scholarly journals Uncertainties in modeling CH<sub>4</sub> emissions from northern wetlands in glacial climates: effect of hydrological model and CH<sub>4</sub> model structure

2009 ◽  
Vol 5 (2) ◽  
pp. 817-851 ◽  
Author(s):  
C. Berrittella ◽  
J. van Huissteden
Keyword(s):  
Ice Cover ◽  
Atmospheric Composition ◽  
Model Structure ◽  
Vegetation Model ◽  
Ch4 Flux ◽  
Tuning Parameters ◽  
Ch4 Production ◽  
Highly Sensitive ◽  
Flux Model ◽  
Earth System Models

Abstract. Methane (CH4) fluxes from northern wetlands may have influenced atmospheric CH4 concentrations at climate warming phases during the 800 000 years and at present global warming. Including these CH4 fluxes in earth system models is essential to understand feedbacks between climate and atmospheric composition. Attempts to model CH4 fluxes from wetlands have been undertaken previously using various approaches. Here, we test a process-based wetland CH4 flux model (PEATLAND-VU) which includes details of soil-atmosphere CH4 transport. The model has been used to simulate CH4 emissions from continental Europe in different glacial climates and the present climate. This paper displays results on the sensitivity of modeling glacial terrestrial CH4 fluxes to basic tuning parameters of the model, to different approaches in modeling of the water table, and to model structure. For testing the model structure, PEATLAND-VU has been compared to a simpler modeling approach based on wetland primary production estimated from a vegetation model (BIOME). The tuning parameters are the CH4 production rate from labile organic carbon and its temperature sensitivity. The modelled fluxes prove comparatively insensitive to hydrology representation, and sensitive to microbial parameters and model structure. Glacial climate emissions are also highly sensitive to assumptions on the extent of ice cover and exposed seafloors. Wetland expansion on low relief exposed seafloor areas, may have compensated for a decrease of wetland area due to continental ice cover.

scholarly journals Uncertainties in modelling CH<sub>4</sub> emissions from northern wetlands in glacial climates: effect of hydrological model and CH<sub>4</sub> model structure

2009 ◽  
Vol 5 (3) ◽  
pp. 361-373 ◽  
Author(s):  
C. Berrittella ◽  
J. van Huissteden
Keyword(s):  
Ice Cover ◽  
Atmospheric Composition ◽  
Model Structure ◽  
Vegetation Model ◽  
Ch4 Flux ◽  
Tuning Parameters ◽  
Ch4 Production ◽  
Highly Sensitive ◽  
Flux Model ◽  
Earth System Models

Abstract. Methane (CH4) fluxes from northern wetlands may have influenced atmospheric CH4 concentrations at climate warming phases during the last 800 000 years and during the present global warming. Including these CH4 fluxes in earth system models is essential to understand feedbacks between climate and atmospheric composition. Attempts to model CH4 fluxes from wetlands have previously been undertaken using various approaches. Here, we test a process-based wetland CH4 flux model (PEATLAND-VU) which includes details of soil-atmosphere CH4 transport. The model has been used to simulate CH4 emissions from continental Europe in previous glacial climates and the current climate. This paper presents results regarding the sensitivity of modeling glacial terrestrial CH4 fluxes to (a) basic tuning parameters of the model, (b) different approaches in modeling of the water table, and (c) model structure. In order to test the model structure, PEATLAND-VU was compared to a simpler modeling approach based on wetland primary production estimated from a vegetation model (BIOME 3.5). The tuning parameters are the CH4 production rate from labile organic carbon and its temperature sensitivity. The modelled fluxes prove comparatively insensitive to hydrology representation, while sensitive to microbial parameters and model structure. Glacial climate emissions are also highly sensitive to assumptions about the extent of ice cover and exposed seafloor. Wetland expansion over low relief exposed seafloor areas have compensated for a decrease of wetland area due to continental ice cover.

scholarly journals Multi-year effect of wetting on CH<sub>4</sub> flux at taiga–tundra boundary in northeastern Siberia deduced from stable isotope ratios of CH<sub>4</sub>

2019 ◽  
Vol 16 (3) ◽  
pp. 755-768 ◽  
Author(s):  
Ryo Shingubara ◽  
Atsuko Sugimoto ◽  
Jun Murase ◽  
Go Iwahana ◽  
Shunsuke Tei ◽  
...  
Keyword(s):  
Water Saturation ◽  
Methane Flux ◽  
Interannual Variations ◽  
Ch4 Emission ◽  
Ch4 Flux ◽  
Ch4 Production ◽  
Year Effect ◽  
Northeastern Siberia ◽  
Order Of Magnitude ◽  
Acetoclastic Methanogenesis

Abstract. The response of CH4 emission from natural wetlands due to meteorological conditions is important because of its strong greenhouse effect. To understand the relationship between CH4 flux and wetting, we observed interannual variations in chamber CH4 flux, as well as the concentration, δ13C, and δD of dissolved CH4 during the summer from 2009 to 2013 at the taiga–tundra boundary in the vicinity of Chokurdakh (70∘37′ N, 147∘55′ E), located on the lowlands of the Indigirka River in northeastern Siberia. We also conducted soil incubation experiments to interpret δ13C and δD of dissolved CH4 and to investigate variations in CH4 production and oxidation processes. Methane flux showed large interannual variations in wet areas of sphagnum mosses and sedges (36–140 mg CH4 m−2 day−1 emitted). Increased CH4 emission was recorded in the summer of 2011 when a wetting event with extreme precipitation occurred. Although water level decreased from 2011 to 2013, CH4 emission remained relatively high in 2012, and increased further in 2013. Thaw depth became deeper from 2011 to 2013, which may partly explain the increase in CH4 emission. Moreover, dissolved CH4 concentration rose sharply by 1 order of magnitude from 2011 to 2012, and increased further from 2012 to 2013. Large variations in δ13C and δD of dissolved CH4 were observed in 2011, and smaller variations were seen in 2012 and 2013, suggesting both enhancement of CH4 production and less significance of CH4 oxidation relative to the larger pool of dissolved CH4. These multi-year effects of wetting on CH4 dynamics may have been caused by continued soil reduction across multiple years following the wetting. Delayed activation of acetoclastic methanogenesis following soil reduction could also have contributed to the enhancement of CH4 production. These processes suggest that duration of water saturation in the active layer can be important for predicting CH4 emission following a wetting event in the permafrost ecosystem.

scholarly journals Ideas and Perspectives: Climate-Relevant Marine Biologically-Driven Mechanisms in Earth System Models

2016 ◽  
Author(s):  
Inga Hense ◽  
Irene Stemmler ◽  
Sebastian Sonntag
Keyword(s):  
Mechanical Properties ◽  
Functional Groups ◽  
Atmospheric Composition ◽  
Marine Biota ◽  
Earth System ◽  
System Models ◽  
System Components ◽  
Optical And Mechanical Properties ◽  
Earth System Models

Abstract. Marine biota drives a number of climate-relevant mechanisms not all of which are included in current Earth system models (ESMs). We identify three classes of mechanisms and distinguish (1) those related to matter cycling via "biogeochemical pumps", (2) those affecting the atmospheric composition via the "biological gas and particle shuttles" and (3) those changing the thermal, optical and mechanical properties of the ocean via the "biogeophysical mechanisms". We argue that to adequately resolve these mechanisms, ESMs need to account for five functional groups, including bulk phyto- and zooplankton, calcifiers as well as coastal gas and surface mat producers. Thereby links to other Earth system components are ensured and a larger number of relevant feedbacks are enabled to take place.

scholarly journals Contribution of recent plant photosynthates of <i>Eriophorum vaginatum</i> and <i>Scheuchzeria palustris</i> to methanogenesis and CH<sub>4</sub> transport at a boreal mire: a <sup>14</sup>C pulse-labeling study

2011 ◽  
Vol 8 (3) ◽  
pp. 4359-4389
Author(s):  
M. Dorodnikov ◽  
K.-H. Knorr ◽  
Y. Kuzyakov ◽  
M. Wilmking
Keyword(s):  
Plant Species ◽  
Plant Biomass ◽  
Vascular Plant ◽  
Eriophorum Vaginatum ◽  
Ch4 Flux ◽  
Ch4 Production ◽  
Scheuchzeria Palustris ◽  
Species Specific ◽  
Ch4 Transport

Abstract. Contribution of recent photosynthates to methanogenesis and plant-mediated methane (CH4) transport were studied on two dominating vascular plant species – Eriophorum vaginatum and Scheuchzeria palustris – at three microform types (hummocks, lawns and hollows) of a boreal natural minerogenic, oligotrophic fen in Eastern Finland. Measurements of total CH4 flux, isolation of shoots from entire peat and 14C-pulse labeling of mesocosms under controlled conditions allowed estimation of plant-mediated CH4 flux and contribution of recent (14C) photosynthates to total CH4. The obtained results showed (i) CH4 flux increases in the order E. hummocks ≤ E. lawns < S. hollows corresponding to the increasing water table level of the microforms as derived from in situ measurements. (ii) Plant-mediated CH4 flux accounted for 38, 31 and 51 % of total CH4 at E. hummocks, E. lawns and S. hollows, respectively. (iii) Contribution of recent photosynthates to methanogenesis accounted for 0.03 % for E. hummocks, 0.06 % for E. lawns and 0.13 % for S. hollows of assimilated 14C. Thus, S. palustris microsites are characterized by a higher efficiency for transporting CH4 from the peat column to the atmosphere when compared to E. vaginatum of drier lawns and hummocks. Contribution of recent plant photosynthates to methanogenesis was not depended on the amount of plant biomass: smaller S. palustris had higher 14CH4 as compared to larger E. vaginatum. Therefore, for the assessment of CH4 production and emission over meso- and macroscales as well as for the implication and development of C modeling of CH4 fluxes, it is necessary to account for plant species-specific processes including CH4 production, consumption and transportation and the attribution of those species to topographic microforms.

Future fires in the Coupled Model Intercomparison Project (CMIP) phase 6

2020 ◽  
Author(s):  
Gitta Lasslop ◽  
Stijn Hantson ◽  
Victor Brovkin ◽  
Fang Li ◽  
David Lawrence ◽  
...  
Keyword(s):  
Land Use ◽  
Fire Regime ◽  
Coupled Model ◽  
Fire Regimes ◽  
Atmospheric Composition ◽  
Cloud Formation ◽  
Burned Area ◽  
Earth System ◽  
System Models ◽  
Earth System Models

&lt;p&gt;Fires are an important component in Earth system models (ESMs), they impact vegetation carbon storage, vegetation distribution, atmospheric composition and cloud formation. The representation of fires in ESMs contributing to CMIP phase 5 was still very simplified. Several Earth system models updated their representation of fires in the meantime. Using the latest simulations of CMIP6 we investigate how fire regimes change in the future for different scenarios and how land use, climate and atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentration contribute to the fire regimes changes. We quantify changes in fire danger, burned area and carbon emissions on an annual and seasonal basis. Factorial model simulations allow to quantify the influence of land use, climate and atmospheric CO&lt;sub&gt;2&lt;/sub&gt; on fire regimes.&lt;/p&gt;&lt;p&gt;We complement the information on fire regime change supplied by ESMs that include a fire module with a statistical modelling approach for burned area. This will use information from simulated changes in climate, vegetation and socioeconomic changes (population density and land use) provided for a set of different future scenarios. This allows the integration of information provided by global satellite products on burned area with the process-based simulations of climate and vegetation changes and information from socioeconomic scenarios.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals What are the greenhouse gas observing system requirements for reducing fundamental biogeochemical process uncertainty? Amazon wetland CH<sub>4</sub> emissions as a case study

2016 ◽  
Vol 16 (23) ◽  
pp. 15199-15218 ◽  
Author(s):  
A. Anthony Bloom ◽  
Thomas Lauvaux ◽  
John Worden ◽  
Vineet Yadav ◽  
Riley Duren ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Climate Science ◽  
Low Earth Orbit ◽  
Biogeochemical Process ◽  
Satellite Mission ◽  
Ch4 Flux ◽  
Process Uncertainty ◽  
Ch4 Production ◽  
Process Controls

Abstract. Understanding the processes controlling terrestrial carbon fluxes is one of the grand challenges of climate science. Carbon cycle process controls are readily studied at local scales, but integrating local knowledge across extremely heterogeneous biota, landforms and climate space has proven to be extraordinarily challenging. Consequently, top-down or integral flux constraints at process-relevant scales are essential to reducing process uncertainty. Future satellite-based estimates of greenhouse gas fluxes – such as CO2 and CH4 – could potentially provide the constraints needed to resolve biogeochemical process controls at the required scales. Our analysis is focused on Amazon wetland CH4 emissions, which amount to a scientifically crucial and methodologically challenging case study. We quantitatively derive the observing system (OS) requirements for testing wetland CH4 emission hypotheses at a process-relevant scale. To distinguish between hypothesized hydrological and carbon controls on Amazon wetland CH4 production, a satellite mission will need to resolve monthly CH4 fluxes at a ∼ 333 km resolution and with a ≤ 10 mg CH4 m−2 day−1 flux precision. We simulate a range of low-earth orbit (LEO) and geostationary orbit (GEO) CH4 OS configurations to evaluate the ability of these approaches to meet the CH4 flux requirements. Conventional LEO and GEO missions resolve monthly ∼ 333 km Amazon wetland fluxes at a 17.0 and 2.7 mg CH4 m−2 day−1 median uncertainty level. Improving LEO CH4 measurement precision by 2 would only reduce the median CH4 flux uncertainty to 11.9 mg CH4 m−2 day−1. A GEO mission with targeted observing capability could resolve fluxes at a 2.0–2.4 mg CH4 m−2 day−1 median precision by increasing the observation density in high cloud-cover regions at the expense of other parts of the domain. We find that residual CH4 concentration biases can potentially reduce the ∼ 5-fold flux CH4 precision advantage of a GEO mission to a ∼ 2-fold advantage (relative to a LEO mission). For residual CH4 bias correlation lengths of 100 km, the GEO can nonetheless meet the  ≤  10 mg CH4 m−2 day−1 requirements for systematic biases ≤ 10 ppb. Our study demonstrates that process-driven greenhouse gas OS simulations can enhance conventional uncertainty reduction assessments by quantifying the OS characteristics required for testing biogeochemical process hypotheses.

Modelling forest management within a global vegetation model—Part 1: Model structure and general behaviour

2010 ◽  
Vol 221 (20) ◽  
pp. 2458-2474 ◽  
Author(s):  
V. Bellassen ◽  
G. Le Maire ◽  
J.F. Dhôte ◽  
P. Ciais ◽  
N. Viovy
Keyword(s):  
Forest Management ◽  
Model Structure ◽  
Vegetation Model ◽  
General Behaviour ◽  
Global Vegetation

scholarly journals Methane paradox in tropical lakes? Sedimentary fluxes rather than water column production in oxic waters sustain methanotrophy and emissions to the atmosphere

2020 ◽  
Author(s):  
Cédric Morana ◽  
Steven Bouillon ◽  
Vimac Nolla-Ardèvol ◽  
Fleur A. E. Roland ◽  
William Okello ◽  
...  
Keyword(s):  
Surface Waters ◽  
Tropical Lakes ◽  
Large Lakes ◽  
Ch4 Flux ◽  
Ch4 Emissions ◽  
Isotope Tracer ◽  
Ch4 Production ◽  
Elevated Water ◽  
Lake Size ◽  
Sunlight Intensity

Abstract. Despite growing evidence that methane (CH4) formation could also occur in well-oxygenated surface freshwaters, its significance at the ecosystem scale is uncertain. Empirical models based on data gathered at high latitude predict that the contribution of oxic CH4 increases with lake size and should represent the majority of CH4 emissions in large lakes. However, such predictive models could not directly apply to tropical lakes which differ from their temperate counterparts in some fundamental characteristics, such as year-round elevated water temperature. We conducted stable isotope tracer experiments which revealed that oxic CH4 production is closely related to phytoplankton metabolism, and is a common feature in five contrasting African lakes. Nevertheless, methanotrophic activity in surface waters and CH4 emissions to the atmosphere were predominantly fuelled by CH4 generated in sediments and physically transported to the surface. Indeed, measured CH4 bubble dissolution flux and diffusive benthic CH4 flux were several orders of magnitude higher than CH4 production in surface waters. Microbial CH4 consumption dramatically decreased with increasing sunlight intensity, suggesting that the freshwater CH4 paradox might be also partly explained by photo-inhibition of CH4 oxidizers in the illuminated zone. Sunlight appeared as an overlooked but important factor determining the CH4 dynamics in surface waters, directly affecting its production by photoautotrophs and consumption by methanotrophs.

scholarly journals Process-based estimates of terrestrial ecosystem isoprene emissions: incorporating the effects of a direct CO<sub>2</sub>-isoprene interaction

2007 ◽  
Vol 7 (1) ◽  
pp. 31-53 ◽  
Author(s):  
A. Arneth ◽  
Ü. Niinemets ◽  
S. Pressley ◽  
J. Bäck ◽  
P. Hari ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Co2 Concentration ◽  
Interactive Effects ◽  
Atmospheric Composition ◽  
Vegetation Model ◽  
Model Framework ◽  
Growth Environment ◽  
Isoprene Emission ◽  
Dynamic Vegetation Model ◽  
Wide Range

Abstract. In recent years evidence has emerged that the amount of isoprene emitted from a leaf is affected by the CO2 growth environment. Many – though not all – laboratory experiments indicate that emissions increase significantly at below-ambient CO2 concentrations and decrease when concentrations are raised to above-ambient. A small number of process-based leaf isoprene emission models can reproduce this CO2 stimulation and inhibition. These models are briefly reviewed, and their performance in standard conditions compared with each other and to an empirical algorithm. One of the models was judged particularly useful for incorporation into a dynamic vegetation model framework, LPJ-GUESS, yielding a tool that allows the interactive effects of climate and increasing CO2 concentration on vegetation distribution, productivity, and leaf and ecosystem isoprene emissions to be explored. The coupled vegetation dynamics-isoprene model is described and used here in a mode particularly suited for the ecosystem scale, but it can be employed at the global level as well. Annual and/or daily isoprene emissions simulated by the model were evaluated against flux measurements (or model estimates that had previously been evaluated with flux data) from a wide range of environments, and agreement between modelled and simulated values was generally good. By using a dynamic vegetation model, effects of canopy composition, disturbance history, or trends in CO2 concentration can be assessed. We show here for five model test sites that the suggested CO2-inhibition of leaf-isoprene metabolism can be large enough to offset increases in emissions due to CO2-stimulation of vegetation productivity and leaf area growth. When effects of climate change are considered atop the effects of atmospheric composition the interactions between the relevant processes will become even more complex. The CO2-isoprene inhibition may have the potential to significantly dampen the expected steep increase of ecosystem isoprene emission in a future, warmer atmosphere with higher CO2 levels; this effect raises important questions for projections of future atmospheric chemistry, and its connection to the terrestrial vegetation and carbon cycle.

scholarly journals Plant-mediated CH<sub>4</sub> transport and contribution of photosynthates to methanogenesis at a boreal mire: a <sup>14</sup>C pulse-labeling study

2011 ◽  
Vol 8 (8) ◽  
pp. 2365-2375 ◽  
Author(s):  
M. Dorodnikov ◽  
K.-H. Knorr ◽  
Y. Kuzyakov ◽  
M. Wilmking
Keyword(s):  
Plant Species ◽  
Plant Biomass ◽  
Vascular Plant ◽  
Species Level ◽  
Ch4 Flux ◽  
Ch4 Production ◽  
Scheuchzeria Palustris ◽  
Species Specific ◽  
Ch4 Transport ◽  
Eastern Finland

Abstract. Plant-mediated methane (CH4) transport and the contribution of recent photosynthates to methanogenesis were studied on two dominating vascular plant species – Eriophorum vaginatum and Scheuchzeria palustris – at three types of microrelief forms (hummocks – E. hummocks, lawns – E. lawns and hollows – S. hollows) of a boreal natural minerogenic, oligotrophic fen in Eastern Finland. 14C-pulse labeling of mesocosms with shoots isolated from entire belowground peat under controlled conditions allowed estimation of plant-mediated CH4 flux and contribution of recent (14C) photosynthates to total CH4. The results showed (i) CH4 flux increased in the order E. hummocks ≤ E. lawns < S. hollows corresponding to the increasing water table level at the relief microforms as adjusted to field conditions. (ii) Plant-mediated CH4 flux accounted for 38, 31 and 51 % of total CH4 at E. hummocks, E. lawns and S. hollows, respectively. (iii) Contribution of recent photosynthates to methanogenesis accounted for 0.03 % for E. hummocks, 0.06 % for E. lawns and 0.13 % for S.hollows of assimilated 14C. Thus, microsites with S. palustris were characterized by higher rates of transported CH4 from the peat column to the atmosphere when compared to E. vaginatum of drier lawns and hummocks. Contribution of recent photosynthates to methanogenesis was dependent on the plant biomass within-species level (E. vaginatum at hummocks and lawns) but was not observed between species: smaller S. palustris had higher flux of 14CH4 as compared to larger E. vaginatum. Therefore, for the assessment of CH4 dynamics over meso- and macroscale as well as for the implication and development of the modeling of CH4 fluxes, it is necessary to account for plant species-specific differences in CH4 production, consumption and transport and the attribution of those species to topographic forms of microrelief.

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