the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Jun 2026
Late Glacial and Holocene landscape and permafrost evolution of the Barentsburg area, West Spitsbergen
Abstract. The postglacial landscape evolution on West Spitsbergen provides insights into the interplay among glacial retreat and rebound, marine transgression, and permafrost aggradation, all of which are driven, or at least superimposed, by climate dynamics. To gain a new understanding of this interplay, a total of 19 permafrost drill cores, complemented by one natural exposure reaching depths of 5–25 m below the surface, were studied. The sampling heights span from 74 m above sea level to 4 m below sea level. The drill transect extends approximately 20 km inland from the marine terraces at Isfjorden (sub-area A), along the Grønfjorden (sub-area B), the Grøndalen (sub-area C), and the Hollendardalen (sub-area D) valleys in the wider Barentsburg area. Detailed cryolithological descriptions, hydrochemical and sedimentological analyses, and radiocarbon dating were employed to infer the spatial and temporal evolution of regional permafrost following deglaciation and sea-level adjustment.
The sediment composition is highly variable, ranging from clayey silt to gravelly sand (mean grain size: ca. 10–10,000 µm). Instead, the biogeochemical composition reveals relatively small differences in total organic carbon (TOC) and total nitrogen (TN) contents, as well as in stable carbon isotope ratios (δ13C) and in the TOC/TN ratio of organic matter. Likewise, the mass-specific magnetic susceptibility data exhibit relatively low variability. Ice and water extracts with low electrical conductivity, relatively low anion and cation concentrations, and a wide spread on the PIPER plot suggest a terrestrial origin of the ground ice. However, in some places, high conductivity and a dominant sodium-chloride composition indicate marine and/or cryopeg influence. Applicable radiocarbon dates are younger than 11 cal kyr BP. Older radiocarbon dates, starting from 37.8 cal kyr BP, are disputable and very likely contaminated by carbon from surrounding Tertiary coal deposits and, therefore, not considered in the present study. Three major stages of Late Glacial and Holocene landscape evolution were identified: (1) deglaciation, (2) marine transgression, and (3) permafrost formation. The latter differentiates into three sub-stages characterized by (a) periglacial, fluvial, and alluvial deposition, (b) pingo formation, and (c) slope and alluvial deposition and pingo degradation.
As the High Arctic and thus the permafrost have recently experienced strong warming and substantial landscape changes, their evolution over geologic timescales warrants fundamental research to better understand climate-permafrost interactions. In this context, the present study provides insights into permafrost's response to Late Glacial and Holocene environmental changes.
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Status: open (until 28 Oct 2026)
- RC1: 'Comment on egusphere-2026-1377', Anonymous Referee #1, 25 Sep 2026 reply
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RC2: 'Comment on egusphere-2026-1377', Anonymous Referee #2, 14 Oct 2026
reply
General comments :
The paper addresses an important knowledge gap regarding the timing of permafrost aggradation and is based on an impressive amount of fieldwork, drill-core material, and analytical data. However, the manuscript currently reads more like a technical report than a focused scientific paper, with extensive descriptive detail but insufficient synthesis and interpretation. The Introduction needs a clearer scientific rationale, the Methods require clarification, and the Results section should be substantially shortened and focused on the findings most relevant to the research objectives. The Discussion, in particular, needs to develop a more coherent interpretation of the evidence, including the cryostratigraphic data, and establish more clearly how the findings advance understanding of postglacial landscape evolution and permafrost aggradation on Svalbard. My main scientific issues in the discussion are as follows:
- The proposed landscape-evolution stages are not sufficiently supported by an integrated interpretation of the evidence.
- The cryostratigraphic observations are not meaningfully discussed.
- The hydrochemical evidence is used too confidently
- The comparison with Adventdalen is introduced but not developed into a meaningful scientific interpretation.
The figures and language also require revision to improve clarity and consistency.
Given the number and scope of the issues identified, my comments become less detailed in the later sections. Nevertheless, the main concerns are substantive and affect the strength of the manuscript's interpretations and conclusions. I recommend major revision.
Abstract: The Abstract would benefit from a clearer statement of the study’s main contributions and their significance within the wider scientific context. In particular, it should more explicitly highlight the key findings, explain how they advance current understanding of the timing of permafrost aggradation following deglaciation, and clarify the broader implications for postglacial landscape development in Svalbard.
Introduction: The Introduction currently reads as a succession of paragraphs summarising background literature, rather than building a focused rationale for the present study. It should be shortened and tailored to the specific research question: the timing of permafrost aggradation following deglaciation and its implications for terrestrial landscape development in Svalbard. The aim is not to provide a general overview of the Quaternary history of Svalbard or permafrost research conducted by the research group, but to establish the context necessary to understand the significance of this study.
Paragraph 2 provides general Quaternary background but does not adequately frame the specific problem of post-deglacial landscape development and permafrost aggradation. Similarly, Lines 72–78 should give greater consideration to previous work in Adventdalen, particularly Gilbert et al. (2018) and Cable et al. (2018), which address closely related questions regarding the timing and development of permafrost in the study area. Relevant work on pingo formation by Hodson et al. and permafrost aggradation by Rotem et al. should also be incorporated where appropriate. These studies are essential for establishing the current state of knowledge, identifying unresolved questions, and demonstrating how the present study advances existing research.
Lines 79–89 should be removed or, where relevant, relocated to the Discussion. Finally, the study objectives outlined in Lines 90–96 should be explicitly linked to the wider scientific context. The Introduction should explain why establishing the timing of permafrost aggradation following deglaciation matters, what knowledge gap the study addresses, and how its findings contribute to our understanding of postglacial landscape development in Svalbard.
Study Site: The description of geology, Quaternary deposits, landscape features, soils, and vegetation is largely generic and reads as background information rather than a focused characterization of the study area. The authors should consider substantially shortening this section and retaining only information directly relevant to the study objectives and interpretation of the results. In particular, the lists of sediment types and landscape features, as well as the general descriptions of Arctic soils and vegetation, should be justified in terms of their relevance to the study. Statements concerning permafrost conditions should also be expressed more precisely and supported by appropriate evidence.
Methods
Fieldwork: This section needs to state how/why the sites were selected for drilling.
Laboratory: This section has a lot am ambiguity and needs to state how each of the analysis is relevant to the research question (i.e. why did you choose these analytical methods?)
The procedure used for hydrochemical analysis of the sediment extracts requires further clarification. The authors should provide a reference for the extraction protocol or justify the selected sediment-to-water ratio (1:5), drying conditions, sieve size, stirring procedure, and filtration timing. In particular, the rationale for filtering the suspension within 3 minutes after stirring should be explained, as these procedural details may affect the measured concentrations.
The authors should clarify how pH was measured. Was it measured directly in thawed ground ice or in water extracts prepared from dried sediment? These methods yield different results and are not directly comparable. The sample preparation and measurement procedures should be specified.
The authors state that electrical conductivity (EC) values were converted to general ion content with an accuracy of ±0.5% and expressed in mg L⁻¹. Please specify the conversion equation, its source, and the calibration procedure used to establish this accuracy. Because the relationship between EC and dissolved ion concentration depends on ionic composition and concentration, the claimed accuracy of ±0.5% requires experimental validation and justification.
The reported precision errors of 5–15% require clarification, particularly for concentrations near the quantification limits. The authors should specify how precision was assessed (e.g., replicate analyses and relative standard deviation) and provide sufficient information to evaluate the analytical quality of the results. In addition, the concentration ranges associated with the reported precision errors appear inconsistent for Na⁺, K⁺, Ca²⁺, and Mg²⁺, as the same range (2–20 mg L⁻¹) is assigned to both 5% and 15% errors. Please verify and correct these ranges. The authors should also clarify whether the reported quantification limits were experimentally determined for the complete extraction and analytical procedure or refer only to the instrument.
The calculation of bicarbonate concentration from inorganic carbon (IC) requires further explanation. The authors assume that carbonate and dissolved CO₂ make negligible contributions to IC based on pH measurements, but this assumption should be supported by the measured pH range and appropriate chemical-equilibrium considerations. Please provide the equation used to convert IC concentrations to bicarbonate concentrations and explain whether other dissolved inorganic carbon species were accounted for.
The suitability of the radiocarbon-dating approach requires further clarification, particularly for the bulk samples. Although terrestrial plant remains are generally appropriate for AMS radiocarbon dating, bulk samples from coal- and shale-bearing settings may contain mixtures of organic carbon with different ages, including reworked material and fossil carbon derived from the bedrock. The authors should clearly distinguish dates obtained from identifiable terrestrial plant remains from those obtained from bulk samples, justify the use of bulk-sample ages, and describe the pretreatment procedures used to minimize contamination. Please also explain how δ¹³C measurements were used in sample selection or age calculation, and discuss the potential effects of reworked or geologically old carbon on the resulting ages. The interpretation of the radiocarbon dates should account for these limitations. This is slightly discussed in the geochronology section, but needs further clarification.
Results
The Results section is 14 pages long with figures (!!!), is largely descriptive and, in places, reads as a list of observations rather than a focused presentation of findings. If I am being honest, I skimmed through large sections of repetitive text that couldn’t keep my attention. The authors should prioritize results that are directly relevant to the study objectives and provide a clearer structure that supports the subsequent Discussion. Unnecessary detail and extensive lists of measurements or observations should be condensed, with greater emphasis on the key patterns, relationships, and findings that are subsequently interpreted in the Discussion. Therefore – my specific comments in this section are limited because this section needs major rewriting. The text should be shortened to at least half of its present state and focus on key differences between the sites.
A few specifics to consider in the results section:
There is an inconsistency in the reporting of electrical conductivity (EC). The Methods section states that EC values were converted to ion content and expressed in mg L⁻¹, whereas the figures and Results section report EC in μS cm⁻¹. The authors should clarify whether the reported values represent electrical conductivity or estimated ion concentration and ensure that the terminology and units are consistent throughout the manuscript. If EC was converted to estimated ion content, the conversion procedure and its justification should also be provided.
The figures are not explicitly referenced in the main text. The authors should ensure that all figures are cited at appropriate points in the text and that multi-panel figures have clearly labelled panels, with specific references to the relevant panels where necessary.
The terminology “gravimetric moisture content” should be clarified and used consistently. However, calling this both “moisture content” and “ice content” is potentially misleading. Based on your methods, you are presenting gravimetric moisture content.
It is unclear why Bbg4, Bbg6, are not presented in the results.
Consider renaming sub-area C2a and b to disambiguate from areas A and B
Section 4.7 would benefit from a clearer presentation of the data, preferably in a figure or, at minimum, a table. In its current form, the information is not well integrated with the rest of the manuscript, making its relevance to the main findings difficult to assess. The authors should improve its presentation and clarify how these data contribute to the study objectives and overall interpretation. Otherwise remove all together.
Discussion
The manuscript would benefit from a more thorough comparison with previous studies from Adventdalen and other relevant areas of Svalbard. This would place the findings in a regional context, help identify similarities and differences in permafrost conditions and aggradation history, and strengthen the discussion of the study’s broader scientific significance.
Geochronology
Prioritizing radiocarbon ages from individual plant remains over bulk-sediment ages is reasonable given the potential contamination by fossil carbon from the surrounding Tertiary coal deposits. However, this does not rule out age biases due to reworking, root intrusion, or sediment mixing. The authors should clarify how the integrity of the dated plant remains was assessed. Furthermore, restricting the interpretation to ages younger than 16 cal kyr BP does not establish that these dates are free from mixing. The authors should justify this cutoff independently and explain the exclusion of older dates, distinguishing between unreliable ages and those that are simply difficult to interpret. Any remaining uncertainty regarding the relationship between the age of the plant remains and the time of sediment deposition should be acknowledged. Overall I am left wondering – what does the radiocarbon dating tell us?
Hydrochemical data
Even as a geochemist, the discussion on hydrochemical data was difficult to follow and focuses on salinization indices without adequately explaining the processes responsible for saline conditions in permafrost. The authors should discuss possible sources of salinity, including freeze concentration, relict marine porewater, and deeper saline groundwater, and assess their plausibility based on the available evidence.
The authors should also distinguish between evidence of salinity, marine influence, and cryopeg formation. Because the analyses use deionized-water extracts, the authors should explain how the extraction procedure may affect the measured electrical conductivity and ionic composition. In addition, the interpretation of marine influence appears inconsistent between some study areas, particularly sub-areas A and B and core Bbg 9. The authors should clarify how the GGV and SMK ratios are interpreted alongside EC and major-ion data. Finally, the claim that cryopegs formed from seawater during pingo formation requires further justification, as the reported hydrochemical data alone do not establish the origin or formation mechanism of the salinity.
Landscape history
The discussion of landscape evolution attempts to integrate the regional deglaciation and relative sea-level history, sedimentological and hydrochemical data from the drilling transect, and paleoenvironmental evidence to define three stages of landscape development. However, the section is currently largely descriptive, and the links between the different lines of evidence are not always sufficiently established.
This is the important part of the manusctipt and requires more attention along with Table 3, which does a good job at summarizing the findings, but is somehow not fully discussed in text. The long list of cores and elevation thresholds makes the discussion difficult to follow.
The discussion should more clearly articulate the study’s main contribution to understanding postglacial landscape evolution and permafrost aggradation in the wider context of Svalbard, supported by comparisons with previous studies from Adventdalen and other relevant areas.
The discussion does not adequately address the cryostratigraphic data, despite their apparent importance to the study. The authors should provide a clearer interpretation of the observed cryostructures and their stratigraphic relationships, and explain what these reveal about the history of permafrost aggradation, ground-ice formation, and subsequent landscape evolution. The cryostratigraphic evidence should be integrated with the sedimentological, geochronological, and hydrochemical results to assess whether it supports the proposed stages of landscape development. In its current form, the discussion relies heavily on sedimentological descriptions and hydrochemical interpretations, while the cryostratigraphic observations are not sufficiently used to develop or substantiate the main conclusions.
The comparison with Adventdalen is potentially important but is not sufficiently developed. The authors state that Holocene landscape dynamics in Adventdalen and Grøndalen differ substantially, yet do not explain the nature of these differences, explore their possible causes, or discuss their implications for the proposed landscape-evolution model. The absence of loess and peat deposits in the present study area also warrants further consideration, including whether it reflects differences in depositional environments, sediment availability, preservation, or permafrost development. Similarly, the contrasting ages of pingos along Adventdalen and the evidence for middle Holocene pingo sediments in the study area should be discussed in terms of the timing and spatial variability of pingo formation and permafrost aggradation. This regional comparison should be integrated with the sedimentological and, particularly, cryostratigraphic evidence to explain what the findings reveal about the different trajectories of landscape evolution. The current concluding statement that the two areas differ substantially is not adequately supported by the discussion presented.
Conclusion
The significance of the study should be articulated more specifically. The general statement about Arctic warming and the importance of understanding long-term climate–permafrost interactions is not, in itself, a strong justification for the study. The authors should explain what new insights their results provide into permafrost aggradation and landscape evolution on Svalbard, and how these findings advance understanding beyond previous regional studies. The significance should emerge from the specific findings and their interpretation, rather than from the general relevance of Arctic warming. The conclusion would be stronger if it identified the principal new findings, acknowledged chronological and interpretive uncertainties, and clarified how this study advances understanding beyond previous studies of Svalbard.
Formatting
The manuscript requires further language editing. There are a few awkward or non-idiomatic expressions throughout the text, which suggest that the English language needs further polishing. These issues occasionally affect clarity and readability. The authors are encouraged to have the manuscript carefully edited by a proficient English-language editor before publication. I attempted to fix the sentences that were the most awkward, but this needs further consideration.
Please check all geographical names against the official Svalbard place-name database and use them consistently throughout the manuscript and figures. Retain established Norwegian names rather than translating their geographical elements into English, and avoid redundant forms such as “Grøndalen Valley” or “Aldegondabreen Glacier.” Use “Svalbard archipelago” rather than “Spitzbergen archipelago,” reserving “Spitsbergen” for the main island. Please also check the use of definite articles and standardize terminology throughout.
Some terms such as active-layer/active layer are used interchangeably throughout. Choose one and stick to it.
Specific comments
Abstract and Introduction
Lines 18–20: Reword for clarity: “The drill transect extends approximately 20 km inland from the marine terraces along Isfjorden (sub-area A), through the Finneset area (sub-area B), Grøndalen (sub-area C), and Hollendardalen (sub-area D), in the wider Barentsburg area.”
Line 25: Format “¹³” as a superscript.
Line 27: The term “ice and water extracts” is scientifically ambiguous. Please distinguish between thawed ground-ice samples and water extracts prepared from sediment.
Lines 31–32: Remove this information from the Abstract if it is not addressed in the study.
Lines 51–52: Remove this sentence.
Lines 52–65: Refocus the Introduction on previous studies that have constrained the timing of permafrost aggradation, particularly following deglaciation. Retain only the key references providing general Quaternary context and add relevant studies specifically addressing permafrost aggradation.
Lines 60–62: Remove these sentences or relocate them to a more appropriate section.
Lines 63–65: The information is potentially relevant, but please clarify its significance for the present study.
Study area and geological setting
Lines 108–109: Consider rewording as follows: “To the east of Grønfjorden, the landscape is further shaped by a network of deeply incised erosion channels cutting into gently dipping rock strata.”
Line 109: Replace “heights” with “elevations” when referring to altitude above sea level.
Lines 110–111: Consider rewording as follows: “West of Grønfjorden, large mountain ranges and intermittent glaciers occur, with relatively high, north–south-oriented ridges intercepting moisture from the Atlantic Ocean.” Please clarify what is meant by “intermittent glaciers.”
Line 111: Check the geographical nomenclature and use official place names consistently.
Line 114: Replace “glacier shrinkage” with “glacier retreat” when referring to changes in glacier termini.
Lines 115–116: Consider rewording as follows: “Between 1936 and 2017, glacier area decreased by an average of 49.5%, and glacier termini retreated by several kilometres.”
Lines 117–172: Consider substantially shortening this section and retaining only information directly relevant to the study objectives and interpretation of the results.
Lines 117–133: The geological setting is difficult to visualize from the text. Consider adding an inset to Figure 1 showing the main geological structures and relevant geological units. If Geology not important from interpretation – shorten to bare minimum.
Lines 122–125: A reference is needed to support these statements.
Lines 124–125: Consider rewording as follows: “Cretaceous sediments are exposed only in a small area along the coast of Grønfjorden and Isfjorden.”
Line 126: Check and standardize the geographical nomenclature.
Lines 127–128: Consider rewording as follows: “Here, ancient rocks associated with the mountain anticline along the western coast of Spitsbergen are exposed at the surface.” Please ensure that “anticline” is the correct geological term for the structure described.
Lines 128–133: Please provide appropriate references.
Lines 135–136: Consider rewording as follows: “Quaternary surficial deposits are perennially frozen, except for the seasonally thawed active layer and taliks.” Please also clarify what is known about the occurrence and extent of taliks in the study area, with supporting references where available (important for the discussion about cryopegs).
Lines 149–153: Remove this historical background, which does not appear necessary for understanding the study.
Lines 153–157: Use climate normals to facilitate comparison with other studies and provide an appropriate reference.
Lines 160–161: Please provide a reference and clarify the relationship between permafrost thickness and the geological and thermal properties of the substrate. Permafrost thickness should not be attributed to surface morphology alone.
Lines 161–164: Remove this general background and report only information relevant to the study.
Lines 164–167: Focus on sites and measurements relevant to the study area rather than Svalbard as a whole. Please consider whether data from Kapp Linné and the relevant CALM active-layer monitoring site are appropriate for comparison.
Lines 168–172: Consider rewording as follows: “The study area comprises five sub-areas (Figure 1, Table 1): (A) marine terraces along Isfjorden, north of Barentsburg; (B) the fjord terrace at Finneset, south of Barentsburg; (C1) the lower reaches of Grøndalen; (C2) the middle reaches of Grøndalen; and (D) Hollendardalen.”
Fieldwork and methods
Line 177: Split the sentence into two. For example: “The outcrop GD 1 was sampled in summer 2015.”
Line 178: Define the acronym RAE-S at first use.
Lines 179–181: Consider rewording as follows: “The device uses no drilling fluid and preserves the frozen state of the core to maintain stratigraphic integrity and prevent contamination of the sediment.”
Line 182: Please clarify what is meant by “upper” and “lower.” Was this classification applied consistently throughout the drilling campaign? If not, consider removing this detail.
Lines 182–184: Consider rewording as follows: “Core sections were retrieved at intervals of 30–50 cm. Each section was described based on its visible characteristics, including grain size, colour, organic matter content, sediment type, and ice structures.”
Line 185: Reword “the cores were sealed” for clarity, specifying how they were sealed if relevant to sample preservation.
Lines 185–187: The sampling and transport procedures are unclear. Do you mean: “Samples were collected at intervals of approximately 0.5–1 m for further analysis. Some samples were transported partially frozen, whereas others were transported unfrozen”? Please specify which samples were kept frozen and which were not, and explain the rationale for these differences.
Line 198: Specify the drying duration and justify the use of 50 °C. Since 105 °C is commonly used for standard gravimetric water-content determination, the authors should explain why a lower temperature was selected, whether this was intended to avoid altering heat-sensitive constituents, and how the drying protocol may affect the results, particularly for sediments with high organic matter content.
Line 200: Reword “line water extraction of dried sediment samples” for clarity and describe the extraction procedure accurately.
Lines 206–213: Check the formatting of all chemical subscripts and superscripts throughout this paragraph.
Line 267: Check the references for accuracy and consistency.
Lines 279–285: This information may be more appropriately placed in the Study Area section or the Discussion, if it is needed to support the interpretation.
Line 287: Please specify the type of deposits being described. Do you mean surface sediments overlying bedrock?
Lines 287–288: How was the permafrost table identified? Were the cores collected while the active layer was thawed? Please clarify the method used to determine the permafrost table.
Line 293: Since the measurement is gravimetric, use “water content” rather than “ice content” unless the method specifically distinguishes ice from liquid water.
Results and Discussion
Line 323: The description of an organic smell adds little to the interpretation when total organic carbon (TOC) is measured. Consider removing it.
Line 431: The description of taste is unnecessary when the chemical composition is analysed. Please remove it.
Lines 657–659: How can the authors establish that ages younger than 16 cal kyr BP are unaffected by mixing? Please justify this age cutoff and explain how the possibility of reworking, root intrusion, or sediment mixing was evaluated.
Lines 699 and 703: Check and standardize the geographical place names.
Lines 917-918: Why are peat and loess not found in your study area?
Figures and tables
Figure 1: Correct “Kolesbay” to “Colesbukta” and “Congress Lake” to “Kongressvatnet.” For consistency with official Svalbard place names, retain Norwegian names such as Aldegondabreen, Bretjørna, Linnévatnet, and Irabreen rather than translating their geographical elements. Avoid redundant forms such as “Grøndalen Valley”; use “Grøndalen,” “Hollendardalen,” and “Colesdalen,” as appropriate. Check all place names against the official TopoSvalbard maps and place-name database. The colours used for sub-areas B and C2 are too similar and should be made more distinguishable. Geographical terminology: Replace “Spitzbergen archipelago” with “Svalbard archipelago.” Use “Spitsbergen” for the main island.
Figure 2: The photographs provide useful context, but a closer view of the relevant features would help readers understand the sites and their geological characteristics.
Table 1: Please explain why some depths are reported as approximate while others are not. Consider rounding all depths to the nearest 0.1 m, where appropriate. Standardize the coordinate precision, as most longitudes are reported to five decimal places but Bbg 1 is reported to six.
Figures 3-8: Label all panels clearly and refer to the relevant panels explicitly in the text. The distinction between “soil” and “sediment” is unclear; define the terminology and classification used in the Methods. The symbols and patterns are difficult to distinguish at the current scale and should be revised for improved legibility. Use consistent symbology for pH and EC, consistent capitalization of axis titles, and consistent formatting of chemical subscripts and superscripts in the legends. Clarify whether anion and cation percentages represent molar or mass fractions. The pH-axis scale is difficult to read. The Methods state that EC is expressed in mg L⁻¹, whereas the figures use μS cm⁻¹; please resolve this inconsistency. Replace “permafrost upper boundary” with “permafrost table” and use consistent line symbology across the figures. Explain why the permafrost table is not shown for some cores in Figure 5 and why some measurements, such as gravimetric water content, are available for only certain cores. These sampling and analytical differences should also be explained in the Methods. Magnetic susceptibility: The axis scale is misleading and should be adjusted to better represent the data range (appropriate for the full dataset). Figure legends and symbols: Remove unnecessary black points from the legend (when the axis clearly states what is shown). Ensure that the legend colours match the plotted data, including the blue points that are not blue in all figures. Consider placing the TOC and TOC/TN labels directly on the plots or using colour-coded axes to reduce the number of legend entries, as appears to have been done in Figure 5.
Figure 3: Correct the typo in “depth” in Bbg 3 and Bbg 5. Consider placing the relevant legend directly below each chart category to make the symbols easier to identify, rather than requiring readers to refer to a distant legend.
Figure 5: Two axis titles (“depth (m)”) are missing in the lower-right panel. Standardize “depth (m bs)” to “depth (m),” if “bs” is not required. Explain why GD-1 is presented on a different scale, and include all relevant cryostructures in the legend.
Figure 8: Standardize “depth (m bs)” to “depth (m),” if “bs” is not required.
Table 2: Specify the material dated for each radiocarbon determination (e.g., individual terrestrial plant remains or bulk sediment).
Citation: https://doi.org/10.5194/egusphere-2026-1377-RC2
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The most valuable point of this paper is the richness data that include grain size, ice contents, ion concentration, AMS dating, TC and TOC contents and so on. After carefully considering the accuracy and errors in all of the data, the authors appropriately present a compelling argument. I would strongly recommend this to be published for TC, after the following minor revisions.
1. Need for more explanation why subdivisions (i.e., Sub-areas A - C) were set. The authors showed close up satellite image as supplement figures, however these figures are not sufficiently providing the materials for the discussions. More precise topographic maps with elevation and/or geomorphic maps would be helpful.
2. I also recommend to include schematic diagram showing the evolution of landscape and permafrost of this region, such as cross-section images during Late Glacial and Holocene.
3. line136: "seasonally unfrozen active layer" ???
4. line 154: -10 deg in 1912 to -2 deg in 2018. Any citation?
5. lines 279-285: Consider to describe such geomorphhic settings and periglacial features in study area or to summarize in a table with references.
6. lines 748-762: consider to move to 'Method'
7. line 764: Piper plot > Fig 10?