Humans and Younger Dryas: Dead end, short detour, or open road to theHolocene?

摘要

Dryas octopetala: the mountain avens, an arctic or alpine tundra plant in the rose family. Its repeated appearance in pollen spectra in southern Scandinavia late in the Last Glacial signaled cold climatic conditions even after the post-Last Glacial Maximum (LGM) retreat of the ice sheet from this region of NW Europe. This flower gave its name to three pollen zones during the convulsive last few millennia of the Pleistocene, as it appeared with deglaciation, then twice again as woods gave way to tundra in areas that-despite upper-middle latitude locations-are now wooded and relatively temperate, thanks to the interglacial Gulf Stream. Although currently perhaps being superseded by nomenclature from the Greenland ice cores, the names Oldest, Older and Younger Dryas (sometimes known as Dryas I, II and HI) have come indelibly to signify cold and tundra, while Belling, Allerad and Preboreal are indicative of warming and forest expansion, all within a roughly 9000 calendar year period between ca.