Water Chemistry and Greenhouse Gas Concentrations in Waterbodies of a Thawing Permafrost Peatland Complex in Northern Norway

Manuscript: Water chemistry and greenhouse gas concentrations in waterbodies of a thawing permafrost peatland complex in northern Norway
Authors: Jacqueline K. Knutson, François Clayer, Peter Dörsch, Sebastian Westermann, Heleen A. de Wit

Dataset Overview

The repository includes one datafile. This dataset includes data collected from the Iškoras field site, located in northern Norway at coordinates 69.34°N, 25.29°E, at an elevation of 381 m a.s.l. The site is a permafrost peatland plateau on the Finnmarksvidda plateau in the Finnmark province.

The study period spans September 2020 to September 2022 and focuses on water bodies within the peat plateau and the adjacent wetland. Sampling and monitoring took place approximately monthly during the ice-free season (May–October) in 2021 and 2022.

Study Area

The study area includes: - Three thermokarst ponds (TK-Pond 1, 2, and 3 also referred to as IS-P-01, IS-P-02, and IS-P-03 in the datafile) - One seasonal drainage channel (TK-Drain referred to as IS-S-01 in the datafile) - Wetland inlet and outlet streams (Inlet, Outlet referred to as IS-S-02 and IS-S-03 respectively in the datafile)

The outlet of the wetland also marks the terminus of the Iškoras catchment.

Between September 2020 and October 2022, a total of nine field campaigns were conducted to monitor: - Water chemistry - Dissolved gases - CO2 emissions - Greenhouse gas (GHG) production via dark incubations

Dataset Contents

The dataset includes measurements and samples taken from the study sites, covering the following parameters: - Water Chemistry (e.g., pH, conductivity, sulfate, silica, ammonium, nitrate, phosphorus) - Dissolved Gases (CO2, CH4) - CO2 Fluxes (diffusive CO2 fluxes from water to atmosphere) - Dark Incubations (rates of dissolved organic matter mineralization and GHG production)

Water Sampling and Analysis Methods

Water samples for chemical analysis were collected using standardized procedures. From each site, 500 mL unfiltered water was collected and transported to the laboratory, where chemical analyses were performed at the Norwegian Institute for Water Research (NIVA).

Parameters measured in the water samples include but are not limited to: - pH - Electrical conductivity (EC) - Sulfate (SO₄²⁻) - Silica (SiO₂) - Ammonium (NH₄⁺) - Nitrate (NO₃⁻) - Total phosphorus (totP) - Total organic carbon (TOC) - Dissolved organic carbon (DOC) - Particulate organic carbon (POC)

Dissolved Gas Analysis

Dissolved gas concentrations (CO2, CH4) were measured using the acidified headspace technique. The analysis was performed at the Norwegian University of Life Sciences (NMBU) using gas chromatography (GC).

CO2 Fluxes

CO2 fluxes from the water to the atmosphere were measured using self-made opaque flux chambers, employing a Senseair K30 sensor to measure pCO2, temperature, and relative humidity at the water-air interface.

Dark Incubations

Short-term dark incubations (18–30 hours) were conducted to estimate dissolved organic matter (DOM) mineralization and GHG production rates. The incubation data were used to calculate: - DIC production rates - DOM mineralization rates - First-order decay rates (k_DOM)

Water Chemistry Analysis

Chemical analyses were conducted at NIVA, and the methods for analysis and quality control are described in the ICP Waters Programme Manual (Gunderson et al., 2025) as well as in the NIVAlab Methods tab of the datafile.

Note: Total nitrogen (totN) was not included in the dataset as it was underestimated due to incomplete digestion procedures.

Absorption Spectra of DOM

The absorption spectra of DOM were measured for wavelengths between 200–900 nm. Specific UV absorbency (sUVa) and the specific UV absorption ratio (SAR) were calculated.