The Alps: glacial landforms from the Younger Dryas Stadial

The Younger Dryas Stadial was characterized by a sharp cooling after the relatively warm Bølling-Allerød Interstadial. Alpine glaciers responded with a significant advance in the tributary valleys and the development of cirque glaciers. Sets of frontal moraines are ascribed to the Egesen stadial mainly based on their position a few kilometres downvalley from the Little Ice Age moraines and their notably blocky character. Cosmogenic nuclide exposure dates suggest advances already at the very end of the Allerød period, as well as glacier stabilization and moraine build-up into the early Holocene. Maximum extents (Egesen max) were reached early on, followed by reaching of successively smaller extents as the Younger Dryas period progressed. In some regions, rock glacier activity dominated the late Younger Dryas. Calculated Egesen ELAs suggest that in addition to aspect and hypsometry, the ELA depression across the Alps varied markedly depending on precipitation, whose rates show a strong reduction gradient from the margins to the axial sectors of the Alpine range. The landscape was covered by open forests with the treeline lowered to below 1700 m a.s.l.