ES-07. Aridification of the United States Northern Great Plains during the 21st Century

Abstract
Climate projections for the United States Northern Great Plains by mid-late 21st century are examined from a large ensemble of 40 climate modeling experiments (CESM1-LENS) to understand changes in atmospheric evaporative demand, evaporative fluxes and soil moisture at monthly timescales. The results show that despite significant increases in annual precipitation, particularly in winter and spring, the region experiences aridification during much of the growing season, with substantial moisture deficits occurring between June and October. The aridification is a result of high temperatures, longer growing season, and greater evaporative losses. From July through September, the aridification is however even more severe when the region experiences unprecedented (relative to historic) levels of soil moisture deficits because of decreasing trends in summer rainfall. This aridification facilitates a heightened risk for extreme droughts in summer and fall for the Northern Great Plains region, along with a six-fold increase in the occurrence of drought conditions that the US Drought Monitor currently classifies as “Extreme”. The poster will also present recent trends in drivers and indicators of aridification in the observed record.