Surface mineralogy and hydrological controls on “hotspots” of dust emission at Etosha Pan, Namibia

Ephemeral lake beds are globally significant sources of atmospheric mineral dust aerosols, yet emissions from these landforms exhibit considerable spatial and temporal variability. The complex interactions between climatic drivers and surface properties that govern dust emissions remain poorly understood, contributing to uncertainties in model predictions of atmospheric dust concentrations and their global effects. In this study, we used multitemporal satellite remote sensing combined with model reanalysis data from 2018 to 2022 to investigate the mineralogical, hydrological, and climatic controls on dust emission “hotspots” at Etosha Pan, Namibia. A record of dust source locations derived from MODIS and MSG-SEVIRI observations was used to identify spatially discrete clusters (hotspots) of recurrent dust emission. Surface mineral composition at these sites was analyzed through linear spectral unmixing of Landsat 8–9 Operational Land Imager data to estimate the relative abundance of evaporite and clay mineral endmembers, with results validated against X-ray diffraction analyses of field-collected sediment samples. Our findings indicate that dust emission hotspots are associated with the formation of evaporite crusts, produced by salt efflorescence following wet-season precipitation and ephemeral flooding. Strong winds during the dry season can disrupt these crusts, exposing large quantities of fine sediments that are extremely susceptible to aeolian entrainment. These results highlight the critical role of surface crust mineralogy, influenced by hydrological history, in controlling dust emission dynamics. This approach provides a transferable framework for identifying and characterizing hydrological and mineralogical controls on dust source regions in other dryland playa environments, with potential applications for improving regional and global dust emission modeling.