of autocorrelation in the residual of the annual CO2 time series causes overconfidence in parameter estimates and predictions. Using interannually varying global temperature observations as forcing provides important information: terrestrial parameter PDFs are shifted and are more sharply constrained when compared to PDFs estimated when forcing the carbon cycle with a simple energy-balance model. Although CO2 observations provide a strong constraint on the total carbon sink, adding independent observations of terrestrial and oceanic fluxes has the potential to reduce uncertainty in predictions of this total sink more rapidly. Assimilating hypothetical annual observations of terrestrial and oceanic CO2 fluxes with realistic uncertainties reduces predictive uncertainties about CO2 sinks in the year 2050 by as much as a factor of 2 compared to assimilating CO2 concentrations alone.

  2. Evaluating the Carbon Cycle of a Coupled Atmosphere-Biosphere Model

    SciTech Connect

    Delire, C; Foley, J A; Thompson, S

    2002-08-21

    We investigate how well a coupled biosphere-atmosphere model, CCM3-IBIS, can simulate the functioning of the terrestrial biosphere and the carbon cycling through it. The simulated climate is compared to observations, while the vegetation cover and the carbon cycle are compared to an offline version of the biosphere model IBIS forced with observed climatic variables. The simulated climate presents some local biases that strongly affect the vegetation (e.g., a misrepresentation of the African monsoon). Compared to the offline model, the coupled model simulates well the globally averaged carbon fluxes and vegetation pools. The zonal mean carbon fluxes and the zonal mean seasonal cycle are also well represented except between 0{sup o} and 20{sup o}N due to the misrepresentation of the African monsoon. These results suggest that, despite regional biases in climate and ecosystem simulations, this coupled atmosphere-biosphere model can be used to explore geographic and temporal variations in the global carbon cycle.

  3. Climate, pCO2 and terrestrial carbon cycle linkages during late Palaeozoic glacial-interglacial cycles

    NASA Astrophysics Data System (ADS)

    Montañez, Isabel P.; McElwain, Jennifer C.; Poulsen, Christopher J.; White, Joseph D.; Dimichele, William A.; Wilson, Jonathan P.; Griggs, Galen; Hren, Michael T.

    2016-11-01

    Earth's last icehouse, 300 million years ago, is considered the longest-lived and most acute of the past half-billion years, characterized by expansive continental ice sheets and possibly tropical low-elevation glaciation. This atypical climate has long been attributed to anomalous radiative forcing promoted by a 3% lower incident solar luminosity and sustained low atmospheric pCO2 (<=300 ppm). Climate models, however, indicate a CO2 sensitivity of ice-sheet distribution and sea-level response that questions this long-standing climate paradigm by revealing major discrepancy between hypothesized ice distribution, pCO2, and geologic records of glacioeustasy. Here we present a high-resolution record of atmospheric pCO2 for 16 million years of the late Palaeozoic, developed using soil carbonate-based and fossil leaf-based proxies, that resolves the climate conundrum. Palaeo-fluctuations on the 105-yr scale occur within the CO2 range predicted for anthropogenic change and co-vary with substantial change in sea level and ice volume. We further document coincidence between pCO2 changes and repeated restructuring of Euramerican tropical forests that, in conjunction with modelled vegetation shifts, indicate a more dynamic carbon sequestration history than previously considered and a major role for terrestrial vegetation-CO2 feedbacks in driving eccentricity-scale climate cycles of the late Palaeozoic icehouse.

  4. Lightweight Carbon-Carbon High-Temperature Space Radiator

    NASA Technical Reports Server (NTRS)

    Miller, W.O.; Shih, Wei

    2008-01-01

    A document summarizes the development of a carbon-carbon composite radiator for dissipating waste heat from a spacecraft nuclear reactor. The radiator is to be bonded to metal heat pipes and to operate in conjunction with them at a temperature approximately between 500 and 1,000 K. A goal of this development is to reduce the average areal mass density of a radiator to about 2 kg/m(exp 2) from the current value of approximately 10 kg/m(exp 2) characteristic of spacecraft radiators made largely of metals. Accomplishments thus far include: (1) bonding of metal tubes to carbon-carbon material by a carbonization process that includes heating to a temperature of 620 C; (2) verification of the thermal and mechanical integrity of the bonds through pressure-cycling, axial-shear, and bending tests; and (3) construction and testing of two prototype heat-pipe/carbon-carbon-radiator units having different radiator areas, numbers of heat pipes, and areal mass densities. On the basis of the results achieved thus far, it is estimated that optimization of design could yield an areal mass density of 2.2 kg/m (exp 2) close to the goal of 2 kg/m(exp 2).

  5. Long-term shifts in life-cycle energy efficiency and carbon intensity.

    PubMed

    Yeh, Sonia; Mishra, Gouri Shankar; Morrison, Geoff; Teter, Jacob; Quiceno, Raul; Gillingham, Kenneth; Riera-Palou, Xavier

    2013-03-19

    The quantity of primary energy needed to support global human activity is in large part determined by how efficiently that energy is converted to a useful form. We estimate the system-level life-cycle energy efficiency (EF) and carbon intensity (CI) across primary resources for 2005-2100. Our results underscore that although technological improvements at each energy conversion process will improve technology efficiency and lead to important reductions in primary energy use, market mediated effects and structural shifts toward less efficient pathways and pathways with multiple stages of conversion will dampen these efficiency gains. System-level life-cycle efficiency may decrease as mitigation efforts intensify, since low-efficiency renewable systems with high output have much lower GHG emissions than some high-efficiency fossil fuel systems. Climate policies accelerate both improvements in EF and the adoption of renewable technologies, resulting in considerably lower primary energy demand and GHG emissions. Life-cycle EF and CI of useful energy provide a useful metric for understanding dynamics of implementing climate policies. The approaches developed here reiterate the necessity of a combination of policies that target efficiency and decarbonized energy technologies. We also examine life-cycle exergy efficiency (ExF) and find that nearly all of the qualitative results hold regardless of whether we use ExF or EF.

  6. Carbon stocks and cycling in the Amazon basin: Measurement and modeling of natural disturbance and recovery using airborne LIDAR

    NASA Astrophysics Data System (ADS)

    Hunter, Maria O'Healy

    Forest structure, the three dimensional distribution of living and dead plant material including live crowns, understory vegetation and coarse woody debris, is the concrete physical form of carbon storage, the framework for biodiversity, and the instantaneous manifestation of disturbance and recovery processes. The frequency of disturbance and rate of decomposition drives the fractions of living and dead biomass, and the size of and intensity of disturbance drives the rate and species composition of forest recovery; both are primary sinks and sources in the carbon cycle. To improve understanding of disturbance and recovery processes, high-resolution airborne LIDAR (light detection and ranging) data from the Amazon region is combined with field measurements to analyze forest structure. These measurements are incorporated into a simple model to estimate light availability and the associated changes in carbon stocks. This work improves the understanding of Amazon forest dynamics and its role in the carbon cycle.

  7. 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.

  8. 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.

  9. The Yeast Cyclin-Dependent Kinase Routes Carbon Fluxes to Fuel Cell Cycle Progression.

    PubMed

    Ewald, Jennifer C; Kuehne, Andreas; Zamboni, Nicola; Skotheim, Jan M

    2016-05-19

    Cell division entails a sequence of processes whose specific demands for biosynthetic precursors and energy place dynamic requirements on metabolism. However, little is known about how metabolic fluxes are coordinated with the cell division cycle. Here, we examine budding yeast to show that more than half of all measured metabolites change significantly through the cell division cycle. Cell cycle-dependent changes in central carbon metabolism are controlled by the cyclin-dependent kinase (Cdk1), a major cell cycle regulator, and the metabolic regulator protein kinase A. At the G1/S transition, Cdk1 phosphorylates and activates the enzyme Nth1, which funnels the storage carbohydrate trehalose into central carbon metabolism. Trehalose utilization fuels anabolic processes required to reliably complete cell division. Thus, the cell cycle entrains carbon metabolism to fuel biosynthesis. Because the oscillation of Cdk activity is a conserved feature of the eukaryotic cell cycle, we anticipate its frequent use in dynamically regulating metabolism for efficient proliferation.

  10. Microstructural Characterization of Nanocrystalline Sn-Coated Carbon Fibre Electrodes Cycled in Li-Ion Cells

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sandeep; Shafiei, Mehdi; Alpas, Ahmet T.

    2015-12-01

    The mechanisms of electrochemical capacity retention and eventual degradation in composite anodes prepared by electrodepositing nanocrystalline Sn coating on carbon fibres (CF), Sn-CF, were studied using in situ optical microscopy, high-resolution scanning and transmission electron microscopy. Specific capacity changes of Sn-CF anodes ( vs Li/Li+) were observed to take place in three stages: during the first two galvanostatic cycles, a rapid capacity decrease (from 1045 to 930 mAh g-1) occurred, which was followed by a steady-state stage where the capacity remained constant at 922 ± 22 mAh g-1. The fast capacity drop of Sn-CF in the first cycle was attributed to the partial decohesion of Sn from CFs although the carbon substrate remained unaffected due to formation of a layer from the solid electrolyte reduction products. The pure Sn electrode with a higher initial specific capacity than the Sn-CF displayed a rapid decrease in the same range, whereas the specific capacity of the uncoated CF was already much lower as the fibres were severely damaged in the first cycle.

  11. Coupling a Supercritical Carbon Dioxide Brayton Cycle to a Helium-Cooled Reactor.

    SciTech Connect

    Middleton, Bobby; Pasch, James Jay; Kruizenga, Alan Michael; Walker, Matthew

    2016-01-01

    This report outlines the thermodynamics of a supercritical carbon dioxide (sCO2) recompression closed Brayton cycle (RCBC) coupled to a Helium-cooled nuclear reactor. The baseline reactor design for the study is the AREVA High Temperature Gas-Cooled Reactor (HTGR). Using the AREVA HTGR nominal operating parameters, an initial thermodynamic study was performed using Sandia's deterministic RCBC analysis program. Utilizing the output of the RCBC thermodynamic analysis, preliminary values of reactor power and of Helium flow rate through the reactor were calculated in Sandia's HelCO2 code. Some research regarding materials requirements was then conducted to determine aspects of corrosion related to both Helium and to sCO2 , as well as some mechanical considerations for pressures and temperatures that will be seen by the piping and other components. This analysis resulted in a list of materials-related research items that need to be conducted in the future. A short assessment of dry heat rejection advantages of sCO2> Brayton cycles was also included. This assessment lists some items that should be investigated in the future to better understand how sCO2 Brayton cycles and nuclear can maximally contribute to optimizing the water efficiency of carbon free power generation

  12. Photoperiodic Regulation of the Seasonal Pattern of Photosynthetic Capacity and the Implications for Carbon Cycling

    SciTech Connect

    Bauerle, William L.; Oren, Ram; Way, Danielle A.; Qian, Song S.; Stoy, Paul C.; Thornton, Peter E; Bowden, Joseph D.; Hoffman, Forrest M; Reynolds, Robert F.

    2012-01-01

    Although temperature is an important driver of seasonal changes in photosynthetic physiology, photoperiod also regulates leaf activity. Climate change will extend growing seasons if temperature cues predominate, but photoperiod-controlled species will show limited responsiveness to warming. We show that photoperiod explains more seasonal variation in photosynthetic activity across 23 tree species than temperature. Although leaves remain green, photosynthetic capacity peaks just after summer solstice and declines with decreasing photoperiod, before air temperatures peak. In support of these findings, saplings grown at constant temperature but exposed to an extended photoperiod maintained high photosynthetic capacity, but photosynthetic activity declined in saplings experiencing a naturally shortening photoperiod; leaves remained equally green in both treatments. Incorporating a photoperiodic correction of photosynthetic physiology into a global-scale terrestrial carbon-cycle model significantly improves predictions of seasonal atmospheric CO{sub 2} cycling, demonstrating the benefit of such a function in coupled climate system models. Accounting for photoperiod-induced seasonality in photosynthetic parameters reduces modeled global gross primary production 2.5% ({approx}4 PgC y{sup -1}), resulting in a >3% ({approx}2 PgC y{sup -1}) decrease of net primary production. Such a correction is also needed in models estimating current carbon uptake based on remotely sensed greenness. Photoperiod-associated declines in photosynthetic capacity could limit autumn carbon gain in forests, even if warming delays leaf senescence.

  13. Effect of evaporite deposition on Early Cretaceous carbon and sulphur cycling.

    PubMed

    Wortmann, Ulrich G; Chernyavsky, Boris M

    2007-04-05

    The global carbon and sulphur cycles are central to our understanding of the Earth's history, because changes in the partitioning between the reduced and oxidized reservoirs of these elements are the primary control on atmospheric oxygen concentrations. In modern marine sediments, the burial rates of reduced carbon and sulphur are positively coupled, but high-resolution isotope records indicate that these rates were inversely related during the Early Cretaceous period. This inverse relationship is difficult to reconcile with our understanding of the processes that control organic matter remineralization and pyrite burial. Here we show that the inverse correlation can be explained by the deposition of evaporites during the opening of the South Atlantic Ocean basin. Evaporite deposition can alter the chemical composition of sea water, which can in turn affect the ability of sulphate-reducing bacteria to remineralize organic matter and mediate pyrite burial. We use a reaction-transport model to quantify these effects, and the resulting changes in the burial rates of carbon and sulphur, during the Early Cretaceous period. Our results indicate that deposition of the South Atlantic evaporites removed enough sulphate from the ocean temporarily to reduce biologically mediated pyrite burial and organic matter remineralization by up to fifty per cent, thus explaining the inverse relationship between the burial rates of reduced carbon and sulphur during this interval. Furthermore, our findings suggest that the effect of changing seawater sulphate concentrations on the marine subsurface biosphere may be the key to understanding other large-scale perturbations of the global carbon and sulphur cycles.

  14. Formulating energy policies related to fossil fuel use: Critical uncertainties in the global carbon cycle

    SciTech Connect

    Post, W.M.; Dale, V.H.; DeAngelis, D.L.; Mann, L.K.; Mulholland, P.J.; O'Neill, R.V.; Peng, T.-H.; Farrell, M.P.

    1990-01-01

    The global carbon cycle is the dynamic interaction among the earth's carbon sources and sinks. Four reservoirs can be identified, including the atmosphere, terrestrial biosphere, oceans, and sediments. Atmospheric CO{sub 2} concentration is determined by characteristics of carbon fluxes among major reservoirs of the global carbon cycle. The objective of this paper is to document the knowns, and unknowns and uncertainties associated with key questions that if answered will increase the understanding of the portion of past, present, and future atmospheric CO{sub 2} attributable to fossil fuel burning. Documented atmospheric increases in CO{sub 2} levels are thought to result primarily from fossil fuel use and, perhaps, deforestation. However, the observed atmospheric CO{sub 2} increase is less than expected from current understanding of the global carbon cycle because of poorly understood interactions among the major carbon reservoirs. 87 refs.

  15. Formulating Energy Policies Related to Fossil Fuel Use: Critical Uncertainties in the Global Carbon Cycle

    DOE R&D Accomplishments Database

    Post, W. M.; Dale, V. H.; DeAngelis, D. L.; Mann, L. K.; Mulholland, P. J.; O`Neill, R. V.; Peng, T. -H.; Farrell, M. P.

    1990-02-01

    The global carbon cycle is the dynamic interaction among the earth's carbon sources and sinks. Four reservoirs can be identified, including the atmosphere, terrestrial biosphere, oceans, and sediments. Atmospheric CO{sub 2} concentration is determined by characteristics of carbon fluxes among major reservoirs of the global carbon cycle. The objective of this paper is to document the knowns, and unknowns and uncertainties associated with key questions that if answered will increase the understanding of the portion of past, present, and future atmospheric CO{sub 2} attributable to fossil fuel burning. Documented atmospheric increases in CO{sub 2} levels are thought to result primarily from fossil fuel use and, perhaps, deforestation. However, the observed atmospheric CO{sub 2} increase is less than expected from current understanding of the global carbon cycle because of poorly understood interactions among the major carbon reservoirs.

  16. Contribution of aboveground plant respiration to carbon cycling in a Bornean tropical rainforet

    NASA Astrophysics Data System (ADS)

    Katayama, Ayumi; Tanaka, Kenzo; Ichie, Tomoaki; Kume, Tomonori; Matsumoto, Kazuho; Ohashi, Mizue; Kumagai, Tomo'omi

    2014-05-01

    Bornean tropical rainforests have a different characteristic from Amazonian tropical rainforests, that is, larger aboveground biomass caused by higher stand density of large trees. Larger biomass may cause different carbon cycling and allocation pattern. However, there are fewer studies on carbon allocation and each component in Bornean tropical rainforests, especially for aboveground plant respiration, compared to Amazonian forests. In this study, we measured woody tissue respiration and leaf respiration, and estimated those in ecosystem scale in a Bornean tropical rainforest. Then, we examined carbon allocation using the data of soil respiration and aboveground net primary production obtained from our previous studies. Woody tissue respiration rate was positively correlated with diameter at breast height (dbh) and stem growth rate. Using the relationships and biomass data, we estimated woody tissue respiration in ecosystem scale though methods of scaling resulted in different estimates values (4.52 - 9.33 MgC ha-1 yr-1). Woody tissue respiration based on surface area (8.88 MgC ha-1 yr-1) was larger than those in Amazon because of large aboveground biomass (563.0 Mg ha-1). Leaf respiration rate was positively correlated with height. Using the relationship and leaf area density data at each 5-m height, leaf respiration in ecosystem scale was estimated (9.46 MgC ha-1 yr-1), which was similar to those in Amazon because of comparable LAI (5.8 m2 m-2). Gross primary production estimated from biometric measurements (44.81 MgC ha-1 yr-1) was much higher than those in Amazon, and more carbon was allocated to woody tissue respiration and total belowground carbon flux. Large tree with dbh > 60cm accounted for about half of aboveground biomass and aboveground biomass increment. Soil respiration was also related to position of large trees, resulting in high soil respiration rate in this study site. Photosynthesis ability of top canopy for large trees was high and leaves for

  17. Forest Carbon Cycling Across Gradients of Disturbance Severity: Patterns and Underlying Mechanisms

    NASA Astrophysics Data System (ADS)

    Gough, C. M.; Bohrer, G.; Nave, L. E.; Nadelhoffer, K. J.; Vogel, C. S.; Bond-Lamberty, B. P.; Goodrich-Stuart, E. J.; Curtis, P.

    2014-12-01

    Ecological disturbances alter biogeochemical processes central to forest carbon (C) storage. Disturbances to forests occur along a continuum of severity, from low intensity disturbance causing the mortality of only a subset of trees to severe stand-replacing disturbance that kills all trees; yet, considerable uncertainty exists in how and why the forest C cycle changes across gradients of disturbance intensity, and whether ecosystem models robustly simulate these responses. At the University of Michigan Biological Station, we are using multiple ecosystem-scale experiments to examine how disturbance intensity affects C cycling and to identify the underlying mechanisms that support recovery of the C cycle. The Forest Accelerated Succession Experiment (FASET), in which a third of all canopy trees were stem girdled within a 39 ha area, employs C cycling measurements within paired treatment and control meteorological flux tower footprints. A separate study examines forest C cycling following stand-replacing clear-cut harvest and fire. We found that net ecosystem production (NEP) was highly resilient following moderate disturbance, but experienced long-term reductions following stand-replacing disturbance. Using a gradient of disturbance severity within the FASET treatment, we found that forest production declined non-linearly with rising disturbance intensity, remaining stable until a threshold of ~60 % tree mortality was exceeded. NEP was sustained following moderate disturbance because of improved canopy light-use efficiency, which compensated for a temporary reduction in leaf area index. Contrastingly, NEP was reduced for several decades at the highest levels of disturbance severity. A model assessment revealed that neither big-leaf nor gap models captured the observed high resilience in NEP following low intensity disturbance, suggesting inadequate representation of the mechanisms supporting C cycling resilience.