Climate-Driven Landscape Change and Thaw Slump Impacts on High Arctic Stream Systems in Eureka, Nunavut, Canada.

Abstract

Permafrost thaw is increasingly threatening infrastructure, ecosystem function and freshwater security. Retrogressive thaw slumps (RTS), for example, are increasing in frequency across the Canadian Arctic, including High Arctic locations. Most knowledge of the hydrological impacts of thaw slumping is based on studies in the Western Canadian and Alaskan Arctic, where thaw slumping is pluvial driven. In the Eureka region, thaw slumping is widespread and linked to warmer summer air temperatures. However, the hydrological impacts of thaw slumps on local streams remain unquantified. This PhD thesis therefore (1) quantifies regional landscape change, (2) isolates the geochemical effects of thaw slumping on nival streams, and (3) evaluates how regional climate influences stream activity in the region of Eureka, Ellesmere Island, Nunavut. Landsat trend analysis spanning from 1999 to 2024 shows that 79.3% of the Fosheim Peninsula experienced significant positive change in greening (vegetation increase), 42.3% in brightness (surface reflectance) and 31.2% in wetness (surface water and ground moisture). Notably, 26% of areas with positive greening trends occur on barren land. Random-forest classification indicates aridification processes on 3.7% of the peninsula. LARCH visual analysis shows substantial geomorphic reorganization, including widespread fluvial erosion and channel migration in the Slidre River system. Over the 25-year period, nine lakes fully or partially drained, and 139 thaw slumps were identified, 60 of which were active in 2024. Stream chemistry from two nival-dominated streams shows that RTS had no impact on stream δD-δ18O but increased dissolved organic carbon and solute concentrations, including elevated chloride downstream of disturbances. Stream-climate interactions indicate that intra-stream temperature variability is governed primarily by channel morphology and temperature inversion rather than thermokarst activity. Climate–temperature relationships shifted between years: air temperature strongly controlled stream temperature in the cold–wet year (avg among sites r = 0.76), whereas solar radiation dominated in the warm–dry year (avg among sites r = 0.56). Stream discharge was greater and more variable in 2022, while suspended sediment and dissolved particulate loads were significantly elevated downstream of RTS during the dry 2023 season (p < 0.001). Collectively, these results show that the region is undergoing rapid climate-driven landscape change, RTS significantly alters stream geochemistry and sediment loads, whereas climatic conditions directly control stream discharge and temperature.