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Permafrost‐underlain watersheds in the subarctic are sensitive to warming as small changes in ground thermal status will alter all components of the hydrological cycle. Globally, observed increases in winter flows and shifting water chemistry have most often been ascribed to permafrost thaw and deepening runoff pathways. However, there remain few studies in headwater catchments that examine coupled flow‐chemistry relations at high frequency over multiple years and seasons to evaluate the implications of environmental change. In this study, we use multi‐year high‐frequency measurement of discharge, specific conductance (SpC) and chromophoric dissolved organic matter (CDOM) along with traditional grab sampling of major ions to understand the sources and pathways of water and evaluate how distinct solutes are mobilized in a well‐studied subarctic basin in Yukon, Canada. Seasonally, the catchment exhibited considerable hysteresis in flow‐solute relations and had both chemostatic and dilution SpC–Q patterns with respect to major ions depending upon season and mobilization CDOM–Q signals. Storm events were extracted from high‐frequency data and normalized C–Q indices were determined and related to flow, catchment and meteorological variables. CDOM–Q events predominantly had an anti‐clockwise hysteresis and increases in DOC concentrations during storms, with some exception in the spring and fall. Conversely, SpC–Q events exhibited clockwise hysteresis and a dilution behaviour during events with less seasonal or inter‐annual variability. Information from this study supports previous conceptual models of thermally regulated runoff generation in a layered soil profile, yet also points to the importance of lateral connectivity and distal sources of solutes. [ABSTRACT FROM AUTHOR]

Permafrost and frozen ground play a critical role in the transfer of water and solutes from the landscape to the stream, and in biogeochemical cycling by acting as a cold season or semi-permanent acquitard. Conceptual models of permafrost hydrology have been well defined for over 40 years, yet renewed interest in the face of climate change and rapid degradation of frozen ground has provided an opportunity to revisit previous paradigms. At the same time, new instruments and techniques to understand coupled hydrological and biogeochemical processes have emerged, providing a more nuanced view of northern catchments. In this presentation, multi-year high frequency data sets of water, specific conductance (SpC) and chromophoric dissolved organic matter (CDOM) from Granger Creek, an instrumented alpine watershed with discontinuous permafrost within the Wolf Creek Research Basin, Yukon Territory, Canada, is presented. Snowmelt and rainfall-runoff events were delineated over multiple years and sub-hourly data was used to generate hysteresis loops for several dozen events. The direction and magnitude of these loops for Q-SpC and Q-CDOM suggest strong seasonal controls on the mechanisms of solute export, which vary for weathering ions compared with dissolved organic matter. Dissolved solutes (as represented by SpC) are largely diluted during freshet and storm events, with Q-SpC hysteresis being greatest during period of low-flow in mid-summer when SpC was large. In contrast, CDOM largely exhibited a mobilization signal with large event and inter-annual variability in hysteresis patterns. In both cases, there were unique signals related to season: freshet, mid-summer low flow and fall wetting. High-frequency and hysteresis direction and magnitude suggest changing proximal and distal sources of solutes and organic material in response to active layer thickening, soil moisture and precipitation intensity; highlighting spatial connections among landscape units not previously reported. Evaluation of these patterns at the headwater scale provides alternate hypotheses for how permafrost landscapes may respond to a changing climate. [ABSTRACT FROM AUTHOR]