| 09 Jul 2026
Impacts of record Antarctic sea ice losses in 2022–2023 on swell-induced flexure of ice shelves
Abstract. Recent case studies have highlighted regional loss of Antarctic sea ice triggering large-scale ice shelf calving events, by allowing damaging ocean swell to reach shelf fronts. Thus, the dramatic and widespread loss of Antarctic sea ice in recent years has implications for the stability of ice shelves. Here, observations and models are used to conduct a broad assessment of changes in swell-induced flexural stress levels experienced by Antarctic ice shelves, with a focus on the record sea-ice lows of 2022 and 2023. Daily time series are constructed for effective lengths of the sea-ice barriers protecting fourteen Antarctic ice shelves, and for the incoming swell, along with yearly values for shelf front thickness, over a decade leading up to and including 2022–2023. The flexural stress levels are generally found to be far greater in 2022 and 2023 than the preceding eight years, and this is shown to be primarily driven by sea-ice loss, although sometimes mitigated by reduced peak periods of incoming swell. Further, it is shown that flexural stress anomalies are strongly correlated with anomalies in effective sea-ice length and peak period, and that an increase or decrease in flexural stress can be predicted by relative changes in sea-ice length and peak period. The findings indicate that more Antarctic ice shelves will become susceptible to enhanced swell-induced flexural stress if sea-ice losses and ice shelf thinning continue. Under these scenarios, predictions are made of when flexural stress will become a dominant contributor to total ice shelf stress for each of the fourteen ice shelves studied.
General comments:
This is easily the most compelling, sophisticated and convincing manuscript I have encountered on the topic of ice-shelf/sea-swell interaction. The manuscript uses sophisticated, creative analytical methods and employs the state-of-the-art data sets. The manuscript is well written and well proof read.
I have no significant questions or challenges to bring up in my review. I regard the manuscript as being very valuable and will be likely read, cited and used as inspiration going forward.
specific comments:
line 34, page 2 “sea ice, in the form of both stationary consolidated face ice and moving pack ice, creates a barrier that” should face be “fast”?
page 2, somewhere in the introduction, it might be worth pointing out that there have been some studies supporting speculation that periodic ice-shelf features, like the “rolls” found on the Ward Hunt Ice Shelf in the Arctic, have an effect that prevents transmission of sea swell with certain frequencies into the wider ice-shelf region. There has been speculation that the only remaining elements of the Ellesmere Ice Shelf witnessed by European explorers in the mid 1800’s are the ones that have these rolls and are thus more robustly protected from sea swell associated with changing Arctic sea ice since the Little Ice Age and into the present day.
A reference to the above: Nekrasov P, MacAyeal DR. Ocean wave blocking by periodic surface rolls fortifies Arctic ice shelves. Journal of Glaciology. 2023;69(278):1740-1750. doi:10.1017/jog.2023.58
page 5 line 85. I’m not sure I understand what a “percentile” variable is… is it a single scalar number or is it a set or population of grid points satisfying some criterion. Perhaps an explanation is not needed due to my not being facile with this, but maybe a comment would help.
Actually many of the variables being described in the well written, but terse algorithm sections are subject to potential misinterpretation by people trying to follow in the footsteps of this study. Perhaps a sentence or two (could be in supplemental material) on what constitutes each variable (is it a set, a population, a scalar, a vector, a parameter?) would help.
Figure 2: it is worth pointing out that some attenuation by the arrangement of ice out in front of the ice shelf front may be also due to Bragg scattering, a la the same process as “rolls” on the Ellesmere Ice Shelf.
Page 11 - It may be worth indicating why thin ice shelves can get >100 kPa vs. thicker ice shelves being more like 10 kPa. Why does flexure stress increase with decreasing thickness… just a basic principle or idea can be mentioned for the curiosity of the reader who may not have experience with this.
page 20 - sometimes p-values and sometimes rho-values appears. Are these different?
Conclusion - It might be worth mentioning that seismological methods might be able to assess damage that is associated with increasing flexural fatigue of the various ice shelves, and give a simple citation that interested readers could follow. It may be that seismological monitoring of ice shelves could assess the damage of increasing sea swell effects in the Antarctic ice shelves.