Aviation response to a widely dispersed volcanic ash and gas cloud from the August 2008 eruption of Kasatochi, Alaska, USA

Abstract

The extensive volcanic cloud from Kasatochi's 2008 eruption caused widespread disruptions to aviation operations along Pacific oceanic, Canadian, and U.S. air routes. Based on aviation hazard warnings issued by the National Oceanic and Atmospheric Administration, U.S. Geological Survey, the Federal Aviation Administration, and Meteorological Service of Canada, air carriers largely avoided the volcanic cloud over a 5 day period by route modifications and flight cancellations. Comparison of time coincident GOES thermal infrared (TIR) data for ash detection with Ozone Monitoring Instrument (OMI) ultraviolet data for SO2 detection shows congruent areas of ash and gas in the volcanic cloud in the 2 days following onset of ash production. After about 2.5 days, the area of SO2 detected by OMI was more extensive than the area of ash indicated by TIR data, indicating significant ash depletion by fall out had occurred. Pilot reports of visible haze at cruise altitudes over Canada and the northern United States suggested that SO2 gas had converted to sulfate aerosols. Uncertain about the hazard potential of the aging cloud, airlines coped by flying over, under, or around the observed haze layer. Samples from a nondamaging aircraft encounter with Kasatochi's nearly 3 day old cloud contained volcanic silicate particles, confirming that some fine ash is present in predominantly gas clouds. The aircraft's exposure to ash was insufficient to cause engine damage; however, slightly damaging encounters with volcanic clouds from eruptions of Reventador in 2002 and Hekla in 2000 indicate the possibility of lingering hazards associated with old and/or diffuse volcanic clouds.

Adsorption of sulfur dioxide on volcanic ashes

“…They may fertilize seawater (Frogner et al 2001;Jones and Gislason 2008) or, depending on their composition, have toxic effects on vegetation, animals, and humans (Oskarsson 1980). In addition, ashes pose a severe hazard for aviation (e.g., Guffanti et al 2010). Chemical interaction between ashes and gases in the eruption cloud is essential for understanding all of these phenomena.…”

Uncertainties in the inverse modelling of sulphur dioxide eruption profiles

“…The third eruption of the Kasatochi volcano was accompanied and followed by massive ash emission, and Alaska Airlines was forced to cancel 44 flights between 10 and 11 August 2008 (O'Malley andHolland 2008). The ash travelled along with the SO 2 for at least three days (Guffanti et al 2010), thus SO 2 may also serve as a proxy for ash in this case. Making available improved methods for providing volcanic eruption source terms as a function of height and in a quantitative manner is one of the objectives of SAVAA.…”

Early in-flight detection of SO<sub>2</sub> via Differential Optical Absorption Spectroscopy: a feasible aviation safety measure to prevent potential encounters with volcanic plumes

“…Also, it can only be a proxy for the greater hazard, volcanic ash, which will fall out and might lead to two different clouds moving in different directions due to wind shear. However, for young clouds (up to three days after emission) SO 2 remains a good tracer for a volcanic cloud with dangerous ash contents (Carn et al, 2009;Guffanti et al, 2010;Schumann et al, 2011;Thomas and Prata, 2011). Even if most of the ash and SO 2 have separated, the SO 2 cloud might still contain fine ash particles (Thomas and Prata, 2011).…”