Dust‐Drought Nexus in the Southwestern United States: A Proxy‐Model Comparison Approach

Abstract

The U.S. Southwest is naturally prone to dust and drought. With a high risk of unprecedented drought in the future due to climate change, changes in the dust cycle are expected. Whereas paleo records of dust deposition from the region suggest that past megadroughts did not coincide with elevated dust levels, modern studies indicate higher dust during drier conditions. To examine this disagreement, we compare regional paleo records to output from the Community Earth System Model Last Millennium Ensemble experiment. We investigate the role of hydroclimate on dust emissions in the model and analyze how modeled dust during megadroughts compares to all other years. We find that bare ground, as directly modulated by the density of vegetation cover and indirectly by hydroclimate, is the primary control on simulated dust emissions in the Southwest. Furthermore, we find slightly (but significantly) higher dust emission during megadroughts than during years without megadroughts in the model. Using a simple forward modeling approach to assess the impact of age uncertainty in the regional dust records, we find that age uncertainty can explain most of the paleo data/model disagreement. The remaining difference could be related to processes that are not included in the model that inhibit dust emissions during drought, including brown vegetation and soil crusts. Our results suggest the dust‐drought nexus is a continuum and that the impact of drought on dust cycling is subtle.

Effect of spatial and temporal “drought legacy” on dust sources in adjacent ecoregions

“…The dust events in the southwestern New Mexico part of the Chihuahuan Desert showed a similar relationship. Dust sources in region contain many ephemeral wetlands (playas) which become barren lands and hot spots of dust emission with excessive drought (Arcusa et al, 2020; Lee et al, 2009; Li et al, 2018; Rivas, 2019; Rivera Rivera et al, 2010). Playa surfaces are dynamic and sediment availability to wind changes rapidly in response to rainfall, water‐table depth, evaporation rate, and disturbance (Briere, 2000; Scuderi et al, 2010; Tollerud & Fantle, 2014; van Pelt et al, 2020), and thus to drought.…”

Decreasing Trends in the Western US Dust Intensity With Rareness of Heavy Dust Events

“…The negative trends in the spring dust concentrations might be explained by the increasing (decreasing) trends in the precipitation/soil moisture (wind speed) over the regions. Studies on the interannual variability of the seasonal average dust intensity (Achakulwisut et al., 2018; Arcusa et al., 2020) and frequency of high dust events (Pu and Ginoux, 2017) show a strong negative correlation between seasonal dust and drought over the region. However, changes in LULC practices also contribute to the dust trends in the region.…”