Emerging Pacific Quasi-Decadal Oscillation Over the Past 70 Years

Quasi-decadal variation in various Pacific regions has been recognized for decades but its spatial-temporal characteristics and generation mechanisms remain poorly understood. Here we show that the sea surface temperature (SST) in the equatorial central Pacific (ECP) exhibits a prominent 11-year periodicity since 1951 but not before. An episodic-like quasi-decadal warm event is initiated in a northeast-southwest tilted belt from the United States' west coast to the ECP. The initial development involves positive feedback between atmospheric heating-induced Rossby waves and underlying SST in the tropical North Pacific. The amplification of ECP warming is primarily due to equatorward heat advection and deepening thermocline, while the zonal advective feedback mainly controls its decay. The quasi-decadal oscillation (QDO) tends to follow the 11-years solar cycle with a 1-to-2-year phase delay, meanwhile, it possibly links to the nonlinear behavior of ENSO. The cause of intensification of the QDO over the past 70 years, however, remains elusive.