Persistent Positive North Atlantic Oscillation Mode Dominated the Medieval Climate Anomaly

作者：Valerie M. Trouet, Jan Esper, Nicholas E. Graham, Andy Baker, James David Scourse, David Frank · 发表于：Science · 年份：2009 · DOI：10.1126/science.1166349 · 被引用次数：1126 · 研究领域：Tree-ring climate responses、Geology and Paleoclimatology Research、Climate variability and models

The Medieval Climate Anomaly (MCA) was the most recent pre-industrial era warm interval of European climate, yet its driving mechanisms remain uncertain. We present here a 947-year-long multidecadal North Atlantic Oscillation (NAO) reconstruction and find a persistent positive NAO during the MCA. Supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker NAO conditions into the Little Ice Age (LIA). Globally distributed proxy data suggest that this NAO shift is one aspect of a global MCA-LIA climate transition that probably was coupled to prevailing La Niña-like conditions amplified by an intensified Atlantic meridional overturning circulation during the MCA.