Department of Earth System Science

Monthly skeletal stable isotope measurements of a Porites australiensis coral from Abraham Reef, Australia, spanning the period from 1981 to 1991, are compared with monthly averaged SST (sea surface temperature) from satellite collected AVHRR (Advanced Very High Resolution Radiometer) and monthly downward surface short-wave insolation (SSI) measurements. We found that the δ¹⁸O values varied as a function of the change in seawater temperature. There were anomalously high δ¹⁸O values in coral that grew during the summer season of the three El Niño events 1982–83, 1987, and 1991. Advection of seawater with higher salinity (and higher δ¹⁸O values) to our site or discrepancies between ocean skin temperature and mixed layer SST are likely reasons for the reduced resolution of δ¹⁸O-based SST. Increased coral δ¹³C values occurred simultaneously with increases in SSI. During most El Niño events the maximum and minimum δ¹³C values were lower than during normal years.