Abstract
Abstract. A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution "provenancing" of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the "provenancing" of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives.
Highlights
M using the Deep Blue algorithm, air mass trajectories derived from different sources including long-travelled desert dust with HYSPLIT model and analysis of meteorological data (LTD), locally-produced mineral dust (LPD) and products of enabled identification of dust source regions with high temporal and spatial resolution
Heavy dust storms over North Africa in spring are associated with Saharan depressions developing in the area of strong baroclinicity between the African continent and the relatively cold Mediterranean Sea (Barkan et al, 2005; Knippertz et al, 2009a; Schepanski et al, 2009; Bou Karam et al, 2010)
Saharan cyclogenesis is often initiated by the formation of deep north–south oriented troughs in the upper atmosphere and associated cold air advection to North Africa whose effect is enhanced by coastal temperature gradient, which is pronounced in spring (Barkan et al, 2005)
Summary
The LTD was sampled from the surface of the Garabashi Glacier on the south-eastern slope of Mt. Elbrus (43◦18 16.8 N, 42◦27 48.4 E) at 3856 m a.s.l. The dust sample was collected with a plastic spatula from a snow-covered area of 1 m2 following the deposition event, stored in a clean plastic bottle and filtered using 0.2 μm filters for particle size distribution and elemental composition analyses. Royer et al (1983) used both SEM and Coulter counter to derive particle size distributions from samples of dust contained in an Antarctic ice core and found that while both methods generated distributions that are similar in shape, SEM measurements produced lower modal value than Coulter counter measurements. The nominal detection limit of trace elements measurements was 5 ppm
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