Mass-balance changes of the debris-covered glaciers in the Langtang Himal, Nepal, from 1974 to 1999

Pellicciotti, Francesca; Stephan, Christa; Miles, Evan; Herreid, Sam; Immerzeel, Walter W.; Bolch, Tobias

doi:10.3189/2015jog13j237

Cited by 161 publications

(203 citation statements)

References 67 publications

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“…Several recent studies suggested that elevation changes on debris-covered and debris-free glaciers are similar in the Himalayas and Karakoram (Gardelle et al, 2013;Kääb et al, 2012;Pellicciotti et al, 2015). Conversely, Nuimura et al (2012) showed that the debris-covered areas are subject to higher rates of lowering than debris-free areas in Khumbu region, though the 400 m difference in mean elevation between the debriscovered and debris-free areas (5102 and 5521 m a.s.l.…”

Section: Spatial Variability Of Elevation Changes Over the Debris-covmentioning

confidence: 84%

“…However, the role played by debris on the surface mass balance of glaciers and, in turn, on the glacier response to climate change remains unclear (Kääb et al, 2012). Indeed, this debris layer insulates the glacier surface from the atmosphere when it reaches a sufficient thickness and complicates the response to climate change compared to clean-ice glaciers (Jouvet et al, 2011;Kirkbride and Deline, 2013;Østrem, 1959;Pellicciotti et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal

et al. 2016

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Abstract. Approximately 25 % of the glacierized area in the Everest region is covered by debris, yet the surface mass balance of debris-covered portions of these glaciers has not been measured directly. In this study, ground-based measurements of surface elevation and ice depth are combined with terrestrial photogrammetry, unmanned aerial vehicle (UAV) and satellite elevation models to derive the surface mass balance of the debris-covered tongue of Changri Nup Glacier, located in the Everest region. Over the debris-covered tongue, the mean elevation change between 2011 and 2015 is −0.93 m year −1 or −0.84 m water equivalent per year (w.e. a −1 ). The mean emergence velocity over this region, estimated from the total ice flux through a cross section immediately above the debris-covered zone, is +0.37 m w.e. a −1 . The debris-covered portion of the glacier thus has an areaaveraged mass balance of −1.21 ± 0.2 m w.e. a −1 between 5240 and 5525 m above sea level (m a.s.l.). Surface mass balances observed on nearby debris-free glaciers suggest that the ablation is strongly reduced (by ca. 1.8 m w.e. a −1 ) by the debris cover. The insulating effect of the debris cover has a larger effect on total mass loss than the enhanced ice ablation due to supraglacial ponds and exposed ice cliffs. This finding contradicts earlier geodetic studies and should be considered for modelling the future evolution of debris-covered glaciers.

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Section: Spatial Variability Of Elevation Changes Over the Debris-covmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal

et al. 2016

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“…The energy balance drives the melt of the debris-covered tongues and several studies point toward a yet unexplained faster surface lowering of the tongues of these glaciers than what can be expected based on the melt suppression by thick debris (Kääb et al, 2012;Gardelle et al, 2013;Pellicciotti et al, 2015;Azam et al, 2018). It is unclear whether this behavior can be attributed to turbulent fluxes, supra-glacial features such as cliffs and ponds, a reduced emergence velocity or other processes (Vincent et al, 2016;Azam et al, 2018).…”

Section: Applications Of Thermal Uav Imagerymentioning

confidence: 87%

Mapping Surface Temperatures on a Debris-Covered Glacier With an Unmanned Aerial Vehicle

et al. 2018

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A layer of debris cover often accumulates across the surface of glaciers in active mountain ranges with exceptionally steep terrain, such as the Andes, Himalaya, and New Zealand Alps. Such a supraglacial debris layer has a major influence on a glacier's surface energy budget, enhancing radiation absorption, and melt when the layer is thin, but insulating the ice when thicker than a few cm. Information on spatially distributed debris surface temperature has the potential to provide insight into the properties of the debris, its effects on the ice below and its influence on the near-surface boundary layer. Here, we deploy an unmanned aerial vehicle (UAV) equipped with a thermal infrared sensor on three separate missions over one day to map changing surface temperatures across the debris-covered Lirung Glacier in the Central Himalaya. We present a methodology to georeference and process the acquired thermal imagery, and correct for emissivity and sensor bias. Derived UAV surface temperatures are compared with distributed simultaneous in situ temperature measurements as well as with Landsat 8 thermal satellite imagery. Results show that the UAV-derived surface temperatures vary greatly both spatially and temporally, with −1.4 ± 1.8, 11.0 ± 5.2, and 15.3 ± 4.7 • C for the three flights (mean ± sd), respectively. The range in surface temperatures over the glacier during the morning is very large with almost 50 • C. Ground-based measurements are generally in agreement with the UAV imagery, but considerable deviations are present that are likely due to differences in measurement technique and approach, and validation is difficult as a result. The difference in spatial and temporal variability captured by the UAV as compared with much coarser satellite imagery is striking and it shows that satellite derived temperature maps should be interpreted with care. We conclude that UAVs provide a suitable means to acquire surface temperature maps of debris-covered glacier surfaces at high spatial and temporal resolution, but that there are caveats with regard to absolute temperature measurement.

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“…In addition, features such as meltwater ponds and ice cliffs in the ablation zone absorb significantly more energy than adjacent debris-covered surfaces. These features may give compensatory high melt rates (e.g., Inoue and Yoshida, 1980;Sakai et al, 1998Sakai et al, , 2000Pellicciotti et al, 2014;Immerzeel et al, 2014a) that support using a thinner average or "effective" debris thickness when assigning an average value to each 2 km grid cell in WRF D3.…”

Section: Specification Of Debris Extent and Thickness In Wrf D3mentioning

confidence: 99%

Impact of debris cover on glacier ablation and atmosphere–glacier feedbacks in the Karakoram

et al. 2015

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Abstract. The Karakoram range of the Hindu-Kush Himalaya is characterized by both extensive glaciation and a widespread prevalence of surficial debris cover on the glaciers. Surface debris exerts a strong control on glacier surface-energy and mass fluxes and, by modifying surface boundary conditions, has the potential to alter atmosphereglacier feedbacks. To date, the influence of debris on Karakoram glaciers has only been directly assessed by a small number of glaciological measurements over short periods. Here, we include supraglacial debris in a high-resolution, interactively coupled atmosphere-glacier modeling system. To investigate glaciological and meteorological changes that arise due to the presence of debris, we perform two simulations using the coupled model from 1 May to 1 October 2004: one that treats all glacier surfaces as debris-free and one that introduces a simplified specification for the debris thickness. The basin-averaged impact of debris is a reduction in ablation of ∼ 14 %, although the difference exceeds 5 m w.e. on the lowest-altitude glacier tongues. The relatively modest reduction in basin-mean mass loss results in part from non-negligible sub-debris melt rates under thicker covers and from compensating increases in melt under thinner debris, and may help to explain the lack of distinct differences in recent elevation changes between clean and debriscovered ice. The presence of debris also strongly alters the surface boundary condition and thus heat exchanges with the atmosphere; near-surface meteorological fields at lower elevations and their vertical gradients; and the atmospheric boundary layer development. These findings are relevant for glacio-hydrological studies on debris-covered glaciers and contribute towards an improved understanding of glacier behavior in the Karakoram.

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Mass-balance changes of the debris-covered glaciers in the Langtang Himal, Nepal, from 1974 to 1999

Cited by 161 publications

References 67 publications

Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal

Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal

Mapping Surface Temperatures on a Debris-Covered Glacier With an Unmanned Aerial Vehicle

Impact of debris cover on glacier ablation and atmosphere–glacier feedbacks in the Karakoram

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