THE SENSITIVITY OF THE SOUTH CHILEAN SNOWLINE TO CLIMATIC-CHANGE

Inferred climatic changes in southern Chile during the Last Glacial Maximum are modelled to investigate the role of the southern Westerlies on the region's glacial history. This is accomplished with a numerical model of the surface energy balance which derives glacial mass balance profiles from existing climatic stations. This provides an independent measure of the regional snowline which is compared with palaeoecological evidence of former snowlines. The modelled snowline mirrors the latitudinal trend of current glacier equilibrium line altitudes. It is most sensitive to temperature changes in regions with high precipitation (46-degrees-50-degrees S) and to precipitation changes in regions with lower precipitation totals (south of 50-degrees and north of 40-degrees). This differential sensitivity with latitude implies that glacial expansion in the region depends on a delicate interplay between cooling induced by the equatorward movement of the oceanic Antarctic Polar Front and access to precipitation comparable to or greater than that of today. The main conclusion is that glacial expansion in southern Chile is associated with the migration of the southern Westerlies towards the equator. The importance of migrating precipitation belts in permitting glacier growth carries the implication that maximum depression of the snowline is unlikely to have been contemporaneous from latitude to latitude.