The southern Kalahari as a dust source: Results from the field

Abstract:

The Kalahari encompasses one of the largest drylands in the Southern Hemisphere and it is a potentially large source of atmospheric dust in its relatively low-dust region. The severe iron depletion in the southern Indian and Atlantic Oceans, the ocean basins that receive much of the Kalahari dust, suggests that even incremental increases in dust export to these basins could have significant impact on ocean productivity. The Kalahari also provides an excellent 'natural laboratory', due to its consistent Kalahari Sands existing along a strong precipitation gradient (from ~850 mm in southern Zambia to ~150 mm in southwestern Botswana) with a range of different land uses and land use intensities.

A large-scale field campaign to evaluate the potential of the southern Kalahari to produce atmospheric dust was established in August, 2013. The goal of the experiment is to evaluate the potential of climate change and land-use to contribute to dust production. The experiment includes measurement of horizontal flux, vegetation structure, and meteorological variables. Novel estimates were made of dust production efficiency (vertical flux produced per unit of horizontal flux) through the coordinated use of active aerosol samplers and passive horizontal sediment traps. In addition, a new stereophotographic method for the estimation of wind-relevant vegetation parameters has been developed for this project.

Our field data and modeling results indicate that land use and climate can have a significant impact on the potential for dust emission from the region, but new field estimates of dust emission efficiency and chemistry suggest that the absolute magnitude of dust emitted from the region might, at present, be lower than previously thought.