Abstract

The 2010 eruption of Eyjafjallajökull caused a paradigm shift in the importance of small volcanic eruptions to commercial aviation and societal infrastructure. The atmospheric wind dispersed fine volcanic ash at low levels over Northern Europe, resulting in closure of airspace for six days and estimated direct losses in excess of 1 Billion €. In this talk I will summarise the consequences of volcanic ash injection into the atmosphere for aviation, the role of Volcanic Ash Advisory Centres (VAAC) in forecasting ash hazard, and the inputs required for their dispersion modelling. I will then present a predictive model of volcanic plumes that describes the bending over of the plume trajectory in a cross-wind and show that model predictions are in accord with a dataset of historic eruptions if the profile of atmospheric wind shear is described. The wind restricts the rise height of volcanic plumes, such that an order of magnitude increase in source mass flux is required to match the rise height of a plume in a quiescent environment. This effect can lead to significant under-prediction of the mass of volcanic ash input into VAAC dispersion modelling. The model can account for the variations in plume height observed during the first explosive phase of the 2010 Eyjafjallajökull eruption using independently measured wind speeds, and this suggests that changes in the observed plume height are better explained by changing meteorology than abrupt changes in the source mass flux.