General comments:

This study investigates the tipping point of the Filchner-Ronne Ice Shelf (FRIS), based on a series of numerical experiments of a sea-ice and ocean model (including ice shelves) forced by present-day atmospheric boundary conditions. The sea ice-ocean model is a component of the Energy Exascale Earth System Model (E3SM) for wider climate sciences. In this study, the authors first show that by adjusting the iceberg meltwater distribution and the mesoscale eddy parameterization (GM coefficient), the unrealistic tipping event of the FRIS ice-shelf basal melt occurred in the standard configuration (CGM-UIB case) can be avoided in the CGM-DIB and VGM-DIB cases. Using the adjusted experimental setups, the authors further examine the increase in the FRIS melting in response to changes in upstream ice-shelf melting and show that a significant rise in EWIS ice-shelf melting can cause the FRIS to experience a tipping point. A rapid increase in ice-shelf basal melt substantially impacts inner ice-sheet changes, potentially contributing to the Antarctic ice-sheet mass loss and the subsequent global sea-level rise. In addition, while the substantial increase in ice-shelf basal melting due to the enhanced contribution of the warm Circumpolar Deep Water onto the southwestern Weddell continental shelf region has been reported in several modeling studies, it is still an interesting topic to be addressed in a coarse-resolution ocean model, which is a part of the climate model. For these reasons, I consider that the topic of this study falls within the scope of The Cryosphere. Although the manuscript in the present format may be clear for those familiar with E3SM and its ocean model biases, I found it very difficult for general readers (including me) to follow the logic smoothly. I suggest revising the manuscript to make it more understandable for a broader audience.

Major comments:

1. While the study highlighted the use of E3SM in many places (e.g., the abstract (L4-6), the last two paragraphs of the introduction (L51-64), and the methods section), actually, this study used only its ocean, sea-ice, and ice-shelf components of it with specifying atmospheric boundary conditions (CORE-II forcing for global sea ice-ocean models). The description throughout the manuscript should be careful not to give the impression that the experiments were conducted with the full ESM. This study is based on a global sea ice-ocean model, and I think it is sufficient to briefly describe these components are part of the E3SM in the methods section.

2. Throughout the manuscript, only a very limited area of the southern Weddell Sea (FRIS) is shown, and there is no information such as place names used in the manuscript. I think a map is required showing the broad area, including the Eastern Wedell Sea and major place names. In addition, it would be better to use the model representations of the coastline/ice-front line and grounding line (instead of the realistic coastal/grounding lines) to show the model’s horizontal resolution clearly.

3. In the experiments where the melt rate of the Eastern Weddell Sea is increased to 4-16m/yr (Section 2.3), I believe it is important to also express these rates in terms of volume (Gt/yr) per unit area. Considering observational data (Lauber et al. 2023), a melt rate increase to 4-16m/yr seems excessively high. If there are any justifications for this rate based on other modeling results or evidence, it should be included in the manuscript. 

Lauber, J., Hattermann, T., de Steur, L., Darelius, E., Auger, M., Nøst, O. A., & Moholdt, G. (2023). Warming beneath an East Antarctic ice shelf due to increased subpolar westerlies and reduced sea ice. Nature Geoscience, 16(10), 877–885. https://doi.org/10.1038/s41561-023-01273-5

4. I understand that freshwater supply and distribution can determine the FRIS tipping, but can you estimate the tipping conditions in ***this model*** by analyzing the freshwater balance on the continental shelf in front of the FRIS? For example, how much Gt or more of freshwater on the southwestern Weddell continental shelf would be required to cause the tipping point?

5. There are two very relevant new papers. The first one is missing, and the second one requires an update of the citation.

Mathiot, P., & Jourdain, N. C. (2023). Southern Ocean warming and Antarctic ice shelf melting in conditions plausible by late 23rd century in a high-end scenario. Ocean Science, 19(6), 1595–1615. https://doi.org/10.5194/os-19-1595-2023

Haid, V., Timmermann, R., Gürses, Ö., & Hellmer, H. H. (2023). On the drivers of regime shifts in the Antarctic marginal seas, exemplified by the Weddell Sea. Ocean Science, 19(6), 1529–1544. https://doi.org/10.5194/os-19-1529-2023

Specific comments:

6. L35-44: There are some useful literature (Thompson et al. 2018 for introducing Antarctic Slope Front/Current, Thoma et al. 2010 for remote linkage between Eastern Weddell Sea and Weddell Sea, and Kusahara and Hasumi 2013 for pathway of the EWIS meltwater). Please consider including the references.

Thompson, A. F., Stewart, A. L., Spence, P., & Heywood, K. J. (2018). The Antarctic Slope Current in a Changing Climate. Reviews of Geophysics, 56(4), 741–770. https://doi.org/10.1029/2018RG000624

Thoma, M., Grosfeld, K., Makinson, K., & Lange, M. A. (2010). Modelling the impact of ocean warming on melting and water masses of ice shelves in the Eastern Weddell Sea. Ocean Dynamics, 60, 480–489. https://doi.org/10.1007/s10236-010-0262-x

Kusahara, K., & Hasumi, H. (2013). Modeling Antarctic ice shelf responses to future climate changes and impacts on the ocean. Journal of Geophysical Research: Oceans, 118(5), 2454–2475. https://doi.org/10.1002/jgrc.20166

7. L73-74: This sentence is incorrect. Dinniman et al. (2016) summarized ocean models, which include ice-shelf cavities, and several ocean models with the same features have been developed since the publication. 

Dinniman, M., Asay-Davis, X., Galton-Fenzi, B., Holland, P., Jenkins, A., & Timmermann, R. (2016). Modeling Ice Shelf/Ocean Interaction in Antarctica: A Review. Oceanography, 29(4), 144–153. https://doi.org/10.5670/oceanog.2016.106

8. L104 Where did you restore the surface salinity, and with what intensity?

9. L109-110: I think that a map of the variable GM calculated in the model is helpful to see the difference from the constant-value case.

10. L115-136: Maps of iceberg melt flux are also helpful to understand the differences among the experiments.

11. Figure 1: Adding Gt/yr to the right axis also makes it easier to compare with other studies and between ice shelves.

12. Figure 2: Information of longitude and latitude is sparse, and it is very difficult to see the latitude information.

13. Figure 4: Is the small map for the T-S plot? If so, please enlarge the map and add depth contours.

14. Figure 7: Without vertical profiles of water properties, it is very difficult to understand the figure.

15. Figure 8: A map of the barotropic stream function is required, with pointing to the observation site M31W and transect C. 

16. Figure 9: Could you add panels of vertical profiles of alongshore current to see the Antarctic Slope Current? Why did you use the potential density anomaly referenced to 1000 m? The other figures used the potential density referenced to the surface (Figs. 4, 7, and 12). Please remove TODO (I think this kind of error should be removed before submission, circulating the manuscript among the authors.).

17. Figure 10: It is very difficult to see the observed range. Please consider revising the color.

18. Figure 12: Please add the experiment names in the figure.

Technical corrections:

19. Title: It is not clear to me what the word “ice-shelf freshwater” stands for in the title. “Antarctic coastal freshening” may be a candidate to replace the word.

This is an interesting and generally well-written paper that discusses the drivers of ice shelf melt regime change in the south-western Weddell Sea as inferred from a relatively coarse resolution global ocean/sea ice model.  The authors discuss how modifications to the model can reduce present day biases in the results, and that those changes are critical to the preservation of the current regime under current climate forcing.  They further investigate the occurrence of a domino effect whereby increased ice shelf melting in the eastern Weddell Sea can trigger regime change in the south-west and describe how coarse resolution models may be pre-disposed to such a change.

The paper is logically structure and the results clearly presented.  The text is pleasingly free of typographic errors and easy to read.  Overall, I would recommend publication more-or-less as is, although the clarity could be improved further with a few minor modifications along the lines suggested below.

Teleconnection:  I question the use of the term teleconnection.  As used in the atmospheric context it refers to a rapid connection between two regions, typically established through a standing planetary wave pattern.  If I understand the discussion here, the links are established slowly through the advection of anomalies by the mean circulation.  I think teleconnection is a slightly misleading description of such a process.

Water masses:  There is a long and often confusing history of water mass names and acronyms, many of them regionally specific, that have appeared in the literature.  While this paper does a reasonable job at navigating a way through that, I think some things could be clearer.  DSW is a term that is not clearly defined in the literature or in this paper.  It is apparently not just another term for HSSW (as used elsewhere?) because at one point it is stated that model DSW corresponds with observed LSSW.  While I think the meanings are for the most part clear, I would encourage the authors to think about adopting the Whitworth et al (1998, Antarctic Research Series, vol 75) classification.  They defined four water masses in the shelf/slope region, and while precise boundaries in T/S are region specific, nomenclature and origin/role are consistent in a circum-continental sense.  In their classification, Shelf Water (SW) is the key water mass, defined as water that is denser than the regional variety of MCDW.  Thus, presence or absence of SW is the key determinant of the transition in melt regime.  Personally, I think Whitworth et al did the community a great service in proposing that simpler, more consistent and more intuitive circum-Antarctic water mass classification, which could clarify the sort of arguments made in this paper were it to be more widely adopted.

Model:  The model naming is sometimes a little unclear.  It is referred to throughout by the acronym ESM, but it is not the ESM used in Commeau at al.  It does not have the interactive atmosphere, but are there any other distinctions?  The various modifications made to the model parallel modifications to the full ESM, I think.  That point only becomes apparent (to this reader at least) when Figure 12 is discussed.  I think it would help if the model structure and experiments were set more clearly in the context of the Commeau et al work in section 2.

Region:  A location map with key features and all the ice shelves mentioned would really help orient readers, especially those less familiar with the region.

Minor comments:

Line 43-44:  I’m not sure what feature you are referring to as the “Antarctic Coastal Countercurrent”.

Line 54-55:  “… the iceberg melt term; …”.

Line 148-153:  I’m confused by what appear to be slightly contradictory statements about the prescribed melt rates.  First you give specific values, but then you say that values are progressively halved relative to the maximum.  Most, but not all quoted values fit that description, but is it superfluous anyway given that you quote specific numbers?  But maybe it is the numbers that are obsolete (?), as they do not appear to coincide with lines in Figure 11 (at least two of them don’t).

Line 165:  “… complete forcing cycle is complete”.  I know what you mean but the wording is a little odd.  A complete cycle is complete by definition.

Line 182:  “… highest melt rates occur near the grounding …”.

Line 233:  “… on the Weddell Sea continental shelf (Fig. 6).”

Line 279:  “ … of these leading to a FRIS …”

Line 289:  “… simulations experiencing rapid transition …”.

Line 321:  This is now the first citation of Figure 7, if my earlier correction is OK.  I still don’t really see that Figure 7 supports the statement.  Did you mean to refer to a different figure again?  Maybe figure 6 again?  In which case, is Figure 7 needed at all?

Line 414:  “… rapid change to continental shelf temperature …”.

Figure 9 caption:  Note to self needs deleting.