NOAA/WDS Paleoclimatology - Espiritu Santo, Vanuatu 446 Year Stalagmite Oxygen Isotope Data

STUDY NOTES: Data include a table of U-Th ages and the d18O record from Taurius Cave on the island of Espiritu Santo (15º32’S, 167º01’E) in Vanuatu that spans ~450 years. The age model for the record is comprised of 31 U/Th Dates, and the top age is assumed to be circa 2005 (year of collection). The average temporal resolution for each d18O measurement is ~3 months/sample. The age model for the sample is based on a MATLAB program that fits piecewise quadratic splines to the U-Th dates. A Monte-Carlo approach is used to constructs alternative age models by allowing each U-Th date to vary according to a normal distribution with mean age (its best estimate) and standard deviation Sigma (its analytical uncertainty) over a 2sigma range. The spread in the alternate age models is a measure of the age uncertainty of each d18O measurement and is listed in the table with the d18O data for each measurement. The d18O data are reported with respect to PDB, and ages are reported as Year Common Era (Year C.E.). Depths without a d18O measurement are identified by NaN.
ABSTRACT SUPPLIED BY ORIGINATOR: Pacific decadal variability (PDV) causes widespread, persistent fluctuations that affect climate, water resources, and fisheries throughout the Pacific basin, yet the magnitude, frequency, and causes of PDV remain poorly constrained. Here we present an absolutely dated, subannually resolved, 446 yr stable oxygen isotope (d18O) cave record of rainfall variability in Vanuatu (southern Pacific Ocean), a location that has a climate heavily influenced by the South Pacific Convergence Zone (SPCZ). The d18O-based proxy rainfall record is dominated by changes in stalagmite d18O that are large (~1 permil), quasi-periodic (~50 yr period), and generally abrupt (within 5-10 yr). These isotopic changes imply abrupt rainfall changes of as much as ~1.8 m per wet season, changes that can be ~2.5x larger than the 1976 C.E. shift in rainfall amount associated with a PDV phase switch. The Vanuatu record also shares little commonality with previously documented changes in the Intertropical Convergence Zone during the Little Ice Age or solar forcing. We conclude that multidecadal SPCZ variability is likely of an endogenous nature. Large, spontaneous, and low-frequency changes in SPCZ rainfall during the past 500 yr have important implications for the relative magnitude of natural PDV possible in the coming century.