Flood variability in the common era: a synthesis of sedimentary records from Europe and North America

ABSTRACT Heavy precipitation events increased over the last century in response to higher atmospheric temperature and associated increases in water vapor content, but little evidence shows that increased heavy precipitation changed flood trends. Short records, containing few extreme flood observations, limit statistical examination of relationships between global temperature, heavy precipitation, and extreme floods. We synthesized European and North American sediment-based paleoflood records extending through at least 900 CE. These records captured flood variability during the warmer Medieval Climate Anomaly (MCA) and cooler Little Ice Age (LIA). Twelve paleoflood chronologies chosen for the analysis suggest an increase in flood frequency since 1000 CE. The largest magnitude floods mostly occurred between 1000 and 1300 CE after peak MCA temperature during a relatively drier overall climate regime. The association found between large magnitude floods during a drier climate may be explained by increased atmospheric water vapor capacity from warmer temperatures that intensified precipitation events. Despite limitations in the number of studies available, extreme flood observations reveal a pattern of large magnitude floods in the late MCA and frequent floods in the LIA. Therefore, temperature–precipitation relationships may influence flood variability, and flood magnitude will likely become more extreme as global temperatures rise.