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Climate of the Past An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/cp-2019-158
https://doi.org/10.5194/cp-2019-158

  23 Jan 2020

23 Jan 2020

Review status: a revised version of this preprint was accepted for the journal CP and is expected to appear here in due course.

Glacial to interglacial climate variability in the southeastern African subtropics (25–20° S)

Annette Hahn1, Enno Schefuß1, Jeroen Groeneveld1,2, Charlotte Miller1,a, and Matthias Zabel1 Annette Hahn et al.
  • 1MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
  • 2Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Potsdam, Germany
  • apresent address: Leeds Trinity University, Brownberrie Ln, Horsforth, Leeds, LS18 5HD, United Kingdom

Abstract. We present a continuous and well-resolved record of climatic variability for the past 100,000 yrs from a marine sediment core taken in Delagoa Bight, off southeastern Africa. In addition to providing a sea surface temperature reconstruction for the past ca. 100,000 yrs, this record also allows a high-resolution continental climatic reconstruction. Climate sensitive organic proxies, like the distribution and isotopic composition of plant-wax lipids as well as elemental indicators for fluvial input and weathering type provide information on climatic changes in the adjacent catchment areas (Incomati, Matola, and Lusutfu rivers). At the transition between glacials and interglacials, shifts in vegetation correlate with changes in sea surface temperature in the Agulhas current. The local hydrology, however, does not follow these orbital-paced shifts. Instead, precipitation patterns follow millennial scale variations with different forcing mechanisms in glacial versus interglacial climatic states. During glacials, southward displacement of the Intertropical Convergence Zone facilitates a transmission of northern hemispheric signals (e.g. Heinrich events) to the southern hemispheric subtropics. Furthermore, the southern hemispheric westerlies become a more direct source of precipitation as they shift northward over the study site, especially during Antarctic cold phases. During interglacials, the observed short-term hydrological variability is also a function of Antarctic climate variability, however, it is driven by the indirect influence of the southern hemispheric westerlies and the associated South African high-pressure cell blocking the South Indian Ocean Convergence Zone related precipitation. As a consequence of the interplay of these effects, small scale climatic zones exist. We propose a conceptual model describing latitudinal shifts of these zones along the southeastern African coast as tropical and temperate climate systems shift over glacial and interglacial cycles. The proposed model explains some of the apparent contradictions between several paleoclimate records in the region.

Annette Hahn et al.

 
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Status: closed
Status: closed
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Annette Hahn et al.

Annette Hahn et al.

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