Preprints
https://doi.org/10.5194/egusphere-2024-562
https://doi.org/10.5194/egusphere-2024-562
28 Feb 2024
 | 28 Feb 2024

Carbon degradation and mobilisation potentials of thawing permafrost peatlands in Northern Norway

Sigrid Trier Kjær, Sebastian Westermann, Nora Nedkvitne, and Peter Dörsch

Abstract. Permafrost soils are undergoing rapid thawing due to climate change and global warming. Permafrost peatlands are especially vulnerable since they are located near the southern margin of the permafrost domain in the discontinuous and sporadic permafrost zones. They store large quantities of carbon (C) which, upon thawing, are decomposed and released as carbon dioxide (CO2), methane (CH4) or dissolved organic carbon (DOC). This study compares carbon degradation in three permafrost peatland ecosystems in Finnmark, Norway, which represent a well-documented chronosequence of permafrost formation. Peat cores from active layer, transition zone and permafrost zone were thawed under controlled conditions and incubated for up until 350 days under initially-oxic or anoxic conditions while measuring CO2, CH4 and DOC production. Carbon degradation varied among the three peat plateaus but showed a similar trend over depth with largest CO2 production rates in the top of the active layer and in the permafrost. Despite marked differences in peat chemistry, post-thaw CO2 losses from permafrost peat throughout the first 350 days in the presence of oxygen reached 67–125 % of those observed from the top of the active layer. CH4 production was only measured after a prolonged anoxic lag phase in samples from transition zone and permafrost, but not in active layer samples. CH4 production was largest in thermokarst peat sampled next to decaying peat plateaus. DOC production by active layer samples throughout 350 days incubation exceeded gaseous C loss (up to 23-fold anoxically), whereas little DOC production or uptake was observed for permafrost peat after thawing. Taken together, permafrost peat in decaying Norwegian peat plateaus degrades at rates similar to active layer peat, while highest CH4 production can be expected after inundation of thawed permafrost material in thermokarst ponds.

Sigrid Trier Kjær, Sebastian Westermann, Nora Nedkvitne, and Peter Dörsch

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-562', Anonymous Referee #1, 26 Mar 2024
  • CC1: 'Comment on egusphere-2024-562', Claire C. Treat, 05 Apr 2024
  • RC2: 'Comment on egusphere-2024-562', Anonymous Referee #2, 12 Apr 2024
Sigrid Trier Kjær, Sebastian Westermann, Nora Nedkvitne, and Peter Dörsch

Data sets

Permafrost peatlands: gas emission and elemental analysis S. T. Kjær et al. https://doi.org/10.5281/zenodo.10696561

Sigrid Trier Kjær, Sebastian Westermann, Nora Nedkvitne, and Peter Dörsch

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Short summary
Permafrost peatlands are thawing due to climate change, releasing large quantities of carbon that degrades upon thawing and is released as CO2, CH4, or dissolved organic carbon (DOC). We incubated thawed Norwegian permafrost peat plateaus and thermokarst pond sediment found next to permafrost for up to 350 days to measure carbon loss. CO2 production was largest initially, while CH4 production increased over time. The largest carbon loss was measured at the top of the peat plateau core as DOC.