East Asian monsoon to El Niño/Southern Oscillation: A shift in the winter climate of Ishigaki Island accompanying the 1988/1989 regime shift, based on instrumental and coral records

The relationship between the coral skeletal oxygen isotope ratio (δ18Ocoral) of a coral core (Porites sp.), which was collected from the inshore area of Ishigaki Island, Japan (24°N, 124°E) and represents 180 years of continuous growth, and sea surface temperature (SST) was examined for the last 30 years. A significant linear correlation was found between winter δ18Ocoral and SST measured at Ishigaki Port (SSTI), which suggests that the winter data from this coral sample is a good proxy for reconstructing past climate change. Furthermore, the winter instrumental SSTI shifted from being related to the East Asian Winter Monsoon to being dependent on the El Niño/Southern Oscillation in response to the 1988/1989 climate regime shift. Since this shift is also captured by the winter δ18Ocoral values, this 180‐year coral core record may provide insight into past climate regime shifts that occurred before instrumental records.