Research Projects

The proposed research will offer the novel and important opportunity to accurately constrain the relationship between the stability of ice in each hemisphere, global ice volume and atmospheric CO₂. If glacial onset was synchronous, then atmospheric CO₂ might have played a dominant role in driving glaciation in both hemispheres. If glacial development was asynchronous, as has been thought, then Northern Hemisphere glaciation probably began in the late Miocene to Pliocene, when atmospheric carbon dioxide levels were stable. The results of this study will allow me to examine, when did the large amount of glacial ice first appeared in each hemisphere during the Cenozoic. This information is critical for assessing competing paradigms for interpreting the deep-sea oxygen isotope record, a primary tool in the study of past climates. These records will indicate whether major transient glaciations occurred during the middle to late Eocene, or if this interval was mostly ice-free. The history of glaciation is controversial, and is of paramount importance for understanding global climate change (Zachos, et al. 2001; Tripati, et al. 2005). This project aims to utilize the innovative 'clumped isotope' thermometer alongside Mg/Ca-derived temperatures and δ¹⁸O to generate the first absolute estimates of temperature and ice volume during the greenhouse-to-icehouse transition (~45–30 Ma). The application of this advanced and analytically intensive clumped isotope thermometer will deliver absolute temperature records for four sites, as well as estimates of seawater Mg/Ca. In contrast, the Mg/Ca temperature proxy is subject to several potential systematic errors, including the slowly changing Mg/Ca ratio of seawater. Our new proxy records of temperature will be combined with foraminiferal δ18O in order to develop detailed reconstructions of seawater δ18O and ice volume. Understanding of the natural environmental changes of our planet on longer timescales can be achieved by the study of natural phenomena which drive the climate. Information about the past climate is obtained by piecing evidence together from various climate proxies. Marine sediments hold a rich archive of information for reconstructing ocean and climate history, contained within their microfossil assemblages, organic matter, CHNS and isotopic composition of fossils and other sediment components. Variations in the oxygen isotopic composition of seawater in the deep Pacific Ocean reflect changes in global ice volume. To estimate ice volume, we will construct a detailed record by using combined mg/ca and oxygen isotope records for fossilized shells of benthic/Planktic foraminifera at sites in the tropical Pacific Ocean. The Pacific Ocean is essential to study in order to calculate ice volume because of the large size of the basin. Currently there are no continuous detailed records from the Pacific for the study interval because of the lack of appropriate material for study.