Radiocarbon Calibration and Application to Geophysics, Solar Physics, and Astrophysics

Abstract

This paper includes a brief history of the calibration of the radiocarbon time scale from the first recognition of the necessity of calibration in 1962 to INTCAL98. Thirty-six years of effort by dendrochronologists and the 14C community have pushed the tree-ring calibration back to 11,854 yr BP. All of this part of the calibration has been done by high-precision beta counting. Uranium-thorium (U-Th) dating of coral samples coupled with accelerator mass spectrometry (AMS) measurement of 14C has extended a fairly detailed calibration back beyond the Bølling warm episode to 15,000 BP. Earlier than 15,000 BP, piecewise linear approximation extends INTCAL98 calibration to 24,200 BP. Blending 1-, 2-, 3-, 10-, and 20-yr tree-ring samples containing regional and data offsets into a decadal time scale does not make an ideal error and bias free ∆14C record. Nevertheless, spectral analysis reveals some statistically significant fundamental frequencies as well as interesting “beat” frequencies and the second harmonic of the around 208-yr cycle that is considered to be solar in origin. Although, some very prominent peaks such as the 88-yr (Gleissberg) are clearly solar in origin, some of the lower frequencies such as of the 512-yr period may have an origin in thermohaline circulation. Thus, INTCAL98 provides useful data for geophysical and solar physics research. Lastly, single year ∆14C analysis would be useful for revealing invaluable information for solar physics, astrophysics and geophysics not accessible by decadal data. We provide several examples.