People do not usually consider the northeastern United States to be a drought-prone region, but new evidence shows that mega-droughts have occurred there in the past. Dorothy Peteet of Columbia University and NASA's Goddard Institute for Space Studies reported at the AGU Fall Meeting in San Francisco, Calif., on her analysis of sediment cores in marshes in New York State. Different chemicals flow into a marsh from freshwater upriver and from saltwater from the ocean; higher concentrations of bromine and calcium, which are more common in saltwater, indicate a drier period. The data indicate that at least three mega-droughts occurred in the past 6000 years, the longest during what scientists term as the “Medieval warm period,” which lasted from about 850 C.E. to 1350 C.E. “People don't think of this area as threatened by droughts because we've been in a wet period,” Peteet said.