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AGU Chapman Conference: Megadrought in Dixieland

DesotoA never-before-seen megadrought made an appearance this morning at the last day of the AGU Chapman Conference. Paul Aharon of the University of Alabama says his latest observations are the first to suggest that drought affected the southeastern United States from about 13,000 to 11,800 years ago – during the so-called Younger Dryas cool period.

The evidence comes from the De Soto Caverns in Alabama. This cave has already offered up rich history of a non-palaeoclimatological kind: it holds a Native American burial ground and an abandoned moonshine distillery from the 1930s, when good-timing Alabamans used to shoot down the stalactites.

Arahon went there to find out how the region’s climate responded to glacial meltwater that poured into the Gulf of Mexico during warm spells at the end of the last glaciation. From oxygen isotopes captured in a De Soto stalagmite, he was able to reconstruct rapid atmospheric responses to certain meltwater pulses. Unexpectedly, however, there was a 1,200-year gap with no new layers during the Younger Dryas.

Aharon says a megadrought is the most likely reason the stalagmite stopped growing. That drought would not have been too early to be felt by humans, he adds: it could explain why megafauna and the prehistoric Clovis culture disappeared from the southeast in the same period.

Anna Barnett

Image: DeSoto Caverns / Flickr user Weedah, Creative Commons license


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