Glacial Lake Changes Research Articles

Heterogeneous changes in global glacial lakes under coupled climate warming and glacier thinning

Global glacial lakes have expanded markedly in recent decades, accompanied by many catastrophic glacial lake outburst floods. However, our understanding of glacial lake evolution and connections with global warming and glacier thinning remains insufficient due to fragmented studies and a lack of standardized mapping. Here we evaluated the glacial lake changes and their drivers, taking care to accurately map glacial lakes while excluding non-glacier fed lakes in the same geographic area. In 2020, a total of 71,508 glacial lakes were identified worldwide, covering an area of 21,770.9±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document}544.2 km2. The total volume of 1280.6±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document}354.1 km3 is equivalent to a sea-level rise of 3.45 mm. Since the 1990s, glacial lake numbers, areas, and volumes increased by 54%, 11%, and 9%, respectively. The spatial evolution patterns align well with resolved large-scale, decadal glacier mass changes. Glacier-fed lakes extensively expanded due to glacier retreat and melting, while ice-dammed lakes were primarily affected by thinning ice dams, resulting in heterogeneous changes and underestimated outburst potential. Under the sustained glacier degradation scenario, the results of this study have implications for further evaluation of glacial lake water resources and outburst risks on a global scale.

Late Glacial and Holocene vegetation and lake changes in SW Yakutia, Siberia, inferred from sedaDNA, pollen, and XRF data

Only a few palaeo-records extend beyond the Holocene in Yakutia, eastern Siberia, since most of the lakes in the region are of Holocene thermokarst origin. Thus, we have a poor understanding of the long-term interactions between terrestrial and aquatic ecosystems and their response to climate change. The Lake Khamra region in southwestern Yakutia is of particular interest because it is in the transition zones from discontinuous to sporadic permafrost and from summergreen to evergreen boreal forests. Our multiproxy study of Lake Khamra sediments reaching back to the Last Glacial Maximum 21 cal ka BP, includes analyses of organic carbon, nitrogen, XRF-derived elements, sedimentary ancient DNA amplicon sequencing of aquatic and terrestrial plants and diatoms, as well as classical counting of pollen and non-pollen palynomorphs (NPP). The palaeogenetic approach revealed 45 diatom, 191 terrestrial plant, and 65 aquatic macrophyte taxa. Pollen analyses identified 34 pollen taxa and 28 NPP taxa. The inferred terrestrial ecosystem of the Last Glacial comprises tundra vegetation dominated by forbs and grasses, likely inhabited by megaherbivores. By 18.4 cal ka BP a lake had developed with a high abundance of macrophytes and dominant fragilarioid diatoms, while shrubs expanded around the lake. In the Bølling-Allerød at 14.7 cal ka BP both the terrestrial and aquatic systems reflect climate amelioration, alongside lake water-level rise and woodland establishment, which was curbed by the Younger Dryas cooling. In the Early Holocene warmer and wetter climate led to taiga development and lake water-level rise, reflected by diatom composition turnover from only epiphytic to planktonic diatoms. In the Mid-Holocene the lake water level decreased at ca. 8.2 cal ka BP and increased again at ca. 6.5 cal ka BP. At the same time mixed evergreen-summergreen forest expanded. In the Late Holocene, at ca. 4 cal ka BP, vegetation cover similar to modern conditions established. This study reveals the long-term shifts in aquatic and terrestrial ecosystems and a comprehensive understanding of lake development and catchment history of the Lake Khamra region.

Potential threats of glacial lake changes to the Sichuan-Tibet Railway

Abstract The Sichuan-Tibet Railway, China's second inland railway to Tibet, is currently being constructed and will run between Chengdu and Lhasa. It will cross the southeastern Tibetan Plateau and be surrounded by glacial lakes, some of which may pose a threat of glacial lake outburst flood (GLOF) events. Both the specific location and the outburst susceptibility of these glacial lakes are largely unknown. In this study, we mapped the glacial lakes using declassified Corona KH-4 and Hexagon KH-9 from the 1960s and Sentinel-2 imagery from 2020 and assessed their spatio-temporal changes. GLOF-susceptibility criteria were established based on historical GLOF events. The results show that the total area (number) of glacial lakes has increased by 22% (20%) from 126.1 ± 2.4 km2 (1662 lakes) in the 1960s to 153.6 ± 11.1 km2 (1994 lakes) in 2020. Of these lakes, this study identified 38 very high and 85 high GLOF-susceptibility lakes; mainly distributed along the Bomi-Nyingchi railway section in the Parlung Zangbo River basin. Four of the very high GLOF-susceptibility glacial lakes may pose a threat to the railway and will require monitoring. The insights from this study can be used to mitigate the risk of GLOFs during the construction and maintenance of the Sichuan-Tibet Railway.

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.

Glacial Lake Changes and Risk Assessment in Rongxer Watershed of China–Nepal Economic Corridor

Glacial lake outburst floods (GLOFs) are one of the most severe disasters in alpine regions, releasing a large amount of water and sediment that can cause fatalities and economic loss as well as substantial damage to downstream infrastructures. The risk of GLOFs in the Himalayas is exacerbated by glacier retreat caused by global warming. Critical economic corridors, such as the Rongxer Watershed, are threatened by GLOFs, but the lack of risk assessment specific to the watershed hinders hazard prevention. In this study, we propose a novel model to evaluate the risk of GLOF using a combination of remote sensing observations, GIS, and hydrological models and apply this model to the GLOF risk assessment in the Rongxer Watershed. The results show that (1) the area of glacial lakes in the Rongxer Watershed increased by 31.19% from 11.35 km2 in 1990 to 14.89 km2 in 2020, and (2) 18 lakes were identified as potentially dangerous glacial lakes (PDGLs) that need to be assessed for the GLOF risk, and two of them were categorized as very high risk (Niangzongmajue and Tsho Rolpa). The proposed model was robust in a GLOF risk evaluation by historical GLOFs in the Himalayas. The glacial lake data and GLOF risk assessment model of this study have the potential to be widely used in research on the relationships between glacial lakes and climate change, as well as in disaster mitigation of GLOFs.

Relationship between the variations in glacier features classified on a large scale with climate variables: a case study of Gangotri Glacier.

Changes in glacier area, glacial lakes, debris cover, and geomorphological features such as debris fans have a significant impact on glacial dynamics. Therefore, precise and timely observation and tracking of glacier surface changes is a necessity. The availability of high spatial resolution remote sensing images has made it viable to analyse the glacier surface changes at a local level. However, with an increase in spatial resolution, the spectral variability increases, giving rise to additional challenges (such as false changes and misregistration) in the change detection process. These challenges can preferably be dealt with using an object-based change detection (OBCD) approach rather than the conventional pixel-based change detection approach. Therefore, this study has proposed an OBCD methodology using high-spatial-resolution remote sensing images to detect changes in glacier features. Variability in glacier features has been further analysed by associating it with important climate variables, that is, air temperature and precipitation. As a case study, the changes in Gangotri Glacier (Uttarakhand Himalayas in India) features have been studied using high-spatial-resolution WorldView-2 and Linear Imaging Self-Scanning System (LISS)-4 images for a 3-year period 2011-2014. The spectral correspondences between glacier surface and non-glacier surface have been handled by considering brightness temperature and slope as ancillary data to improvise their distinction. A change detection accuracy of ~ 84% has been obtained using the OBCD approach. Results further show that the variations in glacier features are in congruence with the climatic observations.

Enhanced glacial lake activity threatens numerous communities and infrastructure in the Third Pole

Glacial lake outburst floods (GLOFs) are among the most severe cryospheric hazards in the Third Pole, encompassing the Tibetan Plateau and surrounding Himalayas, Hindu Kush, and Tianshan Mountains. Recent studies on glacial lake changes and GLOF characteristics and risks in this region have shown scattered and insufficiently detailed features. Here, we conduct an appraisal of the GLOF risks by combining high-resolution satellite images, case-by-case high-precision GLOF modeling, and detailed downstream exposure data. The glacial lake changes from 2018 to 2022 in the region were primarily driven by the accelerated expansion of proglacial lakes. The GLOF frequency has exhibited a significant increasing trend since 1980, with intensified activity in Southeastern Tibet and the China-Nepal border area over the past decade. Approximately 6,353 km2 of land could be at risk from potential GLOFs, posing threats to 55,808 buildings, 105 hydropower projects, 194 km2 of farmland, 5,005 km of roads, and 4,038 bridges. This study directly responds to the need for local disaster prevention and mitigation strategies, highlighting the urgent requirement of reducing GLOF threats in the Third Pole and the importance of regional cooperation.

The response of glaciers and glacial lakes to climate change in the Southeastern Tibetan Plateau over the past three decades

AbstractWith global warming, changes in glaciers and glacial lakes on the Tibetan Plateau call for a serious inspection. The Southeastern Tibetan Plateau (SETP) is a typical monsoonal marine glacier area that is extremely vulnerable to climate change. It is affected by both humid and warm Indian Ocean currents. Outlines of glaciers and glacial lakes in SETP have been extracted from Landsat satellite images with an automatic extraction method based on image compositing with Google Earth Engine and Random Forest algorithm. Alongside the outlines, meteorological data have been collected from 1990 to 2021. The results show that since 1990 the glacier area of SETP has retreated by about 2165.33 km2 (~25.28%), the glacial lake area has increased by about 36.41 km2 (~21.45%), and their number has increased by 477 (~27.32%). The reliability and scientific validity of this study is proven by comparison with existing glacier inventories. By analyzing the meteorological data, the inverse correlation between the glacier area and temperature has been found. Despite decreases in cumulative precipitation, the glacial lake level rise and consequent area expansion have been observed. A fitting equation for the response pattern of glacier changes to temperature and precipitation change is presented and will provide a basis for future studies.

Exploring potential glacial lakes using geo-spatial techniques in Eastern Hindu Kush Region, Pakistan

The study aimed to investigate the potential glacial lakes in response to climate change and the associated risk of glacial lake outburst floods (GLOFs). Remote sensing data and GIS techniques were utilized to analyze glacial lakes, employing empirical models to estimate their area, volume, and depth. The Normalized Difference Water Index (NDWI) was applied to detect changes in glacial lakes using Sentinel imagery. The findings revealed a notable increase in both the number and surface area of glacial lakes over the past two decades. Specifically, the number of glacial lakes rose from 101 in 2000 to 162 in 2020, while their combined surface area expanded from 9.72 km2 to 12.36 km2 during the same period. Among these lakes, 31 were identified as Potentially Dangerous Glacial Lakes (PDGLs), with 6 located in Chitral, 16 in Swat, and 9 in Upper Dir. Two lakes were classified as high potential glacial lakes, with depths estimated at 41.86 ​m and 30.43 ​m. Continued monitoring of these glacial lakes and their susceptibility to GLOFs is crucial in the face of ongoing climate change. Long-term planning and adaptation strategies are necessary to safeguard the well-being and safety of communities residing in these vulnerable regions. By understanding the evolving characteristics of these lakes, researchers and policymakers can better prepare for and mitigate the impacts of GLOFs on downstream communities and infrastructure.

Assessment of lake area in response to climate change at varying elevations: A case study of Mt. Tianshan, Central Asia

Changes in lake area (water surface area) are often considered accurate and sensitive representations of climate change. However, the role that elevation plays in this dynamic is somewhat unclear; studies remain inconclusive as to whether lake responses are consistent across elevation gradients. Here, we used Landsat and keyhole satellite images to quantify lake area changes from the 1960s to 2020 at different elevations in Central Asia's Tianshan Mountains and relate them to both climatic and anthropogenic factors. The results revealed that all low-elevation lakes showed a decreasing trend, and the total area of all monitored low-elevation lakes was reduced by 18.50 %. The total area of the mid-elevation lakes decreased by 0.16 %, while the total area of the high-elevation glacial lakes increased by 4.35 %. Lakes are recharged by a variety of influxes including glacial meltwater and precipitation. Notably, human activities (urban and agricultural water consumption) were the dominant factors in the shrinkage of low-elevation lakes. Climatic factors were the main driving factors of mid-elevation lake changes, and these lakes appeared to be more sensitive to temperature changes than lakes at other elevations. In addition, significant warming dominated area changes in high-elevation proglacial and unconnected glacial lakes. Overall, those results emphasized that when using lakes to reconstruct paleoclimates or predict lake evolution, it is necessary to consider how elevation gradients and recharge types may affect lake sensitivity to variations in climatic and anthropogenic activity.

Evolution Patterns and Outburst Risk Evaluation of Luregou Glacial Lake in Northern Tibet

Affected by global warming, glacial lake outburst events occur frequently on the Qinghai-Tibet Plateau. Glacial lake outburst is characterized by large scale, sudden occurrence, danger and difficulty in prevention and control. Based on the remote sensing interpretation and field investigation of 29 glacial lakes in Luregou basin in the upper reaches of Yigongzangbu basin, four periods in 1976, 1988, 2001 and 2013, the development characteristics, distribution patterns and types of changes in glacial lakes were deeply analyzed. Factors such as changes in glacial lake area, terminal moraine dam, ice avalanche and ice landslides, and glacial lake types were selected to initially construct a rapid rating method for glacial lake outburst risk. Using this method, 29 glacial lake outburst risks were evaluated in Luregou Basin, and the evaluation results showed that the risks were large, medium and small in 5, 6 and 18 places respectively. Furthermore, the outburst mechanism and disaster effect of Ranzeriacuo glacial lake on July 5, 2013 were analyzed in detail.

Glacial lake changes and the identification of potentially dangerous glacial lakes (PDGLs) under warming climate in the Dibang River Basin, Eastern Himalaya, India

Climate warming has caused accelerated glacier recession in the Eastern Himalayas. This phenomenon has consequently resulted in the development of new glacial lakes and expansion of the existing ones. The outbursts of these lakes has the potential to cause flashfloods with negative impacts for the downstream community. This study used Remote Sensing data products to develop a glacial lake database of Dibang River Basin for the year 2020. The multi-temporal Landsat series data was used to examine the surficial changes in glacial lakes larger than 0.1 km2. The key parameters derived from previous glacial lake studies were used to identify the Potentially Dangerous Glacial Lakes (PDGLs) and conduct their hazard assessment. Finally, the Indian Monsoon Data Assimilation and Analysis (IMDAA) data was used to analyze the Temperature and Precipitation trends from 1980 to 2020 to understand timpact of climate change on lake behaviour. Our findings reveal that the study region has 403 glacial lakes with a total area of 55.73 km2 in 2020. The area of selected glacial lakes has increased from 29.96 km2 in 1985 to 32.56 km2 in 2020 at a rate of 0.07 km2 per year. Twelve (12) lakes were identified as PDGLs in the study region. After applying the weighted index method, 4 lakes among them were categorized as high, 5 as medium and 3 as low hazard glacial lakes. The Mann Kendal test of Tmin, Tmax and Tmean revealed an increasing trend with a Z statics value of >0, whereas mean precipitation on the contrary showed a significant decreasing trend with a Z statics value of <0. The changes in climatic variables (i.e., temperature and precipitation) indicate that the warmer conditions prevail in the region, causing glacier shrinking and retreat, formation of new lakes and expansion of existing ones. Hence, we propose the continuous monitoring and assessment of high hazard glacial lakes for the prevention and mitigation of Glacier Lake Outburst Floods (GLOFs) in the study region.

Characterization of Long-Time Series Variation of Glacial Lakes in Southwestern Tibet: A Case Study in the Nyalam County

Glacial lakes are important freshwater resources in southern Tibet. However, glacial lake outburst floods have significantly jeopardized the safety of local residents. To better understand the changes in glacial lakes in response to climate change, it is necessary to conduct a long-term evaluation on the areal dynamics of glacial lakes, assisted with local observations. Here, we propose an innovative method of classification and stacking extraction to accurately delineate glacial lakes in southwestern Tibet from 1990 to 2020. Based on Landsat images and meteorological data, we used geographic detectors to detect correlation factors. Multiple regression models were used to analyze the driving factors of the changes in glacier lake area. We combined bathymetric data of the glacial lakes with the changes in climatic variables and utilized HEC-RAS to determine critical circumstances for glacial lake outbursts. The results show that the area of glacial lakes in Nyalam County increased from 27.95 km2 in 1990 to 52.85 km2 in 2020, and eight more glacial lakes were observed in the study area. The glacial lake area expanded by 89.09%, where we found significant growth from 2015 to 2020. The correlation analysis between the glacial lake area and climate change throughout the period shows that temperature and precipitation dominate the expansion of these lakes from 1990 to 2020. We also discover that the progressive increase in water volume of glacial lakes can be attributed to the constant rise in temperature and freeze–thaw of surrounding glaciers. Finally, the critical conditions for the glacial lake’s outburst were predicted by using HEC-RAS combined with the changes in the water volume and climatic factors. It is concluded that GangxiCo endures a maximum water flow of 4.3 × 108 m3, and the glacial lake is in a stable changing stage. This conclusion is consistent with the field investigation and can inform the prediction of glacial lake outbursts in southwestern Tibet in the future.

Glacier–glacial lake changes and modeling glacial lake outburst flood in Upper Ganga Basin, India

Glacier–glacial lake changes and modeling glacial lake outburst flood in Upper Ganga Basin, India

Changes in Glaciers and Glacial Lakes in the Bosula Mountain Range, Southeast Tibet, over the past Two Decades

Glaciers and glacial lakes in the Bosula Mountain Range need special attention, because their instability may cause disastrous consequences to the downstream settlements and the Sichuan-Tibet Road. The latter is a pivotal traffic line in the Southeast Tibetan Plateau. In order to investigate the state of glaciers and glacial lakes in the Bosula Mountain Range, we estimated the changes in glacier/glacial lake boundaries, glacier surface elevation, and glacier flow velocity between 2000 and 2021 based on multisource remote sensing data. Our results showed that, from the period 2000–2013 to the period 2013–2021, the average shrinking rate of glacier area increased from 0.99 km2/a to 1.74 km2/a, and the average expanding rate of glacial lake area increased from 0.04 km2/a to 0.06 km2/a. From the period 1990–2011 to the period 2015–2019, the average thinning rate of glaciers increased from 0.83 m/a to 1.58 m/a. These results indicate the Bosula Mountain Range is one of the fastest melting glacierized regions in the High Mountain Asia, and the factors that account for this may include quick temperature rise, abundant summer rainfall, and thin debris cover. In spite of strong ice melting, the observed changes in glacier boundaries, surface elevation, and flow velocity show no sign of surge activity, and the frequency of glacier lake outburst has not increased since 1989. Currently, three proglacial lakes that expanded quickly during 2000–2021 are now prominent hazards. They are directly threatened by accidental ice calving and ice avalanche, and their outburst could cause considerable damage to the downstream settlements and the Sichuan-Tibet Road.

Glacial Lake Area Change and Potential Outburst Flood Hazard Assessment in the Bhutan Himalaya

Against the background of climate change-induced glacier melting, numerous glacial lakes are formed across high mountain areas worldwide. Existing glacial lake inventories, chiefly created using Landsat satellite imagery, mainly relate to 1990 onwards and relatively long (decadal) temporal scales. Moreover, there is a lack of robust information on the expansion and the GLOF hazard status of glacial lakes in the Bhutan Himalaya. We mapped Bhutanese glacial lakes from the 1960s to 2020, and used these data to determine their distribution patterns, expansion behavior, and GLOF hazard status. 2,187 glacial lakes (corresponding to 130.19 ± 2.09 km2) were mapped from high spatial resolution (1.82–7.62 m), Corona KH-4 images from the 1960s. Using the Sentinel-2 (10 m) and Sentinel-1 (20 m × 22 m), we mapped 2,553 (151.81 ± 7.76 km2), 2,566 (152.64 ± 7.83 km2), 2,572 (153.94 ± 7.83 km2), 2,569 (153.97 ± 7.79 km2) and 2,574 (156.63 ± 7.95 km2) glacial lakes in 2016, 2017, 2018, 2019 and 2020, respectively. The glacier-fed lakes were mainly present in the Phochu (22.63%) and the Kurichu (20.66%) basins. A total of 157 glacier-fed lakes have changed into non-glacier-fed lakes over the 60 years of lake evolution. Glacier-connected lakes (which constitutes 42.25% of the total glacier-fed lake) area growth accounted for 75.4% of the total expansion, reaffirming the dominant role of glacier-melt water in expanding glacial lakes. Between 2016 and 2020, 19 (4.82 km2) new glacial lakes were formed with an average annual expansion rate of 0.96 km2 per year. We identified 31 lakes with a very-high and 34 with high GLOF hazard levels. These very-high to high GLOF hazard lakes were primarily located in the Phochu, Kurichu, Drangmechu, and Mochu basins. We concluded that the increasing glacier melt is the main driver of glacial lake expansion. Our results imply that extending glacial lakes studies back to the 1960s provides new insights on glacial lake evolution from glacier-fed lakes to non-glacier-fed lakes. Additionally, we reaffirmed the capacity of Sentinel-1 and Sentinel-2 data to determine annual glacial lake changes. The results from this study can be a valuable basis for future glacial lake monitoring and prioritizing limited resources for GLOF mitigation programs.

Changes in glacial lakes in the Poiqu River basin in the central Himalayas

Abstract. The Poiqu River basin is an area of concentration for glaciers and glacial lakes in the central Himalayas, where 147 glacial lakes were identified, based on perennial remote sensing images, with lake area ranging from 0.0002 to 5.5 km2 – a total of 19.89 km2. Since 2004, the retreat rate of glacier has reached as high as 5.0 km2 a−1, while the growth rate of glacial lake has reached 0.24 km2 a−1. We take five typical lakes as our case study and find that the retreat of glacier area reaches 31.2 %, while the glacial lake area has expanded by 166 %. Moreover, we reconstruct the topography of the lake basin to calculate the water capacity and propose a water balance equation (WBE) to explore the lake evolution. By applying the WBE to the five lakes, we calculate the water supplies of the last few years and compare this with the results of field surveys, which are in agreement, within an error of only 1.86 % on average. The WBE also reveals that the water supplies to the lake depend strongly on the altitude. Lakes at low altitudes are supplied by glacier melting, and lakes at high altitudes are supplied by snowmelts. The WBE is not only applicable for predicting future changes in glacial lakes under climate warming conditions but is also useful for assessing water resources from rivers in the central Himalayas.

Spatiotemporal dynamics of glacial lakes (1990\u20132018) in the Kashmir Himalayas, India using Remote Sensing and GIS

This study is perhaps the first attempt to use satellite data (1990–2018) to analyze spatiotemporal changes in glacial lakes over the Kashmir Himalayas supplemented by field studies. Landsat images were used to delineate the spatial extent of glacial lakes at four-time points, i.e., 1990, 2000, 2010 and 2018. The total count of lakes as well as their spatial extent showed a discernible increase. The number increased from 253 in 1990 to 324 in 2018, with a growth rate of 21.4%. The area has increased from 18.84 ± 0.1 km2 in 1990 to 22.13 ± 0.12 km2 in 2018 with a growth rate of 14.7%. The newly formed glacial lakes, including supraglacial lakes, were greater in number than the lakes that disappeared over the study period. All glacial lakes are situated at elevations of 2700 m asl and 4500 m asl. More than 78% of lake expansion in the study region is largely due to the growth of existing glacial lakes. Through area change analysis, our findings reveal that certain lakes show rapid expansion needing immediate monitoring and observation. The analysis of the meteorological variables reveals that minimum and maximum temperatures in the Jhelum basin have shown an increasing trend. Tmax showed an increase of 1.25 °C, whereas Tmin increased to 0.7 °C from 1980 to 2020. On the other hand, precipitation has shown a decreasing trend, which can be attributed to one of the major causes of glacier recession and the expansion of glacial lakes in the Upper Jhelum basin. Consequently, this study could play a significant role in devising a comprehensive risk assessment plan for potential Glacial Lake Outburst Floods (GLOFs) and developing a mechanism for continuous monitoring and management of lakes in the study region.

Estimating the Changes in Glaciers and Glacial Lakes in the Xixabangma Massif, Central Himalayas, between 1974 and 2018 from Multisource Remote Sensing Data

The continuous melting of valley glaciers can impact the water levels of glacial lakes and create glacial lake outburst floods (GLOFs). The Xixabangma massif is one of the most populated areas in the Himalayas and has suffered from multiple GLOFs. To estimate the glacier melting rate in the past four decades and analyze the outburst risk of glacial lakes in the Xixabangma massif, we determined changes in glacier mass balance, glacier area and glacial lake area based on KH-9 images, TanDEM-X images, Landsat images, SRTM DEM and ICESat-2 elevations. Our results show that, from 1974 to 2018, the total glacier area shrank from 954.01 km2 to 752.46 km2, whereas the total glacial lake area grew from 20.90 km2 to 38.71 km2. From 1974 to 2000, 2000 to 2013 and 2013 to 2018, the region-wide glacier mass balance values were −0.16 m w.e./a, −0.31 m w.e./a and −0.29 m w.e./a, respectively. Three glacial lakes, named Gangxico, Galongco and Jialongco, respectively, expanded by 127.14%, 373.45% and 436.36% from 1974 to 2018, and the mass loss rates of their parent glaciers from 2000 to 2013 increased by 81.72%, 122.22% and 160.00% relative to those during 1974 to 2000. The dams of these three lakes are unstable, and their drainage valleys directly connect to a major town and its infrastructure. Due to current high-water levels, possible external events such as ice collapse, landslide, heavy rainfall and earthquakes can easily trigger GLOFs. Hence, we deemed that the Gangxico, Galongco and Jialongco glacial lakes are dangerous and require special attention.

Spatially and Temporally Resolved Monitoring of Glacial Lake Changes in Alps During the Recent Two Decades

Climate warming is intensifying the melting of glaciers and the growth of glacial lakes in the Alps, which has a profound impact on the management of water resources and high-mountain hydropower in this region. However, the research on the spatial distribution and temporal evolution of the Alps glacial lakes of various types still lacks a holistic view. In this study, we developed an inventory of Alps glacial lakes of different types and then obtained the annual areas of these lakes from 2000 to 2019 using JRC Global Surface Water and Global Land Analysis and Discovery data at a resolution of 30 m. A total of 498 glacial lakes (&amp;gt;0.01 km2) with the net area of 33.77 ± 6.94 km2 were identified in the Alps in 2019 and are mainly distributed in the western and central Alps. These Alps glacial lakes, with the area ranging 0.01–1.59 km2, are generally dominated by small-sized ones. The comparison of lakes of different types indicated that ice-uncontacted lakes are dominant in number and area, accounting for 59.4 and 58.4%, respectively. In terms of the elevation distribution, almost half of the lakes are concentrated at the altitude of 2,250–2,750 m (a.s.l.). Meanwhile, the mean altitude of small glacial lakes is higher than that of large lakes. The distribution of ice-contacted lakes and supraglacial lakes were more concentrated, and the mean altitude was higher. During the study period, the number, area, and water volume of glacial lakes were increasing, but the expansion varied between different periods. The changing trends of the glacial lake area and volume were consistent and presents in three stages, as the glacial lake expanded rapidly in the first 5 years and in the last 7 years and remained relatively stable between 2005 and 2012. The number and area of glacier-fed lakes increased rapidly, while the non-glacier-fed lakes were relatively stable. The area change rate of supraglacial lakes was the largest (+47%). This study provides a spatially-complete and temporally-consecutive picture of glacial lake changes in the Alps and can be greatly helpful for future research on climate-glacier-lake interactions, glacial lake outburst floods, and freshwater resources in this region.