MAPPING ROCK GLACIER SURFACE ELEVATION CHANGES IN GREAT BASIN NATIONAL PARK, NEVADA

Mid-latitude, mountain glaciers are important fresh water resources which are sensitive to a rapidly changing climate. Great Basin National Park is home to the sole mapped glacier in the state of Nevada, the Lehman rock glacier – the most pronounced extant cryospheric feature in the Snake Range and likely an important source of base flow for the alpine lakes and streams below, which provide specialized habitat for endemic species. As part of an annual student research experience in Great Basin National Park since 2005, our group has been making observations of climate variability on interannual to centennial scales which have shown evidence of warming. Beginning in 2015, we have undertaken annual aerial surveys of the rock glacier to measure topographic changes. Initially, we used balloon-borne photogrammetry to generate data. Coverage (~50-90%) was incomplete due to logistical difficulties and limited control over the balloon rig. Despite this, digital elevation model (DEM) differencing resolved a net volume loss of 5,300 m³ between 2015 and 2016. In 2018, our team was granted permission by the National Park Service to deploy an unmanned aerial system (UAS) for the first time to map the rock glacier. We flew the UAS over successive days in August 2018 and achieved 100% coverage with over 900 photographs at 80% horizontal and vertical overlap. Using an innovative algorithm to maintain constant elevation based on the previous years’ DEMs, we flew the UAS autonomously at 80 m AGL and 168 m AGL at 8.5 and 20 kmh to test spatial resolution. We will present our new computations of glacier changes through 2018 and discuss how UAS instrument techniques are enabling us to observe alpine cryo-geomorphic dynamics at finer spatial-temporal scales, better understand the processes that drive them, and improve our capability for predicting future landscape evolution in glaciated mountain environments.