Snow–Dust Storm: Unique case study from Iceland, March 6–7, 2013

Iceland is an active dust source in the high-latitude cold region. About 50% of the annual dust events in
the southern part of Iceland take place at sub-zero temperatures or in winter, when dust may be mixed
with snow. We investigated one winter dust event that occurred in March 2013. It resulted in a several
mm thick dark layer of dust deposited on snow. Dust was transported over 250 km causing impurities on
snow in the capital of Iceland, Reykjavik. Max one-minute PM10 concentration measured in Kirkjubæjarklaustur
(20–50 km from the dust source) exceeded 6500 lg m3 while the mean (median) PM10 concentration
during 24-h storm was 1281 (1170) lg m3
. Dust concentrations during the dust deposition in
Reykjavik were only about 100 lg m3
, suggesting a rapid removal of the dust particles by snow during
the transport. Dust sample taken from the snow top layer in Reykjavik after the storm showed that about
75% of the dust deposit was a volcanic glass with SiO2 45%, FeO 14.5%, and TiO2 3.5. A significant
proportion of organic matter and diatoms was also found. This case study shows that severe dust storms
are related also to meteorological conditions, such as winter snow storms, and moist conditions. Small
volcanic dust particles deposited on snow tend to form larger particles (‘‘clumping mechanism’’) resulting
in stronger light absorbance. This is one of the first reports on the ‘‘clumping mechanism’’ observed in
natural conditions. The deposition of Icelandic dust on snow, glaciers and sea ice may accelerate the
thaw, with the potential to increase the anthropogenic Arctic warming.