UK hazards from a large Icelandic effusive eruption
January 2016 - Large gas-rich volcanic eruptions in Iceland have the potential to impact the UK. The Met Office, British Geological Survey (BGS), Centre for Ecology and Hydrology (CEH) and the University of Leeds have conducted a modelling study for the UK Civil Contingencies Secretariat to improve our understanding of the associated hazards. This study provides information on the range of concentrations of sulphur dioxide gas, sulphate aerosol and some halogen species that might be experienced at the surface in the UK and at aviation flight levels during such an eruption. As a result of the study and the associated impact analyses, the hazard from an effusive volcanic eruption has been reduced in the 2015 edition of the UK National Risk Register of Civil Emergencies.
Volcanic eruptions in Iceland have the potential to affect society through both volcanic ash and volcanic gases. In response to the 2010 eruption of Eyjafjallajökull two types of volcanic eruption were added to the UK National Risk Register: an ash-dominated eruption, typified by Eyjafjallajökull, and a gas-dominated or "effusive" eruption, based on the 1783-1784 CE eruption of the Laki volcanic system.
The 9-month long Laki eruption erupted 120 megatons of the volcanic gas sulphur dioxide and 14.7 km3 of lava. For context, this is approximately 10 times more than was emitted from the eruption in the Bárðarbunga volcanic system in August 2014 to February 2015. Historical reports tell of widespread animal and crop loss in Iceland leading to a devastating famine. Further afield, reports and diaries from the UK and Europe during the eruption mention unusual atmospheric phenomena and associated affects on human health. Based on the information available in 2011-2012, an effusive eruption was ranked in the top three hazards to the UK putting it on a par with pandemic influenza and coastal flooding.
The study examined the potential hazard to the UK from a large gas-emitting eruption similar to Laki and produced a technical scientific report, "UK Hazards from a Large Icelandic Effusive Eruption", which has been used to inform the UK National Risk Register.
No two eruptions are the same so the details of the eruption studied were determined from a statistical analysis of an expert elicitation of scientists conducted by BGS. This scenario was used as input for two atmospheric computer models: the Met Office's Met Office Dispersion Model dispersion model and CEH's EMEP4UK model. Over 160 simulations have been conducted looking at the impact of an eruption occurring at some time in a 10 year period.
The findings show that a large gas eruption could lead to periods of very poor air quality in the UK, but that the generally changeable nature of the weather over the UK limits the duration of any individual episode to a few days. The prevailing meteorology is the key influence on which parts of the North Atlantic and Europe could be affected by the volcanic plume at any time.
Air quality would be affected by both sulphur dioxide gas and particulate matter, which is formed as the gas converts to sulphate aerosol through chemical reactions in the atmosphere. Lead author of the report, Claire Witham, Scientific Manager of Volcanic and Chemical Atmospheric Dispersion at the Met Office said: "Particulate matter is a growing air pollution problem in many cities and the levels caused by such a volcanic eruption could reach those seen in recent air quality episodes in places like Beijing".
At the surface in the UK, the annual deposition of sulphur could increase to levels similar to the peak of industrial sulphur pollution in the early 1970s, which would put sensitive ecosystems, particularly those in Scotland, at risk.
At aircraft cruise altitudes, sulphur dioxide concentrations could reach levels equivalent to those that would trigger air quality alerts at the surface. Owing to meteorology and the variable height of the emissions at the volcano, the location of gas plume will likely be very transient meaning that elevated concentrations would not occur at all levels in the atmosphere at the same time.
The work has been funded by the Civil Contingencies Secretariat, Department for Transport, Department of Health, Department of Environment, Food and Rural Affairs and the Government Office for Science. The detailed model data have been used by experts in these Departments to carry out further sector-specific impact analyses.