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Abstract
The North Equatorial Current (NEC) bifurcates at the eastern coast of the Philippines and moves northward as the Kuroshio, a North Pacific western boundary current. The NEC bifurcation point and Kuroshio variability are known to be affected by changes in climate such as the El Niño–Southern Oscillation and the pacific decadal oscillation. However, observational data are not sufficient to examine the mechanisms of decadal fluctuation. Here, we report seasonal radiocarbon data recorded from 1968 to 1995 in coral skeletons northwest of Luzon Island. The data suggest that the East Asian winter monsoon is a dominant factor in the seasonal fluctuations in water mass northwest of Luzon Island. Compared with other coral records reported for Guam, Ishigaki, Con Dao, and Hon Tre Island, the data suggest that the area of the Kuroshio loop current through the Luzon Strait decreased from the 1970s to 1980s as a result of the change in Kuroshio transport and the migration of the NEC bifurcation latitude after a regime shift in 1976.
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1 Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan; Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
2 Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
3 Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan
4 Marine Science Institute, University of the Philippines, Diliman, Quezon City, Philippines
5 Institute of Natural and Environmental Sciences, University of Hyogo, Sanda, Hyogo, Japan