Prebomb to Postbomb ¹⁴C History From the West Side of Palawan Island: Insights Into Oceanographic Changes in the South China Sea

Compared to the natural production of ¹⁴C, thermonuclear tests have produced a globally abnormal ¹⁴C signal. To examine and reconstruct ocean circulation in the South China Sea (SCS), we generated a prebomb to postbomb ¹⁴C time series from a Porites lobata coral from the west side of Palawan Island, Philippines. Results show a diluted early bomb ¹⁴C intrusion in late 1955. We use this record to extend our understanding of the surface ocean circulation in and around the SCS by tracing ¹⁴C labeled water from nuclear test sites. Our postbomb Δ¹⁴C peaked at 154‰ in 1975, which lags ~10 years from the atmospheric peak, consistent with other marine records. This coral record also displayed clear seasonal Δ¹⁴C cycles indicating different surface waters passed the Palawan Island coral site due to seasonal variations of the East Asian Monsoon.