Geochemical Weathering Variability in High Latitude Watersheds

Abstract

High latitude regions across the globe are undergoing severe modifications due to changing climate. A high latitude region of concern is the Gulf of Alaska (GoA) where these changes in hydroclimate undoubtedly effect the hydrogeochemistry of freshwater discharging to the nearshore ecosystems of the region. To fill the knowledge gap of our understanding of freshwater stream geochemistry with the GoA, we compile stream water chemistry data from 162 stream sites across the region. With an inverse model we estimate fractional contributions to solute fluxes from weathering of silicate, carbonate, and sulfide minerals, and precipitation. We asses weathering rates across the region and compare against global river yields. Median fractional contribution of carbonate weathering to total weathering products is 78% across all stream sites, however, there are several streams where silicate weathering is a dominant source of solutes. Weathering by sulfuric acid is elevated in glacierized watersheds. Finally, cation weathering rates are lower in GoA streams compared to the world’s largest rivers, however, weathering rates are similar when compared to a global dataset of glacier fed streams. Due to the climate sensitivity of chemical weathering, we expect future changes to the hydrogeochemistry of river water flux to nearshore ecosystems. We suggest that hydrologic changes driven by glacier ice loss and increased precipitation will alter river water quality and chemical weathering regimes such that silicate weathering may become a more important source of solutes and sulfide oxidation may decrease. This contribution provides a platform to build from for future investigations into changes to stream water chemistry in the region and other high latitude watersheds.