the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Oct 2026
Wave-induced erosion and notch development at the Fimbul Ice Shelf front
Abstract. Ocean waves erode the waterline of Antarctic ice-shelf fronts and carve a thermo-erosional notch. The notch is hidden from satellites, yet it preconditions front collapse and footloose calving, so the link between notch growth and observable front retreat matters for how wave-exposed ice shelves lose mass. We study this link at the Fimbul Ice Shelf, East Antarctica, in January–February 2024. The widely used White et al. (1980) erosion formulation is extended in two directions: a component-wise spectral treatment of irregular seas, and a breaking-aware wave profile that accounts for shoaling over the submerged ice foot revealed by remotely operated vehicle (ROV) profiling. Forced with hourly ERA5 waves, the extended model predicts about 110 m of cumulative waterline erosion over the matched 7 January–27 February window. Satellite observations show considerably more retreat: about 264 m from an S1-guided Sentinel-2 plateau-break method, and 266 m from manually digitised Sentinel-1 fronts over a slightly longer window. Under the baseline assumptions (α = 1, ΔTwi = 1 °C), the model therefore falls short of the observed retreat by a factor of about 2.4. Part of this residual may be hydrodynamic, since post-breaking turbulence is not represented; part may be mechanical, because collapse and footloose calving can convert notch erosion into larger observable retreat. Unmeasured near-ice thermal driving remains a first-order uncertainty, and front-position observations alone cannot separate these contributions.
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Status: open (until 20 Nov 2026)
- RC1: 'Comment on egusphere-2026-4610', Anonymous Referee #1, 21 Oct 2026 reply
Data sets
Ice-Shelf Wave Erosion - Fimbulisen Analysis Code (processed ice-front positions and derived retreat series) Wenjun Lu https://doi.org/10.5281/zenodo.21622437
Model code and software
Ice-Shelf Wave Erosion - Fimbulisen Analysis Code Wenjun Lu https://doi.org/10.5281/zenodo.21622437
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General comments
This paper aims to rigorously model the erosion of the front of the Fimbul ice shelf due to notch development and footloose calving, extending the White et al (1980) LWT approach to unprecedently modelled irregular seas and shoaling and breaking waves. Models are forced by boundary conditions assumed using a Remotely Operated Vehicle (ROV) profiling measured in front of the ice shelf in January-February 2024. Results are compared to satellite observations of the ice front retreat from Sentinel-1 and Sentinel-2.
The authors claim that the theoretical extensions of the LWT formulation are general and can be applied to all wave-exposed ice shelves, if properly constrained/parametrized. This paper has the potential to significantly impact on the scientific community, improving projections of ice discharge and its contribution to sea level rise by representing unprecedently modelled wave-induced frontal erosion in ice-sheet parametrizations.
However, it is unclear how easily the proper parametrization can be applied to all ice shelves fronts, as it has been set up here using in situ measurements from a specific ice shelf. I understand that the purpose of this article is to develop a method that can be widely applied and to draw general conclusions about the relationship between notch growth and the observable retreat of the glacier front. An analysis of the physical and thermodynamic processes observed specifically on this Fimbul glacier platform would significantly strengthen the scope of the results presented by the authors. What do your results say about this ice shelf? Is this erosion seasonal? When is it most intense? Is it even observed when there is sea ice present? What is the link to the local oceanic and atmospheric forcings that affect this ice shelf?
The method used is structured and provides mathematically accurate answers to fundamental scientific questions. A great deal of effort has been made to ensure that this work is reproducible. The figures are clear, the scientific questions are well-formulated, the technical discussion is very in-depth. The models developed in this article are compared with those used previously in order to assess past estimation errors.
Specific comments
Please find below a series of specific questions that would help highlight the impact of your results, determine the extent to which they are reproducible on a large scale, and assess their contribution to our understanding of the mechanical processes involved in the calving of ice shelves:
Technical comments
L35 «Although such spectral extensions”: What are you referring to when you say “such”?
L47 “SAR”: To define.
L50 “surf-zone”: To define.
L48-51 “Under the baseline thermal and calibration assumptions, the modelled waterline erosion is smaller than the observed front retreat. The residual may reflect coupled post breaking surf-zone hydrodynamics and fracture-controlled front collapse, including footloose amplification, while uncertainty in the unmeasured near-ice thermal driving limits quantitative attribution. ” : Are these the limitations of current wave erosion models that you are referring to? Is this a conclusion of your study? If so, do not include it in the introduction. If not, where do you get these claims from?
L116-117 “JONSWAP spectrum” : Can you explain why you use this model, and explain with words what this model represents? Something like: " The JONSWAP (Joint North Sea Wave Project) spectrum is an empirical relationship that characterizes how wind-driven wave energy is distributed across different frequencies in the ocean. It applies to seas that are still developing due to wind influence."
L127 “Hs and Tp:”: End the sentence here. Your sentence was too long.
L128 “zero-upcrossing procedure”: To define.
L203 “3.3 Field site and forcing data”: Could you give more information about the ocean/wind circulation in front of the Fimbul Ice Shelf? It is dominated by Easterlies in the open ocean and there are katabatic winds circulating from inland towards the ice front. How do these strong winds affect wave behavior? What water masses are circulating at the front of the ice shelf at the surface and deep inside the water column?
L206 “austral summer”: Are the surface temperature observed during this summer normal? Exceptional? What average temperature is it?
L220 “−1.9◦C”: Is there a paper that has helped observe or prove what you're claiming? Is this a commonly accepted or used value?
L230 “EW mode”: You defined EW later but you us the abbreviation here. To define here or delete this detail.
L231 “S1-guided near-infrared gradient algorithm”: Is it an algorithm that you wrote? That already exist? Explain.
L244-246 “This guidance absorbs two sources of ambiguity: the S1 delineations themselves carry uncertainty where storms or brash ice obscure the true ice face, and the front can shift between the S1 and S2 acquisition days — retreating through sudden collapse or advancing with the background ice flow.”: How do you deal with that?
L290 “episodic peaks”: What is the frequency of these episodic peaks?
L399 “Wave-energy dissipation is ultimately converted to heat, but any local temperature increase depends on the dissipation volume, residence time, mixing, and advection, and cannot be quantified from the available observations.”: Why can’t we quantify that?
L480 “5.7 Implications for ice-sheet modeling”: To what extent are your models applicable to large-scale modeling? Are they representative of the conditions observed at all ice-shelf fronts? Do the profiles measured by the ROV provide a good estimate that can be extrapolated to other ice shelf fronts and used as reliable boundary conditions, or must every ice foot and every ice front be measured in order to use your models?
L531-533 “While this study is specific to Fimbul Ice Shelf, the theoretical extensions are general: spectral decomposition and the breaking-aware shoaling profile can be applied to wave-exposed ice fronts with open-water fetch, subject to the stated propagation assumptions.”: This is very important and highlight the reproducibility of your work for other locations. It would make a lot of sense to notify that also it in "5.7 Implications of Ice Sheet Models".
Figure 2.b: Add a plot that shows the exact location of the ROV measurements at the front of Fimbulisen. Or mention that the location is on Fig.4.
Figure 3. “db”: Where is db on the figure? Indicating this in the figure would make it easier to visualize the configuration of your model.
Figure 4.: You can maybe show the location of the grounding line, to help easily identify where the ice is floating and where it is grounded. You can also show the track of the ROV where measurements were made.
Figure 10.: It is confusing that the irregular, non-breaking modeled line and the S-2 area- based line are the same color (teal).