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

Summary, in English

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.

• Author: Birgit Wild; Natalia Shakhova; Oleg Dudarev; Alexey Ruban; Denis Kosmach; Vladimir Tumskoy; Tommaso Tesi; Hanna Grimm; Inna Nybom; Felipe Matsubara; Helena Alexanderson; Martin Jakobsson; Alexey Mazurov; Igor Semiletov; Örjan Gustafsson
• Department/s: Quaternary Sciences
• Publishing year: 2022
• Language: English
• Publication/Series: Nature Communications
• Volume: 13
• Issue: 1
• Links: http://dx.doi.org/10.1038/s41467-022-32696-0
• Document type: Journal article
• Publisher: Nature Publishing Group
• Topic: Geochemistry
• Status: Published
• ISBN/ISSN/Other: ISSN: 2041-1723