The SLIPPERY SOILS project (May 1, 2023 – January 31, 2025) is an SPI Exploratory Grant led by Markus Stoffel (University of Geneva) that seeks to improve understanding of frozen debris lobe (FDL) dynamics in the Brooks Range, Alaska. In May 2023, the team traveled along the Dalton Highway to the foot of key FDLs threatening both the highway and the Trans-Alaska Pipeline System. FDLs are slow-moving, landslide-like masses of soil, rocks, trees, and ice—often hundreds of meters across and moving at rates up to several meters per year—that pose serious infrastructure risks. Using dendrogeomorphology, the project analyzes leaning and reaction wood in century-old white spruce to date past lobe movements and assess links to permafrost thaw and climate variability. It tests three hypotheses: that tree-ring anomalies record near-surface flow; that split trunks and exposed roots map the onset and rates of spreading; and that reconstructed FDL dynamics mirror past warming and cooling episodes. A novel coupling of photogrammetric surveys with tree-ring data enables 3D detection of surface changes and associated tree deformation over time. Over 300 full cross-sections of white spruce were sampled during the field campaign, providing a rich archive for reconstructing past geomorphic activity. Findings to date offer annually resolved insights into when and how FDLs moved, informing strategies to predict and mitigate slope instability in Arctic and alpine permafrost regions. This exploratory phase has yielded unprecedented long-term movement records and secured a follow-on grant from the Swiss National Science Foundation for work extending through 2029. For more details, see the Working in moving dirt report and the SLIPPERY SOILS project page.
