Investigating brittle-ice onset and behavior in Antarctic ice cores in preparation for the Hercules dome ice core project

Barnett, Samantha Marie (2023) Investigating brittle-ice onset and behavior in Antarctic ice cores in preparation for the Hercules dome ice core project. Masters thesis, Northern Arizona University.

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Abstract

Ice cores provide highly valuable paleoenvironmental data, but records can be degraded by the occurrence of fractured “brittle ice”. Following bubble closure in ice, internal deformation squeezes bubbles, raising their internal air pressure to near the overburden level. Subsequent release of external pressure during core recovery can allow the internal stresses to exceed the ice strength, causing fracturing in what is known as the “brittle ice zone” (BIZ). The depth range and degree of brittleness varies greatly between ice cores. Site characteristics including accumulation rate and temperature likely affect brittle ice behavior, but strong correlations are not apparent. Despite prior research, the mechanisms controlling BIZs are still not well-understood. Various ice-core observations, together with physical understanding, suggest that BIZ fractures preferentially follow subgrain boundaries, linking bubbles over long distances by way of an interconnected “chessboard” pattern of subgrains anchored to the bubbles. Here, I focus on thin sections from the highly brittle Siple Dome ice core, and compare to the minimally brittle South Pole ice core. Using targeted image processing techniques and analyses, I seek to identify noteworthy relationships between fractures, subgrain boundaries, and bubbles. This study provides initial insights into brittle-ice behavior and its physical properties and establishes a connection between subgrain prevalence and mean grain/bubble sizes in ice cores, revealing that larger grains/bubbles correlate with more severe brittle behavior. In addition, estimates for the Hercules Dome site suggest a brittle-ice zone between 625-1200 m depth with a brittleness factor of ~2 out of 5.

Item Type:	Thesis (Masters)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Brittle Ice; Ice Core; Physical Properties
Subjects:	Q Science > QE Geology
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > School of Earth Sciences and Environmental Sustainability
Date Deposited:	23 Oct 2025 21:27
Last Modified:	23 Oct 2025 21:27
URI:	https://openknowledge.nau.edu/id/eprint/6272

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