Dr Will Defliese - "Mid-Miocene Ocean Temperatures from IODP Site 1120, SW Pacific"
Abstract:
The Middle Miocene Climatic Optimum (MMCO) and Climate Transition (MMCT) were dynamic times in Earth’s climate history, where high pCO2 levels and warm temperatures in the MMCO gave way to global cooling and the reorganization of oceanographic currents during the MMCT. Here we use several independent methods to reconstruct changes in sea surface temperature and ocean water δ18O values during the middle Miocene at IODP Site 1120, southeast of New Zealand. We use Δ47 temperatures and δ18O values of coccoliths as well as δ18O and δ13C values of foraminifera (Gg. Bulloides, Zg. Woodi, Cibicidoides) to provide independent, complimentary records of climate. Significantly, the clumped isotope records show little temperature change across the MMCO to MMCT at Site 1120, with an increase of approximately 0.5‰ VSMOW in seawater δ18O values in the MMCT, which is interpreted as an increase in salinity in response to increased Antarctic glaciation. The lack of significant cooling may be explained by the position of oceanic currents and the paleogeography of Site 1120, especially in comparison to other records in the Southern Ocean.
As part of this talk, I will give an overview of the International Ocean Discovery Program (IODP), and it's contributions to understanding the climate history of Earth. I will also introduce a number of geochemical proxies that are used for climate reconstructions, so even if the above abstract doesn't make much sense now it will by the end of the seminar.