Large fractionations of C and H isotopes related to methane oxidation in Arctic lakes

Cadieux, S. B.; White, Jeffrey R.; Sauer, Peter E.; Peng, Yongbo; Goldman, Amy; Pratt, Lisa M.

doi:10.1016/j.gca.2016.05.004

Cited by 40 publications

(48 citation statements)

References 79 publications

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“…The carbon stable isotopic compositions of CH 4 and CO 2 were measured with an IRMS and are reported as conventional δ 13 C CH 4 and δ 13 C CO 2 values in ‰ along the carbon isotopic scale anchored to Vienna Pee Dee Belemnite (VPDB). CH 4 samples were measured in continuous-flow mode using CH 4 preconcentration and cryofocusing (Miller et al, 2002) and a gas chromatography-oxidation/pyrolysis-IRMS (GC-ox/pyr-IRMS) interface as briefly described by Cadieux et al, (2016). A variable sample extraction time was used to isolate approximately 0.4 μmol of CH 4 from each sample prior to introduction to the GC-ox/pyr-IRMS.…”

Section: Chemical and Isotopic Analysesmentioning

confidence: 99%

Consumption of atmospheric methane in a limestone cave in Indiana, USA

Webster

Mirza

Deli³

et al. 2016

Chemical Geology

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Recent observations suggest that karst landscapes may be an unaccounted sink for atmospheric CH 4 , but questions remain about the processes contributing to sub-atmospheric CH 4 mole fractions in caves. The CH 4 dynamics associated with karst environments were studied over 18 months at 6 locations in Buckner Cave, Southern Indiana by measuring the mole fractions and stable isotopic composition of CH 4 and carbon dioxide (CO 2). CO 2 mole fractions were used to infer seasonal changes in airflow. Samples were obtained on a monthly basis. CH 4 mole fractions ranged from 1.9 ± 0.1 ppm near the cave entrance to 0.1 ± 0.1 ppm in the more remote parts of the cave. The carbon and hydrogen stable isotopic compositions of CH 4 in the cave ranged from-58.7 to +7 ‰ (VPDB) and-170 to +10 ‰ (VSMOW), respectively. The isotopic data suggest that the CH 4 dynamics of Buckner Cave can be

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Section: Chemical and Isotopic Analysesmentioning

confidence: 99%

Consumption of atmospheric methane in a limestone cave in Indiana, USA

Webster

Mirza

Deli³

et al. 2016

Chemical Geology

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“…Methanogenesis in freshwaters mainly occurs in the sediment, where anoxic conditions prevail (Bastviken, ). Besides production by methanogenesis, CH 4 in freshwater systems is subject to microbial aerobic or anaerobic methane oxidation, although the latter appears less important in freshwaters (Bastviken, ; Cadieux et al, ; Oswald et al, ). Sawakuchi et al (), for example, found that methane oxidation reduced the diffusive CH 4 flux by approximately 28–96% in the Amazon River mainstream and in its five largest tributaries.…”

Section: Introductionmentioning

confidence: 99%

Sediment Properties Drive Spatial Variability of Potential Methane Production and Oxidation in Small Streams

2020

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Emissions of the potent greenhouse gas methane (CH 4 ) from streams and rivers are a significant component of global freshwater methane emissions. The distribution of CH 4 production and oxidation within stream sections and in vertical sediment profiles is not well understood, and the environmental controls on CH 4 production and emission in such systems create a significant challenge for assessing larger-scale dynamics. Here we investigate factors driving the spatial variability of sediment potential methane production (PMP) and potential methane oxidation (PMO) in a temperate stream network in Germany. PMP was highly variable, ranging from 5 × 10 −4 to 28.58 μg CH 4 gDW −1 d −1 and PMO ranged from 0.43 μg CH 4 gDW −1 d −1 to 14.41 μg CH 4 gDW −1 d −1 . Important drivers of spatial variability of PMP and PMO in the sediments of the stream main-stem were related to fine sediment fraction and organic carbon content. At smaller spatial scale, that is, in a sub-catchment stream section, the drivers were more complex and included sediment nitrogen and organic carbon content, as well as porewater dissolved organic carbon, dissolved organic matter quality, and metal concentrations. As with reservoirs and impounded rivers, fine sediment deposition and organic carbon content were found to be key controls on the spatial variability of CH 4 production and oxidation. These findings enhance our understanding of CH 4 dynamics, improve the potential for identifying CH 4 production hotspots in small streams, and provide a potential means for upscaling emission rates in larger-scale assessments.Plain Language Summary Globally, streams and rivers emit a significant amount of the highly potent greenhouse gas methane. The methane emitted from streams is mainly produced in sediments. The distribution of production and consumption in stream sections and sediment profiles is not well understood, which creates a significant challenge for estimating, for example, regional methane emissions from streams and rivers. We investigated possible factors controlling the variability from site to site and different depths of methane production and consumption in sediments of a stream network in south-west Germany. Sediment properties, the amount of fine sediment and organic carbon content, were key drivers of this variability in the main stream. In a smaller side arm of the main stream, the drivers were more complex, including nitrogen and organic carbon content of the sediment, but also porewater dissolved organic carbon, dissolved organic matter quality, and metals. As for reservoirs and dammed rivers, the accumulation of fine sediments and organic carbon content was found to be key controls of sediment methane production and consumption. These findings enhance our understanding of methane dynamics, improve the potential for identifying methane production hotspots in small streams, and provide a potential means for upscaling emission rates in larger-scale assessments.

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“…As a result of amplified warming in the Arctic over the past 20 years (IPCC, 2013), Greenland has experienced significant mass loss of the Greenland Ice Sheet (GIS; Nghiem et al, 2012;van As et al, 2012;Hall et al, 2013;Hanna et al, 2013Hanna et al, , 2014. Despite the abundance of lakes on the ice-free margin of Greenland and intense changes to the landscape as the result of warming, there are only a few published studies that have measured CH 4 in Greenlandic lakes (Walter Anthony et al, 2012;Webster et al, 2015;Cadieux et al, 2016;Goldman et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…In doing so, we are able to Sample size is in parentheses. * Can also be found in Cadieux et al (2016). look at differences in CH 4 spatially among the lakes, seasonally by comparing open-water conditions to ice-covered conditions, and annually.…”

Section: Introductionmentioning

confidence: 99%

Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

2017

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Abstract. In thermally stratified lakes, the greatest annual methane emissions typically occur during thermal overturn events. In July of 2012, Greenland experienced significant warming that resulted in substantial melting of the Greenland Ice Sheet and enhanced runoff events. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating on lake thermal structure and methane dynamics and compare these observations with those from the following year, when temperatures were normal. Here, we focus on methane concentrations within the water column of five adjacent small lakes on the icefree margin of southwestern Greenland under open-water and ice-covered conditions from 2012-2014. Enhanced warming of the epilimnion in the lakes under open-water conditions in 2012 led to strong thermal stability and the development of anoxic hypolimnia in each of the lakes. As a result, during open-water conditions, mean dissolved methane concentrations in the water column were significantly (p < 0.0001) greater in 2012 than in 2013. In all of the lakes, mean methane concentrations under ice-covered conditions were significantly (p < 0.0001) greater than under open-water conditions, suggesting spring overturn is currently the largest annual methane flux to the atmosphere. As the climate continues to warm, shorter ice cover durations are expected, which may reduce the winter inventory of methane and lead to a decrease in total methane flux during ice melt. Under openwater conditions, greater heat income and warming of lake surface waters will lead to increased thermal stratification and hypolimnetic anoxia, which will consequently result in increased water column inventories of methane. This stored methane will be susceptible to emissions during fall overturn, which may result in a shift in greatest annual efflux of methane from spring melt to fall overturn. The results of this study suggest that interannual variation in ground-level air temperatures may be the primary driver of changes in methane dynamics because it controls both the duration of ice cover and the strength of thermal stratification.

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Large fractionations of C and H isotopes related to methane oxidation in Arctic lakes

Cited by 40 publications

References 79 publications

Consumption of atmospheric methane in a limestone cave in Indiana, USA

Consumption of atmospheric methane in a limestone cave in Indiana, USA

Sediment Properties Drive Spatial Variability of Potential Methane Production and Oxidation in Small Streams

Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

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