Abstract
The interpretation of the isotopic composition of Andes tropical mountain glaciers is reconsidered using a simple Rayleigh distillation model. It is shown that Andes snowline depression and Huascaran ice core δ18O are consistent with a 3°C drop in sea surface temperature during the Last Glacial Maximum, accompanied by an increase from 40% at present to 60% during the LGM in the annual mean proportion of atmospheric water lost to continental runoff. Broecker's interpretation of Huascaran δ18O as a paleo‐hygrometer is discussed.