Great Plains storm intensity since the last glacial controlled by spring surface warming

Mesoscale convective systems (MCSs) supply a substantial portion of warm-season rainfall to the Great Plains of North America, and they are responsible for severe weather and flooding across the central United States. However, little is known about past behaviour and long-term drivers of these systems, limiting our ability to predict future extreme weather patterns in this region. Here, we generate a 20,000-year-long multiproxy record of storm intensity and hydroclimate variability from central Texas in the southern Great Plains and use transient climate model simulations to diagnose the dynamics of reconstructed changes in the climate of this region. We find that southern Great Plains storm intensity responded dynamically to external forcings associated with glacial boundary conditions and orbital forcing via changes in seasonal land surface warming. Springtime land surface warming steepens the zonal pressure gradient, producing an intensified southerly Great Plains low-level jet, enhancing southerly moisture transport and increasing springtime MCS intensity. Climate models predict a strengthening of the low-level jet in response to future warming, which our study suggests will lead to enhanced MCS activity and an increase in extreme weather across the Great Plains.