Capturing Solid Earth and Ice Sheet interactions: Insights from reinforced ridges in thwaites glacier.

In this paper, the authors use an ice sheet model coupled to a Gravitation, Rotation, and Deformation (GRD) model to investigate the impact of modeling choices on the retreat of the Thwaites glaciers under warming scenarios. They conclude that resolving the grounding line of the ice sheet model has the strongest impact on sea level change estimation compared to the GRD model and the coupling interval. However, they highlight the importance of including a viscoelastic response of a GRD model with a coupling interval of at least 10 years is needed to prevent an overestimation of Thwaites contribution to sea level change.

I would like to thank the authors for the particular care they took in submitting a manuscript that is well written with a sound layout and methodology, and very nice figures. I would encourage its publication after minor revisions.

I will begin with general comments followed by specific ones.

General comments

I think section 2.1 or the description of the ice sheet models could use additional information.

From what I could read, you do not mention the basal sliding law you are using, nor do you mention whether you are using a grounding line parameterization to diagnose the grounding line. You mention a floatation threshold which is vague. In addition, please add how you are applying ocean melt at the grounding line.

I also think that it would be useful to say a few words on how you are performing your model initialization and the dataset you are using for this (e.g., geothermal heat flux, bed topography, …) and at the very least add a figure on the ice sheet initial state (error w.r.t velocities since this is the metric you are choosing) and the drift of your initial state prior to applying the SSP5-8.5 scenario forcing.

While the differences in SLIM and PLUS are described, in section 2.1, their differences are fundamental in the rest of the study. For this reason, I would find it useful to have a table in that section summarizing the differences between both allowing the reader not to have to find the detail in the text.

In section 2.2, please add a figure of the GRD initial state and the bed uplift drift from the GRD model prior to adjusting the ice sheet model.  

I am not sure there is a need for section 2.3. Lines 94-97 belong to section 2.1 and the resolution of the GRD model would fit in section 2.2. In addition, please add whether the ISSM grid is evolving over time or remains fixed throughout the experiment.

Line by line comments

Line 9: replace “difference” by increase or decrease.

Line 48: does this mean that the ISSM and GRD models have grid nodes in common? If not, please add how you perform the regridding from one model to the other.

Line 50: what do you mean by “SMB parameterization”? In the text you clearly state you are using a climatology form RACMO and forcings from CESM2. These are not parameterization but rather forcing choices.

Line 65: “2 weeks to capture …” is it really to capture the rapid changes or is it also necessary to avoid a CFL violation? Maybe both?

Line 68: Please explain this sentence further. What do you mean by icecaps outside of the ASE, do you mean around the world or just in Antarctica? (The previous sentence mentions that your grid covers the entire globe.) Also, if your goal is to focus on the ASE, what is the added value of using GRACE’s trends for SMB outside of the ASE as opposed to keeping the SMB to the value used at initialization?

Line 89: replace “(Ivins et al. 2020 …)” by “Ivins et al. (2020, 2023) and Lau and Faul (2019)”.

Line 99: what do you mean by “major coupled model components”?

Line 104: same comment as in line 50.

Line 194: If by “kilometer scale” you mean ~1km, please rephrase as Leguy et al. (2021) showed that the needed resolution to capture grounding line behavior is model dependent.

Line 200: please replace “twice” by another comparative word (maybe “more”). Until prove such a number, you cannot really claim it.

Line 237-238: Berdahl et al. (2023) showed that variation in basal sliding laws influences the rate of retreat of the grounding line and, in the presence of GIA, the collapse of Thwaites could be reversed.

Figures

Fig. 1: the color scale makes it difficult to distinguish whether the bed is below sea level or slightly positive. I would suggest adjusting the scale so that there is a clear transition between positive and negative base elevation.

If the colorbar is modified in this figure, it should be modified in Figures A2-A4.

References

Berdahl, M., Leguy, G., Lipscomb, W. H., Urban, N. M., & Hoffman, M. J. (2023). Exploring ice sheet model sensitivity to ocean thermal forcing and basal sliding using the Community Ice Sheet Model (CISM). The Cryosphere, 17(4), 1513-1543

Leguy, G. R., Lipscomb, W. H., and Asay-Davis, X. S.: Marine ice sheet experiments with the Community Ice Sheet Model, The Cryosphere, 15, 3229–3253, https://doi.org/10.5194/tc-15-3229-2021, 2021.

See attached pdf.