Based on the monthly Hadley Center sea surface temperature data,Hadley Center Arctic sea ice concentration data,and NCEP/NCAR reanalysis data during 1961-2015,this paper analyzed the abnormal response of Arctic sea ice to EP (eastern Pacific) ENSO events in autumn,and further discussed the possible causes of such an abnormal response.Results show that the response of Arctic sea ice to EP ENSO in autumn is nonlinear.Particularly,the sea ice concentration anomalies in the Kara Sea area (70°-80°N,60°-90°E) are significantly negative both in the EP El Niño and EP La Niña phases.Further analyses reveal that the mechanisms of sea ice anomalies in different EP ENSO phases are significantly different.For EP El Niño years,the suppression of convective activity in the waters near the Philippines stimulates the meridional wave train in the extratropical area.Meanwhile,the southward wind component of the anomalous anticyclonic circulation in response to the wave train in the high latitudes forms warm convection transport to the Kara Sea area and causes sea ice retreat as a result.However,the Kara Sea area is mainly influenced by the westerly anomalies from the open Atlantic Ocean during EP La Niña years.Moreover,both the composite results and the analysis results of individual EP La Niña event show that there is a remarkable westerly jet center over the North Atlantic in autumn,which is conducive to downstream transport of warmer seawater from the open North Atlantic,affecting sea ice in the Kara Sea as a result.The above results show that the nonlinear response of circulation field in the extratropical areas to EP ENSO leads to a significant nonlinear response of Arctic sea ice to EP ENSO in turn.