Mid-Term Report Summary 2 - NEWLOG (New Directions Linking Ocean Geochemistry, Biomineralization and Palaeoclimate) The role of the oceans in climate change is pivotal and strongly linked to the chemistry of carbon dissolved in seawater and converted into the skeletons of marine calcifying organisms. In order to understand controls on past climate we need to know how properties of the oceans changed and the record of such changes on different timescales.. However, we cannot measure these things directly. There is no such thing as preserved seawater. For this reason palaeoceanographers measure environmental parameters that are proxies for the property in which they are interested.The application of biogenic calcium carbonate based proxies especially using foraminifera is pivotal in palaeo-climate reconstruction. Since robust proxy application relies on precise trace element and isotope analyses as much as a process understanding of proxy signal formation during biomineralization, we have worked towards linking these currently largely disconnected fields. • We have determined the coordination and distribution of Mg in foraminiferal tests. While Mg is unevenly distributed, the coordination is homogeneous and indicates an ideal substitution for Ca in the calcite lattice. • The heterogeneous distribution of Mg, typically in the form of alternating high and low Mg bands, is mirrored by a heterogeneous distribution of Mg isotopes.. Taken together these two strands of evidence suggest that there is one mechanism of Mg incorporation into the calcite lattice, but likely two mechanisms of cell physiological Mg supply.• We cultured planktonic foraminifera sampled in the Gulf of Aqaba in a temperature-step experiment and established partition of Mg and Li in foraminifera• We developed a new method to determine boron isotopes and B/Ca ratios in mass limited samples using a micro-distillation method of matrix purification for B isotope ratio. With these two new analytical tools we can simultaneously generate high resolution d11B, B/Ca, and trace element to Ca ratios from chemically cleaned foraminifera, free from post depositional artifacts, to extend our knowledge of seawater carbonate ion history in deep time. • In one application we showed how deep ocean [CO32-] has changed over glacial-interglacial cycles in two major ocean basins.• A second application has been the Mid-Pleistocene Transition (MPT), separating the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios .Our results suggest that the MPT was initiated by an abrupt increase in Antarctic ice volume 900 thousand years ago. We discovered that patterns of foraminifera species are suggestive of changes in ecology and preservation during the Plio-Pleistocene section of the core, which is linked to the climate. • We have modelled changes in the ocean carbon system over the past 100 million years.
