DEBRIS COVER THICKNESS AND MOISTURE CONTENT ON EMMONS GLACIER, MOUNT RAINIER, WA

Mount Rainier in Washington state is a stratovolcano containing several glaciers covered with rocky debris. Thick debris cover can insulate glacier ice and slow melting, but thin debris cover heats the glacier surface, accelerating melt rates. Meltwater from Emmons Glacier supplies cold water and sediment to the Puyallup River watershed, and changes in this supply can have a significant impact on downstream communities. To study the impact of debris cover on Emmons Glacier, we measured its thickness in pits ranging from 8 cm to >77 cm deep; pit walls failed in the deepest pits before the ice surface was reached. Debris sediment samples at each site were taken at surface level and at the bottom of each pit to measure the moisture content. This analysis shows that shallow debris near the center of the glacier has a high moisture content, likely due to the proximity to ice, and thicker debris at the edges of the glacier to have a relatively low moisture content, averaging about 4%. Our results suggest that the glacier has higher melting rates closer to the centerline of the glacier where the debris cover is relatively thin, and lower melting rates closer to the lateral margins of the glacier where debris cover is thicker.