Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica

Shi, Guitao; Hastings, Meredith G.; Yu, Jinhai; Ma, Tianming; Hu, Zhengyi; An, Chunlei; Li, Chuanjin; Ma, Hongmei; Jiang, Su; Li, Yuansheng

doi:https://doi.org/10.5194/tc-12-1177-2018

Articles | Volume 12, issue 4

https://doi.org/10.5194/tc-12-1177-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-12-1177-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 4

Research article

|

05 Apr 2018

Research article |

| 05 Apr 2018

Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica

Guitao Shi, Meredith G. Hastings, Jinhai Yu, Tianming Ma, Zhengyi Hu, Chunlei An, Chuanjin Li, Hongmei Ma, Su Jiang, and Yuansheng Li

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Final revised paper (published on 05 Apr 2018)
Supplement to the final revised paper
Preprint (discussion started on 20 Oct 2017)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review Comments on Shi et al, Nitrate deposition and preservation in the snowpack alnog a traverse from coast to the ice sheet summit (Dome A) in East Antarctica.', Anonymous Referee #1, 25 Nov 2017
- AC1: 'Responses to Referee 1', Guitao Shi, 13 Jan 2018
RC2: 'reviewer comments', Anonymous Referee #2, 05 Dec 2017
- AC2: 'Responses to Referee 2', Guitao Shi, 13 Jan 2018
EC1: 'editor comments', Joel Savarino, 14 Dec 2017
- AC3: 'Responses to Prof. Joel Savarino', Guitao Shi, 13 Jan 2018
AC4: 'R1_Responses to editor and referees', Guitao Shi, 13 Jan 2018
AC5: 'Supporting Information', Guitao Shi, 13 Jan 2018
AC6: 'Incorporated version of the revised manuscript', Guitao Shi, 13 Jan 2018

Peer-review completion

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

AR by Guitao Shi on behalf of the Authors (13 Jan 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Jan 2018) by Joel Savarino

RR by Anonymous Referee #1 (16 Jan 2018)

Suggestions for revision or reasons for rejection

The authors are to be commended for taking all reviewer comments seriously and implementing significant revisions to the manuscript. From my point of view I'd be happy to recommend publication after addressing the points below and carefully rechecking grammar/spelling:

- please add to the introduction & discussion( 4.2) the Halley study, something like:

Significant concentrations of organic nitrates (PAN and alkyl nitrates) were observed in the lower atmosphere at Halley in coastal Antarctica consistent with an oceanic source (Jones et al., 2011). They dominated the NOy budget during the winter, and were on a par with inorganic nitrate compounds during the summer. Although not a direct source of snowpack nitrate, organic nitrates would act as a source of NOx to coastal Antarctica that would ultimately contribute to nitrate within the snowpack (Jones et al., 2011). However, multi-seasonal measurements of surface snow nitrate correlate strongly with inorganic NOy species (especially HNO3) rather than organic (Jones et al., 2011).

- It is great that you include now the atmospheric observations. However, in my view they need to go into the main manuscript not just the supplementary material; e.g. add a panel to Fig.1 showing the variation with distance from the coast and make corresponding amendments to methods, results and discussion. Table S1 (move to main manuscrpt) must also include columns with site ID and sampling day.

As I pointed out before atmospheric NO3- is key to discuss and interpret an air-snow study of nitrate in snow. In fact, this is probably the only Antarctic traverse, which produced HiVol filter samples of atmospheric NO3-, very relevant to the entire discussion in this manuscript.

l77-80 weird phrasing. Better: The late winter/early secondary maximum of nitrate observed in surface snow at coastal and inland locations has been attributed to the stratospheric source based on the nitrate stable isotopic composition (Legrand, 1989; Savarino, 2007; Frey, 2009).

l84-90 I think you really need to distinguish between no3- spikes and no3- variablitly on decadal to centennial or millennial time scales. A statistically significant link between the former and SPEs (solar proton events) has now been refuted. However, a link between the long-term variability of no3- and solar cycles as suggested in Traversi et al. (2012) is very different in terms of time scales and likelyhood of physical processes to be aligned, and may be present at some locations.

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ED: Publish subject to minor revisions (review by editor) (23 Jan 2018) by Joel Savarino

Dear authors

find below the last minor revisions asked during a second round of review. Please take into account these revisions, submit your final revised version and I will accept the manuscript.

regards
Joel

The authors are to be commended for taking all reviewer comments seriously and implementing significant revisions to the manuscript. From my point of view I'd be happy to recommend publication after addressing the points below and carefully rechecking grammar/spelling:

- please add to the introduction & discussion( 4.2) the Halley study, something like:

Significant concentrations of organic nitrates (PAN and alkyl nitrates) were observed in the lower atmosphere at Halley in coastal Antarctica consistent with an oceanic source (Jones et al., 2011). They dominated the NOy budget during the winter, and were on a par with inorganic nitrate compounds during the summer. Although not a direct source of snowpack nitrate, organic nitrates would act as a source of NOx to coastal Antarctica that would ultimately contribute to nitrate within the snowpack (Jones et al., 2011). However, multi-seasonal measurements of surface snow nitrate correlate strongly with inorganic NOy species (especially HNO3) rather than organic (Jones et al., 2011).

- It is great that you include now the atmospheric observations. However, in my view they need to go into the main manuscript not just the supplementary material; e.g. add a panel to Fig.1 showing the variation with distance from the coast and make corresponding amendments to methods, results and discussion. Table S1 (move to main manuscrpt) must also include columns with site ID and sampling day.

As I pointed out before atmospheric NO3- is key to discuss and interpret an air-snow study of nitrate in snow. In fact, this is probably the only Antarctic traverse, which produced HiVol filter samples of atmospheric NO3-, very relevant to the entire discussion in this manuscript.

l77-80 weird phrasing. Better: The late winter/early secondary maximum of nitrate observed in surface snow at coastal and inland locations has been attributed to the stratospheric source based on the nitrate stable isotopic composition (Legrand, 1989; Savarino, 2007; Frey, 2009).

l84-90 I think you really need to distinguish between no3- spikes and no3- variablitly on decadal to centennial or millennial time scales. A statistically significant link between the former and SPEs (solar proton events) has now been refuted. However, a link between the long-term variability of no3- and solar cycles as suggested in Traversi et al. (2012) is very different in terms of time scales and likelyhood of physical processes to be aligned, and may be present at some locations.

Hide

AR by Guitao Shi on behalf of the Authors (30 Jan 2018) Author's response Manuscript

ED: Publish subject to technical corrections (06 Feb 2018) by Joel Savarino

AR by Guitao Shi on behalf of the Authors (13 Feb 2018) Author's response Manuscript

Post-review adjustments

AA: Author's adjustment | EA: Editor approval

AA by Guitao Shi on behalf of the Authors (27 Mar 2018) Author's adjustment Manuscript

EA: Adjustments approved (02 Apr 2018) by Joel Savarino

Short summary

The deposition and preservation of NO₃⁻ across East Antarctica was investigated. On the coast, dry deposition contributes 27–44 % of the NO₃⁻ fluxes, and the linear relationship between NO₃⁻ and snow accumulation rate suggests a homogeneity of atmospheric NO₃⁻ levels. In inland snow, a relatively weak correlation between NO₃⁻ and snow accumulation was found, indicating that NO₃⁻ is mainly dominated by post-depositional processes. The coexisting ions are generally less influential on snow NO₃⁻.