NOAA/WDS Paleoclimatology - Steel Lake, Minnesota 3,100 Year Calcite Oxygen Isotope Data

Paleorecords are key for evaluating the long-term patterns and controls of drought. We analyzed calcite in annually laminated sediments from a Minnesota lake for oxygen-isotopic composition (d18O). The d18O record of the past ~3100 years reveals that droughts of greater severity and duration than during the 20th century occurred repeatedly, especially prior to 300 AD. Drought variability was anomalously low during the 20th century; ~90% of the variability values during the last 3100 years were greater than the 20th-century average. d18O is strongly correlated with the index of the Pacific Decadal Oscillation (PDO) during the past 100 years, and periodicities of the late-Holocene d18O record are similar to those of the PDO. Furthermore, time series of d18O and atmospheric D14C are generally coherent after 700 AD. Both the Pacific climate and solar irradiance probably played a role in drought occurrence, but their effects were non-stationary through the late Holocene.