NOAA/WDS Paleoclimatology - Western Pacific Ocean Coral Growth Rate, d18O, d14C, and Sr/Ca Data from 1945 to 2002 CE

The isotopic and elemental composition of sclerosponge skeletons are used to reconstruct paleoceanographic records. Yet few studies have systematically examined the natural variability in sclerosponge skeletal d18O, growth, and Sr/Ca, and how that may influence the interpretation of sclerosponge proxy records. Here, we analyzed short records in seven specimens of Acanthocheatetes wellsi (high-Mg calcite, 21 mol% Mg) from Palau, four A. wellsi (high-Mg calcite, 21 mol% Mg) from Saipan, and three Astroclera willeyana (aragonite) sclerosponges from Saipan, as well as one long record in an A. wellsi specimen from Palau spanning 1945-2001.5. In Saipan, species-specific and mineralogical effects appear to have a negligible effect on sclerosponge d18O, facilitating the direct comparison of d18O records between species at a given location. At both sites, A. wellsi d18O and growth rates were sensitive to environmental conditions, while Sr/Ca was not. High-resolution d18O analyses confirmed this finding as both A. wellsi and A. willeyana deposited their skeleton following the trends in isotopic equilibrium with seawater, though with a 0.27 pdf mil offset in the case of A. willeyana. In the high Mg-calcite species A. wellsi, Mg may be interfering with Sr incorporation into the skeleton. On multi-decadal timescales, A. wellsi sclerosponge d18O in Palau tracked the Southern Oscillation Index variability post-1977, but not pre-1977, coincident with the switch in the Pacific Decadal Oscillation (PDO) ~1976. This suggests that water mass circulation in the region is influenced by ENSO variability during positive PDO phases, but not during negative ones.