Decadal time scale variability recorded in the Quelccaya summit ice core δ 18 O isotopic ratio series and its relation with the sea surface temperature

The spectral characteristics of the delta /sup 18/O isotopic ratio time series of the Quelccaya ice cap summit core are investigated with the multi taper method (MTM), the singular spectrum analysis (SSA) and the wavelet transform (WT) techniques for the 500 y long 1485-1984 period. The most significant (at the 99.8% level) cycle according to the MTM F-test has a period centered at 14.4 y while the largest variance explaining oscillation according to the SSA technique has a period centered at 12.9 y. The stability over time of these periods is investigated by performing evolutive MTM and SSA on the 500 y long delta /sup 18/O series with a 100 y wide moving window. It is shown that the cycle…