**General Comments**

This manuscript presents a comprehensive assessment of grounding zone (GZ) dynamics across the Amery Ice Shelf (AmIS) using the Differential Range Offset Tracking (DROT) method. The authors produce a spatially extensive dataset of 32 grounding line (GL) positions over a 1,172 km stretch of coastline during 2021, allowing for the characterization of both short-term tidal GL migration and localized long-term retreat. A notable strength of the study lies in its systematic comparison of DROT-derived GLs with independent datasets, including contemporaneous DDInSAR measurements and long-standing GL products (e.g., MEaSUREs, Synthesized GL), establishing the method’s reliability and its applicability in coherence-limited regions. The use of DROT across such a large region represents a valuable technical advancement and offers significant potential for extending GL monitoring coverage elsewhere in Antarctica.

However, while the study is methodologically robust and offers a valuable GL dataset, its interpretation of GL migration modes and grounding zone width correlations shows limited novelty in light of recent work. In particular, the identification of linear, threshold, and asymmetric migration modes largely replicates the classification framework introduced by Freer et al. (2023), and the reported correlations between GZ width and glaciological parameters (e.g., bed slope, ice velocity) parallel earlier insights from Chen et al. (2023). Consequently, the manuscript’s broader scientific contribution to understanding the controls on GL behavior and GZ morphology is somewhat incremental rather than conceptually new. Nonetheless, this work provides a high-quality observational foundation and demonstrates the utility of DROT for grounding line science.

**Specific Comments**

1. L35–40: Consider elaborating on the specific advantages of the DROT method in this context and providing a brief rationale for its selection over other grounding line detection techniques. This would help clarify the methodological motivation at an early stage in the manuscript.
2. L220–222: It would be helpful to clarify the basis on which the GL migration along profile 4 is interpreted as permanent. Specifically, how does Figure 2d/Figure 1c support the conclusion that the observed inland migration exceeds short-term tidal variability?
3. In the phase legend of Figure 3a, it is recommended to use 180° instead of 3.14.
4. For Figures 3b–c, it is recommended to display the grounding lines derived from both methods simultaneously within the same panels, if feasible. This would enable a more direct and intuitive visual comparison between the results.
5. Section 3.2 – Comparison with Other Grounding Line Measurements: It is recommended that the authors consider incorporating a comparison with the dataset available at https://nsidc.org/data/nsidc-0778/versions/1. This product, part of the MEaSUREs program, provides a continent-wide map of short-term grounding line migration zones derived from InSAR during 2018–2020. Given its closer temporal proximity to the 2021 DROT results presented in this study, it would serve as a valuable reference for contextual validation and potentially enhance the robustness of the comparative analysis.
6. L304: The manuscript states a typical offset of 1.5 km between DROT- and DDInSAR-derived grounding lines. Could the authors clarify whether this value represents an average across specific regions? Additionally, the observed differences in this study appear smaller—what factors might account for this discrepancy, and how spatially consistent are these deviations across the Amery Ice Shelf?
7. L355–359: The interpretation of a positive correlation between grounding line migration distance and the absolute double-differential tide range would benefit from further clarification. Does a lower absolute double-differential tide range necessarily imply smaller ice surface deformation? For instance, if the first and second SAR acquisitions occur at high tides and the third and fourth at low tides, substantial ice deformation may occur, yet the computed absolute double-differential tide range could remain small.
8. L375–377: Figure 2e in Chen et al. (2023) similarly demonstrates that the grounding line position of the Lambert and Mellor Glaciers oscillates between two discrete states over timescales of several months. Also, given that the temporal sampling in the present study is sparser than that of Chen et al., it is possible that some short-term transitions or episodic changes may not have been fully captured.
9. Figure 5b: The synchronized grounding line migration observed for the two glaciers suggests a common driving mechanism. Could this be attributed to tidal forcing, or do the authors propose that subglacial hydrological processes—such as simultaneous subglacial lake drainage or basal melting—could exert a temporally comparable influence on both glaciers? Further discussion on the plausibility of shared controls would enhance the interpretation.
10. L455–456: Is this the reason behind the classification of this island as part of the grounding zone in Figure 1c?
11. L570–571: It would be helpful to specify how the along-profile length over which the slopes are calculated was defined. What criteria were used to determine the extent of the landward and seaward segments used in the slope analysis?

1. Summary and general comments

The presented work shows applications of the Differential Range Offset Tracking (DROT) technique to derive Grounding Line (GL) and monitor its short-term migration on the Amery Ice Shelf (AmIS). The same group of authors have a more comprehensive methodology paper published previously: Wallis et al.: Change in grounding line location on the Antarctic Peninsula measured using a tidal motion offset correlation method, The Cryosphere, 18, 4723–4742, https://doi.org/10.5194/tc-18-4723-2024, where the position of the GL is automatically located by using a threshold applied to the DROT displacement fields.

In the current paper a detailed description of the methodology is given focussing on the DROT. The inland limit of the tidal flexure is this time delineated manually in each of the DROT images which correspond to different tide levels and thus the width of the Grounding Zone (GZ) is obtained. The results are presented in dedicated subsections dedicated to (3.1) GZ width and short-term migration, (3.2) Comparison with other GLs (3.3) short term GL migration patterns (3.4) case studies along the AmIS GL.

While the methodology presented here is not new the strengths of the paper lie in the application on a particular large region (AmIS) confirming the GL migration patterns of (Freer et al, 2023) and assessing the GZ width. This parameter should come with the GL position in order to detect long-term migration of the GL and currently there is no method established so far for it. I find the discussion regarding the factors affecting the GZ width very similar to (Chen et al, 2023, Figure 3), a study focussed on the GL of the main glaciers draining on AmIS and not on the entire ice shelf. A citation in Section 4.3 and a comparison to these findings would be valuable.

The present paper can be shortened, some detailed parts (e.g. described in the previous paper) can be moved to Supplement. Instead graphs in the Supplement (S3 – S5) which are discussed in the main paper should appear here. The novelties of the manuscript, the application of DROT method to >1100 km of AmIS boundaries, can thus be highlighted and its originality emphasized.

1. Specific comments, minor comments & typos

Line 23: The Grounding Line is a product of the GCOS ECV Ice Sheets and Ice Shelves and not an ECV by itself.

https://gcos.wmo.int/site/global-climate-observing-system-gcos/essential-climate-variables/ice-sheets-and-ice-shelves

Line 43: add “atmospheric pressure”

Lines 117, 118 “Sentinel-1A” and “Sentinel-1B”

Lines 147 – 156 The description of the IBE correction is identical to Chen et al, 2023 Section 2. This can be shortened to one sentence with citation.

Line 174 – 175: by using point H you can derive the width of the flexure zone, not the width of the GZ. The width of the GZ as far as I see in Fig 2 and explained in Section 3.1 is the range of the displacement gradient where it begins to exceed zero.

Line 195: The GZ of MEaSUREs- Programme https://nsidc.org/data/nsidc-0778/versions/1 should be mentioned here or in Section 3.2 to refer specifically to AmIS.

Line 201 and Figure 2e Profile 5 seems to have a narrow GZ rather than a wide one (like profiles 14 and 15).  

Line 205 Figure 1c labelling the pinning points a to k may be confused with the labels of the subplots in Figures 2 and 4 (and Supplementary S3 – S5). Maybe use brackets for the subplots e.g. (a), (b), etc.

Line 246 (caption of Figure 3) Please be more precise what concerns the “reference lines”. Are these the GLs from DDInSAR?

Line 258 correct citation (Depoorter et al, 2013b)

Section 3.2 is very long. A comparison between DROT and DInSAR was already shown in (Wallis et al, 2024). Starting with line 257 the comparison with the two published datasets (text and Table 2) may be moved to the Supplement or removed. As already mentioned in the paper these datasets do not have the same time stamp as the DROT GLs since they are based on at least 2 decades older data. The discussion on the bias between DDInSAR and DROT GL position should focus on the 2021 datasets. As mentioned above I suggest also to add here the comparison to the MEaSUREs GZ on AmIS.

Line 291 Swap ocean and land. “landward GL” … refer to the GLs closest to the land.

Line 344 -345 Figure 4 and Figure S3 are almost identical. I suggest to add all profiles (those with no clear mode as well) to Figure 4 in the main text where you discuss all patterns (and delete Figure S3 in the supplement). Figure 4 and Figure S3: how is the “0” of the Y-axis defined?

Line 355 Figure S4; Figure 4l R²=0.83 while in Figure S4q R²=0.84; I suggest to mention that the profiles 7,8, and 17 were selected due to their different migration pattern.

Line 371: … it then transits downstream

Line 665 correct reference for Freer et al, 2023

Freer, B. I. D., Marsh, O. J., Hogg, A. E., Fricker, H. A., and Padman, L.: Modes of Antarctic tidal grounding line migration revealed by Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) laser altimetry, The Cryosphere, 17, 4079–4101, https://doi.org/10.5194/tc-17-4079-2023, 2023.

Supplement

 Figure S1 (b): at high tide the GL moves landward, therefore (Fmax, Gmax) correspond to low tide