Accumulation and release of methane from clathrates below the Laurentide and Cordilleran ice sheets

Weitemeyer, Karen; Buffett, B. A.

doi:10.1016/j.gloplacha.2006.03.014

Cited by 29 publications

(51 citation statements)

References 62 publications

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“…Similar rapid increases in methane are seen at the terminations of the previous three glacial periods [Delmotte et al, 2004]. Weitemeyer and Buffett [2006] recently employed a numerical model of the Laurentide-Cordilleran ice sheets to model aerial extent, thickness and thermal conditions at the ice sheet base over the last glacial-interglacial cycle and coupled this model to an inventory of subglacial carbon (derived from inferred distributions of soil and vegetation). They subsequently modeled the spatial distribution of methane clathrate (assuming all soil carbon is converted to methane) over time with ice sheet growth and decay and quantified the timing and amplitude of methane release during ice sheet retreat.…”

Section: Modeling Studiesmentioning

confidence: 95%

“…Only the soil carbon contribution to SOC has received any attention in the literature to date [Zeng, 2003;Weitemeyer and Buffett, 2006]. We attempt to calculate the magnitude of each of these carbon reserves, using areas and extents of the former ice sheets in the Northern Hemisphere during the Weichselian glaciation.…”

Section: Modeling Studiesmentioning

confidence: 99%

“…For example, the change in the dD CH4 of atmospheric methane during the periods of rapid warming which follow cold periods such as the Younger Dryas is not consistent with a marine clathrate contribution [Sowers, 2006], and it is uncertain whether wetlands alone can explain the variation in atmospheric methane concentrations [Valdes et al, 2005] despite the hypothesized rapid increase in the productivity and area of wetlands during periods of climatic warming [Kaplan, 2002;MacDonald et al, 2006]. More recently, several studies have highlighted the potential role of the basal sediments of ice sheets as a potential source of methane during deglaciation [Zeng, 2003;Weitemeyer and Buffett, 2006].…”

Section: Introductionmentioning

confidence: 99%

“…These findings, coupled with observations of elevated methane and carbon dioxide concentrations in the basal regions of ice cores [Tison et al, 1998;Campen et al, 2003], and methane release from subglacial samples during incubation [Skidmore et al, 2000], have been used to imply that subglacial environments may be potential sources of methane to the atmosphere. Numerical modeling conducted as part of these investigations has demonstrated that if all subice sheet soil carbon was converted to methane by subglacial microbes in wet-based areas of the Laurentide Ice Sheet and subsequently stored as clathrates at the ice sheet base, clathrate instability triggered by ice retreat could result in the periodic release of methane to the atmosphere [Weitemeyer and Buffett, 2006], with the potential to significantly impact global atmospheric methane concentrations. Although these methane release events are short-lived (1 ka), they may account for some aspects of the rapid rises in methane during deglaciation present in some paleorecords [Kennet et al, 2003].…”

Section: Introductionmentioning

confidence: 99%

“…[4] The potential significance of subglacial methane production has been highlighted by Zeng [2003] and Weitemeyer and Buffett [2006]. We build on these studies in several important ways.…”

Section: Introductionmentioning

confidence: 99%

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Subglacial methanogenesis: A potential climatic amplifier?

Wadham

Tranter

Tulaczyk

et al. 2008

Global Biogeochemical Cycles

114

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[1] Subglacial environments are a previously neglected component of the Earth's global carbon cycle, a reflection of the view held until recently that they are dominated by abiotic and oxic conditions. Here we provide a realistic assessment of the theory that the basal regions of the ice sheets that formed over North America and Europe during glaciations were host to significant populations of anaerobic microorganisms, including methanogens, able to metabolize organic carbon sequestered during interglacials and overridden during Quaternary glacials. In doing so, we review the current evidence for subglacial methane release during deglaciation, estimate the size of the subglacial reservoir of organic carbon (SOC), and assess the amount of SOC available to subglacial microbes and the likely pathways and rates of carbon turnover. We then discuss the fate of subglacial methane and the potential impact of its release on atmospheric methane concentrations. We calculate that the SOC equates to 418-610 Pg C and includes carbon from terrestrial soils/vegetation, peatlands, lake, and marine sediments. The SOC that is potentially available for microbial conversion to methane is smaller than this estimate due to (1) glacial erosion, (2) accumulation of recalcitrant organic carbon compounds over time, (3) conversion to carbon dioxide by aerobic/anaerobic respiration, and (4) incomplete conversion of labile organic matter to methane. We estimate that the total SOC available for conversion to methane is 63 Pg C. Our estimates of methane production potentials span a wide range because of the current uncertainty surrounding subglacial metabolic rates. We believe, however, that there is a strong likelihood that subglacial microbes could convert 63 Pg of SOC to methane during a glacial cycle. If this were the case, release of this methane from the ice sheet margins during retreat would need to be episodic in order to significantly impact atmospheric methane concentrations. Our findings suggest that it may well be important to consider subglacial environments as active components of the Earth's carbon cycle. Conclusive determination of the potential impact of subglacial methane production on atmospheric methane concentrations during deglaciation, however, awaits more precise determination of the ability of subglacial microbes to degrade organic carbon components and their associated rates of metabolism under in situ conditions.

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Section: Modeling Studiesmentioning

confidence: 95%

Section: Modeling Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…[4] The potential significance of subglacial methane production has been highlighted by Zeng [2003] and Weitemeyer and Buffett [2006]. We build on these studies in several important ways.…”

Section: Introductionmentioning

confidence: 99%

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