[U-13] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia:

[U13-01] Insight to Western Pacific circulation from coral skeletal radiocarbon during the Anthropocene and Holocene

★Invited Papers

*Shoko Hirabayashi^1,2,3, Yusuke Yokoyama², Atsushi Suzuki⁴, Tezer Esat⁵, Yosuke Miyairi², Takahiro AZE², Fernando Siringan ⁶, Yasuo Maeda⁷, Hironobu Kan³ (1.Faculty of Geo-Environmental Science, Rissho University, 2.Atmosphere and Ocean Research Institute, The University of Tokyo, 3.Department of Environmental Changes, Graduate School of Social and Cultural Studies, Kyushu University, 4.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 5.Research School of Physics and Engineering, The Australian National University, 6.Marine Science Institute, University of the Philippines, 7.Institute of Natural and Environmental Sciences, University of Hyogo)

Keywords:Radiocarbon, U/Th dating, Local marine reservoir age, Corals, Kuroshio

Coral skeletal radiocarbon (Δ¹⁴C) records can be used as a sensitive proxy of water mass mixing. Compiling coral skeletal Δ¹⁴C datasets in the western Pacific will contribute to our understanding of the oceanography of the region and its relationship to climate change such as El Nino-Southern Oscillation.

In this study, high-resolution coral skeletal Δ¹⁴C dataset during the Anthropocene and Holocene are reported from the western Pacific. Our Δ¹⁴C data indicates the unusual, rapid Δ¹⁴C increase (early bomb-¹⁴C spikes) in the 1950s related to the “close-in fallout” found in the corals from Ishigaki and Luzon Island. The amplitude of the bomb-¹⁴C spike in the Luzon Island was less than half that in Ishigaki, likely due to upwelling around Luzon Island and the Kuroshio intrusion into the South China Sea. We also calculated the local marine reservoir age (R) and the regional offset (ΔR) during the Holocene using paired analyses of Δ¹⁴C and ²³⁰Th in pristine corals. An abrupt ΔR shift occurred between 5.5 ka BP and 4.0 ka BP in the northwest Pacific. Compared with the previously reported data from the Tropical East Pacific and Great Barrier reef, the timing of the shift is different because the ¹⁴C content of the northwestern Pacific was affected by not only the intensity of upwelling at the Peru-Chile coast, but also by the East Asian monsoon.