Atlantic Multidecadal Variability climate impacts: Idealized Experiments with NCAR and GFDL coupled climate models

We will present results from an ensemble set of the NCAR Community Earth System Model (CESM1) and GFDL Climate Model (CM2.1) fully-coupled simulations in which the sea surface temperatures (SSTs) in the North Atlantic are restored towards the SST anomalies associated with the observed Atlantic Multidecadal Variability (AMV), a fingerprint of multidecadal Atlantic Meridional Overturning Circulation (AMOC) variability. The SST anomalies exclude the anthropogenic effects. We consider climatological anomalies associated with both the negative and positive phases of the AMV. In addition to the experiments where the SST anomalies are imposed over the entire North Atlantic, we perform experiments in which the anomalies are separately imposed only in the northern North Atlantic and only in the tropical Atlantic. Each ensemble set of simulations has been integrated for 10 years, using 30 ensemble members for CESM1 and 100 ensemble members for CM2.1. Our results show that a positive (negative) AMV phase is associated with a negative (positive) phase of the Pacific Decadal Variability (PDV). We also find that AMV has far-reaching global impacts via mechanisms involving atmospheric teleconnections primarily associated with tropical Atlantic SST anomalies.