Evaluating the relative importance of northern African mineral dust sources using remote sensing

Abstract

Abstract. Northern African mineral dust provides the Amazon Basin with essential nutrients during the boreal winter months, when the trajectory of the Saharan dust plume is towards South America. This process, however, is still poorly understood. There is little knowledge of where the dust is coming from, and, thus, little information regarding the concentration of nutrients in the dust. This information is vital to assess the impact it will have on the Amazon. In order to further our understanding of the problem, this study analyses northern African dust sources of the boreal winter dust seasons between the years 2015 and 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 palaeolakes emit the most dust, with the Bodélé Depression as the single largest dust source region. However, 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 with 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.

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).…”

“…However, to our knowledge, our work is the first to show the transport of diatomite from African paleolakes to South America. Previous studies have suggested that multiple paleolakes within the Sahara including the Bodélé Depression and other paleolakes in the western Sahara are active dust sources that can transport mineral aerosols to South America (Bakker et al., 2019; Prospero et al., 2002). These paleolakes could explain the detection of FDs in our samples.…”

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.…”

“…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.…”

Contribution of IASI to the observation of the dust aerosol diurnal cycle over Sahara

“…It can be noted that most such dust source regions correspond to alluvial deposit or paleolakes geomorphic regions (see, in particular, Fig. 3 of Bakker et al, 2019). These areas are identified (red contours) on Fig.…”