Understanding the inter-basin interactions of the Atlantic Multi-decadal Oscillation and the Pacific Decadal Oscillation

Abstract:

Various studies examined the relationship between the Atlantic Multi-decadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) and mainly covered the lead-lag relationship between theirs or the combined impacts. While the AMO may affect the PDO as a background state, less attention is paid to understand these processes. Here, we focus on the modulation of PDO according to the phase of AMO. We compare the structures of SST and atmospheric filed associated with the PDO under a different phase of the AMO. As a result, we find that the PDO’s structures with a same phase change according to the AMO phase. In particular, these differences are evident depending on whether PDO and AMO are in phase or out-of-phase. When AMO and PDO are in-phase, the Pacific Ocean affects the Atlantic Ocean through a Pacific-driven Walker circulation. However, if they are out-of-phase, the Atlantic Ocean affects the Pacific Ocean through Atlantic-driven Walker circulation and local convection in the tropical Atlantic Ocean. To confirm these results, we perform the Atlantic pacemaker experiments using NESM v3, and the model results also support the observations.