Seasonal and Spatial Variability of Atmospheric Emissions from Shipping along the Northern Sea Route

Round 1

Reviewer 1 Report

The paper of "Seasonal and Spatial Variability of Atmospheric Emissions 2 from Shipping along the Northern Sea Route" concerns the study of the seasonal and spatial variabilities of shipping and shipping emissions of NOx, CO, SO2, PM and BC for year 2013 along the North Sea Route. A strong seasonal and spatial variation is found both in shipping traffic and emissions which is associated with ice coverage in the region. It is an interesting and well-written study but I would recommend a better structure.

1 ) I think this work can be further improved with a more clear structure. There are many small sections that can be united with other sections in order to make the message clearer. For example:

• Sections 3.2.1, 3.2.2 and 3.23 
• Sections 4.1.1 and 4.1.2 could also be one single section since both concern the ship traffic
• Sections 4.2.1 and 4.2.2  could also be one single section since both concern the emissions

2) Also in my opinion the section 5 Discussion it makes more sense if it was together with section 4. Results. Since in 5.1  comments and  process concerns the process on ship traffic  it could be together with 4.1 section. Same for 5.2 section, it could be merged with 4.2. In this way all results will be together and comments on these will make more sense. 

 

3) In subsection 3.2.2 you are referring on the different libraries you used to make the gridding. Could you say more words on what method this module uses?

4) Figure 3. Could you please make the labels on colorbars more "friendly" to read? For example 0.1 or 1..

5) Figure 4. you can add in each figure an additional y-axis that will show the actual number of ships (Figure 3). In that case will be easily comparable with each  type of emission distribution.

 

6) I think is too much information having all figures 5,6,7,8 and 9 in main manuscript. I would suggest keeping some of them (the most representative examples that are mostly discussed) and the rest of them could be to a supplement

7) Might giving the Table 2 in a figure (for example a timeseries with one y-axis ice coverage and on the other one the number of ships) would make these numbers easier for a reader to understand? I guess the inverse relationship between them will be obvious.

8) it is not very clear to me whether in Figure 10 the density plots refer to spring and autumn or just in March and September data. If they refer to March and December could you please change the title of these plots accordingly ? If they refer to Spring and autumn I think you can merge Figure 10 with Figure 3 if you finally decide to merge the sections as suggested before (comment 2)

 

9) Any suggestion for future work to add in the end? Please make it more clear.

 

10) Figure 1 is very nice though it is difficult to understand on what the colors of the plot refer to. Could you please add (maybe in the caption) what does the white or the grey colors refer? (for example ice? sea?)

Author Response

Dear Reviewer

Thank you for your comments. We have revised the paper according to your comments and suggestions. Please find our detailed response to your comments in the attached file "Response to comments and suggestions from Reviewer 1". 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

The authors have analyzed seasonal and spatial variability of atmospheric emissions from shipping along the Northern Sea Route(NSR). It is meaningful to analyze atmosphehe emissions from maritime transportation that is required to achive sustiable development goals. This research is also suitable for the purpose of this journal. However, I have the impression that the results of this study are limmited. Therefore, I evaluate of this paper as “Major Revision”. Please check the following points and make appropriate corrections.

Major comments：

・The authors summarized the charactalistics of this study are to investigate the seasonal variability of Arctic shipping and its associated emissions. I could not understand the charactalistics of each previous study. I suggest to add more detailed literature review and mention the characteristics of each previous study.

・I could not understand the basic procedure to analyze atmospheric emissions clearly. I suggest to add the basic procedure of this analysis in sections 3.1.

・I could not understand (eq.1) clearly. How many pollutions, engine type, engine tier,and fuel type, etc. are considered? What is the meaning of phase p? What is the value of EF _ME, EF _{AE, ,} and EF _BO, etc. ? The authors should add the table to summarize these.

・The authors focused on only 2013 and discussed the results in manuscript. I suggest to add the other years analysis (ex. 2014 -2021) and discuss the results. The authors should discuss the difference of time-series analysis for atmosphere emissions.

・In (eq.1) in manuscript, the atmosphere emissions influence to ship speed. I recommend the authors to add seasonal and spatial ship speed analysis. (ex.Where is the high speed area in NSR?) By adding this analysis, It is possible to make clear the influence of high emissions points or areas in NSR by ship speed, the number of ships or the other.

・What is the specification(Length, Breath, Depth, Engine type, any special instrument ,etc) for each type of ships used in NSR? Is it any specification difference considering seasonality.

 

Miner comments：

・The corresponding author information is lacked in manuscript.The asterisk (*) should be added in manuscript.

・Line 223: Fig 3D⇒ Figure 3D.

・Figure 11:CO2, SO2⇒CO₂, SO₂ (Lowercase letters should be used). The authors should checked carefully in the all manuscripts because these typo errors are included in some points.

Author Response

Dear Reviewer

Thank you for your comments. We have revised the paper according to your comments and suggestions. Please find our detailed response to your comments in the attached file.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Thank you for answers and corrections of authors. Some points are improved in the revised paper. However, it remains some questions in this revised paper. Therefore, I evaluate this paper as “Minor Revision”. Followings are comments about the revised paper and your responses.

1. The response to previous third point comment

I have confirmed the ASTD data. I guess level 2 or level 3 access data is utilized in this study. However, level 1 access data includes IMO number, MMSI, etc. The explanations from L284 to L288 (From eq. 1, each point-based ship registration is calculated an associated・・・) 　cause misleading that all of ASTD data can be accessed only ship ID (ASTD-generated), ship size, flag name, ice class, etc. Therefore, the authors should describe what data level was utilized in this study including the explanation of data access level of ASTD system based on the reference.

2. The response to previous fifth point comment

As shown in the results of this study（Fig.4）, it is understandable that there is a correlation between the number of ships and the atmosphere emissions. However, it is still questionable whether the relationship between the ship activity and the atmosphere emissions is comprehensively analyzed. According to Equation (1), ship speed, main engine power, and other factors have an impact on various types of emissions. Since the main engine power varies depending on the size of the vessel, there is a possibility that the relationship between the main engine power and emissions can be analyzed by understanding the average distribution of the ship size. (However, the analysis of main engine based on ship size is expected to be qualitative, and may be difficult to conduct because it requires AIS and main engine data of individual ships.) Analysis of ship speed is considered to be possible with the level 2-3 ATSD data used in this study, because it provides position and time information.

If the purpose of this study is to focus on the ship activity and to show the baseline in 2013, the analysis in this study is not sufficient. Therefore, an analysis of ship speed (ex., average ship speed) and ship size should be added at least. If possibly, it is also better to add ship size analysis. Additionally, the authors should discuss the relationship between the atmosphere emissions and ship activity including number of ships, ship speed, and average size etc. from the viewpoints of a comprehensive perspective.

If it is difficult to add the ship speed analysis and ship size analysis, the authors should describe that ship activity analysis in this study is from the viewpoints of limited aspect so as not cause misleading for readers.

Author Response

Dear Reviewer

Thank you for your comments. We have revised the paper according to your comments and suggestions. Please find the detailed response to your comments in the attached file.

Author Response File: Author Response.docx