Dear Aurich,

Based on the reviews received and your response, I am pleased to accept your manuscript for publication in Climate of the Past. Although I am satisfied that you have responded to the reviewers’ comments, I have some minor editorial suggestions that you may wish to take into account before submitting a final revised manuscript. These are proposed only to help improve the clarity of the manuscript, and the publication of your manuscript is not contingent on their incorporation.

1. The title of the manuscript is perhaps a little ambiguous, inviting the question: “response of what?”. May I suggest that you consider rephrasing it, for example as something like: “Modelling the evolution of pulse-like perturbations in atmospheric carbon and carbon isotopes”, or something more ‘catchy’ perhaps?
2. Page 1, Lines 5-7: there is perhaps a concern here that the abstract gives the impression that carbon perturbations are removed from the atmosphere within “years to centuries”, whereas I think you are listing the processes that act on different timescales. It is important that the casual (lazy?) reader who does not look into the details of the manuscript does not misunderstand this, and get the impression that e.g. anthropogenic emissions of carbon will be removed on a timescale of “years to centuries”. Please consider rephrasing to make this completely clear: e.g. “Atmospheric perturbations… are removed by different processes acting on different timescales. On timescales of years to centuries, … On longer timescales of…, etc…”.
3. Page 1, Line 15: I think one can be overly diffident: perhaps consider writing “Our results suggest that changes in… …of the last glacial period, though model and data uncertainties prevent….”
4. I think that the abstract would help to attract more attention to the manuscript if it ended with a punchy sentence that summarised at least one element of conceptual importance of the study: e.g. in underlining the importance of fluxes to/from the solid earth, on timescales where the ocean-atmosphere has so far typically been assumed to represent a closed system, perhaps?
5. Page 1, Line 21: I would suggest replacing with: “Yet many open questions remain, including for example the offsets in the stable isotope signature…”
6. Page 2, line 6: it seems like the sentence needs to be rounded off somehow, as it is not clear why the statement is relevant. E.g. “…attributed to changes in terrestrial carbon storage (e.g. Bauska et al., 2016, 2018), however other scenarios might be possible/however this remains equivocal/etc…”
7. Page 2, line 8: “…are eventually removed by a few principal processes. In the case of CO2… it is ocean- and land uptake; on millennial timescales, CaCO3 compensation; and finally…”
8. Page 2, line 145: “…3-dimensionsal models remain challenging.”
9. Page 3, line 11: “The pulse experiments represent (i) the sudden…”
10. Page 3, line 18: “Gent-McWilliams” (no space).
11. Page 3, line 19: “…(Ritz et al., 1998), and a single layer…”
12. Page 4, line 3: why not just “dissolution”, instead of redissolution (has it dissolved twice)?
13. Page 7, line 9: it is not clear to me what is meant by “the pulse is released in the first timestep of simulation year 100 instead distributed over the year”. Perhaps “the pulse is released in the first time-step of simulation year 100, rather than being distributed over year 100”…? Please clarify.
14. Page 8, line 12: “To this end, the Python..”, I think.
15. Page 10, line 11: “…84% of the perturbation is removed with a timescale of 6 years… when the perturbation is taken up by the ocean and living vegetation.”, perhaps.
16. Page 10, line 13: “…the decadal and centennial removal/uptake of the perturbation by the land biosphere and deeper ocean”, perhaps. Then again: “3% of the perturbation is finally removed…”
17. Page 10, line 16: If several different solutions are possible, the reader is left wondering how accurate/robust the chosen fits are. Would it be correct and equivalent to state that “..other equally accurate solutions are possible”, for example?
18. Page 11, line 18: it would be useful to give an indication of what a ‘small pulse size’ means, e.g. “for small pulse sizes, 19. Page 11, line 29: “…of the different atmosphere, ocean land biosphere reservoirs.”
20. Page 12, line 12: “…are ventilated within approximately a decade.”
21. Page 12, line 21: “Turning to intermediate timescales (2kyr < t < 20 kyr)..”, perhaps.
22. Page 12, line 26: lithosphere
23. Page 12, line 27: this description of ‘terrestrial neutralization’ makes it hard to distinguish from carbonate compensation. Please clarify the distinction.
24. Page 13, line 6: this sentence is confusing; please clarify what you mean by “the ratio of initial [inventories] when compensation is completed”.
25. Page 13, line n33: in which system; the ocean-atmosphere system?
26. Page 13, line 34: I would suggest “In simulation WEA500, with weathering feedbacks enabled, the long-term removal timescale of Dd13Catm (~70 kyr) is also shorter than the residence time of carbon in [the ocean-atmosphere system?].”
27. Page 14, line 11: I would suggest “In scenario CLO500, we exclude the effect of… and treat .. as a closed system.”
28. Page 16, line 3: I would suggest “The isotopic budget can be defined as the product of the corresponding carbon inventory multiplied by its isotopic signature, in units of [GtC permil].” However, I would also suggest avoiding the use of both ‘budget’ and ‘inventory’ (e.g. see Figure 3 axis labels, vs the caption), and that the word ‘inventory’ be used in preference if this is in fact what is meant by ‘budget’.
29. Page 16, line 8: The last sentence is not clear… do you mean “therefore the burial flux is what ultimately removes the d13C perturbation from the atmosphere-ocean-land biosphere system”?
30. Page 16, line 12: when you write that they increase by 350 GtC “in addition to the pulse input of 500 GtC”, should we expect an increase of 850 GtC? Or do you mean “as a result of the pulse input of 500 GtC”?
31. Page 17, line 21: “This yields an overall burial…”
32. Page 17, line 27: there seems to be a mistake here… do you mean “For CO2, the remaining atmospheric fraction is higher for larger pulse sizes”? And then: “Differences between small pulses are most significant in the first decades; differences between large pulses are most significant in the first millennia”, perhaps?
33. Page 18, line 6: “Third, the response in marine export.. is also non-linear for pulses…”
34. Page 18, line 9: I would suggest “…is smaller for negative, versus positive, pulses of the same magnitude…”
35. Page 19, line 27: I would suggest “This is due to changes in the fractionation… gas exchange at higher temperatures, …growth at elevated CO2 cocnentrations.”
36. Page 19, line 31: useful repetition, “… and less negative signatures in cold high-latitude waters…”
37. Page 21, Figure 6 caption: “…time slices at: 100 yrs (a,b); 1 kyr (c,d); 10 kyr (e,f); and 50 kyr (g,h)…”
38. Page 22, line 15: I think that for consistency you should surely write “..over ~1000 years to 100 kyr after a pulse…”
39. Page 23, line 1: “…and weather feedbacks are lacking… The short-term.. from years to one or two millennia...” perhaps.
40. Page 23, line 6: “The removal of an atmospheric… is not buffered by… chemistry, unlike for CO2.” And then: “The… perturbation is partitioned between the ocean, land… roughly in proportion to their carbon inventories, over ~2 kyr.”
41. Page 23, line 11: “…this chemical buffering hardly affects the atmospheric…”
42. Page 24, line 10: do you mean “this gradient in d13C”? It is not clear what a gradient in Dd13C is (i.e. a gradient in an offset/gradient).
43. Page 24, line 31: Since a new paragraph, repetition of the intended object is useful: “…not a likely explanation of the isotopic offset between the PGM and LGM.”
44. Page 25, line 7-9: this is a but vague; can you say something more specific about what is needed?
45. Page 26, line 13: “…expected for such a fast (<100 yr) increase.”
46. Page 26, last sentence: As suggested for the abstract, it would be ideal if you could add a final sentence that sums up a general conceptual advance or ‘twist’ that this study serves to underline, for example (?) perhaps regarding the importance of ‘open system’ effects on what, so far, have typically been considered relatively short timescales (e.g. glacial-interglacial).

I hope that my suggestions are useful in preparing your final manuscript.

Sincerely,
Luke Skinner