Aeolian dust transport and deposition over crete and adjacent parts of the mediterranean sea

Abstract

Monitoring of dust deposition at several stations on Crete over a three year period has shown that the present-day depositional flux is of the order of 10-100 gm-' yr-l. Most of the dust deposition takes place during a few annual dust 'events' which typically last for 1-3 days. Dust haze episodes are usually associated with southerly or southwesterly winds which transport fine sediment from North Africa. Dust is raised by a wide variety of meteorological conditions which generate strong near-surface winds in the source areas, but major long-range transport events are often associated with cold fronts linked to the passage of deep mid-latitude depressions during winter and spring. Dust haze frequency and deposition rates are highest in western Crete and decrease towards the east, suggesting that transport from Tunisia and neighbouring parts of North Africo is particularly important. The measured rate of dust deposition is well below the minimum level required for loess formation. Deposits which have previously been identified as loess are shown to be uncemented marine mark of Tertiary age. Laboratory analysis of red soils, surface sediments, and bedrock samples has confirmed that many of the soils contain an important aeolian dust component, but it is concluded that a more important source of soil parent material is provided by weathering of local rocks. Many of the soils contain significant amounts of quartz sand which cannot have been transported across the sea from North Africa. Reworking of weathered material and deposited dust is extensive, and is accomplished by both aeolian and fluvial processes. Tectonically-controlled depressions in the mountains and parts of the coastal lowlands have acted as long-term sinks in which a thickness of several metres of sediment and soil has accumulated during the Quaternary.

In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

“…Buat-Ménard and Chesselet, 1979;Martin et al, 1991;Swap et al, 1992;Duce, 1995;Alpert et al, 1998;Mahowald et al, 2009Mahowald et al, , 2011Maher et al, 2010;Liu et al, 2011;Choobari et al, 2014;Li et al, 2016). Desert dust aerosol is of particular interest in the Mediterranean region where it is (i) frequently observed in high concentrations in the troposphere; (ii) is a major component of surface PM 10 Rea et al, 2015), aerosol optical depth (Moulin et al, 1998;Gkikkas et al, 2013;Nabat et al, 2013), atmospheric deposition (Pye, 1992;Vincent et al, 2016); and (iii) affecting the regional air quality (Querol et al, 2009); atmospheric thermodynamics (e.g. Alpert et al, 1998;Chaboureau et al, 2011); radiative budget and climate (e.g.…”

Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution

“…Continuous multi-year data of deposition flux have been reported for dusts transported from desert areas such as central and eastern Asia (Inoue and Naruse, 1987;Yabuki et al, 2005;Hsu et al, 2009;Sun et al, 2003;Ta et al, 2004;Zhang et al, 1993), North America (Reheis, 2006), and the Middle East and Sahara (Ganor et al, 2003;Offer and Goossens, 2004;Pye, 1992;Nihlén et al, 1995;Loye-Pilot and Martin, 1996). Data of shorter (nearly 1 yr or event basis) periods have been reported much more (e.g.…”

Pedogenesis by clay dissolution on acid, low-grade metamorphic rocks under mediterranean forests in southern Tuscany (Italy)

“…This increase is either due to weathering and organic complexation (Fe(II)), or to cycling of these elements in the biological system (Ca, Mn and P; Van Wesemael, 1993a). The large amount of CaO in the AEh horizon of all profiles can probably be attributed to deposition of calcium rich aeolian dust (Pye, 1992).…”