13 Mar 2025

Seasonality of Solute Flux and Water Source Chemistry in a Coastal Glacierized Watershed Undergoing Rapid Change: Wolverine Glacier Watershed, Alaska

Abstract: As glaciers rapidly lose mass, the tight coupling between glaciers and downstream ecosystems results in widespread impacts on global hydrologic and biogeochemical cycling. Knowledge of seasonally changing hydrologic processes and solute sources and signatures is limited. We conducted a broad water sampling campaign to understand the present-day partitioning of water sources and associated solutes in Alaska’s Wolverine Glacier watershed. We established a relationship between electrical conductivity and streamflow at the watershed outlet dividing the melt season into four hydroclimatic periods. Across hydroclimatic periods, we observed a shift in nonglacial source waters from snowmelt-dominated overland and shallow subsurface flow paths to deeper groundwater flow paths. We also observed the shift from a low- to high-efficiency subglacial drainage network and the associated flushing of water stored subglacially with higher solute loads. We used calcium from watershed outlet samples to estimate solute fluxes for each hydroclimatic period across two melt seasons. Between 40% and 55% of Ca2+ export occurred during the late season rainy period. Partitioning of the melt season coupled with a characterization of the chemical makeup and magnitude of solute export provides new insight into a rapidly changing watershed and creates a framework to quantify and predict changes to solute fluxes.