Multi-decadal reduction in glacier velocities and mechanisms driving deceleration at polythermal White Glacier, Arctic Canada

ABSTRACTAnnual and seasonal surface velocities measured continuously from 1960 to 1970 at White Glacier, a 14 km long polythermal valley glacier spanning ~100–1800 m a.s.l., provide the most comprehensive early record of ice dynamics in the Canadian Arctic. Through comparison with differential GPS-derived velocity data spanning 2012–16, we find reductions in mean annual velocity by 31 and 38% at lower elevations (600 and 400 m a.s.l.). These are associated with decreased internal ice deformation due to ice thinning and reduced basal motion likely due to increased hydraulic efficiency in recent years. At higher elevation (~850 m a.s.l.) there is no detectable change in annual velocity and the expected decrease in internal deformation rates due to ice thinning is offset by increased basal motion in both summer and winter, likely attributable to supraglacial melt accessing a still inefficient subglacial drainage system. Decreases in mass flux at lower elevations since the 1960s cannot explain the observed elevation loss of ~20 m, meaning that ice thinning along the glacier trunk is primarily a function of downwasting rather than changing ice dynamics. The current response of the glacier exemplifies steady thinning, velocity slowdown and upstream retreat of the ELA but, because the glacier has an unstable geometry with considerable mass in the 1300–1500 m elevation range, a retreat of the ELA to >1300 plausible within 25–40 years, could trigger runaway wastage.

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The Relevance of Grated Inlets within Surface Drainage Systems in the Field of Urban Flood Resilience. A Review of Several Experimental and Numerical Simulation Approaches

Sustainability ◽

10.3390/su13137189 ◽

2021 ◽

Vol 13 (13) ◽

pp. 7189

Author(s):

Beniamino Russo ◽

Manuel Gómez Valentín ◽

Jackson Tellez-Álvarez

Keyword(s):

Overland Flow ◽

Drainage System ◽

Critical Conditions ◽

Hydraulic Efficiency ◽

Storm Events ◽

Urban Resilience ◽

Urban Flood ◽

Drainage Systems ◽

Surface Drainage ◽

Intense Storm

Urban drainage networks should be designed and operated preferably under open channel flow conditions without flux return, backwater, or overflows. In the case of extreme storm events, urban pluvial flooding is generated by the excess of surface runoff that could not be conveyed by pressurized sewer pipes, due to its limited capacity or, many times, due to the poor efficiency of surface drainage systems to collect uncontrolled overland flow. Generally, the hydraulic design of sewer systems is addressed more for underground networks, neglecting the surface drainage system, although inadequate inlet spacings and locations can cause dangerous flooding with relevant socio-economic impacts and the interruption of critical services and urban activities. Several experimental and numerical studies carried out at the Technical University of Catalonia (UPC) and other research institutions demonstrated that the hydraulic efficiency of inlets can be very low under critical conditions (e.g., high circulating overland flow on steep areas). In these cases, the hydraulic efficiency of conventional grated inlets and continuous transverse elements can be around 10–20%. Their hydraulic capacity, expressed in terms of discharge coefficients, shows the same criticism with values quite far from those that are usually used in several project practice phases. The grate clogging phenomenon and more intense storm events produced by climate change could further reduce the inlets’ performance. In this context, in order to improve the flood urban resilience of our cities, the relevance of the hydraulic behavior of surface drainage systems is clear.

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On the Thermal Regime of a High-Arctic Valley Glacier

Journal of Glaciology ◽

10.3189/s0022143000031476 ◽

1976 ◽

Vol 16 (74) ◽

pp. 119-133 ◽

Cited By ~ 5

Author(s):

Fritz Müller

Keyword(s):

Thermal Regime ◽

Energy Input ◽

Canadian Arctic ◽

High Arctic ◽

Canadian Arctic Archipelago ◽

Valley Glacier ◽

Drilling Technique ◽

Percolation Zone ◽

Mean Annual Air Temperature ◽

Upper Boundary

AbstractThe 10 m temperatures were measured over several years at 16 sites on the White Glacier (lat. 80° N.), Axel Heiberg Island, Canadian Arctic Archipelago. At three sites deep profiles were made using a new drilling technique, reaching a maximum depth of 280 m. Large differences in the 10 m temperatures between locations and from year to year were observed. The deviations of these temperatures from the almost isothermal mean annual air temperature over the glacier are discussed. The heating effect of the melt water in the lower percolation zone was found to be very important. A conceptual model is developed to assess the influence of these irregularities in the energy input at the upper boundary on the thermal regime of the entire glacier. So far a quantitative analysis has been made only for the relatively simple 30 m temperature profile measured on the tongue of the glacier.

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Determining the extent of pressurized flow beneath Storglaciären, Sweden, using results of tracer experiments and measurements of input and output discharge

Journal of Glaciology ◽

10.3189/s0022143000016129 ◽

1995 ◽

Vol 41 (138) ◽

pp. 217-231 ◽

Cited By ~ 2

Author(s):

Jack Kohler

Keyword(s):

Open Channel ◽

Drainage System ◽

Tracer Tests ◽

Tracer Experiment ◽

Northern Sweden ◽

Discharge Data ◽

Input And Output ◽

Valley Glacier ◽

Small Valley ◽

Tracer Experiments

AbstractTwo experiments were conducted on the drainage system beneath the Lower part of the ablation zone of Storglaciären, a small valley glacier in northern Sweden. In the first experiment, over 70 tracer tests were performed in a cluster of moulins during a 1 month period, at sub-daily intervals. In the second experiment, input- and output-discharge signals were measured on the supraglacial melt stream emptying into a moulin and on the proglacial stream to which the moulin drains. The data from these two experiments are used in an idealized model of the subglacial drainage system to calculate the percentage of the system flowing as an open channel. Results from the tracer experiment suggest that the system is pressurized to within 60-340 m of the snout, while analysis of the discharge data indicates pressurized ronduits to within 0-415 m of the snout.

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Hydraulic efficiency of road drainage inlets for storm drainage system under clogging effect

Urban Water III ◽

10.2495/uw160241 ◽

2016 ◽

Cited By ~ 1

Author(s):

R. Veerappan ◽

J. Le

Keyword(s):

Drainage System ◽

Hydraulic Efficiency ◽

Storm Drainage

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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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Character of the Englacial and Subglacial Drainage System in the Lower Part of the Ablation Area of Storglaciären, Sweden, as Revealed by Dye-Trace Studies

Journal of Glaciology ◽

10.3189/s0022143000032263 ◽

1988 ◽

Vol 34 (117) ◽

pp. 217-227 ◽

Cited By ~ 7

Author(s):

Sheliah Z. Seaberg ◽

John Z. Seaberg ◽

Roger Leb. Hooke ◽

Daniel W. Wiberg

Keyword(s):

Hydraulic System ◽

Dispersion Coefficient ◽

Water Pressure ◽

Drainage System ◽

Water Velocity ◽

Northern Sweden ◽

Late Season ◽

Valley Glacier ◽

Small Valley ◽

Glacial Streams

AbstractDuring the 1984 and 1985 melt seasons, flow velocities and dispersive characteristics of the englacial and subglacial hydraulic system on Storglaciären, a small valley glacier in northern Sweden, were studied with the use of dye-trace tests. Similar tests conducted on one of the two principal pro-glacial streams provided a basis for comparison of the combined englacial-subglacial system with the pro-glacial one. Velocities in the two systems were broadly comparable after compensating for the effect of slope differences. However, velocities in the glacial conduits increased almost linearly with discharge. Analysis suggests that this can be explained by an increase in water pressure in the conduits, combined with a decrease in effective sinuosity, as discharge increases. Dispersivity (the ratio of the dispersion coefficient to the water velocity) in the glacial system is high early in the season but decreases progressively during July. This is believed to reflect a change from an extensively braided to a more integrated drainage system. Dispersivity is only slightly lower in the pro-glacial streams than in the late-season glacial conduits, suggesting similar degrees of braiding. However, retardation of dye due to temporary storage is greater in the glacial conduits. This suggests that the glacial streams have a larger number of stable eddies in which dye can be trapped for extended periods of time.

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The impact of jökulhlaups on basal sliding observed by SAR interferometry on Vatnajökull, Iceland

Journal of Glaciology ◽

10.3189/172756507782202810 ◽

2007 ◽

Vol 53 (181) ◽

pp. 232-240 ◽

Cited By ~ 36

Author(s):

Eyjólfur Magnússon ◽

Helmut Rott ◽

Helgi Björnsson ◽

Finnur Pálsson

Keyword(s):

Initial Phase ◽

Water Pressure ◽

Drainage System ◽

Sar Interferometry ◽

Ice Dynamics ◽

Velocity Increase ◽

Basal Sliding ◽

Tunnel System ◽

The Impact ◽

Local Uplift

AbstractWe have analyzed InSAR data from the ERS-1/ERS-2 tandem mission, to study the ice dynamics of Vatnajökull, Iceland, during jökulhlaups from the Skaftá cauldrons and the Grímsvötn geothermal area, which drained under the Tungnaárjökull and Skeiðarárjökull outlets, respectively. During the initial phase of a Grímsvötn jökulhlaup in March 1996, the velocity of Skeiðarárjökull increased up to three-fold (relative to observed velocities in December 1995) over an area up to 8 km wide around the subglacial flood path. Accumulation of water was observed at one location in the flood path. During a small jökulhlaup from the Skaftá cauldrons in October 1995 the velocity on Tungnaárjökull increased up to four-fold over a 9 km wide area. The velocity increase was observed 1.5 days before the floodwater was detected in the river Skaftá. A reduced glacier speed as the flood peaked in Skaftá indicates evolution of the subglacial drainage system from sheet to tunnel flow. The glacier acceleration and local uplift, observed in the early phase of both jökulhlaups, supports the concept that increased water inflow in a narrow tunnel system causes water pressure to rise and forces water into areas outside the channels, thus reducing the coupling of ice with the glacier bed.

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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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