Geography and Geology
An annually resolved pollen record spanning a 39-year period ( 1958 - 1996) from the Sajama Ice Cap, located on the western Bolivian Altiplano, reveals significant interannual variations in both pollen concentration and composition. The pollen assemblages within the annual layers are dominated by typical Altiplano taxa, especially Poaceae and Asteraceae. On an annual basis the pollen concentrations are strongly negatively correlated (Pearson's r = - 0.716) with the Southern Oscillation Index (SOI). Studies from Sajama and other tropical ice caps have shown that during El Nino years, the weather on the Altiplano is decidedly warmer and drier, which enhances ablation on tropical ice caps through increased sublimation. This process results in the concentration of pollen within an annual layer, and thus provides a mechanism to reconstruct past El Nino events, so long as annual resolution is obtainable within the ice core.
Geophysical Research Letters
Reese, C. A.,
Thompson, L. G.
(2007). A Potential Pollen Proxy for ENSO Derived From the Sajama Ice Core. Geophysical Research Letters, 34(9).
Available at: https://aquila.usm.edu/fac_pubs/2009