Snow insulation effects on soil surface temperatures in a snow-fence manipulation experiment

Seasonal snow cover is a key control on winter soil temperature (T_soil) in the Arctic because of its insulating effects. It is still uncertain how variations in soil moisture, climate warming, and vegetation types affect this insulating effect and thus the difference between T_soil and air temperature (ΔT). In this study, we present an analysis of 8 years (2012–2020) of snow dynamics in an Arctic ecosystem manipulation experiment (using snow fences) on Disko Island, West Greenland. We explore the snow insulation effects under four different treatments ((1) mesic tundra heath as a dry site and fen area as a wet site, (2) snow addition because of the snow fence, (3) summer warming using open-top chambers, and (4) shrub removal) on a plot level scale. The ΔT at 5-cm soil depth (ΔT₅) was higher on the snow addition side than on the control side of the snow fences. The ranges of maximum weekly ΔT₅ and annual mean accumulated daily ΔT₅ were from 11.2 to 19.3 ℃ and 1297 to 1631 ℃ on the control side, and from 14.4 to 22.1 ℃ and 1372 to 1830 ℃ on the snow addition side across all study years, respectively. Based on linear mixed-effects models, we conclude that the snow depth was the decisive factor affecting ΔT₅ (p < 0.0001) with a coefficient of 0.05, and found the ΔT₅ to be 1.93 ℃ higher (p < 0.0001) in the wet site than in the dry site during the snow cover season. The change rate of ΔT₅ as the function of snow depth varies with the evolution of snow cover, it is quicker during the period between the day with maximum snow depth to the last day with snow in most experimental plots. During the snow-free season, there were certain lagged effects of the snow cover on T_soil and they offset the warming effects from open-top chambers and shrub removal, i.e., the combination of warming and removal treatments could increase ΔT₅ by 1.71 ℃ on the control side but only 0.83 ℃ on the snow addition side in the dry site. However, the effects of warming and removal treatments on T_soil are limited in the wet site because of a higher soil water content. This study quantifies important dynamics in soil-air temperature offsets linked to both snow and ecosystem changes mimicking climate change and provides a reference for future surface process simulations.