Fluid Migration through Permafrost and the Pool of Greenhouse Gases in Frozen Soils of an Oil and Gas Field
and Alexander Smirnov 8
Round 1
Reviewer 1 Report
The paper is well presented. However, I have some minor editing suggested, please see the attachment for the marked MS.
Comments for author File: 
Comments.pdf
Author Response
I am deeply impressed and grateful to the Reviewer, who is both familar with fluid flows, permafrost and has so deep passion in thoroughly edititing English texts. Thanks for the interest to our work and all improvements you did.
Maps are corrected.
The last two sentences of the Abstract were changed: “Besides the fluid contribution, we estimated an overwintering pool of greenhouse gases in frozen soil for the first time. Being at least 0.01-0.1 % of the soil organic matter mass, these gaseous forms of carbon can be critical for the early-summer Arctic ecosystem functioning.”
Further I did not understand what did yellow fill mean.
All of the typos, articles and grammar was corrected according to the recommendations, except for:
P. 2, par. 2, ln. 4 – changed to “2.3-4.0 wt.%” – I did not put the wt.% after 2.3, similar to the cases below when I show the ranges and use the unit measure only once.
P. 15, par. 4, last four lines – changed to ”can be deduced from geochemical ratios, and distribution patterns of C2H6, C3H8, He, H2. Our evidence suggests that contribution of gases from both sources was likely (Figure 6). In the Subsections below we discuss the nature of the links and the share of the geological sources in the soil gas pool of the oil and gas field”.
P. 16., par. 7, fourth line from the bottom. – deleted “Hence, we may state that it was.”
P. 17, par. 2 from the bottom, line 3 from the bottom – “it could not do the 3 orders”
P. 18, par. 3 from the bottom, line 2 from the bottom – changed to “area average, reflecting favorable”
Reviewer 2 Report
I have read through the manuscript "Fluid Migration through Permafrost and the Pool of Green-house Gases in Frozen Soils of an Oil and Gas Field" submitted for potential publication as a research paper in Remote Sensing. We know little about the activity of geological sources and the pathways of migration of gaseous fluids through the porous mineral matrix filled with ice. This study estimated the effect of geological factors on winter storage of the greenhouse gases in frozen soils by statistical analysis of the geodatabase, and fluid contribution and the wintertime pool of greenhouse gases in frozen soil were assessed for the first time. This is an interesting topic, the manuscript is well written and has an important contribution to the field. I have only a few minor comments (please see below), and I think it can be accepted for publication in Remote Sensing after those issues been addressed.
Keywords: C1/C2+C3 ratio listed in keywords, however, I only see C2/C3 ratio and C1/C2-3 ratio, please double check. I also recommend choosing your keywords carefully. Some of the keywords in the current list, such as CO2, DEM and C1/C2+C3 ratio are not appropriate.
Page 2: “2.3–4.0 wt%. [11],”, the period after % is not necessary, change to “2.3–4.0 wt% [11],”.
Figure 7: add a period sign “.” at the end of the caption for Figure 7 because all other figures have period at the end of the caption.
Author Response
Thank you for your work on carefully reading and correcting our manuscript. We have made all changes which you recommended.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
This was a well done and interesting study. Figures are overall clear and clean. My only major reservation has to do with the physical sampling method described below.
Line 27-28 I would suggest to remove the space between the number and percent sign, but I expect that will be decided by the editor.
Line 46 – Releases that amount of methane per year? Or what time frame?
Line 80 – Is it water table height, or simply water content that is a driver?
Line 108- Change “rise” to “raise” or better yet “increase our”
Lines 140, 244 – the “…” is unusual, I would suggest replacing with “to” or “-“
Section 2 – Good and thorough description of study site.
Line 152-153 – The sentence that begins with “Heaving” is a bit unclear. Please revise.
Line 176 – In my experience, Teflon actually leaches carbon into samples (in our case it was Teflon bottles with seawater). Are you able to check for that in your experiment, i.e. were there any additional samples not packaged with these that you could compare results with? If the same happened here, do you have an idea of how you could remedy this? In the least, is there a previous study you can cite here that also used these types of stoppers for similar work?
Line 269-270 – Change to “…for each sample site (Table A1).”
Line 272 – With the mention of ArcGIS, I would include the company and location, similar to what you’ve done earlier. I see you put this in line 281 but should be moved to it’s first mention.
Line 279- Remove the “-“ between “2-m” to be consistent.
Table A1 – Include how wetness was derived. “Category of landscape” is not a good description.
Line 288 – “in large scale” is unclear.
Line 318 – “Condition” is plural in this sentence.
Line 466- “except for one which?.” ?
Line 492 – Change “low size” to “small size”. I would actually rephrase the sentence to “The small size of He molecules allows it to travel through permafrost faster than other gases” or something similar to that.
Line 512 – “might be contributed to good conditions…” the phrase “good conditions” is unclear here. Being on its own in as a paragraph adds to the confusion.
Author Response
This was a well done and interesting study. Figures are overall clear and clean. My only major reservation has to do with the physical sampling method described below.
Thank you for your high appraisal of our study and the graphics. We introduced clarifications to the methods section and stylistic improvements according to your specific comments, and also performed the spell check by MDPI hired native speakers. We will be glad to include your name in the list of acknowledgements of our paper.
Line 27-28 I would suggest to remove the space between the number and percent sign, but I expect that will be decided by the editor.
Thank you, we have consulted the most cited articles of the journal and have found that there was no space before the percent sign. Corrected throughout the paper.
Line 46 – Releases that amount of methane per year? Or what time frame?
Thank you for clarification, this is the value per year, we have checked and corrected.
Line 80 – Is it water table height, or simply water content that is a driver?
Thank you for being that accurate. In fact, both the water content and water table height are used as proxies of aeration of soils, availability of oxygen, which affects the activity of methanogens and methanothrophs. Changed to “water saturation” because the cited studies consider either to water table or water content.
Line 108- Change “rise” to “raise” or better yet “increase our”
Thank you. We followed your recommendation with “increase our”.
Lines 140, 244 – the “…” is unusual, I would suggest replacing with “to” or “-“
Thank you. We followed your recommendation. Where there were values below zero we replaced with words.
Section 2 – Good and thorough description of study site.
Line 152-153 – The sentence that begins with “Heaving” is a bit unclear. Please revise.
Revised: Intrusive ice is found in the cores of pingos reaching 7 m high and palsas, widely present in the study area.
Line 176 – In my experience, Teflon actually leaches carbon into samples (in our case it was Teflon bottles with seawater). Are you able to check for that in your experiment, i.e. were there any additional samples not packaged with these that you could compare results with? If the same happened here, do you have an idea of how you could remedy this? In the least, is there a previous study you can cite here that also used these types of stoppers for similar work?
Thank you for forcing us to make some additional study on this issue, resulted in additional couple of sentences in the end of sampling paragraphs: Teflon stoppers and tubing are widely used in soil gas and fluid sampling and greenhouse gas measurement systems [49] because of the low permeability and diffusivity [50]. Despite that Teflon could leach carbon into the water [51], we do not expect it have notably biased our gas samples, as the area of contact with the stopper of 18 mm diameter is small. One month of sample storage and transportation to the lab at ambient winter temperature did not allow any notable amount of gas to be formed from the Teflon-derived carbon or diffused into the stopper.
Line 269-270 – Change to “…for each sample site (Table A1).”
Thank you. We added this.
Line 272 – With the mention of ArcGIS, I would include the company and location, similar to what you’ve done earlier. I see you put this in line 281 but should be moved to it’s first mention.
Thank you, added
Line 279- Remove the “-“ between “2-m” to be consistent.
It was removed.
Table A1 – Include how wetness was derived. “Category of landscape” is not a good description.
Thank you. We changed the description of this variable in the table: “Dry, moist, wet or waterlogged land classes following A. Bartsch et al. [48] classification (Table A2)”
Line 288 – “in large scale” is unclear.
Thank you. We removed the whole sentence, because later in the same paragraph we give all the details on resolutions and scales of materials we have analyzed.
Line 318 – “Condition” is plural in this sentence.
Thank you, this is typo. Corrected
Line 466- “except for one which?.” ?
Clarified: “except for the following”
Line 492 – Change “low size” to “small size”. I would actually rephrase the sentence to “The small size of He molecules allows it to travel through permafrost faster than other gases” or something similar to that.
Thank you. We gladly use the phrase which you suggested.
Line 512 – “might be contributed to good conditions…” the phrase “good conditions” is unclear here. Being on its own in as a paragraph adds to the confusion
Yes, all sentence was rephrased.
Reviewer 2 Report
The study explores an important subject of the methane and carbon dioxide emissions related to leakages from arctic hydrocarbon-bearing beds, and potential pathways of migration of gaseous fluids through the porous mineral matrix filled with ice. The study also presents a major dataset from a remote location with limited accessibility, which should be published. However, the text should be substantially revised for clarity, and to highlight the key findings and their significance. Please, also, highlight the key hypotheses and assumptions used in statistical analysis. Also, the Figure 6 should be redesigned to focus on the important results and to eliminate ambiguity.
Line edits:
1. Introduction:
39 -I do not think 'conventionally' is the correct word here; I believe it is simply the recent spike in the amount of arctic research gives this impression;
55-58 -please, rephrase for clarity;
59-60 -please, rephrase for clarity;
64-67 -please, rephrase for clarity;
73-74 -surface fracturing might also result from the processes unrelated to faulting;
88 -providing anoxia;
99-101 -please, rephrase for clarity;
102-107 -please, rephrase for clarity;
112 -the aim #3 appears to mix the study question with a hypothesis, which introduces a potential bias to the research;
2. Materials and Methods
120 -'... composed of sands;'
125 - please, replace 'laid by' and 'resided' for clarity;
126-127 -please, rephrase for clarity;
128-129 -please, rephrase for clarity (also 'diluvium');
135, 137 -please, indicate estimated age of the deposits in years (in addition to names);
140 - please, indicate average temperatures (e.g. for Jan, Jul), and FDD;
145 - is this -2.5 C the average temperature of permafrost? Did you measure (or could refer to) the ground temperature profile?
148 - when did refreezing happened?
152-153 -please, rephrase for clarity;
160 - the Figure 1 indicates that study site is in discontinuous permafrost, which contradicts the text (line 145); please, clarify;
169-172 -please, rephrase for clarity;
176, 182 - please, indicate some preparation details for the sodium chloride solution, and the typical solution to headspace ratio;
196-197 -please, include a reference;
198-- -please, indicate if measurements were calibrated between different instruments;
263-266 -please, indicate all features shown in the Figure 2.
304 -please, give more details on the moisture regime
313-319 -please, rephrase for clarity, and provide the factors used in the analysis;
3. Results
334- the Figures indicate some degree of inverse proportionality between CH4 and CO2, which may indicative of various biodegradation processes (see e.g. Tassi et al. 2015)
366 -Figure 4b should be refined for clarity;
384-386 -please, rephrase for clarity;
410-413, 420-423 -please, rephrase for clarity;
426 -'linked' in which way?
429 -should be Figure 5;
4. Discussion
434 -please, replace 'antagonistic' with e.g. opposed, inverse, etc.
434-436 --please, rephrase;
445 -This Figure is confusing;
454-455 -please, clarify;
461-462 -perhaps, an analysis of stable isotopes in the two gases may give some indication of their sources;
466 -please clarify;
474 -what exactly are the suggested surface sources?
485 -'supports'
495 -which winter?
532 -the moisture control was not shown in the results;
538 -please, clarify 'consisted - constituted';
544-545 -please, clarify;
547 -couldn't you measure the oxidation rates?
548-553 -please, clarify;
555 -please, clarify what molecular masses other than carbon were included;
5. Conclusions
585 -could this be a result of moisture accumulation in the crevasses?
586 -please, replace 'approve'
589-590 -please, rephrase for clarity;
592 -which point it is?
