Abstract
AbstractVolcanic eruptions take place in Iceland about once every 3 to 5 years. Ash emissions from these eruptions can cause significant disruption to air traffic over Europe and the North Atlantic as is evident from the 2010 eruption of Eyjafjallajökull. Sulfur dioxide (SO2) is also emitted by volcanoes, but there are no criteria to define when airspace is considered hazardous or nonhazardous. However, SO2 is a well‐known ground‐level pollutant that can have detrimental effects on human health. We have used the United Kingdom Met Office's NAME (Numerical Atmospheric‐dispersion Modelling Environment) model to simulate SO2 mass concentrations that could occur in European and North Atlantic airspace for a range of hypothetical explosive eruptions in Iceland with a probability to occur about once every 3 to 5 years. Model performance was evaluated for the 2010 Eyjafjallajökull summit eruption against SO2 vertical column density retrievals from the Ozone Monitoring Instrument and in situ measurements from the United Kingdom Facility for Airborne Atmospheric Measurements research aircraft. We show that at no time during the 2010 Eyjafjallajökull eruption did SO2 mass concentrations at flight altitudes violate European air quality standards. In contrast, during a hypothetical short‐duration explosive eruption similar to Hekla in 2000 (emitting 0.2 Tg of SO2 within 2 h, or an average SO2 release rate 250 times that of Eyjafjallajökull 2010), simulated SO2 concentrations are greater than 1063 µg/m3 for about 48 h in a small area of European and North Atlantic airspace. By calculating the occurrence of aircraft encounters with the volcanic plume of a short‐duration eruption, we show that a 15 min or longer exposure of aircraft and passengers to concentrations ≥500 µg/m3 has a probability of about 0.1%. Although exposure of humans to such concentrations may lead to irritations to the eyes, nose and, throat and cause increased airway resistance even in healthy individuals, the risk is very low. However, the fact that volcanic ash and sulfur species are not always collocated and that passenger comfort could be compromised might be incentives to provide real‐time information on the presence or absence of volcanic SO2. Such information could aid aviation risk management during and after volcanic eruptions.
Highlights
Icelandic volcanism features almost all known eruption styles and types, ranging from purely effusive, ash-poor eruptions to purely explosive, ash-dominated eruptions [e.g., Thordarson and Larsen, 2007; Larsen and Eiríksson, 2008]
Rose et al [2003] measured SO2 volume mixing ratios up to 1000 ppbv at 11.3 km altitude, which is of the same order as the maximum SO2 mass concentrations of about 1050 μg/m3 that we find in the 36 h old plume in FL350-FL550 for the short-duration eruption
For the short-duration eruption scenario, we find that SO2 mass concentrations ≥500 μg/m3 could be encountered for 15 min or longer in FL200-FL350 or FL350-FL550, the probability of such an encounter is just under 0.1% (Figure 8c)
Summary
Icelandic volcanism features almost all known eruption styles and types, ranging from purely effusive, ash-poor eruptions to purely explosive, ash-dominated eruptions [e.g., Thordarson and Larsen, 2007; Larsen and Eiríksson, 2008]. The 2010 explosive eruption of Eyjafjallajökull (63.38°N, 19.36°W, 1660 m above sea level (asl)) began on 14 April 2010 and lasted 39 days resulting in severe disruption to air traffic due to the repeated presence of ash plumes in European and North Atlantic airspace [e.g., Schumann et al, 2011; Gudmundsson et al, 2012; Stevenson et al, 2012]. Controlled European airspace was restricted for commercial air traffic during 15–23 April 2010 followed by intermittent restrictions of parts of European airspace in the weeks thereafter. These restrictions resulted from the combination of frequent and persistent northwesterly air flow at the altitude at which significant amounts of fine-grained volcanic ash particles were injected (3–10 km) and the aviation safety protocols in place at the time (i.e., “zero tolerance”) [e.g., Gudmundsson et al, 2012].
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