The cryostratigraphy of thermo-erosion gullies in the Canadian High Arctic demonstrates the resilience of permafrost

Abstract

Thermo-erosion gullies (TEGs) are one of the most common forms of abrupt permafrost degradation. They generally form in ice-wedge polygonal networks where the interconnected troughs can channel runoff water. Although TEGs can form within a single thawing season, it takes them several decades to stabilize completely. While the inception of TEGs has been examined in several studies, the processes of their stabilization remain poorly documented, especially the cryostructures that form following permafrost aggradation in stabilizing TEGs. For this study, we investigated the impacts of two TEGs in the Canadian High Arctic (Bylot Island, NU, Canada) on ground ice content, cryostratigraphic patterns, and geomorphology to examine permafrost recovery following thermal erosion in ice-wedge polygonal tundra. We sampled 17 permafrost cores from two TEGs – one still active (since 1999) and one stabilized (> 100 years old) – to describe the surface conditions, interpret the cryostratigraphic patterns, and characterize the state of permafrost after TEG stabilization. Although the TEG caused discernable cryostratigraphic patterns in permafrost, ground ice content and thaw front depth in the TEGs were comparable to measurements made in undisturbed conditions. We also noted that, once stabilized, TEGs permanently (at the Anthropocene scale) alter landscape morphology and hydrological connectivity. We concluded that, although the formation of a TEG has profound effects in the short and medium term (years to decades) and leaves near-permanent geomorphological and hydrological scars in periglacial landscapes, in the long term (decades to centuries), High Arctic permafrost can recover and return to geocryological conditions similar to those pre-dating the initial disturbance. This suggests that, in stable environmental conditions undergoing natural variability, permafrost can persist longer than the geomorphological landforms in which it forms.