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Data Set ID:
NSIDC-0099

Ice Thickness and Surface Elevation, Southeastern Ross Embayment, West Antarctica, Version 1

Ice surface elevation and ice thickness data are available for a portion of the West Antarctic Ice Sheet. Ice surface elevations and ice thickness data are derived from laser altimetry and radar sounding results. These data are a result of the Corridor Aerogeophysics of the
Southeastern Ross Transect Zone (CASERTZ) experiments of the 1990s. The CASERTZ geophysical surveys were aimed at understanding geological controls on ice streams of the West Antarctic Ice Sheet, ultimately to help assess the potential for ice sheet collapse.

NSIDC does not archive these data.

Parameter(s):
  • Glaciers/Ice Sheets > Glacier Elevation/Ice Sheet Elevation
  • Glaciers/Ice Sheets > Glacier Thickness/Ice Sheet Thickness
  • Snow/Ice > Ice Depth/Thickness
  • Glaciers/Ice Sheets > Ice Sheets
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: -80, 
S: -84, 
E: -104, 
W: -134
Platform(s):AIRCRAFT
Spatial Resolution:Not SpecifiedSensor(s):ALTIMETERS, RADAR, RADAR ECHO SOUNDERS
Temporal Coverage:
  • 27 December 1991 to 2 January 1996
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Donald Blankenship, David Morse, C. Finn, R. Bell, M. Peters, S. Kempf, S. Hodge, M. Studinger, J. Behrendt

Geographic Coverage
Please contact the data provider for the correct Data Citation for this data set.

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Detailed Data Description

Laser altimeter and radar sounding data were collected by a uniquely equipped Twin Otter aircraft, which flew at an altitude of 350 to 1000 m above the surface at an air speed of 120 to 130 knots. Surveys were accomplished with 116 flights in three seasons (1991/92, 1992/93, and 1995/96): 96 flights departed from the CASERTZ field camp and 20 departed from Byrd Surface Camp.

Ice surface elevations were determined by laser altimetry, using a 1000W peak-power infrared unit capable of 1000 pulses per second. Integration of pulses eight times per second allowed for a range determination about every 8 m. In the absence of clouds, range precisions were better than 0.1 m. Range determinations were corrected for aircraft attitude and projected to points on the ice sheet using the absolute position of the aircraft (as determined by GPS).

Ice thickness was measured by airborne radio-echo sounding, using a modified version of the TUD (Technical University of Denmark) radar. Two wing-mounted antennae emitted a 250 ns radar pulse at 60 MHz with a peak power of about 8 kW at a repetition rate of 12.5 kHz. Transmissions were digitized and integrated two to five times per second (i.e., every 12 to 30 m along the track). Processing techniques enhanced the reflection pulse of radar off the base of the ice. In most cases this was the ice-bedrock interface, although in some areas such as the ice shelves the reflection marked an ice-water interface.

Ice thickness was determined by measuring the time between the reflection pulse from the ice surface and the bed return reflection, and converting the time to distance given the radar wave velocity through ice (168.4 meters per microsecond). No firn correction was applied. Ambiguity in determining the precise time of the surface and ice-base pulse, along with variations in firn and ice density, are potential sources of error in the ice thickness determination.

Locator Maps
Map: Area of data set coverage
Figure 1. Area of coverage is indicated by the dark gray box. Crosshairs mark the position of the south pole.
map of coverage, east antarctica
Figure 2. Ice streams of the Ross Embayment of West Antarctica (labeled A through E) shown on the ice sheet surface (top) and subglacial topography (bottom) of Drewry (1983). For the surface topography the contour interval is 500 m. The subglacial topography is represented by a 1000 m contour interval with shaded topography below -1000 m a.s.l. The CASERTZ aerogeophysical survey over the Southeastern Ross Embayment (SERE) is outlined by the box overlying the catchments of ice streams B and C. EWB and BST, respectively, mark the locations of the Ellsworth/Whitmore crustal block and the Bentley Subglacial Trench; Marie Byrd Land (MBL), the Transantarctic Mountains (TAM), and the Ross Ice Shelf (RIS) are shown as well. The star indicates the location of possible active subglacial volcanism (Blankenship et al., 1993). (With permission from Blankenship et al. 2001.)
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Sample Data Record

Two tab-delimited ASCII data files are available.

The file "srfelev.txt" contains ice surface elevations and is formatted as follows:

Season/Flight   Year   Day   Longitude W   Latitude S   Elevation (m)
RTZ2/F20a       1992   8     -123.446438   -82.967063   793.992
RTZ2/F20a       1992   8     -123.387936   -82.969907   799.502
RTZ2/F20a       1992   8     -123.321159   -82.973536   805.261
RTZ2/F20a       1992   8     -123.223722   -82.978829   807.663

The first column provides a season and flight designator (seasons were designated "RTZ2" through "RTZ9", with the last season designated "VTZ1"; after the slash is the flight number "Fxxx"). The second and third columns provide the year and Julian day, respectively, of data acquisition. The fourth and fifth columns provide longitude (in degrees west) and latitude (in degrees south). The sixth column is ice surface elevation in meters above the WGS84 ellipsoid.

The file "icethk.txt" contains ice thickness data and is formatted as follows:

Season/Flight   Year   Day   Longitude W   Latitude S   Thickness (m)
RTZ2/F20a       1992   8     -121.337354   -83.051147   1767.58
RTZ2/F20a       1992   8     -121.286318   -83.052909   1709.12
RTZ2/F20a       1992   8     -121.239291   -83.054516   1664.23
RTZ2/F20a       1992   8     -120.498323   -83.079410   1708.75

The first column provides a season and flight designator (seasons were designated "RTZ2" through "RTZ9", with the last season designated "VTZ1"; after the slash is the flight number "Fxxx"). The second and third columns provide the year and Julian day, respectively, of data acquisition. The fourth and fifth columns provide longitude (in degrees west) and latitude (in degrees south). The sixth column is ice thickness in meters.

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Software and Tools

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Data Acquisition and Processing

Laser altimeter and radar sounding data were collected by a uniquely equipped Twin Otter aircraft, which flew at an altitude of 350 to 1000 m above the surface at an air speed of 120 to 130 knots. Surveys were accomplished with 116 flights in three seasons (1991/92, 1992/93, and 1995/96): 96 flights departed from the CASERTZ field camp and 20 departed from Byrd Surface Camp.

Ice surface elevations were determined by laser altimetry, using a 1000W peak-power infrared unit capable of 1000 pulses per second. Integration of pulses eight times per second allowed for a range determination about every 8 m. In the absence of clouds, range precisions were better than 0.1 m. Range determinations were corrected for aircraft attitude and projected to points on the ice sheet using the absolute position of the aircraft (as determined by GPS). 

Ice thickness was measured by airborne radio-echo sounding, using a modified version of the TUD (Technical University of Denmark) radar. Two wing-mounted antennae emitted a 250 ns radar pulse at 60 MHz with a peak power of about 8 kW at a repetition rate of 12.5 kHz. Transmissions were digitized and integrated two to five times per second (i.e., every 12 to 30 m along the track). Processing techniques enhanced the reflection pulse of radar off the base of the ice. In most cases this was the ice-bedrock interface, although in some areas such as the ice shelves the reflection marked an ice-water interface.

Ice thickness was determined by measuring the time between the reflection pulse from the ice surface and the bed return reflection, and converting the time to distance given the radar wave velocity through ice (168.4 meters per microsecond). No firn correction was applied. Ambiguity in determining the precise time of the surface and ice-base pulse, along with variations in firn and ice density, are potential sources of error in the ice thickness determination.

Derived Images
map of coverage, east antarctica
Figure 3. Ice-sheet surface elevations from CASERTZ airborne laser altimetry over the region encompassing the initiation of rapid basal motion for the ice streams of the southeastern Ross Embayment. Crevassed shear margins for these ice streams as determined by airborne radar sounding are indicated by white shading along the tracklines. C2 and B2 indicate the northern limbs of ice streams C and B, respectively; C1b and C1a indicate the northern and southern tributaries of the southern limb of ice stream C. (With permission from Blankenship et al. 2001.)

map of coverage, east antarctica
Figure 4. Subglacial topography obtained by subtracting ice thickness from CASERTZ airborne radar sounding from the surface elevations of [Figure 1]. The assumed crustal boundary for the Ellsworth/Whitmore crustal block (EWB; -250 m a.s.l.) is shown by the broken red line; the boundary for the Whitmore Mountains/Ross Embayment transitional crust (WRT; -500 m a.s.l.) is indicated by the broken orange line. (With permission from Blankenship et al. 2001.)

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References and Related Publications

Blankenship, D.D., D.L. Morse, C.A. Finn, R.E. Bell, M.E. Peters, S.D. Kempf, S.M. Hodge, M. Studinger, J.C. Behrendt, and J.M. Brozena. 2001. Geologic controls on the initiation of rapid basal motion for West Antarctic ice streams: A geophysical perspective including new airborne radar sounding and laser altimetry results. The West Antarctic Ice Sheet: Behavior and Environment. Antarctic Research Series 77: 105-121. 

Blankenship, D.D., R.E. Bell, S.M.Hodge, J.M Brozena, J.C. Behrendt, and C.A. Finn. 1993. Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability. Nature361: 526-529. 

Drewry, D.J. 1983. Antarctica: Glaciological and Geophysical Folio. Cambridge: Scott Polar Research Institute.

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