Antarctic Subglacial Lake Classification Inventory

Summary

This data set is an Antarctic radar-based subglacial lake classification collection, which focuses on the radar reflection properties of each given lake.

The Subglacial lakes are separated into four categories specified by radar reflection properties. Additional information includes: latitude, longitude, length (in kilometers), hydro-potential (in meters), bed elevation (in meters above WGS84), and ice thickness (in meters).

Source data used to compile this data set were collected between 1998 and 2001. Data are available via FTP as a Microsoft Excel Spreadsheet (XLS), and Tagged Image File Format (TIF).

Citing These Data

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title and version number, dates of the data you used (for example, 2007), publisher: NSIDC, and digital media.

Blankenship, David D., Sasha P. Carter, John W. Holt, David L. Morse, Matthew E. Peters, and Duncan A. Young. 2009. Antarctic Subglacial Lake Classification Inventory. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5CN71VX.

Overview Table

Category	Description
Data format	Microsoft Excel Spreadsheet (.xls), Tagged Image File Format (.tif)
Spatial coverage and resolution	Southernmost Latitude: 90° S Northernmost Latitude: 70° S Westernmost Longitude: 180° W Easternmost Longitude: 180° E
Temporal coverage	Source data used to compile this data set were collected between 1998 and 2001.
File size	Excel File, 68 KB; TIF image file 7.1 MB
Parameter(s)	Lake Type Geographic Coordinates (lat/lon) Bed Elevation Ice Thickness
Procedures for obtaining data	Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s)

Donald D. Blankenship
University of Texas Institute for Geophysics
John A. and Katherine G. Jackson School of Geosciences,
The University of Texas at Austin

Sasha P. Carter
Scripps Institution of Oceanography, UCSD
9500 Gilman Drive
La Jolla CA, 92093
Mail Code: 0225

John W. Holt
University of Texas Institute for Geophysics
John A. and Katherine G. Jackson School of Geosciences
University of Texas at Austin
Phone: 512-471-0487

Technical Contact

Acknowledgements

This research was funded by the National Science Foundation under Cooperative Agreement OPP 91-19379 and OPP 93-19379, as well as NSF grant OPP 99-11617.

2. Detailed Data Description

Format

The data set is in Microsoft Excel (.xls) format viewable with spreadsheet software. A coverage map is available in TIF format.

File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/blankenship_nsidc_0336/ directory. The directory contains four files: an Excel spreadsheet, lake_detect.xls, a Tagged Image File Format (TIF) image, a readme file, and a supplementary Portable Document Format (PDF) file.

File Division

Within the lake_detect.xls file, there are 12 sheets defined by lake type and location. For more information on the lake defining algorithms, please see the article Radar-Based Subglacial Lake Classification in Antarctica on the Geochemistry, Geophysics, Geosystems Web site. A PDF of the article is also available via FTP.

The 12 sheets within the Excel file are named according to their lake type and region. The following table describes the naming system for sheets within the lake_detect.xls file

Example laketype.xls sheet names:

definite_WLK
dim_PPT
fuzzy_LVS
indistinct_PPT

Where:

Table 1. Definition of naming variables in the lake_detect.xls File

Variable	Definition
Lake Type
definite	brighter than surroundings by at least 2 dB, specular across at least 5% of its extent, maintains a reflection coefficient of -10 dB or greater across at least 5% of its extent
dim	specular and brighter than surroundings, but lack the absolute reflectivity of definite lakes; estimated reflection coefficient falls well below -10 dB
fuzzy	high absolute and relative reflection coefficients, but not specular
indistinct	specular, but not brighter than surroundings.
Location
WLK	Wilkes Basin-Dome C
LVS	Lake Vostok Region
PPT	Mercer Ice Stream-South Pole

 

File Size

Excel File, 68 KB; TIF image file 7.1 MB

Spatial Coverage

Study locations were in East Antarctica, including the Mercer Ice Stream, Lake Vostok Region, and Wilkes Basin-Dome C.

Southernmost Latitude: 90° S
Northernmost Latitude: 70° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E

Spatial Coverage Map

Image from Carter, S. P. et. al., 2007

Temporal Coverage

Source data used to compile this data set were collected between 1998 and 2001. For more information, please see the references section of this document.

Parameter or Variable

Parameters include location of lakes as geographic coordinates, lake length, hydro-potential, bed elevation in meters above WGS84, and ice thickness. The Wilkes Basin-Dome C (WLK) spreadsheet also includes the lake number from the Siegert, et al inventory in 2005.

The following table describes the columns in the data files:

Table 3. Description of Columns in the lake_detect.xls file

Column	Description
Latitude/Longitude	Lake location in geographic coordinates
Length	Lake length in kilometers
Hydro-potential	Hydraulic potential, also called hydraulic head, is the sum of the elevation of the water body and the fluid pressure. In this case hydraulic head is equal to the elevation plus ice thickness multiplied by density contrast of ice relative to water or 0.917h_ice + z_bed.
Bed Elevation	Bed elevation, measured as meters above World Geodetic System 84 (WGS84), a standard coordinate frame for the Earth
Ice Thickness	Ice thickness above the lake feature, measured in meters, ±standard error
Number	If applicable, inventory number from Siegert et al., 2005
Notes	Investigator's notes, generally related to lake location

 

Sample Data Record

The following example shows sample data from the definite_WLK spreadsheet in the lake_detect.xls file

Latitude	Longitude	Length (km)	Hydro-potential (m)	Bed Elevation (m above WGS84)	Ice Thickness (m)	Number (from Siegert et al 2005 Inventory)	Notes
-74.07	125.02	35	2845	-890	4072 ±47	6	Concordia got broken up into two overlapping lakes

 

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

The data set is approximately 60KB. Supplementary files are approximately 11MB.

Software and Tools

Data are accessible using standard spreadsheet software.

Related Data Collections

• Antarctic Cryosphere Access Portal (A-CAP)
• MODIS Mosaic of Antarctica (MOA) Image Map

4. Data Acquisition and Processing

The Antarctic Subglacial Lake Classification Inventory lists the locations and categories of lakes in East Antarctica. For more information on data processing, please see the article Radar-Based Subglacial Lake Classification in Antarctica on the Geochemistry, Geophysics, Geosystems Web site. A PDF of the article is also available via FTP.

Sensor or Instrument Description

This data set was developed using laser and radar altimetry measurements, as well as measurements of gravitational and magnetic fields.

Data Source

Source data was obtained from the University of Texas Institute for Geophysics data set for radio echo sounding in East Antarctica. (Holt, et. al., Siegert et. al.)

Derivation Techniques and Algorithms

A lake detection algorithm was used to identify and categorize four major "lake" types using digital ice-penetrating radar data. For details on the algorithm, please see the article Radar-Based Subglacial Lake Classification in Antarctica on the Geochemistry, Geophysics, Geosystems Web site.

5. References and Related Publications

Carter, S. P., D. D. Blankenship, M. E. Peters, D. A. Young, J. W. Holt, and D. L. Morse. 2007. Radar-based subglacial lake classification in Antarctica. Geochemistry, Geophysics, Geosystems VOL. 8, Q03016, doi:10.1029/2006GC001408. PDF available via FTP.

Holt, J. W., D. D. Blankenship, D. L. Morse, D.A. Young, M. E. Peters, S. D. Kempf, and T. G. Richter. 2006. New boundary conditions for the West Antarctic Ice Sheet: Subglacial topography of the Thwaites and Smith glacier catchments. Geophysical Research Letters, 33, doi:10.1029/2005GL025561.

Siegert, M. J., S. P. Carter, I. E. Tabacco, S. Popov, and D. D. Blankenship. 2005. A revised inventory of Antarctic subglacial lakes, Antarct. Sci., 17, 453–460. Download PDF (275 KB)

Refer to Table 4 for related documents available on the NSIDC Web site.

Table 4. Related Documents

Document	Description	URL
Airborne Laser Altimetry of the Thwaites Glacier Catchment, West Antarctica	Related data	http://nsidc.org/data/nsidc-0334.html
Antarctic Aerogeophysics Data	Related data	http://nsidc.org/data/nsidc-0240.html
Ice Thickness and Surface Elevation, Southeastern Ross Embayment, West Antarctica	Related data	http://nsidc.org/data/nsidc-0099.html
Subglacial Topography: Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica	Related data	http://nsidc.org/data/nsidc-0292.html
Antarctic Glaciological Data Center	Project Web site	http://nsidc.org/agdc/

6. Document Information

Acronyms

The following acronyms are used in this document.

Table 5. Acronyms and Abbreviations

Acronym	Description
A-CAP	Antarctic Cryosphere Access Portal
FTP	File Transfer Protocol
TIF	Tagged Image File Format
NSIDC	National Snow and Ice Data Center
PDF	Portable Document Format
URL	Uniform Resource Locator
WGS	World Geodetic System

Document Creation Date

6 February 2009

Document URL

http://nsidc.org/data/docs/agdc/nsidc0336_blankenship/index.html