We would like to sincerely thank the anonymous reviewer for their careful and insightful evaluation of our manuscript. We deeply appreciate the time, effort, and constructive nature of the comments provided. The feedback received is highly valuable for improving the clarity, scope, and scientific strength of the study.

We understand that the review process remains ongoing (until 4 January 2026) and that additional reports may still be received. Therefore, this document presents a provisional and reflective response, outlining how we intend to address the reviewer’s observations in the next revision stage, once all comments have been received.

We respectfully acknowledge the reviewer’s concern regarding the manuscript’s fit within The Cryosphere’s scope. Nonetheless, we would like to emphasise that the journal explicitly welcomes studies addressing permafrost and periglacial processes, cryosphere–climate interactions, and environmental responses to climatic change—themes that are central to our work. The manuscript provides a quantitative and data-oriented characterization an modeling of periglacial cliff retreat in an Antarctic coastal setting, combining multi-temporal photogrammetric analysis (1956–2022) and non-linear statistical approaches. These aspects directly contribute to The Cryosphere’s mission to advance understanding of the physical processes governing cryospheric change, particularly in regions underrepresented in Antarctic permafrost studies. Furthermore, the results have direct implications for infrastructure safety and environmental management near the Spanish and Argentine research stations located at Port Foster, Deception Island—an issue of practical and scientific relevance that aligns with the journal’s interest in cryospheric processes with societal implications.

We accept and fully acknowledge the reviewer’s observation regarding the limited spatial extent (1.5 km) of the analysed coastal segment. However, this scale reflects the spatial range for which high-quality, consistent, and geometrically accurate imagery was available, covering more than six decades. Crucially, the study area is located diametrically opposite the volcanic centres affected by the 1967–1970 eruptions, ensuring that the observed coastal evolution is less affected by volcanic disturbances and instead possibly governed primarily by periglacial, geomorphological, and marine processes. This provides a stable and representative sector for isolating climate-driven erosion mechanisms, according to the available data time scale—a key objective of the research. While modest in size, this high-resolution, data-constrained approach strengthens the reliability of the results and establishes a robust methodological framework that can be extended to larger sectors of Deception Island and other Antarctic coasts in future works.

Improvement and Planned Revisions

We greatly appreciate the reviewer’s detailed and constructive recommendations, which will guide the forthcoming revision of the manuscript once all feedback has been consolidated. The following points summarise our planned improvements:

Broadened Antarctic Context – The Introduction and Study Area sections will be expanded to integrate regional climate analyses, permafrost studies, wave and storm dynamics, and Antarctic Peninsula environmental trends.

Mechanistic Interpretation of Post-2000 Acceleration – The revised Discussion will incorporate some hypotheses linking the observed inflection point in retreat rates to possible regional temperature anomalies, sea-ice decline, and/or changing wave energy regimes.

Quantitative Model Comparison – We plan to re-explain explicit comparative statistics (STDEs, R², AICc, and include confidence intervals) for linear, quadratic, and sigmoidal regressions to strengthen claims regarding model performance. We will refine our uncertainty quantification to include shoreline position and rate uncertainties, complementing the georeferencing and photogrammetric accuracy assessments.

Improved Figure Integration and Clarity – We will try to reorganise figures in the results section to merge related temporal and spatial patterns, improving readability and scientific coherence.

The Discussion will include a new subsection on implications for coastal stability and risk management concerning nearby research facilities.

We thank the reviewer once again for their thoughtful and valuable comments, which we regard as an essential opportunity to strengthen the manuscript. We believe that, with the forthcoming revisions, the manuscript will offer a scientifically rigorous and well-contextualised contribution to understanding Antarctic periglacial coastal dynamics—a topic of growing importance within the cryospheric sciences. These planned revisions will collectively enhance the manuscript’s scientific depth, its alignment with The Cryosphere’s editorial standards, and its contribution to Antarctic periglacial research.

Sincerely yours.

Firstly, the authors would like to thank the reviewer for their consideration in reviewing this work. We understand and appreciate the effort and interest they have shown. Likewise, we sincerely thank the reviewer for their thorough, constructive, and insightful assessment of our manuscript. We greatly appreciate the recognition of the value of long-term coastal observations in Antarctica, as well as the positive evaluation of the structure and methodological robustness of the study. The reviewer’s comments have been extremely helpful in identifying areas where the interpretation and contextualisation of our results can be strengthened, and they will be carefully considered once the full review process is completed.

Below, we respond point by point to the reviewer’s comments.

1) Reviewer comment:

“I definitely miss explanation and interpretation of the results presented. What are the factors affecting the reported nonlinear behaviour and spatial heterogeneity of the erosion?”

Response:

We agree with the reviewer that interpretation of the observed non-linear and spatially heterogeneous erosion patterns is a key aspect that requires careful discussion. In the current manuscript, our primary objective was to present a robust, observation-driven quantification of cliff retreat over a 66-year period using uncertainty-weighted statistical models. We acknowledge that the discussion currently emphasises pattern identification more than process attribution.

Importantly, we deliberately avoided strong causal claims because direct, long-term in situ measurements of ground temperature, active layer thickness, wave energy, or permafrost mechanical properties are not full available for the full study period and area of interest.

However, we agree that a clearer framing of plausible controlling mechanisms—based on existing conceptual models (i.e. Violante, 2009; Castedo et al. 2012; Sunamura, 2015)—identifying and assigning the possible activation mechanisms and their primary responses that, in the periglacial environment of the study area, can cause the cliff to retreat. This includes detailing some elements that, in these conceptual models designed for cliffs in temperate environments, do not explicitly state the effect of the polar environment, such as integrating thermal degradation of permafrost, its geomechanical and hydrological effects (e.g. river discharge and groundwater flow) and marine forcing, or even the possible shear effect of sea ice, which would substantially improve the manuscript. We are currently conducting geophysical surveys and their interpretation related to the identification and 3D modelling of the state and geomechanical properties of the permafrost and the active layer underlying the Spanish Antarctic base and the cliff. So, we plan to strengthen the discussion by explicitly presenting these mechanisms as testable hypotheses, rather than definitive drivers, clearly distinguishing observation from interpretation.

2) Reviewer comment:

“You stated that the acceleration of erosion after 2000 is related to increasing warming of atmosphere – do you have any data to prove it? How does this go together with the cooling trend reported around the Antarctic Peninsula?”

Response:

We fully acknowledge this concern. The acceleration of cliff retreat after ~2000 is an observational result derived from shoreline position time series and regression analysis. At present, the manuscript does not claim a direct causal relationship between atmospheric warming and erosion acceleration, but we agree that some statements could be misinterpreted as implying causality.

The literature shows that the Antarctic Peninsula region exhibits strong spatial and temporal climate variability, including periods of warming followed by partial cooling or stabilisation (e.g. Turner et al., 2016; or the study cited by the reviewer: Oliva et al., 2017). This variability does not contradict our observations but rather suggests that erosion acceleration may be linked to threshold responses in permafrost systems, where cumulative thermal warming or hydrological changes can trigger delayed geomorphic responses.

In addition, more recent studies with longer time series (i.e. Gonzalez-Herrero et al., 2022; Gorodetskaya et al., 2023; Roland et al., 2024) confirm a period of warming in the Antarctic Peninsula region, with notable heat waves, almost half a degree higher than in previous periods, interspersed with brief periods of cooling (as highlighted in the article by Oliva et al., 2017). In a revised version, we would clarify that the post-2000 inflection point coincides with broader environmental changes but is not solely attributable to atmospheric temperature trends alone. We would also explicitly discuss the possibility that internal permafrost degradation, changes in moisture availability, or hydrological focusing (e.g. near the river mouth) play a dominant role.

3) Reviewer comment:

“Why is the erosion so spatially variable? Is there any effect of the research stations? Concentration of erosion near the river mouth suggests thermal degradation rather than mechanical erosion.”

Response:

We strongly agree with this interpretation. The pronounced spatial variability observed along the 1.5 km cliff section, and particularly the enhanced retreat near the river mouth, supports the hypothesis that thermal, hydrogeological and hydrological processes are major drivers, reinforced by the effect caused by human activity at the Spanish Antarctic base. Concentrated surface and subsurface water flow can enhance heat transfer into permafrost, increased by the expansion of the exposed surface area through the gullies that traverse the cliff along the coast, reduce locally shear strength, and promote episodic mass wasting, even in settings with limited wave exposure.

Regarding anthropogenic influence, we acknowledge that the proximity of the Argentine and Spanish research stations introduces potential local effects (e.g. heat dissipation, altered drainage, surface disturbance). While no quantitative data are available to isolate these effects, we agree that their potential role should be discussed explicitly and cautiously, particularly in relation to infrastructure risk and local permafrost stability.

4) Reviewer comment:

“The site is well sheltered from prevailing SW winds… What is then the primary cause of cliff erosion? Is it really a coastal process or just permafrost degradation?”

Response:

This is an important point. Port Foster is a semi-enclosed volcanic caldera, and the study site is indeed partially sheltered from dominant regional wave climates. This setting suggests that classic wave-driven abrasion is likely secondary compared to permafrost-controlled processes, including thermal degradation, frost cracking, and hydrologically driven erosion (Caballero-Martinez et al., 2025).

In a revised discussion, we would more clearly frame the observed retreat as a coastal-periglacial process, where marine influence acts mainly as a boundary condition (e.g. toe removal, moisture supply) rather than the dominant driver. This interpretation aligns with recent studies of periglacial coasts in both polar regions.

5) Reviewer comment:

“I don’t see any discussion of the reported erosion rates, comparison to other sites around Antarctica or Arctic. Is the erosion rate low or high?”

Response:

We agree that broader contextualisation is needed. The retreat rates observed at Port Foster are generally lower than those reported for highly exposed Arctic permafrost coasts but fall within the range reported for sheltered Antarctic coastal environments. Explicit comparison with published Antarctic Peninsula and Arctic datasets would help place our findings within a pan-polar context and avoid overgeneralisation.

This comparison will be incorporated more clearly in a revised discussion section.

6) Reviewer comment:

“Perhaps a detailed geological conditions of the cliff might help in interpretation.”

Response:

We agree. The cliffs are mainly composed of fairly homogeneous, poorly consolidated tephra deposits with low cohesion, on a gently sloping palaeolandscape. These properties probably contribute to the overall behaviour of the cliff, and the spatial heterogeneity of erosion rates is more likely to be due to local variations in its geomechanical characteristics, which are closely linked to the spatial distribution of permafrost and its thermal conditions. Overall, the behaviour of the cliff, due to being the result of multiple interactions of processes acting at different spatial and temporal scales on a heterogeneous geological environment, whose properties also fluctuate over time, is highly non-linear, meaning that the linear models commonly used are not the most advisable.

Although a complete geomechanical characterisation exceeds the scope of the current dataset and this work, we recognise that lithological and thermal contrasts, although relatively unremarkable, may be critical controls and should be discussed more explicitly.

Concluding remark

We would like to thank the reviewer again for their thoughtful and constructive comments. We believe that addressing these points—particularly by strengthening the interpretation, expanding regional context, and clearly distinguishing observation from hypothesis—will significantly enhance the scientific contribution of the manuscript. We will carefully integrate these improvements once the full review process is complete and according to the Editor final decision.

Cited references in the answer

Barlow, J., Lim, M., Rosser, N., Petley, D., Brain, M., Norman, E., & Geer, M. (2012). Modeling cliff erosion using negative power law scaling of rockfalls. Geomorphology, 139, 416-424.https://doi.org/10.1016/j.geomorph.2011.11.006

Caballero-Martinez, O. A., Paredes, C. Roman, A., Navarro, G., & Diez-Minguito, M. (2025). Study of Cliff ridge recession due to wind-induced waves in port Foster (Deception Island, Antarctica). 14th Symposium on River, Coastal, and Estuarine Morphodynamics, RCEM2025, Barcelona, Spain, September 2025.

Castedo, R., Murphy, W., Lawrence, J., & Paredes, C. (2012). A new process–response coastal recession model of soft rock cliffs. Geomorphology, 177, 128-143. https://doi.org/10.1016/j.geomorph.2012.07.020

González-Herrero, S., Barriopedro, D., Trigo, R.M., Lopez-Bustins, J. A., & Oliva, M. (2022). Climate warming amplified the 2020 record-breaking heatwave in the Antarctic Peninsula. Commun Earth Environ 3, 122. https://doi.org/10.1038/s43247-022-00450-5

Gorodetskaya, I.V., Durán-Alarcón, C., González-Herrero, S., Clem, K. R., Zou, X., Rowe, P., ... & Picard, G. (2023). Record-high Antarctic Peninsula temperatures and surface melt in February 2022: a compound event with an intense atmospheric river. npj Clim Atmos Sci 6, 202. https://doi.org/10.1038/s41612-023-00529-6

Oliva, M., Navarro, F., Hrbáček, F., Hernandéz, A., Nývlt, D., Pereira, P., Ruiz-Fernandez, J., & Trigo, R. (2017). Recent regional climate cooling on the Antarctic Peninsula and associated impacts on the cryosphere. Science of the Total Environment, 580, 210-223. https://doi.org/10.1016/j.scitotenv.2016.12.030

Roland, T.P., Bartlett, O.T., Charman, D.J. Anderson, K., Hodgson, D. A., Amesbury, M. J., ... & Fleming, A. (2024). Sustained greening of the Antarctic Peninsula observed from satellites. Nat. Geosci. 17, 1121–1126 (2024). https://doi.org/10.1038/s41561-024-01564-5

Sunamura, T. (2015). Rocky coast processes: with special reference to the recession of soft rock cliffs. Proceedings of the Japan Academy, Series B, 91(9), 481-500. https://doi.org/10.2183/pjab.91.481

Turner, J., Lu, H., White, I., King, J. C., Phillips, T., Hosking, J. S., Bracegirdle, T. J., Marshall, G. J., Mulvaney, R., & Deb, P. (2016). Absence of 21st century warming on Antarctic Peninsula consistent with natural variability. Nature, 535(7612), 411-415. https://doi.org/10.1038/nature18645

Violante, C. (2009), Geohazard in Rocky Coastal Areas. The Geological Society, London, Special Publications, 322, 1–31. https://doi.org/10.1144/SP322.1 

Dear Editor of The Cryosphere Ms Reese,

Regarding the manuscript TC in EGUsphere

Title: Evidence and interpretation of non-linear recession behaviour in a periglacial cliff at Port Foster, Deception Island (South Shetlands, Antarctica)

Author(s): Carlos Paredes et al.

MS No.: egusphere-2025-3269

MS type: Research article

Once the public discussion process for this paper was complete, with the responses to the comments from the reviewers and the community sent, we explicitly finalised the response, in accordance with your instructions.

The team of authors and I remain at your disposal to answer any questions you may have, and we await your decision on our work.

If approved, we will proceed to incorporate the responses, suggestions, and comments from the reviewers, in addition to yours.

Sincerely.