Abstract

KOTZE, Pieter B.. Identification of solar periodicities in southern African baobab δ¹³C record. S. Afr. j. sci. [online]. 2020, vol.116, n.7-8, pp.1-5. ISSN 1996-7489.  http://dx.doi.org/10.17159/sajs.2020/6813.

Spectral analysis using wavelet, Lomb-Scargle and maximum entropy techniques of the proxy rainfall record of northeastern South Africa based on annual carbon isotope (δ¹³C) data obtained from baobab trees for the period 1600 AD - 2000 AD show clear evidence of the presence of characteristic solar periodicities. Solar periodicities that were identified above the 95% confidence level include the ~11-year Schwabe cycle, the ~22-year Hale cycle as well as the 80-110-year Gleissberg cycle. A Morlet wavelet analysis of the δ¹³C data between 1600 AD and 1700 AD shows the effect of the Maunder sunspot minimum on both the Schwabe and Hale cycles during this time. Significance: A spectral analysis of δ¹³C baobab tree ring data for southern Africa between 1600 AD and 2000 AD is presented. The results show - for the first time - that the δ¹³C time series contains the 11-year Schwabe, 22-year Hale as well as the 80-110-year Gleissberg solar periodicities. In addition, the influence of the Maunder sunspot minimum between ~1650 AD and 1715 AD could also be clearly identified in the δ¹³C data for the first time. These findings are of significant importance to investigations of solar influences on climate variability

Keywords : tree ring; carbon isotope data; spectral analysis; solar influences; climate variability.

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