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Transatlantic fluxes of Saharan dust: changing climate through fertilising the ocean? (DustTraffic)
Date du début: 1 oct. 2012, Date de fin: 30 sept. 2017 PROJET  TERMINÉ 

Massive amounts of dust (~1 Billion Ton) are blown from the Sahara into and over the Atlantic Ocean every year. This dust strongly alters the atmosphere through blocking incoming solar radiation [cooling the atmosphere] and trapping outgoing heat that was reflected at the earth’s surface [warming the atmosphere]. In addition, aerosols carry huge amounts of metals and nutrients that can boost marine life, but also vast amounts of microbes, spores, and pathogens that are harmful for both marine- and terrestrial (including human!) life. The net effect of cooling/warming and ocean fertilisation/poisoning is presently far from understood as it depends on a complex set of parameters related to dust emission, dispersal, and deposition. In order to quantify these parameters, I propose to develop and apply a novel approach to study the transatlantic flux of Saharan dust and its environmental effect on the ocean by deploying a transect of seven ocean moorings with a dust-collecting surface buoy below the Saharan dust plume from NW Africa to the Caribbean. Sampling dust in air as well as under water at a biweekly resolution for initially one complete year will for the first time allow to: 1) quantify the seasonal variability in Saharan dust export into the Atlantic, 2) distinguish between high-altitude summer plumes versus low-level winter trade-wind transport, 3) quantify source-to-sink changes in particle size and the related (metal, nutrient, and biological-) composition of the dust, and 4) determine the in situ bio-availability of the associated nutrients and their potential fertilisation of the photic zone. These unique, seasonally and spatially resolved data will bridge the gap between the bi-weekly sediment-trap record off Cape Blanc (NW Africa, since '85) and the daily dust fluxes recorded on Barbados (Caribbean, since '73). Subsequently, the data can be extrapolated back in time in marine sediments, which are an archive for dust transport and carbon pump in the past.