Influence of Sub-Debris Thawing on Ablation and Runoff of the Djankuat Glacier in the Caucasus

Superficial moraines grew in size during the entire 32-year-long period of direct monitoring of water and ice balance of the Djankuat Glacier in the Caucasus. The total area of debris cover on the glacier increased from 0.104 km2 (3% of the entire glacier surface) in 1968 to 0.266 km2 (8% of the glacier) in 1996. Such rapid dynamics of moraine formation greatly influences the ablation rate and distorts fields of mass-balance components. Sub-debris thawing can be calculated by means of a model, which describes the role of debris cover for the thermal properties of a glacier. Its meltwater equivalent depends mainly on debris thickness. In 1983 and 1994 the debris cover was repeatedly mapped over the whole glacier portion that was covered with morainic material. Sub-moraine ablation increases (vs. pure ice surface) under the thin, less than ca. 7-8 cm, debris layer, whereas the thicker debris cover reduces the liquid runoff due to its shielding effect. Zones differing due to their hydrological effect are depicted on the glacier map and the degree of debris influence on ablation is estimated quantitatively. As a whole runoff from debris-covered parts of the Djankuat Glacier has diminished due to the dominant shielding effect. Variation of the terminus is also shown to be dependent on the evolution of superficial moraine.

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Debris cover and the thinning of Kennicott Glacier, Alaska, Part A:in situ mass balance measurements

10.5194/tc-2019-174 ◽

2019 ◽

Author(s):

Leif S. Anderson ◽

Robert S. Anderson ◽

Pascal Buri ◽

William H. Armstrong

Keyword(s):

Mass Balance ◽

High Mountain ◽

Glacier Surface ◽

Ice Dynamics ◽

Air Temperatures ◽

High Resolution Imagery ◽

Debris Cover ◽

The Alps

Abstract. The mass balance of many Alaskan glaciers is perturbed by debris cover. Yet the effect of debris on glacier response to climate change in Alaska has largely been overlooked. In three companion papers we assess the role of debris, ice dynamics, and surface processes in thinning Kennicott Glacier. In Part A, we report in situ measurements from the glacier surface. In Part B, we develop a method to delineate ice cliffs using high-resolution imagery and produce distributed mass balance estimates. In Part C we explore feedbacks that contribute to glacier thinning. Here in Part A, we describe data collected in the summer of 2011. We measured debris thickness (109 locations), sub-debris melt (74), and ice cliff backwasting (60) data from the debris-covered tongue. We also measured air-temperature (3 locations) and internal-debris temperature (10). The mean debris thermal conductivity was 1.06 W (m C)−1, increasing non-linearly with debris thickness. Mean debris thicknesses increase toward the terminus and margin where surface velocities are low. Despite the relatively high air temperatures above thick debris, the melt-insulating effect of debris dominates. Sub-debris melt rates ranged from 6.5 cm d−1 where debris is thin to 1.25 cm d−1 where debris is thick near the terminus. Ice cliff backwasting rates varied from 3 to 14 cm d−1 with a mean of 7.1 cm d−1 and tended to increase as elevation declined and debris thickness increased. Ice cliff backwasting rates are similar to those measured on debris-covered glaciers in High Mountain Asia and the Alps.

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Application of a mass-balance model to a Himalayan glacier

Journal of Glaciology ◽

10.1017/s002214300000143x ◽

1999 ◽

Vol 45 (151) ◽

pp. 559-567 ◽

Cited By ~ 33

Author(s):

Rijan Bhakta Kayastha ◽

Tetsuo Ohata ◽

Yutaka Ageta

Keyword(s):

Mass Balance ◽

Surface Albedo ◽

Balance Model ◽

Mass Balance Model ◽

Mass Balances ◽

Climatic Parameters ◽

Glacier Surface ◽

Temperature And Precipitation ◽

Ice Surface ◽

Good Agreement

AbstractA mass-balance model based on the energy balance at the snow or ice surface is formulated, with particular attention paid to processes affecting absorption of radiation. The model is applied to a small glacier, Glacier AX010 in the Nepalese Himalaya, and tests of its mass-balance sensitivity to input and climatic parameters are carried out. Calculated and observed area-averaged mass balances of the glacier during summer 1978 (June-September) show good agreement, namely -0.44 and -0.46 m w.e., respectively.Results show the mass balance is strongly sensitive to snow or ice albedo, to the effects of screening by surrounding mountain walls, to areal variations in multiple reflection between clouds and the glacier surface, and to thin snow covers which alter the surface albedo. In tests of the sensitivity of the mass balance to seasonal values of climatic parameters, the mass balance is found to be strongly sensitive to summer air temperature and precipitation but only weakly sensitive to relative humidity.

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Unravelling the evolution of Zmuttgletscher and its debris cover since the end of the Little Ice Age

The Cryosphere ◽

10.5194/tc-13-1889-2019 ◽

2019 ◽

Vol 13 (7) ◽

pp. 1889-1909 ◽

Cited By ~ 8

Author(s):

Nico Mölg ◽

Tobias Bolch ◽

Andrea Walter ◽

Andreas Vieli

Keyword(s):

Mass Balance ◽

Ice Age ◽

Aerial Photographs ◽

Dynamic Interactions ◽

Glacier Surface ◽

Ablation Area ◽

Debris Cover ◽

Historic Maps ◽

Length And Area ◽

Flow Velocities

Abstract. Debris-covered glaciers generally exhibit large, gently sloping, slow-flowing tongues. At present, many of these glaciers show high thinning rates despite thick debris cover. Due to the lack of observations, most existing studies have neglected the dynamic interactions between debris cover and glacier evolution over longer time periods. The main aim of this study is to reveal such interactions by reconstructing changes of debris cover, glacier geometry, flow velocities, and surface features of Zmuttgletscher (Switzerland), based on historic maps, satellite images, aerial photographs, and field observations. We show that debris cover extent has increased from ∼13 % to ∼32 % of the total glacier surface since 1859 and that in 2017 the debris is sufficiently thick to reduce ablation compared to bare ice over much of the ablation area. Despite the debris cover, the glacier-wide mass balance of Zmuttgletscher is comparable to that of debris-free glaciers located in similar settings, whereas changes in length and area have been small and delayed by comparison. Increased ice mass input in the 1970s and 1980s resulted in a temporary velocity increase, which led to a local decrease in debris cover extent, a lowering of the upper boundary of the ice-cliff zone, and a strong reduction in ice-cliff area, indicating a dynamic link between flow velocities, debris cover, and surface morphology. Since 2005, the lowermost 1.5 km of the glacier has been quasi-stagnant, despite a slight increase in the surface slope of the glacier tongue. We conclude that the long-term glacier-wide mass balance is mainly governed by climate. The debris cover governs the spatial pattern of elevation change without changing its glacier-wide magnitude, which we explain by the extended ablation area and the enhanced thinning in regions with thin debris further up-glacier and in areas with abundant meltwater channels and ice cliffs. At the same time rising temperatures lead to increasing debris cover and decreasing ice flux, thereby attenuating length and area losses.

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Mass Balance of Four Cirque Glaciers in the Torngat Mountains of Northern Labrador, Canada

Journal of Glaciology ◽

10.3189/s0022143000015525 ◽

1986 ◽

Vol 32 (111) ◽

pp. 208-218

Author(s):

Robert J. Rogerson

Keyword(s):

Mass Balance ◽

Temporal Pattern ◽

Climatic Conditions ◽

Spatial Variations ◽

Equilibrium Line ◽

Positive Mass ◽

Negative Mass ◽

Equilibrium Line Altitude ◽

Ice Surface ◽

Debris Cover

AbstractThe net mass balance of four small cirque glaciers (0.7–1.4 km2) in the Torngat Mountains of northern Labrador was measured for 1981–84, allowing three complete mass-balance years to be calculated. The two largest glaciers experienced positive mass-balance conditions in 1982 while all the glaciers were negative in 1983. The temporal pattern relates directly to general climatic conditions, in particular winter snowfall. Spatial variations of mass balance on the glaciers are the result of several factors including altitude, extent of supraglacial debris cover, slope, proximity to side and backwalls of the enclosing cirque, and the height of the backwall above the ice surface. Abraham Glacier, the smallest studied and with consistently the largest negative mass balance (–1.28 m in 1983), re-advanced an average of 1.2 m each year between 1981 and 1984. Mean equilibrium-line altitude (ELA) for the four glaciers is 1050 m, varying substantially from one glacier to another (+240 to –140 m) and from year to year (+60 to –30 m).

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

The Cryosphere ◽

10.5194/tc-8-377-2014 ◽

2014 ◽

Vol 8 (2) ◽

pp. 377-386 ◽

Cited By ~ 59

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.

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Influence of debris cover on terminus retreat and mass changes of Chorabari Glacier, Garhwal region, central Himalaya, India

Journal of Glaciology ◽

10.3189/2013jog12j180 ◽

2013 ◽

Vol 59 (217) ◽

pp. 961-971 ◽

Cited By ~ 75

Author(s):

D.P. Dobhal ◽

Manish Mehta ◽

Deepak Srivastava

Keyword(s):

Mass Balance ◽

Climate Change Impacts ◽

Ablation Rate ◽

Background Information ◽

Glacier Mass Balance ◽

Mountain Range ◽

Central Himalaya ◽

Himalayan Glaciers ◽

Debris Cover ◽

Wide Variability

AbstractRecent studies of Himalayan glacier recession indicate that there is wide variability in terminus retreat rate and mass balance in the different sectors of the mountain range, primarily linked to the topography and climate of the region. Variable retreat rates of glacier termini and inadequate supporting field data (e.g. mass balance, ice thickness, velocity, etc.) in the Himalayan glaciers make it difficult to develop a coherent picture of climate change impacts. In this study, the results of a detailed mapping campaign and ground-based measurements of ablation rate, terminus retreat and ice loss are reported for the period 2003–10. In addition, background information from an old glacier map (Survey of India, 1962) was compiled and terminus recession measurements were carried out from 1990 field photographs of Chorabari Glacier, central Himalaya. Our ablation stake network results suggest that the influence of debris cover is significant for Chorabari Glacier mass balance and terminus retreat. The terminus survey finds that the glacier is retreating, but at a lower rate than many other non-debriscovered glaciers in the region. The recession and ablation data (particularly in the upper ablation area at higher altitudes) suggest that the ice volume loss of the glaciers is of greater magnitude than the slow terminus retreat and, if the process continues, the lowermost part of the glacier may reduce to a quasi-stationary position while significant ice loss continues.

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Errors in Short-Term Ablation Measurements on Melting Ice Surfaces

Journal of Glaciology ◽

10.3189/s0022143000020785 ◽

1969 ◽

Vol 8 (52) ◽

pp. 91-105 ◽

Cited By ~ 12

Author(s):

Fritz Müller ◽

Charles M. Keeler

Keyword(s):

Mass Balance ◽

Drainage Basin ◽

Weathering Crust ◽

Short Term ◽

Glacier Surface ◽

Long Period ◽

New Methods ◽

Measuring Techniques ◽

Rapid Changes ◽

Radiation Induced

Rapid changes in time and space in the micro-relief of an ablating glacier surface and radiation-induced melt within the uppermost ice layer, termed the “weathering crust”, seriously affect the accuracy of the short-term ablation measurements. The various measuring techniques commonly used (stakes, ablatometers, ablatographs) and some new methods (measurement of discharge from a small supra-glacial drainage basin, and mass loss directly measured on core samples) are critically reviewed and assessed in the light of these phenomena. The implications for studies of heat and mass balance are discussed.It appears that the direct measurement of mass flux is the most accurate means of assessing short-terni ablation rates. The errors in short-term ablation measurements by any method are largely compensatory and consequently do not influence long-period mass-balance estimates.

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Cryoconite on a glacier on the north-eastern Tibetan plateau: light-absorbing impurities, albedo and enhanced melting

Journal of Glaciology ◽

10.1017/jog.2019.41 ◽

2019 ◽

Vol 65 (252) ◽

pp. 633-644 ◽

Cited By ~ 3

Author(s):

YANG LI ◽

SHICHANG KANG ◽

FANGPING YAN ◽

JIZU CHEN ◽

KUN WANG ◽

...

Keyword(s):

Tibetan Plateau ◽

Mass Balance ◽

Glacier Mass Balance ◽

Eastern Tibetan Plateau ◽

The North ◽

Ice Surface ◽

Northern Tibetan Plateau ◽

North Eastern ◽

The Mean

ABSTRACTCryoconite is a dark-coloured granular sediment that contains biological and mineralogical components, and it plays a pivotal role in geochemistry, carbon cycling and glacier mass balance. In this work, we collected cryoconite samples from Laohugou Glacier No. 12 (LHG) on the north-eastern Tibetan Plateau during the summer of 2015 and measured the spectral albedo. To explore the impacts of this sediment on surface ablation, the ice melting differences between the cryoconite-free (removed) ice and the intact layers were compared. The results showed that the mean concentrations of black carbon (BC), organic carbon (OC) and total iron (Fe) in the LHG cryoconite were 1.28, 11.18 and 39.94 mg g−1, respectively. BC was found to play a stronger role in solar light adsorption than OC and free Fe. In addition, ice covered by cryoconite exhibited the lowest mean reflectance (i.e., <0.1). Compared with the cryoconite-free ice surface, cryoconite effectively absorbed solar energy and enhanced glacial melting at a rate of 2.27–3.28 cm d−1, and free Fe, BC and OC were estimated to contribute 1.01, 0.99 and 0.76 cm d−1, respectively. This study provides important insights for understanding the role of cryoconite in the glacier mass balance of the northern Tibetan Plateau.

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The influence of a supraglacial debris cover on the mass balance and dynamics of the Djankuat Glacier, Caucasus, Russian Federation

10.5194/egusphere-egu21-13641 ◽

2021 ◽

Author(s):

Yoni Verhaegen ◽

Oleg Rybak ◽

Victor V. Popovnin ◽

Philippe Huybrechts

Keyword(s):

Mass Balance ◽

Russian Federation ◽

Climatic Conditions ◽

Ice Flow ◽

The Caucasus ◽

Caucasus Region ◽

Debris Cover ◽

Dominant Process ◽

The Russian Federation ◽

The Impact

We have modelled the influence of a supraglacial debris cover on the behavior of the Djankuat Glacier, a northwest-facing and partly debris-covered temperate valley glacier near the border of the Russian Federation and Georgia, which has been selected as a &#8216;reference glacier&#8217; for the Caucasus region by the WGMS. A calibrated 1D coupled ice flow-mass balance-supraglacial debris cover model is used to assess the impact of the melt-altering effect of various supraglacial debris profiles on the overall steady state characteristics of the glacier. Additional experiments are also carried out to simulate the behavior of this specific debris-covered glacier in a warming future climate. The main results show that, when compared to its clean-ice version, the debris-covered version of the Djankuat Glacier exhibits longer but thinner ablation zones, accompanied by lower ice flow velocities, lower runoff production, as well as a dampening of the mass balance-elevation profile near the terminus. Experiments for warming climatic conditions primarily point out towards a significant delay of glacier retreat, as the dominant process for ice mass loss encompasses thinning out of the ablation zone. The above-mentioned effects are modelled to be increasingly pronounced with an increasing thickness and extent of the superimposed supraglacial debris cover.

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Early 21st-century glacier surface mass balance across High Mountain Asia derived from remote sensing

10.5194/egusphere-egu2020-9330 ◽

2020 ◽

Author(s):

Evan Miles ◽

Michael McCarthy ◽

Amaury Dehecq ◽

Marin Kneib ◽

Stefan Fugger ◽

...

Keyword(s):

Remote Sensing ◽

Mass Balance ◽

Surface Velocity ◽

High Mountain ◽

Surface Mass Balance ◽

Equilibrium Line Altitude ◽

Glacier Surface ◽

Surface Mass ◽

Early 21St Century ◽

Debris Cover

Glaciers in High Mountain Asia have experienced intense scientific scrutiny in the past decade due to their hydrological and societal importance. The explosion of freely-available satellite observations has greatly advanced our understanding of their thinning, motion, and overall mass losses, and it has become clear that they exhibit both local and regional variations due to debris cover, surging and climatic regime. However, our understanding of glacier accumulation and ablation rates is limited to a few individual sites, and altitudinal surface mass balance is essentially unknown across the vast region.Here we combine recent assessments of ice thickness and surface velocity to correct observed glacier thinning rates for mass redistribution in a flowband framework to derive the first estimates of altitudinal glacier surface mass balance across the region. We first evaluate our results at the glacier scale with all available glaciological field measurements (27 glaciers), then analyze 4665 glaciers (we exclude surging and other anomalous glaciers) comprising 43% of area and 36% of mass for glaciers larger than 2 km2 in the region. The surface mass balance results allow us to determine the equilibrium line altitude for each glacier for the period 2000-2016.&#160; We then aggregate our altitudinal and hypsometric surface mass balance results to produce idealised profiles for distinct subregions, enabling us to consider the subregional heterogeneity of mass balance and the importance of debris-covered ice for the region&#8217;s overall ablation.We find clear patterns of ELA variability across the region. &#160;9% of glaciers accumulate mass over less than 10% of their area on average for the study period. These doomed&#160; glaciers are concentrated in Nyainqentanglha, which also has the most negative mass balance of the subregions, whereas accumulation area ratios of 0.7-0.9 are common for glaciers in the neutral-balance Karakoram and Kunlun Shan. We find that surface debris extent is negatively correlated with ELA, explaining up to 1000 m of variability across the region and reflecting the importance of avalanching as a mass input for debris-covered glaciers at lower elevations. However, in contrast with studies of thinning rates alone, we find a clear melt reduction for low-elevation debris-covered glacier areas, consistent across regions, largely resolving the &#8216;debris cover anomaly&#8217;.&#160;&#160;Our results provide a comprehensive baseline for the health of the High Asian ice reservoirs in the early 21st Century. The estimates of altitudinal surface mass balance and ELAs will additionally enable novel strategies for the calibration of glacier and hydrological models. Finally, our results emphasize the potential of combined remote-sensing observations to understand the environmental factors and physical processes responsible for High Asia&#8217;s heterogeneous patterns of recent glacier evolution.

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