Temporal Changes in Elevation of the Debris-Covered Ablation Area of Khumbu Glacier in the Nepal Himalaya since 1978

Nuimura, T.; Fujita, Koji; Fukui, Kotaro; Asahi, Katsuhiko; Aryal, Raju; Ageta, Yutaka

doi:10.1657/1938-4246-43.2.246

Cited by 57 publications

(66 citation statements)

References 42 publications

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“…Non-uniform glacier surface displacement is an important consideration if investigating lower magnitude processes such as sub-debris melt, which also requires quantification of glacier emergence velocity (Vincent and others, 2016). Emergence velocity is expected to be low on slow-moving low gradient debris-covered glacier tongues (Nuimura and others, 2011); however, positive surface elevation change was observed in this study (e.g. Fig.…”

Section: Future Workmentioning

confidence: 67%

Quantifying ice cliff evolution with multi-temporal point clouds on the debris-covered Khumbu Glacier, Nepal

et al. 2017

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ABSTRACT. Measurements of glacier ice cliff evolution are sparse, but where they do exist, they indicate that such areas of exposed ice contribute a disproportionate amount of melt to the glacier ablation budget. We . Four ice cliffs, which all featured supraglacial ponds, persisted over the full study period. In contrast, ice cliffs without a pond or with a steep back-slope degraded over the same period. The rate of thermo-erosional undercutting was over double that of subaerial retreat. Overall, 3-D topographic differencing allowed an improved process-based understanding of cliff evolution and cliff-pond coupling, which will become increasingly important for monitoring and modelling the evolution of thinning debris-covered glaciers.

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Section: Future Workmentioning

confidence: 67%

Quantifying ice cliff evolution with multi-temporal point clouds on the debris-covered Khumbu Glacier, Nepal

et al. 2017

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“…Both glaciers are typified by considerable supraglacial relief, with the height difference between peaks and troughs estimated at 20-50 m (observed during 2009 field work and reported in Benn and Owen, 2002). Downwasting or thinning of Khumbu Himalayan glaciers has been observed over the past several decades (Bolch et al, 2008aNuimura et al, 2011). In addition to downwasting, backwasting -the ablation which occurs on exposed ice faces in debris covered areas -is another primary melt mechanism active on Khumbu Himalayan glaciers.…”

Section: Study Areamentioning

confidence: 98%

Geochemical characterization of supraglacial debris via in situ and optical remote sensing methods: a case study in Khumbu Himalaya, Nepal

2012

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Abstract. Surface glacier debris samples and field spectra were collected from the ablation zones of Nepal Himalaya Ngozumpa and Khumbu glaciers in November and December 2009. Geochemical and mineral compositions of supraglacial debris were determined by X-ray diffraction and X-ray fluorescence spectroscopy. This composition data was used as ground truth in evaluating field spectra and satellite supraglacial debris composition and mapping methods. Satellite remote sensing methods for characterizing glacial surface debris include visible to thermal infrared hyper-and multispectral reflectance and emission signature identification, semi-quantitative mineral abundance indicies and spectral image composites. Satellite derived supraglacial debris mineral maps displayed the predominance of layered silicates, hydroxyl-bearing and calcite minerals on Khumbu Himalayan glaciers. Supraglacial mineral maps compared with satellite thermal data revealed correlations between glacier surface composition and glacier surface temperature. Glacier velocity displacement fields and shortwave, thermal infrared false color composites indicated the magnitude of mass flux at glacier confluences. The supraglacial debris mapping methods presented in this study can be used on a broader scale to improve, supplement and potentially reduce errors associated with glacier debris radiative property, composition, areal extent and mass flux quantifications.

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“…7 raises the possibility that stagnant zones will extend farther up many glaciers if the current warming trend continues. Seko et al (1998) and Nuimura et al (2011) have presented evidence for a progressive decrease in velocities in the upper ablation zone of Khumbu Glacier since the 1950s. In the zone of prominent ice pinnacles near Everest Base Camp below Khumbu Icefall, for example, velocities decreased from~56 m yr − 1 to~40 m yr − 1 (1978)(1979)(1980)(1981)(1982)(1983)(1984) and then to~20 m yr − 1 (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004).…”

Section: Ice Velocitiesmentioning

confidence: 99%

“…Combined velocity and thickness data are available for only one glacier (Khumbu Glacier: Gades et al, 2000;Bolch et al, 2008b;Quincey et al, 2009), although coverage is incomplete. Nuimura et al (2011) conducted a mass-continuity analysis of part of Khumbu Glacier, and found that the area below the icefall had undergone little net elevation change, apparently due to the opposing effects of reduced ice flux from the accumulation zone and less negative mass balance. Insufficient data are available for glacier-wide analyses, but in the following sections we use measurements of ice velocity together with theoretical considerations to identify the main controls on the observed patterns of elevation change.…”

Section: Recent Changes In Glacier Volumementioning

confidence: 99%

Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards

Benn

Bolch

Hands³

et al. 2012

Earth-Science Reviews

498

585

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In areas of high relief, many glaciers have extensive covers of supraglacial debris in their ablation zones, which alters both rates and spatial patterns of melting, with important consequences for glacier response to climate change. Wastage of debris-covered glaciers can be associated with the formation of large moraine-dammed lakes, posing risk of glacier lake outburst floods (GLOFs). In this paper, we use observations of glaciers in the Mount Everest region to present an integrated view of debris-covered glacier response to climate change, which helps provide a long-term perspective on evolving GLOF risks. In recent decades, debris-covered glaciers in the Everest region have been losing mass at a mean rate of 0.32 m yr¹, although in most cases there has been little or no change in terminus position. Mass loss occurs by 4 main processes: (1) melting of clean ice close to glacier ELAs; (2) melting beneath surface debris; (3) melting of ice cliffs and calving around the margins of supraglacial ponds; and (4) calving into deep proglacial lakes. Modelling of processes (1) and (2) shows that Everest-region glaciers typically have an inverted ablation gradient in their lower reaches, due to the effects of a down-glacier increase in debris thickness. Mass loss is therefore focused in the mid parts of glacier ablation zones, causing localised surface lowering and a reduction in downglacier surface gradient, which in turn reduce driving stress and glacier velocity, so the lower ablation zones of many glaciers are now stagnant. Model results also indicate that increased summer temperatures have raised the altitude of the rain-snow transition during the summer monsoon period, reducing snow accumulation and ice flux to lower elevations. As downwasting proceeds, formerly efficient supraglacial and englacial drainage networks are broken up, and supraglacial lakes form in hollows on the glacier surface. Ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub-debris melt rates, so extensive lake formation accelerates overall rates of ice loss. Most supraglacial lakes are 'perched' above hydrological base level, and are susceptible to drainage if they become connected to the englacial drainage system. Speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre-existing weaknesses in the ice. Roof collapses can open these voids up to the surface, and commonly provide the nuclei of new lakes. Thus, by influencing both lake drainage and formation, englacial conduits exert a strong control on surface ablation rates. An important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier. Base-level lakes formed behind intact moraine dams can grow monotonically, and in some cases can pose serious GLOF hazards. Glacier termini can evolve in different ways in response to the same climatic forcing, so that potentially hazardous lakes will form in some situations but no...

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Temporal Changes in Elevation of the Debris-Covered Ablation Area of Khumbu Glacier in the Nepal Himalaya since 1978

Cited by 57 publications

References 42 publications

Quantifying ice cliff evolution with multi-temporal point clouds on the debris-covered Khumbu Glacier, Nepal

Quantifying ice cliff evolution with multi-temporal point clouds on the debris-covered Khumbu Glacier, Nepal

Geochemical characterization of supraglacial debris via in situ and optical remote sensing methods: a case study in Khumbu Himalaya, Nepal

Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards

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