Possible linkages of late-Holocene drought in the North American midcontinent to Pacific Decadal Oscillation and solar activity

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 (delta O-18). The delta O-18 record of the past similar to 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; similar to 90% of the variability values during the last 3100 years were greater than the 20th-century average. delta O-18 is strongly correlated with the index of the Pacific Decadal Oscillation (PDO) during the past 100 years, and periodicities of the late-Holocene delta O-18 record are similar to those of the PDO. Furthermore, time series of delta O-18 and atmospheric Delta C-14 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.