This paper presents sea ice lead fraction products that are generated from ice motion vector fields that are in turn derived from Sentinel-1 SAR HH data at 50 m resolution. The products include both accumulated divergence and LKF-based lead fractions. The life cycle of sea ice leads and various properties such as lead width have been investigated. The derived lead fractions were compared against various available satellite microwave, optical, and helicopter-based datasets over the region surrounding R/V Polarstern during MOSAiC in March, 2020.

I recommend this paper for publication after the following comments are addressed.

In Line 543 the authors state that “There are also pronounced differences between LF_{classified_SAR} and the divergence-based lead fractions”. Could you comment in the paper if a combination of the two SAR-based approaches (i.e., from SAR-based ice motion and from the SAR image classification) could take full advantage of SAR data, and could lead to an improved SAR-based lead fraction product.

Minor comments:

Line 23. I suggest replacing “fast new ice formation” with “rapid new ice formation” to avoid any confusion with “fast ice” term.

Line 161. Please explain why HV channel was not used for ice motion detection.

Line 194. Beginning of the sentence with “b1 each lead-fraction …” does not seem to be correct.

Line 197. “Next, b1 the lead” does not sound correct

Line 226. “LFLKF” -> “LF_LKF”.

Line 393-394. Remove comma in “56-112,m”, “56,m”, “1500,m”.

Equations 2-3. It seems that lead fraction uncertainty (sigma_LF) should be dimensionless. However, from equations 2-3 it seems to have a unit [s^-1]. Please explain.

Equation 3. It is not clear why parentheses in “(n)” are required.

Line 421. “spatial scale of ΔL=700 m” -> “spatial scale of L=700 m”

Fig. 5a. It is very difficult to distinguish vertical blue bars and the blue line as they are both blue.

Line 512. “by two magnitudes” -> “by two orders of magnitude”.

Lines 560-561. “LFPMW”->”LF_PMW”.

General comments:

Several different lead-fraction products already exist, but the definition of a lead within these products varies with different retrieval methods. The manuscript derives two lead fractions based on sea-ice divergence, which directly connects leads and to their creation process within sea-ice deformation. These two products are evaluated and compared against six existing products along the long the drift of the MOSAiC expedition in the central Arctic Ocean during winter 2019/2020. Thus, the manuscript presents new methods and data for lead fractions. The evaluation focused on the statistical analysis and deformation history of a single lead and several leads for the whole period. The comparison used snapshots of two different days and the whole period as well. With this analysis, several spatial and temporal scales are covered. Overall, this manuscript provides new insights into the deformation history of leads. Additionally, the direct comparison with other existing products highlights the performance as well as the limitations of different products.

The manuscript is very extensive and thorough. The topic fits well in the scope of the journal and I recommend it for publication, after the comments are addressed.

My main points of the review of the manuscript are about the “presentation quality”. In terms of the presentation quality, I am mainly concerned about inconsistent use of terminology within the paper and inconsistent structures of subsections within sections as well as (sub-)section names not accurately reflecting the content of the sections. Overall, this could be a minor issue but with a manuscript of this length it is easy to get lost. Examples of both are in the specific comments organized by section and technical comments, which are in the attached pdf. I want to highlight that while there are several comments, I do not consider any of these as a major scientific problem. I hope the comments help the authors to review the manuscript and enhance the clarity of it.