Assessing Kuroshio Intrusion–Related Variability Using Paired Coral Cores From Contrasting Reef Environments at Dongsha Atoll, South China Sea

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Abstract The Kuroshio Intrusion (KI), a northwestward extension of the warm and saline Kuroshio Current, enters the South China Sea (SCS) via the Luzon Strait and strongly influences the regional hydroclimate by altering sea surface temperature (SST), salinity, stratification, and circulation. However, isolating the KI signal from local hydrographic variability in proxy records remains challenging. Here, we investigate KI variability using high‐resolution Sr/Ca and δ 18 O records from two Porites coral cores collected from contrasting reef environments at Dongsha Atoll in the northern SCS: DS25 (inner lagoon) and DS86 (outer reef slope). Coral Sr/Ca from both sites correlates well with instrumental SST, confirming its reliability as a temperature proxy. In contrast, coral δ 18 O exhibits site‐specific responses: DS25 primarily reflects local hydrological variability, whereas DS86 record is more sensitive to regional oceanographic variability associated with the KI. We further applied a weighted differential approach to combine δ 18 O anomalies from both cores. Although the resulting dual‐core index shows only a modest improvement in correlation with an independent KI indicator (DS86 alone r = 0.48; dual‐core r = 0.57), the enhancement is not statistically significant. Nevertheless, the analysis demonstrates that pairing corals from hydrologically distinct reef settings can help distinguish local from regional signals, improving the interpretation of coral proxy records in dynamic oceanographic environments.

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