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Nicolaj Krog Larsen

Creep and stick-slip in subglacial granular beds forced by variations in water pressure

Publikation: KonferencebidragKonferenceabstrakt til konferenceForskning

Observations show that the flow velocities of several marine-terminating glaciers and ice streams are strongly linked to variations in the subglacial water pressure and tidal stage. Deformation of subglacial sediments often accounts for much of the flow, but the mechanical behavior of these sediment remains poorly understood. Measurements and laboratory experiments provide important constraints, but existing models have not been able to explain the internal processes driving transitions from stability to stick-slip within the sediment.

In this presentation we use a coupled numerical model of grain and fluid dynamics to show that rapid rearrangements of load-bearing force chains within the granular sediments drive mechanical transitions between stability and failure. Cyclic variations in driving stresses or pore-water pressure give rise to strain-rate dependent creeping motion at stress levels below the point of failure, while disruption of the force-chain network induces fast strain-rate independent flow above it. This finding contrasts previous descriptions of subglacial sediment mechanics, which either assume a rate-dependent rheology regardless of mechanical state or unconditional stability before the sediment is stressed to its yield point.

Our new micro-mechanical computational approach is capable of reproducing important mechanical transitions, and it can explain multimodal velocity patterns observed in marine-terminating glacier and ice stream systems.
StatusUdgivet - 2016
BegivenhedWest Antarctic Ice Sheet Initiative Workshop - Sterling, USA
Varighed: 3 okt. 20166 okt. 2016
Konferencens nummer: 23


WorkshopWest Antarctic Ice Sheet Initiative Workshop

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