ALBERT

Description: Understanding permafrost processes and changes requires long-term observational datasets. This dataset is a continuation of the dataset available from the long-term observational site Samoylov, located in the Lena River Delta, Siberia (72.37°N, 126.48°E). The location is characterized by a cold, dry tundra climate with mean annual air temperature of -11.7°C (using years with complete data between 1998 and 2017). The monthly mean temperatures over this period varied between 9.4°C in the warmest month (July) and -31.7°C in the coldest month (February). The average summer rainfall (June-October) was 145.2 mm. This dataset adds recent years to the observations of meteorological parameters, energy balance, and subsurface observations which have been recorded since 1998. The setup of the active layer monitoring grid (CALM) is explained in Boike et al. (2019). The data provide observations of active layer depth twice per month in summer at 150 points on a regular grid. In addition, the surface type of each point is provided (polygon center, rim high, rim flat, slope, and crack), representing landscape heterogeneity. The observations are suitable for use in integrating, calibrating and testing permafrost as a component in Earth System Models. The resulting quality-controlled dataset serves as a baseline for future studies.

Description: Understanding permafrost processes and changes requires long-term observational datasets. This dataset is a continuation of the dataset available from the long-term observational site Samoylov, located in the Lena River Delta, Siberia (72.37°N, 126.48°E). The location is characterized by a cold, dry tundra climate with mean annual air temperature of -11.7°C (using years with complete data between 1998 and 2017). The monthly mean temperatures over this period varied between 9.4°C in the warmest month (July) and -31.7°C in the coldest month (February). The average summer rainfall (June-October) was 145.2 mm. This dataset adds recent years to the observations of meteorological parameters, energy balance, and subsurface observations which have been recorded since 1998. The setup of the active layer monitoring grid (CALM) is explained in Boike et al. (2019). The data provide observations of active layer depth twice per month in summer at 150 points on a regular grid. In addition, the surface type of each point is provided (polygon center, rim high, rim flat, slope, and crack), representing landscape heterogeneity. The observations are suitable for use in integrating, calibrating and testing permafrost as a component in Earth System Models. The resulting quality-controlled dataset serves as a baseline for future studies.

Description: Thermokarst lagoons represent the transition state from a freshwater lacustrine to a marine environment, and receive little attention regarding their role for greenhouse gas production and release in Arctic permafrost landscapes. We studied the fate of methane (CH4) in sediments of a thermokarst lagoon in comparison to two thermokarst lakes on the Bykovsky Peninsula in northeastern Siberia through the analysis of sediment CH4 concentrations and isotopic signature, methane-cycling microbial taxa, sediment geochemistry, lipid biomarkers, and network analysis. We assessed how differences in geochemistry between thermokarst lakes and thermokarst lagoons, caused by the infiltration of sulfate-rich marine water, altered the microbial methane-cycling community. Anaerobic sulfate-reducing ANME-2a/2b methanotrophs dominated the sulfate-rich sediments of the lagoon despite its known seasonal alternation between brackish and freshwater inflow and low sulfate concentrations compared to the usual marine ANME habitat. Non-competitive methylotrophic methanogens dominated the methanogenic community of the lakes and the lagoon, independent of differences in porewater chemistry and depth. This potentially contributed to the high CH4 concentrations observed in all sulfate-poor sediments. CH4 concentrations in the freshwater-influenced sediments averaged 1.34 ± 0.98 μmol g−1, with highly depleted δ13C-CH4 values ranging from −89‰ to −70‰. In contrast, the sulfate-affected upper 300 cm of the lagoon exhibited low average CH4 concentrations of 0.011 ± 0.005 μmol g−1 with comparatively enriched δ13C-CH4 values of −54‰ to −37‰ pointing to substantial methane oxidation. Our study shows that lagoon formation specifically supports methane oxidizers and methane oxidation through changes in pore water chemistry, especially sulfate, while methanogens are similar to lake conditions.