GLACIAL MELTWATER HYDROCHEMISTRY ON MOUNT RAINIER, WASHINGTON

Mount Rainier is a glaciated peak and active volcano with a history of lahars and glacial outburst floods. In this study, we analyze glacial meltwater as one way to evaluate geologic hazard potential in different sectors of the mountain. We are measuring major ion concentrations in meltwater samples collected from streams at or near glacier termini in Mount Rainier National Park. Preliminary data show constant sulfate levels during the diurnal cycle, and low C-ratios (bicarbonate/[bicarbonate + sulfate]) at the Tahoma and Emmons Glaciers, suggesting a subglacial source of sulfate at both locations. Carbon Glacier meltwater contains relatively low levels of sulfate, with a significant decrease between the diurnal maximum and minimum and a high C-ratio, indicating a supraglacial source of sulfate. Atmospheric influence on glacial hydrology is also likely reflected in chloride, fluoride, nitrate, and bicarbonate concentrations measured in our meltwater samples. Tentative conclusions include that Tahoma Glacier meltwater is in contact with the mountain’s hydrothermal system; this result confirms findings from previous work. Our work also suggests a subglacial source of sulfate at the Emmons Glacier; if confirmed, this result may identify a connection between this subglacial environment and the hydrothermal system. Planned cation analyses and additional sample collection will provide more information about subglacial environments on Mount Rainier, and will extend our characterization of seasonal and geographic changes in meltwater chemistry.