Geospatial patterns of retrogressive thaw slump occurrence and dynamics in West Siberia, Russia

The Arctic is warming nearly four times faster than the global average, making it highly vulnerable to rapid environmental change. Permafrost, which underlies about 15% of the Northern Hemisphere, is thawing both gradually and abruptly. Abrupt thaw can unfold within years or decades, driving strong ecosystem shifts and climate feedbacks. One of its most dynamic features is retrogressive thaw slumps (RTSs)— slope failures in ice-rich permafrost that reshape landscapes and release carbon, sediment, and nutrients. RTSs are widespread across the Arctic and high mountains (e.g., Tibetan Plateau), with their activity closely linked to warming and wetting. Despite a growing recognition, RTS dynamics remain difficult to predict due to heterogeneous ground ice occurrence, limited field data, and the lack of process-based models. Previous work in the West Siberian Arctic, a region with continuous permafrost rich in massive ground ice, was largely confined to site-specific observations or large-scale automatic inventories with large uncertainties. As a result, the region lacked a comprehensive understanding of the extent, distribution, drivers, and evolution of RTS. Furthermore, inconsistent terminology across Russian and North American traditions has hampered comparisons across studies. This dissertation addresses these gaps by (i) reviewing and clarifying the terminology and developmental stages of RTS; (ii) constructing a high-resolution RTS inventory for the Yamal and Gydan peninsulas, derived from an ESRI basemap mosaic of Maxar satellite imagery; (iii) analyzing their spatial clustering and environmental controls using remote-sensing derived datasets and spatial and statistical methods; and (iv) quantifying their temporal dynamics and climatic drivers through historical and modern (PlanetScope) satellite imagery, culminating in a statistical hazard modeling approach. The terminology review shows that the RTS formation process is termed in two different ways: thermokarst and thermodenudation. RTS, as a term itself, includes different stages of landform development and morphology. RTSs in general differ in shape, triggers, ground ice types, position in the relief, activity, concurrent processes, and spatial organization. The new inventory of 6168 West Siberian RTSs mapped across the Yamal and Gydan peninsulas reveals that they are dominated by horseshoe-shaped thermocirques, which mostly experience thermokarst subsidence and lateral thermo-erosion as the main concurrent processes. Over 75% of the identified RTSs occur along lakeshores, affecting >2,400 lakes, with implications for sediment, carbon, and nutrient fluxes, and risks to local communities and aquatic habitats. RTSs in the West Siberian Arctic are highly clustered. These clusters cover 6.9% of Yamal and Gydan and are associated with moist tundra land cover. In Gydan, RTS clusters are located at higher elevations, on rougher terrain, and in areas of greater lake density, whereas such contrasts are weaker in Yamal. Using remote sensing time series, I found that the number of RTSs increased 23-fold since the 1960s, with initiation rates increasing from ≤3 yr⁻¹ (1960s) to ~78 yr⁻¹ (2019–2024). Headwall retreat rates remained comparatively stable (median 1.3 and 1.6 m yr⁻¹). A discrete-time Bayesian hazards model identified summer maximum precipitation as the strongest short-term influencing factor (hazard ratio ≈ 3.9). Arctic winter warming (mean air temperature) was the dominant long-term driver (hazard ratio ≈ 3.1), with an increase of +1.62 standard deviation resulting in a +37 percentage points increase in annual RTS initiation probability. RTS development poses an infrastructure damage risk, which was the highest on Yamal, notably around the Bovanenkovo gas field and transport corridors. By clarifying terminology and documenting regional patterns, this dissertation establishes a clearer foundation for comparing RTS research across the Arctic. The findings from West Siberia reveal how local geomorphic and climatic conditions impact RTS occurrence, also demonstrating the rapid acceleration of their activity. Together, these insights position West Siberia as a critical case study for understanding abrupt thaw processes in a warming Arctic.