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Data Set ID:
NSIDC-0545

MEaSUREs InSAR-Based Ice Velocity of the Amundsen Sea Embayment, Antarctica, Version 1

This data set, part of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Program, provides high-resolution, digital mosaics of ice motion in the Amundsen Sea Embayment (ASE) and West Antarctica, including Pine Island, Thwaites, Haynes, Pope, Smith, and Kohler glaciers. The mosaics were assembled from interferometric synthetic-aperture radar (InSAR) data acquired in 1996, 2000, 2002, and 2006-2012 by various satellites.

See MEaSUREs Ice Velocity Mapping of the Antarctic Ice Sheet Data for related data.

Note: These data are considered provisional pending a review by the MEaSUREs program. Once the data have been reviewed, this statement will be removed.

Geographic Coverage

Parameter(s):
  • Snow/Ice > Ice Velocity
Spatial Coverage:
  • N: -71.9876, S: -80.4614, E: 82.8345, W: -127.3826

Spatial Resolution:
  • 450 m x 450 m
Temporal Coverage:
  • 1 January 2006 to 31 December 2012
  • 1 January 2002 to 31 December 2002
  • 1 January 2000 to 31 December 2000
  • 1 January 1996 to 31 December 1996
Temporal Resolution: 1 year
Data Format(s):
  • Binary
  • NetCDF
Platform(s) ALOS, ERS-1, RADARSAT-1, RADARSAT-2, TDX
Sensor(s): PALSAR, SAR
Version: V1
Data Contributor(s): Eric Rignot, Jeremie Mouginot, Bernd Scheuchl
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.

Rignot, E., J. Mouginot, and B. Scheuchl. 2014. MEaSUREs InSAR-Based Ice Velocity of the Amundsen Sea Embayment, Antarctica, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/MEASURES/CRYOSPHERE/nsidc-0545.001. [Date Accessed].

Literature Citation

As a condition of using these data, we request that you acknowledge the author(s) of this data set by referencing the following peer-reviewed publication.

  • Mouginot, J., E. Rignot, and B. Scheuchl. 2014. Sustained Increase in Ice Discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013, Geophys. Res. Lett.. 41. 1576-1584. http://dx.doi.org/10.1002/2013GL059069

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Detailed Data Description

Format

Data are provided in the following formats:

  • Binary (big endian, IEEE floating point) with ENVI text header files
  • Network Common Data Form (NetCDF), Version 3 (missing values represented by NaN)
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File and Directory Structure

Data are available via HTTPS: https://n5eil01u.ecs.nsidc.org/MEASURES/NSIDC-0545.001/.
Within this directory, there are ten folders for the years 1996, 2000, 2002, and 2006 through 2012, which contain the data files for that year. The 1996 folder contains additional geolocation files and a record spanning netcdf.  Table 1 lists the files within these folders, where YYYY stands for the year the data were acquired.

Table 1. File Descriptions
File Name Description
ASE_ice_velocity_1996-2012.nc NetCDF (Version 3) file
ASE_ice_velocity_YYYY.dat Dual band, band interleaved by pixel (BIP) binary data file with x and y velocities in m/year
ASE_ice_velocity_YYYY.hdr ENVI header for the corresponding velocity .dat file
ASE_ice_velocity_YYYY_err.dat Single band binary file with error estimates in m/year
ASE_ice_velocity_YYYY_err.hdr ENVI header for corresponding error .dat file
ASE_ice_velocity_xaxis.dat Single band binary file with distance (m) in x-direction (see Table 4)
ASE_ice_velocity_xaxis.hdr ENVI header for xaxis.dat file
ASE_ice_velocity_yaxis.dat Single band binary file with distance (m) in y-direction (see Table 4)
ASE_ice_velocity_yaxis.hdr ENVI header for yaxis.dat file

See the File Naming Convention section for a description of the variables in the file names.

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File Naming Convention

This section explains the file naming convention for this data set and includes example file names. Refer to Table 2 for descriptions of the values in the file naming convention.

Naming Convention:
ASE_ice_velocity_YYYY_v01.ext

Example File Names:
ASE_ice_velocity_2000_v01.dat
ASE_ice_velocity_2000_v01.hdr

Table 2. File Naming Convention
Variable Description
ASE_ice_velocity Amundsen Sea Embayment
YYYY Year
err Error estimates file
v01 Version number
.ext File extension:
.dat= binary data file
.hdr=ENVI header file

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File Size

The NetCDF file is approximately 444 MB. Individual velocity and error binary files are approximately 30 MB and 15 MB respectively.

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Volume

The volume of this data set is 145 MB.

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Spatial Coverage

These data lie within the following bounding box that spans the Amundsen Sea Embayment and West Antarctica, including Pine Island, Thwaites, Haynes, Pope, Smith, and Kohler glaciers:

  • Northernmost Latitude: 73.3549° S
  • Southernmost Latitude: 78.0137° S
  • Easternmost Longitude: 82.8345° W
  • Westernmost Longitude: 127.3826° W

Refer to Table 4 for additional information about each satellite's spatial and temporal coverage.

Spatial Resolution

450 m

Projection and Grid Description

Projection
Projection Polar Stereographic South
Description Antarctic Polar Stereographic
Latitude of true origin -90°
Standard parallel -71°
Central meridian
Scale Factor at central meridian 1
Datum WGS 84
Ellipsoid WGS 84
Units meters
EPSG code 3031
PROJ4 description +proj=stere +lat_0=-90 +lat_ts=-71 +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
Reference http://www.spatialreference.org/ref/epsg/3031/
https://nsidc.org/data/atlas/epsg_3031.html
Grid
Number of rows 1707
Number of columns 2268
Units meters
Grid cell x resolution (x-dimension of a pixel in map units) 450 m
Grid cell y resolution (y-dimension of a pixel in map units) 450 m
ulxmap – x-axis map coordinate of the center of the upper-left pixel -1806625.0 m
ulymap – y-axis map coordinate of the center of the upper-left pixel. (YLLCORNER for ASCII data) 227125.0 m
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Temporal Coverage

Data are available for the years 1996, 2000, 2002, and 2006 through 2012. Refer to Table 4 for additional information about each satellite's spatial and temporal coverage.

Temporal Resolution

Annual

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Parameter or Variable

Parameter Description

These maps contain velocity data for the Amundsen Sea Embayment (ASE) and West Antarctica, including Pine Island, Thwaites, Haynes, Pope, Smith, and Kohler glaciers. Data are provided for the years 1996, 2000, 2002, and 2006 through 2012 at a spacing of 450 meters. Each data point provides the velocity (vx and vy respectively) in meters per year as defined by the polar stereographic grid. Error estimates for the velocity magnitude are also provided; however, these values should be interpreted as an indication of relative quality rather than absolute error. Refer to the Error Sources section of this document for more information.

Table 3 contains the names and descriptions of the variables in this data set. YYYY denotes the 4-digit year.

Table 3. Variable Names and Descriptions
Variable Description Dimensions
(col x row)
vx[YYYY] Velocity, m/year in the x-direction. 1707 x 2268
vy[YYYY] Velocity, m/year in the y-direction. 1707 x 2268
err[YYYY] Estimated error in velocity magnitude. 1707 x 2268
xaxis Projected distance (m) to center of column from projection origin (South Pole) 1707 x 1
yaxis Projected distance (m) to center of row from projection origin (South Pole) 1 x 2268

Sample Data Record

The following visualizations show data from MEaSUREs InSAR-based Ice Velocity of the Amundsen Sea Embayment, Antarctica overlaid on the MODIS Mosaic of Antarctica (MOA) Image Map:

Figure 1. Satellite radar interferometry-based ice surface velocity maps for Amundsen Sea Embayment derived using data from ERS 1 (ERS), RADARSAT-1 (R1) in 2000 and 2002, ALOS PALSAR in 2006-2010, RADARSAT-2 (R2) in 2011, and TanDEM-X (TDX) in 2012. Velocities are overlaid on MOA and color coded on a logarithmic scale (Mouginot, J., E. Rignot, and B. Scheuchl, 2014).
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Software and Tools

Software and Tools

Data are accessible using a variety of software packages. For more information about accessing NetCDF-formatted data, see NetCDF Resources at NSIDC.

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Data Acquisition and Processing

Table 4. Source Data Temporal and Spatial Coverage

Year Sensor Mode(s) Incidence Angle(s),
scene center
Rg¹ x Az² Spacing # of Tracks Comments

1996

ERS-1

n/a

23.4

8 x 4

25

Interferometry

2000

RADARSAT-1

Fine, Standard

28.2, 38.6, 44.5

5.4 x 8, 4.6 x 5.3, 
11.6 x 5.1

5

Speckle tracking

2002

RADARSAT-1

Fine, Standard

28.2, 38.6, 44.5

5.4 x 8, 4.6 x 5.3, 
11.6 x 5.1

2

Speckle tracking

2006

ALOS PALSAR

FBS³

39, 47.7

4.7 x 3.3

13

Speckle tracking

2007

ALOS PALSAR

FBS³

39.

4.7 x 3.3

30

Speckle tracking

2008

ALOS PALSAR

FBS³

39.

4.7 x 3.3

30

Speckle tracking

2009

ALOS PALSAR

FBS³

39.

4.7 x 3.3

22

Speckle tracking

2010

ALOS PALSAR

FBS³

39.

4.7 x 3.3

22

Speckle tracking

2011

RADARSAT-2

Standard

41.5

11.8 x 5.3

23

Speckle tracking

2012

TanDEM-X

n/a

46.3

1.4 x 1.8

7

Speckle tracking

¹Range. ²Azimuth. ³Fine Beam Single Polarisation mode.
Data Acquisition Methods

Ice velocities were derived from satellite synthetic aperture radar interferometry (InSAR) data obtained by the following international space agencies:

Data acquisitions between 2006 and 2012 were coordinated through the IPY Space Task Group.

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Derivation Techniques and Algorithms

Processing Steps

These data were generated by using a speckle tracking technique. Refer to the work by Michel and Rignot, 1999 for more information. This was done to derive slant range and azimuth displacements from InSAR data (2000 and later) or interferometric phase analysis (1996). Assuming surface parallel flow, a digital elevation model was used to calculate the two-dimensional displacement field. The method is described in Rignot et al. 2011b and Mouginot et al. 2012. Where multiple data cycles were available for a given year, the resulting velocity products per track were combined to reduce data noise.

Error Sources

The precision of ice flow mapping varies with the geographic location, the technique used for interferometric analysis, the time period of analysis, the repeat cycle, and the amount of data stacking. Error estimates range from +/- 6m/year to +/- 20m/year, with ionospheric perturbations constituting the largest contribution. These estimates take into account the following error sources:

  • error of speckle tracking and interferometric phase analysis respectively
  • errors caused by ionospheric perturbations (strongest in the azimuth direction)
  • data stacking (reduces the error noise as the square root of the number of interferometric pairs averaged)

The total error is the square root of the sum of the independent errors squared. Additional details about the error estimation are provided in Rignot et al. (2011b) and Mouginot et al. (2012).

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Sensor or Instrument Description

Velocity maps were derived from radar interferometry data obtained by several different satellite missions. See Table 4 for details.

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References and Related Publications

Contacts and Acknowledgments

Investigators

Dr. Eric Rignot
University of California, Irvine
Department of Earth System Science
Croul Hall
Irvine, California 92697
USA

Dr. Jeremie Mouginot
University of California, Irvine
Department of Earth System Science
Croul Hall
Irvine, California 92697
USA

Dr. Bernd Scheuchl
University of California, Irvine
Department of Earth System Science
Croul Hall
Irvine, California 92697
USA

Acknowledgments: 

These data were generated through a grant from the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Program.

Spaceborne SAR acquisitions were provided through generous data grants from:

  • ERS 1: European Space Agency (ESA)
  • RADARSAT: Canadian Space Agency (CSA), Alaska Satellite Facility (ASF)
  • ALOS PALSAR: Japan Aerospace Exploration Agency (JAXA), Alaska Satellite Facility (ASF). PALSAR acquisitions (2006-2010) are courtesy of the IPY Space Task Group.
  • RADARSAT-2: Canadian Space Agency (CSA), MacDonald, Dettwiler and Associates Ltd. (MDA). RADARSAT-2 acquisitions (2011) are courtesy of the IPY Space Task Group.
  • TanDEM-X: German Aerospace Center (DLR)

ALOS PALSAR and RADARSAT-2 acquisitions were part of a multi-SAR-sensor effort to provide interferometric SAR coverage of the entire Antarctic continent during the International Polar Year (IPY). Data acquisitions are courtesy of the IPY Space Task Group. Post IPY acquisitions are being coordinated through the Polar Space Task Group.

Document Information

DOCUMENT CREATION DATE

December 2014

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