Last Lateglacial glacier advance in the Gran Paradiso Group reveals relatively drier climatic conditions established in the Western Alps since at least the Younger Dryas

Abstract

The Late Pleistocene to Holocene transition in the Northern Hemisphere was characterized by abrupt millennial-scale climatic changes testified in the Alpine Chain by proxy records derived from glacial landforms and deposits. A detailed reconstruction of the paleo-glaciers during the deposition of the pre-Little Ice Age (LIA) moraines and newly obtained 10Be exposure ages provide information on the timing of a glacier advance in the Gran Paradiso Group (Western Alps, Italy) related to the regional Egesen stadial as a response to the climatic deterioration at around 12.9–11.7 ka (corresponding to the Younger Dryas in northern Europe and to the Greenland stadial 1 in the INTIMATE event stratigraphy). The study area represents a key site to define the behaviour of the Egesen paleo-glaciers, since they are located in a significant climatic area between the moister Maritime Alps and the Northern Alps. The ELA reconstructions and the comparison with other Alpine sectors provide evidence that current relatively drier conditions in the area postdate the LGM and were already present during the Egesen stadial. Our results support a strong positive YD Arctic Oscillation index, which led to drier conditions in southern Europe and caused negative winter precipitation anomalies.