Data_Sheet_1_Silicon Isotopes Reveal a Non-glacial Source of Silicon to Crescent Stream, McMurdo Dry Valleys, Antarctica.PDF

• Main Authors: Catherine Hirst, Sophie Opfergelt, François Gaspard, Katharine R. Hendry, Jade E. Hatton, Susan Welch, Diane M. McKnight, W. Berry Lyons
• Format: Dataset
• Language: unknown
• Published: 2020
• Subjects: Solid Earth Sciences; Climate Science; Atmospheric Sciences not elsewhere classified; Exploration Geochemistry; Inorganic Geochemistry; Isotope Geochemistry; Organic Geochemistry; Geochemistry not elsewhere classified; Igneous and Metamorphic Petrology; Ore Deposit Petrology; Palaeontology (incl. Palynology); Structural Geology; Tectonics; Volcanology; Geology not elsewhere classified; Seismology and Seismic Exploration; Glaciology; Hydrogeology; Natural Hazards; Quaternary Environments; Earth Sciences not elsewhere classified; Evolutionary Impacts of Climate Change; silicon isotopes; hyporheic zone; permafrost; weathering; Antarctica; Arctic; Austral; McMurdo Dry Valleys; Crescent Stream; Antarc*; Climate change
• Online Access: https://doi.org/10.3389/feart.2020.00229.s001; https://figshare.com/articles/dataset/Data_Sheet_1_Silicon_Isotopes_Reveal_a_Non-glacial_Source_of_Silicon_to_Crescent_Stream_McMurdo_Dry_Valleys_Antarctica_PDF/12571901

In high latitude environments, silicon is supplied to river waters by both glacial and non-glacial chemical weathering. The signal of these two end-members is often obscured by biological uptake and/or groundwater input in the river catchment. McMurdo Dry Valleys streams in Antarctica have no deep groundwater input, no connectivity between streams and no surface vegetation cover, and thus provide a simplified system for us to constrain the supply of dissolved silicon (DSi) to rivers from chemical weathering in a glacial environment. Here we report dissolved Si concentrations, germanium/silicon ratios (Ge/Si) and silicon isotope compositions (δ 30 Si DSi ) in Crescent Stream, McMurdo Dry Valleys for samples collected between December and February in the 2014−2015, 2015−2016, and 2016−2017 austral seasons. The δ 30 Si DSi compositions and DSi concentrations are higher than values reported in wet-based glacial meltwaters, and form a narrow cluster within the range of values reported for permafrost dominated Arctic Rivers. High δ 30 Si DSi compositions, ranging from +0.90‰ to +1.39‰, are attributed to (i) the precipitation of amorphous silica during freezing of waters in isolated pockets of the hyporheic zone in the winter and the release of Si from unfrozen pockets during meltwater-hyporheic zone exchange in the austral summer, and (ii) additional Si isotope fractionation via long-term Si uptake in clay minerals and seasonal Si uptake into diatoms superimposed on this winter-derived isotope signal. There is no relationship between δ 30 Si DSi compositions and DSi concentrations with seasonal and daily discharge, showing that stream waters contain DSi that is in equilibrium with the formation of secondary Si minerals in the hyporheic zone. We show that δ 30 Si DSi compositions can be used as tracers of silicate weathering in the hyporheic zone and possible tracers of freeze-thaw conditions in the hyporheic zone. This is important in the context of the ongoing warming in McMurdo Dry Valleys and the supply of more ...