Moraine-dammed Lakes Research Articles

Relations between climate change and mass movement: Perspectives from the Canadian Cordillera and the European Alps

Earth's climate is warming and will continue to warm as the century progresses. High mountains and high latitudes are experiencing the greatest warming of all regions on Earth and also are some of the most sensitive areas to climate change, in part because ecosystems and natural processes in these areas are intimately linked to the cryosphere. Evidence is mounting that warming will further reduce permafrost and snow and ice cover in high mountains, which in turn will destabilize many slopes, alter sediment delivery to streams, and change subalpine and alpine ecosystems. This paper contributes to the continuing discussion of impacts of climate change on mountain environments by comparing and discussing processes and trends in the mountains of western Canada and the European Alps. We highlight the effects of physiography and climate on physical processes occurring in the two regions. Processes of interest include landslides and debris flows induced by glacier debuttressing, alpine permafrost thaw, changes in rainfall regime, formation and sudden drainage of glacier- and moraine-dammed lakes, ice avalanches, glacier surges, and large-scale sediment transfers due to rapid deglacierization. Our analysis points out the value of integrating observations and data from different areas of the world to better understand these processes and their impacts.

The 2020 glacial lake outburst flood process chain at Lake Salkantaycocha (Cordillera Vilcabamba, Peru)

Glacial lakes represent a threat for the populations of the Andes and numerous disastrous glacial lake outburst floods (GLOFs) occurred as a result of sudden dam failures or dam overtoppings triggered by landslides such as rock/ice avalanches into the lake. This paper investigates a landslide-triggered GLOF process chain that occurred on February 23, 2020, in the Cordillera Vilcabamba in the Peruvian Andes. An initial slide at the SW slope of Nevado Salkantay evolved into a rock/ice avalanche. The frontal part of this avalanche impacted the moraine-dammed Lake Salkantaycocha, triggering a displacement wave which overtopped and surficially eroded the dam. Dam overtopping resulted in a far-reaching GLOF causing fatalities and people missing in the valley downstream. We analyze the situations before and after the event as well as the dynamics of the upper portion of the GLOF process chain, based on field investigations, remotely sensed data, meteorological data and a computer simulation with a two-phase flow model. Comparison of pre- and post-event field photographs helped us to estimate the initial landslide volume of 1–2 million m3. Meteorological data suggest rainfall and/or melting/thawing processes as possible causes of the landslide. The simulation reveals that the landslide into the lake created a displacement wave of 27 m height. The GLOF peak discharge at the dam reached almost 10,000 m3/s. However, due to the high freeboard, less than 10% of the lake volume drained, and the lake level increased by 10–15 m, since the volume of landslide material deposited in the lake (roughly 1.3 million m3) was much larger than the volume of released water (57,000 m3, according to the simulation). The model results show a good fit with the observations, including the travel time to the uppermost village. The findings of this study serve as a contribution to the understanding of landslide-triggered GLOFs in changing high-mountain regions.

Can a dam type of an alpine lake be derived from lake geometry? A negative result

Glacial lake outburst floods (GLOFs) represent one of the most serious hazard and risk in deglaciating high mountain regions worldwide and the need for GLOF hazard and risk assessment is apparent. As a consequence, numerous region- and nation-wide GLOF assessment studies have been published recently. These studies cover large areas and consider hundreds to thousands of lakes, prioritizing the hazard posed by them. Clearly, certain simplification is required for executing such studies, often resulting in neglecting qualitative characteristics which would need manual assignment. Different lake dam types (e.g., bedrock-dammed, moraine-dammed) are often not distinguished, despite they control GLOF mechanism (dam overtopping/dam breach) and thus GLOF magnitude. In this study, we explore the potential of easily measurable quantitative characteristics and four ratios to approximate the lake dam type. Our dataset of 851 lakes of the Cordillera Blanca suggests that while variances and means of these characteristics of individual lake types differ significantly (F-test, t-test), value distribution of different geometrical properties can’t be used for the originally proposed purpose along the spectra. The only promising results are obtained for extreme values (selected bins) of the ratios. For instance, the low width to length ratio indicates likely moraine-dammed lake while the high value of ratio indicating round-shape of the lake indicates increased likelihood of bedrock-dammed lake. Overall, we report a negative result of our experiment since there are negligible differences of relative frequencies in most of the bins along the spectra.

An Early Warning System is Established for Cirenmaco, a Moraine-Dammed Lake in Central Himalaya, China

An Early Warning System is Established for Cirenmaco, a Moraine-Dammed Lake in Central Himalaya, China

Misinterpreting proxy data for paleoclimate signals: A comment on Shukla et al. 2020

Shukla et al. explored paleoclimatic signals from a ~8 m thick profile of a moraine-dammed lake in the central Himalaya exposed due to lake burst from a flash flood in 2013. The main objective of their research work is to understand the complex glacial-climate system during late-Holocene. They attempted a novel multi proxy approach for paleoclimate reconstruction but their work suffers from misinterpretation of various proxies and erroneous/misleading discussion. We therefore report following major points in this comment article. (1) Misinterpretation of magnetic parameters: Magnetic susceptibility (χlf) has been used to interpret changes in magnetic mineralogy rather than concentration of magnetic minerals. Susceptibility of anhysteretic remanence (χARM) has been used at several places to indicate presence of superparamagnetic (SP) and multi domain (MD) ferrimagnetic particles rather than single domain (SD) ferrimagnetic (magnetite) particles. Interpreting erroneous negative values of percentage of frequency dependent susceptibility (χfd%) for climate change. (2) Poor chronology: Overlaps in ages of glacial-lake sediments. (3)

Integrated risk assessment of glacier lake outburst flood (GLOF) disaster over the Qinghai–Tibetan Plateau (QTP)

The study analyzed synthetically spatiotemporal distribution and evolution status of moraine-dammed lakes and potential dangerous glacial lakes (PDGLs) in the Qinghai–Tibetan Plateau (QTP) and revealed integrated risk degree of county-based glacier lake outburst floods (GLOFs) disaster by combining hazard of PDGLs, regional exposure, vulnerability of exposed elements, and adaptability and using the analytic hierarchy process and weighted comprehensive method. The results show there are 654 moraine-dammed lakes (> 0.018 km2) with a total area of 200.25 km2 in the QTP in the 2010s, of which 246 lakes with a total area of 78.38 km2 are identified as PDGLs. Compared with 1990s, the number of lakes decreased only by 2.22%, whereas total lake area expanded by 25%. All PDGLs area increased by 84.40% and was higher significantly than 4.06% of non-PDGLs. The zones at very high and high integrated risk of GLOF disasters are concentrated on the middle Himalayas, middle-eastern Nyainqentanglha, and southern Tanggula Mountain. On the county scale, Nyalam, Tingri, Dinggye, Lhozhag, Zhongba, Gamba, Kangma of the Himalayas, and Nierong, Dingqing, Banbar, Baqing, Bomi, and Basu of the Nyainqentanglha are located in the very high-risk zone, whereas other areas have low and very low integrated risk. The regionalization results for GLOF disasters risk are consistent with the distribution of historical GLOF disaster sites.

Glacial Lake Inventory Derived from Landsat 8 OLI in 2016–2018 in China–Pakistan Economic Corridor

The China–Pakistan Economic Corridor (CPEC), a key hub for trade, is susceptible to glacial lake outburst floods. The distributions and types of glacial lakes in the CPEC are not well documented. In this study, cloud-free imagery acquired using the Landsat 8 Operational Land Imager during 2016–2018 was used to delineate the extent of glacial lakes in the mountainous terrain of the CPEC. In the study domain, 1341 glacial lakes (size ≥ 0.01 km2) with a total area of 109.76 ± 9.82 km2 were delineated through the normalized difference water index threshold method, slope analysis, and a manual rectification process. On the basis of the formation mechanisms and characteristics of glacial lakes, four major classes and eight subclasses of lakes were identified. In all, 492 blocked lakes (162 end moraine-dammed lakes, 17 lateral moraine-dammed lakes, 312 other moraine-dammed lakes, and 1 ice-blocked lake), 723 erosion lakes (123 cirque lakes and 600 other erosion lakes), 86 supraglacial lakes, and 40 other glacial lakes were identified. All lakes were distributed between 2220 and 5119 m a.s.l. At higher latitudes, the predominate lake type changed from moraine-related to erosion. From among the Gez, Taxkorgan, Hunza, Gilgit, and Indus basins, most glacial lakes were located in the Indus Basin. The number and area of glacial lakes were larger on the southern slopes of the Karakoram range.

70 years of lake evolution and glacial lake outburst floods in the Cordillera Blanca (Peru) and implications for the future

Climate change, glacier retreat and glacial lake outburst floods (GLOFs) are intertwined. The Cordillera Blanca in Peru has one of the world's longest GLOF records and here we assess the evolution of glacial lakes in the region between 1948 and 2017 and investigate the links to documented GLOFs. We also model future lake evolution under two climate scenarios to provide an assessment of current and future GLOF triggering potential. Our analysis shows that the number of lakes as well as the total lake area has increased during the historical period. The formation of new lakes is, however, not uniform among different lake types with bedrock-dammed lakes exhibiting the largest increase in recent decades. We argue that moraine-dammed lakes have already formed at the majority of potential locations in the Cordillera Blanca and that the next generation of lakes which are expected to form in response to glacier retreat over topographically suitable areas will be predominantly bedrock-dammed. Based on a regional GLOF inventory, we show that the peak frequency of GLOFs occurred from the late 1930s to early 1950s. While GLOFs originating from moraine-dammed lakes dominated in this period, recent GLOFs have originated from bedrock-dammed lakes. At the same time, the majority of GLOFs originated from lakes in a proglacial phase (i.e. in contact with glacier), even though the share of proglacial lakes did not exceed 12% at any time step during the analysed period. While many moraine-dammed lakes evolved into the glacier-detached evolutionary phase, bedrock-dammed lakes became a major lake dam type among proglacial lakes. Over the remainder of the 21st century, a further increase in lake area of up to 10% is anticipated, with up to 50 new bedrock dammed lakes likely to develop as glaciers retreat. There is little difference in lake development and GLOF triggering potential under climate scenarios driven by RCP 2.6 and 8.5. Based on topographic disposition, recent and future lakes do not individually appear more or less susceptible to landslide impact than lakes that already developed earlier in the 20th century. Synthesizing these findings, we forecast that bedrock-dammed lakes will become the dominant source of GLOFs in the next decades. Because such dams are inherently more stable, we expect overall lower GLOF magnitudes compared to documented GLOFs from moraine-dammed lakes.

Lake inventory and potentially dangerous glacial lakes in the Nyang Qu Basin of China between 1970 and 2016

There are a large number of glaciers and lakes developed in the Nyang Qu Basin of China. Recent climate change has significant impacted on the high-mountain glacial environment. Rapid melting of glaciers contributes to the formation and expansion of moraine-dammed lakes which increase the probability of glacial lake outburst floods (GLOFs). We calculated a multi-temporal lake inventory based on (1) topographic maps in the 1970s, (2) satellite imageries from 1990 to 2016, (3) First Chinese Glacier Inventory (FCGI), (4) Glacier Inventory of Southeastern Tibet (GIST) and (5) meteorological data. A total of 880 lakes (>0.01 km2) have been mapped in 2016, with 318 being glacial lakes (GLs) and 462 non-glacier lakes (NGLs). Most of the lakes were mainly located at 4500 m a.s.l. and the lakes dominated by small lakes (<0.1 km2) where the change of their actual sizes are more significant compared to the larger ones. Meanwhile, we found

Climatically driven late Pleistocene – Holocene hydrological system transformation and landscape evolution in the eastern periphery of Chuya basin, SE Altai, Russia

This paper presents the results of geological, geomorphological, geochronological investigations and the analysis of the biological composition of deposits within the high-mountainous Boguty river basin. The main stages of landscape evolution during the last 14 ka have been investigated through 32 radiocarbon dates. The area is located in the most arid southeastern part of Russian Altai and constitutes the eastern periphery of the Chuya intermountain depression, and the western side of the Chikhachev range.Postglacial landscape development of the upper reaches of the Chuya River began from the degradation of its vast glaciation. By 14 ka cal BP the glaciers had either completely melted or retreated above 2500 m above sea level. As a result, numerous lakes occupied open places and five types of these basins can be seen in the modern topography. They are large moraine-dammed lakes connected with the Boguty River, while some basins have been dammed by uplifted tectonic blocks and numerous lakes are of thermokarst origin or are small cirque lakes and temporal lakes fed by seasonal meltwater from meteoric, ground water and permafrost degradation.Large moraine-dammed lakes within the Boguty basin were developed before the Holocene. The water filling these basins was controlled by the height of moraine dams and by the depth of the Boguty river incision. The moraine-dammed Low Boguty Lake formed earlier than 10 ka cal BP. Its partial draining and transformation of littoral zone into peat bog took place about 8.2-7.6 ka cal BP. As a result of the analysis of biological composition, four stages of water level fluctuations in the lacustrine-boggy system were recognized.The specific geomorphic and sedimentary features in the middle part of the Boguty basin determined the recurrence of debris flow events at about 8-7; 2.9-1; 0.65 and 0.3 ka cal BP, but the last event occurred in June 2017.The occurrence of fossil forest soils dating to about 11-8.5 ka cal BP and of charcoals (Larix sibirica Ledeb) of about 8.5-7.8 ka cal BP indicate a prolonged period of developing forest vegetation in the Boguty basin, which is currently treeless. In general, the data suggest that in SE Altai the climate in the first half of the Holocene was warmer and more humid in comparison with the modern one. The second half of the Holocene has been characterized by colder climate conditions accompanied by aridity intensification, which became especially pronounced during the last 2-1.5 ka.

Reconstruction of the 1941 GLOF process chain at Lake Palcacocha (Cordillera Blanca, Peru)

Abstract. The Cordillera Blanca in Peru has been the scene of rapid deglaciation for many decades. One of numerous lakes formed in the front of the retreating glaciers is the moraine-dammed Lake Palcacocha, which drained suddenly due to an unknown cause in 1941. The resulting Glacial Lake Outburst Flood (GLOF) led to dam failure and complete drainage of Lake Jircacocha downstream, and to major destruction and thousands of fatalities in the city of Huaráz at a distance of 23 km. We chose an integrated approach to revisit the 1941 event in terms of topographic reconstruction and numerical back-calculation with the GIS-based open-source mass flow/process chain simulation framework r.avaflow, which builds on an enhanced version of the Pudasaini (2012) two-phase flow model. Thereby we consider four scenarios: (A) and (AX) breach of the moraine dam of Lake Palcacocha due to retrogressive erosion, assuming two different fluid characteristics; (B) failure of the moraine dam caused by the impact of a landslide on the lake; and (C) geomechanical failure and collapse of the moraine dam. The simulations largely yield empirically adequate results with physically plausible parameters, taking the documentation of the 1941 event and previous calculations of future scenarios as reference. Most simulation scenarios indicate travel times between 36 and 70 min to reach Huaráz, accompanied with peak discharges above 10 000 m3 s−1. The results of the scenarios indicate that the most likely initiation mechanism would be retrogressive erosion, possibly triggered by a minor impact wave and/or facilitated by a weak stability condition of the moraine dam. However, the involvement of Lake Jircacocha disguises part of the signal of process initiation farther downstream. Predictive simulations of possible future events have to be based on a larger set of back-calculated GLOF process chains, taking into account the expected parameter uncertainties and appropriate strategies to deal with critical threshold effects.

Hazard from Himalayan glacier lake outburst floods

Sustained glacier melt in the Himalayas has gradually spawned more than 5,000 glacier lakes that are dammed by potentially unstable moraines. When such dams break, glacier lake outburst floods (GLOFs) can cause catastrophic societal and geomorphic impacts. We present a robust probabilistic estimate of average GLOFs return periods in the Himalayan region, drawing on 5.4 billion simulations. We find that the 100-y outburst flood has an average volume of 33.5+3.7/-3.7 × 106 m3 (posterior mean and 95% highest density interval [HDI]) with a peak discharge of 15,600+2,000/-1,800 m3⋅s-1 Our estimated GLOF hazard is tied to the rate of historic lake outbursts and the number of present lakes, which both are highest in the Eastern Himalayas. There, the estimated 100-y GLOF discharge (∼14,500 m3⋅s-1) is more than 3 times that of the adjacent Nyainqentanglha Mountains, and at least an order of magnitude higher than in the Hindu Kush, Karakoram, and Western Himalayas. The GLOF hazard may increase in these regions that currently have large glaciers, but few lakes, if future projected ice loss generates more unstable moraine-dammed lakes than we recognize today. Flood peaks from GLOFs mostly attenuate within Himalayan headwaters, but can rival monsoon-fed discharges in major rivers hundreds to thousands of kilometers downstream. Projections of future hazard from meteorological floods need to account for the extreme runoffs during lake outbursts, given the increasing trends in population, infrastructure, and hydropower projects in Himalayan headwaters.

Prediction of the Maximum Wave Elevation in Moraine-Dammed Lakes during Resonant Earthquake Excitation

AbstractLarge-amplitude water waves can be generated in small lakes, such as moraine-dammed lakes, by resonant earthquake excitation, which may cause the overtopping failure of natural dams and res...

Paleo-shoreline changes in moraine dammed lake Khagiin Khar, Khentey Mountains, Central Mongolia

The formation and evolution of glacier moraine-dammed lakes are closely related to past glacier expansion and retreat. Geomorphic markers such as lacustrine terraces and beach ridges observed in these lakes provide important evidence for regional paleoenvironment reconstruction. We document the magnitude of paleo-shoreline fluctuations and timings of highstands of lake water by using cosmogenic 10Be surface exposure dating and optically stimulated luminescence (OSL) dating on samples collected from lacustrine sediment and bedrock strath in Lake Khagiin Khar. The lake was initially impounded by glacier moraine at the Global Last Glacial maximum (gLGM; 21–19 ka), and the lake reached its maximum paleo-shoreline level of 1840 m at sea level (a.s.l.). At that time, the stored lake water amount was up to seven times greater and the surface area was three times larger than the present values. The paleolake experienced higher shoreline levels at 1832, 1822, and 1817 m a.s.l. and reached the present lake level after 0.4 ka. We interpret that decrease in the paleolake level was caused by spillover. The increase in melt water after the gLGM and the Late Glacial exceeded the storage threshold of the lake, and the paleolake water overflowed across the lowest drainage divides. The lake spilled over across the lowest bedrock ridge at 15.9 ± 0.6 ka, and the outlet was incised since that time at a rate of 3.72 ± 0.15 mm/yr. The initial stream of the Khiidiin Pass River was disturbed by LGM moraine damming and was rerouted into the present course running through moraine after the spillover at 15.9 ± 0.6 ka.

Pleistocene fluvial catastrophes in now arid NW areas of Mongolian Inland drainage basin

Abstract The distribution of glacial landforms and deposits in the upper part of the Mogen-Buren River basin provide evidence for extended ice sheet formation along the Shapshal range in the late Pleistocene. At that time the Mongun-Taiga massif and Chikhachev range were also affected by glaciation. Advanced glaciers blocked the Khindiktig-Khol and Ak-Khol depressions and impounded significantly larger lakes. Overfilling any of the Khindiktig-Khol, Ak-Khol or probably the supraglacial lakes by melt-water caused repeated outburst floods along the Mogen-Buren River into the Achit-Nuur Lake, Mongolian Great Lakes Basin. Significant landscape transformation took place due to geological work of these processes. Specific landforms were generated, including high lake shorelines, lacustrine bars and sediments, marginal channels, indicators of fluvial activity on the floor of the basin, and fluvial transported boulders that mark the flood pathways as well as the specific vertical lithofacies profile of outwash deposits. Available absolute dates suggest some chronological bench marks of the hydrological system transformation in the region. Changing of deposition patterns in the Achit-Nuur Lake about 11,000 cal BP can be assumed from the age-depth model of the lake core ( Sun et al., 2013 ). The period of the maximal lakes filling at 2380 m a.s.l. in the upper part of the Mogen-Buren basin started no later than 14,000 cal BP, based on data from Ak-Khol Lake core ( Blyakharchuk et al., 2007 ). There are no absolute dates that identify the time of partial draining of former Ak-Khol Lake, which was dammed by glacier ice, and its prolonged preservation at 2270 m a.s.l. – the height of the moraine dam. This stage ended before 8200 cal BP. The postglacial hydrological system evolution within the studied area is characterized by formation of local lakes in the Mogen-Buren depression from about 11,600–8800 cal BP. All cataclysmic outburst floods from glacier- and moraine-dammed lakes took place before 11,600 cal BP, and significant hydrological system transformations were completed before 5100 cal BP.

Moraine-dammed glacial lake changes during the recent 40 years in the Poiqu River Basin, Himalayas

Glacier retreat is not only a symbol of temperature and precipitation change, but a dominating factor of glacial lake changes in alpine regions, which are of wide concern for high risk of potential outburst floods. Of all types of glacial lakes, moraine-dammed lakes may be the most dangerous to local residents in mountain regions. Thus, we monitored the dynamics of 12 moraine-dammed glacial lakes from 1974 to 2014 in the Poiqu River Basin of central west Himalayas, as well as their associated glaciers with a combination of remote sensing, topographic maps and digital elevation models(DEMs). Our results indicate that all monitored moraine-dammed glacial lakes have expanded by 7.46 km2 in total while the glaciers retreated by a total of 15.29 km2 correspondingly. Meteorological analysis indicates a warming and drying trend in the Nyalam region from 1974 to 2014, which accelerated glacier retreat and then augmented the supply of moraine-dammed glacial lakes from glacier melt. Lake volume and water depth changed from 1974 to 2014 which indicates that lakes Kangxico, Galongco, and Youmojanco have a high potential for outburst floods and in urgent need for continuous monitoring or artificial excavation to release water due to the quick increase in water depths and storage capacities. Lakes Jialongco and Cirenmaco, with outburst floods in 1981 and 2002, have a high potential risk for outburst floods because of rapid lake growth and steep slope gradients surrounding them.

Lake systems in mountain borders of the Great Lakes Basin of Mongolia: From Pleistocene catastrophes to Holocene gradual evolution (case study from southwestern Tuva)

The paper presents results of integrated geological, geomorphological, geochronological, and geoarchaeological studies in the basin of Lake Ak-Hol located in southwestern Tuva (Russia), in mountains north of the Great Lakes Basin of Mongolia. The Pleistocene-Holocene history of the basin consisted of several stages recorded in terrain and deposition patterns. The highest stand of Lake Ak-Hol (180 m above the present level and 16 times greater area) was due to an ice dam and was coeval to the appearance of organic matter (remnants of higher aquatic plants and algae) in lake sediments about 14 ka cal BP. At the next stage, the lake was impounded by a moraine dam. 14C ages of buried soils indicate that the level of the ice- and moraine-dammed lake fell to below 222 m asl long before 8.5 ka cal BP. Erosion of the moraine dam may correspond to the event of lake drying about 12 ka cal BP evident from a deposition gap in sedimentary cores. That event of sudden drainage may have been the last catastrophic flood into the Great Lakes Basin traceable in the catchment of the Mogen-Buren River. Judging from the obtained 14C ages of sediments from the Mogen-Buren Valley, ice- and moraine-dammed lakes in the Ak-Hol system underwent cataclysmic outburst floods only before 11.6 ka cal BP. In the Holocene, after the moraine dam failure, the lake level changes were controlled solely by climate. The general decreasing trend was repeatedly interrupted by high stand excursions (up to 15 m of relative level rise). Nomad peoples settled on the floor of the highland Ak-Hol basin since the Late Bronze Age. All archaeological sites (from that time to the time of Turkic cultures) mapped in the basin are located above 2220 m asl and lack signatures of water erosion, indicating that the lake never rose above that altitude for the past 3 ka years.

Moraine dam breach and glacial lake outburst flood generation by physical and numerical models

Summary The areas of glacial lakes in the Himalayas continue to increase alarmingly due to global warming with consequent risk of glacial lake outburst flood (GLOF). The outburst is most common for moraine-dammed lakes as a result of a failure of the dam by overtopping and erosion or piping due to seepage. In the present context, GLOF events, especially for the moraine dam failure process needs to be predicted to assess the drastic and detrimental impacts on the downstream river valley. This study focuses on validating an integrated model for simulating the failure of moraine dam by overtopping and erosion using a coupled numerical simulation model. The proposed numerical methodology is validated with the data from experiments in laboratory scale physical models. The results of the model are compared for both the erosional profiles during collapse of the dam and the resulting outflowing flood hydrograph. The primary finding is that the moraine dam height and the volume of the lake upstream of the dam are the most sensitive parameters influencing the GLOF peak. The model is also applied to the field problem of the Tangjiashan lake outburst and dam failure and shows reasonably good agreement with observations. The validated model is also run for the South Lhonak glacial lake in the Sikkim Himalayas, India to obtain the probable flood hydrograph in case of failure of the moraine dam.

Causes and geomorphological effects of large debris flows in the lower valley areas of the Meru and Gangotri glaciers, Bhagirathi basin, Garhwal Himalaya (India)

ABSTRACTThe present study investigates the debris flow occurred in July 2017 at the terminal moraine of the Meru glacier, Bhagirathi basin, Garhwal Himalaya. This event has changed the geomorphology of the Gangotri glacier’s snout and downstream of the Bhagirathi river due to massive debris displacement. The causes of the debris flow were analyzed using Sentinel-2A and Google Earth (GE) images, gridded precipitation data of the Global Precipitation Climatology Centre (GPCC) and the Tropical Rainfall Measuring Mission (TRMM). The chronological analysis of Sentinel-2A satellite and Google Earth (GE) images show the expansion in the size of the moraine-dammed lake at the terminus of Meru glacier, which later breached and triggered the debris flow. The analysis of rainfall data shows that the area received heavy rainfall during the event, triggering a massive debris flow.

Climate change and the global pattern of moraine-dammed glacial lake outburst floods

Abstract. Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.