Preprints
https://doi.org/10.5194/egusphere-2025-184
https://doi.org/10.5194/egusphere-2025-184
29 Jan 2025
 | 29 Jan 2025
Status: this preprint is open for discussion and under review for Biogeosciences (BG).

Water chemistry and greenhouse gas concentrations in waterbodies of a thawing permafrost peatland complex in northern Norway

Jacqueline Kay Knutson, François Clayer, Peter Dörsch, Sebastian Westermann, and Heleen A. de Wit

Abstract. Thermokarst ponds in thawing permafrost landscapes play a considerable role in greenhouse gas (GHG) emissions despite their small size, yet they remain underrepresented in Earth system models. At the Iškoras site in northern Norway, a peat plateau with decaying permafrost and thermokarst ponds adjacent to a wetland, we studied water chemistry, dissolved organic matter (DOM) processing, and GHG fluxes over two years. Thermokarst ponds exhibited low pH, high organic acidity, and high oversaturation of dissolved carbon dioxide (CO2) and especially high dissolved methane (CH4). Adjacent wetland streams, however, with near-neutral pH, showed lower CH4 and organic acidity but significantly higher CO2 emissions despite moderate saturations driven by turbulence and bicarbonate replenishment. By contrast, CO2 emissions in ponds were primarily linked to DOM mineralization.

DOM mineralization rates were similar between ponds and streams, suggesting that environmental factors like pH and microbial community differences counteract DOM lability variations. As permafrost decays and transitions from peat plateaus to wetlands, ponds as hotspots of CH4 emissions will disappear. However, total GHG fluxes across the peatland-wetland continuum will depend on wetland emissions, where CH4 emissions usually are considerable, and the fate of organic matter within the plateau. Lateral DOC fluxes may represent a significant loss of soil organic carbon, highlighting the importance of hydrological connectivity in linking terrestrial and aquatic systems. This study emphasizes the need to account for the relationship between hydrological and chemical processes when assessing C and GHG fluxes in permafrost-impacted regions.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Jacqueline Kay Knutson, François Clayer, Peter Dörsch, Sebastian Westermann, and Heleen A. de Wit

Status: open (until 12 Mar 2025)

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Jacqueline Kay Knutson, François Clayer, Peter Dörsch, Sebastian Westermann, and Heleen A. de Wit
Jacqueline Kay Knutson, François Clayer, Peter Dörsch, Sebastian Westermann, and Heleen A. de Wit

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Short summary
Thawing permafrost at Iškoras in northern Norway is transforming peat plateaus into thermokarst ponds and wetlands. These small ponds show striking oversaturation of dissolved greenhouse gases like carbon dioxide (CO2) and methane (CH4), partly due to organic matter processing. Streams nearby emit CO2 driven by turbulence. As permafrost disappears, carbon dynamics will change, potentially increasing emissions of CH4. This study highlights the need to integrate these changes into climate models.
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