Late Pleistocene climate and circulation history of the western equatorial Pacific
Reconstructions of past climate variability derived from sedimentary archives have highlighted the response of the global climate system to orbital and millennial scale forcings. Investigating these forcings and responses allows us to further understand the present day climate of the Earth, and predict its future evolution under conditions of increased anthropogenic greenhouse gas concentrations. However, in some regions of the world the exact mechanisms of past climate change remain relatively unknown, due to a lack of high-resolution proxy records, and uncertainties in the relationships between climate indices and the proxies themselves. In this work, we attempt to shed light on past variability of the ocean-atmosphere system in the western equatorial Pacific, a region that encompasses the warmest pool of water in the world and thus has a direct effect on global climate through the redistribution of heat and moisture from the tropics to the mid- and high-latitudes. In Study 1 of this thesis, we apply a multi-proxy geochemical analysis to sediment core MD06-3075 situated in the Davao Gulf, southern Mindanao, to investigate past hydrologic variability at the boundary between the Indonesian archipelago and the open Pacific Ocean. In Study 2 we attempt to elucidate changes in deep and intermediate-depth circulation in the West Pacific and ITF over the most recent glacial-interglacial cycle, via a compilation of new and previously published benthic foraminiferal δ13C records. In Study 3, we evaluate the use of two common geochemical proxies for sea surface temperature (SST) reconstructions in the western equatorial Pacific: the Mg/Ca ratio of the planktonic foraminifera Globigerinoides ruber, and the UK’37 alkenone unsaturation index, by compiling new and existing core-top data from the western equatorial Pacific.