1800s and from 1920 to 1940, the latter of which agrees with instrumental records (Gagan et al. 2000). Superimposed on the recent oceanic warming, some locations show distinct patterns of decadal variability, with repeated shifts of several tenths of a degree Celsius.
Figures 5-1 and 5-2 show examples of isotopic and elemental records derived from corals. Using Sr/Ca and U/Ca ratios in eight coral cores from the Great Barrier Reef, Hendy et al. (2002) (Figure 5-1) revealed that above-average SSTs were present in the 18th and 19th centuries, with cooling in the early 20th century and warming until the 1980s (more so for the U/Ca results). Other coral records from the southwestern Pacific (Figure 5-2) display interdecadal changes in the δ18O and Sr/Ca values that reflect both SSTs and changes in the circulation near the South Pacific Convergence Zone (Linsley et al. 2004). These authors conclude that the degree of cross-