FIELD OBSERVATIONS OF GLACIER CHANGE IN MOUNT RAINIER NATIONAL PARK

Mount Rainier National Park in Washington State is home to 25 glaciers that flow down the flanks of the 14,411 foot high stratovolcano. Remote-sensing studies of Mount Rainier reveal significant glacier retreat, warranting further field-based research into the nature and impacts of ice loss. We use high-precision GPS measurements and a time-lapse camera to observe glacier change in remote and rugged locations in the park. We measured surface elevation along transects crossing Emmons Glacier, where slower retreat rates have been attributed to its thick debris cover. Steep slopes and unconsolidated sediment on the glacier surface complicate data collection, but preliminary analyses reveal glacier surface lowering rates of approximately 1 - 4 m/year with wide variability across the debris-covered surface. We also use time lapse imagery to document changes at the terminus of South Tahoma Glacier, where damaging debris flows have originated. Preliminary analysis of imagery reveals approximately 10 - 30 abrupt increases in water discharge per summer month, as evidenced by a widening or darkening of meltwater channels. These events do not correspond with large debris flows documented farther downstream, and suggest that smaller outbursts of glacial meltwater are common. Although some field measurements of glacier change at Mount Rainier are limited to summer months when snowpack is at a minimum, short-term data collection in limited-access locations can nevertheless enhance our understanding of remote-sensing observations by providing information at higher geographic and temporal resolution.