Local-Scale Variability of Soil Temperatures and Controlling Factors in a Discontinuous Permafrost Region
Spatial variability in mean annual soil temperatures is primarily influenced by the thermal decoupling between air- and ground-surface temperature in winter.
Soil temperature in permafrost regions exhibits strong spatial and temporal variability that cannot be explained by weather alone. By acquiring high resolution temperature data, we aimed to understand the local heterogeneity of soil thermal dynamics and their controlling factors – critical information to accurately predict the responses of permafrost environments to climate change.
At 45 discrete locations across the Teller study site watershed, we measured depth-resolved soil temperature over one year at 5- or 10-cm intervals up to 85 cm depth. Soils clustered as cold, intermediate, or warm groups closely matched their co-located vegetation (graminoid tundra, dwarf shrub tundra, and tall shrub tundra, respectively).
We showed that the spatial variability in mean annual soil temperature was primarily driven by diversity in snow cover, which induced variable winter insulation and soil thermal conduction. These effects further extended to the subsequent summer by causing variable latent heat exchanges. Finally, we demonstrated the challenges of predicting soil temperatures by considering the complexity observed in the field data as well as when the observations were reproduced in a model sensitivity analysis.
Citation: Wang C, Shirley IA, Wielandt S, Lamb J, Uhlemann S, Breen AL, Busey RC, Bolton WR, Hubbard S, Dafflon B. 2024. Local-scale heterogeneity of soil thermal dynamics and controlling factors in a discontinuous permafrost region. Environmental Research Letters 19: 034030. https://doi.org/10.1088/1748-9326/ad27bb
Associated Data Citations: Wang et al. 2024. Continuous soil temperature measurements from 2019-10-4 to 2020-10-4, Teller Road Mile 27, Seward Peninsula, Alaska. Next-Generation Ecosystem Experiments (NGEE) Arctic, ESS-DIVE repository. https://doi.org/10.15485/2301692
Shirley et al. 2022. Near-surface hydrology and soil properties drive heterogeneity in permafrost distribution, vegetation dynamics, and carbon cycling in a sub-arctic watershed: Modeling archive. Next-Generation Ecosystem Experiments (NGEE) Arctic, ESS-DIVE repository. https://doi.org/10.5440/1875918.
Contacts & email addresses: Chen Wang (cwang4@lbl.gov); Baptiste Dafflon (bdafflon@lbl.gov)
Clustered soil thermal groups closely matched vegetation types (left). Diverse snow cover influenced by vegetation led to significant variability in winter soil temperatures and thus variability in mean annual temperatures (right).
This research was supported by the Director, Office of Science, Office of Biological and Environmental Research of the US Department of Energy under Contract No. DE-AC02-05CH11231 as part of the Next-Generation Ecosystem Experiments (NGEE Arctic) project.