T23 Geologic Research at Mount Rainier and Other Cascade Volcanoes: Ideal Natural Laboratories for Cutting-Edge Research with Implications to Life Safety and Infrastructure Protection in the Pacific Northwest I

Sunday, 22 October 2017
8:00 AM - 12:00 PM
Chelan 4

GEOCHEMICAL MONITORING OF STAGNANT ICE FOR GLACIER OUTBURST FLOOD HAZARD ASSESSMENT, MOUNT RAINIER NATIONAL PARK

Paper number: T23-13
Program: Technical Sessions
Time: 10:55 AM – 11:10 AM

Authors

Abstract

Outburst flooding (or jökulhlaup) occurs when a large volume of impounded water inside a glacier is rapidly released. Although outburst flooding occurs at low frequency, the impacts can be catastrophic. In 1955, an outburst flood from the Nisqually glacier destroyed Longmire, the operational headquarters of Mount Rainier National Park. There is an empirical association between stagnant (non-moving) glacier ice and destructive outburst floods. Determining the status and level of glacial stagnation is vital for protecting communities and infrastructure located in areas at risk of being impacted by glacial outburst floods.

It is hypothesized that the level of glacial stagnation can be determined from geochemical monitoring of glacial meltwater. A variety of geochemical signals (turbidity, dissolved iron, pH, conductivity, oxidation-reduction potential, total dissolved solids, temperature, and metal ion concentrations) were monitored for meltwater from the Nisqually glacier during the summers of 2012, 2014, 2016, and 2017. These water chemistry parameters were also measured for local streams fed by snowmelt for comparison. Glacial meltwater versus locally derived snowmelt showed a high degree of chemical differentiation. Significant changes in the pH of Nisqually glacier melt water have been observed over the time period, starting at a low point of pH = 6.05±0.11 in 2012, rising to a pH of 6.59±0.26 in 2016. During 2012, a relatively high concentration of dissolved iron (603 ppb on average) was also measured in the meltwater. Dissolved iron has subsequently been decreasing since 2012, reaching levels that are undetectable by field tests in 2017.

During the five years of monitoring, changes in the morphology of the Nisqually glacier have taken place. However, no outburst flooding has occurred during the period. A goal of this project is to correlate the changes in geochemistry to the behavior of the Nisqually glacier. Correlations between water chemistry, meltwater flow, and glacier velocity, as measured via satellite and aerial imagery, will be analyzed for evidence of Nisqually stagnation. Comparisons of geochemical signals for other glaciers at Mount Rainier will be used to investigate the transferability of these techniques.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-301059

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.