NOAA/WDS Paleoclimatology - Black et al. 2004 Cariaco Basin 2000 Year Annual Foraminifer Oxygen Isotope Data

Here we present near-annually resolved oxygen isotope records from two species of planktic foraminifera from the Cariaco Basin that reflect sea surface temperature (SST) and Intertropical Convergence Zone (ITCZ) precipitation-related salinity variations over the Caribbean and tropical North Atlantic spanning the last 2000 years. A strong, broad spatial pattern of correlation exists between foraminiferal δ18O and SSTs over the period of instrumental overlap, but the correlations weaken as they are extended back in time and instrumental SST records become discontinuous. A long-term trend in the Globigerinoides ruber δ18O record can be explained by two different but equally plausible scenarios. First, the increase in δ18O may indicate that tropical summer-fall SSTs have cooled by as much as 2°C over the last 2000 years, possibly as a result of a long-term increase in upwelling intensity. Alternately, comparisons to other studies of ITCZ and regional evaporation/precipitation variability suggest that much of the δ18O record is influenced by decadal- to centennial-scale variations in the mean annual position of the ITCZ and associated rainfall patterns. Similarities between the G. bulloides δ18O record and the 11-year sunspot cycle support prior studies that suggest solar variability plays a role in influencing the hydrologic balance of the circum-Caribbean.