the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The implementation and effectiveness of Calving Algorithms in numerical ice models (CalvingMIP)
Abstract. Ice calving plays a significant role in ice sheet mass loss. Predictions of future ice sheet mass balance require accurate representations of the calving process in numerical ice models to determine rates of future global mean sea level rise. Whilst calving has recently begun to have been implemented in numerical models there has not been a systematic investigation into how this implementation compares between different ice flow models. The Calving Model Intercomparison Project (CalvingMIP) has been established to address this question by providing a framework of experiments to investigate the accuracy of simulated calving rates and how simulated properties at the calving front evolve over time. Our initial focus has been on how calving is implemented in models, therefore focusing on calving algorithms, rather than on how much ice should be calved at a particular time (calving law). Our results, from thirteen different numerical modelling groups, show that the majority of calving algorithms implemented are able to accurately implement a given calving rate with an ice front that evolves smoothly throughout the calving process. These results show that we can have confidence in the models capacity to accurately implement calving laws in the future.
Competing interests: At least one of the (co-)authors is a member of the editorial board of The Cryosphere.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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Status: open (until 05 Jul 2026)
- RC1: 'Comment on egusphere-2026-1962', Anonymous Referee #1, 23 Jun 2026 reply
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CalvingMIP – Calving algorithm simulations James R. Jordan, Frank Pattyn, and The CalvingMIP Team https://zenodo.org/records/20041205
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- 1
This is a valuable community paper and an important first step for systematic evaluation of calving in numerical ice-sheet models. The manuscript is well motivated, the experimental design is appropriate for a phase-1 algorithm-focused MIP, and the results will be useful for model developers and users. I recommend publication after following revision.
1. Line 245, "floating cells adjacent to ....", does this mean CISM only capture floating shelf calving? Can it capture grounded glacier calving activity?
2. Table3, there is a clear resolution mismatch for IMAU UFEMISM (20km) coarser than all the other models. Can results be replaced with 5km resolution simulation instead? In fact, shouldn't IMAU be consistent with NCAR CISM's results with the same resolution (at least for circular domain where calving rate direction doesn't make diffrence)?
3. Have all these models conducted convergence analysis on grid size? Might be a good idea to put it in SI and make sure the paper presents converged result from each model.
4. In conclusion text, the author claims calving algorithm does not make a noticeable difference for the result. To justify that, the author should first justify in table3, other variations do not skew simulation results. (for instance, is it safe to claim in current configureation, HO and SSA has similar results, any scaling argument to justify this? The author has already justified for the circular domain, calving rate direction shouldn't make any difference on the results)
5. Line 385, when interpreting Figure3, I can see the outliers are IMAU & AWI YELMO, is it a typo that the author emphasize PIK PISM intead?
6. Fig.3 and Fig.9 are not consistent. The outlier changes from IMAU & AWI YELMO to IMAU & PIK PISM, why?
7. For each figure, after stating which models deviate from theory/other models, the authors can add more explanation of why that happens, and mitigation strategies to fix that (if possible).
8. The project is very valuable as stated by the author "whilst undertaking the work for this project most models significatnly imporved their results for those initially submitted, both in terms of accuracy as well as spotting previously unnoticed errors in their code". Can the author highlight what bugs in the code for different models were fixed during this project (maybe summarize in a table and attach as SI)? I think the list of "common mistakes to make" is very valuable for students who just start learning ice sheet models. The table can also highlight the mitigation strategy to be implemented in the future, for those models that exhibit limitations during this project.