A MULTIPROXY, HIGH-RESOLUTION RECONSTRUCTION OF HOLOCENE CLIMATE AND DROUGHT CONDITIONS FROM KIRMAN LAKE, EASTERN SIERRA NEVADA, CALIFORNIA, USA

During the past century, California has experienced several multiyear drought events. Dendrochronological and pollen evidence suggest that droughts of even greater magnitude and frequency have occurred in this region throughout the past several millennia. In order to better understand past climate conditions, including drought events, we utilized a multiproxy, paleolimnological approach to develop a high-resolution (multidecadal to subcentennial) record of Holocene climate for the eastern Sierra Nevada, California. In July 2000, a 3.1 m sediment core was recovered from Kirman Lake (2,174 m a.s.l.), which is located west of Bridgeport, California. 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 scrub with sparse populations of pinyon pine and western juniper in the catchment. A basal radiocarbon date corresponding to ~10,500 cal yr B.P. confirms that the sediments recovered encompass the Holocene. High-resolution (0.5 cm and 1.0 cm) loss-on-ignition (LOI) analysis and diatom identification and enumeration were performed on the entirety of the core. In addition, distinct bands of clams and mollusks were studied in detail. Finally, isotope analyses were carried out on 22 clam/mollusk and 20 sediment samples from the core. Previously developed Sierra Nevada diatom-inference models for lake depth (R²=0.84, RMSEP_boot=5.6 m) and salinity (R²=0.99, RMSEP_boot=16.25 mg/L) were successfully applied to the Kirman Lake fossil diatom data to quantitatively reconstruct lake depth and salinity values. Collectively, the LOI, diatom, clam, mollusk, and isotope data suggest that the early Holocene was wetter then present, while the mid Holocene was considerably drier. In contrast, the climate of the late Holocene is generally wetter, but is characterized by greater variability. Specifically, multicentennial wet periods are interrupted by multicentennial dry periods. Results from this study provide a continuous, high-resolution record of climate and drought events for California, which might prove beneficial for the long-term management of limited water resources in this region.