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Atmospheric methane

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


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Journal ArticleDOI
01 Sep 2006
TL;DR: In this paper, a numerical model for the Laurentide-Cordilleran ice sheet was used to assess the aerial extent, thickness, and thermal conditions at the base of the ice sheet as a function of time.
Abstract: Ice-age cycles are associated with large fluctuations in the concentration of atmospheric methane These fluctuations are commonly attributed to changes in wetlands, although clathrates have also been proposed as a potential source We examine the possibility that methane clathrates accumulate below continental ice sheets during an ice age The source of methane is due to microbial decomposition of organic material below the ice sheet Methane is stored in clathrate when the pressure and temperature conditions permit thermodynamic stability Deglaciation releases methane from clathrate into the atmosphere We use a numerical model for the Laurentide–Cordilleran ice sheet [Marshall, SJ, Tarasov, L, Clarke, GKC, Peltier, WR, 2000 Glaciological reconstruction of the Laurentide ice sheet: physical processes and modeling challenges, Can J Earth Sci 37, 769–793] to assess the aerial extent, thickness, and the thermal conditions at the base of the ice sheet as a function of time Both low and high inventories of the organic carbon below the ice sheet are considered, based on soil carbon estimates for tundra and for the present potential vegetation We model the spatial distribution of clathrate as the ice sheet grows and quantify the amplitude and timing of methane releases as the ice sheet retreats The predicted fluctuations in atmospheric methane are 80–200 ppbv, which are comparable to fluctuations recorded in ice cores from Greenland and Antarctica However, clathrates cannot explain the entire atmospheric methane record because there is insufficient methane in clathrate to sustain the elevated atmospheric concentration for more than 1 kyr

37 citations

Journal ArticleDOI
TL;DR: In this paper, the contribution of entrapped gas bubbles to the soil methane (CH4) pool and their role in CH4 emissions in rice paddies open to the atmosphere was investigated.
Abstract: We attempted to determine the contribution of entrapped gas bubbles to the soil methane (CH4) pool and their role in CH4 emissions in rice paddies open to the atmosphere. We buried pots with soil and rice in four treatments comprising two atmospheric CO2 concentrations (ambient and ambient +200 μmol mol−1) and two soil temperatures (ambient and ambient +2 °C). Pots were retrieved for destructive measurements of rice growth and the gaseous CH4 pool in the soil at three stages of crop development: panicle formation, heading, and grain filling. Methane flux was measured before pot retrieval. Bubbles that contained CH4 accounted for a substantial fraction of the total CH4 pool in the soil: 26–45 % at panicle formation and 60–68 % at the heading and grain filling stages. At panicle formation, a higher CH4 mixing ratio in the bubbles was accompanied by a greater volume of bubbles, but at heading and grain filling, the volume of bubbles plateaued and contained ~35 % CH4. The bubble-borne CH4 pool was closely related to the putative rice-mediated CH4 emissions measured at each stage across the CO2 concentration and temperature treatments. However, much unexplained variation remained between the different growth stages, presumably because the CH4 transport capacity of rice plants also affected the emission rate. The gas phase needs to be considered for accurate quantification of the soil CH4 pool. Not only ebullition but also plant-mediated emission depends on the gaseous-CH4 pool and the transport capacity of the rice plants.

37 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured methane fluxes and found that during a wet fall the forest soil turned from a CH4 sink into a large source for several months, while the CH4 emissions from a nearby wetland did not increase.
Abstract: Upland forest soils affect the atmospheric methane (CH4) balance, not only through the soil sink but also due to episodic high emissions in wet conditions. We measured methane fluxes and found that during a wet fall the forest soil turned from a CH4 sink into a large source for several months, while the CH4 emissions from a nearby wetland did not increase. When upscaled to the whole catchment area the contribution of forests amounted to 60% of the annual CH4 emission from the wetlands, while in a normal year the forest soil consumes 10% of the wetland emission. The period of high upland soil emission was also captured by the nearby atmospheric concentration measurement station. Since the land cover within the catchment is representative of larger regions, our findings imply that upland forests in the boreal zone constitute an important part in the global CH4 cycle not previously accounted for.

37 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the emissions of atmospheric methane and carbon dioxide from tallgrass prairie and adjacent wheat and sorghum agricultural plots in Kansas for a 200-day period.
Abstract: Consumption of atmospheric methane and emission of carbon dioxide by soils were measured on unburned and annually burned tallgrass prairie and on adjacent wheat and sorghum agricultural plots in Kansas. Profiles of CH4 and CO2 concentration with soil depth were also measured. Overall patterns of CH4 consumption by soils varied temporally, with soil depth and land use. Mean CH4 consumption for the 200-day sampling period was −1.02 mg CH4 m−2 d−1 (SE=0.13, n=41) for burned prairie, −0.63 (SE=0.09, n=45) for unburned prairie, −0.85 (SE=0.20, n=36) for wheat, and −0.45 (SE=0.08, n=40) for sorghum. Less than 20 % of the variance in CH4 consumption was explained by soil temperature and/or moisture content. Overall patterns of CO2 emission from prairie and agricultural soils varied temporally, but not among land use. Mean CO2 emission for the 200-day sampling period was 15.7 g CO2 m−2 d−1 (SE=1.8, n=41) for burned prairie, 14.5 (SE=1.3, n=45) for unburned prairie, 13.9 (SE=2.1, n=36) for wheat, and 10.3 (SE=2.1, n=40) for sorghum. More than 70% of the variance in prairie CO2 emission rate was explained by soil temperature and moisture. Crop management practices influenced the timing of CO2 emission from agricultural plots but not the net annual rate of emission. Methane concentrations generally decreased and CO2 concentrations increased with soil depth, and the magnitude of CH4 and CO2 flux generally increased with increased magnitude of the soil gas concentration gradient. Fertilization of agricultural fields had no measured effect on CH4 or CO2 flux or on soil gas concentrations.

37 citations

Journal ArticleDOI
TL;DR: Based on measurements of gases trapped in biogenic and abiogenic calcite, the release of methane from permafrost and shelf sediment methane hydrate is deemed the ultimate source and cause for dramatic life-changing global warming (GMAT > 34 degrees C) and oceanic negative-carbon isotope excursion observed at the end Permian as discussed by the authors.

37 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202395
2022153
202175
202077
201974
201872