Browsing by Subject "CH4 EMISSIONS"

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  • Reum, Friedemann; Goeckede, Mathias; Lavric, Jost V.; Kolle, Olaf; Zimov, Sergey; Zimov, Nikita; Pallandt, Martijn; Heimann, Martin (2019)
    Sparse data coverage in the Arctic hampers our understanding of its carbon cycle dynamics and our predictions of the fate of its vast carbon reservoirs in a changing climate. In this paper, we present accurate measurements of atmospheric carbon dioxide (CO2) and methane (CH4) dry air mole fractions at the new atmospheric carbon observation station Ambarchik, which closes a large gap in the atmospheric trace gas monitoring network in northeastern Siberia. The site, which has been operational since August 2014, is located near the delta of the Kolyma River at the coast of the Arctic Ocean. Data quality control of CO2 and CH4 measurements includes frequent calibrations traced to World Meteorological Organization (WMO) scales, employment of a novel water vapor correction, an algorithm to detect the influence of local polluters, and meteorological measurements that enable data selection. The available CO2 and CH4 record was characterized in comparison with in situ data from Barrow, Alaska. A footprint analysis reveals that the station is sensitive to signals from the East Siberian Sea, as well as the northeast Siberian tundra and taiga regions. This makes data from Ambarchik highly valuable for inverse modeling studies aimed at constraining carbon budgets within the pan-Arctic domain, as well as for regional studies focusing on Siberia and the adjacent shelf areas of the Arctic Ocean.
  • Raivonen, Maarit; Smolander, Sampo; Backman, Leif; Susiluoto, Jouni; Aalto, Tuula; Markkanen, Tiina; Mäkelä, Jarmo; Rinne, Janne; Peltola, Olli; Aurela, Mika; Lohila, Annalea; Tomasic, Marin; Li, Xuefei; Larmola, Tuula; Juutinen, Sari; Tuittila, Eeva-Stiina; Heimann, Martin; Sevanto, Sanna; Kleinen, Thomas; Brovkin, Victor; Vesala, Timo (2017)
    Wetlands are one of the most significant natural sources of methane (CH4) to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2). Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peat-land vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2, and oxygen (O-2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O-2 concentrations that affect the CH4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH4 emissions in this model version.
  • Wang, Fenjuan; Maksyutov, Shamil; Janardanan, Rajesh; Tsuruta, Aki; Ito, Akihiko; Morino, Isamu; Yoshida, Yukio; Tohjima, Yasunori; Kaiser, Johannes W.; Janssens-Maenhout, Greet; Lan, Xin; Mammarella, Ivan; Lavric, Jost; Matsunaga, Tsuneo (2021)
    In Asia, much effort is put into reducing methane (CH4) emissions due to the region's contribution to the recent rapid global atmospheric CH4 concentration growth. Accurate quantification of Asia's CH4 budgets is critical for conducting global stocktake and achieving the long-term temperature goal of the Paris Agreement. In this study, we present top-down estimates of CH4 emissions from 2009 to 2018 deduced from atmospheric observations from surface network and GOSAT satellite with the high-resolution global inverse model NIES-TM-FLEXPART-VAR. The optimized average CH4 budgets are 63.40 +/- 10.52 Tg y(-1) from East Asia (EA), 45.20 +/- 6.22 Tg y(-1) from Southeast Asia (SEA), and 64.35 +/- 9.28 Tg y(-1) from South Asia (SA) within the 10 years. We analyzed two 5 years CH4 emission budgets for three subregions and 13 top-emitting countries with an emission budget larger than 1 Tg y(-1), and interannual variabilities for these subregions. Statistically significant increasing trends in emissions are found in EA with a lower emission growth rate during 2014-2018 compared to that during 2009-2013, while trends in SEA are not significant. In contrast to the prior emission, the posterior emission shows a significant decreasing trend in SA. The flux decrease is associated with the transition from strong La Ninna (2010-2011) to strong El Ninno (2015-2016) events, which modulate the surface air temperature and rainfall patterns. The interannual variability in CH4 flux anomalies was larger in SA compared to EA and SEA. The Southern Oscillation Index correlates strongly with interannual CH4 flux anomalies for SA. Our findings suggest that the interannual variability in the total CH4 flux is dominated by climate variability in SA. The contribution of climate variability driving interannual variability in natural and anthropogenic CH4 emissions should be further quantified, especially for tropical countries. Accounting for climate variability may be necessary to improve anthropogenic emission inventories.
  • Ehret, Gerhard; Bousquet, Philippe; Pierangelo, Clemence; Alpers, Matthias; Millet, Bruno; Abshire, James B.; Bovensmann, Heinrich; Burrows, John P.; Chevallier, Frederic; Ciais, Philippe; Crevoisier, Cyril; Fix, Andreas; Flamant, Pierre; Frankenberg, Christian; Gibert, Fabien; Heim, Birgit; Heimann, Martin; Houweling, Sander; Hubberten, Hans W.; Joeckel, Patrick; Law, Kathy; Loew, Alexander; Marshall, Julia; Agusti-Panareda, Anna; Payan, Sebastien; Prigent, Catherine; Rairoux, Patrick; Sachs, Torsten; Scholze, Marko; Wirth, Martin (2017)
    The MEthane Remote sensing Lidar missioN (MERLIN) aims at demonstrating the spaceborne active measurement of atmospheric methane, a potent greenhouse gas, based on an Integrated Path Differential Absorption (IPDA) nadir-viewing LIght Detecting and Ranging (Lidar) instrument. MERLIN is a joint French and German space mission, with a launch currently scheduled for the timeframe 2021/22. The German Space Agency (DLR) is responsible for the payload, while the platform (MYRIADE Evolutions product line) is developed by the French Space Agency (CNES). The main scientific objective of MERLIN is the delivery of weighted atmospheric columns of methane dry-air mole fractions for all latitudes throughout the year with systematic errors small enough (
  • Tsuruta, Aki; Aalto, Tuula; Backman, Leif; Krol, Maarten C.; Peters, Wouter; Lienert, Sebastian; Joos, Fortunat; Miller, Paul A.; Zhang, Wenxin; Laurila, Tuomas; Hatakka, Juha; Leskinen, Ari; Lehtinen, Kari E. J.; Peltola, Olli; Vesala, Timo; Levula, Janne; Dlugokencky, Ed; Heimann, Martin; Kozlova, Elena; Aurela, Mika; Lohila, Annalea; Kauhaniemi, Mari; Gomez-Pelaez, Angel J. (2019)
    We estimated the CH4 budget in Finland for 2004?2014 using the CTE-CH4 data assimilation system with an extended atmospheric CH4 observation network of seven sites from Finland to surrounding regions (Hyytiälä, Kj?lnes, Kumpula, Pallas, Puijo, Sodankylä, and Utö). The estimated average annual total emission for Finland is 0.6?±?0.5 Tg CH4 yr?1. Sensitivity experiments show that the posterior biospheric emission estimates for Finland are between 0.3 and 0.9 Tg CH4 yr?1, which lies between the LPX-Bern-DYPTOP (0.2 Tg CH4 yr?1) and LPJG-WHyMe (2.2 Tg CH4 yr?1) process-based model estimates. For anthropogenic emissions, we found that the EDGAR v4.2 FT2010 inventory (0.4 Tg CH4 yr?1) is likely to overestimate emissions in southernmost Finland, but the extent of overestimation and possible relocation of emissions are difficult to derive from the current observation network. The posterior emission estimates were especially reliant on prior information in central Finland. However, based on analysis of posterior atmospheric CH4, we found that the anthropogenic emission distribution based on a national inventory is more reliable than the one based on EDGAR v4.2 FT2010. The contribution of total emissions in Finland to global total emissions is only about 0.13%, and the derived total emissions in Finland showed no trend during 2004?2014. The model using optimized emissions was able to reproduce observed atmospheric CH4 at the sites in Finland and surrounding regions fairly well (correlation > 0.75, bias
  • Korkiakoski, Mika; Tuovinen, Juha-Pekka; Aurela, Mika; Koskinen, Markku; Minkkinen, Kari; Ojanen, Paavo; Penttila, Timo; Rainne, Juuso; Laurila, Tuomas; Lohila, Annalea (2017)
    We measured methane (CH4) exchange rates with automatic chambers at the forest floor of a nutrient-rich drained peatland in 2011-2013. The fen, located in southern Finland, was drained for forestry in 1969 and the tree stand is now a mixture of Scots pine, Norway spruce, and pubescent birch. Our measurement system consisted of six transparent chambers and stainless steel frames, positioned on a number of different field and moss layer compositions. Gas concentrations were measured with an online cavity ring-down spectroscopy gas analyzer. Fluxes were calculated with both linear and exponential regression. The use of linear regression resulted in systematically smaller CH4 fluxes by 10-45% as compared to exponential regression. However, the use of exponential regression with small fluxes (
  • Machacova, Katerina; Back, Jaana; Vanhatalo, Anni; Halmeenmäki, Elisa; Kolari, Pasi; Mammarella, Ivan; Pumpanen, Jukka; Acosta, Manuel; Urban, Otmar; Pihlatie, Mari (2016)
    Boreal forests comprise 73% of the world's coniferous forests. Based on forest floor measurements, they have been considered a significant natural sink of methane (CH4) and a natural source of nitrous oxide (N2O), both of which are important greenhouse gases. However, the role of trees, especially conifers, in ecosystem N2O and CH4 exchange is only poorly understood. We show for the first time that mature Scots pine (Pinus sylvestris L.) trees consistently emit N2O and CH4 from both stems and shoots. The shoot fluxes of N2O and CH4 exceeded the stem flux rates by 16 and 41 times, respectively. Moreover, higher stem N2O and CH4 fluxes were observed from wet than from dry areas of the forest. The N2O release from boreal pine forests may thus be underestimated and the uptake of CH4 may be overestimated when ecosystem flux calculations are based solely on forest floor measurements. The contribution of pine trees to the N2O and CH4 exchange of the boreal pine forest seems to increase considerably under high soil water content, thus highlighting the urgent need to include tree-emissions in greenhouse gas emission inventories.
  • Machacova, Katerina; Vainio, Elisa; Urban, Otmar; Pihlatie, Mari (2019)
    The role of trees in the nitrous oxide (N2O) balance of boreal forests has been neglected despite evidence suggesting their substantial contribution. We measured seasonal changes in N2O fluxes from soil and stems of boreal trees in Finland, showing clear seasonality in stem N2O flux following tree physiological activity, particularly processes of CO2 uptake and release. Stem N2O emissions peak during the vegetation season, decrease rapidly in October, and remain low but significant to the annual totals during winter dormancy. Trees growing on dry soils even turn to consumption of N2O from the atmosphere during dormancy, thereby reducing their overall N2O emissions. At an annual scale, pine, spruce and birch are net N2O sources, with spruce being the strongest emitter. Boreal trees thus markedly contribute to the seasonal dynamics of ecosystem N2O exchange, and their species-specific contribution should be included into forest emission inventories.
  • Vainio, Elisa; Peltola, Olli; Kasurinen, Ville; Kieloaho, Antti-Jussi; Tuittila, Eeva-Stiina; Pihlatie, Mari (2021)
    Boreal forest soils are globally an important sink for methane (CH4), while these soils are also capable of emitting CH4 under favourable conditions. Soil wetness is a well-known driver of CH4 flux, and the wetness can be estimated with several terrain indices developed for the purpose. The aim of this study was to quantify the spatial variability of the forest floor CH4 flux with a topography-based upscaling method connecting the flux with its driving factors. We conducted spatially extensive forest floor CH4 flux and soil moisture measurements, complemented by ground vegetation classification, in a boreal pine forest. We then modelled the soil moisture with a random forest model using digital-elevation-model-derived topographic indices, based on which we upscaled the forest floor CH4 flux. The modelling was performed for two seasons: May–July and August–October. Additionally, we evaluated the number of flux measurement points needed to get an accurate estimate of the flux at the whole study site merely by averaging. Our results demonstrate high spatial heterogeneity in the forest floor CH4 flux resulting from the soil moisture variability as well as from the related ground vegetation. The mean measured CH4 flux at the sample points was −5.07 µmol m−2 h−1 in May–July and −8.67 µmol m−2 h−1 in August–October, while the modelled flux for the whole area was −7.42 and −9.91 µmol m−2 h−1 for the two seasons, respectively. The spatial variability in the soil moisture and consequently in the CH4 flux was higher in the early summer (modelled range from −12.3 to 6.19 µmol m−2 h−1) compared to the autumn period (range from −14.6 to −2.12 µmol m−2 h−1), and overall the CH4 uptake rate was higher in autumn compared to early summer. In the early summer there were patches emitting high amounts of CH4; however, these wet patches got drier and smaller in size towards the autumn, changing their dynamics to CH4 uptake. The mean values of the measured and modelled CH4 fluxes for the sample point locations were similar, indicating that the model was able to reproduce the results. For the whole site, upscaling predicted stronger CH4 uptake compared to simply averaging over the sample points. The results highlight the small-scale spatial variability of the boreal forest floor CH4 flux and the importance of soil chamber placement in order to obtain spatially representative CH4 flux results. To predict the CH4 fluxes over large areas more reliably, the locations of the sample points should be selected based on the spatial variability of the driving parameters, in addition to linking the measured fluxes with the parameters.
  • Franz, Daniela; Acosta, Manuel; Altimir, Nuria; Arriga, Nicola; Arrouays, Dominique; Aubinet, Marc; Aurela, Mika; Ayres, Edward; Lopez-Ballesteros, Ana; Barbaste, Mireille; Berveiller, Daniel; Biraud, Sebastien; Boukir, Hakima; Brown, Timothy; Bruemmer, Christian; Buchmann, Nina; Burba, George; Carrara, Arnaud; Cescatti, Allessandro; Ceschia, Eric; Clement, Robert; Cremonese, Edoardo; Crill, Patrick; Darenova, Eva; Dengel, Sigrid; D'Odorico, Petra; Filippa, Gianluca; Fleck, Stefan; Fratini, Gerardo; Fuss, Roland; Gielen, Bert; Gogo, Sebastien; Grace, John; Graf, Alexander; Grelle, Achim; Gross, Patrick; Gruenwald, Thomas; Haapanala, Sami; Hehn, Markus; Heinesch, Bernard; Heiskanen, Jouni; Herbst, Mathias; Herschlein, Christine; Hortnagl, Lukas; Hufkens, Koen; Ibrom, Andreas; Jolivet, Claudy; Joly, Lilian; Jones, Michael; Kiese, Ralf; Klemedtsson, Leif; Kljun, Natascha; Klumpp, Katja; Kolari, Pasi; Kolle, Olaf; Kowalski, Andrew; Kutsch, Werner; Laurila, Tuomas; de Ligne, Anne; Linder, Sune; Lindroth, Anders; Lohila, Annalea; Longdoz, Bernhard; Mammarella, Ivan; Manise, Tanguy; Maranon Jimenez, Sara; Matteucci, Giorgio; Mauder, Matthias; Meier, Philip; Merbold, Lutz; Mereu, Simone; Metzger, Stefan; Migliavacca, Mirco; Molder, Meelis; Montagnani, Leonardo; Moureaux, Christine; Nelson, David; Nemitz, Eiko; Nicolini, Giacomo; Nilsson, Mats B.; Op de Beeck, Maarten; Osborne, Bruce; Lofvenius, Mikaell Ottosson; Pavelka, Marian; Peichl, Matthias; Peltola, Olli; Pihlatie, Mari; Pitacco, Andrea; Pokorny, Radek; Pumpanen, Jukka; Ratie, Celine; Rebmann, Corinna; Roland, Marilyn; Sabbatini, Simone; Saby, Nicolas P. A.; Saunders, Matthew; Schmid, Hans Peter; Schrumpf, Marion; Sedlak, Pavel; Serrano Ortiz, Penelope; Siebicke, Lukas; Sigut, Ladislav; Silvennoinen, Hanna; Simioni, Guillaume; Skiba, Ute; Sonnentag, Oliver; Soudani, Kamel; Soule, Patrice; Steinbrecher, Rainer; Tallec, Tiphaine; Thimonier, Anne; Tuittila, Eeva-Stiina; Tuovinen, Juha-Pekka; Vestin, Patrik; Vincent, Gaelle; Vincke, Caroline; Vitale, Domenico; Waldner, Peter; Weslien, Per; Wingate, Lisa; Wohlfahrt, Georg; Zahniser, Mark; Vesala, Timo (2018)
    Research infrastructures play a key role in launching a new generation of integrated long-term, geographically distributed observation programmes designed to monitor climate change, better understand its impacts on global ecosystems, and evaluate possible mitigation and adaptation strategies. The pan-European Integrated Carbon Observation System combines carbon and greenhouse gas (GHG; CO2, CH4, N2O, H2O) observations within the atmosphere, terrestrial ecosystems and oceans. High-precision measurements are obtained using standardised methodologies, are centrally processed and openly available in a traceable and verifiable fashion in combination with detailed metadata. The Integrated Carbon Observation System ecosystem station network aims to sample climate and land-cover variability across Europe. In addition to GHG flux measurements, a large set of complementary data (including management practices, vegetation and soil characteristics) is collected to support the interpretation, spatial upscaling and modelling of observed ecosystem carbon and GHG dynamics. The applied sampling design was developed and formulated in protocols by the scientific community, representing a trade-off between an ideal dataset and practical feasibility. The use of open-access, high-quality and multi-level data products by different user communities is crucial for the Integrated Carbon Observation System in order to achieve its scientific potential and societal value.