Variations in surface and thermocline conditions of the Western Pacific Warm Pool : Insights from Mg/Ca and stable isotopes in foraminifera tests

The Western Pacific Warm Pool (WPWP) is a major source of heat and moisture to the global atmosphere and thus plays a major role in the global climate system. This thesis deals with the reconstruction of past variations in WPWP surface and thermocline conditions with the overarching goal to better understand the regional ocean and climate variability over the last (two) glaciala interglacial cycle(s). The reconstruction is mainly based on records of stable oxygen isotopes (I 18O) and Mg/Ca in planktic foraminifera from marine sediment cores. First, the proxies are calibrated against modern water column data. Then, these calibrations are applied to records from the southern WPWP off Papua New Guinea. The records illustrate the interplay of local and remote forcing on the WPWP on glacial-interglacial and orbital timescales by indicating that (I) variations in the Pacific Walker circulation affect the WPWP on glacial-interglacial timescales, (II) climate variations in the extratropics influence the WPWP thermocline in response to astronomical forcing and (III) precession is the main driver for precipitation over the WPWP.