Turbulent and stochastic dynamics in the climate system: energy transfers, self-organization and abrupt transitions

The Earth’s climate system is highly complex, consisting of many coupled components. Turbulent motions in the atmosphere and oceans across a wide range of spatial and temporal scales are highly important as they not only transport heat from the equator to the poles, but also distribute aerosols, nutrients and pollutants across the globe. These atmospheric and oceanic fluid flows are impacted at large scales by the Earth’s rotation, density stratification and their thin-layer geometry - for instance, the troposphere is around 10km high, but weather systems typically extend over 1000km in the horizontal direction. These factors strongly constrain the behavior of these flows, leading to striking self-organization into large-scale vortices and zonal jets. Moreover, nonlinear feedback mechanisms in this complex system lead in many cases to multiple coexisting metastable states, between which the system can transition abruptly due to intrinsic fluctuations or external (e.g., anthropogenic) forcing. An important example of this is the Atlantic Meridional Overturning Circulation, which is a tipping element in the climate system that has been abruptly shut down and re-emerged in the past. Due to the complexity of the climate system, a hierarchy of models of varying complexity is required to elucidate its properties. In this talk, I will present results from idealized models at the lower-complexity end of this model hierarchy, where key physical insights can be gleaned, namely self-organization in a turbulent dry atmosphere and abrupt transitions between large-scale, hurricane-like vortices and zonal jets or small-scale three-dimensional turbulence. I will also provide an outlook on my future work, including rotating moist convection, which is a key driving mechanism in Earth’s atmosphere, idealized climate modeling and ideas relating to climate engineering.