Modeling modern and Late Pleistocene glacio-climatological conditions in the north Chilean Andes (29-30° S)

An empirical-statistical climate-glacier model is used to reconstruct Late Pleistocene climate conditions in the south-central Andes of northern Chile (29-30degrees S). The model was tested using modern climate data and the results compare favorably with key glaciological features presently observed in this area. Using several glaciers at 29degrees S as case studies, the results suggest an increase in annual precipitation (Delta P = 580 +/- 150 mm, today 400 mm), and a reduction in annual mean temperature (Delta T = -5.7 +/- 0.7 degrees C). These data suggest full glacial LGM (Last Glacial Maximum) conditions for the maximum glacier advances at 29degrees S, a scenario that is asynchronous with the timing of maximum advances north of the Arid Diagonal (18-24degrees S) where late-glacial climate was moderately cold but very humid.The reconstructed case study glaciers at 29degrees S do not allow conclusions to be drawn about the seasonality of precipitation. However, comparison with regional paleodata suggests intensified westerly winter precipitation and a stable position for the northern boundary of the westerlies at similar to27degrees S. However, the meridional precipitation gradients were much steeper than today while the core area of the Arid Diagonal remained fixed between 25-27degrees S.