the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 Sep 2025
Microstructure and ice dynamics – Integrating Grain Properties, Fabric, and Borehole Data in the NEEM Ice Core
Abstract. The physical properties of ice grains, including grain size and orientation, are fundamental to understanding ice flow and deformation processes in polar ice sheets. This study leverages a newly developed large-area scanning microscope (xLASM) and an automated microtome to non-destructively analyze the NEEM ice core's microstructure across 55 cm segments. The resulting microstructural data are compared with continuous flow analysis (CFA) measurements of impurity concentrations, fabric orientation, and shear strain rates over a 16-meter section (2004–2020 m depth) that spans the Last Glacial Maximum and abrupt climatic transitions during Dansgaard-Oeschger event GS-20. Our results reveal strong associations between grain size, impurity concentrations, and shear deformation rates, with impurity-rich, fine-grained stadial ice exhibiting higher shear strain rates. The ice fabric remains stable despite the changes in shear deformation, indicating that, in this case, the fabric is not the cause of the changing deformation.
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- RC1: 'Comment on egusphere-2025-3647', David Prior, 13 Dec 2025
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RC2: 'Comment on egusphere-2025-3647', Christopher Gerbi, 08 Jan 2026
This manuscript has the potential to have a very strong impact for the community. To reach that potential, I feel it needs significant expansion in several areas, described below.
Although the manuscript reports many microstructural metrics and compares them to additional datasets typically associated with paleoclimate, at its heart, the contribution seems to explore the relationship between microstructure and rheology. Ice rheology is of critical importance for a range of cryospheric interpretations and predictions, including sea-level rise, continental ice volume, ocean circulation, and many others. So the topic is of high value. As presently structured, the manuscript provides a significant amount of tantalizing data and suggestive relationships, but lacks the robust analysis to give high confidence to the interpretations. The manuscript also has the opportunity to consider the impact of the microstructure findings on paleoclimate studies. To meet these needs, I expect a fairly thorough rewriting of the document is in order. As such, I won’t provide a line-by-line set of comments here, but will rather focus on the areas where I see the most benefit of expansion.
(1) Full presentation of the methods. First, I suggest making it much clearer in the text what datasets were collected as part of this study and what datasets were taken from previously published work. For the latter, a short methods overview is sufficient, as the reader can learn the details from the other source. For the former, a much more extensive description of the methods would benefit the reader greatly. In particular, the grain size analysis is non-trivial and I didn’t see any reference to an assessment of the validity or uncertainty associated with the Scikit-Image library. Several figures demonstrating how the automated calculations match manual measurements (or references to papers that do include those comparisons) will provide confidence in the data quality. The modeling is not described at all and is also non-trivial. It should be described much more fully if the authors would like to include reference to it in the Discussion.
(2) Full presentation of the data. I suggest the authors provide all the data generated in this study in supplementary material or linked to a repository. The previously published data are presumably in a repository and should be linked as well. It is possible that I missed those references, but I didn’t see any supplementary files.
(3) Multivariate correlation statistical analysis. These data appear strong candidates for a much more robust analysis of correlation among the different metrics. Some reference was made to statistical tests, but the more uniformly the tests are applied, the more confidence given to the interpretations. In addition, I suggest rather than analyzing selected paired datasets, a more comprehensive approach would provide significantly more insight.
(4) Implications. The Discussion section could be expanded significantly to provide the authors’ perspectives on how their findings relate to rheology and paleoclimate interpretations. I am particularly curious to hear how the strain rate variation extrapolates to affect paleoclimate information above and below the transition. For rheology, a broad body of literature has examined the question of influencing factors. The new data contribute to that discussion, and for the contribution to have the most impact, a much more nuanced look is required at the factors involved vis a vis the data themselves. This analysis will rely heavily on the more detailed data presentation and statistical analysis referenced above.
To summarize, the data included here could add valuable information to the ice dynamics field. A more robust treatment of the methods, data, and implications will increase the impact of this work significantly.
Citation: https://doi.org/10.5194/egusphere-2025-3647-RC2
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This is an excellent scientific idea, but the data presentation and analysis are superficial and incomplete and the writing and particularly the use of citations is imprecise and unclear. It needs a lot of work to make this paper publishable. I encourage the authors to do this, as this research is important for our understanding of ice rheology.
The full review, an annotated copy of the manuscript and an EXCEL spreadsheet of calculations are in the supplementary .zip file.