T265 Geologic Research in the Cascades: Understanding Glacier Change, Geologic Hazards, and Mountain Hydrology along an Active Margin in a Changing Climate (Posters)

Wednesday, 25 September 2024
8:00 AM - 5:30 PM
Hall D

MAPPING THE EXTENT OF EMMONS GLACIER, MOUNT RAINIER, WA BETWEEN 1951-2023 USING HIGH-RESOLUTION IMAGERY

Paper number: T265-6
Program: Technical Sessions
Time: 8:00 AM – 5:30 PM

Authors

  • Jose Jimenez Presenting Author
    California State University San Bernardino, San Bernardino, CA
  • Claire Todd
    California State University San Bernardino, San Bernardino, CA
  • Michelle Koutnik
    University of Washington, Seattle, WA

Abstract

Mount Rainier is a stratovolcano in the Cascade Range that hosts 28 glaciers including the debris-covered Emmons Glacier. Emmons Glacier is located on the northeastern side of Mount Rainier and is the largest glacier in the contiguous United States by area and volume. It is concerning that a significant decline in glacier area and volume for Mount Rainier glaciers has been documented by Beason et al. (2023), where they calculated a 41.6% reduction in glacier area at Mount Rainier over the last 125 years. We use periodically collected high resolution orthorectified imagery and National Agricultural Imagery Program 1-meter resolution satellite imagery to hand digitize glacier extent for Emmons Glacier between 1951 to 2023. Manual delineation of glacier extents entails human error such as visual bias, imagery inaccuracies, and annual snowpack variations. To quantify our margin of error in our manual digitization of glacier extents we use the following equations: E1=Ai×(Δp+Δu)×2, where Ai represents the area of a glacier, Δp is pixel accuracy, and Δu is user accuracy. Pixel accuracy is determined by the inherent error of orthorectified imagery, and user accuracy is the mean standard deviation for three different hand digitizations. Potential uncertainty in area is calculated using E2=Ai×Δs×2, simplified to E2=0.05Ai following Beason et al. (2023). Total surface area error, E, is the sum of both calculations, E=E1+E2. Glacier area was in retreat until 1961, when a rock avalanche delivered 14 million cubic yards of rock debris across 4 miles of the lower portion of the glacier as reported by Crandell and Fahnestock in 1965. From 1961 to 1992, the glacier advanced but has been in retreat in the last 3 decades. Our results differ from previously published glacier extents which may have overestimated glacier area. Understanding changes in debris-covered glaciers is crucial due to their complex response to climate change which is evident over the last 72 years in Emmons Glacier’s evolution.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-405211

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