ENSO signals of the twentieth century in an ice core from Nevado Illimani, Bolivia

An ice core from Nevado Illimani in the eastern Bolivian Altiplano was used to establish proxy data for past climate conditions. For this purpose a principal component analysis (PCA) was performed on the records of ionic species of the upper 59.2 m (time period 1887 ± 6 to 1999 A.D.). The first principal component (PC1) shows high loadings of mainly dust-related ions. This signal is inversely correlated on a monthly basis with precipitation on the Bolivian Altiplano. Maxima in the PC1 time series correspond to the dry season on the Altiplano during the austral winter, whereas minima occur during the wet season from November to March. Interannual variability of PC1 reveals correlations with indices of the El Niño-Southern Oscillation (ENSO), showing elevated (reduced) dust values at the Nevado Illimani site during warm (cold) phases. This relationship may be explained by below (above) average December-February precipitation in the Bolivian Altiplano during El Niño (La Niña) episodes. Persistent El Niño events such as those in the years 1915, 1942, and 1993 A.D. seem to imprint very strong dust signals in the Illimani ice core. Out of the six PCs extracted, only the PC1 time series is correlated with the Tropical Southern Atlantic index. Thus we suggest that the major climate variability on the Bolivian Altiplano as recorded in the Nevado Illimani ice core is more closely related to conditions in the Pacific, even though the moisture source at this site is ultimately the Atlantic Ocean. Copyright 2005 by the American Geophysical Union.