Circumglobal transport of aerosolic dust has been traced through radioactive debris, biological material, filtration of air, and oxygen isotope abundance measurements in quartz isolated from dust and from soils and sediments identified as having dust origin. Accretion rates are on the order of a m 106 yr-1 in Recent times but may have been 100 times as rapid during the Pleistocene. Solar heating in arid areas causes a deep layer of mixing. Dust on the order of 600 μg m-s of air, reaching altitudes of 4 to 10 km, can effect diabatic cooling of the mid-troposphere, and possibly increase subsidence and aridity. A strong momentum source is supplied by large-scale cyclonic storms. Descending air enters the mixed volume, producing gusts of strong wind at the ground which break up larger soil aggregates into silt-sizes that are easily transported. Vertical fluxes of soil material during dust storms reach the order of 10 μg cm-2 sec-1. The intensifying pressure gradient moves the dusty air northeastward in the Northern Hemisphere with great speed. For example, Asian dust borne across the Gulf of Alaska, deflected southward along the western boundary of North America, can supply some dust to the Trade Winds reaching Hawaii. Over-grazing of vegetation in arid areas and animal traffic increase dust production. The global significance of aerosols to world climate and to sequestering of air-borne radioactive elements adds impetus to further investigation.
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