the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 20 Nov 2025
HAMSOM-VICE v0.9: Comparison of two variable ice-ocean drag coefficient parameterizations on annual simulations of Bohai Sea ice
Abstract. This study compares the simulation performance of two ice-ocean drag coefficient parameterizations (Scheme1 (original scheme): large-scale roughness parameterization, Scheme2 (newly introduced scheme): small-scale geometric roughness parameterization) for the Bohai sea ice in the 2011/2012 ice season, revealing main component of the ice-ocean drag coefficient (Cdw) and its crucial regulatory role in sea ice dynamic-thermodynamic processes in the Bohai Sea. The findings demonstrate that, for the ice-ocean drag in the thin ice environment of the Bohai Sea, the ice-bottom surface skin drag and the ice floe edge form drag dominate, while the contribution of ice keel-related drag is negligible due to insufficient ice thickness (averaging 20–30 cm). Scheme2 reduces the root mean square error (RMSE) of daily total ice area by 28 % compared to the Scheme1, showing higher simulation accuracy in the overall spatiotemporal ice evolution in the Bohai Sea. While Scheme1 demonstrates closer agreement with the observed length of ice season (underestimating by only 7 days). The result analysis of key sea ice variables and ice-ocean interfacial variables indicates that Cdw can affect the ice velocity through the dynamic feedback mechanism, and the basal freezing/melting through the thermodynamic dual feedback mechanisms.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-4290', Ian Brooks, 02 Feb 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-4290/egusphere-2025-4290-RC1-supplement.pdfCitation: https://doi.org/
10.5194/egusphere-2025-4290-RC1 -
AC1: 'Reply on RC1', Libang Xu, 07 Feb 2026
Dear Prof. Brooks,
Thank you for your detailed and insightful comments. We are carefully reviewing and deliberating on each of your suggestions, and a small amount of additional time is needed for internal discussions and data verification to develop a thorough revision plan and supplementary analyses. We aim to submit a detailed preliminary response within the next 3–5 days. We appreciate your patience and understanding greatly.
Sincerely,
The Authors of HAMSOM-VICE v0.9
Citation: https://doi.org/10.5194/egusphere-2025-4290-AC1 -
AC2: 'Reply on RC1', Libang Xu, 11 Feb 2026
Dear Prof. Brooks,
Here we submit our formal, point-by-point response to your review comments (RC1) on our manuscript. The attached PDF document contains detailed responses to each of your suggestions, including clear explanations of revisions made to the manuscript, justifications for our approach, and supplementary analyses where requested.
We have carefully addressed all the issues raised, and we hope that our revisions and responses will meet your expectations.
Thank you again for your valuable time and constructive feedback, which have greatly helped to improve the quality of our work.
Sincerely,
The Authors of HAMSOM-VICE v0.9
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AC1: 'Reply on RC1', Libang Xu, 07 Feb 2026
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RC2: 'Comment on egusphere-2025-4290', Anonymous Referee #2, 17 Mar 2026
This study presents a comparison of ice-ocean drag coefficient parameterization schemes in the Bohai Sea, a low-latitude thin-ice region. The research topic has clear regional application value, revealing the compositional characteristics of the ice-ocean drag coefficient in the thin-ice environment of the Bohai Sea and providing a reference for the optimization of parameterization in sea ice simulations of low-latitude shelf seas. However, the manuscript has significant issues in language expression, structural logic, results and its presentation, and figure design. In addition, there are deficiencies in the details of the model methodology, quantitative support for comparative analysis, and comparisons with observational data and previous studies. Specific comments are as follows:
1.The overall language lacks rigor and objectivity, and grammatical errors are present(e.g., the abstract). A professional scientific language polish is necessary. . Numerous non-native English expressions are identified throughout the text, including awkward sentence structures, inappropriate preposition usage, subject-verb disagreement, and overuse of the passive voice. Inconsistent expressions are found for the same physical quantity (e.g., "marginal ice zone" is abbreviated as MIZ abruptly in subsequent sections without initial labeling, causing confusion for readers). Some technical terms are translated or expressed non-uniformly (e.g., "skin drag" is redundantly referred to as "surface skin drag" without a consistent nomenclature). A small number of colloquial expressions are used in this academic paper (e.g., phrases such as "it can be seen that" and "this behavior stems from" could be more concise and straightforward).
2 The Cdw parameterization scheme from TS2014 employed in this study was originally developed for Arctic conditions, and its applicability to the Bohai Sea, which is a low-latitude shelf sea with a water depth of approximately 30 m remains unvalidated. The applicability of the same constant parameters selected in schemes to the Bohai Sea has also not been verified. Furthermore, while the TS2014 parameterization scheme is adopted, the ridging geometric parameterization from this study is not used; instead, the parameterization from Steiner (1999) in Scheme 1 is applied for TS2014. In sea ice model, ridging parameterization serves as input data for the drag coefficient and exerts a critical influence on simulation results. This approach is inappropriate when compared the Scheme 1 and Scheme 2.
3 The study only uses data from a single freeze-melt ice season (2011.11–2012.5). A longer series of simulation results should be compared to enhance the generalizability of the findings. The result comparisons in the manuscript are also based on single-day results selected for different stages of this single ice season (e.g., Day 50, Day 70), which is unreasonable.
4 The logical of the manuscript needs to be polished. For example, in the Introduction section: the transition from the general discussion of Bohai Sea ice and sea ice dynamics directly to the ice-ocean drag coefficient is extremely abrupt, leaving readers unable to understand the specific role and position of the drag coefficient. Concise language should be added to clarify that where it is affected at ice-ocean interface, and how it indirectly affects the heat flux at the ice-ocean interface through momentum exchange. The manuscript also fails to combine the regional characteristics of the Bohai Sea to analyze the differences in drag coefficient parameterization between the Bohai Sea and Arctic/high-latitude sea ice regions, resulting in insufficient groundwork. Additionally, it only generally states that "related research is scarce" without sorting out the specific problems in the setting of drag coefficients in existing Bohai Sea ice simulations (e.g., which simulation results exhibit biases due to the use of a constant drag coefficient). In fact, studies comparing drag coefficient schemes do exist, such as Bernner et al. (2021).
5 The description of the development of drag coefficient parameterization in the Introduction is not accurate. In reality, Arya and Hanssen-Bauer & Gjessing (1988) proposed different drag partitioning methods based on distinct ice zone characteristics. Mai (1996) combined these methods. Steele et al. (1989) developed ice-ocean parameterization by referring to atmospheric boundary layer studies. This review section should be revised to be more accurate and comprehensive.
6 The second chapter contains excessive descriptive text about the model while lacking key information. Given that this study focuses on sea ice dynamic behavior, it should emphasize the governing equations and related processes of the sea ice dynamic module. The specific role and position of the drag coefficient are not clearly explained throughout the entire manuscript.
7 The results are confused, with extensive mechanistic analysis interspersed throughout, leading to logical discontinuities. The influence mechanism should be clearly elaborated upfront. The core function of the results section should be to systematically and objectively present simulation data comparisons with observational data. However, this issue is prevalent in Sections 3.1 to 3.3 of the manuscript. In particular, Section 3.3, along with Figures 9 and 12, contains extensive content on how cdw influence on the sea ice thermodynamic processes. It makes readers confused.
8 Transitions between sections are lacking, and the research thread is unclear. For instance, there are no transitional sentences between Section 3.1 (drag coefficient distribution) and Section 3.2 (sea ice variables), and between Section 3.3 (ice-ocean interface variables) to explain how differences in the drag coefficient affect subsequent sea ice variables. This prevents readers from establishing the logical link of "parameterization scheme → drag coefficient → sea ice variables".
9 The comparative is confused, and observational references are lacking. Few of the core figures include observational data, only presenting comparisons between Scheme 1, Scheme 2, and their differences: Figures 3 (drag coefficient), 6 (ice concentration), and 7 (ice thickness) only show the distributions of the two schemes and their differences, without overlaying the spatial distribution of observational data, making it impossible for readers to judge which scheme is more consistent with real-world conditions. Also Figure 8. A large number of difference plots (Scheme 1 – Scheme 2) are used in the manuscript, but the physical meaning of the differences (e.g., positive values indicate Scheme 1 is greater than Scheme 2) is not clearly defined in the figure captions. Difference plots should only serve as supplementary materials, the core comparative plots should be "Scheme 1 vs. observations" and "Scheme 2 vs. observations".
In fact, directly comparing the Cdw results and their component proportions of Scheme 1 and Scheme 2 is scientifically meaningless, as there is no direct observational data to verify and indicate which is more realistic or deviated. Instead, meaningful comparisons should be made by contrasting sea ice physical variables (e.g., ice extent, thickness) and related thermodynamic coefficients influenced by different parameterization schemes with validated observational data.
10 Discussion and Conclusions sections: mechanistic analysis is overly qualitative, comparisons with previous studies are insufficient, and the analysis of study limitations is incomplete.
11 Other minor details require careful checking, such as problems with formula labeling and numbering, the units of parameters, and the format of references.
12 Appendix B is overly verbose and logically disorganized. These results are from TS2014 not authers, and the manuscript should directly specify the general formula of Cdw, its three components, and the determination of input parameters and data for each component. The descriptions in the appendix are repetitive. Otherwise, Figure A1 is not a " we proposed a simplified model….", but a simplified sea ice model designed for deriving the parameterization scheme in the TS2014 study. The description should be objective and realistic.
Citation: https://doi.org/10.5194/egusphere-2025-4290-RC2
Model code and software
HAMSOM-VICE_compile_and_running Bin Jia and Libang Xu https://doi.org/10.5281/zenodo.17063555
Matlab_sea_ice_plotting_script Libang Xu https://doi.org/10.5281/zenodo.17061378
HAMSOM-VICE-result-data-processing-code Bin Jia and Libang Xu https://doi.org/10.5281/zenodo.17060999
The HAMSOM-VICE sea ice model based on Small-scale roughness drag coefficient parameterization, scheme2 Jan O. Backhaus, Maier Reimer, Bernhard Mayer, Bin Jia, Libang Xu, Yu Liu, Xue'en Chen, and Donglin Guo https://doi.org/10.5281/zenodo.17054276
The HAMSOM-VICE sea ice model based on Large-scale roughness drag coefficient parameterization, scheme1 Jan O. Backhaus, Maier Reimer, Bernhard Mayer, Bin Jia, Libang Xu, Yu Liu, Xue'en Chen, and Donglin Guo https://doi.org/10.5281/zenodo.17054212
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