Hydroclimatic and Landscape Controls over Permafrost Disturbance in the Canadian High Arctic

Abstract:

Unusually warm conditions during recent years in the Arctic have led to changes in the properties of the seasonal active layer and the uppermost permafrost. Deep thaw of the active layer in exceedingly warm years causes the emergence of pressurized sediment slurries at surface, called mudboils. An understanding of the processes driving mudboil formation is necessary as these features occur in proximity to and during periods when other forms of permafrost degradation and disturbance occur, particularly active layer detachments. To better improve our understanding of these features, systematic mapping of recent mudboils along with soil and water sampling was undertaken at the Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, Nunavut in 2012 and 2013. Results indicate that these features only occur late in the melt season during especially warm years and in some cases closely follow major rainfall events. High-resolution satellite imagery for the study area was analyzed, and terrain characteristics were determined for areas with mapped mudboil activity. Notably, on a landscape scale, mudboils were significantly associated with polar semi-desert vegetation and bare soil settings, corresponding to increased active layer depth when compared to more vegetated areas. Further, fine-scale occurrence of mudboils appears to be related to differential soil moisture retention and spatially heterogeneous soil water pressurization due to thaw into the ice-rich transient layer in warm years. This research provides insights into the processes and landscape controls over these features to aid in understanding localized soil water response to deep summer thaw, with implications for surface water quality and patterns of permafrost-related degradation and disturbance.