Methane pathways in winter ice of a thermokarst lake–lagoon–coastal water transect in north Siberia

Spangenberg, Ines; Overduin, Pier Paul; Damm, Ellen; Bussmann, Ingeborg; Meyer, Hanno; Liebner, Susanne; Angelopoulos, Michael; Biskaborn, Boris K.; Grigoriev, Mikhail N.; Grosse, Guido

doi:https://doi.org/10.5194/tc-15-1607-2021

Articles | Volume 15, issue 3

https://doi.org/10.5194/tc-15-1607-2021

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

https://doi.org/10.5194/tc-15-1607-2021

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

Articles | Volume 15, issue 3

Research article

|

31 Mar 2021

Research article |

| 31 Mar 2021

Methane pathways in winter ice of a thermokarst lake–lagoon–coastal water transect in north Siberia

Ines Spangenberg, Pier Paul Overduin, Ellen Damm, Ingeborg Bussmann, Hanno Meyer, Susanne Liebner, Michael Angelopoulos, Boris K. Biskaborn, Mikhail N. Grigoriev, and Guido Grosse

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Final revised paper (published on 31 Mar 2021)
Preprint (discussion started on 20 Feb 2020)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Reviewer Comments', Pat Langhorne, 01 Jun 2020
- AC1: 'tc-2019-304 Response to RC1', Paul Overduin, 07 Sep 2020
RC2: 'Reviewer Comments', Blaize Denfeld, 13 Jul 2020
- AC2: 'tc-2019-304 Response to RC2', Paul Overduin, 07 Sep 2020
AC3: 'tc-2019-304-manuscript Track Changes version', Paul Overduin, 07 Sep 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) (05 Oct 2020) by Petra Heil

AR by Paul Overduin on behalf of the Authors (10 Oct 2020) Manuscript

ED: Referee Nomination & Report Request started (27 Oct 2020) by Petra Heil

RR by Pat Langhorne (06 Nov 2020)

Suggestions for revision or reasons for rejection

This paper describes ice on three distinct water bodies, in particular examining the methane within the ice and the physical properties associated with understanding the observed methane concentrations. The authors have taken considerable care to respond to the comments of the reviewers and (in my opinion) the revised version is much improved. The authors are much clearer about the aims of their study, and the description of the science and conclusions is clarified. The paper is now easy to read and almost without typographic error.

As before I alert the editor to the fact that I am not expert on the suite of chemical techniques involved in the study.

I have a few remaining minor comments.

Comment 1: The title of the study (and I do prefer the new title) and the focus of the Introduction and Discussion is on winter ice. However the ice is sampled in spring. I would like some discussion regarding why the authors believe that the measurements are representative of winter. For example is the sampled ice thickness close to the maximum seasonal ice thickness? Is the ice still growing at the time of sampling? For those readers not familiar with the progress of the seasons in this geographic area, it would be useful to relate the seasons to the dates of the year. It would be very useful if the dates of sampling were given in Table 1.

Comment 2: I would still like more information about transport and storage of the cores (for example on p. 5, Sect 3.2). What was the approximate temperature during transport; how long between taking cores and performing the analyses? It is important for the reader to be convinced that there have not been irreversible changes during transport.

Comment 3: Could snow cover be added to Fig. 2 to help the reader understand the temperature measurements and the snow loading described in section 5.3?

Technical Corrections
p. 1: Abstract: Abstract is now much clearer.

p. 5, Table 1: In relation to statement that winter ice, please could you put dates of sampling in the Table.

p. 5, Sect 3.1: We are told the ice was sampled between Apr 5 and 12. But how is April related to winter ice?

p. 6, Line 32: “prior to freezing” or “during freezing”?

p. 7, Line 7: “2 months between sampling and measurement” Thank you – this is the sort of information that I consider important. But I was not sure whether “sampling” meant taking the core or filling the glass bottles.

p. 7, Line 9: replace “shaken” with “shaking”

p. 8, Line 4: Fig. 2 (rather than Fig. 3). Fig. 3 is cited before Fig. 2.

p. 8, Line 19-21: Paragraph break seems to have been placed part way through the description of BY ice. Please check.

p. 8, Line 20: Begin sentence “On the ice of Tiksi Bay, the snow thickness…”

p. 12, Lines 1-2: A rather strange sentence “While the …. (below 80-90 cm)” I think this sentence is unnecessary but I leave this as a decision of the authors.

p. 12, Line 7: “(Fig. 5)”

p. 14, Lines 7-9: This is a repetition of Lines 5-7.

p. 14, Lines 19-21: This could be written more concisely and without repetition.

p. 14, Lines 25-26: Please tell us which months and how these months relate to winter and spring (see Comment 1).

p. 16, Line 6: Please tell us when the onset of ice formation took place on BY.

p. 16, Line 7: Please mark Muostakh Island on Fig. 1.

p. 16, Line 21: delete “s” from “whens”

p. 16, Line 21-22: “The difference between both is within 1‰ for a large range of ice growth rates.” I don’t know what is meant by “both”. Please clarify.

p. 16, Line 35: I could not find a reference to Fig. 7 in the text. I think Fig. 8 is referred to before Fig. 7.

p. 18, Line 1-4: Why should there be mixing of saline water with additional water of meteoric origin when the ice was 90 cm thick? At what approximate time of year did this occur? Why would it take place if additional river outflow was unlikely at that time? Please speculate on a physical reason for your observations.

p. 18, Line 26: Formatting of Angelopoulos et al

p. 19, Line 20-23: “Ice has a high thermal conductivity and is susceptible to quick temperature changes. Since ice temperatures were also observed for windswept areas at LK, decreasing air temperatures from 8 April 2017 (final LK coring day) to 11 April 2017 (LG coring day) explain the generally colder ice temperature profiles at LG.”
I am not convinced by this explanation because the temperature of the ice at depths greater than 100 cm are higher for LK than LG and the air temperature takes some time to propagate to this depth. I suspect that the thickness of the snow cover is much more important since ice has a higher thermal conductivity than snow. More detail on dates of sampling (Comment 1) and a description of the snow cover (Comment 3) may help explain these observations.

p. 19, Line 31: “equilibrium”

p. 19, Line 31 & p. 20, Line 14-30: Snow loading discussion is very interesting. Please see Comment 3.

p. 23, Fig 9: I am surprised that the dashed line is the fit to the plus markers. This figure might be clearer and the fit more obvious if you plotted a linear fit of (13CCH4-(13CCH4)0) versus lnf

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ED: Publish subject to minor revisions (review by editor) (13 Dec 2020) by Petra Heil

tc-2019-304 Submitted on 12 Dec 2019
Methane Pathways in Winter Ice of Thermokarst Lake-Lagoon-Coastal Water Transect in North Siberia

Ines Spangenberg, Pier Paul Overduin, Ellen Damm, Ingeborg Bussmann, Hanno Meyer, Susanne Liebner, Michael Angelopoulos, Boris K. Biskaborn, Mikhail N. Grigoriev, and Guido Grosse

Editor's comments:
==================
Dear Ines, Paul and co-authors.

Thank you for providing a much improved ms to review. This revised version is much easier to follow.

General comments:
* Pls use SI units. For example: 5-14: Change "10 cm" to 0.1 m".
* All measurements, incl for example in 3.3 Hydrochemistry in ice:
Include full specifications or error characteristics for each sensor.
* Pls include some information and discussion on the statistical methods ussed in the manuscript.
* The prevalence and impacts of snowloading on the ice should be discussed in some more detail (p20).
Can you speculate on this process in a changing climate?
* Rewrite the Conclusions section to make more impactful.

Minor comments:
Throughout manuscript:
Pls change "e.g." to "e.g.," and "i.e." to "i.e.,".

2-10: Remove "Generally, ".
2-17: "Escape" from where? -- I would also pr efer to be specific and refer to "ice- and snow-free environments" rather than "in summer".
3-16: Instead of "71° 40’ - 71° 80’ N and 129° 00’ - 129° 30’E" decimal lat and lon would be more contemporary.
3-27: Change "less than 11 m in general" to "largely less than 11 m deep".
3-28: Change "is located southeast" to "is located to the southeast".
3-28: Remove "the" from "the Bykovskaya Channel".
3-33: Correct "can be disturbed by storm events" to "may be disturbed by storm events".
4-Cap1: What does "(c)" in "((c) DigitalGlobe)." mean?
4-1: Correct "Tidally-based sea-level oscillations" to "Sea-level oscillations driven by tides"
4-7: Would you turn "Tab. 1 lists characteristics of the studied water bodies." into an active statement about the water bodies or their characteristics please?
5-3: Correct "cores were drilled" to "cores were recovered".
5-5: Pls make the statement "Tab. 1 lists the mean ice thicknesses of the sampled ice core for the locations." an active one about the ice cores and their thickness.
5-8: Correct "temperature was measured" to "vertical temperature profiles were obtained".
5-8: Correct "every 10 cm," to "every 0.1 m,".
5-12: Can you pls provide the specifications of the sensors used in this study? E.g., resolution and accuracy of the CTD sensors?
5-15: Change "(over 1-2 days)." to "for 1 -- 2 days."
6-23: Correct "An δ 18 O-δD plot gives" to "The comparison of δ 18 O to -δD provides".
6-26: Clarify "equilibrium conditions": Equilibrium of what?
6-29: Change "for the first ice" to "for new ice".
7-7: Correct "kept cold" to "kept cool".
8-7: Correct "The photos were rectified" to "The images were orthorectified".
8-11: Provide info on "R environment". --> I.e., that is is a software based on xxx to do yyy or similar. See your info
on AGISoft. -- Provide info on the 14 distance classes and how they affect the kernel calculations. (So there are no surprises to the reader when "class A seeps" etc. are noted further down in the ms.)
8-15: Remove "densely".
8-19: Correct "was identified" to "were identified".
8-25: Correct "until the depth of about 112 to 114 cm." to "down to a depth of ca 1.12 to 1.14 m."
8-25: What is a "solid" snow cover. This is not a technical term. Change to something like "The snow cover generally had a hard surface and was characterized...".
8-26: Rewrite "thickness of the snow-layer ranged from 0 cm": The thickness cannot be Zero. Instead there is an absence of snow.
8-26: Change "For all cores, no algae inclusions were visible (Strauss et al., 2018)." to "In none of the cores algae inclusions were detected (Strauss et al., 2018)."
9-Fig2: Explain the blue and grey shading. I assume they are for the water and the ice. - It appears that the ice thickness is constant for each profile. Pls correct.
12-Tab2: Rename "site" or "sampling site" to "transect".
12-7: Add close bracket to read "(Fig. 5)."
14-14: Remove "values" from "values ranged".
14-14: Change "The values" to "These values".
14-14: Correct "smaller" to "lower".
14-15: Correct "for the other" to "of the other".
14-15: Remove "values" twice and "the" from "In LG, the".
14-17: Remove "The" and "values".
14-17: Change "The pattern is similar but inverse to the CH 4 concentrations." to "The pattern is inverse to that of the CH 4 concentrations."
14-20: Correct "is quite constant." to "is relative constant."
14-25: Change "A seasonal ice cover is" to "The seasonal ice cover forms".
14-26: Correct "covered by ice for 9 months of the year" to "typically ice covered for about 9 months every year".
14-28: Correct "all increase," to "all increased,".
14-30: Correct "shortens" to "will shorten".
16-21: Correct "whens" to "when".
17-Fig7: Change "studied in this paper" to "under investigation".
18-26: Correct brackets: One more closing than opening brackets.
18-27/28: Not a sentence. Pls rewrite.
18-last para: The use of "later (deeper)" and "earlier (upper)" and similar is confusing. Pls rewrite.
19-6: Use SI units: "60 cm". -- Throughout manuscript.
19-31: Correct "euqilibrium" to "equilibrium".
20-12: Replace "This circumstance clearly shows" with "Our data demonstrate".
20-16: Rewrite "involvement of snow".
20-32: Correct "Fi. 6" to "Fig. 6".
29-22: Should "Walter Anthony, K.," read "Walter Anthony, K.M.,"? - not least for consistency?
References: Not checked, nor cross searched.

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AR by Paul Overduin on behalf of the Authors (14 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (15 Feb 2021) by Petra Heil

AR by Paul Overduin on behalf of the Authors (15 Feb 2021) Author's response Manuscript

Short summary

Thermokarst lakes are common on ice-rich permafrost. Many studies have shown that they are sources of methane to the atmosphere. Although they are usually covered by ice, little is known about what happens to methane in winter. We studied how much methane is contained in the ice of a thermokarst lake, a thermokarst lagoon and offshore. Methane concentrations differed strongly, depending on water body type. Microbes can also oxidize methane in ice and lower the concentrations during winter.