From the journal Environmental Science: Atmospheres Peer review history

30-Jan-2021

Dear Dr Mohr:

Manuscript ID: EA-ART-12-2020-000023
TITLE: Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS

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************

Reviewer 1

Review of “Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS”, by Siegel et al.

This paper by Siegel and co-authors presents molecular composition of semi-volatile species observed on submicron particles during shipborne field study in the high Arctic using a FIGAERO inlet and a high-resolution time-of-flight iodide CIMS instrument. The authors use compound classes to cluster analyze the large number of molecules they identified in the samples as a method to analyze trends with gas-phase precursors of DMS and other oxidation products in the Arctic. They also explore the relative degree of oxidation using O:C ratios, using back trajectories to investigating the differences in the particle composition between air masses that have lingered over ice for longer periods of time and those impacted by recent emissions from ocean leads or regions near Arctic land masses.

The total number of filter samples is quite small (12 in total), and several of the samples are of questionable nature due to possible or likely contamination from the ship exhaust during a period of steaming south. Nevertheless, the authors present some interesting data analyses that are both relevant and valuable to the community.

Overall the paper is well written and needs only some minor changes and edits prior to being published. Care does need to be given to the reference list, however.

Comments

Lines 104-111: This is a well-explained reasoning behind investigating the O:C ratio in bulk aerosol.

Line 143: Can the authors clarify what they mean by “MIZ stations lasted around 24 hours…”?

Lines 172-176: The authors give two different particle loss calculations for particles < 1 micron, including <10% for particles <1 micron and < 1% for particles between 0.1 and 1 micron. Is this what they really mean? And then they go on to say that losses of particles > 1 micron were 27%. This should be fixed or clarified, if it is indeed correct.

Lines 194-196: Include an explanation of why F6 omitted from this study to be analyzed by another analytical method.

Lines 366-378: In the discussion of the back trajectory levels, there is an inconsistency (or confusing notation) between the text here and the text with Fig. S5. In the ESI, the levels are labeled 1-8, with the lowest level of each provided as being 11 m (level 1) through 159 m (level 8.) Here, however, the levels used for the BL are identified as 5-15. This needs to be clarified or fixed.

Lines 385-389: while I understand that the meteorological conditions are provided in several other papers, if there are any relevant details to this work, that might be nice to mention here?

Lines 404-409: Much of the information in Figure 2 is visually lost by the way the sticks overlap with each other. For example, around m/z 270, there is a hint of “Other” (maroon) that is almost completely hidden by the CHON stick (yellow). As a result of the layering, the figure gives an erroneous emphasis on some species groups over others. As well, sometimes there are what appear to be sticks hidden behind other sticks that are the same color, but it’s unclear if that is simply an issue with the resolution of the figure, or the thickness of the sticks at (UMR) unit mass resolution hiding other sticks of the same color. It would make the figure significantly larger, but I think it would be more informative to give a series of stacked plots for each compound class. Also, I’m not sure I understand the value of showing the median of all samples. Presumably, there are significant differences between the high Arctic near the North Pole and the MIZ, or between the samples that are and are not impacted by the influence of ship contamination.

Lines 409-414: The detail that is described here is a perfect example of what would become more obvious if the authors were to split Figure 2 into individual plots of each compound class, because it would be easy to visualize the difference between the large range of molecular sizes of the CHO or CHON molecules, and the periodic nature of the CHOS species.

Lines 421-422: I personally think that the individual filter pie charts are more informative and scientifically relevant, and should be included in the main manuscript, or at the very least, and example of one filter, rather than the less meaningful “all filters” pie chart in Figure 2.

Lines 522-527: While the authors have included the comparison of the different relevant instrumental data in the supplement (Fig S8), in referring to them here in the main text, the authors should give a one or two sentence summary of the results of the comparison in the main text as well.
Line 556: Figure 3 caption – the time series in (a) are said to be the “aerosol sample median signal separated by compound category”, but should these not be the sum of the aerosol sample signal compound category? My understanding is that each filter was analyzed twice, and the first analysis was background-subtracted using the second analysis, but there is no median for a single analysis?

Line ~600: Figure 6 caption – “Aggregated CHO, CHON, CHONS and CHOS median signal of all samples (F1-F13) by carbon number…” (I.e., delete “divided”, as it implied a mathematical division, while you’ve just organized the bar chart “by carbon number”.)

Lines 639-643: MSA is not emitted by the ocean directly, but is a DMS oxidation product that can be taken up into particles and also released from particles in regions of low humidity. Presumably the impact of the ship emissions are not just on the sulfur species, but also the oxidizing regime of the air mass being sampled. This can certainly impact the MSA(g) production and loss.


Technical comments:

Second last line of abstract: delete “e.g.”, which is not necessary.

Line 135: Is the superscripted question mark supposed to be a reference?

Lines 153-154: “were collected… samples were collected…” seems a little repetitive.

Line 190: Eliminate “After being stored frozen,” as it is redundant with the last line of the previous paragraph.

Line 203: Rewrite this sentence to clarify whether the nitrogen gas or the filter were heated from room
temperature to 200 °C. “The temperature of which” is not specific.
Table 1: Consider using “Sample duration (h)” or “Sample length (h)” rather than “Sampling time (h)”.

Line 217: “… identify 1586 ions, 519 of which were…” (were not where)

Line 225: It is preferable to use the term “molar mass” or, if using molecular weight (MW or M.W.), the W is not usually subscripted.

Line 225: “… atmospheric concentration.” (singular).

Line 278: nss has not been defined.

Line 340: the comma separating the reference superscripts should also be superscripted.

Lines 385-385: the descriptions are described is a little self-referential. Perhaps “detailed descriptions… are provided in Brooks et al…”?

Line 472: Barents Sea should have “Sea” capitalized.

Line 493: Figure S9 is mentioned prior to Figure S8 (lines 522 and 600) so their numbers should probably be swapped.

Line 515: “… several orders of magnitude higher.”

Lines 613 and 664: spell out the full word “approximately”.

Line 614: “originates”

Line 617: “Seas” should be capitalized.

Lines 635-639: In the text, numbers reported in scientific notation should be given as as #.## x 10^exp, rather than using #.##e-## notation.

Line 675: “edge” is spelled incorrectly.

Lines 678-679: I think an “as” is missing from this sentence.

Line ~ 706: Figure 8 – the y-axis label for Figure 8b should be on the left side, i.e., the same side as the scale.

Line 719: “… showed qualitatively good agreement…” (delete “a”. )

Line 734: “… gas-phase concentrations.”

Lines 802-1035: There are several issues with the references. I believe that the recommended formatting should have journal abbreviations, rather than full journal names, but the authors have both full journal names and journal abbreviations in their reference list. Further, there are capitalization errors (e.g., lines 816, 948, 964, etc.), incorrect abbreviations (e.g., line 935), and bad data (e.g., lines 836, 839, 928, 938, etc. – “year”?). Also, the instructions for authors state “the names and initials of all authors should be given in the reference”, so the “et al.”s on lines 826, 853, 857, 924, 928, 934, and so on should be expanded to list all the authors.

Lines 853-855: I can’t find this paper anywhere. I’m really not a fan of not including titles or DOIs, but that’s what this journal prefers. Nevertheless, this paper is showing as being in ACPD from 2013, and despite that, I can not find record of it online (in or out of ACPD) with these first four authors.

Lines 856-863: This paper has been published, so the ACP version should be referenced, not the ACPD version. https://doi.org/10.5194/acp-15-7961-2015

Lines 860-864: This paper has been published, so the ACP version should be referenced, not the ACPD version. https://doi.org/10.5194/acp-20-7955-2020. Also, 2019 is the ACPD publication year, not the volume, and the ACP article is 2020.

Line 867: there is no need to qualify the date for this publication as 1996b when using numerical footnoted references.

Line 1031-1033: This publication has no journal name, volume, or pages.

ESI Page 3 – I’m guessing that “Of the samples taken during the transit (F8-F11, Table 1 in the main article), F11 were classified as likely…” – should be “… F8 and F11 were classified as likely…” – based on Table 1, and their classification of 3 or “high risk”.

Figure S4 (ESI page 4) – the caption indicates (a) and (b) components, but these are not labeled on the figure.

Figure S5 (ESI page 5) – in the caption, September 14 00 UTC is confusing, and should be written as 14 September 0:00 UTC or 0 UTC. Similarly, at the top of the page, where the date and time are mentioned, the date could be confused with 14 Sept 2000, using “00 UTC”, so again, I recommend using 0:00 UTC or simply 0 UTC.

Figure S7 caption (ESI page 7): “Volume size distributions (sum) of each aerosol sample F1-F13” seems misleading, as the size distributions were not from the filters. It would be more appropriate to say “Summed volume size distributions corresponding to each aerosol sample.”

Table S4 (ESI page 11): The 5th and 95th percentiles for DMS for IAOE-91 are reversed.

Supplement references (page 11): I believe the same details need to be provided for the ESI references as the main text, so reference [1] should have all authors listed rather than “et al.”, more detail needs to be included for reference [5], and for reference [8], the pages are missing. Either include one or both of: D13308, doi:10.1029/2006JD008183. Also, for references [6] and [7], 1996 is fine, as there is no need for the 1996a and 1996b.

Reviewer 2

This work describes several chemical and microphysical measurements conducted onboard the Swedish Icebreaker, Oden, while moored (to the ice) and during transit out of the central Arctic Ocean in the late summer of 2018. The particular focus is on offline measurements made using a FIGAERO-HRToF-CIMS instrument. Filter samples of the ambient aerosol were collected on the Oden, wrapped in foil and stored in a freezer. In a laboratory, the samples are individually heated to 200 C and analyzed, via mass spectrometry, for evolving compounds that cluster with the CIMS reagent ion (I-). In total, 13 filter samples were collected from September 11 to 19, inclusive, along with two blanks. Individual sampling times ranged from 6-35 hours, and sample #6 was set aside for a different analysis not discussed in this paper. The analyses of all samples yielded 519 compounds that clustered with the reagent ion and are considered valid. The filter samples were collected about 25 m above the sea surface through a combination of tubing, including two short pieces of conductive silicone tubing. The inlet was heated to between 30 C and 40 C to allow for the collection of fog and cloud residuals as well as not-cloud-activated aerosol particles. Samples 8-11 are considered to have possible contamination by the ship’s emissions.

Of the 519 compounds included in the results, 64% are comprised of CHO, 28% of CHON, 5% of CHOS and 2% of inorganic S. The authors conclude 1) that submicron particles in the central Arctic boundary layer during late summer have a large contribution from organic and sulphur molecules, and 2) that the gas-phase and particle-phase compositions did not co-vary in time.

Overall, the presentation is good and the authors have combined a large number of observations together to provide useful knowledge of the chemistry of the Arctic aerosol over the central Arctic Ocean. Neither conclusion is unique to the Arctic in a general sense (see detailed comments below), but I believe both are unique to their particular location and important in that sense. There is a problem with the reference list, which made reviewing a little more difficult.

Detailed Comments:
1) Reference numbering appears to be offset, and presumably some references are missing, since the reference numbers in the text go up to 89, but there are only 84 in the list.

2) As I mention above, I believe the results are important because of the location in the Arctic. However, the conclusion about organic and sulphur compounds in the summer is not unique to the Arctic. Shaw et al. (https://doi.org/10.1029/2010GL042831, 2010) describe one-year of particle chemistry at Utqiagvik, Alaska (formerly known as Barrow), including organics, and Leaitch et al. ( https://doi.org/10.5194/acp-18-3269-2018, 2018) describe over two years of similar measurements at Alert, Nunavut. If, as your title suggests, your measurements are intended to provide more insight into the Arctic submicron aerosol, discussion of the similarities and differences of your results with these other measurements is necessary.

3) Lines 27-30 – This statement, drawn on results of limited trajectory analyses does not adequately reflect our current understanding of Arctic haze. Global transport models, accounting for transport times greater than 10 days, indicate that emissions from Southeast Asia significantly impact surface measurements in the high Arctic during spring (e.g. Qi et al., https://doi.org/10.5194/acp-17-1037-2017, 2017a; Qi et al. https://doi.org/10.5194/acp-17-9697-2017, 2017b; Xu et al., https://doi.org/10.5194/acp-17-11971-2017, 2017). Please revise. The reference number given here (12) corresponds to Mitchell, 1957, which I assume you did not intend.

4) Lines 79-82 – You have not included here more recent results that suggest a stronger role for DMS in CCN formation in the summertime Arctic (e.g. Chang et al., ACP, 2011, in your list; Leaitch et al., https://doi:10.12952/journal.elementa.000017, 2013; Giamarelou et al., https://doi.org/10.1002/2015JD023646, 2015; Willis et al., https://doi:10.5194/acp-16-7663-20162016, 2016; Dall’Osto, et al., https://doi.org/10.1038/s41598-017-03328-1, 2017). A more balanced discussion is needed.

5) Lines 108-110 - Large-scale models are unlikely to consider detailed molecular compositions in order to simulate CCN activity. Simplifications, such as “Kappa” (Petters and Kreidenweis, ACP, 2007), are more likely to be employed. Your discussion here should mention how molecular composition will aid such parameterizations.

6) Lines 167-170 – Syntax problem with this sentence.

7) Line 177 – Collection rather than deposition?

8) Line 194 – Reference numbering here and in many other places.

9) Lines 461-463 – Based on the AMS, ammonium and nitrate were very low compared with SO4=, yet your FIGAERO-based pie chart indicates nitrogen associated with CHO is almost six times higher than S associated with CHO. Please offer some explanation.

10) Lines 494-495 – It may be a colour issue, but it is not evident in Figure 5 that the trajectories associated with samples 1-3 go towards the Canadian Archipelago.

11) Lines 508-510 - A possibility, but, by this statement, it seems that you are saying there was no organic contamination from the ship emissions, which is in direct contrast with sample F8 and F10 that indicate significant organic contamination and little contamination from sulphur. I suggest avoiding this discussion altogether.

12) Lines 513-515 – Do you mean “by the FIGAERO-CIMS” rather than “by the AMS”?

13) Lines 507-527 – I don’t find this discussion convincing of anything. What Figure 4 appears to show is that your FIGAERO-CIMS results only represent a very small fraction of the organic components that are measured by the AMS. Some discussion explaining these large differences seems most relevant here. Also, you introduce Figure 4 before Figure 5.

14) Lines 579-583 – Except that most of the 5-day back air trajectories suggest the aerosols spent all of that time over the central Arctic Ocean. Why then would you expect large differences?

15) Lines 583-585 - Are you trying to say that nothing is significant?

16) Lines 617-620 – Of course, the oxidation products you measure were produced and partitioned to the particle phase during transport from some source region. How else would it happen? Some re-write is needed to explain better what it is you are trying to extract from the 10% emitted in the Arctic BL and the 90% emitted from surrounding seas.

17) Lines 639-641 – This statement fails to address the question, why does MSA follow SA when SA is assumed to be from ship contamination? If the subsequent paragraph (lines 644-660) is intended to answer this question, it needs more clarity.

18) Lines 663-665 - Perhaps true, but you need to mention that it will also depend on oxidant levels and meteorology.

19) A question of curiosity – You show size distributions of volume, which of course are most relevant to your results, but did you see increases in the number concentrations of smaller particles at any point that might be evidence for new particle formation?

We thank both reviewers for their thorough review of our manuscript. In the following we have pasted the reviewers’ comments and added our responses directly below each comment, starting with ">>". Changes in the PDF versions of the manuscript and ESI are highlighted yellow.

Reviewer 1

Comments to the Author
Review of “Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS”, by Siegel et al.

This paper by Siegel and co-authors presents molecular composition of semi-volatile species observed on submicron particles during shipborne field study in the high Arctic using a FIGAERO inlet and a high-resolution time-of-flight iodide CIMS instrument. The authors use compound classes to cluster analyze the large number of molecules they identified in the samples as a method to analyze trends with gas-phase precursors of DMS and other oxidation products in the Arctic. They also explore the relative degree of oxidation using O:C ratios, using back trajectories to investigating the differences in the particle composition between air masses that have lingered over ice for longer periods of time and those impacted by recent emissions from ocean leads or regions near Arctic land masses.

The total number of filter samples is quite small (12 in total), and several of the samples are of questionable nature due to possible or likely contamination from the ship exhaust during a period of steaming south. Nevertheless, the authors present some interesting data analyses that are both relevant and valuable to the community.

Overall the paper is well written and needs only some minor changes and edits prior to being
published. Care does need to be given to the reference list, however.

>> We thank the reviewer for their positive assessment of our paper. We will make sure the reference list is fixed in the revised version.

Comments
Lines 104-111: This is a well-explained reasoning behind investigating the O:C ratio in bulk
aerosol.
>> Thank you!

Line 143: Can the authors clarify what they mean by “MIZ stations lasted around 24 hours…”?
>> There were two MIZ stations and they were both around 24h long. The sentence has been changed to: "During both the transit north- (August) and southward (September), the ship was moored for sampling in the MIZ during 24 h (referred to as MIZ stations)".

Lines 172-176: The authors give two different particle loss calculations for particles < 1 micron, including <10% for particles <1 micron and < 1% for particles between 0.1 and 1 micron. Is this what they really mean? And then they go on to say that losses of particles > 1 micron were 27%. This should be fixed or clarified, if it is indeed correct.
>> The numbers are correct, but the sentence was confusing. We also think that it is more accurate to specify the diameter range boundaries instead of using a “less than” notation. The sentenced has therefore been changed to:
“Inlet particle number losses were calculated to be ~1-8% for smaller particles with diameters Dp=0.01-1µm (~0.5-1% for the accumulation mode, Dp=0.1-1µm), and ~1-75% for larger particles with Dp=1-10µm […] We assume however that the majority of the compounds measured by FIGAERO-CIMS are in the submicron range.”

Lines 194-196: Include an explanation of why F6 omitted from this study to be analyzed by
another analytical method.
>> We have future plans for the comparison of FIGAERO-CIMS filter analyses with other techniques, using different datasets, and therefore try to keep some filters unanalysed from our campaigns. We have added the following clarification: "Sample F6 was omitted to allow for later analysis by other analytical methods (not part of this study). Sample F6 was chosen since it was collected under similar conditions (in terms of the ice drift and sampling duration) to samples F1-F5.”

Lines 366-378: In the discussion of the back trajectory levels, there is an inconsistency (or
confusing notation) between the text here and the text with Fig. S5. In the ESI, the levels are
labeled 1-8, with the lowest level of each provided as being 11 m (level 1) through 159 m (level 8.) Here, however, the levels used for the BL are identified as 5-15. This needs to be clarified or fixed.
>> The number of levels within the BL varied between the individual trajectories between 5 and 15. Fig. S5 is only one example, and this particular trajectory had 8 levels within the BL. This was now clarified in the manuscript as following: "Trajectories initialised (t=0) within the BL (where the number of levels ranged between 5 and 15 for individual trajectories) were averaged to a single trajectory."

Lines 385-389: while I understand that the meteorological conditions are provided in several
other papers, if there are any relevant details to this work, that might be nice to mention here?
>> This has been added: "In this study we present some common parameters including air temperature and relative humidity, fog and cloud occurrence (Fig. S6) and wind speed (section 3.2). The air temperature was below zero throughout the aerosol sampling period and the relative humidity (RH) was in general high (81.3-100%). Fog and cloud events occurred frequently, as is common in the Arctic at this time of the year. Detailed descriptions of the meteorological conditions during the expedition are provided in (Vüllers, 2021) and (Prytherch, J. and Yelland, M. J., 2021)." The references at the end of the sentence were also updated to more recent and relevant publications.

Lines 404-409: Much of the information in Figure 2 is visually lost by the way the sticks overlap with each other. For example, around m/z 270, there is a hint of “Other” (maroon) that is almost completely hidden by the CHON stick (yellow). As a result of the layering, the figure gives an erroneous emphasis on some species groups over others. As well, sometimes there are what appear to be sticks hidden behind other sticks that are the same color, but it’s unclear if that is simply an issue with the resolution of the figure, or the thickness of the sticks at (UMR) unit mass resolution hiding other sticks of the same color. It would make the figure significantly larger, but I think it would be more informative to give a series of stacked plots for each compound class. Also, I’m not sure I understand the value of showing the median of all samples. Presumably, there are significant differences between the high Arctic near the North Pole and the MIZ, or between the samples that are and are not impacted by the influence of ship contamination.

Lines 409-414: The detail that is described here is a perfect example of what would become
more obvious if the authors were to split Figure 2 into individual plots of each compound class, because it would be easy to visualize the difference between the large range of molecular sizes of the CHO or CHON molecules, and the periodic nature of the CHOS species.

Lines 421-422: I personally think that the individual filter pie charts are more informative and
scientifically relevant, and should be included in the main manuscript, or at the very least, and example of one filter, rather than the less meaningful “all filters” pie chart in Figure 2.
>> Reply to the three comments above: We replaced the mass spectrum with the median signal pie chart in Fig. 2 for a mass spectrum separated by compound class to make it easier to see all of the peaks (Fig. 2a). This spectrum still shows the median signal as the idea with this figure is to display at what m/z the different compound classes were found. Below are pie charts for each individual filter (Fig. 2b), as the reviewer suggested. This is the same figure as the previous Fig. S6 in the ESI, but the percentages have been put in a table (Table S3) in the ESI. We hope that this new Fig. 2 will be more informative and easier to read.
Due to the inclusion of the new figure, several smaller changes were made in lines 421-446. The median percentages were removed from the text, as the individual pie charts are shown instead.

Lines 522-527: While the authors have included the comparison of the different relevant
instrumental data in the supplement (Fig S8), in referring to them here in the main text, the
authors should give a one or two sentence summary of the results of the comparison in the main text as well.
>> The following has been added: "Qualitatively, the three techniques agree well especially during the ice drift when sampling conditions were more controlled and there was less impact from ship stack contamination as compared to the periods of transit.”

Line 556: Figure 3 caption – the time series in (a) are said to be the “aerosol sample median
signal separated by compound category”, but should these not be the sum of the aerosol
sample signal compound category? My understanding is that each filter was analyzed twice, and the first analysis was background-subtracted using the second analysis, but there is no median for a single analysis?
>> Yes, the reviewer is correct. This was corrected to “Time series of a) the summed aerosol sample signal separated by compound categories (analysed by FIGAERO-CIMS) […]”

Line ~600: Figure 6 caption – “Aggregated CHO, CHON, CHONS and CHOS median signal of all samples (F1-F13) by carbon number…” (I.e., delete “divided”, as it implied a mathematical division, while you’ve just organized the bar chart “by carbon number”.)
>> Changed as suggested.

Lines 639-643: MSA is not emitted by the ocean directly, but is a DMS oxidation product that can be taken up into particles and also released from particles in regions of low humidity. Presumably the impact of the ship emissions are not just on the sulfur species, but also the oxidizing regime of the air mass being sampled. This can certainly impact the MSA(g) production and loss.
>> The reviewer is correct. We changed this sentence to: "[…] since its only source is DMS, which is emitted from the ocean.", and added the following sentence: "It is possible that gaseous and particulate pollutants in the ship exhaust impact MSA production and partitioning. Therefore, measured MSA (p) and SA (p) may also co-vary in the contaminated samples.”

Technical comments:
Second last line of abstract: delete “e.g.”, which is not necessary.
>> Deleted as suggested.

Line 135: Is the superscripted question mark supposed to be a reference?
>> We do not see a superscripted question mark and therefore think this is a formatting error that has been taken care of in the revised version.

Lines 153-154: “were collected… samples were collected…” seems a little repetitive.
>> Replaced by "During 11-19 September 2018, 13 ambient aerosol samples (referred to as F1-F13) were collected during mooring to the ice floe (the ice drift), when the ship was steaming southward (transit), and in the MIZ station with the engines off (see Table 1). In addition, 2 field blanks B1-B2) were taken during transit and in the MIZ."

Line 190: Eliminate “After being stored frozen,” as it is redundant with the last line of the previous paragraph.
>> Replaced by "The filter samples were analysed with a FIGAERO-CIMS in the laboratory at Stockholm University, Sweden."

Line 203: Rewrite this sentence to clarify whether the nitrogen gas or the filter were heated from room temperature to 200 °C. “The temperature of which” is not specific.
>> It is the N2 temperature that is ramped up, but it leads to a temperature increase of the filter too, as the N2 passes through the filter.
Replaced by "Particles collected on the filter are evaporated by a flow of nitrogen (N2) that is gradually heated from room temperature to 200°C during 20 min […]".

Table 1: Consider using “Sample duration (h)” or “Sample length (h)” rather than “Sampling
time (h)”.
>> Changed to "Sample duration (h)".

Line 217: “… identify 1586 ions, 519 of which were…” (were not where)
>> Typo corrected.

Line 225: It is preferable to use the term “molar mass” or, if using molecular weight (MW or
M.W.), the W is not usually subscripted.
>> Changed to molar mass, and Mw is changed to M.

Line 225: “… atmospheric concentration.” (singular).
>> Changed as suggested.

Line 278: nss has not been defined.
>> Changed to "non-sea-salt sulfate (nss-SO42- […]".

Line 340: the comma separating the reference superscripts should also be superscripted.
>> Changed.

Lines 385-385: the descriptions are described is a little self-referential. Perhaps “detailed
descriptions… are provided in Brooks et al…”?
>> Changed as suggested.

Line 472: Barents Sea should have “Sea” capitalized.
>> Changed.

Line 493: Figure S9 is mentioned prior to Figure S8 (lines 522 and 600) so their numbers
should probably be swapped.
>> The order of the ESI figures and tables is fixed.

Line 515: “… several orders of magnitude higher.”
>> Changed.

Lines 613 and 664: spell out the full word “approximately”.
>> Changed.

Line 614: “originates”
>> Changed.

Line 617: “Seas” should be capitalized.
>> Changed.

Lines 635-639: In the text, numbers reported in scientific notation should be given as as #.##
x 10^exp, rather than using #.##e-## notation.
>> Changed as suggested.

Line 675: “edge” is spelled incorrectly.
>> Corrected.

Lines 678-679: I think an “as” is missing from this sentence.
>> Changed to "DMS is produced far from the inner pack ice area, and as it is advected over the ice it undergoes oxidation."

Line ~ 706: Figure 8 – the y-axis label for Figure 8b should be on the left side, i.e., the same
side as the scale.
>> Changed, and the axis label was also updated according to the comment on lines 635-639 above.

Line 719: “… showed qualitatively good agreement…” (delete “a”. )
>> Changed as suggested.

Line 734: “… gas-phase concentrations.”
>> Changed.

Lines 802-1035: There are several issues with the references. I believe that the recommended formatting should have journal abbreviations, rather than full journal names, but the authors have both full journal names and journal abbreviations in their reference list. Further, there are capitalization errors (e.g., lines 816, 948, 964, etc.), incorrect abbreviations (e.g., line 935), and bad data (e.g., lines 836, 839, 928, 938, etc. – “year”?). Also, the instructions for authors state “the names and initials of all authors should be given in the reference”, so the “et al.”s on lines 826, 853, 857, 924, 928, 934, and so on should be expanded to list all the authors.
>> The format was corrected in the revised version of the manuscript.

Lines 853-855: I can’t find this paper anywhere. I’m really not a fan of not including titles or DOIs, but that’s what this journal prefers. Nevertheless, this paper is showing as being in ACPD from 2013, and despite that, I can not find record of it online (in or out of ACPD) with these first four authors.
>> The reference is updated to the published version: (Tjernström, 2014), https://doi.org/10.5194/acp-14-2823-2014. The older ACPD version: https://doi.org/10.5194/acpd-13-13541-2013.

Lines 856-863: This paper has been published, so the ACP version should be referenced, not the ACPD version. https://doi.org/10.5194/acp-15-7961-2015
>> Changed: (Schwier, 2015)

Lines 860-864: This paper has been published, so the ACP version should be referenced, not the ACPD version. https://doi.org/10.5194/acp-20-7955-2020. Also, 2019 is the ACPD publication year, not the volume, and the ACP article is 2020.
>> Changed: (Cravigan, 2020)

Line 867: there is no need to qualify the date for this publication as 1996b when using
numerical footnoted references.
>> Changed.

Line 1031-1033: This publication has no journal name, volume, or pages.
>> Corrected.

ESI Page 3 – I’m guessing that “Of the samples taken during the transit (F8-F11, Table 1 in the main article), F11 were classified as likely…” – should be “… F8 and F11 were classified as likely…” – based on Table 1, and their classification of 3 or “high risk”.
>> We thank the reviewer for spotting that. It is updated now.

Figure S4 (ESI page 4) – the caption indicates (a) and (b) components, but these are not labeled on the figure.
>> Labels were added.

Figure S5 (ESI page 5) – in the caption, September 14 00 UTC is confusing, and should be
written as 14 September 0:00 UTC or 0 UTC. Similarly, at the top of the page, where the date and time are mentioned, the date could be confused with 14 Sept 2000, using “00 UTC”, so again, I recommend using 0:00 UTC or simply 0 UTC.
>> Changed to “14 September, 00:00 UTC”, also when applicable in the main manuscript.

Figure S7 caption (ESI page 7): “Volume size distributions (sum) of each aerosol sample F1- F13” seems misleading, as the size distributions were not from the filters. It would be more appropriate to say “Summed volume size distributions corresponding to each aerosol sample.”
>> Replaced by “Summed volume size distributions for the collection periods of each aerosol sample […]”.

Table S4 (ESI page 11): The 5th and 95th percentiles for DMS for IAOE-91 are reversed.
>> Changed.

Supplement references (page 11): I believe the same details need to be provided for the ESI references as the main text, so reference [1] should have all authors listed rather than “et al.”, more detail needs to be included for reference [5], and for reference [8], the pages are missing. Either include one or both of: D13308, doi:10.1029/2006JD008183. Also, for references [6] and [7], 1996 is fine, as there is no need for the 1996a and 1996b.
>> This has been corrected.


Reviewer 2

Comments to the Author
This work describes several chemical and microphysical measurements conducted onboard the Swedish Icebreaker, Oden, while moored (to the ice) and during transit out of the central Arctic Ocean in the late summer of 2018. The particular focus is on offline measurements made using a FIGAERO-HRToF-CIMS instrument. Filter samples of the ambient aerosol were collected on the Oden, wrapped in foil and stored in a freezer. In a laboratory, the samples are individually heated to 200 C and nalysed, via mass spectrometry, for evolving compounds that cluster with the CIMS reagent ion (I-). In total, 13 filter samples were
collected from September 11 to 19, inclusive, along with two blanks. Individual sampling times ranged from 6-35 hours, and sample #6 was set aside for a different analysis not discussed in this paper. The analyses of all samples yielded 519 compounds that clustered with the reagent ion and are considered valid. The filter samples were collected about 25 m above the sea surface through a combination of tubing, including two short pieces of conductive silicone tubing. The inlet was heated to between 30 C and 40 C to allow for the collection of fog and cloud residuals as well as not cloud-activated aerosol particles. Samples 8-11 are considered to have possible contamination by the ship’s emissions.

Of the 519 compounds included in the results, 64% are comprised of CHO, 28% of CHON, 5% of CHOS and 2% of inorganic S. The authors conclude 1) that submicron particles in the central Arctic boundary layer during late summer have a large contribution from organic and sulphur molecules, and 2) that the gas-phase and particle-phase compositions did not co-vary in time.

Overall, the presentation is good and the authors have combined a large number of observations together to provide useful knowledge of the chemistry of the Arctic aerosol over the central Arctic Ocean. Neither conclusion is unique to the Arctic in a general sense (see detailed comments below), but I believe both are unique to their particular location and important in that sense. There is a problem with the reference list, which made reviewing a little more difficult.

>> We thank the reviewer for their time to review our paper, and for their positive assessment. We have carefully checked the reference list for the revised version of the manuscript.

Detailed Comments:
1) Reference numbering appears to be offset, and presumably some references are missing, since the reference numbers in the text go up to 89, but there are only 84 in the list.
>> Fixed.

2) As I mention above, I believe the results are important because of the location in the Arctic. However, the conclusion about organic and sulphur compounds in the summer is not unique to the Arctic. Shaw et al. (https://doi.org/10.10 29/2010GL042831, 2010) describe one-year of particle chemistry at Utqiagvik, Alaska (formerly known as Barrow), including organics, and Leaitch et al. (https://doi.org/10.5194/acp-18-3269-2018, 2018) describe over two years of similar measurements at Alert, Nunavut. If, as your title suggests, your measurements are intended to provide more insight into the Arctic submicron aerosol, discussion of the similarities and differences of your results with these other measurements is necessary.
>> We thank the reviewer for suggesting these studies that we were unaware of. They have been added both to the introduction and to the discussion along with another reference: (Willis, 2017).
The following was added in the introduction: “Secondary organic aerosols (SOA) from organic volatile compounds have, through land-based studies in Alaska (Shaw, 2010) and the Canadian archipelago (Willis, 2017) (Leaitch, 2018) and ship-based measurements in the central Arctic Ocean (Chang, 2011), shown to also make up a significant fraction of the submicron aerosol mass in the Arctic. These aerosols originate from both marine biogenic sources and long-range transport from continental areas.”
This has been added to the conclusions: "Similar research has previously been conducted in the Arctic with results comparable to ours using other techniques. However, most of these measurements were conducted in the lower Arctic and on land (Shaw, 2010) (Willis, 2017) (Leaitch, 2018). These studies, along with that presented by (Chang, 2011) from the central Arctic Ocean, have only provided information on those functional groups present while our study also provides information on the molecular composition of the aerosol. As such, this study suggests that the FIGAERO-CIMS can provide new insight into the aerosol chemical composition of the Arctic as well as other pristine environments.”

3) Lines 27-30 – This statement, drawn on results of limited trajectory analyses does not adequately reflect our current understanding of Arctic haze. Global transport models accounting for transport times greater than 10 days, indicate that emissions from Southeast Asia significantly impact surface measurements in the high Arctic during spring (e.g. Qi et al., https://doi.org/10.5194/acp-17-1037-2017, 2017a; Qi et al. https://doi.org/10.5194/acp-17-9697-2017, 2017b; Xu et al., https://doi.org/10.5194/acp-17-11971-2017, 2017). Please revise. The reference number given here (12) corresponds to Mitchell, 1957, which I assume you did not intend.
>> We are thankful to the reviewer for pointing this out. The statement has been corrected as follows: “Aerosol mass loadings in the Arctic show a strong seasonal behaviour, with higher loadings in winter and early spring due to a phenomenon called Arctic haze, (Greenaway, 1950) (Mitchell, 1957) where pollution from Eurasia and North America is transported to the Arctic (Qi L. L.-L., 2017a) (Qi L. L., 2017b) (Xu, 2017)”.
The reference to (Mitchell, 1957) was moved to earlier in the sentence (immediately after mentioning "Arctic haze"), and we also added (Greenaway, 1950). These two papers seem to be standard to cite for the discovery of Arctic haze.

4) Lines 79-82 – You have not included here more recent results that suggest a stronger role for DMS in CCN formation in the summertime Arctic (e.g. Chang et al., ACP, 2011, in your list; Leaitch et al., https://doi:10.12952/journal.elementa.000017, 2013; Giamarelou et al.,
https://doi.org/10.1002/2015JD023646, 2015; Willis et al., https://doi:10.5194/acp-16-7663-
20162016, 2016; Dall’Osto, et al., https://doi.org/10.1038/s41598-017-03328-1, 2017). A more balanced discussion is needed.
>> We thank the reviewer for pointing out these references. We added the following text to the corresponding paragraph: "More recent studies have however provided new evidence for the relationship between DMS and Arctic SOA formation (Quinn, 2002), (Leaitch W. R.-S., 2013) (Willis M. D., 2016), e.g. relatively high MSA-to-sulfate ratios during aerosol growth and correlations between MSA and new particle formation (NPF) events. Knowledge about other SOA precursor gases and compounds has remained limited, since relevant measurements in this region are very scarce."

5) Lines 108-110 - Large-scale models are unlikely to consider detailed molecular compositions in order to simulate CCN activity. Simplifications, such as “Kappa” (Petters and Kreidenweis, ACP, 2007), are more likely to be employed. Your discussion here should mention how molecular composition will aid such parameterizations.
>> The corresponding paragraph was changed as following: "Molecular-level composition data can thus enable calculations of e.g. the hygroscopicity parameter κ (Petters, M. D. and Kreidenweis, S. M., 2007), which can provide a more accurate quantification of CCN ability, or volatility basis sets (VBS) (Donahue, 2012) (Mohr, 2019) formulations, which are used to predict partitioning of compounds between the gas and particle phase. Such numbers are largely not available for the central Arctic Ocean."

6) Lines 167-170 – Syntax problem with this sentence.
>> The sentence was changed to: “Controlled heating (30-40°C) of the inlet prevented clogging of the inlet with ice. In addition, inlet heating led to evaporation of cloud and fog droplets, so that all aerosol particles, whether activated or not, were included in the measurement.”

7) Line 177 – Collection rather than deposition?
>> Changed as suggested.

8) Line 194 – Reference numbering here and in many other places.
>> The references were fixed.

9) Lines 461-463 – Based on the AMS, ammonium and nitrate were very low compared with
SO4=, yet your FIGAERO-based pie chart indicates nitrogen associated with CHO is almost six times higher than S associated with CHO. Please offer some explanation.
>> In the AMS, inorganic nitrate (or ammonium nitrate) is detected separately from organonitrates (here likely are of biogenic origin), which are assigned to the organic fraction measured by AMS (unless specific analysis steps are taken (Kiendler-Scharr, 2009)). “Inorganic” was added to the sentence to clarify this: “Inorganic ammonium, nitrate and chloride from AMS were not included in the analysis as their concentrations were extremely low compared to Org and SO42- and close to the detection limit.”

10) Lines 494-495 – It may be a colour issue, but it is not evident in Figure 5 that the trajectories associated with samples 1-3 go towards the Canadian Archipelago.
>> The reviewer is correct, the respective trajectories go more towards Alaska than the Canadian Archipelago. We changed the corresponding wording to "Beaufort Sea" to make it more specific.

11) Lines 508-510 - A possibility, but, by this statement, it seems that you are saying there was no organic contamination from the ship emissions, which is in direct contrast with sample F8 and F10 that indicate significant organic contamination and little contamination from sulphur. I suggest avoiding this discussion altogether.
>> The reviewer makes a fair point. The following sentence has been removed: "Interestingly, the organic FIGAERO-CIMS signal was on a level comparable to e.g. F5 and F13, which were not considered contaminated. This is an argument for a non-contamination source of these organic compounds, e.g. primary SSA or marine precursor gases."

12) Lines 513-515 – Do you mean “by the FIGAERO-CIMS” rather than “by the AMS”?
>> Yes. We have added "by the FIGAERO-CIMS" to this sentence for clarification.

13) Lines 507-527 – I don’t find this discussion convincing of anything. What Figure 4 appears to show is that your FIGAERO-CIMS results only represent a very small fraction of the organic components that are measured by the AMS. Some discussion explaining these large differences seems most relevant here. Also, you introduce Figure 4 before Figure 5.
>> The FIGAERO-CIMS and AMS results cannot be compared quantitatively in our case, as we do not convert the FIGAERO-CIMS signal to atmospheric concentrations (compare lines 229-239). A comparison of organic compounds (Org in the AMS, CHO, CHON, CHOS, CHONS in the FIGAERO-CIMS) and inorganic compounds (SO42- in the AMS, Inorg. S in the FIGAERO-CIMS can therefore only be on a relative level between instruments. For clarification, the corresponding paragraph was changed as following: “The highest relative and absolute signal from Inorg. S by the FIGAERO-CIMS was found in F11, which was influenced by ship contamination (Table 1). In the AMS, however, the SO42- fraction is lower compared to the periods of other filters. A reason for this could be that not all Inorg. S compounds were detected as SO42- by the AMS, although 92.1% of the Inorg. S signal was made up by SA. Overall, the FIGAERO-CIMS and AMS signals were on similar relative levels in samples with a higher FIGAERO-CIMS signal, e.g. F1-F3 and F12.”
We do not understand the reviewer´s other comment about the introduction of Figure 4 before Figure 5.

14) Lines 579-583 – Except that most of the 5-day back air trajectories suggest the aerosols
spent all of that time over the central Arctic Ocean. Why then would you expect large
differences?
>> For clarification, the sentence was changed as following: "As the samples were collected in different environments (pack ice, transit and MIZ), and Fig. 5 indicates more time spent over the ocean compared to the pack ice for the samples collected later during the measurement period (F8-F13), one would expect the degree of oxygenation (as a measure of aerosol aging processes) to vary between the different samples."

15) Lines 583-585 - Are you trying to say that nothing is significant?
>> We thank the reviewer for pointing this out. We have changed the respective paragraph in the manuscript to be more descriptive:
We have removed the following sentence from the paragraph starting at line 553:
“This is also clear from Fig. 7, which shows the relative fraction of compounds with 1-2, 3-4, 5-6, and >6 oxygen atoms per filter sample. O3-4 compounds vary between 51 and 85% of the total signal, and O5-6 between 9 and 38%.” and moved it to the paragraph starting at line 589. This paragraph has also been changed to the following:
“In Fig. 7, we have taken the compound groups from Fig. 6 and aggregated them further to compound groups with 1-2, 3-4, 5-6, and >6 oxygen atoms. In Fig. 7 we show the relative contributions of the summed signal of all compounds in these respective groups per filter sample. Overall, for all filter samples, compounds with 3-4 oxygen atoms dominated the signal (51-85%), followed by compounds with 5-6 oxygen atoms (9-38%), and compounds with 1-2 oxygen atoms (6–26%). Compounds with >6 oxygen atoms made up 0-10% of the total signal. As the samples were collected in different environments (pack ice, transit and MIZ), and Fig. 5 indicates more time spent over the ocean compared to the pack ice for the samples collected later during the measurement period (F8-F13), one would expect the degree of oxygenation (as a measure of aerosol aging processes) to vary between the different samples. Clear differences between samples from ice floe, transit, or MIZ are however not distinguishable, indicating that the time resolution of data presented here is not necessarily sufficient to clearly separate temporally varying influence of different regional aerosol sources purely based on molecular composition.”

16) Lines 617-620 – Of course, the oxidation products you measure were produced and
partitioned to the particle phase during transport from some source region. How else would it happen? Some re-write is needed to explain better what it is you are trying to extract from the 10% emitted in the Arctic BL and the 90% emitted from surrounding seas.
>> For clarification, the sentence was changed to "The DMS oxidation products we measured in the aerosol samples in the pack ice were therefore likely produced to a large extent during advection over the ice from the surrounding seas. By comparing the concentrations of DMS and its oxidation products in the gas- and particle phase at various distances from the source region, conclusions can be drawn both on source regions as well as the influence of atmospheric transport on the particle chemical composition."

17) Lines 639-641 – This statement fails to address the question, why does MSA follow SA
when SA is assumed to be from ship contamination? If the subsequent paragraph (lines 644-
660) is intended to answer this question, it needs more clarity.
>> The corresponding paragraph was changed as following: "It is possible that gaseous and particulate pollutants in the ship exhaust impact MSA production and partitioning, and therefore measured MSA (p) and SA (p) co-vary also in the contaminated samples."

18) Lines 663-665 - Perhaps true, but you need to mention that it will also depend on oxidant
levels and meteorology.
>> We agree with the reviewer. We have added the following statement: "This is confirmed by the back trajectory analysis in Fig. 5, although current oxidant levels and meteorological conditions along the trajectory will also play a role"

19) A question of curiosity – You show size distributions of volume, which of course are most relevant to your results, but did you see increases in the number concentrations of smaller particles at any point that might be evidence for new particle formation?
>> (Baccarini, 2020) recently published a paper on new particle formation (NPF) observed during this campaign (AO18). We do have number size distribution data for particle diameters 10-921 nm as uploaded as a file to the resubmission, averaged over the time period of the individual filter periods (Figure text: Summed number size distributions for the collection periods of each aerosol sample F1-F13, where Dp is the particle aerodynamic diameter.) (figure for the reviewer’s information only). Obviously, higher time resolution is needed for investigation of NPF, but as mentioned also by the reviewer, this is outside the scope of our paper, not least because we do not expect newly formed particles to exhibit distinguishable signal in the filter samples due to the low mass contributions of very small particles.

In addition to the changes made with the help of the reviewers’ comments, the following has been added to the manuscript:
• Replaced all “United States” by “USA” for coherence.
• A possible second structure (hydroxymethanesulfonic acid) in Table 2. Previously only the structure for monomethyl sulfate was shown. The other molecules have also been remade with clearer structures and higher resolution.
• Several of the table and figure numbers had to be adjusted.
• Other smaller changes in the text that were not mentioned in this document have been marked yellow as well.

References
• Baccarini, A. K. (2020). Frequent new particle formation over the high Arctic pack ice by enhanced iodine emissions. Nature communications, 1-11. doi:https://doi.org/10.1038/s41467-020-18551-0
Chang, R.-W. L. (2011). Aerosol composition and sources in the central Arctic Ocean during ASCOS. Atm. Chem. Phys., 10619-10636. doi:https://doi.org/10.5194/acp-11-10619-2011
• Cravigan, L. T. (2020). Sea spray aerosol organic enrichment, water uptake and surface tension effects. Atmos. Chem. Phys., 7955–7977. doi:https://doi.org/10.5194/acp-20-7955-2020
• Donahue, N. M. (2012). A two-dimensional volatility basis set – Part 2: Diagnostics of organic-aerosol evolution. Atm. Chem. Phys., 615-634. doi:https://doi.org/10.5194/acp-12-615-2012
• Greenaway, K. R. (1950). Experiences with Arctic Flying Weather. London: Royal Meteorological Society, Canadian Branch.
• Kiendler-Scharr, A. Z. (2009). Aerosol Mass Spectrometric Features of Biogenic SOA: Observations from a Plant Chamber and in Rural Atmospheric Environments. Environ. Sci. Technol., 8166–8172. doi:https://doi.org/10.1021/es901420b
• Leaitch, W. R. (2018). Organic functional groups in the submicron aerosol at 82.5° N, 62.5° W from 2012 to 2014. Atmos. Chem. Phys., 3269–3287. doi:https://doi.org/10.5194/acp-18-3269-2018
• Leaitch, W. R.-S. (2013). Dimethyl sulfide control of the clean summertime Arctic aerosol and cloudDMS Control of the Arctic Aerosol and Cloud. Elementa: Science of the Anthropocene, 000017. doi:https://doi.org/10.12952/journal.elementa.000017
• Mitchell, J. M. (1957). Visual range in the polar regions with particular reference to the Alaskan Arctic. J. Atmos. Terr. Phys., 195-211.
• Mohr, C. T.-H. (2019). Molecular identification of organic vapors driving atmospheric nanoparticle growth. Nature Communications, 4442. doi:https://doi.org/10.1038/s41467-019-12473-2
• Petters, M. D. and Kreidenweis, S. M. (2007). A single parameter representation of hygroscopic growth and cloud condensation nucleus activity. Atm. Chem. Phys., 1961-1971. doi:https://doi.org/10.5194/acp-7-1961-2007
• Prytherch, J. and Yelland, M. J. (2021). Wind, convection and fetch dependence of gas transfer velocity in an Arctic sea-ice lead determined from eddy covariance CO2 flux measurements. Global Biogeochemical Cycles, e2020GB006633. doi:https://doi.org/10.1029/2020GB006633
• Qi, L. L. (2017b). Factors controlling black carbon distribution in the Arctic. Atm. Chem. Phys., 1037-1059. doi:https://doi.org/10.5194/acp-17-1037-2017
• Qi, L. L.-L. (2017a). Sources of springtime surface black carbon in the Arctic: an adjoint analysis for April 2008. Atm. Chem. Phys., 9697-9716. doi:https://doi.org/10.5194/acp-17-9697-2017
• Quinn, P. K. (2002). A 3-year record of simultaneously measured aerosol chemical and optical properties at Barrow, Alaska. Journal of Geophysical Research: Atmospheres, AAC 8-1-AAC 8-15. doi:https://doi.org/10.1029/2001JD001248
• Schwier, A. N. (2015). Primary marine aerosol emissions from the Mediterranean Sea during pre-bloom and oligotrophic conditions: correlations to seawater chlorophyll a from a mesocosm study. Atmos. Chem. Phys., 7961-7976. doi:https://doi.org/10.5194/acp-15-7961-2015
• Shaw, P. M. (2010). Arctic organic aerosol measurements show particles from mixed combustion in spring haze and from frost flowers in winter. Geophysical Research Letters. doi:https://doi.org/10.1029/2010GL042831
• Tjernström, M. L. (2014). The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design. Atmos. Chem. Phys., 2823-2869. doi:https://doi.org/10.5194/acp-14-2823-2014
• Vüllers, J. A. (2021). Meteorological and cloud conditions during the Arctic Ocean 2018 expedition. Atm. Chem. Phys., 289-314. doi:https://doi.org/10.5194/acp-21-289-2021
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• Willis, M. D. (2017). Evidence for marine biogenic influence on summertime Arctic aerosol. Geophys. Res. Lett., 6460–6470. doi:https://doi:10.1002/2017GL073359
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08-Mar-2021

Dear Dr Mohr:

Manuscript ID: EA-ART-12-2020-000023.R1
TITLE: Insights into the molecular composition of semi-volatile aerosols in the summertime central Arctic Ocean using FIGAERO-CIMS

Thank you for submitting your revised manuscript to Environmental Science: Atmospheres. After considering the changes you have made, I am pleased to accept your manuscript for publication in its current form. I have copied any final comments from the reviewer(s) below.

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With best wishes,

Dr Nønne Prisle
Associate Editor, Environmental Sciences: Atmospheres

Reviewer 2

The authors have appropriately addressed the review comments, including the uniqueness of their results.

Reviewer 1

The authors have addressed all the reviewer comments, both mine and from the other reviewer. It is in my opinion that the manuscript is ready to be published.