Spatiotemporal propagating decadal signal of ocean heat content and thermocline depth identified in the tropical Pacific

Abstract

Tropical Pacific decadal variability (TPDV) and its mechanisms are essential for understanding long-term variations in global climate. The spatiotemporal pattern of this decadal variation has yet to be clarified. Here, on the basis of observational data with the help of the adaptive data analysis method, we extracted and investigated the spatiotemporal evolution of the tropical Pacific decadal variability in upper ocean heat content (UOHC) and thermocline depth. The tropical decadal signal propagated eastward along the equator from the western Pacific to the eastern Pacific after the 1970s, with a speed of 4–5 cm s−1 yielding a decadal oscillation of approximately 11–13 years. This decadal variability of the thermocline fluctuations (UOHC) was proven to be closely correlated with western wind anomalies since the 1970s and may have been induced by the regime shift of the Pacific decadal oscillation. These peaks of decadal signals corresponded well with the strong El Niño–Southern Oscillation (ENSO) events, reflecting nonlinear rectification of ENSOs on TPDV. Moreover, the TPDV showed a modulating signal on moderate and weak ENSO events.