An unusual jökulhlaup resulting from subglacial volcanism, Sólheimajökull, Iceland

Russell, Andrew J.; Tweed, Fiona S.; Roberts, Matthew J.; Harris, Tim; Guðmundsson, M. T.; Knudsen, Óskar; Marren, Philip M.

doi:10.1016/j.quascirev.2010.02.023

Cited by 47 publications

(55 citation statements)

References 74 publications

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“…This event was well documented and has been physically investigated in detail (Russell et al, 2010). The river channel is located in the south of Iceland and it is about 9 km long and 400-700 m wide.…”

Section: Initial Model Inputmentioning

confidence: 90%

“…As the bed elevation at the outlet is about 1-2 m above sea level, and the effects of the seawater on river flood dynamics at the outlet are not significant, it is assumed that the outflow boundary can be set as a free open boundary. Based on the field observations by (Russell et al, 2010), the sediment material is constituted of various grain-size particles from fine granules to coarse boulders, involving granules (2.8 mm), cobbles (105 mm) and boulders (400 mm) with a density of 2680 kg/m 3 . It was assumed that this flood event is mainly dominated by sheet flow load which is conventionally referred to as bed material load transport at high bottom shear stress.…”

Section: Initial Model Inputmentioning

confidence: 99%

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Multiple effects of sediment transport and geomorphic processes within flood events: Modelling and understanding

Guan

Wright

Sleigh

2015

International Journal of Sediment Research

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Flood events can induce considerable sediment transport which in turn influences flow dynamics. This study investigates the multiple effects of sediment transport in floods through modelling a series of hydraulic scenarios, including small-scale experimental cases and a full-scale glacial outburst flood. A non-uniform, layer-based morphodynamic model is presented which is composed of a combination of three modules: a hydrodynamic model governed by the two-dimensional shallow water equations involving sediment effects; a sediment transport model controlling the mass conservation of sediment; and a bed deformation model for updating the bed elevation. The model is solved by a second-order Godunov-type numerical scheme. Through the modelling of the selected sediment-laden flow events, the interactions of flow and sediment transport and geomorphic processes within flood events are elucidated. It is found that the inclusion of sediment transport increases peak flow discharge, water level and water depth in dam-break flows over a flat bed. For a partial dam breach, sediment material has a blockage effect on the flood dynamics. In comparison with the 'sudden collapse' of a dam, a gradual dam breach significantly delays the arrival time of peak flow, and the flow hydrograph is changed similarly. Considerable bed erosion and deposition occur within the rapid outburst flood, which scours the river channel severely. It is noted that the flood propagation is accelerated after the incorporation of sediment transport, and the water level in most areas of the channel is reduced.

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Section: Initial Model Inputmentioning

confidence: 90%

Section: Initial Model Inputmentioning

confidence: 99%

Multiple effects of sediment transport and geomorphic processes within flood events: Modelling and understanding

Guan

Wright

Sleigh

2015

International Journal of Sediment Research

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“…Most historic jökulhlaups generated by Katla eruptions have drained through neighbouring Kötlujökull onto Mýrdalssandur to the east; however, some floodwaters generated by the 1860 Katla eruption were routed via Sólheimajökull (Hákonarson, 1860;Björnsson et al, 2000). After this event, the eruption centre moved to the northeast, confining jökulhlaups to Kötlujökull and Mýrdalssandur until 1999, when a volcanically-generated jökulhlaup burst from Sólheimajökull (Roberts et al, 2003;Larsen, 2010;Russell et al, 2010). A number of smaller floods generated by geothermal activity are also known to periodically exit the glacier.…”

Section: Site Descriptionmentioning

confidence: 99%

Seasonal release of anoxic geothermal meltwater from the Katla volcanic system at Sólheimajökull, Iceland

et al. 2015

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Understanding patterns of geothermal and volcanic activity at many of Iceland's most active volcanic systems is hampered by thick overlying ice, which prevents direct observation and complicates interpretation of geophysical signals. Katla is a prime example, being a large and restless volcanic system covered by the 740 m thick Mýrdalsjökull ice cap, whose eruptions have triggered some of the most powerful known meltwater floods in historical times. To shed new light on geothermal and subglacial hydrological processes at Katla, we have determined the sulphate isotopic composition of a series of glacial meltwater samples discharged from Sólheimajökull, a valley glacier of Mýrdalsjökull, between 2009 and 2012. Dual isotopic analysis of δ 34 S and δ 18 O in dissolved sulphate allows identification of source mixing processes and chemical evolution during subglacial meltwater transport. Strikingly, meltwater δ 18 OSO 4 signatures indicate redox conditions at the glacier bed, which are inverse to those normally encountered at Arctic and Alpine glaciers. Discharge of reduced, anoxic meltwater in summer, rather than winter, points towards seasonal release of geothermally derived volatile gases. We attribute this to headward expansion of the channelized subglacial drainage system during the summer melt season, accessing key areas of geothermal activity within the Katla caldera. Volatile release may be further enhanced by unloading of overburden pressure due to snowpack melting in the summer season. In winter, restriction of subglacial channels to lower elevations effectively seals geothermal fluids and dissolved gases beneath the ice cap, with only sporadic release permitted by periodic increases in subglacial water pressure. When the subglacial drainage configuration permits access to key geothermal areas, sulphate isotopic signatures thereby form sensitive indicators of geothermal activity occurring deep beneath the Mýrdalsjökull ice cap.

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“…Studies of the hydrogeology of contemporary glaciers and ice sheets have demonstrated that meltwater discharge varies on a range of scales from daily, yearly, through to much longer decadal cycles (see Benn and Evans, 2010;Russell et al, 2010;Boulton, 2006 and references therein). Such variations lead to the repeated build up of meltwater content and pressures in the subglacial environment which can result not only in the initial propagation of the hydrofracture system, but also the periodic reactivation of these features which act as a 'safety valve' (van der Meer et al, 2008;Phillips et al, 2013) releasing pressure built-up within the subglacial hydrogeological system.…”

Section: Interpretation Of the Micromorphologymentioning

confidence: 99%

Hydrofracturing in response to the development of an overpressurised subglacial meltwater system during drumlin formation: an example from Anglesey, NW Wales

Phillips

Hughes

2014

Proceedings of the Geologists' Association

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This paper presents the results of a detailed study of a complex hydrofracture system and host diamictons exposed within a longitudinal section through an elongate drumlin located to the west of Cemlyn Bay, Anglesey, NW Wales. This complex, laterally extensive sand, silt and clay filled hydrofracture system was active over a prolonged period and is thought to have developed beneath the Late Devensian (Weichselian) Irish Sea Ice Stream as it overrode this part of NW Anglesey. The sediment-fill to the hydrofracture system is deformed with kinematic indicators (folds, thrusts, augen) recording a SW-directed sense of shear, consistent with the regional ice flow direction across this part of the island. The lack of any geomorphological evidence for active retreat of the Irish Sea ice across Anglesey, has led to the conclusion that hydrofracturing at the Cemlyn Bay site occurred within the bed of the Irish Sea Ice Stream whilst this relatively faster flowing corridor of ice was actively overriding the island. Shear imposed by the overriding ice led to the development of a subglacial shear zone which facilitated the propagation of the hydrofracture system with the laterally extensive feeder sills occurring parallel to Y-type Riedel shears. Although a subglacial setting beneath the active Irish Sea Ice Stream can be argued for the Cemlyn Bay hydrofracture system, its relationship to the formation of the 'host' drumlin remains uncertain. However, evidence presented here suggests that hydrofracturing may have occurred during the later stages or post landform development in response to the migration of overpressurised meltwater within the bed of the Irish Sea ice; possibly accompanying the local thinning and shutdown of the Irish Sea Ice Stream on Anglesey.

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An unusual jökulhlaup resulting from subglacial volcanism, Sólheimajökull, Iceland

Cited by 47 publications

References 74 publications

Multiple effects of sediment transport and geomorphic processes within flood events: Modelling and understanding

Multiple effects of sediment transport and geomorphic processes within flood events: Modelling and understanding

Seasonal release of anoxic geothermal meltwater from the Katla volcanic system at Sólheimajökull, Iceland

Hydrofracturing in response to the development of an overpressurised subglacial meltwater system during drumlin formation: an example from Anglesey, NW Wales

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