Saharan dust transport over the North Atlantic Ocean
The Sahara Desert is one of the major sources of atmospheric mineral dust that is transported long distances. The westward transport is discussed by means of a two-dimensional, steady-state transport model and measurements in surface air across the North Atlantic. The model is based on the specific flow conditions for this area and considers sedimentation and turbulent diffusion of dust particles. During preferential transport above the trade wind inversion layer, the aerosol is strongly depleted of particles with r > 1 μm within 1,000 km from the source. Particles with 0.1 μm ⩽ r ⩽ 1.0 μm are only inappreciably removed from the dust plume. Actual mineral aerosol mass concentrations and size distributions seem to be approximated best by the model when one assumes a power-law size distribution at the source with ν* = 2 for particles with 0.1μm ⩽ r ⩽ 20 μm. Based on this assumption and supported by turbidity measurements, an annual mass budget has been calculated for Saharan dust transported over the North Atlantic for various distances from the source. About 260 × 106 tons of mineral dust per year leave the Sahara westward. Deep-sea sediment data show no basic discrepancy with values predicted by the model.