Number Of Glacial Lakes Research Articles

Characteristics of the hydrological regime of the periglacial moraine lakes in the Altai

In the last decade glaciers of Inner Asia have been shrinking with acceleration, and the number of glacial lakes has been growing significantly, including those with a high probability of outburst and high-water discharge. The hydrological regime of lakes in the Altai is understudied in comparison with lakes in other high mountain countries. The article is based on our extensive field material on hydrological and morphometric characteristics of moraine lakes collected in the Russian and Mongolian parts of the Altai Mountains and combined with the Earth remote sensing data. We have proposed detailed indicators (criteria) of transgressive, regressive and post-regressive stages of lake development. It allows allow to determine at a qualitative level at what stage a lake is at and to assess its further development. The characteristics of hydrological regime of Altai lakes at different stages of development are described for the first time. Based on the criteria proposed, the classification of glacial and moraine lakes in the Altai high mountains was carried out. It shows that at present most of the lakes are in the transgressive stage. Over the last 22 years, the number of lakes has increased significantly: on the territory of the North Chuya Ridge – from 28 to 60, on the South Chuya Ridge – from 39 to 73, on the Katun Ridge – from 57 to 89, on the territory of the Tavan-Bogdo-Ola massif – from 11 to 19, and on the territory of the Mongun-Taiga massif – from 8 to 11 lakes.

Evidence of climate change - Investigating glacial terminus and lake inventory using earth observation data for mountainous Bhutan

The mapping and monitoring of different types of Glacial lakes through the Geospatial techniques is vital to show the impact of climate changes on the Glacier and alleviate hazards that result from the bursting of Glacial Lakes and cause catastrophic consequences to human lives. The main goal of the present work was to map and analyze different types of glacial lakes in Bhutan during the years 1990, 2000, and 2017. Several sets of satellite images, Landsat-TM for 1990, Landsat ETM + for 2000, and Landsat 8-OLI satellite image for 2017, were used to estimate the changes in the glacial lakes and the inventory study. Several glacial lakes, i.e., moraine-dammed lake, supra glacial lake, lateral moraine lake, erosional lake, medial moraine lake, and end moraine lake, were mapped within these periods. It was found that there was a rapid increase in glacial lakes from 1990 to 2017. The number of glacial lakes in 1990 was increased from 213 to 436 in 2017. It was also observed that the spatial dimensions of some of the glacial lakes increased. The study revealed five end moraine lakes, 40 lateral moraine lakes, 50 supra glacial lakes, 239 erosional lakes, and 15 other moraines dammed lakes in 2017.

Assessment of Continuous Growth of Glacial Lakes in the Teesta River Basin Using Semi-Automated Geospatial Approach

Global warming is one of the primary causes contributing to melting glaciers and shrinking of glaciers moth. Because of the glacier retreat, more lakes increase the risk of flooding in people’s homes and lives. Several studies on the surging glaciers have been conducted by researchers using various techniques, as well as with the aid of multiple models like the Normalized Differential Water Index (NDWI). The Number of glacial lakes is increasing in the Himalayan region due to climate change (rise of the temperature). Some glacial lakes are potentially dangerous so monitoring is very necessary. It is necessary to evaluate such vulnerable lakes. Therefore, current work is carried out to identify such glacial lakes present in the Teesta River Basin (Eastern Himalaya). Spatiotemporal Landsat data for the last four decades at intervals of ten years from 1990 to 2020 has been considered which was cloud-free and spatial resolution of 30 meters. The dataset mentioned above was used for lake identification and delineation. The findings indicate the presence of lakes with respective areas of 275 (18.90 km2), 337 (24.92 km2), 295 (22.96 km2), and 419 (31.44 km2). It has also been observed that the growth rate is increasing with approximate water spread from 1990 to 2000 (+129%), 2000 to 2010 (+106%), and 2010 to 2020 (+136%). The present study aimed to identify such glacial lakes based on their water spreading area, which is an essential step followed in the study of GLOF (Glacial Lake Outburst Flood) as it will be helpful in the identification of hazardous lakes. In that study, we found that eleven glacial lakes are in the potentially dangerous category situated in the upper Teesta Basin due to the presence of glaciers, which gives a clear reason for the time-to-time assessment of such lakes. By the conducted study it has been observed that the number of glacial lakes has increased, due to which water spread has also increased in the area. It can also be demonstrated that GIS (Geographical Information System), along with remote sensing, is one of the best tools for assessing and monitoring such change detection and differentiation of hazardous glacial lakes in the cryosphere, along with the supporting data.

Tracking rapid and slow ice-dammed lake changes through optical satellites and local knowledge: a case study of Tystigbreen in Norway

Abstract The number of glacial lakes has grown globally concurrently with the retreat of glaciers in the last few decades, increasing the risk of potentially hazardous glacial lake outburst floods (GLOFs) and posing a threat to downstream communities. Norway has several known ice-dammed lakes that produce repeated GLOFs but as we show here, the existing GLOF database is incomplete and needs to be improved through continuous monitoring of glaciers and glacial lakes. This study examines the case of an ice cap in central Norway hosting at least four drainage-prone lakes. We reconstruct the sequence of lake drainage events through a combination of remote sensing, ground-truthing and citizen science while scrutinising the applicability of the PlanetScope imagery vs Sentinel-2 and Landsat-8 OLI products. As opposed to the Landsat imagery that often fails to resolve even the largest glacial lakes of Tystigbreen, both PlanetScope and Sentinel-2 are helpful in identifying previously unrecognised glacial lakes and undocumented drainage events. Our analysis suggests that a fusion of the two satellite products may be beneficial for automated tracking of glacial lake changes. We also demonstrate that local knowledge and systematic involvement of citizens in data collection have a potential to enrich GLOF databases.

The evolution of glacial lake and glaciers and their potential impact on glacial debris flow activity in the Palong Zangbu catchment in Southeastern Tibet

Due to warm and humid air currents of the Indian Ocean and the southwest monsoon, the Palong Zangbo catchment in southeastern Tibet has developed oceanic glaciers in the valley, and the activity of glacial debris flows has been gradually intensified under neotectonic activity, frequent earthquakes, climate change, and extreme rainfall. In this paper, the topographic and morphological data of the debris flow basin, the dynamic evolution characteristics of glaciers and glacial lakes were analyzed by using multisource long-term series of remote sensing images. Simultaneously, the distribution of moraines and landslide sources were extracted based on satellite image. In addition, climate change in the study area was analysed using temperature and rainfall data from the last 40 years, revealing that the average temperature in the study area from May to October presented a fluctuating tendency as a whole, especially after 2013, when the temperature gradually increased. As these temperature changes led to continuous melting of the glaciers in the study area, the glacier area decreased from 8,300 km2 in 1988–4,584 km2 in 2019, which decreased nearly 45%. However, the number and area of glacial lakes in the study area gradually increased under a power-law trend, which further led to a significant increase on the possibility of glacial lake rupture in the study area. Due to the joint effects of earthquakes, glacier melting and glacial lake collapse, the debris flows in the study area were well developed, and a total of 122 debris flows were found with varying channel lengths, areas and material sources. Importantly, the characteristics of the glaciers, glacial lakes and climate change in the study area have indicated that the glaciers have retreated, the number of glacial lakes has increased, and the risk of debris flow in this basin will increase in the future. Therefore, it is necessary to strengthen monitoring and early warnings on floods due to glacial lake collapses and debris flows in the study area to improve the risk management of debris flows and floods and the prevention and mitigation of disasters.

Assessing the state, parameter-interlinkages and dynamic shift of glaciers in the western Himalaya

The present study remotely investigates multiple parameters of 25 well-distributed glaciers in the western Himalaya (WH) for ~1990–2015 period to understand their state. Glacier changes for 1990–2000 (pre-2000) and 2000–2015 (post-2000) were analysed separately to assess the shift in glacier dynamics. Results reveal a clear glacier terminus retreat (13.4 ± 2.1 m/y), deglaciation (0.2 ± 0.1%/y), surface velocity slowdown (21%) and increase in number of glacial lakes (28 to 38) as well their area (5%/y) during 1990–2015. Notably, average terminus retreat and deglaciation rates were reduced post-2000 (retreat: 12.5 ± 3.2 m/y; deglaciation: 0.1 ± 0.1%/y) compared to pre-2000 (retreat: 15.3 ± 6.8 m/y; deglaciation: 0.2 ± 0.2%/y). Further, the average surface velocity was found to be increasing (0.9%/y) over 1990–2000. This can be linked with suggested less negative or slightly balanced condition of the WH glaciers over 1990s by previous studies. Present study also finds low downwasting during pre-2000 (−0.24 ± 0.14 m/y). Post-2000, studied glaciers downwasted (−0.50 ± 0.06 m/y) and slowed down (2%/y) significantly showing a decadal time lag in geometrical adjustment. Supraglacial debris, largely influenced by slope characteristics, increased with a uniform rate of 0.9%/y during pre- and post-2000 periods. Systematic analysis of interlinkages among various glacier parameters reveals a large interdependency. Further, presence of debris cover and pro- and supra-glacial lakes modify the glacier response to a great extent. Overall, the present study shows that (a) studied glaciers were in overall depleting phase over 1990–2015, (b) balanced conditions during 1990s prevailed over the studied glaciers, followed by accelerated mass wastage, (c) topography and local surface conditions introduce the intraregional heterogeneity in glacier response to climate.

Spatio-Temporal Distribution Characteristics of Glacial Lakes in the Altai Mountains with Climate Change from 2000 to 2020

The evolution of a glacial lake is a true reflection of glacial and climatic change. Currently, the study of glacial lakes in the Altai Mountains is mainly concerned with the application of high-resolution remote sensing images to monitor and evaluate the potential hazards of glacial lakes. At present, there is no rapid and large-scale method to monitor the dynamical variation in glacial lakes in the Altai Mountains, and there is little research on predicting its future tendency. Based on the supervised classification results obtained by Google Earth Engine (GEE), combined with an analysis of meteorological data, we analyzed the spatial and temporal variations in glacial lakes in the Altai Mountains between 2000 and 2020, and used the MCE-CA-Markov model to predict their changes in the future. According to the results, as of 2020, there are 3824 glacial lakes in the Altai Mountains, with an area of 682.38 km2. Over the entire period, the glacial lake quantity growth rates and area were 47.82% and 17.07%, respectively. The distribution of glacial lakes in this region showed a larger concentration in the north than in the south. Most glacial lakes had areas smaller than 0.1 km2, and there was minimal change observed in glacial lakes larger than 0.2 km2. Analyzing the regional elevation in 100 m intervals, the study found that glacial lakes were predominantly distributed at elevations from 2000 m to 3000 m. Interannual rainfall and temperature fluctuations in the Altai Mountains have slowed since 2014, and the trends for the area and number of glacial lakes have stabilized. The growth of glacial lakes in both number and surface area is expected to continue through 2025 and 2030, although the pace of change will slow. In the context of small increases in precipitation and large increases in temperature, in the future, glacial lakes with faster surface area growth rates will be located primarily in the southern Altai Mountains.

Evaluating the variability of glacial lakes in the Kyrgyz and Teskey ranges, Tien Shan

The northern Tien Shan Mountains are one of the most hazardous areas in Kyrgyzstan due to frequent glacial lake outburst floods (GLOFs). The current status of glacial lakes in this region has not been reported in recent years. Therefore, this study investigates the variations of glacial lakes in the Kyrgyz and Teskey ranges using Sentinel-2 and PlanetScope optical satellite images from 2017 to 2019. Results confirm that there are 800 glacial lakes, of which 351 were in the Kyrgyz and 449 were in the Teskey Range. We found seasonality in the character of glacial lakes, most of which have been found to be unstable during our observation period. 242 glacial lakes showed significant variations in area. We found 46 newly emerging glacial lakes, five of which have rapidly expanded in the year since they formed, while 18 were found to have vanished. Thirteen lakes were found to be short-lived or unstable. In this study, 14 lakes showed a significant expansion of area. Such large variations in the glacial lakes are closely linked to local geomorphological conditions, local climate and glacier melt. We also identified a significant shift in the number of glacial lakes at altitudes over 3,500 m asl. It is associated with the mountain permafrost zone and variations of the glacier terminus. The current study recommends detailed investigation of glacial lakes in each season with the use of remote sensing and field surveys.

Identification of Hazardous Glacial Lakes in the Yarlung Zangbo River Basin Based on Lakes Changes Determined Using Google Earth Engine

Glaciers have melted rapidly in the Yarlung Zangbo River Basin due to recent climate change, which has accelerated the expansion of glacial lakes. We performed a systematic survey of glacial lakes in the Yarlung Zangbo River Basin using the Google Earth Engine platform. This allowed us to map the distribution and monitor the evolution of glacial lakes over seven time periods from 1990 to 2020, using more than 140 Landsat Thematic Mapper and Operational Land Imager images at a 30-m resolution. The results show that there were 2088 glacial lakes in 2020, with a total area of 245.87 km2, mainly distributed at elevations of 3,800–5,800 m above sea level. From 1990 to 2020, the Yarlung Zangbo River Basin glacial lakes expanded by approximately 1.81 km2·a−1. A total of 153 glacial lakes in the Yarlung Zangbo River Basin were assessed. The assessment shows that 153 glacial lakes were divided into very high, high, medium, low, and very low level. The number of glacial lakes in each level is 23, 22, 32, 32, and 44, respectively. The very high and high level glacial lakes were mainly found in the Yi’ong Zangbo River Basin, Parlung Zangbo River Basin, the western of the Yarlung Zangbo River Basin and Nianchu River Basin. These glacial lakes deserve further attention and monitoring.

Current glacier status and ELA changes since the Late Pleistocene in the Hindu Kush Mountains of Afghanistan

• In the HKM, Afghanistan ELA shows less change from Late Pleistocene to the present. • Climate change impacts different sizes of glaciers differently. • Other than climate, slope and elevation can define the recession of glaciers. • Increase in volume and number of glacial lakes is on rise in the HKM, Afghanistan. The glacier cover of the Hindu Kush Mountains of Afghanistan provides a natural laboratory to assess the impact of climate change on the cryosphere. However, to date, not much is known about how the cryosphere in these mountainous regions is responding to climate change. Therefore, using an integrated approach including geospatial technology, climate data, a mass balance study, as well as topographic analysis, we present the first systematic study of glacier fluctuations in the Kokcha sub-basin of the Afghanistan Range for the last 25 years (1990 to 2015). The glacier cover and the number of glaciers in the basin have reduced from 576 km 2 and 1007 in 1990 to 492 km 2 and 998 in 2015 respectively, losing ~84 km 2 (~15%) of the total glaciated area. Besides the mass loss of the glaciers ranges from −0.65 m water equivalent per year and −0.02 m water equivalent per year with an average of −0.20 m water equivalent per year as estimated by the geodetic method. The equilibrium line altitude changes since the Late Pleistocene to the present vary from 810 ± 145 m to 1060 ± 145 m with an average of 722 ± 145 m. The increasing trend of temperature and shifting precipitation seasons have resulted in enhanced glacier recession and the formation of numerous glacial lakes in the basin. In addition to the climatic variables and glacier size, the topographic parameters slope, and elevation are observed to be the dominant factors influencing glacier recession and mass changes in the basin.

Contemporary glacial lakes in the Peruvian Andes

Glacier recession in response to climate warming has resulted in an increase in the size and number of glacial lakes. Glacial lakes are an important focus for research as they impact water resources, glacier mass balance, and some produce catastrophic glacial lake outburst floods (GLOFs). Glaciers in Peru have retreated and thinned in recent decades, prompting the need for monitoring of ice- and water-bodies across the cordilleras. These monitoring efforts have been greatly facilitated by the availability of satellite imagery. However, knowledge gaps remain, particularly in relation to the formation, temporal evolution, and catastrophic drainage of glacial lakes. In this paper we address this gap by producing the most current and detailed glacial lake inventory in Peru and provide a set of reproducible methods that can be applied consistently for different time periods, and for other mountainous regions. The new lake inventory presented includes a total of 4557 glacial lakes covering a total area of 328.85 km2. In addition to detailing lake distribution and extent, the inventory includes other metrics, such as dam type and volume, which are important for GLOF hazard assessments. Analysis of these metrics showed that the majority of glacial lakes are detached from current glaciers (97%) and are classified as either embedded (i.e. bedrock dammed; ~64% of all lakes) or (moraine) dammed (~28% of all lakes) lakes. We also found that lake size varies with dam type; with dammed lakes tending to have larger areas than embedded lakes. The inventory presented provides an unparalleled view of the current state of glacial lakes in Peru and represents an important first step towards (1) improved understanding of glacial lakes and their topographic and morphological characteristics and (2) assessing risk associated with GLOFs.

Cryosphere hazards in Ladakh: the 2014 Gya glacial lake outburst flood and its implications for risk assessment

This article attempts to reconstruct the causes and consequences of the 2014 glacial lake outburst flood (GLOF) event in Gya, Ladakh. We analyse the evolution of the Gya glacial lake using a high temporal and high spatial resolution remote sensing approach. In order to frame the case study in a larger picture, we produce a comprehensive inventory of glacial lakes for the entire Trans-Himalayan region of Ladakh. Changes in the extent and number of glacial lakes have been detected for the years 1969, 1993, 2000/02 and 2018 in order to assess the potential risk of future GLOFs in the region. The remote sensing approach was supported by field surveys between 2014 and 2019. The case study of the Gya GLOF illustrates the problem of potentially hazardous lakes being overlooked in inventories. The broader analysis of the Ladakh region and in-depth analysis of one GLOF lead us to propose an integrated approach for detecting undocumented GLOFs. This article demonstrates the necessity for using multiple methods to ensure robustness of risk assessment. The improved understanding can lead to a more accurate evaluation of exposure to cryosphere hazards and identification of alternative mechanisms and spatial patterns of GLOFs in the Himalaya.

Response of glacial lakes to glacier and climate changes in the western Nyainqentanglha range

The western Nyainqentanglha (WNT) range, located in the transition zone between large-scale atmospheric circulations, has an abundance of glacial lakes and glaciers. In the warmer climate of recent decades, the glacial lakes and glaciers in the WNT range could have changed substantially. Here, glacial lake and glacier changes for the entire WNT range between 1976 and 2018 are examined. The results show that, between 1976 and 2018, the number of glacial lakes (>0.0036 km2) increased by 56% from 192 to 299 and their total area increased by 35% from 6.75 ± 0.13 km2 to 9.12 ± 0.13 km2. The glacial lakes expanded faster in 2001–2018 (0.08 km2/yr) than in 1976–2001 (0.04 km2/yr), and faster on the southern side of the mountain range than on the northern side. Correspondingly, the rates of glacier area shrinkage and surface elevation thinning between 2000 and 2018 were −4.15 km2/yr and −0.29 ± 0.06 m/yr, respectively, greater than the respective rates of −3.91 km2/yr and −0.24 ± 0.11 m/yr in 1976–2000. The glacier retreat and elevation thinning to the south of the main divide are greater than to the north, with the exception of the thinning rate in 2000–2014 which is possibly due to precipitation differences. With the rapid retreat of glaciers, many glacial lakes are changing from proglacial lakes to unconnected glacial lakes. The increases in the number and area of glacial lakes are moving toward higher elevations, accompanying the retreat of glaciers and the increase in the mean elevation of glaciers. The observed increased precipitation also supports the increases of glacial lakes. The accelerating glacier loss and lake expansion in the WNT range imply a strong impact of climate change on the cryosphere over the past few decades.

MONITORING GLACIERS AND GLACIAL LAKES OF CHENAB BASIN USING GEOSPATIAL TOOLS

Glacial lakes are usual phenomenon in the glacierized basin at high elevation. Glacial Lakes Outburst Floods are becoming a cause of concern for the local inhabitants of these retreating glaciers. Therefore, a detail study of the dynamics of river of moving ice and water is of much importance. The present study aims to investigate the dynamics of the glacier using geospatial tools and remote sensing and to make an inventory and monitoring of the glaciers, glacial lakes and water bodies in Chenab river basins of Himalayan region using Resourcesat 2 LISS 4 images and the digital elevation model for the period of 2014 to 2017. Based on the current inventory, 126 glacial lakes and water bodies and 192 glaciers with water spread area more than 30 ha and 700 ha, respectively are monitored. Apart from this, only 2 glacial lakes and water bodies with water spread area in the range 14 to 18 ha were monitored. And 16 glaciers were monitored in the area of 500 ha and above. Most of the glacier lakes and glaciers move in the south east direction with 26 and 33 in numbers respectively. The substantial increase in the number of glacial lakes in the Himalayan region is the matter of concern and therefore need a proper monitoring. Keywords: Glaciers; Glacier lakes; Chenab River; GIS; India.

Hazard assessment of glacial lake outburst floods in Southeast Tibet based on RS and GIS technologies

ABSTRACTGlacial lakes are widely distributed across glaciated mountainous regions such as Southeast Tibet (ST). As a result of climate change, glacial lakes have expanded continually in ST over recent five decades, and ST is seriously suffering from glacial lake outburst floods (GLOFs). Hence, glacial lake investigations and hazard assessments of GLOFs are very necessary to perform and are of great practical significance for this area. The region running from Ranwu to Tongmai (RTR) in ST was selected as a study area. To assess hazard degrees of GLOFs, nine factors (F1–F9) were selected from glacial characteristics: the scale of glacial lakes, meteorological conditions, moraine dam parameters and downstream gullies. Average monthly (May to September) land surface temperatures (LSTs), temperature change rates, and average annual precipitation levels were first calculated using Moderate Resolution Imaging Spectroradiometer (MODIS) LST product and Tropical Rainfall Measuring Mission (TRMM) precipitation data. Then, glacial lake areas, downstream gully slopes, distances to glacial lakes, upper glacier areas, average gradients of upper glaciers, and terminal moraine dam widths were obtained based on Thematic Mapper (TM) and Operational Land Imager (OLI) images and Digital Elevation Model (DEM) data. Finally, the fuzzy comprehensive assessment (FCA) method was used to assess hazard degrees of GLOFs in the study area. According to the results, 135 glacial lakes existed during the study periods, five new glacial lakes formed due to lake collapse and snow and ice melt, and one disappeared due to GLOFs. The number of glacial lakes in the area increased from 130 in 1986 to 134 in 2015, and the total area of glacial lakes increased from 832.77 ha in 1986 to 850.51 ha in 2015 due to lake expansion and GLOFs. Of the 134 glacial lakes present in 2015, 10 are identified as high hazardous lakes, eight are identified as medium hazardous lakes, two are considered low hazardous lakes, and 114 are considered extremely low hazardous lakes. The results illustrate hazard levels of GLOFs in ST, which can help guide future hazard prevention in the area.

Classification of glacial lakes using integrated approach of DFPS technique and gradient analysis using Sentinel 2A data

It is important to identify and locate glacial lakes for assessing any potential hazard. This study presents a combination of semi-automatic method Double-Window Flexible Pace Search (DFPS) and edge detection technique to identify glacial lakes using Sentinel 2A satellite data. Initially, Normalized Difference Water Index (NDWI) has been used to identify water and non-water areas, while DFPS and Edge detection technique has been used to identify an optimum threshold value to distinguish between water and shadow areas. The optimal threshold from DFPS process is 0.21, while threshold value of gradient magnitude using edge detection process is 0.318. The number of glacial lakes identified using the above algorithm is in close agreement with previously published results on glacial lakes in Gangotri glacier using different techniques. Thus, a combination of DFPS and edge detection process has successfully segregated glacial lakes from other features present in Gangotri glacier.

Decadal glacial lake changes in the Koshi basin, central Himalaya, from 1977 to 2010, derived from Landsat satellite images

Changes in glacial lakes and the consequences of these changes, particularly on the development of water resources and management of glacial lake outburst flood (GLOF) risk, has become one of the challenges in the sustainable development of high mountain areas in the context of global warming. This paper presents the findings of a study on the distribution of, and area changes in, glacial lakes in the Koshi basin in the central Himalayas. Data on the number of glacial lakes and their area was generated for the years 1977, 1990, 2000, and 2010 using Landsat satellite images. According to the glacial lake inventory in 2010, there were a total of 2168 glacial lakes with a total area of 127.61 km2 and average size of 0.06 km2 in the Koshi basin. Of these, 47% were moraine dammed lakes, 34.8% bedrock dammed lakes and 17.7% ice dammed lakes. The number of glacial lakes increased consistently over the study period from 1160 in 1977 to 2168 in 2010, an overall growth rate of 86.9%. The area of glacial lakes also increased from 94.44 km2 in 1977 to 127.61 km2 in 2010, a growth rate of 35.1%. A large number of glacial lakes in the inventory are small in size (≤ 0.1 km2). End moraine dammed lakes with area greater than 0.1 km2 were selected to analyze the change characteristics of glacial lakes in the basin. The results show that, in 2010, there were 129 lakes greater than 0.1 km2 in area; these lakes had a total area of 42.92 km2 in 1997, increasing to 63.28 km2 in 2010. The distribution of lakes on the north side of the Himalayas (in China) was three times higher than on the south side of the Himalayas (in Nepal). Comparing the mean growth rate in area for the 33 year study period (1977-2010), the growth rate on the north side was found to be a little slower than that on the south side. A total of 42 glacial lakes with an area greater than 0.2 km2 are rapidly growing between 1977 and 2010 in the Koshi basin, which need to be paid more attention to monitoring in the future and to identify how critical they are in terms of GLOF.

Decadal evolution of glaciers and glacial lakes in the Apolobamba–Carabaya region, tropical Andes (Bolivia–Peru)

ABSTRACTThis paper presents the first decadal quantification of glacier area in the cordilleras Carabaya and Apolobamba in Peru and Bolivia (14°00′–14°39′S; 69°14′–70°19′W). We calculated the changes in glacier area between 1975 and 2015 and the number of glacial lakes between 1985 and 2015 using Landsat images. Glacier shrinkage in our study region was most likely to have caused the expansion of numerous glacial lakes in recent decades. In contrast to observed glacier fluctuations in the western cordilleras of the tropical Andes, continuous glacier shrinkage was observed in the eastern cordilleras of Peru and Bolivia. The estimated glacier mean area loss between 1975 and 2015 in the Cordillera Apolobamba and the Cordillera Carabaya was about 51% and 79%, respectively. Glaciers situated below 5000 m a.s.l. nearly disappeared (93% and 95.5% in the cordilleras Apolobamba and Carabaya, respectively) during this period, but glaciers above 5500 m a.s.l. were relatively stable (13.5% and 31% in Apolobamba and Carabaya, respectively). Further on, glacier area loss by aspect revealed that glaciers oriented towards the Amazon Basin were retreating faster (74.5% and 86%, respectively) than those oriented towards the Pacific coast (40% and 68%, respectively). We observed the formation of 206 new glacial lakes between 1985 and 2015 in these two mountain ranges with an increase in the total area of 3.8 km2, which is a significant growth in just 30 yr.

Using Remote Sensing Data to Quantify Changes in Glacial Lakes in the Chinese Himalaya

To assess changes in glacial lakes in the Chinese Himalaya, 2 inventory phases were conducted on the basis of 278 aerial survey topography maps from the 1970s and 38 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images from the 2000s. In the past 30 years, the number of glacial lakes has decreased, from 1750 to 1680 (a decrease of 4.0%), whereas the average area of glacial lakes expanded from 166.48 to 215.28 km2 (an increase of 29.7%). Between 3400 and 6000 m, glacial lake areas expanded at rates of 2–84% in almost all 100-m elevation bands, and the dominant expansion rates at different elevations were inversely correlated with glacier area retreating rates to some degree. Glacial lake expansion was a dominant contributor to the increase in glacial lake area, accounting for about 67% of the net changes in lake area, whereas newly formed lakes accounted for the remaining 33%.

Changes in glacial lakes and glaciers of post-1986 in the Poiqu River basin, Nyalam, Xizang (Tibet)

Glacial lakes and glaciers are sensitive indicators of recent climate change. In the Poiqu River basin of southern Tibet, 60–100 km NW of Mt. Everest, Landsat imagery defines post-1986 changes in the size and distribution of both glacial lakes and glaciers. Total area of glaciers in the 229-km 2 drainage area has decreased by 20%. The number of glacial lakes with areas in excess of 0.020 km 2 has increased by 11%, and the total area of glacial lakes has increased by 47%. The areas of typical large glacial lakes of the area (Galongco, Gangxico, and Cirenmaco) have increased by 104, 118, and 156%, respectively, and these increases are confirmed by field investigations. Comparing the 1986 data, the area of glaciers in the basin headwaters has decreased by 46.18 km 2 to a present total area of 183.12 km 2, an annual rate of change of 3.30 km 2/year. Trends indicate that the total area of glaciers will continue to decrease and that both the numbers and areas of glacial lakes will continue to increase. Accompanying these trends will be an increased risk of debris flows, formed by entrainment of sediment in glacial-outburst floods and in surges from both failure and avalanche- and landslide-induced overtopping of moraine dams. Based on both the local and world-wide history of catastrophes from flows of these origins, disaster mitigation must be planned and appropriate engineering countermeasures put in place as soon as possible.