Evaluating the Relative Importance of Northern African Mineral Dust Sources Using Remote Sensing

Abstract

<p><strong>Abstract.</strong> Mineral dust from the Sahara and Sahel provides the Amazon Basin with essential nutrients, although the process is still poorly understood. There is little understanding where the dust is coming from, and thus what the concentration of nutrients in the dust is. This information, however, is vital to assess the impact it will have on the Amazon. This study analyses northern African dust sources of the boreal winter dust seasons between the years 2015–2017. It utilises high spatio-temporal resolution remote sensing data from SEVIRI, MODIS, VIIRS and Sentinel-2 to identify dust sources, classify them according to a geomorphic dust source scheme, and quantify the relative importance of source regions by calculating the total dust mass they produce. Results indicate that paleolakes emit the most dust, with the Bodélé Depression as the single largest dust source region, however, that alluvial deposits also produce a substantial amount of dust. During the boreal winter dust seasons of 2015–2017, ~ 36 % of the total dust mass emitted from northern Africa was associated to alluvial deposits, yet this geomorphic category has been relatively understudied to date. Furthermore, sand deposits were found to produce relatively little dust, in contrast to the results of other recent studies.</p>

Atmospheric Transport of North African Dust‐Bearing Supermicron Freshwater Diatoms to South America: Implications for Iron Transport to the Equatorial North Atlantic Ocean

“…The detected FDs in our samples are thought to originate from African paleolakes (Bakker et al, 2019;Ben-Ami et al, 2010;Prospero et al, 2002;Washington & Todd, 2005). Soil from paleolakes is comprised of diatomite, a mixture of low density FDs (0.8 g cm −3 ) and higher density authigenic minerals (2.7 g cm −3 ) (Bristow et al, 2010;Conrad & Lappartient, 1991).…”

Three North African dust source areas and their geochemical fingerprint

“…The most active dust sources in North Africa are desiccated river and lake beds (Prospero et al, 2002), contributing approximately 36% and 64% of total North African winter dust respectively (Bakker et al, 2019). The Western source region (Figure 2) is dominated by dust production from alluvial deposits and palaeolakes in the deserts that surround the Aïr and Adrar Iforas Mountains spanning Algeria, Mali and Niger.…”

“…Key developments include providing the spatial coverage to map the locations of highest dust generation (Engelstaedter et al, 2006;Schepanski et al, 2012) and establishing that there are two main transport pathways westwards, a "northern route" towards the Caribbean which dominates during boreal summer, and a "southern route" towards the Amazon during winter (Engelstaedter et al, 2006;Meng et al, 2017). Yet despite these recent advances, major uncertainties remain in our knowledge of North African dust-producing source regions and our ability to fingerprint their contribution to these export routes (Bakker et al, 2019;Formenti et al, 2011;Scheuvens et al, 2013). This limited knowledge base hinders the development of a comprehensive source-to-sink understanding and adds uncertainty to climatic interpretations that rely on the accumulation of dust in geological archives.…”

“…Second, a large fraction of the Sr and Nd isotope data set currently available does not come from active deflating dust source regions (Abouchami et al, 2013;Blanchet, 2019;Gross et al, 2016;Scheuvens et al, 2013;Zhao et al, 2018). Dust in North Africa is mostly derived from distinct palaeolake-and alluvial-deposits, which are located in the foothills of Saharan mountain ranges (Bakker et al, 2019;Schepanski et al, 2009).…”

Contribution of IASI to the Observation of Dust Aerosol Emissions (Morning and Nighttime) Over the Sahara Desert

“…In particular, Formenti et al (2011) locate six major potential source areas (see their Figure 1): (1) northern Algeria and Tunisia, (2) southern Atlas and western Sahara‐Mauritania, (3) Mali‐Algerian border, (4) central Lybia, (5) Chad Bodele paleo lake, and (6) southern Egypt‐northern Sudan. It can be noted that most of these dust source regions correspond to alluvial deposit or paleolakes geomorphic regions (see Bakker et al, 2019; Damnati, 2000; and Figure 3 of Lézine et al, 2014). These areas are identified (red contours) on Figure 2 showing the good general match between IASI results and this compilation of independent results.…”