Late Pleistocene Climate and Water Budget of the South American Altiplano

Abstract

Geomorphic evidence from the Peruvian-Bolivian Altiplano indicates that during episodes prior to 28,000 and around 12,500-11,000 yr B.P., lakes covered an area about six and four times as large as at present, respectively. Within the constraints of the heat and water budget, model calculations are used to estimate the precipitation rate that would allow hydrologic equilibrium. On this basis it is suggested that rainfall on the Altiplano during the episodes of enlarged lakes was, respectively, some 300 and 200 mm annum⁻¹ larger than at present, representing increases of about 75 and 50%, respectively. Field evidence suggests that the episodes of enlarged lakes on the Altiplano may have preceded or coincided with periods of maximum glaciation in the neigh-boring Andes. In this region with high elevation of the ice equilibrium line, increased precipitation is particularly conducive to glaciation.