HR: 0800h
AN: PP31A-1499    [Abstracts]
TI: Abrupt Millennial Climate Change in the Arizona Desert Inferred From a Speleothem Isotopic Record
AU: * Wagner, J D
EM: jwagner@geo.arizona.edu
AF: Dept. Geosciences, Univ. of Ariozna, Tucson, AZ 85721
AU: Cole, J E
EM: jcole@geo.arizona.edu
AF: Dept. Geosciences, Univ. of Ariozna, Tucson, AZ 85721
AU: Cole, J E
EM: jcole@geo.arizona.edu
AF: Dept. Atmospheric Sciences, Univ. of Arizona, Tucson, AZ 85721
AU: Beck, J W
EM: wbeck@physics.arizona.edu
AF: Accelerator Mass Spectrometry Facility, Dept. of Physics, Univ. of Arizona, Tucson, AZ 85721
AU: Patchett, P J
EM: patchett@geo.arizona.edu
AF: Dept. Geosciences, Univ. of Ariozna, Tucson, AZ 85721
AU: Henderson, G M
EM: Gideon.Henderson@earth.ox.ac.uk
AF: Dept. of Earth Sciences, Univ. of Oxford, Oxford, OX13PR United Kingdom
AB: Although the desert southwest is among the most climatically marginal regions of North America, it lacks well-constrained, continuous climate records over the last glacial cycle. Speleothems commonly preserve long, continuous, high-resolution climate records, and can be precisely dated using U-Th disequilibrium. We present the first such record from a stalagmite from Cave of the Bells (elev. 1700 m), southeast of Tucson, Arizona. High resolution(~20-150 yr) δ¹⁸O data from a sample spanning ~8-54 ka reveal substantial isotopic changes that closely mirror events recorded in Greenland ice cores. We observe a stepwise deglacial shift (with dramatic changes occurring in less than 100-300 years) of 4.5‰ mirroring the Bolling-Allerod-Younger Dryas. The isotopes indicate that the glacial maximum and Younger Dryas were cold/wet relative to the Bolling-Allerod and early Holocene. In the early part of the record (30-54 ka), millennial δ¹⁸O variations of 1-2.5‰ are similar to Dansgaard-Oeschger events, with stadials cooler/wetter than interstadials. Nearly continuous U-Th dating provides precise ages of these events, which agree with previous speleothem work and suggest refinement of initial ice core chronologies. In contrast to previous work on SW caves, we observe no relationship between growth rate and climate. Our results support a link between tropical Pacific and North Atlantic millennial variability. In the modern southwest, El Niño events bring wetter winters (~50% of modern annual precipitation occurs in winter, and winter precipitation dominates the modern cave water supply). Marine records from the Pacific indicate more El Niño-like conditions during the LGM and stadials when we observe cooler/wetter conditions in southern Arizona. Speleothem records from China and Oman indicate weaker monsoons, which today are associated with El Niños, during stadials. This record contributes to understanding the spatial extent and timing of millennial climate fluctuations, which is crucial to determining the forces that drive them.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1105 Quaternary geochronology
DE: 1120 Isotopic disequilibrium dating
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 9350 North America
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005