Abstract
Abstract. We have carried out power spectrum, time-spectrum and bispectrum analyses of the long-term series of the radiocarbon concentrations deduced from measurements of the radiocarbon content in tree rings for the last 8000 years. Classical harmonic analysis of this time series shows a number of periods: 2400, 940, 710, 570, 500, 420, 360, 230, 210 and 190 years. A principle feature of the time series is the long period of ~ 2400 years, which is well known. The lines with periods of 710, 420 and 210 years are found to be the primary secular components of power spectrum. The complicated structure of the observed power spectrum is the result of ~ 2400-year modulation of primary secular components. The modulation induces the appearance of two side lines for every primary one, namely lines with periods of 940 and 570 years, of 500 and 360 years, and 230 and 190 years. The bispectral analysis shows that the parameters of carbon exchange system varied with the ~ 2400-year period during the last 8000 years. Variations of these parameters appear to be a climate effect on the rate of transfer of 14C between the atmosphere and the the ocean.Key words. Meteorology and atmospheric dynamics (climatology; ocean-atmosphere interaction; paleoclimatology)
Highlights
Radiocarbon, 14C, is formed in the Earth’s atmosphere as a result of cosmic ray neutron interactions with nitrogen nuclei: 14N (n, p)14C. 14C decays with a half life of 5730 years
After the discovery of ∼ 2400-year amplitude modulation for the ∼ 210-year cycle (Sonett, 1984) the properties of the ∼ 2400year cycle were discussed by Damon and Linick (1986), Damon (1988), Damon et al (1990)
In the publications of Damon and Sonett (1992) and Damon and Jirikowic (1992) the ∼ 2400-year and ∼ 210-year cycles are considered to be the fundamental ones, most of the other secular cycles discovered in radiocarbon data being harmonic components of the longest cycle
Summary
Radiocarbon, 14C, is formed in the Earth’s atmosphere as a result of cosmic ray neutron interactions with nitrogen nuclei: 14N (n, p)14C. 14C decays with a half life of 5730 years. Variations in the atmospheric concentration of 14C are the result of changes in the Earth’s dipole moment (Elsasser et al, 1956; O’Brien, 1979; Lal, 1988), strengthening or weakening of solar activity (Stuiver and Quay, 1980; Bard et al, 1997) and parameters of radiocarbon exchange system (Oeschger et al, 1975; Siegenthaler et al, 1980; Stocker and Wright, 1996; Goslar et al, 1999). In the publications of Damon and Sonett (1992) and Damon and Jirikowic (1992) the ∼ 2400-year and ∼ 210-year cycles are considered to be the fundamental ones, most of the other secular cycles discovered in radiocarbon data being harmonic components of the longest cycle. For more complete study of interdependence of the ∼ 2400-year variations with other secular components we used bispectral analysis
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call