Since the 1980s, rapid Arctic sea ice loss has been observed, and its potential influences on the midlatitude weather and climate have been extensively examined, but strongly debated. This study instead investigates influences of Arctic sea ice loss on the Eastern Hemisphere westerly wind on the poleward side of the polar front jet (PFJ), which has significantly weakened in winter but strengthened in summer since 1980s. Observational analyses indicate that the Eastern Hemisphere PFJ anomalies in winter and summer are strongly correlated with Northern Hemisphere (NH) atmospheric circulation, surface air temperature and precipitation changes, and that the winter PFJ variability is significantly correlated to Barents-Kara sea ice anomalies from autumn and winter at interannual time scales. About 58% of the observed winter PFJ weakened trend during 1979–2014 is congruent with the autumn sea ice index over the Barents-Kara Seas. Atmospheric model ensemble simulations from four models show that Arctic sea ice loss contributes to Arctic warming in winter and reduces the northern Eurasia-pole temperature contrast, leading to an significant weakening winter PFJ. Ensemble mean effects of four models and each model due to Arctic sea ice loss explain about 10–20% of the observed winter PFJ weakening trend, because the model simulations underestimate observed impacts of sea ice reduction on Arctic troposphere warming. In summer, the strengthening PFJ is mostly controlled by increasing greenhouse gases and sea surface temperature changes outside the Arctic, but is little affected by Arctic sea ice loss. Our observational and numerical results consistently suggest that a dynamical pathway linking observed Arctic sea ice loss to northern Eurasian winter is through its weakening effect on the westerly wind on the poleward side of the PFJ.

自 1980 年代以来，人们观察到北极海冰迅速流失，其对中纬度天气和气候的潜在影响已被广泛研究，但存在激烈争论。相反，这项研究调查了北极海冰损失对极地前沿急流 (PFJ) 极地一侧的东半球西风的影响，自 1980 年代以来，该气流在冬季显着减弱，但在夏季增强。观测分析表明，东半球冬季和夏季的 PFJ 异常与北半球（NH）大气环流、地表气温和降水变化密切相关，冬季 PFJ 变率与秋季以来的巴伦支-卡拉海冰异常显着相关和年际时间尺度的冬季。1979-2014 年间观测到的冬季 PFJ 减弱趋势中约有 58% 与巴伦支海-喀拉海秋季海冰指数一致。四个模型的大气模型集合模拟表明，北极海冰的流失导致冬季北极变暖，并降低了欧亚大陆北部-极地温度对比，导致冬季PFJ显着减弱。由于模型模拟低估了观测到的海冰减少对北极对流层变暖的影响，四个模型的集合平均效应和每个模型由于北极海冰损失解释了大约 10-20% 的观测到的冬季 PFJ 减弱趋势。夏季，增强的PFJ主要受北极以外温室气体增加和海表温度变化的控制，但受北极海冰流失的影响较小。