scholarly journals Estimate Yengisogat Glacier Surface Flow Velocities Using ALOS PALSAR Data Feature-tracking, Karakoram,China

2012 ◽  
Vol 12 ◽  
pp. 646-652 ◽  
Author(s):  
Jiang Zongli ◽  
Liu Shiyin ◽  
Long Sichun ◽  
Wang Xin
Keyword(s):  
Feature Tracking ◽  
Surface Flow ◽  
Alos Palsar ◽  
Glacier Surface ◽  
Flow Velocities

Global mapping of surface flow velocity and re-evaluation of the volume of the world's glaciers

2021 ◽  
Author(s):  
Romain Millan ◽  
Jérémie Mouginot ◽  
Antoine Rabatel ◽  
Mathieu Morlighem
Keyword(s):  
Water Resources ◽  
Flow Velocity ◽  
Sea Level ◽  
Surface Flow ◽  
Glacier Surface ◽  
Ice Flow ◽  
Ice Volume ◽  
The World ◽  
Global Mapping ◽  
Flow Velocities

<p><span>The effects of climate change on water resources and sea level are largely determined by the size of the ice reservoirs around the world, which still remains largely uncertain. Ice flow defines the transfer of ice within a glacier and therefore largely governs the spatial distribution of the ice volume. Although some individual regions have been mapped, there is to date no global and complete view of glacier flow. In this study, we present a global mapping of surface ice flow velocity and use it to revise the ice thickness distribution and volume of glaciers around the world. Glacier surface flow velocities were calculated using Sentinel-2/ESA, Landsat-8/USGS, <span><span>Ven</span></span></span>μ<span>s/CNES-ISA, Pléiades/AirbusD&S and radar data from Sentinel-1/ESA. We designed an automated workflow that (i) downloads the data from institutional or commercial servers, (ii) prepares the images, (iii) launches the feature tracking algorithm, (iv) calibrate the glacier surface velocities, and (v) mosaics the results to obtain filtered and averaged velocity maps. For years 2017 and 2018, glacier surface flow velocities are quantified for every possible repeat cycles from the nominal cycle of the sensor (2-16 days) up to more than one year. This new database of glacier surface flow velocity is used to construct an updated global ice volume based on the well known Shallow Ice Approximation approach. We discuss the quality of our global glacier surface flow velocity product and of our new ice volume reconstruction with respect to existing state of the art estimates and quantify the impact of our results in terms of sea level rise and water resources. <br></span></p>

Dynamics of tidewater surge-type glaciers in northwest Svalbard

2012 ◽  
Vol 58 (207) ◽  
pp. 110-118 ◽  
Author(s):  
Damien Mansell ◽  
Adrian Luckman ◽  
Tavi Murray
Keyword(s):  
Active Phase ◽  
Surface Flow ◽  
Alos Palsar ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Ice Flow ◽  
Compressive Stresses ◽  
Flow Speeds ◽  
Iceberg Calving ◽  
Speed Up

AbstractThe evolution of ice dynamics through surges of four tidewater-terminating glaciers in northwest Svalbard is investigated by remote sensing. A 20 year time series of glacier surface flow speeds and frontal positions is presented covering the recent surges of Monacobreen, Comfortlessbreen, Blomstrandbreen and Fjortende Julibreen. Surface flow speeds were derived using feature tracking between pairs of ERS SAR and ALOS PALSAR images, while frontal positions were taken from the same imagery, as well as more frequent but lower-spatial-resolution Envisat Wide Swath Mode images. During all four surges, increased ice flow caused the tidewater margin to advance while the calving flux was initially reduced to near zero due to compressive stresses limiting crevasse propagation. As ice speed decreased, the terminus continued to advance, until the glacier’s speed had returned to its pre-surge flow rate. Only at this time did the terminus start to retreat and peak iceberg calving flux was established. We conclude that terminus advance closely tracks glacier speed-up, that there is little mass loss through calving during the most active phase of the surge, and that seasonal cycles of terminus positions diminish during the active surge phase.

Analyzing Yengisogat Glacier surface velocities with ALOS PALSAR data feature tracking, Karakoram, China

2012 ◽  
Vol 67 (4) ◽  
pp. 1033-1043 ◽  
Author(s):  
Zong-li Jiang ◽  
Shi-yin Liu ◽  
Juliane Peters ◽  
Jian Lin ◽  
Si-chun Long ◽  
...  
Keyword(s):  
Feature Tracking ◽  
Alos Palsar ◽  
Glacier Surface

scholarly journals Unravelling the evolution of Zmuttgletscher and its debris cover since the end of the Little Ice Age

2019 ◽  
Vol 13 (7) ◽  
pp. 1889-1909 ◽  
Author(s):  
Nico Mölg ◽  
Tobias Bolch ◽  
Andrea Walter ◽  
Andreas Vieli
Keyword(s):  
Mass Balance ◽  
Ice Age ◽  
Aerial Photographs ◽  
Dynamic Interactions ◽  
Glacier Surface ◽  
Ablation Area ◽  
Debris Cover ◽  
Historic Maps ◽  
Length And Area ◽  
Flow Velocities

Abstract. Debris-covered glaciers generally exhibit large, gently sloping, slow-flowing tongues. At present, many of these glaciers show high thinning rates despite thick debris cover. Due to the lack of observations, most existing studies have neglected the dynamic interactions between debris cover and glacier evolution over longer time periods. The main aim of this study is to reveal such interactions by reconstructing changes of debris cover, glacier geometry, flow velocities, and surface features of Zmuttgletscher (Switzerland), based on historic maps, satellite images, aerial photographs, and field observations. We show that debris cover extent has increased from ∼13 % to ∼32 % of the total glacier surface since 1859 and that in 2017 the debris is sufficiently thick to reduce ablation compared to bare ice over much of the ablation area. Despite the debris cover, the glacier-wide mass balance of Zmuttgletscher is comparable to that of debris-free glaciers located in similar settings, whereas changes in length and area have been small and delayed by comparison. Increased ice mass input in the 1970s and 1980s resulted in a temporary velocity increase, which led to a local decrease in debris cover extent, a lowering of the upper boundary of the ice-cliff zone, and a strong reduction in ice-cliff area, indicating a dynamic link between flow velocities, debris cover, and surface morphology. Since 2005, the lowermost 1.5 km of the glacier has been quasi-stagnant, despite a slight increase in the surface slope of the glacier tongue. We conclude that the long-term glacier-wide mass balance is mainly governed by climate. The debris cover governs the spatial pattern of elevation change without changing its glacier-wide magnitude, which we explain by the extended ablation area and the enhanced thinning in regions with thin debris further up-glacier and in areas with abundant meltwater channels and ice cliffs. At the same time rising temperatures lead to increasing debris cover and decreasing ice flux, thereby attenuating length and area losses.

scholarly journals SenDiT: The Sentinel-2 Displacement Toolbox with Application to Glacier Surface Velocities

2019 ◽  
Vol 11 (10) ◽  
pp. 1151
Author(s):  
Teodor Nagy ◽  
Liss M. Andreassen ◽  
Robert A. Duller ◽  
Pablo J. Gonzalez
Keyword(s):  
Feature Tracking ◽  
World Wide ◽  
Satellite Images ◽  
Glacier Surface ◽  
Displacement Maps ◽  
Spatial And Temporal Changes ◽  
Glacier Velocity ◽  
Glacier Flow ◽  
Sentinel 2A ◽  
Sentinel 2

Satellite imagery represents a unique opportunity to quantify the spatial and temporal changes of glaciers world-wide. Glacier velocity has been measured from repeat satellite scenes for decades now, yet a range of satellite missions, feature tracking programs, and user approaches have made it a laborious task. To date, there has been no tool developed that would allow a user to obtain displacement maps of any specified glacier simply by establishing the key temporal, spatial and feature tracking parameters. This work presents the application and development of a unique, semi-automatic, open-source, flexible processing toolbox for the retrieval of displacement maps with a focus on obtaining glacier surface velocities. SenDiT combines the download, pre-processing, feature tracking, and postprocessing of the highest resolution Sentinel-2A and Sentinel-2B satellite images into a semi-automatic toolbox, leaving a user with a set of rasterized and georeferenced glacier flow magnitude and direction maps for their further analyses. The solution is freely available and is tailored so that non-glaciologists and people with limited geographic information system (GIS) knowledge can also benefit from it. The system can be used to provide both regional and global sets of ice velocities. The system was tested and applied on a range of glaciers in mainland Norway, Iceland, Greenland and New Zealand. It was also tested on areas of stable terrain in Libya and Australia, where sources of error involved in the feature tracking using Sentinel-2 imagery are thoroughly described and quantified.

Remote sensing flow velocity of debris-covered glaciers using Landsat 8 data

2015 ◽  
Vol 40 (2) ◽  
pp. 305-321 ◽  
Author(s):  
Lydia Sam ◽  
Anshuman Bhardwaj ◽  
Shaktiman Singh ◽  
Rajesh Kumar
Keyword(s):  
Remote Sensing ◽  
Flow Velocity ◽  
Accuracy Assessment ◽  
Geographical Area ◽  
Surface Flow ◽  
Velocity Estimation ◽  
Surface Velocity ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Glacier Velocity

Changes in ice velocity of a glacier regulate its mass balance and dynamics. The estimation of glacier flow velocity is therefore an important aspect of temporal glacier monitoring. The utilisation of conventional ground-based techniques for detecting glacier surface flow velocity in the rugged and alpine Himalayan terrain is extremely difficult. Remote sensing-based techniques can provide such observations on a regular basis for a large geographical area. Obtaining freely available high quality remote sensing data for the Himalayan regions is challenging. In the present work, we adopted a differential band composite approach, for the first time, in order to estimate glacier surface velocity for non-debris and supraglacial debris covered areas of a glacier, separately. We employed various bandwidths of the Landsat 8 data for velocity estimation using the COSI-Corr (co-registration of optically sensed images and correlation) tool. We performed the accuracy assessment with respect to field measurements for two glaciers in the Indian Himalaya. The panchromatic band worked best for non-debris parts of the glaciers while band 6 (SWIR – short wave infrared) performed best in case of debris cover. We correlated six temporal Landsat 8 scenes in order to ensure the performance of the proposed algorithm on monthly as well as yearly timescales. We identified sources of error and generated a final velocity map along with the flow lines. Over- and underestimates of the yearly glacier velocity were found to be more in the case of slow moving areas with annual displacements less than 5 m. Landsat 8 has great capabilities for such velocity estimation work for a large geographic extent because of its global coverage, improved spectral and radiometric resolutions, free availability and considerable revisit time.

scholarly journals The response of a glacier to a surface disturbance: a case study on Vatnajökull ice cap, Iceland

2000 ◽  
Vol 31 ◽  
pp. 104-110 ◽  
Author(s):  
G. Aðalgeirsdóttir ◽  
G. H. Gudmundsson ◽  
H. Björnsson
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Measurement Errors ◽  
Element Model ◽  
Horizontal Stress ◽  
Surface Flow ◽  
Repeated Measurements ◽  
Ice Cap ◽  
Elevation Changes ◽  
Flow Velocities

AbstractIn the course of a tremendous outburst flood (jökulhlaup) following the subglacial eruption in Vatnajökull, Iceland, in October 1996, a depression in the surface of the ice cap was created as a result of ice melting from the walls of a subglacial tunnel. The surface depression was initially approximately 6 km long, 800 m wide and 100 m deep. This ˚canyon" represents a significant perturbation in the geometry of the ice cap in this area where the total ice thickness is about 200–400 m. We present results of repeated measurements of flow velocities and elevation changes in the vicinity of the canyon made over a period of about 2 years. The measurements show a reduction in the depth of the canyon and a concomitant decrease in surface flow towards it over time. By calculating the transient evolution of idealized surface depressions using both analytical zeroth- and first-order theories, as well as the shallow-ice approximation (SIA) and a finite-element model incorporating all the terms of the momentum equations we demonstrate the importance of horizontal stress gradients at the spatial scale of this canyon. The transient evolution of the canyon is calculated with a two-dimensional time-dependent finite-element model with flow parameters (the parameters A and n of Glen’s flow law) that are tuned towards an optimal agreement with measured flow velocities. Although differences between measured and calculated velocities are comparable to measurement errors, the differences are not randomly distributed. The model is therefore not verified in detail. Nevertheless the model reproduces observed changes in the geometry over a 15 month time period reasonably well The model also reproduces changes in both velocities and geometry considerably better than an alternative model based on the SIA.

Evaluation of the tablets’ surface flow velocities in pan coaters

2016 ◽  
Vol 106 ◽  
pp. 97-106 ◽  
Author(s):  
Rok Dreu ◽  
Gregor Toschkoff ◽  
Adrian Funke ◽  
Andreas Altmeyer ◽  
Klaus Knop ◽  
...  
Keyword(s):  
Surface Flow ◽  
Flow Velocities

scholarly journals Long-term records of glacier surface velocities in the Ötztal Alps (Austria)

2019 ◽  
Author(s):  
Martin Stocker-Waldhuber ◽  
Andrea Fischer ◽  
Kay Helfricht ◽  
Michael Kuhn
Keyword(s):  
Mass Balance ◽  
Glacier Mass Balance ◽  
Data Sets ◽  
Climatic Forcing ◽  
Glacier Surface ◽  
Ice Flow ◽  
Strong Indicator ◽  
Length Changes ◽  
Flow Velocities

Abstract. Climatic forcing affects glacier mass balance and ice flow dynamics on different time scales, resulting in length changes. Mass Balance and length changes are operationally used for glacier monitoring, whereas only a few time series of glacier dynamics have been recorded. With more than 100 years of measurements of ice flow velocities at stakes and stone lines on Hintereisferner and more than 50 years on Kesselwandferner, annual velocity and glacier fluctuation records have similar lengths. Subseasonal variations of ice flow velocities have been measured on Gepatschferner and Taschachferner for nearly a decade. The ice flow velocities on Hintereisferner and especially on Kesselwandferner show great variations between advancing and retreating periods, with magnitudes increasing from the highest to the lowest stakes, making ice flow records at ablation stakes a very sensitive indicator of glacier state. Since the end of the latest glacier advances from the 1970s to the 1980s, the ice flow velocities have decreased continuously, a strong indicator of the negative mass balances of the glaciers in recent decades. The velocity data sets of the four glaciers are available at https://doi.pangaea.de/10.1594/PANGAEA.896741.

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