The manuscript by Nicholas et al. provides a valuable contribution to our understanding of ancient carbon mobilization in the Laptev Sea over the last 16,000 years. Through the combination of high-resolution terrigenous biomarkers and compound-specific 14C dating of n-alkanoic fatty acid methyl esters, the authors trace the contribution of pre-aged organic carbon to the marine environment. The comprehensive use of multiple proxies enhances the robustness of their interpretations.

General comments:

1. In the abstract, you provide the following statement: “However, the regional variations, timing and rate of carbon release from thawing permafrost remain elusive, primarily because of the limited number of deglacial records that document carbon mobilization occurrences.”You need to state more clearly and consistently throughout the manuscript, which of these knowledge gaps this study is addressing (timing/rate/mechanisms?).
2. The structure of 3.2 of the methods section is currently quite confusing and missing some significant information. It requires restructuring to make it flow and to clearly explain to the reader which biomarkers were extracted, how they were extracted (which fractions they came from), and then to clearly but briefly explain the use of each biomarker in this study.
3. Some of the language is quite colloquial and would benefit from being changed to more formal terms, and ensure there is consistency i.e. sea ice/sea-ice

Detailed comments:

Line 25: for clarity and formality, rephrase “from off the Lena River outflow”

Line 44: joining the two sentence together will make it flow better - “global average temperatures (Rantanen et al., 2022) and future warming”

Line 46: change ‘in part’ to ‘partially’

Line 47-48: change ‘might’ to ‘could’

Line 51: remove ‘during’

Line 56: and the mechanisms are also poorly constrained? Is this not also one of the research areas?

Line 60-63: “Moreover, the degree to which mobilized permafrost OM is remineralized is not well constrained either, and the available estimates differ widely (Bröder et al., 2018; Ruben et al., 2024; Tanski et al., 2019; Vonk et al., 2012)” This statement may be unnecessary as it is outside of the scope of this study?

Line 67: which was amplified

Line 68: Remove “The”

Line 70: References needed

Line 73: References needed

Line 79: There is an abrupt shift from the topic of the last paragraph to this one. The paragraph on the last deglaciation would benefit with a brief conclusion of why this period is important for providing insight into your study aim and you can then use this to flow back to the permafrost topic.

Line 103: Briefly define Ice Complex Deposits

Line 106: Remove “were” thawed

Line 107-109: This sentence needs rearranging, so it is clear you are referring to the last deglaciation

112: “well-dated”- mention that it’s 14C dating

119: More detail on the information you are providing- magnitude/timing/mechanisms?

133: change probably to likely- less colloquial

133: Are there any estimations of regional sea levels during the last deglaciation that can be included?

Line 150-152: be clearer about the type of isotope analysis you are referring to here. Is this in reference to the biomarker compound-specific isotope analysis or the analysis conducted for the age model?

Line 154: It is unclear in this paragraph that this is a previously published age model. This needs to be explicit in the first sentence, then describe the methods in more detail

Line 175: change to: “apolar and polar (including GDGTs)”

Line 202: State what you are using to assess biomarker content- peak area?

204-205: Explain what the BIT index is used for

Line 205: State briefly why 6-methyl brGDGTs have been included

Line 210: Add reference- Sinninghe Damste et al., 2002

Line 212-214: Hard to follow the sudden mention of n-alkanoic acids without any reference to their use in this study. Also, when referencing long-chain leaf wax lipids, state which chain-lengths you are referring to.

Line 214: The information on brGDGTs here is confusing- this part needs to go before the BIT index calculation.

Line 223: There needs to be a clear explanation of what RI-OH is- mention that it is based on hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers, their source, and refer to other key references.

Line 300: State the laboratory where this was conducted

Lines 375-381: References to regional SLR

Line 386: The BIT index does not follow the pattern of your other terrestrial markers during the YD. It might be beneficial to explore the potential of in situ production of brGDGTs complicating this signal- either here or in the discussion (i.e. Sinninghe Damsté et al., 2009, GCA; De Jonge et al., 2024, GCA).

Line 469: Change similarly to similar

Line 480: Check spelling

Line 552: It is good to see the Fahl & Stein, 2012 sea-ice record in your supplementary figures, but it might be worth showing some of the other records that are frequently mentioned throughout the discussion

Line 506 and 587: Reference figure S1

Line 595: Especially

Line 657: References to regional SLR

Line 692: Here you refer to it as ICD, but in the introduction you primarily use Yedoma- try to make it consistent throughout

Figures 2 & 3: Really clear and well-produced figures

The paper by Arnaud Nicolas and colleagues titled: "Delivery of aged terrestrial organic matter to the Laptev Sea during the last deglaciation" addresses relevant scientific questions within the scope of CP. It covers a very interesting topic, provides new data, and improves the understanding of the source of terrestrial organic matter in the Arctic during the last deglaciation. The study is based on a single sediment core (PS2458-4) from the Laptev Sea. Notably, while the authors compare their record with other cores in the area, the spatial coverage is limited.

I have, however, a couple of points which I think need to be addressed:

For the GDGT data – are all GDGTs detected assumed to be  produced in situ? I am missing here a bit of detailed insight into the methods, especially for the temperature calibration. Why specifically this and no other calibration has been chosen? There is actually a very recent paper/preprint, which I would encourage the authors to read in regards to the GDGT data interpretation and publication (Bijl et al., 2025, https://doi.org/10.5194/egusphere-2025-1467).

In the discussion: I do not always follow which data are new and which are the legacy data – this also leads to uncertainty if some of the observations are novel, based on the current dataset, or something which was already described by others. Also, the discussion sections seems to be a bit randomly organized and very lengthy. I think it would benefit from having each time interval arranged by various shorter subsections, e.g., "rate of MAR", "preservation of OM", or something like that.

I wonder about the preservation of selected biomarkers analysed here, which can be influenced by several factors, such as sedimentation rate and remobilization?

The text is overall well written, but section 3, especially 3.2, is difficult to follow.