The satellite data over past 30 years indicated that the Arctic sea ice is decling fast. Furthermore, results from the CMIP3 and CMIP5 models showed that the summer Arctic sea ice will disapper at the end of 21st century. Existing data analysis and numerical experiments indicated that the Arctic sea ice cover anomalies can impact the climate at the mid-to-high latitude regions.The aim of the project will assess the maximum intensity of the autumn Arctic sea ice impact on the climate by combination of data analysis and specifically designed numecial experiments (autumn Arctic sea ice will be fully removed)with atmosphere only model (AGCM) and coupled atmosphere -ocean climate model (AOGCM). Difference in the AGCM and AOGCM experiments will illustrate the role of the air-sea coupling on the sea ice impact and the comparison between the ensemble AOGCM simualtions will explore the influence of the ocean initial conditions on the sea ice impact.