Frozen debris lobe stability, a function of thermal and hydrological processes

Frozen debris lobes (FDL) are mass wasting hill slope features found in a region of continuous permafrost in the south-central Brooks Range, near Wiseman, AK. Permafrost temperatures vary with landscape position and elevation but are relatively mild at -1.3 C in the Dietrich River valley. FDL-A, one of the most prominent features due to its movement rate, size and proximity to the Dalton Highway, moves as a flow mainly during summer months, and sliding within a shear zone from 20.2 to 22.8 meters below the lobe surface occurs year round. During drilling we observed the presence of artesian groundwater at various depths near mid-slope in the center line of FDL-A. Artesian water found in the boring may be associated with shear planes in the frozen sediment. In addition, cracks are ubiquitous on the surface, which may be linked to FDL-A's movement and are a likely pathway for liquid water to enter permafrost where it builds liquid water pressure. In this presentation we discuss the physics associated with the observation of liquid water in frozen ground and its implications for potential geologic hazards of this and other FDL's along the Dalton Highway. We also show ground thermal data for the past year on FDL-A. This analysis indicates that there is a relationship between thermal and hydrological processes in permafrost hill slope terrain, and therefore climate change is a crucial factor in the dynamics of FDL's.