From the journal Environmental Science: Atmospheres Peer review history

15-Feb-2023

Dear Dr Ito:

Manuscript ID: EA-CRV-11-2022-000156
TITLE: Marine aerosol feedback on biogeochemical cycles and climate in the Pacific Ocean

Thank you for your submission to Environmental Science: Atmospheres, published by the Royal Society of Chemistry. I sent your manuscript to reviewers and I have now received their reports which are copied below.

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

Reviewer 1

Manuscript entitled “Marine aerosol feedback on biogeochemical cycles and climate in the Pacific Ocean” summarize the progresses in research on organic aerosols, nitrogen, and iron in the marine atmosphere. This manuscript gives us a clearer understanding of the impact of human activities on marine ecosystems and climate through various feedbacks in biogeochemical cycles. The authors integrated field observation, laboratory experiment, and numerical modelling studies, which are essential to foster individual studies into cross-disciplinary research.
This review highlights numerical models, and the combination of field observations, laboratory experiments, and numerical models, which can improve our understanding of biogeochemical cycles. The paper falls in the field of Environmental Science: Atmospheres and could be published in the journal assuming some minor corrections.

1. Abstract: The impacts of human activities on marine ecosystem and climate are mainly introduced, but the contribution of marine sources is not reflected. This is different from the title of the manuscript.
2. Page 3 Lines 15-18 in the right column: “In addition to such physical feedbacks, CCN and INP number concentrations…”. It is suggested to cite references here.
3. Page 3 Lines 29-37 in the right column: This paragraph is about the impact of marine sources on CCN. The sudden mention of forest fire and air pollutants here is quite abrupt, so it is suggested to modify it.
4. Page 4 Lines 1-10 in the left column: Three kinds of material sources summarized in this manuscript are described, which are marine source, natural source and anthropogenic source respectively. I feel there is overlap among the three sources, and hope the authors can modify them.
5. Page 5 Lines 25-28 in the right column: This section mentions the effect of sea ice. I think the connection with the above is not close enough. The authors should explain the effect of sea ice on marine aerosols.
6. Page 7 Lines 5-10 in the right column: There is some overlap between the anthropogenic and terrestrial sources mentioned here.

Reviewer 2

The critical review by Akinori et al. reviews the relevant literature on ocean emissions and deposition to the ocean with a focus on the Pacific Ocean.

Throughout the paper it is not 100% clear when the mentioned study focused on the Pacific Ocean or another ocean region. Particularly when discussing studies in the Arctic and Southern Oceans. This needs to be clarified.
Introduction – it’s not clear if the second paragraph in its entirety refers to Earth system models. There also needs to be more references in that paragraph.
Introduction paragraph number 4 last sentence – appropriate reference is to Jickells 2017 GBC update paper, also has revised estimate of production that results from anthropogenic atmospheric deposition.
Section 2 – requires additional subheadings to clarify the section.
First paragraph first sentence needs references.
Section 2 page 5 first paragraph – it’s not clear how relevant the methods discussion is to the paper.
Figure 4 and others – need to define abbreviations from the source paper or the reader has no choice but to go read the source paper to understand what the figure is showing.

Reviewer 3

Major comments:

This paper reviews marine aerosol emissions and deposition over the Pacific Ocean and their role in biogeochemical cycles and climate. Specifically, it introduces the impact of human activities on marine ecosystems and climate through feedback in biogeochemical cycles, the effects of oceanic emissions and atmospheric deposition of aerosols and nutrients on marine cloud properties and marine biogeochemistry, as well as suggestions for future research. I think it provides a useful summary of the relevant work, and a relatively detailed qualitative description of these processes.

However, in my opinion, this review is lack of the descriptions of some critical quantification, such as:
(1) the source profile of marine aerosols: What are the contributions of sea spray aerosol, secondary marine aerosol, and continental aerosols to the total concentration of marine aerosols? What are their annual production fluxes over the Pacific ocean?

(2) the source profile of CCN and IN in marine atmosphere: which sources account for the largest fraction of CCN or IN?

(3) the contribution of aerosol deposition in the total supply of N and Fe in the Pacific Ocean

(4) the contribution of each aerosol source to the aerosol deposition of N and Fe.

In addition, the production mechanisms of sea spray aerosol and secondary marine aerosol should be introduced. The VOC emission for the ocean should be also described in a quantitative manner.

Specific comments:
The first sentence in the abstract is the same as the first sentence of abstract. Please revise.

Section 2.2: “However, aerosol particle formation from DMS as a precursor gas was extremely rare in the MBL where sea salt particles were abundant as pre-existing particles.4”: I do not think this is right. There is a debate about the relative abundance of SSA and secondary aerosol from DMS oxidation.

“OM in SSA affects not only the hygroscopicity and surface tension that determines the CCN ability of SSA,”: this is not true. The kappa value of SSA is quite constant no matter what its OM content is. See Doug Collins’ GRL paper.

Section 2.3: I would recommend doing a longer introduction on ice-nucleation. The current one is too simple.

“An online INP meter based on the Continuous Flow Diffusion Chamber method is also commercially available, but needs stability.”: no ref is provided.

Section 3.2: what kind of iron is bioaccessible? Are All dissolved iron bioaccessible? I would discuss it at the beginning of the section.

Figure 6: the resolution of this figure is significantly lower than other figures.

This text has been copied from the PDF response to reviewers and does not include any figures, images or special characters.

Manuscript ID: EA-CRV-11-2022-000156
TITLE: Marine aerosol feedback on biogeochemical cycles and climate in the Anthropocene: lessons learned from the Pacific Ocean
Authors: Akinori Ito, Yuzo Miyazaki, Fumikazu Taketani, Yoko Iwamoto, and Yugo Kanaya
Our responses to the comments from Reviewer 1 are included in the followings.
Reviewer: 1
Comments:
Manuscript entitled “Marine aerosol feedback on biogeochemical cycles and climate in the Pacific Ocean” summarize the progresses in research on organic aerosols, nitrogen, and iron in the marine atmosphere. This manuscript gives us a clearer understanding of the impact of human activities on marine ecosystems and climate through various feedbacks in biogeochemical cycles. The authors integrated field observation, laboratory experiment, and numerical modelling studies, which are essential to foster individual studies into cross-disciplinary research.
This review highlights numerical models, and the combination of field observations, laboratory experiments, and numerical models, which can improve our understanding of biogeochemical cycles. The paper falls in the field of Environmental Science: Atmospheres and could be published in the journal assuming some minor corrections.
Response:
We would like to thank the reviewer for his or her constructive comments which helped us to improve the readability of our manuscript substantially. We revised the manuscript following suggestions made by the reviewer.
Comments:
1. Abstract: The impacts of human activities on marine ecosystem and climate are mainly introduced, but the contribution of marine sources is not reflected. This is different from the title of the manuscript.
Response:
We included marine sources in the abstract.
“Atmospheric aerosols over the Pacific Ocean are largely influenced by anthropogenic (e.g., metal production, fossil fuel combustion, and agriculture), marine and terrestrial biogenic, pyrogenic (open biomass burning), and lithogenic (mineral dust) sources”
We revised the title.
“Marine aerosol feedback on biogeochemical cycles and climate in the Anthropocene: lessons learned from the Pacific Ocean”.
Comments:
2. Page 3 Lines 15-18 in the right column: “In addition to such physical feedbacks, CCN and INP number concentrations…”. It is suggested to cite references here.
Response:
We move the references from #8 and #73 to #6 and #7, respectively.
“In addition to such physical feedbacks, CCN and INP number concentrations in the atmosphere are modulated by aerosols and their precursors of marine biogenic origin. 6,7”
Comments:
3. Page 3 Lines 29-37 in the right column: This paragraph is about the impact of marine sources on CCN. The sudden mention of forest fire and air pollutants here is quite abrupt, so it is suggested to modify it.
Response:
We modified the order of the sentences to smooth the flow of the story.
“As a result of various responses of marine biogeochemical activities to increased sea surface temperatures and melting sea ice, the cloud properties in the atmosphere are expected to change and provide feedbacks to the climate change. On the other hand, in areas where phytoplankton growth is primarily limited by nutrient deficiency, nutrients supplied by aerosols and precipitation stimulate the growth of phytoplankton communities. Furthermore, an increase in large-scale forest fires due to climate change is projected to increase nutrient supply to the oceans. At the same time, nutrient deposition from industrial and agricultural sources is projected to increase with expected economic growth in some countries to enhance the phytoplankton productivity in specific regions of the ocean. This is, in turn, expected to enhance reactive gas and aerosol emissions and carbon dioxide (CO2) sink by the marine biogeochemical activities, thereby acting as the negative climate feedback and vice versa.”
Comments:
4. Page 4 Lines 1-10 in the left column: Three kinds of material sources summarized in this manuscript are described, which are marine source, natural source and anthropogenic source respectively. I feel there is overlap among the three sources, and hope the authors can modify them.
Response:
We elucidated the source categories.
“However, there is a large uncertainty in predicting the effects of oceanic (sea salt) and marine biogenic emissions on climate and the effects of atmospheric deposition of nutrients from anthropogenic (e.g., metal production, fossil fuel combustion, and agriculture), lithogenic (mineral dust), and pyrogenic (open biomass burning) sources on marine ecosystems.”
Comments:
5. Page 5 Lines 25-28 in the right column: This section mentions the effect of sea ice. I think the connection with the above is not close enough. The authors should explain the effect of sea ice on marine aerosols.
Response:
As is suggested by reviewers, we limited our discussions on the Pacific only and removed the sentence from the manuscript.
Comments:
6. Page 7 Lines 5-10 in the right column: There is some overlap between the anthropogenic and terrestrial sources mentioned here.
Response:
We elucidated the source categories.
“Future studies should clarify to what extent lithogenic, terrestrial biogenic, pyrogenic and anthropogenic sources also contribute to INPs in the atmosphere,93 as well as their respective roles and relative contributions in conjunction with marine biogenic sources.”  
Our responses to the comments from Reviewer 2 are included in the followings.
Reviewer: 2
Comments:
The critical review by Akinori et al. reviews the relevant literature on ocean emissions and deposition to the ocean with a focus on the Pacific Ocean.
Response:
We would like to thank the reviewer for his or her constructive comments which helped us to improve the readability of our manuscript substantially. We revised the manuscript following suggestions made by the reviewer.
Comments:
Throughout the paper it is not 100% clear when the mentioned study focused on the Pacific Ocean or another ocean region. Particularly when discussing studies in the Arctic and Southern Oceans. This needs to be clarified.
Response:
As is suggested by reviewers, we added Figures 2, 5, and 7 over the Pacific only, and removed the Arctic (> 66 °N) and Southern (< 60 °S) Oceans from the manuscript. We deleted the previous Figure 7 and replaced Figure 5 by the Pacific data.
Comments:
Introduction – it’s not clear if the second paragraph in its entirety refers to Earth system models. There also needs to be more references in that paragraph.
Response:
As is suggested by reviewers, we move the references from #8 and #73 to #6 and #7, respectively, in the second paragraph. We revised the sentences to elucidate that refers to Earth system models.
“An increase in a transient temperature is accompanied by an increase in the optical thickness of clouds due to the phase change process from ice clouds to liquid clouds (i.e., negative climate feedback).4 However, the strength of the negative feedback depends on the treatment of mixed-phase clouds with a mixture of cloud condensation nuclei (CCN) and ice-nucleating particle (INP) in Earth system models.5”
Comments:
Introduction paragraph number 4 last sentence – appropriate reference is to Jickells 2017 GBC update paper, also has revised estimate of production that results from anthropogenic atmospheric deposition.
Response:
We move the references from #83 to #13 in the 4th paragraph and revise the sentence.
“In addition to Fe, anthropogenic reactive nitrogen (N) (oxidized and reduced inorganic and organic compounds) deposition has been suggested to support up to ~3% of the marine biological production but this estimate been revised down to ~0.4%.12,13”
Comments:
Section 2 – requires additional subheadings to clarify the section.
Response:
We added the following sentences.
“To better predict the climate impact of marine aerosols by Earth system models, it is essential to understand the biological, chemical, and physical processes and to find optimal parameterization of sea-to-air emission fluxes of aerosols and their precursors (section 2.1), and subsequent activities of CCN (section 2.2) and INP (section 2.3).”
Comments:
First paragraph first sentence needs references.
Response:
We add previous #16 to this sentence.
“Shipboard measurements have shown that seasonal variation of primary production in the subarctic North Pacific is larger than that in other oceanic regions.18”
Comments:
Section 2 page 5 first paragraph – it’s not clear how relevant the methods discussion is to the paper.
Response:
We deleted the paragraph.
Comments:
Figure 4 and others – need to define abbreviations from the source paper or the reader has no choice but to go read the source paper to understand what the figure is showing.
Response:
We deleted the previous Figure 4 which was not necessarily to explain the text. We deleted the previous Figure 7 and replaced Figure 5 by the Pacific data. We explained abbreviations in Figs. 1 and 7. We replaced SSW with surface seawater in previous Fig. 2.
“After aerosols fall into the surface ocean, bioaccessible Fe binds with organic ligands (FeL), enters the biogeochemical cycle, or is removed via scavenging process.”
“The individual surface seawater data points corresponding to the identical aerosol sampling data are connected with a straight line.”
“The air masses are classified into three broad groups. The first group is mainly transported from the direction of East Asia. The second group is from the central and eastern Pacific. The third group is from the northern North Pacific.” 
Our responses to the comments from Reviewer 3 are included in the followings.
Reviewer: 3
Major comments
This paper reviews marine aerosol emissions and deposition over the Pacific Ocean and their role in biogeochemical cycles and climate. Specifically, it introduces the impact of human activities on marine ecosystems and climate through feedback in biogeochemical cycles, the effects of oceanic emissions and atmospheric deposition of aerosols and nutrients on marine cloud properties and marine biogeochemistry, as well as suggestions for future research. I think it provides a useful summary of the relevant work, and a relatively detailed qualitative description of these processes.
Response:
We would like to thank the reviewer for his or her constructive comments which helped us to improve the quality of our manuscript substantially. We revised the manuscript following suggestions made by the reviewer. Particularly, we described recent findings from laboratory studies of CCN in revised section 2.2.
Comments:
However, in my opinion, this review is lack of the descriptions of some critical quantification, such as:
(1) the source profile of marine aerosols: What are the contributions of sea spray aerosol, secondary marine aerosol, and continental aerosols to the total concentration of marine aerosols? What are their annual production fluxes over the Pacific ocean?
Response:
We show the relative contribution of primary organic aerosols from sea spray and secondary organic aerosols to the total concentration of marine organic aerosols over the Pacific, in comparison with primary organic aerosols from anthropogenic and pyrogenic sources in Fig. 2. The annual emission fluxes from marine biogenic (0.2 Tg for isoprene and 8.6 Tg for glyoxal) and shipping (0.1 Tg) sources over the Pacific are noted in the figure caption.
“To illustrate the annually averaged contribution of primary organic aerosol (POA) from sea spray to the total OA over the Pacific, the comparison with POA from anthropogenic and pyrogenic sources is shown in Fig.2. Here, we use the Integrated Massively Parallel Atmospheric Chemical Transport (IMPACT) model to estimate the source profile of marine aerosols over the Pacific.332”
“The spatial distribution shows that POA from sea spray comprise the majority of the OA over the tropical and subarctic North Pacific while POA from continental sources contribute to the dominate sources over the regions of continental outflow.34,35”
“In addition to POA, the annually averaged contribution of secondary OA (SOA) to the total concentration of OA over the Pacific is shown in Fig.2(d).”
“The spatial distribution shows that SOA from the marine and terrestrial sources is the majority of the OA over the open ocean (Fig.2(d)).”
Additional references:
A. Ito, and T. Miyakawa, Aerosol iron from metal production as a secondary source of bioaccessible iron, Environ. Sci. Technol. 2023, doi:10.1021/acs.est.2c06472.
B. Gantt, M. S. Johnson, N. Meskhidze, J. Sciare, J. Ovadnevaite, D. Ceburnis, and C. D. O’Dowd, Model evaluation of marine primary organic aerosol emission schemes, Atmos. Chem. Phys. 2012, 12, 8553–8566, DOI:10.5194/acp-12-8553-2012.
S. Myriokefalitakis, E. Vignati, K. Tsigaridis, C. Papadimas, J. Sciare, N. Mihalopoulos, M. C. Facchini, M. Rinaldi, F. J. Dentener, D. Ceburnis, N. Hatzianastasiou, C. D. O’Dowd, M. van Weele, and M. Kanakidou, Global modeling of the oceanic source of organic aerosols, Adv. Meteorol., 2010, 939171, DOI:10.1155/2010/939171.
Comments:
(2) the source profile of CCN and IN in marine atmosphere: which sources account for the largest fraction of CCN or IN?
Response:
Further studies are needed for the accurate quantification of the source profile of CCN and IN in marine atmosphere. We added the followings.
“Moreover, SSA number size distribution derived from size-resolved hygroscopicity and particle number size distribution indicates that the contribution of submicrometer SSA to marine CCN might be underestimated in previous studies.68 These studies highlight the need for further identification of submicrometer SSA to quantify the source apportionment of CCN in the atmosphere more accurately.”
“A cloud-resolving model suggests that low marine-derived INP, compared to terrestrial mineral aerosols, suppresses the overestimation of ice clouds and thus complements the underestimation of water clouds over remote ocean.78 The contribution to INP concentrations is calculated using the parameterization derived from samples in sea surface microlayer.7 Thus, physiochemical selectivity in the transfer of OM into the aerosol phase is not accounted for in this parameterization. To accounted for the effects of chemically selective emission and atmospheric processing implicitly, a parameterization is empirically derived from observations of ambient SSA.79 In global model studies, the latter parameterization better reproduce INP associated with marine sources compared to the former parameterization.80,81 Furthermore, coarse and super-coarse dust particles can be transported farther away from the land, and thus the abundance of these particles is substantially underestimated in current models.82 Thus, the relative importance of marine OA as a source of INP in comparison to terrestrial sources and its effect on mixed-phase clouds are still open questions. These studies highlight the need for further identification of chemical composition for larger particle sizes to quantify the source apportionment of INP in the atmosphere more accurately.”
Additional references:
W. Xu, J. Ovadnevaite, K. N. Fossum, C. Lin, R.-J. Huang, D. Ceburnis, C. O’Dowd, Sea spray as an obscured source for marine cloud nuclei. Nat. Geosci. 2022., 15, 282–286, DOI;10.1038/s41561-022-00917-2.
C. S. McCluskey, P. J. DeMott, P.‐L. Ma, and S. M. Burrows, Numerical representations of marine ice‐nucleating particles in remote marine environments evaluated against observations, Geophys. Res. Lett. 2019, 46, 7838–7847. DOI:10.1029/2018GL081861.
X. Zhao, X. Liu, S. M. Burrows, and Y. Shi, Effects of marine organic aerosols as sources of immersion-mode ice-nucleating particles on high-latitude mixed-phase clouds, Atmos. Chem. Phys. 2021, 21, 2305–2327, DOI:10.5194/acp-21-2305-2021.
A. A. Adebiyi, J. F. Kok, B. J. Murray, C. L. Ryder, J.-B. W. Stuut, R. A., Kahn, P. Knippertz, P. Formenti, N. M. Mahowald, C. Pérez García-Pando, M. Klose, A. Ansmann, B. H. Samset, A. Ito, Y. Balkanski, C. Di Biagio, M. N. Romanias, Y. Huang, and J. Meng, A review of coarse mineral dust in the Earth system, Aeolian Res. 2023, 60, 100849, DOI:10.31223/X5QD36.
Comments:
(3) the contribution of aerosol deposition in the total supply of N and Fe in the Pacific Ocean
Response:
We show the contribution of (a) oxidized and (b) reduced N deposition in the total atmospheric supply of N over the Pacific. Note that we focus on atmospheric supply of N and Fe.
“Pacific is the net import of reactive N from the atmosphere to the oceans.100 We show the contribution of oxidized and reduced N deposition in the total atmospheric supply of reactive inorganic N in the Pacific (Fig.5).32 Nitrogen oxides (NOx) emissions are mostly derived from anthropogenic and pyrogenic sources whereas NH3 emissions are dominantly derived from agricultural activities on a global scale. Deposition of oxidized N (12.1 Tg N yr−1) dominates reduced N (7.1 Tg N yr−1) in the Pacific. Large contribution of nitrate deposition can be seen in downstream regions of fossil fuel combustion and biomass burning whereas N deposition is dominated by reduced N over the tropical and southern Pacific.100”
Additional reference:
R. Vet, R. S. Artz, S. Carou, M. Shaw, C.-U. Ro, W. Aas, A. Baker, V. C. Bowersox, F. Dentener, C. Galy-Lacaux, A. Hou, J. J. Pienaar, R. Gillett, M. C. Forti, S. Gromov, H. Hara, T. Khodzher, N. M. Mahowald, S. Nickovic, P. S. P. Rao, and N. W. Reid, A global assessment of precipitation chemistry and deposition of sulfur, nitrogen, sea salt, base cations, organic acids, acidity and pH, and phosphorus, Atmos. Environ. 2014, 93, 3–100, DOI:10.1016/j.atmosenv.2013.10.060.
Comments:
(4) the contribution of each aerosol source to the aerosol deposition of N and Fe.
Response:
Nitrate mostly comes from fossil fuel combustion, whereas ammonium mostly comes from agriculture. We described this associated with Fig. 5, following the comment (3). We show the contribution of atmospheric deposition of bioaccessible Fe from (a) anthropogenic, (b) pyrogenic, and (c) lithogenic aerosols over the Pacific.
“Contribution of bioaccessible Fe deposition from anthropogenic, pyrogenic, and lithogenic aerosols into the Pacific is shown in Fig.7.32 Although lithogenic source dominates in most regions, the anthropogenic source is the major contributor of bioaccessible Fe deposition fluxes to the western North Pacific.”
“The anthropogenic Fe contributes 30–40% of total bioaccessible Fe flux at 158°W between 35°N and 40°N, which is within a range of estimates based on an isotope mass balance (21–59%).140”
Comments:
In addition, the production mechanisms of sea spray aerosol and secondary marine aerosol should be introduced. The VOC emission for the ocean should be also described in a quantitative manner.
Response:
We added the following sentences.
“In the model,20 the POA emissions from the sea surface are calculated as the function of chlorophyll a concentration, wind speed, sea surface temperature, and aerosol diameter.33”
“Natural SOA is produced from the oxidation of isoprene, terpenes, and DMS.34,35 In the model, the concentrations of isoprene in the surface ocean layer is calculated from the empirical relationship between the isoprene concentration and chlorophyll a concentration for two separate sea surface temperature bins.42 The sea surface DMS concentration is obtained from the monthly climatological data set.43 The net flux from the ocean to the atmosphere is then calculated from the concentration gradient for isoprene and DMS across the air-sea interface and the transfer velocity.44,45 An extra glyoxal source of 20 Tg C yr−1 over the oceans46 is evenly distributed in mixing ratio throughout the planetary boundary layer by scaling with the marine isoprene sources.50 The photochemical oxidation of volatile organic compounds (VOCs) and their subsequent reaction in the atmosphere forms oxidized organic gases in the atmosphere.47 In the presence of cloud droplets or aqueous particles, water-soluble gases (e.g., glyoxal, methylglyoxal, and glycolaldehyde) dissolve in the aqueous phase and be further oxidized to form products with lower volatility (e.g., dicarboxylic acids and oligomers).48 These low volatility products are assumed to remain entirely in the particulate phase as aqueous SOA (aqSOA) compounds (i.e., glyoxylic acid, pyruvic acid, oxalic acid, and two classes of oligomers) when cloud water is evaporated.49 The aqSOA mass concentration formed in cloud water is proportionally distributed to the aqSOA mass concentration on the preexisting aerosols. The aqSOA is also formed in the externally mixed wet aerosols.50 The surface-limited uptake process is considered for glyoxal and methylglyoxal on sulfate aerosols only.51”
Additional references:
N. Meskhidze, J. Xu, B. Gantt, Y. Zhang, A. Nenes, S. J. Ghan, X. Liu, R. Easter, and R. Zaveri, Global distribution and climate forcing of marine organic aerosol: 1. Model improvements and evaluation, Atmos. Chem. Phys. 2011, 11, 11689–11705, DOI:10.5194/acp-11-11689-2011.
A. Lana, T. G. Bell, R. Simó, S. M. Vallina, J. Ballabrera-Poy, A. J. Kettle, J. Dachs, L. Bopp, E. S. Saltzman, J. Stefels, J. E. Johnson, and P. S. Liss, An updated climatology of surface dimethlysulfide concentrations and emission fluxes in the global ocean, Global Biogeochem. Cycles 2011, 25, 1–17, DOI:10.1029/2010GB003850.
T. M. Fu, D. J. Jacob, F. Wittrock, J. P. Burrows, M. Vrekoussis, and D. K. Henze, Global budgets of atmospheric glyoxal and methylglyoxal, and implications for formation of secondary organic aerosols, J. Geophys. Res. 2008, 113, D15303, DOI:10.1029/2007jd009505.
S. C. Hackenberg, S. J. Andrews, R. Airs, S. R. Arnold, H. A. Bouman, R. J. W. Brewin, R. J. Chance, D. Cummings, G. Dall'Olmo, A. C. Lewis, J. K. Minaeian, K. M. Reifel, A. Small, G. A. Tarran, G. H. Tilstone, L. J. Carpenter, Potential controls of isoprene in the surface ocean, Global Biogeochem. Cycles 2017, 31, 644–662, DOI:10. 1002/2016GB005531.
P. S. Liss, and P. G. Slater, Flux of gases across the air-sea interface, Nature 1974, 247, 181–184, DOI:10.1038/247181a0.
M. T. Johnson, A numerical scheme to calculate temperature and salinity dependent air-water transfer velocities for any gas, Ocean Sci. 2010, 6, 913–932, DOI:10.5194/os-6-913-2010.
S. Myriokefalitakis, M. Vrekoussis, K. Tsigaridis, F. Wittrock, N. A. Richter, C. Brühl, R. Volkamer, J. P. Burrows, and M. Kanakidou, The influence of natural and anthropogenic secondary sources on the glyoxal global distribution, Atmos. Chem. Phys. 2008, 8, 4965–4981, DOI:10.5194/acp-8-4965-2008.
A. Ito, S. Sillman, J. E. Penner, Effects of additional nonmethane volatile organic compounds, organic nitrates, and direct emissions of oxygenated organic species on global tropospheric chemistry, J. Geophys. Res. 2007, 112, D06309. DOI:10.1029/2005JD006556.
B. Ervens, and R. Volkamer, Glyoxal processing by aerosol multiphase chemistry: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles, Atmos. Chem. Phys. 2010, 10, 8219e8244, DOI: 10.5194/acp-10-8219-2010.
G. Lin, S. Sillman, J. E. Penner, and A. Ito, Global modeling of SOA: the use of different mechanisms for aqueous phase formation, Atmos. Chem. Phys. 2014, 14, 5451e5475. DOI:10.5194/acp-14-5451-2014.
A. Ito, G. Lin, and J. E. Penner, Global modeling study of soluble organic nitrogen from open biomass burning, Atmos. Environ. 2015, 121, 103–112, DOI: 10.1016/j.atmosenv.2015.01.031.
Specific Comments:
The first sentence in the abstract is the same as the first sentence of abstract. Please revise.
Response:
The 1st sentence in the introduction was revised as follows:
“Rapid expansion of human activities has profoundly modulated Earth’s atmosphere, ushering in an era known as the Anthropocene.1”
Comments:
Section 2.2: “However, aerosol particle formation from DMS as a precursor gas was extremely rare in the MBL where sea salt particles were abundant as pre-existing particles.4”: I do not think this is right. There is a debate about the relative abundance of SSA and secondary aerosol from DMS oxidation.
Response:
We modified the sentences.
“On the other hand, to mimic the natural marine systems in laboratory experiments, mesocosm experiments has been promoted to artificially reproduce waves and generate SSA using large waving tanks.58 The results from laboratory experiments suggest that secondary marine aerosols in the presence of OM play the dominant role in affecting the submicrometer SSA, the hygroscopicity of aged SSA, and thus marine cloud properties.59”
Additional reference:
J. K. Mayer, X. Wang, M. V. Santander, B. A. Mitts, J. Sauer, C. M. Sultana, C. D. Cappa and K. A. Prather, Secondary marine aerosol plays a dominant role over primary sea spray aerosol in cloud formation, ACS Cent. Sci., 2020, 6, 2259–2266, DOI: 10.1021/acscentsci.0c00793.
Comments:
“OM in SSA affects not only the hygroscopicity and surface tension that determines the CCN ability of SSA,”: this is not true. The kappa value of SSA is quite constant no matter what its OM content is. See Doug Collins’ GRL paper.
Response:
We deleted the hygroscopicity from the sentence and added the reference in following sentence.
“Field observations and laboratory experiments suggest that hydrocarbons and colloidal substances might significantly contribute to the reduction of hygroscopicity for the SSA and lead to the suppression of CCN activity.31 However, the results from microcosm experiments suggest that changes in chemical composition of SSA associated with biological activity do not strongly affect the hygroscopicity of primary SSA.66 Alternatively, OM coating on SSA reduces the surface tension which may affect the emission flux, particle size distribution, and thus CCN ability of SSA.”
Additional reference:
D. B. Collins, T. H. Bertram, C. M. Sultana, C. Lee, J. L. Axson, and K. A. Prather, Phytoplankton blooms weakly influence the cloud forming ability of sea spray aerosol, Geophys. Res. Lett. 2016, 43, 9975–9983, DOI:10.1002/2016GL069922.
Comments:
Section 2.3: I would recommend doing a longer introduction on ice-nucleation. The current one is too simple.
Response:
We reorganized the introduction and added the previous studies about the marine materials and their particle sizes.
“The surface of a marine diatom species73 and organic material associated with phytoplankton cell exudates7 have been shown to promote freezing at conditions relevant for mixed-phase clouds. Aerosol particles, which are active as INP, have been suggested to be submicrometer size.7,74,75 On the other hand, the majority of INP, which is originated from freshly produced biological material entrained in jet drop SSA, is supermicrometer size.76 Laboratory studies on marine phytoplankton suggest that both biomolecules and microbes contribute to marine INP within SSA.77”
Additional references:
D. A. Knopf, B. Wang, A. Laskin, R. C. Moffet, and M. K. Gilles, Stimulation of ice nucleation by marine diatoms, Nat. Geosci. 2011, 4, 88–90, DOI:10.1038/ngeo1037.
J. Rosinski, P. L. Haagenson, C. T. Nagamoto, and F. Parungo, Nature of ice-forming nuclei in marine air masses, J. Aerosol Sci. 1987, 18, 291–309, DOI:10.1016/0021-8502(87)90024-3.
P. J. DeMott, T. C. Hill, C. S. McCluskey, K. A. Prather, D. B. Collins, R. C. Sullivan, M. J. Ruppel, R. H. Mason, V. E. Irish, T. Lee, C. Y. Hwang, T. S. Rhee, J. R. Snider, G. R. McMeeking, S. Dhaniyala, E. R. Lewis, J. J. Wentzell, J. Abbatt, C. Lee, C. M. Sultana, A. P. Ault, J. L. Axson, M. Diaz Martinez, I. Venero, G. Santos-Figueroa, M. D. Stokes, G. B. Deane, O. L. Mayol-Bracero, V. H. Grassian, T. H. Bertram, A. K. Bertram, B. F. Moffett, G. D. Franc. Sea spray aerosol as a unique source of ice nucleating particles, Proc. Natl. Acad. Sci. USA 2016, 113, 5797–5803, DOI:10.1073/pnas.1514034112.
B. A. Mitts, X. Wang, D. D. Lucero, C. M. Beall, G. B. Deane, P. J. DeMott, and Prather, K. A. Importance of supermicron ice nucleating particles in nascent sea spray, Geophys. Res. Lett. 2021, 48(3), e2020GL089633. DOI: 10.1029/2020gl089633.
C. S. McCluskey, T. C. J. Hill, F. Malfatti, C. M. Sultana, C. Lee, M. V. Santander, C. M. Beall, K. A. Moore, G. C. Cornwell, D. B. Collins, K. A. Prather, T. Jayarathne, E. A. Stone, F. Azam, S. M. Kreidenweis, and P. J. DeMott, A dynamic link between ice nucleating particles released in nascent sea spray aerosol and oceanic biological activity during two mesocosm experiments, J. Atmos. Sci., 2017, 74, 151-166, DOI:10.1175/jas-d-16-0087.1.
Comments:
“An online INP meter based on the Continuous Flow Diffusion Chamber method is also commercially available, but needs stability.”: no ref is provided.
Response:
We deleted the paragraph, as was suggested by the reviewer.
Comments:
Section 3.2: what kind of iron is bioaccessible? Are All dissolved iron bioaccessible? I would discuss it at the beginning of the section.
Response:
We explained bioaccessible Fe in Fig. 1 and at the beginning of the section.
“After aerosols enter the surface ocean, bioaccessible Fe binds with organic ligands (FeL), enters the biological cycle, or is removed via scavenging process.”
“After aerosol deposition into the surface ocean, bioaccessible Fe may: 1) be chelated with organic ligands, 2) be dissolved Fe, or 3) be scavenged into sinking particles (Fig. 1).”
Comments:
Figure 6: the resolution of this figure is significantly lower than other figures.
Response:
This is corrected.

11-Apr-2023

Dear Dr Ito:

Manuscript ID: EA-CRV-11-2022-000156.R1
TITLE: Marine aerosol feedback on biogeochemical cycles and climate in the Anthropocene: lessons learned from the Pacific Ocean

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Reviewer 1

accept

Reviewer 3

I think this manuscript can be accepted now.