Δ14C and δ13C in Annual Tree-Ring Samples from Sequoiadendron Giganteum, AD 998–1510: Solar Cycles and Climate

Time series of annual Δ 14 C and δ 13 C in tree rings of Sequoiadendron giganteum , AD 998–1510, are similar in form. The Δ 14 C series completes, with data of Stuiver and Braziunas (1993), a 957-yr time-series. Discrete Fourier transformation of detrended Δ 14 C reveals periods of 126, 91, 56, 17.6, 13.6, 10.4, and 7.1 yr. Non-random differences exist between decadal averages of the Sequoiadendron Δ 14 C data and data of Stuiver and Becker (1993). Periods of 7–17 yr may correspond to Schwabe or related climatic cycles; these have 10–17-yr periods and amplitudes < 6‰ (AD 1100–1250), and periods near 7 yr with amplitudes up to 10‰ (AD 1380–1420). Abrupt increases in Δ 14 C are mainly less than 5‰, and do not constitute convincing evidence of increased 14 C production from supernovae or solar proton events. The δ 13 C time-series is likely to reflect climate change, and for centennial periodicity lags behind Δ 14 C by 20–40 yr (centennial time-scale) and 25–50 yr (millennial). Phase-shifts between solar luminosity and surface Δ 14 C are 125–175 yr and 20 yr for millennial and centennial cycles, respectively. The study suggests that strongest climate effects may therefore follow peak luminosity by 125–175 yr for millennial cycles and 20–40 yr for centennial cycles.