The relationship between subglacial water pressure and velocity of Findelengletscher, Switzerland, during its advance and retreat

Iken, Almut; Truffer, Martin

doi:10.1017/s0022143000003282

Cited by 183 publications

(155 citation statements)

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“…Jansson, 1995) or even from year to year on a single glacier (i.e. Iken and Truffer, 1997) because the sampled pressure is determined by the configuration of the drainage system and may not represent the effective basal pressure. We stress that our analysis here applies to the late-summer period, when diurnal borehole water-level variations are prevalent, and may not necessarily hold for other times of year.…”

Section: Results and Implicationsmentioning

confidence: 99%

“…Studies linking water pressure and sliding have relied on measurements of the water level in boreholes intersecting the bed as proxy measures of basal water pressure (e.g. Engelhardt and others, 1978;Iken and Bindschadler, 1986;Jansson, 1995;Iken and Truffer, 1997;Sugiyama and Gudmundsson, 2004). Owing to difficult field logistics, much of our understanding of subglacial pressure variations is based on studies utilizing a small number of boreholes and intervals restricted to periods of the ablation season (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Diurnal fluctuations in borehole water levels: configuration of the drainage system beneath Bench Glacier, Alaska, USA

Fudge¹,

Humphrey

Harper

et al. 2008

J. Glaciol.

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Section: Results and Implicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diurnal fluctuations in borehole water levels: configuration of the drainage system beneath Bench Glacier, Alaska, USA

Fudge¹,

Humphrey

Harper

et al. 2008

J. Glaciol.

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“…If basal motion was higher along the drainage axis than elsewhere, then it did not affect a large enough area for this effect to be expressed at the glacier surface. Previous analysis of variations in glacier motion at Findelengletcher (Iken and Truffer, 1997), at StorglaciÌren (Hanson and others, 1998) and at Haut Glacier d' Arolla others, 2001, 2002b) suggest that the spatial extent of regions of high subglacial water pressure/low basal drag is a key component in causing widespread increases in glacier motion.The area of the bed that is affected by high water pressures along the drainage axis will vary depending on the magnitude and the duration of the highwater-pressure event. There appears to be little difference between these characteristics of water pressure at site MA during the first and second 1998 spring events.…”

Section: Second 1998 Spring Eventmentioning

confidence: 94%

Hydrological controls on patterns of surface, internal and basal motion during three “spring events”: Haut Glacier d’Arolla, Switzerland

et al. 2003

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ABSTRACT. Three early-melt-season high-velocity events (or ''spring events'') occurred on Haut Glacier d' Arolla, Switzerland, during the melt seasons of 1998 and 1999. The events involve enhanced glacier velocity during periods of rapidly increasing bulk discharge in the proglacial stream and high subglacial water pressures. However, differences in spatial patterns of surface velocity, internal ice deformation rates, the spatial extent of high subglacial water pressures and in rates of subglacial sediment deformation suggest different hydrological and mechanical controls. The data from two of the events suggest widespread ice^bed decoupling, particularly along a subglacial drainage axis creating the highest rates of basal motion and ''plug flow'' in the overlying ice. The other event showed evidence of less extensive ice^bed decoupling and sliding along the drainage axis with more mechanical support for ice overburden transferred to areas adjacent to decoupled areas. We suggest that: (1) plug flow may be a common feature on glaciers experiencing locally induced reductions in basal drag; (2) under certain circumstances, enhanced surface motion may be due in part to non-locally forced enhanced bed deformation; and (3) subglacial sediment deformation is confined to a depth of the order of centimetres to decimetres.

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“…However, Iken and Truffer (1997) have shown that the latter sliding law does not hold, even if the effective pressure distribution is known.…”

Section: Consequences For Glacier Models and Ice Deformation Studiesmentioning

confidence: 99%

Implications of till deformation on glacier dynamics

2001

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The dynamics of glacier motion is governed, to a large extent, by the properties of the basal interface. In this paper we address the interaction of a glacier with a layer of till at its bed in an attempt to test whether our physical understanding of till is sufficient to explain general features of the observed flow field and changes in geometry of Black Rapids Glacier, Alaska. We also investigate whether or not a till layer has a clear surface-observable signature in the dynamics of the glacier. Towards this end we use a finite element ice-flow model with a Coulomb failure criterion within the basal till layer. We find that simple 'till physics' can be used to describe decadal, seasonal, and short term (hours to days) velocity variations, and possibly uplift events. Mechanisms for each of these variations involve an increase in the extent of till at failure, a transfer of shear stress across the bed, and a consequent increase in ice deformation. 'Effective shape factors' are calculated to permit a simple incorporation of this boundary condition into glacier response models. Our analyses, however, have not resulted in the identification of a clear and unique signature of a till layer in the surface dynamics of the glacier.

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The relationship between subglacial water pressure and velocity of Findelengletscher, Switzerland, during its advance and retreat

Abstract: ABSTRACT. Findeleng letsc he r, Switze rl a nd , a d\'a nced abo ul 250 m betwee n 1979

Cited by 183 publications

References 20 publications

Diurnal fluctuations in borehole water levels: configuration of the drainage system beneath Bench Glacier, Alaska, USA

Diurnal fluctuations in borehole water levels: configuration of the drainage system beneath Bench Glacier, Alaska, USA

Hydrological controls on patterns of surface, internal and basal motion during three “spring events”: Haut Glacier d’Arolla, Switzerland

Implications of till deformation on glacier dynamics

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