The Equilibrium Line Altitude of isolated glaciers during the Last Glacial Maximum-New insights from the geomorphological record of the Monte Cavallo Group (south-eastern European Alps)

Glacier-based reconstructions of Equilibrium Line Altitudes (ELAs) are important to understand changes of temperature and precipitation over longer time scales and may help to validate regional palaeoclimate models. Here, we present new insights into the ELA in the south-eastern part of the European Alps during the Last Glacial Maximum (LGM, 26.5 to 19 ka), based on the geomorphological record of the Monte Cavallo Group (Venetian Prealps, NE-Italy). This mountain range hosted a glacial system that remained isolated from larger valley glaciers in its vicinity and therefore likely responded very dynamically to changes in climatic boundary conditions. Through detailed mapping of glacial sediments and landforms, we were able to constrain the extent of these palaeoglaciers and model their surface geometry and ELA via semi-automated toolboxes in a geographic information system. In the absence of numerical datings, these landforms were related to an LGM advance through geomorphological and stratigraphical means. In a next step, ELAs were also recalculated for other LGM glaciers in the south-eastern Alps, allowing wider palaeoclimatic conclusions to be drawn. These ELAs are in the range of 1100 to almost 1700 m and show a strong E-W gradient with particular low values in the Julian and eastern Carnic Prealps. This pattern indicates that during the LGM a precipitation gradient existed along the southeastern fringe of the Alps, with moisture being preferentially advected to these mountain ranges while the Venetian Prealps in the West received less precipitation. Based on the reconstructed ELAs, annual precipitation sums during the regional LGM glacier culmination (ca. 25.5 to 23.5 ka) are estimated between 1820 and 2920 +/- 750 mm/yr. Those values are largely compatible with data from modern weather stations and indicate no or little reduction in LGM precipitation as it is reported from other parts of the Alps.