Glacier Retreat Amplifies Interannual Variability in Watershed Runoff, Organic Carbon and Nutrient Yields

Abstract Glacier retreat is projected to drive major shifts in the hydrology of many high‐elevation and high‐latitude watersheds. In particular, future decreases in glacier runoff are hypothesized to reduce the stability of hydro‐biogeochemical export. We test this hypothesis using a decade of discharge, dissolved organic carbon, total dissolved nitrogen and soluble reactive phosphorus data from four Alaskan watersheds spanning a gradient in glacier cover. We demonstrate that glacier decline leads to lower and more variable runoff across years, with 2.6–4.3 times greater interannual variability in lightly‐glacierized compared to glacier‐dominated watersheds. Biogeochemical export also became more stochastic with retreat, with up to a five‐fold increase in interannual variability. However, the responses of riverine concentrations and yields to changes in glacier cover varied widely between constituents. Such shifts in the magnitude and stochasticity of hydro‐biogeochemical yields have important implications for the ecological stability of downstream ecosystems.