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Icelandic dust and volcanic ash on snow and ice can cause either melt or insulation effects

Icelandic dust and volcanic ash on snow and ice can cause either melt or insulation effects

Iceland is an important source of dust in the Arctic region. In addition to volcanic eruptions, dust is resuspended from the surface into the atmosphere.

Several Icelandic dust storms occur every year. The dust day frequency is similar to the major desert areas of the world (Mongolia, Iran, etc., excluding Sahara). During volcanic eruptions and dust storms, material is deposited on the glaciers where it influences their energy balance. In Icelandic-Finnish co-operation we have made a series of experiments in Finland to investigate the melt and insulation properties of Icelandic dust particles.

"We used Eyjafjällajökull 2010 eruption ash particles collected on a glacier in Iceland. Indoor and outdoor laboratory and field experiments were carried out at the Finnish Meteorological Institute, Kumpula Campus area, including the snow laboratory of University of Helsinki, Department of Physics", says researcher Outi Meinander. Different amounts of ash were deposited on snow and ice, after which snow properties and melt were measured. Our results showed that a thin ash layer exceeding a certain critical thickness caused insulation. Smaller concentrations increased melt.

Ash with grain size smaller than 500 µm insulated the ice below at a thickness of 9-15 mm. This we called ‘the critical thickness'. For the 90 µm grain size, the insulation thickness was 13 mm. The maximum melt occurred at thickness of 1mm for the larger particles, and at the thickness of < 1-2 mm for the smaller particles. This value we named as ‘the effective thickness'. Earlier, similar threshold dust layer thickness values have been given for Mt St Helens (1980) ash, and Hekla (1947) tephra, for example. Our results were the first ones reported for the Eyjafjällajökull ash.

In Iceland, the dust layers in the nature can be from mm scale up to tens of meters. For example, Eyjafjällajökull dust layer is 30 m close to the vent and 1 m thick 2 km away. On SW Vatnajökull glacier, the dust layer thickness is 0,1 mm. Our results suggest increased melt in areas with smaller amounts of dust, further away from the eruption, inside Iceland and elsewhere. In literature, long-range transported Icelandic dust has been reported to be found even over the Atlantic.

More information:

Researcher Outi Meinander, outi.meinander@fmi.fi

Citation: Dragosics M, O Meinander, T Jónsdóttír, T Dürig, G De Leeuw, F Pálsson, P Dagsson-Waldhauserová and T Thorsteinsson. Insulation effects of Icelandic dust and volcanic ash on snow and ice. Arabian Journal of Geosciences, 9: 126, doi: 10.1007/s12517-015-2224-6, 2016.



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