Tropical forcing of the recent rapid Arctic warming in northeastern Canada and Greenland

摘要

Rapid Arctic wanning and sea-ice reduction in the Arctic Ocean are widely attributed to anthropogenic climate change. The Arctic warming exceeds the global average warming because of feedbacks that include sea-ice reduction and other dynamical and radiative feedbacks. We find that the most prominent annual mean surface and tropospheric warming in the Arctic since 1979 has occurred in northeastern Canada and Greenland. In this region, much of the year-to-year temperature variability is associated with the leading mode of large-scale circulation variability in the North Atlantic, namely, the North Atlantic Oscillation. Here we show that the recent warming in this region is strongly associated with a negative trend in the North Atlantic Oscillation, which is a response to anomalous Rossby wave-train activity originating in the tropical Pacific. Atmospheric model experiments forced by prescribed tropical sea surface temperatures simulate the observed circulation changes and associated tropospheric and surface warming over northeastern Canada and Greenland. Experiments from the Coupled Model Intercompar-ison Project Phase 5 (ref. 16) models with prescribed anthropogenic forcing show no similar circulation changes related to the North Atlantic Oscillation or associated tropospheric warming. This suggests that a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability.%格陵兰和加拿大东北在20世纪后期和21世纪初期所经历的气候变暖在世界上属于最快的之一，而由人类诱发的气候变化通常被认为在其中发挥作用。Qinghua Ding等人发现，所观察到的变暖大约一半可被归因于赤道太平洋海洋表面温度的变化，后者反过来又影响将温暖空气从热带输送到格陵兰和加拿大东北的大尺度大气环流。还需要进一步研究来确定太平洋的变化本身是否是对人类活动对气候系统之影响的一种反应。