Researchers from the University of Arkansas, the Lamont-Doherty Earth Observatory, the University of Arizona, Valdosta State University and the University of Western Ontario will report their findings in an upcoming issue of the journal EOS, Transactions of the American Geophysical Union.
The researchers used drought-sensitive tree ring chronologies that extend back before A.D. 1500 from trees in Western North America, the Southeast and the Great Lakes. They found that dry conditions extended from the Sierra Madre Occidental in Mexico and the Southwest to the Rocky Mountains and the Mississippi Valley throughout the last half of the 1500s. Severe conditions occurred at times in Mexico, the Southwest, Wyoming and Montana, and the Southeast.
Looking back as far as A.D. 1200, no other drought appears to have been as intense, prolonged and widespread as the 16th century megadrought, the researchers found.
Climate varies within a certain envelope, with a drier spell one year and a damp one the next, but in the 1500s "the basement collapsed and went down to another level," said David Stahle, professor of geosciences at the University of Arkansas.
The tree ring records tell of the worst drought in 1,000 years, with an extended period of dryness lasting 40 years in places. Early records from Spanish and English settlements in the Carolinas and Virginia corroborate these findings. You can actually see the correlation between the annual weather variation written Ain archival records and the annual "reports" of the tree rings, Stahle said.
Archival records from the Spanish colony of Santa Elena on Parris Island, S.C., indicate a severe drought from 1566-69. In 1587 -- the year Sir Walter Raleigh's colony on Roanoke Island disappeared -- the Parris Island settlers abandoned their colony. Tree ring records show the year was the region's worst drought in 800 years. |
