Atmospheric methane

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

An attempt to quantify the impact of changes in wetland extent on methane emissions on the seasonal and interannual time scales

Abstract: [1] Climate variability impacts CH4 wetland sources as changes in flux density per unit area and via expansion or contraction of wetland areas in response to surface hydrological processes This paper is a first attempt to isolate the role of varying wetland area on the seasonal and interannual variability of CH4 wetland emissions over the past decade Wetland area extent at monthly intervals was provided over the period 1993–2000 by a suite of satellite observations from multiple sensors The regionally variable fraction of wetland area was optimized using satellite observations of flooded area as a first estimate and further adjusted to match the seasonal cycle of CH4 fluxes retrieved from a global atmospheric inversion Wetland flux densities of CH4 were calculated by coupling the ORCHIDEE global vegetation model with a process-based wetland CH4 emission model, calibrated by optimizing its parameters at the site level against representative CH4 flux time series For boreal bogs north of 50°N, we found that variations in area contributed about 30% to the annual flux For temperate and tropical wetlands, the variations in area has almost no influence on the annual CH4 emissions but contributes significantly to the seasonal behavior, accounting for 40% and 66% of the seasonal amplitude of fluxes, respectively In contrast, the interannual variability of wetland area appears to be the dominant cause of interannual variations in regional CH4 emissions from wetlands at all latitudes (largest in the tropics), with up to 90% of annual flux anomalies explained by wetland area anomalies in some years For example, in 1998, boreal wetlands north of 50°N contributed to approximately 80% of the positive anomaly according to our calculations We also found that climate anomalies can lead to both increased emitting areas and decreased flux densities at the same time, with opposite effects on the total CH4 flux entering the atmosphere With a view to forecasting the future trajectory of atmospheric methane content, our results point to the absolute necessity to be able to predict the variations in wetland extent, a hydrological problem, in order to affirm the reliability of simulations of changing methane emissions perturbed by climate

Methane cycling in the sediments of Lake Washington

Abstract: Aerobic oxidation is important in the cycling of methane in the sediments of Lake Washington. About half of the methane flux from depth is oxidized to CO, in the upper 0.7 cm of the sediments and the remainder escapes into the water column. In terms of the total carbon budget of the lake, the upward flux of methane is insignificant with only about 2% of the carbon fixed by primary production being returned as methane. The upward flux of methane, however, does represent about 20% of the organic carbon decomposed within the sediments. In addition, methane oxidation consumes 7-10% of the total oxygen

Global increase in atmospheric methane concentrations between 1978 and 1980

Abstract: The concentration of methane has been measured in tropospheric air samples collected in remote locations between 55°N and 53°S during six collection periods between November 1977 and November 1980. The observed concentrations of CH4 have increased in each of six latitude locations by an average of 0.052±0.005 ppmv between January 1978 and January 1980. This (1.4±0.2)×1014 gram increase in the total atmospheric burden of CH4 corresponds to 35±12% of the yearly flux of (4.0±1.3)×1014 grams needed to maintain the CH4 concentration in steady-state at its recent level of about 1.6 ppmv. The 1978-1980 excess of about 0.7×1014 grams per year of sources over sinks for CH4 could arise from either an increase in biogenic releases or from a decrease in the average OH radical concentration in the lower troposphere, or from both.

Rapid expansion of northern peatlands and doubled estimate of carbon storage

Abstract: Northern peatlands are an integral part of the global carbon cycle—a strong sink of atmospheric carbon dioxide and source of methane. Increasing anthropogenic carbon dioxide and methane in the atmosphere are thought to strongly impact these environments, and yet, peatlands are not routinely included in Earth system models. Here we present a quantification of the sink and stock of northern peat carbon from the last glacial period through the pre-industrial period. Additional data and new algorithms for reconstructing the history of peat carbon accumulation and the timing of peatland initiation increased the estimate of total northern peat carbon stocks from 545 Gt to 1,055 Gt of carbon. Further, the post-glacial increases in peatland initiation rate and carbon accumulation rate are more abrupt than previously reported. Peatlands have been a strong carbon sink throughout the Holocene, but the atmospheric partial pressure of carbon dioxide has been relatively stable over this period. While processes such as permafrost thaw and coral reef development probably contributed some additional carbon to the atmosphere, we suggest that deep ocean upwelling was the most important mechanism for balancing the peatland sink and maintaining the observed stability. Northern peatlands are estimated to store more than 1,000 Gt of carbon, almost doubling previous estimates, according to a reconstruction of historical peat carbon accumulation.

Spatial variation in high-latitude methane flux along a transect across Siberian and European tundra environments

Abstract: This paper reports results from a transect of methane flux measurements across tundra environments in Siberia and the European Arctic during July and August 1994. Overall, mean CH4 emission was 2.3±0.7 mg m−2 day−1 for the mesic tundra sites and 46.8±5.9 for the wet habitats with large intersite variability. The general scale of emissions was somewhat low compared to assumptions made about them in global methane budgets and models. In particular, the mesic tundra fluxes were lower than what would be expected based on data from similar environments in North America, and there are indications that these environments may be significant atmospheric methane consumers. Consistent consumption rates in combination with the large expanse of dry/mesic tundra environments suggest that it may be necessary to incorporate a high-latitude soil sink term in global methane budgets. However, the wet tundra emissions found between 67° and 77°N in this study were consistently higher than recent findings in comparable environments at much lower latitudes (50°–55°N). High northern latitudes therefore represent a very important player in the global methane budget. When compared across both mesic and wet sites, methane emission increased with increasing soil organic content, soil temperature, and soil moisture. The relationship between soil temperature and methane flux at the wet sites alone was highly significant, and the flux also increased with increasing soil moisture and organic content. No correlations were found between flux and the measured environmental parameters at the mesic sites when treated separately.