Insulation effects of Icelandic dust and volcanic ash on snow and ice

Monika Dragosics,Finnur Pálsson,Tinna Jónsdóttír,Tobias Dürig,Outi Meinander,Pavla Dagsson-Waldhauserová,Throstur Thorsteinsson,Gerrit De Leeuw

doi:10.1007/s12517-015-2224-6

Abstract

In the Arctic region, Iceland is an important source of dust due to ash production from volcanic eruptions. In addition, dust is resuspended from the surface into the atmosphere as several dust storms occur each year. During volcanic eruptions and dust storms, material is deposited on the glaciers where it influences their energy balance. The effects of deposited volcanic ash on ice and snow melt were examined using laboratory and outdoor experiments. These experiments were made during the snow melt period using two different ash grain sizes (1 ϕ and 3.5 ϕ) from the Eyjafjallajokull 2010 eruption, collected on the glacier. Different amounts of ash were deposited on snow or ice, after which the snow properties and melt were measured. The results show that a thin ash layer increases the snow and ice melt but an ash layer exceeding a certain critical thickness caused insulation. Ash with 1 ϕ in grain size insulated the ice below at a thickness of 9–15 mm. For the 3.5 ϕ grain size, the insulation thickness is 13 mm. The maximum melt occurred at a thickness of 1 mm for the 1 ϕ and only 1–2 mm for 3.5 ϕ ash. A map of dust concentrations on Vatnajokull that represents the dust deposition during the summer of 2013 is presented with concentrations ranging from 0.2 up to 16.6 g m−2.

Highlights

The physical and optical properties of snow are influenced by the presence of impurities, in particular by absorbing material such as aerosol particles deposited on the snow surface (e.g., Doherty et al 2010 and Painter et al 2012)
Results from the outdoor and indoor snow experiments with Icelandic ash at Finnish Meteorological Institute (FMI) are presented in this chapter as well as in situ measurements on Vatnajökull depicted in the dust distribution map (Fig. 6)
Our findings suggest that if the ash concentration on snow or ice is small, so the layer thickness is very thin, it has the potential to increase snow melt, but after a threshold the insulation effect begins, and the snow melt is decreased compared to clean ice

Summary

Introduction

The physical and optical properties of snow are influenced by the presence of impurities, in particular by absorbing material such as aerosol particles deposited on the snow surface (e.g., Doherty et al 2010 and Painter et al 2012). Effects of aerosol particles on, for instance, snow melt and albedo (e.g., Meinander et al 2013) and bidirectional reflection (Peltoniemi et al 2009) have been studied for natural snow and during campaigns where impurities were deposited on snow in different quantities (e.g., Meinander et al 2014). The properties of snow and ice on the surface of glaciers in Iceland are influenced by the deposition of dust (Arnalds et al 2014) and, during volcanic eruptions, by volcanic ash. Icelandic ash and dust is mainly basaltic volcanic glass which is deposited in Iceland’s sandy deserts which cover an area over 22.000 km. Icelandic ash and dust is mainly basaltic volcanic glass which is deposited in Iceland’s sandy deserts which cover an area over 22.000 km2 Deserts of this composition are globally unique (Arnalds 2010). The ash from Eyjafjallajökull 2010 was of andesitic composition, slowly progressing from benmorite to thrachyte as the eruption proceeded with a silicic content ranging from ∼58–69 % SiO2. (Gislason et al 2011 and Gudmundsson et al 2012a)

Methods

Results

Conclusion