the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Feb 2025
Accelerated export of terrestrial organic carbon to the Chukchi Sea since pre-industrial times
Abstract. The on-going global warming is causing rapid changes in the carbon cycle of the Arctic. Yet the response of the Arctic to these environmental changes are not fully understood. In this study, we investigate bulk organic parameters (TOC, TN, δ13Corg, δ15N, C/N) and terrestrial n-alkanes (TERR-alkanes) from 19 surface sediments and 5 210Pb-dated sediment cores covering up to the last three centuries from the Chukchi Sea. Downcore profiles indicate increasing OC since the beginning of the Industrial Era in all cores. They also show higher TOC and TN values in southern Chukchi Sea cores coincident with decreasing δ13Corg indicating an increasing contribution of terrestrial OC that is confirmed by TERR-alkanes. Comparison with regional paleo-records and instrumental data emphasize the key role of air temperature and sea ice cover on the OC cycle and vegetation of the surrounding landmasses.
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Status: open (until 01 Apr 2025)
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RC1: 'Comment on egusphere-2025-325', Anonymous Referee #1, 28 Feb 2025
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The authors have obtained a solid data set with great potential to enhance our understanding of arctic carbon dynamics. Thus, I recommend reconsidering the article after major changes have been made.
My biggest issue is the presentation of the data. Figures 2 and 3 (especially 3a!) may be the most careless figures I have ever seen, and I am not even color blind. Further, there are 21 figures and 3 maps in this manuscript, this is a crazy overload! I like that the authors keep their color coding throughout the manuscript, but it would be very helpful if: a) the same colors would be used in the overview of figure 1; b) the N-S legend would actually match the locations on figure 1) – there it looks like the order is N-S: 14R09 – R1 – 14S03 – C07 – LV77-4; c) they come up with names like Alsaka core, or Chukchi Sea core, or Chukotka core – something that one can remember and not just a code that even does not match the overview figure. d) Indicate uncertainties – not just in their figures but in the entire manuscript.
My second big issue is the way that conclusions are drawn. With the amount of computing power and the easy access to scripts/data pipelines, I am struggling to call "here it goes up, here down", still scientific. Especially if the data are not presented in an easy-to-digest way (like mentioned above). For example, they have 2 isotopes and define 3 endmembers, this is perfect for an endmember model like a Markov chain Monte Carlo. Or to use a principle component analysis with all their proxies (FYI: Paq abbreviation is not defined at all). Another suggestion would be to plot your TERR index over precipitation vs the time of your age model to determine what environmental parameters are related to the proxy change. They start to do this in the second part of the manuscript (content and discussion of figures 4 and 5). However, to bin the 5 core sites which lay in completely different locations – several hundreds of km apart (~800km NS and EW!!!) – and are influenced by different river systems and oceanic currents, seam hardly appropriate when comparing it with sea ice cover.
I was excited to read the manuscript, based on your abstract, and I believe it can be a good paper, as they have set the foundation for it. But the current state looks more like a draft to me. Their conclusions are important, but I cannot follow how they got there in the way that the manuscript is structured and presented. However, I think they have all needed to make it a howlsome manuscript, and getting it into a different format should allow them to publish it. I do not attach a supplement file, as I think the entire manuscript needs to be reworked, and as they usually would have to reply to every comment, this would make things just more tedious for them and for me.
Citation: https://doi.org/10.5194/egusphere-2025-325-RC1
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