This data set includes a nested model, that starts at low resolution for the whole Antarctic Ice Sheet, and then embeds higher resolution data at limited domains. There are at least three levels of nesting: whole, regional, and specific ice streams. Investigators focused on the Thwaites Glacier and the Pine Island Glacier. The model was produced using data from (Holt et al. 2006) and (Vaughan et al. 2006). Data are in Network Common Data Form (NetCDF) format and are available via FTP.
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.
Fastook, James. 2007. UMISM Amundsen Sea Sector data set. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5J9649Q.
|Data format||NetCDF (Network Common Data Form)|
|Spatial coverage and resolution||Antarctic Continent at 40 kilometers
Amundsen Sea Embayment at 10 kilometer
Pine Island Glacier at 5 kilometer
Thwaites Glacier at 5 kilometer
|Temporal coverage and resolution||2004/2005 Austral Summers (December 21 through March 21)|
|Tools for accessing data||Ncview|
|File naming convention||netcdf-###.nc|
|File size||Approximately 9.27 MB to 223 MB|
|Parameters||Bed elevation, ice thickness, net annual accumulation or ablation, ice hardness, ice temperature, ice melt rate, and column-average ice velocity|
|Procedures for obtaining data||Data are available via FTP.|
James L. Fastook
Department of Computer Sciences
University of Maine
Orono, ME 04469-5790
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
The National Science Foundation (NSF) supported the development of the model producing these data over many years through several awards. The investigator used flight-line data and surface elevation data from the Airborne Geophysical Survey of the Amundsen Sea Embayment (AGASEA) and the British Antarctic Survey (BAS), respectively.
Data are in NetCDF, which uses rectangular arrays, rows and columns like positions on a checkerboard. For more information on the NetCDF file format, please see the NetCDF Resources at NSIDC Web site. The following table describes the arrays included in each file.
|htice||Ice surface elevation relative to present sea level|
|bedrock||Bed elevation, also relative to present sea level, which varies due to isostatic response to changing load|
|thick||Ice thickness, conceptually the differnce between htice and bedrock|
|adot||Net annual accumulation, if value is positive, or ablation, if value is negative, in meters per year (m/yr) ice equivalent|
|flowa||"Effective" ice hardness (a function of the temperature structure within the ice column)|
|tbed||Temperature at the base of the ice column|
|bmelt||Rate at which ice melts from the base of the ice column, where the bed is at pressure melting point; the source of water for the wthick measurement|
|wthick||Amount of water at the bed, expressed as a "thickness" velocity; a column-average ice velocity (m/yr)|
Files are named according to the convention netcdf-###.nc
|netcdf-a1.nc||44.1 MB||Continent- Glacier cycle at 40 kBP to present|
|netcdf-a2.nc||16.7 MB||Continent- Glacier cycle at present to 2000 years into the future|
|netcdf-a23.nc||223.0 MB||Continent - short run over 200-300 year period|
|netcdf-e1.nc||24.4 MB||Amundsen Embayment - Glacier cycle at 40 kBP to present|
|netcdf-e2.nc||9.27 MB||Amundsen Embayment - Glacier cycle at present to 2000 years into the future|
|netcdf-e22.nc||30.9 MB||Amundsen Embayment - short run over 200-300 year period|
|netcdf-e23.nc||123.0 MB||Amundsen Embayment - short run over 200-300 year period|
|netcdf-e24.nc||123.0 MB||Amundsen Embayment - short run over 200-300 year period|
|netcdf-f1.nc||29.6 MB||Twaites Glacier - Glacier cycle at 40 kBP to present|
|netcdf-f2.nc||37.4 MB||Twaites Glacier - Glacier cycle at present to 2000 years into the future|
|netcdf-f22.nc||78.7 MB||Twaites Glacier - short run over 200-300 year period|
|netcdf-f23.nc||41.2 MB||Twaites Glacier - short run over 200-300 year period|
|netcdf-g1.nc||17.3 MB||Pine Island Glacier - Glacier cycle at 40 kBP to present|
|netcdf-g2.nc||21.9 MB||Pine Island Glacier - Glacier cycle at present to 2000 years into the future|
|netcdf-g22.nc||46.1 MB||Pine Island Glacier - short run over 200-300 year period|
Antarctic Continent at 40 kilometers
Amundsen Sea Embayment at 10 kilometers
Pine Island Glacier at 5 kilometers
Thwaites Glacier at 5 kilometers
2004/2005 Austral Summers
Ice Sheet topography
Net annual accumulation
Effective ice hardness
Temperature at base of ice column
Data are available via FTP.
The volume of the entire data set is approximately 517 MB compressed.
For a list of tools for reading/viewing netCDF files, please see the NetCDF Resources at NSIDC: Software and Tools Web page.
Original ice thickness data collected by RADAR sounders from survey aircraft. Surface elevation collected using RADAR and LASER altimeters.
Original data collected by survey aircraft as part of Airborne Geophysical Survey of the Amundsen Sea Embayment (AGASEA). See: Subglacial Topography: Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica
Model data is derived from University of Maine Ice Sheet model.
Model was used in the embedded mode to do high resolution analysis of the velocity distribution.
Courville, Z. R., M. R. Albert, M. A. Fahnestock, L. M. Cathles, IV, and C. A. Shuman. 2007. Impacts of an accumulation hiatus on the physical properties of firn at a low-accumulation polar site. Journal of Geophysical Research 112, F02030, doi: 10.1029/2005JF000429
Holt, J. W., D. D. Blankenship, D. L. Morse, D. A. Young, M. E. Peters, S. D. Kempf, T. G. Richter, D. G. Vaughan, H. F. J. Corr. 2006. New boundary conditions for the West Antarctic Ice Sheet; subglacial topography of the Thwaites and Smith Glacier catchments. Geophysical Research Letters L09502, doi: 10.1029/2005GL025561
Vaughan, D. G., H. F. J. Corr, F. Ferraccioli, N. Frearson, A. O'Hare, D. Mach, J. W. Holt, D. D. Blankenship, D. L. Morse, D. A. Young. 2006. New boundary conditions for the West Antarctic Ice Sheet; subglacial topography beneath Pine Island Glacier. Geophysical Research Letter doi: 10.1029/2005GL025588.
The following related documents are available on NSIDC's Web site.
|Subglacial Topography: Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica||This data set includes 5 km gridded data from the Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica (AGASEA) conducted during the 2004-2005 austral summer covering the entire catchments of both the Thwaites Glacier and the Pine Islands Glacier.||http://nsidc.org/data/nsidc-0292.html|
|NetCDF Resources at NSIDC||Gives a brief summary of netCDF files, a list of tools for accessing these files, and a list of data sets in netCDF format at NSIDC.||http://nsidc.org/data/netcdf/|
The following acronyms and abbreviations are used in this document.
|AGASEA||Airborne Geophysical Survey of the Amundsen Sea Embayment|
|AGDC||Antarctic Glaciological Data Center|
|BAS||British Antarctic Survey|
|FTP||File Transfer Protocol|
|LGM||Last Glacial Maximum|
|NetCDF||Network Common Data Form|
|NSIDC||National Snow and Ice Data Center|
|SAR||Synthetic Aperature Radar|
|UMISM||University of Maine Ice Sheet Model|
|URL||Uniform Resource Locator|