| Titre | Biogeochemical processes in the active layer and permafrost of a high Arctic fjord valley |
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| Auteur | Jones, E L; Hodson, A J; Thornton, S F; Redeker, K R; Rogers, J; Wynn, P M; Dixon, T; Bottrell, S H; O'Neill, H B |
| Source | Frontiers in Earth Science vol. 8, 342, 2020 p. 1-20, https://doi.org/10.3389/feart.2020.00342  Accès ouvert |
| Image |  |
| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200053 |
| Éditeur | Frontiers in Earth Science |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.3389/feart.2020.00342 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Région | Svalbard |
| Lat/Long OENS | 15.0000 25.0000 79.0000 78.0000 |
| Sujets | pergélisol; géochimie du pergélisol; biogéochimie; fer; carbone; fjords; géochimie; Nature et environnement; Sciences et technologie |
| Illustrations | cartes de localisation; photographies; tableaux; profils; graphiques |
| Programme | Géosciences de changements climatiques Pergélisols |
| Diffusé | 2020 09 02 |
| Résumé | (disponible en anglais seulement)
Warming of ground is causing microbial decomposition of previously frozen sedimentary organic carbon in Arctic permafrost. However, the heterogeneity of the
permafrost landscape and its hydrological processes result in different biogeochemical processes across relatively small scales, with implications for predicting the timing and magnitude of permafrost carbon emissions. The biogeochemical processes of
iron- and sulfatereduction produce carbon dioxide and suppress methanogenesis. Hence, in this study, the biogeochemical processes occurring in the active layer and permafrost of a high Arctic fjord valley in Svalbard are identified from the
geochemical and stable isotope analysis of aqueous and particulate fractions in sediment cores collected from ice wedge polygons with contrasting water content. In the drier polygons, only a small concentration of organic carbon (<5.40 dry weight%)
has accumulated. Sediment cores from these drier polygons have aqueous and solid phase chemistries that imply sulfide oxidation coupled to carbonate and silicate dissolution, leading to high concentrations of aqueous iron and sulfate in the pore
water profiles. These results are corroborated by d34S and d18O values of sulfate in active layer pore waters, which indicate the oxidative weathering of sedimentary pyrite utilising either oxygen or ferric iron as oxidising agents. Conversely, in
the sediments of the consistently water-saturated polygons, which contain a high content of organic carbon (up to 45 dry weight%), the formation of pyrite and siderite occurred via the reduction of iron and sulfate. d34S and d18O values of sulfate in
active layer pore waters from these water-saturated polygons display a strong positive correlation (R2 = 0.98), supporting the importance of sulfate reduction in removing sulfate from the pore water. The significant contrast in the dominant
biogeochemical processes between the water-saturated and drier polygons indicates that small-scale hydrological variability between polygons induces large differences in the concentration of organic carbon and in the cycling of iron and sulfur, with
ramifications for the decomposition pathway of organic carbon in permafrost environments. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Cette étude souligne l'importance de l'évolution du paysage et démontre que l'aggradation du pergélisol et l'accumulation de carbone organique
ont provoqué des changements importants dans les processus biogéochimiques et les réactions de précipitation minérale dans cette plaine d'inondation de l'haut Arctique. Les régimes hydrologiques contrastés des sites d'étude entraînent des différences
marquées dans l'accumulation et la décomposition du carbone organique du pergélisol. À mesure que la température de l'air continue d'augmenter dans l'haut Arctique et que le dégel progresse plus profondément dans le pergélisol, il y aura probablement
des changements majeurs dans le cycle du fer, du soufre et du carbone dans cette vallée, en fonction de l'impact du dégel du pergélisol sur la géomorphologie et l'hydrologie du terrain polygonal en forme de coin de glace. |
| GEOSCAN ID | 326080 |
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