Dust generation on a proglacial floodplain, West Greenland
journal contributionposted on 18.02.2011, 12:53 by Joanna Bullard, Martin J. Austin
The interplay of glacial dynamics, glaciofluvial and aeolian transport in proglacial landscapes plays an important role in local environmental systems and in the global context by affecting the amount of dust generated and transported at different phases of glacial-interglacial cycles. Glacial outwash plains are a significant source of dust, however the processes involved in dust generation on proglacial floodplains are poorly documented. We report a study of the quantity and characteristics of aeolian suspended sediment transport in Sandflugtdalen, a valley containing a proglacial floodplain and aeolian dunefield in West Greenland. Although the surface sediment of both the floodplain and dunefield contain a considerable amount of sand-sized material, wind speeds recorded were insufficiently strong to mobilise this material; this is probably due to the armouring effect of coarser particles in the surface deposits. Nevertheless, fine (dust-sized) aeolian sediments were transported down valley in suspension and the source of this material was a silt-dominated meltwater deposit up valley from the monitoring sites. Dust transport ranged from 0.0008-0.082 g m-w s-1 over seven days and 0.0035-0.011 g m-w s-1 over a further 57 days during which no additional fluvial sediments were deposited. The reduction in sediment transport rate is attributed to both a depleted sediment supply and a decrease in above threshold winds. The supply of fine sediments to this proglacial region is dependent on meltwater suspended sediment loads which are predicted to increase during glacier retreat; reworking of the floodplain during ice retreat may also make more material available for aeolian transport.
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