ABSTRACT                

The El Ni˜no–Southern Oscillation (ENSO) dominates global interannual climate variability and significantly impacts human societies. However, ENSO behavior during the Holocene remains poorly constrained and debated, limiting our ability to assess its long-term dynamics. Here, we present a 2203-year, discontinuous record of annual coral growth rates, derived from 113 U-series-dated fossil corals (Porites lutea) collected from eastern Hainan Island in the northern South China Sea (SCS), spanning 5829–2643 years before present (a BP, relative to 1950 Common Era [CE]). Using a robust calibration between coral growth rate and sea surface temperature (SST), we quantitatively reconstruct annual SST fluctuations in the northern SCS, ranging from 24.2 ◦C to 27.5 ◦C, with a mean of 25.6 ± 0.4 ◦C (1σ), approximately 0.7 ◦C lower than the baseline of 1982–2023 CE. The SST record reveals at least 18 cold periods occurring quasi-periodically at ~200-year intervals, with their durations shortening toward the Late Holocene. Since coral growth rates closely track local SST variability, interannual ENSO signals are reliably preserved in the coral archive. The inferred ENSO variability exhibits pronounced multidecadal modulation, transitioning from weaker-than-present, persistent La Ni˜na-like conditions in the Mid-Holocene (~5800–4200 a BP) to stronger-than-present, prolonged El Ni˜no-like conditions in the Late Holocene (~4200–2600 a BP). These ENSO shifts cannot be fully explained by external forcings such as orbital insolation or volcanic activity, highlighting the predominant role of internal ocean- –atmosphere dynamics in modulating ENSO evolution during the Holocene.