Plucking as an Effect of Water-Pressure Variations at the Glacier Bed

Röthlisberger, Hans; Iken, Almut

doi:10.3189/172756481794352144

Cited by 137 publications

(66 citation statements)

References 12 publications

(12 reference statements)

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“…This process must be modelled. Considerations of bed erosion or debris mass balance require that a quarrying law be introduced, but none exists, although ROthlisberger and Iken (1981) have investigated a mechanism which is highly dependent on fluctuations in water pressure and is aided by a low basal effective pressure. Perhaps the simplest quarrying laws would be of the forms…”

Section: -400)mentioning

confidence: 99%

Debris-Influenced Sliding Laws and Basal Debris Balance

Shoemaker¹

1986

J. Glaciol.

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ABSTRACT. In order to determine the effect of basal debris drag as a component in a sliding law, it is necessary to know the basal debris concentration. Does, for example, this debris concentration exhibit uniformity, in an average sense, across a valley? What effect does a localized region of high Quarryability have on basal debris concentration down-stream? The analysis presented here suggests that, for the case of sparse debris, debris concentration tends to be uniform over the entire bed. Consequently, the debris-drag term in a sliding law will also tend to be uniform.In order to reach the above conclusions, it is necessary to consider debris balance, the balance of the Quarrying, abrasion, and debris-flushing rates. This entails proposing and testing Quarrying and flushing laws, since these laws have not been previously proposed. It is concluded that the Quarrying, flushing, and erosion rates depend weakly on the sliding velocity. Furthermore, the abrasion rate is negligible compared to the Quarrying rate. (This conclusion depends partially on the definition of abrasion.) The Quarrying rate also depends on otht'r factors such as the effective pressure-pressure-fluctuation mechanism; the cross-valley dependency of this mechanism is investigated. The flushing rate is found to depend on the ratio, N-channel area/ bed area, and on average N-channel diameter.

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Section: -400)mentioning

confidence: 99%

Debris-Influenced Sliding Laws and Basal Debris Balance

Shoemaker¹

1986

J. Glaciol.

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“…Following Iken (1981) and Röthlisberger and Iken (1981), we therefore propose the following explanation for our ice velocity observations (Fig. 10).…”

Section: Hydrology and Dynamicsmentioning

confidence: 99%

Variability in ice motion at a land-terminating Greenlandic outlet glacier: the role of channelized and distributed drainage systems

et al. 2016

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ABSTRACT. We use a combination of field observations and hydrological modelling to examine the mechanisms through which variability in meltwater input affects ice motion at a land-terminating Greenlandic outlet glacier. We find a close agreement between horizontal ice velocity, vertical ice velocity and modelled subglacial water pressure over the course of a melt season. On this basis, we argue that variation in horizontal and vertical ice velocity primarily reflects the displacement of basal ice during periods of cavity expansion and contraction, a process itself driven by fluctuations in basal water pressure originating in subglacial channels. This process is not captured by traditional sliding laws linking water pressure and basal velocity, which may hinder the simulation of realistic diurnal to seasonal variability in ice velocity in coupled models of glacial hydrology and dynamics.

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“…Bezinge and others, 1973;Vivian and Zumstein, 1973; Wold and 0strem, 1979). From a scientific point of view, knowledge about glacier bed characteristics is essentially relevant to studies done on glacier sliding, (Ll iboutry, 1979;Weertman, 1979;Iken, 1981; Iken and others, 1983) and to those which deal with processe~ of glacier erosion (Boulton, 1979;Collins, 1979;Rothlisberger and Iken, 1981).Commercial projects mainly utilize core drillings, either from the glacier surface downwards or from already existing rock galleries upwards, to probe the glaCier bed. Scientific studies have to try less expensive methods, such as hot-water drilling (e .…”

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confidence: 99%

Electrical Resistivity Soundings of Glacier Beds: A Test Study on Grubengletscher, Wallis, Swiss Alps

Haeberli¹,

Fisch²

1984

J. Glaciol.

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ABSTRA CT . Elec tri cal res isti vity sounding, usin g electrodes whic h are lowered direc tl y to th e ice-rock interface in bore holes, is proposed as a technique for stud ying the exact position of glacier beds, as well as their lithologica l ch a rac teristics. A test study is d escribed on G rubeng letscher, a pa rtially cold Alpin e glacier in Switzerl a nd. Res ul ts of so undings a long a 400 m long p rofil e indicate that previo us depth determina ti o ns, based on radio echo -soundings, were in gene ral accura te to w ithin less than 50/ 0 of the ac tu al ice thic kness. The resu lts also sho w th at the glacie r rests o n nonconsolid a ted sedimen ts of considera ble thi ckness. The proposed me thod could add substa nti al inform ati o n a bo ut g lacie r sliding a nd g la cier e rosion, if a pplied al o ngsid e conve ntional d ee p drilling projec ts. I NTRODUCTI ONThe beds of existing glaciers are characterized by a wide variety of morphological and lithological conditions . These beds may be rough or smooth depending on the scale considered, and they may consist of rock or unconsolidated sediments. Sediments at glacier beds mayor may not be frozen, and they mayor may not contain ground-water. To know what conditions exist at the glacier bed in a specific case is important for several reasons.Practical applications in connection with the planning and operation of Alpine hydroelectric power stations, such as the installation of subglacial water intakes or rock galleries for water adduction, may require the exact position and the lithological characteristics of glaCier beds (e.g . Bezinge and others, 1973;Vivian and Zumstein, 1973; Wold and 0strem, 1979). From a scientific point of view, knowledge about glacier bed characteristics is essentially relevant to studies done on glacier sliding, (Ll iboutry, 1979;Weertman, 1979;Iken, 1981; Iken and others, 1983) and to those which deal with processe~ of glacier erosion (Boulton, 1979;Collins, 1979;Rothlisberger and Iken, 1981).Commercial projects mainly utilize core drillings, either from the glacier surface downwards or from already existing rock galleries upwards, to probe the glaCier bed. Scientific studies have to try less expensive methods, such as hot-water drilling (e . g. Iken and others, 1977), geophysical soundings (Susstrunk, 1951;Rothlisberger, 1967;Robin, 1975) observations with bore-hole cameras (Engelhardt and others, 1978), or observations in ice tunnels (Boulton, 1979). All these methods furnish information of limited accuracy or point information only. This paper proposes a method by which it is hoped to be able partially to fill this gap: electrical resistivity soundings of glacier beds . Elektrisc he Widerstandssondierunge n mit El e ktrod en, di e in Bohrloche rn direkt a n d e r Eisunte rg re nze in stallie rt we rde n, wcrd en fU r die U nte rsuc hung d er genau en Lage und der lithologischen Charakteristik von G letscherbetten vorgeschl agen. Eine T estmess ung am G rubengletsche r, einem teil weise ka lte n Gletsche r der Schwe...

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Plucking as an Effect of Water-Pressure Variations at the Glacier Bed

Cited by 137 publications

References 12 publications

Debris-Influenced Sliding Laws and Basal Debris Balance

Debris-Influenced Sliding Laws and Basal Debris Balance

Variability in ice motion at a land-terminating Greenlandic outlet glacier: the role of channelized and distributed drainage systems

Electrical Resistivity Soundings of Glacier Beds: A Test Study on Grubengletscher, Wallis, Swiss Alps

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