Aged soils contribute little to contemporary carbon cycling downstream of thawing permafrost peatlands

Tanentzap, Andrew J.; Burd, Katheryn; Kuhn, McKenzie A.; Estop‐Aragonés, Cristian; Tank, Suzanne E.; Olefeldt, David

doi:10.1111/gcb.15756

Cited by 9 publications

(10 citation statements)

References 118 publications

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“…The radiocarbon age of DOC in the water (~ 3800 yr BP) was much older than DIC in the water column and the CO 2 and CH 4 in the bubbles, which is in line with previous peatland thaw lake studies (Gonzalez Moguel et al 2021). The 14 C–DOC age of the lake water closely resembles reported ages of DOC in the pore waters of nearby peat plateau active layers (Tanentzap et al 2021) and had a terrigenous stable carbon isotope (𝛿 13 C) value of −26.9‰ (Karlsson et al 2003), suggesting allochthonous origins. While we only sampled DOC at the center of the lake, our measurements are likely representative of the entire lake due to the lake's size and shallow depth which support an intermittent to continuous well‐mixed environment (Andersen et al 2017; Holgerson et al 2022) and homogenous DOC concentrations across the lake (Stolpmann et al 2021).…”

Section: Discussionsupporting

confidence: 72%

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

Kuhn

Schmidt

Heffernan

et al. 2022

Limnology & Oceanography

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Methane (CH4) and carbon dioxide (CO2) emissions from small peatland lakes may be highly sensitive to climate warming and thermokarst expansion caused by permafrost thaw. We studied effects of thermokarst expansion on ebullitive CH4 and CO2 fluxes and diffusive CH4 fluxes from a peatland thaw lake in boreal western Canada. Ebullitive CH4 fluxes from the thaw edge (236 ± 61 mg CH4 m−2 d−1) were double and quadruple that of the stable lake edge and center, respectively. Modeled diffusive CH4 fluxes did not differ between the thawing and stable edges (~ 50 mg CH4 m−2 d−1) but were double that of the center. Radiocarbon (14C) analysis of CH4 and CO2 bubbles from the thaw edge was older (~ 1211 and 1420 14C yr BP) than from the stable edge and the center (modern to ~ 102 and 50 14C yr BP, respectively). Incubations indicated that deep, old peat sediment was more labile along the thaw edge than in the center. While our study suggested increase CH4 emissions partly derived from millennial‐aged carbon along the thaw edge, accounting for these emissions only increased the estimated total lake CH4 emissions by ~ 10%, which is a much smaller contribution than measured from thermokarst lakes in yedoma regions. Our study suggests that it is important to account for landscape history and lake types when studying the processes that govern the sensitivity of lake greenhouse gas emissions to climate change.

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Section: Discussionsupporting

confidence: 72%

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

Kuhn

Schmidt

Heffernan

et al. 2022

Limnology & Oceanography

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“…Furthermore, laboratory incubation experiments show that a substantial portion of this DOC (20 %-50 %) is labile (Mann et al, 2012(Mann et al, , 2015Holmes et al, 2008;Liu et al, 2019) and as such could be decomposed and released back to the atmosphere as CO 2 or CH 4 from soils, surface waters, or drainages (Kling et al, 1991;Cole et al, 2007;Drake et al, 2015). In fact, increasing terrestrial DOC loads have been linked to increased CO 2 emissions from aquatic systems (Lapierre et al, 2013), although field studies suggest biological activity in Arctic aquatic and anoxic systems may be fueled largely by modern C (Dean et al, 2020;Estop-Aragonés et al, 2020;Tanentzap et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Age and chemistry of dissolved organic carbon reveal enhanced leaching of ancient labile carbon at the permafrost thaw zone

et al. 2022

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Abstract. Climate change will alter the balance between frozen and thawed conditions in Arctic systems. Increased temperatures will make the extensive northern permafrost carbon stock vulnerable to decomposition and translocation. Production, cycling, and transport of dissolved organic carbon (DOC) are crucial processes for high-latitude ecosystem carbon loss that result in considerable export off the Arctic landscape. To identify where and under what conditions permafrost DOC is mobilized in an Arctic headwater catchment, we measured radiocarbon (14C) of DOC and assessed DOC composition with ultraviolet–visible spectroscopy (UV–Vis) of surface waters and shallow and deep subsurface porewaters from 17 drainages in the Barrow Environmental Observatory in Alaska. Samples were collected in July and September 2013 to assess changes in age and chemistry of DOC over time. DOC age was highly variable ranging from modern (19 ‰ Δ14C) to approximately 7000 BP (−583 ‰ Δ14C). DOC age increased with depth, over the summer as the active layer deepened, and with increasing drainage size. DOC quality indicators reflected a DOC source rich in high molecular-weight and aromatic compounds, characteristics consistent with vegetation-derived organic matter that had undergone little microbial processing, throughout the summer and a weak relationship with DOC age. In deep porewaters, DOC age was also correlated with several biogeochemical indicators (including dissolved methane concentration, δ13C, and the apparent fractionation factor), suggesting a coupling between carbon and redox biogeochemistry influencing methane production. In the drained thawed lake basins included in this study, DOC concentrations and contributions of vegetation-derived organic matter declined with increasing basin age. The weak relationship between DOC age and chemistry and consistency in DOC chemical indicators over the summer suggest a high lability of old DOC released by thawing permafrost.

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“…In addition, different measurement techniques (i.e., chronosequence-based changes in C stocks vs. atmospheric flux measurements) may also account for disparate outcomes. In contrast to the stock method, flux measurements do not account for C losses due to winter losses, which can be significant (Natali et al, 2019;Waldrop et al, 2021) nor lateral flow, although measured C loss due to this flow appears to low (Hugelius et al, 2020;Tanentzap et al, 2021). To further understand the factors that determine the magnitude of C lost upon permafrost thaw, this study examines C losses for a thaw chronosequence at a site located in Interior Alaska.…”

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Influence of Permafrost Type and Site History on Losses of Permafrost Carbon After Thaw

et al. 2021

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Northern peatlands play an important role in the global carbon (C) budget and are estimated to store 415 Pg of C (±150 Pg C; Hugelius et al., 2020), which represents ∼20% of the global soil C stock (Jackson et al., 2017). Close to half of this C has been protected from decomposition by permafrost, substrate that has remained frozen for at least two consecutive years (Rodenhizer et al., 2020). Permafrost in northern peatlands reached its maximum extent around 1700 Common Era (CE), with the highest rates of aggradation between 1,200 and 1,950 CE (Treat & Jones, 2018). Much of this permafrost is found in the discontinuous zone, where areas of permafrost are found adjacent to areas of unfrozen soil. In the discontinuous zone, the majority of which resides above 60°N (Brown et al., 1997), the presence of permafrost depends on the

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Aged soils contribute little to contemporary carbon cycling downstream of thawing permafrost peatlands

Abstract: This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 9 publications

References 118 publications

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

High ebullitive, millennial‐aged greenhouse gas emissions from thermokarst expansion of peatland lakes in boreal western Canada

Age and chemistry of dissolved organic carbon reveal enhanced leaching of ancient labile carbon at the permafrost thaw zone

Influence of Permafrost Type and Site History on Losses of Permafrost Carbon After Thaw

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