THE EQUILIBRIUM LINE ALTITUDE (ELA) IN THE SOUTHERN FRINGE OF THE ALPS DURING THE LAST GLACIAL MAXIMUM

Glacier Equilibrium Line Altitudes (ELAs) are important palaeoclimatic proxies in mountainous regions and can be used to obtain quantitative information on precipitation and the atmospheric circulation during past glaciations. This thesis presents a comprehensive reconstruction of the ELA along the southern fringe of the European Alps during the Last Glacial Maximum (LGM). The reconstruction is based on geomorphological mapping of glacial landforms and sediments related to marginal glaciers that throughout the LGM remained isolated from the Alpine Ice Field. Chronological control is provided through surface exposure dating of 25 erratic boulders at several sites. The exposure ages indicate that marginal glaciers had reached their LGM position by ca. 24 ka and that a glacier readvance occurred between 20.5 to 19 ka, at the end of the LGM. This is synchronous to chronologies from major Alpine outlet glaciers suggesting that marginal glaciers responded to the same climatic forcing as did larger glacial systems. The reconstructed palaeoglacier ELAs are as low as 1100 m a.s.l. in the Julian Prealps (south-eastern Alps) and as high as almost 2000 m a.s.l. in the Maritime Alps (south-western Alps). The distinct East-to-West increase in ELAs primarily reflects a precipitation gradient that prevailed along the southern Alpine fringe during the LGM. Precipitation is estimated to have been between 1600 and 2100 mm/yr, which for most sub-sectors of the Alps is similar to present-day mean annual precipitation. The evidence of a wet LGM in the southern Alps is in line with other proxy data and glacier-climate models that have inferred an increased moisture supply to the southern Alps as a result of a south-ward displacement of the polar front after the growth of the Northern Hemisphere ice sheets. Palaeogeographic changes on a regional scale likely determined the way in which this moisture was distributed across the southern face of the Alps. The results of this thesis highlight the sensitive responses of marginal LGM glaciers to climatic changes on both global and regional scales and may serve as ground control for future glacier-climate modelling efforts.