Atmospheric methane

About: Atmospheric methane is a research topic. Over the lifetime, 2034 publications have been published within this topic receiving 119616 citations.

Natural and anthropogenic methane fluxes in Eurasia: a mesoscale quantification by generalized atmospheric inversion

Abstract: . Eight surface observation sites providing quasi-continuous measurements of atmospheric methane mixing ratios have been operated since the mid-2000's in Siberia. For the first time in a single work, we assimilate 1 year of these in situ observations in an atmospheric inversion. Our objective is to quantify methane surface fluxes from anthropogenic and wetland sources at the mesoscale in the Siberian lowlands for the year 2010. To do so, we first inquire about the way the inversion uses the observations and the way the fluxes are constrained by the observation sites. As atmospheric inversions at the mesoscale suffer from mis-quantified sources of uncertainties, we follow recent innovations in inversion techniques and use a new inversion approach which quantifies the uncertainties more objectively than the previous inversion systems. We find that, due to errors in the representation of the atmospheric transport and redundant pieces of information, only one observation every few days is found valuable by the inversion. The remaining high-resolution quasi-continuous signal is representative of very local emission patterns difficult to analyse with a mesoscale system. An analysis of the use of information by the inversion also reveals that the observation sites constrain methane emissions within a radius of 500 km. More observation sites than the ones currently in operation are then necessary to constrain the whole Siberian lowlands. Still, the fluxes within the constrained areas are quantified with objectified uncertainties. Finally, the tolerance intervals for posterior methane fluxes are of roughly 20 % (resp. 50 %) of the fluxes for anthropogenic (resp. wetland) sources. About 50–70 % of Siberian lowlands emissions are constrained by the inversion on average on an annual basis. Extrapolating the figures on the constrained areas to the whole Siberian lowlands, we find a regional methane budget of 5–28 TgCH4 for the year 2010, i.e. 1–5 % of the global methane emissions. As very few in situ observations are available in the region of interest, observations of methane total columns from the Greenhouse Gas Observing SATellite (GOSAT) are tentatively used for the evaluation of the inversion results, but they exhibit only a marginal signal from the fluxes within the region of interest.

Sediment Characteristics and Methane Ebullition in Three Subarctic Lakes

Abstract: Ebullition (bubbling) from climate-sensitive northern lakes remains an unconstrained source of atmospheric methane (CH4) Although the focus of many recent studies, ebullition is rarely linked to t

A multi-year perspective on methane cycling in a shallow peat fen in central new york state, usa

Abstract: Minerotrophic sedge fens are common in sub-arctic regions and are a significant source of atmospheric methane (CH4), yet they have received less attention than other peatlands, such as boreal ombrotrophic bogs, which are smaller sources of CH4. At the process level, CH4 fluxes in sub-arctic systems are limited primarily by cold temperatures, and thus are sensitive to potential climate change. This study examined CH4 dynamics in a temperate sedge-fen to determine controls on the spatial and temporal variability in CH4 fluxes and, therefore, how the biogeochemistry of CH4 in sedge-fen peatlands may respond to predicted changes in climate. We used flux chambers and laboratory peat incubations over a six to seven-year period (1994–2000) to study fluxes, pools, and potential production of CH4 in a peat-forming wetland in central New York State, USA. Results showed that precipitation (i.e., dry years and depth to water table) exerted an important control on annual and seasonal patterns of CH4 fluxes. Mean summer flux rates ranged from 2258 nmol m−2 s−1 in the wettest year to −934 nmol m−2 s−1 (net consumption) in the driest year. CH4 concentrations in the surface peat were as low as 0.01 μatm and as high as 10 matm in the summer months depending on precipitation patterns. In contrast, CH4 concentrations were consistently two to three times greater in sub-surface than in surface peat, and pools persisted during dry years and were temporally less variable. Fluxes were only weakly associated with potential CH4 production rates, which showed little seasonal variation. In-vitro measurements of potential CH4 production did not sufficiently explain fluxes, suggesting a need for improved in-situ methods for measuring CH4 production. Site differences associated with different dominant vegetation had a significant effect on CH4 cycling in all years except the driest, suggesting sensitivity to vegetation changes. These results indicate that predicting responses of fen peatlands to environmental requires an improved understanding of the underlying microbial processes and mechanisms that control CH4 cycling.