An Application of Sea Ice Tracking Algorithm for Fast Ice and Stamukhas Detection in the Arctic

Round 1

Reviewer 1 Report

This is a great and timely study that aims to provide an automated method of fast ice detection. I only have a few comments aimed at improving the paper. 

1) Along with a code make sure to have well-written documentation outlining all tunable algorithm parameters, their acceptable ranges, and how specifically the tuning was done, i.e. what quantitative metric was used to find an optimal parameter. This is necessary to help those who'd be using your work in the future for a different region and would likely need to retune many parameters.

2) The statistics of differences between the AARI and SAR-derived fast ice is great but it is not clear if this is a large difference or not; e.g. depending on the metric chosen and the process under investigation, one could find that the two methods either agree well of disagreeing substantially as to give different conclusions. So it is necessary to include several relevant statistical quantities about the fast ice and compare these statistical quantities using AARI and SAR-derived data. For example, the authors mention in the introduction that the areas and timing of fast ice are changing with climate: are both of these effects captured with both methods? How about the seasonal evolution for a given year: could you plot the time series of the fast ice area for example? do they look similar? Basically, identify the key quantitative metrics that are derived from the new and old fast-ice datasets and make a statistical comparison.

3) It would be useful if you could provide a map highlighting regions in the entire Arctic Ocean where the SAR images exist with a minimum necessary time separation such that your algorithm can be used. Is it virtually everywhere in the Arctic  or are there significant gaps in sar coverage that the method can be used only in specific locations?

4) the writing is clear nearly everywhere but some spellchecking is necessary; in the introduction and elsewhere, make sure not to switch tenses from past to present within the same paragraph. 

5) Finally, I'd suggest the authors to develop and publish the dataset of the detected fast ice for all available SAR data (only the algorithm) such that anyone could study this new dataset directly, without having to reproduce the algorithm.

Thank you for your efforts!

Author Response

Dear Reviewer 1,

thank you for your constructive comments which helped us improve the manuscript and make the algorithm easier to use for the scientific community. We address all your comments point-by-point. Please see the attachment.

On behalf of all co-authors,
Valeria Selyuzhenok

Author Response File: Author Response.pdf

Reviewer 2 Report

Review of manuscript by Valeria Selyuzhenok and Denis Demchev

This is a generally well-written manuscript that addresses an important gap: it provides a technique for full automation of landfast sea ice extent retrieval based on SAR image pairs. Its techniques have wide applicability, and the methodology proposed is suitable. 

I have three major comments which prevent me from recommending publication at this time, but I am confident that the authors can overcome these in a revision. 

I list many other minor comments below this.

Well done to the authors on progressing work in this important field. 

Major:

1. The choice of 150 m displacement threshold seems arbitrary. Was there sensitivity testing to this threshold? Does it depend on the underlying image resolution (i.e., does it differ between Sentinel-1 and ENVISAT?)
2. You cross-comparison between your fast ice edge and the AARI charts shows, in general very poor performance! E.g., Fig 5d: Your technique misses around half of the fast ice. Originally, I couldn’t understand the disconnect between this apparent poor performance vs the good metrics you discuss in Table 1 and Figure 7. But then it occurred to me: Your figures 5 and 6 don’t show the edge of the swath overlap. This is very misleading, and originally made me think your technique had poor performance. Figures 5 and 6 NEED to show the edge of the SAR swath overlap. Without this information, it’s impossible for a reviewer to assess your claims in Table 1 and Fig 7. 
3. Similarly to point 2, Figs 5 and 6 NEED to show the edge of the AARI ice charts (which I suspect end at 160 E).

Minor: 

The English is pretty good throughout the manuscript, but there are limited occurrences of unnatural sounding phrases - e.g., L59-60, L112-113.

Title: I’m not so familiar with the word, but stamukhas isn’t capitalised whereas all other major words are.

L40 - 41: This should be upfront in the first paragraph. 

L66: Change made to make.

L78: Change C-SAR to C-band SAR.

L82: Change is to are (data are plural).

L86: You never mention which mode (resolution) imagery is used here.

L97: It’s worth mentioning here that the AARI charts are done with less objectivity than what you do here. As such, I wouldn’t necessarily refer to them as “validation”. I haven’t used the AARI charts before, but I know the US NIC charts are, at times, completely wrong for the fast ice edge (in the Antarctic, anyway)! What I’m trying to say is, your product is probably a better measure of fast ice than the AARI charts. So don’t call them “validation”, maybe “cross-comparison”.

L103: The names for steps 2 and 3 are inconsistent with names used later in the text.

L107: Reference 20 didn’t use SAR. I think you meant reference 21. And now you can guess who this reviewer is!

L114, and other places: You refer to the SAR signal as weak. But I think you mean homogeneous. Also here, replace “unrecognizable” with “indisctinct”

Around 117: It would be nice to compare this technique with that of Li 2020 (10.1016/j.rse.2020.111736) and Kim 2020 (https://doi.org/10.1016/j.rse.2020.111782).

Fig 3 caption: shoes to shows.

L179: Sentinel typo.

Fig 5: Even with the two lines on panels a and b, I think there are only 6 maps shown here. You said there should be 7.

Conclusions: This information about stamukhas is new here (e.g., 10 km part isn’t shown in the manuscript). Can’t have new information in the conclusions. 

L265: Capital A in Arctic.

Conclusion: Could you comment on applicability to Antarctic fast ice? I assume the presence of grounded icebergs mean this technique can’t be used in those areas?

Author Response

Dear Reviewer 2,

thank you for your constructive comments and efforts to mark out the spelling and grammar mistakes.

Best regards,
Valeria Seluyzhenok on behalf of the co-authors

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thank you for addressing my first round of comments - well done. The results are much more supportable with the swath overlap added. 

Author Response

Thank you for your efforts!