Rock glaciers as probes of Holocene climate, weathering, hydrology and landscape evolution

Rock glaciers are moving boulder-covered tongues of ice found below alpine rock cliffs. Because they persist at lower elevations and in warmer climates than glaciers, rock glaciers support late season stream flow and ecosystems after glaciers have disappeared. Few glaciers remain in Colorado’s mountains, yet thousands of rock glaciers survive. This research promotes understanding of how these important alpine ice reservoirs are maintained or depleted. Through measuring how long rocks have been exposed on the rock glacier surface and the speed of their conveyance away from the cliffs, the research will constrain the last 10,000 years of climate history and landscape evolution in Colorado’s mountains. The research team will promote a broad distribution of their results through a variety of public outreach venues. They will also connect with middle schools near the study area and the outcomes will be used in a new interdisciplinary climate science minor at CU Boulder. The project expands a pilot study on Mt Sopris to two additional Colorado rock glaciers. Modern velocity fields will be measured by image feature tracking, and surface age profiles will be deduced from cosmogenic nuclides. In addition, the project will monitor stream discharge and quality, measure mass balance, conduct differential GPS surveys to document interannual changes in movement, and survey rock headwalls photogrammetrically. The data will constrain numerical modelling that captures the continuum from pure ice glacier to rock glacier and explain differences in their response to climate changes. The project will deepen our understanding of Quaternary alpine landscape change and reignite thinking about the role of lateral headwall cliff recession. The exposure age profiles on the rock glaciers allows substitution of space for time and should catalyze further use of rock glaciers as conveyor belts on which weathering and biological experiments play out. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.