227-5 Quantifying changes in debris cover area on glaciers at Mount Rainier, WA

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology (Posters)

Presenting Author:

Authors:

Abstract:

Mount Rainier, WA holds 10% of the glacial ice in the conterminous United States. Out of its 28 glaciers, 19 have supraglacial debris cover, particularly toward their termini. Our study quantifies changes in supraglacial debris cover area on glaciers in Mount Rainier. We focus on Emmons, Winthrop, and Carbon Glaciers, the largest by area. These glaciers contribute to the Puyallup watershed, supporting over 500,000 citizens, local agriculture, and salmon runs. Debris cover plays a role in the net mass balance of a glacier, as thinner debris accelerates ablation and thicker debris insulates ice from solar radiation, reducing melt. Previous research has suggested that Emmons Glacier advanced in the late 20th century due to a large rockfall that increased the supraglacial debris thickness. By tracking changes in debris cover area, we can inform predictions of continued glacier mass loss, as the expansion of debris cover can result in a layer of thin, heat-absorbing debris which may accelerate melt near debris cover margins. Utilizing NAIP (National Agricultural Imagery Program) imagery, we mapped individual debris units on each glacier surface over multiple years, creating a time series of supraglacial debris cover area. To determine the potential effects of debris area change on glacier mass balance, we compare these supraglacial debris unit maps with glacier surface lowering derived from digital elevation model (DEM) differencing. On Emmons Glacier, we compare direct measurements of debris cover thickness to areas of surface lowering to infer the potential impacts on mass balance. In a recent pilot study of Emmons Glacier, we produced a time series of debris cover growth from 2011 to 2023. During this timeframe, we observe an up glacier expansion of thin englacially-derived debris, as well as small landslide events. Applying these methods to multiple glaciers, we can better understand how the mass balance of Mt. Rainier’s glaciers may respond to changes in debris cover extent.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8208

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