Atmosphere-cryosphere interactions at 21 ka BP in the European Alps

Evidence that during the Last Glacial Maximum (LGM) glaciers extended well into the piedmont plains is still identifiable in the alpine foreland as a system of well-preserved moraines. Glaciers are strongly controlled by temperature and precipitation, and therefore, they are excellent indicators of climate change. Here, we use a regional climate model (RCM) to investigate some of the physical processes sustaining Alpine glaciers during the last phase of the LGM during Greenland Stadial 2 at 21 ka. We find a predominance of convection during summer and increased southwesterly stratiform precipitation over the southern Alps when compared to pre-industrial (PI) conditions. This precipitation pattern, along with lower temperatures, determined summer snowfall extending to low elevations, with a consequent substantial drop of the equilibrium line altitude (ELA), which is consistent with the estimated LGM glacier extent. Our RCM-based estimates of 21 ka ELA at the LGM yield excellent consistency with Alpine ELA reconstructions, further demonstrating the great potential of this technique for use in palaeoclimate studies.