the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Apr 2026
West Antarctic Ice Retreat Temporarily Halted with Transient Rheology in Future Climate Projections
Abstract. Projections of sea-level change and Antarctic Ice Sheet (AIS) stability under anthropogenic climate change hinge upon accurately describing physical feedbacks that link ice dynamics (marine and terrestrial) with the gravitational, rotational and deformational response of the solid Earth to ice and ocean loading changes. In turn, the rate of AIS melting can lower the rate of global mean temperature rise, by promoting sea ice growth and amplifying Earth’s albedo. The marine West Antarctic Ice Sheet (WAIS) is vulnerable to runaway grounding line retreat. However, the rapid viscoelastic rebound of the bedrock in response to ice retreat has been shown to stabilize its grounding line, aided by the low-viscosity mantle beneath the WAIS. Such bedrock deformation is typically modelled with idealized Maxwell viscoelasticity, despite that rock deformation experiments show that additional “transient” creep mechanisms occur over societally relevant (~decadal-centennial) timescales that are missing from the Maxwell model. Here, we simulate future AIS evolution, coupled with self-consistent solid Earth deformation and sea level change, for various emissions scenarios (RCP 2.6, 4.5, 8.5), incorporating transient deformation. This more complete treatment of solid Earth deformation delays grounding line retreat as compared to Maxwell projections, with differences of tens of kilometres persisting for decades at Pine Island and Thwaites Glaciers. Though transient deformation slows glacier retreat, it is unable to prevent the bulk of ice loss and sea-level rise on longer, centennial timescales. Even still, deviations in AIS meltwater flux with transient deformation could affect the pace of global temperature rise in climate model predictions.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-2172', Maria Zeitz, 15 Jun 2026
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RC2: 'Comment on egusphere-2026-2172', Anonymous Referee #2, 03 Jul 2026
In this study, the authors perform coupled ice sheet-sea level simulations to investigate the evolution of the Antarctic ice sheet under RCP climate scenarios. Rather than adopting the standard Maxwell viscoelastic rheology, they consider a transient rheology to represent mantle deformation. They show that, although transient rheology does not prevent long-term ice loss, it delays grounding-line retreat and the associated West Antarctic ice loss compared to simulations using Maxwell rheology. This is an important study which highlights the stabilizing influence of Glacial Isostatic Adjustment (GIA) feedbacks on Antarctic ice sheet retreat. The manuscript is overall well written and should be suited for publication in The Cryosphere after the following points have been addressed.
Specific commentsl.13-15. I suggest deleting this sentence, as the feedback described is not directly relevant to this study and is only one of several feedback mechanisms associated with Antarctic ice sheet melting. Alternatively, rephrase it to state that the rate of Antarctic melting has multiple impacts on the Earth system.
l.17-20: I suggest rephrasing as follows: “Such bedrock deformation is typically modelled using idealised Maxwell viscoelasticity. However, rock deformation experiments show that additional 'transient' creep mechanisms, which are not captured by the Maxwell model, occur over societally-relevant timescales (~decadal to centennial).”
l.27-28: Adjust according to how you decide to address my comment regarding lines 13-15 above.
l.42: DeConto & Pollard, 2016 and Deconto et al., 2021 illustrate the role of MICI in triggering extreme Antarctic ice loss rather than the role of MISI. I am not sure these are the most appropriate references to illustrate marine ice sheet instability mechanisms.
l.40-56. Sergienko et al., 2026 (https://doi.org/10.1038/s41561-026-01941-2) stress how reality is much more complex than Weertman’s and Schoof’s original definitions. It would be worth acknowledging this here. In fact, the influence of bedrock deformation on Antarctic marine ice loss does not necessarily need to be framed through the MISI perspective.
l.63-65: See my previous comment. Could be simply phrased as: “Sea-level rise at a marine grounding line (e.g. from far-field ice loss) promotes further grounding-line retreat.”
l.87: Please clarify what is meant by the ‘bulk mantle’.
l.93: Please clarify what is meant by ‘modern cases’.
l.97: Replace ‘While they assume’ by ‘Assuming a’.
l.101: I would suggest removing ‘even’.
l.101-111: I think the manuscript would benefit from a simple explanation of the fundamental difference between Maxwell viscoelastic rheology and the transient rheology considered here. Since this distinction is central to the paper, it should be introduced more clearly.
l.113: Please clarify what is meant by ‘compliant’.
l.121: I suggest rephrasing as ‘Here, we modify the coupled framework of Gomez et al. (2024) by incorporating transient viscoelastic deformation’.
l.123-127: I suggest splitting this long sentence into two for clarity.
l.133: I suggest ending the sentence after ‘emissions scenarios’, and removing ‘namely’.
l.139-143: I suggest splitting this long sentence for clarity.
l.152: Remove ‘-as just mentioned-’.
l.155: What exactly is meant by ‘a prescribed loading history’ here? Does this refer to Ice-sheet evolution prior to the start of the coupled simulations? Please clarify and specify which loading history is used.
l.180: I suggest removing ‘according to MISI’ here. Evolving grounding line position occurs even without any MISI. I also recommend citing Pollard and DeConto (2020; https://doi.org/10.5194/gmd-13-6481-2020) here.
l.182-184: It would be good to provide more information, or at least a reference, for the PDD scheme used (e.g., parameter values, etc). Similarly, no information is provided on how sub-shelf melting is calculated, while it is a key driver of Antarctic ice loss, nor about the initialisation procedure. How do you initialise such a coupled framework? This should be clarified.
l.188: Is this the calving parameterization of Pollard et al. (2015)? If so, please state this explicitly. Also, does this parameterization include hydrofracturing, or is hydrofracturing turned off?
l.192: What do you mean by ‘in the Main Text’? I suggest rephrasing to avoid confusion.
l.198-199: Please add appropriate references.
l.226-231: This is a very long sentence. I suggest splitting it for clarity.
l.247: I suspect there is a ‘with’ missing in this sentence.
Figure1: It would be helpful to delineate the calving front on the figure to better visualise the ice shelves' extent.
l.263-265: I find the yellow regions somewhat confusing. If, as stated in the caption of Figure 1, the final grounded ice extent for the transient model is contoured in yellow, it means that the yellow regions indicate places where the Maxwell model extends further than the transient one, right? Perhaps consider an alternative way of comparing the two extents.
l.265-269: Please split this sentence after ‘4.5’.
l.275: I am not sure where to visualise the subtle subsidence in East Antarctica. Could you refer to a figure?
Figure 3: For clarity, I would suggest displaying the ice draft as well on those figures. Also, while I clearly see the added value of glacier transects, I would be interested in comparing the spatial pattern of grounding line evolution for both rheologies.
l.295-297: What about RCP8.5? Was the total grounding line retreat identical for both models? If so, please clarify.
l.301: Clarify ‘compared to the Maxwell rheology’.
l.304-307: As mentioned above, I think a 2D comparison of grounding-line evolution between the two rheologies would be valuable, even if only included in the Supplement.
l.328: It would be good to explicitly state that this corresponds to only a few centimetres of sea-level contribution by 2300, compared with a total contribution of approximately 0.6–2.5 m (i.e., only a few percent of the total).
l.332: How do you explain that the reduction in WAIS contribution under transient rheology is larger for eta_high than eta_low under RCP2.6, but the opposite occurs under RCP4.5?
l.334: I find this a little misleading, as 5% is in fact the maximum reduction. It would also be worth clarifying that the highest reductions occur for the lower-emission scenarios.
l.341: Do you observe any influence at all in East Antarctica? It might be interesting to comment somewhere about that, given that you do simulate the whole ice sheet.
l.343-344: Please clarify what is meant by different sensitivities. My interpretation of the Results section is that both cases exhibit delayed grounding-line retreat relative to the Maxwell simulations.
l.345-347: Again, I do not think the simulations demonstrate that grounding-line retreat is driven by marine ice sheet instability. Instead, I believe that retreat is simply driven by the imposed climate forcing. Yet, this does not change the stabilizing influence of GIA. I would suggest reformulating and avoiding explicit reference to MISI.
l.347-349: This point is not entirely clear from the Results section. Please be more specific about the timescales over which rheology influences the simulations. Does this apply across all scenarios? Why does the influence diminish with time? Is it because the climate forcing eventually dominates, or is it an intrinsic property of the rheological model?
l.356: It may be interesting to point out here that any reduction in the rate of sea-level rise resulting from transient rheology is directly relevant for coastal adaptation planning. From the results, I suspect transient rheology has a noticeable effect on the rate of sea-level rise, and this deserves discussion.
l.364: Again, please clarify whether the retreat is inevitable under all forcing scenarios.
l.367-368: Is there a way to verify this interpretation? For example, could bedrock uplift predicted by the two rheologies be compared directly over the relevant period?
l.370: Replace ‘MISI’ with ‘grouding-line retreat’(cf comments above).
l.372: It is not clear to me why I should look specifically at the continuous lines in Fig.6 here.
l.380-383: In line with my earlier comments on the Introduction, I think that this requires a little more information for readers who are not familiar with the Yamauchi and Takei model.
l.387: Please add a reference here.
l.402-405: In line with one of my earlier comments, do you observe this behaviour in your simulations, given that the entire Antarctic Ice Sheet is represented? If so, it would be useful to comment on it.
Figure 7: Are both panels shown for RCP4.5 with MICI enabled? If so, Figure 7b appears to contain a typo, as the title refers to RCP8.5.
l.453: I am not entirely sure what is meant by static ice loading change. Please clarify this so that readers do not need to consult Lau et al.
l.456-460: This is an important point and, in my opinion, could already be introduced in the Introduction as part of the motivation for the study.
l.467: Are you referring to the present study or to Lau et al.? Please clarify.
l.475-481: I agree with the general point, but I believe the situation is more nuanced. For example, Antarctic freshwater input has also been shown to have the potential to enhance Antarctic mass loss by inducing subsurface ocean warming (e.g., Bronselaer et al., 2018; https://www.nature.com/articles/s41586-018-0712-z). It would therefore be worth acknowledging that freshwater feedbacks can act in both directions.
Citation: https://doi.org/10.5194/egusphere-2026-2172-RC2
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Summary
The manuscript studies the interaction between climate change, ice sheet dynamics and the solid earth in West Antarctica. The authors introduce a new modeling approach to the solid earth rheology – a transient viscoelastic rheology, which responds on decadal to centennial time scales relevant to modern ice loss due to anthropogenic climate change – and compare it to the established Maxwell rheology. They find that the retreat of the West Antarctic Ice Sheet in different climate scenarios is consistently slower in simulations with the transient model and the bedrock uplift is stronger. This effect is less pronounced for scenarios with little ice loss and increases for higher ice loss scenarios. However, the long-term response of the ice sheet to a changing climate does not seem to be affected.
General comments
In my opinion the paper is already very good. The topic is of scientific interest and relevant to the community. The methods seem appropriate for the question at hand. The presentation of the research is clear and well structured. The visual representation is compelling. I also appreciate the sensitivity analyses in the supplement.
There are a few points I would like to address:
To add clarity, I would suggest some additional figures with grounding line position along the transect versus time. This might allow the reader to see at once how much slower the grounding line retreats in the transient viscosity model.
Reese, R., Winkelmann, R., and Gudmundsson, G. H.: Grounding-line flux formula applied as a flux condition in numerical simulations fails for buttressed Antarctic ice streams, The Cryosphere, 12, 3229–3242, https://doi.org/10.5194/tc-12-3229-2018, 2018.