Measurement report: Understanding the seasonal cycle of Southern Ocean aerosols

Humphries, Ruhi S.; Keywood, Melita D.; Ward, Jason P.; Harnwell, James; Alexander, Simon P.; Klekociuk, Andrew R.; Hara, Keiichiro; McRobert, Ian M.; Protat, Alain; Alroe, Joel; Cravigan, Luke T.; Miljevic, Branka; Ristovski, Zoran D.; Schofield, Robyn; Wilson, Stephen R.; Flynn, Connor J.; Kulkarni, Gourihar R.; Mace, Gerald G.; McFarquhar, Greg M.; Chambers, Scott D.; Williams, Alastair G.; Griffiths, Alan D.

doi:https://doi.org/10.5194/acp-23-3749-2023

Articles | Volume 23, issue 6

https://doi.org/10.5194/acp-23-3749-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-23-3749-2023

© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 23, issue 6

Measurement report

|

29 Mar 2023

Measurement report |

| 29 Mar 2023

Measurement report: Understanding the seasonal cycle of Southern Ocean aerosols

Ruhi S. Humphries, Melita D. Keywood, Jason P. Ward, James Harnwell, Simon P. Alexander, Andrew R. Klekociuk, Keiichiro Hara, Ian M. McRobert, Alain Protat, Joel Alroe, Luke T. Cravigan, Branka Miljevic, Zoran D. Ristovski, Robyn Schofield, Stephen R. Wilson, Connor J. Flynn, Gourihar R. Kulkarni, Gerald G. Mace, Greg M. McFarquhar, Scott D. Chambers, Alastair G. Williams, and Alan D. Griffiths

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Final revised paper (published on 29 Mar 2023)
Preprint (discussion started on 07 Sep 2022)

Interactive discussion

Status: closed

RC1: 'Comment on acp-2022-568', Anonymous Referee #1, 13 Oct 2022

Humphries et al. provide new seasonally resolved aerosol data over two years from Macquarie Island and combine the new dataset with ship-based observations from the Australian sector of the Southern Ocean. The dataset is valuable as it provides one of the few observations of winter CCN in the region. The seasonal cycle of CN shows a maximum in summer and minimum in winter related to phytoplankton blooms. Slight differences in the timing of the seasonal cycle between various stations is attributed to the variability of phytoplankton in proximal waters. Given the sparse and sporadic measurements in the region and the large uncertainties in aerosol-cloud properties over the Southern Ocean, these data are an important addition to the literature to understand the spatial and temporal variability of CCN over the Southern Ocean. The manuscript is well written and follows a logical structure. I recommend publication and hope the minor comments below are helpful in improving the manuscript.

Minor suggestion

It would be really interesting to include particle size distribution data at Macquarie Island and compare to other sites.

Specific comments

L25 Suggest rewording to “Atmospheric time capsules such as ice cores have been pivotal in reconstructing the past variability of greenhouse gases and a large suite of aerosol constituents. However, ice core proxies are not currently available for all atmospheric parameters” or similar.

L26-27 proxy “of the” atmosphere?

L27-28 I agree that this is the best place to study baseline atmosphere. Its worth noting that the Southern Ocean and high-elevation remote East Antarctic Plateau is now influenced by atmospheric pollution (e.g., lead pollution and synthetic chemicals).

L55 Here is one more: Kremser, S., et al. (2020). "Southern Ocean Cloud and Aerosol data: a compilation of measurements from the 2018 Southern Ocean Ross Sea Marine Ecosystems and Environment voyage." Earth Syst. Sci. Data Discuss. 2020: 1-56.

L300 Air mass back trajectories would help here.

L319-320 Please add reference(s).

Citation: https://doi.org/10.5194/acp-2022-568-RC1
RC2: 'Comment on acp-2022-568', Anonymous Referee #2, 18 Nov 2022

The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-568/acp-2022-568-RC2-supplement.pdf

Citation: https://doi.org/10.5194/acp-2022-568-RC2
AC1: 'Comment on acp-2022-568', Ruhi Humphries, 17 Jan 2023

The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-568/acp-2022-568-AC1-supplement.pdf

Citation: https://doi.org/10.5194/acp-2022-568-AC1

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Ruhi Humphries on behalf of the Authors (17 Jan 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (30 Jan 2023) by Jerome Brioude

AR by Ruhi Humphries on behalf of the Authors (08 Feb 2023)

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Short summary

Observations of aerosols in pristine regions are rare but are vital to constraining the natural baseline from which climate simulations are calculated. Here we present recent seasonal observations of aerosols from the Southern Ocean and contrast them with measurements from Antarctica, Australia and regionally relevant voyages. Strong seasonal cycles persist, but striking differences occur at different latitudes. This study highlights the need for more long-term observations in remote regions.