Projected changes in early summer ridging and drought over the Central Plains

Abstract

Early summer (May-June-July; MJJ) droughts over the Central Plains are often caused by atmospheric ridging, but it is uncertain if these events will increase in frequency or if their influence on drought severity will change in a warming world. Here, we use tree-ring based reconstructions (1500-2020 CE) of MJJ ridging and 0-200 cm soil moisture with six CMIP6 model ensembles to investigate the response of Central Plains drought dynamics to a moderate warming scenario (SSP2-4.5). By the end of the 21st century (2071–2100), precipitation increases in most models during the preceding months (February-March-April), especially over the northern part of the Central Plains, while changes during MJJ are non-robust. By contrast, vapor pressure deficit increases strongly in all models, resulting in five of the six models projecting robust median soil moisture drying and all six models projecting more rapid seasonal soil moisture declines during the transition into the summer. Major ridging events increase in frequency in some models, and there is strong agreement across all models that when ridging events do occur, they will cause more severe soil moisture drought and seasonal drying at the end of the 21st century. The median multi-model response also indicates, by the end of the 21st century, that the Central Plains will experience a 3-fold increase in the risk of drought events equivalent to the the most extreme droughts of the last 500 years. Our results demonstrate that even moderate warming is likely to increase early summer soil moisture drought severity and risk over the Central Plains, even in the absence of robust precipitation declines, and that drought responses to major atmospheric ridging events will be significantly stronger.

Aquifer depletion exacerbates agricultural drought losses in the US High Plains

“…An important implication of our findings is that depletion of groundwater resources is likely to increase significantly the vulnerability of agricultural production to current and future drought risks. Climate change is projected to increase the frequency and severity of extreme drought events in many parts of the world [Ukkola et al, 2020, Chiang et al, 2021, Cook et al, 2020, including in parts of Kansas and Texas [Bradford et al, 2020, Cook et al, 2022, Mullens and McPherson, 2019 where the High Plains Aquifer continues to experience prolonged and significant declines in saturated thickness [Scanlon et al, 2012, Cotterman et al, 2018. Similar trends of increasing drought risks coupled with declining aquifer storage have been reported in other major groundwater irrigated farming systems worldwide [Wada et al, 2010, Döll et al, 2014, Famiglietti, 2014, Feng et al, 2018, Bierkens and Wada, 2019.…”