Biogeophysical controls on soil-atmosphere thermal differences: implications on warming Arctic ecosystems

• Published in: Environmental Research Letters
• Main Authors: J Aalto, D Scherrer, J Lenoir, A Guisan, M Luoto
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2018
• Subjects: thermal variability; microclimate; soil-atmosphere decoupling; soil temperature; structural equation model; snow cover; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Arctic
• Online Access: https://doi.org/10.1088/1748-9326/aac83e; https://doaj.org/article/f7dd1fbaec5a4d0e91e2539b200a81f4

Soil temperature (ST) has a key role in Arctic ecosystem functioning and global environmental change. However, soil thermal conditions do not necessarily follow synoptic temperature variations. This is because local biogeophysical processes can lead to a pronounced soil-atmosphere thermal offset ( ∆T ) while altering the coupling (β T ) between ST and ambient air temperature (AAT). Here, we aim to uncover the spatiotemporal variation in these parameters and identify their main environmental drivers. By deploying a unique network of 322 temperature loggers and surveying biogeophysical processes across an Arctic landscape, we found that the spatial variation in ∆T during the AAT≤0 period (mean ∆T = 6.0 °C, standard deviation ± 1.2 °C) was directly and indirectly constrained by local topography controlling snow depth. By contrast, during the AAT>0 period, ∆T was controlled by soil characteristics, vegetation and solar radiation ( ∆T = −0.6 °C ± 1.0 °C). Importantly, ∆T was not constant throughout the seasons reflecting the influence of β T on the rate of local soil warming being stronger after (mean β T = 0.8 ± 0.1) than before (β T = 0.2 ± 0.2) snowmelt. Our results highlight the need for continuous microclimatic and local environmental monitoring, and suggest a potential for large buffering and non-uniform warming of snow-dominated Arctic ecosystems under projected temperature increase.