the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Jul 2025
The influence of ocean waves on Antarctic sea-ice albedo and seasonal melting, and physical-biological feedbacks
Abstract. Identifying the processes that drive the rapid climatological retreat phase of Antarctica’s annual sea-ice cycle is crucial to understanding, modelling and attributing observed trends and recent high variability in sea-ice extent, and to projecting future sea-ice conditions and impacts accurately. To date, the rapid annual retreat of Antarctic sea ice each spring–summer has been largely attributed to lateral and basal melting of ice floes, enhanced by wave-induced breakup of large floes. Here, based on observations and modelling, we propose that waves play important additional roles in generating previously-neglected surface and interior melting, by removing snow from small floes, flooding them, and pulverising them into slush. Results here show a resultant estimated reduction in albedo by 0.38–0.54, that increases melting by 0.9–5.2 cm day-1 at 60–70o S compared to a snow-covered floe of first-year ice, and depending on surface type, wave-flooding coverage, latitude and ice density. Rapid proliferation of algae within and on the high-light and high-nutrient environment of the wave-modified ice reduces the albedo by a further 0.1 to increase the melt-rate enhancement to 1.1–6.1 cm day-1. Melting is further accelerated by a wave-induced ice–albedo feedback mechanism, similar to that associated with Arctic melt ponds but involving seawater rather than freshwater. This positive feedback is strengthened by ice-algal greening. Floe thinning and weakening by wave-melting initiate additional dynamic–thermodynamic feedbacks by increasing the likelihood of both wave-flooding and flexural breakup, leading to further floe melting. Wave melting and the associated physical–biological feedbacks will likely increase in importance in a predicted stormier and warmer Southern Ocean, and will also become more prevalent in a changing Arctic. There are implications for global weather and climate, the health of the ocean and its ecosystems, fisheries, ice-shelf stability and sea-level rise, atmospheric and oceanic biogeochemistry, and human activities.
Competing interests: Klaus Meiners is on the editorial board
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.- Preprint
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RC1: 'Comment on egusphere-2025-3166', Anonymous Referee #1, 15 Aug 2025
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Review of “The influence of ocean waves on Antarctic sea-ice albedo and seasonal melting, and physical-biological feedbacks” submitted by Massom et al., to The Cryosphere
Recommendation: minor revision
This manuscript is highly appropriate for The Cryosphere as it addresses fundamental cryospheric processes with large implications for climate modelling and polar oceanography.
The manuscript presents a paradigm shift by identifying and quantifying previously neglected wave-driven processes that dramatically accelerate seasonal ice retreat through coupled physical-biological mechanisms. The authors challenge the long-held view that Antarctic sea ice loss is primarily driven by lateral and basal melting, instead demonstrating that ocean waves play crucial additional roles in surface and interior melting through six distinct processes: wave overwashing, buffeting/ponding, deformation ponding, compression flooding, pulverisation, and algal greening.
Despite scare observations due to the inherent challenges of Antarctic fieldwork, the authors have collated and synthesized existing data to make a compelling case that these wave processes reduce ice albedo by 0.38-0.54 compared to snow-covered ice, resulting in extraordinary melt rate enhancements of 0.9-5.2 cm day⁻¹, with biological effects pushing this to 1.1-6.1 cm day⁻¹. The research identifies four positive feedback mechanisms that create self-reinforcing cycles of ice destruction, addressing a critical gap in current climate models, which account for wave effects on floe size distributions but completely miss these thermodynamic and biological processes that may explain why Antarctic sea ice can disappear so rapidly each summer.
Given the inherent challenges of Antarctic fieldwork, the authors' synthesis approach is appropriate. The quantitative estimates, while preliminary, provide essential first-order approximations that will guide future research. The lack of observations reflects the broader challenge of Antarctic research, and the authors appropriately frame this as a first estimate intended to stimulate further investigation. Nonetheless, the work highlights poorly understood processes with profound implications for planetary albedo, global climate feedbacks, and the accuracy of future climate projections in an increasingly stormy Southern Ocean.
I have some minor suggestions to improve the readability of the manuscript.
The terminology is quite complex and sometimes inconsistent. For example:
- I initially found it difficult to get my head around the terminology, e.g., how wave flooding related to the other terms, and especially that it was an umbrella term and not the same as wave compression flooding.
- Clarification on boundaries and distinction between processes. For example, buffeting/ponding and deformation ponding both describe wave-induced surface depressions filled with seawater. Is there a difference between “wave ponds” and “wave-deformation ponds” that warrants this distinction (or could they all be described as “surface-saline ponds” following Ackley and Sullivan, 1994?). I get that one is caused by water splashing over the edges of the floe to get trapped, and the other is caused by the floe being pushed down so it floods from below, but is there an important distinction to the pond that is formed in terms of seasonal melting? An additional confusion is that on line 266 you describe how rafted ice blocks also affect wave pond formation by decreasing freeboard. Could you clarify the importance of the distinctions? If they are distinct, does it make better sense to have wave-buffeting ponding and wave-deformation ponding? i.e., why is one described as 2 separate processes and the other described as 1 process?
- Inconsistent naming, e.g., “wave buffeting” vs “floe-floe buffeting” - why not stick to one term? Please standardise terminology throughout
- It would be helpful to clarify which processes are subprocesses, e.g. churning appears to be a subprocess under wave pulverisation.
- It could be helpful to give the reader a hierarchy of the terms. I provide a suggestion as an example at the end of the review, but this probably needs refining. It would be helpful to be clear on which processes are subprocesses, e.g. churning seems to be a sub-process under wave pulverisation.
Specific comments:
Line 40: consider calling the "wave-induced ice-albedo feedback" a “wave-driven ice-albedo feedback” to match your definition on line 88.
Line 395: please link to Table 1b and/or Table 2 to explain where you got these 4 albedo classes to aid the reader, i.e. different types of wave-modified ice surfaces with increasing levels of albedo reduction.
Line 555: consider calling the “open water-sea ice feedback” and the “ocean-ice albedo feedback” from line 109 the same thing?
Line 567: consistency with the names of the feedback processes to aid readability
Figures and tables:
Figure 3 - I know it is defined on lines 196 and 389, but please define fw on the figure or caption. Suggestion for the caption to make it easier to read and incorporate this information: Wave-driven sea ice melt rate enhancement showing dramatic increases in melting (1-6 cm/day extra) caused by wave flooding and albedo reduction. Results shown for three wave coverage fractions (fw = 0.33, 0.5, 1.0) and four surface darkening scenarios (Δα = 0.38-0.64) across Antarctic latitudes (60-70°S) during austral summer (Nov, Dec, Jan).
Is there a particular reason why you did not include the biological feedbacks in figs 5 and 6 like you did in fig 4? Surely the biological feedbacks work in the same way to enhance all three dynamic-thermodynamic feedbacks?
Overall assessment: This manuscript represents important foundational work that successfully integrates physical oceanography, glaciology, and marine biology to reveal previously hidden mechanisms driving Antarctic sea ice dynamics. While the terminology issues need addressing, the scientific contribution is substantial, and the framework provided will guide future observational and modelling studies. The work appropriately acknowledges its preliminary nature while making a compelling case for the significance of these wave-driven processes.
Hierarchy of new terminology:
WAVE MELTING (Overall concept)
- WAVE FLOODING (Physical inundation processes)
- Wave Overwashing
- Wave Buffeting/Ponding
- Wave Deformation Ponding
- Wave Compression Flooding
- WAVE PULVERISATION (Mechanical breakdown)
- Churning and fragmentation
- WAVE GREENING (Biological processes)
- Algal proliferation and darkening
Citation: https://doi.org/10.5194/egusphere-2025-3166-RC1 -
RC2: 'Comment on egusphere-2025-3166', Anonymous Referee #2, 21 Aug 2025
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This manuscript describes and estimates the contribution of previously overlooked wave-ice processes to Antarctic seasonal sea ice melt and growth, further enhanced by ice-algal feedback. It details seven wave-driven processes: wave overwashing, wave buffeting, wave ponding, wave deformation ponding, wave compression flooding, wave pulverization and wave greening.
It synthesizes observational data from previous studies to provide estimates of melt rate enhancement from wave-driven processes. The authors acknowledge and highlight that a key limitation in this study is the lack of in-situ and remote observations, and make it clear that the presented quantities are estimates that do not evidence a tangible contribution of these processes to sea ice variability but instead provide motivation to further investigate this. This manuscript is appropriate for The Cryosphere as it addresses previously neglected sea ice processes, providing new insight into Antarctic sea ice variability, with important potential implications for climate modeling.
Major comments:
The focus of the paper is on the existence of these potential physical impacts and asserts a rather broad scope (as evidenced by the title). However, as the authors note (L505), they do not examine their large-scale impact. Thus it is hard to understand the overall importance of these effects, and whether they are spatially or temporally confined to highly specific circumstances. There do exist simulations and observational products that capture the large-scale existence of waves in sea ice, as well as ecology, lead fraction, etc., so many of the required datasets are in existence. I think using these datasets is essential to supporting the claims made in the paper as to the potential existence of feedbacks. Otherwise, it is important to narrow the scope of the paper to simply reanalyzing existing limited datasets by changing the title and abstract to better reflect the analyses conducted in the manuscript.
The title impresses upon the reader that the study is an investigation on the influence of waves on seasonal melt and biophysical feedback. However, the final estimated melt-rate enhancements describe a local, immediate influence and do not allude to the significance of such contributions on longer and larger time-scales. It is thus unclear to what extent these wave-driven processes have influence on a regional or pan-polar scale. Some quantification of the percentage contribution of these wave-driven processes relative to seasonal melt/growth rate would be helpful. I suggest presenting a realistic case study or example to demonstrate that the contributions of these processes can considerably account for better calculations of sea ice variability would offer the audience more conviction in the ideas put forth in this manuscript. The methodology for calculating this has already been described in L195-200. While the authors specify this to be out of scope for the study, I think it would provide more compelling evidence to these processes enhancing sea ice melt. .
While being a key component of this manuscript’s title, the ice-algae-albedo feedback (S4.3) lacks supporting evidence to be proposed and is relegated to the discussion section. The results section only draws comparisons of green and non-green wave slush and wave pond, but does not provide indicative evidence of a feedback over time. Suggestion to include time-varying observations that demonstrate this feedback mechanism in the results. For example, comparing the changes in albedo or melt rate between green and non-green ice over time. Otherwise, alternative evidence needs to be provided.
The “wave greening” (S3.1.6) and “ice-algae-albedo feedback” (S4.3) appear to be overlapping, with the former being both a secondary effect of the previously-defined wave-driven processes and an initiation of the latter. A suggestion to remove wave greening as a seventh process.
Minor comments:
- The manuscript is verbose and often reads like a review, which distracts from the key outcomes of this study that may not require them.
- . Suggestions to make Section 1 and sub-sections in Section 3 more concise.
- For example, in the abstract, L40-41: Suggest to rewrite to “by a wave-driven ice-albedo positive feedback mechanism, strengthened by ice-algal greening”
- Figure 1: The capital letters on Fig 1(a) and (c) are not described in the figure caption or in-text. I suggest either removing these or describing them in the caption to improve clarity.
- Figures 5 & 6: Can these figures be combined as two panels side by side? Was there a deliberate decision to leave out the coupled biophysical ice-algal feedback in these two diagrams?
- Tables 1-3: Even though it is defined in the figure captions for Tables 2 & 3, I suggest that adding a sub-column on the left of Table 1 denoting the respective types A-D would make it easier for the audience to contextualize across the tables.
- The manuscript introduces a lot of terminology that are sometimes inconsistent:
- L212: “wave compression flooding”; Figure 2 caption: “wave-compression flooding”
- L216: wave slush; L270: wave slush ice
- L323: “floe oases”; L628: “mini oases”
- “Wave-driven” and “wave-induced” are used to describe different processes and also used interchangeably (e.g. L545 & L548)
- L514: the term “rotting from within” is not used again later in the manuscript.
Citation: https://doi.org/10.5194/egusphere-2025-3166-RC2
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