Reply on RC1

“I reviewed a previous version of this manuscript that was rejected by TC last year. The resubmitted paper has probably been revised based on the previous comments from the reviewers. However, unfortunately, the changes were minor. They are changes in wording and the deletion/increase of a few figures. At least for me, I felt that those were superficial modifications, and accordingly, I couldn’t satisfy with them. Therefore, I recommend rejecting this paper mainly for the following reasons.


the dynamics and polynya events discussed in this paper). Qualitative analysis and visual interpretation of SAR imagery have been used in previous polynya studies (e.g. Hollands and Dierking, 2016; Dai et al., 2020). Inclusion of a backscatter scale is not standard in the literature for such images and including
absolute values would not add to the qualitative analysis. Furthermore, the polynya area and ice production sections are indeed quantitative, and the polynya areas identified by the SIC data are assessed against an image of the 'open' polynya in SAR (Fig 2).
"It can be read that the main focus of this study seems to be on the biological production and chemical processes in the summer coastal polynya (complete ice-free ocean) and the accompanying carbon dioxide absorption. However, the biochemical analyses were not conducted in this study." The main focus of the study is not biological production or chemical processes. We describe the aims of the study in the last paragraph of the introduction (lines 95-101). Biological/chemical processes are mentioned only as a motivation for better understanding polynyas.
"On the other hand, this manuscript estimates sea-ice production in a coastal polynya in winter (A small part may be an open water fraction, but it is mostly covered by frazil ice or thin solid ice). The purpose of estimating production is not clear; what is stated in L. 65 is insufficient. The dense water formed in winter coastal polynyas associated with the prominent ice production is an important source of AABW. This process of bottom water formation is thought to significantly impact the climate system through the transport of heat and substances such as carbon dioxide between the atmosphere and the deep ocean. However, this is not described at all in the manuscript." Mention of the role of ice production in polynyas in AABW formation was removed from this version of the manuscript, upon suggestion of another reviewer, due this region not being an important contributor to AABW formation (e.g. Gordon, 2009). We could re-include mention of the role of ice production in AABW in general, while being clear it is not important in this specific case. Nevertheless, we emphasize that the goal of this paper is not to address bottom water formation and rather the study of the ice formation in polynyas. The importance of polynya ice production is discussed on lines 56-66, but in a revision we will also include mention of the importance of quantifying ice production for understanding the overall sea ice mass balance in the region.
"The use of SAR data is a challenging point in this study. However, as is clear from video S1, it has many temporal and spatial discontinuities. This suggests that it is not suitable for monitoring a coastal polynya whose variability is large." We acknowledge that there are spatial and temporal discontinuities and this is a limitation (e.g. leads to gaps in qualitative analysis and is one of the barriers to an attempt at quantitative analysis) but disagree that this makes it not suitable for qualitative analysis. Processes such as polynya events and back-flow are observable despite these gaps, and indeed are only observable in winter with SAR.
"The authors defined surface conditions in SAR images as follows.  (e.g., 21-23 November 2016;15-17 December 2016;8-10 January 2017). These examples indicate the difficulty of conducting "quantitative" discussions of sea-ice and open water areas from SAR images." We agree and acknowledge that our analysis is qualitative here. We disagree, however, that this discounts the merit of our study. The differences between these key features is generally clear in the context of the images. It was an oversight for us not to mention that open ocean may also have high backscatter during windy conditions -as it the case in the example dates given here. We will mention this in a revision. However, it is clear from the context of the images that these bright areas are open ocean and not sea ice, and therefore it did not lead to mis-interpretations.
"The use of such sparse and unquantifiable data leads to misinterpretation. The authors state that "approximately all of the ice produced between 30 April and 4 November by the main polynya is contained within the red outline on 4 November in Fig. 4" from the SAR images in Video S1 and Fig. 4 (L. 403-405). This is a lack of science to tell this from SAR data alone. It is more natural to assume that the sea ice will grow both thermodynamically and dynamically during this long period of 6-months, resulting in a backscatter similar to that of one-year ice. In any case, this cannot be suggested solely from the SAR images." Fig. 4 that the highlighted area of ice has a distinct backscatter from the pack ice in the region, and it is clear from carefully analyzing the video and imagery that this is ice produced by the polynya during that season. We agree that the ice would continue to grow dynamically and thermodynamically during this period, but that does not contradict that it was initially formed in the polynya.

"The definition of a winter coastal polynya area based on AMSR2 sea-ice concentration (SIC) is questionable. Firstly, this study ignores heat loss and sea-ice production in thin ice areas, the dominant type of sea-ice in winter coastal polynyas. Secondly, an area with SIC <70% was defined as a polynya area, but SIC by the ASI algorithm underestimates SIC in thin ice areas. A similar analysis had to be performed using SIC with other AMSR2 algorithms, and error analysis also had to be performed.
In a previous review, I pointed out the definition of a coastal polynya area. As in the previous manuscript, this manuscript also treats the area where the SIC by AMSR2 is <70% as the polynya (open water) area. The previous manuscript was based on studies of the comparison between a coastal polynya area from the polynya signature simulation method (PSSM) by Markus and Burns (1995) and SIC (Parmiggiani, 2006;Morelli & Parmiggiani, 2013;Preußer et al., 2015). The new manuscript added a comparison with SAR images (Figs. 2b-g). The black low backscatter area (open ocean) in Fig. 2b corresponds to the low SIC area (SIC <70%) in Fig. 2e. Since this is not a SIC map, I do not know the details, but the correspondences between the open ocean and the low SIC (not open ocean) areas seem strange. On the other hand, Figs 2c-d shows a bright bandlike feature, which is considered to be covered with frazil ice. Since no dark areas can be seen, it is assumed that this area is mostly covered with sea ice. In other words, the SIC must be close to 100%. However, the AMSR2 map shows a low SIC of <70%. The two areas certainly coincide, but they are not consistent in terms of SIC" (Fig. 2c-d)