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

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.

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Spatio-temporal variations in glacier surface velocity in the Himalayas

10.5194/esurf-2021-21 ◽

2021 ◽

Author(s):

Yu Zhou ◽

Jianlong Chen ◽

Xiao Cheng

Keyword(s):

Mass Loss ◽

Temporal Variations ◽

Surface Velocity ◽

Glacier Surface ◽

Environmental Forcing ◽

Landsat 7 ◽

Spatio Temporal ◽

Velocity Changes ◽

Glacier Velocity ◽

Glacier Flow

Abstract. Glacier evolution with time provides important information about climate variability. Here we investigate glacier surface velocity in the Himalayas and analyse the patterns of glacier flow. We collect 220 scenes of Landsat-7 panchromatic images between 1999 and 2000, and Sentinel-2 panchromatic images between 2017 and 2018, to calculate surface velocities of 36,722 glaciers during these two periods. We then derive velocity changes between 1999 and 2018, based on which we perform a detailed analysis of motion of each individual glacier, and noted that the changes are spatially heterogeneous. Of all the glaciers, 32 % have speeded up, 24.5 % have slowed down, and the rest 43.5 % remained stable. The amplitude of glacier slowdown, as a result of glacier mass loss, is remarkably larger than that of speedup. At regional scales, we found that glacier surface velocity in winter has uniformly decreased in the western part of the Himalayas between 1999 and 2018, whilst increased in the eastern part; this contrasting difference may be associated with decadal changes in accumulation and/or melting under different climatic regimes. We also found that the overall trend of surface velocity exhibits seasonal variability: summer velocity changes are positively correlated with mass loss, whereas winter velocity changes show a negative correlation. Our study suggests that glacier velocity changes in the Himalayas are more spatially and temporally heterogeneous than previously thought, emphasising complex interactions between glacier dynamics and environmental forcing.

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Glacier velocity measurements in the eastern Yigong Zangbo basin, Tibet, China

Journal of Glaciology ◽

10.3189/2013jog12j234 ◽

2013 ◽

Vol 59 (218) ◽

pp. 1060-1068 ◽

Cited By ~ 11

Author(s):

Chang-Qing Ke ◽

Cheng Kou ◽

Ralf Ludwig ◽

Xiang Qin

Keyword(s):

Feature Tracking ◽

Flow Patterns ◽

Small Scale ◽

Glacier Area ◽

Velocity Measurements ◽

Sar Images ◽

Motion Patterns ◽

The Mean ◽

Glacier Velocity ◽

Glacier Flow

AbstractWe apply the feature-tracking method to L-band synthetic aperture radar (SAR) images to derive detailed motion patterns of glaciers in the Yigong Zangbo basin during summer 2007. The results indicate that the flow patterns are generally constrained by the valley geometry and terrain complexity. The mean velocities of the 12 glaciers were 15–206 m a−1,with a maximum of 423 m a−1 for Glacier No. 5a. The majority of the glaciers exhibited high and low velocities in their upper and lower sections, respectively. The glacier area ranges from 3 to 42 km2. It is found that velocity shows a positive correlation with the glacier area and length. Many small-scale temporal/spatial variations in the glacier flow patterns were observed along the central glacier flowline.

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Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

10.5194/egusphere-egu21-13311 ◽

2021 ◽

Author(s):

Jan Bouke Pronk ◽

Tobias Bolch ◽

Owen King ◽

Bert Wouters ◽

Douglas Benn

Keyword(s):

Flow Line ◽

Surface Velocity ◽

Glacier Surface ◽

Ice Flow ◽

Mass Losses ◽

Himalayan Glaciers ◽

Large Heterogeneity ◽

Glacier Flow ◽

The Ganges ◽

Sentinel 2

Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are likely to occur in coming decades. About 10 % of the Himalayan glacier population terminates into pro-glacial lakes and such lake-terminating glaciers are known to be capable of accelerating total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a 2017-2019 glacier surface velocity dataset, derived from Sentinel 2 imagery, covering most of the Central and Eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers are more than double those of land-terminating glaciers (18.8 vs 8.24 m yr-1) and show substantially more heterogeneity around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which effects about half of the clean-ice lake-terminating glacier population. Also, numerical ice-flow model experiments suggest that changes at the frontal boundary condition can play a key role in accelerating the glacier flow at the front. With continued warming new lake development is likely to happen and will further accelerate future ice mass losses, a scenario not currently considered in regional projections.&#160;

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Proglacial Lakes Elevate Glacier Surface Velocities in the Himalayan Region

10.5194/tc-2021-90 ◽

2021 ◽

Author(s):

Jan Bouke Pronk ◽

Tobias Bolch ◽

Owen King ◽

Bert Wouters ◽

Douglas I. Benn

Keyword(s):

Flow Line ◽

Surface Velocity ◽

Glacial Lakes ◽

Glacier Surface ◽

Ice Flow ◽

Himalayan Glaciers ◽

Large Heterogeneity ◽

Glacier Flow ◽

The Ganges ◽

Sentinel 2

Abstract. Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are likely to occur in coming decades. About 10 % of the Himalayan glacier population terminates into pro-glacial lakes and such lake-terminating glaciers are known to exhibit higher than average total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a composite (2017–2019) glacier surface velocity dataset, derived from Sentinel 2 imagery, covering Central and Eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers are more than double those of land-terminating glaciers (18.8 vs 8.24 m yr−1) and show substantially more heterogeneity around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which effects about half of the clean-ice lake-terminating glacier population. Numerical ice-flow model experiments show that changes at the frontal boundary condition are likely to play a key role in accelerating the glacier flow at the front, with variations in basal friction only being of modest importance. The expansion of current glacial lakes, and the formation of new meltwater bodies will influence the dynamics of an increasing number of Himalayan glaciers in the future; a scenario not currently considered in regional ice loss projections.

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Fusion and mining of glacier surface flow velocity time series

10.5194/egusphere-egu2020-20335 ◽

2020 ◽

Author(s):

Laurane Charrier ◽

Yajing Yan ◽

Elise Koeniguer ◽

Emmanuel Trouvé ◽

Romain Millan ◽

...

Keyword(s):

Time Series ◽

Flow Velocity ◽

Small Time ◽

Surface Flow ◽

Landsat 8 ◽

Glacier Surface ◽

Temporal Sampling ◽

Displacement Maps ◽

Spatio Temporal ◽

Sentinel 2

Glacier response to climate change results in natural hazards, sea level rise and changes in freshwater resources. To evaluate this response, glacier surface flow velocity constitutes a crucial parameter to study. Nowadays, more and more velocity maps at regional or global scales issued from satellite SAR and/or optical images tend to be available online or on-demand. Such amount of data requires appropriate data fusion strategies in order to generate displacement time series with improved precision and spatio-temporal coverage. The improved displacement time series can then be used by advanced multi-temporal analysis approaches for further physical interpretations of the phenomenon under observation. In this work, time series of Sentinel-2 (10~m resolution, every 5 days), Landsat-8 (15~m resolution, every 16 days) and Venus (5~m resolution, every 2 days) images acquired between January 2017 and September 2018, over the Fox glacier in the Southern Alps of New Zealand are investigated. Velocities are generated with an offset tracking technique using an automatic processing chain for every possible repeat cycles (2 days-100 days and 300 days to 400 days). Thousands of velocity maps are available, and they are subject to both uncertainty and data gaps. In order to produce a displacement time series as precise/complete as possible , we propose three fusion strategies: 1) use all the available Sentinel-2 displacement maps with different time spans. The goal is to construct a time series of displacement with respect to a common master by means of an inversion 2) take only Sentinel-2 displacement maps with as small time spans as possible, at the same time, keep as much as possible redundancy in the network to be able to construct a common master displacement time series by inversion 3) follow the previous strategy but use all available displacement maps from 3 sensors, with different temporal sampling and measurement precision taken into account. Afterwards, the common master displacement time series will be analysed by a data mining approach in order to extract unusual spatio-temporal patterns in the time series.

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Glacier Velocity Changes in the Himalayas in Relation to Ice Mass Balance

Remote Sensing ◽

10.3390/rs13193825 ◽

2021 ◽

Vol 13 (19) ◽

pp. 3825

Author(s):

Yu Zhou ◽

Jianlong Chen ◽

Xiao Cheng

Keyword(s):

Mass Loss ◽

Surface Velocity ◽

Winter Period ◽

Glacier Surface ◽

Environmental Forcing ◽

Complex Interactions ◽

Landsat 7 ◽

Velocity Changes ◽

Glacier Velocity ◽

Glacier Flow

Glacier evolution with time provides important information about climate variability. Here, we investigated glacier velocity changes in the Himalayas and analysed the patterns of glacier flow. We collected 220 scenes of Landsat-7 panchromatic images between 1999 and 2000, and Sentinel-2 panchromatic images between 2017 and 2018, to calculate surface velocities of 36,722 glaciers during these two periods. We then derived velocity changes between 1999 and 2018 for the early winter period, based on which we performed a detailed analysis of motion of each individual glacier, and noted that the changes are spatially heterogeneous. Of all the glaciers, 32% have sped up, 24.5% have slowed down, and the rest 43.5% have remained stable. The amplitude of glacier slowdown, as a result of glacier mass loss, is significantly larger than that of speedup. At regional scales, we found that glacier surface velocity in winter has uniformly decreased in the western part of the Himalayas between 1999 and 2018, while increased in the eastern part; this contrasting difference may be associated with decadal changes in accumulation and/or melting under different climatic regimes. We also found that the overall trend of surface velocity exhibits seasonal variability: summer velocity changes are positively correlated with mass loss, i.e., velocity increases with increasing mass loss, whereas winter velocity changes show a negative correlation. Our study suggests that glacier velocity changes in the Himalayas are spatially and temporally heterogeneous, in agreement with studies that previously highlighted this trend, emphasising complex interactions between glacier dynamics and environmental forcing.

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Interannual and Seasonal Variability of Glacier Surface Velocity in the Parlung Zangbo Basin, Tibetan Plateau

Remote Sensing ◽

10.3390/rs13010080 ◽

2020 ◽

Vol 13 (1) ◽

pp. 80

Author(s):

Jing Zhang ◽

Li Jia ◽

Massimo Menenti ◽

Shaoting Ren

Keyword(s):

Seasonal Variability ◽

Global Climate ◽

Meteorological Data ◽

Transverse Velocity ◽

Surface Velocity ◽

Landsat 8 ◽

Velocity Change ◽

Glacier Surface ◽

Glacier Velocity ◽

Glacier Flow

Monitoring glacier flow is vital to understand the response of mountain glaciers to environmental forcing in the context of global climate change. Seasonal and interannual variability of surface velocity in the temperate glaciers of the Parlung Zangbo Basin (PZB) has attracted significant attention. Detailed patterns in glacier surface velocity and its seasonal variability in the PZB are still uncertain, however. We utilized Landsat-8 (L8) OLI data to investigate in detail the variability of glacier velocity in the PZB by applying the normalized image cross-correlation method. On the basis of satellite images acquired from 2013 to 2020, we present a map of time-averaged glacier surface velocity and examined four typical glaciers (Yanong, Parlung No.4, Xueyougu, and Azha) in the PZB. Next, we explored the driving factors of surface velocity and of its variability. The results show that the glacier centerline velocity increased slightly in 2017–2020. The analysis of meteorological data at two weather stations on the outskirts of the glacier area provided some indications of increased precipitation during winter-spring. Such increase likely had an impact on ice mass accumulation in the up-stream portion of the glacier. The accumulated ice mass could have caused seasonal velocity changes in response to mass imbalance during 2017–2020. Besides, there was a clear winter-spring speedup of 40% in the upper glacier region, while a summer speedup occurred at the glacier tongue. The seasonal and interannual velocity variability was captured by the transverse velocity profiles in the four selected glaciers. The observed spatial pattern and seasonal variability in glacier surface velocity suggests that the winter-spring snow might be a driver of glacier flow in the central and upper portions of glaciers. Furthermore, the variations in glacier surface velocity are likely related to topographic setting and basal slip caused by the percolation of rainfall. The findings on glacier velocity suggest that the transfer of winter-spring accumulated ice triggered by mass conservation seems to be the main driver of changes in glacier velocity. The reasons that influence the seasonal surface velocity change need further investigation.

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Contrasting surface velocities between lake- and land-terminating glaciers in the Himalayan region

The Cryosphere ◽

10.5194/tc-15-5577-2021 ◽

2021 ◽

Vol 15 (12) ◽

pp. 5577-5599

Author(s):

Jan Bouke Pronk ◽

Tobias Bolch ◽

Owen King ◽

Bert Wouters ◽

Douglas I. Benn

Keyword(s):

Flow Line ◽

Force Balance ◽

Surface Velocity ◽

Glacier Surface ◽

Ice Flow ◽

Himalayan Glaciers ◽

Large Heterogeneity ◽

Glacier Flow ◽

The Ganges ◽

Sentinel 2

Abstract. Meltwater from Himalayan glaciers sustains the flow of rivers such as the Ganges and Brahmaputra on which over half a billion people depend for day-to-day needs. Upstream areas are likely to be affected substantially by climate change, and changes in the magnitude and timing of meltwater supply are expected to occur in coming decades. About 10 % of the Himalayan glacier population terminates into proglacial lakes, and such lake-terminating glaciers are known to exhibit higher-than-average total mass losses. However, relatively little is known about the mechanisms driving exacerbated ice loss from lake-terminating glaciers in the Himalaya. Here we examine a composite (2017–2019) glacier surface velocity dataset, derived from Sentinel 2 imagery, covering central and eastern Himalayan glaciers larger than 3 km2. We find that centre flow line velocities of lake-terminating glaciers (N = 70; umedian: 18.83 m yr−1; IQR – interquartile range – uncertainty estimate: 18.55–19.06 m yr−1) are on average more than double those of land-terminating glaciers (N = 249; umedian: 8.24 m yr−1; IQR uncertainty estimate: 8.17–8.35 m yr−1) and show substantially more heterogeneity than land-terminating glaciers around glacier termini. We attribute this large heterogeneity to the varying influence of lakes on glacier dynamics, resulting in differential rates of dynamic thinning, which causes about half of the lake-terminating glacier population to accelerate towards the glacier termini. Numerical ice-flow model experiments show that changes in the force balance at the glacier termini are likely to play a key role in accelerating the glacier flow at the front, with variations in basal friction only being of modest importance. The expansion of current glacial lakes and the formation of new meltwater bodies will influence the dynamics of an increasing number of Himalayan glaciers in the future, and these factors should be carefully considered in regional projections.

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