Rock glaciers are common landforms in mountainous areas of the western US. The motion of active rock glaciers is a key indicator of ice content, offering connections to climate and hydrologic systems. Here, we quantified the movement of six rock glaciers in the La Sal and Uinta Mountains of Utah through repeat differential GPS surveying. Networks of 10–41 points on each rock glacier were surveyed in September 2021; July 2022; September 2022; and July 2023. We found that all features are moving with average annual rates of motion from 1.5 ± 0.8 to 18.5 ± 7.5 cm/yr. Rock glaciers move up to 3× faster in the summer than in the winter, and rates of motion were greater in 2023 after a winter with above-average snowfall, emphasizing the role of liquid water availability. Velocities of individual points in the winter of 2021–22 are positively correlated with velocities during the winter of 2022–23, suggesting that spatial variability of motion is not stochastic, but rather reflects internal properties of each rock glacier. Bottom temperature of snow measurements during winter, and the temperature of springs discharging water in summer, suggest that these rock glaciers contain modern permafrost. Radiocarbon data document advance of one rock glacier during the Little Ice Age. Our GPS dataset reveals complicated patterns of rock glacier movement, and the network of survey points we established will be a valuable baseline for detecting future cryosphere change in these mountains.
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Examining the variability of rock glacier meltwater in space and time in high-elevation environments of Utah, United States
Rock glaciers are common geomorphic features in alpine landscapes and comprise a potentially significant but poorly quantified water resource. This project focused on three complementary questions germane to rock glacier hydrology: 1) Does the composition of rock glacier meltwater vary from year to year? 2) How dependent is the composition of rock glacier meltwater on lithology? And 3) How does the presence of rock glaciers in a catchment change stream water chemistry? To address these questions, we deployed automated samplers to collect water from late June through mid-October 2022 in two rock-glacierized mountain ranges in Utah, United States characterized by different lithologies. In the Uinta Mountains of northern Utah, where bedrock is predominantly quartzite, water was collected at springs discharging from two rock glaciers previously shown to release water in late summer sourced from internal ice. In the La Sal Mountains of southeastern Utah, where trachyte bedrock is widespread, water was collected at a rock glacier spring, along the main stream in a watershed containing multiple rock glaciers, and from a stream in a watershed where rock glaciers are absent. Precipitation was also collected, and data loggers for water temperature and electric conductivity were deployed. Water samples were analyzed for stable isotopes with cavity ring-down spectroscopy and hydrochemistry with ICP-MS. Our data show that water discharging from rock glaciers in the Uinta Mountains exhibits a shift from a snowmelt source to an internal ice source over the course of the melt season that is consistent from year to year. We also found that the chemistry of rock glacier water in the two study areas is notably different in ways that can be linked back to their contrasting bedrock types. Finally, in the La Sal Mountains, the properties of water along the main stream in a rock-glacierized basin resemble the properties of water discharging from rock glaciers, and strongly contrast with the water in a catchment lacking rock glaciers. Collectively these results underscore the role of rock glaciers as an agent influencing the hydrochemistry of water in high-elevation stream systems.
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- Award ID(s):
- 1935200
- PAR ID:
- 10413972
- Date Published:
- Journal Name:
- Frontiers in Earth Science
- Volume:
- 11
- ISSN:
- 2296-6463
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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