Limited contribution of permafrost carbon to methane release from thawing peatlands

Cooper, Mark; Estop‐Aragonés, Cristian; Fisher, John G.; Thierry, Aaron; Garnett, Mark H.; Charman, Dan J.; Murton, Julian B.; Phoenix, Gareth K.; Treharne, Rachael; Kokelj, S. V.; Wolfe, S A; Lewkowicz, Antoni G.; Williams, Mathew; Hartley, Iain P.

doi:10.1038/nclimate3328

Cited by 75 publications

(70 citation statements)

References 37 publications

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“…In contrast, dissolved CH 4 in lakes in yedoma permafrost systems in Alaska ranged from modern to old (3,300 years before present) in age (Elder et al, ) but did not contain the very old (~50,000 years and older) C that is found in yedoma permafrost C stores (Walter Anthony et al, ). In nony‐edoma tundra systems, old permafrost C may be more likely to be released as CO 2 (Schuur et al, ) than CH 4 , as old CH 4 derived from old permafrost was not observed in surface emissions despite considerable thaw occurring (Cooper et al, ). Further, if 10°C warming occurred, C release as CO 2 has been shown to have a larger effect on the overall permafrost carbon feedback than CH 4 (after taking into account the higher radiative forcing capacity of CH 4 ), due to higher rates of C release to the atmosphere under dry, oxic conditions (when CO 2 is released) than wet, oxygen‐poor conditions (when CH 4 is released) (Schädel et al, ).…”

Section: Permafrostmentioning

confidence: 99%

Methane Feedbacks to the Global Climate System in a Warmer World

Dean

Middelburg

Röckmann

et al. 2018

Reviews of Geophysics

432

341

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Methane (CH4) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH4 budgets, as well as future shifts in CH4 emissions, have high uncertainties. Climate change has the potential to increase CH4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment‐specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH4 climate feedback up to 2100. Beyond this timescale, CH4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH4 consumption can counterbalance CH4 production under future climate scenarios.

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Section: Permafrostmentioning

confidence: 99%

Methane Feedbacks to the Global Climate System in a Warmer World

Dean

Middelburg

Röckmann

et al. 2018

Reviews of Geophysics

432

341

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“…Despite high accumulation rates of surface peat following thaw, studies along Alaskan thaw chronosequences indicated large net losses of C in the initial decades to centuries following thaw, in the order of <500 to 3,500 g C m −2 yr −1 during the first decade following thaw (Jones et al, 2017;O'Donnell et al, 2012). However, various field studies from areas with different permafrost and developmental histories have found no direct evidence of losses of old soil C as CO 2 or CH 4 following thaw at the magnitude that would be necessary for such large net C losses (Cooper et al, 2017;Estop-Aragonés, Cooper, et al, 2018;Estop-Aragonés, Czimczik, et al, 2018;Klapstein et al, 2014). Projections suggest increased permafrost degradation and thermokarst formation over the next 100 years, with total loss of permafrost from warm discontinuous permafrost regions in the next few decades (Chasmer & Hopkinson, 2017).…”

Section: Introductionmentioning

confidence: 99%

Long‐term Impacts of Permafrost Thaw on Carbon Storage in Peatlands: Deep Losses Offset by Surficial Accumulation

et al. 2020

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Peatlands in northern permafrost regions store a significant proportion of global soil carbon. Recent warming is accelerating peatland permafrost thaw and thermokarst collapse, exposing previously frozen peat to microbial decomposition and potential mineralization into greenhouse gases. Here, we show from a site in the sporadic‐discontinuous permafrost zone of western Canada that thermokarst collapse leads to neither large losses nor gains following thaw, as deep carbon losses are offset by surficial accumulation. We collected peat cores along two thaw chronosequences, from peat plateau, through young (~30 years since thaw), intermediate (~70 years), and mature (~200 years) thermokarst bog locations. Macrofossil and 14C analysis showed synchronicity of peatland development until recent thaw, with wetland initiation ~8,500 cal yr BP followed by succession through peatland stages prior to permafrost aggradation ~1,800 cal yr BP. Analysis and modeling of soil carbon stocks indicated 8.7 ± 12.4 kg C m−2 of carbon accumulated prior to thaw was lost in ~200 years post‐thaw. Despite these losses, there was no observed increase in peat humification as assessed by Fourier transform infrared and C:N ratios. Rapid peat accumulation post‐thaw (9.8 ± 1.6 kg C m−2 over 200 years) offset deeper losses. Our approach constrains the net carbon balance to be between uptake of 27.3 g C m−2 yr−1 and loss of 106.6 g C m−2 yr−1 over 200 years post‐thaw. While our approach cannot determine whether thermokarst bogs in the sporadic‐discontinuous permafrost zone act as long‐term carbon sinks or sources post‐thaw, our study better constrains post‐thaw C losses and gains.

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“…Increasing air temperature is linked to the thawing of permafrost and to increased rates of soil microbial activity (7), which directly lead to greater CH 4 production in soils due to thaw-induced change in surface wetland areas (8). In the tropics, wetland areal extent is also influenced by precipitation, which affects the area of surface inundation, water table depth, and soil moisture that, in turn, promote methanogenesis.…”

mentioning

confidence: 99%

Emerging role of wetland methane emissions in driving 21st century climate change

Zhang

Zimmermann

Stenke

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

239

192

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Wetland methane (CH 4 ) emissions are the largest natural source in the global CH 4 budget, contributing to roughly one third of total natural and anthropogenic emissions. As the second most important anthropogenic greenhouse gas in the atmosphere after CO 2 , CH 4 is strongly associated with climate feedbacks. However, due to the paucity of data, wetland CH 4 feedbacks were not fully assessed in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The degree to which future expansion of wetlands and CH 4 emissions will evolve and consequently drive climate feedbacks is thus a question of major concern. Here we present an ensemble estimate of wetland CH 4 emissions driven by 38 general circulation models for the 21st century. We find that climate changeinduced increases in boreal wetland extent and temperature-driven increases in tropical CH 4 T errestrial wetlands are among the largest biogenic sources of methane contributing to growing atmospheric CH 4 concentrations (1) and are, in turn, highly sensitive to climate change (2). However, radiative feedbacks from wetland CH 4 emissions were not considered in the Coupled Model Intercomparison Project Phase 5 (CMIP5), and Integrated Assessment Models (IAM) assumed anthropogenic sources to be the only driver responsible for the increase of atmospheric CH 4 burden since the 1750s (3). The role of wetland CH 4 emissions, however, may play an increasingly larger role in future atmospheric growth of methane because of the large stocks of mineral and organic carbon stored under anaerobic conditions in both boreal and tropical regions. Paleoclimatological and contemporary observations of the climate sensitivity of wetland methane emissions suggest the potential for a large feedback (4), but there remains large uncertainty in quantifying the actual range of the response (5, 6).Increasing air temperature is linked to the thawing of permafrost and to increased rates of soil microbial activity (7), which directly lead to greater CH 4 production in soils due to thaw-induced change in surface wetland areas (8). In the tropics, wetland areal extent is also influenced by precipitation, which affects the area of surface inundation, water table depth, and soil moisture that, in turn, promote methanogenesis. Elevated CO 2 concentrations can increase ecosystem water use efficiency and thus soil moisture, and also increase soil carbon substrate availability for microbial activities (9). Tropical wetlands, for which a decline in inundation was observed in recent decades (10), are already exposed to increasing frequencies in extreme climate events, e.g., heat waves, floods, and droughts, and changes in rainfall distribution (11) and variability in methane emissions (12). Meanwhile, northern highlatitude ecosystems are experiencing a more rapid temperature increase than elsewhere globally and with increased rates of soil respiration (13), yet, locally at least, no response in methane emissions (14). Despite the importance of these feedbacks noted by the Intergovernmen...

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Limited contribution of permafrost carbon to methane release from thawing peatlands

Cited by 75 publications

References 37 publications

Methane Feedbacks to the Global Climate System in a Warmer World

Methane Feedbacks to the Global Climate System in a Warmer World

Long‐term Impacts of Permafrost Thaw on Carbon Storage in Peatlands: Deep Losses Offset by Surficial Accumulation

Emerging role of wetland methane emissions in driving 21st century climate change

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