Hydroclimate and ENSO variability recorded by oxygen isotopes from tree rings in the South American Altiplano

However, past precipitation changes are poorly constrained due to limited observations and high-resolution paleoproxies. We found that summer precipitation and the El Nino-Southern Oscillation (ENSO) variability are well registered in tree-ring stable oxygen isotopes (delta O-18(TR)) of Polylepis tarapacana in the Chilean and Bolivian Altiplano in the Central Andes (18-22 degrees S, similar to 4,500 m a.s.l.) with the northern forests having the strongest climate signal.

More enriched delta O-18(TR) values were found at the southern sites likely due to the increasing aridity toward the southwest of the Altiplano. The climate signal of P. tarapacana delta O-18(TR) is the combined result of moisture transported from the Amazon Basin, modulated by the SASM, ENSO, and local evaporation, and emerges as a novel tree-ring climate proxy for the southern tropical Andes.