ENSO influence on tree ring data from Chile and Brazil

Abstract

Wavelet spectral analysis was made in tree ring width data from Brazil (27°11’S, 51°59’W) and Chile (49°12’S, 73°50’W) over the period 1876-1994. Southern Oscillation Index-SOI, representative of ENSO phenomena, and Global mean Surface Air Temperature (GAST) data have been analyzed by wavelet transform. A 2-8 year range was selected. Fluctuations were observed in all data, as expected; these indicate the ENSO imprint on tree-ring data. Strong and weak amplitudes alternate, and frequency shifts in the signal were observed. The strongest signals were observed in the 4-8 year band in Chilean tree ring data, near 1906- 1920 and 1930-1950, and in Brazilian tree ring data in the 6-8 year band near 1906 and 1950. SOI spectrum presented a larger number of intense amplitudes as expected, and GAST spectra showed high intensity only in 1906-1928, in the 5-8 year band. The results show a clear ENSO influence on tree growth.