Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic

Michèlle Van Der Does, Laura F. Korte, Chris I. Munday, Geert Jan A. Brummer, Jan Berend W. Stuut

Research output: Contribution to JournalArticleAcademicpeer-review

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.

LanguageEnglish
Pages13697-13710
Number of pages14
JournalAtmospheric Chemistry and Physics
Volume16
Issue number21
DOIs
Publication statusPublished - 4 Nov 2016

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particle size
dust
transect
summer
settling velocity
dust storm
intertropical convergence zone
winter
climate
ocean
sediment trap
regional climate
global climate
climate modeling
spatial variation
grain size
seasonal variation
wind velocity
atmosphere
mineral

Cite this

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title = "Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic",
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.",
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Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic. / Van Der Does, Michèlle; Korte, Laura F.; Munday, Chris I.; Brummer, Geert Jan A.; Stuut, Jan Berend W.

In: Atmospheric Chemistry and Physics, Vol. 16, No. 21, 04.11.2016, p. 13697-13710.

Research output: Contribution to JournalArticleAcademicpeer-review

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