scholarly journals ANTARCTIC ICE SHEET SLOPE AND ASPECT BASED ON ICESAT’S REPEAT ORBIT MEASUREMENT

2017 ◽  
Vol XLII-2/W7 ◽  
pp. 1579-1583
Author(s):  
L. Yuan ◽  
F. Li ◽  
S. Zhang ◽  
S. Xie ◽  
F. Xiao ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Accurate Information ◽  
Surface Slope ◽  
Elevation Change ◽  
Dome A ◽  
Antarctic Ice Sheet ◽  
Surface Slopes ◽  
Track Surface ◽  
Cross Track ◽  
Along Track

Accurate information of ice sheet surface slope is essential for estimating elevation change by satellite altimetry measurement. A study is carried out to recover surface slope of Antarctic ice sheet from Ice, Cloud and land Elevation Satellite (ICESat) elevation measurements based on repeat orbits. ICESat provides repeat ground tracks within 200 meters in cross-track direction and 170 meters in along-track direction for most areas of Antarctic ice sheet. Both cross-track and along-track surface slopes could be obtained by adjacent repeat ground tracks. Combining those measurements yields a surface slope model with resolution of approximately 200 meters. An algorithm considering elevation change is developed to estimate the surface slope of Antarctic ice sheet. Three Antarctic Digital Elevation Models (DEMs) were used to calculate surface slopes. The surface slopes from DEMs are compared with estimates by using in situ GPS data in Dome A, the summit of Antarctic ice sheet. Our results reveal an average surface slope difference of 0.02 degree in Dome A. High resolution remote sensing images are also used in comparing the results derived from other DEMs and this paper. The comparison implies that our results have a slightly better coherence with GPS observation than results from DEMs, but our results provide more details and perform higher accuracy in coastal areas because of the higher resolution for ICESat measurements. Ice divides are estimated based on the aspect, and are weakly consistent with ice divides from other method in coastal regions.

scholarly journals ICESat measurement of Greenland ice sheet surface slope and roughness

2005 ◽  
Vol 42 ◽  
pp. 83-89 ◽  
Author(s):  
Donghui Yi ◽  
H. Jay Zwally ◽  
Xiaoli Sun
Keyword(s):  
Three Dimensional ◽  
Greenland Ice Sheet ◽  
Surface Slope ◽  
Radar Altimeter ◽  
Digital Elevation ◽  
The Cross ◽  
Elevation Model ◽  
Track Surface ◽  
Cross Track ◽  
Along Track

AbstractThe Ice, Cloud and land Elevation Satellite (ICESat) in its 8 day repeat orbit mode provided data not only on the along-track surface slope, but also on the cross-track surface slope from adjacent repeat ground tracks. During the first 36 days of operation, four to five such repeat orbits occurred within 1 km in the cross-track direction. This provided an opportunity to use ICESat data to measure surface slope in the cross-track direction at 1 km scale. An algorithm was developed to calculate the cross-track surface slope. Combining the slopes in the cross-track and along-track directions gives a three-dimensional surface slope at 1 km scale. The along-track surface slope and surface roughness at 10km scale are also calculated. A comparison between ICESat surface elevation and a European Remote-sensing Satellite (ERS-1) 5 km digital elevation model shows a difference of 1–2 m in central Greenland where the surface slope is small, and >20m at the edge of Greenland where the surface slope is large. The large elevation difference at the edge is most likely due to the slope-induced error in radar altimeter measurement. Accurate surface slope data from ICESat will help to correct the slope-induced error of radar altimeter missions such as Geosat, ERS-1 and ERS-2.

scholarly journals Primary results of glaciological studies along an 1100 km transect from Zhongshan station to Dome A, East Antarctic ice sheet

2000 ◽  
Vol 31 ◽  
pp. 198-204 ◽  
Author(s):  
Qin Dahe ◽  
Ren Jiawen ◽  
Kang Jiancheng ◽  
Xiao Cunde ◽  
Li Zhongqin ◽  
...  
Keyword(s):  
Mass Balance ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Ice Cores ◽  
Spatial And Temporal Variability ◽  
Dome A ◽  
Antarctic Ice Sheet ◽  
Zhongshan Station ◽  
Inaccessible Area ◽  
East Antarctic Ice Sheet

AbstractThe Chinese National Antarctic Research Expedition (GHINARE) carried out three traverses from Zhongshan station to Dome A, Princess Elizabeth Land and Inaccessible Area, East Antarctic ice sheet, during the 1996/97 to 1998/99 Antarctic field seasons. The expeditions are part of the Chinese International Trans-Antarctic Scientific Expedition program. In this project, glaciological investigations of mass balance, ice temperature, ice flow, stratigraphy in snow pits and snow/firn ice cores, as well as the glaciochemical study of surface snow and shallow ice cores, have been carried out. In the 1998/99 field season, CHINARE extended the traverse route to 1128 km inland from Zhongshan station. The density profiles show that firnification over Princess Elizabeth Land and Inaccessible Area (290–1100 km along the route) is fairly slow, and the accumulation rate recovered from snow pits along the initial 460 km of the route is 4.6–21 cm (46–210 kg m–2a–1 ) water equivalent. The initial 460 km of the route can be divided into four sections based on the differences of accumulation rate. This pattern approximately coincides with the study on the Lambert Glacier basin (LGB) by Australian scientists. During the past 50 years, the trends of both air temperature and accumulation rate show a slight increase in this area, in contrast to the west side of the LGB. Data on surface accumulation rates and their spatial and temporal variability over ice-drainage areas such as the LGB are essential for precise mass-balance calculation of the whole ice sheet, and are important for driving ice-sheet models and testing atmospheric models.

scholarly journals Land-ice elevation changes from photon-counting swath altimetry: first applications over the Antarctic ice sheet

2015 ◽  
Vol 61 (225) ◽  
pp. 17-28 ◽  
Author(s):  
Duncan A. Young ◽  
Laura E. Lindzey ◽  
Donald D. Blankenship ◽  
Jamin S. Greenbaum ◽  
Alvaro Garcia De Gorordo ◽  
...  
Keyword(s):  
Dynamic Change ◽  
High Surface ◽  
Photon Counting ◽  
Ice Sheet ◽  
Test Case ◽  
Laser Altimeter ◽  
Surface Slopes ◽  
Elevation Changes ◽  
The Alamo ◽  
Cross Track

AbstractSatellite altimetric time series allow high-precision monitoring of ice-sheet mass balance. Understanding elevation changes in these regions is important because outlet glaciers along ice-sheet margins are critical in controlling flow of inland ice. Here we discuss a new airborne altimetry dataset collected as part of the ICECAP (International Collaborative Exploration of the Cryosphere by Airborne Profiling) project over East Antarctica. Using the ALAMO (Airborne Laser Altimeter with Mapping Optics) system of a scanning photon-counting lidar combined with a laser altimeter, we extend the 2003–09 surface elevation record of NASA’s ICESat satellite, by determining cross-track slope and thus independently correcting for ICESat’s cross-track pointing errors. In areas of high slope, cross-track errors result in measured elevation change that combines surface slope and the actual Δz/Δt signal. Slope corrections are particularly important in coastal ice streams, which often exhibit both rapidly changing elevations and high surface slopes. As a test case (assuming that surface slopes do not change significantly) we observe a lack of ice dynamic change at Cook Ice Shelf, while significant thinning occurred at Totten and Denman Glaciers during 2003–09.

scholarly journals Geometric boundary conditions for modelling the velocity field of the Antarctic ice sheet

1996 ◽  
Vol 23 ◽  
pp. 364-373 ◽  
Author(s):  
Jonathan L. Bamber ◽  
Philippe Huybrechts
Keyword(s):  
Velocity Field ◽  
Boundary Conditions ◽  
Ice Sheet ◽  
Surface Elevation ◽  
Surface Velocity ◽  
Ice Thickness ◽  
Antarctic Ice Sheet ◽  
Surface Slopes ◽  
Geometric Boundary ◽  
The Antarctic

This paper presents improved geometric boundary conditions (surface elevation and ice thickness) required as inputs to calculations of the surface-velocity field for the Antarctic ice sheet. A comparison of the two-dimensional horizontal velocity field obtained on the basis of conservation of mass (balance velocity) with the diagnostic velocity field calculated with an ice-sheet model (dynamic velocity) may yield information on shortcomings in the way the ice-sheet model describes the ice flow. Here, the surface-elevation grid is described in detail, as it has been generated specifically for such a study and represents a new standard in accuracy and resolution for calculating surface slopes. The digital-elevation model was generated on a 10 km grid size from over 20 000 000 height estimates obtained from eight 35 d repeat cycles of ERS-1 radar-altimeter data. For surface slopes less than 0.4°, the accuracy is better than 1.5 m. In areas of high surface slope (coastal and mountainous regions), the altimeter measurements have been supplemented with data taken from the Antarctic Digital Database. South of 81.5°, data from the SPRI folio map have been used. The ice-thickness grid was produced from a combination of a redigitization of the SPRI folio and the original radio-echo-sounding flight lines. For areas of grounded ice, the elevation of the bed was estimated from surface elevation and ice thickness. Significant differences (in excess of 25% of ice thickness) were obtained between an earlier digitization of the folio bed-elevation map and the data set derived here. Furthermore, a new value of 25.6 × 106 km3 was obtained for the total volume of the ice sheet and ice shelves, which is a reduction of 12% compared with the original estimate derived during the compilation of the SPRI folio. These differences will have an important influence on the results obtained by numerical ice-sheet models.

scholarly journals Experimental results of elevation change analysis in the Antarctic ice sheet using DEMs from ERS and ICESat data

2014 ◽  
Vol 55 (66) ◽  
pp. 198-204 ◽  
Author(s):  
Zhenxiong Gu ◽  
Tiantian Feng ◽  
Marco Scaioni ◽  
Hangbin Wu ◽  
Jun Liu ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Ice Sheet ◽  
Original Data ◽  
Elevation Change ◽  
Change Analysis ◽  
Antarctic Ice Sheet ◽  
Systematic Effects ◽  
Elevation Changes ◽  
Satellite Radar ◽  
The Antarctic

AbstractThe aim of this research is to investigate elevation changes in the Antarctic ice sheet by comparing two digital elevation models (DEMs) derived from satellite altimetry data covering the period 1994–2004. Data collected by ERS-1/2 satellite radar altimetry and by NASA GLAS/ICESat laser altimetry were used. After preprocessing and resampling at the same spatial resolution, both DEMs were compared in a pointwise fashion and elevation differences computed, which consisted of three main components: (1) actual elevation change, (2) errors in the original data sources and (3) interpolation errors that arose during generation of the DEMs. The objectives of the research were to analyze errors, attempt to mitigate systematic effects when possible, and draw some conclusions about the limitations of using DEM products for computing ice-sheet elevation change at local and continental scales. A linear correlation between errors in elevation differences and surface slope was found in the slope range [0°, 0.4°]. This trend was interpreted as residual slope-induced systematic error and compensated for. Finally, an elevation difference map of the Antarctic ice sheet was generated. Analysis of the derived elevation changes at the drainage basin was also made. Results are compared with the results of previous studies.

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