hide
Free keywords:
-
Abstract:
The greenhouse gas-induced warming in the Arctic is more pronounced than in other parts of the Earth. This Arctic amplification (AA) has large impacts on the local climate and ecosystem. In addition, the temperature gradient between the polar region and the tropical latitudes drives the large-scale atmospheric circulation. It is widely debated if the AA significantly impacts this circulation by modifying the jetstream or the planetary wave generation, for example. One possible pathway involves the troposhere-stratosphere coupling through an enhanced planetary wave propagation. A wide range of observational studies of the last decades support the idea of an Arctic influence on midlatitude weather. On the other hand, signals in climate models are either absent or small compared to the natural variability. The focus of this study is on the stratospheric pathway of the proposed relation. To ensure realistic stratospheric processes, we use the climate-chemistry model EMAC (ECHAM/MESSy Atmospheric Chemistry) with a fully resolved middle atmosphere and an interactive chemistry. Thus, possible ozone feedbacks on the stratospheric circulation are taken into account. Considering the large natural variability, an ensemble of six transient simulations and three timeslice experiments (preindustrial, present and future) were perfomed. We analyse the tropospheric response to the warming particularly the change of the jetstream and the occurrence of atmospheric blockings. Further, a modification of the wave propagation and the stratospheric polar vortex is studied. First results show a strengthening of the winter subtropical jet in the future while the polar night jet weakens with more stratospheric warmings.
