Reconstruction of long-term oceanic pH variability since the Industrial Revolution from chemical composition in corals around Ryukyu Islands

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Massive Porites corals from Ryukyu Islands and Guam Island were investigated to analyze long-term trend and variability of ocean environment in the northwestern Pacific Ocean. Analysis of X-ray images showed that the coral cores collected at Okinoerabu-jima, Ryukyu Islands, have continuous annual skeletal density bands for the last 450 years (A.D. 1560-2011). Stable isotope and trace element analyses of the coral skeleton generated high-resolution time series of ocean environment parameters such as seawater temperature, salinity, pH, etc, over the long term. Climate reconstruction using the proxy data suggests that sea surface waters in the tropical and subtropical northwestern Pacific Ocean possibly have become warmer, fresher, and more acid since the mid-20th century.