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

Abstract

AbstractCompared 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.