Influence of subglacial drainage system evolution on glacier surface motion: Haut Glacier d'Arolla, Switzerland

Abstract. Proglacial icings accumulate in front of many High Arctic glaciers during the winter months, as water escapes from englacial or subglacial storage. Such icings have been interpreted as evidence for warm-based subglacial conditions, but several are now known to occur in front of cold-based glaciers. In this study, we investigate the drainage system of Tellbreen, a 3.5 km long glacier in central Spitsbergen, where a large proglacial icing develops each winter, to determine the location and geometry of storage elements. Digital elevation models (DEMs) of the glacier surface and bed were constructed using maps, differential GPS and ground penetrating radar (GPR). Rates of surface lowering indicate that the glacier has a long-term mass balance of −0.6 ± 0.2 m/year. Englacial and subglacial drainage channels were mapped using GPR, showing that Tellbreen has a diverse drainage system that is capable of storing, transporting and releasing water year round. In the upper part of the glacier, drainage is mainly via supraglacial channels. These transition downglacier into shallow englacial "cut and closure" channels, formed by the incision and roof closure of supraglacial channels. Below thin ice near the terminus, these channels reach the bed and contain stored water throughout the winter months. Even though no signs of temperate ice were detected and the bed is below pressure-melting point, Tellbreen has a surface-fed, channelized subglacial drainage system, which allows significant storage and delayed discharge.

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Surge dynamics and lake outbursts of Kyagar Glacier, Karakoram

10.5194/tc-2016-236 ◽

2016 ◽

Author(s):

Vanessa Round ◽

Silvan Leinss ◽

Matthias Huss ◽

Christoph Haemmig ◽

Irena Hajnsek

Keyword(s):

Water Pressure ◽

Thickness Distribution ◽

Drainage System ◽

High Water ◽

Surface Velocity ◽

Glacier Surface ◽

Lake Volume ◽

Lake Formation ◽

Landsat Satellite ◽

Subglacial Drainage

Abstract. The recent surge cycle of Kyagar Glacier, in the Chinese Karakoram, caused formation of an ice-dammed lake and subsequent glacial lake outburst floods (GLOFs) exceeding 50 and 40 million m3 in 2015 and 2016, respectively. GLOFs from Kyagar Glacier reached double this size in 2002 and earlier, but the role of glacier surging in GLOF formation was previously unrecognised. We present an integrative analysis of the glacier surge dynamics from 2011 to 2016, assessing surge mechanisms and evaluating the surge cycle impact on GLOFs. Over 80 glacier surface velocity fields were created from TanDEM-X, Sentinel-1A and Landsat satellite data. Changes in ice thickness distribution were revealed by a time series of TanDEM-X DEMs. The analysis shows that during a quiescence phase lasting at least 14 years, ice mass built up in a reservoir area at the top of the glacier tongue and the terminus thinned by up to 100 m, but in the two years preceding the surge this pattern reversed. The surge clearly initiated with the onset of the 2014 melt season, and in the following 15 months velocity evolved in a manner consistent with a hydrologically-controlled surge mechanism with dramatic accelerations coinciding with melt seasons, winter deceleration accompanied by subglacial drainage, and rapid surge termination following the 2015 GLOF. Rapid basal motion during surging is seemingly controlled by high water pressure caused by input of surface water into either an inefficient subglacial drainage system or unstable subglacial till. Over 60 m of thickening at the terminus caused potential lake volume to increase more than 40-fold since surge onset, to currently more than 70 million m3, indicating that lake formation should be carefully monitored to anticipate large GLOFs in the near future.

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Geomorphic implications of subglacial drainage configuration: rates of basal sediment evacuation controlled by seasonal drainage system evolution

Sedimentary Geology ◽

10.1016/s0037-0738(01)00241-x ◽

2002 ◽

Vol 149 (1-3) ◽

pp. 5-19 ◽

Cited By ~ 46

Author(s):

Darrel A Swift ◽

Peter W Nienow ◽

Nick Spedding ◽

Trevor B Hoey

Keyword(s):

Drainage System ◽

System Evolution ◽

Subglacial Drainage

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Example of the dependence of ice motion on subglacial drainage system evolution: Matanuska Glacier, Alaska, United States

Glacial Processes Past and Present ◽

10.1130/0-8137-2337-x.11 ◽

1999 ◽

Cited By ~ 3

Author(s):

Staci L. Ensminger ◽

Edward B. Evenson ◽

Richard B. Alley ◽

Grahame J. Larson ◽

Daniel E. Lawson ◽

...

Keyword(s):

United States ◽

Drainage System ◽

System Evolution ◽

Matanuska Glacier ◽

Subglacial Drainage

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Seasonal variations in ice deformation and basal motion across the tongue of Haut Glacier d’Arolla, Switzerland

Annals of Glaciology ◽

10.3189/172756403781816455 ◽

2003 ◽

Vol 36 ◽

pp. 157-167 ◽

Cited By ~ 21

Author(s):

Ian Willis ◽

Douglas Mair ◽

Bryn Hubbard ◽

Peter Nienow ◽

Urs H. Fischer ◽

...

Keyword(s):

Surface Deformation ◽

Water Pressure ◽

Drainage System ◽

System Structure ◽

Glacier Surface ◽

Changing Patterns ◽

Internal Deformation ◽

Internal Velocity ◽

Subglacial Drainage

AbstractRecords of surface motion, englacial tilt and repeat inclinometry are used to determine patterns of surface, internal and basal motion across the tongue of Haut Glacier d’Arolla, Switzerland, over temporal scales ranging from days to months. Findings are interpreted with reference to contemporaneous measurements of subglacial water pressures, and prior knowledge of the glacier’s subglacial drainage-system structure. Long-term inclinometry results show pronounced extrusion flow over a subglacial drainage axis, with basal velocities up to twice those measured at the glacier surface. Deformation profiles are more conventional away from the drainage axis, with basal velocities ∼60–70% of surface velocities. Comparison of long-term tilt rates from repeat inclinometry and englacial tiltmeters shows close correspondence. Englacial tiltmeter data are used to reconstruct internal velocity profiles and to split surface velocities into internal deformation and basal motion contributions over spring, summer and autumn/winter periods. Although, spatial patterns of surface movement are similar between periods, patterns of internal and basal motion are not. Results are interpreted in terms of the location of sticky and slippery spots, with temporally changing patterns of basal drag reflecting changing distributions of water pressure.

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Surge dynamics and lake outbursts of Kyagar Glacier, Karakoram

The Cryosphere ◽

10.5194/tc-11-723-2017 ◽

2017 ◽

Vol 11 (2) ◽

pp. 723-739 ◽

Cited By ~ 37

Author(s):

Vanessa Round ◽

Silvan Leinss ◽

Matthias Huss ◽

Christoph Haemmig ◽

Irena Hajnsek

Keyword(s):

Water Pressure ◽

Thickness Distribution ◽

Drainage System ◽

High Water ◽

Surface Velocity ◽

Glacier Surface ◽

Lake Volume ◽

Lake Formation ◽

Landsat Satellite ◽

Subglacial Drainage

Abstract. The recent surge cycle of Kyagar Glacier, in the Chinese Karakoram, caused formation of an ice-dammed lake and subsequent glacial lake outburst floods (GLOFs) exceeding 40 million m3 in 2015 and 2016. GLOFs from Kyagar Glacier reached double this size in 2002 and earlier, but the role of glacier surging in GLOF formation was previously unrecognised. We present an integrative analysis of the glacier surge dynamics from 2011 to 2016, assessing surge mechanisms and evaluating the surge cycle impact on GLOFs. Over 80 glacier surface velocity fields were created from TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement), Sentinel-1A, and Landsat satellite data. Changes in ice thickness distribution were revealed by a time series of TanDEM-X elevation models. The analysis shows that, during a quiescence phase lasting at least 14 years, ice mass built up in a reservoir area at the top of the glacier tongue, and the terminus thinned by up to 100 m, but in the 2 years preceding the surge onset this pattern reversed. The surge initiated with the onset of the 2014 melt season, and in the following 15 months velocity evolved in a manner consistent with a hydrologically controlled surge mechanism. Dramatic accelerations coincided with melt seasons, winter deceleration was accompanied by subglacial drainage, and rapid surge termination occurred following the 2015 GLOF. Rapid basal motion during the surge is seemingly controlled by high water pressure, caused by input of surface water into either an inefficient subglacial drainage system or unstable subglacial till. The potential lake volume increased to more than 70 million m3 by late 2016, as a result of over 60 m of thickening at the terminus. Lake formation and the evolution of the ice dam height should be carefully monitored through remote sensing to anticipate large GLOFs in the near future.

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Changes in geometry and subglacial drainage derived from digital elevation models: Unteraargletscher, Switzerland, 1927–97

Annals of Glaciology ◽

10.3189/172756405781813528 ◽

2005 ◽

Vol 40 ◽

pp. 20-24 ◽

Cited By ~ 13

Author(s):

Urs H. Fischer ◽

André Braun ◽

Andreas Bauder ◽

Gwenn E. Flowers

Keyword(s):

Water Flow ◽

Digital Elevation Models ◽

Drainage System ◽

System Structure ◽

Water Drainage ◽

Drainage Pattern ◽

Glacier Surface ◽

Digital Elevation ◽

Bed Changes ◽

Subglacial Drainage

AbstractDigital elevation models of the bed and surface of Unteraargletscher, Switzerland, are used to reconstruct the theoretical pattern of basal water drainage for the years 1927, 1947, 1961 and 1997, during which period the glacier was thinning and receding. The theoretical drainage pattern for 1997 compares well, in a broad sense, with the locations of active moulins and the hydraulic connection status of boreholes drilled to the glacier bed. Changes in the basal water-flow pattern over the period 1927–97 that are revealed by the theoretical reconstructions of the subglacial drainage system structure are likely to have resulted from changes in glacier geometry. Concurrent with the retreat and thinning of the glacier, the height of medial moraines increased, probably due to the insulating effect of the debris cover reducing the melt of the underlying ice. This increase of moraine heights has led to the formation of hydraulic barriers at the glacier bed such that water flow has become channelized beneath the ice along drainage axes that parallel the course of the medial moraines on the glacier surface.

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Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by Ground Penetrating Radar

The Cryosphere Discussions ◽

10.5194/tcd-4-2169-2010 ◽

2010 ◽

Vol 4 (4) ◽

pp. 2169-2199

Author(s):

K. Bælum ◽

D. I. Benn

Keyword(s):

Ground Penetrating Radar ◽

Thermal Structure ◽

Drainage System ◽

High Arctic ◽

Differential Gps ◽

Glacier Surface ◽

Drainage Channels ◽

Polythermal Glacier ◽

Ground Penetrating ◽

Subglacial Drainage

Abstract. Proglacial icings accumulate in front of many High Arctic glaciers during the winter months, as water escapes from englacial or subglacial storage. Such icings have been interpreted as evidence for warm-based subglacial conditions, but several are now known to occur in front of cold-based glaciers. In this study, we investigate the drainage system of Tellbreen, a 3.5 km long cold-based polythermal glacier in central Spitsbergen, where a large proglacial icing develops each winter, to determine the location and geometry of storage elements. DEMs of the glacier surface and bed were constructed using maps, differential GPS and GPR. Patterns of surface lowering indicate that the glacier has a long-term mass balance of −0.6 ± 0.2 m/year. Englacial and subglacial drainage channels were mapped using Ground penetrating radar (GPR), showing that Tellbreen has a diverse drainage system that is capable of storing, transporting and releasing water year round. In the upper part of the glacier, drainage is mainly via supraglacial channels. These transition downglacier into shallow englacial "cut and closure" channels, formed by the incision and closure of supraglacial channels. Below thin ice near the terminus, these channels reach the bed and contain stored water throughout the winter months. Even though the bed is below pressure-melting point, Tellbreen has a surface-fed, channelized subglacial drainage system, which allows significant storage and delayed discharge.

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Large-scale integrated subglacial drainage around the former Keewatin Ice Divide, Canada reveals interaction between distributed and channelised systems

10.5194/tc-2020-10 ◽

2020 ◽

Cited By ~ 1

Author(s):

Emma L. M. Lewington ◽

Stephen J. Livingstone ◽

Chris D. Clark ◽

Andrew J. Sole ◽

Robert D. Storrar

Keyword(s):

Spatial Distribution ◽

Dynamic Response ◽

Large Scale ◽

Water Pressure ◽

Pressure Fluctuations ◽

Drainage System ◽

Different Types ◽

Form Part ◽

Subglacial Meltwater ◽

Subglacial Drainage

Abstract. We identify and map traces of subglacial meltwater drainage around the former Keewatin Ice Divide, Canada from ArcticDEM data. Meltwater tracks, tunnel valleys and esker splays exhibit several key similarities, including width, spacing, their association with eskers and transitions to and from different types, which together suggest they form part of an integrated drainage signature. We collectively term these features &apos;meltwater corridors&apos; and propose a new model for their formation, based on observations from contemporary ice masses, of pressure fluctuations surrounding a central conduit. We suggest that eskers record the imprint of a central conduit and meltwater corridors the interaction with the surrounding distributed drainage system. The widespread aerial coverage of meltwater corridors (5–36 % of the bed) provides constraints on the extent of basal uncoupling induced by basal water pressure fluctuations and variations in spatial distribution and evolution of the subglacial drainage system, which will modulate the ice dynamic response.

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Combined measurements of Subglacial Water Pressure and Surface Velocity of Findelengletscher, Switzerland: Conclusions about Drainage System and Sliding Mechanism

Journal of Glaciology ◽

10.3189/s0022143000006936 ◽

1986 ◽

Vol 32 (110) ◽

pp. 101-119 ◽

Cited By ~ 35

Author(s):

Almut Iken ◽

Robert A. Bindschadler

Keyword(s):

Functional Relationship ◽

Water Pressure ◽

Drainage System ◽

High Water ◽

Water Levels ◽

Surface Velocity ◽

Glacier Surface ◽

Measured Velocity ◽

Sliding Mechanism ◽

Velocity Variations

AbstractDuring the snow-melt season of 1982, basal water pressure was recorded in 11 bore holes communicating with the subglacial drainage system. In most of these holes the water levels were at approximately the same depth (around 70 m below surface). The large variations of water pressure, such as diurnal variations, were usually similar at different locations and in phase. In two instances of exceptionally high water pressure, however, systematic phase shifts were observed; a wave of high pressure travelled down-glacier with a velocity of approximately 100 m/h.The glacier-surface velocity was measured at four lines of stakes several times daily. The velocity variations correlated with variations in subglacial water pressure. The functional relationship of water pressure and velocity suggests that fluctuating bed separation was responsible for the velocity variations. The empirical functional relationship is compared to that of sliding over a perfectly lubricated sinusoidal bed. On the basis of the measured velocity-pressure relationship, this model predicts a reasonable value of bed roughness but too high a sliding velocity and unstable sliding at too low a water pressure. The main reason for this disagreement is probably the neglect of friction from debris in the sliding model.The measured water pressure was considerably higher than that predicted by the theory of steady flow through straight cylindrical channels near the glacier bed. Possible reasons are considered. The very large disagreement between measured and predicted pressure suggests that no straight cylindrical channels may have existed.

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