Persistent positive North Atlantic oscillation mode dominated the Medieval Climate Anomaly.
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.
Trouet
Valérie
V
Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland. trouet@wsl.ch
Esper
Jan
J
Graham
Nicholas E
NE
Baker
Andy
A
Scourse
James D
JD
Frank
David C
DC