scholarly journals Quantification of Everest region glacier velocities between 1992 and 2002, using satellite radar interferometry and feature tracking

2009 ◽  
Vol 55 (192) ◽  
pp. 596-606 ◽  
Author(s):  
D.J. Quincey ◽  
A. Luckman ◽  
D. Benn
Keyword(s):  
Feature Tracking ◽  
High Elevation ◽  
Ice Dynamics ◽  
Terminal Moraine ◽  
Ice Surface ◽  
Digital Elevation ◽  
Ablation Pattern ◽  
Satellite Radar ◽  
Glacier Flow ◽  
Elevation Model

AbstractMany glacier snouts in the Himalaya are known to be stagnant and exhibiting low surface gradients, conditions that are conducive to the formation of glacial lakes impounded either by the terminal moraine or by the remnant glacier snout. In this study, we use interferometry and feature-tracking techniques to quantify the extent of stagnation in 20 glaciers across the Everest (Qomolangma; Sagarmatha) region, and subsequently we examine the relationship between local catchment topography and ice dynamics. The results show that only one of the studied glaciers, Kangshung Glacier, is dynamic across its entire surface, with flow rates greater than 40 m a−1 being recorded in high-elevation areas. Twelve other glaciers show some evidence of flow, but are generally characterized by long, stagnant tongues, indicating widespread recession and in situ decay. The remaining seven glaciers show no evidence of flow in any of the available datasets. Hypsometric data suggest that catchment topography plays an important role in controlling glacier flow regimes, with those fed by wide, high-altitude accumulation areas showing the most extensive active ice, and those originating at low elevations exhibiting large areas of stagnant ice. Surface profiles extracted from a SRTM digital elevation model indicate that stagnant snouts are characterized by very low (<2°) surface angles and that down-wasting is the prevalent ablation pattern in the study area.

scholarly journals Subglacial lakes and hydrology across the Ellsworth Subglacial Highlands, West Antarctica

2020 ◽  
Author(s):  
Felipe Napoleoni ◽  
Stewart S.R. Jamieson ◽  
Neil Ross ◽  
Michael J. Bentley ◽  
Andrés Rivera ◽  
...  
Keyword(s):  
West Antarctica ◽  
Ice Streams ◽  
Ice Dynamics ◽  
Systematic Analysis ◽  
Ice Surface ◽  
Digital Elevation ◽  
Radio Echo Sounding ◽  
Ice Sheet Dynamics ◽  
Subglacial Lakes ◽  
Elevation Model

Abstract. Subglacial water plays an important role in ice sheet dynamics and stability. It is often located at the onset of ice streams and has the potential to enhance ice flow downstream by lubricating the ice-bed interface. The most recent subglacial lake inventory of Antarctica mapped nearly 400 lakes, of which ~ 14 % are found in West Antarctica. Despite the potential importance of subglacial water for ice dynamics, there is a lack of detailed subglacial water characterization in West Antarctica. Using radio-echo sounding data, we analyse the ice-bed interface to detect subglacial lakes. We report 37 previously uncharted subglacial lakes and present a systematic analysis of their physical properties. This represents a ~ 60 % increase in subglacial lakes in the region. Additionally, a new digital elevation model of basal topography was built and used to create a detailed hydropotential model of Ellsworth Subglacial Highlands to simulate the subglacial hydrological network. This approach allows us to characterize basal hydrology, subglacial water catchments and connections between them. Furthermore, the simulated subglacial hydrological catchments of Rutford Ice Stream, Pine Island Glacier and Thwaites Glacier do not match precisely with their ice surface catchments.

scholarly journals Subglacial lakes and hydrology across the Ellsworth Subglacial Highlands, West Antarctica

2020 ◽  
Vol 14 (12) ◽  
pp. 4507-4524
Author(s):  
Felipe Napoleoni ◽  
Stewart S. R. Jamieson ◽  
Neil Ross ◽  
Michael J. Bentley ◽  
Andrés Rivera ◽  
...  
Keyword(s):  
West Antarctica ◽  
Ice Streams ◽  
Ice Dynamics ◽  
Systematic Analysis ◽  
Ice Surface ◽  
Digital Elevation ◽  
Radio Echo Sounding ◽  
Ice Sheet Dynamics ◽  
Subglacial Lakes ◽  
Elevation Model

Abstract. Subglacial water plays an important role in ice sheet dynamics and stability. Subglacial lakes are often located at the onset of ice streams and have been hypothesised to enhance ice flow downstream by lubricating the ice–bed interface. The most recent subglacial-lake inventory of Antarctica mapped nearly 400 lakes, of which ∼ 14 % are found in West Antarctica. Despite the potential importance of subglacial water for ice dynamics, there is a lack of detailed subglacial-water characterisation in West Antarctica. Using radio-echo sounding data, we analyse the ice–bed interface to detect subglacial lakes. We report 33 previously uncharted subglacial lakes and present a systematic analysis of their physical properties. This represents a ∼ 40 % increase in subglacial lakes in West Antarctica. Additionally, a new digital elevation model of basal topography of the Ellsworth Subglacial Highlands was built and used to create a hydropotential model to simulate the subglacial hydrological network. This allows us to characterise basal hydrology, determine subglacial water catchments and assess their connectivity. We show that the simulated subglacial hydrological catchments of the Rutford Ice Stream, Pine Island Glacier and Thwaites Glacier do not correspond to their ice surface catchments.

scholarly journals Present dynamics and future prognosis of a slowly surging glacier

2011 ◽  
Vol 5 (1) ◽  
pp. 299-313 ◽  
Author(s):  
G. E. Flowers ◽  
N. Roux ◽  
S. Pimentel ◽  
C. G. Schoof
Keyword(s):  
Mass Balance ◽  
Force Balance ◽  
Surface Velocity ◽  
Internal Dynamic ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Surface ◽  
Glacier Ice ◽  
Glacier Flow ◽  
Negative Balance

Abstract. Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence is not a direct response to the external climate forcing, but whose character (i.e. period, amplitude, mechanism) may depend on the glacier's environmental or climate setting. We examine the dynamics of a small (∼5 km2) valley glacier in Yukon, Canada, where two previous surges have been photographically documented and an unusually slow surge is currently underway. To characterize the dynamics of the present surge, and to speculate on the future of this glacier, we employ a higher-order flowband model of ice dynamics with a regularized Coulomb-friction sliding law in both diagnostic and prognostic simulations. Diagnostic (force balance) calculations capture the measured ice-surface velocity profile only when non-zero basal water pressures are prescribed over the central region of the glacier, coincident with where evidence of the surge has been identified. This leads to sliding accounting for 50–100% of the total surface motion in this region. Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface mass balance, reveal a significant role played by a bedrock ridge beneath the current equilibrium line of the glacier. Ice thickening occurs above the ridge in our simulations, until the net mass balance reaches sufficiently negative values. We suggest that the bedrock ridge may contribute to the propensity for surges in this glacier by promoting the development of the reservoir area during quiescence, and may permit surges to occur under more negative balance conditions than would otherwise be possible. Collectively, these results corroborate our interpretation of the current glacier flow regime as indicative of a slow surge that has been ongoing for some time, and support a relationship between surge incidence or character and the net mass balance. Our results also highlight the importance of glacier bed topography in controlling ice dynamics, as observed in many other glacier systems.

scholarly journals The Reference Elevation Model of Antarctica

2019 ◽  
Vol 13 (2) ◽  
pp. 665-674 ◽  
Author(s):  
Ian M. Howat ◽  
Claire Porter ◽  
Benjamin E. Smith ◽  
Myoung-Jong Noh ◽  
Paul Morin
Keyword(s):  
Laser Altimetry ◽  
Low Contrast ◽  
Continental Scale ◽  
Change Measurement ◽  
Digital Elevation ◽  
Continuous Surface ◽  
Satellite Radar ◽  
Elevation Model ◽  
Surface Covering ◽  
Quality Surface

Abstract. The Reference Elevation Model of Antarctica (REMA) is the first continental-scale digital elevation model (DEM) at a resolution of less than 10 m. REMA is created from stereophotogrammetry with submeter resolution optical, commercial satellite imagery. The higher spatial and radiometric resolutions of this imagery enable high-quality surface extraction over the low-contrast ice sheet surface. The DEMs are registered to satellite radar and laser altimetry and are mosaicked to provide a continuous surface covering nearly 95 % the entire continent. The mosaic includes an error estimate and a time stamp, enabling change measurement. Typical elevation errors are less than 1 m, as validated by the comparison to airborne laser altimetry. REMA provides a powerful new resource for Antarctic science and provides a proof of concept for generating accurate high-resolution repeat topography at continental scales.

scholarly journals A new bed elevation dataset for Greenland

2013 ◽  
Vol 7 (2) ◽  
pp. 499-510 ◽  
Author(s):  
J. L. Bamber ◽  
J. A. Griggs ◽  
R. T. W. L. Hurkmans ◽  
J. A. Dowdeswell ◽  
S. P. Gogineni ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Surface Elevation ◽  
The Arctic ◽  
Ice Thickness ◽  
Data Sampling ◽  
Ice Dynamics ◽  
Bed Elevation ◽  
Digital Elevation ◽  
Arctic Ice ◽  
Elevation Model

Abstract. We present a new bed elevation dataset for Greenland derived from a combination of multiple airborne ice thickness surveys undertaken between the 1970s and 2012. Around 420 000 line kilometres of airborne data were used, with roughly 70% of this having been collected since the year 2000, when the last comprehensive compilation was undertaken. The airborne data were combined with satellite-derived elevations for non-glaciated terrain to produce a consistent bed digital elevation model (DEM) over the entire island including across the glaciated–ice free boundary. The DEM was extended to the continental margin with the aid of bathymetric data, primarily from a compilation for the Arctic. Ice thickness was determined where an ice shelf exists from a combination of surface elevation and radar soundings. The across-track spacing between flight lines warranted interpolation at 1 km postings for significant sectors of the ice sheet. Grids of ice surface elevation, error estimates for the DEM, ice thickness and data sampling density were also produced alongside a mask of land/ocean/grounded ice/floating ice. Errors in bed elevation range from a minimum of ±10 m to about ±300 m, as a function of distance from an observation and local topographic variability. A comparison with the compilation published in 2001 highlights the improvement in resolution afforded by the new datasets, particularly along the ice sheet margin, where ice velocity is highest and changes in ice dynamics most marked. We estimate that the volume of ice included in our land-ice mask would raise mean sea level by 7.36 m, excluding any solid earth effects that would take place during ice sheet decay.

scholarly journals Pluri-decadal (1955–2014) evolution of glacier–rock glacier transitional landforms in the central Andes of Chile (30–33° S)

2017 ◽  
Vol 5 (3) ◽  
pp. 493-509 ◽  
Author(s):  
Sébastien Monnier ◽  
Christophe Kinnard
Keyword(s):  
Feature Tracking ◽  
Central Andes ◽  
Image Feature ◽  
Rock Glacier ◽  
Aerial Photos ◽  
Surface Displacements ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Elevation Model ◽  
Displacement Patterns

Abstract. Three glacier–rock glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955–2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the rock glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of rock glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered glacier areas with large heaving or lowering up to more than ±1 m yr−1. The use of image feature tracking highlighted spatially coherent flow vector patterns over rock glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr−1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, rock glaciers can develop upward at the expense of debris-covered glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and rock glacier development phases. The other landform is a small debris-covered glacier having evolved into a rock glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere against climate change.

scholarly journals Present dynamics and future prognosis of a slowly surging glacier

2010 ◽  
Vol 4 (4) ◽  
pp. 1839-1876
Author(s):  
G. E. Flowers ◽  
N. Roux ◽  
S. Pimentel
Keyword(s):  
Mass Balance ◽  
Surface Profile ◽  
Yukon Territory ◽  
Force Balance ◽  
Surface Velocity ◽  
Internal Dynamic ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Surface ◽  
Glacier Flow

Abstract. Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence is not a direct response to the external climate forcing, but whose character (e.g. period, mechanism) may depend on the glacier's environmental or climate setting. We examine the dynamics of a small (~5 km2) valley glacier in the Yukon Territory of Canada, where two previous surges have been photographically documented and an unusually slow surge is currently underway. To characterize the dynamics of the present surge, and to speculate on the future of this glacier, we employ a higher-order flowband model of ice dynamics with a Coulomb-friction sliding law in both diagnostic and prognostic simulations. Diagnostic (force balance) calculations capture the measured ice-surface velocity profile only when high basal water pressures (55–90% of flotation) are prescribed over the central region of the glacier, consistent with where evidence of the surge has been identified. This leads to sliding accounting for 50–100% of the total surface motion. Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface mass balance, reveal a significant role played by a large bedrock bump beneath the current equilibrium line of the glacier. This bump provides resistance to ice flow sufficient to cause the formation of a bulge in the ice-surface profile. We suggest that the bedrock bump contributes to the propensity for surges in this glacier, such that conditions suppressing ice-bulge formation over the bump may also inhibit surges. In our calculations such a situation arises for sufficiently negative values of mass balance. Collectively, these results corroborate our interpretation of the current glacier flow regime as indicative of a "slow surge", and confirm a relationship between surge incidence or character and the net mass balance. Our results also highlight the importance of glacier bed topography in controlling ice dynamics, as observed in many other glacier systems.

scholarly journals Weighted Visibility Classification and Seating Plan for the Aitken University Centre

2014 ◽  
Vol XL-2 ◽  
pp. 227-234
Author(s):  
T. Allison ◽  
D. Fraser ◽  
E. Stefanakis
Keyword(s):  
Web Application ◽  
Web Applications ◽  
Ice Surface ◽  
Price Levels ◽  
Digital Elevation ◽  
Information Products ◽  
Interactive Map ◽  
Elevation Model ◽  
The University

This paper describes the requirements for a weighted visibility classification of seats in the University of New Brunswick’s (UNB) Aitken University Centre (AUC). Price levels for seats are typically set for sections of seats based on promoter preferences. In a visibility classification, the digital elevation model (DEM) is created for the AUC and includes possible view obstructions. The view obstructions taken into account for this design were the penalty boxes, player bencher, and the rink boards. There were no other major obstructions in the AUC. The visibility calculations compute the number of visible pixels of the rink surface for each seat. It is expected that seats with a higher number of visible pixels will also have better visibility. The number of viewable pixels is weighted by distance to the center of ice surface to account for the preference of seats that are closer to the rink surface. This paper outlines the collection of data, weighted visibility classification method, and the development of information products. There are two main objectives of this weighted visibility classification and seating plan: (a) to demonstrate that a weighted visibility classification is a viable method to classify seats, and that this methodology could be used to set price levels for a venue and (b) create online web applications to suit the functionality for users and venue administrators. The user web application allows the user to pan, zoom and perform limited searches in the interactive map.

scholarly journals Glacier mass balance over the central Nyainqentanglha Range during recent decades derived from remote-sensing data

2019 ◽  
Vol 65 (251) ◽  
pp. 422-439 ◽  
Author(s):  
KUNPENG WU ◽  
SHIYIN LIU ◽  
ZONGLI JIANG ◽  
JUNLI XU ◽  
JUNFENG WEI
Keyword(s):  
Mass Balance ◽  
Remote Sensing Data ◽  
Shuttle Radar Topography Mission ◽  
Topographic Maps ◽  
Glacier Mass Balance ◽  
Glacier Area ◽  
Ice Surface ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Elevation Model

ABSTRACTTo obtain information on changes in glacier mass balance in the central Nyainqentanglha Range, a comprehensive study was carried out based on digital-elevation models derived from the 1968 topographic maps, the Shuttle Radar Topography Mission DEM (2000) and TerraSAR-X/TanDEM-X (2013). Glacier area changes between 1968 and 2016 were derived from topographic maps and Landsat OLI images. This showed the area contained 715 glaciers, with an area of 1713.42 ± 51.82 km2, in 2016. Ice cover has been shrinking by 0.68 ± 0.05% a−1 since 1968. The glacier area covered by debris accounted for 11.9% of the total and decreased in the SE–NW directions. Using digital elevation model differencing and differential synthetic aperture radar interferometry, a significant mass loss of 0.46 ± 0.10 m w.e. a−1 has been recorded since 1968; mass losses accelerated from 0.42 ± 0.20 m w.e. a−1 to 0.60 ± 0.20 m w.e. a−1 between 1968–2000 and 2000–2013, with thinning noticeably greater on the debris-covered ice than the clean ice. Surface-elevation changes can be influenced by ice cliffs, as well as debris cover and land- or lake-terminating glaciers. Changes showed spatial and temporal heterogeneity and a substantial correlation with climate warming and decreased precipitation.

scholarly journals A new velocity map for Byrd Glacier, East Antarctica, from sequential ASTER satellite imagery

2005 ◽  
Vol 41 ◽  
pp. 71-76 ◽  
Author(s):  
Leigh Stearns ◽  
Gordon Hamilton
Keyword(s):  
Cross Correlation ◽  
Thermal Emission ◽  
East Antarctica ◽  
Correlation Technique ◽  
Main Trunk ◽  
Ice Dynamics ◽  
Digital Elevation ◽  
Stereo Imagery ◽  
Elevation Model ◽  
Cross Correlation Technique

AbstractNew ice-velocity measurements are obtained for the main trunk of Byrd Glacier, East Antarctica, using recently acquired Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery. The velocities are derived from the application of a cross-correlation technique to sequential images acquired in 2000 and 2001. Images were co-registered and ortho-rectified with the aid of a digital elevation model (DEM) generated from ASTER stereo imagery. This paper outlines the process of DEM generation, image co-registration and correction, and the application of the cross-correlation technique to obtain ice velocities. Comparison of the new velocity map with earlier measurements of velocity from 1978 indicates that the glacier has undergone a substantial deceleration between observations. Portions of the glacier flowing at speeds of ~850ma–1 in 1978/79 were flowing at ~650ma–1 in 2000/01. The cause of this change in ice dynamics is not known, but the observation shows that East Antarctic outlet glaciers can undergo substantial changes on relatively short timescales.

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