Debris properties and mass-balance impacts on adjacent debris-covered glaciers, Mount Rainier, USA

Peter L Moore,Leah I Nelson,Theresa M D Groth

doi:10.1080/15230430.2019.1582269

Peter L Moore, Leah I Nelson + Show 1 more

Open Access

https://doi.org/10.1080/15230430.2019.1582269

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Abstract

ABSTRACTThe north and east slopes of Mount Rainier, Washington, are host to three of the largest glaciers in the contiguous United States: Carbon Glacier, Winthrop Glacier, and Emmons Glacier. Each has an extensive blanket of supraglacial debris on its terminus, but recent work indicates that each has responded to late twentieth- and early twenty-first-century climate changes in a different way. While Carbon Glacier has thinned and retreated since 1970, Winthrop Glacier has remained steady and Emmons Glacier has thickened and advanced. There are several possible climatic and dynamic factors that can account for some of these disparities, but differences in supraglacial debris properties and distribution have not been systematically evaluated. We combine field measurements and satellite remote sensing analysis from a 10-day period in the 2014 melt season to estimate both the debris thickness distribution and key debris thermal properties on Emmons Glacier. A simplified energy-balance model was then used with debris surface temperatures derived from Landsat 8 thermal infrared bands to estimate the distribution of debris across all three debris-covered termini. The results suggest that differences in summer balance among these glaciers can be partly explained by differences in the thermal resistance of their debris mantles.

Highlights

Mount Rainier has nearly 30 named glaciers flowing down its flanks, including three of the largest in the lower 48 U.S states: Winthrop, Carbon, and Emmons glaciers (Figure 1)
This study is aimed in part at evaluating whether differences in supraglacial debris distribution could explain some of the divergent mass balance trends
A glacier’s response to supraglacial debris is sensitive to the debris thickness and spatial distribution, which vary according to debris sources and are subsequently affected by various transport processes at the glacier surface (Moore 2018)

Summary

Introduction

Mount Rainier has nearly 30 named glaciers flowing down its flanks, including three of the largest (by area) in the lower 48 U.S states: Winthrop, Carbon, and Emmons glaciers (Figure 1). Debris thicknesses can vary greatly over distances as little as a few meters, making the spatial pattern of mass balance on debris-covered glaciers highly complex (Nicholson et al 2018). This poses a challenge for the study of debris impacts, as the local variability makes representative field-based study time- and resourceintensive, while conventional remote-sensing methods

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