Browsing by Subject "carbon cycle"

Sort by: Order: Results:

Now showing items 1-11 of 11
  • Susiluoto, Jouni (2019)
    Finnish Meteorological Institute Contributions 154
    Climate change is one of the most important, pressing, and furthest reaching global challenges that humanity faces in the 21st century. Already affecting daily lives of many directly and everyone indirectly, changes in climate are projected to have many catastrophic consequences. For this reason, researching climate and climate change is needed. Studying complex geoscientific phenomena such as climate change consists of a patchwork of challenging mathematical, statistical, and computational problems. To solve these problems, local and global process models and statistical models are combined with both small in situ observation data sets with only few observations, and equally well with enormous global remote sensing data products containing hundreds of millions of data points. This integration of models and data can be done in a Bayesian inverse modeling setting if the algorithms and computational methods used are chosen and implemented carefully. The methods used in the four publications on which this thesis is based range from high-dimensional Bayesian spatial statistical models and Markov chain Monte Carlo methods to time series modeling and point estimation via optimization. The particular geoscientific problems considered are: finding the spatio-temporal distribution of atmospheric carbon dioxide based on sparse remote sensing data, quantifying uncertainties in modeling methane emissions from boreal wetlands, analyzing and quantifying the effect of climate change on growing season in the boreal region, and using statistical methods to calibrate a terrestrial ecosystem model. In addition to analyzing these problems, the research and the results help to understand model performance and how modeling uncertainties in very large computational problems can be approached, also providing algorithm implementations on top of which future efforts may be built.
  • Cano Bernal, José Enrique; Rankinen, Katri; Thielking, Sophia (Academic Press, 2022)
    Journal of Environmental Management
    The majority of the carbon worldwide is in soil. In a river catchment, the tight relationship between soil, water and climate makes carbon likely to be eroded and transported from the soil to the rivers. There are multiple variables which can trigger and accelerate the process. In order to assess the importance of the factors involved, and their interactions resulting in the changes in the carbon cycle within catchments, we have studied the catchments of 26 Finnish rivers from 2000 to 2019. These catchments are distributed all over Finland, but we have grouped them into three categories: southern, peatland and northern. We have run a boosted regression tree (BRT) analysis on chemical, physical, climatic and anthropogenic factors to determine their influence on the variations of total organic carbon (TOC) concentration. TOC concentration has decreased in Finland between 2000 and 2019 by 0.91 mg/l, driven principally by forest ditching and % old forest in the catchment. Old forest is especially dominant in the northern catchments with an influence on TOC of 40.5%. In southern and peatland catchments, average precipitation is an important factor to explain the changes in TOC whilst in northern catchments, organic fields have more influence.
  • Knyazikhin, Yuri; Schull, Mitchell A.; Stenberg, Pauline; Mõttus, Matti; Rautiainen, Miina; Yang, Yan; Marshak, Alexander; Latorre Carmona, Pedro; Kaufmann, Robert K.; Lewis, Philip; Disney, Mathias I.; Vanderbilt, Vern; Davis, Anthony B.; Baret, Frederic; Jacquemoud, Stephane; Lyapustin, Alexei; Myneni, Ranga B. (2013)
  • Kooijmans, Linda M. J.; Sun, Wu; Aalto, Juho; Erkkilä, Kukka-Maaria; Maseyk, Kadmiel; Seibt, Ulrike; Vesala, Timo; Mammarella, Ivan; Chen, Huilin (2019)
    Understanding climate controls on gross primary productivity (GPP) is crucial for accurate projections of the future land carbon cycle. Major uncertainties exist due to the challenge in separating GPP and respiration from observations of the carbon dioxide (CO2) flux. Carbonyl sulfide (COS) has a dominant vegetative sink, and plant COS uptake is used to infer GPP through the leaf relative uptake (LRU) ratio of COS to CO2 fluxes. However, little is known about variations of LRU under changing environmental conditions and in different phenological stages. We present COS and CO2 fluxes and LRU of Scots pine branches measured in a boreal forest in Finland during the spring recovery and summer. We find that the diurnal dynamics of COS uptake is mainly controlled by stomatal conductance, but the leaf internal conductance could significantly limit the COS uptake during the daytime and early in the season. LRU varies with light due to the differential light responses of COS and CO2 uptake, and with vapor pressure deficit (VPD) in the peak growing season, indicating a humidity-induced stomatal control. Our COS-based GPP estimates show that it is essential to incorporate the variability of LRU with environmental variables for accurate estimation of GPP on ecosystem, regional, and global scales.
  • Müller, Mitro (Helsingin yliopisto, 2020)
    A warming trend of annual average surface temperatures since pre-industrial times has been observed globally. High-arctic area of Svalbard, Norway is undergoing amplified change of annual average temperatures when compared to the global average. Decline of glaciers in western Svalbard has been ongoing for several decades, and in the recent past, rapid biological successions have taken place. These changes have likely had effect on regional scale carbon dynamics at Svalbard’s moss tundra areas. Possibly indicating onset of paludification process of these areas. However, palaeoecological studies from the area are scarce, and the response of high-latitude moss tundra areas to past or ongoing climate change, are still not fully understood. This thesis aimed to bring forward information of changes in recent organic matter and carbon accumulation rates at Svalbard, Norway. Soil profiles were collected from four moss tundra sites, located on coastal areas and fjords descending towards Isfjorden, on the western side of Spitsbergen island. Radiocarbon (14C) and lead (210Pb) dating methods with novel age-depth modelling and soil property analyses, were used to reconstruct recent organic matter and carbon accumulation histories from 1900 AD to 2018 AD. Accumulation histories were supported by meteorological measurements from the area. In addition, annual maximum value Normalized Difference Vegetation Indices for 1985 AD till 2018 AD period were produced, to study vegetation succession in the recent past. Lastly, possibility to predict spatiotemporal variation of soil carbon accumulation with satellite derived vegetation indices was assessed. Development from predominantly mineral soils to organic soils was distinguishable within multiple soil profiles, pointing to potential paludification. Recent apparent carbon accumulation rates showed an increasing trend. Supporting meteorological data and literature suggest that regional abiotic and biotic factors in synergy with weather and climate are contributing to this observed trend. Vegetation indices pointed to major changes in vegetation composition and productivity. However, investigation of relationship between recent carbon accumulation rates and vegetation indices did not produce reliable results. Spatiotemporal heterogeneity of carbon soil-atmosphere fluxes presently imposes large challenges for such modelling. To alleviate this problem, efforts for more efficient synergetic use of field sampling and remote sensing -based material should be undertaken, to improve modelling results.
  • Bechtold, M.; De Lannoy, G. J. M.; Koster, R. D.; Reichle, R. H.; Mahanama, S. P.; Bleuten, W.; Bourgault, M. A.; Brümmer, C.; Burdun; Desai, A. R.; Devito, K.; Grünwald, T.; Grygoruk, M.; Humphreys, E. R.; Klatt, J.; Kurbatova, J.; Lohila, A.; Munir, T. M.; Nilsson, M. B.; Price, J. S.; Röhl, M.; Schneider, A.; Tiemeyer, B. (2019)
    Peatlands are poorly represented in global Earth system modeling frameworks. Here we add a peatland-specific land surface hydrology module (PEAT-CLSM) to the Catchment Land Surface Model (CLSM) of the NASA Goddard Earth Observing System (GEOS) framework. The amended TOPMODEL approach of the original CLSM that uses topography characteristics to model catchment processes is discarded, and a peatland-specific model concept is realized in its place. To facilitate its utilization in operational GEOS efforts, PEAT-CLSM uses the basic structure of CLSM and the same global input data. Parameters used in PEAT-CLSM are based on literature data. A suite of CLSM and PEAT-CLSM simulations for peatland areas between 40 degrees N and 75 degrees N is presented and evaluated against a newly compiled data set of groundwater table depth and eddy covariance observations of latent and sensible heat fluxes in natural and seminatural peatlands. CLSM's simulated groundwater tables are too deep and variable, whereas PEAT-CLSM simulates a mean groundwater table depth of -0.20 m (snow-free unfrozen period) with moderate temporal fluctuations (standard deviation of 0.10 m), in significantly better agreement with in situ observations. Relative to an operational CLSM version that simply includes peat as a soil class, the temporal correlation coefficient is increased on average by 0.16 and reaches 0.64 for bogs and 0.66 for fens when driven with global atmospheric forcing data. In PEAT-CLSM, runoff is increased on average by 38% and evapotranspiration is reduced by 19%. The evapotranspiration reduction constitutes a significant improvement relative to eddy covariance measurements.
  • Park, Sung-Bin; Knohl, Alexander; Migliavacca, Mirco; Thum, Tea; Vesala, Timo; Peltola, Olli; Mammarella, Ivan; Prokushkin, Anatoly; Kolle, Olaf; Lavric, Jost; Park, Sang Seo; Heimann, Martin (2021)
    Climate change impacts the characteristics of the vegetation carbon-uptake process in the northern Eurasian terrestrial ecosystem. However, the currently available direct CO2 flux measurement datasets, particularly for central Siberia, are insufficient for understanding the current condition in the northern Eurasian carbon cycle. Here, we report daily and seasonal interannual variations in CO2 fluxes and associated abiotic factors measured using eddy covariance in a coniferous forest and a bog near Zotino, Krasnoyarsk Krai, Russia, for April to early June, 2013-2017. Despite the snow not being completely melted, both ecosystems became weak net CO2 sinks if the air temperature was warm enough for photosynthesis. The forest became a net CO2 sink 7-16 days earlier than the bog. After the surface soil temperature exceeded similar to 1 degrees C, the ecosystems became persistent net CO2 sinks. Net ecosystem productivity was highest in 2015 for both ecosystems because of the anomalously high air temperature in May compared with other years. Our findings demonstrate that long-term monitoring of flux measurements at the site level, particularly during winter and its transition to spring, is essential for understanding the responses of the northern Eurasian ecosystem to spring warming.
  • Siintola, Asko (Helsingfors universitet, 2012)
    Climate change has been found to be one of the most serious challenges humankind has to face in the future. The link between climate change and forests is based on trees’ ability to use carbon dioxide as a raw material for growth. The growing stock sequesters carbon dioxide from the air to itself and ultimately as the forest is harvested the carbon stored is released and it moves from carbon pool of forests to another carbon pool. As the concept of emissions’ trading is applied to the investigation, a price for sequestered and released carbon can be determined. With the market price for carbon dioxide known, a net present value for the revenues and costs during the forest’s rotation period can be calculated. Using wood for different purposes, however, can result in various climatic benefits. These climatic benefits are described in this study by carbon displacement factors which can be used in determining how much the costs of releasing carbon from forests can be deducted. This study investigates the significance of forest management in a stand level from the climate change mitigation point of view in three Norway spruce (Picea abies, L.) and three Scots pine (Pinus Sylvestris, L.) stands as the previous carbon accounting aspects are taken into consideration. Stand Management Assistant (SMA) software is used in the optimization and simulation calculations. The SMA software is used for calculating the carbon accounting net present values and average carbon storages during the rotation periods of the stands included in the study with different intensities of bioenergy biomass harvesting. This way the level of biomass harvesting for bioenergy that returns with the highest net present value for carbon accounting and/or the highest average carbon storage can be calculated. The calculations are made with two interest rates, two carbon dioxide prices and with climatic benefits from bioenergy or with climatic benefits from bioenergy and forest products included. According to the results it can be stated that the intensification of forest biomass recovery for bioenergy production does not always result in the optimal climate change mitigation. The use of Norway spruce is considered of being the most potential forest-based bioenergy source in Finland. As the climatic benefits from bioenergy use were only taken into consideration, the intensification of recovery of Norway spruce biomass for bioenergy seemed to be most profitable. If, however, the climatic benefits from forest products are included in the investigation as well, the bioenergy use of Norway spruce is no longer optimal for the climate change mitigation. The climatic benefits from Norway spruce material use exceed the benefits from bioenergy use. This means that biomass recovery for bioenergy production does not necessarily result in optimal climate change mitigation.
  • Ehrnsten, Eva; Norkko, Alf; Müller-Karulis, Bärbel; Gustafsson, Erik; Gustafsson, Bo G. (2020)
    Nutrient loading and climate change affect coastal ecosystems worldwide. Unravelling the combined effects of these pressures on benthic macrofauna is essential for understanding the future functioning of coastal ecosystems, as it is an important component linking the benthic and pelagic realms. In this study, we extended an existing model of benthic macrofauna coupled with a physical-biogeochemical model of the Baltic Sea to study the combined effects of changing nutrient loads and climate on biomass and metabolism of benthic macrofauna historically and in scenarios for the future. Based on a statistical comparison with a large validation dataset of measured biomasses, the model showed good or reasonable performance across the different basins and depth strata in the model area. In scenarios with decreasing nutrient loads according to the Baltic Sea Action Plan but also with continued recent loads (mean loads 2012-2014), overall macrofaunal biomass and carbon processing were projected to decrease significantly by the end of the century despite improved oxygen conditions at the seafloor. Climate change led to intensified pelagic recycling of primary production and reduced export of particulate organic carbon to the seafloor with negative effects on macrofaunal biomass. In the high nutrient load scenario, representing the highest recorded historical loads, climate change counteracted the effects of increased productivity leading to a hyperbolic response: biomass and carbon processing increased up to mid-21st century but then decreased, giving almost no net change by the end of the 21st century compared to present. The study shows that benthic responses to environmental change are nonlinear and partly decoupled from pelagic responses and indicates that benthic-pelagic coupling might be weaker in a warmer and less eutrophic sea.
  • 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.
  • Ehrnsten, Eva; Sun, Xiaole; Humborg, Christoph; Norkko, Alf; Savchuk, Oleg P.; Slomp, Caroline P.; Timmermann, Karen; Gustafsson, Bo G. (2020)
    Coastal seas are highly productive systems, providing an array of ecosystem services to humankind, such as processing of nutrient effluents from land and climate regulation. However, coastal ecosystems are threatened by human-induced pressures such as climate change and eutrophication. In the coastal zone, the fluxes and transformations of nutrients and carbon sustaining coastal ecosystem functions and services are strongly regulated by benthic biological and chemical processes. Thus, to understand and quantify how coastal ecosystems respond to environmental change, mechanistic modeling of benthic biogeochemical processes is required. Here, we discuss the present model capabilities to quantitatively describe how benthic fauna drives nutrient and carbon processing in the coastal zone. There are a multitude of modeling approaches of different complexity, but a thorough mechanistic description of benthic-pelagic processes is still hampered by a fundamental lack of scientific understanding of the diverse interactions between the physical, chemical and biological processes that drive biogeochemical fluxes in the coastal zone. Especially shallow systems with long water residence times are sensitive to the activities of benthic organisms. Hence, including and improving the description of benthic biomass and metabolism in sediment diagenetic as well as ecosystem models for such systems is essential to increase our understanding of their response to environmental changes and the role of coastal sediments in nutrient and carbon cycling. Major challenges and research priorities are (1) to couple the dynamics of zoobenthic biomass and metabolism to sediment reactive-transport in models, (2) to test and validate model formulations against real-world data to better incorporate the context-dependency of processes in heterogeneous coastal areas in models and (3) to capture the role of stochastic events.