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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 Antarctic Ice Sheet Velocity and Mapping 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.

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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 1996 to 31 December 1996 1 January 2000 to 31 December 2000 1 January 2002 to 31 December 2002 1 January 2006 to 31 December 2012
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
Metadata XML:	View Metadata Record

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: https://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. https://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	0°
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 E rror 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

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

Michel, R. and E. Rignot. 1999. Flow of Glaciar Moreno, Argentina, from Repeat-Pass Shuttle Imaging Radar Images: Comparison of the Phase Correlation Method with Radar Interferometry. Journal of Glaciology 45(149): 93-100.

Mouginot, J., E. Rignot, and B. Scheuchl. 2014. Sustained Increase in Ice Discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013. Geophysical Research Letters 41(5): 1576–1584. doi: http://dx.doi.org/10.1002/2013GL059069

Mouginot, J., E. Rignot, and B. Scheuchl. 2012. Mapping of Ice Motion in Antarctica Using Interfero-Metric Synthetic-Aperture Radar Data. Remote Sensing 4(9): 2753-2767. doi: http://dx.doi.org/10.3390/rs4092753

Rignot, E., J. L. Bamber, M. R. Van Den Broeke, C. Davis, Y. H. Li, W. J. Van De Berg, and E. Van Meijgaard. 2008. Recent Antarctic Ice Mass Loss from Radar Interferometry and Regional Climate Modelling. Nature Geoscience 1(2): 106-110. doi: http://dx.doi.org/10.1038/ngeo102

Rignot, E., J. Mouginot, M. Morlighem, H. Seroussi, and B. Scheuchl. 2014. Widespread, Rapid Grounding Line Retreat of Pine Island, Thwaites, Smith, and Kohler Glaciers, West Antarctica, from 1992 to 2011. Geophysical Research Letters 41(10): 3502–3509. doi: http://dx.doi.org/10.1002/2014GL060140

Rignot, E., J. Mouginot, and B. Scheuchl. 2011a. Antarctic Grounding Line Mapping from Differential Satellite Radar Interferometry. Geophysical Research Letters 38(10): Art. #L10504. doi: http://dx.doi.org/10.1029/2011GL047109

Rignot, E., J. Mouginot, and B. Scheuchl. 2011b. Ice Flow of the Antarctic Ice Sheet. Science 333: 1427-1430. doi: http://dx.doi.org/10.1126/science.1208336

Scheuchl, B., J. Mouginot, and E. Rignot. 2012. Ice velocity Changes in the Ross and Ronne Sectors Observed Using Satellite Radar Data from 1997 and 2009. The Cryosphere 6: 1019-1030. doi: http://dx.doi.org/10.5194/tc-6-1019-2012

RELATED DATA COLLECTIONS

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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National Snow and Ice Data Center

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

Get Data

Geographic Coverage

Data Citation

Literature Citation

Detailed Data Description

Spatial Resolution

Projection and Grid Description

Temporal Resolution

Parameter Description

Sample Data Record

Software and Tools

Data Acquisition and Processing

Processing Steps

Error Sources

References and Related Publications

Contacts and Acknowledgments

Investigators

Document Information

DOCUMENT CREATION DATE

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

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Geographic Coverage

Data Citation

Literature Citation

Detailed Data Description

Spatial Resolution

Projection and Grid Description

Temporal Resolution

Parameter Description

Sample Data Record

Software and Tools

Data Acquisition and Processing

Processing Steps

Error Sources

References and Related Publications

RELATED DATA COLLECTIONS

Contacts and Acknowledgments

Investigators

Document Information

DOCUMENT CREATION DATE

Find Data

Stay Current

Learn About Snow and Ice

Get Help

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