Glacier Surface Velocity Research Articles

Spatiotemporal variability in surface velocity of large tributary-bearing glaciers of the Indian Himalayas inferred from SAR polarimetry

ABSTRACT Glacier pattern changes directly indicate variability in local climatic circumstances. The present study dealt with the proposition and estimation of spatiotemporal glacier movement using a synthetic aperture radar-derived polarimetric tracking method which revealed improved estimates over four selected large tributary-bearing glaciers (Siachen, Bara Shigri, Gangotri, and Zemu) in the Indian Himalayas. The average estimated velocities in 2021–2022 for the four glaciers were 0.13, 0.06, 0.08 and 0.09 m/day. The thick debris cover hindered the movement temporally in the middle and lower reaches of the glaciers. The effect of meltwater influx along the tributary confluence zone was also witnessed over the glaciers. Comparison and validation with the US National Aeronautics and Space Administration (NASA) Inter-mission Time Series of Land Ice Velocity and Elevation (ITS_LIVE) products has shown the utility of the proposed method in studying the contributions of active feeding tributaries of the glaciers in the ablation zone.

The velocity extraction and feature analysis of glacier surface motion in the Gongar region based on multi-source remote sensing data

The movement of glaciers plays a crucial role in environmental and geological processes, significantly influencing the formation and dynamics of ice bodies. This study leverages feature tracking technology to analyze optical and Synthetic Aperture Radar (SAR) remote sensing imagery, specifically GF-1 optical images and GF-3, Sentinel-1 SAR images, captured during the 2020 to 2021 ablation season in Gongar. The aim was to quantify glacier surface velocities and to evaluate the comparative effectiveness of different remote sensing modalities in capturing these dynamics. Our findings indicate a strong consistency in the spatial distribution of glacier surface velocities derived from diverse remote sensing data sources, with high-precision optical imagery (GF-1) yielding the most accurate velocity measurements, followed by Sentinel-1 SAR data. Notably, large glaciers in Gongar exhibited rapid movements, with an average velocity of 0.16 m/d, primarily at elevations between 4,500 and 6,500 m. The fastest velocities were recorded at approximately 4,500 m elevation. Glaciers with inclines ranging from 10° to 60° displayed the highest velocities within the 20°–30° slope range. It was observed that glaciers on the southeast slope moved faster, exhibiting the highest average surface velocity, in contrast to those on the west slope, which moved more slowly. The surface velocity of the ice tongue region of Krayaylak Glacier that the largest glacier in Pamir, was observed to be lower than 0.6 m/d, indicating a slow movement speed. The study also reveals that the effectiveness of different remote sensing data in detecting glacier velocity in Gongar, with high-resolution data more accurately capturing surface velocities in melting areas or those with slower movement. This study underscores the importance of multi-source remote sensing data in understanding glacier dynamics and contributes valuable insights into the mechanisms driving glacier movements.

Repeat pass imaging-based velocity estimation of Siachen glacier in J&K Himalaya using Sentinel-2 and Landsat-8 data: A comparison with SAR observations

In this study optical data from satellites Sentinel-2 (S-2), Landsat-8 (L-8), and synthetic aperture radar (SAR) data from Sentinel-1(S-1) have been used to estimate the surface velocity of the Siachen Glacier in J&K Himalaya. Repeat-pass optical and SAR data have been processed employing sub-pixel offset tracking (SOT) approach to decipher surface velocity of glaciers during 2013–2018. It is observed that SOT derived 2-D surface velocity using S-2 and L-8 data pairs show more than 70 % correlation over the entire stretch of the glacier. High correlation among velocities from S-2 and L-8 over two years validates one sensor against another for glacier surface movement studies in the Himalaya. This study reveals that the velocity of the glacier varies from ∼120 ma−1 to ∼151 ma−1 during 2013–2018. This study results the movement of glacier using optical sensor and SAR sensor over same geographical zone and similar time zone to evaluate the feature extraction and sensor impact on feature extraction. We have found that all sensors have produced similar results, since data is collected near time frame.

Inferring glacier mass balance from Sentinel-1 derived ice thickness changes using geoinformatics: A case study of Gangotri glacier, Uttarakhand, India

All glaciers respond to climatic changes by fluctuating their mass. Investigations of glacier dynamics are necessary for glacier monitoring. Himalayan glaciers make ongoing glacier observations challenging due to their location in a severe topographic environment and inhospitable terrain. Glacier area contraction or extension, together with a corresponding snout shift, can be linked to oscillations in glacier mass. Sentinel-1 dual-polarized datasets were used in this investigation to retrieve glacier surface velocity. Estimates of ice thickness were enhanced by segmenting the glacier into 100-m height intervals. Also, ice thickness variations between 2017 and 2022 have been used to compute glacier mass balance, and the results for several glacier zones have been briefly analyzed. The study revealed that the maximum surface velocity above Gangotri Glacier was approximately 0.33 m/day, with an estimated average of 0.09 m/day. Surface velocities of the central trunk have been seen to range from 0.12 m/day to 0.23 m/day. Additionally, between 2017 and 2022, the surface velocity was spotted between 0.19 m/day to 0.35 m/day. For the glacier, an average ice thickness of 189 ± 17.01 m was calculated. In the central parts, where the drag was least noticeable, thicknesses up to 587 ± 52.83 m were estimated. In the lower accumulation zone and middle reaches, the thickness was found to be decreasing between 2017 and 2022, which can be attributed to increased melting and glacier slowdown. Due to the increased glacier movement throughout time, the lower accumulation reaches over the main glacier body, and its tributaries have experienced mass balancing rates ranging from −1.3 m.w.e./year to −0.5 m.w.e./year (thickness change between −3 m/year and −0.6 m/year). With the help of previous research and existing data, the results were compared and validated. The suggested algorithm and findings can serve as inputs for satellite-based ice thickness measurements and as fundamental research for the forthcoming NISAR mission (expected by mid-2024) which will carry L- and S-band antennas.

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.

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.

Rock glacier distribution and kinematics in Shigar and Shayok basins based on radar and optical remote sensing

AbstractRecent studies have demonstrated the rock glacier destabilisation and permafrost thawing induced by warming climate represent a continuous threat to life, infrastructure and socio‐economic development in the mountainous regions of the Hindu Kush Himalaya. This study presents the first systematic rock glacier inventory for the Shigar and Shayok basins, quantifying rock glacier geomorphology and kinematics based on morphological evidence using Google Earth images and interferometric synthetic aperture radar (InSAR). The certainty index of each inventoried rock glacier is recorded, along with its geomorphological properties and kinematic attributes. The rock glacier velocity is estimated through the InSAR time series analysis of Sentinel‐1 images from 2020 to 2021, with temporal baselines at 12‐day intervals. We developed a rock glacier inventory consisting of 84 rock glaciers covering an area of 29 km2 for the Shigar Basin and 2206 rock glaciers encompassing 369 km2 for the Shayok Basin. Among these rock glaciers, 69% and 52% are categorised as active rock glaciers, respectively. Rock glaciers in both catchments are confined to elevations between 3600 and 5875 m a.s.l., with a mean area of 0.22 km2. The maximum recorded velocity for active rock glaciers in the Shigar Basin is 101 ± 9 cm year−1, with a median of 27 ± 10 cm year−1, and in the Shayok Basin 114 ± 10 cm year−1 (median of 29 ± 9 cm year−1). Temporal variations in the surface velocities of the rock glaciers reveal that they increase with rising temperatures in both catchments, highlighting the seasonality in the rock glacier surface velocity. In total, we recorded the kinematic attributes of 98% of the inventoried rock glaciers in the study area.

Deformation, Strength and Tectonic Evolution of Basal Ice in Taylor Glacier, Antarctica

AbstractObservation and measurements of ice structure and deformation made in tunnels excavated into the margin of Taylor Glacier, a polythermal glacier in the McMurdo Dry Valleys of Antarctica, reveal a complex, rapidly deforming basal ice sequence. Displacement measurements in the basal ice, which is at a temperature of −18°C, together with the occurrence of cavities and slickenslides, suggest that sliding or rapid deformation in thin zones of high shear occurs at structural discontinuities within the basal zone. Strain measurements show that the highest strain rates occur in ice with average debris concentrations of 26% followed by ice with debris concentrations of around 12%. The lowest strain rates occur in clean bubbly ice that has very low debris concentrations (<0.02%). Deformation within the basal ice sequence is dominated by simple shear but disrupted by folding which results in shortening of the debris‐bearing ice followed by attenuation of the folds due to progressive simple shear which generates predominantly laminar basal ice structures. About 60% of glacier surface velocity can be attributed to deformation within the 4.5 m thick sequence of basal ice that was monitored for this study, and 15% of motion can be attributed to sliding or very localized shear. The combination of high debris concentrations and high strain rates in the debris‐bearing ice results in high rates of abrasion and the production of striated and facetted clasts typical of temperate glaciers, even though the basal ice is at a temperature of −18°C.

Spatiotemporal variations in glacier area and surface velocity of the northern Antarctic Peninsula during 2018–2022

Ice sheet serves as a crucial indicator for assessing climate change. Mass loss in recent remote sensing-based studies indicated that the Antarctic Peninsula has rapid rates of glacier retreat and speed up of surface velocity. However, observations of seasonal variability of ice speed are limited, and glacier-area changes require multi-temporal monitoring. This study investigated the changes in area and surface velocities of ∼375 glaciers on the northern Antarctic Peninsula (NAP) utilizing satellite images acquired by the Sentinel 1&2 satellites during 2018–2022. The results indicate that the glacier area reduced by approximately 166.1 ± 44.2 km2 (−0.2% ± 0.1% per year) during the study period, with an acceleration after 2020 (−0.4% ± 0.3% per year), and the most dramatic reduction happened on the eastern NAP. The maximum annual ice speeds on the NAP generally exceeded 3500 m per year, while the ice speeds in 2021 were the highest (exceeded 4210 m per year). The ice speed variability in austral autumn was higher than in other seasons, meanwhile the summer ice speeds showed an increasing trend. The glacier G012158E47018N, McNeile Glacier, glacier G299637E64094S and Drygalski Glacier showed the most remarkable ice speed variations represented by high daily velocities and strong fluctuations on their termini. Our results demonstrated that the variations in glacier area and seasonal ice speed on the NAP were responsive to the ice–ocean–atmosphere processes. Therefore, seasonal velocity and area variations should be considered when conducting accurate mass balance calculations, model validations and change mechanism analyses under climate warming scenarios.

Deep Learning Low-cost Photogrammetry for 4D Short-term Glacier Dynamics Monitoring

AbstractShort-term monitoring of alpine glaciers is crucial to understand their response to climate change. This paper presents a low-cost multi-camera system tailored for 4D glacier monitoring using deep learning stereo-photogrammetry. Our approach integrates multi-temporal 3D reconstruction from stereo cameras and surface velocity estimation from a monoscopic camera through digital image correlation. To address the challenges posed by wide camera baselines in complex environments, we have integrated state-of-the-art deep learning feature matching algorithms into ICEpy4D, a Python toolkit designed for 4D monitoring (https://github.com/franioli/icepy4d). In a pilot study conducted on the debris-covered Belvedere Glacier (Italian Alps), our stereoscopic setup, with a camera base–height ratio close to one, captured daily images from May to November 2022. Our approach utilized SuperPoint and SuperGlue for feature matching, resulting in a daily 3D reconstruction of the glacier terminus, as traditional SIFT-like feature matching fails in this scenario. Using dense point clouds with decimetric accuracy, we estimated daily ice volume loss and glacier retreat at the terminus. The total ice volume loss was $$63\,000\,\text{m}$$ 63 000 m $${}^{3}$$ 3 and the retreat was $$17.8\,\text{m}$$ 17.8 m . Surface kinematics revealed three times higher surface velocity during the warm season (May–September) than in the fall (September–November). Daily analyses revealed a significant short-term correlation between air temperature, glacier surface velocity and ice ablation, providing insight into the glacier’s response to external forces. The low cost and ease of deployment of the proposed system facilitates replication at other sites for short-term monitoring of glacier dynamics.

Multidecadal Changes in the Flow Velocity and Mass Balance of the Hailuogou Glacier in Mount Gongga, Southeastern Tibetan Plateau

Maritime glaciers in the southeastern Tibetan Plateau (TP) have experienced important changes in mass and dynamics over the past decades, challenging the regional water supply and glacier-related hazards. However, knowledge about long-term variations in the surface velocity and mass balance of maritime glaciers remains incomplete due to the lack of representative observations in the southeastern TP. In this study, offset tracking is employed to measure spatiotemporal variation in the surface velocity of the Hailuogou Glacier (HLG) in Mount Gongga of the southeastern TP using Sentinel-1A imagery, while the time series of the HLG mass balance is reconstructed since 1950 by a physically based energy–mass balance model. Our satellite-based results find that HLG surface velocity shows significant spatial heterogeneity with a double-peak pattern along the flow line, and sustained slowdown below the icefall zone has been observed during the past nearly 40 years, although the icefall zone and the area above it have become relatively active. Our modeling indicates a persistent increase in mass loss over the last seven decades with an average rate of −0.58 m water equivalent (w.e.) year−1, which has accelerated in the past two decades. Sustained slowdown on the glacier is concomitant with pronounced negative mass balance, thereby enhancing glacier wastage in recent decades. The long-term trend in HLG mass loss is mainly driven by an increase in positive air temperature that decreases surface albedo and solid precipitation ratio and increases longwave incoming radiation, besides the influence of supraglacial debris cover. Large-scale atmospheric circulation patterns in the Eurasian region provide important implications for regional-to-local climate variability, unsustainably intensifying the trend of the negative mass balance of the HLG in the southeastern TP in the past two decades.

Proglacial lake evolution coincident with glacier dynamics in the frontal zone of Kvíárjökull, South‐East Iceland

AbstractThe termini of Icelandic glaciers are highly dynamic environments. Pronounced changes in frontal ablation in recent years have consequently changed ice dynamics. In this study, we reveal the inter‐seasonal dynamics of the Kvíárjökull ablation zone and proglacial zone using ArcticDEM and Sentinel‐2 images acquired between 2011 and 2021 and intra‐seasonal dynamics with repeated UAV surveys during summer 2021. Average glacier surface velocity in the ablation zone ranged from 51 m year−1 in 2015 up to 199 m year−1 in 2018, with maxima within the axial zone of the glacier and minima on the glacier edges. Coincidentally, and in accordance with glacier retreat/advance, the ice‐marginal proglacial lake fluctuated in its area, and we interpret that it was also a key factor in the development of the glacier terminus morphology. A complex spatial pattern of glacier surface elevation changes, including thickening in the frontal true left margin of the terminus, is interpreted to be due to variable subglacial topography, relatively fast ice flow from the accumulation zone and an insulating effect of glacier surface debris cover. In contrast, the true right (southern) part of the glacier terminus experienced thinning and retreat/disintegration also during the 2021 summer season, which we attribute to enhanced frontal ablation connected to the intrusion of lake water into the crevassed glacier terminus. Overall, this study suggests that where glaciers are developing ice‐marginal lakes complex patterns of glacier dynamics and mass loss can be expected, which will confound understanding of the short‐term evolution of these environments.

1990–2018年干城章嘉流域冰川物质平衡序列模拟数据集

As a result of climate change, the global glacier shrinkage was observed, and glaciers of different types have experienced distinct changes in their mass budgets. Debris-covered and/or lake-terminating glaciers have been identified in the Kanchenjunga Basin, and the dataset of their mass balance on a long-term scale could provide an important basic data for studies of specific responses of glaciers of various types to climate change. Using the rectified China Meteorological Forcing Dataset, we reconstructed the daily mass balance of glaciers in the Kanchenjunga Basin from 1990 to 2018 through the application of a surface energy balance model. We used a glacier elevation change dataset obtained through geodetic methods to validate the model estimation results, and the results align closely with previously published research results on a multi-year scale. We extracted the surface velocities of glaciers from 1989 to 2018 from the ITS_LIVE dataset and assessed their precision based on the statistical characteristics of the surface movements in the glacier-free regions. This dataset is expected to provide basic data for the studies of the responses of glaciers with different types to climate change, and can also offer valuable references for the studies of glacial hydrological effects and disasters.

Glacier Surface Velocity Variations in the West Kunlun Mts. with Sentinel-1A Image Feature-Tracking (2014–2023)

Glacier velocity is a crucial parameter in understanding glacier dynamics and mass balance, especially in response to climate change. Despite numerous studies on glaciers in the West Kunlun Mts., there is still insufficient knowledge about the details of inter- and intra-annual velocity changes under global warming. This study analyzed the glacier velocity changes in the West Kunlun Mts. using Sentinel-1A satellite data. Our results revealed that: (1) The velocity of glaciers across the region shows an increasing trend from 2014 to 2023. (2) Five glaciers were found to have been surged during the study period, among which two of them were not reported before. (3) The surges in the study region were potentially controlled through a combination of hydrological and thermal mechanisms. (4) The glacier N2, Duofeng Glacier, and b2 of Kunlun Glacier exhibit higher annual velocities (32.82 m a−1) compared to surging glaciers in quiescent phases (13.22 m a−1), and were speculated as advancing or fast-flowing glaciers.

Glacier slowdown and rapid ice loss in the Tinguiririca and Cachapoal Basin, Central Andes of Chile

The central region of Chile is home to nearly 10 million people, 60% of the country's population. This area's water supply is reliant on glacial meltwater from the Andes, especially during the dry summer months. However, the current ice volumes and rates of ice loss remain uncertain in many glacierized Andean basins. Our study investigated the dynamics of glaciers located in the high-altitude Tinguiririca and Cachapoal Basin over the period 2016–2022, by measuring their surface velocity and inverting for changes in ice thickness. We measured the glacier surface velocities using the Glacier Image Velocimetry toolbox on Sentinel 2 images, merging over 6000 individual velocity measurements into median annual velocity maps. We then used ice velocities as input for ice-thickness inversions to calculate ice-thickness maps and ice volumes using an ensemble of four different methods. We detect a decrease in surface velocity from 2016 to 2022 on the Universidad, Cortaderal, Norte Cipreses glaciers and southern part of the Palomo glacier, while the Cipreses glacier and the northern part of the Palomo glacier showed a decrease in velocity between 2016 and 2021 and then an acceleration in 2022. Ice thickness data shows an ice volume loss of between 0.34 ± 0.22 and 0.43 ± 0.18 km3/yr depending on the method used, equivalent to ∼25% of the total ice volume lost from 2016 to 2022. The current rates of ice volume loss are unsustainable beyond the next two decades, reducing or entirely removing the glacial contribution to streamflow and increasing pressure on local water resources.

Thinning and surface mass balance patterns of two neighbouring debris-covered glaciers in the southeastern Tibetan Plateau

Abstract. Debris-covered glaciers are a common feature of the mountain cryosphere in the southeastern Tibetan Plateau. A better understanding of these glaciers is necessary to reduce the uncertainties in regional water resource variability and to anticipate potential cryospheric risks. In this study, we quantified the seasonal thinning and surface mass balance patterns of two neighbouring debris-covered glaciers (23K Glacier and 24K Glacier) in the southeastern Tibetan Plateau with four unpiloted aerial vehicle surveys and in situ measurements. We observed that the thinning of 23K Glacier was ∼2–7 times greater than that of the 24K Glacier for annual and cold periods. The surface velocity of the 24K Glacier is higher than that of the 23K Glacier (∼5–6 times) for all periods. In contrast with the thinning patterns, the surface mass balance patterns of the two glaciers closely agree across the different periods. We found that the surface mass balance distribution strongly correlated with the spatial distribution of debris thickness for both glaciers. Ice cliffs and supraglacial ponds are prevalent on the surface of these glaciers (∼4.4–7.2±0.5 %) and enhance melt overall (enhancement factor: ∼2.5) but do not control the surface mass balance pattern of either glacier. This comparison study of two neighbouring glaciers confirms the significance of both glacier dynamics and debris thickness in controlling thinning and melt for the different debris-covered glaciers of the southeastern Tibetan Plateau in the context of climate change.

Surface Displacement of Hurd Rock Glacier from 1956 to 2019 from Historical Aerial Frames and Satellite Imagery (Livingston Island, Antarctic Peninsula)

In the second half of the 20th century, the western Antarctic Peninsula recorded the highest mean annual air temperature rise in the Antarctic. The South Shetland Islands are located about 100 km northwest of the Antarctic Peninsula. The mean annual air temperature at sea level in this Maritime Antarctic region is close to −2 °C and, therefore, very sensitive to permafrost degradation following atmospheric warming. Among geomorphological indicators of permafrost are rock glaciers found below steep slopes as a consequence of permafrost creep, but with surficial movement also generated by solifluction and shallow landslides of rock debris and finer sediments. Rock glacier surface velocity is a new essential climate variable parameter by the Global Climate Observing System, and its historical analysis allows insight into past permafrost behavior. Recovery of 1950s aerial image stereo-pairs and structure-from-motion processing, together with the analysis of QuickBird 2007 and Pleiades 2019 high-resolution satellite imagery, allowed inferring displacements of the Hurd rock glacier using compression ridge-and-furrow morphology analysis over 60 years. Displacements measured on the rock glacier surface from 1956 until 2019 were from 7.5 m to 22.5 m and surface velocity of 12 cm/year to 36 cm/year, measured on orthographic images, with combined deviation root-mean-square of 2.5 m and 2.4 m in easting and northing. The inferred surface velocity also provides a baseline reference to assess today’s displacements. The results show patterns of the Hurd rock glacier displacement velocity, which are analogous to those reported within the last decade, without being possible to assess any displacement acceleration.

The Formation of an Ice-Contact Proglacial Lake and Its Impact on Glacier Change: A Case Study of the Tanymas Lake and Fedchenko Glacier

Lake-terminating glaciers have some peculiar behaviors compared to land-terminating glaciers, but in-depth observation is still limited regarding their formation, which is crucial for understanding the glacier–lake interaction. Here, the long-term evolutions of Tanymas Lake and the Fedchenko Glacier were investigated based on Landsat images, Google Earth imagery, KH-9 images, glacier surface elevation and velocity change datasets, and meteorological records. The results indicate that Tanymas Lake is both an ice-contact proglacial lake and an ice-dammed lake. It covered an area of 1.10 km2 in September 2022, and it is one of the largest glacial lakes in Pamir and even in HMA. The initial basin of Tanymas Lake is a moraine depression in Tanymas Pass, and the blocked dam is the Tanymas-5 Glacier and its terminal moraine. Tanymas Lake was in an embryonic stage before August 2005, in a formation and expansion stage from August 2005 to September 2018, and in a new expansion stage after September 2018. In this process, the Tanymas terminus of the Fedchenko Glacier also transformed from a land terminus to a partial lake terminus, and then to a complete lake terminus. The formation of Tanymas Lake is associated with the accumulation of glacial meltwater and the blockage of drainage, while the slow expansion of Tanymas Lake is related to the cold climate and slight glacier mass loss of Central Pamir. In the coming decades, with the accelerated mass loss of the Tanymas terminus of the Fedchenko Glacier, the area, depth, and water storage of Tanymas Lake will continue to increase, accompanied by the growing GLOF risk.

Seven-year variation in glacier surface velocity at Narsap Sermia in Southwest Greenland

ABSTRACT Glacier velocity is a critical factor closely related to ice dynamics of the Greenland ice sheet (GrIS). We present variations of ice velocity using space-based synthetic aperture radar (SAR) observations from July 2013 to September 2020. We focus on a tidewater outlet glacier of Narsap Sermia (NS), located in southwest Greenland, which is experiencing significant ice loss. A time series of high spatiotemporal resolution maps of ice velocity was traced by using an offset tracking approach with seven-year SAR acquisitions to understand glacier dynamics in time. We observed seasonal variations showing a dramatic increase in late spring (May) and early summer (June) followed by a sharp decrease in late summer (September). The seasonal variation was confirmed through Seasonal and Trend decomposition using Loess (STL) analysis. Overall, the NS glacier experienced a gradual speed-up of ice velocities. The ice velocity increased by 0.1–0.3 km/year from 2015 to 2017, then after a temporary decrease in 2018, the velocity moved faster by 0.9 km/year in 2020. The speed of glacier movement accelerated as it approached the tidal terminus of the glacier, showing approximately 6.0 km/year in 2020. The ice speed in 2020 increased by 0.9 km/year at the terminus region compared with 2014. We also discuss the relationship between the glacier velocity and temperature data such as air, land surface, and sea surface temperatures.

Glaciological and climatological drivers of heterogeneous glacier mass loss in the Tanggula Shan (Central-Eastern Tibetan Plateau), since the 1960s

AbstractDespite their extreme elevation, glaciers on the Tibetan Plateau are losing mass in response to atmospheric warming, the pattern of which purportedly reflects regional contrasts in climate. Here we examine the evolution of glaciers along ~500 km of the Tanggula Shan, Central-Eastern Tibetan Plateau. Using remotely sensed datasets, we quantified changes in glacier mass, area and surface velocity, and compared these results to time series of meteorological observations, in order to disentangle drivers of glacier mass loss since the 1960s. Glacier mass loss has increased (from −0.21 ± 0.12 m w.e. a−1 in 1960s–2000s, to −0.52 ± 0.18 m w.e. a−1 in 2000s–2015/18) in association with pervasive positive temperature anomalies (up to 1.85°C), which are pronounced at the end of the now lengthened ablation season. However, glacier mass budget perturbations do not mirror the magnitude of temperature anomalies in sub-regions, thus additional factors have heightened glacier recession. We show how proglacial lake expansion and glacier surging have compounded glacier recession over decadal/multi-decadal time periods, and exert similar influence on glacier mass budgets as temperature changes. Our results demonstrate the importance of ice loss mechanisms not often incorporated into broad-scale glacier projections, which need to be better considered to refine future glacier runoff estimates.