Intensification of Pacific tropical instability waves over the recent three decades

Tropical instability waves (TIWs) arise from shear instabilities of equatorial Pacific Ocean currents and are important for the tropical climate and the El Niño–Southern Oscillation. Yet the long-term evolution of TIW activity under climate change remains unclear due to the difficulty in estimating equatorial current velocity. Here we use in situ, satellite altimeter and sea surface temperature observations along with a realistic eddy-resolving ocean simulation to show that TIW activity has intensified in the central equatorial Pacific at ∼12 ± 6% per decade over the recent three decades. The extended satellite data and the ocean model simulation show that the increased TIW activity is probably caused by an enhanced cross-equatorial asymmetric warming in the eastern tropical Pacific. The intensified TIWs lead to increased eddy dynamic heating effects of ∼70% since the 1990s near the equator, with implications for predicting and projecting tropical Pacific climate changes.