Variability and drivers of winter near-surface temperatures over boreal and tundra landscapes

• Main Authors: Tyystjärvi, Vilna Aleksandra, Niittynen, Pekka, Kemppinen, Julia, Luoto, Miska, Rissanen, Tuuli, Aalto, Juha
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; Tundra
• Online Access: https://doi.org/10.5194/egusphere-2023-576; https://noa.gwlb.de/receive/cop_mods_00065993; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00064497/egusphere-2023-576.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-576/egusphere-2023-576.pdf

Winter near-surface temperatures have important implications for ecosystem functioning such as vegetation dynamics and carbon cycling. In cold environments, seasonal snow cover can exert a strong control on the surface temperatures. However, the lack of in situ measurements of both snow cover and surface temperatures over high latitudes has made it difficult to estimate the spatio-temporal variability of this relationship. Here, we quantified the fine-scale variability of winter near-surface temperatures (+2 cm) and snow cover duration using a total of 441 microclimate loggers in seven study areas across boreal and tundra landscapes during 2019–2021. We further examined the drivers behind this variation and the extent to which surface temperatures are buffered from air temperatures during winter. Our results show that while average winter near-surface temperatures stay close to 0 °C across the study domain, there are large differences in their fine-scale variability among the study areas. Areas with large topographical variation, as well as areas with shallow snowpacks, showed the greatest variation in near-surface temperatures and in the insulating effect of snow cover. In the tundra, for example, differences in minimum near-surface temperatures were close to 30 °C. In contrast, flat topography and deep snow cover lead to little spatial variation and decoupling of the near-surface and air temperatures. Quantifying and understanding the landscape-wide variation in winter microclimates improves our ability to predict the local effects of climate change in the rapidly warming boreal and tundra regions.