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 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 of 50°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.
研究目的：以往研究表明，前期秋季巴伦支–喀拉海海冰减少导致了东亚冬季温度的异常偏冷（第一模态）。那么，东亚冬季温度的北冷南暖分布型（第二模态）是否也与北极海冰异常有关呢？
创新要点：提出东亚冬季温度的北冷南暖（不一致）分布型与同期鄂霍次克海海冰增加显著相关。
研究方法：观测资料分析和数值实验模拟相结合
重要结论：鄂霍次克海海冰增加，东亚北部（50N°以北）异常偏冷，进而改变了中纬度和热带的温度梯度，使得东亚高空急流位置偏北。在对流层低层，50N°以北（以南）为偏北风（偏南风）异常，形成东亚北冷南暖的温度异常分布型。