Articles | Volume 20, issue 2
https://doi.org/10.5194/tc-20-981-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-20-981-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Observations of creep of polar firn at different temperatures
Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
X-Here (Future ice-based Hydrogen energy & resilient environments) Trek Laboratory (Establishing), Howard Beach, NY, 11414, USA
Kaitlin Keegan
Department of Geological Sciences & Engineering, University of Nevada, Reno, Reno, NV, 89557, USA
Ian Baker
CORRESPONDING AUTHOR
Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
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Kaitlin M. Keegan, Sarah Day, Yu-Min Chung, and Michael Gardner
EGUsphere, https://doi.org/10.5194/egusphere-2026-1, https://doi.org/10.5194/egusphere-2026-1, 2026
This preprint is open for discussion and under review for Geoscientific Instrumentation, Methods and Data Systems (GI).
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We evaluate the sensitivity of firn microstructural properties computed from x-ray micro-computed tomography (micro-CT) to the binarization threshold step of the image processing process. We found bulk parameters to be largely insensitive, while parameters describing the microstructure’s complexity and connectivity exhibited strong depth-dependent sensitivity. These results highlight the need for a standardized image-processing method for firn micro-CT data to enable comparison of study results.
B. Ilyse Horlings, Annika N. Horlings, Kaitlin M. Keegan, Julia Marks Peterson, and Zoe Courville
EGUsphere, https://doi.org/10.5194/egusphere-2025-5040, https://doi.org/10.5194/egusphere-2025-5040, 2025
This preprint is open for discussion and under review for The Cryosphere (TC).
Short summary
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We investigate the spatial variation of firn microstructure between two cores from Allan Hills Blue Ice Area, Antarctica. Our data show differences in density and intricacy of the pore structure resulting from the presence or absence of wind crusts and faceted grains. Through modeling, we find that these differences are influenced by local variation of the surface slope and wind. Our findings show the importance of understanding firn microstructure across very low-accumulation regions.
Marin Nicole Blaisdell and Ian Baker
EGUsphere, https://doi.org/10.5194/egusphere-2025-4383, https://doi.org/10.5194/egusphere-2025-4383, 2025
Preprint archived
Short summary
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Snow with and without an ice lens was compressed at varying rates to understand how loading affects microstructure and mechanical response. Results show that snow with an ice lens is six-times stronger than without, and both types produced highest stresses at intermediate rates until high strain. Maximum connectivity between ice particles occurred at high strength, when force is adequate to strengthen bonds but insufficient for reconfiguration. This has implications for avalanche forecasting.
Ian E. McDowell, Kaitlin M. Keegan, S. McKenzie Skiles, Christopher P. Donahue, Erich C. Osterberg, Robert L. Hawley, and Hans-Peter Marshall
The Cryosphere, 18, 1925–1946, https://doi.org/10.5194/tc-18-1925-2024, https://doi.org/10.5194/tc-18-1925-2024, 2024
Short summary
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Accurate knowledge of firn grain size is crucial for many ice sheet research applications. Unfortunately, collecting detailed measurements of firn grain size is difficult. We demonstrate that scanning firn cores with a near-infrared imager can quickly produce high-resolution maps of both grain size and ice layer distributions. We map grain size and ice layer stratigraphy in 14 firn cores from Greenland and document changes to grain size and ice layer content from the extreme melt summer of 2012.
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Short summary
The compaction of firn provides valuable insights into the physical processes involved in the transition from snow to ice. Investigations into how temperature influences firn deformation across samples taken from various depths reveal distinct microstructural characteristics, including variations in density and other parameters. Firn exhibits different mechanical behaviors compared to fully dense ice, primarily due to its lower density, elevated temperatures, and increased effective stresses.
The compaction of firn provides valuable insights into the physical processes involved in the...