From greenhouse to icehouse world
The Earth system on tectonic time scales
The long-term evolution from hothouse to icehouse conditions during the Cenozoic (last ~65 million years) is characterized by step-like glaciations of the high latitudes that represent the initial roots for our present climate with bi-polar glaciation and large equator-to-pole temperature differences. Hence, the Cenozoic can serve as a unique test-bed to form a quantitative, process-based understanding of the underlying mechanisms, feedbacks and thresholds of these global scale changes. In this context our research aims to differentiate between classic hypotheses for glaciations that involve e.g. tectonic changes and associated changes in ocean circulation or declining atmospheric CO2 in combination with the Earth’s orbital configuration.
The figure shows a land-sea configuration during the Middle Miocene (~15 million years ago) as incorporated in a complex Earth System Model. For example changes in oceanic gateways such as the Pacific-Atlantic connection and the Atlantic-Indian Ocean gateway via the Mediterranean are thought to represent critical factors for the global scale climate evolution during the Cenozoic (last ~65 million years).
Examples from our research:
Niezgodzki, I., G. Knorr, G. Lohmann, J. Tyszka, and P. Markwick, 2017: Late Cretaceous climate simulations with different CO2 levels and subarctic gateway configurations: A model-data comparison, Paleoceanography, 32, doi: 10.1002/2016PA003055.
Stärz, M., W. Jokat, G. Knorr, and G. Lohmann, 2017: Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge, Nature Communications, 8, doi: 10.1038/ncomms15681.