Late-Holocene flooding and drought in the Northern Great Plains, USA, reconstructed from tree rings, lake sediments and ancient shorelines

摘要

During the AD 1990s the Waubay Lakes complex in eastern South Dakota experienced historically unprecedented high water levels. Property damage from this flooding led to an examination of the occurrence of past pluvial episodes and their relation to climate. A lOOO-year hydroclimate reconstruction was developed from local bur oak (Quercus macrocarpa) tree-ring records and lake-sediment cores. Analysis of lake shoreline and drainage features provides late-Quaternary geomorphic context for this high-resolution record. Tree-ring width and shell geochemistry of the ostracode Candona rawsoni show marked coherence, indicating synchronous responses to moisture balance in vegetation and lake salinity; geomorphic evidence suggests buffering of lake-system expansion during pluvial periods by evaporative dynamics. Pluvial periods display a recurrence frequency of approximately 140-160 years over the past millennium. Prior to AD 1800, both lake highstands and droughts tended towards greater persistence than during the past two centuries. Frequency and timing of hydroclimatic oscillations show strong similarities to records from other sites in the Northern Great Plains (NGP) of North and South Dakota, and incomplete coherence with records of southern Manitoba.