SPIRIT. SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies during the fourth International Polar Year (2007–2009)

Korona, J.; Berthier, Étienne; Bernard, Marc; Rémy, Frédérique; Thouvenot, Éric

doi:10.1016/j.isprsjprs.2008.10.005

Cited by 217 publications

(264 citation statements)

References 26 publications

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“…For our ASTER-derived DEMs we estimated the vertical accuracy for an individual elevation point to be better than 15 m rms for conditions of sufficient optical contrast in the images used, as supported by an extensive test study in eastern Svalbard (Kääb, 2008). The 2008 SPOT 5 HRS (from Satellite Pour l'Observation de la Terre) DEMs have 40 m resolution and vertical accuracy of 10 m with 90 % confidence on surface slopes less than 20 % (Korona et al, 2009), which applies to most of the glacier surfaces studied here. For topography in the fjord, bathymetric contour lines collected in 1999 and 2001 by the Norwegian Hydrographic Service (Carlsen, 2004) were digitised and extrapolated to the shore line to fill data gaps.…”

Section: Digital Elevation Modelsmentioning

confidence: 96%

Surge dynamics in the Nathorstbreen glacier system, Svalbard

2014

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Abstract. Nathorstbreen glacier system (NGS) recently experienced the largest surge in Svalbard since 1936, and this was examined using spatial and temporal observations from DEM differencing, time series of surface velocities from satellite synthetic aperture radar (SAR) and other sources. The upper basins with maximum accumulation during quiescence corresponded to regions of initial lowering. Initial speed-up exceeded quiescent velocities by a factor of several tens. This suggests that polythermal glacier surges are initiated in the temperate area before mass is displaced downglacier. Subsequent downglacier mass displacement coincided with areas where glacier velocity increased by a factor of 100-200 times (stage 2). After more than 5 years, the joint NGS terminus advanced abruptly into the fjord during winter, increasing velocities even more. The advance was followed by up-glacier propagation of crevasses, indicating the middle and subsequently the upper part of the glaciers reacting to the mass displacement. NGS advanced ∼15 km, while another ∼3 km length was lost due to calving. Surface lowering of ∼50 m was observed in some up-glacier areas, and in 5 years the total glacier area increased by 20 %. Maximum measured flow rates were at least 25 m d −1 , 2500 times quiescent velocity, while average velocities were about 10 m d −1 . The surges of Zawadzkibreen cycle with ca. 70-year periods.

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Section: Digital Elevation Modelsmentioning

confidence: 96%

Surge dynamics in the Nathorstbreen glacier system, Svalbard

2014

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“…pointing information, auxiliary and ancillary data) (for more details, see Schenk, 1999). The latter is the approach for both satellite stereo DEMs used in the this study: the ASTER DEMs produced by LPDAAC using the SilcAst software (product AST14) and the SPOT5-HRS DEMs (Bouillon et al, 2006;Korona et al, 2009) The stereoscopic ASTER instrument, in orbit since 1999 aboard the Terra platform, contains a nadir and backward VNIR sensor (0.76-0.86 µm) separated by ≈30 • corresponding to a B/H ratio of 0.6 (ERSDAC, 2005;. The ground swath is 60 km while the image and reported DEM ground resolution is 15 and 30 m, respectively.…”

Section: Stereoscopic Demsmentioning

confidence: 99%

“…The HRS instrument, aboard the SPOT5 satellite since 2002, contains forward and backward panchromatic sensors (0.48-0.7 µm), both 20 • from nadir providing a B/H ratio of 0.8 (Berthier and Toutin, 2008). The 120 km ground swath is twice as large as ASTER, with a ground pixel resolution of 10 m across track and 5 m along track, and a final DEM resolution of 40 m (Korona et al, 2009). …”

Section: Stereoscopic Demsmentioning

confidence: 99%

“…ASTER DEM uncertainty is reported to be typically within 15-60 m RMSE in the vertical depending upon terrain type (Toutin, 2002Kääb et al, 2002;Hirano et al, 2003;Kääb, 2005;Fujisada et al, 2005) and between 15 and 50 m horizontally Iwasaki and Fujisada, 2005). SPOT5 uncertainty is reported to be between 10-25 m vertically (Berthier and Toutin, 2008;Korona et al, 2009) and greater than 15 m in the horizontal (Bouillon et al, 2006;Berthier and Toutin, 2008). In relationship to pushbroom sensors (e.g.…”

Section: Stereoscopic Demsmentioning

confidence: 99%

“…ICESat products are freely available from NSIDC (www.nsidc.org), and are the third global elevation product publicly available and tested in this study. ICESat has been extremely successful for glacier applications in terms of elevation changes (Howat et al, 2008;Pritchard et al, 2009;Moholdt et al, 2010b) but also for determining the accuracy of newer satellite products (Korona et al, 2009) and older topographic maps (Nuth et al, 2010). Two second level products are available, GLA06 for smooth ice sheets and GLA14 for rougher terrain surfaces.…”

Section: Ices At Lidar Profilesmentioning

confidence: 99%

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Co-registration and bias corrections of satellite elevation data sets for quantifying glacier thickness change

2011

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Abstract.There are an increasing number of digital elevation models (DEMs) available worldwide for deriving elevation differences over time, including vertical changes on glaciers. Most of these DEMs are heavily post-processed or merged, so that physical error modelling becomes difficult and statistical error modelling is required instead. We propose a three-step methodological framework for assessing and correcting DEMs to quantify glacier elevation changes: (i) remove DEM shifts, (ii) check for elevation-dependent biases, and (iii) check for higher-order, sensor-specific biases. A simple, analytic and robust method to co-register elevation data is presented in regions where stable terrain is either plentiful (case study New Zealand) or limited (case study Svalbard). The method is demonstrated using the three global elevation data sets available to date, SRTM, ICESat and the ASTER GDEM, and with automatically generated DEMs from satellite stereo instruments of ASTER and SPOT5-HRS. After 3-D co-registration, significant biases related to elevation were found in some of the stereoscopic DEMs. Biases related to the satellite acquisition geometry (along/cross track) were detected at two frequencies in the automatically generated ASTER DEMs. The higher frequency bias seems to be related to satellite jitter, most apparent in the backlooking pass of the satellite. The origins of the more significant lower frequency bias is uncertain. ICESat-derived elevations are found to be the most consistent globally available elevation data set available so far. Before performing regional-scale glacier elevation change studies or mosaicking DEMs from multiple individual tiles (e.g. ASTER GDEM), we recommend to co-register all elevation data to ICESat as a global vertical reference system.

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Greenland subglacial lakes detected by radar

Palmer

Dowdeswell

Christoffersen

et al. 2013

Geophysical Research Letters

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Subglacial lakes are an established and important component of the basal hydrological system of the Antarctic ice sheets, but none have been reported from Greenland. Here we present airborne radio echo sounder (RES) measurements that provide the first clear evidence for the existence of subglacial lakes in Greenland. Two lakes, with areas ~8 and ~10 km2, are found in the northwest sector of the ice sheet, ~40 km from the ice margin, and below 757 and 809 m of ice, respectively. The setting of the Greenland lakes differs from those of Antarctic subglacial lakes, being beneath relatively thin and cold ice, pointing to a fundamental difference in their nature and genesis. Possibilities that the lakes consist of either ancient saline water in a closed system or are part of a fresh, modern open hydrological system are discussed, with the latter interpretation considered more likely.

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SPIRIT. SPOT 5 stereoscopic survey of Polar Ice: Reference Images and Topographies during the fourth International Polar Year (2007–2009)

Cited by 217 publications

References 26 publications

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Co-registration and bias corrections of satellite elevation data sets for quantifying glacier thickness change

Greenland subglacial lakes detected by radar

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