Summertime observations of elevated levels of ultrafine particles in the high Arctic marine boundary layer

Burkart, Julia; Willis, Megan D.; Bozem, Heiko; Thomas, Jennie L.; Law, Kathy; Hoor, Peter; Aliabadi, Amir A.; Köllner, Franziska; Schneider, Johannes; Herber, Andreas; Abbatt, Jonathan P. D.; Leaitch, W. Richard

doi:https://doi.org/10.5194/acp-17-5515-2017

Articles | Volume 17, issue 8

https://doi.org/10.5194/acp-17-5515-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue:

NETCARE (Network on Aerosols and Climate: Addressing Key Uncertainties...

https://doi.org/10.5194/acp-17-5515-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 8

Research article

|

02 May 2017

Research article |

| 02 May 2017

Summertime observations of elevated levels of ultrafine particles in the high Arctic marine boundary layer

Julia Burkart, Megan D. Willis, Heiko Bozem, Jennie L. Thomas, Kathy Law, Peter Hoor, Amir A. Aliabadi, Franziska Köllner, Johannes Schneider, Andreas Herber, Jonathan P. D. Abbatt, and W. Richard Leaitch

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Final revised paper (published on 02 May 2017)
Supplement to the final revised paper
Preprint (discussion started on 08 Aug 2016)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'REVIEWACP2016701', Jost Heintzenberg, 12 Aug 2016
- AC1: 'Responses to Reviewer 1', Julia Burkart, 15 Jan 2017
RC2: 'new particle formation in the Arctic', Anonymous Referee #2, 27 Aug 2016
- AC2: 'Responses to Reviewer 2', Julia Burkart, 15 Jan 2017
RC3: 'Review acp-2016-701', Anonymous Referee #3, 05 Sep 2016
- AC3: 'Responses to Reviewer 3', Julia Burkart, 15 Jan 2017
AC4: 'Manuscript with marked changes', Julia Burkart, 16 Jan 2017

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Julia Burkart on behalf of the Authors (03 Feb 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Feb 2017) by Lynn M. Russell

RR by Jost Heintzenberg (06 Feb 2017)

RR by Anonymous Referee #2 (09 Feb 2017)

Suggestions for revision or reasons for rejection

The overall findings of this paper, that particles can be formed over open Arctic Ocean seems generally justified, but the paper could be more quantitative given the data available and more care could be taken in discussing and justifying assumptions. I do not wish to hold up publication, but more clear and decisive statement could have been made if supported by numbers.

Some specific comments.

The authors have responded to the issues raised relating to inferring particle formation based on measuring sizes between 5 and 20nm, but as far as I can tell they have not been transferred to the manuscript. The author’s response:

Willis et al. (2016) showed that for this environment particles were able to grow to 50 nm low over the open water over approximately one hour, which means that the growth from 1 nm to 10 nm can occur over one minute or less, justifying our use of instruments that are sensitive to 5 nm particles and larger.

Was this added to the paper? This seems to be valuable information that can be used to justify the measurement approach and the critical question of if these events are truly important because they are frequent (not just old remnants of NPF events). It is being claimed here that the growth rate of nm-size particles is 50nm/hr or about 1 nm/min. I find this magnitude of growth remarkable (can it really be that high?). How does this compare with typical nanoparticle growth rates observed in other regions? Give numbers. I would suspect growth rates of 1 or so nm/hr is more typical, 50 nm means the condensing vapors are at very high concentrations, much higher than other regions)? The issue of estimated age of 5-10 nm plumes is critical to interpreting these data and supporting the conclusions.

In the response it was also suggested that the concentrations of the small particles are low so that coagulation is not important. Why not give characteristic lifetimes (give numbers) resulting from coagulation?

I did not understand the following response.

The reviewer suggests that “the new particles in the cleaner region just have a longer life span compared to particles that may have been formed in the other regions that had higher concentrations of pre-existing particles, which depleted the N(5-20) particles faster.” If that were the case, then we would have seen the NPF occur at other locations and not principally associated with the ocean surface.

Why? It is a question of probability. Say you have a very clean region and a more polluted region. New particle formation occurs in both. In the clean region, the newly formed particles in the 5-20nm size range of a characteristic lifetime of a few days due to slow growth and coagulation (the authors may argue that the lifespan is much shorter due to very high growth rates, see above), but in the less pristine environment the 5-20 nm particles have a much smaller lifespan of say a few hours. When you measure these various regions you would “see” NPF mainly in the clean areas (ie, the probability of running into a region where 5-20nm particles exist will be much higher for the clean regions) and one may falsely conclude that this is where most of the new particles are coming from. I think this is essentially the premise of this work. Now this could be refuted if the estimates of lifespans of the newly formed particles at the surface are much shorter, say a few hours. This is why estimates of lifespans are critical to the interpretation of this data.

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ED: Reconsider after minor revisions (Editor review) (10 Feb 2017) by Lynn M. Russell

AR by Julia Burkart on behalf of the Authors (27 Feb 2017) Author's response Manuscript

ED: Publish as is (28 Feb 2017) by Lynn M. Russell

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Short summary

Our aircraft study for the first time systematically investigates aerosol size distributions, including ultrafine particles (5–20 nm in diameter), in the Arctic summertime atmosphere. We find that ultrafine particles occur very frequently in the boundary layer and not aloft, suggesting a surface source of these particles. Understanding aerosol properties and sources is crucial to predict climate and especially important in the Arctic as this region responds extremely fast to climate change.