Zeppenfeld et al. investigated the transfer and composition of marine carbohydrates in the Arctic atmosphere based on samples collected during the PS106 campaign in May-June 2017. Various sea surface compartments showed significant differences in carbohydrate concentrations and enrichment factors. Atmospheric aging of carbohydrates was observed, influenced by enzymatic/microbial activities and abiotic degradation. These findings have implications for cloud properties and interactions between cryosphere, ocean, and atmosphere in the Arctic, with potential feedback mechanisms. The manuscript is well written and very thorough. I only have some general and specific comments below that the authors should address prior to publication in EGUsphere.

General comments:

Abstract: Should contain 1-3 opening sentences that discuss the motivation and important of this study, and briefly define the region (Fram Strait) and time of year (May-Jun 2017).

“Aged” melt ponds: How was the age of the melt ponds determined? It comes up a few times throughout the manuscript but it is not clear how they are defined from newly-formed ponds. Usually this time of year corresponds to relatively new melt ponds, while older ponds are present during the end of summer (e.g., when they form at their deepest depths and even drain).

Was melt pond depths measured? If so, was there any relationship with the presence and production of CCHO in the water and air? That would somewhat get to if there is a relationship with newer versus older ponds.

This is just a minor comment, but ‘chapters’ is used a few times and I think the authors mean ‘sections’.

Specific comments:

Line 23: Define the EF with subscripts after first mention, then just include the values in the parentheses in the rest of the sentence.

Line 28: Does ‘CCHO_fog,atmos’ refer to interstitial aerosol present during fog events? 

Line 40: I think “boreal” is the incorrect word to use here since the focus is on the Arctic Ocean and not the subpolar climate zone.

Lines 40-41: Kerri Pratt’s group has done quite a bit of work on SSA in the Arctic. It would be useful to check out and cite those papers (e.g., Kirpes et al. (2018, 2019), May et al. (2016)).

Lines 41-45: Probably should add a few recent, key references here, even though some of these elude to blowing snow as the source of SSA - Chen et al. (2022), Huang and Jaegle (2017).

Line 47: How does ‘primary marine aerosol particles’ differ from SSA? Maybe just stick to one, common term.

Lines 64-68: Is another difference between dissolved and particulate CCHO due to size, whether they are single carbohydrates or agglomerates of them, respectively? That would make sense to me on a physical basis.

Lines 73-73: Should also cite Alpert et al. (2022). Include Alpert et al. (2022) on lines 870-871 as well.

Line 116: Leads can often be wider than several meters (sometimes 10s), and hundreds of meters long.

Line 149: How was the SML thickness measured/calculated? Was it based on the total mL of SML collected and the collection speed? If so, is that representative of the wider region or is the thickness variable locally?

Line 151: What is meant by ‘closed’ melt ponds? Ice lids on the ponds?

Line 157: I assume the 0.2 um filtration was to remove PBAP?

Lines 281-282: Should say SSA here instead or ‘primary marine aerosol particles’. And also not that it is not just carbohydrates, but also microbial cells and fragments.

Fig SI2: Since there is a bit of discussion on the results in this figure, the authors should strongly consider moving it to the main manuscript.

Lines 453-456: Could this difference also be because the SO/Antarctic pack ice does not have melt ponds that develop in the austral summer? Would make sense why Na+ would correlate better with CCHO in the SO than the Arctic.

Lines 478-480: When and where were these samples collected? That info should be included in the methods.

Lines 507-510: The authors should provide some concrete evidence (i.e., values and citation(s)) from previous Arctic fog studies.

Lines 570-575: It is hard to tell quantitatively how much time air masses spent over the ice, ocean, etc. from Fig SI 3. How was this calculated? The authors should show these calculator results, either in a table or another SI figure.

Lines 603-606: It seems like these assumed sources were defined by the air mass analysis, but akin to my comment above, some additional methodology should be included. For example, was the ‘ice-free ocean’ source determined by each trajectory spending X percentage of time over the ice-free ocean south of the pack ice? What is the difference between ‘marine’ and ‘ice-free ocean’ in this case? Some thresholds for the relative amount of time each trajectory spent over each surface type, and some statistical analysis on these results would help.

Fig SI 4 and 5: First, the panel for pCCHO and a_ph440 is not shown in Fig SI 4. Also, given some of these results seem like an important finding to the manuscript, the panels that are explicitly discussed in detail in the text should be presented as a main figure. The remaining panels could remain in the SI.

References:

Alpert, P. A., Kilthau, W. P., O’Brien, R. E., Moffet, R. C., Gilles, M. K., Wang, B., Laskin, A., Aller, J. Y., and Knopf, D. A.: Ice-nucleating agents in sea spray aerosol identified and quantified with a holistic multimodal freezing model, Science Advances, 8, eabq6842, https://doi.org/10.1126/sciadv.abq6842, 2022.

Chen, Q., Mirrielees, J. A., Thanekar, S., Loeb, N. A., Kirpes, R. M., Upchurch, L. M., Barget, A. J., Lata, N. N., Raso, A. R. W., McNamara, S. M., China, S., Quinn, P. K., Ault, A. P., Kennedy, A., Shepson, P. B., Fuentes, J. D., and Pratt, K. A.: Atmospheric particle abundance and sea salt aerosol observations in the springtime Arctic: a focus on blowing snow and leads, Atmos. Chem. Phys., 22, 15263–15285, https://doi.org/10.5194/acp-22-15263-2022, 2022.

Huang, J. and Jaeglé, L.: Wintertime enhancements of sea salt aerosol in polar regions consistent with a sea ice source from blowing snow, Atmos. Chem. Phys., 17, 3699–3712, https://doi.org/10.5194/acp-17-3699-2017, 2017.

Kirpes, R. M., Bondy, A. L., Bonanno, D., Moffet, R. C., Wang, B., Laskin, A., Ault, A. P., and Pratt, K. A.: Secondary sulfate is internally mixed with sea spray aerosol and organic aerosol in the winter Arctic, Atmos. Chem. Phys., 18, 3937–3949, https://doi.org/10.5194/acp-18-3937-2018, 2018.

Kirpes, R. M., Bonanno, D., May, N. W., Fraund, M., Barget, A. J., Moffet, R. C., Ault, A. P., and Pratt, K. A.: Wintertime Arctic Sea Spray Aerosol Composition Controlled by Sea Ice Lead Microbiology, ACS Cent. Sci., 5, 1760–1767, https://doi.org/10.1021/acscentsci.9b00541, 2019.

May, N. W., Quinn, P. K., McNamara, S. M., and Pratt, K. A.: Multiyear study of the dependence of sea salt aerosol on wind speed and sea ice conditions in the coastal Arctic: ARCTIC SEA SALT AEROSOL, J. Geophys. Res. Atmos., 121, 9208–9219, https://doi.org/10.1002/2016JD025273, 2016.

The authors collected samples from various aquatic and atmospheric sources during the PS106 campaign in May-June 2017. In this study they analyze and compare the combined carbohydrate concentrations, both dissolved and particulate, and discuss mechanisms for their enrichment in the SML and transfer into the air. Their findings add to a severely limited set of data on SML and CCHO concentrations in the Arctic region and have implications for both bio-chemical properties at the air-sea interface as well as CCN and INP formation in the air.  The manuscript is well written, although some grammatical suggestions have been given. General and specific comments are given below which should be addressed prior to publication.

General Comments:

As I was able to see reviewer 1’s comments before giving my review, I have tried to refrain from giving any duplicate suggestions, however please be aware that I am in complete agreement with all of their comments.

It would be nice if you could include information about the trajectories and age of the water masses you sampled from. Similar to air masses, arctic water in ice-free zones, MIZ and leads have long residence times of OM in the surface waters and thus will be impacted by the source of these waters. Did anyone take oxygen samples that you could include?

You compare this study to your other study in the southern ocean a lot. I would suggest to include a broader range of studies for comparison or include a good argument as to why you are comparing these two studies specifically.

During the ice floe camp, how far was your sampling location from RV Polarstern? As you are comparing aerosol measurements sampled on the ship with water samples taken nearby this is important, it would be good to describe the ice flow camp situation in general. How and why was the location or time chosen etc. Additionally, how far from the ice edge did you sample in the leads, this is important to know as later on you discuss the effects of meltwater on SML samples.

Figure SI 1. The zoomed in ice flow image is hard to orientate withing the larger cruise track image, please indicate where in the larger map the ice flow camp occurred.

Specific Comments:

Line 47: (primary marine aerosol particles)

Line 55: “appear” not “appears”

Line 72: “suggested”, “found” or similar, not assumed, assume suggests lack of evidence

Line 83: give reference for bubble scavenging as this is different from bubble bursting

Line 84: “within the bulk water and the SML”

Line 115: open leads can be much larger than several meters, would be good to define the difference between open leads and polynyas as these are often incorrectly used interchangeably, here it seems you use both because you are not sure which your study areas would be classified as, which is fine but should be addressed.

Line 117: “defined by a ..”

Line 134: “eventually”  and "disclose" not the best word choice, try  "The complex nature of these primary emission mechanisms and subsequent atmospheric aging of marine CCHO in the Arctic Ocean are discussed in relation to our findings."

Line 144: how were ages of melt pond determined? How young is young?

Line 157: what was the ambient air temperature when sampling with glass plate? It’s good as a reader to know, as when air temperatures get low enough the SML samples can freeze on the glass plate before they are wiped off and may impact the carbohydrate measurements. However, it’s likely that temperatures weren’t this cold during the time of year you were there.

Line 267: you use sea-ice (hyphenated) here but not elsewhere in the manuscript, be careful to homogenize your grammar choice

Line 286: “eventually” used again. Just leave it out “The influence of the ….”

Line 292: “Among all aqueous samples, regardless … dCCHO (...) and pCCHO (…) concentrations were highly variable”

Line 294: “However, the minimum, maximum and mean values of both dCCHO and pCCHO ranged within the same orders of magnitude”

Line 307: The region comparisons you use for SML CCHO concentrations seem random, you should either compare with other arctic region studies, there have been quite a few studies of SML in the Fram Straight, or refer to overview studies which compare from a large variety of regions (e.g. Wurl et al. 2011. )

Line 317: “80% of the SML samples were moderately or highly enriched in marine carbohydrates, with only a few cases of depletion (7 for dCCHO and 8 …”

Line 319: I’m not sure stating the median concentration is very useful here

Line 358: If release of melt water results in increases of CCHO then shouldn’t you have found significantly higher mean values in your melt ponds and open leads compared to MIZ and ice-free zones? Galgani et al. 2016. in fact have done a similar study and did find this. It would be good for you to address that study and the possible relations and difference it has to your study.

Line 366: Did you compare the salinity of the SML with the dCCHO and pCCHO concentrations? Increased biogenic material in the SML may result in a freshening of the SML. Additionally, Mari et al. 2012 found that in estuaries where there are large salinity gradients, the aggregation properties of TEP changed with salinity, a similar relationship between salinity and the phisico-chemical reactivity of TEP or CCHO may exist in arctic melt ponds and leads, and could show in the ratio of dissolved to particulate CCHO. This would additionally impact the ability for these particles to transfer into the air.

Line 390: “The high Arctic…”

Line 866: remove “in a nut shell”, too informal, no need for it.

References:

Galgani, L., Piontek, J. and Engel, A., 2016. Biopolymers form a gelatinous microlayer at the air-sea interface when Arctic sea ice melts. Scientific Reports, 6(1), p.29465.

Mari, X., Torréton, J.P., Trinh, C.B.T., Bouvier, T., Van Thuoc, C., Lefebvre, J.P. and Ouillon, S., 2012. Aggregation dynamics along a salinity gradient in the Bach Dang estuary, North Vietnam. Estuarine, Coastal and Shelf Science, 96, pp.151-158.

Wurl, O., Miller, L. and Vagle, S., 2011. Production and fate of transparent exopolymer particles in the ocean. Journal of Geophysical Research: Oceans, 116(C7).

Wurl, O., Wurl, E., Miller, L., Johnson, K. and Vagle, S., 2011. Formation and global distribution of sea-surface microlayers. Biogeosciences, 8(1), pp.121-135.