scholarly journals Were Neoarchean atmospheric methane hazes and early Paleoproterozoic glaciations driven by the rise of oxygen in surface environments?

2020 ◽  
Author(s):  
Anshuman Swain ◽  
Alan J Kaufman ◽  
Marcin Kalinowski ◽  
William F Fagan
Keyword(s):  
Initial Conditions ◽  
Interaction Model ◽  
Methane Flux ◽  
Progressive Increase ◽  
Atmospheric Methane ◽  
Methane Cycle ◽  
Deep Time ◽  
Resource Concentration ◽  
Early Proterozoic ◽  
Environmental Controls

AbstractInsofar as methane was the predominant greenhouse gas of the Archean and early Proterozoic eons, its wax and wane in Earth’s atmosphere would have contributed to climate change and the relative flux of harmful UV radiation to surface environments. If correct, understanding the first-order environmental controls (e.g., O2 or resource concentration) of the biological methane cycle might shed light on the repetition of biological, atmospheric and climatic events preserved in the sedimentary rock record between ~2.8 and 2.0 billion years ago. Environmental controls on the dynamics of methane cycling may further explain other repetitious events in deep time, as well as the present-day increase in the methane flux to the atmosphere from wetland environments. In this study, we developed an ecological interaction model to predict the conditions in which methane is preferentially released to the atmosphere, and found that the interplay of resource and O2 availability can cause complex cyclic patterns in methane dynamics that are unrelated to the size and efficiency of any of the microbial communities, to initial conditions, or to other model constraints. Based on these model results, we propose that the cyclicity of methane haze events and glacial episodes in the late Archean and early Proterozoic may have been linked to the progressive increase in oceanic and atmospheric O2 through the interval.

scholarly journals A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

2014 ◽  
Vol 11 (6) ◽  
pp. 7853-7900
Author(s):  
D. Archer
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Continental Margin ◽  
Methane Flux ◽  
Soil Freezing ◽  
Sediment Surface ◽  
Atmospheric Methane ◽  
Pore Waters ◽  
Methane Cycle ◽  
The Impact

Abstract. A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbon (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.

scholarly journals Characterization of Methanotrophic Bacterial Populations in Soils Showing Atmospheric Methane Uptake

1999 ◽  
Vol 65 (8) ◽  
pp. 3312-3318 ◽  
Author(s):  
Andrew J. Holmes ◽  
Peter Roslev ◽  
Ian R. McDonald ◽  
Niels Iversen ◽  
Kaj Henriksen ◽  
...  
Keyword(s):  
Feedback Regulation ◽  
Methane Flux ◽  
Atmospheric Methane ◽  
Methane Cycle ◽  
Bacterial Populations ◽  
Methane Oxidizing Bacteria ◽  
Monooxygenase Gene ◽  
Methane Uptake ◽  
Methane Level

ABSTRACT The global methane cycle includes both terrestrial and atmospheric processes and may contribute to feedback regulation of the climate. Most oxic soils are a net sink for methane, and these soils consume approximately 20 to 60 Tg of methane per year. The soil sink for atmospheric methane is microbially mediated and sensitive to disturbance. A decrease in the capacity of this sink may have contributed to the ∼1% · year−1 increase in the atmospheric methane level in this century. The organisms responsible for methane uptake by soils (the atmospheric methane sink) are not known, and factors that influence the activity of these organisms are poorly understood. In this study the soil methane-oxidizing population was characterized by both labelling soil microbiota with14CH4 and analyzing a total soil monooxygenase gene library. Comparative analyses of [14C]phospholipid ester-linked fatty acid profiles performed with representative methane-oxidizing bacteria revealed that the soil sink for atmospheric methane consists of an unknown group of methanotrophic bacteria that exhibit some similarity to type II methanotrophs. An analysis of monooxygenase gene libraries from the same soil samples indicated that an unknown group of bacteria belonging to the α subclass of the class Proteobacteria was present; these organisms were only distantly related to extant methane-oxidizing strains. Studies on factors that affect the activity, population dynamics, and contribution to global methane flux of “atmospheric methane oxidizers” should be greatly facilitated by use of biomarkers identified in this study.

Captured metagenomics reveals high spatial variability in functional potential in CH4 producing and consuming microorganisms in a temperate Swedish peatland.

2021 ◽  
Author(s):  
Joel White ◽  
Lena Ström ◽  
Dag Ahrén ◽  
Janne Rinne ◽  
Veiko Lehsten
Keyword(s):  
Microbial Communities ◽  
Root Zone ◽  
Water Concentration ◽  
Methane Flux ◽  
Functional Genes ◽  
Molecular Technique ◽  
Atmospheric Methane ◽  
Functional Potential ◽  
Methane Budget ◽  
Methane Metabolism

<p>Microbial communities of methane producing methanogens and consuming methanotrophs play an important role for the earths atmospheric methane budget. Despite their global significance, the functional potential of these communities is poorly understood. To investigate this, we applied the molecular technique, captured metagenomics, to identify the variability in functional diversity of microorganisms involved in the metabolism of methane<sub></sub>in an environmentally controlled laboratory study. Nine plant-peat mesocosms dominated by the sedge Eriophorum vaginatum, with varying coverage, were collected from a temperate natural wetland is Sweden and subjected to a simulated growing season. Samples for analysis of captured metagenomes were taken from the top, bottom and root adjacent zone at the end of the experiment. In addition, over the simulated season, measured gas fluxes of carbon dioxide (CO<sub>2</sub>) and CH<sub>4</sub>, δ<sup>13</sup>C of emitted CH<sub>4</sub> and the pore water concentration of dissolved methane and low molecular weight organic acids were recorded. The functional genes resulting from the captured metagenomes had a higher Shannon α-diversity in the root zone when compared to the bottom and top. Sequences coding for methane metabolism were significantly more diverse in the root and bottom zones when compared to the top. However, the frequency of Acetyl-CoA decarbonylase and methane monooxygenase subunit A were significantly higher in the high emitting methane flux category when compared to the medium and low emitting mesocosms. We conclude that captured metagenomic analyses of functional genes provides a good measure of the functional potential methanogenic and methanotrophic microbial communities. This technique can be used to investigate how methanogens and methanotrophs function in peatlands and thus, contribute to the concentration of atmospheric methane.</p>

scholarly journals Riddles in the cold: Antarctic endemism and microbial succession impact methane cycling in the Southern Ocean

2020 ◽  
Vol 287 (1931) ◽  
pp. 20201134 ◽  
Author(s):  
Andrew R. Thurber ◽  
Sarah Seabrook ◽  
Rory M. Welsh
Keyword(s):  
Microbial Community ◽  
Greenhouse Gas Emission ◽  
Ross Sea ◽  
Methane Flux ◽  
Rrna Gene ◽  
Methane Seep ◽  
Microbial Succession ◽  
Methane Cycle ◽  
16S Rrna Gene Analysis ◽  
Successional Stage

Antarctica is estimated to contain as much as a quarter of earth's marine methane, however we have not discovered an active Antarctic methane seep limiting our understanding of the methane cycle. In 2011, an expansive (70 m × 1 m) microbial mat formed at 10 m water depth in the Ross Sea, Antarctica which we identify here to be a high latitude hydrogen sulfide and methane seep. Through 16S rRNA gene analysis on samples collected 1 year and 5 years after the methane seep formed, we identify the taxa involved in the Antarctic methane cycle and quantify the response rate of the microbial community to a novel input of methane. One year after the seep formed, ANaerobic MEthane oxidizing archaea (ANME), the dominant sink of methane globally, were absent. Five years later, ANME were found to make up to 4% of the microbial community, however the dominant member of this group observed (ANME-1) were unexpected considering the cold temperature (−1.8°C) and high sulfate concentrations (greater than 24 mM) present at this site. Additionally, the microbial community had not yet formed a sufficient filter to mitigate the release of methane from the sediment; methane flux from the sediment was still significant at 3.1 mmol CH 4 m −2 d −1 . We hypothesize that this 5 year time point represents an early successional stage of the microbiota in response to methane input. This study provides the first report of the evolution of a seep system from a non-seep environment, and reveals that the rate of microbial succession may have an unrealized impact on greenhouse gas emission from marine methane reservoirs.

scholarly journals Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements

2017 ◽  
Vol 17 (13) ◽  
pp. 8371-8394 ◽  
Author(s):  
Thibaud Thonat ◽  
Marielle Saunois ◽  
Philippe Bousquet ◽  
Isabelle Pison ◽  
Zeli Tan ◽  
...  
Keyword(s):  
Land Surface ◽  
Transport Model ◽  
Land Surface Model ◽  
Arctic Region ◽  
The Arctic ◽  
Surface Model ◽  
Atmospheric Methane ◽  
Multiple Sources ◽  
Atmospheric Measurements ◽  
Methane Cycle

Abstract. 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 June–July. 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.

scholarly journals Enrichment in <sup>13</sup>C of atmospheric CH<sub>4</sub> during the Younger Dryas termination

2011 ◽  
Vol 7 (5) ◽  
pp. 3287-3324 ◽  
Author(s):  
J. R. Melton ◽  
H. Schaefer ◽  
M. J. Whiticar
Keyword(s):  
Mass Balance ◽  
Gas Hydrates ◽  
Stable Carbon Isotope ◽  
Younger Dryas ◽  
Analytical Techniques ◽  
Carbon Isotope Ratio ◽  
Methane Flux ◽  
Atmospheric Methane ◽  
Stable Carbon ◽  
Thermokarst Lakes

Abstract. The abrupt warming across the Younger Dryas termination (~11 600 yr before present) was marked by a large increase in the global atmospheric methane mixing ratio. The debate over sources responsible for the rise in methane centers on the roles of global wetlands, marine gas hydrates, and thermokarst lakes. We present a new, higher-precision methane stable carbon isotope ratio (δ13CH4) dataset from ice sampled at Påkitsoq, Greenland that shows distinct 13C-enrichment associated with this rise. We investigate the validity of this finding in face of known anomalous methane concentrations that occur at Påkitsoq. Comparison with previously published datasets to determine the robustness of our results indicates a similar trend in ice from both an Antarctic ice core and previously published Påktisoq data measured using four different extraction and analytical techniques. The δ13CH4 trend suggests that 13C-enriched CH4 sources played an important role in the concentration increase. In a first attempt at quantifying the various contributions from our data, we apply a methane triple mass balance of stable carbon and hydrogen isotope ratios and radiocarbon. The mass balance results suggest biomass burning (42–66% of total methane flux increase) and thermokarst lakes (27–59%) as the dominant contributing sources. Our results do not suggest as large a role for tropical wetlands, boreal peatlands or marine gas hydrates as commonly proposed.

scholarly journals An analysis of atmospheric CH<sub>4</sub> concentrations from 1984 to 2008 with a single box atmospheric chemistry model

2012 ◽  
Vol 12 (11) ◽  
pp. 30259-30282 ◽  
Author(s):  
Z. Tan ◽  
Q. Zhuang
Keyword(s):  
Growth Rate ◽  
Atmospheric Chemistry ◽  
Methane Flux ◽  
Methane Emissions ◽  
Atmospheric Methane ◽  
Significant Drop ◽  
Oxidizing Power ◽  
The Mean

Abstract. We present a single box atmospheric chemistry model involving atmospheric methane (CH4), carbon monoxide (CO) and radical hydroxyl (OH) to analyze atmospheric CH4 concentrations from 1984 to 2008. When OH is allowed to vary, the modeled CH4 is 20 ppb higher than observations from the NOAA/ESRL and AGAGE networks for the end of 2008. However, when the OH concentration is held constant at 106 molecule cm−3, the simulated CH4 shows a trend approximately equal to observations. Both simulations show a clear slowdown in the CH4 growth rate during recent decades, from about 13 ppb yr−1 in 1984 to less than 5 ppb yr−1 in 2003. Furthermore, if the constant OH assumption is credible, we think that this slowdown is mainly due to a pause in the growth of wetland methane emissions. In simulations run for the Northern and Southern Hemispheres separately, we find that the Northern Hemisphere is more sensitive to wetland emissions, whereas the southern tends to be more perturbed by CH4 transportation, dramatic OH change, and biomass burning. When measured CO values from NOAA/ESRL are used to drive the model, changes in the CH4 growth rate become more consistent with observations, but the long-term increase in CH4 is underestimated. This shows that CO is a good indicator of short-term variations in oxidizing power in the atmosphere. The simulation results also indicate the significant drop in OH concentrations in 1998 (about 5% lower than the previous year) was probably due to an abrupt increase in wetland methane emissions during an intense EI Niño event. Using a fixed-lag Kalman smoother, we estimate the mean wetland methane flux is about 128 Tg yr−1 through the period 1984–2008. This study demonstrates the effectiveness in examining the role of OH and CO in affecting CH4.

scholarly journals Uncovering the Diversity and Activity of Methylotrophic Methanogens in Freshwater Wetland Soils

mSystems ◽  
2019 ◽  
Vol 4 (6) ◽  
Author(s):  
Adrienne B. Narrowe ◽  
Mikayla A. Borton ◽  
David W. Hoyt ◽  
Garrett J. Smith ◽  
Rebecca A. Daly ◽  
...  
Keyword(s):  
16S Rrna ◽  
Field Experiments ◽  
Meta Analysis ◽  
Methane Flux ◽  
Climatic Conditions ◽  
Freshwater Wetland ◽  
Wetland Soils ◽  
Wetland Soil ◽  
Methane Cycle ◽  
Biogeochemical Models

ABSTRACT Wetland soils are one of the largest natural contributors to the emission of methane, a potent greenhouse gas. Currently, microbial contributions to methane emissions from these systems emphasize the roles of acetoclastic and hydrogenotrophic methanogens, while less frequently considering methyl-group substrates (e.g., methanol and methylamines). Here, we integrated laboratory and field experiments to explore the potential for methylotrophic methanogenesis in Old Woman Creek (OWC), a temperate freshwater wetland located in Ohio, USA. We first demonstrated the capacity for methylotrophic methanogenesis in these soils using laboratory soil microcosms amended with trimethylamine. However, subsequent field porewater nuclear magnetic resonance (NMR) analyses to identify methanogenic substrates failed to detect evidence for methylamine compounds in soil porewaters, instead noting the presence of the methylotrophic substrate methanol. Accordingly, our wetland soil-derived metatranscriptomic data indicated that methanol utilization by the Methanomassiliicoccaceae was the likely source of methylotrophic methanogenesis. Methanomassiliicoccaceae relative contributions to mcrA transcripts nearly doubled with depth, accounting for up to 8% of the mcrA transcripts in 25-cm-deep soils. Longitudinal 16S rRNA amplicon and mcrA gene surveys demonstrated that Methanomassiliicoccaceae were stably present over 2 years across lateral and depth gradients in this wetland. Meta-analysis of 16S rRNA sequences similar (>99%) to OWC Methanomassiliicoccaceae in public databases revealed a global distribution, with a high representation in terrestrial soils and sediments. Together, our results demonstrate that methylotrophic methanogenesis likely contributes to methane flux from climatically relevant wetland soils. IMPORTANCE Understanding the sources and controls on microbial methane production from wetland soils is critical to global methane emission predictions, particularly in light of changing climatic conditions. Current biogeochemical models of methanogenesis consider only acetoclastic and hydrogenotrophic sources and exclude methylotrophic methanogenesis, potentially underestimating microbial contributions to methane flux. Our multi-omic results demonstrated that methylotrophic methanogens of the family Methanomassiliicoccaceae were present and active in a freshwater wetland, with metatranscripts indicating that methanol, not methylamines, was the likely substrate under the conditions measured here. However, laboratory experiments indicated the potential for other methanogens to become enriched in response to trimethylamine, revealing the reservoir of methylotrophic methanogenesis potential residing in these soils. Collectively, our approach used coupled field and laboratory investigations to illuminate metabolisms influencing the terrestrial microbial methane cycle, thereby offering direction for increased realism in predictive process-oriented models of methane flux in wetland soils.

scholarly journals Atmospheric methane flux from bubbling seeps: Spatially extrapolated quantification from a Black Sea shelf area

2010 ◽  
Vol 115 (C1) ◽  
Author(s):  
Jens Greinert ◽  
Daniel F. McGinnis ◽  
Lieven Naudts ◽  
Peter Linke ◽  
Marc De Batist
Keyword(s):  
Black Sea ◽  
Methane Flux ◽  
Shelf Area ◽  
Atmospheric Methane

scholarly journals Limited impact of El Niño – Southern Oscillation on the methane cycle

2018 ◽  
Author(s):  
Hinrich Schaefer ◽  
Dan Smale ◽  
Sylvia E. Nichol ◽  
Tony M. Bromley ◽  
Ross J. Martin ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Mitigation Strategies ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Atmospheric Methane ◽  
Methane Cycle ◽  
Ch4 Production ◽  
The Impact

Abstract. The El Niño – Southern Oscillation (ENSO) has been suggested as a strong forcing in the methane cycle and as a driver of recent trends in global atmospheric methane levels. Such a sensitivity of the global CH4 budget to climate events would have important repercussions for climate change mitigation strategies and the accuracy of projections for future greenhouse forcing. Here, we test the impact of ENSO on the CH4 cycle in a correlation analysis. We use local and global records of methane mixing ratio [CH4], as well as stable carbon isotopic records of atmospheric CH4 (δ13CH4), which are particularly sensitive to the combined ENSO effects on CH4 production from wetlands and biomass burning. We use a variety of nominal, smoothed and detrended time series including growth rate records. We find that at most 38 % of the variability in [CH4] and δ13CH4 is attributable to ENSO, but only for detrended records in the Southern tropics. Trend-bearing records from the Southern tropics, as well as all studied hemispheric and global records show a minor impact of ENSO, i.e.

Sign in / Sign up

Export Citation Format

Share Document