Variable Oceanic Influences on Western North American Drought Over the Last 1200 Years

Cool conditions in the eastern tropical Pacific often bring drought to western North America on interannual timescales. Recent syntheses of available paleoclimate records suggest that past intervals of persistent ‘megadrought’ may have also been due to a cool eastern tropical Pacific, but the strength of such conclusions is limited by a dearth of sea surface temperature (SST) records. We use a new 1200-year record of eastern equatorial Pacific (EEP) SST to explore the context of past megadroughts in western North America. We find that most droughts occurred when EEP SST was below its 20th century mean, with the strongest and longest droughts of the past 1200 years occurring during the period of coolest EEP SST. However, droughts from AD 855–887, 943–1042, and 1375–1408 occurred during periods of both relatively warmer EEP SST and North Atlantic SST, highlighting the potential diversity of controls on drought in western North America.