NOAA/WDS Paleoclimatology - Russell and Spero 2000 Carbonate Ion Effect on Foraminifera Stable Isotopes

We determined the δ18O and δ13C of individual Globigerinoides ruber and Pulleniatina obliquiloculata from sediment traps located from 5°N to 12°S along 140°W in the Pacific Ocean to evaluate the effects of varying [CO3=] on shell δ18O and δ13C. Variations in the offset between shell δ13C and δ13CDIC (Δδ13Cs-DIC) are attributed to differences in [CO3=], temperature, and shell size between sample sites. When Δδ13Cs-DIC of G. ruber was corrected for variations in [CO3=] using the experimental slope of Bijma et al. [1998], the residual Δδ13Cs-DIC was correlated with mixed layer temperature (+0.10±0.04‰ °C−1). The slope of this temperature effect is consistent with experimental results. In P. obliquiloculata, Δδ13Cs-DIC and temperature were strongly anticorrelated (−0.14±0.03‰ C−1). We are unable to separate the influences of [CO3=] and temperature in this species without independent experimental data. Correcting for [CO3=] variability on δ18Os of G. ruber improves the accuracy of estimated sea surface temperatures.