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Data Set ID:
NSIDC-0085

Siple Dome Glaciology and Ice Stream History 1994, 1996, Version 1

The Siple Dome Glaciology and Ice Stream History project was part of Western Divide West Antarctic Ice Cores (WAISCORES), an NSF-funded project to understand the influence of the West Antarctic ice sheet on climate and sea level change. WAISCORES researchers acquired and analyzed ice cores from the Siple Dome, in the Siple Coast region, West Antarctica.

This project supported glaciological studies of Siple Dome and its surroundings between Ice Streams C and D, via two major goals. First, it sought to characterize the dynamic environment and ice stratigraphy of Siple Dome and its surroundings, with the specific mission of assessing Siple Dome as a potential deep core site; and second, to determine whether the configuration of ice stream flow in the region has changed over time. Both goals are relevant to understanding the dynamics of the West Antarctic Ice Sheet (WAIS), its history, and potential future behavior.

This project was a collaboration between Saint Olaf College, the University of Washington, and the National Snow and Ice Data Center at the University of Colorado. It included studies of satellite imagery and acquisition and analysis of field data from GPS, firn cores and snow pits, and ground-based ice-penetrating radar.

Data in this collection were obtained during two Antarctic field seasons in 1994–95 and 1996–97. The data set is available via FTP as Microsoft Excel Spreadsheet (.xls) and ASCII tab delimited (.txt) files. Related notes are available as a Microsoft Word (.doc) or text (.txt) file. Related images and charts are available as Graphics Interchange Format (.gif) and Joint Photographic Experts Group (.jpg) files.

Geographic Coverage

Spatial Coverage:
  • N: -81, S: -83, E: -145, W: -155

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 November 1994 to 28 February 1995
  • 1 November 1996 to 28 February 1997
Temporal Resolution: Not specified
Parameter(s):
  • Glaciers/Ice Sheets > Glacier Elevation/Ice Sheet Elevation
  • Glaciers/Ice Sheets > Glacier Motion/Ice Sheet Motion
  • Snow/Ice > Ice Depth/Thickness
  • Snow/Ice > Ice Motion
  • Glaciers/Ice Sheets > Ice Sheets > Ice Stream
  • Snow/Ice > Ice Velocity
  • Radar > Radar Cross-section
Platform(s) GROUND-BASED OBSERVATIONS
Sensor(s): RADAR
Data Format(s):
  • GIF
  • Microsoft Excel
  • JPEG
  • ASCII Text
Version: V1
Data Contributor(s): Robert Jacobel

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Jacobel, R. 1999. Siple Dome Glaciology and Ice Stream History 1994, 1996, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N5Z31WJQ. [Date Accessed].

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Detailed Data Description

Format

The data set is available as Microsoft Excel (.xls) file, and as an ASCII tab delimited (.txt) file. Supporting documents include image files (.gif and .jpg), and text documents (.doc and .txt).

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File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/SIPLE_DOME/ directory. Table 1 lists the files in this directory:

Table 1. Files in the /AGDC/SIPLE_DOME/data/ directory
File Name Description
sdmdata.xls
sdmdata.txt
Data set, available as a Microsoft Excel (.xls) file, and as an ASCII tab delimited (.txt) file
sdmnotes.doc
sdmnotes.txt
Notes related to the data set, available as a Microsoft Word (.doc) file, and as a text (.txt) file
chart1.gif Surface and Bed Elevation for Siple Dome, 1996
chart2.gif Power vs. Distance for Siple Dome, 1996
chart3.gif Traverse of Siple Dome 1996 Lambert Coordinates
elevation_radar_image.jpg Siple Dome Profile, showing elevation and distance from summit.
locator_map.jpg Radio echo-sounding survey locator map
stackd.gif Contour and mesh surface map of Siple Dome between Ice Streams C and D in West Antarctica
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File Size

The data set contains 11 files ranging in size from 10 KB to 564 KB.

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Volume

The data set is available as a 340 KB ASCII tab delimited (.txt) file, or as a 564 KB Microsoft Excel (.xls) spreadsheet. The entire volume of the data set and supporting documents is about 1 MB.

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Spatial Coverage

Southernmost Latitude: 83° S
Northernmost Latitude: 81° S
Westernmost Longitude: 155° W
Easternmost Longitude: 145° W

Spatial Coverage Map

locator map for Jacobel data
Siple Dome Radio Echo-Sounding Survey Locator Map

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Temporal Coverage

Data were obtained during two Antarctic field seasons (November to February) in 1994–1995 and 1996–1997.

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Parameter or Variable

Parameters in this data set include local coordinates, using a Lambert projection centered at the summit of Siple Dome (-81.65434,-148.8081,623.23), geographic coordinates (latitude and longitude), distance from the Siple Dome summit, surface elevation, and bed elevation. Table 3 describes the columns and derivation techniques for data in the sdmdata.txt and sdmdata.xls file:

Table 2. Parameter Descriptions for the sdmdata File
Column Column Title Description Derivation Notes
A, B Lambert
(-NS and -EW)
Local coordinates using a Lambert projection centered at the summit of Siple Dome (-81.65434,-148.8081,623.23) The 1610 xy points corresponding to the location of radar waveforms points were derived by interpolation at intervals of ~ 100m from a set of 69 static Global Positioning System (GPS) surveys of poles located along the traverse.
C, D Latitude and Longitude Geographic Coordinates Coordinates were taken from the continuous kinematic GPS data set along the traverse with spacing of ~ 70m. Since the location of these points does not correspond exactly with that of the radar waveforms, a program was written to select the closest set of lat/long coordinates for each radar waveform. Thus, these are all measured (not interpolated) data points. However, there were 2 sections for which there were no kinematic GPS data. For these intervals to which no lat/long coordinates could be assigned, the latitude and longitude were both set to 0 (entries 1024-1043 and 1149-1317).
E, G, I Distance from summit along track (km) Cumulative distance away from the summit along the travel path (which wasn't entirely straight) Data were obtained by calculating the distances between successive sets of Lambert coordinates, and then summing them and adjusting the running distance to be referenced to the summit. 
Note: 
Columns 5, 7, and 9 are identical, repeated for graphing purposes.
F HAE - surface Elevation of the surface of Siple Dome in height above ellipsoid (HAE) Data were obtained from the continuous kinematic GPS. The same procedure used in columns 3 & 4 for selection of the closest kinematic GPS value to a radar waveform was used. However, in the intervals where there were no GPS data (see above), the elevations were linearly interpolated between the 2 endpoints of each gap
H HAE - bed Elevation of the bed of Siple Dome in HAE At each of the 1610 points, the 2-way travel time of the radar signal was determined by picking the mid-point time between the maximum and minimum phase of the bed-echo wavelet. These times were converted into depth using a measured average speed of 1.74040e8 m/s. These depths were then subtracted from the surface elevations.
J Power (mV^2/sample) Bed reflection power Bed reflection power as computed from the square of the amplitude integrated over the echo.

Sample Data Record

Lambert
- NS

Lambert 
- EW

Latitude

Longitude

Distance from summit along track (km)

HAE - surface

Distance from summit along track (km)

HAE - bed

Distance from summit along track (km)

Power (mV^2/sample)

-87095.102

9036.6226

-82.42398

-149.90756

-90.034855

110.752

-90.034855

-674.32104

-90.034855

9811.0751

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Software and Tools

Software and Tools

Data are accessible using standard spreadsheet software. Supplementary files are accessible using image and word processing software.

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Data Acquisition and Processing

Data Acquisition Methods

The Siple Dome Glaciology and Ice Stream History project involved two field seasons (November to February) at Siple Dome, the first in 1994–1995 and the second in 1996–1997. During the first season, ice-penetrating radar experiments were undertaken to study the bedrock topography and internal stratigraphy in the vicinity of the summit region to determine its suitability for deep ice coring. An 80 km radar traverse was completed across the north flank of the dome to gather similar data. This traverse was extended across a "scar" feature seen in satellite imagery and hypothesized to be a former shear margin from a relict ice stream. Strain grids were emplaced in the vicinity of the summit and scar regions, and shallow cores were recovered near the summit to measure snow accumulation rates.

Field work during the second field season extended the radar traverse across the southern flank of Siple Dome to complete depiction of bed topography and ice internal stratigraphy. Radar studies to the South also investigated a series of former margin scars of Ice Stream C. Strain grids were resurveyed, and an additional radar traverse with higher resolution was completed across the north flank and scar.

The two field seasons yielded data sets on ice thickness and internal stratigraphy along a traverse from one margin of the dome to the other, as well as a more detailed study of the summit region. Related work done principally by project collaborators resulted in data sets of surface topography and ice velocity, including strain rates in the vicinity of the summit and north scar.

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Processing Steps

These data were processed to extract information about ice flow and history in the vicinity of the dome and near its margins. Radar profiles were analyzed to determine ice thickness and bed topography. Enhancements were made to better depict internal stratigraphy and gain information about the nature of the bed. Information from the strain grids was used together with depictions of the internal stratigraphy by our colleagues at the University of Washington to model ice flow in the vicinity of the divide and on the dome flanks. Together, these studies have been used to interpret ice dynamics and history in the vicinity of Siple Dome in an effort to better understand the evolution of the West Antarctic Ice Sheet.

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Sensor or Instrument Description
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References and Related Publications

Contacts and Acknowledgments

Dr. Robert Jacobel
St. Olaf College
Environmental Studies Program
St. Olaf College
1520 St. Olaf Ave.
Northfield, MN 55057

Acknowledgements: 

This research was supported by NSF OPP grant 9316338.

Document Information

DOCUMENT CREATION DATE

25 February, 2009

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