Area Of Glacial Lakes Research Articles

Examining the glacier-glacial lake interactions of potentially dangerous glacial lakes (PDGLs) under changing climate in Shyok catchment of the Upper Indus Basin

With the ongoing glacier recession, the Himalayan region is witnessing the development of glacial lakes fed by the glacial meltwater. Besides threatening the hydrological regime in the area, the rapid expansion of these lakes at the expense of their feeding glaciers poses a serious risk to the downstream communities in the form of Glacial Lake Outburst Floods, as many of these high-altitude water bodies are vulnerable to this cryospheric disaster under the changing climatic regime. Studying these potentially dangerous glacial lakes (PDGLs) and their feeding glaciers in the context of the changing climate has become crucial in understanding this phenomenon and managing the risk associated with these lakes. The present study focuses on understanding the glacier-lake interactions between the PDGLs and their feeding glaciers under the changing climatic regime. We analyzed the spatio-temporal dynamics of 16 PDGLs, identified in our previous study, and their feeding glaciers for the past three decades (1992–2022), and tried to unravel the relationships between glacier area, glacial lake area, and climatic variables such as temperature and precipitation. The results reveal a rapid expansion of 49.6% in the glacial lake area accompanied by a corresponding glacier recession of 3.27 % and an average terminus retreat of 171 m. The average glacier mass balance was found to be ⁓ −0.22 m w.e. y−1 during this period. The minimum temperature (Tmin) revealed statistically significant increasing trend, whereas the annual precipitation (Pcp) in the area revealed a slightly declining trend in this region. The glacial lake area was found to be in a significant positive correlation with the Tmin and a slight negative correlation with the annual precipitation (Pcp). The glacier area revealed a strong negative correlation with the glacial lake area, Tmax, and the Tmin and a positive correlation with the annual precipitation. The results indicate that the glacial lakes in the region are expanding at the expense of their feeding glaciers under warming climate.

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.

Development genetic and stability classification of seasonal glacial lakes in a tectonically active area—A case study in Niangmuco, east margin of the Eastern Himalayan Syntaxis

The Niangmuco region on the east margin of the Eastern Himalayan Syntaxis features a large number of glacial lakes. The development process and stability classification of glacial lakes is of great significance to the study of seasonal glaciers in the eastern Himalayan margin, with implications for economic development and disaster prevention. Based on Landsat remote sensing image data from 2000 to 2021, this study analyzed the development and change characteristics of glacial lakes in the Niangmuco region during the past 21 years, and classified the stability of lakes with areas >0.02 km2 using the fuzzy consistent matrix method. In this area, 126 glacial lakes were identified within an elevation range of 3044–4156 m with a total area of 10.94 km2. These lakes primarily included glacial erosion lakes, valley lakes, tectonic lakes, and landslide dam lakes. Specifically, glacial erosion lakes accounted for 88.9% of the total number of lakes and 60.3% of the total lake area, followed by valley lakes with 6.3% and 23.7%, respectively. From 2000 to 2010, the total area of glacial lakes decreased from 10.53 km2 to 10.09 km2, which may be attributable to climate fluctuations. Subsequently, the area of lakes increased significantly to 10.94 km2 in 2021, an increase of 0.41 km2. Compared with 2000, among the lakes with a growth rate of 0.019 km2/a in 21 years, glacial erosion lakes exhibited the largest change. Among the classified glacial lakes in the study area, 95.7% were stable and relatively stable, mostly comprising glacial erosion lakes at high altitudes between 3468 and 4156 m. Only 4 unstable and extremely unstable glacial lakes were identified, and they were located near a fault zone. The findings show that the development and the change of glacial lakes in the area are primarily controlled by temperature and precipitation, and the topography and fault activity have important influences on the stability of glacial lakes.

Sub-regional variability in the influence of ice-contact lakes on Himalayan glaciers

Abstract Ice-contact lakes modify glacier geometry and dynamics by shifting the majority of mass loss from the ice surface to the terminus. Lake-terminating glaciers are known to experience greater thinning rates and higher velocities than land-terminating glaciers, but the controls on variability in surface elevation change and ice flow between lake-terminating glaciers in different regions remain poorly explored. We combined existing datasets of glacier velocity, surface elevation change and glacial lake area to characterise the evolution of 352 lake-terminating and land-terminating glaciers within three Himalayan sub-regions between 2000 and 2019. These analyses show that the influence of ice-contact lakes propagates up-glacier across only the lowermost 30% of the hypsometric distribution, even where lakes are well established. We find that ice-contact lakes only affect glacier behaviour when the lakes reach an advanced evolutionary stage; most clearly manifested in the Eastern Himalaya by statistically robust differences in glacier-wide surface elevation change between lake-terminating (–0.68 ± 0.05 m a–1) and land-terminating (–0.54 ± 0.04 m a–1) glaciers. These differences are driven by the presence of a greater number of well-developed ice-contact lakes in the Eastern Himalaya compared to in the Western and Central Himalaya, resulting from greater mass loss rates to date.

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.

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.

Paraglacial transformation and ice‐dammed lake dynamics in a high Arctic glacier foreland, Gåsbreen, Svalbard

AbstractThe structural change of the Svalbard landscape from glacially dominated to paraglacial, that has taken place since the termination of the Little Ice Age (ca. 1900) is expressed by the widespread retreat of glaciers and progressive exposure of glacial landforms. This study provides insights into the rate of post‐LIA deglaciation and associated paraglacial transformation in the foreland of Gåsbreen, one of the first ever investigated glacier systems in the Arctic. Glacier is situated in Sørkapp Land (Southern Spitsbergen), a region characterized by one of the fastest deglaciation rates in the entire Svalbard Archipelago. During the investigated period, 1938–2020, the Gåsbreen was in a recession that accelerated after 1990, leading to its foreland increasing from 2.2 to 5.8 km2. The dynamics of landscape change in the glacier foreland, exposed since the end of LIA, manifested in i.e. the formation of ice‐dammed lakes, degradation in the surface of ice‐cored moraines and the landforms that are underlain by dead‐ice. Mass movements and debris flow on ice‐cored moraines and fluvioglacial processes had a great influence on this transformation. Enhanced proglacial runoff intensified denudation, transport and accumulation of sediments, which resulted, in: an increase in the extent of sandurs and proglacial riverbeds, an increase in the area of glacial lakes, extending and changing of the course of rivers in the glacier foreland. At the same time, the major lake system in the area—Goësvatnet underwent several cycles of filling and draining, often through glacial outburst flooding events.

Upland river planform morphodynamics and associated riverbank erosion: Insights from channel migration of the upper Yarlung Tsangpo river

River meandering and lateral migration, caused by riverbank erosion, is a major global threat to soil, sediment, lands, and habitats. However, compared to the densely populated lowland floodplains, the upland channel morphodynamics of free-flowing rivers in a complex high-elevation alluvial setting have received less attention. In this study, we quantitatively investigated channel morphodynamics and associated frozen bank migration in the upper Yarlung Tsangpo River in the Himalayan headwater basin from the 1980s to the 2010s. By combining remote sensing analysis with field investigations, we found mean migration rates of 244 gravel-bed river bends ranging from 1.63 m/yr in the 1980s to 2.76 m/yr in the 2010s, with a maximum rate of 18.61 m/yr. The highest migration rates were associated with bends that had a width-normalised curvature radius between 3.0 and 5.0 and a sinuosity between 1.2 and 1.5. A ∼69% increase in river-bend migration and 30% more frequent bend cutoffs coincided nicely with the rapid expansion of glacial lakes due to a ∼1 °C increase in mean annual air temperature over the past four decades. Positive correlations were observed between channel migration rate and temperature, mean glacial lake area, and runoff. These results highlight the importance of the unique channel morphodynamics and the intense lateral movements of upland rivers. The close link between these dynamics and climate change suggests that a warmer world may significantly influence bank erosion and associated ecosystem processes of upland alluvial systems, which are essential for comprehending frozen channel dynamics and developing strategies for habitat protection in uplands worldwide.

Post-Little Ice Age glacial lake evolution in Svalbard: inventory of lake changes and lake types

AbstractThe rapid formation of glacial lakes is one of the most conspicuous landscape changes caused by atmospheric warming in glacierised regions. However, relatively little is known about the history and current state of glacial lakes in the High Arctic. This study aims to address this issue by providing the first inventory of glacial lakes in Svalbard, focusing in particular on the post-Little Ice Age evolution of glacial lakes and their typology. To do so, we used aerial photographs and satellite imagery together with archival topographic data from 1936 to 2020. The inventory comprises the development of 566 glacial lakes (146 km2) that were still in direct contact with glaciers during the period 2008–2012. The results show a consistent increase in the total area of glacial lakes from the 1930s to 2020 and suggest an apparent link between climatic and geological factors, and the formation of specific lake dam types: moraine, ice, or bedrock. We also detected 134 glacial lake drainage events that have occurred since the 1930s. This study shows that Svalbard has one of the highest rates of glacial lake development in the world, which is an indicator of the overall dynamics of landscape change in the archipelago in response to climate change.

Inter-Decadal Dynamics of Glacier Area and Supra-glacial Lakes Over Hispar Glacier, Western Karakoram

Glaciers of the central Karakorum region are the primary source of fresh water and lifeline for downstream inhabitants but changing climatic conditions put serious impacts on glaciers which cause rapid ablation and the creation of glacial lakes. Many natural hazards are associated with glaciers and glacial lakes like Glacier lake outburst flood (GLOF). Using Geographic Information System and Remote sensing techniques on Hispar glacier which is part of central Karakorum, the current study applied Landsat (TM, ETM, ETM+, and OLI) and sentinel-2 satellite imagery. Further, mapping to the Hispar glacier is done to know the variations in glacier and supraglacial lakes between 1990 and 2019. According to the results, about 90% of glacial ponds are present in the debris-covered area while only 10% are present in the clean ice and scow area. This study identifies the decreasing trend in the number and the area of glacial lakes. In 1990, about 42 glacial ponds were covering a total area of 0.733km2, whereas, in 2019, 20 glacial lakes were covering an area of 0.18km2. In the last three decades (1990-2019) about 20km2 of clean ice and snow is increased. The findings of climate data revealed that there is a decreasing trend of temperature and an increasing trend of precipitation. Since 1995, about 0.75oC temperature is observed in HRB. The findings of this study somehow support the Karakoram anomaly.

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.

Small outbursts into big disasters: Earthquakes exacerbate climate-driven cascade processes of the glacial lakes failure in the Himalayas

Risk assessments for potential glacial lake outburst floods (GLOFs) are primarily focused on large, rapidly expanding lakes. However, the mechanism of cascading hazards that cause small outbursts to transition into big disasters is poorly understood. We investigated the Gongbatongshaco GLOF in the Himalayas, to reveal a novel disaster model and mechanism, considering increasing regional temperature, glacial lake area, and glacial retreat. Global warming drives glacial retreat, and uncover loose sediment that can be mobilized as debris flows, triggering small glacial lake outbursts in high mountain regions. Sediment generated from earthquake-induced landslides exacerbates the flow magnitude in a valley to increase the disaster risk. Concentrations of inhabitants located in these areas are subject to socioeconomic vulnerability, leading to post-disaster poverty within these communities. A reasonable GLOFs resilient mitigation framework is proposed. The results offer new insights into risk assessment, especially for small glacial lakes in tectonically-active high mountain environments influenced by climate change and earthquake activity.

A robust glacial lake outburst susceptibility assessment approach validated by GLOF event in 2020 in the Nidu Zangbo Basin, Tibetan Plateau

As reports on glacial lake outburst floods (GLOFs) have increased with global warming, a robust GLOF susceptibility assessment approach is critical for disaster prevention and damage reduction. A robust GLOF susceptibility assessment approach, using the Analytic Hierarchy Process (AHP) to assess the potential hazard grades of glacial lakes combined with data from a digital elevation model (DEM), glaciers, remote sensing images, and field investigations, was constructed and applied in the Nidu Zangbo Basin in Nagqu, Tibetan Plateau. From 1988 to 2016, the total number and area of glacial lakes increased in this basin. There were 71 glacial lakes in the Nidu Zangbo Basin with a total area of 3.42 km2 in 2016, among which 14 lakes, accounting for an area>0.05 km2, were considered to be potentially dangerous glacial lakes (PDGLs) in this study. At the end of 2017, the proposed approach identified 6 of 14 PDGLs as high potentially hazardous, among which Jinwucuo, with the highest hazardous score, occurred GLOF event on June 26, 2020, which proves the robustness of the approach. Thus, the GOLF susceptibility in the Nidu Zangbo Basin was suggested to be evaluated regularly with the approach and update monitoring data and remote sensing images. The study provides valuable clues to assess the GLOF susceptibilities in High Mountain Asia (HMA).

Temporal and Spatial Changes and GLOF Susceptibility Assessment of Glacial Lakes in Nepal from 2000 to 2020

Glacial lakes are a sensitive indicator of regional climate change and one of the initiators of glacier disasters. It is of great significance to understand the spatial distribution and change characteristics of glacial lakes for exploring their response patterns to climate change and assessing the glacial lake outburst flood (GLOF) susceptibility. Based on Gaofen-1/6 PMS, Sentinel-2A/2B MSI and Landsat TM/ETM+/OLI images from 2000 to 2020, we integrated geographic information technology and mathematical and statistical methods to analyze the spatial and temporal distribution of glacial lakes in Nepal and their dynamic changes, and further discriminated and evaluated the GLOF susceptibility of glacial lakes. The results show that there were 2420 glacial lakes in Nepal in 2020, mainly distributed within the 4500~5500 m, with an area of 87.21 km2 and a water storage of 1921.72 × 106 m3. The number and area of glacial lakes with each area above 0.01 km2 in Nepal showed an increasing trend from 2000 to 2020, while 499 new glacial lakes were born, 139 lakes disappeared, the area and water storage increased by 19.46 km2, 403.07 × 106 m3, respectively. Glacial lakes at altitudes <3000 m were relatively stable, while the number and area of glacial lakes at altitudes within 4500~5500 m increased rapidly. We assessed the GLOF susceptibility of 40 moraine-dammed glacial lakes with an area above 0.2 km2 in Nepal, and found that there were 8, 12, 14 and 6 glacial lakes with low, medium, high and very high susceptibility, respectively. Among glacial lakes with very high GLOF susceptibility, potential GLOF events of Tsho Rolpa glacial lake, Lower Barun glacial lake and glacial lake with code of GL87091E27797N will cause great harm to downstream regions. GLOFs in Nepal will be in an active status in the future, therefore, the dynamics of glacial lakes and their surroundings should be continuously monitored.

Controls on Alpine Lake Dynamics, Tien Shan, Central Asia

The number and area of alpine lakes in Tien Shan (TS) are rapidly growing in response to a warming climate and retreating glaciers. This paper presents a comparative analysis of lake classification and changes by dividing alpine lakes (within a 10 km buffer of the glacier margins) into four types (supraglacial lakes, proglacial lakes, extraglacial lakes and non-glacial lakes), and subsequently determining the driving forces of change across the TS region from 1990 to 2015. The analysis utilized multiple satellite images and climatic data from gridded data sets and meteorological station observations. The results indicate that the total number and area of glacial lakes continuously increased during the study period, whereas non-glacial lakes intermittently expanded. Specifically, the total number and area of all glacial lakes (supraglacial lakes, proglacial lakes and extraglacial lakes) increased by 45.45% and 27.08%, respectively. Non-glacial lakes, in contrast, increased in quantity and area by 23.92% and 19.01%, respectively. Alpine lakes are closer to glaciers at high altitudes; in fact, some (e.g., proglacial lakes) are connected to glacier termini, and these show the highest expansion speed during the study period. The area of proglacial lakes expanded by 60.32%. Extraglacial lakes expanded by 21.06%. Supraglacial lakes, in marked contrast to the other types, decreased in area by 3.74%. Widespread rises in temperature and glacier wastage were the primary cause of the steady expansion of glacial lakes, particularly those linked to small- and medium-sized glaciers distributed in the Eastern TS where glacial lakes have rapidly increased. Both proglacial and extraglacial lakes expanded by 6.47%/a and 2%/a, respectively, from 1990 to 2015. While these proglacial and extraglacial lakes are located in largely glacierized areas, lakes in the Central TS exhibited the slowest expansion, increasing in area by 1.44%/a and 0.74%/a, respectively. Alterations in non-glacial lake areas were driven by changes in precipitation and varied spatially over the region. This study has substantial implications for the state of water resources under the complex regional changes in climate in the TS and can be used to develop useful water-resource management and planning strategies throughout Central Asia.

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.

Identification of origin and runoff of karst groundwater in the glacial lake area of the Jinsha River fault zone, China

Karst groundwater plays important roles as a water supply and in sustaining the biodiversity and ecosystems of the eastern Qinghai–Xizang Plateau. Owing to the stratigraphic structure, high tectonic activity, and changeable climate of the region, the recharge source, runoff path, and dynamic characteristics of karst groundwater are highly complex, which poses challenges with regard to the protection of water resources and ecology. This study identified the origin and flow processes of karst groundwater in the glacial lake area of the Jinsha River fault zone using satellite remote sensing, hydrochemical and isotope analyses, and flow measurements. Results showed that active faults control the distribution of glacial lakes and the recharge, runoff, and discharge of karst groundwater. Glacial lake water is an important source of karst groundwater in the Jinsha River fault zone area. Specifically, glacial lake water continuously recharges the karst system via faults, fractures, and karst conduits, thereby maintaining the relative stability of karst spring flows. Through hierarchical cluster analysis, two main runoff conduits of karst water were distinguished: one along the Dingqu Fault and the other along the Eastern Zhairulong Fault, which together account for 59% of the total regional karst groundwater flow. The elevation difference between the recharge and discharge areas of the main karst springs is > 1000 m. Groundwater runoff is fast and residence time in the aquifer is short. The dissolution of calcite and dolomite mainly occurs during transit through the groundwater system, and cation exchange is weak. Therefore, the regional karst springs are predominantly HCO3−Ca·Mg type. To protect regional karst water resources and ecology, the monitoring and protection of glacial lakes should be strengthened.

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.

Glacier Mass Balance Changes Over the Turgen Daban Range, Western Qilian Shan, From 1966/75 to 2020

Extensive efforts for quantifying regional glacier mass balance in the Qilian Mountains have been made using the geodetic method, but these estimations were rarely extended back to the period before 2000. This study presents glacier mass budgets in the Turgen Daban Range, over the western Qilian Mountain, from 1966/75 to 2020 by means of the digital elevation models generated by the topographic maps and ASTER images. The results show that the glacier mass decreased by −18.79 ± 12.48 m w.e. during the past 50 years. The average mass loss rate is estimated to be −0.19 ± 0.08 m w.e.a−1 for the 1966/75-2006 period and −0.45 ± 0.17 m w.e.a−1 during 2006–2020, respectively, suggesting a remarkable acceleration of glacier mass loss. This may be attributable to the significant increase in air temperature and the insignificant precipitation increase which cannot offset glacier melting caused by increased temperature. Due to the melting and shrinking of glaciers, the area of glacial lakes increases by 2.83 km2 from 1987 to 2020.