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  • 1.
    Bastviken, David
    et al.
    Linköping University, Department of Thematic Studies, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Ejlertsson, Jörgen
    Linköping University, Department of Thematic Studies, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Tranvik, Lars
    Department of Limnology, Uppsala University, Uppsala, Sweden.
    Measurement of methane oxidation in lakes: A comparison of methods2002In: Environmental Science & Technology, ISSN 0013-936X, Vol. 36, no 15, p. 3354-3361Article in journal (Refereed)
    Abstract [en]

    Methane oxidation in lakes constrains the methane emissions to the atmosphere and simultaneously enables the transfer of methane carbon to pelagic food webs, Several different methods have been used to estimate methane oxidation, but these methods have not previously been compared. In this study, we present methane oxidation estimates from three different lakes during summer and winter, using methods based on the transformation of added (CH4)-C-14, the fractionation of natural methane C-13, and the mass balance modeling of concentration gradients, All methods yielded similar results, including similar differences between lakes and seasons. Average methane oxidation rates varied from 0.25 to 81 mg of C m(-2) d(-1) and indicate that the three methods are comparable, although they to some extent take different processes into account. Critical issues as well as drawbacks and advantages with the used methods are thoroughly discussed. We conclude that methods using the stable isotope or mass balance modeling approach represent promising alternatives, particularly for studies focusing on ecosystem-scale carbon metabolism.

  • 2.
    Carpenter, Stephen R.
    et al.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
    Cole, Jonathan J.
    Institute of Ecosystem Studies, Millbrook, New York, USA.
    Pace, Michael L.
    Institute of Ecosystem Studies, Millbrook, New York, USA.
    Van de Bogert, Matthew
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA; Institute of Ecosystem Studies, Millbrook, New York, USA.
    Bade, Darrren L.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA; Institute of Ecosystem Studies, Millbrook, New York, USA.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Gille, Caitlin M.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
    Hodgson, James R.
    Department of Biology, St. Norbert College, De Pere, Wisconsin, USA.
    Kitchell, James F.
    Center for Limnology, University of Wisconsin, Madison, Wisconsin, USA.
    Kritzberg, Emma S.
    Department of Ecology/Limnology, Lund University, Lund, Sweden.
    Ecosystem subsidies: Terrestrial support of aquatic food webs from C-13 addition to contrasting lakes2005In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 86, no 10, p. 2737-2750Article in journal (Refereed)
    Abstract [en]

    Whole-lake additions of dissolved inorganic C-13 were used to measure allochthony (the terrestrial contribution of organic carbon to aquatic consumers) in two unproductive lakes (Paul and Peter Lakes in 2001), a nutrient-enriched lake (Peter Lake in 2002), and a dystrophic lake (Tuesday Lake in 2002). Three kinds of dynamic models were used to estimate allochthony: a process-rich, dual-isotope flow model based on mass balances of two carbon isotopes in 12 carbon pools; simple univariate time-series models driven by observed time courses of delta(13)CO(2); and multivariate autoregression models that combined information from time series of delta(13)C in several interacting carbon pools. All three models gave similar estimates of allochthony. In the three experiments without nutrient enrichment, flows of terrestrial carbon to dissolved and particulate organic carbon, zooplankton, Chaoborus, and fishes were substantial. For example, terrestrial sources accounted for more than half the carbon flow to juvenile and adult largemouth bass, pumpkinseed sunfish, golden shiners, brook sticklebacks, and fathead minnows in the unenriched experiments. Allochthony was highest in the dystrophic lake and lowest in the nutrient-enriched lake. Nutrient enrichment of Peter Lake decreased allochthony of zooplankton from 0.34-0.48 to 0-0.12, and of fishes from 0.51-0.80 to 0.25-0.55. These experiments show that lake ecosystem carbon cycles, including carbon flows to consumers, are heavily subsidized by organic carbon from the surrounding landscape.

  • 3.
    Dutta, Anupam
    et al.
    Univ Vaasa, Finland.
    Bouri, Elie
    Holy Spirit Univ Kaslik, Lebanon.
    Junttila, Juha
    Univ Jyvaskyla, Finland.
    Uddin, Gazi Salah
    Linköping University, Department of Management and Engineering, Economics. Linköping University, Faculty of Arts and Sciences.
    Does corn market uncertainty impact the US ethanol prices?2018In: Global Change Biology Bioenergy, ISSN 1757-1693, E-ISSN 1757-1707, Vol. 10, no 9, p. 683-693Article in journal (Refereed)
    Abstract [en]

    The growing interest in biofuel as a green energy source has intensified the linkages between corn and ethanol markets, especially in the United States that represents the largest producing and exporting country for ethanol in the world. In this study, we examine the effect of corn market uncertainty on the price changes of US ethanol applying a set of GARCH-jump models. We find that the US ethanol price changes react positively to the corn market volatility shocks after controlling for the effect of oil price uncertainty. In addition, we document that the impact of corn price volatility on the US ethanol prices appears to be asymmetric. Specifically, only the positive corn market volatility shocks are found to influence the ethanol market returns. Our findings also suggest that time-varying jumps do exist in the ethanol market.

  • 4.
    Erkkila, Kukka-Maaria
    et al.
    Univ Helsinki, Finland.
    Ojala, Anne
    Univ Helsinki, Finland.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Biermann, Tobias
    Lund Univ, Sweden.
    Heiskanen, Jouni J.
    Univ Helsinki, Finland.
    Lindroth, Anders
    Lund Univ, Sweden.
    Peltola, Olli
    Univ Helsinki, Finland.
    Rantakari, Miitta
    Univ Helsinki, Finland; Univ Helsinki, Finland.
    Vesala, Timo
    Univ Helsinki, Finland.
    Mammarella, Ivan
    Univ Helsinki, Finland.
    Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 2, p. 429-445Article in journal (Refereed)
    Abstract [en]

    Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2) and methane (CH4) to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, k CC (introduced by Cole and Caraco, 1998), for calculating diffusive flux with the boundary layer method (BLM). We compared CH4 and CO2 fluxes from BLM with k CC and two other gas transfer velocities (k TE and k HE), which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC) and floating chamber (FC) fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajarvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model k TE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajarvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference between CO2 fluxes from shallower and deeper areas. We highlight that while all flux measurement methods have their pros and cons, it is important to carefully think about the chosen method and measurement interval, as well as their effects on the resulting flux.

  • 5. Order onlineBuy this publication >>
    Genero, Magalí Martí
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Microbial Communities in Boreal Peatlands: Responses to Climate Change and Atmospheric Nitrogen and Sulfur Depositions2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Peatlands play a substantial role in regulating the global carbon balance and concentrations of the greenhouse gases CO2 and CH4 in the atmosphere, and are thus of utmost importance from a climate change perspective. Any changes of peatland functions due to natural or anthropogenic perturbations may result in changes in these ecosystem services. Soil microbial communities are essential drivers of biogeochemical processes, including the carbon cycle. In order to fully understand the effect of environmental perturbations on peatland functions, it is essential to understand how microbial communities are affected. The aim of the research presented in this thesis was to investigate the responses of the peat microbial communities to climate change and increased precipitation of nitrogen(N) and sulfur (S) compounds. High-throughput sequencing approaches were used to investigate the taxonomic and functional composition of microbial communities, and quantitative PCR was used to specifically target the methanogen community. Two field studies including three ombrotrophic peatlands each that differed in climatological conditions and atmospheric N and S depositions, were used to investigate and compare the effect of large- and local-scale environmental conditions on microbial communities. The results show that the variation in geo-climatological (temperature and precipitation) and atmospheric deposition conditions along the latitudinal gradient modulate the peat microbial community composition and the abundance of active methanogens to a greater extent thansite-related microhabitats. Furthermore, a tight coupling between the plant community composition of a site and the composition of its microbial community was observed, and was found to be mainly driven by plants rather than microorganisms. These co-occurrence networks are strongly affected by seasonal climate variability and the interactions between species in colder areas are more sensitive to climate change. The long-term effects of warming and increased N and S depositions on the peat microbial communities were further investigated using an 18-year in-situ peatland experiment simulating these perturbations. The impacts of each of these perturbations on the microbial community were found to either multiply or counteract one another, with enhanced N deposition being the most important factor. While the long-term perturbations resulted in a substantial shift in the taxonomic composition of microbial communities, only minor changes occurred in genome-encoded functional traits, indicating a functional redundancy. This could act as a buffer maintaining ecosystem functioning when challenged by multiple stressors, and could limit future changes in greenhouse gases and carbonexchange.

    List of papers
    1. Nitrogen and methanogen community composition within and among three Sphagnum dominated peatlands in Scandinavia
    Open this publication in new window or tab >>Nitrogen and methanogen community composition within and among three Sphagnum dominated peatlands in Scandinavia
    Show others...
    2015 (English)In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 81, p. 204-211Article in journal (Refereed) Published
    Abstract [en]

    Ombrotrophic raised bogs are nutrient poor acidic peatlands accumulating organic matter. They are widely spread on northern latitudes and are substantial sources of methane emissions to the atmosphere being of great concern from a climate change perspective. We investigated the methanogen community composition along microtopographic gradients within three bogs in Scandinavia, receiving different amounts of nitrogen precipitation. Methanogenic community analyses by terminal restriction fragment length polymorphism of the mcrA gene showed different profiles among the three sites, while no in- fluence of the microtopographic gradients was observed. Peat temperature and dissolved organic carbon were the major edaphic variables explaining 38% of the variation of the methanogenic community di- versity among the bogs. The family Methanoregulaceae (hydrogenotrophic methanogens) showed the largest relative proportion and highest activity in all three sites. Quantitative PCR of the mcrA gene and transcripts showed that the most northern site, receiving the lowest atmospheric nitrogen load, had significantly lower abundance and activity of methanogens (4.7 106 and 2.4 104 mcrA copies per gram of soil, respectively), compared to the most southern site (8.2 107 and 4.6 105 mcrA copies per gram of soil, respectively), receiving the highest nitrogen load. No patterns of the mcrA gene and tran- script abundances were observed along the microtopography. The results indicated that the difference in occurrence of methanogens is mainly due to geoclimatological conditions rather than site intrinsic microtopographic variation. The study further suggests that environmental changes on the site intrinsic topography will not affect the methanogenic activity, while increasing average temperatures in Scan- dinavian ombrotrophic raised bogs might contribute to an increase of the methanogenic archaeal activity resulting in an increase of methane production. 

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keywords
    Methanogenic arhcaea, mcrA gene, peatland, microtopography, T-RFLP, qPCR
    National Category
    Ecology Microbiology Environmental Sciences
    Identifiers
    urn:nbn:se:liu:diva-113846 (URN)10.1016/j.soilbio.2014.11.016 (DOI)000350524700024 ()
    Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
    2. Strong long-term interactive effects of warming and enhanced nitrogen and sulphur deposition on the abundance of active methanogens in a boreal oligotrophic mire
    Open this publication in new window or tab >>Strong long-term interactive effects of warming and enhanced nitrogen and sulphur deposition on the abundance of active methanogens in a boreal oligotrophic mire
    Show others...
    2019 (English)In: Mires and Peat, ISSN 1819-754X, E-ISSN 1819-754X, Vol. 24, p. 1-14, article id 29Article in journal (Refereed) Published
    Abstract [en]

    Peatlands play a key role in the carbon cycle by being a considerable source of atmospheric methane. Thus, an understanding of the microbial production of methane is important in relation to environmental changes of peatlands. We applied real-time PCR on the mcrA gene and transcript to investigate the peat methanogen community response to the combined effect of 18 years of simulated warming and deposition of nitrogen (N) and sulphur (S) at a boreal oligotrophic mire in Sweden. The long-term effects of the experimental treatments on the methanogens was highly dependent on interactions between the treatment factors Enhanced N deposition amplified the effect of warming, resulting in a further increase of the abundance of active methanogens. The effect of the perturbations was modulated by the depth horizon, with the strongest effect at the water level, where the interaction between enhanced N and S deposition, and warming, resulted in an increase of active methanogens. These results indicate that increasing average temperatures and simultaneously higher N deposition rates will substantially increase the methanogenic activity in northern ombrotrophic peatlands. These findings strongly highlight the importance of accounting for any possible interactive perturbation effects when investigating the response of peat methanogens to environmental change.

    Place, publisher, year, edition, pages
    Dundee, United Kingdom: Mires and Peat, 2019
    Keywords
    field experiment; mcrA gene and transcript; nitrogen; real-time PCR; warming
    National Category
    Ecology
    Identifiers
    urn:nbn:se:liu:diva-162895 (URN)10.19189/MaP.2019.OMB.398 (DOI)000500515100007 ()
    Note

    Funding Agencies|Swedish Research Council FORMASSwedish Research CouncilSwedish Research Council Formas [2007-666]; Swedish Research Council (VR)Swedish Research Council [621-2011-4901]

    Available from: 2020-01-02 Created: 2020-02-19 Last updated: 2020-02-17Bibliographically approved
  • 6.
    Glaas, Erik
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Thematic Studies, Centre for Climate Science and Policy Research.
    Neset, Tina Simone
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Thematic Studies, Centre for Climate Science and Policy Research.
    Kjellström, Erik
    Linköping University, Department of Thematic Studies, Centre for Climate Science and Policy Research. Swedish Meteorological and Hydrological Institute (SMHI) Norrköping, Sweden.
    Almås, Anders-Johan
    SINTEF Building and Infrastructure, Oslo, Norway.
    Increasing house owners adaptive capacity: Compliancebetween climate change risks and adaptation guidelines in Scandinavia2015In: Urban Climate, ISSN 2212-0955, E-ISSN 2212-0955, Vol. 14, no 1, p. 41-51Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to intensify weather related risks affecting the existing buildingstock. To increase the understanding of how the capacity among individual house ownersto mitigate such risks can be improved, this study analyses the compliance between anticipatedclimate risks and existing adaptation guidelines to house owners in Denmark,Norway and Sweden. The assessment of climate risks is based on a review of climatechange and building research literature. The compilation of available guidelines is basedon an assessment of information from government authorities, municipalities as well asinsurance companies and organizations. Results reveal a high compliance between availableguidelines and risks for already experienced weather risks, while somewhat new risksfrom anticipated climate change impacts are less covered. To better facilitate adaptiveresponses, further adaptation guidelines would earn from explicitly targeting house owners,as well as highlighting relationships between anticipated climate impacts, existingweather risks and individual management practices. Public–private cooperation is identifiedas an important means for making information more accessible and easily available.

  • 7.
    Golebiowska, Izabela
    et al.
    Univ Warsaw, Poland.
    Opach, Tomasz
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Norwegian Univ Sci and Technol NTNU, Norway.
    Rod, Jan Ketil
    Norwegian Univ Sci and Technol NTNU, Norway.
    Breaking the Eyes: How Do Users Get Started with a Coordinated and Multiple View Geovisualization Tool?2020In: Cartographic Journal, ISSN 0008-7041, E-ISSN 1743-2774Article in journal (Refereed)
    Abstract [en]

    Maps are frequently combined with data displays in the form of coordinated and multiple views (CMV). Although CMV are valuable geovisualization tools, novice users may find them complex and thus require explanation. However, no tutorial guidelines have been developed that indicate what is helpful in understanding CMV geovisualization tools. We therefore conducted a study on the learnability of a CMV tool, informed with eye-tracking data, talk-aloud and interaction logs. We have investigated how untrained users work with a CMV geovisualization tool. The study revealed that: (1) despite their initial confusion, users found the tested tool pleasant to play with while getting to grips with how dynamic brushing works, (2) when examining the tools interface, participants mainly looked freely at explanatory elements, such as labels and the legend, but they explored interactive techniques only to a limited degree. We conclude with tips about tutorial design and layout design for CMV tools.

  • 8.
    Jansson, Tobias
    Linköping University, The Tema Institute, Department of Water and Environmental Studies, Department of Geography.
    Provkunskaper: Vilka kunskaper testas i geografiprov?2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna uppsats handlar om vilka olika kunskapsformer som testas i skriftliga prov i geografi på gymnasiet och om hur detta förhåller sig till betygskriterierna. För att besvara detta har tio geografilärares prov analyserats med hjälp av Blooms reviderade taxonomi. Tidigare forskning visar att prov i SO-ämnen nästan enbart testar minneskunskaper. Denna studie bekräftar delvis detta då de analyserade proven domineras av frågor som testar att minnas. Samtidigt finns det en variation i vilka kunskapsformer som testas. Även om lärarna främst testar att minnas fakta- och begreppskunskap, testar också andra kunskapsformer, om än i varierande grad. Det handlar främst om uppgifter som testar att förstå fakta- och begreppskunskap, men även att tillämpa, analysera och värdera begreppskunskap testas, liksom att tillämpa procedurkunskap.

     

    Det finns en viss överensstämmelse mellan lärarnas prov och betygskriterierna, men en tydlig skillnad är att lärarna i studien i högre utsträckning testar att minnas än vad som uttrycks i betygskriterierna. Detta gäller särskilt för de högre betygen. Det är inte heller alla lärare som testar de högre kognitiva processerna, som att tillämpa, analysera och värdera, vilka uttrycks för de högre betygen. Detta innebär en variation mellan lärarna i vad deras prov testar och också att validiteten i proven varierar. En del lärares prov testar ganska väl kunskaper motsvarande betygskriterierna medan andras gör det i mindre grad. Eftersom prov används som underlag för betygsättningen innebär det också att eleverna bedöms på olika grunder.

     

    Det kan finnas olika förklaringar till betoningen på minnesfrågor i proven. Tidigare forskning pekar på svårigheter att tolka kriterierna eller på traditionen. En annan förklaring är bristen på tid, lärarna behöver tid för att utforma prov med mer komplexa frågor och för att rätta dem.

  • 9.
    Karlson, Martin
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. Linköping University, Centre for Climate Science and Policy Research, CSPR.
    Gålfalk, Magnus
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Crill, Patrick
    Stockholm Univ, Sweden.
    Bousquet, Philippe
    LSCE, France.
    Saunois, Marielle
    LSCE, France.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Delineating northern peatlands using Sentinel-1 time series and terrain indices from local and regional digital elevation models2019In: Remote Sensing of Environment, ISSN 0034-4257, E-ISSN 1879-0704, Vol. 231, article id UNSP 111252Article in journal (Refereed)
    Abstract [en]

    The spatial extent of northern peatlands remains highly uncertain in spite of rapidly developing satellite observation datasets. This is limiting progress in the understanding of fundamental biogeochemical processes, such as the global carbon (C) cycle and climate feedback effects on C fluxes. In this study, we evaluated the capabilities of two new satellite datasets that enable regional scale mapping of peatland extent at high spatial resolution, including Sentinel-1 synthetic aperture radar (SAR) and the Arctic digital elevation model (ArcticDEM). Terrain indices and temporal features derived from these datasets provided input to Random Forest models for delineating four main land cover classes (forest, open upland, water and peatland) in an area in northern Sweden consisting of both lowland and mountainous terrain. The contribution of ArcticDEM to the classification accuracy was assessed by comparing the results with those derived when a high quality LiDAR based DEM (LiDEM) was used as alternative model input. This study shows that multi-seasonal SAR alone can produce reasonable classification results in terms of overall accuracy (OA; 81.6%), but also that it has limitations. The inclusion of terrain indices improved classification performance substantially. OA increased to 87.5% and 90.9% when terrain indices derived from ArcticDEM and LiDEM were included, respectively. The largest increase in accuracy was achieved for the peatland class, which suggests that terrain indices do have the ability to capture the features in the geographic context that aid the discrimination of peatland from other land cover classes. The relatively small difference in classification accuracy between LiDEM and ArcticDEM is encouraging since the latter provides circumpolar coverage. Thus, the combination of Sentinel-1 time series and terrain indices derived from ArcticDEM presents opportunities for substantially improving regional estimates of peatland extent at high latitudes.

    The full text will be freely available from 2021-06-17 12:39
  • 10.
    Kylin, Henrik
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Bouwman, Hindrik
    North-West University, South Africa.
    BIOLOGICAL FACTORS REGULATE THE UPTAKE OF AIRBORNE POPS IN “PLANTS” AND THEDEPOSITION OF POPS TO REMOTE TERRESTRIAL ECOSYSTEMS2016In: Organohalogen Compounds, ISSN 1026-4892, Vol. 78, p. 176-179, article id 8.4015Article in journal (Refereed)
  • 11.
    Lauerwald, R.
    et al.
    Université Libre de Bruxelles, Bruxelles, Belgium.
    Regnier, P.
    Université Libre de Bruxelles, Bruxelles, Belgium.
    Figueiredo, V
    University Federal of Rio de Janeiro, Rio de Janeiro, Brazil.
    Enrich Prast, Alex
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. University Federal of Rio de Janeiro, Rio de Janeiro, Brazil.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Lehner, B.
    McGill University, Montreal, Canada.
    Maavara, T.
    Lawrence Berkeley National Laboratory, Berkeley, USA.
    Raymond, P.
    Yale School of Forestry and Environmental Studies, New Haven, USA.
    Natural lakes are a minor global source of N2O to the atmosphere2019In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224Article in journal (Refereed)
    Abstract [en]

    Natural lakes and reservoirs are important, yet not well constrained sources of greenhouse gasses to the atmosphere. In particular for N2O emissions, a huge variability is observed in the few, observation‐driven flux estimates that have been published so far. Recently, a process‐based, spatially explicit model has been used to estimate global N2O emissions from more than 6,000 reservoirs based on nitrogen (N) and phosphorous inflows and water residence time. Here, we extend the model to a dataset of 1.4 million standing water bodies comprising natural lakes and reservoirs. For validation, we normalized the simulated N2O emissions by the surface area of each water body and compared them against regional averages of N2O emission rates taken from the literature or estimated based on observed N2O concentrations. We estimate that natural lakes and reservoirs together emit 4.5±2.9 Gmol N2O‐N yr‐1 globally. Our global scale estimate falls in the far lower end of existing, observation‐driven estimates. Natural lakes contribute only about half of this flux, although they contribute 91% of the total surface area of standing water bodies. Hence, the mean N2O emission rates per surface area are substantially lower for natural lakes than for reservoirs with 0.8±0.5 mmol N m‐2yr‐1 vs. 9.6±6.0 mmol N m‐2yr‐1, respectively. This finding can be explained by on average lower external N inputs to natural lakes. We conclude that upscaling based estimates, which do not distinguish natural lakes from reservoirs, are prone to important biases.

  • 12.
    Pangala, Sunitha R.
    et al.
    Open University, England; University of Lancaster, England.
    Enrich Prast, Alex
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences. University of Federal Rio de Janeiro, Brazil.
    Basso, Luana S.
    IPEN, Brazil.
    Bittencourt Peixoto, Roberta
    University of Federal Rio de Janeiro, Brazil.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Hornibrook, Edward R. C.
    University of Bristol, England; University of British Columbia, Canada.
    Gatti, Luciana V.
    IPEN, Brazil; National Institute Space Research INPE, Brazil.
    Marotta, Humberto
    University of Federal Fluminense, Brazil.
    Silva Braucks Calazans, Luana
    University of Federal Rio de Janeiro, Brazil.
    Monica Sakuragui, Cassia
    University of Federal Rio de Janeiro, Brazil.
    Rodrigues Bastos, Wanderley
    Federal University of Rondonia, Brazil.
    Malm, Olaf
    University of Federal Rio de Janeiro, Brazil.
    Gloor, Emanuel
    University of Leeds, England.
    Bharat Miller, John
    NOAA, CO 80305 USA.
    Gauci, Vincent
    Open University, England.
    Large emissions from floodplain trees close the Amazon methane budget2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 552, no 7684, p. 230-+Article in journal (Refereed)
    Abstract [en]

    Wetlands are the largest global source of atmospheric methane (CH4)(1), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain(2,3), the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling(4,5), pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests(6) and tropical peat swamp forests(7), representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (delta C-13) of -66.2 +/- 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 +/- 1.8 to 21.2 +/- 2.5 teragrams of CH4 a year, in addition to the 20.5 +/- 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a topdown regional estimate of CH4 emissions of 42.7 +/- 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010-2013. We find close agreement between our top-down and combined bottom-up estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources.

  • 13.
    Podgrajsek, E.
    et al.
    Uppsala University, Sweden.
    Sahlee, E.
    Uppsala University, Sweden.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Natchimuthu, Sivakiruthika
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Kljun, N.
    Swansea University, Wales.
    Chmiel, H. E.
    Uppsala University, Sweden.
    Klemedtsson, L.
    University of Gothenburg, Sweden.
    Rutgersson, A.
    Uppsala University, Sweden.
    Methane fluxes from a small boreal lake measured with the eddy covariance method2016In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, p. S41-S50Article in journal (Refereed)
    Abstract [en]

    Fluxes of methane, CH4, were measured with the eddy covariance (EC) method at a small boreal lake in Sweden. The mean CH4 flux during the growing season of 2013 was 20.1 nmol m(-2) s(-1) and the median flux was 16 nmol m(-2) s(-1) (corresponding to 1.7 mmol m(-2) d(-1) and 1.4 mmol m(-2) d(-1)). Monthly mean values of CH4 flux measured with the EC method were compared with fluxes measured with floating chambers (FC) and were in average 62% higher over the whole study period. The difference was greatest in April partly because EC, but not FC, accounted for fluxes due to ice melt and a subsequent lake mixing event. A footprint analysis revealed that the EC footprint included primarily the shallow side of the lake with a major inlet. This inlet harbors emergent macrophytes that can mediate high CH4 fluxes. The difference between measured EC and FC fluxes can hence be explained by different footprint areas, where the EC system sees the part of the lake presumably releasing higher amounts of CH4. EC also provides more frequent measurements than FC and hence more likely captures ebullition events. This study shows that small lakes have CH4 fluxes that are highly variable in time and space. Based on our findings we suggest to measure CH4 fluxes from lakes as continuously as possible and to aim for covering as much of the lakes surface as possible, independently of the selected measuring technique.

  • 14.
    Robroek, Björn J. M.
    et al.
    University of Utrecht, Netherlands; University of Southampton, England.
    Jassey, Vincent E. J.
    University of Toulouse, France.
    Payne, Richard J.
    Manchester Metropolitan University, England; University of York, England.
    Marti, Magali
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Bragazza, Luca
    University of Ferrara, Italy; Ecole Polytech Federal Lausanne, Switzerland; WSL Swiss Federal Institute Forest Snow and Landscape Research, Switzerland.
    Bleeker, Albert
    PBL Netherlands Environm Assessment Agency, Netherlands.
    Buttler, Alexandre
    University of Ferrara, Italy; Ecole Polytech Federal Lausanne, Switzerland.
    Caporn, Simon J. M.
    Manchester Metropolitan University, England.
    Dise, Nancy B.
    Manchester Metropolitan University, England; Centre Ecol and Hydrol, Scotland.
    Kattge, Jens
    Max Planck Institute Biogeochem, Germany; German Centre Integrat Biodivers Research iDiv, Germany.
    Zajac, Katarzyna
    University of Bayreuth, Germany; University of Bayreuth, Germany.
    Svensson, Bo
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    van Ruijven, Jasper
    Wageningen University of and Research Centre, Netherlands.
    Verhoeven, Jos T. A.
    University of Utrecht, Netherlands.
    Taxonomic and functional turnover are decoupled in European peat bogs2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 1161Article in journal (Refereed)
    Abstract [en]

    In peatland ecosystems, plant communities mediate a globally significant carbon store. The effects of global environmental change on plant assemblages are expected to be a factor in determining how ecosystem functions such as carbon uptake will respond. Using vegetation data from 56 Sphagnum-dominated peat bogs across Europe, we show that in these ecosystems plant species aggregate into two major clusters that are each defined by shared response to environmental conditions. Across environmental gradients, we find significant taxonomic turnover in both clusters. However, functional identity and functional redundancy of the community as a whole remain unchanged. This strongly suggests that in peat bogs, species turnover across environmental gradients is restricted to functionally similar species. Our results demonstrate that plant taxonomic and functional turnover are decoupled, which may allow these peat bogs to maintain ecosystem functioning when subject to future environmental change.

  • 15.
    Saunois, Marielle
    et al.
    University of Paris Saclay, France.
    Bousquet, Philippe
    University of Paris Saclay, France.
    Poulter, Ben
    NASA, MD 20771 USA.
    Peregon, Anna
    University of Paris Saclay, France.
    Ciais, Philippe
    University of Paris Saclay, France.
    Canadell, Josep G.
    CSIRO Oceans and Atmosphere, Australia.
    Dlugokencky, Edward J.
    NOAA ESRL, CO 80305 USA.
    Etiope, Giuseppe
    Ist Nazl Geofis and Vulcanol, Italy.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Houweling, Sander
    SRON, Netherlands; Institute Marine and Atmospher Research, Netherlands.
    Janssens-Maenhout, Greet
    European Commiss Joint Research Centre, Italy.
    Tubiello, Francesco N.
    Food and Agriculture Org United Nations FAO, Italy.
    Castaldi, Simona
    Seconda University of Napoli, Italy; FEFU, Russia; Euromediterranean Centre Climate Change, Italy.
    Jackson, Robert B.
    Stanford University, CA 94305 USA.
    Alexe, Mihai
    European Commiss Joint Research Centre, Italy.
    Arora, Vivek K.
    Environm and Climate Change Canada, Canada.
    Beerling, David J.
    University of Sheffield, England.
    Bergamaschi, Peter
    European Commiss Joint Research Centre, Italy.
    Blake, Donald R.
    University of Calif Irvine, CA 92697 USA.
    Brailsford, Gordon
    National Institute Water and Atmospher Research, New Zealand.
    Brovkin, Victor
    Max Planck Institute Meteorol, Germany.
    Bruhwiler, Lori
    NOAA ESRL, CO 80305 USA.
    Crevoisier, Cyril
    Ecole Polytech, France.
    Crill, Patrick
    Bolin Centre Climate Research, Sweden.
    Covey, Kristofer
    Yale University, CT 06511 USA.
    Curry, Charles
    University of Victoria, Canada.
    Frankenberg, Christian
    Jet Prop Lab, CA 91109 USA.
    Gedney, Nicola
    Joint Centre Hydrometeorol Research, England.
    Hoeglund-Isaksson, Lena
    Int Institute Appl Syst Anal, Austria.
    Ishizawa, Misa
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Ito, Akihiko
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Joos, Fortunat
    University of Bern, Switzerland.
    Kim, Heon-Sook
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Kleinen, Thomas
    Max Planck Institute Meteorol, Germany.
    Krummel, Paul
    CSIRO, Australia.
    Lamarque, Jean-Francois
    NCAR, CO 80307 USA.
    Langenfelds, Ray
    CSIRO, Australia.
    Locatelli, Robin
    University of Paris Saclay, France.
    Machida, Toshinobu
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Maksyutov, Shamil
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    McDonald, Kyle C.
    CUNY, NY 10031 USA.
    Marshall, Julia
    Max Planck Institute Biogeochem, Germany.
    Melton, Joe R.
    Environm and Climate Change Canada, Canada.
    Morino, Isamu
    Joint Centre Hydrometeorol Research, England.
    Naik, Vaishali
    NOAA, NJ 08540 USA.
    ODoherty, Simon
    University of Bristol, England.
    Parmentier, Frans-Jan W.
    Lund University, Sweden.
    Patra, Prabir K.
    JAMSTEC, Japan.
    Peng, Changhui
    University of Quebec, Canada.
    Peng, Shushi
    University of Paris Saclay, France.
    Peters, Glen P.
    CICERO, Norway.
    Pison, Isabelle
    University of Paris Saclay, France.
    Prigent, Catherine
    Observ Paris, France.
    Prinn, Ronald
    MIT, MA 02139 USA.
    Ramonet, Michel
    University of Paris Saclay, France.
    Riley, William J.
    Lawrence Berkeley National Lab, CA 94720 USA.
    Saito, Makoto
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Santini, Monia
    Euromediterranean Centre Climate Change, Italy.
    Schroeder, Ronny
    CUNY, NY 10031 USA; University of Hohenheim, Germany.
    Simpson, Isobel J.
    University of Calif Irvine, CA 92697 USA.
    Spahni, Renato
    University of Bern, Switzerland; University of Bern, Switzerland.
    Steele, Paul
    CSIRO, Australia.
    Takizawa, Atsushi
    JMA, Japan.
    Thornton, Brett F.
    Bolin Centre Climate Research, Sweden.
    Tian, Hanqin
    Auburn University, AL 36849 USA.
    Tohjima, Yasunori
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Viovy, Nicolas
    University of Paris Saclay, France.
    Voulgarakis, Apostolos
    Imperial Coll London, England.
    van Weele, Michiel
    KNMI, Netherlands.
    van der Werf, Guido R.
    Vrije University of Amsterdam, Netherlands.
    Weiss, Ray
    University of Calif San Diego, CA 92093 USA.
    Wiedinmyer, Christine
    NCAR, CO 80307 USA.
    Wilton, David J.
    University of Sheffield, England.
    Wiltshire, Andy
    Met Off Hadley Centre, England.
    Worthy, Doug
    Environm Canada, Canada.
    Wunch, Debra
    University of Toronto, Canada.
    Xu, Xiyan
    Lawrence Berkeley National Lab, CA 94720 USA.
    Yoshida, Yukio
    Center for Global Environmental Research, National Institute for Environmental Studies (NIES), Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan.
    Zhang, Bowen
    Auburn University, AL 36849 USA.
    Zhang, Zhen
    NASA, MD 20771 USA; Swiss Federal Research Institute WSL, Switzerland.
    Zhu, Qiuan
    Northwest AandF University, Peoples R China.
    The global methane budget 2000-20122016In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 8, no 2, p. 697-751Article in journal (Refereed)
    Abstract [en]

    The global methane (CH4) budget is becoming an increasingly important component for managing realistic pathways to mitigate climate change. This relevance, due to a shorter atmospheric lifetime and a stronger warming potential than carbon dioxide, is challenged by the still unexplained changes of atmospheric CH4 over the past decade. Emissions and concentrations of CH4 are continuing to increase, making CH4 the second most important human-induced greenhouse gas after carbon dioxide. Two major difficulties in reducing uncertainties come from the large variety of diffusive CH4 sources that overlap geographically, and from the destruction of CH4 by the very short-lived hydroxyl radical (OH). To address these difficulties, we have established a consortium of multi-disciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate research on the methane cycle, and producing regular (similar to biennial) updates of the global methane budget. This consortium includes atmospheric physicists and chemists, biogeochemists of surface and marine emissions, and socio-economists who study anthropogenic emissions. Following Kirschke et al. (2013), we propose here the first version of a living review paper that integrates results of top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models, inventories and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, and inventories for anthropogenic emissions, data-driven extrapolations). For the 2003-2012 decade, global methane emissions are estimated by top-down inversions at 558 TgCH(4) yr(-1), range 540-568. About 60% of global emissions are anthropogenic (range 50-65 %). Since 2010, the bottom-up global emission inventories have been closer to methane emissions in the most carbon-intensive Representative Concentrations Pathway (RCP8.5) and higher than all other RCP scenarios. Bottom-up approaches suggest larger global emissions (736 TgCH(4) yr(-1), range 596-884) mostly because of larger natural emissions from individual sources such as inland waters, natural wetlands and geological sources. Considering the atmospheric constraints on the top-down budget, it is likely that some of the individual emissions reported by the bottom-up approaches are overestimated, leading to too large global emissions. Latitudinal data from top-down emissions indicate a predominance of tropical emissions (similar to 64% of the global budget, amp;lt;30 degrees N) as compared to mid (similar to 32 %, 30-60 degrees N) and high northern latitudes (similar to 4 %, 60-90 degrees N). Top-down inversions consistently infer lower emissions in China (similar to 58 TgCH(4) yr(-1), range 51-72, -14 %) and higher emissions in Africa (86 TgCH(4) yr(-1), range 73-108, + 19 %) than bottom-up values used as prior estimates. Overall, uncertainties for anthropogenic emissions appear smaller than those from natural sources, and the uncertainties on source categories appear larger for top-down inversions than for bottom-up inventories and models. The most important source of uncertainty on the methane budget is attributable to emissions from wetland and other inland waters. We show that the wetland extent could contribute 30-40% on the estimated range for wetland emissions. Other priorities for improving the methane budget include the following: (i) the development of process-based models for inland-water emissions, (ii) the intensification of methane observations at local scale (flux measurements) to constrain bottom-up land surface models, and at regional scale (surface networks and satellites) to constrain top-down inversions, (iii) improvements in the estimation of atmospheric loss by OH, and (iv) improvements of the transport models integrated in top-down inversions. The data presented here can be downloaded from the Carbon Dioxide Information Analysis Center (http://doi.org/10.3334/CDIAC/GLOBAL_METHANE_BUDGET_2016_V1.1) and the Global Carbon Project.

  • 16.
    Saunois, Marielle
    et al.
    University of Paris Saclay, France.
    Bousquet, Philippe
    University of Paris Saclay, France.
    Poulter, Ben
    NASA, MD 20771 USA.
    Peregon, Anna
    University of Paris Saclay, France.
    Ciais, Philippe
    University of Paris Saclay, France.
    Canadell, Josep G.
    CSIRO, Australia.
    Dlugokencky, Edward J.
    NOAA, CO 80305 USA.
    Etiope, Giuseppe
    Ist Nazl Geofis and Vulcanol, Italy; Babes Bolyai University, Romania.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Houweling, Sander
    Netherlands Institute Space Research SRON, Netherlands; Institute Marine and Atmospher Research, Netherlands.
    Janssens-Maenhout, Greet
    European Commiss Joint Research Centre, Italy.
    Tubiello, Francesco N.
    Food and Agriculture Org United Nations FAO, Italy.
    Castaldi, Simona
    Seconda University of Napoli, Italy; FEFU, Russia; Euro Mediterranean Centre Climate Change, Italy.
    Jackson, Robert B.
    Stanford University, CA 94305 USA.
    Alexe, Mihai
    European Commiss Joint Research Centre, Italy.
    Arora, Vivek K.
    Environm and Climate Change Canada, Canada.
    Beerling, David J.
    University of Sheffield, England.
    Bergamaschi, Peter
    European Commiss Joint Research Centre, Italy.
    Blake, Donald R.
    University of Calif Irvine, CA 92697 USA.
    Brailsford, Gordon
    Nat Institute Water and Atmospher Research, New Zealand.
    Bruhwiler, Lori
    NOAA, CO 80305 USA.
    Crevoisier, Cyril
    University of Paris Saclay, France.
    Crill, Patrick
    Department Geol Science, Sweden; Bolin Centre Climate Research, Sweden.
    Covey, Kristofer
    Yale University, CT 06511 USA.
    Frankenberg, Christian
    CALTECH, CA 91125 USA; Jet Prop Lab, CA 91109 USA.
    Gedney, Nicola
    Joint Centre Hydrometeorol Research, England.
    Hoeglund-Isaksson, Lena
    IIASA, Austria.
    Ishizawa, Misa
    National Institute Environm Studies, Japan.
    Ito, Akihiko
    National Institute Environm Studies, Japan.
    Joos, Fortunat
    University of Bern, Switzerland; University of Bern, Switzerland.
    Kim, Heon-Sook
    National Institute Environm Studies, Japan.
    Kleinen, Thomas
    Max Planck Institute Meteorol, Germany.
    Krummel, Paul
    CSIRO, Australia.
    Lamarque, Jean-Francois
    NCAR, CO 80307 USA.
    Langenfelds, Ray
    CSIRO, Australia.
    Locatelli, Robin
    University of Paris Saclay, France.
    Machida, Toshinobu
    National Institute Environm Studies, Japan.
    Maksyutov, Shamil
    National Institute Environm Studies, Japan.
    Melton, Joe R.
    Environm and Climate Change Canada, Canada.
    Morino, Isamu
    National Institute Environm Studies, Japan.
    Naik, Vaishali
    NOAA, NJ 08540 USA.
    ODoherty, Simon
    University of Bristol, England.
    Parmentier, Frans-JanW.
    UiT Arctic University of Norway, Norway.
    Patra, Prabir K.
    JAMSTEC, Japan; JAMSTEC, Japan.
    Peng, Changhui
    University of Quebec, Canada; Northwest AandF University, Peoples R China.
    Peng, Shushi
    University of Paris Saclay, France; Peking University, Peoples R China.
    Peters, Glen P.
    CICERO Centre Int Climate Research, Norway.
    Pison, Isabelle
    University of Paris Saclay, France.
    Prinn, Ronald
    MIT, MA 02139 USA.
    Ramonet, Michel
    University of Paris Saclay, France.
    Riley, William J.
    Lawrence Berkeley National Lab, CA 94720 USA.
    Saito, Makoto
    National Institute Environm Studies, Japan.
    Santini, Monia
    FEFU, Russia; Euro Mediterranean Centre Climate Change, Italy.
    Schroeder, Ronny
    University of New Hampshire, NH 03824 USA.
    Simpson, Isobel J.
    University of Calif Irvine, CA 92697 USA.
    Spahni, Renato
    University of Bern, Switzerland; University of Bern, Switzerland.
    Takizawa, Atsushi
    Japan Meteorol Agency, Japan.
    Thornton, Brett F.
    Department Geol Science, Sweden; Bolin Centre Climate Research, Sweden.
    Tian, Hanqin
    Auburn University, AL 36849 USA.
    Tohjima, Yasunori
    National Institute Environm Studies, Japan.
    Viovy, Nicolas
    University of Paris Saclay, France.
    Voulgarakis, Apostolos
    Imperial Coll London, England.
    Weiss, Ray
    University of Calif San Diego, CA 92093 USA.
    Wilton, David J.
    University of Sheffield, England.
    Wiltshire, Andy
    Hadley Centre, England.
    Worthy, Doug
    Environm Canada, Canada.
    Wunch, Debra
    University of Toronto, Canada.
    Xu, Xiyan
    Lawrence Berkeley National Lab, CA 94720 USA; Chinese Academic Science, Peoples R China.
    Yoshida, Yukio
    National Institute Environm Studies, Japan.
    Zhang, Bowen
    Auburn University, AL 36849 USA.
    Zhang, Zhen
    Swiss Federal Research Institute WSL, Switzerland.
    Zhu, Qiuan
    Northwest AandF University, Peoples R China.
    Variability and quasi-decadal changes in the methane budget over the period 2000-20122017In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 18, p. 11135-11161Article in journal (Refereed)
    Abstract [en]

    Following the recent Global Carbon Project (GCP) synthesis of the decadal methane (CH4) budget over 2000-2012 (Saunois et al., 2016), we analyse here the same dataset with a focus on quasi-decadal and inter-annual variability in CH4 emissions. The GCP dataset integrates results from top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models (including process-based models for estimating land surface emissions and atmospheric chemistry), inventories of anthropogenic emissions, and data-driven approaches. The annual global methane emissions from top-down studies, which by construction match the observed methane growth rate within their uncertainties, all show an increase in total methane emissions over the period 2000-2012, but this increase is not linear over the 13 years. Despite differences between individual studies, the mean emission anomaly of the top-down ensemble shows no significant trend in total methane emissions over the period 2000-2006, during the plateau of atmospheric methane mole fractions, and also over the period 2008-2012, during the renewed atmospheric methane increase. However, the top-down ensemble mean produces an emission shift between 2006 and 2008, leading to 22 [16-32] Tg CH4 yr(-1) higher methane emissions over the period 2008-2012 compared to 2002-2006. This emission increase mostly originated from the tropics, with a smaller contribution from mid-latitudes and no significant change from boreal regions. The regional contributions remain uncertain in top-down studies. Tropical South America and South and East Asia seem to contribute the most to the emission increase in the tropics. However, these two regions have only limited atmospheric measurements and remain therefore poorly constrained. The sectorial partitioning of this emission increase between the periods 2002-2006 and 2008-2012 differs from one atmospheric inversion study to another. However, all top-down studies suggest smaller changes in fossil fuel emissions (from oil, gas, and coal industries) compared to the mean of the bottom-up inventories included in this study. This difference is partly driven by a smaller emission change in China from the top-down studies compared to the estimate in the Emission Database for Global Atmospheric Research (EDGARv4.2) inventory, which should be revised to smaller values in a near future. We apply isotopic signatures to the emission changes estimated for individual studies based on five emission sectors and find that for six individual top-down studies (out of eight) the average isotopic signature of the emission changes is not consistent with the observed change in atmospheric (CH4)-C-13. However, the partitioning in emission change derived from the ensemble mean is consistent with this isotopic constraint. At the global scale, the top-down ensemble mean suggests that the dominant contribution to the resumed atmospheric CH4 growth after 2006 comes from microbial sources (more from agriculture and waste sectors than from natural wetlands), with an uncertain but smaller contribution from fossil CH4 emissions. In addition, a decrease in biomass burning emissions (in agreement with the biomass burning emission databases) makes the balance of sources consistent with atmospheric (CH4)-C-13 observations. In most of the top-down studies included here, OH concentrations are considered constant over the years (seasonal variations but without any inter-annual variability). As a result, the methane loss (in particular through OH oxidation) varies mainly through the change in methane concentrations and not its oxidants. For these reasons, changes in the methane loss could not be properly investigated in this study, although it may play a significant role in the recent atmospheric methane changes as briefly discussed at the end of the paper.

  • 17.
    Schilder, J.
    et al.
    University of Bern, Switzerland; University of Jyvaskyla, Finland.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    van Hardenbroek, M.
    University of Bern, Switzerland; University of Southampton, England.
    Heiri, O.
    University of Bern, Switzerland.
    Spatiotemporal patterns in methane flux and gas transfer velocity at low wind speeds: Implications for upscaling studies on small lakes2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 6, p. 1456-1467Article in journal (Refereed)
    Abstract [en]

    Lakes contribute significantly to the global natural emissions of methane (CH4) and carbon dioxide. However, to accurately incorporate them into the continental carbon balance more detailed surveys of lacustrine greenhouse gas emissions are needed, especially in respect to spatiotemporal variability and to how this affects the upscaling of results. We investigated CH4 flux from a small, wind-shielded lake during 10 field trips over a 14month period. We show that floating chambers may be used to calibrate the relationship between gas transfer velocity (k) and wind speed at 10m height (U-10) to the local system, in order to obtain more accurate estimates of diffusive CH4 flux than by applying general models predicting k based on U-10. We confirm earlier studies indicating strong within-lake spatial variation in this relationship and in ebullitive CH4 flux within the lake basin. However, in contrast to the pattern reported in other studies, ebullitive CH4 flux was highest in the central parts of the lake. Our results indicate positive relationships between k and U-10 at very low U-10 (0-3ms(-1)), which disagrees with earlier suggestions that this relationship may be negligible at low U-10 values. We estimate annually averaged open water CH4 emission from Lake Gerzensee to be 3.6-5.8mmolm(-2)d(-1). Our data suggest that estimates of greenhouse gas emissions from aquatic systems to the atmosphere based on the upscaling of short-term and small-scale measurements can be improved if both spatial and temporal variabilities of emissions are taken into account.

  • 18.
    Thonat, Thibaud
    et al.
    University of Paris Saclay, France.
    Saunois, Marielle
    University of Paris Saclay, France.
    Bousquet, Philippe
    University of Paris Saclay, France.
    Pison, Isabelle
    University of Paris Saclay, France.
    Tan, Zeli
    Pacific Northwest National Lab, WA USA.
    Zhuang, Qianlai
    Purdue University, IN 47907 USA.
    Crill, Patrick M.
    Department Geol Science, Sweden; Bolin Centre Climate Research, Sweden.
    Thornton, Brett F.
    Department Geol Science, Sweden; Bolin Centre Climate Research, Sweden.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Dlugokencky, Ed J.
    NOAA, CO USA.
    Zimov, Nikita
    Northeast Science Stn, Russia.
    Laurila, Tuomas
    Finnish Meteorol Institute, Finland.
    Hatakka, Juha
    NILU Norwegian Institute Air Research, Norway.
    Hermansen, Ove
    NILU Norwegian Institute Air Research, Norway.
    Worthy, Doug E. J.
    Environm Canada, Canada.
    Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements2017In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 13, p. 8371-8394Article in journal (Refereed)
    Abstract [en]

    Understanding the recent evolution of methane emissions in the Arctic is necessary to interpret the global methane cycle. Emissions are affected by significant uncertainties and are sensitive to climate change, leading to potential feedbacks. A polar version of the CHIMERE chemistry-transport model is used to simulate the evolution of tropospheric methane in the Arctic during 2012, including all known regional anthropogenic and natural sources, in particular freshwater emissions which are often overlooked in methane modelling. CHIMERE simulations are compared to atmospheric continuous observations at six measurement sites in the Arctic region. In winter, the Arctic is dominated by anthropogenic emissions; emissions from continental seepages and oceans, including from the East Siberian Arctic Shelf, can contribute significantly in more limited areas. In summer, emissions from wetland and freshwater sources dominate across the whole region. The model is able to reproduce the seasonality and synoptic variations of methane measured at the different sites. We find that all methane sources significantly affect the measurements at all stations at least at the synoptic scale, except for biomass burning. In particular, freshwater systems play a decisive part in summer, representing on average between 11 and 26% of the simulated Arctic methane signal at the sites. This indicates the relevance of continuous observations to gain a mechanistic understanding of Arctic methane sources. Sensitivity tests reveal that the choice of the land-surface model used to prescribe wetland emissions can be critical in correctly representing methane mixing ratios. The closest agreement with the observations is reached when using the two wetland models which have emissions peaking in August-September, while all others reach their maximum in JuneJuly. Such phasing provides an interesting constraint on wetland models which still have large uncertainties at present. Also testing different freshwater emission inventories leads to large differences in modelled methane. Attempts to include methane sinks (OH oxidation and soil uptake) reduced the model bias relative to observed atmospheric methane. The study illustrates how multiple sources, having different spatiotemporal dynamics and magnitudes, jointly influence the overall Arctic methane budget, and highlights ways towards further improved assessments.

  • 19.
    Yang, P.
    et al.
    Fujian Normal Univ, Peoples R China.
    Wang, M. H.
    Fujian Normal Univ, Peoples R China.
    Lai, Derrick Y. F.
    Chinese Univ Hong Kong, Peoples R China.
    Chun, K. P.
    Hong Kong Baptist Univ, Peoples R China.
    Huang, J. F.
    Fujian Normal Univ, Peoples R China.
    Wan, S. A.
    Fujian Normal Univ, Peoples R China.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Tong, C.
    Fujian Normal Univ, Peoples R China.
    Methane dynamics in an estuarine brackish Cyperus malaccensis marsh: Production and porewater concentration in soils, and net emissions to the atmosphere over five years2019In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 337, p. 132-142Article in journal (Refereed)
    Abstract [en]

    Wetlands can potentially affect global climate change through their role in modulating the atmospheric concentrations of methane (CH4). Their overall CH4 emissions, however, remain the greatest uncertainty in the global CH4 budget. One reason for this is the paucity of long-term field measurements to characterize the variability of CH4 emissions from different types of wetlands. In this study, we quantified CH4 emissions from a brackish, oligohaline Cyperus malaccensis marsh ecosystem in the Min River Estuary in southeast China over five years. Our results showed substantial temporal variability of CH4 emissions from this brackish marsh, with hourly fluxes ranging from 0.7 +/- 0.6 to 5.1 +/- 3.7 mg m(-2) h(-1) (mean +/- 1 SD) during the study period. The inter-annual variability of CH4 emissions was significantly correlated with changes in soil temperature, precipitation and salinity, which highlighted the importance of long-term observations in understanding wetland CH4 dynamics. Distinct seasonal patterns in soil CH4 production rates and porewater CH4 concentrations also were observed, and were both positively correlated with CH4 emissions. The seasonal variations of CH4 emissions and production were highly correlated with salinity and porewater sulfate levels. The mean annual CH4 efflux from our site over the five-year period was 23.8 +/- 18.1 g CH4 m(-2) yr(-1), indicating that subtropical brackish tidal marsh ecosystems could release a large amount of CH4 into the atmosphere. Our findings further highlight the need to obtain high-frequency and continuous field measurements over the long term at multiple spatial scales to improve our current estimates of wetland CH4 emissions.

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