Variability of hydrogeochemistry and chemical weathering regimes in high latitude glacierized coastal catchments

Abstract

Accelerated modifications to the hydrology, driven by global climate change, will alter the timing and amount of freshwater discharged from coastal catchments to the intertidal and nearshore habitats of the Gulf of Alaska. Coastal glacierized catchments are important sources of both inorganic and organic matter to the nearshore ecosystem. The Gulf of Alaska is an ecologically diverse ecosystem, that supports commercial, mariculture, and subsistence lifestyles. However, the coastal catchments of the Gulf of Alaska are relatively understudied with respect to solute generation, seasonal cycles of major cations and anions, and chemical weathering regimes. To close the knowledge gap, the present study utilizes a unique set of stream samples compiled from field-based activities and the USGS NWIS from stream sites across the Gulf of Alaska watershed. First, we find that watershed characteristics such as slope, elevation and relief drive the variation in concentration-discharge relationships, while glacier coverage controls solute yields. Second, though glaciers control overall solute yields, the climate dictates the timing of seasonal solute yields. Additionally, we find across the Gulf of Alaska lithology and climate are important controls on major cation and anion concentrations. Finally, we implement a solute mass balance model to estimate fractional contributions to solute flux from silicate, carbonate and precipitation. We find that carbonate weathering is the dominant source of weathering derived solutes, however there are several streams across the Gulf of Alaska in which silicate weathering is an important source of solutes. Overall, the results of this work illustrate the variability in stream chemistry across the Gulf of Alaska, and changing climate regimes will alter the fluxes of solutes and nutrients in the future.