Ice Temperature of Khumbu Glacier

Mae, Shinji

doi:10.5331/seppyo.38.special_37

Cited by 10 publications

(9 citation statements)

References 1 publication

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“…Below the icefall, debris cover increases in extent and thickness towards the terminus, where it is several meters thick. Measurements in shallow boreholes in the upper part of the ablation area indicate perennial cold ice in a surface layer ∼16 m thick, and temperate ice at greater depths (Mae, 1976). Furthermore, pronounced seasonal velocity variations in this area (Kodama and Mae, 1976; Seko and others, 1998; Nakawo and others, 1999) strongly suggest the existence of temperate basal ice beneath the icefall and upper ablation areas.…”

Section: Khumbu Glacier Nepal Himalayamentioning

confidence: 99%

A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers

et al. 2009

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On uncrevassed regions of polythermal glaciers, englacial conduits can form by incision of supraglacial stream channels followed by roof closure. The origin and evolution of examples in Longyearbreen, Svalbard, and Khumbu Glacier, Nepal, were determined by speleological survey. The development of perennial incised channels requires that incision is significantly faster than glacier surface ablation, and thus will be favoured by high meltwater discharges in combination with cool climatic conditions or thick debris cover. Incised canyons can become blocked by drifted winter snow, refrozen meltwater, ice rafting from non-local sources (allochthonous breccias) and roof collapses (autochthonous breccias). Conduit closure can also occur in response to ice creep, particularly at depth. Following isolation from the surface, englacial conduits continue to evolve by vadose incision down to local base level. In the case of Longyearbreen, incision allowed the channel to reach the glacier bed, but on Khumbu Glacier deep incision is prevented because an effectively impermeable terminal moraine provides a high base level for the glacier drainage system. During our period of observations, deeper parts of the Longyearbreen conduit became blocked by a combination of ice accumulation and creep, causing the stream course to be re-routed to higher levels. On that glacier, incision, blockage and upward re-routing are cyclic. We conclude that 'cut and closure' is the dominant mechanism of englacial conduit formation on uncrevassed regions of polythermal glaciers.

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Section: Khumbu Glacier Nepal Himalayamentioning

confidence: 99%

A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers

et al. 2009

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“…The thermal regime of Khumbu Glacier is not well known. Measurements in shallow boreholes in the upper part of the ablation area in the 1970s indicated perennial cold ice in a surface layer ∼16 m thick and temperate ice at greater depths (Mae, 1976). Given the extreme altitude and low temperature of the glacier accumulation area, and rapid flow of ice through the Khumbu icefall, it is probable that cold ice is advected into the upper ablation zone.…”

Section: Khumbu Glaciermentioning

confidence: 99%

Englacial drainage systems formed by hydrologically driven crevasse propagation

Benn¹,

et al. 2009

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Recent work has shown that surface-to-bed drainage systems re-form annually on parts of the Greenland ice sheet and some High Arctic glaciers, leading to speed-up events soon after the onset of summer melt. Surface observations and geophysical data indicate that such systems form by hydrologically driven fracture propagation (herein referred to as ‘hydrofracturing’), although little is known about their characteristics. Using speleological techniques, we have explored and surveyed englacial drainage systems formed by hydrofracturing in glaciers in Svalbard, Nepal and Alaska. In Hansbreen, Svalbard, vertical shafts were followed through ∼60 m of cold ice and ∼10 m of temperate basal ice to a subglacial conduit. Deep hydrofracturing occurred at this site due to a combination of extensional ice flow and abundant surface meltwater at a glacier confluence. The englacial drainage systems in Khumbu Glacier, Nepal, and Matanuska Glacier, Alaska, USA, formed in areas of longitudinal compression and transverse extension and consist of vertical slots that plunge down-glacier at angles of 55° or less. The occurrence of englacial drainages initiated by hydrofracturing in diverse glaciological regimes suggests that it is a very widespread process, and that surface-to-bed drainage can occur wherever high meltwater supply coincides with ice subjected to sufficiently large tensile stresses.

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“…For example, ice thicknesses, bed topographies and basal conditions are commonly assumed or estimated from modelling (Bolch and others, 2012; Huss and Farinotti, 2012; Rowan and others, 2015), while measurements of ice temperature and thermal regime are also extremely limited (e.g. Mae, 1976; Zhang and others, 2013). To our knowledge, no direct measurements exist for either englacial debris content or dynamic regimes (i.e.…”

Section: Introductionmentioning

confidence: 99%

Instruments and methods: hot-water borehole drilling at a high-elevation debris-covered glacier

Miles

Hubbard

et al. 2019

J. Glaciol.

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While hot-water drilling is a well-established technique used to access the subsurface of ice masses, drilling into high-elevation (≳ 4000 m a.s.l.) debris-covered glaciers faces specific challenges. First, restricted transport capacity limits individual equipment items to a volume and mass that can be slung by small helicopters. Second, low atmospheric oxygen and pressure reduces the effectiveness of combustion, limiting a system's ability to pump and heat water. Third, thick supraglacial debris, which is both highly uneven and unstable, inhibits direct access to the ice surface, hinders the manoeuvring of equipment and limits secure sites for equipment placement. Fourth, englacial debris can slow the drilling rate such that continued drilling becomes impracticable and/or boreholes deviate substantially from vertical. Because of these challenges, field-based englacial and subglacial data required to calibrate numerical models of high-elevation debris-covered glaciers are scarce or absent. Here, we summarise our experiences of hot-water drilling over two field seasons (2017–2018) at the debris-covered Khumbu Glacier, Nepal, where we melted 27 boreholes up to 192 m length, at elevations between 4900 and 5200 m a.s.l. We describe the drilling equipment and operation, evaluate the effectiveness of our approach and suggest equipment and methodological adaptations for future use.

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Ice Temperature of Khumbu Glacier

Abstract: Thermal drilling was carried out in August of 1974 on the Khumbu glacier. The drilling site was set at 5360 m above sea-level in the upper part of the ablation area of the glacier. The

Cited by 10 publications

References 1 publication

A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers

A cut-and-closure origin for englacial conduits in uncrevassed regions of polythermal glaciers

Englacial drainage systems formed by hydrologically driven crevasse propagation

Instruments and methods: hot-water borehole drilling at a high-elevation debris-covered glacier

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