Dear Authors,

thanks for replying to the reviewer's comments. Both reviewers have mentioned points that require considerations. I see that you intend to address those. In particular, I would find a more in-depth discussion useful that addresses how this method can be extended to other areas, without the need to tune many ice-shelf specific parameters.

Please provide an revised version, and a track changes version which I will then send out to re-review. Please be aware that I am on fieldwork in Antarctica during mid-December to mid-January.

Kind regards, Reinhard

Dear Authors,

Thank you for submitting your revisions which was positively evaluated in the re-review. The manuscript is now almost ready for publication. Congratulations!

Unfortunately, I do not concur with the reviewer’s judgement of the high presentation quality. Below you will find many comments regarding language, definitions and layout of the manuscript.

In particular, I believe we do not have the same concepts/terminology to describe the different ice dynamic components. Although I understand your desire to differentiate between different mechanisms (e.g. “deformation” and “flow” in equation (1)), I don’t think this is correctly done here (cf comment to L457). Also I believe that InSAR cannot differentiate between those components without external knowledge. This must be worked out more clearly. Another example is that “stress”, “strain” and “strain rates” appear to be used interchangeably but those are surely not the same things.

None of my comments challenge the concepts or findings of the paper, but I still urge them to take them seriously so that the paper can be made more accessible to a wider readership.

Kind regards, Reinhard Drews


L 56 remove „for the first time“. This also doesn’t fit with the reference from 2016.

L 68 “about” -> “around” (?)

L 74 InSAR does not detect “stress field changes”, only if those lead to deformation. Consider rephrasing.

L 95 I don’t think the abbreviation SWIT is needed.

L 110 Again I don’t think InSAR captures “stress”. It captures strain rates related to stress gradients.

Figure 1: Add text “Fig 1c,d” to the white dashed box in Fig 1a.

L 140 I don’t see icebergs being treated here. Remove this example.

L 140 Somehow, I feel this is described more complicated than needed. How can you differentiate in an interferogram between d^{ij}_{LOS} and v^{ij}_{LOS}\Delta^{ij} ? I don’t think you can.

Fig 2a does not show “tidal bending” (nothing is bend here). Replace with “vertical tidal displacement”. Bending only occurs in the grounding zone.

L 166: add “..SAR interferometry captures [the cumulative effect] of spatially…”. Rephrase the stress field component.

L 168 In order for tides to be visible (rather than a constant phase offset) you require a spatially variable tilting of the ice shelf, correct? I don’t understand how you infer that “…the change of vertical position for a given pair of acquisitions shows smooth spatial variations of only a few centimeters”. The interferometric phase lumps all effects (ice-shelf tilting through tides, horizontal ice flow motion,..) together so how do you infer without external evidence that one of the components is small? I agree that horizontal ice-flow is more important than a residual tidal signal in the vertical but the chain of arguments for this is unclear.

L 177 “…crack detection is performed on interferograms containing the information of all three phase components”. This sentence and much of the information in the paragraphs above suggests that you can in theory differentiate between the first three phase components in eq. (1) in an interferogram. I don’t think that this can easily be done (e.g., you would need a model for ice-shelf tilting as a response to spatially variable tides).

L 200 Which DEM is used for the topographic phase correction? What is the effect if the DEM does not capture small-scale variability such as cracks?

L 204 “The phase signal in the interferogram is a sum of the ice motion component, the tidal component and the random phase noise…” . Eq (1) lists four terms, here only three are mentioned. Does this mean one component (supposedly \phi^{ij}_{flow} ) has been removed? I don’t think this is the case. The more I advance through the paper, the less convinced I am that the distinction of \phi^{ij}_{flow} and \phi^{ij}_{defo} is needed.

L 240 All tuning parameters should be explicitly mentioned so that the study is reproducible.

L 247 What is the reason that the 50 m contour line of the TanDEM X DEM is used rather than any published grounding line (e.g., the one displayed Fig 1a)? The clipping will be unnecessarily inaccurate.

L 255 Provide numbers for “small” to keep everything reproducable.

L 319 Here the parameters are provided that I asked for previously. I think this can be presented more succinctly by including the “processing” steps directly in the methods.

L 363 “As already stated above, …” no need to start the sentence like this. Either its worth repeating or it is not.

L 428 remove “))” and “see”.

Figure 10 What does the AA stand for in the title?

L457 “..changes in flow velocity or creep deformation..“. I believe we have different ice dynamic concepts. For me ice-flow has two components one due to internal ice-deformation and one to basal sliding. Both leads to a displacement at the surface. If “creep deformation changes” so does the “ice flow”. I believe what you are trying to distinguish here is “plug flow” (which is the most relevant flow regime for ice shelves with essentially 100% basal sliding and 0% deformation) and other components. Anyway, the way this is written here and also elsewhere repeatedly confuses me.

Later in that sentence only “ice flow” cancels during the doubled differencing. What happens to the “creep deformation” ? Further on in this sentence only the “natural variations…and the deformation” are left in the double differenced interferograms. What do you mean by “natural variations” ? Tides go “naturally” up and down, but this is not what is left in a double differenced interferogram. What is left is the differential tidal signal.

How about something like: “The differential phase of double differenced interferograms is composed out of the differential vertical displacement by tides and time-variable components in the horizontal velocities between the two interferograms.:

Section heading 6.5: Rephrase, InSAR does not see stress field variations. It sees related strain rate patterns.

This entire section starts be reiterating basic concepts of differential interferometry. This should be moved to the methods.

L430 “bulk contribution” seems like an unfortunate term. Define it as “the time-invariant contribution” or something like that.

L 470 Differential interferometry does not “isolate” the signal caused by rifting activity. As stated in the paragraphs before this differential signal still contains other processes (e.g. differential tides). Maybe “amplify”?

L 473 The first interferogram sees the “strain” the second “the stress field” and the third the “fringe pattern”. This is another example where I urge you to use consistent terminology. Please unify the discrepancy of “stress”, “strain”, and “strain rates” throughout the manuscript. Those terms cannot be used interchangeably. I don't think InSAR can pick up any stress patterns.


L 480 “..the observed phase ramp could either correspond to a vertical deformation or to a horizontal displacement..”. I agree, but what about the deformational component that you introduced in eq (1,12)?

L486f Use “the differential phase” when you refer to double differenced interferograms.

L502 “dominates..” -> “..that is larger than the differential tidal displacement in the vertical.”

L526 “iceberg drift”? Icebergs are fully disconnected from the ice sheet. I don’t think this is the case here. Rephrase.

Acknowledgements: Consider thanking the reviewers.

Dear Authors,

thank you for another round of revisions, and thank you for taking my comments into account with a number of changes. From my perspective the paper has further improved and I am now happy to publish it in TC. Congratulations! I hope that other researchers will use and build on your work presented here.

Kind regards, Reinhard Drews