Transient hydrosystems in deglaciating subarctic catchments: insights from a decade of research in the St. Elias Mountain Green Belt

Rapid cryosphere degradation is profoundly transforming hydrological processes in glacierized catchments worldwide. In subarctic environments, glacier retreat progressively reduces the direct contribution of ice melt to streamflow, while other cryospheric and periglacial components become increasingly influential, often in transient and non-linear ways. In particular, permafrost thaw and the reorganization of periglacial landscapes give rise to new, evolving pathways for water storage and transfer.

Over the past decade, we have examined these dynamics in the Shä́r Ndü Chù Duke River watershed, located within Kluane First Nation territory in the St. Elias Mountain Green Belt. Long-term observations reveal that the various cryospheric components of deglaciating valleys respond at different rates, leading to asynchronous shifts in hydrological and hydrogeological processes. As a result, the watershed functions as a continuously evolving hydrosystem rather than progressing toward a single, stable post-glacial state.

Our investigation combines ground-based and drone-borne geophysical surveys, thermal infrared and LiDAR observations, hydrometeorological monitoring, and hydrochemical tracers to characterize both surface and subsurface processes. These complementary methods highlight the growing role of groundwater in watershed outflows, driven by the widespread development of debris-covered and buried ice and by the mantling of formerly glacierized terrain. Such conditions modify surface energy exchanges and promote a transition from relatively direct surface runoff to enhanced infiltration and complex subsurface drainage networks.

Dynamic periglacial landforms, including rock glaciers containing long-lived debris-insulated ice, further disrupt surface–groundwater connectivity and redistribute flow paths across the landscape. Although debris cover slows the degradation of buried ice and permafrost relative to exposed ice, continued cryospheric loss remains inevitable. Collectively, our results demonstrate that hydrological routing in deglaciating subarctic catchments is highly transient, with important implications for the timing, magnitude, and sustainability of northern water resources under continued climate warming.