Role of discrete recharge from the supraglacial drainage system for modelling of subglacial conduits pattern of Svalbard polythermal glaciers

Abstract. Being a determinant factor of the glacier’s dynamic, subglacial water behavior needs a special attention.Water flowing from the glacier’s surface is the principal source supplying the subglacial drainage system. Therefore, insight into the state and evolution of the supraglacial drainage system is crucial for recognition of recharge pattern of the englacial and subglacial drainage pathways. Climate warming causes increased ablation generating higher amount of meltwater and thinning of glacier. Decadal timescale evolution of the supraglacial drainage leads to some modifications of the system in opposition to its nearly stable state on an annual timescale. For two studied glaciers Hansbreen and Werenskioldbreen in southern Svalbard surface meltwater is the main runoff component. During the ablation season 2015, 72.5 % of the total amount was provided by meltwater and 27.5 % by precipitations. Supraglacial catchments were determined on the high resolution digital elevation model using standard watershed modelling tool in ArcGIS, for each water-input area (WIA). Spatialized water runoff calculations for all the main WIAs have been done. Having data on the water sources from catchments delimited on glacier’s surface, modelling of a theoretical pattern of subglacial conduits was done considering discrete water recharge via moulins, shear fractures or crevasses. Classical modelling with an assumption of homogeneous water supply was done for comparison. Several water pressure conditions have been taken into account as well. Results show that models of subglacial drainage system with homogeneous water recharge are more realistic for tidewater glaciers with rather broad permeable firn areas and creased frontal zones, while discrete water recharge models are better for land-terminating glaciers with almost continuous impermeable superficial cold ice layer. Subglacial channel models are assumed to be valid for a minimum period of two decades taking into account evolution of supraglacial drainage system and ice thickness changes of Svalbard polythermal glaciers.

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Role of discrete water recharge from supraglacial drainage systems in modeling patterns of subglacial conduits in Svalbard glaciers

The Cryosphere ◽

10.5194/tc-13-735-2019 ◽

2019 ◽

Vol 13 (3) ◽

pp. 735-752 ◽

Cited By ~ 4

Author(s):

Léo Decaux ◽

Mariusz Grabiec ◽

Dariusz Ignatiuk ◽

Jacek Jania

Keyword(s):

Current Knowledge ◽

Water Pressure ◽

Drainage System ◽

Stable State ◽

Watershed Modeling ◽

Potential Gradient ◽

Water Runoff ◽

Total Runoff ◽

Water Recharge ◽

Elevation Model

Abstract. As the behavior of subglacial water plays a determining role in glacier dynamics, it requires particular attention, especially in the context of climate warming, which is increasing ablation and generating greater amounts of meltwater. On many glaciers, water flowing from the glacier's surface is the main source of supply to the subglacial drainage system. This system is largely influenced by the supraglacial drainage system, which collects meltwater and precipitation and rapidly delivers it to discrete points in the glacier bed via moulins and crevassed areas, called water input areas (WIAs). Models of patterns of subglacial conduits mainly based on the hydrological potential gradient are still regularly performed without taking into account the supraglacial drainage system. We modeled the pattern of subglacial channels in two glaciers located in Svalbard, the land-terminating Werenskioldbreen and the tidewater Hansbreen during the 2015 melt season. We modeled a spatial and a discrete water recharge in order to compare them. First, supraglacial catchments were determined for each WIA on a high-resolution digital elevation model using the standard watershed modeling tool in ArcGIS. Then, interpolated water runoff was calculated for all the main WIAs. Our model also accounts for several water pressure conditions. For our two studied glaciers, during the ablation season 2015, 72.5 % of total runoff was provided by meltwater and 27.5 % by precipitation. Changes in supraglacial drainage on a decadal timescale are observed in contrast to its nearly stable state on an annual timescale. Nevertheless, due to the specific nature of those changes, it seems to have a low impact on the subglacial system. Therefore, our models of subglacial channel are assumed to be valid for a minimum period of two decades and depend on changes in the supraglacial drainage system. Results showed that, for Svalbard tidewater glaciers with large crevassed areas, models of subglacial channels that assume spatial water recharge may be somewhat imprecise but are far from being completely incorrect, especially for the ablation zone. On the other hand, it is important to take discrete water recharge into account in the case of land-terminating Svalbard glaciers with limited crevassed areas. In all cases, considering a discrete water recharge when modeling patterns of theoretical subglacial channels seems to produce more realistic results according to current knowledge.

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A model for interaction between conduits and surrounding hydraulically connected distributed drainage based on geomorphological evidence from Keewatin, Canada

The Cryosphere ◽

10.5194/tc-14-2949-2020 ◽

2020 ◽

Vol 14 (9) ◽

pp. 2949-2976

Author(s):

Emma L. M. Lewington ◽

Stephen J. Livingstone ◽

Chris D. Clark ◽

Andrew J. Sole ◽

Robert D. Storrar

Keyword(s):

Large Scale ◽

Water Pressure ◽

Pressure Fluctuations ◽

Drainage System ◽

Integrated Map ◽

Digital Elevation ◽

Proposed Model ◽

Elevation Model ◽

Spatial Locations ◽

Subglacial Meltwater

Abstract. We identify and map visible traces of subglacial meltwater drainage around the former Keewatin Ice Divide, Canada, from high-resolution Arctic Digital Elevation Model (ArcticDEM) data. We find similarities in the characteristics and spatial locations of landforms traditionally treated separately (i.e. meltwater channels, meltwater tracks and eskers) and propose that creating an integrated map of meltwater routes captures a more holistic picture of the large-scale drainage in this area. We propose the grouping of meltwater channels and meltwater tracks under the term meltwater corridor and suggest that these features in the order of 10s–100s m wide, commonly surrounding eskers and transitioning along flow between different types, represent the interaction between a central conduit (the esker) and surrounding hydraulically connected distributed drainage system (the meltwater corridor). Our proposed model is based on contemporary observations and modelling which suggest that connections between conduits and the surrounding distributed drainage system within the ablation zone occur as a result of overpressurisation of the conduit. 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. Geomorphic work resulting from repeated connection to the surrounding hydraulically connected distributed drainage system suggests that basal sediment can be widely accessed and evacuated by meltwater.

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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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Oscillatory subglacial drainage in the absence of surface melt

The Cryosphere ◽

10.5194/tc-8-959-2014 ◽

2014 ◽

Vol 8 (3) ◽

pp. 959-976 ◽

Cited By ~ 31

Author(s):

C. Schoof ◽

C. A Rada ◽

N. J. Wilson ◽

G. E. Flowers ◽

M. Haseloff

Keyword(s):

Water Pressure ◽

Drainage System ◽

Yukon Territory ◽

Strongly Correlated ◽

Pressure Oscillations ◽

Power Failure ◽

Multiple Data ◽

Data Loggers ◽

Diurnal Cycling ◽

Subglacial Drainage

Abstract. The presence of strong diurnal cycling in basal water pressure records obtained during the melt season is well established for many glaciers. The behaviour of the drainage system outside the melt season is less well understood. Here we present borehole observations from a surge-type valley glacier in the St Elias Mountains, Yukon Territory, Canada. Our data indicate the onset of strongly correlated multi-day oscillations in water pressure in multiple boreholes straddling a main drainage axis, starting several weeks after the disappearance of a dominant diurnal mode in August 2011 and persisting until at least January 2012, when multiple data loggers suffered power failure. Jökulhlaups provide a template for understanding spontaneous water pressure oscillations not driven by external supply variability. Using a subglacial drainage model, we show that water pressure oscillations can also be driven on a much smaller scale by the interaction between conduit growth and distributed water storage in smaller water pockets, basal crevasses and moulins, and that oscillations can be triggered when water supply drops below a critical value. We suggest this in combination with a steady background supply of water from ground water or englacial drainage as a possible explanation for the observed wintertime pressure oscillations.

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Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by ground penetrating radar

The Cryosphere ◽

10.5194/tc-5-139-2011 ◽

2011 ◽

Vol 5 (1) ◽

pp. 139-149 ◽

Cited By ~ 45

Author(s):

K. Bælum ◽

D. I. Benn

Keyword(s):

Ground Penetrating Radar ◽

Thermal Structure ◽

Drainage System ◽

High Arctic ◽

Differential Gps ◽

Glacier Surface ◽

Digital Elevation ◽

Drainage Channels ◽

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 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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Investigating Spatio-temporal Changes in Subglacial Hydrology from Dense Array Seismology.

10.5194/egusphere-egu2020-10710 ◽

2020 ◽

Author(s):

Ugo Nanni ◽

Florent Gimbert ◽

Philippe Roux ◽

Albanne Lecointre

Keyword(s):

Water Flow ◽

Seismic Noise ◽

Water Pressure ◽

Noise Analysis ◽

Drainage System ◽

Dense Array ◽

Noise Sources ◽

Spatio Temporal ◽

Surrounding Areas ◽

Subglacial Drainage

Subglacial hydrology strongly modulates glacier basal sliding, and thus likely exerts a major control on ice loss and sea-level rise. However, the limited direct and spatialized observations of the subglacial drainage system make difficult to assess the physical processes involved in its development. Recent work shows that detectable seismic noise is generated by subglacial water flow, such that seismic noise analysis may be used to retrieve the physical properties of subglacial channelized water flow. Yet, investigating the spatial organisation of the drainage system (e.g. channels numbers and positions) together with its evolving properties (e.g. pressure conditions) through seismic observations remains to be done. The objective of this study is to bring new insights on the subglacial hydrology spatio-temporal dynamics using dense array seismic observations.We use 1-month long ground motion records at a hundred of sensors deployed on the Argenti&#232;re Glacier (French Alps) during the onset of the melt season, when the subglacial drainage system is expected to strongly evolve in response to the rapidly increasing water input. We conduct a multi-method approach based on the analysis of both amplitude and phase maps of seismic signals. We observe characteristic spatial patterns, consistent across those independent approaches, which we attribute to the underlying subglacial drainage system.The phase-driven approach shows seismic noise sources that focuses in the along-flow direction as the water input increases. We identify this evolution as the development of the main subglacial channel whose position is coherent with the one expected from hydraulic potential calculations. During periods of rapid changes in water input (5 days over 31) and concomitant glacier acceleration the amplitude-driven approach shows spatial pattern highly consistent with the seismic noise sources location. At this time, we suggest that the spatial variations in the amplitude are representative of the water pressure conditions in subglacial channels and surrounding areas. Our spatialized observations therefore reveal the spatio-temporal evolution of the subglacial drainage system together with its changing pressure conditions. We observe, for instance, that channels develop at the very onset of the melt-season and rapidly capture the water from surrounding areas. Such unique observations may allow to better constrain the physics of subglacial water flow and therefore strengthen our knowledge on the dynamics of subglacial environments.

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Short-term velocity and water-pressure variations down-glacier from a riegel, Storglaciären, Sweden

Journal of Glaciology ◽

10.3189/s0022143000002689 ◽

1998 ◽

Vol 44 (147) ◽

pp. 359-367 ◽

Cited By ~ 1

Author(s):

Brian Hanson ◽

Roger LeB. Hooke ◽

Edmund M. Grace

Keyword(s):

Water Pressure ◽

Spatial Coherence ◽

Drainage System ◽

Pressure Rise ◽

Surface Velocity ◽

Storm Events ◽

Pressure Cycle ◽

Large Water ◽

Local Water ◽

Subglacial Drainage

AbstractDuring the 1991 94 summer held seasons, time-correlated measure-merits of water pressure and surface speed were made over and down-glacier from a major riegel on Storglaciären, Sweden. Measurements were made at sub-hourly time-scales in order to discern details in the diurnal cycle. Large water-input events, typically associated with rain storms, produced coherent, lagged surface-velocity responses that could be understood in terms of till deformation or decoupling, and these have been discussed elsewhere. The consequences of smaller diurnal water-pressure events w ere more enigmatic, in that acceleration of ice flow generally preceded the onset of the local water-pressure rise. From consideration of these data and other work done on the hydrology of Storglaciären, we infer that the ice in this area is generally pushed from behind via a relaxation in extensional strain across the riegel. Hence, accelerations occur in response to increases in water pressure that occur up-glacier and that precede local water-pressure rises. In addition, following a period of large storm events, surface speeds became more spatially coherent and were in phase with the diurnal water-pressure cycle. This suggests that the large water-pressure events lead to a spatially more homogeneous subglacial drainage system. Sliding laws need to take into account such temporal changes in spatial coherence of the subglacial drainage system.

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Analysis of Morphological Features of Sargalu Region in Sulaymaniyah Governorate, North of Iraq, by using Geographic Information System

Iraqi Journal of Science ◽

10.24996/ijs.2021.62.4.13 ◽

2021 ◽

pp. 1164-1176

Author(s):

Ali Abdul-Jaleel Hussain ◽

Muaid Jassim Rasheed

Keyword(s):

Thermal Emission ◽

Drainage System ◽

Asymmetry Factor ◽

Digital Elevation ◽

The Social ◽

Structural Disturbance ◽

Tectonically Active ◽

Elevation Model ◽

Geological Formations ◽

Tectonic Activities

It is an ideal area of research to examine related indicators to anticipate relative tectonic activities, where there is a broad range of geological formations with elements of different sedimentary rocks. This study includes assessing and evaluating the relative tectonic activities within the Sargalu area by using a morphometric approach, which involved the use of different indices that can explain and help understanding the geometry, development level, lithology, and structural disturbance on a sub-basinal level. The research was accomplished by using ArcGIS 10.5 hydrology tools to design the drainage system of each studied stream. The Advanced Spaceborne Thermal Emission Radiometer (ASTER) satellite imagery data and the Digital Elevation Model (DEM 90m) were used. Moreover, Global Mapper and Statistical Package for the Social Sciences (SPSS) were applied. DEM datasets of ASTER were used for watershed delineation. Also, 14 sub-basins were delineated in the Sargalu area. Morphometric indices used include Shape Related Indices, such as Rc, Bs, Rf, Ls, Re, T, and Af. Basin asymmetry factor (Af) and several geomorphic indices were also utilized. Based on the shape related indices (Rc, Rf, Re, Ls, and Cc), the results were found to be similar and, for most sub-basins, had an elongated nature. The elongated basins are connected with tectonically active areas, while the circulated basins are connected with the tectonically undisturbed environment.

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Erosion rates and sediment yields of glaciers

Annals of Glaciology ◽

10.1017/s0260305500015202 ◽

1996 ◽

Vol 22 ◽

pp. 48-52 ◽

Cited By ~ 36

Author(s):

Jim Bogen

Keyword(s):

Water Pressure ◽

Water Discharge ◽

Drainage System ◽

Sediment Concentration ◽

Pressure Drops ◽

Sediment Yields ◽

Erosion Rates ◽

Slow Moving ◽

The Relationship ◽

Subglacial Drainage

Sediment yields and glacial erosion rates are evaluated for four Norwegian glaciers during the years 1989-93. Annual erosion rates were determined from measurements of sediment load and water discharge in glacial meltwater rivers. The mean sediment yield and the corresponding erosion rate of the valley glaciers Engabreen and Nigardsbreen were found to be 456 t km−2year−1(0.168 mm year−1) and 210 t km−2year−1(0.078 mm year−1), respectively. A small and slow-moving cirque glacier Øvre Beiarbre yielded a rate of 482 t km−2year−1(0.178 mm year−1), and the sub-polar Svalbard glacier Brøggerbreen yielded 613 t km−2year−1(0.226 mm year−1). The erosion rates are low compared to glaciers elsewhere. There are also considerable variations in sediment yields at each glacier from year to year. However, different factors are found to control the variability on each individual glacier. Analysis of the relationship between water discharge and sediment concentration in meltwater rivers suggests that changes in subglacial drainage systems cause variations in sediment availability and the way sediments are melted out from the ice. When water pressure drops, the drainage system in fast-moving, thick valley glaciers deforms at a more rapid rate than in thin, slow-moving ones. New volumes of debris-laden ice are thus more readily available for melting when water pressure next increases. Beneath the thin, slow-moving Øvre Beiarbre, single years with high transport rates and evacuation of sediment are followed by periods of low availability lasting for 2 years or longer. It is suggested that this pattern results from exhaustion of sediment in a stable drainage system, with more sediment becoming available when the position of the subglacial drainage system is changed.

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The meltwater feedbacks on ice dynamics, influence of melt amplitude, duration and extent.

10.5194/egusphere-egu21-1099 ◽

2021 ◽

Author(s):

Basile de Fleurian ◽

Petra M. Langebroeke ◽

Richard Davy

Keyword(s):

Water Pressure ◽

Ice Sheet ◽

Drainage System ◽

Greenland Ice Sheet ◽

System Model ◽

Ice Dynamics ◽

Mountain Glaciers ◽

Different Characteristics ◽

Crucial Parameter ◽

Subglacial Drainage

In recent years, temperatures over the Greenland ice sheet have been rising, leading to an increase in surface melt. This increase however can not be reduced to a simple number. Throughout the recent years we have seen some extreme melt seasons with melt extending over the whole surface of the ice sheet (2012) or melt seasons of lower amplitudes but with a longer duration (2010). The effect of those variations on the subglacial system and hence on ice dynamic are poorly understood and are still mainly deduced from studies based on mountain glaciers.Here we apply the Ice-sheet and Sea-level System Model (ISSM) to a synthetic glacier with a geometry similar to a Greenland ice sheet land terminating glacier. The forcing is designed such that it allows to investigate different characteristics of the melt season: its length, intensity or the spatial extension of the melt. Subglacial hydrology and ice dynamics are coupled within ISSM is coupled to a subglacial hydrology model, allowing to study the response of the system in terms of subglacial water pressure and the final impact on ice dynamics. Of particular interest is the evolution of the distribution of the efficient and inefficient component of the subglacial drainage system which directly impacts the water pressure evolution at the base of the glacier.We note that the initiation of the melt season and the intensity of the melt at this period is a crucial parameter when studying the dynamic response of the glacier to different melt season characteristics. From those results, we can infer a more precise evolution of the dynamics of land terminating glaciers that are heavily driven by their subglacial drainage system. We also highlight which changes in the melt season pattern would be the most damageable for glacier stability in the future.

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