Transit Times and Rapid Chemical Equilibrium Explain Chemostasis in Glacial Meltwater Streams in the McMurdo Dry Valleys, Antarctica

Abstract

AbstractFluid transit time is understood to be an important control on the shape of concentration‐discharge (C‐q) relationships, yet empirical evidence supporting this linkage is limited. We investigated C‐q relationships for weathering‐derived solutes across seven Antarctic glacial meltwater streams. We hypothesized that (H1) solute fluxes in McMurdo Dry Valley streams are reaction limited so that C‐q relationships are characterized by dilution and that (H2) transit time explains between‐stream variability in the degree of C‐q dilution. Results show that C‐q relationships are chemostatic because solute equilibrium times are shorter than stream corridor fluid transit times. Between‐stream variability in the efficiency of solute production is positively correlated with transit time, suggesting that transit time is an important control on the solute export regime. These results provide empirical evidence for the controls on weathering‐derived C‐q relationships and have important implications for Antarctic ecosystems and solute export regimes of watersheds worldwide.