Eolian dust along the eastern margins of the Atlantic Ocean

Eolian dust has been collected from the marine atmosphere of the major wind systems along the eastern margins of the Atlantic Ocean between c. 27°N and c. 34°S. The dust-loadings decreased in the order; northeast trades (average 57 μg m −3 of air) > variable winds of the Intertropical Convergence Zone (average, 0.23 μg m −3 of air) > southeast trades (average, 1.14 μg m −3 of air) > South Atlantic southerly winds (average, 0.07 μg m −3 of air). The dust-loadings reflect the soil characteristics and local meteorological conditions of the adjacent land masses, and it is shown that the Sahara Desert in West Africa has a much greater effect on the dust content of the northeast trades, than the Namib Desert of Southwest Africa has on the dust content of the southeast trades. The < 2 μm clay mineralogy of the dusts has been compared to those of source-area soils and deep-sea sediments. Several important trends have been established: chlorite has only a small variation with latitude; illite decreases towards low latitudes; kaolinite increases in equatorial areas; no specific trends are apparent in the distribution of montmorillonite. The distribution of chlorite, illite and kaolinite in the dusts is similar to that in deep-sea sediments, and reflects the soil clay mineralogy of the adjacent land areas. Eolian dust falling out from the northeast trades can make a significant contribution to the land-derived suspended material in the upper layers of the underlying sea water. However, fallout from the major winds in the South Atlantic Ocean makes up ⪡ 1% of the total land-derived material in the underlying waters.