Project Details
Projekt
Exploring Oligocene climate orbital variability: a perspective from the surface ocean
Applicant
Flavia Boscolo Galazzo, Ph.D.
Subject Area
Geology
Palaeontology
Palaeontology
Term
since 2025
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 565987157
The Oligocene, 34-23 Ma, is a promising time interval to investigate a climate-state similar to what we may be experiencing from the end of the century onwards. Reconstructed atmospheric carbon dioxide concentrations for the Oligocene are in the range of those predicted for the end of the century, yet climate conditions differed a lot from today’s, with much warmer high latitude regions, an Antarctic ice-sheet which might have been one-third of its modern size, and an ice-free Arctic. A much more extensive data coverage for the Oligocene is required to understand the extent to which such dissimilarities with our modern climate may also apply to our future one, hence whether the Oligocene is a good candidate “past climate analogue” to ground-truth future climate predictions from numerical models. A major open question concerning the Oligocene climate is the driving mechanism behind orbitally paced cycles in deep-ocean stable isotope records observed globally. Previous studies suggest that such variability reflects instability of the early Antarctic ice-sheet, waxing and waning through glacial-interglacial cycles punctuating the whole Oligocene. An alternative explanation not requiring large changes in ice-volume, is that the stable isotope cycles in the deep-ocean are driven by deep-water temperature changes. For the interval 28-27 Ma, this interpretation is supported by new clumped isotope temperature data for the deep Southern Ocean, pointing to short-eccentricity paced cycles in bottom water temperature and an essentially stable Antarctic ice-sheet. This new finding calls for an improved understanding of Oligocene climate dynamics and specifically of the link between global climate, cryosphere, ocean circulation and orbital variability at this time. This project seeks to investigate the origin of the bottom-water temperature cycles observed in the Southern Ocean 28-27 Ma by looking at variability in surface water properties. Specifically, by applying a multi-proxy approach based on planktonic foraminifera (δ18O, Mg/Ca, assemblage analysis) from a sub-Antarctic and a distal tropical site, this project will test whether: the bottom water temperature cycles in the Southern Ocean were linked to warming-cooling cycles restricted to the Antarctic sub-polar region (Objective 1); the bottom water temperature cycles in the Southern Ocean were linked to cycles in surface water temperature globally (Objective 2). Testing these two hypotheses will allow to distinguish between a global vs a regional driver for the short-eccentricity paced bottom-water temperature cycles observed in the Southern Ocean, and establish a direct link between orbital variability and Oligocene climate dynamics. This project altogether will provide a wealth of new information about the functioning of the Oligocene climate-ocean-cryosphere system and will pave the way to better understand unipolar glaciated climate modes of the past and of the future.
DFG Programme
Infrastructure Priority Programmes
International Connection
United Kingdom
Cooperation Partner
Dr. David Evans
