Glacier Surge Research Articles

Geomorphological and historical records of the surge-type behaviour of Hansbreen (Svalbard)

Abstract This paper presents geomorphological and historical records of the surge-type behaviour of Hansbreen, one of the most studied tidewater glaciers in Svalbard. The surge-type behaviour of the glacier has not been considered before due to the lack of evidence of this phenomenon. We integrate geomorphological mapping of the terrestrial and submarine forefields with historical data from the 19th and 20th centuries to reconstruct the glacier dynamics and identify the possible timing of surging. Landform assemblages are representative of the surging glacier landsystem, including crevasse-squeeze ridges (CSRs) and submarine streamlined glacial lineations. Abundant CSRs in the outer part of the terrestrial forefield were also documented in the 1980s, but most have been obliterated since then. We suggest the identified surge landsystem was produced during a surge of Hansbreen detected from photographs taken during the Austro-Hungarian expedition in 1872. Historical photogrammetric photos from the Norwegian expedition in 1918 revealed surge-diagnostic features in the glacier surface, including a folded medial moraine and a dense, complex network of crevasses. A potential next surge remains questionable in the following decades due to the low-lying accumulation area of the main stream hindering the mass build-up, but potential surges of the tributary glaciers should not be excluded.

WITHDRAWN: Surging dynamics of unnamed glaciers at the Abi Gamin Peak in the central Himalayas

Surge-type glaciers in the Himalayas have been extensively documented, however, understanding of the mechanisms behind glacier surges remain limited. Herein, based on multi-source remote sensing data, we systematically investigated the characteristics and subglacial processes of the unnamed glacier at Abi Gamin Peak in central Himalayas. Our approach integrated optical stereo photogrammetry, feature tracking, visual interpretation, and glacier velocity decomposition. Our study reveals that the glacier surge was initiated in August 2019 and lasted for less than six months, with rapid acceleration and deceleration phases. During the surge, the glacier transported approximately 0.233 km3 of mass from higher to lower elevations, leading to a thickness increase of >70 m at the glacier terminus. The glacier terminus advanced by >800 m, accompanied by significant expansion of the crevasses. Furthermore, we quantitatively revealed the evolution of basal stresses, strain rates, and sliding velocities during the surge, indirectly characterising the influence of water on it. We contend that the surge in this glacier was primarily driven by subglacial sliding induced by glacier surface meltwater. Significant changes in regional climate serve as external factors that perturb the glacial dynamic equilibrium. The observed characteristics of the unnamed glacier at Abi Gamin Peak indicate that its surge was controlled by a hydrological switch. Notably, our work contributes to an enhanced understanding of glacier surge mechanisms in High Mountain Asia.

Quantifying glacier surging and associated lake dynamics in Amu Darya river basin using UAV and remote sensing data

Quantifying glacier surging and associated lake dynamics in Amu Darya river basin using UAV and remote sensing data

Assessing climate-driven impacts on Karakoram glacier surge: A geospatial analysis highlighting Shishper Glacial Lake outburst flood events (2019–2022) as prime example

The Northern Areas of Pakistan encompass the Hindukush, Karakoram, and Himalayan mountain ranges witnessing glacier surging, exacerbated by climate warming. As glaciers rapidly melt, ravines experience heightened blockage and migration, obstructing stream discharges and forming expansive ice-dammed lakes. The rupture of these natural dams triggers Glacial Lake Outburst Floods downstream in the primary glacier's ravine. The catastrophic Glacial Lake Outburst Floods in 2022 across the Karakoram ranges in Northern Pakistan prompted this study. It focuses on Shishper Glacier Lake. The aim is to provide complete flood observations and their devastating effects on downstream communities. Analysis of Landsat 08 Imagery reveals the evolution of Shishper Glacier Lake from its initiation in November 2018 to the catastrophic GLOF in May 2022. The lake reached a maximum area of 0.32 km2 in 2019 and its successive breaches on June 22, 2019, and May 29, 2020, reduced it to 0.018 km2. Draining continued until July 2021, shrinking the lake area to 0.009 km2. A noteworthy 2.73 °C temperature increase in 2022 correlated with an expansion of the lake area to 0.33 km2, culminating in the GLOF on May 7th, 2022. The study emphasizes the critical need for mapping, assessing, and monitoring surging glaciers and glacier-formed lakes in the Karakoram ranges to safeguard downstream communities from potential hazards.

Reconstructing Glacier Surge Kinematics Using a Numerical Ice‐Flow Model Applied to the Dusty Glacier, St. Elias Mountains, Canada

AbstractLong‐term records of the flow patterns and dynamics of surge‐type glaciers improve our understanding of their underlying dynamic processes, and are critical to better resolve their contribution to a changing cryosphere. We adapt a modeling approach designed to emulate glacier surging and fold kinematics using the full Stokes ice‐flow model Elmer/Ice to simulate surging of the Dusty Glacier, located in the St. Elias Mountains, Canada. We combine distributed mass‐balance and numerical ice‐flow models to reconstruct the fold kinematics of the 2001–2003 surge of the Dusty Glacier by comparing model results to Landsat‐7 and Sentinel‐2 imagery, and assess the sensitivity of centennial‐scale modeled glacier structure to different mass balance and sliding parameterizations. This study demonstrates the feasibility of using the approach to reconstruct the surface structure kinematics of a surge‐type glacier in nature, highlighting its potential application to other surge‐type glaciers and regions.

Combining “Deep Learning” and Physically Constrained Neural Networks to Derive Complex Glaciological Change Processes from Modern High-Resolution Satellite Imagery: Application of the GEOCLASS-Image System to Create VarioCNN for Glacier Surges

The objectives of this paper are to investigate the trade-offs between a physically constrained neural network and a deep, convolutional neural network and to design a combined ML approach (“VarioCNN”). Our solution is provided in the framework of a cyberinfrastructure that includes a +newly designed ML software, GEOCLASS-image (v1.0), modern high-resolution satellite image data sets (Maxar WorldView data), and instructions/descriptions that may facilitate solving similar spatial classification problems. Combining the advantages of the physically-driven connectionist-geostatistical classification method with those of an efficient CNN, VarioCNN provides a means for rapid and efficient extraction of complex geophysical information from submeter resolution satellite imagery. A retraining loop overcomes the difficulties of creating a labeled training data set. Computational analyses and developments are centered on a specific, but generalizable, geophysical problem: The classification of crevasse types that form during the surge of a glacier system. A surge is a glacial catastrophe, an acceleration of a glacier to typically 100–200 times its normal velocity. GEOCLASS-image is applied to study the current (2016-2024) surge in the Negribreen Glacier System, Svalbard. The geophysical result is a description of the structural evolution and expansion of the surge, based on crevasse types that capture ice deformation in six simplified classes.

A Comprehensive Examination of the Medvezhiy Glacier’s Surges in West Pamir (1968–2023)

The Vanj River Basin contains a dynamic glacier, the Medvezhiy glacier, which occasionally poses a danger to local residents due to its surging, flooding, and frequent blockages of the Abdukahor River, leading to intense glacial lake outburst floods (GLOF). This study offers a new perspective on the quantitative assessment of glacier surface velocities and associated lake changes during six surges from 1968 to 2023 by using time-series imagery (Corona, Hexagon, Landsat), SRTM elevation maps, ITS_LIVE, unmanned aerial vehicles, local climate, and glacier surface elevation changes. Six turbulent periods (1968, 1973, 1977, 1989–1990, 2001, and 2011) were investigated, each lasting three years within a 10–11-year cycle. During inactive phases, a reduction in the thickness of the glacier tongue in the ablation zone occurred. During a surge in 2011, the flow accelerated, creating an ice dam and conditions for GLOF. Using these datasets, we reconstructed the process of the Medvezhiy glacier surge with high detail and identified a clear signal of uplift in the surface above the lower glacier tongue as well as a uniform increase in velocities associated with the onset of the surge. The increased activity of the Medvezhiy glacier and seasonal fluctuations in surface runoff are closely linked to climatic factors throughout the surge phase, and recent UAV observations indicate the absence of GLOFs in the glacier’s channel. Comprehending the processes of glacier movements and related changes at a regional level is crucial for implementing more proactive measures and identifying appropriate strategies for mitigation.

Topography and accumulation rate as controls of asynchronous surging behaviour in the eastern and western branches of the Western Kunlun Glacier, Northwestern Tibetan Plateau

ABSTRACT The western Kunlun main peak region is among the areas in High Mountain Asia where surge-type glaciers are highly concentrated. Here, we analyse the surging characteristics of the eastern and western branches of the Western Kunlun Glacier and the factors controlling the asynchronous behaviour of their surges. The eastern branch entered an unstable state in 1999 and remained so until the culmination of its surge in the summer of 2019, spanning 21 years. Conversely, the surge of the western branch commenced in the summer of 2020. The surge duration for this glacier was four years, characterized by a rapid acceleration and deceleration process. Based on the glacier surge characteristics, we posit that western branch of Western Kunlun Glacier was influenced by hydrological mechanisms, while eastern branch was affected by subglacial thermal processes. These process intensifies crevasse formation on the glacial surface, providing conduits for surface meltwater to reach the glacier bed, thus elevating subglacial water pressure. The difference of subglacial hydrology and thermal processes caused by different subglacial topography and mass accumulation rates was the main factor of the asynchronous behaviour of the west and east branches of the West Kunlun glacier.

Dynamic change of a typical surging glacier in the Qinghai tibet plateau based on satellite remote sensing

With global climate change, some mountain glaciers in the Qinghai–Tibet Plateau region are experiencing rapid melting, retreating, and acceleration. Surge-type glaciers are important objects for glacier dynamics research in this region, as sudden surge may threaten human activities and lives. This study focuses on the Shahrek Glacier. Based on multi-source remote sensing images from 2000 to 2023, we generated long-term ice flow velocity maps of the glacier using image template matching technology. Together with its terminus position over this period, the surge dynamics of Shahrek Glacier were analyzed. The glacier surge commenced in September 2016 and terminated in November 2018, reaching a maximum ice velocity of almost 1,200 m/a, which is 9–10 times its ice velocity in the quiescent phase. A substantial change in the magnitude of the ice flow before and after the onset of the Shahrek Glacier surge was observed; the surge comprised five main phases: pre-surge stable, accelerated, surge, decelerated, and stabilized periods. The Shahrek Glacier was retreating from the position of the glacier-terminal ablation zone prior to the onset of leapfrogging. We analyzed the relationship between Shahrek Glacier dynamics and climate and the surge mechanism surge, considering data from meteorological stations in neighboring regions.

Monitoring dynamics of Kyagar Glacier surge and repeated draining of Ice-dammed lake using multi-source remote sensing

Glacier surges, a primary factor contributing to various glacial hazards, has long captivated the attention of the global glaciological community. This study delves into the dynamics of Kyagar Glacier surging and the associated drainage features of its Ice-dammed lake, employing high temporal resolution optical imagery. Our findings indicate that the surge on Kyagar Glacier began in late spring and early summer of 2014 and concluded during the summer of 2016. This surge resulted in the transfer of 0.321 ± 0.012 km3 of glacier mass from the reservoir zone to the receiving zone, leading to the formation of an ice-dammed lake at the glacier's terminus. The lake experienced five outbursts between 2015 and 2019, with the largest discharge occurring in 2017. And the maximum water depth during this period was 112 ± 11 m, resulting in a water storage volume of (158.37 ± 28.32) × 106 m3. On the other hand, our analysis of the relationship between glacier surface velocity and albedo, coupled with an examination of subglacial dynamics, revealed that increased precipitation during the active phase of the Kyagar Glacier results in accumulation of mass in the upper glacier. This accumulation induces changes in basal shear stress, triggering the glacier's transition into an unstable state. Consequently, glacier deformation rates escalate, surface crevasses proliferate, potentially providing conduits for surface meltwater to infiltrate the glacier bed. This, in turn, leaded to elevated basal water pressure, initiating glacier sliding. Furthermore, we postulated that the repetitive drainage of Kyagar Ice-dammed lake was primarily influenced by the opening and closing of subglacial drainage pathways and variations in inflow volumes. Future endeavors necessitate rigorous field observations to enhance glacier surge simulations, deepening our comprehension of glacier surge mechanisms and mitigating the impact of associated glacial hazards.

Hydrological control of the surging behaviour of the Ghujerab River Head Glacier, Karakoram (2019–2023): Insights from high-temporal-resolution remote sensing monitoring

Study regionThe northern region of the Karakoram Range. Study focusKarakoram is a region in High Mountain Asia with many surge-type glaciers. This study employed over 200 high-temporal-resolution remote sensing images and investigated the variations in elevation and velocity of the Ghujerab River Head Glacier (GRHG) from 2019 to 2023. Furthermore, we elucidated the potential controlling mechanisms. New hydrological insights for the regionOur findings revealed that the GRHG, akin to typical surge-type glaciers in Karakoram, started to surge in the spring and finished surging in the summer, with a duration of less than two years. Throughout the surging process, the glacier transferred a mass of 0.11±0.003 km³ from the reservoir area to the receiving area, resulting in a thickening of 91.59±1.04 m at the glacier terminus and thinning of 11.78±1.04 m in the upper glacier. By analysing the mass balance and glacier surface albedo during surging, we proposed that climatic disturbances in the glacier region provided essential material inputs for the surge. Additionally, based on the seasonal evolution pattern of glacier flow velocity, we inferred a close correlation between surging and variations in subglacial hydrology. The duration of acceleration and deceleration during glacier surging, as well as a comparison with existing studies, further support our conclusion. Future research integrating multi-source remote sensing and onsite observations can support numerical simulations to quantitatively reveal the key processes occurring beneath and within glaciers during surge events.

A high-resolution calving front data product for marine-terminating glaciers in Svalbard

Abstract. The mass loss of glaciers outside the polar ice sheets has been accelerating during the past several decades and has been contributing to global sea-level rise. However, many of the mechanisms of this mass loss process are not well understood, especially the calving dynamics of marine-terminating glaciers, in part due to a lack of high-resolution calving front observations. Svalbard is an ideal site to study the climate sensitivity of glaciers as it is a region that has been undergoing amplified climate variability in both space and time compared to the global mean. Here we present a new high-resolution calving front dataset of 149 marine-terminating glaciers in Svalbard, comprising 124 919 glacier calving front positions during the period 1985–2023 (https://doi.org/10.5281/zenodo.10407266, Li et al., 2023). This dataset was generated using a novel automated deep-learning framework and multiple optical and SAR satellite images from Landsat, Terra-ASTER, Sentinel-2, and Sentinel-1 satellite missions. The overall calving front mapping uncertainty across Svalbard is 31 m. The newly derived calving front dataset agrees well with recent decadal calving front observations between 2000 and 2020 (Kochtitzky and Copland, 2022) and an annual calving front dataset between 2008 and 2022 (Moholdt et al., 2022). The calving fronts between our product and the latter deviate by 32 ± 65 m on average. The R2 of the glacier calving front change rates between these two products is 0.98, indicating an excellent match. Using this new calving front dataset, we identified widespread calving front retreats during the past four decades, across most regions in Svalbard except for a handful of glaciers draining the ice caps Vestfonna and Austfonna on Nordaustlandet. In addition, we identified complex patterns of glacier surging events overlaid with seasonal calving cycles. These data and findings provide insights into understanding glacier calving mechanisms and drivers. This new dataset can help improve estimates of glacier frontal ablation as a component of the integrated mass balance of marine-terminating glaciers.

2000–2020年喀喇昆仑山洪扎河流域冰川高程变化数据集

Under the influence of climate warming, glaciers in High Mountain Asia (HMA) have undergone significant recession in recent decades. However, stable or even positive glacier mass budgets have been found in the Karakoram Mountains in the past decades, which is termed as “Karakoram anomaly”. The Hunza Basin, located in the western Karakoram, is a region with concentrated glacier development along the Sino-Pakistan Economic Corridor. The glacier mass balance in Hunza Basin plays an important role in water resource utilization and infrastructure construction. In this study, we used the SRTM DEM (2000) and ZY3-02 stereo images (2020) to obtain the glacier height changes in the Hunza Basin by employing the method of Geodetic (GeoTIFF format with a resolution of 30 m). This study covers an area of around 7600 km2, within the spatial extent of 36°N–37°N, 74°E–76°E. The statistical analysis of the residual movement in the non-glacial region indicates an overall accuracy of about 1.1 m. The findings suggest that glaciers experienced a moderate thinning during the early 21st century, with significant spatial variations. Factors such as debris cover, crevasses, supraglacial lake, ice cliff and glacier surge have distinct influences on glacier height changes. This dataset can be used as basic data for the research on glacier mass balance in the Karakoram, as well as water resources utilization, glacier disaster warning and climate change in the Sino-Pakistan Economic Corridor.

Application of a structured decision‐making process in cryospheric hazard planning: Case study of Bering Glacier surges on local state planning in Alaska

AbstractSurging glaciers are glaciers that experience rapidly accelerated glacier flow over a comparatively short period of time. Though relatively rare worldwide, Alaska is home to the largest number of surge‐type glaciers globally. However, their impact on the broader socioecological system in the state is both poorly understood and under‐researched, which poses a challenge in developing appropriate sustainability decisions in Alaska. We investigated how the surge patterns of the Bering Glacier in Alaska have potentially devastating effects on the local ecological biodiversity of its watershed via a structured decision‐making analysis of the different possible consequences. Specifically, this analysis was conducted to explore the various outcomes of a Bering Glacier surge particularly if humans have an increased presence near the glacier due to the area potentially becoming a state park. This work explored the benefits of applying a risk and decision analytical framework in a cryosphere context, to better understand the socioeconomic impact of glacier surges. This is a novel approach in which a decision analysis tool was used to better understand an environmental sustainability challenge, offering an innovative method to support the achievement of the United Nations Sustainability Development Goals in Alaska. We therefore emphasise the need for integrated biophysical and socioeconomic analyses when it comes to understanding glacier hazards. Our research highlights the importance of understanding and researching biophysical changes as well as using a structured decision‐making process for complicated hazard planning scenarios, exemplified via glaciated regions in Alaska, in order to create adaptation strategies that are sustainable and encompass the range of possible outcomes.

Three Pleistocene glacial advances and a warm episode during MIS-3: Towards a more complete glacial history of the Pamir mountains

Determining the spatial and temporal variations of Pleistocene glaciations is key to understanding present-day climate-driven glacier changes. Glacial chronologies of high-mountain Asia, which are mostly based on cosmogenic 10Be exposure dating of moraine boulders, remain scarce and often inaccurate due to geologically induced age scatter. We present 53 new 10Be exposure ages from rockslides, glacial sediment deposits and glacial erosion surfaces in the southwestern Pamir. In conjunction with previously published 10Be data, we constrain the timing and extent of three major glacial stages in the Pamir. During the Middle Pleistocene, a continuous ice sheet covered most of the Pamir. This stage is older than 200 ka and may have occurred during Marine Isotope Stages (MIS) 8, 10, or 12. The deep valleys of the western Pamir, which contrast with the eastern Pamir plateau, are partly attributed to Middle Pleistocene glacial erosion. Successively less extensive glacial advances occurred during MIS-4/5 (between 60 and 100 ka ago) and during MIS-2 (at 18–22 ka). The last glacial maximum was synchronous in most of the Pamir, except for prolonged glaciation of the Muztagh Ata ice cap until 14 ka ago. Similar to today, Late Pleistocene glaciers were precipitation-limited, with moisture mainly supplied by westerly winds. An episode of increased mass wasting (e.g. Zuvor rockslide: 34 ± 1 ka) and glacier surging correlates with a peak in δ18O values in the Guliya ice core and is attributed to a warmer climate.

A Review of Karakoram Glacier Anomalies in High Mountains Asia

Influenced by global warming, glaciers in High Mountains Asia (HMA) generally show a trend of retreat and thinning, but in Karakoram, Pamir, and West Kunlun there is a trend of glacier stabilization or even a weak advance. In this study, using a bibliometric analysis, we systematically sorted the area, mass balance, and elevation changes of the glaciers in Karakoram and summarized the glacier surges in HMA. The study shows that, since the 1970s, the glaciers in the Karakoram region have experienced a weak positive mass balance, with weakly reducing area and the increasing surface elevation. The north slope of Chogori Peak and the Keltsing River Basin presented a glacier retreat rate with a fast to slow trend. The anomaly is mainly due to low summer temperatures and heavy precipitation in winter and spring in the Karakoram region. There are a large number of surging glaciers in the Karakoram Mountains, the Pamir Plateau, and the West Kunlun region in the western part of HMA, especially in the Karakoram Mountains and the Pamir Plateau, which account for more than 70% of the number of surging glaciers in the entire HMA. The glaciers in the Karakoram and Kunlun Mountains are mainly affected by the synergistic influence of various factors, such as hydrothermal conditions, atmospheric circulation, and topography. However, the glaciers in the Pamir region are mainly influenced by the thermal mechanism of the glacier surge. The glaciers in and around Karakoram are critical to the hydrological response to climate change, and glacial meltwater is an important freshwater resource in arid and semi-arid regions of South and Central Asia, as well as in western China. Therefore, changes in the Karakoram anomaly will remain a hot research topic in the future.

Triggers for multiple glacier detachments from a low-angle valley glacier in the Amney Machen Range, eastern Tibetan Plateau

Large-scale ice avalanches initiated from low-angle glaciers (also known as glacier detachment) remain a scarcely studied and poorly understood phenomenon. Here we re-evaluated the repeat glacier detachments of a low angle (~14°) surging valley glacier in the Amney Machen Range, eastern Tibetan Plateau. Four glacier detachments recorded over a 15-year period (2004–2019) are described in detail based on the combination of satellite image analyses, additional terrain profile analyses and field data. To identify what triggered these high magnitude events, the glacier fluctuations, seismicity, lithology, and regional climate were examined. We find that the factors favouring glacier detachments were anomalous warming, subglacial hydrology, repeated glacier surging, a soft glacier bed, and ice-rock loading from the glacier headwall, though the relative influence of each factor varied in the four events we studied. We confirmed the observation of Paul (2019) that additional ice-rock debris loadings from the headwall were the most important factor for all events. The 2004 event probably was a delayed response to ice-rock loading during the preceding months. The latter three events may have been affected by short-term climate anomalies. The events of 2007 and 2016 were associated with anomalously high temperature: abrupt warming preceded the 2007 event and 2016 was the warmest year on record. The 2019 event followed sustained precipitation and high summer temperatures. Based on the spatial patterns in glacier change, we suggest that climate warming played a limited role in initiation.

A new inventory of High Mountain Asia surging glaciers derived from multiple elevation datasets since the 1970s

Abstract. Glacier surging is an unusual instability of ice flow, and inventories of surging glaciers are important for regional glacier mass balance studies and glacier dynamic studies. Glacier surges in High Mountain Asia (HMA) have been widely reported. However, the completeness of available inventories of HMA surging glaciers is hampered by the insufficient spatial and temporal coverage of glacier change observations or by the limitations of the identification methods. In this study, we established a new inventory of HMA surging glaciers based on glacier surface elevation changes and morphological changes over 4 decades. Three elevation change datasets based on four elevation sources (the KH-9 DEM, NASA DEM, COP30 DEM, and HMA DEM) and long-term Landsat satellite image series were utilized to assess the presence of typical surge features over two time periods (1970s–2000 and 2000–2020). A total of 890 surging and 336 probably or possibly surging glaciers were identified in HMA. Compared to the most recent inventory of surging glaciers in HMA, our inventory incorporated 253 previously unidentified surging glaciers. The number and area of surging glaciers accounted for ∼2.49 % (excluding glaciers smaller than 0.4 km2) and ∼16.59 % of the total glacier number and glacier area in HMA, respectively. Glacier surges were found in 21 of the 22 subregions of HMA (except for the Dzhungarsky Alatau); however, the density of surging glaciers is highly uneven. Glacier surges occur frequently in the northwestern subregions (e.g., Pamir and Karakoram) but less often in the peripheral subregions. The inventory further shows that surge activity is more likely to occur for glaciers with a larger area, longer length, and wider elevation range. Among glaciers with similar areas, the surging ones usually have steeper slopes than non-surging ones. The inventory and elevation change products of identified surging glaciers are available at https://doi.org/10.5281/zenodo.7961207 (Guo et al., 2023).

Mountain Glacier Flow Velocity Retrieval from Ascending and Descending Sentinel-1 Data Using the Offset Tracking and MSBAS Technique: A Case Study of the Siachen Glacier in Karakoram from 2017 to 2021

Synthetic Aperture Radar images have recently been utilized in glacier surface flow velocity research due to their continuously improving imaging technology, which increases the resolution and scope of research. In this study, we employed the offset tracking and multidimensional small baseline subset (MSBAS) technique to extract the surface flow velocity of the Siachen Glacier from 253 Sentinel-1 images. From 2017 to 2021, the Siachen Glacier had an average flow velocity of 38.25 m a−1, with the highest flow velocity of 353.35 m a−1 located in the upper part of a tributary due to the steep slope and narrow valley. The inter-annual flow velocity fluctuations show visible seasonal patterns, with the highest flow velocity observed between May and July and the lowest between December and January. Mass balance calculated by the geodetic method based on AST14DEM indicates that the Siachen Glacier experienced a positive mass change (0.07 ± 0.23 m w.e. a−1) between 2008 and 2021. However, there was significant spatial heterogeneity revealed in the distribution, with surface elevation changes showing a decrease in the glacier tongue while thickness increased in two other western tributaries of the Siachen Glacier. The non-surface parallel flow component is correlated with the strain rate and mass balance process, and correlation analysis indicates a positive agreement between these two variables. Therefore, using glacier flow velocities obtained from the SAR approach, we can evaluate the health of the glacier and obtain crucial factors for the glacier’s dynamic model. Two western tributaries of the Siachen Glacier experienced mass gain in the past two decades, necessitating close monitoring of flow velocity changes in the future to detect potential glacier surges.

Characterization of Three Surges of the Kyagar Glacier, Karakoram

Glaciers experience periodic variations in flow velocity called surges, each of which influences the glacier’s characteristics and the occurrence of downstream disasters (e.g., ice-dammed lake outburst floods). The Karakoram region contains many surging glaciers, yet there are few comprehensive studies of multiple surge cycles. In this work, Landsat, topographic map, Shuttle Radar Topography Mission (SRTM), TerraSAR-X/TanDEM-X, ITS_LIVE, and Sentinel-1 glacier velocity data were used to systematically analyze the characteristics of Kyagar Glacier since the 1970s. Three surging events were identified, with active phases in 1975–1978, 1995–1997, and 2014–2016. The timing of these surges was similar, with a cycle of 19–20 years, an active phase of 3–4 years, and a quiescent phase of 16–17 years. During the quiescent phase, a large amount of ice accumulates in the lower part of the accumulation zone, and the terminal of the tongue thins significantly. According to the most recent surge event (2014–2016), glacier flow accelerated suddenly in the active phase and reached a maximum velocity of 2 ± 0.08 m d−1. Then, the glacier terminal thickened sharply, the reservoir zone thinned by 12 ± 0.2 m, and the terminal receiving zone thickened by 28 ± 0.2 m. The glacier may have entered a quiescent phase after July 2016. The glacier surge causes a large amount of material to transfer from upstream to downstream, forming an ice dam and creating conditions for a glacial lake outburst flood (GLOF). At the termination of the active phase, the subglacial drainage channel became effective, triggering the GLOF. For a period of the quiescent phase, the glacier ablation intensifies and the GLOF repeats constantly. One surge caused 7–8 GLOFs, and then a continuous reduction in the ice dam elevation. Eventually, the ice dam disappeared, and the GLOF no longer continued before the next glacier-surging event.