Anfisa Pismeniuk

• Pismeniuk, Anfisa; Dörsch, Peter; Ippach, Mats Rouven; Willmes, Clarissa; Sheffield, Sunniva Bratli & Pirk, Norbert [Show all 7 contributors for this article] (2026). Wintertime production and storage of methane in thermokarst ponds of subarctic Norway. Biogeosciences. ISSN 1726-4170. 23(4), p. 1497–1514. doi: 10.5194/bg-23-1497-2026. Full text in Research Archive Show summary

  The ongoing climate change in permafrost areas can trigger abrupt thaw processes, leading to the formation of thermokarst lakes and ponds. These water bodies, especially in organic-rich areas, are recognized as strong methane (CH4) emitters during the ice-free periods and have the potential to accumulate large CH4 amounts in and below the ice, which is released during the ice melt. We estimated winter CH4 bottom flux in nine shallow ponds within two permafrost peatlands in Northern Norway, Iškoras and Áidejávri, during the 2023–2024 ice cover season. The cumulative winter CH4 bottom flux ranged from 0.6 to 24 g CH4-C m−2 which at the Iškoras site contributed up to 40 % to the annual CH4 budget. The heterogeneity of the CH4 wintertime accumulation is related to pond depth, differences in vegetation, and the thermokarst pond formation age. The latter was investigated using a space-for-time substitution approach along chronosequences of thermokarst formation spanning more than 70 years. The winter CH4 bottom flux increased from 2 mg CH4-C m−2 d−1 in two-year-old pond to 106 mg CH4-C m−2 d−1 in a pond formed between 30 and 60 years ago. Pond that formed more than 70 years ago and is currently experiencing sedge regrowth exhibited large winter CH4 bottom flux of 59 mg CH4-C m−2 d−1, while older ponds dominated by Sphagnum mosses showed 4 to 10 times smaller CH4 bottom fluxes.

• Schirrmeister, Lutz; Fuchs, Margret C.; Opel, Thomas; Andreev, Andrei; Kienast, Frank & Schneider, Andrea [Show all 26 contributors for this article] (2025). Newly dated permafrost deposits and their paleoecological inventory reveal an Eemian much warmer than today in Arctic Siberia. Climate of the Past. ISSN 1814-9324. 21(7), p. 1143–1184. doi: 10.5194/cp-21-1143-2025. Full text in Research Archive Show summary

  In this study, we integrate geochronological, cryolithological, paleoecological, and modeling data to reconstruct the Last Interglacial (LIG) climate around the New Siberian Islands, revealing significantly warmer conditions compared to today. New luminescence dating of the lacustrine deposits mostly preserved in ice-wedge pseudomorphs of 1–3 m thickness along the Dmitry Laptev Strait indicates ages consistent with the LIG (Marine Isotope Stage (MIS) 5e). Analysis of plant macrofossils and of pollen and faunal records (beetles and chironomids) from these deposits suggests mean temperatures of the warmest month (MTWAs) of 10.3 to 12.9 °C, 9.0 ± 3.0 °C, 8 to 10.5 °C, and 9.4 to 15.3 °C for Bol'shoy Lyakhovsky and of 12.7 to 15.3 °C, 9.7 ± 2.9 °C, 8 to 14 °C, and 12.0–13.8 °C for Oyogos Yar. The fossil-beetle-based mutual climate range for mean temperatures of the coldest month is −34 to −26 °C for Bol'shoy Lyakhovsky and −38 to −26 °C for Oyogos Yar. Our chironomid-based reconstructions of water table depth suggest 1.7 to 5.6 m for Bol'shoy Lyakhovsky, while previous analysis suggested 1.1 to 3.3 m for Oyogos Yar. Pollen-based reconstruction of mean annual precipitation (MAP) suggests 271 ± 56 mm for Bol'shoy Lyakhovsky and 229 ± 22 mm for Oyogos Yar. The first-time application of clumped isotopes to permafrost-preserved biogenic calcite of ostracods and bivalves for Oyogos Yar reconstructed near-surface water temperatures of 10.3 ± 3.0 °C and bottom-water temperatures of 5.3 ± 1.5 °C in thermokarst lakes during summer. In summary, the analyzed proxies suggest summers warmer than today by 5.5 to 12.8 °C for Bol'shoy Lyakhovsky and by 0.2 to 7.5 °C for Oyogos Yar and winters warmer than today by up to 7.1 and 8.4 °C for Bol'shoy Lyakhovsky and Oyogos Yar, respectively. Modern mean annual precipitation values are within the uncertainty range of the reconstructions. Climate model simulations for the LIG from PMIP suggest MTWAs warmer than today for Bol'shoy Lyakhovsky (4.4 ± 1.0 °C compared to 2.5 °C) and colder than today for Oyogos Yar (4.5 ± 1.2 °C compared to 7.8 °C), underestimating the Eemian warming reconstructed from our multiple paleoecological proxies. The LIG warming mainly affected summer conditions, whereas modern and future warming will rather impact winter conditions. As the LIG annual mean temperature is often used as an analog for the future climate in the High Arctic, the proxy–model mismatch highlights the urgent need for more systematic quantitative proxy-based temperature reconstructions in the Arctic and more sophisticated Earth system models capable of capturing Arctic paleoenvironmental conditions.

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• Carlsen, Eira Catharine Lødrup; Pismeniuk, Anfisa; Wei, Jing; Ippach, Mats Rouven; Dörsch, Peter & Westermann, Sebastian [Show all 9 contributors for this article] (2026). FROM PEAT TO PONDS: LANDSCAPE HETEROGENEITY DRIVES METABOLIC NETWORKS AND GREENHOUSE GAS RELEASE FROM THAWING PERMAFROST. Full text in Research Archive Show summary

  As permafrost landscapes degrade, they transform into a hydrological mosaic of dry palsas, collapsing thermokarst slumps, and water-saturated ponds. This physical reorganization creates steep gradients in redox potential and organic matter quality, fundamentally altering the thermodynamic constraints on microbial metabolism. We investigated greenhouse gas (CO2, CH4, N2O) production potentials across several permafrost thaw gradients in sub-Arctic peatlands of Northern Norway, linking landscape-scale changes to genome-resolved metabolic networks. By integrating high-resolution metagenomics with organic matter and greenhouse gas production characterization, we found that thaw features act as distinct thermodynamic bioreactors. In water-saturated, anoxic peat layers, oxygen limitation selects for "slow" metabolic guilds specialized in fermentation and methanogenesis while other oxygenated features are constrained by the quality of organic matter—specifically the accumulation of polyphenols and aromatic compounds acts as a metabolic "latch". We show that the shift from oxic to anoxic conditions triggers a non-linear restructuring of the microbial network, where less efficient central metabolism drives high N2O and CH4 yields but suppressed CO2 production. These findings demonstrate that predicting the permafrost-carbon feedback requires mapping the "metabolic landscape"—where organic matter quality and redox thresholds ultimately tune the greenhouse gas release from thawing landscapes to the atmosphere.

• Carlsen, Eira Catharine Lødrup; Wei, Jing; Lejzerowicz, Franck Laurent Patrick; Ippach, Mats Rouven; Pismeniuk, Anfisa & Kjær, Sigrid Trier [Show all 10 contributors for this article] (2025). Greenhouse gas production kinetics and metabolic traits in thawing permafrost peat. Full text in Research Archive Show summary

  While numerous drivers of greenhouse gas emission (GGE) have been suggested to drive variabilities across thawing landscapes, experimental validations are still widely lacking . Here, I will present results from several experimental studies capturing drivers of GGE across thawing permafrost landscapes like redox, organic matter and microbial source community. Our findings reveal clear responses of the greenhouse gases to redox conditions across the landscape. CO2 production showed a drastic decline when O2 dropped below 100 μM; specifically, under anoxic conditions, CO2 yield and maximum net production rates decreased by around 90 % compared to oxic conditions. CH4 levels remained consistent across O2 gradients, until at least 6 months upon thawing. Functional groups like N2O reducers, fermenters, denitrifiers, and sulfur reducers increased under anoxic conditions, and the reduced CO2 production rates and yields under anoxic conditions were reflected by genomic changes towards reduced central metabolic efficiency. Our data thus points towards critical GGE thresholds under suboxic conditions across thawing landscapes. Moreoever, gas dynamics seem to be primarily influenced by permafrost conditions rather than source community colonization. Our experiments provide increased knowledge on the variable GGE across thawing permaforst landscapes influenced by variable redox conditions and permafrost´s organic matter legacy.

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