A Recent Shift Toward an El Niño‐Like Ocean State in the Tropical Pacific and the Resumption of Ocean Warming

Since approximately 2011, the tropical Pacific has been sharply shifting toward an opposite phase to that observed in the previous decade. This shift has coincided with a recent resumption of global warming after a hiatus in the 2000s. Based on a model‐data analysis using an ensemble empirical mode decomposition, we identified a distinct low‐frequency mode of the sea level in the tropical Pacific and showed its connection to global ocean warming and the suppression of global warming during the early 2000s, as well as the resumption of warming during recent years. Hindcast and model experiments conducted to illustrate the physical mechanism linking the decadal mode to the Pacific Decadal Oscillation‐related trade winds, which regulate the strength of the Equatorial Undercurrent and the surface temperature of the tropical Pacific Ocean, revealed an El Niño‐like state for the last several years. Plain Language Summary In contrast to previous decade, since roughly 2011, sea level in the western tropical Pacific has declined, while sea level in the central‐to‐eastern tropical Pacific has increased. This study focuses on a decadal shift in the tropical Pacific Ocean toward a low‐frequency El Niño‐like state, which coincides with a recent resumption of global warming after a hiatus in the 2000s. Here we identify whether the recent shift is a short‐term change associated with ENSO or longer‐term change and examine how the decadal shift in the Pacific is linked to the recent acceleration of global ocean warming. The model‐data analysis allows us to gain insight into the evolution of sea level and ocean circulation in the Pacific Ocean on decadal time scale, as well as the accuracy and reliability of observed decadal fluctuation. The decadal mode presented here could lead to a better understanding of how sea level and ocean circulation respond to the Pacific climate variability. Key Points A shift toward an El Niño‐like state in the tropical Pacific has been detected since approximately 2011 A distinct decadal mode in the tropical Pacific, coinciding with the recent resumption of global warming, has been identified This decadal mode is closely linked to climate‐related winds that regulate the Equatorial Undercurrent and surface temperature trends