Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

Hahn, Annette; Schefuß, Enno; Andò, Sergio; Cawthra, Hayley C.; Frenzel, Peter; Kugel, Martin; Meschner, Stephanie; Mollenhauer, Gesine; Zabel, Matthias

doi:https://doi.org/10.5194/cp-13-649-2017

Articles | Volume 13, issue 6

https://doi.org/10.5194/cp-13-649-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue:

Southern perspectives on climate and the environment from...

https://doi.org/10.5194/cp-13-649-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 13, issue 6

Research article

|

09 Jun 2017

Research article |

| 09 Jun 2017

Southern Hemisphere anticyclonic circulation drives oceanic and climatic conditions in late Holocene southernmost Africa

Annette Hahn, Enno Schefuß, Sergio Andò, Hayley C. Cawthra, Peter Frenzel, Martin Kugel, Stephanie Meschner, Gesine Mollenhauer, and Matthias Zabel

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Final revised paper (published on 09 Jun 2017)
Supplement to the final revised paper
Preprint (discussion started on 03 Nov 2016)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

SC1: 'Important new offshore palaeoclimate data point for South Africa', Sebastian Luening, 13 Nov 2016
- SC2: 'South African MCA climate', Annette Hahn, 14 Nov 2016
RC1: 'Review on “Linking catchment hydrology and ocean circulation in Late Holocene southernmost Africa” by Hahn et al.', Anonymous Referee #1, 12 Dec 2016
- AC1: 'rebuttal letter - modifications tothe manuscript', Annette Hahn, 30 Jan 2017
RC2: 'Review of Hahn et al. 2016', Anonymous Referee #2, 20 Dec 2016
- AC2: 'Rebuttal Anonymous Referee #2', Annette Hahn, 30 Jan 2017

Peer-review completion

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

ED: Reconsider after major revisions (30 Jan 2017) by Helen Bostock

AR by Anna Wenzel on behalf of the Authors (03 Mar 2017) Author's response

ED: Referee Nomination & Report Request started (18 Mar 2017) by Helen Bostock

RR by Anonymous Referee #2 (03 Apr 2017)

RR by Anonymous Referee #1 (14 Apr 2017)

Suggestions for revision or reasons for rejection

Review on revision of “Southern hemisphere anticyclonic circulation drives climatic conditions and sea surface temperatures in southernmost Africa” by Hahn et al.

Thanks for commenting on my remarks and questions. Many things have been clarified. I still have some concerns to raise:

• Figure capture 4 still has the wrong depth for the “the reworked package at 26 – 66 cm depth” in there.
• As the paper does not have SST data for the LIA timeframe I would be careful with stating in the title of the paper that “Southern hemisphere anticyclonic circulation drives sea surface temperatures in southernmost Africa.” Moreover, with the current title it is not clear what time interval this study covers. Clearly, this is not a modern day study.

• In general, what would shift the SHW during the LIA northward? That could be interesting point to add for the reader. Especially, as a recent compilation (Lechleitner et al., 2017 : “Tropical rainfall over the last two
millennia: evidence for a low latitude hydrologic seesaw.” DOI: 10.1038/srep45809) has shown that during the LIA the ITCZ was generally shifted further south causing wetter conditions in the SH. A more southerly ITCZ would also prompt a southward shift of the subtropical anticyclones hence causing the opposite effect in South Africa during the LIA as stated in the conceptual model explained here. How can these two views be reconciled?

• I am not entirely happy with Figure 5. The way it is now, it is hard to see what indications there are for what environmental trend. Perhaps plotting age on the x-axis and the parameters as stacked y-axis would improve it. Also, giving the parameters arrows for trends will help to see better. I would plot things together which are indicating the same environmental interpretation.
I don´t really see how g,h,i and j panels are adding anything. Aridity in g) is not changing at all throughout the record. h) temperature- if you would add trend lines through the data you could see two steps: lower T until 2500 ka BP and then slightly higher values on average to core top. I don´t see how the Congo Cave data helps with the LIA and MCA interpretation of this study? Potentially just plotting the data from that study together with an axis break in the 4000-1000 ka BP range would also blow up and highlight the LIA MCA data/interval more/ make it more visible!?

I would like to encourage the author to think about a better way to show the data in Figure 5 as this is the main dataset the paper is based on. I think Figure 3 and 7 can be supplement material.

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ED: Publish subject to minor revisions (review by Editor) (15 Apr 2017) by Helen Bostock

AR by Svenja Lange on behalf of the Authors (27 Apr 2017) Author's response

ED: Publish as is (02 May 2017) by Helen Bostock

Short summary

Our study demonstrates that a source to sink analysis in the Gouritz catchment can be used to obtain valuable paleoclimatic information form the year-round rainfall zone. In combination with SST reconstructions these data are a valuable contribution to the discussion of Southern Hemisphere palaeoenvironments and climate variability (in particular atmosphere–ocean circulation and hydroclimate change) in the South African Holocene.