Comprehensive Earth System Modelling for a Permian Earth

The climate system of the Earth is complex, involving several different domains, namely the atmosphere, the ocean, the biosphere and the cryosphere, which interact on climate relevant time scales. To understand processes and their feedbacks in the climate system, a comprehensive Earth System Model are used. In addition to investigate present day climate conditions and the response of the individual domains to climate change, it is also important to know, how past climate states have looked like to potential adapt to global climate change.

Within this project such an Earth System Model is used to simulate climate conditions on Earth during the Permian (262 Mio years before present). In this period the land masses formed a supercontinent „Pangaea“ with only moderate mountain elevations and a large ocean basin (Panthalassic Ocean) as well as a second more confined ocean basin (Tethys ocean). Such a land-sea distribution has implications for the circulation of the atmosphere such as wave activity, but also vertical mixing within the troposphere. Furthermore, these continent configuration has also substantial implications to the energy budget of the climate system. Therefore, it is required to have a suitable representation of the ocean (and its associated meridional heat transport, which is responsible for balancing the energy budget between the tropics and the high latitudes caused by the different solar heating) to realistically simulate the climate conditions during that period. Consequently, in this project the ocean circulation must be simulated explicitly and cannot be described with present day surface conditions. Furthermore, the likely elevated atmospheric CO2 content during that epoch also has implications on vegetation growth, but also the strength of the natural greenhouse effect of the Earth, such that model representations for these processes will also be coupled and applied.

Therefore, in this project we perform coupled simulations of the climate system, including explicit, process based representations of the atmosphere, the ocean (including sea ice) and the biosphere with the chemistry climate model EMAC. Goals are on the hand hand a realistic reproduction of climate during that time period, which will be compared with reconstructed data from palaeoarchives, on the other hand an increased process understanding of tropospheric mixing for the permian and its boundary conditions in comparison with present day scenarios. Furthermore, we are analysing the stability of the climate during that epoch and investigate de-stabilising processes and effects, which might help to understand critical tipping points within the climate system.