Influences of East Asian Winter Monsoon and El Niño‐Southern Oscillation Variability on the Kuroshio Intrusion to the South China Sea Over the Past 60 Years

The Kuroshio intrusion (KI) is a northwestward‐flowing branch of the Kuroshio Current, which enters the South China Sea (SCS) and regulates its temperature, salinity, and water mass exchanges. However, limited direct observations hinder our understanding of KI's mechanisms and responses to climate change. Here, we present a 60‐year bi‐monthly resolved coral oxygen isotope (δ18Oc) record from Dongsha Atoll, the northern SCS. The dry‐season (December–March) δ18Oc record reveals interannual to decadal variabilities of the KI. The impact of the East Asian winter monsoon (EAWM) on Dongsha δ18Oc was more pronounced during the 1970s and 1980s and after the early 2000s, while the influence of the El Niño‐Southern Oscillation (ENSO) on Dongsha δ18Oc was higher between the 1980s and 1990s. The Pacific Decadal Oscillation (PDO) may have a relatively minor effect on KI strength or may indirectly modulate KI strength through its influence on ENSO activities. Our Dongsha δ18Oc record highlight the importance of the EAWM, ENSO, and PDO in predicting future KI changes. Plain Language Summary The Kuroshio intrusion is a branch of the Kuroshio Current. It flows into the South China Sea and affects its temperature, salinity, and water movement. We however know very little how the Kuroshio intrusion responds to climate changes. Here we present a study on the chemical composition of a coral core from Dongsha Atoll in the northern South China Sea. Our study shows that the intrusion varies markedly over the past 60 years and is connected to changes in sea surface salinity. Stronger intrusions align with stronger East Asian winter monsoon intensity and El Niño events. Understanding how the Kuroshio intrusion reacts to climate change is important for effectively managing the potential impacts of global warming on the marine ecosystem. Key Points A 60‐year‐long coral oxygen isotope record from Dongsha Atoll, South China Sea reveals interannual to decadal variations in the Kuroshio intrusion Strong Kuroshio intrusion, corresponding to high sea surface salinity, is identifiable over the past 60 years The Kuroshio intrusion variations are primarily driven by East Asian winter monsoon changes and also influenced by El Niño‐Southern Oscillation