Triple oxygen isotope systematics of evaporation and mixing processes in a dynamic desert lake system

Voigt, Claudia; Herwartz, Daniel; Dorador, Cristina; Staubwasser, Michael

doi:https://doi.org/10.5194/hess-25-1211-2021

Articles | Volume 25, issue 3

https://doi.org/10.5194/hess-25-1211-2021

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

https://doi.org/10.5194/hess-25-1211-2021

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

Articles | Volume 25, issue 3

Research article

|

10 Mar 2021

Research article |

| 10 Mar 2021

Triple oxygen isotope systematics of evaporation and mixing processes in a dynamic desert lake system

Claudia Voigt, Daniel Herwartz, Cristina Dorador, and Michael Staubwasser

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Final revised paper (published on 10 Mar 2021)
Supplement to the final revised paper
Preprint (discussion started on 15 Jun 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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RC1: 'Referee Comment', Anonymous Referee #1, 20 Jul 2020
- AC1: 'Response to Referee #1', Claudia Voigt, 06 Oct 2020
RC2: 'Referee comments on Voigt et al', Anonymous Referee #2, 08 Sep 2020
- AC2: 'Response to Referee #2', Claudia Voigt, 06 Oct 2020

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (08 Oct 2020) by Genevieve Ali

AR by Claudia Voigt on behalf of the Authors (19 Nov 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (25 Nov 2020) by Genevieve Ali

RR by Anonymous Referee #2 (01 Dec 2020)

RR by Anonymous Referee #1 (07 Jan 2021)

Suggestions for revision or reasons for rejection

General Comments
The authors have done a good job revising the manuscript, which has greatly improved the readability and replicability of the results. Nevertheless, there were a few instances of odd structuring (e.g. methods in results, results in discussion) that should be revised. The majority of this revision is minor clarification and rearranging text already within the manuscript. I have highlighted the suggested changes in the specific comments below.

Specific Comments
General comments throughout the manuscript: Throughout, suggest changing “about” to “approximately” for more formality. Check the presented precision of the data. Significance levels change throughout the manuscript (suggest keep to 1 decimal)
P1L28: “The GMWL describes the equilibrium…” There needs to be some context here. The GMWL described the equilibrium of deuterium and oxygen-18 (these isotopes are not mentioned above).
P2L31: suggest changing “from” to “using”
P2L33: I would take out groundwater recharge from here. The C-G model can be applied to pan evaporation (i.e. not continuous groundwater recharge).
P2L37: Suggest adding a reference here.
P3L73: Are these annual average fluctuations? Or seasonal averages
P3L74: Can you provide a value for “calm” as you did for “very windy”?
P3L83: Suggest changing “higher” to “more enriched”
P3L91: Suggest changing “rainy season” to “rainy season (summer)”
P5L133: Suggest revision to “The 600 ml pan dried up…”
P5L136: Swap the numbers to for the order listed (RH then temp)
P5L148: Why is T2 presented before T1? Suggest changing the order.
P6L174: “relative humidity, h, normalized …”
P6L174: Do you mean that the RH at 1.5m is adjusted to the surface based on water surface temperature?
P6L182: I would suggest having the definitions of both α’s earlier with the equations. The causation is fine to keep here.
P6L185: Specify that “n” is the fractionation factor. Again, this would be better to be introduced with the equations above. Please change the location of the n superscript for consistency with the equation.
P7L201: It is odd to switch from using R to denote isotopic composition and δ notation here. If R is different from the isotopic composition δ (i.e. not standardized, in concentration, etc) then it should be specified.
P7L201: If I understand correctly for the later mixing models, you use this equation (δXmix ) for mixing the incoming water. If not, where is δXmix used? It might be better to use the RWS equation from T1 here if that is used for Figure 11.
P7L202: Remove the underline from Xmix
P7L205: Suggest changing to “..mixing processes are likely transient…”
P8L247-248: Increasing and decreasing with relative to what? Time periods?
P9L262-268: Parts of this section seem more suited for the discussion than results. Additionally, the statement of similarities between vapour estimated by OIPC and measured comes before the values of OIPC are given.
P9L272-273: Initial composition is better suited to the methods section rather than results.
P9L276: No need to describe what the n value is again here.
P9L277-281: This should be in the methods section to describe how you get the n value. The reader should know how you will get the n value before the results.
P10L283: I think it would be more correct to say that the fit produces the X n value, suggesting higher than average turbulence (i.e. n < 0.5).
P10L283-286: The comparison to literature and explanation of differences is better given in the discussion than here.
P10L287: As the comparison of δ2HV, δ18OV, and d-excess v is important to understand here, the rationale for examining all three should be moved the methods section alongside the methods of obtaining n. Right now, the examination of δ2HV, δ18OV seem separate and as an afterthought to d-excess. It would help the flow of this section to present the fitting of δ2HV, δ18OV, and d-excess v, then present the sensitivity of d-excess fit n as it gives the most reasonable value (and by reasons described by Gonfiantini et al., 2020).
P10L290: Figure 8 caption is in the incorrect order (should be d-excess, δ18O, the δ2H)
P10L309-320: This discussion of where the C-G model is still deviating from the samples is better served in the discussion section 6.4, on the C-G- applicability.
P11L327: Please provide the most relevant papers from within the study.
P12L355: Which figure is the envelope mixing referring to?
P12: Section 6.3. This whole section appears to be more methods for how to average the temperature and relative humidity of the mixing models than a discussion of the above-presented results. Most of this section should be moved to the methods, with the remaining going to the results (e.g. Section 5.1. presenting the conditions of the salar). This way the effect/change of the residence times can adequately be discussed in Section 6.4.
P13: Section 6.4. There is a great deal of this section that should be in the results as an evaluation of the C-G model robustness rather than in the discussion. The authors have improved on the presentation of mixing, though it restricted primarily to the supplementary material and is not referred to much. Additionally, the references to Fig 9 should be Fig 11. Further discussion of the differences/sensitivity of the C-G model would additionally help this section.
P14L423: I would suggest starting with a conclusion of the system before concluding findings of the C-G model, for consistency with the objectives.
P14L425: A requirement for what? A good estimation using the C-G model?
P14L434: Suggest changing “fall on top of each other” to “overlap”

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ED: Publish subject to minor revisions (review by editor) (19 Jan 2021) by Genevieve Ali

AR by Claudia Voigt on behalf of the Authors (25 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (03 Feb 2021) by Genevieve Ali

Short summary

Evaporation trends in the stable isotope composition (¹⁸O/¹⁶O, ¹⁷O/¹⁶O, ²H/¹H) of throughflow ponds in a hydrologically complex and seasonally dynamic lake system can be reliably predicted by the classic Craig–Gordon isotope evaporation model. We demonstrate that the novel ¹⁷O-excess parameter is capable of resolving different types of evaporation with and without recharge and of identifying mixing processes that cannot be resolved using the classic δ²H–δ¹⁸O system alone.