The PhD defence and trial lecture are fully digital and streamed using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.
Trial lecture
Carbon dioxide variability during the last 500 million years
Conferral summary
In the Cenozoic time (66 – 0 million years ago) the global climate changed from greenhouse to icehouse conditions. Changes in continents and ocean geometry, geography, and topography due to plate tectonics, erosion, and mantle dynamics played an important role in this transition. This thesis explores how the paleobathymetry of Northern Hemisphere oceanic gateways active during Cenozoic, influenced the ocean circulation and climate variations.
Main research findings
Popular scientific article about Straume’s dissertation:
Paleoclimate in the Cenozoic time: Quantifying the role of North Atlantic plate tectonics and mantle processes
For the present day, this study provides a new global sediment thickness map over the seafloor. The work derives mathematical formulas to describe sedimentation trends in the major oceans. These trends depend on oceanic lithospheric age and latitudinal position and can be used to estimate sediment thickness accumulations in oceanic basins through time. A new methodology and tool for reconstructing paleobathymetry of large igneous oceanic plateaus is developed. The new method was used to construct a new global Cenozoic paleogeography model, including detailed reconstructions of the Northern Hemisphere oceanic gateways. The model is based on updated regional plate kinematics, oceanic lithospheric age, sediment thickness, and reconstructed oceanic plateaus and microcontinents. In addition, Northeast Atlantic paleobathymetric variations due to Iceland mantle plume activity are incorporated.
The paleogeographic reconstruction for the Eocene-Oligocene Transition (EOT, ~ 34 million years ago) was implemented in the Norwegian Earth System Model (NorESM) to investigate the effect of the oceanic gateway geometry on ocean circulation and climate. The simulations in the earth system model show that the Atlantic – Arctic gateways can have a large impact on EOT climate variations, and that changes in these gateways can produce climatic changes observed in the proxy record.
Photo and other information:
Press photo: Eivind Olavson Straume, portrait; 500px. Photo: Private
Other photo material: Figure with description as specified in the article above, size 1000px. Illustration/figure: Eivind Olavson Straume.
