Please see attached PDF

See attached.

General comments

The paper is interesting and introduces an empirical algorithm for detecting and monitoring the ice slab regions across the entire Greenland by using Sentinel-1 products. The text is well written and easy to understand. It opens by introducing the scientific problem, the physical mechanism upon which rely the algorithm (interaction between electromagnetic waves and the ice sheet), the regions excluded from the analysis to limit the noise in the problem, and the algorithm itself, along with the methodology for setting up the thresholds. Then it keep on with a suitable description of the results along with a fair discussion about these achievements and the uncertainties in the process. A comparison with previous mapping done with SMAP is also provided. I haven’t found any major issue for the paper publication however I feel that some points should be improved before to proceed.

Specific comments

• The description of the “ten-fold cross-validation scheme” is quite convoluted and not straightforward to understand. It has to be improved.

Minor points

• In several points of the text: I would refrain from the use of statements like “excellent agreement” and prefer something more mild as “fine agreement”.
• lines 65-66: the sentence “…the depth-integrated surface echo measured by the instrument contains information about the near-surface structure” is usually true, however C-band SAR data can be affected also by phenomena originating deep in the ice. For instance subglacial Vostok Lake, Antarctica, clearly visible in the Radarsat image map of Antarctica. I would say something like “…contains information mainly about the near-surface structure”.
• line 78: delete the s at “cms”. It is a SI symbol and doesn’t require the s for the plural.
• Figure 1: the image of Greenland with the A-A’ transect is very useful but must be better highlighted. As it is put, it gets unnoticed since the reader attention goes immediately to the top or bottom panel which are full of colors. Instead the map should be seen first. An option could be moving the top panel legend northwest, and then replace it with the Greenland map. Anyhow any different solution is fine.
• Line 120: what “Agency” means? Also at line 138.
• Line 127: I notice that speckle filtering is not considered in the processing chain while it is a fundamental step for SAR processing at high resolution. Is there a justification for not applying it?
• Figure 2, caption, third line: “We excluded all the regions outside…” I suggest using a positive sentence as in the main body of the paper. “We considered only the regions…” is easier to understand.
• Figure 2, caption: The disclaimer “Contains modified Copernicus Sentinel data 2016-2017, processed by ESA.” makes the text heavy and is not informative at all. I suggest putting the disclaimer in the References and leave here a citation (or write a footnote). The same apply to Figure 1 caption.
• Figure 3, top panel: the colormap of the image makes it difficult to be read given it compress the almost entire information in dark similar colors (F1>0.2). A different colormap should be used.
• Line 332 and on: actually high-resolution data from PALSAR sensor (either onboard ALOS and ALOS-2) are already available without the need of waiting for NISAR or ROSE-L. Perhaps the issues are the full coverage of GrIS, the data of acquisition or the price of the products. I think the sentence can be better formulated.