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Christian-Albrechts-Universität zu Kiel

The major focus of the partner CAU in GATEWAYS is the reconstruction of periods of enhanced precipitation over Southeast Africa using time series of changes in burial rates of terrigenous constituents in marine sediments as well as in isotopic and elemental tracers in marine microfossils or organic compounds from land plants and marine plankton. The more detailed aims are to assess the recurrence of enhanced river discharge episodes in the vicinity of the Zambezi and Limpopo rivers and to determine the timing of such episodes in relation to surface-ocean climatology and Agulhas warm water transport. The impact of such river discharge episodes on ocean salinities and nutrient inventories, including marine ecosystems and biological productivity is investigated. Finally, a quantification of the amount of sediment discharge and carbon deposition/burial in conjunction with terrestrial climate variability and switches between semiarid conditions of Southeast Africa today and episodes of more humid conditions in the past are attempted. Results are compared with the outcome of coupled atmosphere-ocean general circulation models simulating past changes in the hydrological cycle for South Africa and biogeochemical cycles off major rivers.

The analytical progamme on Zambezi and Limpopo deep-sea fan sediment cores comprises paired measurements of d18O as well as Mg/Ca and Ba/Ca ratios on shallow planktonic foraminifera for past changes in river run-off. Biomarker palaeothermometry (Uk37, Tex86) and land plant lipid compound isotope analyses (H/D, C) are executed to infer on past changes in Mozambique Current temperatures in context with precipitation over the continent. Land-ocean material fluxes are investigated by using geochemical analysis of major and minor terrigenous elements and the isotopic characterisation of organic matter. Age models for the sediment archives are developed by radiocarbon dating.

Sediment cores are made available to other project partners for complementary proxy work not established at CAU. Close collaboration on organic specific compound analyses is established with partner NIOZ.

Reconstructions of past changes in sea surface temperatures and variations in the hydrological cycle over South Africa enable to infer on land-ocean climate linkage, is in close connection to the speleothem reconstructions of precipitation executed by partner 6, GIS. The time series providing natural variability in land-ocean linkage between the Agulhas Current System and South African terrestrial climates are available as benchmarks for ocean-atmosphere general circulation experiments cross-linking with partners 3 (IFM-GEOMAR) and 7 (UCT).

Partner Profile

The marine climate research unit at the Institute of Geosciences (IfG) at CAU consists of about 20 researchers at the senior and junior level with expertise in marine geology and palaeoceanography, modelling of coupled ocean-atmosphere and biochemical processes, organic geochemistry and biomarkers, sediment and water geochemistry. The team collaborates with the Leibniz-Laboratory for Radiometric Dating and Stable Isotope Research at the CAU. Measurements are routinely performed at the IfG of chemical, stable isotope and trace element composition of marine and lacustrine sediments, water, and microfossils, stable isotope analysis of specific compounds of organic matter, and radiocarbon dating. Interaction in the climate system and marine processes are investigated by own design and execution of experiments with state-of-the art coupled atmosphere-ocean-biochemical models and data-model comparison.

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