Decline in Ice Coverage and Ice-Free Period Extension in the Kara and Laptev Seas during 1979–2022
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe article submitted for publication mainly contains the results of statistical processing of previously obtained results and may be of interest to those interested in statistics. The presence of the trends themselves and their reliability are basically well known. Although the authors are trying to give some physical explanations for their results, at the same time it is clear that this is not the purpose of their article, and this is confirmed by the poor discussion of the results and the lack of analysis of connections with global trends and indices. It is also unclear why the authors limited themselves to considering only two Arctic seas. Using those products NSIDC-G02202 and G02135 it would be possible to expand their scope of view to the entire Arctic and even Antarctica.
Some notes following the submitted manuscript:
L 52-54. Autors can't help but deal with general large-scale climate indicators as NAO, AMO, etc. since they largely predetermine the nature of regional processes, therefore this should be mentioned here and in further analysis local changes should be ultimately compared somehow with large-scale ones.
L 77. Why the 5% significance level. Why not the more reliable and commonly used levels of 1 or 0.5%? Which of the “statistically significant trends” will become non-significant if the significance level is tightened? After all, conclusions like “statistically significant trends” significantly depend on this level, and 5% seems too low a level.
L 88-96. What is the difference between using NSIDC-G02202 and G02135 data is not entirely clear from the explanations?
L 96-98. Why “calculation of grid cells, which meet the threshold condition, reduces day-to-day variability in the considered sea ice parameters”? Please explain.
L 98. No reference to AARI sea ice charts
L 131-132. Ë—5.2·103 km2/year vs Ë—3.7·103 km2/year. What is the confidence interval of these estimates at least with 5% level?
Figure 2. Very small labels on the axes. Also, partly or completely applies to subsequent figures.
L 140-141. Units differ: km2 compares to km2/year
L 163-170. Please explain what you mean by “frequency of annual sea ice retreat” and why “frequency” is expressed as a percentage? Same for “fast ice frequency” latter in Fig 7.
L 201. The text says October 22, and the table says October 24.
L 358. The numbers 22.3% and 13.8% were not shown in the Results. Before writing about them in conclusions, demonstrate them in the Results section.
Section “Summary and conclusions” includes not only summary and conclusions but also some discussion trying to explain the results. Please rename this section.
In conclusion and in abstract the term “statistically significant trend” must be provided with indication of 5% significance level for those who will start to read your paper from Abstract and Conclusions (as most people do).
Author Response
Dear Reviewer 1! Thank you for taking the time to review our manuscript. We appreciate your feedback and have made the requested changes. You can find the detailed responses to your comments and the corresponding corrected text in the attached files.Dear Reviewer 1! Thank you for taking the time to review our manuscript. We appreciate your feedback and have made the requested changes. You can find the detailed responses to your comments below.
Please see the attachment.
With best regards,
Pavel Shabanov
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsManuscript
“Decline of ice coverage and ice-free period extension in the
Kara and Laptev seas during 1979-2022”
By Pavel Shabanov, Alexander Osadchiev and Natalya Shabanova
Brief summary and general comments
The study explores and attempts to quantify the variability and trends of three variables (dates of sea ice retreat and advance and the resulting duration of the ice-free period) related to sea ice cover for two focal regions of the Arctic Ocean, Sea Kara and Laptev Sea; the study span the time period, from 1979 to 2022.
Applying basic statistical and data exploration methods to the three variables, calculated by processing a large daily SIC dataset, led to several results expressed through standard statistics, spatial and temporal distributions, and trend values.
These results, together with their discussion and interpretation, are interesting and potentially useful for polar research. However, in general, they substantially confirm the already known results obtained in other studies, albeit with some differences. This leads, in my opinion, to a lack of novelty in this manuscript.
Despite this, the work is overall clear and readable (even if, at times, a little verbose and redundant in section 3), and could be published as is with small changes, but with the awareness that the scientific level is quite lacking of novelty.
In the latter case, my simple suggestion to the authors is to try to extract highly informative results, and novelty, by applying more advanced statistical methods, including machine learning techniques, to their processed data.
Other comments:
- Font size of figure labels should be increased.
- Line 46: "Only some" is not good, you could change to "Various studies..." or "Only some studies...".
- Lines 398-410: Do the terms "high degree of confidence", "unlikely" correspond to scales of likelihood and confidence as in the IPCC context? And if so, what research are they based on?
- Line 528: reference 41 should be completed.
Author Response
Dear Reviewer 2! Thank you for taking the time to review our research paper. Your feedback is greatly appreciated and I am grateful for your efforts to help improve our work. I value your insights and input, and I would like to thank you again for your valuable time and consideration
With best regards,
Pavel Shabanov
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsSummary: This paper presents an analysis of the decline of ice coverage in the Kara and Laptev Seas during the period of 1979-2022 using NSIDC passive microwave sea ice concentration data based on NASA’s SMMR and the DMSP SSM/I and SSMIS sensors. In this study, they identify the date of retreat (DOR), date of sea ice advance (DOA), and the total ice-free period of duration (IFP) for both the Kara and Laptev Seas. In both regions, they find a significant decline in the observed sea ice extent and an increase in the duration of the IFP during this period. Specifically, they found average IFP trends of +16.2 days/decade in the Laptev Sea and +20.2 days/decade in the Kara Sea. The authors attribute the inflow of warm water from the Barents Sea to the Kara Sea as the most important process contributing to the sea ice reduction in the study area.
This is a generally well-written paper. Comments below primarily address grammatical corrections. Figures and tables are generally clear and understandable. References are thorough and sufficient. I recommend publication of this paper with minor revisions.
General Comment:
Please comment on the impact of melt ponds on your analysis as the PWM data used in this study can not differentiate between melt ponds and open water (see ref 47).
Specific Comments:
Line 12: identified “the” spatial
Line 55: govern “the” temperature of “the” sea surface
Line 60: feature of “the” study
Line 61: delete “used”
Line 62: add datasets “used in this study”
Line 79: For “the” 1979-2022
Line 85: capitalize Scanning Multichannel Microwave Radiometer
Line 86: capitalize Defense Meteorological Satellite Program
Line 88: calculated “from combinations” of
Line 95: what do you mean by “usage”; possibly reword or rephrase
Line 110: should be “noise”
Line 112: applied “a 7-day”
Line 117: we used “a” conservative
Line 126: replace with “21st”
Figure 2 caption: relabel to “(a) Kara and (b) Laptev
Figure 3 caption: see above; why does x-axis extend to MAR instead of JAN – DEC?
Figure 4: see comment on Fig. 2; add what the orange line represents in the boxplots.
Line 163: “The” rapid
Line 205/206: relabel caption to “LTM for ITP, DOA, and DOR…”
Lines 215-218: The fast ice plots shown in Figure 7 are for the period 2008-2023. Why wasn’t a period chosen consistent with this study period, 1979-2022? Perhaps the satellite data was not available prior to 2008? What is the source of the data used for Figure 7? Please add citation.
Figure 7, 8: see Fig. 2 comments
Lines 272/273: relabel caption to “IFP, DOA, and DOR”
Figure 10, 11: See Fig. 2 comments
Line 368: “depend”
Line 386: “The” area with the …
Comments on the Quality of English Language
Quality of English used is very good. I made some minor edits where some words were missing (e.g., "the").
Author Response
Dear Reviewer 3! We appreciate the time and effort you have put into providing us with feedback on our manuscript. We are grateful for your insightful and positive comments and valuable suggestions on how to improve our paper. We have taken the comments made by you into consideration and made the necessary changes, which are highlighted within the manuscript.
With best regards,
Pavel Shabanov
Author Response File: Author Response.docx
