Assessment of greenhouse gas forcing in the latest Campanian-early Maastrichtian as driver of a potential glaciation in Antarctica
Title
Assessment of greenhouse gas forcing in the latest Campanian-early Maastrichtian as driver of a potential glaciation in Antarctica
General information
The Late Cretaceous was a 25 million year-long period in Earth's history during which average surface temperatures dropped by more than 10°C and atmospheric CO2 concentrations halved by ~400 ppm. The cooling reached its peak during the Campanian-Maastrichtian transition between 73-70 Ma, a period with a shift in the global carbon cycle, falling sea level and a potential glaciation (Campanian-Maastrichtian Boundary Event, CMBE). The data available to date point to a transient long-term change in the Earth system, most likely caused by plate tectonics and non-linear interactions between climate, sea level, ocean circulation and chemistry, as well as continental weathering. The exact causal and temporal relationships of the involved processes are not well understood so far. In this project, we aim to apply a combined approach of proxy data generation and Earth system modelling to test the following hypotheses. 1) The early CMBE is a tectonically-induced feedback of the carbon cycle, accompanied by sea-level fall and deepening of the CCD due to lithospheric cooling. 2) Changes in the weathering regime during the early CMBE altered ocean alkalinity and atmospheric CO2 to a critical threshold necessary for the initial growth of polar ice. 3) The increase in land fraction over Antarctica and persistent cooling supported initial polar ice formation, with the benthic δ18O signal in the late CMBE largely representing an ice volume effect. To test our hypotheses, we will reconstruct relative changes in Southern Ocean’s CCD by backtracking using CaCO3 values from Sites 525 and 690 and a new orbital age model for the CMBE. Comparison with published and well-dated records of sea-level change will allow the consideration of the temporal relationship between climate, carbon cycle and sea level change. Moreover, we will generate new proxy data of weathering intensity (seawater δ7Li) and deep Southern Ocean alkalinity (foraminiferal δ11B) in a resolution of ~50kyr for the CMBE. Performing experiments with the Earth system model CLIMBER-X, a model of medium complexity including a coupled ice sheet model and an interactive carbon cycle will allow to evaluate effects of orbital configuration, atmospheric CO2 and albedo. Finally, we will reconstruct the potential polar ice volume from proxy data. This will be achieved by combining Mg/Ca data from benthic foraminifera as a proxy for bottom-water temperature with already available δ18O from Sites 690 and 525 to calculate the δ18O value of seawater, which is considered as a proxy for ice volume. As result of this project, we will be able to plot changes in Southern Ocean CCD, bottom-water temperature, seawater δ18O and alkalinity between 73-70 Ma on a common orbital timescale. These records will be assessed in context of the Earth system modelling results to determine the critical thresholds for the possible Maastrichtian glaciation of Antarctica.
Start
November, 2025
End
October, 2028
Funding (total)
302000
Funding (GEOMAR)
7000
Funding body / Programme
-
DFG
/ Infrastructure Priority Programmes
Coordination
Goethe-Universität Frankfurt (Goethe University Frankfurt)
Contact
Partners
Goethe-Universität, Germany
Potsdam-Institut für Klimafolgenforschung (PIK), Germany
Ruprecht-Karls-Universität Heidelberg, Germany
Potsdam-Institut für Klimafolgenforschung (PIK), Germany
Ruprecht-Karls-Universität Heidelberg, Germany
