Please see the review of Ackermann et al. (2023) in the attached pdf.

General Comments

The authors present a comprehensive evaluation of interactive icebergs in a set of experiments with the AWI-ESM2.1 Earth System Model, demonstrating an advance in modelling capability that is within the scope of GMD. Multi-centennial experiments are necessary to establish the impacts of icebergs on deep and bottom waters that circulate on these long timescales. To my knowledge, these are the longest ESM experiments undertaken with interactive icebergs, while maintaining suitably high resolution around Antarctica. The separate impacts of iceberg-altered freshwater and heat fluxes are central to understanding the overall impacts of icebergs on the ocean, the latter impact (cooling) being regrettably a late admission to iceberg-ocean coupling in NEMO-ICB. Prospects for coupling with an interactive ice sheet are further promising. Overall, this study provides an advance on previous studies that reported the first implementations and subsequent developments of interactive iceberg modelling, several published in GMD. Methods are clearly outlined, with scope for minor clarification (see specific comments below), and results are sufficient to support conclusions. Following Code Availability, all results should be reproducible with sufficient computing resource. The title clearly reflects the contents of the paper, identifying the ESM by name.

A minor issue is the focus on Antarctica, with Greenland briefly mentioned in the Introduction. For a more complete representation, interactive icebergs can presumably also be seeded around Greenland (and other smaller northern ice caps). I appreciate that Antarctica is the dominant source of icebergs at global scale, but dense water formation in the subpolar North Atlantic may be particularly sensitive to the same processes (perturbing T and S) that are identified around Antarctica. It would be useful for the authors to comment further in Introduction and Discussion on the global impact of icebergs, in particular the net results of perturbations to deep and bottom water formation in both hemispheres. The Abstract provides a clear and concise summary of findings, although more quantitative detail could be provided (see specific comments). Overall presentation is well-structured throughout, and the manuscript is well written, with appropriate level of Supplementary Material.

In summary, the authors provide a compelling case for a relatively straightforward model improvement, of consequence for climate simulation and projection, with the intriguing possibility that neglected appreciation of iceberg influences could explain recent observed variability around. Antarctica (lines 266-269). As a development and technical paper, the manuscript should be suitable for publication in GMD, subject to minor revisions as suggested above and specified below.

Specific Comments

1. Abstract: Provide additional quantitative support for statements, e.g., how much cooling, extent of (%) weakening in stratification.
2. Introduction, from line 25: Given the focus here on a new model capability in AWI-ESM2.1, and earlier comment in the Abstract that ‘only few advanced coupled Earth System models that employ interactive icebergs’, it would be appropriate to more comprehensively summarize these models, perhaps tabulating resolutions tested, details of coupling (with/without heat flux coupling), seeding scheme, duration of simulation, reference/s. This would clearly establish the novelty and leading position this the present model development and study.
3. Introduction, from line 49. Provide more justification for focus on Antarctica and the Southern Ocean in a global model, given the potential importance of Greenland icebergs for dense water formation and properties in the North Atlantic.
4. 5, line 120: clarify what you mean by ‘continuous’, through time, or over space?
5. 5, lines 122-123, and in Fig. 1 caption: I do not quite follow ‘integration of the calving flux over each basin to get total amount of ice discharge’, and Fig. 1a; can this be further explained?
6. 11, Fig. 7: There is considerable multidecadal-to-centennial variability in ocean temperature and AABW indices; while this is not a focus of the study, it is perhaps worthy of more comment and even some explanation.
7. 12, line 208: correct as ‘shelf-region’
8. 13, line 219: do you mean ‘pushed onshore due to Ekman dynamics’? (geostrophy sets up long-shore drift
9. 14, lines 250-251: Remarking that ‘realistic representation of AABW formation along continental shelves is not feasible in out model setup’, can this be further explained; it is a consequence of missing ice shelf cavities, or limited resolution, or both?
10. 15, line 265: In discussing the delay of Southern Ocean greenhouse warming in climate projections due to cooling and freshening, do the authors imply the consequences of increasing iceberg calving? Perhaps be more explicit here.