HR: 11:05h
AN: U42B-04    [Abstracts]
TI: Medieval Drought in the Upper Colorado River Basin
AU: * Meko, D M
EM: dmeko@LTRR.arizona.edu
AF: Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721, United States
AU: Woodhouse, C A
EM: conniew1@email.arizona.edu
AF: Department of Geography and Regional Development, University of Arizona, Tucson, AZ 85721, United States
AB: Paleoclimatic records have consistently identified the Medieval Climate Anomaly (MCA), approximately A.D. 900- 1300, as unusual for the incidence of multi-decadal drought in the western United States. Four newly developed tree-ring chronologies derived from living trees, standing dead trees and logs are examined for evidence of a MCA drought signature in the Upper Colorado River Basin (UCRB). The four chronologies extend to before A.D. 1000, and each has a statistically significant significant linear relationship with annual flow of the Colorado River from 1906 to present (23-48 percent of the flow variance explained). A flow reconstruction based on three chronologies with acceptably high sample depth in the MCA begins in A.D. 762, accounts for 60 percent of the flow variance in the 1906-2003 calibration period, and identifies a drought in the mid-1100s as the most severe multi-decadal drought in the long-term record. Highlights of this inferred drought are 13 consecutive years of below normal flow (A. D. 1143-1155) and a broad window of 62 years (A. D. 1118-1179) with no years of much-above-normal flow. The individual chronologies reveal a spatial pattern of heightened intensity of drought toward the western part of the UCRB, although the drought was also present in the Colorado Rockies. Comparison with other regional paleoclimatic reconstructions from the western United States shows the results are consistent with dry, and probably warm, conditions over the intermountain region. Differences are noted in timing of the mid-1100s drought in the UCRB and epic MCA droughts in the Sierra Nevada of California inferred from tree-ring data and other paleoclimatic evidence. The results emphasize the importance of striving for greater spatial resolution in the paleoclimatic record of drought in western North America.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1812 Drought
SC: Union [U]
MN: 2007 Joint Assembly