个人简介

武炳义，复旦大学特聘教授。长期从事北极海冰-气相互作用及其对东亚气候变化的影响、东亚季风变化机理等方面的研究。

报告摘要

Cold-Eurasia contributes to Arctic warm anomalies

The Barents-Kara Seas are the crucial regions to link the Arctic to the midlatitudes of Eurasia, and winter warm anomalies around these regions have been regarded as a primary reason for cold-Eurasia over the past decade. Thus, the role of cold-Eurasia in resulting Arctic warm anomalies remains unclear. Through observational analyses and simulation experiments forced by prescribed regional ground albedo, this study shows that cold-Eurasia can give rise to Arctic warm anomalies. Observational analyses suggest that winter warm anomalies over the Barents-Kara Seas are originated from atmospheric circulation anomalies in the mid- and high-latitudes and dominantly associated with the positive NAO and the strengthening of Siberian high. The strengthened Siberian high well corresponds to a systematic northward shift of atmospheric circulation over northern Eurasia, the North Atlantic, and northern North America, leading to significant increases in the atmospheric total energy transport into the Barents-Kara Seas. All simulation experiments forced by prescribed regional albedo in Eurasia consistently demonstrate that a regional cooling directly contributes to Arctic warm anomalies, and sometimes the cooling enhances the Siberian high and generates positive 500-hPa height anomalies over around the Ural Mountains through atmospheric subsidence anomalies and energy propagations, leading to warm anomalies over the Barents-Kara Seas. The increase in winter Eurasian snow cover, as one of the crucial factors enhancing the ground albedo, would favor the occurrence of warm Arctic-cold Eurasia, and there is already evidence supporting this deduction. This study implies that on the interannual time scales, winter warm anomalies over the Barents-Kara Seas cannot simply be seen as the cause of winter cold-Eurasia.