scholarly journals The Reference Elevation Model of Antarctica

2019 ◽  
Vol 13 (2) ◽  
pp. 665-674 ◽  
Author(s):  
Ian M. Howat ◽  
Claire Porter ◽  
Benjamin E. Smith ◽  
Myoung-Jong Noh ◽  
Paul Morin
Keyword(s):  
Laser Altimetry ◽  
Low Contrast ◽  
Continental Scale ◽  
Change Measurement ◽  
Digital Elevation ◽  
Continuous Surface ◽  
Satellite Radar ◽  
Elevation Model ◽  
Surface Covering ◽  
Quality Surface

Abstract. The Reference Elevation Model of Antarctica (REMA) is the first continental-scale digital elevation model (DEM) at a resolution of less than 10 m. REMA is created from stereophotogrammetry with submeter resolution optical, commercial satellite imagery. The higher spatial and radiometric resolutions of this imagery enable high-quality surface extraction over the low-contrast ice sheet surface. The DEMs are registered to satellite radar and laser altimetry and are mosaicked to provide a continuous surface covering nearly 95 % the entire continent. The mosaic includes an error estimate and a time stamp, enabling change measurement. Typical elevation errors are less than 1 m, as validated by the comparison to airborne laser altimetry. REMA provides a powerful new resource for Antarctic science and provides a proof of concept for generating accurate high-resolution repeat topography at continental scales.

scholarly journals The Reference Elevation Model of Antarctica

2018 ◽  
Author(s):  
Ian M. Howat ◽  
Claire Porter ◽  
Benjamin E. Smith ◽  
Myoung-Jong Noh ◽  
Paul Morin
Keyword(s):  
Laser Altimetry ◽  
Low Contrast ◽  
Continental Scale ◽  
Digital Elevation ◽  
Stereo Photogrammetry ◽  
Continuous Surface ◽  
Satellite Radar ◽  
Elevation Model ◽  
Surface Covering ◽  
Quality Surface

Abstract. The Reference Elevation Model of Antarctica (REMA) is the first, continental scale Digital Elevation Model (DEM) at a resolution of less than 10 m. REMA is created from stereo-photogrammetry with submeter resolution, optical, commercial satellite imagery. The higher spatial and radiometric resolutions of these imagery enable high quality surface extraction over the low-contrast ice sheet surface. The DEMs are registered to satellite radar and laser altimetry and are mosaicked to provide a continuous surface covering nearly the entire continent. The mosaic includes an error estimate and a time stamp, enabling change measurement. Typical elevation errors are less than 1 meter, as validated by the comparison to airborne laser altimetry. REMA provides a powerful new resource for Antarctic science and provides a proof of concept for generating high resolution, accurate, repeat topography at continental scales.

scholarly journals 21st-century increase in glacier mass loss in the Wrangell Mountains, Alaska, USA, from airborne laser altimetry and satellite stereo imagery

2014 ◽  
Vol 60 (220) ◽  
pp. 283-293 ◽  
Author(s):  
Indrani Das ◽  
Regine Hock ◽  
Etienne Berthier ◽  
Craig S. Lingle
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
High Elevation ◽  
Center Line ◽  
Laser Altimetry ◽  
Tidewater Glaciers ◽  
Airborne Laser ◽  
Digital Elevation ◽  
Stereo Imagery ◽  
Elevation Model

AbstractAlaskan glaciers are among the largest regional contributors to sea-level rise in the latter half of the 20th century. Earlier studies have documented extensive and accelerated ice wastage in most regions of Alaska. Here we study five decades of mass loss on high-elevation, land-terminating glaciers of the Wrangell Mountains (~ 4900 km2) in central Alaska based on airborne center-line laser altimetry data from 2000 and 2007, a digital elevation model (DEM) from ASTER and SPOT5, and US Geological Survey topographic maps from 1957. The regional mass-balance estimates derived from center-line laser altimetry profiles using two regional extrapolation techniques agree well with that from DEM differencing. Repeat altimetry measurements reveal accelerated mass loss over the Wrangell Mountains, with the regional mass-balance rate evolving from –0.07 ± 0.19 m w.e. a–1 during 1957–2000 to –0.24 ± 0.16 m w.e. a–1 during 2000–07. Nabesna, the largest glacier in this region (˜1056 km2), lost mass four times faster during 2000–07 than during 1957–2000. Although accelerated, the mass change over this region is slower than in other glacierized regions of Alaska, particularly those with tidewater glaciers. Together, our laser altimetry and satellite DEM analyses demonstrate increased wastage of these glaciers during the last 50 years.

scholarly journals Assessing ice-cliff backwasting and its contribution to total ablation of debris-covered Miage glacier, Mont Blanc massif, Italy

2014 ◽  
Vol 60 (219) ◽  
pp. 3-13 ◽  
Author(s):  
T.D. Reid ◽  
B.W. Brock
Keyword(s):  
Field Measurements ◽  
Distributed Model ◽  
Short Term ◽  
Model Calculations ◽  
Digital Elevation ◽  
Debris Cover ◽  
Continuous Surface ◽  
Elevation Model ◽  
Miage Glacier ◽  
Mont Blanc Massif

AbstractContinuous surface debris cover strongly reduces the ablation of glaciers, but high melt rates may occur at ice cliffs that are too steep to hold debris. This study assesses the contribution of ice-cliff backwasting to total ablation of Miage glacier, Mont Blanc massif, Italy, in 2010 and 2011, based on field measurements, physical melt models and mapping of ice cliffs using a high-resolution (1 m) digital elevation model (DEM). Short-term model calculations closely match the measured melt rates. A model sensitivity analysis indicates that the effects of cliff slope and albedo are more important for ablation than enhanced longwave incidence from sun-warmed debris or reduced turbulent fluxes at sheltered cliff bases. Analysis of the DEM indicates that ice cliffs account for at most 1.3% of the 1 m pixels in the glacier’s debris-covered zone, but application of a distributed model indicates that ice cliffs account for ~7.4% of total ablation. We conclude that ice cliffs make an important contribution to the ablation of debris-covered glaciers, even when their spatial extent is very small.

scholarly journals CABra: a novel large-sample dataset for Brazilian catchments

2021 ◽  
Vol 25 (6) ◽  
pp. 3105-3135
Author(s):  
André Almagro ◽  
Paulo Tarso S. Oliveira ◽  
Antônio Alves Meira Neto ◽  
Tirthankar Roy ◽  
Peter Troch
Keyword(s):  
Multiple Sources ◽  
Large Sample ◽  
Landscape Characteristics ◽  
Related Data ◽  
Continental Scale ◽  
Daily Streamflow ◽  
Multiple Data ◽  
Digital Elevation ◽  
Catchment Areas ◽  
Elevation Model

Abstract. In this paper, we present the Catchments Attributes for Brazil (CABra), which is a large-sample dataset for Brazilian catchments that includes long-term data (30 years) for 735 catchments in eight main catchment attribute classes (climate, streamflow, groundwater, geology, soil, topography, land cover, and hydrologic disturbance). We have collected and synthesized data from multiple sources (ground stations, remote sensing, and gridded datasets). To prepare the dataset, we delineated all the catchments using the Multi-Error-Removed Improved-Terrain Digital Elevation Model (MERIT DEM) and the coordinates of the streamflow stations provided by the Brazilian Water Agency, where only the stations with 30 years (1980–2010) of data and less than 10 % of missing records were included. Catchment areas range from 9 to 4 800 000 km2, and the mean daily streamflow varies from 0.02 to 9 mm d−1. Several signatures and indices were calculated based on the climate and streamflow data. Additionally, our dataset includes boundary shapefiles, geographic coordinates, and drainage area for each catchment, aside from more than 100 attributes within the attribute classes. The collection and processing methods are discussed, along with the limitations for each of our multiple data sources. CABra intends to improve the hydrology-related data collection in Brazil and pave the way for a better understanding of different hydrologic drivers related to climate, landscape, and hydrology, which is particularly important in Brazil, having continental-scale river basins and widely heterogeneous landscape characteristics. In addition to benefitting catchment hydrology investigations, CABra will expand the exploration of novel hydrologic hypotheses and thereby advance our understanding of Brazilian catchments' behavior. The dataset is freely available at https://doi.org/10.5281/zenodo.4070146 and https://thecabradataset.shinyapps.io/CABra/ (last access: 7 June 2021).

scholarly journals A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

2018 ◽  
Vol 12 (4) ◽  
pp. 1551-1562 ◽  
Author(s):  
Thomas Slater ◽  
Andrew Shepherd ◽  
Malcolm McMillan ◽  
Alan Muir ◽  
Lin Gilbert ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Ice Sheet ◽  
Grid Cells ◽  
Radar Altimeter ◽  
Laser Altimeter ◽  
Ice Shelves ◽  
Digital Elevation ◽  
Spatio Temporal ◽  
Satellite Radar ◽  
Elevation Model

Abstract. We present a new digital elevation model (DEM) of the Antarctic ice sheet and ice shelves based on 2.5×108 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2, and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells north of 88∘ S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3×107 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are −0.30 and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope, especially where elevation measurements were acquired in low-resolution mode; taking this into account, we estimate the average accuracy to be 9.5 m – a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

scholarly journals A new Digital Elevation Model of Antarctica derived from CryoSat-2 altimetry

2017 ◽  
Author(s):  
Thomas Slater ◽  
Andrew Shepherd ◽  
Malcolm McMillan ◽  
Alan Muir ◽  
Lin Gilbert ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Ice Sheet ◽  
Grid Cells ◽  
Radar Altimeter ◽  
Laser Altimeter ◽  
Ice Shelves ◽  
Digital Elevation ◽  
Spatio Temporal ◽  
Satellite Radar ◽  
Elevation Model

Abstract. We present a new Digital Elevation Model (DEM) of the Antarctic ice sheet and ice shelves based on 2.5 × 108 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2 and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells North of 88° S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3 × 107 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are −0.30 m and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope – especially where elevation measurements were acquired in Low Resolution Mode – and, taking this into account, we estimate the average accuracy to be 9.5 m – a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

scholarly journals CABra: a novel large-sample dataset for Brazilian catchments

2020 ◽  
Author(s):  
André Almagro ◽  
Paulo Tarso S. Oliveira ◽  
Antônio Alves Meira Neto ◽  
Tirthankar Roy ◽  
Peter Troch
Keyword(s):  
Multiple Sources ◽  
Large Sample ◽  
Landscape Characteristics ◽  
Related Data ◽  
Continental Scale ◽  
Daily Streamflow ◽  
Multiple Data ◽  
Digital Elevation ◽  
Catchment Areas ◽  
Elevation Model

Abstract. In this paper, we present the Catchments Attributes for Brazil (CABra), which is a large-sample dataset for Brazilian catchments that includes long-term data (30 years) for 735 catchments in eight main catchment attribute classes (climate, streamflow, groundwater, geology, soil, topography, land-cover, and hydrologic disturbance). We have collected and synthesized data from multiple sources (ground stations, remote sensing, and gridded datasets). To prepare the dataset, we delineated all the catchments using the Multi-Error-Removed Improved-Terrain Digital Elevation Model and the coordinates of the streamflow stations provided by the Brazilian Water Agency, where only the stations with 30 years (1980–2010) of data and less than 10 % of missing records were included. Catchment areas range from 9 to 4 800 000 km2 and the mean daily streamflow varies from 0.02 to 9 mm d-1. Several signatures and indices were calculated based on the climate and streamflow data. Additionally, our dataset includes boundary shapefiles, geographic coordinates, and drainage area for each catchment, aside from more than 100 attributes within the attribute classes. The collection and processing methods are discussed along with the limitations for each of our multiple data sources. The CABra intends to improve the hydrology-related data collection in Brazil and pave the way for a better understanding of different hydrologic drivers related to climate, landscape, and hydrology, which is particularly important in Brazil, having continental-scale river basins and widely heterogeneous landscape characteristics. In addition to benefitting catchment hydrology investigations, CABra will expand the exploration of novel hydrologic hypotheses and thereby advance our understanding of Brazilian catchments' behavior. The dataset is freely available at https://doi.org/10.5281/zenodo.4070147.

scholarly journals Quantification of Everest region glacier velocities between 1992 and 2002, using satellite radar interferometry and feature tracking

2009 ◽  
Vol 55 (192) ◽  
pp. 596-606 ◽  
Author(s):  
D.J. Quincey ◽  
A. Luckman ◽  
D. Benn
Keyword(s):  
Feature Tracking ◽  
High Elevation ◽  
Ice Dynamics ◽  
Terminal Moraine ◽  
Ice Surface ◽  
Digital Elevation ◽  
Ablation Pattern ◽  
Satellite Radar ◽  
Glacier Flow ◽  
Elevation Model

AbstractMany glacier snouts in the Himalaya are known to be stagnant and exhibiting low surface gradients, conditions that are conducive to the formation of glacial lakes impounded either by the terminal moraine or by the remnant glacier snout. In this study, we use interferometry and feature-tracking techniques to quantify the extent of stagnation in 20 glaciers across the Everest (Qomolangma; Sagarmatha) region, and subsequently we examine the relationship between local catchment topography and ice dynamics. The results show that only one of the studied glaciers, Kangshung Glacier, is dynamic across its entire surface, with flow rates greater than 40 m a−1 being recorded in high-elevation areas. Twelve other glaciers show some evidence of flow, but are generally characterized by long, stagnant tongues, indicating widespread recession and in situ decay. The remaining seven glaciers show no evidence of flow in any of the available datasets. Hypsometric data suggest that catchment topography plays an important role in controlling glacier flow regimes, with those fed by wide, high-altitude accumulation areas showing the most extensive active ice, and those originating at low elevations exhibiting large areas of stagnant ice. Surface profiles extracted from a SRTM digital elevation model indicate that stagnant snouts are characterized by very low (<2°) surface angles and that down-wasting is the prevalent ablation pattern in the study area.

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