PARENT SESSION
Poster Session #22: Paleoecology.
Wednesday, August 8, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
76
1000 year drought records from tree-rings in the Bighorn Basin, Wyoming.
Gray, Stephen 1, Fastie, Christopher2, Jackson, Stephen1, Betancourt, Julio3, Taylor, Kenton1, 1 2 3
ABSTRACT- Understanding how climate can vary over time is an integral part of natural areas management in the Western United States. With its vast areas of public land and agricultural economy, drought related information is particularly important in the Bighorn Basin of Wyoming. Ring-width chronologies from three tree species at six sites surrounding the Bighorn Basin provide 500-1000+ year proxy records of regional drought. These proxy records show that many severe, multidecadal droughts have occurred in the region over the last millennium, and at least three of these events were of greater magnitude than any droughts recorded in the instrumental record. Droughts of the greatest severity tended to be the most widespread, while less severe, short duration (1-2 yr.) events typically occurred at only one or a few sites, or on only one side of the Bighorn Basin. These records also show that such severe droughts are quasi-periodic, returning at ~50 year intervals. An additional chronology from upper treeline records regional temperature. Together, these proxies suggest cool, wet episodes during the Little Ice Age for the eastern Bighorn Basin and unusual (but not unprecedented) warming during the 20th Century. In the Bighorn Basin, current fire and irrigation policies are based on instrumental (1895-Present) drought records. However, our data indicate that instrumental records do not portray the full range of drought severity and duration we should expect and plan for.
KEY WORDS: drought, climate dynamics, land management