Abstract
AbstractHow landscapes respond to, and evolve from, large jökulhlaups (glacial outburst floods) is poorly constrained due to limited observations and detailed monitoring. We investigate how melt of glacier ice transported and deposited by multiple jökulhlaups during the 2010 eruption of Eyjafjallajökull, Iceland, modified the volume and surface elevation of jökulhlaup deposits. Jökulhlaups generated by the eruption deposited large volumes of sediment and ice, causing significant geomorphic change in the Gígjökull proglacial basin over a 4-week period. Observation of these events enabled robust constraints on the physical properties of the floods which informs our understanding of the deposits. Using ground-based LiDAR, GPS observations and the satellite-image-derived ArcticDEMs, we quantify the post-depositional response of the 60 m-thick Gígjökull sediment package to the meltout of buried ice and other geomorphic processes. Between 2010 and 2016, total deposit volume reduced by −0.95 × 106 m3 a−1, with significant surface lowering of up to 1.88 m a−1. Surface lowering and volumetric loss of the deposits is attributed to three factors: (i) meltout of ice deposited by the jökulhlaups; (ii) rapid melting of the buried Gígjökull glacier snout; and (iii) incision of the proglacial meltwater system into the jökulhlaup deposits.
Highlights
It has been hypothesised that an increase in subglacial eruptions and their consequent jökulhlaups could result from a deglaciation-driven glacio-isostatic response of the Earth’s mantle (Pagli and Sigmundsson, 2008; Carrivick and others, 2009)
We present the results from nine data points that are spatially and temporally representative of the geomorphic processes that influence surface elevation change within the Gígjökull basin
Field observations reveal that these surface depressions are kettle holes likely to be the result of the meltout of buried ice blocks (Fig. 4)
Summary
It has been hypothesised that an increase in subglacial eruptions and their consequent jökulhlaups (glacial outburst floods) could result from a deglaciation-driven glacio-isostatic response of the Earth’s mantle (Pagli and Sigmundsson, 2008; Carrivick and others, 2009). If correct, this process would increase the already high potential for volcano–ice interactions within Iceland, given that over 60% of Icelandic ice masses overlie active volcanic zones (Björnsson, 2002). Following the eruption and jökulhlaups, the Gígjökull basin was characterised by a ∼60 m-thick sequence of coarse fluvioglacial sediment and flood-transported glacier ice, underlying a steeply-sloping progradational fan surface (Fig. 2) (Dunning and others, 2013). Field observations at the time of deposition indicate a composition of up to 80% ice for deposits associated with the jökulhlaup on the 15 April 2010
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