An Inter-basin Teleconnection from the North Atlantic to the Subarctic North Pacific at Multidecadal time scales

Observational evidence suggests that the sub-arctic North Pacific (SANP; 45°–60°N, 155°E–165°W) sea surface temperature (SST) shows pronounced multidecadal variability, which cannot be explained by the Pacific Decadal Oscillation (PDO). Here, we find that the SANP SST multidecadal variability is closely linked to the remote Atlantic Multidecadal Oscillation (AMO), indicating a multidecadal inter-basin teleconnection. The teleconnection can be well reproduced in a set of Atlantic Pacemaker experiments. An atmospheric bridge mechanism for the teleconnection is proposed by analyzing both observations and simulation data. The AMO warm phase generates anomalous ascent and upper-level divergence over the North Atlantic. The upper-level outflows converge towards the subarctic North Pacific, leading to compensating subsidence along with anomalous high pressure there. The enhanced adiabatic descent causes anomalous warming and moistening of the lower troposphere above the SANP basin and increases the downwelling longwave radiation. The warming of the SANP SST is further induced and amplified due to water vapor-longwave radiation-SST positive feedback. The anomalous high also weakens the climatological cyclonic flow of Aleutian low and suppresses the turbulent heat release from ocean to atmosphere, contributing to the SANP SST warming. Our findings suggest that the AMO plays a crucial role in the subarctic North Pacific SST multidecadal variability.