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1. Methane emissions from high-latitude peatlands during the Holocene from a synthesis of peatland records

   https://doi.org/10.5194/egusphere-egu21-6224  

   Treat, C. C.; Jones, M. C.; Brosius, L. S.; Grosse, G.; Walter Anthony, K.; and Frolking, S. (April 2021, EGU General Assembly 2021)

   null (Ed.)

   The sources of atmospheric methane (CH4) during the Holocene remain widely debated, including the role of high latitude wetland and peatland expansion and fen-to-bog transitions. We reconstructed CH4 emissions from northern peatlands from 13,000 before present (BP) to present using an empirical model based on observations of peat initiation (>3600 14C dates), peatland type (>250 peat cores), and contemporary CH4 emissions in order to explore the effects of changes in wetland type and peatland expansion on CH4 emissions over the end of the late glacial and the Holocene. We find that fen area increased steadily before 8000 BP as fens formed in major wetland complexes. After 8000 BP, new fen formation continued but widespread peatland succession (to bogs) and permafrost aggradation occurred. Reconstructed CH4 emissions from peatlands increased rapidly between 10,600 BP and 6900 BP due to fen formation and expansion. Emissions stabilized after 5000 BP at 42 ± 25 Tg CH4 y-1 as high-emitting fens transitioned to lower-emitting bogs and permafrost peatlands. Widespread permafrost formation in northern peatlands after 1000 BP led to drier and colder soils which decreased CH4 emissions by 20% to 34 ± 21 Tg y-1 by the present day. 

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2. Predicted Vulnerability of Carbon in Permafrost Peatlands With Future Climate Change and Permafrost Thaw in Western Canada

   https://doi.org/10.1029/2020JG005872  

   Treat, Claire C.; Jones, Miriam C.; Alder, Jay; Sannel, A. Britta K.; Camill, Philip; Frolking, Steve (May 2021, Journal of Geophysical Research: Biogeosciences)

   Abstract Climate warming in high‐latitude regions is thawing carbon‐rich permafrost soils, which can release carbon to the atmosphere and enhance climate warming. Using a coupled model of long‐term peatland dynamics (Holocene Peat Model, HPM‐Arctic), we quantify the potential loss of carbon with future climate warming for six sites with differing climates and permafrost histories in Northwestern Canada. We compared the net carbon balance at 2100 CE resulting from new productivity and the decomposition of active layer and newly thawed permafrost peats under RCP8.5 as a high‐end constraint. Modeled net carbon losses ranged from −3.0 kg C m⁻²(net loss) to +0.1 kg C m⁻²(net gain) between 2015 and 2100. Losses of newly thawed permafrost peat comprised 0.2%–25% (median: 1.6%) of “old” C loss, which were related to the residence time of peat in the active layer before being incorporated into the permafrost, peat temperature, and presence of permafrost. The largest C loss was from the permafrost‐free site, not from permafrost sites. C losses were greatest from depths of 0.2–1.0 m. New C added to the profile through net primary productivity between 2015 and 2100 offset ∼40% to >100% of old C losses across the sites. Differences between modeled active layer deepening and flooding following permafrost thaw resulted in very small differences in net C loss by 2100, illustrating the important role of present‐day conditions and permafrost aggradation history in controlling net C loss. 

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3. Bugeye Lakes Complex Water Level Sensor Data, Arctic Coastal Plain of northern Alaska, 2021-2022

   https://doi.org/10.18739/A21V5BG0D  

   Jones, Benjamin (January 2023, NSF Arctic Data Center)

   Taken together, lakes and drained lake basins may cover up to 80% of the lowland landscapes in permafrost regions of the Arctic. Lake formation, growth, and drainage in lowland permafrost regions create a terrestrial and aquatic landscape mosaic of importance to geomorphic and hydrologic processes, tundra vegetation communities, permafrost and ground-ice characteristics, biogeochemical cycling, wildlife habitat, and human land-use activities. Our project focuses on quantifying the role of thermokarst lake expansion, drainage, and drained lake basin evolution in the Arctic System. We did this through a combination of field studies, environmental sensor networks, remote sensing, and modeling. This dataset consists of environmental sensor records that record temperature and water level at three lakes in the Bugeye Lakes Complex in 2021 and 2022. Onset HOBO water level loggers (U2OL-04) were deployed in Bugeye Lakes 1, 2, and 4 in 2021 and 2022 to record temperature and pressure changes at 30-minute intervals. Water level was determined in Onset Hoboware Pro v. 3.7.23 using the barometric compensation assistant based on pressure transducer measurements below the water and from nearby atmospheric pressure measurements from a local pressure transducer mounted to pole on the tundra. The sensor data capture the partial drainage of Bugeye Lakes 2 and 4 into Bugeye Lake 1. Bugeye Lakes 1 and 2 also measure snow dam outburst flooding associated with the recently drained lake basins. 

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4. Methane concentrations in dissolved organic carbon (DOC) leachates from permafrost soils collected from the North Slope of Alaska in the summers of 2018 and 2019

   https://doi.org/10.6073/pasta/e386e272d73577e42b2ae1a18fecf6a0  

   Cory, Rose; Rieb, Emma; Polik, Catherine; Ward, Collin; Kling, George (January 2023, Environmental Data Initiative)

   Methane (CH4) concentrations were measured in dissolved organic carbon (DOC) leachates of permafrost soils collected from the frozen permafrost layer at five sites underlying tussock tundra or wet sedge vegetation on the North Slope of Alaska during the summers of 2018 and 2019. 

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5. Rainfall Alters Permafrost Soil Redox Conditions, but Meta‐Omics Show Divergent Microbial Community Responses by Tundra Type in the Arctic

   https://doi.org/10.3390/soilsystems5010017  

   Romanowicz, Karl; Crump, Byron C; Kling, G. W. (March 2021, Soil systems)

   Soil anoxia is common in the annually thawed surface (‘active’) layer of permafrost soils, particularly when soils are saturated, and supports anaerobic microbial metabolism and methane (CH4) production. Rainfall contributes to soil saturation, but can also introduce oxygen, causing soil oxidation and altering anoxic conditions. We simulated a rainfall event in soil mesocosms from two dominant tundra types, tussock tundra and wet sedge tundra, to test the impacts of rainfall‐induced soil oxidation on microbial communities and their metabolic capacity for anaerobic CH4 production and aerobic respiration following soil oxidation. In both types, rainfall increased total soil O2 concentration, but in tussock tundra there was a 2.5‐fold greater increase in soil O2 compared to wet sedge tundra due to differences in soil drainage. Metagenomic and metatranscriptomic analyses found divergent microbial responses to rainfall between tundra types. Active microbial taxa in the tussock tundra community, including bacteria and fungi, responded to rainfall with a decline in gene expression for anaerobic metabolism and a concurrent increase in gene expression for cellular growth. In contrast, the wet sedge tundra community showed no significant changes in microbial gene expression from anaerobic metabolism, fermentation, or methanogenesis following rainfall, despite an initial increase in soil O2 concentration. These results suggest that rainfall induces soil oxidation and enhances aerobic microbial respiration in tussock tundra communities but may not accumulate or remain in wet sedge tundra soils long enough to induce a community‐wide shift from anaerobic metabolism. Thus, rainfall may serve only to maintain saturated soil conditions that promote CH4 production in low‐lying wet sedge tundra soils across the Arctic. 

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