Thaw-Season InSAR Surface Displacements and Frost Susceptibility Mapping to Support Community-Scale Planning in Ilulissat, West Greenland

Round 1

Reviewer 1 Report

The surface deformation caused by freezing and thawing will threaten the integrity of the built environment. In order to fully support the community planning of Ilulissat in western Greenland, this manuscript successfully inverses the average seasonal displacement and long-term deformation rate of Ilulissat using the Sentinel-1 data of the thawing season in Ilulissat from 2015 to 2019 by using the least square inversion scheme. On this basis, they also studied two different methods to infer the measured value of active layer thickness (ALT), and estimated the ice content of the active layer, so as to draw a community-scale ground frost sensitivity map. The research results provide valuable information for risk management and community planning in the Arctic. However, the innovation or improvement of the methods used in this study needs to be further clarified. I encourage further review of the manuscript after minor revisions. Specific suggestions are as follows.

1. There is no explanation why the maximum depth of thawing front modeled by Stefan equation appeared in October 2018, which is more than one month later than the actual measurement results.

2. The format of formula (12) in this manuscript is different from other formulas, please check.

3. The citation format of the manuscript is not standardized, please modify it.

Minor editing of English language required.

Author Response

Dear Reviewer,

Thank you for your feedback and valuable comments on the manuscript. Please see attached our point-by-point response. The manuscript was edited as indicated in the document.

Sincerely,

The Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments are limited to the InSAR component of the manuscript.

The InSAR processing chain describes on pages 5 &6 is common approach, but some arguments should be added justifying only short temporal baselines (6 & 12 days). Extending the temporal baselines to 30 or 36 days would have reduced the residues and better defined the displacement rates. In the same manner, we cannot appreciate the dispersion of those displacement curves estimated from InSAR. Some pluriannual deformation curves as on figure 3, but generated from results data would be beneficial for evaluating the appropriate application of InSAR technique.

Very little information about the impact of the vegetation on the results. What was the impact on the InSAR coherence? Can you relate it to the vegetation density? What was the coherence threshold use for the estimation?

A reference point, corresponding to bedrock, was used for unwrapping the interferograms. Are you sure that was bedrock? Really a stable point? How far this reference point was from the locations of deformation points? Does the use of multi-reference points would have help?

 

Minor points:

P5 L156 and P25 L636 :”a final spatial resolution of 10 m” I think the authors refer to “spatial spacing” not “resolution” which is different. Sentinel-1 has a spatial resolution larger than 10m.

P17 L481: “S has a minimum value of -7.5 cm/yr and is -2.7 +-2.0 cm/yr (μ}1σ)” Displacement unit is “cm” this is not a rate. Also missing a name “ XXX is -2.7”

P17 L490: “The coefficient of determination (R2) was calculated for …” Coeff of determination for which parameter? Long term displacement rate R?

Author Response

Dear Reviewer,

Thank you for your feedback and comments on the manuscript. Please see attached our point-by-point response. The manuscript was edited as indicated in the document.

Sincerely,

The Authors

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

Thank you for well-well written and interesting article. I have a few minor questions and suggestions.

1) Equation 1 does not capture the effect of the grain-particles of the frost. In my opinion, it should have an impact. Can you please comment on this?

2.) Can you please add a sentence describing how you access the quality of the least-squares inversion algorithm. 

3) On page 17, line 499, please replace "Figure 7a and b" with "Figure 7a and 7b".

4) You mention in the discussion section that longer InSAR time series will improve the inversion results. Can you please elaborate how the longer time series will improve the results. Is there a particular trends of interest, or this is just more data produces a better fit?

Thank you!

 

Author Response

Dear Reviewer,

Thank you for your feedback and valuable comments on the manuscript. Please see attached our point-by-point response. The manuscript was edited as indicated in the document.

Sincerely,

The Authors

Author Response File: Author Response.pdf