Response of coastal California hydroclimate  to the Paleocene–Eocene Thermal Maximum

Zhang, Xiaodong; Tipple, Brett J.; Zhu, Jiang; Rush, William D.; Shields, Christian A.; Novak, Joseph B.; Zachos, James C.

doi:https://doi.org/10.5194/cp-20-1615-2024

Articles | Volume 20, issue 7

https://doi.org/10.5194/cp-20-1615-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/cp-20-1615-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 7

Research article

|

25 Jul 2024

Research article |

| 25 Jul 2024

Response of coastal California hydroclimate to the Paleocene–Eocene Thermal Maximum

Xiaodong Zhang, Brett J. Tipple, Jiang Zhu, William D. Rush, Christian A. Shields, Joseph B. Novak, and James C. Zachos

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Final revised paper (published on 25 Jul 2024)
Supplement to the final revised paper
Preprint (discussion started on 14 Nov 2023)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on cp-2023-89', Emily Hollingsworth, 15 Dec 2023

The comment was uploaded in the form of a supplement: https://cp.copernicus.org/preprints/cp-2023-89/cp-2023-89-RC1-supplement.pdf

Citation: https://doi.org/10.5194/cp-2023-89-RC1
- AC1: 'Reply on RC1', Xiaodong Zhang, 24 Mar 2024
  
  The comment was uploaded in the form of a supplement: https://cp.copernicus.org/preprints/cp-2023-89/cp-2023-89-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/cp-2023-89-AC1
RC2:
'Comment on CP 2023-89', Richard Pancost, 09 Feb 2024

Please see attached PDF

Citation: https://doi.org/10.5194/cp-2023-89-RC2
- AC2: 'Reply on RC2', Xiaodong Zhang, 24 Mar 2024
  
  The comment was uploaded in the form of a supplement: https://cp.copernicus.org/preprints/cp-2023-89/cp-2023-89-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/cp-2023-89-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (26 Mar 2024) by Kathleen A. Wendt

AR by Xiaodong Zhang on behalf of the Authors (18 Apr 2024) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (23 Apr 2024) by Kathleen A. Wendt

RR by Emily Hollingsworth (09 May 2024)

RR by Richard Pancost (16 May 2024)

Suggestions for revision or reasons for rejection

The original submission was a very nice contribution to the PETM literature, drawing on an impressive variety of methodologies. The revised version appropriately addressed my comments as well as those of the other reviewer, and I think this is certainly ready for publication. Congratulations to the authors!

I have a few minor comments, some related to presentation and just a few minor suggestions arising from the revised discussion. I hope these are useful in the completion of the manuscript.

The paper still requires some nomenclature tidying – italicise n in n-alkane.

Line 187 – The statement ‘as observed in most other sections’ is a bit misleading, especially with respect to the cited references. Tipple et al. 2011 actually shows the opposite. The post-PETM n-alkane d13C values at Tanzania are depleted relative to pre-PETM value but only for some n-alkanes, not by much and with only limited data.

Line 195: Some grammatical tidying is required here.

Line 200: Is this analytically robust – the values seem to be only 5 permil lower, which would be at the edge of significance (perhaps just add a caveat rather than removing this sentence).

Lines 239-242: I think this is a really nice contribution, but it is a bit hard to follow and I had to read it a few times. It could be succinctly rewritten. Similarly, the figure caption to fig 5 was a bit confusing – if these represent the same areas, do not refer to Lodo in (a) and central coastal California in (b). In fact, it would be useful to show exactly what model grid cells were used to make figure 4c, 4f and 5a,b.

Figure 5: The y-axis should not be MAP but MMP.

Lines 304-305: I think this requires a bit more nuance. The model simulations suggest more extreme events, but not more intense (precipitation) seasonality (Fig. 5a). In fact, this nuance is worth drawing out a bit more in 4.1 since seasonality is so often conflated with extreme events.

Line 317: Handley et al (2008) – Tanzania – do not observe a decrease in d2H across the PETM.

Line 326: Avoid contractions.

Line 331: Specific that this is n-alkane ACL.

Line 336: Also cite Hollingsworth et al. 2024.

Lines 337-356: I am not sure what to suggest for this section. I like this discussion. However, the reader already knows that the model simulations indicate only a small change at this location and of course that is the focus of 4.3. Maybe just rewrite in a manner that acknowledges that the discussion in 4.3 is forthcoming but it is useful to consider alternative offsetting factors.

Line 372 to 373: It is not really a shift of heavy precipitation events, but a shift in the seasonal response of d2H and the length of the growing season.

Lines 373-380: Are these speculation or are they derived directly from interrogation of the model simulations used in this paper?

Lines 382 to 392: Some grammatical polishing is required here.

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ED: Publish subject to technical corrections (16 May 2024) by Kathleen A. Wendt

AR by Xiaodong Zhang on behalf of the Authors (25 May 2024) Manuscript

Short summary

This study is motivated by the current anthropogenic-warming-forced transition in regional hydroclimate. We use observations and model simulations during the Paleocene–Eocene Thermal Maximum (PETM) to constrain the regional/local hydroclimate response. Our findings, based on multiple observational evidence within the context of model output, suggest a transition toward greater aridity and precipitation extremes in central California during the PETM.