Impacts and dynamics of volcanically-generated jökulhlaups, Eyjafjallajökull, Iceland

Background

Eyjafjallajökull, a 1666 m high, glacier-clad, stratovolcano, is known to have erupted on only four occasions: ~500 AD, ~920 AD, 1612 AD and 1821-23 AD (Guðmundsson et al., 2005; Sturkell et al., 2009). Each eruption has resulted in rapid and large-scale glacier ice melt, generating very large jökulhlaups (glacier outburst floods) with peak discharges of 103–104 m3s-1 inundating surrounding populated lowlands (Guðmundsson et al., 2005; Smith & Dugmore, 2006).

On March 3, 2010, the Icelandic Meteorological Office (IMO) informed us of a period of enhanced seismic activity under Eyjafjallajökull during the preceding weeks. Based on the assumption that the exponential increase in both seismic activity and rates of ground deformation represented pre-eruption behaviour, we collected pre-eruption TLS (Terrestrial Laser Scanner) and dGPS survey data from a number of probable jökulhlaup routeways between March 9 and 16, 2010. On March 20, 2010 an effusive flank eruption occurred at the eastern edge of the Eyjafjallajökull ice cap (Fig. 1). This eruption ended on April 12 (IMO).

Eyjafallajokull P

On April 14 (at 01:15 GMT) an explosive subglacial eruption started beneath the 2.5 km-wide summit caldera of Eyjafjallajökull. Within hours, the eruption melted through 200 m of the ice cap and became fully phreatic, producing a major 8.5 km-high volcanic plume. By 07:00 GMT rapid melting of the ice cap generated volcanogenic jökulhlaups that cascaded from Gígjökull and down Núpakotsdalur on the northern and southern flanks of Eyjafjallajökull, respectively. The initial jökulhlaup from Gígjökull reached peak discharge in the Markarfljót 5 hours later damaging Iceland’s ring road near the Markarfljót bridge. Subsequent increases in eruption intensity generated repeated jökulhlaups from Gígjökull that inundated the Markarfljót. At 18:55 GMT on April 15, a jökulhlaup discharged across the surface of Gígjökull prompting the immediate evacuation of population within the entire Markarfljót area. This jökulhlaup was laden with sediment and ice fragments, characterised by a viscous, smooth-surfaced, lobate flow front (advancing at 4 ms 1) followed by a more turbulent fluid flow body suggesting that the frontal wave of this jökulhlaup was hyperconcentrated.

We will provide a unique assessment of the impact of volcanically-generated jökulhlaups on surrounding proglacial fluvial systems during a major subglacial eruption. Our acquisition of very high-quality pre- and post-flood datasets will permit hydrodynamic modelling at an unprecedented resolution and with exceptional spatial and temporal accuracy. Modelling will be robust as field data will allow model calibration and validation. Overall we will provide a notable improvement in understanding of volcanogenic jökulhlaup processes and impacts. This application falls directly into the NERC Science Theme Natural Hazards: reducing casualties and economic losses caused by natural hazards. Quantification and modelling of jökulhlaup hydrograph characteristics will contribute to the better design of roads, bridges and flood defences as well as contributing to the revision of flood inundation maps. Project outcomes will directly benefit the IMO and Icelandic Civil Protection Department who manage and monitor volcanic and hydrological emergencies.

Eyjafallajokull A

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