The Younger Dryas was a sudden cold climate period lasting for about 1100-1300 calendar years during the final deglaciation of the Pleistocene. It interrupted the warm interval of the Allerød period and was followed by the Preboreal period of the Holocene. The Younger Dryas ended around 9600 BC (11550 calendar years BP, occurring at 10000 radiocarbon years BP, a "radiocarbon plateau").

The prevailing theory holds that the Younger Dryas was caused by the shutdown of the Gulf Stream in response to a sudden influx of fresh water from deglaciation in North America. The global climate would then have become locked into the new state until freezing removed the fresh water "lid" from the north Atlantic Ocean.

Although the Younger Dryas had the greatest effect in Europe, it was noted throughout the world including:

Replacement of forest in Scandinavia with glacial tundra (which is the habitat of the dryas plant).

Glaciation or increased snow in mountain ranges around the world.

More dust in the atmosphere, originating from deserts in Asia.

Drought in the Levant, perhaps motivating the Natufian culture to invent agriculture.

The end of the Younger Dryas was very sudden and it has been dated by a variety of methods, with mostly consistent results:

11530±50 BP -- GRIP ice core, Greenland [2]

11530⁺⁴⁰_-60 BP -- Kråkenes Lake, western Norway. [3]

11570 BP -- Cariaco Basin core, Venezuela [4]

11570 BP -- German oak/ pine dendrochronology [5]

11640±280 BP -- GISP2 ice core, Greenland [6]

References and external links

1. http://faculty.washington.edu/wcalvin/teaching/Broecker99.html
2. Spurk et al, Radiocarbon, 40, 1107-1116 (1998)
3. Gulliksen et. al., The Holocene 8, 3 (1998)
4. Hughen et. al., Science v.290 (2000) -- http://www.ngdc.noaa.gov/paleo/pubs/hughen2000/hughen2000.html
5. http://www.pages.unibe.ch/products/scientific_foci/ql_dfg/friedrichabstract.html
6. Alley et al (1993)