Multidecadal shifts of the northern and southern edges of the western Pacific warm pool

Abstract The western Pacific warm pool (WPWP) plays a pivotal role in shaping global climate. Using observational datasets, we uncover significant multidecadal shifts in the northern and southern edges of the WPWP. Heat budget analysis based on century-long ocean model hindcast simulations reveals that the meridional displacements of the WPWP northern edge are mainly caused by surface heat flux variations, while the southern edge’s shifts can be primarily attributed to meridional oceanic heat advection associated with the wind-driven Ekman transport. These meridional movements largely covary with the Atlantic multidecadal variability (AMV), expanding poleward during AMV’s ascending phases and contracting equatorward during descending phase. Multi-model idealized AMV± experiments estimate that trans-basin forcing of the AMV accounts for 47% ± 8% of the observed northern edge shifts and 26% ± 7% of the southern edge changes. Reducing model uncertainties in AMV teleconnections will help to better quantify their impacts on the Pacific decadal climate variability.