Environmental drivers constraining the seasonal variability of satellite-observed methane at Northern high latitudes

Abstract. Methane emissions from Northern high-latitude wetlands are associated with large uncertainties, especially in the rapidly warming climate. Satellite observations of column-averaged methane concentrations (XCH₄) in the atmosphere exhibit variability due to time-varying sources and sinks. In this study, we investigate how environmental variables, such as temperature, soil moisture, snow cover, and the hydroxyl radical (OH) sink of methane, explain the seasonal variability of column-averaged methane concentrations (XCH₄) observed from space over Northern high-latitude wetland areas. We use XCH₄ data obtained from the TROPOMI instrument aboard the Sentinel-5 Precursor satellite, retrieved using the Weighting Function Modified Differential Optical Absorption Spectroscopy (WFMD) algorithm. Environmental variables are derived primarily from meteorological reanalysis datasets, with satellite-based data used for snow cover and soil freeze-thaw dynamics, and modeled data for the OH sink. Our analysis focuses on five case study regions, including two in Finland and three in Russian Siberia, covering the period from 2018 to 2023. Our findings reveal that environmental variables have a systematic impact on XCH₄ variability: the seasonal variability is most strongly influenced by snow cover and soil water volume, while daily variability is primarily affected by soil temperature. Our results are largely consistent with in-situ-based local studies but the role of snow is more pronounced. Our results demonstrate how satellite XCH₄ observations can be used to study the seasonal variability of atmospheric methane over large wetland regions. The results imply that satellite observations of atmospheric composition, along with other Earth Observations as well as meteorological reanalysis data can be jointly informative of the processes controlling the emissions in Northern high latitudes.