| 1. |
- Matsubara, Felipe, 1991-, et al.
(författare)
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Molecular-Multiproxy Assessment of Land-Derived Organic Matter Degradation Over Extensive Scales of the East Siberian Arctic Shelf Seas
- 2022
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 36:12
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Tidskriftsartikel (refereegranskat)abstract
- Global warming triggers permafrost thaw, which increases the release of terrigenous organic matter (terr-OM) to the Arctic Ocean by coastal erosion and rivers. Terrigenous OM degradation in the Arctic Ocean contributes to greenhouse gas emissions and severe ocean acidification, yet the vulnerability of different terr-OM components is poorly resolved. Here, terr-OM degradation dynamics are studied with unprecedented spatial coverage over the World's largest shelf sea system—the East Siberian Arctic Shelf (ESAS), using a multi-proxy molecular biomarker approach. Mineral-surface-area-normalized concentrations of terr-OM compounds in surface sediments decreases offshore. Differences between terr-OM compound classes (lignin phenols, high-molecular weight [HMW] n-alkanes, n-alkanoic acids and n-alkanols, sterols, 3,5-dihydroxybenzoic acids, cutin acids) reflect contrasting influence of sources, propensity to microbial degradation and association with sedimenting particles, with lignin phenols disappearing 3-times faster than total terr-OM, and twice faster than other biomarkers. Molecular degradation proxies support substantial terr-OM degradation across the ESAS, with clearest trends shown by: 3,5-dihydroxybenzoic acid/vanillyl phenol ratios, acid-to-aldehyde ratios of syringyl and vanillyl phenols, Carbon Preference Indices of HMW n-alkyl compounds and sitostanol/β-sitosterol. The combination of terr-OM biomarker data with δ13C/Δ14C-based source apportionment indicates that the more degraded state of lignin is influenced by the relative contribution of river-transported terr-OM from surface soils, while HMW n-alkanoic acids and stigmasterol are influenced by erosion-derived terr-OM from Ice Complex deposits. Our findings demonstrate differences in vulnerability to degradation between contrasting terr-OM pools, and underscore the need to consider molecular properties for understanding and modeling of large-scale biogeochemical processes of the permafrost carbon-climate feedback.
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| 2. |
- Wild, Birgit, et al.
(författare)
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Organic matter composition and greenhouse gas production of thawing subsea permafrost in the Laptev Sea
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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