Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Hartery, Sean; Commane, Róisín; Lindaas, Jakob; Sweeney, Colm; Henderson, John; Mountain, Marikate; Steiner, Nicholas; McDonald, Kyle; Dinardo, Steven J.; Miller, Charles E.; Wofsy, Steven C.; Chang, Rachel Y.-W.

doi:https://doi.org/10.5194/acp-18-185-2018

Articles | Volume 18, issue 1

https://doi.org/10.5194/acp-18-185-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-18-185-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 18, issue 1

Research article

|

08 Jan 2018

Research article |

| 08 Jan 2018

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Sean Hartery, Róisín Commane, Jakob Lindaas, Colm Sweeney, John Henderson, Marikate Mountain, Nicholas Steiner, Kyle McDonald, Steven J. Dinardo, Charles E. Miller, Steven C. Wofsy, and Rachel Y.-W. Chang

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Final revised paper (published on 08 Jan 2018)
Supplement to the final revised paper
Preprint (discussion started on 21 Feb 2017)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of Hartery et al.', Anonymous Referee #2, 07 Mar 2017
- RC3: 'Apologies - Latex error - comment #5 here', Anonymous Referee #1, 28 Mar 2017
- AC3: 'Reply to Reviewer', Rachel Chang, 01 Jul 2017
AC1: 'Updated figures', Rachel Chang, 07 Mar 2017
RC2: 'Review of Hartery et al., Estimating regional scale methane flux and budgets using CARVE aircraft measurements over Alaska', Anonymous Referee #1, 28 Mar 2017
- AC2: 'Reply to Reviewer', Rachel Chang, 01 Jul 2017
AC4: 'Revised manuscript and Supplement', Rachel Chang, 01 Jul 2017

Peer-review completion

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

AR by Sean Hartery on behalf of the Authors (04 Jul 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (31 Jul 2017) by Janne Rinne

RR by Anonymous Referee #1 (31 Aug 2017)

Suggestions for revision or reasons for rejection

The authors have very thoroughly, carefully and satisfactorily addressed all of the comments made in my main review and provided extensive additional material that has followed (and added to) many of the suggested recommendations, especially with regard to the supplementary material, which now distills fluxes (and uncertainties) by aircraft profile/inversion and explains a more meaningful averaging and error analysis. The new manuscript is much more useful to those following the work and much more transparent in its analytical approach and now includes some necessary caveats on the relative efficacy (and uncertainty) of the methods, assumptions and and approaches.
As stated before, the use of aggregate aircraft data such as this to derive measurement-led top-down analyses of regional GHG fluxes is innovative and may open the door to future development and refinement of the general approach.
In my main review, I mentioned that I would comment more on the process linkages of the calculated fluxes to soil T and q etc when I had more confidence in the fluxes themselves. This part of the analysis has now been improved in response to other reviewers' comments and the discussion is interesting, arriving at the conclusion that soil temperature is the dominant control in this study. I agree with that conclusion based on the regression analysis provided. However, I would make a comment that this may only be a conclusion specific to this study and that soil temperature may only manifest a dominant control on CH4 emission if soil remains saturated over the timescale of study. It may be worth mentioning this so that any reader doesn't take home the (potentially incorrect) message that soil T is a dominant control overall. Indeed soils would be expected to be net CH4 sinks if they are not sufficiently moist, so soil moisture thresholds are therefore a pre-requisite in any ability for soil T to make a difference on net flux.

A few very minor technical corrections remain that could be picked up at the copy-editing stage. These include improper hyphenation of quantities and units in a few places, e.g. P.17, line 17 (40-cm should be 40 cm) and one or two others like this.

Overall, the authors should be congratulated on a very ambitious and innovative use of a large and complex dataset and I would recommend publication is ACP.

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ED: Publish subject to technical corrections (15 Sep 2017) by Janne Rinne

AR by Sean Hartery on behalf of the Authors (23 Sep 2017) Manuscript

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Short summary

Methane is the second most important greenhouse gas but its emissions from northern regions are still poorly constrained. This study uses aircraft measurements of methane from Alaska to estimate surface emissions. We found that methane emission rates depend on the soil temperature at depths where its production was taking place, and that total emissions were similar between tundra and boreal regions. These results provide a simple way to predict methane emissions in this region.