Content uploaded by Lindsey I Nicholson
Author content
All content in this area was uploaded by Lindsey I Nicholson on Feb 26, 2018
Content may be subject to copyright.
A preview of the PDF is not available
Response of debris-covered glaciers in the Mount Everest region to recent warming, and implications for outburst flood hazards
Abstract and Figures
In areas of high relief, many glaciers have extensive covers of supraglacial debris in their ablation zones, which alters both rates and spatial patterns of melting, with important consequences for glacier response to climate change. Wastage of debris-covered glaciers can be associated with the formation of large moraine-dammed lakes, posing risk of glacier lake outburst floods (GLOFs). In this paper, we use observations of glaciers in the Mount Everest region to present an integrated view of debris-covered glacier response to climate change, which helps provide a long-term perspective on evolving GLOF risks.
Figures - uploaded by Lindsey I Nicholson
Author content
All figure content in this area was uploaded by Lindsey I Nicholson
Content may be subject to copyright.
... A consensus of studies around the world have reported growth in debris cover and attributed it to the enhanced glacier melting in view of the warming climate (Bhambri et al., 2011;Garg et al., 2017a;Glasser et al., 2016;Lambrecht et al., 2011;Quincey et al., 2009;Tielidze et al., 2020). Enhanced melting leads to glacier thinning and consequent reduction in the glacier velocity (Benn et al., 2012). Since the glacier velocity plays a significant role in redistribution, mobilization and removal of debris cover from the glacier system, reducing velocity negatively impact the efficient debris transfer mechanism allowing thickening and expansion of debris cover (Quincey et al., 2009;Shroder et al., 2000). ...
... The presence of debris dramatically influences the sub-debris melt rates as a function of its thickness influencing the long-term glacier response to climate change (Benn et al., 2012;Hagg et al., 2008;Juen et al., 2014;Nicholson and Benn, 2006;Nicholson et al., 2018;Ö strem, 1959;Zhang et al., 2011). While thick debris exceeding a few centimetre diminishes the melting, thin debris enhances it (Evatt et al., 2015;Herreid and Pellicciotti, 2020;Mattson, 1993;Miles et al., 2020). ...
... Further, debris-covered ablation areas of glaciers, particularly in High Mountain Asia, are often characterized by complex surface encompassing hummocky, rugged topography atop a shallow (or even reversed) longitudinal surface gradient (Miles et al., 2020). Such surface topography is commonly a result of an inverted mass-balance regime, where the maximum ablation rates are experienced in the middle, rather than lower, ablation area (Benn et al., 2012;King et al., 2017;Miles et al., 2020). The ablation gradient inverts because the typical down-glacier increase in debris thickness offsets the effect of higher temperature in lower altitudes (Benn et al., 2012;Benn and Evans, 2010;Brun et al., 2018;Thompson et al., 2016). ...
... Seismological Research Letters can be associated with tropical cyclones and westerly disturbances, respectively, and snow accumulations can occur at high elevations at any time of the year (Benn et al., 2012). ...
This article presents an overview of the first 10 yr of activity of the IO.EVN seismographic broadband station, managed by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS and installed near the Observatory-Laboratory Pyramid, about 6 km from Everest Base Camp (Nepal) at 5000 m above sea level. The IO.EVN station is registered in the International Federation of Digital Seismograph Networks (FDSN; see Data and Resources). It has been in operation since 2014 and played a crucial role during the 2015 crisis following the Gorkha earthquake because it was the closest broad-band seismometer to the epicenter. The site is located in a remote area with ideal conditions for noise attenuation and is suitable for recording environmental microtremors and earthquakes in the Himalayas and worldwide. Khumbu Valley (Mount Everest) is one of the Himalayan regions that has not been struck by significant earthquakes (Mw > 7.8) in living memory. Although the analysis of microseismicity deserves further investigation, this article focuses more on the analysis of seismic noise, which was conducted to identify the various weather and climate phenomena affecting the region. In our case, we have found that for the major weather phenomena such as typhoons the main effect is due to the reflection of ocean waves on the coasts, whereas local effects such as rain and wind during the monsoon are more significant as the noise level of waves is probably constant throughout the year. The Pyramid is an important station for weather and climate, and the role of the IO.EVN could prove relevant in understanding climate change in the future.
... Wide-ranging effects of GLOFs can extend many kilometers downstream and the repercussions could result in property damage, extinction of species, and even human death (Carrivick and Tweed, 2016;Champati Ray et al., 2016). Besides this, Veh et al. (2022)'s recent study from 2022 revealed that there had been 2800 GLOF incidents worldwide and it has also been observed that more GLOFs incidents occurred in the Himalayas than in any other mountain ranges (Richardson and Reynolds, 2000a;Bhambri et al., 2011;Benn et al., 2012;ICIMOD, 2011;Veh et al., 2019). ...
The current investigation has been carried out to determine the potentially dangerous glacial lakes (PDGLs) and glacier recession and in the Bhut and Warwen sub-basins of Chenab basin using the Landsat series of data. In order to assess the glacier dynamics from 2000 to 2020 the consecutive set of 5-year intervals data were used and it is found that, glaciers are shrinked in area as 1049.94 km2 in 2000, to 988.07 km2 in 2020, indicating a notable decrease in glacier extent over the twenty-year period. Further, an empirical approach was used to identify the PDGLs in the study area. The results of PDGLs shows that there are a total of 55 glacial lakes have the potential to be hazardous. Out of them, 11 are classified as high hazard, 18 as moderate hazard; and the remaining 26 are designated as low hazard. The PDGLs in the region have seen a surge in their numbers in the last few decades due to topographical as well as climate variables. The receding of glaciers and the risk of landslides in the region greatly influences PDGLs. The dangers among these lakes in the region have accumulated so much sediments and the glacial melt and their bearing capacity has come up to certain threshold causing the GLOFs and landslide lake outburst floods (LLOFs) in the region.
... Therefore, continuous monitoring of supraglacial lakes and ponds is essential to understand their behavior and implications on a wider scale. This is critical for assessing potential hazards associated with these lakes, as their size and presence can heavily influence glacier stability and hydrological dynamics (Benn et al. 2012;Rounce et al. 2017). ...
Recent climate dynamics denote patterns and variations in climatic conditions and associated cryospheric changes in the Pamir region, affecting downstream ecosystems and communities. The present investigation describes changes in Baralmos glacier and supraglacial lakes, along with related hazards, using meteorological observations, reanalysis products, and high-resolution satellite imagery from 2002 to 2022. Moreover, observations using Unmanned Aerial Vehicles (UAVs) were conducted between 2020 and 2022 to document recent variations. Reanalysis data suggested that there are no obvious trends in annual air temperature and precipitation except for a significant temperature rise in July (the warmest month) of about 1.34°C/decade (p<0.05) and precipitation decrease in December (p<0.05). During the last two decades of investigation, lake areas expanded from 20500 to 62800 ± 21 m2, representing an approximately threefold increase, leading to increased mudflows in the Surkhob river and causing severe damage to property and infrastructures, most prominently during 2020 and 2022. The UAV data reveal an average decrease of −2.7 ± 0.5 m in surface elevation downstream of Baralmos glacier between 2020 and 2022. This study is vital for implementing more intensive measures of the glacial environment and defining suitable mitigation strategies in the Pamir region.
Supraglacial debris modulates the thermal regime and alters glacial melt rates depending on its thickness. Thus, the estimation of debris thickness becomes imperative for predicting the hydrological response and dynamics of such glaciers. This study tests the performance of empirical and thermal resistance-based debris thickness approaches against field measurements on the Hoksar Glacier, Kashmir Himalaya. The aim of this study was accomplished using thermal imageries (Landsat 8 Operational Land Imager [Landsat-OLI], 2017 and Advanced Spaceborne Thermal Emission and Reflection Radiometer [ASTER] Surface Kinetic Temperature Product [AST08], 2017) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA-5) datasets. First, the spatially resolved estimates of debris thickness for the entire debris-covered zone were achieved by establishing an empirical relationship between debris thickness and debris surface temperature (both field and satellite thermal imageries). Second, debris thickness for every pixel of thermal imagery was executed by calculating thermal resistance from the energy balance model incorporating primary inputs from (ERA-5), debris temperature (AST08, Landsat OLI), and thermal conductivity. On comparison with field temperature and thickness measurements with satellite temperature, homogenous debris thickness pixels showed an excellent coherence ( r = 0.9; p < 0.001 for T AST08 and r = 0.88; p < 0.001 for T Landsat OLI for temperature) and ( r = 0.9; p < 0.001 for T AST08 and r = 0.87; p < 0.002 for T Landsat OLI for debris thickness). Both approaches effectively captured the spatial pattern of debris thickness using Landsat OLI and AST08 datasets. However, results specify an average debris thickness of 18.9 ± 7.9 cm from the field, which the empirical approach underestimated by 12% for AST08 and 28% for Landsat OLI, and the thermal resistance approach overestimated by 6.2% for AST08 and 5.1% for Landsat OLI, respectively. Debris thickness estimates from the thermal resistance approach (deviation 11.2% for AST08 and 11.6% for Landsat OLI) closely mirror the field measurements compared to the empirical approach (deviation 26.9% for AST08 and 35% for Landsat OLI). Thus, the thermal resistance approach can solve spatial variability in debris thickness on different heavily debris-covered glaciers globally without adequate knowledge of field measurements.
The local or overall mass balance of a glacier is significantly influenced by the spatial heterogeneity of its overlying debris thickness. Accurately estimating the debris thickness of glaciers is essential for understanding their hydrological processes and the impact of climate change. This study focuses on the Koxkar Glacier in the Tian Shan Mountains, using debris thickness data to compare the accuracy of three commonly used approaches for estimating the spatial distribution of debris thickness. The three measurement approaches include two empirical relationships between the land surface temperature (LST) and debris thickness approaches, empirical relationship approach 1 and empirical relationship approach 2, and the energy balance of debris approach. The analysis also explores the potential influence of topographic factors on the debris distribution. By incorporating temperature data from the debris profiles, this study examines the applicability of each approach and identifies areas for possible improvement. The results indicate that (1) all three debris thickness estimation approaches effectively capture the distribution characteristics of glacial debris, although empirical relationship approach 2 outperforms the others in describing the spatial patterns; (2) the accuracy of each approach varies depending on the debris thickness, with the energy balance of debris approach being most accurate for debris less than 50 cm thick, while empirical relationship approach 1 performs better for debris thicker than 50 cm and empirical relationship approach 2 demonstrates the highest overall accuracy; and (3) topographic factors, particularly the elevation, significantly influence the accuracy of debris thickness estimates. Furthermore, the empirical relationships between the LST and debris thickness require field data and focus solely on the surface temperature, neglecting other influencing factors. The energy balance of debris approach is constrained by its linear assumption of the temperature profile, which is only valid within a specific range of debris thickness; beyond this range, it significantly underestimates the values. These findings provide evidence-based support for improving remote-sensing methods for debris thickness estimation.
Recent studies on climate change in the fragile landscapes of the Indian Himalayan region have shown that they are highly susceptible to climate change. Glaciers, snow, and permafrost interact and respond to climate in distinct ways and there is continual concern about current and projected climate change implications. Floods, landslides, glacial lake outburst floods (GLOFs), and shifting precipitation patterns are all potential hazards in the Baspa River Basin. These risks have the potential to disrupt the region's socioeconomic fabric and imperil human lives, infrastructure, agriculture, and ecosystems. The study aims to map glacial lakes of the Baspa River basin using medium-resolution (15 m) Landsat satellite images for the year 2020. The study used geospatial methods for instance the normalized difference water index (NDWI) including manual vectorization of lakes using Google Earth imagery to conduct a semi-automatic approach for mapping glacial lakes. In 2020, a total of 42 glacial lakes were identified, each with an area equal to or exceeding 0.25 hectares. Also, the study evaluated the spatial and temporal evolution of lakes from 2000 to 2020 in connection to the changing climate within the river basin. This research provides an essential data repository of glacial lakes and lays the underpinning for long-term evaluation and monitoring of GLOF events in the research area.
The Tsho Rolpa Glacier Lake stores about 100x 106 m3 of water behind an unconsolidated moraine dam in the Roiwaling Valley of central Nepal. The 150 m high terminal moraine has been deteriorating rapidly since the last 4-5 years, as buried dead-ice is being exposed. Displacement waves formed by the calving of the Trakarding Glacier terminus into the Tsho Rolpa are increasing in magnitude. Seepage from springs on the distal flank of the end moraine some 50 m below the dam crest and shallow slumps were also observed, and all of these phenomena indicate deterioration of the moraine dam. The majority of past studies suggested lowering the lake level to prevent a glacier lake outburst flood. Engineering work to lower the lake level down to 3 m by constructing an open channel on the terminal moraine began in May 1999 and ended successfully in July 2000. Several studies, including the ground penetrating radar survey, were conducted in association with the construction work. They provided the detailed information on subsurface conditions of the lake area. The construction of the open channel reduced the volume of water available to form a potential glacier lake outburst flood by about 20%. This work demonstrated for the first time in Nepal that such remediation of a glacier lake outburst is quite effective.
Analyses of satellite imagery obtained in 1989-1990 and topographic maps from 1966 have been undertaken for the glacierized areas of Bhutan. It has been found that where supraglacial lakes have formed since 1966, surface gradients of the glaciers concerned were in all cases less than 2°. At gradients of 2-10°supraglacial ponds can form but tend to be transient due to the opening and closing of crevasses. By identifying the conditions under which large supraglacial lakes form it is possible to use these criteria to predict where such lakes may develop in the future. This will allow suitable monitoring programmes to be introduced and, where necessary, suitable engineering remediation works to be undertaken in order to prevent the collection of large volumes of water that may be liable to form glacier lake outburst floods in the future.
Patterns of annual variation of air temperature in the world provide two types of the patterns of ablation rate of the glacier, namely the “summer-maximum” and the “non-maximum” through a year, while those of precipitation and air temperature provide three types of accumulation rate, namely, the above two and the “winter-maximum”. In six combinations of these types, annual variation of balance rate can be classified into the types of the winter-maximum, the non-maximum and the summer-maximum. The “summer-accumulation type glaciers” in the Nepal Himalaya, which have more accumulation in summer than winter in the whole area of a glacier, belong to the non-maximum type of balance rate.
In the case of this type glacier, direct observations of accumulation and ablation are quite difficult, since accumulation and ablation mainly occur simultaneously in summer. Therefore, the methods of estimation of accumulation and ablation are discussed. Accumulation can be estimated on the basis of the linear relation between surface air temperature and the probability of occurrence of solid precipitation in all cases of precipitation. Local characteristics of melting process of precipitation elements which control such relation are described. For the estimation of ablation, the effect of high albedo of new snow is important for the summer-accumulation type. The variation of mass balance through the balance year in the case of the summer-accumulation type is compared with that of the winter-accumulation type.
In 1978, the first detailed glaciological studies were carried out on the small glacier AX010 in a glacier inventory of Dudh Kosi region, in the Nepal Himalaya. Its length, area and highest and lowest elevations in 1978 were 1.7 km, 0.57 km2, 5360 and 4950 m a.s.l., respectively. Two resurveys of its terminus position and/or surface elevations were carried out in 1989 and 1991. The glacier retreated by about 30 and 28 m during the periods 1978–89 and 1989–91, respectively.
In 1995, annual monitoring of this glacier by means of ground survey, stake method and topographical mapping began, in order to obtain its mass balance, surface flow velocity and extent, and link them with climatic conditions. The results obtained in 1995 are summarized as follows: (1) During the period 1991–95, the glacier retreated by 12 m. (2) Associated with the ice-thickness loss in the lower part of the glacier, the horizontal surface velocities along the center line in 1995 (June–October) showed a remarkable decrease on the glacier tongue, to about 50% of those in 1978.
Shrinkage of the glacier in the near future is predicted from a simple model calculation for the case that climatic conditions remain unchanged from 1995. The results show that the present shrinkage should continue and accelerate.
The thickness of supraglacial debris on the Khumbu Glacier, Nepal Himalaya, has been mapped by a combination of direct measurements and morphological and lithological studies. All three processes, englacial, supraglacial, and subglacial, must be considered in establishing the distribution of debris. Taking advantage of the lithological characteristics of the debris and their bedrock source, the denudation rate of the schistose bedrock was estimated to be about 0.02 mm a−1. A rough estimate of the production rate of supraglacial debris indicated that most of the present debris has formed since the last advance of the glacier, which took place a few hundred years B.P.
The debris-covered area of Khumbu Glacier was topographically mapped in 1995 and the morphological evolution was determined by comparing the 1995 maps with those made in 1978. There had been significant changes in the surface morphology during this 17-year period: The area with a rough uneven surface with large relative relief had extended both upglacier and downglacier, and area of high ablation had increased. The glacier shrinkage in the ablation area where there was a thick debris cover was associated with an increase in surface relief and relative height, mainly caused by rapid ablation on exposed ice and lateral erosion at streams and ponds.
The Neoglacial evolution of the Tasman Glacier is reconstructed from the distribution of ice-marginal moraines and from the subglacial topography. The glacier has overridden its margins, creating two shelves of thin ice by c. 3700 years before present (BP) and c. 2000 years BP. The proglacial foreland is dominated by outwash aggradation and lacks pre-nineteenth century terminal moraines. The glacier has experienced successively larger expansions over the Neoglacial period (c. 5000 years), prior to drastic twentieth-century thinning and retreat. Over the same period, uncovered glaciers have shown progressively smaller re-advances. The expansionary tendency of the debris-covered glacier is interpreted as a response to long-term (millennial) accumulation of both subglacial and supraglacial debris. Subglacial aggradation has probably raised the bed of the glacier, promoting debris cover growth and reducing ablation even as less favourable balance regimes developed. Comparison with other glaciers shows that the expansionary tendency is widespread but may be manifest in a variety of sediment-landform associations.
ABSTRACT: 15.1 INTRODUCTION The concept of the glaciated valley landsystem was introduced by Boulton and Eyles (1979) and Eyles (1983b), to describe the characteristic sediments and landforms associated with valley glaciers in upland and mountain environments. By focusing on the scale of the whole depositional basin, the glaciated valley landsystem has a broader compass than most of the other landsystems explored in this book, which are specific to particular depositional environments. Indeed, glaciated valley landsystems may incorporate ice-marginal, supraglacial, subglacial, proglacial, periglacial and paraglacial landsystems, recording the juxtaposition and migration of very different depositional environments. Additionally, because glaciated valleys occur in every latitudinal environment from equatorial to polar regions, the dimensions of climate and glacial thermal regime add even more variability. Thus the 'glaciated valley landsystem' should be regarded as a family of landsystems, which exhibits considerably more variety than suggested by the original Boulton and Eyles model (Fig. 15.1). Despite this variability, landsystems in glaciated valleys tend to have certain recurrent features, as a result of two main factors: 1. the strong influence of topography on glacier morphology, sediment transport paths and depositional basins 2. the importance of debris from supraglacial sources in the glacial sediment budget. In this chapter, we emphasise the contrasts between glaciers with limited supraglacial debris ('clean glaciers') and glaciers with substantial debris covers in their ablation zones ('debris-covered glaciers'), although it should be recognized that intermediate forms occur between these end members. Before examining the landsystems of glaciated valleys, we begin by considering debris sources and transport pathways through valley glaciers, and the ways in which debris cover influences glacier dynamics. 15-Evans-Glacial-15-ppp 5/27/03 2:38 PM Page 372
Full-text · Article · Jan 2004
Field and geophysical studies have allowed us to identify processes leading to ice-cored moraine degradation for three natural dams investigated in Peru and Nepal. As potentially hazardous lakes form on the snouts of debris-covered glaciers they may separate a stagnant ice body from the upper reaches of the glacier to form an ice-cored end-moraine complex. The ice-cored moraines appear to degrade through ablation beneath the debris cover, by localized thermokarst development, and by associated mass movement. Relict glacier structures serve as a focal point for the onset of accelerated thermokarst degradation. Once exposed, the ice core then undergoes accelerated wastage through the combined affects of solar radiation and mechanical failure due to the rheological response of the ice to deepening kettle forms. Continuing degradation reduces the lake freeboard, weakens the moraine dam, and can lead to its catastrophic failure.