June 30, 2025
Daily Glacier Dynamics from GNSS Reflectometry at Gulkana Glacier, Alaska
Posted by Albin Wells
A team of researchers at Carnegie Mellon University joined the U.S. Geological Survey on their seasonal mass balance work at Gulkana Glacier, Alaska to deploy Cryologger Glacier Velocity Trackers (GVTs). The deployments are part of a research project led by PhD student Albin Wells and Prof. David Rounce at Carnegie Mellon University.
🧊 Why Measure Gulkana?
Glaciers in Alaska significantly contribute to global sea-level rise and are experiencing accelerated mass loss at a faster rate than any other glaciated region. The goal of this project was to deploy sensors that yield daily measurements of climatic and dynamic changes of the surface of Gulkana Glacier, Alaska.
Such data are essential for understanding the processes and drivers of glacier mass loss, and for validating remote sensing data products critical to regional glacier change estimates. We built a number of Cryologger systems as a robust low-cost and low-power alternative to commercial GNSS systems.
❄️ Cryologger Deployments by Season
2023
In April 2023, we deployed five Cryologger GVT systems:
- Two at ~1534 m asl
- Two at ~1855 m asl
- One system on stable terrain off-glacier
The stable-terrain system demonstrated horizontal and vertical accuracy within 2 cm using just ~15 minutes of GNSS data. The on-ice systems were deployed in a setup that featured a system on a tripod and a system affixed to an ablation stake.
In addition to tracking glacier velocity, we demonstrated that with ~2 hours of continuous GNSS data, GNSS reflectometry processing can be applied to yield reliable antenna height measurements, and subsequently to derive contemporaneous glacier surface mass balance, surface elevation change, and flux divergence estimates.
2024
Cryologger systems were deployed in April 2024 across six sites on Gulkana Glacier. Equipped with upgraded firmware, the systems logged daily throughout the summer and through much of the winter, capturing:
- Extreme melt and accumulation events
- Velocity speedups and slowdowns
- Subglacial processes contributing to glacier uplift near the terminus
The systems were serviced and re-deployed in April 2025 with a streamlined 6V–12Ah battery and 2W–6V solar panel, all packaged inside a compact enclosure to test the feasibility of an ultra-lightweight, packable setup suitable for fieldwork in harsh alpine environments that are accessible only by foot. The results are ongoing!
📈 An Improvement on Traditional Glaciological Measurements
The Cryologger systems offer new insights to ~60 years of ongoing seasonal glaciological measurements at Gulkana Glacier. The network of Cryologger sensors deployed at Gulkana Glacier, for example, shows a fascinating propagation of velocity increase during the summer—beginning near the terminus and migrating up-glacier—with the duration of speed-ups varying at different sites.
The systems also capture both summer and winter snowfall events, and quantify melt at sub-weekly resolution. Altogether, this enhances our understanding of how the glacier is responding to the climate, provides validation for weather station data, and can be used as calibration data for high-resolution glacier models.
The overall small size and light weight of the systems makes it feasible to install these on ablation stakes with minimal additional effort, and could thus become routine in glacier mass balance monitoring in the future.
🔗 Learn More
This project is described in detail in our recent publication in the Journal of Glaciology:
Wells, A., Rounce, D., Sass, L., Florentine, C., Garbo, A., Baker, E., & McNeil, C. (2024). GNSS reflectometry from low-cost sensors for continuous in situ contemporaneous glacier mass balance and flux divergence. Journal of Glaciology, 1–12. https://doi.org/10.1017/jog.2024.54
For questions or collaboration inquiries, contact the lead author:
📧 Albin Wells
📷 Photo credits: Albin Wells