reproducing the observed Arctic circulation and sea ice development, which is partly due to shortcomings in the representation of physical processes governing air-sea ice-ocean interaction. The improved representation [...] the improved physical representation of polar air-sea ice-ocean interaction on the variability and changes of Arctic atmospheric circulation, Arctic sea ice and mid-latitude atmospheric circulation. Therefore [...] POLEX The linkage between POLar air-sea ice-ocean interaction, Arctic climate change and Northern hemisphere weather and climate EXtremes (POLEX) A Helmholtz - RSF Joint Research Group funded by the Helmholtz