Reconstruction of PALeo-sea water properties in the tropical western Indian Ocean for the last 470 kyrs using Mg/Ca and stable isotopes on planktonic foraminifera: atmospheric versus oceanographic influences (PALIO).

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The tropical western Indian Ocean is a key location for paleoclimate research affected by different oceanographic and atmospheric processes. Annual climate variations are strongly controlled by the Indian Monsoon characterized by bi-annually reversing trade winds. Inter-annual climate variations in the Walker circulation are caused by the Indian Ocean Dipole and El Niño-Southern Oscillation resulting in either heavy flooding or severe droughts like the famine of 2011 in eastern Africa. Oceanographically the tropical western Indian Ocean receives water masses from the Indonesian Gateway area, sub-Antarctic waters that upwell south of the equator, and the outflow waters from the highly saline Red Sea. On the other hand, the tropical western Indian Ocean is a major source for providing water masses to the Agulhas Current system. Thus, the tropical western Indian Ocean has the potential to provide important information on how these different factors have changed in the past, and possibly will change in the future. Unfortunately, until now there were no long sediment cores available covering several glacial-interglacial cycles. GeoB 12613-1, recovered during RV Meteor Cruise M75/2 east of the island of Pemba off Tanzania, provides an open-ocean core with well-preserved sediments covering the last five glacial-interglacial cycles. The research objective of this proposal is to use Mg/Ca and stable isotopes on different species of planktonic foraminifera to test the hypotheses that changes in sea surface temperatures and relative sea surface salinity were de-coupled on orbital time scales; that the water column stratification on both sides of the Indian Ocean including the cross-basin gradients varied on millennial time scales due to changes in the Walker circulation; and that the salt supply to the Agulhas Current system was mainly provided by the Red Sea Outflow Water.