Wind-driven stratification patterns and dissolved oxygen depletion off the Changjiang (Yangtze) Estuary

Liblik, Taavi; Wu, Yijing; Fan, Daidu; Shang, Dinghui

doi:https://doi.org/10.5194/bg-17-2875-2020

Articles | Volume 17, issue 10

https://doi.org/10.5194/bg-17-2875-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Ocean deoxygenation: drivers and consequences – past, present...

https://doi.org/10.5194/bg-17-2875-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 10

Research article

|

29 May 2020

Research article |

| 29 May 2020

Wind-driven stratification patterns and dissolved oxygen depletion off the Changjiang (Yangtze) Estuary

Taavi Liblik, Yijing Wu, Daidu Fan, and Dinghui Shang

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Final revised paper (published on 29 May 2020)
Supplement to the final revised paper
Preprint (discussion started on 30 Oct 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review on Liblik et al', Fabian Große, 17 Nov 2019
- AC2: 'Response to Referee #1', Taavi Liblik, 30 Dec 2019
- AC3: 'Supplement again', Taavi Liblik, 30 Dec 2019
RC2: 'Wind-driven stratification patterns and dissolved oxygen depletion in the area off the Changjiang (Yangtze) Estuary', Anonymous Referee #2, 25 Nov 2019
- AC1: 'Response to Anonymous Referee #2', Taavi Liblik, 30 Dec 2019

Peer-review completion

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

ED: Reconsider after major revisions (02 Jan 2020) by Katja Fennel

AR by Taavi Liblik on behalf of the Authors (03 Jan 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (13 Jan 2020) by Katja Fennel

RR by Fabian Große (25 Jan 2020)

RR by Anonymous Referee #2 (31 Jan 2020)

ED: Reconsider after major revisions (10 Feb 2020) by Katja Fennel

AR by Taavi Liblik on behalf of the Authors (12 Mar 2020) Manuscript

ED: Referee Nomination & Report Request started (19 Mar 2020) by Katja Fennel

RR by Anonymous Referee #2 (05 Apr 2020)

Suggestions for revision or reasons for rejection

Comments:
The abstract needs improvement, a more concise description of processes in these two years and a more specific conclusion about interannual variability. This study focuses on mechanisms on “The seasonal hypoxia in the area has variable location and range” and also interannual variability. So, “the decadal trend reveals expansion and intensification of the dissolved oxygen (DO) depletion” is not necessary here. Observation months should be given in the abstract to make it clear that observations are in different months. And these observations can reflect seasonal variations, as line437-438 says. The conclusion in the last sentence seems too general. The statistical analysis on causes of interannual variability (the relationship between winds and CDW and hypoxia distribution) is of more scientific value. And the finding about it should be mentioned in the abstract.
The conclusions just highlight processes controlling on seasonal variation. The controlling processes associated with interannual variability should be also mentioned. The authors are also expected to improve the language.
Specific comments：
Line29: The value of “hypoxic area” is in 2015, how about 2017?
Line50: I suggest defining hypoxia in the Introduction to make it clear for readers.
Line209: Stratification intensity (for example buoyancy frequency, N2) can be calculated, because both temperature and salinity are available. It would be clearer to indicate weak or strong stratification than surface-bottom density difference.
Line272: I would also suggest that the thermocline/pycnocline intensity and positon can be calculated here. There is criterion about thermocline/pycnocline for shelf waters.
Line440: Wang (2012) also mentioned the influence of Kuroshio intrusion with a statistical analysis.
Line440-445: I do not think the relation to seasonality of wind, CDW and Kuroshio intrusion is your new finding.
Line453-454: What does “the latter” mean? Not quite clear here. Here, the conclusion is just proved by the year of 2017.
Line521-523: It is confused here. Hypoxia is severer in north part in 2017 that in the south part in 2015. And the thickness of hypoxic waters in these two year looks similar, about 20-30 m thick. But it deduced that there is a thicker oxygen-depleted layer in the south part in 2015 according to integrated AOU. The authors can calculate hypoxic water thickness to quantify it.
Line585-586: The two main conditions here, enhanced primary production and KSSW intrusion, are not coordinate factors. Enhanced primary production can be caused by KSSW intrusion induced upwelling. Consider “enhanced primary production and pycnocline dominated by KSSW intrusion and CDW”?
Line49: A comma should be here instead of a dot. It should be a sentence not two sentences.
Line238: at one station

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RR by Fabian Große (13 Apr 2020)

ED: Publish subject to minor revisions (review by editor) (13 Apr 2020) by Katja Fennel

ED: Publish subject to minor revisions (review by editor) (14 Apr 2020) by Marilaure Grégoire (Co-editor-in-chief)

AR by Taavi Liblik on behalf of the Authors (19 Apr 2020) Author's response Manuscript

ED: Publish subject to technical corrections (28 Apr 2020) by Katja Fennel

ED: Publish subject to technical corrections (29 Apr 2020) by Marilaure Grégoire (Co-editor-in-chief)

AR by Taavi Liblik on behalf of the Authors (02 May 2020) Manuscript

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Short summary

Multiple factors have been accused of triggering coastal hypoxia off the Changjiang Estuary. In situ observations, remote sensing and numerical simulation data were used to study dissolved oxygen depletion in the area. Oxygen distributions can be explained by wind forcing and river discharge, as well as concurrent features in surface and deep layer circulation. If summer monsoon prevails, hypoxia more likely occurs in the north while hypoxia in the south appears if the summer monsoon is weaker.