DOI: 10.25921/e6q1-7288
title: NOAA/WDS Paleoclimatology - Tambea - Coral Radiocarbon Data

description: A bimonthly coral-based record of the postbomb radiocarbon content of Solomon Sea surface waters is interpreted to reflect mixing of subtropical surface water and that advected in from the east by the equatorial branch of the South Equatorial Current (SEC). Annual mean d14C has a dynamic range of nearly 175 per mil, with a total range of nearly 200per mil. Prebomb values average -56 per mil and the annual mean postbomb maxima occurs in 1985 with a value of +117 per mil. Interannual variability in the record reflects surface current variations in conjunction with surface wind changes associated with ENSO. During El Niņo years the waters of the Solomon Sea reflect a stronger influence of waters advected in from the east by the SEC and less "pure" subtropical water. This is most likely accomplished by a southward shift of the equatorward branch of the SEC during El Niņo. There is an overall decrease in the relative proportion of eastern tropical water that is interpreted as a decrease in the strength and intensity of the shallow circulation of the tropical Pacific during the latter portion of the twentieth century. If validated, this secular trend bears strongly upon the rate of extratropical-tropical recirculation and the redistribution of heat and salt within the tropical Pacific.
description: Tambea-2 coral radiocarbon (14C) timeseries on upper 0.92 m of core. LONGITUDE: 160E. LATITUDE: 9S. WATER DEPTH: 14m. CORAL SPECIES: Porites australiensis. CORE LENGTH: 2.3 meters. DATE OF COLLECTION: July 1995. Coral radiocarbon (Delta-14C) on untreated, low-speed drilled samples. Precision is ±4.5 per mil as documented by an in-house homogenized coral standard, and presented as AGE CORRECTED DELTA-14C [see Stuiver & Polach, 1977]. Cores were taken from a 2.26 meter Porites australiensis coral on the southwest side of Guadalcanal Island (160E 9S), <15m bottom depth, in July of 1995 by D. Schrag & M. Moore. Reference area is offshore Tambea Resort. Cores were split and cleaned with distilled water. After identifying the major vertical growth axis, the coral was sequentially sampled at 2 mm increments with a low-speed drill. Splits (~1 mg) were reacted in vacuo in a modified autocarbonate device at 90°C and the purified CO2 analyzed on a gas source stable isotope ratio mass spectrometer. The remaining sample splits (~10 mg) were placed in individual reaction chambers, evacuated, heated, and then acidified with orthophosphoric acid at 90°C. The evolved CO2 was purified, trapped, and converted to graphite in the presence of cobalt catalyst in individual reactors [Vogel et al., 1987]. Graphite targets were measured at the Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory [Davis et al., 1990]. Radiocarbon results are reported as Delta-14C (per mil) as defined by Stuiver and Polach [1977] and include the d13C correction obtained from the stable isotope results. Analytical precision and accuracy of the radiocarbon measurements is ±4.5 per mil (1s) based on repeated analyses of an in-house homogenized near-modern coral and accepted secondary and tertiary radiocarbon standards.