Project Details
Projekt
Carbon cycle and ice sheet interactions towards and during the Eocene-Oligocene Transition
Applicant
Eleni Anagnostou, Ph.D.
Subject Area
Geology
Oceanography
Oceanography
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 467590255
Earth’s temperature has varied in the past in response to the Earth’s orbital variations in relation to the sun, and to changes in concentrations of atmospheric greenhouse gases such as carbon dioxide (CO2). However, theory and modelling studies suggest the CO2 threshold for Antarctic Ice Sheet (AIS) melting and ice sheet growth are not the same, and there is instead a dependence on the direction of change, which is known as hysteresis. The magnitude of this hysteresis for the entire AIS, and the underlying mechanism(s), is currently debated. Considering the long-term future stability of AIS in the face of a warming climate, and hence the ultimate magnitude of future sea level rise, critically rests on the magnitude of this phenomenon, the geologic record could be the key in quantifying and understanding this hysteresis. It has been shown that ~34 million years ago, a decline of atmospheric CO2 concentrations through a threshold of ~700 ppm drove the first largescale continental glaciation of Antarctica. However, existing records show that the ice sheet margin waxed and waned at that time while atmospheric CO2 varied within the range projected for year 2100 under business-as-usual emission scenarios. Additionally, the late Eocene to Oligocene period demonstrates a largely unexplored cyclicity in records related to seawater temperature, ice volume, and carbon cycle, which suggest dynamic carbon and temperature/ice sheet variability, largely following the rhythm of incoming radiation by the sun. This period therefore offers an opportunity to document the magnitude and nature of AIS hysteresis under high CO2. This proposal will achieve that, using a newly recovered carbonate-rich sediment sequence from Exp. 378, with the integration of a carbon cycle model with geochemical analysis of boron isotopes (for pH-CO2 reconstructions), carbon isotopes (for carbon cycling), oxygen isotopes (for ice volume and seawater temperature reconstructions) and Mg/Ca ratios (for seawater temperature reconstructions) in well-preserved planktonic and benthic foraminifera. The novel, high fidelity, orbitally resolved CO2 and δ18Osw record that will be reconstructed for the interval 33 to 39 Ma, will contribute to state-of-the-art computational techniques of the observed ice volume and CO2 relationships across the interval to provide a new understanding of the mechanisms driving the interaction between ice sheets and CO2 concentrations in high CO2 worlds.
DFG Programme
Infrastructure Priority Programmes
