scholarly journals Influence of Supraglacial Debris Thickness on Thermal Resistance of the Glaciers of Chandra Basin, Western Himalaya

2021 ◽  
Vol 9 ◽  
Author(s):  
Lavkush Kumar Patel ◽  
Parmanand Sharma ◽  
Ajit Singh ◽  
Sunil Oulkar ◽  
Bhanu Pratap ◽  
...  
Keyword(s):  
Surface Air Temperature ◽  
Western Himalaya ◽  
Ablation Rate ◽  
Effective Control ◽  
Thermal Resistivity ◽  
Atmospheric Conditions ◽  
Glacier Surface ◽  
Near Surface ◽  
Covered Area ◽  
Debris Cover

A large number of glaciers in the Hindu-Kush Himalaya are covered with debris in the lower part of the ablation zone, which is continuously expanding due to enhanced glacier mass loss. The supraglacial debris transported over the melting glacier surface acts as an insulating barrier between the ice and atmospheric conditions and has a strong influence on the spatial distribution of surface ice melt. We conducted in-situ field measurements of point-wise ablation rate, supraglacial debris thickness, and debris temperature to examine the thermal resistivity of the debris pack and its influence on ablation over three glaciers (Bara Shigri, Batal, and Kunzam) in Chandra Basin of Western Himalaya during 2016–2017. Satellite-based supraglacial debris cover assessment shows an overall debris covered area of 15% for Chandra basin. The field data revealed that the debris thickness varied between 0.5 and 326 cm, following a spatially distributed pattern in the Chandra basin. The studied glaciers have up to 90% debris cover within the ablation area, and together represent ∼33.5% of the total debris-covered area in the basin. The supraglacial debris surface temperature and near-surface air temperature shows a significant correlation (r = > 0.88, p = < 0.05), which reflects the effective control of energy balance over the debris surface. The thermal resistivity measurements revealed low resistance (0.009 ± 0.01 m2°C W−1) under thin debris pack and high resistance (0.55 ± 0.09 m2°C W−1) under thick debris. Our study revealed that the increased thickness of supraglacial debris significantly retards the glacier ablation due to its high thermal resistivity.

scholarly journals Impact of varying debris cover thickness on ablation: a case study for Koxkar Glacier in the Tien Shan

2014 ◽  
Vol 8 (2) ◽  
pp. 377-386 ◽  
Author(s):  
M. Juen ◽  
C. Mayer ◽  
A. Lambrecht ◽  
H. Han ◽  
S. Liu
Keyword(s):  
Remote Sensing ◽  
Field Measurements ◽  
Tien Shan ◽  
Shielding Effect ◽  
Glacier Surface ◽  
Glacier Terminus ◽  
Covered Area ◽  
Debris Cover ◽  
High Resolution Satellite Imagery ◽  
Cover Thickness

Abstract. To quantify the ablation processes on a debris covered glacier, a simple distributed ablation model has been developed and applied to a selected glacier. For this purpose, a set of field measurements was carried out to collect empirical data. A morphometric analysis of the glacier surface enables us to capture statistically the areal distribution of topographic features that influence debris thickness and consequently ablation. Remote-sensing techniques, using high-resolution satellite imagery, were used to extrapolate the in situ point measurements to the whole ablation area and to map and classify melt-relevant surface types. As a result, a practically applicable method is presented that allows the estimation of ablation on a debris covered glacier by combining field data and remote-sensing information. The sub-debris ice ablation accounts for about 24% of the entire ice ablation, while the percentage of the moraine covered area accounts for approximately 32% of the entire glacierized area. Although the ice cliffs occupy only 1.7% of the debris covered area, the melt amount accounts for approximately 12% of the total sub-debris ablation and 2.5% of the total ablation respectively. Our study highlights the influence of debris cover on the response of the glacier terminus in a particular climate setting. Due to the fact that melt rates beyond 0.1 m of moraine cover are highly restricted, the shielding effect of the debris cover dominates over the temperature and elevation dependence of the ablation in the bare ice case.

scholarly journals Impact of debris cover on glacier ablation and atmosphere-glacier feedbacks in the Karakoram

2015 ◽  
Vol 9 (2) ◽  
pp. 2259-2299 ◽  
Author(s):  
E. Collier ◽  
F. Maussion ◽  
L. I. Nicholson ◽  
T. Mölg ◽  
W. W. Immerzeel ◽  
...  
Keyword(s):  
Coupled Model ◽  
Surface Boundary ◽  
Glacier Surface ◽  
Near Surface ◽  
Mass Fluxes ◽  
Surface Boundary Conditions ◽  
Boundary Layer Development ◽  
Debris Cover ◽  
The Difference ◽  
Strong Control

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 atmosphere-glacier 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 modelling 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 an simplified specification for mapping debris thickness. The basin-averaged impact of debris is a reduction in ablation of ~7%, although the difference exceeds 2.5 m w.e. on the lowest-altitude glacier tongues. The modest reduction in 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 elevations changes between clean and debris-covered 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 behaviour in the Karakoram.

scholarly journals Reconciling High Glacier Surface Melting in Summer with Air Temperature in the Semi-Arid Zone of Western Himalaya

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1561 ◽  
Author(s):  
Bhanu Pratap ◽  
Parmanand Sharma ◽  
Lavkush Patel ◽  
Ajit T. Singh ◽  
Vinay Kumar Gaddam ◽  
...  
Keyword(s):  
Air Temperature ◽  
Arid Zone ◽  
Summer Precipitation ◽  
Western Himalaya ◽  
Surface Melting ◽  
Phase Changes ◽  
Lapse Rate ◽  
Glacier Surface ◽  
Near Surface ◽  
Temperature Lapse Rate

In Himalaya, the temperature plays a key role in the process of snow and ice melting and, importantly, the precipitation phase changes (i.e., snow or rain). Consequently, in longer period, the melting and temperature gradient determine the state of the Himalayan glaciers. This necessitates the continuous monitoring of glacier surface melting and a well-established meteorological network in the Himalaya. An attempt has been made to study the seasonal and annual (October 2015 to September 2017) characteristics of air temperature, near-surface temperature lapse rate (tlr), in-situ glacier surface melting, and surface melt simulation by temperature-index (T-index) models for Sutri Dhaka Glacier catchment, Lahaul-Spiti region in Western Himalaya. The tlr of the catchment ranges from 0.3 to 6.5 °C km−1, varying on a monthly and seasonal timescale, which suggests the need for avoiding the use of standard environmental lapse rate (SELR ~6.5 °C km−1). The measured and extrapolated average air temperature (tavg) was found to be positive on glacier surface (4500 to 5500 m asl) between June and September (summer). Ablation data calculated for the balance years 2015–16 and 2016–17 shows an average melting of −4.20 ± 0.84 and −3.09 ± 0.62 m w.e., respectively. In compliance with positive air temperature in summer, ablation was also found to be maximum ~88% of total yearly ice melt. When comparing the observed and modelled ablation data with air temperature, we show that the high summer glacier melt was caused by warmer summer air temperature and minimum spells of summer precipitation in the catchment.

scholarly journals Impact of varying debris cover thickness on catchment scale ablation: a case study for Koxkar glacier in the Tien Shan

2013 ◽  
Vol 7 (6) ◽  
pp. 5307-5332 ◽  
Author(s):  
M. Juen ◽  
C. Mayer ◽  
A. Lambrecht ◽  
H. Haidong ◽  
L. Shiyin
Keyword(s):  
Remote Sensing ◽  
Field Measurements ◽  
Ground Truth ◽  
Tien Shan ◽  
Shielding Effect ◽  
Catchment Scale ◽  
Glacier Surface ◽  
Glacier Terminus ◽  
Covered Area ◽  
Debris Cover

Abstract. To quantify the ablation processes on a debris covered glacier, a simple distributed ablation model has been developed and applied to a selected glacier. For this purpose, a bundle of field measurements was carried out to collect empirical data. A morphometric analysis of the glacier surface enables us to statistically capture the areal distribution of topographic features that influence debris thickness and consequently ablation. Remote sensing techniques, using high resolution satellite imagery, were used to extrapolate the ground truth results to the whole ablation area and to map and classify melt-relevant surface types. As a result, a practically applicable method is presented, that allows the estimation of ablation on a debris covered glacier by combining field data and remote sensing information. The sub-debris ice ablation accounts for about 19% of the entire ice ablation, while the percentage of the moraine covered area accounts for approximately 32% of the entire glacerized area. Although the ice cliffs occupy only 1.7% of the debris covered area the melt amount accounts for approximately 15% of the total sub-debris ablation and 2.7% of the total ablation respectively. Our study highlights the influence of debris cover on the response of the glacier terminus to climate warming. Due to the fact that melt rates beyond 0.1m of moraine cover are highly restricted the shielding effect of the debris cover dominates over the temperature- and elevation dependence of the ablation in the bare ice case.

scholarly journals A Detailed Cloud Fraction Climatology of the Upper Indus Basin and Its Implications for Near-Surface Air Temperature*

2015 ◽  
Vol 28 (9) ◽  
pp. 3537-3556 ◽  
Author(s):  
N. Forsythe ◽  
A. J. Hardy ◽  
H. J. Fowler ◽  
S. Blenkinsop ◽  
C. G. Kilsby ◽  
...  
Keyword(s):  
Air Temperature ◽  
Cloud Cover ◽  
Large Fraction ◽  
Surface Air Temperature ◽  
Indus Basin ◽  
Radiative Effect ◽  
Atmospheric Conditions ◽  
Near Surface ◽  
Cloud Radiative Effect ◽  
Seasonal And Diurnal Variations

Abstract Clouds play a key role in hydroclimatological variability by modulating the surface energy balance and air temperature. This study utilizes MODIS cloud cover data, with corroboration from global meteorological reanalysis (ERA-Interim) cloud estimates, to describe a cloud climatology for the upper Indus River basin. It has specific focus on tributary catchments in the northwest of the region, which contribute a large fraction of basin annual runoff, including 65% of flow originating above Besham, Pakistan or 50 km3 yr−1 in absolute terms. In this region there is substantial cloud cover throughout the year, with spatial means of 50%–80% depending on the season. The annual cycles of catchment spatial mean daytime and nighttime cloud cover fraction are very similar. This regional diurnal homogeneity belies substantial spatial variability, particularly along seasonally varying vertical profiles (based on surface elevation). Correlations between local near-surface air temperature observations and MODIS cloud cover fraction confirm the strong linkages between local atmospheric conditions and near-surface climate variability. These correlations are interpreted in terms of seasonal and diurnal variations in apparent cloud radiative effect and its influence on near-surface air temperature in the region. The potential role of cloud radiative effect in recognized seasonally and diurnally asymmetrical temperature trends over recent decades is also assessed by relating these locally observed trends to ERA-Interim-derived trends in cloud cover fraction. Specifically, reduction in nighttime cloud cover fraction relative to daytime conditions over recent decades appears to provide a plausible physical mechanism for the observed nighttime cooling of surface air temperature in summer months.

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

2015 ◽  
Vol 9 (4) ◽  
pp. 1617-1632 ◽  
Author(s):  
E. Collier ◽  
F. Maussion ◽  
L. I. Nicholson ◽  
T. Mölg ◽  
W. W. Immerzeel ◽  
...  
Keyword(s):  
Coupled Model ◽  
Surface Boundary ◽  
Glacier Surface ◽  
Near Surface ◽  
Mass Fluxes ◽  
Debris Cover ◽  
Elevation Changes ◽  
The Difference ◽  
Glacier Modeling ◽  
Strong Control

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 atmosphere–glacier 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 debris-covered 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.

scholarly journals Atmospheric Processes and Climatological Characteristics of the 79N Glacier (Northeast Greenland)

2019 ◽  
Vol 147 (4) ◽  
pp. 1375-1394 ◽  
Author(s):  
Jenny V. Turton ◽  
Thomas Mölg ◽  
Dirk Van As
Keyword(s):  
Air Temperature ◽  
Wrf Model ◽  
Surface Air Temperature ◽  
Greenland Ice Sheet ◽  
Cloud Formation ◽  
Atmospheric Conditions ◽  
Subsequent Increase ◽  
Near Surface ◽  
Surface Mass ◽  
Atmospheric Processes

Abstract The Nioghalvfjerdsfjorden glacier (the 79 fjord, henceforth referred to as 79N) has been thinning and accelerating since the early 2000s, as a result of calving episodes at the front of the glacier. As 8% of the Greenland Ice Sheet area drains into 79N, changes in the stability of 79N could propagate into the interior of Greenland. Despite this concern, relatively little is known about the atmospheric conditions over 79N. We present the surface atmospheric processes and climatology of the 79N region from analyses of data from four automatic weather stations (AWS) and reanalysis data from ERA-Interim. Over the floating section of the glacier, the annual average air temperature is −16.7°C, decreasing to −28.5°C during winter. Winds over the glacier are predominantly westerly and are of katabatic origin. Over the last 39 years the near-surface air temperature has increased at a rate of +0.08°C yr−1. In addition, we find that large, rapid (48 h) temperature increases (>10°C) occur during the five-month dark period (November–March). Eight (±4) warm-air events occur annually from 1979 to 2017. We use the Weather Research and Forecasting (WRF) Model to simulate a particular warm-air event with above-freezing air temperatures between 30 November and 2 December 2014. The warm event was caused by warm-air advection from the southeast and a subsequent increase in the longwave radiation toward the surface due to low-level cloud formation. The frequent nature of the temperature jumps and the magnitude of the temperature increases are likely to have an impact on the surface mass balance of the glacier by bringing the skin temperatures to the melting point.

scholarly journals Role of Debris Cover in the Thermal Physics of Glaciers

1986 ◽  
Vol 32 (111) ◽  
pp. 255-266 ◽  
Author(s):  
A. N. Bozhinskiy ◽  
M. S. Krass ◽  
V. V. Popovnin
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Ablation Rate ◽  
Perfect Agreement ◽  
Glacier Surface ◽  
Controlling System ◽  
Run Off ◽  
Debris Cover ◽  
Central Caucasus

AbstractA mathematical model is presented of non-stationary melting processes of ice including particles of morainic material. The problem is treated as a Stephen-type one with the phase boundary of ice melting being located under the debris cover. The main terms of the heat-balance equation for a glacier surface are solar radiation and convective heat transfer. The quantitative relationships characterizing the effect of glacier run-off augmentation from under a thin layer of debris cover are obtained for different bulk moraine concentrations inside the ice. The concept of equivalent time is introduced. It is defined as the time elapsed until the moment the sub-moraine ice-ablation rate becomes equal to the ablation rate of clean ice. This moment signifies the beginning of the shielding stage. Thus, a glacier can be considered as a self-controlling system with respect to its summer run-off. A series of numerical tests for Djankuat glacier, Central Caucasus, has been carried out. The dynamics of moraine-cover growth and alterations of seasonal ablation rate under debris show perfect agreement between the computed data and the results of 14 years of direct observations. Some practical recommendations concerning artificial blackening of a glacier surface for augmentation of liquid run-off are presented. Conditions promoting increase of run-off are: relatively high albedo, relatively low summer air temperature, and relatively small convective heat transfer between the air and the ice surface. The method of artificially blackening a glacier surface is by means of a durable thin dark polymer film. In conclusion, some further aspects of the problem are discussed.

scholarly journals Influence of debris cover and altitude on glacier surface melting: a case study on Dokriani Glacier, central Himalaya, India

2015 ◽  
Vol 56 (70) ◽  
pp. 9-16 ◽  
Author(s):  
Bhanu Pratap ◽  
D.P. Dobhal ◽  
Manish Mehta ◽  
Rakesh Bhambri
Keyword(s):  
Ablation Rate ◽  
Surface Melting ◽  
Ice Melting ◽  
Glacier Surface ◽  
Ablation Area ◽  
Himalayan Glaciers ◽  
Debris Cover ◽  
Cover Thickness ◽  
Glacier Ablation

AbstractMost of the central Himalayan glaciers have surface debris layers of variable thickness, which greatly affect the ablation rate. An attempt has been made to relate debris-cover thickness to glacier surface melting. Thirty stakes were used to calculate ablation for debris-covered and clean ice of Dokriani Glacier (7 km2) from 2009/10 to 2012/13. Our study revealed significant altitude-wise difference in the rate of clean and debris-covered ice melting. We found a high correlation (R2 = 0.92) between mean annual clean-ice ablation and altitude, and a very low correlation (R2 = 0.14) between debris-covered ice melting and altitude. Debris-covered ice ablation varies with variation in debris thickness from 1 to 40 cm; ablation was maximum under debris thicknesses of 1–6 cm and minimum under 40 cm. Even a small debris-cover thickness (1–2 cm) reduces ice melting as compared to that of clean ice on an annual basis. Overall, debris-covered ice ablation during the study period was observed to be 37% less than clean-ice ablation. Strong downwasting was also observed in the Dokriani Glacier ablation area, with average annual ablation of 1.82 m w.e. a–1 in a similar period. Our study suggests that a thinning glacier rapidly becomes debris-covered over the ablation area, reducing the rate of ice loss.

scholarly journals Air temperature distribution and energy-balance modelling of a debris-covered glacier

2016 ◽  
Vol 62 (231) ◽  
pp. 185-198 ◽  
Author(s):  
THOMAS E. SHAW ◽  
BEN W. BROCK ◽  
CATRIONA L. FYFFE ◽  
FRANCESCA PELLICCIOTTI ◽  
NICK RUTTER ◽  
...  
Keyword(s):  
Energy Balance ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
High Elevation ◽  
Lapse Rate ◽  
Balance Model ◽  
Linear Temperature ◽  
Near Surface ◽  
Ice Melt ◽  
Debris Cover

ABSTRACTNear-surface air temperature is an important determinant of the surface energy balance of glaciers and is often represented by a constant linear temperature gradients (TGs) in models. Spatio-temporal variability in 2 m air temperature was measured across the debris-covered Miage Glacier, Italy, over an 89 d period during the 2014 ablation season using a network of 19 stations. Air temperature was found to be strongly dependent upon elevation for most stations, even under varying meteorological conditions and at different times of day, and its spatial variability was well explained by a locally derived mean linear TG (MG–TG) of −0.0088°C m−1. However, local temperature depressions occurred over areas of very thin or patchy debris cover. The MG–TG, together with other air TGs, extrapolated from both on- and off-glacier sites, were applied in a distributed energy-balance model. Compared with piecewise air temperature extrapolation from all on-glacier stations, modelled ablation, using the MG–TG, increased by <1%, increasing to >4% using the environmental ‘lapse rate’. Ice melt under thick debris was relatively insensitive to air temperature, while the effects of different temperature extrapolation methods were strongest at high elevation sites of thin and patchy debris cover.

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