Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 13697-13710, 2016
http://www.atmos-chem-phys.net/16/13697/2016/
doi:10.5194/acp-16-13697-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
04 Nov 2016
Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic
Michèlle van der Does1, Laura F. Korte1, Chris I. Munday1, Geert-Jan A. Brummer1,2, and Jan-Berend W. Stuut1,3 1NIOZ, Royal Netherlands Institute for Sea Research, Department of Ocean Systems, and Utrecht University, Texel, the Netherlands
2Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
3MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
Abstract. Mineral dust has a large impact on regional and global climate, depending on its particle size. Especially in the Atlantic Ocean downwind of the Sahara, the largest dust source on earth, the effects can be substantial but are poorly understood. This study focuses on seasonal and spatial variations in particle size of Saharan dust deposition across the Atlantic Ocean, using an array of submarine sediment traps moored along a transect at 12° N. We show that the particle size decreases downwind with increased distance from the Saharan source, due to higher gravitational settling velocities of coarse particles in the atmosphere. Modal grain sizes vary between 4 and 32 µm throughout the different seasons and at five locations along the transect. This is much coarser than previously suggested and incorporated into climate models. In addition, seasonal changes are prominent, with coarser dust in summer and finer dust in winter and spring. Such seasonal changes are caused by transport at higher altitudes and at greater wind velocities during summer than in winter. Also, the latitudinal migration of the dust cloud, associated with the Intertropical Convergence Zone, causes seasonal differences in deposition as the summer dust cloud is located more to the north and more directly above the sampled transect. Furthermore, increased precipitation and more frequent dust storms in summer coincide with coarser dust deposition. Our findings contribute to understanding Saharan dust transport and deposition relevant for the interpretation of sedimentary records for climate reconstructions, as well as for global and regional models for improved prediction of future climate.

Citation: van der Does, M., Korte, L. F., Munday, C. I., Brummer, G.-J. A., and Stuut, J.-B. W.: Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic, Atmos. Chem. Phys., 16, 13697-13710, doi:10.5194/acp-16-13697-2016, 2016.
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Short summary
We studied seasonal and spatial variations in particle size of Saharan dust deposition along a transect in the Atlantic Ocean, using an array of moored submarine sediment traps. We show a downwind decrease in particle size, but seasonal changes are also prominent. In addition, the dust is much coarser than previously suggested and incorporated into climate models.
We studied seasonal and spatial variations in particle size of Saharan dust deposition along a...
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