Evidence of an LGM cooling in NW-Argentina (22°S) derived from a glacier climate model

Abstract

A climate glacier model is used to interpret late Pleistocene maximum glaciations in the NW-Argentinan Andes (22°S). According to the model, massive cooling combined with a moderate precipitation increase is necessary to explain maximum glacier extension. Even given a factor of 2–4 precipitation increase, the model indicates that temperatures must have been lowered by 4.5–8°C, suggesting that maximum glaciation probably occurred during full glacial times of MIS 2 (25–18 ka). This conclusion is supported by dated proglacial lake sediments and evidence of past glacial geometry. The extremely long tongues and low accumulation area ratios indicate that ablation was reduced during cold periods in agreement with the model. A strong relationship exists between glacier geometry and prevailing climate. Contrary to the precipitation-controlled Late Glacial (12–10 ka) maximum glaciation of the arid Central Andes in southern Peru and northern Chile, the glaciations on the much more humid eastern Andean slope are mainly controlled by temperature and therefore reached their maximum extent during the MIS 2 cold conditions.