Mapping of Amery Ice Shelf, Antarctica, Surface Features by Satellite Altimetry (original) (raw)
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Monitoring continental ice sheets by satellite altimetry
Advances in Space Research, 1993
Altimeter data are helpful in monitoring the evolution of polar caps as well as constraining their dynamics. In the recent years, our group has quantified the impact of the so-called volume echo on the determination of the surface height, analyzed the effect of surface roughness on the intensity of the radar signal, adapted an inverse technique for mapping the topography of the ice sheets and its error, including correction of the surface slope effect and finally used the Antarctica ice sheet topography deduced from Seasat data to estimate the rheological parameters of the ice flow.
Observations of the surface properties of the ice sheets by satellite radar altimetry
J. Glaciol, 1989
and averaged satellite altimeter return, it is demonstrated that time profiles of altimeter return can be used to provide important information on the surface properties of the ice sheets. Altimeter ice-sheet radar echoes from low altitudes and/or relatively low latitudes are, in general, dominated by surface scattering and, in Greenland, the area of surface-dominated return broadly coincides with the zone of summer melting. Seasonal variations in the echo wave-form shapes are neg ligible in all regions studied, with the possible exception of an area near the margin of the Greenland dry-snow zone. In general, the model explains well the observed variations in mean wave-form shape, but small discrepances between the model wave forms and the recorded wave forms indicate that sub-surface layers may be influencing the shape of the return. The possibility of deriving quantitative estimates of surface properties is explored by fitting model returns to averaged altimeter wave forms from the Wilkes Land plateau in Antarctica. Surface roug hness can be measured unambiguously from the wave-form data, but estimations of other parameters, such as grain-size, snow density, and snow temperature are found to be ambiguous because different surface parameters have a similar influence on the shape of the return. Despite this, the derived estimates compare well with ground-b ased observations and suggest that the satellite altimeter may have an important role to play in providing information on the surface properties of the ice sheets.
Journal 0/ …, 1989
A comprehensive survey of the Larsen Ice Shelf has been conducted using precise orbit and retracked Seasat radar-altimeter data with editing of erroneous values resulting from intrumental artefacts. Contour maps of elevation and radar back-scatter (with absolute accuracies of I m and 2 dB, respectively) have been produced and it has also been possible to map rifts, grounding points, rough terrain, and about 30% of the ice shelf's seaward margin. Ice thicknesses derived from these elevation data show broad agreement with those derived from previous airborne radio-echo surveys. The maps of parameters measured by Seasat represent a very substantial improvement over those previously available. They thus provide a reference against which comparison may be made with a view to detecting substantial climatic changes. This is of particular interest since, as the most northerly major ice shelf in Antarctica, the Larsen Ice Shelf may be more sensitive than others to global climatic trends. J , 67 66 65 64 Ridley and others: Characteristics of the Larsen lee Shelf J ) 64 65 66 Lat. Deg. S 67 68 69
Antarctic Ice Sheet and Radar Altimetry: A Review
Remote Sensing, 2009
Altimetry is probably one of the most powerful tools for ice sheet observation. Our vision of the Antarctic ice sheet has been deeply transformed since the launch of the ERS1 satellite in 1991. With the launch of ERS2 and Envisat, the series of altimetric observations now provides 19 years of continuous and homogeneous observations that allow monitoring of the shape and volume of ice sheets. The topography deduced from altimetry is one of the relevant parameters revealing the processes acting on ice sheet. Moreover, altimeter also provides other parameters such as backscatter and waveform shape that give information on the surface roughness or snow pack characteristics.
Antarctic ice-shelf thickness from satellite radar altimetry
Journal of Glaciology, 2011
Ice-shelf thickness is an important boundary condition for ice-sheet and sub-ice-shelf cavity modelling. It is required near the grounding line to calculate the ice flux used to determine ice-sheet mass balance by comparison with the upstream accumulation. In this mass budget approach, the accuracy of the ice thickness is one of the limiting factors in the calculation. We present a satellite retrieval of the ice thickness for all Antarctic ice shelves using satellite radar altimeter data from the geodetic phases of the European Remote-sensing Satellite (ERS-1) during 1994-95 supplemented by ICESat data for regions south of the ERS-1 latitudinal limit. Surface elevations derived from these instruments are interpolated on to regular grids using kriging, and converted to ice thicknesses using a modelled firn-density correction. The availability of a new spatial variable firn-density correction significantly reduces the error in ice thickness as this was previously the dominant error source. Comparison to airborne data shows good agreement, particularly when compared to SOAR CASERTZ data on the largest ice shelves. Biases range from -13.0 m for areas where the assumption of hydrostatic equilibrium breaks down, to 53.4 m in regions where marine ice may be present.
Analysis and simulation of altimeter performance for the production of ice sheet topographic maps
1985
Satellite-borne, radar altimeters have already demonstrated an ability to produce high-precision, topographic maps of the ice sheets . Seasat operated in a tracking mode, designed for use over oceans, but successfully tracked much of the flatter regi ons of the ice sheet to ± 72 0 latitude. ERS-l will extend coverage to ± 82 0 latitude and will be equipped with an ocean mode similar to that of Seasat and an ice mode designed to permit tracking of the steeper, peripheral regions. The ocean mode will be used over the flatter regions, because of its greater precision.
Exploratory Investigation on the Use of Inland Water, Land and Ice Satellite Altimetry
This is an internal Technical Report prepared by GAIA Inc., Memphis, Tennessee (D. Christodoulidis) and the Canadian Geodetic Survey, EMR Canada (D. Delikaraoglou) in the context of the Joint USA-Canada Project on the "Development ofa Cryospheric Information System for the Monitoring of Global Climate Change in Canada". It deals with the problem of the radar altimeter functional response over the continental ice sheets, which is considerable more complex than over the oceans. Causal factors identified in this complicated response include sloping surfaces, undulating ice surfaces with characteristic wavelengths at the same spatial scale as the altimeter's beam-limited footprint, and off-track reflections. Retracking methods using the altimeter's return pulse waveforms were applied on available GEOSAT altimeter data and show that the radar altimeter data is a very valuable source of topographic information of the continental ice sheets, including the inland seas (e.g...
Mapping the grounding zone of the Ross Ice Shelf, Antarctica, using ICESat laser altimetry
Annals of Glaciology, 2010
We use laser altimetry from the Ice, Cloud, and land Elevation Satellite (ICESat) to map the grounding zone (GZ) of the Ross Ice Shelf, Antarctica, at 491 locations where ICESat tracks cross the grounding line (GL). Ice flexure in the GZ occurs as the ice shelf responds to short-term sea-level changes due primarily to tides. ICESat repeat-track analysis can be used to detect this region of flexure since each repeated pass is acquired at a different tidal phase; the technique provides estimates for both the landward limit of flexure and the point where the ice becomes hydrostatically balanced. We find that the ICESat-derived landward limits of tidal flexure are, in many places, offset by several km (and up to $60 km) from the GL mapped previously using other satellite methods. We discuss the reasons why different mapping methods lead to different GL estimates, including: instrument limitations; variability in the surface topographic structure of the GZ; and the presence of ice plains. We conclude that reliable and accurate mapping of the GL is most likely to be achieved when based on synthesis of several satellite datasets.
Remote Sensing of Environment, 2008
The primary purpose of ice-sheet altimetry is to monitor the changes in ice-sheet topography which may impact on global sea-level. However, the altimetric signal is sensitive to different properties of the snowpack, and therefore can also be used to determine these properties. The radar altimeter onboard the European Space Agency's ENVISAT satellite provides a dual-frequency dataset at Ku (13.6 GHz) and S band (3.2 GHz). In this paper, these signals are studied over the Antarctic ice-sheet during the 4 first years of the mission (2002)(2003)(2004)(2005)(2006), in order to retrieve snowpack properties.