Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400&thinsp;kyr

Toyos, María H.; Winckler, Gisela; Arz, Helge W.; Lembke-Jene, Lester; Lange, Carina B.; Kuhn, Gerhard; Lamy, Frank

doi:https://doi.org/10.5194/cp-18-147-2022

Articles | Volume 18, issue 1

https://doi.org/10.5194/cp-18-147-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/cp-18-147-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 1

Research article

|

27 Jan 2022

Research article |

| 27 Jan 2022

Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 kyr

María H. Toyos, Gisela Winckler, Helge W. Arz, Lester Lembke-Jene, Carina B. Lange, Gerhard Kuhn, and Frank Lamy

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Final revised paper (published on 27 Jan 2022)
Supplement to the final revised paper
Preprint (discussion started on 27 Jul 2021)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on cp-2021-85', G. Cortese, 17 Sep 2021

Thanks for the opportunity to review this manuscript, see my comments in the attached Supplement.

Citation: https://doi.org/10.5194/cp-2021-85-RC1
- AC1:
  'Reply on RC1', María H. Toyos, 20 Oct 2021
  Dear Editor and Reviewers,
  We are grateful for your comments and the constructive feedback and suggestions that helped us to improve the manuscript. We modified the manuscript accordingly, including figures, and supplementary material, and will upload the revised version as per Editor’s request. In the attached letter, we outline the response to each of the comments using the following color code:
  Original text from the reviewers in black
  
  Our response in blue
  
  Because a couple of issues were raised by both reviewers, our extended response can be found under Reviewer 1.
  Sincerely yours,
  María H. Toyos (on behalf of all co-authors)
  
  Citation: https://doi.org/10.5194/cp-2021-85-AC1
RC2:
'Comment on cp-2021-85', Louisa Bradtmiller, 22 Sep 2021

The manuscript by Toyos and coauthors presents a new, high-quality, high-resolution record of various biogenic and lithoigenic proxies in the Drake Passage over several glacial cycles. The high resolution of the data and the relatively long (for the Southern Ocean) span of the record are espeically useful in this fairly under-studied region. Finally, the fact that their records have been Th-normalized avoids many pitfalls of working in the SO, where sediment focusing and winnowing can be intense.

I have relatively brief comments due to 1) the overall high quality of the study and presentation and 2) the incredibly thorough comments already provided by another reviewer. First, I agree with the previous comments that it would be helpful to hear more about how much/little the age model changed as a result of tuning to high/low Fe contents. This could come in the text, or could easily be illustrated with a supplemental figure. I am also intrigued by the consistent difference between % opal measured in the different labs in samples with high terrigenous content. The methods section says sample sizes at UdeC were between 50-70mg. Were they varied intentionally due to changes in terr. content? The alkaline extractin method is sensitive to sample size; for example, for a sample with >75% terr. content, a sample size of 100mg might be warranted. The methods don't say if the same sample sizes were used at AWI. This could account for some of the difference. I am not worried about this in terms of the overall conclusions of the study, but additional detals about AWI sample sizes could be included in methods. Lastly, I appreciate the care taken by the authors to consider the possibility that not all (or, as they point out, a varying amount) of the added Fe was bioavailable. Too many studies in this region assume that any Fe input is an automatic link to productivity. Even if we don't have the tools to reconstruct bioavailble Fe content, including this nuance in the discussion is a welcome change.

In summary, this is a high-quality study and a well-written manuscript. I concur with nearly all of the extensive specific comments by an earlier reviewer, and commend the authors on a very strong contribution.

Citation: https://doi.org/10.5194/cp-2021-85-RC2
- AC2:
  'Reply on RC2', María H. Toyos, 20 Oct 2021
  Dear Editor and Reviewers,
  We are grateful for your comments and the constructive feedback and suggestions that helped us to improve the manuscript. We modified the manuscript accordingly, including figures, and supplementary material, and will upload the revised version as per Editor’s request. In the attached letter, we outline the response to each of the comments using the following color code:
  Original text from the reviewers in black
  
  Our response in blue
  
  Because a couple of issues were raised by both reviewers, our extended response can be found under Reviewer 1.
  Sincerely yours,
  María H. Toyos (on behalf of all co-authors)
  
  Citation: https://doi.org/10.5194/cp-2021-85-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to minor revisions (review by editor) (26 Oct 2021) by Erin McClymont

AR by María H. Toyos on behalf of the Authors (09 Nov 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (17 Nov 2021) by Erin McClymont

Short summary

Past export production in the southeast Pacific and its link to Patagonian ice dynamics is unknown. We reconstruct biological productivity changes at the Pacific entrance to the Drake Passage, covering the past 400 000 years. We show that glacial–interglacial variability in export production responds to glaciogenic Fe supply from Patagonia and silica availability due to shifts in oceanic fronts, whereas dust, as a source of lithogenic material, plays a minor role.