Alpine Younger Dryas glaciers as palaeo-precipitation gauges

Abstract

AbstractMoraines of the Younger Dryas ˚Egesen Stadial", which are widespread features in the Alps, are a valuable terrestrial data source for quantitative palaeoclimatic studies. The depression of the early Younger Dryas (Egesen-I) equilibrium-line altitude (ELA) shows a distinct spatial pattern. It was greatest (about –450 to –500 m vs present day) m areas exposed towards the west and northwest. In the central, more sheltered valleys it was on the order of –300 m or less. Summer temperature depression, which can be derived from the Younger Dryas timberline depression, was on the order of –3.5 K. The stochastic glacier-climate model of Ohmura and others (1992), which relates summer temperature and precipitation at the ELA, is used to infer precipitation change. Results are compared with those obtained from the glacial-meteorological approach of Kuhn (1981a). The two models produce highly similar results. During the early Younger Dryas, climate in the central valleys of the Alps seems to have been considerably drier than today In areas open to the west and northwest, precipitation seems to have been the same as today or even slightly higher. These results, which are based on a rather dense network of data points, agree well with results from permafrost-climate studies and the more qualitative information from palaeobotanical research. They also support the results from atmospheric general circulation models for the Younger Dryas in Europe, which point towards a more zonal type of circulation.