Sun-earth relationship studied by tree growth rings in conifers from holocene and triassic / Relação sol-terra estudada através de anéis de crescimento de coníferas do holoceno recente e do triássico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The study of the Sun and of its energy flux variations is recent and fully experimental. For this reason , if is very important develop studies in order to understand the past and predict the future using natural records at the Earth surface to monitor solar variations and their effects on climate. The studies about the Sun s variations and Sun-Earth-Climate relationships are possible because there exists natural records that cover long time interval, such as, for example, tree growth rings, which may represent good records of climate variations in the past. In this work a study of Sun-Earth relationships was developed using tree growth rings of araucarias (Araucaria angustifolia) in the present time and in silicified Mesozoic wood ("petrified trees" of 200 million years ago), both collected in the Rio Grande do Sul State, Brazil. From the Araucaria angustifolia collected in Severiano de Almeida and Passo Fundo were obtained chronology average for 359 and 264yr respectively. The petrified samples, collected in São Pedro do Sul and Mata, lead to 15 time series, with 28 to 159 tree growth rings. In the study of tree rings time series of the present and of the past (petrified samples), the method of classical spectral analysis, iterative regression, was used for the search of periodicities and trends contained in tree growth. The wavelet method was also used to verify the periodicities and amplitudes found as a function on time. The analysis of the time series of the tree growth rings thicknesses (petrified and not petrified samples), using the method of the iterative regression indicates representative periods of the solar activity of 11 (Schwabe cycle), 22 (Hale cycle), 52 (4^th harmonic of the Suess cycle) and 80 (Gleissberg cycle) years, with a significance statistics of 95%. This may show a possible influence of the solar activity in the growth of the trees in the recent past, in last the 300 years, as in the distant past, at about 200 million years ago. Also low periods at 2 to 7 years, were found that can represent a response of the trees to local climatic conditions at their respective epochs of life. It was verified through the study of tree growth rings from Triassic and from the present times that the solar activity presented basically the same periods. The wavelet analysis has shown that it exist a good agreement of the time series of tree growth rings with the 11 year solar cycle, for the Minimum and Maximum solar activity periods, such as the Minimum of Dalton and the Modern Maximum. The cross-wavelet analysis between the chronologies of Passo Fundo, Severiano de Almeida and the series of the anomaly of temperature and of the South Oscillation Index (SOI), have shown that the temperature and the SOI are both influencing the araucaria growth in the periods between 2-8 years.

ASSUNTO(S)

dendrochronology análise de dados climatology data analysis interactions atividade solar solar terrestrial dendrocronologia solar cycles solar activity climatologia interação sol-terra ciclos solares

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