Using Ground-Penetrating Radar to Infer Ice Wedge Characteristics Proximal to Water Tracks

Abstract

Massive ground ice in Arctic regions underlain using continuous permafrost influences hydrologic processes, leading to ground subsidence and the release of carbon dioxide and methane into the atmosphere. The relation of massive ground ice such as ice wedges to water tracks and seasonally saturated hydrologic pathways remains uncertain. Here, we examine the location of ice wedges along a water track on the North Slope of Alaska using Ground-Penetrating Radar (GPR) surveys, in situ measurements, soil cores, and forward modeling. Of nine unique GPR surveys collected in the summers of 2022 and 2023, seven exhibit distinctive “X”-shaped reflections above columnar reflectors that are spatially correlated with water track margins. Forward modeling of plausible geometries suggests that ice wedges produce reflection patterns most similar to the reflections observed in our GPR profiles. Additionally, a large magnitude (∼71 mm) rain event on 8 July 2023 led to a ground collapse that exposed four ice wedges on the margin of the studied water track, ∼100 m downstream of our GPR surveys. Together, this suggests that GPR is a viable method for identifying the location of ice wedges as air temperatures in the Arctic continue to increase, we expect that ice wedges may thaw, destabilizing water tracks and causing ground collapse and expansion of thermo-erosional gullies. This ground collapse will increase greenhouse gas emissions and threaten the Arctic infrastructure. Future geophysical analysis of upland Arctic hillslopes should include additional water tracks to better characterize potential heterogeneity in permafrost vulnerability across the warming Arctic.