Clean Glacier Research Articles

A Comprehensive Inventory, Characterization, and Analysis of Rock Glaciers in the Jhelum Basin, Kashmir Himalaya, Using High-Resolution Google Earth Data

Rock glaciers are crucial freshwater resources, yet detailed knowledge about their distribution, characteristics, and dynamics in the Himalayan region is scarce. This study presents a comprehensive rock glacier inventory of the Jhelum basin, Kashmir Himalaya, India, using high-resolution Google Earth data. We identified 240 rock glaciers covering an area of 41.24 ± 2.2 km2, with ~76% classified as active, ~20% inactive, and 3.7% relict. The average areas and lengths of these rock glacier types were 0.19 km2, 0.06 km2, and 0.29 km2, and 699 m, 426 m, and 952 m, respectively. Most rock glaciers (~90%) were oriented northwards (N, NE, NW), while only 5% faced southwards (S, SE, SW). The lower limit of permafrost in the Jhelum basin is about 3316 m asl. Furthermore, we estimated the ice storage of rock glaciers in the Jhelum basin at 0.80 ± 0.13 km3, equivalent to 0.72 ± 0.12 km3 of water volume. This study enhances our understanding of permafrost distribution and the characteristics and dynamics in the basin. Given their greater resilience to climate change compared to clean glaciers, the hydrological significance of rock glaciers is expected to increase under projected climate change scenarios. This study highlights their importance as a vital water resource amidst the accelerated recession of clean glaciers.

Analysis of the temporal variations in glaciers’ surface area in Alaknanda River Basin, Uttarakhand

Abstract This study presented detailed analysis of glacier surface extent in the Alaknanda river basin, Western Himalaya, using Landsat series data, land surface temperature and digital elevation model (DEM). The clean glaciers were delineated using automatic glacier extraction index (AGEI) and the debris-covered glaciers were extracted by utilizing slope and land surface temperature. The generated glaciers map was compared and cross-checked with Randolph Glacier Inventory (RGI v5.0) and sharp google earth image. The reduction in glacier surface area was observed by 367.364 sq. km from 1994 (1150.471 sq. km) to 2015 (783.107 sq. km) at the shrinkage rate of 1.45% per annum. The shrinkage rate was higher from 2006 to 2015 (2.43% per annum) than from 1994 to 2006 (0.78% per annum). The glacier count expanded from 314 (1994) to 360 (2015) due to the fragmentation of individual glaciers. The elevation range of 5000–5500 m above m.s.l. hosted maximum number of glaciers and glacial coverage. The debris-covered glaciers showed deglaciation at the rate of 0.59% per annum from 1994 to 2015. The total area occupied by glacier extent was about 25% of the total basin in the year 1994, 23% in the year 2006 and 17% in the year 2015.

Spatial variability in melting on Himalayan debris-covered glaciers from 2000 to 2013

Glaciers covered by debris are widespread in the Himalayas. Debris layer makes the melting process of glaciers complicated, and the correlation between the spatial melt differences of glacier and its surface features is still not clear. The aim of this study was to identify possible causes of thickness changes for Himalayan debris-covered glaciers. Firstly, three high resolution Digital Elevation Model (DEM) datasets including SRTM DEM, AW3D and TanDEM-X DEM were used to estimate glacier thickness changes from 2000 to 2013. By checking and removing geometric displacements, systematic deviations and elevation-related bias, as well as correction of radar wave penetration depth in the clean glacier areas, reliable thickness change information in this complex glaciated region were provided. Then debris thicknesses on the glaciers were estimated. The surface lowering caused by ice cliffs or supraglacial ponds significantly reduces debris thickness. Finally, some surface features including debris thicknesses, spatial patterns of supraglacial ponds and ice cliffs extracted from high-resolution satellite images in different times, were comprehensively used to evaluate the main drivers of glacier melting differences. Results demonstrate that spatial variability of glacier melting in Himalayas is caused by the combined effects of debris thicknesses, ice cliffs and supraglacial lakes, with different dominant factors for different regions. The thickened glacier region, which mostly appears above 5300 m a.s.l., with minimal debris cover, displayed large patches of thickening and partial serious thinning in the debris-free areas. Although the thick debris layer (> 0.20 m) would slow down the glacier melting at the low-elevations, it leads to the heavy glacier thinning for the regions located 5000–5300 m a.s.l., where there are dense ice cliffs. In some areas with >1 m of average debris thickness, glaciers have thinned slowly because of erosion from the ice cliffs or large supraglacial ponds. Area and number of cliffs have proven to be key factors in controlling regional ablation for debris-covered glaciers, and supraglacial lakes serve as assistance.

Warming Has Accelerated the Melting of Glaciers on the Tibetan Plateau, but the Debris-Covered Glaciers Are Rapidly Expanding

Glacier changes on the Tibetan Plateau are of great importance for regional climate and hydrology and even global ecological changes. It is urgent to understand the effect of climate warming on both clean and debris-covered glaciers on the Tibetan Plateau. This study used the double RF method and Landsat series images to extract clean glaciers and debris-covered glaciers on the Tibetan Plateau from 1985 to 2020 and analyzed their temporal and spatial changes under the background of climate change. The total area of glaciers on the Tibetan Plateau showed a retreating trend from 1985 to 2020, with an average retreat rate of −0.5 % yr−1. The area of clean glaciers showed a significant retreating trend, with a retreat rate of −0.55 % yr−1. The area of debris-covered glaciers showed an expanding trend, with an expanding rate of 0.62 % yr−1. The clean glaciers retreated faster in the southeast and slower in the northwest, while the debris-covered glaciers expanded in most basins. The debris-covered glaciers were generally located at lower elevation areas than those of the clean glaciers. The slopes of clean glaciers were mainly in the range of 0–50°, while the slopes of debris-covered glaciers were mainly in the range of 0–30°. Climate warming was a main driver of glacier change. The clean glacier area was correlated negatively with average temperature in summer and positively with average precipitation in winter, while the debris-covered glacier area was correlated positively with both. The results of the study may provide a basis for scientific management of glaciers on the Tibetan Plateau in the context of climate warming.

Explaining the natural and anthropogenic factors driving glacier recession in Kashmir Himalaya, India.

Glaciers across the Kashmir Himalayan region are melting at an accelerated pace compared to other regions across the Himalayan arc. This study analyzed the recession patterns of nine glaciers in the Kashmir Himalaya region over 28years between 1992 and 2020 using satellite images and field measurements. The recession patterns were correlated with debris cover, topographic factors, and ambient black carbon (BC) concentration at glacier sites. HYSPLIT model was used to track the air mass sources at a 7-day time-step from September 1, 2014, to September 28, 2014, over the selected region. All nine glaciers revealed high recession as indicated by changes in the area (average recession: 20.8%) and snout position (~ 14m a-1). The relative percentage of debris on each glacier varied between ~ 0% (clean glacier) and 43%. Although the investigated glaciers lie in the same climatological regime, their topographical behavior is dissimilar with mean altitude ranging between 4000 and ~ 4700m asl and the average slope varying from 17 to 24°. All the investigated glaciers are north-facing except G3 (southerly aspect). Our results indicate anomalously high ambient BC concentrations, ranging from 500 to 1364ngm-3, at the glacier sites, higher than previously studied for glaciers in the Himalayas and neighboring Tibetan Plateau. The backward air-mass trajectory modeling indicated both local and global sources of particulate matter in the study area. A comparative analysis of BC measurements and glacier recession with the studies conducted across high Asia indicated the influence of BC in accelerating the melting of glaciers in the Kashmir region.

Positive mass budgets of high-altitude and debris-covered fragmented tributary glaciers in Gangotri Glacier System, Himalaya

Glacier-wide mass balances (MBs) of the Gangotri, Chaturangi, Raktavaran, Meru, and Gangotri Glacier System are reconstructed with a temperature-index (T-index) model using bias-corrected ERA5 data at a daily temporal resolution over 1979–2020. The model output is calibrated against available geodetic MB for Gangotri Glacier System and validated with satellite-derived snow line altitudes (SLAs) for Gangotri Glacier. Gangotri and Meru glaciers show mean mass wastage of –0.88 ± 0.31 m w. e. a‒ˡ (meter water equivalent per year) and ‒0.17 ± 0.29 m w. e. a‒ˡ, respectively whereas the mass budgets of fragmented tributary Chaturangi and Raktavaran glaciers are positive with the mean values of 0.49 ± 0.17 m w. e. a‒ˡ and 0.62 ± 0.15 m w. e. a‒ˡ, respectively over 1979–2020. Gangotri Glacier’s tongue is covered by thick debris having several supra-glacial lakes and ice cliffs (considered as melting hotspots); therefore, despite the presence of thick debris, we assume the melting over this area as of a clean glacier. The whole Gangotri Glacier System shows a moderate wastage of ‒0.27 ± 0.25 m w. e. a‒ˡ. The positive MBs of the Raktavaran and Chaturangi glaciers are due to their high area-elevation distribution and heavily debris-covered tongues. The positive MBs on these fragmented tributary glaciers are due to non-climatic topographic reasons and should not be misunderstood as climate change deniers or compared with Karakoram Anomaly. Modelled MBs are most sensitive to the threshold temperature for melt. The altitudinal MB sensitivities to all model parameters become negligible above 6,200 m a.s.l.

Debris-cover impact on glacier melting in the Upper Indus Basin

Out of 4530 glaciers covering ∼4770 km2 in the Upper Indus Basin, viz., Chenab, Zanaskar and Suru sub-basins, we selected topographically and morphologically homogeneous set of 98 glaciers; 56 debris-covered and 42 clean to assess the impact of debris-cover on glacier melting. Satellite data analysis from 2000 to 2017 showed that the debris-covered glaciers have melted slower (2.49 ± 0.05%; 0.15%a−1) than the clean glaciers (4.07 ± 0.03%; 0.24%a−1). The intra-basin analysis revealed that clean and debris-covered glaciers in the Chenab have melted 2.34 ± 0.17% and 1.1 ± 0.30% (0.14%a−1 and 0.06%a−1) and retreated 8.82 ± 2.67ma−1 and 5.7 ± 2.67ma−1 respectively. Similarly, clean and debris-covered glaciers in the Zanaskar have melted at similar rates of 4.58 ± 0.07% and 4.55 ± 0.21% (0.27%a−1 and 0.25%a−1) and retreated 10.0 ± 2.67ma−1 and 8.4 ± 2.67ma−1 respectively. Clean and debris-covered glaciers in the Suru have melted 5.56 ± 0.09% and 4.53 ± 0.14% (0.33%a−1 and 0.27%a−1) and retreated 9.6 ± 2.67ma−1 and 7.0 ± 2.67ma−1 respectively. Extensive debris-cover of ∼32.3% modulates glacier loss in the Chenab and sparse debris-cover of 11.4% and 6.4% in the Suru and Zanaskar enhances the melting of the debris-covered glaciers. Overall, debris-covered glaciers melted slower than the clean glaciers, with inter- and intra-basin variations, suggesting that debris-cover plays a complex but significant role in modulating glacier melting under climate change.

Controls on the relative melt rates of debris-covered glacier surfaces

Supraglacial debris covers 7% of mountain glacier area globally and generally reduces glacier surface melt. Enhanced energy absorption at ice cliffs and supraglacial ponds scattered across the debris surface leads these features to contribute disproportionately to glacier-wide ablation. However, the degree to which cliffs and ponds actually increase melt rates remains unclear, as these features have only been studied in a detailed manner for selected locations, almost exclusively in High Mountain Asia. In this study we model the surface energy balance for debris-covered ice, ice cliffs, and supraglacial ponds with a set of automatic weather station records representing the global prevalence of debris-covered glacier ice. We generate 5000 random sets of values for physical parameters using probability distributions derived from literature, which we use to investigate relative melt rates and to isolate the melt responses of debris, cliffs and ponds to the site-specific meteorological forcing. Modelled sub-debris melt rates are primarily controlled by debris thickness and thermal conductivity. At a reference thickness of 0.1 m, sub-debris melt rates vary considerably, differing by up to a factor of four between sites, mainly attributable to air temperature differences. We find that melt rates for ice cliffs are consistently 2–3× the melt rate for clean glacier ice, but this melt enhancement decays with increasing clean ice melt rates. Energy absorption at supraglacial ponds is dominated by latent heat exchange and is therefore highly sensitive to wind speed and relative humidity, but is generally less than for clean ice. Our results provide reference melt enhancement factors for melt modelling of debris-covered glacier sites, globally, while highlighting the need for direct measurement of debris-covered glacier surface characteristics, physical parameters, and local meteorological conditions at a variety of sites around the world.

River Response to Melting Cryosphere Since Late Quaternary in the Pir Panjal Range of NW Himalaya

Rambiara River basin, a sub-basin of the Upper Indus, is dotted with fluvial and glacial geomorphic landforms. The presence of large number of glacial landforms like moraines, cirques, aretes, U-shaped valleys, etc. reflects the enormous erosive power of the past glaciers. During the Last Glacial Maximum (LGM), glaciers on average were 200 m thick and extended more than 10 km from the present-day cirque marks. Rock glaciers outnumber the clean glaciers that cover an area of 0.22 and 1.25 km2, respectively, in the basin. Glacial lakes are the prominent features in the higher reaches of the basin and occupy an area ranging from 0.01 to 0.70 km2. Downstream, the river is characterized by large channel width, anomalous sinuosity, braided pattern, and the presence of unpaired fluvial terraces. The large channel width depicts the enormous discharge from the glacial- and snow-melt during the Late Pleistocene when glaciers covered most of the Pir Panjal. After LGM, the glacier cover and the river discharge significantly decreased as highlighted by a large number of braided bars and the narrow stream to which the river is reduced. The warming trends observed across the Himalayas encompassing the Pir Panjal Range since the last century has further contributed significantly to the glacier recession in the basin.

Anthropogenic climate change drives melting of glaciers in the Himalaya.

The Himalayan glaciers provide water to a large population in south Asia for a variety of purposes and ecosystem services. As a result, regional monitoring of glacier melting and identification of the drivers are important for understanding and predicting future cryospheric melting trends. Using multi-date satellite images from 2000 to 2020, we investigated the shrinkage, snout retreat, thickness changes, mass loss and velocity changes of 77 glaciers in the Drass basin, western Himalaya, India. During this period, the total glacier cover has shrunk by 5.31 ± 0.33 km2. The snout retreat ranged from 30 to 430m (mean 155 ± 9.58m). Debris cover had a significant impact on glacier melting, with clean glaciers losing ~ 5% more than debris-covered glaciers (~ 2%). The average thickness change and mass loss of glacier have been - 1.27 ± 0.37 and - 1.08 ± 0.31m w.e.a-1, respectively. Because of the continuous melting and the consequent mass loss, average glacier velocity has reduced from 21.35 ± 3.3m a-1 in 2000 to 16.68 ± 1.9m a-1 by 2020. During the observation period, the concentration of greenhouse gases (GHGs), black carbon (BC) and other pollutants from vehicular traffic near the glaciers increased significantly. Increasing temperatures, caused by a significant increase in GHGs, black carbon and other pollutants in the atmosphere, are driving glacier melting in the study area. If the current trend continues in the future, the Himalayan glaciers may disappear entirely, having a significant impact on regional water supplies, hydrological processes, ecosystem services and transboundary water sharing.

De-icing landsystem model for the Universidad Glacier (34° S) in the Central Andes of Chile during the past ~660 years

Reconstructing latest Holocene (<1000 years) glacial landscape development in the Central Andes of Chile (30–35° S) is key for understanding the response of the cryosphere during periods of negative glacier mass balance, such as the current one. The excellently preserved glacial landscape produced during the latest ice advance and retreat cycle is of particular interest for examining the detailed response of glaciers to deglaciation. To establish a conceptual model of glacier behavior under warm and dry climatic conditions, we reconstructed and dated the recent glacial history of the Universidad Glacier (34° S) through detailed geomorphological mapping and 10Be cosmogenic surface exposure dating. Our mapping describes a landsystem that spans from the current ice front to ~3 km down-valley, where a mosaic of glacial landforms includes mounded relief; sinkholes; debris-filled stripes; moraine belts; flutings; and a prominent basal till plain. Our 10Be ages suggest that the Universidad Glacier has fluctuated in its forefield since the 13th – 15th centuries CE. We propose that the glacier evolved from a clean glacier to a debris-covered glacier, to an ice-cored moraine, and finally, to a massive dead-ice topography. This deglacial evolution intermittent and potentially reset by multiple standstills and/or re-advances during the overall retreat. The implication is that phases of active ice were followed by stagnation associated with progressive melting of dead ice under the supraglacial debris layer. Similar geomorphic features and processes are recorded in the present-day Universidad Glacier ablation zone, denoting a recurrent reconditioning over time analogous to the glacier's evolution during the latest Holocene.

Glacier changes in the Chhombo Chhu Watershed of the Tista basin between 1975 and 2018, the Sikkim Himalaya, India

Abstract. Glaciers of the Tista basin represent an important water source for mountain communities and a large population downstream. The article presents observable changes in the Chhombo Chhu Watershed (CCW) glacier area of the Tista basin, the Sikkim Himalaya. The CCW contains 74 glaciers (&gt; 0.02 km2) with a mean glacier size of 0.61 km2. We determined changes in glaciers from the declassified Hexagon Keyhole-9 (KH-9) (1975), Landsat 5 Thematic Mapper (TM) (1989), Landsat 7 Enhanced Thematic Mapper Plus (ETM+) (2000), Landsat 5 TM (2010), and Sentinel-2A (2018) images. The total glacier area in 1975 was 62.6 ± 0.7 km2; and by 2018, the area had decreased to 44.8 ± 1.5 km2, an area loss of 17.9 ± 1.7 km2 (0.42 ± 0.04 km2 a−1). Clean glaciers exhibited more area loss of 11.8 ± 1.2 km2 (0.27 ± 0.03 km2 a−1) than partially debris-covered and maximally debris-covered glaciers. The area loss is 5.0 ± 0.4 km2 (0.12 ± 0.01 km2 a−1) for partially covered glaciers and 1.0 ± 0.1 km2 (−0.02 ± 0.002 km2 a−1) for maximally covered glaciers. The glacier area loss in the CCW of the Sikkim Himalaya is 0.62 ± 0.5 km2 a−1 during 2000–2010, and it is 0.77 ± 0.6 km2 a−1 during 2010–2018. Field investigations of selected glaciers and climatic records also support the glacier recession in the CCW due to a significant increase in temperature (0.25 ∘C a−1) and more or less static precipitation since 1995. The dataset is now available from the Zenodo web portal: https://doi.org/10.5281/zenodo.4457183 (Chowdhury et al., 2021).

An automatic method for clean glacier and nonseasonal snow area change estimation in High Mountain Asia from 1990 to 2018

Large-scale glacier area expansion or shrinkage is among the most conspicuous indicators of regional and global climate change. Glacier extraction from satellite images is an essential step in large-scale area change monitoring. However, glacier extraction is usually influenced by cloud cover and seasonal snow, and thus far, there is no effective and automatic method to monitor glacier area change in large regions. In this study, a new method ‘multi-temporal minimum NDSI composite’ is proposed for clean glacier and nonseasonal snow extraction, and the results agree well with the glacier inventory (excluding the debris part), except in Himalayan regions where non-seasonal snow exists widely out of glaciers. This method is also used to estimate the glacier and nonseasonal snow area changes in High Mountain Asia (HMA) over the past 29 years. With this method, we can use abundant Landsat images of summer seasons from continuous years to composite a cloud-free and seasonal snow-free glacial image pixel by pixel. Glacial maps for the whole HMA are produced every 10 years beginning in 1990, so glacier changes are presented in different subregions and periods. The number of images which is used to composite a glacial map in each pixel is also given for uncertainty analysis. According to the results, the clean glacier and nonseasonal snow area in HMA decreased by −0.43 ± 0.19%/a during 1990–2018 but had high temporal and spatial heterogeneity. Clean glacier and nonseasonal snow area decreased rapidly during 1990–2000, slowed down during 2000–2010, and then sped up during 2010–2018. The fastest reductions were in Hengduan Shan at rates of approximately −1.05 ± 0.09%/a, and the only area with growth (at a rate of 0.50 ± 0.11%/a) was in West Kun Lun during 1990–2018.

Updated inventory of glacier ice in New Zealand based on 2016 satellite imagery

AbstractThe only complete inventory of New Zealand glaciers was based on aerial photography starting in 1978. While there have been partial updates using 2002 and 2009 satellite data, most glaciers are still represented by the 1978 outlines in contemporary global glacier databases. The objective of this project is to establish an updated glacier inventory for New Zealand. We have used Landsat 8 OLI satellite imagery from February and March 2016 for delineating clean glaciers using a semi-automatic band ratio method and debris-covered glaciers using a maximum likelihood classification. The outlines have been checked against Sentinel-2 MSI data, which have a higher resolution. Manual post processing was necessary due to misclassifications (e.g. lakes, clouds), mapping in shadowed areas, and combining the clean and debris-covered parts into single glaciers. New Zealand glaciers cover an area of 794 ± 34 km2 in 2016 with a debris-covered area of 10%. Of the 2918 glaciers, seven glaciers are &gt;10 km2 while 71% is &lt;0.1 km2. The debris cover on those largest glaciers is &gt;40%. Only 15 glaciers are located on the North Island. For a selection of glaciers, we were able to calculate the area reduction between the 1978 and 2016 inventories.

The satellite observed glacier mass changes over the Upper Indus Basin during 2000\u20132012

Decadal glacier thickness changes over the Upper Indus Basin in the Jammu and Kashmir Himalaya were estimated using the TanDEM-X and SRTM-C Digital Elevation Models (DEMs) from 2000 to 2012. In the study area 12,243 glaciers having 19,727 ± 1,054 km2 area have thinned on an average of − 0.35 ± 0.33 m a−1 during the observation period. The highest thinning of − 1.69 ± 0.60 m a−1 was observed in the Pir Panjal while as the marginal thinning of − 0.11 ± 0.32 m a−1 was observed for the glaciers in the Karakoram. The observed glacier thickness changes indicated a strong influence of the topographic parameters. Higher thickness reduction was observed on the glaciers situated at lower altitudes (− 1.40 ± 0.53 m a−1) and with shallower slopes (− 1.52 ± 0.40 m a−1). Significantly higher negative thickness changes were observed from the glaciers situated on the southern slopes (− 0.55 ± 0.37 m a−1). The thickness loss was higher on the debris-covered glaciers (− 0.50 ± 0.38 m a−1) than on the clean glaciers (− 0.32 ± 0.33 m a−1). The cumulative glacier mass loss of − 70.32 ± 66.69 Gt was observed during the observation period, which, if continued, would significantly affect the sustainability of water resources in the basin.

Volume-area scaling for debris-covered glaciers

AbstractA volume-area scaling relation is commonly used to estimate glacier volume or its future changes on a global scale. The presence of an insulating supraglacial debris cover alters the mass-balance profile of a glacier, potentially modifying the scaling relation. Here, the nature of scaling relations for extensively debris-covered glaciers is investigated. Theoretical arguments suggest that the volume-area scaling exponent for these glaciers is ~7% smaller than that for clean glaciers. This is consistent with the results from flowline-model simulations of idealised glaciers, and the available data from the Himalaya. The best-fit scale factor for debris-covered Himalayan glaciers is ~60% larger compared to that for the clean ones, implying a significantly larger stored ice volume in a debris-covered glacier compared to a clean one having the same area. These results may help improve scaling-based estimates of glacier volume and future glacier changes in regions where debris-covered glaciers are abundant.

Quantifying the sensitivity of band ratio methods for clean glacier ice mapping

Many methods and techniques utilize a combination of different bandwidths in the visible, NIR (Near Infrared), and SWIR (Shortwave Infrared) regions for glacier ice mapping. In this study, we investigated and compared various techniques to map the clean ice area of the glaciers using Landsat 8 and Sentinel 2 images. The effectiveness of different techniques and effects of different sensors on the mapping accuracy was also assessed in the Dhauliganga basin of Pithoragarh district, Uttarakhand state of India. Also, the time series composite of Sentinel-1 SAR (Synthetic Aperture Radar) data was used as reference data for estimating the bare or clean glacier ice area. It was reported from the study that clean ice/snow areas mapped using band ratios Red/SWIR and NIR/SWIR from Landsat 8 were overestimated by 4.41% and 4.94% respectively which were larger as compared to Sentinel 2. The most rigorous and well-known technique for glacier mapping, NDSI (Normalized Difference Snow Index) was also checked for both sensors. Clean ice/snow areas mapped from NDSI were found to be 1.35% less as compared to Red/SWIR and 2.62% greater as compared to NIR/SWIR bands of the Landsat 8. However using the same bands from the Sentinel 2, NDSI overestimated 0.67% and 5.27% respectively over both the ratios.

Physical, chemical, and biological characteristics of supraglacial pools on a debris-covered glacier in Mt. Gongga, Tibetan Plateau

ABSTRACT Meltwater habitats are found on glacier surfaces worldwide, but much of the current understanding of these habitats comes from clean glaciers sprinkled with cryoconite. Cryoconite is windblown dust particles covered with biological material that form small meltwater holes due to difference in the albedo of cryoconite compared to clean ice. However, no information is available on the physical, chemical, and biological characteristics of supraglacial pools on debris-covered glaciers. We measured physical and chemical variables and sampled macroinvertebrates from forty-six supraglacial pools during the summers of 2018 and 2019 on the debris-covered Hailuogou Glacier in southeastern Tibet. Our physical and chemical results indicated that the sampled supraglacial pools exhibited a greater diversity of shapes, were larger, contained larger substrate sizes, and had greater substrate diversity than cryoconite holes. The sampled supraglacial pools frequently contained Chironomidae (Diptera) and Isotomidae (Collembola), which are macroinvertebrate taxa that are uncommon in cryoconite holes. Chironomidae occurrence and abundance was not correlated with any measured environmental variable. The best predictors of Isotomidae and macroinvertebrate occurrence and abundance were conductivity, ice to water surface depth, and number of supraglacial pools within 5 m. Our results highlight the uniqueness of supraglacial pools on a debris-covered glacier in southeastern Tibet.

Glacier Dynamics in Changme Khangpu Basin, Sikkim Himalaya, India, between 1975 and 2016

This study provides a high resolution glacier database in the Changme Khangpu Basin (CKB) using LANDSAT 8 (2014) and Sentinel-2A image (2016), mapping of 81 glaciers that cover a 75.78 ± 1.54 km2 area. Composite maps of land surface temperature, slope and Normalized differential Snow Index have been successfully utilized in delineating near accurate debris cover boundary of glaciers. The cumulative controlling parameters of aspect, elevation, slope, and debris cover have been assessed to evaluate the nature of glacier distribution and dynamics. The local topographic settings seem to have significantly determined the glacier distribution in the CKB. Almost 20% area erstwhile under glacier cover has been lost since 1975 at an average rate of −0.453 ± 0.001 km2a−1. The recent decade (2001–2016) has witnessed a higher rate of area shrinkage (−0.665 ± 0.243 km2a−1), compared to a relatively lower rate of recession (−0.170 ± 0.536 km2a−1) between 1988 and 2001. The lower rates of glacial recession can most likely be induced regionally due to relatively cooler decadal late summer temperatures and peak in the monsoon spell. Glaciers with western and north-western aspects showed more vulnerability to area loss than the rest of the aspects. Lower altitude glaciers have receded faster than ones perched up on higher elevations. The rate of glacier area recession has been nearly twice that on clean glaciers as compared to debris-covered glaciers in the CKB.

The impact of supraglacial debris on proglacial runoff and water chemistry

Debris is known to influence the ablation, topography and hydrological systems of glaciers. This paper determines for the first time how these influences impact on bulk water routing and the proglacial runoff signal, using analyses of supraglacial and proglacial water chemistry and proglacial discharge at Miage Glacier, Italian Alps. Debris does influence the supraglacial water chemistry, but the inefficient subglacial system beneath the debris-covered zone also plays a role in increasing the ion contribution to the proglacial stream. Daily hydrographs had a lower amplitude and later discharge peak compared to clean glaciers and fewer diurnal hydrographs were found compared to similar analysis for Haut Glacier d’Arolla. We attribute these observations to the attenuating effect of the debris on ablation, smaller input streams on the debris-covered area, a less efficient subglacial system, and possible leakage into a raised sediment bed beneath the glacier. Strongly diurnal hydrographs are constrained to periods with warmer than average conditions. ‘Average’ weather conditions result in a hydrograph with reverse asymmetry. Conductivity and discharge commonly show anti-clockwise hysteresis, suggesting the more dilute, rapidly-routed melt component from the mid-glacier peaks before the discharge peak, with components from higher up-glacier and the debris-covered areas arriving later at the proglacial stream. The results of this study could lead to a greater understanding of the hydrological structure of other debris-covered glaciers, with findings highlighting the need to include the influence of the debris cover within future models of debris-covered glacier runoff.