Debris-covered Glacier Tongues Research Articles

Monitoring glacier thinning rate in Rongbuk Catchment on the northern slope of Mt. Qomolangma from 1974 to 2021

Glacier melting in the Himalayas provides indispensable water resources for downstream inhabitants. Glacier mass balance (MB) studies have important implications for hazard management of glacial lake outburst floods (GLOFs). However, Himalayan glacier MB results vary considerably among different studies with large uncertainties in satellite-based geodetic measurements, highlighting the necessity for further independent investigations and validation from multiple satellite platforms. Based on InSAR, photogrammetry, and laser altimetry techniques, we generate nine data sets of surface elevation differences (Dh) to study glacier geodetic MB in Rongbuk Catchment at the northern slope of Mt. Qomolangma. The data sets include five consecutive time periods over the last 48 years, i.e., 1974–2000, 2000–2006, 2006–2012, 2012–2015, and 2015–2021, and four overlapping periods of 1974–2012, 1974–2015, 2000–2015, and 1974–2021. The main results are summarized as follows. 1) Based on common reference DEM, geodetic MB was −0.21 ± 0.11 m w.e.a–1 in 1974–2000, −0.22 ± 0.05 m w.e. a–1 in 1974–2015, and −0.20 ± 0.03 m w.e. a–1 in 1974–2021. Geodetic MB presented negative twice since 2000 as measured by ordinary, consecutive short-term analysis, which was −0.41 ± 0.11 m w.e.a–1 in 2000–2006, −0.50 ± 0.54 m w.e.a–1 in 2006–2012, and −0.45 ± 0.11 m w.e.a–1 in 2015–2021. 2) Data validation by in-situ stake-observations at 5350, 5450, and 5500 m a.s.l in 1959–1960 and the 2000s, our results demonstrated convincing altitude effects on glacier change. Between 5150 m a.s.l. and 5800 m a.s.l., Dh presented a more downwasting rate with increasing altitude. While above 5800 m a.s.l., Dh became less negative with increasing altitude, and glaciers presented thickening trend above 6200 m a.s.l. 3) With the difference of Dh by 10 m altitude intervals (DDh), we located a sharp surface lowering zone on the debris-covered glacier tongue at 5240 ± 20 m in the 1970s. We postulated that it could be the glacier terminus under debris cover, which moved upward by 190 ± 20 m in the past five decades. With DDh, we also defined the turning point altitude at 5800 m ± 20 m, where Dh began to increase to be less negative with altitude. Moreover, summer temperature change and the number of melting days clearly explained the Dh change with altitude. 4) Glacier contribution to runoff was estimated by 30 ± 16 % from 1974 to 2021, however, our data also showed that approximately 70 % of runoff was from melting glaciers in 2015–2021, implying an amplifying effect of recent global warming on glacier contributions. In summary, our findings proved that DDh was an effective indicator for exploring mountain glacier change. The varying results revealed here indicates that more studies would be helpful to define and predict glacier, climatic and hydrological changes in the Himalayas with multiple techniques and observations based on a common reference over long term.

Steep ice – progress and future challenges in research on ice cliffs

AbstractIce cliffs are features along ice sheet margins, along tropical mountain glaciers, at termini of mountain glaciers and on debris-covered glacier tongues, that have received scattered attention in literature. They cover small relative areas of glacier or margin surface respectively, but have been involved in two apparent anomalies. On the one hand, they have been identified as potential hotspots of extreme melt rates on debris-covered tongues contributing to their relatively rapid ablation, compared to the surrounding glacier surface. On the other hand, they appear where the ice margin is stable (or temporarily advancing) even under conditions of negative mass balance. In this manuscript, we recapitulate why ice cliffs remain interesting features to investigate and what we know about them so far. We conclude by suggesting to further investigate their genesis and variable morphology and their potential as windows into past climates and processes.

On the influence of debris cover on glacier morphology: How high-relief structures evolve from smooth surfaces

Debris-covered glaciers receive increasing attention during the current period of sustained negative mass balance and expanding debris cover. The debris cover induces various feedback mechanisms that shape the evolution of the glacier geometry, and also the glacier surface. Although the surface morphology of many debris-covered glaciers is markedly different from that of debris-free glaciers, only a few studies have combined different processes to investigate these characteristic glacier surfaces in order to improve our knowledge of glacier evolution on a wider spatial and temporal scale. Debris-covered glacier tongues can consist of parts with a smooth surface as well as surfaces of high local relief with abundant ice cliffs in the lower end. In this study we analysed the evolution of the surface features of Zmuttgletscher, a debris-covered glacier in Switzerland, over a period of 140 years using time series of historic maps, high resolution digital elevation models and glacier velocities, as well as data on debris cover extent and thickness. Our results reveal insights into the up-glacier expansion of the debris cover over time and the formation of medial moraines in the prolongation of the uppermost areas where debris emerged on the glacier surface. Moraine ridge prominence increased during periods of negative mass balance, and troughs developed in debris-free areas between ridges, persisting even after a continuous debris cover had developed. The changing surface morphology inhibits across-glacier meltwater flow, both supra- and subglacially. Accordingly, we found that large cryo-valleys with ice cliffs have formed down-glacier of the troughs where meltwater runoff accumulates. The meanders of these valleys have enlarged over time, especially by ice cliff backwasting at steep slopes, and most of the glacier width today is affected by such high-relief erosion features. We find that about 75% of all ice cliffs are located in this high-relief zone. The volume lost at these erosion features has increased by a factor of five since the 1980s, but is still very small in comparison to the high glacier-wide thinning rates.

Recent slowdown and thinning of debris-covered glaciers in south-eastern Tibet

Recent large-scale remote sensing studies have shown that glacier mass loss in south-eastern Tibet, specifically in the eastern Nyainqêntanglha Range exceeds the average in High Asia. However, detailed studies at individual glaciers are scarce and the drivers behind the observed changes are poorly constrained to date. Employing feature tracking techniques on TerraSAR-X data for the periods 2008/2009, 2012/2013 and 2013/2014 we found measurable surface velocities through to the glacier terminus positions of five debris-covered glacier tongues. This is contrary to debris-covered glaciers in other parts of High Asia, where stagnant glacier tongues are common. Our feature tracking results for the 2013/2014 period suggest an average deceleration of 51% when compared with published Landsat velocities for the period 1999/2003. Further, we estimated surface elevation changes for the five glaciers from recently released one arc second resolution elevation data obtained during the Shuttle Radar Topography Mission in 2000 and an interferometrical derived TanDEM-X elevation model for the year 2014. With an average rate of −0.83 ± 0.57 m a−1 we confirm strong surface lowering in the region, despite the widely discussed insulation effect of debris cover. Beside the influence of thermokarst processes and delayed response times of debris-covered glaciers, we highlight that abundant monsoonal summer rainfall might contribute significantly to the pronounced negative mass balances in the study region.

Glacial lake evolution in the southeastern Tibetan Plateau and the cause of rapid expansion of proglacial lakes linked to glacial-hydrogeomorphic processes

Glacial lakes, as an important component of the cryosphere in the southeastern Tibetan Plateau (SETP) in response to climate change, pose significant threats to the downstream lives and properties of people, engineering construction, and ecological environment via outburst floods, yet we currently have limited knowledge of their distribution, evolution, and the driving mechanism of rapid expansions due to the low accessibility and harsh natural conditions. By integrating optical imagery, satellite altimetry and digital elevation model (DEM), this study presents a regional-scale investigation of glacial lake dynamics across two river basins of the SETP during 1988–2013andfurther explores the glacial-hydrogeomorphic process of rapidly expanding lakes. In total 1278and1396 glacial lakes were inventoried in 1988and2013, respectively. Approximately 92.4% of the lakes in 2013 are not in contact with modern glaciers, and the remaining 7.6% includes 27 (1.9%) debris-contact lakes (in contact with debris-covered ice) and 80 (5.7%) cirque lakes. In categorizing lake variations, we found that debris-contact proglacial lakes experienced much more rapid expansions (∼75%) than cirque lakes (∼7%) and non-glacier-contact lakes (∼3%). To explore the cause of rapid expansion for these debris-contact lakes, we further investigated the mass balance of parent glaciers and elevation changes in lake surfaces and debris-covered glacier tongues using time-series Landsat images, ICESat altimetry, and DEM. Results reveal that the upstream expansion of debris-contact proglacial lakes was not directly associated with rising water levels but with a geomorphological alternation of upstream lake basins caused by melting-induced debris subsidence at glacier termini. This suggests that the hydrogeomorphic process of glacier thinning and retreat, in comparison with direct glacial meltwater alone, may have played a dominant role in the recent glacial lake expansion observed across the SETP. Our findings assist in understanding the expansion mechanism of debris-contact proglacial lakes, which facilitates early recognition of potential glacial lake hazards in this region.

Decadal evolution of a very small heavily debris-covered glacier in an Alpine permafrost environment

AbstractGlacier response to climate forcing can be heterogeneous and complex, depending on glacier system characteristics. This article presents the decadal evolution of the Tsarmine Glacier (Swiss Alps), a very small and heavily debris-covered cirque glacier located in the Alpine periglacial belt. Archival aerial photogrammetry and autocorrelation of orthophotos were used to compute surface elevation, volume and geodetic mass changes, as well as horizontal displacement rates for several periods between 1967 and 2012. A GPR survey allowed us to investigate glacier thickness (15 m mean) and volume (4 × 106m3) in 2015 and to anticipate its future evolution. Different dynamics occurred in recent decades because of the heterogeneous surface characteristics. The climate-sensitive upper debris-free zone contrasts with the progressively stagnant heavily debris-covered glacier tongue. Between 1967 and 2012, the glacier lost 1/3 of its initial volume (2 × 106m3). The average mass balance stabilised at ~−0.3 m w.e. a−1since 1999. Compared with other local glaciers, the Tsarmine Glacier shows a particular decadal behaviour both in time (divergence of mass balance since the 2000s) and space (inverted ablation pattern). This might be explained by the combined influence of debris cover, shadow, snow redistribution and permafrost conditions on this very small glacier.

Variability of air temperature over a debris-covered glacier in the Nepalese Himalaya

AbstractEstimates of melt from debris-covered glaciers require distributed estimates of meteorological variables and air temperature in particular. Meteorological data are scarce for this environment, and spatial variability of temperature over debris is poorly understood. Based on multiple measurements of air and surface temperature from three ablation seasons (2012–14) we investigate the variability of temperature over Lirung Glacier, Nepal, in order to reveal how air temperature is affected by the debris cover and improve ways to extrapolate it. We investigate how much on-glacier temperature deviates from that predicted from a valley lapse rate (LR), analyse on-glacier LRs and test regression models of air temperature and surface temperature. Air temperature over the debris-covered glacier tongue is much higher than what a valley LR would prescribe, so an extrapolation from off-glacier stations is not applicable. An on-glacier LR is clearly defined at night, with strong correlation, but not during the day, when the warming debris disrupts the elevation control. An alternative to derive daytime air temperature is to use a relationship between air and surface temperature, as previously suggested. We find strong variability during daytime that should be accounted for if these regressions are used for temperature extrapolation.

Improving semi-automated glacier mapping with a multi-method approach: applications in central Asia

Abstract. Studies of glaciers generally require precise glacier outlines. Where these are not available, extensive manual digitization in a geographic information system (GIS) must be performed, as current algorithms struggle to delineate glacier areas with debris cover or other irregular spectral profiles. Although several approaches have improved upon spectral band ratio delineation of glacier areas, none have entered wide use due to complexity or computational intensity. In this study, we present and apply a glacier mapping algorithm in Central Asia which delineates both clean glacier ice and debris-covered glacier tongues. The algorithm is built around the unique velocity and topographic characteristics of glaciers and further leverages spectral and spatial relationship data. We found that the algorithm misclassifies between 2 and 10 % of glacier areas, as compared to a ~ 750 glacier control data set, and can reliably classify a given Landsat scene in 3–5 min. The algorithm does not completely solve the difficulties inherent in classifying glacier areas from remotely sensed imagery but does represent a significant improvement over purely spectral-based classification schemes, such as the band ratio of Landsat 7 bands three and five or the normalized difference snow index. The main caveats of the algorithm are (1) classification errors at an individual glacier level, (2) reliance on manual intervention to separate connected glacier areas, and (3) dependence on fidelity of the input Landsat data.

First surface velocity maps for glaciers of Monte Tronador, North Patagonian Andes, derived from sequential Pléiades satellite images

AbstractWe apply cross-correlation to Pléiades satellite images to generate accurate, high-resolution monthly surface velocity maps of Monte Tronador glaciers between March and June 2012. Measured surface displacements cover periods as short as 19 days, with a precision of ∼0.58 m (11 m a−1). These glaciers follow a radial flow pattern, with maximum surface speeds of ∼390 m a−1 associated with steep icefalls. The lower reaches of the debris-covered tongues of Verde and Casa Pangue glaciers are almost stagnant, whereas Ventisquero Negro, another debris-covered glacier, shows acceleration at the front due to calving into a proglacial lake. Low-elevation debris-covered glacier tongues show increasing velocities at the beginning of the accumulation season, whereas higher-elevation, clean-ice tongues reduce their speed during this period. This contrasting behavior is probably in response to an increase in water input to the subglacial system from winter rainfall events at low elevations and a decrease in meltwater production at higher elevations. These sequential velocity maps can help to identify the controls on glacier surface velocity, aid in the delimitation of ice divides and could also contribute to more realistic calibration of ice-flux-mass–balance models in this glacierized area.

Past surface instability of Miage debris-covered glacier tongue (Mont Blanc Massif, Italy): a decadal-scale tree-ring-based reconstruction

Debris-covered glaciers may host several biological forms that colonize the debris cover, especially if the glacier tongue reaches sufficiently low altitudes (down to about 1700 m a.s.l. at Miage Glacier, Western Italian Alps) thus allowing also tree growth. Supraglacial trees colonizing the debris-covered tongue are strongly influenced in growth and distribution by substrate characteristics and instability. The tree age distribution at Miage Glacier presents a positive gradient towards the glacier terminus, which was found to be related to the decreasing glacier surface velocity. By analysing tree-ring growth anomalies on the glacier and at a control site at the tree line over the 20-year period 1987–2006, it was found that trees growing on the glacier presented the highest percentages of abrupt growth changes (AGCs)>+70% with respect to the four previous years. Considering tree displacement on the glacier surface over the same 20-year period and the recorded AGCs, it was found that the central-lower portion of the southern lobe towards the margins was the most unstable. The temporal analysis of AGC>+40% confirmed a period of higher glacier surface instability, reaching a maximum in the years 1988 (on lobe S) and 1989 (on lobe N), probably related to the passage of a kinematic wave in the glacier tongue. Our analysis suggests that supraglacial trees hold useful information on the glacier tongue dynamics and that both AGC>+70% and AGC>+40% may be used as a proxy for substrate instability in spatio-temporal reconstructions in the Alpine environment.

A comparison of glacier melt on debris-covered glaciers in the northern and southern Caucasus

Abstract. The glacier coverage in the Caucasus Mountains underwent considerable changes during the last decades. In some regions, the observed reduction in glacier area is comparable to those in the European Alps and the extent of supra-glacial debris increased on many glaciers. Only a few glaciers in the Caucasus are monitored on a regular basis, while for most areas no continuous field measurements are available. In this study, regional differences of the conditions for glacier melt with a special focus on debris covered glacier tongues in the well-studied Adyl-su basin on the northern slope of the Caucasus Mountains (Russia) is compared with the Zopkhito basin which has similar characteristics but is located on the southern slope in Georgia. The paper focuses on the effect of supra-glacial debris cover on glacier summer melt. There are systematic differences in the distribution and increase of the debris cover on the glaciers of the two basins. In the Adyl-su basin an extensive debris cover on the glacier tongues is common, however, only those glacier tongues that are positioned at the lowest elevations in the Zopkhito basin show a considerable extent of supra-glacial debris. The observed increase in debris cover is considerably stronger in the north. Field experiments show that thermal resistance of the debris cover in both basins is somewhat higher than in other glaciated regions of the world, but there is also a significant difference between the two regions. A simple ablation model accounting for the effect of debris cover on ice melt shows that melt rates are considerably higher in the northern basin despite a wider debris distribution. This difference between the two regions can be attributed to different meteorological conditions which are characterised by more frequent cloud cover and precipitation in the south. Furthermore ablation is strongly influenced by the occurrence of supra-glacial debris cover in both basins, reducing the total amount of melt on the studied glaciers by about 25 %. This effect mitigates glacier retreat in the lower sectors of the ablation zones considerably. The sensitivity to moderate changes in the debris cover, however, is rather small which implies only gradual changes of the melt regime due to debris cover dynamics during the near future.

La dynamique des glaciers dans le contexte du changement climatique : les géomorphosites révélateurs du bouleversement des paysages et des environnements montagnards

The retreat of glaciers worldwide, from the Alpine areas to Antarctica, in the course of the last few decades, is frequently mentioned as a clear and unambiguous sign of global warming. In the Alps, although the warming experienced since the early 1980s is synchronous with warming at the global scale, nevertheless its amplitude is greater and it represents roughly a two-fold amplification of the global climate signal. As a result of this rapid climate change, many small glaciers could disappear in the next few decades. These small glaciers, common in the Alps, are also important in terms of environmental and economic systems. The rapid “disintegration” of Alpine glaciers has already been discussed in previous studies ; less attention, however, has been paid to their role as changing and potentially vanishing geomorphosites. Most Alpine glaciers, in fact, subject to rapid change driven by climate, are now responsible for unexpected environmental impacts, which in the Italian Alps have only been partially investigated. This paper analyses and discusses features and evolution in two representative glacier geomorphosites included in the official “Geosites Inventory” of the Lombardy region (Italy). In Lombardy (Italian Alps) 348 glaciers covered an area of about 92 km2 in 2003. They were found to have decreased in area by about 21 % in the period 1990-2003. The geomorphosites analysed are the Forni Glacier, the largest valley glacier in the Italian Alps, and the Val Viola glacierised basin, where various small glaciers with well-preserved moraine ridges (dating from the upper Holocene to the present) can be found. Both the geosites are located in areas identified as “Sites of Community Importance” (SCI) under directive 92/43/EEC ; furthermore, the Forni Glacier is also located in a protected area, the Stelvio National Park. These glacier geomorphosites represent well the variations affecting all Alpine glaciers ; these variations are not only driving significant changes in the morphology and ecology of the present mountain landscape, but at the same time are shaping newly formed morphologies, which may develop into smaller geomorphosites with significant value from a scientific and cultural point of view. The changes include thermokarst features such as kettles and supraglacial lakes, debris-covered glacier tongues frequently without any direct connections with the actual glacier, rounded rock outcrops emerging from the glacier surface which increase ice melting and accelerate glacier shrinkage, ice contact and moraine-dammed lakes where calving phenomena occur and icebergs drift loose, moraines affected by ice core melting with subsequent collapse and generation of mud and debris flows.

Identification of glacier motion and potentially dangerous glacial lakes in the Mt. Everest region/Nepal using spaceborne imagery

Abstract. Failures of glacial lake dams can cause outburst floods and represents a serious hazard. The potential danger of outburst floods depends on various factors like the lake's area and volume, glacier change, morphometry of the glacier and its surrounding moraines and valley, and glacier velocity. Remote sensing offers an efficient tool for displacement calculations and risk assessment of the identification of potentially dangerous glacial lakes (PDGLs) and is especially helpful for remote mountainous areas. Not all important parameters can, however, be obtained using spaceborne imagery. Additional interpretation by an expert is required. ASTER data has a suitable accuracy to calculate surface velocity. Ikonos data offers more detail but requires more effort for rectification. All investigated debris-covered glacier tongues show areas with no or very slow movement rates. From 1962 to 2003 the number and area of glacial lakes increased, dominated by the occurrence and almost linear areal expansion of the moraine-dammed lakes, like the Imja Lake. Although the Imja Lake will probably still grow in the near future, the risk of an outburst flood (GLOF) is considered not higher than for other glacial lakes in the area. Potentially dangerous lakes and areas of lake development are identified. There is a high probability of further lake development at Khumbu Glacier, but a low one at Lhotse Glacier.

Planimetric and volumetric glacier changes in the Khumbu Himal, Nepal, since 1962 using Corona, Landsat TM and ASTER data

AbstractMultitemporal space imagery from 1962 (Corona KH-4), 1992 (Landsat TM), 2001 and 2005 (Terra ASTER) was used to investigate the glacier changes in the Khumbu Himal, Nepal. The ice coverage in the investigation area decreased by about 5% between 1962 and 2005, with the highest retreat rates occurring between 1992 and 2001. The debris coverage increased concomitantly with the decrease in total glacier area. The clean-ice area decreased by >10%. Digital terrain model (DTM) generation from the early Corona KH-4 stereo data in this high-relief terrain is time-consuming, and the results still contain some elevation errors. However, these are minor in the snow-free areas with gentle slopes. Thus comparison of the surfaces of the debris-covered glacier tongues based on the Corona DTM and an ASTER DTM is feasible and shows the downwasting of the debris-covered glaciers. The highest downwasting rates, more than 20 m (>0.5 m a−1), can be found near the transition zone between the active and the stagnant glacier parts of the debris-covered glacier tongues. The downwasting is lower, but still evident, in the active ice areas and at the snout with thick debris cover. All investigated debris-covered glaciers in the study area show similar behaviour. The estimated volume loss for the investigated debris-covered glacier tongues is 0.19 km3.

Early recognition of glacial lake hazards in the Himalaya using remote sensing datasets

Glacier recession in high-Himalayan catchments leads to the formation of moraine-dammed lakes on many debris-covered glacier tongues. Such lakes are hazardous to communities and infrastructure downstream because of their potential to breach catastrophically, and their early recognition is required if remedial efforts are to be timely and cost-effective. Whilst the development of supraglacial lakes is known to begin as a series of ponds that subsequently coalesce into a larger lake, the relationship between glacier dynamics and lake formation is not well understood. Using ERS-1 and ERS-2 Synthetic Aperture Radar (SAR) data, SPOT-5 optical imagery and historical aerial photography, information is presented on the dynamics and structure of glaciers in Tibet (China) and Nepal that drain the southern side of the Himalaya. Glacier velocity data derived from interferometry show that where lakes are developing on debris-covered tongues the ice is virtually stagnant (displacements < 5 m a − 1 ). Furthermore, elevation data from Digital Elevation Models (DEMs) derived from aerial photography and SPOT-5 HRS data reveal that supraglacial lake formation is prevalent where glacier surface gradients are less than 2° from the glacier terminus, supporting empirical observations from previous work. The resolution offered by the DEMs and SAR data allows variations in transverse glacier elevations and velocities to be detected, such that the pattern of lake development on an individual glacier can be identified. Whilst the glacier surface gradient provides the boundary conditions favourable for lake formation, local variations in glacier velocity and surface morphology between flow units control the precise location of lake growth. Integrating the surface gradient and velocity information into a single analysis highlights those glaciers that are particularly vulnerable to lake development over an expected decadal timescale. The wider application of these techniques, based on remote sensing data, is particularly suitable for ‘first-pass’ hazard assessments and for regions where field access is difficult due to severe terrain, political sensitivity or financial constraints.

Dynamics of an active rock glacier (Ötztal Alps, Austria)

The rock glacier Innere Ölgrube, located in a small side valley of the Kauner Valley (Ötztal Alps, Austria), consists of two separate, tongue-shaped rock glaciers lying next to each other. Investigations indicate that both rock glaciers contain a core of massive ice. During winter, the temperature at the base of the snow cover (BTS) is significantly lower at the active rock glacier than on permafrost-free ground adjacent to the rock glacier. Discharge is characterized by strong seasonal and diurnal variations, and is strongly controlled by the local weather conditions. Water temperature of the rock glacier springs remains constantly low, mostly below 1°C during the whole melt season. The morphology of the rock glaciers and the presence of meltwater lakes in their rooting zones as well as the high surface flow velocities of &gt;1 m/yr point to a glacial origin. The northern rock glacier, which is bounded by lateral moraines, evolved from the debris-covered tongue of a small glacier of the Little Ice Age with its last highstand around A.D. 1850. Due to the global warming in the following decades, the upper parts of the steep and debris-free ice glacier melted, whereas the debris-covered glacier tongue transformed into an active rock glacier. Due to this evolution and due to the downslope movement, the northern rock glacier, although still active, at present is cut off from its ice and debris supply. The southern rock glacier has developed approximately during the same period from a debris-covered cirque glacier at the foot of the Wannetspitze massif.

Combining satellite multispectral image data and a digital elevation model for mapping debris-covered glaciers

Automated glacier mapping from satellite multispectral image data is hampered by debris cover on glacier surfaces. Supraglacial debris exhibits the same spectral properties as lateral and terminal moraines, fluvioglacial deposits, and bedrock outside the glacier margin, and is thus not detectable by means of multispectral classification alone. Based on the observation of low slope angles for debris-covered glacier tongues, we developed a multisource method for mapping supraglacial debris. The method combines the advantages of automated multispectral classification for clean glacier ice and vegetation with slope information derived from a digital elevation model (DEM). Neighbourhood analysis and change detection is applied for further improvement of the resulting glacier/debris map. A significant percentage of the processing can be done automatically. In order to test the sensitivity of our method against different DEM qualities, it was also applied to a DEM obtained from ASTER stereo data. Additionally, we compared our multisource approach to an artificial neural network (ANN) classification of debris, using only multispectral data. While the combination with an ASTER-derived DEM revealed promising results, the ANN classification without DEM data does not.