Under recent Arctic warming, boreal winters have witnessed severe cold surges over both Eurasia and North America, bringing about serious social and economic impacts. Here, we investigated the changes in daily surface air temperature (SAT) variability during the rapid Arctic warming period of 1988/89–2015/16, and found the daily SAT variance, mainly contributed by the sub-seasonal component, shows an increasing and decreasing trend over eastern Eurasia and North America, respectively. Increasing cold extremes (defined as days with daily SAT anomalies below 1.5 standard deviations) dominated the increase of the daily SAT variability over eastern Eurasia, while decreasing cold extremes dominated the decrease of the daily SAT variability over North America. The circulation regime of cold extremes over eastern Eurasia (North America) is characterized by an enhanced high-pressure ridge over the Urals (Alaska) and surface Siberian (Canadian) high. The data analyses and model simulations show the recent strengthening of the high-pressure ridge over the Urals was associated with warming of the Barents-Kara seas in the Arctic region, while the high-pressure ridge over Alaska was influenced by the offset effect of Arctic warming over the East Siberian-Chukchi seas and the Pacific decadal oscillation (PDO)-like sea surface temperature (SST) anomalies over the North Pacific. The transition of the PDO-like SST anomalies from a positive to negative phase cancelled the impact of Arctic warming, reduced the occurrence of extreme cold days, and possibly resulted in the decreasing trend of daily SAT variability in North America. The multi-ensemble simulations of climate models confirmed the regional Arctic warming as the driver of the increasing SAT variance over eastern Eurasia and North America and the overwhelming effect of SST forcing on the decreasing SAT variance over North America. Therefore, the regional response of winter cold extremes at midlatitudes to the Arctic warming could be different due to the distinct impact of decadal SST anomalies.

中文翻译：

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近期北极变暖下欧亚大陆东部和北美冬季极端寒冷的相反趋势

在近期北极变暖的背景下，北半球的冬季在欧亚大陆和北美都出现了严重的寒潮，带来了严重的社会和经济影响。在这里，我们调查了 1988/89-2015/16 北极快速变暖期间每日地表气温 (SAT) 变化的变化，发现每日 SAT 变化，主要由亚季节成分贡献，显示出增加和分别在欧亚大陆东部和北美呈下降趋势。增加的极端寒冷（定义为每日 SAT 异常低于 1.5 标准差的天数）主导了欧亚大陆东部每日 SAT 变异的增加，而减少的极端寒冷主导了北美每日 SAT 变异的减少。欧亚大陆东部（北美洲）的极端寒冷环流状况的特点是乌拉尔（阿拉斯加）和西伯利亚（加拿大）地表高压脊上的高压脊增强。数据分析和模型模拟表明，近期乌拉尔高压脊的加强与北极地区巴伦支-卡拉海的变暖有关，而阿拉斯加高压脊则受到北极偏移效应的影响。东西伯利亚-楚科奇海变暖和北太平洋类似太平洋年代际振荡 (PDO) 的海面温度 (SST) 异常。类 PDO 海温异常由正相向负相转变，抵消了北极变暖的影响，减少了极冷日的发生，并可能导致北美每日 SAT 变异性呈下降趋势。气候模型的多集合模拟证实了区域北极变暖是欧亚大陆东部和北美 SAT 方差增加的驱动因素，以及 SST 强迫对北美 SAT 方差减小的压倒性影响。因此，由于年代际海温异常的明显影响，中纬度冬季极端寒冷对北极变暖的区域响应可能有所不同。