Placing modern droughts in historical context in the Ohio Valley using tree-rings

The temporal variability and severity of pre-instrument record summer droughts in the Ohio River Valley (Illinois, Indiana, and Ohio, USA) are not well understood. This study attempts to help fill this gap in Ohio Valley drought knowledge by using tree-ring chronologies from Illinois, Indiana, and Ohio to reconstruct summer (June through August) PDSI. We found that recent meteorological droughts of 1988 and 2012 are not unusual in the context of those reconstructed for the interval of 1680–2012. Droughts prior to 1895 (when the instrument-based record began) were more severe and lasted, on average, 1.5 times longer than those after 1895. The North American Drought Atlas represents droughts well for this region, but we found that drought severity was not homogeneous across the three sites. This indicates drought in the Ohio River Valley should be examined at a sub-regional level and suggests a need for a finer spatial representation of tree-ring chronologies in the Ohio Valley. Given the context of historical drought variability, the reconstructions suggest this region should be prepared for droughts that may be more severe and longer lasting than those recently observed.