Using Permafrost Disturbance Susceptibility Maps to Understand Processes that Drive Permafrost Degradation

Abstract:

Continued changes to the thermal, hydrological and geotechnical conditions of permafrost have led to degradation and changes in the active layer resulting in increased permafrost disturbance across the Canadian High Arctic. Active layer detachments (ALDs) and mudboils, two forms of permafrost disturbance, are both triggered by high pore-water pressure resulting from deep active layer thaw and increased precipitation. Recent work completed at the Cape Bounty Arctic Watershed Observatory (CBAWO), in the Canadian High Arctic, has found that these two features of permafrost disturbance are associated with distinct environments; ALDs are commonly found on vegetated slopes, whereas mudboils occur on flat, less vegetated terrain. This implies that on transitional slopes pore water pressures may continue to increase resulting in ALDs in these areas over others. Mudboils act as an indicator of potentially hazardous subsurface fluid pressures that may lead to slope failure. Susceptibility maps generated using predictive modeling approaches can provide insight into landscape characteristics driving the formation of both types of features by identifying areas with high, moderate, and low susceptibility to future disturbance.

Permafrost slope disturbance susceptibility models have been successfully applied to a study area at CBAWO to identify areas prone to future slope disturbance. Using a generalized additive model (GAM), the model was fitted for disturbed and undisturbed locations using GIS-derived geomorphological predictor variables including: slope, potential incoming solar radiation, wetness index, curvature, geology, and distance to water. Current modeling is underway to produce mudboil susceptibility maps using the same predictor variables, with the addition of vegetation. Comparison of the resulting susceptibility maps can be used to understand the relation between the two forms of disturbance through the assessment of their spatial distribution. Both active layer detachments and mudboils are driven by similar climatic and landscape phenomena, and as such, greater knowledge of the spatial links between them is needed to understand the nature of future permafrost degradation.