Paper No. 125-7
Presentation Time: 2:30 PM-6:30 PM
EVIDENCE FOR A NORTHERN DUST BOWL: HEIGHTENED WIND EROSION AND DUST SOURCES DURING THE 1930S IN THE NORTHERN GREAT PLAINS, USA
The 1930s Dust Bowl Drought was a widespread environmental catastrophe that caused large-scale soil erosion and dust storms across the Southern Great Plains (SGP), U.S. In contrast, the Northern Great Plains (NGP) has been largely overlooked as a region affected by the Dust Bowl despite incidental evidence for severe soil erosion and drought conditions. This study compiles climatic data and observations on land surface conditions, archived dust storm accounts, and agriculture census reports for South Dakota during the 1930s that underscore the severity of drought conditions in the NGP. Documented is heightened dust storm activity, severe wind erosion, and multi-year drought conditions. PI-SWERL measurements of PM10 dust flux from analogous soils in South Dakota emphasize the susceptibility of NGP soils to erosion based on recorded dust storm windspeeds of > 20 m/s during the drought. These extreme climate conditions and multi-day dust storm occurrences in South Dakota are associated with a dynamic high-pressure ridge over the northwestern U.S. and adjacent southern Canada, creating strong northwesterly winds across the NGP that exceed threshold velocities for aeolian sand entrainment. These synoptic conditions are associated with a reversal of the atmospheric pressure gradient with air flow from the NW to SE. This weakened the Great Plains Low Level Jet and provided little to no penetration of moisture from the Gulf of Mexico, leading to record-breaking drought conditions and widespread dust storms in the NGP. Peak dust storm years and drought occurrence in South Dakota were out-of-phase with peak years of Dust Bowl conditions in the SGP. This evidence suggests a “Northern Dust Bowl” occurred as a separate landscape-scale response to severe climate variability in the 1930s, independent of the well-known Dust Bowl of the SGP.