General Comments

The paper submitted by Li et al. describes a permafrost dataset compiled from measurements made along an oil pipeline route in NE China. The dataset includes information on ground temperatures, soil moisture along with results of geophysical surveys and meteorological data. Instrumented sites are located at various distances from the pipeline and are both on the right-of-way (ROW) and in undisturbed terrain off the ROW which facilitates characterization of impacts of pipeline characterization, similar to that done along other pipelines (e.g. Burgess and Smith 2003; Burgess et al. 2010; Johnson and Hegdel 2008). Such datasets and associated analysis are valuable because they can be utilized for model calibration and validation and also to evaluate mitigation techniques to reduce impacts and improve design of future infrastructure projects (e.g. Burgess et al. 2010). For these reasons, the paper and associated database should of interest to engineers and those involved in environmental impact assessment. However the manuscript does require a number of revisions before it can be accepted for publication.

As mentioned above, this is not the first time monitoring programs have been established along pipeline routes in permafrost regions and the data utilized to evaluation design performance, effectiveness of mitigation techniques as well as the lessons learned being used for design of other projects. For example, there are several papers and reports on two pipeline corridors in NW North America (Norman Wells to Zama (NWZ) oil pipeline NWT Canada and Alyeska oil pipeline in Alaska). These include for example Burgess et al. (2010); Burgess and Smith (2003); Smith and Burgess (2010); Croft et al. (2021); Mosely et al. (2021); Johnson and Hegdel (2008), as well as other reports referenced in these. Data compilations are available for the NWZ pipeline (Smith et al. 2004, 2008) and may also be available for the Alyeska oil pipeline. It would be useful to refer to these other studies in both the introduction to provide the rationale for compilation of similar databases and also when interpreting the results of data analysis.

The paper could be better organized and some important information should be provided. In particular, Section 2 (Study site and instrumentation) could be better written and include some information from Section 3 (Data description). It would be better to clearly describe the instrumentation used to measure each variable (i.e. ground temperature, moisture content, air temperature etc.) and use a table to indicate which variables are measured at each site/borehole. This would reduce repetition and enhance clarity. Some of the information in Section 3 also describes instrumentation and should be moved to Section 2 so that all methods appear in the same section.

Information on distance of boreholes from the pipe centre line for those on the ROW needs to be clearly provided. Also, the ROW width at each site should be provided as well as the distance from the ROW edge for boreholes that are in the undisturbed terrain off the ROW. This information is important as it provides information on the amount of disturbance there might be at each site. This information could be provided in a table or as site plans in the supplementary information.

Section 3 doesn’t really provide a clear description of the data in the dataset but rather provides some information on instrumentation as well as presentation of some of the data in graphic form and interpretation of the results. It would be useful to have a brief and clear description of the data. For example, are hourly, daily, annual mean values provided; if annual values provided, what is the time period (calendar or hydrologic year) and how do you deal with missing values; describe any processing done to ensure data quality and any derived parameters that might be included in the dataset. The presentation of the data and interpretation of results could be in a separate section.

A number of specific comments are provided below. Some of these are editorial while others are related to clarity of the content. I hope the authors find the comments helpful in preparing an improved manuscript that should be acceptable for publication.

Specific Comments

L19-20 – suggested revision: “In 2011 we initiated a….”

L21-24 – Not clear. Do you mean you compiled an integrated dataset on the ground thermal state utilizing the various types of data that are mentioned in the first part of the sentence. You should revise to be clear.

L24–26 – Are you referring to the undisturbed sites off the ROW? Revise to be clear. A revision is also suggested: “Results demonstrate that permafrost has warmed between 2011-2020 in the vicinity of SLLP, manifested as an increase in ground temperature at depth likely in response to climate change.”

L28 – Insert “an: between “as” and “insulation”

L37-38 – I suggest you remove the older references (ones between 1999 and 2008) and add more recent ones such as Etzelmuller et al. (2020); Zhao et al. (2020) and Liu et al. (2021). You could also cite the most recent BAMS State of the Climate sections on permafrost (i.e. Smith et al. 2021 and Noetzli et al. 2021).

L39 – You could delete the older Zhang et al. ref and add newer ones such as Burke et al. (2020) and other recent papers (you could also cite most recent IPCC reports of 6^th Assessment).

L41 – I think you can delete the older references here (before 2010) as you have several recent ones.

L70-71 – Permafrost presence/absence is inferred or interpreted from the ERT results rather than “detected”. A revision is suggested: “… electrical resistivity tomography (ERT) surveys were used to determine the distribution of frozen and unfrozen ground in the vicinity of the CCOPs……ERT surveys to characterize freeze-thaw dynamics in….”

L68-74 – I don’t think you need this much detail here as it should be covered in the methods section (section 2). You could just say that boreholes were instrumented to measure ground temperatures and ERT surveys were used to delineate frozen and unfrozen ground.

L82 – replace “are” with “were”

L88-90 – Revision suggested “Between 1972 and 2017, MAAT increased at a …” You can also delete “climate wetting”.

L91 – You can delete the last part of the sentence from “retrieved” onward. The additional information can be provided in the Table (or its caption) if you need to provide references to previous studies.

L92-93 – Suggested revision – “Permafrost is warm with mean annual ground temperature…….ranging from -1.8 to -0.4°C. The reference may not be necessary as it seems to be a textbook, rather than a reference that specifically reports on MAGT in the region – perhaps one of the other papers in the list would be more suitable.

L95-97 – Suggested revision – “The XA site, located in a permafrost wetland, is the most northern site and has the lowest air temperature, while……China has the highest air temperature and permafrost occurs in isolated patches.

L99-100 – Can’t you just say it is ice-rich permafrost?

L108 – replace “built” with “installed”

L111 – You could just say when the hole was drilled and instrumentation installed. It isn’t clear why it is important to say that it was finished 6 months before installation ofAWS. If it was a long drilling time and likely caused significant disturbance to the thermal regime just give the number of days of drilling and the implication of this.

L119 – How far off the ROW were these sites – this information should be provided.

L118-139 – Some of the detail could be reduced by putting some of the information in a table (or figure) such as the distance from the pipe, or depth of borehole. The table could also summarize all the instrumentation or surveys at a site, i.e. add this information to Table 3 for example. In this section you could just mention the instrumentation used to acquire information on the various parameters such as GT, soil moisture etc. You should also indicate how wide the ROW is at each site as this will give the reader an indication of the amount of the disturbance.

L122-123 – Don’t you mean the boreholes were drilled vertically? (rearrange sentence)

L129 – Weren’t thermistor cables used in other BHs?

L134 – Do you mean precision (resolution) rather accuracy here? Wouldn’t accuracy be more related to the temperature sensor?

L148 Table 2 – The resolution/precision of instrumentation, including the dataloggers used should also be provided.

L151 – Table 3 – You could just give the maximum measurement depth in the table as the various measurement depths would be included in the database. Alternatively, you could include this additional information as a supplementary information table. You could then include the additional information in the table suggested in an earlier comment (distance from pipe, ROW width at each site, and whether BH is on or off ROW).

L153 – Section 3 - Data description – You seem to be confusing methodology with dataset description. Much of this information including type of instrumentation used should be included in Section 2 which describes methods including instrumentation. In some cases such as Section 3.2 there is a repeat of the instrumentation description that was given in Section 2. Section 3 also presents results, analysis and discussion so some consideration should be given to revising the organization of sections.

L190 – Fig. 3b doesn’t clearly show the relationship between GT and latitude and whether it is linear or not. MAGT at DZAA for each undisturbed site could be plotted vs latitude to better show this.

L192-193 – Are you sure this isn’t an issue with the sensors?

L197-199 – A bit confusing as Fig. 4 shows seasonal variation.

L199-200 – Are you referring to the thermal offset here?

L201-204 – A couple of other things to consider: ALT also responds more to shorter-term variations in air temperature compared to the deeper ground temperatures for which the higher frequency variations are filtered out. ALT will therefore show more interannual variability as shown in Fig. 5. The ground at JB is ice-rich, and melting of ground ice as thaw progresses deeper into the ground can lead to surface subsidence and consolidation of the unfrozen material. Changes in ALT over time can be relatively small as ice-rich material thaws compared to sites where excess ice is negligible. See for example Nyland et al. (2021), O’Neill et al. (2019).

L217-218 – The key thing is that insulation doesn’t prevent heat transfer but reduces it.

L219-221 – As well as the effect of the pipe, any ROW disturbance such as changes to the surface, clearing of vegetation will also have an effect on the ground thermal regime. These changes could also effect the ground thermal regime off ROW (lateral heat transfer). See for example some of the publications on the Norman Wells pipeline mentioned earlier and also Burgess and Smith (2003), Smith and Riseborough (2010).

L225 – It isn’t clear why this is an artificial permafrost table – is this the site with thermosyphons? If so, it should be mentioned first.

L228-230 – Are you referring to surface settlement (subsidence) here?

L245 – Figure 8 – Consider reversing the colour scale and using blue for higher resistivity (colder ground –permafrost) and red for lower resistivity (warmer ground – unfrozen). This is more intuitive and has been done in other papers presenting ERT results. If some of the transect is off ROW, indicate the ROW edge. Was there a topographic survey done? – no change in ground elevation is shown.

L246 – There acronym TPCT isn’t really needed – just say thermosyphons in the rest of the paragraph.

L246-262 – The papers mentioned earlier on the Alaska Alyeska oil pipeline might be relevant here as the effect of thermosyphons are described.

L269 – Volumetric moisture content doesn’t really have units. (dimensionless) You could give as %.

References

Burgess MM, Oswell J, Smith SL 2010. Government-industry collaborative monitoring of a pipeline in permafrost – the Norman Wells Pipeline experience, Canada. In: GEO2010, 63rd Canadian Geotechnical Conference and the 6th Canadian Permafrost Conference, Calgary, Sept 2010. GEO2010 Calgary Organizing Committee, pp 579-586. https://www.aina.ucalgary.ca/scripts/mwimain.dll/116/2/3/72659?RECORD&DATABASE=CPC

Burgess MM, Smith SL 2003. 17 years of thaw penetration and surface settlement observations in permafrost terrain along the Norman Wells pipeline, Northwest Territories, Canada. In: Phillips M, Springman SM, Arenson LU (eds) Proceedings of 8th International Conference on Permafrost, Zurich Switzerland, July 2003. A.A. Balkema, pp 107-112

Burke EJ, Zhang Y, Krinner G (2020) Evaluating permafrost physics in the Coupled Model Intercomparison Project 6 (CMIP6) models and their sensitivity to climate change. The Cryosphere 14:3155-3174. doi:10.5194/tc-14-3155-2020

Croft PE et al. 2021. Slope Stabilization along a Buried Crude-Oil Pipeline in Ice-Rich Permafrost. Proceedings of The Regional Conference on Permafrost 2021 and the 19^th International Conference on Cold Regions Engineering, American Society of Civil Engineers. p. 339-350 https://doi.org/10.1061/9780784483589

Etzelmüller, B. et al. (2020).Twenty years of European mountain permafrost dynamics — the PACE legacy. Environ. Res. Lett. 15, 104070.

Johnson ER and Hegdel LA 2008. Permafrost related performance of the Trans Alaska oil pipeline. Proc. 9^th Int. Conf. on Permafrost, Fairbanks Alaska. 857-864

Liu et al. 2021. Permafrost warming near the northern limit of permafrost on the Qinghai–Tibetan Plateau during the period from 2005 to 2017: A case study in the Xidatan area. Permafrost and Periglacial Processes 32:323–334. https://doi.org/10.1002/ppp.2089

Mosley, L et al. 2021. Alyeska’s 40-Plus Years of Experience with Heat Pipes on the Trans-Alaska Pipeline System. Proceedings of The Regional Conference on Permafrost 2021 and the 19th International Conference on Cold Regions Engineering, American Society of Civil Engineers. p. 327-338 https://doi.org/10.1061/9780784483589

Noetzli J, Christiansen HH, Hrbáček F, Isaksen K, Smith SL, Zhao L, Streletskiy DA (2021) [Global Climate] Permafrost Thermal State [in "State of the Climate in 2020"]. Bulletin of the American Meteorological Society 102 (8):S42-S44. doi:10.1175/BAMS-D-21-0098.1

Nyland, K.E., Shiklomanov, N.I., Streletskiy, D.A., Nelson, F.E., Klene, A.E., Kholodov, A.L., 2021. Long-term Circumpolar Active Layer Monitoring (CALM) program observations in Northern Alaskan tundra. Polar Geogr. 44, 167–185. https://doi.org/10.1080/1088937X.2021.1988000

O’Neill, H.B., Smith, S.L., Duchesne, C., 2019a. Long-term permafrost degradation and thermokarst subsidence in the Mackenzie Delta area indicated by thaw tube measurements, in: Cold Regions Engineering 2019. American Society of Civil Engineers, Reston, VA, pp. 643–651. doi:10.1061/9780784482599

Smith SL, Romanovsky VE, Isaksen K, Nyland KE, Kholodov AL, Shiklomanov NI, Streletskiy DA, Farquharson LM, Drozdov DS, Malkova GV, Christiansen HH (2021) [Arctic] Permafrost [in "State of the Climate in 2020"]. Bulletin of the American Meteorological Society 102 (8):S293-S297. doi:10.1175/BAMS-D-21-0086.1

Smith SL, Burgess MM 2010. Long-term field observations of cyclical and cumulative pipe and ground movements in permafrost terrain, Norman Wells Pipeline, Northwest Territories Canada. In: GEO2010, 63rd Canadian Geotechnical Conference and the 6th Canadian Permafrost Conference, Calgary, Sept. 2010. GEO2010 Calgary Organizing Committee, pp 595 https://www.aina.ucalgary.ca/scripts/mwimain.dll/116/2/4/72661?RECORD&DATABASE=CPC-602

Smith SL, Riseborough DW (2010) Modelling the thermal response of permafrost terrain to right-of-way disturbance and climate warming. Cold Regions Science and Technology 60 (1):92-103

Smith SL, Burgess MM, Riseborough D, Chartrand J (2008) Permafrost and terrain research and monitoring sites of the Norman Wells to Zama pipeline – Thermal data collection and case histories, April 1985 to September 2001. Geological Survey of Canada Open File 5331. doi:10.4095/224831

Smith SL, Burgess MM, Riseborough D, Coultish T, Chartrand J (2004) Digital Summary Database of Permafrost and Thermal Conditions – Norman Wells Pipeline Study Sites. Geological Survey of Canada Open File 4635. doi:10.4095/215482

Zhao, L. et al. (2020)Changing climate and the permafrost environment on the Qinghai–Tibet (Xizang) plateau. Permafrost and Periglac Process 31, 396–405.

General comments

This paper presents an integrated dataset on the permafrost along the China Russia crude oil pipeline in northeast China, which is an important complement to the current global permafrost database. These data are of great significance to the stability of linear infrastructures (e.g., pipeline, highway, railway), the validation of numerical simulation models, as well as the prediction of permafrost evolution process (degradation or aggradation). However, the manuscript still needs some revisions to reach a publishable level. My detailed comments as well as some suggestions are listed as below. Hope these comments will be useful to the authors to improve the manuscript.

Detailed comments

Line 35: It should be better to say “the Earth’s cryosphere”.

Line 35-36, rewrite, “the thermal state” of permafrost” is not a component of cryosphere

Line 67: State Key Laboratory of Frozen Soil Engineering (SKLFSE), not soils. Check

Line 69: Delete the definite article “the” before electrical resistivity tomography (ERT).

Line 76: You can delete the comma before “in Northeast China”, or keep the comma, but delete “in” before Northeast China.

Line 82: “…… were established ……”

Line 84: “…… was primarily based on ……”

Line 90: Delete “climate wetting at”.

Line 108: “…… was installed ……”

Line 110-111: The sentence in the parenthesis is confusing. Do you mean the borehole was drilled 6 months before the installation of AWS? If so, you can just give the exact date when the bole was drilled to avoid any confusion.

Line 116: Do you mean “wireless data transmission”? This also appears in line 157. Check!

Line 145: “…… other profiles were done using ……”

Line 147: “…… least-squares method was employed for ……”

Line 181: “…… protected by steel tube ……”

Line 187: Be careful to use “would be” herein, you can just say “…… which was mainly related to the local topography ……”

Line 193: Should say intra-permafrost groundwater.

Figure 3. I noticed that there are “zero curtain” phenomena in the left panel (a1-a4) of Fig. 3, but the duration time of zero curtain of each curve is not the same. The authors should explain the possible reasons for this (I suppose this is mainly related to the in situ soil water/ice content of the permafrost sites).

Figure 6: To facilitate comparison, I suggest using the same range of values in the vertical axis (GT) for each subfigure. (Same for the left and right panels in Fig. 3)

Line 228-229: This deepening of the permafrost table and warming of permafrost has exposed the pipelines to thawed low-bearing foundation soils. This sentence has two subjects, so you should use have instead of has.

Line 230: the CRCOP-I had locally settled down ……

Line 233: In the parenthesis, you can refer to the literature Zhang, T. (2011) when explaining “talik”.

Zhang, T., 2011. Talik. In: Singh, V.P., Singh, P., Haritashya, U.K. (eds) Encyclopedia of Snow, Ice and Glaciers. Encyclopedia of Earth Sciences Series. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-2642-2_563

Line 234-236: Why you used 300 ohm·m here? In my knowledge, this value can vary greatly from place to place around the world. The authors should give a criterion or any references to support their choice (e.g., Schön, J. H., 1996; Christof Kneisel et al., 2008). Also, you said “boundary”, it is a little bit confusing. I understand you mean the boundary between unfrozen and frozen zones. So, my suggested wording is: electrical resistivity value of 300 ohm·m was used as the critical value to identify the boundary between frozen and unfrozen zones.

Schön, J. H. (1996). Physical properties of rocks. Handbook of geophysical exploration. Pergamon Press.

Christof Kneisel, Christian Hauck, Richard Fortier, & Brian Moorman, 2008. Advances in Geophysical Methods for Permafrost Investigations, Permafrost and Periglacial Processes, 19: 157–178, DOI: 10.1002/ppp.616

Line 254: Lower rate, not slower rate.

Line 256: Delete “the” before “cooling rate”.

Line 257-258: “abnormal changes in 0 °C isotherm observed in Figures 9b, 9c, and 9d ……” Here, the using of “observed” is strange to me. Figures can never observe anything by itself. So, just say “showed in figures 9b, 9c ……”

Line 259: intra-permafrost groundwater.

Figure 10: Should give the unit for VWC, m3/m3 or %.

Line 287: The MAGT at 15 m depth……

Line 289: I suggest using “occurred” rather than “observed”.

Line 292: the ERT results.

This paper presents an in-situ observational dataset on permafrost thermal regimes along the China-Russia Crude Oil Pipeline (CRCOP) route in northeast China, consisting of meteorological observations, soil temperature and soil moisture content data, and electrical resistivity tomography (ERT) data. The analysis of this dataset shows that the operation of CRCOP has had profound effects on the thermal state of the ground. The results are useful for better understanding the responses of permafrost to climate change and engineering activities. This dataset is valuable for evaluating the integrity of pipelines and the effectiveness of measures to mitigate the permafrost thaw, as well as for validating numerical models. The manuscript is overall well organized and written, but there are still some shortcomings that need to be addressed.

Specific comments

1, Please enhance the description of data processing (e.g. how do you deal with missing data and how these missing data affect the results?) in the revised manuscript. This will be important for full understanding of this dataset.

2, Warm-oil pipeline dissipates heat into the surrounding permafrost, resulting in thermal and physical disturbances to the pipeline right-of-way. These disturbances can compromise pipeline integrity and pose the potential risk of oil leakage. Therefore, in-situ permafrost monitoring has been made along several important pipeline routes (e.g. the Norman Wells pipeline and Trans-Alaska oil pipeline) , where reliable first-hand data has been collected. I suggest the authors mention those important studies as background to this study.

3, Section 2. I found the locations of the sites are not accurate enough, rounded to two decimal places. The locations of boreholes and ERT profiles are not given in the manuscript, nor in the associated dataset. I suggest the author can provide accurate locations (at least four decimal places in unit degrees) for these mentioned locations.

4, Ground temperature was automatically collected by the dataloggers of RTB37a36V3 and CR3000 or measured manually with Fluke 87/89. Please provide a description of the errors occurring in these measurements.

5, The ROW widths are equal at each monitoring site? Please give a clear description.

6, Figure 3, seems problematic in the caption. According to the caption, column (a) indicates the active layer, but ground temperatures in XT in (a2-4) were measured below zero degrees for several consecutive years, which actually implies permafrost at this depth.

7, In Lines 110-111, please give exact timing for the borehole drilling.

8, Line 232 to 240, ERT results show that a talik formed around CRCOP I is much larger than that around CRCOP II. What is the reason?

9, Line 255-257, it’s difficult to directly observe the 1.5 m cooling range of two-phase closed thermosyphons and the 4 m lateral extent of thermal disturbance in Fig.9c and d, please clarify this point.

10, In Figure 8 and Appendix D, please use blue for higher resistivity and red for lower resistivity in ER images, like the color scheme in Figure 9. This is more intuitive for readers.

11, In Figure 10, please add the unit for soil volumetric liquid water content.