Observed winter(December–February)surface air temperature over East Asia(0°–60°N,100–140°E)(TEA)shows non-uniform variation during 1979–2013,with cooling and weak warming north and south of40°N.To understand this,the authors perform statistical analysis(linear regression and composite)on the observed data.The results suggest that reduced(increased)autumn sea ice cover in the Barents-Kara Sea(BK-ASIC)lowers(warms)TEA over northern East Asia,which is consistent with previous studies.In comparison,increased(decreased)winter sea ice cover in the Sea of Okhotsk(O-WSIC),warms(cools)the air over southern East Asia.The mechanism can be described as follows:When the BK-ASIC decreases,the East Asian winter monsoon tends to be stronger with an intensified Siberian high,leading to cooling over northern East Asia.An O-WSIC increase is associated with cold anomalies north of 50°N,altering the meridional temperature gradient between the midlatitudes and tropics,and leading to a northward shift of the East Asian jet steam in the upper troposphere.In the low atmosphere,anomalous northeasterly winds prevail north of50°N and anomalous southerly winds control the southern coast of East Asia,contributing to the weak warming over southern East Asia.Version 3 of the Community Atmosphere Model also provides evidence for the impact of increased O-WSIC on the warm southern mode of TEA. Observed winter (December-February) surface air temperature over East Asia (0 ° -60 ° N, 100-140 ° E) (TEA) shows non-uniform variation during 1979-2013, with cooling and weak warming north and south of 40 ° N.To understand this, the authors perform statistical analysis (linear regression and composite) on the observed data. The results suggest that reduced (increased) autumn sea ice cover in the Barents-Kara Sea (BK-ASIC) lowers (warms) TEA over northern East Asia, which is consistent with previous studies. In contrast, increased (decreased) winter sea ice cover in the Sea of ​​Okhotsk (O-WSIC), warms (cools) the air over southern East Asia. as follows: When the BK-ASIC decreases, the East Asian winter monsoon tends to be stronger with an intensified Siberian high, leading to cooling over northern East Asia. An O-WSIC increase is associated with cold anomalies north of 50 ° N, altering the meridional temperature gradient between the midlatitudes and tropics, and leading to a northward shift of the East Asian jet steam in the upper troposphere. the low atmosphere, anomalous northeasterly winds prevail north of50 ° N and anomalous southerly winds control the the southern coast of East Asia, contributing to the weak warming over southern East Asia. Versions 3 of the Community Atmosphere Model also provides evidence for the impact of increased O-WSIC on the warm southern mode of TEA.