HR: 1340h
AN: PP43A-0600    [Abstracts]
TI: A Holocene Record of Climate Change from the Sierra Nevada, CA, USA: A Paleolimnological Perspective of California Drought
AU: * Moser, K A
EM: katrina.moser@geog.utah.edu
AF: University of Utah Dept. of Geography, 260 South Central Campus Dr. Rm. 270, Salt Lake City, UT 84112-9155
AU: MacDonald, G M
EM: macdonal@geog.ucla.edu
AF: UCLA, Dept. of Geography, 1255 Bunche Hall, Los Angeles, CA 90095
AU: Bloom, A M
EM: ambloom@ilstu.edu
AF: University of Utah Dept. of Geography, 260 South Central Campus Dr. Rm. 270, Salt Lake City, UT 84112-9155
AU: Bloom, A M
EM: ambloom@ilstu.edu
AF: Illinois State University Department of Geography-Geology , Campus Box 4400, Normal, IL 61790-4400
AU: Potito, A
EM: potito@ucla.edu
AF: UCLA, Dept. of Geography, 1255 Bunche Hall, Los Angeles, CA 90095
AU: Porinchu, D F
EM: dporinch@csulb.edu
AF: Ohio State University Dept. of Geography, 1036 Derby Hall 154 North Oval Mall, Columbus, OH 43210
AB: Drought has had disastrous impacts on western North American ecosystems, economies and society, and for many regions is predicted to be a likely consequence of future climate change. The instrumental record, however, spans too short a period to provide the full range of drought variability (including frequency, duration and magnitude), which is critical information to anticipate and prepare for future drought events. Paleolimnology provides a means to reconstruct long-term (1000s of years) climate records from which to determine drought variability. Here we present a Holocene drought record from the eastern Sierra Nevada, CA, USA, and compare this record to similar records from western North America in order to explore spatial variability of Holocene drought. A 3.1 m sediment core was retrieved from Kirman Lake (2,174 m a.s.l.), located west of Bridgeport, CA. At present, Kirman Lake is a relatively small (11.9 ha), shallow (3.8 m), slightly alkaline (pH=7.6), freshwater (salinity=92.7 mg/L), oligotrophic (TP=13.9 μg/L) lake with no inflow and only seasonal outflow. Vegetation surrounding the lake is dominated by sagebrush with some pinyon pine and western juniper in the catchment. Diatoms were identified and enumerated every ~1cm for the top 256cm, which provides a chronological resolution of between 18 to 99 years per sample. Robust diatom-inference models for lake depth and salinity were developed from a 60-lake calibration data set from the Sierra Nevada and applied to fossil diatoms identified in the Kirman Lake sediment core. Results indicate that between ~8,000 and ~3,000 calendar years B.P. conditions were considerably drier than present. A dramatic change in effective moisture (precipitation-evaporation) occurred at approximately 3,000 calender years B.P., when conditions became generally wetter, but also more variable. These conditions have continued to the present. Isotope and mollusc data from the same Kirman Lake core support this interpretation, as do charcoal records from nearby lakes. The striking change in drought conditions at ~3,000 years is approximately coincident with changes in the frequency of El Ni\~{n}o events. The Kirman Lake record is compared to similar records from western North America, and the spatial variability of this change provides clues to the possible forcing mechanisms driving this change.
DE: 3344 Paleoclimatology
DE: 1812 Drought
DE: 1600 GLOBAL CHANGE (New category)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting