サンゴ化石の地球化学記録から復元される氷期／間氷期の大気海洋変動

抄録

The interaction of tropical and subtropical sea-surface waters with the atmosphere on seasonal, interannual, and decadal timescales is one of the sources of climate changes. Understanding the Quaternary history of climate and ocean variability requires knowledge of how the ocean-atmosphere system operated in the past. Hermatypic scleractinian corals, especially Porites sp., are one of the best archives for extending the short and rather sparse instrumental record of sea-surface observations at monthly resolution. Coupled determinations of Sr/Ca ratio and oxygen isotope composition in fossil corals can yield high-resolution time series of sea-surface temperature and salinity with precise chronology, reconstructing seasonal-to-decadal climatic variability associated with the monsoon, the El Niño/Southern Oscillation, and the Pacific Decadal Oscillation during the Quaternary. This paper is a review of coral paleoclimatology, highlighting selected studies on coral-based climate reconstructions of surface ocean conditions during the Holocene, the last deglaciation, and the last interglacial. Although potential biases in paleoclimate reconstructions caused by diagenetic alteration, inter-colony offset, the past seawater chemistry, and errors of thermometers should be handled carefully, future works on skeletal geochemistry in corals with advanced analytical and statistical methods will provide a paleo-observational constraint on climate model simulations of ocean-atmosphere variability for the past.