Upwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunity

Jacobs, Erik; Bittig, Henry C.; Gräwe, Ulf; Graves, Carolyn A.; Glockzin, Michael; Müller, Jens D.; Schneider, Bernd; Rehder, Gregor

doi:https://doi.org/10.5194/bg-18-2679-2021

Articles | Volume 18, issue 8

https://doi.org/10.5194/bg-18-2679-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-18-2679-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 8

Research article

|

30 Apr 2021

Research article |

| 30 Apr 2021

Upwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunity

Erik Jacobs, Henry C. Bittig, Ulf Gräwe, Carolyn A. Graves, Michael Glockzin, Jens D. Müller, Bernd Schneider, and Gregor Rehder

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Final revised paper (published on 30 Apr 2021)
Supplement to the final revised paper
Preprint (discussion started on 07 Oct 2020)
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 of bg-2020-365', Anonymous Referee #1, 09 Nov 2020
- AC1: 'Response to Reviewer #1', Erik Jacobs, 10 Dec 2020
RC2: 'bg-2020-365', Anonymous Referee #2, 16 Nov 2020
- AC2: 'Response to Reviewer #2', Erik Jacobs, 10 Dec 2020

Peer-review completion

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

ED: Reconsider after major revisions (14 Dec 2020) by Carolin Löscher

AR by Erik Jacobs on behalf of the Authors (18 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (25 Jan 2021) by Carolin Löscher

RR by Anonymous Referee #1 (06 Feb 2021)

Suggestions for revision or reasons for rejection

Comments on ‘Upwelling-induced trace gas dynamics in the Baltic Sea inferred from 8 years of autonomous measurements on a ship of opportunity’ by Jacobs et al.
Revised ms re-submitted to Biogeosci Discuss; ms# bg-2020-365.

The manuscript (ms) under review has been revised according to the comments of the two reviewers. Thus, the ms has been improved. However, there are still some points which should be addressed in a further revision.

Major point
The ms still reads like a technical report. The introduction has been rewritten substantially, however, the authors fail to state the overarching scientific objectives(s) of their study. There is a list of points at the end of the Introduction, but this reads like a table of contents. The authors may want to rephrase this.

Minor points (line number refer to the revised ms with ‘track change’ on.

Line (L) 8: What is meant by ‘surface expression’. Please explain and rephrase.

L20: ‘addressing the environmentally important process of upwelling’: At least for their study the authors explicitly state that they cannot estimate the importance of upwelling. Please rephrase.

L32/33: ‘leading to increased concentrations of reduced compounds’: This is statement is wrong. In areas with ongoing upwelling we can measure enhanced concentrations of CO2 in the OMZ and thus in the upwelled waters found at the ocean surface. (you may check the figures in the ms.) CO2 cannot be classified as belonging to the group of ‘reduced compounds’.

L55/56: What is meant by ‘offers the potential to study […] early and with a high signal intensity’. Please explain and rephrase.

L57: ‘Balitc’ should read ‘Baltic’.

L75: What is meant by ‘exports’? Please rephrase.

L91: ‘N/P ratios’: please give definition.

L96-99: I do not see how ‘highly resolved quantification’ can be critical to derive climate projections. I guess it makes more sense to argue that temporal and spatial trends estimated from high resolution time-series measurements are urgently needed for climate projections.

L119: ‘in regions that are more important for global trace gas fluxes and budgets’: This statement is too vague. Please rephrase.

L127: ‘Test whether a long-term trend can be inferred …’: This is a good point, however, I do not see any proper test/statistical treatment of the data in the ms which is addressing this point. Instead; I find a discussion (see e.g. L476-488 on page 22) why this is not possible. So, this point should be rephrased in the introduction, because the authors promise too much here.

L145: ‘very small influence of temperature on density’: I guess no physical oceanographer will subscribe to this statement. The influence of temperature on density might be negligible in this case but in general the influence cannot be called ‘very small’. Please rephrase.

L152: replace ‘near-atmospheric concentrations.’ with ‘near-atmospheric mole fractions.’.

L483: ‘…other than variability using the methods we presented here.’ What is meant by this? Please explain and rephrase.

L533: ‘potentially greater impact on global trace gas fluxes than the Baltic Sea.’ This statement needs a quantification of the trace gas emissions caused by upwelling in the Baltic Sea (and a comparison with data from other areas). However, the authors discuss why this is not possible (see L429-434 on page 19). So, please rephrase this statement.

L550/551: ‘other relevant effects’. This is a very vague statement. Please explain and give more details here.

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ED: Publish subject to minor revisions (review by editor) (14 Feb 2021) by Carolin Löscher

AR by Erik Jacobs on behalf of the Authors (28 Feb 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (23 Mar 2021) by Carolin Löscher

AR by Erik Jacobs on behalf of the Authors (23 Mar 2021)

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Short summary

We use a unique data set of 8 years of continuous carbon dioxide (CO₂) and methane (CH₄) surface water measurements from a commercial ferry to study upwelling in the Baltic Sea. Its seasonality and regional and interannual variability are examined. Strong upwelling events drastically increase local surface CO₂ and CH₄ levels and are mostly detected in late summer after long periods of impaired mixing. We introduce an extrapolation method to estimate regional upwelling-induced trace gas fluxes.