Organic matter composition and greenhouse gas production of thawing subsea permafrost in the Laptev Sea

• Published in: Nature Communications
• Main Authors: Wild, Birgit, Shakhova, Natalia, Dudarev, Oleg, Ruban, Alexey, Kosmach, Denis, Tumskoy, Vladimir, Tesi, Tommaso, Grimm, Hanna, Nybom, Inna, Matsubara, Felipe, Alexanderson, Helena, Jakobsson, Martin, Mazurov, Alexey, Semiletov, Igor, Gustafsson, Örjan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2022
• Subjects: Geochemistry; laptev; Laptev Sea; Ocean acidification; permafrost; Tundra
• Online Access: https://lup.lub.lu.se/record/20c85a05-89b3-4160-b766-71952d076e86; https://doi.org/10.1038/s41467-022-32696-0

Subsea permafrost represents a large carbon pool that might be or become a significant greenhouse gas source. Scarcity of observational data causes large uncertainties. We here use five 21-56 m long subsea permafrost cores from the Laptev Sea to constrain organic carbon (OC) storage and sources, degradation state and potential greenhouse gas production upon thaw. Grain sizes, optically-stimulated luminescence and biomarkers suggest deposition of aeolian silt and fluvial sand over 160 000 years, with dominant fluvial/alluvial deposition of forest- and tundra-derived organic matter. We estimate an annual thaw rate of 1.3 ± 0.6 kg OC m−2 in subsea permafrost in the area, nine-fold exceeding organic carbon thaw rates for terrestrial permafrost. During 20-month incubations, CH4 and CO2 production averaged 1.7 nmol and 2.4 µmol g−1 OC d−1, providing a baseline to assess the contribution of subsea permafrost to the high CH4 fluxes and strong ocean acidification observed in the region.