Dissolved gases in frozen basal water from the NGRIP borehole: implications for biogeochemical processes beneath the Greenland Ice Sheet

Christner, Brent C.; Montross, Galena G.; Priscu, John C.

doi:10.1007/s00300-012-1198-z

Cited by 19 publications

(17 citation statements)

References 28 publications

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“…However, our interpretation is supported by recent reports of elevated CH 4 concentrations and methanogenic Archaea in the discharge waters emanating from this same subglacial cave (Dieser et al, 2014). Other studies also report evidence for subglacial methane emissions (Walter Anthony et al, 2012;Boyd et al, 2010;Wadham et al, 2008;Christner et al, 2012). Further study of CH 4 concentrations and stable isotopic analyses of subglacial air are in progress and should yield valuable insight into CH 4 dynamics in the interior and at the base of ice sheets.…”

Section: Discussionsupporting

confidence: 87%

Ground-Level Concentrations of Atmospheric Methane in Southwest Greenland Evaluated Using Open-Path Laser Spectroscopy and Cavity-Enhanced Absorption Spectroscopy

Webster

White

Pratt

2015

Arctic, Antarctic, and Alpine Research

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Section: Discussionsupporting

confidence: 87%

Ground-Level Concentrations of Atmospheric Methane in Southwest Greenland Evaluated Using Open-Path Laser Spectroscopy and Cavity-Enhanced Absorption Spectroscopy

Webster

White

Pratt

2015

Arctic, Antarctic, and Alpine Research

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“…Therefore, the abundance of phylotypes related to obligately aerobic species ( Figure 5) together with methanogens and other known anaerobes in the orders Anaerolineales (p51%) and Holophagales (p19%; Figure 4a) was consistent with a range of redox conditions existing in the environment beneath the ice sheet. Previous studies have provided evidence for methanogenesis in subglacial sediments from alpine valley glaciers (Boyd et al, 2010) and beneath polar ice sheets (Christner et al, 2012) including Russell Glacier (Stibal et al, 2012b). The dissolved methane concentrations we documented in subglacial outflow waters ranged between 2.7 and 83 mM and were similar in magnitude to values reported in freshwater wetlands (Devol et al, 1988) and temperate swamps (Amaral and Knowles, 1994).…”

Section: Discussionsupporting

confidence: 66%

“…Measurements of methane excesses in basal ice (Souchez et al, 1995;Miteva et al, 2009) and frozen water (Christner et al, 2012) have suggested that methanogenesis occurs beneath the Greenland Ice Sheet. It is also possible that the erosion of preglacial permafrost through glaciological processes could provide an additional source of legacy methane under the ice (Miteva et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet

et al. 2014

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Microbial processes that mineralize organic carbon and enhance solute production at the bed of polar ice sheets could be of a magnitude sufficient to affect global elemental cycles. To investigate the biogeochemistry of a polar subglacial microbial ecosystem, we analyzed water discharged during the summer of 2012 and 2013 from Russell Glacier, a land-terminating outlet glacier at the western margin of the Greenland Ice Sheet. The molecular data implied that the most abundant and active component of the subglacial microbial community at these marginal locations were bacteria within the order Methylococcales (59-100% of reverse transcribed (RT)-rRNA sequences). mRNA transcripts of the particulate methane monooxygenase (pmoA) from these taxa were also detected, confirming that methanotrophic bacteria were functional members of this subglacial ecosystem. Dissolved methane ranged between 2.7 and 83 lM in the subglacial waters analyzed, and the concentration was inversely correlated with dissolved oxygen while positively correlated with electrical conductivity. Subglacial microbial methane production was supported by d 13 C-CH 4 values between À 64% and À 62% together with the recovery of RT-rRNA sequences that classified within the Methanosarcinales and Methanomicrobiales. Under aerobic conditions, 498% of the methane in the subglacial water was consumed over B30 days incubation at B4 1C and rates of methane oxidation were estimated at 0.32 lM per day. Our results support the occurrence of active methane cycling beneath this region of the Greenland Ice Sheet, where microbial communities poised in oxygenated subglacial drainage channels could serve as significant methane sinks.

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“…In particular, subglacial environments have been proposed as habitats for methanogens, and several lines of evidence have been presented for microbial CH 4 production therein. They include elevated CH 4 concentrations found in basal ice of ice sheets and glaciers (Campen et al, ; Christner et al, ; Souchez et al, ), accumulation of CH 4 in clathrates below ice sheets (Weitemeyer & Buffett, ), and molecular and biogeochemical evidence in subglacial waters (Dieser et al, ). Long‐term laboratory incubation experiments yielded additional evidence for a CH 4 production potential in subglacial sediments (Boyd et al, ; Stibal, Wadham, et al, ; Wadham et al, ).…”

Section: Introductionmentioning

confidence: 99%

Occurrence and Origin of Methane Entrapped in Sediments and Rocks of a Calcareous, Alpine Glacial Catchment

et al. 2018

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Glacial ecosystems are an important indicator of climate change, and dynamics of the greenhouse gas methane (CH 4 ) in these systems has become a major research topic of late. We investigated occurrence and origin of recently discovered, sediment-entrapped CH 4 within the Wildstrubel glacial catchment (Switzerland) using geochemical analyses on gas extracted from sediments and rocks, including gas content and CH 4 stable isotope measurements, and computation of gas wetness (ratio of CH 4 to ethane and propane). We also examined the potential occurrence of microbial CH 4 production in subglacial, supraglacial, and glacier forefield sediments based on molecular analyses targeting mcrA (a marker gene for microbial CH 4 production) and based on observed CH 4 production during laboratory incubation experiments. Substantial amounts of entrapped CH 4 were detected in all sediment (65.7 ± 28.6 μg CH 4 /g) and most rock samples (up to 145.5 μg CH 4 /g). Similar gas wetness (0.7-126.7) and CH 4 stable isotope values (δ 13 C CH4 : À26.9‰ to À31.2‰, δD CH4 : À118.5‰ to À158.6‰) in sediment and rock samples provided strong evidence that entrapped CH 4 was of common, thermogenic origin. Molecular analyses (up to~10 5 mcrA gene copies per gram) and laboratory incubation experiments (production rates up to 1.55 μg CH 4 g À1 day À1 ) provided evidence for local hot spots of viable methanogens in waterlogged, glacier forefield sediments but not in subglacial sediments. Nonetheless, microbial CH 4 production appeared to be only of minor importance at our field site, as indicated by results of our geochemical analyses. Our findings illustrate the crucial importance of appropriate geochemical analyses to provide solid evidence on the origin of CH 4 in glacial systems.Plain Language Summary The potent greenhouse gas methane was recently discovered to be trapped in sediments of glacier forefields in the Swiss Alps, in particular in those sediments that are derived from limestone bedrock. Here we assess the occurrence and origin of this trapped methane in one specific glacial system, which exhibited highest methane concentrations in a previous survey. We find substantial amounts of methane trapped in sediments and rocks throughout the glacial system. Our geochemical data provide robust evidence that the methane trapped in sediments and rocks is largely derived from ancient organic matter, which was deposited together with the limestone-forming sediments, and subsequently converted to methane by heat and pressure during formation of the limestone bedrock. Conversely, biological methane production by microorganisms appears to be of minor importance at this site. Our findings show that a combination of methods was essential for identifying the ancient origin of trapped methane in sediments and rocks of this glacial system.

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Dissolved gases in frozen basal water from the NGRIP borehole: implications for biogeochemical processes beneath the Greenland Ice Sheet

Cited by 19 publications

References 28 publications

Ground-Level Concentrations of Atmospheric Methane in Southwest Greenland Evaluated Using Open-Path Laser Spectroscopy and Cavity-Enhanced Absorption Spectroscopy

Ground-Level Concentrations of Atmospheric Methane in Southwest Greenland Evaluated Using Open-Path Laser Spectroscopy and Cavity-Enhanced Absorption Spectroscopy

Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet

Occurrence and Origin of Methane Entrapped in Sediments and Rocks of a Calcareous, Alpine Glacial Catchment

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