Linking tundra vegetation, snow, soil temperature, and permafrost

• Main Authors: Grünberg, Inge, Wilcox, Evan J., Zwieback, Simon, Marsh, Philip, Boike, Julia
• Format: Text
• Language: English
• Published: 2020
• Subjects: Arctic; Trail Valley Creek; Valley Creek; Active layer thickness; permafrost; Tundra
• Online Access: https://doi.org/10.5194/bg-2020-88; https://www.biogeosciences-discuss.net/bg-2020-88/

Soil temperatures in permafrost regions are highly heterogeneous on small scales, in part due to variable snow and vegetation cover. Moreover, the temperature distribution that results from the interplay of complex biophysical processes remains poorly constrained. Sixty-eight temperature loggers were installed to record the distribution of topsoil temperatures at the Trail Valley Creek study site in the Northwestern Canadian Arctic. The measurements were distributed across six different vegetation types characteristic for this landscape. Two years of topsoil temperature data were analysed statistically to identify temporal and spatial characteristics and their relationship to vegetation, snow cover and active layer thickness. The mean annual topsoil temperature varied between −3.7 °C and 0.1 °C within a 1.2 km distance, with an approximate average across the landscape of −2.3 °C in 2017 and −1.7 °C in 2018. The observed variation can, to a large degree, be explained by variation in snow cover. Differences in height between vegetation types cause spatially variable snow depth during winter, leading to spatially variable snow melt timing in spring, causing pronounced differences in topsoil mean temperature and temperature variability during those time periods. Summer topsoil temperatures were quite similar below most vegetation types, and not consistently related to active layer thickness at the end of August. The small-scale pattern of vegetation and its influence on snow cover height and snow melt governs the annual topsoil temperature in this permafrost-underlain landscape.