Jan Streffing

• Our unintentional large-scale geoengineering project, characterized by a rapid in- crease in greenhouse gas concentrations, poses significant challenges in predicting and mitigating global and regional consequences. Climate researchers worldwide are constructing and refining climate models to understand and navigate the complex Earth system state and evolution. This thesis focuses on my contributions to this endeavor, specifically the construction, evaluation, and application of the AWI-CM3 coupled climate model. Additionally, I address the importance of improving the energetic consistency across the critical interface between the atmosphere and ocean. This research was conducted as part of the DFG collaborative Research Center Transregio (TRR) 181 ”Energy Transfers in Atmosphere and Ocean”, which aims to develop mathematically rigorous tools for climate analysis and modelling. By focusing on the interactions between the atmosphere and ocean, I strive to enhance our under- standing of the exchange of heat, momentum, and mass, while incorporating model components for sea ice and river runoff. I review the selection and method of computation for physical interface fluxes, introduce of stochastic remapping to conserve information across the coupling interface, and adapt vertical ocean mixing parameterizations to enhance the realism of the AWI-CM3 model. Through these efforts, I aim to contribute to the development of a comprehensive Earth System Model and advance our understanding of climate change and its societal implications.