WorldWideScience

Sample records for carbon cycle

  1. Seeing the Carbon Cycle

    Science.gov (United States)

    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,…

  2. The carbon cycle revisited

    Science.gov (United States)

    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.

  3. Global Carbon Cycle

    OpenAIRE

    Probst, Jean-Luc; Faure, Hugues; Veizer, Jan

    1999-01-01

    The European Union of Geosciences held its 9th biannual meeting in Strasbourg, March 23–27, 1997. During this meeting, Symposium N8 18, Global carbon Cycle, was held under the sponsorship of the IGCP 1 n8404 on the «Terrestrial Carbon in the past 125 Ka», the INQUA 2 Carbon Commission and the ESCOBA-Biosphere 3 project of the EC Environment and Climate Programme. The «Global Carbon Cycle» Symposium attracted 28 oral and poster presentations and about one hundred par...

  4. The carbon dioxide cycle

    Science.gov (United States)

    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.

  5. Changing global carbon cycle

    International Nuclear Information System (INIS)

    Full text: The increase in atmospheric carbon dioxide (C02) is the single largest human perturbation on the earth's radiative balance contributing to climate change. Its rate of change reflects the balance between anthropogenic carbon emissions and the dynamics of a number of terrestrial and ocean processes that remove or emit C02. It is the long term evolution of this balance that will determine to large extent the speed and magnitude of the human induced climate change and the mitigation requirements to stabilise atmospheric C02 concentrations at any given level. In this talk, we show new trends in global carbon sources and sinks, with particularly focus on major shifts occurring since 2000 when the growth rate of atmospheric C02 has reached its highest level on record. The acceleration in the C02 growth results from the combination of several changes in properties of the carbon cycle, including: acceleration of anthropogenic carbon emissions; increased carbon intensity of the global economy, and decreased efficiency of natural carbon sinks. We discuss in more detail some of the possible causes of the reduced efficiency of natural carbon sinks on land and oceans, such as the decreased net sink in the Southern Ocean and on terrestrial mid-latitudes due to world-wide occurrence of drought. All these changes reported here characterise a carbon cycle that is generating stronger than expected climate forcing, and sooner than expected

  6. Carbon cycle makeover

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Kump, Lee R.

    2013-01-01

    remaining in sediments after respiration leave a residual of oxygen in the atmosphere. The source of oxygen to the atmosphere represented by organic matter burial is balanced by oxygen sinks associated with rock weathering and chemical reaction with volcanic gases. This is the long-term carbon and oxygen...... geochemical cycle. But Earth is an old planet, and oxygen levels have changed through time (2). On page 540 of this issue, Schrag et al. (3) challenge the most commonly used geochemical approach to assess long-term changes in the coupled oxygen and carbon cycles....

  7. New Relationship in Carbon Cycle

    OpenAIRE

    Aleksei Naumov

    2012-01-01

    The problem of carbon dioxide accumulation in the atmosphere is closely related to the biological carbon cycle processes insufficiently studied from the global viewpoint. Based on data obtained from the literature on net primary production (NPP) and soil respiration (SR) of world ecosystems, a quantitative analysis of the relationship between these basic parameters of the production/destruction phase of the carbon cycle is offered in this paper. A direct correspondence (equality in carbon equ...

  8. Mirador - Carbon Cycle and Ecosystems

    Data.gov (United States)

    National Aeronautics and Space Administration — Earth Science data access made simple. This Focus Area deals with the cycling of carbon in reservoirs and ecosystems as it changes naturally, is changed by humans,...

  9. Simple ocean carbon cycle models

    Energy Technology Data Exchange (ETDEWEB)

    Caldeira, K. [Lawrence Livermore National Lab., CA (United States); Hoffert, M.I. [New York Univ., NY (United States). Dept. of Earth System Sciences; Siegenthaler, U. [Bern Univ. (Switzerland). Inst. fuer Physik

    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. Carbon Cycling with Nuclear Power

    Science.gov (United States)

    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.

  11. An introduction to global carbon cycle management

    Science.gov (United States)

    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.

  12. The Hamburg oceanic carbon cycle circulation model. Cycle 1

    International Nuclear Information System (INIS)

    The carbon cycle model calculates the prognostic fields of oceanic geochemical carbon cycle tracers making use of a 'frozen' velocity field provided by a run of the LSG oceanic circulation model (see the corresponding manual, LSG=Large Scale Geostrophic). The carbon cycle model includes a crude approximation of interactions between sediment and bottom layer water. A simple (meridionally diffusive) one layer atmosphere model allows to calculate the CO2 airborne fraction resulting from the oceanic biogeochemical interactions. (orig.)

  13. Rock weathering and Carbon cycle

    Science.gov (United States)

    Strozza, Patrick

    2010-05-01

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

  14. Carbon cycling in Lake Superior

    Science.gov (United States)

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

    2005-06-01

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

  15. Carbon Stock and Carbon Cycle of Wetland Ecosystem

    OpenAIRE

    Zeng, Zhangquan; Zhang, Canming; LI, JIAO; Yang, Nan; Li, Xiquan; Niu, Yandong; Wu, Zijian

    2014-01-01

    Wetland ecosystem is an essential ecosystem in the world. Its organic carbon stock and carbon cycle are important basis of global carbon cycle researches and also major contents of global climate change researches. Researches have shown that wetland protection and restoration can promote carbon accumulation and reduce emission of greenhouse gases. This paper discussed influence of carbon stock and carbon balance of wetland ecosystem and emission of greenhouse gases, as well as the relationshi...

  16. Carbon Stock and Carbon Cycle of Wetland Ecosystem

    Institute of Scientific and Technical Information of China (English)

    Zhangquan; ZENG; Canming; ZHANG; Jiao; LI; Nan; YANG; Xihao; LI; Yandong; NIU; Zijian; WU

    2014-01-01

    Wetland ecosystem is an essential ecosystem in the world. Its organic carbon stock and carbon cycle are important basis of global carbon cycle researches and also major contents of global climate change researches. Researches have shown that wetland protection and restoration can promote carbon accumulation and reduce emission of greenhouse gases. This paper discussed influence of carbon stock and carbon balance of wetland ecosystem and emission of greenhouse gases,as well as the relationship between wetland and global climate changes. Finally,it made prospect on researches about carbon cycle of Dongting Lake.

  17. The economic implications of carbon cycle uncertainty

    OpenAIRE

    Smith, Steven J.; Edmonds, James A.

    2011-01-01

    This paper examines the implications of uncertainty in the carbon cycle for the cost of stabilizing carbon dioxideconcentrations. Using a state of the art integrated assessment model, we find that uncertainty in our understanding of thecarbon cycle has significant implications for the costs of a climate stabilization policy, with cost differences denominatedin trillions of dollars. Uncertainty in the carbon cycle is equivalent to a change in concentration target of up to 100 ppmv.The impact o...

  18. Climate extremes and the carbon cycle

    OpenAIRE

    Reichstein, Markus; Bahn, Michael; Ciais, Philippe; Vicca, Sara; et al.

    2013-01-01

    Abstract: The terrestrial biosphere is a key component of the global carbon cycle and its carbon balance is strongly influenced by climate. Continuing environmental changes are thought to increase global terrestrial carbon uptake. But evidence is mounting that climate extremes such as droughts or storms can lead to a decrease in regional ecosystem carbon stocks and therefore have the potential to negate an expected increase in terrestrial carbon uptake. Here we explore the mechanisms and impa...

  19. Carbon cycle modeling calculations for the IPCC

    International Nuclear Information System (INIS)

    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 CO2 concentrations and the output was CO2 emissions), and the ''forward calculations'' (input was CO2 emissions and output was CO2 concentrations). In particular, we have derived carbon dioxide concentrations and/or emissions for several scenarios using our coupled climate-carbon cycle modelling system

  20. Carbon cycle: storage beneath mangroves

    OpenAIRE

    BOUILLON, S

    2011-01-01

    In the face of continued deforestation, the high carbon stocks in mangrove forests unveiled by Donato et al. provide a strong incentive to consider mangrove ecosystems as priority areas for conservation. Furthermore, these results highlight the need for scientists and funding agencies to address uncertainties regarding the fate of the carbon after land clearance. Only a handful of studies have quantified the loss of sediment carbon after mangrove clear-cutting – but all suggest that these los...

  1. Life cycle assessment of carbon xerogels

    OpenAIRE

    Melon, Raphaëlle; Renzoni, Roberto; Léonard, Alexandre; Job, Nathalie; Léonard, Angélique

    2012-01-01

    In the framework of the SOMABAT European project, a life cycle assessment applied to the production of 1 kg of carbon xerogels was carried out by comparing three drying technologies (vacuum, microwave and convective drying). These carbon materials with controlled texture are thought to be used as active material at the anode side of Li-polymer battery.

  2. Permafrost soils and carbon cycling

    OpenAIRE

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

    2015-01-01

    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...

  3. Cycling of black carbon in the ocean

    OpenAIRE

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

    2016-01-01

    Black carbon (BC) is a byproduct of combustion from wildfires and fossil fuels and is a slow-cycling component of the carbon cycle. Whether BC accumulates and ages on millennial timescales in the world oceans has remained unknown. Here, we quantified dissolved BC (DBC) in marine dissolved organic carbon (DOC) isolated by solid phase extraction (SPE) 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 ...

  4. Chemical Oceanography and the Marine Carbon Cycle

    Science.gov (United States)

    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.

  5. Atmospheric carbon dioxide and the global carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Trabalka, J R [ed.

    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)

  6. Dynamics of the carbon cycle

    International Nuclear Information System (INIS)

    The short article describes the development of the increase in atmospheric CO2 in the past 35 years. The interdependence between CO2 levels and changes in fuel consumption is discussed, but other contributing cycles are discussed as well, e.g. enhanced timber production, ocean warming, reverse ocean currents in the South Pacific. (VHE)

  7. Understanding the Carbon Cycle : A Jigsaw Approach

    Science.gov (United States)

    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.

  8. Global Carbon Cycle of the Precambrian Earth

    DEFF Research Database (Denmark)

    Wiewióra, Justyna

    The carbon isotopic composition of distinct Archaean geological records provides information about the global carbon cycle and emergence of life on early Earth. We utilized carbon isotopic records of Greenlandic carbonatites, diamonds, graphites, marbles, metacarbonates and ultramafic rocks to...... investigate carbon fluxes between Precambrian Earth’s mantle and crust and to trace the evolution of life in the Eoarchaean oceans. The world’s desire for diamonds gives us a unique opportunity to obtain insight into the nature of metasomatic fluids affecting the subcratonic lithospheric mantle (SCLM) beneath...

  9. Evolution of Sustainable Carbon Cycling Processes in China

    Institute of Scientific and Technical Information of China (English)

    Zhuang Yahui; Zhang Hongxun; Wang Xiaoke; Fang Jinyun

    2004-01-01

    This report summarizes the surveys on carbon inventories and initiatives on sustainable carbon cycling taken by RCEES. The first part of this report deals with the concept of sustainable carbon cycling, the historical evolution of carbon cycling processes in China, carbon pool enhancement, value addition, carbon sequestration and carbon balance.The second part covers the modeling of carbon dynamics, emission inventories of various carboncontaining greenhouse gases and their potential abatement measures.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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,...

  12. Hyperdominance in Amazonian forest carbon cycling

    OpenAIRE

    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; Petronelli, Pascal; Andrade, Ana

    2015-01-01

    While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few â € hyperdominantâ €™ 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 mos...

  13. The Carbon Cycle at the Nile Headwaters

    Science.gov (United States)

    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

  14. THE C2 OXIDATIVE PHOTOSYNTHETIC CARBON CYCLE.

    Science.gov (United States)

    Tolbert, N. E.

    1997-06-01

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

  15. Soil Carbon and Nitrogen Cycle Modeling

    Science.gov (United States)

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

    2012-12-01

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

  16. Cycling of black carbon in the ocean

    Science.gov (United States)

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

    2016-05-01

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

  17. Carbon cycle uncertainty in the Alaskan Arctic

    Directory of Open Access Journals (Sweden)

    J. B. Fisher

    2014-02-01

    Full Text Available 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 for each quantity. Mean annual uncertainty (σ/x 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.

  18. Hyperdominance in Amazonian forest carbon cycling

    Science.gov (United States)

    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

  19. What determines the magnitude of carbon cycle-climate feedbacks?

    OpenAIRE

    Matthews, H Damon; Eby, Michael; Ewen, Tracy; Friedlingstein, Pierre; Hawkins, Barbara J

    2007-01-01

    Positive feedbacks between climate change and the carbon cycle have the potential to amplify the growth of atmospheric carbon dioxide and accelerate future climate warming. However, both the magnitude of and the processes which drive future carbon cycle- climate feedbacks remain highly uncertain. In this study, we use a coupled climate-carbon model to investigate how the response of vegetation photosynthesis to climate change contributes to the overall strength of carbon cycle-climate feedbac...

  20. Tropical Cyclones and the Carbon Cycle

    Science.gov (United States)

    Zimmerman, N. L.; Emanuel, K.

    2010-12-01

    The relationship between tropical cyclones and the carbon cycle poses an interesting question: tropical surface waters are generally quite warm and poor in nutrients, but the mixing in tropical cyclones entrains potentially large amounts of cold, nutrient-rich water. As the cold anomaly warms, there is a tendency toward over-saturation of carbon dioxide, and thus a net outgassing from the ocean to the atmosphere, but because nutrients are mixed into the photic zone, there is a simultaneous phytoplankton bloom which removes carbon from the mixed layer. The amount of carbon taken up into biota by the induced biological activity can in some cases create a net undersaturation of carbon dioxide in spite of the warming of entrained cold water, and therefore cause a net ingassing of carbon in the wake of a tropical cyclone. This is, however, only a short-term effect. Phytoplankton have a short life cycle, and the detritus they leave behind sinks and remineralizes; that which remineralizes below the climatological mixed layer represents a long-term sink of carbon from the atmosphere to the mixed layer, but the remainder will quickly return to the atmosphere. Both the warming of the mixed layer and the induced phytoplankton bloom are easily observable, but neither the sign nor the magnitude of the net effect is intuitive. To illuminate the question, a simple one-dimensional model is formulated which simulates the behavior of the upper few hundred meters of the ocean in response to tropical cyclone-induced mixing. Phytoplankton (and its remains), Nitrate, and Dissolved Inorganic Carbon are tracked, and the model is both initialized and forced with the best possible approximation to real chemical concentrations, winds, and heat fluxes, and the effect of the storm is estimated by comparing model behavior with the storm included and with the storm removed from observations. It is shown that the model performs acceptably well compared to such observations as exist. The model is

  1. Increase of carbon cycle feedback with climate sensitivity: results from a coupled climate and carbon cycle model

    OpenAIRE

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

    2011-01-01

    Coupled climate and carbon cycle modelling 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 greater warming. In this paper we investigate the sensitivity of this feedback for year 2100 global warming in the range of 0 to 8 K. Differing climate sensitivities to increased CO2content are imposed on the carbon cycle models for the same emissions. Emissions from the SRES A2 sc...

  2. Carbon footprint estimation of municipal water cycle

    Science.gov (United States)

    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

  3. Marine carbon cycling following end Cretaceous extinction

    Science.gov (United States)

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

    2010-05-01

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

  4. The changing carbon cycle of the coastal ocean

    OpenAIRE

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

    2013-01-01

    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 ...

  5. Carbonate-silicate cycle models of the long-term carbon cycle, carbonate accumulation in the oceans, and climate

    International Nuclear Information System (INIS)

    Several models of the long-term carbon cycle, incorporating models of the carbonate-silicate cycle, were developed and utilized to investigate issues relating to global climate and the causes and consequences of changes in calcium carbonate accumulation in the oceans. Model results indicate that the marked mid-Cretaceous (120 Ma) global warming could be explained by increased rates of release of carbon dioxide from subduction-zone metamorphism and mid-ocean-ridges, in conjunction with paleogeographic factors. Since the mid-Cretaceous, the primary setting for calcium carbonate accumulation in the oceans has shifted from shallow-water to deep-water environments. Model results suggest that this shift could have major consequences for the carbonate-silicate cycle and climate, and lead to significant increases in the flux of metamorphic carbon dioxide to the atmosphere. Increases in pelagic carbonate productivity, and decreases in tropical shallow-water area available for neritic carbonate accumulation, have both been proposed as the primary cause of this shift. Two lines of evidence developed here (one involving a statistical analysis of Tertiary carbonate-accumulation and oxygen-isotope data, and another based on modeling the carbonate-silicate cycle and ocean chemistry) suggest that a decrease in tropical shallow-water area was more important than increased pelagic productivity in explaining this shift. Model investigations of changes in ocean chemistry at the Cretaceous/Tertiary (K/T) boundary (66 Ma) indicate that variations in deep-water carbonate productivity may affect shallow-water carbonate accumulation rates through a mechanism involving surface-water carbonate-ion concentration. In the aftermath of the K/T boundary event, deep-water carbonate production and accumulation were significantly reduced as a result of the extinction of calcareous plankton

  6. Biogeochemical Cycles of Carbon and Sulfur

    Science.gov (United States)

    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.

  7. Carbon dioxide direct cycle modular reactor

    International Nuclear Information System (INIS)

    Recently, as the micro gas-turbine power generation is clean for environment and has high convenience, it is focused as a small size dispersion electric source for super markets, hospitals, factories, and so on. And, a modular high temperature gas reactor (PBMR) adopting the gas turbine is also focused recently, and is progressed on its construction in South Africa and reported on construction plan of the Exelon Inc. in U.S.A. PBMR has specific safety for a small size and pebble-bed reactor and also has some characters on low construction cost similar to that of LWR due to simplification and small size module adoption of its plant. The PBMR uses helium for its coolants, of which exit temperature is set for at 900degC to get higher thermal efficiency. This is because of its adoption of Brayton cycle to fast reduce the efficiency with falling temperature. However, as helium is a costly and easy-emission vapor, it is desired to alternate to cheaper and more difficult-emission vapor. Here were introduced on carbon dioxide (CO2) direct cycle using carbon dioxide with extremely higher thermal efficiency than helium and its applicability to nuclear reactors. (G.K.)

  8. An isopycnic ocean carbon cycle model

    Directory of Open Access Journals (Sweden)

    K. M. Assmann

    2010-02-01

    Full Text Available 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.

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

    OpenAIRE

    Bjerrum, Christian J.; Donald E Canfield

    2011-01-01

    The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We inter...

  10. Monitoring the Carbon Cycle from Space

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  12. Supercritical carbon dioxide cycle control analysis.

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-04-11

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

  13. Supercritical carbon dioxide cycle control analysis

    International Nuclear Information System (INIS)

    This report documents work carried out during FY 2008 on further investigation of control strategies for supercritical carbon dioxide (S-CO2) Brayton cycle energy converters. The main focus of the present work has been on investigation of the S-CO2 cycle control and behavior under conditions not covered by previous work. An important scenario which has not been previously calculated involves cycle operation for a Sodium-Cooled Fast Reactor (SFR) following a reactor scram event and the transition to the primary coolant natural circulation and decay heat removal. The Argonne National Laboratory (ANL) Plant Dynamics Code has been applied to investigate the dynamic behavior of the 96 MWe (250 MWt) Advanced Burner Test Reactor (ABTR) S-CO2 Brayton cycle following scram. The timescale for the primary sodium flowrate to coast down and the transition to natural circulation to occur was calculated with the SAS4A/SASSYS-1 computer code and found to be about 400 seconds. It is assumed that after this time, decay heat is removed by the normal ABTR shutdown heat removal system incorporating a dedicated shutdown heat removal S-CO2 pump and cooler. The ANL Plant Dynamics Code configured for the Small Secure Transportable Autonomous Reactor (SSTAR) Lead-Cooled Fast Reactor (LFR) was utilized to model the S-CO2 Brayton cycle with a decaying liquid metal coolant flow to the Pb-to-CO2 heat exchangers and temperatures reflecting the decaying core power and heat removal by the cycle. The results obtained in this manner are approximate but indicative of the cycle transient performance. The ANL Plant Dynamics Code calculations show that the S-CO2 cycle can operate for about 400 seconds following the reactor scram driven by the thermal energy stored in the reactor structures and coolant such that heat removal from the reactor exceeds the decay heat generation. Based on the results, requirements for the shutdown heat removal system may be defined. In particular, the peak heat removal

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

    DEFF Research Database (Denmark)

    Bjerrum, Christian J.; Canfield, Donald Eugene

    2011-01-01

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

  15. Carbon cycle: Global warming then and now

    Science.gov (United States)

    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.

  16. The Role of Urbanization in the Global Carbon Cycle

    OpenAIRE

    Churkina, Galina

    2016-01-01

    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 ~2...

  17. Analysis of an Integrated Carbon Cycle for Storage of renewables

    OpenAIRE

    Martin Streibel; Natalie Christine Nakaten; Thomas Kempka; Michael Kühn

    2013-01-01

    Excess electricity from wind and sun can be transformed into hydrogen and with carbon dioxide subsequently into methane. When needed, electricity is regained in a combined cycle plant burning the methane. To close the carbon cycle carbon dioxide is captured on site. Two subsurface storage formations for both gases are required for the technology. Our regional showcase of two German cities, Potsdam and Brandenburg/Havel, demonstrates that about 30% of their electricity demand can be provided i...

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

    OpenAIRE

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

    2014-01-01

    Oceanic dissolved organic carbon (DOC) contains as much carbon as Earth’s atmosphere, yet its cycling timescales and composition remain poorly constrained. We use serial oxidation experiments to measure the quantitative distribution of carbon isotopes inside the DOC reservoir, allowing us to estimate both its cycling timescales and source distribution. We find that a large portion of deep water DOC has a modern radiocarbon age and a fast turnover time supported by particle dissolution. In add...

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

    Energy Technology Data Exchange (ETDEWEB)

    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 Dioxide Direct Cycle Modular Reactors for Decentralized Energy Sources

    International Nuclear Information System (INIS)

    Carbon dioxide is achievable higher cycle efficiency than helium in a direct gas turbine cycle system due to the real gas effect or inter molecular attraction force in the compression process especially in the vicinity of the critical points. Analyzing the cycle thermal performance of full, partial and non condensation cycles, the cycle efficiency is highest in the partial condensation cycle. A fast reactor employing the partial condensation cycle is expected to be a potential alternative option to LMFRs, allowing higher cycle efficiency than LMFRs at the same core outlet temperature, and excluding the problems related to safety, cost and maintenance. A thermal reactor employing the partial condensation cycle provides higher cycle efficiency (48%) at the moderate core outlet temperature of 650? than that of PBMR (46%) operated at 900? (author)

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

    Science.gov (United States)

    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.

  2. The role of urbanization in the global carbon cycle

    Directory of Open Access Journals (Sweden)

    Galina eChurkina

    2016-01-01

    Full Text Available 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.

  3. Carbon cycling and storage in mangrove forests.

    Science.gov (United States)

    Alongi, Daniel M

    2014-01-01

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

  4. Carbon Cycling and Storage in Mangrove Forests

    Science.gov (United States)

    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.

  5. Ectomycorrhizal fungi slow soil carbon cycling.

    Science.gov (United States)

    Averill, Colin; Hawkes, Christine V

    2016-08-01

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

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

    Science.gov (United States)

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

    2014-10-01

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

  7. Glassy carbon supercapacitor: 100,000 cycles demonstrated

    Energy Technology Data Exchange (ETDEWEB)

    Baertsch, M.; Braun, A.; Schnyder, B.; Koetz, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    A 5 V glassy carbon capacitor stack was built consisting of four bipolar and two end-plate electrodes. More than 100,000 charging/discharging cycles were applied to test the stability of the double-layer capacitor. Low and high frequency resistances were measured as a function of the number of cycles. (author) 2 figs., 1 ref.

  8. The carbon cycle and global warming

    International Nuclear Information System (INIS)

    Five land-use-based approaches can be used to slow the buildup of CO2 in the atmosphere: slowing or stopping the loss of existing forests, thus preserving current carbon reservoirs; adding to the planet's vegetative cover through reforestation or other means, thus enlarging living terrestrial carbon reservoirs; increasing the carbon stored in nonliving carbon reservoirs such as agricultural soils; increasing the carbon stored in artificial reservoirs, including timber products; and substituting sustainable biomass energy sources for fossil fuel consumption, thus reducing energy-related carbon emissions. These approaches are all based on the same basic premise: adding to the planet's net carbon stores in vegetative cover or soil, or preventing any net loss, will help moderate global warming by keeping atmospheric CO2 levels lower than they would otherwise be. Because biotic policy options appear capable of contributing significantly to the mitigation of global warming while also furthering many other public policy objectives, their role deserves careful consideration on a country-by-country basis

  9. The role of urbanization in the global carbon cycle

    Science.gov (United States)

    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.

  10. Interglacials, Milankovitch Cycles, Solar Activity, and Carbon Dioxide

    OpenAIRE

    Marsh, Gerald E.

    2014-01-01

    The existing understanding of interglacial periods is that they are initiated by Milankovitch cycles enhanced by rising atmospheric carbon dioxide concentrations. During interglacials, global temperature is also believed to be primarily controlled by carbon dioxide concentrations, modulated by internal processes such as the Pacific Decadal Oscillation and the North Atlantic Oscillation. Recent work challenges the fundamental basis of these conceptions.

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

    Science.gov (United States)

    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.

  12. The changing global carbon cycle: Linking plant-soil carbon dynamics to global consequences

    Science.gov (United States)

    Chapin, F. S., III; McFarland, J.; McGuire, David A.; Euskirchen, E.S.; Ruess, R.W.; Kielland, K.

    2009-01-01

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

  13. Global Carbon Cycle and the Optimal Time Path of a Carbon Tax.

    OpenAIRE

    Farzin, Y.H.; Tahvonen, O.

    1996-01-01

    The existing models of fossil fuel consumption with carbon accumulation imply that the optimal time path of carbon tax is either hump-shaped or monotonically decreasing. These models specify the decay of atmospheric carbon as a constant rate of total concentration. The authors extend this specification to more accurately reflect the global carbon cycle models of climatologists and show that this extension changes the basic economic properties of the optimal carbon tax. Their analysis reveals ...

  14. Simulated Carbon Cycling in a Model Microbial Mat.

    Science.gov (United States)

    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.

  15. Vegetation and carbon cycle dynamics in Holocene

    Science.gov (United States)

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

    2009-04-01

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

  16. Soil organic matter as factor of carbon cycle in nature

    International Nuclear Information System (INIS)

    Soil organic matter represents mos important pool of carbon in nature. Have been estimated content about 2000 Pg of carbon in soil cover of Earth and about 500 Pg C in plant biomass. In the global C cycle we can identify about 60 Pg C yearly removed from soil into the air and same quantities of C removed from air back to the soil. Carbon (as CO2 mainly) is directly emitted into the air from soil organic matter (after mineralization and back carbon removing from air into the soil is realized through soil and plant living biomass. (Author)

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2014-12-01

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

  19. Observing terrestrial ecosystems and the carbon cycle from space

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-02-06

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

  20. Advanced Supercritical Carbon Dioxide Brayton Cycle Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark [Univ. of Wisconsin, Madison, WI (United States); Sienicki, James [Argonne National Lab. (ANL), Argonne, IL (United States); Moisseytsev, Anton [Argonne National Lab. (ANL), Argonne, IL (United States); Nellis, Gregory [Univ. of Wisconsin, Madison, WI (United States); Klein, Sanford [Univ. of Wisconsin, Madison, WI (United States)

    2015-10-21

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

  1. Life cycle analysis, Carbon footprint, Sustainability

    OpenAIRE

    Watkins, Richard

    2015-01-01

    The aim of Life Cycle Analysis is to try and evaluate the environmental impact of a device (or process), taking into account all the important contributing factors over its life. This can include the construction impacts and end of life issues, as well as any impact during the actual “use-phase” of the device. In the context of retail refrigeration, by far the dominant environmental impact results from the use of energy to run the refrigeration plant. This also applies to almost anything ...

  2. Reconciling carbon-cycle concepts, terminology, and methods

    OpenAIRE

    Chapin, F. S.; Woodwell, G. M.; Randerson, J. T.; Rastetter, E.B.; Lovett, G. M.; Baldocchi, D.D.; Clark, D. A.; Harmon, M. E.; Schimel, D. S; Valentini, R.; Wirth, C.; Aber, J. D.; Cole, J.J.; Goulden, M. L.; J. W. Harden

    2006-01-01

    Recent projections of climatic change have focused a great deal of scientific and public attention on patterns of carbon (C) cycling as well as its controls, particularly the factors that determine whether an ecosystem is a net source or sink of atmospheric carbon dioxide (CO2). Net ecosystem production (NEP), a central concept in C-cycling research, has been used by scientists to represent two different concepts. We propose that NEP be restricted to just one of its two original definitions-t...

  3. Bacterial carbon cycling in a subarctic fjord

    DEFF Research Database (Denmark)

    Middelboe, Mathias; Glud, Ronnie N.; Sejr, Mikael Kristian

    2012-01-01

    In this seasonal study, we examined the environmental controls and quantitative importance of bacterial carbon consumption in the water column and the sediment in the subarctic Kobbefjord, Greenland. Depth-integrated bacterial production in the photic zone varied from 5.0 ± 2.7 mg C m−2 d−1 in...... February to 42 ± 28 mg C m−2 d−1 in May and 34 ± 7 mg C m−2 d−1 in September, corresponding to a bacterial production to primary production ratio of 0.34 ± 0.14, 0.07 ± 0.04, and 0.08 ± 0.06, respectively. Based on measured bacterial growth efficiencies (BGEs) of 0.09–0.10, pelagic bacterial carbon...... consumption was 54 ± 59 mg C m−2 d−1, 1194 ± 329 mg C m−2 d−1, and 689 ± 115 mg C m−2 d−1 in February, May, and September, respectively, which corresponded to 367%, 71%, and 87% of pelagic primary production. The average annual sediment respiration corresponded to 121 mg C m−2 d−1 and accounted for 17% of...

  4. Past and present of sediment and carbon biogeochemical cycling models

    Directory of Open Access Journals (Sweden)

    F. T. Mackenzie

    2004-01-01

    Full Text Available The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2 concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification

  5. Decay of cacti and carbon cycling

    Science.gov (United States)

    Garvie, Laurence A. J.

    2006-03-01

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

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

    Science.gov (United States)

    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

  7. Anthropogenic chemical carbon cycle for a sustainable future.

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Warren, William A.

    2015-01-01

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

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

    Science.gov (United States)

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

    2007-01-01

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

  10. Microbial control over carbon cycling in soil

    Directory of Open Access Journals (Sweden)

    JoshuaSchimel

    2012-09-01

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  13. Simulation of terrestrial carbon cycle balance model in Tibet

    Institute of Scientific and Technical Information of China (English)

    WANGJianlin:; HUDan; SUNZibao

    2003-01-01

    Based on climate material, the simplified terrestrial carbon cycle balance (TCCB) model was established, which is semi-mechanism and semi-statistics. Through TCCB model, our estimate indicates that the southeastern part of the Tibetan Plateau has much higher carbon content, and we have calculated the litter carbon pool, NPP, carbon fluxes and described their spatial characteristics in this region. Based on the TCCB model simulation, NPP in Tibet is 1.73 × 108tC/a, soil organic input rate is 0.66 × l08 tC/a, litter mineralization rate is 1.07× l08tC/a, vegetation litterfall rate is 1.73× l08 tC/a, the litter carbon pool is 7.26 × l08 tC, and soil decomposition rate is 309.54 × l08tC/a. The carbon budget was also analyzed based on the estimates of carbon pool and fluxes. The spatial distributions of carbon pools and carbon fluxes in different compartments of terrestrial ecosystem were depicted with map respectively in Tibet. The distribution of NPP, vegetation litterfall rate, litter, litter mineralization rate, soil organic input rate and the soil decomposition rate were abstracted with temperature, precipitation, fractional vegetation and land feature.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2016-04-01

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

  16. Cenozoic carbon cycle imbalances and a variable weathering feedback

    Science.gov (United States)

    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 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 increased the reactivity of the surface of the Earth. Increasing feedback strength through the Cenozoic reconciles mass balance in the carbon cycle with

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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).

  20. Biological productivity and carbon cycling in the Arctic Ocean

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Primary production, bacterial production, particulate organic carbon fluxes and organic carbon burial rates were quantified during the summer period of 1999 in the Arctic Ocean via 14C uptake, 3H uptake, 234Th/238U disequilibrium and 210Pbex dating, respectively. The integrated primary production in the water column was as high as 197 mmolC/(m2@d) in the Chukchi shelf and was 3.8 mmolC/(m2@d) in the Canada Basin. These rates are higher than those reported previously. The ratios of bacterial production to primary production in the study region were higher than 0.5, indicating that microbial activity is not depressed but important in cold Arctic waters. 234Th/238U disequilibria were evident at the station in the Canada Basin. The presence of significant 234Th deficiency suggested that scavenging and removal processes are also important to biogeochemical cycles of trace elements in the Arctic Ocean. Particulate organic carbon export flux was estimated to be 1.0 mmolC/(m2@d). Measurements of sediment excess 210Pb profile in the Chukchi shelf allowed us to estimate the amount of organic carbon buried in the bottom sediment, which ranged from 25 to 35 mmolC/(m2@d) and represented about 59%-82% of the mean primary production in the euphotic zone. Overall, our results indicated that the Arctic Ocean has active carbon cycling and is not a biological desert as previously believed. Therefore, the Arctic Ocean may play an important role in the global carbon cycle and climate change.

  1. Hydrological and biogeochemical constraints on terrestrial carbon cycle projections

    Science.gov (United States)

    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.

  2. Explaining the seasonal cycle of the globally averaged CO2 with a carbon-cycle model

    OpenAIRE

    G. A. Alexandrov

    2014-01-01

    The seasonal changes in the globally averaged atmospheric carbon-dioxide concentrations reflect an important aspect of the global carbon cycle: the gas exchange between the atmosphere and terrestrial biosphere. The data on the globally averaged atmospheric carbon-dioxide concentrations, which are reported by Earth System Research Laboratory of the US National Oceanic & Atmospheric Administration (NOAA/ESRL), could be used to demonstrate the adequacy of the global carbon-cycl...

  3. Modelling of cycling of lithium battery with microporous carbon electrode

    Directory of Open Access Journals (Sweden)

    D. Portnyagin

    2008-12-01

    Full Text Available Charge/discharge cycles of lithium cell with microporous carbon electrode under potentiodynamic control have been modelled. Predictions of the models with variable and constant diffusion coefficient neglecting the electric field inside the particle (CPM, DFM are compared to the predictions of the models with variable and constant diffusion coefficient in which electrostatic interaction inside the particles of carbon electrode (CPME, DFME is taken into account. There is observed a considerable difference between both. Electrostatic interactions of lithium ions with each other and the charge distributed inside the particle promote intercalation during the discharge of the cell and deintercalation during the charge. The dependance of the effect of hysteresis during the cycling of the cell on the rate of change of the applied voltage is studied. The larger is the speed of change of the applied voltage the more effective is hysteresis. We have also obtained concentration profiles at different stages of charge/discharge process.

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

    Science.gov (United States)

    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

  5. Carbon and nitrogen cycling in thermally heated sediments

    Science.gov (United States)

    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

  6. Life cycle water use of low-carbon transport fuels

    International Nuclear Information System (INIS)

    In society's quest to mitigate climate change it is important to consider potential trade-offs in climate solutions impacting other environmental issues. This analysis explores the life cycle water consumption of alternative low-carbon energy sources for transportation. Energy sources analyzed include both biofuels used in internal combustion engines and low-carbon electricity generation methods used in conjunction with electric vehicles. Biofuels considered are corn-based ethanol, soybean biodiesel, cellulosic ethanol from switchgrass, and microbial biodiesel. Electricity sources analyzed are coal with carbon sequestration, photovoltaic cells, and solar concentrators. The assessment method used is hybrid life cycle assessment (LCA), which combines materials-based process method and the economic input-output (EIO) method. To compare these technologies on an even footing the life cycle water use to propel a passenger vehicle one mile is estimated. All technologies evaluated showed an increase in water consumption compared to unleaded gasoline when water use from vehicle manufacturing was included. Scale-up calculations showed that mass adoption of electric vehicles and some configurations of algae and switchgrass systems could potentially contribute to the decarbonization of transportation with tolerable increases in overall water consumption. Irrigated crop based biofuels however were found to have significant potential impact on water resources when scaled up to macroscopic production levels. (author)

  7. Life cycle water use of low-carbon transport fuels

    International Nuclear Information System (INIS)

    In society's quest to mitigate climate change it is important to consider potential trade-offs in climate solutions impacting other environmental issues. This analysis explores the life cycle water consumption of alternative low-carbon energy sources for transportation. Energy sources analyzed include both biofuels used in internal combustion engines and low-carbon electricity generation methods used in conjunction with electric vehicles. Biofuels considered are corn-based ethanol, soybean biodiesel, cellulosic ethanol from switchgrass, and microbial biodiesel. Electricity sources analyzed are coal with carbon sequestration, photovoltaic cells, and solar concentrators. The assessment method used is hybrid life cycle assessment (LCA), which combines materials-based process method and the economic input-output (EIO) method. To compare these technologies on an even footing the life cycle water use to propel a passenger vehicle one mile is estimated. All technologies evaluated showed an increase in water consumption compared to unleaded gasoline when water use from vehicle manufacturing was included. Scale-up calculations showed that mass adoption of electric vehicles and some configurations of algae and switchgrass systems could potentially contribute to the decarbonization of transportation with tolerable increases in overall water consumption. Irrigated crop based biofuels however were found to have significant potential impact on water resources when scaled up to macroscopic production levels.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    OpenAIRE

    Friedlingstein, P.; Dufresne, J.-L.; Cox, P.M.; Rayner, P.

    2011-01-01

    Future climate change induced by atmospheric emissions of greenhouse gases is believed to have a large impact on the global carbon cycle. Several offline studies focusing either on the marine or on the terrestrial carbon cycle highlighted such potential effects. Two recent online studies, using ocean–atmosphere general circulation models coupled to land and ocean carbon cycle models, investigated in a consistent way the feedback between the climate change and the carbon cycle. These two studi...

  10. A review on Life Cycle Assessment, Life Cycle Energy Assessment and Life Cycle Carbon Emissions Assessment on buildings

    International Nuclear Information System (INIS)

    Highlights: • Three streams of life cycle studies, namely LCA, LCEA and LCCO2A, were compared. • Previous findings from the three streams were reviewed. • Cases led to discrepancies of results arising from different types of life cycle studies were discussed. • Limitations in using life cycle studies as decision tools for building design were identified. - Abstract: This paper provides a review on three streams of life cycle studies that have been frequently applied to evaluate the environmental impacts of building construction with a major focus on whether they can be used for decision making. The three streams are Life Cycle Assessment (LCA), Life Cycle Energy Assessment (LCEA) and Life Cycle Carbon Emissions Assessment (LCCO2A). They were compared against their evaluation objectives, methodologies, and findings. Although they share similar objectives in evaluating the environmental impacts over the life cycle of building construction, they show some differences in the major focuses of evaluation and methodologies employed. Generally, it has been revealed that quite consistent results can be derived from the three streams with regard to the relative contribution of different phases of life cycle. However, discrepancies occur among the findings obtained from the three streams when different compositions of fuel mixes are used in power generation, or when the overall impacts are not contributed mostly by greenhouse gases emissions. The use of different functional units in different studies also makes it difficult to compare results with benchmarks or results from previous studies. Besides, there are drawbacks in boundary scoping, methodology framework, data inventory and practices which impair their usefulness as a decision making support tool for sustainable building designs

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

    Science.gov (United States)

    Galvez, Matthieu Emmanuel; Gaillardet, Jérôme

    2012-11-01

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

  12. Resistance Responses of Carbon Fiber Cement to Cycled Compressive Stresses

    Institute of Scientific and Technical Information of China (English)

    SHUI Zhonghe; LI Chao; LIAO Weidong

    2005-01-01

    The stress-resistance relationship of carbon fiber cement was studicd. Attention has been paid to explore the improvement of the stress-resistance sensitivity under cycled stress restriction. The prismy carbon fiber cement sensors were pre-fabricated. The factors such as contents of carbon fibers, silica fume, dispersant and the w/ c were taken into account. The electrical resistance variations with the dynamic and static loads were simulated using a strain-controlled test machine. The test results show that there is an optimal fiber content, with which the compression-sensitivity achieves a high level. The addition of silica fume can improve the sensitivity. Urder the optimal test conditions, the measured resistances can greatly correspond with the changes of the load.

  13. Current views on the regulation of autotrophic carbon dioxide fixation via the Calvin cycle in bacteria

    OpenAIRE

    Dijkhuizen, L; Harder, W

    1984-01-01

    The Calvin cycle of carbon dioxide fixation constitutes a biosynthetic pathway for the generation of (multi-carbon) intermediates of central metabolism from the one-carbon compound carbon dioxide. The product of this cycle can be used as a precursor for the synthesis of all components of cell material. Autotrophic carbon dioxide fixation is energetically expensive and it is therefore not surprising that in the various groups of autotrophic bacteria the operation of the cycle is under strict m...

  14. Quantification of net carbon flux from plastic greenhouse vegetable cultivation: A full carbon cycle analysis

    International Nuclear Information System (INIS)

    Plastic greenhouse vegetable cultivation (PGVC) has played a vital role in increasing incomes of farmers and expanded dramatically in last several decades. However, carbon budget after conversion from conventional vegetable cultivation (CVC) to PGVC has been poorly quantified. A full carbon cycle analysis was used to estimate the net carbon flux from PGVC systems based on the combination of data from both field observations and literatures. Carbon fixation was evaluated at two pre-selected locations in China. Results suggest that: (1) the carbon sink of PGVC is 1.21 and 1.23 Mg C ha-1 yr-1 for temperate and subtropical area, respectively; (2) the conversion from CVC to PGVC could substantially enhance carbon sink potential by 8.6 times in the temperate area and by 1.3 times in the subtropical area; (3) the expansion of PGVC usage could enhance the potential carbon sink of arable land in China overall. - Highlights: → We used full carbon (C) cycle analysis to estimate the net C flux from cultivation. → The plastic greenhouse vegetable cultivation system in China can act as a C sink. → Intensified agricultural practices can generate C sinks. → Expansion of plastic greenhouse vegetable cultivation can enhance regional C sink. - The conversion from conventional vegetable cultivation to plastic greenhouse vegetable cultivation could substantially enhance carbon sink potential by 8.6 and 1.3 times for temperate and subtropical area, respectively.

  15. Importance of vegetation dynamics for future terrestrial carbon cycling

    International Nuclear Information System (INIS)

    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

  16. Importance of vegetation dynamics for future terrestrial carbon cycling

    Science.gov (United States)

    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

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

    International Nuclear Information System (INIS)

    The supercritical carbon dioxide (S-CO2) Brayton cycle is under development at Argonne National Laboratory as an advanced power conversion technology for Sodium-Cooled Fast Reactors (SFRs) as well as other Generation IV advanced reactors as an alternative to the traditional Rankine steam cycle. For SFRs, the S-CO2 Brayton cycle eliminates the need to consider sodium-water reactions in the licensing and safety evaluation, reduces the capital cost of the SFR plant, and increases the SFR plant efficiency. Even though the S-CO2 cycle has been under development for some time and optimal sets of operating parameters have been determined, those earlier development and optimization studies have largely been directed at applications to other systems such as gas-cooled reactors which have higher operating temperatures than SFRs. In addition, little analysis has been carried out to investigate cycle configurations deviating from the selected 'recompression' S-CO2 cycle configuration. In this work, several possible ways to improve S-CO2 cycle performance for SFR applications have been identified and analyzed. One set of options incorporates optimization approaches investigated previously, such as variations in the maximum and minimum cycle pressure and minimum cycle temperature, as well as a tradeoff between the component sizes and the cycle performance. In addition, the present investigation also covers options which have received little or no attention in the previous studies. Specific options include a 'multiple-recompression' cycle configuration, intercooling and reheating, as well as liquid-phase CO2 compression (pumping) either by CO2 condensation or by a direct transition from the supercritical to the liquid phase. Some of the options considered did not improve the cycle efficiency as could be anticipated beforehand. Those options include: a double recompression cycle, intercooling between the compressor stages, and reheating between the turbine stages. Analyses carried

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

    Science.gov (United States)

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

    2016-02-01

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

  19. Extent of partial ice cover due to carbon cycle feedback in a zonal energy balance model

    OpenAIRE

    C. Huntingford; Hargreaves, J. C.; Lenton, T. M.; Annan, J. D.

    2003-01-01

    A global carbon cycle is introduced into a zonally averaged energy balance climate model. The physical model components are similar to those of Budyko (1969) and Sellers (1969). The new carbon components account for atmospheric carbon dioxide concentrations and the terrestrial and oceanic storage of carbon. Prescribing values for the sum of these carbon components, it is found that inclusion of a closed carbon cycle reduces the range of insolation over which stable partial ice cover solutions...

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

    Energy Technology Data Exchange (ETDEWEB)

    Steinfeld, G. [Energy Research Corp., Danbury, CT (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Theroux, Susanna [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; Hartman, Wyatt [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; He, Shaomei [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; Univ. of Wisconsin, Madison, WI (United States); Tringe, Susannah [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.

    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.

  3. Proceses in the Southern Ocean carbon cycle: Dissolution of carbonate sediments and inter-annual variability of carbon fluxes

    OpenAIRE

    Hauck, Judith

    2012-01-01

    The Southern Ocean (SO) carbon cycle is and will be undergoing various changes in a high-CO2 world. This thesis analyzes two key processes: dissolution of carbonate sediments on Antarctic shelves and inter-annual variability of upper ocean carbon fluxes. In the first part of the thesis, the main question is whether dissolution of carbonate sediments from Antarctic shelves can be a negative feedback to ocean acidification. Patterns in the CaCO3 distribution are related to primary production in...

  4. Why are East Asian ecosystems important for carbon cycle research?

    Institute of Scientific and Technical Information of China (English)

    FANG JingYun; TANG YanHong; SON Yohan

    2010-01-01

    @@ The global carbon cycle is one of the most important biogeochemical cycles.Through photosynthesis, green plants absorb CO2 from the atmosphere to produce organic matters, such as sugars, and covert solar energy into chemical energy.The organic matters are then used by all other life forms including humans.When ecosystems and atmosphere are in dynamic equilibrium, the flow of CO2 from the atmosphere into the biosphere because of photosynthesis should be equivalent to the flow of CO2 released back into the atmosphere by respiration.However, during the past century atmospheric CO2 concentration has increased substantially because of the burning of fossil fuels.It is highly likely that the atmospheric increase has resulted in global warming and sea level rise, as suggested by the Intergovernmental Panel on Climate Change (IPCC) [1].

  5. Methane hydrate in the global organic carbon cycle

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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 CO2 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: ► A method for including temporary surface albedo and carbon cycle changes in Life Cycle Impact Assessment (LCIA) is elaborated. ► Concepts are applied to a single bioenergy case whereby a range of feedstock productivities are shown to influence results. ► Results imply that case- and site-specific characterization factors can be essential for a more informed impact assessment. ► Uncertainties and limitations of the proposed methodologies are elaborated.

  7. How life affects the geochemical cycle of carbon

    Science.gov (United States)

    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.

  8. Soil organic matter dynamics and the global carbon cycle

    International Nuclear Information System (INIS)

    The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C·yr-1 is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. We will review many of the major factors that influence soil organic matter dynamics that need to be explicitly considered in development of global estimates of carbon turnover in the world's soils. We will also discuss current decomposition models that are general enough to be used to develop a representation of global soil organic matter dynamics

  9. The SML pump of carbon cycles in oceans

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Different from the solution/physical pump, biological pump and continental shelf pump of carbon cycle in oceans, a new pump named "surface microlayer (SML) pump" is developed based on data obtained from marine investigations and lab study. The SML pump has: (1) left-right dissymmetry of "pH-depth" curve; (2) the non-linearity of "concentration-depth" curve; and (3) difference of affecting confine of the SML pump. The issue of "source" or "sink" of atmospheric CO2 in the Yellow Sea and South China Sea is discussed.

  10. Superior flexibility of a wrinkled carbon shell under electrochemical cycling

    KAUST Repository

    Li, Qianqian

    2014-01-01

    Nanocarbon composites have been extensively employed in engineering alloy-type anodes in order to improve the poor cyclability caused by the enormous volume changes during lithium (Li+) insertion/extraction. The chemical vapor deposited wrinkled carbon shell (WCS) shows high electrical conductivity, excellent thermal stability and remarkable mechanical robustness, which help in retaining the structural integrity around the tin (Sn) anode core despite ∼250% variation in volume during repetitive lithiation and delithiation. In situ transmission electron microscopy reveals no embrittlement in the lithiated WCS, which fully recovers its original shape after severe mechanical deformation with no obvious structural change. Further analysis indicates that the capacity to accommodate large strains is closely related to the construction of the carbon shell, that is, the stacking of wrinkled few-layer graphenes. Both the pre-existing wrinkles and the few-layer thickness render the carbon shell superior flexibility and good elasticity under bending or expansion of the interior volume. Moreover, the WCS possesses fast lithium ion diffusion channels, which have lower activation barriers (∼0.1 eV) than that on a smooth graphene (∼0.3 eV). The results provide an insight into the improvement in cycle performance that can be achieved through carbon coating of anodes of lithium ion batteries. © 2014 The Royal Society of Chemistry.

  11. Including an ocean carbon cycle model into iLOVECLIM (v1.0)

    OpenAIRE

    N. Bouttes; Roche, D. M.; V. Mariotti; L. Bopp

    2015-01-01

    The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a climate model to understand and simulate past and future changes of the carbon cycle. In particular, natural variations of atmospheric CO2 have happened in the past, while anthropogenic...

  12. Including an ocean carbon cycle model into iLOVECLIM (v1.0)

    OpenAIRE

    N. Bouttes; Roche, D. M.; V. Mariotti; L. Bopp

    2015-01-01

    The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a climate model to understand and simulate past and future changes of the carbon cycle. In particular, natural variations of atmospheric CO2 have happened in the past, while anthropogenic...

  13. Terrestrial Carbon Cycle Feedback to Climate Warming: Experimental Evidence

    Science.gov (United States)

    Luo, Y.; Zhou, X.; Sherry, R.

    2006-12-01

    Global climate modeling has demonstrated that climate warming would stimulate respiratory CO2 release from the terrestrial ecosystems to the atmosphere, which in turn leads to more warming in the climate system. This positive feedback between the climate change and the terrestrial carbon cycle can form a vicious cycle that potentially leads to a dangerous threat to ecosystem functioning and service. Some of the key processes underlying this feedback loop, however, have not been carefully examined by experimental studies. Those key processes include temperature sensitivity of ecosystem carbon influx; regulation of carbon processes by warming-induced changes in species composition, and nutrient and water availability; and phenology and timing of ecosystem processes under warming. We have conducted two warming experiments in a Southern Great Plains prairie to examine ecosystem responses to climate warming. We used infrared heaters to elevate soil temperature by approximately 2.0 and 4.0 oC, respectively, during the experimental period. Our results indicate that plant biomass growth increased by approximately 20% in the warmed plots in comparison to that in the control plots. The increased plant productivity likely resulted from extended length of growing seasons since warming advanced phenology of early-flowering species and delayed phenology of late-flowering species, leading to an extension of the growing season. Leaf photosynthesis, however, was not strongly affected by warming. Warming also considerably increased C4 plant biomass and caused slight decreases in growth of C3 plants. Increased C4 biomass and litter production resulted in decreases in quality and decomposition of bulk litter at the ecosystem scale, leading to an increase in litter mass at the soil surface. Soil respiration did not significantly increase in the first two years but increased by 8-10% in the last several years, largely due to increased root respiration and litter pool sizes. We did not

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

    DEFF Research Database (Denmark)

    Thum, T.; Raisanen, P.; Sevanto, S.;

    2011-01-01

    . The new model formulation produced soil carbon stock estimates that were much closer to measured values. It also captured better the seasonal cycle of the direct CO2 exchange measurements at the three grassland sites considered (RMS error reduced by 12%), while for the five forest sites also analyzed......The response of soil organic carbon to climate change might lead to significant feedbacks affecting global warming. This response can be studied by coupled climate-carbon cycle models but so far the description of soil organic carbon cycle in these models has been quite simple. In this work we used...... the coupled climate-carbon cycle model ECHAM5/JSBACH (European Center/Hamburg Model 5/Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg) with two different soil carbon modules, namely (1) the original soil carbon model of JSBACH called CBALANCE and (2) a new soil carbon model Yasso07, to study...

  15. Modelling the carbon cycle though Neoproterozoic Earth system changes

    Science.gov (United States)

    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. Interannual Variations of MLS Carbon Monoxide Induced by Solar Cycle

    Science.gov (United States)

    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.

  17. Influence of sulfur compounds on the terrestrial carbon cycle

    Science.gov (United States)

    Eliseev, A. V.

    2015-11-01

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

  18. Climate-carbon cycle feedbacks under stabilization: uncertainty and observational constraints

    OpenAIRE

    Jones, Chris D.; Cox, Peter M.; Huntingford, Chris

    2011-01-01

    Avoiding ‘dangerous climate change’ by stabilization of atmospheric CO2 concentrations at a desired level requires reducing the rate of anthropogenic carbon emissions so that they are balanced by uptake of carbon by the natural terrestrial and oceanic carbon cycles. Previous calculations of profiles of emissions which lead to stabilized CO2 levels have assumed no impact of climate change on this natural carbon uptake. However, future climate change effects on the land carbon cycle are predict...

  19. Biochar and biological carbon cycling in temperate soils

    Science.gov (United States)

    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

  20. Evaluation of carbon-14 life cycle in reactors VVER-1000

    International Nuclear Information System (INIS)

    This work is aimed at the evaluation of carbon-14 life cycle in light water reactors VVER-1000. Carbon-14 is generated as a side product in different systems of nuclear reactors and has been an issue not only in radioactive waste management but mainly in release into the environment in the form of gaseous effluents. The principal sources of this radionuclide are in primary cooling water and fuel. Considerable amount of C-14 is generated by neutron reactions with oxygen 17O and nitrogen 14N present in water coolant and fuel. The reaction likelihood and consequently volume of generated radioisotope depends on several factors, especially on the effective cross-section, concentrations of parent elements and conditions of power plant operating strategies. Due to its long half-life and high capability of integration into the environment and thus into the living species, it is very important to monitor the movement of carbon-14 in all systems of nuclear power plant and to manage its release out of NPP. The dominant forms of radioactive carbon-14 are the hydrocarbons owing to the combinations with hydrogen used for absorption of radiolytic oxygen. These organic compounds, such as formaldehyde, methyl alcohol, ethyl alcohol and formic acid can be mostly retained on ion exchange resins used in the system for purifying primary cooling water. The gaseous carbon compounds (CH4 and CO2) are released into the atmosphere via the ventilation systems of NPP. Based on the information and data obtained from different sources, it has been designed a balance model of possible carbon-14 pathways throughout the whole NPP. This model includes also mass balance model equations for each important node in system and available sampling points which will be the background for further calculations. This document is specifically not to intended to describe the best monitoring program attributes or technologies but rather to provide evaluation of obtained data and find the optimal way to upgrade

  1. The role of lakes in carbon cycling in boreal catchments

    Energy Technology Data Exchange (ETDEWEB)

    Rantakari, M.

    2010-07-01

    Lakes are an important component of ecosystem carbon cycle through both organic carbon sequestration and carbon dioxide and methane emissions, although they cover only a small fraction of the Earth's surface area. Lake sediments are considered to be one of rather permanent sinks of carbon in boreal regions and furthermore, freshwater ecosystems process large amounts of carbon originating from terrestrial sources. These carbon fluxes are highly uncertain especially in the changing climate. The present study provides a large-scale view on carbon sources and fluxes in boreal lakes situated in different landscapes. We present carbon concentrations in water, pools in lake sediments, and carbon gas (CO{sub 2} and CH{sub 4}) fluxes from lakes. The study is based on spatially extensive and randomly selected Nordic Lake Survey (NLS) database with 874 lakes. The large database allows the identification of the various factors (lake size, climate, and catchment land use) determining lake water carbon concentrations, pools and gas fluxes in different types of lakes along a latitudinal gradient from 60 deg N to 69 deg N. Lakes in different landscapes vary in their carbon quantity and quality. Carbon (C) content (total organic and inorganic carbon) in lakes is highest in agriculture and peatland dominated areas. In peatland rich areas organic carbon dominated in lakes but in agricultural areas both organic and inorganic C concentrations were high. Total inorganic carbon in the lake water was strongly dependent on the bedrock and soil quality in the catchment, especially in areas where human influence in the catchment is low. In inhabited areas both agriculture and habitation in the catchment increase lake TIC concentrations, since in the disturbed soils both weathering and leaching are presumably more efficient than in pristine areas. TOC concentrations in lakes were related to either catchment sources, mainly peatlands, or to retention in the upper watercourses. Retention

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

    Science.gov (United States)

    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.

  3. Toward explaining the Holocene carbon dioxide and carbon isotope records: Results from transient ocean carbon cycle-climate simulations

    OpenAIRE

    Menviel, L.; F. Joos

    2012-01-01

    [1] The Bern3D model was applied to quantify the mechanisms of carbon cycle changes during the Holocene (last 11,000 years). We rely on scenarios from the literature to prescribe the evolution of shallow water carbonate deposition and of land carbon inventory changes over the glacial termination (18,000 to 11,000 years ago) and the Holocene and modify these scenarios within uncertainties. Model results are consistent with Holocene records of atmospheric CO2 and δ13C as well as the spatiotempo...

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

    Science.gov (United States)

    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.

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

    International Nuclear Information System (INIS)

    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

  6. The geological carbon cycle and the global warming / climate debate

    International Nuclear Information System (INIS)

    The extensively cited seasonal carbon cycle describes the size and the annual fluxes between the temporary reservoirs (ocean, atmosphere, biosphere and soils). Compared with these large annual fluxes (approx. 200 GtC/y) the human contribution seems to be of minor amount and is currently (2011) in the range of 4-5%. However, in the geological carbon cycle, which describes the nearly equal amounts of input (volcanoes etc.) and output (sediments) into and from the temporary reservoirs, the human contribution has now reached 30-50 times the average natural level (9.5 Gt C/y versus ca. 0.2-0.3Gt C/y). In the long-term range (1-10x106y), the variable, but much smaller net imbalance between these geological sources und sinks was responsible for the atmospheric CO2-level in the last 400 My (since then comparable temporary reservoirs exist) and influenced via the various feedbacks the climate on earth. In nearly 95% of this long time the climate system was in (nearly) equilibrium conditions and changes occurred extremely slow. Whenever a certain range of higher rate of change of these driving forces were reached, it had - together with other effects - severe influence on the evolution of life, causing 5 large and many minor 'geological accidents'. Based on isotope geochemistry and a fairly good time resolution by orbitally tuned cyclostratigraphy (astrochronology) in the sedimentary record, we are able to quantify these rates of change with reasonable errors. It turns out that the present rate of change - caused by the C-based fossil energy use - is one to two orders of magnitude more rapid than these severe events (impacts excluded) in the earth system. A vast amount of data is available from the ice age cycles. Climate geology (e.g. the group of M. Sarnthein) made considerable progress in understanding the related geological/oceanic processes and proposed a reasonably constrained mass balance of CO2 during the last cycle, which could help us to understand the future

  7. Hydrological effects on carbon cycles of Canada's forests and wetlands

    International Nuclear Information System (INIS)

    The hydrological cycle has significant effects on the terrestrial carbon (C) balance through its controls on photosynthesis and C decomposition. A detailed representation of the water cycle in terrestrial C cycle models is essential for reliable estimates of C budgets. However, it is challenging to accurately describe the spatial and temporal variations of soil water, especially for regional and global applications. Vertical and horizontal movements of soil water should be included. To constrain the hydrology-related uncertainty in modelling the regional C balance, a three-dimensional hydrological module was incorporated into the Integrated Terrestrial Ecosystem Carbon-budget model (InTEC V3.0). We also added an explicit parameterization of wetlands. The inclusion of the hydrological module considerably improved the model's ability to simulate C content and balances in different ecosystems. Compared with measurements at five flux-tower sites, the model captured 85% and 82% of the variations in volumetric soil moisture content in the 0-10 cm and 10-30 cm depths during the growing season and 84% of the interannual variability in the measured C balance. The simulations showed that lateral subsurface water redistribution is a necessary mechanism for simulating water table depth for both poorly drained forest and peatland sites. Nationally, soil C content and their spatial variability are significantly related to drainage class. Poorly drained areas are important C sinks at the regional scale, however, their soil C content and balances are difficult to model and may have been inadequately represented in previous C cycle models. The InTEC V3.0 model predicted an annual net C uptake by Canada's forests and wetlands for the period 1901-1998 of 111.9 Tg C/yr, which is 41.4 Tg C/yr larger than our previous estimate (InTEC V2.0). The increase in the net C uptake occurred mainly in poorly drained regions and resulted from the inclusion of a separate wetland parameterization

  8. Assessing the Information Content in Environmental Modelling: A Carbon Cycle Perspective

    OpenAIRE

    Ian G. Enting

    2008-01-01

    A model represents the way in which information about the world is captured in a form that can be manipulated for application to new situations. However, quantification of `model error' presents formidable challenges. Various inverse problems in carbon cycle modelling are presented as illustrations of the issues. A `maximum-entropy' representation of carbon cycle response is used to explore techniques for non-parametric estimation of carbon cycle uncertainty.

  9. The terrestrial carbon cycle on the regional and global scale : modeling, uncertainties and policy relevance

    NARCIS (Netherlands)

    Minnen, van J.G.

    2008-01-01

    Contains the chapters: The importance of three centuries of climate and land-use change for the global and regional terrestrial carbon cycle; and The terrestrial C cycle and its role in the climate change policy

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

    Science.gov (United States)

    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.

  11. Explaining the seasonal cycle of the globally averaged CO2 with a carbon cycle model

    OpenAIRE

    G. A. Alexandrov

    2014-01-01

    The discrepancy between simulated and observed globally averaged monthly atmospheric concentrations of carbon dioxide could be attributed either to deficiencies in the observation network or to inadequacies in the global carbon cycle models. This paper shows that model results could be brought closer to observations by improving model components that describe the seasonal changes in the storage of quickly decaying fractions of litter.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  14. Features of supercritical carbon dioxide Brayton cycle coupled with reactor

    International Nuclear Information System (INIS)

    In order to obtain acceptable cycle efficiency, current helium gas turbine power cycle technology needs high cycle temperature which means that the cycle needs high core-out temperature. The technology has high requirements on reactor structure and fuel elements materials, and also on turbine manufacture. While utilizing CO2 as cycle working fluid, it can guarantee to lower the cycle temperature and turbo machine Janume but achieve the same cycle efficiency, so as to enhance the safety and economy of reactor. According to the laws of thermodynamics, a calculation model of supercritical CO2 power cycle was established to analyze the feature, and the decisive parameters of the cycle and also investigate the effect of each parameter on the cycle efficiency in detail were obtained. The results show that supercritical CO2 power cycle can achieve quite satisfied efficiency at a lower cycle highest temperature than helium cycle, and CO2 is a promising working fluid. (authors)

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

    Science.gov (United States)

    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. PMID:26732346

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

    Science.gov (United States)

    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...

  17. Further Studies on Oceanic Biogeochemistry and Carbon Cycling

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Directory of Open Access Journals (Sweden)

    P. Ciais

    2013-07-01

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

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

    Science.gov (United States)

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

    2013-07-01

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

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

    Science.gov (United States)

    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.

  2. Response of the terrestrial carbon cycle to the El Niño-Southern Oscillation

    OpenAIRE

    Qian, Haifeng; Joseph, Renu; Zeng, Ning

    2011-01-01

    Land plays a dominant role in the interannual variability of the global carbon cycle. The canonical warming and drying of the terrestrial tropics observed during El Niño events calls for the study of the role of precipitation and temperature on carbon cycle variability. Here we use a dynamic vegetation and terrestrial carbon model vegetation-global-atmosphere-soil (VEGAS) to investigate the response of terrestrial carbon cycle to El Niño-Southern Oscillation (ENSO) for the period 1980–2004. T...

  3. Carbon Cycle Variability Due to the Atlantic Meridional Overturning Circulation

    Science.gov (United States)

    McKinley, G. A.; Breeden, M.

    2014-12-01

    The North Atlantic is the most intense region of CO2 uptake by the world oceans. Though characterization of the mean sink is robust across methodologies [1], a detailed understanding of variability remains lacking, seriously complicating interpretation of observations [2,3]. We investigate the causes of decadal scale variability in the North Atlantic carbon cycle using a regional numerical simulation driven by realistic climate for 1948-2013 and preindustrial atmospheric pCO2. Modeled decadal-timescale variability in air-sea CO2 fluxes and surface ocean pCO2 are dominantly controlled by basin-averaged sea surface temperature (SST). This SST signal is composed of two parts: the Atlantic Multidecadal Oscillation (AMO), associated with the model AMOC, and a positive trend. AMO dominates long-term pCO2 variability, with positive AMO leading to pCO2 declines in the subpolar gyre and pCO2 increases in the subtropical gyre. Decomposition of pCO2 into chemical (pCO2-chem) and temperature (pCO2-SST) drivers is instructive. Maximum positive AMO causes subpolar pCO2-SST to increase by ~10 uatm, but also for pCO2-chem to decline by ~20 uatm. Reduced subpolar pCO2-chem is due to reduced supply of dissolved inorganic carbon (DIC) by winter deep mixing and to enhanced DIC horizontal divergence. On net, positive AMO substantially depresses subpolar North Atlantic pCO2. AMO had maximum negative amplitude in the 1980s and maximum positive amplitude in the mid-2000s, which coincides with the observed record of surface ocean pCO2 [2]. This model suggests that the changing sign of AMO drove trends in the natural component of surface ocean pCO2 of approximately -7 uatm / decade in the subpolar gyre since the 1980s. This trend is significant in comparison to observed changes in surface ocean pCO2 [3], and thus impacts our understanding of the changing ocean carbon sink in this critical region. [1] Schuster et at 2013 [2] McKinley et al. 2011, McKinley and Fay 2013 [3] Metzl et al. 2010

  4. Uncertainty in climate-carbon-cycle projections associated with the sensitivity of soil respiration to temperature

    International Nuclear Information System (INIS)

    Carbon-cycle feedbacks have been shown to be very important in predicting climate change over the next century, with a potentially large positive feedback coming from the release of carbon from soils as global temperatures increase. The magnitude of this feedback and whether or not it drives the terrestrial carbon cycle to become a net source of carbon dioxide during the next century depends particularly on the response of soil respiration to temperature. Observed global atmospheric CO2 concentration, and its response to naturally occurring climate anomalies, is used to constrain the behaviour of soil respiration in our coupled climate-carbon-cycle GCM. This constraint is used to quantify some of the uncertainties in predictions of future CO2 levels. The uncertainty is large, emphasizing the importance of carbon-cycle research with respect to future climate change predictions

  5. Integrating Natural Gas Hydrates in the Global Carbon Cycle

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Optimising the FAMOUS climate model: inclusion of global carbon cycling

    Directory of Open Access Journals (Sweden)

    J. H. T. Williams

    2012-10-01

    Full Text Available FAMOUS fills an important role in the hierarchy of climate models, both explicitly resolving atmospheric and oceanic dynamics yet being sufficiently computationally efficient that either very long simulations or large ensembles are possible. An improved set of carbon cycle parameters for this model has been found using a perturbed physics ensemble technique. This is an important step towards building the "Earth System" modelling capability of FAMOUS, which is a reduced resolution, and hence faster running, version of the Hadley Centre Climate model, HadCM3. Two separate 100 member perturbed parameter ensembles were performed; one for the land surface and one for the ocean. The land surface scheme was tested against present day and past representations of vegetation and the ocean ensemble was tested against observations of nitrate. An advantage of using a relatively fast climate model is that a large number of simulations can be run and hence the model parameter space (a large source of climate model uncertainty can be more thoroughly sampled. This has the associated benefit of being able to assess the sensitivity of model results to changes in each parameter. The climatologies of surface and tropospheric air temperature and precipitation are improved relative to previous versions of FAMOUS. The improved representation of upper atmosphere temperatures is driven by improved ozone concentrations near the tropopause and better upper level winds.

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

    Science.gov (United States)

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

    2016-02-01

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

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

    Science.gov (United States)

    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.

  9. Feedback of global warming to soil carbon cycling in forest ecosystems

    International Nuclear Information System (INIS)

    Thus in this study the simulation of soil carbon cycling and dynamics of its storage in several types of mature forests developed from the cool-temperate to the tropics was carried out for quantitatively assessing carbon loss from the soil under several scenarios of global warming, based on the model of soil carbon cycling in forest ecosystems (Nakane et al. 1984, 1987 and Nakane 1992). (J.P.N.)

  10. Characterizing post-industrial changes in the ocean carbon cycle in an Earth system model

    OpenAIRE

    Matsumoto, Katsumi; Tokos, Kathy S.; Chikamoto, Megumi O.; Ridgwell, Andy

    2011-01-01

    Understanding the oceanic uptake of carbon from the atmosphere is essential for better constraining the global budget, as well as for predicting the air-borne fraction of CO2 emissions and thus degree of climate change. Gaining this understanding is difficult, because the ‘natural’ carbon cycle, the part of the global carbon cycle unaltered by CO2 emissions, also responds to climate change and ocean acidification. Using a global climate model of intermediate complexity, we assess the evolutio...

  11. Modelling the inorganic ocean carbon cycle under past and future climate change

    International Nuclear Information System (INIS)

    This study used a coupled ocean-atmosphere-sea ice model with an inorganic carbon component to examine the inorganic ocean carbon cycle with particular reference to how climate feedback influences future uptake. In the last 150 years, the increase in atmosphere carbon dioxide (CO2) concentrations have been higher than any time during the Earth's history. Although the oceans are the largest sink for carbon dioxide, it is not know how the ocean carbon cycle will respond to increasing anthropogenic carbon dioxide concentrations in the future. Climate feedbacks could potentially reduce further uptake of carbon by the ocean. In addition to examining past climate transitions, including both abrupt and glacial-interglacial climate transitions, this study also examined the sensitivity of the inorganic carbon cycle to increased atmospheric carbon dioxide. Atmospheric carbon dioxide levels were also projected under a range of global warming scenarios. Most simulations identified a transient weakening of the North Atlantic and increased sea surface temperatures (SST). These positive feedbacks act on the carbon system to reduce uptake. However, the ocean has the capacity to take up 65 to 75 per cent of the anthropogenic carbon dioxide increases. An analysis of climate feedback on future carbon uptake shows that oceans store 7 per cent more carbon when there are no climate feedbacks acting on the system. Sensitivity experiments using the Gent McWilliams parameterization for mixing associated with mesoscale eddies show a further 6 per cent increase in oceanic uptake. Inclusion of sea ice dynamics resulted in a 2 per cent difference in uptake. This study also examined changes in atmospheric carbon dioxide concentration that occur during abrupt climate change events. Changes in ocean circulation and carbon solubility cause significant increases in atmospheric carbon dioxide concentrations when melt water episodes are simulated in both hemispheres. The response of the carbon cycle

  12. Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling

    OpenAIRE

    Goll, D. S.; V. Brovkin; Parida, B.R.; Reick, C. H.; Kattge, J.; Reich, P. B.; van Bodegom, P.M.; Niinemets, Ü.

    2012-01-01

    Terrestrial carbon (C) cycle models applied for climate projections simulate a strong increase in net primary productivity (NPP) due to elevated atmospheric CO2 concentration during the 21st century. These models usually neglect the limited availability of nitrogen (N) and phosphorus (P), nutrients that commonly limit plant growth and soil carbon turnover. To investigate how the projected C sequestration is altered when stoichiometric constraints on C cycling are consid...

  13. Transporting carbon dioxide recovered from fossil-energy cycles

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-07-24

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

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

    Science.gov (United States)

    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

  15. The UK transport carbon model: An integrated life cycle approach to explore low carbon futures

    International Nuclear Information System (INIS)

    Current debate focuses on the need for the transport sector to contribute to more ambitious carbon emission reduction targets. In the UK, various macro-economic and energy system wide, top-down models are used to explore the potential for energy demand and carbon emissions reduction in the transport sector. These models can lack the bottom-up, sectoral detail needed to simulate the effects of integrated demand and supply-side policy strategies to reduce emissions. Bridging the gap between short-term forecasting and long-term scenario “models”, this paper introduces a newly developed strategic transport, energy, emissions and environmental impacts model, the UK Transport Carbon Model (UKTCM). The UKTCM covers the range of transport–energy–environment issues from socio-economic and policy influences on energy demand reduction through to life cycle carbon emissions and external costs. The model is demonstrated in this paper by presenting the results of three single policies and one policy package scenario. Limitations of the model are also discussed. Developed under the auspices of the UK Energy Research Centre (UKERC) the UKTCM can be used to develop transport policy scenarios that explore the full range of technological, fiscal, regulatory and behavioural change policy interventions to meet UK climate change and energy security goals. - Research highlights: ►New strategic transport, energy, emissions and environmental impacts model. ►Tool to develop and analyse full consequences of multiple scenarios of transport policy packages. ►Novel approach to modelling demand for new vehicles by market and technology. ►Model available for use by research community via http://www.ukerc.ac.uk/support/tiki-index.php?page=UK+Transport+Carbon+Model.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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. PMID:27203178

  19. Nonlinearity of Ocean Carbon Cycle Feedbacks in CMIP5 Earth System Models

    OpenAIRE

    Schwinger, Jörg; Schwinger, Jörg; Tjiputra, Jerry F.; Heinze, Christoph; Bopp, Laurent; Christian, James R.; Gehlen, Marion; Ilyina, Tatiana; Jones, Chris D.; Salas-Mélia, David; Salas-Mélia, David; Segschneider, Joachim; Séférian, Roland; Séférian, Roland; Totterdell, Ian

    2014-01-01

    Carbon cycle feedbacks are usually categorized into carbon-concentration and carbon-climate feedbacks, which arise owing to increasing atmospheric CO2 concentration and changing physical climate. Both feedbacks are often assumed to operate independently: that is, the total feedback can be expressed as the sum of two independent carbon fluxes that are functions of atmospheric CO2 and climate change, respectively. For phase 5 of the Coupled Model Intercomparison Project (CMIP5), radiatively and...

  20. A Study of Carbon Footprint Calculation of Home Electronics Based on Life Cycle Assessment

    OpenAIRE

    Yu Liu; Xiaoyong Pan; Zhihong Zhuang; Ling Peng; Dong Li

    2013-01-01

    Since, the world climate conference in Copenhagen 2009, low carbon has become the mainstream of the society. Low carbon gets trendy in the area of home electronics and the carbon emission calculation and evaluation draws attention from the home electronics enterprises that have already accumulated some knowledge on this issue. In this study, the carbon emission is assessed from the view of life cycle, consisting of both the direct emission and the indirect ...

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

    Science.gov (United States)

    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.

  2. Performance comparison of different supercritical carbon dioxide Brayton cycles integrated with a solar power tower

    International Nuclear Information System (INIS)

    In this study, a thermodynamic comparison of five supercritical carbon dioxide Brayton cycles integrated with a solar power tower was conducted. The Brayton cycles analyzed were simple Brayton cycle, regenerative Brayton cycle, recompression Brayton cycle, pre-compression Brayton cycle, and split expansion Brayton cycle. A complete mathematical code was developed to carry out the analysis. A heliostat field layout was generated and then optimized on an annual basis using the differential evolution method, which is an evolutionary algorithm. The heliostat field was optimized for optical performance and then integrated with the supercritical CO2 Brayton cycles. Using the results of the optimization, a comparison of net power outputs and thermal efficiencies for these cycles was performed. The findings demonstrated that the highest thermal efficiency was achieved using the recompression Brayton cycle, at June noontime. The maximum integrated system thermal efficiency using this cycle was 40% while the maximum thermal efficiency of this cycle alone was 52%. The regenerative Brayton cycle, although simpler in configuration, shows comparable performance to the recompression Brayton cycle. This analysis was carried out for Dhahran, Saudi Arabia. - Highlights: • The heliostat field of the solar power tower optimized and its optical efficiency identified. • Performance of the solar power tower integrated with five sCO2 Brayton Cycles was assessed. • Recompression supercritical CO2 Brayton cycle has the best performance. • The regenerative supercritical CO2 Brayton cycle has the second best performance

  3. Monitoring, modelling and managing Canada's forest carbon cycle

    International Nuclear Information System (INIS)

    This paper presents information concerning the management of carbon stocks both globally and in Canada, with reference to the fact that forests may contribute to carbon emissions problems. Global fossil carbon emissions statistics were provided, as well as data of forest area per capita in Canada and various countries. Details of forest management options and carbon accounting with reference to the Kyoto Protocol were reviewed. An explanation of forest management credits in national accounts was provided. An explanation of carbon sinks and carbon sources was also presented, along with details of stand level carbon dynamics. A model for calculating landscape level carbon stocks was presented, with reference to increasing and decreasing disturbances. A hypothetical landscape example was provided. It was concluded that age-class structure affect the amount of carbon stored in landscape; age-class structure also affect carbon dynamics; and responses reflect the change in disturbance regimes. An overview of international reporting requirements was presented. Canadian harvests equal 54,000 tonnes of carbon per year. It was recommended that managed forests could increase carbon in forests while also managing carbon harvests to meet society's needs. A chart presenting forest management details was presented, along with a hypothetical landscape example and a forecast for cumulative changes after 50 years, The benefits and challenges of forest management were reviewed as well as options regarding salvaging and deforestation avoidance. A carbon budget model was presented. It was concluded that forests in Canada could be used in a greenhouse gas management strategy. However, changes in disturbance may mean the difference between net source or net sink. Details of biomass were presented and multi-mode combustion facilities. The feasibility of biomass as a fuel source was discussed, with reference to hydrogen fuel. Gas composition profiles were provided, as well as details of

  4. Microbial Enzyme Activity and Carbon Cycling in Grassland Soil Fractions

    Science.gov (United States)

    Allison, S. D.; Jastrow, J. D.

    2004-12-01

    Extracellular enzymes are necessary to degrade complex organic compounds present in soils. Using physical fractionation procedures, we tested whether old soil carbon is spatially isolated from degradative enzymes across a prairie restoration chronosequence in Illinois, USA. We found that carbon-degrading enzymes were abundant in all soil fractions, including macroaggregates, microaggregates, and the clay fraction, which contains carbon with a mean residence time of ~200 years. The activities of two cellulose-degrading enzymes and a chitin-degrading enzyme were 2-10 times greater in organic matter fractions than in bulk soil, consistent with the rapid turnover of these fractions. Polyphenol oxidase activity was 3 times greater in the clay fraction than in the bulk soil, despite very slow carbon turnover in this fraction. Changes in enzyme activity across the restoration chronosequence were small once adjusted for increases in soil carbon concentration, although polyphenol oxidase activity per unit carbon declined by 50% in native prairie versus cultivated soil. These results are consistent with a `two-pool' model of enzyme and carbon turnover in grassland soils. In light organic matter fractions, enzyme production and carbon turnover both occur rapidly. However, in mineral-dominated fractions, both enzymes and their carbon substrates are immobilized on mineral surfaces, leading to slow turnover. Soil carbon accumulation in the clay fraction and across the prairie restoration chronosequence probably reflects increasing physical isolation of enzymes and substrates on the molecular scale, rather than the micron to millimeter scale.

  5. The carbon cycle in the old-growth forests

    OpenAIRE

    Motta R

    2008-01-01

    According to a recent paper published in Nature (Luyssaert et al. 2008) the old-growth forests remove carbon dioxide from the atmosphere and should be considered an important carbon sink at the planetary level. This finding is discussed both in relation to the traditional hypothesis that considered the old-growth forests "neutral" in the carbon balance, and in relation to the present and future importance of this sink at the local and at the planetary level.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Global geochemical cycles of carbon, sulfur and oxygen

    Science.gov (United States)

    Walker, J. C.

    1986-01-01

    Time resolved data on the carbon isotopic composition of carbonate minerals and the sulfur isotopic composition or sulfate minerals show a strong negative correlation during the Cretaceous. Carbonate minerals are isotopically heavy during this period while sulfate minerals are isotopically light. The implication is that carbon is being transferred from the oxidized, carbonate reservoir to the reservoir of isotopically light reduced organic carbon in sedimentary rocks while sulfur is being transferred from the reservoir of isotopically light sedimentary sulfide to the oxidized, sulfate reservoir. These apparently oppositely directed changes in the oxidation state of average sedimentary carbon and sulfur are surprising because of a well-established and easy to understand correlation between the concentrations of reduced organic carbon and sulfide minerals in sedimentary rocks. Rocks rich in reduced carbon are also rich in reduced sulfur. The isotopic and concentration data can be reconciled by a model which invokes a significant flux of hydrothermal sulfide to the deep sea, at least during the Cretaceous.

  8. The Carbon Cycle as the Main Determinant of Glacial-Interglacial Periods

    CERN Document Server

    de la Cuesta, Diego Jiménez; Núñez, Darío; Rumbos, Beatriz; Vergara-Cervantes, Carlos

    2013-01-01

    An intriguing problem in climate science is the existence of Earth's glacial cycle. We show that it is possible to generate these periodic changes in climate by means of the Earth's carbon cycle as the main source factor. The carbon exchange between the Ocean, the Continent and the Atmosphere is modeled by means of a Lotka-Volterra three species system and the resulting atmospheric carbon cycle is used as the unique radiative forcing mechanism. It is shown that the carbon dioxide and temperature paths that are thus obtained have the same qualitative structure as the 100 kyr glacial-interglacial cycles depicted by the Vostok ice core data, reproducing the asymmetries of rapid heating--slow cooling, and short interglacial--long glacial ages.

  9. A Study on Life Cycle CO2 Emissions of Low-Carbon Building in South Korea

    Directory of Open Access Journals (Sweden)

    Su-Hyun Cho

    2016-06-01

    Full Text Available There have been much interest and many efforts to control global warming and reduce greenhouse gas (GHG emissions throughout the world. Recently, the Republic of Korea has also increased its GHG reduction goal and searched for an implementation plan. In buildings, for example, there have been technology developments and deployment policies to reduce GHG emissions from a life cycle perspective, covering construction materials, building construction, use of buildings and waste disposal. In particular, Korea’s Green Standard for Energy and Environmental Design is a certification of environmentally-friendly buildings for their energy saving and reduction of environmental pollution throughout their lives. In fact, the demand and adoption of the certification are rising every year. In construction materials and buildings, as a result, an environmentally-friendly aspect has become crucial. The importance of construction material and building development technologies that can reduce environmental load by diminishing GHG emissions in buildings has emerged. Moreover, there has been a rising necessity to verify the GHG reduction effects of buildings. To assess the reduction of carbon emissions in the buildings built with low-carbon construction technologies and materials, therefore, this study estimated life cycle carbon emissions in reference buildings in which general construction materials are used and in low-carbon buildings. For this, the carbon emissions and their reduction from construction materials (especially concrete between conventional products and low-carbon materials were estimated, using Life Cycle Assessment (LCA. After estimating carbon emissions from a building life cycle perspective, their reduction in low-carbon buildings compared to the reference buildings was reviewed. The results found that compared to conventional buildings, low-carbon buildings revealed a 25% decrease in carbon emissions in terms of the reduction of Life Cycle

  10. Power source life cycle assessment by the Bilan Carbone method

    International Nuclear Information System (INIS)

    Bilan Carbone is a method to assess the amount of spent energy in the form of CO2 formation and its impacts on climate change (carbon footprint). The method assesses each steps in power production, finds hidden energy flows for modelling future energy scenarios. The principles of the method are outlined and an example of its application is presented. (orig.)

  11. Atmospheric Carbon Dioxide and the Global Carbon Cycle: The Key Uncertainties

    Science.gov (United States)

    Peng, T. H.; Post, W. M.; DeAngelis, D. L.; Dale, V. H.; Farrell, M. P.

    1987-12-01

    The biogeochemical cycling of carbon between its sources and sinks determines the rate of increase in atmospheric CO{sub 2} concentrations. The observed increase in atmospheric CO{sub 2} content is less than the estimated release from fossil fuel consumption and deforestation. This discrepancy can be explained by interactions between the atmosphere and other global carbon reservoirs such as the oceans, and the terrestrial biosphere including soils. Undoubtedly, the oceans have been the most important sinks for CO{sub 2} produced by man. But, the physical, chemical, and biological processes of oceans are complex and, therefore, credible estimates of CO{sub 2} uptake can probably only come from mathematical models. Unfortunately, one- and two-dimensional ocean models do not allow for enough CO{sub 2} uptake to accurately account for known releases. Thus, they produce higher concentrations of atmospheric CO{sub 2} than was historically the case. More complex three-dimensional models, while currently being developed, may make better use of existing tracer data than do one- and two-dimensional models and will also incorporate climate feedback effects to provide a more realistic view of ocean dynamics and CO{sub 2} fluxes. The instability of current models to estimate accurately oceanic uptake of CO{sub 2} creates one of the key uncertainties in predictions of atmospheric CO{sub 2} increases and climate responses over the next 100 to 200 years.

  12. Life Cycle Analysis of Carbon Flow and Carbon Footprint of Harvested Wood Products of Larix principis-rupprechtii in China

    Directory of Open Access Journals (Sweden)

    Fei Lun

    2016-03-01

    Full Text Available Larix principis-rupprechtii is a native tree species in North China with a large distribution; and its harvested timbers can be used for producing wood products. This study focused on estimating and comparing carbon flows and carbon footprints of different harvested wood products (HWPs from Larix principis-ruppechtii based on the life cycle analysis (from seedling cultivation to HWP final disposal. Based on our interviews and surveys, the system boundary in this study was divided into three processes: the forestry process, the manufacturing process, and the use and disposal process. By tracking carbon flows of HWPs along the entire life cycle, we found that, for one forest rotation period, a total of 26.81 tC/ha sequestered carbon was transferred into these HWPs, 66.2% of which were still stored in the HWP when the rotation period had ended; however, the HWP carbon storage decreased to 0.25 tC/ha (only 0.9% left in the 100th year after forest plantation. The manufacturing process contributed more than 90% of the total HWP carbon footprint, but it was still smaller than the HWP carbon storage. In terms of the carbon storage and the carbon footprint, construction products had the largest net positive carbon balance compared to furniture and panel products. In addition, HWP are known to have a positive impact on global carbon mitigation because they can store parts of the sequestered carbon for a certain period of time and they have a substitution effect on carbon mitigation. Furthermore, there still exist great opportunities for carbon mitigation from HWPs through the use of cleaner energy and increasing the utilization efficiency of wood fuel.

  13. Major role of marine vegetation on the oceanic carbon cycle

    Directory of Open Access Journals (Sweden)

    N. Caraco

    2004-10-01

    Full Text Available The carbon burial in vegetated sediments, ignored in past assessments of carbon burial in the ocean, was evaluated using a bottom-up approach derived from upscaling a compilation of published individual estimates of carbon burial in vegetated habitats (seagrass meadows, salt marshes and mangrove forests to the global level and a top-down approach derived from considerations of global sediment balance and a compilation of the organic carbon content of vegeatated sediments. Up-scaling of individual burial estimates values yielded a total carbon burial in vegetated habitats of 111 Tg C y-1. The total burial in unvegetated sediments was estimated to be 126 Tg C y-1, resulting in a bottom-up estimate of total burial in the ocean of 244 Tg C y-1, two-fold higher than estimates of oceanic carbon burial that presently enter global carbon budgets. The organic carbon concentrations in vegetated marine sediments exceeds by 2 to 10-fold those in shelf/deltaic sediments. Top-down recalculation of ocean sediment budgets to account for these, previously neglected, organic-rich sediments, yields a top-down carbon burial estimate of 197 Tg C y-1, with vegetated coastal habitats contributing about 50%. Even though vegetated carbon burial contribute about half of the total carbon burial in the ocean, burial represents a small fraction of the net production of these ecosystems, estimated at about 3031 Tg C y-1, suggesting that bulk of the benthic NEP must support excess respiration in other compartments, such as unvegetated sediments and the coastal pelagic compartment. The total excess organic carbon available to be exported to the ocean is estimated at between 769 to 3177 Tg C y-1, the bulk of which must be respired in the open ocean. Widespread loss of vegetated coastal habitats must have reduced carbon burial in the ocean by about 30 Tg C y-1, identifying the destruction of these ecosystems as an important loss of CO2 sink capacity in the biosphere.

  14. Major role of marine vegetation on the oceanic carbon cycle

    Directory of Open Access Journals (Sweden)

    C. M. Duarte

    2005-01-01

    Full Text Available The carbon burial in vegetated sediments, ignored in past assessments of carbon burial in the ocean, was evaluated using a bottom-up approach derived from upscaling a compilation of published individual estimates of carbon burial in vegetated habitats (seagrass meadows, salt marshes and mangrove forests to the global level and a top-down approach derived from considerations of global sediment balance and a compilation of the organic carbon content of vegeatated sediments. Up-scaling of individual burial estimates values yielded a total carbon burial in vegetated habitats of 111 Tmol C y-1. The total burial in unvegetated sediments was estimated to be 126 Tg C y-1, resulting in a bottom-up estimate of total burial in the ocean of about 244 Tg C y-1, two-fold higher than estimates of oceanic carbon burial that presently enter global carbon budgets. The organic carbon concentrations in vegetated marine sediments exceeds by 2 to 10-fold those in shelf/deltaic sediments. Top-down recalculation of ocean sediment budgets to account for these, previously neglected, organic-rich sediments, yields a top-down carbon burial estimate of 216 Tg C y-1, with vegetated coastal habitats contributing about 50%. Even though vegetated carbon burial contributes about half of the total carbon burial in the ocean, burial represents a small fraction of the net production of these ecosystems, estimated at about 3388 Tg C y-1, suggesting that bulk of the benthic net ecosystem production must support excess respiration in other compartments, such as unvegetated sediments and the coastal pelagic compartment. The total excess organic carbon available to be exported to the ocean is estimated at between 1126 to 3534 Tg C y-1, the bulk of which must be respired in the open ocean. Widespread loss of vegetated coastal habitats must have reduced carbon burial in the ocean by about 30 Tg C y-1, identifying the destruction of these ecosystems as an important loss of CO

  15. Life cycle carbon emission flow analysis for electricity supply system: A case study of China

    International Nuclear Information System (INIS)

    The carbon emission embodied in trade is fundamental for allocation of responsibility between producers and consumers. This paper quantitatively analyzes embodied carbon emissions along the life cycle of electricity supply, based on network theory. A modified carbon emission flow model is established, based on life cycle assessment considering power losses. There is also a case study of China's interregional electricity supply system in 2010, focusing on two carbon emission carriers, electricity coal transportation and electricity transmission. Results show that the total carbon emission flow reached 169.355 MtCO2eq, i.e., 4.67% of the life cycle carbon emission. Of this, 61.1% was carried by electricity coal transportation before power generation and transmission, owing to an uneven distribution of coal resources. The eastern and southern regions are the major net sinks of carbon emission flows, representing 52.9% and 27.8% of the total, respectively, because of their enormous energy imports. In contrast, the Sanxi region and central China are major net sources of carbon emission flow. The proposed model may help allocate environmental responsibility among different regions, to guarantee balanced trans-regional development. - Highlights: • Hybrid model of LCA and carbon emission flow analysis is established. • Power supply system of China is abstracted as topological network. • Half of the carbon emission flow is carried by fuel transportation system

  16. The seasonal cycle of carbon dioxide on Mars

    Science.gov (United States)

    James, Philip B.; Kieffer, Hugh H.; Paige, David A.

    1992-01-01

    Results of Viking investigations relevant to the CO2 cycle on Mars are presented, and the extensive modeling efforts directed towards understanding this cycle and its couplings to the seasonal cycles of water and dust are reviewed. It is found that winter condensation is suppressed either because the solid CO2 deposits are inefficient radiators or because of the scattering effects of CO2 clouds. With regard to the qualitative difference between the spring regression curves and between the wind systems for the two seasonal caps, it is suggested that the greater amount of aerosols in the atmosphere during northern winter results in a greater proportion of atmospheric condensation there than in the south. The seasonal pressure curves obtained by the Viking Landers during four Martian years are remarkably similar. It is suggested that the CO2 cycle is not sensitive to atmospheric dust and the meteorological variations accompanying global storms or that some subtle cancellation between different mechanisms suppresses variations.

  17. Terrestrial-marine carbon cycle coupling in ~500-m.y.-old phosphatic brachiopods

    Science.gov (United States)

    Cowan, Clinton A.; Fox, David L.; Runkel, Anthony C.; Saltzman, Matthew R.

    2005-01-01

    Carbon isotope Compositions (??13C) of inarticulate brachiopod shells from Upper Cambrian sandstone in the cratonic interior of Laurentia record a 5??? positive excursion that correlates biostratigraphically with the global Steptoean positive isotopic carbon excursion. A consistent 6??? negative displacement in brachiopod ??13C relative to carbonate values is interpreted to represent an onshore-offshore gradient in the isotopic composition of dissolved inorganic carbon in Cambrian seawater. Thus, these ???500-m.y.-old chitinophosphatic brachiopod shells preserve evidence for carbon cycle coupling between the ancient atmospheric, oceanic, and terrestrial reservoirs in the time before embryophytic land plants. ?? 2005 Geological Society of America.

  18. Simulations of the global carbon cycle and anthropogenic CO2 transient

    International Nuclear Information System (INIS)

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

  19. Ice core-based isotopic constraints on past carbon cycle changes

    OpenAIRE

    Fischer, H.; J. Schmitt; Eggleston, S.; Schneider, R.; Elsig, J.; F. Joos; Leuenberger, M.; T. F. Stocker; P. Köhler; J. Chappellaz

    2015-01-01

    High-precision ice core data on both atmospheric CO2 concentrations and their carbon isotopic composition (δ13Catm) provide improved constraints on the marine and terrestrial processes responsible for carbon cycle changes during the last two interglacials and the preceding glacial/interglacial transitions.

  20. The Impact of Agricultural Soil Erosion on the Global Carbon Cycle

    Science.gov (United States)

    Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 Pg/year to a sink of the same magnitude. By using Caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced...

  1. Characterizing post-industrial changes in the ocean carbon cycle in an Earth system model

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Katsumi; Tokos, Kathy S.; Chikamoto, Megumi O. (Geology and Geophysics, Univ. of Minnesota, MN (United States)), e-mail: katsumi@umn.edu; Ridgwell, Andy (School of Geographical Sciences, Univ. of Bristol, Bristol (United Kingdom))

    2010-10-22

    Understanding the oceanic uptake of carbon from the atmosphere is essential for better constraining the global budget, as well as for predicting the air-borne fraction of CO{sub 2} emissions and thus degree of climate change. Gaining this understanding is difficult, because the 'natural' carbon cycle, the part of the global carbon cycle unaltered by CO{sub 2} emissions, also responds to climate change and ocean acidification. Using a global climate model of intermediate complexity, we assess the evolution of the natural carbon cycle over the next few centuries. We find that physical mechanisms, particularly Atlantic meridional overturning circulation and gas solubility, alter the natural carbon cycle the most and lead to a significant reduction in the overall oceanic carbon uptake. Important biological mechanisms include reduced organic carbon export production due to reduced nutrient supply, increased organic carbon production due to higher temperatures and reduced CaCO{sub 3} production due to increased ocean acidification. A large ensemble of model experiments indicates that the most important source of uncertainty in ocean uptake projections in the near term future are the upper ocean vertical diffusivity and gas exchange coefficient. By year 2300, the model's climate sensitivity replaces these two and becomes the dominant factor as global warming continues

  2. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model

    Directory of Open Access Journals (Sweden)

    R. E. Zeebe

    2011-06-01

    Full Text Available The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  3. Hydrological effects on carbon cycles of Canada’s forests and wetlands

    OpenAIRE

    Ju, Weimin; Chen, Jing M.; Black, T.; Barr, Alan G.; McCaughey, Harry; Roulet, Nigel T.

    2011-01-01

    The hydrological cycle has significant effects on the terrestrial carbon (C) balance through its controls on photosynthesis and C decomposition. A detailed representation of the water cycle in terrestrial C cycle models is essential for reliable estimates of C budgets. However, it is challenging to accurately describe the spatial and temporal variations of soil water, especially for regional and global applications. Vertical and horizontal movements of soil water should be included. To constr...

  4. Ewing Symposium in Honor of Taro Takahashi: The controversial aspects of the contemporary [carbon] cycle

    Energy Technology Data Exchange (ETDEWEB)

    Broecker, Wallace Smith

    2001-12-31

    This Ewing Symposium in honor of Taro Takahashi's work on the carbon cycle was held at Lamont-Doherty Earth Observatory, Palisades, New York, on October 26-27, 2000. A program and set of abstracts are appended to this report. A summary of the meeting (included in this report) will be published in Global Biogeochemical Cycles. The theme of the symposium was the magnitude and cause of excess carbon storage on the north temperate continents. Disagreement exists on the relative roles of forest regrowth and fertilization by excess fixed nitrogen and carbon dioxide, as well as the distribution of this storage. Phenomena playing important roles include pre-anthropogenic gradients in carbon dioxide, the so-called rectification effect, uptake and release of carbon dioxide by the ocean, soil nitrogen dynamics, atmospheric carbon-13 gradients, and the role of fire.

  5. Carbon dioxide power cycles using liquid natural gas as heat sink

    International Nuclear Information System (INIS)

    Liquefied natural gas (LNG) is recognized as a source of usable cryogenic exergy for power cycles. The performance of conventional cycles are calculated. A binary steam-Organic Rankine Cycle (ORC) at 550 deg. C has an efficiency of about 52%, somewhat higher than that of a nitrogen Brayton cycle (50.7% at 700 deg. C). Carbon dioxide is recognized as an almost ideal medium for implementing single fluid condensation cycles. Its proven practical use both at low temperature (by the refrigeration industry) and at high temperature (by the nuclear reactor industry) makes it suitable for direct utilization without any extended preliminary research. A carbon dioxide cycle in its basic configuration featuring a pump, a regenerator, a heater and a condenser is much simpler than the binary steam-ORC cycle but has a lower efficiency (around 47%). All condensing cycles (ORC,CO2,...) exhibit a limited capability of exploiting the whole cryogenic exergy of LNG in that they cannot heat the natural gas at temperatures above the condensation temperature. This drawback is fully overcome in nitrogen Brayton cycles which can heat LNG up to ambient temperature. Slightly modifying the basic CO2 cycle so that it can partially use free thermal energy from sea water increases efficiency to 51%. Multiple condensation cycles allow a better overall performance at the cost of a more complex layout. Compound CO2 cycles, featuring also a gas compressor, exhibit an improved thermodynamics by reducing the temperature difference within the regenerator, with the result of increasing the overall efficiency at values better than those of both binary and Brayton cycles. At 600 deg. C top temperature, for example, a compound cycle at 100 bar maximum pressure has an efficiency of 55.3% (52.3% for a binary steam-ORC cycle at 550 deg. C, 150 bar steam parameters; 46.5% for the nitrogen cycle at 600 deg. C top temperature).

  6. Carbon cycle: A hump in ocean-air exchange

    Science.gov (United States)

    Reddy, Christopher M.

    2016-06-01

    Semivolatile organic compounds from fossil fuels or incomplete combustion are ubiquitous. A suite of circumglobal measurements of their oceanic and atmospheric concentrations reveals large carbon fluxes through the deposition of these compounds.

  7. Life cycle study. Carbon dioxide emissions lower in electric heating than in oil heating

    Energy Technology Data Exchange (ETDEWEB)

    Heikkinen, A.; Jaervinen, P.; Nikula, A.

    1996-11-01

    A primary objective of energy conservation is to cut carbon dioxide emissions. A comparative study on the various heating forms, based on the life cycle approach, showed that the carbon dioxide emissions resulting form heating are appreciably lower now that electric heating has become more common. The level of carbon dioxide emissions in Finland would have been millions of tonnes higher had oil heating been chosen instead of electric heating. (orig.)

  8. Optimal Dynamic Carbon Taxation in a Life-Cycle Model with Distortionary Fiscal Policy

    OpenAIRE

    Rausch, Sebastian; Abrell, Jan

    2014-01-01

    We quantitatively characterize optimal carbon, capital, and labor income taxes in an economy-climate integrated assessment model that features overlapping generations and distortionary fiscal policy. First, we show that the optimal carbon tax significantly differs from the Pigouvian carbon levy in a first-best setting with overlapping generations in which fully rational households optimize over finite lifetimes. The key driving force behind this result is the life-cycle structure of the our m...

  9. Durability based life cycle assessment of concrete with supplementary cementitious materials exposed to carbonation

    OpenAIRE

    Van den Heede, Philip; De Belie, Nele

    2015-01-01

    Until now, it remains unclear how "green" concrete compositions with high volumes of supplementary cementitious materials really are, especially when subject to carbonation-induced steel corrosion. This paper results from accelerated carbonation tests for high-volume fly ash (HVFA) and fly ash + silica fume (FA+SF) concrete. They served as input for a probabilistic service life prediction on fib Bulletin 34, and a subsequent life cycle assessment. the inverse effective carbonation resistance ...

  10. Including a full carbon cycle into the iLOVECLIM model (v1.0)

    OpenAIRE

    N. Bouttes; Roche, D. M.; V. Mariotti-Epelbaum; L. Bopp

    2014-01-01

    The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a climate model to understand and simulate past and future changes of the carbon cycle. In particular, natural variations of atmospheric CO2 have happened in the past, wh...

  11. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

    International Nuclear Information System (INIS)

    The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon-climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr-1 is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback. (author)

  12. New Adsorption Cycles for Carbon Dioxide Capture and Concentration

    Energy Technology Data Exchange (ETDEWEB)

    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

  13. High sensitivity of future global warming to land carbon cycle processes

    International Nuclear Information System (INIS)

    Unknowns in future global warming are usually assumed to arise from uncertainties either in the amount of anthropogenic greenhouse gas emissions or in the sensitivity of the climate to changes in greenhouse gas concentrations. Characterizing the additional uncertainty in relating CO2 emissions to atmospheric concentrations has relied on either a small number of complex models with diversity in process representations, or simple models. To date, these models indicate that the relevant carbon cycle uncertainties are smaller than the uncertainties in physical climate feedbacks and emissions. Here, for a single emissions scenario, we use a full coupled climate–carbon cycle model and a systematic method to explore uncertainties in the land carbon cycle feedback. We find a plausible range of climate–carbon cycle feedbacks significantly larger than previously estimated. Indeed the range of CO2 concentrations arising from our single emissions scenario is greater than that previously estimated across the full range of IPCC SRES emissions scenarios with carbon cycle uncertainties ignored. The sensitivity of photosynthetic metabolism to temperature emerges as the most important uncertainty. This highlights an aspect of current land carbon modelling where there are open questions about the potential role of plant acclimation to increasing temperatures. There is an urgent need for better understanding of plant photosynthetic responses to high temperature, as these responses are shown here to be key contributors to the magnitude of future change. (letter)

  14. Carbon cycle history through the Middle Jurassic of Hungary

    Science.gov (United States)

    Price, Gregory; Fozy, Istvan; Galacz, Andras

    2016-04-01

    A carbonate carbon isotope curve from the Aalenian-Bathonian interval is presented from the Obanya valley, of the Mecsek Mountains, Hungary. This interval is less well constrained and studied that other Jurassic time slices. The Obanya valley lies in the eastern part of the Mecsek Mountains, between Obanya and Kisujbanya and provides excellent exposures of a near continuous Aalenian to Lower Cretaceous sequence. It is not strongly affected by tectonics, as compared to other sections of eastern Mecsek of the same age. In parts, a rich fossil assemblage has been collected; the Bathonian ammonites are especially valuable as this locality. The pelagic Middle Jurassic is represented by thin-bedded limestones (the Obanya Limestone) and is overlain by Upper Jurassic siliceous limestones and radiolarites (the Fonyaszo Limestone). The new data indicates a series of positive anomalies within the late Aalenian and early-middle Bajocian. These data are comparable with carbonate carbon isotope recorded from other Tethyan margin sediments. Our integrated biostratigraphy and carbon isotope stratigraphy enables us to improve stratigraphic correlation and age determination of the examined strata.

  15. Change impact analysis on the life cycle carbon emissions of energy systems – The nuclear example

    International Nuclear Information System (INIS)

    Highlights: • This paper evaluates the life cycle carbon emission of nuclear power in a scenario based approach. • It quantifies the impacts to the LCA results from the change in design parameters. • The methodology can give indications towards preferred or favorable designs. • The findings contribute to the life cycle inventories of energy systems. - Abstract: The life cycle carbon emission factor (measured by t-CO2/GW h) of nuclear power is much lower than those of fossil fueled power generation technologies. However, the fact of nuclear energy being a low carbon power source comes with many assumptions. These assumptions range from system and process definitions, to input–output definitions, to system boundary and cut-off criteria selections, and life cycle inventory dataset. However, there is a somewhat neglected but critical aspect – the design aspect. This refers to the impacts on the life cycle carbon emissions from the change in design parameters related to nuclear power. The design parameters identified in this paper include: (1) the uranium ore grade, (2) the critical process technologies, represented by the average initial enrichment concentration of 235U in the reactor fuel, and (3) the size of the nuclear power reactor (measured by the generating capacity). If not properly tested, assumptions in the design aspect can lead to an erroneous estimation on the life cycle carbon emission factor of nuclear power. In this paper, a methodology is developed using the Process Chain Analysis (PCA) approach to quantify the impacts of the changes in the selected design parameters on the life cycle carbon emission factor of nuclear power. The concept of doing so broadens the scope of PCAs on energy systems from “one-off” calculation to analysis towards favorable/preferred designs. The findings from the analyses can serve as addition to the life cycle inventory database for nuclear power as well as provide indications for the sustainability of nuclear

  16. Carbon cycling along the land to ocean continuum (Invited)

    Science.gov (United States)

    Ciais, P.; Regnier, P.; Friedlingstein, P.; Mackenzie, F. T.; Gruber, N.; Raymond, P. A.

    2013-12-01

    A fraction of atmospheric CO2 taken up on land through photosynthesis and chemical weathering is transported laterally from upland terrestrial ecosystems into the ocean. Global carbon budget estimates have assumed that the lateral transport and sources / sinks along this aquatic continuum have remained unchanged. Based upon the recent review of Regnier et al., the main flux components of carbon fluxes along the land to ocean continuum will be presented, together with more recent estimates of CO2 outgassing fluxes from rivers and lakes. The potential origin of carbon delivered to rivers will be discussed, as well as missing components in the system such as wetlands and flooded regions. How these processes could be incorporated in Earth System Models will be presented.

  17. Durability of Lining Concrete of Subsea Tunnel under Combined Action of Freeze-thaw Cycle and Carbonation

    Institute of Scientific and Technical Information of China (English)

    TIAN Li; CHEN Jingru; ZHAO Tiejun

    2012-01-01

    Through the fast freeze-thaw cycle test,accelerated carbonation test,and natural carbonation test,the durability performance of lining concrete under combined action of freeze-thaw cycle and carbonation were studied.The experimental results indicate that freeze-thaw cycle apparently accelerates the process of concrete carbonation and carbonation deteriorates the freeze resistance of concrete.Under the combined action of freeze-thaw cycle and carbonation,the durability of lining concrete decreases.The carbonation depth of lining concrete at tunnel openings under freeze-thaw cycles and tunnel condition was predicted.For the high performance concrete with proposed mix ratio,the lining concrete tends to be unsafe because predicted carbonation depth exceeds the thickness of reinforced concrete protective coating.Adopting other measurements simultaneously to improve the durability of lining concrete at the tunnel openings is essential.

  18. Quantitative assessment of the differential impacts of arbuscular and ectomycorrhiza on soil carbon cycling.

    Science.gov (United States)

    Soudzilovskaia, Nadejda A; van der Heijden, Marcel G A; Cornelissen, Johannes H C; Makarov, Mikhail I; Onipchenko, Vladimir G; Maslov, Mikhail N; Akhmetzhanova, Asem A; van Bodegom, Peter M

    2015-10-01

    A significant fraction of carbon stored in the Earth's soil moves through arbuscular mycorrhiza (AM) and ectomycorrhiza (EM). The impacts of AM and EM on the soil carbon budget are poorly understood. We propose a method to quantify the mycorrhizal contribution to carbon cycling, explicitly accounting for the abundance of plant-associated and extraradical mycorrhizal mycelium. We discuss the need to acquire additional data to use our method, and present our new global database holding information on plant species-by-site intensity of root colonization by mycorrhizas. We demonstrate that the degree of mycorrhizal fungal colonization has globally consistent patterns across plant species. This suggests that the level of plant species-specific root colonization can be used as a plant trait. To exemplify our method, we assessed the differential impacts of AM : EM ratio and EM shrub encroachment on carbon stocks in sub-arctic tundra. AM and EM affect tundra carbon stocks at different magnitudes, and via partly distinct dominant pathways: via extraradical mycelium (both EM and AM) and via mycorrhizal impacts on above- and belowground biomass carbon (mostly AM). Our method provides a powerful tool for the quantitative assessment of mycorrhizal impact on local and global carbon cycling processes, paving the way towards an improved understanding of the role of mycorrhizas in the Earth's carbon cycle. PMID:26011828

  19. Role of Photoheterotrophic Bacteria in the Marine Carbon Cycle

    Czech Academy of Sciences Publication Activity Database

    Koblížek, Michal

    Washington DC: AAAScience, 2011, s. 49-51. ISBN N R&D Projects: GA ČR GAP501/10/0221 Institutional research plan: CEZ:AV0Z50200510 Keywords : photoheterotrophic bacteria * marine microbiology * microbial carbon pump Subject RIV: EE - Microbiology, Virology

  20. Dependency of climate change and carbon cycle on CO2 emission pathways

    International Nuclear Information System (INIS)

    Previous research has indicated that the response of globally average temperature is approximately proportional to cumulative CO2 emissions, yet evidence of the robustness of this relationship over a range of CO2 emission pathways is lacking. To address this, we evaluate the dependency of climate and carbon cycle change on CO2 emission pathways using a fully coupled climate–carbon cycle model. We design five idealized pathways (including an overshoot scenario for cumulative emissions), each of which levels off to final cumulative emissions of 2000 GtC. The cumulative emissions of the overshoot scenario reach 4000 GtC temporarily, subsequently reducing to 2000 GtC as a result of continuous negative emissions. Although we find that responses of climatic variables and the carbon cycle are largely independent of emission pathways, a much weakened Atlantic meridional overturning circulation (AMOC) is projected in the overshoot scenario despite cessation of emissions. This weakened AMOC is enhanced by rapid warming in the Arctic region due to considerable temporary elevation of atmospheric CO2 concentration and induces the decline of surface air temperature and decrease of precipitation over the northern Atlantic and Europe region. Moreover, the weakened AMOC reduces CO2 uptake by the Atlantic and Arctic oceans. However, the weakened AMOC contributes little to the global carbon cycle. In conclusion, although climate variations have been found to be dependent on emission pathways, the global carbon cycle is relatively independent of these emission pathways, at least superficially. (letter)

  1. China’s Forests and Their Impact on Global Carbon Cycle

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Forests have multiple benefits and functions, including mitigation of climate change. The impacts of forests on the global carbon cycle include forests as carbon sinks, wood-based products as carbon sinks, bio-energy, and production and use of non-timber products. In the past decades, forest cover of China has increased from 8.6% to 18.21% by large-scale afforestation and conversion of cropland into forests. Forest biomass carbon (C) stock increased from 4.3 Pg C (1 Pg C = 1 015 g C) in the early 1980s to 5...

  2. Global carbon cycle perturbation across the Eocene-Oligocene climate transition

    Science.gov (United States)

    Armstrong McKay, David I.; Tyrrell, Toby; Wilson, Paul A.

    2016-02-01

    The Eocene-Oligocene transition (EOT), ~34 Ma, marks a tipping point in the long-term Cenozoic greenhouse to icehouse climate transition. Paleorecords reveal stepwise rapid cooling and ice growth across the EOT tightly coupled to a transient benthic δ13C excursion and a major and permanent deepening of the carbonate compensation depth (CCD). Based on biogeochemical box modeling, Merico et al. (2008) suggested that a combination of (1) glacioeustatic sea level fall-induced shelf-basin carbonate burial fractionation and (2) shelf carbonate weathering can account for the carbon cycle perturbation, but this finding has been questioned. Alternative proposed mechanisms include increased ocean ventilation, decreased carbonate burial, increased organic carbon burial, increased silicate weathering, and increased ocean calcium concentration. Here we use an improved version of the biogeochemical box model of Merico et al. (2008) to reevaluate these competing hypotheses and an additional mechanism, the expansion of "carbon capacitors" such as permafrost and peatlands. We find that changes in calcium concentration, silicate weathering, and carbonate or organic carbon burial each yield a response that is fundamentally at odds with the form and/or sign of the paleorecords. Shelf-basin carbonate burial fractionation (CCD change), plus shelf carbonate weathering, sequestration of 12C-enriched carbon into carbon capacitors, and possibly increased ocean ventilation (δ13C excursion), offers the best fit to the paleorecords. Further work is needed to understand why the EOT carbon cycle perturbation is so unique when the forcing mechanisms hypothesized to be responsible (cooling and ice growth) are not peculiar to this event.

  3. Climate Cycling on Early Mars Caused by the Carbonate-Silicate Cycle

    CERN Document Server

    Batalha, Natasha E; Haqq-Misra, Jacob; Kasting, James F

    2016-01-01

    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 fo...

  4. The changing carbon cycle at Mauna Loa Observatory

    OpenAIRE

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

    2007-01-01

    The amplitude of the CO2 seasonal cycle at the Mauna Loa Observatory (MLO) increased from the early 1970s to the early 1990s but decreased thereafter despite continued warming over northern continents. Because of its location relative to the large-scale atmospheric circulation, the MLO receives mainly Eurasian air masses in the northern hemisphere (NH) winter but relatively more North American air masses in NH summer. Consistent with this seasonal footprint, our findings indicate that the MLO...

  5. Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

    International Nuclear Information System (INIS)

    This report contains the description of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For system development, a computer code was developed to calculate heat balance of 100% power operation condition. Based on the computer code, the S-CO2 Brayton cycle energy conversion system was constructed for the KALIMER-600. Using the developed turbomachinery models, the off-design characteristics and the sensitivities of the S-CO2 turbomachinery were investigated. For the development of PCHE models, a one-dimensional analysis computer code was developed to evaluate the performance of the PCHE. Possible control schemes for power control in the KALIMER-600 S-CO2 Brayton cycle were investigated by using the MARS code. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na/CO2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO2 gas. The long term behavior of a Na/CO2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

  6. Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jae Eun; Kim, S. O.; Seong, S. H.; Eoh, J. H.; Lee, T. H.; Choi, S. K.; Han, J. W.; Bae, S. W

    2007-12-15

    This report contains the description of the S-CO{sub 2} Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For system development, a computer code was developed to calculate heat balance of 100% power operation condition. Based on the computer code, the S-CO{sub 2} Brayton cycle energy conversion system was constructed for the KALIMER-600. Using the developed turbomachinery models, the off-design characteristics and the sensitivities of the S-CO{sub 2} turbomachinery were investigated. For the development of PCHE models, a one-dimensional analysis computer code was developed to evaluate the performance of the PCHE. Possible control schemes for power control in the KALIMER-600 S-CO{sub 2} Brayton cycle were investigated by using the MARS code. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na/CO{sub 2} boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO{sub 2} gas. The long term behavior of a Na/CO{sub 2} boundary failure event and its consequences which lead to a system pressure transient were evaluated.

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

    Science.gov (United States)

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

    2015-08-01

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

  8. Workshop highlights iron dynamics in ocean carbon cycle

    OpenAIRE

    Johnson, Kenneth S.; Moore, J. Keith; Smith, Walker O

    2002-01-01

    The role of iron in regulating the flux of carbon through the surface layer of the ocean has become increasingly apparent during the past 15 years. Before that time, the analytical challenges of measuring trace (parts per trillion) iron concentrations from iron ships using gear suspended on an iron wire precluded oceanographers from making accurate measurements. Laboratory experiments were invariably conducted with samples that were seriously contaminated with elevated iron concentrations. We...

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

    OpenAIRE

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

    2009-01-01

    Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy ≈60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming...

  10. The cycling of carbon into and out of dust

    CERN Document Server

    Jones, Anthony P; Koehler, Melanie; Fanciullo, Lapo; Bocchio, Marco; Micelotta, Elisabetta; Verstraete, Laurent; Guillet, Vincent

    2014-01-01

    Observational evidence seems to indicate that the depletion of interstellar carbon into dust shows rather wide variations and that carbon undergoes rather rapid recycling in the interstellar medium (ISM). Small hydrocarbon grains are processed in photo-dissociation regions by UV photons, by ion and electron collisions in interstellar shock waves and by cosmic rays. A significant fraction of hydrocarbon dust must therefore be re-formed by accretion in the dense, molecular ISM. A new dust model (Jones et al., Astron. Astrophys., 2013, 558, A62) shows that variations in the dust observables in the diffuse interstellar medium (nH = 1000 cm^3), can be explained by systematic and environmentally-driven changes in the small hydrocarbon grain population. Here we explore the consequences of gas-phase carbon accretion onto the surfaces of grains in the transition regions between the diffuse ISM and molecular clouds (e.g., Jones, Astron. Astrophys., 2013, 555, A39). We find that significant carbonaceous dust re-processi...

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

    Science.gov (United States)

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

    2015-12-01

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

  12. Increasing the Confidence of African Carbon Cycle Assessments

    Science.gov (United States)

    Ardö, Jonas

    2016-04-01

    Scarcity of in situ measurements of greenhouse gas (GHG) fluxes hamper calibration and validation of assessments of carbon budgets in Africa. It limits essential studies of ecosystem function and ecosystem processes. The wide range reported net primary production (NPP) and gross primary production (GPP) for continental African is partly a function of the uncertainty originating from this data scarcity. GPP estimates, based on vegetation models and remote sensing based models, range from ~17 to ~40 Pg C yr‑1 and NPP estimates roughly range from ~7 to ~20 Pg C yr‑1 for continental Africa. According to the MOD17 product does Africa contribute about 23 % of the global GPP and about 25 % of the global NPP. These percentages have recently increased slightly. Differences in modeled carbon use efficiency (i.e. the NPP/GPP ratio) further enhance the uncertainty caused by low spatial resolution driver data sets when deriving NPP from GPP. Current substantial uncertainty in vegetation productivity estimates for Africa (both magnitudes and carbon use efficiency) may be reduced by increased abundance and availability of in situ collected field data including meteorology, radiation, spectral properties, GHG fluxes as well as long term ecological field experiments. Current measurements of GHGs fluxes in Africa are sparse and lacking impressive coordination. The European Fluxes Database Cluster includes ~24 African sites with carbon flux data, most of them with a small amount of data in short time series. Large and diverse biomes such as the evergreen broad leafed forest are under-represented whereas savannas are slightly better represented. USA for example, with 171 flux site listed in FLUXNET has a flux site density of 17 sites per million km2, whereas Africa has density of 0.8 sites per million km2. Increased and coordinated collection of data on fluxes of GHGs, ecosystem properties and processes, both through advanced micro meteorological measurements and through cost

  13. Sustainable management of the global carbon cycle through geostorage of wood.

    Science.gov (United States)

    Kreysa, Gerhard

    2009-07-20

    Combustion of fossil energy sources has caused the carbon inventory of the atmosphere to increase by more than 200 Gt. It will be almost impossible to prevent it from growing by at least another 400 Gt in the present century. Theoretically, there exists only one single possibility to effect a decline of the resultant increase in atmospheric CO(2) concentration: the excess carbon has to be removed from the carbon cycle by transferring it into an environment in which it is safe from oxidation, just as is the case for the deposits of fossil fuels. Only natural photosynthesis offers the possibility of efficiently fixing carbon dioxide from the air and removing it from the carbon cycle through geostorage of the resulting biomass. The present paper shows, in the context of an initial feasibility study, that the use of forests and the geostorage of wood in an environment corresponding to lignite deposits represents the ecologically most sensible and economical variant of removal of carbon from the carbon cycle and, thereby, reclamation of the atmosphere. PMID:19554607

  14. Global redox cycle of biospheric carbon: Interaction of photosynthesis and earth crust processes.

    Science.gov (United States)

    Ivlev, Alexander A

    2015-11-01

    A model of the natural global redox cycle of biospheric carbon is introduced. According to this model, carbon transfer between biosphere and geospheres is accompanied by a conversion of the oxidative forms, presented by CO2, bicarbonate and carbonate ions, into the reduced forms, produced in photosynthesis. The mechanism of carbon transfer is associated with two phases of movement of lithospheric plates. In the short-term orogenic phase, CO2 from the subduction (plates' collisions) zones fills the "atmosphere-hydrosphere" system, resulting in climate warming. In the long-term quiet (geosynclynal) phase, weathering and photosynthesis become dominant depleting the oxidative forms of carbon. The above asymmetric periodicity exerts an impact on climate, biodiversity, distribution of organic matter in sedimentary deposits, etc. Along with photosynthesis expansion, the redox carbon cycle undergoes its development until it reaches the ecological compensation point, at which CO2 is depleted to the level critical to support the growth and reproduction of plants. This occurred in the Permo-Carboniferous time and in the Neogene. Shorter-term perturbations of the global carbon cycle in the form of glacial-interglacial oscillations appear near the ecological compensation point. PMID:26477601

  15. FOREST ECOLOGY. Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models.

    Science.gov (United States)

    Anderegg, W R L; Schwalm, C; Biondi, F; Camarero, J J; Koch, G; Litvak, M; Ogle, K; Shaw, J D; Shevliakova, E; Williams, A P; Wolf, A; Ziaco, E; Pacala, S

    2015-07-31

    The impacts of climate extremes on terrestrial ecosystems are poorly understood but important for predicting carbon cycle feedbacks to climate change. Coupled climate-carbon cycle models typically assume that vegetation recovery from extreme drought is immediate and complete, which conflicts with the understanding of basic plant physiology. We examined the recovery of stem growth in trees after severe drought at 1338 forest sites across the globe, comprising 49,339 site-years, and compared the results with simulated recovery in climate-vegetation models. We found pervasive and substantial "legacy effects" of reduced growth and incomplete recovery for 1 to 4 years after severe drought. Legacy effects were most prevalent in dry ecosystems, among Pinaceae, and among species with low hydraulic safety margins. In contrast, limited or no legacy effects after drought were simulated by current climate-vegetation models. Our results highlight hysteresis in ecosystem-level carbon cycling and delayed recovery from climate extremes. PMID:26228147

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

    Science.gov (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Dong Liu

    2015-06-01

    Full Text Available 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.

  18. Carbon and nitrogen stoichiometry and nitrogen cycling rates in streams.

    Science.gov (United States)

    Dodds, Walter K; Martí, Eugenia; Tank, Jennifer L; Pontius, Jeffrey; Hamilton, Stephen K; Grimm, Nancy B; Bowden, William B; McDowell, William H; Peterson, Bruce J; Valett, H Maurice; Webster, Jackson R; Gregory, Stan

    2004-08-01

    Stoichiometric analyses can be used to investigate the linkages between N and C cycles and how these linkages influence biogeochemistry at many scales, from components of individual ecosystems up to the biosphere. N-specific NH4+ uptake rates were measured in eight streams using short-term 15N tracer additions, and C to N ratios (C:N) were determined from living and non-living organic matter collected from ten streams. These data were also compared to previously published data compiled from studies of lakes, ponds, wetlands, forests, and tundra. There was a significant negative relationship between C:N and N-specific uptake rate; C:N could account for 41% of the variance in N-specific uptake rate across all streams, and the relationship held in five of eight streams. Most of the variation in N-specific uptake rate was contributed by detrital and primary producer compartments with large values of C:N and small values for N-specific uptake rate. In streams, particulate materials are not as likely to move downstream as dissolved N, so if N is cycling in a particulate compartment, N retention is likely to be greater. Together, these data suggest that N retention may depend in part on C:N of living and non-living organic matter in streams. Factors that alter C:N of stream ecosystem compartments, such as removal of riparian vegetation or N fertilization, may influence the amount of retention attributed to these ecosystem compartments by causing shifts in stoichiometry. Our analysis suggests that C:N of ecosystem compartments can be used to link N-cycling models across streams. PMID:15179578

  19. Monolith catalysts for closed-cycle carbon dioxide lasers

    Science.gov (United States)

    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.

  20. Synthesis on the carbon budget and cycling in a Danish, temperate deciduous forest

    DEFF Research Database (Denmark)

    Wu, Jian; Larsen, Klaus Steenberg; van der Linden, Leon; Beier, Claus; Pilegaard, Kim; Ibrom, Andreas

    2013-01-01

    within the ecosystem. The results showed that this temperate deciduous forest was a moderate carbon sink (258±41gCm−2 yr−1) with both high rates of gross primary production (GPP, 1881±95gCm−2 yr−1) and ecosystem respiration (Re, 1624±197gCm−2 yr−1). Approximately 62% of the gross assimilated carbon was......A synthesis of five years (2006–2010) of data on carbon cycling in a temperate deciduous forest, Sorø (Zealand, Denmark) was performed by combining all available data from eddy covariance, chamber, suction cups, and biometric measurements. The net ecosystem exchange of CO2 (NEE), soil respiration......, tree growth, litter production and leaching of dissolved inorganic and organic carbon were independently estimated and used to calculate other unmeasured ecosystem carbon budget (ECB) components, based on mass balance equations. This provided a complete assessment of the carbon storage and allocation...

  1. The impact of agricultural soil erosion on the global carbon cycle

    Science.gov (United States)

    Van Oost, Kristof; Quine, T.A.; Govers, G.; De Gryze, S.; Six, J.; Harden, J.W.; Ritchie, J.C.; McCarty, G.W.; Heckrath, G.; Kosmas, C.; Giraldez, J.V.; Marques Da Silva, J.R.; Merckx, R.

    2007-01-01

    Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year -1 to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year-1 resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO2.

  2. Carbon footprint evaluation at industrial park level: A hybrid life cycle assessment approach

    International Nuclear Information System (INIS)

    Industrial parks have become the effective strategies for government to promote sustainable economic development due to the following advantages: shared infrastructure and concentrated industrial activities within planned areas. However, due to intensive energy consumption and dependence on fossil fuels, industrial parks have become the main areas for greenhouse gas emissions. Therefore, it is critical to quantify their carbon footprints so that appropriate emission reduction policies can be raised. The objective of this paper is to seek an appropriate method on evaluating the carbon footprint of one industrial park. The tiered hybrid LCA method was selected due to its advantages over other methods. Shenyang Economic and Technological Development Zone (SETDZ), a typical comprehensive industrial park in China, was chosen as a case study park. The results show that the total life cycle carbon footprint of SETDZ was 15.29 Mt, including 6.81 Mt onsite (direct) carbon footprint, 8.47 Mt upstream carbon footprint, and only 3201 t downstream carbon footprint. Analysis from industrial sector perspectives shows that chemical industry and manufacture of general purpose machinery and special purposes machinery sector were the two largest sectors for life cycle carbon footprint. Such a sector analysis may be useful for investigation of appropriate emission reduction policies. - Highlights: ► A hybrid LCA model was employed to calculate industrial park carbon footprint. ► A case study on SETDZ is done. ► Life cycle carbon footprint of SETDZ is 15.29 Mt. ► Upstream and onsite carbon footprints account for 55.40% and 44.57%, respectively. ► Chemical industry and machinery manufacturing sectors are the two largest sectors

  3. 金刚石与深部碳循环%Diamond and deep carbon cycle.

    Institute of Scientific and Technical Information of China (English)

    张舟; 张宏福

    2011-01-01

    深部碳循环是全球碳循环研究中不可或缺的部分.较之表层碳,人类对地球深部碳储库的储量、碳的迁移方式和交换量都缺乏清晰认识.作为来自地球深部的碳单质矿物,金刚石是研究深部碳循环的绝佳样品.近年来原位微区分析技术的突飞猛进为研究金刚石及深部碳循环提供了良好条件.文中对表层与深部碳交换、深部碳储库及金刚石矿物学性质进行了介绍,并通过金刚石及其包裹体的稳定同位素组成,探讨了金刚石的形成机制及含碳流体/熔体的性质与来源问题.%Deep carbon cycle is an indispensable part of global carbon cycle While extensive research has been done on surface carbon cycle, there is still little understanding of the carbon in deep earth. We do not know bow much carbon is stored in deep repository, nor do we quantify the migration of carbon between different repositories and its exchange with earth's surface. As a simple substance mineral of carbon from deep earth, diamond is a wonderful window of glimpsing deep carbon cycle. Recent rapid development of in-situ micro-analysis techniques provides strong support for diamond and deep carbon cycle research. This article makes a brief introduction on carbon exchange between surface and deep earth, deep carbon repositories and mineral characteristics of diamond. Subsequently, a discussion is made for mechanism of diamond formation, characteristics and sources ot deep earth's carbon-containing fluid/melt through stable isotopes compositions of diamond and its inclusion.

  4. Linking carbon and water cycles using stable isotopes across scales: progress and challenges

    Directory of Open Access Journals (Sweden)

    C. Werner

    2011-03-01

    Full Text Available Stable isotope analysis is a powerful tool for tracing biogeochemical processes in the carbon and water cycles. One particularly powerful approach is to employ multiple isotopes where the simultaneous assessment of the D/H,18O/16O and/or 13C/12C in different compounds provide a unique means to investigate the coupling of water and carbon fluxes at various temporal and spatial scales. Here, we present a research update on recent advances in our process-based understanding of the utilization of carbon, oxygen and hydrogen isotopes to lend insight into carbon and water cycling. We highlight recent technological developments and approaches, their strengths and methodological precautions with examples covering scales from minutes to centuries and from the leaf to the globe.

  5. Modern biofuels life-cycle effects on black carbon emissions and impacts

    Science.gov (United States)

    Campbell, J.; Spak, S.; Mena-Carrasco, M.; Carmichael, G. R.; Chen, Y.; Tsao, C.

    2010-12-01

    The rapid growth of modern biofuels production (primarily ethanol) contributes to increased black carbon and co-pollutant emissions, particularly due to the field burning of agriculture wastes and the indirect land use impacts of forest clearing. U.S. bioenergy policy has already mandated life-cycle emissions thresholds for greenhouse gases from biofuels but there is still a need to incorporate black carbon and other short-lived climate forcers into these metrics. Thus, an understanding of the biofuels sector for black carbon and co-pollutant emissions and impacts remains a critical knowledge gap. Here we combine high-resolution agronomic data and regional chemical transport modeling to consider the life-cycle emissions of black carbon from sugarcane ethanol production in Brazil. Furthermore, we explore the potential for significant radiative forcing from the pre-harvest burning of sugarcane fields and the indirect land use emissions associated with deforestation.

  6. Land and ocean carbon cycle feedback effects on global warming in a simple Earth system model

    OpenAIRE

    Lenton, Timothy M.

    2011-01-01

    A simple Earth system model is developed by coupling a box model of the global carbon cycle to an energy-balance approximation of global temperature. The model includes a range of feedback mechanisms between atmospheric CO2, surface temperature and land and ocean carbon cycling. It is used to assess their effect on the global change being driven by anthropogenic CO2 emissions from fossil fuel burning and land-use change. When tuned to reach the 1990 level of atmospheric CO2, the model CO2 pre...

  7. Carbon and Energy Footprints of Prefabricated Industrial Buildings: A Systematic Life Cycle Assessment Analysis

    OpenAIRE

    Emanuele Bonamente; Franco Cotana

    2015-01-01

    A systematic analysis of green-house gases emission (carbon footprint) and primary energy consumption (energy footprint) of prefabricated industrial buildings during their entire life cycle is presented. The life cycle assessment (LCA) study was performed in a cradle-to grave approach: site-specific data from an Italian company, directly involved in all the phases from raw material manufacturing to in-situ assembly, were used to analyze the impacts as a function of different design choices. F...

  8. The African contribution to the global climate-carbon cycle feedback of the 21st century

    Science.gov (United States)

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

    2008-12-01

    Future climate change will have impact on global and regional terrestrial carbon balances. The fate of African tropical forests over the 21st century has been investigated through global coupled climate carbon cycle model simulations. Under the SRES-A2 socio-economic CO2 emission scenario of the IPCC, and using the Institut Pierre Simon Laplace coupled ocean-terrestrial carbon cycle and climate model, IPSL-CM4-LOOP, we found that the warming over African ecosystems induces a reduction of net ecosystem productivity, making a 20% contribution to the global climate-carbon cycle positive feedback. However, the African rainforest ecosystem alone makes only a negligible contribution to the overall feedback, much smaller than the one arising from the Amazon forest. This is first because of the two times smaller area of forest in Africa, but also because of the relatively lower local land carbon cycle sensitivity to climate change. This beneficial role of African forests in mitigating future climate change should be taken into account when designing forest conservation policy.

  9. On the relative roles of carbonate and molecular CO2 in subduction zones: implications for Earth's deep carbon cycle (Invited)

    Science.gov (United States)

    Manning, C. E.; Kavner, A.; Chopelas, A.

    2010-12-01

    Subduction-zone volcanism returns oxidized carbon (chiefly CO2) to Earth’s surface reservoirs. However, the mechanism by which this carbon is transferred from the slab to the arc-magma source region is uncertain. Phase equilibrium studies of subduction zones indicate that in the absence of fluids carbonate minerals are quite stable along slab P-T paths, so their simple breakdown cannot be a significant mechanism for CO2 loss, at least to subarc depths. Alternatively, CO2 can be generated from slab carbonates by infiltration of an H2O-rich fluid, driving reactions that can be modeled by aragonite + quartz = wollastonite + CO2. However, the high P and low T of subduction zones causes maximum CO2 concentrations to remain low at depths model mineral assemblages of the slab (e.g., jadeite-paragonite-quartz) or mantle wedge (talc-olivine) is 4-6. Because CaCO3 solubility increases strongly with decreasing pH, the dissolved carbonic acid concentration in slab fluids is likely higher by 5 to 500x. Because of these substantial pH effects, carbonic acid may be the dominant form of oxidized carbon as it is transported from the slab to the site of melting in subduction zones, and thus likely plays a key role in the operation of the Earth’s deep carbon cycle.

  10. From life-cycle assessment towards life-cycle design of carbon dioxide capture and utilization

    OpenAIRE

    von der Assen, Niklas

    2016-01-01

    The increasing use of fossil resources will inevitably lead to CO2 emissions and an increasing atmospheric CO2 concentration. The increased CO2 concentration is one of the main reasons for the earth's global warming. To mitigate global warming and the depletion of fossil resources, CO2 can be captured and subsequently utilized as alternative carbon source for fuels, chemicals and materials. However, both CO2 capture and utilization (CCU) typically require energy whose provision is again asso...

  11. Nitrogen restrictions buffer modeled interactions of water with the carbon cycle

    Science.gov (United States)

    Huang, Yuanyuan; Gerber, Stefan

    2016-01-01

    Terrestrial carbon and water cycles are coupled at multiple spatiotemporal scales and are crucial to carbon sequestration. Water related climate extremes, such as drought and intense precipitation, can substantially affect the carbon cycle. Meanwhile, nitrogen is a limiting resource to plant and has therefore the potential to alter the coupling of water and carbon cycles on land. Here we assess the effect of nitrogen limitation on the response of the terrestrial carbon cycle to moisture anomalies using Geophysical Fluid Dynamics Laboratory's land surface model LM3V-N. We analyzed the response of three central carbon fluxes: net primary productivity (NPP), heterotrophic respiration (Rh), and net ecosystem productivity (NEP, the difference between NPP and Rh) and how these fluxes were altered under anomalies of the standardized precipitation and evapotranspiration index (SPEI). We found that globally, the correlations between each of the carbon flux and SPEI depended on the timescale and a strong legacy effect of SPEI anomalies on Rh. Consideration of nitrogen constraints reduced anomalies in carbon fluxes in response to extreme dry/wet events. This nitrogen-induced buffer constrained the growth of plants under wet extremes and allowed for enhanced growth during droughts. Extra gain of soil moisture from the downregulation of canopy transpiration by nitrogen limitation and shifts in the relative importance of water and nitrogen limitation during dry/wet extreme events are possible mechanisms contributing to the buffering of modeled NPP and NEP. Responses of Rh to moisture anomalies were much weaker compared to NPP, and N buffering effects were less evident.

  12. LASCAT - DESIGN OF CATALYTIC MONOLITHS FOR CLOSED-CYCLE CARBON DIOXIDE LASERS

    Science.gov (United States)

    Guinn, K.

    1994-01-01

    Pulsed carbon dioxide lasers are useful in many areas, including aeronautics, space research, and weather monitoring. Most applications require a closed-cycle carbon dioxide laser, which is more portable and self-sustaining than an open-cycle system. Without a fresh carbon dioxide supply and provisions for byproduct disposal, the closed-cycle laser must recycle the carbon monoxide and oxygen gas produced by the lasing of carbon dioxide. The recombination of the carbon monoxide and oxygen gas byproducts to form a constant supply of carbon dioxide requires an active catalyst, which must be carefully designed to optimize laser performance in accordance with design requirements specific to the laser's application. LASCAT (Design of Catalytic Monoliths for Closed-Cycle Carbon Dioxide Lasers) aids in the design of the monolith catalyst by simulating the results of design decisions on the performance of the laser. In portable laser systems, considerations of size, weight, and cost are critical. LASCAT provides the opportunity for the designer to explore trade-offs between the catalyst activity, catalyst dimensions, monolith dimensions, pressure drop (a result of gas flow through the monolith), Oxygen gas conversion, and other variables. The program uses a flexible, simplified model of the monolith catalyst designed to determine the bulk-avarage gas temperature, composition, and pressure along its length. The user specifies values for the several parameters which define the catalyst's operating conditions, including monolith dimensions, gas inlet properties, thermal operation properties, and catalyst properties. LASCAT provides results which indicate whether the experimental design meets user-defined constraints such as limits on conversion rate, maximum gas temperature, and monolith weight. LASCAT is written in FORTRAN 77 and is designed for use with any text or character-based terminal or computer display. The program requires roughly 40 KB memory. LASCAT was developed

  13. Assessing the role of soil chemoautotrophs in carbon cycling: An investigation into isotopically labelled soil microorganisms

    OpenAIRE

    Hart, Kris M.

    2011-01-01

    Recently observed increases in atmospheric CO2 have created great interest in carbon capture technologies and natural sinks of this major component of the carbon cycle. Humic substances are a large, operationally defined fraction of soil organic matter. It was thought that humic substances consist of cross-linked macromolecular structures forming a distinct class of compounds. However, it was recently concluded by members of my research group that the vast majority of humic material in soils,...

  14. Prospective life cycle carbon abatement for pyrolysis biochar systems in the UK

    International Nuclear Information System (INIS)

    Life cycle assessment (LCA) of slow pyrolysis biochar systems (PBS) in the UK for small, medium and large scale process chains and ten feedstocks was performed, assessing carbon abatement and electricity production. Pyrolysis biochar systems appear to offer greater carbon abatement than other bioenergy systems. Carbon abatement of 0.7-1.3 t CO2 equivalent per oven dry tonne of feedstock processed was found. In terms of delivered energy, medium to large scale PBS abates 1.4-1.9 t CO2e/MWh, which compares to average carbon emissions of 0.05-0.30 t CO2e/MWh for other bioenergy systems. The largest contribution to PBS carbon abatement is from the feedstock carbon stabilised in biochar (40-50%), followed by the less certain indirect effects of biochar in the soil (25-40%)-mainly due to increase in soil organic carbon levels. Change in soil organic carbon levels was found to be a key sensitivity. Electricity production off-setting emissions from fossil fuels accounted for 10-25% of carbon abatement. The LCA suggests that provided 43% of the carbon in the biochar remains stable, PBS will out-perform direct combustion of biomass at 33% efficiency in terms of carbon abatement, even if there is no beneficial effect upon soil organic carbon levels from biochar application. - Research highlights: → Biochar systems offer greater carbon abatement than combustion or gasification. → Carbon abatement of 0.7-1.4t CO2e/dry tonne of feedstock processed was found. → Change in soil organic carbon stocks induced by biochar is the key sensitivity. → Biochar systems produce less electricity then combustion or gasification.

  15. An investigation into linearity with cumulative emissions of the climate and carbon cycle response in HadCM3LC

    OpenAIRE

    Liddicoat, S. K.; Booth, B. B. B.; M. M. Joshi

    2016-01-01

    We investigate the extent to which global mean temperature, precipitation, and the carbon cycle are constrained by cumulative carbon emissions throughout four experiments with a fully coupled climate-carbon cycle model. The two paired experiments adopt contrasting, idealised approaches to climate change mitigation at different action points this century, with total emissions exceeding two trillion tonnes of carbon in the later pair. Their initially diverging cumulative emissions trajectories ...

  16. Responses in Arctic marine carbon cycle processes: conceptual scenarios and implications for ecosystem function

    Directory of Open Access Journals (Sweden)

    Helen S. Findlay

    2015-04-01

    Full Text Available The Arctic Ocean is one of the fastest changing oceans, plays an important role in global carbon cycling and yet is a particularly challenging ocean to study. Hence, observations tend to be relatively sparse in both space and time. How the Arctic functions, geophysically, but also ecologically, can have significant consequences for the internal cycling of carbon, and subsequently influence carbon export, atmospheric CO2 uptake and food chain productivity. Here we assess the major carbon pools and associated processes, specifically summarizing the current knowledge of each of these processes in terms of data availability and ranges of rates and values for four geophysical Arctic Ocean domains originally described by Carmack & Wassmann (2006: inflow shelves, which are Pacific-influenced and Atlantic-influenced; interior, river-influenced shelves; and central basins. We attempt to bring together knowledge of the carbon cycle with the ecosystem within each of these different geophysical settings, in order to provide specialist information in a holistic context. We assess the current state of models and how they can be improved and/or used to provide assessments of the current and future functioning when observational data are limited or sparse. In doing so, we highlight potential links in the physical oceanographic regime, primary production and the flow of carbon within the ecosystem that will change in the future. Finally, we are able to highlight priority areas for research, taking a holistic pan-Arctic approach.

  17. The oceanic response to carbon emissions over the next century: investigation using three ocean carbon cycle models

    International Nuclear Information System (INIS)

    A recent study of coupled atmospheric carbon dioxide and the biosphere found alarming sensitivity of next-century atmospheric pCO2 (and hence planetary temperature) to uncertainties in terrestrial processes. Here we investigate whether there is similar sensitivity associated with uncertainties in the behaviour of the ocean carbon cycle. We investigate this important question using three models of the ocean carbon cycle of varying complexity: (1) a new three-box oceanic carbon cycle model; (2) the HILDA multibox model with high vertical resolution at low latitudes; (3) the Hadley Centre ocean general circulation model (HadOCC). These models were used in combination to assess the quantitative significance (to year 2100 pCO2) of potential changes to the ocean stimulated by global warming and other anthropogenic activities over the period 2000-2100. It was found that an increase in sea surface temperature and a decrease in the mixing rate due to stratification give rise to the greatest relative changes in pCO2, both being positive feedbacks. We failed to find any comparable large sensitivity due to the ocean

  18. The carbon cycle and biogeochemical dynamics in lake sediments

    Science.gov (United States)

    Dean, W.E.

    1999-01-01

    The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO2 and accompanying increase in pH also may increase the production of CaCO3. However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO3 and therefore a decrease in the rain rate of CaCO3 to the sediment-water interface.

  19. A life-cycle carbon footprint of Yosemite National Park

    International Nuclear Information System (INIS)

    Like cities, many large national parks in the United States often include “urban” visitor and residential areas that mostly demand (rather than produce) energy and key urban materials. The U.S. National Park Service has committed to quantifying and reducing scopes 1 and 2 emissions by 35% and scope 3 emissions by 10% by 2020 for all parks. Current inventories however do not provide the specificity or granularity to evaluate solutions that address fundamental inefficiencies in these inventories. By quantifying and comparing the importance of different inventory sectors as well as upstream and downstream emissions in Yosemite National Park (YNP), this carbon footprint provides a case study and potential template for quantifying future emissions reductions, and for evaluating tradeoffs between them. Results indicate that visitor-related emissions comprise the largest fraction of the Yosemite carbon footprint, and that increases in annual visitation (3.43–3.90 million) coincide with and likely drive interannual increases in the magnitude of Yosemite′s extended inventory (126,000–130,000 t CO2e). Given this, it is recommended that “per visitor” efficiency be used as a metric to track progress. In this respect, YNP has annually decreased kilograms of GHG emissions per visitor from 36.58 (2008) to 32.90 (2011). We discuss opportunities for reducing this measure further. - Highlights: • A potential template for inventorying GHG emissions in national parks is presented. • Given variability in visitation, GHG/visitor is a better metric to measure efficiency. • Yosemite has reduced from 36.58 kg (2008) GHG emissions/visitor to 32.90 (2011)

  20. A carbon dioxide partial condensation direct cycle for advanced gas cooled fast and thermal reactors

    International Nuclear Information System (INIS)

    A carbon dioxide partial condensation direct cycle concept has been proposed for gas cooled fast and thermal reactors. The fast reactor with the concept are evaluated to be a potential alternative option to liquid metal cooled fast reactors, providing comparable cycle efficiency at the same core outlet temperature, eliminating the safety problems, simplifying the heat transport system and making easier plant maintenance. The thermal reactor with the concept is expected to be an alternative solution to current high temperature gas cooled reactors (HTGRs) with helium gas turbines, allowing comparable cycle efficiency at the moderate temperature of 650 C instead of 800 C in HTGRs. (author)

  1. Winter spring dynamics in sea-ice carbon cycling in the coastal Arctic Ocean

    Science.gov (United States)

    Riedel, Andrea; Michel, Christine; Gosselin, Michel; LeBlanc, Bernard

    2008-12-01

    An understanding of microbial interactions in first-year sea ice on Arctic shelves is essential for identifying potential responses of the Arctic Ocean carbon cycle to changing sea-ice conditions. This study assessed dissolved and particulate organic carbon (DOC, POC), exopolymeric substances (EPS), chlorophyll a, bacteria and protists, in a seasonal (24 February to 20 June 2004) investigation of first-year sea ice and associated surface waters on the Mackenzie Shelf. The dynamics of and relationships between different sea-ice carbon pools were investigated for the periods prior to, during and following the sea-ice-algal bloom, under high and low snow cover. A predominantly heterotrophic sea-ice community was observed prior to the ice-algal bloom under high snow cover only. However, the heterotrophic community persisted throughout the study with bacteria accounting for, on average, 44% of the non-diatom particulate carbon biomass overall the study period. There was an extensive accumulation of sea-ice organic carbon following the onset of the ice-algal bloom, with diatoms driving seasonal and spatial trends in particulate sea-ice biomass. DOC and EPS were also significant sea-ice carbon contributors such that sea-ice DOC concentrations were higher than, or equivalent to, sea-ice-algal carbon concentrations prior to and following the algal bloom, respectively. Sea-ice-algal carbon, DOC and EPS-carbon concentrations were significantly interrelated under high and low snow cover during the algal bloom ( r values ≥ 0.74, p algae are primarily responsible for the large pools of DOC and EPS-carbon and that similar stressors and/or processes could be involved in regulating their release. This study demonstrates that DOC can play a major role in organic carbon cycling on Arctic shelves.

  2. Thermodynamic analysis of gas – steam combined cycle with carbon dioxide (CO2 emissions saving

    Directory of Open Access Journals (Sweden)

    Alka Gupta, Om Prakash, S.K. Shukla

    2011-03-01

    Full Text Available In this paper, cogeneration or combined heat and power (CHP cycle has been analyzed in order to improve the efficiency of the gas – steam combined cycle and utilization of waste heat. The efficiency of the combined cycle is improved by decreasing the compressor inlet temperature (CIT and increasing the turbine inlet temperature (TIT. It is observed that the cycle offers the advantage of making efficient use of the energy available in the fuel and in turn, eliminate some portion of pollution associated with the power generation. The study also reveals that if this cycle is being employed for cogeneration, there is a significant saving (11.60% in the amount of Carbon dioxide (CO2 emitted by the coal-fired thermal power plants.

  3. An approach to include soil carbon changes in life cycle assessments

    DEFF Research Database (Denmark)

    Petersen, Bjørn Molt; Knudsen, Marie Trydeman; Hermansen, John Erik;

    2013-01-01

    to estimate carbon sequestration to be included in LCA is suggested and applied to two examples where the inclusion of carbon sequestration is especially relevant: 1) Bioenergy: removal of straw from a Danish soil for energy purposes and 2) Organic versus conventional farming: comparative study of...... soybean production in China. The suggested approach considers the time of the soil CO2 emissions for the LCA by including the Bern Carbon Cycle Model. Time perspectives of 20, 100 and 200 years are used and a soil depth of 0–100 cm is considered. The application of the suggested method showed that the...

  4. Aquatic carbon cycling in the conterminous United States and implications for terrestrial carbon accounting.

    Science.gov (United States)

    Butman, David; Stackpoole, Sarah; Stets, Edward; McDonald, Cory P; Clow, David W; Striegl, Robert G

    2016-01-01

    Inland water ecosystems dynamically process, transport, and sequester carbon. However, the transport of carbon through aquatic environments has not been quantitatively integrated in the context of terrestrial ecosystems. Here, we present the first integrated assessment, to our knowledge, of freshwater carbon fluxes for the conterminous United States, where 106 (range: 71-149) teragrams of carbon per year (TgC⋅y(-1)) is exported downstream or emitted to the atmosphere and sedimentation stores 21 (range: 9-65) TgC⋅y(-1) in lakes and reservoirs. We show that there is significant regional variation in aquatic carbon flux, but verify that emission across stream and river surfaces represents the dominant flux at 69 (range: 36-110) TgC⋅y(-1) or 65% of the total aquatic carbon flux for the conterminous United States. Comparing our results with the output of a suite of terrestrial biosphere models (TBMs), we suggest that within the current modeling framework, calculations of net ecosystem production (NEP) defined as terrestrial only may be overestimated by as much as 27%. However, the internal production and mineralization of carbon in freshwaters remain to be quantified and would reduce the effect of including aquatic carbon fluxes within calculations of terrestrial NEP. Reconciliation of carbon mass-flux interactions between terrestrial and aquatic carbon sources and sinks will require significant additional research and modeling capacity. PMID:26699473

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

    Science.gov (United States)

    Mannino, Antonio

    2008-01-01

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

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

    Science.gov (United States)

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

    2013-04-01

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

  7. Key issues and options in accounting for carbon sequestration and temporary storage in life cycle assessment and carbon footprinting

    DEFF Research Database (Denmark)

    Brandao, Miguel; Levasseur, Annie; Kirschbaum, Miko U. F.;

    2013-01-01

    footprinting (CF) are increasingly popular tools for the environmental assessment of products, that take into account their entire life cycle. There have been significant efforts to develop robust methods to account for the benefits, if any, of sequestration and temporary storage and release of biogenic carbon...... and CF. Several viewpoints and approaches are presented in a structured manner to help decision-makers in their selection of an option from competing approaches for dealing with timing issues, including delayed emissions of fossil carbon. Results: Key issues identified are that the benefits of...

  8. Interactions of the marine phosphorus and carbon cycles

    Science.gov (United States)

    Froelich, P. N.

    1984-01-01

    About 30 to 50% of the fluvial P-input to the oceans derives from release of reactive-P from particles during their passage through estuaries. The input is matched by P-removal into three approximately equivalent sink: (1) burial in phosphorites on productive shelves; (2) burial with (org) in the deep-sea; and (3) burial with biogenic calcite in the deep-sea. The P/C burial ratio in these three phases is very different: P/C (org) approximately .004; P/C (CaCO3) approximately .001; and P/C (PHOS) approximately .03. The removal mechanisms are all coupled to primary production in the surface ocean, but the details of the feedback mechanisms controlling the steady-state nutrient and carbon budgets in the sea are doscured by lack of knowledge of how the P/C ratios in the sinks adjust, and how shifts in oceanic nutrients affect oceanic ecology and the relative fraction of biogenic CaCO3 and (org) production.

  9. Impact of climate change on carbon cycle in freshwater ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Kankaala, P.; Ojala, A.; Tulonen, T.; Haapamaeki, J.; Arvola, L. [Helsinki Univ., Lammi (Finland). Lammi Biological Station

    1996-12-31

    The impacts of the expected climate change on Finnish lake ecosystems were studied with the biota of the mesohumic Lake Paeaejaervi, southern Finland. Experimental conditions, from small-scale experiments on single species level to a large-scale ecosystem manipulation, were established to simulate directly the future climate and/or loading of nutrients and dissolved organic matter (DOM) from the drainage area. The experimental studies were accomplished by modelling the carbon flow in the pelagic food web as well as the growth of littoral macrophytes. The main hypothese tested were as follows: As a consequence of the climate change (rising temperature and increasing precipitation) the loading of nutrients and dissolved organic matter (DOM) from the drainage area to the lake will increase. In the pelagic zone this will be first reflected i higher productivity of primary producers and bacteria, but will later affect the entire food chain. Increase in atmospheric CO{sub 2} concentration and ambient temperature as well as longer growing season will enhance the overall productivity of littoral macrophytes. The higher productivity of the littoral zone will be reflected in the pelagic zone an thus may change the whole ecosystem of the lake

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2009-12-01

    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 sources

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

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Atul [University of Illinois, Urbana-Champaign; Yang, Xiaojuan [University of Illinois, Urbana-Champaign; Kheshgi, Haroon [Exxon Mobil Research and Engineering; Mcguire, David [University of Alaska; Post, Wilfred M [ORNL

    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

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

    Science.gov (United States)

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

    1998-01-01

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

  14. Towards real energy economics: Energy policy driven by life-cycle carbon emission

    International Nuclear Information System (INIS)

    Alternative energy technologies (AETs) have emerged as a solution to the challenge of simultaneously meeting rising electricity demand while reducing carbon emissions. However, as all AETs are responsible for some greenhouse gas (GHG) emissions during their construction, carbon emission 'Ponzi Schemes' are currently possible, wherein an AET industry expands so quickly that the GHG emissions prevented by a given technology are negated to fabricate the next wave of AET deployment. In an era where there are physical constraints to the GHG emissions the climate can sustain in the short term this may be unacceptable. To provide quantitative solutions to this problem, this paper introduces the concept of dynamic carbon life-cycle analyses, which generate carbon-neutral growth rates. These conceptual tools become increasingly important as the world transitions to a low-carbon economy by reducing fossil fuel combustion. In choosing this method of evaluation it was possible to focus uniquely on reducing carbon emissions to the recommended levels by outlining the most carbon-effective approach to climate change mitigation. The results of using dynamic life-cycle analysis provide policy makers with standardized information that will drive the optimization of electricity generation for effective climate change mitigation.

  15. Potential multiple steady-states in the long-term carbon cycle

    CERN Document Server

    Tennenbaum, Stephen; Schwartzman, David

    2013-01-01

    Modelers of the long term carbon cycle in Earth history have previously assumed there is only one stable climatic steady state. Here we investigate the possibility of multiple steady states. We find them in Abiotic World, lacking any biotic influence, resulting from possible variations in planetary albedo in different temperature, atmospheric carbon dioxide level regimes, with the same weathering forcing balancing a volcanic source to the atmosphere, ocean pool. In Plant World modeling relevant to the Phanerozoic, we include the additional effects of biotic enhancement of weathering on land, organic carbon burial, oxidation of reduced organic carbon in terrestrial sediments and the variation of biotic productivity with temperature, finding a second stable steady state appearing between twenty and fifty degrees C. The very warm early Triassic climate may be the prime candidate for an upper temperature steady state. Given our results, the anthropogenic driven rise of atmospheric carbon dioxide could potentially...

  16. The Environmental Impact of Industrial Bamboo Products: Life-cycle Assessment and Carbon Sequestration

    NARCIS (Netherlands)

    Vogtlander, J.G.; Van der Lugt, P.

    2014-01-01

    This report gives a Life-Cycle Assessment (LCA) and carbon footprint analysis on a selection of industrial bamboo products. The LCA is made for cradle-to-gate, plus the end-of-life stages of the bamboo products. For end-of-life it is assumed that 90% of the bamboo products are incinerated in an elec

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

    Science.gov (United States)

    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…

  18. Seasonal carbon cycling in a Greenlandic fjord: an integrated pelagic and benthic study

    DEFF Research Database (Denmark)

    Sørensen, Heidi Louise; Meire, Lorenz; Juul-Pedersen, Thomas;

    2015-01-01

    Climate change is expected to have a pronounced effect on biogeochemical cycling in Arctic fjords, but current insight on the biogeochemical functioning of these systems is limited. Here, we present seasonal data on primary production, export of particulate organic carbon (POC), and the coupling to...

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

    Science.gov (United States)

    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…

  20. ELEVATED CO2 INCREASES MICROBIAL CARBON SUBSTRATE USE AND N CYCLING IN MOJAVE DESERT SOILS

    Science.gov (United States)

    We assessed the effects of elevated atmospheric CO2 on microbial carbon (C) and nitrogen (N) cycling in Mojave Desert soils using extracellular enzyme activities (EEAs), community-level physiological profiles (CLPPs), and gross N transformation rates. Soils were collected from unvegetated interspac...

  1. The evolving global cycles of carbon and of radiocarbon during the industrial era

    International Nuclear Information System (INIS)

    The industrial era has been characterised by significant injections of carbon dioxide (CO2) into the atmosphere as a result of both industrial activities and changes in land use (forest destruction). Approximately half of this accumulated excess has been removed from the atmosphere to be absorbed in the oceans and assimilated into vegetation. Globally-aggregated models of the perturbed carbon cycle, in conjunction with reconstructions of the CO2 emission record, can account for the observed growth in atmospheric CO2 quite well, but leave the partitioning between these two major sinks poorly determined. The distinctive 'isotopic signatures' among the atmospheric sources and sinks of carbon allows further elucidation. In particular, the atmospheric 'bomb 14CO2' generated in significant quantities by atmospheric detonations of nuclear weapons in the few years to ca 1962 provided an opportunity to study the dynamics of 14C-labelled CO2. Some recent research has challenged our understanding of the perturbed carbon cycle, suggesting that it is not compatible with the observed tropospheric record of 14C/12C during the nuclear era. The author reports results using an established yet simple carbon-cycle model to show that the dynamics of carbon and its isotopes can indeed be simultaneously reconciled with observational records (or proxy records) during the industrial era, including both tropospheric records and the so-called GEOSECS oceanic record of bomb 14C. A key distinctive feature of the model is the 'forward integration' driven even-handedly by inputs of carbon from both industrial sources and land use change, and by bomb 14C, consistently with reconstructed emission or production patterns. The key carbon reservoir appears to be the terrestrial biosphere which is commencing recovery from a century of forest destruction. (author)

  2. Process contributions of Australian ecosystems to interannual variations in the carbon cycle

    Science.gov (United States)

    Haverd, Vanessa; Smith, Benjamin; Trudinger, Cathy

    2016-05-01

    New evidence is emerging that semi-arid ecosystems dominate interannual variability (IAV) of the global carbon cycle, largely via fluctuating water availability associated with El Niño/Southern Oscillation. Recent evidence from global terrestrial biosphere modelling and satellite-based inversion of atmospheric CO2 point to a large role of Australian ecosystems in global carbon cycle variability, including a large contribution from Australia to the record land sink of 2011. However the specific mechanisms governing this variability, and their bioclimatic distribution within Australia, have not been identified. Here we provide a regional assessment, based on best available observational data, of IAV in the Australian terrestrial carbon cycle and the role of Australia in the record land sink anomaly of 2011. We find that IAV in Australian net carbon uptake is dominated by semi-arid ecosystems in the east of the continent, whereas the 2011 anomaly was more uniformly spread across most of the continent. Further, and in contrast to global modelling results suggesting that IAV in Australian net carbon uptake is amplified by lags between production and decomposition, we find that, at continental scale, annual variations in production are dampened by annual variations in decomposition, with both fluxes responding positively to precipitation anomalies.

  3. Carbon Cycling, Climate Regulation, and Disturbances in Canadian Forests: Scientific Principles for Management

    Directory of Open Access Journals (Sweden)

    Jean-Sébastien Landry

    2015-01-01

    Full Text Available Canadian forests are often perceived as pristine and among the last remaining wilderness, but the majority of them are officially managed and undergo direct land use, mostly for wood harvest. This land use has modified their functions and properties, often inadvertently (e.g., age structure but sometimes purposefully (e.g., fire suppression. Based on a review of the literature pertaining to carbon cycling, climate regulation, and disturbances from logging, fire, and insect outbreaks, we propose five scientific principles relevant for Canadian managed forests. Among these, a principle we wish to highlight is the need to properly account for the management-related fossil fuel emissions, because they will affect the global carbon cycle and climate for millennia unless massive atmospheric carbon dioxide removal becomes a reality. We also use these five principles to address questions of current interest to research scientists, forest managers, and policy makers. Our review focusses on total ecosystem carbon storage and various mechanisms through which forests affect climate, in particular albedo and aerosols forcings—including how disturbances influence all these elements—but also touches on other ecosystem goods and services. Our review underscores the importance of conducting >100-year time horizon studies of carbon cycling, climate regulation, and disturbances in Canadian managed forests.

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

    Science.gov (United States)

    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. PMID:26196334

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

    Science.gov (United States)

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

    2009-01-01

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

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

    Science.gov (United States)

    Willeit, Matteo; Ganopolski, Andrey

    2016-04-01

    PALADYN is presented, a new comprehensive and computationally efficient land surface-vegetation-carbon cycle model designed to be used in Earth system models of intermediate complexity for long-term simulations and paleoclimate studies. The model treats in a consistent manner the interaction between atmosphere, terrestrial vegetation and soil through the fluxes of energy, water and carbon. Energy, water and carbon are conserved. The model explicitly treats permafrost, both in physical processes and as important carbon pool. The model distinguishes 9 surface types of which 5 are different vegetation types, bare soil, land ice, lake and ocean shelf. Including the ocean shelf allows to treat continuous changes in sea level and shelf area associated with glacial cycles. Over each surface type the model solves the surface energy balance and computes the fluxes of sensible, latent and ground heat and upward shortwave and longwave radiation. It includes a single snow layer. The soil model distinguishes between three different macro surface types which have their own soil column: vegetation and bare soil, ice sheet and ocean shelf. The soil is vertically discretized into 5 layers where prognostic equations for temperature, water and carbon are consistently solved. Phase changes of water in the soil are explicitly considered. A surface hydrology module computes precipitation interception by vegetation, surface runoff and soil infiltration. The soil water equation is based on Darcy's law. Given soil water content, the wetland fraction is computed based on a topographic index. Photosynthesis is computed using a light use efficiency model. Carbon assimilation by vegetation is coupled to the transpiration of water through stomatal conductance. The model includes a dynamic vegetation module with 5 plant functional types competing for the gridcell share with their respective net primary productivity. Each macro surface type has its own carbon pools represented by a litter, a fast

  7. Improvement of cycle performance for silicon/carbon composite used as anode for lithium ion batteries

    International Nuclear Information System (INIS)

    The silicon/carbon composite was prepared by mixing the silicon, graphite and pitch in the tetra-hydrofuran solution followed by pyrolyzing the blends after the evaporation of solvent. The electrochemical performance of the silicon/carbon anode for lithium ion batteries was improved by the treatment of composite powders with KCl aqueous solutions. Scanning electron microscope (SEM) observation and electrochemical impedance spectroscopy (EIS) results showed that the morphology stability of the composite electrodes can be kept during the electrochemical charge/discharge process. The composite electrode of silicon/carbon composite showed an initial reversible capacity of 575 mAh g-1 and still maintained a high reversible capacity of 506 mAh g-1 after 40 cycles with the capacity loss of ∼0.3% per cycle.

  8. Belowground Carbon Cycling Processes at the Molecular Scale: An EMSL Science Theme Advisory Panel Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Hess, Nancy J.; Brown, Gordon E.; Plata, Charity

    2014-02-21

    As part of the Belowground Carbon Cycling Processes at the Molecular Scale workshop, an EMSL Science Theme Advisory Panel meeting held in February 2013, attendees discussed critical biogeochemical processes that regulate carbon cycling in soil. The meeting attendees determined that as a national scientific user facility, EMSL can provide the tools and expertise needed to elucidate the molecular foundation that underlies mechanistic descriptions of biogeochemical processes that control carbon allocation and fluxes at the terrestrial/atmospheric interface in landscape and regional climate models. Consequently, the workshop's goal was to identify the science gaps that hinder either development of mechanistic description of critical processes or their accurate representation in climate models. In part, this report offers recommendations for future EMSL activities in this research area. The workshop was co-chaired by Dr. Nancy Hess (EMSL) and Dr. Gordon Brown (Stanford University).

  9. Earth's Early Biosphere and the Biogeochemical Carbon Cycle

    Science.gov (United States)

    DesMarais, David

    2004-01-01

    Our biosphere has altered the global environment principally by influencing the chemistry of those elements most important for life, e g., C, N, S, O, P and transition metals (e.g., Fe and Mn). The coupling of oxygenic photosynthesis with the burial in sediments of photosynthetic organic matter, and with the escape of H2 to space, has increased the state of oxidation of the Oceans and atmosphere. It has also created highly reduced conditions within sedimentary rocks that have also extensively affected the geochemistry of several elements. The decline of volcanism during Earth's history reduced the flow of reduced chemical species that reacted with photosynthetically produced O2. The long-term net accumulation of photosynthetic O2 via biogeochemical processes has profoundly influenced our atmosphere and biosphere, as evidenced by the O2 levels required for algae, multicellular life and certain modem aerobic bacteria to exist. When our biosphere developed photosynthesis, it tapped into an energy resource that was much larger than the energy available from oxidation-reduction reactions associated with weathering and hydrothermal activity. Today, hydrothermal sources deliver globally (0.13-1.1)x10(exp l2) mol yr(sup -1) of reduced S, Fe(2+), Mn(2+), H2 and CH4; this is estimated to sustain at most about (0.2-2)xl0(exp 12)mol C yr(sup -1) of organic carbon production by chemautotrophic microorganisms. In contrast, global photosynthetic productivity is estimated to be 9000x10(exp 12) mol C yr(sup -1). Thus, even though global thermal fluxes were greater in the distant geologic past than today, the onset of oxygenic photosynthesis probably increased global organic productivity by some two or more orders of magnitude. This enormous productivity materialized principally because oxygenic photosynthesizers unleashed a virtually unlimited supply of reduced H that forever freed life from its sole dependence upon abiotic sources of reducing power such as hydrothermal emanations

  10. Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling

    Directory of Open Access Journals (Sweden)

    D. S. Goll

    2012-09-01

    Full Text Available Terrestrial carbon (C cycle models applied for climate projections simulate a strong increase in net primary productivity (NPP due to elevated atmospheric CO2 concentration during the 21st century. These models usually neglect the limited availability of nitrogen (N and phosphorus (P, nutrients that commonly limit plant growth and soil carbon turnover. To investigate how the projected C sequestration is altered when stoichiometric constraints on C cycling are considered, we incorporated a P cycle into the land surface model JSBACH (Jena Scheme for Biosphere–Atmosphere Coupling in Hamburg, which already includes representations of coupled C and N cycles.

    The model reveals a distinct geographic pattern of P and N limitation. Under the SRES (Special Report on Emissions Scenarios A1B scenario, the accumulated land C uptake between 1860 and 2100 is 13% (particularly at high latitudes and 16% (particularly at low latitudes lower in simulations with N and P cycling, respectively, than in simulations without nutrient cycles. The combined effect of both nutrients reduces land C uptake by 25% compared to simulations without N or P cycling. Nutrient limitation in general may be biased by the model simplicity, but the ranking of limitations is robust against the parameterization and the inflexibility of stoichiometry. After 2100, increased temperature and high CO2 concentration cause a shift from N to P limitation at high latitudes, while nutrient limitation in the tropics declines. The increase in P limitation at high-latitudes is induced by a strong increase in NPP and the low P sorption capacity of soils, while a decline in tropical NPP due to high autotrophic respiration rates alleviates N and P limitations. The quantification of P limitation remains challenging. The poorly constrained processes of soil P sorption and biochemical mineralization are identified as the main uncertainties in the strength of P limitation

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

    Science.gov (United States)

    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. PMID:26667055

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

    Science.gov (United States)

    Esposito, Mario

    2016-04-01

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

  13. Modelling carbon dynamics from urban land conversion: fundamental model of city in relation to a local carbon cycle

    Directory of Open Access Journals (Sweden)

    Schellnhuber Hans-Joachim

    2006-08-01

    Full Text Available Abstract Background The main task is to estimate the qualitative and quantitative contribution of urban territories and precisely of the process of urbanization to the Global Carbon Cycle (GCC. Note that, on the contrary to many investigations that have considered direct anthropogenic emission of CO2(urbanized territories produce ca. 96–98% of it, we are interested in more subtle, and up until the present time, weaker processes associated with the conversion of the surrounding natural ecosystems and landscapes into urban lands. Such conversion inevitably takes place when cities are sprawling and additional "natural" lands are becoming "urbanized". Results In order to fulfil this task, we first develop a fundamental model of urban space, since the type of land cover within a city makes a difference for a local carbon cycle. Hence, a city is sub-divided by built-up, „green" (parks, etc. and informal settlements (favelas fractions. Another aspect is a sub-division of the additional two regions, which makes the total number reaching eight regions, while the UN divides the world by six. Next, the basic model of the local carbon cycle for urbanized territories is built. We consider two processes: carbon emissions as a result of conversion of natural lands caused by urbanization; and the transformation of carbon flows by "urbanized" ecosystems; when carbon, accumulated by urban vegetation, is exported to the neighbouring territories. The total carbon flow in the model depends, in general, on two groups of parameters. The first includes the NPP, and the sum of living biomass and dead organic matter of ecosystems involved in the process of urbanization, and namely them we calculate here, using a new more realistic approach and taking into account the difference in regional cities' evolution. Conclusion There is also another group of parameters, dealing with the areas of urban territories, and their annual increments. A method of dynamic forecasting

  14. Vegetation Dynamics and Carbon-Nitrogen Cycles in NCAR CLM4-CNDV Under Changing Climate

    Science.gov (United States)

    Sakaguchi, K.; Zeng, X.; Shao, P.

    2012-12-01

    The global biogeochemical cycle has become a major component of climate change studies. There are numerous important aspects in the biogeochemical feedbacks to the externally forced climate, and two of them are vegetation dynamics and coupling of carbon-nitrogen cycles. It is well established that evolution of vegetation cover substantially influences biogeophysical interactions with the atmosphere. More recently several studies suggest that the nitrogen cycle can significantly change the feedback of the land biosphere to the warming climate (commonly noted as γ) and to the increase of CO2 (β) compared to the models considering only the carbon cycle. The number of such studies is still small, however, particularly with dynamic vegetation models. Here we report several characteristics of a global land model NCAR CLM4-CNDV, which simulates the interactions between the vegetation dynamics and carbon-nitrogen cycles (but not the anthropogenic land use and land cover changes). A series of global off-line simulations are run with reanalysis-based atmospheric data as well as the model output from one member of the fully coupled CCSM4 simulations contributing to phase five of the Coupled Model Intercomparison Project (CMIP5). They cover pre-industrial conditions, the historical period, and future projection under RCP8.5 scenario in CMIP5. The topics will include the diagnosis of the simulated vegetation distribution, global-scale quantities (total carbon storage, average albedo, etc), and the sensitivity of the land carbon pool to warming climate and CO2 (γ, β). For the vegetation dynamics, grid-level evolution in time from the initial conditions to quasi-equilibrium and the regional change over the tropics and Arctic regions in the future will be summarized. The other results will be compared to previous studies on carbon-nitrogen coupling within NCAR CLM to augment them by dynamic vegetation and/or transient simulations extending to the future. The results will be

  15. Fingerprints of changes in the terrestrial carbon cycle in response to large reorganizations in ocean circulation

    Directory of Open Access Journals (Sweden)

    A. Bozbiyik

    2011-03-01

    Full Text Available CO2 and carbon cycle changes in the land, ocean and atmosphere are investigated using the comprehensive carbon cycle-climate model NCAR CSM1.4-carbon. Ensemble simulations are forced with freshwater perturbations applied at the North Atlantic and Southern Ocean deep water formation sites under pre-industrial climate conditions. As a result, the Atlantic Meridional Overturning Circulation reduces in each experiment to varying degrees. The physical climate fields show changes qualitatively in agreement with results documented in the literature, but there is a clear distinction between northern and southern perturbations. Changes in the physical variables, in turn, affect the land and ocean biogeochemical cycles and cause a reduction, or an increase, in the atmospheric CO2 concentration by up to 20 ppmv, depending on the location of the perturbation. In the case of a North Atlantic perturbation, the land biosphere reacts with a strong reduction in carbon stocks in some tropical locations and in high northern latitudes. In contrast, land carbon stocks tend to increase in response to a southern perturbation. The ocean is generally a sink of carbon although large reorganizations occur throughout various basins. The response of the land biosphere is strongest in the tropical regions due to a shift of the Intertropical Convergence Zone. The carbon fingerprints of this shift, either to the south or to the north depending on where the freshwater is applied, can be found most clearly in South America. For this reason, a compilation of various paleoclimate proxy records of Younger Dryas precipitation changes are compared with our model results. The proxy records, in general, show good agreement with the model's response to a North Atlantic freshwater perturbation.

  16. Regional carbon dynamics in monsoon Asia and its implications for the global carbon cycle

    Science.gov (United States)

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; Pan, S.; Liu, J.; McGuire, A.D.; Moore, B., III

    2003-01-01

    Data on three major determinants of the carbon storage in terrestrial ecosystems are used with the process-based Terrestrial Ecosystem Model (TEM) to simulate the combined effect of climate variability, increasing atmospheric CO2 concentration, and cropland establishment and abandonment on the exchange of CO2 between the atmosphere and monsoon Asian ecosystems. During 1860-1990, modeled results suggest that monsoon Asia as a whole released 29.0 Pg C, which represents 50% of the global carbon release for this period. Carbon release varied across three subregions: East Asia (4.3 Pg C), South Asia (6.6 Pg C), and Southeast Asia (18.1 Pg C). For the entire region, the simulations indicate that land-use change alone has led to a loss of 42.6 Pg C. However, increasing CO2 and climate variability have added carbon to terrestrial ecosystems to compensate for 23% and 8% of the losses due to land-use change, respectively. During 1980-1989, monsoon Asia as a whole acted as a source of carbon to the atmosphere, releasing an average of 0.158 Pg C per year. Two of the subregions acted as net carbon source and one acted as a net carbon sink. Southeast Asia and South Asia were sources of 0.288 and 0.02 Pg C per year, respectively, while East Asia was a sink of 0.149 Pg C per year. Substantial interannual and decadal variations occur in the annual net carbon storage estimated by TEM due to comparable variations in summer precipitation and its effect on net primary production (NPP). At longer time scales, land-use change appears to be the important control on carbon dynamics in this region. ?? 2003 Elsevier Science B.V. All rights reserved.

  17. Carbon cycling and phytoplankton responses within highly-replicated shipboard carbonate chemistry manipulation experiments conducted around Northwest European Shelf Seas

    Science.gov (United States)

    Richier, S.; Achterberg, E. P.; Dumousseaud, C.; Poulton, A. J.; Suggett, D. J.; Tyrrell, T.; Zubkov, M. V.; Moore, C. M.

    2014-03-01

    The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which in part likely reflects inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series of highly replicated (n = 8), short term (2-4 days) multi-level (≥ 4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically different experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterized by a suppression of net growth for small sized cells (< 10 μm), were observed in the majority of the experiments, irrespective of nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO2 and hence lower buffer capacity. The results thus emphasize how biological-chemical feedbacks may be altered in the future ocean.

  18. Phytoplankton responses and associated carbon cycling during shipboard carbonate chemistry manipulation experiments conducted around Northwest European shelf seas

    Science.gov (United States)

    Richier, S.; Achterberg, E. P.; Dumousseaud, C.; Poulton, A. J.; Suggett, D. J.; Tyrrell, T.; Zubkov, M. V.; Moore, C. M.

    2014-09-01

    The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2) is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which may reflect community/environment-specific responses or inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series (n = 8) of short-term (2-4 days) multi-level (≥4 conditions) carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically separated experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterised by a suppression of net growth for small-sized cells (<10 μm), were observed in the majority of the experiments, irrespective of natural or manipulated nutrient status. Remaining between-experiment variability was potentially linked to initial community structure and/or other site-specific environmental factors. Analysis of carbon cycling within the experiments revealed the expected increased sensitivity of carbonate chemistry to biological processes at higher pCO2 and hence lower buffer capacity. The results thus emphasise how biogeochemical feedbacks may be altered in the future ocean.

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

    Science.gov (United States)

    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. PMID:27114518

  20. Modeling the grazing effect on dry grassland carbon cycling with modified Biome-BGC grazing model

    Science.gov (United States)

    Luo, Geping; Han, Qifei; Li, Chaofan; Yang, Liao

    2014-05-01

    Identifying the factors that determine the carbon source/sink strength of ecosystems is important for reducing uncertainty in the global carbon cycle. Arid grassland ecosystems are a widely distributed biome type in Xinjiang, Northwest China, covering approximately one-fourth the country's land surface. These grasslands are the habitat for many endemic and rare plant and animal species and are also used as pastoral land for livestock. Using the modified Biome-BGC grazing model, we modeled carbon dynamics in Xinjiang for grasslands that varied in grazing intensity. In general, this regional simulation estimated that the grassland ecosystems in Xinjiang acted as a net carbon source, with a value of 0.38 Pg C over the period 1979-2007. There were significant effects of grazing on carbon dynamics. An over-compensatory effect in net primary productivity (NPP) and vegetation carbon (C) stock was observed when grazing intensity was lower than 0.40 head/ha. Grazing resulted in a net carbon source of 23.45 g C m-2 yr-1, which equaled 0.37 Pg in Xinjiang in the last 29 years. In general, grazing decreased vegetation C stock, while an increasing trend was observed with low grazing intensity. The soil C increased significantly (17%) with long-term grazing, while the soil C stock exhibited a steady trend without grazing. These findings have implications for grassland ecosystem management as it relates to carbon sequestration and climate change mitigation, e.g., removal of grazing should be considered in strategies that aim to increase terrestrial carbon sequestrations at local and regional scales. One of the greatest limitations in quantifying the effects of herbivores on carbon cycling is identifying the grazing systems and intensities within a given region. We hope our study emphasizes the need for large-scale assessments of how grazing impacts carbon cycling. Most terrestrial ecosystems in Xinjiang have been affected by disturbances to a greater or lesser extent in the past

  1. Recent geographic variations in terrestrial carbon cycle based on new production efficiency model

    Science.gov (United States)

    Sasai, T.; Ichii, K.; Yamaguchi, Y.

    2003-12-01

    The terrestrial carbon budget must be understood more accurately for the prediction of future changes in climate and carbon cycle. The goal of this study is to estimate spatial and temporal patterns of the carbon fluxes more accurately using the newly developed terrestrial biosphere model and satellite data. Our model consists of terrestrial carbon cycle and hydrology submodels. An advantage is a new approach in the LUE (Light Use Efficiency) concept, which calculates temperature and water stress factor in LUE model from a photosynthetic model and stomatal conductance formulation. In carbon cycle model, GPP is calculated from the LUE concept and satellite-based fPAR dataset. The soil carbon cycle model is based on CENTURY model with optimized water and temperature factor. Hydrological submodel is based on BIOME3, calculating ET is used by Penman-Monteith method. The model was run for 18 years (1982-1999) on a global scale, and we simulated the geographic distributions of the terrestrial carbon fluxes. We have checked simulated vegetation growth limiting factor with stress factor of MODIS NPP algorithm. Large differences were found in the northern mid and high latitude forests because soil moisture stress is not incorporated into MODIS NPP algorithm. Although responses of stress factors in MODIS NPP algorithm are mostly similar to our theoretically based one, our model works well in the soil moisture limited regions. Global total NPP was estimated at 61.7GtC/yr, and total NEP variations are strongly related with ENSO. Validation using measured values from the GPPDI database showed that our NPP estimation was within a reasonable range. The temporal patterns of the terrestrial carbon flux showed that NPP increased in the northern middle/high latitudes, central Africa, and India. In contrast, NPP decreased in the south Amazon region, the middle latitudes of the southern hemisphere, a part of North America, and Southeast Asia. Sensitivity analysis indicated that NPP

  2. Role of organic soils in the world carbon cycle: problem definition and research needs

    Energy Technology Data Exchange (ETDEWEB)

    Armentano, T.V. (ed.)

    1979-01-01

    The following goals were addressed in the workshop: review and analysis of available data on carbon in organic soils from the past century to the present; assessment of the probable flux of carbon to and from organic soils in the near future; identification of major data inadequacies which preclude reliable analysis of the principal processes influencing carbon flux in organic soils; and proposal of research initiatives which could improve understanding of organic deposits in relation to the carbon cycle within a time frame of two to four years. The major finding of the workshop is that the organic soils are important in the overall carbon budget. Histosols and gleysols, the major organic soil deposits of the world, normally sequester organic carbon fixed by plants. They may now be releasing enough carbon to account for nearly 10% of the annual rise in atmospheric content of CO/sub 2/. Current annual release of carbon from organic soils is estimated to fall within the range of 0.03 to 0.37 x 10/sup 9/ t, a release equivalent to 1.3% to 16% of the annual increase of carbon in the atmosphere. Present annual releases of carbon from the Everglades Agricultural Area in Florida and the Sacramento-San Joaquin Valley in California are estimated at 0.017 x 10/sup 9/ tons. Annual sequestering of carbon by undrained organic soils has been estimated at about 0.045 x 10/sup 9/ tons. Several strategies for peatland management are available, including creation, preservation, functional designation, and use of wetlands for agriculture and energy supply.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    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.

  4. Carbonate concretions as a significant component of ancient marine carbon cycles: Insights from paired organic and inorganic carbon isotope analyses of a Cretaceous shale

    Science.gov (United States)

    Loyd, S. J.

    2014-12-01

    Carbonate concretions often occur within fine-grained, organic-rich sedimentary rocks. This association reflects the common production of diagenetic minerals through biologic cycling of organic matter. Chemical analysis of carbonate concretions provides the rare opportunity to explore ancient shallow diagenetic environments, which are inherently transient due to progressive burial but are an integral component of the marine carbon cycle. The late Cretaceous Holz Shale (~80 Ma) contains abundant calcite concretions that exhibit textural and geochemical characteristics indicative of relatively shallow formation (i.e., near the sediment-water interface). Sampled concretions contain between 5.4 and 9.8 wt.% total inorganic carbon (TIC), or ~45 and 82 wt.% CaCO3, compared to host shale values which average ~1.5 wt.% TIC. Organic carbon isotope compositions (δ13Corg) are relatively constant in host and concretion samples ranging from ­-26.3 to -24.0‰ (VPDB). Carbonate carbon isotope compositions (δ13Ccarb) range from -22.5 to -3.4‰, indicating a significant but not entirely organic source of carbon. Concretions of the lower Holz Shale exhibit considerably elevated δ13Ccarb values averaging -4.8‰, whereas upper Holz Shale concretions express an average δ13Ccarb value of -17.0‰. If the remaining carbonate for lower Holz Shale concretions is sourced from marine fluids and/or dissolved marine carbonate minerals (e.g., shells), a simple mass balance indicates that ~28% of concretion carbon was sourced from organic matter and ~72% from late Cretaceous marine inorganic carbon (with δ13C ~ +2.5‰). Upper Holz Shale calculations indicate a ~73% contribution from organic matter and a ~27% contribution from inorganic carbon. When normalized for carbonate, organic contents within the concretions are ~2-13 wt.% enriched compared to host contents. This potentially reflects the protective nature of cementation that acts to limit permeability and chemical destruction of

  5. Climate and carbon cycle dynamics in a CESM simulation from 850–2100 CE

    Directory of Open Access Journals (Sweden)

    F. Lehner

    2015-02-01

    Full Text Available Under the protocols of the Paleoclimate and Coupled Modelling Intercomparison Projects a number of simulations were produced that provide a range of potential climate evolutions from the last millennium to the end of the current century. Here, we present the first simulation with the Community Earth System Model (CESM, which includes an interactive carbon cycle, that continuously covers the last millennium, the historical period, and the twenty-first century. Besides state-of-the-art forcing reconstructions, we apply a modified reconstruction of total solar irradiance to shed light on the issue of forcing uncertainty in the context of the last millennium. Nevertheless, we find that structural uncertainties between different models can still dominate over forcing uncertainty for quantities such as hemispheric temperatures or the land and ocean carbon cycle response. Comparing with other model simulations we find forced decadal-scale variability to occur mainly after volcanic eruptions, while during other periods internal variability masks potentially forced signals and calls for larger ensembles in paleoclimate modeling studies. At the same time, we fail to attribute millennial temperature trends to orbital forcing, as has been suggested recently. The climate-carbon cycle sensitivity in CESM during the last millennium is estimated to be about 1.3 ppm °C−1. However, the dependence of this sensitivity on the exact time period and scale illustrates the prevailing challenge of deriving robust constrains on this quantity from paleoclimate proxies. In particular, the response of the land carbon cycle to volcanic forcing shows fundamental differences between different models. In CESM the tropical land dictates the response to volcanoes with a distinct behavior for large and moderate eruptions. Under anthropogenic emissions, global land and ocean carbon uptake rates emerge from the envelope of interannual natural variability as simulated for the last

  6. Climate and carbon cycle dynamics in a CESM simulation from 850 to 2100 CE

    Science.gov (United States)

    Lehner, F.; Joos, F.; Raible, C. C.; Mignot, J.; Born, A.; Keller, K. M.; Stocker, T. F.

    2015-07-01

    Under the protocols of phase 3 of the Paleoclimate Modelling Intercomparison Project, a number of simulations were produced that provide a range of potential climate evolutions from the last millennium to the end of the current century. Here, we present the first simulation with the Community Earth System Model (CESM), which includes an interactive carbon cycle, that covers the last millennium. The simulation is continued to the end of the twenty-first century. Besides state-of-the-art forcing reconstructions, we apply a modified reconstruction of total solar irradiance to shed light on the issue of forcing uncertainty in the context of the last millennium. Nevertheless, we find that structural uncertainties between different models can still dominate over forcing uncertainty for quantities such as hemispheric temperatures or the land and ocean carbon cycle response. Compared to other model simulations, we find forced decadal-scale variability to occur mainly after volcanic eruptions, while during other periods internal variability masks potentially forced signals and calls for larger ensembles in paleoclimate modeling studies. At the same time, we were not able to attribute millennial temperature trends to orbital forcing, as has been suggested recently. The climate-carbon-cycle sensitivity in CESM during the last millennium is estimated to be between 1.0 and 2.1 ppm °C-1. However, the dependence of this sensitivity on the exact time period and scale illustrates the prevailing challenge of deriving robust constraints on this quantity from paleoclimate proxies. In particular, the response of the land carbon cycle to volcanic forcing shows fundamental differences between different models. In CESM the tropical land dictates the response to volcanoes, with a distinct behavior for large and moderate eruptions. Under anthropogenic emissions, global land and ocean carbon uptake rates emerge from the envelope of interannual natural variability by about year 1947 and 1877

  7. Responses of ecosystem carbon cycling to climate change treatments along an elevation gradient

    Science.gov (United States)

    Wu, Zhuoting; Koch, George W.; Dijkstra, Paul; Bowker, Matthew A.; Hungate, Bruce A.

    2011-01-01

    Global temperature increases and precipitation changes are both expected to alter ecosystem carbon (C) cycling. We tested responses of ecosystem C cycling to simulated climate change using field manipulations of temperature and precipitation across a range of grass-dominated ecosystems along an elevation gradient in northern Arizona. In 2002, we transplanted intact plant–soil mesocosms to simulate warming and used passive interceptors and collectors to manipulate precipitation. We measured daytime ecosystem respiration (ER) and net ecosystem C exchange throughout the growing season in 2008 and 2009. Warming generally stimulated ER and photosynthesis, but had variable effects on daytime net C exchange. Increased precipitation stimulated ecosystem C cycling only in the driest ecosystem at the lowest elevation, whereas decreased precipitation showed no effects on ecosystem C cycling across all ecosystems. No significant interaction between temperature and precipitation treatments was observed. Structural equation modeling revealed that in the wetter-than-average year of 2008, changes in ecosystem C cycling were more strongly affected by warming-induced reduction in soil moisture than by altered precipitation. In contrast, during the drier year of 2009, warming induced increase in soil temperature rather than changes in soil moisture determined ecosystem C cycling. Our findings suggest that warming exerted the strongest influence on ecosystem C cycling in both years, by modulating soil moisture in the wet year and soil temperature in the dry year.

  8. Novel use of cavity ring-down spectroscopy to investigate aquatic carbon cycling from microbial to ecosystem scales

    NARCIS (Netherlands)

    Maher, D.T.; Santos, I.S.; Leuven, J.R.F.W.; Oakes, J.M.; Erler, D.V.; Carvalho, M.C.; Eyre, B.D.

    2013-01-01

    Development of cavity ring-down spectroscopy (CRDS) has enabled real-time monitoring of carbon stable isotope ratios of carbon dioxide and methane in air. Here we demonstrate that CRDS can be adapted to assess aquatic carbon cycling processes from microbial to ecosystem scales. We first measured in

  9. Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China

    DEFF Research Database (Denmark)

    Chen, Hao; Li, Dejun; Gurmesa, Geshere Abdisa;

    2015-01-01

    Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling on...... rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle....

  10. Effect of land use change on the carbon cycle in Amazon soils

    Science.gov (United States)

    Trumbore, Susan E.; Davidson, Eric A.

    1994-01-01

    The overall goal of this study was to provide a quantitative understanding of the cycling of carbon in the soils associated with deep-rooting Amazon forests. In particular, we wished to apply the understanding gained by answering two questions: (1) what changes will accompany the major land use change in this region, the conversion of forest to pasture? and (2) what is the role of carbon stored deeper than one meter in depth in these soils? To construct carbon budgets for pasture and forest soils we combined the following: measurements of carbon stocks in above-ground vegetation, root biomass, detritus, and soil organic matter; rates of carbon inputs to soil and detrital layers using litterfall collection and sequential coring to estimate fine root turnover; C-14 analyses of fractionated SOM and soil CO2 to estimate residence times; C-13 analyses to estimate C inputs to pasture soils from C-4 grasses; soil pCO2, volumetric water content, and radon gradients to estimate CO2 production as a function of soil depth; soil respiration to estimate total C outputs; and a model of soil C dynamics that defines SOM fractions cycling on annual, decadal, and millennial time scales.

  11. River under anthropogenic stress: An isotope study of carbon cycling in the Vistula, Poland

    International Nuclear Information System (INIS)

    Rivers play an important role in global carbon cycling as they transform and transport substantial amounts of carbon derived from the terrestrial systems to the oceans. Riverine carbon cycling is affected by anthropogenic influences on hydrology, chemistry and biology of the river and its catchment. The Vistula, one of the most mineralized rivers of the world, drains industrialized and agriculturally-used areas populated by almost 23 million inhabitants. Moreover, much of the industrial and domestic wastewaters discharged into the Vistula river are untreated or insufficiently treated. High levels of pollution have serious environmental and economical consequences. For example, they limit use of Vistula waters as a source of drinking water and for industrial purposes. Pollutants transported by the Vistula river significantly influence water quality far into the open Baltic Sea. The aim of the paper is to show how stable isotope techniques can be used to assess human impact on sources, fluxes and fate of dissolved inorganic carbon (DIC) and other pollutants in rivers, taking the Vistula river as an example. Vistula waters were sampled over a one-year period at Krakow (upper reaches), where the anthropogenic influences are at the extreme, and at the river mouth. Two campaigns were undertaken to sample the Vistula river along its course in summer and in autumn. Analyses of river water included temperature, pH, alkalinity, conductivity, dissolved oxygen, δ13C of dissolved inorganic carbon and stable isotope composition of water (δ18O and δ2H)

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Cao, Long

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

  14. B/Ca ratio of foraminifers : a proxy for the carbon cycle in the ocean

    OpenAIRE

    Coadic, Romain

    2012-01-01

    It has been shown recently that the B/Ca ratio of planktonic foraminifers depends on the seasurface water pH, while benthic foraminifer B/Ca depends on the carbonate ion saturation of deep water. This new tracer could allow to better constrain the variations of oceanic carbon cycle, especially during the glacial-interglacial transitions (G/IG) of the Pleistocene. The objectives of this thesis were therefore : (1) to develop the foraminiferal B/Ca analysis by mass spectrometry (ICP-QMS) at LSC...

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

    Science.gov (United States)

    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

  16. Distribution and preservation of black carbon in the East China Sea sediments: Perspectives on carbon cycling at continental margins

    Science.gov (United States)

    Huang, Liang; Zhang, Jing; Wu, Ying; Wang, Jinlong

    2016-02-01

    We determined the concentrations and radiocarbon (14C) compositions of black carbon (BC) in the sediments of the East China Sea (ECS). The BC concentrations, which were in the range of 0.30-1.52 mg/g, accounted for 12-65% of the total organic carbon (TOC). The distribution of BC in ECS sediments was controlled by factors such as grain size, distance from the coast, and deposition rate. Radiocarbon measurements of BC yielded ages of 6350-10,440 years before present (BP), suggesting that the percentage of BC derived from biomass combustion was in the range of 29-48%. The BC burial flux in sediments of the ECS was estimated to be ∼1.39×106 t/yr, which was similar to burial fluxes reported for shelf sediments in other areas. However, the magnitude of the total BC sink was far greater than that of any other shelf regions studied to date, indicating the global importance of BC accumulation in the ECS, and the magnitude of BC input from large rivers (e.g., the Changjiang). The riverine delivery of BC to the ECS (73%) was far greater than that of atmospheric flux (27%). Further study of the BC cycle and the interactions of BC with other organic compounds in marginal seas was required to better understand the role of BC in the global carbon cycle.

  17. Second Law of Thermodynamics Analysis of Transcritical Carbon Dioxide Refrigeration Cycle

    Institute of Scientific and Technical Information of China (English)

    杨俊兰; 马一太; 管海清; 李敏霞

    2004-01-01

    In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy analysis model is applied. The effects of heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures on the exergy loss, exergy efficiency and the coefficient of performance (COP) of the expansion turbine cycle are analyzed. It is found that the great percentages of exergy losses take place in the gas cooler and compressor. Moreover, heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures have strong influence on the exergy efficiency, COP and the exergy loss of each component. The analysis shows that there exists an optimal heat rejection pressure corresponding to the maximum exergy efficiency and COP, respectively. The results are of significance in providing theoretical basis for optimal design and the control of the transcritical carbon dioxide system with an expansion turbine.

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

    Science.gov (United States)

    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

  19. Cycle du carbone et risques environnementaux dans les écosystèmes prairiaux

    OpenAIRE

    Chabbi, Abad; Cellier, Pierre; Rumpel, Cornelia; Gastal, Francois; Lemaire, Gilles

    2012-01-01

    Au sein des territoires de polyculture-élevage, la prairie et les cultures fourragères pérennes jouent un rôle essentiel dans certaines fonctions environnementales, (i) maintien de la qualité des sols, (ii) régulation du cycle de l’azote et du carbone (iii) séquestration du carbone dans les sols (iv) maintien de la biodiversité …. Or, la gestion et la conduite de la praire peuvent avoir des conséquences sur les couplages et découplages entre cycles de C et N, et in fine sur la séquestration e...

  20. Development of Specific Rules for the Application of Life Cycle Assessment to Carbon Capture and Storage

    Directory of Open Access Journals (Sweden)

    Michela Gallo

    2013-03-01

    Full Text Available Carbon Capture and Storage (CCS is a very innovative and promising solution for greenhouse gases (GHG reduction, i.e., capturing carbon dioxide (CO2 at its source and storing it indefinitely to avoid its release to the atmosphere. This paper investigates a set of key issues in the development of specific rules for the application of Life Cycle Assessment (LCA to CCS. The following LCA-based information are addressed in this work: definition of service type, definition of functional unit, definition of system boundaries, choice of allocation rules, choice of selected Life Cycle Inventory (LCI results or other selected parameters for description of environmental performance. From a communication perspective, the specific rules defined in this study have been developed coherently with the requirements of a type III environment label scheme, the International EPD® System, according to the ISO 14025 standard.

  1. Modeling forest carbon cycle response to tree mortality: Effects of plant functional type and disturbance intensity

    Science.gov (United States)

    Frasson, Renato Prata de Moraes; Bohrer, Gil; Medvigy, David; Matheny, Ashley M.; Morin, Timothy H.; Vogel, Christoph S.; Gough, Christopher M.; Maurer, Kyle D.; Curtis, Peter S.

    2015-11-01

    Natural and anthropogenic disturbances influence ecological succession and impact the carbon cycle. Understanding disturbance effects and ecosystem recovery is essential to carbon modeling. We hypothesized that (1) species-specific disturbances impact the carbon cycle differently from nonspecific disturbances. In particular, disturbances that target early-successional species will lead to higher carbon uptake by the postrecovery, middle- and late-successional community and (2) disturbances that affect the midsuccessional deciduous species have more intense and long-lasting impacts on carbon uptake than disturbances of similar intensity that only affect the early-successional species. To test these hypotheses, we employed a series of simulations conducted with the Ecosystem Demography model version 2 to evaluate the sensitivity of a temperate mixed-deciduous forest to disturbance intensity and type. Our simulation scenarios included a control (undisturbed) case, a uniform disturbance case where we removed 30% of all trees regardless of their successional status, five cases where only early-successional deciduous trees were removed with increasing disturbance intensity (30%, 70%, 85%, and 100%), and four cases of midsuccessional disturbances with increasing intensity (70%, 85%, and 100%). Our results indicate that disturbances affecting the midsuccessional deciduous trees led to larger decreases in carbon uptake as well as longer recovery times when compared to disturbances that exclusively targeted the early-successional deciduous trees at comparable intensities. Moreover, disturbances affecting 30% to 100% of early-successional deciduous trees resulted in an increased carbon uptake, beginning 6 years after the disturbance and sustained through the end of the 100 year simulation.

  2. Carbon and water cycling in lake-rich landscapes: Landscape connections, lake hydrology, and biogeochemistry

    Science.gov (United States)

    Cardille, Jeffrey A.; Carpenter, Stephen R.; Coe, Michael T.; Foley, Jonathan A.; Hanson, Paul C.; Turner, Monica G.; Vano, Julie A.

    2007-06-01

    Lakes are low-lying connectors of uplands and wetlands, surface water and groundwater, and though they are often studied as independent ecosystems, they function within complex landscapes. One such highly connected region is the Northern Highland Lake District (NHLD), where more than 7000 lakes and their watersheds cycle water and carbon through mixed forests, wetlands, and groundwater systems. Using a new spatially explicit simulation framework representing these coupled cycles, the Lake, Uplands, Wetlands Integrator (LUWI) model, we address basic regional questions in a 72-lake simulation: (1) How do simulated water and carbon budgets compare with observations, and what are the implications for carbon stocks and fluxes? (2) How do the strength and spatial pattern of landscape connections vary among watersheds? (3) What is the role of interwatershed connections in lake carbon processing? Results closely coincide with observations at seasonal and annual scales and indicate that the connections among components and watersheds are critical to understanding the region. Carbon and water budgets vary widely, even among nearby lakes, and are not easily predictable using heuristics of lake or watershed size. Connections within and among watersheds exert a complex, varied influence on these processes: Whereas inorganic carbon budgets are strongly related to the number and nature of upstream connections, most organic lake carbon originates within the watershed surrounding each lake. This explicit incorporation of terrestrial and aquatic processes in surface and subsurface connection networks will aid our understanding of the relative roles of on-land, in-lake, and between-lake processes in this lake-rich region.

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

    Science.gov (United States)

    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.

  4. The hourly life cycle carbon footprint of electricity generation in Belgium, bringing a temporal resolution in life cycle assessment

    International Nuclear Information System (INIS)

    Highlights: • This paper brings a temporal resolution in LCA of electricity generation. • Dynamic life cycle assessment of electricity production in Belgium for 2011. • The overall average GWP per kW h is 0.184 kg CO2eq/kW h. • The carbon footprint of Belgian electricity ranges from 0.102 to 0.262 kg CO2eq/kW h. - Abstract: In the booming research on the environmental footprint of, for example, electrical vehicles, heat pumps and other (smart) electricity consuming appliances, there is a clear need to know the hourly CO2 content of one kW h of electricity. Since the CO2 footprint of electricity can vary every hour; the footprint of for example an electric vehicle is influenced by the time when the vehicle is charged. With the availability of the hourly CO2 content of one kW h, a decision support tool is provided to fully exploit the advantages of a future smart grid. In this paper, the GWP (Global Warming Potential) per kW h for each hour of the year is calculated for Belgium using a Life Cycle Assessment (LCA) approach. This enables evaluating the influence of the electricity demand on the greenhouse gas emissions. Because of the LCA approach, the CO2 equivalent content does not only reflect activities related to the production of the electricity within a power plant, but includes carbon emissions related to the building of the infrastructure and the fuel supply chain. The considered feedstocks are nuclear combustible, oil, coal, natural gas, biowaste, blast furnace gas, and wood. Furthermore, renewable electricity production technologies like photovoltaic cells, hydro installations and wind turbines are covered by the research. The production of the wind turbines and solar panels is more carbon intensive (expressed per generated kW h of electricity) than the production of other conventional power plants, due to the lower electricity output. The overall average GWP per kW h is 0.184 kg CO2eq/kW h. Throughout the 2011 this value ranges from a minimum of 0

  5. Environmental impact associated with activated carbon preparation from olive-waste cake via life cycle assessment

    OpenAIRE

    Hjaila, Kefah; Baccar, Rym; Sarrà, Montserrat; Gasol, C.M.; Blánquez, Paqui

    2013-01-01

    he life cycle assessment (LCA) environmental tool was implemented to quantify the potential environmental impacts associated with the activated carbon (AC) production process from olive-waste cakes in Tunisia. On the basis of laboratory investigations for AC preparation, a flowchart was developed and the environmental impacts were determined. The LCA functional unit chosen was the production of 1 kg of AC from by-product olive-waste cakes. The results showed that impregnation using H3PO4 pres...

  6. Simulation of an integrated gasification combined cycle with chemical-looping combustion and carbon dioxide sequestration

    International Nuclear Information System (INIS)

    Highlights: • A chemical-looping combustion based integrated gasification combined cycle is simulated. • The energetic performance of the plant is analyzed. • Different hydrogen-content synthesis gases are under study. • Energy savings accounting carbon dioxide sequestration and storage are quantified. • A notable increase on thermal efficiency up to 7% is found. - Abstract: Chemical-looping combustion is an interesting technique that makes it possible to integrate power generation from fuels combustion and sequestration of carbon dioxide without energy penalty. In addition, the combustion chemical reaction occurs with a lower irreversibility compared to a conventional combustion, leading to attain a somewhat higher overall thermal efficiency in gas turbine systems. This paper provides results about the energetic performance of an integrated gasification combined cycle power plant based on chemical-looping combustion of synthesis gas. A real understanding of the behavior of this concept of power plant implies a complete thermodynamic analysis, involving several interrelated aspects as the integration of energy flows between the gasifier and the combined cycle, the restrictions in relation with heat balances and chemical equilibrium in reactors and the performance of the gas turbines and the downstream steam cycle. An accurate thermodynamic modeling is required for the optimization of several design parameters. Simulations to evaluate the energetic efficiency of this chemical-looping-combustion based power plant under diverse working conditions have been carried out, and a comparison with a conventional integrated gasification power plant with precombustion capture of carbon dioxide has been made. Two different synthesis gas compositions have been tried to check its influence on the results. The energy saved in carbon capture and storage is found to be significant and even notable, inducing an improvement of the overall power plant thermal efficiency of

  7. Autochthonous and allochthonous carbon cycling in a eutrophic flow-through wetland

    OpenAIRE

    Maynard, JJ; Dahlgren, RA; O'Geen, AT

    2014-01-01

    Wetland environments are important sites for the cycling and retention of terrestrially derived organic matter and nutrients. Wetland treatment of agricultural runoff has been shown to improve water quality and promote carbon sequestration. However, the potential role of eutrophic wetlands as a source of algal loading contributing to downstream hypoxia has prompted interest in understanding algal productivity and export from these systems. This study, in the San Joaquin Valley, California, qu...

  8. Carbon Cycling, Climate Regulation, and Disturbances in Canadian Forests: Scientific Principles for Management

    OpenAIRE

    Jean-Sébastien Landry; Navin Ramankutty

    2015-01-01

    Canadian forests are often perceived as pristine and among the last remaining wilderness, but the majority of them are officially managed and undergo direct land use, mostly for wood harvest. This land use has modified their functions and properties, often inadvertently (e.g., age structure) but sometimes purposefully (e.g., fire suppression). Based on a review of the literature pertaining to carbon cycling, climate regulation, and disturbances from logging, fire, and insect outbreaks, we pro...

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

    DEFF Research Database (Denmark)

    Frank, Dorothea; Reichstein, Markus; Bahn, Michael;

    2015-01-01

    Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extre...... remote sensing vs. ground‐based observational case studies reveals that many regions in the (sub‐)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon–climate feedbacks....

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

    Science.gov (United States)

    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. Evaluation of carbon dioxide blends with isopentane and propane as working fluids for organic Rankine cycles

    International Nuclear Information System (INIS)

    The main theme of this paper is to study the flammability suppression of hydrocarbons by blending with carbon dioxide, and to evaluate these mixtures as possible working fluids in organic Rankine cycle for medium temperature concentrated solar power applications. The analysis takes into account inevitable irreversibilities in the turbine, the pump, and heat exchangers. While the isopentane + CO2 mixture suffers from high irreversibility mainly in the regenerator owing to a large temperature glide, the propane + CO2 mixture performs more or less the same as pure propane albeit with high cycle pressures. In general, large temperature glides at condensing pressures extend the heat recovery into the two-phase dome, which is an advantage. However, at the same time, the shift of the pinch point towards the warm end of the regenerator is found to be a major cause of irreversibility. In fact, as the number of carbon atoms in alkanes decreases, their blend with CO2 moves the pinch point to the colder end of the regenerator. This results in lower entropy generation in the regenerator and improved cycle efficiency of propane + CO2 mixtures. With this mixture, real cycle efficiencies of 15–18% are achievable at a moderate source temperature of 573 K. Applicability for a wide range of source temperatures is found to be an added advantage of this mixture. -- Highlights: ► Non-water based working fluids and their mixtures for power generation. ► Results for carbon dioxide blends with isopentane and propane. ► Appropriation of irreversibilities in cycle components. ► Entropy generation based on pinch point of regenerator and heat source temperature

  12. Tertiary carbonate-dissolution cycles on the Sierra Leone Rise, eastern equatorial Atlantic Ocean

    Science.gov (United States)

    Dean, W.E.; Gardner, J.V.; Cepek, P.

    1981-01-01

    Most of the Tertiary section on Sierra Leone Rise off northwest Africa consists of chalk, marl, and limestone that show cyclic alterations of clay-rich and clay-poor beds about 20-60 cm thick. On the basis of biostratigraphic accumulation rates, the cycles in Oligocene and Miocene chalk have periods which average about 44,000 years, and those in Eocene siliceous limestone have periods of 4000-27,000 years. Several sections were sampled in detail to further define the cycles in terms of content of CaCO3, clay minerals, and relative abundances of calcareous nannofossils. Extending information gained by analyses of Pleistocene cores from the continental margin of northwest Africa to the Tertiary cycles on Sierra Leone Rise, both dilution by noncarbonate material and dissolution of CaCO3 could have contributed to the observed relative variations in clay and CaCO3. However, dissolution of CaCO3 as the main cause of the carbonate-clay cycles on the Sierra Leone Rise, rather than dilution by clay, is suggested by the large amount of change (several thousand percent) in terrigenous influx required to produce the observed variations in amount of clay and by the marked increase in abundance of dissolution-resistant discoasters relative to more easily dissolved coccoliths in low-carbonate parts of cycles. The main cause of dissolution of CaCO3 was shoaling of the carbonate compensation depth (CCD) during the early Neogene and climatically induced fluctuations in the thickness of Antarctic Bottom Water. ?? 1981.

  13. Development of advanced off-design models for supercritical carbon dioxide power cycles

    International Nuclear Information System (INIS)

    In the search for increased efficiency of utility-scale electricity generation, Brayton cycles operating with supercritical carbon dioxide (S-CO2) have found considerable interest. There are two main advantages of a S-CO2 Brayton cycle compared to a Rankine cycle: 1) equal or greater thermal efficiencies can be realized using significantly smaller turbomachinery, and 2) heat rejection is not limited by the saturation temperature of the working fluid, which has the potential to reduce or completely eliminate the need for cooling water and instead allow dry cooling. While dry cooling is especially advantageous for power generation in arid climates, a reduction of water consumption in any location will be increasingly beneficial as tighter environmental regulations are enacted in the future. Because daily and seasonal weather variations may result in a plant operating away from its design point, models that are capable of predicting the off-design performance of S-CO2 power cycles are necessary for characterizing and evaluating cycle configurations and turbomachinery designs on an annual basis. To this end, an off-design model of a recuperated Brayton cycle was developed based on the radial turbomachinery currently being investigated by Sandia National Laboratory. (authors)

  14. Deep water convection and biogeochemical cycling of carbon in the Northern North Atlantic

    International Nuclear Information System (INIS)

    In 1998, the Danish Research Council launched the Global Change project 'Biochemical cycling of carbon and ocean circulation in the Northern North Atlantic'. The overall aim of the project was to describe the effect of high latitude carbon dynamics on the global ocean-atmosphere carbon system, in general, and on the atmospheric pCO2 in particular. At present, knowledge concerning the seasonal differences in turnover rates of organic material in polar and sub-polar regions is limited. Thus, in order to achieve the aim of the project, it was necessary to obtain biological and chemical rate measurements for production and mineralization of dissolved and particulate organic material at high latitudes and relate these to ocean dynamics at different times of the year. This was investigated in the project by performing three cruises to the Greenland Sea area at different times of the year. The purpose of the present chapter is to give a review of: 1) The physical environment of the Northern North Atlantic (ocean circulation, deep convection, North Atlantic Oscillation) and its variability including the recent trends of importance to climate change. 2) The chemical and biological processes of importance to carbon cycle and the importance of the carbon cycle to our understanding of climate variability. Additionally preliminary results from the Danish global change investigation in the Greenland Sea will be presented. With regard to circulation it is concluded that the deep water in the Greenland Sea continues to warm up, indicating that the deep water formation in this area is reduced. The biological investigations are providing a highly needed basic knowledge of the structure and function of the pelagic food web as well as of the microbial food web of the intermediate and deep water. These studies form a basis for assessing the productivity, export mechanisms, mineralization rates and mineralization depth-scales in these areas. Especially the questions about the production

  15. Carbon cycling and mineral weathering in the Sava River catchment in Slovenia

    International Nuclear Information System (INIS)

    Global environmental change has been identified as one of the most urgent issues of earth science research. Much research effort has addressed the role of the terrestrial reservoir in modulating carbon storage, and in turn, how the rapid cycling of carbon at the earth's surface over the next few hundreds of years will affect earth's surface environment. The chemical interactions among carbonate minerals (calcite and dolomite), organic carbon and the natural hydrologic cycle link the atmospheric and terrestrial carbon reservoirs on short time scales. Among the minerals comprising surface rocks and soils, only carbonate minerals appear capable of maintaining equilibrium in the face of rising atmospheric CO2 injections from fossil fuel burning. Rapid carbonate mineral weathering reactions also largely regulate the pH and ionic strength of terrestrial aquatic systems and so have ecologic and environmental impacts. We are investigating the geochemical dynamics using major elemental, stable isotope, and hydrogeochemical parameters to better understand carbon mass transport of the Sava river drainages in Slovenia. Importantly, the Sava catchment is the largest catchment in Slovenia and at the same time one of the tributary streams of the Danube river, the second largest river in Europe. The weathering of the Danube river represents one of the largest carbon fluxes in the world. Rock weathering contributes a significant portion of HCO3- - to most rivers and thus has a strong influence on their carbon cycle. First results in the Sava River catchment indicate that the watershed exhibit typical 1:2 ratio of divalent cations to bicarbonate ion consistent with simple carbonate mineral dissolution in pure water. The Mg/Ca mole ratios are higher than 0.5 with 1 mol Ca for 0.5 mol Mg, the ratio predicted for equilibration in systems where calcite and dolomite dissolution proceed together. The concentration of DIC is high in the Sava River and lies well above the average

  16. Water cycle dynamic increases resilience of vegetation under higher atmospheric carbon dioxide concentration

    Science.gov (United States)

    Lemordant, L. A.; Gentine, P.; Stéfanon, M.; Drobinski, P. J.; Fatichi, S.

    2015-12-01

    Plant stomata couple the energy, water and carbon cycles. Photosynthesis requires stomata to open to take up carbon dioxide. In the process water vapor is released as transpiration. As atmospheric CO2 concentration rises, for the same amount of CO2 uptake, less water vapor is transpired, translating into higher water use efficiency. Reduced water vapor losses will increase soil water storage if the leaf area coverage remains similar. This will in turn alter the surface energy partitioning: more heat will be dissipated as sensible heat flux, resulting in possibly higher surface temperatures. In contrast with this common hypothesis, our study shows that the water saved during the growing season by increased WUE can be mobilized by the vegetation and help reduce the maximum temperature of mid-latitude heat waves. The large scale meteorological conditions of 2003 are the basis of four regional model simulations coupling an atmospheric model to a surface model. We performed two simulations with respectively 2003 (CTL) and 2100 (FUT) atmospheric CO2 applied to both the atmospheric and surface models. A third (RAD) and a fourth (FER) simulations are run with 2100 CO2 concentration applied to respectively the atmospheric model only and the surface model only. RAD investigates the impact of the radiative forcing, and FER the response to vegetation CO2 fertilization. Our results show that the water saved through higher water use efficiency during the growing season enabled by higher atmospheric carbon dioxide concentrations helps the vegetation to cope during severe heat and dryness conditions in the summer of mid-latitude climate. These results demonstrate that consideration of the vegetation carbon cycle is essential to model the seasonal water cycle dynamic and land-atmosphere interactions, and enhance the accuracy of the model outputs especially for extreme events. They also have important implications for the future of agriculture, water resources management, ecosystems

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

    Science.gov (United States)

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

    2008-12-01

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

  18. The impact of Indonesian peatland degradation on downstream marine ecosystems and the global carbon cycle.

    Science.gov (United States)

    Abrams, Jesse F; Hohn, Sönke; Rixen, Tim; Baum, Antje; Merico, Agostino

    2016-01-01

    Tropical peatlands are among the most space-efficient stores of carbon on Earth containing approximately 89 Gt C. Of this, 57 Gt (65%) are stored in Indonesian peatlands. Large-scale exploitation of land, including deforestation and drainage for the establishment of oil palm plantations, is changing the carbon balance of Indonesian peatlands, turning them from a natural sink to a source via outgassing of CO2 to the atmosphere and leakage of dissolved organic carbon (DOC) into the coastal ocean. The impacts of this perturbation to the coastal environment and at the global scale are largely unknown. Here, we evaluate the downstream effects of released Indonesian peat carbon on coastal ecosystems and on the global carbon cycle. We use a biogeochemical box model in combination with novel and literature observations to investigate the impact of different carbon emission scenarios on the combined ocean-atmosphere system. The release of all carbon stored in the Indonesian peat pool, considered as a worst-case scenario, will increase atmospheric pCO2 by 8 ppm to 15 ppm within the next 200 years. The expected impact on the Java Sea ecosystems is most significant on the short term (over a few hundred years) and is characterized by an increase of 3.3% in phytoplankton, 32% in seagrass biomass, and 5% decrease in coral biomass. On the long term, however, the coastal ecosystems will recover to reach near pre-excursion conditions. Our results suggest that the ultimate fate of the peat carbon is in the deep ocean with 69% of it landing in the deep DIC pool after 1000 years, but the effects on the global ocean carbonate chemistry will be marginal. PMID:26416553

  19. Role of temperate zone forests in the world carbon cycle: problem definition and research needs

    Energy Technology Data Exchange (ETDEWEB)

    Armentano, T.V.; Hett, J. (eds.)

    1979-01-01

    The proceedings of a workshop on carbon uptake and losses from temperate zone forests are presented. The goals of the workshop were to analyze existing data on growth and utilization of the temperate zone forest carbon pool and to identify further research needs in relation to the role of temperate forests in the global carbon cycle. Total standing stock and growth recovery transients were examined for most of the temperate region over a period from pre-settlement times to the present, with emphasis on the last three decades. Because of data availability, certain regions and topics were covered more in detail than others. Forest inventory data from most of the commercial timberlands of the north temperate zone suggest these forests have functioned over the past several decades as an annual sink for about 10/sup 9/ metric tons of carbon. Thus, net growth of these forests has withdrawn carbon from the atmosphere at a rate equivalent, approximately, to 50% of the annual rise in atmospheric carbon. Various data inadequacies make this estimate probably no more precise than plus or minus half of the value. Analysis of growth and vegetation changes in New England and the southeastern United States shows that forest biomass has partly recovered since extensive clearing took place in the 18th and 19th centuries. This regrowth represents a net withdrawal of carbon (carbon sink) from the atmosphere in recent decades, although the difference in pool size between present and original forests means that, in the longer term, the two regions have functioned as carbon sources.

  20. Transformation of Graphitic and Amorphous Carbon Dust to Complex Organic Molecules in a Massive Carbon Cycle in Protostellar Nebulae

    Science.gov (United States)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    More than 95% of silicate minerals and other oxides found in meteorites were melted, or vaporized and recondensed in the Solar Nebula prior to their incorporation into meteorite parent bodies. Gravitational accretion energy and heating via radioactive decay further transformed oxide minerals accreted into planetesimals. In such an oxygen-rich environment the carbonaceous dust that fell into the nebula as an intimate mixture with oxide grains should have been almost completely converted to CO. While some pre-collapse, molecular-cloud carbonaceous dust does survive, much in the same manner as do pre-solar oxide grains, such materials constitute only a few percent of meteoritic carbon and are clearly distinguished by elevated D/H, N-15/N-16, C-13/C-12 ratios or noble gas patterns. Carbonaceous Dust in Meteorites: We argue that nearly all of the carbon in meteorites was synthesized in the Solar Nebula from CO and that this CO was generated by the reaction of carbonaceous dust with solid oxides, water or OH. It is probable that some fraction of carbonaceous dust that is newly synthesized in the Solar Nebula is also converted back into CO by additional thermal processing. CO processing might occur on grains in the outer nebula through irradiation of CO-containing ice coatings or in the inner nebula via Fischer-Tropsch type (FTT) reactions on grain surfaces. Large-scale transport of both gaseous reaction products and dust from the inner nebula out to regions where comets formed would spread newly formed carbonaceous materials throughout the solar nebula. Formation of Organic Carbon: Carbon dust in the ISM might easily be described as inorganic graphite or amorphous carbon, with relatively low structural abundances of H, N, O and S . Products of FTT reactions or organics produced via irradiation of icy grains contain abundant aromatic and aliphatic hydrocarbons. aldehydes, keytones, acids, amines and amides.. The net result of the massive nebular carbon cycle is to convert

  1. Sedimentary Iron Cycling and the Origin and Preservation of Magnetization in Platform Carbonate Muds, Andros Island, Bahamas

    OpenAIRE

    Maloof, Adam C.; Kopp, Robert E.; Grotzinger, John P.; Fike, David A; Bosak, Tanja; Vali, Hojotollah; Poussart, Pascale M.; Weiss, Benjamin P.; Kirschvink, Joseph L

    2007-01-01

    Carbonate muds deposited on continental shelves are abundant and well-preserved throughout the geologic record because shelf strata are difficult to subduct and peritidal carbonate units often form thick, rheologically strong units that resist penetrative deformation. Much of what we know about pre-Mesozoic ocean chemistry, carbon cycling, and global change is derived from isotope and trace element geochemistry of platform carbonates. Paleomagnetic data from the same sediments would be invalu...

  2. Testing Elementary Cycles Formulation of Quantum Mechanics in Carbon Nanotubes and Superconductivity

    CERN Document Server

    Dolce, Donatello

    2016-01-01

    Elementary Cycles are intrinsic periodic phenomena, classical in the essence, whose classical relativistic dynamics reproduce the complete coherence (perfect recurrences) typically associated to the pure quantum behaviours of elementary particles. They can be regarded as effective representations of 't Hooft Cellular Automata. By means of Elementary Cycles physics we obtain a consistent, intuitive, novel derivation of the peculiar quantum dynamics of electrons in Carbon Nanotubes, as well as of Superconductivity fundamental phenomenology. In particular we derive, from classical arguments, the essential electronic properties of graphene systems, such as energy bands and density of states. Similarly, in the second part of the paper, we derive the Superconductivity fundamental phenomenology in terms of simple geometrical considerations, directly from the Elementary Cycles dynamics rather than from empirical aspects and effective quantities connected to the microscopical characteristics of materials as in the sta...

  3. A framework to study nuclear power plant life-cycle carbon release

    International Nuclear Information System (INIS)

    Expansion of nuclear power is a critical strategy for greenhouse gas emissions reduction in China. As a safe and economical and clean energy source, it is always regarded as practical technology for large-scale deployment and car bon-free. However, from the life cycle perspective, nuclear power production is not 100% greenhouse gas free. From uranium mining, concentrating, to the construction and operation of nuclear power plants and nuclear waste treatment until decommissioning of nuclear facilities, greenhouse gas emissions are involved. A life cycle framework is developed with related data to evaluate of generation of greenhouse gases per kilowatt as well as the influential uncertainties. An economic scenario analysis is also applied to calculate the incremental electricity generation cost caused by the carbon e- mission in the life cycles of the technologies. The results demonstrated that the nuclear energy will become more competitive particularly if there is a carbon trade system. Moreover, the greenhouse gas emission during the nuclear power plant life-cycle will be greatly reduced if more advanced technologies were applied in the nuclear sector. (authors)

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

    Science.gov (United States)

    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. PMID:26404735

  5. Climatic Controls of Soil Carbon Cycling Across a Gradient of Sonoran Desert Ecosystems

    Science.gov (United States)

    Rasmussen, C.

    2009-04-01

    Arid and semiarid lands cover roughly 36% to 40% of global land area, highlighting the importance these ecosystems play in the global carbon cycle. The controls of arid and semiarid ecosystem carbon cycle processes, such as soil organic matter turnover and mineral weathering, remain poorly understood. To address this knowledge gap, we established a set of long-term soil monitoring sites across a gradient of semiarid ecosystems in the Sonoran Desert of the Southwestern USA. These sites were established as part of the Critical Zone Exploration Network (CZEN), sponsored by the US National Science Foundation. The primary objectives of the Sonoran Desert Environmental Gradient (SDEG) include: (i) characterizing climate forcing controls of soil physical, chemical and biological processes, and the flux of chemical species from soils to surface waters; and (ii) developing predictive models of carbon cycle response to climate and climate change. Particular attention is given to the bimodal precipitation regime characteristic of the SDEG ecosystems and the relative impact of warm versus cold precipitation on biogeochemical processes. The SDEG spans a steep elevation and environmental gradient on granitic parent materials near Tucson, Arizona, USA. Elevation ranges from 800-2650 m a.s.l. with concurrent shifts in climatic regime. Specifically, mean annual air temperature decreases (20-10 °C) and mean annual precipitation increases (30-85 cm) with elevation, with concomitant changes in vegetation from mixed desert-scrub (forest (>2000 m). We sampled soil and regolith material from each of vegetation community across the SDEG and established a long-term soil-moisture and temperature monitoring network. Pedon physicochemical data, coupled with elemental mass balance, radiocarbon analyses of soil organic matter, and terrestrial cosmogenic nuclide (10Be) analyses indicate substantial variation in carbon cycling across the SDEG. Soil morphology suggests the dominant pedogenic

  6. Carbon cycling and phytoplankton responses within highly-replicated shipboard carbonate chemistry manipulation experiments conducted around Northwest European Shelf Seas

    Directory of Open Access Journals (Sweden)

    S. Richier

    2014-03-01

    Full Text Available The ongoing oceanic uptake of anthropogenic carbon dioxide (CO2 is significantly altering the carbonate chemistry of seawater, a phenomenon referred to as ocean acidification. Experimental manipulations have been increasingly used to gauge how continued ocean acidification will potentially impact marine ecosystems and their associated biogeochemical cycles in the future; however, results amongst studies, particularly when performed on natural communities, are highly variable, which in part likely reflects inconsistencies in experimental approach. To investigate the potential for identification of more generic responses and greater experimentally reproducibility, we devised and implemented a series of highly replicated (n = 8, short term (2–4 days multi-level (≥ 4 conditions carbonate chemistry/nutrient manipulation experiments on a range of natural microbial communities sampled in Northwest European shelf seas. Carbonate chemistry manipulations and resulting biological responses were found to be highly reproducible within individual experiments and to a lesser extent between geographically different experiments. Statistically robust reproducible physiological responses of phytoplankton to increasing pCO2, characterized by a suppression of net growth for small sized cells (pCO2 and hence lower buffer capacity. The results thus emphasize how biological-chemical feedbacks may be altered in the future ocean.

  7. Enhancement of non-CO2 radiative forcing via intensified carbon cycle feedbacks

    Science.gov (United States)

    MacDougall, Andrew H.; Knutti, Reto

    2016-06-01

    The global carbon cycle is sensitive to changes in global temperature and atmospheric CO2 concentration, with increased temperature tending to reduce the efficiency of carbon sinks and increased CO2 enhancing the efficiency of carbon sinks. The emission of non-CO2 greenhouse gases warms the Earth but does not induce the CO2 fertilization effect or increase the partial-pressure gradient between the atmosphere and the surface ocean. Here we present idealized climate model experiments that explore the indirect interaction between non-CO2 forcing and the carbon cycle. The experiments suggest that this interaction enhances the warming effect of the non-CO2 forcing by up to 25% after 150 years and that much of the warming caused by these agents lingers for over 100 years after the dissipation of the non-CO2 forcing. Overall, our results suggest that the longer emissions of non-CO2 forcing agents persists the greater effect these agents will have on global climate.

  8. The Effect of Sediment Disturbance on the Carbon and Nitrogen Cycles Within Coastal Marine Lakes

    Science.gov (United States)

    Mills, A. R.; Wilson, S. R.; Jolley, D. F.

    2006-12-01

    A system allowing the ex situ quantification of the nitrogen cycle and various carbonaceous species (Organic Carbon, carbon dioxide, methane) in the air, water and sediment has been developed and used to monitor the effects of sediment disturbance on the nitrogen and carbon cycles. Measurements are made using standard wet chemical techniques for the sediment and water phases, and FTIR spectroscopy for the real-time monitoring of gas concentrations. Sediment collected from two temperate marine lakes on the eastern coast of Australia has been examined. In the laboratory it was found that the methane flux peaked three days after the initial disturbance; nitrous oxide flux peaked after 12 days while carbon dioxide flux varied throughout the experiment. Nitrite and nitrate concentrations in the overlying water peaked at the end of the second and third weeks, respectively. The total quantity of nitrogen within the system increased by ~ 35%. Sediment disturbance led to an initial release of nitrogenous nutrients from the sediment to the overlying water that were rapidly readsorbed to sediment particles and sequestered back into the sediment phase. The same technology was also adapted to allow this research to be undertaken in the field and used to study three new temperate marine sites within Lake Illawarra, New South Wales, Australia.

  9. Inorganic Carbon Cycling and Biogeochemical Processes in an Arctic Inland Sea (Hudson Bay)

    Science.gov (United States)

    Burt, William; Thomas, Helmuth; Miller, Lisa; Granskog, Mats; Papakyriakou, Tim; Pengelly, Leah

    2016-04-01

    The distributions of CO2 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 ocean 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 (δ18OH2O and δ13CDIC), to provide a detailed assessment of carbon cycling processes throughout the bay. Surface distributions of carbonate parameters reveal the particular importance of freshwater inputs in the southern portion of the bay. 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 during deep water circulation around the bay. Based on TA data we surmise that the deep waters in the Hudson Bay are of Pacific origin.

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

    Science.gov (United States)

    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.

  11. The role of tropical deforestation in the global carbon cycle: Spatial and temporal dynamics

    Science.gov (United States)

    Houghton, R. A.; Skole, David; Moore, Berrien; Melillo, Jerry; Steudler, Paul

    1995-01-01

    'The Role of Tropical Deforestation in the Global Carbon cycle: Spatial and Temporal Dynamics', was a joint project involving the University of New Hampshire, the Marine Biological Laboratory, and the Woods Hole Research Center. The contribution of the Woods Hole Research Center consisted of three tasks: (1) assist University of New Hampshire in determining the net flux of carbon between the Brazilian Amazon and the atmosphere by means of a terrestrial carbon model; (2) address the spatial distribution of biomass across the Amazon Basin; and (3) assist NASA Headquarters in development of a science plan for the Terrestrial Ecology component of the NASA-Brazilian field campaign (anticipated for 1997-2001). Progress on these three tasks is briefly described.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. Changes in the carbon cycle of Amazon ecosystems during the 2010 drought

    International Nuclear Information System (INIS)

    Satellite remote sensing was combined with the NASA-CASA (Carnegie Ames Stanford Approach) carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO2 uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon river basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO2 to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to those for forests outside the main river floodplains.

  14. Changes in the carbon cycle of Amazon ecosystems during the 2010 drought

    Energy Technology Data Exchange (ETDEWEB)

    Potter, Christopher [NASA Ames Research Center, Moffett Field, CA (United States); Klooster, Steven; Hiatt, Cyrus; Genovese, Vanessa [California State University Monterey Bay, Seaside, CA (United States); Castilla-Rubio, Juan Carlos, E-mail: chris.potter@nasa.gov [Planetary Skin Institute, Silicon Valley, CA (United States)

    2011-07-15

    Satellite remote sensing was combined with the NASA-CASA (Carnegie Ames Stanford Approach) carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO{sub 2} uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon river basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO{sub 2} to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to those for forests outside the main river floodplains.

  15. The role of metal–organic frameworks in a carbon-neutral energy cycle

    Science.gov (United States)

    Schoedel, Alexander; Ji, Zhe; Yaghi, Omar M.

    2016-04-01

    Reducing society's reliance on fossil fuels presents one of the most pressing energy and environmental challenges facing our planet. Hydrogen, methane and carbon dioxide, which are some of the smallest and simplest molecules known, may lie at the centre of solving this problem through realization of a carbon-neutral energy cycle. Potentially, this could be achieved through the deployment of hydrogen as the fuel of the long term, methane as a transitional fuel, and carbon dioxide capture and sequestration as the urgent response to ongoing climate change. Here we detail strategies and technologies developed to overcome the difficulties encountered in the capture, storage, delivery and conversion of these gas molecules. In particular, we focus on metal–organic frameworks in which metal oxide ‘hubs’ are linked with organic ‘struts’ to make materials of ultrahigh porosity, which provide a basis for addressing this challenge through materials design on the molecular level.

  16. Changes in the Carbon Cycle of Amazon Ecosystems During the 2010 Drought

    Science.gov (United States)

    Potter, Christophera; Klooster, Steven; Hiatt, Cyrus; Genovese, Vanessa; Castilla-Rubino, Juan Carlos

    2011-01-01

    Satellite remote sensing was combined with the NASA-CASA carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production (NPP) in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO2 uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon River basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO2 to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to forests outside the main river floodplains.

  17. Management Tools and Potential of Dry Miombo Woodland in Carbon Cycling

    DEFF Research Database (Denmark)

    Mwakalukwa, Ezekiel Edward

    Abstract Tools to support sustainable management of dry Miombo woodlands and precise assessment of carbon storage and sequestration potential are in most cases lacking in Tanzania. Accordingly, using Gangalamtumba Village Land Forest Reserve as a case study area located in Iringa region, this the......Abstract Tools to support sustainable management of dry Miombo woodlands and precise assessment of carbon storage and sequestration potential are in most cases lacking in Tanzania. Accordingly, using Gangalamtumba Village Land Forest Reserve as a case study area located in Iringa region......, this thesis aims to develop management tools and generate information that will enhance our understanding of the actual and potential contribution of dry Miombo woodlands in carbon cycling. This is done through a detailed assessment of floristic composition, structure, species associations and through...

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

    Retallack, G. J.

    2003-12-01

    Soils play an important role in the carbon cycle as the nutrition of photosynthesized biomass. Nitrogen fixed by microbes from air is a limiting nutrient for ecosystems within the first flush of ecological succession of new ground, and sulfur can limit some components of wetland ecosystems. But over the long term, the limiting soil nutrient is phosphorus extracted by weathering from minerals such as apatite (Vitousek et al., 1997a; Chadwick et al., 1999). Life has an especially voracious appetite for common alkali (Na+ and K+) and alkaline earth (Ca2+ and Mg2+) cations, supplied by hydrolytic weathering, which is in turn amplified by biological acidification (Schwartzmann and Volk, 1991; see Chapter 5.06). These mineral nutrients fuel photosynthetic fixation and chemical reduction of atmospheric CO2 into plants and plantlike microbes, which are at the base of the food chain. Plants and photosynthetic microbes are consumed and oxidized by animals, fungi, and other respiring microbes, which release CO2, methane, and water vapor to the air. These greenhouse gases absorb solar radiation more effectively than atmospheric oxygen and nitrogen, and are important regulators of planetary temperature and albedo (Kasting, 1992). Variations in solar insolation ( Kasting, 1992), mountainous topography ( Raymo and Ruddiman, 1992), and ocean currents ( Ramstein et al., 1997) also play a role in climate, but this review focuses on the carbon cycle. The carbon cycle is discussed in detail in Volume 8 of this Treatise.The greenhouse model for global paleoclimate has proven remarkably robust (Retallack, 2002), despite new challenges ( Veizer et al., 2000). The balance of producers and consumers is one of a number of controls on atmospheric greenhouse gas balance, because CO2 is added to the air from fumaroles, volcanic eruptions, and other forms of mantle degassing (Holland, 1984). Carbon dioxide is also consumed by burial as carbonate and organic matter within limestones and other

  20. Projecting Carbon Cycling Trajectories in Forests of the Upper Midwest, USA: Has Carbon Storage Peaked?

    Science.gov (United States)

    Curtis, P. S.; Gough, C. M.; Vogel, C. S.; Hardiman, B.; Bohrer, G.; Nave, L. E.

    2008-12-01

    The mixed deciduous forests of the upper Midwest, USA are approaching an ecological threshold in which dominant early successional aspen and birch trees are reaching maturity and beginning to senesce, giving way to a canopy that is more species diverse and structurally heterogeneous. Widespread ecological changes in maturing forests of the upper Midwest are predicted to reduce terrestrial C storage in the region; however, no empirical evidence exists to support this hypothesis. At the University of Michigan Biological Station in northern Michigan, we are combining long-term C cycling measurements with a large-scale experimental manipulation to forecast how forest C storage will change in response to ongoing succession and disturbance, and to climate variation. At the plot scale, 10-yr trajectories of increasing wood net primary production were accompanied by significant increases in leaf area index (LAI), which were positively correlated with successional advances in canopy species diversity as late-successional species grew into predominately aspen and birch canopies. Surveys of canopy structure indicate that more species diverse canopies support greater LAI by increasing the vertical distribution of leaf area. These results suggest that forests of the upper Midwest may store more C if, as predicted, their canopies become more species diverse and structurally heterogeneous. To examine changes in forest C cycling following successional transition from mature aspen and birch to a young mixed conifer-deciduous ecosystem, we accelerated forest succession by stem girdling all aspen and birch (>6,700 trees, ~35% canopy LAI) within a 39 ha area in Spring 2008. The Forest Accelerated Succession ExperimenT (FASET) will test the hypothesis that forest net ecosystem production will decline temporarily following an initial disturbance that results in partial canopy defoliation and subsequently increase as canopies become more biologically and structurally complex. Our goal is

  1. Anthropogenic Deforestation and its Effect on the Carbon Cycle of Europe Over the Past Three Millennia

    Science.gov (United States)

    Kaplan, J. O.; Krumhardt, K. M.

    2008-12-01

    Over the past three millennia, both climate and anthropogenic land use and land cover change (LULUC) have substantially affected the European landscape. Anthropogenic deforestation for agriculture and pasture has been the most significant of these land cover changes, though climate variability itself may have had an impact on European ecosystems. In this study we attempt to quantify the influence of both LULUC and climate change on the carbon cycle of Europe during preindustrial time, and speculate on the ramifications for global atmospheric composition and biogeochemical feedbacks to the climate system. To quantify the effect of millennial-scale climate change and LULUC on the carbon cycle over the past three millennia, we assembled spatially explicit datasets of these quantities and ran a dynamic global vegetation model (LPJ-DGVM) in a number of experiments and sensitivity tests on a high-resolution grid for Europe. Climate data needed to run LPJ were synthesized from gridded datasets of mean monthly temperature and precipitation based on multiproxy climate reconstructions. Though it is certain that many European countries were substantially deforested before 1850, no coherent data set of the progression of deforestation that occurred during preindustrial time was available to us. We have therefore created a 10km, annually resolved gridded time series of European LULUC for the past three millennia by digitizing and synthesizing a database of population history for Europe and finding a relationship between population density, land quality for agricultural and pastoral activities, and anthropogenic deforestation. With these input data, we ran a series of experiments and sensitivity tests with LPJ to simulate the effect that changes in climate, LULUC and length- of-run (starting the run at 1700, 1850 or 1900) have on European carbon storage and its trajectory at year 2000. Climate variability in Europe over the past three millennia years caused modest reductions in

  2. Land use changes and their relations with carbon cycles over the past 300 a in China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Land use and land cover in China have changed greatly during the past 300 a, indicated by the rapid abrupt decrease of forest land area and the rapid increase of cropland area, which can affect terrestrial carbon cycle greatly. The first-hand materials are used to analyze main characteristics for land use and land cover changes in China during the study period. The following conclusions can be drawn from this study. The cropland area in China kept increasing from 60.78×106 hm2 in 1661 to 96.09×106 hm2 in 1998. Correspondingly, the forest land area decreased from 248.13×106 hm2 in 1700 to 109.01×106 hm2 in 1949. Affected by such changes, the terrestrial ecosystem carbon storage decreased in the mean time. Car-bon lost from land use and land cover changes mainly consist of the loss from vegetation biomass and soil. In the past 300 a, about 3.70 PgC was lost from vegetation biomass, and emissions from soil ranged from 0.80 to 5.84 PgC. The moderate evaluation of soil losses was 2.48 PgC. The total loss from vegetation and soil was between 4.50 and 9.54 PgC. The moderate and optimum evaluation was 6.18 PgC. Such carbon losses distribution varied spatially from region to region. Carbon lost more significantly in Northeast China and Southwest China than in other regions, because losses of forest land in these two regions were far greater than in the other regions during the past 300 a. And losses of carbon in the other regions were also definite, such as Inner Mongolia, the western part of South China, the Xinjiang Uygur Autonomous Region, and the Qinghai-Tibet Plateau. But the carbon lost very little from the traditional agricultural regions in China, such as North China and East China. Studies on the relationship between land use and land cover change and carbon cycle in China show that the land use activities, especially those related to agriculture and forest management, began to affect terrestrial carbon storage positively in recent years.

  3. NASA/GSFC Research Activities for the Global Ocean Carbon Cycle: A Prospectus for the 21st Century

    Science.gov (United States)

    Gregg, W. W.; Behrenfield, M. J.; Hoge, F. E.; Esaias, W. E.; Huang, N. E.; Long, S. R.; McClain, C. R.

    2000-01-01

    There are increasing concerns that anthropogenic inputs of carbon dioxide into the Earth system have the potential for climate change. In response to these concerns, the GSFC Laboratory for Hydrospheric Processes has formed the Ocean Carbon Science Team (OCST) to contribute to greater understanding of the global ocean carbon cycle. The overall goals of the OCST are to: 1) detect changes in biological components of the ocean carbon cycle through remote sensing of biooptical properties, 2) refine understanding of ocean carbon uptake and sequestration through application of basic research results, new satellite algorithms, and improved model parameterizations, 3) develop and implement new sensors providing critical missing environmental information related to the oceanic carbon cycle and the flux of CO2 across the air-sea interface. The specific objectives of the OCST are to: 1) establish a 20-year time series of ocean color, 2) develop new remote sensing technologies, 3) validate ocean remote sensing observations, 4) conduct ocean carbon cycle scientific investigations directly related to remote sensing data, emphasizing physiological, empirical and coupled physical/biological models, satellite algorithm development and improvement, and analysis of satellite data sets. These research and mission objectives are intended to improve our understanding of global ocean carbon cycling and contribute to national goals by maximizing the use of remote sensing data.

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

    Science.gov (United States)

    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

  5. Sulfate-reducing microorganisms in wetlands – fameless actors in carbon cycling and climate change

    Directory of Open Access Journals (Sweden)

    Michael ePester

    2012-02-01

    Full Text Available 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 (bisulfite 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 towards 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.

  6. Derivation of a northern-hemispheric biomass map for use in global carbon cycle models

    Science.gov (United States)

    Thurner, Martin; Beer, Christian; Santoro, Maurizio; Carvalhais, Nuno; Wutzler, Thomas; Schepaschenko, Dmitry; Shvidenko, Anatoly; Kompter, Elisabeth; Levick, Shaun; Schmullius, Christiane

    2013-04-01

    Quantifying the state and the change of the World's forests is crucial because of their ecological, social and economic value. Concerning their ecological importance, forests provide important feedbacks on the global carbon, energy and water cycles. In addition to their influence on albedo and evapotranspiration, they have the potential to sequester atmospheric carbon dioxide and thus to mitigate global warming. The current state and inter-annual variability of forest carbon stocks remain relatively unexplored, but remote sensing can serve to overcome this shortcoming. While for the tropics wall-to-wall estimates of above-ground biomass have been recently published, up to now there was a lack of similar products covering boreal and temperate forests. Recently, estimates of forest growing stock volume (GSV) were derived from ENVISAT ASAR C-band data for latitudes above 30° N. Utilizing a wood density and a biomass compartment database, a forest carbon density map covering North-America, Europe and Asia with 0.01° resolution could be derived out of this dataset. Allometric functions between stem, branches, root and foliage biomass were fitted and applied for different leaf types (broadleaf, needleleaf deciduous, needleleaf evergreen forest). Additionally, this method enabled uncertainty estimation of the resulting carbon density map. Intercomparisons with inventory-based biomass products in Russia, Europe and the USA proved the high accuracy of this approach at a regional scale (r2 = 0.70 - 0.90). Based on the final biomass map, the forest carbon stocks and densities (excluding understorey vegetation) for three biomes were estimated across three continents. While 40.7 ± 15.7 Gt of carbon were found to be stored in boreal forests, temperate broadleaf/mixed forests and temperate conifer forests contain 24.5 ± 9.4 Gt(C) and 14.5 ± 4.8 Gt(C), respectively. In terms of carbon density, most of the carbon per area is stored in temperate conifer (62.1 ± 20.7 Mg

  7. Design of catalytic monoliths for closed-cycle carbon dioxide lasers

    Science.gov (United States)

    Herz, R. K.; Guinn, K.; Goldblum, S.; Noskowski, E.

    1989-01-01

    Pulsed carbon dioxide (CO2) lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers in hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalyst and design methods for implementation of catalysts in CO2 laser systems. A monolith catalyst section model and associated design computer program, LASCAT, are presented to assist in the design of a monolith catalyst section of a closed cycle CO2 laser system. Using LASCAT,the designer is able to specify a number of system parameters and determine the monolith section performance. Trade-offs between the catalyst activity, catalyst dimensions, monolith dimensions, pressure drop, O2 conversion, and other variables can be explored and adjusted to meet system design specifications. An introduction describes a typical closed-cycle CO2 system, and indicates some advantages of a closed cycle laser system over an open cycle system and some advantages of monolith support over other types of supports. The development and use of a monolith catalyst model is presented. The results of a design study and a discussion of general design rules are given.

  8. Comprehensive description of the carbon cycle of an ancient temperate broadleaved woodland

    Directory of Open Access Journals (Sweden)

    K. Fenn

    2010-05-01

    Full Text Available There exist very few comprehensive descriptions of the productivity and carbon cycling of forest ecosystems. Here we present a description of the components of annual Net Primary Productivity (NPP, Gross Primary Productivity (GPP, autotrophic and heterotrophic respiration, and ecosystem respiration (RECO for a temperate mixed deciduous woodland at Wytham Woods in southern Britain, calculated using "bottom-up" biometric and chamber measurements (leaf and wood production and soil and stem respiration. These are compared with estimates of these parameters from eddy-covariance measurements made at the same site. NPP was estimated as 7.0±0.8 Mg C ha−1 yr−1, and GPP as 20.3+1.0 Mg C ha−1 yr−1, a value which closely matched to eddy covariance-derived GPP value of 21.1 Mg C ha−1 yr−1. Annual RECO was calculated as 18.9±1.7 Mg C ha−1 yr−1, close to the eddy covariance value of 19.8 Mg C ha−1 yr−1; the seasonal cycle of biometric and eddy covariance RECO estimates also closely matched. The consistency between eddy covariance and biometric measurements substantially strengthens the confidence we attach to each as alternative indicators of site carbon dynamics, and permits an integrated perspective of the ecosystem carbon cycle. 37% of NPP was allocated below ground, and the ecosystem carbon use efficiency (CUE, = NPP/GPP calculated to be 0.35±0.05, lower than reported for many temperate broadleaved sites.

  9. Comprehensive description of the carbon cycle of an ancient temperate broadleaved woodland

    Science.gov (United States)

    Fenn, K.; Malhi, Y.; Morecroft, M.; Lloyd, C.; Thomas, M.

    2010-05-01

    There exist very few comprehensive descriptions of the productivity and carbon cycling of forest ecosystems. Here we present a description of the components of annual Net Primary Productivity (NPP), Gross Primary Productivity (GPP), autotrophic and heterotrophic respiration, and ecosystem respiration (RECO) for a temperate mixed deciduous woodland at Wytham Woods in southern Britain, calculated using "bottom-up" biometric and chamber measurements (leaf and wood production and soil and stem respiration). These are compared with estimates of these parameters from eddy-covariance measurements made at the same site. NPP was estimated as 7.0±0.8 Mg C ha-1 yr-1, and GPP as 20.3+1.0 Mg C ha-1 yr-1, a value which closely matched to eddy covariance-derived GPP value of 21.1 Mg C ha-1 yr-1. Annual RECO was calculated as 18.9±1.7 Mg C ha-1 yr-1, close to the eddy covariance value of 19.8 Mg C ha-1 yr-1; the seasonal cycle of biometric and eddy covariance RECO estimates also closely matched. The consistency between eddy covariance and biometric measurements substantially strengthens the confidence we attach to each as alternative indicators of site carbon dynamics, and permits an integrated perspective of the ecosystem carbon cycle. 37% of NPP was allocated below ground, and the ecosystem carbon use efficiency (CUE, = NPP/GPP) calculated to be 0.35±0.05, lower than reported for many temperate broadleaved sites.

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

    Science.gov (United States)

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

    2009-05-01

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

  11. Ceramic carbon electrode-based anodes for use in the copper-chlorine thermochemical cycle

    International Nuclear Information System (INIS)

    Sol-gel chemistry is becoming more popular for the synthesis of electrode materials. For example, the sol-gel reaction can be performed in the presence of a carbon black to form a ceramic carbon electrode (CCE). The resultant CCE structure contains electronically conductive carbon particle pathways that are bound together via the ceramic binder, which can also promote ion transport. Furthermore, the CCE structure has a high active surface area and is chemical and thermally robust. We have investigated CCE materials prepared using 3-aminopropyl trimethoxysilane. Electrochemical experiments (cyclic voltammetry, electrochemical impedance spectroscopy) were performed to characterize their suitability as anode electrode materials for use in the electrochemical step of the Cu-Cl thermochemical cycle. Our initial results have shown that CCE-based electrodes vastly outperform a bare carbon electrode, and thus are highly promising and cost-effective electrode material. Subsequent experiments involved the manipulation of the relative ratio of organosilane carbon precursors to gauge its impact on electrode properties and performance. An overview of the materials characterization and electrochemical measurements will be presented. (author)

  12. Rubisco without the Calvin cycle improves the carbon efficiency of developing green seeds.

    Science.gov (United States)

    Schwender, Jörg; Goffman, Fernando; Ohlrogge, John B; Shachar-Hill, Yair

    2004-12-01

    Efficient storage of carbon in seeds is crucial to plant fitness and to agricultural productivity. Oil is a major reserve material in most seeds, and these oils provide the largest source of renewable reduced carbon chains available from nature. However, the conversion of carbohydrate to oil through glycolysis results in the loss of one-third of the carbon as CO2. Here we show that, in developing embryos of Brassica napus L. (oilseed rape), Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase) acts without the Calvin cycle and in a previously undescribed metabolic context to increase the efficiency of carbon use during the formation of oil. In comparison with glycolysis, the metabolic conversion we describe provides 20% more acetyl-CoA for fatty-acid synthesis and results in 40% less loss of carbon as CO2. Our conclusions are based on measurements of mass balance, enzyme activity and stable isotope labelling, as well as an analysis of elementary flux modes. PMID:15592419

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Middleton, Bobby [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pasch, James Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kruizenga, Alan Michael [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Walker, Matthew [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    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

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

    Science.gov (United States)

    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.

  16. Carbon Dioxide Effects Research and Assessment Program. The role of tropical forests on the world carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Brown, S.; Lugo, A. E.; Liegel, B. [eds.

    1980-08-01

    Tropical forests constitute about half of the world's forest and are characterized by rapid rates of organic matter turnover and high storages of organic matter. Tropical forests are considered to be one of the most significant terrestrial elements in the equation that balances the carbon cycle of the world. As discussed in the paper by Tosi, tropical and subtropical latitudes are more complex in terms of climate and vegetation composition than temperate and boreal latitudes. The implications of the complexity of the tropics and the disregard of this complexity by many scientists is made evident in the paper by Brown and Lugo which shows that biomass estimates for tropical ecosystems have been overestimated by at least 100%. The paper by Brown shows that that rates of succession in the tropics are extremely rapid in terms of the ability of moist and wet forests to accumulate organic matter. Yet, in arid tropical Life Zones succession is slow. This leads to the idea that the question of whether tropical forests are sinks or sources of carbon must be analyzed in relation to Life Zones and to intensities of human activity in these Zones. The paper by Lugo presents conceptual models to illustrate this point and the paper by Tosi shows how land uses in the tropics also correspond to Life Zone characteristics. The ultimate significance of land use to the question of the carbon balance in a large region is addressed in the paper by Detwiler and Hall.

  17. Exomoon climate models with the carbonate-silicate cycle and viscoelastic tidal heating

    Science.gov (United States)

    Forgan, Duncan; Dobos, Vera

    2016-04-01

    The habitable zone for exomoons with Earth-like properties is a non-trivial manifold, compared to that of Earth-like exoplanets. The presence of tidal heating, eclipses and planetary illumination in the exomoon energy budget combine to produce both circumstellar and circumplanetary habitable regions. Analytical calculations suggest that the circumplanetary habitable region is defined only by an inner edge (with its outer limits determined by orbital stability). Subsequent calculations using 1D latitudinal climate models indicated that the combined effect of eclipses and ice-albedo feedback can produce an outer edge to the circumplanetary habitable zone. But is this outer edge real, or an artefact of the climate model's relative simplicity? We present an upgraded 1D climate model of Earth-like exomoon climates, containing the carbonate-silicate cycle and viscoelastic tidal heating. We conduct parameter surveys of both the circumstellar and circumplanetary habitable zones, and we find that the outer circumplanetary habitable edge remains provided the moon's orbit is not inclined relative to that of the planet. Adding the carbonate-silicate cycle pushes the circumplanetary habitable zone outwards, by allowing increases in atmospheric partial pressure of carbon dioxide to boost the greenhouse effect. Viscoelastic tidal heating widens the habitable zone compared to standard, fixed-Q models. Weakening the tidal heating effect due to melting allows moons to be habitable at higher eccentricity, and pushes the inner circumstellar and circumplanetary habitable zone boundary inwards.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bauerle, William L. [Colorado State University, Fort Collins; Oren, Ram [Duke University; Way, Danielle A. [Duke University; Qian, Song S. [Duke University; Stoy, Paul C. [Montana State University; Thornton, Peter E [ORNL; Bowden, Joseph D. [Colorado State University, Fort Collins; Hoffman, Forrest M [ORNL; Reynolds, Robert F. [Clemson University

    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.

  19. A GEO Hyperspectral Mission For Continental-Scale Carbon Cycle Observations

    Science.gov (United States)

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

    2004-01-01

    For both terrestrial and ocean carbon cycle science objectives, a hyperspectral geostationary sensor should enable the development of new remote sensing measurements for important but as yet unobservable variables, and 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 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 continuous, narrow (5 nm) bands, 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 scenarios. The GSFC Carbon Team has been pursuing a geostationary hyperspectral instrument, which would revolutionize our knowledge of biological processes on land, in the ocean, and along the coast by providing multiple, diurnal coverage. Preliminary studies in Goddard's Instrument Synthesis and Analysis Laboratory (ISAL) indicate that we can meet many of our science requirements: full spectral coverage (360-1000 nm); narrow bandwidths (5-10 nm); adequate ground resolution (100-200 m); and continental-scale coverage 4-6 times per day; all the while achieving a signal to noise ratio of

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

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, Daniel H. [Cornell Univ., Ithaca, NY (United States)

    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.

  1. Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system

    Science.gov (United States)

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

    2014-07-01

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

  2. Climate and carbon cycle variations in the 20th and 21st centuries in a model of intermediate complexity

    Science.gov (United States)

    Eliseev, A. V.; Mokhov, I. I.; Karpenko, A. A.

    2007-02-01

    The climate model of intermediate complexity developed at the Oboukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM), has been supplemented by a zero-dimensional carbon cycle model. With the carbon dioxide emissions prescribed for the second half of the 19th century and for the 20th century, the model satisfactorily reproduces characteristics of the carbon cycle over this period. However, with continued anthropogenic CO2 emissions (SRES scenarios A1B, A2, B1, and B2), the climate-carbon cycle feedback in the model leads to an additional atmospheric CO2 increase (in comparison with the case where the influence of climate changes on the carbon exchange between the atmosphere and the underlying surface is disregarded). This additional increase is varied in the range 67 90 ppmv depending on the scenario and is mainly due to the dynamics of soil carbon storage. The climate-carbon cycle feedback parameter varies nonmonotonically with time. Positions of its extremes separate characteristic periods of the change in the intensity of anthropogenic emissions and of climate variations. By the end of the 21st century, depending on the emission scenario, the carbon dioxide concentration is expected to increase to 615 875 ppmv and the global temperature will rise by 2.4 3.4 K relative to the preindustrial value. In the 20th 21st centuries, a general growth of the buildup of carbon dioxide in the atmosphere and ocean and its reduction in terrestrial ecosystems can be expected. In general, by the end of the 21st century, the more aggressive emission scenarios are characterized by a smaller climate-carbon cycle feedback parameter, a lower sensitivity of climate to a single increase in the atmospheric concentration of carbon dioxide, a larger fraction of anthropogenic emissions stored in the atmosphere and the ocean, and a smaller fraction of emissions in terrestrial ecosystems.

  3. Astrochronology of the Late Turonian: implications for the behavior of the carbon cycle at the demise of peak greenhouse

    Czech Academy of Sciences Publication Activity Database

    Laurin, Jiří; Čech, S.; Uličný, David; Štaffen, Z.; Svobodová, Marcela

    2014-01-01

    Roč. 394, May (2014), s. 254-269. ISSN 0012-821X R&D Projects: GA ČR GAP210/10/1991; GA MŠk LH12041 Institutional support: RVO:67985530 ; RVO:67985831 Keywords : Turonian * Coniacian * Milankovitch * astrochronology * carbon isotopes * carbon cycle Subject RIV: DB - Geology ; Mineralogy Impact factor: 4.734, year: 2014

  4. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4

    Directory of Open Access Journals (Sweden)

    R. E. Zeebe

    2012-01-01

    Full Text Available The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  5. Long-term soil warming and Carbon Cycle Feedbacks to the Climate System

    Energy Technology Data Exchange (ETDEWEB)

    Melillo, Jerry M.

    2014-04-30

    The primary objective of the proposed research was to quantify and explain the effects of a sustained in situ 5oC soil temperature increase on net carbon (C) storage in a northeastern deciduous forest ecosystem. The research was done at an established soil warming experiment at the Harvard Forest in central Massachusetts – Barre Woods site established in 2001. In the field, a series of plant and soil measurements were made to quantify changes in C storage in the ecosystem and to provide insights into the possible relationships between C-storage changes and nitrogen (N) cycling changes in the warmed plots. Field measurements included: 1) annual woody increment; 2) litterfall; 3) carbon dioxide (CO2) efflux from the soil surface; 4) root biomass and respiration; 5) microbial biomass; and 6) net N mineralization and net nitrification rates. This research was designed to increase our understanding of how global warming will affect the capacity of temperate forest ecosystems to store C. The work explored how soil warming changes the interactions between the C and N cycles, and how these changes affect land-atmosphere feedbacks. This core research question framed the project – What are the effects of a sustained in situ 5oC soil temperature increase on net carbon (C) storage in a northeastern deciduous forest ecosystem? A second critical question was addressed in this research – What are the effects of a sustained in situ 5{degrees}C soil temperature increase on nitrogen (N) cycling in a northeastern deciduous forest ecosystem?

  6. Finite Element Modeling of Thermal Cycling Induced Microcracking in Carbon/Epoxy Triaxial Braided Composites

    Science.gov (United States)

    Zhang, Chao; Binienda, Wieslaw K.; Morscher, Gregory; Martin, Richard E.

    2012-01-01

    The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composite

  7. Super-critical carbon dioxide based brayton cycle for Indian High Temperature Reactors

    International Nuclear Information System (INIS)

    The most effective way to improve economic competitiveness of NPPs is to enhance its efficiency which has remained static at around 33% since the first commercial LWR came into operation. New generation reactor designs including the six Gen-IV reactor concepts aim to increase the NPPs efficiency to almost 50%. This is proposed to be achieved by high temperature designs using Brayton cycle based power conversion systems. World over, Super-critical Carbon dioxide Brayton Cycle (SCBC) for power generation is an important R and D area. High efficiency SCBC power conversion system is proposed as power conversion system for Indian Molten Salt Breeder Reactor (IMSBR) and Innovative High Temperature Reactor (IHTR). This section provides the details regarding design and development of SCBC for these reactors. (author)

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

    Science.gov (United States)

    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

  9. Peritidal carbonate cycles induced by carbonate productivity variations:A conceptual model for an isolated Early Triassic greenhouse platform in South China

    Institute of Scientific and Technical Information of China (English)

    Wan Yang; Dan JLehrmann

    2014-01-01

    Eustasy has commonly been invoked to explain peritidal carbonate cyclicity, but is dififcult to explain cycles formed in a greenhouse climate when eustasy is minimal. We propose that peritidal cycles on an Early Triassic isolated carbonate platform in Guizhou, South China, were formed by hierarchical carbonate productivity variations. Most of the 149 shallowing-upward cycles are typically terminated by lfooding over intertidal facies and con-tain rare supratidal facies and no prolonged subaerial exposure. Low-diversity benthos in the platform interior during the post-end-Permian biotic recovery were sensitive to environmental perturbations, which caused variations in benthic sediment productivity in the subtidal carbon-ate factory. The perturbations may be driven by changes in salinity and degree of eutrophica-tion, or repeated platform mini-drowning by anoxic and/or CO2-charged deep water upwelled onto the banktop. They were modulated by Milankovitch orbitally-driven climatic and oceano-graphic factors as suggested by the hierarchical stacking pattern and spectral signals of these cycles. A one-dimensional conceptual model shows that hierarchical productivity variations alone may generate hierarchical peritidal carbonate cycles under conditions of constant sub-sidence and no sea-level lfuctuation.

  10. Mycorrhizal Controls on Nitrogen Uptake Drive Carbon Cycling at the Global Scale

    Science.gov (United States)

    Shi, M.; Fisher, J. B.; Brzostek, E. R.; Phillips, R.

    2015-12-01

    Nearly all plants form symbiotic relationships with one of two types of mycorrhizal fungi—arbuscular mycorrhizae (AM) and ectomycorrhizal (ECM) fungi, which are essential to global biogeochemical cycling of nutrient elements. In soils with higher rates of nitrogen and phosphorus mineralization from organic matter, AM-associated plants can be better adapted than ECM-associated plants. Importantly, the photosynthate costs of nutrient uptake for AM-associated plants are usually lower than that for ECM-associated plants. Thus, the global carbon cycle is closely coupled with mycorrhizal controls on N uptake. To investigate the potential climate dependence of terrestrial environments from AM- and ECM-associated plants, this study uses the Community Atmosphere Model (CAM) with a plant productivity-optimized N acquisition model—the Fixation and Uptake of Nitrogen (FUN) model—integrated into its land model—the Community Land Model (CLM). This latest version of CLM coupled with FUN allows for the assessment of mycorrhizal controls on global biogeochemical cycling. Here, we show how the historical evolution of AM- and ECM-associations altered regional and global biogeochemical cycling and climate, and future projections over the next century.

  11. An unexpected role for mixotrophs in the response of peatland carbon cycling to climate warming

    Science.gov (United States)

    Jassey, Vincent E. J.; Signarbieux, Constant; Hättenschwiler, Stephan; Bragazza, Luca; Buttler, Alexandre; Delarue, Frédéric; Fournier, Bertrand; Gilbert, Daniel; Laggoun-Défarge, Fatima; Lara, Enrique; T. E. Mills, Robert; Mitchell, Edward A. D.; Payne, Richard J.; Robroek, Bjorn J. M.

    2015-11-01

    Mixotrophic protists are increasingly recognized for their significant contribution to carbon (C) cycling. As phototrophs they contribute to photosynthetic C fixation, whilst as predators of decomposers, they indirectly influence organic matter decomposition. Despite these direct and indirect effects on the C cycle, little is known about the responses of peatland mixotrophs to climate change and the potential consequences for the peatland C cycle. With a combination of field and microcosm experiments, we show that mixotrophs in the Sphagnum bryosphere play an important role in modulating peatland C cycle responses to experimental warming. We found that five years of consecutive summer warming with peaks of +2 to +8°C led to a 50% reduction in the biomass of the dominant mixotrophs, the mixotrophic testate amoebae (MTA). The biomass of other microbial groups (including decomposers) did not change, suggesting MTA to be particularly sensitive to temperature. In a microcosm experiment under controlled conditions, we then manipulated the abundance of MTA, and showed that the reported 50% reduction of MTA biomass in the field was linked to a significant reduction of net C uptake (-13%) of the entire Sphagnum bryosphere. Our findings suggest that reduced abundance of MTA with climate warming could lead to reduced peatland C fixation.

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

    Science.gov (United States)

    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. PMID:23409918

  13. Effects on the ocean carbon cycle from solar radiation management types of geoengineering

    Science.gov (United States)

    Lauvset, Siv; Tjiputra, Jerry

    2016-04-01

    Climate engineering is often brought up in the climate mitigation and adaptation discussions. Such action can be viewed as an additional method for reducing the impacts of global warming. However, much more research is required in order to assess both the feasibility and the safety of such methods. We present results from the Norwegian Earth System model (NorESM) for a future RCP8.5 scenario where solar radiation management in the form of stratospheric sulfur injection has been performed in order to limit the global warming. Since the CO2 emissions continue in this future, the impact climate engineering has on the global and regional ocean carbon sink is a key part of this research. We show that while global surface acidification is not significantly enhanced under climate engineering, there are significant changes in the ocean carbon cycle driven by changes in circulation and stratification, and changes in biological production.

  14. Effects of Lime and Concrete Waste on Vadose Zone Carbon Cycling

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, Søren; Postma, D.;

    2014-01-01

    In this work we investigate how lime and crushed concrete waste (CCW) affect carbon cycling in the vadose zone and explore whether these amendments could be employed to mitigate climate change by increasing the transport of CO2 from the atmosphere to the groundwater. We use a combination...... of experimental and modeling tools to determine ongoing biogeochemical processes. Our results demonstrate that lime and CCW amendments to acid soil contribute to the climate forcing by largely increasing the soil CO2 efflux to the atmosphere. In a series of mesocosm experiments, with barley (Hordeum vulgare L...... and lime treatments increased the dissolved inorganic carbon (DIC) percolation flux by about 150 and 100%, respectively,compared to the controls. However, concurrent increases in the CO2 efflux to the atmosphere (ER) were more than one order of magnitude higher than increases in the DIC percolation flux...

  15. High-cycle Fatigue Life Extension of Glass Fiber/Polymer Composites with Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Christopher S Grimmer; C K H Dharan

    2009-01-01

    The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) to the matrix results in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture of nanotubes bridging across nano-scale cracks and from nanotube pull-out from the matrix are mechanisms that can improve the fatigue life. An energy-based model was proposed to estimate the additional strain energy absorbed in fatigue. The distributed nanotubes in the matrix appear to both distribute damage as well as inhibit damage propagation resulting in an overall improvement in the fatigue strength of glass fiber composites.

  16. Carbon dioxide seasonal cycle in the sea euphotic zone - a study in the Sargasso Sea

    International Nuclear Information System (INIS)

    Between 1750 and 1990, the human activities (mainly fossil carbon combustion and deforestation) have lead to an increase of the CO2 concentration in the atmosphere. Nevertheless, the carbon dioxide actively takes part to the greenhouse effect and then to the energetic balance of the climatic system. The study which is carried out consists of the forecasting of the CO2 future concentrations in the atmosphere (from 10, 100 years). The chosen site (BATS: Bermuda Atlantic Time-series Study) is located in the Sargasso Sea. The factors leading to seasonal variations have been determined. Several bio-geochemical models have been developed in order to on the one hand simulate the seasonal dynamics of the mixture layer observed in the Bats site and on the other hand explain the main characteristics of the observed phytoplankton seasonal cycle, of its nutriments and of the dissolved oxygen. (O.M.)

  17. Novel Supercritical Carbon Dioxide Power Cycle Utilizing Pressured Oxy-combustion in Conjunction with Cryogenic Compression

    Energy Technology Data Exchange (ETDEWEB)

    Brun, Klaus; McClung, Aaron; Davis, John

    2014-03-31

    The team of Southwest Research Institute® (SwRI) and Thar Energy LLC (Thar) applied technology engineering and economic analysis to evaluate two advanced oxy-combustion power cycles, the Cryogenic Pressurized Oxy-combustion Cycle (CPOC), and the Supercritical Oxy-combustion Cycle. This assessment evaluated the performance and economic cost of the two proposed cycles with carbon capture, and included a technology gap analysis of the proposed technologies to determine the technology readiness level of the cycle and the cycle components. The results of the engineering and economic analysis and the technology gap analysis were used to identify the next steps along the technology development roadmap for the selected cycle. The project objectives, as outlined in the FOA, were 90% CO{sub 2} removal at no more than a 35% increase in cost of electricity (COE) as compared to a Supercritical Pulverized Coal Plant without CO{sub 2} capture. The supercritical oxy-combustion power cycle with 99% carbon capture achieves a COE of $121/MWe. This revised COE represents a 21% reduction in cost as compared to supercritical steam with 90% carbon capture ($137/MWe). However, this represents a 49% increase in the COE over supercritical steam without carbon capture ($80.95/MWe), exceeding the 35% target. The supercritical oxy-combustion cycle with 99% carbon capture achieved a 37.9% HHV plant efficiency (39.3% LHV plant efficiency), when coupling a supercritical oxy-combustion thermal loop to an indirect supercritical CO{sub 2} (sCO{sub 2}) power block. In this configuration, the power block achieved 48% thermal efficiency for turbine inlet conditions of 650°C and 290 atm. Power block efficiencies near 60% are feasible with higher turbine inlet temperatures, however a design tradeoff to limit firing temperature to 650°C was made in order to use austenitic stainless steels for the high temperature pressure vessels and piping and to minimize the need for advanced turbomachinery features

  18. Rate My Data: Quantifying the Value of Ecological Data for Models of Terrestrial Carbon Cycle

    OpenAIRE

    Keenan, Trevor; Davidson, Eric; Munger, James; Richardson, Andrew

    2013-01-01

    Primarily driven by concern about rising levels of atmospheric CO2, ecologists and earth system scientists are collecting vast amounts of data related to the carbon cycle. These measurements are generally time-consuming and expensive to make, and, unfortunately, we live in an era where research funding is increasingly hard to come by. Thus, important questions are: ‘Which data streams provide the most valuable information? ’ and, ‘How much data do we need? ’ These questions are relevant not...

  19. The Environmental Impact of Industrial Bamboo Products: Life-cycle Assessment and Carbon Sequestration

    OpenAIRE

    Vogtlander, J.G.; Van der Lugt, P.

    2014-01-01

    This report gives a Life-Cycle Assessment (LCA) and carbon footprint analysis on a selection of industrial bamboo products. The LCA is made for cradle-to-gate, plus the end-of-life stages of the bamboo products. For end-of-life it is assumed that 90% of the bamboo products are incinerated in an electrical power plant, and 10% will end-up in landfill, which is considered to be a realistic scenario for the Netherlands (NEN 8006) and Western Europe. In addition to the standard LCA (ISO 14040 and...

  20. The role of plant-soil interactions in peatland carbon cycling at a Scottish wind farm

    OpenAIRE

    Richardson, Harriett Rose

    2014-01-01

    Northern peatlands play an important role in the cycling of carbon (C) globally, and contain up to one third of the world’s soil C despite only covering a small percentage of its land surface (Gorham, 1991). Changes in climate and land use are increasing the vulnerability of these vast C stocks, by altering the conditions favourable for peat accumulation and therefore C sequestration. The establishment of wind farms on peatlands is increasing in the UK, as a result of the growing need for sus...

  1. Effects of Nitrogen and Phosphorus Additions on Carbon Cycling of Tropical Mountain Rainforests in Hainan, China

    Science.gov (United States)

    Lai, J.

    2015-12-01

    Nitrogen (N) and Phosphorus (P) deposition is projected to increase significantly in tropical regions in the coming decades, which has changed and will change the structure and function of ecosystems, and affects on ecosystem Carbon (C) cycle. As an important part in global C cycle, how the C cycle of tropical rainforests will be influenced by the N and P deposition should be focused on. This study simulated N and P deposition in a primary and secondary forest of tropical mountain rainforest in Jianfengling, Hainan, China, during five-year field experiment to evaluate the effects of N and P deposition on C cycling processes and relate characteristics. Six levels of N and P treatments were treated: Control, Low-N, Medium-N, High-N, P and N+P. The relative growth rates (RGR) of tree layer in treatment plots were different from that in control plots after years of N and P addition. Simulated N and P deposition also increased ANPP in primary forest. N and P addition changed the growth of trees by altering soil nutrient and microbial activities. N and P addition increased soil organic carbon (SOC) and total N (TN) content, and significantly increased soil total P (TP) content, not changing soil pH. During the whole process of N and P addition, as net nitrification rate and net N mineralization rate were promoted by N and P addition, and effective N content (nitrate) of soil increased in the plot treated with N treatments compared to the control treatment. The microbial P content was increased by N and P addition, and microbial N was not changed. The increasing N deposition may enhance soil nutrient and stimulate growth of trees, which will lead to an increase of the C sequestration.

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

    Science.gov (United States)

    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. PMID:26568424

  3. Pasture degradation modifies the water and carbon cycles of the Tibetan highlands

    Directory of Open Access Journals (Sweden)

    W. Babel

    2014-12-01

    Full Text Available The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments investigating changes of surface properties and processes together with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan Plateau. We connected measurements of micro-lysimeter, chamber, 13C labelling, and eddy covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyse how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while a change in the sum of evapotranspiration over a longer period cannot be confirmed. The results show an earlier onset of convection and cloud generation, likely triggered by a shift in evapotranspiration timing when dominated by evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a significant influence on larger scales.

  4. Pasture degradation modifies the water and carbon cycles of the Tibetan highlands

    Directory of Open Access Journals (Sweden)

    W. Babel

    2014-06-01

    Full Text Available The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments coupling changes of surface properties and processes with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan plateau. We coupled measurements of micro-lysimeter, chamber, 13C labeling, and eddy-covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyze how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while the total sum of evapotranspiration remains unaffected. The results show an earlier onset of convection and cloud generation, likely triggered by enhanced evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a~significant influence on larger scales.

  5. Pasture degradation modifies the water and carbon cycles of the Tibetan highlands

    Science.gov (United States)

    Babel, W.; Biermann, T.; Coners, H.; Falge, E.; Seeber, E.; Ingrisch, J.; Schleuß, P.-M.; Gerken, T.; Leonbacher, J.; Leipold, T.; Willinghöfer, S.; Schützenmeister, K.; Shibistova, O.; Becker, L.; Hafner, S.; Spielvogel, S.; Li, X.; Xu, X.; Sun, Y.; Zhang, L.; Yang, Y.; Ma, Y.; Wesche, K.; Graf, H.-F.; Leuschner, C.; Guggenberger, G.; Kuzyakov, Y.; Miehe, G.; Foken, T.

    2014-12-01

    The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments investigating changes of surface properties and processes together with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan Plateau. We connected measurements of micro-lysimeter, chamber, 13C labelling, and eddy covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyse how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while a change in the sum of evapotranspiration over a longer period cannot be confirmed. The results show an earlier onset of convection and cloud generation, likely triggered by a shift in evapotranspiration timing when dominated by evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a significant influence on larger scales.

  6. Accounting for carbon cycle feedbacks in a comparison of the global warming effects of greenhouse gases

    International Nuclear Information System (INIS)

    Greenhouse gases other than CO2 make a significant contribution to human-induced climate change, and multi-gas mitigation strategies are cheaper to implement than those which limit CO2 emissions alone. Most practical multi-gas mitigation strategies require metrics to relate the climate warming effects of CO2 and other greenhouse gases. Global warming potential (GWP), defined as the ratio of time-integrated radiative forcing of a particular gas to that of CO2 following a unit mass emission, is the metric used in the Kyoto Protocol, and we define mean global temperature change potential (MGTP) as an equivalent metric of the temperature response. Here we show that carbon-climate feedbacks inflate the GWPs and MGTPs of methane and nitrous oxide by ∼ 20% in coupled carbon-climate model simulations of the response to a pulse of 50 x 1990 emissions, due to a warming-induced release of CO2 from the land biosphere and ocean. The magnitude of this effect is expected to be dependent on the model, but it is not captured at all by the analytical models usually used to calculate metrics such as GWP. We argue that the omission of carbon cycle dynamics has led to a low bias of uncertain but potentially substantial magnitude in metrics of the global warming effect of other greenhouse gases, and we suggest that the carbon-climate feedback should be considered when greenhouse gas metrics are calculated and applied.

  7. Climate Change Impacts on the Organic Carbon Cycle at the Land-Ocean Interface

    Science.gov (United States)

    Canuel, E. A.; Cammer, S. S.; McIntosh, H.; Pondell, C. R.

    2012-12-01

    Humans have modified estuaries across the globe by altering the delivery of water, sediments and elements such as carbon and nitrogen that play important roles in biogeochemical processes. These activities have caused declines in the health and quality of estuarine ecosystems globally and this trend will likely continue due to increasing population growth in coastal regions, expected changes associated with climate change, and their interaction with each other, leading to serious consequences for the ecological and societal services they provide. A key function of estuaries is the transfer and transformation of carbon and biogenic elements between land and ocean systems. The anticipated effects of climate change on biogeochemical processes in estuaries are likely to be both numerous and complex but are poorly understood. Climate change has the potential to influence the carbon cycle in estuaries through anticipated changes to organic matter production, transformation, burial and export. Estuarine biogeochemical processes will likely be altered by: 1) sea level rise and increased storm intensity which will amplify the erosion and transfer of terrigenous materials, 2) increases in water temperatures which will enhance the rates of biological and biogeochemical processes (e.g., enzyme kinetics, decomposition rates, and remineralization), while simultaneously decreasing the concentration of dissolved oxygen, 3) changes in particle (or sediment) loadings in response to altered patterns of precipitation and river runoff, and 4) altered inputs of nutrients and dissolved organic materials to coastal waters, also resulting from changing precipitation and runoff. In this presentation, we review the effects of climate change on the carbon cycle in estuaries, with a focus on the temperate estuaries of North America.

  8. A two-dimensional model of the passive coastal margin deep sedimentary carbon and methane cycles

    Directory of Open Access Journals (Sweden)

    D. E. Archer

    2012-03-01

    Full Text Available We present a new geologic-time and basin-spatial scale model of the continental margin methane cycle. The model, SpongeBOB, is used to simulate evolution of the carbon cycle in a passive sedimentary continental margin in response to changing oceanographic and geologic forcing over a time scale of 140 million years. The model is somewhat less sensitive to temperature than our previous results with a one-dimensional model, but is more sensitive to reasonable changes in POC than it is to reasonable changes in temperature. This behavior could lead to higher inventories of hydrate during hothouse climate conditions, rather than lower as generally assumed, due to the enrichment of the sediments in organic carbon. The hydrate inventory in the model is extremely sensitive to the ability of methane bubbles to rise within the sediment column, and how far gas-phase methane can get through the sediment column before it redissolves when it reaches undersaturated conditions. Hydrate formation is also sensitive to deep respiration of migrating petroleum in the model. The geochemistry of the sediment column is altered by the addition of vertical high-permeability chimneys intended to mimic the effects of heterogeneity in the real sediment column due to faults and chimneys, and produces results consistent with measured pore-water tracers SO42− and 129I. Pore water DIC concentrations are consistent with chemical weathering at depth within the sediment column. The carbon isotopic composition of the DIC is consistent with a methane production efficiency from POC of 50%, which is somewhat lower than redox balance with the H/C of organic matter in the model. Other phenomena which we simulated had only small impact on the hydrate inventory, including thermogenic methane, dissolved organic carbon, and sediment transport characteristics.

  9. Climate-change effects on soils: Accelerated weathering, soil carbon and elemental cycling

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nikolla

    2015-04-01

    Climate change [i.e., high atmospheric carbon dioxide (CO2) concentrations (≥400 ppm); increasing air temperatures (2-4°C or greater); significant and/or abrupt changes in daily, seasonal, and inter-annual temperature; changes in the wet/dry cycles; intensive rainfall and/or heavy storms; extended periods of drought; extreme frost; heat waves and increased fire frequency] is and will significantly affect soil properties and fertility, water resources, food quantity and quality, and environmental quality. Biotic processes that consume atmospheric CO2, and create organic carbon (C) that is either reprocessed to CO2 or stored in soils are the subject of active current investigations, with great concern over the influence of climate change. In addition, abiotic C cycling and its influence on the inorganic C pool in soils is a fundamental global process in which acidic atmospheric CO2 participates in the weathering of carbonate and silicate minerals, ultimately delivering bicarbonate and Ca2+ or other cations that precipitate in the form of carbonates in soils or are transported to the rivers, lakes, and oceans. Soil responses to climate change will be complex, and there are many uncertainties and unresolved issues. The objective of the review is to initiate and further stimulate a discussion about some important and challenging aspects of climate-change effects on soils, such as accelerated weathering of soil minerals and resulting C and elemental fluxes in and out of soils, soil/geo-engineering methods used to increase C sequestration in soils, soil organic matter (SOM) protection, transformation and mineralization, and SOM temperature sensitivity. This review reports recent discoveries, identifies key research needs, and highlights opportunities offered by the climate-change effects on soils.

  10. Carbon dioxide effects research and assessment program. A comprehensive plan. Part I. The global carbon cycle and climatic effects of increasing carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Slade, David H.

    1980-08-01

    Initial plans for research of the carbon dioxide (CO/sub 2/) and climate issue were prepared in 1978 and were reviewed extensively at that time by federal agencies and members of the scientific community. Since then the plans have been used to guide early phases of the Department of Energy's and the nation's efforts related to this issue. This document represents a revision of the 1978 plan to (a) reflect recent ideas and strategies for carbon cycle research, and (b) expand the scope of research on climatic responses to increasing atmospheric concentrations of CO/sub 2/. The revised plan takes into account a number of investigations already being supported by various agencies, and it attempts to build on or add to existing research where there is a crucial need for information directly related to the CO/sub 2/ issue. It should be recognized that this document is the first section of a comprehensive plan on the overall consequences of increasing concentrations of CO/sub 2/, and includes guidelines for research on the Global Carbon Cycle and Climatic Effects of Increasing CO/sub 2/.

  11. Multi-scale observation and cross-scale mechanistic modeling on terrestrial ecosystem carbon cycle

    Institute of Scientific and Technical Information of China (English)

    CAO Mingkui; YU Guirui; LIU Jiyuan; LI Kerang

    2005-01-01

    To predict global climate change and to implement the Kyoto Protocol for stabilizing atmospheric greenhouse gases concentrations require quantifying spatio-temporal variations in the terrestrial carbon sink accurately. During the past decade multi-scale ecological experiment and observation networks have been established using various new technologies (e.g. controlled environmental facilities, eddy covariance techniques and quantitative remote sensing), and have obtained a large amount of data about terrestrial ecosystem carbon cycle. However, uncertainties in the magnitude and spatio-temporal variations of the terrestrial carbon sink and in understanding the underlying mechanisms have not been reduced significantly. One of the major reasons is that the observations and experiments were conducted at individual scales independently, but it is the interactions of factors and processes at different scales that determine the dynamics of the terrestrial carbon sink. Since experiments and observations are always conducted at specific scales, to understand cross-scale interactions requires mechanistic analysis that is best to be achieved by mechanistic modeling. However, mechanistic ecosystem models are mainly based on data from single-scale experiments and observations and hence have no capacity to simulate mechanistic cross-scale interconnection and interactions of ecosystem processes. New-generation mechanistic ecosystem models based on new ecological theoretical framework are needed to quantify the mechanisms from micro-level fast eco-physiological responses to macro-level slow acclimation in the pattern and structure in disturbed ecosystems. Multi-scale data-model fusion is a recently emerging approach to assimilate multi-scale observational data into mechanistic, dynamic modeling, in which the structure and parameters of mechanistic models for simulating cross-scale interactions are optimized using multi-scale observational data. The models are validated and

  12. Peanut shell derived hard carbon as ultralong cycling anodes for lithium and sodium batteries

    International Nuclear Information System (INIS)

    The peanut shells derived porous hard carbons (PSDHCs) by pyrolysis have been investigated as anodes of lithium/sodium batteries (LIBs/NIBs). Directly from the starting peanut shells, 600°C is found to be the favorable pyrolysis temperature for preparation of the PSDHC sample (PSDHC-600) with the best electrochemical performances for LIB applications. Furthermore, from the activated peanut shells in KOH solution, the produced PSDHC-600A by pyrolysis at 600°C is observed to offer greatly enhanced Li+/Na+ ion storages. For LIB applications, PSDHC-600A delivers a retained capacity of 474 mAhg−1 after 400 cycles at 1 Ag−1, larger than 314 mAhg−1 of PSDHC-600. At a high current rate of 5 Ag−1, PSDHC-600A sustains over 10000 cycles with no obvious sign of fade in capacity, and a capacity of 310 mAhg−1 is still retained. For NIB applications, a capacity of 193 mAh g−1 is retained after 400 cycles at 0.25 Ag−1, higher than 130 mAhg−1 of PSDHC-600. Even at 1 Ag−1, PSDHC-600A can be stably cycled over 3000 cycles, and a capacity of 129 mAhg−1 is still retained. In comparison to PSDHC-600, the enhanced electrochemical properties of PSDHC-600A can be attributed to the finer porous structure with the increased percentage of nanoscale pores of diameter less than 2 nm and the larger specific surface area

  13. The scavenging processes controlling the seasonal cycle in Arctic sulphate and black carbon aerosol

    Science.gov (United States)

    Pringle, K.; Browse, J.; Carslaw, K. S.; Arnold, S.; Boucher, O.

    2013-12-01

    The seasonal cycle in Arctic aerosol is typified by high concentrations of large aged anthropogenic particles transported from lower latitudes in the late Arctic winter and early spring followed by a sharp transition to low concentrations of locally sourced smaller particles in the summer. However, multi-model assessments show that many models fail to simulate a realistic cycle. Here, we use a global aerosol microphysics model (GLOMAP) and surface-level aerosol observations to understand how wet scavenging processes control the seasonal variation in Arctic black carbon (BC) and sulphate aerosol. We show that the transition from high wintertime concentrations to low concentrations in the summer is controlled by the transition from ice-phase cloud scavenging to the much more efficient warm cloud scavenging in the late spring troposphere. This seasonal cycle is amplified further by the appearance of warm drizzling cloud in the late spring and summer boundary layer. Implementing these processes in GLOMAP greatly improves the agreement between the model and observations at the three Arctic ground-stations Alert, Barrow and Zeppelin Mountain on Svalbard. The SO4 model-observation correlation coefficient (R) increases from: -0.33 to 0.71 at Alert (82.5N), from -0.16 to 0.70 at Point Barrow (71.0N) and from -0.42 to 0.40 at Zeppelin Mountain (78N). The BC model-observation correlation coefficient increases from -0.68 to 0.72 at Alert and from -0.42 to 0.44 at Barrow. Observations at three marginal Arctic sites (Janiskoski, Oulanka and Karasjok) indicate a far weaker aerosol seasonal cycle, which we show is consistent with the much smaller seasonal change in the frequency of ice clouds compared to higher latitude sites. Our results suggest that the seasonal cycle in Arctic aerosol is driven by temperature-dependent scavenging processes that may be susceptible to modification in a future climate.

  14. A simple global carbon and energy coupled cycle model for global warming simulation: sensitivity to the light saturation effect

    International Nuclear Information System (INIS)

    A simple Earth system model, the Four-Spheres Cycle of Energy and Mass (4-SCEM) model, has been developed to simulate global warming due to anthropogenic CO2 emission. The model consists of the Atmosphere-Earth Heat Cycle (AEHC) model, the Four Spheres Carbon Cycle (4-SCC) model, and their feedback processes. The AEHC model is a one-dimensional radiative convective model, which includes the greenhouse effect of CO2 and H2O, and one cloud layer. The 4-SCC model is a box-type carbon cycle model, which includes biospheric CO2 fertilization, vegetation area variation, the vegetation light saturation effect and the HILDA oceanic carbon cycle model. The feedback processes between carbon cycle and climate considered in the model are temperature dependencies of water vapor content, soil decomposition and ocean surface chemistry. The future status of the global carbon cycle and climate was simulated up to the year 2100 based on the 'business as usual' (IS92a) emission scenario, followed by a linear decline in emissions to zero in the year 2200. The atmospheric CO2 concentration reaches 645 ppmv in 2100 and a peak of 760 ppmv approximately in the year 2170, and becomes a steady state with 600 ppmv. The projected CO2 concentration was lower than those of the past carbon cycle studies, because we included the light saturation effect of vegetation. The sensitivity analysis showed that uncertainties derived from the light saturation effect of vegetation and land use CO2 emissions were the primary cause of uncertainties in projecting future CO2 concentrations. The climate feedback effects showed rather small sensitivities compared with the impacts of those two effects. Satellite-based net primary production trends analyses can somewhat decrease the uncertainty in quantifying CO2 emissions due to land use changes. On the other hand, as the estimated parameter in vegetation light saturation was poorly constrained, we have to quantify and constrain the effect more accurately

  15. Global Carbon Cycle Perturbations and Implications for Arctic Hydrology during the Paleocene-Eocene Thermal Maximum

    Science.gov (United States)

    Cui, Y.; Kump, L.; Diefendorf, A. F.; Freeman, K. H.

    2011-12-01

    The Paleocene-Eocene Thermal Maximum (PETM; ca. 55.9 Ma) was an interval of geologically abrupt global warming lasting ~200 ka. It has been proposed as an ancient analogue for future climate response to CO2 emission from fossil fuel burning. The onset of this event is fueled by a large release of 13C-depleted carbon into the ocean-atmosphere system. However, there is a large discrepancy in the magnitude of the carbon isotope excursion (CIE) between marine and terrestrial records. Here we present new organic geochemical data and stable carbon isotope records from n-alkanes and pristane extracted from core materials representing the most expanded PETM section yet recovered from a nearshore marine early Cenozoic succession from Spitsbergen. The low hydrogen index and oxygen index indicate that organic matter has been thermally altered, consistent with n-alkanes that do not show a clear odd-over-even predominance as reflected by the low and constant carbon preference index. The δ13C records of long chain n-alkanes from core BH9-05 track the δ13C recorded in total organic carbon, but are ~3% more negative prior to the CIE, ~4.5% more negative during the CIE, and ~4% more negative after the CIE. An orbital age model derived from the same core suggests the CIE from n-alkanes appears more abruptly onset than the bulk organic carbon, indicating possibly climate-induced modification to the observed feature in n-alkanes. In addition, the carbon isotope values of individual long-chain (n-C27 to n-C31) n-alkanes tend to become less negative with increasing chain length resulting in the smallest magnitude CIEs in longer chain lengths (i.e. n-C31) and the largest magnitude CIEs in shorter chain lengths (i.e. n-C27). We are currently considering the effect of plant community and paleoclimate on the observed pattern of CIE in n-alkanes to evaluate carbon cycle perturbations and Arctic hydrology changes during the PETM. One interpretation of these patterns is that there was an

  16. Temperate carbonate cycling and water mass properties from intertidal to bathyal depths (Azores, N-Atlantic

    Directory of Open Access Journals (Sweden)

    M. Wisshak

    2010-05-01

    Full Text Available The rugged submarine topography of the Azores supports a diverse heterozoan association resulting in intense biotically-controlled carbonate production and accumulation. In order to characterise this cold-water (C factory a 2-year experiment was carried out to study the biodiversity of hardground communities and for budgeting carbonate production and degradation along a bathymetrical transect from the intertidal to bathyal 500 m depth.

    Seasonal temperatures peak in September (above a thermocline and bottom in March (stratification diminishes with a decrease in amplitude and absolute values with depth, and with tidal-driven short-term fluctuations. Measured seawater stable isotope ratios and levels of dissolved nutrients decrease with depth, as do the calcium carbonate saturation states. The photosynthetic active radiation shows a base of the euphotic zone in ~70 m and a dysphotic limit in ~150 m depth.

    Bioerosion, being primarily a function of light availability for phototrophic endoliths and grazers feeding upon them, is ~10 times stronger on the illuminated upside versus the shaded underside of substrates in the photic zone, with maximum rates in the intertidal (−631 g/m2/yr. Rates rapidly decline towards deeper waters where bioerosion and carbonate accretion are slow and epibenthic/endolithic communities take years to mature. Accretion rates are highest in the lower euphotic zone (955 g/m2/yr, where the substrate is less prone to hydrodynamic force. Highest rates are found – inversely to bioerosion – on downward facing substrates, suggesting that bioerosion may be a key factor governing the preferential settlement and growth of calcareous epilithobionts on downward facing substrates.

    In context of a latitudinal gradient, the Azores carbonate cycling rates plot between known values from the cold-temperate Swedish Kosterfjord and the tropical Bahamas, with a total range of two orders in

  17. Combined Climate and Carbon-Cycle Effects of Large-Scale Deforestation

    Energy Technology Data Exchange (ETDEWEB)

    Bala, G; Caldeira, K; Wickett, M; Phillips, T J; Lobell, D B; Delire, C; Mirin, A

    2006-10-17

    The prevention of deforestation and promotion of afforestation have often been cited as strategies to slow global warming. Deforestation releases CO{sub 2} to the atmosphere, which exerts a warming influence on Earth's climate. However, biophysical effects of deforestation, which include changes in land surface albedo, evapotranspiration, and cloud cover also affect climate. Here we present results from several large-scale deforestation experiments performed with a three-dimensional coupled global carbon-cycle and climate model. These are the first such simulations performed using a fully three-dimensional model representing physical and biogeochemical interactions among land, atmosphere, and ocean. We find that global-scale deforestation has a net cooling influence on Earth's climate, since the warming carbon-cycle effects of deforestation are overwhelmed by the net cooling associated with changes in albedo and evapotranspiration. Latitude-specific deforestation experiments indicate that afforestation projects in the tropics would be clearly beneficial in mitigating global-scale warming, but would be counterproductive if implemented at high latitudes and would offer only marginal benefits in temperate regions. While these results question the efficacy of mid- and high-latitude afforestation projects for climate mitigation, forests remain environmentally valuable resources for many reasons unrelated to climate.

  18. Peritidal carbonate cycles induced by carbonate productivity variations:A conceptual model for an isolated Early Triassic greenhouse platform in South China

    Institute of Scientific and Technical Information of China (English)

    Wan; Yang; Dan; J.Lehrmann

    2014-01-01

    Eustasy has commonly been invoked to explain peritidal carbonate cyclicity,but is difficult to explain cycles formed in a greenhouse climate when eustasy is minimal.We propose that peritidal cycles on an Early Triassic isolated carbonate platform in Guizhou,South China,were formed by hierarchical carbonate productivity variations.Most of the 149 shallowing-upward cycles are typically terminated by flooding over intertidal facies and contain rare supratidal facies and no prolonged subaerial exposure.Low-diversity benthos in the platform interior during the post-end-Permian biotic recovery were sensitive to environmental perturbations,which caused variations in benthic sediment productivity in the subtidal carbonate factory.The perturbations may be driven by changes in salinity and degree of eutrophication,or repeated platform mini-drowning by anoxic and/or CO2-charged deep water upwelled onto the banktop.They were modulated by Milankovitch orbitally-driven climatic and oceanographic factors as suggested by the hierarchical stacking pattern and spectral signals of these cycles.A one-dimensional conceptual model shows that hierarchical productivity variations alone may generate hierarchical peritidal carbonate cycles under conditions of constant subsidence and no sea-level fluctuation.

  19. A comprehensive theory for the coupling between terrestrial carbon and water cycles, supported by stable carbon isotope measurements from leaves

    Science.gov (United States)

    Wang, H.; Cornwell, W.; Wright, I. J.; Prentice, I. C.

    2014-12-01

    Stomata actively regulate the CO2 concentration inside plant leaves, which co-determines the biochemical rate of photosynthesis. Stomatal behaviour thus controls leaf-level water-use efficiency and the 'exchange rate' between the terrestrial carbon and hydrological cycles. Least-cost theory (based on the hypothesis that plants minimize the combined unit costs of maintaining the capacities for water transport and carbon uptake) predicts that (a) long-term mean values of the ci/ca ratio, i.e. the ratio of leaf-internal to ambient CO2 concentration, should be independent of both photon flux density and ca; and (b) these values should vary systematically with growing-season vapour pressure deficit, growth temperature, and atmospheric pressure. Stable carbon isotope (δ13C) measurements provide an integrated measure of the ci/ca in C3 plants. A number of previous studies have focused on the aridity dependence of δ13C. The temperature dependence seems to have been overlooked, but the elevation dependence has been known for a long time: plants at high elevations have systematically lowered ci/ca, and correspondingly increased photosynthetic capacity (Vcmax). Why this should be is a long-standing puzzle: there are various speculative explanations in the literature, and a certain amount of controversy. By contrast, least-cost theory provides quantitative predictions of all three environmental effects. We have analysed a large (3652) set of δ13C measurements from C3 plants, spanning all latitudes and biomes, and shown that these predictions are quantitatively consistent with environmental dependences that can be shown in the measurements using a generalized linear model. This analysis implies the ability to predict ci/ca ratios for large-scale terrestrial ecosystem modelling. Combined with the long-standing 'co-ordination hypothesis' for the control of photosynthetic capacity, least-cost theory provides a basis for a remarkably simple global model for gross primary

  20. Imminent ocean acidification projected with the NCAR global coupled carbon cycle-climate model

    Directory of Open Access Journals (Sweden)

    M. Steinacher

    2008-11-01

    Full Text Available Ocean acidification from the uptake of anthropogenic carbon is simulated for the industrial period and IPCC SRES emission scenarios A2 and B1 with a global coupled carbon cycle-climate model. Earlier studies identified seawater saturation state with respect to aragonite, a mineral phase of calcium carbonate, as a key variable governing impacts on corals and other shell-forming organisms. Globally in the A2 scenario, water saturated by more than 300%, considered suitable for coral growth, vanishes by 2070 AD (CO2≈630 ppm, and the ocean volume fraction occupied by saturated water decreases from 42% to 25% over this century. The largest simulated pH changes worldwide occur in Arctic surface waters, where hydrogen ion concentration increases by up to 185%. Projected climate change amplifies the decrease in Arctic surface mean saturation and pH by more than 20%, mainly due to freshening and increased carbon uptake in response to sea ice retreat. Modeled saturation compares well with observation-based estimates along an Arctic transect and simulated changes have been corrected for remaining model-data differences in this region. Aragonite undersaturation in Arctic surface waters is projected to occur locally soon and to become more widespread as atmospheric CO2 continues to grow. The results imply that surface waters in the Arctic Ocean will become corrosive to aragonite, with potentially large implications for the marine ecosystem, if anthropogenic carbon emissions are not reduced and atmospheric CO2 not kept below 450 ppm.

  1. Impacts of large-scale climatic disturbances on the terrestrial carbon cycle

    Directory of Open Access Journals (Sweden)

    Lucht Wolfgang

    2006-07-01

    Full Text Available Abstract Background The amount of carbon dioxide in the atmosphere steadily increases as a consequence of anthropogenic emissions but with large interannual variability caused by the terrestrial biosphere. These variations in the CO2 growth rate are caused by large-scale climate anomalies but the relative contributions of vegetation growth and soil decomposition is uncertain. We use a biogeochemical model of the terrestrial biosphere to differentiate the effects of temperature and precipitation on net primary production (NPP and heterotrophic respiration (Rh during the two largest anomalies in atmospheric CO2 increase during the last 25 years. One of these, the smallest atmospheric year-to-year increase (largest land carbon uptake in that period, was caused by global cooling in 1992/93 after the Pinatubo volcanic eruption. The other, the largest atmospheric increase on record (largest land carbon release, was caused by the strong El Niño event of 1997/98. Results We find that the LPJ model correctly simulates the magnitude of terrestrial modulation of atmospheric carbon anomalies for these two extreme disturbances. The response of soil respiration to changes in temperature and precipitation explains most of the modelled anomalous CO2 flux. Conclusion Observed and modelled NEE anomalies are in good agreement, therefore we suggest that the temporal variability of heterotrophic respiration produced by our model is reasonably realistic. We therefore conclude that during the last 25 years the two largest disturbances of the global carbon cycle were strongly controlled by soil processes rather then the response of vegetation to these large-scale climatic events.

  2. Estimating Biomass Burning Emissions for Carbon Cycle Science and Resource Monitoring & Management

    Science.gov (United States)

    French, N. H.; McKenzie, D.; Erickson, T. A.; McCarty, J. L.; Ottmar, R. D.; Kasischke, E. S.; Prichard, S. J.; Hoy, E.; Endsley, K.; Hamermesh, N. K.

    2012-12-01

    Biomass burning emissions, including emissions from wildland fire, agricultural and rangeland burning, and peatland fires, impact the atmosphere dramatically. Current tools to quantify emission sources are developing quickly in a response to the need by the modeling community to assess fire's role in the carbon cycle and the land management community to understand fire effects and impacts on air quality. In a project funded by NASA, our team has developed methods to spatially quantify wildland fire emissions for the contiguous United States (CONUS) and Alaska (AK) at regional scales. We have also developed a prototype web-based information system, the Wildland Fire Emissions Information System (WFEIS) to make emissions modeling tools and estimates for the CONUS and AK available to the user community. With new funding through two NASA programs, our team from MTRI, USFS, and UMd will be further developing WFEIS to provide biomass burning emissions estimates for the carbon cycle science community and for land and air quality managers, to improve the way emissions estimates are calculated for a variety of disciplines. In this poster, we review WFEIS as it currently operates and the plans to extend the current system for use by the carbon cycle science community (through the NASA Carbon Monitoring System Program) and resource management community (through the NASA Applications Program). Features to be enhanced include an improved accounting of biomass present in canopy fuels that are available for burning in a forest fire, addition of annually changing vegetation biomass/fuels used in computing fire emissions, and quantification of the errors present in the estimation methods in order to provide uncertainty of emissions estimates across CONUS and AK. Additionally, WFEIS emissions estimates will be compared with results obtained with the Global Fire Emissions Database (GFED), which operates at a global scale at a coarse spatial resolution, to help improve GFED estimates

  3. Environmental and climatic changes during Valanginian (Early Cretaceous) perturbations of the carbon cycle

    Science.gov (United States)

    Kujau, A.; Heimhofer, U.; Hochuli, P. A.; Schouten, S.; Thierry, A.; Morales, C.; Mutterlose, J.

    2011-12-01

    After a long-lasting period of relatively stable conditions during the late Jurassic to earliest Cretaceous, the Valanginian was a time of climatic and environmental perturbations. Proposed changes include fluctuations in atmospheric pCO2, an accelerated hydrologic cycling, a cooling phase, and changes in composition and abundances of the marine fauna. A prominent perturbation of the global carbon cycle is documented in a globally recorded positive δ13C shift. Widespread storage of Corg-rich sediments in ocean basins, probably accompanied by anoxic conditions has long been supposed to explain for the positive carbon isotope anomaly. However, no widespread deposition of black shales has been shown for the Valanginian. Research on the Valanginian carbon cycle has focused on marine environmental changes, while studies on continental archives are scarce. This study deals with stable isotope chemostratigraphy, spore-pollen assemblages, palynofacies, and organic geochemistry of two successions located in the northwestern Tethyan realm (Vocontian Basin, SE France) and the Carpathian seaway (Polish Trough, central Poland). For both sites no evidence for anoxic conditions in the form of the occurrence of specific biomarkers like isoreniratene are found. Spore-pollen assemblages from both localities show many similarities in terms of composition, diversity and abundances of taxa. Both are dominated by conifer pollen and fern spores. During the initial phase of the δ13C shift the palynological compositions of both sites are quite diverging. Here, the French site is characterized by a decrease in spore abundances not being observed for the Polish site. This is followed by a peak in fern spores for both sites. Bulk Corg and algal-derived pristane and phytane follow the positive isotope shift of Ccarb with a lead of ~200 kyrs. Land plant derived long chain C27 n-alkanes for the Vocontian Basin as well show this positive shift while for the site at the Carpathian seaway the

  4. Dissolved organic carbon export and internal cycling in small, headwater lakes

    Science.gov (United States)

    Stets, Edward G.; Striegl, Rob; Aiken, George R.

    2010-01-01

    Carbon (C) cycling in freshwater lakes is intense but poorly integrated into our current understanding of overall C transport from the land to the oceans. We quantified dissolved organic carbon export (DOCX) and compared it with modeled gross DOC mineralization (DOCR) to determine whether hydrologic or within-lake processes dominated DOC cycling in a small headwaters watershed in Minnesota, USA. We also used DOC optical properties to gather information about DOC sources. We then compared our results to a data set of approximately 1500 lakes in the Eastern USA (Eastern Lake Survey, ELS, data set) to place our results in context of lakes more broadly. In the open-basin lakes in our watershed (n = 5), DOCX ranged from 60 to 183 g C m−2 lake area yr−1, whereas DOCR ranged from 15 to 21 g C m−2 lake area yr−1, emphasizing that lateral DOC fluxes dominated. DOCX calculated in our study watershed clustered near the 75th percentile of open-basin lakes in the ELS data set, suggesting that these results were not unusual. In contrast, DOCX in closed-basin lakes (n = 2) was approximately 5 g C m−2 lake area yr−1, whereas DOCR was 37 to 42 g C m−2 lake area yr−1, suggesting that internal C cycling dominated. In the ELS data set, median DOCX was 32 and 12 g C m−2 yr−1 in open-basin and closed-basin lakes, respectively. Although not as high as what was observed in our study watershed, DOCX is an important component of lake C flux more generally, particularly in open-basin lakes.

  5. Influences of the Landscape on Life Cycle Carbon Intensity of Biofuels

    Science.gov (United States)

    Adler, P. R.; Del Grosso, S.; Parton, W. J.; Spatari, S.

    2011-12-01

    Biofuels derived from first (sugar and starch based) and second (lignocellulosic) generation agricultural feedstocks will continue to expand into the market between now and 2022 as incentivized through the federal Energy Independence and Security Act (EISA). Nitrogen use is one of the key environmental concerns within the life cycle since it is both the dominant source of life cycle greenhouse gas (GHG) emissions (energy from N fertilizer production and N2O emissions) and poses risks of reactive N movement throughout agricultural landscapes and watersheds. The other dominant components of the feedstock production on life cycle GHG emissions are tillage and land use change impacts on soil organic carbon (SOC). Opportunities to reduce reactive N through winter double crops may satisfy the dual goal of mitigating N2O emissions and reducing NO3 loses while meeting the objectives of EISA. However, changes in N2O, NO3, and SOC are variable within the agricultural landscape due to soil texture, climate, and crop rotation history thereby increasing the complexity of developing mitigation recommendations. Moreover, the inherent variability in N2O emissions makes it difficult to develop single life cycle carbon intensity profiles for specific fuel pathways that apply across the US, since those pathways will have geographic dependencies. Estimating the expected changes in N2O and SOC is an integral part of quantifying the life cycle GHG profile of biofuels derived from winter double crop feedstocks, while NO3 losses affect both indirect N2O emissions and water quality. The biogeochemical model DayCent was used to simulate the impact of growing winter barley as a double crop following corn before soybean establishment during the winter fallow period for six states in the Mid Atlantic region of the Eastern US on SOC and direct and indirect N2O. EPA is currently reviewing the addition of an advanced fuel pathway for winter barley in the Mid Atlantic region as part of the RFS2

  6. Gasoline-powered serial hybrid cars cause lower life cycle carbon emissions than battery cars

    Science.gov (United States)

    Meinrenken, Christoph J.; Lackner, Klaus S.

    2011-04-01

    Battery cars powered by grid electricity promise reduced life cycle green house gas (GHG) emissions from the automotive sector. Such scenarios usually point to the much higher emissions from conventional, internal combustion engine cars. However, today's commercially available serial hybrid technology achieves the well known efficiency gains from regenerative breaking, lack of gearbox, and light weighting - even if the electricity is generated onboard, from conventional fuels. Here, we analyze emissions for commercially available, state-of the-art battery cars (e.g. Nissan Leaf) and those of commercially available serial hybrid cars (e.g., GM Volt, at same size and performance). Crucially, we find that serial hybrid cars driven on (fossil) gasoline cause fewer life cycle GHG emissions (126g CO2e per km) than battery cars driven on current US grid electricity (142g CO2e per km). We attribute this novel finding to the significant incremental life cycle emissions from battery cars from losses during grid transmission, battery dis-/charging, and larger batteries. We discuss crucial implications for strategic policy decisions towards a low carbon automotive sector as well as relative land intensity when powering cars by biofuel vs. bioelectricity.

  7. Peatlands and the carbon cycle: from local processes to global implications – a synthesis

    Directory of Open Access Journals (Sweden)

    H. Rydin

    2008-04-01

    Full Text Available Although peatlands cover only 3% of the Earth's land surface, boreal and subarctic peatlands store about 15–30% of the world's soil carbon as peat. Despite their potential for large positive feedbacks to the climate system through sequestration and emission of greenhouse gases, peatlands are not explicitly included in global climate models and therefore in predictions of future climate change. In April 2007 a symposium was held in Wageningen, the Netherlands, to advance our understanding of peatland C cycling through integration across disciplines and research approaches and to develop a more synthetic picture of the present and future role of peatlands in the global C cycle and their interactions with the climate system. This paper aims to synthesize the main findings of the symposium, focusing on (i small-scale processes, (ii C fluxes at the landscape scale, and (iii peatlands and climate. The paper concludes with a summary of the main drivers of the C balance of peatlands, and proposes directions for new research to reduce key uncertainties in our knowledge of C cycling in peatlands in order to facilitate the explicit inclusion of these ecosystems in a new generation of earth system models.

  8. Characterisation of Organic Matter and Carbon Cycling in Rehabilitated Lignite-rich Mine Soils

    International Nuclear Information System (INIS)

    Open-cast lignite mining in the Lusatian mining district resulted in rehabilitated mine soils containing up to four organic matter types: (1) recent plant litter, (2) lignite deposited by mining activity, (3) carbonaceous ash particles deposited during amelioration of the lignite-containing parent substrate and (4) airborne carbonaceous particles deposited during contamination. The influence of lignite-derived carbon types on the organic matter development and their role in the soil carbon cycle was unknown. This paper presents the findings obtained during a six year project concerning the impact of lignite on soil organic matter composition and the biogeochemical functioning of the ecosystem. The organic matter development after rehabilitation was followed in a chronosequence of rehabilitated mine soils afforested in 1966, 1981 and 1987. A differentiation of the organic matter types and an evaluation of their role within the ecosystem was achieved by the use of 14C activity measurements, 13C CPMAS NMR spectroscopy and wet chemical analysis of plant litter compounds. The results showed that the amount and degree of decomposition of the recent organic matter derived from plant material of the 30 year old mine soil was similar to natural uncontaminated forest soil which suggests complete rehabilitation of the ecosystem. The decomposition and humification processes were not influenced by the presence of lignite. On the other hand it was shown that lignite, which was thought to be recalcitrant because of its chemical structure, was part of the carbon cycle in these soils. This demonstrates the need to elucidate further the stabilisation mechanisms of organic matter in soils

  9. Characterisation of Organic Matter and Carbon Cycling in Rehabilitated Lignite-rich Mine Soils

    Energy Technology Data Exchange (ETDEWEB)

    Rumpel, Cornelia [Universite Pierre et Marie Curie, CNRS, Laboratoire de Biogeochimie des Milieux Continentaux (France)], E-mail: rumpel@ccr.jussieu.fr; Koegel-Knabner, Ingrid [Technische Universitaet Muenchen, Lehrstuhl fuer Bodenkunde (Germany)

    2003-01-15

    Open-cast lignite mining in the Lusatian mining district resulted in rehabilitated mine soils containing up to four organic matter types: (1) recent plant litter, (2) lignite deposited by mining activity, (3) carbonaceous ash particles deposited during amelioration of the lignite-containing parent substrate and (4) airborne carbonaceous particles deposited during contamination. The influence of lignite-derived carbon types on the organic matter development and their role in the soil carbon cycle was unknown. This paper presents the findings obtained during a six year project concerning the impact of lignite on soil organic matter composition and the biogeochemical functioning of the ecosystem. The organic matter development after rehabilitation was followed in a chronosequence of rehabilitated mine soils afforested in 1966, 1981 and 1987. A differentiation of the organic matter types and an evaluation of their role within the ecosystem was achieved by the use of {sup 14}C activity measurements, {sup 13}C CPMAS NMR spectroscopy and wet chemical analysis of plant litter compounds. The results showed that the amount and degree of decomposition of the recent organic matter derived from plant material of the 30 year old mine soil was similar to natural uncontaminated forest soil which suggests complete rehabilitation of the ecosystem. The decomposition and humification processes were not influenced by the presence of lignite. On the other hand it was shown that lignite, which was thought to be recalcitrant because of its chemical structure, was part of the carbon cycle in these soils. This demonstrates the need to elucidate further the stabilisation mechanisms of organic matter in soils.

  10. Carbon and Energy Footprints of Prefabricated Industrial Buildings: A Systematic Life Cycle Assessment Analysis

    Directory of Open Access Journals (Sweden)

    Emanuele Bonamente

    2015-11-01

    Full Text Available A systematic analysis of green-house gases emission (carbon footprint and primary energy consumption (energy footprint of prefabricated industrial buildings during their entire life cycle is presented. The life cycle assessment (LCA study was performed in a cradle-to grave approach: site-specific data from an Italian company, directly involved in all the phases from raw material manufacturing to in-situ assembly, were used to analyze the impacts as a function of different design choices. Four buildings were analyzed and results were used to setup a parameterized model that was used to study the impacts of industrial prefabricated buildings over the input parameter space. The model vs. data agreement is within 4% for both carbon and energy footprint. The functional unit is 1 m3 of prefabricated building, considering a 50-year lifetime. The results of the four buildings decrease from 144.6 kgCO2eq/m3 and 649.5 kWh/m3 down to 123.5 kgCO2eq/m3 and 556.8 kWh/m3 as the building floor area increases from 1048 m2 to 21,910 m2. The use phase accounts for the major impact (approximate 76%. It is found that the carbon footprint is proportional to the energy footprint, the proportional factor being 0.222 kgCO2eq/kWh within 0.5% accuracy. Finally, a systematic study of the sensitivity of input parameters (insulation, lifetime, foundation type is presented.

  11. Carbon Footprint Analysis for Mechanization of Maize Production Based on Life Cycle Assessment: A Case Study in Jilin Province, China

    Directory of Open Access Journals (Sweden)

    Haina Wang

    2015-11-01

    Full Text Available The theory on the carbon footprint of agriculture can systematically evaluate the carbon emissions caused by artificial factors from the agricultural production process, which is the theoretical basis for constructing low-carbon agriculture and has important guiding significance for realizing low-carbon agriculture. Based on farm production survey data from Jilin Province in 2014, this paper aims to obtain a clear understanding of the carbon footprint of maize production through the following method: (1 one ton of maize production was evaluated systematically by using the Life Cycle Assessment (LCA; (2 the carbon emissions of the whole system were estimated based on field measurement data, (3 using the emission factors we estimated Jilin’s carbon footprint for the period 2006–2013, and forecasted it for the period from 2014 to 2020 using the grey system model GM (1, 1.

  12. A New Global LAI Product and Its Use for Terrestrial Carbon Cycle Estimation

    Science.gov (United States)

    Chen, J. M.; Liu, R.; Ju, W.; Liu, Y.

    2014-12-01

    For improving the estimation of the spatio-temporal dynamics of the terrestrial carbon cycle, a new time series of the leaf area index (LAI) is generated for the global land surface at 8 km resolution from 1981 to 2012 by combining AVHRR and MODIS satellite data. This product differs from existing LAI products in the following two aspects: (1) the non-random spatial distribution of leaves with the canopy is considered, and (2) the seasonal variation of the vegetation background is included. The non-randomness of the leaf spatial distribution in the canopy is considered using the second vegetation structural parameter named clumping index (CI), which quantifies the deviation of the leaf spatial distribution from the random case. Using the MODIS Bidirectional Reflectance Distribution Function product, a global map of CI is produced at 500 m resolution. In our LAI algorithm, CI is used to convert the effective LAI obtained from mono-angle remote sensing into the true LAI, otherwise LAI would be considerably underestimated. The vegetation background is soil in crop, grass and shrub but includes soil, grass, moss, and litter in forests. Through processing a large volume of MISR data from 2000 to 2010, monthly red and near-infrared reflectances of the vegetation background is mapped globally at 1 km resolution. This new LAI product has been validated extensively using ground-based LAI measurements distributed globally. In carbon cycle modeling, the use of CI in addition to LAI allows for accurate separation of sunlit and shaded leaves as an important step in terrestrial photosynthesis and respiration modeling. Carbon flux measurements over 100 sites over the globe are used to validate an ecosystem model named Boreal Ecosystem Productivity Simulator (BEPS). The validated model is run globally at 8 km resolution for the period from 1981 to 2012 using the LAI product and other spatial datasets. The modeled results suggest that changes in vegetation structure as quantified

  13. Dynamic hybrid life cycle assessment of energy and carbon of multicrystalline silicon photovoltaic systems.

    Science.gov (United States)

    Zhai, Pei; Williams, Eric D

    2010-10-15

    This paper advances the life cycle assessment (LCA) of photovoltaic systems by expanding the boundary of the included processes using hybrid LCA and accounting for the technology-driven dynamics of embodied energy and carbon emissions. Hybrid LCA is an extended method that combines bottom-up process-sum and top-down economic input-output (EIO) methods. In 2007, the embodied energy was 4354 MJ/m(2) and the energy payback time (EPBT) was 2.2 years for a multicrystalline silicon PV system under 1700 kWh/m(2)/yr of solar radiation. These results are higher than those of process-sum LCA by approximately 60%, indicating that processes excluded in process-sum LCA, such as transportation, are significant. Even though PV is a low-carbon technology, the difference between hybrid and process-sum results for 10% penetration of PV in the U.S. electrical grid is 0.13% of total current grid emissions. Extending LCA from the process-sum to hybrid analysis makes a significant difference. Dynamics are characterized through a retrospective analysis and future outlook for PV manufacturing from 2001 to 2011. During this decade, the embodied carbon fell substantially, from 60 g CO(2)/kWh in 2001 to 21 g/kWh in 2011, indicating that technological progress is realizing reductions in embodied environmental impacts as well as lower module price. PMID:20860380

  14. Glacial marine carbon cycle sensitivities to Atlantic ocean circulation reorganization by coupled climate model simulations

    Directory of Open Access Journals (Sweden)

    M. O. Chikamoto

    2011-04-01

    Full Text Available A series of Last Glacial Maximum (LGM marine carbon cycle sensitivity experiments is conducted to test the effect of different physical processes, as simulated by two atmosphere-ocean general circulation model (AOGCM experiments, on the atmospheric pCO2. One AOGCM solution exhibits an increase in North Atlantic Deep Water (NADW formation, whereas the other mimics an increase in Antarctic Bottom Water (AABW associated with a weaker NADW. Due to enhanced gas solubility associated with lower sea surface temperature, both experiments generate a reduction of atmospheric pCO2 by about 20–23 ppm. However, neither a weakening of NADW nor an increase of AABW formation causes a large atmospheric pCO2 change. A marked enhancement in AABW formation is required to represent the reconstructed vertical gradient of dissolved inorganic carbon (DIC during LGM conditions. The efficiency of Southern Ocean nutrient utilization reduces in response to an enhanced AABW formation, which counteracts the circulation-induced ocean carbon uptake.

  15. Effect of an Internal Heat Exchanger on Performance of the Transcritical Carbon Dioxide Refrigeration Cycle with an Expander

    Directory of Open Access Journals (Sweden)

    Zhenying Zhang

    2014-11-01

    Full Text Available The effect of the internal heat exchanger (IHE on the performance of the transcritical carbon dioxide refrigeration cycle with an expander is analyzed theoretically on the basis of the first and second laws of thermodynamics. The possible parameters affecting system efficiency such as heat rejection pressure, gas cooler outlet temperature, evaporating temperature, expander isentropic efficiency and IHE effectiveness are investigated. It is found that the IHE addition in the carbon dioxide refrigeration cycle with an expander increases the specific cooling capacity and compression work, and decreases the optimum heat rejection pressure and the expander output power. An IHE addition does not always improve the system performance in the refrigeration cycle with an expander. The throttle valve cycle with IHE provides a 5.6% to 17% increase in maximum COP compared to that of the basic cycle. For the ideal expander cycle with IHE, the maximum COP is approximately 12.3% to 16.1% lower than the maximum COP of the cycle without IHE. Whether the energy efficiency of the cycle by IHE can be improved depends on the isentropic efficiency level of the expander. The use of IHE is only applicable in the cases of lower expander isentropic efficiencies or higher gas cooler exit temperatures for the refrigeration cycle with an expander from the view of energy efficiency.

  16. Quantifying and Reducing Climate-Carbon Cycle Feedback Uncertainties: Analysis of CMIP5 Earth System Model Feedbacks

    Science.gov (United States)

    Hoffman, F. M.; Randerson, J. T.

    2011-12-01

    Increasing atmospheric carbon dioxide (CO2) concentrations, resulting from anthropogenic perturbation of the global carbon cycle, are altering the Earth's climate. Climate change is expected to induce feedbacks on future CO2 concentrations and on the climate system itself. These feedbacks are highly uncertain, potentially large, and difficult to predict using Earth System Models (ESMs). In order to reduce the range of uncertainty in climate predictions, model representation of feedbacks must be improved through comparisons with contemporary observations. In this study, we quantify the terrestrial and ocean carbon storage sensitivity to climate and atmospheric CO2 concentration of ESMs participating in the Climate Model Intercomparison Project Phase 5 (CMIP5) following the methodology of Friedlingstein et al. (2006). In order to evaluate the models' abilities to capture the 21st century carbon cycle and to offer possible constraints on the modeled feedback strengths, comparisons with contemporary observations will be made over three different time scales: seasonal to annual, interannual to decadal, and decadal to centennial. A conceptual framework for evaluating climate-carbon cycle feedbacks in global models--employing best-available observational data--will be presented, along with results from application of this framework to CMIP5 model output. Included in the analysis will be prototype model evaluation benchmarks of the carbon cycle being designed for the International Land Model Benchmarking (ILAMB) Project.

  17. Simulated and observed trends in key variables of the Arctic marine carbon cycle

    Science.gov (United States)

    Goris, Nadine; Heinze, Christoph; Lauvset, Siv; Petrenko, Dmitry; Pozdnyakov, Dmitry; Schwinger, Jörg

    2013-04-01

    For the Arctic region, a thorough monitoring of the marine carbon cycle is important, as the general "polar amplification" of climate change also translates into the biogeochemical realm. As compared to the global ocean, the sink for human-produced CO2 is fairly small in the Arctic Ocean itself. Nevertheless, it is important to follow up this Arctic sink as a further control of the regional carbon budget and to record changes in the marine carbon cycle on the way towards a "blue Arctic". Since observations on the Arctic are rare, the EU FP7 MONARCH-A project tries to enable adequate descriptions of the status and evolution of the Arctic region Earth system components by generating time series of observation datasets and model hindcasts. In terms of the marine carbon cycle, this analysis focuses mainly on the key variables pCO2 and primary productivity. For oceanic pCO2, the comprehensive data-sets SOCAT and LDEO were combined, while measurements of atmospheric CO2 were collected from the GLOBALVIEW-CO2 data integration project. Monthly Primary Production fields were retrieved from the sensors MODIS and SeaWiFs. In order to get an overall picture of the behavior and trends of those key variables, in addition the physical-biogeochemical model MICOM-HAMOCC-M was employed. The investigation showed that both oceanic and atmospheric pCO2 are consistent variables which have a regular annual cycle and a similar behaviour all over the Arctic for both model and data. In contrast, primary production shows an irregular annual cycle in both range and form, varying over the Arctic. While a few well distributed measurement stations with continuous observations are sufficient to get a comprehensive picture for consistent variables like pCO2, it is relatively difficult and costly to get a comprehensive record of non-consistent variables. Since the provided data-set for primary production covers a relatively short time-scale, it was neither possible to confidently validate the model

  18. Simulating the global atmospheric black carbon cycle: a revisit to the contribution of aircraft emissions

    Directory of Open Access Journals (Sweden)

    J. Hendricks

    2004-06-01

    Full Text Available The black carbon (BC burden of the upper troposphere and lowermost stratosphere (UTLS is investigated with the general circulation model (GCM ECHAM4. The special focus is the contribution of aircraft emissions to the UTLS BC loading. Previous studies on the role of aircraft emissions in the global BC cycle either neglect BC sources located at the Earth's surface or simplify the BC cycle by assuming pre-defined BC residence times. Here, the global BC cycle including emissions, transport, and removal is explicitly simulated. The BC emissions considered include surface sources as well as BC from aviation. This enables a consistent calculation of the relative contribution of aviation to the global atmospheric BC cycle. As a further extension to the previous studies, the aviation-induced perturbation of the UTLS BC particle number concentration is investigated. Several sensitivity studies were performed to evaluate the uncertainties associated with the model predictions. The simulated UTLS BC concentrations are compared to in-situ observations. The simulations suggest that the large-scale contribution of aviation to the UTLS BC mass budget typically amounts to only a few percent, even in the most frequented flight regions. The aviation impact far away from these regions is negligible. The simulated aircraft contributions to the UTLS BC particle number concentration are much larger compared to the corresponding mass perturbations. The simulations suggest that aviation can cause large-scale increases in the UTLS BC particle number concentration of more than 30% in regions highly frequented by aircraft. The relative effect shows a pronounced annual variation with the largest relative aviation impact occurring during winter.

  19. Constraining carbon sources and cycling of endolithic microbial communities in the Atacama Desert

    Science.gov (United States)

    Ziolkowski, L. A.; Slater, G. F.; Davila, A.; Wierzchos, J.

    2010-12-01

    The Atacama Desert, one of the driest places on Earth, is considered a suitable analog for the extremely arid, oxidizing conditions on the surface of Mars. Recent observations suggest the presence of evaporitic deposits on the surface of Mars, such as those found in the Atacama. Halites in the Atacama have been shown to be hygroscopic and are colonized by photosynthetic microbes. While there is considerable evidence for the decrease in abundance and diversity of microbes closer to the hyper-arid core of the Atacama, experimental studies have thus far have yet to estimate the sources of carbon to these communities and the rate at which they cycle. To address these questions, we characterized the isotopic composition (13C and 14C) microbial community biomarkers from four distinct sites in the Atacama. Sites ranged from halites in the hyper-arid core (Yungay, Salar Grande) to volcanic rock and gypsum near the Monturaqui Crater. Our analysis of the phospholipids fatty acids (PLFA) and glycolipid fatty acid (GLFA) methyl esters of the endoliths agreed with previous studies: the abundance and diversity of microbes decreases approaching the hyper-arid core. The total PLFA and GLFA concentrations were lower at Yungay than Salar Grande and higher in the gypsum and volcanic rock samples. Changes in the mole percentage distribution of the PLFA and GLFA illustrated that the endolithic communities inhabiting the volcanic rock and gypsum were more complex than those inhabiting the halites. ∂13C of both PLFA and GLFA showed that non-halite lipids were less depleted in 13C than halite-lipids. This suggested a difference in carbon source or cycling. The 14C content of PLFA and GLFA varied by up to 250 per mil. Endolith PLFA and GLFA from the gypsum had radiocarbon signatures comparable to the modern atmosphere, which suggests that the predominant source of carbon to the system is the modern atmosphere and that lipids are cycling rapidly in this system. However, at the other three

  20. Supercritical Carbon Dioxide Brayton Power Conversion Cycle Design for Optimized Battery-Type Integral Reactor System

    International Nuclear Information System (INIS)

    Supercritical carbon dioxide (SCO2) promises a high power conversion efficiency of the recompression Brayton cycle due to its excellent compressibility reducing the compression work at the bottom of the cycle and to a higher density than helium or steam decreasing the component size. Therefore, the high SCO2 Brayton cycle efficiency as high as 45 % furnishes small sized nuclear reactors with economical benefits on the plant construction and maintenance. A 23 MWth BORIS (Battery Optimized Reactor Integral System) is being developed as a multipurpose reactor. BORIS, an integral-type optimized fast reactor with an ultra long life core, is coupled to the SCO2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO2 Brayton cycle of BORIS consists of a 16 MW turbine, a 32 MW high temperature recuperator, a 14 MW low temperature recuperator, an 11 MW pre-cooler and 2 and 2.8 MW compressors. Entering six heat exchangers between primary and secondary system at 19.9 MPa and 663 K, the SCO2 leaves the heat exchangers at 19.9 MPa and 823 K. The promising secondary system efficiency of 45 % was calculated by a theoretical method in which the main parameters include pressure, temperature, heater power, the turbine's, recuperators' and compressors' efficiencies, and the flow split ratio of SCO2 going out from the low temperature recuperator. Test loop SOLOS (Shell-and-tube Overall Layout Optimization Study) is utilized to develop advanced techniques needed to adopt the shell-and-tube type heat exchanger in the secondary loop of BORIS by studying the SCO2 behavior from both thermal and hydrodynamic points of view. Concurrently, a computational fluid dynamics (CFD) code analysis is being conducted to develop an optimal analytical method of the SCO2 turbine efficiency having the parameters of flow characteristics of SCO2 passing through buckets of the turbine. These simultaneous experimental and analytical methods for designing

  1. The carbon cycle, and its evolution: from the geological era to the pre-industrial era

    International Nuclear Information System (INIS)

    As an introduction, the paper gives an overview of the evolution of the atmosphere before and during the geological era, the advent of the vegetable kingdom and photosynthesis, the formation of coal, petroleum and natural gas deposits, and the ocean contribution to the equilibrium of the CO2 content in the atmosphere. These processes were very slow, and their knowledge relies essentially on models. Closer to us, the analyses of air bubbles enclosed within the polar ice cover gives accurate values of the CO2 content over the last hundred thousand years. This content influenced the climate and, reciprocally, the climate influenced the equilibrium between the atmospheric and CO2 contents in the ocean and continental biomass. On the continents, the vegetation uses CO2 mainly in the spring for its growth whereas it produce CO2 when the organic matters are rotting in the fall. The same thing exists in the oceans, where a huge quantity of carbon is also under the form of carbonates and bicarbonates. Before the industrial revolution, an equilibrium was continuously adjusted between the CO2 contents in the atmosphere and the oceans: this carbon was carried to the ocean bottom in down-welling zones by various phenomena, explaining the reason for its higher CO2 content, where it was released in the up-welling zones. This natural equilibrium has been destroyed since the beginning of the industrial era, by the production of an excess of CO2 At the present time half of the CO2 industrial emissions is stored in the atmosphere, the other half is naturally split between the ocean and the continental biomass. This paper is a review of this long history and describes the present level of knowledge of the processes that control the carbon cycle. (author)

  2. Did the emergence of animals have an impact on the carbon cycle of the ocean floor?

    Science.gov (United States)

    Meysman, Filip; Maire, Olivier; Bockelmann, Frank; van Oevelen, Dick; Glud, Ronnie

    2010-05-01

    The first animals appeared at or near the ocean floor, and paleontologists have suggested that the ensuing Cambrian explosion resulted in a regime shift in the biogeochemical functioning of the ocean floor. The newly evolved animals rapidly adopted a burrowing lifestyle, and as result, sediments became mixed and reworked, thus "bulldozing" the microbial mats that had covered the ocean floor in the Precambrian. Sedimentary redox conditions also changed, as burrow networks were flushed with oxygenated overlying water. But did the emergence of large burrowing fauna truly have an impact on the carbon cycle of the ocean? Here, we try to answer this question by looking at the present-day situation, that is, we estimate how large the impact is of large burrowing fauna on organic carbon processing in the ocean floor. We addressed this by a global synthesis and model analysis of the in situ oxygen uptake rate in marine sediments, where the oxygen uptake is used as a proxy for organic carbon mineralization. The total oxygen uptake can be split into a diffusive oxygen uptake, linked to oxygen supply by diffusion across the sediment water interface, and a faunal mediated uptake, linked to faunal respiration and bio-irrigation. Our results show that the faunal mediated contribution to the total oxygen uptake is about 20% for the global ocean floor and 45% for the global continental shelves. About 25% of this faunal mediated contribution is explained by direct respiration of macrofauna and meiofauna, the other 75% is linked to the stimulation of microbial decomposition through bio-irrigation. Overall, our analysis suggests a large imprint of benthic fauna on the sedimentary processing of organic carbon, particularly in continental shelves and coastal sediments. This then suggests that the evolution of large burrowing fauna may have had a substantial impact on the rate of mineralization and sequestration of organic matter in marine sediments.

  3. Palaeo-equatorial temperatures and carbon-cycle evolution at the Triassic- Jurassic boundary: A stable isotope perspective from shallow-water carbonates from the UAE

    Science.gov (United States)

    Honig, M. R.; John, C. M.

    2013-12-01

    The Triassic-Jurassic boundary was marked by global changes including carbon-cycle perturbations and the opening of the Atlantic Ocean. These changes were accompanied by one of the major extinction events of the Phanerozoic. The carbon-cycle perturbations have been recorded in carbon isotope curves from bulk carbonates, organic carbon and fossil wood in several Tethyan locations and have been used for chemostratigraphic purposes. Here we present data from shallow-marine carbonates deposited on a homoclinal Middle Eastern carbonate ramp (United Arab Emirates). Our site was located at the equator throughout the Late Triassic and the Early Jurassic, and this study provides the first constraints of environmental changes at the low-latitudes for the Triassic-Jurassic boundary. Shallow-marine carbonate depositional systems are extremely sensitive to palaeoenvironmental changes and their usefulness for chemostratigraphy is being debated. However, the palaeogeographic location of the studied carbonate ramp gives us a unique insight into a tropical carbonate factory at a time of severe global change. Stable isotope measurements (carbon and oxygen) are being carried out on micrite, ooids and shell material along the Triassic-Jurassic boundary. The stable isotope results on micrite show a prominent negative shift in carbon isotope values of approximately 2 ‰ just below the inferred position of the Triassic-Jurassic boundary. A similar isotopic trend is also observed across the Tethys but with a range of amplitudes (from ~2 ‰ to ~4 ‰). These results seem to indicate that the neritic carbonates from our studied section can be used for chemostratigraphic purposes, and the amplitudes of the carbon isotope shifts provide critical constraints on the magnitude of carbon-cycle perturbations at low latitudes across the Triassic-Jurassic boundary. Seawater temperatures across the Triassic-Jurassic boundary will be constrained using the clumped isotope palaeo-thermometer applied

  4. Effects of climate variability and functional changes on carbon cycling in a temperate deciduous forest

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jian

    2013-03-15

    Temperate forests are globally important carbon (C) stocks and sinks. A decadal (1997-2009) trend of increasing C uptake has been observed in an intensively studied temperate deciduous forest, Soroe (Zealand, Denmark). This gave the impetus to investigate the factors controlling the C cycling and the fundamental processes at work in this type of ecosystem. The major objectives of this study were to (1) evaluate to what extent and at what temporal scales, direct climatic variability and functional changes (e.g. changes in the structure or physiological properties) regulate the interannual variability (IAV) in the ecosystem C balance; (2) provide a synthesis of the ecosystem C budget at this site and (3) investigate whether terrestrial ecosystem models can dynamically simulate the trend of increasing C uptake. Data driven analysis, semi-empirical and process-based modelling experiments were performed in a series of studies in order to provide a complete assessment of the carbon storage and allocation within the ecosystem and clarify the mechanisms responsible for the observed variability and trend in the ecosystem C fluxes. Combining all independently estimated ecosystem carbon budget (ECB) datasets and other calculated ECB components based on mass balance equations, a synthesis of the carbon cycling was performed. The results showed that this temperature deciduous forest was moderately productive with both high rates of gross primary production and ecosystem respiration. Approximately 62% of the gross assimilated carbon was respired by the living plants, while 21% was contributed to the soil as litter production, the latter balancing the total heterotrophic respiration. The remaining 17% was either stored in the plants (mainly as aboveground biomass) or removed from the system as wood production. In general, the ECB component datasets were consistent after the cross-checking. This, together with their characterized uncertainties, can be used in model data fusion

  5. Light-dark (12:12) cycle of carbon and nitrogen metabolism in Crocosphaera watsonii WH8501: relation to the cell cycle.

    Science.gov (United States)

    Dron, Anthony; Rabouille, Sophie; Claquin, Pascal; Le Roy, Bertrand; Talec, Amélie; Sciandra, Antoine

    2012-04-01

    This study provides with original data sets on the physiology of the unicellular diazotrophic cyanobacterium Crocosphaera watsonii WH8501, maintained in continuous culture in conditions of obligate diazotrophy. Cultures were exposed to a 12:12 light-dark regime, representative of what they experience in nature and where growth is expected to be balanced. Nitrogen and carbon metabolism were monitored at high frequency and their dynamics was compared with the cell cycle. Results reveal a daily cycle in the physiological and biochemical parameters, tightly constrained by the timely decoupled processes of N(2) fixation and carbon acquisition. The cell division rate increased concomitantly to carbon accumulation and peaked 6 h into the light. The carbon content reached a maximum at the end of the light phase. N(2) fixation occurred mostly during the dark period and peaked between 9 and 10 h into the night, while DNA synthesis, reflected by DNA fluorescence, increased until the end of the night. Consequently, cells in G1- and S-phases present a marked decrease in their C:N ratio. Nitrogen acquisition through N(2) fixation exceeded 1.3- to 3-fold the nitrogen requirements for growth, suggesting that important amounts of nitrogen are excreted even under conditions supposed to favour balanced, carbon and nitrogen acquisitions. PMID:22188053

  6. Can we bet on negative emissions to achieve the 2°C target even under strong carbon cycle feedbacks?

    Science.gov (United States)

    Tanaka, K.; Yamagata, Y.; Yokohata, T.; Emori, S.; Hanaoka, T.

    2015-12-01

    Negative emission technologies such as Bioenergy with Carbon dioxide Capture and Storage (BioCCS) play an ever more crucial role in meeting the 2°C stabilization target. However, such technologies are currently at their infancy and their future penetrations may fall short of the scale required to stabilize the warming. Furthermore, the overshoot in the mid-century prior to a full realization of negative emissions would give rise to a risk because such a temporal but excessive warming above 2°C might amplify itself by strengthening climate-carbon cycle feedbacks. It has not been extensively assessed yet how carbon cycle feedbacks might play out during the overshoot in the context of negative emissions. This study explores how 2°C stabilization pathways, in particular those which undergo overshoot, can be influenced by carbon cycle feedbacks and asks their climatic and economic consequences. We compute 2°C stabilization emissions scenarios under a cost-effectiveness principle, in which the total abatement costs are minimized such that the global warming is capped at 2°C. We employ a reduced-complexity model, the Aggregated Carbon Cycle, Atmospheric Chemistry, and Climate model (ACC2), which comprises a box model of the global carbon cycle, simple parameterizations of the atmospheric chemistry, and a land-ocean energy balance model. The total abatement costs are estimated from the marginal abatement cost functions for CO2, CH4, N2O, and BC.Our preliminary results show that, if carbon cycle feedbacks turn out to be stronger than what is known today, it would incur substantial abatement costs to keep up with the 2°C stabilization goal. Our results also suggest that it would be less expensive in the long run to plan for a 2°C stabilization pathway by considering strong carbon cycle feedbacks because it would cost more if we correct the emission pathway in the mid-century to adjust for unexpectedly large carbon cycle feedbacks during overshoot. Furthermore, our

  7. Water masses as a unifying framework for understanding the Southern Ocean Carbon Cycle

    Directory of Open Access Journals (Sweden)

    D. Iudicone

    2011-05-01

    Full Text Available The scientific motivation for this study is to understand the processes in the ocean interior controlling carbon transfer across 30° S. To address this, we have developed a unified framework for understanding the interplay between physical drivers such as buoyancy fluxes and ocean mixing, and carbon-specific processes such as biology, gas exchange and carbon mixing. Given the importance of density in determining the ocean interior structure and circulation, the framework is one that is organized by density and water masses, and it makes combined use of Eulerian and Lagrangian diagnostics. This is achieved through application to a global ice-ocean circulation model and an ocean biogeochemistry model, with both components being part of the widely-used IPSL coupled ocean/atmosphere/carbon cycle model.

    Our main new result is the dominance of the overturning circulation (identified by water masses in setting the vertical distribution of carbon transport from the Southern Ocean towards the global ocean. A net contrast emerges between the role of Subantarctic Mode Water (SAMW, associated with large northward transport and ingassing, and Antarctic Intermediate Water (AAIW, associated with a much smaller export and outgassing. The differences in their export rate reflects differences in their water mass formation processes. For SAMW, two-thirds of the surface waters are provided as a result of the densification of thermocline water (TW, and upon densification this water carries with it a substantial diapycnal flux of dissolved inorganic carbon (DIC. For AAIW, principal formatin processes include buoyancy forcing and mixing, with these serving to lighten CDW. An additional important formation pathway of AAIW is through the effect of interior processing (mixing, including cabelling that serve to densify SAMW.

    A quantitative evaluation of the contribution of mixing, biology and gas exchange to the DIC evolution per water mass reveals that

  8. Impact of brine-induced stratification on the glacial carbon cycle

    Directory of Open Access Journals (Sweden)

    N. Bouttes

    2010-04-01

    Full Text Available During the cold period of the Last Glacial Maximum (LGM, about 21 000 years ago atmospheric CO2 was around 190 ppm (Monnin et al., 2001, much lower than the pre-industrial concentration of 280 ppm. The causes of this substantial drop remain partially unresolved, despite intense research. Understanding the origin of reduced atmospheric CO2 during glacial times is crucial to comprehend the evolution of the different carbon reservoirs within the Earth system (atmosphere, terrestrial biosphere and ocean. In this context, the ocean is believed to play a major role as it can store large amounts of carbon (Sigman and Boyle, 2000, especially in the abyss, which is a carbon reservoir that is thought to have expanded during glacial times. To create this larger reservoir, one possible mechanism is to produce very dense glacial waters, thereby stratifying the deep ocean and reducing the carbon exchange between the deep and surface ocean (Paillard and Parrenin, 2004. The existence of such very dense waters has been inferred in the LGM deep Atlantic from sediment pore water salinity (Adkins et al., 2002. Based on these observations, we study the impact of a brine mechanism on the glacial carbon cycle. This mechanism relies on the formation and rapid sinking of brines, very salty water released during sea ice formation, which brings salty dense water down to the bottom of the ocean. It provides two major features: a direct link from the surface to the deep ocean along with an efficient way of setting a strong stratification. We show with the CLIMBER-2 coupled carbon-climate model (Petoukhov et al., 2000 that such a brine mechanism can account for a significant decrease in atmospheric CO2 and contribute to the glacial-interglacial change. This mechanism can be amplified by low vertical diffusion resulting from the brine-induced stratification. The results obtained substantially improve the modeled glacial distribution of oceanic

  9. Impact of brine-induced stratification on the glacial carbon cycle

    Directory of Open Access Journals (Sweden)

    N. Bouttes

    2010-09-01

    Full Text Available During the cold period of the Last Glacial Maximum (LGM, about 21 000 years ago atmospheric CO2 was around 190 ppm, much lower than the pre-industrial concentration of 280 ppm. The causes of this substantial drop remain partially unresolved, despite intense research. Understanding the origin of reduced atmospheric CO2 during glacial times is crucial to comprehend the evolution of the different carbon reservoirs within the Earth system (atmosphere, terrestrial biosphere and ocean. In this context, the ocean is believed to play a major role as it can store large amounts of carbon, especially in the abyss, which is a carbon reservoir that is thought to have expanded during glacial times. To create this larger reservoir, one possible mechanism is to produce very dense glacial waters, thereby stratifying the deep ocean and reducing the carbon exchange between the deep and upper ocean. The existence of such very dense waters has been inferred in the LGM deep Atlantic from sediment pore water salinity and δ18O inferred temperature. Based on these observations, we study the impact of a brine mechanism on the glacial carbon cycle. This mechanism relies on the formation and rapid sinking of brines, very salty water released during sea ice formation, which brings salty dense water down to the bottom of the ocean. It provides two major features: a direct link from the surface to the deep ocean along with an efficient way of setting a strong stratification. We show with the CLIMBER-2 carbon-climate model that such a brine mechanism can account for a significant decrease in atmospheric CO2 and contribute to the glacial-interglacial change. This mechanism can be amplified by low vertical diffusion resulting from the brine-induced stratification. The modeled glacial distribution of oceanic δ13C as well as the deep ocean salinity are substantially improved and better agree with reconstructions from

  10. Insights into deep-time terrestrial carbon cycle processes from modern plant isotope ecology

    Science.gov (United States)

    Sheldon, N. D.; Smith, S. Y.

    2012-12-01

    While the terrestrial biosphere and soils contain much of the readily exchangeable carbon on Earth, how those reservoirs function on long time scales and at times of higher atmospheric CO2 and higher temperatures is poorly understood, which limits our ability to make accurate future predictions of their response to anthropogenic change. Recent data compilation efforts have outlined the response of plant carbon isotope compositions to a variety of environmental factors including precipitation amount and timing, elevation, and latitude. The compilations involve numerous types of plants, typically only found at a limited number of climatic conditions. Here, we expand on those efforts by examining the isotopic response of specific plant groups found both globally and across environmental gradients including: 1) ginkgo, 2) conifers, and 3) C4 grasses. Ginkgo is presently widely distributed as a cultivated plant and the ginkgoalean fossil record spans from the Permian to the present, making it an ideal model organism to understand climatic influence on carbon cycling both in modern and ancient settings. Ginkgo leaves have been obtained from a range of precipitation conditions (400-2200 mm yr-1), including dense sampling from individuals and populations in both Mediterranean and temperate climate areas and samples of different organs and developmental stages. Ginkgo carbon isotope results plot on the global C3 plant array, are consistent among trees at single sites, among plant organs, and among development stages, making ginkgo a robust recorder of both climatic conditions and atmospheric δ13C. In contrast, a climate-carbon isotope transect in Arizona highlights that conifers (specifically, pine and juniper) record large variability between organs and have a very different δ13C slope as a function of climate than the global C3 plant array, while C4 plants have a slope with the opposite sign as a function of climate. This has a number of implications for paleo

  11. Aspects of the carbon cycle in terrestrial ecosystems of Northeastern Smaaland

    International Nuclear Information System (INIS)

    Boreal and temperate ecosystems of the northern hemisphere are important for the future development of global climate. In this study, the carbon cycle has been studied in a pine forest, a meadow, a spruce forest and two deciduous forests in the Simpevarp investigation area in southern Sweden (57 deg 5 min N, 34 deg 55 min E). Ground respiration and ground Gross Primary Production (GPP) has been measured three times during spring 2004 with the closed chamber technique. Soil temperature, soil moisture and Photosynthetically Active Radiation (PAR) were also measured. An exponential regression with ground respiration against soil temperature was used to extrapolate respiration over spring 2004. A logarithmic regression with ground GPP against PAR was used to extrapolate GPP in meadow over spring 2004. Ground respiration is affected by soil temperature in all ecosystems but pine, but still it only explains a small part of the variation in respiration and this indicates that other abiotic factors also have an influence. Soil moisture affects respiration in spruce and one of the deciduous ecosystems. A comparison between measured and extrapolated ground respiration indicated that soil temperature could be used to extrapolate ground respiration. PAR is the main factor influencing GPP in all ecosystems but pine, still it could not be used to extrapolate GPP in meadow since too few measurements were done and they were from different periods of spring. Soil moisture did not have any significant effect on GPP. A Dynamic Global Vegetation Model, a DGVM called LPJ-GUESS, was downscaled to the Simpevarp investigation area. The downscaled DGVM was evaluated against measured respiration and soil organic acids for all five ecosystems. In meadow, it was evaluated against Net Primary Production, NPP. For the forest ecosystems, it was evaluated against tree layer carbon pools. The evaluation indicated that the DGVM is reasonably well downscaled to the Simpevarp investigation area and

  12. Aspects of the carbon cycle in terrestrial ecosystems of Northeastern Smaaland

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern [Lund Univ., Geobiosphere Science Centre (Sweden). Physical Geography and Ecosystems Analysis

    2006-02-15

    Boreal and temperate ecosystems of the northern hemisphere are important for the future development of global climate. In this study, the carbon cycle has been studied in a pine forest, a meadow, a spruce forest and two deciduous forests in the Simpevarp investigation area in southern Sweden (57 deg 5 min N, 34 deg 55 min E). Ground respiration and ground Gross Primary Production (GPP) has been measured three times during spring 2004 with the closed chamber technique. Soil temperature, soil moisture and Photosynthetically Active Radiation (PAR) were also measured. An exponential regression with ground respiration against soil temperature was used to extrapolate respiration over spring 2004. A logarithmic regression with ground GPP against PAR was used to extrapolate GPP in meadow over spring 2004. Ground respiration is affected by soil temperature in all ecosystems but pine, but still it only explains a small part of the variation in respiration and this indicates that other abiotic factors also have an influence. Soil moisture affects respiration in spruce and one of the deciduous ecosystems. A comparison between measured and extrapolated ground respiration indicated that soil temperature could be used to extrapolate ground respiration. PAR is the main factor influencing GPP in all ecosystems but pine, still it could not be used to extrapolate GPP in meadow since too few measurements were done and they were from different periods of spring. Soil moisture did not have any significant effect on GPP. A Dynamic Global Vegetation Model, a DGVM called LPJ-GUESS, was downscaled to the Simpevarp investigation area. The downscaled DGVM was evaluated against measured respiration and soil organic acids for all five ecosystems. In meadow, it was evaluated against Net Primary Production, NPP. For the forest ecosystems, it was evaluated against tree layer carbon pools. The evaluation indicated that the DGVM is reasonably well downscaled to the Simpevarp investigation area and

  13. Environmental assessment of amine-based carbon capture Scenario modelling with life cycle assessment (LCA)

    Energy Technology Data Exchange (ETDEWEB)

    Brekke, Andreas; Askham, Cecilia; Modahl, Ingunn Saur; Vold, Bjoern Ivar; Johnsen, Fredrik Moltu

    2012-07-01

    This report contains a first attempt at introducing the environmental impacts associated with amines and derivatives in a life cycle assessment (LCA) of gas power production with carbon capture and comparing these with other environmental impacts associated with the production system. The report aims to identify data gaps and methodological challenges connected both to modelling toxicity of amines and derivatives and weighting of environmental impacts. A scenario based modelling exercise was performed on a theoretical gas power plant with carbon capture, where emission levels of nitrosamines were varied between zero (gas power without CCS) to a worst case level (outside the probable range of actual carbon capture facilities). Because of extensive research and development in the areas of solvents and emissions from carbon capture facilities in the latter years, data used in the exercise may be outdated and results should therefore not be taken at face value.The results from the exercise showed: According to UseTox, emissions of nitrosamines are less important than emissions of formaldehyde with regard to toxicity related to operation of (i.e. both inputs to and outputs from) a carbon capture facility. If characterisation factors for emissions of metals are included, these outweigh all other toxic emissions in the study. None of the most recent weighting methods in LCA include characterisation factors for nitrosamines, and these are therefore not part of the environmental ranking.These results shows that the EDecIDe project has an important role to play in developing LCA methodology useful for assessing the environmental performance of amine based carbon capture in particular and CCS in general. The EDecIDe project will examine the toxicity models used in LCA in more detail, specifically UseTox. The applicability of the LCA compartment models and site specificity issues for a Norwegian/Arctic situation will be explored. This applies to the environmental compartments

  14. Authigenic carbonate precipitation at the end-Guadalupian (Middle Permian) in China: Implications for the carbon cycle in ancient anoxic oceans

    Science.gov (United States)

    Saitoh, Masafumi; Ueno, Yuichiro; Isozaki, Yukio; Shibuya, Takazo; Yao, Jianxin; Ji, Zhansheng; Shozugawa, Katsumi; Matsuo, Motoyuki; Yoshida, Naohiro

    2015-12-01

    Carbonate precipitation is a major process in the global carbon cycle. It was recently proposed that authigenic carbonate (carbonate precipitated in situ at the sediment-water interface and/or within the sediment) played a major role in the carbon cycle throughout Earth's history. The carbon isotopic composition of authigenic carbonates in ancient oceans have been assumed to be significantly lower than that of dissolved inorganic carbon (DIC) in seawater, as is observed in the modern oceans. However, the δ13Ccarb values of authigenic carbonates in the past has not been analyzed in detail. Here, we report authigenic carbonates in the uppermost Guadalupian (Middle Permian) rocks at Chaotian, Sichuan, South China. Monocrystalline calcite crystals black mudstone/chert sequence that was deposited on a relatively deep anoxic slope/basin along the continental margin. Textures of the crystals indicate in situ precipitation on the seafloor and/or within the sediments. The calcite precipitation corresponds stratigraphically with denitrification and sulfate reduction in the anoxic deep-water mass, as indicated by previously reported nitrogen and sulfur isotope records, respectively. Relatively high δ13Ccarb values of the authigenic carbonates (largely -1 ‰) compared with those of organic matter in the rocks (ca. -26 ‰) suggest that the main carbon source of the carbonates was DIC in the water column. The calcite crystals precipitated in an open system with respect to carbonate, possibly near the sediment-water interface rather than deep within the sediments. The δ13Ccarb values of the carbonates were close to the δ13CDIC value of seawater due to mixing of 13C-depleted remineralized organic carbon (that was released into the water column by the water-mass anaerobic respiration) with the large DIC pool in the oceans. Our results imply that δ13Ccarb values of authigenic carbonates in the anoxic oceans might have been systematically different from the values in the oxic

  15. Supercritical carbon dioxide Brayton power conversion cycle for battery optimized reactor integral system

    International Nuclear Information System (INIS)

    Supercritical carbon dioxide (SCO2) promises a high power conversion efficiency of the recompression Brayton cycle due to its excellent compressibility reducing the compression work at the bottom of the cycle and to a higher density than helium or steam decreasing the component size. The SCO2 Brayton cycle efficiency as high as 45% furnishes small sized nuclear reactors with economical benefits on the plant construction and maintenance. A 23 MWth lead-cooled Battery Optimized Reactor Integral System (BORIS) is being developed as an ultra-long-life, versatile-purpose, fast-spectrum reactor. BORIS is coupled to the SCO2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO2 Brayton cycle of BORIS consists of a 16 MW turbine, a 32 MW high temperature recuperator, a 14 MW low temperature recuperator, an 11 MW precooler and 2 and 2.8 MW compressors. Entering six heat exchangers between primary and secondary system at 19.9 MPa and 663 K, the SCO2 leaves the heat exchangers at 19.9 MPa and 823 K. The promising secondary system efficiency of 45% was calculated by a theoretical method in which the main parameters include pressure, temperature, heater power, the turbine's, recuperators' and compressors' efficiencies, and the flow split ratio of SCO2 going out from the low temperature recuperator. Development of Modular Optimized Brayton Integral System (MOBIS) is being devised as the SCO2 Brayton cycle energy conversion cycle for BORIS. MOBIS consists of Loop Operating Brayton Optimization Study (LOBOS) for experimental Brayton cycle loop and Gas Advanced Turbine Operation Study (GATOS) for the SCO2 turbine. Liquid-metal Energy Exchanger Integral System (LEXIS) serves to couple BORIS and MOBIS. LEXIS comprises Physical Aspect Thermal Operation System (PATOS) for SCO2 thermal hydraulic characteristics, Shell-and-tube Overall Layout Optimization Study (SOLOS) for shell-and-tube heat exchanger, Printed-circuit Overall

  16. Deep Crustal Metamorphic Carbon Cycling in Collisional Orogens: What do we Really Know?

    Science.gov (United States)

    Ague, J.

    2012-12-01

    The classic study of Bowen (1940) showed that CO2 is lost during metamorphic heating of common carbonate-bearing rocks. Despite tremendous progress in our understanding of devolatilization since Bowen's time, the fact remains that the metamorphic CO2 flux from active mountain belts is one of the most poorly-understood components of the global C cycle. A basic question is: do large fluid fluxes accompany collisional orogenesis? It has been argued that metamorphic rocks are overpressured and, thus, permeability is low and fluid fluxes are limited. In contrast, field-based studies commonly estimate large time-integrated fluxes of the order of 103 m3 m-2 or more. These opposing viewpoints can be reconciled by recognizing that large fluxes can pass through rocks on geologic timescales even if permeability is low, and that transient events such as fracturing can greatly increase permeability and facilitate flow. Large regional fluxes make possible significant CO2 transfer from the deep roots of mountain belts to the shallow hydrosphere and atmosphere. Important prograde CO2 release processes include "internally-buffered" reactions, fluid infiltration, carbonate mineral dissolution, and oxidation of graphite (or diamond). The relative roles of these processes, particularly the latter two, are topics of active research. Regardless of process, however, field-based results commonly show prograde loss of 10 to 15 kg CO2 per 100 kg rock for a range of carbonate mineral-bearing lithologies from sub-greenschist to upper amphibolite facies metamorphism. Could this CO2 make a real difference to C cycling? A new assessment of the mean loss of CO2 from metamorphic sequences in New England, USA, for example, yields a minimum release rate of about 1018 mol Ma-1 during the Acadian orogeny (Devonian). This is comparable to Kerrick and Caldeira's (1993) threshold needed to affect global atmospheric temperatures. Flow around large, deep-seated intrusions could easily produce even larger

  17. Numerical investigation of climate factors impact on carbon cycle in the East Asian terrestrial ecosystem

    Energy Technology Data Exchange (ETDEWEB)

    Mabuchi, K. [Meteorological Research Institute, Tsukuba (Japan); Takahashi, K. [Japan Meteorological Agency, Tokyo (Japan); Nasahara, K.N. [Univ. of Tsukuba (Japan). Inst. of Agricultural and Forest Engineering

    2009-07-01

    The present state of environmental problems due to global warming resulting from increases of greenhouse gases has reached new levels. The international treaty known as the United Nations Framework Convention on Climate Change (UNFCCC) was adopted in 1992 to begin to consider what can be done to reduce global warming. The Kyoto Protocol, adopted in 1997 at the third Conference of the Parties to the UNFCCC (COP 3), proposed a worldwide reduction of greenhouse gas emission. Under these conditions, it became necessary to monitor the increases of greenhouse gases, especially carbon dioxide, and to conduct research to further understand the mechanisms of interactions between environmental changes and the carbon balance. Estimations of the carbon dioxide budget are of great importance in taking the proper steps to deal with increased concentrations due to anthropogenic emissions, and in predictions of future concentration levels. The main components of the carbon dioxide budget are anthropogenic emissions, atmospheric concentration, the exchange between the atmosphere and ocean, and the exchange between the atmosphere and terrestrial ecosystems. Among these components, the role of the terrestrial ecosystem is still uncertain, due to the heterogeneity of that system. Using a regional climate model that includes a terrestrial biosphere model, numerical simulations were performed to clarify the mechanism of the carbon cycle between the terrestrial ecosystem and the atmosphere and to investigate the climate factors impact on the carbon cycle in the East Asian terrestrial ecosystem. Model verifications were performed with regard to the principal elements: precipitation and vegetation phenology. The variations of the atmospheric carbon dioxide concentration simulated by the model were validated using the data at six in situ observatories. After the confirmations of the model performance, regional features of the impact of climate factors on the gross primary production (GPP

  18. Competition of sulphation and carbonation reactions during looping cycles for CO2 capture by CaO-based sorbents.

    Science.gov (United States)

    Manovic, Vasilije; Anthony, Edward J

    2010-03-25

    Two types of sorbents are investigated here (natural limestone and highly reactive calcium aluminate pellets) to elucidate their reactivity in terms of sulphation and carbonation and determine the resulting effect on looping cycles for CO(2) capture. The sorbents are tested in a thermogravimetric analyzer (TGA) apparatus using typical synthetic flue gas mixtures containing 15% CO(2) and various concentrations of SO(2). The sulphation and carbonation conversions were determined during sulphation/carbonation/calcination cycles. The sorbent morphology and its changes were determined by means of a scanning electron microscope (SEM). The results showed that sulphation, that is, the formation of CaSO(4) at the sorbent surface, is a cumulative process with increasing numbers of reaction cycles, which hinders sorbent ability to capture CO(2). In the case of high sorbent reactivity, as determined by its morphology, the unfavorable effect of sulphation is more pronounced. Unfortunately, any increase in the temperature in the carbonation stage accelerates sulphation more than carbonation as a result of higher activation energy for the sulphation reaction. The SEM analyses showed that although sulphation and carbonation occur during cycles involving calcination, an unreacted core/partially sulphated shell sorbent particle pattern is formed. The main outcomes of this research indicate that special attention should be paid to the sulphation when more reactive and more expensive, synthetic CaO-based sorbents are used for CO(2) capture looping cycles. Desulphurization of flue gas before CO(2) capture appears to be essential because CO(2) looping cycles are so strongly affected by the presence of SO(2). PMID:20050624

  19. Assessing and Synthesizing the Last Decade of Research on the Major Pools and Fluxes of the Carbon Cycle in the US and North America: An Interagency Governmental Perspective

    Science.gov (United States)

    Cavallaro, N.; Shrestha, G.; Stover, D. B.; Zhu, Z.; Ombres, E. H.; Deangelo, B.

    2015-12-01

    The 2nd State of the Carbon Cycle Report (SOCCR-2) is focused on US and North American carbon stocks and fluxes in managed and unmanaged systems, including relevant carbon management science perspectives and tools for supporting and informing decisions. SOCCR-2 is inspired by the US Carbon Cycle Science Plan (2011) which emphasizes global scale research on long-lived, carbon-based greenhouse gases, carbon dioxide and methane, and the major pools and fluxes of the global carbon cycle. Accordingly, the questions framing the Plan inform this report's topical roadmap, with a focus on US and North America in the global context: 1) How have natural processes and human actions affected the global carbon cycle on land, in the atmosphere, in the oceans and in the ecosystem interfaces (e.g. coastal, wetlands, urban-rural)? 2) How have socio-economic trends affected the levels of the primary carbon-containing gases, carbon dioxide and methane, in the atmosphere? 3) How have species, ecosystems, natural resources and human systems been impacted by increasing greenhouse gas concentrations, the associated changes in climate, and by carbon management decisions and practices? To address these aspects, SOCCR-2 will encompass the following broad assessment framework: 1) Carbon Cycle at Scales (Global Perspective, North American Perspective, US Perspective, Regional Perspective); 2) Role of carbon in systems (Soils; Water, Oceans, Vegetation; Terrestrial-aquatic Interfaces); 3) Interactions/Disturbance/Impacts from/on the carbon cycle. 4) Carbon Management Science Perspective and Decision Support (measurements, observations and monitoring for research and policy relevant decision-support etc.). In this presentation, the Carbon Cycle Interagency Working Group and the U.S. Global Change Research Program's U.S. Carbon Cycle Science Program Office will highlight the scientific context, strategy, structure, team and production process of the report, which is part of the USGCRP's Sustained

  20. Exomoon Climate Models with the Carbonate-Silicate Cycle and Viscoelastic Tidal Heating

    CERN Document Server

    Forgan, Duncan

    2016-01-01

    The habitable zone for exomoons with Earth-like properties is a non-trivial manifold, compared to that of Earth-like exoplanets. The presence of tidal heating, eclipses and planetary illumination in the exomoon energy budget combine to produce both circumstellar and circumplanetary habitable regions. Analytical calculations suggest that the circumplanetary habitable region is defined only by an inner edge (with its outer limits determined by orbital stability). Subsequent calculations using 1D latitudinal climate models indicated that the combined effect of eclipses and ice-albedo feedback can produce an outer edge to the circumplanetary habitable zone. But is this outer edge real, or an artefact of the climate model's relative simplicity? We present an upgraded 1D climate model of Earth-like exomoon climates, containing the carbonate-silicate cycle and viscoelastic tidal heating. We conduct parameter surveys of both the circumstellar and circumplanetary habitable zones, and we find that the outer circumplane...

  1. INFLUENCE OF THERMAL CYCLING ON MICROSTRUCTURE AND THERMAL EXPANSION OF CARBON FIBRES/COPPER COMPOSITES

    Directory of Open Access Journals (Sweden)

    Pavol Štefánik

    2009-06-01

    Full Text Available The preparation of copper matrix reinforced by high modulus carbon fibres (Thornel K1100 as well as the microstructure and dilatation changes during thermocycling is presented.Unidirectional composites with two types of matrix - pure copper and/or copper alloy with 0.2 wt. % of chromium - were thermally cycled between 30-600 °C three times.The composite with pure Cu exhibited larger voids and weak interfacial bonding. Due to the chemical reaction with K1100 fibres a reactive interfacial bonding has been formed. During thermocycling the hysteresis, but no large disintegration was observed. The coefficients of thermal expansion (CTEs strongly depend on fibre orientation. In direction parallel to the fibre orientation in the temperature range of 220-500°C CTEs were very low (0.7-1.0x10-6/K, but in perpendicular direction the CTEs were higher than that of pure copper.

  2. A SIMULATION OF CO2 UPTAKE IN A THREE DIMENSIONAL OCEAN CARBON CYCLE MODEL

    Institute of Scientific and Technical Information of China (English)

    金心; 石广玉

    2001-01-01

    A three-dimensional ocean carbon cycle model which is a general circulation model couple.d with simple biogeochemical processes is used to simulate CO2 uptake by the ocean. The OGCM used is a modified version of the Geophysical Fluid Dynamics Laboratory modular ocean model (MOM2). The ocean chemistry and a simple ocean biota model are included. Principal variables are .total CO2, alkalinity and phosphate. The vertical profile of POC flux observed by sediment traps is adopted, the rain ratio, a ratio of production rate of calcite against that of POC, and the bio-production efficiency should be 0. 06 and 2 per year, separately. The uptake of anthropogenicCO2 by the ocean is studied. Calculated oceanic uptake of anthropogenic CO2 during the 1980s is 2. 05× 10 15g (Pg) per year. The regional distributions of global oceanic CO2 are discussed.

  3. Ocean and Atmospheric Profiling Lidar Observations and Its Link to Ocean Carbon Cycle

    Science.gov (United States)

    Hu, Yongxiang

    2010-01-01

    This study introduces space-based ocean and atmospheric profiling lidar for improving modeling and understanding of ocean carbon cycle. Unique measurements from space-based profiling lidars include (1) the global ocean surface mean square slope measurements for improving air-sea turbulence exchange estimates; (2) the backscatter and beam attenuation measurements for improving the global estimate of partial pressure of CO2 of the ocean with the reduction of uncertainties in primary productivity estimates. Global statistics of CALIOP integrated ocean subsurface backscatter measurements of coastal waters will be presented. The study will also assess the impact of CALIOP on the uncertainty reduction of primary productivity and the improvement of CO2 partial pressure estimates. Ocean surface roughness statistics, its applications in air-sea interaction and its comparisons with other measurements will also be presented

  4. Biogeochemical Cycles of Carbon and Sulfur on Early Earth (and on Mars?)

    Science.gov (United States)

    DesMarais, D. J.

    2004-01-01

    The physical and chemical interactions between the atmosphere, hydrosphere, geosphere and biosphere can be examined for elements such as carbon (C) and sulfur (S) that have played central roles for both life and the environment. 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. 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. These multiple roles of C and S interact across a network of elemental reservoirs interconnected by physical, chemical and biological processes. These networks are termed biogeochemical C and S cycles.

  5. 14C Activity and Global Carbon Cycle Changes over the Past 50,000 Years

    Science.gov (United States)

    Hughen, K.; Lehman, S.; Southon, J.; Overpeck, J.; Marchal, O.; Herring, C.; Turnbull, J.

    2004-01-01

    A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation.

  6. Indanthrone derived disordered graphitic carbon as promising insertion anode for sodium ion battery with long cycle life

    International Nuclear Information System (INIS)

    We report facile, one step synthesis of disordered graphitic carbon by high temperature (1000 °C) pyrolysis of indanthrone dye (ID). The pyrolysed carbon is disordered in nature and the same is clearly evidenced by various analytical techniques like X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy. Na-insertion properties of such indanthrone dye derived disordered graphitic carbon (IDDGC) is evaluated in half-cell assembly (Na/IDDGC). The test cell delivered a reversible capacity of ∼160 mAh g−1 at current density of 25 mA g−1. In addition, excellent cycling profiles are noted for such IDDGC, which retains ∼67% of initial reversible capacity after 500 cycles. The present study clearly highlights the importance of disorder in the graphitic carbon for efficient Na-ion storage

  7. Life cycle inventory analysis of bio-based polyester production by genetically engineered bacteria from renewable carbon sources

    Energy Technology Data Exchange (ETDEWEB)

    Tsuge, T.; Akiyama, M.; Doi, Y. [Tokyo Inst. of Technology, SORST Group of Japan Science and Technology Corp., Tokyo (Japan). Dept. of Innovative and Engineered Materials]|[RIKEN Inst., Saitama (Japan). Polymer Chemistry Lab

    2003-07-01

    Since the oil crisis in the 1970s, polydroxyalkanoates (PHAs) have been considered to be an environmentally sound substitute for oil because they are biodegradable, leave no waste and are made from renewable resources such as glucose, sucrose and vegetable oils. This study was conducted to predict the production cost of a polydroxyalkanoates (PHA) copolyester using soybean oil as a carbon source. PHAs are used as biodegradable thermoplastics. They are bio-based polymers which can be made from various microorganisms. This simulation study used a recombinant strain of Ralstonia eutropha harboring a PHA synthase gene from Aeromonas caviae. Life cycle inventories of energy consumption and carbon dioxide emissions were calculated and compared with other microbial production of poly3-hydroxybutyrate from glucose as a carbon source. It was determined that life cycle inventories of energy consumption and carbon dioxide emissions of bio-based polymers are significantly lower than those of typical petrochemical polymers. 10 refs., 3 tabs., 4 figs.

  8. International Workshop on Carbon Cycling and Coral Reef Metabolism; Sangosho no tanso junkan ni kansuru kokusai workshop hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-10-16

    The paper described the International Workshop on Carbon Cycling and Coral Reef Metabolism which was held at Miyako-jima, Okinawa Pref. on October 17-24, 1995. In the workshop, researchers got together which are involved in marine chemistry, marine biology, coral ecology, and environmental science, and discussed the carbon cycling and metabolism of coral reef. Discussions were made on what the coral reef ecosystem is, and what the definition of a sink or a source for CO2 is. Also discussed were scales of how much time and space should be considered to make these issues clear. Further, it was proposed that it was necessary to investigate carbon balance of both the whole system and the components of the system and to keep track of mass transfer among neighboring components of the system. Seventeen presentations were given. The workshop obtained a definite consensus on carbon balance of the coral reef system. 123 refs., 39 figs., 9 tabs.

  9. Energy generation and the sulfur-carbon cycles: Final technical report for period March 1981 thru February 1985

    International Nuclear Information System (INIS)

    The aim of this research was to understand the role of anaerobic bacteria in natural and man-influenced carbon cycles in nature. The major goal was to elucidate how sulfur metabolism influenced organic decomposition in aquatic sediments. The research compared these processes in two different anaerobic ecosystems: the sulfate-depleted sediments of Lake Mendota, Wisconsin and the sulfate-saturated sediments of Great Salt Lake, Utah. The approach was both ecological and physiological, and employed both in situ characterization of carbon and sulfur metabolism with radiotracers and laboratory species isolation-characterization studies with pure and defined mixed cultures to demonstrate the prevalent environmental paths of carbon electrons, and sulfur during the anaerobic decomposition of organic matter. The significance of this research encompassed fundamental knowledge of the carbon sulfur cycles, applied knowledge on the microbial genesis of flammable gas and oil and extended knowledge on the diversity and metabolic activity of obligately anaerobic bacteria in nature. 13 refs

  10. Microbial carbon cycling in Lost City hydrothermal chimneys and other serpentinite-hosted ecosystems (Invited)

    Science.gov (United States)

    Brazelton, W. J.; Lang, S. Q.; Morrill, P. L.; Twing, K. I.; Crespo-Medina, M.; Morgan-Smith, D.; Früh-Green, G. L.; Schrenk, M. O.

    2013-12-01

    Ultramafic rocks formed in the Earth's mantle and uplifted into the crust represent an immense but poorly described reservoir of carbon. The biological availability of this rock-hosted carbon reservoir is unknown, but the set of geochemical reactions known as serpentinization can mobilize carbon from the subsurface and trigger the growth of dense microbial communities. Serpentinite-hosted ecosystems such as the chimney biofilms of the Lost City hydrothermal field can support dense populations of bacteria and archaea fueled by the copious quantities of H2 and methane (CH4) released by serpentinization (1-5). The metabolic pathways involved, however, remain unknown, and conventional interpretations of genomic and experimental data are complicated by the unusual carbon speciation in these environments. Carbon dioxide is scarce due to the highly reducing, high pH conditions. Instead, the predominant forms of carbon are CH4 and formate (5). Despite its natural abundance, however, direct evidence for CH4-derived biomass is lacking (1,4,5), and the role of formate is potentially significant but largely unexplored (1,5). To gain a more generalized perspective of carbon cycling in serpentinite-hosted ecosystems, we have recently investigated fluids and rocks collected from serpentinizing ophiolites in California, Canada, and Italy. Our results point to potentially H2-utilizing, autotrophic Betaproteobacteria thriving in shallow, oxic-anoxic transition zones and anaerobic Clostridia inhabiting anoxic, subsurface zones (1,6). The carbon sources utilized by the Clostridia are unknown, but preliminary metagenomic evidence is consistent with a fermentation-style metabolic strategy that may be conducive to an oxidant-limited, subsurface environment. Curiously, despite the abundance of H2 and CH4 in these continental springs, none of the geochemical, genomic, or experimental results obtained thus far contain any evidence for biological methanogenesis (1,6). This is in stark

  11. On the peritidal cycles and their diagenetic evolution in the Lower Jurassic carbonates of the Calcare Massiccio Formation (Central Apennines)

    OpenAIRE

    Brandano Marco; Corda Laura; Tomassetti Laura; Testa Davide

    2015-01-01

    This paper shows the environmental changes and high-frequency cyclicity recorded by Lower Jurassic shallow-water carbonates known as the Calcare Massiccio Formation which crop out in the central Apennines of Italy. Three types of sedimentary cycle bounded by subaerial erosion have been recognized: Type I consists of a shallowing upward cycle with oncoidal floatstones to rudstones passing gradationally up into peloidal packstone alternating with cryptoalgal laminites and often bounded by desic...

  12. Climate-induced interannual variability of marine primary and export production in three global coupled climate carbon cycle models

    Directory of Open Access Journals (Sweden)

    B. Schneider

    2008-04-01

    Full Text Available Fully coupled climate carbon cycle models are sophisticated tools that are used to predict future climate change and its impact on the land and ocean carbon cycles. These models should be able to adequately represent natural variability, requiring model validation by observations. The present study focuses on the ocean carbon cycle component, in particular the spatial and temporal variability in net primary productivity (PP and export production (EP of particulate organic carbon (POC. Results from three coupled climate carbon cycle models (IPSL, MPIM, NCAR are compared with observation-based estimates derived from satellite measurements of ocean colour and results from inverse modelling (data assimilation. Satellite observations of ocean colour have shown that temporal variability of PP on the global scale is largely dominated by the permanently stratified, low-latitude ocean (Behrenfeld et al., 2006 with stronger stratification (higher sea surface temperature; SST being associated with negative PP anomalies. Results from all three coupled models confirm the role of the low-latitude, permanently stratified ocean for anomalies in globally integrated PP, but only one model (IPSL also reproduces the inverse relationship between stratification (SST and PP. An adequate representation of iron and macronutrient co-limitation of phytoplankton growth in the tropical ocean has shown to be the crucial mechanism determining the capability of the models to reproduce observed interactions between climate and PP.

  13. The scavenging processes controlling the seasonal cycle in Arctic sulphate and black carbon aerosol

    Directory of Open Access Journals (Sweden)

    J. Browse

    2012-08-01

    Full Text Available The seasonal cycle in Arctic aerosol is typified by high concentrations of large aged anthropogenic particles transported from lower latitudes in the late Arctic winter and early spring followed by a sharp transit