Glacier Body Research Articles

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.

Glacial geomorphology of the Notsarula and Chanchakhi river valleys, Georgian Caucasus

ABSTRACT Detailed glacial geomorphological maps are valuable for identifying target sites for palaeoglaciological reconstructions and thus for palaeoclimate inferences. In this study, we present the first detailed glacial geomorphological mapping of the landform assemblages produced by the former glaciers in the Notsarula (42°45′44″N 43°38′29″E) and Chanchakhi (42°42′5″N 43°40′42″E) river valleys, Georgian Caucasus. Our goal is to create a high-resolution (1:33,000 scale) glacial geomorphological map of this area (237 km2) and provide a detailed and accurate distribution of glacier-related features (see Main Map). Several field investigations between 2010 and 2022 along with detailed remote sensing surveys have been conducted for this glacial geomorphological mapping. The mapped landforms indicate multiple readvance or stillstands of valley glaciers across the study area. The largest and complex glacier body likely existed in the Bubistskali River gorge (42°43′16″N 43°43′32″E). Well-preserved moraine landforms in this valley suggest at least five large and several relatively small glacier readvances or stillstands occurred during the Late Quaternary. The simple-valley-type (without branches) glaciers were also probably present in other tributary valleys of the Chanchakhi River basin at that time. This map can be used for further geomorphological investigation as well as to support future geochronological work in the Greater Caucasus.

Surface area change detection of snow/ice cover over Zemu Glacier of Sikkim Himalaya

This study assessed the snow/ice surface area changes over the Zemu Glacier in the Eastern Himalayas. Zemu is considered to be the largest glacier in the Eastern Himalayas located in the Sikkim State of India. Change detection in the snow/ice surface areal extent of the Zemu Glacier was delineated from the year 1945 using US Army Map Service-Topographical Sheets and Landsat imageries available from 1987 to 2020. The results obtained solely focus on surface-change delineation using remote sensing satellite data and GIS software. Landsat imagery of the years 1987, 1997, 2009, 2018, and 2020 was used for snow and ice pixel extraction. Normalized Difference Snow Index (NDSI), Snow Cover Index (S3), and new band ratio index were used to extract the pure snow and ice pixels, fresh snow, and debris-covered snow/ice area and pixels mixed with shadow to demarcate the surface area changes. Manual delineation was required and undertaken for better results. A slope raster image was generated from Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data to delineate the slope and hill shade. The results illustrate that the snow/ice surface covering the glacier had an area of 113.5km2 in the year 1945 which was reduced to 78.31km2 in the year 2020 indicating a total snow/ice surface area loss of 31% in 75years. A loss of 11.45% was observed from 1945 to 1987 in the areal extent, while from 1987 to 2009, a decadal loss of approximately 7% was observed. The surface area loss of 8.46% from 2009 to 2018 led to infer the maximum loss of snow and ice over the glacier body at a rate of 0.94% per year. Between the years 2018 and 2020, the glacier lost 1.08% of its surface area. The Accumulation Area Ratio (AAR) considering the accumulation and ablation areas of the glacier indicated a gradual decline of the accumulation zone in the recent years. Global Land Ice Measurement from Space (GLIMS) program data with RGI version 6.0 was used as a reference to demarcate the areal extent of Zemu Glacier. The study gained above 80% of overall accuracy by generating a confusion matrix in ArcMap. The analysis of this seasonal snow/ice cover showed that there has been a drastic decline in the surface snow/ice cover area over the Zemu Glacier over the years 1987 to 2020 and NDSI; S3 analysis provided improved results to delineate snow/ice cover area over such steep terrain topography of Sikkim Himalaya.

Where does a glacier end? Integrated geophysical, geomorphological and photogrammetric measurements to image geometry and ice facies distribution

In this study we integrated different techniques, spanning from Ground Penetrating Radar to geomorphological and photogrammetric data, to characterize the glacial and proglacial environments of the Sforzellina Glacier (Central Alps, Italy). Direct data highlighted the presence of debris-covered ice and even of dead ice patches in front of the actual glacier terminus. Such an information was further proved by geophysical data. We try to correlate the dead ice patches occurrence with several parameters such as debris cover thickness, ground temperature, solar radiation, elevation, velocity of glacier retreat, and dip of the topographic surface without finding relevant correlations, except for the local bedrock morphology. In fact, the latter factor seems to be crucial to make the favourable conditions to dead ice patches formation and preservation with time.Since ice is not always outcropping, while dead ice patches never outcrop because they are hidden by continuous debris cover, classical glaciological monitoring techniques are not always successfully applicable.On the basis of the obtained results, we argue that estimates of glacier extension just related to surficial information, like in the case of exclusive use of remote sensing data and outcropping ice monitoring, can produce relevant underestimations. The presence of hidden ice patches, even not strictly part of the glacier body, is further important to quantify the total water equivalent, as well as to make affordable forecasts of the future glaciers evolution.

Glacier retreat in Himachal from 1994 to 2021 using deep learning

Traditional glacier identification using satellite data involves making basic band combinations, image processing, and calculations based on the spectral properties of glacier bodies. The results from computer processing of satellite data are sometimes affected by segmentation and thresholding techniques, due to which water bodies, rock surfaces, and other features are classified as glaciers. Deep learning (DL) based methods for image classification, object detection, and segmentation have proven to be very efficient and accurate in recent years. Deep learning-based simple semantic network U-Net has been utilized in various disciplines for image processing and efficient image segmentation. This paper emphasizes the application of this simple semantic segmentation network, i.e., U-net, for glacier identification using Indian Remote sensing (IRS) and Landsat satellite data with some improvement in segmentation and glacier identification. The glaciers in the Himachal Pradesh province of India, located in the Western Indian Himalayas are identified, segmented, and mapped using the U-net. The glaciers for the past three decades, i.e. from 1994 to 2021 mapped in the study area to assess the impact of climate change on glacial retreat. The suggested technique can automate the entire glacial mapping process, has a greater identification accuracy of 95 percent, and is less time-consuming. The glaciated area in Himachal Pradesh decreased at a rate of 67.84 km2 per annum from 4020.6 km2 in 1994–2198.5 km2 in 2021. It is observed that from 1994 to 2021, the glacier area decreased approximately by a percentage loss of 1.678 per annum, with decreasing decadal trend from 2.31% in 1994–2001 to 1.398 in 2011–2021.

Study on the Ablation of the Glacier Covered by Mineral Dust in Alpine Regions

Glaciers, known as solid reservoirs, are important water supply sources in northwest China. In this paper, mineral dust collected from a Chinese alpine mining area (Beizhan iron mine) and an ice cube (with a 225 cm2 section and a volume of 1000 mL) were employed via a delicate physical experiment to study the ablation of glaciers covered by mineral dust in alpine regions. After that, the ablation mechanism was revealed using the energy conservation theory. The main findings are as follows: (1) When the solar radiation intensity is 993 W/m2, the glacier ablation rate increases by 13.9% (from 282 to 321.2 mL/h) as the mineral dust coverage rate increases from 0% to 42.7%. (2) When the mineral dust coverage rate remains at 30%, the glacier ablation rate increases by 11.6% (from 291.8 to 325.78 mL/h) as the solar radiation intensity increases from 1007 to 1153 W/m2. (3) When the solar radiation intensity and mineral dust coverage rate remain unchanged, the ablation rate of the glacier covered by the mineral dust inversely increases with the dust particle size. The ablation rates of the particle size gradings C, B, and A (the dust particle sizes of gradings A, B, and C in 0.0375–0.075 mm, 0.075–0.125 mm, and 0.125–0.25 mm accounted for 5%:50%:45%, 30%:40%:30%, and 70%:30%:0%, respectively) were 293.4, 301.2, and 305.6 mL /h, respectively, and the corresponding ablation rates increased by 2.7% and 1.5%. (4) The smaller the average particle size of the mineral dust, the greater the contribution to the ablation rate; a 1 °C temperature increase to the glacier ablation rate is equivalent to 29.1%, 33.6%, and 40.6% increases in dust coverage for particle size classes C, B, and A. (5) The mineral dust covering the glacier surface could not only reduce the reflectivity of the glacier surface to solar radiation but could also continuously transfer the absorbed radiant energy and its own chemical energy to the glacier body, accelerating the glacier’s meltwater speed. The findings of this paper can provide the necessary theoretical basis for mineral dust control and glacier water conservation in alpine mining areas.

Evolution of Glacial Lake Cochrane During the Last Glacial Termination, Central Chilean Patagonia (∼47°S)

Large ice-dammed lakes developed along the eastern margin of the Patagonian Ice Sheet (PIS) during the Last Glacial Termination (T1). Their spatial/temporal evolution, however, remains poorly constrained despite their importance for deciphering fluctuations of the shrinking PIS, isostatic adjustments, and climate forcing. Here we examine the distribution and age of shoreline features deposited or sculpted by Glacial Lake Cochrane (GLC) in the Lago Cochrane/Pueyrredón (LCP) basin, Central Patagonia, following recession of the LCP glacier lobe from its final Last Glacial Maximum (LGM) moraines. GLC drained initially toward the Atlantic Ocean and continuing ice shrinking opened new drainage routes allowing the discharge toward the Pacific Ocean. We identify five clusters of lake terraces, shorelines, and deltas between elevations ∼600–500 (N5), ∼470–400 (N4), ∼360–300 (N3), ∼230–220 (N2), and ∼180–170 masl (N1) throughout the LCP basin. The distribution of these clusters and associated glaciolacustrine deposits provide constraints for the evolving position of the damming glacier bodies. Elevation gradients within the landform clusters reveal glacio-isostatic adjustments that enable us to quantify the magnitude of deglacial rebound and construct isostatically corrected surfaces for the different phases in the evolution of GLC. Our chronology, based principally on radiocarbon dates from lake sediment cores and new OSL dating, suggests that these phases developed between ∼20.7–19.3 ka (N5), ∼19.3–14.8 ka (N4), ∼14.8–11.3 ka (N3), and shortly thereafter (N2 and N1). The N3 landforms are the most ubiquitous, well-preserved, and voluminous, attributes that resulted from a ∼3,500-year long period of glacial stability, enhanced sediment supply by peak precipitation regime, and profuse snow and ice melting during the most recent half of T1. This scenario differs from the cold and dry conditions that prevailed during the brief N5 phase and the moderate amount of precipitation during the N4 phase. We interpret the limited development of the N2 and N1 landforms as ephemeral stabilization events following the final and irreversible disappearance of GLC after N3. This event commenced shortly after the onset of an early Holocene westerly minimum at pan-Patagonian scale at ∼11.7 ka, contemporaneous with peak atmospheric and oceanic temperatures in the middle and high latitudes of the Southern Hemisphere.

DISTRIBUTION AND EVOLUTION OF ICE APRONS IN A CHANGING CLIMATE IN THE MONT-BLANC MASSIF (WESTERN EUROPEAN ALPS)

Abstract. Ice Apron (IA) is a poorly studied ice feature, commonly existing in all the world’s major mountain regions. This study aims to map the locations of the IAs in the Mont Blanc massif (MBM), making use of the very high-resolution optical satellite images from 2001, 2012 and 2019. 423 IAs were identified and accurately delineated in the MBM on the images from 2019, and their topographic characteristics were studied. We generated our own Digital Elevation Model (DEM) at 4 m resolution since the freely available products predominantly suffer from significant inconsistencies, especially in steep mountain areas. Results show that most IAs exist at elevations above the regional Equilibrium Line Altitude (ELA), on steep slopes, on concave surfaces, on northern and southern aspects and on the most rugged terrains. They are also commonly associated with steep slope glaciers as 85% of them occur on these glaciers’ headwalls. A comparison between 2001 and 2019 shows that IAs have lost around 29% of their area over a period of 18 years. This is significant and the rate of area loss is very alarming in comparison with the larger glacier bodies. We also studied the effect of topographic parameters on the area loss. We found that topographic factors like slope, aspect, curvature, elevation and Terrain Ruggedness Index (TRI) strongly influence the rate of area loss of IAs.

Anomalous glacier thinning due to climate feedback mechanism in the Himalaya and evidences in other mountain ranges

The heterogeneous ice-melt of glaciers in the Himalaya and other mountain ranges is often associated with debris cover, slope, precipitation, and temperature. However, this study ascertains that the climate feedback mechanism introduced due to meltwater influx of retreating tributary glaciers accelerates the melting of the main glacier body. Such regions have shown high elevation change at the surface, leading to a higher ice-mass loss. The point locations of meltwater influx are identified, and a relationship is presented between the density of meltwater influx points and glacier thinning. The existing mass balance models do not account for this process, thereby underestimating the current and the future mass loss. It is recommended that future mass loss prediction/projection models should consider the influence of the climate feedback system.

Ice sheet velocity tracking by Sentinel-1 satellite images at Graham Coast Kyiv Peninsula

The study of Antarctic glaciers and ice sheets velocity is one of the most discussed topics. Such high interest in this topic is primarily because the ice from the Antarctic glaciers, which gets to the ocean, significantly affects the ocean level and the global climate. Development of modern satellite technologies for Earth remote sensing made it possible to elaborate a number of methods for ice sheets’ displacements estimation and calculation of such displacements velocities. This work uses remote sensing data from the satellite system Copernicus Sentinel-1 to estimate the ice cover velocities in the Kyiv Peninsula in the time interval from December 2020 to March 2021. To this end, 10 radar images of the study area from early December to the end of March were used with an interval of 12–14 days. All selected images were analyzed in pairs to establish changes on the surface for the selected time interval. GRD-format images from Copernicus Sentinel-1 satellite, corrected for Earth's ellipsoid shape, were used. Based on the offset tracking operation, we calculated the speeds of ice cover movements within the Kyiv Peninsula for each pair of images with approximately two weeks' time difference. As a result, the speed of ice movements varies considerably and at the glacier mouth can reach 3.5–4 meters per day. Also, the rate of ice displacement in the glacier body changed over time. Thus, the highest ice velocities were in the glacier's mouth. However, short-term time intervals of intensification were recorded for the rear and even the marginal parts of the glaciers in contact with the ice sheet. Thus, the lowest part of the glacier activating sequence leads to the upper part shifting. Notably, this increase in the displacement of ice cover was recorded in February, one of the warmest months in this part of Antarctica.

More dynamic than expected: an updated survey of surging glaciers in the Pamir

Abstract. The investigation of surging glaciers using remote sensing has recently seen a strong increase as freely available satellite data and digital elevation models (DEMs) can provide detailed information about surges that often take place in remote and inaccessible regions. Apart from analysing individual surges, satellite information is increasingly used to collect valuable data on surging glaciers. Related inventories have recently been published for several regions in High Mountain Asia including the Karakoram or parts of the Pamir and western Kunlun Shan, but information for the entire Pamir is solely available from a historic database listing about 80 glaciers with confirmed surges. Here we present an updated inventory of confirmed glacier surges for the Pamir that considers results from earlier studies and is largely based on a systematic analysis of Landsat image time series (1988 to 2018), very high-resolution imagery (Corona, Hexagon, Bing Maps, Google Earth) and DEM differences. Actively surging glaciers (e.g. with advancing termini) were identified from animations and flicker images and the typical elevation change patterns (lowering in an upper reservoir zone and thickening further down in a receiving zone). In total, we identified 206 spatially distinct surges within 186 glacier bodies mostly clustered in the northern and western part of the Pamir. Where possible, minimum and maximum glacier extents were digitised, but often interacting tributaries made a clear separation challenging. Most surging glaciers (n=70) are found in the larger size classes (>10 km2), but two of them are very small (<0.5 km2). We also found several surges where the length of the glacier increased by more than 100 %. The created datasets are available at: https://doi.org/10.1594/PANGAEA.914150 (Goerlich et al., 2020).

Discovering anomalous dynamics and disintegrating behaviour in glaciers of Chandra-Bhaga sub-basins, part of Western Himalaya using DInSAR

Glacier velocity is one of the important parameters to know about glacier dynamics, its mass and health. Understanding glacier velocity also assists in the analysis of ice thickness, ice flux and mass balance. Furthermore, basin/sub-basin wise studies are helpful to understand the climate change over that region instead of monitoring individual glaciers. In the current study, the spatial distribution of glacier velocity is generated for the entire Chandra and Bhaga sub-basins, in the Lahaul-Spiti district of Himachal Pradesh, India, using Advanced Land Observing Satellite-2/Phased Array type L-band Synthetic Aperture Radar-2 (ALOS-2/PALSAR-2) differential interferometry pair images with a 14-days temporal gap. The glaciers in Chandra sub-basin are found to have a high flow rate as compared to the glaciers in Bhaga sub-basin. Local slope and ice thickness, which decrease towards the terminus in general, control the movement of valley glaciers, and lower movement rate is observed for most of glaciers towards the terminus/frontal area. However, a few glaciers of Bhaga sub-basin demonstrate an accelerated movement in their frontal areas. This irregular behaviour is also studied in this work and it is discovered that terrain slope and influx of melting water from adjacent glaciers are the major causes for such behaviour of these glaciers. They are, therefore, prone to accelerated mass loss compared to other glaciers in the sub-basin. Another key finding of the anomalous glacier dynamics study is the disintegrating behaviour of glaciers, which is also identified by interpreting the responses of physical scattering mechanisms retrieved from glaciers using fully polarimetric ALOS-2/PALSAR-2. Warming temperatures are expected to cause glacier retreat and separation of tributary glaciers from the main glacier body. Melt water from tributary glaciers can further accelerate glacier flow and ice melt in lower part of glacier trunk. This can lead to formation of dead ice zones and disintegration of Himalayan glaciers, which are supported by numerous tributary glaciers. Therefore, we expect that the loss in glacier area due to warming will be larger than the present prediction, where mass loss is considered from conventional way.

Toward the Acoustic Detection of Two‐Phase Flow Patterns and Helmholtz Resonators in Englacial Drainage Systems

AbstractPassive acoustic monitoring has revolutionized the characterization of industrial processes and the acoustic wavefield in various environments. However, cryospheric acoustic phenomena remain largely unknown, especially at medium and small scales. Furthermore, the englacial drainage system is poorly documented, even though it is fundamental for understanding water routing through the glacier body. Here I present the first‐of‐its‐kind in situ records of periodic or sustained acoustic signals generated by water drainage through crevasses at the calving front of a glacier, in this case a Greenlandic tidewater glacier. The generative mechanisms of gurgling and bubbling noise are explained as flow‐induced sounds that are excited by intermittent air‐water two‐phase flow and Helmholtz resonance, respectively. This paper demonstrates that there is the tremendous potential to study near‐surface glacier systems using acoustic methods and detect different flow patterns in englacial conduits from their acoustic signatures, both of which can significantly advance our understanding of glaciological processes.

ГЕОФИЗИЧЕСКИЕ ИЗЫСКАНИЯ В РАЙОНЕ СТАНЦИИ ПРОГРЕСС, ВОСТОЧНАЯ АНТАРКТИДА, В СЕЗОН 63-Й РАЭ (2017/18 Г.)

In recent years, when organizing works of the Russian Antarctic Expedition (RAE), considerable attention is given to the safety of logistics operations carried out at Russian stations and field bases. The main factors that threaten polar explorers are extensive systems of cracks and water breakthroughs, confined to the marginal, the most dynamic part of the outlet glaciers, in the area of which the most part of stations are located. One example of the impact of these processes on transport communications in Antarctica is the breakthrough of an intraglacial reservoir in the Dolk glacier near the station Progress (Larsemann Hills, Eastern Antarctica) in the season of the 62nd RAE (2016/17). The outburst resulted in the formation of a huge hole in the glacier body and an extensive system of cracks directed towards its flanks. This took place on the part of the route connecting the Progress Station with the point of organization the sledge-tractor train marches to inner regions of the Antarctic continent. Thus, this destroyed the transport links between these points. That is why during the seasonal works of the 63rd RAE (2017/18) geophysical surveys were carried out around the hole by means of the GPR profiling for the purpose to find the best way and organize a new all-season route. The GPR soundings performed at frequencies of 900 and 150 MHz, made possible to fix numerous cracks and large volumes of melt water accumulations in the near-surface part of the ice layer. The analysis of the obtained time sections and the assessment of the depths of cracks and watered areas did show that the detected objects in the glacier body were not dangerous for advancing of the sledge-caterpillar equipment passing by the hole. These surveys allowed planning the optimal new route, after which it was rolled up and put into operation. The logistical connection between the station and the airfield has been restored. Until the end of the field season, the new all-season route was actively used for transportation.

Internal structure of rock glaciers in Altai (The case of talus rock glacier in Dzhelo River Valley)

In 2019, a comprehensive study of the internal structure of the talus rock glacier in the Dzhelo River valley was carried out (North-Chuya Range). The identification of the internal structure was performed using electrical resistivity tomography and GPR sounding. In order to compare the internal structure of the rock glacier with its surface morphology, we carried out aerial photography and constructed a digital terrain model. The study revealed that the depth of the rock-ice core varies from 2.5-3 m to 10 m, and the thickness ranges from 7 m to 30 m. The consolidation cores of the rock-ice material are confined to inter-ridge depressions in the rock glacier body. The potential volume of a rock-ice core is 800 thousand m3, which is 53% of the rock glacier total volume, the ice volume in the rock-ice core can be as much as 400 thousand m3.

New insights into ice accumulation at Galena Creek Rock Glacier from radar imaging of its internal structure

AbstractThe ice-cored Galena Creek Rock Glacier, Wyoming, USA, has been the subject of a number of studies that sought to determine the origin of its ice. We present new observations of the rock glacier's internal structure from ground-penetrating radar to constrain ice and debris distribution and accumulation. We imaged dipping reflectors in the center of the glacier that are weak and discontinuous, in contrast to strong reflectors toward the edge of the cirque beneath large debris-avalanche chutes. These reflectors form a network of concave-up, up-glacier dipping layers. We interpret these as englacial debris bands formed by large debris falls buried by subsequent ice and snow accumulation. They are discontinuous where ice outpaces debris accumulation, but with sufficient debris accumulation an interleaved pattern of ice and debris layers can form. We propose a model in which the ice in these interleaved layers is snowfall preserved by debris-facilitated accumulation. Large debris falls that occur in early spring bury sections of the snowpack, which are then preserved through summer and incorporated into the rock glacier body over time. This study highlights the importance of sequential accumulation of ice and debris for understanding the dynamics of rock glaciers and debris-covered glaciers.

A new model of rock glacier dynamics

Rock glaciers have traditionally been described as periglacial landforms and thus associated genetically with the presence of permafrost and a seasonal active layer. They have also been described as glacigenic in origin, in which the main rock glacier body contains glacier ice at depth. Other rock glaciers can be considered as relict where they contain no interstitial ice and are functionally inactive. Although all rock glaciers are to some extent polygenic, there is no clear, simple test that can be used to distinguish between different rock glacier types. This study proposes a simple and testable model for rock glacier classification based on their behaviour from evidence reported from the literature. The study then proposes an interpretive evolutionary model describing the temporal evolution of rock glacier surface movement through the year that can inform on its dynamical controls. This analysis provides an easily-deployed interpretive framework for the origins of rock glaciers.

Going against the flow: Testing the hypothesis of pulsed axial glacier flow

AbstractHypothesised lobe‐like flow of a temperate glacier in southeast Iceland, proposed from an analysis of ice surface crevassing patterns, is appraised from both empirical and theoretical perspectives. The hypothesis comprises the migration of individual lobes (or ‘pulses’) of ice through the glacier body, with central lobes migrating more rapidly along a narrow, central, ‘axial flow corridor’. Our alternative hypothesis is that crevasse patterns at this glacier reflect simple surface ice responses to stresses caused by flow over uneven bed topography. To substantiate our rejection of the lobe‐like, pulsed axial flow hypothesis, we provide: (a) evidence for a prominent transverse foliation that exhibits no evidence of shear of the required magnitude to support the hypothesis; and (b) an analysis of ice surface displacement, obtained by feature tracking, that shows a uniform flow field throughout the glacier tongue. We argue that caution needs to be exercised when interpreting glacier flow solely from crevasse patterns and observations of minor displacements along near‐surface fractures and other features. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

Deglaciation and its impact on permafrost and rock glacier evolution: New insight from two adjacent cirques in Austria

Glaciers and permafrost are strongly linked to each other in mid-latitude mountain regions particularly with polythermal glaciers. This linkage is not only climatically defined but also in terms of geomorphic and glaciological processes. We studied two adjacent cirques located in the Central Austria. We focussed on the deglaciation since the Little Ice Age (LIA) maximum (c.1850CE) and its relevance for permafrost and rock glacier evolution since then. One cirque is occupied by a glacier remnant whereas the second one is occupied by an active rock glacier which was partly overridden by a glacier during the LIA. We applied a multidisciplinary approach using field-based techniques including geoelectrics, geodetic measurements, and automatic monitoring as well as historic maps and photographs, remote sensing, and digital terrain analysis. Results indicate almost complete deglaciation by the end of the last millennium. Small-scale tongue-shaped landforms of complex origin formed during the last decades at finer-grained slope deposits below the cirque headwalls. Field evidences and geophysics results proved the existence of widespread sedimentary ice beneath a thin veneer of debris at these slopes. The variable thickness of the debris layer has a major impact on differential ablation and landform evolution in both cirques. The comparison of digital elevation models revealed clear mass losses at both cirques with low rates between 1954 and 2002 and significantly higher rates since then. The central and lower part of the rock glacier moves fast transporting sediments and ice downvalley. In contrast, the upper part of the rock glacier is characterised by low debris and ice input rates. Both effects cause a significant decoupling of the main rock glacier body from its nourishment area leading eventually to rock glacier starvation. This study demonstrates the importance of a decadal-scale and multidisciplinary research approach in determining the development of alpine landforms over both space and time.

Early 21st century glacier thickness changes in the Central Tien Shan

Although studies based on satellite gravimetry (2003−2010) and laser altimetry (2003–2009) measurements have achieved region-wide glacier mass change for the Tien Shan, the dynamic process of glacier yet to be closely monitored and understood so that its impact can be assessed accurately. In this study, we investigated region-wide glacier thickness change in the Central Tien Shan (CTS) during 2000–2012 by differencing the Shuttle Radar Topographic Mission (SRTM) digital elevation model (DEM) with a newly constructed DEM from 27 TanDEM-X images. For a total glacier area of 7239.8±527.2km2, an average glacier thickness change rate of −0.24±0.22m/a was derived. This result agrees well with the result based on satellite laser altimetry measurements reported earlier (−0.31±0.41m/a). With temporal synchronization, a fine spatial resolution and wide coverage, our measurements are able to reveal abundant glacier change features and dependencies in the CTS. Firstly, the lower mountains have seen a more severe glacier decline, and the glaciers facing the prevailing wind (westerlies) have experienced a greater decline because of the stronger evaporation. Furthermore, those glaciers lying along the extremely high Meridian mountain range have obviously gained mass in their upper reaches, because the air current from the west is blocked and lifted by the Meridian mountain range. Secondly, for the entire glacier body, the theoretical hyperbolic dependence between debris thickness and ice decline was very difficult to establish. Some huge glaciers covered by heavy debris have still experienced a severe decline. However, even though the heavy debris did not prevent the ablation, its attenuating effects were considerable. Thirdly, for the glaciers that surged before 2000, the mass gain in the restoring zones has not been enough to cover the mass loss in ablation zones. Some large glaciers surged again during 2000–2012; however, with much lower magnitudes than in previous surges. In general, the surge glaciers have experienced a greater decline than the non-surge glaciers. Fourthly, due to the ice front calving and subglacial thermal erosion, glaciers connected to proglacial lakes have receded and thinned much more rapidly than the land-terminated glaciers. Overall, the glaciers in the CTS are more stable than those in other parts of the Tien Shan. However, the glacier state there is still alarming. A moderate average thinning rate was derived because the drastic thinning in the ablation zones was balanced by the slight thinning in the broad accumulation zones.