LiDAR Detection of Permafrost Change

Permafrost is a dominant feature of Arctic and boreal landscapes, and permafrost surfaces are changing. Beyond gradual warming, water-driven heat transfer has the potential to change permafrost dominated landscapes dramatically and quickly. Due to record (2014) and near-record (2016) wet summers, permafrost landscapes near Fairbanks Alaska have undergone a substantial localized transformation from elevated runoff and resultant thermokarst development. When ground ice thaws, volume displacements occur and the surface subsides or erodes entirely. These developments have dramatic implications for water routing and infrastructure. Before mechanistic analyses can occur regarding drivers of surface change the magnitude and location of change must be detected, but this is a sizeable challenge. Our objective was to detect surface changes and identify where they occur to assess the potential for permafrost thaw and attendant terrain subsidence elsewhere. A short (less than 3 years) time series of repeat airborne LiDAR measurements were used to investigate permafrost-geomorphology interactions at three permafrost-dominated sites near Fairbanks, Alaska. Distinct and relatively rapid localized changes in surface elevation were tied to record precipitation received in summer 2014. Aerial imagery was also assessed to see if these surface changes were identifiable using other means and more universally available coarser-scale datasets. Readily identifiable changes resulting from surface subsidence and inundation were observed along with inchoate plant vigor decline. These results suggest multi-temporal LiDAR collections at the local to regional scales are particularly useful in detecting landscape change. Challenges were identified in utilizing disparate LiDAR datasets where some datasets were of higher resolution than others. Hydrologic events and the landscape's response to them are a growing concern for infrastructure design and development in areas with permafrost.