scholarly journals Geostatistical methods for mapping Antarctic ice surfaces at continental and regional scales

2000 ◽  
Vol 30 ◽  
pp. 76-82 ◽  
Author(s):  
Ute Christina Herzfeld ◽  
Ralf Stosius ◽  
Marcus Schneider
Keyword(s):  
Surface Elevation ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Sea Level Changes ◽  
Ice Streams ◽  
Geostatistical Methods ◽  
Ice Surface ◽  
Geophysical Study ◽  
Satellite Radar ◽  
The Antarctic

AbstractThe Antarctic ice sheet plays a major role in the global system and the large ice streams discharging into the circumpolar sea represent its gateways to the world’s oceans. Satellite radar-altimeter data provide an opportunity for mapping surface elevation at kilometer resolution with meter accuracy. Geostatistical methods have been developed to accomplish this. We distinguish two goals in mapping the Antarctic ice surface: (a) construction of a continent-wide atlas of maps and digital terrain models, and (b) calculation of maps and models suitable for the study of individual glaciers, ice streams and ice shelves. The atlases consist of accurate maps of ice-surface elevation compiled from Seasat, Geosat and ERS-1 altimeter data, covering all of Antarctica surveyed by Geosat (to 72.1° S) and by ERS-1 (to 81.5° S). With a 3 km grid they are the highest-resolution maps available today with continent-wide coverage. The resolution permits geophysical study and facilitates monitoring of changes in ice-surface elevation and changes in flux across the ice-ocean boundary, which is essential for monitoring sea-level changes.

scholarly journals Boundary conditions of an active West Antarctic subglacial lake: implications for storage of water beneath the ice sheet

2013 ◽  
Vol 7 (3) ◽  
pp. 2979-2999 ◽  
Author(s):  
M. J. Siegert ◽  
N. Ross ◽  
H. Corr ◽  
B. Smith ◽  
T. Jordan ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Surface Elevation ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Local Flow ◽  
Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Ice Surface ◽  
The Antarctic

Abstract. Repeat-pass IceSat altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts (notable exceptions are Lake Whillans and three in the Adventure Subglacial Trench). Here we present targeted RES and radar altimeter data from an "active lake" location within the upstream Institute Ice Stream, into which 0.12 km3 of water is calculated to have flowed between October 2003 and February 2008. We use a series of transects to establish an accurate appreciation of the influences of bed topography and ice-surface elevation on water storage potential. The location of surface height change is over the downslope flank of a distinct topographic hollow, where RES reveals no obvious evidence for deep (> 10 m) water. The regional hydropotential reveals a sink coincident with the surface change, however. Governed by the location of the hydrological sink, basal water will likely "drape" over existing topography in a manner dissimilar to subglacial lakes where flat strong specular RES reflections are measured. The inability of RES to detect the active lake means that more of the Antarctic ice sheet bed may contain stored water than is currently appreciated. Variation in ice surface elevation datasets leads to significant alteration in calculations of the local flow of basal water indicating the value of, and need for, high resolution RES datasets in both space and time to establish and characterise subglacial hydrological processes.

scholarly journals Boundary conditions of an active West Antarctic subglacial lake: implications for storage of water beneath the ice sheet

2014 ◽  
Vol 8 (1) ◽  
pp. 15-24 ◽  
Author(s):  
M. J. Siegert ◽  
N. Ross ◽  
H. Corr ◽  
B. Smith ◽  
T. Jordan ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Surface Elevation ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Local Flow ◽  
Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Ice Surface ◽  
The Antarctic

Abstract. Repeat-pass ICESat altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts (notable exceptions are Lake Whillans and three in the Adventure Subglacial Trench). Here we present targeted RES and radar altimeter data from an "active lake" location within the upstream Institute Ice Stream, into which at least 0.12 km3 of water was previously calculated to have flowed between October 2003 and February 2008. We use a series of transects to establish an accurate depiction of the influences of bed topography and ice surface elevation on water storage potential. The location of surface height change is downstream of a subglacial hill on the flank of a distinct topographic hollow, where RES reveals no obvious evidence for deep (> 10 m) water. The regional hydropotential reveals a sink coincident with the surface change, however. Governed by the location of the hydrological sink, basal water will likely "drape" over topography in a manner dissimilar to subglacial lakes where flat strong specular RES reflections are measured. The inability of RES to detect the active lake means that more of the Antarctic ice sheet bed may contain stored water than is currently appreciated. Variation in ice surface elevation data sets leads to significant alteration in calculations of the local flow of basal water indicating the value of, and need for, high-resolution altimetry data in both space and time to establish and characterise subglacial hydrological processes.

scholarly journals Seasonal variation in the apparent height of the East Antarctic ice sheet

1997 ◽  
Vol 24 ◽  
pp. 191-198 ◽  
Author(s):  
D. Yi ◽  
C. R. Bentley ◽  
M. D. Stenoien
Keyword(s):  
Seasonal Variation ◽  
Accumulation Rate ◽  
Surface Elevation ◽  
Secular Change ◽  
Radar Signal ◽  
Real Surface ◽  
Radar Altimeter ◽  
Depth Of Penetration ◽  
Orbit Error ◽  
Satellite Radar

A satellite radar altimeter can be used to monitor surface elevation change over polar ice sheets. Thirty-five months of Geosat Exact Repeat Mission (ERM) data from November 1986 to September 1989 over a section of East Antarctica (69–72.1 ∘S, 80–140∘ E) have been used in this study. A model that considers both surface and volume scattering was used to retrack the altimeter waveforms. Surface elevations for each month after the first three were compared to the average elevations for the first 3 months through a crossover method. The averaged crossover elevation difference changed with time in a way that suggests a yearly cycle in surface elevation. The average amplitude of the cycle is about 0.6 m. We have been unable to find any satisfactory explanation for the observed changes, in terms of either sources of error or contributors to real surface-height changes. We strongly suspect that orbit error plays a major role in producing the variations, although we know of no quantitatively satisfactory source of a quasi-seasonal variation in orbit error. Other possible contributors include a real seasonal variation in accumulation rate, seasonal changes in the delay of the radar signal as it propagates through the atmosphere, unmodeled variations in the depth of penetration of the radar pulse into the firn, changes in the thickness of the ice and the firn zone in response to seasonal variations in pressure and temperature, and the inverted barometer effect. Even though we do not know the cause of the variations, the results show the importance of comparing elevations at the same time of year for observations that are not continuous, while at the same time showing that even annually spaced measurements may not be free of substantial errors associated with interannual variability. The quasi-periodic variations obscure any evidence of a moderate secular change in surface height, if there is one, but a dramatic lowering at rates approaching 1 ma–1, such as are known elsewhere in Antarctica, can definitely be ruled out.

scholarly journals Using the temporal variability of satellite radar altimetric observations to map surface properties of the Antarctic ice sheet

1998 ◽  
Vol 44 (147) ◽  
pp. 197-206 ◽  
Author(s):  
Benoît Legrésy ◽  
Frédérique Rémy
Keyword(s):  
Ice Sheet ◽  
Temporal Variations ◽  
Radar Altimeter ◽  
Height Measurement ◽  
Radar Echoes ◽  
Measuring Surface ◽  
Antarctic Continent ◽  
Ice Sheet Mass Balance ◽  
Satellite Radar ◽  
The Antarctic

AbstractThe problem of measuring surface height and snowpack characteristics from satellite radar altimeter echoes is investigated. In this paper, we perform an analysis of the ERS1 altimeter dataset acquired during a 3 day repeat orbit. The analysis reveals that there are temporal variations in shapes of the radar altimeter echo and that these variations are linked to meteorological phenomena. The time- and space-scales over which these variations apply are a few to tens of days and a few hundred kilometres, respectively. This phenomenon, if not accounted for, can create error in the height measurement. A numerical echo model is used to recover snowpack characteristics by taking advantage of the temporal variations of the radar echoes. A map of penetration depth of the radar waves in the Ku band over the Antarctic continent is obtained and suggests that grain-size produces the dominant effect on radar extinction in the snowpack at this frequency. Finally, a procedure is proposed to correct the height measurement within the context of ice-sheet mass-balance survey.

Ice Surface Elevation of Central Marie Byrd Land

1962 ◽  
Vol 4 (31) ◽  
pp. 121-123 ◽  
Author(s):  
J. C. Behrendt ◽  
R. J. Wold ◽  
F. L. Dowling
Keyword(s):  
Surface Elevation ◽  
Ice Shelf ◽  
Ice Surface ◽  
Altimetric Data ◽  
The Antarctic

An ice surface map of central Marie Byrd Land has been compiled from aero-altimetric data taken on 14,000 km. of flight lines during the Antarctic summer of 1960–61 using standard aircraft equipment. A large depression sloping down towards the Filchner Ice Shelf was determined and earlier known features in the area are shown in greater detail.

scholarly journals Ice-Sheet Surface Elevation and Changes Observable by Satellite Radar Altimetry

1979 ◽  
Vol 24 (90) ◽  
pp. 491-493 ◽  
Author(s):  
H. Jay Zwally ◽  
R. L. Brooks ◽  
H. Ray Stanley ◽  
W. J. Campbell
Keyword(s):  
Drainage Basin ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
The State ◽  
Surface Elevation ◽  
Radar Altimeter ◽  
Major Question ◽  
The Status ◽  
Satellite Radar ◽  
Ice Sheet Dynamics

Abstract A major question in ice-sheet dynamics is the state of balance between the net mass input and ice flow. Since an imbalance produces a change in surface elevation, the state of balance can be studied by monitoring the elevation, and this has been accomplished by surface-leveling techniques in a few locations. Due to the requirement for accurate and repetitive measurements over large areas, it is not practical to determine the status of balance of an entire ice sheet or even a major drainage basin by conventional techniques. Now, recent results from satellite-borne radar altimeter measurements over the Greenland ice sheet demonstrate the feasibility of accurately measuring and monitoring the topography of large ice masses. The application of this new technique offers the possibility of making a meaningful mass-balance determination and for detecting actual or potential ice-sheet surges.

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