Preprint Review Version 1 This version is not peer-reviewed

A Window into Africa’s Past Hydroclimates: The SISAL_V1 Database Contribution

Version 1 : Received: 30 September 2018 / Approved: 1 October 2018 / Online: 1 October 2018 (15:13:01 CEST)

A peer-reviewed article of this Preprint also exists.

Braun, K.; Nehme, C.; Pickering, R.; Rogerson, M.; Scroxton, N. A Window into Africa’s Past Hydroclimates: The SISAL_v1 Database Contribution. Quaternary 2019, 2, 4. Braun, K.; Nehme, C.; Pickering, R.; Rogerson, M.; Scroxton, N. A Window into Africa’s Past Hydroclimates: The SISAL_v1 Database Contribution. Quaternary 2019, 2, 4.

Journal reference: Quaternary 2019, 2, 4
DOI: 10.3390/quat2010004

Abstract

Africa spans the hemispheres from temperate region to temperate region, has a long history of hominin evolution and yet has a relatively poorly understood Quaternary climate history. Speleothems, as archives of terrestrial hydroclimate variability, can help reveal this history, and here we review the progress made to date, with a focus on the first version of the Speleothem Isotopes Synthesis & Analysis (SISAL) database. The geology of Africa has limited development of large karst regions to four areas - the northern and eastern coasts bordering the Mediterranean and the Indian Ocean, west Africa and southern Africa. Exploitation of the speleothem palaeoclimate archives in these regions is uneven, with long histories of research in South Africa and Morocco but no investigations elsewhere e.g. West Africa. Consequently, the evidence of past climate change reviewed here is irregularly sampled in both time and space. Nevertheless, we show evidence of migration of the monsoon belt, with enhanced rainfall during interglacials observed in northeast Africa, southern Arabia and the northern part of southern Africa. Evidence from East Africa also indicates significant centennial scale rainfall variability. In northwestern and southern Africa precession and eccentricity influence speleothem growth, largely through changing synoptic storm activity.

Subject Areas

speleothem; hydroclimate; monsoon; ITCZ; SISAL; oxygen isotopes

Comments (1)

Comment 1
Received: 5 November 2018
Commenter: Andy Baker
The commenter has declared there is no conflict of interests.
Comment: I enjoyed reading your preprint. I thought it was just great – the depth and breadth of the literature review in particular. I learnt a lot.

I had a few very minor comments. They are:
1. In the abstract, I found the description of the karst regions relatively confusing compared to those you define in the map. I guess I have a bias to East Africa, but I couldn’t describe that as ‘coastal’.
2. In the climate descriptions, I thought that you might like to designate the hemisphere for the westerlies, since both Africa straddles both N and S hemispheres.
3. Figure 2. We all keep reworking these old maps! I wondered if you could put the speleothem sites in colour, so they stand out a bit more? And I also whether you would want to add even more to the maps, to help the reader when you come to the subsequent text. For example, the NW in January could have a boundary line to show the region influenced by the NAO. Maybe something is also possible for the IOD (could be trickier though?).
4. It would be cool to see maps of d18O of modern rainfall (iso-GCM?) and C3/C4 vegetation (actual or vegetation model). Even cooler would be a comparison of between this and speleothem records for different time slices (modern, mid-Holocene, etc.). It is probably enough for a separate paper. I also liked the boxplot of the d18O and d13C for the different caves, and wondered if you’d considered plotting these also as a scatter plot (d18O vs d13C) at the continental scale. With some colour coding for modern C3 vs C4 vegetation and the time period, could you elucidate regions or times where you might expect climate trends vs fractionation? You start to head in this direction in the d13C section
5. Very pedantically, I wasn’t sure about the last line of section 5. I don’t think we should comment on the accessibility or safety etc.
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