变暖背景下北极海冰减少在冬季北半球高纬大陆降雪增加中的作用

过去的几个冬季中，北美、欧洲、西伯利亚和东亚大部分地区经历了冷冬和强降雪，而这与北极海冰的快速减少有关。尽管北极海冰减少在冷冬和强降雪中的作用仍存在争议，但这种新兴的气候反馈在未来变暖背景下是否会持续仍值得关注。中等排放情境下的气候模式模拟结果揭示，欧洲东北部、亚洲中部北部、北美北部的冬季降雪增加会成为贯穿21世纪的一个稳健的特征。21世纪这些区域冬季降雪增加的主要原因是北极秋季海冰的减少（很大的外部强迫），而冬季北极涛动的变化（北半球主要的自然变化形态）对降雪增加的作用很小。这一结果不仅体现在多模式平均上，而且每个单独模式的结果依然如此。我们认为海冰-降雪之间的强反馈作用可能已经出现，并且在接下来的几十年中这种强反馈作用可能会增强，北半球高纬地区的强降雪事件也会增加。

The role of diminishing Arctic sea ice in increased winter snowfall over northern high-latitude continents in a warming environment

Large parts of North America, Europe, Siberia, and East Asia have experienced cold snaps and heavy snowfalls for the past few winters, which have been linked to rapid decline of Arctic sea ice. Although the role of reduction in Arctic sea ice in recent cold and snowy winters is still a matter of debate, there is considerable interest in determining whether such an emerging climate feedback will persist into the future in a warming environment. Here we show that increased winter snowfall would be a robust feature throughout the 21st century in the northeastern Europe, central and northern Asia and northern North America as projected by current-day climate model simulations under the medium mitigation scenario. We argue that the increased winter snowfall in these regions during the 21st century is due primarily to the diminishing autumn Arctic sea ice (largely externally forced). Variability of the winter Arctic Oscillation (dominant mode of natural variability in the Northern Hemisphere), in contrast, has little contribution to the increased winter snowfall. This is evident in not only the multi-model ensemble mean, but also each individual model (not model-dependent). Our findings reinforce suggestions that a strong sea ice-snowfall feedback might have emerged, and would be enhanced in coming decades, increasing the chance of heavy snowfall events in northern high-latitude continents.