Surface velocity variations of glaciers on Kenai Peninsula, Alaska, 2014-2019

2021 ◽  
Author(s):  
Ruitang Yang ◽  
Regine Hock ◽  
Shichang Kang ◽  
Donghui Shangguan ◽  
Wanqin Guo
Keyword(s):  
Time Series ◽  
Velocity Profile ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Spatiotemporal Variations ◽  
Outburst Flood ◽  
Mean Velocity ◽  
Kenai Peninsula ◽  
Speed Up ◽  
Offset Tracking

<p>We characterize the spatiotemporal variations surface velocity of glaciers on the Kenai Peninsula, Alaska, using intensity offset tracking on a set of repeat-pass Sentinel-1 data and TerraSAR-X data. We derived 92 velocity fields and generated time-averaged annual and seasonal surface velocity maps for the period October 2014 to December 2019, as well as time series surface velocity profiles along centerlines for individual glaciers. We find considerable spatial and seasonal variations in surface velocity in the study area, especially a pronounced average spring speedup of 50% averagely compared to annual mean velocity. Ice velocities varied systematically between glaciers with different terminus types. Generally, the pixel-averaged velocity of tidewater and lake-terminating glaciers are up to 2 and 1.5 times greater than those of the land-terminating glaciers, respectively. For Bear glacier, with the analysis of surface velocity profile and the terminus change, we state this glacier retreat and accelerate. While the time-series result shows the velocity speed-up of the Bear glacier synchronizes well with the ice-damaged lake outburst flood (GLOF) events.</p>

scholarly journals A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity

2020 ◽  
Vol 14 (1) ◽  
pp. 211-227 ◽  
Author(s):  
Ian Joughin ◽  
David E. Shean ◽  
Benjamin E. Smith ◽  
Dana Floricioiu
Keyword(s):  
Time Series ◽  
Brittle Failure ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Relative Timing ◽  
Elevation Data ◽  
Speed Up ◽  
Dominant Influence

Abstract. The speed of Greenland's fastest glacier, Jakobshavn Isbræ, has varied substantially since its speed-up in the late 1990s. Here we present observations of surface velocity, mélange rigidity, and surface elevation to examine its behaviour over the last decade. Consistent with earlier results, we find a pronounced cycle of summer speed-up and thinning followed by winter slowdown and thickening. There were extended periods of rigid mélange in the winters of 2016–2017 and 2017–2018, concurrent with terminus advances ∼6 km farther than in the several winters prior. These terminus advances to shallower depths caused slowdowns, leading to substantial thickening, as has been noted elsewhere. The extended periods of rigid mélange coincide well with a period of cooler waters in Disko Bay. Thus, along with the relative timing of the seasonal slowdown, our results suggest that the ocean's dominant influence on Jakobshavn Isbræ is through its effect on winter mélange rigidity, rather than summer submarine melting. The elevation time series also reveals that in summers when the area upstream of the terminus approaches flotation, large surface depressions can form, which eventually become the detachment points for major calving events. It appears that as elevations approach flotation, basal crevasses can form, which initiates a necking process that forms the depressions. The elevation data also show that steep cliffs often evolve into short floating extensions, rather than collapsing catastrophically due to brittle failure. Finally, summer 2019 speeds were slightly faster than the prior two summers, leaving it unclear whether the slowdown is ending.

Image stereoscopic models for the advanced analysis of landslide deformation and thickness

2021 ◽  
Author(s):  
Mathilde Desrues ◽  
Renaud Toussaint ◽  
Jean-Philippe Malet
Keyword(s):  
Time Series ◽  
Surface Displacement ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Deformation Analysis ◽  
Moving Mass ◽  
Optical Images ◽  
Spatial Coverage ◽  
Advanced Analysis

<p>The analysis of surface displacement and velocity fields from time series of terrestrial optical images is a useful tool for monitoring gravitational instabilities. It allows to define the state of instability of the slope, its evolution in time, its spatial coverage and to identify if the movement is progressing. Other types of information can also be extracted from landslide surface velocity fields such as the tangential and normal deformation or the strain fields that highlight areas of compression/extension (Travelletti et al., 2014) that can even allow to assess the mechanical properties of the moving mass (Baum et al., 1998). However, applying such advanced approaches necessitates to be able to compute the 3D displacements and deconvolute the normal and tangential displacements.</p><p>Landslide ground motion can be measured by various geodetic techniques either in-situ and point-based, or remote and giving access to spatially distributed information. In this study, we privileged a low-cost remote sensing method based on the use of a Single Lens Reflex (SLR) cameras. We acquired data at high frequency (i.e., time-lapse photography) from two fixed cameras at the Montgombert landslide.</p><p>The velocity fields were extracted from a time series of 13 images by applying the TSM (Tracing Surface Motion; Desrues et al. 2019) code. To detect tangential and normal displacements, we developed a methodology to construct the 3D displacements directly from the correlation results from the pairwise combination of the two monoscopic velocity fields, and further conducted a deformation analysis.</p><p>To estimate the thickness of the moving mass from the 3D displacements derived from the stereoscopic optical images, we propose a methodology based on the law of mass conservation (i.e., displacement incompressible) by invoking the rheology of the material involved (Booth et al., 2013). In order to take into account, in this model, a more complex slip geometry, we introduced a disbonding parameter that marks the presence of a dislocation area at the top limit of the moving mass which traduces a non-zero velocity at the sliding surface.</p><p>We present the methodology of reconstruction of the 3D displacements with a stereoscopic approach and of estimation of the landslide thickness by applying them to the Montgombert use case (Savoie, French Alps). The calculated displacement fields are consistent with in-situ data and the estimated depths, suggesting a shallow sliding, are consistent with geotechnical information.</p>

scholarly journals Retrieving and Verifying Three-Dimensional Surface Motion Displacement of Mountain Glacier from Sentinel-1 Imagery Using Optimized Method

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1793
Author(s):  
Yanqiang Wang ◽  
Jun Zhao ◽  
Zhongqin Li ◽  
Mingjun Zhang ◽  
Yuchun Wang ◽  
...  
Keyword(s):  
Time Series ◽  
Three Dimensional ◽  
Measurement Data ◽  
Surface Velocity ◽  
Special Importance ◽  
Mountain Glacier ◽  
Surface Motion ◽  
Mountain Glaciers ◽  
3D Surface ◽  
Offset Tracking

The time series study of glacier movement is of special importance for rational management of freshwater resources, studying glacier evolution, understanding mechanism of glacier movement, and assessing disasters caused by glacier movement. In this paper, we put forward an optimization scheme for the shortcomings in the calculation method of using remote sensing to invert the three-dimensional (3D) surface motion displacement of glacier. The optimized method consists of Offset Tracking method, Optimizing the offset tracking results by means of iterative filtering, OT-SBAS technology and Conversion of 3D surface motion displacement of glacier. The Urumqi Glacier No. 1 was selected to test the optimized method. The 3D surface motion displacement of Urumqi Glacier No. 1 was retrieved by using the optimized method based on the ascending and descending Sentinel-1 datasets from 19 April to 29 August 2018. The distribution of 3D surface velocity of the Urumqi Glacier No. 1 was obtained in time series, and the accuracy of the inversion results was evaluated by using the field measurement data. The results show that the accuracies of the inverted displacements of east branch of Urumqi Glacier No. 1 (UG1E) were about 0.062, 0.063, and 0.152 m in the east, north and vertical directions, and these values for the west branch (UG1W) were 0.015, 0.020 and 0.026 m, respectively. It is indicated that using Sentinel-1 ascending and descending data and using the optimized method to retrieve the 3D surface motion displacement of glacier should satisfy the requirements of inversing the 3D surface motion displacement of high-latitude mountain glaciers in China.

scholarly journals Global time series and temporal mosaics of glacier surface velocities, derived from Sentinel-1 data

2021 ◽  
Author(s):  
Peter Friedl ◽  
Thorsten Seehaus ◽  
Matthias Braun
Keyword(s):  
Time Series ◽  
Speckle Tracking ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Synthetic Aperture ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Data Set ◽  
Time Series Analyses ◽  
Very High

Abstract. Consistent and continuous data on glacier surface velocity are important inputs to time series analyses, numerical ice dynamic modelling and glacier mass flux computations. Since 2014, repeat-pass Synthetic Aperture Radar (SAR) data is acquired by the Sentinel-1 satellite constellation as part of ESA’s (European Space Agency) Copernicus program. It enables global, near real time-like and fully automatic processing of glacier surface velocity fields at up to 6-day temporal resolution, independent of weather conditions, season and daylight. We present a new near global data set of glacier surface velocities that comprises continuously updated scene-pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution. The velocity information is derived from archived and new Sentinel-1 SAR acquisitions by applying feature and speckle tracking. The data set covers 12 major glaciated regions outside the polar ice sheets and is generated in an HPC (High Performance Computing) environment at the University of Erlangen-Nuremberg. The velocity products are freely accessible via an interactive web portal that provides capabilities for download and simple online analyses: http://retreat.geographie.uni-erlangen.de. In this paper we give information on the data processing and how to access the data. For the example region of Svalbard, we demonstrate the potential of our products for velocity time series analyses at very high temporal resolution and assess the quality of our velocity products by comparing them to those generated from very high resolution TerraSAR-X SAR (Synthetic Aperture Radar) and Landsat-8 optical (ITS_LIVE, GoLIVE) data. We find that Landsat-8 and Sentinel-1 annual velocity mosaics are in an overall good agreement, but speckle tracking on Sentinel-1 6-day repeat acquisitions derives more reliable velocity measurements over featureless and slow moving areas than the optical data. Additionally, uncertainties of 12-day repeat Sentinel-1 mid-glacier scene-pair velocities are less than half (< 0.08 m d−1) of the uncertainties derived for 16-day repeat Landsat-8 data (0.17–0.18 m d−1).

scholarly journals Spatial and temporal evolution of rapid basal sliding on Bench Glacier, Alaska, USA

2005 ◽  
Vol 51 (172) ◽  
pp. 49-63 ◽  
Author(s):  
Kelly R. Macgregor ◽  
Catherine A. Riihimaki ◽  
Robert S. Anderson
Keyword(s):  
Temporal Evolution ◽  
Surface Velocity ◽  
Mean Velocity ◽  
Surface Uplift ◽  
Ice Surface ◽  
Velocity Wave ◽  
Basal Sliding ◽  
Hydrologic System ◽  
Speed Up ◽  
Cavity System

AbstractWe measured the surface velocity field during the summers of 1999 and 2000 on the 7 km long, 185 m thick Bench Glacier, Alaska, USA. In the spring of both years, a short-lived pulse of surface velocity, 2-4 times the annual mean velocity, propagated up-glacier from the terminus at a rate of ~200-250md-1. Displacement attributable to rapid sliding is ~5-10% of the annual surface motion, while the high-velocity event comprised 60-95% of annual basal motion. Sliding during the propagating speed-up event peaked at 6-14 cm d-1, with the highest rates in mid-glacier. Continuous horizontal and vertical GPS measurements at one stake showed divergence and then convergence of the ice surface with the bed as the velocity wave passed, with maximum surface uplift of 8-16 cm. High divergence rates coincided with high horizontal velocities, suggesting rapid sliding on the up-glacier side of bedrock steps. Initiation of the annual speed-up event occurred during the peak in englacial water storage, while the glacier was entirely snow-covered. Basal motion during the propagating speed-up event enlarges cavities and connections among them, driving a transition from a poorly connected hydrologic system to a well-connected linked-cavity system. Sliding is probably halted by the development of a conduit system.

scholarly journals Near-Field Remote Sensing of Surface Velocity and River Discharge Using Radars and the Probability Concept at 10 U.S. Geological Survey Streamgages

2020 ◽  
Vol 12 (8) ◽  
pp. 1296 ◽  
Author(s):  
John W. Fulton ◽  
Christopher A. Mason ◽  
John R. Eggleston ◽  
Matthew J. Nicotra ◽  
Chao-Lin Chiu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Time Series ◽  
Real Time ◽  
River Discharge ◽  
Near Field ◽  
Geological Survey ◽  
Surface Velocity ◽  
Mean Velocity ◽  
Probability Concept ◽  
Conventional Methods

Near-field remote sensing of surface velocity and river discharge (discharge) were measured using coherent, continuous wave Doppler and pulsed radars. Traditional streamgaging requires sensors be deployed in the water column; however, near-field remote sensing has the potential to transform streamgaging operations through non-contact methods in the U.S. Geological Survey (USGS) and other agencies around the world. To differentiate from satellite or high-altitude platforms, near-field remote sensing is conducted from fixed platforms such as bridges and cable stays. Radar gages were collocated with 10 USGS streamgages in river reaches of varying hydrologic and hydraulic characteristics, where basin size ranged from 381 to 66,200 square kilometers. Radar-derived mean-channel (mean) velocity and discharge were computed using the probability concept and were compared to conventional instantaneous measurements and time series. To test the efficacy of near-field methods, radars were deployed for extended periods of time to capture a range of hydraulic conditions and environmental factors. During the operational phase, continuous time series of surface velocity, radar-derived discharge, and stage-discharge were recorded, computed, and transmitted contemporaneously and continuously in real time every 5 to 15 min. Minimum and maximum surface velocities ranged from 0.30 to 3.84 m per second (m/s); minimum and maximum radar-derived discharges ranged from 0.17 to 4890 cubic meters per second (m3/s); and minimum and maximum stage-discharge ranged from 0.12 to 4950 m3/s. Comparisons between radar and stage-discharge time series were evaluated using goodness-of-fit statistics, which provided a measure of the utility of the probability concept to compute discharge from a singular surface velocity and cross-sectional area relative to conventional methods. Mean velocity and discharge data indicate that velocity radars are highly correlated with conventional methods and are a viable near-field remote sensing technology that can be operationalized to deliver real-time surface velocity, mean velocity, and discharge.

scholarly journals Surface speed and frontal ablation of Kronebreen and Kongsbreen, NW-Svalbard, from SAR offset tracking

2014 ◽  
Vol 8 (6) ◽  
pp. 6193-6233 ◽  
Author(s):  
T. Schellenberger ◽  
T. Dunse ◽  
A. Kääb ◽  
J. Kohler ◽  
C. H. Reijmer
Keyword(s):  
Water Pressure ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Gps Measurements ◽  
Ice Flow ◽  
Area Loss ◽  
Continuous Gps ◽  
Offset Tracking ◽  
Frontal Ablation ◽  
Data Surface

Abstract. Kronebreen and Kongsbreen are among the fastest flowing glaciers on Svalbard, and therefore important contributors to glacier mass loss from the archipelago through frontal ablation. Here, we present a time series of area-wide surface velocity fields from April 2012 to December 2013 based on offset tracking on repeat high-resolution Radarsat-2 Ultrafine data. Surface speeds reached up to 3.2 m d−1 near the calving front of Kronebreen in summer 2013 and 2.7 m d−1 at Kongsbreen in late autumn 2012. Additional velocity fields from Radarsat-1, Radarsat-2 and TerraSAR-X data since December 2007 together with continuous GPS measurements on Kronebreen since September 2008 revealed complex patterns in seasonal and interannual speed evolution. Part of the ice-flow variations seem closely linked to the amount and timing of surface melt water production and rainfall, both of which are known to have a strong influence on the basal water pressure and lubrication. In addition, terminus retreat and the associated reduction in backstress appear to have influenced the speed close to the calving front, especially at Kongsbreen in 2012 and 2013. Since 2007, Kongsbreen retreated up to 1800 m, corresponding to a total area loss of 2.5 km2. In 2011 the retreat of Kronebreen of up to 850 m, responsible for a total area loss of 2.8 km2, was triggered after a phase of stable terminus position since ~1990. The retreat is an important component of the mass balance of both glaciers, in which frontal ablation is the largest component. Total frontal ablation between April 2012 and December 2013 was estimated to 0.21–0.25 Gt a−1 for Kronebreen and 0.14–0.16 Gt a−1 for Kongsbreen.

scholarly journals Global time series and temporal mosaics of glacier surface velocities derived from Sentinel-1 data

2021 ◽  
Vol 13 (10) ◽  
pp. 4653-4675
Author(s):  
Peter Friedl ◽  
Thorsten Seehaus ◽  
Matthias Braun
Keyword(s):  
Time Series ◽  
Temporal Resolution ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Optical Data ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Data Set ◽  
Time Series Analyses ◽  
Very High

Abstract. Consistent and continuous data on glacier surface velocity are important inputs to time series analyses, numerical ice dynamic modeling and glacier mass flux computations. Since 2014, repeat-pass synthetic aperture radar (SAR) data have been acquired by the Sentinel-1 satellite constellation as part of the Copernicus program of the EU (European Union) and ESA (European Space Agency). It enables global, near-real-time-like and fully automatic processing of glacier surface velocity fields at up to 6 d temporal resolution, independent of weather conditions, season and daylight. We present a new global data set of glacier surface velocities that comprises continuously updated scene-pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution. The velocity information is derived from archived and new Sentinel-1 SAR acquisitions by applying a well-established intensity offset tracking technique. The data set covers 12 major glacierized regions outside the polar ice sheets and is generated in an HPC (high-performance computing) environment at the University of Erlangen-Nuremberg. The velocity products are freely accessible via an interactive web portal that provides capabilities for download and simple online analyses: http://retreat.geographie.uni-erlangen.de (last access: 6 October 2021). In this paper, we give information on the data processing and how to access the data. For the example region of Svalbard, we demonstrate the potential of our products for velocity time series analyses at very high temporal resolution and assess the quality of our velocity products by comparing them to those generated from very high-resolution TerraSAR-X SAR and Landsat-8 optical (ITS_LIVE, GoLIVE) data. The subset of Sentinel-1 velocities for Svalbard analyzed in this paper is accessible via the GFZ Potsdam Data Services under the DOI https://doi.org/10.5880/fidgeo.2021.016 (Friedl et al., 2021). We find that Landsat-8 and Sentinel-1 annual velocity mosaics are in an overall good agreement, but speckle tracking on Sentinel-1 6 d repeat acquisitions derives more reliable velocity measurements over featureless and slow-moving areas than the optical data. Additionally, uncertainties of 12 d repeat Sentinel-1 mid-glacier scene-pair velocities have less than half (< 0.08 m d−1) of the uncertainties derived for 16 d repeat Landsat-8 data (0.17–0.18 m d−1).

scholarly journals Surface speed and frontal ablation of Kronebreen and Kongsbreen, NW Svalbard, from SAR offset tracking

2015 ◽  
Vol 9 (6) ◽  
pp. 2339-2355 ◽  
Author(s):  
T. Schellenberger ◽  
T. Dunse ◽  
A. Kääb ◽  
J. Kohler ◽  
C. H. Reijmer
Keyword(s):  
Water Pressure ◽  
Back Stress ◽  
Velocity Fields ◽  
Surface Velocity ◽  
Ice Flow ◽  
Area Loss ◽  
Continuous Gps ◽  
Offset Tracking ◽  
Frontal Ablation ◽  
Data Surface

Abstract. Kronebreen and Kongsbreen are among the fastest-flowing glaciers on Svalbard and, therefore, important contributors to the total dynamic mass loss from the archipelago. Here, we present a time series of area-wide surface velocity fields from April 2012 to December 2013 based on offset tracking on repeat high-resolution Radarsat-2 Ultrafine data. Surface speeds reached up to 3.2 m d−1 near the calving front of Kronebreen in summer 2013 and 2.7 m d−1 at Kongsbreen in late autumn 2012. Additional velocity fields from Radarsat-1, Radarsat-2 and TerraSAR-X data since December 2007 together with continuous GPS measurements on Kronebreen since September 2008 revealed complex patterns in seasonal and interannual speed evolution. Part of the ice-flow variations seem closely linked to the amount and timing of surface meltwater production and rainfall, both of which are known to have a strong influence on the basal water pressure and hence basal lubrication. In addition, terminus retreat and the associated reduction in back stress appear to have influenced the speed close to the calving front, especially at Kongsbreen in 2012 and 2013. Since 2007, Kongsbreen retreated up to 1800 m, corresponding to a total area loss of 2.5 km2. In 2011 the retreat of Kronebreen of up to 850 m, responsible for a total area loss of 2.8 km2, was triggered after a phase of stable terminus position since ~ 1990. Retreat is an important component of the mass balance of both glaciers, in which frontal ablation is the largest component. Total frontal ablation between April 2012 and December 2013 was estimated to 0.21–0.25 Gt a−1 for Kronebreen and 0.14–0.16 Gt a−1 for Kongsbreen.

Sign in / Sign up

Export Citation Format

Share Document