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Variability of radiocarbon during the 1760s in monthly corals from the Galapagos Island

  • Author(s): Druffel, Ellen R M
  • Griffin, Sheila
  • Hwang, Jeomshik
  • Komada, Tomoko
  • Beaupre, Steven R
  • Druffel-Rodriguez, Kevin C
  • Santos, Guaciara
  • Southon, John R
  • et al.
Creative Commons Attribution 4.0 International Public License
Abstract

Radiocarbon (∆14C) measurements of monthly samples from a Galapagos surface coral are among the first data sets from the new Keck Carbon Cycle Accelerator Mass Spectrometry laboratory at the University of California, Irvine. An average ∆14C value of -62‰ is obtained for 144 measurements of samples from monthly coral bands that lived from about AD 1760-1771 (±6 yr). High ∆14C values were found during January through March, when upwelling was weak or absent at the Galapagos Islands. Low ∆14C values were obtained mid-year during strong upwelling. The average seasonal variability of ∆14C was 15-25‰, which is greater than that at other tropical and subtropical locations in the Pacific Ocean because of intense seasonal upwelling at this site. Periods of sustained high ∆14C values were found during 1762-1763 and 1766. A spectral analysis revealed that the spectral density for the ∆14C data displays most of its variance at the 5-yr cycle, which is reflective of El Nio periodicity during the 20th century.

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