Continuously Shrinking Early Autumn Barents–Kara Sea Ice Hinders East Asian Winter Monsoon Forecasting

Abstract The previously robust linkage between early autumn (September–October) sea ice concentration (SIC) in the Barents–Kara Seas (BKS) and the subsequent East Asian Winter Monsoon (EAWM) has undergone a significant decadal shift, weakening markedly after 2007. The correlation coefficient between early autumn BKS SIC and the EAWM index dropped from −0.521 during 1979–2007 to −0.101 during 2008–2023. This dramatically weakened linkage is attributed to the continuous and substantial reduction in BKS SIC that has led to nearly ice‐free conditions and a marked decrease in its interannual variability. Compared to 1979–2007, the associated atmospheric circulation anomalies during 2008–2023 show a diminished tropospheric response and a fundamental reversal in the stratospheric pathway. These profound changes in BKS SIC severely hinder the predictability of the EAWM in recent decades.