A regime shift in the interhemispheric teleconnection between the Yellow and East China Seas and the southeastern tropical Pacific during the boreal summer

A drastic regime shift is observed in the early summer connection between the Yellow and East China Seas (YECS) and the tropical Pacific in the early 2000s through statistical estimations on reconstructed datasets for the period 1982–2020. During the pre-2003 period, prior to the regime shift, the summer sea surface temperatures (SSTs) in the YECS were modulated by local oceanic and atmospheric processes, along with their marginal coupling to the tropical Pacific. In contrast, an interhemispheric coupling emerges between the YECS and southeastern tropical Pacific after the regime shift. This teleconnection is attributed to a reduced El Niño signature in the tropical Pacific, which favors the emergence of the South Pacific meridional mode (SPMM) independently from the El Niño-Southern Oscillation signals. The SPMM-related SST anomalies invoke changes in rainfall and vertical motion over the western tropical Pacific, activating the western North Pacific subtropical high over the Philippine Sea. This atmospheric circulation system acts as an atmospheric bridge to mediate the air-sea interacted variability associated with the SPMM into the YECS. The susceptibility of the YECS to atmospheric forcing highlights the role of SST in the YECS as a potential indicator of global-scale climate change.