The Shift of Southern Hemisphere Storminess under Anthropogenic Climate Change around Antarctica and its Impacts - (SACAI)

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The proposal aims at the investigation of southern hemisphere cyclone development, its variability and extremes under present climate conditions, its possible shift under anthropogenic forcing conditions, and its impacts on the climatic system of Antarctica. By means of a multi-model ensemble the southern hemisphere cyclone development towards the end of this century will be estimated and measures of uncertainty will be deduced. This will include a special focus on extreme cyclones. Cyclone systems are, by their related transient eddies, responsible for freshwater fluxes into Antarctica, and thus contribute to the transmission of any global climate change signature towards Antarctica. Especially, the following questions will be addressed: What are the characteristics of SH cyclone and storm development under anthropogenic climate change and what is the range of expected changes from the perspective of state-of-the-art climate models? What are the impacts on the Antarctic climate system caused by a shift of the cyclonic activity over the Southern Ocean under anthropogenic climate change? Additionally, investigations will be carried out estimating the impact of stratospheric variability on tropospheric and ocean circulations. Therefore, simulations with the new state-of-the-art Atmosphere- Ocean Chemistry-Climate Model (AOCCM) ECHAM5-MESSy-O will be performed and analysed. The specific model configuration allows us to simulate the feedback between the Antarctic atmosphere and the Southern Ocean in a changing climate taking the vertical coupling between the stratosphere and the troposphere into account, in particular the response of surface climate to the Antarctic ‘ozone hole’ and increasing greenhouse gas (GHG) concentrations.