ABSTRACT In permafrost regions, hydrological and biogeochemical processes are substantially influenced by ground thaw dynamics. However, seasonal and interannual changes in ground thaw are difficult to measure at catchment and regional scales. Prior studies have used stream chemistry to indicate water flowpaths at catchment scales by taking advantage of vertical differences in solute sources, but the consistency of these chemical tracers across varying Arctic landscapes is poorly understood. In this study, we analysed nine potential thaw depth tracers (Ba, Ca, Fe, K, Mg, Na, S, Si and Sr) for three consecutive thaw seasons (June through early September, 2021–2023) across three catchments with different landscape characteristics in the continuous permafrost region of northern Alaska, United States. We used generalised additive models to test which solutes made effective tracers of thaw depth across catchments, based on significant concentration–discharge relationships and seasonality. Five solutes met the criteria for an effective thaw tracer in at least one catchment, but there was no single tracer that worked across all three catchments, with the differences likely due to variation in catchment characteristics (e.g., geology, soils, lake coverage). Tracking ground thaw dynamics via stream chemistry is a promising approach that complements modelling and point measurements of thaw by filling gaps in spatial and temporal scales. Overcoming the current limitations of observing ground thaw across spatial scales, seasons and years is needed as thaw dynamics will become increasingly important in Arctic systems experiencing both warming and hydrologic intensification.
Grose et al. (Wed,) studied this question.