Modern and last local glacial maximum snowlines in the Central Andes of Peru, Bolivia, and Northern Chile

Late Pleistocene snowlines in the central Andes were 500-1200 m lower than at present. Radiocarbon dates imply that the late-Pleistocene glacial maxim um in the region occurred prior to 20 C-14 ka, but lack of maximum limiting ages adds considerable uncertainty to the exact timing. Snowline modeling demonstrates that snowlines in the eastern and western cordilleras of the c entral Andes respond differently to temperature and precipitation changes. In the eastern cordillera, the snowline is near the level of the annual 0 d egrees C isotherm and melting occurs throughout the year. Here snowlines ar e sensitive to temperature changes, but relatively insensitive to accumulat ion changes. In the western cordillera, the snowline rises 1000 higher owin g to increasing aridity, and the snowline exhibits a much stronger sensitiv ity to accumulation changes. The consistent 1200 m snowline depression alon g the eastern cordilleras of the central Andes can be modeled by a mean ann ual cooling of 5-9 degrees C. This is inconsistent with the < 2 degrees C c ooling in tropical sea-surface temperatures suggested by CLIMAP reconstruct ions. The 800-1000 m snowline depression in the western cordillera cannot b e accounted for solely by cooling, but also requires an increase in precipi tation. (C) 1998 Elsevier Science Ltd. All rights reserved.