scholarly journals Dynamics of Dalk Glacier in East Antarctica Derived from Multisource Satellite Observations Since 2000

2020 ◽  
Vol 12 (11) ◽  
pp. 1809
Author(s):  
Yiming Chen ◽  
Chunxia Zhou ◽  
Songtao Ai ◽  
Qi Liang ◽  
Lei Zheng ◽  
...  
Keyword(s):  
East Antarctica ◽  
Surface Velocity ◽  
Cyclic Behavior ◽  
Glacier Terminus ◽  
Digital Elevation ◽  
Ice Velocity ◽  
Velocity Changes ◽  
Elevation Model ◽  
Surface Ice

Monitoring variability in outlet glaciers can improve the understanding of feedbacks associated with calving, ocean thermal forcing, and climate change. In this study, we present a remote-sensing investigation of Dalk Glacier in East Antarctica to analyze its dynamic changes. Terminus positions and surface ice velocities were estimated from Landsat and Sentinel-1 data, and the high-precision Worldview digital elevation model (DEM) was generated to determine the location of the potential ice rumple. We detected the cyclic behavior of glacier terminus changes and similar periodic increases in surface velocity since 2000. The terminus retreated in 2006, 2009, 2010, and 2016 and advanced in other years. The surface velocity of Dalk Glacier has a 5-year cycle with interannual speed-ups in 2007, 2012, and 2017. Our observations show the relationship between velocity changes and terminus variations, as well as the driving role of the ice rumple. Ice velocity often increases after calving events and continuous retreats. The loss of buttressing provided by an ice rumple may be a primary factor for increases in ice velocity. Given the restriction of the ice rumple, the surface velocity remains relatively stable when the glacier advances. The calving events may be linked to the unstable terminus caused by the ice rumple.

scholarly journals Interferometric radar observations of Glaciares Europa and Penguin, Hielo Patagónico Sur, Chile

1999 ◽  
Vol 45 (150) ◽  
pp. 325-337 ◽  
Author(s):  
Richard R. Forster ◽  
Eric Rignot ◽  
Bryan L. Isacks ◽  
Kenneth C. Jezek
Keyword(s):  
Space Shuttle ◽  
Phase Coherence ◽  
Surface Velocity ◽  
Interferometric Synthetic Aperture Radar ◽  
Low Coherence ◽  
Ice Surface ◽  
Digital Elevation ◽  
Ice Velocity ◽  
Elevation Model ◽  
High Degree

AbstractRepeat-pass L-band interferometric synthetic aperture radar (InSAR) data for part of Hielo Patagónico Sur, Chile, were collected by the space-shuttle-based Spaceborne Imaging Radar C (SIR-C) over a 4 day span in October 1994. Three co-registered complex SAR images are used to generate phase-coherence maps, a digital elevation model (DEM) and an ice-velocity map. The phase-coherence maps indicate low coherence in the 5–15 km approaching the termini due to large displacements, ice deformation and melting. However, the coherence is high over nearly all of the remaining imaged icefield. Ice-velocity precision is greater than 2 cm d−1, while the DEM is good to about 25 m. A flow divide between two of the glaciers is mapped by locating a narrow band of near-zero ice velocity. Horizontal ice-surface velocity profiles calculated along flowlines show there is a high degree of spatial variability reaching a peak value of 5.5 m d−1 located 3.5 km from the terminus of Glaciar Europa. Longitudinal strain rates along the center lines calculated from these velocities at the locations of the initiation of crevassing are used to compute the tensile strength of ice (169–224 kPa).

scholarly journals Interferometric radar observations of Glaciares Europa and Penguin, Hielo Patagónico Sur, Chile

1999 ◽  
Vol 45 (150) ◽  
pp. 325-337 ◽  
Author(s):  
Richard R. Forster ◽  
Eric Rignot ◽  
Bryan L. Isacks ◽  
Kenneth C. Jezek
Keyword(s):  
Space Shuttle ◽  
Phase Coherence ◽  
Surface Velocity ◽  
Interferometric Synthetic Aperture Radar ◽  
Low Coherence ◽  
Ice Surface ◽  
Digital Elevation ◽  
Ice Velocity ◽  
Elevation Model ◽  
High Degree

AbstractRepeat-pass L-band interferometric synthetic aperture radar (InSAR) data for part of Hielo Patagónico Sur, Chile, were collected by the space-shuttle-based Spaceborne Imaging Radar C (SIR-C) over a 4 day span in October 1994. Three co-registered complex SAR images are used to generate phase-coherence maps, a digital elevation model (DEM) and an ice-velocity map. The phase-coherence maps indicate low coherence in the 5–15 km approaching the termini due to large displacements, ice deformation and melting. However, the coherence is high over nearly all of the remaining imaged icefield. Ice-velocity precision is greater than 2 cm d−1, while the DEM is good to about 25 m. A flow divide between two of the glaciers is mapped by locating a narrow band of near-zero ice velocity. Horizontal ice-surface velocity profiles calculated along flowlines show there is a high degree of spatial variability reaching a peak value of 5.5 m d−1located 3.5 km from the terminus of Glaciar Europa. Longitudinal strain rates along the center lines calculated from these velocities at the locations of the initiation of crevassing are used to compute the tensile strength of ice (169–224 kPa).

scholarly journals The propagation of a surge front on Bering Glacier, Alaska, 2001–2011

2013 ◽  
Vol 54 (63) ◽  
pp. 221-228 ◽  
Author(s):  
James Turrin ◽  
Richard R. Forster ◽  
Chris Larsen ◽  
Jeanne Sauber
Keyword(s):  
Feature Tracking ◽  
Average Rate ◽  
Surface Velocity ◽  
Ablation Zone ◽  
Ice Surface ◽  
Glacier Terminus ◽  
Bering Glacier ◽  
Landsat 7 ◽  
Ice Velocity ◽  
Recent Activity

AbstractBering Glacier, Alaska, USA, has a ∼20 year surge cycle, with its most recent surge reaching the terminus in 2011. To study this most recent activity a time series of ice velocity maps was produced by applying optical feature-tracking methods to Landsat-7 ETM+ imagery spanning 2001-11. The velocity maps show a yearly increase in ice surface velocity associated with the down-glacier movement of a surge front. In 2008/09 the maximum ice surface velocity was 1.5 ±0.017 km a-1 in the mid-ablation zone, which decreased to 1.2 ±0.015 km a-1 in 2009/10 in the lower ablation zone, and then increased to nearly 4.4 ± 0.03 km a-1 in summer 2011 when the surge front reached the glacier terminus. The surge front propagated down-glacier as a kinematic wave at an average rate of 4.4 ±2.0 km a-1 between September 2002 and April 2009, then accelerated to 13.9 ± 2.0 km a-1 as it entered the piedmont lobe between April 2009 and September 2010. The wave seems to have initiated near the confluence of Bering Glacier and Bagley Ice Valley as early as 2001, and the surge was triggered in 2008 further down-glacier in the mid-ablation zone after the wave passed an ice reservoir area.

scholarly journals A new Greenland digital elevation model derived from ICESat-2

2021 ◽  
Author(s):  
Yubin Fan ◽  
Chang-Qing Ke ◽  
Xiaoyi Shen
Keyword(s):  
High Accuracy ◽  
Great Accuracy ◽  
Model Fit ◽  
Kriging Interpolation ◽  
Additional Time ◽  
Spatiotemporal Model ◽  
Digital Elevation ◽  
Ice Velocity ◽  
Image Pairs ◽  
Elevation Model

Abstract. Greenland digital elevation models (DEMs) are indispensable to fieldwork, ice velocity calculations and mass change estimations. Previous DEMs provided Greenland elevation information for different periods, but long temporal coverage introduced additional time uncertainty to scientific research. To provide a high-resolution DEM with a definite time, approximately 5.8 × 108 ICESat-2 observations from November 2018 to November 2019 were used to generate a new DEM for both the ice sheet and glaciers in peripheral Greenland. A spatiotemporal model fit process was first performed at 500 m resolution. To improve ICESat-2 data utilization, DEMs with 1 km and 2 km resolution across all of Greenland and an additional 5 km resolution in southernmost Greenland were used to fill the DEM gaps. Kriging interpolation was used to fill the remaining 2 % of void grids that were insufficiently observed by ICESat-2 measurements. IceBridge mission data acquired by the Airborne Topographic Mapper (ATM) Lidar system were used to evaluate the accuracy of the newly generated ICESat-2 DEM. Overall, the ICESat-2 DEM had a median difference of −0.48 m for all of Greenland, which agreed well with the IceBridge data, and the performance in the calculated and interpolated grids was similar. Better accuracy could be observed in the northern basins due to the larger proportion of calculated grids with 500 m resolution. The ICESat-2 DEM showed significant improvements in accuracy compared with other altimeter-derived DEMs. Compared to the DEM generated by image pairs, the accuracy was also significantly higher than those of the 1 km ArcticDEM and TanDEM. Similar performance between the ICESat-2 DEM and 500 m ArcticDEM indicated the high accuracy and reliability of the ICESat-2 DEM. Moreover, the ICESat-2 DEM performed better on northern aspects than the 500 m ArcticDEM. Overall, the ICESat-2 DEM showed great accuracy stability under various topographic conditions, hence providing a time-accurate DEM with high accuracy that will be helpful to study elevation and mass balance changes in Greenland. The Greenland DEM and its uncertainty are available at (https://data.tpdc.ac.cn/en/disallow/07497631-047548b5-ba53-c17f9076c72f/, Fan et al, 2021).

scholarly journals The Role of Spatial Analysis in Detecting the Consequence of the Factory Sites : Case Study of Assalaya Factory-Sudan

2018 ◽  
Vol 31 ◽  
pp. 12004
Author(s):  
Amar Sharaf Eldin Khair ◽  
Purwanto ◽  
Henna RyaSunoko ◽  
Omer Adam Abdullah
Keyword(s):  
Spatial Analysis ◽  
Analysis Data ◽  
Geographical Information ◽  
Nile River ◽  
Digital Elevation ◽  
White Nile ◽  
Elevation Model ◽  
Factory Site

Spatial analysis is considered as one of the most important science for identifying the most appropriate site for industrialization and also to alleviate the environmental ramifications caused by factories. This study aims at analyzing the Assalaya sugarcane factory site by the use of spatial analysis to determine whether it has ramification on the White Nile River. The methodology employed for this study is Global Position System (GPS) to identify the coordinate system of the study phenomena and other relative factors. The study will also make use Geographical Information System (GIS) to implement the spatial analysis. Satellite data (LandsatDem-Digital Elevation Model) will be considered for the study area and factory in identifying the consequences by analyzing the location of the factory through several features such as hydrological, contour line and geological analysis. Data analysis reveals that the factory site is inappropriate and according to observation on the ground it has consequences on the White Nile River. Based on the finding, the study recommended some suggestions to avoid the aftermath of any factory in general. We have to take advantage of this new technological method to aid in selecting most apt locations for industries that will create an ambient environment.

scholarly journals Synergetic merging of Cartosat-1 and RAMP to generate improved digital elevation model of Schirmacher oasis, east Antarctica

2014 ◽  
Vol XL-8 ◽  
pp. 517-524 ◽  
Author(s):  
S. D. Jawak ◽  
A. J. Luis
Keyword(s):  
Digital Elevation Model ◽  
Accuracy Assessment ◽  
East Antarctica ◽  
Interpolation Methods ◽  
Digital Elevation ◽  
Schirmacher Oasis ◽  
Elevation Data ◽  
Interpolation Techniques ◽  
Elevation Model ◽  
Better Than

Available digital elevation models (DEMs) of Antarctic region generated by using radar altimetry and the Antarctic digital database (ADD) indicate elevation variations of up to hundreds of meters, which necessitates the generation of local DEM and its validation by using ground reference. An enhanced digital elevation model (eDEM) of the Schirmacher oasis region, east Antarctica, is generated synergistically by using Cartosat-1 stereo pair-derived photogrammetric DEM (CartoDEM)-based point elevation dataset and multitemporal radarsat Antarctic mapping project version 2 (RAMPv2) DEM-based point elevation dataset. In this study, we analyzed suite of interpolation techniques for constructing a DEM from RAMPv2 and CartoDEM-based point elevation datasets, in order to determine the level of confidence with which the interpolation techniques can generate a better interpolated continuous surface, and eventually improves the elevation accuracy of DEM from synergistically fused RAMPv2 and CartoDEM point elevation datasets. RAMPv2 points and CartoDEM points were used as primary data for various interpolation techniques such as ordinary kriging (OK), simple kriging (SK), universal kriging (UK), disjunctive kriging (DK) techniques, inverse distance weighted (IDW), global polynomial (GP) with power 1 and 2, local polynomial (LP) and radial basis functions (RBF). Cokriging of 2 variables with second dataset was used for ordinary cokriging (OCoK), simple cokriging (SCoK), universal cokriging (UCoK) and disjunctive cokriging (DCoK). The IDW, GP, LP, RBF, and kriging methods were applied to one variable, while Cokriging experiments were employed on two variables. The experiment of dataset and its combination produced two types of point elevation map categorized as (1) one variable (RAMPv2 Point maps and CartoDEM Point maps) and (2) two variables (RAMPv2 Point maps + CartoDEM Point maps). Interpolated surfaces were evaluated with the help of differential global positioning system (DGPS) points collected from study area during the Indian Scientific Expedition to Antarctic (ISEA). Accuracy assessment of the RAMPv2 DEM, CartoDEM, and combined eDEM (RAMPv2 + CartoDEM) by using DGPS as ground reference data shows that eDEM achieves much better accuracy (average elevation error 8.44 m) than that of existing DEM constructed by using only CartoDEM (13.57 m) or RAMPv2 (41.44 m) alone. The newly constructed eDEM achieves a vertical accuracy of about 7 times better than RAMPv2 DEM and 1.5 times better than CartoDEM. After using accurate DGPS data for accuracy assessment, the approximation to the actual surface of the eDEM extracted here is much more accurate with least mean root mean square error (RMSE) of 9.22 m than that constructed by using only CartoDEM (RMSE = 14.15 m) point elevation data and RAMPv2 (RMSE = 69.48 m) point elevation data. Our results indicate that, the overall trend of accuracy for the interpolation methods for generating continuous elevation surface from CartoDEM + RAMPv2 point elevation data, based on RMSE, is as follows: GP1 > IDW > GP2 > OK > LP2 > DK > LP1 > RBF > SK > UK. In case of cokriging interpolation methods, OCoK yields more accurate eDEM with the least RMSE of 8.16 m, which can be utilized to generate a highly accurate DEM of the research area.. Based on this work, it is inferred that GP2 and OCok interpolation methods and synergistic use of RAMPv2 and CartoDEM-based point elevation datasets lead to a highly accurate DEM of the study region. This research experiment demonstrates the stability (w.r.t multi-temporal datasets), performance (w.r.t best interpolation technique) and consistency (w.r.t all the experimented interpolation techniques) of synergistically fused eDEM. On the basis of average elevation difference and RMSE mentioned in present research, the newly constructed eDEM may serve as a benchmark for future elevation models such as from the ICESAT-II mission to spatially monitor ice sheet elevation.

Glacier displacement on Comfortlessbreen, Svalbard, using 2-pass differential SAR interferometry (DInSAR) with a digital elevation model

Polar Record ◽  
2011 ◽  
Vol 48 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Nora Jennifer Schneevoigt ◽  
Monica Sund ◽  
Wiley Bogren ◽  
Andreas Kääb ◽  
Dan Johan Weydahl
Keyword(s):  
Synthetic Aperture Radar ◽  
Digital Elevation Model ◽  
Sar Interferometry ◽  
Synthetic Aperture ◽  
Synthetic Aperture Radar Interferometry ◽  
Glacier Terminus ◽  
Digital Elevation ◽  
Reference Images ◽  
Elevation Model ◽  
Aperture Radar

ABSTRACTDifferential synthetic aperture radar interferometry (DInSAR) exploits the coherence between the phases of two or more satellite synthetic aperture radar (SAR) scenes taken from the same orbit to separate the phase contributions from topography and movement by subtracting either phase. Hence pure terrain displacement can be derived without residual height information in it, but only the component of movement in line-of-sight direction is represented in a differential interferogram. Comfortlessbreen, a recently surging glacier, flows predominantly in this direction with respect to the European Remote Sensing satellites ERS-1 and ERS-2. Four C-band SAR scenes from spring 1996 were selected because of the high coherence between the respective pairs of the 1-day repeat-pass tandem mission of the ERS sensors. 2-pass DInSAR is performed in combination with a SPOT5 (Satéllite pour l'Observation de la Terre 5) SPIRIT (SPOT5 stereoscopic survey of Polar Ice: Reference Images and Topography) digital elevation model (DEM) from 2007. The different processing steps and intermediate image products, including unwrapping and generation of displacement maps, are detailed in order to convey the DInSAR processing chain to the beginner in the field of interferometry. Maximum horizontal displacements of 18 to 20 cm d−1 in ground range direction can be detected at the glacier terminus, while a few centimetres per day characterised most of the middle and upper portions of Comfortlessbreen in spring 1996.

scholarly journals Monitoring surging glaciers of the Pamirs, central Asia, from space

2008 ◽  
Vol 48 ◽  
pp. 125-134 ◽  
Author(s):  
V.M. Kotlyakov ◽  
G.B. Osipova ◽  
D.G. Tsvetkov
Keyword(s):  
Remote Sensing ◽  
Central Asia ◽  
Satellite Images ◽  
Initial Information ◽  
Unstable Regime ◽  
Landsat 7 ◽  
Ice Velocity ◽  
Velocity Changes ◽  
Academy Of Sciences

AbstractThe evolution of surging glaciers of the Pamirs, central Asia, has been studied using repeat remote-sensing surveys in the Institute of Geography, Russian Academy of Sciences, since the early 1970s. We use images obtained from national Resurs-F satellites (1972–91), as well as Landsat 7 and Terra (1999–2006), to provide a basis for monitoring of surging glaciers, aimed at developing their inventory, studying the causes and mechanisms of surges and examining the timing and extent of glacial catastrophes. The inventory from the early 1990s allows identification of 215 glaciers with a dynamically unstable regime. We discovered 51 surging glaciers. Up until 2006, 10 more surges had occurred. We use stereoscopic deciphering and photogrammetric processing of consecutive satellite images to study the morphology and ice-velocity changes of several compound surging glaciers. We analyze the results of monitoring of Bivachny and Oktyabr’sky glaciers from 1972 to 1991 and Sugran glacier from 1972 to 2006. Two surges of Sugran glacier occurred during this time: an internal surge in 1976–80, and a surge with glacier tongue advance as far as 4.5 km in 2000–05. The role of damming in compound glacier systems is examined. Satellite-based monitoring is now the only method for obtaining initial information about the state and fluctuations of such glaciers.

Multi-decadal ice-velocity and elevation changes of a monsoonal maritime glacier: Hailuogou glacier, China

2010 ◽  
Vol 56 (195) ◽  
pp. 65-74 ◽  
Author(s):  
Yong Zhang ◽  
Koji Fujita ◽  
Shiyin Liu ◽  
Qiao Liu ◽  
Xin Wang
Keyword(s):  
Thermal Emission ◽  
Surface Elevation ◽  
Aerial Photographs ◽  
Differential Gps ◽  
Glacier Surface ◽  
Ablation Area ◽  
Glacier Terminus ◽  
Digital Elevation ◽  
Elevation Changes ◽  
Ice Velocity

AbstractDigital elevation models (DEMs) of the ablation area of Hailuogou glacier, China, produced from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data obtained in 2009, differential GPS (DGPS) data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long- and short-term glacier surface elevation change (dh/dt). The mean dh/dt of the ablation area over 43 years (1966–2009) is −1.1 ± 0.4 m a−1. Since 1989 the thinning has accelerated significantly. Ice velocities measured by DGPS at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus, ranging from 41.0 m a−1 approaching the glacier terminus to a maximum of 205.0 m a−1 at the base of an icefall. Our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades. Changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics, which are driven by different factors for different regions and periods.

scholarly journals Decadal GPS-derived ice surface velocity along the transect from Zhongshan Station to and around Dome Argus, East Antarctica, 2005–16

2018 ◽  
Vol 59 (76pt1) ◽  
pp. 1-9 ◽  
Author(s):  
Yang Yuande ◽  
Ke Hao ◽  
Wang Zemin ◽  
Li Fei ◽  
Ding Minghu ◽  
...  
Keyword(s):  
High Resolution ◽  
Ground Truth ◽  
East Antarctica ◽  
Surface Velocity ◽  
Interferometric Synthetic Aperture Radar ◽  
Gps Measurements ◽  
Zhongshan Station ◽  
Ice Surface ◽  
Ice Velocity ◽  
Ice Sheet Dynamics

ABSTRACTUsing repeat GPS measurements during 2005–16, we calculated and updated two-dimensional high-resolution decadal ice surface velocity estimates along the traverse route from Zhongshan Station to and around Dome Argus, East Antarctica. Along the 71 sites of the transect, the magnitudes of ice velocity increased from near 0 in Dome Argus to 1, 10 and ~100 m a−1 at the sites DT416, DT333 and LT980, respectively. The comparison between GPS and interferometric synthetic aperture radar (InSAR) derived results agree well when the magnitude of the ice surface velocities is faster than 5 m a−1, and disagree for slower flow velocities. A scale value 1.15 and 0.12 can be applied to InSAR derived results over this region with ice surface velocity larger and <5 m a−1, respectively. We attributed the cause of the discrepancy to the insensitivity of InSAR to the magnitude of low ice surface velocities, thus confirming the importance of GPS fieldwork-based ground truth high-resolution ice velocity estimates to constrain ice-sheet dynamics.

Sign in / Sign up

Export Citation Format

Share Document