Catchment Controls on Solute Exports in a Small Headwater Catchment Underlain with Discontinuous Permafrost

Abstract:

Understanding the controls on solute generation processes in headwater catchments underlain with permafrost will be essential in predicting how catchment exports are likely to change with a warming Arctic and increased permafrost thaw. In this work, concentration-discharge dynamics and chemostatic classifications are used to assess catchment-scale controls on solute generation and exports in a small (~2.25 km²) headwater catchment underlain by discontinuous permafrost on the Seward Peninsula of western Alaska. Concentration-discharge dynamics are key indicators of catchment function and when coupled with discharge measurements and hydrological event tracers, like stable water isotopes, solute concentration behavior becomes a powerful tool to infer catchment-scale hydrological processes such as: solute sources, hydrological flowpaths, residence times, storage dynamics, weathering processes, biogeochemical behavior, and the mass of solute exports. This work capitalizes on co-located, high resolution concentration and discharge measurements to infer catchment-scale solute generation processes at three drainage locations within a small headwater catchment underlain with discontinuous permafrost. Furthermore, a summer storm enabled the evaluation of solute concentration-discharge response to a large hydrological event, while stable water isotopes enabled an appraisal of the contributions of event water. Based on the current controls on solute generation processes, the likely evolution of solute exports with increased permafrost thaw are speculated.