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Volume 17, issue 16 | Copyright

Special issue: The Saharan Aerosol Long-range Transport and Aerosol-Cloud-interaction...

Atmos. Chem. Phys., 17, 10163-10193, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Aug 2017

Research article | 30 Aug 2017

Seasonal provenance changes in present-day Saharan dust collected in and off Mauritania

Carmen A. Friese1, Johannes A. van Hateren2,a, Christoph Vogt1,3, Gerhard Fischer1, and Jan-Berend W. Stuut1,2 Carmen A. Friese et al.
  • 1University of Bremen, Marum-Center of Marine Environmental Sciences, 28359 Bremen, Germany
  • 2NIOZ-Royal Netherlands Institute for Sea Research, Department of Ocean Systems, and Utrecht University, 1790 AB, Den Burg Texel, the Netherlands
  • 3ZEKAM, Crystallography, Geosciences, University of Bremen, 28359 Bremen, Germany
  • anow at: Vrije Universiteit Amsterdam, Faculty of Earth Sciences, 1081 HV Amsterdam, the Netherlands

Abstract. Saharan dust has a crucial influence on the earth climate system and its emission, transport and deposition are intimately related to, e.g., wind speed, precipitation, temperature and vegetation cover. The alteration in the physical and chemical properties of Saharan dust due to environmental changes is often used to reconstruct the climate of the past. However, to better interpret possible climate changes the dust source regions need to be known. By analysing the mineralogical composition of transported or deposited dust, potential dust source areas can be inferred. Summer dust transport off northwest Africa occurs in the Saharan air layer (SAL). In continental dust source areas, dust is also transported in the SAL; however, the predominant dust input occurs from nearby dust sources with the low-level trade winds. Hence, the source regions and related mineralogical tracers differ with season and sampling location. To test this, dust collected in traps onshore and in oceanic sediment traps off Mauritania during 2013 to 2015 was analysed. Meteorological data, particle-size distributions, back-trajectory and mineralogical analyses were compared to derive the dust provenance and dispersal. For the onshore dust samples, the source regions varied according to the seasonal changes in trade-wind direction. Gibbsite and dolomite indicated a Western Saharan and local source during summer, while chlorite, serpentine and rutile indicated a source in Mauritania and Mali during winter. In contrast, for the samples that were collected offshore, dust sources varied according to the seasonal change in the dust transporting air layer. In summer, dust was transported in the SAL from Mauritania, Mali and Libya as indicated by ferroglaucophane and zeolite. In winter, dust was transported with the trades from Western Sahara as indicated by, e.g., fluellite.

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This article deals with an investigation on the seasonal change in the sources of Saharan dust deposited in and off Mauritania using mineralogy. Onshore, dust was sourced from Western Sahara and a local source during summer and from Mauritania and Mali during winter. Offshore, dust was sourced from Mauritania, Mali and Libya during summer and from Western Sahara during winter. The outcome of the study has important implications for the reconstruction of past climates using dust deposits.
This article deals with an investigation on the seasonal change in the sources of Saharan dust...