Holocene environmental changes in the Atacama Altiplano and paleoclimatic implications

Abstract

Strengthened summer monsoon brought tropical/continental moisture as far south as 25oS during late-glacial and early Holocene times. Precipitation rates in the Altiplano of the western Andes (24oS) increased to 500 mm yr-1 compared to <200 mm yr-1 today. There is evidence of dramatically decreasing lake levels between 8 400 and about 3 000 yr B.P., and conditions drier than today were established. This arid period was interrupted by low-frequency but heavy storms. The monsoon precipitation belt advanced once again in several stages to its current position (200 mm yr-1 isohyeta at 24oS) around 3 000 yr B.P. The reasons for these changes are not known: the variable circulation in the E-Pacific, teleconnections to the northern hemisphere, environmental changes in the source area of the moisture (i.e. tropical continent), or internal forcing due to changes in the radiation budget of the Altiplano are considered as possible explanations.