Characteristics of Icelandic Dust Sources: Particle Size, Morphology and Geochemistry
Thomas W Mockford
1, Joanna Bullard1, Throstur Thorsteinsson2
1Department of Geography, Loughborough University, Loughborough, Leicestershire, UK, 2Institute of Earth Sciences, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland
There is increasing evidence for high magnitude dust storms in High Latitude Cold Climate (HLCC) regions. Yet, aeolian processes in these areas are understudied and therefore our knowledge of these systems is limited. Understanding dust emissions from HLCC regions is of increasing importance because future climate scenarios indicate that glacial outwash plains, the main dust sources, will expand as terrestrial ice masses contract. As in the subtropics, the geomorphological and sedimentological signatures of HLCC dust sources vary according to local sediment supply, geomorphological history and meteorological conditions. The aim of this paper is to characterise two Icelandic dust sources; one active ephemeral channel system which is seasonally recharged by a large glacial river, and a relict outwash deposit formed by Holocene catastrophic flood deposits. Both areas have been identified as contemporary dust sources from field observations and satellite imagery.
Samples of surface sediments and suspended sediments within dust storms (up to 2.5 m) were collected during two spring field seasons (June 2014/2015). These were characterised using particle size (PSA) and scanning electron microscope (SEM) analyses. For example, the modal particle size on the poorly-sorted relict outwash deposit was 653µm (coarse sand) whilst the suspended particles at this site were extremely fine with a mode of 1.15 µm. This suggests highly selective aeolian entrainment at this source. In contrast, the modal particle size in the ephemeral channel system was 39.78µm (coarse silt) and the entrained sediments were only slightly finer at 30.07µm. This paper also highlights contrasts in the particle morphology and geochemistry. The implications of these differences in source characteristics and the potential implications for local and regional transport of dust as well as human health are explored.