Desert dust - Climatic Change in Deserts - page 145

Figure 9.1. Map showing modern dust source regions and major directions of dust
transport. (Adapted from Pewe, 1981 , fig.1, and Harrison et al., 2001 , fig.1a.)
In fact, during glacial stages, dust fluxes measured mainly in deep-sea cores were
between three and five times greater than during interglacial times (Maher et al., 2010 ;
McGee et al., 2010 ). In Antarctic ice cores, times of maximum dust accumulation were
also synchronous with times of minimum temperature and with times of minimum
carbon dioxide concentrations measured from trapped air bubbles in the ice (Petit
et al., 1981 ; Petit et al., 1999 ; Jouzel et al., 2007). Disentangling a precise climatic
signal from these fluctuations in dust accumulation rates is far from easy, given that
dust production, transport and deposition are determined by a variety of factors,
including changes in wind velocity and gustiness, source area and extent, vegetation
cover, dust transport paths and deflation from glacial outwash deposits (Pewe, 1981 ;
McTainsh, 1987 ; Maher et al., 2010 ; McGee et al., 2010 ).
9.3 Origins and physical characteristics of desert dust
There have been many attempts to distinguish between wind-blown dust particles
formed as a result of desert weathering processes, such as salt-weathering or abrasion
between moving sand grains, and those formed as a result of frost-shattering or gla-
cial abrasion in glaciated and periglacial landscapes (Smalley and Vita-Finzi, 1968 ;
Vita-Finzi and Smalley, 1970 ; Goudie et al., 1979 ;Pye, 1987 ). Wind is certainly com-
petent to undercut small sandstone hillocks in the Sahara ( Figure 9.2 ). Such efforts,
while useful to our understanding of particle micromorphology (Coude-Gaussen and
Rognon, 1983 ), are somewhat chimerical when it comes to disentangling the origin
of desert dust. Many deserts are flanked by high, glaciated mountain ranges, such